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Biomedical subjects

M Chen

Publications and source records attributed to M Chen.

At least 937 records · Page 52Linked to original sources
PubMed1979

Effects of prostaglandin synthesis inhibitors on human insulin secretion and carbohydrates tolerance.

Prostaglandin E (PGE) has been hypothesized to be an endogenous regulator of carbohydrate metabolism because it decreases human insulin secretion and carbohydrate tolerance. This report compares the effects of four inhibitors of PGE synthesis on the acute insulin response to glucose and subsequent glucose disappearance rates. Ibuprofen, acetylsalicylic acid and sodium salicylate treatments in normal volunteers were associated with augmented insulin secretion and improved glucose tolerance while indomethacin had the opposite effects. In view of these findings and the known effects of PGE on carbohydrate metabolism, we suggest that the effects of indomethacin may have been due to an action of the drug other than inhibiting PGE synthesis.

Adult↗
PubMed1979

Differentiation by TICAS analysis of cell populations of tracheal aspirates from hamsters with squamous-cell carcinoma.

Individual cells from the tracheal aspirates of hamsters exposed to benzo-a-pyrene were scanned at .5 mum in three colors. Features relating to size, shape, and color were extracted and calculated by computer. The single cells were then classified by these features into separate populations with varying degrees of atypia, extending up to frank cancer cells. A high degree of accuracy was attained in classification by these methods.

Animals↗
PubMed1979

Effect of monensin and lasalocid-sodium on the growth of methanogenic and rumen saccharolytic bacteria.

It is thought that monensin increases the efficiency of feed utilization by cattle by altering the rumen fermentation. We studied the effect of monensin and the related ionophore antibiotic lasalocid-sodium (Hoffman-LaRoche) on the growth of methanogenic and rumen saccharolytic bacteria in a complex medium containing rumen fluid. Ruminococcus albus, Ruminococcus flavefaciens, and Butyrivibrio fibrisolvens were inhibited by 2.5 mug of monensin or lasalocid per ml. Growth of Bacteroides succinogenes and Bacteroides ruminicola was delayed by 2.5 mug of monensin or lasalocid per ml. Populations of B. succinogenes and B. ruminicola that were resistant to 20 mug of either drug per ml were rapidly selected by growth in the presence of each drug at 5.0 mug/ml. Selenomonas ruminantium was insensitive to 40 mug of monensin or lasalocid per ml. Either antibiotic (10 mug/ml) inhibited Methanobacterium MOH, Methanobacterium formicicum, and Methanosarcina barkeri MS. Methanobacterium ruminantium PS was insensitive to 40 mug of monensin or 20 mug of lasalocid per ml. The methanogenic strain 442 was insensitive to 40 mug of monensin but sensitive to 10 mug of lasalocid per ml. The results suggest that monensin or lasalocid acts in the rumen by selecting for succinate-forming Bacteroides and for S. ruminantium, a propionate producer that decarboxylates succinate to propionate. The selection could lead to an increase in rumen propionate formation. Selection against H(2) and formate producers, e.g. R. albus, R. flavefaciens, and B. fibrisolvens, could lead to a depression of methane production in the rumen.

Journal Article↗
PubMed1978

Treatment of hypertriglyceridemia with para-aminosalicylic acid-C: a possible mechanism of action.

The effect of para-aminosalicylic acid-C (PAS-C, 8 g/day) on lipid metabolism was studied on a metabolic ward in nine subjects with primary endogenous hypertriglyceridemia. During 2 wk on a basal isocaloric liquid formula diet (40% fat, 45% carbohydrate), PAS-C reduced plasma triglyceride (-41.9 +/- 18.9%, p less than .01, -x +/- SD), cholesterol (-22.8 +/- 12.9%, p less than .005), and a very low density lipoprotein triglyceride (p less than .001) and cholesterol (p less than .01) levels without changing the cholesterol content of low density or high density lipoproteins. Similar effects occurred on a fat-free, 85% carbohydrate diet. Decreases in very low density lipoproteins correlated with changes in both total triglyceride (r = .99, p less than .01) and cholesterol (r = .70, p less than .05). Treatment with PAS-C reduced the plasma triglyceride removal rate related to lipoprotein lipase (-14.6 +/- 14.1%, p less than .02), but did not alter plasma postheparin lipolytic activity or the apparent Km for substrate-enzyme interaction. Kinetic data obtained during the prolonged heparin infusion fit the linearized Michaelis-Menten model for subjects with endogenous hypertriglyceridemia. The reduction in the plasma triglyceride concentration during PAS-C treatment was a function of the decrease in triglyceride removal rate (r = .74, p less than .025) without alternation in the maximal removal capacity related to lipoprotein lipase. This suggests that under the steady state conditions of these studies, the decrease in plasma triglyceride concentration was due to a reduction in endogenous triglyceride production. Free fatty acid metabolism, glucose homeostasis, fat absorption, and thyroid function did not change. These results suggest that PAS-C lowers plasma triglyceride and cholesterol levels in hypertriglyceridemic subjects reducing endogenous very low density lipoprotein production and/or secretion into the circulation.

