bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoresponsive Fischer 344 Rats are Reproductively Inhibited by Melatonin and Differ in 2‐[125I] Iodomelatonin Binding from Nonphotoresponsive Sprague‐Dawley Rats
Authors: Heideman P. D. , Bierl C. K. , Sylvester C. J.
Published: March 2003

Many temperate‐zone species use photoperiod as an environmental cue to regulate reproductive timing. Strains of laboratory rats differ in their responsiveness to photoperiod, with the Fischer 344 (F344) strain being the most responsive known. F344 rats and closely related strains that differ in photoresponsiveness may be useful models to study the mechanisms and genetic basis for photoresponsiveness. We tested two hypotheses: (i) that melatonin mediates photoresponsiveness in F344 rats, as is the case in all other mammals tested, and (ii) that the location, abundance, or affinity of melatonin receptors, as estimated by the amount and location of binding of the radioligand 2‐[125I]‐iodomelatonin (IMEL) in the brain, might cause variation in photoresponsiveness among rat strains. Melatonin injections 1 h before lights off in a stimulatory photoperiod (L14 : D10) induced reproductive inhibition and reduced weight gain in a manner similar to short days of L8 : D16, while injections of ethanolic saline vehicle did not. Interestingly, melatonin injections administered during an inhibitory photoperiod (L10 : D14) caused greater inhibition of both reproduction and weight gain than short photoperiod alone. Pinealectomized F344 rats implanted subcutaneously with melatonin in a silastic capsule did not differ in testis size or body weight from controls with blank implants. The brains and pars tuberalis of the pituitary from photoresponsive F344 rats and nonphotoresponsive Harlan Sprague‐Dawley (HSD) rats were processed for autoradiography using IMEL. We found significantly higher specific IMEL binding in the anterior and posterior regions of the paraventricular nucleus of the thalamus (PVNt) and reuniens nucleus of the thalamus of F344 rats than in the same areas in HSD rats. There were no differences between strains in specific IMEL binding in the medial PVNt, anteroventral and anterodorsal nucleus of the thalamus, suprachiasmatic nucleus, or the pars tuberalis. These results indicate that melatonin mediates photoresponsiveness in F344 rats. In addition, they provide support for the hypothesis that F344 rats may be photoresponsive due to differences from other strains in the location, density, or affinity of melatonin receptors.
Evidence for Direct Involvement of β‐Catenin in Phorbol Ester‐Induced Neurite Outgrowth in GT1‐1 Hypothalamic Neurones
Authors: Sun W. , Lee H. , Choe Y. , Cho S. , Kim D. H. , Kim K.
Published: March 2003

Gonadotropin‐releasing hormone (GnRH) is a pivotal neuroendocrine regulator controlling reproductive functions. However, the scattered distribution of GnRH neurones in the mammalian brain has hindered studies on the development and differentiation of GnRH neurones. In the present study, we used the immortalized GnRH‐producing GT1‐1 cells to examine whether activation of protein kinase C (PKC) pathway with 12‐O‐tetradecanoyl‐13‐acetate (TPA) induces morphological and functional differentiation of GnRH neurones. TPA induced neurite outgrowth and inhibited proliferation of GT1‐1 cells that were specifically antagonized by cotreatment of PKC inhibitor, calphostin C. The functional significance of TPA‐induced differentiation of GT1‐1 cells was manifested in part by the changes in the effects of γ‐aminobutyric acid (GABA) on intracellular Ca2+ levels. In untreated GT1‐1 cells, activation of GABA‐A receptor with 10 µM muscimol increased intracellular Ca2+ levels, whereas such stimulatory effects disappeared in GT1‐1 cells bearing neurites. Accordingly, muscimol could not stimulate GnRH release in TPA‐treated GT1‐1 cells. To elucidate the molecular mechanism underlying TPA‐induced neurite outgrowth, we performed differential display reverse transcription‐polymerase chain reaction. Among several genes that are affected by TPA treatment, we found a significant induction of β‐catenin mRNA expression. Along with the rapid induction of β‐catenin protein levels, we observed that β‐catenin was reallocated from cell–cell adhesion sites to the growth cones within 3 h of TPA treatment. Transient transfection studies with green fluorescent protein as a reporter gene demonstrated that β‐catenin overexpression alone can promote neurite outgrowth in GT1‐1 cells. Moreover, TPA was found to increase the transcription‐activational roles of β‐catenin. Together, these data provide evidence that β‐catenin is involved in the TPA‐induced functional differentiation of immortalized GnRH neurones.
Regulation by Osmotic Stimuli of Galanin‐R1 Receptor Expression in Magnocellular Neurones of the Paraventricular and Supraoptic Nuclei of the Rat
Authors: Burazin T. C. D. , Larm J. A. , Gundlach A. L.
Published: March 2003

