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L Zizine

Publications and source records attributed to L Zizine.

At least 19 recordsLinked to original sources
PubMed1989

Evidence for a cold-induced aldosterone stimulation in the rat.

This study was undertaken to determine the secretion of aldosterone by male Long-Evans rats acclimated for six weeks to moderate cold (15 C), in comparison with rats maintained at thermo-neutral temperature (28 C). The following determinations were made: corticosteroids in plasma and adrenals, PRA, and hydromineral balance. Cold acclimation highly increased the plasma and adrenal levels of aldosterone and corticosterone. The cold stimulation of aldosterone was induced neither by the renin-angiotensin system, nor by alterations of hydromineral balance: PRA, plasma sodium and potassium concentrations, blood hematocrit, and hydromineral balance at 15 C and 28 C did not differ. Moreover this stimulation was induced neither by ACTH, nor by any other hypophyseal factors, since plasma aldosterone levels remained high in hypophysectomized rats. This study provides evidence of an aldosterone stimulation which appeared during moderate cold acclimation; the origin of this stimulation must be investigated.

Adrenal Glands↗
PubMed1986

Hypophysectomy and the sympatho-adrenal system in cold acclimation.

Hypophysectomy does not impair the increase in weight of brown adipose tissue and adrenals following cold acclimation of the rat. In brown fat, the cold-induced increases in NE and 5 HT contents are not modified by hypophysectomy. In adrenals, hypophysectomy does not change the NE content, but a fall in epinephrine content was observed.

Acclimatization↗
PubMed1985

Effect of temperature on lipoprotein lipase and lipogenic enzyme activities in brown adipose tissue of hypophysectomized rats.

It has been shown that the same modifications on the composition of brown adipose tissue (BAT) which are normally induced following cold stimulation are also observed in hypophysectomized rats acclimated either at 28 degrees C or 15 degrees C. To test the possibility of BAT stimulation in hypophysectomized rats, we have determined some enzymatic activities known to modulate the energy supply to that organ. Seven week old Long-Evans rats were hypophysectomized. Three weeks later, they were exposed to either 28 degrees C or 15 degrees C ambient temperature for five or six weeks. Hypophysectomized rats were compared to age matched or weight matched controls. Total lipoprotein lipase activity (LPL) (triglyceride uptake) was enhanced in BAT of 28 degrees C hypophysectomized rats compared to controls. Cold acclimation led to a large increased activity. Total LPL activity was comparable in BAT of hypophysectomized and control rats. Total malic enzyme and glucose-6-phosphate dehydrogenase activities (in situ lipogenesis) were doubled in BAT of 28 degrees C hypophysectomized compared to controls. A large enhancement was observed in BAT of either 15 degrees C control or 15 degrees C hypophysectomized rats. Among the studied organs (liver, white adipose tissue, heart, BAT) hypophysectomy promotes the three enzyme activities only in BAT. These variations were discussed with relation to the effect of hypophysectomy on brown adipose tissue at 15 degrees C and 28 degrees C.

Adipose Tissue↗
PubMed1985

Effects of cold acclimation on adipose tissue lipolysis and cellularity in the hypophysectomized rat.

The study investigated the effects of hypophysectomy and cold acclimation on cellularity and lipolytic capacity of adipose tissue. Hypophysectomized rats (H) were compared to age matched or weight matched controls. Rats were exposed to either 28 degrees C or 15 degrees C ambient temperature for five weeks. In H, despite the inhibition of body growth, it was observed that the growth of epididymal adipose tissue is not entirely inhibited. In comparison with weight matched controls, increase in tissue weight is found to be due to an adipocyte hypertrophy without changes in cell number. No effect of cold acclimation on adipose tissue weight, cellularity and insulinemia were observed in the H group. The in vitro lipolysis effect of norepinephrine was suppressed in 28 degrees C H; a partial recovery of this effect was observed after cold acclimation. This fact is not dependent on adipocyte size, but possibly on structural or metabolic modifications.

Acclimatization↗
PubMed1984

Brown adipose tissue and thermogenesis in hypophysectomized rats in relation to temperature acclimation.

The aim of this work was to test the role of pituitary dependent hormones in cold-induced non-shivering thermogenesis. In the 28 degrees C-acclimated rat, hypophysectomy inhibited body growth and led to an atrophy of thyroid and adrenals. In brown adipose tissue (BAT) some alterations were induced which are usually observed after cold acclimation of the animal: increase in relative weight, decreases in the relative amount of lipids, increases in the amounts of protein and DNA and modification of the proportions of several phospholipid fatty acids; moreover, basal lipolysis, in vitro, was enhanced to the same extent as that following cold acclimation of the normal rat. The in vivo stimulation by norepinephrine (NE) of O2 consumption (test for nonshivering thermogenesis) and of fatty acid release into blood were suppressed. Progressive cold acclimation of the hypophysectomized rats at 15 degrees C led to a hypertrophy of BAT to the same extent as in the sham-operated animals. The in vivo sensitivity to NE was partially restored. The results suggest that hypophysectomy does not suppress the ability to acclimate to moderate cold by means of BAT dependent non-shivering thermogenesis. However, the low ability to produce heat seems to indicate that pituitary or pituitary-dependent hormones are necessary to optimize the cold stimulation of brown fat thermogenesis.

Acclimatization↗
PubMed1983

In vivo effects of indomethacin and cyclophosphamide on CFU-GM proliferation and cyclic nucleotide levels in bone marrow of mice.

The effects of indomethacin (6 mg/kg daily, orally, for 4 days) or cyclophosphamide (150 mg/kg, a single dose, intraperitoneally) on myelopoiesis were studied in mice. A hyperplasia of the committed stem cell compartment (rise in the recognizable myeloid precursors, increase of both colony forming capacity and number of CFU-GM in S-phase) associated to an increase of cyclic AMP and GMP amounts in bone marrow cells of treated mice were observed. These results suggest a possible relationship between the in vitro enhancement of proliferative activity of CFU-GM and the in vivo increase of both cyclic nucleotide levels in medullary environment.

Animals↗
PubMed1980

Effect of in vitro treatment with indomethacin on mouse granulocyte-macrophage colony-forming cells in culture (CFUC). Possible role of prostaglandins.

The effect of indomethacin (6 mg/kg daily orally for 2, 3 or 4 days) on myelopoiesis was studied in mice by estimating 1) differential cell counts of bone marrow, 2) proliferation of the CFUC in presence of GM-CSF, 3) proliferative state of CFUC after tritiated thymidine suicide. After 4 days of treatment, a rise in the recognizable myeloid precursors, an increase of both the colony forming capacity and the number of CFUC in S-phase were observed. These data suggest that indomethacin produced an hyperplasia of the committed stem cell compartment. The decrease of PGE2 amounts in bone marrow cells following treatment with indomethacin could explain the hyperplasia observed. These in vivo results are in accordance with the in vitro data which show that PG could control the proliferation and differentiation of myeloid progenitor cells.

Animals↗
PubMed1979

Prostaglandins E2 and F alpha levels in white and brown adipose tissues of cold acclimated rats as measured by a new micromethod.

A new micro-method was used to determine the effects of cold acclimation of rats on the levels of prostaglandin E2 and F alpha in both white and brown adipose tissues. Whereas PGF alpha levels were significantly higher than PGE2 levels in white fat, no difference between the amounts of the two prostaglandins was observed in brown fat. In both tissues, cold acclimation did not induce any change in prostaglandin levels.

Acclimatization↗