Physical fitness of the Czechoslovak population between the ages of 12 and 55 years. Pulmonary ventilation.

Examination of ventilation function in an average population showed that maximum minute ventilation in adults fell with advancing age. Males had higher values than females, the highest values being attained, in both sexes, at 18 (117 and 83 1/min respectively). Tidal volume during loading, expressed as a percentage of vital capacity, rose with advancing age in all groups of males and females (from 53% at 18 to 64% at 55 in males and from 51% to 59% in females). The ventilation equivalents for O2 and CO2 attained optimum values at a load of 100 W in males and at 50 W in females. On increasing the load they rose in both sexes--in females more than in males. Percentual utilization of O2 from the inspired air was greatest in males at a load of about 100 W (4.8--5%) and in females at about 50 W (4.3--4.8%). At higher loads it fell faster in females than in males. In males, the respiratory quocient attained the value 1 at a load of about 2 W/kg body weight and in females at 1.5 W/kg. At maximum loading it was over 1 in all the age categories. No differences between males and females were observed, but males, in maximum loading, gave the greatest absolute and the greatest relative performance.     

Estimation of human fetal-placental unit metabolic rate by application of the Bohr principle

The Bohr Principle via continuous indirect calorimetry was used to estimate human fetal-placental unit metabolic rate in 12 normal women undergoing elective caesarean section under continuous lumbar epidural anaesthesia. Maternal oxygen consumption decreased after umbilical cord clamping and after placental removal. Fetal-placental unit oxygen consumption was 10.7 +/- 1.3 ml/min per kg (mean +/- SEM). Fetal oxygen consumption was 6.8 +/- 1.4 ml/min per kg. Placental oxygen consumption was 37 +/- 12 ml/min per kg. Fetal-placental unit carbon dioxide production was 9.2 +/- 1.2 ml/min per kg. These mean values agree favourably with measurements of uterine and fetal metabolism from other mammalian species. Maternal minute ventilation decreased with removal of the fetal-placental unit, and this decrease was found to be linearly related to the fetal-placental unit carbon dioxide production.     

The effects of substrate utilization, manipulated by caffeine, on post-exercise oxygen consumption in untrained female subjects

The effect of substrate utilization manipulated by caffeine on post-exercise oxygen consumption was investigated in five untrained females (age = 21 +/- 1.5 years), following 90 min of treadmill walking at 55% maximal oxygen consumption. Each subject participated in the two trials (control and experimental) within 2 weeks of each other. Immediately following the measurement of resting oxygen consumption, subjects consumed one of the two test beverages 60 min prior to exercise: 5 mg of caffeine per kg of body-weight in 200 ml of orange juice (CA) or 200 ml of orange juice (C). Assignment of CA and C was made in a random, double blind fashion. Immediately prior to the exercise phase (0 min) resting oxygen consumption was again measured. Following exercise, subjects returned to the same pre-exercise sitting position where respiratory data was collected over 1 h. No significant differences were found in resting oxygen consumption and respiratory exchange ratio (R) prior to caffeine ingestion (-60 min). One hour after caffeine ingestion (0 min) oxygen consumption and free fatty acid (FFA) levels increased significantly compared to C. During and 1 h following exercise, oxygen consumption and FFA levels were significantly greater, with R values being significantly lower in CA compared to C. These findings provide further evidence that metabolic substrate is somehow implicated in elevating oxygen consumption following exercise cessation.     

Physical fitness of Czechoslovak population between the ages of 12 and 55 years. Pulse rate and blood pressure.

In loading test of a representative sample of the Czechoslovak population aged 12--55 years, the authors, examined the reaction of the pulse rate and blood pressure (in watts--W) to loading on a bicycle ergometer. On increasing the submaximal load, the pulse rate rose linearly with age--more gradually in the phase of growth and along an approximately the same trend from the age of 18. The course in adult women corresponded to the course in boys aged about 13. The maximum pulse rate fell linearly in correlation to age, by about 4--5 beats for every 10 years, from 195/min in 12-year-old boys and 198/min in girls. The working capacity at pulse rate 170 (W 170) attained the maximum at 25 years (men 198, women 112 W). The systolic pressure rose non-linearly with loading. It increased more rapidly at lower loads. Children had the smallest pressure reaction and the oldest subjects the greatest. Diastolic pressure fell gradually and non-linearly with loading. The maximum blood pressure values, according to age, rose from 138/56 torr in the oldest males and from 139/57 to 182/84 torr in females.     

