bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melatonin Regulates the Phosphorylation of CREB in Ovine Pars Tuberalis*
Authors: McNulty S. , Rosst A. W. , Barrettt P. , Hastings M. H. , Morgan P. J. 
Published: September 2006

AbstractThis study investigated whether melatonin could modulate the phosphorylation of the calcium/cyclic AMP response‐element binding‐protein (CREB) within primary cell cultures of ovine pars tuberalis (oPT) and pars distalis (oPD). Gel shift assays confirmed the presence of nuclear factors able to alter the electrophoretic mobility of a 32P‐labelled CRE oligonucleotide. Two shifted bands were observed probably due to monomer and dimer binding to the CRE. Each band was supershifted by antisera directed against both CREB and the phosphorylated form of CREB (P‐CREB), consistent with a specific role of CREB proteins in transcriptional regulation. To study the physiological role of CREB, the nuclear immunoreactivity for P‐CREB was followed in primary cultures of oPT given different pharmacological treatments. Cells stimulated with forskolin responded with a robust time‐ and dose‐dependent increase in nuclear phospho‐CREB immunoreactivity (P‐CREB‐ir), confirming that activation of this transcription factor occurred through the cyclic AMP‐PKA pathway. Maximal stimulation was achieved within 15 min and persisted for up to 1 h. Treatment with melatonin alone did not alter basal P‐CREB‐ir levels, yet melatonin inhibited the forskolin‐induced increase in P‐CREB‐ir in a dose‐dependent manner (IC50 of between 10−10M and 10−8 M melatonin when tested against 1 μM forskolin). In contrast, in primary cultures of oPD, melatonin failed to block forskolin‐stimulated increases in either the content of cyclic AMP or the intensity of nuclear P‐CREB‐ir, confirming that the action of melatonin upon P‐CREB‐ir is tissue specific. These results demonstrate that, consistent with its inhibitory effect on the activation of PKA within oPT, melatonin prevents or reverses the phosphorylation of CREB induced by activation of the cyclic AMP signal transduction pathway. Therefore melatonin has the potential to regulate gene expression in the oPT by acting upon the CREB transcription factor. However, this paper also shows that 12‐0‐tetradecanoylphorbol‐13‐acetate (TPA) which activates PKC also leads to the phosphorylation of CREB in oPT cells, suggesting the potential involvement of other signal transduction pathways in the transcriptional regulation of these cells.
Hypothalamic Estrogen Receptor‐lmmunoreactivity in Prepubertal vs Adult Female Guinea Pigs
Authors: Olster Deborah H. 
Published: September 2006

AbstractJuvenile guinea pigs (18–20 days old) rarely display lordosis in response to estradiol and progesterone treatments that elicit sexual behavior in adult females. Nor do immature animals release a preovulatory‐like surge of luteinizing hormone in response to estradiol. In vitro radioligand binding assays have revealed similar concentrations of estrogen receptors in thehypothalamus and preoptic area of prepubertal and adult guinea pigs. The aim of the present study was to compare estrogen receptor‐immunoreactivity in a variety of forebrain regions of immature and adult guinea pigs, to determine whether age differences in estrogen receptor levels inmore discrete portions of the hypothalamus and preoptic area exist. Forebrain tissue from juvenile (17 days) and adult females (> 6 weeks), ovariectomized 6 days previously, was processed forestrogen receptor‐immunoreactivity, using Abbott Laboratories' H222 anti‐human estrogen receptor antibody. Juveniles had estrogen receptor‐immunoreactive cells in all of the same regions as adults: medial preoptic area, medial preoptic nucleus, bed nucleus of the stria terminalis, periventricular, paraventricular, dorsomedial and arcuate nuclei, ventrolateral and anterior hypothalamic regions, and amygdala. Among the areas in which estrogen receptor‐immunoreactivity was quantified (medial preoptic area, medial preoptic nucleus, anterior periventricular nucleus, arcuate nucleus and ventrolateral hypothalamus), the only region in which an age difference in estrogen receptor‐immunostaining was observed was the rostral portion of the ventrolateral hypothalamus. Juvenile females had, on average, 30% fewer estrogen receptor‐immunoreactive cells in asample of this region than adults (440 ± 25 vs 626 ± 25, P = 0.001). These data are consistent with the hypothesis that insufficient estrogen receptors in the rostral ventrolateral hypothalamus may underlie, in part, the markedly deficient responses of juvenile female guinea pigs to estradiol.
Down‐Regulation of Estrogen Receptor Immunoreactivity by 17β‐estradiol in the Guinea Pig Forebrain
Authors: Meredith John M. , Auger Catherine J. , Blaustein Jeffrey D. 
Published: September 2006

