[Effect of nuclear radiation on rat model of decompression sickness induced by large depth rapid floating escape]

Objective: To investigate the effects of different doses of nuclei exposure at different time on morbidity, mortality, and damage indicators in a rat model of decompression sickness caused by rapid flotation escape at a large depth. Methods: Eighty male SD rats were randomly divided into blank control group, escape control group and six intervention groups (escape at 4 hours after 4 Gy radiation, escape at 4 hours after 6 Gy radiation, escape at 4 hours after 12 Gy radiation, escape at 8 hours after 4 Gy radiation, escape at 8 hours after 6 Gy radiation, escape at 8 hours after 12 Gy radiation). Rats in intervention groups were exposed to different doses of γ-ray (4,6,12 Gy, respectively), and then were carried out a large depth and rapid buoyancy escape experiment (maximum pressure depth of 150 m). The changes of lung W/D, spleen index and plasma IL-1β levels were analyzed. Results: Compared with the blank control group, decompression sickness incidence and mortality of rats in escape groups after nuclear exposure were increased significantly. In 4 Gy and 6 Gy irradiation groups, higher morbidity and mortality were observed in rats which escaped at 4 h post nuclear exposure when compared with rats in 8 h groups. Consistent with the changes in morbidity and mortality, the wet / dry ratio of lung tissue, the pathological damage of lung tissue, and the decrease of spleen index showed the same trends: the changes were obvious at 4 h after lower doses nuclear radiation (4 Gy and 6 Gy), not at 8 h. However, these indicators all changed markedly at 4 and 8 h after higher doses nuclear radiation (12 Gy). Plasma IL-1β levels were significantly increased in each post-radiation exposure group when compared with the blank control group and the exposed control group. Conclusion: Nuclear radiation-induced lung injury, the damaged immune function and elevated plasma inflammatory factor concentrations increase the risk of decompression sickness after rapid ascent.

PDTC ameliorates decompression induced-lung injury caused by unsafe fast buoyancy ascent escape via inhibition of NF-κB pathway

Nuclear factor kappa B (NF-κB) is the critical transcriptional factor in the pathogenesis of acute lung injury (ALI). NF-κB regulates the expression changes of inflammatory factors such as tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and interleukin 6 (IL-6). In a previous study we showed that decompression sickness (DCS) caused by simulated unsafe fast buoyancy ascent escape (FBAE) could result in ALI, which was characterized by expression changes of inflammatory factors in rat lung tissue. The purpose of the present work was to study the roles of NF-κB and TNF-α in the process of DCS-induced rat lung injury caused by simulated unsafe FBAE. The research methods aimed to detect the rat lung tissue messenger ribonucleic acid (mRNA) and protein level variations of NF-κB, inhibitory ×B (I×B), TNF-α, IL-1β, IL-6, IL-10 and IL-13 by using pretreatment of the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) and TNF-α antibody (Ab). Our experimental results demonstrated that PDTC could improve the survival rate of the rats with DCS caused by unsafe FBAE more effectively than TNF-α Ab. However, the inhibition of TNF-α Ab on the nuclear translocated protein expression of NF-κB was more effective than PDTC. Both PDTC and TNF-α Ab can abrogate the increment of the rat lung tissue mRNA levels of TNF-α, IL-1β, IL-6 and protein levels of NF-κB, TNF-α, IL-1β effectively and increase the rat lung tissue content of I×B significantly. In conclusion, TNF-α-mediated NF-κB signaling may be one of the critical signaling pathways in the pathogenesis of DCS-induced rat lung injury caused by simulated unsafe FBAE. PDTC may ameliorate this type of injury partly through inhibiting the NF-κB pathway.

Expression changes of TNF-α, IL-1β and IL-6 in the rat lung of decompression sickness induced by fast buoyancy ascent escape

Fast buoyancy ascent escape is the general submarine escape manner adopted by the majority of naval forces all over the world. However, if hyperbaric exposure time exceeds the time limit, fast buoyancy ascent escape has a high risk to result in decompression sickness (DCS). Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 have been all implicated in the process of inflammation associated with acute lung injury (ALI). Our work demonstrated that DCS caused by simulated fast buoyancy ascent escape could induce ALβ in the rat model. The purpose of the present work was to study the expression changes of TNF-α, IL-1β and IL-6 in the rat lung affected by DCS caused by simulated fast buoyancy ascent escape. The lung tissue mRNA levels of TNF-α, Il-1β and Il-6 were significantly increased at 0.5 hour after DCS caused by simulated fast buoyancy ascent escape. The lung contents of TNF-α, IL-1β and IL-6 were at an expression peak at 0.5 hour, although showing no statistical difference when compared with the normal control group. In conclusion, the rat lung expression variations of TNF-α, IL-1β and IL-6 are the most obvious at 0.5 hour within 24 hours after the lung injury by DCS caused by simulated fast buoyancy ascent escape.

