Hepatic lipase and the clearing reaction: studies in euthyroid and hypothyroid subjects

Eight patients with primary hypothyroidism were compared to eleven euthyroid subjects with regard to the effects of a single i.v. dose of heparin on plasma lipoprotein concentrations (the "clearing reaction"). The hypothyroid patients were moderately hypercholesterolemic but had normal plasma triglyceride levels. Maximal activities of hepatic lipase (HL) and lipoprotein lipase (LPL) were lower in the hypothyroid than in the normal subjects. The hypothyroid patients demonstrated a significant decrease in total plasma cholesterol levels after heparin injection (from 8.36 +/- 0.70 mmol/l to 7.55 +/- 0.62 mmol/l, P less than 0.02). The maximal activity of HL after heparin was significantly correlated to the decrease in plasma cholesterol levels (P less than 0.05) and in LDL-cholesterol levels (P less than 0.01). The euthyroid subjects demonstrated a smaller decrease in total plasma cholesterol concentrations (from 5.53 +/- 0.31 to 5.08 +/- 0.28 mmol/l, P less than 0.05). In this group, the fall in cholesterol levels was not correlated to maximal HL activity. The reduction in plasma triglyceride levels after heparin was similar and significant (P less than 0.01) in both groups. These data support the view that decreased activity of HL contributes to the dyslipoproteinemia seen in hypothyroidism. They are also in accordance with the notion that HL is involved in the elimination of cholesterol from plasma.     

Effect of age on changes in flow rates and airway conductance after a deep breath

The effects of aging on changes in maximal expiratory flow rates and specific airway conductance after a deep breath were evaluated in 64 normal subjects. Flow rates (Vp) on partial expiratory flow-volume curves (PEFV), initiated from 60-70% of the vital capacity (VC), were compared with those (Vc) on maximal flow-volume curves (MEFV), initiated from total lung capacity (TLC), at a lung volume corresponding to 25% of VC on the MEFV curves. Specific airway conductance was measured before (sGaw) and after a deep inspiration (sGawDI). Bronchodilation after inspiration to TLC was inferred by Vp/Vc less than 1 and sGaw/sGawDI less than 1. The mean Vp was less than Vc. However, the ratio Vp/Vc increased significantly with age (r = 0.75, P less than 0.001). Specific conductance also increased after a deep inspiration (sGaw less than sGawDI). The ratio sGaw/sGawDIj increased slightly but significantly with age (r = 0.28, P less than 0.02). Measurement of lung elastic recoil pressures before and after a deep breath in a subgroup of patients (n = 14) suggested that the age-related increase in Vp/Vc was secondary to a decrement in the ability of a deep breath to decrease the upstream airway resistance. These findings suggest that even though changes in airway size after a deep breath as measured by sGaw/sGawDI have minimal age dependence, aging diminishes expiratory flow rates of MEFV curves relative to PEFV curves because of a decrease in the ability of a deep breath to increase the size of the peripheral airways.     

Running endurance in 27-h-fasted humans

Nine male marathon runners were exercised to exhaustion to determine the effects of a 27-h fast on endurance performance. Each subject completed two exercise tests at the same treadmill speed (set at 70% maximal O2 uptake), one following a 27-h fast and one 3 h after a preexercise meal, in random order. Fasting caused a 44.7 +/- 5.8% (SE) decrease in endurance performance (P less than 0.01). Blood, muscle, psychological, and ventilatory data were examined to determine the cause of the decreased performance. Fasting caused significant increases in O2 uptake (9.3 +/- 2.0%), heart rate (8.4 +/- 2.4%), and rating of perceived exertion, ventilation, and psychological fatigue, evident within the first 60 min of exercise. There were no differences in plasma glucose or epinephrine levels. Muscle glycogen degraded at the same rate (0.482 +/- 0.146 vs. 0.470 +/- 0.281 mumol.g-1.min-1 in the nonfasted and fasted tests, respectively) despite lower respiratory exchange ratio and elevated free fatty acid levels, which may partially explain the elevated O2 uptake. Lactate, insulin, and norepinephrine were all increased in the fasted test (P less than 0.05). The increase in norepinephrine (r = 0.79, P less than 0.01), the diameter of type I muscle fibers (r = 0.70, P less than 0.05), and ending insulin levels (r = -0.88, P less than 0.01) were correlated with endurance time in the fasted state. Fatigue in endurance running for 27-h fasted humans appears to be related to a combination of physiological, psychological, metabolic, and hormonal changes.     

