bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Heterogeneity in Hereditary Thrombophilia
Authors: Reitsma Pieter H.
Published: April 2003

Venous thromboembolism is a multifactorial disease that depends on variable combinations of acquired and genetic risk factors. The genetic risk factors include loss-of-function mutations in the genes that encode proteins with clot-restraining function, and gain-of-function mutations in procoagulant factors. The loss-of-function mutations are heterogeneous and comprise any mutation that impairs gene function. On the whole, these mutations are rare, with fewer than 1/200–500 individuals affected. This low prevalence in the population is probably caused by the loss of mutant alleles from the gene pool through critically ill homozygous subjects. The gain-of-function mutations in procoagulant proteins differ from the loss-of-function mutations in at least three important respects: these are more homogeneous (factor V Leiden and PT 20210), homozygous individuals are relatively mildly affected, and these are relatively prevalent (3–15%) in Caucasian populations.
New Insights into Extended Prophylaxis after Orthopaedic Surgery – the North American Fragmin Trial Experience
Authors: Hull Russel D.
Published: April 2003

It is well-known that peri-operative and post-operative venous thrombosis are common. Trials in Europe have shown that extended out-of-hospital prophylaxis with a low-molecular-weight heparin reduces the rate of deep vein thrombosis in patients undergoing elective hip surgery. North American investigators of limited-outcome descriptive studies, however, have suggested that out-of-hospital prophylaxis is not necessary. To resolve this uncertainty, NAFT (North American Fragmin Trial) was conducted, the results of which are summarized in this paper. The findings of NAFT support the favourable findings of the European studies on extended prophylaxis. Furthermore, European data have shown extended out-of-hospital prophylaxis to be cost-effective. On the basis of the aggregate data, it is felt that the A2 recommendation made by the Fifth American College of Chest Physicians consensus conference for extended prophylaxis should be changed to an A1 recommendation.
Efficacy and Tolerability of Angiotensin II Type 1 Receptor Antagonists in Dialysis Patients Using AN69 Dialysis Membranes
Authors: Tepel Martin , van der Giet Marcus , Zidek Walter
Published: April 2003

Aims and Methods: Our aim was to evaluate the antihypertensive efficacy and tolerability of angiotensin II type 1 (AT1) receptor antagonists. Valsartan or candesartan cilexetil was administered to 11 dialysis patients with elevated blood pressure. The patients (6 male, 5 female; mean age ± SD 61±11 years) were on regular bicarbonate hemodialysis three times weekly for more than 3 months using acrylonitrile and sodium methallyl sulfonate copolymer (AN69) dialysis membranes. Results: Within 252 days after administration of the AT1 receptor antagonists the systolic blood pressure was significantly reduced from 161±13 to 130±12 mmHg (p<0.001), whereas the diastolic blood pressure did not change significantly (76±8 vs. 71±8 mmHg; p>0.05). In addition, heart rate (75±7 vs. 80±8/min), body weight, and laboratory variables (hemoglobin, creatinine, blood urea nitrogen, serum potassium, serum sodium, serum calcium, and total protein) showed no significant changes. During 1,188 hemodialysis sessions using AN69 membranes, no hypersensitivity reactions occurred after administration of AT1 receptor antagonists. Conclusion: The results indicate that once–daily administration of AT1 receptor antagonists efficiently reduces the systolic blood pressure in hemodialysis patients.
Renal Hemodynamics in Young and Old Spontaneously Hypertensive Rats during Intrarenal Infusion of Arginine Vasopressin
Authors: Christiansen Rolf E.F. , Roald Anca B. , Gjerstad Camilla , Tenstad Olav , Iversen Bjarne M.
Published: April 2003

Background/Aims: To gain insight into the effect of arginine vasopressin (AVP) on renal hemodynamics in hypertensive rats, we investigated the vasoconstrictive response to AVP on total renal blood flow (RBF) and total and zonal glomerular filtration rate (GFR) in young and old spontaneously hypertensive rats (SHR). A hypothesis of increased AVP sensitivity in the juxtamedullary cortex of SHR was tested. Methods: Total RBF and total and zonal GFR were studied in 10- and 40-week-old SHR and normotensive Wistar-Kyoto rats (WKY). RBF was recorded by a flowmeter before infusion of AVP and immediately after injection of a bolus dose of 10 ng AVP. Whole kidney GFR and its intracortical distribution was measured by the tubular uptake of 125I- and 131I-labelled aprotinin before and during a continuous infusion of AVP 5 ng/min. Ligand binding measurements of preglomerular V1a receptors were performed in young and old rats. Results: RBF decreased by 43 ± 3% in 10-week SHR (9.2 ± 0.5 vs. 5.2 ± 0.3 ml·min–1·g–1), significantly more than 10-week WKY where RBF decreased by 35 ± 3% (9.6 ± 0.7 vs. 6.5 ± 0.5 ml·min–1·g–1) (p < 0.05). The effect of AVP on RBF was attenuated in 40-week-old rats where the decline in RBF was 29 ± 5% in SHR and 23 ± 4% in WKY (p > 0.05). GFR decreased by 6 ± 3% (1.03 ± 0.04 vs. 0.96 ± 0.04 ml·min–1·g–1, p < 0.05) in 10-week SHR and was unchanged in 10-week WKY (1.10 ± 0.07 vs. 1.08 ± 0.04 ml·min–1·g–1, p > 0.10). GFR decreased by 11 ± 10% in 40-week SHR and by 4 ± 4% in 40-week WKY (p > 0.05). AVP infusion significantly increased filtration fraction in all groups except 40-week SHR, indicating that AVP has the strongest vasoconstrictive effect on postglomerular vessels. The intrarenal distribution of GFR was unchanged in the normotensive and hypertensive groups. V1a receptor density was upregulated in young SHR compared to young WKY (p < 0.05), but downregulated in old compared to young SHR (p = 0.05). Conclusion: The results indicate that AVP sensitivity is not increased in the juxtamedullary cortex in SHR and the reduced vasoconstrictive effect in old SHR is due to a reduced density of V1a receptors.
Effects of Angiotensin II on the Renal Antioxidant Activities of Borderline Hypertensive Rats
Authors: Ha Jeoung-Hee , Jin Da-Qing , Shin Son-Moon , Moon Han-Gu , Lee Eun-Sil , Park Yong-Hoon
Published: April 2003

