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Biomedical subjects

G C Yang

Publications and source records attributed to G C Yang.

At least 55 records · Page 3Linked to original sources
PubMed1989

Can ciguatera be a sexually transmitted disease?

Ciguatera is a type of food poisoning associated with the consumption of contaminated marine fish. We report two cases in which painful ejaculation in an affected male and dyspareunia in an unaffected female following her partner's ejaculation suggest the sexual transfer of the responsible agent, ciguatoxin (CTX). Immunoassay of semen samples for CTX were not diagnostic, but the sensitivity and timing of the test employed may have precluded detection of small quantities of the toxin. We conclude that CTX may be present in the semen of men affected with ciguatera toxicity and be capable of producing symptomatology in both males and females during sexual intercourse.

Ciguatera Poisoning↗
PubMed1987

Proliferation of esophageal epithelial cells among residents of Linxian, People's Republic of China.

Histopathologic and tritiated thymidine labeling subjects were carried out on esophageal biopsy specimens of 44 human subjects with cytologic evidence of dysplasia from Linxian, People's Republic of China, a high-risk area for esophageal cancer. With the use of histopathologic criteria, 10 cases showed evidence of dysplasia, 20 hyperplasia, and 14 a near-normal morphology when compared with 21 normal cases studied previously from Jiaoxian, a low-risk area for esophageal cancer in the People's Republic of China. Significantly increased labeling indices were found in the esophageal mucosa of the dysplasia and hyperplasia subjects. There was a gradient of increased expansion in the basal layer of proliferating cells progressing from normal to hyperplasia to dysplasia, with the expansion twice as high in the epithelial cell lining in dysplasia when compared with the findings in the normal and near-normal groups. The correlation of proliferative abnormalities with the severity of precancerous lesions of the esophagus indicates that labeling studies may provide a sensitive adjunct to evaluate risk status and any modifications that might result from nutritional intervention.

Biopsy↗
PubMed1986

Mechanism of the protective activity of ICRF-187 against alloxan-induced diabetes in mice.

ICRF-187, (+)-1,2-bis(3,5-dioxopiperazine-1-yl)propane, has been shown to protect against alloxan diabetes (el-Hage et al., 1981). Since alloxan-induced pancreatic beta cell damage is thought to be mediated through the generation of highly reactive oxygen radicals by a metal catalyzed reaction involving both superoxide anion and hydrogen peroxide, in the present study the protective activity of ICRF-187 was compared with that of free radical scavengers, microsomal enzyme inhibitors and chelating agents. The free radical scavengers DMSO, vitamin E and WR2721 markedly reduced alloxan-induced hyperglycemia. ICRF-187 was found not to interact with superoxide anions, and there is no evidence to indicate that any of the known biological effects of ICRF-187 are mediated through free radical scavenging activity. SKF-525 and cimetidine, known inhibitors of drug metabolizing enzymes, also protected against the diabetogenic action of alloxan. Since it was found that ICRF-187 did not alter hexobarbital sleeping time, this compound must protect by a mechanism other than microsomal enzyme inhibition. Since the chelating agents EDTA and DETAPAC were found to protect against alloxan diabetes, ICRF-187 or its hydrolytic products, which are structurally similar to EDTA, could function as chelating agents. Transitional metals such as iron, zinc and copper were found to bind preferentially to a hydrolysis product of ICRF-187. Chelation of iron by ICRF-187 or its hydrolytic products could decrease in vivo formation of reactive oxygen radicals and provide a means for protecting against chronic anthracycline cardiotoxicity and alloxan diabetes.

Alloxan↗
PubMed1985

Depolymerization of microtubules increases the motional freedom of molecular probes in cellular plasma membranes.

