bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Suckling on NADPH‐Diaphorase (Nitric Oxide Synthase, NOS) Reactivity and NOS Gene Expression in the Paraventricular and Supraoptic Nuclei of Lactating Rats
Authors: Otukonyong E. E. , Okere C. O. , Johnstone L. E. , Murata T. , Kaba H. , Higuchi T.
Published: March 2003

This study examined the effect of suckling on nicotinamide adenine dinucleotide phosphate diaphorase (NADPH‐d, a histochemical marker for nitric oxide synthase, NOS) reactivity and neuronal NOS mRNA expression in the paraventricular (PVN) and supraoptic (SON) nuclei of lactating rats. Freely nursing (non‐separated) dams and those separated from pups for 12 h and then reunited for 0, 15, 30, 60, 90, 120 and 180 min were used for the study. Dams separated from pups and sacrificed at time zero (without reunion) showed a significant decrease in NADPH‐d staining and NADPH‐d positive cells as well as in the NOS mRNA expression in the PVN and SON compared to that observed in non‐separated dams. Reunion with pups and restoration of suckling significantly increased NADPH‐d reactivity after 15, 30, 60 min, but not after 90, 120 and 180 min compared to non‐reunited pups‐deprived dams. A pattern of NADPH‐d reactivity and neuronal NOS mRNA expression indistinguishable from that observed during free lactation was reinstated shortly (15 min) after the restoration of suckling stimulus, suggesting that the NADPH‐d reactivity in lactation depends on the presence of the suckling stimulus. These results show that suckling stimulus may play a modulatory role in the regulation of NOS reactivity in the magnocellular neurones of the hypothalamic PVN and SON during lactation.
Effects of Female Pheromones on Gonadotropin‐Releasing Hormone Gene Expression and Luteinizing Hormone Release in Male Wild‐Type and Oestrogen Receptor‐α Knockout Mice
Authors: Gore A. C. , Wersinger S. R. , Rissman E. F.
Published: March 2003

Pheromones are an important class of environmental cues that affect the hypothalamic‐pituitary‐gonadal axis in a variety of vertebrate species, including humans. When male mice contact female‐soiled bedding, or urine, they display a reflexive luteinizing hormone (LH) surge within 30 min. Aside from the requirement that males have gonads to show this response, the physiological mechanisms that underlie this pituitary response are unknown. In this experiment, we asked if female pheromones acted at the level of gonadotropin‐releasing hormone (GnRH) gene expression to affect this hormone response. In addition, we also examined the contribution of one of the oestrogen receptors (ERα) by studying this neuroendocrine reflex in wild‐type and oestrogen receptor‐α knockout (ERαKO) males. Both ERαKO and wild‐type males showed the expected LH surge, 45 and 90 min after contact with female pheromones. Males housed in clean bedding or bedding soiled by another adult male did not display the LH elevation. Interestingly, this dramatic change in LH concentrations was not accompanied by any alterations in GnRH mRNA expression or levels of primary transcript in the preoptic area‐anterior hypothalamus. The one exception to this was a significant increase in GnRH mRNA expression in tissue collected from wild‐type males exposed to bedding from another male. This is particularly intriguing since LH was not elevated in these males. These data replicate and extend our previous finding that ERαKO males do exhibit an LH surge in response to female pheromones. Thus, this neuroendocrine response is regulated by a steroid receptor other than ERα and does not require alterations in GnRH mRNA expression.
Seasonal Regulation of Membrane and Intracellular Corticosteroid Receptors in the House Sparrow Brain
Authors: Breuner C. W. , Orchinik M.
Published: March 2003

A number of studies have demonstrated seasonal regulation of the adrenocortical response to stress, or of corticosteroid binding globulins, but very few studies have examined seasonal regulation of corticosteroid receptor levels. As a result, there have been few attempts to produce an integrated picture of seasonal plasticity of the stress response. We measured baseline and stress‐induced corticosterone (CORT), corticosteroid binding globulin and neuronal cytosolic and membrane corticosteroid receptor levels in male and female, wild‐caught house sparrows (Passer domesticus) during three different seasons over the annual cycle (nesting, molting and winter). We identified three neuronal corticosteroid receptors in the house sparrow brain: two intracellular receptors and one membrane‐associated receptor. Little is known about corticosteroid receptors in neuronal membranes of avian and mammalian species, but we found that the levels of membrane corticosteroid receptors varied seasonally, being lowest during the nesting season. Cytosolic corticosteroid receptor numbers (both low and high affinity receptors) also varied seasonally. In contrast to the membrane bound receptors, however, the numbers of low and high affinity cytosolic receptors were lowest during winter. In addition, mean levels of total basal and stress‐induced CORT in the plasma varied seasonally. Both basal and stress‐induced levels of total CORT were significantly higher during nesting than during winter or molt. Finally, corticosteroid binding globulin levels in plasma were also seasonally regulated, in a pattern similar to total CORT, so that estimated free CORT levels did not vary between seasons. These data indicate that multiple components of the stress response are seasonally regulated in birds obtained from wild populations. Interactions between these regulated components provide a basis for seasonal differences in behavioural and physiological responses to stress.
Cells of the Arcuate Nucleus and Ventromedial Nucleus of the Ovariectomized Ewe that Respond to Oestrogen: A Study Using Fos Immunohistochemistry
Authors: Clarke I. J. , Pompolo S. , Scott C. J. , Rawson J. A. , Caddy D. , Jakubowska A. E. , Pereira A. M.
Published: March 2003

