bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence that brain glucose availability influences exercise‐enhanced extracellular 5‐HT level in hippocampus: a microdialysis study in exercising rats
Authors: Béquet F. , Gomez‐Merino D. , Berthelot M. , Guezennec C. Y. 
Published: March 2003

ABSTRACTThe relationship between brain glucose and serotonin is still unclear and no direct evidence of an action of brain glucose on serotonergic metabolism in central fatigue phenomena has been shown yet. In order to determine whether or not brain glucose could influence the brain 5‐hydroxytryptamine (5‐HT) system, we have monitored in microdialysis the effects of a direct injection of glucose in rat brain hippocampus on serotonergic metabolism [i.e. 5‐HT, 5‐hydroxyindoleacetic acid (5‐HIAA) and tryptophan (TRP)], during high intensive treadmill running. The injection was performed just before and after exercise. We have shown that glucose induced a decrease of brain 5‐HT levels to a minimum of 73.0 ± 3.5% of baseline after the first injection (P < 0.01) and to 68.5 ± 5.5% of baseline after the second injection (P < 0.01) and consequently prevented the exercise‐induced 5‐HT enhanced levels. We have observed the same phenomenon concerning the 5‐HIAA, but brain TRP levels were not decreased by the injections. In conclusion, this study demonstrates that brain glucose can act on serotonergic metabolism and thus can prevent exercise‐induced increase of 5‐HT levels. The results also suggest that extracellular brain glucose does not act on the synthesis way of 5‐HT, but probably on the release/reuptake system.
Altered sarcoplasmic reticulum function in rat diaphragm after high‐intensity exercise
Authors: Matsunaga S. , Inashima S. , Tsuchimochi H. , Yamada T. , Hazama T. , Wada M. 
Published: March 2003

ABSTRACTThe present study examined the effects of acute high‐intensity exercise on Ca2+ uptake and release rates and Ca2+‐adenosine triphosphatase (ATPase) activity of the sarcoplasmic reticulum (SR) from the costal diaphragm. The rats were run on a treadmill at an estimated requirement of 100% of maximal O2 consumption until fatigued (average time to exhaustion: 4.79 min). Muscle lactate and inorganic phosphate after exercise were increased by 65% (P < 0.05) and 35% (P < 0.05), respectively. With exercise, Ca2+ uptake and release, which were detected in homogenates using the Ca2+ fluorescent dye indo‐1, were decreased by 24% (P < 0.05) and 22% (P < 0.05), respectively. The reduction in Ca2+ uptake was paralleled by decreased activity of SR Ca2+‐ATPase in both the absence and presence of Ca2+ ionophore. These findings demonstrate that, in the diaphragm as well as in the locomotor muscles that have been explored in previous studies, the attenuations of the SR function is brought about by acute high‐intensity exercise. These changes in the SR of the diaphragm may contribute, at least in part, to deteriorations in exercise tolerance and work productivity resulting from repetitive physical activities.
Proposed role of the paraventricular nucleus in cardiovascular deconditioning
Authors: Mueller P. J. , Cunningham J. T. , Patel K. P. , Hasser E. M. 
Published: March 2003

AbstractAim: Cardiovascular deconditioning occurs in individuals exposed to prolonged spaceflight or bedrest and is associated with the development of orthostatic intolerance. Although the precise mechanisms remain to be fully elucidated, astronauts returning from space or bedrest patients returning to normal upright posture present with decreases in plasma volume and alterations in autonomic function. The hindlimb unloaded (HU) rat has been a useful model to study the effects of cardiovascular deconditioning as it mimics many of the changes that occur after spaceflight and bedrest.Results: Experiments performed in HU rats suggest that cardiovascular deconditioning attenuates baroreflex mediated sympathoexcitation and enhances cardiopulmonary receptor mediated sympathoinhibition. These alterations appear to be due to changes in the central nervous system and may contribute to the pre disposition towards orthostatic intolerance associated with cardiovascular deconditioning. The paraventricular nucleus (PVN) of the hypothalamus is important in basal and reflex control of sympathetic outflow. Recent evidence suggests that nitric oxide (NO) is an important inhibitory neurotransmitter in the PVN and that alterations in nitroxidergic transmission in the PVN may be involved in elevated sympathetic tone in certain disease states.Conclusion: Based on evidence from other laboratories and published and preliminary data from our own laboratories, this review proposes a role for the PVN in cardiovascular deconditioning. In particular, we discuss the hypothesis that increased NO in the PVN contributes to the altered cardiovascular reflexes observed following deconditioning and how these reflexes may be related to the orthostatic intolerance observed after prolonged spaceflight or bedrest.
Medullary and supramedullary mechanisms regulating sympathetic vasomotor tone
Authors: Dampney R. A. L. , Horiuchi J. , Tagawa T. , Fontes M. A. P. , Potts P. D. , Polson J. W. 
Published: March 2003

