bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural characterization of isolated rat Kupffer cells by transmission X‐ray microscopy
Authors: SCHARF J.‐G. , SCHNEIDER G. 
Published: March 2003

SummaryThe ultrastructure of primary cultured rat Kupffer cells was studied using transmission X‐ray microscopy as well as transmission electron microscopy. X‐ray microscopical images of intact, hydrated Kupffer cells demonstrated structures such as cell nucleus separated by a nuclear membrane and filaments concentrated in the perinuclear area. Within the cytoplasm, a number of vacuoles were visible; some of these were crescent‐shaped vacuoles that were half X‐ray lucent, half X‐ray dense; others were uniformly dense. The number of crescent‐shaped vacuoles was predominant. After phagocytosis of haematite particles, enlarged vacuoles containing the ingested material were visible within the cytoplasm of Kupffer cells while crescent‐shaped vacuoles were no longer detectable. Densitometric analysis of the two types of vacuole revealed that the X‐ray absorption of the uniform vacuole was approximately half that of the dense part of the crescent‐shaped vacuoles. This observation led to speculation on the existence of only one type of vacuole in the cytoplasm of Kupffer cells. The different morphological aspects — crescent‐shaped versus uniform vacuoles — might be due to different three‐dimensional orientation with respect to the image plane. Using transmission electron microscopy, the morphology of vacuoles differed more widely in diameter, density and shape. Two main types of vacuole were identified: electron‐lucent and electron‐dense. Based on the observation of only one type of vacuole by transmission X‐ray microscopy, the different morphological aspects of vacuoles obtained by transmission electron microscopy could be explained by imaging several different sections of a crescent‐shaped vacuole. From the present data it can be concluded that transmission X‐ray microscopy is a versatile technique that reveals the ultrastructure of intact, unsectioned biological specimens in their aqueous environment, thereby allowing a more comprehensive interpretation of data obtained by transmission electron microscopy.
Centrifuge polarizing microscope. I. Rationale, design and instrument performance
Authors: Inoué S. , Knudson R. A. , Goda M. , Suzuki K. , Nagano C. , Okada N. , Takahashi H. , Ichie K. , Iida M. , Yamanaka K. 
Published: March 2003

We first describe early uses of the centrifuge for deciphering physical properties and molecular organization within living cells, as well as the development and use of centrifuge microscopes for such studies. The rationale for developing a centrifuge microscope that allows high‐extinction polarized light microscopy to observe dynamic fine structures in living cells is next discussed. We then describe a centrifuge polarizing microscope (CPM) that we developed for observing fine structural changes in living cells which are being exposed to up to ≈ 11 500 times earth's gravitational field (g).With the specimen housed in a rotor supported on an air spindle motor, and imaged through an external microscope illuminated by a precisely synchronized flash of less than 10 ns duration from a Nd:YAG laser, the image of the spinning object remains steady up to the maximum speed of 11 700 rev min−1, or up to ≈ 11 500 × g. The image is captured, at up to 25 frames s−1, by an interference‐fringe‐free CCD camera that is synchronized to the centrifuge rotor. At all speeds (in 100 rev min−1 increments), the image is resolved to better than 1 µm, while birefringence of the specimen, housed in a specially designed specimen chamber that suffers low‐stress birefringence and prevents leakage of the physiological solutions, is detected with a retardance sensitivity of better than 1 nm. Differential interference contrast and fluorescence images (532 nm excitation) of the spinning specimen can also be generated with the CPM.The second part of this study (Inouéet al., J. Microsc. 201 (2001) 357–367, describes several biological applications of the CPM that we have explored. Individual live cells, such as oocytes and blood cells, are supported on a sucrose or Percoll density gradient while other cells, such as cultured fibroblasts and Dictyostelium amoebae, are observed crawling on glass surfaces. Observations of these cells exposed to the high G fields (centripetal acceleration/g) in the CPM are yielding many new results that lead to intriguing questions regarding the organization and function of fine structures in living cells and related quasi‐fluid systems.
Preparation of transmission electron microscopy cross‐section specimens of crack tips using focused ion beam milling
Authors: Huang Y. Z. , Lozano‐Perez S. , Langford R. M. , Titchmarsh J. M. , Jenkins M. L. 
Published: March 2003

