Biomedical subjects

S R Vincent

Publications and source records attributed to S R Vincent.

At least 91 records · Page 5Linked to original sources

PubMed1988

Different times of origin of choline acetyltransferase- and somatostatin-immunoreactive neurons in the rat striatum.

Two populations of aspiny interneurons have been identified in the mammalian striatum, one cholinergic and the other using the neuropeptide somatostatin as a neurotransmitter. The times at which these 2 cell populations undergo their final mitosis were studied by injecting tritiated thymidine into timed pregnant rats and then processing the brains of the progeny as young adults for immunohistochemistry with monoclonal antibodies to choline acetyltransferase and somatostatin followed by autoradiography. Choline acetyltransferase-immunoreactive neurons became postmitotic in a caudal-to-rostral gradient; the occurrence of final mitosis was maximal on embryonic day (E) 12 at the most caudal level and on E15 at the most rostral. A more subtle lateral-to-medial gradient was also observed in the precommissural striatum. In contrast, no obvious gradients were seen with somatostatin-immunoreactive neurons; regardless of their location within the striatum, these neurons underwent their final mitosis on days E15-16, towards the end of cholinergic neurogenesis. These results indicate that although both cholinergic and somatostatin-containing cells represent interneuronal populations in the striatum, they display distinctly different spatiotemporal patterns of neurogenesis.

Animals↗

PubMed1987

Decibeldome.

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Baseball↗

PubMed1987

The distribution of somatostatin-immunoreactive neurons and fibers in the rat cerebral cortex: light and electron microscopic studies.

The distribution of somatostatin (SOM)-immunoreactive neurons in rat motor and somatosensory cortices was studied by immunohistochemistry at both light and electron microscopic levels. Three types of SOM-positive neurons were described. Type A cells are large to medium in size, multipolar in shape and have 3-5 long primary cell processes. Type B cells are medium to small, fusiform in shape and have two primary processes. These two subtypes show abundant subcellular organelles and are heavily stained throughout their cytoplasm. Type C cells are small, ovoid or fusiform in shape and are lightly stained. These previously undescribed cells are the largest SOM-immunoreactive population in the cortex. Ultrastructurally they have few subcellular organelles and only a patchy immunostaining in the cytoplasm. SOM-immunoreactive neurons occur in all cortical layers except I, and are most numerous in layer V of the somatosensory and motor cortex. In SOM-positive dendrites, electron-dense immunoreactive/peroxidase end product is primarily associated with microtubules. Fine deposits also occur deep to the postsynaptic membrane asymmetric synapses making contact with such dendrites.

Animals↗

PubMed1987

Distribution of phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive neurons in the avian brain.

The distribution of neurons immunoreactive to tyrosine hydroxylase and phenylethanolamine-N-methyltransferase (PNMT) were described in adjacent sections of the avian medulla oblongata. PNMT-positive neurons were found in two bilaterally symmetrical columns in the ventrolateral and dorsomedial medulla. Within the ventrolateral column, PNMT cells were centered in and around the lateral paragigantocellular and lateral reticular nuclei. In the dorsomedial medulla, PNMT neurons were concentrated within and around the nucleus of the tractus solitarius. The distribution of PNMT-immunoreactive neurons in the avian medulla is similar to those observed in mammals, except there appears to be a greater number of PNMT-positive cells in the bird.

Adrenergic Fibers↗

PubMed1987

Effects of MPTP poisoning on central somatostatin and substance P levels in the mouse.

The effects of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) on the levels of the neuropeptides somatostatin and substance P, were examined in various brain regions of C57 mice. Two weeks after injections of MPTP (2 X 30, 2 X 40 and 2 X 50 mg/kg i.p.) a dose-dependent decrease in striatal catecholamine levels was observed. There was also a dose-dependent increase in nigral somatostatin immunoreactivity and no reduction in striatonigral substance P levels. These results are in contrast with the changes observed in peptide levels in post-mortem Parkinson's brains.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1987

Somatostatin immunoreactivity in the cat adrenal medulla. Localization and characterization.

