Search PubMed⌕ Search

Biomedical subjects

A Kuroshima

Publications and source records attributed to A Kuroshima.

At least 19 recordsLinked to original sources
PubMed1995

Effects of fasting and refeeding on some metabolic characteristics of rat brown adipose tissue.

To investigate the effects of fasting and refeeding on rat interscapular brown adipose tissue (BAT), we determined in vitro oxygen consumption, in vitro lipolysis, DNA content and composition of fatty acid (FA). Fasting decreased the weights of body and BAT, and the DNA content of BAT. Fasting reduced both basal oxygen consumption and basal lipolysis of BAT. Fasting also suppressed the noradrenaline- and glucagon-induced increases in both oxygen consumption and lipolysis of BAT. In both triglyceride and phospholipid FA of BAT the extent of unsaturation was increased by fasting. Refeeding restored all of these parameters to the control level. These observations indicate that fasting reduces both oxygen consumption and lipolysis of BAT, resulting in reduced thermogenesis, while fasting could stimulate BAT in certain phases of its function as observed in FA composition.

Adipose Tissue, Brown↗
PubMed1995

[Regulation of thermoregulatory thermogenesis].

Two modes of heat production exist which are involved in body temperature regulation with decreasing environmental temperature: shivering thermogenesis and more efficient nonshivering thermogenesis (NST). Enhanced NST is mediated by the activated sympathetic nervous activity and increased secretions of hormonal factors such as glucagon through an enhanced lipid utilization. Moreover, cold acclimation causes an increased responsiveness of the organism to these factors. Noradrenaline-induced secretion of glucagon is also enhanced by cold acclimation. Chronic administration of glucagon simulates cold acclimation, resulting in an improved cold tolerance by an increased NST. Brown adipose tissue (BAT) is a major site for nonshivering thermogenesis (NST) during metabolic cold acclimation. Cold acclimation causes a hyperplasia as well as an enhanced metabolic capacity of BAT cell. BAT function is mainly regulated by sympathetic noradrenaline and several hormonal factors such as glucagon. BAT possesses rich blood supply by which its high thermogenic capacity and an efficient transfer of heat are maintained. Noradrenaline and glucagon increases not only heat production, but also blood flow in BAT. Nitric oxide (NO), endothelium-derived relaxing factor, is involved in noradrenaline-, glucagon- and cold-induced increases of blood flow through BAT. Noradrenaline-induced BAT thermogenesis is suggested to be mediated by NO. NO synthase occurs in BAT cell in addition to endothelium of BAT vessel. These findings indicate that NO may be a signalling molecule for an enhanced NST during cold acclimation. Moreover, BAT contributes to adaptation to overfeeding, nonthermal stress and fever by means of producing heat, playing a role as adaptive organ in overall energy metabolism.

Acclimatization↗
PubMed1994

Involvement of nitric oxide in noradrenaline-induced increase in blood flow through brown adipose tissue.

N omega-nitro-L-arginine methyl ester (L-NAME) (80 mg), a NO synthase blocker, completely abolished noradrenaline (NA)-induced increase in blood flow through brown adipose tissue (BAT) in the urethan-anesthetized rat. L-NAME suppressed NA-induced increase in blood flow dose-dependently. L-arginine (80 mg), but not D-arginine (80 mg), reversed the inhibitory effect of L-NAME (0.8 mg). NA-induced increase in BAT temperature was also decreased by L-NAME. These results suggest that nitric oxide mediates NA-induced increase in BAT blood flow.

Adipose Tissue, Brown↗
PubMed1994

Antitumor activities and immunochemical properties of the cell-wall polysaccharides from Aureobasidium pullulans.

