Protective effect of ascorbic acid on the breakdown of proteins exposed to hydrogen peroxide in chicken skeletal muscle. Ascorbic acid is believed to protect cells from oxidative damage by reacting with oxygen-derived free radicals. We investigated whether ascorbic acid would affect the rate of breakdown of skeletal muscle proteins in extracts exposed to hydrogen peroxide. Ascorbic acid (20 mmol/L) alone had little or no effect on the rate of ATP-independent or ATP-dependent breakdown of proteins in chicken skeletal muscle. Pretreatment of chicken skeletal muscle extracts with 10 mmol/L H2O2 resulted in a complete loss of ATP-dependent proteolysis and a significant increase (14- to 15-fold) in the rate of ATP-independent protein breakdown. Ascorbic acid (20 mmol/L) did not prevent H2O2 (10 mmol/L) from inactivating the ATP-dependent proteolytic pathway in skeletal muscle. However, ascorbic acid (20 mmol/L) prevented the H2O2-induced increase in the ATP-independent proteolysis of endogenous muscle proteins. Ascorbic acid also slowed the rate of hydrolysis of exogenously added [3H]superoxide dismutase exposed to H2O2 and inhibited the enhanced degradation of [3H]lysozyme and H2O2-treated [3H]superoxide dismutase by the proteolytic systems exposed to H2O2. Thus ascorbic acid seems to inhibit the H2O2-induced increase in ATP-independent proteolysis 1) by preventing damage to proteins by H2O2 resulting in a decreased supply of substrates for the ATP-independent degradative system and 2) by preventing activation of the proteolytic enzymes that participate in the energy-independent degradation of H2O2-treated proteins.


Rat hepatic coenzyme A is redistributed in response to mitochondrial acyl-coenzyme A accumulation. Coenzyme A without an acyl-thioester (CoASH) is required for numerous cellular reactions, and sequestration of CoASH as acyl-CoAs may impair metabolic function. Increased total CoA protects the cell from acyl-CoA accumulation, and enhanced CoA biosynthesis may represent a compensatory response in metabolic disease. To test the hypothesis that cellular CoA is redistributed from the cytosol to the mitochondria in response to mitochondrial acyl-CoA accretion, the subcellular distribution of hepatic CoA was determined by differential centrifugation and measurement of the mitochondrial marker enzyme citrate synthase. Liver from control, clofibrate-treated and hydroxycobalamin[c-lactam] (HCCL)-treated rats were used. Clofibrate increased total hepatic CoA concentration 2.2-fold, whereas HCCL (which causes inhibition of L-methylmalonyl-CoA mutase and consequent propionyl- and methylmalonyl-CoA accumulation) increased it threefold. However, clofibrate did not affect the percentage of total CoA in the mitochondria (control: 44 +/- 3%, clofibrate: 49 +/- 5%), and HCCL-treatment induced a marked redistribution of CoA into the mitochondria (HCCL: 78 +/- 8%). Redistribution of total CoA was also induced acutely by incubation of hepatocytes from control rats with 10 mmol/L propionate. Thus, redistribution of the cellular CoA pool can help maintain CoASH availability as mitochondrial acyl-CoA accumulation occurs and may be an important compensatory response to metabolic injury.


Copper-marginal and copper-deficient diets decrease aortic prostacyclin production and copper-dependent superoxide dismutase activity, and increase aortic lipid peroxidation in rats. Agonist challenged aortic prostacyclin production was examined in copper-adequate, -marginal and -deficient rats fed AIN-based diets providing 6.7, 1.7 and 0.8 micrograms Cu/g, respectively. Aortic rings were incubated in Krebs-Henseleit salts, 10 mmol/L HEPES buffer, pH 7.4, 95%:5% O2:CO2, 37 degrees C, and equilibrated for 1 h. Equilibrated rings were challenged with buffer (basal), 273.0 nmol/L thrombin and angiotensin II at 84.6 pmol/L and 846.0 pmol/L. Prostacyclin production, determined at 10 minutes by RIA as 6-keto prostaglandin F1 alpha, in basal and 84.6 pmol/L angiotensin II ring incubations was significantly reduced by 28 to 48% in copper-deficient rats. With thrombin or 846.0 pmol/L angiotensin II prostacyclin production was significantly reduced by 18 to 55% in copper-marginal and copper-deficient rats. Copper-dependent superoxide dismutase activity was significantly depressed by 30 and 57% in aortae of copper-marginal and copper-deficient rats. Lipid peroxidation, estimated by the thiobarbituric acid test, was significantly increased by 85% in copper-deficient rats, with a nonsignificant 40% increase in aortae from copper-marginal rats. The results suggest that the decreases in aortic prostacyclin production in aortae from both copper-deficient and copper-marginal rats are associated, in a dose-dependent manner, with copper-dependent superoxide dismutase depression and increases in aortic lipid peroxidation.


Plasma esterase-1 (ES-1) activity in rats is influenced by the amount and type of dietary fat, and butyryl cholinesterase activity by the type of dietary fat. In previous work, we studied, under conditions of ad libitum food consumption, the effect of amount and type of dietary fat on plasma esterase-1 (ES-1) and butyryl cholinesterase activity in rats. This was done by the isoenergetic replacement of dietary fat by carbohydrates or by another fat source. The observed change in enzyme activity could theoretically be determined by either the dietary omission or the addition or by the combination. In the present work, we studied under restricted feeding conditions the effect of supplemental energy in various forms to determine the effect of the supplement alone. Supplemental coconut fat, but not isoenergetic amounts of either glucose or casein, raised plasma ES-1 activity. None of these supplements influenced butyryl cholinesterase activity. In a second experiment, we demonstrated that the ES-1 enhancing effect of supplemental coconut fat also occurred with fish oil, whereas the stimulatory effects of olive oil and corn oil were less pronounced. Supplemental fish oil, but not the three other fats, significantly reduced the depression in butyryl cholinesterase activity. Plasma cholesterol concentration was negatively associated with butyryl cholinesterase activity, but was not related to ES-1 activity. The two esterases were not correlated with plasma triglyceride concentration. We conclude that both the amount and type of fat in the diet of rats have specific influences on plasma ES-1 activity and that butyryl cholinesterase activity is affected by the type of fat.


Copper and selenium deficiencies do not enhance the cardiotoxicity in rats due to chronic doxorubicin treatment. This study tests the hypothesis that Cu and Se deficiencies enhance doxorubicin-induced cardiotoxicity and anemia. Male Sprague-Dawley rats (n = 48) were fed Cu and Se-adequate (+Cu+Se), Cu-deficient (-Cu), Se-deficient (-Se) or Cu and Se-deficient (-Cu-Se) diets for 5.5 wk. Doxorubicin (4 mg/kg body wt) or saline was administered once weekly for the last 4 wk of the study. Copper deficiency was confirmed by 79% lower liver Cu, 67% lower liver Cu,Zn superoxide dismutase (Cu,Zn SOD) activity and 76% lower erythrocyte Cu,Zn SOD activity. Selenium deficiency was confirmed by 90% lower liver glutathione peroxidase activity. Rats fed the -Cu diet had greater reductions in hematocrit than did those fed the +Cu diet after administration of doxorubicin. Doxorubicin, Cu deficiency and Se deficiency all produced electrocardiographic abnormalities and ultrastructural anatomical lesions. However, the dietary deficiencies did not enhance doxorubicin-induced cardiotoxicity. Doxorubicin, but not Cu or Se deficiency, raised lipid peroxidation 16% in liver (P < 0.01) and 18% in heart (not significant). These data suggest that the cardiomyopathies caused by doxorubicin and Cu and Se deficiencies have some similarities, but cardiac changes may be related to mechanisms other than lipid peroxidation.


Modified eggs are compatible with a diet that reduces serum cholesterol concentrations in humans. The National Cholesterol Education Program (NCEP) guidelines recommend dietary restriction of fat and cholesterol to reduce high circulating cholesterol concentrations in adult Americans. Thus, diet counselors recommend consumption of fewer than four egg yolks per week. The present protocol was designed to determine whether the efficacy of an NCEP diet would be reduced by the incorporation of 12 modified eggs per week, and whether the resulting low fat, high cholesterol diet would increase serum lipid concentrations in adults with initial undesirably high (5.17-7.76 mmol/L) concentrations of serum total cholesterol. Feeding a controlled ration to laying hens produced modified eggs that consistently contained more vitamin E and iodine, and more unsaturated fat, than generic eggs. Subjects were randomly assigned to and NCEP diet including either no whole eggs or 12 whole study eggs a week. Ninety-eight subjects completed the parallel study. Subjects in both groups significantly reduced their serum total, LDL and HDL cholesterol (P < 0.001 for total and LDL cholesterol, P < 0.02 for HDL cholesterol) over the 6 wk of study. No significant differences were found between diet groups. We conclude that the study eggs did not adversely affect measured lipid concentrations when added to a low fat diet that favorably alters lipid profiles in hypercholesterolemic subjects.


Uptake of lycopene and its geometrical isomers is greater from heat-processed than from unprocessed tomato juice in humans. Lycopene and beta-carotene are the most abundant carotenoids in human blood and tissues. Although lacking provitamin A activity, lycopene may be biologically active by contributing to the antioxidative defense system of the organism. We studied the uptake of lycopene from processed (boiled with 1% corn oil for 1 h) and unprocessed tomato juice in humans. Lycopene concentrations in human serum increased only when processed tomato juice was consumed. Lycopene uptake varied with individuals, but peak serum concentrations were always reached between 24 and 48 h. The carotenoid was eliminated from serum with a half-life of 2-3 d. The increase in peak serum concentrations was dose-dependent but not linear with the dose. Repeated doses led to a continual rise of lycopene in human serum. Of the different geometrical isomers (all-trans, 9-cis and 13-cis), the cis isomers seemed to be somewhat better absorbed than the all-trans form.


