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Biomedical subjects

J F Powell

Publications and source records attributed to J F Powell.

At least 109 records · Page 6Linked to original sources
PubMed1985

Synaptic interaction between catecholaminergic neurons and substance P-immunoreactive axons in the caudal part of the nucleus of the solitary tract of the rat: demonstration by the electron microscopic mirror technique.

The 'mirror technique' was applied in immunoelectron microscopy to demonstrate the synaptic relationship between neuronal structures containing catecholamines and substance P in the caudal part of nucleus of the solitary tract in the rat, using antisera against tyrosine hydroxylase and substance P. Substance P-immunoreactive axon terminals were shown to make two types of synaptic contacts (asymmetrical and symmetrical) with catecholaminergic neurons. It is concluded that substance P afferents can directly affect catecholaminergic neurons in this nucleus via synapses.

Animals↗
PubMed1985

An arcuato-paraventricular and -dorsomedial hypothalamic neuropeptide Y-containing system which lacks noradrenaline in the rat.

The origins of neuropeptide Y-like immunoreactive (NPYI) fibers in the paraventricular and dorsomedial hypothalamic nuclei of the rat were examined using immunohistochemistry. Destruction of the arcuate nucleus resulted in a marked decrease of NPYI fibers ipsilaterally in these nuclei, suggesting that most of NPYI fibers in these nuclei originate from NPYI neurons in the arcuate nucleus. These NPYI systems did not contain noradrenalin.

Animals↗
PubMed1985

Neuropeptide Y-like immunoreactive structures in the rat stomach with special reference to the noradrenaline neuron system.

The origins and overall distribution of neuropeptide Y-like immunoreactive (NPYI) structures in the rat stomach were investigated by immunofluorescent staining of muscle strips from rats subjected to chemical and surgical neurotomy. The present study has demonstrated that the majority of NPYI fibers in the myenteric plexus and along the blood vessels in the muscle layers originate from NPYI cell bodies located in the celiac ganglion, which also contains noradrenaline. The remaining NPYI fibers in the circular and longitudinal muscle layer and a small number of NPYI fibers in the myenteric plexus do not contain noradrenaline and are of intrinsic origin. Noradrenaline fibers in the muscle layer are not associated with blood vessels. They originate from the celiac ganglion but do not contain NPYI structures.

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PubMed1985

Three dimensional analysis of retinal neuropeptides and amine in the chick.

Three dimensional analysis of retinal neuropeptides and monoamine-containing amacrine cells were performed on flat-mount preparations of the chick retina by using indirect immunofluorescence method. somatostatin (SOM), neurotensin (NT), leu-enkephalin (ENK), vasoactive intestinal polypeptide (VIP), substance P (SP), corticotropin releasing factor (CRF), avian pancreatic polypeptide (APP), glucagon (GLC), 5-hydroxytryptamine (5HT) and tyrosine hydroxylase (TH) were examined with specific antisera. To localize these substances in the amacrine cells, and to see in which layers their processes arborize, frozen sections were examined. There were four patterns of distribution. (1) Substances with more immunoreactive cells in the central than in the peripheral portions (SOM, NT, VIP, SP, GLC, 5HT), (2) Substances with more immunoreactive cells in the peripheral portion than in the central portion (APP), (3) Substances for which such cells were evenly distributed (TH), and (4) Substances with more immunoreactive cells in the inferior than in the superior portion (CRF). Subtypes were identified among the amacrine cells containing single peptides or monoamine.

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PubMed1985

Efferent synaptic connections of grafted dopaminergic neurons reinnervating the host neostriatum: a tyrosine hydroxylase immunocytochemical study.

