bluuebunny/crossref_metadata_2025 huggingface dataset:
Prenatal Diagnosis of Schizencephaly by Fetal Magnetic Resonance Imaging
Authors: Denis Delphine , Maugey-Laulom Brigitte , Carles Dominique , Pedespan Jean-Michel , Brun Muriel , Chateil Jean-François
Published: April 2003

Schizencephaly is a neuronal migration anomaly characterized by gray matter lined clefts extending from the ventricle to the cortical surface leading to specific lesions, well demonstrated by imaging. The lips of the clefts can be fused or separated. Prognosis is related to the extend of the involved cortex. Both genetic and acquired factors can be responsible for this pathology. Three cases of antenatal diagnosed open schizencephaly are reported. Two cases are unilateral and one is bilateral. A cerebral anomaly has been detected in all cases by routine ultrasonography (US) revealing a ventricular dilatation with cortical associated abnormalities. Prenatal magnetic resonance imaging (MRI) permitted the diagnosis in the 3 cases. All cases had led to abortion because of the importance of the cortical defect. The aim of this report is to point out the importance of fetal MRI in the diagnosis of migration disorder and to discuss the medical implications. Indeed, MRI is better suited than US for the prenatal diagnosis of schizencephaly, being able to detect normal and abnormal brain cellular migration, especially with fast imaging (HASTE sequences). With its multiplanar imaging capability, MRI demonstrates the cleft extending from the pial surface to the ventricular ependyma and thus provides characteristic diagnosis of this disorder. Moreover, ventricular dilatation, a frequent anomaly detected by US should be completed with MRI in order to research a neuronal migration disorder.
Murine Cytomegalovirus Homologues of Cellular Immunomodulatory Genes
Authors: Davis-Poynter Nicholas J. , Degli-Esposti Mariapia , Farrell Helen E.
Published: April 2003

The study of ‘molecular mimicry’ or ‘genetic piracy’, with respect to the utilisation of cellular genes captured and modified during the course of virus evolution, has been an area of increasing research with the expansion in virus genome sequencing. Examples of cellular immunomodulatory genes which have been captured from hosts have been identified in a number of viruses. This review concentrates upon studies of murine cytomegalovirus (MCMV), investigating the functions of viral genes homologous to G protein-coupled receptors, MHC class I and chemokines. The study of recombinant MCMV engineered with specific disruptions of these genes has revealed their significance during virus replication and dissemination within the host. In the case of the latter two classes of genes, evidence suggests they interfere with cellular immune responses, although the detailed mechanisms underlying this interference have yet to be delineated.
Update on Antiviral DNA Vaccine Research (1998–2000)
Authors: Schultz Jan , Dollenmaier Günter , Mölling Karin
Published: April 2003

DNA vaccines can induce protective cellular and humoral immune responses and have therefore been used during the last decade to develop vaccines against a variety of different pathogens. Because current antiviral vaccines predominantly generate humoral immunity, DNA immunization may be especially useful to provide long-term protection against viral diseases that also require cellular immunity (e.g. HIV). A significant number of articles published in the field of DNA vaccines are dealing with viral diseases, reflecting the need for better and alternative vaccination strategies against viruses. The success of DNA immunization depends on a variety of parameters (e.g. type of antigen, method of application and usage of adjuvants). Therefore, different strategies have been explored to modulate the induced immune response with respect to the requirements necessary to protect against a specific pathogen (e.g. induction of mucosal or cell-mediated immunity). The following article provides an update on different aspects of antiviral DNA vaccine research that have previously been reviewed by others.
Mechanism of Protection against Influenza A Virus by DNA Vaccine Encoding the Hemagglutinin Gene
Authors: Operschall E. , Pavlovic J. , Nawrath M. , Mölling K.
Published: April 2003

Influenza A virus with its two major antigenic surface proteins hemagglutinin (HA) and neuraminidase (NA) is a widely used model to study DNA immunizations in mice and other animals. Natural protection against influenza A virus infection is mediated by antibodies, which mostly are not protective against antigenic shift or drift variants of the original virus. Therefore, it would be a major task to induce a protective cellular immune re- sponse to more conserved proteins or epitopes. Injection of plasmid encoding a viral antigen is known to induce cellular as well as humoral immunity. In this study we investigate the mechanism of protection after intramuscular vaccination of C57Bl/6 mice with a DNA vaccine encoding HA of influenza A/PR/8/34. After a single injection, only a small percentage of mice survive the lethal challenge with homologous virus. The amount of protection can be doubled by applying a booster injection. Furthermore, by coinjection of plasmids encoding cytokines GM-CSF and IL-12, respectively, nearly all of the mice are protected. Mice with specific defects in the cellular immune response [perforin knockout (P–/–) mice] and in the humoral immune response [IgD/IgM knockout (µMT) mice], respectively, have been immunized with HA DNA with or without cytokine DNA. Protection could only be induced in P–/– mice, whereas µMT mice succumbed to the infection. Moreover, when µMT mice were infected with only 0.75 ×50% lethal dose they died all the same, whereby mice that had been depleted of CD8+ T cells before infection showed an even greater progression of illness. Altogether these results demonstrate that antibodies mediate protection after immunization with plasmid coding for HA of influenza A virus, and that booster immunizations and coinjection of plasmids encoding GM-CSF or IL-12 can improve this protection.
Inflammation in Chronic Venous Insufficiency: Is the Problem Insurmountable?
Authors: Takase Shinya , Delano Frank A. , Lerond Laurence , Bergan John J. , Schmid-Schönbein Geert W.
Published: April 2003

