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Biomedical subjects

G Barbanel

Publications and source records attributed to G Barbanel.

46 records · Page 3Linked to original sources
PubMed1985

[Demonstration of prolactin flow into the cerebrospinal fluid of the alert rat in a pulsatile circhoral manner by push-pull cannulation of the 3d ventricle].

In 8 male unanesthetized rats, sequential sampling of cerebrospinal fluid (CSF) from a push-pull cannula implanted into the 3rd ventricle revealed that prolactin was present in this fluid, where it displayed circhoral pulsatility resembling the temporal variations in plasma prolactin observed in the same animals. Although basal prolactin levels were lower in the CSF than in the plasma, the amplitude of the circhoral prolactin pulses was twice as great in the CSF as in the plasma compartment. The possible origin and role of CSF prolactin are discussed.

Animals↗
PubMed1984

Diurnal variations in estradiol binding site concentrations in the hypothalamus, pituitary and uterus of prepuberal rats.

Available cytosolic estradiol binding sites (EBS) were estimated at 6 h intervals over a 24 h period in individual extracts of uteri, pituitaries and hypothalami from intact, ovariectomized or hypophysectomized 28-day old rats, maintained from birth in a 12 h light-12 h dark photoperiod. Plasma estrogen levels were also recorded, in intact rats, they displayed a 20% rise during daytime. In the uterus and pituitary of ovariectomized rats EBS concentrations exceeded by one third those of intact controls. In intact animals, significant diurnal variations in EBS were observed in both these tissues, with increased daytime levels. These variations appeared to depend on the amount of estrogen in the plasma, as they were not observed in spayed rats. No diurnal variations in EBS were apparent in the hypothalamus of intact animals, but they did occur in ovariectomized rats, and even more significantly in hypophysectomized rats, although the latter had lower EBS concentrations than spayed animals. These variations were presumed to result from the interference of pituitary-controlled hormones other than estrogens in the regulation of EBS levels.

Animals↗
PubMed1980

Postnatal development of estradiol receptor in female and male rats.

The concentration of available cytoplasmic estradiol receptor was quantified in the postnatal hypothalamus and pituitary of male and female rats, aged from 4 to 28 days. The uterine receptor was measured in female rats. The method used was designed to avoid non-specific contamination of cytosol from very young animals by plasma proteins, especially alpha-feto-protein (AFP). In the hypothalamus, the concentration of estradiol binding sites was maximal 6 days after birth, and declined until day 28 to low constant level. In the pituitary, the estradiol receptor concentration increased from day 4 and reached a plateau at 13--14 days, whereas in the uterus, the concentration of cytoplasmic binding sites rose up to day 10--12, and then markedly decreased.

Aging↗
PubMed1977

Development of a microassay for estradiol receptors.

The calculation of equilibrium binding constants for a specific receptor-hormone interaction requires the exact determination of the unbound ligand concentration and the specifically bound concentration at equilibrium. These determinations usually require corrections for the contribution of non-specific binding. We introduce several parameters allowing equilibrium concentrations to be calculated from experimental concentration values; these parameters can be measured for the particular receptor assay procedure used. These parameters are used in a microassay of estradiol-receptor complex by selective retention on DE-81 cellulose paper.

Animals↗
PubMedDate not supplied

Chronic orthostatic and antiorthostatic restraint induce neuroendocrine, immune and neurophysiologial disorders in rats.

