Vasopressin and galanin expression in the hypothalamus of two African rodents, Taterillus gracilis and Steatomys caurinus, subjected to water-restriction.

The expression of arginine-vasopressin (AVP) and galanin (GAL) was studied by immunohistochemistry and in situ hybridization in the hypothalamus of two species of African rodents. In the wild, these animals experience successive arid and wet seasons that alternately stimulate their antidiuretic and diuretic systems. In this study, animals were subjected to both standardized laboratory conditions and to eight days of water-restriction.

Effects of 17 days of head-down bed rest on hydro-electrolytic regulation in men.

Prolonged periods of head-down bed rest (HDBR) are commonly used to mimic the effects of microgravity. HDBR has been shown to produce, as in space, a cephalad redistribution of circulating blood volume with an increase in central blood volume which induces the early adaptations in blood volume regulating hormones. Changes in atrial natriuretic peptide (ANP), arginine vasopressin (AVP), renin activity and aldosterone have been observed.

Plasma compartment filling after exercise or heat exposure.

Purpose: The present study was assessed to study the restoration of the vascular compartment by rehydration after heat exposure or exercise.

Methods: Eight subjects completed four trials in a randomized order: 2.7% dehydration of body mass by passive controlled hyperthermia once with rehydration and once without rehydration during recovery, and 2.

Hyperhydration induced by glycerol ingestion: hormonal and renal responses.

The simultaneous time courses of hydromineral hormones (renin-aldosterone system, arginine vasopressin, and atrial natriuretic peptide) and renal responses were examined during and after the completion of hyperhydration induced by glycerol and fluid ingestion. Eight healthy young male Caucasian subjects participated in two separate trials, each including three consecutive phases in a thermoneutral environment. Phases 1 and 3 involved a 90-min period at rest, while phase 2 involved a 120-min period at rest designed to provide either (i) euhydration (control trial) or (ii) hyperhydration induced by ingestion of glycerol (1.

Comparison of passive heat or exercise-induced dehydration on renal water and electrolyte excretion: the hormonal involvement.

The effects of hydromineral hormones and catecholamines on renal water and electrolyte excretion were examined during and after dehydration induced by either passive heat or exercise. Eight healthy young Caucasian subjects participated in three separate trials, each including three consecutive phases. Phases 1 and 3 involved a 90-min period at rest in a thermoneutral environment, while phase 2 involved a 120-min period designed to provide: (1) euhydration (control trial), (2) passive heat-induced dehydration of 2.

Effects of a 60-day confinement on the blood pressure, hormonal responses and body fluids of a mixed crew.

During the EXEMSI experiment, an international crew of 4 subjects (1 woman and 3 men) was confined for 60 days in a normobaric diving chamber (with 1060 mbar atmospheric pressure) to simulate life in a space station and to assess the effects of confinement on psychological and physiological factors. Blood pressure and blood volume regulating hormones (atrial natriuretic peptide, renin, aldosterone) and urine data (24-h urine outputs, ionogram) were measured before (BDC: baseline data collection), during (D: day) and after (R: recovery) confinement. We also measured energy expenditure and total body water, 14 days before, and after 27 days of confinement, by the double-labeled water method.

Influence of head-down bed rest on the circadian rhythms of hormones and electrolytes involved in hydroelectrolytic regulation.

We investigated in six men the impact of a 17-day head-down bed rest (HDBR) on the circadian rhythms of the hormones and electrolytes involved in hydroelectrolytic regulation. This HDBR study was designed to mimic an actual spaceflight. Urine samples were collected at each voiding before, during and after HDBR.

Endocrine responses to 7 days of head-down bed rest and orthostatic tests in men and women.

The objective of this study was to investigate plasma volume (PV), total body water, hormones and hydroelectrolyte responses in eight males (25-40 years) and eight females (25-31 years) during 7 days of exposure to simulated microgravity (-6 degrees head-down bed rest, HDBR). Bed rest is a model that has commonly been used to simulate spaceflight. Heart rate (HR), blood pressure (BP) and vasoactive hormone responses were studied before and after HDBR during a 10-min stand test.

Cardiac natriuretic peptide response to water restriction in the hormonal adaptation of two semidesert rodents from West Africa (Steatomys caurinus, Taterillus gracilis).

Two African rodents, Taterillus gracilis and Steatomys caurinus, native to regions of alternate dry and wet seasons, were studied under laboratory conditions. These species differ in estivation behavior, one undergoing pseudoestivation and the other strong estivation. One group of animals of each species was provided with unlimited access to seed and vegetables rich in water, mimicking the food availability of the wet season (control group).

