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PubMed2000

The effect of 2G on mouse circadian rhythms.

This study examined the effect of chronic 2G exposure on the regulation of body temperature (T(b)), activity (ACT), and circadian rhythms of mice. Five mice were implanted with biotelemetry units to record T(b) and ACT. The mice exhibited a stable daily mean of T(b) (37.1 +/- 2.1 degrees C) and ACT and robust circadian rhythms during the control 1G period. Mice exhibited a significant decline in T(b) (30.1 +/- 1.5 degrees C; t(4)=8.32, p<.01) and cessation of ACT within two hours following 2G onset. After 6 hours of continuous 2G exposure there was a recovery in T(b) (34.4 +/- 1.6 degrees C) that remained significantly below that of baseline (t(4)=3.66, p<.05). A similar pattern of recovery was seen following 12 hours of continuous 2G for ACT. A slower pattern of adaptation toward baseline levels occurred steadily over the next 6-13 days. Exposure to 2G also caused an immediate 4 day loss in circadian rhythm amplitude in both T(b) and ACT. Recovery to new steady state levels was achieved by 8 days and 13 days, respectively. These results demonstrate that under chronic 2G, the recovery time for the homeostatic steady-state values and circadian rhythms are shorter for the mouse than for the rat. These differences may be related to the scaling effects of 2G resulting from the mass difference between mice and rats.

Activity Cycles↗
PubMed1997

Investigating gender differences under conditions of fatigue in a simulated high G aerial combat environment.

Advances in technology have equipped high-performance combat aircraft with the capability of delivering higher and higher sustained acceleration or G-forces on the pilots flying them. While the physiological effects of increased g-forces on the human body continue to be investigated, studies examining the effects of acceleration on the cognitive abilities of high-performance aircraft pilots remain sparse. Additionally, as higher technology is making its way into the cockpit, so are female pilots. With even fewer studies investigating women's physiological and cognitive tolerances to the stressors in the high-performance cockpit and flight environment, Dr. Chelette's study aimed to investigate these issues. Examining pilot workload, flight task abilities, and the effects of sleeplessness on both male and female pilots, Dr. Chelette's results revealed findings that will make their way into the high-performance cockpit of the future.

Acceleration↗
PubMed1969

Studies of human adaptation to space flight effects under low-calorie diet conditions.

Experiments were performed to establish the activity and performance of man kept on a low-calorie (1800) diet and exposed to some space flight effects. The diet consisted of canned foods with an optimal proportion of basic nutrients and amino acids. Three series of experiments were carried out on 18 healthy male subjects. Each series involved pre- and post-test examinations and 15-day tests. The first series dealt with the effect of low-calorie diets as such; the second one covered the effect of low-calorie diets combined with bed rest; and the third series revealed the above effect aggravated by exposing test subjects to bed rest and acceleration. In the course of the experiments, the state of the central nervous and cardiovascular systems, the function of external respiration, the digestive function, the kinesthetic apparatus, metabolic processes and immunological resistance of the body were studied. In addition, test subjects underwent thorough clinical examinations. The paper presents results of the experiments.

Adaptation, Physiological↗
PubMed2001

Stability in velocity of otolith-ocular reflex with different stimulus frequencies during step-mode linear acceleration.

Velocity changes in the otolith-ocular reflex (OOR) during a step mode of lateral linear acceleration were examined by electrooculography (EOG) in 4 normal subjects. They were oscillated in darkness at a constant stimulus frequency of 0.175 Hz with 4 different G-levels between 0.2-0.4 G and at a constant G-level of 0.3 G with 4 different stimulus frequencies between 0.115-0.215 Hz. The OOR velocity was increased linearly by elevation of the G-level, though the increase varied considerably among subjects. On the other hand, changes in the stimulus frequency had minimal effect on the OOR velocity. The results indicate that the OOR response property is frequency-independent at a low stimulus-frequency range, even when the head was oscillated rectangularly instead of sinusoidally.

Acceleration↗
PubMed2002

[Changes in heart rate and blood pressure under push pull maneuver simulated on a tilt table].

Objective. Push-pull maneuver (PPM) was simulated using a tilt table to assess detailed cardiovascular responses and the simulation model. Method. Ten healthy fighter pilots were exposed to 3 times transition of body position of head-up tilt (HUT) for 1 min-->head-down tilt (HDT) for 10 s, 15 s and 20 s respectively-->HUT for 1 min in randomized sequences. The rate of tilt table rotation was 45 degrees /s. Heart-level arterial blood pressure was monitored with 4 s intervals, and HR was continuously monitored by ECG. Result. HR and BP fell significantly during HDT compared with those during HUT; upon subsequent HUT, HR and BP were significantly less than those during previous HUT, except BP at 11-15 s. Conclusion. Cardiovascular responses to PPM can be simulated with a tilt table. It is suggested that the tilt table model is valid in simulating the PPM.

