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Biomedical subjects

B Meister

Publications and source records attributed to B Meister.

At least 91 records · Page 5Linked to original sources
PubMed1994

Reorganization of neural peptidergic systems in the median eminence after hypophysectomy.

Earlier studies have shown the formation of a novel neural lobe after hypophysectomy, an experimental manipulation that causes transection of neurohypophyseal nerve fibers and removal of pituitary hormones. The mechanisms that underly this regenerative process are poorly understood. The localization and number of peptide-immunoreactive (-IR) fibers in the median eminence were studied in normal rats and in rats at different times of survival after hypophysectomy using indirect immunofluorescence histochemistry. The number of vasopressin (VP)-IR fibers increased in the external layer of the median eminence in 5 d hypophysectomized rats. Oxytocin (OXY)-IR fibers decreased in the internal layer and progressively extended into the external layer. At long survival times (9 and 16 months) both VP- and OXY-IR fibers had a bilayered distribution occupying both the external and internal layers. Double-labeling experiments combining VP and tyrosine hydroxylase antisera as well as OXY and growth hormone-releasing factor antisera showed that injured neurosecretory fibers growing into the external layer displaced fibers from parvocellular cells originally located there. As a result, there was essentially an inversion in the distribution of these fibers within the median eminence. Galanin (GAL)- and cholecystokinin (CCK)-IR fibers exhibited a similar pattern of distribution after the lesion. Thus, after 5 d there was an increase in GAL- and CCK-IR fibers in the internal layer. At 14 and 30 d, the number of GAL- and CCK-IR fibers progressively decreased, but after longer survivals (9 and 16 months) there was a dramatic reappearance. Dynorphin (DYN)-LI showed a dramatic increase at all levels of the median eminence at short survival times after hypophysectomy, followed by a subsequent decrease to a final stage of a few, strongly immunoreactive fibers in the external layer at longer survival times. Vasoactive intestinal polypeptide (VIP)- and peptide histidine-isoleucine (PHI)-IR fibers in hypophysectomized animals had already contacted portal vessels 5 d after hypophysectomy, and from then on progressively increased in numbers. Finally, most of the peptide fibers described above formed dense innervation patterns around the large blood vessels along the lateral borders of the median eminence. The present results show that hypophysectomy induces a wide variety of changes in hypothalamic neurosecretory fibers. Not only is the expression of several peptides in these fibers modified following different survival times, but a reorganization of the distribution of immunoreactive fibers within the median eminence is demonstrated. The hypothesis is raised that regeneration of injured neurosecretory fibers may be dependent on changes in the expression of peptides possessing trophic actions.

Animals↗
PubMed1994

Patterns of messenger RNA expression for adrenergic receptor subtypes in the rat kidney.

The distribution of mRNA for the rat alpha-1 A/D, alpha-1B, alpha-2A/D (RG20), alpha-2B (RNG), alpha-2C (RG10), beta-1 and beta-2 adrenergic receptors were studied in the rat kidney using in situ hybridization. After hybridized sections were exposed to autoradiography film or dipped in photographic emulsion and counterstained with hematoxylin and eosin, specific and selective labeling patterns characteristic for each probe in the kidney were observed. Labeling with the probe to the alpha-1A/D receptor was only observed in vessels in the renal parenchyma and in the ureter. Alpha-1B receptor mRNA was demonstrated in the outer and inner stripe of the outer medulla, corresponding to segment S3 of proximal tubules and the thick ascending limb of loop of Henle. Alpha-2A/D receptor mRNA was distributed in the inner stripe of the outer medulla and in the inner medulla, corresponding to collecting tubules, and in the ureter. The strongest signal in the kidney was obtained with the alpha-2B receptor probe, showing labelling in the outer stripe of the outer medulla with tubular rays radiating into the cortex, coinciding with segment S3 of proximal tubules. Weak labeling obtained with the alpha-2C receptor probe was present in the renal medulla. Labeling obtained with the probe to the beta-1 receptor was seen in the entire cortex and to a lesser extent also in the outer medulla. In addition, beta-1 receptor mRNA was shown in perirenal adipose tissue and in the ureter. Labeling obtained with the probe to the beta-2 receptor was demonstrated in the outer and inner stripe of the outer medulla.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Glutamate transporter mRNA and glutamate-like immunoreactivity in spinal motoneurones.

