PubMed Health⌕ Search

Biomedical subjects

T Yahata

Publications and source records attributed to T Yahata.

At least 91 records · Page 5Linked to original sources
PubMed1989

Noradrenaline-induced changes in rat brown adipose tissue glucagon.

Brown adipose tissue (BAT) glucagon level was higher in cold-acclimated rats (CA) than in warm controls (WC). Noradrenaline (NA) injection increased BAT glucagon levels in both WC and CA with increases in plasma glucagon levels. The magnitude of increase was significantly greater in CA for plasma glucagon, while it did not differ for BAT between groups. However, BAT glucagon was kept at a higher level in CA after NA injection than in WC.

Acclimatization↗
PubMed1989

[Studies on regulation of the function of thermogenic tissue, brown adipose tissue (BAT) by means of tissue culture method].

In order to clarify the regulatory mechanism of BAT function, the effects of noradrenaline (NA) (6mM), insulin (I) (40nM), glucagon (G) (400nM) and nerve growth factor (NGF) (2-10nM), alone or in combination, were investigated directly in BAT from neonatal rats (ca. 3 days old), cultured in 10% fetal bovine serum-medium 199 in 95% air-5% CO2 gas phase at 33 degrees C for 1 to 2 weeks. I stimulated lipid accumulation and enlarged outgrown cell size, but mitochondria in the cells of tissue block were smaller and their cristae less distinct. I + G enlarged nucleus and cytoplasm, and suppressed the lipid accumulation induced by I, but mitochondria in the cells of tissue block were larger and their cristae became more prominent than those of I-added cells. G induced the similar changes to those by I + G. I + NA also induced the similar effects to those by I + G, but their mitochondria size did not differ from that of I-added cells. NGF caused the similar effects of those by G, inducing the development of mitochondria, rough endoplasmic reticulum and Golgi complex. These results suggest that multiple factors such as NA, I, G and NGF regulate differentiation and functional development of BAT.

Adipose Tissue↗
PubMed1988

Physical training and fasting erythrocyte activities of free radical scavenging enzyme systems in sedentary men.

Effects of 10 weeks of physical training on free radical scavenging enzyme systems in erythrocytes were investigated in 7 sedentary healthy male students. The training consisted of running over 5 km, 6 times/week. Their maximum oxygen uptake and 12 min walk-run performance increased significantly after training. Of the antioxidant enzyme systems examined in the erythrocytes, both catalase activity and concentration and total glutathione reductase (GR) activity also showed significant increases following the training. The erythrocyte GR activity coefficient also increased significantly. These results suggest that chronic aerobic exercise increases riboflavin requirements and has some positive effects on antioxidative processes.

Adolescent↗
PubMed1988

Effect of noradrenaline on plasma hormones and metabolites in cold-acclimated rats.

The effects of noradrenaline (NA) injection (40 micrograms/100 g, i.p.) on plasma glucagon, corticosterone (CS), deoxycorticosterone (DOCS), glucose, and free fatty acids (FFA) were investigated in cold-acclimated rats (CA) and warm controls (WC). The CA were transferred to warm control temperature ca. 18 h prior to NA or saline injection. The animals were decapitated and the trunk blood was collected 0, 10, 20, and 40 min after the injection. Plasma glucagon level increased significantly during the experimental period after NA, while saline did not influence its level. The magnitude of increase as assessed by 95% confidence interval was significantly greater in CA than in WC. Plasma CS and DOCS were significantly increased by saline injection, but NA caused greater elevations of these steroid-hormones. The magnitudes of increases were also greater in CA. In contrast to the hormonal responses, NA-induced increases of plasma glucose and FFA levels were smaller in CA than in WC. These results suggest that glucagon and glucocorticoids are released, at least partly, by NA, and these thermogenic factors act in synergism, enhancing nonshivering thermogenesis through an accelerated utilization of energy substrates such as glucose and FFA.

Acclimatization↗
PubMed1988

Effect of physical training on immunoreactive gamma-glutamyltransferase in human plasma.

