Biomedical subjects

O Cherubini

Publications and source records attributed to O Cherubini.

6 recordsLinked to original sources

PubMed1989

Sex-related differences in the activity of liver mitochondrial alpha-glycerophosphate dehydrogenase in the rat.

The rat liver mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) is an enzyme that markedly responds to thyroid hormone administration. Its activity is considered a good index of thyroid status in peripheral tissues. In this study alpha-GPD activity and the binding characteristics of nuclear T3 receptors (maximal binding capacity, MBC, and affinity constant, Ka) were compared in male and female rats. Basal alpha-GPD activity in adult females was significantly higher than in the age-matched males. The same difference was observed in immature animals. The cyclic physiological variations in the ovarian steroid hormones during the estrous cycle did not significantly affect alpha-GPD activity, MBC or Ka. Orchiectomy or replacement doses of testosterone administered to orchiectomized rats, had no effect on alpha-GPD activity compared to sham-operated normal males. In females, neither oophorectomy nor testosterone injection to oophorectomized animals induced changes in the enzyme activity. Liver nuclear T3-content, MBC and Ka revealed no systematic differences in both sexes. The T3-induced alpha-GPD activity after a single large dose of T3 designed to fully saturate the nuclear sites for a 24 h period, was significantly higher in female compared to male rats. The kinetics of alpha-GPD showed an identical Km in both sexes, while Vmax was significantly higher in the females. The data suggest that the factors leading to the different activity of alpha-GPD in both sexes, although unknown, may be not related to the sex-hormone differences.

Animals↗

PubMed1986

Relationship between the increase in liver nuclear triiodothyronine-receptor sites and malic enzyme activation by dexamethasone.

Previous works have indicated that a glucocorticoid excess results in an increase in the maximal binding capacity of nuclear T3-receptors (MBC) and in the activity of cytosolic malic enzyme (ME) in the liver of the rat. In this paper, studies were undertaken to evaluate the degree of dependency between the changes in the nuclear T3-receptor number and the induction of a specific metabolic response of T3 evaluated by the activity of ME. The injection of graded daily doses of dexamethasone to adrenalectomized animals (Ax) induced a dose-related increase in MBC and ME activity, and their maximal values were reached with the same dose of dexamethasone. The time-related changes in MBC and ME after the administration of a daily dose of dexamethasone indicated that both parameters followed a progressive-time increase which was evident 24 h after the glucocorticoid until the highest level's were reached. MBC and ME were measured in thyroidectomized (Tx) rats and Tx plus Ax rats injected with dexamethasone (Tx + Ax + D). MBC increased significantly in Ax animals treated with dexamethasone (Ax + D) and in Tx + Ax + D compared with the Tx and control groups. ME activity was very low in Tx animals and dexamethasone injection to Tx + Ax animals did not increase the enzyme activity as occurred in the Ax group where the serum T3 level was in the normal range. These data indicate that the increase in ME activity by dexamethasone administration was associated to a simultaneous increase in the number of liver nuclear T3-receptors. Dexamethasone injected to hypothyroid animals failed to induce a ME activation as it was found in animals with normal T3 levels, suggesting a T3-mediated action of dexamethasone on ME activity by modification of the nuclear T3-receptor number.

Animals↗

PubMed1984

In vitro interaction of opioid peptides with phospholipids. Formation and characterization of complexes.

Interaction of Leu- and Met-enkephalin with phosphatidylserine has been studied by chromatographic and spectrophotometric techniques. The main results of our investigation may be summarized as follows: i) Both enkephalins bind to phosphatidylserine; ii) no difference between the two enkephalins is noticeable; and iii) with both peptides the binding phenomenon leads to the formation of two complexes with a definite stoichiometry which are sterically much smaller than the original vesicles. On the basis of the submitted data, a tentative model of the newly formed complexes is provided.

Acylation↗

PubMed1983

Enkephalin-binding systems in human plasma.

Three amino acid-containing fractions present in human plasma are shown to bind both leu and met-enkephalin: serum albumin and two species of a much lower molecular weight, in all likelihood polypeptides. The amount of enkephalin associated with serum albumin seems comparatively smaller than that associated with the two low molecular weight systems. These systems jointly are apparently capable of binding a significant part of the circulating enkephalins. The possibility is suggested that the interactions described may play a role in maintaining the integrity of circulating enkephalins.

Amino Acids↗

PubMed1983

Nuclear triiodothyronine receptors and metabolic response in perinatally protein-deprived rats.

Pregnant rats from day 14 of pregnancy and pups were fed a control diet (24% casein) or a deprived diet (8% casein) to obtain a control and a pre- and post-natal protein-deprived group. From 50 days of age, all groups were fed a balanced commercial stock diet for different periods. A significant reduction in body weight was observed in the perinatally protein-deprived group (PPD) after the different periods of nutritional recovery studied. Maximal binding capacity (MBC) and apparent affinity constant (Ka) of liver nuclear T3-receptors in the PPD group were similar to those in the control group. Mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) and cytosolic malic enzyme (ME) activity were significantly increased in the PPD group in all the periods of nutritional recovery studied, except in the 8 months old group where it was non-significant. Plasma T3 levels were higher in rats 3 and 15 days after the removal of the hypoprotein diet while it was normal after longer periods of nutritional recovery. Serum T4 was not modified in any group. The results indicate that protein undernutrition during perinatal life may induce an activation of hepatic T3-dependent enzymes which persists even after long periods of nutritional recovery. The lack of modification at the nuclear T3-receptor level, where supposedly the first T3-signal takes place, raises the possibility of an amplification of this signal at a step beyond the receptor.

Age Factors↗

PubMed1983

Selective alterations in hepatic nuclear T3-receptors and enzyme responses by glucocorticoid deficit or excess.

Glucocorticoid deficit in rats induced by adrenalectomy for a 10-day period resulted in an increase in the apparent association constant (Ka) of the liver nuclear T3-receptor while maximal binding capacity (MBC) remained unaltered compared to the intact (sham-operated) animals and to adrenalectomy plus dexamethasone (Sx + D) animals. In addition, a significant increase in the basal activity of liver mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) was observed, while cytosolic malic enzyme (ME) activity was not modified in this situation. Dexamethasone injection (5 mg/kg/day for 4-5 days) to previously adrenalectomized animals (Sx + D) induced a significant increase in MBC of nuclear T3-receptors. On the other hand, Ka value and alpha-GPD activity were restored to the values found in the control group. However, basal activity of ME as well as the response of this enzyme to a saturating dose of T3 was substantially increased by dexamethasone treatment. A non-specific in vitro effect of dexamethasone on MBC and ME was excluded as these parameters were not modified when dexamethasone was added immediately before the in vitro assays. The present study indicates that glucocorticoid deficit or excess is able to induce changes at the level of the nuclear T3-receptor site. The increase in the activity of cytolic ME induced by dexamethasone injection was associated with a simultaneous increase in the T3-receptor capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