Contribution of skin to whole-body protein synthesis in rats at different stages of maturity. This study assessed whole-body and tissue protein metabolism and the contribution of skin to whole-body protein synthesis during the post-weaning development of rats. Protein fractional synthesis rate was measured in muscle, skin and the whole body of 70-, 160-, 315- and 586-g rats by use of a continuous infusion of L-[U-14C]lysine. Rates of protein synthesis were then calculated, based on the tissue free and protein-bound lysine specific radioactivity at the end of the infusion. The fractional protein synthesis rate declined progressively in the skin (from 19.6 to 8.0%/d), in muscle (from 18.9 to 4.8%/d) and in whole body (from 25.0 to 8.5%/d) throughout post-weaning development. Absolute synthesis rates [g/(d.100 g body wt)] of whole-body and muscle proteins decreased by 54 and 50%, respectively. On the other hand, the amount of skin protein synthesized per 100 g body wt was 35% greater in 160-g and 315-g rats than in 70-g and 586-g rats. The absolute synthesis rate of muscle proteins as a percentage of whole-body protein synthesis remained fairly constant at a value close to 24%, whereas the skin contribution to whole-body protein synthesis increased from 12% in 70-g rats to 26% in 586-g rats.


Comparison of measured carbon dioxide production with that obtained by the isotope dilution technique in neonatal pigs: observations on site of infusion. Fifteen newborn pigs (1.5 kg) were used to estimate CO2 "production" over a 5-h experiment. In each piglet, the average expired air CO2 irreversible loss rate measured over 15-min intervals was compared with an estimate of CO2 "produced" by a continuous infusion of NaH14CO3 into either the aortic artery (seven pigs) or the portal vein (eight pigs). The specific radioactivity (Bq/mumol) of the expired CO2 taken over consecutive 15-min intervals during the 5-h period was fitted to an exponential model to predict the specific radioactivity at steady state. This specific radioactivity was used to calculate the total CO2 irreversible loss rate and to correct for the difference in tracer infused in relation to tracer excreted at 5 h (76 to 78%). The estimated CO2 "produced" tended to be higher (P < 0.12) when the aortal rather than the portal infusion site was used [571 vs. 498 mumol/(min.kg0.75)]. The isotope dilution technique significantly (P < 0.05) overestimated the expired air CO2 regardless of whether the aortal [571 vs. 469 mumol/(min.kg0.75)] or portal [498 vs. 447 mumol/(min.kg0.75)] routes of infusion were used.


Evaluation of [1-14C]-medium-chain fatty acid oxidation by neonatal piglets using continuous-infusion radiotracer kinetic methodology. In vivo oxidation rates of systemically infused medium-chain fatty acids were evaluated using neonatal pigs. Unanesthetized piglets (1.6 kg, n = 20) were housed in respiration chambers for total collection of expired CO2 and were continuously infused with [1-14C]-7:0, 8:0, 9:0 or 10:0 fatty acids via a central catheter. The fatty acids were administered at rates of 25, 50 or 100 mumol/min for 5 h and provided 74 kBq of 14C per h. Total expired CO2 was collected over consecutive 15-min intervals for determination of the amount and specific radioactivity of expired CO2. Portal blood samples were drawn from umbilical vein catheters for determination of 3-hydroxy-butyrate and plasma fatty acid concentrations. Infusion and oxidation rates (mmol/min) were multiplied by the molar ATP yield for each fatty acid (i.e., 52, 61, 69 and 78 mmol ATP/mmol fatty acid for 7:0 through 10:0, respectively) to adjust for differences in molar energy content of the various fatty acids. Expressed in this way, fatty acid oxidation rate was proportional to the rate of infusion and accounted for 63% of that infused. The various fatty acids were oxidized equally well, regardless of chain length, and satisfied up to 60 to 70% of the animals' energy requirements, depending on the rate of infusion. These data are discussed in relation to previous work from our laboratory that has shown significant effects of fatty acid chain length on utilization of orally administered medium-chain triglyceride supplements.


Lipid peroxidation products are elevated in fish oil diets even in the presence of added antioxidants. Purified corn and fish oil diets with different types and concentrations of antioxidants were evaluated for oxidation products. In addition, a determination of different organ and carcass oxidation product levels was performed. Peroxide value and thiobarbituric acid assays were performed on the diets immediately after mixing (0 h) and 24, 48 and 72 h after being fed to mice. The AIN-recommended level of antioxidant addition (butylated hydroxytoluene, 0.02 g/100 g oil) and even the addition of 100 times this level (2 g/100 g oil), although decreasing the level of oxidation products, failed to totally prevent oxidative deterioration in diets high in fish oil. Furthermore, other antioxidants added in excess to the fish oil diets also failed to completely suppress oxidative deterioration of the diets and, in addition, when fed daily to mice for a period of 4 wk, caused an accumulation of lipid peroxidation products in certain organs (e.g., heart, skeletal muscle, mammary glands) and in the carcass. These results provide evidence that in the preparation of fish oil diets, the addition of antioxidants at the AIN-recommended level, or even levels substantially higher, does not completely suppress oxidative deterioration of experimental diets.


Dietary sucrose enhances insulin secretion of aging Fischer 344 rats. Male Fischer 344 rats, ages 6, 12 and 26 mo, were fed a diet containing either sucrose or cornstarch (66% by weight) for 4 mo. The effects of age and dietary sucrose on glucose-stimulated insulin secretion were evaluated in whole perfused pancreases and isolated islets of Langerhans, and by intra-arterial glucose administration. In addition, glucose responsiveness of beta-cells was measured by following the rate of glucose oxidation in isolated islets. There was no significant effect of age on glucose-stimulated insulin secretion of whole perfused pancreases and islets of Langerhans. There was, however, a significant main effect of sucrose feeding on insulin secretion. That is, whole perfused pancreases and islets of Langerhans isolated from rats fed sucrose vs. starch diets secreted more insulin in response to glucose. This effect was most pronounced in the 26-mo-old rats. In general, islet glucose oxidation rates, and responses to the in vivo glucose, did not differ among the groups. We conclude that alterations in glucose-stimulated insulin secretion with age more closely reflect changes in diet rather than aging per se.


Uptake of 5-formyltetrahydrofolate in isolated rat liver mitochondria is carrier-mediated. We have characterized the uptake of 5-formyltetrahydrofolate into isolated rat liver mitochondria. Uptake of 5-formyltetrahydrofolate, 5-methyltetrahydrofolate and folic acid was linear for the first 2 min of incubation. 5-Methyltetrahydrofolate and 5-formyltetrahydrofolate were accumulated in mitochondria to 3.7- and 4.3-fold, respectively. 5-Formyltetrahydrofolate transport showed a pH optimum at 5.5 and was saturable with an apparent Km = 2.80 mumol.L-1 and Vmax = 3.49 pmol.min-1.mg protein-1. Uptake of 5-formyltetrahydrofolate was inhibited by the structural analog 5-methyltetrahydrofolate and, to a much lesser extent, folic acid and methotrexate. Uptake was not inhibited by various substrates of known mitochondrial transporters, e.g., succinate, malate, citrate, glutamate and phosphate, nor was uptake inhibited by the sulfhydryl reagent, N-ethylmaleimide. Uptake was not stimulated by preloading of mitochondria with malate or aspartate. Uptake of 5-formyltetrahydrofolate was not affected by the proton ionophore carbonyl cyanide 4-trifluoromethoxyphenyl-hydrazone nor by collapsing the electrical gradient with valinomycin. These results indicate that 5-formyltetrahydrofolate uptake into mitochondria via a carrier-mediated system specific for the reduced, naturally occurring folates. The folates, once in the mitochondria, may be converted to the polyglutamylated forms, which will not readily diffuse out of the mitochondria.


Increasing intake of soybean protein or casein, but not cod meal, reduces nephrocalcinosis in female rats. Female weanling rats were fed diets with soybean protein, casein or cod meal at 171, 342 or 513 mmol nitrogen/100 g for 3 wk. The diets were isonitrogenous and balanced for fat, cholesterol, calcium, magnesium and phosphorus. Cod meal feeding at 171 and 342 mmol nitrogen/100 g diet produced lower kidney calcium concentrations than the feeding of either soybean protein or casein. Increasing protein intakes were associated with reduced kidney calcium concentrations in the rats fed either soybean protein or casein but not in those fed cod meal. The anti-nephrocalcinogenic effect of increasing intakes of soybean protein may relate to the lowering of urinary phosphorus concentration. Increasing intakes of casein probably inhibited nephrocalcinogenesis by lowering urinary pH and raising urinary magnesium concentration. Increasing cod meal concentrations in the diet lowered urinary pH and raised urinary magnesium and calcium concentrations, but the effects on nephrocalcinogenesis of these changes probably counteracted each other.


Endogenous allantoin excretion in response to changes in protein supply in sheep. Endogenous allantoin derives from the breakdown of tissue nucleic acids. This study examined the effect of changes in protein supply on endogenous allantoin excretion by sheep. The animals were nourished by infusions of volatile fatty acids into the rumen and casein into the abomasum, thus avoiding ruminal microbial fermentation (i.e., no supply of exogenous nucleic acids). While a constant energy supply was maintained, the protein supply was altered in one of two ways: 1) changed from 0 to 3000 mg casein-N/kg metabolic weight (W0.75) per day in progressive steps; or 2) completely removed from an initial constant level [500 mg N/(kg W0.75.d)]. With the first alteration, endogenous allantoin excretion was not directly affected by the daily N input or N retention, but was linearly correlated with the cumulative N retention. With the second alteration, allantoin excretion increased (35-145%) on the first day after removal of the protein supply and then fell to a level equivalent to, or lower than, that before protein removal. The results suggest that the changes in endogenous allantoin excretion may reflect remodeling of the metabolic state of the animal during periods when protein supply fluctuates.


Altered zinc metabolism occurs in murine lethal milk syndrome. The lethal milk (lm) mutation in mice causes Zn deficiency in pups nursed by lm dams. To examine tissue Zn distribution and Zn transport to milk and pups, 65Zn was administered to lactating normal and lm dams. Transport of 65Zn to milk of lm dams was approximately 50% of that transported to milk of normal dams. The lower milk 65Zn resulted in significantly less 65Zn uptake by tissues of the nursing pups. The decrease in 65Zn transport to the milk was accompanied by a significant increase in 65Zn uptake and metallothionein mRNA levels in kidney of the lm dams. The elevated Zn uptake and metallothionein expression was tissue specific and could be a reflection of altered zinc transport from mammary gland to milk. Polyacrylamide gel electrophoresis and Western transfer of mammary gland proteins from lm dams showed that a 30-kDa protein bound more 65Zn in vitro compared with proteins from normal mammary gland. Normal pups nursed by dams of the lm genotype had down-regulated metallothionein expression due to Zn deficiency. The genetic defect in lm mice decreases Zn transport to milk, thus explaining the neonatal Zn deficiency seen in normal mice fostered by lm dams. The greater metallothionein expression in dams of the lm genotype could be a secondary manifestation of altered tissue zinc distribution or a primary effect on a metallothionein regulatory mechanism.


