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Biomedical subjects

H K Wang

Publications and source records attributed to H K Wang.

61 records · Page 4Linked to original sources
PubMed1990

[The structure of astrachrysosid A and the study of 2D-NMR on astrasieversianin XV and 7,2'-dihydroxy-3',4'-dimethoxy-isoflavane-7-O-beta-D-glycoside].

Six compounds were isolated from the root of Astragalus chrysopterus Bunge. One of them was identified as a new triterpenoid glycoside, named astrachrysoside A. Its structure was elucidated as 3-O-[alpha-L-rhamnopyranosyl (1----2) beta-D-xylopyranosyl]-cycloastragenol on the basis of physicochemical evidence and chemical reactions. The others were shown to be known compounds, astrasieversianin XV (II), 7,2'-dihydroxy-3',4'-dimethoxy-isoflavane-7-O-beta-D-glucoside (III), soyasaponin I, daucosterol and beta-sitosterol. Full assignment of the chemical shift signals of II and III were established by various 2D-NMR techniques.

Chemical Phenomena↗
PubMedDate not supplied

Photopatterning of antibodies on biosensors.

The immobilization of biomolecules on surfaces in defined micropatterns has become increasingly important for the development of new diagnostic devices and high-throughput genetic and drug screening protocols. We describe the synthesis and testing of thiol-reactive, photoactivatable linkers that will permit laser micropatterning or photolithographic patterning of surfaces. In these linkers, a benzophenone photophore is tethered through a variable-length poly(ethylene glycol) hydrophilic spacer to a maleimide group. Spacers containing one to five ethylene glycol units were examined. Antibodies were photoimmobilized on polystyrene waveguides and the resulting biosensors were used for fluorescence immunoassays. The spacer with five ethylene glycol units optimally decreased the steric interactions among large molecules (antibodies and antigens) and increased binding capacity and response rate of the biosensor. Two different sandwich assay protocols were examined. In the first, the antigen and fluorescently labeled second antibody were added sequentially to the biosensor ("stepwise"). In the second, the antigen and antibody were premixed before injection into the biosensor ("premixed"). The stepwise protocol gave a significantly higher response than that of the premixed protocol. Although the premixed protocol is more convenient, the stepwise protocol provides enhanced sensitivity.

Antibodies↗
PubMedDate not supplied

Lymphocytic subsets and histopathologic changes associated with the development of heart transplant arteriosclerosis.

Transplantation of vascularized organ allografts is associated with the development of arteriosclerosis in the vessels of the donor graft. We have recently examined the distribution of lymphocytic/mononuclear inflammatory cell subsets and histopathologic changes seen in the sequential development of transplant arteriosclerosis in cardiac allografts exchanged between inbred rat strain combinations (LEW-to-F344) that differ for weak histocompatibility loci. The donor grafts were harvested at 7, 14, 21, 28, 50 to 65, and 90 days after transplantation, and the vascular lesions were characterized for the immunopathologic changes associated with the chronic rejection of the grafts. The inflammatory cell infiltration of the graft myocardium was present as early as 7 days after transplantation (53.37 +/- 9.06 inflammatory cells/high-power field), and the accumulation of cells increased at 3 and 4 weeks after transplantation (112.12 +/- 16.58 and 130.40 +/- 21.24 cells/high-power field, respectively). The infiltrating inflammatory cells in the grafts at 4 weeks after transplantation were predominantly ED-1+ macrophages (63.39%), with a substantial number of OX19+ T lymphocytes (28%), OX8+ Tc/s cells (25.4%), 3.2.3+ natural killer cells (16.89%), W3/25+ Th cells (20.2%), and a small number of OX33+ B lymphocytes (1.13%) and interleukin-2 receptor+ T lymphocytes (2.6%). Among the T-cell population, most (87.6%) were positive (R73+) for T-cell receptors. The arteriosclerotic lesions present in the cardiac grafts exhibited a gradual increase in severity of the vascular intimal proliferation and a similar pattern of increased intensity of cellular infiltration. The lesions were infiltrated with inflammatory cells beginning in the first week and increasing for the first month after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Combination therapy with Brequinar sodium and cyclosporine synergistically prolongs hamster-to-rat cardia xenograft survival.

The accelerated rejection of hamster cardiac xenografts by Lewis rat recipients is due primarily to a humoral immune response. Traditional immunosuppressive agents, including cyclosporine, FK 506, and rapamycin, have not been effective in prolonging the rejection of xenografts in this model. We have recently examined the ability of the combination of cyclosporine and a new immunosuppressive agent, Brequinar sodium, to prevent the rejection of hamster xenografts. Prolongation of xenograft survival by treatment with Brequinar sodium alone (3 mg/kg/day) was minimally effective, with a median survival of 5.5 days. Conversely, a combination of Brequinar sodium (3 mg/kg/day) and cyclosporine (10 mg/kg/day), was associated with a significant prolongation of median graft survival (> 100 days). A quantitative analysis of the dose-effect relationship of Brequinar sodium and cyclosporine demonstrated a potent synergistic interaction for this combination therapy (combination index < 1). A sharp increase occurred in the binding of immunoglobulin M antibodies at day 4 after transplantation in the serum of untreated and cyclosporine-treated Lewis recipients of cardiac xenografts, whereas a clear decrease occurred in anti-hamster immunoglobulin M antibody production during this period of time in the animals treated by combined immunosuppression. Inhibition of anti-donor immunoglobulin M antibody production, as evaluated by the direct enzyme-linked immunosorbent assay and 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide measurements, extended for more than 100 days after transplantation in the combination therapy group.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