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Biomedical subjects

B Mess

Publications and source records attributed to B Mess.

At least 37 records · Page 2Linked to original sources
PubMed1983

Emergence of production of the brain peptides.

The onset of the synthesis of the releasing and inhibiting hormones, associated with their identified primary structures (LHRH, somatostatin), has been studied successfully in some vertebrates. It is known from radioimmunoassay and immunohistological studies that the synthesis of LHRH, TRH and somatostatin begins in the brain of different mammalian species (rat, mouse, guinea pig, man) during embryonic life. Much less is known about this phenomenon in birds. According to very scarce immunohistological data, the first traces of identifiable LHRH appear in the brain of the chicken on day 5 1/2 of embryonic life, while somatostatin appears on the 12th embryonic day. It is remarkable, both in mammals and birds, that the onset of trophic hormone secretion usually proceeds that of the releasing and inhibiting hormones. This would indicate that the releasing and inhibiting hormones do not play a significant role in the embryonic differentiation and induction of hormone secretion of the fetal adenohypophysis.

Animals↗
PubMed1982

Immunohistochemical localization of the luteinizing hormone releasing hormone (LHRH)-containing structures in the central nervous system of the domestic fowl.

The location of LHRH-containing neuronal elements was investigated in the domestic fowl by means of immunohistochemical techniques. LHRH antisera were raised against synthetic LHRH in the rabbit. The antiserum used in the present study cross-reacted with LHRH of mammalian and avian tissues. LHRH-immunoreactive perikarya are located in the preoptic and in the septal areas, and in the bulbus olfactorius; however, no LHRH-immunoreactive perikarya were found in the tuberal part of the hypothalamus. LHRH-immunoreactive fibers course from these areas toward the median eminence mainly along the wall of the third ventricle in the form of a periventricular network. Originating from the same cell groups other fibers run caudally immediately above the optic chiasma, forming the median bundle of the tractus preoptico-infundibularis. The third bundle running toward the OVLT is named the tractus preoptico-terminalis. In addition to these structures, LHRH-containing fibers and terminals were also present in different regions of the limbic system, in the dorsal part of the hippocampus, in the tuberculum and bulbus olfactorius, as well as in the optic lobe, nuclei commissurales tectales, organon subcommissurale, periaqueductal area, and pars ventralis mesencephali. The general distribution of the LHRH system in the chicken corresponds principally to that described previously in rodents (Sétáló et al. 1976, 1978). However, some subtle differences were demonstrated between the location of the LHRH system in birds and mammals.

Animals↗
PubMed1981

Role of the serotoninergic neuron system of the brain stem on the release of thyrotrophic and luteinizing hormone.

1. Decrease of brain serotonin concentration, elicited by either parachlorophenylalanine treatment, surgical interruption of the ascending serotoninergic fibres, or by pinealectomy provokes an enhanced release both of TSH and LH. 2. Increased serotonin content of the brain, produced by intraventricular, intrahypothalamic or systemic administration of serotonin, results in a significant inhibition of the release of these two trophic hormones. 3. It is concluded that the serotoninergic neuron system of the brain stem represents an inhibitory mechanism in the neuroendocrine circuit regulating pituitary trophic hormone release.

Animals↗
PubMed1979

Inhibitory role of brain stem serotoninergic neuron system on thyroid function in rat.

Thyroid function was investigated in adult male rats following the use experimental procedures which inhibit the activity of serotoninergic neuron system. Pharmacological blockade of the biosynthesis of sertonin by repeated administration of para-chlorophenylalanine (pCPA), or interruption (by Halász knife) of the serotoninergic pathways of the brain stem which terminate on hypothalamic nuclei equally resulted in an augmentation of the following parameters of hypothalamo-hypophysial-thyroid activity: T/S ratio, pituitary and blood TSH levels and blood thyroxine concentration as well as TRH content of the hypothalamus. The results suggest that the central nervous serotoninergic neuron system plays an inhibitory role in the regulation of TSH secretion, presumably acting upon the hypothalamus, thereby inhibiting hypothalamic TRH secretion.

Animals↗
PubMed1979

Effect of the fungal toxin (zearalenone) on the reproductive system and fertility of male and female rats.