Adaptation, Physiological↗
PubMed2002

Effects of repeated + Gz forces on masticatory muscles.

OBJECTIVE: To study the effects of repeated + Gz forces on masticatory muscles. METHODS: 48 male Wistar rats were randomly divided into 4 groups. Group A was normally fed. Group B was only fixed with rat-kept devices for 5 minutes. Group C was borne + 1 Gz for 5 minutes. Group D was repeatedly exposed + 10 Gz (each for 30 s, onset rate about 0.5 G/s, 5 times/d with + 1 Gz 1 minute intervals, 4 d/wk, 3 weeks in total). The histological changes of the masseter, temporal and lateral pterygoid muscles were observed. RESULTS: No abnormal changes were observed in Group A, B and C. But pathological changes could be found in group D. The wrench and deformation of muscular fibers, the dissolution of partial myofibril, the swelling of mitochondria, the reduce of hepatin from the masseter and lateral pterygoid muscles could be found. CONCLUSIONS: Repeated + Gz stresses could induce the damage of masticatory muscles in different degrees.

Animals↗
PubMed1999

Effects of tea polyphenols on cardiac function and myocardial ultrastructure in rats after repeated +Gz stress.

Objective. To observe the effects of tea polyphenols (TP) on cardiac function and myocardial ultrastructure in rats after repeated +10 Gz stress. Method. Twenty four male Wistar rats were randomly divided into three groups (n=8 each): group A (control), group B (+10 Gz), group C (+Gz with TP). Group B and C were repeatedly exposed to +10 Gz (each for 30 s, onset rate about 0.5 G/s, 3 times/d with +1 Gz 1 min intervals, 3 d/wk, 4 weeks in total), but group A was only submitted to +1 Gz. TP (200 mg kg-1) was given orally to group C about 1 h prior to the +Gz experiment, and distilled water was given to group A and B. Function of isolated rat working hearts and myocardial ultrastructure were observed. Result. A significant decrease of left ventricular systolic pressure (LVSP) and injury of myocardial structure in rats were demonstrated after repeated +10 Gz stress. But TP could remarkably elevate the LVSP and improve myocardial ultrastructural injury in +10 Gz stressed rats. Conclusion. These results indicated that repeated high G exposure may produce cardiac structural and functional injuries in rats which might be partly related to free radical metabolism; and antioxidant TP had significant protective effects on the hearts of +Gz stressed rats.

Acceleration↗
PubMed1999

[Integrated protection capability afforded by a new type capstan anti-G equipment and anti-G straining maneuver].

Objective. To investigate the integrated protection capability afforded by a new type capstan anti-G equipment and anti-G straining maneuver, as a result we discussed the feasibility of protection for 8 G 10 s (rapid onset runs at 2 G/s) acceleration using an associated precept with the above both anti-G measures. Method. This study was accomplished using the human centrifuge with rapid onset at 2 G/s. First, we determined the relaxed +Gz tolerance of nine male aviation students, and then determined theirs most + Gz tolerance while thereinto the five aviation students using a new type capstan anti-G suit (NKH) + a new type anti-G valve (NKT) + L-1 anti-G straining maneuver (L-1) and the other four aviation students using a new type capstan counterpressure suit (NDC) + the new type anti-G valve (NKT) + L-1. Result. The most +Gz tolerance of five students was 8.80 +/- 0.27 G while using NKH + NKT + L-1 and was higher than their relaxed +Gz tolerance at 4.60 +/- 0.42 G (P< 0.01) and that the most +Gz tolerance of four students was 8.75 +/- 0.50 G while using NDC + NKT + L-1 and was higher than their relaxed +Gz tolerance at 4.50 +/- 0.46 G (P< 0.01). Conclusion. Pilot will be capable against the 8 G 10 s (rapid onset runs at 2 G/s) effectively using the new type capstan anti +/- G equipment and anti +/- G straining maneuver, and the provided precept has availability.

Acceleration↗
PubMed2002

Relaxed acceleration tolerance in female pilot trainees.

