Living at high altitude in combination with sea-level sprint training increases hematological parameters but does not improve performance in rats

The regimen of aerobic training at sea level with recovery at high altitude has been used by athletes to improve performance. However, little is known about the effects of hypoxia when combined with sprint interval training on performance. The aim of the present study was to determine the effect of a “living high-sprint training low” strategy on hemoglobin, hematocrit and erythropoietin levels in rats. We also wanted to test whether the addition of a hypoxic stress to the program of daily treadmill running at high speeds induces expressional adaptations in skeletal muscle and affects performance. The protein content of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), cytochrome C, pyruvate dehydrogenase kinase (PDK1), heat shock protein 70 (HSP70), manganese superoxide dismutase (MnSOD) and citrate synthase activity were determined in different muscle fiber types in our animals (red and white gastrocnemius muscle). We also determined the maximal aerobic velocity (MAV) before and after the training period. A total of 24 male Wistar rats (3 month old) were randomly divided into four experimental groups: the normoxic control group (n = 6), the normoxic trained group (n = 6), the hypoxic control group (12 h pO₂ 12%/12 h pO₂ 21%) (n = 6) and the hypoxic trained group (12 h pO₂ 12%/12 h pO₂ 21%). Living in normobaric hypoxia condition for 21 days significantly increased hemoglobin, hematocrit and erythropoietin levels in both the rest and the trained groups. The trained animals (normoxia and hypoxia) significantly increased their maximal aerobic velocity. No changes were found in the skeletal muscle in PGC-1α, cytochrome C, PDK1, HSP70, MnSOD protein content and in the citrate synthase activity in any experimental group. Regardless of whether it is combined with sprint interval training or not, after 21 days of living at high altitude we found a significant increase in the hematological values determined in our study. However, contrary to our starting hypothesis, the combination of normobaric hypoxia and sprint training did not improve MAV in our animals.     

Diurnal normobaric moderate hypoxia raises serum erythropoietin concentration but does not stimulate accelerated erythrocyte production

This study was performed to examine the effect of diurnal normobaric hypoxia on hematological parameters. Eleven healthy male volunteers were randomly selected to be in either the hypoxic group (n=6) or the control group (n=5). The hypoxic group was exposed to 8 h of normobaric hypoxia in hypoxic tent systems that elicited a target peripheral O₂ saturation of 81±2% on three consecutive days. The control group spent three consecutive 8-h days in modified tent systems that delivered normoxic air into the tent. Venous blood samples were collected before the exposure (days –5, 0), after each day of the exposure (days 1, 2, 3), and for 3 weeks after the exposure (days 7, 10, 13, 17, 24). Serum erythropoietin concentration significantly increased from 9.1±3.3 U·L⁻¹ to 30.7±8.6 U·L⁻¹ in the hypoxic group. Although there were significant increases in hematocrit (4%), hemoglobin concentration (5%), red blood cell count (4%) on day 7 in the hypoxic group, these observations were likely due to dehydration or biological variation over time. There was no significant change in early erythropoietic markers (reticulocyte counts or serum ferritin concentration), which provided inconclusive evidence of accelerated erythroid differentiation and proliferation. The results suggest that the degree of hypoxia was sufficient to stimulate increased erythropoietin production and release. However, the duration of hypoxic exposure was insufficient to propagate the erythropoietic cascade.     

<Superscript>31</Superscript>P magnetic resonance spectroscopy study of the human visual cortex during stimulation in mild hypoxic hypoxia