Glutamate is the major excitatory neurotransmitter in the central nervous system. The release of glutamate is terminated by rapid uptake of glutamate into the presynaptic nerve terminals and into surrounding glial cells. Recently, a neuronal glutamate transporter was cloned from rabbit small intestine, thereby providing the possibility to study the distribution of cells that express glutamate transporter mRNA. Using oligonucleotide probes and in situ hybridization, glutamate transporter mRNA was demonstrated in large cell bodies, presumably motoneurones, in the thoracic spinal cord of the rabbit. Immunohistochemical analysis with rabbit polyclonal antibodies to glutamate showed immunoreactivity in the cytoplasm of large cell bodies in the ventral horn, presumably motoneurones, of the rat spinal cord. Glutamate-LI was in addition demonstrated in the motor end plate in hindlimb muscle of the rat, as visualized by double-labelling with mouse monoclonal antibodies to synaptophysin. Taken together, these data raise the possibility that glutamate has a function at the vertebrate neuromuscular junction.

Amino Acid Transport System X-AG↗
PubMed1993

Increased alpha 1B-adrenoreceptor mRNA levels in the rat kidney after thyroidectomy.

Oligonucleotide probes were designed to sequences of the rat alpha 1B- and alpha 2B-adrenergic receptor mRNA and used for in situ hybridization histochemistry on tissue sections of kidneys from control and thyroidectomized rats. Both alpha 1B- and alpha 2B-receptor mRNA labelling was demonstrated in proximal tubule cells in the outer stripe of the outer medulla, with tubular rays radiating into the cortex. Thyroidectomy induced a more than 4-fold increase in mRNA for the alpha 1B-receptor in the kidney, whereas no change in alpha 2B-receptor mRNA levels could be demonstrated in thyroidectomized rats as compared to control animals. The results suggest that thyroid hormone plays an important role in regulating expression of alpha 1B-receptors in renal tubule cells.

Animals↗
PubMed1993

Large calibre primary afferent neurons projecting to the gracile nucleus express neuropeptide Y after sciatic nerve lesions: an immunohistochemical and in situ hybridization study in rats.

Using immunohistochemistry and in situ hybridization, we studied changes in expression of some neuropeptides in large and medium-sized neurons in lumbar 4 and 5 rat dorsal root ganglia projecting to the gracile nucleus, in response to peripheral axotomy. Fourteen days after unilateral sciatic nerve transection, many large neurons and some medium-sized neurons in ipsilateral dorsal root ganglia were strongly neuropeptide Y-positive. Galanin-, vasoactive intestinal polypeptide (VIP)- and peptide histidine-isoleucine (PHI)-like immunoreactivities coexisted with neuropeptide Y-like immunoreactivity in some of these neurons. After axotomy numerous large and medium-sized cells contained neuropeptide Y mRNA in the ipsilateral ganglia, whereas no hybridization was seen in the contralateral or control ganglia. Cross-sectioned, large neuropeptide Y-positive fibres were observed in a somatotopically appropriate zone within the ipsilateral gracile fasciculus. A dense network of neuropeptide Y-immunoreactive, large nerve fibres and terminals was seen in the ipsilateral gracile nucleus. A small number of galanin- and VIP/PHI-like immunoreactive nerve fibres and terminals were also observed in adjacent sections. Neuropeptide Y-like immunoreactivity colocalized with galanin- or VIP/PHI-like immunoreactivity in some nerve fibres. None of these neuropeptide immunoreactivities could be detected in nerve fibres and terminals in the control or contralateral gracile nucleus. These findings suggest that neuropeptides, in addition to their role in small dorsal root ganglion neurons, may have a function in large and medium-sized dorsal root ganglion neurons projecting to laminae III and IV in the dorsal horn as well as to the gracile nuclei, as a part of their response to peripheral axotomy.