One of the hallmarks of venous insufficiency is an elevated venous pressure. While a number of mechanisms have been proposed for vascular and parenchymal cell damage following venous pressure elevation, such as white cell infiltration, a key question remains as to what degree venous occlusion and flow interruption per se may constitute a risk factor in venous disease. To gain an insight into this mechanism, we examined the effect of venous occlusion followed by reperfusion. A draining venule (circa 50 µm) in the rat mesentery was occluded with a micropipette (1 h) followed by reperfusion (1 h). The procedure serves to raise the microvascular pressure to about 31 mm Hg during the occlusion while the flow is completely stopped in the local venous and capillary network. Parenchymal cell death in the mesentery was monitored by propidium iodide (PI) labeling. The number of PI-positive cells significantly increased predominantly during reperfusion. A 1-week treatment with a micronized purified flavonoid fraction (100 mg/kg/day) served to significantly reduce parenchymal cell death as well as leukocyte rolling, adhesion to postcapillary venule, and migration into the tissue both during occlusion and reperfusion. The results indicate, that even in an initially symptomless tissue, flow reduction combined with microvascular pressure elevation during venous occlusion results in tissue damage not only during reperfusion (as in arterial occlusion) but also during occlusion.
Adhesion Molecule Expression in Postischemic Microvascular Dysfunction: Activity of a Micronized Purified Flavonoid Fraction
Authors: Korthuis Ronald J. , Gute Dean C.
Published: April 2003

Ischemia and reperfusion (I/R) induces neutrophil infiltration in skeletal muscle that is localized to the ischemic region. To transmigrate at ischemic regions, granulocytes must first arrest in the postcapillary venular segment of the microcirculation. Initially, leukocytes roll along the endothelium of these venules, a weak adhesive interaction that is mediated by the selectins (L-, E-, and P-selectin). Leukocyte rolling functions to slow the neutrophil during its transit through the microcirculation, thereby allowing it to monitor its local environment for the presence of activating factors arising from the ischemic tissues. When activated, the rolling granulocyte is rendered capable of forming the stronger adhesive interactions that allow the cell to become arrested in postcapillary venules in the ischemic region. These adhesive interactions are mediated by a leukocyte glycoprotein complex designated CD11/CD18 and intercellular adhesion molecule-1 (ICAM-1) expressed on endothelial cells. The stationary neutrophil uses the gradient in concentration of soluble chemoattractants liberated from ischemic tissues as a directional cue to move from the vascular to extravascular compartment, being guided in its transit across the endothelium by interactions with platelet endothelial cell adhesion molecule-1 (PECAM-1), an adhesive molecule localized to the interendothelial cleft. This paper reviews current understanding of the mechanisms underlying the establishment of leukocyte/endothelial cell interactions in postischemic skeletal muscle in terms of specific adhesion molecules that participate in neutrophil sequestration after I/R. Discovery of the molecular determinants of neutrophil/endothelial cell adhesion has uncovered potential mechanisms whereby agents exhibiting anti-adhesive properties may act. The micronized purified flavonoid fraction (450 mg diosmin, 50 mg hesperidin) prevents I/R-induced leukocyte adhesion in skeletal muscle. This anti-adhesive effect appears to be mediated at least in part by inhibition of induced expression of ICAM-1.
A Common 936 C/T Mutation in the Gene for Vascular Endothelial Growth Factor Is Associated with Vascular Endothelial Growth Factor Plasma Levels
Authors: Renner Wilfried , Kotschan Sabine , Hoffmann Christine , Obermayer-Pietsch Barbara , Pilger Ernst
Published: April 2003

Background: Vascular endothelial growth factor (VEGF) is an important regulator of angiogenesis. Strong interindividual variations of VEGF plasma levels have been reported previously. Aim of the present study was to search for mutations in the 3′ untranslated region (3′-UTR) of the VEGF gene and to analyze their relation to VEGF plasma levels. Methods: The complete 3′-UTR (nucleotide 700–2622) of the VEGF gene was screened for sequence variations by single-strand conformation polymorphism (SSCP) analysis. Frequencies of mutated alleles were determined in 119 healthy subjects; VEGF plasma levels were analyzed in a subgroup of 23 healthy men aged 18–36 years. Results: Three novel mutations (702 C/T, 936 C/T, 1612 G/A) were found, allele frequencies of 702T, 936T and 1612A were of 0.017, 0.160 and 0.471, respectively. VEGF plasma levels were significantly lower in carriers of the 936T allele (9.1 ± 2.7 pg/ml, mean ± SEM) than in noncarriers (28.0 ± 5.5 pg/ml, p = 0.033), whereas the 702 C/T and the 1612 G/A mutations showed no association with VEGF plasma levels. The 936 C/T exchange led to the loss of a potential binding site for transcription factor AP-4, although the functionality of this binding site remains unclear. Conclusion: We have found three common mutations in the VEGF gene; one of them, a 936 C/T exchange, may be an important determinant of VEGF plasma levels.
Scanning Laser-Doppler Flowmetry of Rat Cerebral Circulation during Cortical Spreading Depression
Authors: Nielsen Alexander Norup , Fabricius Martin , Lauritzen Martin
Published: April 2003

Scanning laser-Doppler flowmetry (SLDF) generates two-dimensional images of blood flow. This study compared SLDF to conventional laser-Doppler flowmetry (LDF) in the cerebral circulation. Test stimuli were episodes of cortical spreading depression (CSD) elicited in brains of halothane anaesthetised rats (n = 9). The LDF instrument used two wavelengths of laser light to record relative changes of cerebral blood flow (CBF) up to an approximate depth of 250 µm (543 nm) and 500 µm (780 nm). Under resting conditions, SLDF images showed a heterogeneous pattern of flow in pial vessels with high flow rates in arterioles, and lower rates in venules and small vessels (<30 µm). Arterioles constituted about 6%, venules 12% and small vessels 2% of the image area, while approximately 80% were background with a laser-Doppler signal corresponding to zero calibration. During CSD, the relative increase of area was largest for small vessels and less for venules and arterioles. Similar changes were observed for blood flow in the three vessel structures. For both wavelengths of LDF, flow changes correlated with SLDF (r ≈ 0.7). In conclusion, SLDF provides images of flow in pial vessels and capillaries at, or just beneath the cortical surface. SLDF and LDF are complementary, but cannot substitute for one another as they measure flow in different layers of the cortex.
Temporal Aspects of Ca2+ and Myosin Phosphorylation during Myogenic and Norepinephrine-Induced Arteriolar Constriction
Authors: Zou Hui , Ratz Paul H. , Hill Michael A.
Published: April 2003

