The hunt for a cure for Parkinson's disease

Several exciting new scientific advances have been made in the past decade toward both understanding the causes of and finding a cure for Parkinson's disease. Heartened by an acceleration in research findings in the past several years, the government has recently called for an infusion of funds from both the National Institutes of Health and private foundations into this burgeoning area of biomedical research. Most currently available conventional treatments for the disease only temporarily delay symptom presentation while doing nothing to halt disease progression. However, the rapidly accelerating pace of research in this field has left researchers hopeful that Parkinson's will be the first major age-related neurodegenerative disease for which we have a viable cure. In this article, advances in various areas of Parkinson's disease research are reviewed.

The ontogeny of scarless healing II: EGF and PDGF-B gene expression in fetal rat skin and fibroblasts as a function of gestational age

Twenty years ago, surgeons noted the ability of early-gestation fetal skin to heal in a scarless manner. Since that time, numerous investigators have attempted to elucidate the mechanisms behind this phenomenon. As a result of this effort, it is now well established that many animals undergo a transition late in development from scarless cutaneous healing to a scar-forming, adultlike phenotype. The authors have been interested in the role played by cytokines known to be involved in the adult wound-healing process and how they relate to scarless repair. They therefore asked the following question: Are genes for epidermal growth factor (EGF) and platelet-derived growth factor-B (PDGF-B) expressed differentially as a function of gestational age in fetal rat skin and dermal fibroblasts? To answer this question, skin from fetal Sprague-Dawley rats (N = 56) at time points that represented both the scarless and scar-forming periods of rat gestation was harvested. In addition, fibroblasts derived from fetal rat skin were cultured in vitro at similar times. These cells were expanded in culture and, when confluent, total ribonucleic acid from both fibroblasts and whole skin was extracted and subjected to Northern blot analysis with probes for EGF and PDGF-B. Results demonstrated that neither EGF nor PDGF-B gene expression changed markedly as a function of gestational age in fetal fibroblasts alone. In whole skin, however, both EGF and PDGF-B demonstrated a marked decrease in gene expression with increasing gestational age. Furthermore, the most striking decrease in gene expression for both cytokines came between 16 and 18 days of gestation-the transition point between scarless and scar-forming repair in the fetal rat. These data suggest that EGF and PDGF may play a role in the mechanism of scarless cutaneous repair. Moreover, it appears that fetal fibroblasts are not the cell type responsible for this differential gene expression. These results raise questions about the unique cytokine milieu likely to be present during the time of scarless healing and the cells that ultimately guide the mechanisms leading to skin regeneration.

The tetrahymena ribozyme cleaves a 5'-methylene phosphonate monoester approximately 10(2)-fold faster than a normal phosphate diester: implications for enzyme catalysis of phosphoryl transfer reactions

Single-atom substrate modifications have revealed an intricate network of transition state interactions in the Tetrahymena ribozyme reaction. So far, these studies have targeted virtually every oxygen atom near the reaction center, except one, the 5'-bridging oxygen atom of the scissile phosphate. To address whether interactions with this atom play any role in catalysis, we used a new type of DNA substrate in which the 5'-oxygen is replaced with a methylene (-CH2-) unit. Under (kcat/Km)S conditions, the methylene phosphonate monoester substrate dCCCUCUT(mp)TA4 (where mp indicates the position of the phosphonate linkage) unexpectedly reacts approximately 10(3)-fold faster than the analogous control substrates lacking the -CH2- modification. Experiments with DNA-RNA chimeric substrates reveal that the -CH2- modification enhances docking of the substrates into the catalytic core of the ribozyme by approximately 10-fold and stimulates the chemical cleavage by approximately 10(2)-fold. The docking effect apparently arises from the ability of the -CH2- unit to suppress inherently deleterious effects caused by the thymidine residue that immediately follows the cleavage site. To analyze the -O- to -CH2- modification in the absence of this thymidine residue, we prepared oligonucleotide substrates containing methyl phosphate or ethyl phosphonate at the reaction center, thereby eliminating the 3'-terminal TA4 nucleotidyl group. In this context, the -O- to -CH2-modification has no effect on docking but retains the approximately 10(2)-fold effect on the chemical step. To investigate further the stimulatory influence on the chemical step, we measured the "intrinsic" effect of the -O- to -CH2- modification in nonenzymatic reactions with nucleophiles. We found that in solution, the -CH2- modification stimulates chemical reactivity of the phosphorus center by <5-fold, substantially lower in magnitude than the stimulatory effect in the catalytic core of the ribozyme. The greater stimulatory effect of the -CH2- modification in the active site compared to in solution may arise from fortuitous changes in molecular geometry that allow the ribozyme to accommodate the phosphonate transition state better than the natural phosphodiester transition state. As the -CH2- unit lacks lone pair electrons, its effectiveness in the ribozyme reaction suggests that the 5'-oxygen of the scissile phosphate plays no role in catalysis via hydrogen bonding or metal ion coordination. Finally, we show by analysis of physical organic data that such interactions in general provide little catalytic advantage to RNA and protein phosphoryl transferases because the 5'-oxygen undergoes only a small buildup of negative charge during the reaction. In addition to its mechanistic significance for the Tetrahymena ribozyme reaction and phosphoryl transfer reactions in general, this work suggests that phosphonate monoesters may provide a novel molecular tool for determining whether the chemical step limits the rate of an enzymatic reaction. As methylene phosphonate monoesters react modestly faster than phosphate diesters in model reactions, a similarly modest stimulatory effect on an enzymatic reaction upon -CH2- substitution would suggest rate-limiting chemistry.

Differential expression of transforming growth factor-beta receptors I and II and activation of Smad 3 in keloid fibroblasts

Keloids represent a dysregulated response to cutaneous wounding that results in an excessive deposition of extracellular matrix, especially collagen. However, the molecular mechanisms regulating this pathologic collagen deposition still remain to be elucidated. A previous study by this group demonstrated that transforming growth factor (TGF)-beta1 and -beta2 ligands were expressed at greater levels in keloid fibroblasts when compared with normal human dermal fibroblasts (NHDFs), suggesting that TGF-beta may play a fibrosis-promoting role in keloid pathogenesis.To explore the biomolecular mechanisms of TGF-beta in keloid formation, the authors first compared the expression levels of the type I and type II TGF-beta receptors in keloid fibroblasts and NHDFs. Next, they investigated the phosphorylation of Smad 3, an intracellular TGF-beta signaling molecule, in keloid fibroblasts and NHDFs. Finally, they examined the regulation of TGF-beta receptor II by TGF-beta1, TGF-beta2, and TGF-beta3 ligands. Our findings demonstrated an increased expression of TGF-beta receptors (types I and II) and increased phosphorylation of Smad 3 in keloid fibroblasts relative to NHDFs. These data support a possible role of TGF-beta and its receptors as fibrosis-inducing growth factors in keloids. In addition, all three isoforms of recombinant human TGF-beta proteins could further stimulate the expression of TGF-beta receptor II in both keloids and NHDFs. Taken together, these results substantiate the hypothesis that the elevated levels of TGF-beta ligands and receptors present in keloids may support increased signaling and a potential role for TGF-beta in keloid pathogenesis.

