bluuebunny/crossref_metadata_2025 huggingface dataset:
Glutamatergic Synaptic Inputs to Mouse Supraoptic Neurons in Calcium‐Free Medium in vitro/e1
Authors: Inenaga Kiyotoshi , Honda Eiko , Hirakawa Teruyuki , Nakamura Shuichi , Yamashita Hiroshi
Published: March 2003

The effects of Ca2+‐free perfusion medium on excitatory postsynaptic currents (EPSCs) and potentials (EPSPs) were studied by whole‐cell recordings from neurons of the supraoptic nucleus (SON) in trimmed slice preparations of mouse hypothalamus. EPSCs evoked with either focal stimulation to the SON or perfusion of slices with high K+‐medium, spontaneous EPSCs (sEPSCs) and miniature EPSCs (mEPSCs) recorded from neurons of the SON were blocked by the glutamate receptor antagonist kynurenic acid (1 mM). While EPSCs evoked by focal stimulation were abolished in the presence of Ca2+‐free perfusion medium; sEPSCs and mEPSCs remained. Neither the frequency nor the amplitude of the sEPSCs and mEPSCs significantly changed during the application of Ca2+‐free perfusion medium. Perfusion of slices with high K+‐medium increased the mEPSC frequency compared with that recorded in normal Ca2+‐containing perfusion medium. In contrast, mEPSC frequency did not change during perfusion with Ca2+‐free high K+‐medium. In current‐clamp mode sEPSPs were observed during the perfusion with Ca2+‐free medium. Some sEPSPs recorded in Ca2+‐free medium were sufficiently large to evoke action potentials. These results imply that spontaneous glutamatergic synaptic inputs to the hypothalamic neurosecretory cells exist in Ca2+–free perfusion medium. Thus, the present study suggests that Ca2+‐free medium does not always block the synaptic transmission in hypothalamic slice preparations.
Negative Regulation of Gonadotropin‐Releasing Hormone and Gonadotropin‐Releasing Hormone Receptor Gene Expression by a Gonadotropin‐Releasing Hormone Agonist in the Rat Hypothalamus
Authors: Han  , Kang  , Seong  , Geum  , Suh  , Kim
Published: March 2003

There exists evidence for the presence of ultrashort loop feedback circuits of gonadotropin‐releasing hormone (GnRH) secretion in the hypothalamus. It is, however, uncertain whether a similar mechanism is involved in the regulation of GnRH gene expression in vivo. Furthermore, little is known about the regulation of GnRH receptor (GnRHR) expression in the brain. In the present study, we examined the regulation of GnRH and its receptor gene expression by GnRH in vivo. A GnRH agonist, [D‐Ala6, des‐Gly10]GnRH‐ethylamide (des‐Gly GnRH), was administered by intracerebroventricular (i.c.v.) injection via the lateral ventricle of ovariectomized and estradiol (OVX+E)‐treated rats. The amounts of GnRH and GnRHR mRNA were measured in the preoptic area (POA) and posterior mediobasal hypothalamus (pMBH) micropunch samples from individual rat brain slices by respective competitive reverse transcription‐polymerase chain reactions. The i.c.v. administration of des‐Gly GnRH significantly decreased GnRH and GnRHR mRNA expression in a dose‐and time‐related manner: des‐Gly GnRH (6 ng) suppressed GnRH and GnRHR mRNA expression within 2 h, and the suppression was maintained without significant variation until 8 h after treatment. Treatment with Antide, [N‐Ac‐
d‐Nal(2)1, pCl‐
d‐Phe2,
d‐Pal(3)3, Lys(Nic)5,
d‐Lys(Nic)6, Lys(iPR)8,
d‐Ala10]GnRH (10 ng), a potent GnRH antagonist, did not alter GnRH mRNA expression, but prevented des‐Gly GnRH‐induced suppression of GnRH mRNA expression. Antide alone decreased GnRHR mRNA expression, but failed to alter agonist‐induced suppression of GnRHR mRNA expression. These results demonstrate the existence of an ultrashort loop feedback mechanism for GnRH gene expression in the POA, along with homologous down‐regulation of GnRHR mRNA expression in the pMBH.
Isolation and Pharmacological Characterization of Two Functional Splice Variants of Corticotropin‐Releasing Factor Type 2 Receptor from Tupaia belangeri
Authors: Palchaudhuri  , Hauger  , Wille  , Fuchs  , Dautzenberg§
Published: March 2003

From brain, heart and muscle tissue of the tree shrew (Tupaia belangeri), a higher order mammal, cDNA clones were isolated that encoded two functional splice variants of the corticotropin‐releasing factor (CRF) type 2 receptor (CRF‐R2). The first, full‐length splice variant, amplified from brain and heart tissue, encoded a CRF receptor protein that is 410 amino acids in length and ≈96% homologous to human CRF‐R2α. The second, full‐length splice variant, derived from skeletal muscle tissue, encoded a 437‐amino acid CRF receptor protein that is ≈92% homologous to human CRF‐R2β. Semiquantitative reverse transcriptase polymerase chain reaction (RT‐PCR) amplifications and RNase protection analyses, showed that tree shrew CRF‐R2α (tCRF‐R2α) and tree shrew CRF‐R2β (tCRF‐R2β) were coexpressed in brain tissue but not in heart and skeletal muscle tissue. Finally, human embryonic kidney 293 (HEK293) cells stably transfected with tCRF‐R2α and tCRF‐R2β were used to demonstrate that the CRF analogs urocortin and sauvagine bind with significantly greater affinity (21‐ to 140‐fold) to these two CRF‐R2 splice variants than do human/rat and ovine CRF analogs. In keeping with these results of our CRF binding studies, EC50 values were substantially lower for urocortin‐and sauvagine‐stimulated than for h/rCRF‐and oCRF‐stimulated cyclic AMP accumulation in HEK293 cells stably transfected with tCRF‐R2α or tCRF‐R2β cDNAs. The tree shrew therefore constitutes an important animal model in which to investigate the role of CRF receptor subtypes in the stress response.
Immunoreactive Neurotensin in Gonadotrophs and Thyrotrophs is Regulated by Sex Steroid Hormones in the Female Rat
Authors: Bello  , Hernández  , González  , Reyes  , Negrín  , Marrero  , Sánchez‐Criado  , Tramu  , Alonso
Published: March 2003

