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Biomedical subjects

R A Nelson

Publications and source records attributed to R A Nelson.

At least 19 recordsLinked to original sources
PubMed1992

Cortisol levels during prolonged exercise: the influence of menstrual phase and menstrual status.

The purpose of this study was to determine the influence of menstrual phase and menstrual status on the cortisol response during 90 minutes of treadmill running at 60% VO2max. Eight eumenhorrheic athletes were tested in the early follicular (EF) (day 3-5), late follicular (LF) (day 13-15) and mid-luteal (ML) (day 22-24) phases. Six amenorrheic athletes were tested on two separate occasions. The resting cortisol levels were similar in each menstrual phase and overall a decreasing pattern of cortisol response to exercise was observed in all menstrual phases (P greater than .05). The amenorrheic athletes had a significantly greater (P less than .01) pattern of cortisol response than was observed in eumenorrheic athletes. The net increment in cortisol levels during exercise were distinctly greater (P less than .01) in amenorrheic than eumenorrheic athletes (amenorrheic: 413.8 +/- 113.1, eumenorrheic: EF: -482.8 +/- 88.3, LF: -311.8 +/- 102.1, ML: -386.3 +/- 146.2 nmol.l-1). In conclusion the cortisol levels are independent of menstrual phase. Also a larger cortisol increment is observed in amenorrheic athletes in response to prolonged submaximal exercise. The elevated cortisol levels in amenorrheics at rest and throughout exercise provides further evidence that disturbances in the hypothalamic-pituitary-adrenal function are associated with exercise-induced amenorrhea, although the site(s) of physiological disturbance have not been identified.

Adult↗
PubMed1992

Substrate oxidation and GH responses to exercise are independent of menstrual phase and status.

The purpose of this study was to determine the extent to which growth hormone (GH) and energy substrate utilization are influenced by basal sex steroid levels during prolonged submaximal exercise across menstrual phase and status. Also the 17 beta-estradiol (E2) and progesterone responses during prolonged exercise were compared according to menstrual phase and menstrual status. Six amenorrheic (AMc) athletes and seven eumenorrheic (EUc) athletes ran at 60% VO2max for 90 min and serial blood samples were taken at rest, every 10 min throughout exercise, and 5 and 15 min post-exercise. The EUc athletes were tested in the early follicular phase (EF) (days 3-5), the late follicular phase (LF) (days 14-16) and the mid-luteal phase (ML) (days 22-25). The incremental GH response to exercise, measured by area under the curve, was consistent with previous reposts and was not altered according to menstrual phase or status (EF-37.5 +/- 11.5, LF-61.9 +/- 11.5, ML-48.1 +/- 12.8 micrograms.1-1.90 min-1). Furthermore, carbohydrate and fat utilization during exercise were not influenced by basal sex steroid levels associated with menstrual phase or status. The incremental E2 response to exercise in AMc athletes was significantly smaller than seen in EUc athletes (AMc-208.1 +/- 44.0, EF-383.0 +/- 116.4, LF-204.7 +/- 84.1, ML-45.1 +/- 18.4 pmol.1(-1).90 min-1), although the pattern of release is similar between groups. In conclusion, GH levels and substrate utilization are independent of both menstrual phase and status; hence, menstrual phase has no negative ramifications on metabolism during exercise. Amenorrhea does not result in metabolic consequences during prolonged exercise by influencing substrate utilization.

Adolescent↗
PubMed1992

Discrepancies among predictors of desirable weight for black and white obese adolescent girls.

Desirable weights were determined for 26 black and white, postmenarchal girls (11 to 15 years old) with juvenile-onset obesity. Each subject was measured for height, weight, triceps and subscapular fatfolds, and body density by underwater weighing (UWW). Body mass indexes and desirable weights were determined by UWW, from the US National Health Examination Survey (NHES) data, and from the Slaughter fatfold equation to estimate body fat. Desirable weights obtained from NHES growth charts were consistently lower than those obtained from UWW, especially for blacks (P less than .01). Findings from both the Slaughter fatfold equation and percent body fat from UWW indicated that growth charts provide lower-than-appropriate weight goals for both black and white obese girls. Results of our study suggest that health professionals should consider a measurement of body composition or at least increase desirable weights by 10% to 30% when setting weight recommendations from weight-for-height charts for obese adolescent girls.