Delipidated cell walls from Aureobasidium pullulans were fractionated systematically. The cell surface heteropolysaccharide contains D-mannose, D-galactose, D-glucose, and D-glucuronic acid (ratio, 8.5:3.9:1.0:1.0). It consists of a backbone of (1-->6)-alpha-linked D-mannose residues, some of which are substituted at 0-3 with single or beta-(1-->6)-linked D-galactofuranosyl side chains, some terminated with a D-glucuronic acid residue, and also with single residues of D-glucopyranose, D-galactopyranose, and D-mannopyranose. This glucurono-gluco-galactomannan interacted with antiserum against Elsinoe leucospila, which also reacted with its galactomannan, indicating that both polysaccharides contain a common epitope, i.e., at least terminal beta-galactofuranosyl groups and also possibly internal beta-(1-->6)-linked galactofuranose residues. It was further separated by DEAE-Sephacel column chromatography to gluco-galactomannan and glucurono-gluco-galactomannan. The alkali-extracted beta-D-glucan was purified by DEAE-cellulose chromatography to afford two antitumor-active (1-->3)-beta-D-glucans. One of the glucans (M(r), 1-2 x 10(5)) was a O-6-branched (1-->3)-beta-D-glucan with a single beta-D-glucosyl residue, d.b., 1/7, and the other (M(r), 3.5-4.5 x 10(5)) had similar branched structure, but having d.b., 1/5. Side chains of both glucans contain small proportions of beta-(1-->6)- and beta-(1-->4)-D-glucosidic linkages.

Antineoplastic Agents↗
PubMed1994

Lipid interference with fluorometric assay of DNA in adipose tissues under various conditions.

Interference by lipids with fluorometric assay of DNA in adipose tissues using Hoechst 33258 was investigated. Mixed glycerides shifted the emission maximum of standard DNA and induced a dose-dependent increase in fluorescence intensity. Glycerides in the samples containing a known concentration of DNA yielded erroneously higher DNA concentrations. The DNA concentrations obtained from acetone-defatted white and brown adipose tissues (WAT and BAT) were lower than those of non-defatted ones, while DNA content did not differ in low lipid-containing skeletal muscle between defatted and non-defatted samples, indicating that large amounts of lipids interfere with DNA measurement using Hoechst 33258 and that acetone defatting is a simple method to avoid this interference. Using this defatting method, the cellularity of WAT and BAT was estimated in rats under various experimental conditions. Cold-acclimation and repetitive immobilization stress decreased the body weight gain and the epididymal WAT weight. Sucrose overfeeding increased WAT weight but not body weight. These treatments of 4 weeks' duration did not induce any significant difference in WAT cell number from controls, while cold-acclimation increased the tissue cell number as well as the BAT weight.

Acetone↗
PubMed1992

Postnatal changes in fatty acids composition of brown adipose tissue.

It has been demonstrated that thermogenic activity of brown adipose tissue (BAT) is higher during the early postnatal period, decreasing towards a low adult level. The present study examined postnatal changes in the lipid composition of BAT. BAT from pre-weaning rats at 4 and 14 days old showed the following differences in lipid composition compared to that from adults of 12 weeks old. (i) Relative weight of interscapular BAT to body weight was markedly greater. (ii) BAT-triglyceride (TG) level was lower, while BAT-phospholipid (PL)level was higher. (iii) In TG fatty acids (FA) polyunsaturated fatty acids (PU; mol%), arachidonate index (AI), unsaturation index (UI) and PU/saturated FA (SA) were higher; rare FA such as eicosadienoate, bishomo-gamma-linolenic acid and lignoceric acid in mol % were also higher. (iv) In PL-FA monounsaturated FA (MU) in mol % was lower; PU mol %, AI and UI were higher. These features in BAT of pre-weaning rats resembled those in the cold-acclimated adults, suggesting a close relationship of the PL-FA profile to high activity of BAT.

Adipose Tissue, Brown↗
PubMed1992

Effects of running training on in vitro brown adipose tissue thermogenesis in rats.

Brown adipose tissue (BAT) is a major site of nonshivering thermogenesis (NST) during cold acclimation for most mammals. Repetitive nonthermal stress such as immobilization has been shown to enhance the capacity of NST as cold acclimation. In the present study, the effects of running training, another type of nonthermal stress, were investigated on in vitro thermogenesis and the cellularity of interscapular BAT in rats. The rats were subjected to treadmill running for 30 min daily at 30m/min under 8 degrees inclination for 4-5 weeks. In vitro thermogenesis was then measured in minced tissue blocks incubated in a Krebs-Ringer phosphate buffer containing glucose and albumin at 37 degrees C, using a Clark type oxygen electrode. The trained rats showed less body weight gain during the experiment. The weights of BAT and epididymal white adipose tissue were smaller in the trained rats. Noradrenaline- and glucagon-stimulated oxygen consumption were also significantly smaller in the trained rats. The tissue DNA level was greater in the trained rats, but the DNA content per tissue pad did not significantly differ. The results indicate that running training reduces BAT thermogenesis, possibly as an adaptation to conserve energy substrates for physical work.