Adaptations to a 7-day head-down bed rest with thigh cuffs.

Purpose: Thigh cuffs were two elastic strips fixed at the upper part of each thigh, which limits the shift of fluid from the legs into the cardio-thoracic region. The purpose of this study was to examine the effects of thigh cuffs on hormonal and plasma volume responses and orthostatic tolerance during a 7-day head-down bed rest (HDBR).

Methods: Orthostatic tolerance, plasma volume, total body water, blood volume-regulating hormones, and hydro-electrolyte responses were measured in eight healthy men (age range, 25-40 yr), using thigh cuffs 10 h daily during 7 d of -6 degrees HDBR.

Better preservation of endothelial function and decreased activation of the fetal renin-angiotensin pathway with the use of pulsatile flow during experimental fetal bypass.

Objective: Pulsatile flow was shown to overcome the progressive rise in peripheral and placental vascular resistances observed during steady-flow bypass, this rise being counteracted by inhibition of nitric oxide synthase. This study quantifies the release of endothelial vasoactive substances during a 60-minute in utero model of fetal bypass.

Methods: Fetuses were randomly allocated into 1 of 2 groups (steady flow, n = 8, or pulsatile flow, n = 13) and subjected to bypass through central cannulation and perfusion with either a centrifugal or pulsatile (125 beats x min(-1)) blood pump.

Plasma volume changes during and after acute variations of body hydration level in humans.

This study examined plasma volume changes (deltaPV) in humans during periods with or without changes in body hydration: exercise-induced dehydration, heat-induced dehydration and glycerol hyperhydration. Repeated measurements of plasma volume were made after two injections of Evans blue. Results were compared to deltaPV calculated from haematocrit (Hct) and blood haemoglobin concentration ([Hb]).

Changes in the sympathetic nervous system induced by 42 days of head-down bed rest.

Changes in autonomic nervous system activity could be linked to the orthostatic intolerance (OI) that individuals suffer after a spaceflight or head-down bed rest (HDBR). We examined this possibility by assessing the sympathetic nervous system activity during 42 days of HDBR in seven healthy men. Heart rate variability was studied with the use of power spectral analysis, which provided indicators of the sympathetic (SNSi) and parasympathetic (PNSi) nervous system influences on the heart.

Presence of atrial natriuretic peptide in two desert rodents: comparison with rat.

Atrial natriuretic peptide (ANP) was characterized and assayed in plasmas, hearts, and brains of two Algerian desert rodents, Psammomys obesus and Meriones libycus along with vasopressin, which was assayed in hypophyses and hypothalami. Using reverse-phase high-performance liquid chromatography and radioimmunoassay, we showed, in plasmas and hearts of both species of desert rats, the presence of peptides similar to rat N- and C-terminal ANP but in lower amounts than in Wistar rats. Conversely, C-terminal ANP was abundantly detected in hypophyses from Meriones libycus rats.

Cardiovascular and hormonal changes induced by a simulation of a lunar mission.

Background: This is the first simulation of a 14-d lunar mission including 6 d on the Moon.

Hypothesis: We hypothesized that a lunar gravity simulation in the middle of a head-down tilt (HDT) might result in some reversal of body fluid/hormonal responses, and influence cardiovascular deconditioning.

Methods: Six men (28 +/- 2.

Haematocrit, plasma volume and noradrenaline in humans during simulated weightlessness for 42 days.

Previous results from our laboratory demonstrate that changes in haematocrit (Hct) and haemoglobin concentration (Hb) underestimate the relative (%) change in plasma volume (PV) in seated subjects during simulation of weightlessness by water immersion. Therefore, we examined whether changes in Hct and Hb would accurately reflect the changes in PV in seven subjects during simulation of weightlessness by another model, 6 degrees head-down tilted bed rest (HDBR), for 42 days. Since we have previously observed unexpectedly high plasma levels of noradrenaline (NA) in astronauts during space flight, we also took the opportunity to measure this variable.

Effects of hydration state on hormonal and renal responses during moderate exercise in the heat.

The effects of hydromineral hormones and catecholamines on renal concentrating ability at different hydration states were examined in five male volunteers while they performed three trials. Each of these trials comprised a 60-min exercise bout on a treadmill (at 50% of maximal oxygen uptake) in a warm environment (dry bulb temperature, 35 degrees C; relative humidity, 20-30%). In one session, subjects were euhydrated before exercise (C).

Restraint vs. hindlimb suspension on fluid and electrolyte balance in rats.