Oestrogen produces a positive feedback effect on the secretion of gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) when implanted into the ventromedial/arcuate nucleus of the ovariectomized (OVX) ewe. This has led to the belief that it is in this area of the hypothalamus that oestrogen causes the preovulatory surge in GnRH/LH. To date, however, the cell types that are integral to this response have not been identified. The present study aimed to examine cellular responsiveness to oestrogen in this region of the brain using Fos immunohistochemistry and further aimed to determine the cell type that shows an acute response to oestrogen. OVX ewes (n = 4–6 per group) were given i.m. injections of oestradiol benzoate or oil (vehicle) and were killed 1–6 h later. Brains were perfused for immunohistochemistry. The number of cells in the arcuate nucleus which were immunopositive for Fos was greater (two‐ to fourfold) in the oestradiol benzoate‐treated OVX ewes (n = 5) 1 h after injection. The number of Fos‐positive cells in the ventromedial hypothalamic nucleus was 10‐fold greater in the oestradiol benzoate‐treated ewes 1 h after injection. Because there were high levels of Fos‐immunoreactive cells in oil‐treated ewes, we repeated the experiment with i.v. injection of 50 µg oestrogen or vehicle (n = 5). With this latter procedure, we found that oestrogen injection caused a significant increase in the number of Fos immunoreactive cells in the arcuate nucleus within 1 h, but there was no response in the ventromedial hypothalamus. To further characterize the types of cells that might respond to oestrogen, we double‐labelled cells for Fos and either adrenocorticotropin hormone, neuropeptide Y or tyrosine hydroxylase (a marker for dopaminergic cells). These cell types could account for less than 30% of the total number of cells that were Fos‐positive and oestrogen treatment did not cause an increase in the Fos labelling of any of these types of cell. These data show that oestrogen activates cells of the arcuate/ventromedial hypothalamus within 1 h of injection and that this response could relate to the feedback effects of this gonadal hormone. The majority of cells that produce Fos following oestrogen injection are of unknown phenotype. The data further suggest that induction of cells of the ventromedial hypothalamic nucleus require more prolonged oestrogen stimulus than cells of the arcuate nucelus.
Chronic Antidepressant Treatments Decrease Pro‐Opiomelanocortin mRNA Expression in the Pituitary Gland: Effects of Acute Stress and 5‐HT1A Receptor Activation
Authors: Jensen J. B. , Mørk A. , Mikkelsen J. D.
Published: March 2003

Consistent findings in depressed patients are hyperactivity in the hypothalamic‐pituitary‐adrenal (HPA) axis with high plasma concentrations of adrenocorticotropic hormone and cortisol. Long‐term antidepressant treatments seem to normalize this hyperactivity, suggesting a link between the HPA axis and the action of antidepressant treatments. The present study was carried out to study the effects of antidepressant treatments on pro‐opiomelanocortin (POMC) mRNA expression, with a focus on interaction with acute stress and 5‐HT1A receptor activation. Male rats were treated for 21 days with saline, citalopram, fluoxetine, moclobemide or desipramine, and the expression of POMC mRNA in the anterior pituitary was analysed by semi‐quantitative in situ hybridization. All antidepressants, but not saline, cocaine and haloperidol, reduced POMC mRNA expression. The decrease in POMC mRNA was not observed until 9 days of citalopram treatment. Decreased POMC mRNA levels were also observed after 14 days of repeated electroconvulsive stimulation. The decreased POMC mRNA levels did not affect the stress‐induced POMC mRNA increase, measured following swim stress and restraint stress. Finally, using Fos as a marker for neural activity, we showed attenuation of 8‐OH‐DPAT‐stimulated activity in the paraventricular nucleus following 21 days of citalopram treatment. In conclusion, antidepressant treatments decrease basal POMC mRNA expression without affecting the acute stress response, and the reduced POMC mRNA may be related to reduced 5‐HT1A‐stimulated hypothalamic output.
Paradoxical Effects of Chronic Morphine Treatment on the Temperature and Pituitary‐Adrenal Responses to Acute Restraint Stress: A Chronic Stress Paradigm
Authors: Houshyar H. , Cooper Z. D. , Woods J. H.
Published: March 2003

Body temperature and pituitary‐adrenal responses to restraint (15 min or 4 h) stress were evaluated in nondependent and morphine‐dependent rats. Male Sprague‐Dawley rats were treated twice daily with increasing doses of morphine (10–100 mg/kg, s.c.) for 16 days. Transmitters were implanted in the peritoneal cavity to monitor body temperature and blood was collected for hormone assays. Acute withdrawal from chronic morphine treatment was associated with reduced body weight, increased adrenal weight and decreased thymus weight. Sixteen days after termination of chronic morphine treatment, rats had recovered normal adrenal size, but still displayed marked thymus involution and reduced body weight. Restraint‐induced hyperthermia was attenuated in morphine‐dependent rats that had undergone 12‐h withdrawal. Sixteen days after withdrawal, rats still had not fully recovered the hyperthermic response to restraint. Chronic morphine treatment resulted in a marked elevation of basal corticosterone concentrations. Despite the negative‐feedback effects of elevated basal corticosterone concentrations, morphine‐dependent rats that had undergone 12‐h withdrawal displayed a potentiated and prolonged corticosterone response to restraint stress. In contrast, rats that had undergone 8‐day and 16‐day morphine withdrawal had recovered normal basal pituitary‐adrenal activity, but displayed significantly reduced and shorter adrenocorticotropic hormone and corticosterone responses to restraint. These results suggest that chronic morphine dependence is a chronic stressor, resulting in profound and long‐lasting changes in the temperature and pituitary‐adrenal responses to acute restraint stress in a time‐dependent manner. This morphine‐dependence model may be useful in understanding the role that hormonal stress responses play in the maintenance and relapse to opioid use in humans.
Differential Responsivity of the Hypothalamic‐Pituitary‐Adrenal Axis to Glucocorticoid Negative‐Feedback and Corticotropin Releasing Hormone in Rats Undergoing Morphine Withdrawal: Possible Mechanisms Involved in Facilitated and Attenuated Stress Responses
Authors: Houshyar H. , Galigniana M. D. , Pratt W. B. , Woods J. H.
Published: March 2003

