PubMed Health⌕ Search

Biomedical subjects

N Pace

Publications and source records attributed to N Pace.

At least 37 records · Page 2Linked to original sources
PubMed1983

Effects of weightlessness on body composition in the rat.

Five male rats were exposed to 18.5 days of weightlessness in the Soviet mission COSMOS 1129 (flight group) and killed after reentry. They were immediately dissected into three major body subdivisions: musculoskeletal system, skin, and pooled viscera analyzed for fat, water, solids, and six elements. These results, expressed as percentages of the fat-free body or its components, were compared with two groups of terrestrial controls: one subjected to a flight simulation in a spacecraft mock-up and the other under standard vivarium conditions. Relative to the control groups the flight group showed 1) a reduced fraction of total body water, 2) a net shift of body water from skin to viscera, 3) a marked diminution in fraction of extracellular water in the fat-free body, 4) a marked reduction in fraction of bone mineral, 5) no change in the quantity of stored fat or adrenal masses, and 6) a net increase in total muscle mass as indicated by total body creatine, protein, and body cell mass.

Adipose Tissue↗
PubMed1983

Evaluation of a Reverse Gradient Garment for prevention of bed-rest deconditioning.

A Reverse Gradient Garment (RGG) was used to intermittently induce venous pooling in the extremities of a magnitude similar to that seen in going from a lying to standing position during the course of a 15-d period of horizontal bed rest. Venous pooling failed to improve bed-rest-induced losses in +2.5 Gz and +3.0 Gz centrifugation tolerance or to prevent increased heart-rate responses to lower-body negative pressure (LBNP). Four subjects served as controls, four were treated. Tests during the 7-d recovery period showed fluid/electrolyte and body composition values to have returned to pre-bed-rest levels with continued depression of acceleration tolerance times (56% decreased at +2.5 Gz and 74% decreased at +3.0 Gz compared to pre-bed-rest levels) and exaggerated blood insulin response on glucose tolerance testing (blood insulin for treated group increased 95% at 1 h before bed rest and 465% during recovery). This study demonstrates that the physiologic changes after bed rest persist for significant periods of time. Acceleration tolerance time proved to be a sensitive test for the deconditioning process.

Acceleration↗
PubMed1982

Worksite-based behavioral treatment of mild hypertension.

Two behaviorally-oriented, nonpharmacological treatments - rational-emotive therapy/assertiveness training (RET/AT) and anxiety management training (AMT) - and one control treatment - hypertension education counseling (HEC) - were compared in reducing blood pressures of 22 white-collar mold hypertensives in a worksite setting. Results showed significant reductions by posttreatment in diastolic pressures of participants in the two behavioral treatment conditions, but no significant differential treatment effect across groups. Systolic pressure reductions by postreatment were significant only in the RET/AT training condition. Reductions were generally maintained at an either-week follow-up.

Adult↗
PubMed1980

Energy status and oxidation-reduction status in rat liver at high altitude (3.8 km).

Adult male rats were exposed to 3.8-km altitude for intervals ranging from 1 h-60 d. Liver samples were taken under light ether anesthesia and were examined by enzymatic analyses. Within 1-6 h of hypoxic exposure, ATP levels decreased while ADP and AMP levels increased, producing a fall in calculated ATP/ADP and adenylate charge ratios. Concurrently, lactate/pyruvate and alpha-glycerophosphate/dihydroxyacetone phosphate ratios increased markedly. Direct measurements of cellular pyridine nucleotides indicated increased NADH/NAD and NADPH/NADP ratios. Levels of total adenosine phosphates and pyridine nucleotides decreased in a significant accompanying response. Many metabolite levels and calculated ratios returned to near-normal values within 1 week of exposure, indicating secondary intracellular adjustments to hypoxic stress; however, persistence of that stress is reflected in lactate concentrations and both substrate redox ratios. Results support and explore concepts that increased oxidation-reduction status and decreased energy status are primary events during hypoxia.