Effects of mild hypoxic hypoxia on cerebral energy state, as assessed by phosphocreatine (PCr)/γ-ATP and inorganic phosphate (P_i)/(P_i + PCr) ratios and intracellular pH (pH_i) in the human visual cortex, were studied using ³¹P nuclear magnetic resonance spectroscopy (MRS) at 3 T. The working hypothesis that, during compromised O₂ availability obtained by hypoxic hypoxia, both cerebral energy state and pH_i decline due to insufficient O₂ supply for energy metabolism was addressed. Under baseline hypoxic hypoxia, with blood O₂ saturation ranging from 0.95 to 0.83, neither the PCr/γ-ATP and P_i/(P_i + PCr) ratios nor pH_i was affected, thus, showing that cerebral energy metabolism was maintained. Contrary to the formulated hypothesis, visual stimulation during hypoxic hypoxia influenced neither the indicator ratios for energy state nor pH_i in the occipital cortex. Taking these results, together with previous observations showing that cerebral blood flow responses are the same in size both in euoxia and in hypoxia at this depth (Mintun et al. in Proc Natl Acad Sci USA 98:6859–6864, 2001; Tuunanen et al. in J Cereb Blood Flow Metab 26:263–273, 2006a), it is concluded that O₂ delivery to the brain during mild hypoxic hypoxia meets the demand by the energy metabolism both under baseline and stimulated states.     

Acute short-term hyperoxia followed by mild hypoxia does not increase EPO production: resolving the "normobaric oxygen paradox"

Recent findings suggest that besides renal tissue hypoxia, relative decrements in tissue oxygenation, using a transition of the breathing mixture from hyperoxic to normoxic, can also stimulate erythropoietin (EPO) production. To further clarify the importance of the relative change in tissue oxygenation on plasma EPO concentration [EPO], we investigated the effect of a consecutive hyperoxic and hypoxic breathing intervention. Eighteen healthy male subjects were assigned to either IHH (N = 10) or CON (N = 8) group. The IHH group breathed pure oxygen (F_iO₂ ~ 1.0) for 1 h, followed by a 1-h period of breathing a hypoxic gas mixture (F_iO₂ ~ 0.15). The CON group breathed a normoxic gas mixture (F_iO₂ ~ 0.21) for the same duration (2 h). Blood samples were taken just before, after 60 min, and immediately after the 2-h exposure period. Thereafter, samples were taken at 3, 5, 8, 24, 32, and 48 h after the exposure. During the breathing interventions, subjects remained in supine position. There were significant increases in absolute [EPO] within groups at 8 and 32 h in the CON and at 32 h only in the IHH group. No significant differences in absolute [EPO] were observed between groups following the intervention. Relative (∆[EPO]) levels were significantly lower in the IHH than in the CON group, 5 and 8 h following exposure. The tested protocol of consecutive hyperoxic-hypoxic gas mixture breathing did not induce [EPO] synthesis stimulation. Moreover, the transient attenuation in ∆[EPO] in the IHH group was most likely due to a hyperoxic suppression. Hence, our findings provide further evidence against the “normobaric O₂ paradox” theory.     

Dynamics of metabolic compensation and hematological changes in chicken (Gallus gallus) embryos exposed to hypercapnia with varying oxygen

In day 15 chicken embryos, we determined the time course responses of acid-base balance and hematological respiratory variables during 24 h exposure to 15, 20, 40 or 90% O₂, in the presence of 5% CO₂. Hypercapnic respiratory acidosis was initially (2 h) only slightly (∼20%) compensated by metabolic alkalosis in normoxic/hyperoxic embryos. After 6 h, respiratory acidosis was partially (∼40-50%) compensated not only in normoxic/hyperoxic embryos, but also in hypoxic embryos. However, partial metabolic compensation in 15% O₂ could not be preserved after 24 h. Preservation of metabolic compensation required oxygen concentration ([O₂]) above 20%, but the magnitude of partial metabolic compensation was unrelated to [O₂]. Hematocrit (Hct), together with mean corpuscular volume (MCV), markedly increased in hypercapnic hypoxia, and was maintained at 24 h due to a subsequent increase in red blood cell concentration ([RBC]). In contrast, Hct, together with MCV, decreased in hypercapnic normoxia/hyperoxia accompanied by a subsequent decrease in [RBC] at 24 h. Regulation of variables takes place similarly irrespective of environmental [O₂] above 20%, matching acid-base regulation.     

