Search PubMed⌕ Search

Biomedical subjects

C Gharib

Publications and source records attributed to C Gharib.

At least 127 records · Page 7Linked to original sources
PubMed1993

European isolation and confinement study. Water and salt turnover.

Intake and output of water were studied in six male subjects from six European countries during 28 days of isolation and confinement in order to assess whether the observed reactions can be compared with those observed during space travel. On the average, the subjects drank 17.5 ml/kg/day fluids. An additional 25 ml/kg/day was recruited from food intake and metabolism. The lowest fluid intake of 11.3 and 12.1 ml/kg/day was shown by two subjects who concurrently lost 3 to 4% of body weight. Three subjects maintained body weight, and one subject gained. A linear correlation existed between the total water output and the fluid intake by drinking. The time series of fluid intake, urine output, and sodium excretion revealed a weekly pattern for these parameters, characterized by low values on Sundays and high values on Fridays. This pattern was most apparent for sodium excretion. Low water turnover rates were seen in the first week of isolation; in the last week the values were above average. In conclusion, it can be said that with respect to the water balance, strong individual differences and time dependent variations (day to day, week to week) of the respective parameters have to be taken into account for the data analysis during such long-term studies.

Adult↗
PubMed1993

Norepinephrine content in discrete brain areas and neurohypophysial vasopressin in rats after a 9-d spaceflight (SLS-1).

The norepinephrine (NE) content in discrete brain areas and the vasopressin content in the neurohypophysial system were assessed in rats after a 9-d spaceflight and after a recovery period (9 d). The NE content in the locus coeruleus decreased significantly in spaceflight rats (2.9 +/- 0.3 vs. 8.9 +/- 0.7 pmol.structure-1 for control rats, p < 0.001), but showed no difference between control and flight animals after a 9-d recovery. These findings were probably due to an acute stress undergone during landing. The NE content was unchanged in the A2 and A5 cell groups. In rats flown aboard SLS-1, the vasopressin content was increased in the posterior pituitary (1.47 +/- 0.1 vs. 0.86 +/- 0.1 micrograms.structure-1, for control rats, p < 0.01), and was significantly decreased in the hypothalamus (8.95 +/- 2.0 vs. 17.6 +/- 2.2 ng.structure-1, for control rats, p < 0.05). We conclude that the NE depletion in the locus coeruleus and the alteration in vasopressin release were consistent with an acute stress, likely occurring during and/or after landing. These changes tend to mask the actual neuroendocrine modifications caused by microgravity.

Animals↗
PubMed1993

Effects of 28-day isolation (ESA-ISEMSI'90) on blood pressure and blood volume regulating hormones.

The aim of this study was to determine what effects social isolation and confinement stress had on the volume regulating hormones. In six healthy male subjects, during a 28-d isolation and confinement study (ESA-ISEMSI'90), hematocrit, blood pressure and resting heart rate, plasma cortisol, renin, aldosterone, arginine vasopressin levels besides the electrolyte (Na+, K+) balance and plasma creatinine were measured. During the confinement, an elevated systolic blood pressure (p < 0.01) was observed together with an increase in MHPG corresponding to an elevated mental work load. The pattern displayed by volume regulating hormones (increased values for renin, aldosterone (p < 0.05) and arginine vasopressin) was not only characteristic of confinement stress but also reflected changes in the water and electrolyte metabolism. The increased creatinine levels seen throughout the study were regarded as consequences of hypohydration, and an enhanced muscular catabolism due to reduced physical activity. A similar pattern of hormone modifications was obtained in a head down tilt of the same duration, indicating that some of the described modifications are probably related to isolation and confinement stress.

Adult↗
PubMed1993

Central and peripheral norepinephrine turnover after hindlimb suspension in the rat.

After a 9-d hindlimb suspension, the turnover rate of norepinephrine (NE) in rats was determined in A1, A2 (rostral and caudal), A5 and A6 cell groups, as well as in peripheral target organs (heart and kidneys). The NE turnover rate decreased after hindlimb suspension respectively in caudal A2 (67.5%, p < 0.001), rostral A2 (63%, p < 0.001) and in A5 cell groups (62.5%, p < 0.001), but remained unchanged in A1 and A6 regions. The peripheral sympathetic outflow response was selectively modified: in suspended rats, the NE turnover was mainly decreased in atria (79%, p < 0.001) and in ventricles (44%, p < 0.001); there were no biochemical changes in kidneys. It was concluded that a 9-d hindlimb suspension: 1) impaired the noradrenergic neuron activity of A2 and A5 cell groups, which are involved in the central cardiovascular regulation, and particularly in the baroreceptor reflex mechanism; and 2) mainly altered the cardiac NE turnover and induced a selective response of peripheral target organs.