Neurones of the supraoptic nucleus (SON) and the magnocellular and parvocellular divisions ofthe paraventricular nucleus (PVN) express galanin and [125I]galanin binding sites. Although the precise role(s) of galanin in these different cell populations is still unknown, it has been shown to regulate the electrophysiological, neurochemical and secretory activity of magnocellular neurones.In light of the well‐described effects of hyperosmotic stimuli, such as salt‐loading on magnocellular neurone activity and galanin synthesis and release, and the recent identification of multiple galanin receptors in brain, this study assessed the possible regulation of galanin receptor subtype expression in the PVN/SON of salt‐loaded, dehydrated and food‐deprived rats. Gal‐R1 mRNA was abundant in the SON (and magnocellular PVN) of control rats and levels were increased in these same cells after 4 days of salt‐loading (2% NaCl solution as drinking water) or water deprivation. The density of specific [125I]galanin(1–29) binding and the intensity of Gal‐R1‐like immunostaining were also increased in the characteristically enlarged, magnocellular neurones of the PVN and SON after these treatments. Gal‐R2 mRNA was detected in the parvocellular PVN, but levels were not altered by the hyperosmotic stimuli. In contrast, food deprivation (4 days), which has been shown to reduce levels of several neurochemical markers in magnocellular neurones, produced a significant reduction in Gal‐R1 (and galanin) mRNA levels in the SON, but no consistent change in neurone size, [125I]galanin binding levels, or Gal‐R1 immunostaining. Along with previous findings from this and other laboratories, these data suggest that the expression of galanin and Gal‐R1 receptors is regulated in parallel with functional and morphological changes in hypothalamic magnocellular neurones. Furthermore, Gal‐R1 immunoreactivity was primarily detected in somatodendritic areas and thus galanin may influence the activity of these cells, particularly vasopressin synthesis/release, via autocrine or paracrine activation of Gal‐R1 receptors, especially during long‐lasting stimulation.
Central Orexin‐A Activates Hypothalamic‐Pituitary‐Adrenal Axis and Stimulates Hypothalamic Corticotropin Releasing Factor and Arginine Vasopressin Neurones in Conscious Rats
Authors: Al‐Barazanji K. A. , Wilson S. , Baker J. , Jessop D. S. , Harbuz M. S.
Published: March 2003

The effects of centrally injected orexin‐A on plasma adrenocorticotropin (ACTH) and corticosterone levels and corticotropin releasing factor (CRF) and arginine vasopressin (AVP) mRNA in the parvocellular cells of the paraventricular nucleus (PVN) of the rat were investigated. In animals implanted previously with a lateral brain ventricle and femoral artery cannula, a single i.c.v. injection of orexin‐A (10 µg/rat) resulted in a rapid, significant increase in plasma ACTH and corticosterone concentrations. Plasma ACTH reached a peak (12.5‐fold greater than basal levels) at 30 min, which was maintained over 120 min before declining towards control levels by 240 min. Plasma corticosterone concentrations reached a peak (6.7‐fold greater than basal levels) at 30 min. Orexin‐A at a higher dose (30 µg/rat) also produced a rapid increase in plasma ACTH and corticosterone concentrations. The area under the curve for plasma levels of ACTH was similar for both doses of orexin‐A. In a second study, orexin‐A (10 µg/rat) was injected i.c.v. and brains and pituitaries were rapidly removed after 240 min. In situ hybridization histochemistry revealed that CRF and AVP mRNA levels were significantly increased in the parvocellular cells of the PVN. Pro‐opiomelanocortin mRNA levels in the pituitary gland were not significantly elevated in response to orexin‐A. These results suggest that orexin‐A is able to act centrally to activate the hypothalamic‐pituitary‐adrenal axis involving stimulation of both CRF and AVP expression.
Microinfusion of a Nitric Oxide Donor in Discrete Brain Regions Activates the Hypothalamic‐Pituitary‐Adrenal Axis
Authors: Seo D. O. , Rivier C.
Published: March 2003

We previously showed that the intracerebroventricular injection of the nitric oxide (NO) donor 3‐morpholino‐sydnonimine (SIN‐1) released adrenocorticotropic hormone (ACTH) and upregulated transcripts for corticotropin‐releasing factor (CRF) and vasopressin in the paraventricular nucleus (PVN) of the rat hypothalamus. In the present work, we microinfused SIN‐1 into the PVN itself, the amygdala, the hippocampus or the frontal cortex to identify the brain regions that modulate the influence of NO on the hypothalamic‐pituitary‐adrenal (HPA) axis. Microinfusion into the PVN, which contains most of the CRF and vasopressin neurones that control HPA axis activity, significantly released ACTH. Microinfusion into the amygdala or the hippocampus, areas which also regulate HPA axis activity, similarly increased plasma ACTH levels. However, these responses were smaller and showed a delayed onset, compared to that observed following PVN treatment. In contrast, microinfusion of SIN‐1 into the frontal cortex, which is not believed to exert a major direct influence on the HPA axis, was without effect. The observation that compared to microinfusion into the PVN, peak ACTH levels were both smaller and delayed when SIN‐1 was microinfused into the amygdala or the hippocampus, and that SIN‐1 only increased NO levels when injected into the PVN, suggests that the NO donor injected outside the PVN activates this nucleus by targeting pathways that connect it to these other regions rather than by leakage. Collectively, our results provide important clues regarding the putative role of these regions in modulating the influence of NO on the HPA axis.
Polyamine Regulation of the Rat Pro‐Opiomelanocortin Gene Expression in AtT‐20 Cells
Authors: Yamamori E. , Iwasaki Y. , Aoki Y. , Nomura A. , Tachikawa K. , Ariyoshi Y. , Mutsuga N. , Morishita M. , Yoshida M. , Asai M. , Oiso Y. , Saito H.
Published: March 2003