AbstractLow amplitude pulses of estradiol‐17β (E2‐17β) are more effective than large single bolus injections or constant exposure to E2‐17β in inducing progesterone‐facilitated sex behavior in female rats and guinea pigs. The present study examined whether the increased responsiveness to E2‐17β is due to an increase in the number of estrogen receptors in the estrogen receptor rich areas of the hypothalamus and amygdala.Initial studies examined the rapid effects (20 min) of a high dose of E2‐17β (50 μg) on estrogen receptor immunostaining using either the H222 antibody or the ER 21 antiserum. ER 21 immunostaining was not affected by the E2‐17β treatment suggesting that it binds to both occupied and unoccupied estrogen receptors. Therefore the ER 21 antiserum was used to characterize the regulation of estrogen receptor immunoreactivity (ER‐IR) by E2‐17β.ER‐IR was examined for 48 h and serum E2‐17β for 24 h following a 2 μg s.c. injection of E2‐17β (a dose similar to that used in multiple pulse paradigms). Serum E2‐17β peaked 15 to 30 min following the injection and returned to baseline values by 1 h. In all but one area maximal suppression of ER‐IR occurred at 12 h.In summary, 1) decreases in estrogen receptor immunoreactivity following E2‐17β are consistent with studies in which estrogen receptors were assayed by binding assays and estrogen receptor mRNA was determined by in situ hybridization; 2) the ER 21 antiserum is able to detect both occupied and unoccupied estrogen receptors and 3) H222 immunoreactivity is influenced by the presence of E2‐17β, so that the level of H222‐IR is a reflection of ligand/receptor binding dynamics.The data suggest that up‐regulation of estrogen receptors does not account for the increase in behavioral sensitivity which is observed following multiple pulses of E2‐17β.
Activation of Vasopressin Neurons in Aging and Alzheimer's Disease
Authors: Lucassen P. J. , Salehi A. , Pool C. W. , Gonatas N. K. , Swaab D. F. 
Published: September 2006

AbstractThe supraoptic (SON) and paraventricular nuclei (PVN) of the human hypothalamus are production sites of vasopressin (AVP) and oxytocin (OXT). Although the hypothalamus is affected in Alzheimer's disease (AD), previous work has not only shown that in these two nuclei no neurons are lost, neither during aging nor in AD, but that the number of AVP‐expressing neurons and their nucleolar size had even increased with age. These observations indicated that the peptide synthesis of the AVP neurons was activated in the oldest age‐groups. Recently published, qualitative observations, using the area of the Golgi Apparatus (GA) as a sensitive parameter for neurosecretory activity, confirmed the activation of SON and PVN neurons with age in human; however, in this report the neurons were not identified according to their neuropeptide content. In the present quantitative study we determined whether the AVP neurons were indeed activated as a result of the aging process in controls and AD patients. We applied a polyclonal antiserum directed against the medial cisternae of the GA on formalin‐fixed, paraffin‐embedded tissue sections taken from the dorsolateral SON (dl‐SON) of 10 controls and 10 AD patients, and performed our measurements in this area that is known to be predominantly occupied (90–95%) by AVP neurons. In addition, the sparse OXT cells present in the area of study, were excluded from the measurements on the basis of alternative sections stained for OXT. In the dl‐SON, the area occupied by the GA and the cellular profile area per patient were quantified by means of image analysis. The results show a significant increase in GA area with age in controls and in AD, demonstrating an activation of the AVP neurons in the dl‐SON of the human hypothalamus in these two conditions. No changes were observed in the cellular profile areas with age, neither in the controls nor in AD, suggesting that the GA area is a much more sensitive parameter for monitoring activity changes in post‐mortem material than neuronal size. It is proposed that this activation of AVP cells with age, which has been suggested to be a compensatory response to the age‐related loss of AVP receptors in the kidney, might be the basis of the stability of these neurons in aging and AD.
Pituitary Adenylate Cyclase Activating Peptide‐38 (PACAP‐38), PACAP‐27, and PACAP Related Peptide (PRP) in the Rat Median Eminence and Pituitary
Authors: Mikkelsen Jens D. , Hannibalt Jens , Fahrenkrugt Jan , Larsen Philip J. , Olcese James , McArdle Craig 
Published: September 2006

