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B M Chronwall

Publications and source records attributed to B M Chronwall.

At least 55 records · Page 3Linked to original sources
PubMed1988

Rat intermediate lobe in culture: dopaminergic regulation of POMC biosynthesis and cell proliferation.

The effects of the selective D-2 selective agonist, quinpirole, on biosynthesis of proopiomelanocortin (POMC) and cell proliferation rate of cultures of rat intermediate lobe (IL) have been examined. Primary cultures of rat IL were prepared by mechanically dispersing IL lobules in medium. Following a six day incubation, approximately 25% of the cells settled onto the culture plate and began to extend into a monolayer. Quinpirole markedly reduced immunoreactive beta-endorphin levels in the medium and POMC mRNA in both the attached and floating lobules. The incorporation of 35S-methionine into 32 kDa POMC, a 18-22 kDa complex of proteins, a 16 kDa protein and a 15 kDa protein was decreased significantly in both the attached and floating lobules. In contrast, the proliferation in the floating, but not the attached, cells was inhibited by quinpirole. The floating IL lobule appears to provide a reasonably faithful model of the dopaminergic regulation of IL function in vivo, while the attached IL cells may provide an interesting tool to study the regulation of IL cell proliferation.

Animals↗
PubMed1988

Rat intermediate lobe in culture: a histological and biochemical characterization.

The histology, immunohistochemistry, peptide synthesis and secretion as well as proliferation rate of rat intermediate lobe (IL) were studied in primary cultures. The cultures contained two populations of cells: melanotrophs either organized in free floating lobules or in lobules which attached to the dishes and formed a monolayer. Both populations retained their in vivo morphology: polyhedral cells with smooth, ovoid nuclei and a large number of cytoplasmic secretory coated vesicles, a well developed Golgi apparatus, abundant mitochondria and extensive areas of rough endoplasmic reticulum. The melanotrophs stained with varying intensity for alpha-MSH and in situ hybridization showed the presence of pro-opiomelanocortin (POMC) mRNA. 35S-methionine incorporation combined with 2-D gel electrophoresis demonstrated POMC peptide synthesis and radioimmunoassay confirmed its secretion into the medium. 3H-thymidine uptake in the attached melanotrophs was considerably higher than that in the free-floating melanotrophs, demonstrating the dependency of proliferation rate on the cytoarchitecture of the explant. The retention of melanotroph morphology, biosynthetic and proliferative capacity in vitro affords a valid model system for studying POMC gene expression.

Animals↗
PubMed1988

Dopaminergic regulation of the biosynthetic activity of individual melanotropes in the rat pituitary intermediate lobe: a morphometric analysis by light and electron microscopy and in situ hybridization.

The primary cell type of the intermediate lobe (IL) of the rat pituitary is a polyhedral secretory cell with a smooth ovoid nucleus. The results of this study demonstrate, however, that IL melanotropes are a heterogeneous cell population. Melanotropes differed in the tinctorial properties of their cytoplasm; some cells appeared distinctly darker, others lighter, and cells staining in intermediate shades were also found. Electron microscopical morphometry revealed that darkly staining melanotropes have a denser cytosol and contain a greater amount of rough endoplasmic reticulum, mitochondria, and secretory vesicles than light cells. In addition, in situ hybridization studies, using a POMC probe, showed that POMC mRNA was distributed unevenly among melanotropes in a pattern comparable to the distribution of light and dark cells. These studies further demonstrated that dopaminergic drug treatments, which are known to alter the secretion of POMC-related peptides from the IL, produced parallel changes in both the histological staining properties and the amount of POMC mRNA per cell. Haloperidol treatment dramatically increased the number of dark melanotropes and the amount of POMC mRNA in each cell and eliminated the cellular heterogeneity in both staining properties and the distribution of POMC mRNA. After bromocriptine treatment the number of light melanotropes increased, and each cell contained reduced levels of POMC mRNA. These findings indicate that individual melanotropes maintain different levels of biosynthetic activity and that treatments that alter the secretion of POMC peptides affect both the rate of POMC synthesis in individual melanotropes and the cellular heterogeneity of the IL.

Animals↗
PubMed1987

Localization of neuropeptide Y messenger ribonucleic acid in rat and mouse brain by in situ hybridization.

