Epidemiology of Staphylococcus aureus during space flight

Abstract Staphylococcus aureus was isolated over 2 years from Space Shuttle mission crewmembers to determine dissemination and retention of bacteria. Samples before and after each mission were from nasal, throat, urine, and feces and from air and surface sampling of the Space Shuttle. DNA fingerprinting of samples by digestion of DNA with Sma I restriction endonuclease followed by pulsed-field gel electrophoresis showed S. aureus from each crewmember had a unique fingerprint and usually only one strain was carried by an individual. There was only one instance of transfer between crewmembers. Strains from interior surfaces after flight matched those of crewmembers, suggesting microbial fingerprinting may have forensic application.     

Mutations induced in Drosophila during space flight.

To examine the possible effects of space radiation on living organisms, fruit flies Drosophila melanogaster were loaded on the US Space Shuttle Endeavour, and after the flight we have analyzed two types of mutations, sex-linked recessive lethal mutations induced in male reproductive cells and somatic mutations which give rise to morphological changes in hairs growing on the surface of wing epidermal cells. Wild type strains and a radiation-sensitive strain mei-41 were used. The frequencies of sex-linked recessive lethal mutations in flight groups were 2 and 3 times higher for wild type Canton-S and mei-41 strains, respectively, than those in ground control groups. By contrast, the frequencies of wing-hair somatic mutations differed little between flight and control groups. The possibility that the space environment causes mutations in certain types of cells such as male reproductive cells, is discussed.     

Slide staining device for use during space flight.

A slide staining device is described that performs Gram and Wright stains during space flight. Reagents and liquid wastes are contained within a closed system.     

Permanent depression of plasma cGMP during long-term space flight

The purpose of this study was to investigate plasma concentrations of cyclic guanosine monophosphate (cGMP) and atrial natriuretic peptide (ANP) during and after real and simulated space flight. Venous blood was obtained 3 min after the beginning and 2 min after the lower body negative pressure maneuver in two cosmonauts preflight (supine), inflight, and postflight (supine) and in five other subjects before, at the end, and 4 days after a 5-day head-down tilt (-6 degrees) bed rest. In cosmonaut 1 (10 days in space), plasma cGMP fell from preflight 4.3 to 1.4 nM on flight day 6, and was 3.0 nM on the fourth day after landing. In cosmonaut 2 (438 days in space), it fell from preflight 4.9 to 0.5 nM on on flight day 3, and stayed <0.1 nM with 5, 9, and 14 months in space, as well as on the fourth day after landing. Three months after the flight his plasma cGMP was back to normal (6.3 nM). Cosmonaut 2 also displayed relatively low inflight ANP values but returned to preflight level immediately after landing. In a ground-based simulation on five other persons, supine plasma cGMP was reduced by an average of 30% within 5 days of 6 degrees head-down tilt bed rest. The data consistently demonstrate lowered plasma cGMP with real and simulated weightlessness, and a complete disappearance of cGMP from plasma during, and shortly after long-duration space flight.     

Slide staining device for use during space flight.

A slide staining device is described that performs Gram and Wright stains during space flight. Reagents and liquid wastes are contained within a closed system.     

Hemoglobin mass in humans during a space flight and its simulation

The review is a retrospective of the studies on body fluids and the hematopoietic system during long space missions and physiological simulation, in particular, the noninvasive carbon monoxide method of the determination of hemoglobin mass. The method is used to assess protein synthesis in general and the mass of the circulating blood. In microgravity, the amount of extracellular fluid, including blood plasma, hydration level, hemoglobin, and hematocrit, decrease. The number of erythrocytes also decreases, which is followed by the appearance of their abnormal forms. All these alterations are responsible for the so-called erythrocytopenic syndrome observed in microgravity. The possible factors and mechanisms of syndrome development and its dependence on the level of body hydration are discussed. The review attempts to generalize and interpret the known results and the up-to-date state of these investigations.     

Circadian rhythms of salivary cortisol content during long-term space flight

Adaptation mechanisms of adrenal function related to secretion of cortisol were studied under conditions of microgravity. Parameters of diurnal rhythms of salivary cortisol were studied by Russian cosmonauts on board orbital station Mir during long-term space flights (SF). The preflight circadian rhythms of salivary cortisol in cosmonauts were characterized by the morning maximum occurring at 9∶43 a.m., the fluctuation amplitude 6.05 nmol/1, and the daily average concentration 8.79 nmol/l. The characteristics of cortisol diurnal rhythm changed under conditions of long-term space flight. On average, the rhythm measure and amplitude decreased after two months of flight. The postflight maximum concentration of free cortisol tended to occur later in the day. Evidently, the motor activity during SF, i.e., prophylactic exercises along with other factors, significantly influenced the parameters of cortisol circadian rhythm that was revealed by the individual variability of findings during the flight. After the long-term SF, individual ratios of salivary and plasma cortisol levels increased against the background of increased plasma content of the hormone, i.e., the fraction of free, physiologically active hormone in the total pool of circulating molecules decreased.     