AbstractPituitary adenylate cyclase activating peptide (PACAP) is a member of the vasoactive intestinal peptide‐like peptide family. It is found in the hypothalamus, where the PACAP precursor is processed to form PACAP‐38, the C‐terminal truncated PACAP‐27 and PACAP related peptide (PRP). Both PACAPs are potent stimulators of anterior pituitary adenylate cyclase activity, but the physiologically relevant anatomical sources of PACAP and possible importance of PRP in this regard are poorly understood. Using immunocytochemistry with epitope‐specific antisera, we now show that PACAPS38, PACAP27‐ and PRP‐positive nerve fibres are all present in the rat median eminence. The major immunoreactive species present was PACAP38. Numerous PACAP38‐immmunoreactive nerve fibres were observed in the internal layer and a few were present in the posterior pituitary lobe. The external layer of the median eminence contained a few PACAP‐38‐immunoreactive fibres and PACAP‐38‐positive nerve terminals were rarely seen in the perivascular portal spaces. Surprisingly, delicate PACAP‐38‐positive nerve fibres were identified in the anterior pituitary lobe intermingled between the pituitary cells although none of the secretory pituitary cells contained immunoreactive PACAP38, PACAP27 or PRP and preproPACAP mRNA was not detected in the gland by Northern blotting or in situ hybridization. PACAP‐27‐ and PRP‐immunoreactive nerve fibres and terminals were found in the same locations as PACAP‐38 although generally in lower numbers. Specific radioimmunoassays and HPLC revealed that PACAP‐38 accounts for the vast majority of the adenohypophyseal PACAP‐immunoreactivity, whereas PACAP‐27 and PRP were found in low to undetectable concentrations. In primary cultures of rat pituitary cells and in the clonal gonadotrope‐derived aT3‐1 cell line, PACAP‐27 and PACAP‐38 were equipotent stimulators of cAMP accumulation, whereas PRP was ineffective. We conclude that the distribution of PACAP‐imrnunoreactive nerve fibres in the hypothalamus of the adult male rat is not that expected for a classic releasing factor suggesting that other sources of PACAP are relevant for stimulation of anterior pituitary cells or that the hypothalamic PACAP system is activated under specific endocrine or developmental conditions.
Vasoactive Intestinal Polypeptide in the Suprachiasmatic Nucleus of the Mink (Mustela vison) Could Play a Key Role in Photic Induction
Authors: Martinet Lise , Bonnefond Catherine , Peytevin Jocelyne , Monnerie Régine , Marcilloux Jean Claude 
Published: September 2006

AbstractThe present study was conducted to visualize neuropeptides in the SCN of a mustelid, the American mink in which seasonal cycles of reproduction rely totally on the annual changes in day length. At this time, data in mustelids are lacking. Results were obtained with in situ hybridization (ISH) using synthetic oligonucleotide vasopressin (AVP) and somatostatin (SOM) and with single and dual immunohistochemistry (IHC) performed with antisera against AVP, SOM, vasoactive intestinal polypeptide (VIP), gastrin releasing peptide (GRP) and met‐enkephalin (Met‐ENK) in untreated (AVP and VIP) or colchicine (SOM, Met‐ENK and GRP) treated adult male and female mink. The most striking result, evidenced by ISH as well as IHC was the lack of AVP, SOM and Met‐ENK immunoreactive (ir)‐neurons in the SCN. In contrast, strongly VIP ir‐perikarya were widely distributed within the SCN and gave rise to a dense network of fibres extending within the periventricular (peVA) and subparaventricular (subPVA) areas. Weakly GRP ir‐perikarya were also observed in the median part of the SCN. Dual IHC revealed that the magnocellular neurons located just dorsal to the SCN, in the peVA and subPVA co‐stored AVP with VIP, SOM or Met‐ENK. The lack of SCN AVP and SOM ir‐neurons, reported for the first time in a mammalian species, raises the question of their implication in the functions of the circadian pacemaker and its entrainment by the light/dark cycle in other species. The significance of the large neurons co‐storing peptides in the terminal field of VlPergic fibres originating in the SCN has also to be determined. These results suggest that VIP could be of major importance in processing photic information mediating circadian entrainment and consequently annual rhythms.
Opposing Neuroendocrine Actions of the Natriuretic Peptides: C‐Type and A‐Type Natriuretic Peptides do not Interact with the same Hypothalamic Cells Controlling Prolactin Secretion
Authors: Samson Willis K. , Huang Fong‐Lee S. , Fulton R. Jerrold 
Published: September 2006