Afferent Pathways↗
PubMed1993

Oxytocin modulates the effects of galanin in carrageenan-induced hyperalgesia in rats.

In the present study we have investigated the effects of galanin and/or oxytocin on carrageenan-induced hyperalgesia, the relationship between oxytocin and galanin-containing nerve fibers in the spinal cord and the influence of galanin on oxytocin secretion. Galanin (1 microgram) given intrathecally (i.t.) decreased significantly the mechanical nociceptive threshold of the carrageenan-treated hindpaw, with no significant effect on thermal nociception. The decrease in the mechanonociceptive threshold exerted by galanin was modulated by oxytocin (1 microgram, i.t.) administered simultaneously. There was a close relationship between galanin- and oxytocin-immunoreactive fibers in the dorsal horn of the thoracic spinal cord, although there was no evidence for colocalization. Galanin 0.1 and 1 microgram given intracerebroventricularly or intraperitoneally significantly decreased the oxytocin level in plasma 60 min after injection. Taken together, these data indicate that galanin may contribute to mechanical hyperalgesia by inhibiting the release of oxytocin from nerve terminals in the spinal cord and that oxytocin may be a potential analgesic agent.

Animals↗
PubMed1993

[Transporters for neurotransmitters. A new gene family with characteristic features].

Neurotransmitter transporters terminate synaptic transmission by rapid sodium-dependent reaccumulation of released transmitter in the presynaptic nerve terminal. The transporters are major sites of action for psychostimulants such as amphetamine and cocaine, for antidepressants, and for neurotoxins that induce parkinsonism. The transporters for monoamines, choline, GABA (gamma-aminobutyric acid), glycine and glutamine have recently been cloned and characterised. Elucidation of the primary structures has shown that, with the exception of the glutamate transporter, the various proteins manifest substantial amino acid conservation and the presence of 12 putative transmembrane regions. The lack of homology with other proteins suggests these transporter proteins to represent a new gene family. Preliminary findings suggest the distribution of neurotransmitter gene expression to match that of presynaptic markers of the respective transmitter systems, though in some areas the distribution of transporter mRNA expression has been found to be uneven. There is evidence suggesting neurotransmitter transporters to be involved in the pathophysiology of certain neurodegenerative diseases, and there are indications that drugs affecting transporter proteins may assume increasing clinical importance.

Carrier Proteins↗
PubMed1993

Interleukin-3, interleukin-6, granulocyte-macrophage colony-stimulating factor and erythropoietin cord blood levels of preterm and term neonates.

The cascade of known haematopoietic growth factors controlling granulomonopoiesis and erythropoiesis includes interleukin-3 (IL-3), interleukin-6 (IL-6), granulocyte-macrophage colony-stimulating factor (GM-CSF), and erythropoietin (EPO). Elevated endogenous IL-3 and IL-6 cord blood levels in infection-free premature and mature neonates may reflect their possible role for expansion of haematopoietic progenitor cells, granulocytes and monocytes. Within the erythroid lineage a synergistic action of IL-3, IL-6 and EPO can be assumed. To identify the regulatory role in fetal haematopoietic expansion cord blood plasma levels of these haematopoietic growth factors were assessed in 19 premature and 20 mature infants using commercial enzyme-linked immunosorbent assay and enzyme-amplified sensitivity immuno assay test kits. Peripheral blood IL-3, GM-CSF and EPO were studied in 5 and 10 premature infants respectively. Compared with cord blood levels we found a decline in EPO levels but no decrease of IL-3 and GM-CSF during the 1st month of life. We conclude that postnatal decrease in plasma burst-promoting activity levels in preterm infants is mainly explained by low postnatal EPO levels.

Erythropoietin↗
PubMed1993

Gene expression and chemical diversity in hypothalamic neurosecretory neurons.

