Physiological aspects of swimming performance for persons with disabilities. The purpose of this study was to evaluate the various factors involved in the performances of three groups of swimmers with disabilities. These factors were average VO2max (Av-VO2max) measured during swimming and gliding factors measured by the passive drag. Thirty-four swimmers with disabilities were assigned into three groups ranging from more disabilities to fewer disabilities. The first group (G I) included 13 subjects in wheelchairs, the second group (G II) 10 subjects walking with technical aids, and the third group (G III) 11 swimmers with disabilities walking without any help. For G I, the performances and Av-VO2max were lower (P < 0.05) than for G II and G III while the passive drag was higher than for G III (P < 0.05). The performances, Av-VO2max, and passive drag were not statistically different between G II and G III. Some of the swimmers had a pronounced amyotrophia of the lower extremities (i.e., reduced volume of inactive muscles). The height from the top of the head to the beginning of the bilateral amyotrophia was called "height without amyotrophia" (HWA). In the whole group, passive drag was not related to the mass or the height but to the ratio mass/HWA (r = 0.71, P < 0.01). However, within each group, passive drag was mainly related to the mass (r = 0.63, 0.78, 0.62, P < 0.01, for G I, G II, and G III respectively). Performances of a 100-m and 400-m swim were mainly related to Av-VO2peak (r = 0.81 and 0.79, P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)


Endurance training enhances critical power. The present investigation was conducted to determine whether critical power (CP) assesses the ability to perform continuous aerobic exercise and to determine whether training-induced changes in aerobic endurance are reflected by changes in the slope, but not the y-intercept of the CP function. Twelve healthy, active, but untrained male students (mean age +/- SD = 19.1 +/- 0.8 yr) undertook 8 wk of cycle ergometer endurance training (30-40 min a day, three times a week) at an intensity corresponding to their CP. Six control subjects of similar age and initial training status refrained from regular exercise for the same period. Before and immediately following the training period, each of the 18 participants completed three cycle ergometer tests to determine their CP function, an incremental exercise task to establish their maximal oxygen uptake (VO2max), and 40 min of continuous cycle ergometry at or near their calculated CP. CP was significantly correlated with endurance time at 270 W (r = 0.65, P < 0.05) and with the mean power that could be maintained for 40 min (r = 0.87-0.95, P < 0.01), but overestimated the latter by less than 6%. In response to endurance training, CP increased from a mean of 196 +/- 40.9 W to 255 +/- 28.4 W (31%) (ANCOVA, P < 0.01), while the mean power output maintained for 40 min of exercise increased from 190 +/- 34.5 W to 242 +/- 34.9 W (28%). VO2max increased from 49.2 +/- 7.8 ml.kg-1.min-1 to 53.4 +/- 6.4 ml.kg-1.min-1 (8.5%) (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)


Serum sex hormones and endurance performance after a lacto-ovo vegetarian and a mixed diet. Serum sex hormones and endurance performance after a lacto-ovo vegetarian and a mixed diet. Med. Sci. Sports Exerc., Vol. 24, No. 11, pp. 1290-1297, 1992. The effect of a lacto-ovo vegetarian (V) and a mixed, meat-rich (M) diet on the level of serum sex hormones, gonadotropins, and endurance performance of eight male endurance athletes was investigated in a 2 x 6 wk cross-over study. The energy contribution from carbohydrate, fat, and protein was 58%, 27%, and 15% on the V diet and 58%, 28%, and 14 E% on the M diet. For total fasting serum testosterone (T) there was a significant interaction between diet and time (P < 0.01). Thus, the V diet resulted in a lower total T level (13.7, 9.8-32.4 nmol.l-1) (median and range) compared with the M diet (17.4, 11.8-33.5 nmol.l-1). During exercise after 6 wk on the diets total T was also significantly lower on the V than on the M diet (P < 0.05). Serum free testosterone, however, did not differ significantly during the 6 wk dietary intervention periods and neither did serum concentrations of sex hormone binding globulin, dihydrotestosterone, dehydroepiandrosterone sulphate, 4-androstenedione, estrone, estradiol, estrone sulphate, or gonadotropins. Endurance performance time was higher for six and lower for two after the mixed diet compared with the vegetarian diet. This was not significant, however. In conclusion, 6 wk on a lacto-ovo vegetarian diet caused a minor decrease in total testosterone and no significant changes in physical performance in male endurance athletes compared with 6 wk on a mixed, meatrich diet.


Validity of bioelectrical impedance equations for estimating fat-free weight in lean males. The present study examined the validity of bioelectrical impedance (BIA) equations for estimating fat-free weight (FFW) in lean males (X +/- SD = 9.1 +/- 2.2% fat) by comparing the estimates with values obtained from underwater weighing. Sixty-eight Caucasian male volunteers served as subjects. Cross-validation analyses included examination of the constant error (CE), standard error of the estimate (SEE), r, and total error (TE). The results indicated that the equations of Oppliger et al. (16), which resulted in small TE (1.70 kg) and CE (-0.02 kg) values, most accurately estimated FFW. Simple linear regression showed that FFW was more highly correlated with body weight (BW) (r = 0.98, P < 0.0001) and resulted in a lower SEE (1.68 kg) than either height2/resistance (Ht2/R) (r = 0.81, P < 0.0001; SEE = 5.12 kg) or the independent variable (weight x resistance)/height2 [WR/Ht2] utilized by the manufacturer of the BIA analyzer (r = 0.15, P > 0.05; SEE = 8.59 kg). Multiple regression showed that when WR/Ht2, Ht2/R, resistance, body mass index, Ht2, and/or Ht was added to the prediction equation, which utilized BW alone, they accounted for less than 1% additional variance and reduced the SEE by < or = 0.16 kg. The results indicated that BW alone estimated FFW as accurately as any of the BIA equations in lean males.


Accuracy of RPE from graded exercise to establish exercise training intensity. The purpose of this investigation was to examine the accuracy of an exercise intensity prescription based upon perceptual responses obtained during a graded exercise test. Fifteen physically active men completed a graded exercise test (GXT) on a motor driven treadmill. Heart rate (HR), oxygen uptake (VO2), and RPE were measured each minute. An RPE intensity prescription was calculated as 75% of heart rate reserve from the GXT heart rate and RPE data. A minimum of 48 h later the subjects completed 10 min of exercise (EXT) on a level treadmill at the prescribed RPE. The subjects set the treadmill speed to elicit an exercise intensity equal to the prescribed perception of effort. There were significant mean differences (P < 0.05) in heart rate between the GXT (161.8 +/- 1.3) and EXT (154.9 +/- 4.5). However, by minute 6 the subjects were within four beats.min-1 of the target heart rate. There were no significant differences (P > 0.05) between GXT and EXT for VO2 (36.1 +/- 5.2, 33.1 +/- 6.4) and VE (64.1 +/- 10.8, 58.4 +/- 13.5) respectively. The present investigation demonstrates that a subject's perceptual response to a GXT can be used to accurately prescribe exercise intensity during level treadmill running. The intensity selected was within a typical range used for exercise prescription. The advantage of RPE as a method of exercise prescription is that an individual does not need to stop during exercise and measure a heart rate, but can make pace adjustments while exercising based solely upon the perception of effort.


[Chronic hepatic cytolysis syndrome in southern Africa]. Accidental discovery of a moderate and durable increase of transaminases in an asymptomatic patient is a more frequent possibility thanks to the development of methodological case findings activities. Most of the time, it is an isolated anomaly of which import and consequences have been already reviewed and published. Steatosis and chronic hepatitis are, by far, the most frequent etiologies in Western Countries. But the right importance of that syndrome in tropical hepatology has not been yet described. If we want to transpose results and what has to be done namely liver biopsy, to African medical practice, we have to take into due consideration local pathology, diagnosis facilities and/or therapeutic possibilities. The present article reviews the present knowledge on chronic liver cytolysis syndrome and discusses its interest in tropical Medicine.


[Infection by the human immunodeficiency virus and leprosy]. The author is reviewing the literature about the association HIV infection and leprosy. So he concludes: 1) there is no correlation between leprosy incidence and HIV infection incidence, despite similarity as far as immuno-system is concerned. 2) Effect of HIV infection on leprosy demands further studies of nervous leprosy pathology. 3) Tendency to increase of such and association is foreseeable, speaking of epidemiocity in developing countries as well as in leprosy foci in Southern Asia and India.


[Vesicovaginal fistulas: etiopathogenic and therapeutic aspects in Senegal]. Obstetrical vesico-vaginal fistulas are still very common in developing countries, because of to the difficulties of medical facilities. From a series of 123 cases recorded during 6 years, we analyse their epidemiological, anatomo-clinical, and therapeutic aspects. A simplified classification is purposed.


[Acute periurethritis: 155 cases].

[Acute periurethritis: 155 cases]. Severe complications of urethral stricture, acute peri-urethral phlegmon can be localized or diffuse. They are characterized by polymicrobial infections. The mortality rates about 7% is the privilege of diffuses forms. The treatment associates medical and surgical procedures, and consists in polyantibiotherapy and excision of suppurative lesions. From a series of 155 cases we analyse the pathogenical, clinical and therapeutical aspects.


[Measles control in the 1990s: perspectives of prevention and eradication with special reference to Africa]. A discussion of knowledge gained on measles during the 1980s leads to an outline of research priorities for the 1990s. Special emphasis is laid on the vaccine schedule, with particular emphasis on two dose schedules, on virus dissemination from town to country, and on two pronged strategies for town and country.


[Infectious endocarditis. Experience of a service in Brazzaville. 47 cases]. The aim of this study was to report the authors' experience of infective endocarditis (IE) from 47 cases collected between 1976 to 1991. Infective endocarditis (IE) was documented with surgical (n = 9), microbiological (n = 26), and echocardiographic (n = 30) criteria. There were 11 male, 36 female: mean age, 26.2 +/- 10.3 years (extremes: 17 and 47). The authors noted a great importance of gynecological portal entry (13 cases), acute infective endocarditis (23 cases i.e. 48.9%), heart failure (39 cases i.e. 82.9%), and pulmonary (4 cases i.e. 8.5%) and systemic (8 cases i.e. 17.0% embolism. Surgical treatment was impossible in Brazzaville. Trans-thoracic echocardiography was performed in 38 cases and revealed vegetations in 30 cases i.e. 78.9%. Twenty patients died (42.5%) because heart failure. There was no significant difference in letality between infective endocarditis treated surgically or no, between native valve or prosthetic valve infective endocarditis, between culture negative or culture positive infective endocarditis (IE). This study corroborate that infective endocarditis is a heavy illness, characterized by high frequency of heart failure. The authors insist upon the prevention of infective endocarditis.


