[Change of transcription level of photoreceptor-specific CRX gene in the peripheral blood of the participants of an arctic world oceanic international flight]. / Izmenenie urovnya transkriptsii fotoretseptor-spetsifichnogo gena CRX u uchastnikov arkticheskogo krugosvetnogo pereleta.

The CRX gene encoding the cone-rod homeobox protein is a specific photoreceptor transcription factor crucial for retinal function. Persons temporarily residing in the Arctic zone during the polar summer may suffer from disturbances associated with extremely high ambient illumination. These environmental changes are mediated by retinal photoreceptors; therefore, it is important to study the expression of retinal genes in order to assess individual capacities of sensory adaptation to polar day conditions. PURPOSE: To reveal the dynamics of CRX expression level in humans after a prolonged temporary exposure to polar day conditions. MATERIAL AND METHODS: The study included 6 pilots (males from 39 to 69 y.o.) who participated in the Arctic World Oceanic International Flight Sever Vash (West to East, from 62°N 74°E to 72°N 114°E). Samples of peripheral blood for RNA isolation were collected at the start and at the end of the flight. The level of mRNA in the samples was evaluated based on the data of quantitative real-time PCR of the CRX gene, as well as the b2M and TBP housekeeping genes (reference). RESULTS: Expression of the CRX gene in the studied group (p<0.01) was revealed; the total average level of mRNA was about 3 times higher prior to, and approximately 7 times higher after normalization to the b2M gene. Five pilots had increased expression of the CRX gene within the range of -1.53 to -3.07 (Z-score of <0 before the flight and >0 after the flight). In one pilot, the level of CRX expression was higher at the start, but it reduced by the end of the circumnavigation flight. CONCLUSIONS: The results confirm the hypothesis that the CRX gene is expressed after a prolonged temporary exposure to polar day conditions. It was also revealed that during rapid adaptation, equal changes in the illumination of retinal photoreceptors lead to different individual dynamics of CRX expression.

[Disturbances of Autonomic Regulation of Cardiovascular System at Different Working Regimes with Night Shifts].

Aim        To study temporal and spectral characteristics of heart rhythm variability (HRV) in night shift workers.Materials and methods       Along with traditional risk factors, conditions of labor contribute to development of cardiovascular morbidity, including night shift work, which can be associated with disorders of the autonomic regulation detected by analysis of HRV. This study included 100 healthy men. 74 of them were engaged in shift work, including 53 men with rotating shift work, 21 men with fixed night shifts, and 26 men with day-time work. HRV was analyzed by data of 5-min electrocardiogram recording (background recording and orthostatic test).Results   Night-shift workers had decreases in total power of regulation (ТР, SDNN) and in the parasympathetic branch (HF, pNN50). Rotating night-shift workers displayed significant decreases in SDNN and pNN50 and pronounced changes in the VLF / LF / HF ratio in the orthostatic test.Conclusion            In work with night shifts, the type of autonomic regulation differs from the "standard" functioning of the autonomic nervous system (ANS). This study showed different effects of night work regimens on HRV indexes. With the rotating shift work, the ANS dysregulation was more profound and was evident by a significant decrease in the ANS total tone and parasympathetic activity (SDNN, pNN50) compared to night shifts with fixed working hours. The excessive weakening of the parasympathetic component in the passive orthostatic test can be considered as an early marker for ANS maladaptation.

ECG voltage modifications as response to gravity changes.

The aim of the study was to analyze ECG (QRS) voltage responses to body fluid shift due to gravity chances. Acute changes in gravity were created by two ways: 1) changes in gravity value during parabolic flights (within 27 subjects 45 ECG have been analyzed); 2) changes in gravity direction due to rotation of the body during postural tests (within 11 subjects 14 ECG have been analyzed). Results and conclusions. Gravity change leads to body fluid shift and changes of intrathoracic organs and tissues electroconduction. It influences on ECG voltage. During parabolic flights in up-right position: R amplitude in Z axis increases in hypergravity (+0.19 mV) and decreases in microgravity (-0.24 mV). During postural tests, R amplitude in Z axis increases in orthostatic position (+0.09 mV) and decreases in antiorthostatic position (-0.025 mV). Changes in QRS voltage during parabolic flights are more important than during postural tests. This could be due to more effective blood redistribution during parabolic flights.

