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Biomedical subjects

M Nakaya

Publications and source records attributed to M Nakaya.

113 records · Page 7Linked to original sources

Effect of physical fitness and training on physiological responses to hypogravity.

The studies on the orthostatic tolerance during the hypodynamics exposure seem to be significant in connection with the selection, training and health maintenance of astronauts. Using male human subjects of various physical fitness levels, fluctuations of their physical fitness through 2 weeks of vigorous athletic training were measured in many parameters. For some of the subjects, the effects of 6 hr thermal neutral water immersion exposure in head out supine position on the physical fitness parameters and orthostatic tolerability were compared before training with after training. The results obtained were as follows: (1) Before training, orthostatic tolerability before hypodynamics exposure increased, following the physical fitness levels; the value after the hypodynamics exposure decreased in all the cases, but no differences were observed between the physical fitness levels. (2) As a result of training an increase of the physical fitness capacity was observed. The increase of orthostatic tolerability before hypodynamics exposure was noticed except for athletes. (3) Before hypodynamics exposure the urinary excretion of noradrenaline on non-athlete subjects increased as the physicsl fitness level increased. The values were decreased by physical training, the more so the better the physical fitness. After hypodynamics exposure the same relation was observed. But for athletes the values remain more stable and the decrease by hypodynamics exposure was not so distinctive. Such decreased reaction to hypodynamic conditions seems to reveal the neuro hormonal mechanism for the detrimental adaptation of athletes to hypodynamics. These results suggest that stable athletes do not always have low orthostatic tolerability, but do not respond well to hypodynamic conditions, at least from the orthostatic point of view. The mechanism seems related to sympathetic nerve activity.

Adolescent↗

Does motilin control interdigestive pepsin secretion in the dog?

Pepsin output in the Heidenhain pouch, plasma motilin concentration, and contractile activity in the pouch and the main stomach were investigated in five dogs. During the interdigestive state, the pepsin output was significantly increased with a cyclic increase in contractile activity in both the pouch and main stomach at approximately 100-min intervals. The plasma immunoreactive motilin (IRM) concentration fluctuated during the interdigestive state, and, peaks of IRM concentration coincided with the maximum pepsin secretory activity. Exogenous administration of motilin (0.5 micrograms/kg-hr) increased contractile activity in the main stomach and pouch quite similar to the natural interdigestive migrating contractions (IMC), and increased pepsin output significantly. Atropine pre-treatment suppressed the naturally-occurring and motilin-induced pepsin output and contractions in the pouch. It is concluded that pepsin output and contractions in the Heidenhain pouch increase in close association with the IMC in the main stomach during the interdigestive state and these cyclic motor and secretory events in the vagally denervated fundic pouch are most likely regulated by motilin through the intramural cholinergic pathway.

Animals↗

Is schizophrenic symptomatology independent of the phase of the illness?

The difference in symptomatology between the acute and post-acute phase of schizophrenia was examined in the present study using prospective and longitudinal assessment of 86 newly admitted schizophrenic patients. In the acute phase of illness, four symptom components emerged (negative symptoms, excited, delusional/hallucinatory, and thought disorder) and three components were evident (negative symptoms, mixed symptoms, and thought disorder) in the post-acute phase. The negative component in the post-acute phase had the same composition as that in the acute phase. The composition of thought disorder barely persisted over the phase of illness. These findings suggest that the negative symptom component is stable while the difference in the phase of illness has some effects on the symptom structure of schizophrenia.

Acute Disease↗

Analysis of caspases that are activated during apoptosis in leukemia U937 cells in response to geranylgeraniol.

Affinity labeling showed that active caspases with molecular masses of 20 kDa, 19 kDa, and 17 kDa were formed upon treatment of human leukemia U937 cells with GGO. These caspases are quite similar to those activated by treatments with other apoptosis-inducers, such as VP16 and camptothecin, suggesting that similar caspases, such as caspases 3 and 6, are activated during apoptosis in U937 cells that is induced by a variety of apoptosis-inducing stimuli. An inhibitor of caspases, Z-Asp-CH2DCB, inhibited DNA fragmentation in response to GGO in vivo by blocking the cleavage of 20-kDa to 17-kDa peptides. This cleavage is catalyzed by caspase 3 itself or by a caspase-3-like protease. In contrast, other inhibitors of caspases such as Z-DEVD-FMK and Z-VAD-FMK, inhibited the processing of the caspase 3 precursor p32 to 20-kDa and 17-kDa peptides, a result which suggests that these inhibitors inhibited other upstream caspases. Treatment of U937 cells with GGO resulted in the release of cytochrome c from mitochondria prior to DNA fragmentation and the release of cytochrome c was inhibited by Zn2+ ions and by a chelator of Ca2+ ions but not by inhibitors of caspases such as Z-Asp-CH2DCB or Z-VAD-FMK. These results suggest that intracellular free Ca2+ ions, and some caspases that are inhibited by Zn2+ ions, but not by Z-Asp-CH2DCB or Z-VAD-FMK are necessary for the release of cytochrome c that is caused by the treatment with GGO.

Affinity Labels↗