bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional cardiac expression and concentration of natriuretic peptides in patients with severe chronic heart failure
Authors: Hystad M. E. , Geiran O. R. , Attramadal H. , Spurkland A. , Vege Å. , Simonsen S. , Hall C.
Published: March 2003

The purpose of this study was to examine the regional cardiac mRNA expression and concentration of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) in relation to the circulating peptide concentrations in patients with chronic heart failure (CHF). The myocardial mRNA levels and peptide concentrations of BNP and ANP were analysed in seven different regions of the heart from patients undergoing cardiac transplantation. Autopsy samples from individuals without known cardiovascular disease were used as controls. The plasma levels of natriuretic peptides and their N‐terminal propeptides, Nt‐proBNP and Nt‐proANP, were measured in the CHF patients and healthy volunteers. In the autopsy specimens, the atrial regions appeared to contain the highest peptide levels for BNP as well as ANP, the atrioventricular ratio being 12–262 and 72–637‐fold, respectively. In the CHF patients there was a relative shift towards the ventricle for BNP, reducing the atrioventricular ratio to 6–16‐fold. The circulating concentrations of BNP/Nt‐proBNP in the CHF patients correlated closely to the BNP mRNA expression in most myocardial regions including the left ventricle (r=0.72, P < 0.001). For circulating concentrations of ANP/Nt‐proANP, such correlation were limited to the left atrium free wall (r=0.66, P < 0.002). Thus, of the two natriuretic peptides, BNP/Nt‐proBNP may be a better reflector of left ventricular overload.
Effects of motility on epithelial transport in the human descending duodenum
Authors: Mellander A. , Järbur K. , Hemlin M. , Sjövall H.
Published: March 2003

The aim of the study was to determine how motility affects the balance between absorptive and secretory ion transport in the proximal human small intestine. Thirty‐two healthy subjects and 16 patients (eight with villus atrophy, eight with normal duodenal biopsies) were studied. The absorptive sodium flux was estimated by measurement of bicarbonate absorption with a double‐lumen perfusion technique. The secretory chloride flux was calculated from the ratio between the continuously recorded transmural potential difference (PD) and the epithelial parallel resistance, which was measured in forceps biopsies by square‐wave current analysis. Graded variations in contraction frequency were obtained by recording during defined time periods before, during and after phase III of the migrating motor complex (MMC). Bicarbonate was absorbed by a process that led to CO2 formation, and both bicarbonate absorption and luminal PCO2 increased with contraction frequency. The motility‐related PCO2 rise was reduced in patients with villus atrophy and by removal of bicarbonate from the perfusate. A higher motor activity was also associated with a larger PD (more lumen negative). Both the absorptive and the secretory fluxes were thus enhanced by motility. The estimated absorptive flux was approximately twice as large as the secretory flux during periods of low motor activity, and four times as large during submaximal motor activity. We conclude that motor activity affects both absorptive and secretory mucosal function in a quantifiable manner. Information about the behaviour of the respective linkage functions may make it possible to model the intestinal absorption process in vivo.
Mitochondrial myopathies
Authors: Larsson N.‐G. , Oldfors A.
Published: March 2003

The first description of a patient with mitochondrial myopathy and deficient respiratory chain function was reported by Luft and coworkers almost 40 years ago. Subsequent studies in the 1970s and 1980s relied on a combination of morphological and biochemical methods to identify patients with mitochondrial disorders. However, the aetiology and pathogenesis remained largely unsolved and there was poor correlation between laboratory findings and clinical phenotypes. The fact that both mitochondrial DNA (mtDNA) and nuclear genes are necessary for the biogenesis of the respiratory chain, suggested that mutations of either genome might cause mitochondrial myopathy. This prediction has been verified during the last decade and pathogenic mutations of both genomes have been identified. This rapid accumulation of genetic information has lead to many good correlations between genotype and phenotype in mitochondrial disorders. The challenge for the future will be to elucidate molecular details of pathogenic processes and to develop effective treatments for patients with respiratory chain dysfunction.
Pre‐conditioning activates adenosine utilization in a cost‐effective way during myocardial ischaemia
Authors: Wikström G. , Kavianipour M. , Ronquist G. , Waldenström A.
Published: March 2003

During pre‐conditioning the interstitial concentration of adenosine, in contrast to lactate, presents a die‐away curve‐pattern for every successive episode of ischaemia. This die‐away pattern might not necessarily be attributed to diminished adenosine production. The present study was undertaken to investigate whether pre‐conditioning alters the metabolic turnover of adenosine as observed by the lactate production during ischaemia. Interstitial levels of metabolites in pre‐conditioned (n=21) and non‐preconditioned (n=21) porcine hearts were monitored with microdialysis probes inserted in both ischaemic and non‐ischaemic tissue in an open chest heart model. Three subgroups perturbated with either plain microdialysis buffer (control), buffer containing adenosine (375 μM), or buffer containing deoxyadenosine (375 μM) were studied. All animals were subjected to 90 min of equilibrium microdialysis before 40 min of regional myocardial ischaemia and 120 min of reperfusion. Pre‐conditioning consisted of four repetitive episodes of 10 min of ischaemia and 20 min of reperfusion. Significantly higher levels of inosine and lactate were found in the ischaemic tissue of the pre‐conditioned subgroup receiving adenosine (P < 0.05) compared with the other two subgroups receiving deoxyadenosine and plain buffer, respectively. This difference was only valid for pre‐conditioned ischaemic myocardium, and hence equal amounts of inosine and lactate were produced in the non‐preconditioned ischaemic myocardium regardless of the presence of adenosine or deoxyadenosine. In the non‐ischaemic myocardium baseline levels of metabolites were measured in all subgroups. Pre‐conditioning favoured degradation of exogenous adenosine to inosine successively ending up in enhanced lactate production. This was probably because of the involvement of the hexose monophosphate pathway in the pre‐conditioned ischaemic myocardium. This route may therefore be supplementary in energy metabolism as a metabolic flow can be started by adenosine ending up in lactate without initial adenosine 5′‐triphosphate (ATP) investment. Utilization of adenosine in this way may also explain the successive die‐away pattern of adenosine seen in consecutive pre‐conditioning cycles.
Nitric oxide and the role of blood pressure variability to the kidney
Authors: Nafz B. , Seeliger E. , Persson P. B.
Published: March 2003

