Biomedical subjects

A Cintra

Publications and source records attributed to A Cintra.

At least 37 records · Page 2Linked to original sources

PubMed1993

Induction of c-fos immunoreactivity in tyrosine hydroxylase and phenylethanolamine-N-methyltransferase immunoreactive neurons of the medulla oblongata of the rat after phosphate-buffered saline load in the urethane-anaesthetized rat.

We have studied the induction of c-fos immunoreactivity (c-fos IR) in catecholaminergic and vasopressinergic immunoreactive neurons after repeated phosphate-buffered saline (PBS) loading or after repeated elicitation of the baroreceptor reflex via repeated infusion of the vasoconstrictor agent L-phenylephrine. About 75% and 30%, respectively, of the tyrosine-hydroxylase immunoreactive (IR) cell bodies of the ventral noradrenaline (NA) A1/adrenaline (A) C1 and dorsal NA A2/A C2 areas and 60% and 30%, respectively, of the phenylethanolamine N-methyltransferase IR nerve cells of the adrenaline C1 and C2 areas and 25% of the vasopressin (VP) IR neurons of the supraoptic (SO) nucleus developed nuclear c-fos IR after repeated PBS loading. This phenomenon remained unaltered by the repeated elicitation of the baroreceptor reflex. These results suggest that the activation of volume receptors promotes homeostatic responses via activation of early genes in subsets of central medullary noradrenaline and adrenaline neurons and SO VP neurons of the urethane-anaesthetized rat.

Amino Acid Sequence↗

PubMed1993

Coexistence of c-Fos and glucocorticoid receptor immunoreactivities in the CRF immunoreactive neurons of the paraventricular hypothalamic nucleus of the rat after acute immobilization stress.

By means of triple immunofluorescence procedures the codistribution and coexistence of glucocorticoid receptor (GR), c-Fos and corticotropin-releasing factor (CRF) immunoreactive (IR) nerve cell profiles have been analyzed within the paraventricular hypothalamic nucleus at various rostrocaudal levels following acute immobilization stress (2 h) in the male rat. One population of CRF IR neurons is shown to contain both nuclear GR and c-Fos immunoreactivities following the stress, while another contains GR immunoreactivity alone. These results indicate heterogeneities among parvocellular CRF paraventricular hypothalamic nerve cell populations in the response to acute immobilization stress.

Animals↗

PubMed1993

Corticosterone increases FGF-2 (bFGF) immunoreactivity in the substantia nigra of the rat.

The effects of acute and subchronic (7 days) administrations of the adrenocortical hormone corticosterone on basic fibroblast growth factor (bFGF, FGF-2) immunoreactivity were studied in the substantia nigra of the rat by semiquantitative immunocytochemistry coupled with image analysis. Corticosterone was able to increase FGF-2 immunoreactivity in different nigral subregions and cell types (astrocytes and neurones) depending on the duration of the treatment. These results open up the possibility that stress hormones can modulate the trophic state of the substantia nigra through an action on FGF-2.

Animals↗

PubMed1993

Glucocorticoid regulation of angiotensinogen gene expression in discrete areas of the male rat brain. An in situ hybridization study.

The regulation of angiotensinogen gene expression by glucocorticoids has been described in several studies. Kalinyak and Perlman reported on a 60% increase of angiotensinogen expression in the rat brain after dexamethasone treatment with a single, high-dose injection. The purpose of the present study was to investigate whether a general upregulation of angiotensinogen expression or a region-specific upregulation underlies these findings. By using in situ hybridization and computer-assisted microdensitometry we evaluated the regional changes in angiotensinogen expression following dexamethasone treatment. Angiotensinogen expression was strongly stimulated in several areas (medial septum and locus ceruleus), while only moderately in others (hypothalamus, medulla). An interesting finding is the difference in glucocorticoid receptor regulation among the circumventricular organs. The subfornical organ displayed no changes in angiotensinogen-mRNA, whereas the area postrema showed an increase. Furthermore, the angiotensinogen expression in the median eminence decreased substantially. The nature of these effects will form the subject of further investigations. In conclusion we demonstrated an overall increase but certain heterogeneities in angiotensinogen expression after dexamethasone treatment, a pattern which suggests different degrees of glucocorticoid receptor regulation of the angiotensinogen gene in certain areas of the brain, probably mainly dependent on the degree of glial glucocorticoid receptor presence.

Angiotensinogen↗

PubMed1993

Prenatal development of glucocorticoid receptor gene expression and immunoreactivity in the rat brain and pituitary gland: a combined in situ hybridization and immunocytochemical analysis.