Influence of heat stress and acclimation on maximal aerobic power

Thirteen male volunteers performed cycle ergometer maximal oxygen uptake (VO2max tests) in moderate (21 degrees C, 30% rh) and hot (49 degrees C, 20% rh) environments, before and after a 9-day heat acclimation program. This program resulted in significantly decreased (P less than 0.01) final heart rate (24 bt X min-1) and rectal temperature (0.4 degrees C) from the first to last day of acclimation. The VO2max was lower (P less than 0.01) in the hot environment relative to the moderate environment both before (8%) and after (7%) acclimation with no significant difference (P greater than 0.05) shown for maximal power output (PO max, watts) between environments either before or after acclimation. The VO2max was higher (P less than 0.01) by 4% after acclimation in both environments. Also, PO max was higher (P less than 0.05) after acclimation in both the moderate (4%) and hot (2%) environments. The reduction in VO2max in the hot compared to moderate environment was not related to the difference in core temperature at VO2max between moderate and hot trials, nor was it strongly related with aerobic fitness level. These findings indicate that heat stress, per se, reduced the VO2max. Further, the reduction in VO2max due to heat was not affect be state of heat acclimation, the degree of elevation in core temperature, or level of aerobic fitness.     

Relationships between maximal muscle oxidative capacity and blood lactate removal after supramaximal exercise and fatigue indexes in humans.

The present study investigated whether blood lactate removal after supramaximal exercise and fatigue indexes measured during continuous and intermittent supramaximal exercises are related to the maximal muscle oxidative capacity in humans with different training status. Lactate recovery curves were obtained after a 1-min all-out exercise. A biexponential time function was then used to determine the velocity constant of the slow phase (gamma(2)), which denoted the blood lactate removal ability. Fatigue indexes were calculated during all-out (FI(AO)) and repeated 10-s cycling sprints (FI(Sprint)). Biopsies were taken from the vastus lateralis muscle, and maximal ADP-stimulated mitochondrial respiration (V(max)) was evaluated in an oxygraph cell on saponin-permeabilized muscle fibers with pyruvate + malate and glutamate + malate as substrates. Significant relationships were found between gamma(2) and pyruvate + malate V(max) (r = 0.60, P < 0.05), gamma(2) and glutamate + malate V(max) (r = 0.66, P < 0.01), and gamma(2) and citrate synthase activity (r = 0.76, P < 0.01). In addition, gamma(2), glutamate + malate V(max), and pyruvate + malate V(max) were related to FI(AO) (gamma(2) - FI(AO): r = 0.85; P < 0.01; glutamate + malate V(max) - FI(AO): r = 0.70, P < 0.01; and pyruvate + malate V(max) - FI(AO): r = 0.63, P < 0.01) and FI(Sprint) (gamma(2) - FI(Sprint): r = 0.74, P < 0.01; glutamate + malate V(max) - FI(Sprint): r = 0.64, P < 0.01; and pyruvate + malate V(max) - FI(Sprint): r = 0.46, P < 0.01). In conclusion, these results suggested that the maximal muscle oxidative capacity was related to blood lactate removal ability after a 1-min all-out test. Moreover, maximal muscle oxidative capacity and blood lactate removal ability were associated with the delay in the fatigue observed during continuous and intermittent supramaximal exercises in well-trained subjects.     