Blood pressure variability is buffered by at least two mechanisms: the arterial baroreceptor reflex and nitric oxide (NO). Only recently is the importance of blood pressure variations on cardiovascular control being investigated. Here we report of a study performed in conscious dogs, in which renovascular hypertension was induced. Reduction of renal arterial pressure (RAP) to 85 mmHg for 24 h elicited profound hypertension by 60 mmHg (vs. control: 110 ± 3 mmHg; P < 0.01). This was accompanied by reduced volume and sodium excretion (–48% of control, P < 0.01 and –80% of control, P < 0.01, respectively) and augmented renin release by more than two‐fold (P < 0.01). This intervention was compared with a protocol in which RAP was reduced to the same mean value, however, RAP oscillated by ±10 mmHg at 0.1 Hz. This manoeuvre led to a transient increase in NO3 excretion in urine (P < 0.01), blunted antidiuresis (–14% of control) as well as antinatriuresis (–40% of control) and attenuated the increased renin release by 30% (P < 0.05). In consequence, the magnitude of blood pressure increase was only half as high as that observed during static reduction of RAP (P < 0.01). It is concluded that blood pressure oscillations to the kidney have a profound influence on water and electrolyte balance and on renin release, which alleviates the onset of Goldblatt hypertension.
In vitro culture and characterization of gene targeted mouse endothelium
Authors: Kevil C. G. , Bullard D. C.
Published: March 2003

Endothelial cells play a crucial role in maintaining cardiovascular homeostasis. Although many cardiovascular disorders involve endothelial cell dysfunction, the specific cellular and molecular mechanisms involved are not well known. We sought to establish a reproducible method of endothelial cell isolation from gene targeted mice to specifically examine endothelial pathophysiological mechanisms. Primary aortic endothelial cell cultures were established from wild type and intercellular adhesion molecule‐1 (ICAM‐1) deficient mice. Isolation of mouse aortic endothelial cells (MAEC) by fluorescent activated cell sorting routinely resulted in pure, homogenous, primary cultures. Wild type and ICAM‐1 deficient endothelial cell morphology was similar, with both cultures showing cobblestone morphology and DiI‐Ac‐LDL staining. Monocyte adhesion to ICAM‐1 deficient aortic endothelial cells was decreased by 86% as compared with wild type MAEC. Monocyte adhesion was also determined using YN‐1, an ICAM‐1 blocking antibody. YN‐1 decreased monocyte adhesion to wild type aortic endothelial cells by 25%, whereas YN‐1 did not further decrease monocyte adhesion to ICAM‐1 deficient MAEC. These data demonstrate that gene targeted endothelial cell cultures are an effective means of identifying specific cellular and molecular mechanisms involved in endothelial cell physiology and dysfunction.
Concentric force enhancement during human movement
Authors: Finni T. , Ikegawa S. , Komi P. V.
Published: March 2003

In order to understand the possible mechanisms contributing to enhanced concentric performance in stretch–shortening cycle exercises in vivo the present study examined knee extension torque, electromyogram (EMG) activity and fascicle length of the vastus lateralis muscle in maximal and submaximal human movements. Maximal concentric knee extensions (120° s–1) were done after pre‐stretch and pre‐isometric conditions by nine volunteers. During shortening at the knee angle of 115° (180° = extended) the knee extension torque was found to be greater in pre‐stretch condition (272 vs. 248 N m, P < 0.05) although the torque level prior to shortening was smaller than in pre‐isometric condition (268 vs. 314 N m, P < 0.05). At the moment of torque enhancement the EMG activity levels or fascicle lengths did not differ between the conditions. It is proposed that besides specific experimental conditions the present enhancement may be related to longer fascicle length prior to shortening (by 4.1 cm, P < 0.05) in pre‐stretch condition and to modified length–tension properties. Fascicle length behaviour was found to play an important role also in unilateral, submaximal sledge‐jump conditions where pre‐loading was altered but the concentric net impulse and joint angular movements were the same. In repeated drop jumps with greater pre‐load the changes in fascicle length were smaller than in the counter movement jump that was characterized by a lower force and activity level in the eccentric phase. Results from the present maximal and submaximal loading conditions suggest that the benefits of stretch–shortening cycle muscle function may come through different interactive mechanisms that may be task specific.
Influence of controlled hypoxia and radical scavenging agents on erythropoietin and malondialdehyde concentrations in humans
Authors: FREUDENTHALER S. M. , SCHREEB K.‐H. , WIESE A. , PILZ J. , GLEITER C. H.
Published: March 2003

