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Biomedical subjects

M Lee

Publications and source records attributed to M Lee.

At least 1,117 records · Page 62Linked to original sources
PubMed1977

Mutagenicity screening of five methyl carbamate insecticides and their nitroso derivatives using mutants of Salmonella typhimurium LT2.

The mutagenic activity of five methyl carbamate insecticides-carbaryl, baygon, BUX-Ten, landrin and methomyl-and their nitroso derivatives were investigated using histidine auxotrophs-his TA98, his TA100, his TA1535, his TA1537 and his TA1538--of Salmonella typhimurium LT2 derived by Ames. The methyl carbamate insecticides did not cause a signficant increase in the number of revertant colonies in any of the strains used. In contrast, the nitroso derivatives of the carbamate insecticides greatly increased the number of colonies on plates inoculated with strains his TA100 and his TA1535. We conclude that the nitroso derivatives of the tested methyl carbamate insecticides are potent mutagens; whereas, the parent insecticides are non-mutagenic.

Carbamates↗
PubMed1977

Alcoholism and gun control.

The recurring dilemma of having to deal with an intoxicated person in possession of a gun uttering homicidal or suicidal threats along with the current debate on gun control prompted this controlled survey of the characteristics of individuals with problems arising from the joint abuse of alcohol and possession of a gun. A comparison of the data point to violence as being the most significant differentiating variable involved. This violent potential was reflected by the presence among the alcoholics involved of more past and present antisocial traits, a higher rating on the Nicol's scale of violence, more offences committed against the person and homicidal behaviour. The availability of a gun was a significant factor. No correlation was found between the severity of the drinking problem and the risk of dangerous handling of a gun. The need for more stringent gun controls is supported but their implications to the physician and especially the psychiatrist as a potential guarantor for a licence application ought to be further explored by the professional bodies involved.

Adult↗
PubMed1977

Evidence for carrier-mediated transport of melphalan by L5178Y lymphoblasts in vitro.

Mechanism of transport of the alkylating agent [14C]melphalan was investigated in L5178Y lymphoblasts in vitro. A time course of melphalan uptake was approximately linear for 5 to 10 min and thereafter entered a plateau region. Evidence that unidirectional influx of melphalan is carrier mediated was that uptake obeyed simple Michaelis-Menten kinetics, that it demonstrated chemical specificity, and that the cell/medium distribution ratio of drug decreased with increasing extracellular drug concentration. The kinetic parameters for melphalan transport consisted of a Km (mean +/- S.E.) of 1.53 +/- 0.18 X 10(-4) M and a transport capacity (Vmax) of 3.48 +/- 0.31 X 10(-17) mole/min/cell. Findings suggesting that transport was at least in part energy dependent and not simply a passive process were that drug uptake was temperature sensitive and sodium dependent. Analysis of cell sap constituents indicated the presence of intact drug within the cell. The percentage of radioactivity (mean +/- S.D.) found in the cell sap fraction was 95.8 +/- 2.2% of total cell activity, and 92.6 +/- 4.1% of this was trichloroacetic acid soluble. Thin-layer chromatography of the cell sap fraction and medium each revealed that the majority of radioactivity migrated as a single peak with an RF value identical with that obtained for free drug. The alkylating potential of intact drug complicated interpretation of the finding of apparent uphill transport against a concentration gradient. This observation, together with the relatively low cell-medium ratio (mean +/- S.D.) of 3.07 +/- 1.07, favors the concept that melphalan transport occurs by a facilitated diffusion process, although an active transport system has not been entirely excluded. The relative insensitivity of melphalan uptake to a wide range of metabolic inhibitors also suggests that transport is by a facilitated diffusion mechanism rather than an active process. Other alkylating agents and several amino acids including the L and D isomers of phenylalanine did not inhibit melphalan transport; thus a native substrate was not identified for the melphalan carrier and transport was by a mechanism separate from that of other alkylating agents.

Antimetabolites↗
PubMed1977

An eye screening program in a Chinese-Canadian community.

A screening program staffed by ophthalmologists, ophthalmology residents, ophthalmic assistants, social workers and Chinese-speaking volunteers and directed at a Chinese immigrant community, was conducted at the Mount Sinai Hospital, Toronto. The Chinese population had been hesitant to use our hospital facilities and we hoped to overcome their fears, as well as to detect previously undiagnosed ocular problems. The program succeeded in finding many eye problems, some serious, and in encouraging this immigrant group to come for proper medical care. We describe the method of setting up and conducting such an undertaking, which involved the Departments of Ophthalmology and Social work, hospital administrators and volunteers from the community.

China↗
PubMed1976

Transport of amino acids in intact 3T3 and SV3T3 cells. Binding activity for leucine in membrane preparations of ehrlich ascites tumor cells.

Transport of amino acids into 3T3 and SV3T3 (SV40 virus-transformed 3T3) cells was measured on glass cover slips. The 3T3 and SV3T3 cells contain both A (alanine preferring) and L (leucine prefferring) systems for neutral amino acid transport. Initial rates of uptake of amino acids are about twofold higher in SV3T3 than in 3T3 cells. Other parameters measured, however, do not indicate marked differences in the transport of amino acids by the two cell types. L-system amino acids, such as leucine, are subject to trans-stimulation in both cell lines, whereas A-system amino acids, such as alanine and glycine, are not. Leucine was transported to higher levels in confluent cells than in nonconfluent cells. Glycine, however, shows distinctly less transport activity as the cells become confluent. Ehrlich ascites cell plasma membranes were prepared and assayed for amino acid-binding activity. Leucine-binding activity was detected by equilibrium dialysis in Triton X-100-treated membrane preparations.

