PubMed Health⌕ Search

Biomedical subjects

B E Maley

Publications and source records attributed to B E Maley.

34 records · Page 2Linked to original sources
PubMed1987

A comparison of GABA- and GAD-like immunoreactivity within the area postrema of the rat and cat.

The immunohistochemical localization of gamma-aminobutyric acid (GABA) was compared to that of glutamate decarboxylase (GAD) in the rat and cat area postrema with the aid of a polyclonal antibody produced in rabbits directed against GABA. In both the rat and cat, dense and very dense accumulations of GABA-like immunoreactive (GABA-LI) varicosities were present throughout the area postrema. GABA-LI cell bodies were present in both species and were evenly distributed throughout the area postrema's extent. However, the rat area postrema contained more GABA-LI cell bodies and varicosities than the cat area postrema. In the cat area postrema, a range of cell sizes were immunostained with the GABA antibody. The GAD antibody, however, failed to reveal cell bodies in the area postrema of the cat, thus indicating that the GABA polyclonal antibody may be a better indicator of GABA-containing somata. Although the mechanism of action of GABA in the area postrema is not understood, it is possible that GABA may play a role in the different functions of the area postrema in emetic and nonemetic species.

Animals↗
PubMed1987

The response of cultured gonadotrophs to inhibin: the role of calcium mobilization.

The role of calcium mobilization and calmodulin activation in the induction of the selective suppression of follicle stimulating hormone (FSH) release by the gonadal protein inhibin was assessed employing a rat gonadotroph monolayer culture system. Inhibin, in porcine follicular fluid (60 microliters/ml), did inhibit FSH release in the face of GnRH stimulation. Antagonism of calcium mobilization with verapamil (10(-4) M) and dantrolene (10(-4) M) failed to restore the FSH response when administered with GnRH and inhibin. Trifluoperazine (10(-4) M), a calmodulin antagonist acted similarly. Cellular calmodulin content increased in response to gonadotropin-releasing hormone (GnRH), as did the concentration of cGMP, while both responses were prevented by the administration of inhibin. Trifluoperazine suppressed cGMP concentration to levels below baseline. These data suggest that while calmodulin and the cyclic nucleotides do not mediate the cellular response to inhibin, they may play a role in the control of gonadotropin synthesis. A link may exist between calmodulin, the concentration of which increased in response to GnRH and was suppressed by inhibin, and the elevation of cellular cGMP content induced by GnRH. Further investigation is warranted to assess a possible action of inhibin which is antagonistic to that of calcium in the transduction of GnRH stimulation into FSH release by the pituitary gonadotroph.

Animals↗
PubMed1987

Cyclic nucleotides and suppression of follicle-stimulating hormone release by inhibin.

The relative roles of the cyclic nucleotide messengers cAMP and cGMP in the suppression of follicle-stimulating hormone (FSH) secretion in response to inhibin (IBN) were assessed employing rat gonadotropes in monolayer culture. While exposure of cells to gonadotropin-releasing hormone (GnRH) induced a significant increase in the amounts of both FSH and luteinizing hormone (LH) released into the culture medium, these responses were dampened by the administration of IBN (in porcine follicular fluid). Addition of cGMP to the system failed to restore FSH release, while cAMP restored basal FSH release. Modulation of nucleotide metabolism with theophylline, sodium nitroprusside, and a protein kinase inhibitor failed to overcome the IBN-induced suppression of FSH release. The cellular content of calmodulin increased in response to GnRH, a response antagonized by IBN. Cellular levels of cGMP were also increased by GnRH, but this response was unaltered by IBN. The administered drugs all failed to reverse these effects of IBN. These data indicate that the IBN-induced suppression of FSH release is not dependent upon the cyclic nucleotides cAMP and/or cGMP. However, a role in the maintenance of basal FSH synthesis and release for cAMP is indicated.

Animals↗
PubMed1987

Colocalization of prolactin and growth hormone within specific adenohypophyseal cells in male, female, and lactating female rats.

