bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexually Dimorphic Expression of sst1 and sst2 Somatostatin Receptor Subtypes in the Arcuate Nucleus and Anterior Pituitary of Adults Rats
Authors: Zhang  , Beaudet  , Tannenbaum
Published: March 2003

The pattern of growth hormone (GH) secretion and rate of somatic growth are markedly sexually dimorphic, but the underlying neuroendocrine mechanisms are far from clear. In the present study, we tested the hypothesis that the sexual dimorphism of GH secretion may be due to gender‐related differences in the transduction of somatostatin’s actions in brain and/or pituitary. To accomplish this, we compared the distributional pattern and level of expression of two somatostatin receptor subtypes, sst1 and sst2, in the brain and pituitary of adult male and female rats by in‐situ hybridization using 35S‐labelled antisense riboprobes. In the brain, the hybridization pattern and labelling density of sst1 and sst2 mRNA‐expressing cells, as revealed by computer‐assisted image analysis, in areas including the cerebral cortex, medial habenula (MHb) and ventromedial hypothalamic nucleus (VMN), were similar in male and female rats. In contrast, there was a marked sex‐related difference in sst1 expression in the arcuate nucleus of the hypothalamus; both the number and labelling density of sst1 mRNA‐expressing cells were two‐ to threefold greater in males than in females and this significant increase was homogenous throughout the rostrocaudal extent of the nucleus. No gender‐related differences in arcuate sst2 mRNA levels were found. At the level of the anterior pituitary, the labelling density of sst2 mRNA in males was significantly higher than that of females. No sex‐related difference in pituitary sst1 mRNA was observed. These results demonstrate a sexual dimorphism in the expression of two somatostatin receptor subtypes, sst1 and sst2, at the level of the arcuate nucleus and anterior pituitary, respectively. Such dimorphism suggests a differential involvement of sst1 and sst2 in GH regulation with respect to gender, and may imply roles for sst2 and sst1 in transducing somatostatin’s actions on pituitary somatotrophs and GH‐releasing hormone‐containing arcuate neurones, respectively, to generate the lower basal and higher GH pulse levels characteristic of the male rat.
Activity of Vasopressinergic Neurones of the Human Supraoptic Nucleus os Age‐ and Sex‐Dependent
Authors: Ishunina  , Salehi  , Hofman  , Swaab
Published: March 2003

In the human hypothalamus, arginine‐vasopressin (AVP) is produced for a major part by the neurones of the supraoptic nucleus (SON). Since plasma AVP levels in men were reported to be higher than those of women and we did not find a sex difference in the neurone number, a higher vasopressinergic neurone activity was supposed to be present in the SON of men. Therefore we studied the size of the Golgi‐apparatus (GA), which has been demonstrated previously to be a sensitive parameter for protein synthetic ability of neurones, in 15 men and 17 women ranging in age from 29 to 94 years. A polyclonal antibody against immunoaffinity purified MG‐160, a sialoglycoprotein of the medial cisternae of the GA was applied on paraffin‐embedded sections containing the dorsolateral SON ( dl‐SON) from which 90–95% of neurones are vasopressinergic. SON areas that contain oxytocin (OT) cells were excluded on the basis of adjacent sections stained with a monoclonal antibody against OT. By means of an image analysis system the size of the GA and the cellular profile area were determined in dl‐SON neurones with a nucleolus. Our results showed indeed an age‐dependent sex difference in the size of the GA that appeared to be twice as large in young men (≤50 years old) than in young women of the same age. The size of the GA increased with age in women but not in men. In addition, the mean cell profile area, another measure for neuronal activity, was significantly larger in young men than in young women and was in old women larger than in young women. In conclusion, these data show the presence of a sex‐dependent age‐difference in the activity of vasopressinergic neurones in dl‐SON which may relate to differences in AVP and sex hormone levels and kidney AVP receptors.
Photo‐Induction of Hypothalamic Gonadotrophin Releasing Hormone‐I mRNA in the Domestic Chicken: a Role for Oestrogen?
Authors: Dunn  , Sharp
Published: March 2003

Photoinduced changes in GnRH neuronal function were investigated in prepubertal and in mid‐pubertal cockerels and somatically mature hens. Photostimulation of short day mid‐pubertal cockerels and somatically mature out‐of‐lay hens for 7 days significantly increased (P<0.05) total hypothalamic gonadotrophin releasing hormone‐I (GnRH‐I) mRNA. The increase in GnRH‐I mRNA was associated with increased (P<0.05) plasma LH in the hens but not mid‐pubertal cockerels. Photostimulation of short day prepubertal cockerels for 7 days also stimulated LH release (P<0.05) but in contrast did not increase total hypothalamic GnRH‐I mRNA. Plasma LH and hypothalamic GnRH‐I mRNA were depressed in (P<0.001) short day prepubertal cockerels chronically treated with oestradiol benzoate (0.5 mg/kg, on alternate days). However, photostimulation of oestrogenized prepubertal cockerels for 7 days stimulated LH release (P<0.001) and increased hypothalamic GnRH‐I mRNA (P<0.001). It is concluded that photostimulatory inputs to GnRH neurones have the potential to increase GnRH‐I mRNA transcription or stability and to increase GnRH‐I release. The extent to which increased levels of GnRH‐I mRNA or increased GnRH release from GnRH neurones are observed after photostimulation may depend on the interaction between the drive on GnRH‐I neurone function, which increases at the onset of puberty, and the inhibitory action of oestrogen produced locally in the hypothalamus.
Effects of Central and Peripheral Injection of Leptin on Food Intake and on Brain Fos Expression in the Otsuka Long‐Evans Tokushima Fatty Rat with Hyperleptinaemia
Authors: Niimi  , Sato  , Yokote  , Tada  , Takahara
Published: March 2003

