bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Cellular Energy Metabolism on Contractions of Porcine Carotid Artery Smooth Muscle
Authors: Dillon Patrick F.
Published: April 2003

A number of cellular metabolites, including inorganic phosphate and ADP, have been proposed to regulate the contractions of smooth muscle. Hypothesizing that one of these would have a greater influence than the others, parallel experiments using tissue mechanics and 31P-NMR allowed comparison of several metabolic components with the generation of force in porcine carotid artery smooth muscle during long-term contractions. Pi, ADP, ATP, PCr, free energy, pH, and free Mg2+ were determined from phosphate spectra during a control-hypoxia-postcontrol sequence generated during K+ stimulation by replacement of oxygen with nitrogen using either pyruvate or glucose as substrate. Both pH and free Mg2+ were significantly lower in control pyruvate-supplied tissues than in glucose-supplied tissues. Mechanical experiments following the same protocol produced variations in force. The pyruvate series produced the greater range of mechanical and metabolic changes. Linear and logarithmic regression analysis found the order of correlation with force to be highest for Pi, followed by pH, free energy, PCr, ATP, ADP, and free Mg2+. The results are consistent with models for the regulation of myosin ATPase by free phosphate inhibition. The results are inconsistent with models of ADP as a regulator of smooth muscle force. Perturbations which alter intracellular phosphate, such as creatine loading, may produce side effects on the contractions of vascular smooth muscle.
Modern Strategy for Diagnosis and Treatment of Pulmonary Embolism
Authors: Laaban J.P.
Published: April 2003

Various techniques are available for the diagnosis of pulmonary embolism (PE), including pulmonary angiography, perfusion-ventilation lung scanning, D-dimer measurement, venous ultrasonography and, most recently, helical computerized tomography of the chest. The advantages and disadvantages of these techniques, used alone or in combination, are briefly discussed. Studies have indicated that treatment with low-molecular-weight heparin (LMWH), as well as being more convenient to administer, is as safe and effective as standard heparin therapy in acute PE. However, the efficacy and safety of LMWH in patients with acute PE and haemodynamic instability requires verification. Finally, the indications of inferior vena caval filters and thrombolytic therapy are outlined.
Direct Thrombin Inhibitors
Authors: Anand S.
Published: April 2003

Direct thrombin inhibitors may offer advantages over indirect thrombin inhibitors in the management of patients with acute coronary syndromes (ACS). Two direct thrombin inhibitors, hirudin and bivalirudin, have been investigated in Phase II and Phase III clinical trials. Based on the results of a meta-analysis of study data from 25,000 patients, hirudin appears to be more effective than unfractionated heparin (UFH) in the treatment of patients with ACS, but it is associated with an increased rate of major bleeding. A meta-analysis of a smaller patient population has suggested that bivalirudin, too, may be more efficacious than UFH and may also be safer.
Is There a Role for Thrombolytic Therapy in Venous Thromboembolism?
Authors: Sanson Bernd-Jan , Büller Harry
Published: April 2003

Theoretically, thrombolytic therapy would appear to offer benefits over standard heparin therapy in the treatment of venous thromboembolism based on the more rapid resolution of thrombus. In this paper, the results of clinical trials performed with thrombolytic agents in the initial treatment of both deep vein thrombosis (DVT) and pulmonary embolism (PE) are reviewed. Although there have been positive findings with surrogate markers, studies to date have failed to demonstrate that thrombolytic therapy is associated with an improved long-term clinical outcome in patients with DVT or PE. Recent reports have suggested that thrombolytic agents could be clinically useful in a subgroup who have right ventricular dysfunction on echocardiography. Randomized clinical trials, with clinically relevant endpoints, are required to determine the efficacy and safety of thrombolytic therapy in these patients.
Management of Pregnancy in Women with Thrombophilia
Authors: Conard Jacqueline , Horellou Marie-Hélène , Samama Meyer-Michel
Published: April 2003

Hereditary thrombophilia increases the risk of thrombosis during pregnancy and postpartum. The recommendations resulting from the Fifth American College of Chest Physicians (ACCP) Consensus Conference on Antithrombotic Therapy were published in Chest in late 1998. However, levels of evidence on this subject were low (C2). Furthermore, since publication of this ACCP consensus, new studies have demonstrated the safety of low-molecular-weight heparins (LMWHs) in pregnant women. In addition, it is now clear that all thrombophilias are not associated with the same level of thrombotic risk: factor V Leiden mutation and factor II 20210A variant are associated with a lower risk than antithrombin deficiency. Consequently, the ACCP recommendations have been reconsidered in the light of a more widespread use of LMWH and taking into account the differences in the level of risk of the different thrombophilias. A prophylaxis of thrombosis in pregnant women with thrombophilia is proposed based on published data and our personal experience. Although laboratory monitoring is usually not required during treatments with LMWH, it seems to be needed in pregnant women who receive long-term treatments.
Optimal Management of Pregnant Women with Acute Venous Thromboembolism
Authors: Bates Shannon M.
Published: April 2003

Venous thromboembolism (VTE) is an important cause of obstetric morbidity and mortality. Its management during pregnancy is problematic because anticoagulants, the cornerstone of initial therapy for VTE, may have significant foetal as well as maternal side effects. Unfractionated heparin has been the anticoagulant of choice in pregnancy; however, there is growing clinical experience with low-molecular-weight heparin (LMWH) in this patient population. A recently published systematic review of the literature suggests that the use of LMWH during pregnancy is not associated with adverse foetal/infant outcomes. Moreover, its long-term use appears to be safe for the mother, as symptomatic osteoporosis, bleeding and heparin- induced thrombocytopenia occurred only infrequently. There are limited data regarding the efficacy of anticoagulant therapy in the treatment of VTE during pregnancy, and treatment recommendations have largely been extrapolated from data in non-pregnant patients and case series of pregnant patients. This paper will briefly review the challenges and areas of controversy associated with the use of anticoagulants in the treatment of pregnancy-associated VTE.
Aspects of the Clinical Management of Hereditary Thrombophilia: A Personal Perspective
Authors: Mannucci Pier M.
Published: April 2003