By means of in situ hybridization and immunocytochemical techniques it has been possible to follow the prenatal development of glucocorticoid receptor (GR) messenger RNA (mRNA) expression and GR immunoreactivity (IR) in the rat brain from embryonic day (E) 15 to 22. A 700-base-pair GR cDNA fragment was used for RNA probe generation. In the immunocytochemical analysis a mouse monoclonal antibody (IgG2a) against the rat liver GR was used in combination with the indirect fluorescence technique or the avidin-biotin immunoperoxidase method. At E15 till E22 a moderate to strong GR mRNA signal was observed within the neuro-epithelium from the medulla oblongata to the telencephalon. A moderate to strong labelling was also present within the paraventricular hypothalamic nucleus, the arcuate nucleus, the nucleus raphe magnus, the nucleus raphe obscurus and the locus coeruleus. In these areas a weak to moderate nuclear GR IR developed in nerve cells 1 or 2 days after the appearance of the GR mRNA signal. From E15 the adenohypophysis showed the strongest expression of GR mRNA. At E17 a strong GR IR was especially demonstrated in the nuclei of many pituitary cells, some exhibiting adrenocorticotropin IR. The results open up the possibility that there exist active GR in embryonic life capable of regulating proliferation events within the adenohypophysis and the neuro-epithelia of the brain. This embryonic GR may modulate the development of inter alia neuro-endocrine areas such as the paraventricular and arcuate nuclei and arousal-related areas such as the central 5-hydroxytryptamine and noradrenaline neuronal systems. Provided that this embryonic GR is capable of becoming activated by glucocorticoids in fetal life, it may mediate several neurochemical and behavioural impairments caused by prenatal stress.

Animals↗

PubMed1992

Molecular cloning of PEC-60 and expression of its mRNA and peptide in the gastrointestinal tract and immune system.

The peptide PEC-60, structurally related to the pancreatic secretory trypsin inhibitor, inhibits glucose-induced insulin secretion. Here we report on the structure of a cDNA clone from pig duodenum encoding PEC-60. The cDNA encodes a 86-amino acid long precursor protein containing a 26-amino acid signal sequence, implying that the mature PEC-60 peptide is secreted from cells. Analysis of porcine duodenum demonstrated a high expression of a 0.6-kilobase long PEC-60 mRNA in this tissue, as well as the presence of strong PEC-60-like immunoreactivity in the cytoplasm of the majority of the goblet cells of the epithelium. High levels of PEC-60 mRNA were also found in the bone marrow and the peripheral blood and moderate levels in the spleen. A strong PEC-60-like immunoreactivity was localized in the monocytes of peripheral blood. Radioimmunoassay revealed high levels of pig PEC-60-like immunoreactivity in pig plasma suggesting that the PEC-60 peptide is efficiently released from cells. These findings imply that the gastrointestinal peptide PEC-60 is formed, stored, and secreted from monocytes present within the bone marrow and in the peripheral blood, indicating a role of the PEC-60 peptide in the immune system in addition to its function as a gastrointestinal peptide.

Amino Acid Sequence↗

PubMed1992

Muscarinic modulation of acetylcholine release from slices of guinea pig nucleus basalis magnocellularis.

Spontaneous and electrically evoked endogenous acetylcholine release and [3H]-choline efflux from slices of guinea pig nucleus basalis magnocellularis (nbM) were studied. Tetrodotoxin reduced the spontaneous endogenous release by 55%, while the Ca(2+)-free medium reduced it by about 30%. Evoked [3H]-choline efflux was Na+ and Ca2+ dependent and frequency related. Physostigmine, 30 microM, nearly halved the stimulation-evoked efflux; atropine, 0.15 microM, not only antagonized, but even reversed this effect into facilitation. Pirenzepine, 1 microM, and AFDX 116, 1 microM, were less effective than atropine, and reversed the inhibitory effect of physostigmine only when applied together. 4-DAMP, 0.01 microM, was ineffective. These findings indicate that acetylcholine release in guinea pig nbM slices is inhibited by the cooperation of muscarinic autoreceptors, possibly belonging to the M1 and M2 subclasses.

Acetylcholine↗

PubMed1992

Presence of strong glucocorticoid receptor immunoreactivity within hypothalamic and hypophyseal cells containing pro-opiomelanocortic peptides.