Effect of lithium on the double-quantum behavior of 23Na in normal human erythrocytes. The double-quantum behavior of 23Na in the presence of different concentrations of Li in human erythrocytes was investigated. The 23Na double-quantum signal was quenched in both the extracellular and the intracellular compartments with increasing concentration of Li in each compartment, along with an increase in the 23Na T1 both intra- and extracellularly. Some extracellular quenching could be observed at the near therapeutic concentration of 2 mM Li. The ratio of slow to fast spin-spin (T2) relaxation times, obtained from the dependence of the double-quantum signal on creation time, approached unity at an overall Li concentration of 40 mM. These results provide evidence that Li and Na compete for both intra- and extracellular binding sites in erythrocytes.


[A new case report of omphalocele in a newborn (Kamenge University Hospital Center at Bujumbura, Burundi)]. A new case report of new born baby's omphalocele allows us to precise the embryological data indispensable to understand the genesis of this pathology. The future of the primitive intestinal loop and the explanation of the temporary physiological hernia, are the basis of such phenomenons rarely reported and they complete the three cases' report recently published.


[Scleroma and rhinoscleroma].

[Scleroma and rhinoscleroma]. Scleroma is a specific granulomatous disease of bacterial origin, chronic evolution, with election in respiratory tracts; nose lesion is practically constant and so justifies the term Rhinoscleroma. Although they are many endemic foci throughout the world and in particular in Africa, it is an uncommon disease, often not recognized for polymorphic. The cases recorded out of already known foci concerned generally migrants; autochtonous cases in France are really infrequent. Within the evolutive lesions diagnosis is made out of the isolation of the responsible germ (Klebsiella rhinoscleromatis) and the presence of the specific Mikulicz' cell. To find out localizations in the same patient, we utilize X Rays and endoscopy. Antibiotic therapy is of long duration but treats the affection and prepares the way of surgery intervention to eliminate cicatricial deformities. Relapses are caused by shortness of therapy and some difficulty to monitor patients. Mortel in the past, scleroma should nowadays, be better recognized to be better treated and cured.


A novel method for fat suppression in RARE sequences. Rapid acquisition relaxation-enhanced (RARE) sequences (Hennig et al., Magn. Reson. Med. 3, 823 (1986)) utilize one or several Carr-Purcell-Meiboom-Gill (CPMG) echo trains to sample a number of k-space lines each repetition time TR. The technique can rapidly generate multislice T2-weighted images which, as a rule, are strikingly similar in contrast to conventional T2-weighted spin-echo (SE) images. An exception to this rule is the appearance of very bright signal from fat in T2-weighted RARE images as compared to conventional T2-weighted SE images. To reduce this fat signal, we introduce a time delay, tau c, between the 90 degrees x and first 180 degrees y pulse of each echo train such that a phase angle of pi/2 develops between fat and the reference (water) line at echo maxima. The technique leads to single-acquisition fat suppression without the use of frequency-selective saturation pulses and concomitant loss of slices per TR. A Bloch equation analysis is used to identify two major mechanisms contributing to suppression of off-resonance spins such that w tau c = pi/2. Namely, the CPMG sequence becomes a CP sequence with no self-correction properties for imperfect 180 degrees pulses leading to enhanced signal decay, and the raw k-space data matrix become segmented into blocks alternately multiplied by +/- i, leading to signal dispersion following Fourier transformation.


[Mycobacterium fortuitum in a patient with human immunodeficiency syndrome (AIDS) in Benin)]. The authors report a case of Mycobacterium Fortuitum infection in one AIDS patient. This case underlines the interest for the clinicians to investigate systematically a possible infection by Mycobacterium fortuitum in all AIDS patients with pulmonary tuberculosis.


Validation of 13C NMR measurement of human skeletal muscle glycogen by direct biochemical assay of needle biopsy samples. Recent developments in 13C nuclear magnetic resonance (NMR) spectroscopy have permitted noninvasive assessment of glycogen concentration in human skeletal muscle. Before these indirect measurements could be accepted as accurate, it was essential that validation should be carried out by comparing the widely used method of muscle biopsy and direct biochemical assay for glycogen concentration with measurement by NMR. Eight normal subjects underwent six NMR scans of gastrocnemius and three biopsies of the same muscle on the same day. The overall mean for muscle glycogen concentration was 87.4 mM by NMR and 88.3 mM by biopsy. There was a close correlation between the pairs of observations on each subject (R = 0.95; P less than 0.0001). The mean coefficient of variation for NMR measurement was 4.3 +/- 2.1% and that for biopsy was 9.3 +/- 5.9%. The performance of the muscle biopsies was accompanied by a small but significant rise in plasma-free fatty acids (529 +/- 157 to 667 +/- 250; P less than 0.01), epinephrine (17 +/- 6 to 25 +/- 8 pg/ml; P less than 0.02), and norepinephrine (318 +/- 119 to 400 +/- 140 pg/ml; P less than 0.02) but no change in plasma glucose, plasma insulin, nor muscle glycogen concentration assessed by NMR. The study demonstrates that in vivo 13C NMR measurement of human muscle glycogen can be regarded as accurate, and the technique is associated with a higher precision that biopsy with direct biochemical assessment.


[Variation of the parasite density of Plasmodium falciparum in asymptomatic carriers: consequences for malaria chemoresistance studies]. During the studies on malaria chemoresistance, we noted great variations in parasite density of Plasmodium falciparum between screening in the morning and final selection in the afternoon, in asymptomatic people. To better understand this phenomenon, we conducted a study in october 1987 on primary school children in a village near the city of Bobo-Dioulasso, at the peak malaria prevalence. We performed 3 blood-smears at 8 a.m., 2 p.m. and 8 p.m., on Day 0 and Day 4, to an initial number of 86 children, aged from 6 to 9 years. By the end of the study 44 children remained who fulfilled the inclusion criteria Among them 35 showed a parasitaemia on Day 0 and 9 remained negative. On Day 4, 28 were positive and 16 remained negative. Of the 35 children positive at entry to the study 16 remained continuously positive, the others were negative on at least one occasion. Of the 28 children positive on Day 4, 14 remained continuously positive. For the 16 people with a parasitaemia continuously positive on Day 0.7 (43.7 p. cent) became spontaneously negative on Day 4. But considering the small size of our sample, the analysis of the nycthemeral variation and of the variation between the two days did not show a significant difference. Further studies involving a greater number of blood-smears during a longer period and concerning more people, should be conducted. The possibility of spontaneous negativation of the parasitaemia without drug absorption shows that there are some cases of false malaria chemosensitivity that are declared when the in vivo tests are not coupled with in vitro tests.


[Evaluation of an indirect hemagglutination test for the serodiagnosis of amebiasis]. 167 sera have been tested to appreciate the value of an indirect hemagglutination test (Amibiase HAI FUMOUZE) comparatively to an agglutination test of sensibilized particles of latex (Bichro latex Amibe Fumouze BLA) Amibiase HAI test comes out as sensitive and specific for the detection of antibodies in patients suffering from visceral amoebiasis. But some antibodies are also detected in patients with an antecedent of amoebiasis, as it is usually the case with some other techniques. A high positivity of the indirect hemagglutination test, and the concordance between the test HAI and the BLA one are in favour of a visceral amoebiasis. While lower rates or discrepancy between the two tests may evoke an hidden infestation in patients coming out or originated from endemic zones.


Charge dependence of the distribution of contrast agents in rat cerebral ventricles. Previous studies of MRI contrast resulting from the intracerebral administration of several contrast agents have suggested that the distribution of these agents may be dependent on the net charge. In order to further evaluate the significance of this parameter, the distribution of both aquo and CDTA-chelated lanthanide and transition metal ions in the cerebral ventricles of rats has been evaluated based on their enhancement of MRI contrast. The agents were injected directly into the lateral ventricles of Sprague-Dawley rats. Each of five different positively charged paramagnetic metal ions tested selectively enhanced the inner cellular layers of ventricular luminal wall of the rat brain, while such enhancement was absent using the corresponding negatively charged metal-CDTA complexes. The abundance of negatively charged residues on the cell surface of the inner luminal layers is suggested to be the source of the observed charge affinity. Differences in the distribution of Mn2+ ions administered intracerebrally compared with intraperitoneal (ip) injection suggest that while the first treatment may result primarily in uncomplexed aquo ions which then interact with the luminal surface, manganese ions administered ip behave more like chelated ions and are most probably complexed to transferrin.


On the application of ultra-fast RARE experiments. The ultra-fast application of the RARE experiment is described in detail, with special emphasis on its multifarious applications with preparation experiments that produce transverse magnetization. The factors affecting the temporal evolution of the magnetization during the experiment are described, and the implications for the slice profile when using a Gaussian refocusing pulse are experimentally examined. The choice of phase-encoding scheme for use with preparation experiments is discussed, as is the use of various phase-encoding schemes to reduce line broadening in the phase-encoding direction if a number of averages are acquired. An explanation for the decomposition of the echo are into two components if the read gradient is imbalanced is given, and the experimental conditions necessary for the coherent addition of these two echo groups are described. An alternative sequence that removes one of these groups from the acquisition window is proposed. The sensitivity of the sequence to flow and motion is investigated, and the drastic loss of signal in this situation explained. The in vivo and in vitro application of preparation experiments leading to the accurate measurement of T1, T2, diffusion constant, and magnetization transfer characteristics is presented. The implementation of zoom-imaging using spin- and stimulated-echo preparation is described, and 3D in vivo spin-echo zoom images are presented. Simple phantom experiments demonstrating the feasibility of chemical-shift selective and spectroscopic imaging are also given.


Breast coil design for low-field MRI.

Breast coil design for low-field MRI. Four double-breast coils were designed for the low-field resistive magnet MR imaging of female breasts at 0.02, 0.04, and 0.1 T. The signal-to-noise ratio is optimized by shaping the coils, by constructing two different size coils at 0.02 T, and by using special wire for the turns of the solenoidal coils. The approximate linear dependence of the SNR on the Larmor frequency is estimated.