Dietary casein and soybean protein affect the concentrations of serum cholesterol, triglyceride and free amino acids in rats. This work was undertaken to investigate the concentrations of free amino acids in blood after food was withheld from growing, male Wistar rats fed cholesterol-free, low fat (1 g corn oil/100 g) diets with casein or soybean protein for 2 wk. A diet containing 22.5 or 23.5 g/100 g of soybean protein was hypocholesterolemic compared with a diet containing 20.0 g casein/100 g diet. A comparison of serum amino acids in soybean protein-fed vs. casein-fed rats showed that, whereas concentrations of many amino acids were lower in the soybean protein-fed rats compared with the casein-fed groups, glycine was the only amino acid having a higher concentration. Further, alanine was significantly lower in the soybean protein-fed rats compared with the casein-fed rats, and the protein-induced differences in glycine and alanine concentrations of unfed rats were reproducible. When diets containing 15.0% casein or 30.0% soybean protein, a casein diet supplemented with glycine and a soybean protein diet supplemented with methionine were compared, the changes in serum glycine and alanine correlated with the changes in serum cholesterol. Concentrations of several amino acids, particularly valine, leucine and tyrosine, also changed when serum cholesterol concentrations varied, but these effects could not be explained by our experiments. The results suggest that a change in serum concentration of glycine and alanine of unfed rats may be related to the change in serum cholesterol concentration.


Fat intake and clofibrate administration have interrelated effects on liver cholesterol concentration and serum butyryl cholinesterase activity in rats. Rats were fed for 15 d purified diets with different amounts of coconut fat, and with or without clofibrate. Fat was added at the expense of an isoenergetic amount of glucose. The hypolipidemic action of clofibrate was not influenced by the amount of fat in the diet. Clofibrate did not affect liver cholesterol concentration in rats fed the low fat diet, but it counteracted the rise in liver cholesterol seen in rats fed the high fat diet. This could relate to the observed raised intestinal clofibrate-hydrolyzing activity of rats fed the high fat diet, because hydrolysis of clofibrate gives rise to its biologically active form. In rats fed the low fat diet, but not in those fed the high fat diet, clofibrate raised the activity of serum esterase-1, which (unlike esterase-2) does not hydrolyze clofibrate. Possibly, the dramatic stimulatory effect of fat feeding on serum esterase-1 activity had overruled any influence of clofibrate. Clofibrate elevated serum butyryl cholinesterase activity, with this effect being amplified by fat feeding. High levels of dietary fat in the absence of dietary clofibrate did not alter serum butyryl cholinesterase activity. Clofibrate did not change butyryl cholinesterase and esterase-1 activities in small intestine. The high fat diet caused slightly higher levels of butyryl cholinesterase activity in small intestine, but markedly raised intestinal esterase-1 activity. This study shows that certain effects of clofibrate and a high fat diet are interrelated.


Structure of dietary pectin, iron bioavailability and hemoglobin repletion in anemic rats. The effects of the degree of esterification (DE) and the molecular weight (MW) of pectins on iron bioavailability were investigated in anemic rats. The pectins prepared differed (in DE and MW, respectively) as follows: P-A (73%, 860,000), P-B (75%, 89,000), P-C (22%, 1,260,000) and P-D (24%, 114,000). Rats were fed an iron-deficient diet (8 mg Fe/kg diet) for 14 d. The anemic rats were then fed a ferrous sulfate-supplemented basal diet (47 mg Fe/kg diet) or the basal diet containing one of the pectins (80 g/kg diet) for 10 d. None of the pectins used caused any significant reduction in the bioavailability of ferrous sulfate. Addition of pectin P-B to the diet resulted in significantly greater iron repletion. Compared with control rats fed with ad libitum access or pair-fed, rats fed P-B showed higher (P < 0.05) hemoglobin regeneration efficiency, hematocrit, serum iron concentration, and transferrin saturation, and lower unsaturated iron-binding capacity and total iron-binding capacity. Pectins P-A and P-D also slightly improved the hematological indices compared with P-C and control. The observed effects were dependent on the physicochemical properties of each pectin as determined by its MW and DE.


A longitudinal study of nurses' attitudes toward caring for patients with AIDS in Erie County. The purpose of this study was to examine nurses' attitudes toward caring for patients with AIDS in a longitudinal context. Results of the 1990 survey were compared with those of a survey conducted in 1986 for the purpose of examining changes in attitudes over time. Findings indicated that there were no significant differences between the 1986 and 1990 scores on the attitude scales. The results of the study indicated that many nurses still have fears and concerns about caring for patients with AIDS.


American nursing: 100 years of conflicting ideas and ideals. Based on historical research about nursing sponsors, actors, activities, preparation, and location of work, this paper identifies divisive themes that have recurred in American nursing throughout its history. The conflictive areas discussed are: ideals, gender, the search for status and the use of exclusion, the merger of training and practice, and the differences between ordinary nurses and nursing leaders.


What is nursing research: evolving approaches to methods and content. In addressing what constitutes nursing research in the 1990s, approaches to conducting nursing research and examples of studies are discussed in the context of historical forces. The early studies were characteristically educational in focus and quantitative by design. Nursing research has come a long way in regard to foci of the questions asked, diversity of approaches to knowledge development, and sophistication of research methods. Three approaches are described to illustrate the diversity in nursing research: quantitative, qualitative, and triangulation.


Perinatal outcome for women in prison.

Perinatal outcome for women in prison. Pregnancy outcome for 233 women in prison was reviewed. This group of patients presented with multiple perinatal high-risk factors: history of illicit drug use (71%), smoking (70%), and obstetrical (27%), medical (21%), nutritional (20%), and infectious complications (20%). Maternal morbidity was uncommon and the overall cesarean section rate for all prisoners was 16%. There was 1 stillbirth and 236 live-born infants, all of whom were discharged in good health. Prematurity (3%) and delivery of small-for-gestational-age (SGA) (8%) infants was less common among 187 women who received adequate prenatal care than in 46 prisoners with poor or late prenatal care (prematurity 20% and SGA 28%). Good perinatal outcome for women in prison can be achieved if comprehensive prenatal care is available.


Thromboxane synthetase inhibition produces maternal and fetal vasodilation during ovine pregnancy-induced hypertension: a Doppler flow velocimetric study. Changes in maternal and fetal umbilical arterial vasoreactivity during ovine pregnancy-induced hypertension and following intravenous administration of CGS 12970 [3-methyl-2-(3-pyridyl)-1-indoleoctanoic acid] were assessed. Continuous wave Doppler flow velocimetry was used to assess vascular reactivity during normotensive baseline, during ovine pregnancy-induced hypertension triggered by a 72-hour fast, and following thromboxane synthetase inhibition with CGS 12970. Uterine and umbilical arterial systolic/diastolic flow ratios increased significantly with the onset of sustained hypertension. After thromboxane synthetase inhibition, uterine and umbilical artery systolic/diastolic flow ratios were not different from baseline, and maternal blood pressure had returned to baseline values. These data indicate that thromboxane produces maternal and fetal vasoconstriction during ovine pregnancy-induced hypertension. Furthermore, these data provide strong evidence that thromboxane synthetase inhibition allows vasodilation, resulting in improved maternal and fetal condition.


Is cord blood erythropoietin a marker of intrapartum hypoxia? A sensitive assay was used to compare the biological activity of cord serum erythropoietin in two groups of infants born with or without labor-induced hypoxia. The mean cord serum erythropoietin activity in 161 infants delivered after vaginal labor was 116 +/- 36 mU/mL, and was indistinguishable from that observed in 23 infants delivered by preplanned, elective cesarean section, 114 +/- 12 mU/mL (P = .75). The bioassay measured effective erythropoietin activity, including the contribution of potentiators in serum. These results indicate that duration and intensity of labor are insufficient to cause a significant increase in effective erythropoietin activity.


Perinatal toxicology screening.

Perinatal toxicology screening. Accurate identification of substance abusing mothers and their infants is critical for appropriate medical management as well as the collection of accurate information on the effects of illicit drug use on perinatal morbidity, mortality, and long-term neurobehavioral outcome in the infants. This study examines the differences found using two methods for urine toxicology screening at the time of obstetrical admission to the hospital. The institution of universal screening identified significantly more women than were previously identified through the use of a risk-directed protocol (P less than .0001). Women identified using either protocol were significantly more likely than toxicology-negative women to have had poor prenatal care and to have smoked and used alcohol during pregnancy (P less than .001). In the population studied, the multiple criteria needed to accurately identify mothers with positive-toxicology screens would also include screening over one half of the toxicology-negative mothers.


Congenital complete heart block associated with maternal anti-Ro antibody: a case report. The presence of anti-Ro antibody in maternal serum is a serologic marker for increased risk of the development of congenital complete heart block in the fetus. Current etiology and evaluation of these mothers and their fetuses are examined. A case report is presented.


Sudden fetal death in women with well-controlled, intensively monitored gestational diabetes. An intensive antepartum monitoring system for women with gestational diabetes mellitus was evaluated over a 5-year period. Early diagnosis and liberal treatment with insulin was concomitantly followed with non-stress testing: weekly from 28 to 34 weeks' gestation and semi-weekly thereafter. Despite maternal euglycemia and satisfactory antepartum assessment, three fetal deaths occurred within 72 hours of reassuring fetal monitoring. Additionally, 24 (7%) fetuses were delivered on the basis of a low biophysical profile score (less than 6) at term. The stillbirth rate for women with gestational diabetes was 7.7/1000, whereas the stillbirth rate for nondiabetic low-risk patients was 4.8/1000. Women with gestational diabetes continue to be in a high-risk category for antepartum fetal death, requiring intensive monitoring with consideration for timely delivery.


