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Biomedical subjects

R Dudley

Publications and source records attributed to R Dudley.

26 records · Page 2Linked to original sources
PubMed1995

Rebound severe methemoglobinemia from ingestion of a nitroethane artificial-fingernail remover.

We describe life-threatening methemoglobinemia in a child who ingested a nitroethane artificial-fingernail remover initially mistaken to be an acetone-based polish remover. Nitroethane-induced methemoglobinemia may be delayed and recurrent; patients ingesting this substance may warrant close observation for at least 24 hours. Care givers are cautioned to determine the precise substance involved in ingestions of potentially toxic fingernail products.

Cosmetics↗
PubMed1995

Extraordinary flight performance of orchid bees (Apidae: Euglossini) hovering in heliox (80% He/20% O2)

Limits to insect flight performance are difficult to evaluate because the full range of aerodynamic capabilities cannot be easily elicited or controlled. Invasive experimental manipulations, such as tethering and weight addition, may adversely affect the biomechanics of the flight system as a whole. Because air density is a major determinant of aerodynamic force production, gas mixtures of variable density can be used to investigate insect flight performance non-invasively. Three species of orchid bee hovering in heliox (80 % He/20 % O2) exhibited dramatic increases in lift and power output relative to flight in normal air. Stroke amplitude increased significantly in heliox, while wingbeat frequency was unchanged; the Reynolds numbers of the wings decreased on average by 41 %. Although lift performance of airfoils generally degrades at lower Reynolds numbers, mean lift coefficients in heliox increased significantly relative to values for hovering in normal air. Mean muscle mass-specific power output for flight in heliox mixtures ranged from 130 to 160 W kg-1, substantially exceeding values determined from isolated asynchronous muscle preparations as well as limits postulated from the results of load-lifting experiments. The use of variable-density gas mixtures to examine animal flight performance is a simple yet powerful manipulation that will permit a new evaluation of both insect and vertebrate flight mechanics.

Journal Article↗
PubMed1995

Oxandrolone therapy in constitutionally delayed growth and puberty. Bio-Technology General Corporation Cooperative Study Group.

BACKGROUND: Male adolescents with constitutional delay of growth and puberty may have significant psychosocial difficulties related to their sexual immaturity and short stature. The purpose of this study was to test the hypothesis that 1 year of oxandrolone therapy would increase growth velocity and thereby improve psychosocial functioning in boys with constitutional delay of growth and pubertal development. METHODS: Forty boys (ages 11 to 14.7 years) with delayed pubertal development and short stature were recruited from the pediatric endocrine clinics of 14 medical centers. The boys were randomized using a block design stratified for age to receive either oxandrolone (0.1 mg/kg daily for 1 year) or an identical-appearing placebo tablet, using a double-masked design. RESULTS: Growth velocity in the oxandrolone-treated boys was significantly greater than in the control boys (9.5 vs 6.8 cm/y). Likewise, the mean height SD score increased 0.41 in the oxandrolone group, whereas it decreased 0.03 in the control group. Those in the oxandrolone group gained 2.4 kg more than those in the placebo group. Mean predicted adult heights did not change in either group. The mean rates of pubertal progression were equivalent in both groups. Self-image (Piers-Harris Self Concept Scale) and social competence (Child Behavior Profile) were normal at baseline in both groups and did not change significantly over the course of the study in either group. No complications of oxandrolone therapy were identified. CONCLUSIONS: This randomized, placebo-controlled trial demonstrates that low-dose oxandrolone can increase both height and weight velocity in boys with delayed puberty safely. Under the conditions of this study, however, the increased growth velocity in the oxandrolone-treated boys was not associated with a greater improvement in psychosocial status compared with the control boys.

Adolescent↗
PubMed1994

FLIGHT PHYSIOLOGY OF NEOTROPICAL BUTTERFLIES: ALLOMETRY OF AIRSPEEDS DURING NATURAL FREE FLIGHT

Airspeed measurements during natural free flight were made on a total of 270 neotropical butterflies representing 62 species. Morphological data were obtained from the same individuals for which airspeeds had been determined. Flight speed was positively correlated with body mass, thoracic mass and wing loading. Controlling for body mass, higher wing loadings were correlated with increased flight speed. Flight speed and wing aspect ratio were negatively correlated. No consistent correlations were found between airspeed and wing length, wing area or body length. Released butterflies and butterflies encountered in natural free flight did not differ substantially in flight speed allometry. The observed scaling of flight speeds was similar to that derived for a much smaller sample of butterflies flying in an insectary, although absolute values of flight speed were approximately three times higher in natural flight and correlation coefficients of allometric regressions were typically lower. These results suggest that butterfly airspeeds under natural conditions can reasonably be predicted from morphological measurements, and that studying flight in enclosed spaces preserves the allometry of flight speeds.

Journal Article↗
PubMed1992

Contrasting leaf phenotypes control seasonal variation in water loss in a tropical forest shrub.

Psychotria marginata, a shrub common to humid tropical forests in Central America, produces leaves in two seasonal flushes with contrasting morphology and physiology. Leaf production is bimodal with a major peak at the beginning of the annual wet season and a secondary peak at the end of the wet season. Together these peaks account for 75-87% of annual leaf production. Leaves produced just prior to the dry season have higher specific mass and, during drought, have lower stomatal conductances and higher water-use efficiencies. Plants irrigated during two consecutive dry seasons continued to produce leaves with these morphological and physiological differences, indicating that this feature has been strongly canalized by some factor other than water availability in this highly predictable yet seasonal habitat. The bimodal leaf production results in acclimation to changing conditions through co-occurring leaves that lack the physiological plasticity usually associated with acclimation. Heterophylly of this form suggests that the moderate drought of the dry season has been a significant selective factor for understory plants.

Journal Article↗
PubMed1986

Adenosine modulation of fat cell responsiveness to insulin and oxytocin.

We have investigated the effects of adenosine on the stimulation of glucose oxidation and lipogenesis by oxytocin and insulin in rat epididymal adipocytes. The addition of adenosine deaminase (1 U/ml) to the assay medium reduced the maximal oxytocin response (glucose oxidation and lipogenesis) to between 25 and 50% of the maximum response in control cells. The maximal response to insulin was not appreciably affected under these conditions. The addition of adenosine (10 or 30 microM) increased the cell sensitivity to oxytocin by elevating the maximum rate of oxytocin-stimulated glucose metabolism. Adenosine also increased the cell sensitivity to insulin by decreasing its ED50. A change in ED50, however, was observed only when control or adenosine-treated cells were compared to adenosine deaminase-treated cells; but not when control and adenosine-treated cells were compared. On its own, adenosine also caused an appreciable increase in both glucose oxidation and lipogenesis (ED50 approximately equal to 3 microM adenosine). The difference in the effect of adenosine on oxytocin action, compared with the effect on insulin action, points to differences in the mechanisms by which insulin and oxytocin stimulate glucose metabolism in adipocytes.

Adenosine↗
PubMed1978

Who supports public employees strikes?

This research found that strikes by public employees are most likely to be tolerated by younger people, by citizens who feel city wages should be higher, by blue-collar workers, by black people and by citizens dissatisfied with their treatment by police officers. Respondents to this survey did not distinguish among categories of public employees when evaluating the desirability of strikes.

Collective Bargaining↗