The capillary network: a link between IVIM and classical perfusion. MR measurements based on motion encoding gradients, such as intravoxel incoherent motion imaging, could provide, in principle, information on flowing blood volume and blood velocity. This note shows that, in addition, the knowledge of the capillary network organization may provide a link between these measurements and those obtained by conventional and MR perfusion techniques based on tracer uptake by tissues.


T1 values of phosphomonoester and phosphocreatine of brain show no significant change during development. Changes in apparent 31P spin-lattice relaxation times (T1) associated with brain development were investigated in rat pups. While analysis of variance showed strong age dependency in [PME]/[ATP] and [PCr]/[ATP], the T1 values of PME, PCr, and ATP did not show any age dependency. The studies indicate that in contrast to the data which indicated aging-related changes in the T1 values of PME, the observed changes in PME during neonatal development are likely to be quantitative in nature.


Detection and assignment of the glucose signal in 1H NMR difference spectra of the human brain. The difference between 1H NMR spectra obtained during eu- and hyperglycemia exhibited well-resolved glucose peaks between 3 and 4 ppm as demonstrated by comparison with solution spectra. Estimated increases were consistent with recent 13C NMR quantitations of intracerebral glucose. Difference spectra were measured in 36-ml volumes from the human brain every 3 min.


Evaluation of experimental early acute cerebral ischemia before the development of edema: use of dynamic, contrast-enhanced and diffusion-weighted MR scanning. The ability of dynamic, contrast-enhanced, magnetic susceptibility-weighted scanning to delineate early experimental acute cerebral infarction was compared with that of heavily T2-weighted and diffusion-weighted spin echo scanning. Spontaneously hypertensive rats, which had undergone right middle cerebral artery occlusion, were studied from 15 min to 3 h post ligation on a 1.5-T clinical whole-body imager. In contrast to the diffusion- and T2-weighted spin echo scans, the dynamic, contrast-enhanced technique clearly and consistently delineated the nonperfused regions as early as 15 min post ligation.


A nuclear magnetic resonance investigation of the upper airways in ferrets. I. Effects of histamine and methacholine. Alterations induced in the upper airways of ferrets by intranasal provocation with methacholine (MC) and histamine (HS) were monitored using proton magnetic resonance imaging (MRI) and spin-spin relaxation rate (R2) measurements. Both MC and HS cause a significant increase in the MRI signal intensity and a decrease in R2 in the nasal turbinates. A dose-dependent response is observed for 20 to 315 nmol of HS, with a maximum increase in intensity of ca. 50% occurring above 80 nmol. A single unilateral challenge with MC yields a 62 +/- 3% increase in intensity. Control animals (saline-treated) show little change in image intensity. MC and HS cause decreases in the proton R2 by -27.0 +/- 5.5% and -17.2 +/- 4.3%, respectively. These data are indicative of an accumulation of fluid in the nasal airways. MRI provides an effective means to monitor changes in the nasal airways which occur as a result of pharmacological treatment.


A nuclear magnetic resonance investigation of the upper airways in ferrets. II. Contrast-enhanced imaging to distinguish vascular from other nasal fluids. Proton magnetic resonance imaging (MRI), used in conjunction with the intravascular contrast agent albumin-(Gd-DTPA), provides a means to distinguish vascular fluids from other nasal fluids in the upper airways. Ferrets were given an intravenous dose of albumin-(Gd-DTPA) followed by an intranasal challenge with either histamine (HS) or methacholine (MC). An observed increase in image intensity indicates that HS and MC both cause an accumulation of fluids in the nasal turbinate region. The MRI data are also influenced by the presence of blood, which contains the contrast agent, and a clear distinction can be made between vascular fluids and other nasal fluids (i.e., cellular and glandular secretions). The results show that HS causes an increase in vascular fluids in the nasal turbinates while MC does not. This methodology represents a new means to investigate airway pharmacology and the pathophysiology associated with various pharmacological agents, allergens, or viral infections.


Magnetic resonance imaging of myocardial kinematics. Technique to detect, localize, and quantify the strain rates of the active human myocardium. A magnetic resonance imaging (MRI) method is presented to detect, localize, and quantify myocardial kinematics by measuring the material rate-of-strain tensor at each pixel in gated NMR images of the heart. The immediate, local effect of muscular activity is self-deformation, and the strain tensor is the basic mathematical device by which such deformation may be quantified. The present method, called "strain-phase" MRI (SP-MRI), entails four steps: (1) the velocity of the myocardium is encoded by means of a set of motion-sensitive NMR image acquisitions, one image per velocity component; (2) the spatial derivatives of the velocity are computed at each pixel; (3) the velocity-derivative data are combined to compute an approximation of the strain-rate tensor of the myocardium at each pixel; and (4) the strain-rate tensor data are simplified to produce a color-coded functional image which represents strain-rate components which are of particular biomedical interest in the myocardium. We present a quantitative SP-MRI methodology suited to conventional MRI, and in addition present an "echo-planar" methodology, able to produce qualitative functional images of myocardial kinematics at almost real-time speeds. Two-dimensional strain-phase MRI data acquired in normal human subjects are presented. These data demonstrate the practicability of SP-MRI in vivo, that SP-MRI resolves myocardial kinematics at the single-pixel scale, having resolution comparable to that of conventional MRI, and that SP-MRI data may have a signal-to-noise ratio up to 50% as great as that of the conventional MRI data from which they are produced. SP-MRI measurements of the local instantaneous strain rates in the human left ventricular myocardium are quantitatively consistent with known transmural average values of myocardial strain.


The design of liposomal paramagnetic MR agents: effect of vesicle size upon the relaxivity of surface-incorporated lipophilic chelates. The 1/T1 NMRD profiles of lipid vesicles with the paramagnetic ion Gd attached via a chelate covalently linked to the membrane surface show a peak at approximately 20 MHz indicating that fluctuations of approximately 10(-8) s contribute to the form of the dispersion profile. If the correlation time for fluctuations of the paramagnetic chelate on the membrane surface is much less than the correlation time for rotation of the lipid vesicle, it would be expected that the measured 1/T1 relaxation rate for solvent protons should be invariant with vesicle size above a certain minimum vesicle diameter. We show that this is indeed the case for vesicles in the size range 50 to 400 nm average diameter and discuss general design considerations for the preparation of vesicle-associated MR contrast agents based upon paramagnetic chelates either trapped within the vesicle interior or attached to the membrane surface.


Measurement of blood-brain barrier permeability in a tumor model using magnetic resonance imaging with gadolinium-DTPA. Sequential MR imaging with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) and sequential measurements of plasma Gd-DTPA concentration by inductively coupled plasma atomic emission spectroscopy (ICP-AES) were used to estimate the blood-to-tissue transport coefficient (Ki) in the 36B-10 rat glioma model. For these measurements, tissue Gd-DTPA concentration was estimated from tumor enhancement by correlation with calibration measurements obtained by ICP-AES analysis of tumor tissue. The 14 animals for which Ki was calculated can be grouped into those imaged at 11 days following tumor implantation, at 13-18 days, and at 20 days. The mean (+SEM) Ki values for these groups were 1.1 + 0.24, 9.2 + 0.8, and 13.4 + 1.7 ml/kg-min, respectively. These results correspond well with published data obtained by quantitative autoradiography. It is concluded that frequent sequential imaging and a graphical approach to Ki calculation are promising methods for determining the blood-to-tissue transport coefficient noninvasively by contrast-enhanced MRI.


Determination of concentrations by time domain fitting of proton NMR echo signals using prior knowledge. A fast and flexible time domain iterative fitting procedure that can be used to fit free induction decays as well as echo-like signals is described. Damping constants of the first and second part of the echo do not have to be identical. Prior knowledge can be used to diminish the number of parameters to be fitted, which results in an improved accuracy. It is shown how prior knowledge is mathematically incorporated in the Gauss-Newton method. From proton NMR measurements of model solutions actual prior knowledge is extracted. With this knowledge relative concentrations are determined from a mixture of metabolites. The fitted results agree with the true values within the margins of the noise. After some minor changes the same prior knowledge was successfully used to analyze a series of in vivo rat brain measurements.


Relationship between the degree of unsaturation of dietary fatty acids and adipose tissue fatty acids assessed by natural-abundance 13C magnetic resonance spectroscopy in man. Natural-abundance 13C magnetic resonance spectroscopy was used for determining noninvasively the relative concentration of mono- and polyunsaturated fatty acids of adipose tissue in two groups of volunteers. The first consisted of subjects who had followed a fat-reduced diet for at least half a year before the 13C measurements. The second were control subjects who were on a usual high-fat diet. The ratio of unsaturated to total fatty acids in adipose tissue determined by 13C MRS correlated significantly with the same ratio in fat of the diet composition estimated by a dietician according to food records. The results indicate that 13C MRS is capable of assessing the degree of unsaturation of dietary fatty acids consumed during the preceding months.


Determination of absolute phosphate metabolite concentrations in RIF-1 tumors in vivo by 31P-1H-2H NMR spectroscopy using water as an internal intensity reference. The absolute metabolite quantification method of Thulborn and Ackerman [J. Magn. Reson. 55, 357 (1983)] in which the tissue water proton signal is used as an internal intensity standard and its more recent variation in which NMR peak intensities are referenced to that of the natural abundance deuterium signal of water [Li et al., SMRM Abstr. 2, 825 (1988); Song et al., Magn. Reson. Med. 25, 45 (1992) have been implemented to obtain absolute phosphate metabolite concentrations in subcutaneous RIF-1 tumors during untreated growth and following treatment with 5-fluorouracil. The equivalence of these two hydrogen isotopes as intensity standards and the validity of their use in the determination of absolute metabolite concentrations in vivo by NMR has been demonstrated. On matched in vivo and extract tumor samples (n = 5), excellent agreement has been obtained between nucleoside triphosphate concentrations determined by NMR and those derived by HPLC analysis for the control tumors. Following 3 days of untreated growth, absolute concentrations of phosphate metabolites in RIF-1 tumors (n = 10) decreased significantly, except for the Pi concentration which did not vary. For the treated tumors (n = 10) there were no changes in metabolite concentrations except for a decrease in the PCr and, possibly, Pi concentrations. The PCr/Pi ratio in the latter tumors did not change. These observations suggest that changes in absolute metabolite concentrations may be more sensitive indices of response to therapy than changes in metabolite peak amplitude ratios, a parameter commonly used to express in vivo NMR data.


