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Biomedical subjects

J H Liang

Publications and source records attributed to J H Liang.

17 recordsLinked to original sources
PubMed2002

A fast automatic RBS/w channeling system for damage depth profiling.

A computer-aided data acquisition coupling with goniometer-control system dedicated for damage depth profile measurements is established. The channeling direction searching is performed along tilt and azimuth directions. The system includes a computer code to convert the measured spectra into damage depth profile. The analyzing time for each sample requires approximately 20-30 min. The damage depth profiles of the self-implanted (100) silicon samples are in reasonable agreement with the calculated results yielded by the SRIM Monte-Carlo simulation code.

Journal Article↗
PubMed2001

Immunolocalization of proliferating cell nuclear antigen (PCNA) in cynomolgus monkey (Macaca fascicularis) testes during postnatal development.

The age-related distribution of proliferating cell nuclear antigen (PCNA) in the testes of cynomolgus monkeys (Macaca fascicularis) during postnatal development was detected using light-microscopic immunohistochemistry. In neonatal testes, some PCNA-positive spermatogonia, Sertoli cells, peritubular cells, and Leydig cells were detected. In early infantile testes, only a few of these cell types were positive. In late infantile testes, the numbers of positive cells were greater than in the earlier developmental stages. In pubertal testes, the numbers of positive spermatogonia, spermatocytes, Sertoli cells, peritubular cells, and Leydig cells were considerably higher. In adult testes, a larger percentage of spermatogonia and spermatocytes was positive, and peritubular cells and Leydig cells were occasionally positive; secondary spermatocytes, spermatids, and Sertoli cells were not positive. We concluded that immunolocalization of PCNA can serve as a tool for studying proliferation status in developing testes of cynomolgus monkeys. A relatively low proliferative activity in early infantile testes and a remarkable increase of proliferative activity in pubertal testes correlate with the fluctuations of steroidogenic functions during postnatal development in cynomolgus monkeys.

Aging↗
PubMed2000

The characterization of angiogenesis inhibitor from shark cartilage.

An angiogenesis inhibitor isolated from shark cartilage, SCF2, has been characterized. SCF2 was shown to have specific angiogenesis-inhibiting activity in endothelial cell culture assays. Results of structural and functional studies indicate that the inhibitor is not a typical protein. It is a heat-stable proteoglycan, which contains keratan sulfate units and peptide. Gel filtration chromatography shows that the molecular weight of the angiogenesis inhibitor is about 10 kd.

Angiogenesis Inhibitors↗
PubMed2000

Comparison of the effects of two fixatives for immunolocalization of testosterone in the testes of the cynomolgus monkey, mouse and rat.

We compared the effect of two fixatives, Bouin's fixative and neutralized buffered 4% formaldehyde (10% formalin), for immunolocalization of testosterone in the testes of cynomolgus monkeys, mice and rats. In the samples fixed with Bouin's fixative, immunoreactive testosterone was detected as intense deposits in the cytoplasm of Leydig cells of monkeys and mice. Immunoreactive testosterone was detected not only in Leydig cells of rats but also moderately shown within tubules. Immunoreactive testosterone could not be detected in the testes of monkeys, mice or rats fixed with neutralized buffered formalin because of the poor morphology caused by the fixative. It is concluded that Bouin's fixative is a suitable fixative for immunolocalization of testosterone in the testes of cynomolgus monkeys, mice and rats.

Acetic Acid↗
PubMed1999

Localization of immunoreactive testosterone and 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase in cynomolgus monkey (Macaca fascicularis) testes during postnatal development.

The age-related expression of testosterone and 3beta-HSD in the testes of cynomolgus monkeys was detected using light-microscopic immunocytochemistry. Intense deposits of immunoreactive testosterone were labeled in parts of Leydig cells in neonatal, late infantile, pubertal, and adult testes, and only a few Leydig cells in early infantile testes. The immunoreactive 3beta-HSD was labeled in parts of Leydig cells and in all Sertoli cells in neonatal, late infantile, pubertal, and adult testes, whereas only a few Leydig cells, but no Sertoli cells, were labeled in early infantile testes. The fluctuations of testosterone and 3beta-HSD expression in testes correlated well with those already observed plasma testosterone levels during postnatal development in cynomolgus monkeys.