This study was aimed to study the angiotensin II (Ang II)-induced antioxidant changes in the kidney of borderline-hypertensive rats (BHR). We measured renal antioxidant enzyme activities, and glutathione (GSH) contents and lipid peroxide levels in relation to the age of subjects. In the antioxidant enzyme assays, consistent changes were not observed in relation to age. However, in the assay for reduced GSH, nonenzymatic antioxidant, contents of adult and aged rats were much greater than those of weanling rats. Subcutaneous injection of pressor dose of human Ang II (200 µg/kg over 90 min) significantly reduced enzymatic activities in the weanling (4-week-aged) and adult (10-week-aged) BHR. However, in the relatively aged (16-week-aged) rats, Ang II did not alter enzymatic activities. Renal GSH contents of aged BHR, were highly increased by Ang II. Renal lipid peroxide levels of weanling and adult BHR were increased by Ang II, but decreased in the aged rats. However, these characteristic changes of renal antioxidant due to Ang II of the BHR could not be observed in the age-matched control, Wistar-Kyoto rats (WKR). From these results, it can be concluded that impacts of oxidative stress on the kidney of BHR may be greater in the young rats.
Bacterial Pneumonia at King Abdulaziz University Hospital: A Comparison between Hospital- and Community-Acquired
Authors: Akbar Daad H. , Ahmad Maimona M. , Altahawi Ahmed T.
Published: April 2003

Objectives: To compare community- and hospital-acquired pneumonia (CAP, HAP) with respect to causative organisms, antimicrobial susceptibility, mortality and risk factors associated with high mortality. Methods: From March 1998 to December 1999, the medical charts of patients at King Abdulaziz University Hospital older than 14 years of age with a diagnosis of pneumonia were reviewed. The following data regarding the patient’s age, sex, type of pneumonia, admission to intensive care unit (ICU), type of organism isolated, antibiotic susceptibility, outcome, presence of hypotension, tachycardia, tachypnea, disturbed level of consciousness, and renal failure were recorded. Results: A total of 324 patients were studied (248 HAP, 76 CAP). Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae were the commonest isolates in CAP, while Pseudomonas spp. and Enterobacter spp. were more common in HAP. Pathogens isolated from CAP were more susceptible to ampicillin, co-amoxiclav, ciprofloxacin, cefuroxime, tetracycline and erythromycin, whereas isolates of HAP showed more sensitivity to aminoglycosides and imipenem. Mortality was higher in HAP compared to CAP: 50 versus 21%, respectively (p < 0.001). Risk factors associated with high mortality were a more advanced age, tachycardia, hypotension, a disturbed level of consciousness, renal failure and ICU admission. Conclusion: Older less expensive antibiotics can still be used in the treatment of both CAP and HAP, while the newer more expensive antibiotics should be kept in reserve to prevent the development of resistance.
Physicians’ Attitudes towards Euthanasia in Kuwait
Authors: Askar Alia H. Gh. , Nakhi Muneera Ben , Al-Rashidi Khadeijah , Al-Musabbahie Bashayer A.M. , Shah Nasra M.
Published: April 2003

Objectives: The attitudes of physicians in Kuwait towards euthanasia were examined. An additional objective was to examine whether physician characteristics such as nationality, qualifications, years of experience and/or religion affect their attitude toward euthanasia. A comparison was also made between the experience of physicians who generally treat terminally ill patients and those who generally treat non-terminally ill patients in terms of attitudes toward hastening death to alleviate suffering. Methods: A descriptive study using a self-administered questionnaire was conducted among 228 physicians working in 5 selected government hospitals. The response was 92%. Results: Nearly 92% of all the respondents did not support the provision of means for terminally ill patients to commit suicide while 8% did. A majority favored providing pain killers and comfort even if this hastens the patient’s death. About 20% of the physicians felt that the Ministry of Health should allow euthanasia under certain restricted conditions. About 47% of Hindu, 23% of Christian and 17% of Muslim physicians agreed to the legalization of euthanasia. Approximately 27% of physicians who were frequently exposed and 10% of those who were rarely exposed to terminally ill patients reported that they had been asked to hasten death. Physicians in Kuwait have not dealt with euthanasia as much as physicians in other countries such as Australia and are much less favorable towards it. Conclusion: The findings of this survey indicate that a minority of physicians in Kuwait believe that euthanasia should be legalized under certain conditions. Thus, there is a need for the medical community and the Ministry of Health to recognize and deal with this controversial topic.
Molecular Genetic Control of Retinal Development
Authors: Choy Kwong Wai , Baum Larry , Lam Dennis Shun Chiu , Pang Chi Pui
Published: April 2003

