Aviation, space, and environmental medicine最新文献

Background: Operational environments expose pilots and astronauts to sustained acceleration (G loading) and whole-body vibration, alone and in combination. Separately, the physiological effects of G loading and vibration have been well studied; both have effects similar to mild exercise. The few studies of combined G loading and vibration have not reported an interaction between these factors on physiological responses.

Methods: We tested the effects of G loading (+1 and +3.8 G(x)) and vibration (0.5 gx at 8, 12, and 16 Hz), alone and in combination, on heart and respiration rate.

Results: We observed an effect of G loading on heart rate (average increase of 23 bpm, SD 12) and respiration rate (average increase of 5 breaths per minute, SD 5), an effect of vibration on heart rate, and an interaction on heart rate. With vibration, we observed heart rate increases of 4 bpm (SD: 3) with no increase in respiration rate. In the +1 G(x) condition, the largest heart rate increase occurred during low-frequency (8 Hz) vibration, while at +3.8 G(x), the largest heart rate increase occurred during high-frequency (16 Hz) vibration, demonstrating interaction.

Discussion: Consistent with previous reports, our G-loading and vibration effects are similar to mild exercise. In addition, we observed an interaction between G loading and vibration on heart rate, with maximum heart rates occurring at a higher vibration frequency at +3.8 G(x) compared to +1 G(x). The observed interaction demonstrates that G-loading and vibration effects are not independent and can only be properly assessed during combined exposure.

Background: General aviation accidents involving children are rare, but when they do happen, little is known about the children involved, including their age, restraint status, and injuries. This lack of information is due to the fact that the National Transportation Safety Board (NTSB) did not always collect detailed data about passengers involved in accidents.

Methods: Consequently, in 2011, NTSB investigators collected detailed information on children involved in general aviation accidents and this report provides a summary of the outcomes.

Results: During 2011, 19 general aviation accidents and incidents included 39 children who were 14 yr old and younger. In total, 26 children sustained fatal injuries, 2 sustained serious injuries, 5 sustained minor injuries, and 6 sustained no injuries. All of the children less than 2 yr old were restrained in a child restraint system and sustained no injuries in the accidents.

Discussion: At least one 4-yr-old child would have benefited from being restrained in a child restraint system. In addition, in two accidents, it was determined that children were likely sharing a single seat belt. This year-long data collection regarding children involved in general aviation accidents provided substantial information concerning age, restraint status, and injuries. In response to issues identified, the NTSB made improvements to its aviation data management system to routinely collect this information for future investigations and enable subsequent evaluation of the data regarding child passengers involved in general aviation accidents over the long term.

Introduction: Reliable culturing methods for primary articular chondrocytes are essential to study the effects of loading and unloading on joint tissue at the cellular level. Due to the limited proliferation capacity of primary chondrocytes and their tendency to dedifferentiate in conventional culture conditions, long-term culturing conditions of primary chondrocytes can be challenging. The goal of this study was to develop a suspension culturing technique that not only would retain the cellular morphology, but also maintain the gene expression characteristics of primary articular chondrocytes.

Methods: Three-dimensional culturing methods were compared and optimized for primary articular chondrocytes in the rotating wall vessel bioreactor, which changes the mechanical culture conditions to provide a form of suspension culture optimized for low shear and turbulence. We performed gene expression analysis and morphological characterization of cells cultured in alginate beads, Cytopore-2 microcarriers, primary monolayer culture, and passaged monolayer cultures using reverse transcription-PCR and laser scanning confocal microscopy.

Results: Primary chondrocytes grown on Cytopore-2 microcarriers maintained the phenotypical morphology and gene expression pattern observed in primary bovine articular chondrocytes, and retained these characteristics for up to 9 d.

Discussion: Our results provide a novel and alternative culturing technique for primary chondrocytes suitable for studies that require suspension such as those using the rotating wall vessel bioreactor. In addition, we provide an alternative culturing technique for primary chondrocytes that can impact future mechanistic studies of osteoarthritis progression, treatments for cartilage damage and repair, and cartilage tissue engineering.

Introduction: U.S. astronauts undergo extensive job-related screening and medical examinations prior to selection in order to identify candidates optimally suited for careers in spaceflight. Screening medical standards evolved over many years and after extensive spaceflight experience. These standards assess health-related risks for each astronaut candidate, minimizing the potential for medical impact on future mission success. This document discusses the evolution of the Shuttle-era medical selection standards and the most common reasons for medical dis-qualification of applicants.

Methods: Data for astronaut candidate finalists were compiled from medical records and NASA archives from the period of 1978 to 2004 and were retrospectively reviewed for medically disqualifying conditions.

Results: During Shuttle selection cycles, a total of 372 applicants were disqualified due to 425 medical concerns. The most common disqualifying conditions included visual, cardiovascular, psychiatric, and behavioral disorders. During this time period, three major expert panel reviews resulted in refinements and alterations to selection standards for future cycles.

