Pflügers Archiv : European journal of physiology.
Publisher:
Springer.
Frequency: Monthly (except Apr.),
Country: Germany
Language: ger
Start Year:1968 -
ISSN:
0031-6768 (Print)
1432-2013 (Electronic)
0031-6768 (Linking)
1432-2013 (Electronic)
0031-6768 (Linking)
Impact Factor
4.5
2022
| NLM ID: | 0154720 |
| (OCoLC): | 01762182 |
| (DNLM): | P09920000(s) |
| Coden: | PFLABK |
| LCCN: | 85643301 |
| Classification: | W1 PF482 |
Exercise regulates shelterin genes and microRNAs implicated in ageing in Thoroughbred horses. Ageing causes a gradual deterioration of bodily functions and telomere degradation. Excessive telomere shortening leads to cellular senescence and decreases tissue vitality. Six proteins, called shelterin, protect telomere integrity and control telomere length through telomerase-dependent mechanisms. Exercise training appears to maintain telomeres in certain somatic cells, although the underlying molecular mechanisms are incompletely understood. Here, we examined the influence of a single bout of vigorous exercise training on leukocyte telomerase reverse transcriptase (TERT) and shelterin gene...
Adaptive response of equine intestinal Na+/glucose co-transporter (SGLT1) to an increase in dietary soluble carbohydrate. Experimental and epidemiological evidence suggests that consumption of hydrolyzable carbohydrate, hCHO (grain), by horses is an important risk factor for colic, a common cause of equine mortality. It is unknown whether the small intestinal capacity to digest hCHO and/or to absorb monosaccharides is limiting, or even if horses can adapt to increased carbohydrate load. We investigated changes in the brush-border membrane carbohydrate digestive enzymes and glucose absorptive capacity of horse small intestine in response to increased hCHO. Expression of the Na(+)/glucose co-transporter, SGLT1, was...
Scaling of skeletal muscle shortening velocity in mammals representing a 100,000-fold difference in body size. To fully understand the effect of scaling on skeletal muscle shortening velocity (V (0)), it is important to know which phenotypic characteristics drive the changes between species. The purpose of the current investigation was to compare the effects of body mass and femur length, as an estimate of total limb length, on V (0) in species that cover a 100,000-fold range of body masses. Using the slack test procedure, V (0) was determined for fibers expressing types I and IIa myosin heavy chain (MyHC) isoforms in the mouse, rat, dog, human, horse, and rhinoceros under identical experimental condit...
Development of baroreflex and endocrine responses to hypotensive stress in newborn foals and lambs. The aims of this study were to compare and contrast the development of the cardiac baroreflex and endocrine responses to acute hypotensive stress in healthy newborn pony foals and lambs during the first two weeks of postnatal life. Methods: Under general anaesthesia, seven Welsh pony foals and six Welsh Mountain lambs were catheterised with hind limb artery and vein catheters. Following post-surgical recovery, at 1 week and 2 weeks of age, blood pressures of the animals were raised and lowered acutely by intravenous infusion of phenylephrine and sodium nitroprusside, respectively. During hypot...
Growth dynamics of lipizzan horses and their comparison to other horse breeds. A typical body format of Slovenian Lipizzan horse was investigated. The study included 6 foals (5 colts and 1 filly) at the Lipica stud farm. They were measured from birth to twenty-seven months and again at forty-four months of age. Measurements included body length, chest circumference, withers height and body mass. All those measurements were statistically evaluated and compared to some other horse breeds to determine the similarity of the growth dynamics of those horse breeds. It was concluded that the parameters of the head and neck reached their full growth at the age of 27 months and al...
Early and long-term changes of equine skeletal muscle in response to endurance training and detraining. Twenty-four 4-year-old Andalusian (Spanish breed) stallions were used to examine the plasticity of myosin heavy chain (MHC) phenotype and the metabolic profile in horse skeletal muscle with long-term endurance-exercise training and detraining. Sixteen horses underwent a training programme based on aerobic exercises for 8 months. Afterwards, they were kept in paddocks for 3 months. The remaining eight horses were used as controls. Three gluteus medius muscle biopsy samples were removed at depths of 20, 40 and 60 mm from each horse before (month 0), during (month 3) and after (month 8) training,...
