bluuebunny/crossref_metadata_2025 huggingface dataset:
Perinatal Developmental Changes in Expression of the Neuropeptide Genes Preoptic Regulatory Factor‐1 and Factor–2, Neuropeptide Y and GnRH in Rat Hypothalamus
Authors: Nowak  , Gore
Published: March 2003

The preoptic regulatory factor genes, PORF‐1 and PORF‐2, are expressed in the rat brain in a regional‐, age‐ and gender‐dependent fashion. They are also expressed in the testis, where PORF‐2 mRNA localizes to dividing germ cells while PORF‐1 mRNA is associated with newly differentiated sperm. This suggests that PORF‐1 and PORF–2 may play distinct roles in cell growth and differentiation. Moreover, the two preoptic regulatory factors are also highly expressed in the immature and mature rat hypothalamus, and their expression is modulated by gonadal hormones. Therefore, in the present study we investigated the expression of these two factors in neuroendocrine regions of the developing rat brain by addressing the following questions. First, are PORF‐1 and PORF–2 mRNAs expressed during perinatal development in the preoptic area‐anterior hypothalamus (POA‐AH) and medial basal hypothalamus (MBH), and how do their levels vary? Second, are there gender differences in their expression? We also compared expression of the PORF mRNAs with those of neuropeptide Y (NPY) and gonadotropin‐releasing hormone (GnRH), which play critical neuroendocrine roles, in these brain regions. PORF‐1, PORF‐2, and NPY mRNAs in the POA‐AH and MBH, and GnRH mRNA in the POA‐AH, were quantified by RNase protection assay at embryonic day (E) 18–19, and postnatal days (P) 0, 5, 10 and 15 in male and female rats. The results show that the four neuropeptide genes are regulated differentially during the perinatal‐prepubertal period. PORF‐1 mRNA shows age‐related increases in expression from E18–E19 to P15 in POA‐AH and MBH, without significant gender differences. In contrast, PORF‐2 mRNA shows both age and gender differences in expression in these brain regions, with decreases occurring during the same time period in development. NPY mRNA increases similarly in males and females with age in POA‐AH and MBH during this period. GnRH mRNA does not change during this period. Taken together with previous studies, the results suggest possible roles for PORF‐1 and NPY in the pubertal process, since their expression is maximal from the prepubertal to the early pubertal period. The observation of highest levels of expression of PORF‐2 in embryonic neuroendocrine tissues suggests a possible involvement of this neuropeptide in prenatal/neonatal developmental events.
GABAA Receptor Mediated Elevation of Ca2+ and Modulation of Gonadotrophin‐Releasing Hormone Action in αT3‐1 Gonadotropes
Authors: Williams B. , Bence M. , Everest H. , Forrest‐Owen W. , Lightman S. L. , McArdle C. A.
Published: March 2003

γ‐amino butyric acid (GABA) is the major inhibitory neurotransmitter in the CNS, mediating fast inhibitory synaptic transmission, by activating GABAA receptors. However, these GABA‐gated Cl− channels can also be excitatory, causing depolarization, and increasing Ca2+ entry via voltage‐operated Ca2+ channels (VOCCs). Evidence exists for excitatory ionotropic GABA receptors in anterior pituitary cells, including gonadotropes, but these have not been directly characterized and their pharmacology remains controversial. Here we have measured the cytosolic Ca2+ concentration ([Ca2+]i) in αT3–1 gonadotropes, to test for expression of excitatory GABA receptors. The GABAA agonists, GABA and muscimol, both caused rapid, robust and dose‐dependent increases in [Ca2+]i (EC50 values 2.7 and 1 μm), whereas the GABAB agonist, baclofen, did not. The GABAA antagonist, bicuculline, inhibited muscimol's effect, whereas the GABAB antagonist, phaclofen, did not. The neuroactive steroid 5α‐pregnan‐3α‐ol‐11,20‐dione (an allosteric activator of GABAA receptors) increased [Ca2+]i, and this effect, like that of muscimol, was inhibited by picrotoxin. The muscimol effect on [Ca2+]i was blocked by the VOCC antagonist, nifedipine, or by Ca2+‐free medium. When cells were pretreated with muscimol this increased the spike phase of the [Ca2+]i response to subsequent stimulation with gonadotropin‐releasing hormone (GnRH). Similar amplification was seen in muscimol‐pretreated cells stimulated with GnRH in Ca2+‐free medium, but not when cells were pretreated with muscimol in Ca2+‐free medium. The amplification was not, however, GnRH receptor‐specific, because the spike response to ionomycin was also increased by muscimol pretreatment. These data provide the first direct evidence for expression of excitatory GABAA receptors, and the first demonstration of acute steroid effects, on GnRH‐responsive pituitary cells. They also reveal a novel mechanism by which GABAA activation modulates GnRH action, raising the possibility that this may also influence gonadotrophin secretion from non‐immortalized gonadotropes.
Evidence Suggesting that the Potentiating Action of Neuropeptide Y on Luteinizing Hormone (LH)‐Releasing Hormone‐Induced LH Release Remains Unaltered in Aged Female Rats
Authors: Sahu A.
Published: March 2003