Hyperleptinaemia is observed in obese animals and humans, suggesting that leptin resistance rather than leptin deficiency is a characteristic feature of obesity. This study was designed to determine whether peripherally or centrally administered leptin is effective on the short‐term food intake and expression of Fos protein in the hypothalamus in the Otsuka Long‐Evans Tokushima Fatty (OLETF) or Long‐Evans Tokushima Otsuka (LETO) rat, as a control. The OLETF rat exhibits a polygenic syndrome of hyperphagia, obesity, hyperinsulinaemia, and hyperglycaemia. Male OLETF rats of 5, 8, and 14 weeks of age became heavier than LETO rats. Serum leptin concentrations were not significantly different between LETO and OLETF rats at the age of 5 weeks, but in 8‐ and 14‐week‐old OLETF rats were increased to 3.4 and 2.9 times those of LETO rats, respectively. The 8‐week‐old OLETF and LETO rats were given intraperitoneal (i.p.) injections with recombinant mouse leptin to measure the kinetics. There was a dramatic increase in plasma leptin concentration at 1 h, a decline by 3 h, and the concentrations 6 h after injection were similar to the basal levels. There were no significant difference between OLETF and LETO rats. In LETO rats at 5, 8 and 14 weeks of age, i.p. injection of leptin significantly decreased food intake. Whereas 5‐week‐old OLETF rats responded to leptin with a decrease in food intake, 8‐ and 14‐week‐old OLETF rats became resistant to peripherally administered leptin. In contrast, intracerebroventricular (i.c.v.) injections of leptin were very effective in inhibiting food intake in both OLETF and LETO rats at 14 weeks of age. Intraperitoneal injection of leptin in the LETO rats at each age increased the number of Fos‐positive nuclei detected in the ventromedial hypothalamic (VMH), the dorsomedial hypothalamic (DMH) and arcuate nuclei, whereas there was no significant increase in the number of cells expressing c‐fos protein in the hypothalamus of the 8‐ and 14 week‐old OLETF rats with hyperleptinaemia. On the other hand, increased expression of c‐fos protein in the VMH, DMH and arcuate nuclei following i.c.v. injection of leptin was observed in both OLETF and LETO rats at 5, 8 and 14 weeks of age. These data demonstrated that obese OLETF rats are peripherally leptin resistant, while they retain sensitivity to centrally administered leptin.
Hormonal and Cellular Brain Mechanisms Regulating the Amplexus of Male and Female Water Frog (Rana esculenta)
Authors: Gobbetti  , Zerani
Published: March 2003

The role of nitric oxide (NO) synthase, prostaglandin E2–9‐ketoreductase, and aromatase brain activities in regulating frog amplexus was assessed in the water frog (Rana esculenta). Plasma concentrations of testosterone were higher, and concentrations of 17β‐oestradiol lower, in amplexing males than in unamplexing males; while concentrations of testosterone and PGE2 were lower, and those of 17β‐oestradiol and PGF2α higher, in amplexing females compared to unamplexing females. Hormone release rescued from frog brains in vitro mirrored plasma hormone measures. Brain aromatase activity was lower in amplexing males; NO synthase was lower and PGE2–9‐ketoreductase and aromatase were higher in amplexing females. In male brains, PGE2–9‐ketoreductase inhibitor decreased PGF2α release and increased that of PGE2; aromatase inhibitor decreased 17β‐oestradiol and increased testosterone release. In female brains, NO donor and PGE2–9‐ketoreductase inhibitor increased testosterone and PGE2 release and decreased that of 17β‐oestradiol and PGF2α; NO synthase inhibitor decreased testosterone release and PGE2 and increased 17β‐oestradiol and PGF2α release; PGF2α decreased testosterone release and increased 17β‐oestradiol release; aromatase inhibitor decreased 17β‐oestradiol release and increased testosterone release. In female brains, NO donor and PGE2–9‐ketoreductase inhibitor decreased PGE2–9‐ketoreductase and aromatase activities; PGF2α increased aromatase activity; NO synthase inhibitor increased PGE2–9‐ketoreductase and aromatase activity. The data suggest that, in amplexing female brains, external and/or internal stimuli inhibit NO synthase, decreasing NO and activating PGE2–9‐ketoreductase; in turn, PGF2α increases aromatase activity and 17β‐oestradiol release; while, in amplexing male brains, stimuli inhibit aromatase activity, thereby increasing testosterone production.
κ‐Opioid Receptor Activation Inhibits Post‐Spike Depolarizing After‐Potentials in Rat Supraoptic Nucleus Neurones In Vitro
Authors: Brown  , Ghamari‐Langroudi  , Leng  , Bourque
Published: March 2003