There is a paucity of evidence-based medicine regarding the clinical management of patients with inherited thrombophilia, and randomized controlled multinational clinical trials of anticoagulant prophylaxis, particularly of secondary prophylaxis, in this population are urgently required. For acute episodes of venous thromboembolism, no data suggest that patients with thrombophilia should be treated differently to those without thrombophilia. Based on the results of a retrospective study, it is recommended that all thrombophilic individuals receive short- term thromboprophylaxis with unfractionated heparin or low-molecular-weight heparin when they are to be exposed to circumstantial risk factors (e.g. surgery, prolonged immobilization, pregnancy and puerperium). In the absence of specifically designed clinical trials, secondary prophylaxis should be based on common sense and clinical experience. From this standpoint, it is recommended that low-risk patients be treated with oral anticoagulants for 6 months, whereas high-risk patients should receive lifelong anticoagulant therapy. Which treatment strategy to adopt for intermediate-risk patients is more controversial – prolongation of oral anticoagulant therapy to at least 12 months is suggested.
Does Inflammation Contribute to Thrombotic Events?
Authors: Esmon Charles T.
Published: April 2003

Recent studies have focused on a myriad of mechanisms by which inflammation can potentiate blood clotting. Inflammatory mediators like endotoxin and tissue necrosis factor (TNF)-α can cause the expression of tissue factor on monocytes and, possibly, endothelium, thereby initiating the coagulation cascade. Activation of the complement system can lead to exposure of membrane surfaces capable of amplifying the initial tissue factor stimulus by facilitating the assembly of the factor VIIIa-factor IXa and the factor Xa-factor Va complexes. Inflammatory mediators, particularly interleukin-6, can also increase the levels of fibrinogen, an acute-phase reactant. In addition, the inflammatory mediators can elevate the levels of plasminogen activator inhibitor, thus suppressing the fibrinolytic system. These studies alone, however, do not prove that inflammation can trigger clinically relevant thrombus formation in vivo. For instance, TNF-α has been studied in cancer patients as a potential cure for cancer, and even though these patients are hypercoaguable, thrombosis was not commonly observed as a side effect of the near-lethal doses of TNF-α that were administered. Based on primate studies, inflammatory mediators like TNF-α can promote clot deposition effectively only if there is reduced flow and inhibition of the natural anticoagulant pathways. The requirement for multiple simultaneous injurious events probably explains why inflammation alone is not observed as a major cause of thrombosis.
Continuing Out-of-Hospital Prophylaxis following Major Orthopaedic Surgery: What Now?
Authors: Dahl Ola E.
Published: April 2003

Post-surgical deep vein thrombosis (DVT) is often underdiagnosed by clinical assessment alone. Subclinical DVT is a major source of pulmonary embolism, which is an important cause of death, particularly following total hip replacement surgery. Results from pathophysiological studies and recently conducted, prospective double-blind venographic studies in Europe and North America suggest that, in patients undergoing total hip replacement surgery, thromboprophylaxis with a low-molecular-weight heparin should be continued for at least 5 weeks post-operatively to minimize this serious complication.
Low-Molecular-Weight Heparin as a Bridge to Timely Revascularization in Unstable Coronary Artery Disease – an Update of the Fragmin during Instability in Coronary Artery Disease II Trial
Authors: Wallentin Lars
Published: April 2003

This article summarizes the design and findings – both at 3 months and at 1 year follow-up – of the Fragmin during Instability in Coronary Artery Disease (FRISC) II trial. This multicentre randomized trial compared both an early invasive with an early non-invasive stategy, and prolonged treatment with dalteparin as opposed to placebo, in patients with unstable coronary artery disease. The results show that an early invasive strategy with coronary angiography and, if appropriate, revascularization procedures within 7 days after admission reduces the subsequent rate of mortality and myocardial infarction. The benefits of the invasive treatment were noticeably more marked in patients with any high-risk indicator – for example, male gender, age above 65 years, previous severe angina, or signs of ischaemia (ST depression on ECG) or of myocardial damage (elevated levels of troponin T). Treatment with dalteparin reduced the risk of death and myocardial infarction in high-risk (i.e. troponin-positive) patients, particularly during the first month of treatment. However, continuation with dalteparin therapy after revascularization procedures conferred no benefit. It is concluded that extended treatment with dalteparin is useful as a bridge to revascularization in this high-risk subgroup of patients with unstable coronary artery disease.
Cost-Effectiveness of Prolonged Out-of-Hospital Prophylaxis with Low-Molecular-Weight Heparin following Total Hip Replacement
Authors: Bergqvist David , Jönsson Bengt
Published: April 2003

Several studies have demonstrated that prolongation of thromboprophylaxis after elective hip replacement significantly reduces the frequency of venographically demonstrated deep vein thrombosis. This paper reports an economic evaluation of prolonged prophylaxis with low-molecular-weight heparin (LMWH), based on outcome data from one of these trials. Analysis showed a net saving per patient of 3,400 Swedish kronor. Consequently, if the costs of administering the LMWH – which includes the cost of teaching the patient to self-administer whilst in hospital and the cost of a follow-up visit by a district nurse to ensure compliance – are below this amount, the intervention will prove to be cost saving.
Thromboprophylaxis with Low-Molecular- Weight Heparin: Economic Considerations
Authors: Mätzsch Thomas
Published: April 2003