Opioid action on luteinizing hormone secretion in newborn pigs: paradoxical effect of naloxone

German Landrace piglets, 6-7 days of age, received either saline (9 males, 8 females), 0.5 mg naloxone/kg body weight (7 males, 7 females), 2.0 mg naloxone/kg (7 males, 8 females) or 0.5 mg DADLE (potent leu-enkephalin analog)/kg (7 males, 7 females) through a catheter inserted into the jugular vein 2-4 days previously. Male or female piglets were allocated randomly, within litter, to the different experimental groups. Blood samples were withdrawn for a period of 240 min at 10-min intervals for the first 60 min following injection and at 20-min intervals for the rest of the test period. Piglets were separated from their mother via a detachable wall and were allowed to suckle every 50 min. DADLE failed to alter plasma levels of LH in both males and females. Naloxone induced a significant (P less than 0.01) decrease in LH concentrations in females 10 to 60 min after injection (saline: 2.3 +/- 0.2 ng/ml plasma (SEM); 0.5 mg naloxone/kg: 1.0 +/- 0.2 ng/ml plasma and 2 mg naloxone/kg 1.2 +/- 0.4 ng/ml plasma). In males low doses of naloxone reduced plasma LH levels 10 to 40 min after injection (saline: 2.0 +/- 0.3 ng/ml plasma and 0.5 ng naloxone/kg: 1.1 +/- 0.3 ng/ml), whereas a decrease in plasma LH levels occurred 80 to 140 min after injection of high doses of naloxone (saline: 2.1 +/- 0.2 ng/ml and 2 mg naloxone/kg: 1.0 +/- 0.2 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Supramaximal test results of male and female speed skaters with particular reference to methodological problems

Six male and six female elite speed skaters were tested during two bicycle ergometer tests: a 30 s sprint test and a 2.5 min supra maximal test. During the 2.5 min test oxygen consumption was measured every 30 s. The males showed 30-31% higher mean power output values both during the sprint test (1103 versus 769 Watt) and during the 2.5 min test (570 versus 390 Watt). Maximal oxygen consumption was 31% higher for the males than for the females (5.10 versus 3.50 1.min-1). However, when expressed per kilogram lean body weight (LBM), power output and oxygen consumption was equal for both sexes. Differences between present and previous results are most likely due to methodological problems with the estimation of load during the supra maximal test. Subjects appear to experience difficulties in distributing their power output over the 2.5 min if they are tested for the first time. For experienced skaters and cyclists, fixed levels of 19 W.kgLBM-1 as initial load setting for the sprint test and 8 W.kg LBM-1 for the 2.5 min test are recommended.     

Circulating blood volume of the Japanese monkey (Macaca fuscata) by means of the dye T-1824

The circulating blood volume has been measured in 65 healthy Japanese monkeys (Macaca fuscata) with the dye T-1824 (Evans blue). The values obtained were 83 ± 13 ml/kg in females, and 85 ± 12 ml/kg in females, almost the same as the figures reported in man.Sex difference of blood volume has been reported to be present in man, but from the data obtained here no significant difference was found in the Japanese monkey.In young monkeys aged from 1 to 5.5 years, the blood volume was 77 ± 5 ml/kg in males, and 78 ± 4 ml/kg in females. The blood volume of the monkey was found to increase with age; a significant difference was demonstrated between adult males and young males.     

Treadmill economy in girls and women matched for height and weight.