The presence of nuclear glucocorticoid receptor immunoreactivity (GR IR) was studied in the adrenocorticotropin (ACTH), beta-Endorphin (beta-END) and alpha-melanocyte stimulating hormone (alpha-MSH) IR neuronal populations of the rat hypothalamus and hypophysis using double immunolabelling techniques. All the nuclei of the ACTH/beta-END/alpha-MSH IR neurons of the arcuate and periarcuate nuclei were strongly GR IR in the 48 h colchicine treated animal, but very few alpha-MSH-like IR perikarya located in the dorsal and lateral hypothalamus displayed nuclear GR IR. GR IR was present in the ACTH/beta-END corticotrophs and absent in the intermediate lobe of the hypophysis. The data provide morphological evidence for a glucocorticoid action through a nuclear GR in the arcuate ACTH/beta-END/alpha-MSH IR neurons and the ACTH/beta-END corticotrophs, whereas the alpha-MSH-like IR neurons of the lateral hypothalamus and the melanotropes of the intermediate lobe may not be directly affected by glucocorticoids under normal conditions.

Adrenocorticotropic Hormone↗

PubMed1992

Involvement of local ischemia in endothelin-1 induced lesions of the neostriatum of the anaesthetized rat.

The present study examines the possibility that lesions induced by intrastriatal injections of endothelin-1 (ET-1, 0.43 nmol/0.5 microliter) are ischemic in nature due to a vasoconstriction of the cerebral microvessels. In time course and dose-response experiments with ET-1 and in comparisons with ET-3, the volume of the lesions has been determined based mainly on the disappearance of striatal nerve cells, using a computer assisted morphometrical analysis. The blood flow in the neostriatum close to the site of injection of ET-1 was determined acutely by Laser-Doppler flowmetry. The acute metabolic effects of ET-1 were also studied on striatal superfusate levels of lactate, pyruvate, dopamine and its metabolites DOPAC (3,4-dihydroxyphenylacetic acid) and homovanillic acid (HVA) using an intrastriatal microdialysis probe. Dose related striatal lesions were observed with ET-1 (0.043-0.43 nmol) with a peak lesion volume after 24-48 h and the possible existence of a penumbra area. ET-3 showed a reduced potency to produce striatal lesions compared to ET-1. The lesions induced by ET-1 were prevented by coinjection with dihydralazine, a vasodilator drug. Acutely ET-1 (0.43 nmol/0.5 microliter) produced a prolonged reduction of the cerebral blood flow down to 40% of control values and temporary increases of striatal lactate and DA efflux, the latter change being very marked. Also a significant reduction of DOPAC and HVA was observed. These neurochemical changes were all prevented by treatment with dihydralazine.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗

PubMed1992

Intramembrane interactions between neurotensin receptors and dopamine D2 receptors as a major mechanism for the neuroleptic-like action of neurotensin.

Evidence has been presented that behavioral actions of NT, inducing its neuroleptic-like action, can be explained on the basis of NT-D2 intramembrane receptor-receptor interactions in the basal ganglia, unrelated to the coexistence phenomenon, leading to reduced affinity and transduction of the D2 agonist binding site. By reducing selectively D2 receptor transduction at the pre- and postsynaptic level, the NT receptor appears capable of switching the DA synapses towards a D1 receptor-mediated transduction, illustrating how receptor-receptor interactions can increase the functional plasticity of central synapses (FIG. 12).

Animals↗

PubMed1991

Neuropeptide Y/angiotensin II interactions in central cardiovascular regulation of the rat.

Neuropeptide Y (NPY)/angiotensin II (ANG II) interactions have been studied in the central nervous system of the rat in view of their co-distribution and their opposing role in central cardiovascular control using quantitative receptor autoradiography and measurements of mean arterial blood pressure (MAP), heart rate and respiratory rate. The receptor autoradiographical experiments show that incubation with ANG II (10 nM) produces an increase in porcine (p) iodinated NPY-(1-36) [125I]pNPY-(1-36) binding within the dorsal strip (ds) of the nucleus tractus solitarius (nTS). Immunocytochemical analysis of intracisternally injected ANG II indicated that it could reach this area, in addition to the periventricular gray of the medulla oblongata, the pons and the periventricular part of the dorsal thalamus and dentate gyrus. Furthermore, a threshold dose of ANG II given intracisternally (3 nmol/rat) together with a dose (75 pmol/rat) of pNPY-(1-36) close to its ED50 value for reducing MAP, not only counteracts the vasodepressor action of pNPY-(1-36) but also leads to a marked increase of MAP. Also the bradycardic and bradypneic actions of pNPY-(1-36) are counteracted by this dose of ANG II. In contrast, a threshold dose of pNPY-(1-36) does not counteract the pressor action of an ED50 dose of ANG II (10 nmol/rat) but even enhances the peak pressor action of ANG II. These results may be explained on the basis that central ANG II receptor activation leads to an uncoupling of the NPY Y1 receptor, which mediate the vasodepressor action of pNPY-(1-36) and which is preferentially labeled by [125I]pNPY-(1-36).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1991

Corticosterone treatment counteracts lesions induced by neonatal treatment with monosodium glutamate in the mediobasal hypothalamus of the male rat.