Ontogeny of expression of transforming growth factor-beta 1 (TGF-beta 1), TGF-beta 3, and TGF-beta receptors I and II in fetal rat fibroblasts and skin

Fetal cutaneous wounds that occur in early gestation heal without scar formation. Although much work has been done to characterize the role of transforming growth factor-beta (TGF-beta) isoforms in the adult wound repair process, their function in fetal scarless wound repair is not well understood. The authors hypothesized that the pattern of expression for TGF-beta isoforms and their receptors may influence the phenotypic transition from scarless to scar-forming repair observed during fetal gestation. Using time-dated fetal Sprague-Dawley rat fibroblasts and unwounded skin at gestational ages 14, 16, 18, and 21 days postcoitum of the scarless (< or =16 days) and scar-forming (>16 days) periods of gestation (term = 21.5 days), the authors analyzed the endogenous messenger RNA (mRNA) levels of TGF-beta 1 and TGF-beta 3 and their signaling receptors TGF-beta-RI and TGF-beta-RII. Northern blot analyses in both fibroblasts and unwounded skin revealed that levels of TGF-beta 1 were not differentially expressed, whereas more TGF-beta 3 mRNA transcript was found in early than in late gestation. Fibroblast expression of TGF-beta-RI showed no substantial differences, whereas expression of TGF-beta-RII increased during gestation. In contrast, expression of both TGF-beta-RI and TGF-beta-RII in unwounded skin showed decreasing levels as a function of gestational age. The differential levels of TGF-beta 1 and TGF-beta 3 suggest that the ratio of these cytokines may provide a predominantly antiscarring or profibrotic signal upon wounding during the scar-free or scar-forming periods of gestation, respectively. Furthermore, lower amounts of the ligand-binding TGF-beta-RII seen in early gestation fibroblasts suggest a decreased ability to perceive ligand during the period of scarless repair.

Discoidin domain receptors and their ligand, collagen, are temporally regulated in fetal rat fibroblasts in vitro

The biochemical regulation of collagen deposition during adult cutaneous wound repair is poorly understood. Likewise, how collagen is perceived and modulated in fetal scarless healing remains unknown. Recently, discoidin domain receptors-1 and 2 (DDR1 and DDR2) with tyrosine kinase activity have been identified as novel receptors for collagen. In light of these findings, it was speculated that the production of collagen receptors DDR1 and DDR2 by fetal fibroblasts may be temporally regulated to correlate with the ontogeny of embryonic scar formation. More specifically, because DDRs directly bind collagen and transmit the signals intracellularly, it was hypothesized that they may play an important role in fetal scarless healing by ultimately regulating and modulating collagen production and organization. As part of a fundamental assessment to elucidate the role of DDRs in scarless fetal wound repair, the endogenous expression of DDR1, DDR2, collagen I, and total collagen, as a function of fetal Sprague-Dawley rat skin fibroblasts of different gestational ages, representing scar-free (<E16.5 days) and scar-forming (>E16.5) periods was determined. Using explanted dermal fibroblasts of gestational days E13.5, E16.5, E18.5, and E21.5 (term gestation = 21.5 days) fetuses (n = 92), [3H]proline incorporation assay and Northern and Western blotting analysis were performed to compare the expressions of these molecules with scar-free and scar-forming stages of embryonic development. These results revealed a pattern of increasing collagen production with increasing gestational ages, whereas DDR1 expression decreased with increasing gestational age. This observation suggests that elevated levels of DDR1 may play an important role in scarless tissue regeneration by early gestation fetal fibroblasts. In contrast, DDR2 was expressed by fetal rat fibroblasts at a similar level throughout gestation. These data demonstrate for the first time the temporal expression of collagen and DDR tyrosine kinases in fetal rat fibroblasts as a function of gestational ages. Overall, these data suggest that differential temporal expression of the above-mentioned molecules during fetal skin development may play an important role in the ontogeny of scar formation. Future studies will involve the characterization of the biomolecular functions of these receptor kinases during fetal wound repair.

Place learning in virtual space. III: Investigation of spatial navigation training procedures and their application to fMRI and clinical neuropsychology

This paper describes the utilization of a desktop virtual environment task, the Computer-Generated (C-G) Arena, in the study of human spatial navigation. First, four experiments examined the efficacy of various training procedures in the C-G Arena. In Experiment 1, participants efficiently located a hidden target after only observing the virtual environment from a fixed position (placement learning). In Experiment 2, participants efficiently located a hidden target after only observing an experimenter search the virtual environment (observational learning). In Experiment 3, participants failed to display a latent learning effect in the virtual environment. In Experiment 4, all training procedures effectively taught participants the layout of the virtual environment, but the observational learning procedure most effectively taught participants the location of a hidden target within the environment. Finally, two experiments demonstrated the application of C-G Arena procedures to neuroimaging (Experiment 5) and neuropsychological (Experiment 6) investigations of human spatial navigation.

Cellular signaling by tyrosine phosphorylation in keloid and normal human dermal fibroblasts

Keloids represent a dysregulated response to cutaneous wounding that results in disfiguring scars. Unique to humans, keloids are characterized by an accumulation of extracellular matrix components. The underlying molecular mechanisms of keloid pathogenesis, however, remain largely uncharacterized. Similarly, cellular signaling mechanisms, which may indicate inherent differences in the way keloid fibroblasts and normal human dermal fibroblasts interact with extracellular matrix or other cells, have not been investigated. As part of a fundamental assessment of cellular response to injury in keloid fibroblasts, phosphorylation studies were performed using three different keloid (n = 3) and normal human dermal (n = 3) fibroblast cell lines. These studies were undertaken to elucidate whether keloid and normal human dermal fibroblasts exhibit different tyrosine kinase activity. Initially, distinct tyrosine phosphorylation patterns of keloid and normal human dermal fibroblasts were demonstrated. Next, the phosphorylation patterns were correlated with known molecules that may be important to keloid pathogenesis. On the basis of molecular weight, it was hypothesized that the highly phosphorylated bands seen in keloid fibroblasts represented epidermal growth factor receptor (EGFR); discoidin domain receptor 1 (DDR1); and Shc, an adaptor protein known to bind many tyrosine kinases, including EGFR and DDR1. Individual immunoblotting using EGFR, DDR1, and Shc antibodies revealed greater expression in keloid fibroblasts compared with normal human dermal fibroblasts. These data substantiate for the first time the finding of greater phosphorylation by the above-mentioned molecules, which may be important in keloid pathogenesis.

Maximizing comfort and minimizing ischemia: a comparison of four methods of spinal immobilization

OBJECTIVE

To determine which of four methods of spinal immobilization causes the least ischemic pain.

METHODS

A prospective, nonblinded comparative trial was conducted at a statewide emergency medical services training facility using a convenience sample of emergency medical technician students. After lying motionless for 10 minutes, students evaluated each device using a 10-centimeter visual analog scale. Subjective comfort was used as a measure of ischemia.

