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Biomedical subjects

H T Wang

Publications and source records attributed to H T Wang.

At least 19 recordsLinked to original sources
PubMed1995

Isolation and characterization of a tyrosinase from the skin of the white silky fowl (Gallina lanigera) employing copper saturated diethylaminoethyl-cellulose.

Tyrosinase was purified to apparent homogeneity from the skin of the White Silky fowl (Gallina lanigera). Under alkaline conditions copper ions from a complex with the diethylaminoethyl moiety of DEAE-cellulose, allowing the purification of the enzyme in a one step chromatography. In polyacrylamide gel electrophoresis containing sodium dodecyl sulfate the purified tyrosinase displays a single band with a relative molecular mass of 66,000 Da. The crystalline tyrosinase was obtained from 32-33% saturated solution of ammonium sulfate. The enzyme catalyzes the o-hydroxylation of L-tyrosine to L-dihydroxyphenylalanine as well as the oxidation of pyrocatechol to o-benzoquinone. For the pyrocatechol oxidation the Michaelis Menten constant Km, is calculated to be around 1.19 x 10(-3) M.

Animals↗
PubMed1995

Identification of an idiotypic peptide recognized by autoantibodies in human immunodeficiency virus-1-infected individuals.

Antibodies against HIV-1 proteins in HIV-1-infected individuals share a cross-reactive idiotype defined by the monoclonal antiidiotypic antibody 1F7 (5). Using a computer algorithm based on the molecular recognition theory, regions of inverse hydropathy between the variable sequence of 1F7 and human monoclonal anti-HIV-1 antibodies were identified, which are assumed to be involved in idiotype-antiidiotype contacts. A peptide was designed from the proposed contact in the variable heavy chain framework 3-complementarity determining region 3 (FR3-CDR3) of human antibodies and was synthesized. This peptide is recognized by the antiidiotype 1F7 and inhibits the binding of 1F7 to human anti-HIV-1 antibodies which express the 1F7 idiotype. A survey of normal and HIV-1-infected sera revealed the presence of antibodies in infected sera which bind to the FR3-CDR3 peptide. The biological relevance of autoantibodies against a self idiotope associated with HIV-1 infection is discussed in the context of the regulation of the antibody response to HIV-1.

Algorithms↗
PubMed1995

Effects of small-volume infusion of 7.5% hypertonic saline/6% dextran-70 on the cardiovascular function of traumatic-hemorrhagic shock rats at high altitude.

This study was designed to evaluate the effects of small-volume infusion of 7.5% hypertonic saline/6% dextran-70 (HSD) on the cardiovascular function of traumatic-hemorrhagic shock rats at simulated high altitude. 32 rats were randomly divided into four groups: 1) normal saline (NS)-treated group, 2) .9% NaCl/6% dextran-70 (Dex)-treated group, 3) 7.5% hypertonic saline (HS)-treated group, and 4) 7.5% hypertonic saline/6% dextran-70 (HSD)-treated group. The rats were exposed to a simulated high altitude of 4,000 m in a hypobaric hypoxic chamber, and traumatic-hemorrhagic shock was inflicted through fracture of the shaft of the left femur and bleeding from femoral vein to reduce mean arterial pressure (MAP) to 6.00 +/- .67 kPa within 5 min. The MAP was kept at this level for 1 h, and then a bolus intravenous injection of 4 mL/kg NS, Dex, HS, or HSD were given to the rats, respectively. In the 5 h period after treatment, it was found that MAP, left ventricular systolic pressure, maximal rate of left ventricular pressure rise and drop (+/- dp/dtmax) were significantly higher in HSD group than in the NS, Dex and HS groups. It can be concluded that 1) HSD can improve the cardiovascular function and hemodynamics of traumatic-hemorrhagic shock rats at simulated high altitude and 2) HSD is more effective than HS.

Altitude↗
PubMed1994

Cloning, sequence, and disruption of the Saccharomyces diastaticus DAR1 gene encoding a glycerol-3-phosphate dehydrogenase.

The Saccharomyces diastaticus DAR1 gene was cloned by complementation in an Escherichia coli strain auxogrophic for glycerol-3-phosphate. DAR1 encodes an NADH-dependent dihydroxyacetone phosphate reductase (sn-glycerol-3-phosphate dehydrogenase [G3PDase; EC 1.1.1.8]) homologous to several other eukaryotic G3PDases. DAR1 is distinct from GUT2, which encodes a glucose-repressed mitochondrial G3PDase, but is identical to GPD1 from S. cerevisiae, a close relative of S. diastaticus. The level of DAR1-encoded G3PDase was increased about threefold in a medium of high osmolarity. Disruption of DAR1 in a haploid S. cerevisiae was not lethal but led to a decrease in cytoplasmic NADH-dependent G3PDase activity, an increase in osmotic sensitivity, and a 25% reduction in glycerol secretion from cells grown anaerobically on glucose.

