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Biomedical subjects

D M Wong

Publications and source records attributed to D M Wong.

35 records · Page 2Linked to original sources
PubMed1989

Structure of the human hepatic triglyceride lipase gene.

The structure of the human hepatic triglyceride lipase gene was determined from multiple cosmid clones. All the exons, exon-intron junctions, and 845 bp of the 5' and 254 bp of the 3' flanking DNA were sequenced. Comparison of the exon sequences to three previously published cDNA sequences revealed differences in the sequence of the codons for residues 133, 193, 202, and 234 that may represent sequence polymorphisms. By primer extension, hepatic lipase mRNA initiates at an adenine 77 bases upstream of the translation initiation site. The hepatic lipase gene spans over 60 kb containing 9 exons and 8 introns, the latter being all located within the region encoding the mature protein. The exons are all of average size (118-234 bp). Exon 1 encodes the signal peptide, exon 4, a region that binds to the lipoprotein substrate, and exon 5, an evolutionarily highly conserved region of potential catalytic function, and exons 6 and 9 encode sequences rich in basic amino acids thought to be important in anchoring the enzyme to the endothelial surface by interacting with acidic domains of the surface glycosaminoglycans. The human lipoprotein lipase gene has been recently reported to have an identical exon-intron organization containing the analogous structural domains [Deeb & Peng (1989) Biochemistry 28, 4131-4135]. Our observations strongly support the common evolutionary origin of these two lipolytic enzymes.

Amino Acid Sequence↗
PubMed1989

Postnatal development of the rostral solitary nucleus in rat: dendritic morphology and mitochondrial enzyme activity.

Morphological and metabolic development of the gustatory zone of the rostral nucleus of the solitary tract (NST) was examined in rat. Transganglionic transport of horseradish peroxidase (HRP) was used to visualize the organization of gustatory projections to the rostral gustatory NST in rats aged postnatal day 1 (P1) to P34. Golgi impregnation studies were performed to analyze morphological development of dendrites in regions of the rostral NST that were identified as anterior tongue terminal fields. Results demonstrate that afferent fibers of the anterior tongue project to the rostral NST in rats as young as P1. The volume of NST terminal fields increased from P1 to approximately P16-P20, and was adult-like after approximately P20. Developmental increases in terminal field volume resulted from a preferential expansion in the rostrocaudal plane. Planar length of first-order dendrites associated with fusiform, multipolar, and ovoid neurons, and second-order dendrites of fusiform and ovoid neurons, increased approximately three-fold between P4 and P16-20. First-order dendritic length for all morphological types was adult-like after approximately 20-25 days of age, whereas second-order dendritic length of multipolar neurons increased significantly between P30 and P60-70. Histochemical studies confirmed that activity of the mitochondrial respiratory enzymes cytochrome c oxidase (EC 1.9.3.1), succinate dehydrogenase (EC 1.3.99.1), and NADH-dehydrogenase (EC 1.6.99.3) increased monotonically during the developmental period in which planar growth of first-order dendrites was observed. The present results, in combination with results from previous studies, indicate that morphological and metabolic development fo the NST occurs concomitantly with morphological development of taste receptors and peripheral gustatory nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1989

Virus-like infectious agent (VLIA) is a novel pathogenic mycoplasma: Mycoplasma incognitus.

The newly recognized pathogenic virus-like infectious agent (VLIA), originally reported in patients with AIDS but also known to be pathogenic in previously healthy non-AIDS patients and in non-human primates, was cultured in cell-free conditions using a modified SP-4 medium and classified as a member of the order Mycoplasmatales, class Mollicutes. The infectious microorganism is tentatively referred to as Mycoplasma incognitus. M. incognitus has the unique biochemical properties of utilizing glucose both aerobically and anaerobically, as well as having the ability to metabolize arginine. Among all known human mycoplasmas, these specific biochemical characteristics were found previously only in a rarely isolated species, M. fermentans. In comparison with M. fermentans, M. incognitus appears to be even more fastidious in cultivation requirements and fails to grow in all tested mycoplasma media other than modified SP-4 medium. In addition, M. incognitus grows much more slowly, has a smaller spherical particle size and occasional filamentous morphology, and forms only irregular and very small colonies with diffuse edges on agar plates. Antigenic analysis using polyclonal and monoclonal antibodies and DNA analysis of sequence homology and restriction enzyme mappings in M. incognitus, M. orale, M. hyorhinis, M. hominis, M. pneumoniae, M. fermentans, M. arginini, M. genitalium, M. salivarium, Ureaplasma urealyticum, and Acholeplasma laidlawii revealed that M. incognitus is distinct from other mycoplasmas, but is most closely related to M. fermentans.