The tail-cast suspension rat model has been developed in ground laboratories interested in space physiology for extensive study of mechanisms causing the pathophysiological syndrome associated with space flights. We used individually-caged male rats to explore the effects of acute and chronic (7d) orthostatic restraint (OR) and head-down anti-orthostatic restraint (AOR) on a series of physiological variables. The acute restraint study showed that (1) the installation of the OR device induced an acute reaction for 2 days, with a substantial rise in ACTH (x2) and CORT (x6), and that (2) the head-down tilt from OR to AOR induced (i) within 10 min and lasting 60 min a 2-fold rise in the intra-cerebro-ventricular pressure (Picv) monitored with an icv telemetric recording system, which receded to normal between 60 and 120 min; and (ii) within 30 min a short-lived 4-fold rise in plasma ACTH and CORT levels. Chronic OR induced (1) the suppression of the diurnal ACTH/CORT rhythm, with increased mean levels, especially for ACTH, (2) a degraded circadian locomotor activity rhythm manifested by a significant reduction in the spectral power of the 24h periodicity and a concomitant emergence of shorter (ultradian) periodicities, (3) an associated, but less pronounced alteration of the diurnal rhythm in body temperature; and (4) a marked increase in baseline plasma levels of IL-1 beta and an increased reactivity in cytokine release following an E. coli endotoxin (LPS) challenge. AOR induced (1) a similar obliteration of the circadian ACTH/CORT rhythm, (2) the loss of close correlation between ACTH and CORT, (3) a generalized increase in baseline plasma IL-1 beta levels and (4) more extensive degradation of the circadian periodicity for both locomotor activity and, to a lesser extent, body temperature, replaced by dominant spectral powers for ultradian periodicities (3 to 10h). In conclusion, both experimental paradigms--but AOR more than OR--caused a blockade of the circadian rhythmicity of major physiological variables, the loss of normal correlations between ACTH and CORT, and inflammatory-immune hyperreactivity. These pathophysiological disorders may all be parts of a complex chronic stress syndrome.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Effects of thyroid hormones on the ontogeny of oestradiol-binding sites in the rat.

The effects of neonatal hypothyroidism on the development of cytoplasmic oestradiol-binding sites were studied in the hypothalamus, pituitary and uterus of the rat. Between 7 and 28 days the total number of binding sites was significantly reduced in all three tissues, whereas the actual concentrations of binding sites were dramatically depressed throughout the period considered in the pituitary only. Adequate replacement therapy by L-thyroxine almost completely reversed all these effects in 14-day-old rats, and administration of excessive L-thyroxine even raised pituitary binding-site concentrations to above normal. On the other hand, plasma oestrogen levels, which were depressed in hypothyroid animals, fell even further, whatever the L-thyroxine therapy. Hence, thyroid hormones appear to stimulate oestradiol binding-site levels directly rather than indirectly via plasma oestrogen titres. The specific modulatory effect of L-thyroxine on oestradiol-binding sites in various types of pituitary cells is discussed.

Aging↗
PubMedDate not supplied

Chronic restraint enhances interleukin-1-beta release in the basal state and after an endotoxin challenge, independently of adrenocorticotropin and corticosterone release.

To explore the interactions between the hypothalamic-pituitary-adrenocortical axis and the immune system under stress conditions, we used an experimental rat model for chronic tail-restraint devised earlier for ground studies in space physiology. The system was used in two positions: (1) the orthostatic restraint position (OR) and (2) the antiorthostatic position (AOR) after the rat hind limbs had been raised by a head-down tilt. After 7 days of either restraint, sequential blood samples were taken via an indwelling aortic cannula, before and at various time intervals between 15 and 300 min after an intravascular infusion of 25 micrograms/kg lipopolysaccharide (LPS). The plasma titers of adrenocorticotropin (ACTH), corticosterone (CORT) and interleukin-1 beta (IL-1 beta) were assayed. Under basal conditions, both OR and AOR restraints induced a 5-fold increase in IL-1 beta with no significant changes in ACTH and CORT levels. A robust increase in all three variables was observed after LPS injection. However, the IL-1 beta response to LPS was significantly higher in both restrained groups than in controls. Both the amplitude and the percentage of individually restrained rats displaying elevated IL-1 beta levels were increased up to 5 h. In contrast, the ACTH and CORT post-LPS responses were normal in the OR group. They were unusually dissociated in the AOR rats, which displayed depressed ACTH levels associated with slightly increased CORT levels. Our results suggest that immune-neuroendocrine responses to chronic restraint stress may differ from those generally observed in acute stress.

Adrenocorticotropic Hormone↗