Amino Acid Sequence↗
PubMed1994

Duplex ultrasound of extracranial carotid artery in a male patient of Takayasu's arteritis: a case report.

Takayasu's arteritis is a chronic inflammatory disease of artery. Its etiology is still uncertain. The disease mostly involves aorta and its major branches. We recently examined a young male patient using duplex Doppler ultrasound (DUS). High resolution real-time ultrasound revealed long-segment stenosis over common carotid arteries on both sides and internal carotid arteries, mostly due to adventitia thickening. Doppler ultrasound showed increased blood velocity of bilateral common carotid arteries with spectral broadening. B-mode findings correlated well with those of Doppler's, and all the information obtained from DUS was compatible with those of angiography. DUS is helpful in diagnosis of Takayasu's arteritis and provides hemodynamic data of the diseased carotid arteries. It can also be used as an effective tool for follow-up in patients with Takayasu's arteritis.

Adult↗
PubMed1993

A non-lymphoma idiotype is indicative and predictive for B cell malignancies in AIDS.

The 1F7 idiotype previously defined (J Immunol 147:933;1991 and Eur J Immunol 22:1749;1992) is expressed on antibodies reactive to different proteins of HIV (gp41, p24, gp120). Since serum levels of 1F7 (IgM or IgG) are significantly higher in patients with HIV lymphoma as opposed to HIV-infected individuals, normal controls and non-HIV lymphoma patients, we hypothesized the B-cell neoplasms were the source of the idiotype. However, immunohistochemistry on cryostat sections revealed no 1F7 idiotype signal on neoplastic B-cells nor tumor infiltrative T-cells (n = 8). Interestingly, reactive lymphocytosis adjacent to tumor masses and reactive follicular hyperplastic controls (n = 5) exhibited significant 1F7 reactivity. The reactivity appeared in paracortical and perifollicular lymphoid regions, predominantly regions of B, T and antigen presenting cells in lymph nodes or tonsils. A survey of electrophoretically defined paraproteins with anti-HIV specificities derived from HIV-infected patients showed no Western blot reactivity with the 1F7 anti-idiotypic antibody. Therefore, the idiotype does not appear to be a direct product of B-cell neoplasia or abnormal B-cell proliferation, but is produced by B cell clones responding to HIV infection. This high level of serum 1F7 reactivity could be an important clue in the pathogenesis of HIV lymphomas and confers a highly predictive serological test for HIV lymphoma.

Animals↗
PubMed1991

Generation and specificity of monoclonal anti-idiotypic antibodies against human HIV-specific antibodies. I. Cross-reacting idiotopes are expressed in subpopulations of HIV-infected individuals.

In this study we have generated monoclonal anti-idiotypic antibodies against human monoclonal and polyclonal anti-HIV antibodies in seropositive sera. A human anti-gp41 mAb (H2, IgM kappa) was used to immunize BALB/c mice and to prepare hybridoma anti-antibodies that react with H2 and not with normal human IgM. Similar monoclonal anti-antibodies were made in BALB/c mice immunized with Ig fraction prepared from a pool of HIV-seropositive sera. Both kinds of anti-idiotypic antibodies reacted with antibodies in pools of seropositive sera and with individual seropositive sera but not with normal human Ig or seronegative sera. The Id-positive Ig from single donors were isolated on two different anti-Id immunoabsorbents and shown to bind to p24 and gp120, respectively. The detection and isolation of idiotypically cross-reactive human anti-HIV antibodies from seropositive donors demonstrated, for the first time, the existence of shared Id expressed by antibodies against HIV Ag. The utility of cross-reacting anti-idiotypic antibodies as tools to dissect the network regulation of the anti-viral immunity in AIDS is discussed.

Animals↗
PubMed1990

Degradation of poly(ester) microspheres.

Biodegradable polymeric microspheres have been prepared by spray drying, precipitation, rotary evaporation and press grinding methods. Erosion of microspheres of poly(lactide), poly(3-hydroxybutyrate), copolymers of lactide and glycolide, and copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate at 85 degrees C and 37 degrees C have been studied using ion chromatography, nuclear magnetic resonance, residual mass measurements, viscometry and gel permeation chromatography. Such studies demonstrated that these polyester matrices degraded via (1) random chain scission and (2) release of soluble monomeric and oligomeric products. Protein release from microspheres prepared by these methods indicated that most of the protein is released before the polymer matrix loses weight.

Biodegradation, Environmental↗
PubMed1990

Nucleotide sequence and promoter analysis of SPO13, a meiosis-specific gene of Saccharomyces cerevisiae.

