Search PubMed⌕ Search

Biomedical subjects

T Petrov

Publications and source records attributed to T Petrov.

36 records · Page 2Linked to original sources
PubMed1994

Electrical stimulation of the central nucleus of the amygdala induces fos-like immunoreactivity in the hypothalamus of the rat: a quantitative study.

The effect of electrical stimulation of an important forebrain autonomic structure, the central nucleus of the amygdala (CNA), on c-fos expression in three hypothalamic nuclei was studied in rat with immunocytochemistry to reveal the protein (Fos) encoded by the immediate early gene (IEG). Image analysis was used to quantify the Fos immunoreactive neurons within the supraoptic (SON), paraventricular (PVN), and arcuate (AN) nuclei. Stimulation for 60 min induced a statistically significant increase of the number of Fos immunoreactive neurons in all three nuclei ipsilateral to the CNA stimulation site. Double immunocytochemical staining (Fos and vasopressin or Fos and oxytocin) was employed to evaluate the participation of different subpopulations of neurons within the SON and PVN in response to CNA stimulation. In the SON, the increased number of Fos immunoreactive nuclei following the stimulation was observed in the vasopressin and oxytocin-secreting cells within this nucleus. In the PVN, the increase in the number of Fos immunoreactive neurons was predominantly within the parvocellular compartment. These studies demonstrate that IEG expression in hypothalamic neurons can be evoked as a result of afferent stimulation from the CNA. Activation of peptide- and hormone-containing neurons within the SON, PVN and AN, through mono- or multisynaptic pathways, may play a role in hormonal and autonomic responses.

Amygdala↗
PubMed1994

Distribution of the tight junction-associated protein ZO-1 in circumventricular organs of the CNS.

The immunofluorescent distribution of ZO-1, a tight junction-associated protein, was studied in murine circumventricular organs. These regions generally express a less restrictive blood-brain barrier than is found in other areas of the CNS. In the remaining brain parenchyma, where a characteristic blood-brain barrier exists, ZO-1 was localized in discrete, continuous lines along blood vessels, presumably in association with endothelial cell tight junctions. The ependymal cells in the ventricular walls displayed a more punctate pattern of ZO-1 distribution, indicative of discontinuous tight junctions. In two of the circumventricular organs examined, the median eminence and the subfornical organ, many capillaries lacked detectable ZO-1 immunoreactivity while the apical aspects of the specialized ependymal cells (tanycytes) revealed an unbroken ZO-1 distribution. Scant labelling of ZO-1 in blood vessels was found in the area postrema, and only weak and discontinuous ZO-1 labelling was present in the ventricular wall. Capillaries of the organum vasculosum laminae terminalis expressed ZO-1 immunoreactivity which was comparable to the pattern observed in CNS regions with typical blood-brain barrier. The subcommissural organ, known to contain a blood-brain barrier, also displayed continuous ZO-1 staining in blood vessels. Unbroken ZO-1 distribution was observed in the specialized ependymal cells adjacent to both the organum vasculosum laminae terminalis and subcommissural organ. These immunocytochemical data demonstrate a distribution of ZO-1 in CNS parenchyma outside the circumventricular organs that is consistent with an organization of tight junctions which prevent free paracellular exchange of substances between blood and neuropil but which allow for continuity between CSF and the neuronal environment. The ZO-1 staining pattern in blood vessels and ventricular walls of the circumventricular organs is heterogeneous despite the prevalent absence of a functional blood-brain barrier.

Animals↗
PubMed1993

Branching projections of catecholaminergic brainstem neurons to the paraventricular hypothalamic nucleus and the central nucleus of the amygdala in the rat.

In this study, we have employed triple fluorescent-labelling to reveal the distribution of catecholaminergic neurons within three brainstem areas which supply branching collateral input to the central nucleus of the amygdala (CNA) and the hypothalamic paraventricular nucleus (PVN): the ventrolateral medulla (VLM), the nucleus of the solitary tract (NTS) and the locus coeruleus (LC). The catecholaminergic identity of the neurons was revealed by immunocytochemical detection of the biosynthetic enzyme, tyrosine hydroxylase. The projections were defined by injections of two retrograde tracers, rhodamine- and fluorescein-labelled latex microspheres, in the CNA and PVN, respectively. In the VLM and NTS, the greatest incidence of neurons which contained both retrograde tracers was found at the level of the area postrema. These neurons were mainly located within the confines of the A1/C1 (VLM) and A2 (NTS) catecholaminergic neuronal groups. Double-projecting neurons in the LC (A6) were distributed randomly within the nucleus. It was found that 15% in the VLM, 10% in the NTS and 5% in the LC of the retrogradely labelled cells projected via branching collaterals to the PVN and CNA. One half of these neurons in the VLM and NTS were catecholaminergic, in contrast to the LC where virtually all double-retrogradely labelled neurons revealed tyrosine hydroxylase immunoreactivity. In the other brainstem catecholaminergic cell groups (A5, A7, C3), no catecholaminergic neurons were found that supplied branching collaterals to the CNA and PVN. Our results indicate that brainstem neurons may be involved in the simultaneous transmission of autonomic-related signals to the CNA and the PVN. Catecholamines are involved in these pathways as chemical messengers. Brainstem catecholaminergic and non-catecholaminergic neurons, through collateral branching inputs may provide coordinated signalling of visceral input to rostral forebrain sites. This may lead to a synchronized response of the CNA and PVN for the maintenance of homeostasis.