The present study was carried out to evaluate a model of a hypoxic stimulus of erythropoietin (EPO) production in humans and to investigate the role of free oxygen radicals in human EPO production. The study was conducted as an open, randomized, parallel, placebo‐controlled trial. Thirty‐six healthy male volunteers received a hypoxic treatment (13% O2) with a respiration mask for 6 h. During the period of hypoxia, the volunteers received as a short‐term treatment either 1200 mg thioctic acid, or N‐acetylcysteine 600 mg or placebo (0.9% sodium chloride). The EPO concentration in plasma increased up to 290% of the baseline level in all three groups. No statistically significant differences of AUCEPO(0–48 h) could be demonstrated between the groups. The malondialdehyde (MDA) concentration in plasma increased significantly (P < 0.001) 2 h after termination of hypoxia (mean 129.8 ± 6.8% of the baseline) in all three groups. Conclusions: Taken together, our in‐vivo results do not support a gross modulatory effect of a short‐term treatment with radical scavenging agents on EPO‐production during or after hypoxia in humans, as derived from the detected changes of MDA‐concentrations in peripheral plasma.
The cystic fibrosis transmembrane conductance regulator is not a base transporter in isolated duodenal epithelial cells
Authors: PRAETORIUS J. , FRIIS U. G. , AINSWORTH M. A. , SCHAFFALITZKY DE MUCKADELL O. B. , JOHANSEN T.
Published: March 2003

Duodenal epithelial bicarbonate secretion has previously been shown to be greatly impaired in mice deficient of the cystic fibrosis transmembrane conductance regulator (CFTR). It has been proposed that transmembranal bicarbonate transport occurs through the CFTR channel itself. In the present study, the transport of acid/base equivalents across the plasma membrane of proximal duodenal epithelial cells from CFTR deficient mice was compared with that of cells from normal littermates. Mixed epithelial cells from both villi and crypts were isolated from proximal duodenum and intracellular pH was assessed by cuvette‐based fluorescence spectrometry using the pH sensitive dye 2′,7′‐bis‐(2‐carboxyethyl)‐5‐(and‐6)‐carboxyfluorescein. The steady state intracellular pH, the acid extrusion rate and the alkaline extrusion rate were unaffected by CFTR deficiency in the presence of CO2/HCO3–. Forskolin had no effect on acid extrusion or alkaline extrusion rates. In control experiments without CO2/HCO3–, the intrinsic buffering capacities, the steady state intracellular pH and the acid extrusion rates were equivalent in the cells from CFTR deficient mice and normal littermates. The results are consistent with a model where acid/base transport is almost exclusively mediated by the previously described transporters in the murine duodenum (i.e. Na+/H+ exchange, Cl–/HCO3– exchange and Na+ : HCO3– cotransport). There were no evidence for significant CFTR dependent HCO3– transport in proximal duodenal epithelial cells of mixed villus and crypt origin.
Dopamine‐induced inhibition of Na+‐K+‐ATPase activity requires integrity of actin cytoskeleton in opossum kidney cells
Authors: GOMES P. , SOARES‐DA‐SILVA P.
Published: March 2003

The present study evaluated the importance of the association between Na+‐K+‐ATPase and the actin cytoskeleton on dopamine‐induced inhibition of Na+‐K+‐ATPase activity. The approach used measures the transepithelial transport of Na+ in monolayers of opossum kidney (OK) cells, when the Na+ delivered to Na+‐K+‐ATPase was increased at the saturating level by amphotericin B. The maximal amphotericin B (1.0 μg mL–1) induced increase in short‐circuit current (Isc) was prevented by ouabain (100 μM) or removal of apical Na+. Dopamine (1 μM) applied from the apical side significantly decreased (29 ± 5% reduction) the amphotericin B‐induced increase in Isc, this being prevented by the D1‐like receptor antagonist SKF 83566 (1 μM) and the protein kinase C (PKC) inhibitor chelerythrine (1 μM). Exposure of OK cells to cytochalasin B (1 μM) or cytochalasin D (1 μM), inhibitors of actin polymerization, from both cell sides reduced by 31 ± 4% and 36 ± 3% the amphotericin B‐induced increase in Isc and abolished the inhibitory effect of apical dopamine (1 μM), but not that of the PKC activator phorbol‐12,13‐dibutyrate (PDBu; 100 nM). Colchicine (1 μM) failed to alter the inhibitory effects of dopamine. The relationship between Na+‐K+‐ATPase and the concentration of extracellular Na+ showed a Michaelis–Menten constant (Km) of 44.1 ± 13.7 mM and a Vmax of 49.6 ± 4.8 μA cm–2 in control monolayers. In the presence of apical dopamine (1 μM) or cytochalasin B (1 μM) Vmax values were significantly (P < 0.05) reduced without changes in Km values. These results are the first, obtained in live cells, showing that the PKC‐dependent inhibition of Na+‐K+‐ATPase activity by dopamine requires the integrity of the association between actin cytoskeleton and Na+‐K+‐ATPase.
The neuropeptide PACAP contributes to the glucagon response to insulin‐induced hypoglycaemia in mice
Authors: PERSSON K. , AHRÉN B.
Published: March 2003

