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Biomedical subjects

R Favier

Publications and source records attributed to R Favier.

84 records · Page 5Linked to original sources
PubMed1983

Catecholamines and metabolic responses to submaximal exercise in untrained men and women.

The influence of exercise on blood borne substrates in relation to plasma catecholamine (CA) levels has been studied in untrained subjects (eight men and eight women). Subjects pedalled a bicycle ergometer for 20 min at a workload approximating to 80% maximal aerobic power. During exercise women reacted similarly to men except that their weight loss and hematocrit were significantly lower. At the end of the bicycling test, plasma dopamine (DA), norepinephrine (NE) and epinephrine (E) concentrations increased similarly in both groups. There was no significant difference in blood energy substrates between men and women except that the plasma free fatty acid (FFA) level was significantly higher in the female. When fitness levels were similar, the previously reported sex-related difference in response to exercise seemed to disappear. The lack of correlation between blood borne substrates variations and CA changes raised the question whether other hormonal factors combined with CA could play a role in the mobilization of energy substrates during exercise.

Adult↗
PubMed1983

Ventilatory transients during exercise: peripheral or central control?

The fast component of the ventilatory changes that occur at the transition phases of exercise was studied in awake dogs trained to run on a treadmill. Two questions were examined: firstly, is the fast ventilatory component modified by changes in venous return to the lungs, such as those consecutive either to increased work loads or to beta adrenergic blockade?, and secondly, is this component altered by central ventilatory depressants? The results showed that at the onset of exercise, there is no correlation between the instantaneous increment in ventilation and the intensity of exercise, but at the end of the treadmill run, the fall in ventilation is closely linked to the power of the work performed. Ventilatory transients observed either at the start or at the end of exercise remain unaffected by administration of a beta-adrenergic blocking agent. But central depressant effects on ventilation caused by narcotic analgesics or hypnotic drugs altered the breathing pattern of the fast component of exercise-induced ventilatory changes. It is concluded that the instantaneous changes in ventilation occurring at the transition phases of exercise are controlled by mechanoreceptor mechanisms, but cerebral control is superimposed on the reflex control in regulating both tidal volume and breathing rate.

Animals↗
PubMed1982

Effects of chronic lung denervation on breathing pattern and respiratory gas exchanges during hypoxia, hypercapnia and exercise.

The influence of vagal fibres from the lung on ventilatory responses to hypercapnia, hypoxia and exercise was studied in two intact dogs (C) and two chronically lung denervated dogs (C.L.D.). In intact dogs, inspiration duration did not change as tidal volume increased in response to increased chemical drives. Chronic lung denervation did not affect the hypercapnia- or hypoxia-induced elevations in V, despite significant changes in breathing pattern. During exercise, oxygen consumption was similar for C and C.L.D. animals. V for a given oxygen uptake was the same in C and C.L.D. dogs, but VT was higher in C.L.D. animals at all levels of exercise. It is concluded that vagal fibres from the lung play a role in determining the breathing pattern, but are not required for a normal ventilatory response to hypercapnia, hypoxia and exercise. Interaction between vagal sensory input and specific structures sensitive to chemical or physical stimuli is discussed.

Animals↗
PubMed1982

[Maximal oxygen uptake in French children in relation to age, sex and physical training].

1. Maximal oxygen uptake (VO2 max) was determined in 451 boys and girls ranging from 11 to 16 years and divided in two groups. Group I (n = 287) was considered as an untrained reference group. Group II (n = 174) was regularly trained. This group concerned school-children affiliated to a swimming club and trained 5 to 10 h per week. Body growth is nearly the same in the two groups until puberty but, at 15-16 years in the boys, 14-16 years in the girls, height and weight are higher in group II. 2. In group I, between 11 and 16 years, VO2 max increases by 50% in boys against only 25% in girls. For the same age, VO2 max remained smaller in girls, even before puberty although there is no difference in body growth. At 11 years, specific VO2 max averaged 47 ml . min-1 . kg-1 in boys and 40 ml . min-1 . kg-1 in girls and decreases with age only in sedentary girls down to 37 ml . min-1 . kg-1. From the results presented here it appears that maximal oxygen uptake in the average french schoolchild is similar to those of subjects from different countries with same cultural and socio-economical level. 3. In group II, VO2 max is similar in both sexes at 11-12 years old, and then up to 16 years of age increases more rapidly in boys (+100%) than in girls (+50%). Specific VO2 max ranges between 57 and 62 m. min-1 . kg-1 in boy swimmers and averages 53 ml . min-1 . kg-1 in girl swimmers. The influence of physical training on aptitude development is discussed and compared with previously published data.