Amygdala↗
PubMed1992

The hypothalamic paraventricular and lateral parabrachial nuclei receive collaterals from raphe nucleus neurons: a combined double retrograde and immunocytochemical study.

Retrograde tracer injections of fluorescein- and rhodamine-labelled latex microspheres centered in the parvicellular zone of the hypothalamic paraventricular nucleus and pontine lateral parabrachial nucleus revealed that 36% of the labelled neurons in the dorsal raphe nucleus send collaterals to both structures. These cells were organized in a well-distinguishable cluster within the dorsal raphe nucleus. By combining retrograde tracing with immunocytochemistry, it was found that less than 8% of the double-labelled cells stained positively for serotonin. Of the remaining raphe nuclei that were examined, only the median raphe nucleus contributed a minor nonserotoninergic projection to the paraventricular or lateral parabrachial nuclei. Few of the retrogradely labelled cells in the median raphe nucleus contained both tracers. These results suggest that nonserotoninergic and serotoninergic neurons in the dorsal raphe nucleus, via collateral branching, may simultaneously influence the activity of two central nervous system nuclei involved in autonomic control.

Animals↗
PubMed1991

Differential distribution of GABA- and serotonin-containing afferents on an identified central neuron.

The distributions of gamma-aminobutyric acid (GABA)- and serotonin (5-HT)-containing terminals impinging on the surface of the Mauthner (M-) cell were studied at the light microscopic level using double immunofluorescent labeling and were compared with that of the glycine receptor. The latter was visualized indirectly, using a monoclonal mouse antibody which recognizes its 93-kDa associated protein. This neuron has two large principal dendrites: one extending ventrorostrally (ventral dendrite) and the other dorsolaterally (lateral dendrite). There are also two other classes of smaller processes: one that projects ventrally (small ventral dendrites) and one penetrating in the axon cap (cap dendrites), a peculiar neuropil surrounding the initial segment of the M-cell axon. A cellular regionalization of these afferent systems was found: GABA boutons, labeled for glutamic acid decarboxylase (GAD), were localized preferentially on the lateral dendrite while 5-HT-filled endings predominated on the ventral one. The density of these two classes of inputs was comparable in the other areas of the M-cell: less of their terminals were in contact with the soma outside the axon cap, and more numerous boutons, which presented either GABA or 5-HT immunoreactivities, were apposed to the small ventral dendrites. This preferential pattern of innervation differed with the ubiquitous presence of glycine receptor clusters on the M-cell membrane. Finally no evidence of a colocalization of GABA and 5-HT in afferent endings was detected at any portion of the M-cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[The early scintigraphic diagnosis of bone metastases in prostatic carcinoma].

Fifty-nine patients, 58 to 88 years of age, with prostate cancer comprise the study group. Screening studies were made in doubtful diagnosis and vague complaints, as well as repeated scintigraphic controls in histologically proven cancer. The most common localization of the bone lesions were: pelvis, ribs, lumbar and thoracic vertebrae. Distribution of the zones of enhanced drosition, effect of treatment and eventual connection between scintigraphic and histologic finding are noted. Patients without X-ray evidence of bone metastases or with evidence of single metastases, frequently had extensive dissemination of the metastatic process when whole-body bone scintigraphy was made.

Aged↗
PubMed1990

[Hyperfiltration in diabetic patients].