The SPO13 gene, required for meiosis I segregation in Saccharomyces cerevisiae, produces two developmentally regulated transcripts (1.0 and 1.4 kilobases) that differ in length at their 5' ends. The shorter transcript is sufficient to complement the spo13-1 mutation and contains a major open reading frame encoding a highly basic protein of 33.4 kilodaltons. A fragment upstream (-170 to -8) of the open reading frame confers meiosis-specific transcription on a spo13-HIS3 fusion. Deletions at the 5' end of spo13-lacZ fusions define a region between -140 and -80 that is essential for meiosis-specific expression. This region acts in an orientation-independent manner and is responsive to the MAT-RME regulatory cascade. It contains a 10-base-pair sequence, TAGCCGCCGA, found in a number of meiosis-specific genes, that appears to be required for SPO13 expression. This sequence is identical to URS1, a ubiquitous mitotic repressor element.

Amino Acid Sequence↗
PubMed1989

Computing motion in the primate's visual system.

Computing motion on the basis of the time-varying image intensity is a difficult problem for both artificial and biological vision systems. We will show how one well-known gradient-based computer algorithm for estimating visual motion can be implemented within the primate's visual system. This relaxation algorithm computes the optical flow field by minimizing a variational functional of a form commonly encountered in early vision, and is performed in two steps. In the first stage, local motion is computed, while in the second stage spatial integration occurs. Neurons in the second stage represent the optical flow field via a population-coding scheme, such that the vector sum of all neurons at each location codes for the direction and magnitude of the velocity at that location. The resulting network maps onto the magnocellular pathway of the primate visual system, in particular onto cells in the primary visual cortex (V1) as well as onto cells in the middle temporal area (MT). Our algorithm mimics a number of psychophysical phenomena and illusions (perception of coherent plaids, motion capture, motion coherence) as well as electrophysiological recordings. Thus, a single unifying principle 'the final optical flow should be as smooth as possible' (except at isolated motion discontinuities) explains a large number of phenomena and links single-cell behavior with perception and computational theory.

Algorithms↗
PubMed1987

Developmental regulation of SPO13, a gene required for separation of homologous chromosomes at meiosis I.

Previous studies have demonstrated that the SPO13 gene is required for chromosome separation during meiosis I in Saccharomyces cerevisiae. In the presence of the spo13-1 nonsense mutation, MATa/MAT alpha diploid cells complete a number of events typical of meiosis I including premeiotic DNA synthesis, genetic recombination, and spindle formation. Disjunction of homologous chromosomes, however, fails to occur. Instead, cells proceed through a single meiosis II-like division and form two diploid spores. In this paper, we report the cloning of this essential meiotic gene and an analysis of its transcription during vegetative growth and sporulation. Disruptions of SPO13 in haploid and diploid cells show that it is dispensible for mitotic cell division. Diploids homozygous for the disruptions behave similarly to spo13-1 mutants; they sporulate at wild-type levels and produce two-spored asci. The DNA region complementing spo13-1 encodes two overlapping transcripts, which have the same 3' end but different 5' ends. The major transcript is 400 bases shorter than the larger, less abundant one. The shorter RNA is sufficient to complement the spo13-1 mutation. While both transcripts are undetectable or just barely detectable in vegetative cultures, they each undergo a greater than 70-fold induction early during sporulation, reaching a maximum level about the time of the first meiotic division. In synchronously sporulating populations, the transcripts nearly disappear before the completion of ascus formation. Nonsporulating cells homozygous for the mating-type locus show a small increase in abundance (less than 5% of the increase in sporulating cells) of both transcripts in sporulation medium. These results indicate that expression of the SPO13 gene is developmentally regulated and starvation alone, independent of the genotype at MAT, can trigger initial induction.

Chromosomes↗
PubMed1985

A cis-acting sequence promotes removal of simian virus 40 DNA from the replication pool.

Pulse-labeled simian virus 40 (SV40) DNA is removed from the pool of molecules available for replication (i.e., it ceases to reenter replication) a few hours after synthesis. We studied this cessation of reentry with mutants containing different deletions in the structural genes of SV40. The DNAs of two independent deletion mutants, dl-1007 (24% deletion) and dl-1003 (8% deletion), were used as templates for further DNA synthesis (i.e., they reentered replication) to a greater extent than was wild-type DNA. The alteration in reentry kinetics was not because the DNAs were smaller; other deletion mutations that were from 76 to 85% of the length of wild-type DNA (dl-BE and dl-1133 with a deletion in the late region and F8dl with a deletion in the early region) did not reenter replication to a greater extent than the wild type did. Cotransfection experiments showed that the mutant phenotypes of dl-1007 and dl-1003 were poorly complemented, if at all, by the wild type. Thus, we propose that there is a cis-acting sequence located in the HindIII E fragment of SV40, not present in either of these mutants, that promotes the efficient removal of DNA from the replication pathway.

Animals↗