Hematological parameters of lambs infected experimentally with Haemonchus contortus and supplemented with selenium and vitamin E

The aim of the present study was to determine the effect of supplementation with selenium and vitamin E on the hematological parameters of lambs infected experimentally with Haemonchus contortus. Thirty female lambs were distributed into the following groups: group 1, infected animals; group 2, infected and supplemented animals; group 3, controls; group 4, noninfected and supplemented animals. Groups 1 and 2 received 5,000 larvae of H. contortus (L3) orally per animal. In groups 2 and 4, supplementation with 0.1 mg/kg sodium selenite (1.67%) and 2,000 IU of vitamin E, administered intramuscularly, was performed on day 0. Blood sampling was performed on days 0, 20, 30, 45, 60, and 80 to determine the hemogram. Eggs per gram of feces (EPG) was quantified on days 0, 20, 45, and 80. In relation to the number of erythrocytes, hematocrit, hemoglobin, total leukocytes, and lymphocytes, principal differences were observed when parasitized groups were compared with the supplemented-only group, where the latter maintained the highest levels. In lambs supplemented with vitamin E and selenium, there was an increase in cellular immune response mediated by neutrophils.     

Sub-chronic oral toxicity study in Sprague-Dawley rats with hypoxia mimetic cobalt chloride towards the development of promising neutraceutical for oxygen deprivation

The present study evaluates the toxicity from sub-chronic administration of CoCl₂ (12.5 mg cobalt kg^?1 BW for 7 days) to male Sprague-Dawley rats in view of the beneficial effects of CoCl₂ in animals and for developing efficacious therapeutic regimen in humans. 32 rats weighing 200±25 g were used for all experiments. Blood was collected for hematological and biochemical analysis and various organs were dissected after perfusion of animals under anesthesia for other analyses. Mean feed consumption and feed conversion efficiency values were comparable across all study groups; however, hematological analysis depicted a significant increase in hemoglobin, hematocrit and RBC in the entire cobalt-supplemented groups, which are a component of its beneficial effect. There was a significant increase in monocytes, granulocytes and WBC after 1 and 24 h, which were comparable with control after 7 days. Other biochemical analyses also showed no change with respect to control. Though the metal content increased significantly in liver initially (1 and 24 h) after treatment, it was equivalent to control after 7 days. Moreover, histopathological analysis revealed no evidence of changes that could be attributed to cobalt pretreatment. It is therefore reasonable to conclude that the present study supports further use of the present dose of CoCl₂, which was found to be nontoxic.     

Effects on hematological and biochemical parameters in albino mice fed Ipomoea batatas leaf aqueous extract

The leaf aqueous extract of Ipomoea batatas was investigated for hematological and biochemical effects in mice. The acute toxicity test recorded no death, even at the highest dose of 1,600 mg/kg. The animals were divided into two groups. The first group was given 800 mg of the extract for 28 days while the second group that served as the control received water for the same period. No significant changes in hematological parameters such as packed cell volume, hemoglobin concentration, and the red blood cell count. The erythrocytic indices such as mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration did not change significantly. There was a significant (p < 0.05) increase in the level of WBC in the group that received the extract. The activities of the serum enzymes, alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase also did not change significantly. The pentobarbitone sleeping time showed significant (p < 0.001) increase in the mean sleeping time when the group that received the extract was compared with the control.     

Addition of a combination of onion (Allium cepa) and coconut (Cocos nucifera) to food of sheep stops gastrointestinal helminthic infections

Sheep with gastrointestinal nematodes and cestodes were fed on three farms with a combination of specially prepared extracts of onion (Allium cepa) and coconut (Cocos nucifera) for 8 days containing each 60 g coconut and onion extract, combined with milk powder and/or polyethylene glycol (PEG) propylencarbonate (PC). In all cases, the worm stages disappeared from the feces and were also not found 9 and 20 days after the end of the feeding with this plant combination. Since all treated animals increased their body weight considerably (when compared to untreated animals), worm reduction was apparently as effective as it was shown in previous laboratory trials with rats and mice (Klimpel et al., Parasitol Res, in press, 2010; Abdel-Ghaffar et al., Parasitol Res, in press, 2010; in this volume).     

Reduced hypoxic ventilatory response with preserved blood oxygenation in yoga trainees and Himalayan Buddhist monks at altitude: evidence of a different adaptive strategy?