Adolescent↗
PubMed1981

Carotid chemoreceptor function in ventilatory and circulatory O2 convection of exercising dogs at low and high altitude.

Awake dogs were studied before (control) and after chronic bilateral carotid denervation (denervated) at rest and running for 3 min on a treadmill at 8 km . h-1 and at various grades, in an altitude chamber operated either at 140 m or at 4000 m for 3 h. Steady-state pulmonary ventilation (Vg) and breathing pattern (VT, fR), oxygen consumption (MO2), O2 concentrations (C) and pressures (P) in the arterial (a) and mixed venous blood (v), hematocrit (Ht) and acid-base status in arterial blood, and heart frequency (fH) were measured. From these data cardiac output (Vb) and stroke volume (Vs), ventilatory and circulatory requirements (Vg/Mo2, Vb/MO2), extraction of O2 from inspired gas (EairO2) and blood (EbO2), and capacitance coefficient of blood for oxygen (beta bO2) were calculated. Ventilatory responses to transient O2-inhalation were also studied and the aortic (AP) and pulmonary (PP) blood pressures measured in resting conditions. 1. After chronic carotid denervation the hypoxic chemoreflex drive of ventilation was reduced by about half, maximal MO2 remained unaffected at 140 m, but at 4000 m decreased 50% compared to 30% in controls. 2. In all experimental conditions, Vg/MO2, PaO2 and CaO2 were less in denervated animals than in controls, and EairO2, PaCO2 and H+ ion concentration were higher. 3. At 140 m, circulatory O2 convective transport was identical in the two groups of dogs. At 4000 m, beta bO2 increased similarly in both groups, but Vb and Vb/MO2 were higher in denervated dogs than in controls, in relation with reduced CaO2-CVO2 difference which contributed to restore PVO2 towards higher values. 4. At 140 m, mean resting AP and PP were similar in both groups of dogs. At 4000 m, AP increased not significantly in controls, and decreased in denervated animals; PP increased in controls, but not in denervated dogs. It is concluded that integrity of the arterial chemoreceptor drive is essential in determining the eupneic level of ventilation and normal acid-base status of the blood in both resting and exercising dogs, at low and at high altitude, and in reducing the O2 circulatory requirement at high altitude. At 4000 m, the lack of carotid chemosensitivity is accompanied by severe hypoxemia, in association with hypercapnia and acidosis, and by increased cardiac blood flow, most presumably due to decreased peripheral resistance and increased venous return; despite these compensatory changes in circulatory O2 convective transport, denervated animals reach a maximum O2 uptake at lower work load than controls.

Adaptation, Physiological↗
PubMed1979

[Adrenergic response to intense muscular activity in sedentary subjects as a function of emotivity and training].

Seven male sedentary human subjects were studied during intense muscular work (80% of maximal oxygen uptake) performed either for 15 min or until exhaustion (mean duration: 47 +/- 2 min). Plasma catecholamines were estimated before and after the experiment by means of an original fluorimetric assay. Epinephrine or norepinephrine were individually isolated from plasma and assayed in single extracts by a highly sensitive fluorimetric method. Epinephrine and norepinephrine levels as low as 15 ng per liter were detectable by this procedure in human plasma. The adrenergic pattern was found to be greatly different from one subject to another and related to emotivity: the effect of this factor was revealed by the predominance of epinephrine in plasma at rest or under exercise (ratio NA/A less than 1). In nonemotive subjects (ratio NA/A greater than 1 at rest) plasma epinephrine and norepinephrine increased progressively during exercise. Increments after exercise were higher for norepinephrine changes; however, the fact that epinephrine concentrations correlated significantly with norepinephrine suggests a simulataneous and coordinated stimulation of adrenal glands and orthosympathetic nervous system. In emotive subjects (ratio NA/A less than 1 at rest) the apprehension of muscular work promoted a difference in catecholamine responses: norepinephrine release was not affected by subject's anxiety, while epinephrine secretion, already elevated before the test, reached a high degree of magnitude in the first minutes of muscular work, remaining nearly constant until exhaustion. Physical training of nonemotive subjects, during 2 months with two intense exercises by a week, reduced strongly norepinephrine release after exhaustive muscular work. In the same conditions, the adrenal-medullary response was not significantly modified when compared with untrained subjects. Our results suggest that the adrenergic behaviour during exercise is a function of effort intensity to be supplied; catecholamines seem to be important factors in regulating body homeostasy during muscular work in man. In addition, emotive subjects exhibit amplified adrenal-medullary response, which may be related to psychological stimuli.

