A critical analysis of postulated pathogenetic mechanisms in amyloidogenesis. This review has examined several of the major thrusts in amyloid research, past and present. The data concerning amyloid precursor quantity, primary protein and gene structure, and precursor proteolysis have shown that there are contradictions that must be resolved before these elements can be reamalgamated into a unified view of amyloidogenesis. One possibility is presented in Figure 2. A general hypothesis of amyloid formation that accounts for the uniformity of fibril structure, amyloid staining properties, and the specific selection of precursors and their specific anatomic localization in each form of amyloid has yet to be proposed. Some of these questions may be answered by an analysis of common structural constituents in amyloid deposits. Analyzing amyloid generation in the context of these common elements separates amyloid research into several specific areas (Figure 2). The first area concerns factors that govern the expression of amyloid precursor protein genes, thus providing adequate quantities of the precursor, if such a precursor pool does not already exist. Without such a pool, amyloid deposition clearly cannot occur. The second area concerns information as to where these precursors usually bind and/or exert their normal function. Once determined, this information will likely indicate the site or sites where the particular precursor may give rise to amyloid deposits. The last area concerns factors at these local sites that govern the interaction of the precursor with basement membrane or related extracellular matrix elements that would define both the site and the final common pathway for amyloid deposition.


Immunological functions and in vivo cell-cell interactions of T cells in the spleen. The spleen is an important lymphoid organ, involved in immune responses against all types of antigen that appear in the circulation. Its complex anatomical organization, with distinct compartments containing specialized cell types, provides a microenvironment which allows different cell-cell interactions and determines the direction of developing immune responses. In this review we evaluate the vast amount of in vitro data dealing with antigen presentation, cell-cell interactions, T and B cell activation, and the immunoregulatory role of cytokines, as suggested to be involved in immune responses. As a basis for understanding of in vivo processes, these in vitro data will be related to discrete phenomena of in vivo immune responses, such as antigen localization/trapping, cell migration patterns of immunocompetent cells, cytokine production, and antibody formation in the different compartments of the spleen. Finally, we try to bring order to the sequence of events that occur in the spleen after antigenic challenge by presenting an in vivo model for T cell dependent and T cell independent immune responses.


Immunological functions of splenic B-lymphocytes. The spleen is a key lymphoid organ for generating B-lymphocyte (B cell)-mediated humoral immunity. This review examines the key features and functions of splenic B cells. Splenic B cell subsets, including virgin, memory, and CD5+ B cells, are characterized by their phenotypic markers and functions. Structural aspects of the spleen, including red pulp, follicles, periarterial lymphoid sheaths (PALS), and germinal centers, are related to the B cells localized in these areas. The migratory behavior of B cells in these splenic compartments is considered in the context of antigen exposure, adhesion molecules, and migratory stimuli. Antigen-specific B cells in the spleen are examined with an emphasis on their in situ characteristics assessed by immunocytochemical methods. This includes the detection of antigen-binding antibody-forming cells (AFC), idiotype-producing AFC, and the application of computer-aided imaging to analyze these cells. Interactions between splenic B cells and other cell types, such as T-lymphocytes (T cells) and antigen-processing/presenting cells like macrophages and dendritic cells, are briefly examined. Cytokines that influence splenic B cells are reviewed. Interactions between B cells and the neuroendocrine system are discussed briefly. The functions of splenic B cells are considered. Antibody production, cytokine synthesis, and potential immunoregulatory activities are considered.


Morphogenesis of human immunodeficiency virus type 1. Human immunodeficiency virus (HIV) has been implicated as the etiologic agent of acquired immunodeficiency syndrome and is a member of the sub-family Lentivirinae within the family Retroviridae. HIV type 1 (HIV-1) contains three major genes, gag, pol and env, which code for (1) core proteins, (2) a protease, reverse transcriptase and integrase, and (3) envelope glycoproteins, respectively. The core proteins p17, p24 and p15 are derived from gag precursor, p55, by endoproteolytic cleavage. The two nucleic-acid-binding proteins p7 and p9 are synthesized from p15 by proteolytic cleavage. These two structural proteins are apparently needed for the ribonucleoprotein-core formation. The envelope glycoproteins gp120 and gp41 (gp120-gp41 complex) are also generated by cleavage env precursors, gp160. The assembly of HIV-1 particles, like other retroviruses, appears to involve the association of the env precursor gp160 with the gag proteins. There are several factors which influence the assembly and budding process of HIV-1. In this article, we describe important events in HIV-1 morphogenesis and factors which influence this aspect of the HIV-1 life cycle.


Immunological characteristics of the putative CD4-binding site of the HIV-1 envelope protein. As an extension of previous studies demonstrating the immunosuppressive properties of gp120, we have analyzed the immunological characteristics of gp120 peptides, derived principally from its putative CD4-binding site. Our studies indicate that peptides derived from this region do not stimulate proliferation of lymphocytes from HIV-seropositive donors with relatively normal numbers of CD4+ lymphocytes. No significant proliferation was observed in response to various concentrations of peptide, even in the presence of interleukin-2 (IL-2). Significant proliferation of these lymphocytes was observed in response to two recall antigens, cytomegalovirus (CMV) and tetanus toxoid (TT), and these responses were augmented by IL-2. Peripheral blood mononuclear cells from HIV-seronegative donors were cultured in the presence of TT and CMV and the peptides derived from gp120. Proliferation in the presence of these recall antigens was inhibited by these peptides in a dose-dependent manner. These studies demonstrate that at high concentrations, peptides from the putative CD4-binding site can inhibit proliferation of lymphocytes from normal donors in response to a recall antigen. The apparent immunosuppressive properties of this region highlight the pathogenic role played by HIV-1 envelope protein interactions with host cells.


Regulated expression of human immunodeficiency virus type 1 in human glial cells: induction of dormant virus. Human neural cells are susceptible to infection with human immunodeficiency virus type 1 (HIV-1) in vitro; however, virus replication in these cells is strongly restricted. To understand the mechanism of this restriction, we examined the regulation of HIV-1 expression in glial cell cultures expressing high levels of HIV-1 after transfection of infectious viral DNA and selection. In all cases, high HIV-1 expression declined to low basal levels within 4-8 weeks of cultivation. The decrease in HIV-1 protein production wa paralleled by the decline in the relative levels of the 9.2-, 4.3- and 1.8-kilobase HIV-1 transcripts, but not by significant loss of HIV-1 DNA. Analysis of one long-term cell culture revealed 5 full-length unrearranged HIV-1 DNA copies per cell, but no viral transcripts on Northern blots, and minimal production of infectious virus. HIV-1 replication in these cells was markedly augmented by treatment with sodium butyrate (Na But) and to a lesser extent by 5-azacytidine, dibutyryl AMP and human herpes virus type 6. The virus induced by Na But was infectious. Transient expression assays revealed that Na But was more effective than phorbol myristate acetate in increasing the HIV-1 promoter activity in glial cells. Thus, one phase where glial cells can limit HIV infection is the expression of viral RNA from stable HIV provirus. However, such provirus remains responsive to inductive signals and may be activated to produce infectious HIV.


Synthetic cyclodextrin derivatives inhibit HIV infection in vitro. The AIDS pandemic has stimulated the search for safe potent antiviral agents. To date, only AZT has been approved as a therapeutic agent for the treatment of HIV infection. It is likely that a large number of antiviral compounds would be necessary to control a life-long infection. We have utilized the rigid structure of the cyclodextrin molecule to determine the minimal components necessary for anti-HIV activity. Utilizing this targeted approach to drug design, we demonstrate the antiviral effects of candidate compounds from the family of cyclodextrins. We report that polysulfated cyclodextrins mediate significant anti-HIV effects which include blocking infectivity and syncytia formation mediated by the HIV viruses. Several other substituted forms of cyclodextrins did not mediate significant antiviral effects. Further results demonstrate that the polysulfated cyclodextrins mediated no specific antiviral effects against already infected human cells. These results demonstrate that the antiviral activities of this class of compounds are centered around early events in the viral life cycle. These in vitro results suggest that such molecules may be of importance in antiretroviral therapeutic regimes.


Human immunodeficiency virus type 1 tropism for human macrophages. Human immunodeficiency virus (HIV) infects cells of the monocyte/macrophage lineage in addition to lymphocytes, and infection of these cells may be responsible for viral persistence and dissemination, encephalopathy of the acquired immunodeficiency syndrome and other sequelae of HIV infection. We have developed an in vitro model utilizing peripheral-blood monocyte-derived macrophages to study HIV-1 infection of macrophages. HIV-1 isolates vary greatly in their ability to infect and replicate in macrophages, from highly restricted to highly productive infection. Productively infected macrophages undergo syncytium formation but remain viable in culture and support sustained levels of virus production for prolonged periods. Transformed monocytoid and lymphoid cell lines, however, show very different patterns of permissiveness for HIV-1 strains and do not reflect their corresponding primary cell types in studies of host cell tropism. Studies on viral entry show that the CD4 molecule, known to be the HIV receptor on lymphoid cells, is expressed at low levels on the surface of macrophages as well, where it functions as the receptor for viral entry. Therefore, differential host cell tropism does not result from the use of an alternative macrophage-specific receptor instead of CD4.


Regulation of HIV-1 gene expression by cellular transcription factors. The human CD4+ T lymphocytes in the peripheral blood represent a major target for HIV-1 infection in vivo. In the quiescent state T lymphocytes are nonpermissive for the propagation of HIV-1. Antigenic or mitogenic stimulation of T lymphocytes triggers a cascade of biochemical events that lead to cellular proliferation and activation of transcription and replication of HIV-1. Transcription of HIV-1 provirus in infected T cells is regulated by the interaction of both viral proteins and cellular transcription factors with the viral long terminal repeat (LTR) sequences. HIV-1 LTR has been shown to contain recognition sequences for many cellular transcription factors. These include both positive and negative regulatory factors. Interplay of cellular proteins involve both the upstream and downstream regions of the viral LTR. Our full understanding of the transcriptional regulation of HIV-1 provirus will require isolation and characterization of each of these cellular factors which bind to the HIV-1 LTR. Mutational analyses of HIV-1 LTR indicate that not all these various cellular factors are absolutely essential for the regulation of LTR-mediated viral gene expression, but their presence or absence may determine the course of HIV-1 replication in the infected cells. A balance between the inhibitory host transcription factors and the stimulatory cellular and/or viral protein factors possibly determine the final consequence of HIV-1 replication and pathogenesis.