Yoga induces long-term changes in respiratory function and control. We tested whether it represents a successful strategy for high-altitude adaptation. We compared ventilatory, cardiovascular and hematological parameters in: 12 Caucasian yoga trainees and 12 control sea-level residents, at baseline and after 2-week exposure to high altitude (Pyramid Laboratory, Nepal, 5,050 m), 38 active lifestyle high-altitude natives (Sherpas) and 13 contemplative lifestyle high-altitude natives with practice of yoga-like respiratory exercises (Buddhist monks) studied at 5,050 m. At baseline, hypoxic ventilatory response (HVR), red blood cell count and hematocrit were lower in Caucasian yoga trainees than in controls. After 14 days at altitude, yoga trainees showed similar oxygen saturation, blood pressure, RR interval compared to controls, but lower HVR (−0.44 ± 0.08 vs. −0.98 ± 0.21 l/min/m/%SaO₂, P < 0.05), minute ventilation (8.3 ± 0.9 vs. 10.8 ± 1.6 l/min, P < 0.05), breathing rate (indicating higher ventilatory efficiency), and lower red blood cell count, hemoglobin, hematocrit, albumin, erythropoietin and soluble transferrin receptors. Hypoxic ventilatory response in monks was lower than in Sherpas (−0.23 ± 0.05 vs. −0.63 ± 0.09 l/min/m/%SaO₂, P < 0.05); values were similar to baseline data of yoga trainees and Caucasian controls, respectively. Red blood cell count and hematocrit were lower in monks as compared to Sherpas. In conclusion, Caucasian subjects practicing yoga maintain a satisfactory oxygen transport at high altitude, with minimal increase in ventilation and with reduced hematological changes, resembling Himalayan natives. Respiratory adaptations induced by the practice of yoga may represent an efficient strategy to cope with altitude-induced hypoxia.     

Differential Genetic Etiology of Reading Difficulties as a Function of IQ: An Update

In order to test the hypothesis that the genetic etiology of reading disability differs as a function of IQ, composite reading performance data from 308 pairs of identical (monozygotic, MZ) twins and 440 pairs of fraternal (dizygotic, DZ) twins (254 same-sex and 186 opposite-sex) in which at least one member of each pair was classified as reading-disabled were subjected to multiple regression analysis (DeFries and Fulker, Behav Genet 15:467–473, 1985; Acta Genet Med Gemellol 37:205–216, 1988). In the total sample, heritability of the group deficit in reading performance (h_g²) was .61 (±.06). However, results of fitting an extended regression model to reading performance and IQ data suggested that the genetic etiology of reading disability differs as a linear function of IQ (p ≤ .04). When the basic regression model was fitted separately to data from twin pairs with Wechsler (Examiner's manual: Wechsler intelligence scale for children—revised, 1974; Examiner's manual: Wechsler adult intelligence scale—revised, 1981) Full Scale IQ scores in the upper and lower 25% of the sample, resulting estimates of h_g² were .75 (±.12) and .50 (±.10), respectively (p ≤ .045). These results suggest that reading difficulties in children with a higher IQ are due substantially to genetic influences and may require intensive remediation efforts.     

血小板源生长因子可促进低氧的牛肺动脉平滑肌细胞核内NF-κB表达

目的:为探讨血小板源生长因子(platelet-derived growth factor,PDGF)受体信号转导途径的介质分子之一过氧化氢( H₂O₂ )在低氧的肺动脉平滑肌细胞(pulmonary artery smooth muscle cell,PASMC )增殖中是否起作用。方法:应用共聚焦显微镜、细胞免疫组织化学及Western印迹杂交等方法,检测了低氧的PASMC PDGF受体途径中的H₂O₂的变化及PDGF和H₂O₂对细胞核内与增殖作用相关的核转录因子NF-κB表达量的影响。 结果:PDGF可使常氧的PASMC中H₂O₂浓度增高,但明显降低低氧的PASMC中H₂O₂的量;同一浓度的H₂O₂,作用于常氧的PASMC,则引起核NF-κB的表达量增加,但对低氧的PASMC核NF-κB有明显的抑制作用;同时加入PDGF和H₂O₂的低氧的PASMC较仅以H₂O₂作用的低氧的PASMC,核NF-κB的量显著增加。结论:PDGF受体的信号转导途径在低氧的PASMC同常氧的PASMC相反,H₂O₂为抑制因子,对细胞可能产生损伤作用,PDGF可抑制低氧的PASMC产生H₂O₂并达到促进NF-κB表达增强的目的,从而使胞内与增殖相关的基因表达增强,最终达到低氧条件下表达增强的PDGF对低氧性PASMC过度增殖的正反馈调节作用。     