Previous studies demonstrated that maintenance of steady-state myogenic tone requires Ca2+-dependent myosin phosphorylation. The present studies furthered these observations by examining temporal relationships among Ca2+, myosin phosphorylation and vessel diameter during acute increases in intraluminal pressure and norepinephrine stimulation. Rat cremaster muscle arterioles were cannulated and loaded with the Ca2+-sensitive indicator fura-2. The extent of myosin phosphorylation was measured using two-dimensional gel electrophoresis. Acute increases in intraluminal pressure caused a biphasic increase in intracellular Ca2+ ([Ca2+]i), characterized by a transient peak followed by a decline to a steady-state level which remained significantly higher than control values. Peak [Ca2+]i was significantly related to vessel distension and increased with the change in wall tension. Increased intraluminal pressure resulted in a monophasic increase in myosin phosphorylation that was significantly correlated with instantaneous wall tension. In general, norepinephrine induced larger [Ca2+]i transients and a biphasic myosin phosphorylation pattern. The results demonstrate: (a) major roles for Ca2+ and myosin phosphorylation in arteriolar myogenic and norepinephrine-induced responses; (b) that changes in Ca2+ and phosphorylation during a myogenic response are related to changes in wall tension, and (c) differences in Ca2+ and phosphorylation patterns between the two modes of contraction reflect possible differences in underlying signaling mechanisms. The data further emphasize that spontaneous arteriolar tone represents a state of maintained smooth muscle activation that requires increases in [Ca2+]i and myosin light-chain phosphorylation.
Electrophysiological Basis of Arteriolar Vasomotion in vivo
Authors: Bartlett Iain S. , Crane Glenis J. , Neild Timothy O. , Segal Steven S.
Published: April 2003

We tested the hypothesis that cyclic changes in membrane potential (Em) underlie spontaneous vasomotion in cheek pouch arterioles of anesthetized hamsters. Diameter oscillations (∼3 min–1) were preceded (∼3 s) by oscillations in Em of smooth muscle cells (SMC) and endothelial cells (EC). Oscillations in Em were resolved into six phases: (1) a period (6 ± 2 s) at the most negative Em observed during vasomotion (–46 ± 2 mV) correlating (r = 0.87, p < 0.01) with time (8 ± 2 s) at the largest diameter observed during vasomotion (41 ± 2 µm); (2) a slow depolarization (1.8 ± 0.2 mV s–1) with no diameter change; (3) a fast (9.1 ± 0.8 mV s–1) depolarization (to –28 ± 2 mV) and constriction; (4) a transient partial repolarization (3–4 mV); (5) a sustained (5 ± 1 s) depolarization (–28 ± 2 mV) correlating (r = 0.78, p < 0.01) with time (3 ± 1 s) at the smallest diameter (27 ± 2 µm) during vasomotion; (6) a slow repolarization (2.5 ± 0.2 mV s–1) and relaxation. The absolute change in Em correlated (r = 0.60, p < 0.01) with the most negative Em. Sodium nitroprusside or nifedipine caused sustained hyperpolarization and dilation, whereas tetraethylammonium or elevated PO2 caused sustained depolarization and constriction. We suggest that vasomotion in vivo reflects spontaneous, cyclic changes in Em of SMC and EC corresponding with cation fluxes across plasma membranes.
Extended Prophylaxis against Venous Thromboembolism following Total Hip and Knee Replacement
Authors: Hull Russell D. , Pineo Graham F.
Published: April 2003

The recently reported reductions in the incidence of post-operative venous thromboembolism (VTE) are related to the widespread use of prophylactic anticoagulants. Many uncertainties remain with regard to the most effective ways to use thromboprophylaxis, however. The trend towards shorter hospital stays means that patients may receive less than the recommended 7–10 days of prophylaxis. Prolonged periods of thromboprophylaxis may be beneficial for patients at high risk of post-operative VTE, such as those undergoing major orthopaedic surgery. The relative rarity of symptomatic deep vein thrombosis and pulmonary embolism means that very large patient populations are required for studies that rely on clinical endpoints, but studies using venographic endpoints have shown 28–35 days of prophylaxis with low-molecular-weight heparin to be more effective than 10–14 days. Other factors that may influence the efficacy of thromboprophylaxis include the timing of the first injection and the choice of agent.
Aspirin in the Treatment and Prevention of Cardiovascular Disease
Authors: Gaziano J. Michael , Skerrett P.J. , Buring Julie E.
Published: April 2003

