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Biomedical subjects

R A Nelson

Publications and source records attributed to R A Nelson.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1989

Relationship of client participation to psychotherapy.

Dimensions of client participation in psychotherapy were assessed to investigate whether participation is unidimensional or multidimensional, stable over therapy, and/or related to measures of psychotherapy outcome. Participation dimensions included compliance with scheduling (lateness, rescheduling, no-show) and with homework assignments (completion of a daily diary and relaxation home-practice), reported acceptance of the credibility of therapy rationale, satisfaction with global and specific aspects of therapy, expectation of personal improvement in anxiety symptomatology, self-rated engagement in therapy activities, and reported judgments about therapist characteristics and relationship qualities. Outcome measures included assessor ratings, daily client self-report of anxiety severity, and questionnaire measures. Subjects were 30 clients participating in a 12-session generalized anxiety disorder comparative treatment study in which they receive progressive relaxation training plus either cognitive therapy or nondirective therapy. Across clients in both treatment groups, behavioral compliance measures were poorly intercorrelated and unrelated to the other participation measures. Canonical correlation of participation variables with change on pre-post outcome measures showed a significant relationship between some participation variables representing satisfaction with specific aspects of therapy and the therapeutic relationship and improvement in daily level of subjective anxiety.

Anxiety Disorders↗
PubMed1988

Treatment and follow-up of obesity in adolescent girls.

An intervention program was conducted for 12 postmenarche, 12-15-year-old obese girls. Weight Winners, a multicomponent and multidisciplinary after-school intervention program, was developed in which behavior modification, aerobic exercise, and modeling appropriate behaviors for weight control were emphasized. Evaluation made before and immediately after the intervention and at a nine-month follow-up suggested that the after-school treatment program was successful in: 1) reducing the rate of gain and decreasing body weight by 11% while maintaining lean tissue and resting energy expenditure (REE), and 2) improving eating and exercise behaviors. Significant changes in eating behaviors (p less than 0.05) were: more low-calorie, nutritionally dense foods were consumed; the frequency and amount eaten decreased; and the speed of eating slowed. Implementing a fee contingent on attendance and on record keeping appeared to reduce attrition. Subjects cited the Weight Winners program, aerobic exercise, changes in eating behaviors, group and family support, and encouragement and praise from the group leaders as important contributions to their success in weight control. Barriers to change were reported by participants as boredom, hunger, lack of family and peer support, and having food in sight. An increase in lean tissue was associated with both improved self-esteem (p less than 0.05) and improved self-control (p less than 0.05). Subjects who had been obese the longest were the most responsive to hunger cues (p less than 0.05).

Adolescent↗
PubMed1988

Annual changes in serum sex steroids in male and female black (Ursus americanus) and polar (Ursus maritimus) bears.

The adaptation of black and polar bears to their environments is proportional to the severity of climate and food restriction. Both black and polar bears mate during the spring, despite differences in their recent metabolic state. Reproductive activity in black bears follows 4 mo of torpor, whereas reproduction in polar bears occurs prior to torpor. The goals of this study were to measure the annual changes in serum sex steroids in male and female black and polar bears, and to determine if changes in serum levels of these steroids were associated with metabolic condition or photoperiod. Serum testosterone (T) concentrations were elevated during spring in black and polar bears. Moreover, this increase in serum T in polar bears during spring was correlated with age and testis size. Serum progesterone (P4) concentrations increased in pregnant polar bears in fall coincident with the time of expected implantation. No increases in serum P4 were observed in nonpregnant black and polar bears. Serum estradiol (E2) was elevated in nonpregnant and pregnant polar bears 2 mo prior to the time of expected implantation. We found that serum sex steroids measured in black and polar bears change independent of torpor. Therefore, our results suggest that photoperiod may be a more important regulator of serum steroid levels and reproduction than metabolic condition.

Animals↗
PubMed1988

Effects of electrolyte and nutrient solutions on performance and metabolic balance.

Three commercial sport drinks, solutions of their individual minerals and glucose, and water were used to maintain water balances in six men during 4 h of physical activity in a 35 degrees C room. Each solution was provided for 5 consecutive days to each man during the 12-wk study. Complete mineral and water balances (including sweat losses) were conducted. Oxygen consumption and carbon dioxide production were measured during two levels of sub-maximal and during a maximal treadmill performance test. All of the solutions, including water, were equally effective in maintaining water and mineral balances, and moderate physical performance while the men were consuming an adequate all liquid diet. All of the solutions containing carbohydrates increased respiratory exchange ratios. These increases were significant during maximal performance for only two of the commercial products. These two products also produced the higher values for most of the performance evaluations, although they were not generally significantly different from values obtained while other solutions or water were consumed. The major benefit of these commercial sport drinks are their prevention of hypohydration due to an increase in voluntary fluid intakes.