AbstractAim:Neurons in the rostral ventrolateral medulla (RVLM) that project directly to sympathetic preganglionic neurons in the spinal cord play a critical role in maintaining tonic activity in sympathetic vasomotor nerves. Intracellular recordingsin vivofrom putative RVLM presympathetic neurons have demonstrated that under resting conditions these neurons display an irregular tonic firing rate, and also receive both excitatory and inhibitory synaptic inputs. This paper will briefly review some recent findings on the role of glutamate, GABA and angiotensin II (Ang II) receptors in maintaining the tonic activity of RVLM presympathetic neurons.Results:Based on these findings, the following hypotheses will be discussed: (1) RVLM neurons receive tonic glutamatergic excitatory inputs, which originate from both medullary and supramedullary sources; (2) at least some neurons that project to and tonically inhibit RVLM presympathetic neurons are themselves tonically inhibited by GABAergic inputs originating from neurons in the caudalmost part of the ventrolateral medulla (caudal pressor area); (3) under normal conditions, Ang II receptors in the RVLM do not contribute significantly to the tonic activity of RVLM presympathetic neurons, but may do so in abnormal conditions such as heart failure or neurogenic hypertension; (4) RVLM presympathetic neurons maintain a significant level of tonic resting activity even when glutamate, GABA and Ang II receptors on the neurons are completely blocked. Under these conditions, the tonic activity is a consequence either of the intrinsic membrane properties of the neurons (autoactivity) or of synaptic inputs mediated by receptors other than glutamate, GABA or Ang II receptors.Conclusion:The current evidence indicates that the resting activity of RVLM presympathetic neurons is determined by the balance of powerful tonic excitatory and inhibitory synaptic inputs. Ang II receptors also contribute to the raised resting activity of these neurons in some pathological conditions.
Arousal increases baroreflex inhibition of muscle sympathetic activity
Authors: Gunnar Wallin B. , Donadio V. , Karlsson T. , Kallio M. , Nordin M. , Elam M. 
Published: March 2003

AbstractAim: Surprising sensory stimuli causing arousal are known to evoke short‐lasting activation of human sympathetic activity in skin but not in muscle nerves. In fact, anecdotal observations suggest that muscle sympathetic activity may be inhibited. To test this hypothesis, the effects of surprising somatosensory (electrical skin pulses) or visual (flash) stimuli on multiunit muscle sympathetic activity were studied in 36 healthy subjects, aged 19–71 years.Methods: The stimuli were given either 200 or 400 ms after the R‐wave of the electrocardiogram. Dummy stimuli, consisting of trigger pulses without sensory stimuli, served as controls.Results: On a group basis, a single sensory stimulus of either type attenuated the amplitude of one or two sympathetic bursts, while no such effects occurred after dummy stimuli. Individually, the inhibition was evoked by at least one stimulus modality or delay in 16 subjects, whereas in three subjects no significant inhibition occurred. Electrodermal signs of skin sympathetic activation were present in all subjects. Compared with one, five repeated electrical skin pulses induced only minor additional inhibition of muscle sympathetic activity, indicating marked habituation of the neural response. In nine subjects, the experiments were repeated once and in three subjects twice (with intervals of 2–3 months); in 11 of the12 subjects, the sympathetic effects were reproducible. In the group of subjects without significant sympathetic inhibition the stimuli induced a small, transient increase of mean blood pressure, which was not present in the group with sympathetic inhibition.Conclusion: The finding that different sensory stimuli induce similar effects that habituate markedly on repetition suggests that the inhibition of muscle sympathetic activity is because of arousal. The interindividual differences in sympathetic and blood pressure effects may be part of interindividual differences in behavioural responses to stress.
The influence of food supplementation on a coastal dune rodent community
Authors: Koekemoer A. C. , Van Aarde R. J. 
Published: March 2003