The human retina is the peripheral portion of the visual system. It contains a great diversity of neuronal cell types, including six major neuronal cell types and one glial cell type organized in a laminar structure. Current models for retinal neuron differentiation suggest that the formation of a specific retinal neuron is determined by the intrinsic properties of the retinal progenitor and extrinsic cues from the retinal environment, and yet few intrinsic gene products have been identified that direct this process. Through recent developments in mouse and human genetics, and also by the use of molecular biological techniques, we are beginning to understand the genetic control of the differentiation and function of these molecules in the retina. Several transcription factors, such as the Pax6 gene, and neural transcription factors (bHLH) together with the Notch and Delta signaling pathway have been implicated in retinal cell subtype specification. The aim of this review is to summarize the current status of molecular genetic findings in the developing retina.
Vascular, Axonal and Glial Pathogenesis of Periventricular Leukomalacia in Fetuses and Neonates
Authors: Takashima S. , Hirayama A. , Okoshi Y. , Itoh M.
Published: April 2003

Periventricular leukomalacia (PVL) in prematurely born infants is an important cause of cerebral palsy and intellectual impairment. In the pathogenesis of PVL, both the developing vasculature and differentiating glial progenitor cells within the deep white matter are susceptible to ischemia and very important as predisposing factors. Axonal swellings, which occur as the first signs of PVL, are found in fetuses as well as neonates, and cellular activation secondary to intrauterine infection may also predispose to PVL. Causal factors include cerebral hypoperfusion in the perinatal period, which leads to axonal damage, glutamate release, elevated production of cytokines in microglia and nerve growth factor in astrocytes, and finally an increased plasticity in neurons and oligodendrocytes. Cellular reactivities such as nestin expression following PVL may represent important indicators for determining the effective time for treatment and rehabilitation.
Normal and Abnormal Development of the Human Cerebral Cortex
Authors: Chan Wood Yee , Kostovic Ivica , Takashima Sachio , Feldhaus Christian , Stoltenburg-Didinger Gisela , Verney Catherine , Yew David , Ulfig Norbert
Published: April 2003

The functional organization of the developing human brain does not only differ substantially from that of the mature brain, but it also undergoes continuous changes. During fetal brain development, transient neuronal circuitries are formed which are essential for the subsequent development of mature projections. Transitory connections are linked to transient structures which are particularly prominent in the human fetal brain and are susceptible to damage under pathological circumstances. The First International Symposium on Normal and Abnormal Development of the Human Fetal Brain aimed to gather basic information on these transitory organizations and the major developmental events that occur in the fetal brain. This paper summarizes a roundtable discussion at the symposium on transient characteristics and injuries in the developing human cerebral cortex. An overview of cortical development is first presented and then the development of several fetal structures, including the subventricular zone, ganglionic eminence, marginal zone, subplate and cortical plate, is discussed with regard to their important contribution to the formation of the correct fiber projections in the adult. The last section focuses on the anomalies that are commonly found in the premature fetal brain on the one hand and on the other hand are related to the transitory characteristics of the developing brain.
Specific Serotonin Reuptake Inhibitor-Induced Decreases in Lymphocyte Activity Require Endogenous Serotonin Release
Authors: Pellegrino Trisha C. , Bayer Barbara M.
Published: April 2003

Objectives: We have previously reported that acute administration of the specific serotonin reuptake inhibitor (SSRI), fluoxetine, resulted in a decrease in mitogen-induced blood lymphocyte proliferation. The present studies further examine the specificity of this response to serotonin reuptake systems and the potential role of endogenous serotonin in mediating these effects. Methods: Male Sprague-Dawley rats were treated intraperitoneally with the SSRIs, fluoxetine (6–10 mg/kg) or sertraline (20 mg/kg), dopamine and norepinephrine reuptake inhibitors, GBR 12909 and desipramine, respectively (6 mg/kg) or the serotonin precursor, 5-hydoxytryptophan (5-HTP, 50 mg/kg) 2 h prior to sacrifice. The serotonin-depleting agents, p-chlorophenylalanine (PCPA, 2 × 200 mg/kg) or the serotonin-lesioning agent, p-chloroamphetamine (PCA, 2 × 10 mg/kg) were administered intraperitoneally 5–7 days prior to fluoxetine (10 mg/kg) administration. Results: Unlike the SSRIs, which significantly suppressed lymphocyte proliferation responses, selective norepinephrine or dopamine reuptake inhibition had no effect on lymphocyte proliferation. Elevation of extracellular serotonin levels with the serotonin precursor, 5-HTP, resulted in a similar decrease in lymphocyte proliferation as that seen with SSRI administration. Conversely, decreases in endogenous serotonin following PCA or PCPA treatment prevented the fluoxetine-induced decreases in lymphocyte proliferation. Conclusions: These results suggest that decreases in mitogen-induced lymphocyte proliferation following acute fluoxetine administration were due to elevations in extracellular serotonin following reuptake inhibition.
Mathematical Exploration of Pulsatility in Cultured Gonadotropin-Releasing Hormone Neurons
Authors: Gordan John D. , Attardi Barbara J. , Pfaff Donald W.
Published: April 2003

Pulsatile gonadotropin-releasing hormone (GnRH) release has been demonstrated in cultures of an immortalized line of GnRH expressing neurons (GT1 cells) in experiments by four different research groups. Pulsatile release is known to play a crucial role in GnRH-mediated signaling in vivo, and thus deserves theoretical and quantitative consideration, especially as GT1 cells are presumably genetically homogeneous. Here we have modeled idealized GT1 cells with a differential equation/logic based modeling program, Stella II. We have created a network of ‘neurons’, with randomized (within the same preset limits for each neuron) thresholds, number and weight of connections to other neurons, and build-up of signal; as well as continuous decay of stored signal. Surprisingly, we found that with this minimal set of assumptions, without any sort of predefined pacemaking cells, it is possible to create pulsatility similar to that observed in the laboratory. A variety of different parameter sets was found to produce these pulses. Network behaviors similar to those of GT1 cells depended on the degree of interconnection between neurons and their functioning within a critical range of network excitability. These findings allow for a clearer consideration of the critical elements of such networks as well as experimental predictions regarding the production of pulsatile behavior.
Distribution and Diurnal Variations of the Mu Opioid Receptor Expression in the Arcuate Nucleus of the Male Rat
Authors: Mitchell Valérie , Prévot Vincent , Beauvillain Jean Claude
Published: April 2003