Chronic morphine treatment produces profound and long‐lasting changes in the pituitary‐adrenal responses to stressful stimuli. The purpose of the present study was to explore the mechanisms involved in these altered stress responses. Chronic morphine administration increased basal plasma concentrations of corticosterone and adrenocorticotropic hormone (ACTH), which peaked at 36 h after the final morphine injection and returned to normal levels within 84‐h. Whole brain glucocorticoid receptor protein expression was reduced (approximately 70%) in morphine‐treated rats 4‐h after the final morphine injection and these levels recovered within 16‐h. Twelve hours following morphine withdrawal, rats displayed normal ACTH, but potentiated and prolonged corticosterone responses to restraint stress. Both the ACTH and corticosterone responses to restraint in acutely withdrawn rats were insensitive to dexamethasone. Furthermore, acutely withdrawn rats displayed reduced ACTH but prolonged corticosterone responses to peripheral corticotropin releasing hormone (CRH) administration. These findings suggest that the normal ACTH and enhanced corticosterone responses to stress in acutely withdrawn rats involved decreased sensitivity of negative‐feedback systems to glucocorticoids, reduced pituitary responsivity to CRH, and enhanced sensitivity of the adrenals to ACTH. Eight days following morphine withdrawal, rats displayed dramatically reduced ACTH, but normal corticosterone responses to restraint stress. These rats displayed enhanced sensitivity to dexamethasone and normal pituitary‐adrenal responses to CRH. These data suggest that the reduced ACTH responses to stress in 8‐day withdrawal rats involved increased sensitivity of negative‐feedback systems to glucocorticoids as well as reduced CRH and/or AVP function in response to stress. Taken together, the results of this study illustrate some of the mechanisms mediating altered stress responsivity in rats that have received chronic morphine treatment.
Sucrose Intake and Corticosterone Interact with Cold to Modulate Ingestive Behaviour, Energy Balance, Autonomic Outflow and Neuroendocrine Responses During Chronic Stress
Authors: Bell M. E. , Bhargava A. , Soriano L. , Laugero K. , Akana S. F. , Dallman M. F.
Published: March 2003

In adrenalectomized (ADX) rats, either corticosterone replacement or increased sucrose intake will restore body weight gain, uncoupling protein‐1, fat depot mass, food intake and corticotropin‐releasing factor mRNA expression to normal. Here, we tested the potential interactions between sucrose intake and circulating corticosterone on behavioural, metabolic, autonomic and neuroendocrine responses to the stress of cold. Rats were left intact, sham‐ADX, or ADX and replaced with pellets that provided normal, basal (30%B) or high stress (100%B) constant circulating concentrations of corticosterone ± sucrose. More calories were consumed in cold than at room temperature (RT), provided that corticosterone concentrations were elevated above mean daily basal values in cold. Neither increased sucrose nor increased chow ingestion occurred in cold if the rats were ADX and replaced with 30%B. However, sucrose drinking in this group markedly ameliorated other responses to cold. By contrast, ADX30%B rats not drinking sucrose fared poorly, and none of the metabolic or endocrine variables were similar to those in sham‐ADX controls. ADX100%B group in cold, resembled intact rats without sucrose; however, this group was metabolically abnormal at RT. We conclude that drinking sucrose lowers stress‐induced corticosterone secretion while reducing many responses to cold; elevated corticosterone concentrations in the stress‐response range are essential for the normal integrated cold‐induced responses to occur.
Hormonal and Behavioural Responses of Paradoxical Sleep‐Deprived Rats to the Elevated Plus Maze
Authors: Suchecki D. , Tiba P. A. , Tufik S.
Published: March 2003