Several lines of evidence suggest that one of the mechanisms by which the hypothalamic neuropeptide Y plays an obligatory role in the preovulatory luteinizing hormone (LH) discharge in young rats is to potentiate the action of LH‐releasing hormone (LHRH) on LH release at the level of the pituitary. This study examined whether an alteration in the potentiating action of neuropeptide Y on LHRH‐induced LH release may contribute to the attenuation or absence of LH surges during female reproductive ageing. Young regularly cycling (2–3‐month‐old) and old constant oestrous (19–20‐month‐old) rats ovariectomized for 7 days were primed with oestradiol‐17β‐filled Silastic capsules. Two days later, rats received s.c. progesterone at 09.00 h and then were injected i.p. with either saline or pentobarbital at 13.30 hours. Pentobarbital‐treated rats received i.v. pulses of neuropeptide Y, LHRH, a combination of neuropeptide Y and LHRH, or saline, every 30 min from 14.00 to 18.00 h via a jugular cannula. Hourly blood samples were collected between 11.00 and 21.00 h. In old rats, the progesterone‐induced LH surge was significantly attenuated and delayed as compared to that of young rats. Pentobarbital injection completely blocked the LH surge. Neuropeptide Y pulses alone had no significant effect on LH release. In contrast, LHRH pulses increased LH release in both age groups, although the response was significantly reduced in older rats. While combined pulses of neuropeptide Y and LHRH significantly increased LH release in both young and old rats as compared to that of LHRH alone, the potentiating action of neuropeptide Y on LHRH‐induced LH release remained unchanged between the two age groups. These results, together with our recent demonstration of altered hypothalamic neuropeptide Y neuronal activity in middle‐aged pro‐oestrous rats, suggest that a deficit in neuropeptide Y secretion and action in the hypothalamus, rather than a decrease in pituitary responsiveness to neuropeptide Y, may partially be responsible for the absence of LH surges in old rats.
Thyroxine Modulates Corticotropin‐Releasing Factor but not Arginine Vasopressin Gene Expression in the Hypothalamic Paraventricular Nucleus of the Developing Rat
Authors: Dakine N. , Oliver C. , Grino M.
Published: March 2003

Neonatal rats were daily injected with 100 μg/kg T4 and killed at 4, 8 or 15 days. Circulating corticosterone and corticosteroid binding globulin concentrations increased in 8‐ and 15‐day‐old rats after T4 treatment. Plasma adrenocorticotropic hormone (ACTH) concentrations, pituitary ACTH content and pro‐opiomelanocortin mRNA expression were unaffected in T4‐treated rats. T4 treatment induced an increase in corticotropin‐releasing factor (CRF) mRNA expression in the whole population of CRF synthesizing cells of the paraventricular nucleus (PVN) that became significant at day 8 and disappeared at day 15. Double labelling in situ hybridization revealed that CRF gene expression in the CRF+/arginine vasopressin (AVP)+ subpopulation was increased at days 4 and 8 and decreased at day 15. CRF immunoreactivity in the zona externa of the median eminence increased with age but was not affected by the experimental hyperthyroidism. The degree of CRF and AVP colocalization, the concentration of AVP mRNA in the parvo and magnocellular cell bodies of the PVN and the density of immunoreactive AVP in the zona interna or zona externa of the median eminence did not change after T4 treatment. Our data demonstrate that experimental hyperthyroidism accelerates the maturation of hypothalamic CRF gene expression, including in particular in the CRF+/AVP+ subpopulation, during the stress hyporesponsive period. These observations suggest that the physiological peak of plasma thyroxine that occurs between days 8–12 may participate in the maturation of hypothalamic CRF cells.
Vasopressin and Oxytocin Neurones of Hypothalamic Supraoptic and Paraventricular Nuclei Co‐Express mRNA for Type‐1 andType‐2 Corticotropin‐Releasing Hormone Receptors
Authors: Arima H. , Aguilera G.
Published: March 2003

The presence of corticotropin‐releasing hormone (CRH) receptors type‐1 (CRHR‐1) and type‐2 (CRHR‐2α) in the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei, and the effects of i.c.v. injection of CRH and urocortin on arginine vasopressin (AVP) and oxytocin release, have suggested that CRH ligands have a role in osmoregulation. In this study, double labelling in situ hybridization using 35S‐labelled CRHR‐1 or CRHR‐2α and digoxigenin‐labelled AVP, oxytocin or CRH riboprobes was employed to examine the localization of CRHR‐1 or CRHR‐2α mRNA in the SON and PVN of control and osmotically stimulated rats. Rats received an i.p. hypertonic saline (1.5 M) injection or isotonic saline injection (controls), or 2% NaCl intake (salt loading) or tap water (controls) for 12 days. While CRHR‐1 mRNA was undetectable in the SON and PVN in control rats, its expression was increased markedly at 4 h after i.p. hypertonic saline injection or after 12 days salt loading. Of the cells labelled with digoxigenin‐AVP, 53% in the SON and 90% in the PVN coexpressed CRHR‐1 mRNA after i.p. hypertonic saline injection. In oxytocinergic neurones, 73% in the SON and 91% in the PVN showed CRHR‐1 autoradiographic grains higher than background levels after i.p. hypertonic saline injection. In addition, i.p. hypertonic saline induced CRHR‐1 mRNA expression in digoxigenin‐CRH stained cells in the parvocellular PVN. CRHR‐2α transcripts were present in both the SON and PVN under basal conditions, and salt loading, but not acute i.p. hypertonic saline injection, further stimulated this expression. Double labelling in situ hybridization showed colocalization of CRHR‐2α mRNA with AVP and oxytocin mRNA in the SON. These studies support a role for CRH and urocortin regulating the hypothalamo‐neurohypophyseal system, and suggest a direct action of the peptides in the magnocellular neurones.
Differential In Vitro Secretion of Gonadotropin‐Releasing Hormone (GnRH) and [Hydroxyproline9]GnRH from the Rat Hypothalamus During Postnatal Development
Authors: Rochdi L. , Théraulaz L. , Enjalbert A. , Gautron J.‐P.
Published: March 2003