Endogenous agonists acting at κ‐opioid receptors modulate the discharge activity of hypothalamic supraoptic nucleus vasopressin cells in vivo. Phasic activity in vasopressin cells is known to depend critically on intrinsic mechanisms involving post‐spike depolarizing after‐potentials and we hypothesized that inhibition of phasic bursting by an endogenous κ‐agonist may result from reducing the magnitude of depolarizing after‐potentials. To investigate this possibility, intracellular sharp electrode recordings were obtained from supraoptic nucleus cells impaled in superfused explants of rat hypothalamus. Bath application of the selective κ‐agonist, U50,488H (0.1–1 μM), decreased the spontaneous firing rate of magnocellular neurosecretory cells (by 94.0±4.5% at 1 μM, mean±SEM; P=0.02, n=4). U50,488H did not alter membrane potential (0.9±0.8 mV hyperpolarization at 1 μM, P=0.17, n=8) or input resistance (11.0±4.5% increase at 1 μM, P=0.09, n=5). U50,488H (0.1 and 1 μM, both n=5) reduced depolarizing after‐potential amplitude (by 29.9±9.3 and 78.0±10.6%, respectively, P<0.001) in eight cells in which the baseline membrane potential was kept constant by dc‐current injection and in which a depolarizing after‐potential was evoked every 25–40 s by a brief (40–80 ms) train of 3–6 action potentials (the number of spikes in the trains was kept constant for each cell). Thus, κ‐opioid receptor activation reduces depolarizing after‐potential amplitude in supraoptic nucleus cells and this may underlie the reduction in burst duration of vasopressin cells caused by an endogenous κ‐agonist in vivo.
Preferential Potentiation by Nitric Oxide of Spontaneous Inhibitory Postsynaptic Currents in Rat Supraoptic Neurones
Authors: Ozaki  , Shibuya  , Kabashima  , Isse  , Noguchi  , Ueta  , Inoue  , Shigematsu  , Yamashita
Published: March 2003

Magnocellular neurones in the supraoptic nucleus and paraventricular nucleus express mRNA for nitric oxide synthase (NOS) and the expression becomes more prominent when the release of vasopressin or oxytocin is stimulated. It has also been reported that NO donors inhibit the electrical activity of supraoptic nucleus neurones, but the mechanism involved in the inhibition remains unclear. In the present study, to know whether modulation of synaptic inputs into supraoptic neurones is involved in the inhibitory effect of NO, we measured spontaneous excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs) from rat supraoptic nucleus neurones in slice preparations identified under a microscope using the whole‐cell mode of the slice‐patch‐clamp technique. The NO donor, S‐nitroso‐N‐acetylpenicillamine (SNAP), reversibly increased the frequency of spontaneous IPSCs mediated by GABAA receptors, without affecting the amplitude, indicating that NO potentiated IPSCs via a presynaptic mechanism. The NO scavenger, haemoglobin, suppressed the potentiation of IPSCs by SNAP. On the other hand, SNAP did not cause significant effects on EPSCs mediated by non‐NMDA glutamate receptors. The membrane permeable analogue of cGMP, 8‐bromo cGMP, caused a significant reduction in the frequency and amplitude of both IPSCs and EPSCs. The results suggest that NO preferentially potentiates the inhibitory synaptic inputs into supraoptic nucleus neurones by acting on GABA terminals in the supraoptic nucleus, possibly via a cGMP‐independent mechanism. The potentiation may, at least in part, account for the inhibitory action of NO on the neural activity of supraoptic neurones.
Regional and Selective Effects of Oestradiol and Progesterone on NMDA and AMPA Receptors in the Rat Brain
Authors: Cyr  , Ghribi  , Di Paolo
Published: March 2003

We investigated the effect of 10 months ovariectomy and a correction therapy, 2 weeks before the rats were killed, of oestradiol, progesterone or their combination on NMDA and AMPA receptor binding in the hippocampus, dentate gyrus, striatum, nucleus accumbens and frontal cortex of the rat brain as well as on amino acid levels in frontal cortex. NMDA and AMPA binding densities were assayed by autoradiography using, respectively, l‐[3H]glutamate and [3H]AMPA; amino acid concentrations were measured by high performance liquid chromatograhy (HPLC) coupled with UV detection. Ovariectomy was without effect on NMDA and AMPA binding density in all brain regions assayed except in the hippocampal CA1 region and dentate gyrus where it decreased NMDA binding density compared to intact rats values. Oestradiol restored and increased NMDA binding density in the CA1 subfield and the dentate gyrus of ovariectomized rats but, by contrast, it decreased binding density in the striatum and in the frontal cortex while having no effect in the CA2/3 subfield of the hippocampus and in the nucleus accumbens. Oestradiol was without effect on AMPA binding density in the hippocampus and the dentate gyrus but it reduced AMPA binding density in the striatum, the frontal cortex and the nucleus accumbens. Progesterone, and oestradiol combined with progesterone, decreased NMDA but not AMPA binding density in the frontal cortex of ovariectomized rats, and they were without effect on these receptors in the other brain regions assayed. Amino acid concentrations in the frontal cortex were unchanged after ovariectomy or steroid treatments. The effect of oestradiol in the hippocampus confirmed in the present study and our novel findings in the frontal cortex, striatum and nucleus accumbens may have functional significance for schizophrenia and neurodegenerative diseases.
In Vitro Effects of Oestradiol on Galanin Gene Expression in Rat Anterior Pituitary Cells
Authors: Ponchon M. , Lause P. , Maiter D.
Published: March 2003

