Publications by authors named "Smith Johnston"

Background: Insulin resistance affects a substantial proportion of patients with rheumatoid arthritis (RA). Skeletal muscle mitochondrial dysfunction results in the accumulation of lipid intermediates that interfere with insulin signaling. We therefore sought to determine if lower oxidative phosphorylation and muscle mitochondrial content are associated with insulin resistance in patients with RA.

View Article and Find Full Text PDF

For over 50 yr, investigators have studied the physiological adaptations of the human system during short- and long-duration spaceflight exposures. Much of the knowledge gained in developing health countermeasures for astronauts onboard the International Space Station demonstrate terrestrial applications. To date, a systematic process for translating these space applications to terrestrial human health has yet to be defined.

View Article and Find Full Text PDF

Study Objectives: Prescription sleep aids are frequently used in the general population and even more frequently in spaceflight. To evaluate the risk to operational safety, a ground-based, double-blind, placebo-controlled study on the emergent awakening effects of zolpidem and zaleplon was conducted.

Methods: N = 34 participants (age M = 42.

View Article and Find Full Text PDF

Purpose: Cancer survivors are at greater risk of comorbidities and functional decline due to physiological and psychological stress which can be measured by salivary cortisol. If saliva is used, multiple samples must be collected to accurately quantify long-term stress; however, fingernail (FN) and toenail (TN) clippings offer an opportunity to measure retrospective cortisol levels in a non-invasive manner.

Methods: Three sets of FN and TN clippings were collected at 12-month intervals in conjunction with saliva samples from cancer survivors (n = 109) participating in two clinical trials.

View Article and Find Full Text PDF

Background: The environment of spaceflight may elevate an astronaut's clinical risk for specific diseases. The purpose of this study was to derive, as accurately as currently possible, an assessment of in-flight clinical "incidence" data, based on observed clinical symptoms in astronauts on board the International Space Station (ISS).

Methods: Electronic medical records were examined from 46 long-duration ISS crew members, each serving approximately a 6-month mission on board the ISS, constituting 20.

View Article and Find Full Text PDF

The measurement of bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) is the Medical Assessment Test used at the NASA Johnson Space Center to evaluate whether prolonged exposure to spaceflight increases the risk for premature osteoporosis in International Space Station (ISS) astronauts. The DXA scans of crewmembers' BMD during the first decade of the ISS existence showed precipitous declines in BMD for the hip and spine after the typical 6-mo missions. However, a concern exists that skeletal integrity cannot be sufficiently assessed solely by DXA measurement of BMD.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

Unlabelled: This report documents the effects of photorefractive keratectomy (PRK) in an astronaut during a 12-day Russian Soyuz mission to the International Space Station in 2008. Changing environmental conditions of launch, microgravity exposure, and reentry create an extremely dynamic ocular environment. Although many normal eyes have repeatedly been subject to such stresses, the effect on an eye with a relatively thin cornea as a result of PRK has not been reported.

View Article and Find Full Text PDF

Introduction: Astronauts have complained of back pain occurring during spaceflight, presumably due to the elongation of the spine from the lack of gravity. Herniated nucleus pulposus (HNP) is known to occur in aviators exposed to high Gz and has been diagnosed in several astronauts in the immediate post-spaceflight period. It is unknown whether astronauts exposed to microgravity are at added risk for developing HNP in the post-spaceflight period due to possible in-flight intervertebral disc changes.

View Article and Find Full Text PDF
Article Synopsis
  • NASA's "Vision for Space Exploration" program, initiated in 2004, plans for long-duration missions to the Moon and Mars, necessitating advanced preflight medical screenings to reduce disease risks in space.
  • Countermeasures like artificial gravity and current techniques from the International Space Station aim to combat health issues during these missions, especially concerning the unknown effects of radiation exposure.
  • Missions, particularly to Mars, will require autonomous medical systems due to long isolation periods, with a focus on including medical personnel and basic surgical capabilities within the crew.
View Article and Find Full Text PDF

Introduction: The medical community of the International Space Station (ISS) has developed joint medical standards and evaluation requirements for Space Flight Participants ("space tourists") which are used by the ISS medical certification board to determine medical eligibility of individuals other than professional astronauts (cosmonauts) for short-duration space flight to the ISS. These individuals are generally fare-paying passengers without operational responsibilities.

Material And Context: By means of this publication, the medical standards and evaluation requirements for the ISS Space Flight Participants are offered to the aerospace medicine and commercial spaceflight communities for reference purposes.

View Article and Find Full Text PDF

Manned spaceflight is inherently risky and results in unique problems from a trauma and medical perspective. Emergency care under these special physiologic and environmental conditions calls for novel techniques for diagnosis and therapy.

View Article and Find Full Text PDF

Introduction: The International Space Station will need to be as capable as possible in providing Advanced Cardiac Life Support (ACLS) and cardiopulmonary resuscitation (CPR). Previous studies with manikins in parabolic microgravity (0 G) have shown that delivering CPR in microgravity is difficult. End tidal carbon dioxide (PetCO2) has been previously shown to be an effective non-invasive tool for estimating cardiac output during cardiopulmonary resuscitation.

View Article and Find Full Text PDF

Background: Medical operations on the International Space Station will emphasize the stabilization and transport of critically injured personnel and so will need to be capable of advanced trauma life support (ATLS).

Methods: We evaluated the ATLS invasive procedures in the microgravity environment of parabolic flight using a porcine animal model. Included in the procedures evaluated were artificial ventilation, intravenous infusion, laceration closure, tracheostomy, Foley catheter drainage, chest tube insertion, peritoneal lavage, and the use of telemedicine methods for procedural direction.

View Article and Find Full Text PDF