Deep-sea water improves cardiovascular hemodynamics in Kurosawa and Kusanagi-Hypercholesterolemic (KHC) rabbits.

Deep-sea water is rich in minerals, e.g., Mg, Ca, and K which have been considered to be associated with prevention of cardiovascular disease. We investigated the effect of deep-sea water on cardiovascular hemodynamics in Kurosawa and Kusanagi-Hypercholesterolemic (KHC) rabbits. Deep-sea water was pumped in the offing of Cape Muroto in Japan and the mineral constituents were refined to a degree of hardness of 1,000. Twenty four 4-month-old KHC rabbits were given refined deep-sea water (n=12) and tap water (n=12) for 6 months. Pressure and flow waves at the ascending aorta were recorded under pentobarbital anesthesia. Systolic, diastolic, pulse and mean arterial pressures and total peripheral resistance were significantly lower in the deep-sea water group than in the control group. There were no significant differences in changes in serum lipid levels, plasma renin and angiotensin converting enzyme activities and electrolyte levels except for Mg(2+) after the feeding of the water between the two groups. A slight increase in serum Mg(2+) level in the deep-sea water group may not account for the inhibition of mild hypertension. From our results, we conclude that deep-sea water could improve cardiovascular hemodynamics, even though the factors which affect the blood pressure are still unknown.

Mood change and immune status of human subjects in a 10-day confinement study.

INTRODUCTION: Stress is a known factor that causes changes in leukocyte distribution or depression in lymphocyte proliferation. We reported previously that a 10-d confinement caused changes in immune status. Here we report the relationship between mood changes and immune parameters in the subjects confined for 10-d. METHODS: There were 10 subjects (age 20-27 yr, mean 22.8 yr) who participated in a 10-d confinement study. They were divided into 2 groups with regard to their psychological aspects and their immune parameters were then compared. Blood samples were taken once before, three times during, and once after confinement. The percentages of granulocytes, natural killer (NK) cells, and cells positive for CD69, an early activation marker, were analyzed by flow cytometry. Face scale was employed to estimate subjects' mood. RESULTS: The group that showed an increase in mood scale toward the end of the confinement showed changes in all immune parameters. In contrast, less marked changes were seen in the group that showed no mood changes throughout the experiment. DISCUSSION: These results indicate that the observed immune changes were related to the mood changes, and that mood change seems to be one of the causes of the immunological changes seen in confined environments, such as in space stations or submarines. The percentages of NK cells, granulocytes, and CD69 expression may be useful criteria for detecting immunological deterioration caused by stress, or for selecting astronauts who are immunologically stable against the challenge of confinement stress.

Effects of 10-day confinement on the immune system and psychological aspects in humans.

We investigated the changes in percentages of leukocyte subpopulations, natural killer (NK) cells, CD69-expressing lymphocytes, and psychological aspects in 10 subjects who participated in a 10-day confinement study. Suppression of lymphocyte proliferative reaction and changes in leukocyte distribution are known to occur in space. These responses are similar to those induced by psychological stress. Ground-based confinement studies are suitable for validating the effects of stress arising only due to confinement. Two groups, consisting of five male subjects (ages 20-27 yr, mean 22.8 yr) each, participated in a 10-day confinement study. Blood samples were taken once before, three times during, and once after the confinement and activated with an anti-CD2 agonistic antibody cocktail. The percentages of leukocyte subpopulations, NK (CD45(+)CD56+) cells, and activated lymphocytes (CD45(+)CD69+) were measured by flow cytometric assay. The face scale test was used to measure psychological aspects. The percentage of CD69+ lymphocytes decreased during the period of confinement. This was mostly caused by changes in the ratio between NK and non-NK lymphocytes. The face scale showed that the subjects' moods improved toward the postconfinement period. Consistent with the face scale, the percentages of innate immune cells, such as NK cells and granulocytes, increased during the postconfinement period. We concluded that the changes in the distribution of immune cells caused by stress plays an important role in suppression of proliferative reactivity. The observed physiological reactions were specific to the confined environment, and the stress caused by confinement plays a role in the immune changes observed in space.

Regulation of gastric motility at simulated high altitude in conscious rats.

