bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunocytochemistry of Amino‐Acids in the Rodent Pituitary Using Extremely Specific, Very High Titre Antisera
Authors: Pow D. V. 
Published: September 2006

AbstractThe compartmental interrelationships of the metabolically related amino‐acids glutamate, GABA and glutamine and the metabolically unrelated amino‐acids taurine and glycine in the rodent pituitary, were investigated by light microscopic immunocytochemistry using highly specific antisera. Glutamate‐like immunoreactivity was abundant in astrocytes in the posterior pituitary. Glutamine immunoreactivity was present only at low levels in the posterior pituitary, but was abundant in astrocytes within the intermediate lobe. Other glia‐like ceils in the anterior pituitary were also glutamine‐immunoreactive. GABA immunoreactivity was abundant in the intermediate lobe but absent from anterior and posterior lobes. The GABA immunoreactivity mainly took the form of small punctata, the majority of which were in intimate apposition to the glutamine‐immunoreactive glia. Strong taurine immunoreactivity was present in astrocytes in the posterior pituitary but only weak labelling was present in intermediate and anterior lobes of the pituitary. Specific glycine immunoreactivity was not detected in the pituitary. These results suggest that glutamate‐immunoreactive astrocytes in the posterior pituitary, unlike glia in loci such as the retina, do not convert much, if any, of their glutamate content into glutamine (or if they do, it is rapidly further metabolized to another compound), whereas those astrocytes in the intermediate lobe do contain glutamine. The spatial association of GABAergic fibres with glutamine‐positive astrocytes raises the possibility that astrocytes in the intermediate lobe receive a GABAergic innervation. Glutamate, glutamine and taurine (or their metabolites) may have roles as neuroactive substances regulating pituitary secretion.
Androgenic Regulation of Expression of β‐Tubulin Messenger Ribonucleic Acid in Motoneurons of the Spinal Nucleus of the Bulbocavernosus
Authors: Matsumoto Akira , Arai Yasumasa , Hyodo Susumu 
Published: September 2006

AbstractExpression of β‐tubulin mRNA was examined in androgen‐sensitive motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in adult male rats by in situ hybridization histochemistry using cDNA encoding mouse β‐tubulin. Hybridizable β‐tubulin mRNA was localized in the somata and proximal dendrites of SNB motoneurons. Removal of androgen by castration significantly reduced the expression level of β‐tubulin mRNA in the SNB motoneurons, whereas the change was prevented by testosterone treatment. On the contrary, castration or testosterone treatment did not induce any changes in the expression level of β‐tubulin mRNA in the androgen‐insensitive motoneurons of the retrodorsolateral nucleus. These results suggest that androgen regulates the expression of β‐tubulin gene in the SNB motoneurons and may provide evidence for the molecular mechanisms of hormonally‐induced neuronal plasticity in the SNB motoneurons.
The Adenylyl Cyclase‐Cyclic AMP System Modulates Morphological and Functional Development of Hypothalamic β‐Endorphin Neurons in Culture
Authors: Yang Zhiyu , Huang Weiqing , Lee Dan , Copolov David L. , Lim Alan T. 
Published: September 2006