3-Hydroxysteroid Dehydrogenases↗
PubMed1998

Localization of testosterone and 3beta-hydroxysteroid dehydrogenase/delta5-delta4-isomerase in cynomolgus monkey (Macaca fascicularis) testes.

The enzyme 3beta-hydroxysteroid dehydrogenase/delta5-delta4-isomerase (3beta-HSD) is essential for the biosynthesis of all classes of steroid hormones, including androgens. We localized testosterone and 3beta-HSD by light microscopic immunocytochemistry in the testes of adult cynomolgus monkeys. Immunoreactive testosterone was located as intense deposits in the labeled cytoplasm of Leydig cells, and located weakly in the interstitial tissues, basement membranes, and the regions near tubular walls within tubules. Immunoreactive 3beta-HSD was located in the cytoplasm of all Sertoli cells and was especially intense in the parts near tubular walls and located weakly to intensely in the cytoplasm of some Leydig cells. This is the first immunocytochemical evidence that Sertoli cells of cynomolgus monkeys, as well as Leydig cells, are involved in biosynthesis of androgens.

Animals↗
PubMed1996

[Experimental study on different concentration alcohol humidifying oxygen supply improving hypoxia caused by pulmonary edema].

In order to research the best alcoholic concentration in the humidifying bottle when pneumonedema oxygen inhalation, 32 rabbits, divided into 4 groups, are replicated into pneumonedema models using method of rapid transfusion, and given oxygen inhalation with 20%, 50%, 70%, and 90% alcohol as humidifying agent (shortly called alcoholic oxygen). The results are as follows: using 20% alcohol as humidifying agent, the increasing amplitude of blood PaO2 is 147.30% (P < 0.001), the injury to the pulmonary bronchial mucosa and the wall of pulmonary alveoli is slight; using 50% alcohol, the increasing amplitude of blood PaO2 is 39.46% (P < 0.001), the injury to the parts mentioned above exacerbates and bronchiole cavity mucosa has moderate bleeding; using 70% alcohol, the increasing amplitude of blood PaO2 is 21.97% (P < 0.05), pneumorrhagia occurs; using 90% alcohol, the increasing amplitude of blood PaO2 is 94.46% (P < 0.01), a great number of blood cells aggregate inside the pulmonary alveoli and the bronchiole. This study proves that choosing 20% alcohol as humidifying agent has the best result, and as well, the explanation of the mechanism of alcohol suppressing foam, meaning being able to decrease only the surface tension of the foam inside the pulmonary alveoli, is incomprehensive, and the nature of the material itself forming foam has decisive function.

Administration, Inhalation↗
PubMed1991

Mutations in the draT and draG genes of Rhodospirillum rubrum result in loss of regulation of nitrogenase by reversible ADP-ribosylation.

Reversible ADP-ribosylation of dinitrogenase reductase forms the basis of posttranslational regulation of nitrogenase activity in Rhodospirillum rubrum. This report describes the physiological effects of mutations in the genes encoding the enzymes that add and remove the ADP-ribosyl moiety. Mutants lacking a functional draT gene had no dinitrogenase reductase ADP-ribosyltransferase (DRAT, the draT gene product) activity in vitro and were incapable of modifying dinitrogenase reductase with ADP-ribose in vivo. Mutants lacking a functional draG gene had no dinitrogenase reductase-activating glycohydrolase (DRAG, the draG gene product) activity in vitro and were unable to remove ADP-ribose from the modified dinitrogenase reductase in vivo. Strains containing polar mutations in draT had no detectable DRAG activity in vitro, suggesting likely cotranscription of draT and draG. In strains containing draT and lacking a functional draG, dinitrogenase reductase accumulated in the active form under derepressing conditions but was rapidly ADP-ribosylated in response to conditions that cause inactivation. Detection of DRAT in these cells in vitro demonstrated that DRAT is itself subject to posttranslational regulation in vivo. Mutants affected in an open reading frame immediately downstream of draTG showed regulation of dinitrogenase reductase by ADP-ribosylation, although differences in the rates of ADP-ribosylation were apparent.