Glomerular filtration and effective renal plasma flow were studied in 24 patients with diabetes mellitus type I (mean age 29.8 +/- 10.5 years) and 20 patients with diabetes mellitus type II (mean age 54 +/- 11 years) and duration of diabetes 5.7 +/- 6 and 11.3 +/- 10 years respectively. There were no clinical signs of nephropathy in all patients studied (the albustick test was negative). The results were compared with those of 30 healthy controls. Out of the 24 patients with diabetes mellitus type I 10 (41%) were with hyperfiltration and from the 20 patients with diabetes mellitus type II only one was with hyperfiltration. The speed of albumin secretion in the diabetic patients with hyperfiltration was 39.9 +/- 42.9 micrograms/min and was significantly higher than that of the diabetic patients without hyperfiltration--26.2 +/- 22.7 micrograms/min. The albuminuria was in a moderate positive correlation with the glomerular filtration. The possible mechanism taking part in the development of hyperfiltration syndrome in diabetes are discussed.

Adult↗
PubMed1987

[Improving the diagnostic potentials of isotope nephrography with 131I-hippuran].

In order to eliminate the false positive and the false negative results in the control isotopic nephrographic examinations due to the minute diuresis determination of the difference between the time of appearance of T-maximum of both kidneys is recommended. When the earlier (respectively the later) appearance of T max. is due to improved (or deteriorated) renal function the difference between the two T max. increases (or decreases). When the change in the time of appearance of the two T max. is due to the minute diuresis the difference between them remains unchanged.

Adolescent↗
PubMedDate not supplied

Characterization of peptidergic efferents from the lateral parabrachial nucleus to identified neurons in the rat dorsal raphe nucleus.

The peptidergic content of the lateral parabrachial nucleus (LPB) efferents to the dorsal raphe nucleus (DRN) was studied by combining visualization of the anterogradely transported tracer Phaseolus vulgaris leucoagglutinin within fibers that were immunocytochemically stained for neurotensin (NT), calcitonin gene-related peptide (CGRP) or galanin (GAL). The identity of DRN target neurons was determined with simultaneous immunocytochemical labelling for serotonin, the major transmitter within the nucleus. Within the DRN, we estimated that about two-thirds of the anterogradely labelled fibers arising from the LPB also showed peptidergic immunoreactivity. NT was the most commonly observed neuropeptide in LPB neuronal efferents directed to the DRN, followed by CGRP and GAL. The peptidergic afferents in the DRN were oriented preferentially in the dorsoventral plane. Peptidergic fibers from the LPB possessed varicosities (diameters not exceeding 3 microns) and were apposed on serotoninergic neuronal somata. Some of the anterogradely labelled peptidergic fibers were not associated with cells showing immunoreactivity for serotonin. The present results suggest that NT-ergic, CGRP-ergic and GAL-ergic neurons within the LPB are in contact with serotoninergic and non-serotoninergic neurons within the DRN. Since the DRN is known to project to the LPB, it is likely that bi-directional interconnections between these nuclei exist. Such linkages may provide anatomical substrates for coordinated autonomic responses.

Animals↗
PubMedDate not supplied

Acute alterations of endothelin-1 and iNOS expression and control of the brain microcirculation after head trauma.

The biosynthetic equilibrium between endothelin-1 (ET-1, a vasoconstricting agent) and nitric oxide (NO, a gas with vasodilating effects) is thought to play a role in the autoregulation of microvessel contractility and maintenance of adequate perfusion after traumatic brain injury. ET-1 is a constitutively expressed peptide, while the gene that encodes for the inducible nitric oxide synthase (iNOS, an enzyme responsible for the synthesis of excessive and toxic amounts of NO) is solely activated after brain injury. We employed the Marmarou acceleration impact model of brain injury (400 g from 2 m) to study the effect of closed head trauma on the rat brain microcirculation. Following head trauma we analyzed changes of cerebral cortex perfusion using laser Doppler flowmetry and ultrastructural alterations of endothelial cells. We temporally correlated these changes with the expression of ET-1 (immunocytochemistry) and iNOS (in situ hybridization) to assess the role of these vasoactive agents in vascular contractility and cortical perfusion. Cortical perfusion was reduced by approximately 50% during the second hour as compared to values during preceding time points after TBI, reached a peak minutes before 3 h, and subsequently showed a trend towards normalization. A significant reduction in the lumen of microvessels and severe distortion of their shape were observed after the fourth hour post-trauma. At the same time period ET-1 expression in endothelial cells was stronger than in microvessels of control animals. ET-1 expression was further increased at 24 h after TBI. iNOS mRNA synthesis was strongly upregulated in the same cells at 4 h but was undetectable at 24 h post trauma. Our combined functional, cellular and molecular approach supports the notion that ET-1 and iNOS are expressed differentially in time within individual endothelial cells of cortical microvessels for the control of cortical blood flow following closed head trauma. This differential expression further indicates a reciprocal interaction in the synthesis of these two molecules which may underlie the control of microvascular autoregulation.

Animals↗