AbstractIn rats, opioidergic β‐endorphin (βEP1–31) is produced and released from neurons of arcuate nuclei in the hypothalamus. Although the neuropeptide has been implicated in sexual maturation and stress‐induced reproductive dysfunction, the intra‐hypothalamic regulation of βEP neurons remains unclear. Employing long‐term monolayer cultures of neonatal rat hypothalamic cells, we report here that 4 days of treatment with 10 μM forskolin increased approximately 3‐fold (P<0.01) the proportion of immunoreactive (ir)‐ βEP positive neurons bearing neurites. In addition, treatment of forskolin also enhanced ir‐βEP release (634 ± 59 pg/well; mean β SE, n = 4, P<0.01) by 14‐fold and ir‐βEP content (119±13 pg/well; P<0.01) by 2‐fold above that of vehicle‐treated cultures; in both instances, the EC50 and the Emax, of forskolin were approximately 10μM and 100 μM, respectively. The forskolin‐stimulated release of ir‐βEP was mimicked by cholera toxin and (Bu)2cAMP treatment in a dose‐related manner, but not by pertussis toxin. Although by itself 3‐isobutyl‐1‐methyl‐xanthine (100μM) only doubled ir‐βEP secretion, it markedly potentiated the stimulatory effect of forskolin. This forskolin‐induced stimulation was reversible and in cultures re‐exposed to the same drug within the first 24 h period, there was a marked increase in the stimulated release of ir‐βEP (P < 0.05); re‐challenge of forskolin at later stages, however, induced a smaller but significant secretion of ir‐βEP (P<0.01) compared to that of vehicle‐treated control cultures. Sephadex G‐50 gel Chromatographie profile of the media prepared from forskolin‐treated cultures revealed a major ir‐βEP peak of 3 K M. Highperformance liquid chromatography analysis showed that ir‐βEP of the 3 K M, species was eluted with a retention time similar to that of synthetic rat βEP1–31. We thus conclude that the adenylyl cyclase‐cAMP system plays an important role in the modulation of βEP1–31 production and release from hypothalamic βEP neurons in culture. Furthermore, the functional responsiveness and the orphological development of these neurons are affected, at least in part, by the intrinsic activity of the adenylyi cyclase‐cAMP system.
Ultrastructural Evidence for Changes in Synaptic Input to the Hypothalamic Luteinizing Hormone‐Releasing Hormone Neurons in Photosensitive and Photorefractory Starlings
Authors: Parry Dilys M. , Goldsmith Arthur R. 
Published: September 2006

AbstractNeural input to the hypothalamic luteinizing hormone‐releasing hormone (LHRH) neurons was investigated in male starlings (Sturnus vulgaris) using electron microscopy combined with immunocytochemistry. Birds (4 to 6 in each group) were sampled at four stages of a photoperiodically induced reproductive cycle: (a) sexually immature but photosensitive, under short days; (b) during sexual maturation after 7 to 25 long days; (c) during gonadal regression after 35 to 50 long days; and (d) when fully photorefractory after 11 months exposure to long days. The length of the perikaryal membrane, the number and length of axo‐somatic terminals in contact with it and the number and length of synaptic modifications within the terminals were measured for a minimum of six LHRH neurons in each brain. The number of axo‐somatic terminals per neuron and the number per unit length of perikaryal membrane did not differ in birds of groups (a), (b) and (c), but was significantly greater (P<0.05) in the fully refractory birds (group d). Similarly, the number of synaptic modifications was significantly greater (P<0.05) in group (d) than in the other groups. These results are consistent with increased neural input to the LHRH perikarya in photorefractory birds after prolonged exposure to long days, although there was no indication of a change in input at the time of gonadal regression.
Vasostatins, Comprising the N‐terminal Domain of Chromogranin A, Suppress Tension in Isolated Human Blood Vessel Segments
Authors: Aardal Sidsel , Helle Karen B. , Elsayed Said , Reed Rolf K. , Serck‐Hanssen Guldborg 
Published: September 2006

AbstractChromogranin A (CGA) belongs to a family of highly acidic proteins which are co‐stored and co‐released with the catecholamines from the mammalian adrenal gland and occur in nmolar concentrations in the human circulation. A vascular function for the adrenomedullary released and circulating CGA has yet to be established. The present study reports on the novel vasoinhibitory effect of the N‐terminal domain of the adrenomedullary CGA in isolated segments of the human internal thoracic artery (ITA) and saphenous vein (SV). The collective term vasostatin(s) refers to N‐terminal fragments (CGA1–76 and CGA1–113) of apparent molecular weights 7 to 22 kD, to indicate their vascular inhibitory effects. The sustained contractions evoked by the potent vasoconstrictor peptide, endothelin‐1 (ET‐1) were suppressed when ITA and SV segments were preincubated for 15 min with vasostatins (72 nM). The vasoinhibitory effects were not dependent on an intact endothelium and suppression of the response to 35 nM ET‐1 was ∼77% and ∼40% in endothelium‐denuded ITA and SV segments, respectively. In endothelium‐denuded SV segments the vasostatins suppressed the maximal sustained tension response but not the potency for ET‐1, indicating that the vasostatin effect did not involve interference with ET‐1 binding to its vascular receptor. Preincubation of endothelium‐denuded SV segments with nifedipine (1 μM) inhibited the sustained response to ET‐1 ≥10 nM by 50%. By the same protocol a 20 to 40% suppression of the contraction evoked by ET‐1 ≥10 nM was obtained in segments preincubated with vasostatins (72 nM), suggesting that inhibition of Ca2 channel opening might indirectly contribute to the effect of vasostatins on the sustained response to ET‐1. The mechanisms for these inhibitory effects of vasostatins on the sustained ET‐1 contractions in human blood vessels remain to be elucidated.
Chromogranin A: Secretion of Processed Products from the Stimulated Retrogradely Perfused Bovine Adrenal Gland
Authors: Helle Karen B. , Marley Philip D. , Angeletti Ruth Hogue , Aunis Dominique , Galindo Estelle , Small David H. , Livett Bruce G. 
Published: September 2006