Ammonia↗
PubMed1990

Endothelial cells as a source of oxygen-free radicals. An ESR study.

Endothelial cells were subjected to anoxia/reoxygenation in order to simulate some of the free radical mechanisms occurring in ischaemia/reperfusion. With ESR and spin trapping using the spin traps 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and 3,3,5,5-dimethyl-1-pyrroline-1-oxide (M4PO), the results show that upon reoxygenation of endothelial cells, following a period of anoxia, these cells generate superoxide (O2-.). Cytotoxicity of the spin traps was measured by standard trypan blue exclusion methods. Cell injury or death was measured at various times during reoxygenation by lactate dehydrogenase (LDH) release. Experiments using oxyupurinol, SOD, CAT and a combination of SOD and CAT show that while oxypurinol partially prevents spin adduct formation, the combination of SOD and CAT is more effective in doing so. These results suggest that the majority of the oxygen radicals produced by endothelial cells are done so exogenously. The results also suggest that endothelial cells are not only a source of oxygen radicals but also a target.

Animals↗
PubMed1988

Dinitrogenase with altered substrate specificity results from the use of homocitrate analogues for in vitro synthesis of the iron-molybdenum cofactor.

The in vitro synthesis of the iron-molybdenum cofactor (FeMo-co) of nitrogenase requires homocitrate (2-hydroxy-1,2,4-butanetricarboxylic acid). Homocitrate is apparently synthesized by the nifV gene product. In the absence of homocitrate, no FeMo-co is formed in vitro, as determined from coupled C2H2 reduction assays and the lack of 99Mo label incorporation into apodinitrogenase. Several organic acids were tested for their ability to replace homocitrate in the FeMo-co synthesis system. With appropriate homocitrate analogues, aberrant forms of FeMo-co are synthesized that exhibit altered substrate specificity and inhibitor susceptibility. Homoisocitrate (1-hydroxy-1,2,4-butanetricarboxylic acid) and 2-oxoglutarate facilitated the incorporation of 99Mo into apodinitrogenase in the FeMo-co synthesis system, yielding a dinitrogenase that effectively catalyzed the reduction of protons but not C2H2 or N2. Citrate also promoted the incorporation of 99Mo into apodinitrogenase, and the resulting holodinitrogenase reduced protons and C2H2 effectively but not N2. In addition, proton reduction from this enzyme was inhibited by CO. The properties of the homodinitrogenase formed in the presence of citrate were reminiscent of those of the Klebsiella pneumoniae NifV- dinitrogenase. We also observed low rates of HD formation from NifV- dinitrogenase compared to those from the wild-type enzyme. No HD formation was observed with the dinitrogenase activated in vitro in the presence of citrate. We propose that in vivo NifV- mutants utilize citrate for FeMo-co synthesis.

Enzyme Activation↗
PubMed1987

The electron spin resonance study on primary photochemical reaction of hematoporphyrin derivative.

The rate of oxygen consumption and the yield of free radical anion of hematoporphyrin derivative (HPD) in aqueous solutions of HPD and pyrocatechol were measured by the probe 2,2,6,6-tetramethyl-4-piperidone-1-oxyl. It has been found that both singlet oxygen and free radical mechanisms exist simultaneously in primary photochemical reactions, and there is a competition between both mechanisms. When the oxygen concentration in solutions comes down to 12-14% of the stanting level, the predominant mechanism can be changed from the singlet oxygen to the free radical. Whether HPD exists in aggregation state is very important to photosensitization mechanisms. In the presence of the aggregation state of HPD, the predominant mechanism is the free radical, and photosensitization effects of HPD are all the better.

Catechols↗