Phasing spin-echo-acquired 31P spectroscopic images using complex conjugate data reversal. A simple method has been developed for phasing 31P spectroscopic images acquired with short echo-time (1-2 ms) spin-echo sequences. The technique is based on reconstructing complete echoes in the time domain by the reversal of the complex conjugate of the data. After Fourier analysis, a magnitude reconstruction is used, which no longer broadens the lines. Advantages of the method compared to other phasing procedures are discussed.


Feasibility of 19F imaging of perfluorochemical emulsions to measure myocardial vascular volume. 19F magnetic resonance images were obtained of the ventricular walls of isolated rabbit hearts perfused with a perfluorochemical (PFC) emulsion. Since the PFC is known to stay within the vascular space in normal myocardial tissue, the 19F signal should reflect myocardial vascular volume. 19F MRI of PFC emulsions represents a new investigational tool for the study of coronary vascular volume.


13C and 1H NMR study of the metabolic degradation of 4-pentenoate in different dog nephron segments. The metabolism of 4-pentenoate in isolated kidney tubules has been investigated by 1H and 13C NMR. The 4-pentenoate metabolite, 3-keto-4-pentenoyl-CoA, accumulated in proximal tubules only and its formation could be competitively inhibited by octanoate. 4-Pentenoate was metabolized in thick ascending limbs but not in papillary collecting ducts.


Use of fluid-attenuated inversion-recovery pulse sequences for imaging the spinal cord. Fourteen patients with disease of the spinal cord were imaged with fluid-attenuated inversion-recovery (FLAIR) sequences in which the inversion time was chosen to substantially reduce or null the signal from CSF. Lesions were seen with greater conspicuity than with conventional contrast-enhanced and -unenhanced T1- and T2-weighted sequences in 11 cases.


NMR venography using the susceptibility effect produced by deoxyhemoglobin. A new angiography technique using the susceptibility effect is proposed. Blood containing deoxyhemoglobin is more paramagnetic than surrounding tissue and thereby produces a susceptibility effect at blood-tissue interfaces. By use of a specially tailored RF pulse, signals from normal tissues are suppressed while the signals from blood interfaces, where strong susceptibility-induced fields are created, are enhanced. The design and characteristic behavior of the tailored RF pulse are discussed and experimental results obtained using both a phantom and a human volunteer with a 2.0-T whole-body NMR system are also presented.


Atraumatic quantitation of cerebral perfusion in cats by 19F magnetic resonance imaging. We have noninvasively produced low-resolution, quantitative nuclear magnetic resonance images of cerebral blood flow in 2-ml voxels in eight cats. Typical signal-to-noise of 4 to 1 was obtained in cerebral voxels in 16.5-s epochs. Mean flow during normocapnia (paCO2 = 39 +/- 4 mm Hg) and hypercapnia (paCO2 = 62 +/- 4 mm Hg) was 53 +/- 20 ml/100 g-min and 140 +/- 36 ml/100 g-min, respectively. Fast flows in normocapnia were 94 +/- 13 and 182 +/- 39 ml/100 g-min in hypercapnia. These results suggest that an atraumatic quantitative imaging assessment of cerebral perfusion may be possible in humans using these techniques.


An NMR phased array for human cardiac 31P spectroscopy. A four-coil phased-array 31P NMR receiver was designed and tested for human cardiac applications, to determine whether the combination of relatively high signal-to-noise ratio (SNR) and large field of view produced in 1H imaging is also realized for in vivo 31P spectroscopy. Spectra were acquired in parallel from an array of four overlapping 6.5-cm surface coils using one- and two-dimensional phase-encoding pulse sequences and were optimally combined to yield composite spectroscopic images. The phased array was found to generate useful 31P spectra from a 2.5-fold wider lateral region around the anterior myocardium than a single receiver of the same size as the array elements, with no increase in imaging time. In addition, the sensitive depth was increased by up to 2 cm over that of a single coil. Spectra could be acquired in roughly 15 min from a region extending to the middle of the heart, with voxel sizes of 2 x 2 x 4 cm3. For the average heart voxel, the SNR of the combined spectrum was higher than that of the best spectrum from any one coil in the array by 30%, with some voxels showing an increase as high as 60%.


Glycogen detection by in vivo 13C NMR: a comparison of proton decoupling and polarization transfer. The performance of gated proton decoupling and polarization transfer with respect to glycogen detection by 13C NMR was investigated. Experiments were performed on a 1.5-T whole-body scanner using a 13C surface coil in combination with a proton head coil. Spectra were acquired from a glycogen phantom and from the lower leg of a healthy volunteer using proton decoupling and the polarization transfer method SINEPT. The signal strength of the C1 resonance of glycogen was determined and compared to a reference spectrum acquired without any form of sensitivity enhancement. In the phantom experiment both decoupling and SINEPT produced a signal gain of 3.5. Under in vivo conditions, the signal gain was approximately 2.5 for both techniques. We conclude that decoupling and polarization transfer are equivalently useful techniques for glycogen detection.


Simultaneous MR acquisition of arterial and brain signal-time curves. Regional cerebral blood flow (rCBF) provides important information about local neuronal functional and cerebrovascular status. Determination of rCBF requires sequential measurements of tracer concentration in arterial blood and brain tissue unless the tracer is trapped in the brain in proportion to rCBF. Since gadopentate dimeglumine is not trapped within brain tissue, we have developed the simultaneous dual FLASH pulse sequence (SDFLASH) which sequentially measures the MR signal change in both the internal carotid artery and brain parenchyma simultaneously during the passage of a bolus of paramagnetic contrast material.


Quantitative MRI of the prostate and uterus in monkeys. Quantitative MRI has been carried out in the prostate, seminal vesicles, uterus, and ovaries in the pig-tailed monkey, Macaca nemestrina. T2-weighted, fat-suppressed, multislice experiments were performed at 2.35 T. Eight males, 14 ovariectomized females, and 20 intact females were studied. In the prostate, the caudal and cranial lobe were readily distinguished since the latter had a longer T2 value. For all tissues and organs, interanimal variations were large (up to 12-fold variation in volume), but reproducibility was excellent in the prostate and in the ovariectomized monkey uterus with coefficients of variation (CV) of 3 and 5%, respectively. In the intact monkey uterus, cycle-cycle reproducibility was good with CVs of 6-10% in the myometrium and 14-18% in the endometrium. In the follicular phase, endometrial growth (+3.8% day-1, P < 0.001) was accompanied by myometrial shrinkage (-1.6% day-1, P < 0.001), while in the luteal phase, growth was seen in both tissues (+4.3% day-1, P < 0.001 and +1.4% day-1, P < 0.001, respectively). The great value of these MRI techniques in obtaining data in pharmacological efficacy studies of endocrine drugs, and in limiting the number of animals used, is discussed.


The loss of small objects in variable TE imaging: implications for FSE, RARE, and EPI. The importance to MR image quality of the order of acquisition of different phase-encoded views with sequences that have variable TR and TE has been recently reported. It has been shown that the effective point spread function (PSF) may be manipulated by varying TE or TR, or both, with each phase-encoding step. This paper explores the behavior of the PSF in a variable TE sequence and its dependence on both imaging and tissue parameters. It is shown that the PSF is different for each tissue type and that its effect on tissue contrast is a function of both the shape and size of the structure. The important problem of signal loss from small objects that arises when the effective PSF is broad and the difficulty in detecting this phenomenon in practical MR images is illustrated. It is shown that the PSF can produce significant blurring and loss of object contrast in fast spin-echo images but that this blurring may be not be obvious in practice because the noise is unaffected by the PSF. It is also shown that the signal from small lesions with short T2 can easily be lost through this blurring mechanism. The importance of signal loss from small objects and its implication for the clinical use of such sequences as fast spin-echo or rapid acquisition relaxation-enhanced and echo planar imaging is stressed.


Direct observation of the magnetization exchange dynamics responsible for magnetization transfer contrast in human cartilage in vitro. Saturating irradiation far off-resonance can lead to diminution in the water signal seen in MRI, giving rise to magnetization transfer contrast. This results from transfer of magnetization between "solid" protons with restricted motion, which give rise to a band some tens of kilohertz wide, and the narrow signal from mobile protons. In the work reported here a high-power pulse spectrometer, which can detect signals from both mobile and immobile protons, was used to investigate the dynamics of magnetization transfer in cartilage in vitro. Magnetization transfer in modified Hoffman-Forsén inversion transfer experiments was well-described by a single rate constant model; full analytical solutions are offered for the resultant biexponential magnetization recovery curves. The use of pulsed methods to generate magnetization contrast may in some circumstances offer advantages over the steady-state saturation methods used hitherto.


Purification and characterisation of an extracellular metalloprotease, serine protease and haemolysin of Aeromonas hydrophila strain B32: all are lethal for fish. Three different lethal (for rainbow trout, Salmo gairdneri) extracellular toxins were purified by HPLC from the culture supernatants of Aeromonas hydrophila strain B32 which had been isolated from rainbow trout. A metalloprotease, MW 38 kDa, was stable at 56 degrees C for 10 min, had no cytotoxic activity and and LD50 of 150 ng/g fish. In narrow range isoelectric-focusing (IEF) the enzyme had 11 isomers with (pls) between 4.12 and 4.8. A serine protease (22 kDa) was stable at 56 degrees C for 10 min, possessed cytotoxic activity and had an LD50 of 150 ng/g fish. In IEF, multiple isomers possessed pls between 4.5-5.2. The haemolysin had alpha-haemolytic activity (68 kDa) multiple isomers in IEF with pl range 4.5-5.1 and an LD50 of 2 micrograms/g fish. It was stable after heating to 56 degrees C for 20 min, 60 degrees C for 10 min and possessed esterase activity on beta-naphthyl acetate. These latter properties suggest it may be a novel haemolysin distinct from alpha- and beta-haemolysin.


