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Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

At least 721 records · Page 40Linked to original sources
PubMed1996

Efficacy of BMS-180194 against experimental cytomegalovirus infections in immunocompromised mice.

A new antiviral nucleoside, BMS-180194 [1R-(1 alpha, 2 beta, 3 alpha)]- 2-amino-9[2,3-bis(hydroxymethyl)cyclobutyl]-1,9dihydro-6H-purin-6- one, is a broad spectrum antiviral agent. The antiviral effectiveness of BMS-180194 against murine cytomegalovirus (MCMV) infection in immunocompromised C57BL/6 mice was investigated and was compared to that of ganciclovir (GCV). LP-BM5 murine retrovirus complex-induced immunocompromised C57BL/6 mice were challenged with MCMV then treated intraperitoneally or per os with various doses of BMS-180194 ranging from 30 to 3 mg/kg/day. When administered intraperitoneally, BMS-180194 was effective against MCMV-mediated mortality in a dose-dependent manner demonstrating a 50% protective dose (PD50) of 3.12 mg/kg/day which was comparable to that of GCV. There was a marked reduction in organ MCMV titers in BMS-180194-treated animals (10-10,000- fold lower than the placebo controls). Similar findings were observed when the compound was administered orally. Interestingly, oral BMS-180194 demonstrated a similar antiviral efficacy as that obtained by the parental route of administration suggesting a high oral bioavailability of the compound. Oral ganciclovir treatment, however, required more than a 4-fold higher amount of GCV to confer the same degree of protection obtained by a parenteral route of administration. Oral BMS-180194 was also effective in reducing the organ MCMV titer in genetically severe combined immunodeficient (SCID) mice. The parenteral or oral antiviral efficacy of BMS-180194 was comparable to that of parenteral ganciclovir against MCMV infection in the present study. Doses of BMS-180194 employed in the present study showed no toxicity to mice. These results suggest that BMS-180194 may be of value as an oral antiviral agent for treatment of opportunistic CMV infections in immunocompromised individuals.

Administration, Oral↗
PubMed1996

The immunodominant proteins of reticuloendotheliosis virus.

The antigenic profiles of three REV prototype strains, CSV, SNV and REV-T and eight Israeli isolates were analysed by SDS-PAGE and immunoblotting with convalescent chicken serum, three mAbs, 11A25, 11C237 and 11C100, a rabbit antiserum to REV-T whole virus (Cui et al., 1986) and a rabbit antiserum to REV-A p30 gag protein (Tsai et al., 1985). Under both reducing (+DTT) and non-reducing conditions of SDS-PAGE, a major immunodominant 75-100 kDa band was shared by all strains examined. In contrast to the chicken serum that recognized both continuous and discontinuous epitopes on the 75-100 kDa band of all the isolates, the mAbs and the two rabbit sera behaved otherwise. Only the DTT-resistant epitopes on the 75-100 kDa band of REV-T were recognized by the rabbit antisera and the mAb 11C237, and only the DTT-labile epitopes of REV-T 75-100 kDa antigen were detected by mAb 11C100. The two mAbs 11A25 and 11C237 detected discontinuous epitopes of all the strains except SNV, while the rabbit antisera recognized the discontinuous epitopes on the 75-100 kDa band of all the 11 strains. The rabbit antisera and mAb 11C237 detected additional lower molecular weight proteins and the mAb 11C237 also detected three proteins of high molecular weight under non-reducing conditions only. The p30 antiserum detected the low molecular weight proteins demonstrating their gag gene-encoded identity. From these results we conclude that the major immunogen of REV is the 75-100 kDa protein that contains both continuous and discontinuous epitopes. With this panel of antibodies the eight new isolates appeared to belong antigenically to REV subtype 3 (Chen et al., 1987).

Animals↗
PubMed1996

Fluconazole distribution to the brain: a crossover study in freely-moving rats using in vivo microdialysis.

