Health challenges including behavioral problems in long-duration spaceflight.

Over the past 60 years, our ability to live and work in space has evolved. From short sojourns in small spacecraft to landing on the moon and residing in an orbiting international space station, we have learned to adapt to an extreme environment and safely return home. Human missions to the Moon, Mars, and exploration of deep space are different. This paper summarizes the challenges of providing medical care, specifically mental health care during long-duration flights. Considerable information about challenges that crews bound for Mars will face is available. Literature regarding this issue is summarized. This manuscript provides a short historical summary of long-duration spaceflight to date; the challenges including limited communication with mission controllers on Earth; and, a summary of the behavioral impacts space flight has had on humans. A look at how the future autonomous systems might support physical and mental health when definitive care is millions of miles away, is also provided. Human spaceflight to Mars or other distant sites will require new approaches to mission preparedness and inflight medical support systems. Exploration class missions will be more autonomous than anything deployed until now. The concepts of telemedicine that have aptly supported crews from the 1960s to the present will no longer be in real-time. While communication between Earth and Mars is possible, it will be characterized by significant time delays. Mars-based crews will need to have systems onboard and on Mars to support all health and performance issues.

Atrazine Transport through a Soil-Epikarst System.

Row crop and livestock production contaminate soils and groundwater of the karst aquifers within south-central Kentucky's Pennyroyal Plateau. Transport of atrazine from field application to the epikarstic drainage system beneath a field with active row-crop farming was investigated. The Crumps Cave study site is a shallow autogenic drainage system with a recharge area of ∼1 ha that contains two epikarst drains (WF-1 and WF-2) which were monitored for atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA) concentrations from January 2011 to May 2012. Atrazine concentrations in both drains did not increase above winter background levels for nearly 2 mo after application when levels suddenly spiked and reached peak concentrations for the study during an event in May 2011. Atrazine, DEA, and DIA were detected in 100% of samples, and metabolites accounted for 54 to 94% of the monthly total loads, except in May 2011. Median dealkylated metabolite/atrazine ratios (DMAR) were ∼5:1 at both sites, and seasonal DMAR patterns corresponded with changes in soil temperature. These data support the hypothesis that a combination of sorption and degradation in the soil column above the epikarst controlled the transport of atrazine and its metabolites. This resulted in delayed atrazine transport after application and prolonged transport of atrazine and its weakly sorbed metabolites to the epikarst aquifer. Management practices that reduce herbicide inputs, such as diverse crop rotations, cover crops, and use of low-rate and strong-sorbing herbicides, would improve groundwater quality in areas of the Corn Belt with intensive row cropping on karst topography.

Online health-searching behavior among HIV-seropositive and HIV-seronegative men who have sex with men in the Baltimore and Washington, DC area.

BACKGROUND: Searching online for health information is common among American adults. However, there have been few studies to investigate the online health-searching behaviors among men who have sex with men (MSM) with human immunodeficiency virus (HIV). OBJECTIVE: To estimate the prevalence of Internet use among HIV-seropositive MSM and compare their online behaviors with HIV-seronegative men with chronic disease(s). METHODS: This study was performed at the Baltimore/Washington, DC site of the Multicenter AIDS Cohort Study (MACS). A total of 200 MACS participants were asked to answer a self-administered questionnaire on a first-come basis during a semiannual study visit (from July to November 2011); 195 (97.5%) participants completed the survey. Multiple logistic regression models were used to investigate the factors influencing their online health-searching behaviors. RESULTS: The median age of the 195 MSM participants was 57 years, 64.6% were white, 59.0% were employed, and 88.2% had Internet access at home and/or other locations. Of the 95 HIV-seropositive participants, 89.5% currently used highly active antiretroviral therapy (HAART) and 82.1% had Internet access. After adjusting for age and race/ethnicity, the HIV-seropositive participants were less likely to perform online searches for general disease-related information compared to the HIV-seronegative men with chronic disease(s) (OR 0.20, 95% CI 0.06-0.68, P=.01). There were no statistically significant associations with HIV status and searching for new medications/treatments (OR 0.55, 95% CI 0.19-1.55, P=.26) or support/advice from other patients (OR 0.52, 95% CI 0.18-1.53, P=.24). Increasing age by 5 years led to a decrease by 29% in the odds of online health-related searches for general information (OR 0.71, 95% CI 0.52-0.98, P=.03) and 26% for support/advice from other patients (OR 0.74, 95% CI 0.56-0.98, P=.03). A decrease of 25% for new medications/treatments was also seen, but was not statistically significant (OR 0.75, 95% CI 0.57-1.01, P=.06). CONCLUSIONS: This study shows that HIV-seropositive MSM have similar online health-searching behaviors as HIV-seronegative men with chronic disease(s). Independent of HIV status, older MSM are less likely to perform online health-related searches.