In addition to regulating anterior pituitary function by being released from the median eminence, mammalian neurotensin (NT) may also exert an autocrine or a paracrine action within the anterior pituitary. In this study, using double immunostaining with elution restaining, we identified the specific anterior pituitary cells which express NT immunoreactivity (NT‐IR) during the rat oestrous cycle. In the normal cycling rat, NT‐IR was present in both gonadotrophs and thyrotrophs and displayed plastic changes along the oestrous cycle. Both the number of TSH‐NT positive cells and the intensity of immunological reaction were elevated during dioestrus, and decreased through pro‐oestrus and early oestrus. NT‐IR was also high in both follicle stimulating hormone (FSH)‐ or luteinizing hormone (LH)‐positive cells during early pro‐oestrus, and decreased during late pro‐oestrus. Treatment of intact rats with either the anti‐oestrogens Tamoxifen or LY117018, or the anti‐progestagen RU486 prevented the normal expression of NT‐IR in thyroid‐stimulating hormone (TSH)‐, FSH‐, and LH‐positive cells during pro‐oestrus. Bilateral ovariectomy induced a dramatic reduction in the number of NT‐IR cells. This effect was completely prevented by treatment of ovariectomized rats with oestradiol and progesterone, and was unaffected by the concurrent administration of a GnRH antagonist. Furthermore, administration of an anti‐oestrogen together with an anti‐progestagen to ovariectomized‐oestrogen, progesterone‐treated rats, blocked the stimulatory effect of ovarian hormones on NT‐IR in anterior pituitary cells. These findings demonstrate that, in female rats, NT is specifically localized in gonadotrophs or thyrotrophs. In addition, they strongly suggest that changes in circulating concentrations of ovarian steroids may control both NT synthesis in, and release from, these cells.
Norepinephrine Regulation of Growth Hormone Release from Goldfish Pituitary Cells. I. Involvement of α2 Adrenoreceptor and Interactions With Dopamine and Salmon Gonadotropin‐Releasing Hormone
Authors: Lee  , Chan  , Chang  , Yunker  , Wong
Published: March 2003

Adrenergic regulation of growth hormone (GH) release in the goldfish was examined in vitro using dispersed goldfish pituitary cells under column perifusion. Norepinephrine and epinephrine suppressed basal GH release from goldfish pituitary cells in a reversible and dose‐dependent manner. At high doses, a transient rebound of GH release was observed after termination of norepinephrine and epinephrine treatment. In this study, the dose‐dependence of adrenergic inhibition on basal GH release was mimicked by the α2 agonists clonidine and UK14304. Basal GH secretion, however, was not affected by the β agonist isoproterenol and α1 agonist methoxamine. In addition, the inhibitory actions of norepinephrine and clonidine on basal GH release were blocked by the α2 antagonists yohimbine and RX821002. The β antagonist propranolol and α1 antagonists prasozin and benoxathian were not effective in this respect. Salmon gonadotropin‐releasing hormone (sGnRH) and dopamine, two known GH‐releasing factors in fish, stimulated GH release from goldfish pituitary cells and their GH‐releasing actions were inhibited by simultaneous treatment with norepinephrine. Furthermore, the GH rebound after norepinephrine treatment was significantly enhanced by prior exposure to sGnRH and this effect was not observed with dopamine treatment. These results, taken together, suggest that in the goldfish adrenergic input at the pituitary level inhibit basal GH release through activation of α2 adrenoreceptors. This α2 inhibitory influence may interact with dopaminergic and GnRH input to regulate GH secretion from goldfish pituitary cells. The ‘post‐inhibition’ GH rebound after NE treatment and its sensitivity to sGnRH potentiation may also represent a novel mechanism for GH regulation in fish.
B219/OB‐R 5′–UTR and Leptin Receptor Gene‐Related Protein Gene Expression in Mouse Brain and Placenta: Tissue‐Specific Leptin Receptor Promoter Activity
Authors: Mercer  , Moar  , Hoggard  , Strosberg  , Froguel  , Bailleul
Published: March 2003