Depolymerization of microtubules resulted in an increase in the motional freedom of molecular probes in the plasma membranes of Chinese hamster ovary cells expressed by the order parameter, S, measured with two different lipid-soluble spin label probes, 5-doxyl stearic acid and 16-doxyl methylstearate. Treatment with a variety of microtubule-depolymerizing agents, including Colcemid, colchicine, vinblastine, podophyllotoxin, and griseofulvin, all had similar effects on motional freedom of the probes whereas beta-lumicolchicine was inactive. Several independent lines of evidence suggest that these changes in motional freedom of the probes were not the direct result of the interaction of these relatively hydrophobic drugs with the plasma membrane: the effects of the drugs were not immediate; the dose response of the Colcemid effect was the same as the dose response for depolymerization of microtubules; taxol, which stabilizes microtubules but does not affect motional freedom in the membranes, blocked the effect of Colcemid on motional freedom; a mutant cell line which is resistant to colchicine because of reduced uptake of the drug showed no effects of colchicine on probe motional freedom; and a Colcemid-resistant mutant cell line with an altered beta-tubulin showed no effect of Colcemid on motional freedom in the membrane. These results support the hypothesis that microtubules might affect, directly or indirectly, plasma membrane functions.

Animals↗
PubMed1985

Dose dependency of aflatoxin B1 binding on human high molecular weight DNA in the activation of proto-oncogene.

The binding of aflatoxin B1, AFB1, a potent hepatocarcinogen, to various high molecular weight (HMW) DNAs from human normal liver and two liver cancer cell lines, Alexander primary liver carcinoma (PLC) and Mahlavu hepatocellular carcinoma (hHC) and from NIH/3T3 cell have been investigated. The kinetics of AFB1 binding to these DNAs showed similar initial rates but the extents of binding to the PLC and hHC DNAs seemed to be slightly higher. Preferential AFB1 bindings were identified in both PLC and hHC DNAs compared to normal liver DNA when analyzed by restriction endonuclease digestions and agarose gel electrophoresis. A critical AFB1 binding dosage, ranging 100 to 460 fmole/microgram DNA, was found to activate the carcinogenic effect of the Mahlavu hHC HMW DNA, but not normal liver HMW DNA, rendering it capable of inducing focal transformation in NIH/3T3 cell. Excessive AFB1 binding on the hHC and PLC HMW DNAs resulted in an "over-kill" of both cell transformation capability and templating activity of the DNA.

Aflatoxin B1↗
PubMed1984

Studies on the action of nystatin on cultured rat myocardial cells and cell membranes, isolated rat hearts, and intact rats.

The action of nystatin, a polyene antibiotic, was studied in rat myocardial cells, isolated rat hearts, and intact rats. Myocardial cells responded to 10 and 25 micrograms nystatin/ml with arrhythmias that could be minimized by elevated concentrations of K+ and Mg2+ or reversed by washing the cells. Similarly, the isolated heart responded to 100 micrograms nystatin/ml with arrhythmias that could be tempered by addition of elevated concentrations of K+ and Mg2+. The i.v. injection of the drug caused heart failure in intact animals at the 4-mg/kg dose level. At the subcellular level, nystatin made the myocardial cell membranes more rigid, as measured by electron spin resonance spectrometry. These findings indicate a parallel between physiocochemical changes caused by nystatin in the myocardial cell membrane and the biological changes caused by this drug in myocardial cells, isolated heart, and heart of the intact animal.

Animals↗
PubMed1982

A wide field electron microscopic analysis of the fiber constituents of the major splanchnic nerve in cat.

The fiber composition of the left major splanchnic nerve was studied in cats by electron microscopy. Comparisons were made between normal and partially degenerated nerve specimens following ventral rhizotomy (T3-L1), or spinal nerve division (T3-L1). Normal, major splanchnic nerves contained 2,500-4,000 myelinated and 10,000-15,000 unmyelinated fibers. Preganglionic fibers included approximately 90% of the finely myelinated (1-7 micrometers) and over 50% of the unmyelinated fibers. Removal of the sensory and preganglionic components by spinal nerve division revealed a third postganglionic fiber category. This included 13-38 small myelinated (1-5 micrometers) and 1,645-7,619 unmyelinated fibers. Finally, a comparison of normal and partially degenerated nerve specimens of both groups (ventral rhizotomy and spinal nerve cut) indicated that splanchnic afferents are made up of virtually all of the 120-350 large myelinated (8-14 micrometers) and 10% of the small myelinated (1-7 micrometers) fibers. A preliminary estimate indicated that about 10-20% of the unmyelinated fibers were sensory. The implications of these findings are discussed.

Animals↗
PubMed1981

Spin immunoassay.

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Blood Proteins↗
PubMed1980

Total-field electron-microscopic examination of thin tissue slices via surface-embedding and multiple-mesa technics.