The localization of PRL and GH within adenohypophysial cells has been investigated with immunocytochemical methodology using colloidal gold of different sizes. Classically, using morphological criteria at the light and electron microscope levels, two types of individual cells have been described which, it is believed, exclusively produce either PRL or GH, i.e. mammotrophs and somatotrophs. Since it has been reported that some gonadotrophs may colocalize and secrete both FSH and LH, and that some unidentified cells release both PRL and GH, we designed a study to investigate whether PRL and GH are present only in their respective specific cells or may be colocalized in mammotrophs and somatotrophs or possibly other types of cells within the pars distalis. Using immunocytochemistry at the electron microscope level we were able to label the two hormones with different sizes of colloidal gold bound to a second antibody and visualize them within pituitary cells. Two different primary antibodies to PRL and GH as well as a more purified antibody to GH were used. Pituitaries from cycling and lactating female rats and adult males were processed appropriately for electron microscopic studies. After sectioning, individual grids were treated with either primary antibodies for PRL or GH, or the same grid was treated sequentially with these two antibodies. All primary antibodies were absorbed with the heterologous hormone before usage. The second antibodies were bound to colloidal gold particles of either 10 nm (for GH) or 20 nm (for PRL) diameter, so that selective visualization of the two hormones could be achieved within the same cells. It was observed that mammotrophs immunolabeled only for PRL, and somatotrophs labeled only for GH regardless of the source of the antibody. However, an atypical small granule cell, a possible mammosomatotroph, colabeled consistently for both PRL and GH in all types of animals used and with antibodies from all of above sources. This report gives for the first time morphological evidence for the existence of pituitary cells that colocalize both PRL and GH in the normal rat pituitary gland. The possibility that these bihormonal cells represent stem cells which may give rise to both mammotrophs and somatotrophs under appropriate stimulation or that they may release both hormones under the influence of unspecific stimuli is suggested.

Animals↗
PubMed1986

Immunocytochemical localization of gamma-aminobutyric acid in the rat hippocampal formation.

gamma-Aminobutyric acid (GABA) was detected immunocytochemically in the rat hippocampal formation utilizing a new antiserum made against GABA conjugated to bovine serum albumin. GABA immunoreactivity was found to be concentrated in pericellular networks of fibers around both dentate granule and hippocampal pyramidal neurons. Ultrastructural analysis indicated that GABA-immunoreactive (IR) terminals most often contained small clear vesicles and made symmetrical contacts with somata and dendritic shafts of hippocampal neurons. In addition, numerous GABA-IR neurons resembled basket interneurons that have been described in previous reports.

Animals↗
PubMed1986

Immunohistochemical demonstration of serotonin neurons in autonomic regions of the rat spinal cord.

The immunohistochemical distribution of serotonin neurons in normal and transected spinal cords of rats was examined. Intraspinal serotonin neurons were immunostained as far rostral and caudal as T3 and Co1, respectively. All serotonin neurons were located in lamina VII and X, and most were located in spinal autonomic areas. Both bipolar and multipolar neurons were observed with many of the neurons oriented longitudinally to the long axis of the cord. Spinal neurons immunostained for serotonin were visible with and without L-tryptophan and monoamine oxidase inhibitor pretreatment.

Animals↗
PubMed1986

A simplified technique for rapid immunofluorescent assessment of cellular hormonal content.

Currently applied techniques for immunofluorescent staining of cultured cells are time consuming and not amenable to experimental design. Monolayers of rat anterior pituitary cells were stained in situ with rabbit follicle-stimulating hormone antiserum. Excision of the culture surfaces produced samples that were easy to handle and score for immunoreactivity without sacrificing resolution. The staining of in situ monolayers of cultured cells allows for assessment of both the secretory behavior and the hormonal content of the cells.

Animals↗
PubMed1986

Immunohistochemical colocalization of GABA and insulin in beta-cells of rat islet.

gamma-Aminobutyric acid (GABA) is found in high concentrations in the pancreatic islet. In addition, enzymes regulating the level of GABA (L-glutamate decarboxylase and GABA-alpha-ketoglutarate transaminase) have been immunohistochemically localized in the medullary cells of the islet. In this study, an immunofluorescence and elution/restaining protocol is used to determine the distribution of GABA and either insulin, glucagon, or somatostatin in a tissue section. GABA was not detected within the islet alpha- or delta-cells but was determined to be localized within the insulin-containing beta-cells.

Animals↗
PubMed1985

The ultrastructural localization of enkephalin and substance P immunoreactivities in the nucleus tractus solitarii of the cat.