Rapidity of responding to a hypoxic challenge during exercise

The ability to modify power output (PO) in response to a changing stimulus during exercise is crucial for optimizing performance involving an integration system involving a performance template and feedback from peripheral receptors. The rapidity with which PO is modified has not been established, but would be of interest relative to understanding how PO is regulated. The objective is to determine the rapidity of changes in PO in response to a hypoxic challenge, and if change in PO is linked to changes in arterial O₂ saturation (S _aO₂). Well-trained cyclists performed randomly ordered 5-km time trials. Subjects began the trials breathing room air and switched to hypoxic (HYPOXIC, F_IO₂ = 0.15) or room (CONTROL, F_IO₂ = 0.21) air at 2 km, then to room air at 4 km. The time delay to begin decreasing S _aO₂ and PO and to recover S _aO₂ and PO on to room air was compared, along with the half time (t _1/2) during the HYPOXIC trial. Mean S _aO₂ and PO between 2 and 4 km were significantly different between CONTROL and HYPOXIC (94 ± 2 vs. 83 ± 2% and 285 ± 16 vs. 245 ± 19 W, respectively). There was no difference between the time delay for S _aO₂ (31.5 ± 12.8 s) and in PO (25.8 ± 14.4 s) or the recovery of S _aO₂ (29.0 ± 7.7 s) and PO (21.5 ± 12.4 s). The half time for decreases in S _aO₂ (56.6 ± 14.4 s) and in PO (62.7 ± 20.8 s) was not significantly different. Modifications of PO due to the abrupt administration of hypoxic air are related to the development of arterial hypoxemia, and begin within ~30 s.     

Carbon monoxide inhibits hypoxic pulmonary vasoconstriction in rats by a cGMP-independent mechanism

 Hypoxia activates erythropoietin-producing cells, chemoreceptor cells of the carotid body and pulmonary artery smooth muscle cells (PSMC) with a comparable arterial PO₂ threshold of some 70 mmHg. The inhibition by CO of the hypoxic responses in the two former cell types has led to the proposal that a haemoprotein is involved in the detection of the PO₂ levels. Here, we report the effect of CO on the hypoxic pulmonary vasoconstriction (HPV). Pulmonary arterial pressure (PAP) was measured in an in situ, blood-perfused lung preparation. PAP in normoxia (20% O₂, 5% CO₂) was 15.2±1.8 mmHg, and hypoxia (2% O₂, 5% CO₂) produced a ΔPAP of 6.3±0.4 mmHg. Addition of 8% or 15% CO to the hypoxic gas mixture reduced the ΔPAP by 88.3±2.7% and 78.2±6.1% respectively. The same levels of CO did not affect normoxic PAP nor reduced the ΔPAP produced by angiotensin II. The effect of CO was studied after inhibition of the NO-cyclic guanosine monophosphate (cGMP) cascade with N-methyl-l-arginine (5·10^–5 M) or methylene blue (1.4·10^–4 M). It was found that both inhibitors more than doubled the hypoxic ΔPAP without altering the effectiveness of CO to inhibit the HPV. In in vitro experiments we verified the inhibition of guanylate cyclase by measuring the levels of cGMP in segments of the pulmonary artery. Cyclic GMP levels were 1.4±0.2 (normoxia), 2.5±0.3 (hypoxia) and 3.3±0.5 pmole/mg tissue (hypoxia plus 8% CO); sodium nitroprusside increased normoxic cGMP levels about fourfold. Methylene blue reduced cGMP levels to less than 10% in all cases, and abolished the differences among normoxic, hypoxic and hypoxic plus CO groups. It is concluded that CO inhibits HPV by a NO-cGMP independent mechanism and it is proposed that a haemoprotein could be involved in O₂-sensing in PSMC. Received: 17 March 1997 / Received after revision: 10 June 1997 / Accepted: 11 July 1997     