AbstractThe two major members of the family of natriuretic peptides (NPs) in brain, A‐type natriuretic peptide (ANP) and C‐type natriuretic peptide (CNP) exert opposing actions on the neuroendocrine regulation of prolactin (PRL) secretion. We have targeted for compromise and destruction cells within the diencephalon which bear receptors for ANP (NPR‐A receptors), CNP (NPR‐B receptors), or both peptides (NPR‐C receptors) using novel cytotoxin cell targeting methodology in order to determine if the neuroendocrine effects of these two peptides are exerted on similar cell systems. In animals pretreated with ANP conjugated to the cytotoxic A chain of ricin, central administration of a dose of ANP which is known to inhibit PRL secretion did not alter PRL levels in plasma; however, subsequent administration of CNP elicited the stimulation of PRL secretion. In rats pretreated with CNP‐ricin A chain conjugate, a treatment we hypothesize targets for destruction CNP responsive cells, ANP injection did inhibit PRL secretion, while the stimulatory effect of CNP was absent. These results suggest that the neuroendocrine effects of these two natriuretic peptides on PRL secretion are expressed on different cellular elements of the hypothalamo‐pituitary axis. Furthermore, they reveal that neither peptide acts directly on the tuberoinfundibular dopamine system since pretreatment with either cytotoxin conjugate failed to alter basal PRL levels. Thus ANP and CNP do not appear to express opposing actions on the same cell systems, suggesting the recruitment of each peptide individually by differing, unique stimuli for PRL release.
Central Glucopenia Induced by 2‐Deoxy‐D‐Glucose Stimulates Somatostatin Secretion in the Rat
Authors: Sato Makoto , Murao Koji , Matsubara Shuji , Niimi Michio , Chihara Kazuo , Takahara Jiro 
Published: September 2006

AbstractThe mechanisms involved in 2‐deoxy‐D‐glucose (2‐DG)‐induced growth hormone (GH) suppression in the rat were examined. Conscious male rats were given 2‐DG by intracerebroventricular (icv) injection and the pulsatile GH secretion was monitored for 6 h. The single icv injection of 2‐DG (8 mg/rat) eliminated pulsatile GH secretion in conscious rats. Pretreatment with somatostatin (SS) antiserum completely restored the suppressed GH secretion in the 2‐DG treated rats. Hypothalamic GH‐releasing hormone (GRH) and SS mRNA levels were not altered by single and multiple icv injections of 2‐DG. These findings suggest that 2‐DG‐induced GH suppression is primarily due to hypersecretion of SS without a significant change at the transcription level in the rat.
Long‐Term Antidepressant Treatment Reduces Behavioural Deficits in Transgenic Mice with Impaired Glucocorticoid Receptor Function
Authors: Montkowski Alexandra , Barden Nicholas , Wotjak Carsten , Stec Ingemar , Ganster Julia , Meaney Michael , Engelmann Mario , Reul Johannes M. H. M. , Landgraf Rainer , Holsboer Florian 
Published: September 2006

AbstractImpaired cognitive function and enhanced activity of the hypothalamic‐pituitary‐adrenocortical system are among the cardinal symptoms of major depression in humans that resolve after successful antidepressant treatment. We used a transgenic mouse model expressing antisense RNA complementary to that of glucocorticoid receptor (GR) mRNA to test the hypothesis that reduced GR function can cause these clinical disturbances. The transgenic mice show profound behavioural changes in a number of animal tests that are indicative of cognitive impairment. These mice also have elevated plasma corticotropin concentrations in response to stress. After long‐term treatment with moclobemide, a reversible inhibitor of monoamine oxidase type A that acts clinically as an antidepressant, both the behavioural deficits and the hormonal alterations disappeared. These observations suggest that a transgenic mouse with GR dysfunction may be a useful model for investigation of drug effects on the cognitive and neuroendocrine aspects of depression.
LHRH Pulse Generator is Stimulated by Naloxone in the Pentobarbital‐Blocked Proestrous Rat
Authors: Kimura Fukuko , Jinnai Kayoko , Sano Akane 
Published: September 2006

AbstractPrevious studies by us and others led us to hypothesize that there are separate LHRH pulse and surge generators in the rat brain. The present study was designed to detect the activity of LHRH pulse generator by checking changes in LH secretion and the multiunit activity (MUA) of the arcuate‐median eminence region of the hypothalamus during infusions of naloxone (NAL, 2 mg/h) in the proestrous rat in which the LHRH surge generator activity was blocked by pentobarbital sodium (PB, 32 mg/kg bw, ip). The animals were subjected to blood sampling in the morning (1000–1300 h) or afternoon (1400–1700), and injected with PB at 09.45 or 13.45, respectively. During saline infusions in the rat given PB injection at either 09.45 or 13.45, serum LH levels were low but fluctuated significantly, suggesting a pulsatile secretion in either the morning or the afternoon period. The pulse intervals were an average 28.2 min in the morning and 42.2 min in the afternoon. NAL infusions decreased the pulse interval significantly, to 22.0 min in the morning and to 27.0 min in the afternoon. In the electrophysiological experiment, characteristic increases in the MUA (volleys), which occur in association with the initiation of an LH pulse and therefore are considered to represent an increased activity of the LHRH pulse generator, appeared during NAL (5 mg/h) infusions in either the morning or the afternoon. These results strongly suggest that separate LHRH pulse and surge generators exist in the brain, and that, even during the critical period of proestrus, the activity of LHRH pulse generator is disclosed by PB, which, on the other hand, arrests the surge generator.
The Effect of NO‐Donors in Bovine and Rat Pineal Cells: Stimulation of cGMP and cGMP‐Independent Inhibition of Melatonin Synthesis
Authors: Maronde E. , Middendorff R. , Mayer B. , Olcese J. 
Published: September 2006