The effects of 10-week physical training on both the activity and concentration of gamma-glutamyltransferase (gamma-GT) in plasma were investigated on 7 sedentary healthy male students. The training consisted of running over 5 km, 6 times/week. The maximal oxygen uptake (Vo2max) and 12-min field performance increased significantly after training, from 43.5 and 2,683.7 to 48.1 ml.kg-1.min-1 and 2,931.1 m, respectively. After training the resting plasma gamma-GT concentration decreased to half, whereas the gamma-GT activity did not vary substantially. The training did not affect the response to the Vo2max test of either concentration or activity of gamma-GT. These results may suggest that plasma gamma-GT concentration is useful as an index of the extent of physical training.

Adolescent↗
PubMed1987

Stress- and cold-induced adrenocortical responses in repetitively immobilized or cold-acclimated rats.

To evaluate the role of adrenocortical hormones in stress- or cold-induced nonshivering thermogenesis, plasma corticosterone (CS) and deoxycorticosterone (DOCS) were measured with the aid of HPLC under various conditions. Repetitive immobilization stress (3 h/day, for 1 or 4 weeks) elevated the resting level (24 h after the last immobilization) of CS, but not DOCS. Acute stress (immobilization for 30 min) or cold exposure (-5 degrees C for 15 min) caused marked increases of CS and DOCS in both nonstressed naive controls and repetitively stressed rats. Four weeks, but not 1 week, of repetitive immobilization stress potentiated the responsiveness of CS to both acute stress and cold, and that of DOCS to acute stress, but not to cold. Cold acclimation (5 degrees C, 4 weeks) significantly elevated both corticosteroids but did not affect the resting levels (18 h after being transferred to 25 degrees C) or the responsiveness of both CS and DOCS to either acute stress or cold. These results suggest that repetitive immobilization stress, but not cold acclimation, could enhance nonshivering thermogenesis, at least in part, through an improvement in the responsiveness of adrenocortical hormone secretion to acute stress or cold.

Acclimatization↗
PubMed1987

Effects of cold and immobilization stress on noradrenaline turnover in brown adipose tissue of rat.

Noradrenaline (NA) turnover of the interscapular brown adipose tissue (BAT) was determined in order to evaluate a role of sympathetic NA of this tissue in an enhanced nonshivering thermogenesis which had been previously evidenced in the repetitively stressed rats by immobilization (daily 3-h immobilization for 4 weeks) and the cold-acclimated ones (5 degrees C, 4 weeks). The disappearance rate of NA from the BAT following blockade of NA synthesis with alpha-methyl-p-tyrosine was adopted for estimation of NA turnover of the tissue. Cold acclimation increased both fractional turnover rate (%/h) (k) and turnover rate (ng/(g BAT.h)). Repetitive immobilization stress also elevated turnover rate, but not k. In the warm non-stressed controls acute cold exposure to -5 degrees C and acute immobilization stress elevated the turnover rate. The effect of cold exposure was significantly greater than that of immobilization stress for both indices of NA turnover. In the cold-acclimated rats acute cold exposure increased k as well as turnover rate, but not acute immobilization stress. In the repetitively immobilized rats both acute cold exposure and acute immobilization stress elevated k and turnover rate. These results indicate that immobilization enhances sympathetic activity of thermogenic tissue, BAT. The results also suggest that the extent of sympathetic participation is not necessarily the same between the cold-acclimated and the stressed rats.

Acclimatization↗
PubMed1987

Effect of acute cold exposure on ACTH and zinc concentrations in human plasma.

Effects of acute cold exposure (10 degrees C for 60 min) on the concentrations of adrenocorticotropin (ACTH) and zinc in plasma were investigated in seven healthy male students. There were no significant changes in total zinc, albumin-bound zinc, and alpha 2-macroglobulin-bound zinc concentrations throughout the experimental period. On the other hand, ACTH concentration increased markedly during cold exposure. In addition, a statistically significant inverse relationship existed between the changes in ACTH and albumin-bound zinc values during the experiment. These results suggest that acute cold exposure produces elevated plasma ACTH levels, with resulting zinc redistribution in the human body.

Adrenocorticotropic Hormone↗
PubMed1987

Cold-induced changes in glucagon of brown adipose tissue.