The neuropeptide pituitary adenylate cyclase‐activating polypeptide (PACAP) is a neuropeptide in the autonomic nerves innervating the pancreatic islets and previous studies have shown that it stimulates insulin and glucagon secretion. It is known that autonomic nerve activation contributes to the glucagon response to hypoglycaemia. In the present study, we evaluated whether PACAP is involved in this glucagon response by examining the glucagon response to insulin‐induced hypoglycaemia in mice genetically deleted of the specific PACAP receptor, the PAC1 receptor. We found that insulin (1 U kg–1 ip) reduced circulating glucose to a hypoglycaemic level of ≈2.5 mmol L–1 in PAC1R–/– mice and their wild‐type counterparts with no difference between the groups. However, the glucagon response to this hypoglycaemia was markedly impaired in the PAC1R–/– mice. Thus, after 120 min, plasma glucagon was 437 ± 79 ng L–1 in wild‐type mice vs. only 140 ± 36 ng L–1 in PAC1R–/– mice (P=0.004). In contrast, the glucagon response to intravenously administered arginine (0.25 g kg–1) was the same in the two groups of mice. We conclude that PACAP through activation of PAC1 receptors contribute to the glucagon response to insulin‐induced hypoglycaemia. Therefore, the glucagon response to hypoglycaemia is dependent not only on the classical neurotransmitters but also on the neuropeptide PACAP.
Effect of exercise on the rat mammary gland: implications for carcinogenesis
Authors: WESTERLIND K. C. , MCCARTY H. L. , GIBSON K. J. , STRANGE R.
Published: March 2003

Physical activity has been associated with decreased risk for developing breast cancer yet to date, the mechanism remains unknown. The purpose of this investigation was to evaluate the effects of moderate exercise training on the normal mammary gland in an attempt to identify alterations or differences that might be associated with tumour inhibition. A total of 170 female Sprague–Dawley rats were randomized to baseline (n=10), exercise (EX; n=80), or sham‐exercise groups (SHAM; n=80). Treadmill training (20–25 m min–1, 15% grade, 30 min day–1, 5 days week–1) was started at 28 days of age (DOA). Animals were killed at 28, 42, 56, 70 and 84 DOA. Mammary glands were evaluated by histology and immunohistochemistry. Terminal end buds (TEB), structures susceptible to carcinogenesis, were counted. Sexual maturation, estradiol and progesterone, and organ and muscle weights were also evaluated. No differences in growth, sexual maturation, or steroid hormones were observed in response to training. No difference in the number of TEBs was observed at any timepoint between EX and SHAM. Proliferation was significantly increased at 56 DOA and tended to be increased at 42 and 70 DOA in the EX animals whereas cell death was significantly increased at 70 DOA and tended to be increased at 84 DOA in the EX animals. These data suggest no difference in the number of carcinogen‐susceptible structures as a result of moderate exercise. The changes in cell proliferation and apoptosis with exercise training suggest altered cell turnover that will necessitate future study particularly with relevance to carcinogenesis.
Are early clinical effects of cholesterol lowering mediated through effects on inflammation?
Authors: Olsson A. G. , Schwartz G. G. , Jonasson L. , Linderfalk C.
Published: March 2003

In a randomized, double‐blind trial in 3086 patients with unstable angina pectoris or non‐Q wave myocardial infarction we investigated if 80 mg of atorvastatin daily could improve outcome of cardiovascular events during a short period of time (16 weeks) compared with placebo. Baseline LDL cholesterol was 3.2 mmol L−1 (124 mg dL−1) and decreased by 40% to 1.9 mmol L−1 (72 mg dL−1) during atorvastatin treatment. The primary endpoint, which was a composite of death, non‐fatal acute myocardial infarction, cardiac arrest with resuscitation or recurrent symptomatic myocardial ischaemia with objective evidence and requiring emergency rehospitalization occurred in 228 patients (14.8%) in the atorvastatin group and 269 patients (17.4%) in the placebo group. The relative risk was0.84 and 95% confidence interval was 0.70–1.00 (P = 0.048). Thus for patients with acute coronary syndromes, lipid‐lowering therapy with high dose atorvastatin reduces recurrent ischaemic events in the short‐term. A possible mechanism behind this rapid clinical effect induced by statin treatment is on inflammatory processes. Recent studies strongly suggest that acute T‐cell activation is involved in the pathogenesis of unstable angina. In another study we investigated whether circulating T cells showed signs of activation in patients with stable angina pectoris (SA). Systemic venous blood samples were taken from 38 men with SA and 42 healthy controls. The T‐cell receptor expression was assessed by three‐colour flow cytometry using monoclonal antibodies against CD3,CD4, CD8, CD25 and human leucocyte antigen (HLA)‐DR. Soluble interleukin‐2 receptor (sIL‐2R) was measured as the circulating form in serum. Levels of circulating CD3+ and CD4+ T cells tended to be higher in patients compared with controls. Patients were also shown to have a significant increase in CD4+ T cells expressing the activation markers CD25 (P < 0.05) and HLA‐DR (P < 0.01). Furthermore, serum levels of sIL‐2R were significantly higher (P < 0.001) in patients than in controls. We also observed that the T‐cell response was more pronounced in patients without simvastatin treatment (n = 18) compared with simvastatin‐treated patients (n = 20). In conclusion, our findings indicate that a continuous immune system activation takes place in patients with chronic angina pectoris, predominantly involving proliferation of CD4+ T cells. Statin treatment seems to be able to decrease this inflammatory response.
Lipophilic oestrogen derivatives contained in lipoprotein particles
Authors: Tikkanen M. J. , Vihma V. , Höckerstedt A. , Jauhiainen M. , Helisten H. , Kaamanen M.
Published: March 2003