Animals↗
PubMed1992

Effect of a five-week swimming program on rat bone: a histomorphometric study.

To specify the exercise-induced changes on different skeletal sites, the effect of a 5-week endurance swim training was studied in rats. Eighteen Lyon strain (Sprague-Dawley) 5-week old female rats were divided into nine sedentary and nine swimming rats. Each swim training session was increased by 15 minutes from 2-6 hours per day. A histomorphometric study was performed at the primary and secondary spongiosa of the distal femur and at the secondary spongiosa of lumbar and thoracic vertebral bodies. After training, bone loss was observed in the secondary spongiosa of lumbar vertebral bodies (24.7%) and in the primary spongiosa of distal femur (15.2%). A tendency to bone loss was also detected in the secondary spongiosa of distal femur (10.8%), whereas no change was detected in thoracic vertebral bodies. In secondary spongiosa, bone loss was accompanied with a thinning of trabeculae. Total eroded surfaces and osteoid surfaces were significantly decreased in the three studied skeletal sites, suggesting a decreased bone turnover. The decreased thickness of osteoid seams in both lumbar vertebrae and distal femur could mean that the osteoblastic activity has also been altered at the cell level, leading to thinning of trabeculae. Five-week swim training with such duration and intensity of exercise appears unable to increase bone volume in rats and, therefore, causes adverse effects. The three studied bones seemed to adapt differently to experimental conditions. The lack of ground reaction forces induced by water immersion might have contributed to the observed bone loss. "Normal" gravity would be an important cofactor in the osteogenic effects of exercise.

Adaptation, Physiological↗
PubMed1992

Presence of atrial natriuretic factor and cyclic guanosine monophosphate in saliva. Comparison of plasma and salivary concentrations during a head-down tilt.

Using a specific and sensitive radio-immunoassay involving separation and extraction procedures, we measured the concentration of saliva and plasma atrial natriuric factor (ANF) and cyclic guanosine monophosphate (cGMP) in men before and during a 10 h head-down tilt at -6 degrees. Saliva values closely correlated with plasma for ANF (r = 0.7-0.95) and for cGMP (r = 0.65-1). During this dynamic test, the mean concentrations of ANF and cGMP were significantly higher after 15 and 45 min, respectively, this increase persisting for 3.5 h. We concluded that the concentration of ANF in saliva may be significantly affected by a marked fluid shift from the lower to the upper half of the body. This is the first time that the presence of ANF and cGMP has been demonstrated in saliva. The great advantage of studying saliva is that it can be obtained non-invasively in athletes or during space flight. This methodology will be used during the Soviet-French space flight (Antares Project) planned for 1992.

Adult↗
PubMed1992

Hormonal responses to exercise during moderate cold exposure in young vs. middle-age subjects.

The influence of moderate cold exposure on the hormonal responses of atrial natriuretic factor (ANF), arginine vasopressin (AVP), catecholamines, and plasma renin activity (PRA) after exhaustive exercise was studied in 9 young and 10 middle-aged subjects. Exercise tests were randomly performed in temperate (30 degrees C) and cold (10 degrees C) environments. Heart rate, oxygen consumption, and peripheral arterial blood pressure were measured at regular intervals. Blood samples were collected before and immediately after exercise at 30 or 10 degrees C. Plasma sodium and potassium concentrations as well as hemoglobin and hematocrit were measured, and the change in plasma volume was calculated. At rest and during exercise, oxygen consumption was similar during exposure to both temperate and cold temperatures. During submaximal exercise intensities, the rise in heart rate was blunted while the increase in systolic blood pressure was significantly greater at 10 than at 30 degrees C. The increases in plasma sodium and potassium concentrations after exhaustion were similar between environments, as was the decrease in plasma volume. In both groups, all plasma hormones were significantly elevated postexercise, with the AVP response similar at 10 and 30 degrees C. However, the norepinephrine and ANF responses were significantly greater while the PRA response was significantly reduced at 10 degrees C. In the middle-aged subjects the epinephrine response to exercise was higher at 10 than at 30 degrees C. The greater ANF and reduced PRA responses to exercise in the cold may have resulted from central hemodynamic changes caused by cold-induced cutaneous vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Results of a 4-week head-down tilt with and without LBNP countermeasure: I. Volume regulating hormones.

