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Biomedical subjects

M Tateiwa

Publications and source records attributed to M Tateiwa.

At least 19 recordsLinked to original sources
PubMed1977

Effects of thyroxine and cold exposure on hypothalamic TRH levels in rats with various pituitary-thyroid states.

The hypothalamic content and concentration of thyrotropin-releasing hormone (TRH) were determined by radioimmunoassay in normal, thyroidectomized, hypophysectomized and cold-exposed rats with or without thyroxine. In normal animals, the single administration of thyroxine (1,5 and 20 microgram/100 g B.W.) altered neither the content nor the concentration of TRH in the hypothalamus. However, seven days' administration of this hormone resulted in the dose-dependent increase in the hypothalamic TRH levels. In thyroidectomized rats the hypothalamic TRH levels were slightly reduced in spite of the marked increase of plasma TSH levels and decrease of pituitary TSH levels. In the animals given thyroxine (10 microgram/100 g B.W.) for 7 days in addition to thyroidectomy, however, the TRH levels exceeded that in the animals which underwent throidectomy alone. The hypothalamic TRH levels were markedly reduced in hypophysectomized rats. Conversely, in hypophysectomized rats given 7 days' thyroxine (1 and 5 microgram/100 g B.W.), the levels were increased dose-dependently. In cold-exposed rats, the plasma TSH levels roughly doubled, but the TRH levels remained unchanged. These findings strongly suggest that the feedback site of thyroxine extends not only to the pituitary gland but also to the hypothalamus, and that thyroxine has an increasing effect of the hypothalamic TRH level, though the mechanism(s) remain to be clarified.

Acclimatization↗
PubMed1975

Diurnal variation of the human urinary TRH excretion measured by radioimmunoassay.

Urine TRH was estimated by the radioimmunoassay which was accomplished according to the method of Bassiri and Utiger. Minimum detectable dose of TRH was 25 pg and recovery of TRH ranged from 72% to 112% in our laboratory. Intraassay coefficients of variation were 5.4% to 14.0% and interassay variations were 10.6% to 15.0%. Of the TRH analogues tested, only two (Ser-His-Pro-NH2, Thr-His-Pro-NH2) had potent reactivity to anti-TRH serum in large dose of 100 ng/tube. Urine samples were kept at -20 degrees C after adjusted to pH 3.0 because the inactivation of TRH in urine was markedly dependent on temperature and pH value. Using this radioimmunoassay, diurnal variation of the urinary TRH excretion at regular intervals in normal subjects was observed. Peak TRH excretion occurred around early morning, while minimum of the excretion was observed around noon. Total urinary TRH excretion of 24 hours was 817-1579 ng (M+/-SE: 1241+/-89 ng) in normal subjects. In patients with chronic renal failure, urinary excretions of TRH was obviously lower than those of normal subjects.

Adolescent↗