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Biomedical subjects

S W Chen

Publications and source records attributed to S W Chen.

At least 73 records · Page 4Linked to original sources
PubMed1989

[The adult respiratory distress syndrome associated with miliary tuberculosis].

Two cases of pathologically confirmed miliary pulmonary tuberculosis complicated with ARDS were presented. Both had systemic lupus erythematous and used maintenance dose of corticosteroid. Case one developed respiratory distress and severe hypoxemia one day postpartum and chest radiograph revealed nodular and miliary infiltrations and pleural effusion. The patient was intubated and placed on a volume-cycled ventilator. A FIO2 of 70% and a PEEP of 0.98 kPa were required to maintain the oxygen tension at 6.95 kPa. The effective compliance of the lung decreased progressively and the patient died 5 days later. Autopsy revealed disseminated tuberculosis extensively involving the lungs, the liver and kidney. The alveoli were filled with edematous fluid with formation of hyaline membranes and micro-atelectasis. Case two developed respiratory distress and pulmonary edema at the third month of pregnancy. Cardiopulmonary arrest occurred when trying to intubate the patient. Postmortem needle puncture of the lungs and liver revealed charges comparable with tuberculosis and ARDS. In considering the relatively high incidence of pulmonary tuberculosis in China, the percentage of miliary tuberculosis as a potential cause of ARDS might not be very low. It is important to maintain a high index of suspicion for this treatable precipitating disorder and initial appropriate therapy early enough in patients with ARDS.

Adult↗
PubMed1988

Evidence for two conductance/exchange pathways for chloride in rat parotid secretory granules.

Electron probe x-ray microanalysis was used to determine that bromide is localized to rat parotid secretory granules at early stages of an in situ Cl/Br washout experiment. Chloride efflux and bromide influx across the secretory granule membrane occurred with a time order of minutes. Since the Cl washout data indicated minimal Cl binding within the granule, and therefore minimal Br binding, the Br localization results suggest the presence of two or more anion conductance/exchange pathways in the granule membrane for the Cl (Br) ion.

Animals↗
PubMed1988

Human ovarian theca cells are a source of renin.

Human ovarian follicular fluid contains renin-like activity. In normal women, circulating levels of prorenin, the biosynthetic precursor of renin (EC 3.4.23.15), change in parallel with changes in progesterone during the menstrual cycle. Therefore, the ovary has been implicated as a source of plasma prorenin. In the present studies, we report the finding of high concentrations of prorenin in human ovarian follicular fluid (3000 ng.ml-1.hr-1 vs. 10-40 ng.ml-1.hr-1 in normal human plasma) obtained from follicles of women prepared for in vitro fertilization. The inactive renin-like enzyme was identified as prorenin by its activation characteristics, its molecular weight of 47,000, which is the same as that for recombinant prorenin, and its cross-reactivity with human renal renin antibodies. Culture of isolated human theca cells and isolated granulosa cells indicated that prorenin is secreted by theca cells but not by granulosa cells. Prorenin production by theca cells peaked during the first 10 days of culture and gradually decreased by 17 days. Active renin levels were 10% or less of the prorenin levels. Prorenin was barely detectable in medium from granulosa cells cultured for 24 days. Immunohistochemical staining of human ovaries (n = 5) with anti-human renin antibody demonstrated the presence of renin primarily in theca cells. These studies suggest that the theca cell is the source of the large quantities of prorenin in human ovarian follicular fluid.

Enzyme Precursors↗
PubMed1988

N-terminal sequences of gamma-crystallins from the amphibian lens and their homology with gamma-crystallins of other major classes of vertebrates.

gamma-Crystallins were isolated from the homogenate of frog eye lenses (Rana catesbeiana) by exclusion gel chromatography and further purified by cation-exchange chromatography. They were the only group of crystallins possessing free amino groups amenable to sequence analysis by Edman degradation. Comparison of the amino acid contents of the purified subfractions of gamma-crystallins indicated their close relatedness in amino acid compositions and probably sequence homology as well. The amino-terminal sequence analysis of the purified gamma-crystallin subfractions showed extensive homology between these amphibian gamma-crystallin polypeptides themselves and also those from other vertebrate species, suggesting the existence of a multigene family and their close relatedness to gamma-crystallins of other vertebrates. The sequence comparison of the gamma-crystallin polypeptides from all major classes of vertebrates has provided strong support for the divergent evolution of gamma-crystallin family.

Amino Acid Sequence↗
PubMed1988

Production and further characterization of an alkaline elastase produced by alkalophilic bacillus strain ya-B.

The characteristics of the obligate alkalophilic Bacillus sp. strain Ya-B, which produces alkaline elastase extracellularly, were examined. This strain grew at pH 7.0 only in the presence of 1% or more NaCl. Its fatty acid distribution pattern was similar to that of other Bacillus species in which iso-C(15) and anteiso-C(15) were the most abundant fatty acids. About 120 mg of enzyme was recovered from 1 liter of culture broth in a medium (pH 10.1) containing mainly glucose, soymeal, and glycerol. The antiserum against this enzyme did not recognize microbial proteinases, such as subtilisins, but reacted with proteinase C, which was purified from commercial pronase. Chemical modification studies revealed that certain histidine and tyrosine residues might be involved in the enzyme activity. This enzyme underwent a partial unfolding at pHs higher than 12.0, as indicated by the circular dichroism study.

Journal Article↗
PubMed1988

The complete amino-acid sequence of a basic phospholipase A2 in the venom of Bungarus fasciatus.