Adult↗
PubMed1978

Aluminum induced pulmonary granulomatosis.

The association of aluminum dusts and pulmonary fibrosis with emphysema in workers in the aluminum processing and manufacturing industries is well established. The early and minimal reactions of the lungs to the aluminum dusts are not known. This report presents the first case of pulmonary granulomatosis associated with aluminum inhalation. The occupational history of this patient was thoroughly examined, and the aluminum was identified by electron probe microanalysis of the lung biopsy specimen. The granulomatous response in this patient was similar to that observed in rabbits following aluminum dust inhalation. Hypersensitivity or individual idiosyncrasy may play a role in the development of the pulmonary granulomas following exposure to aluminum.

Adult↗
PubMed1978

Restoration of the acute insulin response by sodium salicylate. A glucose dose-related phenomenon.

Adult-onset diabetics have markedly diminished or absent acute insulin responses to glucose that can be partially restored by sodium salicylate infusion. To determine whether this restoration of the acute insulin response is glucose dose dependent and whether complete restoration can be achieved, adult-onset diabetics with a mean fasting plasma glucose value of 216 +/- 20 mg. per deciliter (x +/- S.E.) were stimulated with various doses of intravenous glucose. Restoration occurred in a glucose dose-dependent manner. Complete restoration could not be achieved with the maximal tolerable glucose dose (80 gm.). Second phase insulin secretion also improved in a glucose dose-dependent manner. These findings are compatible with the hypothesis that defective insulin secretion in adult-onset, hyperglycemic diabetics is not due to absolute deficiency of insulin but may be a result of defective recognition of glucose signals by pancreatic B-cells--a defect that can be partially reversed by sodium salicylate.

Adult↗
PubMed1977

myo-Inositol Metabolism in Lilium longiflorum Pollen: Uptake and Incorporation of myo-Inositol-2-H.

Germinating Lilium longiflorum pollen absorbs and metabolizes myo-inositol-2-(3)H (MI-2-(3)H) with a pronounced lag when label is supplied from the beginning of germination. If MI-2-(3)H is given after 3 hours of germination, incorporation of labeled metabolic products into pollen tube polysaccharides is constant over a range of 0.56 mm to 2.78 mm MI. When MI-2-(3)H is supplied as a 0.5-hour pulse 3 hours after germination, the proper precursor-product relationship to tube wall polysaccharides is observed. Replacing 10% of the germination media with sigmatic exudate from a compatible cultivar hastens germination and tube elongation. Enhanced MI metabolism accompanies tube growth in this exudate-enriched media.

Journal Article↗
PubMed1977

Effect of a myo-Inositol Antagonist, 2-O, C-Methylene-myo-Inositol, on the Metabolism of myo-Inositol-2-H and d-Glucose-1-C in Lilium longiflorum Pollen.

2-O,C-Methylene-myo-inositol (MMO), a myo-inositol (MI) antagonist, inhibits germination and tube elongation of pollen from Lilium longiflorum cv. Ace or 44. The presence of 5 mm MMO in Dickinson's pentaerythritol medium (Plant Physiol. 43:1-8) partially blocks germination. The tubes produced are short and fail to elongate. In the presence of MI, MMO's toxic effect is blocked. As little as 0.56 mm MI will maintain normal germination in the presence of 43 mm MMO, and pollen tubes continue to elongate for 2 to 3 hr. Eventually, the toxic action of MMO prevents further growth. MMO does not inhibit UDP-d-glucose dehydrogenase from lily pollen.Uptake of MI-2-(3)H and incorporation of tritium into galacturonic acid and pentose units of tube wall pectin are blocked by MMO. The site of this inhibition is undertermined. Uptake of d-glucose-1-(14)C and incorporation of (14)C into 70% ethyl alcohol-insoluble polysaccharides of germinated pollen are not blocked by MMO, but distribution of label into polysaccharide product is altered. In MMO-treated pollen, very little (14)C is found in uronic acid or pentose units. At 30 mm MMO, about two-thirds of the carbon flow from d-glucose to these pectic components is interrupted. MMO also alters d-glucose metabolism in the 70% ethyl alcohol-soluble fraction, but the compound involved must still be identified.These results offer fresh evidence of an intermediary role for MI during UDP-d-glucuronate biosynthesis in germinated pollen.