SummaryThe preparation of transmission electron microscope (TEM) thin foil specimens from metal alloys containing cracks is usually thwarted by the difficulty in preventing preferential erosion of material along the flanks and at the tips of cracks. Recent developments in focused ion beam (FIB) micromachining methods have the potential to overcome this inherent problem. In this article we describe the development of new procedures, one using FIB alone and the other using a combination of FIB with more conventional ion milling to generate TEM specimens that largely retain the microstructural information at stress corrosion cracks in austentic alloys. Examples of corrosion product phase identification and interfacial segregation are included to verify that detailed information is not destroyed by ion bombardment during specimen preparation.
The application of a hot deformation SEM stage, backscattered electron imaging and EBSD to the study of thermomechanical processing
Authors: Huang Y. , Humphreys F. J. , Brough I. 
Published: March 2003

SummaryThe technique of combining in situ hot‐deformation and high resolution electron backscattered diffraction (EBSD) has been applied to study the mechanisms operating during the thermomechanical processing of metals. A simple hot tensile‐straining stage is installed in a field emission gun scanning electron microscope equipped with an EBSD system and has been used successfully for a number of preliminary investigations. These investigations include substructure formation, dynamic subgrain and grain growth, superplastic deformation in aluminium alloys, and dynamic recrystallization in copper. Despite the surface topography, which inevitably increases during plastic deformation, channelling contrast backscattered electron micrographs have been successfully obtained after strains of up to ∼50%. Good quality EBSD maps have been obtained after strains of up to 100%. Most observations and measurements from the in situ experiments are consistent with what is known about the mechanisms occurring in the bulk. The microstructures revealed in the centre of the in situ samples after later repolishing are generally similar to those at the surface.
Estimation of tissue layer level by sequential morphological reconstruction
Authors: Landini G. , Othman I. E. 
Published: March 2003

SummaryAn automated method for labelling layers of clustered elements in two dimensional images based on morphological operations is presented here. Unlike the various distance transforms for regular lattices, the procedure deals successfully with clusters composed of different shaped and sized elements and provides a distance measure, in number of layers, from each element in the cluster to any other reference element (or elements). The method was applied to histological sections of two different types of polystratified epithelia. Local clusters in the different cell profile layers can subsequently be used to define the orientation of the tissue layers relative to each element in it.
Glucocorticoids Regulate Pituitary Growth Hormone Secretagogue Receptor Gene Expression
Authors: Tamura H. , Kamegai J. , Sugihara H. , Kineman R. D. , Frohman L. A. , Wakabayashi I. 
Published: March 2003

AbstractGlucocorticoids regulate growth hormone (GH) secretion by modulating both hypothalamic and pituitary function. At the level of the pituitary, glucocorticoids increase GH and GH‐releasing hormone receptor (GHRH‐R) gene expression. To test if glucocorticoids might also regulate the pituitary expression of the recently identified GH secretagogue (GHS) receptor, GHS‐R; adult male rats were adrenalectomized or sham operated, and treated with the synthetic glucocorticoid (dexamethasone, 200 µg/day) or vehicle for 8 days. Pituitary GHS‐R mRNA levels were assessed by reverse transcriptase polymerase chain reaction (RT‐PCR). Adrenalectomy decreased pituitary GHS‐R mRNA to 45% of vehicle‐treated, sham‐operated rats (P < 0.05). Administration of dexamethasone increased GHS‐R mRNA levels in sham‐operated as well as in adrenalectomized rats (199 ± 24% (P < 0.05) and 369 ± 48% (P < 0.01) of vehicle‐treated controls). Addition of dexamethasone to primary rat pituitary cell cultures increased GHS‐R mRNA levels in a dose‐ and time‐dependent manner while the transcriptional inhibitor, actinomycin D, completely blocked the stimulatory action of dexamethasone. Taken together, these results suggest glucocorticoids directly increase pituitary GHS‐R mRNA levels by stimulating GHS‐R gene transcription.
Steroid Implants in the Medial Preoptic Area or Ventromedial Nucleus of the Hypothalamus Activate Female Sexual Behaviour in the Musk Shrew
Authors: Veney S. L. , Rissman E. F. 
Published: March 2003