Randomized trials of aspirin have been conducted in three main populations: patients with evolving acute myocardial infarction (MI), patients with a history of cardiovascular disease and apparently healthy subjects. Initiating aspirin therapy within 24 h after the onset of symptoms of an acute MI results in conclusive reductions in the risk of nonfatal reinfarction, nonfatal stroke and total cardiovascular death. In a wide range of patients with prior occlusive cardiovascular disease, aspirin reduces the risks of nonfatal MI, nonfatal stroke and vascular death. In primary prevention trials, aspirin has been shown to reduce the risk of a first MI in men; limited data make it difficult to draw conclusions regarding its effect on stroke and total cardiovascular death. Randomized data from studies in women and other populations are lacking. Until more data are available, the decision to use aspirin in primary prevention should be based on the clinical judgment of the physician and it should be used as an adjunct in the management of other cardiovascular disease risk factors.
Podocyte Injury Predicts Prognosis in Patients with IgA Nephropathy Using a Small Amount of Renal Biopsy Tissue
Authors: Hishiki Toshimasa , Shirato Isao , Takahashi Yutaka , Funabiki Kazuhiko , Horikoshi Satoshi , Tomino Yasuhiko
Published: April 2003

To predict the progression in patients with IgA nephropathy, we analyzed glomerular lesions except for sclerosis, adhesion and/or crescents in 34 patients with this disease by morphometric analysis. Levels of urinary protein excretion (UP), creatinine clearance (Ccr), serum creatinine (sCr) and mean blood pressure (MBP) at the time of renal biopsy were used as the clinical parameters. The slope of 1/sCr was also used as a prognostic parameter. Renal specimens were obtained by echo-guided biopsy. In PAS-stained light microscopic renal sections, three midsections of open glomeruli were selected and photographed. Stereologic estimation was performed as follows: absolute values of glomerular volume (VG), glomerular surface area (SG), podocyte and nonpodocyte cell number per glomerulus (NG(pod) and NG(Non-pod)), glomerular surface area covered by one podocyte SG/NG(pod)) and glomerular volume occupied by one nonpodocyte cell (VG/NG(Non-pod)). There was a significant correlation between the levels of UP and the change of podocyte injury parameters (NG(pod) and SG/NG(pod)) or NG(Non-pod). NG(pod) was negatively but SG/NG(pod) and NG(Non-pod) were positively correlated with UP. SG/NG(pod) or NG(Non-pod) was correlated with MBP. NG(pod), SG/NG(pod), NG(Non-pod), UP or MBP was significantly correlated with the slope of 1/sCr. High specificity was observed for NG(pod), SG/NG(pod) and MBP. High sensitivity was also observed for NG(Non-pod) and UP. It appears that podocyte injury might provide additional prognostic information in patients with IgA nephropathy.
Pattern of Candidiasis in the Newborn: A Study from Kuwait
Authors: Al-Essa Mazen , Khan Ziauddin , Rashwan Nabil , Kazi Ahmed
Published: April 2003

Objectives: To determine the rate and pattern of Candida infection in a large neonatal unit in Kuwait. Methods: A prospective study of all newborn infants who were admitted to the neonatal intensive care unit (NICU) at Maternity Hospital in Kuwait during the year of 1997 and who were suspected of having Candida infection were collected and analyzed. Method of selection of neonates, laboratory parameters and possible risk factors of the infection were identified and defined. Results:Candida infection was recognized in 22 (8.4%) cases out of 263 total infants admitted to the NICU. All the proven cases originated from 168 infants of birth weight less than 2,000 g with an incidence of 13%. In addition, Candida infection was suspected and treated without positive culture in 15 infants (5.7%). Cases with proven Candida sepsis had longer mean duration of endotracheal intubation (p < 0.03) and total parenteral nutrition (p < 0.03) and more episodes of concomitant bacterial infection (p < 0.01) compared to infants with suspected candidiasis. Conclusion: For an early diagnosis of candidiasis, a high index of suspicion in septic low-birth weight infants is always warranted since the clinical and laboratory diagnostic parameters are difficult to differentiate between suspected and proven cases.
Effective Method of Teaching Psychiatry to Undergraduate Medical Students: The Student Perspective
Authors: Fido Abdullahi , Al-Kazemi Raghad
Published: April 2003

Objectives: A search of the literature revealed that there are no studies of the effectiveness of teaching strategies from the medical students’ perspective. This study aims to explore medical students’ views on various teaching methods in psychiatry. Materials and Methods: A questionnaire describing several learning methods including clinical or bedside teaching, independent study, lectures, teaching aids, verbal/nonverbal behavior, and small-group teaching was administered to sixth-year medical students of the Faculty of Medicine, Health Sciences Center, Kuwait University. Results: Eighty-three percent of the students surveyed thought that well-delivered lectures were the most preferable learning method. Fifty-five percent agreed that live patient presentations were the most effective teaching aid. Independent study and small-group teaching were negatively viewed by 75% of the students. Slides/overheads and video presentations were evaluated by students as the last useful teaching methods. Factors cited as helpful in teaching included an enthusiastic interactive lecturer, a clear, audible voice, and visual teaching materials. Conclusion: This finding suggests that medical students are able to differentiate between effective and ineffective teaching methods in psychiatry and because of this they remain among the keenest critics of the education they receive.
Development of the Vestibular System
Authors: Lai C.H. , Chan Y.S.
Published: April 2003

This review mainly focuses on the development of the vestibular system in humans and other mammals, but reference is made to anurans and other species where applicable. In the first section, the steps involved in the development of undifferentiated cells into mature vestibular receptors are analysed. Available data indicate that in humans, maturation of the vestibular receptor and its afferent innervations involves a similar sequence of events as in other mammalian species. In the second section, morphological and physiological aspects of the maturation of the central vestibular system are presented. Undifferentiated neuron precursors have been identified in specific segregrated domains of the hindbrain neural tube, and these can develop into secondary vestibular neurons with unique properties. Several neuronal populations in the vestibulospinal and vestibulo-ocular pathways have been found to correlate with rhombomeric domains at early embryonic stages. In rodents, the vestibular system continues to develop postnatally in terms of morphology and function until it achieves its final form. The postnatal changes in the properties of vestibular nuclear neurons are chronologically matched with structural changes and serve to prime the development of vestibular-induced reflexes.
Catecholamine, Indoleamine and Corticosteroid Responses in Mice Bearing Tumors
Authors: Chuluyan H. Eduardo , Wolcott R. Michael , Chervenak Rob , Dunn Adrian J.
Published: April 2003