In order to evaluate the role of glucagon in brown adipose tissue (BAT) function under cold or stress, the changes in immunoreactive glucagon of BAT and plasma as well as uptake and metabolism of radioactive glucagon (125I-G) in this tissue were studied in rats. Glucagon per g fresh tissue was higher in the dorso-cervical BAT than in the interscapular BAT. In warm controls (WC), acute cold exposure (-5 degrees C, 15 min) (CE) or stress (immobilization, 30 min) (AS) elevated glucagon of both sites of BAT as well as plasma. In cold-acclimated animals (CA), the resting levels of BAT glucagon, but not plasma glucagon, were higher than WC. CE caused elevation of plasma glucagon, but not BAT glucagon in CA. AS did not affect glucagon levels in both plasma and BAT in CA. Cold acclimation did not influence 125I-G uptake by BAT, but resulted in a rather lower 125I-G level in plasma and liver. The present results suggest that BAT is a target tissue for glucagon to cause nonshivering thermogenesis in response to cold or stress and that turnover of glucagon is enhanced by cold acclimation.

Acclimatization↗
PubMed1987

Technetium-99m-labeled monoclonal antibody with preserved immunoreactivity and high in vivo stability.

Recent availability of monoclonal antibodies (MoAb) and their radiolabeling through the use of the bifunctional chelating agents (BCA) have become an alternative procedure for in vivo radioimmunodetection. Using a newly synthesized BCA, a p-carboxyethylphenylglyoxal-di(N-methylthiosemicarbazone) (CE-DTS), the coupling and technetium-99m (99mTc) labeling of monoclonal IgG against hCG were carried out. In the system presented, factors affecting stability and immunoreactivity were examined. Immunoreactivity of the original IgG (56C) was preserved by conjugating one CE-DTS molecule per molecule of IgG (56C) using the phosphorylazide method, however, 99mTc labeling pH affected the immunoreactivity and limited the 99mTc labeling reaction between pH 4.5 and 6.2. A screening of labeling conditions, such as pH, reaction time, and reducing agent system were then carried out. Technetium-99m-labeled IgG (56C), [99mTc]CE-DTS-IgG (56C), showed good stability upon incubation with mice sera and comparable mice biodistribution to that of indium-111 (111In) DTPA-IgG (56C). Thus, these results indicate the excellent potential of CE-DTS as a BCA for labeling MoAb with 99mTc.

Animals↗
PubMed1986

Maternal plasma concentrations of catecholamines and cyclic nucleotides during labor and following delivery.

In plasma obtained from seven mothers before, during, and after normal labor and delivery, catecholamine and cyclic nucleotide concentrations were investigated. Dopamine concentration showed a significant elevation on admission to hospital in labor and there were marked increases in norepinephrine and epinephrine concentrations during labor at 10 cm cervical dilatation and immediately after delivery, respectively. No significant change in dopa, cAMP, or cGMP was found during the experimental period. However, since the van Beaumont quotient (J.Appl. Physiol. 34, 102-106) for cAMP did not follow the reduction in plasma volume, the concentration appeared to rise during labor. Positive correlations were observed between epinephrine on one hand, and heart rate and systolic blood pressure on the other, as well as between norepinephrine and cAMP, respectively, during labor. The diminution of epinephrine on the fourth day postpartum might reflect a reduction of emotional stress concomitant with labor. cAMP was found to be quickly cleared from the bloodstream within 2 hours after delivery. These results suggest that plasma concentrations of epinephrine and cAMP, especially epinephrine, are indices of maternal psychological and physiological stress during labor and following delivery.

Adult↗
PubMed1986

Zinc metabolism in human blood during acute exposure to cold.

Effects of acute exposure to cold (10 degrees C for 60 min) on the concentrations of zinc and related proteins in red blood cells and in plasma were studied on seven male students. Lower concentrations of total zinc and of zinc derived from carbonic anhydrase I (CA-I) in red blood cells were found during cold exposure and 15 min after cold exposure, whereas no significant changes occurred in the concentration of zinc derived from carbonic anhydrase II (CA-II) or Cu2Zn2 superoxide dismutase (SOD1). The decrease in total zinc concentration in red blood cells was mostly due to that in CA-I concentration. On the other hand, there were not any changes in total zinc, albumin-bound zinc, and alpha 2-macroglobulin-bound zinc concentrations in plasma during the experimental period. These results, together with the marked hemoconcentration during cold exposure, suggest that cold stress induces an efflux of zinc from plasma.