Polyamines are a ubiquitous group of amines that play diverse biological roles. In the anterior pituitary, intracellular polyamine levels are reported to show diurnal changes, although the biological significance remains to be elucidated. In this study, we examined the effects of polyamines on the transcriptional activity of the rat pro‐opiomelanocortin (POMC) gene using AtT20PL, a clone of the AtT20 cell line in which an approximately 0.7 kb of the rat POMC 5′ promoter‐luciferase fusion gene was stably incorporated. The results showed that three representative polyamines (putrescine, spermidine and spermine) all stimulated POMC promoter activity in a time‐ and dose‐related manner, spermine showing the most potent effect (maximum approximate three‐fold increase). This effect was not observed under treatment with actinomycin D, suggesting the effect of polyamine at the transcriptional level. On the other hand, methylglyoxal bis (guanylhydrazone), an inhibitor of polyamine synthesis, showed the opposite effect, further supporting the positive role of intracellular polyamines. Taken together, our findings suggest that polyamines are involved in the regulation of POMC gene expression (especially in terms of diurnal changes) in corticotroph cells. The precise molecular mechanisms of polyamine effects await further research.
Action of Glucocorticoids on Survival of Nerve Cells: Promoting Neurodegeneration or Neuroprotection?1
Authors: Ábrahám I. M. , Harkany T. , Horvath K. M. , Luiten P. G. M.
Published: March 2003

Extensive studies during the past decades provided compelling evidence that glucocorticoids (GCs) have the potential to affect the development, survival and death of neurones. These observations, however, reflect paradoxical features of GCs, as they may be critically involved in both neurodegenerative and neuroprotective processes. Hence, we first address different aspects of the complex role of GCs in neurodegeneration and neuroprotection, such as concentration dependent actions of GCs on neuronal viability, anatomical diversity of GC‐mediated mechanisms in the brain and species and strain differences in GC‐induced neurodegeneration. Second, the modulatory action of GCs during development and ageing of the central nervous system, as well as the contribution of altered GC balance to the pathogenesis of neurodegenerative disorders is considered. In addition, we survey recent data as to the possible mechanisms underlying the neurodegenerative and neuroprotective actions of GCs. As such, two major aspects will be discerned: (i) GC‐dependent offensive events, such as GC‐induced inhibition of glucose uptake, increased extracellular glutamate concentration and concomitant elevation of intracellular Ca2+, decrease in GABAergic signalling and regulation of local GC concentrations by 11β‐hydroxysteroid dehydrogenases; and (ii) GC‐related cellular defence mechanisms, such as decrease in after‐hyperpolarization, increased synthesis and release of neurotrophic factors and lipocortin‐1, feedback regulation of Ca2+ currents and induction of antioxidant enzymes. The particular relevance of these mechanisms to the neurodegenerative and neuroprotective effects of GCs in the brain is discussed.
Role for the Pineal and Melatonin in Glucose Homeostasis: Pinealectomy Increases Night‐Time Glucose Concentrations
Authors: La Fleur S. E. , Kalsbeek A. , Wortel J. , Van Der Vliet J. , Buijs R. M.
Published: March 2003

The effects of melatonin on glucose metabolism are far from understood. In rats, the biological clock generates a 24‐h rhythm in plasma glucose concentrations, with declining concentrations in the dark period. We hypothesized that, in the rat, melatonin enhances the dark signal of the biological clock, decreasing glucose concentrations in the dark period. We measured 24‐h rhythms of plasma concentrations of glucose and insulin in pinealectomized rats fed ad libitum and subjected to a scheduled feeding regimen with six meals equally distributed over the light/dark cycle and compared them with previous data of intact rats. Pinealectomy dampened the amplitude of the 24‐h rhythm in plasma glucose concentrations in rats fed ad libitum, and abolished it completely in rats subjected to the scheduled feeding regimen, while plasma insulin concentrations did not change under both conditions. Pinealectomy abolished the nocturnal decline in plasma glucose concentrations irrespective of whether rats were fed ad libitum or subjected to the scheduled feeding regimen. Melatonin replacement restored 24‐h mean plasma glucose concentrations in pinealectomized rats that were subjected to the scheduled feeding regimen but, interestingly, it did not restore the 24‐h rhythm. Melatonin treatment also resulted in higher meal‐induced insulin responses, probably mediated via an increased sensitivity of the β‐cells. Taken together, our data demonstrate that the pineal hormone, melatonin, influences both glucose metabolism and insulin secretion from the pancreatic β‐cell. The present study also demonstrates that removal of the pineal gland cannot be compensated by mimicking plasma melatonin concentrations only.
Salsolinol is a Putative Endogenous Neuro‐intermediate Lobe Prolactin‐Releasing Factor
Authors: Tóth B. E. , Homicskó K. , Radnai B. , Maruyama W. , DeMaria J. E. , Vecsernyés M. , Fekete M. I. K. , Fülöp F. , Naoi M. , Freeman M. E. , Nagy G. M.
Published: March 2003

The isolation and identification of a prolactin‐releasing factor (PRF) from the neuro‐intermediate lobe of the pituitary gland has been pursued for over a decade. Using high‐pressure liquid chromatography with electrochemical detection (HPLC‐ECD) and gas chromatography/mass spectrometry (GC/MS) (R)‐salsolinol (SAL) (a dopamine‐related stereo‐specific tetrahydroisoquinoline) was found to be present in neuro‐intermediate lobe as well as median eminence extracts of male, intact‐, and ovariectomized female rats. Moreover, analysis of SAL concentrations in neuro‐intermediate lobe revealed parallel increases with plasma prolactin in lactating rats exposed to a brief (10 min) suckling stimulus following 4‐h separation. SAL appears to be a selective and potent stimulator of prolactin secretion in vivo and it was without effect on the secretion of other pituitary hormones. We have also found that SAL can elevate prolactin release, although to a lesser extent, in pituitary cell cultures as well as in hypophysectomized rats bearing anterior lobe transplants under the kidney capsule. Lack of interference of SAL with [3H]‐spiperone binding to AP homogenates indicates that SAL does not act at the dopamine D2 receptor. Moreover, [3H]‐SAL binds specifically to homogenate of AL as well as neuro‐intermediate lobe obtained from lactating rats. Taken together, our data clearly suggest that SAL is synthesized in situ and this compound can play a role in the regulation of pituitary prolactin secretion.
The Affinity and Activity of the Multiple Hormone Response Element in the Proximal Promoter of the Human Oxytocin Gene
Authors: Stedronsky K. , Telgmann R. , Tillmann G. , Walther N. , Ivell R.
Published: March 2003