Postoperative thromboembolic events are a major cost factor for every healthcare system. Although thromboprophylaxis carries its own costs, the application of a thromboprophylactic regimen is cost-effective in most instances, at least in high-risk patients. A regimen of general postoperative prevention of deep vein thrombosis is always more cost-effective than surveillance programmes with treatment after diagnosis, and is almost always more cost-effective than no prophylaxis. For patients with a high risk of postoperative thromboembolism, such as after orthopaedic surgery, low-molecular-weight heparins have a rather clear advantage over prophylaxis with unfractionated heparin and warfarin, also in terms of cost- effectiveness. With regard to moderate-risk patients, such as after general surgery, the economic benefits are less clear. However, since the results of economic analyses are heavily dependent on the healthcare system, and since there are methodological difficulties and uncertainties connected with the analyses, the implications are difficult – if not impossible – to generalize. There is an urgent need for further prospective studies, which should be performed with defined economic variables a priori and in close cooperation with health economists.
Low-Molecular-Weight Heparins in the Management of Unstable Angina
Authors: Agnelli Giancarlo , Sonaglia Francesco
Published: April 2003

Low-molecular-weight heparins (LMWHs) are derivatives of unfractionated heparin (UFH) and have a more favourable pharmacokinetic profile and a more predictable anticoagulant effect than UFH. These features allow the subcutaneous injection of weight-adjusted doses of LMWHs without monitoring of blood coagulation, and this results in cost savings. Clinical trials have shown that combined therapy with aspirin and LMWHs is significantly more effective than aspirin alone in reducing the risk of cardiac events in the acute treatment of patients affected by unstable angina. LMWHs have also been shown to be at least as safe and effective as UFH in reducing the incidence of death and myocardial infarction in patients with unstable angina. LMWHs appear to be at least as safe as UFH with regard to major bleeding risk. When given as extended therapy, LMWHs have been shown to be superior to placebo at 30 and 45 days, with an acceptable risk of bleeding. Additionally, LMWHs can be used as a ‘bridge’ to revascularization in patients for whom early invasive treatment is not readily available.
Current Knowledge of the Platelet Glycoprotein IIb/IIIa Receptor Antagonists for the Treatment of Coronary Artery Disease
Authors: Berkowitz Scott D.
Published: April 2003

Understanding of the pivotal role of the platelet surface membrane glycoprotein (GP) IIb/IIIa receptor in platelet aggregation at the injured coronary plaque in acute coronary syndromes has led to recent pharmacologic strategies that focus on inhibition of this final common pathway. Several intravenous medications directed specifically at this receptor (called platelet GP IIb/IIIa receptor antagonists; GPAs) have emerged. These include the human-murine chimeric monoclonal antibody Fab fragment abciximab, the peptide antagonist eptifibatide and the peptidomimetics tirofiban and lamifiban. To date, over 33,000 patients have been studied with these compounds in 11 large, randomized placebocontrolled trials which have established the effectiveness of these drugs in conditions where platelet aggregation and thrombosis play major contributing roles such as in high-risk coronary intervention, myocardial infarction and unstable angina. GPAs have been proven to be effective in reducing ischemic complications when used as an adjunct to percutaneous coronary revascularization or the management of acute ischemic syndromes. They are well tolerated and safe, provided concomitant use with other antithrombotics (e.g. heparin) is carefully managed and platelet counts are monitored.
Thiazide-Sensitive Cotransporter mRNA Expression Is Not Altered in Three Models of Hypertension
Authors: Moreno Gabriela , Bobadilla Norma A. , González-Salazar Jorge , Mercado Adriana , Tapia Edilia , Hong Enrique , Herrera-Acosta Jaime , Gamba Gerardo
Published: April 2003

Background/Aims: Several lines of evidence support that the kidney is involved in the increase of arterial blood pressure, and some genetic studies suggest that the thiazide-sensitive Na+:Cl– cotransporter could be implicated in the development of hypertension. In the present study, we analyzed the Na+:Cl– cotransporter mRNA levels in the kidney during the development of hypertension in three experimental models. Methods: The first model included 18 spontaneously hypertensive rats studied at 4, 10, and 16 weeks of age. The second model included 28 Wistar rats with two-kidney, one-clip Goldblatt hypertension studied at 7, 14, 21, and 28 days. The third model included 6 Wistar rats treated with NG-nitro-L-arginine methyl ester during 10 days. Respective controls were studied for all models. At the end of each experimental period, the systolic blood pressure was measured in the tail by plethysmography. Individual renal cortex total RNA was extracted, and the mRNA levels of the thiazide-sensitive Na+:Cl– cotransporter were assessed following a semiquantitative RT-PCR strategy. Results: All experimental models developed systemic hypertension. However, the level of mRNA expression of the Na+:Cl– cotransporter did not change in any of the models studied as compared with their respective controls. Conclusion: Our results suggest that a change in mRNA levels of the thiazide-sensitive Na+:Cl– cotransporter is not associated with the development of hypertension in spontaneously hypertensive rats, in rats with renovascular hypertension, nor in rats with hypertension induced by nitric oxide synthesis inhibition.
Pathophysiology of Cyclosporine-Induced Nephrotoxicity in Humans: A Role for Nitric Oxide?
Authors: Gossmann Jan , Radounikli Androniki , Bernemann Alexander , Schellinski Oliver , Raab Hans-Peter , Bickeböller Ralf , Scheuermann Ernst-Heinrich
Published: April 2003