PURPOSE: The purpose of this study was to determine if the microdialysis sampling technique is feasible to study the central nervous system distributional kinetics of a novel triazole antifungal agent, fluconazole, in an awake, freely-moving rat model, and to determine fluconazole distribution to the extracellular fluid (ECF) of the brain. METHODS: The relative recovery of the microdialysis probes (CMA-12) was determined in vitro and in vivo by retrodialysis using UK-54,373, a fluorinated analog of fluconazole. Sprague-Dawley rats received 10 mg/kg and 20 mg/kg fluconazole IV bolus doses in a crossover design, and brain extracellular fluid fluconazole concentrations were monitored using microdialysis and on-line HPLC analysis. The plasma fluconazole concentration vs. time data were determined using sequential blood sampling and HPLC analysis. RESULTS: There was no statistical difference between relative probe recoveries for both fluconazole and UK-54,373, either in vitro or in vivo, and probe recoveries did not change during the course of the in vivo crossover experiment. Fluconazole rapidly distributes into in the brain ECF and the average brain distribution coefficient (brain/plasma AUC ratio) was 0.60 +/- 0.18 and was independent of dose. Plasma pharmacokinetic parameters were linear in the dose range studied. CONCLUSIONS: Fluconazole rapidly reaches a distributional equilibrium between brain extracellular fluid and plasma, and the distribution to the brain is substantial and not dependent on dose over a two-fold range. Furthermore, the results indicate that microdialysis utilizing UK-54,373 as the in vivo retrodialysis probe calibrator is a feasible method to study the transport of fluconazole into the central nervous system.

Animals↗
PubMed1996

The binding of cyclosporin A to human plasma: an in vitro microdialysis study.

PURPOSE: The human plasma binding of cyclosporin A was studied in vitro using the technique of microdialysis. The effect of temperature on the overall binding interaction between cyclosporin A and human plasma was also investigated. METHODS: Flow-through loop-type microdialysis probes were constructed from fused silica tubing and regenerated cellulose tubing with a MWCO of 13000 daltons. Probes were perfused with phosphate buffer (0.5 microliters/min) and the concentration of 3H-cyclosporin A in the well-mixed medium (plasma or buffer) was 1200 ng/ml. Relative recoveries of cyclosporin A from plasma or buffer were determined for each probe by separate experiments to measure the solute gain or loss with reference to the perfusate. RESULTS: Recoveries determined by loss were significantly greater than those determined by gain and in each case temperature dependent, with higher recoveries at higher temperatures. The plasma free fraction of cyclosporin A calculated from the recovery data and the perfusate to plasma concentration ratios was dependent on temperature in a log-linear fashion. Mean +/- s.d. plasma free fractions expressed in percent were 33.5 +/- 4.6, 17.9 +/- 3.6, 6.2 +/- 0.8, 3.0 +/- 0.6, and 1.5 +/- 0.2 at temperatures of 4, 10, 20, 30, and 37 degrees C, respectively. Assuming that the enthalpy of binding is constant over the temperature range studied and pseudo-first order conditions exist, the binding reaction at these temperatures was spontaneous, endothermic (delta H = 74.0 kJ/mole), and entropically driven (delta S = 0.274 kJ/mole/deg). CONCLUSIONS: These results show that the free fraction of cyclosporin A in human plasma is dependent on temperature with the fraction unbound decreasing with temperature in the range of 4 to 37 degrees C. The thermodynamic parameters for the binding of cyclosporin A to plasma components indicate that the reaction is a spontaneous endothermic reaction that is mainly entropy driven, similar to the partitioning of lipophilic molecules from an aqueous to a hydrophobic phase. Moreover, these results show that microdialysis is a feasible method to determine the binding interactions between plasma and cyclosporin A, which indicates the method may be suitable for other difficult binding studies where the solutes have nonspecific binding to separation devices.

Blood Proteins↗
PubMed1996

Porcine CD3 epsilon: its characterization, expression and involvement in activation of porcine T lymphocytes.

The cloning, characterization and expression of porcine CD3 epsilon and establishment of its role in T-cell activation using an anti-porcine CD3 epsilon monoclonal antibody, as described here, provides a first step towards a greater understanding of the porcine immune response. Porcine CD3 epsilon was cloned from a porcine T-cell cDNA library by polymerase chain reaction and found to have up to 72% identity with other CD3 epsilon chains, retaining all the necessary primary structural motifs for correct functioning of porcine CD3 epsilon. When expressed in COS7 cells porcine CD3 epsilon was an intracellularly localized, monomeric 23,000 MW protein exhibiting no evidence of N-glycosylation. A monoclonal antibody, PPT3, recognized expressed porcine CD3 epsilon and activated porcine T cells as demonstrated by stimulation of calcium mobilization, an increase in protein tyrosine phosphorylation and proliferation. These results further reaffirm and identify CD3 epsilon as an important cell surface protein involved in signal transduction of activation signals in porcine T cells.