Transient hyperammonemia of the newborn: a vascular complication of prematurity? Transient hyperammonemia of the newborn is an overwhelming disease manifested by hyperammonemic coma in ill premature infants. A summary of evidence is presented supporting the hypothesis that this syndrome is a vascular complication caused by shunting of blood away from the portal circulation of the liver into the systemic circulation with subsequent lack of ammonia removal. Alternative, nontraditional approaches of investigation and therapy targeting the hepatic portal circulation should be explored in patients with transient hyperammonemia of the newborn.


Waxing and waning hyperinflation in congenital cystic adenomatoid malformation of the lung. This report describes a newborn with respiratory distress, waxing and waning left lung hyperinflation, and pulmonary hemorrhage. This atypical presentation of congenital cystic adenomatoid malformation of the lung has not been previously reported, posed a major diagnostic problem, and delayed potentially lifesaving surgery.


Limitations in the usefulness of urine latex particle agglutination tests and hematologic measurements in diagnosing neonatal sepsis during the first week of life. We present findings regarding the usefulness of urine latex particle agglutination (LPA) testing for group B streptococcus (GBS) antigen, as well as hematologic values, in diagnosing sepsis during the 1st week of life. Of 475 inborn neonates evaluated, 27 (5.7%) had confirmed sepsis, 47 (9.9%) had indeterminate findings precluding further classification, and 401 (84.4%) were not septic. We examined the following: (1) total white blood cell count (WBC); (2) total polymorphonuclear leukocytes (PMNs); (3) total immature PMNs; (4) immature to total (I:T) neutrophil ratio; (5) immature to mature (I:M) neutrophil ratio; (6) platelet count; (7) a 6-point hematologic score based on the preceding values; and (8) urine LPA for GBS. The positive predictive values of the six hematologic values, as well as the hematologic score, were disappointingly low. Using higher I:T ratios (greater than or equal to 0.30 or 0.40) marginally increased the positive predictive values. More than 60% of our ill, nonseptic neonates had I:T ratios greater than or equal to 0.20. Of 15 infants with culture-proven systemic (blood or cerebrospinal fluid) GBS infection who were tested with urine LPA for GBS antigen, only 4 had positive results. Nineteen infants had positive urine LPAs with concomitant negative blood cultures. Urine cultures were obtained from 18 of these infants. No organisms were isolated from any of these specimens. The mothers of 7 of the infants with positive LPAs and negative blood cultures had received intrapartum antibiotics. Of the remaining 12 infants, the urine LPA was repeated in 8 and results were negative in each case.(ABSTRACT TRUNCATED AT 250 WORDS)


Effects of dexamethasone on pulmonary function following extubation. Dexamethasone is often given to intubated neonates to facilitate successful extubation. To study the effects of dexamethasone on pulmonary function immediately following extubation, we conducted a randomized, blinded, placebo-controlled trial in 51 infants. All infants had been intubated for a minimum of 3 days but no more than 30 days. Mean weight at extubation was 2.41 kg in treated infants, 2.25 kg in control infants. When infants were deemed ready for extubation, dexamethasone 0.5 mg/kg/dose or an equal volume of normal saline was given in three doses 8 hours apart. The final dose was given 1 hour before extubation. Esophageal pressure, air flow integrated to tidal volume (Vt), respiratory rate, and heart rate were measured before extubation, immediately following extubation, and every 20 minutes for 80 minutes. Total pulmonary resistance (RTP), dynamic lung compliance (CL), and minute ventilation (VE) were calculated. Forty-two infants completed the study; 19 infants received dexamethasone and 23 received placebo. There was no difference between the two groups in gestational age, weight at study, or length of intubation. Vt, RTP, VE, and CL were not significantly different between the two groups over time; however, RTP increased over time in the placebo group. Heart rate was significantly lower in the dexamethasone group. We conclude that dexamethasone appears to have limited effect on pulmonary function immediately following extubation in the population studied. Further studies should evaluate the drug effect beginning at least 1 hour after extubation.


Magnetic resonance imaging in full-term infants with repetitive focal seizures. We report two full-term infants who developed repetitive focal seizures within the first 48 hours of life. Neither infant had predisposing factors and there were no abnormalities on a computed tomography (CT) scan performed on day 2 of life. Magnetic resonance imaging (MRI) performed during the second week of life showed a focal hemorrhagic infarction in both patients. We conclude that either an MRI or a contrast-enhanced CT scan should be obtained within 1 week in patients in whom the initial imaging technique failed to reveal a focal lesion, at which time a cerebral infarction can be diagnosed with greater sensitivity.


Emotion in women undergoing amniocentesis in the second trimester of pregnancy. A descriptive study was conducted to determine the emotions of women at three points during the amniocentesis process. A volunteer convenience sample of 60 women who were undergoing a first amniocentesis in the second trimester of pregnancy participated in the study. Participants completed a demographic and an amniocentesis information survey upon entry into the study. An emotion scale was administered at three specific times. Results showed that positive emotions increased significantly as the process unfolded. Some negative emotions decreased over time. Correlation of the information score and the emotion score demonstrated no significant relationship between these variables.


The high-risk infant environment. Part 2. The role of caregiving and the social environment. Neonatal intensive care units are essential for the successful care of very immature and sick infants. The technology of NICUs has contributed significantly to the reduction of neonatal mortality and improvement of neonatal outcome. While the outcome for high-risk neonates has vastly improved over the past three decades, a number of infants sustain injuries and complications that result in long-term disabilities. It is now clear that some of the long-term problems of high-risk infants are a result of the environment and care practices and are not attributable to the original disease or condition that necessitated intensive care. There is accumulating evidence that environmental factors and care practices can interact with disease processes in ways that can increase morbidity, and possibly mortality. In addition to developmental and behavioral problems, there is growing evidence of effects on visual function and perhaps other sensory systems. Many of the environmental and care factors may cause delay in recovery and increase NICU time or unnecessary discomfort, yet not produce long-term disabilities or problems, as currently assessed. Many of the potential behavioral and developmental problems, as well as many of the potential problems with visual, auditory, and other modes of sensory discrimination, are not included in the usual follow-up assessments. The absence of data or the limitations of existing studies are not a cause for comfort or the assumption that the environment and care practices are safe or not harmful.(ABSTRACT TRUNCATED AT 250 WORDS)


Effects of transcutaneous monitor electrode heat on skin servo-controlled environments. This study tested the hypotheses that (1) the heat generated by a transcutaneous monitor electrode is sufficient to decrease skin servo-controlled radiant warmer heat output when it is positioned next to the operating skin servo-thermistor, and (2) the decrease in radiant warmer heat output is enough to lower body temperatures or cause a heat-conserving response in a baby. Seventeen newborns less than or equal to 5 days old, gestational age 29 to 40 weeks, cared for under radiant warmers were studied before and for 30 minutes after juxtaposition of the transcutaneous monitor electrode and the skin servo-controlled thermistor. Mean radiant warmer heat output, measured as watt-hours/5 minute periods, decreased for the first 15 minutes after movement, mainly in the infants cared for under an older model radiant warmer. Mean skin temperature and foot temperature decreased, and esophageal-foot temperature gradient increased for those under the older model radiant warmer. Despite differences in the gestational age of the infants under the older compared with the newer model radiant warmer, multiple regression analysis indicated a significant effect of the model of radiant warmer on the results. Many factors can influence the proper functioning of servo-controlled heating systems, including the type of electronic logic and extraneous sources of heat. These factors require more study, and should be considered in the evaluation of thermal control problems.


Sudden deterioration of intubated newborn: four steps to the differential diagnosis and initial management. This paper provides guidelines to determine the differential diagnosis and treatment of sudden deterioration of an endotracheally intubated newborn infant. Since such an event is most often secondary to a mechanical problem, simple adjustment of the ventilator in response to blood gas analysis will only rarely be sufficient to stabilize the infant. The proposed algorithm integrates history, physical examination, investigations, and therapeutic intervention (of which manual ventilation is the keystone). We hope that such an algorithm may help training physicians, nurses, and respiratory therapists to minimize the risk for the infant as well as the time required to provide an efficient resuscitation. This algorithm may be used both in the neonatal intensive care unit and in the delivery room as a complement to the recommendations of the American Heart Association, in case of poor response to the resuscitation. Modifications to this protocol should be allowed according to specific characteristics of each infant and to the equipment available.


An interesting case presentation: a possible new route for perinatal acquisition of Chlamydia. Chlamydia trachomatis is currently the most common sexually transmitted disease in the United States. The prevalence in pregnant women ranges between 2% and 47%. It is well known that C trachomatis can be transmitted from the genital tract of an infected mother to her newborn infant, causing conjunctivitis or pneumonia or both, along with their longstanding complications. A review of the literature failed to show, however, conclusive evidence of transmission of infection to the newborn infant when the infant was born by cesarean section with intact amniotic membranes. We present a case of a young black woman with a history of chlamydia cervicitis during pregnancy whose infant was delivered by cesarean section because of failure to progress. She gave birth to a healthy term infant who developed ophthalmia neonatorum on the 3rd day of life. Examinations of conjunctival scrapings with direct fluorescent staining (chlamydia MicroTrak) performed on the 1st and 3rd day of life were positive. The initial test was performed because of the maternal history. The infant was mildly symptomatic at the time the study was repeated for confirmation. Our findings strongly suggest the possibility of either transmembrane or transplacental route of infection in the pathogenesis of neonatal chlamydia infection. Further study is needed to confirm this possibility.


The effectiveness of preemployment drug screening in the prediction of employment outcome. Studies of adverse employment outcomes associated with positive preemployment drug screens have tracked employees for only about 1 year. Changes in drug use after hire may invalidate the predictions of employment outcome in later years which are essential for cost-benefit analyses. This blinded, prospective cohort study tracks absence, industrial accidents, occupational injuries, discipline, and turnover in 2537 screened employees through an average of 2 years. Marijuana-positive urines predicted increased turnover, accidents, injuries, discipline, and absence, but these risks appeared lower in the second year than the first. Cocaine-positive urines predicted increased turnover, accidents, injuries, discipline, and absence at levels not consistently different than the first year. Cost-benefit analyses of drug screening project employment risks throughout employees' careers. This study raises the possibility that elevated risks may decrease after the first year.


