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B Flerkó

Publications and source records attributed to B Flerkó.

At least 37 records · Page 2Linked to original sources
PubMed1985

Axovascular relationships in developing median eminence of perinatal rats with special reference to luteinizing hormone-releasing hormone projections.

Topographical relationships of neurosecretory axons with the capillaries of the primary portal plexus were studied in the median eminence of rats from the 14th fetal till the 9th postnatal day by means of electron microscopy combined with morphometric analysis. Special attention was given to the light and electron microscopic immunocytochemical examination of luteinizing hormone-releasing hormone projections to the median eminence. Neurosecretory axons possessing secretory granules and clear microvesicles were first observed in the median eminence at the 14th fetal day. However, all of them were situated at a distance from the primary portal plexus. By the 20th fetal day, neurosecretory axons reached the external basal lamina of the primary portal plexus giving rise to so-called axovascular contacts. Some axons even penetrated into the perivascular space, apparently facilitating the neurohormone delivery into the hypophysial portal circulation. From that time on, both the number of the axons abutting on the external basal lamina and the entire area of axovascular contacts increased gradually. As to luteinizing hormone-releasing hormone axons, they grew into the median eminence from the 18th fetal day concentrating in older fetuses and neonates either over the primary portal plexus, or around the infundibular recess of the 3rd ventricle. After birth, the concentration and distribution of luteinizing hormone-releasing hormone axons within the median eminence became similar to those of adults. Luteinizing hormone-releasing hormone axons were found to arise from the neurons of septopreoptic area including the diagonal band of Broca. These data suggest the onset of neurohormone release in the median eminence from the 14th fetal day followed by the establishment of the hypothalamic control over the pituitary functions during the perinatal period in rats.

Animals↗
PubMed1985

Re-evaluation of "frontal deafferentation" studies on the regulation of ACTH secretion in the light of CRF immunohistology.

Frontal afferents to the medial basal hypothalamus of the rat were interrupted by a Halász knife, and 4 weeks later the brains were processed for immunostaining of CRF-fibers. It was found that such intervention saves most of the CRF immunoreactive fibers of the paraventriculo-infundibular tract. Some of the conflicting results of earlier deafferentation studies are discussed on the basis of CRF immunohistology.

Adrenocorticotropic Hormone↗
PubMed1984

Gonadotropin-releasing hormone (GnRH) neurons and pathways in the rat brain.

Gonadotropin-releasing hormone (GnRH) neurons and their pathways in the rat brain were localized by immunocytochemistry in 6- to 18-day-old female animals, by use of thick frozen or vibratome sections, and silver-gold intensification of the diaminobenzidine reaction product. GnRH-immunoreactive perikarya were observed in the following regions: olfactory bulb and tubercle, vertical and horizontal limbs of the diagonal band of Broca, medial septum, medial preoptic and suprachiasmatic areas, anterior and lateral hypothalamus, and different regions of the hippocampus (indusium griseum, Ammon's horn). In addition to the known GnRH-pathways (preoptico-terminal, preoptico-infundibular, periventricular), we also observed GnRH-immunopositive processes in several major tracts and areas of the brain, including the medial and cortical amygdaloid complex, stria terminalis, stria medullaris thalami, fasciculus retroflexus, medial forebrain bundle, indusium griseum, stria longitudinalis medialis and lateralis, hippocampus, periaqueductal gray of the mesencephalon, and extracerebral regions, such as the lamina cribrosa, nervus terminalis and its associated ganglia. By use of the silver-gold intensification method we present Golgi-like images of GnRH perikarya and their pathways. The possible distribution of efferents from each GnRH cell group is discussed.

Animals↗
PubMed1984

Application of the silver-gold intensified 3,3'-diaminobenzidine chromogen to the light and electron microscopic detection of the luteinizing hormone-releasing hormone system of the rat brain.

A highly sensitive, recently developed immunohistological method is introduced in the present study with special emphasis on the luteinizing hormone-releasing hormone system of the rat brain. The method utilizes the specific capability of the diaminobenzidine endproduct, a frequently used chromogen in immunocytochemistry, to produce and bind silver grains from a special physical developer, following suppression of the argyrophilia of the nervous tissue by thioglycolic acid. Metal deposition into the immunolabelled structures results in a real Golgi-like appearance of immunoreactive profiles. Specificity of this silver method was confirmed by ultrastructural analysis, which showed that unlabelled elements did not bind silver. Using this method, more immunoreactive neurons and fibres were visualized than compared with the results of the traditional peroxidase-antiperoxidase method. The luteinizing hormone-releasing hormone-synthesizing neurons proved to be fusiform, exhibiting either smooth or rough surfaced contour. Unlabelled terminals established axo-somatic synapses on labelled perikarya. The juxtaposition of immunoreactive luteinizing hormone-releasing hormone profiles suggest the possibility of self-regulation within the luteinizing hormone-releasing hormone system. The main advantages of the method are the increased sensitivity with preserved selectivity and wide applicability in different fields of neuroscience (peptide and transmitter immunocytochemistry, double labelling, horseradish peroxidase tract tracing, X-ray analysis).

3,3'-Diaminobenzidine↗
PubMed1983

Ultrastructural characteristics of immunolabelled, corticotropin releasing factor (CRF)-synthesizing neurons in the rat brain.