Using an in situ hybridization method with radioactively labeled riboprobes, the distribution of µ-opioid-receptor-expressing cells was investigated in the arcuate nucleus (ARC) of the male rat. We simultaneously tested the hypothesis that expression of µ-opioid receptor mRNA displayed diurnal variations in neurons of the ARC, and an image analysis system was used to measure cellular levels of µ-opioid receptor expression. Rats were sacrificed in groups of 5 at 06.00, 12.00 and 20.00 h. In the ARC, µ-opioid receptor mRNA was expressed in scattered neurons located in ventromedial, ventrodorsal and ventrolateral portions. The level of expression was very low in sections taken from animals sacrificed at 06.00 and 12.00 h. The level of µ-opioid receptor mRNA expression was significantly (p < 0.001) increased in neurons of animals killed at 20.00 h in comparison with the other hours of the day, i.e. 06.00 and 12.00 h. However, the number and general distribution of µ-receptor-expressing neurons did not vary across these time points (p > 0.05). In conclusion, this study presents evidence for the presence of low levels of µ-opioid-receptor-expressing cells in the ARC. We observed that the receptor synthesis increases in the evening. These results suggest that the µ-opioid receptor may play a significant role in modulating the processing of neuropeptides located in this nucleus. The daily rhythm in µ-receptor expression is brought together with the diurnal fluctuation in pro-opiomelanocortin mRNA and the circadian variation in β-endorphin concentrations in the ARC.
Chronic Melatonin Treatment Counteracts Glucocorticoid-Induced Dysregulation of the Hypothalamic-Pituitary-Adrenal Axis in the Rat
Authors: Konakchieva Rossitza , Mitev Yuri , Almeida Osborne F.X. , Patchev Vladimir K.
Published: April 2003

Transient exposure of rats to high doses of dexamethasone (DEX; 500 µg/day for 5 days) produced a host of symptoms that are indicative of hypothalamic-pituitary-adrenal (HPA) axis dysregulation, such as increased adrenocortical secretion over 24 h, blunted and prolonged secretory response to emotional stress, refractoriness of adrenocorticotropin in vitro release to stimulation with the secretagogues corticotropin-releasing hormone (CRH) and vasopressin, decreased levels of mRNA encoding type II corticosteroid receptors in the hippocampus and increased numbers of transcripts encoding CRH in the paraventricular nucleus. Daily administration of melatonin (MEL; 80 µg/kg) concomitantly with, and for 5 days after discontinuation of, glucocorticoid treatment ‘normalized’ most of the symptoms of impaired HPA regulation caused by the exposure to DEX. While none of the treatments used caused major shifts in circadian patterns of corticosterone secretion, MEL administration was associated with diminished overall corticosterone secretion and increased sensitivity to glucocorticoid feedback. Taken together, these findings indicate that chronic MEL treatment may protect several regulatory components of the HPA axis from glucocorticoid-induced deterioration.
Effect of Glutamate Receptor Agonists on Catecholamine Secretion in Bovine Chromaffin Cells
Authors: González María Pilar , Herrero María Teresa , Vicente Susana , Oset-Gasque María Jesús
Published: April 2003

In this study, the effects of glutamate and glutamate receptor agonists in cultured chromaffin cells from bovine adrenal medulla were investigated. It was found that glutamate increases basal catecholamine (CA) secretion in a dose-dependent manner. This effect is mimicked by specific agonists of the four known glutamate receptors N-methyl-D-aspartate (NMDA), quisqualate/(RS)-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), kainate (KA), and trans-(+)-1-amino-1,3-cyclopentane dicarboxylic acid (t-ACPD), which increased both basal and nicotine-evoked CA secretion. The NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid, 6-cyano-7-nitroquinoxaline-2,3-dione, an antagonist of KA and AMPA receptors, and L-(+)-2-amino-3-phosphonopropionic acid, an antagonist of the t-ACPD receptor, inhibited the stimulatory effect of related glutamate agonists. Hexamethonium, an antagonist of the nicotinic receptor, failed to influence glutamate agonists except for a 15% inhibition of KA. The increase in CA secretion produced by a 100 µM concentration of glutamate agonists was about 20–60% of that obtained with 10 µM of nicotine, an agonist of the physiological stimulatory cholinergic receptor. The increase in CA secretion produced by glutamate was accompanied by both an increase in bisoxonol fluorescence, suggesting membrane depolarization, and by an increase in intracellular Ca2+ concentrations. Results obtained with image analysis on single cells indicated that the percentage of cells which respond to the stimulation of 50 µM of glutamate is 42%. From these results, we conclude that glutamate, through its four known glutamate receptors, can increase both basal and nicotine-evoked CA secretion in chromaffin cells by a process which involves membrane depolarization and an increase in intracellular calcium levels.
Molecular Cloning and Characterization of a Highly Basic Protein, IA-4, Expressed in Pancreatic Islets and Brain
Authors: Donadel Giulia , Marinos Nancy , DeSilva Mark G. , Lu Jia , Notkins Abner L. , Lan Michael S.
Published: April 2003