Steroid fatty acid esters constitute a unique family of lipophilic hormones carried exclusively in circulating lipoproteins. Our studies have focused on the formation of 17β fatty acid esters of labelled oestradiol in in vitro incubations with human ovarian follicular fluid and plasma and demonstrated the accumulation of these labelled derivatives in lipoprotein particles. The oestradiol esters are formed in a reaction catalysed by lecithin : cholesterol acyltransferase in association with high‐density lipoprotein particles and they can be transferred to low‐density lipoprotein particles in a process mediated by cholesteryl ester transfer protein. Using a novel quantitative method for the determination of oestradiol esters their endogenous concentrations in follicular fluid and in early and late pregnancy plasma have been determined. In addition, using labelled genistein and its chemically synthesized fatty acid esters, we also demonstrated that phytoestrogen derivatives could be incorporated in lipoprotein particles. Both oestradiol and genistein contain aromatic hydroxyl groups which cause them to exert powerful antioxidant activity in lipid‐aqueous systems in vitro. The physiological role of the steroidal fatty acid esters remains to be elucidated. In theory, the hormonal esters might form a reservoir constituted by esterified hormones stored in lipoprotein particles and perhaps in fat tissue, or they might use lipoproteins as vehicles for endocrine transport, or they could act as antioxidant protection of the lipoprotein particles. Enzyme systems necessary for the formation of lipophilic oestrogen and phytoestrogen derivatives as well as for their incorporation in lipoprotein particles are present in human body fluids. Because of their water‐insolubility, steroid fatty acid esters are carried exclusively by circulating lipoproteins. These esters can provide antioxidant protection for lipoprotein particles.
Substrate utilization in sea level residents during exercise in acute hypoxia and after 4 weeks of acclimatization to 4100 m
Authors: Lundby C. , Van Hall G.
Published: March 2003

To investigate the effect of acclimatization to hypoxia on substrate utilization, eight sea level residents were studied during exercise at the same relative (rel) and absolute (abs) work rate as at sea level (SL), under acute (AH), and after 4 weeks exposure to 4100 m altitude (CH). Carbohydrate (CHO) and fat oxidation during exercise at SL were 2.0 ± 0.2 and 0.3 ± 0.0 g min−1, respectively. At AHabs and CHabs CHO oxidation increased (P < 0.05) to 2.5 ± 0.2 and 2.3 ± 0.1 for CHO, and fat oxidation decreased (P < 0.05) to 0.2 ± 0.01 and 0.2 ± 0.01 g min−1, respectively. Exercise in AHrel and CHrel did not cause a change in the relative CHO and fat oxidation compared with SL, the absolute rate of CHO oxidized being 1.7 ± 0.1 and 1.7 ± 0.02 g min−1, respectively, and fat oxidation was 0.2 ± 0.02 g min−1 in ACrel and 0.3 ± 0.02 g min−1 in CHrel. In conclusion, substrate utilization is unaffected by AH and CH, when the work rate is matched to the same relative intensity as at SL.
Nandrolone decanoate pre‐treatment attenuates unweighting‐induced functional changes in rat soleus muscle
Authors: Joumaa W. H. , Bouhlel A. , Bigard X. , Léoty C.
Published: March 2003

The effect of nandrolone decanoate pre‐treatment (15 mg kg−1 week−1, for 6 weeks) was tested on the changes in mass and contractile properties of soleus muscle associated with 3 weeks of hindlimb suspension. Male rats were assigned to four groups (eight animals/group): control, nandrolone decanoate hindlimb‐loaded, hindlimb‐unweighted and nandrolone decanoate hindlimb‐unweighted. Compared with age‐matched control values, suspension induced a reduction in relative muscle mass and a shift in tension characteristics from slow‐towards fast‐twitch type. Nandrolone decanoate pre‐treatment of suspended animals (nandrolone decanoate hindlimb‐unweighted vs. nandrolone decanoate hindlimb‐loaded) partially spared the relative soleus mass. Furthermore, (1) the relative twitch tension (nandrolone decanoate hindlimb‐loaded: 5.4 ± 0.7%; nandrolone decanoate hindlimb‐unweighted: 5.1 ± 0.5%), (2) the time to peak tension (nandrolone decanoate hindlimb‐loaded: 152 ± 9 ms; nandrolone decanoate hindlimb‐unweighted: 167 ± 15 ms), (3) the time constant of relaxation (nandrolone decanoate hindlimb‐loaded: 274 ± 12 ms; nandrolone decanoate hindlimb‐unweighted: 245 ± 20 ms), (4) the relative K+ contracture tension (nandrolone decanoate hindlimb‐loaded: 81.7 ± 3.8%; nandrolone decanoate hindlimb‐unweighted: 86.9 ± 4.2%) and (5) the relative caffeine contracture tension (0.5 mm) (nandrolone decanoate hindlimb‐loaded: 5.2 ± 0.8%; nandrolone decanoate hindlimb‐unweighted: 5.9 ± 1.1%) were not significantly modified. The present results demonstrate that exogenously provided nandrolone decanoate pre‐treatment attenuates functional changes occurring in soleus muscle subject to unweighting.
The paraventricular nucleus: an important component of the central neurocircuitry regulating sympathetic nerve outflow
Authors: Kenney M. J. , Weiss M. L. , Haywood J. R.
Published: March 2003

AbstractAim: The sympathetic nervous system plays an important role in the regulation of physiological homeostasis under basal conditions and in response to acute and chronic stressors. It is known that multiple levels of the neuroaxis, including the paraventricular nucleus (PVN) of the hypothalamus, are involved in regulation of efferent sympathetic nerve discharge (SND). This review focuses on the role of the PVN in regulation of functional characteristics of efferent SND.