The clinical and immunogenetic features of patients with autoantibodies to the nucleolar antigen PM-Scl. The clinical and laboratory features of 32 patients with anti-PM-Scl were studied. Patients with this rare autoantibody suffered from a homogenous overlap connective tissue disease defined by Raynaud phenomenon (32/32), features of scleroderma (31/32), arthritis (31/32, erosive in 9/32), myositis (28/32), lung restriction (25/32), calcinosis (15/32), and sicca (11/32). Significant renal and neurologic involvement was uncommon. All patients examined (22/22) had HLA-DR3, and 50% of these patients were homozygous. Our patients responded favorably to moderate immunosuppression and, with therapy, the disease generally has a good prognosis; over 50% of our series (17/32) remained well on minimal or no immunosuppression after a median follow-up of 8 years.


Gaucher disease. Clinical, laboratory, radiologic, and genetic features of 53 patients. We have reviewed our experiences with the clinical, laboratory, radiologic, and genetic features of 53 patients with Gaucher disease. Most were evaluated during early adult life, with a mean age of 33 years. Our patients were evaluated in a referral center, and therefore the data need to be interpreted with caution when applied to the general patient population, which includes a greater proportion of very mild cases. Thirty-nine patients were Ashkenazi Jews, 13 were non-Jewish and 1 was half-Jewish. The most common presenting symptom was bleeding related to splenomegaly and thrombocytopenia. The chronic symptoms, evaluated an average of 20 years after the diagnosis had been established, were mainly skeletal. Splenectomy had been performed in 43% of our patients and there was no evidence that this procedure accelerated the progression of liver and bone involvement. DNA from the patients was examined for 20 different mutations. The association between the 1226G/1226G genotype and a milder clinical course, and between the 1226G/84GG and 1226/1448C genotypes with more severe clinical manifestations, was confirmed. Repeated follow-up examinations in 29 patients revealed that in the majority of the patients, progression of the disease occurs during childhood, adolescence, or early adulthood with a marked tendency for stabilization thereafter. This observation suggests that Gaucher disease in most of the patients is not a relentless progressive disorder but a rather stable disorder during adulthood. The indications for the newly introduced intravenous enzyme replacement therapy as well as of future experimental treatments should be examined in the light of the natural history of the disease.


Spontaneous hemothorax. Report of 6 cases and review of the literature. We present 6 cases of spontaneous hemothorax and comprehensively review the medical literature on this subject. We categorize the reported causes and offer a rational diagnostic approach to patients with nontraumatic hemothorax. We recommend specific treatments for specific etiologies, and emphasize the importance of well-established surgical principles for the treatment of hemothorax. Our suggestions should enable physicians to accurately diagnose and expeditiously treat patients with spontaneous hemothorax.


Mysticete (baleen whale) relationships based upon the sequence of the common cetacean DNA satellite. The genomes of all extant cetaceans are characterized by the presence of the so-called common cetacean DNA satellite. In the mysticetes (whalebone whales) the repeat length of the satellite is 1,760 bp. In the odontocetes (toothed whales), other than the family Delphinidae, the repeat length is usually approximately 1,740 bp. The Delphinidae are characterized by a repeat length of approximately 1,580 bp. It has been shown in odontocetes that the satellite evolves in concert and that differences between species, with respect to the sequence of the satellite, correspond reasonably well to their evolutionary distances. In the present study the sequence of the satellite was determined in three repeats in each of seven mysticete species, and a consensus for each species established. Parsimony and neighbor-joining analyses based upon sequences of all repeats showed that the primary evolutionary distinction among the mysticetes is between the Balaenidae sensu stricto (i.e., the bowhead whale and the right whale) and all remaining species, including the pygmy right whale, a species that usually has been included in the Balaenidae. The comparisons also showed that the humpback whale and the gray whale were approximately equidistant from the blue whale and the fin whale (genus Balaenoptera). Concerted evolution of the satellite was also demonstrated among the mysticetes, but it appeared to evolve more slowly in the mysticetes than in the odontocetes.


Evolution of the expression of the Gld gene in the reproductive tract of Drosophila. During the preadult development of Drosophila melanogaster, the GLD (glucose dehydrogenase) gene (Gld) is expressed in a variety of tissues, including the immature reproductive tract. At the adult stage the expression of Gld becomes largely restricted to the reproductive tract of males and females. We examined the expression of GLD in the adult reproductive tract of 50 species in the genus Drosophila, as well as in those of a few representative species from four other closely related genera. GLD exhibits considerable organ-specific diversity in the reproductive tract of males and females. Among these species, five male GLD phenotypes and six female GLD phenotypes were found. In contrast, the preadult expression of GLD in representative species from each distinct adult pattern type was determined and found to be highly conserved in both the immature reproductive tract and non-reproductive organs. Moreover, the set of reproductive organs that express GLD during preadult development is equivalent to the sum of the five male and six female adult GLD phenotypes. To initially define the contribution of cis- versus trans-acting factors responsible for differences in adult GLD expression between two of these species--D. melanogaster and D. pseudoobscura--we transferred the D. pseudoobscura Gld to the genome of D. melanogaster and investigated its expression. GLD expression patterns of these transformants displayed characteristics that are unique to both species, suggesting the presence of both cis- and trans-acting differences between these two species.


Sequence evolution in mitochondrial ribosomal and ND-1 genes in lepidoptera: implications for phylogenetic analyses. A 2,256-bp sequence of the mitochondrial genome of a lepidopteran (Spodoptera frugiperda) contains tRNAs for valine and leucine, the 16S rRNA, and three-quarters of the ND-1 presumptive protein-coding gene. A 64-bp stretch of unknown function was located between the rRNA and leucine tRNA. Sequence divergence in the 16S rRNA obtained from alignment with published insect sequences is consistent with phylogenetic hypotheses, in that Diptera and Lepidoptera are more closely related to each other (24% sequence divergence) than either is to Hymenoptera (31%). Within the ND-1 gene, sequences for four additional Lepidoptera were generated for a 314-bp region and contrasted with published sequences for the locust and Drosophila. Sequence divergence in this region was consistent with accepted phylogenetic relationships, but results of parsimony analyses were not. Cladograms consistently recovered accepted higher level relationships (monophyly of Lepidoptera), despite high homoplasy, but were unable to resolve superfamily and family relationships within Lepidoptera, regardless of the outgroup or character subset analyzed. Character analysis indicated that homoplasy was decreased at higher levels when first- and second-codon sites were used exclusively. At the lowest level (families), resolution was enhanced by inclusion of third-codon sites. Inability of molecular data to recover a well-established phylogeny may be rectified by additional characters or taxa, but it is clear that homoplasy is sufficiently high to caution against the acceptance of relationships generated with this molecular region that are not extremely robust.


Complete congruence between morphological and rbcL-based molecular phylogenies in birches and related species (Betulaceae). Estimations of phylogenies from morphological and molecular data often show contrasting results. We compared morphological and molecular phylogenies in an ancient family of woody dicots, the Betulaceae (birch family). The phylogeny of the family was estimated from parsimony analysis of morphological characters in the genera Alnus, Betula, Carpinus, Corylus, Ostrya, and Ostryopsis and from parsimony and distance-matrix analyses of DNA sequences of the chloroplast gene encoding the large subunit of ribulose-1,5-biphosphate carboxylase (rbcL) in the genera Alnus, Betula, Carpinus, Corylus, and Ostrya and in two outgroups, Quercus and Liquidambar. The topologies obtained by the different methods were completely congruent, and bootstrapping strongly supported the division of the family Betulaceae into two major clades, Betuleae (Alnus and Betula) and Coryleae (other members). Only slightly more homoplasy was present in the rbcL sequence data set than in the morphological set. Relative-rate tests indicated that the Coryleae clade had a faster rate of rbcL evolution than did the Betuleae clade. Heterogeneity of rates of morphological evolution also paralleled those for rbcL.


The 5S ribosomal RNA gene in Pythium species: two different genomic locations. The 5S ribosomal RNA (rRNA) genes in eukaryotes may occur either interspersed with the other rRNA genes in the ribosomal DNA (rDNA) repeat, or in separate tandem arrays, or dispersed throughout the genome. In Pythium species and in several related Oomycetes, polymerase chain reaction (PCR) amplification of the nontranscribed spacer (NTS) region with one primer specific for the 5S gene revealed, with several exceptions, that the 5S rRNA gene was present in the rDNA repeat of those species with filamentous sporangia and was absent from the rDNA repeat of those with globose or unknown sporangia. When present, the gene was located approximately 1 kb downstream of the large-subunit rRNA gene and on the strand opposite that on which the other rRNA genes were located. This was confirmed in P. torulosum by sequencing of the gene and its flanking regions. The 5S rRNA genes of P. ultimum were found in tandem arrays outside the rDNA repeat. Evidence of dispersed 5S rRNA sequences was also observed. For many of the species of Pythium having the 5S gene in the NTS, the region between the large-subunit rRNA gene and the 5S gene was found to have length heterogeneity. Oomycetes related to Pythium were also found to have the 5S gene in the NTS, although sometimes in the opposite orientation. This may mean that the presence of the gene in the NTS is ancestral for the Oomycetes and that the absence of the gene in the NTS in those Pythiums with globose sporangia is due to loss of the gene from the rDNA repeat in an ancestor of this group of species. These results favor the view that 5S rRNA gene linkage to the rRNA cistron existed prior to the unlinked arrangement seen in most plants and animals.


Group I introns within the nuclear-encoded small-subunit rRNA gene of three green algae. Four group I introns from the nuclear-encoded (18S) rRNA genes of three chlorophycean green algae are described; two are in Dunaliella parva, and one each is in D. salina and Characium saccatum. The introns within the gene in the latter two organisms are located at the sites equivalent to the 5' and 3' introns of D. parva, respectively. All four introns lack open reading frames and are relatively small, 381-447 bp. Both primary- and secondary-structural features place these introns within subgroup IC1 described by Michel and Westhof. Phylogenetic relationships of the three intron-containing taxa and their relatives, as inferred from comparisons of 18S rDNA sequences, suggest that inheritance of the introns along with the gene can account for their present distribution. The discovery of these four introns, in addition to two others known to exist in other chlorophycean green algae, suggests that group I introns within the 18S rRNA gene may be relatively common in the green algae.