Prophylactic surgery prior to extended-duration space flight: is the benefit worth the risk?

This article explores the potential benefits and defined risks associated with prophylactic surgical procedures for astronauts before extended-duration space flight. This includes, but is not limited to, appendectomy and cholecystesctomy. Furthermore, discussion of treatment during space flight, potential impact of an acute illness on a defined mission and the ethical issues surrounding this concept are debated in detail.

A pilot study to evaluate the effect of splanchnic nerve stimulation on body composition and food intake in rats.

BACKGROUND: Systemic sympathetic stimulation with caffeine and ephedrine increased metabolic rate, reduced food intake, and improved body composition but had systemic adverse events. We hypothesize that selective sympathetic stimulation of the upper gastrointestinal tract will preserve the advantages of systemic sympathetic stimulation without its adverse events. This study evaluated the effect of splanchnic nerve stimulation on metabolic rate, food intake, and body composition. METHODS: Sixteen Sprague Dawley rats had monopolar electrodes placed on the superior common splanchnic nerve innervating the celiac ganglia. An indifferent electrode was placed subcutaneously on the back. The animals were placed on a 60% fat diet, and eight rats were stimulated for 6 weeks. The stimulation was advanced over 3 days from 0.6 mA to 3 mA. Metabolic rate and food intake were measured daily; weight change was monitored weekly, and body composition was determined by nuclear magnetic resonance (NMR) at the end of the study. Four of the eight animals had metabolic rate measured three times over 2-day periods at 0 mA, 1 mA, and 3 mA of stimulation in a metabolic chamber. RESULTS: Except for the first week of stimulation, there was no difference in body weight between the stimulated and control groups. Cumulative food intake was less in the stimulated group (p<0. 001). The lean-to-fat ratio was greater in the stimulated group (p<0. 01), and the animals that received incremental stimulation showed significantly augmented metabolic rate (p<0. 02). CONCLUSIONS: Splanchnic nerve stimulation decreased food intake, increased metabolic rate, and improved body composition.

Scanning optical pyrometer for measuring temperatures in hollow cathodes.

Life-limiting processes in hollow cathodes are determined largely by the temperature of the electron emitter. To support cathode life assessment, a noncontact temperature measurement technique which employs a stepper motor-driven fiber optic probe was developed. The probe is driven inside the hollow cathode and collects light radiated by the hot interior surface of the emitter. Ratio pyrometry is used to determine the axial temperature profile. Thermocouples on the orifice plate provide measurements of the external temperature during cathode operation and are used to calibrate the pyrometer system in situ with a small oven enclosing the externally heated cathode. The diagnostic method and initial measurements of the temperature distribution in a hollow cathode are discussed.

Forelimb and hindlimb forces in walking and galloping primates.

One trait that distinguishes the walking gaits of most primates from those of most mammalian nonprimates is the distribution of weight between the forelimbs and hindlimbs. Nonprimate mammals generally experience higher vertical peak substrate reaction forces on the forelimb than on the hindlimb. Primates, in contrast, generally experience higher vertical peak substrate reaction forces on the hindlimb than on the forelimb. It is currently unclear whether this unusual pattern of force distribution characterizes other primate gaits as well. The available kinetic data for galloping primates are limited and present an ambiguous picture about peak-force distribution among the limbs. The present study investigates whether the pattern of forelimb-to-hindlimb force distribution seen during walking in primates is also displayed during galloping. Six species of primates were video-recorded during walking and galloping across a runway or horizontal pole instrumented with a force-plate. The results show that while the force differences between forelimb and hindlimb are not significantly different from zero during galloping, the pattern of force distribution is generally the same during walking and galloping for most primate species. These patterns and statistical results are similar to data collected during walking on the ground. The pattern of limb differentiation exhibited by primates during walking and galloping stands in contrast to the pattern seen in most nonprimate mammals, in which forelimb forces are significantly higher. The data reported here and by Demes et al. ([1994] J. Hum. Evol. 26:353-374) suggest that a relative reduction of forelimb vertical peak forces is part of an overall difference in locomotor mechanics between most primates and most nonprimate mammals during both walking and galloping.

Trabecular bone in the bird knee responds with high sensitivity to changes in load orientation.

Wolff's law of trajectorial orientation proposes that trabecular struts align with the orientation of dominant compressive loads within a joint. Although widely considered in skeletal biology, Wolff's law has never been experimentally tested while controlling for ontogenetic stage, activity level, and species differences, all factors that may affect trabecular bone growth. Here we report an experimental test of Wolff's law using a within-species design in age-matched subjects experiencing physiologically normal levels of bone strain. Two age-matched groups of juvenile guinea fowl Numida meleagris ran on a treadmill set at either 0 degrees (Level group) or 20 degrees (Incline group), for 10 min per day over a 45-day treatment period. Birds running on the 20 degrees inclined treadmill used more-flexed knees than those in the Level group at midstance (the point of peak ground reaction force). This difference in joint posture enabled us to test the sensitivity of trabecular alignment to altered load orientation in the knee. Using a new radon transform-based method for measuring trabecular orientation, our analysis shows that the fine trabecular bone in the distal femur has a high degree of correspondence between changes in joint angle and trabecular orientation. The sensitivity of this response supports the prediction that trabecular bone adapts dynamically to the orientation of peak compressive forces.