A substraction library was constructed from mouse insulinoma (βTC-1) and glucagonoma (αTC-1) cell lines. Differential screening and sequencing revealed a novel cDNA clone, IA-4, which was expressed in the islets of Langerhans and the brain. IA-4 cDNA is 1,007 bp in length and predicts a protein of 187 amino acids with a molecular mass of 19,940 D. Examination of the amino acid sequence showed a high content of arginine (18.7%), proline (14.4%), alanine (16.0%), leucine (13.4%) and glycine (9.6%). The deduced pI value is 12.5 indicating a highly basic protein. Northern blot analysis revealed a 1-kb mRNA highly expressed in brain, trigeminal ganglia and cell lines of neuroendocrine origin. Rabbit polyclonal antiserum raised against a synthetic IA-4 peptide, designated Pep-1, not only reacted with IA-4 recombinant protein, but also immunostained the islets of Langerhans and large neurons of the hippocampus, cerebral cortex, spinal cord, dorsal ganglia and Purkinje cells of the cerebellum. The high expression of IA-4 protein in neuroendocrine cells and its unique amino acid sequence suggest that IA-4 may have an important, but still undetermined, function in these special cell types.
Increase of Gonadotropin-Releasing Hormone Concentration in Pituitary Portal Blood after Substance P Administration in Male Rats
Authors: Walczewska Anna , Szkudlarek Urszula , Jakubowska-Naziemblo Barbara , Dziedzic Barbara , Traczyk Wladyslaw Z.
Published: April 2003

Substance P (SP) affects gonadotropin release from the anterior pituitary gland. In the present study we tested whether SP exerts this effect through GnRH release into pituitary portal blood in intact male rats (INT), orchidectomized rats with s.c. chronically implanted empty Silastic capsule (ORCX), testosterone capsule (ORCX + T), and 17β-estradiol capsule (ORCX + E2). The pituitary glands were exposed by the transpharyngeal approach under urethane-chloralose anesthesia. Then, the stalk portal vessels were cut and three 30-min portal blood samples were collected. Each first sample of blood was treated as a control before 0.2 ml injection of normal saline, 5 µg, or 25 µg of SP in 0.2 ml of normal saline into the internal carotid artery. GnRH concentration in the purified portal plasma were measured by RIA. Injection of SP into the internal carotid artery caused a significant increase in GnRH concentration in pituitary portal plasma only in INT rats. The higher dose of SP markedly increased GnRH concentration in the 1st blood sample (p < 0.001) and in the 2nd blood sample GnRH concentration was lower but still significant higher than prior SP injection (p < 0.05). The lower dose of SP increased GnRH concentration later, only in the 2nd portal blood sample after intracarotid SP injection (p < 0.001). Injection of normal saline had no effect on GnRH concentration in pituitary portal blood in INT rats. In ORCX, ORCX testosterone- and estrogen-implanted rats portal plasma GnRH concentrations were not changed significantly after injection of both doses of SP. These results indicate that SP stimulates GnRH release into pituitary portal blood and the influence of SP on GnRH neurons depends on the levels of circulating gonadal steroid hormones.
Effects of Ovariectomy on Cerebral Blood Flow of Rats
Authors: Holschneider Daniel P. , Scremin Oscar U.
Published: April 2003

Recent reports suggest that estrogens may enhance cognitive function in postmenopausal women and women suffering from dementia of the Alzheimer’s type. One of several proposed mechanisms of action of estrogen has been an improvement in cerebral blood flow (CBF). The current study examined the effects of estrogen deprivation resulting from ovariectomy on the CBF of rats using the quantitative autoradiographic 14C-iodoantipyrine technique. CBF was assessed in passively restrained, awake adult rats at 6 weeks following ovariectomy (n = 10) or sham surgery (n = 10). Rats demonstrated marked endometrial atrophy and a decrease in uterine weight (mean 78%) in response to ovariectomy. Ovariectomized animals did not differ from control animals both in the magnitude and the topography of cortical or subcortical CBF, including the medial preoptic area, amygdala, arcuate nucleus and anterior hypothalamus, areas previously associated with high estrogen binding. These results suggest that in young, surgically ovariectomized animals, hormonal factors do not significantly contribute to changes in basal CBF.
Effects of Dexamethasone and Alprazolam, a Benzodiazepine, on the Stimulatory Effect of Hexarelin, a Synthetic GHRP, on ACTH, Cortisol and GH Secretion in Humans
Authors: Arvat Emanuela , Maccagno Barbara , Ramunni Josefina , Di Vito Lidia , Gianotti Laura , Broglio Fabio , Benso Andrea , Deghenghi Romano , Camanni Franco , Ghigo Ezio
Published: April 2003