In vivo there appears to be a marked association between oestrogen levels and the expression of the oxytocin (OT) gene in most tissues. Transfection and DNA‐protein binding experiments using high levels of either oestrogen receptor (ER)α or ERβ imply a direct interaction of these transcription factors with the multiple hormone response element (HRE) at approximately −160 from the transcription start site of the OT gene in most species. In an extensive set of experiments, we show, using both transfection and protein‐DNA binding, that low to moderate amounts of either oestrogen receptor, while being able to interact directly with a classic oestrogen response element (ERE) fail to interact with the human OT −160 HRE. Instead, this element, similar to its bovine counterpart, has a high affinity for the orphan receptors steroidogenic factor 1 and chicken ovalbumin upstream promoter transcription factor. Second, the human and bovine OT promoter can be made artificially responsive towards oestrogen in a cotransfection system over‐expressing ERα or ERβ, but not in cells expressing natural levels of these steroid receptors. Interestingly, nuclear extracts from both ERα‐positive MCF7 cells and ERα‐negative MDA‐MB231 cells both contain a transcription factor which binds specifically to both the hOT‐HRE element and to a classic ERE, and which has orphan receptor‐like binding properties rather than those of an oestrogen receptor. Together, these and other results suggest that oestrogen action in vivo on the OT gene in all species is more likely to involve a DNA‐independent mechanism than classic direct interactions with dimeric oestrogen receptors.
Penetration of Endogenous Steroid Hormones Corticosterone, Cortisol, Aldosterone and Progesterone into the Brain is Enhanced in Mice Deficient for Both mdr1a and mdr1b P‐Glycoproteins
Authors: Uhr M. , Holsboer F. , Müller M. B.
Published: March 2003

Numerous investigations have confirmed an important role for multidrug‐resistance gene 1‐type P‐glycoproteins (MDR1‐type P‐gps) in the blood–brain barrier, protecting the brain against the accumulation of a wide range of toxic xenobiotics and drugs. Several studies have provided evidence in vitro that certain steroid hormones are transported by MDR1‐type P‐gps; however, the question of whether this might also apply to the situation in vivo still remained to be determined. We used mice deficient for both murine mdr1a and mdr1b P‐gps [mdr1a/1b(−/−)] to determine the uptake of [3H]‐cortisol, [3H]‐corticosterone, [3H]‐aldosterone and [3H]‐progesterone into the plasma, brain, testes, liver, spleen, pituitary and adrenal glands. We provide evidence that the access of the endogenous steroid hormones corticosterone, cortisol and aldosterone is regulated by MDR1‐type P‐gps in vivo. As peripherally administered steroid hormones accumulate in the brain of mice deficient for MDR1‐type P‐gps, mdr1a/1b proteins are likely to transport these hormones out of the brain, providing a kinetic barrier to their entry. Intracerebral progesterone concentrations are influenced by MDR1‐type P‐gp function as well; however, the effects are only small. In addition, all four endogenous glucocorticoid hormones accumulated in the testes of mdr1a/1b(−/−) mice. Our findings underline the importance of MDR1‐type P‐gps as an endogenous barrier system controlling the access of endogenous steroid hormones at the blood–brain barrier to maintain homeostatic control and to protect central nervous system neurones.
Localization of Oestrogen Receptors in the Sensory and Motor Areas of the Spinal Cord in Japanese Quail (Coturnix japonica)
Authors: Evrard H. C. , Balthazart J.
Published: March 2003

In Japanese quail, the presence of aromatase (oestrogen synthase) in the dorsal horn of the spinal cord suggests that spinal sensory processes might be controlled by local actions of oestrogens. This is supported by the presence of oestrogen receptors and aromatase in the dorsal horn of the spinal cord in rats, and by the alteration of sensitivity by oestrogens in various mammalian species and also in canaries. We investigated whether oestrogens that are locally produced in the quail spinal cord can bind to specific receptors in the vicinity of their site of synthesis. We demonstrate the presence of numerous oestrogen receptor α‐immunoreactive (ERα‐ir) cell nuclei, predominantly in laminae II and, to a lesser extent, I and III of the dorsal horn of the spinal cord (i.e. in the area where aromatase was previously identified). ERα‐ir cells were also seen in various parts of the intermediate zone (laminae V–VII). This presence of ERα‐ir cells in the dorsal horn and intermediate zone fits in well with the distribution of ERα‐ir cells in homologous areas in mammals, including rats. Only a few labelled cells were found in the ventral horn in the cervical, brachial, thoracic and first lumbar segments, but a conspicuous dense group of large ERα‐ir cells was identified in lamina IX of the ventral horn in synsacral segments 8–10, which contain the motoneurones innervating the muscles of the cloacal gland. The presence of ERα‐ir cells in lamina IX of these synsacral segments in quail contrasts with the finding that motoneurones innervating penile muscles in rats contain androgen, but not oestrogen receptors, and are influenced by androgens rather than by oestrogens. Together, these data suggest that spinal actions of oestrogens may modulate the sensory and motor systems that participate in reproduction, as well as other nonreproductive functions in quail.
Lipopolysaccharide Endotoxin Potentiates the Effect of Osmotic Stimulation on Vasopressin Synthesis and Secretion in the Rat Hypothalamus
Authors: Grinevich V. , Ma X.‐M. , Jirikowski G , Verbalis J. , Aguilera G.
Published: March 2003