Leptin receptor (OB‐R) splice variants either encode proteins with different 3′ cytoplasmic domains or have different 5′ untranslated regions (UTR), indicative of dual promoters. The B219/OB‐R promoter transcribes only OB‐R transcripts, whereas the OB‐R/GRP promoter initiates transcription of both OB‐R and another protein of unknown function, called the leptin receptor gene‐related protein (OB‐RGRP). We compared expression of B219/OB‐R 5′–UTR and OB‐RGRP mRNAs by in situ hybridization. We thus assessed, by inference, the contributions of the two promoters to the leptin receptor transcript pool, in murine brain or in placenta, a tissue with abundant leptin receptor mRNA. Expression of B219/OB‐R 5′–UTR mRNA (and thus by inference B219/OB‐R promoter activity) in brain was similar in both distribution and relative intensity to OB‐R mRNA. OB‐RGRP mRNA (and thus by inference OB‐R/GRP promoter activity) was widely distributed in murine brain, with elevated expression in the hypothalamic regions that express the leptin receptor mRNA, including the paraventricular nucleus. B219/OB‐R 5′–UTR mRNA, but not OB‐RGRP mRNA, was upregulated in hypothalamus of obese ob/ob mice. In placenta, B219/OB‐R 5′–UTR mRNA was restricted to the maternal interface, and transcription of both long and short leptin receptor splice variants in the main body of the tissue thus proceeds via the OB‐R/GRP promoter, strongly indicative of tissue‐specific promoter usage.
Evidence That Members of the TGFβ Superfamily Play a Role in Regulation of the GnRH Neuroendocrine Axis: Expression of a Type I Serine‐Threonine Kinase Receptor for TGRβ and Activin in GnRH Neurones and Hypothalamic Areas of the Female Rat
Authors: Prevot  , Bouret  , Croix  , Takumi  , Jennes  , Mitchell  , Beauvillain
Published: March 2003

The present study was designed to determine whether transforming growth factor (TGF)β and/or activin participate in the regulation of the gonadotropin releasing hormone (GnRH) neuroendocrine axis in vivo. Single‐label in situ hybridization histochemistry was used to determine the anatomical distribution of a TGFβ and activin type I receptor (B1) mRNA, in the adult female rat hypothalamic areas that are known to be important sites for the regulation of reproduction. Dual‐label in situ hybridization histochemistry was performed to determine whether B1 mRNA was expressed in GnRH neurones. The results of these studies revealed an extensive distribution of B1 mRNA in the hypothalamic regions, including diagonal bands of Broca, preoptic area, arcuate nucleus and median eminence. In the median eminence, B1 mRNA was detected in tanycytes and in the endothelial cells of the pituitary portal blood capillaries. Dual‐label in situ hybridization histochemistry showed that 31±5% of GnRH neurones expressed B1 mRNA, thus providing evidence that TGFβ and/or activin can act directly on GnRH neurones to modulate their activity. Taken together, these data provide morphological arguments in favour of a participation of TGFβ and/or activin in the regulation of reproduction at the hypothalamic level.
Vasopressin Regulation of Noradrenaline Release Within the Supraoptic Nucleus
Authors: Ludwig M. , Onaka T. , Yagi K.
Published: March 2003

The effect of electrically evoked dendritic vasopressin release on noradrenaline release into the hypothalamic supraoptic nucleus was assessed by in vivo microdialysis in conjunction with high pressure liquid chromatography and electrochemical detection. Electrical activation of magnocellular supraoptic neurones by stimulation of their axons at the level of the neural lobe significantly increased noradrenaline release into the nucleus (2.5‐fold, P<0.03). This increase was completely blocked by administration of a nonpeptide vasopressin V1a receptor antagonist via the microdialysis probe. These data suggest that dendritically released vasopressin facilitates noradrenaline release into the hypothalamic nucleus.
Corticosteroid Effects on Serotonin Responses in Granule Cells of the Rat Dentate Gyrus
Authors: Karten Y. J. G. , Stienstra C. M. , Joëls M.
Published: March 2003

Granule cells in the rat dentate gyrus contain mineralocorticoid and glucocorticoid receptors to which the adrenal hormone corticosterone binds with differential affinity. These cells also express various receptor‐subtypes for serotonin (5‐HT), including the 5‐HT1A receptor which mediates a membrane hyperpolarization accompanied by a decrease in membrane resistance. Earlier studies have shown that removal of corticosterone by adrenalectomy, particularly in the dentate gyrus, results in enhanced expression of the 5‐HT1A receptor mRNA and increased 5‐HT1A receptor binding capacity. This was normalized by activation of mineralocorticoid receptors or concurrent activation of both receptor types. In the present, intracellular recording study in vitro, we examined if the altered levels of 5‐HT1A receptor mRNA and protein are associated with changes in the response to 5‐HT. We found that the hyperpolarization and resistance decrease induced in granule cells by a submaximal (10 µM) dose of 5‐HT were unaltered 2–4 days after adrenalectomy, indicating a dissociation between corticosteroid actions on 5‐HT1A receptor mRNA/protein levels and functional responses to 5‐HT. Subsequent occupation of mineralocorticoid receptors in vitro significantly suppressed the 5‐HT induced change in resistance, 1–4 h after steroid application. Compared to this, concurrent activation of glucocorticoid receptors led to large responses to 5‐HT. This modulation by steroids was not observed with a higher dose of 5‐HT (30 µM). The data suggest that with moderate amounts of 5‐HT, corticosteroids affect the information flow through the dentate gyrus such that excitatory transmission is promoted with predominant mineralocorticoid receptor activation and attenuated with additional glucocorticoid receptor occupation.
The Differential Regulation of CART Gene Expression in a Pituitary Cell Line and Primary Cell Cultures of Ovine Pars Tuberalis Cells
Authors: Barrett P. , Morris M. A. , Moar K. M. , Mercer J. G. , Davidson J. A. , Findlay P. A. , Adam C. L. , Morgan P. J.
Published: March 2003