Changes of decartograms under gravitational acceleration and microgravity.

The Decarto technique was used to study the orthogonal ECGs recorded in 23 subjects during parabolic flights (44 records). A parameter of the instantaneous decartograms, namely the activation area (AA), which is the total area of the depolarization front projection on the image sphere, was analyzed. We compared the values of AA during the periods of horizontal flight, upward parts of all parabolas, and the initial 10 s of microgravity of all parabolas. According to the characteristics of the vectorcardiograms and AA, all subjects were subdivided into 3 groups: with increased electric activity of the right ventricle (I), the left ventricle (II) and both ventricles (III). Changes of AA with change of gravitational levels in these groups showed some differences. In groups I and II, the AA of the initial part of the QRS complex increased during microgravity and decreased during hypergravity. In group III it decreased during microgravity and changed variously during hypergravity. The AA of the middle part of the QRS complex decreased during microgravity and increased during hypergravity, and these changes were more pronounced in group III. The changes of AA in groups I and II may be explained by the Brody effect. In group III, AA seems to be influenced by some additional factors, possibly by changes in the intramyocardial or intraventricular blood volume. The AA of the last part of the QRS complex increased during microgravity and decreased during hypergravity in all groups. This may be explained by an effect of mutual neutralization of depolarization fronts related to the changes of the QRS duration.(Fig. 3, Ref. 4)

Parasympathetic activity during parabolic flight, effect of LBNP during microgravity.

BACKGROUND/HYPOTHESIS: During parabolic flight, in the standing position, changes are partly due to an acute shift in fluid between the lower extremities, the head and the thorax (Vaïda P, et al. J Appl Physiol 1997; 82:1091-7; and Bailliart O, et al. J Appl Physiol 1998; 85:2100-5). We hypothesized that modifications of parasympathetic activity associated with changes in hydrostatic pressure gradients induced by changes in gravity could be detected by analysis of short time periods. METHODS: We assessed heart rate variability (HRV) in 11 healthy volunteers by indices of temporal analysis (NN, SDNN, RMSSD) and normalized indices such as coefficients of variation CV-SDNN and CV-RMSSD and ratio SDNN/RMSSD. A lower body negative pressure (LBNP) at -50 mm Hg was randomly applied during the microgravity phase (0 Gz) to counteract the lack of hydrostatic pressure in the lower part of the body. RESULTS: NN, CV-SDNN and CV-RMSSD decreased during hypergravity phases and increased during microgravity and during early normogravity (1 Gz) period at the end of parabolas. With LBNP changes are less pronounced at 0 Gz and in the 1 Gz post parabolic period. CONCLUSION: We concluded that parasympathetic nervous activity is recordable by temporal analysis of HRV during short periods of time. LBNP applied during 0 Gz phase reduced the parasympathetic activation at 0 Gz and post parabolic 1 Gz.

Echocardiographic evaluation in 485 aeronautical workers exposed to different noise environments.

INTRODUCTION: Vibroacoustic disease (VAD) is a heterogeneous and systemic entity, caused by long term (> or =10 yr) exposure to noise environments characterized by large pressure amplitude and low frequency (LPALF) (> or =90 dB SPL, < or = 500 Hz), and not explained by other possible etiologic agents. The goal of this study was to identify possible structural changes in hearts of men with suspected VAD. METHODS: A total of 485 men were divided into 3 noise groups: no noise exposure (< or =70 dB), n = 48 (Group I); moderate noise exposure, (>70dB and < 90 dB), n = 113 (Group II); and intense noise exposure (> or =90 dB), n = 324 (Group III). Echo-Doppler studies were performed (HP SONOS 1500) and recorded on coded videotapes. Three observers performed blinded evaluations of 26 echo-Doppler parameters. For the purpose of the present study only 12 morphological parameters were compared among the groups: thickening of the mitral, aortic, tricuspid, and pulmonary valves, pericardium and endocardium; mitral valve regurgitation, prolapse and ruptured chordae tendinae; and inflow velocities. Thickness and severity of the applicable parameters were scored in seven-grade scale (0,0.5,1, ...,3). RESULTS: All evaluated parameters were statistically significantly different in Group I vs. Group III, except flow velocity E. Comparison of Group I vs. Group II revealed statistically significant differences in mitral, aortic, tricuspid and pericardial thickening, with the strongest evidence for mitral and pericardial structures. CONCLUSIONS: This confirms the results of previous studies. Occupational exposure to noise environments characterized by LPALF noise causes structural changes in the heart. Mitral valve and pericardial thickening constitute the first signs of VAD.