RESULTS

Comfort scores were significantly different for all methods (F = 101, p < 0.001). A backboard padded with a gurney mattress and eggcrate foam (the equivalent of a spinal rehabilitation bed) caused the least ischemic pain (9.6 cm, 95% CI, 8.9 to 9.8 cm). A backboard padded with a gurney mattress was the second most comfortable device (7.0 cm, 95%/CI, 6.4 to 7.4 cm). A backboard padded with a folded blanket was the third most comfortable (3.3 cm, 95% CI, 2.6 to 4.9 cm). The backboard alone caused the most pain (0.8 cm, 95% CI, 0.7 to 2.1 cm).

CONCLUSION

Increasing the amount of padding on a backboard decreased the amount of ischemic pain caused by immobilization.

The use of newborn rats and an adenoviral gene delivery vector as a model system for wound-healing research

An attractive experimental method to elucidate the role of growth factors and cytokines in cutaneous wound healing would be to overexpress or "knock out" a molecule using a gene delivery vector and observe the impact on the wound repair process. As a first step toward developing an adenoviral gene delivery procedure to study wound repair, the authors injected beta-galactosidase (beta-gal) adenoviruses either subcutaneously or intradermally into the dorsal skin of 10-day-old postnatal Sprague-Dawley rats. Histological analysis and beta-gal staining were used to determine the expression and localization of the transferred gene. Beta-gal expression was observed as early as day 1 and up to day 7 postintradermal injection and day 9 postsubcutaneous injection, with no obvious inflammatory reaction detected at the injection sites. Furthermore, as expected, greater beta-gal expression was observed in the dermis of intradermally injected rats compared with the dermis of subcutaneously injected rats. Next, the authors sought to determine whether cutaneous wounds would heal before dissipation of the transferred gene. They created incisional and excisional wounds on the backs of similar-age rats. They found that incisional wounds closed by day 5 postwounding, whereas excisional wounds closed by day 14 postwounding. Their study demonstrated that an adenoviral vector delivered a gene efficiently into newborn rat skin and maintained the gene expression for at least as long as it would take for an incisional wound to heal. The combined use of newborn rat wound models and an adenoviral vector may provide a useful in vivo system to define the biological roles of growth factors and cytokines involved in the wound repair process. These discoveries may lead to the development of gene therapy approaches for abnormal wound healing.

Integrated temporal regulation of the photorespiratory pathway. Circadian regulation of two Arabidopsis genes encoding serine hydroxymethyltransferase

The photorespiratory pathway is comprised of enzymes localized within three distinct cellular compartments: chloroplasts, peroxisomes, and mitochondria. Photorespiratory enzymes are encoded by nuclear genes, translated in the cytosol, and targeted into these distinct subcellular compartments. One likely means by which to regulate the expression of the genes encoding photorespiratory enzymes is coordinated temporal control. We have previously shown in Arabidopsis that a circadian clock regulates the expression of the nuclear genes encoding both chloroplastic (Rubisco small subunit and Rubisco activase) and peroxisomal (catalase) components of the photorespiratory pathway. To determine whether a circadian clock also regulates the expression of genes encoding mitochondrial components of the photorespiratory pathway, we characterized a family of Arabidopsis serine hydroxymethyltransferase (SHM) genes. We examined mRNA accumulation for two of these family members, including one probable photorespiratory gene (SHM1) and a second gene expressed maximally in roots (SHM4), and show that both exhibit circadian oscillations in mRNA abundance that are in phase with those described for other photorespiratory genes. In addition, we show that SHM1 mRNA accumulates in light-grown seedlings, although this response is probably an indirect consequence of the induction of photosynthesis and photorespiration by illumination.

Cadherin repertoire determines partner-specific gap junctional communication during melanoma progression

Reduced gap junction activity has long been implicated in tumorigenesis. To elucidate the potential role of intercellular communication in melanoma development, we examined gap junctional capability of melanocytic cells from various stages of tumor progression in coculture models using dye transfer assays. Normal melanocytes coupled with keratinocytes by gap junctional formation, whereas melanoma cells did not. Instead, melanoma cells communicated among themselves and with fibroblasts. This switch in communication partners coincided with a shift from E-cadherin to N-cadherin expression during melanoma development. Forced expression of E-cadherin by adenoviral gene transfer in N-cadherin-expressing melanoma cells restored gap junctional compatibility with keratinocytes. Our data suggest that (1) melanocyte transformation is associated with loss of the pre-existing gap junctional activity with keratinocytes but a concomitant gain of communication with a newly juxtaposed cell type, the fibroblasts, (2) the specificity of gap junctional formation during melanoma development is determined by the cadherin profile on the melanocytic cells and (3) the overall gap junctional activity of melanocytic cells is not reduced with transformation.

The effect of mutations in the HIV-1 nucleocapsid protein on strand transfer in cell-free reverse transcription reactions

Interactions between the nucleocapsid protein (NC) and reverse transcriptase of HIV-1 have been shown to promote the initiation of reverse transcription. We assayed the effect of NC on later events, using a strand transfer system with donor and acceptor HIV RNA templates and found that the presence of NC resulted in increased synthesis of full-length strand-transferred (FLST) DNA. This effect also occurred with mutated forms of NC that lacked both zinc fingers, or that contained a point mutation (histidine-->cysteine) at amino acid 23. In contrast, NC-derived proteins containing only the proximal or distal zinc fingers, or lacking the N- and C-termini, were all unable to catalyze the synthesis of FLST DNA. Band-shift assays using both the mutated and wild-type forms of these proteins revealed that all the NC proteins promoted strand association between (-) strong-stop DNA [(-)ssDNA] and acceptor RNA. The zinc finger motifs were dispensable for full-length processive reverse transcription, and the N- and C-termini were required; however, all NC domains were dispensable for association of (-)ssDNA and acceptor RNA. This suggests that annealing is a less stringent reaction than DNA polymerization.

Interactions between human immunodeficiency virus type 1 reverse transcriptase, tRNA primer, and nucleocapsid protein during reverse transcription

An early step in the life cycle of human immunodeficiency virus type 1 is the reverse transcription of the viral RNA genome into double-stranded DNA, which is subsequently translocated to the cell nucleus. It is then integrated into host DNA and serves as a template for viral gene expression. Reverse transcription is catalyzed by the viral enzyme reverse transcriptase and is a complex process comprising a series of RNA-dependent DNA polymerization, DNA-dependent DNA polymerization, and RNase H reactions. Strand transfer reactions are required to complete the process. Reverse transcription is initiated when a molecule of host cell tRNA(lys3), which serves as a primer, is bound to the primer binding site of viral genomic RNA. The viral nucleocapsid protein is involved in each of the initiation of reverse transcription and in subsequent strand transfer or template-switching events. We review the interactions among reverse transcriptase, viral genomic RNA, the tRNA primer of reverse transcription, and viral nucleocapsid protein in the various steps of reverse transcription, including primer placement, initiation, and processive synthesis.