Activation of the hypothalamic‐pituitary‐adrenal (HPA) axis is observed immediately after 96 h of paradoxical sleep (PS) deprivation. However, when individually or group PS‐deprived rats are challenged with a mild stressor, they exhibit a facilitation of the corticosterone response, and a faster return to basal levels than control rats. Because the housing condition influences coping behaviour, we tested whether the type of PS deprivation (individually or in group) influenced anxiety‐like behaviour in the elevated plus‐maze and the accompanying adrenocorticotropin (ACTH) and corticosterone responses. Individually (I‐DEP) or group deprived (G‐DEP) rats and their appropriate control groups were either killed immediately after 96 h of sleep deprivation (time‐point 0 or ‘basal’) or exposed to a 5‐min test on the elevated plus maze and sampled 5, 20 or 60 min after test onset. Control of I‐DEP rats showed reduced locomotor activity and augmented anxiety‐like behaviour, replicating the effects of social isolation. Although I‐DEP rats exhibited higher motor activity than cage control rats, these groups did not differ in regard to the percentage of entry and time spent in the open arms. G‐DEP rats, in turn, ambulated more, entered and remained longer in the open arms, exhibiting less anxiety‐like behaviour. PS‐deprived rats exhibited higher ACTH and corticosterone ‘basal’ secretion than control rats. For all groups, peak ACTH secretion was reached at the 5‐min time‐point, returning to unstressed basal levels 60 min after the test, except for G‐DEP rats, which showed a return at 20 min. Peak levels of corticosterone occurred at 5 min for PS‐deprived groups and at 20 min for control groups. G‐DEP rats showed a return to ‘basal’ unstressed levels at 20 min, whereas the I‐DEP and control groups did so at 60 min. A negative correlation between exploration in the open arms and hormone concentrations was observed. These data indicate that housing condition influences the subsequent behaviour of PS‐deprived rats in the EPM which, in turn, seems to determine the secretion profile of ACTH and corticosterone in response to the test.
Corticotropin‐Releasing Factor Neurones of the Central Nucleus of the Amygdala Mediate Locus Coeruleus Activation by Cardiovascular Stress
Authors: Curtis A. L. , Bello N. T. , Connolly K. R. , Valentino R. J.
Published: March 2003

Hypotensive stress engages corticotropin‐releasing factor (CRF) release within the rat locus coeruleus (LC), which activates LC neurones, initiating norepinephrine release in forebrain and activation of forebrain electroencephalographic activity. This study identified CRF afferents to the LC that are engaged during hypotensive stress. One of two potential CRF afferents, the central nucleus of the amygdala (CNA) or bed nucleus of the stria terminalis (BNST), was electrolytically lesioned and LC activation during hypotensive stress was quantified. Neither lesion altered LC spontaneous discharge rate or activation by intra‐LC administered CRF. By contrast, LC activation by hypotensive stress was greatly attenuated in CNA‐lesioned, but not BNST‐lesioned, rats. Hypotensive stress‐induced changes in transcriptional activation were immunohistochemically identified in CRF neurones that were retrogradely labelled from the LC region. c‐fos immunoreactivity was prevalent in the paraventricular nucleus of the hypothalamus (PVN), CNA and BNST. However, only the PVN contained a substantial number of neurones that were doubly immunolabelled for CRF and c‐fos, and few of these were retrogradely labelled from the LC. By contrast, immunoreactivity for the phosporylated form of cyclic AMP response‐element binding protein (PCREB) was prevalent in CRF neurones in the CNA and BNST. Moreover, approximately one‐third of the PCREB‐expressing CRF neurones in the CNA were retrogradely labelled from the LC. These electrophysiological and anatomical findings implicate the CNA as a primary source of CRF that activates the LC during hypotensive stress. Additionally, CREB phosphorylation, rather than c‐fos induction, is associated with hypotensive activation of CRF‐CNA neurones that project to the LC.
Effects of Leptin on Arcuate Pro‐Opiomelanocortin and Cocaine‐Amphetamine‐Regulated Transcript Expression Are Independent of Circulating Levels of Corticosterone
Authors: Vrang N. , Kristensen P. , Tang‐Christensen M. , Larsen P. J.
Published: March 2003

In the hypothalamic arcuate nucleus, neurones that coexpress cocaine‐amphetamine‐regulated transcript (CART) and α‐melanocyte‐stimulating hormone [α‐MSH; pro‐opiomelanocortin (POMC) derived] peptides exert catabolic actions and are stimulated by leptin. However, leptin treatment also affects other circulating factors that influence hypothalamic gene expression. Notably, the hypercorticosteronaemia of ob/ob mice is lowered by leptin treatment. To examine the interaction between glucocorticoids and leptin on POMC/CART mRNA expression, an experiment combining leptin and adrenalectomy (ADX) in leptin deficient ob/ob mice was carried out. Obese ob/ob and lean littermate Ob/? mice were ADX or sham‐operated. ADX mice received a pellet containing 25% corticosterone subcutaneously. Seven days postoperatively, mice were injected intraperitoneally for 5 days with either recombinant human leptin or vehicle. On the sixth day, the mice were decapitated and the brains removed and trunk blood was collected for corticosterone analysis. Plasma concentrations of corticosterone were elevated in all ob/ob groups compared to Ob/?. For both ob/ob and Ob/? groups, corticosterone concentrations exhibited a decline across groups: vehicle‐sham>leptin‐sham>ADX‐vehicle>ADX‐leptin. Leptin inhibited food intake and bodyweight in ob/ob‐sham and ob/ob‐ADX to a similar extent, whereas no effect of leptin was observed in Ob/? mice. Similarly, leptin caused an identical increase in arcuate POMC and CART mRNA expression in ob/ob‐sham and ob/ob‐ADX compared to vehicle. The present data support the view that leptin influences arcuate POMC and CART mRNA expression directly, and that the effect is not modulated by corticosterone across a wide range of circulating corticosterone concentrations.
Thyroid Hormone Regulation of N‐Methyl‐d‐Aspartic Acid Receptor Subunit mRNA Expression in Adult Brain
Authors: Lee P. R. , Brady D. , Koenig J. I.
Published: March 2003

