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Biomedical subjects

K Yagi

Publications and source records attributed to K Yagi.

At least 739 records · Page 41Linked to original sources
PubMed1976

Distribution of type A and B monamine oxidase activities in the central nervous system of rat and chick.

The distribution of type A and B monamine oxidase (MAO) activities in the central nervous system (CNS) of rat and chick was investigated using 5-hydroxytryptamine and beta-phenylethylamine as specific substrates. The distribution of type A MAO was similar to that of type B MAO in rat CNS, but quite different in chick CNS. This may be ascribed to the difference in animal species. The major part of MAO activity in the spinal cord was found to be type A.

Animals↗
PubMed1976

Formation of lipoperoxide in isolated sciatic nerve by chinoform-ferric chelate.

Effects of chinoform and chinoform-ferric chelate on formation of lipoperoxide in isolated sciatic nerve were investigated. Free chinoform did not increase the lipoperoxide level, while chinoform-ferric chelate significantly increased it. Assuming that the lipoperoxide formed denatures the associated protein in the nerve, the effect of chinoform-ferric chelate could explain, at least partly, the demyelination of nerve tissues caused by massive doses of chinoform.

Animals↗
PubMed1976

A simple fluorometric assay for type B monoamine oxidase activity in rat tissues.

A simple fluorometric assay for monoamine oxidase (MAO) [EC 1.4.3.4] activity towards beta-phenylethylamine (PEA) was devised. The procedure consists in measuring the disappearance of PEA fluorometrically. The disappearance of PEA was completely inhibited by pargyline, a potent inhibitor of MAO. MAO activity for PEA was linear with 10 mg to 100 mg of liver tissue in 3 ml of reaction mixture for up to 90 min of incubation. Using this method, the V max values and the apparent Km values of MAO for PEA in several rat tissues were determined, and compared with those for benzylamine and 5-hydroxytryptamine (5-HT).

Animals↗
PubMed1976

Ca2+-induced conformational changes of spin-labeled g2 chain bound to myosin and the effect of phosphorylation.

One of the low molecular weight components of myosin, g2, was isolated by alkali treatment of myosin and was chemically modified with a spin label reagent, 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. The label on g2 showed a rather weakly immobilized ESR spectrum and it was clearly affected by Ca2+; the half-maximal change was at around pCa 4. The spin-labeled g2 was incorporated into myosin by exchange with the intrinsic g2 of myosin in 0.6 M KSCN or 4 M LiC1. The label on g2 became strongly immobilized on association with myosin. Under the conditions used, ESR spectral change due to Ca2+ occurred at two different concentration ranges, which were as low as pCa 8 and at around pCa 4. Phosphorylated g2 was isolated from myosin after the protein kinase [EC 2.1.1.37]-catalyzed phosphorylation of myosin and it was also modified with the maleimide label. Dephosphorylation of the phosphorylated g2 was performed using E. coli alkaline phosphatase [EC 3.1.3.1]. The effects of Ca2+ on the ESR spectra of phosphorylated and dephosphorylated g2 were investigated on the state associated with myosin. A change in the ESR spectrum from strongly immobilized to weakly immobilized states was observed with both g2 chains on the addition of Ca2+. However, the effective concentration ranges of Ca2+ were quite different; around pCa 4 for the phosphorylated g2 and around pCa 8 for the dephosphorylated g2. The results indicate that g2 undergoes a conformational change at physiological levels of Ca2+ sufficient to saturate troponin, but it does not do so after phosphorylation.

Alkaline Phosphatase↗
PubMed1976

Inhibition and facilitation of antidromically identified tubero-infundibular neurones following stimulation of the median eminence in the rat.

1. Stimulation of the median eminence of female rats inhibited the spontaneous firing of antidromically identified tubero-infundibular units. Some units could be inhibited by stimuli subthreshold for the antidromic spike. A conditioning stimulus of subthreshold intensity for the antidromic spike also delayed or abolished the invasion of the soma and dendrites of the same unit by antidromic action potentials evoked by a suprathreshold stimulus given 2-10 msec later. 2. Although strychnine (0-2 mg/kg, i.v.) did not significantly alter the inhibition evoked by stimulation of the median eminence, it was abolished by picrotoxin (2-6 mg/kg, iv.). 3. In seven of the fifty-seven identified units examined stimulation of the median eminence facilitated the spontaneous firing. However, after an i.v. injection of picrotoxin the facilitory response was observed in thirty-seven of the forty-six units tested. Post-stimulus time histograms obtained from the same unit before and after an injection of picrotoxin demonstrated that the latency and duration of the facilitation did not always coincide with that of the inhibition. 4. After an injection of picrotoxin the field potential evoked by antidromic stimulation of the median eminence consisted of a small positive wave followed by a negative wave. Frequently the negative wave of the field potential was accompanied by a convulsive discharge. The latency of the negative wave appears to be identical to that of the facilitation seen in nearby single units. 5. The facilitation evoked by antidromic stimulation in the presence of picrotoxin was blocked by an i.v. injection of alpha-methyl-p-tyrosine (250 or 375 mg/kg). None of the nine units sampled from rats pre-treated with alpha-methyl-p-tyrosine injected twice I.P. (250 mg/kg for each) were facilitated by stimulation of the median eminence following I.V. picrotoxin, while eight of the eleven units sampled from control rats pre-treated with L-tyrosine could be facilitated by antidromic stimulation. 6. These results suggest that tuber-infundibular neurosecretory neurones are inhibited and facilitated by neural pathways which could involve the axon collaterals of the neruosecretory neurones which project to the external layer of the median eminence. It is also suggested that GABA-releasing neurones mediate the inhibition and catecholaminergic neurones are involved in the facilitory pathways. Presumably the facilitation is normally masked by the activity of the GABA-releasing neurones.

Animals↗
PubMed1976

Protective effect of dexamethasone on enhancement of blood-brain barrier permeability caused by electroconvulsive shock.

Penetration of Evans blue from the brain blood vessel into the brain tissue was increased by electroconvulsive shock (ECS), indicating the enhancement of the bloodbrain barrier (BBB) permeability. The staining with Evans blue was most prominent in the thalamus. The enhancement was scarcely observed 60 min after ECS, suggesting that the effect is of a temporary nature. Dexamethasone could protect BBB from its enhancement caused by ECS.

Animals↗
PubMed1975

Low molecular weight components (g-chains) of myosin from rabbit skeletal muscle. Separation, amino acid compositions and contents in myosin.

Low molecular weight components (g1, g2, and g3) were isolated from rabbit skeletal muscle myosin and their amino acid compositions were analyzed. One mole tryptophan was found in g1 and in g2, but none in g3. One mole of acetic acid was found per mole of each g-chain and it was concluded that the N-terminal groups of all three g-chains are acetylated. The minimum molecular weight of the g-chains were estimated from their amino acid compositions. It was estimated by SDS-disc electrophoresis that 1 mole of myosin contained 0.90, 1.7, and 0.63 moles of g1, g2, and g3, respectively. Similar values were obtained with psoas muscle myosin, but in heavy meromyosin prepared from skeletal muscle myosin the content of g2 was much lower, and that of g3 was much higher.

Amino Acids↗