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Biomedical subjects

C S Leach

Publications and source records attributed to C S Leach.

At least 19 recordsLinked to original sources
PubMed1978

Stress levels of ambulance paramedics and fire fighters.

Responses to Rahe and job stress questionnaires and urinary concentrations of cortisols and catecholamines served to indicate work related stress in 56 fire fighters and 67 paramedics. Although the average Rahe test scores, indicative of stress arising from life events, were comparable, those of the job stress test were statistically significantly higher for the paramedics. The paramedics felt their jobs more exhausting, less satisfying and requiring too much responsibility. For the paramedics, statistically significant higher levels of epinephrine and elevated levels of norepinephrine were found for the work as compared to the off day. For fire fighters, higher levels of cortisol and norepinephrine evident on the off day rather than the work day apparently reflect the relatively light work load experienced during the span of urine collections.

Adult↗
PubMed1978

Evaporative water loss in man in a gravity-free environment.

Daily evaporative water losses (EWL) during the three Skylab missions were measured indirectly using mass and water-balance techniques. The mean daily values of EWL for the nine crew members who averaged 1 h of daily exercise were: preflight 1,750 +/- 37 (SE) ml or 970 +/- 20 ml/m2 and inflight 1,560 +/- 26 ml or 860 +/- 14 ml/m2. Although it was expected the EWL would increase in the hypobaric environment of Skylab (one-third atmosphere). an average decrease from preflight sealevel conditions of 11% was measured. The results suggest that weightlessness decreased sweat losses during exercise and possibly reduced insensible skin losses as well. The weightlessness environment apparently promotes the formation of an observed sweat film on the skin surface during exercise by reducing convective flow and sweat drippage, resulting in high levels of skin wettedness that favor sweat suppression.

Body Water↗
PubMed1977

Observations in energy balance in man during spaceflight.

An investigation was undertaken of the changes in metabolic energy balance which occur in weightlessness. Daily energy intake was determined each day throughout the 28-, 59-, and 84-day flights for each of the nine Skylab astronauts. The energy content of the urine and feces was also measured. Changes in body composition were inferred from measurements of weight, volume, water, and total exchangeable potassium before and after flight. During flight changes were followed by a daily measurement of body mass and by metabolic balance. Examination of the data reveal losses in body weight during the 1st and 2nd mo of flight, a loss in body water and protein during the 1st mo, and a loss of fat during the 1st, 2nd, and 3rd mo of flight. The energy input was about 41.7 kcal/kg per day on the ground, and 43.7 kcal/kg per day after 3 mo in space. The increase in net energy input of about 1.6% per mo is significant (P less than 0.05). When the net energy input is expressed on the basis of total body potassium, the increase in the resulting "noramlized" net energy input of about 3.7% per mo is also significant (P less than 0.05).

Body Composition↗
PubMed1977

Nutrition and responses to zero gravity.

Prior to the Mercury program, extensive efforts were undertaken to find ways of minimizing the mass of in-flight food systems. Such efforts were directed to the use of dehydrated, energy-dense foodstuffs and to the possibilities of nutrient recyclization. As the space program became a reality, nutritional scientists were more concerned with the mechanics of food consumption in weightless flight and with the problems of structuring convention foods in a way that would facilitate their use in weightlessness. It soon became clear that there was no substantial impediment to normal gastrointestinal function in flight, and attention was shifted to more subtle metabolic phenomenons. It became apparent that slight changes occurred in skeletal density, muscle mass, and overall body composition. Recognition of these changes led to extensive ground-based simulation studies and carefully designed in-flight experiments. Data are presented on the requirements for metabolic energy in flight and on the losses that have been observed in the major elemental constituents of the body. It is concluded that convincing evidence is not yet avialable on the ability of man to adapt to long-term weightless flight. Although his nutritional requirements are qualitatively similar during flight, the sophisticated manipulation of nutrient profiles shows promise of counteracting some of the deteriorative processes that are known to occur.

Aerospace Medicine↗
PubMed1977

The urinary excretion of collagen degradation products by quadriplegic patients and during weightlessness.

Urinary total hydroxyproline, peptide-bound hydroxyproline, hydroxylysine glycosides, and calcium were measured in three healthy individuals subjected to weightlessness for eighty-four days and in three young quadriplegic patients. The former group had significant calciuria but no evidence of collagen degradation. The latter group, however, had conspicuous calciuria and also excreted large amounts of collagen breakdown products. This documented degradation of matrix may be related to the continuous calciuria, osteoporosis, and cutaneous dystrophic changes occurring in quadriplegics.

Calcium↗
PubMed1977

Prolonged weightlessness effect on postflight plasma thyroid hormones.

Blood drawn before and after spaceflight from the nine Skylab astronauts showed a statistically significant increase in mean plasma thyroxine (T-4) of 1.4 microgram/dl and in thyroid-stimulating hormone (TSH) of 4 muU/ml. Concurrent triiodothyronine (T-3) levels decreased 27 ng/dl indicating inhibited conversion of T-4 to T-3. The T-3 decrease is postulated to be a result of the increased cortisol levels noted during and following each mission. These results confirm the thyroidal changes noted after the shorter Apollo flights and show that thyroid hormone levels change during spaceflight.

Cholesterol↗
PubMed1976

Metabolic and endocrine studies: the second manned Skylab mission.