Age-related augmentation of plasma catecholamines during dynamic exercise in healthy males

Although plasma norepinephrine (NE) increases with age in response to a variety of submaximal adrenergic stimuli, the effect of age on plasma catecholamine levels during maximal aerobic effort and during submaximal work at a fixed percent of peak O2 consumption (VO2) is unknown. We therefore measured NE, epinephrine (E), and VO2 at rest and during graded maximal treadmill exercise in 24 healthy male volunteers (ages 22-77 yr) from the Baltimore Longitudinal Study of Aging who were rigorously screened to exclude the presence of cardiovascular disease. At rest neither heart rate (HR) nor VO2 were age related. Resting NE (pg/ml) was not age related, but resting E (pg/ml) was higher in male subjects 68-77 yr old (group III) than in those aged 22-37 (group I) or 44-55 yr (group II), P less than 0.01. Maximal HR (beats/min) showed a strong inverse relationship to age (203.5 - 0.65 age, r = -0.80, P less than 0.001). Peak VO2 in milliliters per kilogram total body weight per minute decreased with age (47.7 - 0.23 age, r = -0.71, P less than 0.001). At maximal effort both NE (P less than 0.01) and E (P less than 0.05) were higher in group III than in either of the younger groups. At submaximal work levels NE and E also increased with age, and when normalized for relative effort at loads between 45 and 80% of peak VO2 both NE and E were higher in the group III male subjects, although statistical significance was reached for NE (P less than 0.01) but not for E (P = 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)     

Muscle cross-sectional area, force production and relaxation characteristics in women at different ages

Thirty women, divided among three different age groups, i.e. 30 years (range 26-35; n = 10), 50 years (range 46-55; n = 10) and 70 years (range 66-75; n = 10) volunteered as subjects for examination of the characteristics of the muscle cross-sectional area (CSA), maximal voluntary isometric force, isometric force-time and relaxation-time of their leg extensor muscles. The CSA of the quadriceps femoris muscle in the youngest age group was slightly larger (NS) than in the middle-aged group and much larger (P less than 0.01) than in the oldest age group whose CSA was markedly smaller (P less than 0.01) than the middle-aged group. Maximal force in the youngest group was slightly greater (NS) than in the middle-aged group and much greater (P less than 0.01) than in the oldest group whose values were markedly smaller (P less than 0.05) than the middle-aged group. The individual values in CSA correlated with maximal force both in the total subject sample (r = 0.82; P less than 0.001) and in the three age groups separately (r = 0.72; P less than 0.01; r = 0.86; P less than 0.01 and r = 0.67; P less than 0.05, respectively). When the force values were related to the CSA of the muscle, the mean values of 45.4 N.cm-2, SD 5.6, 47.6 N.cm-2, SD 5.0 and 46.8 N.cm-2, SD 7.0 for the three groups did not differ significantly from each other.(ABSTRACT TRUNCATED AT 250 WORDS)     

Met-enkephalin, β-endorphin and cortisol responses to sub-maximal exercise after sleep disturbances

The present study compared the effects of partial sleep deprivation and the effects of an intake of a hypnotic compound (zolpidem) prior to bedtime, on sleep and on hormonal and metabolic adaptations to subsequent exercise. Sleep deprivation consisted of a delayed bedtime and an early getting-up time. Eight young subjects, who slept well and were highly trained athletes, were enrolled in this study. Sleep was recorded polygraphically and the following afternoon exercise was performed on a cycle ergometer for 30 min at 75% of maximal oxygen consumption (VO2max) after a 10-min warm up. Met-enkephalin, beta-endorphin, cortisol, and lactate concentrations were measured at rest and during exercise. The data obtained after experimental sleep, with and without medication were compared with those obtained in the reference condition with normal sleep. Both types of sleep reduction decreased the total sleep time, stage 2 sleep, and rapid eye movement sleep, whereas zolpidem administration did not modify either the duration of sleep or the sleep stages. After the reference night, plasma met-enkephalin did not show any significant change at the end of the submaximal exercise, whereas beta-endorphin, cortisol, and lactic acid concentrations increased significantly in all subjects. The changes in concentration in beta-endorphin were significantly related to the changes in cortisol (r = 0.78; P less than 0.01) and to the changes in plasma lactic acid (r = 0.58; P less than 0.05). Cortisol concentrations were also related to lactic acid values (r = 0.94; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Glycogen depletion during prolonged exercise: influence of glucose, fructose, or placebo