Statistical properties of bootstrap estimation of phylogenetic variability from nucleotide sequences. I. Four taxa with a molecular clock. The statistical properties of sample estimation and bootstrap estimation of phylogenetic variability from a sample of nucleotide sequences are studied by using model trees of three taxa with an outgroup and by assuming a constant rate of nucleotide substitution. The maximum-parsimony method of tree reconstruction is used. An analytic formula is derived for estimating the sequence length that is required if P, the probability of obtaining the true tree from the sampled sequences, is to be equal to or higher than a given value. Bootstrap estimation is formulated as a two-step sampling procedure: (1) sampling of sequences from the evolutionary process and (2) resampling of the original sequence sample. The probability that a bootstrap resampling of an original sequence sample will support the true tree is found to depend on the model tree, the sequence length, and the probability that a randomly chosen nucleotide site is an informative site. When a trifurcating tree is used as the model tree, the probability that one of the three bifurcating trees will appear in > or = 95% of the bootstrap replicates is < 5%, even if the number of bootstrap replicates is only 50; therefore, the probability of accepting an erroneous tree as the true tree is < 5% if that tree appears in > or = 95% of the bootstrap replicates and if more than 50 bootstrap replications are conducted. However, if a particular bifurcating tree is observed in, say, < 75% of the bootstrap replicates, then it cannot be claimed to be better than the trifurcating tree even if > or = 1,000 bootstrap replications are conducted. When a bifurcating tree is used as the model tree, the bootstrap approach tends to overestimate P when the sequences are very short, but it tends to underestimate that probability when the sequences are long. Moreover, simulation results show that, if a tree is accepted as the true tree only if it has appeared in > or = 95% of the bootstrap replicates, then the probability of failing to accept any bifurcating tree can be as large as 58% even when P = 95%, i.e., even when 95% of the samples from the evolutionary process will support the true tree. Thus, if the rate-constancy assumption holds, bootstrapping is a conservative approach for estimating the reliability of an inferred phylogeny for four taxa.


Freeing phylogenies from artifacts of alignment. Widely used methods for phylogenetic inference, both those that require and those that produce alignments, share certain weaknesses. These weaknesses are discussed, and a method that lacks them is introduced. For each pair of sequences in the data set, the method utilizes both insertion-deletion and amino acid replacement information to estimate a pairwise evolutionary distance. It is also possible to allow regional heterogeneity of replacement rates. Because a likelihood framework is adopted, the standard deviation of each pairwise distance can be estimated. The distance matrix and standard error estimates are used to infer a phylogenetic tree. As an example, this method is used on 10 widely diverged sequences of the second largest RNA polymerase subunit. A pseudo-bootstrap technique is devised to assess the validity of the inferred phylogenetic tree.


The effect of unequal transversion rates on the accuracy of evolutionary parsimony. Evolutionary parsimony is an easy-to-use method of phylogenetic inference that is based on nucleic acid sequences and that does not require the assumption that evolutionary processes in the various sites on the molecule are identical. It does, however, require a parameter constraint, known as the "balanced transversion" assumption. We show that the accuracy of the procedure is fairly insensitive to moderate violations of this assumption--and that the procedure thus is applicable under more general conditions than previously thought.


[Pseudoneurotic syndromes in copper mine workers]. In 59 miners of mine front places and 50 workers who performed their work on the places situated outside of mine work places the neurological examination was carried out. The nervous over-excitability syndromes connected with suffering from disturbances of sleep, headache and over-excitement in 62% of mine front places miners and in 28% of the other workers were noted. The probable causes of the nervous over-excitability syndrome occurred in the miners of copper mine were discussed.


[Evaluation of mental functions in workers exposed to metallic mercury, inorganic lead and carbon disulfide]. The aim of the study was to determine the similarities and differences between the groups of dysfunctions detectable using psychologic tests in workers exposed to metallic mercury, inorganic lead and carbon disulfide. The study groups included male workers examined in the Clinic of Occupational Diseases of the Institute of Occupational Medicine in Lodz. The subjects were supposed to the chronically intoxicated with Hg (27 persons), Pb (40 persons) and CS2 (40 persons). A wide variety of tests was used to examine reference groups matched appropriately according to sex, age and level of education. The comparative analysis of results showed that the range and extend of a decrease in psychic functions depend on the type of a neurotoxic agent. The most serious disorders (frequently those of organic brain disease type) were found in subjects exposed to CS2. Exposure to metallic mercury resulted in functional disorders of the psychic sphere, while exposure to inorganic lead caused some minor functional changes. The results of the psychological examination of the subjects may be useful both for individual analysis and for screening.


[Evaluation of the usefulness of enzyme tests for the diagnosis of the effects of various organic solvents in the conditions of occupational exposure]. The aim of the study was to evaluate the suitability of enzymatic tests for estimating the effects of organic solvents upon the organisms of daily exposed workers. The analysis was undertaken in 572 workers exposed to such solvents as toluene, xylene, cresols and benzine. Periodical examination was carried out for the purposes of the study. The level of excreting organic solvents' metabolites in urine and serum enzymes' activity were determined. Also, the activity of alanine and aspartate aminotransferases and of plasmatic cholinesterase was determined. The results of the study support the necessity of applying the enzymatic tests as a basic method of evaluating the toxic activity of organic solvents.


[Exposure to organic solvent vapors during production of lacquers for automobile painting]. This study was aimed at the development and improvement of the methods for determining solvent vapours to estimate occupational exposure in paint and varnish shops. Gas chromatographic method and mass spectrometry (GC-MS) were applied respectively for quantitative determination and identification of toxic substances in the work-room air in plants manufacturing carbamide car paints and commonly used phthalic paints. Particular attention was paid to aromatic hydrocarbon components of farbasol: ethyltoluenes, propylbenzene, isopropylbenzene, mesitylene, hemimelitene, pseudocumene, diethylbenzenes and cymene. These hydrocarbons constitute about 95% of farbasol. At present, the evaluation of exposure in paint and varnish factories and in paint shops in Poland is insufficient because of the lack of TLV values for the above solvents, as well as inadequate methods of determination used in majority of laboratories.


[Bibliographic and documentary activities in the fields of occupational medicine and toxicology]. Great variety of world's medical literature demands elaborating specific bibliographic publications. The authors present a review of world's medical bibliographies with special stress put on occupational medicine and toxicology. The role of indexing languages in the preparation of bibliographies was emphasized. Also, the bibliographic publications edited at the Institute of Occupational Medicine in Lodz were presented. The usefulness of this literature for the specialists in toxicology and occupational medicine was discussed.


[Principles of developing the register of chemical substances in Poland]. The author present the principles for establishing the register of chemical substances in Poland. After considering different world's registers of chemical compound it was observed that the rules of creating this sort of register in the USA are most suitable for the Polish demands. It was suggested that the criterion of classifying a given substance to the register should be the chemical's content 100 kg. For the substances known as cancerogenic this threshold level is going to be 5 kg. Moreover, the principles and a schedule for preparing such a register are specified. One of the most important conditions that must be fulfilled in order to establish the register is applying the relevant legal regulations.


[Etiopathogenetic factors of degenerative diseases of the spine and the effects of exertion and working conditions]. The work was based on literature concerning the etiopathogenesis of spondylosis and on communications estimating the effects of work conditions upon generating or intensification of degenerative disease syndromes. Traumas, micro-traumas, excessive static and dynamic workload are very important etiopathogenetic factors. The most frequently analysed occupational hazards comprise exercise body position at work, type of the movements performed, exposure to vibration. According to most authors, work conditions and ways of performing a given job may be listed among the factors that affect degenerative changes of the spinal cord.


[Asbestos substitutes and their biological action. I. Types, use, exposure and MPEL]. Referring to literature, the authors present problems of exposure to asbestos, its production and MACs in Poland. In our country artificial mineral fibres are produced in seven plants employing about 2000 workers. These plants produce basalt wool, sag wool and glass fibres used in industrial and building insulating materials and in cement and mortar additives and as a free insulating material. Mean concentrations of total dust at the work-posts measured in 1986-1989 ranged between 1.06 mg/m3 and 3.10 mg/m3. Concentrations of respirable fibres ranged from 0.041 fibre/cm3 to 0.173 fibre/cm3. In Poland, the MAC for mineral fibres for total dust amounts to 4 mg/m3 and for respirable mineral fibres to 2 fibres/cm3.


[Reference values of selected parameters of lung functions in the population of Bogdanka coal miners]. The aim of the study was to construct and test new equations for calculating FEV1, ITGV and FVC predictive values. Our examined population consisted of 2058 coal miners working underground in Bogdanka colliery (Lublin Basin). The following persons were excluded from out considerations: 1. smokers, 2. miners with pulmonary or allergic diseases history, 3. patients with chronic cough, sputum production or symptoms of chronic rhinitis, 4. persons with bronchial hyperreactivity. Finally, our standard group consisted of 353 coal miners. On the basis of our standard group data, new equations for calculating predictive values were formulated using the multiple regression model. According to these new equations and to equations elaborated by other authors, we calculated predictive values for FEV1, FVC and ITGV in our standard population and expressed results of measurements in percentages of different predictive values. Our predictive values in the standard population were significantly higher than the other authors' values. Percentages of predicted values were lower in the same comparison. We believe that observed differences are linked to a possible self-selection phenomenon in occupationally exposed population, relatively small maximum age of our standard group, possible differences in anthropometric features among examined populations and excluding hyperreactives. Our results seem to emphasize the need of greater attention to the paid on more restrictive use of the specially formulated equations in separate age compartments.


The molecular basis for positive regulation of cys promoters in Salmonella typhimurium and Escherichia coli. Most genes required for cysteine biosynthesis in Salmonella typhimurium and Escherichia coli are positively regulated by cysB, which encodes a transcriptional activator belonging to the LysR family of regulatory proteins. CysB protein binds just upstream of the -35 region of positively regulated promoters, where in the presence of inducer it facilitates formation of a transcription initiation complex. CysB protein also autoregulates its own synthesis by binding to the cysB promoter as a repressor. Cysteine down-regulates the pathway by inhibiting synthesis of O-acetylserine, a direct cysteine precursor and possibly an inducer of gene expression. O-Acetylserine spontaneously isomerizes to N-acetylserine, which is clearly an inducer. Sulphide and thiosulphate provide additional regulation by acting as anti-inducers. Inducer stimulates CysB protein binding to sites involved in positive regulation, and inhibits binding to the negatively autoregulated cysB promoter. For three sites with unknown function, binding is stimulated at one and inhibited at the other two.