Viral determinants of cellular tropism.

Viral determinants of cellular tropism. Cells of mononuclear phagocyte lineage are the predominant cell type producing human immunodeficiency virus type 1 (HIV-1) in extravascular tissues; HIV-1 infection of mononuclear phagocytes may be directly related to primary disease manifestations and also appears to contribute to the immune deficiency of AIDS. Whereas peripheral blood lymphocytes are permissive for nearly all strains of HIV-1, only some HIV-1 strains replicate efficiently in mononuclear phagocytes. Recombinant virus strains have been used to identify a 157-amino acid region of gp120 that can confer macrophage tropism. This region is distinct from the principal CD4 binding domain of gp120 and includes the major type-specific neutralizing epitope located in the third hypervariable domain, V3. Quantitative assay of HIV-1-specific DNA by polymerase chain reaction early after infection suggests that HIV-1 strain differences in macrophage tropism are determined at the level of entry. These studies suggest that target cell interactions with gp120 in addition to or in conjunction with the CD4 binding domain are necessary for efficient entry into mononuclear phagocytes.


Analysis of the viral determinants underlying replication kinetics and cellular tropism of human immunodeficiency virus. Human immunodeficiency viruses (HIVs) isolated from infected individuals show genetic and biological diversity. To delineate the genetic determinants underlying specific biological characteristics such as rate of replication and cellular tropism, generation of hybrid HIV using viruses which exhibit distinct biological feature is essential. We have used three different infectious HIV proviral DNAs, designated pZ6, pHXB2 and pARV, derived from HIVZr6, HIVHTLV-IIIB and HIVSF-2 strains, respectively, to construct hybrid HIV. Proviral DNAs differed in their ability to direct the synthesis of viral particles upon transfection into cells and the viruses derived from the molecular clones exhibited different cellular tropism. Three different methods were utilized to generate hybrid HIV, including construction of hybrid proviral DNA using molecular techniques, intracellular ligation of viral DNA fragments and the homologous recombination approach. The chimeric proviral DNAs with exchanges involving only the long terminal repeat (LTR) region indicated that LTR does not exert influence on the overall level of virus production despite extensive differences in the U3 region of the LTR. Regarding the cellular tropism of HIV, the virus derived from pHXB2 productively infected CEMx174 cells. On the other hand, pARV-derived virus did not show productive infection of CEMx174 cells. The hybrid HIV containing the 3'-end of the genome from pARV and the 5'-end of the genome from pHXB2 was effective in infecting CEMx174 cells. However, the converse hybrid containing the 5'-pARV and the 3'-pHXB2 was not effective in infecting CEMx174 cells. These results suggest that differences in the genes outside of env and nef may play a role in the ability of virus to infect a certain cell type.


The role of monocyte/macrophages and cytokines in the pathogenesis of HIV infection. The monocyte/macrophage system, which is characterized by a high degree of heterogeneity, is a target of the human immunodeficiency virus (HIV) in vitro as well as in vivo. Both bone-marrow-derived precursor elements and circulating monocytes are infectable in vitro and have also been found infected in seropositive individuals. However, terminally differentiated macrophages are the most commonly infected cells found in vivo in addition to the CD4+ T lymphocytes. Several immunoregulatory cytokines have been shown to either up-regulate or suppress virus replication/expression in vitro in cells belonging to the monocyte/macrophage lineage by affecting both transcriptional as well as posttranscriptional events. The observation that elevated levels of several of these cytokines are present in HIV-infected individuals suggests that they may play an important role as regulators of virus expression in vivo.


Evolutionary origins of the transforming growth factor-beta gene family. A molecular phylogeny for the transforming growth factor-beta (TGF-beta) gene family based on a comparison of nucleotide sequences is proposed. A phylogenetic tree constructed from these sequences shows that the family evolved from a common ancestral gene that came into existence at about the time of arthropod and chordate divergence. This model suggests that the present day TGF-beta gene family consists of four members: TGF-beta 1 (= TGF-beta 4), TGF-beta 2, TGF-beta 3, and TGF-beta 5. The molecular phylogeny and Southern hybridization data also suggest that the proteins for mammalian TGF-beta 1 and chicken TGF-beta 4 are the products of homologous rather than duplicated genes. If the gene duplication event that produced the ancestral gene for TGF-beta 1 occurred before the divergence of birds and mammals, then sufficient time would have elapsed to generate these quite distinct avian and mammalian TGF-beta 1 proteins. Therefore, the TGF-beta family contains four distinct proteins, TGF-beta 1, 2, 3, and 5.


cDNA cloning and sequence analysis of beta ig-h3, a novel gene induced in a human adenocarcinoma cell line after treatment with transforming growth factor-beta. Transforming growth factor-beta (TGF-beta) is capable of affecting the proliferation of many cell types. To identify novel genes whose protein products may mediate cellular responses to this factor, a cDNA library was made from mRNA isolated from a human lung adenocarcinoma cell line (A549) that had been treated for 3 days with TGF-beta. The library was screened by differential hybridization and a cDNA clone, beta ig-h3, was isolated. This gene was induced up to 20-fold in A549 cells after 2 days of treatment with TGF-beta 1. It was also induced in several other cell lines, including PC-3 and H2981. DNA sequence analysis of beta ig-h3 indicated that it encoded a novel protein, beta IG-H3, of 683 amino acids, which contained an amino-terminal secretory sequence and a carboxy-terminal Arg-Gly-Asp (RGD) sequence that can serve as a ligand recognition site for several integrins. beta IG-H3 also contained short amino acid regions homologous to similar regions in Drosophila fasciclin-I and four homologous internal domains, which can be folded into a potential bivalent structure and could act as a bridge between cells expressing the appropriate ligand. beta ig-h3 RNA was detected in several cell lines and tissues. COS cells transfected with plasmids encoding beta IG-H3 secreted a major 68-kD protein that was detected by immunoblotting using antipeptide antibodies. Since beta ig-h3 is induced in several cell lines whose proliferation is affected by TGF-beta 1, it may be involved in mediating some of the signals of this multifunctional growth modulator.


Molecular cloning and characterization of a novel Rel/NF-kappa B family member displaying structural and functional homology to NF-kappa B p50/p105. The NF-kappa B transcription factor has been implicated in the inducible expression of many genes, including inflammatory, immune, and acute-phase response genes. NF-kappa B consists of two subunits, 50K and 65K polypeptides. The genes encoding p50 and p65 have sequence similarities with the c-rel proto-oncogene and the Drosophila maternal effect gene dorsal. We describe the cloning and characterization of a novel rel-related gene encoding a 98K product that shares extensive homology with the p105 precursor of the NF-kappa B p50 protein, containing both a Rel homology and SWI6/ankyrin repeat domain. We demonstrate that p98 is proteolytically processed in vivo to generate a 55K polypeptide, which binds to kappa B sites. p55 is capable of forming heterocomplexes with other Rel/NF-kappa B family members, which can bind to kappa B motifs in vitro, and stimulate transcription of reporter genes containing these cis-elements in vivo. The identification of a homolog for NF-kappa B p50/p105, termed p55/p98, gives further support to the idea that NF-kappa B is a collection of structurally related complexes of which contribute to the pleiotropic regulatory processes originally assigned to NF-kappa B.


The retinoblastoma protein region required for interaction with the E2F transcription factor includes the T/E1A binding and carboxy-terminal sequences. Recent experiments in understanding the mechanism of the retinoblastoma protein (RB) function have revealed the existence of several cellular proteins that are complexed with RB. One of these cellular proteins is the E2F transcription factor, which was originally identified due to its inducibility by E1A during an adenovirus infection. The E2F recognition sequence is found in the promoters of several cellular genes involved in growth control, including several oncogenes. In this report, we provide evidence that the interaction of E2F and RB is mediated through a region on RB where viral oncogenes such as SV40 T antigen and adenovirus E1A bind and where tumorigenic mutations also cluster. Additional carboxy-terminal sequences are also required for the interaction with E2F. These observations provide evidence for a direct connection between tumor suppressor function and the gene expression program leading to cellular growth regulation.


Insulin-producing cells contain a cell-specific repressor activity that functions through multiple E-box sequences. The cis-acting DNA element known as the E box (consensus sequence CAxxTG) plays an important role in the transcription of a number of cell-specifically expressed genes. The rat insulin I gene, for example, contains two such sequences (IEB1 and IEB2) that are recognized specifically by a characteristic beta cell nuclear factor insulin enhancer factor 1 (IEF1). To define the role of these elements better, we tested for cooperative interactions between the IEB sequences. Transfection experiments were performed with a series of plasmids containing the elements separated by different distances. Transcriptional activity in vivo is only modestly affected (less than two-fold) when the distances between the IEB elements are changed by a half-integral number of double-helical turns. Surprisingly, plasmids bearing four and six copies of the IEB motif showed sharply reduced activity as compared to those with two copies. In vitro DNA-binding studies revealed that this effect was not due to inability of IEF1 to bind to multiple copies of IEB. Moreover, multiple copies of the IEB sequence were able to inhibit activity of a cis-linked Moloney sarcoma virus (MSV) or insulin enhancer upon transfection to beta cells but not to other cell types. The above data are consistent with the view that beta cells contain a cell-specific repressor molecule capable of binding to multiple copies of IEB and thereby inhibiting transcription. This interpretation was further strengthened by in vivo competition and trans-activation experiments. The beta-cell-specific repressor activity identified by these studies may play an important role in mediating gene expression in insulin-producing cells, perhaps by regulating the access of helix-loop-helix transcription factors to E-box sequence elements.


The down-regulation of albumin transcription during regeneration is due to the loss of HNF-1 and the D-site transcription factors. Liver regeneration has served as an important in vivo model for studying the control of differentiation. The molecular mechanisms responsible for the negative regulation of the albumin promoter during regeneration have not been examined previously. Changes in the proteins interacting with the albumin promoter were characterized using nuclear extracts prepared from the livers of rats undergoing chemically induced regeneration. Reduction in the activities of both hepatocyte nuclear factor-1 (HNF-1) and factors binding to the D site are responsible for the loss of albumin transcription during regeneration. No evidence for the involvement of a transcriptional repressor in this process was found.