The cocaine‐amphetamine regulated transcript (CART) encodes for a protein which has an important role in the regulation of appetite and body weight. To date, no details of the molecular events and signal transduction pathways which regulate this gene are available. We report the identification of CART gene expression in the GH3 pituitary cell line. We have used activators of the cAMP or protein kinase C (PKC) signal transduction pathways to show that, in GH3 cells, CART is transcriptionally up‐regulated by activators of the cAMP signal transduction pathway. We also identify CART gene expression in ovine pars tuberalis (PT) tissue and primary cell cultures. In PT cells in contrast to GH3 cells, CART gene expression is upregulated by activators of the PKC signal transduction pathway. Cultured cells have provided a valuable resource for the detailed analysis of specific regulatory mechanisms underlying transcriptional or translational regulation of genes, signal transduction events and many other cellular processes. GH3 and PT cells may therefore provide a resource for the further detailed molecular analysis of the events regulating CART gene expression and processing.
Repeated Antenatal Glucocorticoid Treatment Decreases Hypothalamic Corticotropin Releasing Hormone mRNA but not Corticosteroid Receptor mRNA Expression in the Fetal Guinea‐Pig Brain
Authors: McCabe L. , Marash D. , Li A. , Matthews S. G.
Published: March 2003

Approximately 10% of pregnant women are treated with synthetic glucocorticoids in late gestation, to promote fetal lung maturation. The effectiveness of this treatment has led to the use of repeated dose regimens, with little knowledge of the impact on neuroendocrine development. Animal studies have recently shown that repeated fetal glucocorticoid exposure can lead to permanent changes in hypothalamic‐pituitary‐adrenal (HPA) function in offspring. In this study, we hypothesized that such treatment modifies corticotropin releasing hormone (CRH), glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) systems in the developing limbic system and hypothalamus. Pregnant guinea‐pigs were treated with dexamethasone, betamethasone or vehicle on days 40,41,50,51,60 and 61 of gestation (birth = 68 days). On day 62, guinea‐pigs were killed and the fetuses rapidly removed. Glucocorticoid treatment resulted in a dose‐dependent reduction in plasma cortisol concentrations in both male and female fetuses. There was also a significant reduction in CRH mRNA expression in the hypothalamic paraventricular nucleus. In contrast, exposure to glucocorticoid increased MR mRNA expression in the hippocampus (CA1/2 and CA3) and dentate gyrus of female fetuses. There was a small but significant increase in GR mRNA expression in limbic structures in male fetuses following treatment with 1 mg/kg dexamethasone. However, there was no significant effect of glucocorticoid exposure on hippocampal GR mRNA expression in female fetuses, or hypothalamic GR mRNA in either males or females. In conclusion, repeated maternal glucocorticoid treatment inhibits fetal HPA function. The fact that CRH mRNA levels were reduced indicates that synthetic glucocorticoids enter the fetal brain. By contrast, fetal glucocorticoid exposure does not downregulate GR mRNA, and increases MR mRNA expression. The latter likely reflects removal of circulating endogenous ligand (cortisol). These alterations may form the basis for permanently modified HPA activity in later life.
Identification of Efferent Neural Pathways from the Lamina Terminalis Activated by Blood‐Borne Relaxin
Authors: Sunn N. , McKinley M. J. , Oldfield B. J.
Published: March 2003

The ovarian hormone relaxin, in addition to its role in pregnancy, exerts an action on the brain to influence oxytocin and vasopressin secretion, water drinking, and cardiovascular function. Intravenous (i.v.) infusion of relaxin causes an acute water drinking response, confirming its role as a dipsogenic hormone. The aim of this study was to determine whether neurones in the lamina terminalis, which project to the hypothalamic paraventricular and supraoptic nuclei, are activated by elevated levels of circulating relaxin in conscious rats. Immunocytochemistry combined with retrograde neuronal tracing with cholera toxin B subunit conjugated to cholera toxin B (CTB‐gold) was used to identify populations of neurones responding with elevated cells of Fos protein to i.v. relaxin administration and which project to these specific hypothalamic sites. Neurones exhibiting Fos were present in the outer parts of the subfornical organ (SFO), the dorsal part of the organum vasculosum (OVLT), the supraoptic nucleus and the paraventricular nucleus. These did not occur in control rats with i.v. infusions of isotonic saline. Approximately 90% of neurones concentrated in the outer parts of the SFO and in the dorsal OVLT showed both retrogradely transported CTB‐gold and Fos in response to i.v. infusion of relaxin. These data support a role for relaxin acting on the brain to regulate body fluid and electrolyte homeostasis by activating neural pathways subserving water drinking, vasopressin and oxytocin secretion.
Maintaining Cell Sensitivity to G‐Protein Coupled Receptor Agonists: Neurotensin and the Role of Receptor Gene Activation
Authors: Souazé F.
Published: March 2003

In the last few years, a number of studies have brought new insights into the fundamental mechanisms of cell desensitization and internalization of G‐protein coupled receptors. Such studies have demonstrated that cells remain desensitized from a few minutes to several hours, after exposure to high concentrations of agonist. However, in vivo, agonists such as hormones are always present, even in small amounts, and such long desensitization is not conceivable, since constant stimulation of cells is required for physiological responses. Under such circumstances, cells would require a means to permanently maintain sensitivity to various internal or external stimuli. In the present review, we have taken as an example the expression of the high affinity neurotensin receptor, a seven transmembrane G‐protein coupled receptor, upon prolonged exposure to its agonist, and observed that cells remained sensitive only if the receptor gene was activated by the agonist. Consequently, new receptors were synthesized, and either delivered to the cell surface or accumulated in submembrane pools. This regulation takes place only after prolonged and intense agonist stimulation. Under these conditions, it is proposed that receptor turnover is accelerated in proportion to the agonist concentration in order to allow the cells to produce an adapted cellular response to external stimuli. Such mechanisms thus play a key role in cell sensitivity to hormones.
The Role of Leptin in the Regulation of Energy Balance and Adiposity
Authors: Van Dijk Gertjan
Published: March 2003