Ultrastructural changes in somatosensory cortex of albino rats during space flight

For the first time, mammalian brain has been studied during space flight aboard NASA orbital laboratory Spacelab-2. The main ultrastructural differences in the somatosensory cortex of the brain fixed under microgravity conditions and after landing include an increased number of degenerating presynaptic axon terminals after landing. Apparently, this is due to a sharp increase in afferent impulsation in the cortex during and after landing.     

Graviperception in the flagellate Euglena gracilis during a shuttle space flight

During a recent space flight, gravitaxis of the unicellular photosynthetic flagellate, Euglena gracilis, was studied on board of the American shuttle Columbia. Accelerations were varied between 0 and 1.5 x g using a slow rotating centrifuge microscope (NIZEMI). The cells showed a sigmoidal response curve for the dependence of the precision of gravitaxis on acceleration which is indicative of the involvement of an active, physiological gravireceptor with a threshold at g-values < or = 0.16 x g and a saturation at g-values > or = 1 x g. No adaptation to microgravity was found during the prolonged space mission. After return the cells showed a normal gravitactic behavior at 1 x g. Since the cells are heavier than water, their swimming velocity is affected by sedimentation. The velocity distribution at different accelerations closely follows Stokes' law for sedimentation indicating that, in contrast to the ciliate Paramecium, E. gracilis, does not show any gravikinesis.     

Environmental stressors during space flight: potential effects on body temperature

1. Organisms may be affected by many environmental factors during space flight, e.g., acceleration, weightlessness, decreased pressure, changes in oxygen tension, radiofrequency radiation and vibration. 2. Previous studies of change in body temperature--one response to these environmental factors--are reviewed. 3. Conditions leading to heat stress and hypothermia are discussed.     

Genomic analyses of microbial virulence

Genomic sequencing of bacterial pathogens is providing an increasing wealth of new data. It is, however, still unclear how this information can be used to develop new experimental approaches. Here, we describe recent efforts to complement existing bacterial genetics with genomic methods for the study of pathogenesis.     

Comparative analysis of preventive efficacy of different modes of locomotor training in space flight

According to the results of the experiment performed on board the International Space Station with participation of 15 Russian cosmonauts, comparative analysis of efficacy of two models of preventive measures used by the Russian members of long-term space missions is carried out: intense interval training in the aerobic–anaerobic power zone (recommended model) and continuous low-intensity exercises in the aerobic power zone of muscle activity energy supply. Interval training in space flight provided the maintenance of the level of physical performance close to the pre-flight level as indicated by the maximum running speed, physiological value of work, and the lactate level after performing the standard load. We describe putative mechanisms of counteraction to adaptive rearrangement of the propulsion system in zero gravity and expand understanding of the laws governing human body’s interaction with Earth’s gravitational field. The research results presented in this paper show the high preventive efficacy of interval training compared with regular aerobic training, which is very important now in the time of searching for means and methods of prevention of hypogravitational alterations during interplanetary missions.     

Artificial gravity in space flight

Clearly, physiologic adaptation to terrestrial life for all animals is assured only by frequent encounters with gravity. Indeed, upon exposure to weightlessness in space flight, losses of physiologic functions quickly begin. Some physiologic parameters change more rapidly than others, but the deconditioning process starts rapidly. The rates of functional losses for all affected parameters are interesting in that they appear to approach a limit; i.e., losses of these functions may not continue until indefinitely. The regulation of this functional asymptotic response to space is not known, but probably based on functional requirements of the body to life itself and perhaps genetic expression. The latter controlling mechanism (DNA) functions only on aquatic (weightless) animals on Earth--land animals must stimulate these physiologic functions as they relate to gravity on a regular frequent basis. This loss of regulation upon entering the weightless environment is fascinating since land-based animals including the humans have evolved from millions (perhaps billions) of years of terrestrially adapted ancestors. One would expect some DNA involvement in the regulation of its physiology, but it appears to be absent. Therefore, if the functional debilitation of space is to be denied, we must begin to understand the adaptation process of the sole basis for the control of our physiologic processes on land; i.e., how gravity regulates our biologic functions. To learn about this regulatory mechanism, some inquiry into how aquatic animals first adapted to living on land might be helpful.     

Heart, and peripheral arteries and veins during the 14 month MIR space flight

Ultrasound Doppler imaging and electrocardiography were used to study hemodynamic responses to spaceflight onboard the Mir space station. Cardiovascular adaptation was studied at rest and during the use of thigh cuffs or "Bracelets" for weightlessness countermeasures. Specific changes in hemodynamic parameters are presented and discussed, along with an evaluation of the effectiveness of the Bracelet countermeasures.