Distribution of salicylic acid in human stratum corneum following topical application in vivo: a comparison of six different formulations

Distribution of salicylic acid in human stratum corneum from treatment of six different formulations was assessed by quantitation of drug content in sequentially tape-stripped stratum corneum after a single 2-h dose was applied unoccluded to skin on the ventral forearm of four female subjects. The profile and total amounts of stratum corneum removed in 20 tape-strips varied among different types of formulations. With or without normalization by the total stratum corneum weights removed, the extent of drug delivery to the stratum corneum decreased in the following order: SA (5%) > > SAC (10%), Duofilm (16.7%) > TSSS (2%) > SAO (10%), Salic (2.5%), the percentage in parentheses indicating the salicylic acid concentration in each formulation. The greatest topical bioavailability was observed for the alcoholic solution containing glycerol (SA). The 10% collodion formulation (SAC) was found to deliver an amount of salicylic acid into the stratum corneum 2-fold greater than 10% ointment formulation (SAO). Use of absorption ointment (TSSS) also increased the uptake of salicylic acid into the stratum corneum in comparison with formulations based on simple ointment (SAO) and oil in water (o/w) cream (Salic). The partitioning of salicylic acid from collodion formulations (SAC and Duofilm) appeared to be concentration-independent. The results of this study indicate that topical bioavailability of salicylic acid in the stratum corneum varies substantially among different formulations.

Expression of E-cadherin/catenin complex in nasopharyngeal carcinoma: correlation with clinicopathological parameters

The E-cadherin/catenin complex plays an essential role in maintaining intimate intercellular associations and is considered to be involved in tumor metastasis and suppressing invasion by cancer cells. We have analyzed the expression of E-cadherin/catenin complex in a series of nasopharyngeal carcinoma (NPC) specimens using immunohistochemistry and immunoblotting. Data are correlated with the patients' clinicopathological parameters, including the clinical stage, presence of intracranial invasion, presence of lymph node or distant metastasis, and histological grading. The E-cadherin/catenin complex is down-expressed in most of the samples examined. Correlation with clinicopathological parameters shows that expression of alpha- and beta-catenin is associated with the occurrence of intracranial invasion.

Function and sequence analyses of tumor suppressor gene p53 of CHO.K1 cells

The tumor suppressor gene p53 plays an important role in guarding genomic integrity. When induced in response to environmental results, the gene product of p53 functions as a transcription factor to transactivate genes involved in arresting the cell cycle and as a facilitator of DNA repair. In contrast, the status of p53 in Chinese hamster ovary (CHO) cells, commonly used as a model system for various studies including those involving the cell cycle and transformation, remains an enigma. In this study, the function and sequence of p53 in CHO.K1 cells were investigated. The level of p53 proteins was elevated on ultraviolet (UV) irradiation of the cells, and the proteins formed specific complexes as probed with DNA containing p53-binding sequences. Its activities toward responsive promoters were inducible by UV in a dose-dependent manner. Although p53 in CHO.K1 contained a single missense mutation at codon 211, the mutation apparently had no effect on the functional properties of the protein. The CHO.K1 cells on X-ray irradiation failed to arrest at G1 phase even when the cells were transfected with a wildtype human p53 gene, indicating that the failure probably was not caused by dysfunction of its p53, but by some other mechanism. This result is consistent with the finding that p21(Waf1/Cip1) is undetectable in UV-treated CHO.K1 cells, whereas Gadd45 is induced by UV light in the cells.

A comparison of the composition of silk proteins produced by spiders and insects

Proteins that are highly expressed and composed of amino acids that are costly to synthesize are likely to place a greater drain on an organism's energy resources than proteins that are composed of ingested amino acids or ones that are metabolically simple to produce. Silks are highly expressed proteins produced by all spiders and many insects. We compared the metabolic costs of silks spun by arthropods by calculating the amount of ATP required to produce their component amino acids. Although a definitive conclusion requires detailed information on the dietary pools of amino acids available to arthropods, on the basis of the central metabolic pathways, silks spun by herbivorous, Lepidoptera larvae require significantly less ATP to synthesize than the dragline silks spun by predatory spiders. While not enough data are available to draw a statistically based conclusion, comparison of homologous silks across ancestral and derived taxa of the Araneoidea seems to suggest an evolutionary trend towards reduced silk costs. However, comparison of the synthetic costs of dragline silks across all araneomorph spiders suggests a complicated evolutionary pattern that cannot be attributed to phylogenetic position alone. We propose that the diverse silk-producing systems of the araneoid spiders (including three types of protein glues and three types of silk fibroin), evolved through intra-organ competition and that taxon-specific differences in the composition of silks drawn from homologous glands may reflect limited or fluctuating amino acid availability. The different functional properties of spider silks may be a secondary result of selection acting on different polypeptide templates.

Roles of the human immunodeficiency virus type 1 nucleocapsid protein in annealing and initiation versus elongation in reverse transcription of viral negative-strand strong-stop DNA

To study the initiation of human immunodeficiency virus type 1 reverse transcription, we have used the viral nucleocapsid protein (NC7) to anneal tRNA3Lys primer onto viral genomic RNA and have then eliminated NC7 from this primer-template complex by digestion with proteinase K and phenol-chloroform extraction of residual protein. Our data show that saturating concentrations of NC7 resulted in the formation of an active tRNA-template complex that yielded enhanced production of full-length negative-strand strong-stop DNA [(-)ssDNA] and that this complex remained active even after the elimination of NC7. While both of the two Zn finger motifs found within NC7 were essential for efficient elongation, NC protein that contained a point mutation in the first Zn finger or that was devoid of both Zn fingers yielded primer-template complexes that could still be initiated in 1-base-extension assays. In contrast, the use of heat annealing to produce primer-template complexes resulted in proportions of full-length (-)ssDNA lower than those seen with NC protein, and the addition of NC protein to such preformed primer-template complexes was able to reverse this defect only to a marginal extent.

Neutralizing antibodies directed against the V3 loop select for different escape variants in a virus with mutated reverse transcriptase (M184V) than in wild-type human immunodeficiency virus type 1

The M184V substitution in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) encodes high-level resistance to the (-)-enantiomer of 2',3'-dideoxy-3'-thiacytidine (3TC) and low-level resistance to each of 2',3'-dideoxycytidine (ddC) and 2',3'-dideoxyinosine (ddI). This mutation also results in decreased HIV replication fitness in primary cells, diminished RT processivity, and increased RT fidelity. To assess the effect of this substitution on genetic variation in the HIV env region, we cultured both M184V-containing and wild-type BH10 in MT-4 cells in the presence of the neutralizing monoclonal antibody 447-52D, targeted to the GPGR epitope within the V3 loop of gp120. Outgrowth of viruses resistant to neutralization was followed by sequence analysis of the V3 loop by standard methodology. Wild-type HIV first showed escape after 15-22 days in culture. Sequence analysis revealed an arginine-to-lysine change within the GPGR epitope in the V3 loop (R20K, AGA --> AAA) in six of six clones sequenced after day 36. In contrast, M184V-containing HIV first showed escape between days 25 and 32 and sequence analysis revealed an aspartate-to-tyrosine change at amino acid 5 in V3 (N5Y; AAC --> TAC) in two of six clones at day 36 and in five of five clones at day 55. Similar results were obtained in two independent antibody selection protocols. The escape mutation in the wild type is consistent with the G --> A hypermutation observed in wild-type HIV-1, recently shown to cause an initial M184I change (before M184V) in 3TC-treated patients. In contrast, the N5Y substitution seen with M184V-containing HIV-1 is an A --> T transversion in V3.