AbstractFemale musk shrews are induced ovulators that do not exhibit a spontaneous behavioural oestrous cycle. Testosterone produced by the ovaries and adrenal glands, is the major steroid hormone in circulation at times of mating, and as such, regulates sexual behaviour. In the first experiment, we identified the neural site(s) of action for testosterone. Hormone implants were placed in one of three targeted brain regions. The neural sites selected were the medial anterior division of the bed nucleus of the stria terminalis (BNSTMA), medial preoptic area (mPOA) and the ventromedial nucleus of the hypothalamus (VMN). Ovariectomized females who received a unilateral testosterone propionate implant in either the mPOA or VMN, were significantly more likely to display sexual behaviour as compared to females who received an implant in the BNSTMA or any other hypothalamic nucleus. In experiments 2 and 3, we investigated whether the behavioural effects of testosterone propionate were mediated by an oestrogen receptor or the androgen receptor. Ovariectomized females that received oestradiol (E2) implants in either the mPOA or VMN were more likely to display receptivity, and had significantly shorter behavioural latencies, as compared to females implanted with either dihydrotestosterone or cholesterol. These data show that neural aromatization of testosterone to E2 in the mPOA or VMN is necessary for optimal activation of female musk shrew sexual behaviour. This finding implies a degree of neural redundancy in the networks that control the expression of sexual receptivity.
Differences in Arginine Vasotocin Gene Transcripts and Cortisol Secretion in Trout with High or Low Endogenous Melanin‐Concentrating Hormone Secretion
Authors: Gilchriest B. J. , Tipping D. J. , Hake L. , Levy A. , Baker B. I. 
Published: March 2003

AbstractPrevious studies on trout suggest that melanin‐concentrating hormone (MCH) acts at both hypothalamic and pituitary levels to restrain the release of adrenocorticotropic hormone and hence cortisol during stress. Using in situ hybridization, the present work examined whether high rates of MCH secretion were associated with changes in the synthesis of arginine vasotocin (AVT), one of the corticotropin secretogogues. It also examined whether high endogenous MCH secretion restrains cortisol secretion during intense as well as mild stress, and how exogenous MCH affects the rise in plasma cortisol following injection stress. Trout were reared in black‐ or white‐coloured tanks for 1 year or more to achieve maximal differences in MCH secretion. Following a mild stress, cortisol secretion was greater in black‐reared fish with low MCH secretion which is in line with previous findings but, following a more severe stress, plasma cortisol concentrations were similar in the two groups. Injection of MCH into black‐adapted fish restrained the stress‐induced rise in plasma cortisol concentration during the first hour but did not affect final cortisol values. In two separate experiments, AVT mRNA levels were significantly lower in the hypothalamus of black‐reared fish. Possible explanations for this include a greater negative‐feedback restraint by cortisol, which is likely to rise higher in black‐adapted fish during the moderate, daily stresses of aquarium life; or the possibility that exposure to a white background may be psychologically stressful, stimulating AVT transcription. The possibility that MCH directly stimulates AVT transcription cannot be excluded but seems less likely. The results suggest that while MCH may restrain the release of hypothalamo‐pituitary stress hormones under moderately stressful conditions, it does not restrain AVT synthesis.
Effect of Nitric Oxide Synthase Inhibition on Fos Expression in the Hypothalamus of Female Rats Following Central Oxytocin and Systemic Urethane Administration
Authors: Popeski N. , Woodside B. 
Published: March 2003

AbstractThree experiments were carried out to investigate the pattern of neuronal activation induced by central oxytocin administration and its modulation by nitric oxide (NO). First, we compared the induction of Fos‐like immunoreactivity (lir) in the supraoptic (SON) and paraventricular (PVN) nuclei and medial preoptic area (MPOA) after central oxytocin administration between nonlactating and lactating rats. Next, we investigated whether NO modulated Fos induction following central oxytocin administration using a nitric oxide synthase (NOS) inhibitor, Nω‐nitro‐l‐arginine methyl ester (l‐NAME). Finally, to determine whether the effects of NOS inhibition on Fos induction would generalize to stimuli other than oxytocin, we compared Fos‐lir in the SON and PVN of lactating and nonlactating rats following l‐NAME and urethane administration. In the first two experiments, oxytocin (50 ng in 2 µl) or vehicle was administered into the third ventricle. l‐NAME (50 mg/kg) was given by an intraperitoneal (i.p.) injection 30 min before oxytocin administration (experiment 2) or an i.p. injection of urethane (1.4 g/kg) (experiment 3). In all experiments, lactating rats were tested on day 12 or 13 postpartum and nonlactating females at least 11 days after surgery or the start of the experiment. Central oxytocin infusion induced Fos expression in the SON and PVN in lactating and nonlactating rats and in the MPOA and bed nucleus of the stria terminalis in lactating rats. Overall, lactating rats that received l‐NAME and oxytocin had a greater number of cells showing Fos‐lir in both the SON and PVN. Conversely, l‐NAME administration reduced Fos‐lir in the SON and PVN in oxytocin‐stimulated nonlactating rats. In urethane‐treated rats, l‐NAME administration did not change Fos‐lir in lactating rats but reduced Fos‐lir in nonlactating rats. These data suggest that the role of NO in modulating the activity of neurones in discrete nuclei in the hypothalamus varies across reproductive state and with the stimulus presented.
Bradykinin and Angiotensin II‐Induced [Ca2+]i Rise in Cultured Rat Pituitary Folliculo‐Stellate Cells
Authors: Sudo T. , Sakuma Y. , Kato M. 
Published: March 2003