While the pituitary galanin gene is highly responsive to oestrogen stimulation in vivo, in vitro effects of oestrogens on pituitary galanin gene expression have been less studied. We therefore examined the short‐term effects of 17β‐oestradiol on galanin synthesis by dispersed rat anterior pituitary cell cultures and investigated the mechanisms by which oestrogens may modulate galanin gene expression. 17β‐oestradiol increased galanin mRNA expression in a dose‐dependent manner, with a maximal increase observed at a concentration of 10−7 M. The 17β‐oestradiol (10−7 M)‐induced increase in galanin mRNA expression varied from 3‐ to 20‐fold (average 12‐fold) depending upon the experiments and was also time‐dependent, reaching significance after 6 h. A 1‐h exposure of anterior pituitary cells to 17β‐oestradiol was sufficient to induce markedly galanin mRNA expression after 24 h (by 16‐fold) and 48 h (by 25‐fold). Tamoxifen administered simultaneously with or following 17β‐oestradiol treatment completely abolished the oestrogen‐induced increase of galanin mRNA levels. Cycloheximide (10 μg/ml), a protein synthesis inhibitor, also blocked 17β‐oestradiol‐induced galanin gene expression. Using transcription blockade by actinomycin D, we observed similar decreases of pituitary galanin mRNA concentrations, in the presence and absence of 17β‐oestradiol, implying no oestrogen effect on mRNA stability. We conclude that oestrogens stimulate rat pituitary galanin gene expression, mainly through a transcriptional mechanism, and that this effect requires persistent binding of the hormone to its nuclear receptor and newly synthesized protein intermediates.
Is the Mineralocorticoid Receptor in Brown Norway Rats Constitutively Active?
Authors: Marissal‐Arvy N. , Ribot E. , Sarrieau A. , Mormède P.
Published: March 2003

In a previous study using corticosterone treatment of adrenalectomized rats, we hypothesized that mineralocorticoid receptor (MR)‐related mechanisms are constitutively active and that glucocorticoid receptor (GR)‐mediated mechanisms are more efficient in Brown Norway rats compared to Fischer 344 (F344) rats. In order to discriminate the mineralocorticoid from the glucocorticoid actions exerted by corticosterone, F344 and Brown Norway adrenalectomized rats were treated with increasing doses (1, 5 and 25 μg/ml of drinking water) of deoxycorticosterone (DOC, MR‐specific ligand) or RU 28362 (GR‐specific ligand). These rats were compared with long‐term adrenalectomized (ADX) untreated rats and sham‐ADX rats. This study confirms our previous results, notably the lack of effect of ADX on body weight and fluid intake in Brown Norway rats. Moreover, DOC treatment had no effect in Brown Norway rats whereas the higher dose restored fluid intake of the F344 ADX group to sham values. These results support the hypothesis of a constitutive activation of the MR and therefore the insensitivity of this receptor to its ligand in Brown Norway rats. Alternatively, RU 28362 treatment induced greater weight loss, decrease in food intake, anxiolysis, thymus involution, and decrease in plasma transcortin concentration and pituitary corticosteroid receptor densities in Brown Norway rats than in F344 rats, which is consistent with greater efficiency of GR mechanisms in Brown Norway rats than in F344 rats. Therefore, these strains are of great utility to disentangle MR and GR effects on complex phenotypes.
Effect of Season on Neuropeptide Y and Galanin within the Hypothalamus of the Ewe in Relation to Plasma Luteinizing Hormone Concentrations and the Breeding Season: An Immunohistochemical Analysis
Authors: Barker‐Gibb  , Clarke
Published: March 2003

Within the hypothalamus, neurones that express neuropeptide Y (NPY) and galanin have been implicated in the regulation of gonadotropin‐releasing hormone (GnRH) and gonadotropin secretion. We aimed to determine the extent to which the expression of these two neuronal systems is linked to the seasonal reproductive cycle, and the effect of chronic oestrogen treatment. Immunohistochemical analysis was used to examine changes between the breeding season and anestrus in ovariectomized (OVX) ewes with or without oestrogen treatment (s.c. implants for 2 weeks). Serial blood sampling established plasma luteinizing hormone (LH) profiles, and the ewes were subsequently killed and the brains perfused for immunohistochemistry. In OVX ewes, the amplitude of LH pulses was greater in the nonbreeding season than in the breeding season. Oestrogen treatment caused a marked reduction in plasma LH concentrations during anestrus, but not in the breeding season. The number of cells in the arcuate nucleus/median eminence region (ARC‐ME) that stained for NPY was lower in ewes killed in anestrus (September) than in ewes killed in the breeding season (May), but there was no seasonal change in the number of galanin‐stained cells. Within season, oestrogen treatment did not affect NPY‐ or galanin‐cell number. There was no effect of season or oestrogen on the area of varicose fibres/terminals for either peptide in the ARC‐ME, but galanin immunostaining was more intense during the breeding season. We conclude that the amount of NPY in cell bodies of the ARC‐ME is lower in ewes in the nonbreeding season; this could reflect a steroid‐independent effect of photoperiod. We also conclude that the long‐term negative‐feedback effect of oestrogen on GnRH/LH secretion does not appear to be mediated by NPY‐ or galanin‐containing neurones in the ewe.
Effect of Melatonin Treatment on 24‐h Variations in Responses to Mitogens and Lymphocyte Subset Populations in Rat Submaxillary Lymph Nodes
Authors: Castrillón P. O. , Esquifino A. I. , Varas A. , Zapata A. , Cutrera R. A. , Cardinali D. P.
Published: March 2003