Adenosine Diphosphate↗
PubMed1980

Distribution of gene frequencies and discrimination probabilities for 22 human blood genetic systems in four racial groups.

Gene frequencies were computed in four racial categories from 5956 blood donors from California, Hawaii, Mexico City, and Texas. Calculations were based on the phenotypic distribution of 22 blood genetic systems including 7 blood groups and 15 genetically controlled polymorphic proteins and enzymes. Matching probabilities for 20 systems were approximately 1 in 100 000 Asians, 1 in 200 000 blacks, 1 in 330 000 Mexicans, and 1 in 1 000 000 whites. The complementary discrimination probability, which measures the likelihood that two random individuals do not match, was, for practical purposes, unity. The combined new technology for blood grouping and electrophoresis using cellulose acetate membranes provides a powerful individualizing and discriminating tool for forensic science investigation.

Alanine Transaminase↗
PubMed1980

Energy status and oxidation-reduction status in rat liver at high altitude (3.8 km).

Adult male rats were exposed to 3.8-km altitude for intervals ranging from 1 h-60 d. Liver samples were taken under light ether anesthesia and were examined by enzymatic analyses. Within 1-6 h of hypoxic exposure, ATP levels decreased while ADP and AMP levels increased, producing a fall in calculated ATP/ADP and adenylate charge ratios. Concurrently, lactate/pyruvate and alpha-glycerophosphate/dihydroxyacetone phosphate ratios increased markedly. Direct measurements of cellular pyridine nucleotides indicated increased NADH/NAD and NADPH/NADP ratios. Levels of total adenosine phosphate and pyridine nucleotides decreased in a significant accompanying response. Many metabolite levels and calculated ratios returned to near-normal values within 1 week of exposure, indicating secondary intracellular adjustments to hypoxic stress; however, persistence of that stress is reflected in lactate conentrations and both substrate redox ratios. Results support and explore concepts that increased oxidation-reduction status and decreased energy status are primary events during hypoxia.

Adenine Nucleotides↗
PubMed1979

Continuous metabolic and cardiovascular measurements on a monkey subject during a simulated 6-day Spacelab mission.

In May 1977 the NASA Ames Research Center and NASA Johnson Space Center jointly conducted a test of the feasibility of performing various types of biological and medical experiments during future Spacelab flight missions. One of the experiments was designed to examine the effects of weightlessness on several basic parameters of metabolic and cardiovascular function in an adult nonhuman primate. The subject animal, a 10 kg male pig-tailed monkey (Macaca nemestrina), was prepared 3 months before the test with a surgically implanted NASA/Ames biotelemetry unit to provide continuous measurements of body temperature and selected cardiovascular parameters. Three days before the simulated "launch" the animal was inserted into a fiberglass pod system to provide continuous measurement of respiratory gas exchange. The pod system was installed in a Spacelab mock-up and all physiological data channels were recorded continuously for 2.6 days prior to "launch", for 6.3 days during "flight", and for 1.8 days after "landing". The experiment was tended entirely by the Spacelab flight crew during the "flight" period. Statistically significant diurnal variation was noted in oxygen consumption and carbon dioxide production rates, body temperature and heart rate, but not in respiratory quotient or blood pressure. A transient increase of the parametric values was noted during the latter portion of the "flight" period, possibly occasioned by increased flight crew activity. The high quality of the continuous data obtained during the 10.7-day total experiment period demonstrates the feasibility of performing sound physiological experimentation on nonhuman primates in the Spacelab environment.

Adaptation, Physiological↗
PubMed1979

Racial classifications based on blood group protein systems.

Two methods employing frequencies of blood group phenotypes are assessed as methods of accurately classifying individuals into racial categories. The data used consist of eleven blood group protein systems from 5043 males distributed into four ethnic categories (white, black, Chicano/Amerindian, and Asian). Both methods work equally well and yield a rate of misclassification of about 22%. Also included is a discussion of two probabilistic calculations relevant to employing blood group protein systems in the context of an identification tool.