Background: The causes for the nephrotoxicity of cyclosporine A (CsA) have not been fully elucidated. Intrarenal vasoconstriction induced by several different mediators, both in humans and experimental animals, have been proposed. Methods: We studied prostaglandin metabolites, endothelin and nitric oxide in kidney transplant patients receiving their first CsA dose. Prostaglandin metabolites in the urine and endothelin and nitric oxide (NO2/NO3) in urine and plasma were measured in 14 patients before and 3 and 6 h after oral ingestion of CsA (10 mg/kg b.w.). Clearances for inulin and p-aminohippuric acid (PAH) were measured before and in two separate 3-hour periods after CsA. Blood pressure, heart rate, and CsA blood levels were also determined. Results: Clearances of inulin and PAH decreased progressively after CsA dosage while renal vascular resistance increased. Nitric oxide plasma levels decreased in nearly all patients from 21.0 ± 2.8 to 19.1 ± 2.6 (p = 0.003) and then rose slightly to 19.5 ± 2.5 µmol/l (p = 0.1) 3 and 6 h after CsA ingestion, respectively. Urinary excretion of NO2/NO3 decreased nonsignificantly from 269 ± 38.8 to 259 ± 27.7 and 254 ± 41.6 µmol/min (p = 0.5 and 0.5). At the same time, urinary prostaglandin E2 and 6-keto-prostaglandin F1α excretion rate declined significantly [from 1,187 ± 254 to 1,186 ± 351 and 730 ± 148 pg/min (p = 0.27 and 0.02) and from 697 ± 115 to 645 ± 134 and 508 ± 58.2 pg/min (p = 0.34 and 0.05)]. Urinary thromboxane B2 and plasma and urinary endothelin first increased and then decreased nonsignificantly. Mean arterial pressure rose from 107 ± 2.5 to 110 ± 2.6 and 114 ± 3.4 mm Hg (p = 0.1 and 0.05). Conclusion: The pathophysiology of CsA-induced acute renal vasoconstriction involves several different mechanisms including a decrease of the vasodilating prostaglandins E2 and 6-keto-prostaglandin F1α and possibly nitric oxide.
Transjugular Renal Biopsy
Authors: Rychlík Ivan , Petrtýl Jaromír , Tesař Vladimír , Stejskalová Alena , Žabka Jiří , Brůha Radan
Published: April 2003

Background: Transjugular renal biopsy (TJRB) is still a novel technique of renal tissue sampling exploiting the transjugular route. TJRB should be performed particularly in situations when the percutaneous route is precluded, i.e. especially in patients with clotting disorders. In the past, only a few papers reported the experience with larger numbers of patients. The goal of this paper is to analyze our experience with TJRB. Methods and Results: From 1993 to 1999, 67 patients, mean age 49.8 years (SD ± 10.2), male/female ratio 40/27, underwent TJRB. Fifty-two patients (78%) suffered from renal insufficiency and 19 of them (28%) were on dialysis treatment at the time of TJRB. Arterial hypertension was recorded in 42%. The combined kidney and liver biopsy (46%) and clotting disorders (39%) were the most frequent indications for performing TJRB. Renal tissue was yielded in 53 patients (79%) but a sample sufficient for histological diagnosis was taken in 49 (73%), reaching on average 10.8 glomeruli. Altogether 19 different histological entities were disclosed and out of them, vascular nephrosclerosis (12%), necrotizing and crescentic glomerulonephritis, IgA nephropathy (IgAN) and amyloidosis (three latter per 10%) represented the most frequent diagnoses. TJRB was combined with liver biopsy in 31 patients (46%) and/or hepatic vein catheterization in 22 patients (33%) confirming portal hypertension in 8. The clinically significant liver histology was found in 20 patients, of them cirrhosis/fibrosis in 8, chronic hepatitis in 4 and steatosis in 5. Among those 20 patients, IgAN was disclosed as the most common renal diagnosis (6). Clinically symptomatic complications were recorded in 12 cases (18%) but 9 of them suffered from clotting disorders. Complications included development of subcapsular hematoma in 6 cases, macroscopic hematuria in 4 cases, and hypovolemic hemorrhagic shock in 2. One patient had to undergo surgical treatment. Dividing the patients into a subgroup with or without clotting disorders, the complication rate was 34 vs. 7%. Conclusions: TJRB is a new diagnostic method, which, looking at its indications, facilitates the diagnosis of glomerulopathies in patients who could not be considered for percutaneous renal biopsy, particularly due to clotting disorders. The technical aspect of this procedure plays a fundamental role in the final risk/benefit ratio but if done correctly it involves acceptable risk and is well tolerated.
A 3-Year Retrospective Study of Community-Acquired Pneumonia in Kuwait with Emphasis on Microbial Aetiology
Authors: Awadh-Behbehani Nasser , Bitar Zuhair , Al-Enezi Fatima , Al-Mutairi Sana , Al-Azemi Mohamed , Al-Sayeq Faisal
Published: April 2003

Background: There has not been any published study on community-acquired pneumonia (CAP) in Kuwait. The aim of this study is to determine the clinical characteristics of adult patients with CAP as well as the microbial aetiology and the treatment of CAP. Methods: A retrospective study of all CAP cases admitted to the three acute care hospitals in Kuwait over a 3-year period, 1993–1995, was done. Results: There were 290 patients identified, mean age 41 ± 19 years, of which 57% were males. The patients were divided into three groups (mild, moderate and severe) according to standard published criteria: mild 27.5%, moderate 61%, and severe 11.5%. The microbial aetiology was identified for only 15% of the total cases, 11.5% of the mild group, 14% of the moderate, and 22.5% of the severe. The most common organisms identified were Streptococcus pneumoniae 32%, Mycoplasma pneumoniae 20%, Haemophilus influenzae 14%, Mycobacterium tuberculosis 11%, gram-negative organisms other than Haemophilus species 11% and others 12%. There were 243 (84%) patients who received a single antibiotic as initial therapy while the rest received a combination of antibiotics. The most common antibiotics used were macrolide 28%, ampicillin 24%, a combination of antibiotic 17%, third-generation cephalosporin 12% and others 19%. Conclusion: The rate of identification of microbial aetiology in CAP is poor in Kuwait. There are 27.5% of the patients who can be classified as mild and probably the majority of them can be treated as out-patients. Based on these results, we have started a prospective study to better evaluate the microbial aetiology of CAP in Kuwait.
Age-Dependent Changes in 24-Hour Rhythms of Thymic and Circulating Growth Hormone and Adrenocorticotropin in Rats Injected with Freund’s Adjuvant
Authors: Esquifino Ana I. , Bonacho Manuel García , Arce Agustín , Cutrera Rodolfo A. , Cardinali Daniel P.
Published: April 2003