AbstractStudies of the rodent community in regenerating coastal dune forest areas north of Richards Bay, South Africa, have indicated that a number of species occupy newly rehabilitating areas. Unstable environmental conditions result in habitat changes, rather than competitive interactions, being the major determinant of rodent community development. This led to the present study, which investigated the effects of supplementary food on rodent assemblages. We attempted to stabilize food availability in order to elucidate some of the mechanisms responsible for the development of the rodent community. By only increasing an existing portion of the resource spectrum, we reduced species diversity, probably through dominance by competitive superior exploiters of the augmented resource. Thus, species diversity decreased with food supplementation, as a result of an increase in the abundance of Mastomys natalensis rather than because of a change in the number of species or the abundance of other species.
Effects of large herbivores and fire on the regeneration of Acacia erioloba woodlands in Chobe National Park, Botswana
Authors: Barnes Myra E. 
Published: March 2003

Abstract Acacia erioloba woodlands provide important forage and shade for wildlife in northern Botswana. Mortality of mature trees caused by browsing elephants has been well documented but the lack of regeneration of new trees has received little attention. Annual growth of new shoots and changes in height were measured to determine the influence of elephants and small ungulate browsers, rainfall and fire on the growth and survival of established A. erioloba seedlings from 1995 to 1997 in the Savuti area of Chobe National Park. All above‐ground vegetation was removed from 40% of established seedlings in 1995 and 28% in 1997 by browsing elephants, and the mean height of remaining seedlings decreased from >550 mm to <300 mm. When seedlings browsed by kudu, impala and steenbok but not elephants are considered, mean seedling height increased <50 mm per year, even though mean new shoot growth remaining at the end of the dry season was 100–200 mm. Fires burned portions of the study area in 1993 and 1997, killing above‐ground vegetation, but most established A. erioloba seedlings survived, producing coppice growth from roots. While elephants and fire caused the greatest reduction in established seedling height and number, small browsers suppressed growth, keeping seedlings vulnerable to fire and delaying growth to reproductive maturity.
Feeding ecology and foraging behaviour of impala Aepyceros melampus in Lake Mburo National Park, Uganda
Authors: Wronski Torsten 
Published: March 2003

AbstractIntersexual and seasonal variation in foraging behaviour of impala (Aepyceros melampus), was studied in the Lake Mburo National Park, Uganda. There was a moderate seasonal difference in foraging efficiency (as measured by ‘acceptable food abundance’), with a minimum in dry season and a maximum in Rainy season. The variation between sexes was more distinct with a pronounced minimum in time spent browsing of males in early wet season. By distinguishing between feeding time spent grazing and feeding time spent browsing the seasonal variation was confirmed. The proportion of foraging time spent feeding (expressed as ‘food ingestion rate’) showed an inverse pattern with a maximum in the late dry season (75.5%), decreasing values throughout the Rainy season and a minimum in early dry season (57.8%). Differences between sexes were explained in terms of reproductive demands and seasonal balance in terms of moderate climate throughout the year. Impala foraging patterns in the bimodal tropics (two Rainy seasons) is discussed and compared with unimodal tropics. The findings are matched against current ideas on optimal foraging.
Addressing management questions for Ngorongoro Conservation Area, Tanzania, using the Savanna modelling system
Authors: Boone Randall B. , Coughenour Michael B. , Galvin Kathleen A. , Ellis James E. 
Published: March 2003

AbstractNgorongoro Conservation Area (NCA), in northern Tanzania, is a multiple‐use area of importance to Maasai pastoralists and wildlife conservation. We adapted the Savanna modelling system to the NCA, creating an Integrated Management and Assessment System that allows users to assess responses to alternative management actions. We used the system to conduct fifteen experiments reflecting potential management questions. Results suggest that: the distribution of rainfall throughout the year may have a greater impact on the ecosystem than its quantity; cattle may be near a carrying capacity determined not by forage limitations but because of disease risks; increasing survival and reducing disease in livestock yields greater returns than increasing birth rates; allowing livestock to graze in areas where they are currently excluded may lead to a slight increase in livestock populations, but sometimes leads to large declines in wildlife populations; few ecosystem effects were noted when households and cultivation were allowed to grow at 3% per year for 15 years; and when up to 5% of the study area was in cultivation, there were declines ≤16% in livestock and wildlife populations, except for elephants, which declined by 48%. Users may modify our experiments using tools we have developed, or address other NCA management questions.
Body size and measurement of species diversity in large grazing mammals
Authors: Oindo Boniface O. 
Published: March 2003