AbstractChromogranin A (CGA) is a member of a family of highly acidic proteins co‐stored and co‐secreted with adrenaline and noradrenaline in the adrenal medulla. A number of biologically active fragments of CGA (CGAFs) have been characterized including a group of small N‐terminal fragments collectively named vasostatins due to their vascular inhibitory activity. In the present study, the release of CGAFs, including CGA N‐terminal fragments, from the isolated, retrogradely perfused bovine adrenal gland, has been studied under basal conditions and during nerve stimulation and perfusion with acetylcholine. The CGAFs were characterized by SDS‐PAGE followed by immunoblotting with antisera to specific sequences within the CGA molecule. Many different CGAFs were released during stimulation of the glands. Antisera to CGA1–40 and CGA44–76 detected a 7 kD protein whose release was increased during stimulation. This component co‐migrated with synthetic CGA1–76, was not immunoreactive to antisera to CGA79–113 or CGA124–143, and was seen whether or not the serine protease inhibitor aprotinin was present in the perfusion medium. The release of an ∼ 18 kD component, which stained with antisera to CGA1–40, CGA44–76 and CGA79–113, but not to chromostatin (CGA124–143), was also increased during stimulation. Components of 22 kD and larger were detected with antisera to chromostatin, but not with antisera to CGA1–40, CGA44–78 and CGA79–113. Two of these components of 22 to 24 kD were enhanced during nerve stimulation in the presence of aprotinin. The results indicate that processed Chromogranin A fragments are secreted from the bovine adrenal medulla during stimulation of chromaffin cells. The major fragments secreted appear to be the N‐terminal fragments of CGA, CGA1–76 and CGA1–113, which would arise as a result of processing of CGA at the first and second pairs of basic amino acids. A number of larger CGAFs, possibly containing the chromostatin sequence CGA124–143 at their N‐terminal, and components similar in size to intact CGA and to proteoglycan forms of CGA, are also secreted from the perfused bovine adrenal gland during stimulation.
Changes in Oxytocin Immunoreactivity and mRNA Expression in the Sheep Brain during Pregnancy, Parturition and Lactation and in Response to Oestrogen and Progesterone
Authors: Broad K. D. , Kendrick K. M. , Sirinathsinghji D. J. S. , Keverne E. B. 
Published: September 2006

AbstractThe effects of pregnancy, parturition and lactation and exogenous treatments with oestradiol and progesterone on oxytocin (OXY) immunoreactivity and gene expression in the sheep brain were investigated. Immunocytochemistry was used to demonstrate that increased OXY‐immunoreactivity occurred in cells of the paraventricular (PVN) and supraoptic nuclei (SON), the bed nucleus of the stria terminalis (BNST), the anterior commissural nuclei (ACN) and the periventricular part of the medial preoptic area (PvMP). Oxytocin immunoreactive terminals were also seen in the accessory olfactory nucleus, the glomerular and peri‐glomerular layers of the olfactory bulb, the lateral septum, the zona incerta and the pars compacta of the substantia nigra. Compared to ovariectomized and late pregnant animals, the intensity of immunoreactivity was increased in all of these oxytocinergic elements at parturition, during lactation and following exogenous treatment with oestradiol. The OXY‐immunoreactivity was also more intense in late pregnant animals compared to ovariectomized ones. Quantitative in situ hybridization histochemistry showed that cells in the PVN, SON, BNST and PvMP all showed significantly increased expression of OXY mRNA in animals at parturition and during lactation compared to late pregnant or ovariectomized animals. Expression levels in late pregnant animals were also significantly higher than in ovariectomized ones. Progesterone treatment significantly increased OXY mRNA in the PVN, SON, BNST and PvMP whereas oestradiol treatment was only effective in the PVN, BNST and PvMP. Combined treatment with these steroids did not significantly increase OXY mRNA levels in comparison with their administration alone.These results show that OXY‐immunoreactivity and mRNA expression are at their highest in the sheep brain when maternal behaviour is induced. The increased synthesis/storage of the peptide at parturition may be due to changes in circulating concentrations of both progesterone and oestradiol during late pregnancy.
Centrally Injected lnterleukin‐1 Beta Inhibits the Hypothalamic LHRH Secretion and Circulating LH Levels via Prostaglandins in Rats
Authors: Rivest Serge , Rivier Catherine 
Published: September 2006