Hexarelin (HEX) is a synthetic GHRP which acts on specific receptors at both the pituitary and the hypothalamic level to stimulate GH release both in animals and in humans. Like other GHRPs, HEX possesses also acute ACTH and cortisol-releasing activity similar to that of hCRH. The mechanisms underlying the stimulatory effect of GHRPs on hypothalamo-pituitary-adrenal (HPA) axis are still unclear, although a CNS-mediated action has been demonstrated. In 6 normal healthy young women (26–34 years) we studied the effects on ACTH and cortisol secretion of HEX (2.0 µg/kg i.v. at 0 min) alone and preceded by dexamethasone (DEXA, 1 mg p.o. at 23.00 h on the previous night) or alprazolam (ALP, 0.02 mg/kg p.o. at –90 min), a benzodiazepine which binds to GABA receptors and possesses CRH-mediated inhibitory activity on HPA axis. ACTH and cortisol secretion after saline administration as well as the GH response to HEX alone and preceded by DEXA or ALP were also studied. HEX administration elicited an increase in ACTH (peak vs. baseline, mean ± SEM: 28.0 ± 6.7 vs. 11.7 ± 2.2 pg/ml, p < 0.05) and cortisol secretion (162.6 ± 15.0 vs. 137.7 ± 12.6 µg/l, p < 0.05). DEXA pretreatment strongly inhibited basal ACTH (3.2 ± 0.7 pg/ml, p < 0.01) and cortisol levels (11.3 ± 2.5 µg/l, p < 0.001) and abolished the ACTH and cortisol responses to HEX (3.6 ± 0.9 pg/ml, p < 0.01 and 10.7 ± 2.0 µg/l, p < 0.001), respectively. On the other hand, ALP pretreatment did not significantly modify basal ACTH (7.9 ± 2.0 pg/ml) and cortisol levels (127.6 ± 14.5 µg/l) but abolished the HEX-induced ACTH and cortisol secretions (8.6 ± 2.4 pg/ml, p < 0.05 and 111.0 ± 6.0 µg/l, p < 0.05), respectively. ACTH and cortisol levels after HEX when preceded by ALP overlapped with those recorded during saline. HEX induced a clear GH response (peak at 15 min vs. baseline: 65.5 ± 20.5 vs. 2.2 ± 0.7 µg/l, p < 0.03) which was blunted by ALP (peak at 15 min: 21.5 ± 5.5 µg/l, p < 0.05) while it was not modified by DEXA pretreatment (78.7 ± 7.6 µg/l). In conclusion, our present data demonstrate that the ACTH- and cortisol-releasing effect of HEX is abolished by either dexamethasone or alprazolam, a benzodiazepine, which is even able to blunt the GH-releasing activity of the hexapeptide. These findings suggest that, in physiological conditions, the stimulatory effect of GHRPs on HPA axis is sensitive to the negative glucocorticoid feedback and could be mediated by GABAergic mechanisms; the latter seem also involved in the GH-releasing activity of GHRPs.
Increased Expression of Magnocellular Vasopressin mRNA in Rats with Deoxycorticosterone-Acetate Induced Salt Appetite
Authors: Grillo Claudia A. , Saravia Flavia , Ferrini Monica , Piroli Gerardo , Roig Paulina , García Silvia I. , de Kloet E. Ronald , De Nicola Alejandro F.
Published: April 2003

The neuropeptides arginine vasopressin (AVP) and oxytocin (OT) have been implicated in the genesis of hypertension due to deoxycorticosterone acetate (DOCA)-salt treatment of uninephrectomized rats. In this work, we studied if DOCA treatment of intact rats in doses arousing a salt appetite (a prehypertensive state), modulated mRNA for AVP and OT in the hypothalamus. Male Sprague-Dawley rats were offered both tap water and 3% NaCl in separate bottles and received vehicle or subcutaneous injections of 10 mg DOCA on alternate days for 7 days (4 injections) or 17 days (9 injections). They developed a preference for 3% NaCl solutions 24–48 h after treatment. Brain slices from rats killed on the 8th or 18th day were exposed to 35S-labeled probes encoding prepro-AVP mRNA or OT mRNA, respectively. Expression of these mRNAs was measured in the magnocellular and parvocellular divisions of the paraventricular nucleus (PVN) and magnocellular cells of the supraoptic nucleus (SON). No changes were obtained in neuropeptide mRNA levels in the parvocellular division of the PVN between control and the two groups of DOCA-treated rats. However, DOCA-treated animals presented an increased number of grains per cell for AVP mRNA in the magnocellular division of the PVN and in magnocellular cells of the SON, as shown by group mean comparisons and frequency histograms. No changes were detected for OT mRNA. In a second series of studies, control or DOCA-treated rats were offered 3% NaCl or water as the only choice. Animals drinking 3% NaCl showed increased AVP and OT mRNA levels, whether they received DOCA or not. However, AVP mRNA levels in both nuclei were higher in DOCA-treated rats drinking 3% NaCl than in controls drinking salt solution. In comparison, control and DOCA-treated rats drinking water showed lower levels of AVP mRNA. OT mRNA levels in the SON remained unchanged in the same groups. The results suggest that in the magnocellular cells of the PVN and SON, increments in AVP mRNA are obtained following increments in salt intake produced by either mineralocorticoid treatment or exclusive salt drinking. In rats offered salt solution and water to drink, DOCA effects on AVP mRNA developed before changes occurred in serum sodium levels. Because combined DOCA + salt treatment induced a higher response in terms of AVP mRNA expression, we suggest that AVP could be a target of the central effects of the mineralocorticoid.
Role of Growth Hormone (GH)-Releasing Hormone and Somatostatin on Leptin-Induced GH Secretion
Authors: Carro E. , Señarís R.M. , Seoane L.M. , Frohman L.A. , Arimura A. , Casanueva F.F. , Diéguez C.
Published: April 2003

Leptin is a hormone secreted by the adipocytes that regulates food intake and energy expenditure. It is known that growth hormone (GH) secretion is markedly influenced by body weight, being suppressed in obesity and cachexia, and recent data have demonstrated that GH release is regulated by leptin levels. Although one of the sites of action of leptin is likely to be the hypothalamus, since leptin receptor mRNA is particularly abundant in several hypothalamic nuclei, the mechanisms by which leptin regulates GH secretion are not yet known. The aim of the present study was to investigate whether leptin could act at the hypothalamic level modulating somatostatin and GH-releasing hormone (GHRH) expression. The administration of anti-GHRH serum (500 µl, i.v.) completely blocked leptin-induced GH release in fasting rats. In contrast, the treatment with anti-somatostatin serum (500 µl, i.v.) significantly increased GH release in this condition. Furthermore, leptin administration (10 µg, i.c.v.) to intact fasting animals reversed the inhibitory effect produced by fasting on GHRH mRNA levels in the arcuate nucleus of the hypothalamus, and increased somatostatin mRNA content in the periventricular nucleus. Finally, leptin administration (10 µg, i.c.v.) to hypophysectomized fasting rats increased GHRH mRNA levels, and decreased somatostatin mRNA content, indicating an effect of leptin on hypothalamic GHRH- and somatostatin-producing neurons. These findings suggest a role for GHRH and somatostatin as mediators of leptin-induced GH secretion.
Regulation of Gonadal and Somatotropic Axis by Chronic Intraventricular Infusion of Insulin-Like Growth Factor 1 Antibody at the Initiation of Puberty in Male Rats
Authors: Pazos Fernando , Sánchez-Franco Franco , Balsa José , López-Fernandez Judith , Escalada Javier , Cacicedo Lucinda
Published: April 2003