Thyroid hormone is an essential modulator of brain development, but little is known about its actions in the adult brain. Hypothyroidism is associated with gene expression changes in both central and peripheral nervous tissue. Functional consequences of adult‐onset hypothyroidism include an inability to produce long‐term potentiation in rat hippocampus and impaired learning and memory in both rats and man. Long‐term potentiation is a form of learning that is dependent on functional N‐methyl‐d‐aspartic acid (NMDA)‐preferring ionotropic glutamate receptors. This work examines the expression of ionotropic glutamate receptor subunit mRNA following surgical thyroidectomy with or without thyroid hormone replacement. In situ hybridization histochemistry was used to determine the mRNA levels of the NMDA receptor subunits NR1, NR2A, NR2B, the AMPA receptor subunit GluR1, and the kainate receptor subunit KA2. Reducing circulating concentrations of thyroid hormone by surgical removal of the thyroid gland 2 weeks before sacrifice decreased the expression of NR1 mRNA exclusively in the hippocampus. Conversely, hyperthyroidism selectively reduced NR2B mRNA expression in the dorsal hippocampus. Altering thyroid hormone status had no effect on the expression of KA2 or GluR1 subunit mRNA. The regulation of expression of NR1 and NR2B mRNA by thyroid hormone is a novel mechanism for explaining the relationship between thyroid hormone and cognitive function.
Photoperiodic and Temporal Influences on Chemosensory Induction of Brain Fos Expression in Female Prairie Voles
Authors: Hairston J. E. , Ball G. F. , Nelson R. J.
Published: March 2003

Prairie voles (Microtus ochrogaster) typically stop breeding during winter. Male prairie voles respond to winter day lengths with gonadal regression, whereas female voles are relatively unresponsive to photoperiod. Unlike commonly studied laboratory rodents, female prairie voles do not exhibit spontaneous oestrous cycles. Instead, females are induced into oestrus by chemosensory cues from conspecific male urine. The present study investigated the interaction among day length, chemosensory cues and the initial brain responses during oestrus induction in female voles. A single drop of male conspecific urine, saline or skimmed milk was applied to the nares of female prairie voles housed for 9 weeks in either long (LD 16 : 8 h) or short (LD 8 : 16 h) days. Animals were killed 0.5, 1, 2 or 24 h after chemosensory treatment and their brains were processed for Fos immunocytochemistry. Body mass and ovarian fat pad mass were higher, but uterine and ovarian mass were lower, in short‐day compared to long‐day females. Regardless of photoperiod, Fos‐ immunoreactivity increased in the granule layer of the accessory olfactory bulb (AOB), the supraoptic nucleus and bed nucleus of the stria terminalis (BNST) (anterior medial) in females treated with male urine compared to the two control groups. Fos staining intensified in the AOB, medial and posterocortical medial amygdala and BNST (posterior ventral), 1 h and 2 h after urine treatment. In the medial preoptic area, anterior and lateral hypothalamus, and ventromedial nucleus of the hypothalamus, Fos‐immunoreactivity was elevated in females 2 h after receiving urine. Overall, long‐day females displayed higher Fos expression in response to urine than females maintained in short days. These results identify a putative neural circuitry of oestrus induction in this species, and provide an approximate time line of activation in the brain circuit responsible for oestrus induction in prairie voles.
Two‐dimensional configuration of the myoneural junctions of human masticatory muscle detected with matrix electrode
Authors: Tokunaga  , Baba  , Tanaka  , Kashiwagi  , Kimura  , Kawazoe
Published: March 2003

Motor unit action potentials (MUAPs) propagate bidirectionally from the myoneural junction along the muscle fibre. The propagation of excitation within single motor units can be detected during sustained isometric contraction using a surface electrode array. Electromyographic (EMG) signals from an adjacent pair of contacts along the muscle fibres show a very similar wave form with a time shift. In the present study, EMG signals of the masseter and the temporal muscles were obtained from two male adults during clenching in the intercuspal position using the multichannel surface electrode with 17 × 11 contacts. The two‐dimensional location of the myoneural junction for each column from the source of the propagation was estimated. Each of the myoneural junctions was located in the lower portion of the masseter muscle and in the upper portion of the temporal muscle. However, the junction was distributed within 10 mm along the muscle fibres at different contraction levels in each muscle. This noninvasive technique of multiple surface electrodes enabled us to add to knowledge of the anatomical structure of the masticatory muscles examined.
Densities and sizes of main masticatory muscles in patients with internal derangements of temporomandibular joint obtained by computed tomography
Authors: RauStia  , Oikarinen  , Pyhtinen
Published: March 2003

Computed tomography (CT), due to its excellent resolution capacity, is a suitable method to examine the soft and bony structures of the masticatory system. The aim of this study was to compare densities and sizes of the masseter and medial and lateral pterygoid muscles obtained by CT between the symptomatic and asymptomatic side in patients with internal derangement of the temporomandibular joint (TMJ). The aim was also to correlate these variables to sex and age, duration of the symptoms, diagnosis and dentition. The material consisted of 33 patients (26 women, 7 men, mean age 37 years, range 14–74 years) whose TMJs were examined by CT and whose coronal CT scans were available. Diagnosis in the symptomatic TMJ was confirmed in operation. No statistically significant difference was seen in mean densities and sizes of the masticatory muscles between the symptomatic and asymptomatic side. The duration of the symptoms, however, correlated positively to the density of the lateral pterygoid muscles in patients with complete dentition. The age of the patients in this group correlated negatively to the size of the masseter muscles. It can be concluded that patients with internal derangements of TMJ with a long duration of symptoms have structural changes in their masticatory muscles which are detectable by CT.
A comparison between horizontal splint and repositioning splint in the treatment of ‘disc dislocation with reduction’. Literature meta‐analysis
Authors: Santacatterina  , Paoli  , Peretta  , Bambace  , Beltrame
Published: March 2003