AbstractThe presence of soluble guanylate cyclase in the pineal and its regulation by adrenergic pathways has been well documented. Recent evidence points to adrenergically stimulated nitric oxide generation as a mechanism for coupling this pathway. To what extent nitric oxide (NO) signalling can influence adrenergically stimulated melatonin synthesis has not been investigated. Cyclic guanosine 3′,5′‐monophospate (cGMP) signal transduction in the bovine pineal has also received little attention. We describe in the present report: 1) a dose‐dependent elevation of cGMP in response to the nitrovasodilators, sodium nitroprusside (SNP) and 3‐morpholino‐sydnonimine (SIN‐l), 2) a dose‐dependent inhibition of melatonin synthesis by SNP and SIN‐1, but not by 8‐Br‐cGMP in both bovine and rat pineal cell cultures, which is not due to cytotoxicity as judged by two different approaches, and 3) immunohistochemical evidence for the presence of nitric oxide synthase (NOS) (EC 1.14.23.‐) in the intact bovine pineal gland and in cultured bovine pinealocytes. These data support the view that NOS is a component of the cGMP‐generating system in mammalian pinealocytes. Although NO‐donor molecules are also potent activators of cGMP accumulation, they may have other important actions in the pineal, namely the inhibition of adrenergic‐stimulated melatonin synthesis. As SNP and SIN‐1 exerted this inhibitory effect on cells regardless of whether they were stimulated by isoproterenol, forskolin or 8‐Br‐CAMP it would appear that NO‐donors can act ‘downstream’ from the receptor/adenylate cyclase level.
Expression of Biologically Active Procorticotrophin‐Releasing Hormone (proCRH) in Stably Transfected CHO‐K1 Cells: Characterization of Nuclear proCRH
Authors: Morrison Ewan , Tomasec Peter , Linton Elizabeth A. , Lowry Philip J. , Lowenstein Pedro R. , Castro Maria G. 
Published: September 2006

AbstractCorticotrophin‐releasing hormone (CRH) is a 41 amino acid neuropeptide which is cleaved at a pair of dibasic amino acids from a larger precursor molecule (pre‐proCRH) by the action of endopeptidases. In cells possessing a regulated secretory pathway, sorting of proneuropeptides and prohormones occurs within the trans‐Golgi network, where they are finally packaged into secretory vesicles to be released in response to an external stimulus. Such cells also possess a constitutive secretory pathway, and neuropeptides are also translocated into this subcellular compartment. We have recently established stably transfected CHO‐K1 cells expressing the rat pre‐proCRH cDNA, and shown that proCRH was localized within the secretory pathway and the nucleus of transfected cells. Both the cytoplasmic and nuclear species of IR‐CRH displayed an apparent molecular weight of approximately 19 kDa, consistent with the size of the uncleaved CRH precursor molecule.In this paper, we further characterized the bitopological, i.e. nuclear and cytoplasmic localization of proCRH within transfected CHO‐K1 cells. Immunoreactive nuclear CRH was not extractable using detergents (Triton X‐100 and CHAPS), 10 mM salt washes or RNase digestion but could be abolished by digestion with DNase I. These results therefore suggest that nuclear proCRH is in close association with DNA/chromatin. Treatment of transfected cells with inhibitors of protein and RNA synthesis for up to 24 h had no effect upon immunoreactive nuclear CRH, indicating that it is very stable with a long half life. Brefeldin A treatment had no effect upon the nuclear translocation of newly synthesized proCRH, suggesting that late stages of the secretory pathway (i.e. post rough endoplasmic reticulum compartments) of the transfected cells do not play a role in proCRH nuclear transport. We also demonstrate that proCRH synthesized within stably transfected CHO‐K1 cells is capable of stimulating ACTH release from primary cultures of anterior pituitary cells, therefore showing for the first time that the intact precursor is also biologically active and could act as an ACTH secretagogue in‐vivo.