Adipose Tissue, Brown↗
PubMed1992

Effects of chronic administration of noradrenaline and glucagon on in vitro brown adipose tissue thermogenesis.

The in vitro brown adipose tissue (BAT) oxygen consumption stimulated by noradrenaline (NA) or glucagon (G) was significantly lower in chronically NA-treated rats and that of G-treated rats did not differ as compared with that of vehicle-treated control animals. In vitro thermogenic response of BAT in NA-treated rats was consistent with that induced by cold acclimation.

Acclimatization↗
PubMed1992

Effect of immobilization stress on in vitro and in vivo thermogenesis of brown adipose tissue.

Repetitive intermittent stress such as immobilization has been shown to induce an improved cold tolerance through an enhanced capacity of nonshivering thermogenesis (NST), causing positive cross adaptation between nonthermal stress and cold. In the present study, effect of 3-h-daily immobilization stress for 4-5 weeks was investigated on in vitro and in vivo thermogenesis of interscapular brown adipose tissue (BAT). In vitro thermogenesis was measured in the minced tissue blocks incubated in Krebs-Ringer phosphate buffer with glucose and albumin at 37 degrees C, using a Clark-type oxygen electrode. The stressed rats showed less body weight gain during the experiment. The BAT weight, its protein and DNA contents were significantly greater in the stressed rats. Basal, noradrenaline- and glucagon-stimulated oxygen consumptions were significantly greater in the stressed rats. In vivo thermogenesis was assessed by the changes of temperatures in colon (Tcol), BAT (TBAT), and tail skin (Tsk) induced by noradrenaline or glucagon infusion in the anesthetized rats. Noradrenaline and glucagon increased the TBAT and the extent of increase was greater in the stressed rats. These results indicate that cross adaptation between nonthermal stress and cold may be mediated through an enhanced thermogenic activity of BAT.

Acclimatization↗
PubMed1992

Effects of cold acclimation on cold-induced changes in lipid metabolism of rat brown adipose tissue.

Effects of acute cold exposure (0 degree C, 12 h) on lipid metabolism of the interscapular brown adipose tissue (BAT) were studied in warm controls (25 degrees C) (WC) and cold-acclimated rats (5 degrees C, 4 weeks) (CA). 1) We confirmed that cold acclimation brought about decreased BAT triglyceride (TG) level and increased BAT phospholipid (PL) level. The indexes of unsaturation, such as unsaturation index and polyunsaturated fatty acids/saturated fatty acids ratio, of bulky fatty acids (FA) (palmitic, stearic, oleic, and linoleic acids) decreased in TG, while those increased in PL. Rare FA (eicosadienoic acid, homo-gamma-linoleinic acid, lignoceric acid) level, which were about five times higher in PL than TG in WC, decreased in both TG and PL in CA. 2) Effect of acute cold exposure in WC: The level as well as the amount of TG in BAT was greatly reduced and the indexes of unsaturation in TG-FA increased. The most part of reduced TG (85%) was explained by the bulky FA. Rare FA explained only 1.1% of reduced TG. PL level in BAT did not change, but its amount decreased. The indexes of unsaturation increased in PL-FA. 3) Effect of acute cold exposure in CA: CA was placed in warm temperature of 25 degrees C before cold exposure. In contrast with the cold-reduced TG in WC, either the level or the total amount of TG in BAT did not change, but the indexes of unsaturation in TG-FA decreased. The level as well as the total amount of PL in BAT increased. The arachidonic index and arachidonate in PL-FA decreased, but the indexes of unsaturation did not change. These results indicate as a whole that acute cold exposure as well as cold acclimation influences BAT lipid metabolism in FA compositions as well as amount of TG and PL, suggesting that such changes are related to thermogenic activity of this tissue.

Acclimatization↗
PubMed1991

Effects of cold stress on glutathione and related enzymes in rat erythrocytes.

Effects of acute and chronic cold stress on glutathione and related enzymes in rat erythrocytes were investigated. Blood from both cold-acclimated (CA) and cold-adapted (CG) rats had significantly lower concentrations of glutathione than blood from control animals. Superoxide dismutase activity was increased significantly in CA rats and tended to rise in CG rats. Activity of glutathione peroxidase in erythrocytes was inconsistent in that it tended to increase in CA rats but decreased significantly in CG rats. The results may imply that CG rats suffered deleterious effects of hydrogen peroxide. On the other hand, there were marked decreases in glutathione peroxidase and glutathione reductase activities in acutely cold-exposed rats in conjunction with unchanged levels of glutathione. In all treatments the state of riboflavin metabolism was estimated to be adequate, since no increases were observed in the erythrocyte glutathione reductase activity coefficient.