The neurochemical and endocrine responses to inoculation of mice with the murine lymphoma cell line AW5E was studied. This cell line was chosen because it is NK cell lysis resistant and thus does not induce a normal immune response. Immune activation has long been known to be a potent stimulator of the hypothalamo-pituitary-adrenocortical (HPA) axis as well as brain catecholamine and indoleamine metabolism, involving increases in the brain concentrations of catabolites of norepinephrine (NE) and serotonin (5-HT), as well as free tryptophan. Mice injected intravenously with AW5E tumor cells exhibited small increases in plasma corticosterone and hypothalamic NE and 5-HT catabolites one day after injection. There were no significant changes after 6 or 8 days, but a sustained increase in hypothalamic NE and 5-HT metabolism appeared 10 days after injection. There were similar, but more limited changes in the brain stem and prefrontal cortex. On the last day tested (day 14), plasma corticosterone was slightly elevated, as were hypothalamic dopamine, NE and 5-HT catabolites and tryptophan. These results indicate that inoculation with AW5E tumor cells increases brain catecholamine and serotonin metabolism, the hypothalamus being the most sensitive region. The most marked increases occurred in the few days preceding death, and thus may be associated with the pathology of the tumor growth.
Decrease in Brain Cytochrome P450 Enzyme Activities during Infection and Inflammation of the Central Nervous System
Authors: Monshouwer Mario , Agnello Davide , Ghezzi Pietro , Villa Pia
Published: April 2003

The effect of infection and inflammation of the central nervous system (CNS) on cytochrome-P450-dependent activities in brain, spinal cord and liver microsomes was determined. For this, two models were used: (1) the intracerebroventricularly injected lipopolysaccharide (LPS) model and (2) the experimental auto-immune encephalomyelitis (EAE) model. In the LPS model, aminopyrine N-demethylase (AMND) and ethoxycoumarin O-deethylase (ECOD) activities (both P450 dependent) were significantly decreased (35 and 20%, respectively) in brain microsomes. In the EAE model, only ECOD activity was significantly lower (18%). In the liver, a decrease in total P450, AMND and ECOD activities was only observed in the LPS model. In both models, tumour necrosis factor (TNF) was significantly elevated in brain and spinal cord tissues. In serum, TNF was only detectable in the LPS model. It is concluded that an infection or inflammation located in the CNS, which is accompanied by high TNF levels, results in a decrease in P450-dependent metabolism not only in the liver but in the brain as well.
Glucocorticoid Regulation of Hypothalamic Proopiomelanocortin
Authors: Wardlaw Sharon L. , McCarthy Kieran C. , Conwell Irene M.
Published: April 2003

Although glucocorticoids clearly inhibit proopiomelanocortin (POMC) gene transcription and peptide synthesis in the anterior pituitary, the effects of glucocorticoids on POMC in the hypothalamus are still unclear, even though most POMC neurons in the arcuate nucleus are known to have glucocorticoid receptors. In this study, we have therefore examined the effect of adrenalectomy (ADX) and glucocorticoid replacement on POMC mRNA and peptide (β-EP and α-MSH) levels in the medial basal hypothalamus (MBH) of the rat. POMC mRNA was measured by a sensitive solution hybridization S1 nuclease protection assay, and β-EP and α-MSH were measured by radioimmunoassay. In a first experiment, animals were studied 7 days after ADX or sham surgery. The mean POMC mRNA concentration was 1.01 ± 0.14 pg/µg RNA (means ± SE) in the intact animals and decreased to 0.55 ± 0.07 pg/µg RNA in the MBH of the ADX animals (p < 0.005). β-EP levels decreased in parallel from 4.30 ± 0.18 to 3.36 ± 0.11 ng/mg protein (p < 0.001); α-MSH levels decreased from 3.25 ± 0.21 to 2.41 ± 0.16 ng/mg protein (p < 0.005). In a second experiment, animals were studied 2 weeks after ADX. POMC mRNA levels again fell significantly from 1.15 ± 0.19 pg/µg RNA in the intact animals to 0.51 ± 0.06 pg/µg in the ADX animals (p < 0.01). β-EP levels fell also, but this was not significant. In a third experiment, all animals underwent ADX, and half of them received daily subcutaneous injections of dexamethasone (20 µg). Nine days after ADX, the mean POMC mRNA level was 0.66 ± 0.04 pg/µg RNA in the saline-treated animals and increased to 0.98 ± 0.08 pg/µg RNA in the dexamethasone-treated animals (p < 0.005). A parallel increase in β-EP levels from 5.03 ± 0.41 to 6.01 ± 0.53 ng/mg protein was also noted, but this was not statistically significant. We conclude that POMC gene expression is significantly inhibited in the MBH at 1 and 2 weeks after ADX. This effect was reversed by glucocorticoid replacement with doses close to the physiological range. The parallel changes in POMC mRNA and peptide levels strongly suggest that, in contrast to the anterior pituitary, low doses of glucocorticoids stimulate the biosynthesis of POMC in the MBH of ADX rats.
Effects of Galanin and the Galanin Receptor Antagonist Galantide on Plasma Catecholamine Levels during a Psychosocial Stress Stimulus in Rats
Authors: Ceresini Graziano , Sgoifo Andrea , Freddi Marilena , Musso Ezio , Parmigiani Stefano , Del Rio Graziano , Valenti Giorgio
Published: April 2003