A basic phospholipase A2 (PLA2) was isolated and purified from the venom of Bungarus fasciatus. Four kinds of enzymes, lysyl endopeptidase, endoproteinase Asp-N, endoproteinase Glu-C and trypsin, were employed to elucidate the complete primary structure by means of gas-phase sequencing. The amino-acid sequence reveals 118 amino-acid residues containing seven pairs of half-cystine. It has 78% and 61% structural identities with PLA2 from Bungarus multicinctus and Naja melanoleuca DE-II, respectively.

Amino Acid Sequence↗
PubMed1987

Sequence comparison of gamma-crystallins from the reptilian and other vertebrate species.

Lens crystallins were isolated from homogenates of reptilian eye lenses (Caiman crocodylus apaporiensis) by gel-permeation chromatography and characterized by gel electrophoresis, and amino acid and N-terminal sequence analyses. Four fractions corresponding to alpha-, delta/epsilon/beta-, beta- and gamma-crystallins were identified on the basis of their electrophoretic patterns as revealed by SDS gel electrophoresis. Comparison of the amino acid contents of reptilian crystallins with those of mammals suggests that each orthologous class of crystallins from the evolutionarily distant species still exhibits similarity in their amino acid compositions and probably sequence homology as well. All fractions except that of gamma-crystallin were found to be N-terminally blocked. N-terminal sequence analysis of the purified gamma-crystallin subfractions showed extensive homology between the reptilian gamma-crystallin polypeptides themselves and also those from other vertebrate species, suggesting the existence of a multigene family and their close relatedness to gamma-crystallins of other vertebrates.

Alligators and Crocodiles↗
PubMed1986

The amino-terminal sequences of four major carp gamma-crystallin polypeptides and their homology with frog and calf gamma-crystallins.

Four major gamma-crystallin subfractions have been isolated from the carp (Cyprinus carpio) and their N-terminal sequences determined by Edman protein sequencing. Extensive homologies indicative of close relatedness in their primary structure were found in these four gamma-crystallin polypeptides. Comparison of the carp N-terminal sequences with those of mammalian and amphibian gamma-crystallins also showed a high degree of homology present in their N-terminal segments despite the dissimilarity of amino acid compositions of fish gamma-crystallins to those of higher classes of vertebrates. The distinct yet closely-related partial sequences of carp gamma-crystallins could account for the profound microheterogeneity detected in the characterization of carp crystallins, suggesting the presence of a multigene family for gamma-crystallin in the lowest class of vertebrates, i.e. the fish.

Amino Acid Sequence↗
PubMed1985

[The detoxification of Naja naja atra venom and preparation of potent antivenin].

The 99.2% toxicity of Naja naja atra venom can be detoxified by treatment with 0.25% GA (glutaraldehyde) solution at pH 6.8 and still remains its antigenicity. Using the GA treated venom incorporated with Freund's complete adjuvant as immunogen, the titer of immune horse sera can be enhanced rapidly. The modified immunization method not only shortened the period of immunization (from 180 to 60 days), but also increased the potency of immune sera (from 75 to 170 units). The method also diminished the mortality rate of the horse during the immunization period (from 37 to 0%) and increased the antibody production rate (from 20 to 100%), as compared to Tanaka's method. With the present method, significant economic effects can be achieved. The neutralization antibody titer of Naja naja atra antivenin could be elevated 3.55 times through purification of the antivenin with the pepsin digestion method. The antivenin recovery rate using the pepsin digestion method was about 55.44%. The solubility of lyophilized antivenin was significantly improved by the addition of 2% glycine. In addition to an increase of antivenin potency and purity, the problem of an inadequate production rate has also been resolved. Now lyophilized antivenin can be supplied even to remote areas, thus providing excellent opportunities for clinical application. This Institute has already adopted this new immunization schedule in lieu of the old Tanaka method.

Animals↗
PubMed1984

Pathogenesis of gastric ulceration produced by acetazolamide in rats.

The present experiment demonstrated that relatively high doses of acetazolamide (100 and 200 mg/kg s.c.) induced severe gastric hemorrhagic ulceration in rats. This ulceration was aggravated by oral administration of HC1, but was inhibited by NaHCO3. Further, the severity of ulceration was also decreased by pretreatment with methysergide, chlorpheniramine, or cimetidine. These protective effects were affirmed by an increase in serotonin and histamine released from the stomach after acetazolamide treatment. Acetazolamide injection also increased the protein level, but reduced the sialic acid content in the gastric secretion, indicating that the gastric mucosal barrier may have been damaged. Prostaglandin E2 content of the gastric mucosa was not affected by the drug; however, carbonic anhydrase activity was markedly reduced in a dose-dependent manner. Thus, it is suggested that the ulceration induced by acetazolamide is mainly due to the inhibition of carbonic anhydrase activity and mucus secretion. The increases in serotonin and histamine released may also have been contributing factors for gastric ulcer formation.

Acetazolamide↗
PubMed1983

The lack of effects of somatostatin on gastric responses induced by electrical vagal stimulation.

The effects of somatostatin on ulcer formation, gastric acid secretion and histamine release were assessed during vagus nerve stimulation in rats. Direct electrical vagal stimulation significantly increased histamine release and acid output in gastric secretion but decreased mast cell counts in gastric glandular mucosa. Hemorrhagic ulceration on the gastric glandular mucosa was also observed. Somatostatin pretreatment (10 micrograms/kg) did not inhibit gastric ulcer formation, gastric acid secretion or histamine release induced by vagal stimulation. Cimetidine (an H2 blocker) pretreatment, however, significantly decreased gastric acid secretion as well as ulcer formation. The present study indicates the direct vagal stimulation increases gastric acid secretion and ulcer formation. These effects are partially histamine dependent. Somatostatin did not inhibit histamine release induced by vagal stimulation and reflects the inability of the drug to prevent ulcer formation and gastric output under these conditions in rats. However, the inhibition of basal gastric acid secretion produced by somatostatin might be useful clinically in humans.

Animals↗