Expression changes of inflammatory factors in the rat lung of decompression sickness induced by fast buoyancy ascent escape

Fast buoyancy ascent escape is one of the major naval submarine escape maneuvers. Decompression sickness (DCS) is the major bottleneck to increase the depth of fast buoyancy ascent escape. Rapid decompression induces the release of inflammatory mediators and results in tissue inflammation cascades and a protective anti-inflammatory response. In our previous study, we found that DCS caused by simulated fast buoyancy ascent escape could induce acute lung injury (ALI) and the expression changes of the proinflammatory cytokines: tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β and IL-6 in rat lung tissue. In order to study the expression change characteristics of TNF-α, IL-1β, IL-6, IL-10 and IL-13 in the rat lung of DCS caused by simulated fast buoyancy ascent escape, we detected the rat lung mRNA and protein levels of TNF-α, IL-1β, IL-6, IL-10 and IL-13 at 0.5 hour after DCS caused by simulated fast buoyancy ascent escape (fast escape group), compared with the normal control group (control group) and diving DCS (decompression group). We observed that DCS caused by simulated fast buoyancy ascent escape could increase the mRNA levels of TNF-α, IL-1β, IL-6, IL-10, and the protein levels of TNF-α, IL-10 in rat lung tissue. At the same time, we found that the protein level of IL-13 was also downregulated in rat lung tissue. TNF-α, IL-10 and IL-13 may be involved in the process of the rat lung injury of DCS caused by simulated fast buoyancy ascent escape. In conclusion, the expression changes of inflammatory factors in the rat lung of DCS caused by simulated fast buoyancy ascent escape were probably different from that in the rat lung of diving DCS, which indicated that the pathological mechanism of DCS caused by simulated fast buoyancy ascent escape might be different from that of diving DCS.

The research progress of diving medicine in China

Diving medicine is one of the branches of military medicine, and plays an important role in naval development. This review introduces the progress of researches on undersea and hyperbaric physiology and medicine in the past few years in China. The article describes our research achievement in conventional diving and its medical support, researches on saturation diving and its medical support, submarine escape and its medical support, effects of hyperbaric environments and fast buoyancy ascent on immunological and cardiological functions. Diving disorders (including decompression sickness and oxygen toxicity) are also introduced.

[Effect of a simulated He-O2 saturation dive to 65 msw on oxidative stress in humans]

OBJECTIVE

To investigate whether a simulated He-O2 saturation dive to 65 msw would affect oxidative balance in humans.

METHODS

Seven divers participated in a simulated saturation dive to 0.75 MPa (65 msw). 24-h urine samples were collected twice before, twice during, and twice after the dive, then were analyzed for contents of superoxide dismutase (SOD), malondialdehyde (MDA), total amino acid (T-AA) and total anti-oxidant capacity (T-AOC). Meanwhile, total urine volume and body weight were measured.

RESULTS

The content of T-AA was higher. (P < 0.05) than the base value in final decompression, but reverse to normal at one week after decompression. There were no changes in contents of SOD, MDA and T-AOC during and after the dive compared with their basic value. Total urine volume was lower (P < 0.05, vs basic value) at first day in chamber, then returned to normal. Body weight gradually increased after compression till the end of decompression (higher than basic value, P < 0.05).

CONCLUSION

These data indicate that simulated saturation dive to 65 msw may not induce obvious oxidative damage, but it is necessary to monitor 24-h urine volume and oxidative sress by time in order to prevent from tissue injury.

[Change of coagulation and fibrinolysis in rabbit model with acute decompression sickness and its mechanism]

This study was purposed to investigate the changes in coagulation and fibrinolysis pathways in rabbits suffered from the acute decompression sickness(DCS). Model of DCS in rabbits was established. Survival rate and symptoms of DCS in animal model was monitored. The prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (Fib), fibrinogen degradation product (FDP) and D-dimers were measured before compression and at 0, 3, 24 hours after decompression by latex agglutination semiquantitative methods. The changes of plasmin-antiplasmin complex (PAP), fibrinopeptide A (FPA), plasminogen activator inhibitor 1 (PAI-1) and thrombomodulin (TM) were measured by ELISA at different time points after decompression. The results showed that the model of DCS in rabbits was successfully established. There was a statistically significant extension in APTT, TT, increase of Fib concentration at 15 minutes after decompression, the changes were peaked at 3 hours and recovered at 24 hours after decompression. The concentration of FDP significantly decreased at 3 hours after decompression. The concentration of D-dimers significantly increased at 24 hours after decompression in rabbits model with DCS. FPA concentration was significantly increased at 15 minutes and recovered at 24 hours after decompression. PAP concentration was increased after decompression, but had no significant changes. PAI-1 could not be detected. TM significantly increased after decompression. It is concluded that the acute DCS significantly impacts on blood coagulation system in rabbit model. It is shown that hypocoagulation occurred at initial time and hyperfibrinolysis subsequently, which varied with time. The damage of blood vessel endothelium may be one of the causes of these variations.