Objective: To analyze the 24-hour changes in thymic and serum concentration of growth hormone (GH) and adrenocorticotropin (ACTH) and their correlation with thymic concentrations of glutamate, aspartate, taurine and GABA in young and old rats during the acute phase of adjuvant’s arthritis. Methods: Young (50-day-old) and old (18-month-old) rats were injected subcutaneously with Freund’s adjuvant or its vehicle (paraffin oil containing 15% mannide monooleate). Eighteen days later, they were killed at six different time intervals throughout a 24-hour cycle. Serum and thymic levels of GH and ACTH were measured by radioimmunoassay. Thymic amino acid concentration was measured by HPLC. A quantitative assessment of arthritis was made in an independent group of rats by plethysmography. Results: Old rats injected with Freund’s adjuvant exhibited fewer clinical signs of inflammation than young rats. Significant 24-hour changes in thymic and serum GH occurred, except for serum GH in adjuvant’s vehicle-treated old rats. Aging augmented thymic GH and decreased serum GH. Immunization with Freund’s adjuvant did not modify GH concentration. Thymic and serum concentration of GH correlated negatively. Thymic ACTH varied significantly over 24 h with maxima during the dark phase, except in Freund’s adjuvant-treated young rats. Maximal serum ACTH levels occurred in the late afternoon except in Freund’s adjuvant-treated old rats which showed maxima at night. Immunization with Freund’s adjuvant augmented thymic and circulating concentrations of ACTH. Thymic and serum concentration of ACTH correlated positively. Thymic concentration of glutamate, aspartate and taurine decreased in aged rats and correlated significantly with thymic ACTH. Conclusion: The results support the existence of a thymic compartment of GH and ACTH that may be independently regulated.
Differential Expression and Regulation of Leptin Receptor Isoforms in the Rat Brain: Effects of Fasting and Oestrogen
Authors: Bennett Pamela A. , Lindell Kajsa , Karlsson Cecilia , Robinson Iain C.A.F. , Carlsson Lena M.S. , Carlsson Björn
Published: April 2003

Leptin affects body weight and reproduction mainly via receptors in the central nervous system. Different isoforms of the leptin receptor (leptin-R) exist, including a long isoform (leptin-RL) with signalling capacity and short isoforms (leptin-RS) with unknown function. The aim of this study was to examine leptin-R gene expression in different regions of the brain under conditions with altered body weight, in the female rat, including ovariectomy (OVX), oestradiol (E2) treatment, fasting and a genetic model of obesity (Zucker fa/fa). Leptin-R gene expression was analysed by in situ hybridization using probes recognizing all receptor isoforms (leptin-R) or specifically leptin-RL. Transcripts recognized by the leptin-R probe were abundant in the choroid plexus (CP), arcuate nucleus (ARC), ventromedial nucleus (VMN), thalamus (TH) and piriform cortex (PC). Leptin-RL transcripts were detected in the ARC, VMN, TH and PC but not in the CP. Although no sex difference was observed, leptin-R gene expression was reduced by E2 administration and increased by OVX. Administration of E2 reduced leptin-RL gene expression in the ARC and VMN but did not alter the expression in the TH or PC. OVX had no effect on the expression of leptin-RL mRNA. Fasting also caused a differential regulation of leptin-R mRNAs, with an increase in abundance of leptin-RL transcripts in the TH despite a decrease in leptin-R in this area. Obese Zucker rats had a similar pattern of expression with an increased expression of leptin-RL transcripts in all brain areas analysed and a decrease in leptin-R gene expression. These results demonstrate a differential regulation of leptin-RL and leptin-RS which could provide a mechanism for regulating access to, and sensitivity of, discrete regions of the brain for circulating leptin. We suggest that fasting and E2 alter the balance between leptin-RL and leptin-RS and that this could increase tissue sensitivity to leptin.
Endotoxin Induces Interleukin-1β and Nitric Oxide Synthase mRNA in Rat Hypothalamus and Pituitary
Authors: Satta Maria Antonia , Jacobs Richard Anthony , Kaltsas Gregory Athanasios , Grossman Ashley Barry
Published: April 2003

