bluuebunny/crossref_metadata_2025_split huggingface dataset:
Okadaic acid inhibits relaxant neural transmission in rat gastric fundus in vitro
Authors: STORR M. , FÖLMER R. , KURJAK M. , SCHUSDZIARRA V. , ALLESCHER H. D. 
Published: March 2003

ABSTRACTThe aim of the present study was to characterize the influence of the phosphatase type 1 and 2A inhibitor okadaic acid on non‐adrenergic, non‐cholinergic (NANC) neurotransmission in the rat gastric fundus. Okadaic acid (10−6 M), an inhibitor of protein phosphatases 1 and 2A, did not show any influence on the basal tonus or on a contraction plateau induced by 5‐HT (10−7 M) within 30 min of observation. When okadaic acid (10−6 M) was applied 10 min prior to 5‐HT (10−7 M), the contraction plateau of serotonin was unchanged. To investigate the inhibitory neurotransmission, the muscle strips were pre‐contracted using 5‐HT (10−7 M), and inhibitory stimuli were applied at the contraction plateau, which was stable over 30 min. The inhibitory effects of vasoactive intestinal peptide (VIP), nitric oxide (NO) and electrical field stimulation (EFS, 40 V, 0.5 ms, frequencies ranging from 0.5 to 16 Hz) were examined. When okadaic acid (10−6 M) was applied prior to EFS‐induced NANC relaxation, significant attenuation of the inhibitory response was demonstrated (16 Hz: control: −92.4 ± 1.9%; okadaic acid 10−7 M: –60.7 ± 6.1%; okadaic acid 10−6 M: –25.3 ± 3.4%; n=11; P < 0.01). By contrast, neither the concentration‐dependent inhibitory actions of VIP (10−11–10−8 M) (VIP 10−8 M: –100%; VIP 10−8 M + okadaic acid 10−6 M: –89.9 ± 8.3%; n=8; n.s) nor that of diethylamine nitric oxide (DEA‐NO) (3 × 10−7–10−4 M) (DEA‐NO 10−4 M: –95.3 ± 8.4%; DEA‐NO 10−4 M + okadaic acid 10−7 M: –98.3 ± 6.3%; DEA‐NO 10−4 M + okadaic acid 10−6 M: 96.5 ± 7.6%; n=9; n.s.) on 5‐HT induced contraction were altered by pre‐incubation with okadaic acid (10−6 M). This is the first report that supports the concept that protein phosphatases 1 and 2A may contribute to the regulation of rat gastric fundus motility. The protein phosphatase inhibitor okadaic acid significantly reduces electrically induced inhibitory NANC responses, while leaving direct muscular effects of the inhibitory NANC neurotransmitters VIP and NO unaffected – suggesting a neural site of action. The potential roles of protein phosphatases on NANC neurotransmission remain to be clarified in detail, as this might offer a new pathway for modulating smooth‐muscle function.
Mechanisms of genioglossus responses to inspiratory resistive load in rabbits
Authors: ALEKSANDROVA N. P. , GOLOUBEVA E. V. , ISAEV G. G. 
Published: March 2003

ABSTRACTThe purpose of the present study has been to determine whether pharyngeal dilator muscles participate in inspiratory load compensatory responses and if so, to elucidate role of upper airway mechanoreceptors in these responses. The experiments were performed on anaesthetized rabbits. Each animal was tested in three ways by the imposition of inspiratory resistive load: (1) at upper airways via face mask, (2) at the tracheostomic cannula placed below larynx (all upper airway receptors were `bypassed') and (3) at the mouth after the section of the hypoglossus nerves (motor denervation of genioglossus muscle). The inspiratory load applied to the upper airways evoked significant increases in integrated genioglossus activity (to 129 ± 14.7% of control) and its inspiratory duration (to 113 ± 5% of control) already within the first loaded breath (P < 0.05). The increases in the inspiratory activity of musculius genioglossus were relatively greater than the simultaneous increases in the activity of the diaphragm. Motor denervation of the pharynx dilator muscles (including m. genioglossus) increased airway resistance to 184 ± 19% of control (P < 0.05) and induced obstructive alterations in the breathing pattern during unloaded breathing: decrease in maximal inspiratory flow (–13%) and increase in the level of negative oesophageal pressure (+14%) and the peak diaphragm activity (+6%). After nervi hypoglossus sections additional increases in motor and pressure outputs were required in order to maintain unaltered ventilation at the same degree of loading as before denervation. The results indicate that the pharyngeal dilator muscles have a role in compensation of added inspiratory load. Activation of these muscles facilitate the load compensating function of `pump' muscles by decreasing airway resistance. Tracheostomy did not reduce the genioglossus response to inspiratory loading, ruling out any role for upper airways receptors in the genioglossus response to inspiratory load compensations.
Induction of heme oxygenase in guinea‐pig stomach: roles in contraction and in single muscle cell ionic currents
Authors: Kadinov B. , Itzev D. , Gagov H. , Christova T. , Bolton T. B. , Duridanova D. 
Published: March 2003