This study conducted on the crewmembers of Skylab 3 was designed to evaluate the endocrinological adaption resulting from extend exposure to a space flight environment by identifying changes in hormonal and associated fluid and electrolyte parameters. The three men served as their own controls and were on a constant dietary intake. Complete metabolic collections were performed beginning 21 d before the flight, continuing throughout the flight, for 18 d postflight. Changes in fluid and electrolyte balance have been correlated with weight loss, changes in the excretion of aldosterone, vasopressin, and fluid compartments. Inter-individual variability was demonstrated in most experimental indices measured; however, statistically significant patterns have emerged which include: decreases in body weight and ADH, increases in plasma renin activity, and elevations in urinary catecholamines, aldosterone and cortisol concentrations. Urinary sodium was increased in flight but potassium was only slightly changed. Total body exchangeable K was slightly decreased in all three of the crewmen. Total body water and extracellular fluid were decreased postflight in almost all cases. The measured changes are consistent with the prediction that a relative increase in thoracic blood volume upon transiton to the zero gravity environment is interpretated as a true volume expasion resulting in a net fluid loss. This, in association with other factors, ultimately results in a reduction in intravascular volume leading to an increase in renin and a secondary aldosteronism. Once these compensatory mechanisms are effective in reestablishing positive water balance, the crewemn are considered to be essentially adapted to the space environment. Although the physiological cost of this adaptation must reflect the electrolyte deficit and perhaps other factors, it is assumed that the compensated state is adequate for the demands of the environment; however, this new homeostatic set is not believed to be without physiological cost and could, except with proper precautions, reduce the functional reserve of exposed individuals.

Adrenocorticotropic Hormone↗
PubMed1976

Changes in glucose, insulin, and growth hormone levels associated with bedrest.

Changes in plasma glucose, insulin, and growth hormone (HGH) resulting from exposure to 56 d of bedrest were determined in five healthy young male subjects. Blood samples were collected by repeated venous puncture at 4-h intervals for 48-h periods before bedrest, at 10, 20, 30, 42 and 54 d after confinement to bed and at 10 and 20 d after bedrest. Changes in the daily levels of these factors for each subject were expressed as the mean of the six samples per 24-h period. The level of HGH dropped after 10 d of bedrest, then showed a 1.5-fold increase at 20 d (p less than 0.05) and subsequently decreased gradually reaching levels of 2.5 mg/ml/24 h, well below pre-bedrest controls of 4.2 mg/ml/24 h, by the 54th d. In spite of a marked increase in the daily plasma insulin levels during the first 30 d of bedrest, glucose levels remained unchanged. Beyond 30 d of bedrest, insulin began decreasing toward pre-bedrest levels and glucose followed with a similar reduction to below the control levels of 75 mg/100 ml/24 h on day 54. The daily mean changes reflect a change in the amplitude of the diurnal variation. The daily peak in plasma insulin shifted progressively to the late evening during the bedrest period.

Adult↗
PubMed1975

Acomparative study of two methods of urine preservation.

In preparation for the conduct of biochemical experiments in the Skylab Orbital Workshop a study was performed on the stability of various chemical constituents in urine in 2 different techniques for preservation and storage. Urine samples were either vacuum dried or frozen and maintained in storage at minus 20 degrees for periods of up to 10 weeks. The urinary constituents studied included aldosterone, antidiuretic hormone, epinephrine, norepinephrine, urea, nitrogen, creatine, hydroxyproline, 17-hydroxycorticosteroids, calcium, sodium potassium, chloride, magnesium and phosphate. Some degradation of urinary compounds was observed after both treatments. The rate and variability of destruction following the vacuum drying treatment, however, was greater than for freezing. It was concluded that only the freezing treatment could be used to preserve with predictable loss the urinary samples which would be returned to earth following the conclusion of each Skylab flight.

Aldosterone↗
PubMed1975

Calcium and phosphorus change of the Apollo 17 crew members.

In association with the 12.6-day lunar flight of Apollo 17, calcium and phosphorus intake and excretion were determined for the crew members before and during the mission. The study showed increased urinary and fecal phosphorus and increased fecal calcium during weightlessness. The calculated mean calcium "loss" for the three crew members was 0.2 percent of estimated total body calcium and phosphorus "loss" was 0.7 percent of estimated total body phosphorus. The ratio of phosphorus lost compared to calcium indicated a reduction in both bone and soft tissue. These changes may be attributed not only to the hypogravia of the lunar and circumlunar environment, but possibly also to disturbances in gastrointestinal absorption.

Bone and Bones↗
PubMed1975

Plasma thyroxine changes of the Apollo Crewman.

Blood drawn from Apollo crew member; to the mission, at recovery, and postmission was used to examine the effect Apollo mission activities have on tyroid hormone levels. At recovery, statistically significant increases in thyroxine and the free thyroxine index were found. Serum cholesterol and triglycerides were decreased. No change of statistical significance was found in the T3 binding percentage, total serum proteins, and albumin. We conclude that apollo activities and environment caused the postmission increase in serum cholesterol may be one result of the increased thyroxine activity.

Aerospace Medicine↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: appendix III. evaluation of viscera and other tissues.

Histopathological findings in the lungs, livers, bone marrows, small intestines, gonads, kidneys, and other tissues of the four pocket mice (Perognathus longimembris) that survived the Apollo XVII flight were evaluated in the light of their immediate environment and as targest of HZE cosmic ray particles. Results of this study failed to disclose changes that could be ascribed to the HZE particle radiation. Decreased numbers of erythropoietic cells in the bone marrow of the flight mice were probably related to the increased oxygen pressure. The small intestine showed no changes. Ovaries and tests appeared normal. Two of the three surviving male flight mice displayed early stages of spermatogenesis, just as ground-based controls did at the same season. Abnormalities were also not found in the thyroid, parathyroids, adrenals, or kidneys. The status of the juxtaglomerular apparatus could not be evaluated. The lungs exhibited nonspecific slight rections. A variety of incidental lesions were noted in the livers of both the flight mice and their controls. The heart muscle showed nothing that could be regarded as pathological. Sections of skeletal muscle examined were free from significant change.

Adrenal Cortex↗