Hypothalamic neurosecretory neurons transcribe, translate, store, and secrete a large number of chemical messengers. The neurons contain hypothalamic signal substances that regulate the secretion of anterior pituitary hormones as well as the neurohypophysial peptides vasopressin and oxytocin. In addition to the classical hypophysiotropic hormones, a large number of neuropeptides and classical transmitters of amine and amino acid nature are present in the same cells. This is particularly evident in the magnocellular neurons of the supraoptic and paraventricular nuclei, and in parvocellular neurons of the arcuate and paraventricular nuclei. The changes in gene expression induced by experimental manipulations and the colocalization chemical messengers in hypothalamic neurosecretory neurons and its possible significance is summarized in this review.

Animals↗
PubMed1993

Cellular expression of angiotensin type-1 receptor mRNA in the kidney.

Angiotensin II has multiple renal effects that are important in the regulation of renal hemodynamics and electrolyte secretion, and binding sites for angiotensin II have been demonstrated in different cells of the kidney. In the present study the cellular localization of mRNA for the angiotensin type 1 (AT1) subtype of the angiotensin II receptor was studied in adult rat kidney using a cRNA probe and in situ hybridization. Strong labeling was demonstrated in tubule cells of the inner and outer stripe of the outer medulla. In emulsion-dipped sections, counter-stained with hematoxylin-eosin, labeling was identified in segment S3 of proximal tubules and in the thick ascending limb of loop of Henle (mTAL). The results suggest expression of AT1-receptor mRNA with a distinct compartmentalization within the nephron.

Animals↗
PubMed1993

Distribution of dopamine- and cAMP-dependent phosphoprotein (DARPP-32) in the developing and mature kidney.

DARPP-32 is a dopamine- and cAMP-regulated inhibitor of protein phosphatase-1 (PP-1). Dopamine and DARPP-32 regulate sodium reabsorption in renal tubules by inhibiting the activity of Na+,K(+)-ATPase. We here report the pre- and postnatal distributions of DARPP-32 in the kidney as demonstrated by immunoblotting and immunohistochemistry. With immunoblotting we examined the abundance of DARPP-32 and the functionally similar but more widespread inhibitor of PP-1, inhibitor-1 (I-1). We compared their relative abundance in the renal cortex, renal medulla and neostriatum from the brain, where DARPP-32 is greatly enriched. DARPP-32 levels in the adult rat were fourfold higher in the neostriatum than in the renal medulla and 13-fold higher than in the renal cortex. I-1 levels were approximately the same in the neostriatum and in the renal medulla and 2.5-fold higher in neostriatum than in the renal cortex. Between postnatal day 10 (PN10) and 40 (PN40) DARPP-32 abundance increased 1.3-fold in the neostriatum, 1.4-fold in the renal cortex and sixfold in the medulla. The abundance of I-1 did not increase in the striatum from PN10 to PN40 but increased 1.5-fold in the renal cortex and threefold in the renal medulla. Thus, during the time of maturation of tubular transport function, the levels of both PP-1 inhibitors increased in the kidney, the largest increase being found in the renal medulla. With immunohistochemistry strong DARPP-32-like-immunoreactivity (DARPP-32-LI) was detected in the ureteral buds from gestational day 18 and up to postnatal day 8 when nephrogenesis was completed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Catechol-O-methyltransferase mRNA in the kidney and its appearance during ontogeny.

Catechol-O-methyltransferase (COMT), primarily present as a soluble cytosolic form (S-COMT), inactivates catechols. The recent cloning of the rat and human S-COMT from placenta has allowed us to synthesize complementary oligonucleotide probes to study the localization of COMT mRNA during development in the rat kidney and in the adult human kidney using in situ hybridization histochemistry. In the adult rat kidney, COMT mRNA was detected in segment S3 of proximal tubule cells in the outer stripe of the outer medulla, and thick ascending limb of loop of Henle (TAL) in the inner stripe. COMT mRNA was detected in the prenatal rat kidney as early as on day 18. In the human kidney, strong hybridization signal was seen in the medulla and in tubule segments of the cortex. In the adult rat kidney, COMT mRNA was in addition demonstrated in the transitional epithelium of the ureter. The results suggest synthesis of COMT and inactivation of catechols along the distal parts of proximal tubules, in TAL cells, and in the epithelium of the ureter.

