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Biomedical subjects

M Chan

Publications and source records attributed to M Chan.

At least 163 records · Page 9Linked to original sources
PubMed1979

Mixed agglutination in microtiter U-trays.

The principle of mixed agglutination with cell cultures was applied to those cells which could not be obtained as monolayer cell cultures. Artificial monolayers of freshly isolated cells from various tissues were prepared in poly-L-lysine-coated wells of a microtiter U-tray. By means of this technique, murine alloantigens, H-2 private specificities and Thy-1 antigens were demonstrated on cells from thymus, brain, spleen, kidney and liver. Ia.2 antigen was detected on splenocytes but not on thymocytes or fibroblast L cells. Evidence was also presented that HLA A and B locus antigens could be demonstrated on human thymocytes. Sensitivity of this test was shown to be at least 100 times higher than that of the standard lymphocytotoxicity test for detection of HLA antigens.

Absorption↗
PubMed1977

Ventricular preexcitation syndrome. Accessory left atrioventricular connection and rhabdomyomatous myocardial fibers.

A necropsy study of the heart of a 16-year-old girl with ventricular preexcitation syndrome and supraventricular tachycardia showed an accessory left atrioventricular connection partially within the mitral valve. Both the accessory pathway and the ventricular musculature showed multiple foci of cardiac muscle fibers with rhabdomyomatous features having the characteristic appearance of rhabdomyomatosis. The case is discussed in the context of a literature review of necropsy findings in cases of ventricular preexcitation.

Adolescent↗
PubMed1976

Biosynthesis of diacylglycerols by rat intestinal mucosa in vivo.

The biosynthesis of diacylglycerols was studied in rat intestinal mucosa during in vivo absorption of a low molecular weight fraction fraction of butter oil and of the corresponding medium and long chain fatty acids. The experimental fat solutions were given by stomach tube to the animals after a 24-h fast and mucosal scraping were collected 3 h later. The lipids were isolated and the acylclycerols determined by combined thin-layer chromatography gas-liquid chromatography techniques and stereospecific analyses. Free fatty acid feeding led mainly to sn-1,2-diacyl-glycerols, which contained exogenous and endogenous fatty acids. During triacylglycerol feeding, both sn-1,2-and sn-2,3-diacylglycerols were recovered in significant amounts from the intestinal mucosa. The composition of the sn-2,3-diacylglycerols corresponded to that with exogenous fatty acids but the sn-1,2-diacylglycerols clearly contained both exogenous and endogenous fatty acids. In all cases it was possible to isolate endogenous sn-1,2-diacylglycerols made up largely of species with linoleic and arachidonic acids in the 2 position and palmitic and stearic acids in the 1 position, which apparently were not converted to triacylglycerols. The in vivo reacylation of 2-monoacylglycerols via both sn-1,2- and sn-2,3-diacylglycerols is in agreement with similar findings in vitro with everted sacs of rat intestinal mucosa.

Animals↗
PubMed1975

Inhibition of RNA synthesis by acetyl salicylate and actinomycin D during early development in the mouse.

Experiments were designed to ascertain and compare the effects of acetyl salicylate and actinomycin D on RNA synthesis in mouse oocytes in vitro and in vivo. After exposure to the drugs the effects on RNA synthesis were measured by incorporation of [3H]uridine and autoradiography. The results indicate that acetyl salicylate inhibits RNA synthesis in the treated oocytes as does actinomycin D. The only difference in the effects of these two drugs is that salicylate inhibits RNA synthesis to a much lesser degree than does actinomycin D. Effects from a short exposure to salicylate may be reversible; the same effects with actinomycin D cannot be reversed. In utero exposure of the female fetus may lead to partial or total sterility (depending on the dose and time of exposure) of that fetus and/or abnormal development of the progeny from those mice (F2). These results suggest that RNA synthesis in early oogenesis is a vital part of later development of the oocytes in adult mouse ovary. Inhibition of RNA may be one of the causes of malformations and sterility.

Animals↗
PubMed1974

Effect of temperature on the growth and cell wall chemistry of a facultative thermophilic Bacillus.