Amino Acid Sequence↗
PubMed1996

Preparation of monoclonal anti-porcine CD3 antibodies and preliminary characterization of porcine T lymphocytes.

The CD3-T-cell receptor complex is the clonotypic surface structure by which T lymphocytes recognize foreign antigens and are subsequently activated. Because of the low immunogenicity of the CD3 molecules, anti-CD3 monoclonal antibodies (mAb) are difficult to prepare and have not been available in several species. Following isolation of porcine CD3, 14 anti-porcine CD3 mAb were prepared, which define six groups of CD3-epsilon epitopes, coprecipitate two types of TCR and reveal considerable heterogeneity of CD3 expression amongst lymphocyte subpopulations. Thus, both CD3 positive and negative subpopulations of CD2 or CD8 positive cells were found in the blood. The density of CD3 on CD2+ or CD8+ cells was relatively low and heterogeneous, whereas the CD2-, CD8- or MAC320+ T cells expressed CD3 at a higher and more homogeneous level. Finally, in the thymus, staining with anti-CD3 resolved large thymocytes into two subsets: one expressing a high level of CD3 and the other being negative. In contrast, small thymocytes expressed CD3 at a low and more homogeneous level. Immunohistological studies confirmed the presence of clearly detectable CD3 in thymus medulla and the T-cell regions of peripheral lymphoid tissues. Most of the mAb were mitogenic, when presented to peripheral blood mononuclear cells in immobilized form. The anti-CD3 mAb also induced redirected cytotoxicity which was shown to be Fc receptor dependent.

Animals↗
PubMed1996

Phenotypic classification of porcine lymphocyte subpopulations in blood and lymphoid tissues.

The pig is a useful model for the heterogeneity of the mammalian immune system and has also recently received attention as a possible source of organs for human transplantation. Here we report a detailed analysis of porcine lymphocyte phenotypes. Peripheral blood alpha beta T cells consisted of four subsets (CD4+8-, CD4+8lo, CD4-8lo and CD4-8hi) and gamma delta T cells of three (CD2-4-8-, CD2+4-8lo and CD2+4-8-). There were in addition, a large proportion of non-T-non-B lymphocytes with CD2+3-4-8lo surface immunoglobulin-negative phenotype containing natural killer (NK) activity. A striking observation was the relatively low frequency of alpha beta T cells in the blood of young pigs. Similar phenotypes were also identified in the cells from peripheral lymphoid tissues, though the proportions of the gamma delta T cells and the non-T-non-B lymphocytes in the lymph nodes and tonsil were much lower and the majority of the gamma delta T cells in the lymphoid tissues bore CD2 and or CD8. In thymus, the small thymocytes were predominantly CD3-4+8+ while the mature large thymocytes displayed phenotypes similar to those of peripheral T cells. Thus this work has directly defined porcine alpha beta and gamma delta T cells demonstrated the T-cell nature of the unique CD4+8+ subset of peripheral lymphocytes, revealed the high heterogeneity of the CD8+ cells, and established the phenotype of NK cells. The functional properties of these defined porcine lymphocyte subsets can now be experimentally determined in health and disease.

Animals↗
PubMed1996

Tumor necrosis factor microsatellites define a Crohn's disease-associated haplotype on chromosome 6.