A pink bacterium as a reporter system signaling expression of a recombinant protein. We describe a set of expression vectors, pEX-PINK/0-3, for high-level production of (un)fused target proteins. The vectors incorporate a 'pink' reporter element, which signals in vivo the expression status of a target gene. A target sequence is cloned between the lambda PL promoter and the downstream mammalian cytochrome b5 gene. Thermo-induction drives transcription of a dicistronic mRNA from which the target protein and cytochrome b5 are independently and concurrently synthesized. Positive expression is indicated by visual transformation of bacteria from a grey/translucent to a bright pink color derived from tandemly expressed holocytochrome b5. The signal can be monitored in vivo spectrophotometrically.


Isolation of a yeast gene encoding a protein homologous to the human Tat-binding protein TBP-1. We have cloned a putative yeast homolog of the gene encoding the human Tat-binding protein, TBP-1. The gene termed TBPY encodes a 45,243-dalton protein displaying a heptad repeat of hydrophobic amino acids reminiscent of a leucine zipper. Secondary structure predictions suggest the possibility of formation of an amphipathic helix that could further be organized into a coiled-coil. Additionally, the protein product of TBPY shows amino acid signatures characteristic of a large family of RNA and DNA helicases. We propose that the hydrophobic region of yTBP-1 participates in self-dimerization or heterodimerization.


Two mRNAs are transcribed from the human gene for choline acetyltransferase. The product of the choline acetyltransferase (ChAT) gene is the enzyme that synthesizes the neurotransmitter acetylcholine. A 14.4-kb portion of the human ChAT gene contains 7 exons, which are estimated to comprise approximately one-third of the human protein coding sequence by comparison with porcine ChAT mRNA. Two of the exons were used to identify polyadenylated human ChAT gene transcripts on Northern blots. An exon with 84% identity to the region of porcine ChAT mRNA that codes for the amino terminus of the corresponding protein detected 6,000- and 2,300-nucleotide mRNAs in RNA isolated from human CHP134 neuroblastoma cells. Only the 2,300-nucleotide mRNA was detected by a second probe containing an exon with 96% identity to porcine ChAT mRNA in the domain that encodes amino acids 204-263 of the predicted porcine ChAT protein. Further evidence that two species of human mRNA are produced from the human ChAT gene was obtained from nuclease protection assays using an antisense RNA probe prepared from a human ChAT cDNA clone. Total RNA isolated from either CHP134 cells or adult human nucleus basalis protected 525- and 400-nucleotide fragments of this probe, confirming the presence of two species of RNA that differ by the inclusion of an internal exon. cDNA clones of each of these transcripts have been isolated. Their sequences suggest that the 2,300-nucleotide mRNA encodes enzymatically active human ChAT, while translation of the 6,000-nucleotide mRNA would be terminated prematurely by a shift in the reading frame. These results indicate that a complex pattern of transcription produces two mRNAs with different coding potentials from the human ChAT gene.


The isolation of evolutionarily conserved Eag I end-clones from mouse chromosome 17 using cloned DNA. To isolate DNA markers from mouse chromosome 17, a genomic phage library was constructed from the mouse-hamster CMGT cell hybrid RcE-B52. This hybrid contains a chromosomal fragment from the distal end/flanking region of the t complex on mouse chromosome 17. Recombinants of mouse origin were identified by using a panel of mouse-specific repetitive sequences as a probe. A total of 1,500 mouse phage recombinants were isolated. These were found to represent 250-300 individual recombinants, comprising about 4 Mbp of cloned mouse DNA. The pooled mouse recombinant phages were used to construct an Eag I end-library. This was achieved by the specific insertion of a marker plasmid in Eag I recognition sites when present in the mouse inserts of the recombinant phages. The Eag I end-fragments were subsequently subcloned using a simple procedure taking advantage of the inserted plasmid. A total of 56 individual Eag I end-fragments were identified. These were found to contain recognition sites for rare cutting enzymes at high frequency. A large proportion (73%) were found to be evolutionarily conserved in human DNA. Furthermore, a significant fraction of these fragments, two of six tested, appears to detect specific cDNAs in a 8.5-day mouse embryo cDNA library.


Immunoelectron microscopic detection of the hepatitis B virus major surface protein in dilated perinuclear membranes of yeast cells. The major surface protein of hepatitis B virus produced in Saccharomyces cerevisiae can be recovered from cell lysates in the form of 22-mm lipoprotein particles. Immunoelectron microscopy was applied to investigate site and time of particle assembly. Thin sections of yeast cells revealed that production of the S protein provoked a dilation of the endoplasmic reticulum. Dilated areas were specifically labeled with a polyclonal antibody raised against glutaraldehyde-treated yeast-derived HBsAg particles. In contrast to previous postulates of particle formation during cell lysis and extract preparation, these results suggest that particle formation in yeast occurs in the endoplasmic reticulum and that transport of particles along the secretion pathway is blocked.


Direct PCR sequencing of dystrophin polymorphic CACA alleles after purification to remove shadow bands. A method is described that allows the sequencing of polymerase chain reaction (PCR) products containing CACA repeats. The method was tested using a DNA polymorphism that exists at the 3' end of the dystrophin gene. This polymorphism consists of a variation in the length of a CACA dinucleotide repeat. Four alleles from a total of 16 individuals were sequenced at this locus after the DNA sequence had been amplified by the PCR. Five examples of each of the common alleles were sequenced. For each allele all five sequences were the same. The only example of a rare allele was also sequenced. The PCR products of DNA sequences containing dinucleotide repeats consist of a number of bands differing by 2 bp below the most intense main band. Previously, direct sequencing of the PCR products lead to ambiguities and smearing at and above the CACA repeat. In this paper, the main PCR band was cut out of a sequencing gel and directly sequenced to give a clear DNA sequence. Our results indicate that for a particular allele, all individuals had exactly the same DNA sequence. This implies that with the appropriate choice of oligonucleotide primers, polymorphisms could be detected without electrophoresis.


Cytochrome P-455 nm complex formation in the metabolism of phenylalkylamines. XIII. Enzyme interactions with a series of beta-alkyl-substituted 2-phenylethanamines and corresponding N-hydroxylamines. The formation of Metabolic Intermediate (MI) complexes from a series of beta-alkylsubstituted 2-phenylethanamines and corresponding N-hydroxylamines is investigated during NADPH-dependent metabolism in liver microsomes from phenobarbital pretreated rats. The beta-alkyl substituents are methyl, dimethyl, ethyl, di-ethyl, n-propyl, di-n-propyl and i-propyl groups. The amines are synthesized by LiAlH4-reduction of the corresponding nitriles, which are prepared through alkylation of the enolate anion of phenylacetonitrile. The hydroxylamines are prepared either by oxidation of the corresponding benzylimines with m-chloroperbenzoic acid and subsequent hydrolysis of the initially formed 3-phenyloxaziridines, or by H2O2-mediated oxidation of the corresponding amines in the presence of catalytic amounts of sodium tungstate, followed by reduction with cyanoborohydride. The amines are found to be completely devoid of complexing activity, while the hydroxylamines form the MI complex at high rates. Complex formation from these substrates thus parallels the known behaviour of 2-phenylethanamine and its corresponding N-hydroxylamine. Since N-oxygenation is known to be a prerequisite for MI complex formation from amines our results suggest that the beta-alkylated 2-phenylethanamines are metabolized exclusively through other pathways. In accordance with this hypothesis, capillary GC-analysis of the incubation mixture of 2-phenylpropanamine shows no formation of N-hydroxylated metabolites; only 2-phenylpropanol, a metabolite formed through the deamination pathway, is found.


A quantitative structure-activity relationship for some dopamine D2 antagonists of benzamide type. A quantitative structure-activity relationship (QSAR) for some 6-methoxybenzamides having 1-ethyl-2-pyrrolidinylmethyl side chains with respect to the inhibition of [3H]spiperone binding is established using the PLS method. An experimental design approach to select the training set compounds is demonstrated. The established relationship between structure and in vitro activity indicates the dominating influence of the substituents in the 3-position as well as the importance of (S)-configuration in the side chain. A methoxy substituent in the 5-position is also beneficiary for high activity. Both salicylamides and non-salicylamides could be accommodated in the analysis, which supports the notion of a common binding site in the receptor.


Investigation of the applicability of a tensile testing machine for measuring mucoadhesive strength. The applicability of a tensile testing machine (M30K, JJ Lloyd Instruments Ltd, GB) is investigated for measuring mucoadhesive strengths. A sample of an aqueous dispersion of a polymer with expected mucoadhesive properties is placed between two homemade discs of polyoxymethylene. The upper disc is mounted on a movable part of the machine while the lower disc is fixed on the stationary frame. A tensile force is submitted and the maximum detachment force at fracture and the adhesion work are estimated from the force displacement curve recorded. In some experiments, native mucous tissue of the large intestine of pigs was glued to the upper disc. Four polymers polycarbophil (Carbopol EX-55), carboxypolymethylene (Carbopol 934P), hydroxypropylmethylcellulose (Methocel K4M), and sodium alginate, are used in five different concentrations. At least three measurements are made of each polymer and concentration. Viscosity and osmolality are determined. By standardizing the time of sample equilibration and the run rate before measurement, it is possible to get good reproducibility of the tensile values. Based on the maximum nominal breaking force and the work consumed, it is concluded that the tensile strength is dependent both on the concentration and the type of polymer. The conclusions are the same independent of whether mucous pig tissue is used, or not. The same rank order in adhesive properties of the polymers is achieved as from using modified surface tensiometers.


Bioassay-guided isolation of serotonin from fruits of Solanum tuberosum L. An ethanol extract of the fruits of Solanum tuberosum was partitioned between water and petroleum ether. The aqueous fraction had contractive effect on the isolated guinea-pig ileum. Chromatography of this fraction on Sephadex LH-20 and silica gel was monitored by the guinea-pig ileum test and resulted in isolation of serotonin. HPLC analysis of the content of serotonin in fruits, leaves and tubers of the plant, showed that the fruits and leaves contained 7.5 micrograms and 2 micrograms, respectively, of serotonin/g fresh weight. In agreement with previous observations, no serotonin was detected in the tubers.