Results: The available experimental evidence indicates that the level of efferent sympathetic nerve activity is altered after microinjection of numerous substances into the PVN, including excitatory amino acids,γ‐aminobutyric acid (GABAA) receptor agonists and antagonists, and PVN nitric oxide synthase inhibitors. In addition, antagonism of PVN GABAAreceptors changes the pattern of synchronized discharge bursts in efferent sympathetic nerves and enhances the frequency‐domain coupling between low‐frequency bursts in sympathetic nerve pairs. Finally, PVN microinjections of excitatory amino acids (l‐glutamate,d,l‐homocysteic acid) have been shown to produce non‐uniform changes in the level of efferent sympathetic nerve activity.

Conclusion: These findings support the concept that the PVN is an important component of the central neurocircuitry regulating functional characteristics (basal level of activity, bursting pattern, and relationships between discharges in nerves innervating different targets) of efferent sympathetic nerve outflow.
Transmission of signals through sympathetic ganglia – modulation, integration or simply distribution?
Authors: McLachlan E. M.
Published: March 2003

Aim: On structural grounds, synaptic transmission in sympathetic ganglia is potentially complex with extensive divergence and convergence between preganglionic and postganglionic neurones. In this review, the focus is on what constitutes a functional synapse in sympathetic ganglia and how intracellular recordings have enabled us to identify how the transmission process operates in vivo.

Results: Only one or two suprathreshold or ‘strong’ inputs are involved in activating each postganglionic neurone. The functional significance of the subthreshold or ‘weak’ inputs remains obscure. The strong inputs, and sometimes the weak ones as well, respond in the same way during reflexes. The expansion of ineffective weak connections enables the rapid restoration of functional control after lesions that damage preganglionic neurones. These novel connections may generate erroneous reflex responses after spinal injury. Postganglionic discharge in vivo consists of the summed firing of the strong preganglionic inputs limited, at high preganglionic discharge rates, by the properties of the afterhyperpolarization.

Conclusion: Preganglionic signals are distributed widely through paravertebral ganglia with little modification.
Vestibular activation of sympathetic nerve activity
Authors: Ray C. A. , Carter J. R.
Published: March 2003

Aim: The vestibulosympathetic reflex refers to sympathetic nerve activation by the vestibular system. Animal studies indicate that the vestibular system assists in blood pressure regulation during orthostasis. Although human studies clearly demonstrate activation of muscle sympathetic nerve activity (MSNA) during engagement of the otolith organs, the role of the vestibulosympathetic reflex in maintaining blood pressure during orthostasis is not well‐established. Examination of the vestibulosympathetic reflex with other cardiovascular reflexes indicates that it is a powerful and independent reflex. Ageing, which is associated with an increased risk for orthostatic hypotension, attenuates the vestibulosympathetic reflex. The attenuated reflex is associated with a reduction in arterial pressure.

Conclusion: These findings suggest that the vestibulosympathetic reflex assists in blood pressure regulation in humans, but future studies examining this reflex in other orthostatically intolerant populations are necessary to address this hypothesis.
Sympathetic activation in human heart failure: diverse mechanisms, therapeutic opportunities
Authors: Floras J. S.
Published: March 2003

Plasma noradrenaline (NA) concentrations relate both to the severity of heart failure, and to its impact on survival, but have shortcomings that limit their usefulness as measures of sympathetic discharge. Neural recordings and the isotopic dilution method for determining organ‐specific rates of NA spillover into plasma have enhanced our understanding of mechanisms responsible for sympathetic activation. Because the arterial baroreceptor reflex control of heart rate is impaired in heart failure, a parallel reduction in the reflex inhibition of sympathetic outflow has been assumed. However, human heart failure is characterized by rapidly responsive arterial baroreflex regulation of muscle sympathetic nerve activity (MSNA), attenuated cardiopulmonary reflex modulation of MSNA, and activation of a cardiac‐specific sympatho‐excitatory reflex related to increased cardiopulmonary filling pressures. Together, these baroreceptor mediated mechanisms account only, in part, for the time course and magnitude of adrenergic activation in heart failure. Non‐baroreflex sympatho‐excitatory mechanisms include: a metaboreflex arising from exercising skeletal muscle, mediated, in part, by adenosine, co‐existing sleep apnoea, and pre‐junctional facilitation of NA release. Thus, sympathetic activation in the setting of impaired systolic function reflects the net balance and interaction between augmented excitatory and diminished inhibitory influences. Variation, between patients, in the dynamics, magnitude and progression of sympathetic activation mandates an individualized approach to investigation and therapy. Excessive sympathetic outflow to the heart and periphery can be addressed by several complimentary strategies: attenuating these sympatho‐excitatory stimuli, modulating the neural regulation of NA release, and blocking the actions of catecholamines at post‐junctional receptors.
Sympathetic nerve activity and neurotransmitter release in humans: translation from pathophysiology into clinical practice
Authors: Esler M. , Lambert G. , Brunner‐La Rocca H. P. , Vaddadi G. , Kaye D.
Published: March 2003

Aim:  There has been a revolution in cardiovascular neuroscience in recent years with, in some cases, translation into clinical practice of the knowledge of pathophysiology gained through application of sympathetic nerve recording and catecholamine isotope dilution methodology.