AbstractFolliculo‐stellate cells of the anterior pituitary are thought to modulate pituitary hormone secretion through a paracrine mechanism. Angiotensin II and pituitary adenylate cyclase‐activating polypeptide (PACAP) have previously been shown to increase the intracellular Ca2+ concentration ([Ca2+]i) of these cells. In the present study, we examined the effects of various peptides such as bradykinin, angiotensin II, endothelin‐1, PACAP, galanin and neurotensin by Ca2+‐imaging of folliculo‐stellate cells in primary culture. Bradykinin and angiotensin II increased [Ca2+]i in folliculo‐stellate cells. Both responses were completely suppressed by thapsigargin and were significantly suppressed by the phospholipase C inhibitor, U‐73122. Ryanodine did not significantly modify the responses. A B2 antagonist and angiotensin II receptor antagonist inhibited the response induced by bradykinin and angiotensin II, respectively. Endothelin‐1 and PACAP increased [Ca2+]i in fewer than 50% of folliculo‐stellate cells but galanin and neurotensin did not influence [Ca2+]i in any of the folliculo‐stellate cells tested. These results indicate that bradykinin and angiotensin II increase [Ca2+]i in folliculo‐stellate cells by activating phospholipase C through B2 receptor and AT1 receptor, respectively, and that endothelin‐1 and PACAP also increase [Ca2+]i in some folliculo‐stellate cells.
Intracerebroventricular Adrenomedullin Stimulates the Hypothalamic‐Pituitary‐Adrenal Axis, the Sympathetic Nervous System and Production of Hypothalamic Nitric Oxide
Authors: Shan J. , Krukoff T. L. 
Published: March 2003

AbstractWe tested the hypothesis that central adrenomedullin stimulates activity of the hypothalamic‐pituitary‐adrenal (HPA) axis and sympathetic output from the brain, and we assessed the effects of central adrenomedullin on the nitric oxide (NO) system in the brain. In conscious rats, intracerebroventricular (i.c.v.) injections of adrenomedullin (2 nmol/kg) increased arterial pressure and heart rate, with return to baseline values within 20 min and 65 min of injections, respectively. Adrenomedullin injections augmented expression of tyrosine hydroxylase mRNA in the locus coeruleus after 4 h. Plasma concentrations of adrenocorticotropic hormone, measured with radioimmunoassay, were also increased by adrenomedullin. i.c.v. Adrenomedullin stimulated Fos expression in neurones within autonomic centres including the paraventricular nucleus (PVN) of the hypothalamus, arcuate nucleus, locus coeruleus, nucleus of the tractus solitarius and area postrema. In the PVN, large proportions of corticotropin releasing factor‐ and NO‐producing neurones were activated (Fos positive). NO production, measured with nitrate/nitrite assays, was elevated in the hypothalamus, but not brainstem, of adrenomedullin‐treated rats compared to controls. We conclude that centrally administered adrenomedullin stimulates activity of the HPA axis, the sympathetic nervous system, and the hypothalamic NO system.
Long‐Term Undernutrition Followed by Short‐Term Refeeding Effects on the Corticotropin‐Releasing Hormone Containing Neurones in the Paraventricular Nucleus: An Immunohistochemical Study in Sheep
Authors: Chaillou E. , Baumont R. , Tramu G. , Tillet Y. 
Published: March 2003

