bluuebunny/crossref_metadata_2025_split huggingface dataset:
β ‐Adrenoceptor agonist sensitizes the dopamine‐1 receptor in renal tubular cells
Authors: Brismar H. , Agrèn M. , Holtbäck U. 
Published: March 2003

ABSTRACTThe renal effects of dopamine are mainly mediated via the dopamine‐1 receptor (D1 receptor). This receptor is recruited from intracellular compartments to the plasma membrane by dopamine and atrial natriuretic peptide (ANP), via adenylyl cyclase activation. We have studied whether isoproterenol, a β‐adrenoceptor (β‐AR) agonist that may interact with dopamine in the regulation of rat renal Na+, K+‐adenosine triphosphatase (ATPase) activity, can recruit D1 receptors to the plasma membrane. The spatial regulation of D1 receptors was examined using confocal microscopy techniques in LLCPK cells and the functional interaction between dopamine and isoproterenol was examined by studying their effects on Na+, K+‐ATPase activity in microdissected single proximal tubular segments from rat. Isoproterenol was found to translocate the D1 receptors from the interior of the cell towards the plasma membrane. The recruitment of dopamine 1 receptors was found to be cyclic adenosine phosphate (cAMP) dependent, while protein kinase C (PKC) activation was not involved. The functional studies on Na+, K+‐ATPase activity showed that the effect of isoproterenol was abolished by a D1‐like receptor antagonist (SCH 23390), and mediated via protein kinase A (PKA) and PKC dependent pathways. The results provide an explanation for the interaction between G protein‐coupled receptors. The effects of isoproterenol on Na+, K+‐ATPase activity can be explained by a heterologous recruitment of D1 receptors to the plasma membrane.
Reduced calcium tolerance in rat cardiomyocytes after myocardial infarction
Authors: Sjaastad I. , Bentzen J. G. , Semb S. O. , Ilebekk A. , Sejersted O. M. 
Published: March 2003

ABSTRACTDuring ischaemia and reperfusion the intracellular Na+ concentration is elevated in the cardiomyocytes and the cells are depolarized, both favouring reverse mode Na,Ca‐exchange loading of the cell with Ca2+. We examined whether cardiomyocytes from rats with congestive heart failure (CHF) and younger rats (HINCX) which both have a high expression of the Na,Ca‐exchanger protein (NCX) showed reduced tolerance to extracellular Ca2+. The CHF was induced in Isofluran anaesthetized rats by left coronary artery ligation. Isolated cardiomyocytes were loaded with Fura‐2AM and 140 mm Na+ and exposed to 0.05 mm Ca2+. Expression of the Na,Ca‐exchanger protein was analysed. Fura‐2 340/380 ratio rose more rapidly in HINCX and CHF than in SHAM, and the rise was abolished by Ni2+. Hypercontracture developed more frequently in HINCX and CHF than in SHAM cells. The amount of NCX was 54% higher in HINCX and 76% higher in CHF compared with SHAM. Na+‐loaded cardiomyocytes from CHF and HINCX rats are more susceptible to Ca2+ overload than SHAM cells because of the increased capacity for Na,Ca‐exchange.
Muscle morphology, self‐reported physical activity and insulin resistance syndrome
Authors: Hedman A. , Byberg L. , Reneland R. , Lithell H. O. 
Published: March 2003

ABSTRACTIn a population‐based sample of 475 men the associations between muscle morphology, self‐reported physical activity (PA) and insulin resistance (IR) syndrome were investigated. Also, we studied to what degree muscle morphology contributes to the association between PA and IR syndrome. Muscle morphology and the components of IR syndrome were compared in four groups categorized according to self‐reported habitual PA data. We found a significantly higher percentage of type I fibres, fibre area and number of capillaries around the fibres and a lower proportion of type IIB fibres with higher level of PA. The relative distribution of type I fibres and capillarization were positively related to high density lipoprotein (HDL) cholesterol and negatively to serum triglycerides (TG) and plasminogen activator inhibitor‐1 (PAI‐1) activity. The percentage of type IIB fibres was were inversely related to HDL cholesterol and positively to serum TG, PAI‐1 activity and resting heart rate. Insulin sensitivity was positively and independently related to PA level (P < 0.001). Regression analysis including all relevant variables regarding insulin sensitivity indicated that the significant explanatory variables left in the equation were body mass index (BMI), glucose intolerance, PAI‐1 activity, serum free fatty acid concentration, proportion of type IIB fibres, HDL cholesterol level, drug treatment, PA level, and waist‐to‐hip ratio, which together explained 55% of the variation in the insulin sensitivity index. In conclusion, both fibre type distribution and muscle capillary density might contribute to the beneficial effect of PA on IR syndrome.
Responses of the bronchial and pulmonary circulations to short‐term nitric oxide inhalation before and after endotoxaemia in the pig
Authors: Middelveld R. J. M. , Alving K. 
Published: March 2003