The distribution of neuropeptide Y (NPY) messenger ribonucleic acid (mRNA) in the rat and mouse brain has been examined. A 28-mer oligonucleotide probe complementary to a distinctive region of NPY mRNA was 3'-end labeled with [35S]-deoxycytosine triphosphate ([35S]-dCTP) by using terminal transferase and was hybridized to fixed sections of rat and mouse brain. The hybridization of the labeled probe to the mRNA in the tissue section was then detected autoradiographically. A strong hybridization signal was seen corresponding to the arcuate nucleus of the hypothalamus. Scattered NPY-mRNA-containing cell bodies were seen throughout the cerebral cortex. Experiments which compared the distribution of NPY mRNA with immunohistochemically detected NPY indicated a similar distribution in the arcuate nucleus of the hypothalamus and cerebral cortex. These results indicate that active transcription of the NPY gene occurs within the brain and this transcription takes place in NPY-containing cell bodies.

Amino Acid Sequence↗
PubMed1987

Immunocytochemical localization of factor VIII-related antigen in tumors of the human central nervous system.

Using both immunohisto- and immunocytochemical techniques with periodate-lysine-paraformaldehyde (PLP) fixation, we have studied the distribution of Factor VIII-related antigen (FVIIIR:Ag) in 12 cases of tumors of the human central nervous system (CNS) and one sample of non-tumor brain tissue. FVIIIR:Ag was found both extracellularly and intracellularly. It was localized in the vascular lumen, between endothelial cells, and in the endothelial cell basement membrane. In the endothelial cell cytoplasm, FVIIIR:Ag was found in the endoplasmic reticulum, perinuclear space, and in intracytoplasmic vacuoles and vesicles. Characteristic of malignant tumors (six out of seven) was a strongly-positive dilated endoplasmic reticulum. This may reflect increased FVIIIR:Ag synthesis in the endothelial cells of malignant tumors. Only one of five benign tumors showed such staining. Six of 12 tumors and the non-tumor brain showed perinuclear FVIIIR:Ag. Both ad- and abluminal vesicles in the tumor endothelial cells contained FVIIIR:Ag suggesting that endocytosis, transcellular transport, and/or endocytosis, as well as FVIIIR:Ag synthesis occurs. The non-tumor brain showed normal capillary structure and very little FVIIIR:Ag immunoreactivity. The relationship of these FVIIIR:Ag abnormalities to the hypercoagulable state seen in some malignant brain tumor patients remains to be clarified.

Antigens↗
PubMed1987

Histological evaluation of the dopaminergic regulation of proopiomelanocortin gene expression in the intermediate lobe of the rat pituitary, involving in situ hybridization and [3H]thymidine uptake measurement.

The melanotroph, a polyhedral secretory cell with an ovoid smooth nucleus, is the primary cell type of the intermediate lobe (IL) of the rat pituitary. The melanotrophs are not uniform, but differ in the tinctorial properties of their cytoplasm; some cells appear distinctly darker, others lighter, and cells staining in intermediate shades are also found. In addition, in situ hybridization using proopiomelanocortin (POMC) probes shows an uneven distribution of POMC mRNA among melanotrophs, indicating that different cells maintain different levels of biosynthetic activity. Dopaminergic drugs known to alter the secretion of POMC-related peptides from the IL produced parallel changes in histological staining properties and the amount of POMC mRNA per cell, as determined by in situ hybridization. Acute bromocriptine treatment (6 h) produced a dramatic reduction in grain counts over melanotroph cytoplasm (to 10% of the control levels). A similar reduction persisted after chronic treatment. Six hours after a single haloperidol injection, the grain counts were 180% of control levels. After chronic haloperidol treatment, they were further elevated to 300% of control levels. Chronic bromocriptine and haloperidol treatment also changed the thickness of the IL. Bromocriptine reduced and haloperidol treatment increased the number of cell layers in the IL by changing the rate of cell proliferation. Thus, haloperidol treatment significantly increased and bromocriptine treatment significantly decreased the number of melanotrophs labeled by [3H]thymidine. The mitotic index followed the same trend. These results suggest that dopamine regulation of the IL acts by two different mechanisms: POMC gene expression and cellular proliferation. The change in POMC gene expression is the cell's first rapid response. The influence on the cell cycle appears after subchronic and chronic treatment.