Asian People↗
PubMed1978

Changes in the body composition of monkeys during long-term exposure to high acceleration fields.

Adult, 10-14 kg, male pig-tailed monkeys (Macaca nemestrina) were subjected to continuous centrifugation for 7 months in acceleration fields up to 2.5 g. Several major parameters of body composition, body-fluid distribution, and hematology were evaluated at various levels of high g by in vivo analytical techniques. Statistically significant decreases in total body mass, lean body mass, total body water, extracellular water content and interstitial water content proportional to the level of high g were also demonstrated. Body cell mass, total body fat, dry body mass, lean body solids, and red cell volume did not change significantly. Significant decreases in red cell count, blood hemoglobin level and venous hematocrit value accorded with the plasma volume and red cell volume findings. Total plasma protein concentration did not change significantly. The results indicate a substantial loss of total body mass in the form of body water. The loss apparently occurred from the interstitial spaces of the body in the face of a sizeable increase in plasma volume. Physiological significance of the body composition and fluid distribution changes at high g is discussed and compared to the changes described for astronauts at low g. Current theory of fluid-balance physiology favors the concept that interstitial volume and blood volume are tightly coupled and change in the same direction. However, it appears that the changes which occur where the ambient acceleration field is varied may represent an exception to the general hypothesis for the regulation of the extracellular fluid volume.

Acceleration↗
PubMed1978

Frequency distribution and discrimination probability of twelve protein genetic variants in human blood as functions of race, sex, and age.

Fresh blood samples were obtained from 6004 whites, 1025 blacks, 1596 Chicano/Amerindians, and 3053 Asians of California and Hawaii. The samples were typed for ABO and Rh groups and were analyzed electrophoretically for ten genetically determined protein variant systems. The effects of race, age, and sex on phenotypic frequencies within each of the twelve genetic systems were investigated. Large frequency differences were found between races but not between different age and sex subgroups within races. It was also demonstrated that the twelve genetic systems behaved statistically independently. Discrimination probabilities were computed for each of the four ethnic groups. These serve as a measure of the effectiveness of the twelve genetic systems examined in individualizing blood samples. The method is discussed for computing the probability that a randomly chosen individual of a given ethnic group possesses the same blood phenotypes as found in a predetermined sample of blood. The results presented here should prove useful in the investigation of civil and criminal cases involving blood samples.

ABO Blood-Group System↗
PubMed1977

Effects of growth, diving history, and high altitude on blood oxygen capacity in harbor seals.

Blood volume and body composition measurements were carried out on diving and nondiving harbor seals, Phoca vitulina. There were small, statistically significant differences in several red blood cell parameters between diving and nondiving seals, but the effect was superimposed on uniformly large blood volumes ranging from 11 to 12% of body weight found in all the animals. It is suggested that the large blood oxygen transport and storage capacity is not so much a direct result of the apneic diving experience, but an expression of phylogenetic control. The development of blood volume during early growth was closely related to the increase in lean body mass. In spite of the inherently large blood volume, this marine mammal when exposed to high altitude for 85 days at an elevation of 3.1 km above sea level appeared to exhibit typical mammalian erythropoietic and ventilatory responses to long-term, mild hypoxia. Thus, it probably cannot be considered to be preacclimatized to high altitude.

Age Factors↗
PubMed1977

Continuous 30-day measurements utilizing the monkey metabolism pod.

We have previously described a fibreglass pod system which makes possible quantitative physiological measurements to study the effects of weightlessness on 10-14-kg adult monkeys maintained in comfortable restraint under space flight conditions. Recent improvements in the system have allowed continuous measurements to be made of respiratory gas exchange, cardiovascular function, and mineral balance for periods of up to 30 days on pig-tailed monkeys. It has also been possible to operate two pods which share one set of instrumentation, thereby permitting simultaneous measurements to be made on two animals by commutating signal outputs from the pods. In principle, more than two pods could be operated in this fashion. The system is compatible with Spacelab design. Representative physiological data from ground tests of' the system are presented.

Adaptation, Physiological↗