Vasopressin secreted by magnocellular neurones of the hypothalamic supraoptic and paraventricular nuclei is essential for water balance. In this study, we examined magnocellular neurone responses to osmotic stimulation in vehicle‐injected controls or rats receiving an intraperitoneal (i.p.) injection of 250 µg/100 g of lipopolysaccharide (LPS), 3 h or 6 h earlier. LPS injection had no effect on plasma vasopressin concentrations in control rats but it caused marked and transient potentiation of the responses to a single i.p. injection of hypertonic saline (five‐ and two‐fold, 3 and 6 h after LPS, respectively). The enhancement of plasma vasopressin responses was independent of plasma sodium concentrations or changes in blood pressure. Basal vasopressin mRNA expression in the paraventricular and supraoptic nuclei decreased slightly 6 h after LPS injection, without changes in vasopressin transcription as indicated by vasopressin heteronuclear (hn) RNA levels. Parvocellular neurones showed expected increases in vasopressin hnRNA expression following LPS injection and a further increase after i.p. hypertonic saline injection (due to the painful component). In contrast to magnocellular vasopressin mRNA expression, the effects of LPS and hypertonic saline injections in parvocellular neurones were additive and not synergistic. Light microscopic immunohistochemical examination revealed an increase in size of vasopressin but not oxytocin axonal terminals in the neural lobe 3 h after LPS injection. Osmotic stimulation caused marked depletion of vasopressin immunoreactivity in axonal terminals of the neural lobe in both control and LPS‐pretreated rats. The changes in vasopressin axon terminals were accompanied by induction of interleukin (IL)‐1β and IL‐6 in the posterior pituitary. The data show that endotoxemia causes morphological and functional alterations of the hypothalamic neurohypophyseal system, resulting in facilitation rather than inhibition of vasopressin synthesis, and secretion in response to osmotic stimulation.
Effect of Intracerebroventricular Administration of the Octadecaneuropeptide on the Expression of Pro‐Opiomelanocortin, Neuropeptide Y and Corticotropin‐Releasing Hormone mRNAs in Rat Hypothalamus
Authors: Compère V. , Li S. , Leprince J. , Tonon M. C. , Vaudry H. , Pelletier G.
Published: March 2003

Intracerebroventricular (i.c.v.) administration of the octadecaneuropeptide (diazepam‐binding inhibitor [33–50]; ODN) exerts a potent anorexigenic effect in the rat. We studied the effect of ODN on three neuropeptides involved in feeding behaviour: the orexigenic peptide neuropeptide Y (NPY) and two anorexigenic peptides, corticotropin‐releasing hormone (CRH) and the pro‐opiomelanocortin (POMC)‐derived peptide α‐melanocyte‐stimulating hormone. The effect of i.c.v. administration of ODN (0.1 µg/kg and 1 µg/kg) on mRNA expression of the peptides in male rat hypothalamus was evaluated by semiquantitative in situ hybridization. In the arcuate nucleus, NPY‐expressing neurones were mostly found in the inner zone in close proximity of the third ventricle. ODN at the dose of 0.1 µg/kg induced a significant decrease of 17.4% in NPY mRNA expression, while the depressing effect was more marked (31.4%) with the highest dose of ODN (1 µg/kg). POMC‐expressing neurones were more laterally located in the arcuate nucleus. Administration of ODN at 0.1 µg/kg and 1 µg/kg doses induced increases of 33.5% and 27.4% in POMC mRNA expression, respectively. Labelling obtained with the CRH cRNA probe was essentially distributed throughout the medial parvocellular area of the hypothalamic paraventricular nucleus. ODN, at doses of 0.1 and 1 µg/kg, resulted in 17.8% and 32.8% decreases in CRH mRNA expression, respectively. The present data suggest that ODN might exert its anorexigenic effect by increasing mRNA expression of POMC and decreasing mRNA expression of NPY in the arcuate nucleus.
Effects of storage, thermal and load cycling on a new reinforced glass–ionomer cement
Authors: Yap Adrian U. J.
Published: March 2003

The objective of this in‐vitro study was to determine the influences of storage, thermal and load cycling as well as combinations of these treatment procedures on the microleakage patterns of a new ‘condensable’ silver reinforced restorative glass–ionomer cement (Shofu Hi‐Dense®). Class II preparations with gingival margins in dentine were made on 50 freshly extracted, non‐carious molar teeth and restored with Shofu Hi‐Dense® according to the manufacturer’s instructions. The restorations were subsequently stored for 1 week, finished and randomly assigned into five groups of 10 and treated as follows: Group 1 ‐ control (uncycled); Group 2 ‐ thermocycled; Group 3 ‐ mechanically load cycled; Group 4 ‐ three months storage, uncycled; Group 5 ‐ three months storage, thermal and load cycled. The storage medium throughout the experiment was artificial saliva at 37°C. All treatment procedures had no significant influence on microleakage at the enamel–cement interface. These treatment modalities, however, resulted in a significant increase in leakage at the dentine–cement interface. With the exception of the 1 week storage, uncycled group, the dentine–cement interface had significantly greater leakage than the enamel–cement interface.
Curing depth of a composite veneering material polymerized with seven different laboratory photo‐curing units
Authors: Tanoue  , Matsumura  , Atsuta
Published: March 2003

