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Biomedical subjects

S Y Hwang

Publications and source records attributed to S Y Hwang.

65 records · Page 4Linked to original sources
PubMed1989

Occupational risk of decreased plasma cholinesterase among pesticide production workers in Taiwan.

To determine the influence of ventilation control and work practices on the health of workers potentially exposed to organophosphate and carbamate compounds, we examined a total of 989 employees from pesticide factories in Taiwan during 1986-1987. Each employee was examined by a physician, and a blood sample was drawn for plasma cholinesterase, complete blood count, and liver and renal function tests. Forty-one employees with medical conditions that might alter the plasma cholinesterase were excluded. Results showed that 43 of 515 production employees had decreased plasma cholinesterase as compared with four of 340 non-production employees. Production employees working under adequate ventilation control seemed to have a lower prevalence of decreased plasma cholinesterase than those under inadequate ventilation control, although the difference was not statistically significant (p = 0.242). There was a significant association between the level of housekeeping and work practices and the prevalence of decreased plasma cholinesterase (p = 0.022). We conclude that inadequate ventilation control and poor work practices may create a potential danger of pesticide poisoning among production employees in Taiwan and should be corrected immediately.

Chemical Industry↗
PubMed1989

Portage transport of sulfanilamide and sulfanilic acid.

Sulfanilic acid, in contrast to sulfanilamide, has poor in vitro antibacterial activity. Paradoxically, it has been shown to be a more effective inhibitor than sulfanilamide of dihydropteroic acid synthase. In order to circumvent the presumed permeability barrier to sulfanilic acid, advantage was taken of the technique of portage transport. Derivatives of the compound were prepared in which it was linked via its primary amino group to the alpha-carbon of glycine residues in di- and tripeptides. L-Alanyl-L-alanyl-L-2-[(4-sulfophenyl)amino]glycine proved to be 207 times more potent than sulfanilic acid and 8 times more active than either sulfanilamide or L-alanyl-L-alanyl-L-2-[[4-(aminosulfonyl)-phenyl]amino]glycine when tested against Escherichia coli. These findings confirm that the weak in vitro activity of sulfanilic acid is due to its limited ability to penetrate the bacterial membrane. They also emphasize the ability of portage transport to reveal therapeutic capability that had been attenuated by poor drug permeation.

Anti-Bacterial Agents↗
PubMed1989

[Globus hystericus--reports on 25 ENT cases and literature review].

From October 1987 to March 1988, 25 cases (15 males and 10 females) with the globus hystericus were evaluated at 804 Army General Hospital. All patients underwent complete physical examination, routine laboratory work-up, roentgenographic examination of paranasal sinuses, cervical region and chest, upper G-I series, fiberoptic endoscopy and esophagoscopy. 2.3% of the patients in this study had the globus hystericus, the male to female ratio was 1.5:1, the mean ages were 51 years, the average educational level was low, the endoscopic findings were vallecular cyst in 3 cases (12%), epiglottic cyst in 2 cases (8%), the roentgenographic findings were maxillary sinusitis in 3 cases (12%), cervical osteophytes in 9 cases (36%) gastric ulcer, duodenal ulcer and diverticulum in 1 cases (4%) respectively. We analyzed the positive findings and reviewed the literature.

Adult↗
PubMed1988

Rapid determination of kinetic constants by competitive spectrophotometry.

The use of competitive spectrophotometry to measure kinetic constants for enzyme-catalyzed reactions is described. The equation for the progress curve characterizing the kinetic behavior of an enzyme acting simultaneously on two alternative substrates is derived. By the addition of a competition term to the integrated Michaelis-Menten equation, the kinetic constants of an alternative substrate can be evaluated by measuring the competition with a substrate of known kinetic constants in a single experiment. Studies are presented involving the enzymes leucine aminopeptidase (LAP) and carboxypeptidase A (CPA). The results obtained with LAP and CPA showed that the kinetic constants determined using competitive spectrophotometry were in agreement with values cited in the literature or with values determined by single substrate enzyme kinetics.

Binding, Competitive↗
PubMed1987

Properties of gamma-glutamyl arylamidase activity of the heavy subunit of gamma-glutamyl arylamidase from Bacillus sp. strain No. 12.

gamma-Glutamyl arylamidase of Bacillus sp. strain No. 12, composed of two heavy (Mr 56,000) and two light (Mr 46,000) subunits, was dissociated and inactivated by mild SDS treatment. The activity was restored in the isolated heavy subunit but not in the light subunit when SDS was removed by dialysis. The restored activity of the heavy subunit was similar to that of the native enzyme with regard to substrate specificity and inhibition and activation by alpha- and gamma-glutamyl compounds, free amino acids, peptides, enzyme inhibitors, and anti-native enzyme antibody.

Amidohydrolases↗
PubMed1986

Determination of leucine aminopeptidase using phenylalanyl-3-thia-phenylalanine as substrate.

The peptide mimetic L-phenylalanyl-L-3-thiaphenylalanine has been shown to facilitate a sensitive and simple determination of leucine aminopeptidase. A colorimetric assay, employing Ellman's reagent to detect the thiophenol released upon hydrolysis of the dipeptide, has been developed. Under the experimental conditions employed the substrate has a Km of 0.054 mM and a kcat of 5800 min-1 and can distinguish sharply between leucine aminopeptidase and aminopeptidase M.

Aminopeptidases↗
PubMedDate not supplied

Expression of transforming growth factor (TGF)-beta1 and TGF-beta type II receptor in preneoplastic lesions during chemical hepatocarcinogenesis of rats.

Transforming growth factor (TGF)-beta1 is an important apoptotic growth inhibitor of hepatocyte proliferation, and the expression of TGF-beta1, which regulates cell proliferation, is closely associated with the expression level of TGF-beta type II receptor (TGR2). Moreover, TGF-beta1 expression has been regarded to be an important change in hepatocarcinogenesis, We undertook this study to investigate the gene expression and protein localization of TGF-beta1 and TGR2 and their relationship with apoptosis in the chemically induced hepatocarcinogenesis of the rat, as produced using Solt and Farber's method, during the promotion stage (up to 56 days after partial hepatectomy). Northern blot analysis showed a slight, but not a significant, increase in TGF-beta1 transcripts, and a significant decrease in the TGR2 transcripts during the later stage of our experiments (42 days after partial hepatectomy). Immunohistochemical study showed that TGF-beta1-positive preneoplastic hepatocytes increased with time, and this correlated with an increase of TGR2 negative or reduced TGR2 expressed preneoplastic lesions. The TUNEL method revealed that apoptotic cells increased with time and were more numerous in the adjacent liver parenchyme than preneoplastic lesions. Our data suggest that the expressions of TGF-beta1 and TGR2 are significantly altered during the promotion stage of hepatocarcinogenesis of rat and that these changes might contribute to the development and progression of preneoplastic lesions.

Animals↗