Somatostatin-like immunoreactivity was detected within the adrenal gland of the cat using specific monoclonal antibodies. Immunohistochemical studies demonstrated a few somatostatin-immunoreactive nerve fibers within the adrenal medulla. In addition, a large population of chromaffin cells in the cat adrenal medulla displayed intense somatostatin-like immunoreactivity. Similar cells were not observed in rat or guinea pig adrenal glands, although they were found in human material. The somatostatin-positive cells in the cat adrenal medulla often possessed short immunoreactive processes similar to those seen in somatostatin-immunoreactive paracrine cells of the gut. Characterization of the somatostatin-like immunoreactivity of the cat adrenal by high performance liquid chromatography and radioimmunoassay indicated that somatostatin-28 may account for over 90% of the observed immunoreactivity. It is suggested that somatostatin-28 may have a paracrine or endocrine role in the feline adrenal medulla.

Adrenal Medulla↗

PubMed1987

The immunohistochemical localization of choline acetyltransferase in the cat brain.

The distribution of neurons displaying choline acetyltransferase (ChAT) immunoreactivity was examined in the feline brain using a monoclonal antibody. Groups of ChAT-immunoreactive neurons were detected that have not been identified previously in the cat or in any other species. These included small, weakly stained cells found in the lateral hypothalamus, distinct from the magnocellular rostral column cholinergic neurons. Other small, lightly stained cells were also detected in the parabrachial nuclei, distinct from the caudal cholinergic column. Many small ChAT-positive cells were also found in the superficial layers of the superior colliculus. Other ChAT-immunoreactive neurons previously detected in rodent and primate, but not in cat, were observed in the present study. These included a dense cluster of cells in the medial habenula, together with outlying cells in the lateral habenula. Essentially all of the cells in the parabigeminal nucleus were found to be ChAT-positive. Additional ChAT-positive neurons were detected in the periolivary portion of the superior olivary complex, and scattered in the medullary reticular formation. In addition to these new observations, many of the cholinergic cell groups that have been previously identified in the cat as well as in rodent and primate brain such as motoneurons, striatal interneurons, the magnocellular rostral cholinergic column in the basal forebrain and the caudal cholinergic column in the midbrain and pontine tegmentum were confirmed. Together, these observations suggest that the feline central cholinergic system may be much more extensive than previous studies have indicated.

Animals↗

PubMed1987

Topographic relations of cholinergic and noradrenergic neurons in the feline pontomesencephalic tegmentum: an immunohistochemical study.

The immunohistochemical localization of the neurotransmitter synthesizing enzymes choline acetyltransferase, tyrosine hydroxylase and dopamine-beta-hydroxylase was examined in the feline pontomesencephalic tegmentum. Examination of adjacent sections stained for either choline acetyltransferase, tyrosine hydroxylase or dopamine-beta-hydroxylase immunoreactivity, as well as individual sections doubly stained for both choline acetyltransferase and tyrosine hydroxylase immunoreactivity, unequivocally demonstrated that noradrenergic and cholinergic neurons were extensively intermingled in the brainstem tegmentum of the cat. This contrasts with the situation in various other species, where neurons utilizing these two neurotransmitters are discretely localized in distinct nuclei. Furthermore, the present studies demonstrate the existence of two types of choline acetyltransferase immunoreactive neurons in the feline tegmentum: the magnocellular neurons of the pedunculopontine and laterodorsal tegmental nuclei which stain histochemically for NADPH diaphorase, plus a population of small spindle-shaped neurons in the medial and lateral parabrachial nuclei which do not stain positively for NADPH diaphorase. The data are discussed with respect to several influential hypotheses of sleep cycle control.

Animals↗

PubMed1987

Neurotransmitters in the mammalian striatum: neuronal circuits and heterogeneity.

The major input and output pathways of the mammalian striatum have been well established. Recent studies have identified a number of neurotransmitters used by these pathways as well as by striatal interneurons, and have begun to unravel their synaptic connections. The major output neurons have been identified as medium spiny neurons which contain gamma-aminobutyric acid (GABA), endogeneous opioids, and substance P. These neurons project to the pallidum and substantia nigra in a topographic and probably chemically organized manner. The major striatal afferents from the cerebral cortex, thalamus, and substantia nigra terminate, at least in part, on these striatal projection neurons. Striatal interneurons contain acetylcholine, GABA, and somatostatin plus neuropeptide Y, and appear to synapse on striatal projection neurons. In recent years, much activity has been directed to the neurochemical and hodological heterogeneities which occur at a macroscopic level in the striatum. This has led to the concept of a patch-matrix organization in the striatum.

Acetylcholine↗

PubMed1986

Somatostatin immunoreactivity in the entopeduncular projection to the lateral habenula in the rat.