An investigation of a workplace cluster of Bell's palsy. We undertook a study to confirm the existence of an apparent cluster of Bell's palsy in an industrial plant ("W4"), and to test etiologic hypotheses regarding chemical exposures, immune suppression, and infectious etiologies. Cases were enumerated by questionnaire. Employees with a history of Bell's palsy ("cases") were invited to participate in a study that included medical history, T cell studies, viral and Lyme disease serologies, and blink reflex studies. Thirty-three unaffected volunteers from W4 and 32 from a comparison building were also tested. Extensive environmental studies were carried out in W4, evaluating infectious, chemical, and radiation exposures. The lifetime incidence of self-reported Bell's palsy was 11.6/10,000 person-years (P-Y) in W4 and 2.4 cases/10,000 P-Y in the comparison building (RR = 4.8, P < .05); the comparison rate was similar to that reported in previous population studies. When restricted to cases occurring after the onset of work, the W4 incidence was 29.2 cases/10,000 P-Y, compared to 4.8 cases/10,000 P-Y in the comparison building (RR = 6.1, P < .05). The cases and noncases did not differ with respect to clinical histories or infectious disease titers. The W4 noncases had small but significant decreases in T lymphocyte (1974 +/- 86 vs 2291 +/- 103) and CD4 (1083 +/- 318 vs 1459 +/- 494) counts compared to the remote noncases. The cases had significantly prolonged RR1, LR1, and LFC values compared to both groups of noncases. No medical or environmental factors were identified that could explain an excess of disease.


Factors associated with adherence to breast cancer screening among working women. This study identified sociodemographic, knowledge, attitude, and social influence correlates of obtaining mammograms among employed women age 40 and over. Telephone interviews were conducted with 798 women who worked at 39 different work sites. Eighty-four percent of respondents had ever had a mammogram, and 72% had had one at the recommended interval for their age group. The only personal characteristic that was associated with past mammography use was having a co-worker, friend, or relative with a history of breast cancer. Logistic regression analyses indicated that a doctor's advice to have a mammogram, knowledge of screening guidelines, knowing someone with breast cancer, and the beliefs that mammography is effective and that mammography is necessary in the absence of symptoms were associated independently with past use of mammography. Three factors contributed independently to explaining adherence to mammography guidelines: younger age, knowledge of guidelines for one's own age group, and the belief that breast cancer is curable. The findings suggest that emphasizing the recommended guidelines, the need for and benefits of mammography in educational programs, and offering low-cost or free mammography at the workplace, can further increase appropriate utilization among working women.


Use of PCB blood levels to assess potential exposure following an electrical transformer explosion. Following the explosion of a transformer, passersby, building occupants, and cleanup personnel had potential exposure to the transformer dielectric fluid containing polychlorinated biphenyls (PCBs). As part of a medical evaluation, blood serum was analyzed for PCBs, and the concentrations found were similar to that of a regional comparison group (median 4.0 ng/mL or parts per billion, range 1-10, n = 60). Some workers employed by the utility company that owned the transformer had potential exposure to PCBs in the past. This positive comparison group had significantly higher serum PCB concentrations, related to known direct contact (median 5.0, mean 14 ng/mL, 1-187, n = 25) or not (median 4.0, mean 11 ng/mL, 2-72, n = 17). Therefore, in this investigation, elevation of serum PCB levels could be related to past contact during work with transformers, but not to potential short-term exposure at the time of a transfer explosion.


Occupational reintegration of long-term cancer survivors. To determine the long-term psychosocial consequences of cancer related to work, a postal survey was conducted among 849 long-term survivors of cancer in the southwest Netherlands. Forty-four percent of the responders who worked at the time of the diagnosis of cancer returned to their job, 24% of them part-time. Fourteen percent experienced impediments at work after return. Absenteeism in this group does not differ from that in the year prior to the moment of diagnosis. There is a small decrease in promotional and financial prospects.


Comparison of mother's occupation and industry from the birth certificate and a self-administered questionnaire. Maternal occupations recorded on birth certificates are a potential data source for evaluation of reproductive hazards, but may not accurately identify jobs held during the sensitive first trimester. Mothers' occupation and industry during 1 month before and 3 months after conception were reported on 1,760 mailed questionnaires. These were compared to mothers' most recent occupation and industry recorded on birth certificates. Overall, 72% of occupations and 77% of industries reported on the birth certificate agreed with that recorded on the questionnaire. Agreement was similar for mothers of normal and malformed infants. Among those that did not agree, 344 (75%) disagreed on the mother's employment status during the periconceptional period, rather than the actual occupation. For surveillance and hypothesis-generation using birth certificate data, it is important to obtain a correct description of whether the mother held a job outside the home during sensitive periods of her pregnancy.


Mushroom worker's lung. Detection of antibodies against Shii-take (Lentinus edodes) spore antigens in Shii-take workers. Indoor cultivation of the edible mushroom Shii-take (Lentinus edodes) regularly leads to symptoms of mushroom worker's lung (MWL) in workers. An immunologic test is described allowing detection of IgG type antibodies against Shii-take spore antigens. It was found that MWL patients employed in Shii-take picking (n = 5) have significantly increased antibody titres against Shii-take spore antigens. Different control groups, viz, MWL patients employed in the cultivation of the white button mushroom Agaricus bisporus (n = 14) and of the oyster mushroom Pleurotus spp (n = 3), patients with Bechterew's syndrome (n = 7), sarcoidosis (n = 7), rheumatoid arthritis (n = 9), and healthy controls were found in the same range of low titres. The use of protective masks during picking reduced complaints of the workers (n = 14). However, their antibody titres increased with duration of employment despite the protection.


Streptococcus suis meningitis. A severe noncompensated occupational disease. Meningitis caused by Streptococcus suis type 2, a rare disease first recognized in 1968 (108 cases worldwide in 1989), is contracted by occupational exposure to pigs and often results in very severe disabilities (definitive deafness and ataxia in 50% of cases). We report the case of an employee in a rendering plant whose initial symptom was deafness. A detailed analysis of medical and veterinary literature is provided concerning the epidemiology of the disease, the clinical forms in man, bacteriological diagnosis and the role of the pig as healthy carrier. It is recommended that this occupational disease be officially recognized for compensation in France.


Cognitive dysfunction in a patient with long-term occupational exposure to ethylene oxide. Role of ethylene oxide as a causal factor. This case illustrates a comprehensive approach to assessing causality in a woman with apparent cognitive dysfunction, as measured by neuropsychological testing, and a 10-year history of occupational exposure to ethylene oxide. The analysis included a multidisciplinary examination of the patient, which took place several years after the termination of her exposure. In addition, all of the patient's prior medical and psychiatric records were reviewed, as were the records of her employer to ascertain her exposure history. Our evaluation revealed a pattern of neuropsychological findings not consistent with nervous system damage secondary to an organic effect of ethylene oxide. A more likely causal hypothesis is adopted: the patient's apparent cognitive dysfunction had a psychiatric etiology. This case also illustrates the potential impact of a patient's involvement in legal proceedings related to claims of neurocognitive dysfunction.


Micro-architecture and composition of artery walls: relationship to location, diameter and the distribution of mechanical stress. We reviewed the structural basis of the mechanical properties of the arterial wall, in order to establish a coherent micro-anatomical basis for the differences in compliance among different arteries and a framework for assessing changes in the mechanical properties of specific individual arteries in relation to changing physical stresses. The data and concepts presented here were derived from both earlier and ongoing work. Features that assure stability and integrity in relation to blood flow (wall shear stress) and pressure (mural tensile stress) were examined. Particular attention was paid to the morphogenetic and biosynthetic means by which arteries adapt to normal or abnormal modifications of these forces, particularly in relation to growth, location in the arterial tree and geometric configuration. Thickness, composition and architecture of the artery wall, including thickness and composition of the intima, are normally determined by the stresses imposed by pressure and flow. Vessel radius is closely associated with flow, so that a normal baseline level of mean shear stress of about 15 dyn/cm2 is maintained or restored. Wall thickness and composition are determined by wall tension in relation to pressure and radius. Baseline levels of tensile stress differ with location but appear to be similar for homologous vessels. Changes in flow that modify the radius also modify wall tension. Changes in wall thickness and composition are likely to cause changes in compliance, due to altered flow and/or pressure patterns; these changes in compliance may be adaptive rather than destructive. Changes in the compliance of specific arteries over time may be used to evaluate the progression and severity of the conditions underlying these changes.


Dynamic non-invasive measurements of arterial diameter and wall thickness. Non-invasive measurements of arterial diameter and wall thickness are critical in characterizing the onset and development of vascular disease. A precise dynamic method was proposed and tested for this purpose. A non-invasive method of measuring the variations in diameter and thickness of human arteries throughout the cardiac cycle was developed, using a high-precision ultrasonic echo-tracking system. An adaptive filtering technique was used to suppress artefacts caused by the layered tissue structure of the vessel wall. Based on decorrelation of microstructure noise, this technique improved the detectability of the wall interfaces, which allowed a determination of thickness and diameter. The accuracy and reproducibility of the method were tested by measurements of plastic films with known thicknesses. The discrepancies between standard micrometer and pulse-echo measurement were consistently less than 5 microns for film thicknesses ranging from 220 to 800 microns. The difference between two successive measurements was less than 2 microns. The identity of the measured vascular interfaces was checked in two ways. First, experiments on fixed bovine carotid arteries showed that the identified echogenic interfaces corresponded to the actual anatomical structure, as obtained by acoustic microscopy. Second, the radial artery thickness and diameter were extrapolated to obtain the change in wall volume over one cardiac cycle. The volume was found to be nearly constant, indicating incompressibility. This method will make it possible to obtain new information on atherogenesis and other vascular diseases.


First- and third-order models for determining arterial compliance. Engineering models of the arterial vasculature have been used to describe vascular properties of resistance and compliance. These approaches have used either Fourier frequency analysis, based on transmission line equations, or time domain analysis of the circuit equations describing modified Windkessel models of the vasculature. A third-order, four-element modified Windkessel model can reproduce arterial pressure waveforms, including both exponential and oscillatory pressure decays observed during the diastolic portion of the cardiac cycle. A method to determine both capacitive and oscillatory compliance of the arterial vasculature was developed, and the effect of these compliance properties on the blood pressure waveform was examined.