Since its discovery, leptin (a 167‐amino acid product of the OB gene) has quickly moved to the forefront as an important hormone for regulation of energy balance. It closes a feedback loop from adipose tissue to hypothalamic neuropeptide‐containing neural circuitry involved in regulation of food intake and neuroendocrine/autonomic outflow. While increased central leptin signalling reduces adiposity via a reduction in food intake, it also has remarkable metabolic effects that promote leanness, independent of food intake. These include: (i) increased energy expenditure, (ii) in‐place degradation of fat, and (iii) increased thermogenesis. Hypothalamic neurones that synthesize corticotropin releasing hormone and melanocortins (i.e. α‐melanocyte‐stimulating hormone and agouti‐related protein) are likely effector pathways that mediate the anorexigenic and metabolic effects of leptin. Activation of sympathetic outflow (via neuropeptidergic effector pathways of central leptin) to a number of tissues that store fat might be an important mechanism through which these peripheral metabolic effects are elicited. It is proposed that these peripheral metabolic effects contribute to the satiating properties of leptin.
The Melanocortin Agonist Melanotan‐II Reduces the Orexigenic and Adipogenic Effects of Neuropeptide Y (NPY) but Does not Affect the NPY‐Driven Suppressive Effects on the Gonadotropic and Somatotropic Axes in the Male Rat
Authors: Raposinho P. D. , White R. B. , Aubert M. L.
Published: March 2003

Neuropeptide Y (NPY) is a strong orexigenic neurotransmitter also known to modulate several neuroendocrine axes. α‐Melanocyte‐stimulating hormone (MSH) is an essential anorectic neuropeptide, acting on hypothalamic MC3/4 receptor subtypes. When given as an intracerebroventricular bolus injection, Melanotan‐II (MT‐II), a non selective MC receptor agonist, inhibits feeding, suppresses the NPY orexigenic action, and reduces basal insulinaemia. We evaluated the effects of a 7‐day central infusion of MT‐II (15 nmol/day) given either alone or in association with NPY (5 nmol/day) in male Sprague‐Dawley rats. MT‐II produced almost full anorexia for 1–2 days but then feeding gradually returned to normal despite continued MT‐II infusion. When coinfused with NPY, MT‐II also produced the same initial anorectic episode but then maintained feeding to upper normal levels, thus cancelling the hyperphagia driven by NPY. Whereas NPY infusion produced a doubling of fat pad weight, MT‐II reduced adiposity by a factor of two compared to pair‐fed rats, and vastly curtailed the NPY‐driven increase in fat pad weight. MT‐II infusion also significantly curtailed the NPY‐induced rise in insulin and leptin secretions. NPY infusion significantly inhibited hypothalamic pro‐opiomelanocortin mRNA expression, most likely cancelling the α‐MSH anorectic activity. As expected from previous studies, chronic NPY infusion strongly inhibited both the gonadotropic and somatotropic axes, and coinfusion of MT‐II did not reverse these NPY‐driven effects, in sharp contrast with that seen for the metabolic data. MT‐II infusion alone had little effect on these axes. In conclusion, chronic MT‐II infusion generated a severe but transient reduction in feeding, suggesting an escape phenomenon, and clearly reduced fat pad size. When coinfused with NPY, MT‐II was able to cancel most of the NPY effects on feeding, but not those on the neuroendocrine axes. It appears therefore that, as expected, NPY and α‐MSH closely interact in the control of feeding, whereas the neural pathways by which NPY affects growth and reproduction are distinct and not sensitive to MC peptide modulation.
A Gonadotropin‐Releasing Hormone Insensitive, Thapsigargin‐Sensitive Ca2+ Store Reduces Basal Gonadotropin Exocytosis and Gene Expression: Comparison with Agonist‐Sensitive Ca2+ Stores
Authors: Johnson J. D. , Klausen C. , Habibi H. , Chang J. P.
Published: March 2003

We examined whether distinct Ca2+ stores differentially control basal and gonadotropin (GTH‐II)‐releasing hormone (GnRH)‐evoked GTH‐II release, long‐term GTH‐II secretion and contents, and GTH‐II‐β mRNA expression in goldfish. Thapsigargin (Tg)‐sensitive Ca2+ stores mediated neither caffeine‐evoked GTH‐II release, nor salmon (s)GnRH‐ and chicken (c)GnRH‐II‐stimulated secretion; the latter responses were previously shown to involve ryanodine (Ry)‐sensitive Ca2+ stores. Surprisingly, Tg decreased basal GTH‐II release. This response was attenuated by prior exposure to sGnRH and caffeine, but was insensitive to the phosphatase inhibitor okadaic acid, the inhibitor of constitutive release brefeldin A and cGnRH‐II. GTH‐II‐β mRNA expression was decreased at 24 h by 2 µm Tg, and by inhibiting (10 µm Ry) and stimulating (1 nm Ry) Ry receptors. Transient increases in GTH‐II‐β mRNA were observed at 2 h and 12 h following 10 µm and 1 nm Ry treatment, respectively. Effects of Tg, Ry and GnRH on long‐term GTH‐II secretion, contents and apparent production differed from one another, and these changes were not well correlated with changes in GTH‐II‐β mRNA expression. Our data show that GTH‐II secretion, storage and transcription can be independently controlled by distinct Ca2+ stores.
Oestradiol‐Dependent and ‐Independent Modulation of Tyrosine Hydroxylase mRNA Levels in Subpopulations of A1 and A2 Neurones with Oestrogen Receptor (ER)α and ERβ Gene Expression
Authors: Curran‐Rauhut M. A. , Petersen S. L.
Published: March 2003