The aim of this study was to investigate the role played by the neuropeptide galanin (GAL) in the regulation of sympathoadrenal function. We evaluated the effects of rat GAL (rGAL) and of the putative GAL receptor antagonist galantide (GLT) on epinephrine (E) and norepinephrine (NE) plasma levels in conscious freely moving male rats, during a psychosocial stress condition. Four groups of male rats were challenged by a stress stimulus, obtained by exposing the animals to a resident conspecific fighter (intruder model), following an intravenous injection with (1) rGAL + saline (SAL), (2) GLT + SAL, (3) rGAL + GLT, or (4) SAL + SAL. Plasma levels of both E and NE were also measured in an additional group of male rats not exposed to any stressor stimulus. The results (mean ± SEM) showed that rats exposed to the stressor stimulus (intruder rats) exhibited a significant increase above baseline in circulating levels of both E (peak values of 834.13 ± 115.13 pmol/l vs. basal values of 309.31 ± 32.93 pmol/l; p < 0.01) and NE (peak values of 5,299.03 ± 450.62 pmol/l vs. basal values of 2,798.24 ± 311.56 pmol/l; p < 0.01) in comparison to control, nonstressed rats. The comparison of the areas under the curve response (AUC) among treatments in the intruder rats revealed that rGAL + SAL injections resulted in a further increase in E levels when compared to SAL + SAL treatment (AUC values: 8.26 ± 0.64 vs. 25.38 ± 5.52 nmol/l/20 min in SAL + SAL vs. rGAL + SAL treatment, respectively; p < 0.02). No significant changes in stress-induced E plasma levels were found following GLT + SAL treatment in comparison to SAL + SAL injections. When the intruder rats were submitted to rGAL + GLT injections, the increments in E levels were found to be higher than those observed following SAL + SAL treatment (AUC values: 8.26 ± 0.64 vs. 36.00 ± 13.76 nmol/l/20 min in SAL + SAL vs. rGAL + GLT treatment, p < 0.03); however, the values were not significantly different from those observed in rGAL + SAL-injected rats. No significant changes in stress-induced NE levels were found in either treatment group when compared to SAL + SAL-injected intruder rats. The results of this study demonstrate that rGAL administration leads to an increase in the E response to the stress stimulus without any effect on NE response. Galantide does not affect either the physiological stress-induced elevation of plasma catecholamines or the effects of rGAL on E plasma levels in response to stress. Therefore, GLT does not appear to behave as a GAL receptor antagonist in the regulation of sympathoadrenal function in rats.
Blockade of the Oestrogen-Induced Luteinizing Hormone Surge in Ovariectomized Ewes by a Highly Selective Opioid µ-Receptor Agonist: Evidence for Site of Action
Authors: Walsh John P. , Clarke Iain J.
Published: April 2003

Endogenous opioid systems in the hypothalamus inhibit gonadotropin-releasing hormone (GnRH) secretion, and a reduction in this inhibitory input (disinhibition) is thought to be part of the neural mechanism of the preovulatory GnRH/luteinizing hormone (LH) surge. We showed previously that intracerebroventricular infusion of the highly specific opioid µ-receptor agonist DAMGO delayed the oestrogen-induced LH surge in ovariectomized (OVX) ewes, whereas both δ- and ĸ-agonists were ineffective. The aim of the present study was to establish the anatomical site of this effect. The most likely hypothalamic sites of action are the medial preoptic area (MPOA), where most GnRH perikarya are located in sheep, and/or the median eminence (ME), where GnRH fibres terminate on hypophysial portal blood vessels. Conscious, unrestrained OVX ewes with permanent bilateral guide tubes implanted into either the MPOA or the mediobasal hypothalamus (MBH), close to the ME, were injected (im) with oestradiol benzoate (EB) 50 µg (t = 0 h). In this model, EB elicits a time-delayed surge in LH secretion after 13–19 h. Jugular venous blood was sampled at half-hourly intervals from –2 to 0 h, and from 10 to 26 h. From 12 to 20 h, bilateral infusions of either the highly specific opioid µ-agonist DAMGO (40 nmol/h bilaterally) or saline were given into the MPOA or MBH at 2.5 µl/h. Guide tube placements were confirmed histologically. The mean (± SEM) time to the onset of the LH surge was significantly (p < 0.01) increased in the animals (n = 9) that received DAMGO infusion into the MPOA (20.5 ± 1.4 vs. 15.7 ± 0.6 h in the saline-infused controls). The effect was clearly apparent in 6/9 of the DAMGO-infused animals. The mean (± SEM) time to LH surge onset was also significantly (p < 0.01) increased in the animals (n = 8) that received DAMGO infusion into the MBH (19.7 ± 1.2 vs. 14.3 ± 0.5 h). In this case, the effect was clearly apparent in 4/8 of the DAMGO-infused animals. We conclude that bilateral infusion of DAMGO into either the MPOA or the MBH can delay the EB-induced LH surge in OVX ewes. These data provide further evidence for dual hypothalamic sites of opioid regulation of GnRH secretion, and are consistent with the hypothesis that disinhibition from opioid tone at both the MPOA and MBH/ME is permissive of the preovulatory GnRH/LH surge.
Evidence for a Role of Bradykinin Neurons in the Control of Gonadotropin-Releasing Hormone Secretion
Authors: Shi Beien , Mahesh Virendra B. , Bhat Ganapathy K. , Ping Lin , Brann Darrell W.
Published: April 2003