Plasma cortisol and beta-endorphin concentrations in trained and over-trained standardbred racehorses. The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks slow- and moderate-intensity treadmill training. The standardised treadmill exercise test consisted of 2 min at velocities corresponding to 30, 50, 70 and 100% of maximum O2 consumption. Over-training, defined as a significant decrease in body...
Skeletal muscle adaptations to prolonged training, overtraining and detraining in horses. Thirteen standard-bred horses were trained intensively for 34 weeks and detrained for 6 weeks to study skeletal muscle adaptations to prolonged training, overtraining and detraining. Training included endurance (phase 1, 7 weeks), high-intensity (phase 2, 9 weeks) and overload training (OLT) (phase 3, 18 weeks). During phase 3, horses were divided into two groups, OLT and control (C), with OLT horses performing greater intensities and durations of exercise than C horses. Overtraining was evident in OLT horses after week 31 and was defined as a significant reduction in treadmill run time in res...
Urea-stimulated K-Cl cotransport in equine red blood cells. The effect of urea and its interactions with oxygen tension (PO2), cell volume and inhibitors of protein phosphatases/kinases (PP/PK) on the K influx into equine red blood cells were studied. K influx was measured using 86Rb as a radioactive tracer for K. As in other species, Cl-dependent K influxes were stimulated by urea, with peak fluxes occurring at about 750 mM. This effect was not mediated via changes in cell volume or following formation of cyanate, the hydrolysis product of urea. Stimulation by urea was prevented by pre-treatment with calyculin A (100 nM) at all urea concentrations tes...
The effects of oxygenation upon the Cl-dependent K flux pathway in equine red cells. The effects of oxygen tension (PO2) upon the K influx pathways of equine red cells have been studied using 86Rb+ as congener for K. Equilibration of cells in 100% nitrogen led to a low and Cl-independent K flux. Change to an atmosphere of 100% air led to a rapid sixfold increase in K flux. The oxygen-activated flux was entirely Cl dependent and was maintained for up to 3 h. Oxygenation-evoked activation was dependent upon PO2 over the physiological range with little effect up to 70% saturation of haemoglobin with oxygen but significant effects between 70 and 100%. K flux at low PO2 was unaffec...
Elevated myoplasmic calcium in exercise-induced equine rhabdomyolysis. Exertional rhabdomyolysis is a myopathy of unknown pathophysiology. We measured intracellular resting calcium concentration ([Ca2+]i) by means of Ca(2+)-selective microelectrodes in intercostal muscle fibers from horses suffering from rhabdomyolysis, and from horses with no evidence of neuromuscular disorder. [Ca2+]i was several-fold higher in muscle fibers from horses suffering from rhabdomyolysis when compared to controls. Treatment of rhabdomyolytic horses with dantrolene, an agent that prevents Ca2+ release from the sarcoplasmic reticulum, reduced [Ca2+]i toward control values, and acceler...
Stimulation of KCl co-transport in equine erythrocytes by hydrostatic pressure: effects of kinase/phosphatase inhibition. The effects of hydrostatic pressure on the KCl co-transporter of equine erythrocytes were studied to determine factors involved in its regulation. Pressure (0.1-40MPa) increased Cl-dependent K+ transport; in the presence of the putative kinase inhibitor N-ethylmaleimide (NEM) which stimulates the transporter, or the phosphatase inhibitor calyculin A, pressure had no significant effect. The sequential application of NEM and calyculin A clamped the transporter at about 30% of maximal flux compared to NEM alone; pressure also had no further effect. These results suggest that pressure acts on the ...
Effect of exercise on hexokinase distribution and mitochondrial respiration in skeletal muscle. Horses were subjected to treadmill running at 65% (submaximal) or 100% (maximal) VO2,max to examine the effects of exercise on subcellular distribution of hexokinase (HK) and on mitochondrial respiration. It is hypothesized that the fraction of HK bound to mitochondria will be reduced due to an elevation of glucose-6-phosphate (G-6-P) concentration in the exercising muscle and that such release of HK from mitochondria will depress oxidative phosphorylation. Changes in muscle G-6-P concentration, pH, subcellular HK distribution, mitochondrial respiration and other metabolites were determined in...
