Artificial hypobiosis as a method of G-force negative impact reduction

Abstract

Dynamic gravitational acceleration, known as a G-force, is an extreme factor for some professions. G-force negative impact realizes in central nervous system adequate functioning disturbance, resulting from oxygen starvation of tissues due to hemodynamic disorders. Known methods of G-force protection are aimed at increasing the maximum short-term G-force value, but not its total safe duration. In a number of studies, in order to increase the maximum value of the tolerated overload, we introduced laboratory animals into a state of artificial hypobiosis. The authors noted a decrease in mortality with an increase in the maximum value of the overload force. There were no data on manifestations of disorders of the central nervous system and recovery time, as well as changes in the safe duration of overload.
 The study aims to assess the change in the safe G-force duration while artificial hypobiosis.
 Scientists have used Syrian male hamsters weighing 95.5=0.5 g (M=m) in the study. We have divided the animals into groups — experimental and control.
 To induce artificial hypobiosis, the researchers administered intramuscular injections of a suspension of α-methyldopa to animals of the experimental group. The control group received of 0.9% NaCl. We have carried out dynamic gravitational acceleration modeling using a centrifuge (r=0.62 m). The animals of both groups were conscious, with positive G-forces pointing downward (head-pelvis).
 Within 10 seconds (s), the centrifuge rotation speed was increased till the chosen G-force value, G: 30 (angular velocity (ω)=21.79 rad/s), 40 (ω=25.16 rad/s) or 70 (ω=33.28 rad/s). G-force exposure set time, s: 20, 50, 80, 110 or 140. After a complete stop for 10 seconds, the general condition of the animals, injuries, hemorrhages, breathing, heart contractions were assessed. We monitored the surviving animals, assessed consciousness, determined coordination disorders in accordance with the following criteria: animal posture, productive movement, unstable gait, circular motion, reclining on the side. The time of restoration of coordination was also determined. The researchers have observed the animals during the following days to assess the daily survival rate. Necropsy was performed on all non-surviving animals.
 Survival in the control group: 30 G: 80 s — 5/6; 40 G: 20 s — 6/6, 50 s — 6/6, 80 s — 3/6; 70 G: 20 s — 6/6, 50 s — 4/6, 80 s — 0/10. Survival in the experimental group: 70 G: 50 s — 6/6, 80 s — 10/10, 110 s — 10/10, 140 s — 2/6.
 After acceleration of 70 G 50 s in animals of the experimental group, coordination disorders were weakly expressed, the coordination recovery time was 1.8±0.3 s, in animals of the control group, violations were assessed as significant, the recovery time was 4.5±0.3 s, which is 2.5 times (p<0.01) more.
 On the following day, tremor persisted in 3 animals of the control group 40 G 80 c. In the remaining animals of all groups, no coordination disorders or peculiarities were detected.
 We did not find any external injuries in any animal. Also, the scientists did not reveal a violation of the integrity of tissues according to the results of histological examination.
 The authors have proved a 5.5-fold increase in the time of safe stay of animals in a state of artificial hypobiosis during dynamic overloads. There was a 2.5-fold decrease in the coordination recovery time in animals in a state of artificial hypobiosis.
 Ethics. Studies involving laboratory animals were conducted in compliance with the necessary regulations (the Helsinki Declaration of 2000 on Humane Treatment of Animals and the "Rules for carrying out work using experimental animals" (Order of the Ministry of Health of the USSR No. 755 of 12.08.1977)). The Ethics Committee of Izmerov Research Institute of Occupational Health approved the protocol of the study.