Biological roles of the Escherichia coli RuvA, RuvB and RuvC proteins revealed. In Escherichia coli, the ruvA, ruvB and ruvC gene products are required for genetic recombination and the recombinational repair of DNA damage. New studies suggest that these three proteins function late in recombination and process Holliday junctions made by RecA protein-mediated strand exchange. In vitro, RuvA protein binds a Holliday junction with high affinity and, together with RuvB (an ATPase), promotes ATP-dependent branch migration of the junction leading to the formation of heteroduplex DNA. The third protein, RuvC, which acts independently of RuvA and RuvB, resolves recombination intermediates by specific endonucleolytic cleavage of the Holliday junction.


In vitro phosphorylation of AlgR, a regulator of mucoidy in Pseudomonas aeruginosa, by a histidine protein kinase and effects of small phospho-donor molecules. AlgR is a transcriptional regulator of mucoidy in Pseudomonas aeruginosa, a critical virulence factor expressed in cystic fibrosis. AlgR belongs to the superfamily of bacterial signal transduction systems, and has been shown to bind to the algD promoter, a critical point in the regulation of mucoidy. This protein, like other typical response regulators, contains highly conserved residues known to be critical for the phosphorylation and signal transduction processes. However, a typical second component interacting with AlgR has not been identified. Here we demonstrate that AlgR undergoes phosphorylation in vitro when interacting with the well-characterized histidine protein kinase CheA. These results indicate that AlgR is capable of undergoing phosphorylation typical of other two-component signal transduction systems. Moreover, the phosphotransfer reaction between CheA and AlgR was found to be affected by the presence of carbamoyl phosphate, acetyl phosphate, and salts of phosphoramidic acid, recently shown to act as small-molecular-weight phospho-donors in the process of phosphorylation of several response regulators. These findings suggest that AlgR may react with intermediary metabolites such as carbamoyl phosphate and acetyl phosphate, and that these processes may play a role in the control of mucoidy in P. aeruginosa.


Frameshifting in the expression of the Escherichia coli trpR gene. The trpR gene of Escherichia coli carries an open reading frame that encodes the trp repressor, 108 amino acids long. Here we show that translation of an additional (+1) reading frame of trpR occurs both in vivo and in vitro. This results in the synthesis of a stable +1 frame polypeptide. Using site-specific mutagenesis, immunological techniques and amino acid sequencing we have found that the N-terminus of the +1 frame product and that of the known 0 frame product are identical but that their C-termini differ. Our results are discussed in relation to the role of natural frameshifting as a regulatory mechanism of gene expression in general, and with respect to tryptophan biosynthesis in particular.


Expression of the Opc protein correlates with invasion of epithelial and endothelial cells by Neisseria meningitidis. Whereas capsulate strains of Neisseria meningitidis are dependent on pili for adhesion to human endothelial and epithelial cells, strains which lacked assembled pili and were partially capsule-deficient adhered to and invaded human endothelial and epithelial cells if they expressed the Opc protein. Bacteria expressing low or undetectable levels of Opc protein failed to adhere to or invade eukaryotic cells. In addition, the presence of OpaAC751 protein on the surface of bacteria did not increase bacterial interactions with host cells. Association of Opc-expressing bacteria was inhibited by antibodies against Opc. Invasion was dependent on the host-cell cytoskeletal activity and was inhibited by cytochalasin D. In some cells, infected at the apical surface, bacteria emerging from basal surface were detected by electron microscopy. Opc is found in diverse meningococci and may represent a common virulence factor which facilitates adherence and invasion by these bacteria.


Transcriptional regulation of the redD transcriptional activator gene accounts for growth-phase-dependent production of the antibiotic undecylprodigiosin in Streptomyces coelicolor A3(2). Transcription of redD, the activator gene required for production of the red-pigmented antibiotic undecylprodigiosin by Streptomyces coelicolor A3(2), showed a dramatic increase during the transition from exponential to stationary phase. The increase in redD expression was followed by transcription of redX, a biosynthetic structural gene, and the appearance of the antibiotic in the mycelium, and coincided with the intracellular appearance of ppGpp. However, ppGpp production elicited either by nutritional shift-down of, or addition of serine hydroxamate to, exponentially growing cultures had no stimulatory effect on redD transcription. The presence of redD on a multicopy plasmid resulted in elevated levels of the redD transcript and production of redX and undecylprodigiosin during exponential growth; the normal growth-phase-dependent production of undecylprodigiosin appeared to be mediated entirely through the redD promoter, which shows limited similarity to the consensus sequence for the major class of eubacterial promoters.


Transcriptional control, translation and function of the products of the five open reading frames of the Escherichia coli nir operon. Five open reading frames designated nirB, nirD, nirE, nirC and cysG have been identified from the DNA sequence of the Escherichia coli nir operon. Complementation experiments established that the NirB, NirD and CysG polypeptides are essential and sufficient for NADH-dependent nitrite reductase activity (EC 1.6.6.4). A series of plasmids has been constructed in which each of the open reading frames has been fused in-phase with the beta-galactosidase gene, lacZ. Rates of beta-galactosidase synthesis during growth in different media revealed that nirB, -D, -E and -C are transcribed from the FNR-dependent promoter, p-nirB, located just upstream of the nirB gene: expression is co-ordinately repressed by oxygen and induced during anaerobic growth. Although the nirB, -D and -C open reading frames are translated into protein, no translation of nirE mRNA was detected. The cysG gene product is expressed from both p-nirB and a second, FNR-independent promoter, p-cysG, located within the nirC gene. No NADH-dependent nitrite reductase activity was detected in extracts from bacteria lacking either NirB or NirD, but a mixture of the two was as active as an extract from wild-type bacteria. Reconstitution of enzyme activity in vitro required stoichiometric quantities of NirB and NirD and was rapid and independent of the temperature during mixing. NirD remained associated with NirB during the initial stages of purification of the active enzyme, suggesting that NirD is a second structural subunit of the enzyme.


The glucose kinase gene of Streptomyces coelicolor A3(2): its nucleotide sequence, transcriptional analysis and role in glucose repression. Mutants (glk) of Streptomyces coelicolor A3(2) that are resistant to the non-utilizable glucose analogue 2-deoxyglucose are deficient in glucose kinase activity, defective in glucose repression, and usually unable to utilize glucose. A 2.9 kb BclI fragment, previously shown to restore a wild-type phenotype to a glk deletion mutant that lacks the entire segment, contains two complete open reading frames that would encode proteins of 20.1 kDa (ORF2) and 33.1 kDa (ORF3). ORF3 is transcribed from its own promoter, and also from a promoter that initiates transcription upstream of ORF2. A derivative of the temperate phage phi C31 containing ORF3 alone restored a wild-type phenotype when used to lysogenize the deletion mutant. The product of ORF3 is homologous to members of a family of repressor proteins encoded by xylR in Bacillus subtilis and Lactobacillus pentosus, and by nagC in Escherichia coli. Although this might suggest that ORF3 encodes a positive activator for glucose kinase, rather than the enzyme itself, ORF3 restored the ability to metabolize glucose to an E. coli glk mutant, and activity gels of cell extracts of E. coli containing ORF3 cloned in the pT7-7 expression vector demonstrated that the ORF3 product has glucose kinase activity.


Cloning and genetic characterization of a Helicobacter pylori flagellin gene. Helicobacter pylori produces polar sheathed flagella, which are believed to be essential for the bacterial colonization of the human gastric mucosa. Here we report on the cloning and genetic characterization of a H. pylori gene encoding the subunit of the flagellar filament, the flagellin. Screening of a genomic library of H. pylori with an oligonucleotide probe derived from the N-terminal amino acid sequence of purified flagellin resulted in a recombinant plasmid clone carrying the flagellin-encoding gene flaA on a 9.3 kb Bg/II fragment. The nucleotide sequence of flaA revealed an open reading frame of 1530 nucleotides, encoding a protein with a predicted molecular mass of 53.2 kDa, which is similar in size with the purified flagellin protein in SDS-polyacrylamide gel electrophoresis. Sequence alignment of H. pylori flagellin (FlaA) with other bacterial flagellins demonstrates a high degree of similarity in the amino-terminal and carboxy-terminal regions, including those of the closely related genus Campylobacter (56% overall identity with Campylobacter coli flaA), but little homology in the central domain. Southern hybridizations of chromosomal DNA with flaA-specific probes did not reveal the presence of additional homologous flagellin genes in H. pylori. Sequence analysis of the flaA flanking regions and mapping of the flaA mRNA start site by a primer extension experiment indicated that transcription of the gene is under the control of a sigma 28-specific promoter sequence in H. pylori. The region upstream of the flaA promoter is subject to local DNA modification, resulting in the masking of two out of three closely linked HindIII restriction sites in the chromosome of strain 898-1. Escherichia coli strains harbouring the recombinant plasmid did not produce full-length flagellin and data obtained with FlaA fusion proteins using an E. coli plasmid expression system suggest that a distinct nucleotide sequence in the gene interferes with productive translation of this protein in E. coli.


Cloning of mycobacterial histidine synthesis genes by complementation of a Mycobacterium smegmatis auxotroph. Histidine-requiring auxotrophs of Mycobacterium smegmatis were isolated following N-methyl-N'-nitro-N-nitrosoguanidine treatment. One of these mutants, his5, was transformed with an M. smegmatis shuttle cosmid library, and complementing clones were isolated at a frequency of approximately 1%. A 2.3 kb fragment was subcloned and sequenced, and found to contain the start of an operon including the hisD gene and part of the hisC gene. No hisG gene was detected upstream of hisD, suggesting that the regulation of histidine biosynthesis in mycobacteria may differ from that of Escherichia coli. The strategy used here will allow the molecular genetics of complex mycobacterial-specific biosynthetic pathways involved in the virulence of pathogenic species to be studied.


A multinomial modeling analysis of the mnemonic benefits of bizarre imagery. A series of experiments was conducted to explore the cognitive processes that mediate the bizarreness effect, that is, the finding that bizarre or unusual imagery is recalled better than common imagery. In all experiments, subjects were presented with noun pairs that were embedded within bizarre or common sentences in a mixed-list design. None of the experiments produced a bizarreness effect for cued recall; however, for two of the experiments, the bizarre noun pairs were remembered significantly better than the common pairs for free recall. To determine if these differences were due to the storage or retrieval of the items, a multinomial model for the analysis of imagery mediation in paired-associate learning was developed and applied to the data from the experiments. The model revealed that bizarre sentences benefited the retrieval of the noun pairs but not their storage within memory. The empirical and modeling results are discussed relative to previous findings and theories on the bizarreness effect.