AbstractIntracerebroventricular (icv) infusion of interleukin‐1ß (IL‐1ß) significantly lowers plasma LH levels in castrated male rats, and interferes with LHRH release into the median eminence of proestrus female rats. We have investigated the potential role of arachidonic acid metabolites in mediating these inhibitory effects, by administering indomethacin (INDO, a cyclooxygenase inhibitor) or nor‐ dihydroguaiaretic acid (NDGA, a lipoxygenase inhibitor) 15 min prior to injection of the cytokine. While not measurably altering basal LH or LHRH secretion in castrated or proestrus rats, respectively, INDO completely reversed the action of IL‐1ß on the secretion of these 2 hormones. In contrast, NDGA did not alter IL‐1‐induced decreases in LH release.The peripheral administration of endotoxin (LPS) also interferes with LH release. Because the iv injection of IL‐1 does not alter LH secretion, this effect is believed to be at least in part mediated by increased synthesis of cytokines within the CNS. We observed that in contrast to results obtained in rats injected with IL‐1 icv, INDO did not reverse the inhibitory action of LPS. Our results thus suggest either that central IL‐1 is not the primary modulator of LPS‐induced decrease in LH values, or that pathways other than those involving arachidonic acid are important.In conclusion, we have shown that: 1) the ability of IL‐1ß to decrease the activity of the HPG axis is dependent on arachidonic acid metabolites (in particular those formed through the eicosanoid cyclooxygenase route); 2) under circumstances of increased IL‐1ß levels within the CNS, prostaglandins exert an overall inhibitory effect on the hypothalamic LHRH secretion and plasma LH levels in rats.
A Functional Promoter Directing Expression of a Novel Type of Rat Mineralocorticoid Receptor mRNA in Brain
Authors: Castrén Maija , Damm Klaus 
Published: September 2006

AbstractThe authors have identified two types of hippocampal cDNAs for the rat mineralocorticoid receptor (rMR) which are identical in the protein coding domain but differ in their 5′‐untranslated sequences. One of these clones encodes a novel type of rMR cDNA with a high homology to a previously described human MR cDNA isolated from the kidney. A genomic clone containing the 5′‐end of the rat MR gene was isolated. The 12.7 kb genomic region contains the 5′‐coding exon with the translational start site and contiguous DNA sequences encoding the N‐terminal domain of the rMR. A 240 bp region homologous to the 5′‐untranslated sequences of the novel rMR cDNA was located 5.2 kb upstream the protein coding region. Characterization of the nucleotide sequence preceding this exon revealed several features characteristic for promoters of so‐called ‘housekeeping genes'. The sequence analyzed is 635 bp in length, is rich in G + C nucleotides (63%) and lacks TATA or CAAT regulatory elements. It contains three putative binding sites for transcription factor Sp1 as well as several short sequences that are similar to known cis‐acting enhancers or binding sites for transcription factors. In transient transfection experiments employing the luciferase reporter gene and the CV1 cell line this region exhibits substantial promoter activity. These experiments demonstrate that expression of the rat MR gene in the hippocampus results in at least two transcripts with different 5′‐untranslated exons. This sequence information together with the nucleotide sequences upstream of one of the exons, which were shown to encode a functional promoter, provide a valuable tool to elucidate the mechanisms involved in the tissue‐specific regulation of the rat MR gene.
Depolarizing Action of Secretory Granule Protein 7B2 on Rat Supraoptic Neurosecretory Neurons
Authors: Senatorov Vladimir V. , Yang Charles R. , Marcinkiewicz Mieczyslaw , Chrétien Michel , Renaud Leo P. 
Published: September 2006

