Relationship between G-induced Loss of Consciousness and Parameters of Vestibulo-ocular Reflex / 항공우주의학회지

BACKGROUND: Vestibular reflexes, such as vestibulo-sympathetic reflex, have been considered as an important physiologic mechanism to maintain peripheral vascular resistance in case of orthostatic stress. Vestibular function may play an important role not only in maintaining spatial orientation, but also in determining G-tolerance. The purpose of this study was to investigate the possible contribution of vestibular function to G-tolerance. METHODS: Vestibular function was measured indirectly in 86 subjects by analyzing vestibulo-ocular reflex (VOR) using a rotating chair test. They were also exposed to +6Gz acceleration for 30 seconds with rapid onset run (1 G/sec). After G-exposure, they were classified into the Pass and the G-LOC group according to their success or failure to maintain consciousness during G-exposure. The VOR parameters of the G-LOC group were compared with those of the Pass group. RESULTS: While VOR gain values of one subset of the G-LOC group (low gain G-LOC group, N=8) were significantly lower than those of the Pass group at rotation frequencies of 0.02, 0.04, 0.08, and 0.32 Hz, VOR gain values of the other subset of the G-LOC group (high gain G-LOC group) were significantly higher than those of the Pass group at all rotation frequencies. There was no difference of VOR phase value between the Pass and the G-LOC groups. CONCLUSIONS:This study suggests the vestibular function may be involved in determining G-tolerance. According to VOR gain values, we were able to recognize two distinct G-LOC subgroups compared with the Pass group. The difference between afferent or efferent vestibular flows and target organ response can be a possible explanation for different VOR parameters of G-LOC subgroups.

Effects of Female Hormones and Menstrual Cycle on Female Relaxed G-Tolerance / 항공우주의학회지

BACKGROUND: With increasing number of female pilots who fly high-performance aircraft, the gender specific factors have become one of the most important aeromedical considerations. It has been raised that the changes of serum female hormone levels by menstrual cycle may affect vasoregulation and female G-tolerance ultimately. However, the exact relationship between serum female hormone levels and G-tolerance is still unknown. Moreover, well-controlled subjects without taking oral contraceptives are needed to examine the possible effect of menstrual cycle on female G-tolerance. The purpose of this study was to determine how female hormones and menstrual cycle affect female relaxed G-tolerance. METHODS: Eight female subjects were studied to test their relaxed G-tolerance. Seven out of 8 subjects had regular menstrual cycle during the study period. Each subject were exposed to human centrifuge once a week for 4 weeks (one complete menstrual cycle) and blood samplings were performed twice at 2nd and 4th week just before exposure to human centrifuge. The profile of centrifuge training consisted of gradual-onset run (0.1 G/sec) acceleration to the visual endpoint. RESULTS: The changes of 4 different serum female hormone levels failed to show any trend related to relaxed G-tolerance including estrogen. There was no significant difference in relaxed G-tolerance in any menstrual cycle time points. CONCLUSION: We conclude that the changes of female hormone levels and the menstrual cycle have no effect on female relaxed G-tolerance.

Effect of Hyperbaric Oxygen on Intercellular Adhesion Molecule-1 Expression in Rat Kidney / 항공우주의학회지

BACKGROUND: Although hyperbaric oxygen (HBO) -100% oxygen at two to three times the atmospheric pressure at sea level-has a number of beneficial biochemical, cellular, and physiologic effects, it is intrinsically associated with the potential for producing mild to severe toxic effects. The contribution of the cellular adhesion molecules and macrophages in the renal oxygen toxicity is not well understood. Thus, we have investigated the toxic effect of HBO expressed by the analysis of intercellular adhesion molecule-1 (ICAM-1) and infiltration of macrophages in rat kidney. METHODS: Male Sprague-Dawley rats weighing about 250 g were exposed to HBO at 3 ATA of 100% O2 for 4 hours. The expression of ICAM-1 and infiltration of CD68-positive macrophages were serially observed by immunohistochemical analysis. RESULTS: At 3 days after HBO exposure, CD68-positive macrophage counts were increased in glomeruli and tubulointerstitium of kidney. The expression of ICAM-1 was enhanced 1 day after HBO exposure and increased more for 3 days. There was a significant correlation between ICAM-1 expression and macrophage accumulation in the glomeruli. At 7 days after HBO, those alterations recovered to normal status. CONCLUSION: The 4-hour HBO exposure induced ICAM-1 expression and macrophage accumulation in the kidney and these change lasted for 3 days. Therefore, sustained activation of macrophages in renal oxygen toxicity may occur after prolonged (more than 4 hours) or repetitive exposures to HBO.

The Results of Aeromedical Consultation, ROKAF: 1991-2000

BACKGROUND: This study is aimed to analyze the results of aeromedical consultation of ROKAF for recent 10 years. METHODS: We reviewed the records of all ROKAF rated personnel who developed a medical problem requiring aeromedical consultation during the period from 1991 to 2000. RESULTS: We collected 263 cases. The most frequent clinical categories were ENT and musculoskeletal problems. In the group of fighter pilots, 30 cases were classified into permanent grounding. Chronic hepatitis and Herniated disc were the main causes. In the group of undergraduate pilots, aerotitis media by high altitude flight and airsickness by high performance flight, were the main causes. CONCLUSION: According to this study, we need to reinforce the supervision about the revealed major causes.

Enhanced in vitro and in vivo Bystander Effect by Double Transfer of Herpes Simplex Virus Thymidine Kinase Gene

OBJECTIVE: The bystander effect, the phenomenon that non-transduced tumor cells can be killed along with the transduced cells, enables suicidal gene therapy feasible in spite of low efficiency of gene transfer at present time. Increment of thymidine kinase activity in the cells through double copy insertion of HSVtk gene may lead to increased bystander effect in vitro and in vivo, therefore enhancing the therapeutic potential of suicidal gene therapy. To examnine this hypothesis, we did an experiment to improve bystander effect by using double transfer of HSVtk gene into 9L tuomr cells. METHODS: We transduced 9L glioblastoma cells which had one copy or two copies of HSVtk gene using retroviral vector. Two different retroviral vector plasmids containing HSVtk gene were made employing pBabePuro or LXSN plasmid whose selection markers were puromycin and G418, respectively(LtkSP and LtkSN). Recombinant retrovirus was produced from ecotrophic PA317 packaging cells. Infection of the 9L cells with LtkSP recombinant retrovirus and selection with puromycin was done in vitro to make 9L/LtkSP(9LtkS). These cells were infected again with LtkSN recombinant retrovirus and selected under G418 to establish cells containing two copies of HSVtk gene, 9L/LtkSP/ LtkSN(9LtkD). RESULTS: By measuring the intracellular amount of phosphorylated 3H-GCV, 9LtkD cell lines showed significantly increased HSVtk activity, being 70% higher than that of 9LtkS cell lines. The sensitivity to GCV was also markedly increased. In vitro bystander effect, examined by coculturing with HSVtk gene transduced cells and 9L cells, was significantly increased on 9LtkD cell lines. To evaluate the in vivo bystander effect, 9LtkD/9L(20%:80%) cells or 9LtkS/9L (20%:80%) cells were implanted into the brains of Fisher 344 inbred rats, followed by administration of ganciclovir. Rats implanted with 9LtkD/9L cells showed better tumor regression and longer survival than those of 9LtkS/9L after treatment with ganciclovir. CONCLUSION: These results suggest that increasing herpes simplex virus thymidine kinase activity by introducing double copy of HSVtk gene into tumor cells would improve in vitro and in vivo bystander effect, and lead to enhanced efficacy of suicidal gene therapy.