Adipose Tissue↗
PubMed1992

Effects of oral contraceptives on hormonal and metabolic responses during exercise.

This study examined the influence of oral contraceptives (OC) on GH and PRL responses and on energy substrate utilization during prolonged submaximal exercise in moderately active women (21-30 yr). Eight women taking OC (OC) and eight women with normal menstrual cycles (C) performed a standardized treadmill test of 90 min at 50% maximal oxygen uptake. Blood samples were withdrawn from an indwelling venous catheter during a 2-h rest period, at 10-min intervals during exercise and at 3 and 15 min of recovery. Serum concentrations of glucose, GH, PRL, E2, and P4 were assayed. Carbohydrate and fat utilization were estimated from respiratory exchange ratios. Basal serum levels of GH, PRL, and glucose were not significantly different (P greater than 0.05) between OC and C. OC had significantly higher (P less than 0.05) serum GH levels than C at 10 and 20 min of exercise, but the integrated areas for GH responses were not different (P = 0.059). Serum PRL levels significantly decreased (P less than 0.05) during exercise, and PRL responses were similar for the two groups. OC exhibited significantly lower blood glucose levels (P less than 0.05) during exercise and utilized significantly lower total grams of carbohydrate (P less than 0.05) during exercise than C. In conclusion, OC use was associated with enhanced GH responses, lower glucose levels, and diminished carbohydrate utilization during prolonged exercise. These results indicated that OC users demonstrated a greater carbohydrate-sparing ability than eumenorrheic women, which may be related to the contra-insulin effects of GH. The lower blood glucose levels, however, suggest the sparing of carbohydrate may act to compensate for decreased hepatic glucose output, similar to animal data.

Adult↗
PubMed1991

Prevalence of type I spinal muscular atrophy in North Dakota.

In order to establish the incidence and prevalence of type I spinal muscular atrophy (SMA Werdnig-Hoffmann disease) in North Dakota, we reviewed the death certificates for the past 8 years. Between 1980 and 1987 the prevalence of was 1.5 per 10,000. The incidence was 1 in 6,720. This suggests a carrier frequency of 1 in 41 in North Dakota with a gene frequency of 0.0122. In North Dakota, type I spinal muscular atrophy appears to be 3 to 10 times more common than in other locations.

Death Certificates↗
PubMed1991

Biochemical changes in skeletal muscles of denning bears (Ursus americanus).

1. Biopsies of the extensor hallucis longus (EHL) and gastrocnemius (G) muscles of four captive black bears (Ursus americanus) were obtained prior to denning (PRE), during denning (DEN) and following the Spring arousal (POST). 2. Glycogen, triglyceride and protein concentrations did not differ significantly between the three groups. Likewise, the activity of citrate synthase, a mitochondrial oxidative enzyme, was not significantly different between the three groups. 3. DNA concentrations in DEN samples increased 30% compared to other groups while RNA concentrations were significantly elevated in POST samples. The RNA/DNA ratios were significantly depressed during DEN. 4. These results suggest a degree of muscle atrophy during DEN, with the potential for an increased capacity for muscle protein synthesis following the Spring arousal.

Adaptation, Physiological↗
PubMed1991

Quantitation of energy expenditure by infrared thermography.

The objective of this study was to adapt infrared thermography (IRT) to measure heat loss in human beings. IRT images were digitized and a mean body surface temperature was computed; heat losses caused by radiation, convection, and evaporation were calculated by using these data. Because subjects were standing during the procedure a small amount of heat was conducted through the feet; this heat was ignored. Total heat loss measured by IRT was not significantly different from values calculated from simultaneous indirect calorimetry (IC) determinations in fasting health subjects and in postsurgical patients receiving a constant infusion of energy. In healthy subjects, after eating the patterns of response to IRT and IC were as predicted from previous direct calorimetry data. Heat loss measured by IC increased first, 30 min postprandially, followed by an increase in heat loss at 60 min as measured by IRT. It was concluded that IRT as a noninvasive method can be used to quantitate heat loss in human beings.