Obesity‐related hypertension:  An earlier hypothesis, based on findings in most models, was that weight gain in obesity is due in part to sympathetic nervous underactivity reducing thermogenesis. Microneurography and regional noradrenaline spillover measurements in human obesity have disproven this hypothesis, weakening the case for the use of β3‐adrenergic agonists to stimulate thermogenesis. Sympathetic nerve firing rates in post‐ganglionic fibres directed to the skeletal muscle vasculature are increased, as is renal sympathetic tone, with a doubling of the spillover rate of noradrenaline from the kidneys. Given these findings, antiadrenergic antihypertensive drugs may be the preferred agents for obesity‐related hypertension, but this has not been adequately tested.

Essential hypertension:  Whether stress causes high blood pressure, previously hotly debated, has been under recent review by an Australian Government body, the Specialist Medical Review Council. Despite medicolegal implications, the ruling was that stress is one proven cause of hypertension. The judgment was reached after consideration of the epidemiological evidence, but in particular the described neural pathophysiology of essential hypertension: (a) persistent sympathetic nervous stimulation is commonly present, (b) suprabulbar projections of noradrenergic brainstem neurones are activated and (c) adrenaline is released as a cotransmitter in sympathetic nerves. These were taken to be biological markers of stress.

Cardiac failure:  At one time, the failing heart was thought to be sympathetically denervated. Longterm administration of inotropic adrenergic agonists, to provide the cardiac catecholamine stimulation thought to be lacking, increased mortality. Noradrenaline isotope dilution methodology subsequently demonstrated that the sympathetic outflow to the heart was preferentially activated, cardiac noradrenaline spillover being increased as much as 50‐fold. The level of stimulation of the cardiac sympathetic nerves was the most powerful predictor of death. These observations provide the theoretical foundation for the very successful introduction of β‐adrenergic blockers for treatment of heart failure.
Changes in termite (Isoptera) communities due to the clearance and cultivation of tropical forest in Uganda
Authors: Okwakol Mary J. N.
Published: March 2003

Changes in termite communities following clearance and cultivation of part of Mabira Forest Reserve were studied. The study sites included natural forest, a cleared but not cultivated site and six sites cultivated for different periods, ranging from 1 to 20 years.

A total of 25 species, includingOdontotermes amanicus(Sjostedt) andMicrotermes luteus(Harris), both not previously identified in Uganda, was recorded in the natural forest. Forest clearance resulted in drastic reduction of the number of species to about 40% of what existed in the natural forest, while cultivation led to further elimination, leaving only four and two species, respectively, in the 1‐ and 20‐year‐old banana groves.

The study showed that termite species diversity declines when the natural forest is cleared and cultivated. It is suggested that reduction in termite diversity alters ecological processes and may result in diminishing productivity with time.
Pre‐infection events in non‐nodulating species of African Acacia
Authors: Harrier L. A. , Whitty P. , Sutherland J. M. , Sprent J. I.
Published: March 2003

Non‐nodulation occurs sporadically throughout the family Leguminosae, the genus Acacia is unusual as there are a range of species which are consistently non‐nodulating, but which are closely related to species able to form nodules. A comparative study of these and coexisting related nodulating species has been made to establish whether the non‐nodulating species exhibited any pre‐infection characteristics which are typical of their nodulating counterparts. The non‐nodulating species did not form any nodule‐like structures, but exhibited pre‐infection characteristics such as rhizobial attachment similar to that of their nodulating counterparts. The root exudate of nodulating A. polyacantha contained stimulatory compounds which aided binding of rhizobia to the roots of the non‐nodulating species and nodulation was completely inhibited when A. polyacantha was co‐cultured with a non‐nodulating species.
Movement Patterns and Home Range Of The Bongo (Tragelaphus Eurycerus) In The Rain Forest Of The Dzanga National Park, Central African Republic
Authors: Klaus‐Hügi Corinne , Klaus Gregor , Schmid Bernhard
Published: March 2003

Bongos (Tragelaphus eurycerusOgilby) were studied for 8 months in the Dzanga National Park, Central African Republic. Tracks were followed and mapped with a compass and a pedometer to study movement patterns and home range. Natural licks were shown to be central points in the home range of the bongos: they visited the licks recurrently to consume soil, but also to forage on grass and herb species, and for social reasons. Forest areas far from licks were used much less than forest areas close to licks. When a lick was visited, distances between two resting sites were longer than in the forest without lick visits, caused by a direct and straight movement from the denser forest areas toward a lick. The study area of about 150 km2was presumably occupied by two groups of bongos. One of them seemed to split temporarily into two subgroups. Groups were not larger than 10–20 individuals. Estimated home ranges were at least 49 km2and 19 km2for the two groups, respectively. Estimated density in the Dzanga National Park was 0.25 bongos per km2.This study shows the importance of natural licks for the largest social forest antelope, the bongo, and provides information which is important for its future conservation.
Ranging behaviour and habitat usage in black rhinoceros, Diceros bicornis, in a Kenyan sanctuary
Authors: Tatman Susan C. , Stevens‐Wood Barry , Smith Vincent B. T.
Published: March 2003