Many neurons within the ipsilateral entopeduncular nucleus were retrogradely labelled following the stereotaxic injection of the fluorescent tracer True Blue into the lateral habenula of the rat. These neurons also displayed somatostatin immunoreactivity when examined with a monoclonal antibody to cyclic somatostatin. Excitotoxic lesions of the entopeduncular nucleus resulted in a loss of the dense somatostatin terminal field normally present in the lateral habenula. These results indicate that the neuropeptide somatostatin is present in the projection from the entopeduncular nucleus to the lateral habenula.

Animals↗

PubMed1986

The distribution of tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyltransferase immunoreactive neurons in the feline medulla oblongata.

The distributions and morphological characteristics of neurons displaying immunoreactivity to the catecholamine synthetic enzymes tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT) were examined in adjacent sections of the feline medulla oblongata. TH-positive neurons were found in two bilaterally symmetrical columns in the ventrolateral and dorsomedial medulla. Within the ventrolateral medulla, TH-positive neurons were found within the lateral reticular formation throughout the entire rostrocaudal extent of the medulla. In the dorsomedial medulla, TH-immunoreactive perikarya were localized to the nucleus of the tractus solitarius including the commissural subnucleus, the dorsal motor nucleus of the vagus, and the area postrema. DBH-positive neurons had distributions and morphologies similar to those of the TH-immunoreactive cells with three exceptions: TH-positive neurons far outnumbered DBH-positive neurons in the area postrema; slightly greater numbers of TH-positive neurons were seen in the commissural nucleus of the tractus solitarius; and, caudal to the obex, only TH-positive neurons were seen within the dorsal motor nucleus of the vagus. PNMT-immunoreactive neurons were found in all the nuclear regions of the medulla where both TH- and DBH-positive neurons were seen. However, the PNMT immunoreactive perikarya had a somewhat more restricted distribution along the rostrocaudal axis. In the ventrolateral medulla, PNMT-positive cells extended rostrally only as far as the retrofacial nucleus and caudally only to the obex. Within the dorsomedial medulla, PNMT immunoreactive cells were found from just rostral to the area postrema to the medullary-spinal cord junction. These findings demonstrate that the distributions of TH, DBH, and PNMT immunoreactive perikarya in the medulla of the cat are generally similar to those seen in the rat insofar as these neurons are arranged in longitudinal columns in both species. However, significant differences exist with regard to the cytoarchitectonic borders within which immunoreactive perikarya can be found and the rostrocaudal extent of the PNMT-positive cell groups in these two species.

Animals↗

PubMed1986

Histochemistry of MPTP oxidation in the rat brain: sites of synthesis of the parkinsonism-inducing toxin MPP+.

Systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is toxic to the nigrostriatal dopaminergic neurons and produces a syndrome similar to Parkinson's disease. Conversion of MPTP to 1-methyl-4-phenylpyridine (MPP+) by monoamine oxidase-B (MAO-B) appears necessary for this neurotoxicity. When MPTP was used as the substrate for the histochemical localization of monoamine oxidase activity on sections of the rat brain, only a few specific sites were found in which MPTP oxidation to MPP+ occurs. These include the noradrenergic and serotoninergic neurons of the brainstem and the histamine neurons of the caudal hypothalamus. Dopamine neurons themselves do not display the capacity to oxidize MPTP. It is proposed that the conversion of MPTP to MPP+ occurs via MAO-B within serotonin and histamine neurons which may innervate the substantia nigra where the toxin MPP+ could be released and then taken up into the dopamine neurons.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1986

Somatostatin- and neuropeptide Y-immunoreactive neurons in the neocortex in senile dementia of Alzheimer's type.

Morphological changes in neocortical somatostatin- and neuropeptide-Y-immunoreactive cells in senile dementia of the Alzheimer type (SDAT) were studied using light-microscopic immunohistochemical methods. The density of somatostatin-immunoreactive cells in the neocortex did not decrease in cases of SDAT compared with aged normal subjects. However, many somatostatin-positive fibers were abnormally swollen and bulbous in shape and they were often observed within senile plaques. The morphology of these swollen and bulbous fibers was similar to that of the swollen neurites present in senile plaques demonstrated by the silver-impregnation method. Similar fiber abnormalities were observed in sections stained with antibodies to neuropeptide Y. Somatostatin-positive cells in aged normal subjects were distributed from layer II through to the subcortical white matter. These cells were multipolar, bitufted, or pyramidal in shape, with the majority of cells being of the multipolar type. Neuropeptide Y-positive cells also were distributed from layer II through to the subcortical white matter. Most of these cells were multipolar, but a few bipolar cells were also observed. We suggest that a primary degenerative process might begin at the fiber terminals of the somatostatin neuronal system in the neocortex in SDAT.