ABSTRACTThe role of heme oxygenase reaction products in modulation of stomach fundus excitability was studied. The presence of constitutive heme oxygenase 2 was verified in myenteric ganglia by immunohistochemistry. The role of inducible heme oxygenase isoenzyme was investigated after invivo treatment of animals with CoCl2 (80 mg kg−1 b.w) injected subcutaneously 24 h before they were killed. This treatment resulted in increased production of bilirubin and positive staining for the inducible isoform in stomach smooth muscle and vast induction in the liver. In both control and treated animals haemin, applied to the bath as a substrate of heme oxygenase caused significant decrease of prostaglandin F2α‐induced tone, and ameliorated the relaxatory response of the fundic strips to electrical field stimulation. Both effects were antagonized by Sn‐protoporphyrin IX, competitive heme oxygenase inhibitor, and were found to be neuronally dependent. In single freshly isolated smooth muscle cells from control animals haemin caused a concentration‐dependent increase of the whole cell K+ currents, which was not affected by Sn‐protoporphyrin IX, cyclic guanosine monophosphate (cGMP)‐dependent protein kinase or guanylyl cyclase antagonists, but was reversed by various antioxidants and abolished by an NO scavenger. In cells from treated animals the K+ current increasing effect of haemin did not depend on the presence of antioxidants, but was abolished by protein kinase G and guanylyl cyclase inhibitors, depletors of intracellular Ca2+ pools or Sn‐protoporphyrin IX. Biliverdin did not affect contraction or ionic currents. Thus, this is the first study demonstrating that heme oxygenase is an inducible enzyme in guinea‐pigs, which exerts a modulatory role on gastric smooth muscle excitability via carbon monoxide production.
Exposure of rats to hyperoxia enhances relaxation of isolated aortic rings and reduces infarct size of isolated hearts
Authors: Tähepõld P. , Elfström P. , Eha I. , Kals J. , Taal G. , Talonpoika A. , Valen G. , Vaage J. , Starkopf J. 
Published: March 2003

ABSTRACTExposure of rats to hyperoxia before organ harvesting protected their isolated hearts against global ischaemia–reperfusion injury in a previous study. The present study investigates whether hyperoxia influences vasomotor function and regional ischaemia of the heart. Isolated rings of the thoracic aorta were obtained from rats immediately or 24 h after in vivo exposure to 60 min of hyperoxia (>95% O2), and the in vitro dose–response to phenylephrine (PHE), prostaglandin F2α (PGF2α) and endothelin‐1 (ET‐1), acetylcholine (Ach) and sodium nitroprusside (SNP) was assessed. Hyperoxia in vivo increased the relaxation of aortic rings to Ach and SNP, while it delayed contraction to PHE. The effect was more evident when the vessels were harvested immediately rather than 24 h after hyperoxic exposure. In separate experiments rat hearts were isolated immediately after hyperoxia, buffer‐perfused, and subjected to 30 min of regional ischaemia and reperfused for 120 min. Infarct size was determined by triphenyl tetrazolium chloride staining. Hyperoxia significantly reduced infarct size. In normoxic controls 23.0 ± 8.3% of the area at risk was infarcted, while in hyperoxic animals infarct size was 14.8 ± 5.6% of the area at risk (P = 0.012). Exposure of rats to hyperoxia modifies the vasomotor response of isolated aortic rings, and reduces the infarct size of isolated rat heart. These novel aspects of hyperoxic treatment require further studies to explore the potential of its clinical application.
Absorption of biologically active peptide hormones from the small intestine of rat
Authors: Wheeler S. , Mcginn B. J. , Lucas M. L. , Morrison J. D. 
Published: March 2003