Wistar male rats were injected s.c. with melatonin (30 μg) or vehicle, 1 h before lights off, for 11 days. Ten days after beginning melatonin treatment, rats received Freund’s complete adjuvant or its vehicle s.c., and after 2 days, they were sacrificed at six different time intervals throughout a 24‐h cycle. The mitogenic effect of lipopolysaccharide (LPS) and concanavalin A (Con A), the activity of ornithine decarboxylase (ODC) and the relative size of lymphocyte subset populations were measured in submaxillary lymph nodes. In control rats, the mitogenic effects of LPS and Con A and ODC activity peaked during the afternoon. Injection of Freund’s adjuvant induced a 10‐h shift in the diurnal rhythm of the mitogenic effect of LPS to attain maximal values at night. Melatonin pretreatment blunted the daily variations in the mitogenic activity of Con A or LPS and, when given to Freund’s adjuvant‐injected rats, augmented mesor and amplitude of diurnal rhythm in ODC activity. Maxima in B cell number occurred at night whereas those of T and B‐T cell number occurred during the afternoon. During the early phase of immunization tested, the number of B cells augmented and the amplitude of its diurnal rhythmicity increased both after immunization and following melatonin pretreatment. Maxima of 24‐h rhythms in CD4+ and CD4+/CD8+ cell populations occurred during the afternoon while those of CD8+ cells occurred at late night. Melatonin significantly augmented CD4+ cell number and decreased CD8+ cell number; it therefore augmented the CD4+:CD8+ ratio. The results suggest that pretreatment with a pharmacological dose of melatonin exerts immunomodulating effects at an early, preclinical, phase of Freund’s adjuvant‐induced arthritis in rats.
The Effect of the Alpha‐2‐Adrenergic Agonist, Clonidine, on Secretion Patterns and Rates of Adrenocorticotropic Hormone and its Secretagogues in the Horse
Authors: Alexander S. L. , Irvine C. H. G.
Published: March 2003

Alpha‐2‐adrenoceptor activation may lower adrenocorticotropic hormone (ACTH) by reducing secretagogue input and/or increasing the release of an inhibitory factor (CIF). To investigate this, we gave clonidine, an α‐2‐agonist, to seven horses, and collected pituitary venous blood every minute for 20 min before treatment and 40 min after treatment. Six horses were given saline vehicle. Mean secretion rates of corticotrophin‐releasing hormone (CRH), arginine vasopressin (AVP) and ACTH were calculated before and during four 5‐min then two 10‐min periods after clonidine or saline. Reduction in ACTH secretion without corresponding changes in CRH and/or AVP would imply the presence of CIF. Secretion rates of ACTH (P = 0.008) and AVP (P = 0.0005) fell after clonidine and remained lower than baseline values for 20 min and 10 min, respectively. The CRH secretion rate decreased slightly but not significantly after clonidine. In controls, hormone secretion rates did not alter during the experiment. Multiple linear regression showed that CRH and AVP secretion accounted for 69% (treated) or 45% (controls) of the variation in ACTH secretion (P < 0.0001 for each). CRH alone contributed 80% (treated) or 76% (controls) of the fit to this model, which is consistent with the concept that CRH ‘sets the gain’ of the response of corticotrophs to fluctuations in AVP. Accordingly, minute‐to‐minute changes in pituitary concentrations of AVP and ACTH were synchronous when all data were considered (% concordant changes: controls, 68%, P < 0.0001; treated, 76%, P < 0.0001) and the percentage of concordant movement was unaffected by clonidine (before 72%; after 73%; P = 0.80). In treated horses but not controls, the ratio between the secretion rates of ACTH and AVP fell (P = 0.009), while the ACTH : CRH ratio tended to fall after clonidine, implying reduced responsiveness to stimulation. Moreover, one horse showed a drop in ACTH and a rise in CRH and AVP secretion after clonidine. We conclude that in horses α‐2‐adrenoceptor activation lowers ACTH secretion primarily by reducing the secretion of AVP and possibly CRH. While there was some evidence that a CIF may participate in the clonidine‐induced suppression of ACTH, the subtlety of the discordance between ACTH and its secretagogues in most horses and the rarity of complete dissociation indicate that it does not play a major role.
Differential Regulation of Leptin Receptor But Not Orexin in the Hypothalamus of the Lactating Rat
Authors: Brogan R. S. , Grove K. L. , Smith M. S.
Published: March 2003

During lactation, hypothalamic levels of neuropeptide Y (NPY) and agouti related protein (AGRP) mRNA are increased, while pro‐opiomelanocortin (POMC) mRNA is decreased. Serum leptin levels are also decreased during lactation. These changes may underlie the large increases of both food and water intake that occur in concert with milk production. However, additional hypothalamic substances, such as the novel peptide, orexin, may be involved. In addition, in the presence of chronically suppressed levels of serum leptin, there may be a change in leptin receptor expression in the hypothalamus. The objectives of the present study were to determine if orexin and leptin receptor mRNA levels were changed during lactation. Rats were studied on dioestrus of the oestrous cycle or on day 10 postpartum (the lactating animals were suckling eight pups). Orexin mRNA levels in the lateral hypothalamus did not differ between dioestrus and lactation. There was a significant increase in leptin receptor mRNA levels in the supraoptic nucleus during lactation compared to dioestrus. Furthermore, leptin receptor protein, as determined by immunocytochemistry, was colocalized in virtually all vasopressin and oxytocin cells in the supraoptic nucleus. Lactating animals exhibited a decrease in leptin receptor mRNA in the ventromedial hypothalamic nucleus whereas no change was apparent in other hypothalamic areas compared to the dioestrus animals. These results demonstrate that changes in orexin do not appear to contribute to the increase in food intake during lactation. It is likely that the increases in NPY and ARGP, coupled with the decrease in POMC, are primarily responsible for sustaining the chronic hyperphagia of lactation. The changes observed in leptin receptor expression in the hypothalamus, along with the suppression of serum leptin levels, also suggest that the leptin signalling system may play a significant role in the regulation of food and water intake during lactation.
Seasonal Variation in Androgen‐Metabolizing Enzymes in the Diencephalon and Telencephalon of the Male European Starling (Sturnus vulgaris)
Authors: Riters L. V. , Baillien M. , Eens M. , Pinxten R. , Foidart A. , Ball G. F. , Balthazart J.
Published: March 2003