Total-field electron-microscopic examination of tissue slices of 50--200 micrometers thickness, used in various prestaining methods, can be accomplished by combining the following two technics: surface-embedding, a process in which the thin tissue slice remains on one plane during embedding, so that its entire cross section can be obtained; multiple-mesa technic, a trimming process to obtain multiple targets for examination on the same field. The two technics are described in detail.

Humans↗
PubMed1980

Aflatoxin and Reye's syndrome: a case control study.

Aflatoxin levels were determined in serum and urine of 17 patients with Reye's syndrome and in control subjects. No significant difference in aflatoxin levels was found for the two groups. However, 23% of all persons studied had levels of aflatoxin indicative of recent exposure. Aflatoxin levels were associated with ingestion of cornmeal and corn bread but not peanut-containing products. This prevalence of aflatoxin may be of public health importance.

Adolescent↗
PubMed1977

Purification of flagellar cores of Vibrio cholerae.

A procedure is described for the purification of the cores of flagella sheared from Vibrio cholerae. V. cholerae is a monotrichous organism whose flagellar core (FC) is enclosed within a sheath. The purification procedure consists of several cycles of differential centrifugation and cesium chloride density-gradient ultracentrifugation in the presence of a neutral detergent, Triton X-100. Purity of the FC preparations is assessed by electron microscopy, polyacrylamide gel electrophoresis, and chemical analysis. The purified FC preparations are devoid of flagellar sheaths and free from detectable cell wall and cytoplasmic contamination. Antibody prepared in rabbits against purified FC reacts with the flagellum of intact V. cholerae or purified FC as seen by ferritin-labeled antibody studies. Purified FC is composed of a single protein subunit with an estimated molecular weight of 45,000 g/mol and a density of about 1.3 g/cm3.

Bacterial Proteins↗
PubMed1975

Wide-field electron microscopy. A rapid method for the study of histologic material that provides a bridge between light and electron microscopy.

Wide fields of tissue can be rapidly examined by electron microscopy by use of Formvar films for the support of ultrathin sections on slot grids. The intervention of the grid bars of conventional mesh grids is avoided, and a continuous micrograph of the specimen at scanning magnifications can be obtained. Enough material is sublimed from the section and the supporting film by deliberate exposure to the electron beam to permit one to obtain an image with good contrast. This method of examination, which takes in all about two hours, permits examination of an extensive area of tissue in relation both to its topography at low magnifications and to its ultrastructural detail, and accordingly adds to electron microscopy a dimension characteristic of the lower powers of the light microscope. It offers the histopathologist the option of using micrographs taken during the scanning survey of a tissue to detect regions that can be readily re-examined at high magnification in the same ultrathin section.

Animals↗
PubMed1975

An in vitro and in vivo investigation of the phototoxic effect and its amelioration with radioprotective compounds.

Electron spin resonance spectroscopy has been used to demonstrate that the phototoxic antimalarial drug, 6,8-dichloro-2-phenyl-a-2-piperidnylquinolinemethanol (WR 7930), when irradiated with long-wave ultraviolet (UV) light (lambda greater than 320 nm) while held in a glassy matrix at 73 degrees K, enters a triplet state and releases hydrogen atoms in its environment. The steady-state concentration of triplet WR 7930 molecules and of hydrogen atoms is reduced 2 to 3 times when mercaptoethylamine (MEA) is also present in the UV-irradiated glass. Organosulfur radicals form on MEA while hydrogen atoms and triplet-state molecules are reduced in number. Hydrogen atoms and triplet WR 7930 molecules are considered as mediators of the phototoxicity of the antimalarial drug. Thus, hydrogen atom scavanging and chemical quenching of the triplet state are possible mechanisms by which protection against phototoxic effects could be gained. Protection is demonstrated in mice receiving 20 mg per kg WR 7930 intraperitoneally and exposed to long-wave UV for 20 hr when the radioprotective aminothiol-forming compound, 2-(3-aminopropylamino) ethyl dihydrogen phosphorothioate (WR 2721), is administered at 400 mg per kg immediately before irradiation. When no protective drug is administered concurrently, WR 7930 administration results in intense erythema, edema, and eventual necrosis of ear tissues.

Animals↗