ABSTRACTThe physiological responses of the bronchial circulation to acute lung injury and endotoxin shock are largely unexplored territory. This study was carried out to study the responsiveness of the bronchial circulation to nitric oxide (NO) inhalation before and after endotoxaemia, in comparison with the pulmonary circulation, as well as to study changes in bronchial blood flow during endotoxaemia. Six anaesthetized pigs (pre‐treated with the cortisol‐synthesis inhibitor metyrapone) received an infusion of 10 µg/kg endotoxin during 2 h. Absolute bronchial blood flow was measured via an ultrasonic flow probe around the bronchial artery. The pigs received increasing doses of inhaled NO over 5 min each (0, 0.2, 2 and 20 ppm) before and after 4 h of endotoxaemia. The increase in bronchial vascular conductance during 5 min of inhalation of 20 ppm NO before endotoxin shock was significantly higher (area under curve (AUC) 474.2 ± 84.5% change) than after endotoxin shock (AUC 118.2 ± 40.4%, P < 0.05 Mann–Whitney U‐test). The reduction of the pulmonary arterial pressure by 20 ppm NO was not different. A short rebound effect of the pulmonary arterial pressure occurred after discontinuation of inhaled NO before endotoxaemia (AUC values above baseline 54.4 ± 19.7% change), and was virtually abolished after endotoxaemia (AUC 6.1 ± 4.0%, P = 0.052, Mann–Whitney U‐test). Our results indicate that the responsiveness of the bronchial circulation to inhalation of increasing doses of inhaled NO during endotoxin shock clearly differ from the responsiveness of the pulmonary circulation. The reduced responsiveness of the bronchial circulation is probably related to decreased driving pressure for the bronchial blood flow. The absence of the short rebound effect on pulmonary arterial pressure (PAP) after induction of shock could be related to maximum constriction of the pulmonary vessels at 4 h.
Fatty acids are important for the Frank–Starling mechanism and Gregg effect but not for catecholamine response in isolated rat hearts
Authors: Pagliaro P. , Chiribiri A. , Gattullo D. , Penna C. , Rastaldo R. , Recchia F. A. 
Published: March 2003

ABSTRACTIn some pathophysiological conditions myocardial metabolism can switch from mainly long chain fatty acid (LCFA) oxidation to mainly glucose oxidation. Whether the predominant fatty acid or glucose oxidation affects cardiac performance has not been defined. In a buffer perfused isovolumetrically contracting rat heart, oxidation of endogenous pool LCFA was avoided by inhibiting carnitine‐palmitoyl‐transferase I (CPT‐I) with oxfenicine (2 mm). In order to restore fatty acid oxidation, hexanoate (1 mm), which bypasses CPT‐I inhibition, was added to the perfusate. Three groups of hearts were subjected to either an increase in left ventricular volume (VV, +25%) or an increase in coronary flow (CF, +50%), or inotropic stimulation with isoproterenol (10−8 and 10−6 m). The increase in VV (the Frank–Starling mechanism) increased rate–pressure product (RPP) by 21 ± 2% under control conditions, but only by 6 ± 2% during oxfenicine‐induced CPT‐I inhibition. The contractile response to changes in VV recovered after the addition of hexanoate. Similar results were obtained in hearts, in which an increase in CF was elicited (the Gregg phenomenon). Isoproterenol caused a similar increase in contractility regardless of the presence of oxfenicine or hexanoate. In all groups, a commensurate increase in oxygen consumption accompanied the increase in contractility. The fatty acid oxidation is necessary for an adequate contractile response of the isolated heart to increased pre‐load or flow, whereas the inotropic response to adrenergic β‐receptor stimulation is insensitive to changes in substrate availability.
Nitric oxide: a local signalling molecule controlling the activity of pre‐autonomic neurones in the paraventricular nucleus of the hypothalamus
Authors: Stern J. E. , Li Y. , Zhang W. 
Published: March 2003

