bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron energy‐loss near‐edge structure studies at the atomic level: reliability of the spatial difference technique
Authors: Scheu C. 
Published: March 2003

SummaryThe spatial difference technique was applied to determine the interface‐specific components of electron energy‐loss near‐edge structures and the results are in good agreement to those obtained by atomic column resolved measurements averaged over one atomic layer. In previous studies an experimental set‐up had been chosen where the scanning areas, which are used to measure electron energy‐loss spectra, were symmetrical in respect to the location of the investigated interfaces. In the present study, an asymmetric setting of the scanning areas was applied, which allows the interfacial signals to be determined directly. Comparing the results of the different measurements shows that the spatial difference technique is valid and can be used to obtain information about the electronic structure of interfaces where single atomic column resolved measurements are not yet possible.
Amorphous solid water produced by cryosectioning of crystalline ice at 113 K
Authors: AL‐Amoudi A. , Dubochet J. , Studer D. 
Published: March 2003

SummaryAmorphous solid (vitreous) water can be obtained by a number of methods, including quick freezing of a very small volume of pure water, low pressure condensation of water vapour on a cold substrate or transformation of hexagonal ice (the ice which is naturally formed) under very high pressure at liquid nitrogen temperature. Larger volumes can be vitrified if cryoprotectant is added or when samples are frozen under high pressure. We show that a sample of 17.5% dextran solution or mouse brain tissue, respectively, frozen under high pressure (200 MPa) into cubic or hexagonal ice can be transformed into vitreous water by the very process of cryosectioning. The vitreous sections obtained by this procedure differ from cryosections obtained from vitreous samples by the irregular aspect of the sections and by small but significant differences in the electron diffraction patterns. For the growing community of cryo‐ultramicrotomists it is important to know that vitrification can occur at the knife edge. A vitreous sample is considered to show the best possible structural preservation. The sort of vitrification described here, however, can lead to bad structural preservation and is therefore considered to be a pitfall. Furthermore, we compare these sections with other forms of amorphous solid water and find it similar to high density amorphous water produced at very high pressures (about 1 GPa) from hexagonal ice and annealed close to its transformation temperature at 117 K.
The effect of the reinforcing carbon on the microstructure of pitch‐based granular composites
Authors: Méndez A. , Santamaría R. , Granda M. , Menéndez R. 
Published: March 2003

SummaryCarbon composites were prepared with four pitches (a commercial impregnating coal‐tar pitch, two thermally treated pitches and an air‐blown pitch) and four granular carbons (anthracite, graphite, green petroleum coke and foundry coke). Granular carbon/pitch proportions were optimized for each composite and differed in the characteristics of the single components. Interactions of the pitch with the granular carbons during pyrolysis and their subsequent effects on the microstructure of the final composite were monitored by light microscopy. The results show that the light texture of the matrix and the porosity of the composite depend not only on the chemical composition of the pitch but also on the specific granular carbon used as reinforcing material. The same pitch may generate different light textures depending on the characteristics of the carbon. Composites from thermally treated pitches and graphite show highly ordered matrices orientated in the direction of graphite planes. Graphite particles seem to exert a huge influence on mesophase development during the pyrolysis of the treated pitches, affecting not only the orientation of the mesophase, but also reducing the rate of mesophase formation. On the other hand, when green petroleum coke is used with the thermally treated pitches, matrices show a small size light texture, due to the high reactivity of the pitch in the presence of this granular carbon. The porosity of the composites is controlled by both the pitch and the granular carbon.
Vasopressin and Oxytocin Neurones of Hypothalamic Supraoptic and Paraventricular Nuclei Co‐Express mRNA for Type‐1 andType‐2 Corticotropin‐Releasing Hormone Receptors
Authors: Arima H. , Aguilera G. 
Published: March 2003

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

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

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

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

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

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

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

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

AbstractDouble‐label immunohistochemistry was employed to establish whether immunoreactivity for the β subtype of the oestrogen receptor (ERβ‐IR) is present in gonadotropin releasing hormone (GnRH)‐containing cells. In the immortalized GnRH cell line, GT1‐7, almost all nuclei were immunoreactive for ERβ. In the preoptic area of ovariectomized rats, more than one‐half of the GnRH neurones (52.0–63.5%) contained ERβ‐IR within the nucleus; a smaller proportion of these neurones (5–10%) displayed a particularly intense nuclear signal for ERβ. The presence of ERβ‐IR in the nuclei of GT1‐7 cells and GnRH neurones is consistent with recent reports of ERβ mRNA in these cells. Oestrogen treatment reduced the percentage of GnRH neurones with detectable ERβ‐IR. The range of signal intensity for ERβ and the incidence of the ERβ signal in GnRH neurones were comparable following double‐label immunohistochemistry involving either bright field or fluorescent techniques. These findings raise the possibility that ERβ receptors mediate direct effects of oestrogen on GnRH neurones.
Marginal leakage in class II‐restorations after use of ceramic‐inserts luted with different materials
Authors: Hahn  , Schaller  , Müllner  , Hellwig  
Published: March 2003

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