The corticotropin releasing factor (CRF)-synthesizing perikarya and neural processes were detected at ultrastructural level in the hypothalamic paraventricular nucleus and in the median eminence of control and colchicine-pretreated rats. The unlabelled antibody peroxidase-antiperoxidase complex (PAP) immunohistochemical method was used in a pre-embedding manner, on thick, non-frozen sections. In CRF-perikarya, neurosecretory granules (80-120 nm in diameter), free ribosomes, and the rough endoplasmic reticulum were labelled. Unlabelled axon terminals formed asymmetric synapses on CRF-containing perikarya and dendrites. Immunolabelled axons terminated in the palisadic zone of the median eminence.

Animals↗
PubMed1982

Immunohistochemical study of the onset of hormone synthesis in LH-RH and somatostatin neurons in rat brain.

The onset of hormone synthesis in LH-RH and somatostatin neurons of the brain was studied in rats using the unlabelled antibody-PAP immunohistochemical method. LH-RH appeared in detectable amounts first in neuronal perikarya in the preoptic region of fetuses sacrificed on the 17th day of gestation. Minute amounts of LH-RH could already be detected in some nerve fibers of the preoptic region of fetuses on the 18th gestational day. On the 19th day the vascular organ of the lamina terminalis (OVLT) and on the 20th day the median eminence (ME) already contained loose networks of nerve fibers and axon terminals accumulating LH-RH. Somatostatin perikarya and axon terminals with detectable amounts of the hormone appeared simultaneously on the first postnatal day in the anterior periventricular region and the median eminence, respectively. Somatostatin containing nerve fibers became detectable in OVLT first on the 2nd day of life.

Animals↗
PubMed1982

The effect of perinatal oestrogen treatment on the troph-hormone secreting cells of the anterior pituitary of the rat.

Late effect of the perinatal administration of oestradiol dipropionate on pituitary gonadotrophs and the morphology of the LH-RH neuronal system was tested both in male and female rats. Oestrogen caused a severe reduction in the number and size of immunodetectable gonadotrophs in both sexes. By the 90th day of life, however, immunomorphology and distribution of the gonadotroph cells had became normal, and also the LH-RH system of the animals was similar to that of the intact controls. The lack of vaginal cycles indicated, however, that oestrogen might have permanently impaired higher brain centers regulating cyclic gonadotroph hormone release.

Animals↗
PubMed1981

The luteinizing hormone releasing hormone-containing pathways and their co-termination with tanycyte processes in and around the median eminence and in the pituitary stalk of the rat.

The origin, course and termination of two luteinizing hormone releasing hormone (LH-RH)-containing pathways were studied in the brain of rats by immunohistochemistry. In addition, the joint termination of LH-RH-containing nerve terminals and tanycyte processes over a rostro-caudally elongated belt surrounding the median eminence (ME) is described. The preoptico-infundibular tract originates from neurons confined to a pyramid-shaped area between the anterior commissure, the organum vasculosum laminae terminalis (OVLT) and the most caudal level of the suprachiasmatic nucleus (SCH). The axons of these neurons form three fascicles. Fibres of the median fascicle run in caudal direction on the dorsal and ventral surfaces of the optic chiasma. Fibres of the medial fascicle run along the lateral border of the SCH towards the retrochiasmatic area. Fibres of the lateral fascicle course laterally in close contact with the concave dorsomedial surface of the optic tract. These latter fibres gradually turn in medial direction and reach the lateral margin of the ME. The caudal LH-RH fibre tract was characterized only partially because the perikarya giving rise to these fibres were not identified. The fibres run rostrally among the ependymal cells of the mesencephalic aqueduct and form two fascicles. The fibres of the mammillary fascicle enter, and seem to terminate, in the medial mammillary nucleus, while the fibres of the tuberal fascicle course rostrally and join the fibres of the preoptico-infundibular tract. The surface areas of the brain along which LH-RH fibres terminate (retrochiasmatic area, inframammillary region, lateral margin of the ME) were found to display a special surface covering formed by tanycyte processes. The course of LH-RH fibre tracts described here is in good agreement with earlier experimental results on the localization of neural pathways controlling ovulation and the secretion of pituitary gonadotropic hormones. The significance of the joint termination of LH-RH fibres and tanycyte processes, especially in areas where portal capillaries are absent, remains unclear.

Animals↗
PubMed1978

On the intracerebral locus for androgenization of female rats.

Comparison of control and androgenized rats has revealed that many nerve terminals ending on arcuate nerve cells of rats treated neonatally with testosterone phenylpropionate show a decrease in dense-core vesicles, and an increase in the number of clear vesicles and of vesicles that exhibit various degrees of electron density. The same changes were observed in nerve terminals ending on preoptic neurons of rats androgenized neonatally. These findings are discussed in view of the intracerebral locus for androgenization of female rats.

Animals↗
PubMed1978

Ontogenesis of the LH-RH-containing neuronal elements in the hypothalamus of the rat.

LH-RH-containing neuronal elements were detected earliest in the median eminence and in the vascular organ of the lamina terminalis of newborn rats. The peroxidase-labeled antibody method was used. Since the synthesis of the gonadotrophic hormones starts already on the 18th day of intrauterine life in the rat, this finding does not support the view that LH-RH could have inductive effect on the differentiation of the gonadotropic cells of the anterior pituitary gland.

Animals↗