Animals↗
PubMed1987

Products of cells cultured from gliomas. VI. Immunofluorescent, morphometric, and ultrastructural characterization of two different cell types growing from explants of human gliomas.

Explants derived from human gliomas have been characterized with respect to their cellular outgrowth pattern after 1-22 weeks in culture. A mat of cells which were fibronectin (FN)-positive and glial fibrillary acidic protein (GFAP)-negative (hereafter designated FN+ cells) with a polygonal, flat morphology covered the growth substrate in a swirling pattern for a mean diameter of 9.2 mm around FN+ explants. FN+ cells showed ruffled plasmalemma, dilated rough endoplasmic reticulin (RDR), and extracellular filamentous strands. Rare desmosomes were compatible with at most minor leptomeningeal components or differentiation. FN+ cells predominated in six of seven cultures at passage 2, and their features were the same from various high-grade gliomas and gliosarcoma. Around other explants, elongated or stellate cells which were GFAP+ and FN- grew in a netlike pattern with little cell-to-cell contact. These GFAP+ cells surrounded explants at a mean diameter of 2 mm, substantially less than FN+ cells (P less than 0.005), and they grew more slowly than FN+ cells around explants. GFAP+ cells had an area/perimeter ratio which was less than that of FN+ cells. GFAP+ cells contained abundant intracellular filaments, rare desmosomes, and narrow RER cisternae. In mixed explants, GFAP+ cells often grew on top of FN+ cells. Individual cells which stained for both GFAP and FN were evident only from one glioma (8% doubly positive). Cells negative for both proteins resembled FN+ cells morphologically. Frozen sections of original glioma tissue showed FN+ vessel walls and GFAP+ parenchyma. Results are evidence for very early overgrowth of a preexistent FN+ cell type distinct from the GFAP+ parenchymal cell. The features of this distinct cell type are mesenchymal and resemble the proliferating vascular elements of gliomas in situ. The tendency for GFAP+ cells to grow on top of these FN+ cells suggests a feeder layer interaction. More knowledge of the origins and interactions of these two cell types may increase our understanding of the mechanism of antigenic changes in gliomas and may provide clues to improved therapeutic approaches.

Antigens, Neoplasm↗
PubMed1986

Localization of proopiomelanocortin mRNA in functional subsets of neurons defined by their axonal projections.

In situ cDNA:mRNA hybridization is a technique that has been developed for the visualization of cDNA:mRNA hybrids in individual cells. To use this technique to answer questions of regulation in heterogeneous populations of cells in the brain, it must be combined with other procedures allowing for the identification of functional subgroups of neurons. We report here a procedure by which in situ cDNA:mRNA hybridization may be combined with retrograde axonal tracing using the fluorescent tracer fast blue. Using this technique, it now becomes possible to measure mRNA regulation in functional subsets of cells defined by their axonal projections.

Animals↗
PubMed1985

Deafferentation causes a loss of presynaptic bombesin receptors and supersensitivity of substance P receptors in the dorsal horn of the cat spinal cord.

Bombesin (BN)- and substance P (SP)-containing neurons are found in the dorsal root ganglia, and project to the dorsal horn of the spinal cord. The present study was undertaken to determine if chronic deafferentation of the cat spinal cord would affect BN or SP receptors in the spinal cord. Ten and 30 days after a unilateral lumbosacral dorsal rhizotomy, BN and SP receptor binding was evaluated autoradiographically using iodinated ligands to bind to these receptors in vitro. The normal distribution of BN receptors detected by this method was restricted to the head of the dorsal horn. Deafferentation caused a 38% and 22% decline in BN receptor binding in laminae I-IV at 10 or 30 days postoperatively, respectively. These data suggest that 'presynaptic' BN receptors are found on the central nervous system terminals of primary sensory afferents. Normal SP receptor distribution was most dense in lamina X, not in the superficial laminae of the dorsal horn. Deafferentation caused an initial decline in SP receptor binding in laminae I-II, followed by a 14% increase at 30 days in comparison to the unoperated side of the spinal cord. This delayed supersensitivity of SP receptors was confirmed in a separate experiment using a homogenate binding assay. These data are discussed with respect to the potential roles of receptor supersensitivity or subsensitivity in the development of deafferentation-induced changes in reactivity of dorsal horn neurons to nociceptive and non-nociceptive stimuli.