We examined the influence of various carbohydrates of fuel homeostasis and glycogen utilization during prolonged exercise. Seventy-five grams of glucose, fructose, or placebo were given orally to eight healthy males 45 min before ergometer exercise performed for 2 h at 55% of maximal aerobic power (VO2max). After glucose ingestion, the rises in plasma glucose (P less than 0.01) and insulin (P less than 0.001) were 2.4- and 5.8-fold greater than when fructose was consumed. After 30 min of exercise following glucose ingestion, the plasma glucose concentration had declined to a nadir of 3.9 +/- 0.3 mmol/l, and plasma insulin had returned to basal levels. The fall in plasma glucose was closely related to the preexercise glucose (r = 0.98, P less than 0.001) and insulin (r = 0.66, P less than 0.05) levels. The rate of endogenous glucose production and utilization rose similarly by 2.8-fold during exercise in fructose group and were 10-15% higher than in placebo group (P less than 0.05). Serum free fatty acid levels were 1.5- to 2-fold higher (P less than 0.01) after placebo than carbohydrate ingestion. Muscle glycogen concentration in the quadriceps femoris fell in all three groups by 60-65% (P less than 0.001) during exercise. These data indicate that fructose ingestion, though causing smaller perturbations in plasma glucose, insulin, and gastrointestinal polypeptide (GIP) levels than glucose ingestion, was no more effective than glucose or placebo in sparing glycogen during a long-term exercise.     

Effect of mild-to-moderate airflow limitation on exercise capacity

To determine the effect of mild-to-moderate airflow limitation on exercise tolerance and end-expiratory lung volume (EELV), we studied 9 control subjects with normal pulmonary function [forced expired volume in 1 s (FEV1) 105% pred; % of forced vital capacity expired in 1 s (FEV1/FVC%) 81] and 12 patients with mild-to-moderate airflow limitation (FEV1 72% pred; FEV1/FVC % 58) during progressive cycle ergometry. Maximal exercise capacity was reduced in patients [69% of pred maximal O2 uptake (VO2max)] compared with controls (104% pred VO2max, P less than 0.01); however, maximal expired minute ventilation-to-maximum voluntary ventilation ratio and maximal heart rate were not significantly different between controls and patients. Overall, there was a close relationship between VO2max and FEV1 (r2 = 0.62). Resting EELV was similar between controls and patients [53% of total lung capacity (TLC)], but at maximal exercise the controls decreased EELV to 45% of TLC (P less than 0.01), whereas the patients increased EELV to 58% of TLC (P less than 0.05). Overall, EELV was significantly correlated to both VO2max (r = -0.71, P less than 0.001) and FEV1 (r = -0.68, P less than 0.001). This relationship suggests a ventilatory influence on exercise capacity; however, the increased EELV and associated pleural pressures could influence cardiovascular function during exercise. We suggest that the increase in EELV should be considered a response reflective of the effect of airflow limitation on the ventilatory response to exercise.     

Peak blood ammonia and lactate after submaximal, maximal and supramaximal exercise in sprinters and long-distance runners

