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Biomedical subjects

M Sakakura

Publications and source records attributed to M Sakakura.

At least 55 records · Page 3Linked to original sources
PubMed1978

Fluctuated changes in the rat hypothalamic content of corticotropin releasing factor around the peak of the circadian rhythm.

It is well known that hypothalamic corticotropin releasing factor (CRF) activity shows a marked circadian rhythm with the peak around 16 o'clock and the minimal level around 8 o'clock, followed by almost parallel changes of plasma corticosterone. But the circadian variations of CRF activity at short intervals (22 or 23 min) around 16 o'clock has not been obvious. In this experiment, we demonstrated fluctuated changes of CRF content in the non-stressed rat hypothalamus with 22 or 23 min intervals around the peak at a quarter past 16 o'clock.

Animals↗
PubMed1977

Study on the exocrine pancreatic function by the oral administration of N-benzoyl-L-tyrosyl-para-aminobenzoic acid.

N-benzoyl-L-tyrosyl-p-aminobenzoic acid (Bz-ty-PABA) was orally administered to 11 controls, 10 patients with chronic pancreatitis, 7 patients with diabetes mellitus and 6 patients with liver cirrhosis. The cumulative 6 h recovery rate of PABA in the urine was significantly lower (P less than 0.005) in patients with chronic pancreatitis (49.1 + or - 10.1 percent), diabetes mellitus (50.4 + or - 20.4 percent) and liver cirrhosis (52.5 + or - 13.0 percent) than in the control group (79.5 + or - 12.0 percent) (mean + or -S.D.). This test is considered to be useful in the diagnosis of pancreatic exocrine insufficiency, especially in chronic pancreatitis. Patients with diabetes mellitus frequently has demonstrable abnormality of pancreatic exocrine function. Liver cirrhosis causing severe impairment of liver functions seemed to interfer with the elimination of PABA.

4-Aminobenzoic Acid↗
PubMed1976

Studies on fast feedback mechanisms by endogenous glucocorticoids.

Negative feedback in the hypothalamic-pituitary-adrenal axis by exogenous glucocorticoids has been well established, but it is still in doubt whether ACTH-releasing factor (CRF) activity in the hypothalamus is inhibited by endogenous glucocorticoids under conditions of stress. In our first experiment, CRF activity in the hypothalamus of rats was significantly increased, 2 min after onset of immobilization, for 2 min; a rapid drop of CRF activity followed immediately. On the other hand, the concentration of plasma corticosterone changed more slowly; it was increased at 5 min, and showed a progressive further increase until 17 min after the administration of the immobilization stress. A high plateau level persisted for the next 8 min, after which the concentration of plasma corticosterone fell, reaching the control level at 40 min. In order to test for negative feedback inhibition by endogenous glucocorticoids in the hypothalamic-pituitary-adrenal axis, a 2nd immunobilization stress was administered to rats 5 or 23 min after the 1st stress, and hypothalamic CRF activity and plasma corticosterone were examined after the 2nd stress. When the 2nd stress was applied 5 min after the start of the 1st stress, during the phase of a gradual increase of endogenous glucocorticoids, CRF activity was not increased 2 min after the 2nd stress. In contrast, an increase of CRF activity and plasma corticosterone was observed when the 2nd stress was administered 23 min after the onset of the 1st stress, during the phase of a high plateau level of endogenous plasma corticosterone. These data suggest that CRF activity in the hypothalamus is governed by a fast feedback, rate-sensitive mechanism.

Adrenocorticotropic Hormone↗
PubMed1976

Time course of hypothalamic CRF activity after the administration of two different stresses.

The time course of hypothalamic corticotropin-releasing factor (CRF) activity after the administration of ether stress was different from that after immobilization stress. The maximal response CRF activity was observed 2 min after ether stress, followed by a precipitous decrease 5 min after the stress. A gradual increase of CRF activity was subsequently observed for several minutes with fluctuated changes. Thus, response pattern was vibratory. But under immobilization stress, markedly fluctuant changes of CRF activity seen in the case of ether stress did not appear after the maximal response observed at 2 min, indicating that the response pattern was not vibratory. On the other hand, the concentration of plasma corticosterone increased significantly 5 min after the ether or immobilization stress with the peak value around 17 min.

Animals↗
PubMed1975

Inhibition of luteinizing hormone secretion induced by synthetic LRH by long-term treatment with glucocorticoids in human subjects.

The response of luteinizing hormone to a single injection of synthetic LRH was established in 6 women and 7 men following an intramuscular dose of 0.2mg or 0.1mg. Significant increases of serum LH were observed in 30 min. Pretreatment with metyrapone for one day (4.5 g/sugject injection of synthetic LRH (0.1 MG/SUBJECT). Seven women, 21-48 years of age who were treated with prednisolone for a least 11/2 months were examined for responsiveness of the anterior pituitary to a single injection of synthetic LRH (0.2 MG). The secretion of LH was markedly suppressed and maximal serum levels of LH WERE OBSERVED 90 MIN FOLLOWING LRH injection.

Adult↗