Non-invasive ultrasound detection of endothelial dysfunction.

With high resolution ultrasound we assessed endothelial function in subjects at risk of atherosclerosis. We used ACUSON 128XP/10 system with 7.0 MHz linear array transducer. Three groups of patients (pts) were studied: 12 patients with essential hypertension, ten patients with 2A familial hyperholesterolamia and ten controls without vascular risk factors. We measured the diameter of brachial artery at rest, during reactive hyperaemia (with increased flow causing endothelium-dependent dilation), and after sublingual 0.01 mg nitroglycerin (causing endothelium-independent dilation). Flow-mediated dilation is not impaired in essential hypertension (9. 4%) compared with controls (9.5%) and impaired in patients with familial hyperholesterolaemia (3.0%). NTG-induced dilation is not impaired in familial hyperholesterolaemia (16.6%) and essential hypertension (14.5%) compared with controls (20.5%). The effect of hypolipidaemic influence (probucol and plasmapheresis) was assessed in a separate study. These results demonstrate the capability of ultrasound in detection of endothelial dysfunction, and suggest that endothelial dysfunction in patients with familial hyperholesterolaemia is one of the risk factors for atherosclerosis. The parameters of endothelial function may be used as markers of hypolipidemic influence on patients with hyperholesterolaemia.

Interview with Dr. Oleg Atkov [interview by Winston Huff].

Last summer International Space University (ISU) was held in Huntsville, Alabama. Leading international space experts came to take part in the activities. Dr. Oleg Atkov, a Russian cardiologist who was also a cosmonaut for eight months in 1984, has extensive experience in cardiovascular medicine and first-hand experience in issues of life support, making him a valuable resource. He also serves on the Journal's Advisory Board. Winston Huff took advantage of the unique opportunity of having Valery Aksamentov, Paul Wieland, and Dr. Atkov together in Huntsville to conduct a general discussion of issues important to those studying life support. Dr. Valery Aksamentov was involved for many years in the development of the Russian life support systems. Dr. Aksamentov now leads the only university program specializing in life support at the University of Alabama in Huntsville. His command of both languages and his technical knowledge were critical to the success of this discussion. Paul Wieland from NASA Marshall Space Flight Center is involved with the development of the life support systems for the space station. He and Dr. Aksamentov are topic coordinators for the Journal. The following interview was conducted at the University of Alabama in Huntsville on August 16, 1993.

[Baroreflex control and circadian variability of arterial blood pressure in patients with "mild" hypertension and hemodynamically insignificant atherosclerotic lesions of the carotid arteries]. / Baroreflektornyi kontrol i sutochnaia variabelnost AD u bolnykh s "miagkoi" arterialnoi gipertoniei i gemodinamicheski neznachimym ateroskleroticheskim porazheniem sonnykh arterii.

Sinocarotid baroreflex control by means of the neck chamber technique (-40 mm Hg, 4 min) and blood pressure monitoring with a SpaceLabs 90207 system were performed in 45 patients with mild essential hypertension who were divided into 2 groups: (1) those with hemodynamically insignificant carotid atherosclerotic lesions (n = 19) and (2) those without them (n = 26). Group 1 patients showed a decreased cardiochronotropic component of baroreflex control, higher blood pressure variability and less pronounced nocturnal blood pressure fall. The above facts are likely to contribute to progression of essential hypertension and aggravation of target organ lesions.