We reviewed the literature from 1985 to 1996 concerning the preliminary treatment of disc dislocation with reduction (DDWR) by means of occlusal splints, pinpointing two main methods. The conflicting results of many papers induced us to make a literature meta‐analysis of those articles with the necessary requirements in order to verify the effectiveness of the two therapeutic means more frequently used in DDWR; the repositioning splint and the bite plane. A statistical comparison between the two kinds of treatment has demonstrated that the repositioning splint is more effective both in the resolution of the articular click and of the pain at a level of

P≤ 0·00001, which is noteworthy and highly significant.
Antibacterial temporary filling materials: the effect of adding various ratios of Ag‐Zn‐Zeolite
Authors: Hotta M. , Nakajima H. , Yamamoto K. , Aono M.
Published: March 2003

SUMMARY The effect of a new type of antibacterial temporary filling material was evaluated. Ag‐Zn‐Zeolite (Bactekiller®, Kanebo, Japan) and SiO2 filler were incorporated into urethane acrylate monomer paste in amounts of 5/55, 10/50, 20/40 and 30/30 wt%, respectively. The present study was designed to use a dye penetration test to measure direct inhibition of bacterial growth of four oral bacteria (Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Streptococcus sanguis). The amounts of silver and zinc ions released from these materials were measured by atomic absorption spectrophotometry. The results indicated that the occurrence of marginal leakage was low in all of these materials. These materials exhibited prominent in‐vitro antibacterial activity against S. mutans and S. mitis. The Ag‐Zn‐Zeolite in these materials was able to release very small but detectable amounts of Ag and Zn even 4 weeks after the immersion started. The larger the amounts of Ag‐Zn‐Zeolite that were incorporated, the greater the release of silver and zinc. However, it appears that increasing antibacterial activity is not promoted by the higher ratio of Ag‐Zn‐Zeolite.
Masticatory performance and chewing experience with implant‐retained mandibular overdentures
Authors: Geertman M. E. , Slagter A. P. , Van M. A. , Hof ‘t , Van Waas M. A. J. , Kalk W.
Published: March 2003

The relationship between masticatory performance and chewing experience has not yet been explored for patients with implant‐retained overdentures. Although many relationships have been found between parameters of objective and subjective oral function, the structure of these relationships remain unclear. Therefore, we studied in a randomized clinical trial the relationship between the comminution of an artificial test food, i.e. masticatory performance, and the subjective chewing experience. The trial involved a comparison between two groups receiving implant treatment and one group receiving conventional complete dentures (CD). The implant treatment involved either a mainly implant‐supported mandibular overdenture on a transmandibular implant (TMI) or an implant‐tissue‐supported mandibular overdenture on two IMZ implants (IMZ). Masticatory performance as well as chewing experience were substantially better for the implant‐retained overdentures compared with the complete denture group. No significant differences emerged between the TMI and the IMZ group. A multiple regression analysis did not provide any comprehensibility in the relationship between masticatory performance and the variables of chewing experience. In the linear structural relation analysis (LISREL) no direct relationship was found between masticatory performance and functional complaints mandibular denture. The results show that an improvement in masticatory performance does not imply the same improvement in chewing experience and vice versa.
Awareness/relaxation training and transcutaneous electrical neural stimulation in the treatment of bruxism
Authors: Treacy K.
Published: March 2003

Twenty‐three bruxists with a short history of dysfunction were randomly assigned to three treatment groups, MART (Muscular Awareness Relaxation Training), TENS (Transcutaneous Electrical Neural Stimulation), and a control group. The experimental time was 4 months, with a total of 20 treatment sessions for each experimental group. The MART group, decreased their left and right pterygoid‐masseter and left and right frontalis electromyographic (EMG) activity significantly after treatment as compared with the TENS and the control group. Further, the MART group decreased their number of breaths per minute, increased their maximum opening of the mouth after treatment to a significantly higher degree as compared with the TENS and control groups.
Five year evaluation of class III composite resin restorations in cavities pre‐treated with an oxalic‐ or a phosphoric acid conditioner
Authors: Van Dijken J. W. V. , Olofsson A. L. , Holm C.
Published: March 2003

An oxalic acid solution has been proposed as a conditioning agent for resin composite restorations in two commercial adhesive systems. The durability of 163 class III restorations, including 12 class IV restorations, in cavities pre‐treated with an oxalic acid total etch technique or an enamel etch with phosphoric acid was studied. Each of 52 patients received at least one of each of three experimental restorations. The restorations were evaluated yearly with slightly modified United States Public Health Service (USPHS) criteria. After 5 years 95% of the restorations were evaluated as acceptable. Reasons for failure were the fracture of four fillings, including three class IV, secondary caries contiguous to two fillings and a non‐acceptable colour match for one restoration. For eight class III restorations a fracture of the incisal tooth structure was registered. No differences were seen between the three experimental restorations.
Incline and length of guiding elements in untreated naturally grown dentition
Authors: Kulmer S. , Ruzicka B. , Niederwanger A. , Moschen I.
Published: March 2003