The present study provides evidence of a novel neuronal pathway for the control of GnRH secretion involving bradykinin neurons. Bradykinin neurons were shown by immunohistochemistry to be densely localized in several regions of the brain including the cortex, hippocampus and supraoptic nucleus, as well as two regions critical in the control of GnRH secretion, the organum vasculosum of the lamina terminalis and arcuate nucleus. Bradykinin dose-dependently stimulated GnRH release from male and proestrous female rat hypothalami in vitro. Antagonist studies revealed that bradykinin effects are mediated by the bradykinin B2 receptor. The effect of bradykinin on GnRH release is not mediated by the classical major transmitter, glutamate, as glutamate antagonists had no effect on bradykinin stimulation of GnRH release. Rather, bradykinin appears to act directly on the GnRH neuron as bradykinin stimulated GnRH release directly from immortalized GnRH (GT1-7) neurons in vitro, and immunoblot studies revealed that the bradykinin B2 receptor is present in GT1-7 neurons. The bradykinin B2 receptor was also demonstrated in the rat hypothalamus and pituitary by immunoblotting. Bradykinin-induced exocytosis of GnRH appears to involve activation of the PKC signaling pathway, as a PKC inhibitor blocked bradykinin-induced GnRH release. Finally, bradykinin neurons appear to be important mediators of steroid signals in the hypothalamus to produce the LH surge, as central administration of a B2 antagonist, but not a B1 antagonist, significantly attenuated the steroid-induced LH surge in the ovariectomized female rat.
Acute Estradiol and Progesterone Administration Reduced Cardiovascular and Catecholamine Responses to Mental Stress in Menopausal Women
Authors: Del Rio Graziano , Velardo Antonino , Menozzi Renata , Zizzo Giuseppe , Tavernari Valeria , Venneri Maria Grazia , Marrama Paolo , Petraglia Felice
Published: April 2003

Steroid hormones are involved in the regulation of sympathoadrenal activity. Since the effect of sex steroids on the cardiovascular system and catecholamine secretion could also be exerted through an acute, nongenomic mechanism, we have studied the response to mental stress (color word test, CWT) in a group of 15 menopausal women during estrogen (100 µg of estradiol by patch), progesterone (100 mg i.m.) or placebo administration. Systolic blood pressure (SBP) increased during CWT in the three sessions (F = 11.0, p < 0.001) but the area under the curve of SBP was higher during placebo (2,855 ± 131 mm Hg·min) than during estradiol (2,585 ± 139 mm Hg·min) and progesterone (2,553 ± 179 mm Hg·min, p < 0.05 for both). Plasma epinephrine increased during CWT in the three sessions (F = 31.1, p < 0.001) and the plasma epinephrine response to mental stress was higher during placebo than during estradiol administration (F = 4.3, p < 0.01). The area under the curve of epinephrine was 10,342 ± 1,348 pmol/min·l during placebo and 7,280 ± 818 pmol/min·l during estradiol (p < 0.03). The plasma glycerol levels at the end of CWT were higher during placebo (0.26 ± 0.04 nmol/l) than during estradiol (0.19 ± 0.03 mmol/l) and progesterone (0.17 ± 0.04 mmol/l) administration (p < 0.05 for both). No significant differences were found in the responses of diastolic blood pressure, heart rate, norepinephrine and cortisol to mental stress during placebo and estradiol or progesterone administration. This study demonstrates that acute steroid administration is able to modify the cardiovascular and catecholamine response to mental stress in menopausal women.
Characterization of the Dopaminergic Input to the Pituitary Gland throughout the Estrous Cycle of the Rat
Authors: DeMaria Jamie E. , Livingstone John D. , Freeman Marc E.
Published: April 2003

Changes in the concentrations of dopamine (DA) and its major metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were characterized in the pituitary gland throughout the 4-day estrous cycle of the rat. Female rats were sacrificed at 2- to 3-hour intervals throughout each day of the 4-day estrous cycle. Pituitary glands were removed, and the concentrations of DA and DOPAC were determined by high-performance liquid chromatography coupled to electrochemical detection. The concentration of prolactin (PRL) in serum from these same animals was determined by radioimmunoassay. The concentration of DA in the anterior lobe was constant throughout most of the 4-day estrous cycle. Prior to initiation of the proestrous surge of PRL, there were significant (p <0.05) decreases in the concentrations of both DA and DOPAC in the anterior lobe which returned to elevated baseline levels just prior to the termination of the proestrous surge of PRL. The concentrations of DA and DOPAC in the intermediate lobe exhibited a daily rhythm. However, in the intermediate as well as in the anterior lobe, there were significant (p < 0.001) decreases in the concentrations of both DA and DOPAC, coincident with the initiation of the proestrous surge of PRL. Similarly, coincident with the peak of the proestrous surge of PRL, there were significant (p < 0.001) increases in the concentrations of DA and DOPAC in the intermediate lobe, followed by a return to basal levels and resumption of the daily rhythm. The pattern of the concentrations of DA and DOPAC in the neural lobe was also daily in nature, with peaks occurring between 13.00 and 15.00 h each day of the 4-day estrous cycle. These data, taken together: (1) confirm that a decrease of the concentrations of DA and DOPAC occurs in the anterior lobe prior to the proestrous surge of PRL; (2) reveal that DA is released in a daily pattern at intermediate and neural lobes, and (3) suggest an apparent role for DA released to the intermediate lobe in the regulation of the proestrous surge of PRL.
Bromocriptine Reduces Obesity, Glucose Intolerance and Extracellular Monoamine Metabolite Levels in the Ventromedial Hypothalamus of Syrian Hamsters
Authors: Luo Shuqin , Meier Albert H. , Cincotta Anthony H.
Published: April 2003