Synthesis and antihypertensive activity of imidazo[2,1-b]-thiazoles bearing a 2,6-dichlorophenyl group. A number of imidazo[2,1-b]thiazoles bearing a 2,6-dichlorophenyl group as hydrazone or as amide were prepared and tested in rats as antihypertensive agents. Only compounds bearing a chlorine at position 6 were active.


[Overview of HIV infections in pediatric population]. A general overview of HIV infection/AIDS in the pediatric population, in Mexico, is provided. The principal categories of transmission in our country are: 45.5% perinatal, 44.0% following transfusion for hemophilia or for other reasons, and less frequently sexual transmission. In the United States and Europe, similar patterns are seen with perinatal transmission being the most important route, at higher percentages than ours. The number of cases of HIV infection in children continues to grow worldwide, primarily reflecting the problem in the adult population.


[Central nervous system pathology in children with AIDS]. The neuropathological manifestations of AIDS in children vary widely and includes, among others: cerebral atrophy, basal ganglia calcification, corticospinal tract demyelinization, and HIV encephalomyelitis with multinucleated cells. The purpose of this work is to inform the postmortem CNS findings in 14 pediatric AIDS patients which were studied from January 1986 to February 1992, at the Hospital Infantil de México Federico Gómez. Basal ganglia vascular calcification, HIV multinucleated cells, and corticospinal tract demyelinization, were significantly less frequent (P < 0.01) in our patients than those informed in the literature. Opportunistic CNS infections found in our patients were produced by microorganisms commonly described in adults. We think that these differences may be explained because the majority of our patients acquired the infection trough blood transfusion at an age in which the CNS is fully developed. The pattern of HIV transmission in our country has been changing recently with an increase in the number of perinatal cases. We also think that in the near future we will observe a change in the neuropathological findings of our pediatric AIDS population.


[Neurologic manifestations in pediatric patients with AIDS]. Since the first cases of childhood AIDS were reported, the neurological involvement has been more frequently recognized. Several motor, intellectual and conductual changes as well as unexplained abnormalities have been described due to CNS infections. Findings have shown HIV to affect the CNS although it is unknown as to when the viral invasion actually occurs. This report describes the neurological manifestations found in pediatric patients with HIV infection at the Hospital Infantil de Mexico and their correlations with CT scans, EEGs, auditory evoked potentials, I.Q.s and postmortem findings. The medical records of 60 symptomatic HIV infected children, stages P0 to P2, are reviewed. Neurological abnormalities were found in 51 patients, 20 of which (39.2%) were due to perinatal infection with symptoms starting, on the average at 11 months 7 days (from the initial contact) taking into consideration in utero exposure. Nine cases (17.6%) were patients infected through transfusions with symptoms appearing on the average at 24 months 8 days; 2 cases (3.9%) were of unknown origin. The CT scans, EEGs and psychometric evaluations of the HIV infected patients correlated well with the clinical findings.


[AIDS in children. Experience at the National Institute of Pediatrics]. We describe retrospectively the experience with 44 cases of AIDS from January 1987 to October 1991 at the Instituto Nacional de Pediatria, a tertiary care children hospital in Mexico City. All patients with 2 ELISA and a positive Western Blot test were included. Thirty three patients were infected perinatally (75%) and 11 through blood transfusion (25%). Fourty one patients belonged to the P2 classification of the Centers for Disease Control. Chronic diarrhea (77%), lymphadenopathy (75%), hepatomegaly/splenomegaly (70%) and oral candidiasis (61%) were the most common clinical findings. Twenty patients died (45.4%). No statistical relation were found between survival rate and the way of transmission and age at onset. Autopsy was performed in 14 patients and revealed a sharp decrease of lymphoid tissue at all levels with severe thymic atrophy.


[Perinatal transmission of AIDS. Experience at the National Institute of Perinatology]. From January 1989 to February 1992, 19 pregnant women infected with human immunodeficiency virus (HIV) were attended at the Instituto Nacional de Perinatologia in Mexico City, all of them at the end of pregnancy as well as 15 of their offspring. Sexual transmission was found in 15 patients; the initial classification of 16 was CDC II, only one case with AIDS, and during pregnancy 2 cases changed their clinical status. Absolute CD4 count in 2 cases was lower 20%, None of 10 had positive VDRL and one case showed a positive PPD. All neonates were at term and eutrophics. During their first 3 months of life, 2 had an infectious disease and died. The serologic follow-up at the moment reports 3 having HIV infection (20%), 3 no HIV infection and 9 in study are sero-positive.


[AIDS in children. 8 years experience at La Raza Medical Center Infectology Hospital, Mexican Social Security Institute]. The objective for this work was to describe the transmission mechanisms and the clinical behavior of 60 HIV-infected pediatric patients. We studied children from newborn to 15 years old according to the CDC criteria. From January 1985 to February 1992, were evaluated 60 patients, 40 males and 20 females; 25 with perinatal transmission (23 transplacental and 2 breast-feeding), 22 hemophiliacs, 12 by blood transfusion and 1 by intramuscular injection with contaminated needle. The disease was symptomatic in 50 patients, asymptomatic in 5 and indeterminate in 5 cases. Up to date, 28 children are in phase P2, 10 in P0 and P1, and 22 patients have died. The clinical manifestations in 50 patients were: altered growth and development in 50, generalized lymphadenopathy in 30, severe infections in 23, fever in 15, hepatosplenomegaly in 15, chronic diarrhea in 10, and HIV-encephalopathy in one. It is concluded what at present time perinatal transmission is the main mechanism.


[Bacterial infections in children with AIDS]. The importance of bacterial infections in children with AIDS was emphasized when they were included within the CDC classification system for children under 13 years of age infected with the HIV. The information available in Mexico on frequency, types of infections and causative agents is scarce. In this study, the frequency and microbiology of bacterial infections in children with AIDS seen at the Hospital Infantil de Mexico Federico Gomez is reported. From September 1985 to December 1991, we found 72 HIV infected children, 6 were classified P0, 6 as asymptomatic (P1) and 60 as symptomatic infections (P2). From this last group, 50 were secondarily infected with bacteria; there was a total of 129 episodes of bacterial infections, averaging 2.5 episodes per patient. Respiratory infections were the most frequent (74.41%), followed by septicemia (10.07%), skin and underlying tissue infections (6.96%) and urinary tract infections (6.17%). Infections of the CNS and deep abscesses were less frequent. Overall mortality rate was 76%, however only in 18 children (36%) was it directly attributed to the bacterial infections. Etiology was documented in 46 episodes (33.65%) of which 30 (65.31%) were gram-negative bacteria and 16 (34.78%) were gram-positive. The best possible methodology must be used for the etiologic diagnosis of bacterial infections in children with AIDS in order to select the most appropriate treatment for severe or recurrent bacterial infections.


[Oral manifestations in HIV positive children]. Oral manifestations of HIV infection in children include oral candidiasis, herpetic stomatitis, oral hairy leukoplakia, parotid gland swelling, and other bacterial, viral and mycotic infections. The frequency and natural history of those disorders are not fully defined. The purpose of this work is to inform the oral findings in 57 HIV infected children studied at the Hospital Infantil de Mexico. All 57 patients presented nonspecific gingivitis; however it was not feasible to associate it with the HIV infection; in 28 oral candidiasis was observed, and in 3 cases herpetic stomatitis was documented. Oral candidiasis was found regardless the patient's sex, age, clinical stage, treatment, and mode of transmission of the HIV infection. It has been considered that oral candidiasis is a good marker of immunodeficiency; however, in our patients this correlation was not observed. Also, other HIV-associated oral manifestations were not observed in these cases. The severity and rapid clinical course presented by our patients, may explain both, the lack of correlation between candidiasis and immunodeficiency as well as the absence of other lesions.


[Nephrotic syndrome associated with AIDS in children]. Several renal and renal-related disturbances have been described in patients with AIDS (acquired immune deficiency syndrome), in adults and children as well. These are mainly electrolyte and acid-base imbalance, acute renal failure and nephrotic syndrome. The latter is usually steroid non-responder. The renal histopathological lesions described more commonly are minimal change, mesangial hyperplasia and focal segmental glomerulosclerosis. Herein, we describe a 5 year-old with AIDS, that developed nephrotic syndrome, characterized by edema, ascites, hypoalbuminemia and massive proteinuria. A percutaneous renal biopsy showed mesangial proliferation. She did not respond to a 6 week treatment with prednisone. She died with sepsis after several viral and bacterial infections.


[Coronary arteriopathy associated with cardiomyopathy in an adolescent with AIDS]. The purpose of this paper is to inform the case of a 15 years old male patient who died as a consequence of acquired immunodeficiency syndrome (AIDS) complications. The postmortem examination showed a coronary lesion which, to the best of our knowledge, has not been previously described. This vasculopathy was restricted to the coronary arteries; myocardial changes similar to those described in AIDS-associated dilated cardiomyopathy were also present. The coronariopathy was indistinguishable from that described in the blood vessels of the brain in patients with AIDS-related cerebral arteriopathy. We also reviewed the autopsy material from another 14 children who died of AIDS, an in none of them exhibited similar changes in the coronary arteries. In addition we present the clinical findings and some theoretical considerations regarding the pathogenesis of the lesions.


[Health care worker relationship with HIV infected patients or AIDS patients]. The roll of the health care worker (HCW) providing care to HIV-infected patients or living with AIDS has became an important issue in the course of the epidemic, and has impacted the evolution of these patients. Diverse studies have shown that the acceptance of the HCW to care for these patients is related to the degree of education in regards to the subject. There is a positive correlation between knowledge about universal precautions and mechanisms of transmission with the willingness to care for HIV-infected patients. This review shows several studies that have been developed in order to assess the attitudes among HCW's toward HIV-infected patients and the phenomen HIV/AIDS as public health problem. In addition, political issues are discussed in regards to measure protection to HCW as well as HIV-infected patients.