The incline and length of guiding elements, i.e. marginal ridges and lingual surfaces of front teeth, marginal ridges and internal cusp slopes of premolars and molars, play an important role in dentistry. Since the so far reported values differ considerably, it was the purpose of the present investigation to replicate the measurements, including all the occlusal landmarks proposed and defined by previous investigators. The measurements were performed on 34 pairs of mounted casts from a selected group of untreated, naturally grown dentitions from adolescents of mean age 14 years. The upper casts were mounted with a face bow, the kinematic hinge axis and the left incisura infraorbitalis representing the posterior and anterior reference points. The lower pinned casts were mounted joint related. All measurements were carried out with a computer‐aided, three‐dimensional digitizer. The inclines were expressed as angles related to the axis‐orbital‐plane. Taking the proposed occlusal landmarks as a basis, the inclines of guiding elements were found to be in agreement with previously reported values, despite ethnic and racial differences of the various study‐populations. The values, however, differed markedly when measurements based on individual, functional relevant landmarks were compared to measurements based on anatomical, easy identifiable or mathematically constructed landmarks. The successive decrease of the inclines of the guiding elements from the central incisors to the second molars could be confirmed, the molars displaying very flat inclines. Interestingly, 9% of the first molars and 21% of the second molars showed negative values, pointing to a functional arrangement characterized by a buccally oriented occlusal surface of those teeth. Combined with the finding that the length of the guiding elements of the anterior teeth was almost twice as long as that of the posterior teeth, the results corroborate the occlusal concept of an anterior–posterior sequence of the guiding elements, or a so‐called sequential guidance with front‐canine‐dominance.
Comparative evaluation of secondary heat treatment and a high intensity light source for the improvement of properties of prosthetic composites
Authors: Tanoue N. , Matsumura H. , Atsuta M.
Published: March 2003

This study determined the hardness and water solubility of two prosthetic composites polymerized with three curing modes for the purpose of evaluating the influence of secondary heating and a high intensity light source on resulting material properties. Two prosthetic composite materials (Artglass and Dentacolor) were cured with the following methods: (1) exposure by means of a photo‐curing unit with a xenon stroboscopic light source (Dentacolor XS) for 120 s; (2) exposure with the xenon unit for 120 s, followed by heating in an oven (KL 100) at 100 °C for 15 min; and (3) exposure by means of a photo‐curing unit with two metal halide lamps (Hyper LII) for 120 s. Knoop hardness and water solubility were determined according to standardized testing methods. Although post‐cure heat treatment considerably elevated the Knoop hardness number for both materials, the greatest hardness number was generated with the use of the metal halide unit. Water solubility of the Dentacolor material was lowest when the material was cured with the metal halide unit, followed by the secondary heated group, whereas, solubility of the Artglass material was unaffected by the curing modes. This suggests that the use of a high intensity light source is more effective than the application of secondary heating for improving the post‐curing properties of composites.
Viscoelastic properties of denture base resins obtained by underwater test
Authors: Hiromori K. , Fujii K. , Inoue K.
Published: March 2003

The viscoelastic properties of denture base polymers, such as poly(methylmethacrylate) (PMMA), polycarbonate (PC), polysulfone (PSF) and polyethersulfone (PES) which have been used in current clinical dentistry were investigated. In addition, water absorption, diffusion coefficient of water into material, cubical expansion, specific volume and residual monomer were also determined. From the results of this study, the viscoelastic behaviours of the denture base polymers in water have been discussed. The relaxation modulus (Er(5)) which was calculated using a stress at 5 s from the start of measurement for the specimen which reached an equilibrium moisture content (wet specimen), decreased from 23·1 to 25·5% compared with that of PMMA stored in a desiccator (37 °C) for 1 week (dry specimen). In contrast, this decreasing ratio was 7·0 to 10·0% for PC, PSF and PES. It is suggested that this phenomenon is caused by the increase of specific volume (cm3/g) with water absorption in each material. The water absorption of the PMMA group was relatively large in comparison with other material and was 1·81–1·85%. This value was within the range from 0·38 to 1·74% for PC, PSF and PES. The diffusion coefficients of water for PC, PSF and PES increased by approximately 1·5–2·7 times that of PMMA. Furthermore, the coefficient of cubical expansion of the wet specimen was larger than that of the dry specimen. The increasing ratio was 1·03–1·10 times for the PMMA group and 1·18–2·38 times for PC, PSF and PES. The variation of Er(5) of the PMMA group with temperature in water was larger than those of PC, PSF and PES.
Mandibular positions and jaw‐closing muscle activity during sleep
Authors: Yugami K. , Yamashita S. , Ai M. , Takahashi J.
Published: March 2003

The aim of this study was to clarify the relationship between the mandibular position with tooth contacts and jaw‐closing muscle activity during sleep using electromyography and newly devised equipment for detecting tooth contacts and also to confirm the validity of this system. Five males volunteered for this study and three of them reported their bruxing during sleep. Occurrences of tooth contacts at eccentric mandibular positions in addition to the intercuspal position during sleep were detected using micro photo sensors and sensor targets prepared for the individuals. Electromyographic activities (EMG) from right and left masseter and anterior tempolar muscles were also recorded. Results of the polygraphic recordings demonstrated that the mandibular positions during bruxism could be distinguished clearly whether it's in the right or left position, or has no lateral deviation, and further, that bruxing events could be categorized based on mandibular position pattern. The relationship between the mandibular position and muscle activity could be evaluated using this system. The study suggested the validity of the system for measuring nocturnal bruxing events.
Improved bonding of adhesive resin to sintered porcelain with the combination of acid etching and a two‐liquid silane conditioner
Authors: Kato H. , Matsumura H. , Ide T. , Atsuta M.
Published: March 2003