Contribution of nitric oxide to cerebral blood flow regulation under hypoxia in rats

This study was designed to clarify whether nitric oxide (NO) participates in the regulation of local cerebral blood flow (CBF) during hypoxia (inhalation of 15% O₂ in N₂). The CBF response to hind-paw stimulation (evoked CBF) of Sprague-Dawley (SD) rats was measured by laser-Doppler flowmetry. Physiological variables, such as heart rate, mean blood pressure, and PaCO₂ during hypoxia, were identical to those under normoxic conditions. Hypoxia increased the baseline CBF (17.5 ± 14.3%) and the normalized peak amplitude of evoked CBF (31.1 ± 18.5%) relative to those during normoxia. When an NOS inhibitor was infused intravenously, these differences were abolished in both the baseline CBF or evoked CBF between normoxic and hypoxic conditions, whereas the heart rate decreased and the mean blood pressure increased during hypoxia in comparison with these during normoxia. The field potential was constant under all experimental conditions. These results suggest that NO plays a major role in the regulation of baseline and evoked CBF during hypoxia.     

Respiratory muscle endurance training: effect on normoxic and hypoxic exercise performance

The aim of this study was to investigate the effect of respiratory muscle endurance training on endurance exercise performance in normoxic and hypoxic conditions. Eighteen healthy males were stratified for age and aerobic capacity; and randomly assigned either to the respiratory muscle endurance training (RMT = 9) or to the control training group (CON = 9). Both groups trained on a cycle-ergometer 1 h day⁻¹, 5 days per week for a period of 4 weeks at an intensity corresponding to 50% of peak power output. Additionally, the RMT group performed a 30-min specific endurance training of respiratory muscles (isocapnic hyperpnea) prior to the cycle ergometry. Pre, Mid, Post and 10 days after the end of training period, subjects conducted pulmonary function tests (PFTs), maximal aerobic tests in normoxia ([(V)\dot] {\dot{V}} O_2maxNOR), and in hypoxia ([(V)\dot] {\dot{V}} O_2maxHYPO; F_IO₂ = 0.12); and constant-load tests at 80% of [(V)\dot] {\dot{V}} O_2maxNOR in normoxia (CLT_NOR), and in hypoxia (CLT_HYPO). Both groups enhanced [(V)\dot] {\dot{V}} O_2maxNOR (CON: +13.5%; RMT: +13.4%), but only the RMT group improved [(V)\dot] {\dot{V}} O_2maxHYPO Post training (CON: −6.5%; RMT: +14.2%). Post training, the CON group increased peak power output, whereas the RMT group had higher values of maximum ventilation. Both groups increased CLT_NOR duration (CON: +79.9%; RMT: +116.6%), but only the RMT group maintained a significantly higher CLT_NOR 10 days after training (CON: +56.7%; RMT: +91.3%). CLT_HYPO remained unchanged in both groups. Therefore, the respiratory muscle endurance training combined with cycle ergometer training enhanced aerobic capacity in hypoxia above the control values, but did not in normoxia. Moreover, no additional effect was obtained during constant-load exercise.     