Abstract Aim:  The gas molecule nitric oxide (NO) has been shown to modulate autonomic function by acting both peripherally and centrally. Accumulating evidence indicates that the paraventricular nucleus (PVN) of the hypothalamus is an important locus mediating central NO actions on autonomic function, under both physiological and pathological conditions. However, the cellular targets and mechanisms mediating NO actions within the PVN are still poorly understood.Results:  By combining in vitro patch‐clamp recordings with neuronal tract tracing techniques, we show that neuronal excitability of autonomic‐related neurones in the PVN is tonically inhibited by an endogenous NO input. Furthermore, immunohistochemical studies show that ∼25% of autonomic‐related PVN neurones express neuronal nitric oxide synthase, suggesting that at least a proportion of them contribute to the cellular sources of NO within the PVN.Conclusion:  In summary, this work suggests that NO modulation of the firing activity of autonomic‐related PVN neurones constitutes an efficient mechanism mediated central NO regulation of autonomic function.
Short‐term responses of rehabilitating coastal dune forest ground vegetation to livestock grazing
Authors: Wassenaar Theo D. , Van Aarde Rudi J. 
Published: March 2003

AbstractWe investigated the responses of the ground vegetation in a 17‐year‐old coastal dune forest plant community to four levels of experimentally applied livestock grazing (three grazing levels and one ungrazed control) from May 1994 to March 1996. The effects of grazing were apparently subordinate to site‐specific intrinsic vegetation change and there were some indications that rainfall interacted with grazing level. Grazing had some apparent but no significant effects on plant species composition, significantly affected plant species richness over time, and significantly increased the range of species richness and vegetation cover values as well as the relative abundance and numbers of plant species with erect growth forms. Vegetation cover changed significantly over time, independently of grazing. Our results point to two important, easily measured mechanisms for the conservation management of coastal dune forests – the interaction of disturbance type with plant growth form and the increase of variation in community structural variables under disturbance. These mechanisms, although they potentially have wide application and predictive power, have not been studied adequately.
Aspects of the feeding ecology of Sargochromis codringtonii in Lake Kariba, Zimbabwe
Authors: Moyo Ngonidzashe A. G. 
Published: March 2003

Abstract Sargochromis codringtonii
has always been considered a good candidate for the biological control of snails. However, there is lack of data on the feeding ecology of this species. The diet of
S. codringtonii
was examined by an analysis of stomach contents. The food of adult
S. codringtonii
in Lake Kariba is dominated by prosobranch snails. Pulmonate snails form a small insignificant component of the diet of
S. codringtonii
, and the reasons for this are discussed. Electivity indices were used to investigate prey selection.
S. codringtonii
does not show a particular preference for any snail species. It feeds on any snail species that is readily available. A morphometrical analysis of the feeding structures of
S. codringtonii
showed that the fish is well adapted to handling a molluscivorous diet. The daily food consumption of
S. codringtonii
was estimated over different seasons using the
Elliot & Persson (1978
) model [
J. Anim. Ecol.47.977–991]. Estimates of food consumption indicate that the fish consumed 14.0% of their dry body weight per day in summer and this falls to 4.5% in winter. The low consumption of pulmonates means that S. codringtonii cannot be a successful biological control agent against the vectors of schistosomiasis.
Vegetation structure and ecology of the Cufada Lagoon (Guinea‐Bissau)
Authors: Catarino Luís , Martins Eurico S. , Diniz Maria Adélia 
Published: March 2003

AbstractThe Cufada Lagoon, in the southern part of Guinea‐Bissau, West Africa, is a shallow lagoon with a surface area of 190 ha in the rainy season. The vascular flora and physico‐chemical characteristics of the lagoon were studied in December 1997 (end of the wet season) and May 1998 (dry season). The lagoon water is soft, with acid pH, low conductivity and low transparency. The maximum depth is 2.25 m in the rainy season and 1.20 m in the dry season.A total of 46 vascular plant species were recorded, 32 being emergent macrophytes, mostly Gramineae and Cyperaceae, five floating‐leaved, three submerged, one surface‐floating and also five shrubs.Cluster analysis of the floristic data shows two main groups of inventories in both seasons, grouping almost nine‐tenths of the vegetation samples. The inventories in these groups correspond to two main vegetation types and can be spatially arranged. In the deepest inner part of the lagoon, Nymphaea lotus is the most important species, while Oryza longistaminata dominates in the shallower part. In spite of the shallow depth, the middle of the lagoon remains uncolonized by macrophytes. The main factors limiting the colonization by plants of the lagoon seem to be the low mineral and nutrient content of the water and its low transparency.
The occurrence and ecology of a marine hydrobiid mudsnail in the southern hemisphere: the Knysna Estuary, South Africa
Authors: Barnes R. S. K. 
Published: March 2003