In adult rats with a unilateral 6-hydroxydopamine-induced destruction of the nigrostriatal dopamine (DA) pathway, grafts of embryonic substantia nigra can establish a new dopaminergic terminal fiber plexus in the previously denervated neostriatum and compensate for some of the behavioral deficits induced by the nigrostriatal lesion. In the present study the synaptic connections of the ingrowing DA fibers from the graft were analyzed ultrastructurally, using immunocytochemical localization of tyrosine hydroxylase (TH), in animals whose lesion-induced motor asymmetry had been completely compensated for by the nigral grafts. In two of the animals, horseradish peroxidase-wheatgerm agglutinin conjugate was injected into the graft in order to trace possible reciprocal afferent connections to the graft from the host striatum. TH-immunoreactive axons from the graft were seen to make abundant symmetric synapses with neuronal elements in the host neostriatum. Between 85 and 90% of these synapses were on dendritic shafts and spines, and the rest were on neuronal perikarya. Two principal targets were identified: dendrites of spiny neurons, the majority of which are likely to be striatal projection neurons; and the cell bodies of giant neurons, most (or perhaps all) of which are known to be cholinergic interneurons. The synapses made on dendritic spines, which constituted about 40% of all TH-positive synapses formed by the TH-positive neurons in the graft, resembled those seen in normal animals, both in that they made contacts with spine necks and in that they invariably were associated with an asymmetric TH-negative synapse contacting the spine head. The innervation of the giant cell perikarya, which constituted about 6% of all TH-positive synapses found, was strikingly abnormal in that the graft-derived TH-positive fibers formed dense pericellular "baskets" selectively around the giant cell bodies. Such arrangements were never seen in the normal striatum, nor did they occur in the intact contralateral striatum in the grafted animals. It is proposed that this apparent dopaminergic hyperinnervation from the graft could provide a powerful inhibition of the cholinergic interneurons in the reinnervated host striatum, and that such an inhibitory mechanism could assist in the graft-induced functional recovery by potentiating the functional effects of DA synapses terminating on the spiny efferent neurons. This dual innervation may thus help to explain why restoration of only a small proportion of the striatal DA innervation by the graft is sufficient to induce complete compensation of, e.g., motor asymmetry in the lesioned rats.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1984

Growth of central substance P-containing neurons into superior cervical ganglia transplanted in the spinal cord of adult rats.

Superior cervical ganglia (SCG) contain substance P-like immunoreactive (SP-IR) fibers but not SP-IR neurons. In the present study, SCG were excised from adult rats and transplanted into the same animal's spinal thoracic cord (Th10). One or two weeks after the operation, SP-IR fibers from the host spinal cord or a higher level had grown and entered the transplanted SCG where they formed direct contacts with SCG neurons. However, these phenomena could not be observed when dorsal root ganglia (L4), which contained numerous SP-IR cells, were transplanted into their own spinal cord (Th10). This suggests that the SP-IR neuron system in the adult is able to grow "new axons' to the grafted tissue to form a "new SP-IR' neuronal circuit when the grafted tissue has lost its own SP-IR input.

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PubMed1984

Tyrosine hydroxylase-immunoreactive neurons of the hypothalamus: a light and electron microscopic study.

The localization and morphology of neurons, processes, and neuronal groups in the rat hypothalamus containing tyrosine hydroxylase-like immunoreactivity were studied using an antiserum to bovine tyrosine hydroxylase. This antiserum was thoroughly characterized by precipitation of enzyme activity, immunoblotting, and precipitation of cell-free translation products; a single molecular weight band was recognized by the antiserum. Absorption of the antiserum with purified tyrosine hydroxylase abolished immunocytochemical staining, while addition of bovine dopamine beta-hydroxylase had no effect on immunostaining. Immunoreactive cells were found throughout the hypothalamus. Significant numbers of cells were found in the arcuate, periventricular, dorsomedial hypothalamus/zona incerta, posterior hypothalamic regions (A11-A14), and paraventricular nucleus, as previously described, and in addition, in the preoptic area, adjacent to the anterior commissure, medial and lateral to the suprachiasmatic nucleus, dorsal to and in the supraoptic nucleus, at the lateral borders of the ventromedial nucleus, and in the dorsal and ventral lateral hypothalamus. None of the immunoreactive cell groups are totally separated from adjacent cell groups. Dendritic overlap occurs between any two adjacent groups. From cell counts of 30 micron coronal sections, we estimate the hypothalamus has about 12,000 cells based on raw counts, or 8000 immunoreactive cells after correction for possible split cells. Mean soma size varied considerably from one immunoreactive group to another. Cells in the caudal part of the dorsomedial hypothalamus/zona incerta region were the largest, with a mean diameter of 25 micron, while cells in the anterior commissural and posterior hypothalamic group were among the smallest, with mean diameters of 10 micron. The largest immunoreactive cells in the hypothalamus had volumes in excess of ten times greater than the smallest immunoreactive cells. Tyrosine hydroxylase immunoreactivity was found in dendrites in every region of the hypothalamus, sometimes extending hundreds of micrometers from the perikaryon of origin. Although adjacent cell groups were not distinctly separated, the dendritic arbors of the different cell groups differed greatly. Dendritic and somatic appendages were found on some cells, particularly in the paraventricular nucleus. Immunoreactive dendritic arbors were particularly large in cells seen on horizontal sections through the caudal dorsomedial hypothalamic group and through the anterior hypothalamus. Only slight dendritic trees were observed in the rostral dorsomedial hypothalamus/zona incerta region, and in the pericommissural group.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1984

Tyrosine hydroxylase-immunoreactive boutons in synaptic contact with identified striatonigral neurons, with particular reference to dendritic spines.