AbstractA novel precursor neuropeptide termed 7B2 is present within specific brain areas, including the hypothalamic magnocellular neurosecretory neurons, and appears to be processed to smaller fragments. In order to determine whether specific C‐terminal fragments of 7B2 might exert local effects on neurosecretory cells, we used intracellular current‐clamp recordings in supraoptic neurons maintained in superfused hypothalamic explants to evaluate membrane potential and resistance changes in 25 supraoptic nucleus neurons during bolus applications of 7B2174–186 and two other C‐terminal peptide fragments 7B2156–173 and 7B2141–150. In 15 supraoptic neurons, only the 7B2174–186 fragment induced a gradual 2–8 mV membrane depolarization that lasted for 4 to 30 min and was accompanied by 15 + 8% reduction in input resistance. Immunocytochemical identification of the recorded cells revealed that both vasopressin (VP)‐ and oxytocin (OT)‐containing neurons were depolarized by 7B2174–186. These data suggest that 7B2174–186 is a biologically active fragment of 7B2 and may regulate the excitability of magnocellular supraoptic nucleus neurons.
Decreased Population Spike in CA1 Hippocampal Area of Adrenalectomized Rats after Repeated Synaptic Stimulation
Authors: Joëls M. , Fernhout B. 
Published: September 2006

AbstractPopulation spikes, evoked in the CA1 hippocampal area by stimulation of the Schaffer collaterals at various intensities, were recorded over a period of 70 min in slices from 7‐day adrenalectomized (ADX) or sham‐operated rats. Slices from sham‐operated rats with intermediate plasma corticosterone levels (between 0.5 and 5μg corticosterone/100 ml plasma) at the start of the experiment displayed very stable synaptic responses. However, the responses recorded in slices from rats with lower or higher corticosterone levels gradually declined, with repeated stimulation. Similarly, a significant decline of the population spike over time was observed in slices from ADX rats, particularly with low stimulus intensities; characteristics of the compound EPSP were much more stable. The decline of the population spike amplitude was alleviated when: 1) single rather than repeated stimulation was applied; 2) the experiments were performed in the presence of 20 mM glucose; or, 3) moderately high (10−8 or 10−7 M) concentrations of corticosterone were administered in vitro; low (10−9 M) or high (10−6 M) corticosterone concentrations in vitro did not improve the stability of the synaptic response in slices from ADX rats. These data suggest that intermediate levels of corticosterone are necessary to maintain the stability of the Schaffer collateral input to CA1 neurons. With very low or high corticosterone levels, CA1 neurons apparently fail to respond to synaptic stimulation, over time. The possible mechanisms underlying this bell‐shaped dose response curve for corticosterone are discussed.
Formation of Neurons in the Sexually Dimorphic Anteroventral Periventricular Nucleus of the Preoptic Area of the Rat: Effects of Prenatal Treatment with Testosterone Propionate
Authors: Nishizuka Masako , Sumida Hiroyuki , Kano Yasuhiko , Aral Yasumasa 
Published: September 2006

AbstractAn examination was made of neurogenesis in the anteroventral periventricular nucleus (AVPv) of the preoptic area of the rat using bromodeoxyuridine (BrdU), a thymidine analog, and a BrdU‐specific antibody. Cells in the AVPv of adult rats were labeled with the antibody when BrdU was injected into pregnant rats once during day 13 to 18 of gestation, but not during day 10 to 12 nor 19 to 20 of gestation nor on postnatal day 1, indicating that neurogenesis of the AVPv occurs during a limited period from day 13 to 18 of gestation. Next, to examine the effects of androgen on neurogenesis, BrdU was injected once on day 15 into pregnant rats that also received injections of testosterone propionate (TP). The number of BrdU‐labeled cells in the AVPv was similar in control female and male fetuses and female fetuses from pregnant rats that received daily injections of TP during days 14 to 16, when fetuses were examined on day 17 of gestation. These results suggest that the neurogenesis that was recognized by labeling with BrdU was not affected by the treatment with TP. On day 21 of gestation, BrdU‐labeled cells in the AVPv of control male fetuses and female fetuses that received TP during days 14 to 18 were fewer in number than those in female fetuses of the control group, whereas treatments with TP during days 14 to 16 and during days 17 to 18 did not cause any significant decrease in number of BrdU‐labeled cells. These findings support the hypothesis that elimination of a population of cells, for example, by cell death as described previously, is enhanced in male fetuses and in female fetuses treated with TP repetitively.