Adult↗
PubMed1988

Studies on the biosynthesis of the antibiotic crisamicin A and carbon-13 magnetic resonance assignments.

The biosynthesis of crisamicin A, a novel dimeric isochromanequinone antibiotic from Micromonospora purpureochromogenes subsp. halotolerans has been investigated by [1-13C] and [2-13C] labeled acetate precursor feeding experiments. Analysis of the proton noise decoupled and off resonance 13C NMR spectra of 13C enriched and unenriched crisamicin A and their acetate derivatives indicated the biosynthesis via the polyketide pathway, as expected. Further analysis of the enriched spectra allowed the complete assignment of the carbon signals. Of particular interest was the establishment of the linkage between the two monomeric halves of the molecule and determination of the location of the phenolic hydroxyls.

Anti-Bacterial Agents↗
PubMed1988

Blood chemistry of black bears from Pennsylvania during winter dormancy.

Twenty-four serum chemistries were measured in blood samples collected from 20 adult female black bears (Ursus americanus) and their offspring, including 14 yearlings and 37 cubs, in northeastern Pennsylvania during winter 1984. Four other captive adult females were bled before, during, and after they were subjected to unseasonably warm temperatures during February. Levels of serum urea nitrogen (SUN) and creatinine were lower (P less than 0.05), and iron was higher (P less than 0.05) in male cubs compared to female cubs; serum chemistries were similar (P greater than or equal to 0.05) between sexes for yearlings. Total protein, albumin and creatinine levels increased with age of bears, whereas chloride, alkaline phosphatase, potassium, inorganic phosphorus and SUN/creatinine were higher (P less than 0.05) in cubs than in yearlings and adults. The relatively high serum calcium in cubs was probably related to rapid bone development and dietary intake of calcium during winter dormancy in cubs. Low serum calcium in adults was attributed to lactation and a lack of dietary intake. Urea/creatinine ratios averaged 5.5 and 4.6 for yearling females and males, respectively, 6.3 for adult females, and 29.0 and 22.8 for female and male cubs, respectively. Levels of serum chemistries of black bears apparently are relatively stable during winter denning, when bears are without food or water and do not urinate or defecate for several months. This stability indicates that black bears are resistant to the extremes in extrinsic environmental conditions. Abnormal blood chemistry values may indicate metabolic stresses that are not being controlled by bears.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Measurement uncertainties of long-term 222Rn averages at environmental levels using alpha track detectors.

More than 250 replicate measurements of outdoor Rn concentration integrated over quarterly periods were made to estimate the random component of the measurement uncertainty of Track Etch detectors (type F) under outdoor conditions. The measurements were performed around three U mill tailings piles to provide a range of environmental concentrations. The measurement uncertainty was typically greater than could be accounted for by Poisson counting statistics. Average coefficients of variation of the order of 20% for all measured concentrations were found. It is concluded that alpha track detectors can be successfully used to determine annual average outdoor Rn concentrations through the use of careful quality control procedures. These include rapid deployment and collection of detectors to minimize unintended Rn exposure, careful packaging and shipping to and from the manufacturer, use of direct sunlight shields for all detectors and careful and secure mounting of all detectors in as similar a manner as possible. The use of multiple (at least duplicate) detectors at each monitoring location and an exposure period of no less than one quarter are suggested.

Air Pollutants↗
PubMed1987

Human leukocytic antigens in autoimmune sensorineural hearing loss.

Susceptibility to many autoimmune diseases is associated with inheritance of certain Human Leukocytic Antigens (HLA), determinants which have become diagnostic or prognostic markers. In this study of HLA antigen frequencies among patients with autoimmune sensorineural hearing loss, 39 patients with this otologic disorder were typed for HLA-A, B, C, and DR antigens. A significant increase of Cw7 occurred in 51% of patients compared to 21% of 627 matched controls (relative risk, 3.95). Trends towards increased frequencies of Cw4, B35 and reduced frequency of DR4 were also observed. These data suggest a possible immunogenetic predisposition to this otologic disorder. The presence of Cw7 may facilitate the diagnosis of autoimmune sensorineural hearing loss.

Adolescent↗