Incompressibility of the human arterial wall: an in vitro ultrasound study. The assumption that the arterial wall behaves like incompressible material simplifies the analysis of arterial wall elasticity. Experimental evidence for the incompressibility assumption has been obtained directly by volume-displacement and radiological methods. Recent developments in ultrasound technology have made it possible to take direct, high-resolution measurements of the internal diameter and wall thickness of an artery and thus calculate the cross-sectional area of the arterial wall. The objective of this study was to determine the cross-sectional area of the arterial wall in vitro at different levels of strain in order to demonstrate the incompressibility assumption. Two different types of fresh, human, medium-sized arteries were studied, the internal mammary artery, and a less elastic and more muscular artery, the radial artery. The internal diameter and wall thickness were measured with an ultrasonic echo-tracking device (NIUS 1; Asulab, Neuchâtel, Switzerland) over 1-min steps of increasing intra-arterial pressure (0, 50, 100, 150 and 175 mmHg). The cross-sectional area of the arterial wall of the radial and internal mammary artery remained unchanged under different levels of strain. Since the artery length remained constant during the pressure increases, the lack of change in the cross-sectional area of the arterial wall suggests that the arterial wall of human medium-sized arteries is essentially incompressible.


Non-invasive measurements of arterial compliance in hypertensive compared with normotensive adults. To determine differences in arterial compliance attributable to hypertension. Since measurements of arterial compliance have tended to vary in the past according to the method used, a new technique comprising carotid ultrasound and simultaneous, calibrated, carotid pressure waveform measurements was tested in 43 hypertensives and 43 control subjects matched for age, gender and body size. There was a significant reduction in compliance among the hypertensive patients, as estimated by the elastic modulus and the ratio of stroke volume to pulse pressure. However, when the non-linearity of the pressure-volume relationship and the impact of distending pressure were taken into account, by the arterial stiffness index and by the increase in arterial wall thickness associated with hypertension by Young's modulus, there were no significant differences in arterial compliance between the two groups.


Conclusions on the measurement of arterial wall thickness: anatomic, physiologic and methodologic considerations. To discuss the use of new ultrasonic techniques that make it possible to visualize elastic (carotid) and muscular (radial) capacitance arteries non-invasively. Measurements of carotid wall thickness and the detection of atheromas are related to arterial pressure, to other risk factors and to the risk of subsequent complications. The use of high-frequency ultrasound (7.5-10 MHz), measurements of far wall thicknesses in areas free of atheromas at end-diastole (by ECG gating or pressure waveform recording) and descriptions of the size and characteristics of atherosclerotic plaques allow a non-invasive assessment of vascular hypertrophy and atherosclerosis in hypertensive patients. Careful attention to methodologic and physiologic factors is needed to provide accurate information about the anatomy of the dynamically pulsating arterial tree.


Introduction to large artery properties as a target for risk reduction by antihypertensive therapy. To review the effect of antihypertensive drugs on pulsatile stress and shear stress. Mortality and morbidity in hypertension are better correlated with systolic than diastolic blood pressure, indicating a pulsatile stress effect. Distensibility and compliance are large artery properties and important determinants of pulsatile stress. beta-Blockers with vasodilating properties, several selective beta 1-blockers, angiotensin converting enzyme inhibitors and calcium antagonists are first-line antihypertensive drugs that improve these properties of large arteries. The impact of shear stress on the ill effects associated with hypertension is not clear. Some but not all classes of antihypertensive drugs can improve large artery properties, and thereby alleviate pulsatile stress.


Physiological and pharmacological changes in the carotid artery pressure-volume curve in situ in rats. To measure the mechanical properties of the rat carotid artery as affected by physiological and pharmacological changes. We used an in situ measurement method that did not affect the anatomy, vascularization or innervation of the carotid artery, in normotensive and in spontaneously hypertensive rats (SHR), to evaluate the effects of ageing, hypertension and acute or chronic drug-induced vasorelaxation. The compliance-pressure curve was characterized, under baseline conditions, by two phases, an ascending component in the lower pressure ranges and a descending component in the higher pressure ranges. In younger or older normotensive rats the maximum value of carotid compliance was observed for values of transmural pressure that approximated those of the operating mean blood pressure. For any given value of transmural pressure, carotid compliance was lower in the hypertensive rats, whether younger (3 months) or older (18 months), than in normotensive rats. This finding was particularly striking for transmural pressures below 125 mmHg, and held true even after the administration of potassium cyanide. Consequently, the reduced compliance in the hypertensive rats was attributed predominantly to structural changes in the arterial wall. Moreover, in the hypertensive rats there was a dissociation between the operating arterial blood pressure level and the maximum value of carotid arterial compliance. Thus in young SHR, whereas the operating systemic blood pressure was shifted toward higher values (> 175 mmHg), the maximum value of carotid compliance was observed for pressure levels close to 125 mmHg. This dissociation was more pronounced in older SHR (mean blood pressure 200 mmHg; maximum compliance 75 mmHg). The acute administration of vasodilators or of potassium cyanide induces relaxation of vascular smooth muscle and increases compliance for distension pressures of up to 125 mmHg. Since the drugs had no effects on arterial compliance at higher pressure levels, we conclude that in SHR acute vasorelaxation can increase operating compliance only if blood pressure is reduced. In contrast, chronic treatment with vasodilating agents is able to increase compliance even for higher blood pressure levels. Therefore, we suggest that chronic treatment can improve the elastic properties of the arterial wall through changes in the arterial wall structure.


Sodium, large arteries and diuretic compounds in hypertension. Clinical and experimental data have shown that different antihypertensive drugs do not cause similar changes in arterial compliance for an equipotent blood pressure reduction. There are no clear data on the effects of sodium and diuretics on the visco-elastic properties of the hypertensive arterial wall. Cross-sectional epidemiological studies suggest that for given values of age and blood pressure, pulse wave velocity is lower in the presence than in the absence of a low sodium intake. Longitudinal studies indicate that in hypertensive subjects, a low sodium intake is associated with a larger brachial artery diameter than that seen with a high sodium intake. In hypertension in the elderly and in severe hypertension with end-stage renal disease, a sodium overload reduces arterial compliance and distensibility independently of blood pressure changes. In animal studies, the diuretic compounds cycletanine and indapamide increase systemic and carotid compliance independently of blood pressure changes. In contrast, in a crossover study in hypertensive subjects, the diuretic agent hydrochlorothiazide did not change arterial compliance and pulse wave velocity while the calcium entry-blocker felodipine did improve these hemodynamic parameters. The studies reviewed indicate that sodium may act on the arterial wall independently of blood pressure changes. the contribution made by counter-regulatory mechanisms, which may be related to the renin-angiotensin and the sympathetic nervous systems, might explain the differences between the clinical and the experimental changes observed with diuretic compounds.


Drug-induced changes in mechanics and structure of cerebral arterioles. Cerebral arterioles in stroke-prone spontaneously hypertensive rats (SHRSP) undergo remodeling with a reduction in external diameter, paradoxically becoming more distensible, despite hypertrophy of the vessel wall. Two concepts have been proposed. (1) Remodeling of cerebral arterioles is an important mechanism, in addition to hypertrophy, of encroachment on the vascular lumen in SHRSP. (2) Increases in arteriolar distensibility partly compensate cerebral arterioles for other factors, such as hypertrophy and remodeling, which reduce the dilator capacity of these arterioles in chronic hypertension. Recently, we have studied the effects of reducing blood pressure by drug treatment or carotid clipping on hypertrophy and remodeling of cerebral arterioles in SHRSP. Our findings suggest that (1) pulse pressure may be a more important stimulus than mean pressure for hypertrophy of cerebral blood vessels and (2) remodeling of cerebral arterioles may occur independently of hypertrophy. Treatment that effectively prevents vascular hypertrophy during chronic hypertension may not be effective in preventing remodeling, and may therefore fail to restore cerebral vascular function to normal.


Cardiac and vascular effects of chronic angiotensin converting enzyme inhibition at subantihypertensive doses. We performed two sets of experiments in order to prevent or to regress cardiac and vascular hypertrophy, using antihypertensive and subantihypertensive doses of the angiotensin converting enzyme inhibitor zabicipril. Spontaneously hypertensive rats (SHR) begin to develop hypertension at less than 4 weeks of age and reach stable hypertension levels after 12-14 weeks. The blood pressure increase is accompanied by the development of cardiac and vascular hypertrophy. Treatment of SHR in utero and up to the age of 20 weeks with an antihypertensive dose of zabicipril (1 mg/kg per day) not only prevented the development of high blood pressure but also the development of cardiac and vascular hypertrophy. This effect was demonstrated by a significant decrease in left ventricular weight and the number of smooth muscle cell layers in the vascular media, media thickness and the media:lumen ratio in mesenteric arteries. In contrast, antihypertensive treatment with the Ca2+ antagonist verapamil (100 mg/kg per day) and the subantihypertensive dose of zabicipril (0.01 mg/kg per day) did not affect the development of cardiac and vascular hypertrophy. We found a significant increase in the length and surface density of myocardial capillaries after treatment with zabicipril at 1 mg/kg per day, indicating that the capillary density had improved and therefore that the oxygen supply of the heart was improved. Similar findings were observed with the low dose of zabicipril in SHR, although these rats had high blood pressure and cardiac and vascular hypertrophy. Treatment of adult SHR for 16 weeks with zabicipril at 1 mg/kg per day completely normalized their blood pressure levels. This effect was accompanied by a regression of left ventricular but not of vascular hypertrophy. Treatment with an antihypertensive dose of verapamil or with a subantihypertensive dose of zabicipril had no effect on cardiac and vascular hypertrophy.


Clinical relevance of distal arterial compliance. To calculate the compliance of resistance vessels. Pressure-flow data (plethysmographic and sphygmomanometric) were obtained non-invasively from six normal and six hypertensive subjects, and the results were compared with similar data obtained previously from large blood vessels. The parameter used to represent compliance was extensibility (E), defined as the percentage change in radius for a given change in pressure. The hand vessels of hypertensive subjects (E = 0.126 +/- 0.034/mmHg) were significantly stiffer (P < 0.02) than those of the normotensive subjects (E = 0.272 +/- 0.047/mmHg); and the values of E for the resistance vessels were larger than those for the large arteries.