BACKGROUND & AIMS: HLA class II associations have been described in Crohn's disease (CD) and ulcerative colitis (UC) and may be markers for other closely linked genes that are involved in disease pathogenesis. The tumor necrosis factor (TNF) locus, which contains the genes for TNF-alpha and TNF-beta, is located on chromosome 6 within the major histocompatibility complex loci. To investigate potential genetic associations in inflammatory bowel disease at the TNF locus, we studied 75 patients with CD, 73 patients with UC, and 60 ethnically matched controls using microsatellite markers. METHODS: Five TNF microsatellite loci (TNFa, TNFb, TNFc, TNFd, and TNFe) were typed using polymerase chain reaction. RESULTS: A CD-associated allelic combination, TNFa2b1c2d4e1, was found in 24% of patients with CD, 4.1% of patients with UC (P=0.001; odds ratio, 7.4; CD vs. UC), and 6.7% of control subjects (P=0.01; odds ratio, 4.4 CD vs. controls). This TNF haplotype was associated with the previously described HLA-DR1/DQ5 combination in CD. CONCLUSIONS: The TNFa2b1c2d4e1 allelic combination is the strongest genetic risk factor described in CD and, with HLA class II alleles, defines a group of markers on chromosome 6 that extends from HLA class II to upstream of the TNF-beta gene.

Alleles↗
PubMed1996

Perinuclear antineutrophil cytoplasmic antibodies in patients with Crohn's disease define a clinical subgroup.

BACKGROUND & AIMS: Antineutrophil cytoplasmic antibodies (ANCA) have been consistently detected in a subgroup of patients with Crohn's disease (CD). This study was designed to determine whether serum ANCA expression in patients with CD characterizes an identifiable clinical subgroup. METHODS: The study population consisted of 69 consecutive patients with an established diagnosis of CD as determined by a combination of characteristic clinical, radiographic, endoscopic, and histopathologic criteria. Sera from the patients were analyzed for the presence of ANCAs using the fixed neutrophil enzyme-linked immunosorbent assay (ELISA) assay. Perinuclear ANCA (pANCA)-positive and cytoplasmic ANCA (cANCA)-positive results by ELISA were confirmed by indirect immunofluorescence staining. Clinical profiles of the ANCA-positive patients with CD were compared with those of patients with CD not expressing ANCA (ANCA-negative). RESULTS: pANCA-positive patients with CD have endoscopically and/or histopathologically documented left-sided colitis and symptoms of left-sided colonic inflammation, clinically reflected by rectal bleeding and mucus discharge, urgency, and treatment with topical agents. One hundred percent of patients with CD expressing pANCA had "UC-like" features. CONCLUSIONS: In patients with CD, serum pANCA expression characterizes a UC-like clinical phenotype. Stratification of CD by serum pANCA provides evidence of heterogeneity within CD and suggests a common intestinal mucosal inflammatory process among a definable subgroup of patients with CD and UC expressing this marker.

Adult↗
PubMed1996

Angiotensin II regulation of neuromodulation: downstream signaling mechanism from activation of mitogen-activated protein kinase.

Angiotensin II (Ang II) stimulates expression of tyrosine hydroxylase and norepinephrine transporter genes in brain neurons; however, the signal-transduction mechanism is not clearly defined. This study was conducted to determine the involvement of the mitogen-activated protein (MAP) kinase signaling pathway in Ang II stimulation of these genes. MAP kinase was localized in the perinuclear region of the neuronal soma. Ang II caused activation of MAP kinase and its subsequent translocation from the cytoplasmic to nuclear compartment, both effects being mediated by AT1 receptor subtype. Ang II also stimulated SRE- and AP1-binding activities and fos gene expression and its translocation in a MAP kinase-dependent process. These observations are the first demonstration of a downstream signaling pathway involving MAP kinase in Ang II-mediated neuromodulation in noradrenergic neurons.

Angiotensin II↗
PubMed1996

Coordinate genetic regulation of glycogen catabolism and biosynthesis in Escherichia coli via the CsrA gene product.

The carbon storage regulator gene, csrA, encodes a factor which negatively modulates the expression of the glycogen biosynthetic gene glgC by enhancing the decay of its mRNA (M. Y. Liu, H. Yang, and T. Romeo, J. Bacteriol. 177:2663-2672, 1995). When endogenous glycogen levels in isogenic csrA+ and csrA::kanR strains were quantified during the growth curve, both the rate of glycogen accumulation during late exponential or early stationary phase and its subsequent rate of degradation were found to be greatly accelerated by the csrA::kanR mutation. The expression of the biosynthetic genes glgA (glycogen synthase) and glgS was observed to be negatively modulated via csrA. Thus, csrA is now known to control all of the known glycogen biosynthetic genes (glg), which are located in three different operons. Similarly, the expression of the degradative enzyme glycogen phosphorylase, which is encoded by glgY, was found to be negatively regulated via csrA in vivo. The in vitro transcription-translation of glgY was also specifically inhibited by the purified CsrA gene product. These results demonstrate that localization of glycogen biosynthetic and degradative genes within the Escherichia coli glgCAY operon facilitates their coordinate genetic regulation, as previously hypothesized (T. Romeo, A. Kumar, and J. Preiss, Gene 70:363-376, 1988). The csrA gene did not affect glycogen debranching enzyme, which is now shown to be encoded by the gene glgX.