Arabidopsis mutants define an in vivo role for isoenzymes of aspartate aminotransferase in plant nitrogen assimilation

Arabidopsis contains five isoenzymes of aspartate aminotransferase (AspAT) localized to the cytosol, chloroplast, mitochondria, or peroxisomes. To define the in vivo function of individual isoenzymes, we screened for Arabidopsis mutants deficient in either of the two major isoenzymes, cytosolic AAT2 or chloroplastic AAT3, using a native gel activity assay. In a screen of 8,000 M2 seedlings, three independent mutants deficient in cytosolic AAT2 (aat2) and two independent mutants deficient in chloroplastic AAT3 (aat3) were isolated. Mapping of aat2 and aat3 mutations and the five AspAT genes (ASP1-ASP5) established associations as follows: the mutation affecting aat2 maps with and cosegregates with ASP2, one of two expressed genes for cytosolic AspAT; the mutation affecting aat3 maps to the same location as the ASP5 gene encoding chloroplastic AspAT. Phenotypic analysis of the aat2 and aat3 mutants revealed a dramatic aspartate-related phenotype in one of the mutants deficient in cytosolic AAT2. The aat2-2 mutant displays an 80% reduction in levels of aspartate transported in the phloem of light-grown plants, and a 50% reduction in levels of asparagine transported in dark-adapted plants. These results indicate that cytosolic AAT2 is the major isoenzyme controlling aspartate synthesized for nitrogen transport in the light, and that this aspartate pool is converted to asparagine when plants are dark adapted.

Induction of calcitonin gene-related peptide-like immunoreactivity in hippocampal neurons following ischemia: a putative regional modulator of the CNS injury/immune response

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and immune cell modulator. In two studies within the hippocampal formation (HF), CGRP-like immunoreactivity (CGRP-LI) was increased in the inner molecular layer of the dentate gyrus after adrenalectomy and in mossy cells after colchicine-induced destruction of granule neurons. Given the increase in CGRP-LI following damage to the granule cell region of the HF, we investigated another trauma model, ischemia, that targeted different areas of the HF, CA1 region, and subiculum to ascertain the regional expression of this peptide after insult. Following ischemia, light microscopic evaluation showed CGRP-LI in basket cell-like neuronal perikarya within the dorsal subiculum and CA1 region of the hippocampus and in varicose fibers within the CA2 region of the hippocampus. Control rats rarely expressed CGRP-LI within neurons in these regions. In ischemic brains, double-labeled immunocytochemistry with antibodies to various neural markers demonstrated co-localization of CGRP-LI primarily within surviving subicular and CA1 cells resembling interneurons containing parvalbumin-LI or calbindin-LI. Electron microscopic analysis of the CA1 region from ischemic brains showed that CGRP-LI was contained in terminals with numerous small synaptic vesicles that formed symmetric synapses with perikarya and large dendrites of pyramidal cells, some of which were degenerating. Collectively, the data from this study and our previous study indicate that damage induces CGRP-LI expression in interneurons and nonprincipal cells in the area of damage, and we hypothesize that CGRP expression in surviving neurons within damage-related regions of the hippocampus is likely to be an important, and possibly a protective, component of the response of the nervous system to injury.

Higher fidelity of RNA-dependent DNA mispair extension by M184V drug-resistant than wild-type reverse transcriptase of human immunodeficiency virus type 1

Reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) has low fidelity compared with RTs of other retroviruses and cellular DNA polymerases. We and others have previously found that the fidelity of DNA-dependent DNA polymerization (DDDP) of M184V-mutated HIV-1 RT is significantly higher than that of wild-type RT. Viruses containing the M184V substitution are highly resistant to (-)-2'-dideoxy-3'-thiacytidine (3TC) in vitro and in patients treated with 3TC monotherapy. It was of interest to determine the fidelity of RNA-dependent DNA polymerization (RDDP) of M184V RT compared with wild-type because this step occurs first in reverse transcription; errors made during this step may be copied in subsequent polymerization steps. Using an in vitro mispaired primer extension assay, M184V-mutated RT exhibited 3-49-fold decreased frequency of mispair extension compared with wild-type RT. Fidelity differences between M184V and wild-type RT were most marked in extension of A:G (49-fold) and A:C (16-fold) mispairs, with only a marginal (3-fold) decrease in the extension of A:A mispairs. RT containing a methionine to isoleucine (M184I) mutation showed only slight increases in RDDP fidelity compared with wild-type, ranging from 1.5- to 6-fold increases. Of the three RTs tested, wild-type RT was the most error-prone, with mispair extension frequencies ranging from 6.674 x 10(-1) to 7.454 x10(-2).

Persistence of porcine reproductive and respiratory syndrome virus in intensive farrow-to-finish pig herds

An epidemiological study of porcine reproductive and respiratory syndrome (PRRS) within pig herds was conducted in 8 intensive farrow-to-finish pig farms. Persistence of PRRS virus (PRRSV) in pig herds was demonstrated by regular postmortem examination on 2 farms for a period of 2 y. Virus isolation and serum neutralization (SN) tests were performed on the sera collected from 9 groups of pigs (10 pigs/group) of various ages on 8 pig farms. Except for 1 farm, isolation rates of PRRSV reached the highest level of 70 to 100% of pigs 6 to 8 wk of age, which coincided with the lowest levels of maternal immunity. In 1 pig herd, sows (39 in total) with SN titers of < or = 1:2, 1:4-1:8, and > or = 1:16 were designated as groups 1, 2, and 3, respectively. Sera were obtained from their progeny (3 pigs randomly selected from each litter) at various ages from 0 to 22 weeks. A positive correlation (r = 0.377, P < 0.001) between the SN titers of sows and those of their progeny (1-week-old piglets) was observed. Pigs at the age of 6 wk, only 7.9% of group 1 pigs compared to 72.4% of group 3 pigs were seropositive. A significant difference (P < 0.01) in the percentage of pigs with PRRSV viremia among the 3 groups was observed, with the lowest level found in group 3 pigs. The isolation rates of PRRSV from serum reached the maximum at the age of 9 wk for all 3 groups. The results indicated that passively acquired serum antibodies conferred a protective effect for piglets; however, loss of passive immunity at various ages of pigs produced susceptible pigs that resulted in PRRSV persistence in the pig herds. Pigs 6 to 9 weeks old were the major reservoir for PRRSV in farrow-to-finish pig herds.