Anxiety↗
PubMed1979

[Chemoreflexive drive of ventilation and noradrenaline stimulus in man].

O2 chemoreflex drive of ventilation was studied before and after an intravenous infusion of L-norepinephrine (9 microgram/min), inducing a plasmatic hormone concentration similar to that obtained during submaximal exercise. The ventilation increasing rapidly at the beginning of the infusion was stabilized after 30 min : the ventilation was two times the reference value. The O2 chemoreflex drive of ventilation increased during norepinephrine infusion. When man was transiently switched from hypoxia to pure O2 (O2 test) the maximal fall of ventilation was two times the reference response. This increase in the chemoreflex drive, although the physico-chemical blood state was unchanged, may be explained by a norepinephrine chemoreceptor sensitization. Such a mechanism could partly explain the increase of O2 chemoreflex drive observed during muscular exercise.

Adult↗
PubMed1978

[O2 chemoreflex drive of ventilation in the awake rat (author's transl)].

Resting ventilation, arterial pH and gas tensions in the arterial blood and ventilatory responses to transient O2 inhalation were studied by plethysmography, under normoxic and hypoxic (FIO2 = 0.12) conditions, in the awake rat before and after chronic bilateral denervation of the carotid bodies. 1. In the intact rat, the O2-chemoreflex drive of ventilation controlled about 50% of the normoxic minute volume, and 85% in hypoxia. 2. Chronic bilateral carotid body denervation reduced the chemoreflex drive to half, and was accompanied by a hypoventilation with arterial hypercapnia. 3. In acute hypoxia hyperventilation was reduced in carotid-body denervated animals, and was accompanied by a light respiratory insufficiency. These results suggest that the rat has a powerful arterial chemoreflex drive of breathing which is essential in determining the eupneic level of ventilation in acute hypoxia.

Acid-Base Equilibrium↗
PubMedDate not supplied

Mitochondrial H2O2 production is reduced with acute and chronic eccentric exercise in rat skeletal muscle.

Oxidative stress with acute/chronic exercise has been so far examined using exercise involving a combination of concentric and eccentric contractions, but skeletal muscles are likely to be injured to a greater extent by pliometric contractions. In the present study, the effects of acute and chronic bouts of downhill running exercise on mitochondrial hydrogen peroxide (H2O2) generation (fluorimetric detection of a dimer with homovanillic acid in presence of horseradish peroxidase) and oxygen consumption in conjunction with antioxidant enzymes activity were examined. The results show that acute eccentric exercise was accompanied by a significantly reduced mitochondrial H2O2 production that is likely due to a decrease in complex I of the electron transport chain (ETC). On the other hand, eccentric training leads to positive adaptations, reflected by a higher citrate synthase activity and decreased mitochondrial H2O2 production. The decrease in mitochondrial H2O2 cannot be attributed to alterations in antioxidant capacities but rather to changes in mitochondrial membrane composition characterized by an increased polyunsaturated to saturated fatty acids ratio, and decreased contents in arachidonic acid and plasmalogens. These results suggest that changes in mitochondrial membrane properties with eccentric training can affect H2O2 production by muscle mitochondria. It is hypothesized that these changes resulted in a mild uncoupling sufficient to reduce electron back flow through complex I of the ETC, the major generator of reactive oxygen species by skeletal muscle mitochondria.

Animals↗