The effects of glucocorticoids on monosodium glutamate-induced neurotoxicity in the neonatal basal hypothalamus were studied by means of semiquantitative immunocytochemistry for tyrosine hydroxylase, growth hormone releasing factor and luteinizing hormone releasing hormone. Neonatal monosodium glutamate treatment induced a marked decrease in tyrosine hydroxylase immunoreactive neurons in the arcuate nucleus and growth hormone releasing factor immunoreactive nerve terminals in the median eminence. These effects were significantly antagonized by the coadministration of corticosterone. Corticosterone alone had no effect on the parameters studied. No significant change in luteinizing hormone releasing hormone immunoreactivity in the median eminence was detected after any treatment. These results demonstrate that corticosterone, possibly acting via type II corticosterone receptors which are highly enriched in the arcuate neurons, can exert a protective action on glutamate-induced neurotoxicity.

Animals↗

PubMed1991

Changes in striatal dopamine neurohistochemistry and biochemistry after incomplete transient cerebral ischemia in the rat.

To evaluate the development of striatal ischemic cell damage in relation to alterations in dopamine (DA) transmission, one year old male Wistar rats underwent a 15 min incomplete cerebral ischemia (ICI) induced by occlusion of the common carotid arteries and by hypovolemic hypotension. The animals were divided into the following experimental groups: sham operated rats, rats with ICI without reperfusion, and rats with ICI followed by 60 min, 24 h, 72 h and 144 h of recirculation. The ischemia induced striatal lesions were investigated in serial coronal brain sections, stained with cresylviolet or immunostained for dopamine and cAMP regulated phosphoprotein (DARPP-32), for tyrosine hydroxylase (TH) and for glial fibrillary acidic protein (GFAP) immunoreactivities (IR). Measurements of striatal dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels were made on analogous experimental groups using HPLC methods. Signs of degeneration in small to medium sized neurons were already seen after 60 min of postischemic reperfusion together with slight decreases of DARPP-32 IR and increases of GFAP IR. The damage continued to increase up to 144 h, and after 24 h of recirculation there were clearly defined areas of reduced DARPP-32 IR, overlapping with increased TH IR and increased GFAP IR. The levels of DA, DOPAC and HVA increased sharply after 60 min (151%, 462% and 201%, respectively) remained high after 24 h and normalized after 72 h of recirculation. The DA metabolism was high after 60 min and had already normalized after 24 h of recirculation. The increased DA metabolism in striatal nerve terminals in response to ischemic injury may reflect an early degenerative change in the DA terminals. The long-lasting increase in TH IR may to some extent represent an adaptive change in response to the disappearance of DA receptor-containing nerve cells. Based on the present findings it is possible that an increased D1 transmission in neostriatum immediately following the ischemic injury may contribute to striatal nerve cell degeneration in which an enhancement of NMDA receptor transduction may be implicated.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1991

Limited distribution of pertussis toxin in rat brain after injection into the lateral cerebral ventricles.

In vivo administration of pertussis toxin is often used to study the involvement of guanine nucleotide binding proteins in signal transduction. Especially when it is administered in the brain the effect is often poor. This could be due to the fact that pertussis toxin does not reach the area of interest. To evaluate the extent to which pertussis toxin is distributed in rat brain after intraventricular injection, different techniques were used. Immunohistochemical studies with an antibody against pertussis toxin showed that immunoreactivity was limited to periventricular brain structures less than 0.5 mm from the lumen. The highest immunoreactivity was seen 16-24 h after injection. After 96 h the labeling was very weak. The proportion of guanine nucleotide binding proteins that were ADP-ribosylated by in vivo injection of pertussis toxin into the ventricles as assessed by in vitro [32P]-back-ADP-ribosylation was very low 48 h after the injection, in all regions studied. Direct injection of pertussis toxin into the brain caused a marked ADP-ribosylation localized to the region injected that was maximal at 72 h after injection. At 96 h there were also effects after control injections, indicating non-specific effects. Synaptosomal membranes and other membranes were equally affected by pertussis toxin. The results suggest that in studies regarding the effect of pertussis toxin treatment on signal transduction, the toxin must be injected very close to the brain region of interest and, furthermore, that the rats should be killed 48-72 h after injection. In case of lack of effect on the response of interest one should examine whether the ADP-ribosylation of pertussis toxin-sensitive guanine nucleotide binding proteins in the area of concern has been affected.