In the medial and commissural subdivisions of the nucleus tractus solitarii enkephalin and substance P immunoreactivities were localized within synaptic terminals, unmyelinated axons, and neuronal cell bodies. Both enkephalin and substance P immunoreactivities were contained within synaptic terminals which had a mixture of small clear vesicles and dense core vesicles. The presence of dense core vesicles within both the enkephalin- and substance P-immunoreactive terminals was a consistent feature, although they were not associated with the actual synaptic junction. While enkephalin- and substance P-immunoreactive terminals shared a similar morphology, their respective distributions along the dendritic tree were quite distinct. Enkephalin-immunoreactive terminals contacted mainly the cell body and proximal portions of the dendritic tree. In contrast, substance P-immunoreactive terminals synapsed predominantly with spines and shafts of small to medium-sized dendrites. Few substance P-immunoreactive terminals contacted proximal dendrites and they were never presynaptic to the neuronal cell body. This apparent segregation of synaptic terminals on neurons suggests that enkephalin synapses have a more pronounced effect than substance P terminals.

Animals↗
PubMed1985

Cholecystokinin-octapeptide like immunoreactivity in the area postrema of the rat and cat.

The distribution of cholecystokinin-8 (CCK-8)-like immunoreactivity in the area postrema of the rat and cat was visualized using the peroxidase, antiperoxidase technique. In the rat the greatest amount of immunostaining occurred in peripheral regions of the area postrema at intermediate and rostral levels. Caudally, scattered immunoreactivity predominated. After colchicine treatment, numerous immunoreactive somata were observed throughout the area postrema. The cat area postrema had a different and more complex pattern of immunostaining than the rat. Moderate to dense accumulations of immunostaining occurred in the ventromedial region of the area postrema bordering the solitary tract and dorsal vagal nuclei. The central region of the area postrema possessed scattered amounts of immunoreactivity at rostral levels. Following colchicine treatment, no visible CCK-8-like immunoreactive cell bodies were observed in the cat area postrema. Results of the present investigation provide morphological evidence for the role of CCK-8 in cardiovascular regulation and satiety. The difference in the distribution of CCK-8 in the rat and cat suggest a possible role in the emetic reflex.

Animals↗
PubMed1980

Early development of the inferior olivary complex in pouch young opossums. II. An electron microscopic study.

At birth the inferior olivary complex (IOC) is not present in the caudal ventro-medial brainstem of the opossum. In the 3-7-day-old animal (15-19 days post-conception), this same region does contain neurons of the developing IOC. The immature neurons are characterized by large, centrally placed nuclei surrounded by a thin rim of cytoplasm. The neuropil contains numerous small-diameter profiles which contain bundles of filaments and scattered microtubules. Occasional synaptic endings, containing round clear vesicles, contact large, flocculent profiles. By 10-14 days of age, the olivary complex begins to separate into individual nuclei; however, the olivary cell bodies and the surrounding neuropil exhibit many of the same features as in the 3-7-day-old opossums. In opossums 21-25 days old, there is an increase in varicosities and irregular contours along many of the dendritic shafts. Furthermore, synaptic terminals, possessing round clear vesicles, now contact the soma, dendritic shafts, dendritic varicosities, spines, and large, flocculent profiles. Terminals containing pleomorphic vesicles or a mixture of clear and large granular vesicles are presynaptic only to dendritic spines or large, flocculent profiles. Neuroglial cell bodies have been identified at all ages examined. It is not until days 65-68 that pre- and postsynaptic elements are organized into synaptic clusters (glomeruli), which are typical of the adult. Spiny appendages and small-diameter dendrites comprise the central core of the clusters which are surrounded by synaptic endings containing a variety of vesicle types. Thus it would appear that subsequent to their initial arrival (day 16-17), the synaptic relationships of cerebellar and midbrain afferents are modified to reflect their adult configuration by days 65-68. This extended period of development (postnatal days 3-68) for the olivary complex provides a good model for assessing the effects of experimental manipulations.

Animals↗
PubMed1978

The synaptic terminations of certain midbrain-olivary fibers in the opossum.