Estimating transit time for capillary blood in selected muscles of exercising animals. The mean minimal capillary transit time was estimated in muscles of various animals using a combination of physiological and morphometric methods. Radioactive microspheres were injected intravascularly in various animals running on a treadmill at maximum oxygen consumption rate (VO2,max) to label blood flow to individual muscles. The muscles were then removed and preserved by standard methods for electron microscopy. The volume density of mitochondria was measured to assess muscle oxidative capacity. Capillary densities in muscle cross-sections, capillary diameters and tortuosities were incorp...
Respiratory and metabolic responses in the horse during moderate and heavy exercise. Thoroughbred horses were exercised to fatigue on a treadmill at 62% and 100% of their VO2max. Hypoxemia occurred at the onset of exercise under both exercise conditions. This hypoxemia persisted to fatigue during the heavy exercise but progressively diminished as the exercise continued and had disappeared by the end of exercise at the lighter load. As a result of the hypoxemia the oxygen content of arterial blood during exercise at VO2max was 17% below its carrying capacity. However, under both experimental conditions the CaO2 still exceeded that of rest owing to an elevation in hemoglobin con...
The effect of high-intensity exercise on the respiratory capacity of skeletal muscle. The effect of high-intensity exercise on the respiratory capacity of skeletal muscle was studied in horses which ran five 600-m bouts on a track with 2 min of rest between exercise bouts, or once to fatigue on a treadmill at an intensity that elicited the maximal oxygen uptake. Venous blood and biopsy samples of the middle gluteal muscle were collected at rest, after each exercise bout, and 30 and 60 min post-exercise. Blood samples were analyzed for lactate concentration and pH and muscle samples for metabolites, pH, and respiratory capacity. Venous blood and muscle pH declined to 6.91 +/- 0....
Total muscle mitochondrial volume in relation to aerobic capacity of horses and steers. The relationship between maximal oxygen consumption rate (VO2max) and mitochondrial content of skeletal muscles was examined in horses and steers (n = 3 each). Samples of the heart left ventricle, diaphragm, m. vastus medialis, m. semitendinosus, m. cutaneous thoracicus and m. masseter, as well as samples of muscles collected in a whole-body sampling procedure, were analyzed by electron microscopy. VO2max per kilogram body mass was 2.7 x greater in horses than steers. This higher VO2max was in proportion to the higher total volume of mitochondria in horse versus steer muscle when analyzed from...
Cardiovascular and respiratory responses to submaximal exercise training in the thoroughbred horse. Cardiovascular and respiratory responses to submaximal exercise training were investigated in 6 thoroughbred racehorses. Oxygen uptake, heart rate (HR) and arteriovenous oxygen content difference were measured during incremental treadmill exercise tests, before and after 7 weeks of treadmill training. Cardiac output during exercise was calculated by the direct Fick technique. Maximal oxygen uptake (VO2max) was increased by 23% after training, from 129.7 ml/kg/min to 160.0 ml/kg/min. The treadmill speed at which VO2max was attained increased by 19%. The increased aerobic power after training wa...
Cardiorespiratory adjustments to tethered-swimming in the horse. The cardiorespiratory and metabolic responses to various levels of tethered-swimming were evaluated in 5 sedentary horses. Cardiac output (Q) and heart rate (HR) correlated highly (r = 0.89 and 0.94 respectively) with work effort (WE) expressed as kg pulled . kg body wt-1 . 10-2. While swimming, stroke volume (SV) was reduced at the lowest workloads, but increased with increasing WE so that at the highest workloads it had returned to the on-land standing SV. Pressures in the pulmonic as well as on both sides of the systemic circulation were considerably elevated by this form of exercise, altho...
Effect of exercise on systemic blood pressure and heart rate in horses. Carotid loops were prepared in 3 horses several months prior to the experiments. Systemic blood pressure was recorded at rest and during exercise by insertion of a plastic cannula into the carotid artery. The pressure transducer was fixed at the neck of the animal. The blood pressure signal was transmitted by telemetry. When the horses were standing under the rider, the following results were obtained: heart rate 38 +/- 5 beats-min-1, systolic pressure 115 +/- 15, disstolic pressure 83 +/- 10, mean pressure 97 +/- 12, and pulse pressure 32 +/- 9 mm Hg. During steady gallop at a mean speed of 5...