The morphology and cell wall composition of Bacillus coagulans, a facultative thermophile, were examined as a function of growth temperature. The morphology of the organism varied when it was grown at different temperatures; at 37 C the organism grew as individual cells which increased in length with increasing growth temperature. At 55 C it grew in long chains of cells. Cell wall prepared from cells grown at 37 C contained 44% teichoic acid by weight, whereas cells grown at 55 C contained 29% teichoic acid. Teichoic acid from these cells was a polymer of glycerol phosphate containing galactose and ester alanine. The ratio of ester alanine to phosphate was significantly higher in cell walls and teichoic acid from 37 C-grown cells compared with those from 55 C-grown cells. Other differences observed were that cells grown at 55 C contained a lower level of autolytic ability, produced cell walls which bound more Mg(2+), and contained less peptide cross-bridging in its peptidoglycan layer than cells grown at 37 C.

Alanine↗
PubMed1974

Observations on the bisulfite reductase (P582) isolated from Desulfotomaculum nigrificans.

The bisulfite reductase (P582) from Desulfotomaculum nigrificans was purified to homogeneity as judged by polyacrylamide gel electrophoresis. By colorimetric methods of analysis, the products of bisulfite reduction by this enzyme were determined to be trithionate, thiosulfate, and sulfide. Of these, trithionate was consistently found to be the major product, whereas the latter two were formed in lesser quantities. When [(35)S]bisulfite was incorporated as substrate, no labeled sulfide was detected. Furthermore, when trithionate and thiosulfate were isolated from reaction mixtures and chemically degraded, (35)S was found in all three sulfur atoms of trithionate; however, only the inner sulfur atom of thiosulfate was radioactive. From these data we conclude that the bisulfite reductase of D. nigrificans reduces bisulfite to trithionate and that thiosulfate and sulfide are endogenous side products of the reaction.

Bacteria↗
PubMed1973

Spin-labeling studies on the membrane of a facultative thermophilic bacillus.

Spin-labeling studies were conducted to elucidate the rigidity and viscosity of the membrane of a facultative thermophilic bacillus. By employing nitroxide stearate probes, it was observed that this fatty acid was incorporated into the membrane fraction. Electron spin resonance spectroscopy indicated that cells grown at 55 C contained a membrane which was more rigid and viscous than the membrane from cells grown at 37 C.

Bacillus↗
PubMed1971

Fatty acid composition of thermophilic, mesophilic, and psychrophilic clostridia.

The fatty acid composition of two thermophilic anaerobes was determined, and the results were compared with those from a mesophilic and a psychrophilic anaerobe. Notable differences were that the thermophiles contained a higher content of saturated straight- and branched-chain fatty acids, and, of the latter, iso C(15) was the predominant type. The mesophile and psychrophile were characterized by having a higher percentage of unsaturated fatty acids. An unidentified fatty acid, present in all of the organisms, was purified from the psychrophile. By physical and chemical analysis the structure of the unknown acid was resolved and found to be the unsaturated cyclopropane fatty acid, 12,13-methylene-9-tetradecenoic acid.

Anaerobiosis↗
PubMedDate not supplied

Influence of fluconazole on antipyrine kinetics in rats.

The present study was undertaken to examine the effect of fluconazole on in vivo drug metabolism in rats, using the model substrate antipyrine. Oral doses of fluconazole, 20 mg/kg, were administered once (acutely) or twice daily for 4 days (chronically). Control animals received oral drug vehicle. Antipyrine kinetics were determined following an intravenous dose of 20 mg/kg given either 1 or 12 h after the single or last dose of fluconazole respectively. Acute fluconazole treatment significantly increased antipyrine half-life by 250% and reduced its clearance by 50%, without affecting its volume of distribution. Chronic treatment with fluconazole failed to affect antipyrine pharmacokinetics. This study demonstrates that acute fluconazole inhibits the metabolism of antipyrine in rats.

Administration, Oral↗
PubMedDate not supplied

Disposition of epirubicin in an oily contrast medium after intravenous and intrahepato-arterial administration in liver cancer: a preliminary report.