Effectiveness of 3TC in HIV clinical trials may be due in part to the M184V substitution in 3TC-resistant HIV-1 reverse transcriptase

OBJECTIVE

To measure the extent of HIV resistance to (-)-2',3'-dideoxy-3'-thiacytidine (3TC, lamivudine) within the context of monotherapy and to assess the presence of the M184V substitution in the case of 3TC-resistant viruses. Whether the success of 3TC in clinical trials could be due, in part, to an increase in the fidelity of HIV reverse transcriptase conferred by the M184V substitution was also considered.

METHODS

Two separate monotherapy studies were evaluated, one involving adults with CD4 counts > or = 300 x 10(6)/l, and the second involving children, some of whom had received antiretroviral treatment previously, while others were drug naive. Peripheral blood and plasma samples were collected regularly, and HIV isolation and determinations of drug median inhibitory concentration values were performed using umbilical cord mononuclear cells as targets. Amplification of the 184 mutation was performed by the polymerase chain reaction, using specific primer pairs. Fidelity determinations using purified, recombinant HIV reverse transcriptase derived from either wild-type virus or viruses that contained the 184V substitution were performed.

RESULTS

Phenotypic resistance was detected in almost all subjects at times ranging from 8-20 weeks after initiation of therapy. The 184V substitution was usually detected prior to the occurrence of phenotypic resistance to 3TC. Fidelity determinations revealed that the 184V substitution conferred an approximately 5- to 10-fold increase in HIV reverse transcriptase fidelity. In addition, titres of patient sera tested for their ability to neutralize autologous sequential viral isolates were stabilized in patients receiving 3TC therapy as opposed to other drugs.

CONCLUSIONS

Resistance to 3TC developed in virtually all subjects treated with this drug, and was associated with the appearance of an M184V mutation in HIV reverse transcriptase. The clinical benefit of 3TC therapy may be attributable in part to selection of viruses that are less able to replicate and mutate than the wild types.

Enhanced fidelity of 3TC-selected mutant HIV-1 reverse transcriptase

Monotherapy with (-)2',3'-dideoxy-3'-thiacytidine (3TC) leads to the appearance of a drug-resistant variant of human immunodeficiency virus-type 1 (HIV-1) with the methionine-184 --> valine (M184V) substitution in the reverse transcriptase (RT). Despite resulting drug resistance, treatment for more than 48 weeks is associated with a lower plasma viral burden than that at baseline. Studies to investigate this apparent contradiction revealed the following. (i) Titers of HIV-neutralizing antibodies remained stable in 3TC-treated individuals in contrast to rapid declines in those treated with azidothymidine (AZT). (ii) Unlike wild-type HIV, growth of M184V HIV in cell culture in the presence of d4T, AZT, Nevirapine, Delavirdine, or Saquinavir did not select for variants displaying drug resistance. (iii) There was an increase in fidelity of nucleotide insertion by the M184V mutant compared with wild-type enzyme.

AMPA receptors in the rat and primate hippocampus: a possible absence of GluR2/3 subunits in most interneurons

Amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors are assembled from the four subunits GluR1, 2, 3, 4 (or GluRA, B, C, D). AMPA channels that do not contain the GluR2 subunit are permeable to calcium. Recent studies indicate that excitotoxic as well as epileptic and ischemic cell damage may be mediated not only by N-methyl-Daspartate receptors, but also by AMPA receptors. The majority of interneurons in the hippocampus are resistant, but subsets of interneurons are consistently damaged in different disease states. Single immunolabeling using antibodies against AMPA receptor subunits, together with double immunolabeling for calcium-binding proteins (parvalbumin, calbindin and calretinin) and the neuropeptide somatostatin, were performed to study GluR1-4 immunoreactivity in interneuronal populations and principal cells. The ultrastructure of GluR1-4 labeled neurons was also examined using electron microscopy. With the exception of calbindin-positive interneurons, GluR2/3 was absent from hippocampal interneurons in both rat and monkey. In the rat, interneurons were more strongly immunoreactive against GluR1 than principal cells. In the monkey, immunoreactivity for GluR4 in interneurons was stronger than for GluR1. All GluR subunits were confined to spines, dendritic membrane and cytoplasm surrounding the nucleus but absent from axons and presynaptic terminals. Our findings suggest that hippocampal principal cells and interneurons express different complements of AMPA receptor subunits. Furthermore, the absence of GluR2 and/or GluR3 in both vulnerable and resistant interneurons subtypes indicates that knowledge of receptor subunit composition is not sufficient to predict neuronal vulnerability.

Development of a new scale for measuring acculturation: the Taiwan Aboriginal Acculturation Scale (TAAS)

As part of the Taiwan Aboriginal Study Project (TASP), a new acculturation scale (the Taiwan Aboriginal Acculturation Scale, or TAAS) has been developed among the aboriginal minorities of Austronesian origin in Taiwan. The design of the original 54 items was based on Milton Gordon's concept of assimilation in association with a careful consideration of cross-cultural validity. These items were administered to 144 subjects stratified by age and sex who were randomly sampled from four major Taiwanese aboriginal groups. Item analysis and factor analysis were applied to select an 18-item scale which has three subscales (factors): cultural assimilation, social assimilation, and social attitude. Results of validity and reliability studies of the TAAS were found to be acceptable. The development of TAAS demonstrates the applicability of the concept of acculturation as a process that involves changes both in attitude, and in behaviour, to non-western societies.

GABAergic inhibition of granule cells and hilar neuronal synchrony following ischemia-induced hilar neuronal loss

In the dentate gyrus, granule cells are ischemia-resistant, but at least five types of predominantly spiny hilar neurons are extremely vulnerable to ischemia. Many of the ischemia-sensitive subtypes of hilar neurons appear to be involved in: (i) the regulation of GABAergic inhibition in the dentate gyrus, and (ii) the generation of hilar neuronal synchrony. The present study examined functional consequences of ischemia-induced hilar neuronal loss on GABAergic inhibition of granule cells and hilar neuronal synchrony. Transient (15 min) forebrain ischemia was induced by a modification of the four-vessel-occlusion method producing a substantial hilar neuronal loss as demonstrated by the Gallyas silver stain method. Three months later, we have examined spontaneous and stimulus-evoked inhibitory postsynaptic currents mediated by both GABA(A) and GABA(B) receptors, and inhibitory bursts induced by 4-aminopyridine (50 microM) using whole-cell recordings in coronal brain slices maintained at 34-36 degree C in the presence of excitatory amino acid receptor blockers. Spontaneous dentate spikes reflecting hilar neuronal synchrony and synaptic responses evoked by perforant path stimulation were also recorded in vivo to assess synchrony and inhibition in the dentate gyrus. In spite of significant damage to several types of hilar neurons, there were no marked differences in the conductance, kinetics, and 4-aminopyridine-induced burst frequencies of synaptic GABA(A) and GABA(B) responses in granule cells. Furthermore, both paired-pulse inhibition and dentate spikes appeared to be normal in vivo. We conclude that there appears to be little impairment of GABAergic inhibition of granule cells or of hilar neuronal synchrony three months following a massive ischemic damage to spiny hilar neurons.