The gases nitric oxide (NO) and carbon monoxide (CO) may be involved in hypothalamo-pituitary-adrenal axis (HPA) modulation. In the brain, NO is synthesized by two forms of NO synthase (NOS), a constitutive neuronal form (nNOS) and an inducible form (iNOS). There are also a constitutive heme oxygenase (HO2) and an inducible form (HO1) which generate CO. We have therefore investigated the effect of peripheral lipopolysaccharide (LPS) administration on the gene expression of these enzymes along with interleukin-1β (IL-1β) gene expression in the hypothalamus, pituitary and liver. Male Wistar rats (200–250 g body weight) were injected intraperitoneally with endotoxin (Escherichia coli, 055 B5) dissolved in sterile normal saline [250 µg/kg first group, 2.5 mg/kg (second group) and 6.25 mg/kg (third group)] in a final volume of 0.5 ml, or saline alone in the control group. The first and the second groups were studied 1, 3, 8 and 24 h after LPS (n = 4 per group); the third group was studied at 3 h. Total RNA was extracted from the hypothalamus, pituitary and liver, and cDNA was made using standard reverse transcriptase methods. Duplex polymerase chain reaction (PCR) was standardised in order to quantify the expression of a specific gene in relation to the ‘house-keeping’ gene β-actin. The specific genes studied were iNOS, nNOS, HO1, HO2 and IL-1β. The PCR products were separated on agarose gel and densitometric analysis of the bands allowed semi-quantification. In the second group, iNOS and IL-1β were induced in hypothalamus, pituitary and liver, showing a peak at 3 h (p < 0.001), returning to baseline levels at 24 h. Neuronal NOS was not expressed in the liver under basal conditions or after LPS; in the hypothalamus and pituitary, nNOS was expressed basally but there was no change after LPS. In the first group, iNOS and IL-1β were again induced in all three tissues studied, but with a delayed time course compared to the second and third groups; the peak change for IL-1β occurred at 8 h (p < 0.05), again returning to baseline levels at 24 h. The peak for iNOS occurred at 24 h. HO1 and HO2 were expressed in all three tissues under basal conditions; HO1 was increased at 1 h in the liver in the second group, and at 3 h in the pituitary in the third group. There was no change in either HO1 or HO2 in the hypothalamus at any dose at any time point. We conclude that IL-1β and iNOS are induced in rat hypothalamus and pituitary following various doses of endotoxin. We speculate that while IL-1β may mediate stimulation of the HPA by endotoxin, NO generation may be involved in the counter-regulation of this response.
Components of the Neuronal Exocytotic Machinery in the Anterior Pituitary of the Ovariectomised Ewe and the Effects of Oestrogen in Gonadotropes as Studied with Confocal Microscopy
Authors: Thomas Steven G. , Takahashi Masami , Neill Jimmy D. , Clarke Iain J.
Published: April 2003

We have investigated exocytotic proteins in ovine pituitary cells and sought to identify changes in expression of these proteins related to the effects of estrogen on luteinising hormone (LH) secretion in the ovariectomised ewe. Sheep were treated with either oestradiol benzoate, or oil (i.m.) and blood samples collected for LH assay. Pituitaries were perfusion-fixed and dual-label immunohistochemistry was performed to identify hormone-secreting cells, and colocalise synaptic proteins within different cell types. Synaptophysin, SNAP-25, VAMP-2, rab3A, Munc-18-1, α/β-SNAP, csp, and secretogranin II were detected in gonadotropes and somatotropes. Lactotropes were positive for SNAP-25 and synaptophysin (other synaptic proteins not investigated). Synaptotagmin I was detected in gonadotropes and lactotropes, but not somatotropes. Synaptophysin, SNAP-25, synaptotagmins I, II and III, VAMP-2, rab3A, Munc-18-1, α/β-SNAP, csp, and secretogranin II were detected in nerve fibres of the posterior lobe. Membrane staining for SNAP-25 and weak cytoplasmic labelling for both synaptotagmin I and secretogranin II were detected in the intermediate lobe. Syntaxin and complexin II antibodies did not label any region of the ovine pituitary. Oestrogen treatment, to induce a pre-ovulatory-like LH surge, caused migration of LH-containing secretory granules toward the plasma membrane of gonadotropes, but did not alter the percentage of gonadotropes expressing each exocytotic protein. Oestrogen treatment caused a similar redistribution of csp and secretogranin II staining in gonadotropes. We conclude that synaptic protein expression is not altered in the anterior pituitary at the time when LH secretion is maximal. The ubiquitous distribution of many exocytotic proteins suggests that all hormone-secreting cells of the pituitary gland contain the same, or similar exocytotic machinery, but distinct ‘activating factors’ are required to selectively trigger the secretion of individual hormones.
Neurohypophysial Peptides Stimulate the Phosphorylation of Pre-T Cell Focal Adhesion Kinases
Authors: Martens Henri , Kecha Onafar , Charlet-Renard Chantal , Defresne Marie-Paule , Geenen Vincent
Published: April 2003

Thymic oxytocin (OT) behaves as a cryptocrine signal targeted at the outer surface of thymic epithelial cell plasma membrane from where OT is able to interact with neurohypophysial peptide receptors expressed by pre-T cells. Immature T cells bear a receptor of the V1 subtype, while OT receptors are predominantly expressed by cytotoxic CD8+ lymphocytes. In both T cell types, neurohypophysial peptide receptors transduce OT via the phosphoinositide pathway. Protein tyrosine phosphorylation is an early event of T cell activation. Western blots of murine pre-T cells (RL12-NP line) proteins probed with anti-phosphotyrosine (PY-20) revealed a great number of proteins the phosphorylation of which increased either with OT or vasopressin treatment. Two were immunoprecipitated with anti-focal adhesion kinase (FAK) mAb 2A7 and were identified one as p125FAK and the other as a coprecipitating 130-kDa protein. The p125FAK is connected to the Ras/MAPK pathway and is also implicated in TCR/CD3 signalling in T cell. Another protein phosphorylated by OT in RL12-NP was identified as paxillin, a 68-kDa protein localised at focal adhesion sites and associated with p125FAK. These results indicate that phosphorylation of focal adhesion kinase may be induced in pre-T cell by thymic OT.
Plasma Melatonin Rhythm is Maintained in Human African Trypanosomiasis
Authors: Claustrat Bruno , Buguet Alain , Geoffriau Martine , Bogui Pascal , Mouanga Gaston , Stanghellini André , Dumas Michel
Published: April 2003