Adenosine Diphosphate Ribose↗

PubMed1991

Prominent expression of acidic fibroblast growth factor in motor and sensory neurons.

Several growth factors originally characterized and named for their action on a variety of cells have more recently been suggested to be importantly involved in the development and maintenance of the nervous system. Acidic fibroblast growth factor (aFGF) is a member of a family of seven structurally related polypeptide growth factors. The cells responsible for expression of aFGF in the nervous system of adult rats have been identified using an affinity-purified antibody to aFGF in immunohistochemical studies and synthetic oligonucleotide probes for in situ hybridization studies. High levels of aFGF expression were observed in motoneurons, primary sensory neurons, and retinal ganglion neurons. Glial cells did not express detectable amounts of aFGF. Confocal and electron microscopic analysis suggested that a large portion of aFGF immunoreactivity was associated with the cytoplasmic face of neuronal membranes, consistent with the hypothesis that aFGF is a sequestered growth factor.

Animals↗

PubMed1991

Central peptidergic neurons as targets for glucocorticoid action. Evidence for the presence of glucocorticoid receptor immunoreactivity in various types of classes of peptidergic neurons.

By means of double immunolabeling procedures it has been possible to demonstrate glucocorticoid receptor (GR) immunoreactivity (IR) in large numbers of various peptidergic neurons of the brain including neurons containing gastrointestinal peptides, opioid peptides, and peptides with a hypothalamic hormone function. For each peptide system, however, marked heterogeneities exist among brain regions. Thus, in the neocortex and the hippocampal formation most of the brain peptide neurons lack GR IR, while the same types of peptide neurons in the arcuate and paraventricular nucleus [e.g. neuropeptide Y (NPY), somatostatin (SRIF) and the cholecystokinin (CCK) neurons] possess strong GR IR. Furthermore, in the arcuate, parvocellular part of the paraventricular nuclei and the central amygdaloid nucleus practically all the peptidergic neurons are strongly GR IR, while in the lateral hypothalamus, mainly the neurotensin (NT) and galanin (GAL) IR neurons are GR IR. These marked differences among areas probably reflect functional differences dependent upon their participation in stress regulated circuits. All the paraventricular NT, corticotropin-releasing factor (CRF), growth hormone-releasing factor (GRF), thyrotropin-releasing hormone (TRH) and SRIF IR neurons appear to contain GR IR, while the luteinizing hormone-releasing hormone (LHRH) IR neurons lack GR IR, underlying the importance of glucocorticoids (GC) in controlling endocrine function. Finally, the GC may influence pain and mood control mainly via effects on enkephalin (ENK) neurons especially in the basal ganglia (mood) and on all beta-endorphin (beta-END) neurons of the arcuate nucleus, while most of the dynorphin neurons are not directly controlled by GC.

Animals↗

PubMed1991

Strongly glucocorticoid receptor immunoreactive neurons in the neonatal rat brain.

Brain glucocorticoid receptor (GR) immunoreactivity was studied in the neonatal rat. Already at postnatal days 1-3 strongly GR immunoreactive (IR) neurons were found in the arcuate and paraventricular hypothalamic nuclei. Moderately to strongly GR IR neurons were found in the locus coeruleus and raphe nuclei, while only weakly GR IR neurons were present in the CA1 and CA2 areas of the hippocampus. GR IR increases steadily during the postnatal period reaching adult levels at day 16. Thus, GR may play a role in the maturation of these hypothalamic nuclei and the 5-hydroxytryptamine and noradrenaline neurons, and GR may provide a basis for the ability of stress-induced increases of glucocorticoids to influence distinct brain circuits during postnatal development.

Aging↗

PubMed1991

Basic FGF is present in dopaminergic neurons of the ventral midbrain of the rat.

Immunocytochemistry procedures and 6-hydroxy-dopamine-induced degeneration of dopamine nerve cells provided evidence that practically all tyrosine hydroxylase immunoreactive (IR) neurons of the substantia nigra and ventral tegmental area contain cytoplasmic basic fibroblast growth factor immunoreactivity (bFGF IR), while many astroglial cells in the neostriatum and substantia nigra contain nuclear bFGF IR. RNA blot analysis demonstrated strong expression of a major 3.7 kb bFGF mRNA in the substantia nigra and ventral tegmental area. These results indicate that bFGF may be a significant growth factor in the DA neurons.

Animals↗