AbstractEarlier published records of the gastropod Hydrobia from the warm temperate Knysna Lagoon on the Indian Ocean coast of South Africa are in error. Nevertheless, an animal hitherto identified as an Assiminea (Assimineidae) or as a Tomichia (Pomatiopsidae) is in fact a Hydrobia s.l., and it does occur intertidally within the Knysna system. The same species also occurs in salt pans in the cool temperate Great Berg Estuary on the Atlantic coast of South Africa. This extends the distribution of confirmed species of the dominant coastal hydrobiid mudsnails of the northern hemisphere into the southern hemisphere. H. knysnaensis (Krauss) occurs patchily at low density near the head of the Knysna Estuary in waters of low salinity. This appears to be a suboptimal habitat, and it is suggested that Hydrobia is restricted to this zone as a result of interference competition from potamidid mudwhelks and ocypodid crabs. The prevalence of potamidids and ocypodids in the tropics and in the temperate southern hemisphere may account for the rareness or absence of hydrobiids in these areas. Unlike its equally intertidal relative, the widespread North Atlantic/Arctic H. ulvae, H. knysnaensis develops directly like other Hydrobia.
Effects of annual rainfall and habitat types on the body mass of impala (Aepyceros melampus) in the Zambezi Valley, Zimbabwe
Authors: Bourgarel M. , Fritz H. , Gaillard J‐M. , De Garine‐Wichatitsky M. , Maudet F. 
Published: March 2003

AbstractBody mass is often considered as a good indicator of body condition of individuals in ungulates, hence of their fitness, and thus, may be used as an index to monitor the status of populations subject to harvesting schemes. Here, we report the influence of annual rainfall (a proxy for primary production) and habitat on the body mass of impala in a population cropped for meat in a communal area of Zimbabwe. We analyzed the data from 2 contrasted years for rainfall, in two different habitats. In the good year (i.e. high annual rainfall) impala were heavier than in the poor year, and adult females seemed to be less affected than males by variation in primary production. We show that adult males were suffering from a seasonal decrease in body mass, supposedly linked to the rut, particularly in good habitat. Overall, the habitat effect appeared to be dominated by the rainfall effect, and this may be due to the very high animal densities in the good habitat, i.e. fast resource depletion. Our results also suggest that males (juvenile and adult) are more susceptible to changes in food resource abundance and quality than females, which supports previous studies on sexually dimorphic and polygynous species.
Circadian rhythm of melatonin and prostaglandin in modulation of stress‐induced gastric mucosal lesions in rats
Authors: Kato K. , Murai I. , Asai S. , Takahashi Y. , Nagata T. , Komuro S. , Mizuno S. , Iwasaki A. , Ishikawa K. , Arakawa Y. 
Published: March 2003

Background:We previously demonstrated the circadian variation of water‐immersion restraint stress (WRS)‐induced gastric mucosal lesions in rats.Aim:To investigate the roles of melatonin and prostaglandin in the gastric mucosa in circadian modulation of WRS.Methods:Fasted rats were subjected to 4‐h WRS during both the diurnal and nocturnal phases of a light/dark cycle. Mucosal lesions, serum melatonin concentrations, mucosal generation of prostaglandin E2 (PGE2) and mucosal gene expressions of cyclooxygenase (COX)‐1 and ‐2 were evaluated.Results:Lesion area after 4‐h stress during the dark phase was significantly smaller than that in light‐phase controls. Serum melatonin concentration in control rats during the light phase was significantly increased 4 h after WRS, but PGE2 generation was decreased by 48% as compared to that in intact mucosa before stress. In the dark phase, melatonin concentration after 4‐h WRS was significantly depressed as compared with the control level at the corresponding time. PGE2 concentrations after 4‐h WRS in the dark phase were not decreased compared with the control level at the corresponding time, although PGE2 level was significantly lower than that in light‐phase controls. Expression of COX‐1 and COX‐2 mRNA was detected after exposure to stress in both the light and dark phases.Conclusion:These results suggest that circadian rhythm has an important role in the formation of stress‐induced gastric mucosal lesions in rats. The circadian rhythm of melatonin responses and PGE2 generation may contribute to nocturnal/diurnal rhythmicity of gastric mucosal defences between day and night.
Effect of taurine on ulcerogenic response and impaired ulcer healing induced by monochloramine in rat stomachs
Authors: Kato S. , Umeda M. , Takeeda M. , Kanatsu K. , Takeuchi K. 
Published: March 2003

