Epinephrine, norepinephrine, and dopamine during a 4-day head-down bed rest.

Head-down bed rest at an angle of 6 degrees was used as an experimental model to simulate the hemodynamic effects of microgravity, i.e., the shift of fluids from the lower to the upper part of the body. The sympathoadrenal activity during acute (from 0.5 to 10 h) and prolonged (4 days) head-down bed rest was assessed in eight healthy men (24 +/- 1 yr) by measuring epinephrine (E), norepinephrine (NE), dopamine (DA), and methoxylated metabolite levels in their plasma and urine. Catecholamine (CA) and methoxyamine levels were essentially unaltered at any time of bed rest. Maximal changes in plasma were on the second day (D2): NE, 547 +/- 84 vs. 384 +/- 55 pg/ml; DA, 192 +/- 32 vs. 141 +/- 16 pg/ml; NS. After 24 h of bed rest, heart rate decreased from 71 +/- 1 to 63 +/- 3/min (P less than 0.01). Daily dynamic leg exercise [50% maximum O2 uptake (VO2 max)] used as a countermeasure did not alter the pattern of plasma CA during bed rest but resulted in a higher urinary NE excretion during postexercise recovery (+45% on D2; P less than 0.05). The data indicate no evident relationship between sympathoadrenal function and stimulation of cardiopulmonary receptors or neuroendocrine changes induced by central hypervolemia during head-down bed rest.

[Occupational asthma and rhinitis: challenge tests and nasal hyperreactivity: current practice and future perspectives]. / Asthmes et rhinites professionnels: tests réalistes et hyper-réactivité nasale: pratique actuelle et perspectives d'avenir.

Nasal hypersensitivity is defined by an exaggerated response to certain specific stimuli such as a work-related agent, non-specific stimuli (irritant effect), or to allergic or inflammation mediators. The study of nasal hypersensitivity always involves provocation tests with other practical assays. In the occupational context, the provocation test most routinely used are "challenge tests", carried out with suspected substances provided by the patient, and non-specific tests with mediators (histamine and carbachol). Three complementary techniques-rhinomanometry, intranasal expiratory flow, and nasal lavage with cell and mediator studies, aim at three objectives. These are principally diagnostic and physiopathological, but are also possibly therapeutic. The authors describe in detail the technique of passive anterior rhinomanometry, nasal challenge tests and cholinergic challenges leading to a better understanding of non-specific nasal hypersensitivity. Future prospects concern the establishment of dose-response reactivity curves, exploration of the intranasal expiratory flows and research into nasal lavages with the study of cells and mediators released.

[Occupational asthma and rhinitis: challenge tests and nasal hyperactivity: present practice and future perspectives]. / Asthmes et rhinites professionnels: tests réalistes et hyper-réactivité nasale: pratique actuelle et perspectives d'avenir.

Nasal hypersensitivity is defined by an exaggerated response to certain specific stimuli such as a work-related agent, non-specific stimuli (irritant effect), or to allergic or inflammation mediators. The study of nasal hypersensitivity always involves provocation tests with other practical assays. In the occupational context, the provocation test most routinely used are "challenge tests", carried out with suspected substances provided by the patient, and non-specific tests with mediators (histamine and carbachol). Three complementary techniques-rhinomanometry, intranasal expiratory flow, and nasal lavage with cell and mediator studies, aim at three objectives. These are principally diagnostic and physiopathological, but are also possibly therapeutic. The authors describe in detail the technique of passive anterior rhinomanometry, nasal challenge tests and cholinergic challenges leading to a better understanding of non-specific nasal hypersensitivity. Future prospects concern the establishment of dose-response reactivity curves, exploration of the intranasal expiratory flows and research into nasal lavages with the study of cells and mediators released.

Effects of right atrial stretch on plasma renin activity.

In anaesthetized dog, right atrial stretch leads in the first five minutes to a decrease in plasma renin activity, when measured in inferior vena cava just above the renal veins. Bilateral cervical vagotomy increases plasma renin activity. After vagotomy, atrial stretch no longer has any effect on plasma renin activity. The results support the hypothesis of a control of renin secretion originating from atrial volume receptors.

[Challenge provocation tests and nonspecific bronchial hyperreactivity in occupational asthma]. / Tests de provocation réalistes et hyper-réactivité bronchique non spécifique dans l'asthme professionnel.

The aim of the study is to determine the interest of realistic challenge (nasal and bronchial) in occupational respiratory symptoms appearing during work. 75 patients were included in the study. The protocol included prick tests, measuring total and specific IgE, spirometry and metacholine test to assess bronchial hyperreactivity (BHR), realistic challenge by rhinomanometry and plethysmography measuring NR (nasal resistance) and RWA (Airway resistance). The test was considered positive if the RWA and/or NR were increased by 100%. 68% of the tests were positives in rhinomanometry and/or plethysmography. There is an BHR in 68% cases of occupational asthma. There is a quite strong correlation between the positivity of the realistic tests and the existence of a non specific BHR.

[Challenge provocation tests and non-specific bronchial hyperactivity in occupational asthma]. / Tests de provocation réalistes et hyper-réactivité bronchique non spécifique dans l'asthme professionnel.