Bacterial Proteins↗
PubMed1996

Length changes in the joining segment between domains 5 and 6 of a group II intron inhibit self-splicing and alter 3' splice site selection.

Domain 5 (D5) and domain 6 (D6) are adjacent folded hairpin substructures of self-splicing group II introns that appear to interact within the active ribozyme. Here we describe the effects of changing the length of the 3-nucleotide segment joining D5 to D6 [called J(56)3] on the splicing reactions of intron 5 gamma of the COXI gene of yeast mitochondrial DNA. Shortened variants J(56)0 and J(56)1 were defective in vitro for branching, and the second splicing step was performed inefficiently and inaccurately. The lengthened variant J(56)5 had a milder defect-splicing occurred at a reduced rate but with correct branching and a mostly accurate 3' splice junction choice. Yeast mitochondria were transformed with the J(56)5 allele, and the resulting yeast strain was respiration deficient because of ineffective aI5 gamma splicing. Respiration-competent revertants were recovered, and in one type a single joiner nucleotide was deleted while in the other type a nucleotide of D6 was deleted. Although these revertants still showed partial splicing blocks in vivo and in vitro, including a substantial defect in the second step of splicing, both spliced accurately in vivo. These results establish that a 3-nucleotide J(56) is optimal for this intron, especially for the accuracy of 3' splice junction selection, and indicate that D5 and D6 are probably not coaxially stacked.

Base Sequence↗
PubMed1996

Videokeratography database of normal human corneas.

AIM: To form a database of videokeratography patterns and quantitative indices describing normal human corneas using the absolute scale. METHODS: Both eyes of 195 normal subjects were examined with a TMS-1 videokeratoscope. Videokeratographs were divided into 10 categories based on a classification scheme devised from the absolute scale and analysed with 10 quantitative indices devised to describe phenotypic features of keratoconus videokeratographs. Correlations were sought between videokeratograph patterns and quantitative indices. Additionally, data were analysed for differences in age, sex, and ethnicity. RESULTS: For symmetric videokeratography patterns, analysis in the absolute scale was similar to a previous study done in the normalised scale. In the asymmetric categories, analyses differed markedly. Using the absolute scale and our classification scheme more variation in normal videokeratography patterns could be appreciated. There was good correlation between quantitative indices and videokeratography patterns. Neither videokeratography patterns nor indices differed significantly between sex, ethnic groups, or age using two way analysis of variance. CONCLUSIONS: Pattern analysis of videokeratographs in the absolute scale using, a standard classification scheme, may be more useful in trying to determine whether a cornea is normal or represents subtle early disease than analysis in the normalised scale. Quantitative indices could remove the subjectivity from the decision making process thus facilitating universal reproducibility of videokeratography data interpretation.

Adult↗
PubMed1996

Role of prostaglandins and calcitonin gene-related peptide in central vagal cholinergic-dependent protection against gastric injury in urethane-anesthetized rats.

The influence of central vagal activation induced by the thyrotropin-releasing hormone (TRH) analog, RX 77368, injected intracisternally on gastric mucosal injury produced by 60% ethanol (4 ml.kg-1) was investigated in urethane-anesthetized rats. RX 77368 (3, 10 and 30 ng) inhibits dose dependently macroscopic gastric damage induced by intragastric administration of 60% ethanol by 18, 43 and 77%, respectively. The cytoprotective effect of intracisternal RX 77368 (30 ng) was completely blocked by cervical vagotomy, atropine (2 mg.kg-1 s.c.), and CGRP8-37 (100 micrograms.kg-1 i.v.) and partially inhibited by indomethacin (5 mg.kg-1 i.p.). Vagotomy, atropine, indomethacin and CGRP8-37 alone did not modify gastric mucosal lesions induced by ethanol in rats injected intracisternally with saline. The present data show that intracisternal injection of TRH analog in urethane-anesthetized rats protects against ethanol-induced gastric injury through vagal cholinergic dependent pathways which recruit prostaglandins and CGRP mechanisms.