In seasonally breeding songbirds, seasonal fluctuations occur in serum testosterone (T) concentrations and reproductive behaviours. Many T‐dependent behaviours are regulated by the activity of androgenic and oestrogenic metabolites within specific brain regions. Male European starlings breed in spring when circulating T concentrations peak. T and its metabolites act within portions of the diencephalon to regulate the pituitary‐gonadal axis and to activate courtship and copulation. Song in male starlings is critical for mate attraction during the breeding season and is regulated by steroid‐sensitive nuclei in the telencephalon and diencephalon. Outside the breeding season, T is undetectable, however, males continue to sing at high levels. This suggests that singing outside of the breeding season might not be T‐dependent as it appears to be in the spring. Alternatively, singing when T is low might continue to be regulated by T due to increased sensitivity of the brain to the action of the steroid. This increased sensitivity could be mediated by changes in intracellular T metabolism leading to increased production of active or decreased production of inactive metabolites. To explore the relationship between T‐metabolism and reproductive behaviour, we analysed seasonal changes in the activity of four brain T‐metabolizing enzymes: aromatase, 17β‐hydroxysteroid dehydrogenase (17β‐HSDH), 5α‐reductase (all three convert T into active metabolites) and 5β‐reductase (converts T into an inactive metabolite) in the diencephalon and telencephalon. In the anterior and posterior diencephalon, the highest aromatase was observed in spring when this region is critical for courtship and copulation. In the telencephalon, aromatase was highest and 5β‐reductase was lowest throughout the winter months well prior to the reproductive season and these enzymes presumably maximize T‐activity within this region. Although these data do not indicate whether the metabolic changes occur specifically within song nuclei, these findings are compatible with the idea that singing in male starlings outside the breeding season may be regulated by steroids despite the presence of low serum T concentrations. Overall, seasonal changes in T‐metabolizing enzymes appear to play a significant role in seasonal changes in behaviour and reproductive physiology.
β‐Endorphin Cells in the Arcuate Nucleus: Projections to the Supraoptic Nucleus and Changes in Expression During Pregnancy and Parturition
Authors: Douglas A. J. , Bicknell R. J. , Leng G. , Russell J. A. , Meddle S. L.
Published: March 2003

Supraoptic nucleus oxytocin neurone activity and secretion are inhibited in late pregnancy and parturition by endogenous opioids. Here, we investigated alterations in the projections and gene expression of β‐endorphin/pro‐opiomelanocortin neurones in the arcuate nucleus in the pregnant rat. All regions of the arcuate nucleus were found to contain cells immunoreactive for β‐endorphin fluorescent microbeads retrogradely transported from the supraoptic nucleus, and double‐labelled neurones (β‐endorphin plus microbeads), showing that β‐endorphin neurones throughout the arcuate nucleus project to the supraoptic nucleus. There was an increase in the number of β‐endorphin‐immunoreactive cells in the arcuate nucleus and an increase in the density of β‐endorphin fibres within the supraoptic nucleus and peri‐supraoptic region in late pregnancy and parturition, suggesting enhanced expression of β‐endorphin and increased β‐endorphin innervation of the supraoptic nucleus. Pro‐opiomelanocortin mRNA expression in the arcuate nucleus increased in late compared to early pregnancy: the number of positive neurones significantly increased in the caudal region. Fos expression (an indicator of neuronal activation) in the arcuate nucleus was colocalized in β‐endorphin neurones in both proestrus and parturient rats, but the number of positive cells did not increase during parturition, suggesting lack of activation of β‐endorphin neurones at birth. Thus, β‐endorphin cells in the arcuate nucleus project to the supraoptic nucleus and increased innervation during pregnancy may explain the enhanced endogenous opioid inhibition of oxytocin neurones.
Chemical Coding of GABAB Receptor‐Immunoreactive Neurones in Hypothalamic Regions Regulating Body Weight
Authors: Bäckberg M. , Collin M. , Ovesjö M.‐L. , Meister B.
Published: March 2003

γ‐aminobutyric acid (GABA) interacts with hypothalamic neuronal pathways regulating feeding behaviour. GABA has been reported to stimulate feeding via both ionotropic GABAA and metabotropic GABAB receptors. The functional form of the GABAB receptor is a heterodimer consisting of GABAB receptor‐1 (GABABR1) and GABAB receptor‐2 (GABABR2) proteins. Within the heterodimer, the GABA‐binding site is localized to GABABR1. In the present study, we used an antiserum to the GABABR1 protein in order to investigate the cellular localization of GABABR1‐immunoreactive neurones in discrete hypothalamic regions implicated in the control of body weight. The colocalization of GABABR1 immunoreactivity with different chemical messengers that regulate food intake was analysed. GABABR1‐immunoreactive cell bodies were found in the periventricular, paraventricular (PVN), supraoptic, arcuate, ventromedial hypothalamic, dorsomedial hypothalamic, tuberomammillary nuclei and lateral hypothalamic area (LHA). Direct double‐labelling showed that glutamic acid decarboxylase (GAD)‐positive terminals were in close contact with GABABR1‐containing cell bodies located in all these regions. In the ventromedial part of the arcuate nucleus, GABABR1‐immunoreactive cell bodies were found to contain neuropeptide Y, agouti‐related peptide (AGRP) and GAD. In the ventrolateral part of the arcuate nucleus, GABABR1‐immunoreactive cell bodies were shown to contain pro‐opiomelanocortin and cocaine‐ and amphetamine‐regulated transcript. In the LHA, GABABR1 immunoreactivity was present in both melanin‐concentrating hormone‐ and orexin‐containing cell populations. In the tuberomammillary nucleus, GABABR1‐immunoreactive cell bodies expressed histidine decarboxylase, a marker for histamine‐containing neurones. In addition, GAD and AGRP were found to be colocalized in some nerve terminals surrounding GABABR1‐immunoreactive cell bodies in the parvocellular part of the PVN. The results may provide a morphological basis for the understanding of how GABA regulates the hypothalamic control of food intake and body weight via GABAB receptors.
Puberty: Mind and Body
Authors: Ebling Fran
Published: March 2003