The differential secretion of gonadotropin‐releasing hormone (GnRH) and [hydroxyproline9]GnRH (HypGnRH) has been recently reported from the adult rat hypothalamus. We report here in vitro cosecretion of HypGnRH and GnRH by the hypothalamus of 2–45 day‐old‐rats and provide evidence that they are differentially regulated throughout development. The secretion of both forms of GnRH was increased in a dependent manner during depolarization by high K+ solutions, and was stimulated by forskolin and 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), activators of adenylate cyclase and protein kinase C pathways, respectively. The proportion of HypGnRH in the release of GnRH‐like peptides remained stable and high (33–40%) under basal and K+‐induced conditions until days 13 and 21, respectively. By contrast, the proportion of HypGnRH in the total GnRH‐like content of the developing hypothalamus continuously decreased (from 37% to 14%). Similarly, the proportion of HypGnRH: total GnRH‐like material released remained stable in TPA‐ (30%) and forskolin‐ (50%) induced secretion until postnatal day 8. Evaluation of release over tissue store ratios revealed a 1.3‐to 2.8‐fold higher release of HypGnRH compared to GnRH according to the different secretions and postnatal periods examined. The preferential recruitment of HypGnRH was maintained under basal and K+ conditions during postnatal development, but it disappeared under TPA stimulation from day 13 onwards. After forskolin stimulation, the preferential mobilization of HypGnRH was markedly reduced from day 2 to day 13 but recovered its high perinatal level during puberty. Taken together, our results support the hypothesis that HypGnRH may play a specific role in development. In addition, a specific function of this peptide taking place during puberty through the activation of the adenylate cyclase pathway is suggested.
Evidence that Oestradiol Attenuates β‐Adrenoceptor Function in the Hypothalamus of Female Rats by Altering Receptor Phosphorylation and Sequestration
Authors: Ansonoff M. A. , Etgen A. M.
Published: March 2003

Activation of β‐adrenoceptors in the hypothalamus (HYP) and preoptic area (POA) inhibits both gonadotropin release and reproductive behaviour in female rats. Exposure of female rats for 48 h to physiologically relevant doses of oestrogen attenuates β‐adrenoceptor function in the HYP and POA as indicated by reduced isoproterenol (β‐adrenoceptor agonist) stimulation of adenylyl cyclase activity. Reduced β‐adrenoceptor coupling to G protein in the HYP‐POA from oestrogen‐exposed female rats correlates with attenuation of β‐adrenoceptor function. To examine potential mechanisms underlying receptor‐G protein uncoupling, initial experiments tested the hypothesis that oestrogen attenuation of β‐adrenoceptor function in the HYP and POA involves receptor phosphorylation. Activation of endogenous serine/threonine phosphatases with protamine restores agonist‐stimulated cAMP accumulation in HYP slices from oestrogen‐exposed female rats to control levels. Additional experiments examined whether oestrogen‐induced changes in β‐adrenoceptor binding density and/or subcellular localization correlate with the attenuation of β‐adrenoceptor function in the HYP and POA. Oestrogen treatment does not alter total β‐adrenoceptor binding density in the HYP or POA. However, oestrogen significantly reduces cell surface binding of the hydrophilic β‐adrenoceptor antagonist [3H] CGP 12177 to intact HYP and POA slices. At the same time, oestrogen decreases the fraction of β‐adrenoceptors localized in a light vesicle fraction following sucrose density gradient centrifugation. Therefore, oestrogen attenuates β‐adrenoceptor signalling in the HYP‐POA by uncoupling the β‐adrenoceptor from G protein, perhaps by promoting receptor phosphorylation. Furthermore, a significant fraction of β‐adrenoceptors in the HYP and POA are no longer accessible to hydrophilic ligands, but are not internalized. Thus, physiological doses of oestrogen may facilitate reproductive behaviour and gonadotropin release, in part, by stabilizing β‐adrenoceptor phosphorylation in the HYP and POA, thereby uncoupling the receptors from G protein.
Substance P Downregulates Basal and Gonadotropin‐Releasing Hormone‐Induced Gonadotropin In Vitro Secretion by Pituitary Gland of Crested Newt, Triturus carnifex
Authors: Gobbetti A. , Petrelli C. , Zerani M.
Published: March 2003

The possible role of Substance P (SP) was studied in the modulation of basal and gonadotopin‐releasing hormone (GnRH)‐induced gonadotropin secretion in the urodele crested newt, Triturus carnifex. During prereproduction, reproduction (noncourtship and courtship), refractory, recovery and aestivation, male and female pituitaries were incubated with medium‐alone, GnRH, SP, GnRH receptor antagonist (antide), and SP receptor antagonist (L‐703606). Since antisera raised against gonadotropins are not available for this species, we measured these hormones indirectly through their effects on the secretion of testicular androgens and ovarian progesterone from gonads superfused with the preincubated pituitaries. Pituitaries of both sexes preincubated with medium‐alone, GnRH, GnRH plus L‐703606, and GnRH plus SP plus L‐703606 increased steroid secretion during prereproduction, noncourtship, courtship, and recovery; the increase induced by the pituitaries incubated with medium‐alone was lower during prereproduction, noncourtship, and recovery. Pituitaries preincubated with SP, GnRH plus SP, GnRH plus SP plus antide, and SP plus antide did not change basal steroid secretion in any of the reproductive phases considered. Antide, L‐703606, GnRH plus antide, GnRH plus SP plus antide plus L‐703606, SP plus L‐703606, and antide plus L‐703606 experimental groups showed the same results as those with medium‐alone. These results suggest that SP downregulates gonadotropin release in both Triturus carnifex sexes. In addition, an antagonist role, through receptor‐independent mechanisms, exists between GnRH (upregulation) and SP (downregulation) in the modulation of pituitary.
The Gonadotropin‐Releasing Hormone Neurosecretory System of the Jerboa (Jaculus orientalis) and its Seasonal Variations
Authors: El Ouezzani S. , Tramu G. , Magoul R.
Published: March 2003