We investigated differences in walking (80 m/min) and running (147 m/min) economy [submaximal oxygen consumption (VO(2) (submax))] between adolescent girls (n = 13; age = 13.3 +/- 0.9 yr) and young women (n = 23; age = 21.0 +/- 1.5 yr). Subjects were matched for height (158.7 +/- 2.9 cm) and weight (52.1 +/- 3.0 kg). Anthropometric measures (height, weight, breadths, skinfolds) and preexercise oxygen consumption were obtained on all subjects before submaximal and maximal treadmill exercise. Anthropometric measures were similar between groups, as was maximal oxygen consumption (girls, 47.7 +/- 5.2; women, 47.5 +/- 5.7 ml. kg(-1). min(-1)). VO(2) (submax) was significantly greater (P < 0.0002) in girls compared with women during both walking (16.4 +/- 1.7 vs. 14.4 +/- 1. 1 ml. kg(-1). min(-1)) and running (38.1 +/- 3.7 vs. 33.9 +/- 2.4 ml. kg(-1). min(-1)). Preexercise oxygen consumption (4.4 vs. 3.9 ml. kg(-1). min(-1)) accounted for only a fraction of the differences found in exercise economy. Although heart rate and respiratory frequency were greater in the girls in both walking (118 +/- 11 vs. 104 +/- 12 beats/min and 31 +/- 3 vs. 25 +/- 4 breaths/min, respectively; P < 0.002) and running (180 +/- 15 vs. 163 +/- 17 beats/min and 47 +/- 11 vs. 38 +/- 8 breaths/min; P < 0.005), this did not likely account for a large part of the difference in VO(2) (submax) between groups.     

Reference values of pulmonary diffusing capacity for nitric oxide in an adult population.

Our objective was to create reference values for single-breath DLNO based on a sample of non-smoking healthy males and females using a short breath-hold time. The sample included 130 individuals varied in age (18-85 yr), height (149-190 cm), and weight (49.4-102.6 kg). The subjects performed single-breath-hold maneuvers at rest inhaling 41 +/- 6 ppm NO and a standard diffusion mixture. The breath-hold time was 5.5 +/ -0.6 s. Multiple linear regression with backward elimination of the independent variables age, weight, gender, and either measured lung volume (called alveolar volume or VA) or height revealed specific prediction equations for DLNO. Inserting VA instead of height into the regression equation determined how much of an abnormality of DLNO was due to gas exchange versus low lung volume. The predicted DLNO adjusted for lung volume (ml/min/mmHg) = DLNO = 73.1 + 17.26 x (VA)+17.56 x (gender) - 1.0 x (age). The predicted DLNO unadjusted for lung volume (ml/min/mmHg) = -20.1 + 1.167 x (height)+31.81 x (gender) - 1.21 x (age). For gender, 1 = males, 0 = females; VA = liters; height = cm. Age, gender and VA (lung volume) were the best predictors of DLNO and DLCO. Weight was not a good independent predictor of DLNO or DLCO. When normalizing for height and age, women have 650 ml lower forced vital capacity, 660 ml lower VA, and a 6 and 32 ml/min/mmHg lower DLCO and DLNO, respectively, compared to men. Normalizing for lung volume and age, women have, on average, a 3.2 and 18 ml/min/mmHg lower DLCO and DLNO, respectively, compared to men.     

Oxygen consumption is maintained in fetal sheep during prolonged hypoxaemia.

Experiments were conducted in 12 chronically-catheterized pregnant sheep to examine the effect of prolonged hypoxaemia secondary to the restriction of uterine blood flow on fetal oxygen consumption. Surgery was performed at 115 days gestation to place a teflon vascular occluder around the maternal common internal iliac artery and for insertion of vascular catheters. Following a 5-day recovery period, uterine blood flow was reduced in 6 animals for 24 hours and in 6 animals, the occluder was not adjusted. Fetal arterial PO2 decreased from 19.9 +/- 2.0 mmHg to 12.8 +/- 2.0 mmHg and 11.0 +/- 2.0 mmHg at 1 and 24 hours respectively in the experimental group and did not change the control group. Fetal pH decreased from 7.34 +/- 0.01 to 7.25 +/- 0.03 and 7.29 +/- 0.02 at 1 and 24 hours of hypoxaemia respectively. Fetal arterial lactate concentrations remained elevated throughout the experimental period with maximum concentrations of 6.6 +/- 2.1 mmol/l being present at 4 hours compared to 1.3 +/- 0.2 mmol/l during the control period. Umbilical blood flow increased from 186 +/- 19 ml/min/kg to 251 +/- 39 ml/min/kg at 1 h of hypoxaemia and returned to 191 +/- 21 ml/min/kg at 24 h. In association with the progressive fall in oxygen delivery to the fetus, oxygen extraction increased from 0.33 +/- 0.04 to 0.43 +/- 0.04 and 0.54 +/- 0.05 at 1 and 24 hours, respectively. Overall oxygen consumption by the fetus remained unchanged from control values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nifedipine inhibits the hypoxia-induced decrease in plasma renin activity in conscious dogs.