In human African trypanosomiasis (sleeping sickness), sleep and wake episodes are sporadically distributed throughout the day and the night. Plasma melatonin, sleep-wakefulness and rectal temperature rhythms were studied in 9 Congolese patients suffering from sleeping sickness compared to 6 healthy controls submitted to the same light/dark regime. The circadian distribution of the sleep-wake cycle was disturbed in relation to the severity of the disease. As controls, patients maintained a very distinct plasma melatonin nyctohemeral rhythm which displayed a significant phase advance (1:08 ± 0:43 and 2:34 ± 0:31 mean ± SD, in patients and controls respectively; p < 0.01, U test), as well as a persistent rectal temperature rhythm (mesor 36.67 ± 0.29 and 36.74 ± 0.13°C, amplitude 0.29 ± 0.16 and 0.32 ± 0.13°C, acrophase 13:53 ± 2:47 and 15:32 ± 0:36 for patients and controls respectively). No alteration of these rhythms was observed after treatment. In African controls we observed plasma melatonin characteristics similar to those of European controls, especially for the onset and the duration of the secretion and the stability of the rhythm, despite a different light/dark regime. The dissociation observed between the 3 rhythms (melatonin, temperature and sleep-wake cycle) is discussed, taking into consideration a functional compartmentalization of the suprachiasmatic nuclei or more likely a disruption of the neural pathway between the circadian clock and structures involved in the regulation of the sleep-wake cycle, related to the activity of compounds released by the parasites or host cells.
Role of Corticotropin-Releasing Hormone in Gastrin-Releasing Peptide-Mediated Regulation of Corticotropin and Corticosterone Secretion in Male Rats
Authors: Garrido Margarita M. , Martin Sonsoles , Ambrosio Emilio , Fuentes José A. , Manzanares Jorge
Published: April 2003

Gastrin-releasing peptide (GRP) exerts several functions within the hypothalamus and may be involved in the regulation of pituitary hormone secretion. The purpose of this study was to investigate the central effect of GRP on hypothalamic-pituitary-adrenal axis activity in the male rat. Intracerebroventricular (i.c.v.) but not intravenous administration of GRP (1, 10, 100 ng/rat) increased plasma ACTH and corticosterone concentrations in a dose-dependent manner. The highest dose (100 ng/rat) of GRP increased plasma ACTH and corticosterone 4- and 14-fold, respectively. This increase peaked at 30–60 min after i.c.v. injection, decreased gradually and returned to baseline levels 240 min after GRP administration. The i.c.v. administration of (Leu13-ψ-CH2NH-Leu14) bombesin, a competitive and specific GRP receptor antagonist, had no effect on ACTH and corticosterone secretion; however, a dose of 1 µg/rat completely blocked the increase of both hormones induced by GRP (10 ng). By using α-helical (9–41) corticotropin-releasing factor (CRF), a competitive antagonist of CRF, the role of CRF on GRP-induced ACTH and corticosterone secretion was also explored. α-Helical (9–41) CRF (10 µg/rat) blocked the increase in ACTH and corticosterone secretion induced by GRP (10 ng). The results obtained in this study suggest that GRP increases the secretion of ACTH and corticosterone in the plasma by acting centrally on GRP receptors, and that endogenous GRP receptor ligands do not tonically regulate ACTH and corticosterone secretion. Furthermore, the hypothalamus-pituitary-adrenal-activating effects induced by GRP appear to be mediated, at least in part, by CRF.
Inhibin Suppresses in vivo Growth Hormone Secretion
Authors: Carro Eva , Señarís Rosa M. , Mallo Federico , Diéguez Carlos
Published: April 2003

Although the effects of inhibin on gonadotropin synthesis and secretion have been extensively studied, the role of inhibin in the neuroregulation of in vivo growth hormone (GH) secretion still remains to be elucidated. In the present work, we investigated the effects of inhibin on spontaneous GH secretion in three different groups of conscious adult male rats: intact, gonadectomized, and dihydrotestosterone (DHT)-treated gonadectomized animals. We found that inhibin administration (100 µg/kg, i.v.) led to a marked suppression in spontaneous GH secretion in all the groups studied. This significant decrease was assessed by the area under the curve in intact (311.1 ± 163.3 vs. 3,882.1 ± 1,084.6 ng/ml/6 h, p < 0.01), gonadectomized (416.6 ± 120.9 vs. 2,078.5 ± 298.4 ng/ml/6 h, p < 0.01) and gondadectomized rats treated with DHT (755.0 ± 102.3 vs. 4,539.3 ± 1,670.6 ng/ml/6 h, p < 0.01). Furthermore, intravenous inhibin significantly reduced in vivo GH responses to GHRH (10 µg/kg, i.v.) in both intact and gonadectomized rats. These findings suggest a role of inhibin on in vivo GH secretion in the male rat.
Potassium Channel Blockers Have Minimal Effect on Repolarization of Spontaneous Action Potentials in Rat Pituitary Lactotropes
Authors: Sankaranarayanan Sethuraman , Simasko Steven M.
Published: April 2003