The volume regulating hormones were studied during a 4-week head-down tilt (CNES HDT) in five subjects with and without (controls) lower body negative pressure (LBNP). LBNP was applied 3 times a day for 3 weeks, 4 times a day for 4 d, and 6 times a day for 3 d the last week. In both groups we observed a significant decrease in body weight (3% in controls, 0.8% in LBNP), a significant increase in plasma renin activity and aldosterone (with an amplification of their rhythms), and a significant decrease in norepinephrine with no difference between the two groups. The only major hormonal difference was observed for atrial natriuretic factor (ANF), which decreased significantly in the control group and increased in the LBNP group. These results are compared with the improvement in orthostatic tolerance (OT) after HDT in the LBNP group in the same protocol (17). We conclude that many factors could be involved in the improvement of OT. The results suggest that better conservation of plasma volume in the LBNP group might have prevented a decrease in ANF. Whether ANF plays a role in the regulation of baroreceptor reflex with an improvement in OT is currently unknown.

Aldosterone↗
PubMed1992

Results of a 4-week head-down tilt with and without LBNP countermeasure: II. Cardiac and peripheral hemodynamics--comparison with a 25-day spaceflight.

Cardiovascular hemodynamics were assessed by ultrasound echography and Doppler during a 28-d head-down tilt "CNES HDT: 87-88," and during the 25-d French-Soviet spaceflight "Aragatz 88." For both studies we used the same ultrasound methodology. The main hemodynamic parameters of the left heart function and of the peripheral arterial system (cerebral, renal, femoral arteries) were measured four times during the HDT (day 7, 14, 21, 28) and twice post-HDT. The same measurements were performed six times during the flight (day 4, 5, 15, 18, 20, 24) and five times postflight. During the HDT, two groups were studied: six subjects no countermeasures and six subjects with repeated lower body negative pressure (LBNP). In the first group the cardiac volumes and the cardiac output were significantly decreased, whereas in the group with LBNP these parameters were superior to the basal value. In the group without LBNP the cerebral flow was maintained because of a decrease of the brain vascular resistance. In this group the renal vascular resistance was decreased as inflight. In the lower limbs we observed a loss of the vasomotor control. The vascular resistance was decreased after the end of the HDT and the subjects suffered orthostatic intolerance. In the population with LBNP, we did not observe the same decrease of vascular resistance during the HDT, and after the HDT no sign of orthostatic intolerance was observed. During the flight, the left ventricular volume was significantly decreased. The carotid flow was maintained owing to a decrease of the cerebral vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Effects of acute exercise and prolonged exercise training on blood pressure, vasopressin and plasma renin activity in spontaneously hypertensive rats.

The purpose of this study was to investigate the effect of swimming training on systolic blood pressure (BPs), plasma and brain vasopressin (AVP), and plasma renin activity (PRA) in spontaneously hypertensive rats (SHR) during rest and after exercise. Resting and postexercise heart rate, as well as blood parameters such as packed cell volume (PCV), haemoglobin concentration (Hb), plasma sodium and potassium concentrations ([Na+], [K+]) osmolality and proteins were also studied. Hypophyseal AVP had reduced significantly after exercise in the SHR, whereas PRA had increased significantly in the Wistar-Kyoto (WKY) strain used as normotensive controls. Plasma AVP concentration increased in both strains. By the end of the experiment, training had reduced body mass and BPs by only 10% and 6%, respectively. Maximal oxygen uptake was increased 10% and plasma osmolality 2% by training. The postexercise elevation of heart rate was not significantly attenuated by training. A statistically significant reduction in postexercise plasma osmolality (10%) and [Na+] (4%) was observed. These results suggested that swimming training reduced BPs. Plasma and brain AVP played a small role in the hypertensive process of SHR in basal conditions because changes in AVP contents did not correlate with those of BPs. Moreover, there were no differences between SHR and WKY in plasma, hypophyseal and hypothalamic AVP content in these basal conditions. Finally, during moderate exercise a haemodilution probably occurred with an increase of plasma protein content. This was confirmed by the exercise-induced increase of plasma AVP and the reduction of hypophyseal AVP content, suggesting a release of this hormone, which probably contributed to the water retention and haemodilution.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Endothelin and atrial natriuretic peptide after exercise performed until exhaustion in the rat.