Acute hypoxia induces a decrease in plasma renin activity (PRA), mediated, e.g., by an increase in adenosine concentration, calcium channel activity, or inhibition of ATP-sensitive potassium channels. The decrease in PRA results in a decrease in angiotensin II (AngII) and plasma aldosterone concentration (PAC). This study investigates whether these hypoxia-induced mechanisms can be inhibited by the L-type voltage-dependent calcium channel antagonist nifedipine. Eight conscious, chronically tracheotomized dogs received a low sodium diet (0.5 mmol Na x kg body wt(-1) x day(-1)). The dogs were studied twice in randomized order, either with nifedipine infusion (1.5 microg x kg body wt(-1) x min(-1), Nifedipine) or without (Control). The dogs were breathing spontaneously: first hour, normoxia [inspiratory oxygen fraction (FiO2)=0.21]; second and third hour hypoxia (FiO2=0.1). In Controls, PRA (6.8+/-0.8 vs. 3.0+/-0.5 ngAngI x ml(-1) x min(-1)), AngII (13.3+/-1.9 vs. 7.3+/-1.9 pg/ml), and PAC (316+/-50 vs. 69+/-12 pg/ml) decreased during hypoxia (P<0.05). In Nifedipine experiments, PRA (6.5+/-0.9 vs. 10.5+/-2.4 ngAngI x ml(-1) x min(-1)) and AngII (14+/-1.1 vs. 18+/-3.9 pg/ml) increased during hypoxia, whereas the decrease in PAC (292+/-81 vs. 153+/-41 pg/ml) was blunted (P<0.05). These results foster the idea that the hypoxia-induced decrease in PRA involves L-type calcium channel activity.     

Comparison of cardiorespiratory responses of moderately trained men and women using two different treadmill protocols

In practice, the Bruce protocol is the most commonly used treadmill protocol to assess maximal oxygen consumption (V(.-)O2max). It has been suggested that a running protocol (e.g., Astrand) may elicit a comparatively higher V(.-)O2max and different cardiorespiratory responses when applied to moderately trained runners. Thus, the purpose of this study was to compare V(.-)O2max and other cardiorespiratory responses as elicited by the standard Bruce and a modified Astrand treadmill protocol in moderately trained runners. Fifteen women (age = 21 years, height = 171.5 cm, weight = 63 kg, and body fat = 18%) and 15 men (age = 26 years, height = 177 cm, weight = 72 kg, and body fat = 9%) who were moderately trained runners completed a standard Bruce and modified Astrand protocol (random order), separated by approximately 7 days. Heart rate, Borg ratings of perceived exertion, blood pressure, and pulmonary gas exchange variables were measured during the exercise tests using standard laboratory procedures. This study revealed V(.-)O2max values between the Bruce protocol (51.3 +/- 11.6 ml x kg(-1) x min(-1)) and modified Astrand (51.5 +/- 10.9 ml x kg(-1) x min(-1)) were not significantly different in either the men or the women. However, the Bruce protocol elicited significantly higher maximum treadmill time in men and maximum respiratory exchange ratio (RERmax) and maximum minute ventilation (VEmax) values in both genders. Conversely, the modified Astrand elicited a higher HRmax. These data suggest that V(.-)O2max in both moderately trained men and women runners is independent of treadmill protocol despite differences in HRmax, RERmax, and VEmax.     