The distribution of cells expressing gonadotropin‐releasing hormone (GnRH) immunoreactivity was examined in the brain of adult jerboa during two distinct periods of the reproductive cycle. During spring–summer, when the jerboa is sexually active, a high density of cell bodies and fibres immunoreactive (IR) for GnRH was observed at the level of separation of the frontal lobes, in the medial septal nucleus (MS) and in the diagonal band of Broca (DBB), in the preoptic area (POA), in the organum vasculosum laminae terminalis (OVLT), in the retrochiasmatic area and hypothalamus. In autumn, when the jerboa is sexually inactive, GnRH‐immunoreactivity was less intense than during spring–summer. In the POA, we noted a 55% decrease in the number of GnRH containing cells with no change in cell numbers in the MS‐DBB. Furthermore, a lower density of GnRH immunopositive axon fibres is observed in all the previously mentioned structures and the immunoreaction intensity was very weak particularly within the median eminence and OVLT. Independently of the season, the GnRH immunoreactivity within neurones and fibres was similar in jerboas living in captivity and in jerboas living in their natural biotope. The effects of photoperiod on the density of POA‐GnRH and arcuate nucleus β‐endorphin‐containing cells were studied in jerboas maintained in long day [(LD) 16‐h light, 8‐h dark] and short day [(SD) 8‐h light, 16‐h dark] for 8 weeks. In the POA, the GnRH‐IR cell number was not significantly altered by the photoperiod. Similarly, in the mediobasal hypothalamus, the number of β‐endorphin‐IR neurones was not affected by such a parameter. Consequently, the GnRH seasonal variations cannot be correlated to changes in the photoperiod alone.
Maternal Odours Induce Fos in the Main But Not the Accessory Olfactory Bulbs of Neonatal Male and Female Ferrets
Authors: Chang Y.‐M. , Kelliher K. R. , Baum M. J.
Published: March 2003

Previous research demonstrated that exposing gonadectomized adult ferrets to odours in oestrous female bedding induced nuclear Fos‐immunoreactivity (Fos‐IR; a marker of neuronal activity) in the main as opposed to the accessory olfactory system in a sexually dimorphic fashion, which was further augmented in both sexes by treatment with testosterone propionate. Ferrets are born in an altricial state and presumably use maternal odour cues to locate the nipples until the eyes open after postnatal (P) day 23. We investigated whether maternal odours augment neuronal Fos preferentially in the main versus accessory olfactory system of neonatal male and female ferret kits. Circulating testosterone levels peak in male ferrets on postnatal day P15, and mothers provide maximal anogenital stimulation (AGS) to males at this same age. Therefore, we assessed the ability of maternal odours to augment Fos‐IR in the accessory olfactory bulb (AOB), the main olfactory bulb (MOB) and other forebrain regions of male and female ferret kits on P15 and investigated whether artificial AGS (provided with a paintbrush) would further enhance any effects of maternal odours. After separation from their mothers for 4 h, groups of male and female kits that were placed for 1.5 h with their anaesthetized mother had significantly more Fos‐IR cells in the MOB granule cell layer and in the anterior‐cortical amygdala, but not in the AOB cell layer, compared to control kits that were left on the heating pad. Artificial AGS failed to amplify these effects of maternal odours. Maternal odours (with or without concurrent AGS) failed to augment neuronal Fos‐IR in medial amygdaloid and hypothalamic regions that are activated in adult ferrets by social odours. In neonatal ferrets of both sexes, as in adults, socially relevant odours are detected by the main olfactory epithelium and initially processed by the MOB and the anterior‐cortical amygdala. In neonates, unlike adults, medial amygdaloid and hypothalamic neurones either do not respond to these inputs or respond in a manner that fails to induce Fos expression.
Effect of Repeated Lipopolysaccharide Administration on Tissue Cytokine Expression and Hypothalamic‐Pituitary‐Adrenal Axis Activity in Rats
Authors: Grinevich, V. , Ma, X.‐M. , Herman, J. P. , Jezova, D. , Akmayev I. , Aguilera G.
Published: March 2003