Tyrosine hydroxylase-immunoreactive fibres in the rat neostriatum were studied in the electron microscope in order to determine the nature of the contacts they make with other neural elements. The larger varicose parts of such fibres contained relatively few vesicles and rarely displayed synaptic membrane specializations; however, thinner parts of axons (0.1-0.4 micron) contained many vesicles and had symmetrical membrane specializations, indicative of en passant type synapses. By far the most common postsynaptic targets of tyrosine hydroxylase-immunoreactive boutons were dendritic spines and shafts, although neuronal cell bodies and axon initial segments also received such input. Six striatonigral neurons in the ventral striatum were identified by retrograde labelling with horseradish peroxidase and their dendritic processes were revealed by Golgi impregnation using the section-Golgi procedure. The same sections were also developed to reveal tyrosine hydroxylase immunoreactivity and so we were able to study immunoreactive boutons in contact with the Golgi-impregnated striatonigral neurons. Each of the 280 immunoreactive boutons examined in the electron microscope displayed symmetrical synaptic membrane specializations: 59% of the boutons were in synaptic contact with the dendritic spines, 35% with the dendritic shafts and 6% with the cell bodies of striatonigral neurons. The dendritic spines of striatonigral neurons that received input from immunoreactive boutons invariably also received input, usually more distally, from unstained boutons that formed asymmetrical synaptic specializations. A study of 87 spines along the dendrites of an identified striatonigral neuron showed that the most common type of synaptic input was from an individual unstained bouton making asymmetrical synaptic contact (53%), while 39% of the spines received one asymmetrical synapse and one symmetrical immunoreactive synapse. It is proposed that the spatial distribution of presumed dopaminergic terminals in synaptic contact with different parts of striatonigral neurons has important functional implications. Those synapses on the cell body and proximal dendritic shafts might mediate a relatively non-selective inhibition. In contrast, the major dopaminergic input that occurs on the necks of dendritic spines is likely to be highly selective since it could prevent the excitatory input to the same spines from reaching the dendritic shaft. One of the main functions of dopamine released from nigrostriatal fibres might thus be to alter the pattern of firing of striatal output neurons by regulating their input.

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PubMed1984

Characteristics of a new human neuroblastoma cell line which differentiates in response to cyclic adenosine 3':5'-monophosphate.

A new human cell line, TR14 , has been established in tissue culture from biopsy material of a primary neuroblastoma tumor. Most TR14 cells have short processes and grow mainly in clumps adhering to cells attached to the substratum. TR14 cells form colonies in soft agar demonstrating anchorage independence of growth and produce tumors in nude mice with histologies similar to that of the patient's tumor. The neurotransmitter-synthesizing activity of these cells is predominantly cholinergic with only a minor adrenergic component, since the activity of choline acetyltransferase is about 20-fold greater than that of tyrosine hydroxylase. Treatment with N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate induces TR14 neuroblastoma cells to extend fine, long processes or neurites. This morphological change is accompanied by elevated numbers of cytoplasmic dense-core vesicles observed by electron microscopy and an increase in the activities of neurotransmitter-synthesizing enzymes. Differentiation therefore occurs at the levels of cellular morphology, ultrastructure, and biochemistry. Prostaglandin E1 and cholera toxin can also induce differentiation, but a range of other agents including dimethyl sulfoxide, nerve growth factor, butyrate, corticosteroids, and 5-bromodeoxyuridine is ineffective. The concomitant induction of both morphological and biochemical differentiation therefore appears to be exclusively a cyclic adenosine 3':5'-monophosphate-mediated event in this cell line.

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PubMed1982

Immunological studies of human monoamine oxidases.

Antisera have been raised against monoamine oxidase preparations from human placenta and platelets. These antisera have been employed to characterize membrane-bound enzyme from a variety of human sources including liver, heart, and brain. The comparisons were based on a displacement radioimmunoassay system with soluble placental monoamine oxidase, previously labelled specifically with [3H]pargyline, as antigen. All forms of enzyme investigated demonstrated immunological cross reaction; however, the placental enzyme appeared to possess determinants not exhibited by the enzyme from the platelets or other tissues examined.

Blood Platelets↗
PubMed1981

The proportion of neurons in the rat neostriatum that project to the substantia nigra demonstrated using horseradish peroxidase conjugated with wheatgerm agglutinin.

Following the injection of small volumes of horseradish peroxidase conjugated with wheatgerm agglutinin into the substantia nigra of the rat, a high proportion of the total neuronal population in parts of the ipsilateral neostriatum was retrogradely labelled with horseradish peroxidase. Quantitative estimates in 1-micrometer plastic sections showed that 68.5% of 1011 neurons counted project to the substantia nigra.

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