[Medical facilities for women and children infected with HIV]. The phenomena HIV infection and acquired immunodeficiency syndrome (AIDS) among women and children is an important concern for underdeveloped and developing countries and has became a Public Health problem. The medical facilities required for care of these patients are special and demand a comprehensive approach and multidisciplinary team-work. In this way, the patients would receive adequate care for their needs. This review includes the antecedents of the HIV infection among women and children. Mechanisms of transmission, and the current model of medical care that exists in some developed countries. Finally, a commentary is made in regards to the importance of continuing medical education of the health-term in order to confront the AIDS epidemic.


[Do AIDS cases in adolescence really exist?]. Adolescents are a specific population group, with risk practices for the acquisition of sexually transmitted diseases. The Centers for Diseases Control consider the adolescents specific group ranging between 13-19 years and they reported, until September 1991 that 0.4% of global AIDS cases corresponded to this group. In Mexico, we did an analysis of the AIDS cases reported at AIDS Surveillance Committee until September 1991, and found that 1.4% of the global AIDS cases corresponded to adolescents. The AIDS transmission pattern in adolescents is different from adults and children. It is very important to classify adolescents as a specific group in health surveillance and to considered all the factors related to them for AIDS prevention strategies.


[Repercussions of blood transmission in the epidemiology of AIDS-HIV infection in Mexican children]. The first case of AIDS associated with contaminated blood products occurred in a child; with this 2 very important situations were recognized, firstly, the possibility of transmitting the disease through blood products, and secondly, that children are not exempt from acquiring the disease. Intimately related to transfusions of contaminated blood products are perinatal AIDS cases. With the measures set forth by the Mexican Government in order to prevent the transmission of HIV-1 through contaminated blood product, a decrease in cases of AIDS acquired through transfusions in expected in the near future. Not so for cases of perinatal AIDS, where educational campaigns directed towards women and high risk groups will have to be established.


The spectrum of leukomalacia using cranial ultrasound. The spectrum of leukomalacia using cranial ultrasound is discussed. Transient densities not evolving into cystic lesions may represent a mild degree of leukomalacia when persisting for at least a week. A unilateral parenchymal density may be due to bleeding into an ischaemic area, but can also be due to a venous infarction. Cystic leukomalacia can be confidently diagnosed using appropriate equipment and performing sequential scans. A distinction should be made between cysts in the periventricular white matter and cysts in the deep white matter, as the latter carries a higher risk for cerebral visual impairment. Careful ophthalmological examination of these infants will enable us to identify infants with cerebral visual impairment during the first few months of life, allowing the use of special programs aimed at promoting visual development.


Visual acuity of low- and high-risk neonates and acuity development during the first year. Binocular grating acuity of 65 neonates was measured using Teller acuity cards. At the time of testing, age corrected for prematurity ranged from -3 weeks to 2 weeks. On the basis of clinical data, serial ultrasound scans and EEG recording newborns were divided into 4 subgroups: fullterm low-risk (FLR, n = 22); preterm low-risk (PLR, n = 20); preterm medium-risk (PMR, n = 9) and preterm high-risk (PHR, n = 14). Mean visual acuity of PLR infants (0.86 cy/deg; S.D. 0.34 oct) was not significantly different from that of FLR newborns (0.80 cy/deg; S.D. 0.71 oct); the lower variability of the PLR infants might possibly be caused by their longer postnatal experience. Within the preterm groups, mean visual acuity of PLR newborns was found to be significantly higher than that of PMR (0.73 cy/deg; S.D. 0.26 oct) and PHR infants (0.73 cy/deg; S.D. 0.35 oct). This difference can not be explained by dissimilarities in postnatal or corrected age. Brain impairment, as documented by US scans and EEG recording could account for these findings. Longitudinal data are needed in order to substantiate these findings and correlate them with later neurological and neuro-imaging outcome. Preliminary results of an ongoing longitudinal study suggest acuity development of most, but not all, PHR infants, in whom a cystic-periventricular leukomalacia had been diagnosed, to be worse than that of low- and medium-risk infants.


Visual field and grating acuity development in low-risk preterm infants during the first 2 1/2 years after term. The effect of early visual experience on visual field size and grating acuity development was studied longitudinally in 36 appropriate for gestational age (AGA) and 26 small for gestational age (SGA) low-risk preterm infants. These were selected out of 194 very low birth weight (VLBW) infants (birthweight less than 1500 g) born in 1985 and 1986. Criteria for inclusion as low-risk were the absence of neurological, respiratory, circulatory and alimentary problems in the neonatal period; no retinopathy of prematurity and no evidence of abnormality on the neonatal cranial ultrasound scans. Binocular field sizes were assessed using kinetic arc perimetry. Binocular grating acuity was tested by means of the prototype version of the acuity card procedure. Results were compared with norms obtained in control fullterms in earlier studies. Infants were tested at 6 weeks, 6, 6, 9 and 12 months of age from the expected term date. Twenty-two of these infants were retested at 2 1/2 years of corrected age. Visual field size and visual acuity estimates of (both AGA and SGA) low-risk, VLBW preterms and control fullterms overlapped at all test ages, except for a slight but significantly faster development of the upper and the lower visual field at 6 weeks corrected age in the preterm group. These results indicate that for clinical purposes visual experience before the expected term date has not only no measurable effect on the normal development of behavioural acuity, but also no accelerating effect on the development of peripheral vision.


Visual segmentation of oriented textures by infants. The infant's visual system contains orientation-sensitive mechanisms from the first weeks of life. Differences in texture orientation can serve as a basis for rapid preattentive localization and segmentation in adults. We tested whether infants could use their orientation-sensitive mechanisms in the same way, by forced-choice preferential looking, using displays of line segments oriented at 45 degrees in a rectangular patch and 135 degrees in the surrounding region. Performance was compared with that for displays of similar elements with uniform orientation but with the patch defined by luminance contrast. Infants of 14-18 weeks old showed consistent preference for both orientation- and contrast-defined patches, indicating the ability to segment the field by orientation. Infants of 8-12 weeks performed comparably to the older infants on contrast-based segmentation but did not show a statistically significant preference with orientation-based segmentation. In a second experiment, preference was also tested for a region of mixed orientation versus a region of uniform orientation. The 14-18-week-olds did not show this preference, suggesting that their preference for the discrepant texture patch genuinely reflected texture segmentation and not simply the presence of two different orientations on one side of the display. The results are discussed in terms of the possible maturation of intracortical connections subserving texture grouping and segmentation.


Texture segregation in infants and children. Segregation of textures based on differences in line orientation and blob size was tested in adults, infants and children, with a forced-choice preferential looking technique. Preference for a figure defined by differences in blob size already occurs in 2-month-old infants. In contrast, preference for a figure differing from the background by the orientation of its elements emerges at the end of the first year of life and becomes adult-like by school age.


The Rotterdam C-chart: norm values for visual acuity and interocular differences in 5-year-old children. Common C-charts are often not suitable for developmental studies and assessment of visual acuity in young and visual impaired children, because of unequal steps between lines, uncomparable crowding, inadequate number of large optotypes on the first line and ceiling effects. Therefore a new C-chart (the Rotterdam C-chart) was developed on which optotypes on successive lines decreased in 1/3-octave steps (0.1-log steps) and on which crowding was comparable over the entire chart. Norm values for binocular and monocular visual acuity at test distances of 6 m and 40 cm and norm values for interocular acuity differences in 5-year-old children were determined by testing 201 5-year-olds with this chart. Results were compared to those obtained in 24 young adults. Although mean binocular and monocular acuity of the 5-year-olds were significantly lower than in adults, the distribution of acuity assessments were similar in the children and adults. Therefore, the Rotterdam C-chart seems suitable for developmental studies and for the assessment of visual acuity in young and visually impaired children.


The development of parafoveal and mid-peripheral human retina. The morphological development of parafoveal retina (1-1.5 mm from the foveal center) and the mid-peripheral (4 mm from the foveal center) human retina has been studied from fetal (F) 26 weeks to adulthood. At both retinal points, all layers and neuronal types are present at F26 weeks. In parafovea at F26 weeks photoreceptors have only a rudimentary inner segment and no outer segments. Short outer segments are present on both rods and cones at F36 weeks. By postnatal (P) 5-8 days the inner retina is relatively mature. Photoreceptors have elongated basal axons which cause the photoreceptor layer to become much thicker than in prenatal retina. At birth cone inner segments are untapered, but rod inner segments have already reached their adult width of 2 microns. Both rod and cone inner and outer segments are 30-50% of adult length. By 13 months both inner and outer retina are mature appearing, with the photoreceptors accounting for half the retinal thickness due to the elongation of the fibers of Henle. Cone outer segments elongate up to P5 years and rod outer segments to P13 years. At mid-peripheral or rod-ring retina outer segments are present on rods at F26 weeks and on cones at F36 weeks. At birth the inner retina is adultlike. The outer plexiform layer becomes thicker up to P45 months due to the elongation of fibers of Henle. At birth both rod and cone mid-peripheral inner segments are slightly longer and outer segments are 50% longer than in parafoveal retina. By P5 years mid-peripheral rod outer segments are slightly longer than in parafoveal retina, and this changes little thereafter. This anatomical study has found that the photoreceptors in peripheral rod-ring retina develop earlier than those in more central retina, and in turn parafoveal photoreceptors develop well in advance of foveal cones. This suggests that human neonates may utilize more peripheral retinal regions for some aspects of visual function before foveal cone vision becomes dominant.


Development of accommodation and convergence in infancy. Paraxial photorefraction was used to assess the development of accommodation and convergence in a large sample of infants under 1 year of age. The infants viewed small dolls placed at various distances (200-25 cm). The majority of infants at all ages demonstrated appropriate convergence for target distance, regardless of manifest refractive error. However, accommodation lagged behind convergence in development. Infants under 2 months tended to demonstrate either flat accommodation responses with a fixed plane of focus at around 30 cm, or accommodated appropriately for near targets, but failed to relax their accommodation sufficiently for the more distant targets. Thus, the focussing error increased with increasing target distance. Since the manifest refractive error was estimated by extrapolating the accommodation function to 0 diopters demand, these infants demonstrated spuriously myopic behavior. After 2 months, the majority of infants showing emmetropic behavior had accommodation responses that changed appropriately with target distance. However, infants with myopic or hyperopic manifest refractive errors displayed a variety of accommodative styles.