This study determined the bond strengths of adhesive resins joined to a feldspathic porcelain (VMK 68) for the purpose of developing the most durable surface preparation for the porcelain. Three porcelain surfaces—ground, air‐abraded with alumina, and etched with hydrofluoric acid—were prepared. A two‐liquid porcelain conditioner that contained both 4‐methacryloyloxyethyl trimellitate anhydride (4‐META) and a silane coupler (Porcelain Liner M) was used as the priming agent. Each of the two liquid components of the conditioner was also used individually in order to examine the effects of the respective chemical ingredients on adhesive bonding. Two methyl methacrylate (MMA)‐based resins initiated with tri‐n‐butylborane (TBB) either with or without 4‐META (MMA‐TBB and 4‐META/MMA‐TBB resins) were used as the luting agents. Shear bond strengths were determined both before and after thermocycling. Shear testing results indicated that thermocycling was effective for disclosing poor bonding systems, and that both mechanical and chemical retention were indispensable for bonding the porcelain. Of the combinations assessed, etching with hydrofluoric acid followed by two‐liquid priming with the Porcelain Liner M material generated the most durable bond strength (33·3 MPa) for the porcelain bonded with the 4‐META/MMA‐TBB resin (Super‐Bond C&B).
Conduct of an algorithm in quantifying simulated palatal surface tooth erosion
Authors: Chadwick R. G. , Mitchell H. L.
Published: March 2003

In order to test the ability of an algorithm to quantify simulated palatal erosion, a total of 10 extracted permanent upper central incisors were mounted in brass blocks. Baseline impressions were recorded using an addition cured silicone impression material in a metal impression tray. Once set and removed from the teeth, the impressions were coated twice with a high silver content electroconductive paint, applied using a brush, before being backed up with die stone to form an electroconductive replica. Each tooth was then subject to three treatments: application of phosphoric acid etchant gel for 60 s, application of etchant gel for 120 s and immersion for 3 h in Diet Coca‐Cola*. After each one the replication process was repeated. Thereafter all replicas were mapped using a computer controlled electrical probe and the resultant digital terrain models (DTMS) compared using a surface matching and difference detection algorithm (SMADDA). Surface matching was unsuccessful only in one instance. As the duration of the insult increased, so did the proportion of the surface that underwent change to a maximum of 33·3%. Anatomical site was significantly (P < 0·05) associated with the susceptibility to erosion. The cingulum periphery appeared most resistant to this. The algorithmic approach offers much scope for monitoring dental erosion as acid dissolution of the tooth’s surface appears to occur gradually. The cingulum region appears relatively more resistant to this process than other tooth sites and thus facilitates the process of surface matching. Further testing is however, required to determine precisely the algorithm’s upper tolerance level.
Oral habits among adolescent girls and their association with symptoms of temporomandibular disorders
Authors: Winocur E. , Gavish A. , Finkelshtein T. , Halachmi M. , Gazit E.
Published: March 2003

Aim: To evaluate the contribution of certain parafunctional activities to the presence of temporomandibular disorder (TMD) symptoms among teenage girls, with special emphasis to gum chewing and jaw play. Methods: A total of 323 girls, aged 15–16 years, were randomly selected from a religious junior high school. The girls responded to a questionnaire on oral habits and TMD symptoms.Results: Gum chewing was a very prevalent habit (62·4%), performed daily (mean chewing time 3·95 h day−1). Girls who chewed intensively (more than 4 h day−1) showed associations with pain in the ear area during function and at rest, as well as with joint noises. Jaw play, although reported by only 14·3%, was significantly associated with pain in the ear area during function and at rest, feeling of tiredness of the jaw while chewing, joint noises, catch and lock. All oral parafunctions, except chewing gum, were associated with jaw play and with each other. Conclusions: Jaw play was the most detrimental habit in TMD; intensive gum chewing was a potentially contributing factor for joint noises and pain. Oral parafunctions (except chewing gum) were significantly associated between themselves and suggest a behavioural pattern of ‘jaw hyperactivity’.
A study of factors for successful splint capture of anteriorly displaced temporomandibular joint disc with disc repositioning appliance
Authors: Kurita Hiroshi , Ohtsuka Akiko , Kurashina Kenji , Kopp Sigvard
Published: March 2003

The purpose of this study was to analyse the factors which influenced the success of disc recapture by the insertion of a disc repositioning appliance. Fifty‐one joints with joint clicking that occurred at both middle to late opening and late closing (near maximum cuspation) of the mandible were splinted with a mandibular full‐coverage repositioning appliance. The clinical and MR findings were compared between the joints with successful and unsuccessful splint disc capture. Thirty‐two clicking joints with reducibly displaced discs (DDWR) had successful disc recapture, while six of 19 joints with displaced disc without reduction (DDWOR). Unsuccessful joints with DDWOR had significantly higher prevalence of deformed disc and joint effusion, higher VAS quantitative pain score, and severe disc displacement especially in medial part of the joint (P < 0·05). From the results of this study joints with DDWR can be expected to have successful disc recapture with the insertion of the appliance. In joints with DDWOR, presence of inflammatory conditions, changed disc morphology and extensive disc displacement in medial part of the joint are negative factors.