Journal Article↗
PubMed1977

Influence of CH4 production by Methanobacterium ruminantium on the fermentation of glucose and lactate by Selenomonas ruminantium.

A method is described for increasing the production of H2 from glucose or lactate by Selenomonas ruminantium by sequential transfers in media containing pregrown Methanobacterium ruminantium. The methanogen uses the H2 formed by the selenomonad to reduce CO2 to CH4. Analysis of fermentation products from glucose showed that lactate was the major product formed from glucose by S. ruminantium alone. Several sequential transfers in the presence of the methanogen caused a marked decrease in lactate production, which was accompanied by an increase in acetate. When lactate was the fermentation substrate, S. ruminantium alone produced propionate, acetate, and CO2. Addition to the pregrown methanogen in the sequential transfer procedure caused a significant decrease in the production of propionate and an increase in acetate formed from lactate. These results are interpreted in terms of the influence of H2 utilization by the methanogen on the production of H2 versus lactate or propionate from reduced pyridine nucleotides by S. ruminantium.

Acetates↗
PubMed1977

A role for prostaglandin E in defective insulin secretion and carbohydrate intolerance in diabetes mellitus.

Prostaglandin E(2) (PGE(2)) infusion in normal humans inhibited acute insulin responses to a glucose (5 g i.v.) pulse (response before PGE(2) = 593 +/- 104%; during PGE(2) = 312+/-55%; mean+/-SE, mean change 3-5 min insulin,% basal, P < 0.005). This effect was associated with a decrease in glucose disappearance rates (K(G) before PGE(2) = 0.73+/-0.07; during PGE(2) = 0.49+/-0.06%/min, P < 0.025). Acute insulin responses to arginine (2 g i.v.) were not affected by PGE(2) (response before PGE(2) = 592+/-164%; during PGE(2) = 590+/-118%; P = NS). Infusion of sodium salicylate (SS), an inhibitor of endogenous prostaglandin synthesis, augmented acute insulin responses to glucose in normals (response before SS = 313+/-62%; during SS = 660+/-86%; P < 0.001). In adult-onset diabetes with fasting hyperglycemia, SS restored absent acute insulin responses to glucose (20 g i.v.) pulses (response before SS = 5+/-6%; during SS = 97+/-24%; P < 0.005). This was accompanied by a fourfold augmentation in second phase insulin secretion (second phase before SS = 1,696+/-430%; during SS = 5,176+/-682%; change 10-60 min insulin, muU/ml.min,% basal, P < 0.001) and by acceleration of glucose disappearance rates (K(G) before SS = 0.56+/-0.06; during SS = 1.02+/-0.17%/min, P < 0.005). These findings uniquely demonstrate that (a) PGE(2) inhibits glucose-induced acute insulin responses and decreases glucose disposal in nondiabetic humans and (b) SS restores acute insulin responses, augments second phase insulin secretion, and accelerates glucose disposal in hyperglycemic, adultonset diabetics. It is hypothesized that endogenous PGE synthesis may play a role in defective insulin secretion and glucose intolerance in diabetes mellitus.

Adult↗
PubMed1976

Identification of additional antigenic sites on Dane particles and the tubular forms of hepatitis B surface antigen.

Additional antigenic sites, distinct from those present on spherical 20 nm diam. particles of hepatitis B surface antigen (HBsAg), are exposed on the surface of Dane particles and tubular forms of HBsAg. The immunological relationship of these sites to e-antigen, an antigen detected earlier in HBsAg-positive sera from patients with chronic hepatitis, cirrhosis or acute hepatitis but not in healthy HBsAg-carriers, was established by immune electron microscopy and affinity chromatography. These findings suggest that e-antigen may be potentially useful in active immunization against hepatitis B.

Acute Disease↗