The effects of chronic immune challenge on cytokine expression and hypothalamic‐pituitary‐adrenal axis (HPA) axis responses to stress were studied in Wistar rats after administration of increasing doses of lipopolysaccharide (LPS). Repeated LPS (R‐LPS) decreased body weight and increased adrenal weight and pituitary pro‐opiomelanocortin mRNA levels. LPS injection increased plasma adrenocorticotropic hormone (ACTH) and corticosterone but the effect was attenuated in R‐LPS. Plasma corticosterone but not ACTH responses to restraint were also reduced in R‐LPS. Basal and restraint‐stimulated corticotropin releasing hormone (CRH) mRNA levels were lower in R‐LPS, but responses to a new LPS injection were similar to controls. In contrast, type 1 CRH receptor (CRH‐R1) mRNA responses to both LPS and restraint were blunted in R‐LPS. Vasopressin mRNA levels in parvocellular neurones were higher in R‐LPS, and increased further after restraint but not after a new LPS injection. Glucocorticoid receptor (GR) levels in the paraventricular nucleus (PVN) increased after a single LPS or R‐LPS (24 h after the last injection) but declined after a new injection in R‐LPS. Interleukin (IL)‐1β and IL‐6 mRNAs increased in the pituitary, spleen and circumventricular organs after single or R‐LPS, suggesting that cytokines may contribute to the activation of the HPA axis though pathways from the circumventricular organs as well as paracrine effects in the pituitary. The data show that (i) adaptation of the HPA axis during repeated LPS injection involves increases in vasopressin : CRH expression ratios in parvocellular neurones; (ii) that hypothalamic CRH and vasopressin responses to acute stimulation are independent of CRH‐R1 expression in the PVN; and (iii) there is a dissociation between pituitary and adrenal responses to acute stress suggesting a decrease of adrenal sensitivity to ACTH.
Immunohistochemical Localization of Calbindin D‐28k in the Migratory Pathway from the Rat Olfactory Placode
Authors: Toba Y. , Ajiki K. , Horie M. , Sango K. , Kawano H.
Published: March 2003

The spatiotemporal localization of calbindin D‐28k (Calb), a calcium‐binding protein, was examined immunohistochemically in the developing rat olfactory system with special reference to cell migration from the olfactory placode. Calb immunoreactivity was first detected at embryonic day 12 (E12) in a few cells just outside the olfactory epithelium, and at E13, Calb‐immunoreactive cells were found scattered in the laminin‐rich mesenchyme. By E14, Calb‐immunoreactive cells had increased in number and were seen along the entire migratory route between the vomeronasal organ, a derivative of the medial olfactory pit, and the ventromedial surface of the telencephalic vesicle. Calb neurones were not seen in the olfactory epithelium, a derivative of the lateral olfactory pit. Although the distribution pattern of Calb‐immunoreactive cells was similar to that of luteinizing hormone releasing hormone (LHRH)‐producing neurones, which are known to originate in the vomeronasal organ and migrate into the forebrain, Calb and LHRH immunoreactivities were contained in separate neuronal populations. Calb‐immunoreactive cells were localized along the vomeronasal nerves, identified by labelling the vomeronasal organ with the lipophilic dye, DiI, and strongly immunoreactive for neural cell adhesion molecule (NCAM). These data strongly suggest that, in addition to LHRH neurones, the rat vomeronasal organ generates Calb‐immunoreactive neurones which migrate along the vomeronasal nerves to enter the forebrain. The final fate and functional importance of these cells remains to be determined.
Oestrogen Receptor β‐Immunoreactivity in Gonadotropin Releasing Hormone‐Expressing Neurones: Regulation by Oestrogen
Authors: Kalló I. , Butler J. A. , Barkovics‐Kalló M. , Goubillon M.‐L. , Coen C. W.
Published: March 2003

Double‐label immunohistochemistry was employed to establish whether immunoreactivity for the β subtype of the oestrogen receptor (ERβ‐IR) is present in gonadotropin releasing hormone (GnRH)‐containing cells. In the immortalized GnRH cell line, GT1‐7, almost all nuclei were immunoreactive for ERβ. In the preoptic area of ovariectomized rats, more than one‐half of the GnRH neurones (52.0–63.5%) contained ERβ‐IR within the nucleus; a smaller proportion of these neurones (5–10%) displayed a particularly intense nuclear signal for ERβ. The presence of ERβ‐IR in the nuclei of GT1‐7 cells and GnRH neurones is consistent with recent reports of ERβ mRNA in these cells. Oestrogen treatment reduced the percentage of GnRH neurones with detectable ERβ‐IR. The range of signal intensity for ERβ and the incidence of the ERβ signal in GnRH neurones were comparable following double‐label immunohistochemistry involving either bright field or fluorescent techniques. These findings raise the possibility that ERβ receptors mediate direct effects of oestrogen on GnRH neurones.
Flexural strength of a provisional resin material with fibre addition
Authors: Chung  , Lin  , Wang
Published: March 2003

The effect of fibre addition on the flexural strength of a resin was studied. A provisional material (ALIKE®; GC America Inc.) was used as the control and resinous matrix. Silane treated glass fibre was selected for the reinforcing treatment. In order to determine the geometric influence on the strength, ordered fibres (1 w/o) were immersed within a resinous matrix in four different locations. In addition, randomly dispersed fibres, 5 mm in length, were blended at 1 w/o up to 8 w/o with acrylic powder and moulded into rectangular specimens (34 mm × 9 mm × 8 mm) with P : L = 2 : 1. Ten specimens were prepared for each group. A three‐point flexural test was run using a span of 25 mm at a rate of 5 mm/min. The strength values were collected and analysed with ANOVA and Scheffe tests. The strengths of the specimens with orientated fibre addition ranged from 49·4 (s.d. = 5·7) to 64·5 (6·7) MPa and the control was 54·3 (4·0) MPa. In the dispersed groups, the strengths obtained ranged from 55·9 (5·9) to 87·3 (7·9) MPa. The results disclosed that inclusion of orientated fibres horizontally on the tension side of the specimens significantly improved the flexural strength compared with the control (P < 0·05). An optimal strength was obtained in the group of provisional resin containing 5 w/o dispersed fibre. Incorporation of glass fibres significantly improved the flexural strength of the resin and the dispersed method is more efficient than the orientated inclusion method.
Analysis of residual ridges and ridge relationship by three‐dimensional reconstruction method
Authors: Kawahata  , Kamashita  , Nishi  , Hamano  , Nagaoka
Published: March 2003