The purpose of this study was to elucidate the difference in peak blood ammonia concentration between sprinters and long-distance runners in submaximal, maximal and supramaximal exercise. Five sprinters and six long-distance runners performed cycle ergometer exercise at 50% maximal, 75% maximal, maximal and supramaximal heart rates. Blood ammonia and lactate were measured at 2.5, 5, 7.5, 10 and 12.5 min after each exercise. Peak blood ammonia concentration at an exercise intensity producing 50% maximal heart rate was found to be significantly higher compared to the basal level in sprinters (P less than 0.01) and in long-distance runners (P less than 0.01). The peak blood ammonia concentration of sprinters was greater in supra-maximal exercise than in maximal exercise (P less than 0.05), while there was no significant difference in long-distance runners. The peak blood ammonia content after supramaximal exercise was higher in sprinters compared with long-distance runners (P less than 0.01). There was a significant relationship between peak blood ammonia and lactate after exercise in sprinters and in long-distance runners. These results suggest that peak blood ammonia concentration after supramaximal exercise may be increased by the recruitment of fast-twitch muscle fibres and/or by anaerobic training, and that the processes of blood ammonia and lactate production during exercise may be strongly linked in sprinters and long-distance runners.     

Energy cost of front-crawl swimming in women

The purpose of this study was to examine the relationship between the energy cost of swimming per unit distance (Cs) at different velocities (v) and performance level, body size and swimming technique in women. A total of 58 females swimmers were studied. Three performance levels (A, B, C) were determined, ranging from the slower (A) to the faster (B, C). At level C and at 1.1 m.s-1, Cs,1.1 was reduced by 7% when directly compared to level B. The Cs,1.1 was reduced by 10% when calculated per unit of height (h) and by 37% when calculated per unit of h and hydrostatic lift (HL). For the whole group of swimmers, the equation regression was Cs,1.1 = 0.27 h-2.38 HL - 7.5 (r = 0.53, P less than 0.01). To evaluate the specific influence of arm length two groups of long- and short-armed swimmers were selected among swimmers of similar h and performance. The Cs was significantly higher (P less than 0.05) by 12%, SD 2.2%, for short-armed than for long-armed swimmers. To evaluate the influence of different types of swimming technique, two other groups of similar performance and anthropometric characteristics were selected. The Cs was significantly higher (P less than 0.05) by 12%, SD 4.5% for swimmers using for preference their legs rather than their arms. The Cs of the sprinters was 15.7%, SD 2% higher than that of the long-distance swimmers. For all groups, Cs increased with v on average by 8% to 11% every 0.1 m.s-1. These findings showed that Cs variations of these women were close to those previously demonstrated for men. The Cs depends on performance level, body size, buoyancy, swimming technique and v.     

Serum hormones and physical performance capacity in young boy athletes during a 1-year training period

Serum hormones and physical performance capacity in boy athletes (AG; n = 19) were investigated during a 1-year training period (between the ages of 11.6 and 12.6 years). Six young untrained boys served as the control group (CG). The mean serum testosterone concentration increased significantly in AG (P less than 0.05) following the training period from 2.92 nmol.l-1, SD 1.04 to 5.81 nmol.l-1, SD 1.33. Significant differences were not observed in the cortisol, sex hormone binding globulin and growth hormone levels during the follow-up period. The AG clearly increased speed (P less than 0.001), speed-strength (P less than 0.01-P less than 0.001) and anaerobic capacity (P less than 0.001) whereas CG had only slight increases (NS) in physical performance capacity during a 1-year period. During the last 6-month training period significant positive correlations (r = 0.49-0.58; P less than 0.05-P less than 0.01) were observed in AG between the relative changes in testosterone, testosterone:cortisol ratio and growth hormone and the relative performance change in speed, maximal isometric force and endurance, respectively. At the end of the period significant positive correlations were observed in all subjects between the level of testosterone and speed-strength (r = 0.52-0.64; P less than 0.01-P less than 0.001) and anaerobic capacity (r = 0.49; P less than 0.05). It was concluded that an increase in anabolic activity with the synchronous training already has positive effects on trainability and physical performance capacity at an early stage in puberty.     