Patch-clamp techniques were used in primary cultures of rat lactotropes and the rat pituitary clonal cell line GH3 to determine the population characteristics of spontaneous action potentials and the nature of the currents responsible for repolarization of spontaneous action potentials. Spontaneous action potentials were observed in 75% of lactotropes (74/99) and 80% of GH3 cells (42/51). Lactotropes exhibited broad and shallow action potentials (average duration 460 ms, peak –17 mV, slope of upstroke 0.5 mV/ms) compared to the GH3 cells which displayed narrow and tall action potentials (average duration 177 ms, peak –10 mV, slope of upstroke 1.6 mV/ms). Blockers of potassium currents were used to determine the role of specific potassium currents in the repolarization process. Spontaneous action potentials in lactotropes were largely unaffected by 4-aminopyridine (4AP), charybdotoxin, and apamin. Tetraethylammonium (TEA) caused only an small increase in peak amplitude and, in a subset of cells, a small increase in duration. In contrast, in GH3 cells, TEA, 4AP, charybdotoxin, and apamin all caused a significant increase in duration, while TEA and charybdotoxin also caused an increase in peak amplitude. Further, apamin caused a positive shift in the afterhyperpolarization voltage. In lactotropes, strong buffering of intracellular calcium with calcium chelators (EGTA or BAPTA) caused a profound increase in action potential duration. Thus, repolarization of action potentials in lactotropes is a calcium-dependent process, but unlike GH3 cells, is not mediated by calcium-dependent potassium currents, nor is it strongly influenced by voltage-dependent potassium currents.
Mineralocorticoid Receptor also Modulates Basal Activity of Hypothalamus-Pituitary-Adrenocortical System in Humans
Authors: Deuschle Michael , Weber Bettina , Colla Michael , Müller Matthias , Kniest Anja , Heuser Isabella
Published: April 2003

Hippocampal mineralocorticoid (MRs) and glucocorticoid receptors (GRs) have been demonstrated to regulate the activity of the hypothalamus-pituitary-adrenocortical (HPA) system. To elucidate the role of the hippocampal MR in the circadian activity of the human HPA system, we studied diurnal secretory profiles of corticotropin (ACTH) and cortisol in 10 healthy male humans before and after an 8-day treatment with the MR antagonist spironolactone. 24-hour blood sampling at 30-min intervals was performed for estimation of cortisol (q30) and ACTH (q120). Saliva cortisol was measured for estimation of unbound cortisol. At the end of the 24-hour sampling period a corticotropin-releasing hormone (CRH) challenge was performed. High plasma concentrations of the active metabolite canrenone were achieved (begin of sampling: 2,653 ± 693 nmol/l; end of sampling: 747 ± 177 nmol/l). There was a significant increase in the diurnal minima (37.1 ± 13.3 vs. 23.7 ± 8.9 nmol/l, p < 0.02) and mean cortisol (193.5 ± 25.8 vs. 173.0 ± 23.0 nmol/l, p < 0.03) plasma concentrations. However, the diurnal peak concentrations and pulsatile secretory features were unchanged after spironolactone treatment. For saliva cortisol, the only significant treatment difference was a decrease in the diurnal amplitude of cortisol relative to the diurnal mean concentration (2.56 ± 0.47 vs. 3.11 ± 0.87, p < 0.03). After spironolactone treatment there was a decrease in diurnal mean ACTH concentrations (46.2 ± 14.4 vs. 41.8 ± 10.3 pmol/l). There was no difference in the ACTH and cortisol response after infusion of CRH before and after spironolactone treatment. CBG plasma concentrations were significantly increased (22.4 ± 2.3 vs. 19.2 ± 2.7 mg/l, p < 0.01) after spironolactone treatment, which possibly contributed to the observed increase in plasma cortisol. In summary, as predicted from animal studies we found significant effects of MR antagonization to be restricted to time windows of low HPA system activity. These findings are similar to the effects of aging upon the HPA system. However, the effect of spironolactone treatment was small, suggesting that the HPA system activity in humans is modulated but not regulated by the hippocampal MR.
The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland
Authors: Roh Sang-Gun , Clarke Iain J. , Xu Ru-Wei , Goding James W. , Loneragan Kylie , Chen Chen
Published: April 2003

We have studied the direct effect of leptin on the secretion of GH from the anterior pituitary gland of the sheep. Using primary cultures of ovine pituitary cells, leptin (10–9–10–7 M) treatment for 30 min did not affect basal or GHRH (10–7 M)-stimulated GH secretion. Following treatment for 24 h, a dose of 10–7 M leptin stimulated basal GH secretion. In contrast, doses of 10–7 and 10–8 M leptin inhibited GHRH-stimulated GH secretion after 24 h of treatment. These results suggest that leptin can have long-term effects on the somatotropes, but no acute effect. Furthermore, leptin appears to have opposite effects on basal and GHRH-stimulated GH secretion.
Role of Phosphodiesterases in the Regulation of Gonadotropin- Releasing Hormone Secretion in GT1 Cells
Authors: Sakakibara Hideya , Conti Marco , Weiner RichardI.
Published: April 2003

Increases in the level of cAMP stimulate the secretion of GnRH from GT1 GnRH neuronal cells. We hypothesized that cyclic nucleotide phosphodiesterases (PDEs), the enzymes that hydrolyze cAMP, may constitute a negative feedback signaling mechanism for GnRH regulation by decreasing the level of cAMP. GT1 cells were shown to express three PDEs by RT-PCR analysis: the cAMP-specific PDE4B and PDE4D and the calmodulin-dependent PDE1B. A splice variant of PDE4D, PDE4D3, which is activated when phosphorylated by cAMP-dependent protein kinase (PKA), was identified in GT1 cells by Western analysis. Consistent with PDEs negatively regulating GnRH secretion, treatment with the nonselective PDE inhibitor, IBMX, stimulated GnRH secretion 137% in 30-min static cultures. Furthermore, treatment with the PDE4-specific inhibitors Rolipram and RS-25344 increased GnRH secretion 48 and 125%, while treatment with the PDE1-specific inhibitor 8-MeoM-IBMX only caused a modest increase of 28%. In perifusion studies a rapid multi-fold stimulation of GnRH secretion was observed following treatment with IBMX, Rolipram or RS-25344. In conclusion, the level of PDE activity appears to be an important negative feedback signal for GnRH secretion. We hypothesize that activation of PDE4D3 by PKA may constitute a negative feedback signaling pathway which participates in the regulation of cAMP levels.