AbstractSpecies are by definition different from each other. This fact favours ranking rather than additive indices. However, ecologists have measured species diversity in terms of species richness, or by combining species richness with the relative abundance of species within an area. Both methods raise problems: species richness treats all species equally, while relative abundance is not a fixed property of species but varies widely temporally and spatially, and requires a massive sampling effort. The functional aspect of species diversity measurement may be strengthened by incorporating differences between species such as body size as a component of diversity. An index of diversity derived from a measure of variation in body size among species is proposed for large grazing mammals. The proposed diversity index related positively to species abundance, indicating that the use of body size as a surrogate for diversity is adequate. Because the proposed index is based on presence or absence data, the expensive and time consuming counting of individuals per species in each sampling unit is not necessary.
Species composition of termites of the Nyika plateau forests, northern Malawi, over an altitudinal gradient
Authors: Donovan Sarah E. , Eggleton Paul , Martin Andy 
Published: March 2003

AbstractTermites were surveyed at three altitudes (Brachystegia woodland at 1676 m and 1905 m, and Juniper woodland at 2210 m) in forests within the Nyika Plateau, northern Malawi. Sampling was by a standardized 100 m transect protocol. Termite diversity was highest in the mid‐altitude site and lowest in the Juniper forest. The assemblages were dominated by soil‐feeding termites in the Termitidae subfamilies Apicotermitinae and Termitinae, and included one new soldierless Apicotermitinae genus. The structure of the assemblages was clearly due to a mixture of altitudinal and site history factors. This was especially true of the lowest altitude forest where burning and other anthropogenic disturbance factors appear to have reduced termite diversity relative to the mid‐altitude site. The Nyika plateau shows a much higher diversity at mid‐altitudes than similar SE Asian sites, probably due to the larger area of highland in Africa than in SE Asia. In addition, the clade composition of the Nyika assemblages differs completely from that found at similar altitudes in SE Asia. This preliminary study supports the hypothesis that mid‐ to high‐ altitude assemblages in both SE Asia and Africa appear to be derived from depauperated random subsets of the lowland fauna rather than from clades specifically adapted to higher altitudes.
Persistent increase in myofibroblasts in Helicobacter heilmannii‐infected mice but not in Helicobacter pylori‐infected Mongolian gerbils: colocalization of COX‐2 and bFGF immunoreactivity
Authors: Nakamura M. , Takahashi S. , Matsui H. , Nishikawa K. , Akiba Y. , Ishii H. 
Published: March 2003

Background:The clinical significance of Helicobacter heilmannii infection remains uncertain, owing to the lack of a specific detection method. Recently, we reported a marked increase in myofibroblasts in the early stage of Helicobacter pylori infection in Monglian gerbils.Aim:The present study was designed to clarify changes in myofibroblasts, and in the immunoeactivities of basic fibroblast growth factor, cyclooxygenase‐2 and inducible nitric oxide synthase after H. pylori infection in Monglian gerbils and H. heilmannii infection in mice.Methods:After oral inoculation, changes in the location of bacteria and the immunoreactivity of myofibroblasts, basic fibroblast growth factor, cyclooxygenase‐2 and inducible nitric oxide synthase were stained with the indirect immunofluorescent method and observed by confocal laser microscopy.Results:In H. heilmannii‐infected mice, the increases in myofibroblasts and in immunoreactivities of these three markers were sustained 12 months after infection. In H. pylori‐infected Monglian gerbils, however, these increases were significant at 3 months but had returned to control levels at 12 months.Conclusions:Two types of Helicobacter infection showed different patterns of myofibroblast proliferation, coinciding with the extent of inflammation. These findings suggest that this difference may be related to the consequences of the infection.
The effect of heparin on trinitrobenzene sulphonic acid‐induced colitis in the rat
Authors: Fries  , Pagiaro  , Canova  , Carraro  , Gasparini  , Pomerri  , Martin  , Carlotto  , Mazzon  , Sturniolo  , Longo  
Published: March 2003