The electrocardiogram of the Beagle dog: reference values and effect of sex, genetic strain, body position and heart rate

The aim of the study was to establish a database for electrocardiographic parameters of Beagle dogs used for toxicological studies and to evaluate the influence of supplier, sex, heart rate (HR) and body position for electrocardiogram (ECG) recording on ECG parameters. Peripheral ECG leads were recorded from 934 female and 946 male dogs from Marshall Farms and 27 females and 30 males from Harlan, either standing on a table or restrained in a hammock. HR, RR, PQ and QT intervals, P and QRS duration and P-wave amplitude were measured. There were no major differences between sexes for ECG parameters. The axis of the heart was shifted to the left when the animals were restrained in a hammock compared to when they were standing on a table. The PQ interval was higher (about 9%) in Harlan than in Marshall dogs. HR was negatively correlated with QT (coefficient of linear correlation: r=-0.61 to -0.74), which emphasizes the need for a formula correcting QT interval for HR when interpreting changes in QT interval. HR was also negatively correlated with PQ intervals (r=-0.26 to -0.11), whereas a positive correlation was found between HR and the amplitude of the P wave (r=0.21-0.34). The level of the respiratory sinus arrhythmia (SA) was quantified by calculating the ratio of maximum to minimum RR interval measured over a 10 s period. This ratio was negatively correlated with HR (r =-0.49 to -0.33). Therefore, at high HRs, SA was less marked than at low HRs, but it did not completely disappear. Analysis of beat-to-beat variation indicated that QT and PQ intervals and the amplitude of P wave fluctuated over time and the degree of this variability was positively correlated with the level of SA. In conclusion, we have established reference values for the duration and/or amplitude of some ECG parameters both in terms of means and variability over the recording period, and we have evaluated the influence of body position, genetic strain and HR on the ECG parameters. These data can be used as baseline for the interpretation of the ECG of Beagle dogs.     

Relationships between force-time characteristics of the isometric midthigh pull and dynamic performance in professional rugby league players

There is considerable conflict within the literature regarding the relevance of isometric testing for the assessment of neuromuscular function within dynamic sports. The aim of this study was to determine the relationship between isometric measures of force development and dynamic performance. Thirty-nine professional rugby league players participated in this study. Forty-eight hours after trial familiarization, participants performed a maximal isometric midthigh pull, with ～120-130° bend at the knee, countermovement jump (CMJ), and a 10-m sprint. Force-time data were processed for peak force (PF), force at 100 milliseconds (F100ms), and peak rate of force development (PRFD). Analysis was carried out using Pearson's product moment correlation with significance set at p < 0.05. The PF was not related to dynamic performance; however, when expressed relative to body weight, it was significantly correlated with both 10-m time and CMJ height (r = -0.37 and 0.45, respectively, p < 0.05). The F100ms was inversely related to 10-m time (r = -0.54, p < 0.01); moreover, when expressed relative to body weight, it was significantly related to both 10-m time and CMJ height (r = -0.68 and 0.43, p < 0.01). In addition, significant correlations were found between PRFD and 10-m time (r = -0.66, p < 0.01) and CMJ height (r = 0.387, p < 0.01). In conclusion, this study provides evidence that measures of maximal strength and explosiveness from isometric force-time curves are related to jump and sprint acceleration performance in professional rugby league players.     

Evaluation of live trivalent vaccine of measles AIK-C strain, mumps Hoshino strain and rubella Takahashi strain, by virus-specific interferon-gamma production and antibody response

