PubMed Health⌕ Search

Biomedical subjects

M B Hancock

Publications and source records attributed to M B Hancock.

At least 19 recordsLinked to original sources
PubMed1991

Projections from the rostral ventrolateral medulla to brainstem monoamine neurons in the rat.

Following the iontophoretic deposition of Phaseolus vulgaris leucoagglutinin (PHA-L) into the rostral ventrolateral medulla (RVL), two-color immunoperoxidase staining was employed to demonstrate contiguity between PHA-L-immunoreactive (PHA-LI) varicose fibers and boutons and brainstem monoaminergic cells. Black-stained PHA-LI cells in the deposition site were found to be located among amber-stained phenylethanolamine N-methyl transferase-immunoreactive (PNMT-I) neurons of the C1 cell group. RVL projections were contiguous with PNMT-I neurons of the C1, C2 and C3 cell groups, with tyrosine hydroxylase-immunoreactive (TH-I) neurons of the A1, A2 and A5 cell groups, and with serotonin-immunoreactive (5-HT-I) neurons of the B1, B2 and B3 cell groups. Preliminary findings of this study have been presented previously (Soc. Neurosci. Abstr., 15 (1989) 451).

Animals↗
PubMed1990

Evidence for projections from the rostral medullary raphe onto medullary catecholamine neurons in the rat.

Following the iontophoretic deposition of Phaseolus vulgaris leucoagglutinin (PHA-L) into the rostral medullary raphe, which included portions of the caudal nucleus raphe magnus, rostral nucleus raphe pallidus, rostral nucleus raphe obscurus and rostral nucleus reticularis paragigantocellularis, two-color immunoperoxidase staining was employed to demonstrate contiguity between PHA-L-immunoreactive (PHA-LI) varicose fibers and boutons and medullary catecholamine (CA) cells. Raphe projections were contiguous with phenylethanolamine N-methyltransferase-immunoreactive (PNMTI) neurons in the C1, C2 and C3 cell groups and with tyrosine hydroxylase-immunoreactive (THI) neurons in the A1 and A2 cell groups. Contiguity between PHA-LI processes and medullary CA cells was observed most frequently in the C1 cell group. Preliminary findings of this study have been presented previously.

Animals↗
PubMed1989

Evidence for substance P, serotonin and oxytocin input to medullary catecholamine neurons with diencephalic projections.

Using the retrograde transport of horseradish peroxidase (HRP) in combination with two-color immunoperoxidase staining, boutons stained with antisera to substance P (SP), serotonin (5HT) and oxytocin (OX) have been observed in contiguity with neurons in the rostral and caudal medulla that showed immunoreactivity for phenylethanolamine N-methyl transferase (PNMT) and tyrosine hydroxylase (TH), respectively, and which were backfilled with HRP injected into the diencephalon. The juxtaposition of these immunostained structures indicates that SP, 5HT and OX released from fibers in the medulla may affect the activity of adrenergic and noradrenergic medullary neurons that project to the diencephalon. Moreover, the presence of 5HT- and OX-immunoreactive processes in contiguity with medullary CA cells that send fibers to the diencephalon indicates that the raphe nuclei and the paraventricular nucleus of the hypothalamus can directly influence ascending pathways that are known to innervate the hypothalamus and appear to effect changes in vasopressin release.

Animals↗
PubMed1988

Evidence for direct projections from the nucleus of the solitary tract onto medullary adrenaline cells.

The anatomic relationships between projections from the intermediate portion of the nucleus of the solitary tract (NTS) and phenylethanolamine N-methyl transferaselike-immunoreactive (PNMT-LI) cells in the medulla oblongata were analyzed in Sprague-Dawley rats by using two-color immunoperoxidase staining combined with the anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L). PHA-L was iontophoretically deposited in the intermediate region of the NTS and the subjacent dorsal motor nucleus of the vagus (DMX) at the level of the middle of the area postrema. Black-stained PHA-L-immunoreactive (PHA-LI) fibers and terminals were present throughout the length of the ipsilateral NTS, where many were seen in close apposition to amber-stained PNMT-LI cells belonging to the C2 cell group. Less profuse PHA-LI projections were present in the contralateral NTS, especially at the level of the PHA-L deposit. Bundles of smooth fibers emerged from the lateral edge of the DMX and could be followed to the ventrolateral surface of the medulla; these were likely vagal efferent fibers. PHA-LI terminal arborizations were prominent in the region of the nucleus ambiguus (NA) and amongst PNMT-LI cells in the lateral C1 cell group ventral to NA. Multiple sites of contiguity between PHA-LI varicose fibers or boutons and PNMT-LI cells in C1 were observed frequently and probably represent sites of functional connection.

Animals↗
PubMed1988

Immunocytochemical evidence for substance P and serotonin input to medullary bulbospinal adrenergic neurons.

