Effect of thigh cuffs on haemodynamic changes of the middle cerebral artery and on orthostatic intolerance induced by 10 days head-down bed rest.

Thigh cuffs are used by cosmonauts to limit fluid shift during space flight, but the appropriate level of cuff pressure and the duration of application to optimize their beneficial effects require further detailed investigations. In the present study, 10 days head-down tilt (HDT) bed rest was performed to assess the effects of thigh cuffs (40 mmHg, 10 h/day) on haemodynamic changes of the middle cerebral artery (MCA) and on orthostatic tolerance in six healthy male volunteers. Another six healthy male volunteers without thigh cuffs served as the control group.

[Repeated body position change training can improve human head-down tilt tolerance].

Aim: To verify the hypothesis that repeated body position change training can improve human head-down tilt (HDT) tolerance.

Methods: Six young healthy subjects were trained with repeated position change for 9 times and 11 days according to protocol of alternative head-down and head-up tilts, each time of training lasted for about 35 min. Their HDT tolerance (- 30 degrees/30 min) were determined before and after training.

Compliance changes in femoral veins of rabbits after 21 days of simulated weightlessness.

Increased venous compliance in lower limbs may be contributed to postflight orthostatic intolerance; however, direct animal studies to address the changes of venous compliance to microgravity have been rare. The purpose of this study was to determine compliance changes in femoral veins of rabbits after 21 days of head-down rest. Head-down rest -20 dgrees rabbit model was used to simulate weightlessness.

[Dynamic responses of human body and human surrogate to different impacts under 30 degrees supine position].

Objective: To study the difference between the dynamic responses of human body and human surrogate under 30 degrees supine position, and to discuss impact probability of substituting human body with human surrogate in impact tests.

Method: Five volunteers experienced half-sine impact pulses, averaged 4.76, 8.

[Role of ROK in contraction of rat femoral arteries after 14 d tail suspension].

Objective: To determine the role of Rho associated kinase (ROK) in contraction of rat femoral arteries after 14 d tail suspension.

Method: Male Wistar rats were randomly divided into control group (CON) and 14 d -30 degrees tail suspension group (TS14d). Analysis was performed on the contractile responses of perfused femoral arterial rings from both TS14d and CON rats to KCl, phenylephrine (PE), and U-46619 in the presence of Y-27632.

Effect of lower body negative pressure on orthostatic tolerance and cardiac function during 21 days head-down tilt bed rest.

The purpose of the present study was to investigate the changes of orthostatic tolerance and cardiac function during 21 d head-down tilt (HDT) bed rest and effect of lower body negative pressure in the first and the last week in humans. Twelve healthy male volunteers were exposed to -6 degrees HDT bed rest for 21 d. Six subjects received -30 mmHg LBNP sessions for 1 h per day from the 1st to the 7th day and from the 15th to the 21st day of the HDT, and six others served as control.

Effect of lower-body negative pressure on cerebral blood flow velocity during 21 days head-down tilt bed rest.

Background: The purpose of this study was to investigate cerebral blood flow (CBF) velocity in humans during 21 days of head-down tilt (HDT) bed rest with and without lower-body negative pressure (LBNP).

Material/methods: Twelve healthy male volunteers were exposed to -6 degrees HDT bed rest for 21 days. Six subjects received -30 mmHg LBNP sessions for 1 h per day from the 1st to the 7th day and from the 15th to the 21st day of HDT, and six others served as controls.

[Changes of ERK1/2 in femoral arteries of tail-suspended rats and their effects on contractility].

Objective: To study changes of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in femoral arteries of tail-suspended rats and their effects on contractility.

Method: Microgravity was simulated by elevating the hindquarters of Wistar rats to produce hindlimb unweighting (HU). In the absence or presence of prazosin and PD98059 respectively, isometric tension of vessel rings from femoral arteries in response to norepinephrine (NE) was determined by in vitro perfusion technique; Basal total ERK1/2 level and phosphorylated ERK1/2 level stimulated by norepinephrine in the absence or presence of prazosin and PD98059 respectively were detected by Western blotting-enhanced chemically lightening system.