Adult↗
PubMed1991

Development and use of statistical survey criteria for release of materials at a former uranium processing facility.

To minimize the amount of waste and to recover reusable resources during demolition of radioactively contaminated facilities, building construction material and equipment can be efficiently and successfully surveyed using statistical methods described in this article. A radioactive contamination survey strategy aimed at reducing survey technician labor while still providing assurance that only uncontaminated material is released for salvage is discussed. Provided is the survey method, rationale, and results of three case studies where this method was successfully employed at a former uranium processing facility.

Construction Materials↗
PubMed1991

Menière's disease: an immune complex-mediated illness?

The cause of Menière's disease is unknown. Recent clinical research suggests that one etiology is immune-mediated damage to the inner ear. The diagnosis of autoimmune Menière's syndrome is largely based on history, response to steroids, or results of nonspecific laboratory tests such as serological studies. Polyethylene glycol (PEG) assay was used to determine levels of circulating immune complexes (CIC) in 30 patients with Menière's disease and 20 control subjects. Patients with Menière's disease had a statistically significant elevation of serum circulating immune complexes when compared to the control group. This suggests that CICs may be involved in the pathogenesis of Menière's disease, either as a direct cause of damage, or as a by-product of an underlying autoimmune abnormality. Therapeutic implications include use of plasmapheresis to remove the complexes or CIC monitoring to serve as a marker for treatment efficacy.

Adult↗
PubMed1990

Applications of thin layer chromatography, high performance liquid chromatography and mass spectrometry in the fermentation and isolation of the antibiotic nybomycin.

Thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and mass spectrometry (MS) methods have been developed for the analysis of the antibiotic nybomycin, its derivatives deoxynybomycin and nybomycin acetate, during the fermentation and isolation of nybomycin. Using a quantitative HPLC based assay, the time course of nybomycin production (nybomycin titers) in 1000 liter fermentations was determined. Desorption chemical ionization mass spectrometry (DCI/MS) of standard nybomycin samples, fermentation broth samples and purified fractions suggested the co-production of deoxynybomycin which was not reported previously from this organism. TLC and HPLC were used to confirm the presence of deoxynybomycin in the crude extracts of fermentation broths.

Anti-Bacterial Agents↗
PubMed1990

Seasonal serum urea-creatinine ratios in wild and captive American badgers, Taxidea taxus.

1. Blood samples were taken from 22 American badgers in the field during different seasons and analysed for urea and creatinine. 2. The urea-creatinine ratio (U/C) of these animals did not decrease during the winter as previously reported for black bears. This suggests that the badger, unlike the bear, does not demonstrate a winter physiological state of protein conservation. 3. This may be the consequence of intermittent ingestion of protein by the badger during the winter, or due to biochemical mechanisms unique to the bear which allows for protein turnover and resynthesis. 4. Captive badgers fasted in the laboratory during the winter also did not exhibit lower U/C ratios and protein catabolism, compared to a summer fast, thereby supporting the latter hypothesis that badgers do not have an adjustment in protein catabolism during the winter season.

Animals↗
PubMed1990

Membrane transport of sodium ions in erythrocytes of the American black bear, Ursus americanus.

1. Membrane transport of Na ions was investigated in red blood cells of bears by methods of measurement of unidirectional isotopic fluxes. 2. Like red blood cells of dogs, bear red cells contain a high Na concentration and low concentrations of K and ATP. 3. As in dog red cells, Na efflux from bear cells was not inhibited by ouabain but was activated by the presence of Ca in the medium, possibly indicating the presence of a Na-Ca exchange mechanism. 4. ATP depletion of cells was accelerated by Ca in the medium, consistent with the presence of a strong ATP-dependent Ca pump. 5. As in other carnivore red cells, Na influx into bear cells was strongly activated by shrinkage and inhibited by swelling. Shrinkage-activated influx was blocked by amiloride. 6. Amiloride-sensitive influx was activated by cytoplasmic Ca and also correlated with the presence of a Na-dependent, amiloride-sensitive H loss. 7. Amiloride-sensitive Na influx exhibited a strong seasonal cycle with a minimum in the middle of the hibernation period, suggesting a possible avenue of cellular energy conservation.