Light and the neonatal eye.

Light and the neonatal eye. The lighting environment where the baby born prematurely is placed is different from that experienced in utero. As early exposure to light may affect the immature visual system we have attempted to quantify the neonatal ocular light dose. Lighting surveys performed in 7 neonatal units (NNUs) suggested that mean unit illuminance was 470 lux (range 192-890 lux) and intensive care areas within the NNU were significantly brighter than their corresponding low dependency nurseries. The spectral power distribution of fluorescent lights in NNUs was weighted towards the blue end of the spectrum. Datalogging studies demonstrated that between about 30% and 98% of environmental light was incident on the eyelid, which acts as a predominantly red-pass filter, permitting 21% transmission at 700 nm with less than or equal to 5% transmission at 580 nm. Eye-lid opening frequency was quantified: 45% less than or equal to 26 weeks gestational age and decreasing to 7% at 28 weeks gestational age. The onset of the pupillary reflex to light was between 30 and 34 weeks postmenstrual age, the mean diameter was 3.46 mm before this event and 3.02 mm afterwards. Retinal irradiance values calculated from these data show that it is a function of postmenstrual age. Further studies are required to determine its effect on the immature visual system.


Detection and maturation of VEP albino asymmetry: an overview and a longitudinal study from birth to 54 weeks. The genetic anomaly in albinism prevents adequate melanin metabolism within the fetal eye cup and stalk. This results in severe disruption of pre- and postnatal retinal development and the condition of abnormal temporal retinal projections. The obligate misrouting of retinal-geniculate-cortical projections in albinism can be detected in the topographical representation across the occiput of the visual evoked potential (VEP). Age-dependent misrouting detection methods are described which yield 100% detection rates with zero false positives across the life span. By combining appropriate state-defined neonatal recording procedures with the albino infant VEP test paradigm, the presence of aberrant optic pathway projections was observed in a 5-day-old full-term infant. Maximum asymmetry was observed within a long-latency window of the response which shifted during the postpartum period to shorter latencies. Longitudinal studies show two specific latency regions of significant VEP asymmetry. The first occurs within 40-70 ms after stimulus onset and remains constant across the age range. The second, more robust, cluster of asymmetry occurs within a longer latency window and shows an age-related shift towards shorter latencies. The decreasing latency of this asymmetry is concomitant with normal maturational changes of the evoked response. These results show that VEP misrouting can be extended to reliable albino diagnosis within the neonatal period and to the assessment of visual maturation.


Early development of the subcortical and cortical pathway involved in optokinetic nystagmus: the cat as a model for man? The optokinetic reflex undergoes qualitative changes during the first postnatal weeks in kittens or months in human babies. Under monocular stimulus conditions, a clear preference for temporonasal stimulus directions at moderate velocities is replaced by a symmetrical, broad velocity range horizontal optokinetic nystagmus (OKN) over these periods. Evidence is presented for the cat that development changes in OKN can be related to maturation of neuronal response properties in the nucleus of the optic tract (NOT) in the pretectum. NOT cells in 3-week-old kittens are already direction-selective but all of them are exclusively or predominantly driven by the contralateral eye. Only starting with the 4th week of life NOT cells become more binocular and respond to a broader spectrum of stimulus velocities. This step in maturation coincides with the time when the cortical input to the NOT becomes functional.


Neuroimaging and functional outcome of neonatal leukomalacia. Leukomalacia is a major cause of neurological impairment in the high-risk newborn. It can be identified during the early postnatal period by means of ultrasound (US) imaging of the brain, through the anterior fontanel. Magnetic resonance imaging (MRI) permits an optimal differentiation of brain tissue and of its abnormalities, without resorting to ionizing radiation or intravenous contrast. It is particularly appropriate for following the evolution of leukomalacia, after fontanel closure. Ninety-five fullterm and preterm infants with cystic and non-cystic leukomalacia, documented by US, were clinically followed-up until at least 12 months of corrected age. Thirty-two had a severe neurological outcome (mainly cerebral palsy, sometimes associated with mental retardation and/or cerebral visual impairment). The prognosis was worse in cystic leukomalacia than in prolonged flare. Electroencephalogram (EEG) carried out in the first 2 weeks of life provided valuable indexes of further outcome, especially for US findings of more uncertain prognosis. MRI was carried out at around 12 months of corrected age, by means of an apparatus operating at 0.5 Tesla. The main categories of abnormalities observed were the following: cystic lesions, enlarged ventricles with irregular outlines, delayed myelination, high intensity areas in the long TR (repetition time) images within the white matter, cortical atrophy. MRI findings correlated well with the results of US imaging and often with motor, cognitive and visual impairments. Nevertheless, clinical features cannot be predicted by neuroimaging alone and a comprehensive approach, including longitudinal functional and electrophysiological testing, is highly recommended.


OKN asymmetries in orthoptic patients: contributing factors and effect of treatment. Monocular optokinetic nystagmus (MOKN) was measured (EOG) in response to horizontally moving square wave gratings (0.2 c/deg, 27 and 35 deg/s) in 58 children with amblyopia and/or strabismus (experimental group); the data were compared with that collected from 24 children (aged 3-8 years) with no visual problems (control group). We found OKN asymmetries most often associated with strabismus of early age of onset (less than 2 years). In these children the MOKN asymmetry often occurred in both eyes. In children with later onset strabismus the asymmetry was often confined to the amblyopic eyes. We repeated the measurements on 18 experimental children after 1-3 years of treatment (patching the dominant eye) and compared the results with those recorded in 12 fully binocular control children retested after 1-2 years. Large OKN asymmetries before treatment were still present after the patching treatment. However there was a small, but significant (P = 0.05, t-test), improvement in the nasal-temporal (N-T) slow-phase velocity in the affected eyes of the experimental group, which was not correlated with improvements in visual acuity or linked to the presence of strabismus and/or amblyopia. The main contributing factors to asymmetric OKN affecting both eyes of early onset strabismus seem to be to poor binocularity which would not improve during patching treatment. OKN asymmetries in amblyopic eyes may also result from reduced cortical sensitivity from that eye, which may be minimally improved by patching treatment. Our results suggest a shorter sensitive period of development for OKN pathways than for the development of cortical visual pathways.


On the onset of eye-head coordination in infants. Head movements have been studied in newborns, during a visual pursuit and in relation with ocular movements, in order to know whether head movements help the ocular activity or impede it. The infants were tested three times during the first month of life. They were placed in a seated position, with the head held upright, but free to move. The results provided evidence that eyes and head were directionally coupled at as early as 2 weeks and that the interval between eye and head rotation decreases from the age of 2-4 weeks. This suggests that the beginnings of ocular-motor coordination are present from the first month of life in human infants.


Results of photorefractometric screening for amblyogenic defects in children aged 20 months. This report evaluates the validity of a preventive programme in a population which underwent refractometric screening at the ages of 20 months and 4 years. In 1987, 1,046 children born in 1985 in the territory of the Veneto National Health Unit No. 19 were invited to undergo screening for amblyogenic factors such as meridional hyperopia greater than or equal to +2.50 diopters (D), myopia less than or equal to -2.50 D, anisometropia greater than or equal to 2 D, opacity of the dioptric media and strabismus. The test method was non-cycloplegic photorefractometry (PhR). Seven hundred and ninety-five children were tested (76%); positive cases underwent subsequent cycloplegic autorefractometry (AR) and corrective lenses were prescribed as necessary. In 1989, an eye test was performed on 653 children who had taken part in the previous PhR screening and on 350 similar children who had not: the test included evaluation of visual acuity, stereopsis and AR. An eye with a corrected visual acuity of less than 0.7 was considered amblyopic. PhR demonstrated a sensitivity of 80%, a specificity of 96% and a positive prediction rating of 46% in the identification of amblyogenic factors. The prevalence of amblyopia at 4 years of age in the group which had undergone previous screening was 1.07% vs. 2.57% in the group which had not (P: not significant). The progress of the myopia was studied in a group with full optical correction used continuously (Group A) and in a control group under-corrected by at least 1.5 D (Group B).(ABSTRACT TRUNCATED AT 250 WORDS)


Acuity card procedures and the linearity of grating resolution development during the first year of human infants. Since the early times of preferential looking (PL), improvement of procedures to test visual resolution in infants has reached the point where the technique is spreading to clinical practice as it is applicable to a large range of age with a high degree of reliability. Acuity cards allow estimation of bi- and monocular acuity in a few minutes. Data from the literature, obtained with various PL techniques and procedures are compared to explain some incongruities. Procedures for presentation of the cards and criteria for threshold determination can greatly bias the data when they do not take into account the infant's behavioral requirements. To test the linearity of the development of visual resolution, a series of grating acuity measurements was performed on a population of 11 normal infants, regularly tested during their first year of life in optimal conditions. It was observed that: (1) grating acuity develops very regularly during the first year, (2) the two eyes never differ from each other by more than the smallest difference measurable with the equipment used (one half-octave), (3) binocular acuity appears to slightly exceed monocular acuity. These results stress the need for early detection of deviation from the norm and prompt therapeutic action.


Conditioning, habituation and behavioral reorganization factors in chronic cocaine effects. Rats were administered cocaine (50.0 mg/kg i.p.) daily for 7 days in a Pavlovian paradigm either immediately prior (paired group) or 30 min following (unpaired group) a 20-min placement in an open field test environment. After 7 days of drug withdrawal, the animals were retested 3 days apart, once with saline and once with cocaine (50 mg/kg). Measurement of locomotion as distance traversed (m) revealed a higher level of locomotion in the paired group on all test trials. Analysis of the paired vs. unpaired differences indicated an antihabituation effect of cocaine rather than a hyperlocomotion or a conditioned locomotor effect. Rotation pattern analysis for each animal showed a new frequency distribution of rotations across four categories of diameter size in the paired but not in the unpaired group by Day 5. This new pattern was characterized by a shift in skewness toward large greater than or equal to 55 cm diameter rotations. These qualitative changes in rotation pattern point to a context specific behavioral reorganization process in response to repeated cocaine drug treatment.