The fertility-inhibiting effects of long-term (8 weeks) consumption of maize infected with a fungus producing F2 toxin (zearalenone) was studied in adult male and female albino rats. The fertility rate was further decreased by 25-30% if the animals were kept on contaminated diet up to 14 weeks. The gonadal weight was decreased, follicular maturation and spermatogenesis were disturbed. The toxic diet consumed by mothers during pregnancy and lactation induced permanent changes in reproductive organs, disorders in vaginal cyclicity and disturbed fertility in the offspring. Neonatal administration of purified F2 toxin provoked similar changes. It is suggested that this fungal toxin may cause sterility syndrome in the offspring, similar to that produced by androgen or estrogen administration.

Animals↗
PubMed1978

Effect of melatonin on induction of ovulation in the light- induced constant estrous-anovulatory syndrome and possible role of the brain serotoninergic system.

Continuous light (CL) induces constant estrous anovulatory (CEA) syndrome and blockade of pineal gland activity. Chronic treatment with metatonin is able to overcome the anovulatory state in about 70% of CL-CEA rats, and the luteinizing effect of melatonin is significantly counteracted either by feeding the animals with a tryptophan-poor diet or by injecting methiothepin, a blocker of central serotoninergic receptors. It appears that melatonin elicits luteinization in CL-CEA rats through the brain serotoninergic system.

Animals↗
PubMed1978

Lesions of some central nervous structures result in altered pituitary-thyroid response to acute decrease of blood thyroid hormone level.

Eight groups (3--6 animals each) of rats weighing 350--400 g were subjected to electrolytic lesions of various parts of habenular, thalamic and hypothalamic areas of brain. On the 6th day after the lesion the level of blood thyroid hormone was acutely decreased with the aid of isovolemic exchange transfusion (IET) of thyroid hormone free blood suspension. The level of thyroxine (T4) in plasma was measured before and during 180 min after IET with the aid of specific radioimmunoassay and the changes of its post-transfusion level were evaluated. It was found that in three groups of animals bearing large bilateral lesions either in lateral ventral thalamus or in a central inferior thalamus the response of T4 level during the post-transfusion period is similar to that found in intact control groups from previous experiments. This consists in an increase of T4 level nearly to the initial value within about 120--150 min after IET. In contrast, there was only a slight post-transfusion increase of T4 level in one group with small central lesion in medial superior thalamus and no increase in two groups bilaterally lesioned in habenular area and in another two groups lesioned either in a central part of dorsal hypothalamus or in a central dorsal part of ventral basal hypothalamus. It was concluded that some parts of brain may be involved in managing the appropriate response of pituitary-thyroid axis to acute decrease of thyroid hormone level, no plausible explanation of the mechanism ofthe observed phenomena being offered.

Animals↗
PubMed1977

Acute decrease of blood thyroid hormone by isovolemic exchange transfusion as a stimulus for pulse TSH release and its modifications by CNS Lesions.

The level of thyroid hormone in blood has been acutely decreased by about 20--30% within 20 min with the aid of isovolemic exchange transfusion (IET) of thyroid hormone free blood cell suspension (THFBCS) in three groups of rats: (1) intact control (C); (2) median eminence (ME)-lesioned; (3) thalamus (TH)-lesioned. The levels of thyroxine (T4) and TSH were measured by specific radioimmunoassay (RIA) before the transfusion and for 180 min after that. The level of T4 increased to the initial value at about 120 min after IET in C and ME-lesioned rats, while in TH it remained decreased until 180 min. Furthermore, at the end of IET the level of TSH in C and ME-lesioned rats was about 2--3 time higher than the initial value and its continuous decrease was observed until 180 min. In contrast, in TH-lesioned rats the increase of TSH level was delayed, being significant at 60 min only. It was concluded that IET of THFBCS acts as a stimulus of acute TSH release which was remarkably inhibited in TH-lesioned animals. In addition, the destruction of most of the ME did not apparently influence this response, as shown by essentially similar data obtained in C and ME-lesioned rats.

Animals↗
PubMed1977

The role of the pineal gland in the regulation of LH-release in rats with different types of the anovulatory syndrome.