To determine the effect of hindlimb suspension on body fluid volume, salt and water balance, and relevant hormones, two series of experiments were performed in an experimental protocol including periods of isolation (7 days), horizontal attachment (7 days), and suspension (14 days). 1) During the first experiment, water and electrolyte balance, arginine vasopressin (AVP), and guanosine 3',5'- cyclic monophosphate (cGMP) were determined in urine, atrial natriuretic peptide in plasma and atria, and renin concentration and AVP in plasma in 30 rats. 2) During the second experiment, blood volume and extracellular fluid volume were measured by a dilution technique (Evans blue and sodium thiocyanate) in another 30 rats.

Cardiovascular and hormonal response during a 4-week head-down tilt with and without exercise and LBNP countermeasures.

To determine whether exercise and Lower Body Negative Pressure (LBNP) during 28 days of -6 degrees head-down tilt (HDT) would modify orthostatic tolerance and blood volume regulating hormones, twelve healthy men were assigned to either a no- countermeasure (No-CM, n=6), or a countermeasure (CM, n=6) group. LBNP sessions consisted of 15 minutes exposure to -30 mm Hg, on days 16, 18, 20 and 22-28 of HDT. Muscular exercise began on day 8 and consisted of combined graded dynamic and isometric resistance bilateral leg exercise on a specially designed supine ergometer, in two sessions of 15-20 min.

Water balance during and after marathon running.

To describe the time course of plasma volume alterations and the changes in the plasma concentrations of hormones regulating water balance in relation to a marathon race, six experienced marathon runners (five men, one women) aged 28 (SD 6) years were studied during and for the 3 days following a treadmill marathon run at 68 (SD 5) percent of maximal oxygen consumption. Haematocrit, haemoglobin, plasma protein (Prot) and electrolyte (Na+, K+) concentration, osmolality (osm), plasma concentrations of renin (Ren), aldosterone (Ald) and atrial natriuretic peptide (ANP) were determined at rest in a sitting position (T(-30)), and then after 30 min in an upright posture (R(0)), while running a marathon at 10 km (R(10)), 30 km (R(30)) and 42.2 km (R end), and after the marathon at 30 min (T(30)), 60 min (T(60)), 120 min (T(120)) and 24 h (TD(+1)), 48 h (TD(+2)) and 72 h (TD(+3)).

Comparison of a 4-day confinement and head-down tilt on endocrine response and cardiovascular variability in humans.

The aim of this study was to determine the effects of a 4-day head-down tilt (HDT; -6 degrees) and 4-day confinement on several indicators that might reflect a state of cardiovascular deconditioning on eight male subjects. Measurements were made of endocrine responses, heart rate variability and spontaneous baroreflex response (SBR) slope before, during and after each intervention. Plasma volume decreased by 10 percent after the 4-day HDT.

Diurnal rhythms of plasma renin activity, atrial natriuretic peptide and arterial pressure during head-down bed rest in humans.

The effects of prolonged head-down bed rest on the rhythms of several parameters (blood pressure, heart rate, haematocrit, plasma renin activity (PRA), atrial natriuretic peptide (ANP) were assessed in six healthy men, aged 33 (SEM 2) years, who were submitted to bed rest for 28 days (D1-28). Systolic and diastolic blood pressure (BPs and BPd) and heart rate were measured at 0700 and 1900 hours; circulating PRA and ANP were determined from blood samples drawn at 0800, 1000, 1200, 1500, 1800 and 2200 hours before bed rest (D - 5), D1, 2, 7, 20, 27 during bed rest and post bed rest (D + 2). The BPs was the lowest at 0700 hours and increased at 1900 hours.

Hormonal, water balance, and electrolyte changes during sixty-day confinement.

The EXEMSI experiment has made it clear that it is difficult to perform psychological and physiological protocols satisfactorily in the same study. It is, therefore, essential that the objectives of study be defined clearly before the start. While behavioral and psychological studies may be possible and provide valid results for a small group of mixed gender, it is more difficult to conduct valid physiological studies due to large differences between individuals and even in the same individual over time.

Blood volume regulating hormones, fluid and electrolyte modifications during 21 and 198-day space flights (Altair-MIR 1993).

During the Altair MIR '93 mission we studied several parameters involved in blood volume regulation. The experiment was done on two cosmonauts before (B-60, B-30), during (D6, D12, D18 for French and D7, D12, D17 for Russian) and after the flight (R+1, R+3 and R+7). Space flight durations were different for two cosmonauts: for the Russian the flight duration was 198 days and for the French 21 days.