Oxygen distribution and consumption in the cat retina during normoxia and hypoxemia

Oxygen tension (PO2) was measured with microelectrodes within the retina of anesthetized cats during normoxia and hypoxemia (i.e., systemic hypoxia), and photoreceptor oxygen consumption was determined by fitting PO2 measurements to a model of steady-state oxygen diffusion and consumption. Choroidal PO2 fell linearly during hypoxemia, about 0.64 mmHg/mmHg decrease in arterial PO2 (PaO2). The choroidal circulation provided approximately 91% of the photoreceptors' oxygen supply under dark-adapted conditions during both normoxia and hypoxemia. In light adaptation the choroid supplied all of the oxygen during normoxia, but at PaO2's less than 60 mmHg the retinal circulation supplied approximately 10% of the oxygen. In the dark-adapted retina the decrease in choroidal PO2 caused a large decrease in photoreceptor oxygen consumption, from approximately 5.1 ml O2/100 g.min during normoxia to 2.6 ml O2/100 g.min at a PaO2 of 50 mmHg. When the retina was adapted to a rod saturating background, normoxic oxygen consumption was approximately 33% of the dark-adapted value, and hypoxemia caused almost no change in oxygen consumption. This difference in metabolic effects of hypoxemia in light and dark explains why the standing potential of the eye and retinal extracellular potassium concentration were previously found to be more affected by hypoxemia in darkness. Frequency histograms of intraretinal PO2 were used to characterize the oxygenation of the vascularized inner half of the retina, where the oxygen distribution is heterogeneous and simple diffusion models cannot be used. Inner retinal PO2 during normoxia was relatively low: 18 +/- 12 mmHg (mean and SD; n = 8,328 values from 36 profiles) in dark adaptation, and significantly lower, 13 +/- 6 mmHg (n = 4,349 values from 19 profiles) in light adaptation. Even in the dark-adapted retina, 30% of the values were less than 10 mmHg. The mean PO2 in the inner (i.e., proximal) half of the retina was well regulated during hypoxemia. In dark adaptation it was significantly reduced only at PaO2's less than 45 mmHg, and it was reduced less at these PaO2's in light adaptation.     

Cardiovascular effects of training for a marathon run in unfit middle aged men.

The effects of a 30 week exercise programme on serum lipid values, blood pressure, and cardiac function were assessed in a group of sedentary men aged 35-50 training for their first marathon. Mean serum cholesterol concentration (n = 33) fell by 12% from 6.54 (SE 0.18) to 5.76 (0.15) mmol/l (mean fall 0.78 mmol/l; 95% confidence interval 0.52 to 1.04 mmol/l), serum triglyceride concentration (n = 33) by 22% from 1.56 (0.17) to 1.21 (0.09) mmol/l (mean fall 0.34 mmol/l; 95% confidence interval 0.12 to 0.56 mmol/l), and mean blood pressure (n = 27) by 10% from 102 (2) to 92 (2) mm Hg (mean fall 10 mm Hg; 95% confidence interval 7 to 13 mm Hg). These changes were not explained by changes in body composition. Peak exercise left ventricular end diastolic volume (n = 16) increased with training; as a result of this and an increased exercise left ventricular ejection fraction peak exercise cardiac output increased from 19.9 (1.2) to 23.1 (3.0) l/min (mean rise 3.2 l/min; 95% confidence interval 1.5 to 5.0 l/min). Maximum oxygen consumption increased from 33.9 (1.6) to 39.0 (1.3) ml/kg/min (mean rise 5.0 ml/kg/min; 95% confidence interval 1.8 to 8.2 ml/kg/min). This study showed favourable effects on coronary risk factors and cardiac function and supports the place of regular exercise in coronary prevention programmes.     

Thermoregulation in rats during early postnatal maturation: importance of nitric oxide