Background:It is well known that neutrophil‐derived hypochlorous acid interacts with ammonia (NH4OH) to generate monochloramine (NH2Cl) and that NH2Cl irritates the gastric mucosa and impairs ulcer healing.Aim:To examine the effect of taurine, a hypochlorous acid scavenger, on the mucosal ulcerogenic and the impaired healing response induced by NH2Cl in rat stomachs, in comparison with those of methionine and glycine.Methods and results:Under anaesthesia, oral administration of NH2Cl (120 mmol/L) produced severe lesions in male Sprague–Dawley rat stomachs. Taurine (10–100 mg/kg) given p.o. 30 min prior to NH2Cl dose‐dependently prevented these lesions in response to NH2Cl. This action was mimicked by methionine (3–30 mg/kg) but not by glycine (10–100 mg/kg). Under urethane anaesthesia, mucosal exposure to NH4OH (120 mmol/L) caused a marked reduction of potential difference (PD) in the ex vivo chambered stomachs after induction of ischaemia, resulting in severe lesions. These ulcerogenic and PD responses by NH4OH plus ischaemia were also mitigated by taurine and methionine, but not glycine, applied to the chamber 20 min before the onset of NH4OH plus ischaemia. Moreover, oral administration of 100% ethanol produced severe haemorrhagic lesions in rat stomachs, all of which rapidly healed within 7 days after lesion induction. Daily administration of NH2Cl (20 mmol/L) significantly delayed the healing of these lesions, but recovery of this impaired healing response was obtained by concurrent administration of taurine. Both taurine and methionine showed a potent scavenging effect against NH2Cl in vitro.Conclusions:(1) NH2Cl generated either exogenously or endogenously damages the gastric mucosa and impairs the healing response; (2) taurine exerts a prophylactic effect against the deleterious effects of NH2Cl, mainly due to its scavenging action against NH2Cl; and (3) this effect of taurine may be useful for treatment of gastritis associated with Helicobacter pylori infection.
Ten‐year prospective follow‐up study on the relationship between Helicobacter pylori infection and progression of atrophic gastritis, particularly assessed by endoscopic findings
Authors: Sakaki N. , Kozawa H. , Egawa N. , Tu Y. , Sanaka M. 
Published: March 2003

Aim:To ascertain the progression of atrophic gastritis due to Helicobacter pylori infection, we conducted a 10‐year prospective follow‐up study with annual endoscopy of the stomach.Methods:Prospective endoscopic observation was started in 53 subjects in 1989 and 1990 after informed consent was obtained. The progression of atrophic gastritis was evaluated mainly by the endoscopic pattern of atrophy. Histological assessment was performed on biopsy specimens taken from the lesser curvature of the lower corpus. By 2000, 43 patients (20 males, 23 females, mean age 56.7 years at entry) had completed at least 10 years of endoscopic follow‐up.Results:Eight H. pylori‐negative patients with normal fundic mucosa showed no change endoscopically or histologically. In 35 H. pylori‐positive patients, the progression of histological atrophy was observed in 46% and intestinal metaplasia was observed in 49%. Fifteen of 35 H. pylori‐positive cases exhibited a cephaloid shift of the endoscopic atrophic border. The cephaloid shift of the atrophic area occured suddenly. The cumulative progression rate of atrophic patterns was 6% after 2 years, 22% after 4 years, 34% after 6 years and 43% after 10 years. These atrophic changes were related to neutrophil infiltration.Conclusion:The progression of atrophic gastritis is a result of chronic active gastritis caused by H. pylori infection.