The effect of different doses of testosterone propionate was investigated in provoking the development of the constant estrous anovulatory (CEA) syndrome in the rat. A direct relationship was observed between the dose of neonatally administered androgen (NA) and the percentage occurrence of this syndrome. Pinealectomy and superior cervical sympathetic ganglionectomy elicited the development of marked thecal luteinization in the NA-CEA rat, but the formation of corpora lutea was limited after these operations. The efficacy of pinealectomy and ganglionectomy in provoking luteinization was inversely related to the dose of testosterone used for neonatal androgenization. The LH-RH sensitivity of the adenohypophysis to release LH was decreased in the NA animals, as well as in the light-induced CEA syndrome (LCE), whereas it was increased in those CEA rats in which this syndrome was provoked by frontal hypothalamic deafferentation (FHD). Pinealectomy and ganglionectomy were able to elicit ovulation and luteinization in the FHD animals, but were ineffective in the LCE and high dose NA rats. The results are discussed in relation to those reported by others, in an attempt to explain the multitude of dissociated effects.

Animals↗
PubMed1976

Brain serotonin and estradiol retention in the hypothalamus and pituitary of the rat.

In order to investigate whether the capacity of hypothalamic and anterior pituitary tissue to concentrate and retain estradiol is affected by serotonin (5-HT), 3H-estradiol (3HE2) retention in these structures was measured after 5-HT synthesis inhibition by either parachlorophenylalanine (PCPA) or 6-fluoro-tryptophane (6 FTrp), or after destruction of midbrain raphe nuclei containing 5-HT cell bodies, as well as after administration of the 5-HT precursor 5-hydroxytryptophane (5-HTP). No modification in 3HE2 retention was observed after tryptophane hydroxylase inhibitors of raphe lesions; administration of the precursor only increased the steroid retention at very high, nonphysiological dose levels. It is concluded that the interaction of 5-HT with gonadotropic release cannot be accounted for by a direct effect on specific estrogenic receptors, but occurs at a different level of gonadotropic release regulating structures or directly on LH-RH neurons.

5-Hydroxytryptophan↗
PubMed1976

Changes in hypothalamic serotonin concentration following manipulations on the gonadotrophic gonadal axis of the constant estrous anovulatory (CEA) rat.

The effect of pinealectomy or of injection of luteinizing hormone (LH) containing pituitary extract on the serotonin concentration of the hypothalamus was comparatively investigated in female rats with three different types of constant estrous anovulatory (CEA) syndrome. CEA syndrome was provoked by frontal hypothalamic deafferentation (FHD), by neonatal androgen treatment (NA) and by exposure of continuous illumination (light induced constant estrous; LCE syndrome). Pinealectomy caused an increase in hypothalamic serotonin concentration in the FHD rat, but failed to increase it in the NA and LCE group. The injection of crude anterior pituitary extract, however, provoked significant elevation of the hypothalamic serotonin concentration equally in all three types of CEA syndrome. Ovariectomy in itself failed to cause any significant change in the serotonin level of the brain. However, pinealectomy or the injection of LH containing pituitary extract proved to be effective also in the ovariectomized CEA animals. It is concluded that the increase in the brain-serotonin concentration of CEA rats, observed after pinealectomy or after injection of LH containing crude pituitary estract, is running through a hypothalamo-pituitary mechanism rather than through the hormone secreting activity of the ovaries.

Animals↗
PubMed1976

Investigation of luteinizing-inducing effect of pinealectomy or thyroidectomy in different types of anovulatory syndromes in rats.

The luteinizing-inducing effect of pinealectomy and of thyroidectomy was investigated in the constant estrous anovulatory (CEA) syndrome caused either by frontal hypothalamic deafferentation (FHD) or by neonatal androgen treatment (NA). Thyroidectomy failed to induce luteinization in both types of CEA syndrome. However, pinealectomy provoked the formation of corpora lutea in FHD, but not in NA induced CEA syndrome. It was concluded that the luteinizing-inducing effect of pinealectomy is a specific consequence of the removal of the pineal hormone-like principles. The differences in the mechanism of development of the CEA syndrome following FHD or NA might account for the failure of pinealectomy to elicite luteinization in the NA induced CEA rat.

Animals↗