There has been increasing experimental evidence to suggest that insulin-like growth factor 1 (IGF-I) may be one of the essential regulators in the reproductive system of the rat. IGF-I is synthesized in the hypothalamus and IGF-I immunoreactivity increases during puberty. Consequently we hypothesized that centrally located IGF-I might contribute to the initiation of puberty. Centrally located IGF-I was immunoneutralized to assess this hypothesis. Male Wistar rats, 28 days old, were infused intracerebroventricularly with specific purified IgGs from rabbit IGF-I antiserum (IGF-I-Ab). The intracerebroventricular administration of IGF-I-Ab resulted in a reduction in testicular weight and consequently in delayed pubertal development. There was also a reduction in serum testosterone, pituitary immunoreactive (IR) luteinizing hormone (LH) and serum IR follicle-stimulating hormone (FSH). The accumulation of βLH mRNA was not modified, whereas βFSH mRNA was increased. An increment in the serum growth hormone (GH) levels was also observed. There were no significant alterations in hypothalamic IR growth hormone releasing factor content, although IR somatostatin (SRIH) content was increased by IGF-I-Ab. The body weight gain remained unaltered. As a whole, our study suggests that centrally located IGF-I influences pubertal development, production and release of gonadotropins and supports the finding that endogenous centrally located IGF-I plays a role at the initiation of puberty in the male rat. It also gives support to the physiological role of centrally located IGF-I in the release of GH mediated by hypothalamic SRIH at the initiation of puberty.
Estrogenic Stimulation of Hypothalamic-Limbic System Metabolism in Ageing Diabetic C57BL/KsJ Mice
Authors: Garris David R.
Published: April 2003

The therapeutic influences of estrogen treatment on age- and diabetes-related declines in regional brain glucose utilization (RBGU) rates were evaluated in 8- to 20-week-old female C57BL/KsJ normal (+/?) and diabetic (db/db) mice. Following either oil vehicle (oil: 0.1 ml) or estradiol (E: 1 µg/3.5 days) treatments starting at 3 weeks of age, RBGU rates were subsequently determined at 8, 12, 16 and 20 weeks of age. A gradual decline in the basal rate of brain glucose utilization was observed in all control (oil- and E-treated) groups between 8 and 20 weeks. Expression of the hyperglycemic-obese diabetes syndrome in db/db mice resulted in a significant reduction in RBGU rates between 8 and 20 weeks relative to control values. In estrogen-sensitive hypothalamic, septal and amygdaloid regions, E therapy modulated RBGU rates in db/db mice relative to oil-treated diabetics, but did not significantly alter utilization rates in +/? mice. In cortical samples, E therapy had no significant influence on glucose utilization rates in either control or diabetic groups. A noticeable pattern of maturation-associated decline in CNS glucose utilization rates in all brain regions resulted in comparable regional metabolic indices being exhibited by all groups at 20 weeks of age, with the exception of the diabetes-associated exacerbation of RBGU rates in the oil-treated db/db group. These data demonstrate that the normal development-related decline in regional brain carbohydrate metabolism is accelerated by the diabetes syndrome, and that E therapy can modulate the syndrome-associated suppression of glucose utilization in steroid-sensitive CNS loci. These data suggest that the depressive influences of the diabetes syndrome on brain carbohydrate utilization rates may be therapeutically modified in recognized CNS regions possessing steroid-sequestering, metabolically responsive neurons.
Dehydroepiandrosterone Response to the Adrenocorticotropin Test and the Combined Dexamethasone and Corticotropin-Releasing Hormone Test in Patients with Multiple Sclerosis
Authors: Kümpfel Tania , Then Bergh Florian , Friess Elisabeth , Uhr Manfred , Yassouridis Alexander , Trenkwalder Claudia , Holsboer Florian
Published: April 2003

Basic and clinical research suggest that disturbed neuroendocrine function may be involved in the pathogenesis and course of autoimmune diseases including multiple sclerosis (MS). Dehydroepiandrosterone (DHEA) in this connection is of particular interest as it appears to have effects on the immune system. Moreover, DHEA levels are decreased in chronic inflammatory diseases. To further investigate the role of DHEA in MS, we administered the adrenocorticotropin (ACTH) stimulation test and the combined dexamethasone and corticotropin-releasing hormone (DEX-CRH) test to 24 patients with active MS (13 women, 11 men; age 39 ± 2 years, mean ± SEM; Expanded Disability Status Scale, EDSS score 4.4 ± 0.4, mean ± SEM; 12 with acute relapse, 12 with chronic progression) and to 18 healthy controls matched for age and sex (8 women, 10 men; age 37 ± 3 years). There were no statistically significant differences in the plasma cortisol response to ACTH between any groups. In the DEX-CRH test, plasma cortisol concentrations showed higher values before (DEX-pretreated) and after CRH stimulation in the MS patients than in the controls (AUCcortisol 738.3 ± 154.5 vs. 295.7 ± 55.8; p < 0.05), this finding was more pronounced in chronic progressive patients. DHEA concentrations were decreased in MS patients (AUC DHEA 14.4 ± 1.6 vs. 23 ± 2.4; p < 0.05) and cortisol/DHEA ratios were increased in the patients compared to the controls (p < 0.05). There was a positive correlation between the EDSS score and maximum cortisol/DHEA ratio (r = 0.45; p = 0.031). As with the hypothalamic-pituitary-adrenal axis system, our results suggest a dysfunction in the DHEA secretion in patients with MS.
Neuroendocrine Secretory Protein 55 (NESP55): Alternative Splicing onto Transcripts of the GNAS Gene and Posttranslational Processing of a Maternally Expressed Protein
Authors: Weiss Ulrike , Ischia Rudolph , Eder Susanne , Lovisetti-Scamihorn Paola , Bauer Richard , Fischer-Colbrie Reiner
Published: April 2003