Animals↗
PubMed1976

Microtubules and pancreatic amylase release by mouse pancreas in vitro.

The effects of vinblastine and colchicine on pancreatic acinar cells were studied by use of in vitro mouse pancreatic fragments. Vinblastine inhibited the release of amylase stimulated by bethanechol, caerulein, or ionophore A23187. Inhibition required preincubation with vinblastine,and maximum inhibition was observed after 90 min. Inhibition was relatively irreversible and could not be overcome by a high concentration of stimulant. Inhibition could also be produced by colchicine although longer preincubation was required and inhibition was only partial. Uptake of [3H]vinblastine and [3H]colchicine by pancreatic fragments was measured and found not to be responsible for the slow onset of inhibition by these drugs. In incubated pancreas, microtubules were present primarily in the apical pole of the cell and in association with the Golgi region. Vinblastine, under time and dose conditions that inhibited the release of stimulated amylase, also reduced the number of microtubules. The only other consistent structural effects of vinblastine were the presence of vinblastine-induced crystals and an increased incidence of autophagy. The remainder of cell structure was not affected nor were overall tissue ATP and electrolyte contents or the stimulant-induced increase in 45Ca++ efflux. It is concluded that the antisecretory effects of vinblastine and colchicine are consistent with a microtubular action, but that acinar cell microtubules are more resistant to the drugs than many other cell types.

Adenosine Triphosphate↗
PubMed1976

Acquired sensory control of satiation in man.

Lean male and female subjects who had been taking their meals as usual were given a 100 ml drink of starch immediately before a sandwich lunch. In the training phase,65 per cent starch was given before lunches which included a yoghurt-based dessert of one flavour and 5 per cent starch was given before another flavour. Subjects who initially ate lunches of similar size following the two drinks began after several pairings to take larger lunches following dilute starch than following concentrated starch. In extinction tests, identical 35 per cent starch drinks were given before lunches including desserts of either flavour. Lunches including the flavour hitherto paired with dilute starch remained larger than lunches including the other flavour, at least initially in extinction. Some of the difference in intake occurred in the dessert itself. None was attributable to differences in the early stage of the lunches. These results extend to man recent demonstrations that the satisfying power of a foodstuff is in part acquired by association of its sensory characteristics with some consequence of ingesting the nutrients which are consistently taken with or in that food. This consequence may be rapid intestinal absorption of glucose during or shortly after sensory input. The nature of the intake-suppressing response remains to be determined.

Appetite↗
PubMed1976

Vitamin E supplementation and glutathione peroxidase activity.

Both excess dietary vitamin E and vitamin E deficiency in rats can significantly depress the activity of GSH peroxidase in liver and plasma of rats. Of all the six levels of vitamin E tested in this study, the dietary level of vitamin E found to maintain the maximum activity of GSH peroxidase in tissues of rats was somewhere between 25 and 250 IU/kg diet. This study conclusively indicates that the excess dietary vitamin E represses GSH peroxidase activity.

Animals↗
PubMed1976

Regulation of transport in mammalian cell culture.

The regulation of amino acid transport has been investigated in Balb/3T3 cells. Transport for neutral amino acids in animal tissues is carried out by two distinct systems. The transport activity of the A system (alanine preferring) is inhibited by high internal of substrate amino acids, a process termed trans-inhibition. In contrast, the L system transport activity is greatly stimulated by high internal levels of substrate, a phenomenon termed trans-stimulation. Regulation of amino acid transport in animal cells occurs by a repression-derepression mechanism or by a feedback inhibition or feedback stimulation process. The level of endogenous amino acids is shown to be important in the regulation of transport activity. Cells which are slow growing or quiescent have increased levels of endogenous amino acids, which in turn effect the transport activity. The A system transport activity is decreased in quiescent cells, whereas L system transport activity increases. Conditions which effect endogenous amino acid levels have an effect on transport activity. Feedback regulation of transport activity through the amino acid pool levels is another way animal cells can regulate transport activity.

Alanine↗
PubMed1976

How phlebotomy affects the erythrocyte metabolism of high- and low-glutathione sheep.

Erythrocyte glutathione concentration increases dramatically in low-glutathione sheep of the Finnish-Landrace breed. To determine if this phenomenon occurs in low-glutathione sheep of the Corriedale or Merino type, the packed cell volume was decreased to less than 16 by phlebotomy. Glutathione concentrations increased in high- and low-glutathione sheep. Low-glutathione sheep returned to pre-phlebotomy levels by the 18th day; high-glutathione sheep increased, then decreased below pre-phlebotomy levels for the duration of the experiment. Packed cell volumes increased linearly (1-07 per cent per day) for 19 days. The maximum reticulocyte percentage (11-4) occurred on the eight day. Some erythrocyte enzymes increased as the mean cell age decreased, but some did not change. Erythrocyte adenosine-5'-triphosphate and creatine appear to be related to the reticulocyte count.

Animals↗