The purpose of this study was to develop a diagnostic system with which to determine the adequate area for artificial tooth arrangement on the posterior residual ridge. Edentulous plaster models and occlusion rims were measured by a non‐contact type shape measurement system. Three trigonal pyramids and their impressions on the occlusion rims were used as landmarks for the analysis and superimposition of the analysis results for the upper and lower ridges. The data points were obtained at intervals of 0·5 mm in the lateral direction and of 0·25 mm in the anteroposterior direction, and were interpolated by cubic spline curves in the lateral direction. When the ridge contour of the reconstructed image came in contact with the tangent line inclined at 30° to the tentative plane of occlusion at the buccal and lingual sides in the frontal section, the area between their points of contact on both sides was comparatively flat and was regarded as adequate for the artificial posterior tooth arrangement in this study. This diagnostic system seems to be useful in determining the adequate area for the artificial tooth arrangement on the posterior residual ridges of edentulous plaster models and in displaying their horizontal relationship.
Curing depth of four composite veneering materials polymerized with different laboratory photo‐curing units
Authors: Tanoue  , Matsumura  , Atsuta
Published: March 2003

Post‐curing properties of composite materials are influenced by the type of base monomer, activation system, filler content, and also by the type of light source employed. This study examined curing depth of four composite veneering materials polymerized by means of two different high‐intensity photo‐curing units for the purpose of evaluating the curing performance of the combinations of composite material and photo‐curing unit. Two microfilled and two hybrid composite materials designed for prosthetic veneer were assessed. The composite materials were cured using two photo‐curing units, one with a xenon light source and one with two metal halide light sources, and exposure periods varied from 20 to 90 s. Curing depth of the materials was determined with a scraping technique described by the International Organization for Standardization (ISO 4049). Three‐factor analysis of variance revealed that the depth of cure was influenced by the type of composite material as well as by the photo‐curing unit, and also by the exposure period (P = 0.0001). A microfilled composite material (Dentacolor) demonstrated the greatest depth of cure (4.69 mm) after 90 s irradiation with a metal halide unit (Hyper LII). of the two photo‐curing units, the metal halide curing unit consistently exhibited greater depth of cure than the xenon curing unit (Dentacolor XS). Longer exposure increased the depth of cure for all combinations.
Strains and tensile stress distribution in loaded disc‐shaped ceramic specimens. An FEA study
Authors: Abu‐hassan M. I. , Abu‐hammad O. A. , Harrison A.
Published: March 2003

SUMMARY Disc‐shaped specimens are frequently tested in order to establish an understanding of the properties of ceramic material. In this study three‐dimensional finite element stress analysis has been used to investigate the loading characteristics of this shape of specimen and the effect of incorporating scratches and voids into its structure. The results indicated that stress increased as loading was carried out nearer to the centre of the specimen. The presence of cracks did not affect these stresses whereas the presence of a void resulted in a very high stress concentration.
Evaluation of an optical instrument for objective assessment of oral mucosal erythema
Authors: Bagg J. , Moseley H.
Published: March 2003

SUMMARY This study evaluated the sensitivity and reproducibility of an optical instrument, the Erythema Meter, for quantifying erythema of palatal mucosa. The instrument is based on the principle that haemoglobin in the vasculature selectively absorbs green light but has little effect on red light and allows derivation of an ‘erythema index’. Non‐clinical investigations were carried out by taking a series of Erythema Meter readings from each colour block on a red check‐standard used by graphic artists for colour reproduction. For clinical assessment, 20 dentate patients with healthy palatal mucosa and 40 complete denture wearers (20 with denture stomatitis and 20 with healthy palatal mucosa) were enrolled, and palatal erythema determined both visually and using the Erythema Meter. Two weeks later the Erythema Meter readings for the 40 patients with healthy palatal mucosa were repeated, to allow assessment of the reproducibility of the Erythema Meter scores. The median erythema index was 12 (range 2–38) for dentate patients with healthy palatal mucosa and 5 (range 0–29) for denture wearers with healthy palatal mucosa. For denture stomatitis patients the median erythema index was 95 (range 36–117). The overall reproducibility coefficient was 88%. Visual scoring correlated poorly with the Erythema Meter scores for those with moderate degrees of erythema. The Erythema Meter provides an objective and reproducible means of measuring the degree of erythema of the palatal mucosa.
Viscoelastic properties of tissue conditioners – influence of molecular weight of polymer powders and powder/liquid ratio and the clinical implications
Authors: Murata  , Hamada  , Taguchi  , Shigeto  , Nikawa
Published: March 2003

summary The effect of the molecular weight of polymer powders and the polymer powder/liquid ratio on the viscoelastic properties after gelation of tissue conditioners was studied by means of a stress relaxation test. The results are summarized as follows. The lower‐molecular‐weight polymer powders produced the larger flow after gelation especially at long times. The use of a lower powder/liquid ratio produced a greater flow after gelation at both short times and long times. The difference in the molecular weight of polymer powders and the powder/liquid ratio was found to have no influence on changes in viscoelastic properties with the passage of time. It would be possible to control the viscoelastic properties of tissue conditioners suitable for each clinical purpose by making variations in composition and structure.
Marginal leakage in class II‐restorations after use of ceramic‐inserts luted with different materials
Authors: Hahn  , Schaller  , Müllner  , Hellwig
Published: March 2003