A trivalent measles-mumps-rubella live virus vaccine, containing measles AIK-C strain, mumps Hoshino strain, and rubella Takahashi strain, was evaluated in 229 children, aged 1 to 5 years. The vaccine induced a high seroconversion rate: 221 (98.7%) out of 224 subjects initially seronegative for measles virus, 167 (93.3%) out of 179 initially seronegative for mumps virus, and 212 (99.1%) out of 214 initially seronegative for rubella virus. It also induced a sufficient cellular immunity against each of the three viruses in over 90% of the subjects, as judged by virus-specific interferon-gamma (IFN-gamma) production. Virus-specific IFN-gamma production was observed 10 days after vaccination by stimulation with measles virus and rubella virus and 14 days after vaccination by stimulation with mumps virus. Mumps-virus-specific IFN-gamma production was observed in 7 out of 12 recipients without seroconversion for mumps virus. And measles-virus-specific IFN-gamma production was demonstrated in one out of three recipients without seroconversion for measles virus. A significant correlation was observed between the serum antibody and IFN-gamma production six weeks after vaccination for measles virus (r = 0.201, P less than 0.01) and for mumps virus (r = 0.174, P less than 0.05) but not for rubella virus (r = -0.045, P less than 0.05). The incidence of febrile reactions of greater than or equal to 37.5 C was quite low, 14.4%, and that of greater than or equal to 39 C occurred in only 1.3% of the recipients. These results suggested that the trivalent vaccine induced sufficient humoral and cellular immunity and yet resulted in no more untoward reaction than observed from the measles vaccine alone.     

Supplementation of postmenopausal women with fish oil does not increase overall oxidation of LDL ex vivo compared to dietary oils rich in oleate and linoleate

Although replacement of dietary saturated fat with monounsaturated and polyunsaturated fatty acids (MUFA and PUFA) has been advocated for the reduction of cardiovascular disease risk, diets high in PUFA could increase low density lipoprotein (LDL) susceptibility to oxidation, potentially contributing to the pathology of atherosclerosis. To investigate this possibility, 15 postmenopausal women in a blinded crossover trial consumed 15 g of sunflower oil (SU) providing 12.3 g/day of oleate, safflower oil (SA) providing 10.5 g/day of linoleate, and fish oil (FO) providing 2.0 g/day of eicosapentaenoate (EPA) and 1.4 g/day of docosahexaenoate (DHA). During CuSO(4)-mediated oxidation, LDL was depleted of alpha-tocopherol more rapidly after FO supplementation than after supplementation with SU (P = 0.0001) and SA (P = 0.05). In LDL phospholipid and cholesteryl ester fractions, loss of n-3 PUFA was greater and loss of n-6 PUFA less after FO supplementation than after SU and SA supplementation (P < 0.05 for all), but loss of total PUFA did not differ. The lag phase for phosphatidylcholine hydroperoxide (PCOOH) formation was shorter after FO supplementation than after supplementation with SU (P = 0.0001) and SA (P = 0.006), whereas the lag phase for cholesteryl linoleate hydroperoxide (CE18:2OOH) formation was shorter after FO supplementation than after SU (P = 0.03) but not SA. In contrast, maximal rates of PCOOH and CE18:2OOH formation were lower after FO supplementation than after SA (P = 0.02 and 0.0001, respectively) and maximal concentrations of PCOOH and CE18:2OOH were lower after FO supplementation than after SA (P = 0.03 and 0.0006, respectively). Taken together, our results suggest that FO supplementation does not increase the overall oxidation of LDL ex vivo, especially when compared with SA supplementation. Consequently, health benefits related to increased fish consumption may not be offset by increased LDL oxidative susceptibility.-- Higdon, J. V., S. H. Du, Y. S. Lee, T. Wu, and R. C. Wander. Supplementation of postmenopausal women with fish oil does not increase overall oxidation of LDL ex vivo compared to dietary oils rich in oleate and linoleate. J. Lipid Res. 2001. 42: 407--418.     

Exercise training prevents decline in stroke volume during exercise in young healthy subjects.