Endothelin-1(ET) is a recently discovered endothelium-derived vasoconstrictor peptide. Plasma concentrations of immunoreactive (IR-) endothelin were investigated in rats by radioimmunoassay after extraction of endothelin on Sep-Pak Cartridges. In control rats, a mean concentration of 1.03 +/- 0.2 pg/ml was found. After exercise performed until semi-exhaustion or exhaustion, the mean plasma concentration of IR-endothelin decreased. An increase of Atrial Natriuretic Peptide plasma was observed immediately after exercise. There was a negative correlation between Endothelin and Atrial Natriuretic Peptide (r = -0.73, p less than 0.001). This is the first time that this increase following exercise is shown in normotensive rat. The mechanisms of the decrease of Endothelin are unclear. One hypothesis could be that the decrease in Endothelin is related to its rapid removal by the different tissues, specially the lungs.

Animals↗
PubMed1991

Activity of the sympathoadrenal system in cosmonauts during 25-day space flight on station Mir.

The activity of the sympathoadrenal system in cosmonauts was studied by measuring plasma and urinary catecholamines and their metabolites and conjugates. The appliance Plasma 02 was used for collecting, processing, and storing blood and urine samples from the cosmonauts during the course of a 25-day flight on board the station Mir. Plasma and urine concentrations of adrenaline (A), noradrenaline (NA), and dopamine (DA) as well as urinary levels of vanillylmandelic acid (VMA) and homovanillic acid (HVA), and plasma levels of catecholamine sulphates were determined before, during and after the space flight. Plasma NA levels were slightly elevated on day 9 and plasma A on day 20, whereas plasma DA levels were unchanged. However, most of the changes were within the normal range of control values. Sulphates of plasma catecholamines did not change during flight but they were significantly elevated after landing. Urinary levels of A, NA, DA, VMA, and HVA were comparable with preflight values but were elevated at the different intervals studied after landing. The results obtained suggest that in the short period of about 9 days of the cosmonaut's stay in space the sympathoadrenal system was slightly activated indicating a mild stressful influence of the initial period of flight. This short-term space flight compared to long-term flight did not as markedly activate the sympathoadrenal system during the process of re-adaptation to Earth's gravity after landing. Our data suggest that weightlessness is not a stressful factor activating the sympathoadrenal system but it sensitizes the responsiveness of this system during the re-adaptation period after space flight.

Adaptation, Physiological↗
PubMed1991

Naloxone effect on ANP in trained and untrained rats.

1. The effect of a dose of naloxone (1 mg.kg-1 b.w.) on peripheral (plasma, atria) and central (hypothalamus, hypophysis) levels of atrial natriuretic peptide (ANP) was investigated in the rat. 2. In control rats, an acute subcutaneous dose of naloxone produced no significant change in plasma ANP, but a decrease (NS) in atrial ANP concentration. 3. In physically conditioned animals, naloxone produced a significant decrease in atrial ANP levels. Receptor sensitivity may thus be involved in this differential response. 4. In hypothalamus and hypophysis, no effect on ANP concentrations was seen after a high dose of naloxone whether in control or in physically conditioned animals, suggesting peripheral and central ANP might be differently regulated, at least after chronic endurance physical training.

Animals↗
PubMed1991

Hormonal and metabolic changes during a strenuous tennis match. Effect of ageing.

The effect of a strenuous tennis match was studied in 9 young (21.2 +/- 1.9 yr) and 10 veteran women players (46.5 +/- 1.3 yr) of equivalent skill. Each match was carried out during the summer (ambient temperature 27 +/- 1 degree C), as an official competition, under conditions as similar as possible. Heart rate (HR) was monitored throughout the match, weight loss was evaluated and pre- and post-match values of haematocrit, plasma lactate, free fatty acid (FFA), glycemia, ionogram, norepinephrine (NOR), epinephrine, arginine vasopressin (AV) concentrations and plasma renin activity (PRA) were measured. Plasma volume was calculated. While mean HR remained steady in young players, it increased progressively in veteran players as the match went on and reached a very high level towards the end of the match. When post-match values were compared to pre-match values, the mean results were: no substantial changes in plasma lactate and electrolyte concentrations, a large increase in FFA, no increase in epinephrine, a moderate rise in NOR and a large increase in PRA and AV. Despite a similar weight loss, a large drop in plasma volume occurred only in veteran players, who also showed FFA and AV values greater than in young players. During these strenuous matches the large response of hormones which control body fluid probably contributed to the limiting of changes in water and electrolyte balances. However, under similar conditions marked differences occurred as a function of ageing concerning the control of plasma volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