Properties of laboratory‐cured composite materials are affected by the type of activation system as well as by the photo‐curing unit light source. This study examined curing depth of a composite veneering material polymerized by means of various photo‐curing units with the aim of evaluating the curing performance of the light sources. A microfilled composite material designed for prosthetic veneer was cured with seven photo‐curing units. The light sources of the units were halogen/fluorescent, xenon, metal halide, fluorescent, halogen, halogen and mercury lamps. Exposure periods were 20, 30, 60 and 90 s. The curing depth of the material was determined using the method described by the International Organization for Standardization (ISO 4049). Two‐factor analysis of variance revealed that the depth of cure was influenced both by the type of curing unit and by the exposure period (P = 0.0001). Among the seven photo‐curing units, a metal halide curing unit consistently exhibited the greatest depth of cure. For all units, longer exposure increased the depth of cure.
Speech intelligibility following maxillectomy with and without a prosthesis: an analysis of 54 cases
Authors: Umino S. , Masuda G. , Ono S. , Fujita K.
Published: March 2003

To statistically evaluate the factors that influenced speech following maxillectomy, the speech intelligibility (SI) in 54 patients was measured with and without a prosthesis. The mean SI score without a prosthesis in all patients was 35.7 ± 22.7% and that with a prosthesis was 84.9 ± 12.7%. The results of the postmaxillectomy SI statistical analysis revealed that an oro–nasal communication was one of the factors that influenced SI without a prosthesis. The resection of the anterior portion of the soft palate was one of the factors that influenced SI with a prosthesis, which suggested that for some of these patients we should consider specific surgical treatment, aimed at the reconstruction in the deep defect extending to the intratemporal fossa. A new classification of maxillary defects has been proposed which will help to predict the grade of postmaxillectomy speech disorder following surgery.
The relationship between signs and symptoms of temporomandibular disorders and bilateral occlusal contact patterns during lateral excursions
Authors: Watanabe  , Yatani  , Kuboki  , Matsuka  , Terada  , Orsini  , Yamashita
Published: March 2003

The relationship between signs and symptoms of temporomandibular disorders (TMD) and bilateral occlusal contact patterns was investigated in 143 TMD patients (mean age: 34·0 ± 15·9 years; 38 male and 105 female). In addition to an interview regarding chief complaints and accompanying symptoms various muscles and the temporomandibular joints were palpated bilaterally and occlusal analyses were made. Only 5 out of 108 paired variables were found to be significantly associated by using the chi‐squared test. Medial pterygoid muscle pain on palpation showed significant associations with the occlusal contact pattern (P < 0·005), especially working side contacts (interocclusal tooth contacts on the working side) (P < 0·005), during contralateral excursions; sternocleidomastoid muscle pain on palpation showed a significant association with balancing side contacts (interocclusal tooth contacts on the balancing side) during ipsilateral excursions P < 0·05); shoulder stiffness and pain in the eye showed significant associations with balancing side contacts during contralateral excursions (P < 0·05). The results show only a weak relationship between some TMD symptomatology and bilateral occlusal contact patterns during lateral excursions. The findings suggesting the specific laterality of a few TMD signs and symptoms associated with particular occlusal contacts may deserve closer case–control study.
The variability of bite force measurement between sessions, in different positions within the dental arch
Authors: Tortopidis D. , Lyons M. F. , Baxendale R. H. , Gilmour W. H.
Published: March 2003

The effect of measuring bite force with different patterns of transducer on different occasions was studied. Maximum voluntary bite force was measured in eight volunteers. Three transducer positions, each with a different pattern of transducer, were used; between the anterior teeth, between the second premolar and the first molar on one side and between the second premolars and first molars on both sides. Visual feedback of force was provided. Two sets of five maximum clenches were recorded with a rest period in between. This sequence was repeated for each transducer and the experiment was repeated on three different days. The highest forces were measured with the bilateral posterior transducer (mean 580 N, s.d. 235) and the lowest on the anterior transducer (mean 286 N, s.d. 164). The standard deviations of the bite force mean values were used as an indication of the variability and were subjected to a non‐parametric anova (Kruskal–Wallis). The forces recorded with each transducer position were significantly different between the transducers (P < 0·01) and the maximum bite force showed least variability when measured between the posterior teeth on one side only. There was little difference in bite force between the three different sessions (P ≥ 0·05) when measured in the same position within the dental arch, whichever of the three positions that may be.
Propagation of various tooth impacts in the human body
Authors: Yamashita R. , Suenaga H. , Yamabe Y. , Torisu T. , Fujii H.
Published: March 2003

The purpose of this study was to investigate how far tooth impacts were propagated in the body and whether the propagation would be influenced by posture. The impacts were propagated to all recording sites on the head and neck of the 10 examinees tested. In the recordings on the limbs, even at the most distal site, the number of examinees detecting the vibration was seven out of nine examinees. These results showed that the impacts exerted on the tooth were propagated to distal sites of limbs through the bones and soft tissues and implied that the propagated vibration would influence the whole of the body. On the other hand, as the amplitude of propagated vibration was influenced by posture and recording site, the posture during jaw functioning appears to be important.
Mathematical shape matching as a tool in tooth wear assessment – development and conduct
Authors: Mitchell H. L. , Chadwick R. G.
Published: March 2003