Experiments were carried out to determine the role of nitric oxide in mediating autonomic and behavioral thermoregulatory control in rat pups on postnatal days 1-2, 5-6, and 10-11. For an experiment, each pup received a subcutaneous injection of vehicle, NG-nitro-D-arginine methyl ester (D-NAME; 100 mg/kg), or NG-nitro-L-arginine methyl ester (L-NAME; 100 mg/kg) before being placed in a metabolic chamber or in a thermocline with a linear temperature gradient of 23 to 43 degrees C. In the metabolic chamber, oxygen consumption and core temperature were measured as ambient temperature was decreased from 40 to 15 degrees C over a 60-min period. Decreasing ambient temperature elicited an increase in oxygen consumption in all age groups that received vehicle or d-NAME. The lower critical temperature and peak oxygen consumption upon exposure to cold after vehicle were 41 +/- 10 ml x kg(-1) x min(-1) at 30 degrees C, 43 +/- 12 ml x kg(-1) x min(-1) at 28 degrees C, and 55 +/- 11 ml x kg(-1) x min(-1) at 25 degrees C in the 1- to 2-, 5- to 6-, and 10- to 11-day-old pups, respectively. Administration of L-NAME abolished the oxygen consumption response to cold in the 1- to 2- and 5- to 6-day-old pups and significantly attenuated the oxygen consumption response to cold in the 10- to 11-day-old pups. Selected ambient temperature in the thermocline was not significantly affected by prior administration of D-NAME or L-NAME compared with vehicle. Thus our data provide evidence that the nitric oxide system plays a role in mediating autonomic but not behavioral thermoregulatory control in rat pups during early postnatal maturation.     

Age-related thermoregulatory differences during core cooling in humans

The current study assessed sympathetic neuronal and vasomotor responses, total body oxygen consumption, and sensory thermal perception to identify thermoregulatory differences in younger and older human subjects during core cooling. Cold fluid (40 ml/kg, 4 degrees C) was given intravenously over 30 min to decrease core temperature (Tc) in eight younger (age 18-23) and eight older (age 55-71) individuals. Compared with younger subjects, the older subjects had significantly lower Tc thresholds for vasoconstriction (35.5 +/- 0.3 vs. 36.2 +/- 0.2 degrees C, P = 0.03), heat production (35.2 +/- 0.4 vs. 35.9 +/- 0.1 degrees C, P = 0.04), and plasma norepinephrine (NE) responses (35.0 vs. 36.0 degrees C, P < 0.05). Despite a lower Tc nadir during cooling, the maximum intensities of the vasoconstriction (P = 0.03) and heat production (P = 0.006) responses were less in the older compared with the younger subjects, whereas subjective thermal comfort scores were similar. Plasma NE concentrations increased fourfold in the younger but only twofold in the older subjects at maximal Tc cooling. The vasomotor response for a given change in plasma NE concentration was decreased in the older group (P = 0.01). In summary, aging is associated with 1) a decreased Tc threshold and maximum response intensity for vasoconstriction, total body oxygen consumption, and NE release, 2) decreased vasomotor responsiveness to NE, and 3) decreased subjective sensory thermal perception.     

Depth equilibration of a shallow-water cichlid fish

The cichlid Melanochromis exasperatus has a natural distribution which is restricted to a single island in Lake Malawi, Africa. Diving observations indicated that it does not occur below 4.5 m depth. Measurements of depth equilibration in a pressure tank showed that males can equilibrate to a depth of 25 m and females to 18 m. Mean maximum sustained rate of depth equilibration was 2 m day⁻¹. M. exasperatus survived a pressure decrease of 40% every 12 h from the maximum equilibration depth to the surface. The fish swim actively during the day but rest on the bottom at night when they are equilibrated to a depth 1 m deeper than ambient. Reduced activity at night is reflected in a drop in oxygen consumption to nearly half of the daytime active value.     

Oxidation of combined ingestion of glucose and fructose during exercise.

The purpose of the present study was to examine whether combined ingestion of a large amount of fructose and glucose during cycling exercise would lead to exogenous carbohydrate oxidation rates >1 g/min. Eight trained cyclists (maximal O(2) consumption: 62 +/- 3 ml x kg(-1) x min(-1)) performed four exercise trials in random order. Each trial consisted of 120 min of cycling at 50% maximum power output (63 +/- 2% maximal O(2) consumption), while subjects received a solution providing either 1.2 g/min of glucose (Med-Glu), 1.8 g/min of glucose (High-Glu), 0.6 g/min of fructose + 1.2 g/min of glucose (Fruc+Glu), or water. The ingested fructose was labeled with [U-(13)C]fructose, and the ingested glucose was labeled with [U-(14)C]glucose. Peak exogenous carbohydrate oxidation rates were approximately 55% higher (P < 0.001) in Fruc+Glu (1.26 +/- 0.07 g/min) compared with Med-Glu and High-Glu (0.80 +/- 0.04 and 0.83 +/- 0.05 g/min, respectively). Furthermore, the average exogenous carbohydrate oxidation rates over the 60- to 120-min exercise period were higher (P < 0.001) in Fruc+Glu compared with Med-Glu and High-Glu (1.16 +/- 0.06, 0.75 +/- 0.04, and 0.75 +/- 0.04 g/min, respectively). There was a trend toward a lower endogenous carbohydrate oxidation in Fruc+Glu compared with the other two carbohydrate trials, but this failed to reach statistical significance (P = 0.075). The present results demonstrate that, when fructose and glucose are ingested simultaneously at high rates during cycling exercise, exogenous carbohydrate oxidation rates can reach peak values of approximately 1.3 g/min.     