Oestradiol (E2) induces luteinizing hormone‐releasing hormone (LHRH) hypersecretion, thereby triggering LH surge release in ovariectomized (OVX) rats. Neural signals responsible for the surge are marked by a morning increase in LHRH gene expression and an afternoon increase in LHRH release. Evidence suggests that subpopulations of noradrenergic neurones may be responsible for one or both of these signals. To further investigate this issue, we examined effects of E2on the activity of A1 and A2 noradrenergic neurones, as reflected in changes in tyrosine hydroxylase (TH) mRNA expression, on the day of LH surge release. We then used dual‐labelin situhybridization to determine whether E2‐induced changes occurred primarily in A1 and A2 subdivisions wherein most noradrenergic neurones expressed oestrogen receptor (ER)α and/or ERβ mRNA. We found that in all subdivisions, levels of TH mRNA were higher in E2‐ than oil‐treated rats at 12.00 h. These differences resulted from a decline in TH mRNA expression in oil‐treated rats, as well as a rise in levels in E2‐treated rats between 10.00 h and 12.00 h. During the afternoon, TH mRNA expression in most A1 and A2 subdivisions peaked at 14.00 h when LH surge release began. However, in all but the middle and caudal A2 subdivisons, levels were similar in E2‐treated and control rats at this time. This was attributable to a widespread increase in TH mRNA expression between 12.00 h and 14.00 h in OVX rats. There was no evidence that E2induced changes in TH mRNA expression preferentially in regions wherein most neurones contained ERα or ERβ mRNA. Our findings suggest that E2activation of middle and caudal A2 neurones, in conjunction with the widespread E2‐independent activation of noradrenergic neurones in other subdivisions, may play a role in the induction of LH surge release.
In vivo and in vitro study of fungal presence and growth on three tissue conditioning materials on implant supported complete denture wearers
Authors: Kulak  , Kazazoglu
Published: March 2003

In this study three type of tissue conditioning materials were used in vitro and in vivo to investigate the presence and growth of Candida albicans, considered to be the pathogenic member of the genus. In vitro test results of different tissue conditioners showed that they have a tendency to have an inhibiting effect on C. albicans at the third day of incubation. For the in vivo tests tissue conditioners were placed in existing maxillary prosthesis of 21 patients who had been treated with endosseous dental implants (seven in each group). The results showed that yeast forms were observed after 3 days in two patients’ dentures which were relined with Fitt. Yeasts forms were also seen in three patients’ dentures after 6 days, two of them relined with Fixo‐gel and the other one relined with Visco‐gel. The hyphal form of Candida was seen in four patients’ dentures, relined with Fitt, and also in three patients’ dentures, relined with Fixo‐gel and Visco‐gel.
Restorative treatment need assessment by dentally and nondentally trained subjects
Authors: Lamb  , Ellis  , Patel
Published: March 2003

A study was carried out which compared how two groups of people, one with clinical dental experience and one without, assessed restorative dental treatment need. Using a visual analogue scale, a group of final year dental students (n = 50) and nonclinical university students (n = 50) assessed the extent to which they considered common dental imperfections, viz. spacing of the upper anterior teeth and discolouration of upper anterior teeth, warranted restorative correction. The group of dental students judged the necessity for treatment of discolouration to be more urgent than correction of spacing. The nondental group did not differentiate between the degrees of need. Data were non‐normal in distribution but the use of appropriate statistical tests showed the differences in mean assessments to be significant.
Correlation of the characteristics of temporomandibular joint and tooth contact sounds
Authors: Prinz
Published: March 2003

In this study tooth contact sounds have been compared with temporomandibular joint (TMJ) sounds elicited during opening and closing movements. One hundred and eight subjects were instructed to open as far as possible and then close with sufficient force to produce a tooth contact sound. At least four cycles from each subject were recorded on tape, The first and last sounds in the recording were the tooth contact sounds, these were identified automatically. The mean duration and rise time of each tooth contact sound was calculated and their standard deviations for each subject were calculated to give a measure of the reproducibility. The number and mean amplitude of TMJ sounds occurring during tooth separation were also calculated for each cycle. Highly significant correlations were found between the number and amplitude of the TMJ sounds within a cycle and the duration and rise time, and particularly their standard deviations. Acoustic quiescence during the open–close cycle was associated with short, reproducible tooth contact sounds characterized by a short rise time. The longest and most variable tooth contact sounds were associated with TMJ sounds in all three phases of the open–close cycle. This supports previous clinical findings associating occlusal interferences with TMJ dysfunction.
Influence of polymerization initiator for base monomer on microwave curing of composite resin inlays
Authors: Urabe H. , Nomura Y. , Shirai K. , Yoshioka M. , Shintani H.
Published: March 2003