ABSTRACTAbsorption of the 4, 10 and 34 amino acid forms of gastrin from the small intestine has been investigated in anaesthetized rats. The method of assessment of successful absorption of the hormone into the systemic circulation was when the amount of acid secreted by the stomach over consecutive 15‐min periods was increased. When the natural hormones were infused into the ileum in a relatively high dose, there was no increase in gastric acid secretion, indicating that they had not been absorbed. Each of the forms of gastrin was conjugated at the free amino terminus to the carboxyl group of cholic acid. Subsequent infusion of the conjugated form of gastrin into the ileum, this time in relatively low doses, resulted in substantial and prolonged increases in gastric acid secretion, indicating that these hormones had been successfully absorbed. In addition, conjugation of the 10 and 34 amino acid forms of gastrin with cholic acid was shown to increase markedly the potency in evoking an increase in gastric acid secretion in response to intravenous injection of the hormone. Absorption of the gastrin conjugates was specific to the ileum thus indicating that they had been absorbed through the bile salt transporters.
Intimal plaque development and oxidative stress in cholesterol‐induced atherosclerosis in New Zealand rabbits
Authors: Heinle H. , Brehme U. , Friedemann G. , Frey J.‐C. , Wolf A. T. , Kelber O. , Weiser D. , Schmahl F. W. , Lang F. , Schneider W. 
Published: March 2003

AbstractAlthough oxidative stress is well known in atherogenesis, the origin, nature and kinetics of free radicals involved have not been well described till now. Here, we correlated parameters of oxidative stress with cellular components during induction and stabilization of aortic intimal lesions which were induced in rabbits by feeding a cholesterol‐enriched diet for 6 weeks and a normal diet for further 68 weeks. Plasma lipids, aortic plaque size and composition (macrophages, smooth muscle cells, oxidized LDL by morphometry), as well as aortic radical production (by luminol‐enhanced chemiluminescence and TEMPO‐9AC fluorescence) were measured after various time points. The parameters of oxidative stress were correlated with the different cellular components of the aortic plaques. The plaques increased until week 21, no significant regression was found until week 74, plasma cholesterol was maximal at week 6. Macrophages, oxidized LDL and generation of different species of free radicals were increased during plaque development, yet with different time kinetics. Whereas chemiluminescence correlated only weakly with the amount of intimal macrophages, strong correlations were found between TEMPO fluorescence and smooth muscle cells (r = 0.4778, P < 0.001) and between macrophages and oxidized LDL (r = 0.5896, P < 0.0001). Different indicators of oxidative stress were increased during plaque progression and stabilization. However, the various correlations show, that distinct types of reactive species secreted probably from macrophages and smooth muscle cells contribute to oxidative stress in the different phases of plaque development.
Vasopressin increases milk flow and milk fat concentration in the goat
Authors: Olsson K. , Malmgren C. , Olsson K. K. , Hansson K. , Häggström J. 
Published: March 2003

AbstractAim:  The aim of this study was to investigate whether physiological doses of vasopressin affect milk flow and milk composition in goats.Methods:  Six goats were given vasopressin intravenously at doses of 0.1 ng kg−1 min−1 (a low dose, VL), 0.3 ng kg−1 min−1 (a medium dose, VM) and 1.0 ng kg−1 min−1 (a high dose, VH), oxytocin at 10 ng kg −1min−1 and 0.15 m NaCl during 90 min at random.Results:  Milk flow increased from 1.3 ± 0.2 to 3.5 ± 1.0 g min−1 (VL), from 1.8 ± 0.4 to 4.3 ± 0.6 g min−1 (VM) and from 1.5 ± 0.2 to 7.9 ± 0.9 g min−1 (VH) during the first 30‐min infusions (all P < 0.001), respectively, and then declined. The response to oxytocin corresponded to that of VH. Milk fat concentration increased from 2.1 ± 0.1 to 3.3 ± 0.4% during VH and from 2.8 ± 0.6 to 4.1 ± 0.6% during oxytocin (both P < 0.001), and tended to increase during VM and VL. The mammary blood flow of four goats was studied with ultrasound during VH and oxytocin infusion. Milk flow increased from 1.8 ± 0.4 to 4.7 ± 1.0 g min−1 during VH and from 1.9 ± 0.3 to 12.4 ± 2.4 g min−1 during oxytocin (both P < 0.001). Mammary blood flow decreased from 262 ± 37 to 53 ± 7 mL min−1 (P < 0.001) during VH, but did not change during oxytocin.Conclusion:  We conclude that vasopressin increases milk flow and milk fat concentration and suggest that vasopressin, like oxytocin, acts on the myoepithelial cells.
Effects of heat stress on baroreflex function in humans
Authors: Crandall Craig G. , Cui Jian , Wilson Thad E. 
Published: March 2003