The efficiency of using prefabricated ceramic inlays to prevent microleakage has been discussed in different investigations. The purpose of this study was to evaluate the marginal microleakage of a new glass ceramic inlay system in combination with two different composite luting materials and one polyacid‐modified composite, respectively. Standardized class II cavities (n = 60) were filled with (1) Empress® inlays fixed with a highly viscous luting composite as a control group, and with glass ceramic inlays (Cerana®) in combination with (2) a highly viscous luting composite, (3) a low‐viscous luting composite and (4) a polyacid‐modified composite, respectively. After thermocycling the marginal quality was analysed with scanning electron microscopy, and the dye penetration along the cavity walls was measured. The use of the Cerana® inlays with a polyacid‐modified composite resin did not reveal a good marginal adaption. However, the combination of the Cerana® and the Empress® inlays with the highly viscous composite exhibited a comparable marginal fit. Within the limitations of an in vitro study it is concluded that the combination of the new glass ceramic inlays with a polyacid‐modified composite cannot be recommended for clinical use.
Macroscopic osseous changes in the temporomandibular joint related to dental attrition in Japanese macaque skull
Authors: Matsuka Y. , Iijima T. , Suzuki K. , Kuboki T. , Yamashita A.
Published: March 2003

The purpose of this study was to investigate the relationship between osseous changes in the temporomandibular joint (TMJ) and dental attrition in the Japanese macaque. One hundred and thirty Japanese macaque skulls (54 male and 76 female) from animals which had been bred in the same environment, were randomly sampled from a collection at the Primate Research Institute of Kyoto University. The age at death had been recorded in all cases. TMJ osseous changes were independently evaluated by three examiners, and were defined as an irregular surface or a perforated compact bone layer with a markedly irregular surface on either the temporal or condylar components. Age was a significant factor in predicting TMJ osseous changes (P < 0·001). A strong relation was observed between age and dental attrition (P < 0·001), while dental attrition was not a significant factor in predicting TMJ osseous changes (P = 0·334). The prevalence TMJ osseous changes in male animals was slightly higher than in females (P = 0·057). The results of this study suggest that osseous changes in the macaque TMJ are mainly related to age, not to dental attrition.
Comparison of conventional and resin‐modified glass–ionomer luting cements in the retention of post‐crowns by fatigue loading
Authors: Mitchell  , Orr
Published: March 2003

Fatigue testing may be used for in vitro evaluation of luting cements, allowing comparison of materials under controlled conditions. It is recognized that glass–ionomer cements are materials which are susceptible to microcracking, even during curing prior to load application, and their failure can be related to crack propagation. The aim of this study was to compare the retention of post‐crowns cemented with conventional and resin‐modified glass–ionomer cements, the latter having significantly greater fracture toughness, under cyclic loads which are representative of physiological service. A custom‐designed fatigue machine was used for three tests each comprising 18 specimens in a modified randomized complete block programme. Correlation of load amplitude to endurance was low, as expected from static test experience, but cement comparison was made through Kaplan‐Meier survival and cumulative hazard functions. Differences in the performance of the cements were indicated, but were not statistically significant in this study, although analysis by Cox’s proportional hazards model indicated that significance may be gained by a larger study.
Success rates for two different types of post‐and‐cores
Authors: Ottl P. , Lauer H. ‐cH.
Published: March 2003

The objective of our follow‐up study was to evaluate the success of two different types of partially prefabricated post‐and‐core systems following crown placement. Two hundred and thirty‐seven Permador® posts and 49 Radix® posts were evaluated clinically. Radiological follow‐up was performed for 230 Permador® posts and 47 Radix® posts. The restorations had been in situ for an average of 3·9 years (Permador® posts) and 2·3 years (Radix® posts), respectively. Root canal fillings were evaluated as to their length, their homogeneity and their flushness with the walls of the root canal. The post‐and‐cores were evaluated for their orientation in the root canal and for the length of the inserted post relative to the length of the root. The position of the post was classified as centric in 78·0% of the restorations followed, and eccentric in 19·5%, while 2·5% showed a root perforation. The minimal requirement that the length of the post‐and‐core should at least be equal to the length of the clinical crown was met in 85% of the cases. Eighteen (6·3%) of the 286 teeth examined had to be extracted. There were significant correlations between insertion periods, horizontal bone loss, length of the root canal filling, and position of the post on one hand and tooth loss on the other.
Whiplash injuries of the temporomandibular joint in motor vehicle accidents: Speculations and facts
Authors: MCKAY D.C. , CHRISTENSEN L.V.
Published: March 2003