Microwave polymerization was used to make composite resin inlays and the effect examined of the concentration of polymerization initiator for the base monomer. The monomers used were 2,2‐bis[4‐(3‐methacriloxy‐2‐hydroxypropoxy) phenyl] propane (Bis‐GMA) and triethyleneglycol dimethacrylate (TEGDMA). Bis‐GMA and TEGDMA were mixed in a ratio of 6:4 by weight and were separated into five groups. To each group was added benzoyl peroxide (BPO) in the ratios of 0·1, 0·3, 0·5, 0·7 and 0·9 wt% as the polymerization initiator. These were used as the base monomers. The results showed that the degree of conversion of the cured sample increased with increasing concentration of BPO from 0·1 to 0·5 wt%, however there was no significant difference at 0·5, 0·7 and 0·9 wt% (P>0·01). Compression strength, diametral tensile strength and the Knoop hardness showed a similar tendency as the degree of conversion. No significant difference was recorded in the Knoop hardness between the top and the bottom surfaces (P>0·01), which suggested a uniform polymerization in the cured sample. Thus, microwave polymerization would be an efficacious method for making resin inlays with the addition of BPO to the base monomer (Bis‐GMA:TEGDMA, 6:4). The maximum conversion was found at a concentration of 0·5 wt%.
Comparison of a short examination procedure with an extensive diagnostic protocol for the diagnosis of temporomandibular disorders
Authors: Miller V.J. , Bookhan V. , Cheshankova E. , Moipolai P. , Setzer S.
Published: March 2003

Eighty‐nine patients who complained of temporomandibular disorders were examined using a short and long examination procedure. Seventy were females and 19 males. Mean age of the group was 31·53 years, with a range from 11 to 73 years. The agreement between the two examination procedures was tested using the Kappa statistic. This gave a value of 0·876 (P<0·001). This allowed rejection of the hypothesis that the agreement found between the two procedures was due to chance alone.
Surgical treatment of trigeminal neuralgia
Authors: Hong‐Sai Loh
Published: March 2003

Patients who had uncontrolled pain with Carbamazepine therapy and those who suffered adversely from its side effects were selected for this safe, simple and repeatable surgery. Pain‐free periods were achieved for at least 2 years. Functional difficulty was not experienced in the affected numb areas. When it recurred, pain was less intense and was better controlled with a reduced dosage of Carbamazepine. In four cases, after alvusion of the involved nerves, a suitable‐sized titanium screw was inserted into the mental and infra‐orbital foramina. Obturation of the foramen prevented nerve regeneration, which further prolonged the pain remission period.
A clinical evaluation of 76 implant‐supported superstructures in the composite grafted maxilla
Authors: Kaptein M. L. A. , DE Putter C. , DE Lange G. L. , Blijdorp P. A.
Published: March 2003

The aim of the study was to evaluate the material behaviour and nature of implant‐supported superstructures in function. A total of 37 overdentures, 26 fixed partial and 13 fixed full dentures with a mean lifetime of 40 months were clinically evaluated in relation to damage, occlusion and articulation, parafunction, retentive devices, hygiene and speech problems. In general 70% of all superstructures were damaged. Fixed partial dentures were significantly less damaged than overdentures and fixed full dentures (P<0·001). A significant high percentage of newly gained parafunction was found (P<0·05).
The contribution of mechanoreceptive neurones in the gingival tissues to the masticatory–parotid salivary reflex in man
Authors: Scott B. J. J. , Bajaj J. , Linden R. W. A.
Published: March 2003

The masticatory–parotid salivary reflex has been studied in fully dentate subjects. Salivary flow was recorded by siting a modified Lashley cup over the orifice of the parotid duct on one side of the mouth. Subjects chewed on small pieces of silicone rubber for 1‐min periods which resulted in a reflex secretion of parotid saliva. The secretion was greatest when the subject chewed on the same side of the mouth (ipsilateral) as the salivary flow was recorded. Less salivary flow resulted when the subjects chewed on the opposite side of the mouth (contralateral). Selected areas of the buccal or lingual gingival tissues were then anaesthetized on the side ipsilateral to the Lashley cup. Anaesthesia of the lingual and buccal gingival tissues together resulted in a reduction of salivary flow in response to similar chewing cycles. Anaesthesia of the lingual gingival tissues alone also resulted in a reduction of salivary flow, but anaesthesia of the buccal gingival tissues alone did not. During mastication it is likely that mechanoreceptors in the gingival tissues will be stimulated which may result in salivary flow. This requires further study as other mechanoreceptive neurones are also known to be involved in the masticatory–parotid salivary reflex.
The effect of polishing systems on microleakage of tooth‐coloured restoratives. Part 2: Composite and polyacid‐modified composite resins
Authors: Yap A. U. J. , Wong M. L. , Lim A. C. Y.
Published: March 2003

The purpose of this in vitro study was to investigate the effect of polishing systems on the microleakage of composite and polyacid‐modified composite resins. Class V cavities were prepared at the cemento‐enamel junction of 80 freshly extracted posterior teeth. The prepared teeth were randomly divided into two groups and restored with conventional or polyacid‐modified composite resins. The restored teeth were stored in distilled water at 37 °C for 1 week after removal of excess restorative with diamond finishing burs. The restored teeth were then divided into four groups of ten and finished/polished using the following systems: Two Striper micron finishing system (MFS), Sof‐Lex XT (Sof‐Lex), Enhance composite finishing and polishing system (Enhance), and Shofu composite finishing kit (Shofu). The finished restorations were subjected to dye penetration testing. Results showed that the microleakage resistance at both enamel and dentin margins of composite and polyacid‐modified composite resins are not significantly affected by the different polishing systems.
Finite element analysis of stress relaxation in soft denture liner
Authors: Sato Y. , Abe Y. , Okane H. , Tsuga K.
Published: March 2003