Aged↗

PubMed1986

Absence of adrenaline neurons in the guinea pig brain: a combined immunohistochemical and high-performance liquid chromatography study.

The distributions of catecholamine (CA) neurons in the medulla oblongata of the guinea pig and rat were compared using immunohistochemistry with rabbit antisera against the CA synthesizing enzymes, tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (D beta H) and phenylethanolamine-N-methyltransferase (PNMT). TH and D beta H distributions were similar in the two species. In contrast, the central nervous systems of both normal and colchicine-treated guinea pigs failed to demonstrate immunoreactivity for PNMT, the synthetic enzyme for adrenaline. The concentrations of biogenic amines in the hypothalamus and medulla were determined in guinea pig and rat tissues by high-performance liquid chromatography with electrochemical detection. No adrenaline was detected in the guinea pig brain. Thus it appears that guinea pigs lack central neurons capable of synthesizing adrenaline.

Adrenergic Fibers↗

PubMed1986

The effects of cysteamine on dopamine-mediated behaviors: evidence for dopamine-somatostatin interactions in the striatum.

The effects of prior treatment with cysteamine, a drug which appears to deplete selectively the neuropeptide somatostatin, on apomorphine-induced stereotypy and amphetamine-induced locomotor activity and conditioned place preferences were investigated. Twelve hours following systemic cysteamine injections apomorphine-induced stereotypy was attenuated and striatal somatostatin levels were reduced by half. Systemic cysteamine also decreased the motor stimulant effects of amphetamine, without influencing the rewarding properties as determined by the conditioned place preference procedure. Direct injections of cysteamine into the nucleus accumbens also decreased the locomotor response to amphetamine, and produced a local reduction in somatostatin levels in the accumbens. Cysteamine did not appear to alter monoamine turnover in the striatum after either systemic or intra-accumbens injections. These results suggest that somatostatin in the nucleus accumbens and caudate-putamen modulates the motor, but not the reinforcing properties of dopaminergic drugs, possibly via an action postsynaptic to dopamine-releasing terminals. Furthermore, it is evident from these results that cysteamine is an important tool with which to study the central actions of somatostatin.

Amphetamine↗

PubMed1986

The localization of central cholinergic neurons.

Over the past decade our understanding of the localization of central cholinergic neurons has greatly increased. Interest in these systems has also intensified due to the involvement of cholinergic mechanisms in Alzheimer's disease. The distribution of central cholinergic neurons is reviewed, focusing on recent work in experimental animals. The pharmacohistochemical procedure for acetylcholinesterase and the development of antibodies to choline acetyltransferase are two of the major technical advances that have shaped our knowledge of the distribution of central cholinergic neurons. The results, advantages and limitations of both techniques are discussed. A discussion of the phenomenon of coexistence of acetylcholine with neuroactive peptides in central neurons is also included.

Acetylcholinesterase↗

PubMed1986

Neuropeptides and NADPH-diaphorase activity in the ascending cholinergic reticular system of the rat.

A major group of cholinergic neurons is present in the midbrain and pontine tegmentum. These cells could be selectively stained using either monoclonal antibodies to choline acetyltransferase, the pharmacohistochemical acetylcholinesterase procedure, or reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry. Using these three techniques, the precise distribution of this cell group was determined. By combining these techniques with immunohistochemical staining for various neuropeptides, examples of peptide-cholinergic coexistence could be demonstrated in this cell group. Approximately 30% of these cholinergic neurons displayed substance P immunoreactivity. Most of these cells also showed corticotropin-releasing factor immunoreactivity and bombesin/gastrin-releasing peptide immunoreactivity. These results therefore provide evidence for the coexistence of various neuropeptides together with NADPH-diaphorase activity in the ascending cholinergic reticular system.

Acetylcholinesterase↗

PubMed1985

Acetylcholinesterase and somatostatin-immunoreactivity coexist in human neocortex.

Immunohistochemistry was combined with enzyme histochemistry to examine the localization of somatostatin (SOM) and acetylcholinesterase (AChE) in the human neocortex. Many of the SOM-immunoreactive cortical neurons were found to display specific AChE activity. Similar coexistence was seen in the rat cortex. In contrast, AChE and SOM appear to be present in distinct cell groups in the human caudate nucleus.

Acetylcholinesterase↗