The quantitative assessment of restoration and tooth wear usually requires fixed reference points from which measurements are made. In longitudinal patient follow‐up the loss or erosion of such points may preclude measurement and an alternative approach is to seek regions of coincidence and conflict in digital models of before and after wear surfaces, with a continuous refinement of the parameters of the coordinate transformations, until the closest correspondence between them is found. A computer program has been written to implement the algorithm and assess the technique’s capacity to find the match between surfaces both artificially generated and from tooth replicas recorded from patients at different epochs. The program was able to achieve the desired ends, demonstrating the utility of the technique in tooth wear assessment but identifying the need to refine the program further to enhance both its difference detection capabilities and level of automation. Examination of the theory and practical experience highlighted certain situations when user understanding is invaluable to ensure a satisfactory solution. This strengthened the investigators’ resolve against reliance upon commercially based surface fitting programs whose basis may not be fully understood. Notwithstanding this surface matching is a powerful tool in the investigation of dental wear.
Relationship of masticatory mandibular movements to masticatory performance of dentate adults: a method study
Authors: Ow R. K. K. , Carlsson G. E. , Karlsson S
Published: March 2003

This study evaluated a sieve method for measuring masticatory performance and determined the associations between masticatory performance and masticatory mandibular movements. Ten dentate adults and three complete denture‐wearing subjects participated in the study. The masticatory performance indices for these subjects were determined after a 10 s masticatory sequence and another sequence that ended at the swallowing threshold. Almond was used as the test food and almond fragments were sized using a standard 0·65 mm square size brass wire sieve. Masticatory mandibular movements were simultaneously recorded by an optoelectronic device. The reproducibility of the masticatory performance tests was good (

r

= 0·98 and 0·82 for the 10 s and swallowing threshold test indices, respectively). The masticatory performance indices were markedly different between dentate and denture‐wearing subjects. The 10 s masticatory performance index in the dentate subjects, showed moderate to rather strong correlation with all parameters of mandibular velocity (

r

= 0·6–0·7). The 10 s index also showed a strong negative correlation to the duration of the occlusal level phase and the total duration of the chewing cycle (

r

= –0·7 to –0·8) in the dentate subjects. This study confirms that masticatory performance levels are relatively stable and associated with the efficacy of specific masticatory mandibular movement parameters.
A 2‐year follow‐up of mandibular posture following an increase in occlusal vertical dimension beyond the clinical rest position with fixed restorations
Authors: Ormianer Z. , Gross M.
Published: March 2003

While resting mandibular posture is continuously changing, repeatable relations of ‘physiologic rest position’ (PRP) and ‘clinical rest position’ (CRP) are described in the literature. The PRP is defined as a position of minimal muscle activity and CRP as a more closed clinical reference relation. Relaxed resting posture (RRP) is a repeatable postural range obtained by operator‐induced relaxation techniques. This article reports on measurements of mandibular posture in a patient group following an increase in occlusal vertical dimension (OVD) with fixed restorations beyond CRP over 2 years. The relationship of CRP and RRP in the restored and a non‐restored control group is compared. The relationship of RRP and corresponding masseteric EMG values to baseline minimal EMG levels is reported for both groups. Resting face height adapted to the increased OVD and remained consistent over 1 and 2 years. The RRP was greater and significantly different from CRP in both groups (

P

= 0·0001). Results indicated that both CRP and RRP were postural ranges and not specific postural positions. The RRP occurred at minimum baseline EMG levels for both groups and appears to be consistent with physiologic rest position. The possibility of achieving minimal EMG levels at varying interocclusal rest space relations is discussed.
Dentine hypersensitivity: the effects of brushing desensitizing toothpastes, their solid and liquid phases, and detergents on dentine and acrylic: studiesin vitro
Authors: West N. , Addy M. , Hughes J.
Published: March 2003

Dentine exhibiting symptoms of dentine hypersensitivity has tubules open at the dentine surface and patent to the pulp. The mechanisms whereby dentinal tubules are exposed is ill understood but probably involves a variety of abrasive and/or erosive agents. This study

in vitro

examined the quantitative and qualitative effects of toothpastes, their solid and liquid phases and detergents on dentine and acrylic. Abrasion of dentine and acrylic were measured by surfometry. Morphological changes to dentine were assessed by scanning electron microscopy. Abrasion of dentine and acrylic by toothpastes increased with increasing brushstrokes with marked differences in the extent of abrasion between different pastes. Brushing dentine with water or detergents produced progressive abrasion but which appeared to plateau around 2 μm loss. Water and detergents produced minimal effects on acrylic. At 5000 strokes dentine abrasion by solid phases was less than the parent toothpastes but the ranking order of abrasivity was the same as the parent toothpastes. Loss of dentine produced by liquid phases was minimal and in the order of 1–2 μm. Observationally, all toothpastes removed at least the dentine smear layer to expose many tubules; with one desensitizing product leaving a particulate deposit occluding most tubules. The solid phases of the toothpaste produced identical morphological changes to the parent paste. The liquid phases and detergents all exposed dentinal tubules by 5000 strokes. Water had little or no effect on the dentine smear layer. It is concluded that toothpastes, solid phase, liquid phase and detergents have the potential to abrade or erode dentine to a variable degree and result in tubule exposure. The effects of the liquid phases and detergents appear limited to the removal of the smear layer. Such detrimental effects seen

in vitro

could have relevance to the aetiology and management of dentine hypersensitivity. Toothpaste formulations which despite exposing tubules have ingredients capable of occluding tubules may be an area of development for such products.
Stress distribution and abutment tooth mobility of distal‐extension removable partial dentures with different retainers: an in vivo study
Authors: Igarashi Y. , Ogata A. , Kuroiwa A. , Wang C. H.
Published: March 2003