To gather knowledge related to establishing criteria for selecting soft denture liners for individual patients, the effects of certain properties of soft denture liners on stress distribution were evaluated by two‐dimensional finite element analysis. A partial mandibular edentulous ridge crest was modelled. Six combinations of thickness (mucosa: 1 or 2 mm; soft denture liner: 1, 2, or 3 mm) and 18 combinations of Young's modulus (mucosa: three kinds; soft denture liner: six kinds) were analysed. The ratio of maximum to minimum stress in the mucosa (stress ratio) was calculated to estimate stress concentration. In the case of thin mucosa (1 mm thickness), the lower the Young's modulus of the soft denture liner, the lower the stress ratio. However, if the soft denture liner had a lower Young's modulus than the mucosa, stress concentrated adversely. These results suggest that the elasticity of the soft denture liner should match the elasticity of the mucosa to obtain the optimum cushioning effect.
Bolus dimensions in normal chewing
Authors: Prinz J. F. , Heath M. R.
Published: March 2003

Samples of 17 different types of chewing gum weighing between 0·3 and 22 g were presented to eight subjects. After chewing the samples for between 20 and 100 strokes the boluses of gum were removed from the mouth and their length was measured. Bolus length increased with weight from 0·3 to 4 g, but remained constant between 4 and 18 g at which point it began to increase once more. The range of sizes associated with this plateau is similar to the range of sizes of natural bites with other foods.
Evaluation of stresses caused by dentin pin with finite elements stress analysis method
Authors: ErsÖz E.
Published: March 2003

The aim of the present study was to show the dimensions and the amount of stresses caused by pins on dentin. Mathematically modelled stainless steel and titanium pins were applied to mandibular first molar teeth with extensive crown destruction. The stress caused by the pins was examined with the finite elements method (FEM). In both types of pin, the maximum diffuse and the dense stress areas were located at the bottom of the pin channel. It is believed that these stresses should be taken into consideration when evaluating the advantages and disadvantages of pin application to teeth with destroyed crowns.
Comparison of the transfer precision of three different impression materials in combination with transfer caps for the Frialit®‐2 system
Authors: Lorenzoni M. , Pertl C. , Penkner K. , Polansky R. , Sedaj B. , Wegscheider W. A.
Published: March 2003

Transfer of the precise position of implants to a master cast is a prerequisite for accurate and passive fit of the superstructure. Implants lack the mobility of natural teeth and, therefore, inaccurate frameworks result in stress within the mechanical parts and the implant–bone interface. Various impression methods have been described to achieve accurate reproduction of the intra‐oral relation of the implants. The aim of this experimental study was to compare three different impression materials (polyether, polyvinyl siloxane, hydrocolloid) with the Frialit®‐2 system and with the indirect technique. In addition, the use of transfer caps (TCs) to improve transfer precision was tested with all three materials. All measurements were performed using a three‐dimensional (3D) co‐ordinate measuring machine that is capable of locating points in space and calculating the relative distortions as angles of tilt (rot‐XY, rot‐XZ, rot‐YZ) and 3D displacement. The results suggest that addition‐silicone (a‐silicone) and polyether are the materials of choice for implant transfer procedures. The use of TCs resulted in a significantly reduced rotation in the XY‐plane but did not improve the absolute 3D displacement. A‐silicone with the use of TCs proved to be most precise. Comparison between polyether and polyvinyl siloxane showed significant differences in the XY‐rotation and the 3D displacement in favour of the silicone. Because the mean distortions between the original model and the master casts were about 100 μm, absolutely precise fit may be unattainable owing to the physical properties of the materials. Further studies will have to evaluate the amount of tolerable stress at the implant–bone interface.
Comparison of dentine hypersensitivity in selected occidental and oriental populations
Authors: Gillam D. G. , Seo H. S. , Newman H. N. , Bulman J. S.
Published: March 2003

Epidemiological data on dentine hypersensitivity (DH) prevalence are limited. Few studies have compared prevalence between populations. The aim of this investigation, therefore, was to compare the perception and prevalence of DH in two distinct non‐periodontal practice populations, one U.K. and one Korean. Completed questionnaires from 557 patients (230 males and 327 females, comprising 115 males and 162 females, mean age 41·7 years (s.d.=14·36), U.K. and 115 males and 165 females, mean age 29·7 years (s.d.=11·86), Korean) were collected. Analysis was by frequency distribution and cross‐tabulation (Statistical Package for the Social Sciences (SPSS)). DH prevalence was similar and at levels comparable with those reported previously. Prevalence was higher in the third and fourth decades in both populations. Although there were no differences between U.K. or Korean males and U.K. or Korean females, there was a significant difference between gender reporting of DH, with more females complaining of DH than males (standard normal deviation (SND)=4·3, 95% confidence interval (CI)=0·1134–0·2736). DH appeared to be regarded by patients as not severe in most cases, so treatment was not generally sought. Of those who claimed to have sought treatment, a significant number had received restorative treatment. Of those patients, only 23·3% of U.K. and ≤2% of Korean patients claimed to have used a desensitizing dentifrice. Pain from DH was reported as low grade (slight, occasional) occurring over 5 years in both populations. Cold appeared to be the most reported stimulus in the two populations. Less periodontal surgery had been undertaken in these two populations (12·6% U.K. and 7·1% Korean) compared with those referred to a teaching hospital periodontal department (34·5%). This compared favourably with previous findings in the general dental population (15·5%). Discomfort following hygiene therapy did not appear to last ≥7 days in either population. The results indicated that there were no significant differences between U.K.‐ and Korean‐based populations in their perception of DH, with the exception that more females complained of sensitivity than males in both groups. Overall, DH was not considered a major dental problem by most patients in either of the populations.