Summary Puberty is the attainment of fertility − the ability to reproduce. It occurs because our brains begin to secrete one key hormone, gonadotropin‐releasing hormone. This causes the pituitary gland to induce maturation of the testis and the ovary, which then produce sex steroid hormones and mature sperm and eggs. We should be concerned that the age at which puberty begins is decreasing in many countries. Puberty starts when adequate growth and energy storage has occurred, so the earlier age of puberty may reflect recent increases in adolescent obesity resulting from more sedentary lifestyles.
Examination of the diagnostic value and estimation of the chaos phenomenon in masticatory movement using fractal dimension in patients with temporomandibular dysfunction syndrome
Authors: Morinushi  , Kawasaki  , Masumoto  , Shigeta  , Ogura  , Takigawa
Published: March 2003

The aim of this study was to estimate the chaos phenomenon (chaos) in masticatory movements using the fractal dimension (FD), and to examine the diagnostic value of the fractal dimension in comparing stomatognathic functional disturbances with normal stomatognathic function. The subjects were all high school students and included nine subjects presenting with acceptable normal occlusion, 18 subjects with TMJ dysfunction syndrome and seven subjects with tooth crowding. Masticatory movements were obtained during free, right side, and left side gum‐chewing and were used to calculate the capacity dimension in the FD. Chaos in the masticatory movement was estimated by the FD saturated with some constant value to an increase of embedding dimension (approached a plateau). In the crowding group, the FD was also significantly high on the sagittal plane in comparison with the normal. In the patients with pain, the FD on the sagittal plane was significantly high. In the patients with pain and closed lock, the FD on the frontal plane was significantly high. However, in the patients with pain and with reduction of anterior disc displacement, the FD was significantly low on the horizontal plane. These findings suggest that chaos is present in masticatory movements and the difference in the FD are of diagnostic value in evaluation of the relationship between FD and stomatognathic functional disturbance.
Effects of honey consumption on enamel microhardness in normal versus xerostomic patients
Authors: Sela MO. , Shapira  , Grizim  , Lewinstein  , Steinberg  , Gedalia  , Grobler
Published: March 2003

summary The aim was to investigate the effect of honey on the microhardness of enamel in normal and xerostomic patients. Normal subjects and patients who were xerostomic after neck irradiation, wearing prosthetic appliances with slabs of human enamel inserted, were asked to consume a single teaspoonful of pure honey, pH 3·9. Measurements of the saliva pH were taken before, during and after a 5 min exposure to the honey. The pH of the honey–saliva mixtures decreased significantly from about 6 to 4 in both groups, returning to the baseline pH after the mixture was swallowed. The initial microhardness of the surface of the enamel slabs decreased significantly after consumption of a teaspoonful of the honey in the subjects with a regular saliva flow, whereas in the irradiated dry‐mouth patients, no enamel microhardness decrease occurred. The supposed solubility‐reducing factor present in honey which, according to the literature remains active in the absence of saliva, but will be inactivated by salivary enzymes, gives some support to the hypothesis that honey is less cariogenic in dry‐mouth subjects. The absence of adequate controls in the present study prevents the investigation of how specific this effect is to honey.
Polymetallism and osseointegration in oral implantology: pilot study on primate
Authors: Foti B. , Tavitian P. , Tosello A. , Bonfil J.‐J. , Franquin J.‐C.
Published: March 2003

In oral implantology, successful results in osseointegration are obtained in the medium term (6–12 months) with commercially pure titanium implants. However, current superstructures can be of a different nature (precious metal or titanium) and of different manufacture (cast or machine‐produced). Polymetallism between the implant and the superstructure may lead to conditions of galvanic corrosion, and influence osseointegration. The study described establishes, on the one hand, the procedures of animal experimentation in primates and on the other, the techniques of analysis of histological sections. The first technique of analysis is based on histomorphometry and leads to the definition of an osseointegration index. The second technique of analysis consists of X spectrometry by dispersion of energy which enables a spectral analysis of selected points below the crestal neck of the implant (vulnerable area in the case of corrosive attack) to be obtained. It is noted that after 6 months, two of which were of activation, osseointegration did not vary according to the nature of the superstructure (precious alloy or titanium). After 2 months, the presence of a precious alloy superstructure lead to titanium migration towards the area around the cervical region of the implant (10–50 μm). This phenomenon did not occur with a titanium implant. It can therefore be presumed that polymetallism leads to detectable corrosion after 2 months but without apparent modification of osseointegration.
Modulation of jaw reflexes by remote noxious stimulation and mental state: possible association with psychological measurements of mental stress and occupation
Authors: Cadden S. W. , Van Der Glas H. W. , Van Der Bilt A.
Published: March 2003