Effects of medial and lateral septal lesions on acquisition of a place and cue radial maze task. Rats with lesions limited to either the medial septal (MS) or dorsolateral septal (LS) nuclei were trained on a place and cue version of the radial maze using a procedure that permits determination of both reference memory (RM) and working memory (WM). Following training the presence or absence of hippocampal theta for MS and LS groups was determined. The results showed that both MS- and LS-lesioned rats were impaired in acquisition. Specifically, the pattern of results indicated a general impairment in working memory that was found on both the place and cue tasks together with impaired acquisition of the place (but not the cue) task. While both septal lesion groups evidenced a similar impairment, rats in the MS group made more errors than LS rats on several components of the tasks. Electroencephalographic recordings revealed that hippocampal theta was not affected in the LS group but was abolished in rats with MS lesions. Thus, it appears that the functional role of the septo-hippocampal system cannot be fully described by a single mechanism or process but rather several processes seem to be affected when the septal area is damaged.


Unilateral lesion in the tuberomammillary nucleus region: behavioral asymmetries and effects of histamine precursor. The subnuclei of tuberomammillary nucleus are located in the posterior part of the hypothalamus adjacent to the basolateral surface of the mammillary bodies. The neurons of this nucleus innervate extensive parts of the brain with several transmitters, particularly with histamine. In fact, they represent the only source of histaminergic projections in the brain. The present study deals with the effects of a lesion in this region on behavior. Unilateral electrolytic direct current (DC) lesions in the tuberomammillary nucleus led to an asymmetry in thigmotactic scanning; i.e., at 11 days, but not 1 day postlesion, the rats scanned the walls of an open field more with the vibrissae contralateral to the lesion than with those of the ipsilateral side. Furthermore, they emitted more ipsiversive than contraversive wide angle turns. The behavioral asymmetries are, in general, opposite in direction to those induced by lesion of the neighboring lateral hypothalamus and substantia nigra, indicating that they are specific to the tuberomammillary region destroyed. Application of the histamine precursor histidine led to a compensation of these asymmetries, suggesting that the tuberomammillary's histaminergic efferents are functionally related to the lesion-induced behavioral effects.


Duration of retrograde amnesia induced by tetrodotoxin inactivation of the parabrachial nuclei is inversely related to the intensity of footshock in rat's passive avoidance response. Previous work has demonstrated that in rats post-trial bilateral functional blockade of the parabrachial nuclei by local injection of tetrodotoxin (10 ng in 1 microliter) partially disrupts retention of an overtrained passive avoidance response. The time-course of functional blockade disrupting effects on passive avoidance response has been studied by altering both the acquisition-tetrodotoxin injection interval and footshock intensity as independent variables. When week footshocks (0.8 mA) were delivered, functional ablation of the parabrachial nuclei was still effective when induced up to 8 days after acquisition training. On the other hand, when rats were shocked with the stronger stimuli (1.2 mA), 2 days after acquisition functional ablation was no longer effective. The results are discussed in terms of unconditioned stimulus (US) intensity and engram consolidation.


Raised glucose levels enhance scopolamine-induced acetylcholine overflow from the hippocampus: an in vivo microdialysis study in the rat. Behavioural studies in both humans and animals have shown that an acute rise in circulating glucose levels at or around the time of training enhances subsequent retention performance and can also afford protection from the amnesia produced by posttraining injections of scopolamine. In an attempt to directly investigate the neurochemical basis for these effects of glucose we have tested the hypothesis that raised glucose levels may enhance acetylcholine (ACh) synthesis and release in the brain during conditions of increased neuronal activity, induced either by training or pharmacological challenge, via a microdialysis study using rats. Microdialysate concentrations of ACh overflow from the hippocampus of fasted rats induced by i.p. injections of scopolamine (1 mg/kg) combined with concurrent s.c. injections of either glucose (2 g/kg) or saline were compared in successive 15-min samples using an on-line HPLC system. Scopolamine injections resulted in an immediate 10-20-fold increase in hippocampal ACh overflow which subsequently progressively declined over a 4-h period to pretreatment baseline levels. The combined injection of glucose with scopolamine resulted in a highly significant enhancement (19.4%; P less than 0.01) in ACh content of the first two samples as compared to saline-injected controls. These results provide the first direct experimental evidence that raised glucose levels, via increased availability of acetyl-coenzyme A (acetyl-coA), transiently facilitates ACh synthesis and release during conditions of increased neuronal activity. This enhancement of ACh availability during states of cholinergic neuronal activation may underlie the previously observed facilitatory effects of glucose on memory performance and its protection from scopolamine-induced amnesia.


The spatial distribution of attention in S-R compatibility. In certain choice reaction time experiments the subjects, although not specifically instructed to do so, perform a parcellation of space into right and left components. Previous research has shown that when the stimulus locations are marked on the screen, the subdivision of space into right and left halves is bound to the point where the subject has been instructed to focus selective attention. It is not known whether, in the absence of specific instructions, subjects are able to focus selective attention between stimulus locations when no marker is present. We tried to clarify this problem by introducing a 'probe' stimulus that could map the spatial distribution of attention in subjects engaged in a compatibility task. The results suggest that, in the absence of visual cues marking the stimulus positions, attention is kept in the disengaged modality before the presentation of the stimuli. In this state of disengagement a powerful tendency to orient to the rightmost side of the display, within each visual field, is apparent. Various interpretations of this finding are discussed.


Effect of lesions in the ectostriatum and Wulst on species and individual discrimination in pigeons. Pigeons were trained on species (pigeon vs. quail) or individual (pigeon vs. pigeon) discrimination in an operant chamber with a video screen. Still video images were used as discriminative stimuli. After the pigeons had accomplished the discrimination tasks, they received lesions of the Wulst or the ectostriatum. While damage to the Wulst did not disrupt either task, the ectostriatal damage caused deficits selectively in individual discrimination. These dissociations between the tasks and between the lesion sites are comparable to the previous experiments on natural and pseudoconcept. Species discrimination seems to share common brain mechanisms with other natural concept discrimination.


Copulatory stimuli in rats induce heat abbreviation through effects on genitalia but not through effects on central nervous mechanisms supporting the steroid hormone-induced sexual responsiveness. Male copulatory stimuli in various animal species abbreviate the length of the period of their female conspecifics' heat. Such effect can be explained in some species as the result of copulation-induced alterations in ovarian hormone secretion (e.g. reflex ovulators). Other species require a different explanation: specifically, interactions in the hypothalamus between effects of steroid hormones and inhibitory neural afferents from the genital area have been hypothesized to play a role in some laboratory animals such as guinea pigs, hamsters and rats. However, the evidence in support of heat abbreviation through copulatory stimuli in rats is at best equivocal. There is obvious need for its unequivocal demonstration prior to any further analysis of the potential mechanism of action. The present study intended to find a model in support of the concept of 'centrally induced' heat abbreviation in rats. Virgin rats during 'natural heat' were examined with or without allowing them the opportunity to pace male copulatory activities. Ovariectomized, steroid hormone-treated rats were studied with minor or ample experience with sexual activities in prior tests and, also, with or without the opportunity to 'pace' male sexual acts. None of the experimental models revealed unequivocal support for detrimental effect of large numbers of intromittive copulations on 'central mechanisms' regulating heat duration. It rather seemed that frequent intromittive copulations and ejaculates affected the 'peripheral' genital tract (vulva, vagina, cervix) making further copulation of a highly aversive quality so that sexual encounters were avoided or prevented. This effect was noticed with great inter-individual variability. The conclusion is drawn that rats do not show the counterpart of heat abbreviation reportedly occurring rapidly and reliably in guinea pigs after a limited amount of vaginal/cervical stimulation through copulation or insertions of a glass-rod.


6-Hydroxydopamine lesions of the medial prefrontal cortex fail to influence cocaine-induced place conditioning. This study investigated the involvement of medial prefrontal cortex (mPFC) dopamine in cocaine place conditioning using a totally balanced place conditioning design. Presynaptic dopamine terminals of the mPFC were lesioned by bilaterally infusing the selective neurotoxin 6-hydroxydopamine (6-OHDA). These lesions significantly depleted dopamine (-83%) and norepinephrine (-70%) in the mPFC but there were no significant reductions in either the nucleus accumbens or in the caudate-putamen compared with sham-operated controls. Furthermore, serotonin levels were not affected in any of the brain regions investigated. These lesions failed to attenuate place conditioning induced by the intraperitoneal (i.p. 10 mg/kg) administration of cocaine when compared to sham lesioned controls. In addition, there were no significant differences in spontaneous locomotor activity between the two groups during the preconditioning phase or the test phase. These results suggest that 6-OHDA lesions which produced profound depletions of dopamine and norepinephrine in the mPFC did not alter the rewarding efficacy of cocaine as measured by the place conditioning paradigm.


Photothrombotic lesions of the frontal cortex impair the performance of the delayed non-matching to position task by rats. The effects of photochemically induced lesions of the frontal cortex on the short-term memory capacity of the rat have been investigated using the delayed non-matching to position task. Pretrained animals received lesions and were tested 4 days after surgery and twice per week for 3 weeks. The lesions produced a profound impairment of performance of this task which was still evident 3 weeks after surgery. Spontaneous locomotor activity was recorded 7 days after surgery and no difference was found between the control and lesion group. These effects indicated a generalized disruption of performance of this task in the absence of motor dysfunction. These results suggest that photothrombotic lesions of the frontal cortex can produce reliable, long-term behavioural deficits.


Properties of trypsin and of acid phosphatase immobilized in sol-gel glass matrices. Trypsin and acid phosphatase-containing silica sol-gel glasses were obtained by mixing a solution of an enzyme with polyethylene glycol (PEG) 6000 and tetramethoxy orthosilicate at room temperature, followed by gelation and drying. Activity of the immobilized trypsin toward small substrates, such as N-benzoyl-L-arginine-4-nitroanilide at its Km, for the best preparations equaled that of the soluble enzyme. Polylysine (M(r) less than or equal to 13,000) and aprotinin (M(r) = 6,500) inhibited this activity. Larger polylysines as well as soybean trypsin inhibitor (M(r) = 20,100) were ineffective. The sol-gel-entrapped trypsin activity was stable when sol-gel glasses were incubated at ambient temperature (pH 7.5) for several months. In comparison, trypsin, immobilized in sol-gel glass by surface adsorption and incubated under the same conditions overnight, was completely autodigested. The firm interaction between the protein molecules and the silica matrix stabilized the enzymes. Thus, the half-life of sol-gel-entrapped acid phosphatase at 70 degrees C (pH 8.0) was two orders of magnitude larger than that of the enzyme in solution. Transparent, mechanically and chemically stable bioactive sol-gel glasses may be used for the development of robust on-line biochemical photodetection sensors and for the purposes of chemical catalysis.