We examined whether reductions in body fat stores and insulin resistance in Syrian hamsters induced by bromocriptine are associated with reductions in daily norepinephrine (NE) and serotonin activities as indicated by their extracellular metabolite levels in the ventromedial hypothalamus (VMH). High levels of these monoamines within the VMH have been suspected to induce obesity and insulin resistance. Microdialysate samples from the VMH of freely moving obese male hamsters (BW: 208 ± 5 g) were collected hourly over a 25-hour period before bromocriptine treatment, during the first day of and after 2 weeks of bromocriptine treatment (800 µg/animal daily, i.p.), and body composition and glucose tolerance analyses were conducted before and after 2 weeks of treatments. The microdialysate samples were analyzed by HPLC for metabolites of serotonin: 5-hydroxy-indoleacetic acid (5-HIAA), NE: 3-methoxy-4-hydroxy-phenylglycol (MHPG), and dopamine: homovanillic acid (HVA). Bromocriptine treatment for 14 days significantly reduced body fat by 60% and areas under the glucose and insulin curves during a glucose tolerance test by 50 and 46%, respectively. Concurrently, extracellular VMH contents of 5-HIAA, MHPG, and HVA were reduced by 50, 29 and 66%, respectively (p < 0.05). Similarly, VMH 5-HIAA and MHPG contents were 48 and 44% less, respectively (p < 0.05), in naturally glucose-tolerant hamsters compared with naturally glucose-intolerant hamsters. Bromocriptine induced reductions of body fat, and improvements in glucose intolerance may result in part from its ability to decrease serotonin and NE activities in the VMH.
Food Deprivation Decreases mRNA and Activity of the Rat Dopamine Transporter
Authors: Patterson Terrell Ann , Brot Michelle D. , Zavosh Aryana , Schenk James O. , Szot Patricia , Figlewicz Dianne P.
Published: April 2003

We have hypothesized that the midbrain dopamine (DA) neurons are a target for insulin action in the central nervous system (CNS). In support of this hypothesis, we have previously demonstrated that direct intracerebroventricular infusion of insulin results in an increase in mRNA levels for the DA reuptake transporter (DAT). In this study, 24- to 36-hour food deprivation was used as a model of decreased CNS insulin levels, to test whether DAT mRNA levels, DAT protein concentration or DAT functional activity would be decreased. DAT mRNA levels, assessed by in situ hybridization, were significantly decreased in the ventral tegmental area/substantia nigra pars compacta (VTA/SNc) (77 ± 7% of controls, p < 0.05) of food-deprived (hypoinsulinemic) rats. Binding of a specific high-affinity DAT ligand (125I-RTI-121) to membranes from brain regions of fasted or free-feeding rats provided an estimate of DAT protein, which was unchanged in both of the major terminal projection fields, the striatum and nucleus accumbens (NAc). In addition, we utilized the rotating disk electrode voltametry technique to assess possible changes in the function of the DAT in fasting (hypoinsulinemic) rats. The Vmax of DA uptake was significantly decreased (87 ± 7% of control, p < 0.05), without a change in the Km of uptake, in striatum from fasted rats. In vitro incubation with a physiological concentration (1 nM) of insulin resulted in an increase of striatal DA uptake to control levels. We conclude that striatal DAT function can be modulated by fasting and nutritional status, with a contribution by insulin.
Effects of Diabetes and Estradiol on Norepinephrine Release in Female Rat Hypothalamus, Preoptic Area and Cortex
Authors: Karkanias George B. , Morales José C. , Etgen Anne M.
Published: April 2003

These studies determined whether diabetes and estradiol treatment altered norepinephrine (NE) release from hypothalamus, preoptic area (POA), and cortical slices from ovariectomized (OVX) female rats. Animals were sacrificed 12 days after the onset of streptozotocin-induced diabetes and 48 h following vehicle or estradiol injection. Brain slices were preloaded with 3H-NE, and release was evoked twice (S1 and S2) by electrical stimulation. Diabetes increased hypothalamic NE release during S1 regardless of the administration of vehicle or estradiol. Neither estradiol treatment nor diabetes alone affected NE release during S2 in the hypothalamus or POA. Estradiol treatment elevated NE release in the POA during S2 but only in diabetic animals. Moreover, estradiol elevated cortical NE release during S2 regardless of the presence or absence of disease. We also examined whether α2-adrenoceptor regulation of NE release was influenced by diabetes or hormone treatment. Enhancement of NE release by α2-adrenoceptor antagonism was evident in all 3 brain regions. However, α2-adrenoceptor regulation of NE release was unaffected by diabetes and hormone treatment. These findings suggest that diabetes alters NE release in the hypothalamus/POA of female rats. Additionally, this work identifies a novel action of estradiol to enhance stimulated NE release in the cortex of female rats.
Preferential Expression of sst2A over sst2B Somatostatin Receptor Splice Variant in Rat Brain and Pituitary
Authors: Sarret Philippe , Botto Jean-Marie , Vincent Jean-Pierre , Mazella Jean , Beaudet Alain
Published: April 2003

The expression of sst2A and sst2B somatostatin (SRIH) receptor splice variants was examined by polymerase chain reaction (PCR) in rat brain and pituitary. Two sets of primers chosen to recognize either both sst2A and sst2B or only the sst2B transcript yielded bands of the size predicted from the cloned sst2A and sst2B sequences in both mouse and rat tissue extracts. Accordingly, experiments carried out on mouse brain extracts and on AtT-20 pituitary cells yielded sst2A/sst2B expression ratios comparable to those previously published. As in the mouse, rat pituitary extracts contained both sst2A and sst2B transcripts. By contrast, various cerebral regions in which both sst2A and sst2B forms were detected in the mouse contained only sst2A form in rat brain, with the exception of the cerebral cortex which also showed weak sst2B expression. No sst2B mRNA was detected in the arcuate nucleus/median eminence complex, indicating that the sst2A form is the one that is associated with growth-hormone-releasing-hormone-containing neurons documented to express sst2 receptors in this region. Finally, only sst2A transcripts were detected in rat astrocytes in culture, suggesting that this form of the receptor is responsible for sst2-mediated effects of SRIH on these cells.