Animals↗
PubMed1989

Identification of Mycoplasma incognitus infection in patients with AIDS: an immunohistochemical, in situ hybridization and ultrastructural study.

Monoclonal antibodies (Mabs) were developed against antigens from a pure culture of Mycoplasma incognitus grown in modified SP-4 medium. All the Mabs obtained were shown to react only with M. incognitus, and not with other species of human mycoplasma. The Mabs identified M. incognitus immunohistologically in thymus, liver, spleen, lymph node, or brain from 22 patients with AIDS, as well as in 2 placentas delivered by patients with AIDS. Using an 35S-labeled DNA probe specific for M. incognitus and in situ hybridization technique, we also identified M. incognitus-specific genetic material in these tissues. Furthermore, ultrastructural studies of the specific areas of tissues which were highly positive for M. incognitus antigens revealed characteristic structures of mycoplasma organisms. These mycoplasma-like particles could be identified intracellularly and extracellularly. Histopathology of the tissues infected by M. incognitus varied from no pathological changes to fulminant necrosis with or without an associated inflammatory reaction. M. incognitus, a novel pathogenic mycoplasma, was cytopathic and cytocidal.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Factors influencing Clostridium botulinum spore germination, outgrowth, and toxin formation in acidified media.

Clostridium botulinum type A spores were inoculated at a level of 10(7) spores per ml into sterile beef media with protein concentrations of 1, 2, 3, 4, or 6% and acidified to pH values of 2.01 to 4.75 with hydrochloric acid or 4.19 to 4.60 with citric acid. All experimental manipulations, including blending, acidification, inoculation, incubation (30 degrees C), and analyses, were conducted in an anaerobic chamber-incubator in which atmospheric oxygen levels were maintained below 2 ppm (2 microliters/liter). Under these strict anaerobic conditions (oxidation-reduction values in media ranging from -370 to -391 mV), C. botulinum spores were consistently found to germinate, grow, and produce toxin below pH 4.6. The boundary between toxic and atoxic samples in HC1-acidified beef media was mediated by titratable acidity, pH, and protein concentration. A limiting acidity was not established for the citrate-acidified samples; all blends tested (1, 2, 3, and 4% protein and titratable acidities of 0.091 to 0.453%) became toxic within 5 weeks. At the same pH and protein concentration, citric acid was less effective than HC1 in preventing the germination of C. botulinum spores. Higher levels of cell proliferation in the beef protein, as well as enhanced gas production and putrefactive degradation, indicated that beef was a better substrate than soy for C. botulinum spores under these conditions. Reducing the inoculum to 10(4) delayed but did not prevent spore outgrowth and toxin release at pH levels below 4.6.

Anaerobiosis↗
PubMed1986

Chemical and biological characterization of the galactose binding lectins from Trichosanthes kirilowii root tubers.

Three galactose binding isolectins have been isolated from Trichosanthes kirilowii root tubers. Two of the isolectins, TK-I and TK-II, are similar in many aspects including molecular weight, amino acid composition, NH2-terminal amino acid residue, blood group and carbohydrate specificities, immunodiffusion and immunoelectrophoretic behavior, hemagglutinating and insulinomimetic activities, and in possessing subunits with different molecular weights. Compared to TK-I and TK-II, lectin TK-III has a larger molecular weight, subunits with the same molecular weight, a single and distinctive NH2-terminal amino acid residue, a different isoelectric point and lower hemagglutinating activity. The three lectins share common antigenic determinants in their structures. beta-Linked terminal oligosaccharides containing D-galactose inhibit hemagglutination induced by the lectins with a higher potency than alpha-linked oligosaccharides. The lectins are non-mitogenic and did not inhibit the concanavalin-A induced mitogenic response of lymphocytes.