AbstractThe effect of nutritional level on the immunoreactivity of corticotropin‐releasing hormone (CRH) in neurones of the hypothalamic paraventricular nucleus was described in sheep, a ruminant, whose feeding strategy differs from that of monogastric species. Two groups of ewes were underfed (40%), or fed at maintenance (100%) for 167 days, after which one‐half of each group was killed or ad libitum refed (at least 150% of maintenance) for 4 days before killing. The presence of CRH in the paraventricular nucleus was examined by immunohistochemistry. The number of CRH immunoreactive neurones was increased in underfed ewes, but without modification of the plasma concentration of cortisol, indicating that the rise of CRH was not released in the portal blood nor linked to the pituitary‐adrenal axis. Refeeding did not modify significantly the number of CRH immunoreactive neurones in the nucleus although these neurones were increased, only in refed ewes that were previously underfed. These data differ from those for rats and mice where CRH expression is decreased or not modified by underfeeding which could reflect different effects of undernutrition on CRH immunoreactive neurones in monogastric compared to ruminants species.
Comparison of Somatostatin Receptor Expression in Human Gliomas and Medulloblastomas
Authors: Cervera P. , Videau C. , Viollet C. , Petrucci C. , Lacombe J. , Winsky‐Sommerer R. , Csaba Z. , Helboe L. , Daumas‐Duport C. , Reubi J. C. , Epelbaum J. 
Published: March 2003

AbstractThe expression of the five somatostatin receptor subtypes, sst1–5 was compared on tissue containing glial tumours (glioblastomas or oligodendrogliomas), medulloblastomas, and on normal human cortex. By semiquantitative reverse transcription coupled to polymerase chain reaction, the receptor expression profiles were high in cortex and in tissue containing oligodendrogliomas. It was moderate in medulloblastomas. Tissue containing glioblastomas displayed lower expression of somatostatin receptor subtypes, sst1 and sst3 being mostly expressed. By 125I‐Tyr0DTrp8 somatostatin‐14 or 125I‐Leu8DTrp22 Tyr25 somatostatin‐28 autoradiography combined with synaptophysin immunohistochemistry, it was possible to differentiate between isolated tumoral cell component infiltrating the cerebral parenchyma (cortex or white matter) and tumoral tissue (without residual parenchyma) in glioblastomas or oligodendrogliomas. Glial tumoral tissue per se presented few somatostatin receptors. By contrast, medulloblastoma tumoral cells exhibited numerous octreotide sensitive somatostatin receptors. sst2 immunocytochemistry demonstrated immunostaining of neuronal cells and neuropile; sst2 and sst3 immunostaining was identified on glioblastoma proliferating vessels endothelial cells and on medulloblastomas tumoral cells. Faint sst2 immunostaining among glial tumoral cells was due to microglia, while glioma cells did not significantly stain. In summary, medulloblastoma tumoral cells express sst2/sst3 receptors at a high level while glioma cells do not. In gliomas, sst expression is restricted to endothelial cells on proliferating vessels (displaying both sst2 and sst3 receptors), including parenchyma and reactive microglia (only sst2). The differential expression of sst2/sst3 receptors on gliomas and medulloblastomas has implications for the therapy of these tumours.
Progestin Receptor Immunoreactivity Within Steroid‐Responsive Vasopressin‐Immunoreactive Cells in the Male and Female Rat Brain
Authors: Auger C. J. , De Vries G. J. 
Published: March 2003

AbstractProgestin receptor immunoreactivity is found in the same regions of the bed nucleus of stria terminalis (BST) and centromedial amygdala (CMA) as steroid‐responsive vasopressin immunoreactive (AVP‐ir) cells. To test whether AVP‐ir cells express progestin receptors, brains of male rats were stained immunocytochemically for arginine vasopressin as well as progestin receptors. In BST and CMA, over 95% of AVP‐ir cells contained progestin receptor immunoreactivity. In contrast, none of the AVP‐ir cells in the suprachiasmatic, supraoptic and paraventricular nuclei expressed progestin receptor immunoreactivity. To study whether progestin receptor expression in AVP‐ir cells in the BST and CMA is responsive to gonadal steroids, male and female rats were castrated and implanted with either empty capsules or capsules filled with testosterone or oestradiol, respectively. Ten days later, brains were processed for AVP and progestin receptor immunoreactivity. Although there was no effect of hormonal status on the percentage of colocalized cells, the level of progestin receptor immunoreactivity was higher in rats that received gonadal steroids than those that did not. The presence of progestin receptor immunoreactivity in steroid responsive AVP‐ir cells, and the responsiveness of this expression to gonadal hormones, is consistent with the possibility that the effects of gonadal steroids on AVP‐ir expression in the BST and CMA may be mediated at least in part by progestin receptors.