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Biomedical subjects

T Namba

Publications and source records attributed to T Namba.

At least 271 records · Page 15Linked to original sources
PubMed1982

Diminution of chemically induced lung neoplasia in mice by phenobarbital pre-treatment.

Pre-treatment of 21-day-old ICR/Jcl mice with 75 micrograms/g of phenobarbital significantly reduced the yields of lung tumors induced by 4-nitroquinoline-1-oxide (4NQO) and furylfuramide. Dimethylbenz[a]anthracene (DMBA)- and urethane-induced lung tumorigenesis was also reduced, but was not significantly different from that in mice receiving only the carcinogen. However, 6 consecutive treatments with phenobarbital (40 micrograms/g) in adult mice greatly reduced urethane-induced lung tumorigenesis. Post-treatment with an equal dose of phenobarbital showed neither diminution nor enhancement of tumorigenesis.

4-Nitroquinoline-1-oxide↗
PubMed1982

Neuromuscular transmission in neonatal mice injected with serum globulin of myasthenia gravis patients.

Neuromuscular transmission was studied in neonatal mice following injection with serum globulin of patients with myasthenia gravis (MG). Compared to controls, these mice showed significant reduction in successive muscle action potentials evoked by repetitive nerve stimulation, amplitude of miniature endplate potentials, and postjunctional sensitivity to acetylcholine. There was no change in evoked isometric tension, quantal content of endplate potentials, or input resistance of the endplate membrane. These results confirm earlier reports of neuromuscular block in animals following injection of globulin of myasthenic patients, and demonstrate that decrease in amplitude of evoked potentials and of miniature endplate potentials is due to reduction in sensitivity to acetylcholine rather than in input resistance of the postsynaptic membrane. These findings are compatible with a postsynaptic defect in MG caused by a humorally mediated autoimmune mechanism.

Adult↗
PubMed1982

Motor endplate cholinesterase in human skeletal muscle.

The activity and properties of cholinesterase (ChE) of the motor endplate and its fractions were studied in isolated human skeletal muscle. This preparation was used since the ChE activity of the membrane preparation was localized only in the motor endplate. The endplate ChE was stable in the isolated membrane for 4 weeks at 4 degrees C. The specific activity of the extracted ChE of human muscle membrane was 29.6% higher than that of the original membrane. Studies with specific substrates and ChE inhibitors indicated that most of the ChE of human muscle membrane and its fractions was acetylcholinesterase, and that the minor component was pseudocholinesterase. A Michaelis-Menten constant of 3.82 mM was estimated in the endplate ChE, and 0.88 mM in the extracted ChE of the endplate. The extracted human endplate ChE was separated into three fractions by Sephadex G-200 chromatography, and into two fractions by acrylamide gel electrophoresis.

Acetylcholinesterase↗
PubMed1982

Inhibition of human motor endplate cholinesterase by anticholinesterase compounds.

The inhibition of human motor endplate cholinesterase by anticholinesterase compounds was studied using isolated muscle membrane preparation. Ambenonium was most potent, and edrophonium was least potent in inhibiting motor endplate cholinesterase. The slope of the regression line for inhibition of motor endplate cholinesterase was greatest for ambenonium, and smallest for neostigmine and edrophonium. These compounds were less potent inhibitors of plasma cholinesterase. Ambenonium was more specific, and other compounds were less specific inhibitors of motor endplate cholinesterase. In myasthenic patients, these compounds produced adequate inhibition of motor endplate cholinesterase even in the presence of relatively mild plasma cholinesterase inhibition.

Cholinesterase Inhibitors↗
PubMed1982

Cholinesterase activity of the motor endplate in rat intercostal muscle.

Cholinesterase activity was localized solely in the motor endplate of the membrane in rate intercostal muscle. The diameter of rat motor endplates in the gradient dimension was 31.9 micrometers. The cholinesterase activity per unit protein of the soluble fraction of rat muscle membrane was 35.6% higher than the original membrane. From studies with specific substrates and cholinesterase inhibitors, the cholinesterase activity of rat muscle membrane and its soluble fraction consists of more than 90% acetylcholinesterase and less than 10% pseudocholinesterase.

Animals↗
PubMed1982

Cholinesterase of skeletal muscle and its subcellular components.

The cholinesterase activity of skeletal muscle and its subcellular components, including motor endplates, was compared chemically in human, mouse and rat. The total cholinesterase activity of muscle per unit protein was in the descending order of human, mouse and rat. Cholinesterase was present in all subcellular components fractionated by differential centrifugation, and was greatest in the microsome fraction followed, in descending order, by the mitochondria, myofibril, and supernatant fractions. Each of these fractions had greater cholinesterase activity in human muscle than in mouse muscle, and in mouse muscle than in rat muscle. The ratio of the activity of the microsome fraction to the activity of muscle homogenate was 11.1 in human, 4.6 in mouse and 3.4 in rat. Because of its relatively greater proportion, the myofibril fraction seems to contribute most to the total cholinesterase activity of muscle. Muscle membrane contained high cholinesterase activity of motor endplates, and the activity was greater than the activity of the microsome fraction in rat. Cholinesterase activity per motor endplate was in the descending order of rat, human and mouse, and the variation was less than the variation in the total muscle cholinesterase activity among these species.

Cholinesterases↗
PubMed1982

[Inhibitory effect of antineoplastic agents on human cholinesterases].

Human motor endplate acetylcholinesterase was inhibited in vitro by alkylating antineoplastic agents, most strongly by mechlorethamine, followed by DTIC, ACNU, cyclophosphamide and ifosfamide. Eleven other antineoplastic agents did not inhibit the enzyme substantially nor interfered with cholinesterase measurement. Cyclophosphamide and mechlorethamine inhibited human plasma pseudocholinesterase most strongly, followed by thiotepa, ACNU, DTIC, ifosfamide and BCNU. Mechlorethamine, ACNU and ifosfamide inhibited the motor endplate and plasma cholinesterase practically equally, DTIC inhibited motor endplate cholinesterase more strongly, while cyclophosphamide was a more selective inhibitor of plasma cholinesterase. Inhibition of human red blood cell acetylcholinesterase was identical to that of motor endplate acetylcholinesterase; therefore, red cells would be a preferable indicator in monitoring cholinesterase inhibition by antineoplastic agents.

Acetylcholinesterase↗
PubMed1981

Inhibition of the mutagenicity of cooked-beef basic fraction by its acidic fraction.

By using the Salmonella/microsome system, it was found that the activity of mutagens present in the basic fraction of cooked-ground-beef was completely suppressed by addition of the acidic fraction obtained from the cooked-beef. The suppression was ascribable to the presence of oleic acid in the acidic fraction. This finding indicates that no, or diminished, mutagenicity would be found in materials containing fat.

Animals↗