Antifertility effect of busulfan and DL-6-(N-2-pipecolinomethyl)-5-hydroxy-indane maleate (PMHI) in coyotes (Canis Latrans )

Antifertility effects of busulfan were evaluated using adult coyotes. In addition, antifertility effects of PMHI were evaluated in adult males. Adult males and females were alloted randomly to the following treatments: (1) untreated control, (2) a single oral dose of 3 mg busulfan/kg of body weight (BW) or (3) two oral doses of 3 mg busulfan/kg BW given nine days apart. The untreated males were used as controls in both experiments. Additional male coyotes were allotted randomly to PMHI treatments as follows: (1) a single oral dose of 2 mg PMHI/kg BW, or (2) two oral doses of 1 mg PMHI/kg BW given seven days apart. Blood samples were taken from females and serum analyzed for progesterone by radioimmunoassay. Males were hemicastrated (left testicle) 30 days after onset of treatment. The right testicle was removed 30 days later. Testes and epididymides were fixed in 10% buffered formalin and prepared for histologic examination. For females developing corpus luteum (CL), the maximum peak progesterone concentration for those given two doses of busulfan was less (P<0.05) than that for untreated controls and single-dose females (16.9, 22.4 and 26.3 ng/ml, respectively). The double treatment of busulfan prevented more females (4 of 10) from developing CL (P<0.08) than controls (0 of 7) or single-dose females (1 of 9). None of the busulfan-treated male coyotes had histologic evidence of spermatogenesis 60 days after the onset of treatment. The oral dose or doses of PMHI did not result in complete degeneration of seminiferous tubules. Busulfan given orally did not cause any adverse reactions, but orally administered PMHI often induced vomiting within 18 min after treatment. We conclude that busulfan is capable of affecting male and female reproductive parameters, but PMHI appears to have little effect on spermatogenesis in coyotes when given orally in a single- or a double-dose.     

Metabolic equivalents during scooter exercise

The purpose of this study was to determine the metabolic equivalents (METs) for scooter exercise (riding a scooter, scootering) and to examine the energy expenditure and the heart rate response, so that the results can be used in health promotion activities. Eighteen young adults (10 males and 8 females) participated in scootering on a treadmill at three different speeds for six minutes each. Before, during, and after the exercise, pulmonary ventilation, oxygen uptake (VO(2)), carbon dioxide product, respiratory exchange ratio (R), and heart rate (HR) were measured. These measurements kept steady states from the 3rd to 6th minute of each different speed session. The MET values acquired during scootering at 80 m.min(-1), 110 m.min(-1), and 140 m.min(-1) were 3.9, 4.3, and 5.0, respectively. Calculated using VO(2) (ml.kg(-1).min(-1))x[4.0+R], the energy consumption for scootering at each speed was 67.0+/-10.6, 73.3+/-10.2, and 84.8+/-7.9 cal.kg(-1).min(-1), respectively. The regression equation between scootering speed (X, m.min(-1)) and VO(2) (Y, ml.kg(-1).min(-1)) is Y=0.062X+8.655, and the regression equation between HR (X, beats.min(-1)) and VO(2)reserve (Y, %) is Y=0.458X-11.264. These equations can be applied to both females and males. Thus, scootering at 80 to 140 m.min(-1) might not be sufficient to improve the cardiorespiratory fitness of young male adults similar to the participants, but it may contribute many healthy benefits to most female adults and even male adults, and improve their health and fitness at the faster speeds.