Summary Referring to the temporomandibular joint (TMJ) of the human mandibular locomotor system, it has been asserted that displacement of the TMJ disc and inflammation of TMJ tissues are the results of acute and indirect trauma to the TMJ; on occasion this is allegedly experienced in motor vehicle accidents and commonly known as a TMJ whiplash injury. It is postulated that the TMJ whiplash injury is released in the occupant or occupants of a target vehicle when its rear end is impacted by the front end of a bullet vehicle. On the basis of detailed analyses of TMJ trauma/pain histories and TMJ magnetic resonance images, presented as circumstantial evidence in favour of the postulated TMJ whiplash injury, and detailed analyses of the mathematical biophysics of the mandibular locomotor system as well as direct experimental evidence, it is concluded that the postulated TMJ whiplash injury does not exist as a single and independent disease entity caused by motor vehicle accidents. If TMJ disc displacement and inflammation are present, they are expressions of an insidious and progressive pre—existing (pre—accident) disease entity that is comprised of TMJ synovitis/osteoarthritis (phase of inflammation with presence of immune system cells), TMJ internal derangement (phase of disc displacement and deformation with presence of proteinases), and TMJ osteoarthrosis (phase of degeneration with absence of immune system cells). For the asserted TMJ whiplash manoeuvre and ensuing injury to occur as postulated, the laws of physics and biology would have to be suspended.
The influence of finishing time on the marginal seal of a resin‐modified glass–ionomer and polyacid‐modified resin composite
Authors: Lim C. C. , Neo J. , Yap A.
Published: March 2003

The aim of this study was to compare the effect of immediate and delayed finishing on the microleakage of encapsulated resin‐modified glass–ionomer, Fuji II LC®and a polyacid‐modified resin composite, Dyract® compomer at both the enamel and dentine margins. Standardized Class V cavities were prepared along the cemento–enamel junction on buccal and palatal surfaces of 24 freshly extracted non‐carious premolars. Equal numbers of buccal and palatal cavities in each group were restored with Fuji II LC® and Dyract® compomer following the manufacturer’s instructions. The groups with delayed finishing were restored 1 week earlier, stored in saline at 37 °C and finished on the same day as the groups with immediate finishing. The specimens were then thermocycled 500 times and subjected to dye penetration testing. The results showed that both materials leaked more at the dentine than enamel margins for both regimes of finishing methods. There was no statistical difference in the microleakage of Dyract® finished immediately or later at enamel and dentine margins and Fuji II LC® finished immediately or later in dentine. However, a statistical difference existed between the microleakage in Fuji II LC® finished immediately and later in enamel.
A calculation method for the range of occluding phase at the lower incisal point during chewing movements using the curved mesh diagram of mandibular excursion (CMDME)
Authors: Hayasaki H. , Nakata S. , Nishijima N. , Okamoto A. , Minematsu K. , Yamasaki Y. , Nakata M.
Published: March 2003

The purpose of this study was to develop a method for calculating the range of the occluding phase in chewing movements. In this study, we defined ‘range’ as the distance of the movement at the lower incisal point while the mandible moves with tooth contact. First, mandibular excursions were measured using an opto‐electronic movement analysis system, which can measure mandibular movement with six degrees‐of‐freedom at a sampling frequency of 100 Hz. With use of this measurement data, the curved mesh diagram of mandibular excursion (CMDME) previously reported was made. Then, chewing movements were measured using the same analysis system. The movements were separated into their component chewing cycles. Finally, we calculated the distance between each cycle and the CMDME. The occluding range of our subject was 0·4 mm at the closing phase and 3·4 mm at the opening phase. These results suggest that tooth contact occurs during chewing movement and demonstrate that the range of the occluding phase for the opening and closing phases of a subject can be calculated without morphological data from a dental cast.
The effect of composite resin application and radiation techniques on dye penetration in class II direct composite resin restorations
Authors: Ziskind D. , Venezia E. , Mass E. , Hirschfeld Z.
Published: March 2003

This study examined the effect of the application of resin composite and radiation techniques on dye penetration in class II direct composite resin restorations. For the restorative procedure, the light‐cone and the incremental layering techniques were used. The null hypothesis of this experiment was, that both techniques have the same influence on dye penetration. Evaluation of dye penetration in the restoration/tooth interface was performed in 20 extracted premolars and molars. On each tooth, two class II cavities were prepared. The cervical margin of the proximal boxes were located in dentin or in enamel. When the gingival margin of the cavity was located in enamel, a significant lower level of dye penetration of the the test group was found (Wilcoxon rank test, P=0·0102). This study showed that the application of a transparent cone seems to be more effective than the three increments technique in the mechanical separation of the first composite increment. Transmitting the curing light into the proximal box, seems to have no positive effect on dye penetration in class II direct composite resin restorations.
The effect of an oral prosthesis on the quality of life for head and neck cancer patients
Authors: Moroi H. H. , Okimoto K. , Terada Y.
Published: March 2003

The quality of life (QOL) in patients with cancer in the head and neck regions has become an increasingly important factor in medical treatment. We examined the effect of a prosthesis on the QOL based on the patients’ own subjective evaluations. Sixty‐eight head and neck cancer patients who had been treated in the Department of Prosthetic Dentistry of the Faculty of Dentistry, Kyushu University, were compared with 35 denture wearers as a control. General denture satisfaction in the control group showed a statistical correlation with eating (P<0·01, t‐test; ρ=0·72, Spearman rank correlation), aesthetic satisfaction (P<0·01, ρ=0·57) and pain (P<0·01, ρ=0·51). On the other hand, for cancer patients, general denture satisfaction showed a statistical correlation with not only eating (P<0·01, ρ=0·34), aesthetic satisfaction (P<0·01, ρ=0·33) and pain (P<0·01, ρ=0·41) but also health (P<0·01, ρ=0·33) and mental well‐being (P<0·01, ρ=0·41). A statistical correlation between the Denture score and the QOL score was thus observed in cancer patients (P<0·0001, ρ=0·56), while the correlation for the control group was not statistically significant. This study showed that oral prostheses for head and neck cancer patients are important factors not only for eating but also for the overall patient QOL.