Animals↗
PubMed1990

Membrane transport of potassium ions in erythrocytes of the American black bear, Ursus americanus.

1. Membrane transport of K ions was investigated in red blood cells of bears by methods of measurement of unidirectional isotopic fluxes. 2. Unlike red cells of dogs, red cells of bears exhibited a significant, though small, component of ouabain-sensitive K influx. 3. Ouabain-insensitive K influx, as in other carnivore cells, was activated by swelling and inhibited by shrinkage. Swelling-induced K influx was dependent upon presence of chloride ions but was not inhibited by furosemide or bumetanide. 4. Ouabain-sensitive K influx was largest with ATP and with high concentration of Na in the cell, but it persisted in the absence of cytoplasmic Na or ATP. It was also resistant to the drug, harmaline, at a concentration that in other cells fully inhibits ouabain-sensitive K influx. 5. It was concluded that under such adverse conditions ouabain-sensitive K influx represents another mode of the Na/K pump not fully described elsewhere. 6. Also, as in low K red cells of sheep and goat, apparent absence of Na/K pump activity in carnivore red cells may represent suppression rather than elimination of activity. 7. Ouabain-insensitive K influx showed a seasonal pattern with minima occurring in early winter, earlier than for the minimum observed in Na influx. 8. Ouabain-sensitive K influx tended to be lower in the hibernation season of the bear, but the seasonal pattern was not consistent.

Adenosine Triphosphate↗
PubMed1990

Respiratory distress syndrome and tracheoesophageal fistula: management with high-frequency ventilation.

An 1180-g infant with esophageal atresia and tracheoesophageal fistula developed life-threatening respiratory distress syndrome. Conventional mechanical ventilation resulted in gastric perforation and pneumoperitoneum. High-frequency ventilation stabilized the infant, permitting distal occlusion of the esophagus with a Silastic band. Fistula ligation was subsequently performed under more optimal physiologic conditions.

Esophageal Atresia↗
PubMed1990

Auditory brain stem implant: effect of tumor size and preoperative hearing level on function.

The auditory brain stem implant is an investigational device designed to provide hearing sensations to patients without functioning auditory nerves. We analyzed results from 17 implants in 15 patients to determine if tumor size or preoperative hearing level might be related to proper device function. We found no significant correlation between preoperative hearing level or tumor size and device function. We also found no significant correlation between preoperative hearing level and tumor size in these 15 patients.

Adolescent↗
PubMed1990

Calcium and bone metabolic homeostasis in active and denning black bears (Ursus americanus).

Decreased mechanical use of the skeleton results in osteoporosis in all species that have been studied, including humans. The unique metabolic adaptations of denning bears, however, suggest that these animals have evolved osteoregulatory mechanisms to protect against osteoporosis. The authors studied calcium and bone metabolism in black bears during three seasons: summer, winter, and spring. The serum calcium concentration did not change despite the fact that the bears remained metabolically active, recumbent, and anuric for four months. Furthermore, after four months of skeletal inactivity, bone mass and other parameters of osseous metabolism, including bone formation and mineral apposition rates were unchanged over summer values. A hypermetabolic state was observed after spring arousal in response to resumed skeletal loading. These findings suggest that bears may produce an osteoregulatory mechanism that prevents bone loss during prolonged periods of skeletal inactivity. Such a substance could have potential therapeutic applications for human beings.

Adaptation, Physiological↗
PubMed1990

The case for dietary management of the older hypertensive.

If the expense or side effects of antihypertensive drug therapy become a serious problem, dietary therapy can be a worthwhile option. The dietary prescription for treatment of hypertension usually involves modifications in energy, fat, and minerals. Weight, blood cholesterol, and triglycerides should be controlled through dietary management. Sodium's effect on blood pressure is controversial and not clearly defined; however, sodium restriction is usually prescribed for hypertensive patients because of potential benefits. Other minerals that may affect blood pressure include potassium and calcium. Good dietary intake of both minerals has been associated with lowered blood pressure. An accompanying scenario illustrates the effectiveness of dietary management.

Aged↗