Comparative immunocytochemical localization of enkephalin and somatostatin in the median eminence, hypothalamus and adjacent areas of the guinea-pig brain.

Because of the presence of an enkephalin-related substance in the somatostatin terminals of the median eminence, an investigation was carried out on the staining for enkephalin of the somatostatin-containing perikarya localized in the hypothalamic periventricular nucleus. Only an occasional and weak enkephalin immunoreactivity was detected in these perikarya, making the common synthesis of the two peptides unlikely. Moreover, our results demonstrate an enkephalin staining in other fibers of the median eminence clearly distinct from the somatostatin ones. Enkephalin was demonstrated in perikarya distributed in the septum, preoptic area, dorsal and ventromedial hypothalamus, all regions known to possibly project into the median eminence. In none of these sites was enkephalin found in association with somatostatin. The present morphological results support the hypothesis that enkephalins may exert their GH-releasing effect at the hypothalamic level and suggest that enkephalins might directly modulate the somatostatin release into the blood of the portal plexus.

Circadian and cyclic LHRH variations in the organum vasculosum of the lamina terminalis of female and male rats.

The organum vasculosum of the lamina terminalis (OVLT) was investigated by immunofluorescence and quantitative electron microscopic methods, and its LHRH content was measured at intervals during the estrous cycle and in male rats. A well-defined circadian rhythm in the LHRH content was demonstrated in the OVLT. The highest value was observed on the day of proestrus with peaks at noon and in the late afternoon. The amount of LHRH was about the same in the male as in the female rats on the day of diestrus 1. The OVLT in both sexes contained LHRH-positive fibers and terminals, but less immunofluorescence was visible on the day of diestrus and in the male animals. Quantitative electron microscopic analysis shows that in the OVLT nerve terminals, abutting on the basement membrane, more granulated vesicles (80-90 nm in diameter) are present on the day of proestrus than on any other day of the cycle or in the male. Our results suggest that the OVLT may participate in some way in the control of the cyclic gonadotrophic function of the anterior pituitary and/or in the behavioral effect of sexual hormones.

Immunoreactivity for beta-endorphin in LH-RH neurons of the fetal human hypothalamus.

A peptide immunochemically related to beta-endorphin was detected in some LH-RH neurons of the fetal human hypothalamus by comparison of adjacent sections stained for beta-endorphin and for LH-RH. In the same section, by successive staining and after antibody elution, both peptides were again revealed in the same neuron. The significance of the presence of the beta-endorphin-like material in LH-RH neurons is discussed.

[Melatonin and gonadoliberin (LH-RH) cells in rat hypothalamus]. / Mélatonine et cellules à gonadolibérine (LH-RH) de l'hypothalamus du rat.

Immature female rats were induced to ovulate by an injection of pregnant mare serum: melatonin, intraperitonealy injected, induce an increase of LH-RH immunoreactive neurons in the hypothalamus. These neurons are localized in septo preoptic, infundibular and premammillary areas.

[Hypothalamic LH-RH neuronal modifications after prolactine intraventricular infusion in the guinea pig (author's transl)]. / Modification des neurones hypothalamiques à LH-RH après injection intraventriculaire de prolactine chez le cobaye.

Ovine prolactine injected at doses of either 31,25 to 500 microgram by lateral intraventricular route in male guinea pigs, affects LH-RH hypothalamic neurons within 2 to 24 hours. After this treatment there is an increase of LH-RH immunoreactive material in eminential terminals and in numerous small granules of hypothalamic neuronal cell bodies. This accumulation of immunoactive LH-RH in pericaryon and in terminals can be interpreted as stimulation of LH-RH synthesis. Preliminary results of radioimmunoassayed plasmatic LH level, 2 h after PRL infusion, are in agreement with this hypothesis. The probability that short feed-back by PRL or PIF secretion would simultaneously be able to check LH-RH secretion is discussed.

[Effects of atropine sulfate on the hypothalamic LH-RH cells of the guinea-pig]. / Effets du sulfate d'atropine sur les cellules à LH-RH de l'hypothalamus du cobaye

A single 30 mg/kg., s.c. injection of atropine sulfate into male guinea pigs produces a storage of LH-RH immunoreactive material in hypothalamic neurons. In diestrus female there is no increase of immunoreactive LH-RH substance in neuron and in eminential terminals; the rate of LH-RH synthesis may be still slight. The LH-RH immunoreactive neuronal increase, in male may be related to an atropine blockade of LH-RH portal cession, perhaps via infundibular dopaminergic neurons.

[Further observations on the presence of iron in the articuler synovial membrane]. / Secondes vues sur la présence de fer dans la synoviale articulaire

In 1971, a study of 66 synovial biopsy samples indicated that the presence of ferric deposits in the subintimal synovial tissue was of real semiological value in the diagnosis of rheumatoid synovitis. In 1975, a study of 228 synovial biopsy samples led the authors to reconsider this finding: the presence of ferric deposits in the subintimal synovial tissue was far from being a constant feature in rheumatoid synovitis and it was seen with similar frequency in other forms of chronic inflammatory rheumatism and also in several other joint conditions. The origin of the synovial iron and the influence it may have on the development of the rheumatoid processes remain obscure.

[Hypothalamic mechanism of the antiovulatory action of sulpiride]. / Mécanisme hypothalamique de l'action anti ovulatoire du sulpiride

The antiovulatory effect of sulpiride is mediated via inhibition of the LH-RH release: when given during 10 days in guinea pigs, sulpiride is able to promote an increase of LH-RH immunoreactive substance in anterior hypothalamic and suprachiasmatic neurons. This storage probably related with inhibition of LH-RH release, is permitted by catecholamines, since metatyrosine administration prevent this sulpiride effect. On the other hand, when administered to hamsters sulpiride is able to promote stimulation of hypothalamic catecholaminergic neurons of tubero infundibular and anterior periventricularis nuclei. The hypothalamic aminergic action upon sulpiride antiovulatory effect is discussed.