Background:Reduced blood coagulability seems to protect against inflammatory bowel disease; pilot studies using heparin in patients with inflammatory bowel disease have reported positive results.Aim:To evaluate the effects of heparin treatment on microangiographic and on inflammatory parameters in experimental colitis, induced by trinitrobenzene sulphonic acid (TNBS)‐ethanol.Methods:Four groups of rats: (i) controls (saline enema), TNBS‐induced colitis with (ii) sham treatment (saline, s.c.), (iii) dexamethasone (0.25 mg/kg/day s.c.) and (iv) heparin (500 U/kg t.d.s., s.c.). Microangiography was performed 2 and 4 days after colitis induction. Partial thromboplastin time, colonic wet weight, macroscopic damage score and mucosal myeloperoxidase (MPO) activity were determined at day 4.Results:TNBS‐induced colitis caused a reduction in visible bowel wall vessels, which was prevented by heparin (P < 0.05) but not by steroids. The macroscopic damage scores and colon wet weights were similar in all colitis groups. Compared to untreated colitis the MPO activity in heparin‐treated animals was of borderline significance.Conclusions:Heparin treatment improved microangiographic features and reduced inflammation to a certain degree. Steroids delayed development of colon hypoperfusion, but were ineffective on MPO activity. It remains to be determined if the observed effects are due to the antithrombotic activity of heparin or to an anti‐inflammatory action.
Which form of erythromycin should be used to treat gastroparesis? A pharmacokinetic analysis
Authors: Ehrenpreis  , Zaitman  , Nellans  
Published: March 2003

Background:Erythromycin is a macrolide antibiotic that exhibits prokinetic effects. It has been shown to enhance antral contractility and accelerates gastric emptying rates, primarily by stimulating motilin receptors.Aim:To determine the optimal dosage form of erythromycin for use as a prokinetic agent.Methods:Eight normal volunteers and three patients with documented gastroparesis ingested 250 mg erythromycin in tablet, suspension and intravenous forms. Serum erythromycin levels were determined at frequent intervals. These data were plotted vs. time and analysed for lag time, time to maximum concentration (tmax), maximum concentration (Cmax) and bioavailability (F).Results:The absorption kinetics of the erythromycin suspension was notable for short lag times and early tmax, while lag times and tmax were delayed with the tablet form. Median lag time was 15 min for the suspension vs. 90 min for the tablet (P < 0.005). Median tmax for the suspension was 45 min vs. 180 min for the tablet (P < 0.005). A non‐significant decrease in F was seen with the suspension compared to the tablet (P = 0.12).Conclusion:Based on the kinetic data from this study, erythromycin suspension is the ideal dosage form for administration of this drug as a prokinetic agent.
glycyrrhizin as a potential treatment for chronic hepatitis C
Authors: Rossum T. G. J. Van , Vulto  , Man R. A. De , Brouwer  , Schalm  
Published: March 2003

Chronic hepatitis C is a slowly progressive liver disease that may evolve into cirrhosis with its potential complications of liver failure or hepatocellular carcinoma. Current therapy with α‐interferon is directed at viral clearance, but sustained response is only achieved in 20–40% of patients without cirrhosis, and less than 20% in patients with cirrhosis who have the greatest need for therapy. Treatment for those who do not respond to anti‐viral therapy is highly desirable.In Japan glycyrrhizin has been used for more than 20 years as treatment for chronic hepatitis. In randomized controlled trials, glycyrrhizin induced a significant reduction of serum aminotransferases and an improvement in liver histology compared to placebo. Recently, these short‐term effects have been amplified by a well‐conducted retrospective study suggesting that long‐term usage of glycyrrhizin prevents development of hepatocellular carcinoma in chronic hepatitis C.The mechanism by which glycyrrhizin improves liver biochemistry and histology are undefined. Metabolism, pharmacokinetics, side‐effects, and anti‐viral and hepatoprotective effects of glycyrrhizin are discussed.