Human fatty acid synthase: properties and molecular cloning

Fatty acid synthase (FAS; EC 2.3.1.85) was purified to near homogeneity from a human hepatoma cell line, HepG2. The HepG2 FAS has a specific activity of 600 nmol of NADPH oxidized per min per mg, which is about half that of chicken liver FAS. All the partial activities of human FAS are comparable to those of other animal FASs, except for the beta-ketoacyl synthase, whose significantly lower activity is attributable to the low 4'-phosphopantetheine content of HepG2 FAS. We cloned the human brain FAS cDNA. The cDNA sequence has an open reading frame of 7512 bp that encodes 2504 amino acids (M(r), 272,516). The amino acid sequence of the human FAS has 79% and 63% identity, respectively, with the sequences of the rat and chicken enzymes. Northern analysis revealed that human FAS mRNA was about 9.3 kb in size and that its level varied among human tissues, with brain, lung, and liver tissues showing prominent expression. The nucleotide sequence of a segment of the HepG2 FAS cDNA (bases 2327-3964) was identical to that of the cDNA from normal human liver and brain tissues, except for a 53-bp sequence (bases 3892-3944) that does not alter the reading frame. This altered sequence is also present in HepG2 genomic DNA. The origin and significance of this sequence variance in the HepG2 FAS gene are unclear, but the variance apparently does not contribute to the lower activity of HepG2 FAS.

Ethanol enhances muscarinic cholinergic neurotransmission in rat hippocampus in vitro

Previous studies from our laboratory showed that ethanol enhances muscarinic excitatory responses in rat hippocampal neurons in vivo and, like muscarinic agonists, reduces the M-current (IM) in these neurons in vitro. Therefore, we used extracellular and intracellular recording techniques in the hippocampal slice preparation to examine the mechanisms underlying this ethanol-muscarinic interaction. Surprisingly, superfusion or local application of low concentrations of acetylcholine (ACh), carbachol (CCh) or muscarine reduced the amplitudes of CA1 field potentials evoked by stratum radiatum (SR) stimulation. This effect was blocked by 1 microM atropine but was independent of the method of agonist application, the site of application or the SR stimulus paradigm. In intracellular and extracellular single unit recordings, cholinergic depressions of field potentials were correlated with: (1) depolarization of pyramidal neurons; (2) spike discharge increases; (3) reduction of amplitudes of postsynaptic potentials and (4) reduction of late afterhyperpolarizations (AHPs). Superfusion of low ethanol concentrations (11-22 mM) alone had little effect on SR-evoked field potentials but enhanced (by 10-90%) both the depressions of evoked field potentials and depolarizations elicited by the muscarinic agonists. Ethanol (22-44 mM) also enhanced both the amplitude and duration of the muscarinic slow excitatory postsynaptic potentials (sEPSPs) recorded intracellularly in CA1 and CA3 neurons. This effect was enhanced by eserine and blocked by atropine, verifying involvement of muscarinic receptors. These results suggest that: (1) caution be used in interpreting results of field potential studies regarding drug-induced excitability changes; and (2) ethanol in just-intoxicating concentrations enhances endogenous muscarinic synaptic transmission as well as responses to exogenous muscarinic agonists.

Molecular basis of glucose-6-phosphate dehydrogenase (G6PD) deficiency in three Taiwan aboriginal tribes

We have investigated glucose-6-phosphate dehydrogenase (G6PD) deficiency in 220 unrelated aboriginal male subjects who belong to three different tribes (Saisiat, Ami, and Yami) in Taiwan. Our results show that the G6PD deficiency rates for Saisiat, Ami, and Yami people are 9.0% (6/67), 6.1% (6/99), and 0% (0/54), respectively. Among these deficiency cases, 4 of 6 (66.7%) Saisiat subjects have the 493 A-->G mutation and one carries the 1376 G-->T mutation, whereas, in Ami subjects, we found that four of six (66.7%) affected males have the 592 C-->T mutation and one carries the 493 A-->G mutation. These results contrast with our previous findings for Taiwan Chinese, in whom the 1376 G-->T mutation is the major mutant allele and accounts for 52.3% of the deficiency cases. This is the first report of G6PD deficiency characterized at the DNA level in Taiwan aboriginal populations.

Effect of cerebral ischemia on calcium/calmodulin-dependent protein kinase II activity and phosphorylation

The effects of cerebral ischemia on calcium/calmodulin-dependent kinase II (CaM kinase II) were investigated using the rat four-vessel occlusion model. In agreement with previous results using rat or gerbil models of cerebral ischemia or a rabbit model of spinal cord ischemia, this report demonstrates that transient forebrain ischemia leads to a reduction in CaM kinase II activity within 5 min of occlusion onset. Loss of activity from the cytosol fractions of homogenates from the neocortex, striatum, and hippocampus correlated with a decrease in the amount of CaM kinase alpha and beta isoforms detected by immunoblotting. In contrast, there was an apparent increase in the amount of CaM kinase alpha and beta in the particulate fractions. The decrease in the amount of CaM kinase isoforms from the cytosol but not the particulate fractions was confirmed by autophosphorylation of CaM kinase II after denaturation and renaturation in situ of the blotted proteins. These results indicate that ischemia causes a rapid inhibition of CaM kinase II activity and a change in the partitioning of the enzyme between the cytosol and particulate fractions. CaM kinase II is a multifunctional protein kinase, and the loss of activity may play a critical role in initiating the changes leading to ischemia-induced cell death. To identify a structural basis for the decrease in enzyme activity, tryptic peptide maps of CaM kinase II phosphorylated in vitro were compared. Phosphopeptide maps of CaM kinase alpha from particulate fractions of control and ischemic samples revealed not only reduced incorporation of phosphate into the protein but also the absence of a limited number of peptides in the ischemic samples. This suggested that certain sites are inaccessible, possibly due to a conformational change, a covalent modification of CaM kinase II, or steric hindrance by an associated molecule. Verifying one of these possibilities should help to elucidate the mechanism of ischemia-induced modulation of CaM kinase II.

Short-term and long-term changes in the postischemic hippocampus

We have demonstrated a far more widespread and selective ischemic cell damage than previously thought. In area CA3, a distinct subpopulation of interneurons, characterized by their spiny dendrites and their calretinin content, was selectively vulnerable in the absence of any other CA3 involvement. In the dentate hilus, four different types of spiny cells were consistently damaged. The common denominator in these two cell groups is the presence of spines on their dendrites and hence the greater density of mossy fiber innervation they receive. A common mechanism of cell death may be the presence of non-NMDA receptor subtypes that are highly permeable to calcium. We speculate that they may constitute an important control mechanism in the CA3 region and the hilus, and impairment of this mechanism may be causal to delayed neuronal death in CA1. We have also shown that neuronal degeneration does not end after delayed cell death of CA1 pyramidal cells. Our results suggest that there is progressive degeneration throughout the life of the animal and degeneration of additional cell populations (e.g. CA1 interneurons and CA3 pyramidal cells) may also occur secondary to the insult.