Anesthesia↗
PubMed1996

Lack of cross talk between alpha1-adrenergic and angiotensin type 1 receptors in neurons of spontaneously hypertensive rat brain.

Norepinephrine causes downregulation of angiotensin II (Ang II) receptors in Wistar-Kyoto rat (WKY) brain neuronal cultures. The aim of this study was to compare the cross talk between Ang II and alpha1-adrenergic receptors in these neuronal cultures. Norepinephrine causes a 66 percent decrease in Bmax of Ang II type 1 (AT1) receptors in neuronal cultures of WKY brain. This decrease is mediated by the interaction of norepinephrine with the alpha1a-adrenergic receptor subtype. Norepinephrine also causes a decrease in mRNA levels for AT1 receptors. A maximal decrease of 83 percent in AT1, receptor mRNA is observed in 8 hours with 100 micromol/L norepinephrine, is blocked by 5-methyluradipil, and involves inhibition of AT1 receptor transcription. Furthermore, decreases in the AT1 receptor and its mRNA are associated with a significant attenuation of AT1 receptor-mediated stimulation of norepinephrine transporter mRNA in WKY brain neurons. In contrast, norepinephrine does not decrease AT1 receptors or mRNA and has no effect on Ang II stimulation of norepinephrine transporter mRNA in neuronal cultures of spontaneously hypertensive rat brain. Thus, these data show that norepinephrine-mediated downregulation of AT1 receptors is associated with a parallel decrease in AT1 mRNA and Ang II stimulation of norepinephrine transporter mRNA and involves the alpha1a-adrenergic receptor in neurons of WKY brain. This cross talk between the two receptors is lacking in neurons of spontaneously hypertensive rat brain.

Animals↗
PubMed1996

Computer evaluation of second tarsometatarsal joint dislocation.

Using computer-assisted techniques, this study analyzes the mean contact area of the articular surface of the second tarsometatarsal joint. The articular contact area decreased proportionate to the displacement in both males and females, but it was consistently greater in males than in females for all simulated displacements. The reduction in the contact area was the highest with dorsolateral displacement compared with the lateral and dorsal displacements. Dorsolateral displacement of the second metatarsal of 3 mm led to 38.6% reduction in the contact area, compared with 33.1% and 20.2% reduction with lateral and dorsal displacements, respectively. This study shows that even minor degrees of displacement not apparent on plain radiographs lead to significant decrease in the contact area of the second tarsometatarsal joint. Careful evaluation of second tarsometatarsal injuries with computed tomography is recommended to detect minor degrees of displacement.

Computer Simulation↗
PubMed1996

Mutations affecting the development of the embryonic zebrafish brain.

In a large scale mutagenesis screen for embryonic mutants in zebrafish, we have identified 63 mutations in 24 loci affecting the morphogenesis of the zebrafish brain. The expression of marker genes and the integrity of the axonal scaffold have been studied to investigate abnormalities in regionalization, neurogenesis and axonogenesis in the brain. Mutants can be broadly classified into two groups, one affecting regionalization along the anterior-posterior or dorsal-ventral axis, and the other affecting general features of brain morphology. The first group includes one locus that is required to generate the anlage of the midbrain-hindbrain boundary region at the beginning of somitogenesis. Four loci were identified that affect dorsal-ventral patterning of the brain, including the previously described cyclops locus. Mutant embryos of this class show a reduction of ventral neuroectodermal structures and variable fusion of the eyes. The second group includes a large class of mutations affecting the formation of brain ventricles. Analysis of this class reveals the requirement of a functional cardiovascular system for ventricle enlargement during embryogenesis. Mutations in one locus lead to the formation of supernumerary primary neurons, a phenotype reminiscent of neurogenic mutants in Drosophila. Other mutant phenotypes described here range from abnormalities in the fasciculation and outgrowth of axons to defects in the diameter of the neural tube. The identified loci establish the genetic foundation for a further analysis of the development of the zebrafish embryonic brain.

Animals↗