Concreteness effects in free recall: the roles of imaginal and relational processing. Two experiments reevaluated the possible role of mental imagery in free recall of concrete and abstract words. In Experiment 1, the number and rate of list presentations were manipulated. Incidental recall following an imagery rating task yielded reliable concreteness effects after two presentations but not after a single presentation, regardless of presentation rate. In Experiment 2, we examined the effects of relational (categorization) and item-specific (imagery rating) processing tasks on memory for categorically related or unrelated concrete and abstract words. Concreteness effects were obtained when unrelated words were sorted into categories but not when they were rated on imagery. Related words failed to yield concreteness effects under any orienting condition. The results support the view that the presence or absence of concreteness effects in free recall depends on the relative salience of distinctive and relational information. This conclusion constrains theoretical explanations of the role of mental imagery in memory and cognition.


Degree of learning, interpolated tests, and rate of forgetting. The purpose of the two experiments reported here was to observe the effects of degree of learning, interpolated tests, and retention interval, primarily on the rate of forgetting of a list of words, and secondarily on hypermnesia for those words. In the first experiment, all the subjects had one study trial on a list of 20 common words, followed by two tests of recall. Half of the subjects had further study and test trials until they had learned the words to a criterion of three correct consecutive recalls. Two days later, half of the subjects under each learning condition returned for four retention tests, and 16 days later, all the subjects returned for four tests. Experiment 2 was similar, except that all the subjects had at least three study trials followed by four recall tests on Day 1, intermediate tests were given 2 or 7 days later, and they all had final tests 14 days later. The results showed that rate of forgetting was attenuated by an additional intermediate set of tests but not by criterion learning. Hypermnesia was generally found over the tests that were given after a retention interval of 2 or more days. The best predictor of the amount of hypermnesia over a set of tests was the difference between overall cumulative recall and net recall on the first test of the set.


The influence of retrieval on retention. Four experiments tested the hypothesis that successful retrieval of an item from memory affects retention only because the retrieval provides an additional presentation of the target item. Two methods of learning paired associates were compared. In the pure study trial (pure ST condition) method, both items of a pair were presented simultaneously for study. In the test trial/study trial (TTST condition) method, subjects attempted to retrieve the response term during a period in which only the stimulus term was present (and the response term of the pair was presented after a 5-sec delay). Final retention of target items was tested with cued-recall tests. In Experiment 1, there was a reliable advantage in final testing for nonsense-syllable/number pairs in the TTST condition over pairs in the pure ST condition. In Experiment 2, the same result was obtained with Eskimo/English word pairs. This benefit of the TTST condition was not apparently different for final retrieval after 5 min or after 24 h. Experiments 3 and 4 ruled out two artifactual explanations of the TTST advantage observed in the first two experiments. Because performing a memory retrieval (TTST condition) led to better performance than pure study (pure ST condition), the results reject the hypothesis that a successful retrieval is beneficial only to the extent that it provides another study experience.


Sentence encoding and implicitly activated memories. Some words have fewer direct associates than others, and, when words varying in set size are studied in a list-learning task, those with smaller sets are more likely to be recalled. This set-size effect is found in cued recall when the words are studied in the absence of related words, but not when studied in the presence of related words. Related words provide context and theoretically inhibit irrelevant associates. The present research determined that set-size effects are found when words are encoded in sentence contexts. In contrast to list-learning experiments, the results of three experiments found such effects even when lexically related words were present in the sentences. Other findings indicated that target-set-size effects were determined by the proximity of related words in the sentence and the nature of the test cue. The results are discussed in relation to a model for explaining set-size effects and to selective findings from the sentence-comprehension literature.


Supernatural beliefs, natural kinds, and conceptual structure. This article presents cross-cultural evidence in support of the notion that adults' natural kind concepts are theory based but may be informed by knowledge/belief systems other than the biological. Three groups of subjects from western Nigeria--rural, urban, and elite--participated in the study. Subjects heard stories describing alterations of appearance; that is, one natural kind was made to resemble another in both ritual and nonritual contexts. Subjects then were required to judge the identity of the altered item and to give an explanation for the category judgment. It was predicted that subjects would make more nonpreservation-of-identity category judgments supported by supernatural explanations in the ritual contexts and that subjects' use of supernatural explanations would reflect the extent of their engagement with the supernatural. The first prediction was borne out; the second prediction was only partially supported. Discussion of the results emphasizes the importance of exploring the role of sociocultural factors in conceptual structure.


The effects of syntactic structure on letter detection in adjacent function words. In the present study, we examined letter detection in very frequent function-word sequences. It has been claimed that such sequences are processed in a unitized manner, thus preempting access to their constituent letters. In contrast, we showed that letter detection in the words for and the (1) was no more difficult when the words appeared in adjacent locations in a sentence (familiar) than when they appeared apart (less familiar sequence) and (2) was contingent upon the words' syntactic roles within the phrase. Thus, letter detection in for was easier when the sequence was separated by a clause boundary than when the words were part of the same clause. The advantage derived from clause separation was strongest when a comma divided clauses. These results challenge the unitization account of the "missing-letter" effect in common phrases and support a position where this phenomenon is seen to reflect the extraction of phrase structure during reading.


The retrieval of controlled and automatic aspects of meaning on direct and indirect tests. The literature concerning implicit memory presents conflicting evidence on the importance of meaning in recovering recently studied words. When the same cues are used during testing, indirect instructions reduce levels of processing effects relative to those obtained with direct instructions, suggesting that meaning is not as likely to be retrieved on indirect tests. However, with certain cues, meaning set size of the studied words affects performance even under indirect instructions, suggesting that meaning is retrieved on such tests. The purpose of the present experiments was to resolve this apparent inconsistency. In Experiment 1, the effects of levels of processing and meaning set size were evaluated under direct and indirect test instructions, with the use of stem and word-fragment cues. In other experiments, beginning and ending stem cues were compared, and levels, set size, and instructional effects were evaluated using meaning cues. The findings indicated that levels effects were determined more by test instructions than by test cues, and that set size effects were determined more by test cues than by test instructions. Implications are discussed for transfer-appropriate processing viewpoints and for a model in which it is assumed that performance is determined by searching either explicit or implicit memories.


The word-superiority effect and phonological recoding. Previous work indicates that the locus of the word-superiority effect in letter detection is nonvisual and that letter names, but not letter shapes, are more accessible in words than in nonwords, that is, scrambled collections of letters (e.g., Krueger & Shapiro, 1979; Krueger & Stadtlander, 1991; Massaro, 1979). The nonvisual (verbal or lexical) coding may be phonological, or it may be more abstract. In the present study, a word advantage in the speed of letter detection was found even when the target letter was silent in the six-letter test word (e.g., s in island). Other test words varied in their frequency of occurrence in English and number of syllables (1, 2, or 3). The word advantage was larger for higher frequency words but was not affected by syllable length. The presence of unpronounceable nonwords and silent letters in the words discouraged reliance upon the phonological code but did not thereby eliminate the word advantage. Thus, the word-superiority effect with free viewing is not based entirely upon phonological recoding.


Process generalization and the prediction of performance on mental imagery tasks. Kosslyn (1980, 1983) theorized that performance measures on imagery tasks may vary as a function of the existence of independent processes in imaging ability. The present study determined whether improvement can be made in performance on such tasks with practice. It also considered whether performance on such tasks improves with practice and whether this improvement generalizes. Experiment 1 determined whether improvement in a mental rotation task generalizes to improvement in a geometric analogies task, with both tasks weighted in Kosslyn's find process, but not in a line drawing memory task weighted in Kosslyn's regenerate process. In Experiment 2, we examined generalization in improvement from a geometric analogies task to a mental rotation task. In Experiment 3, we tested whether improvement in an animal imagery task (Kosslyn, 1975) generalizes to improvement in a line drawing memory task, with both tasks weighted in Kosslyn's regenerate process, but not to improvement in a mental rotation task. Performance improved with practice on all tasks. Furthermore, performance improved from one task to another only if both tasks loaded on the same process.


Age of acquisition, not word frequency, affects object naming, not object recognition. Word frequency is widely believed to affect object naming speed, despite several studies in which it has been reported that frequency effects may be redundant upon age of acquisition. We report, first, a reanalysis of data from the study by Oldfield and Wingfield (1965), which is standardly cited as evidence for a word frequency effect in object naming; then we report two new experiments. The reanalysis of Oldfield and Wingfield shows that age of acquisition is the major determinant of naming speed, and that frequency plays no independent role when its correlation with other variables is taken into account. In Experiment 1, age of acquisition and phoneme length proved to be the primary determinants of object naming speed. Frequency, prototypicality, and imageability had no independent effect. In Experiment 2, subjects classified objects into two semantic categories (natural or man-made). Prototypicality and semantic category were the only variables to have a significant effect on reaction time, with no effect of age of acquisition, frequency, imageability, or word length. We conclude that age of acquisition, not word frequency, affects the retrieval and/or execution of object names, not the process of object recognition. The locus of this effect is discussed, along with the possibility that words learned in early childhood may be more resistant to the effects of brain injury in at least some adult aphasics than words learned somewhat later.


The tip-of-the-tongue phenomenon: blocking or partial activation? Tip-of-the-tongue states may represent the momentary unavailability of an otherwise accessible word or the weak activation of an otherwise inaccessible word. In three experiments designed to address these alternative views, subjects attempted to retrieve rare target words from their definitions. The definitions were followed by cues that were related to the targets in sound, by cues that were related in meaning, and by cues that were not related to the targets. Experiment 1 found that compared with unrelated cues, related cue words that were presented immediately after target definitions helped rather than hindered lexical retrieval, and that sound cues were more effective retrieval aids than meaning cues. Experiment 2 replicated these results when cues were presented after an initial target-retrieval attempt. These findings reverse a previous one (Jones, 1989) that was reproduced in Experiment 3 and shown to stem from a small group of unusually difficult target definitions.