Four modified silver methods for thick sections of formaldehyde-fixed mammalian central nervous tissue: 'dark' neurons, perikarya of all neurons, microglial cells and capillaries

Four reliable silver methods for the visualization of acute or advanced phases of neuronal damage have been modified so that they can be performed with good results on materials freshly fixed with transcardial perfusion of buffered formaldehyde for other silver methods and immunocytochemical techniques. The four modified methods respectively stain: (1) the somata and dendrites of 'dark' (impaired) neurons, (2) the perikarya of all neurons, (3) microglial cells, and (4) capillaries. Without the present modifications the 'dark' neuron method is only effective with glutaraldehyde fixation while the other three methods predominantly stain myelin in freshly fixed mammalian nervous tissue.

Sex differences in minor psychiatric morbidity among three aboriginal groups in Taiwan: the effects of lineage

Sex differences in minor psychiatric morbidity (MPM) have been investigated among three aboriginal groups in Taiwan. The study included both ethnographic observation and a sample survey (N = 733) using a modified Clinical Interview Schedule. The findings lend support to the hypothesis that although a female excess of MPM will be found among the patrilineal group (the Bunun), the reverse will be observed in the matrilineal group (the Ami); no such difference will be found in the bilateral group (the Atayal). Further analysis revealed sex differences in the mean duration of MPM and similar incidence ratios between two sexes in these three groups. Possible sociocultural explanations are proposed.

Vulnerability of mossy fiber targets in the rat hippocampus to forebrain ischemia

Much of the work on forebrain ischemia in the hippocampus has focused on the phenomenon of delayed neuronal death in CA1. It is established that dentate granule cells and CA3 pyramidal cells are resistant to ischemia. However, much less is known about interneuronal involvement in CA3 or ischemic injury in the dentate hilus other than the fact that somatostatin neurons in the latter lose their immunoreactivity. We combined two sensitive methods--heat-shock protein (HSP72) immunocytochemistry and a newly developed Gallyas silver stain for demonstrating impaired cytoskeletal elements--to investigate the extent of ischemic damage to CA3 and the dentate hilus using the four-vessel-occlusion model for inducing forebrain ischemia. HSP72-like immunoreactivity was induced in neuronal populations previously shown to be vulnerable to ischemia. In addition, a distinct subset of interneurons in CA3 was also extremely sensitive to ischemia, even more so than the CA1 pyramidal cells. These neurons are located in the stratum lucidum of CA3 and possess a very high density of dendritic spines. In silver preparations, they were among the first to be impregnated as "dark" neurons, before CA1 pyramidal cells; microglial reaction was also initiated first in the stratum lucidum of CA3. Whereas CA1 damage was most prominent in the septal half of the hippocampus, hilar and CA3 interneuronal damage had a more extensive dorsoventral distribution. Our results also show a far greater extent of damage in hilar neurons than previously reported. At least four hilar cell types were consistently compromised: mossy cells, spiny fusiform cells, sparsely spiny fusiform cells, and long-spined multipolar cells. A common denominator of the injured neurons in CA3 and the hilus was the presence of spines on their dendrites, which in large part accounted for the far greater number of mossy fiber terminals they receive than their non-spiny neighbors. We suggest that the differential vulnerability of neuronal subtypes in these two regions may be attributed to their extremely dense innervation by the mossy fibers and/or the presence of non-NMDA receptor subtypes that are highly permeable to calcium. In addition, early impairment of these spiny CA3 cells and hilar neurons after ischemia may be causal to delayed neuronal death in the CA1 pyramidal cells.

The growth of Chinese minority populations

This is a review of recent demographic trends among the 55 recognized minority ethnic groups in China, which have a total population of 91.2 million. Reasons for the rapid growth among many of these populations since the 1960s are analyzed. They include "the significant improvement of public health in the 1950s and 1960s, the leniency in the implementation of the birth control policies in minority communities, the relatively high birth and fertility rates in these communities, and the reaffirmation of racial identity in the 1980s."

Maternal-fetal histocompatibility in intrauterine growth retarded and normal weight babies

PROBLEM

To determine whether risk for intrauterine growth retardation (IUGR) is increased in HLA-DQA1 compatible pregnancies.

METHOD

Paired maternal and cord blood samples were obtained from 30 IUGR and 31 non-IUGR pregnancies delivered at a university hospital. Samples were typed for eight HLA-DQA1 alleles using 10 sequence-specific oligonucleotides probes. Associations between IUGR and HLA-DQ compatibility status, and other risk factors were examined using logistic regression analysis.

RESULTS

HLA-DQ compatibility and history of spontaneous abortion were not individually significant risk factors for IUGR; however, there was an interactive effect between these two factors and IUGR (P = 0.085) that improved the overall fit of the logistic model (P < 0.001). No individual allele was more common in IUGR pregnancies.

CONCLUSIONS

HLA compatibility per se is not associated with sufficient inhibition of fetal growth to result in IUGR as defined. However, in women with a history of spontaneous abortion, HLA compatibility may have an effect.

Delayed degeneration of the optic tract and neurons in the superior colliculus after forebrain ischemia

Neuronal damage induced by 15-min forebrain ischemia was investigated in adult rats 1-5 days (short-term group) and 1-5 months (long-term group) after the initial ischemic attack. In addition to the vulnerable areas reported previously, we observed that the optic tract was also very susceptible. Degeneration of the optic tract and subsequent transsynaptic cell death in the superior colliculus developed slowly and was observed only in the long-term group. The delayed, progressive neuronal damage in this sensory system may serve as a suitable model to investigate the mechanisms of long-term changes in the injured brain.

An experimental study of the osteogenicity of free periosteal allografts with cyclosporine A administration

Free tibial periosteum was grafted onto the dorsum (m. cutaneous trunci) of Sprague-Dawley rats to examine its osteogenic potential. The animals were divided into 3 groups based on type of: A. autogenous periosteum, B. allogeneic periosteum and C. allogeneic periosteum, and treated with cyclosporine A immunosuppression. The osteogenic response was evaluated radiologically and histologically. This study indicates that in this model periosteal allografts with immunosuppression of the recipient result in osteogenesis. Clinical application of the technique will only be possible if immunosuppressive methods with minimal morbidity are developed so that they can be used for prolonged periods.

A community study of mental disorders among four aboriginal groups in Taiwan

In this paper background, objectives, methodology and a few preliminary findings of a comparative epidemiological study of mental disorders among four aboriginal groups in Taiwan are presented. The study includes both a cross-sectional sample survey (N = 993) and prospective cohort studies involving psychoses, minor psychiatric morbidity, alcoholism, suicide, and accidental death. The total response rate to the sample survey was 98.3%; respondents were found to be representative. A preliminary analysis found very high rates of death from suicide, accidents and chronic liver and lung disease with a previous history of alcoholism in many of these deaths. Implications of these findings and studies of risk factors of all these health problems and their relationships are discussed.