Stroke volume (SV) increases above the resting level during exercise and then declines at higher intensities of exercise in sedentary subjects. The purpose of this study was to determine whether an attenuation of the decline in SV at higher exercise intensities contributes to the increase in maximal cardiac output (Qmax) that occurs in response to endurance training. We studied six men and six women, 25 +/- 1 (SE) yr old, before and after 12 wk of endurance training (3 days/wk running for 40 min, 3 days/wk interval training). Cardiac output was measured at rest and during exercise at 50 and 100% of maximal O2 uptake (Vo2max) by the C2H2-rebreathing method. VO2max was increased by 19% (from 2.7 +/- 0.2 to 3.2 +/- 0.3 l/min, P less than 0.001) in response to the training program. Qmax was increased by 12% (from 18.1 +/- 1 to 20.2 +/- 1 l/min, P less than 0.01), SV at maximal exercise was increased by 16% (from 97 +/- 6 to 113 +/- 8 ml/beat, P less than 0.001) and maximal heart rate was decreased by 3% (from 185 +/- 2 to 180 +/- 2 beats/min, P less than 0.01) after training. The calculated arteriovenous O2 content difference at maximal exercise was increased by 7% (14.4 +/- 0.4 to 15.4 +/- 0.4 ml O2/100 ml blood) after training. Before training, SV at VO2max was 9% lower than during exercise at 50% VO2max (P less than 0.05). In contrast, after training, the decline in SV between 50 and 100% VO2max was only 2% (P = NS). Furthermore, SV was significantly higher (P less than 0.01) at 50% VO2max after training than it was before. Left ventricular hypertrophy was evident, as determined by two-dimensional echocardiography at the completion of training. The results indicate that in young healthy subjects the training-induced increase in Qmax is due in part to attenuation of the decrease in SV as exercise intensity is increased.     

Effect of aerobic training on forced expiratory airflow in exercising asthmatic humans

Pulmonary function after exercise was evaluated in 22 asthmatic subjects before and after a 36-session training sequence of aerobic exercise. Training did not change pulmonary function values, except for a small increase in maximal voluntary ventilation (P less than 0.02), which was attributed to respiratory muscle training. After aerobic training, both external work at a given heart rate and peak O2 consumption increased by 30 and 15%, respectively. At the same minute ventilation (VE), immediate postexercise forced expiratory airflow was higher after training (P less than 0.02), and reduction in forced expiratory airflow during the first 9 min postexercise was less after training (P less than 0.01). The posttraining airflow response to the pretraining work load was, as expected, less than the pretraining response (P less than 0.02). Although the difference in maximal-to-minimal airflow at the same VE was similar before and after training, the airflow increase accounted for 50% of the response after training compared with 16% of the pretraining response. Furthermore the strong negative correlation (P less than 0.01) between maximal and minimal airflow both pre- and posttraining indicates that exercise-induced bronchospasm (EIB) severity is, in part, determined by the degree of exercise-induced bronchodilation. We conclude that aerobic training significantly increases exercise-induced bronchodilation and diminishes EIB.     

Effects of focal cooling of medulla oblongata structures on quiet breathing in cats

Experiments were carried out on 16 anaesthetized, non-paralysed cats to determine the effects of unilateral, successive focal cooling of the nuclei of the dorsal and ventral respiratory groups (DRG, VRG) of the medulla oblongata on quiet breathing parameters. The results of cold block tests of the respiratory nuclei showed that: 1. Compared with the control state, cooling of the ventrolateral part of the nucleus solitarii (vl. NTS) and the rostral part of the nucleus retroambigualis (r. NRA) to 20 degrees C or 15 degrees C decreased the respiration rate (p less than 0.001), prolonged the inspiration time (p less than 0.01 and p less than 0.001 respectively) and the development of apneustic breathing. A decrease in the inspiratory pleural pressure values (p less than 0.01) was found after cooling the r. NRA region to 15 degrees C. In 45% of the cases of cooling of the vl. NTS and 66.7% of cooling of the r. NRA to 15 degrees C, an incidence of short inspiratory efforts was observed. 2. Focal cooling of the nucleus retrofacialis (nucl. RF) region to 20 degrees C always arrested rhythmic respiration. 3. The effects of unilateral focal cooling of the respiratory nuclei were always bilaterally symmetrical and, after discontinuing cooling, reversible. 4. The findings indicate that the inspiratory neurones of the r. NRA participate more in regulation of the intensity of inspiration than those of the vl. NTS, while the nucl. RF region may be a part of central regulatory mechanisms essential for the maintenance of rhythmic breathing in cats.