Using two-color immunoperoxidase staining combined with the retrograde transport of horseradish peroxidase injected into the rostral thoracic spinal cord, substance P-immunoreactive (SPI) and serotonin-immunoreactive (5HTI) varicosities have been observed in contiguity with medullary bulbospinal phenylethanolamine N-methyl transferase-immunoreactive (PNMTI) neurons of the C1, C2, and C3 cell groups. Since PNMTI terminals in the spinal cord are concentrated among sympathetic preganglionic neurons (SPGN) in the intermediolateral cell column, the close anatomical associations shown in the present study indicate that substance P- and serotonin-containing pathways in the medulla likely affect activity of SPGN via adrenergic bulbospinal neurons.

Adrenergic Fibers↗
PubMed1988

Colocalization of calcitonin gene-related peptide and somatostatin in pancreatic islet cells and inhibition of insulin secretion by calcitonin gene-related peptide in the rat.

Calcitonin gene-related peptide (CGRP)- and somatostatin (SRIF)-containing cells were identified by immunocytochemical techniques in pancreatic islet cells of the rat. CGRP-containing cells were found primarily in the peripheral portion of the pancreatic islets. In addition, CGRP-containing cells also contained somatostatin, which identifies the islet CGRP-containing cells as D cells. In the present study, we also tested the effect of CGRP on gastrin-releasing peptide (GRP; 10(-9) M)- or cholecystokinin (CCK-8, 10(-9) M)-stimulated release of insulin from isolated rat islets in vitro. At concentrations of 10(-8)-10(-11) M, CGRP inhibited GRP- and CCK-8-stimulated release of insulin significantly when compared with GRP or CCK-8 alone. At the lowest concentration of CGRP (10(-11) M), the inhibitory effect of CGRP on CCK-8-stimulated release of insulin was statistically significant (p less than 0.05) and exceptionally potent (65-90% inhibition). We have also found that CGRP does not stimulate the release of SRIF from isolated islet cells. These findings suggest that CGRP may play a regulatory role in the release of insulin.

Animals↗
PubMed1987

Oxytocin-immunoreactive projections onto medullary adrenaline neurons.

With the use of two-color immunoperoxidase staining, oxytocin-like immunoreactive (OLI) processes have been observed along the surface of phenylethanolamine N-methyl transferase-like immunoreactive (PNMTLI) cells in the ventrolateral and dorsomedial medulla of the rat. OLI boutons were also observed on PNMTLI cells retrogradely labeled with HRP injected into the rostral thoracic spinal cord. The close spatial relationships between OLI processes and PNMTLI cells argues for a functional connection which could provide for direct hypothalamic control of medullary adrenaline cells involved in cardiovascular regulation.

Adrenergic Fibers↗
PubMed1984

Substance P-immunoreactive processes on 5HT/SP-immunoreactive medullary cells.

Two-color immunoperoxidase staining has been used to localize substance P (SP)-immunoreactive processes on neurons in the caudal medulla that exhibited both serotonin (5HT)- and SP-immunoreactivity (5HTI/SPI cells). The punctate SP-immunoreactive processes were present on 5HTI/SPI cells in the raphe nuclei and ventral reticular formation. This close association suggests that activity in bulbospinal 5HT/SP pathways, which can influence sympathetic preganglionic neurons, may be affected by the release of SP in the brainstem.

Animals↗
PubMed1984

Visualization of peptide-immunoreactive processes on serotonin-immunoreactive cells using two-color immunoperoxidase staining.

The sequential application of the peroxidase-antiperoxidase (PAP) technique with nickel-intensified DAB and with DAB alone was used to visualize black peptide-immunoreactive endings on amber serotonin-immunoreactive cells in 1-2-micron paraffin sections of the hamster medulla. Met-enkephalin- and substance P-positive terminals were present on serotonin cells in the raphe nuclei, the ventral reticular formation, and in the nucleus interfascicularis hypoglossi. The presence of enkephalin-immunoreactive endings on medullary serotonin-immunoreactive cells correlates with the analgesia and autonomic changes that result from the application of morphine or met-enkephalin to the medulla.

Animals↗
PubMed1983

Localization of biotinylated gonadotropin releasing hormone on pituitary monolayer cells with avidin-biotin-peroxidase complexes.

The new avidin-biotin-peroxidase complex (ABC) technique was used to localize the [D-Lys6] analog of gonadotropin releasing hormone (GnRH), labeled with biotin, on pituitary monolayer cultures from female rats. Staining was diffuse, or in patches, on the surface of 10-17% of the cells 30 sec-3 min after the addition of 10(-10)-10(-12) M biotin-labeled GnRH. In parallel studies, double stains for gonadotropins showed label on 16.3 +/- 2% of the monolayers. Capping was evident by 3 min after exposure and the stain appeared in dense patches, vesicles, or granules 10-30 min after exposure. The stain was abolished by the addition of a 10- to 100-fold excess of unlabeled [D-Lys6] GnRH. Biotinylated GnRH released luteinizing hormone (LH) and follicle stimulating hormone (FSH) and was either equipotent or 10 times more potent than the unlabeled analog in multiple dose-response tests. The ED50 of the 4 hr release was 0.075 nM for LH and 0.02 nM for FSH. Competitive binding assays showed that the binding affinity of the biotinylated GnRH was within the range found for the unlabeled analog (0.7 nM-IC50). This report describes the localization of biotinylated GnRH on the surfaces of cells exposed to low concentrations of the analog with a technique that requires minimal manipulation of the cells, and is performed in less than one day.