Comparing several equations that predict peak VO2 using the 20-m multistage-shuttle run-test in 8-10-year-old children

This study compared the validity of reported equations as predictors of peak VO₂ in 8–10-year-old children. Participants (90 boys and girls aged 8–10 years) performed the multistage-shuttle-run-test (MSRT) and peak VO₂ was measured in field using a portable gas analyser. The equations that estimated peak VO₂ from the MSRT performance were chosen according to the age range of this study. As follows, the FITNESSGRAM reports and the equations of Leger et al. (Can J Appl Sport Sci 5: 77–84, 1988), Barnett et al. (Pediatr Exerc Sci 5:42–50, 1993), Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004) and Fernhall et al. (Am J Ment Retard 102:602–612, 1998) were used to estimate the peak VO₂ and compared with the directly measured value. The equation of Leger et al. (Can J Appl Sport Sci 5: 77–84, 1988) provided a mean difference (d) of 4.7 ml kg⁻¹ min⁻¹ and a 1.0 slope. The equation of Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004)(a) using maximal speed (MS) showed a higher d (5.4) than the remaining using total laps d (4.2). The equation of Barnett et al. (Pediatr Exerc Sci 5:42–50, 1993)(a) that includes triceps skinfold and MS showed the highest d (6.1) but the smallest range (24.1) and slope (0.6). Data from the FITNESSGRAM had the smallest d (1.8 ml kg⁻¹ min⁻¹), but also had the highest range between limits of agreement (28.6 ml kg⁻¹ min⁻¹) and a 1.2 slope. The lowest slope (0.4) and range (22.2 ml kg⁻¹ min⁻¹) were observed using the equation of Fernhall et al. (Am J Ment Retard 102:602–612, 1998). Log transformation of the data revealed that the equations of Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004)(a) (1.1*/÷1.25) and Fernhall et al. (Am J Ment Retard 102:602–612, 1998) (1.17*/÷1.25) showed the closest agreement among all, but they still yield unsatisfactory accuracy.     

Regional blood flow responses to hypoxia and exercise in altitude-adapted rats

Regional blood flow, determined as the fractional distribution of ¹³⁷Cs, was measured at rest and during swimming exercise in control rats raised at sea level and in rats altitude-adapted by exposure to a barometric pressure of 440 mmHg for approximately 6 weeks. During both normoxic and hypoxic (11% O₂) resting conditions, the altitude-adapted rats exhibited regional distributions of blood flow that differed significantly from those in the control animals. During normoxic and hypoxic swimming, significant redistributions of blood flow were noted in the control animals compared to the resting conditions. Ventricular, diaphragmatic, and working muscle blood flows were increased at the expense of the renal and splanchnic circulations, with a more marked redistribution during the hypoxic swims. Similar redistributions of blood flow were exhibited by the exercising altitude-adapted rats, except that renal and hepatic perfusion was maintained at a significantly higher level during both the normoxic and hypoxic swims. Blood lactate concentrations in control rats during hypoxic exercise were strikingly increased, suggesting that the lactate metabolizing ability of the liver and kidneys was impaired. In the altitude-adapted rats, however, blood lactate levels after exercise were significantly lower than those observed in the control animals. It is suggested that the degree of polycythemia may have determined the magnitude of the blood flow redistribution and the extent of lactate metabolism impairment.Research sponsored in part by the Air Force Office of Scientific Research, Air Force Systems Command, under Grant AFOSR 73-2455.     

Seasonal changes in hematological parameters of Catla catla (Hamilton 1822)

Hematological parameters are repeatedly used as an essential diagnostic tool to assess the health condition of fish. The purpose of this study was to assess the reference values of some hematological parameters of Catla, Catla catla collected from a freshwater pond in a tropical climate of India from July 2008 to June 2010. Variations in hematological parameters such as hemoglobin, erythrocyte count, total leucocyte count, hematocrit, mean corpuscular volume (MCV), and mean corpuscular hemoglobin concentration (MCHC) of fish were compared according to sex and seasonal differences. Analysis of variance showed that there were significant differences between sexes and the results indicated that blood parameters levels between the sexes in summer were significantly different than that measure in other seasons except mean corpuscular hemoglobin (MCH) and MCHC value (P?<?0.05). The number of total leukocyte levels was found to be higher in female fish especially in reproductive seasons, but the levels of hemoglobin, hematocrit, and MCV values were high in male fish in an annual period. However, there was no difference in MCH and MCHC values between the sexes and seasons throughout the study period. These may be related to season of sampling and changing physiological cycles during these months. The correlations between measured hematological parameters were also determined.