AbstractIntroduction: Heat stress significantly reduces orthostatic tolerance in humans. The mechanism(s) causing this response remain unknown. The purpose of this review article is to present data pertaining to the hypothesis that reduced orthostatic tolerance in heat stressed individuals is a result of heat stress induced alterations in baroflex function.Methods: In both normothermic and heat stressed conditions baroreflex responsiveness was assessed via pharmacological and non‐pharmacological methods. In addition, the effects of heat stress on post‐synaptic vasoconstrictor responsiveness were assessed.Results: Generally, whole body heating did not alter baroreflex sensitivity defined as the gain of the linear portion of the baroreflex curve around the operating point. However, whole body heating shifted the baroreflex curve to the prevailing (i.e. elevated) heart rate and muscle sympathetic nerve activity. Finally, the heat stress impaired vasoconstrictor responses to exogenous administration of adrenergic agonists.Conclusion: Current data do not support the hypothesis that reduced orthostatic tolerance associated with heat stress in humans is due to impaired baroreflex responsiveness. This phenomenon may be partially due to the effects of heat stress on reducing vasoconstrictor responsiveness.
Why do human postganglionic neurones primarily only fire once during a sympathetic burst?
Authors: Macefield V. G. , Elam M. 
Published: March 2003

AbstractAim:  Single‐unit recordings from muscle vasoconstrictor, cutaneous vasoconstrictor and sudomotor neurones in awake human subjects have shown that they tend to fire only once per sympathetic burst. We review the firing properties of human sympathetic neurones and examine the idea that the short duration of a sympathetic burst may limit the number of times a neurone can fire, using the human skeletomotor system as a model for the sympathetic nervous system.Results:  It is known that human α motor neurones usually fire in long trains during voluntary contractions, but what of their pattern when constrained by a brief burst? We recorded from single motor units in the tibialis anterior muscle while subjects generated brief electromyogram bursts in the intervals between heart beats, with a duration similar to that of muscle sympathetic bursts. Eight motor units fired mostly one spike per burst, with a pattern identical to that of sympathetic neurones.Conclusion:  These results suggests that were it not for the constraint of the bursting pattern, individual sympathetic neurones would – like α motor neurones – tend to fire in long trains.
Sympathetic nerve activity in obstructive sleep apnoea
Authors: Narkiewicz K. , Somers V. K. 
Published: March 2003

AbstractThe mechanisms underlying the link between obstructive sleep apnoea (OSA) and cardiovascular disease are not completely established. However, there is increasing evidence that autonomic mechanisms are implicated. A number of studies have consistently shown that patients with OSA have high levels of sympathetic nerve traffic. During sleep, repetitive episodes of hypoxia, hypercapnia and obstructive apnoea act through chemoreceptor reflexes and other mechanisms to increase sympathetic drive. Remarkably, the high sympathetic drive is present even during daytime wakefulness when subjects are breathing normally and no evidence of hypoxia or chemoreflex activation is apparent. Several neural and humoral mechanisms may contribute to maintenance of higher sympathetic activity and blood pressure. These mechanisms include chemoreflex and baroreflex dysfunction, altered cardiovascular variability, vasoconstrictor effects of nocturnal endothelin release and endothelial dysfunction. Long‐term continuous positive airway pressure treatment decreases muscle sympathetic nerve activity in OSA patients. The vast majority of OSA patients remain undiagnosed. Unrecognized OSA may contribute, in part, to the metabolic and cardiovascular derangements that are thought to be linked to obesity, and to the association between obesity and cardiovascular risk. Furthermore, acting through sympathetic neural mechanisms, OSA may contribute to or augment elevated levels of blood pressure in a large proportion of the hypertensive patient population.
A seasonal feast: long‐term analysis of feeding behaviour in the spotted hyaena (Crocuta crocuta)
Authors: Cooper Susan M. , Holekamp Kay E. , Smale Laura 
Published: March 2003