Afferent Pathways↗
PubMed1985

Biochemical and histochemical characterization of ranatensin immunoreactive peptides in rat brain: lack of coexistence with bombesin/GRP.

An antibody to des-pyroglutamyl ranatensin (RT 2-11) has been prepared and has been used to histochemically and biochemically identify ranatensin-like immunoreactivity (irRT) in the rat brain. The most most prominent stained cell group was situated in the dorsal tegmental pons. Areas of immunoreactive fibers were found in the ventral hippocampus, septal area and the hypothalamus. A similar distribution was found by radioimmunoassay data. The distribution of irRT was compared to that of bombesin-like immunoreactivity (irBN). The two peptides have different though partly overlapping distributions. Gel filtration of brain extracts show that the molecular size of irRT is similar to that of synthetic RT. However, HPLC characterization of irRT indicated that the immunoreactive material is different from synthetic RT and also different from irBN and irGRP. These results indicate the presence of two separate peptide systems, one RT-like, the other BN-like, in the mammalian CNS.

Animals↗
PubMed1985

Anatomy and physiology of the neuroendocrine arcuate nucleus.

The arcuate nucleus surrounds the ventral part of the third ventricle and contains densely packed small neurons with 1-3 dendrites. At least fifteen transmitters and neuropeptides have been found in perikarya of arcuate neurons. Each transmitter and neuropeptide have a characteristic distribution. In many cases distributions overlap (for example, dopamine and somatostatin, dopamine and neurotensin, neuropeptide Y and somatostatin) and alpha-MSH and beta-endorphin seem to have identical distributions but there are also distinctive neuronal populations containing only one of the described transmitters or neuropeptides (neuropeptide Y and alpha-MSH). Studies show extensive colocalization of dopamine and neurotensin and sparse colocalization of dopamine and GABA, neuropeptide Y and FMRF-NH2 and neuropeptide Y and somatostatin. Colocalization does not seem to be the rule in the arcuate, however, it is possible that colocalization may vary with the physiological state or sex of the animal. It also should be noted that our techniques may not be sensitive enough. To study efferent projections as a possible organizing principle within the arcuate, retrograde fluorescent tracing was combined with transmitter and neuropeptide immunohistochemistry. Mainly NPY and alpha-MSH neurons were studied and both peptides are present in projections to the preoptic area as well as to the midbrain periaqueductal gray. Some arcuate neurons were found to have collateral axons to both these areas. The arcuate communicates primarily with the pituitary gland, hypothalamus, limbic system, midbrain periaqueductal gray and autonomic nuclei of the brain stem. In this way, the arcuate may be involved in integrating emotional, sensory, vegetative homeostatic and autonomic functions with endocrine functions.

Animals↗
PubMed1985

Pancreatic polypeptide immunoreactivity in rat brain is actually neuropeptide Y.

Radioimmunoassay was combined with high pressure liquid chromatography and immunohistochemistry to establish the identity of pancreatic polypeptide-like immunoreactive material in the central nervous system of the rat. Antisera to avian pancreatic polypeptide, bovine pancreatic polypeptide, the invariant amidated carboxyterminal hexapeptide fragment of mammalian pancreatic polypeptides and the structurally related peptide, neuropeptide Y, were used immunocytochemically to localize neurons containing immunoreactive pancreatic polypeptide-like material in rat brain. Adjacent brain sections stained by the indirect immunofluorescent technique and single sections from double-staining experiments demonstrated that identical fibers and perikarya stained for pancreatic polypeptide-like immunoreactive material by antisera directed against each of the four peptides. Characterization of pancreatic polypeptide-like immunoreactive material in chromatographed rat brain extracts by radioimmunoassay using antisera to either neuropeptide Y or the carboxy-terminal portion of the pancreatic polypeptide molecule revealed that the major peak of immunoreactive material, as measured by either assay, appeared to co-elute with synthetic porcine neuropeptide Y. A minor peak of immunoreactive material co-eluting with peptide YY standard was indicated by the neuropeptide Y radioimmunoassay. This was contrasted by data obtained from chromatographic profiles of rat pancreas, which showed that the main immunoreactive peak, as measured by the neuropeptide Y assay, co-eluted with porcine peptide YY, with a minor peak co-eluting with porcine neuropeptide Y. The main peak of immunoreactive material in pancreas, as measured by the pancreatic polypeptide carboxy-terminal radioimmunoassay, eluted considerably earlier than standard peptide YY, neuropeptide Y and bovine pancreatic polypeptide, and is probably identical to rat pancreatic polypeptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The anatomy of neuropeptide-Y-containing neurons in rat brain.