Animals↗
PubMed1982

A serotonin-immunoreactive fiber system in the dorsal columns of the spinal cord.

Serotonin-immunoreactive fibers have been observed in the dorsal columns of the golden hamster spinal cord. The fibers were visualized using the PAP method which was intensified with a DAB-nickel substrate. The fibers were arranged preferentially in the mid-sagittal plane, and many were observed coursing from the dorsal columns into the dorsal gray matter. This serotonin-immunoreactive pathway may play a role in analgesia produced by dorsal column stimulation.

Animals↗
PubMed1982

Separate populations of lumbar preganglionic neurons identified with the retrograde transport of horseradish peroxidase (HRP) and 4,6-diamidino-2-phenylindole (DAPI).

Horseradish peroxidase (HRP) was applied to the central cut end of the intermesenteric trunk or the caudal lumbar sympathetic trunk in golden hamsters. Preganglionic cells labeled from the intermesenteric trunk were located in the intermediolateral cell column, bilaterally, and in the dorsal commissural nucleus. The segmental distributions of the cells in these two nuclear groups were similar. Preganglionic neurons labeled from the lumbar sympathetic trunk were located mainly in the ipsilateral intermediolateral cell column. The simultaneous application of HRP to one trunk and 4,6-diamidino-2-phenylindole (DAPI) to the other delineated two separate preganglionic cell populations. Cells labeled from the two trunks were distributed as above. HRP-filled cells and DAPI-filled cells were intermixed in the intermediolateral cell column ipsilateral to the backfilled sympathetic trunk. No double labeled cells were present. The results show that the dorsal commissural nucleus in the lumbar cord preferentially innervates prevertebral ganglia, that lumbar paravertebral ganglia are innervated by cells located mainly in the ipsilateral intermediolateral cell column, and that paravertebral and prevertebral ganglia are innervated by non-overlapping sets of lumbar preganglionic neurons.

Afferent Pathways↗
PubMed1982

Leu-enkephalin, substance P, and somatostatin immunohistochemistry combined with the retrograde transport of horseradish peroxidase in sympathetic preganglionic neurons.

Preganglionic neurons in the lower lumbar spinal cord were labeled with horseradish peroxidase applied to the cut ends of the intermesenteric trunk in golden hamsters. A black granular reaction product was obtained in HRP-labeled cells by soaking spinal cord tissue in a cobalt chloride solution prior to treatment with diaminobenzidine (DAB) and hydrogen peroxide. Spinal cord sections containing labeled preganglionic neurons were processed with the immunoperoxidase (PAP) technique. Immunoreactive processes appeared as rust-brown beads. Concentrations of beaded processes exhibiting enkephalin-like, substance P-like (SPI) and somatostatin-like (SOMI) immunoreactivity were present around HRP-labeled preganglionic neurons in the intermediolateral cell column and in the dorsal commissural nucleus. Immunoreactivity was also present in the superficial dorsal horn, the dorsolateral funiculus and around the central canal. A prominent fiber system exhibiting SPI and SOMI extended from the ventral white matter to the ventral horn.

Adrenergic Fibers↗
PubMed1981

Responses of spinothalamic tract cells in the thoracic spinal cord of the monkey to cutaneous and visceral inputs.

Somatovisceral convergence was demonstrated in recordings from 15 of 16 spinothalamic tract cells in the lower thoracic spinal cords of anesthetized monkeys. Inputs were produced by mechanical (or sometimes electrical) stimulation of the skin over the lower trunk and by electrical stimulation of the greater splanchnic nerve through a buried electrode. The volley in the greater splanchnic nerve was monitored using a buried electrode on the sympathetic chain. Spinothalamic tract cells could be excited by activity in A delta and C fibers, but no effects produced by A beta fibers were noted. In some cases inhibitory effects were observed due to movement of hair on the trunk, and inhibitory interactions could be demonstrated between cutaneous and visceral afferent volleys.

Animals↗
PubMed1979

A preganglionic autonomic nucleus in the dorsal gray commissure of the lumbar spinal cord of the rat.

The distribution in the spinal cord of the rat of preganglionic neurons sending fibers into the hypogastric nerve was determined with the retrograde transport of horseradish peroxidase (HRP). Labeled cells were present in the intermediate gray matter of spinal segments L1-L2. The majority (81%) of HRP-filled cells formed a continuous column along the midline in the dorsal gray commissure. This cell column was termed the dorsal commissural nucleus (DCN). The remainder of HRP-labeled cells were present bilaterally in the middle and lateral regions of the intermediate gray; the majority of the latter cells were located along the lateral border of the intermediate gray. The present finding of a midline preganglionic autonomic cell column in the spinal cord of a mammal is contrary to previous reports, in which sympathetic preganglionic neurons have been localized primarily in the lateral intermediate gray. The DCN may be species-specific and related to the system of short adrenergic neurons present in the pelvis.

Animals↗