Acclimatization↗
PubMed1986

Absence of vasoactive intestinal peptide (VIP) innervation of adipose tissues.

Occurrence of vasoactive intestinal peptide (VIP) in the white and brown adipose tissues was examined in the rats using the immunofluorescence method. VIPergic innervation was observed in the jejunum, while it was not observed in the adipose tissues. The similar findings were obtained in the cold-acclimated and heat-acclimated animals.

Adipose Tissue↗
PubMed1986

Thermal and metabolic responses of repetitively immobilized rats to acute heat exposure.

Repetitively immobilized rats (3 hr/day, 4 weeks) exhibited less increase in the colonic temperature during acute heat exposure at 38 degrees C for 60 min. The magnitude of increase in oxygen consumption during heat exposure did not differ between the controls and the stressed rats. The results suggest that an immobilization stress could develop cross adaptation to heat, possibly by means of enhanced heat dissipating capacity.

Adaptation, Physiological↗
PubMed1985

Effect of food restriction on cold adaptability of rats.

To determine the role of the nutritional state in nonshivering thermogenesis during cold adaptation, cold adaptability was compared between cold-adapted (5 degrees C for 4-5 weeks) rats fed ad libitum and cold-adapted rats pair fed with warm controls having the same food intake. Cold-adapted pair-fed rats suffered a significant loss in body weight during cold exposure. However, brown adipose tissue (BAT) in both cold-adapted ad libitum fed and cold-adapted pair-fed rats was enlarged to the same extent as compared with that in control rats. Fat-free dry matter in BAT also increased in cold-adapted ad libitum fed and cold-adapted pair-fed rats to the same extent. Cold tolerance as assessed by the change in the colonic temperature at -5 degrees C was improved relative to control rats and was the same for cold-adapted ad libitum fed and cold-adapted pair-fed rats. Nonshivering thermogenesis as estimated by the noradrenaline-induced increase in oxygen consumption was significantly greater in the cold-exposed rats and there was no significant difference between cold-adapted ad libitum fed and cold-adapted pair-fed rats. These results suggest that an improved cold tolerance by means of nonshivering thermogenesis in brown adipose tissue is closely related to the low temperature itself but not the increased food intake which occurred in the cold.

Adaptation, Physiological↗
PubMed1985

Lasting consistency of cold adaptability in rats reared in cold for many generations.

Wistar rats were successively reared in cold at 5 degrees C from 1969 to 1984. The historical changes observed in these rats were reported. The cold-adapted rats reared in cold for 8 to 11 successive generations (C8-11G) were examined on their cold tolerance and non-shivering thermogenesis. C8-11G rats showed greater nonshivering thermogenesis than that of the warm-adapted control group (W), and rats exposed to cold for periods of 2 to 8 weeks (C). The nonshivering thermogenesis of C8-11G rats was diminished to a similar level to that of W and C rats by administration of a ganglion blocker, of reserpine, or of beta-adrenoceptor blocker. The de-adapted rats reared in warm at 25 degrees C for 3 generations after being reared for many generations in cold (DA-3G) showed much more nonshivering thermogenesis as compared to W rats. Cold tolerance of DA-3G rats was at a level of intermediate between that of W and C rats. Brown adipose tissue (BAT) weight of DA-3G rats was similar to that of C rats, while chemical composition of BAT in DA-3G rats differed from that of C and W rats.

Adaptation, Physiological↗
PubMed1985

Changes in the colonic temperature and metabolism during immobilization stress in repetitively immobilized or cold-acclimated rats.

Effect of immobilization stress on the rat colonic temperature and metabolism was studied in a warm environment of 25 degrees C. Immobilization for 3 hr caused hyperthermia accompanied by increased oxygen consumption (VO2) in the warm controls. The hyperthermic effect of immobilization was accelerated after 1 week repetition of daily immobilization and it was lessened after 2 to 4 week repetition of daily immobilization. The magnitude of VO2 increase was the same throughout the experimental period of 4 weeks during the immobilization. Hypothermia was never observed during immobilization. Immobilization-induced hyperthermia was significantly potentiated in the cold-acclimated rats, while VO2 increase did not differ between cold-acclimated rats and warm controls. These results suggest that immobilization stress causes the changes in body temperature through thermogenic and heat-loss mechanisms.

Analysis of Variance↗