[Human-centered ergonomical study and applications in manned spacecraft project of China].

High G and weightlessness are two important environment factors that are unavoidable during spaceflight. They will bring key effects on astronauts' posture and working efficiency. In this paper, on the basis of experience of China first manned spacecraft project in the past 10 years, the concept of space ergonomics and its role in the project were reviewed.

[Changes of reactivity of rabbit femoral venous rings after 21 d simulated weightlessness].

Objective: To study the effects of simulated weightlessness on reactivity of leg veins.

Method: Vascular bathing technique was used to measure the contractile responses of rabbit femoral venous rings to Ht, PE and KCl, and the dilatory responses to ACh and SNP after horizontal confinement or head-down tilt confinement for 21 d.

Result: After simulated weightlessness for 21 d, the contractile response of rabbit femoral venous rings to higher concentrations of PE and KCl decreased significantly (P<0.

[Probe into characteristics of Taraxacum mongolicum ultramicro-power].

Objective: To observe and study the tissue characteristics of T. mongolicum ultramicro-power and dissolving-out characteristics of effective compositions.

Method: By microscopic observation and thin-layer chromatography.

[Review of influence of landing impact on human body (correction of boby) and its medical evaluation].

Landing impact is the dynamic factor that manned spaceship will inevitably meet after the mission has been completed, and impact force may cause damages to human tissues [correction of tissuses] and organs, even death. This paper described the characteristics of pathological and dynamic response of human body to landing impact, and discussed various related factors such as impact angle, fetters, design of cushion, harness and terrain condition. Medical evaluation of +Gx, +Gz, +/- Gy impacts were summarized.

[Effects of simulated microgravity on cardiovascular function and counter effect of lower body negative pressure].

Studies on effect of simulated microgravity on cardiovascular function and counter effect of lower body negative pressure (LBNP) in recent years were summarized. The mechanism of simulated microgravity induced orthostatic intolerance may involve the reduction of cardiovascular function and cerebral blood flow, and endocrine changes. The significance of mathematical model in the study of mechanism of microgravity induced orthostatic intolerance was also discussed.

[Effects of 21 d -6 degrees bed rest on diastolic function of human left ventricle].

Objective. To investigate the effects of head down bed rest (HDBR), the simulated weightlessness, on the diastolic function of human left ventricle, and to discuss its role in cardiovascular deconditioning after space flight. Method.

[Changes of leg compliance during weightlessness or simulated weightlessness].

Weightlessness or simulated weightlessness causes increase of leg compliance. It leads to more blood pooling in the legs and less blood returning to the heart during orthostatic test, which may partly explain the occurrence of orthostatic intolerance induced by weightlessness or simulated weightlessness. This article is a review covering published materials about the methods of measurement, mechanisms and countermeasures of the increase of leg compliance during weightlessness or simulated weightlessness.

Effect of lower body negative pressure against orthostatic intolerance induced by 21 days head-down tilt bed rest.

Background: Exposure to actual or simulated weightlessness is known to induce orthostatic intolerance in humans. Many different methods have been suggested to counteract orthostatic hypotension. The repetitive or prolonged application of lower body negative pressure (LBNP) has shown beneficial effects to counter orthostatic intolerance, but devoting so much time to countermeasures is not compatible with space mission objectives or costs.

Effects of repeated brain ischemia induced by rapid lower body negative pressure on brain water and Na+,K+-ATPase activity in rats.

Background: It has been demonstrated that during +Gz exposure cerebral blood flow is significantly reduced resulting in brain ischemia. Animal centrifuge models are commonly used to investigate the mechanisms of +Gz-induced loss of consciousness (G-LOC) and their pathophysiological effects on the brain. These dynamic models are limited because we currently are unable to obtain accurate measures of membrane ion flux or single cell electrophysiological responses from animals under centrifugation.