Assessment of the arterial distension waveform using Doppler signal processing. To determine the distension waveform of an artery. Ultrasound signals returned by moving structures were processed by pulsed Doppler in order to detect the displacement of the signals with respect to the transducer as a continuous function of time. The results of two sample volumes combined, one located at the anterior and the other at the posterior wall of an artery, yielded the distension waveform of the artery. The distance between the sample volumes in combination with the distension from diastole to systole provided the local distensibility and compliance coefficients. To prevent any part of the structure under observation from moving outside the sample volume, the position of the sample volume was adjusted according to the displacement detected. A disadvantage with this method is that the phase interference of closely spaced structures, i.e. layers of the arterial wall, and the readjustment of the sample volume position may cause artifacts but these can be effectively suppressed by proper processing. The phase delay between two distension waveforms assessed simultaneously at a known distance can provide the local pulse wave velocity. Subsequently, the Moens-Korteweg relationship, expressing the relationship between pulse wave velocity and the distensibility coefficient, can be used to estimate the distensibility coefficient without measuring the local pulse pressure. The techniques, however, need further evaluation.


Non-invasive method for the assessment of non-linear elastic properties and stress of forearm arteries in vivo. To propose a method for obtaining non-invasive highly accurate measurements of arterial diameter, thickness and pressure at a single location on a peripheral arm artery, and use this data to estimate the status of the arterial wall. Diameter and thickness were measured with an A-mode ultrasonic echo-tracking device, with a precision of close to 1 micron. Pressure was measured with a photoplethysmograph at the finger level. A simple hemodynamic model was used to estimate, from the measured pressure pulse, the pressure waveform at the diameter-measuring site. The collected data made it possible to assess (1) the elastic response of the artery, through the compliance and distensibility, (2) the loading conditions, through the average stress-diameter curve and (3) the elastic properties of the wall material, through the incremental modulus of elasticity. This information can be used to assess the overall status of the arterial wall.


In vitro assessment of diameter-pressure relationship in carotid arteries from normotensive and spontaneously hypertensive rats. To compare the mechanical properties of carotid arteries from normotensive and spontaneously hypertensive rats. The pressure-diameter relationships of carotid arteries from nine normotensive adult Wistar-Kyoto (WKY) and nine spontaneously hypertensive rats (SHR) were measured in vitro under control conditions and after poisoning the smooth muscle cells with potassium cyanide. Changes in diameter due to changes in transmural pressure were determined with an ultrasonic dimensiometer (12 MHz). The diameter values were determined from the transit times of the pair of echoes given by the proximal and distal walls. The carotid artery was submitted to stepwise increases in pressure of 25 mmHg, from 0 to 200 mmHg; each pressure level was maintained for 5 min before the arterial diameter was recorded. The carotid artery pressure-diameter relationship was a sigmoid curve in both strains. At the same level of pressure, the diameter of the carotid artery from SHR was significantly larger than that from normotensive rats (P < 0.05). Furthermore, the diameter values measured at the operating mean arterial pressure (roughly 100 mmHg for WKY rats and 150 mmHg for SHR) were markedly different (P < 0.001). In both strains, the diameter under passive conditions (with potassium cyanide) was significantly larger than that measured under control conditions (P < 0.01). Carotid arteries from SHR were significantly stiffer than those from WKY rats. Due to the pressure-dependency of the arterial wall stiffness, the increased arterial stiffness reported in hypertensive rats in vivo is related to an increase in distending arterial pressure and also to a significant reduction in the intrinsic compliance of the arterial wall.


Inhomogeneities in arterial wall properties under normal and pathological conditions. To determine whether there are inhomogeneities in arterial wall distensibility with age and hypertension. It has been known for some years that arteries lose their elasticity with increasing age and that they are less distensible in subjects with established and borderline hypertension than in age-matched controls. In the carotid artery changes in arterial wall properties are not homogeneously distributed along the bifurcation. Both in older subjects and in those with borderline hypertension the loss of distensibility is most pronounced in the carotid artery bulb, while in borderline hypertensives the proximal part of the bulb, where the baroreceptors are predominantly located, is more affected than other parts of the bulb. The loss of distensibility in the bulb may explain the diminished baroreceptor sensitivity observed in older subjects. The pronounced involvement of the proximal part of the bulb in the decreased distensibility in borderline hypertensives suggests that local stiffening, probably leading to disturbed baroreceptor sensitivity, may contribute to the development of hypertension in these patients. The pattern of inhomogeneities in wall distensibility in borderline hypertensives at a relatively young age (average 38 years) is similar to that seen in older normotensive subjects (average age 57 years), supporting the idea that arteries age faster in hypertensives than in normotensives. In management of the borderline hypertensive patient, consideration should be given to preventing early ageing of the arterial wall rather than following arterial blood pressure.


Variability in arterial diameter and compliance: compliance modulation reserve. Some antihypertensive drugs are known to increase arterial compliance in hypertensives; how far compliance can be increased is unknown. We studied eight mildly hypertensive patients to determine how far radial artery compliance can be acutely increased, i.e. the extent of the compliance modulation reserve. We evaluated radial artery compliance by a new technique, assessing it throughout the cardiac cycle before and after the intra-arterial infusion of a vasodilator agent (papaverine). Before papaverine, compliance decreased progressively through diastolic to systolic blood pressure values. This was the case also during the papaverine infusion. However, over the full systolo-diastolic pressure range, compliance was increased by about 40% with papaverine. In hypertensive subjects radial artery compliance can be markedly increased on a acute basis, indicating that those antihypertensive drugs that improve compliance have a considerable reserve to act upon.


Relationship between low-frequency oscillations of blood pressure and changes in arterial diameter. To study spontaneous variations in radial artery compliance. Compliance was evaluated non-invasively by an echo-tracking system, and variations in sympathovagal tone were analysed by a spectral analysis of continuous blood pressure recordings using a Fast Fourier algorithm. We studied 23 healthy volunteers, aged 25 +/- 4 years (mean +/- SD), at rest, on two occasions at least one day apart (5 +/- 3 days). There were no significant differences between the means of the arterial compliance measurements and those of the corresponding spectral analysis. However, the magnitude of change in the low-frequency periods (4-66 mHz) was significantly related (P less than 0.01) to a significant and inverse change in compliance for the same level of blood pressure. While it is possible to use spectral analysis to measure the effect of autonomic nervous regulation on radial artery properties, low-frequency periods cannot be safely ascribed to sympathetic effects alone. Other effects must also be taken into account in measurements of radial artery distensibility.


Effects of diurnal variability and exercise training on properties of large arteries. To examine the diurnal variability in arterial distensibility and compliance and to study the effects of exercise training on these large artery properties. Vessel wall properties of the elastic common carotid and muscular brachial arteries were measured non-invasively with a vessel wall movement detector system in 12 healthy volunteers. Properties of the common carotid, the femoral and the brachial arteries were studied in 15 sedentary males in comparison with 15 male cyclists. Diurnal changes in the carotid and brachial arteries were similar. Blood pressure decreased at night while arterial diameter increased. Distensibility decreased and compliance was preserved at night. The vessel wall properties of the carotid artery did not differ between the sedentary males and the cyclists, but the femoral and brachial arteries were more elastic in the cyclists. The diameter of the femoral artery was larger in the cyclists. We found a diurnal pattern in changes in diameter and distensibility of elastic and muscular large arteries. Compliance, the buffering capacity of larger arteries, was preserved at night. The supplying femoral artery was larger and more distensible in cyclists. Exercise training did not affect the elastic carotid artery, but improved vessel wall properties of the brachial, and maybe also of other, muscular large arteries.


Changes in arterial compliance induced by physical training in hammer-throwers. Physical training induces multiple changes in the cardiovascular system which allow an increased performance along with increased oxygen consumption. The present study was designed to investigate whether the changes include an increase in arterial compliance. In six normotensive right-handed hammer-throwers (aged 21.3 +/- 1.8 years, mean +/- SE) we measured radial artery diameter continuously via a new non-invasive echo-tracking device, and beat-to-beat blood pressure. Arterial compliance was calculated by an arctangent model. In each subject measurements were made from both the left and the right arm. The data were compared with those obtained in six age-matched normotensive controls. Compared to the controls, the hammer-throwers had similar blood pressure, a lower heart rate and plasma norepinephrine and a higher left ventricular mass index and radial artery diameter. In the athletes, right radial artery compliance was significantly greater than either right or left radial artery compliance in the sedentary subjects (+61 and 63%, P < 0.05). It was also significantly greater than contralateral radial artery compliance (+53 +/- 8%, P < 0.05). Physical training is accompanied by an increase in arterial compliance. In our hammer-throwers this increase was mainly evident in the more highly trained arm, suggesting that local mechanisms are involved in this phenomenon.


Effect of mental stress on the tone of a medium-sized muscular artery. We studied the effects of mental stress on the tone of the radial artery, a medium-sized muscular artery. Using an A-mode echo-tracking device coupled to a photoplethysmograph, we took continuous measurements of the radial artery diameter, heart rate and finger arterial pressure in six healthy young volunteers. Under mental stress, the heart rate increased from 63 +/- 4 to 74 +/- 4 beats/min (mean +/- SEM, P < 0.01) and systolic pressure from 123 +/- 5 to 140 +/- 6 mmHg (P < 0.05). No consistent modification in the arterial diameter was observed at this time. The activation of sympathetic nerve activity induced by mental stress does not cause a significant contraction in the radial artery.


Abnormalities of vascular compliance in hypertension, aging and heart failure. Diastolic arterial pulse wave analysis and a modified Windkessel model were used to evaluate the vascular response to hypertension, heart failure and aging. Compared to age-matched normal subjects, arterial compliance was reduced in patients with hypertension and heart failure, particularly in the vessels that contribute to resonances or oscillations in the pulse wave. In elderly subjects, the capacitive function of the arteries and compliance of the smaller arteries that contribute to oscillations were both reduced. These small-vessel structural or functional abnormalities may serve as a marker for disease and for the response to therapy.