SummaryThe feeding behaviour of the Talek clan of spotted hyaenas in the Masai Mara National Reserve, Kenya, was monitored continuously for 7 years. Talek hyaenas adapted to large temporal variations in prey abundance by being opportunistic predators. During the first half of the year, the hyaenas fed on resident ungulates, and their diet consisted mainly of topi and Thomson's gazelles. Upon arrival of the migratory herds of wildebeest and zebra from the Serengeti, Talek hyaenas switched to feeding on the wildebeest which provided them with a superabundance of food for about 3 months. After the migratory animals returned to the Serengeti, Talek hyaenas experienced a period of reduced prey abundance due to the temporary dispersion of resident ungulates. At this time hyaenas hunted the few remaining wildebeest, and also increased their use of the remaining resident animals. Although Talek hyaenas were generally opportunistic in their feeding behaviour, they did exhibit clear dietary preference for larger prey species, particularly wildebeest. Finally, carrion comprised only 5% of the biomass consumed by Talek hyaenas, the lowest proportion of carrion in the diet of any Crocuta population studied to date.
Notes and records
Authors: Muchoki Charles H. K. 
Published: March 2003

Sustainable use and management of resources require regular monitoring. In the case of animals, their numbers and distributions are important in determining future trends. The data can also be used for planning and management needs such as habitat use and design of park boundaries ( Norton‐Griffiths, 1978).Aerial surveys in East Africa have collected data on animal numbers and other environmental parameters coinciding with wet, intermediate and dry seasons and hence determining animal movements in relation to their food supply ( Western, 1975;
Norton‐Griffiths, 1978;
Sinclair & Norton‐Griffiths, 1979). Population trends of animals and their food supply has a bearing on their sustained management in an ecosystem as noted by
Kalikawe & Kgathi (1993),
Lamprey (1984),
Kahurananga (1981),
Western (1973) among others. The Department of Resource Surveys and Remote Sensing has been conducting aerial surveys in Ewaso Nyiro basin since 1977 and the cardinal objective of this paper is to present and explain an analysis of animal population trends in this basin spanning a period of 20 years, which is invaluable to the sustainable management of the basin’s biodiversity.
Effect of gap size and age on climber abundance and diversity in Budongo Forest Reserve, Uganda
Authors: Babweteera Fred , Plumptre Andrew , Obua Joseph 
Published: March 2003

A study of the effects of gap size and age on climber abundance and diversity was carried out in Budongo Forest Reserve in Uganda. Data were collected from compartments N5, W21, B1 and B3. Stump records were used to locate and estimate the ages of 78 gaps. Sample plots 5 × 5 m were set up in the gaps to assess climber abundance and diversity.Climbers were more abundant and diverse in gaps that were more than 400 m2, 15 months old and had more than 25% canopy opening. Momordica foetida was the most abundant climber species occurring on stems, branches and crowns of seedlings and saplings. Therefore, in order to keep natural regeneration free from climber tangles and produce good quality timber, climber control should be a major activity in tropical high forest management.
Seasonal abundance, reproduction and hunting of common quail Coturnix coturnix in the Eastern Cape Province, South Africa
Authors: Kerley Graham I. H. , Watson Justin J. , Boshoff André F. 
Published: March 2003

AbstractThis study investigated the potential overlap between breeding and hunting seasons for a population of common quail Coturnix coturnix in the Alexandria District. Seasonal abundance (assessed as the number of birds flushed per unit effort), sex ratios and reproductive condition (based on gonad sizes) of the quail were measured over a period of 16 months, including two hunting seasons. Hunting impacts were assessed in terms of the number of birds killed per unit of hunting effort. Quail exhibited a spring peak in abundance and reproduction, which coincided with the legal hunting season, and bird numbers varied markedly between years. Sex ratio varied, with males dominating early in spring. Hunters killed nearly 60% of the birds flushed, and hunter efficiency was positively correlated with the abundance of quail. These results confirm the dilemma for managers, as quail are currently hunted during the main breeding season and offtakes are high. The development of management strategies is hampered by a lack of understanding of the population biology and ecology, and impacts of hunting. A number of possible hunting strategies are discussed. Since current harvests may not be sustainable, further research is necessary.