The distribution of neuropeptide Y in the central nervous system of adult male rats was investigated using indirect immunofluorescence, the peroxidase-antiperoxidase technique and by radioimmunoassay of microdissected brain regions. The different methods were in good agreement and showed that neuropeptide Y had a widespread distribution and was present in extremely high concentrations. The highest concentrations of neuropeptide Y were found in the paraventricular hypothalamic nucleus and hypothalamic arcuate nucleus, which also contained the highest density of immunoreactive fibers and numbers of perikarya, respectively. The suprachiasmatic nucleus, median eminence, dorsomedial hypothalamic nucleus and paraventricular thalamic nucleus showed high concentrations as well as high densities of fibers. Moderate concentrations were found in the bed nucleus of the stria terminalis, although a high density of fibers was found. Areas with moderate concentrations and densities of fibers were the medial preoptic area, anterior hypothalamic area, periventricular nucleus, posterior hypothalamus and the medial amygdaloid nucleus. The nucleus of the solitary tract contained a low concentration of neuropeptide Y although a high number of immunoreactive perikarya was found in colchicine-treated rats. Low concentrations were also measured in the cerebral cortex, yet relatively high numbers of cell bodies and fibers were found dispersed through the cortex. The extremely high concentrations and widespread distribution of neuropeptide Y in the central nervous system suggests a number of important physiological roles for this neurotransmitter candidate.

Animals↗
PubMed1984

Coexistence of neuropeptide Y and somatostatin in rat and human cortical and rat hypothalamic neurons.

The distribution and coexistence of neuropeptide Y (NPY) and somatostatin (SOM) were evaluated in rat and human cerebral cortex and in the rat hypothalamic arcuate nucleus (n) using double immunofluorescent staining in which primary antisera were raised in different species. The results of the study indicate extensive coexistence of NPY and SOM in both rat and human cortex but only occasional coexistence in the rat arcuate n.

Adult↗
PubMed1984

Development of GABAergic neurons in rat visual cortex as identified by glutamate decarboxylase-like immunoreactivity.

The development of glutamate decarboxylase (GAD)-like immunoreactivity was studied in albino rats. GAD-positive structures appeared and accumulated in a characteristic temporo-spatial sequence: from embryonic day 18 onwards in lamina (L) I and subplate; after birth in L I-II, L IV-V and deep L VI including white matter; after two weeks in superficial L I, L II to L III-IV border, L V and L VI-white matter. GAD-positive axon varicosities formed perisomatic 'baskets' on L V pyramids on postnatal day 8 and a few days later on those L II-III. During the third week GAD-positive structures attained adult densities and established different laminar patterns in the primary and secondary visual areas.

Animals↗
PubMed1984

A role for bombesin in sensory processing in the spinal cord.

Bombesin (BN)-containing neuronal processes were demonstrated in laminae I and II of the dorsal horn of the cat, rat, and mouse spinal cord by immunocytochemistry and radioimmunoassay. Dorsal rhizotomy in the cat resulted in a marked decrease in BN immunoreactivity in the dorsal horn indicating that BN is contained in primary sensory afferents. BN-binding sites were also localized in superficial laminae of the dorsal horn. The presence of both BN and BN-binding sites in the dorsal horn suggested that BN may be involved in sensory processing in the spinal cord. Consistent with this hypothesis, it was demonstrated that an injection of BN into the spinal cord caused a biting and scratching response indicative of sensory stimulation. The effect was similar to that observed after injection of substance P into the cord with the exception that the BN effect lasted about 100 times longer than that induced by substance P. Taken together, these data indicate that BN may be a neurotransmitter of primary sensory afferents to the spinal cord.

Afferent Pathways↗