Adipose Tissue↗
PubMed1985

An anti-I-A murine monoclonal antibody which cross-reacts with HLA-DR2.

A murine monoclonal antibody, 12.7G3, directed against an Ia antigen encoded by genes in the I-Ab subregion of the H-2 genetic complex, was found to be cytotoxic against human B lymphocytes. When tested against a random panel of normal human donors, the reactivity of 12.7G3 exhibited a correlation coefficient of 0.58-0.68 with cells expressing HLA-DR2. Antibody reactivity segregated with HLA-DR2 in two families studied. Binding of 12.7G3, as detected by immunofluorescence using flow microfluorometry, was positive for two human cell lines, GM 3161 and HFB-1, both expressing HLA-DR2, and negative for two other cell lines, GM 3104 (DR1,1) and GM 3164 (DR4,4).

Animals↗
PubMed1983

Enhancement of reactivity of HLA-Cw antisera by extending the incubation time.

HLA-Cw antisera showing weak cytotoxic activity when tested at 1 1/2 hours in the conventional HLA-A,B, Cw testing procedure, were found to react better in the test using an extended incubation period of 3 hours. Of the 71 sera which were tested, 15 (21%) sera demonstrated an increase in anti-HLA-Cw reactivity against cells from donors possessing the corresponding Cw antigen. In addition, the use of B cells in the testing procedure appeared to be more favorable than T cells in the enhancement of reactivity of weak HLA-Cw antisera.

B-Lymphocytes↗
PubMed1983

Cross reactivity in the HLA region.

Cross-reactivity in the HLA region was studied by adsorbing each of 33 monospecific HLA antisera individually with known platelets from 90 different donors. The residual cytotoxicity following adsorption in each combination of platelet sample and antiserum was assessed against known homologous target lymphocytes. This study has confirmed a majority of the previously known cross-reactive pattern and has revealed new patterns. A more significant observation is that allelic cross-reactivity of broad antigens such as A9, A10 and Bw16, was somewhat narrowed to a given split of these antigens in several instances; e.g., cross-adsorption of A1 antiserum by Aw24, and not Aw23; of A2 antiserum by A26, and not A25; and of B5 antiserum by Bw39, and not Bw38.

Adsorption↗
PubMed1979

Immune activation by T-independent antigens: lack of effect of macrophage depletion on the immune response to TNP-LPS, PVP and dextran.

Carrageenan, a sulphated polysaccharide, and rabbit anti-mouse macrophage serum, were used to inhibit macrophage function in BALB/c mice as well as to deplete macrophages from spleen cell cultures in an attempt to determine the requirement for macrophages in the immune response to several thymus-independent antigens. Carrageenan inhibited macrophage function and was cytotoxic at low concentrations. The ability of T and B lymphocytes to undergo mitogen-induced proliferation in the presence of PHA and PLS, respectively, was not affected by in vitro exposure of lymphoid cells to carrageenan. BALB/c mice injected with carrageenan demonstrated a suppressed immune response to SRBC, a thymus-dependent antigen, but not to E. coli LPS, polyvinyl-pyrrolidone or dextran B-1355S, all of which are known to be thymus independent antigens. The sensitivity of the in vivo immune response to SRBC after depletion of macrophages by carrageenan treatment was confirmed in vitro using the Marbrook--Diener culture system. The in vitro immune response to TNP-LPS was unaffected by either carrageenan treatment or treatment of BALB/c spleen cells with AMS and complement. The results of experiments which utilized the two anti-macrophage reagents, carrageenan and AMS, both in vivo and in vitro systems, suggest that the immune response to thymus-independent antigens does not require the participation of macrophages.

Animals↗
PubMed1978

In vitro induction of Lyt surface markers on precursor cells incubated with thymosin polypeptides.

Induction of precursor T cells by thymosin fraction 5 was found to generate a population of cells bearing the Lyt 1+, 2+, and 3+ phenotype and functionally capable of providing T-cell helper activity in vitro. However, when the component polypeptides of thymosin fraction 5 were similarly analyzed, several displayed inductive activities quite different from those of the parent preparation. These results suggest that variations in the polypeptide composition determine, to a large part, the inductive properties of a thymosin preparation and that such variations in vivo may serve as a regulatory system for T-cell maturation.

Animals↗