Recent studies established a novel genomically imprinted gene located 45 kb upstream of the human GNAS1 locus. This locus encoded for the Neuroendocrine Secretory Protein with an apparent molecular weight of 55,000 (NESP55), which is transcribed exclusively from the maternal allele. We sequenced rat and human NESP55 and investigated tissue-specific splicing of its mRNA and posttranslational modifications of the protein in various tissues. Alternative mRNA splicing of NESP55 was analyzed by sequencing of cDNA clones, RT-PCR and Northern blotting. Two main splice variants, which were generated in a tissue-specific manner, were identified: The open reading frame encoding NESP55 was spliced onto exons 2–13 of Gsα in the adrenal medulla, pituitary and the brain. In addition, in the pituitary a second shorter, prominent mRNA transcript was generated by splicing of NESP55 onto exons 2, 3 and N1 of Gsα. Several of the cDNA clones isolated contained inverted repeats of 50–150 bp at their 5′ or 3′ termini, which might form hairpin stems and thus alter mRNA stability. The NESP55 open reading frame encoded a hydrophilic protein of 28,018 Da (human) and 29,218 Da (rat), respectively, which resembled the class of acidic, neuroendocrine secretory proteins collectively called chromogranins. NESP55 is highly conserved among mammalian species. It is posttranslationally acidified by the addition of keratan sulfate glycosaminoglycan chains and differentially processed by endopeptidases in various endocrine and neuronal tissues.
Acute-Stress-Induced Facilitation of the Hypothalamic-Pituitary-Adrenal Axis
Authors: Wong Y. Nancy , Cassano Jr. William J. , D’mello Anil P.
Published: April 2003

It has been hypothesized that the hypothalamic-pituitary-adrenal (HPA) axis responds to a stressor by secreting facilitatory and inhibitory factors. During a stressor, the relative magnitude of secretion of these factors determines the responsiveness of the HPA axis to a subsequent stressor. Previous studies have suggested that corticosterone (B) secreted during the first stressor is an inhibitory factor. We hypothesized that the transient removal of the inhibitory factor, B, during the first stressor would result in the secretion of only facilitatory factors. This would cause the HPA axis to exist in a state of hyperresponsiveness, and to hypersecrete corticotropin (ACTH) and B in response to a second stressor. Therefore, our primary objective was to demonstrate stress-induced facilitation of the HPA axis response to a subsequent stressor. Male Sprague-Dawley rats were subjected to a 1-hour physical immobilization stressor (IMM) or administered a single dose of ACTH on day 1. B response during these treatments was markedly but transiently attenuated with an 100 mg/kg i.p. dose of aminoglutethimide (AG). Twenty-four hours later, rats were subjected to an intraperitoneal saline injection stressor. B and ACTH levels were measured 15 min after the injection stressor. Rats treated with AG plus IMM on day 1 hypersecreted B and ACTH after the injection stressor on day 2. These results suggest that immobilization stress induces facilitation of both pituitary and adrenal responses. Exogenous administration of ACTH- to AG-pretreated rats on day 1, in lieu of immobilization stress, did not affect the responsiveness of the HPA axis on day 2. This suggests that ACTH secreted during the first stressor does not play an important role in acute-stress-induced facilitation.
Proenkephalin and Opioid μ-Receptor mRNA Expression in Ovine Hypothalamus across the Estrous Cycle
Authors: Walsh John P. , Rao Alexandra , Thompson Robert C. , Clarke Iain J.
Published: April 2003

The neural mechanism underlying the preovulatory surge of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) is thought to include reduced opioid inhibition of GnRH secretion (disinhibition). Possible mechanisms for disinhibition include reduced endogenous opioid peptide or receptor mRNA expression. Proenkephalin and opioid µ-receptor mRNA expression were measured by in situ hybridization using 35S-labeled cRNA probes and computer-assisted grain counting in hypothalamic nuclei of ovary-intact ewes (n = 4) killed on day 10 of the luteal phase or 24 or 48 h into the follicular phase. In a second experiment, proenkephalin and µ-receptor mRNA expression were compared in ewes killed on day 10 of the luteal phase or during the preovulatory LH surge. Cells expressing proenkephalin mRNA were more widely distributed in ovine hypothalamus than previously described. In the periventricular nucleus, there was a significant reduction in the grain count per cell and the number of labeled cells during the follicular phase and during the LH surge, as compared to the luteal phase. In the ventromedial hypothalamus, there was a significant reduction in the grain count per cell during the follicular phase and LH surge as compared to the luteal phase, but no change in the number of labeled cells. No differences in proenkephalin mRNA expression were detected in the medial septum, diagonal band of Broca, preoptic area, anterior hypothalamic area or paraventricular nucleus across the estrous cycle. Cells expressing opioid µ-receptor mRNA were also widely distributed. No difference in µ-receptor mRNA expression was detected in the medial septum, diagonal band, medial preoptic area, anterior hypothalamus or bed nucleus of the stria terminalis across the cycle. We conclude that in sheep, proenkephalin gene expression in the periventricular nucleus and ventromedial hypothalamus is reduced during the follicular phase and at the time of the LH surge. This may be part of the neural mechanism underlying the GnRH/LH surge in this species.