Three types of retainers (wrought wire clasp, Aker's cast clasp, and conical crown telescopic retainer) designed for distal‐extension removable partial dentures (RPDs) were assessed in two Kennedy class I patients’ mouths. The assessment, included the ratio of denture base shearing load and mobility of the terminal abutments when loaded on a free‐end RPD occlusal surface. The mean values of denture base shearing ratios of wrought wire clasp, Aker's clasp and conical crown telescope were 60, 42 and 20%, respectively. The abutment mobility of the three types of retainers were all within the ‘mobile ability area’ except the wrought wire clasp for patient A's right side. The greatest tooth mobility was observed with the wrought wire clasps, followed by Aker's clasp and the conical crown telescopic retainer. From the analysis the following was concluded: (i) different retainers do influence the occlusal load distribution; (ii) the occlusal load distributed to the free‐end saddle is closely related to the connecting rigidity of the retainer; (iii) mucosal support has an indispensable role in sharing the occlusal load with various retainers, even the rigid telescopic retainer.
Bite force, endurance and masseter muscle fatigue in healthy edentulous subjects and those with TMD 1
Authors: Tortopidis D. , Lyons M. F. , Baxendale R. H.
Published: March 2003

It is well known that bite force and EMG activity are considerably reduced in edentulous patients, but the susceptibility of their jaw‐closing muscles to localized fatigue is less certain. This information is even less clear for edentulous subjects who have TMD. Eleven healthy edentulous subjects and 10 edentulous subjects with TMD participated in this study. Maximum bite force was measured first, with the transducer placed on the canine‐first premolar region bilaterally, and then two rapid relaxations were made from a brief voluntary clench to 50% of maximum. A sustained voluntary clench of 50% of maximum was then maintained and endurance time was noted. EMG was recorded from both masseter muscles and the median frequency of the power spectrum of the EMG from 2 s at the beginning of the sustained clench and 2 s at the end was subsequently calculated. Two more rapid relaxations from brief clenches were performed immediately after the sustained clench. The mean maximum bite force in the healthy group was 115 N (SD±41) and in the TMD group was 75 N (SD±22), this difference being significant (P=0·0013). The mean endurance time in the healthy group was 86 s (SD±51) and in the TMD group was 63 s (SD±20). The percentage change in the median frequency in the healthy group as a result of the sustained contraction was 6% (left) and 8·6% (right) and in the TMD group was 13·9% (left) and 12·8% (right). The percentage change in the mean relaxation half time for the healthy group was 28·5% and for the TMD group was 72%, a significant difference (P=0·0046). It was apparent that the maximum bite force was low in edentulous subjects and was further reduced in edentulous TMD subjects; endurance time was reduced in TMD subjects; fatigue resistance of the masseter muscles was reduced in TMD subjects.
The stress reducing capacity of unfilled resin in a Class V cavity
Authors: Rees J. S. , O'dougherty D. , Pullin R.
Published: March 2003

This study examined the stress reducing capacity of varying thicknesses of unfilled resin in a Class V cavity. A two dimensional plane strain mesh of a Class V cavity, 3 mm in diameter and 2 mm deep, was produced and the thickness of the unfilled resin layer was varied from 0 to 80 μm. A polymerization shrinkage of 1·5% was applied to the composite resin and the interfacial forces examined. The maximum shear stresses were found to occur along the pulpal floor of the restoration at the unfilled resin–dentine interface. The maximum shear stress values varied from 11·1 to 22·4 MPa and the shear stresses decreased by up to 38% as the thickness of the unfilled resin increased to 80 μm.
In vitro cytotoxicity of dental casting alloys over 8 months
Authors: Wataha J. C. , Lockwood P. E. , Nelson S. K. , Rakich D.
Published: March 2003

Although in vitro cytotoxicity tests have been a valuable part of the biological testing of dental casting alloys, these tests are generally limited by their short‐term nature (≪168 h). The objective of the current study was to measure the in vitro cytotoxicity of representative types of dental casting alloys over a relatively long‐term interval (months) and compare longer‐term cytotoxicity with that seen initially. Polished casting alloy samples were exposed to cell‐culture medium for 30‐day intervals. During the last 3 days of each interval, the medium was changed to provide a 3‐day extract which was then placed on fibroblast or macrophage cultures for 48 h. The mitochondrial activity of the cells was measured and compared to control cultures to assess the cytotoxic effect of the alloys. The cytotoxic effect was plotted versus time of medium exposure. The total time of exposure was 8 months. For most alloys, the mitochondrial response was constant over the 8 months, indicating that the cytotoxic effect of the alloys did not change significantly after extended exposure to the medium. A trend of improving biological response was suspect for a reduced‐gold alloy, but this trend was not statistically significant. The mitochondrial activity of the macrophages was less sensitive to the alloy extracts than the activity of the fibroblasts, which was significantly suppressed for several alloy types. However, mitochondrial activity of the macrophages was significantly increased for several alloys in the early time intervals. The total noble metal content of the alloys was not necessarily predictive of the biological response. Thus, it appears that in this indirect test of in vitro cytotoxicity, the short‐term cytotoxicity is predictive of the longer‐term for many types of dental casting alloys.