Arterial dilatory reserve in congestive heart failure. The purpose of this study was to determine whether there are abnormalities in flow-mediated large vessel relaxation in patients with congestive heart failure (CHF). The radial arterial diameter and flow responses upon the release of 10 min of forearm arterial occlusion (reactive hyperemia) were measured with ultrasound and Doppler devices. In patients with CHF there was a 26% reduction in peak blood flow (P = 0.09) compared to age-matched controls. However, the increase in arterial diameter that followed the peak blood flow was reduced by 49% in CHF (P < 0.01). The causes of the abnormal flow-mediated large artery relaxation in CHF are unclear; both structural and endothelial abnormalities may contribute.


Estimating the elastic modulus of non-atherosclerotic elastic arteries. Non-invasive measurements of the diameter and wall thickness of arteries in vivo, combined with recordings of pressure, permit the assessment of some mechanical aspects of arteries in vivo. However, arteries are anisotropic cylinders with complex elastic properties which can only be determined by a detailed evaluation. Many of the parameters required to calculate the anisotropic circumferential elastic modulus cannot be obtained in patients in vivo, or can be obtained only with difficulty. Experiments were performed to assess the true anisotropic circumferential elastic modulus, and to find simpler methods of estimation. One hundred and twenty dog carotid arteries were mounted in vitro and were extended to four lengths, 120, 130, 160 and 180% of the retracted length. The different lengths were applied in random order. The vessels were pressurized in steps while the longitudinal force and vessel diameter were measured. When a reproducible mechanical behavior was observed, the pressure, diameter and longitudinal force were recorded. These values were used to calculate the longitudinal elastic modulus, the circumferential-longitudinal Poisson's ratio and the true anisotropic circumferential elastic modulus with respect to the dimensions of the fully unloaded vessel. A number of simpler expressions were then evaluated for their value as approximations of the true anisotropic modulus. Excellent estimates were obtained with a variety of expressions. These methods may be useful for non-invasive assessments of the elastic properties of non-atherosclerotic arteries in patients.


Determinants of isolated systolic hypertension in the elderly. To study the determinants (or mechanisms) of isolated systolic hypertension in the elderly. Pulsatile blood pressure and flow (multisensor catheter) were measured in the ascending aorta and impedance spectra were calculated in 18 subjects undergoing cardiac catheterization. Nine subjects (mean +/- SEM age 58 +/- 1.4 years) had increased aortic systolic (166 +/- 2.3 mmHg, P < 0.001), mean (116 +/- 2.1 mmHg, P < 0.02) and pulse blood pressure (83 +/- 2.1 mmHg, P < 0.001) and normal diastolic blood pressure (84 +/- 2.0 mmHg, NS) and constituted the isolated systolic hypertension group. The other nine age-matched (58 +/- 1.1 years) subjects had normal aortic systolic and diastolic blood pressure and constituted the normotensive control group. Both static (peripheral vascular resistance) and dynamic (characteristic impedance and wave reflection) components of left ventricular external load (aortic input impedance) were elevated in the isolated systolic hypertensives compared to the normotensive subjects; peripheral vascular resistance was 44% higher (P < 0.001), characteristic impedance (index of aortic stiffness) was 107% higher (P < 0.001), the first harmonic of impedance moduli (index of wave reflection) was 57% higher (P < 0.004) and the first impedance moduli minimum was shifted to a higher frequency (from 3.4 +/- 0.2 Hz to 4.2 +/- 0.13 Hz, P < 0.008) in the group with isolated systolic hypertension. The changes in impedance spectra in the isolated systolic hypertensives indicate that the cross-sectional area of the peripheral vascular bed was reduced and that the aorta and large arteries were stiffer, producing an increased pulse wave velocity and an early return of pulse wave reflection in systole. The marked increase in arterial stiffness in isolated systolic hypertension offset the increase in diastolic blood pressure that would have been expected from an increase in peripheral vascular resistance alone, and early return of the reflected pressure wave augmented aortic pressure throughout systole and accounted for the large increase observed in systolic and pulse pressure in the aorta.


Arterial compliance and distensibility in spontaneously hypertensive rats. These studies were undertaken in intact spontaneously hypertensive rats (SHR) to assess whether the elastic behavior of conduit arteries changes as a function of age. We studied 16-week-old (n = 10) and 36-week-old (n = 10) SHR under fluothane anesthesia. Diameter-, compliance-, and distensibility-pressure curves were established non-invasively for the carotid artery by means of a high-precision ultrasonic echo-tracking device. Intra-arterial pressure was monitored simultaneously in the contralateral carotid artery. Mean blood pressure was 197 +/- 6 and 185 +/- 3 mmHg (mean +/- SEM) in the younger and older SHR, respectively. No significant difference was observed between the two groups of rats in the diameter-, compliance- and distensibility-pressure curves. These results suggest that the elastic behavior of elastic arteries is not necessarily altered with aging in rats with genetic hypertension.


Ageing and wave reflection.

Ageing and wave reflection. To determine the effects of wave reflection on the increase in arterial pressure that occurs with age and its association with concomitant changes in both the magnitude and contour of the arterial pressure pulse. While age-related changes in mean pressure are similar in central and peripheral arteries, changes in pulse pressure and pulse waveform features are different. Because of the specific architectural, geometrical and elastic properties of the arterial vasculature, wave reflection plays an important role in determining peak pressure, the value usually specified as systolic pressure. While the late systolic increase usually determines peak systolic pressure in the central aorta, it is not necessarily related to the peak pressure in the periphery. Peak pressure depends on the timing and intensity of wave reflection, which is a function of the state of the peripheral microvasculature and the elastic properties of the large conduit arteries. Ageing causes changes in both the terminal and central vasculature, so that the intensity of the wave reflection and the transmission properties of arteries affect the arterial pulse to different degrees. Therefore, age-related changes that are observed in the central pressure pulse are different from those observed in the pulse when measured in a limb. Thus the contribution of wave reflection to the determination of peak arterial pressure is not the same at all locations. These findings have profound implications for therapeutic strategies aimed at altering systolic pressure and for a proper assessment of the alteration in cardiac load that occurs with age or with antihypertensive therapy, when measurements are taken in a limb.


Opposing effects of ageing on distal and proximal large arteries in hypertensives. Hypertension has been reported to accelerate the alterations in large arteries induced by ageing. Distal large arteries have been poorly investigated in contrast to proximal large arteries. The objectives of this cross-sectional study were (1) to compare the storage capacity of different arterial sites in normotensive subjects or hypertensive patients; and (2) to compare the different arterial sites with respect to the effects of ageing on storage capacity, in normotensives and in hypertensives. Two recently developed ultrasonic echo-tracking devices, offering a high resolution for the assessment of internal arterial diameter and its systolo-diastolic variations, were used to measure end-diastolic diameter, absolute (change at end-systole minus change at end-diastole) and relative (absolute change divided by change at end-diastole) changes in diameter with stroke and the absolute change in cross-sectional area (3.14 x the end-diastolic diameter x half the absolute stroke change in diameter) at the site of the common carotid artery, the abdominal aorta, the common femoral artery, the brachial artery and the radial artery in 50 untreated essential hypertensive patients and 32 normotensive subjects. In both groups, the end-diastolic diameter increased with age for the common carotid artery and the abdominal aorta but not for the common femoral, brachial or radial arteries. In the normotensives, the relative stroke change in diameter was negatively correlated with age for the common carotid artery (P < 0.001) and the abdominal aorta (P < 0.001), and not correlated for the common femoral, brachial and radial arteries. In hypertensives, the relative stroke change in diameter was negatively correlated with age for the common carotid artery (P < 0.05) and the abdominal aorta (P < 0.05), positively correlated with age for the common femoral (P < 0.05) and the radial arteries (P < 0.05) and not correlated for the brachial artery. Similar results were observed for the relationships between the absolute change in cross-sectional area and age. In hypertensives, enlargement of the proximal large arteries offsets the decrease in the relative stroke change in diameter and maintains an adequate storage capacity. It thus appears that ageing exerts opposing effects on central elastic large arteries and distal muscular medium-sized arteries.


Body height as a determinant of carotid pulse contour in humans. The aim of this study was to assess the effect of body height on arterial wave reflections and the carotid pulse pressure contour in humans. In 85 men, the carotid pulse wave and arterial wave reflections were determined from the common carotid artery pulse contour as recorded by applanation tonometry using a Millar micromanometer-tipped probe. The arterial wave reflection was calculated as the ratio of the height of the late systolic peak to the total height of the carotid pulse wave. The reflected wave was timed from the foot of the pressure wave to the foot of the late systolic peak. Multiple regression analysis showed that body height and aortic pulse wave velocity were the principal determinants of travel time of the reflected wave and of arterial wave reflections (P < 0.0001), short stature being associated with a short travel time and increased reflections (P < 0.0001). Body height is a determinant of arterial wave reflections and peak systolic blood pressure in humans.


Pharmacological potential for reversing the ill effects of ageing and of arterial hypertension on central aortic systolic pressure. Systolic arterial pressure is an important risk factor for future cardiovascular morbidity and mortality. PULSATILE LOAD: The aortic systolic pressure with which the heart interacts is determined by pulsatile vascular load. In particular, wave reflections from peripheral sites affect peak central aortic systolic pressure but not brachial systolic pressure. DRUG POTENTIAL: Drugs that reduce wave reflection and hence reduce the pulsatile vascular load in addition to reducing peripheral resistance have the potential to reduce target organ damage to a greater extent than drugs that reduce mean pressure and resistance alone.


Contrast detection in luminance and chromatic noise. We measured detection thresholds for a vertically oriented 1.2-cycle-per-degree sine-wave grating embedded in spatiotemporal broadband noise. Noise and signal were modulated in different directions in color space around an equal-energy white point. When signal and noise were modulated in the same direction, we observed a linear relationship between noise spectral density and signal energy at threshold. The slope of this function was the same whether the modulation was along a luminance axis or a red-green axis. If the signal was on one axis and the noise was on the other, no masking was observed. These results support the notion of two independent and equally efficient mechanisms tuned to these directions. We then measured threshold elevations for masks with both chromatic and luminance components. When signal and noise were modulated along the same line (for example, bright red and dark green), thresholds were elevated. When we inverted the phase of the chromatic component of the noise relative to the luminance component (bright green and dark red), the masking effect disappeared, even though the amount of noise in the putative luminance and chromatic mechanisms was exactly the same as before. This implies that detection performance is limited by mechanisms sensitive to both luminance and chromatic contrast signals. We characterized these mechanisms by their spectral tuning curves.