Combined electrophysiological and psychophysical experiments were performed on 15 human subjects to investigate the possible effects of perceived stress or mental occupation on jaw reflexes. Electromyographic recordings were made from the masseter and anterior temporalis muscles, of the series of excitatory and inhibitory reflexes evoked by tapping on an upper incisor tooth. The reflexes were modified by application of painful cold (3 °C) stimuli to the subject's hand (remote noxious stimulation) or by the subject undertaking mental exercises (the 17 times table). The resulting changes in the reflexes usually involved transient increases in EMG activity around the interfaces between successive inhibitory and excitatory responses. Both the remote noxious stimuli and the mental exercises usually produced increases in both stress and mental occupation as assessed using visual analogue scales. However, correlations between these psychological effects and the effects on the reflexes were generally weak or absent. We conclude that the modulation of jaw reflexes by remote noxious stimuli or mental activity is not likely to be dependent on an individual's conscious awareness of a change in mental state. On the other hand, data from a related study suggest that the effects on the reflex may be more closely related to the autonomic responses to stress.
Head, neck and trunk movements accompanying jaw tapping
Authors: Yamabe Y. , Yamashita R. , Fujii H.
Published: March 2003

Several studies have examined the functional relationship between mandibular movement and head or body posture, but head and body motion during jaw movement have not been extensively investigated. Ten healthy participants performed repetitive jaw tapping movement. Piezoelectric accelerometers were attached on the surfaces of the participant's forehead, mentum, and over the spinous processes of the sixth cervical, twelfth thoracic and third lumbar vertebrae. The direction in which the antero‐posterior acceleration signals appeared around the onsets of jaw opening and closing were observed for the period from the 6th to the 25th strokes of the jaw tapping. Around the onset of jaw opening, the forehead and the lumbar vertebra tended to move posteriorly, but the cervical and thoracic vertebrae moved anteriorly with significant frequencies. The directions of the motions of these locations reversed themselves at the beginning of jaw closing; so the motions of the forehead and the lumbar vertebra were opposed again to the ones of the cervical and thoracic vertebrae. The results suggest that the head extend–flex motion often accompanied the jaw open–close movement, and the motions of the neck and trunk existed, which would serve the purpose of promoting the mandible to move smoothly.
Oral habits and their association with signs and symptoms of temporomandibular disorders in adolescent girls
Authors: Gavish A. , Halachmi M. , Winocur E. , Gazit E.
Published: March 2003

A group of 248 randomly selected high school girls, aged 15–16 years, completed a questionnaire and were examined clinically with regard to various oral habits and signs and symptoms of temporomandibular disorders (TMD). Common habits reported in the literature, such as gum chewing, nail biting, biting foreign objects, clenching and bruxism, eating seeds and crushing ice, as well as two less reported habits, ‘jaw play’ and continuous arm leaning, were evaluated. The most outstanding finding was the high prevalence and intensity of gum chewing among our study group: 92% of the girls chewed daily and 48% chewed gum for more than 3 h a day (intensive gum chewing). Statistically significant associations were found between intensive gum chewing and muscle sensitivity (P<0·001) and joint noises (P<0·05), and between crushing ice and muscle sensitivity to palpation (P<0·005). A positive association was found between ‘jaw play’ and joint disturbances: reported joint noises (P<0·01), catching of the joint (P<0·01) and joint tension (P<0·001). A positive association was also found between arm leaning and reported joint noises (P<0·05), catching (P<0·05), and joint tension (P<0·005). There was no association between the presence of bruxism and muscle sensitivity to palpation or joint disturbances. The potential harmful effects of intensive gum chewing, ‘jaw play’, continuous arm leaning and ice crushing are presented in this study. In light of these findings, the professional community should address these habits with proper data gathering, examination and consultation.
Pulp reactions to different preparation techniques on teeth exhibiting periodontal disease
Authors: Zöllner A. , Gaengler P.
Published: March 2003

To evaluate the histopathological outcome of two preparation techniques (featheredge preparation/shoulder preparation) on teeth exhibiting pulp reactions due to age and periodontal disease, 11 teeth were prepared for full veneer crowns. Laboratory made resin crowns were fixed with a zinc phosphate cement for a period of 90 days. After extraction, adjacent pulpal areas were histopathologically rated according to the BRD criteria comprising the parameters (i) Bacterial invasion, (ii) Regenerative parameters, (iii) Degenerative parameters. Degenerative reactions were more correlated with tooth preparation than with advanced periodontal disease. The severity of endondontal reactions depends more on remaining dentin thickness than on the type of preparation.
Penetration of the pulp chamber by carbamide peroxide bleaching agents on teeth restored with a composite resin
Authors: GÖkay O. , TunÇbİlek M. , Ertan R.
Published: March 2003

This in vitro study was performed to evaluate the effect of various concentrations of carbamide peroxide bleaching agents on the pulp chambers of teeth restored by a composite resin. Forty‐nine human extracted anterior teeth were used. All the teeth were sectioned 3 mm apical of the cemento–enamel junction and the intracoronal tissue removed. The teeth were separated into the seven groups each containing seven teeth. Twenty‐eight teeth were used as controls (groups I–IV), standardized cavities were prepared with the remaining 21 teeth (groups V, VI, VII), and restored with a hybrid composite resin (XR Herculite). Acetate buffer was placed in the pulp chamber to absorb and stabilize any peroxide that might penetrate. Group I was exposed only to distilled water. Groups II and V were applied with 10% CP (Contrast PM), groups III and VI were applied with 15% CP (Contrast PM), groups IV and VII were applied with 35% CP (Quik Start) and left for 30 min at 37 °C. Then, the acetate buffer solution in the pulp chamber of each tooth was removed and the chamber was then rinsed twice with 100 ml of distilled water. The contents then had leucocryctal violet and enzyme horseradish peroxidase added. The optical density of the resulting blue solution was determined spectrophotometrically, and was converted into microgram equivalents of hydrogen peroxide. A higher level of bleaching agent penetrated into the pulp chamber in the restored teeth than in the sound teeth.