Discussion: Shuttle-era screening, testing, and specialist evaluations evolved through periodic expert reviews, evidence-based medicine, and astronaut medical care experience. The Shuttle medical program contributed to the development and implementation of NASA and international standards, longitudinal data collection, improved medical care, and occupational surveillance models. The lessons learned from the Shuttle program serve as the basis for medical selection for the ISS, exploration-class missions, and for those expected to participate in commercial spaceflight.

Introduction: Anxiety and psychological concerns may pose a challenge to future commercial spaceflight. To help identify potential measures of anxiousness and indicators of flight-related stress, the psychiatric histories and anxiousness responses of volunteers exposed to G forces in centrifuge-simulated spaceflight acceleration profiles were examined.

Methods: Over 2 d, 86 individuals (63 men, 23 women), 20-78 yr old, underwent up to 7 centrifuge runs. Day 1 consisted of two +G(z) runs (peak = +3.5 G(z)) and two +Gx runs (peak = +6.0 G(x)). Day 2 consisted of three runs approximating suborbital spaceflight profiles (combined +G(x) and +G(z)). Hemodynamic data were collected during the profiles. Subjects completed a retrospective self-report anxiety questionnaire. Medical monitors identified individuals exhibiting varying degrees of anxiousness during centrifuge exposure, medical histories of psychiatric disease, and other potential indicators of psychological intolerance of spaceflight.

Results: The retrospective survey identified 18 individuals self-reporting anxiousness, commonly related to unfamiliarity with centrifuge acceleration and concerns regarding medical history. There were 12 individuals (5 men, 7 women, average age 46.2 yr) who were observed to have anxiety that interfered with their ability to complete training; of these, 4 reported anxiousness on their questionnaire and 9 ultimately completed the centrifuge profiles. Psychiatric history was not significantly associated with anxious symptoms.

Discussion: Anxiety is likely to be a relevant and potentially disabling problem for commercial spaceflight participants; however, positive psychiatric history and self-reported symptoms did not predict anxiety during centrifuge performance. Symptoms of anxiousness can often be ameliorated through training and coaching. Even highly anxious individuals are likely capable of tolerating commercial spaceflight.

Background: The Mars-105 project was aimed at simulating crew's activities, workload, and communication during a mission to Mars, evaluating the homeostatic adaptations to prolonged confinement and cohabitation.

Methods: Fasting plasma glucose (FPG) and insulin, C-peptide, leptin, cortisol, and NGF and BDNF plasma levels were monitored in six healthy nonsmoking male subjects taking part in a 105-d Mars mission simulation. Samples were collected from each subject before (0 wk), during (2.5 wk; 5 wk; 10 wk; 15 wk), and after confinement (+1 wk).

Results: Confinement resulted in impaired glucometabolic parameters, since FPG increased during the first 5 wk (baseline: 85.2 ± 10.8 mg · dl⁻¹; 2.5 wk: 98.4 ± 4.7 mg · dl⁻¹; 5 wk: 92.5 ± 6.0 mg · dl⁻¹) and insulin dropped at 2.5 wk (baseline: 14.4 ± 4.8 mU · L⁻¹; 2.5 wk: 7.7 ± 2.1 mU · L⁻¹), subsequently returning to baseline values. HOMA-IR paralleled plasma insulin, dropping to 1.8 ± 0.5 at 2.5 wk (baseline: 3.0 ± 1.2). At all time-points tested, plasma leptin levels were decreased (baseline: 4.4 ± 3.3 ng · dl⁻¹; 2.5 wk: 1.6 ± 1.2 ng · dl⁻¹; 5 wk: 1.3 ± 0.8 ng · dl⁻¹; 10 wk: 1.5 ± 1.1 ng · dl⁻¹; 15 wk:1.7 ± 0.8 ng · dl⁻¹), whereas cortisol levels were increased (baseline: 10.8 ± 4.9 ng · dl⁻¹; 2.5 wk: 16.8 ± 3.5 ng · dl⁻¹; 5 wk: 18.1 ± 7.6 ng · dl⁻¹; 10 wk: 18.1 ± 8.3 ng · dl⁻¹; 15 wk:14.2 ± 4.4 ng · dl⁻¹), resulting in a negative correlation between these hormones. BDNF levels increased only at 5 and 10 wk (baseline: 67.1 ± 36.0 pg · ml⁻¹; 5 wk: 164 ± 54 pg · ml⁻¹; and 10 wk: 110.2 ± 28.9 pg · ml⁻¹).

Discussion: The data obtained with the Mars-105 experiment suggest that environmental stress has a strong impact upon metabolic and stress response, indicating the need for further studies and the implementation of specific countermeasures.