The aim of the present study was to examine the effects of acute exposure to hypobaric hypoxia on gastric and colonic motilities. Wistar rats, which were instrumented chronically with strain gauge force transducer to measure gastric and colonic motilities, were exposed acutely to hypobaric hypoxia [0.5 atmosphere absolute (ATA, 380 Torr)] over 1 h. In a separate group, the gastric branches of the vagal nerves were cut and underwent the same experimental protocol. Each contraction wave of the stomach and colon was analyzed into frequency and area under the curves, which were then averaged every 10 min. Acute exposure to 0.5 ATA resulted in significant (P < 0.05) decreases in frequency and area of gastric contraction wave by 0.5 +/- 0.1 cycles/min and 64.6 +/- 4.0%, respectively. Gastric vagotomy abolished completely the suppression in the area observed in the intact rats during the 0.5-ATA exposures. Colonic motility increased significantly only at the start and end of exposure to 0.5 ATA and sham exposure [1 ATA (760 Torr), time control] in both intact and vagotomized rats. These data suggest that the acute suppression of the area of the gastric contraction wave that occurred during 0.5-ATA exposure is likely to be mediated by the vagal nerve.

Autonomic mechanisms of bradycardia during nitrox exposure at 3 atmospheres absolute in humans.

BACKGROUND: This experiment was designed to examine the involvement of the autonomic nervous systems and intrinsic component in the occurrence of hyperbaric bradycardia. METHODS: Eight male divers were exposed to a N2-O2 (Nitrox) environment at 3 atmospheres absolute (ATA) for 7 d. The heart rate (HR), plasma norepinephrine (NE), and a spectral power of the variability of cardiac interval were measured during a 4-d predive control period, a 7-d saturation period at 3 ATA, and a 4-d postdive period. In each dive period, atropine and propranolol were administered intravenously for cholinergic blockade and beta-adrenergic blockade, respectively. RESULTS: Basal HR decreased by -10% (p < 0.05) during the saturation period compared with that of the predive control. The HR after an administration of atropine was attenuated by 5.5 +/- 2.4% (p < 0.05) during hyperbaric exposure. The HR after a simultaneous administration of atropine and propranolol, the intrinsic HR, was similar throughout the dive periods. Plasma NE decreased at 3 ATA (p < 0.05). The basal level of high-frequency power of cardiac interval variability, an index of cardiac parasympathetic modulation, remained unchanged throughout the dive period, whereas this power was eliminated by atropine administration. CONCLUSIONS: These results suggest that reduced sympathetic activity plays a primary role in the reduction of HR in the present hyperbaric environment.

Changes in sleep patterns during simulated nitrox saturation diving to 20 and 30 meters.

This study assessed the effect of a nitrogen-oxygen (N2-02) saturation diving environment on nocturnal sleep and the differences in sleep on diving depth. We measured and recorded the standard polysomnograph and heart rate for a total of 459 nights on 27 divers who performed the N2-O2 saturation simulation dive an 20- and 30-m equivalent depths as well as their subjective feelings of fatigue. From the last half of the period on the bottom to the postdive period of both saturation diving depths, our main findings included a prolongation of sleep latency, shortened total sleep time, a decreased sleep efficiency index, and increased feelings of fatigue. During the bottom period and decompression period, the total number of awakenings and the awakenings from rapid eyes movement (REM) sleep increased. This was slightly greater at the 30-m equivalent depth. From these facts, we assumed that the deterioration of sleep at the 20- and 30-m nitrox saturation dives was predominantly relative to being restricted in a closed environment for a long time and the lack of physical activity of the divers. No recovery of sleep was observed in the postdive period. A difference in the effects on sleep by the dive depth was not found.

Sleep patterns during 30-m nitrox saturation dives and in a confined atmospheric environment.

Sleep patterns during saturation dives equivalent to a 30-m depth (pressurized condition) and habitation in a confined environment at 1 atm absolute pressure (non-pressurized condition) were studied to determine the effects of environmental pressure. Eight inexperienced divers experienced the pressurized condition of the saturation dives, and nine healthy subjects experienced the non-pressurized condition. Standard polysomnographs were recorded for 262 nights. For both conditions, reductions in total sleep time accompanied by lengthening in sleep latency and reduction in sleep efficiency were observed from the latter part of the experiments through to the recovery periods. These findings suggest that changes were related to psychological and physiological stresses caused by long stays in a confined environment and not by the environmental pressure.