The aim of the study is to determine the interest of realistic challenge (nasal and bronchial) in occupational respiratory symptoms appearing during work. 75 patients were included in the study. The protocol included prick tests, measuring total and specific IgE, spirometry and metacholine test to assess bronchial hyperreactivity (BHR), realistic challenge by rhinomanometry and plethysmography measuring NR (nasal resistance) and RWA (Airway resistance). The test was considered positive if the RWA and/or NR were increased by 100%. 68% of the tests were positives in rhinomanometry and/or plethysmography. There is an BHR in 68% cases of occupational asthma. There is a quite strong correlation between the positivity of the realistic tests and the existence of a non specific BHR.

[Radioimmunoassay of urinary oxytocin in man]. / Dosage radioimmunologique de l'ocytocine urinaire chez l'homme.

A radioimmunoassay (RIA) for oxytocin (OT) in urine is described. 125I-OT was prepared, and antibodies were raised in rabbits against OT coupled to bovine serumalbumine. This allowed us to set up of RIA for OT which limit of detection is 1.25 pg/tube (0.6 microU). The use of an extraction procedure using CG50 Amberlite is essential. The recovery after extraction reaches 70.5%. pH 5 is the optimum pH were urine samples must be stored. The superposition of the elution peak of endogenous OT on that of exogenous hormone is an argument in favour of the validity of such an extraction procedure. Daily urinary excretion of OT reaches 9.58 mU +/- 3.48 in 18 healthy young men.

[Urinary elimination of oxytocin and vasopressin measured by radioimmunoassay in different phases of the menstrual cycle in women]. / Elimination urinaire d'ocytocine et de vasopressine mesurées par radioimmunodosage au cours des différentes phases du cycle menstruel chez la femme.

Urinary arginine-vasopressin (AVP) and oxytocin (OT) excretion were measured by radioimmunoassay and studied in 3 normally cycling women. No difference for AVP and OT excretion was found between the different phases of the menstrual cycle. But in one subject with a typical pre-menstrual syndrom (weight gain of 1.5 kg), a significant statistical difference was found in AVP excretion (p less than 0.05) between the pre-ovulatory (25.3 +/- 3.08 ng/24 h) and the post-ovulatory (39.45 +/- 5.59 ng/24 h) phase. The well known stimulatory effect of estrogen as judged from plasma studies on neurohypophyseal hormones was thus difficult to demonstrate in urine. These results could be explained by the fact that the kidney destroys both AVP and OT, but OT at a higher rate than AVP.

Plasma vasopressin, renin activity, and aldosterone: effect of exercise and training.

The influence of endurance-training on hematocrit, plasma vasopressin, renin activity, and aldosterone changes at rest and at the end of an exercise performed until exhaustion at a given and constant relative work-load (87% of maximal oxygen uptake) has been studied in four untrained subjects submitted to a 5-month training. At the end of this period, maximal oxygen uptake increased of 15.2% (p less than 0.01). Hematocrit at rest slightly rose after training, and if exercise constantly induced increases in hematocrit before (p less than 0.001) and after training (p less than 0.005), the per cent increase after training was lower than before (p less than 0.05). Comparison between the importance of weight loss and hematocrit variation showed that when untrained subjects become trained the variation of hematocrit after exercise becomes smaller while weight loss is more important (p less than 0.01). Plasma renin activity (PRA), aldosterone (Aldo) and vasopressin (AVP) levels, compared to control values, displayed a significant increase after exercise before as well as after training. Control values remained unchanged after training for aldosterone and AVP, but were significantly lower (p less than 0.05) for PRA. This latter observation could be explained by the change in blood volume induced by exercise.

Plasma AVP, neurophysin, renin activity, and aldosterone during submaximal exercise performed until exhaustion in trained and untrained men.

The effect of intense muscular work (80% of maximal oxygen uptake) on responses of plasma hormones involved in electrolyte and water balance were measured in 14 male subjects. They were divided into three groups according to their maximal oxygen uptake and the duration of exercise performed until exhaustion: well trained subjects (group I), trained subjects (group II), and untrained subjects (group III). Pulmonary gas exchange, heart rate, rectal and skin temperature, and weight loss were measured as well as hematocrit and plasma and urine sodium and potassium concentrations. Rectal temperature increased significantly in all subjects after exhaustion. The variation of hematocrit was smallest and the weight loss greatest in the well-trained subjects. Plasma aldosterone, renin activity (PRA), vasopressin (AVP), and neurophysin (Np) displayed highly significant increases after exercise in all three groups: PRA was increased 4.5 times (p < 0.01), aldosterone 13 times (p < 0.05), Np 2.6 times (p pe 0.05), and AVP 4.8 times (p < 0.05). Nevertheless, there was no correlation between the changes in PRA and those in plasma aldosterone, nor between aldosterone and plasma sodium or potassium. At the urinary level, the only striking observation was that free water clearance tends to become positive after exercise. Our results provide evidence that this kind of exercise produces a highly significant increase in plasma levels of the hormones involved in electrolyte and water balance. They also indicate that it is among the well-trained subjects that sweat loss is highest though the hematocrit increase is the smallest; this suggests that water is shifted more efficiently from the extravascular compartment.