Animals↗
PubMed1990

Effects of exercise stress and cold stress on glutathione and gamma-glutamyltransferase in rat liver.

Effects of acute and chronic stress (exercise and cold) on glutathione and gamma-glutamyltransferase (gamma GT) in the rat liver were investigated. Such stress, except for in the case of acute exercise, had no definite influence on the glutathione level. On the other hand, gamma GT activity in both the extramicrosomal and microsomal fractions varied substantially, suggesting that acute exercise increases the release ability of the microsomal membrane of the rat liver, and that swimming training and long-term cold exposure stabilize the membrane. Immunoreactive gamma GT, however, did not always correlate with the enzyme activity, especially in the extramicrosomal fraction. Cross-adaptation appeared to exist between swimming training and chronic cold exposure.

Animals↗
PubMed1990

Changes in fasting-induced adrenocortical secretion of cold-acclimated rats.

Effect of cold acclimation on fasting-induced adrenocortical and metabolic responses was studied in rats. The animals were acclimated to cold by exposure to 5 degrees C for 4 weeks. The warm control animals were kept at 25 degrees C for the same period. Fasting for 48 h decreased the body weight to the same extent in warm controls (WC) and cold-acclimated rats (CA). Plasma free fatty acids concentration increased by fasting, but the degree of increase did not differ between WC and CA. Plasma glucose level decreased in WC, while it increased in CA by fasting. Plasma corticosterone level was significantly higher in CA than in WC. Fasting increased the level in both groups, and the extent of increase as assessed by 95% confidence interval was significantly greater in CA as compared with that in WC. The present results indicate that fasting-induced glucocorticoid secretion is potentiated by cold acclimation, suggesting a possible role of this hormone in some metabolic changes in fasting.

Acclimatization↗
PubMed1990

Cold-induced and postnatal changes in brown adipose tissue ganglioside levels.

Effects of cold and postnatal development were studied on brown adipose tissue (BAT) ganglioside levels in rats. Interscapular BAT was defatted by cold acetone before ganglioside extraction. Gangliosides were determined using HPTLC. Major ganglioside in BAT was found to be GM3. BAT GM3 level per g of fresh tissue weight as well as fat-free dry matter significantly increased in cold-acclimated rats (CA) and in rats reared in cold for 27 generations. BAT GM3 level per g of fresh weight as well as fat-free dry matter was significantly higher in 4-day- and 14-day-old rats than that in adult animals (12 weeks old). It was also shown that the higher levels of BAT GM3 were associated with greater BAT weight relative to body weight. These results suggest that BAT ganglioside, especially GM3, is implicated in growth and/or function of BAT in terms of cold-induced and postnatal changes of this tissue.

Acclimatization↗
PubMed1989

Increased ACTH response to corticotropin-releasing factor in cold-adapted rats in vivo.

We have recently reported that chronically repeated restraint stress results in improved cold tolerance in rats via an increased activity of nonshivering thermogenesis, a characteristic metabolic change observed during cold adaptation, suggesting the presence of cross-adaptation between cold and stress. It is well established that the hypothalamic-pituitary-adrenal (HPA) axis is activated in various stress responses. In the present study, therefore, we examined whether cold adaptation would alter the adrenocorticotropic hormone (ACTH)-releasing state in vivo using freely moving, conscious rats chronically implanted with intra-atrial cannulas. There was no difference in the basal levels of plasma ACTH between warm control and cold-adapted rats. On the other hand, the ACTH response to the intravenous administration of corticotropin-releasing factor (CRF; 2 micrograms/animal) was significantly elevated in cold-adapted rats. However, the injection of 10 micrograms of CRF, which was considered as a dose to elicit the maximal ACTH response, resulted in similar ACTH release patterns between the two groups. These changes in the responsiveness of ACTH secretion have been observed in rats chronically exposed to stressful conditions. The results demonstrated in the present study, therefore, provide further evidence for our hypothesis that there may exist cross-adaptation between cold and nonthermal stress.

Adaptation, Physiological↗