The nuclear origin and distribution of midbrain-olivary fibers has been described in a previous study utilizing axonal transport techniques (Linauts and Martin, '78a). The present report extends their results to the electron microscopic level and details the postsynaptic distribution of such fibers. Lesions within the ventral periaqueductal grey and adjacent tegmentum, the red nucleus or the nucleus subparafascicularis result in electron dense axon terminals within the olive at survival times of 48, 72 and 96 hours. At 72 hours, many degenerating presynaptic profiles shrink, become irregular in shape and are totally or partially surrounded by glial processes. The principal olivary nucleus contains the majority of these profiles. However, the subparafascicular terminals are more abundant in the rostral and intermediate parts of the medial accessory nucleus and the rubral terminals are concentrated within the dorsal lamella of the principal nucleus. The nuclear location of the degenerating terminals was determined by examination of 1 micrometer plastic sections cut in the transverse plane from each block face prior to thin sectioning. Degenerating terminals were counted in three cases, one from each of the three lesion sites described above. When taken together these cases show that just over 50% of the degenerating terminals are presynaptic to spiny appendages and are located within the synaptic clusters (glomeruli) described previously (King, '76). The percentage of degenerating terminals in the glomeruli increases to 70% when the lesion is in the ventral periaqueductal grey and adjacent tegmentum. The remaining degenerating terminals contact dendritic shafts outside the astrocytic boundaries of the synaptic clusters. The synpatic vesicle populations within the degenerating terminals vary with the location of the lesion. Lesions in the ventral periaqueductal grey and the adjacent tegmentum result in the degeneration of terminals with either clear spherical vesicles or endings with both clear spherical vesicles and a variable number of large dense core vesicles. In contrast, the primary degenerative changes that occur after destruction of the red nucleus or the nucleus subparafascicularis are in terminals with clear spherical vesicles. When the synaptic complex was present in the plane of section, regardless of the site of the lesion, the degenerating terminals could be classified as Gray's type I. Thus, we have demonstrated that afferents from the mesencephalon terminate within synpatic clusters located in the principal and medial accessory (part A) subnuclei of the inferior olive. Although the mesencephalic afferents have multiple origins (Linauts and Martin, '78a), many of their synaptic terminals contact spiny appendages within the synaptic clusters. This postsynaptic site also receives cerebellar terminals (King et al., '76). The origin of presynaptic profiles within the synaptic clusters that contain clear pleomorphlic vesicles is yet to be determined.

Animals↗
PubMedDate not supplied

Distribution of neurotensin-like immunoreactivity in rat and cat area postrema.

The distribution of neurotensin-like immunoreactive (NT-LI) fibers and cell bodies in the area postrema (AP) of rat and cat, utilizing the peroxidase, antiperoxidase (PAP) technique, is described. In the rat, the greatest accumulation of NT-LI fibers were present along the borders of the AP, while there were very few NT-LI fibers in central regions. In the cat, scattered NT-LI fibers occupied the majority of the central AP, while moderate numbers of NT-LI fibers were present at the ventromedial border. In more rostral cat AP levels, the number of NT-LI fibers decreased. NT-LI somata were present in rat AP, but were lacking in cat AP. The localization of NT within the AP suggests that the cardiovascular and gastric effects attributed to NT may be mediated, in part, through the AP.

Animals↗
PubMedDate not supplied

Substance P binding sites in the nucleus tractus solitarius of the cat.

Substance P binding sites in the nucleus tractus solitarius were visualized with receptor autoradiography using Bolton-Hunter [125I]substance P. Substance P binding sites were found to have distinct patterns within the cat nucleus tractus solitarius. The majority of substance P binding sites were present in the medial, intermediate and the peripheral rim of the parvocellular subdivisions. Lower amounts of substance P binding sites were present in the commissural, ventrolateral, interstitial and dorsolateral subdivisions. No substance P binding sites were present in the central region of the parvocellular subdivision or the solitary tract. The localization of substance P binding sites in the nucleus tractus solitarius is very similar to the patterns of substance P immunoreactive fibers previously described for this region. Results of this study add further support for a functional role of substance P in synaptic circuits of the nucleus tractus solitarius.

Animals↗
PubMedDate not supplied

Cholecystokinin octapeptide immunoreactivity in the nucleus tractus solitarius of the cat.

The nucleus tractus solitarius possessed distinct patterns of cholecystokinin immunoreactive fibers and cell bodies within its various subdivisions. The commissural, medial, intermediate, parvocellular, dorsolateral and interstitial subdivisions contained relatively dense amounts of CCK immunolabelled fibers. In contrast, CCK immunoreactivity within the ventrolateral subdivision consisted of a few scattered fibers and small neurons. The commissural, intermediate, medial, dorsolateral and parvocellular subdivisions contained CCK immunoreactive neurons following colchicine treatment. The presence of CCK in the NTS suggest that it may be involved as a neuromodulator and/or neurotransmitter in circuitry that mediate cardiovascular, respiratory, gastrointestinal and taste functions.

Animals↗