BACKGROUND: Female pilots now fly many types of aircraft including military fighters capable of maneuvers that produce high, sustained acceleration in the +Gz axis. Although women have participated as subjects in various centrifuge studies, little is known about the acceleration tolerance of female pilots. METHODS: Between April 1995 and December 1997, 17 female pilot trainees were studied at the Institute of Aerospace Medicine, Bangalore, India. The subjects were 23.2 +/- 1.4 yr old and led physically active lives. Their relaxed +Gz tolerance limits (defined as peripheral light loss) were tested using the High G and Disorientation Demonstrator. The protocol included a series of rapid onset runs (RORs) to tolerance followed by a single gradual onset run (GOR) to tolerance. RESULTS: The mean ROR tolerance was 4.2 +/- 0.4 G. The mean GOR tolerance was 5.2 +/- 0.6 G. Three of the subjects were unable to complete the GOR due to severe nausea. Two women reported breast discomfort at levels of 3.5 G and beyond. No other problems were reported. CONCLUSIONS: The acceleration tolerances for the female pilot trainees were comparable to those for male pilots previously studied in our laboratory.

Acceleration↗
PubMed1999

[Technical consideration of setting up a specification for human centrifuge evaluation of anti-G equipment].

Anti-G equipment needs to be evaluated using human centrifuge before further developed. However, there isn't a general specification for human centrifuge evaluation of anti-G equipment. From related literature and from our over thirty years experience in this area, we sum up to five aspect technical consideration below: human centrifuge, medical specification for using human in +Gz stress experiment, anti-G equipment experimental assembly, principle should be abided by during human centrifuge evaluation of anti-G equipment. We hope that the technical considerations mentioned in the paper should be helpful to the work of setting up a specification for human centrifuge evaluation anti-G equipment. After we have a specification, the research will be conducted orderly and the anti-G [correction of an-G] equipment will be developed sequentially.

Acceleration↗
PubMed2002

[Effects of +Gx stress on contractility of rat diaphragm and its mechanism].

Objective. To observe the effect of sustained +Gx exposure on contractility of rat diaphragm and explore its mechanism. Method. Forty-two male Wistar rats were randomly divided into control group (underwent +1 Gx exposure, n=21) and experiment group (underwent +15 Gx for 3 min, n=21). The tension of rat diaphragm in vivo, contents of nucleoside phosphates and lactic acid in diaphragm and ultrastructure of diaphragm were measured and observed respectively. Result. 1) Compared with pre- +Gx, low-frequency tension of diaphragm of experiment group decreased significantly (P<0.01), whereas high-frequency tension did not significantly decrease after +Gx (P>0.05). As to the control group, however, the tension of diaphragm tested at a wide range of frequencies was almost unchanged (P>0.05). 2) Compared with control group, ATP decreased (P<0.01), while ADP and lactic acid contents in diaphragm increased significantly (P<0.05 and P<0.01) after +Gx in experiment group. In addition, ratios of ADP/AMP and AMP/ATP increased significantly (P<0.01). 3) After +Gx exposure, hypoxic changes in ultrastructure of rat diaphragm occurred in experiment group, but not in control group. Conclusion. Sustained +Gx exposure could cause diaphragm muscle fatigue, which was possibly due to changes in energy metabolism and ultrastructure of rat diaphragm induced by hypoxia under +Gx stress.

Acceleration↗
PubMed2002

[Influences of repeated lower +Gz exposures on high +Gz exposure induced brain injury in rats].

Objective. To explore the influence of repeated lower +Gz exposures on high +Gz exposure induced brain injury in rats. Method. Forty SD male rats were randomly divided into control group (5 rats), +10 Gz/5 min group (5 rats) +4 Gz exposure one time, three times and five times group (10 rats each group). After 1 d or 6 d of +4 Gz exposure each group were exposed to +10 Gz again. Three days after +10 Gz exposure the neuron damage was observed by light microscope in HE stained section. Result. There was no brain damage after repeated +4 Gz/3 min exposure 5 times so it was reasonable to use this exposure intensity as ischemia stimulation. +10 Gz/5 min exposure could result in irreversible neuron damage such as neuron degeneration and coagulation necrosis. The experiment results suggested that after +10 Gz/5 min exposure there were degenerated neurons in cortex, hippocampus and thalamus. The number of degenerated neurons were obviously decreased in cortex, hippocampus and thalamus when exposed to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. Conclusion. The degree of neuron damage was obviously slight at the time of exposure to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. The ischemia tolerance at the time of exposure to +Gz was similar to other brain ischemia.

Animals↗