Influences of limb proportions and body size on locomotor kinematics in terrestrial primates and fossil hominins.

During locomotion, mammalian limb postures are influenced by many factors including the animal's limb length and body mass. Polk (2002) compared the gait of similar-sized cercopithecine monkeys that differed limb proportions and found that longer-limbed monkeys usually adopt more extended joint postures than shorter-limbed monkeys in order to moderate their joint moments. Studies of primates as well as non-primate mammals that vary in body mass have demonstrated that larger animals use more extended limb postures than smaller animals. Such extended postures in larger animals increase the extensor muscle mechanical advantage and allow postures to be maintained with relatively less muscular effort (Polk, 2002; Biewener 1989). The results of these previous studies are used here to address two anthropological questions. The first concerns the postural effects of body mass and limb proportion differences between australopithecines and members of the genus Homo. That is, H. erectus and later hominins all have larger body mass and longer legs than australopithecines, and these anatomical differences suggest that Homo probably used more extended postures and probably required relatively less muscular force to resist gravity than the smaller and shorter-limbed australopithecines. The second question investigates how animals with similar size but different limb proportions differ in locomotor performance. The effects of limb proportions on gait are relevant to inferring postural and locomotor differences between Neanderthals and modern Homo sapiens which differ in their crural indices and relative limb length. This study demonstrates that primates with relatively long limbs achieve higher walking speeds while using lower stride frequencies and lower angular excursions than shorter-limbed monkeys, and these kinematic differences may allow longer-limbed taxa to locomote more efficiently than shorter-limbed species of similar mass. Such differences may also have characterized the gait of Homo sapiens in comparison to Neanderthals, but more experimental data on humans that vary in limb proportions are necessary in order to evaluate this question more thoroughly.

Adaptive and phylogenetic influences on musculoskeletal design in cercopithecine primates.

Broad allometric studies of the musculoskeletal system have frequently sought to explain how locomotor variables have been influenced by body mass. To examine animals that vary widely in body mass, these studies have included taxa that differ in their locomotor adaptations and phylogenetic relatedness. Because these sources of diversity could obscure the effects of body mass, this study was designed to test the effects of adaptive differences in limb proportions and phylogeny, as well as body mass, on locomotor kinematics and extensor muscle mechanical advantage. More specifically, two hypotheses were tested in a sample of closely related animals: (i) that, among animals with similar body mass, those with longer limb segments should adopt more extended limb postures to moderate the joint and midshaft bending moments that they experience, and (ii) that body mass will have similar influences on joint posture and joint moments in closely related and diverse mammalian samples. Three-dimensional kinematic and synchronous force-platform data were collected for six individual cercopithecine monkeys ranging in mass from 4kg to 24kg and at a range of walking speeds. Comparisons among three monkeys with similar body mass but different limb segment lengths reveal a significant effect of limb proportion on posture. That is, animals with longer limbs frequently use more extended limb postures and can have correspondingly lower joint moments. The scaling of locomotor variables across the entire sample of closely related monkeys was generally similar to published results for a diverse sample of mammals, with larger monkeys having more extended limb postures, lower joint moments and greater effective mechanical advantage (EMA) for their limb extensor musculature. Ankle EMA, however, did not increase with body mass in the primate sample, suggesting that clade-specific adaptive differences (e.g. the use of arboreal supports by primates) may constrain the effects of body mass.

Central retinal artery occlusion by proxy: a cause for sudden blindness in an airline passenger.

The use of gas media in ophthalmologic procedures is relatively commonplace. Scleral buckle and pneumatic retinopexy procedures using air-gas mediums are a widely accepted treatment for retinal detachment. We present a patient who had a scleral buckle with pneumatic retinopexy performed and subsequently flew in a commercial airliner 2 wk later. The patient experienced sudden blindness due to central retinal artery occlusion brought about by expansion of the air bubble when the aircraft reached cruise altitude and a cabin pressure of 8000 ft. The intraocular pressure exceeded the central artery pressure thereby collapsing the artery. The patient's symptoms were relieved when an onboard flight surgeon identified the problem and the cabin pressure was reset to 2000 ft. Flying after an ophthalmic procedure that incorporates intraocular gas may have complications due to the bubble expansion in accordance with Boyle's Law. The ophthalmologic surgeon must be diligent in forewarning patients of the potential complications of flying for weeks to months after a procedure that utilizes intraocular gas.