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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
PubMed1986

[Effect of ganglionectomy (superior cervical ganglia) at normal temperature and exposure to cold on the circadian rhythm of liver glycogen and blood glucose levels of the Wistar rat with regard to the pineal gland].

Liver glycogen content and blood glucose level of 80 male Wistar rats were measured 4 times a day, 30 d after following surgeries: sham-operation without exposure to cold, sham-operation with exposure to cold (283 K, 72 h before killing), extirpation of the ganglia cervicalia superiora (GX) without exposure to cold, extirpation of the ganglia cervicalia superiora with exposure to cold (283 K, 72 h before killing). Exposure to cold alone as well as GX with and without exposure to cold modify the unimodal daily patterns (curves were calculated by means of empirical regression) of liver glycogen content and blood glucose level: there are changes from contrary localization of the maxima (and minima) of both, liver glycogen content and blood glucose level (exposure to cold alone) to nearly equal localization (GX alone). Compared to control group, all surgeries reduce the liver glycogen content statistical-significantly and also enhance the blood glucose level. Combination of GX with exposure to cold shows the strongest effect. In this case, the influence of GX is visible, but the effect is not significantly different from this of exposure to cold alone, which causes a high activation of the metabolism. To the contrary, a statistically significant influence is to be seen after GX alone, but the effect is lower than this one of exposure to cold. Extirpation of the ganglia cervicalia superiora and the resulting sympathetic denervation of the pineal gland is answered by comparable reactions of the investigated parameters as the extirpation of the pineal gland itself (90 d post operationem). Diminuation of liver glycogen content and enhancement of blood glucose level characterize the influence of gangliectomy (30 d post operationem) in this way, that the ratio of effect of factors causing hypo- and hyperglycemia is changed in favour of the latter.

Animals↗
PubMed1984

Localization of corticotropin-releasing factor-containing neurons in the brain of the domestic fowl. An immunohistochemical study.

The corticotropin-releasing factor (CRF)-containing neurons were investigated in the brain of the domestic fowl by means of the peroxidase-antiperoxidase technique at the light-microscopic level. The detection of CRF-immunoreactivity was facilitated by silver intensification. CRF-containing perikarya were found in the paraventricular, preoptic and mammillary nuclei of the hypothalamus and in some extrahypothalamic areas (nuclei dorsomedialis and dorsolateralis thalami, nucleus accumbens septi, lobus parolfactorius, periaqueductal gray of the mesencephalon, nucleus oculomotorius ventralis). Immunoreactive nerve fibers and terminals were demonstrated in the external zone of the median eminence and the organum vasculosum of the lamina terminalis. These results indicate that an immunologically demonstrable CRF-neurosecretory system also exists in the avian central nervous system.

Animals↗
PubMed1984

Studies on the inhibitory effect of apomorphine and bromocryptine on basal and TRH induced level of TSH and PRL in hypothyroid rats under pentobarbiturate anesthesia.

Groups of male rats were inserted with polyethylene tubings into femoral artery and vein under pentobarbiturate anesthesia and small blood samples were frequently taken for the estimation of TSH and PRL under maintaining isovolemia. After a single injection of apomorphine (12 mg kg-1) or bromocryptine (20 mg kg-1) much more expressed effect of these drugs on a decrease of PRL level in plasma was found than that on a decrease of TSH level and similar observation was made with the use of continuous i.v. infusion of apomorphine (50 micrograms in 20 microliter per min for 180 min). Finally, under the above dose of infused apomorphine, the effect of TRH on the increase of TSH level was depressed at the 30th min as compared to that 0 and 120th min of infusion. In addition, at 120 min of infusion the effect of TRH was significantly higher than that at 0 min. These results suggest that the effect of apomorphine may take place at the pituitary level.

Anesthesia↗
PubMed1983

Depressive effect of LHRH on the numbers of "synaptic" ribbons and spherules in the pineal gland of diestrous rats.

Previous studies have shown that LHRH or LHRH-like substances are present in the pineal gland. In order to investigate whether exogenous LHRH may affect the pineal gland, in the present study the effects of a single dose of LHRH (1 microgram, i.p.) on pineal "synaptic" ribbons and spherules as well as serum melatonin levels were examined in diestrous Wistar rats. One hour after the injection both ribbons and spherules exhibited a statistically significant decrease in number. Serum melatonin levels were not affected. It is concluded that humoral feedback mechanisms may exist between the hypothalamus and the pineal gland.

Animals↗
PubMed1983

Opioidergic regulation of thyroid activity: possible interference with the serotonergic system.

Acute systemic administration of (D-Met2, pro5-NH2)-enkephalin (ENKamide), a very potent enkephalin analog, and of morphine not only diminished the basal levels of serum TSH under resting conditions, but also significantly reduced the enhanced serum TSH concentrations induced by goitrogen treatment or by bilateral thyroidectomy. Acute administration of opiates failed to inhibit the pituitary TSH response to exogenous TRH administration. The TSH release-inhibiting effect of ENKamide was reversed by pretreatment with the serotonin synthesis inhibitor, para-chlorophenylalanine (pCPA) or with the central serotonin receptor blocker, metergoline. These results furnish evidence in favour of the following concepts: (a) opioid compounds equally influence the tonic release of the TRH-TSH system under resting conditions, and also suppress the reactive changes of this circuit following specific loads, leading to an activation of this system; (b) opioids do not act directly at the pituitary level in inhibiting TSH secretion, but rather seem to suppress the release of TRH from the hypothalamus; (c) they may exert their inhibitory effect on the activity of the TRH-TSH-thyroid system by increasing the activity of the central nervous serotonergic system.

Animals↗
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↗
PubMed1982

Central nervous regulation of pituitary TSH response induced by thiouracil treatment or by thyroidectomy.

The serotoninergic neuron system of the midbrain and hypothalamus was previously shown to inhibit the basal secretion of the TRH-TSH-thyroid axis. The aim of the present study was to investigate the influence of the serotoninergic system on the TSH response of the adenohypophysis to specific loads. Serum TSH levels were determined 7 days after thyroidectomy or the beginning of thiouracil administration. Animals were simultaneously treated either by intrahypothalamic implantation of serotonin-containing needles or by intraventricular or daily subcutaneous injections of the same drug. The thiouracil-induced goitre formation and increase in serum TSH concentration were significantly diminished by serotonin treatment. Similarly, the thyroidectomy-induced rapid rise in TSH blood level was also remarkably inhibited in the serotonin-treated animals. Serotonin was proved to influence rather TRH-output than pituitary TSH secretion, since exogenous TRH, injected to serotonin-pretreated animals had the same TSH-mobilizing potency as found in the not premedicated group. It is concluded that besides the inhibition of the basal secretion of the TRH-TSH-thyroid axis by serotonin, there is an integrative role of the serotoninergic system in the mediation of the reactivity of this circuit in reply to specific influences loading pituitary-thyroid function.

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↗