Interaction of carboplatin with carrier human erythrocytes. The antineoplastic drug Carboplatin (CBDCA) was encapsulated in human erythrocytes by means of transient hypotonic hemolysis, followed by isotonic resealing. Up to 5 mg/ml of packed cells could be entrapped, with about 70% cell recovery. In vitro incubation of the CBDCA-loaded erythrocytes in autologous plasma caused a very slow release of the drug from the cells (12% approximately in 3 h). The encapsulation conditions, performed at a low hematocrit, in order to obtain high amounts of the drug inside the carriers, impaired the metabolic properties of the loaded erythrocytes significantly. In particular, an almost complete disappearance of GSH was observed. Analysis of the intraerythrocytic metabolism of CBDCA showed that, in spite of its relatively high stability in aqueous solutions, in hemolysates and in the loaded erythrocytes a significant percentage of CBDCA is rapidly converted to other species that still retain an antiproliferative activity in vitro. This fast conversion could be extensively inhibited by previous conversion of oxyhemoglobin to methemoglobin or carbomonoxyhemoglobin, suggesting an important role of heme iron in this process. Encapsulation of CBDCA in selectively targeted human erythrocytes may represent a therapeutic strategy for increasing the drug concentration in specific organs, notably liver.


Biosynthesis of cholesterol linoleate by polyethylene glycol-modified cholesterol esterase in organic solvents. Cholesterol esterase modified with polyethylene glycol was able to dissolve in some highly hydrophobic solvents such as benzene and toluene, and catalyze the synthesis of cholesterol linoleate with time dependency in the reverse of the usual reaction in aqueous solvents. Enzymatic cholesterol linoleate synthesis followed Michaelis-Menten kinetics which depended on the concentration of cholesterol and linoleic acid. When more than 20 mM of both substrates was used, the specific activity in this esterification was 200-250 nmol/min/mg protein. The apparent Km value for cholesterol and linoleic acid was 3.7 and 7.6 mM, respectively. The possibility of using such a modified enzyme for the synthesis of less stable cholesterol esters is discussed.


Mechanistic and structural studies on Rhodococcus ATCC 39484 nitrilase. Rhodococcus ATCC 39484 produced a nitrilase when induced with isovaleronitrile. The enzyme was obtainable pure in milligram amounts, had a subunit Mr of 40 kDa, and demonstrated a substrate-induced activation related to aggregation of subunits to form a 560-kDa complex. The enzyme had a broad substrate specificity, had a pH optimum of 7.5, was stable up to 40 degrees C, and had one disulfide bridge and two free cysteine residues, one of which appeared to be catalytically essential. The N-terminal sequence was determined and found to have 78.3% homology, in a 23-residue overlap, with Klebsiella ozaenae nitrilase. The enzyme was inhibited competitively by benzylamine and benzaldehyde and irreversibly by benzyl bromide. However, benzyl bromide was shown to be nonspecific, causing multiple alkylation. Acid quenching of enzyme-substrate mixtures allowed for the detection of covalent enzyme-substrate complexes using mass spectrometry. The covalent intermediate is suggested to be either a thioimidate or an acylenzyme and a reaction mechanism consistent with this observation and also the inhibitor results is proposed. The rate of breakdown of the covalent intermediates was found to be rate limiting even for substrates with undetectable rates of hydrolysis or those with very slow rates of intermediate formation. For phenylacetonitrile, a poor substrate, in addition to acid, approximately 2% of the product was the corresponding amide. This result suggests that a tetrahedral intermediate is formed which, for selected substrates, can break down anomalously to produce amide in place of the normal acid product. Under the conditions used in this study all other substrates tested were converted to acid.


Effect of 5,7-unsaturated sterols on ethanol tolerance in Saccharomyces cerevisiae. Structural membrane lipids are known to contribute to the high ethanol resistance of Saccharomyces cerevisiae (2, 4, 17). By manipulating the yeast cellular sterol level by changing the carbon-to-nitrogen source ratio in the chemostat growth medium, high delta 5,7-sterol levels were found to increase the resistance of yeast populations to ethanol-induced death. The resistance of the erg2 (delta 8----delta 7-sterol isomerase) mutant to ethanol-induced death was generally comparable with that of the delta 5,7-sterol-synthesizing strain. In contrast, the sensitivity of anaerobic growth to inhibition by ethanol was higher in the erg2 mutant in comparison with the delta 5,7-sterol-synthesizing strains but a high level of those sterols increased the vulnerability of anaerobic growth to ethanol inhibition.


The zygomatico-temporal approach to the skull base: a critical review of 11 patients. The zygomatico-temporal approach to the base of the skull is a relatively new but established surgical technique. The approach involves the removal of the zygomatic bone to provide access to the skull base, middle cranial fossa, parasellar region and interpeduncular cistern with minimal brain retraction. An excellent view of the bifurcation of the basilar artery and suprasellar region is provided. The outcome of 11 patients undergoing this procedure is reported with particular reference to the post-operative morbidity and the cosmetic result.


Does thrombin prevent cerebral vasospasm following aneurysmal subarachnoid haemorrhage? Fibrinopeptide A (FPA) levels which have been shown to be a quantitative index of thrombin generation, were measured in blood and cerebrospinal fluid (CSF) samples from patients following subarachnoid haemorrhage (SAH) and from a control population. The levels found in samples obtained in patients following SAH are compared with those found in controls and also correlated with clinical grade on admission as assessed by the Glasgow Coma Score and the World Federation of Neurological Surgeons' grading system, and with the amount of subarachnoid blood seen on CT, the occurrence of ischaemic deterioration, the occurrence of low-density change on CT, the presence of vasospasm on angiography, clinical outcome as assessed by the Glasgow Outcome Score 3 months following the ictus, and the incidence of ischaemia as a cause of death or disability as assessed 3 months following the ictus. The levels of FPA found in blood and CSF from patients following SAH were significantly raised when compared with those found in controls. There was significant correlation between blood FPA levels and the amount of subarachnoid blood seen on initial CT. CSF FPA levels had a statistically significant correlation with outcome as assessed at 3 months post-ictus. No statistically significant correlation was found between blood or CSF FPA levels and any of the other variables studied.


Mechanical complications of the reservoirs and flushing devices in ventricular shunt systems. Complications of valve reservoirs or flushing devices are seldom reported as a cause of shunt malfunction. The authors document their experience in six cases of mechanical complications of shunting devices. Two cases presented with collapse and intracranial migration of the valve reservoir, a complication that has not been reported previously. In two cases, the plastic dome became disconnected from the metallic base of the reservoir. A fifth patient, with an integral shunt system, showed a fracture in the soldered join of the distal tube to the reservoir dome. The last patient had the valve reservoir partially collapsed by bone growth at the time of shunt revision.


An in vitro study of the effect of photodynamic therapy on human meningiomas. Despite being benign CNS tumours, meningiomas are not always curable and the likelihood of recurrence depends upon the completeness of initial removal. Adjuvant therapy for incompletely resected meningiomas is generally unsatisfactory and such lesions continue to pose difficult management problems. Photodynamic therapy (PDT) has been employed in the management of recurrent cerebral gliomas but its activity against meningiomas has not been specifically studied. An in vitro study of the effects of PDT against a variety of meningiomas was therefore conducted. It was found that PDT using haematoporphyrin derivative as a photosensitizing drug showed dose-dependent activity against a variety of histological subtypes of meningioma. The activity of PDT against meningiomas should be investigated further and may eventually provide a useful form of adjuvant therapy for incompletely resected lesions.


Pressure and blood flow in pituitary adenomas measured during transsphenoidal surgery. In 48 patients undergoing transsphenoidal surgery for pituitary adenoma, the intrasellar pressure was recorded during surgery. In 14 patients, adenoma blood flow was measured with the technique of local injection of 133xenon. Median intrasellar pressure was 30 mmHg (range 8-62), n = 48, and median adenoma blood flow was 8 ml/100 g/min (range 0-37), n = 14. In two patients, blood flow in the anterior pituitary gland was measured, and values of 26 and 22 ml/100 g/min were obtained. The finding that intrasellar pressure is above central venous and intracranial pressure suggests the possibility that the adenoma and the anterior pituitary gland are supplied not only with venous blood, but receive an additional arterial supply at a less  than normal arterial pressure. In three cases perfusion pressures that caused arrest of adenoma blood flow were found, and these observations are discussed with reference to pituitary apoplexy.


Computer-generated titanium cranioplasty: report of a new technique for repairing skull defects. A review of 40 cases of titanium cranioplasty fabricated from impressions taken of the defect through the patient's scalp in the conventional way showed that 23% were ill-fitting and 41% of frontal plates had a poor aesthetic result. Attributable factors were difficulty in defining the defect border accurately and limited information of the surrounding tissue architecture which led to strains produced during insertion. Inadequate communication between surgeon and prosthetist compounded these difficulties. A prospective study of six cases fabricated from CT computer-generated models of challenging cranial defects appears to show significant improvements in plate design, resulting in better plate adaptation, stability and aesthetic contour. Plate insertion was rapid (mean time 27 min) thereby minimizing operating time. This paper also discusses the advantages of the enhanced information derived from CT and describes the potential for pre-craniotomy template and matching cranioplasty, thereby permitting a one-stage procedure.


Intradural spinal cavernomas.

Intradural spinal cavernomas. Intradural cavernomas are rare vascular lesions of the spinal cord. Four cases of histologically verified cavernomas of the cord are reported, of which two were extramedullary and two were intramedullary in location. Progressive neurological deficit was the presenting feature in three cases while one patient had a rapid evolution of neurological deficits and was found at surgery to have had bled from the extramedullary lesion. All the patients were subjected to surgery and total excision of the cavernomas was carried out in each case. While two patients improved after surgery the other two remained static. The available literature on spinal cord cavernomas is reviewed.