The present study reports findings on the disposition of epirubicin after an intrahepato-arterial administration of the Lipiodol-drug complex, prepared by mixing the drug-aqueous phase with the iodized oil by ultra-sonification, in 14 patients with histologically proven hepatoma or hepatomegaly with serum alpha-fetoprotein level above 500 micrograms.l-1. The volume of Lipiodol used was 5 ml and the epirubicin dose was 50 mg.m-2. Blood samples were obtained at various time intervals up to 72 h post-dose. Serum concentrations of epirubicin were measured by liquid chromatography with fluorometric detection. The area under serum concentration-time curve (AUCinfinity0) was higher in the Lipiodol-epirubicin group (n = 8) while the clearance was faster and elimination t1/2 and mean residence time shorter in the plain epirubicin group (n = 3). However, interindividual variation in metabolism of epirubicin would affect serum level of the drug. In three patients who were given intravenous and intrahepato-arterial injections (90 mg.m-2) of plain epirubicin and Lipiodol-drug complex, the relative bioavailability of Lipiodol-epirubicin complex (F = 0.76 and 0.45) was lower than that of plain epirubicin (F = 0.80 and 0.73) in two patients while it was approximately 100% (F = 1.06 and 1.20) in one patient. It is likely that liver function of the patients might be modified by the disease state over a period of 3 months in the cross-over study. Further studies with larger patient samples are required to confirm if there is a targeting effect of the Lipiodol-drug complex toward hepatoma using a better formulation of the drug in Lipiodol.

Adult↗
PubMedDate not supplied

Adverse drug events as a cause of hospital admission in the elderly.

BACKGROUND: Previous studies of adverse drug events (ADE) as a cause of hospital admission in the elderly have often been limited in their ability to assess fully the impact and potential for prevention because they either did not include all categories of ADE and/or did not assess severity and preventability. AIMS: To assess the frequency, severity and preventability of ADE causing emergency medical admissions in the elderly. METHODS: Cross-sectional survey of 219 patients aged 75 years and over who were consecutive unplanned admissions to acute medical units of the Royal Hobart Hospital in an 8-week period during August and September 1998. RESULTS: Seventy-three of 240 (30.4%) admissions may have been a result of ADE. Patients admitted because of ADE were taking more drugs than those admitted for other reasons. Most ADE were adverse drug reactions to a single (46%) or multiple drugs (25%). Non-compliance, omission or cessation of indicated treatment accounted collectively for 26% of admissions. Of all ADE admissions 53.4% were considered definitely preventable. The commonest causative drugs were cardiovascular drugs (48.4%), and the commonest manifestations were falls and postural hypotension (24.1%), heart failure (16.9%) and delirium (14.5%). ADE categories in which a high proportion of admissions was both severe and definitely preventable were non-compliance and omission of indicated treatment. CONCLUSIONS: Adverse drug events are a common preventable cause of unplanned medical admissions in the elderly. Non-compliance and omission of indicated treatment are causes of ADE-related admissions that are both preventable and frequently associated with severe ADE.

Aged↗
PubMedDate not supplied

The prevalence and nature of back pain in an industrial complex: a questionnaire and radiographic and HLA analysis.

A questionnaire relating to presence and nature of back pain was distributed to all 10,150 employees (59% men) of an industrial complex. The questionnaire was returned by 2892 subjects (65% men). Of these, 1880 (65% of responders or 19% of total) reported a history of back pain. One hundred twenty-four described their back pain as insidious in onset, persisting for at least three months, developing at less than 40 years of age, being associated with morning stiffness, and showing improvement with exercise. Three hundred sixty-seven subjects scored four of these five features. Pelvic radiographs of 342 persons were available for blind evaluation. Sixteen patients (12 men) were shown to have definite ankylosing spondylitis (Grade III or IV sacroiliitis or HLA B27-associated Grade II sacroiliitis). Only one of these persons was known to have spondylitis. The majority of these symptomatic patients had been seen by both medical and nonmedical practitioners.

Adolescent↗