Home range area and habitat utilization by translocated black rhinoceros Diceros bicornis were studied at Sweetwaters Rhino Sanctuary in the Laikipia district of Kenya. Home ranges were estimated from sightings and tracking data; home range area was very variable between individuals (range 2.25–14.39km2, minimum convex polygons), and was independent of age or sex. Groups of rhinoceros shared common home ranges, with little or no overlap between groups; each group consisted of one adult male, one or more adult females and their calves, and sometimes immature animals. Rhinoceros utilize a variety of habitats, but within these show positive selection for certain habitats. Home ranges generally included more Euclea bush, and less grassland and Acacia bush than expected. Rhinoceros make use of regular resting places, or bedding sites, generally situated in bushland in secluded areas, often in dense thickets. Rhinoceros defaecate at dung piles or middens. Middens are located throughout the range not just on the boundaries; the highest density of middens was found in riverine woodland, and the lowest density in grassland and Acacia bush.
Habitat constraints limit the distribution and population density of redwing francolin, Francolinus levaillantii, in the highland grasslands of Mpumalanga province, South Africa
Authors: Jansen R. , Robinson E. R. , Little R. M. , Crowe T. M.
Published: March 2003

We investigated a variety of habitat characteristics along a land‐use gradient in an attempt to determine which factors may have influenced the population decline of redwing francolin, Francolinus levaillantii, in commercial pasture farms in the highland grasslands of Mpumalanga province, South Africa. Within three microhabitats (wetlands, rocky outcrops and grassland), number and diversity of food plants, height of the sward and percentage cover were significantly lower in habitat exposed to commercial grazing with sheep. Increased cover and height of the sward were positively correlated with higher diversity and availability of francolin food plants. Crop analyses revealed a lower intake in the number of food plant species, but higher incidence of invertebrates, ingested by birds collected in heavily grazed and frequently burned grasslands. Intestinal caecae were significantly (P < 0.001) longer in birds collected from grazed/burned grasslands – possibly associated with a low quality, more fibrous diet. Both the quantity and quality of habitat in terms of food abundance, diversity and cover are important factors influencing the distribution of redwing francolin in these grasslands.
Butterfly populations in two forest fragments at the Kenya coast
Authors: Rogo Lucie , Odulaja Adedapo
Published: March 2003

Species richness, diversity and composition of butterflies in two Kenya coastal forest remnants, Muhaka and Mrima hill, were investigated. Sixty‐three species were recorded from each forest remnant from a total of 1329 individuals. Species accumulation curves for both forests did not reach an asymptote. High species similarity was recorded between the forest interior and the surrounding matrix, primarily due to invasion of the forest interior clearings by the savanna species. Despite their small sizes, these forest remnants were found to maintain viable populations of true forest butterflies. However, the number of species was less than half that recorded from the larger forest reserve of Arabuko‐Sokoke, located in the same geographical area. Records from Muhaka forest show species unique to it, not found in the larger forest reserves, underscoring the importance of small remnants in the preservation of forest biodiversity. The high species similarity between the forest remnants implied that if habitat corridors were created, gene flow between these remnants and other larger forest reserves would be possible. This would reduce the isolation of true forest butterfly populations within the remnants and potential local extinction.
Porewater nutrient profiles and nutrient sediment–water exchange in a tropical mangrove waterway, Mapopwe Creek, Chwaka Bay, Zanzibar
Authors: Mohammed Salim M. , Johnstone Ron W.
Published: March 2003

Sediments were examined in the Mapopwe Creek, a tidally dominated mangrove waterway in the Chwaka Bay mangrove forest, Zanzibar, to assess their significance in the nutrient dynamics of the mangrove forest and the adjacent bay. Porewater concentrations of dissolved ammonium and that of soluble reactive phosphorus (SRP) were generally higher during the dry season than during the wet season. NO3− plus NO2− concentration averaged 1 µm and did not vary much between the two periods. Fluxes of ammonium ranged from −575 to 523 µm m−2 h−1 and those of SRP from −55.7 to 69.5 µm m−2 h−1. Measurements of NOx did not show any consistent fluxes of this dissolved nitrogen species. Variations of flux rates between the two seasons were not significant even though there were small variations in the flux direction in both nutrients. Results imply that Mapopwe sediments are a source of NH4+ but act as a sink for SRP.
The impact of elephants on the marula tree Sclerocarya birrea
Authors: Gadd Michelle E.
Published: March 2003

This study determined the abundance, density and population structure of the marula tree, Sclerocarya birrea, in three game reserves in South Africa, and assessed patterns and amounts of new and cumulative impact of elephants. Elephant feeding was very patchy so several attributes of individual trees, sampled transects and communities that might influence elephant herbivory were investigated. The incidence and type of elephant impact (bark, branch or stem breakage) were significantly related to tree diameter, but not to fruiting nor proximity to roads. At the transect level, elephant impact was influenced by density of marula trees, but was not influenced by proximity to roads, nor proportion of marula trees bearing fruits in the vicinity. At the community level, elephant impact was higher on reserves with higher total marula densities. Fourfold differences in elephant densities (0.08–0.30 elephants km−2) did not explain marula consumption: the percentage of trees with branch damage was similar across reserves and bark damage was inversely proportional to elephant density. Variation across reserves may reflect local and landscape‐level marula tree abundance, differences in alternative food plants and individual feeding habits. The recorded levels of impact appeared to be sustainable because mortality rates were low, affected trees often recovered, and small trees were not preferentially preyed upon.