Aging↗
PubMed1993

Effect of galanin on plasma levels of oxytocin and cholecystokinin.

Galanin, oxytocin and cholecystokinin (CCK) are peptides that influence feeding behaviour. Galanin has been found to stimulate food intake and oxytocin and CCK have been suggested to be satiety agents. The present study was performed in order to investigate if galanin influences the secretion of oxytocin and CCK as a possible indication of a functional relationship between these peptides with respect to their influence on feeding behaviour. Galanin (0.1 and 1 micrograms) was administered intracerebroventricularly (i.c.v.) and intraperitoneally (i.p.) to anaesthetized rats and blood samples were collected 20 and 60 min after administration. Plasma levels of oxytocin and CCK were measured with radioimmunoassay. Galanin, 0.1 and 1 microgram, caused a significant decrease in oxytocin levels after 60 min, both when administered i.c.v. and i.p. In contrast, CCK levels increased following i.c.v. and also i.p. galanin. The possible mechanisms by which galanin causes a decrease in oxytocin and an increase in CCK levels are discussed.

Animals↗
PubMed1993

Galanin stimulates the release of cholecystokinin from nerve fibres in the pituitary neurointermediate lobe.

Galanin (GAL), a 29 amino acid peptide, is present in magnocellular neurones in the paraventricular and supraoptic nuclei with projections to the neurohypophysis. The effect of GAL on the release of vasopressin, oxytocin and cholecystokinin (CCK) from rat neural lobes was investigated using an in vitro method. GAL in a concentration of 10(-6) M did not affect basal or K(+)-induced release of vasopressin or oxytocin. In contrast, GAL (10(-6) M) significantly stimulated basal and K(+)-stimulated release of CCK. Double-labelling immunofluorescence histochemistry of the neurohypophysis showed that GAL-immunoreactive (-IR) fibres co-contained vasopressin-like immunoreactivity (-LI), whereas the majority of oxytocin-IR fibres were CCK-IR. There was no evidence for colocalization of GAL with CCK or oxytocin. The data suggest a stimulatory role of GAL on CCK release via a paracrine effect on neighbouring oxytocin-CCK-containing nerve fibres.

Animals↗
PubMed1993

Dopamine transporter mRNA in neurons of the rat hypothalamus.

The membrane-bound dopamine transporter (DAT) protein terminates dopaminergic neurotransmission by rapid reaccumulation of dopamine into presynaptic nerve endings. The distribution of neurons expressing DAT mRNA was investigated in the rat hypothalamus using in situ hybridization histochemistry and oligonucleotide probes to sequences of rat DAT mRNA. DAT mRNA-containing cell bodies were demonstrated in the ventral aspect of the periventricular nucleus (A14 dopamine cell group), in the zona incerta (A13), in the dorsomedial part of the arcuate nucleus (A12), and in scattered regions of the posterior hypothalamus. There was no labelling in magnocellular neurons of the supraoptic or paraventricular nuclei, or in neurons of the ventrolateral division of the arcuate nucleus, areas previously shown to contain the dopamine-synthesizing enzyme tyrosine hydroxylase. The results suggest that hypothalamic dopamine neurons have an active uptake mechanism for dopamine, however, that DAT mRNA levels may be considerably lower than those encountered in the ventral midbrain.

Animals↗
PubMed1993

Molecular mechanisms involved in catecholamine regulation of sodium transport.

The catecholamines dopamine and norepinephrine, play a central role in the regulation of sodium homeostasis and blood pressure. Dopamine inhibits tubular Na+, K(+)-ATPase activity and increases sodium excretion. Norepinephrine stimulates Na+, K(+)-ATPase activity and decreases urinary sodium excretion. The signaling pathway by which these two opposite first messengers regulate Na+, K(+)-ATPase activity involves the dopamine-specific protein phosphatase-1 inhibitor, DARPP-32, and the norepinephrine-activated protein phosphatase-2B, calcineurin. Aberrations in the renal dopamine/norepinephrine system may be the cause of alterations in the regulation of sodium excretion during ontogeny and in salt-sensitive hypertension.

Animals↗