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Biomedical subjects

R Dunn

Publications and source records attributed to R Dunn.

At least 145 records · Page 8Linked to original sources
PubMed1979

Percentage reinforcement and choice.

Pigeons responded on identical concurrent variable-interval schedules (choice phase), producing outcomes of either periodic reinforcement schedules always terminating in reinforcement (reliable schedule) or otherwise identical schedules providing reinforcement on only a percentage of instances (percentage reinforcement schedule). Comparisons of this type constituted two assessments of the generality of preference for percentage reinforcement reported by Kendall (1974). In a third set of conditions, a reliable schedule was pitted against a percentage reinforcement schedule in which the more negative outcome was a leaner schedule of reinforcement (rather than nonreinforcement, as in the other two conditions). In all three types of conditions, the schedule providing the higher rate of reinforcement was preferred. Results from a subsequent manipulation suggest that Kendall's contrasting results may have depended on the fact that the stimuli in his choice phase (unlit keys) were physically identical to the stimulus correlated with the nonchosen outcome in his outcome phase.

Journal Article↗
PubMed1978

The purification and properties of valine tRNAs of Drosophila melanogaster.

The valine transfer ribonucleic acids of Drosophila melanogaster have been purified by column chromatography on BD-cellulose, Sepharose 6B, and RPC-5. Three major species were analyzed for base composition and coding properties. Valyl-tRNAVal3a binds strongly to ribosomes in the presence of GUA and to a lesser extent with GUU and GUG. Valyl-tRNAVal3b binds strongly in the presence of GUG and very poorly if at all with the other three triplets whereas valvyl-tRNAVal4, which contains inosine, binds strongly in the presence of GUU, GUC, and GUA and weakly with GUG.

Animals↗
PubMed1975

An analysis of five serine transfer ribonucleic acids from Drosophila.

Crude tRNA from adult Drosophila melanogaster was fractionated on bensoylated-diethylaminoethyl cellulose columns. The eluate was assayed for both amino acid acceptance and cytokinin activity. Most of the cytokinin activity was associated with a peak of serine acceptance. The five major serine tRNAs were purified by chromatography on benzoylated-dietyhlaminoethyl cellulose and reversed phase chromatography-5 columns. The major species, tRNA7-Ser was isolated from this tRNA and was shown to be N-6-(delta-2-isopentenyl)adenosine (i-6A) on the basis of ultraviolet and mass spectral data. The nucleoside somposition of all five serine tRNAs was determined directly and by the 3-H derivative method. They all contain pseudouridine, ribothymidine, 1-methyladenosine, 5-methylcytosine, N-2-dimethylguanosine, 5, 6-hydrouridine, and 3-methylcytosine, while two contain an unidentified nucleoside, and one containes 1-methylguanosine. These techniques also confirmed the presence of i-6A in tRNA7-Ser as well as showing its presence in tRNA6-Ser and tRNA4-Ser. These three tRNA-Ser species exhibit marked changes in elution from reversed phase chromatography-5 columns as a function of temperature and this may be related to their minor base composition. The tRNAs-Ser were bound to ribosomes in response to the following triplets: tRNA2-Ser, AGU, AGC; tRNA4-Ser, UCG; tRNA5-Ser, AGU, AGC; tRNA7-Ser, UCG.

Adenosine↗
PubMed1967

Bat ears.

Explore the source record for details and available documents.

Ear Deformities, Acquired↗
PubMedDate not supplied

HMG CoA reductase-inhibitor-related myopathy and the influence of drug interactions.

We report four cases of rhabdomyolysis and severe, disabling myopathy associated with HMG CoA reductase-inhibitor therapy. Patient developed symptoms following the addition of roxithromycin to combination lipid-lowering therapy with simvastatin and gemfibrozil. Patients 2 and 3 became symptomatic after developing acute on chronic renal impairment while taking simvastatin. The muscle biopsy of patient 3 revealed a necrotizing myopathy and the presence of inclusion bodies. Patient 4 developed symptoms within 4 weeks of starting cerivastatin monotherapy. The four cases illustrate the importance of considering the potential for drug interactions and making appropriate dosage adjustments for renal insufficiency in patients receiving HMG CoA reductase therapy.

Aged↗
PubMedDate not supplied

The virtual mole clinic: preliminary results from the Plymouth skin cancer screening study using telemedicine.

This study evaluated a skin cancer screening service between primary and secondary care in Plymouth using a store and forward telemedicine system. The primary objective was to minimize the time from a patient presenting to a GP with a suspicious lesion to the lesion being assessed and diagnosed by a plastic surgeon. This study retrospectively assessed the practical, technical and operational aspects of incorporating telemedicine into everyday practice and patient satisfaction. Both the GP practice and plastic surgeons were equipped with the appropriate technology for creating, transmitting and accessing an electronic telemedicine record (ETR) via an ISDN 2 line. Patients with suspicious lesions accessed the GP via Mole Check Clinics. The GP captured and transmitted an ETR consisting of digital images and relevant clinical data. In a virtual mole clinic, the plastic surgeon accessed and reviewed the ETR. The expert opinion was entered directly into the ETR and transmitted to the GP within 48 hours. All patients were offered a face-to-face consultation at a real mole clinic within 7 days. Outcomes demonstrated patient and clinician satisfaction and the ability to deliver high quality diagnostic images and resulting expert opinion. This study informed a larger study for future applications of telemedicine.

Humans↗
PubMedDate not supplied

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation.

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Clinical Trials as Topic↗
PubMedDate not supplied

Accommodating nursing students' diverse learning styles.

The authors present a framework for understanding diverse learning style/cognitive-style models and assessment instruments, review the literature on learning styles in general and the Dunn and Dunn Model specifically, and identify research areas for nursing educators. The authors challenge previous research with nurses and nursing students that focused on group, rather than individual interventions. They also explain why instruments that focus on only one or two constructs on a bipolar continuum, rather than on multiple learning-style constructs, restrict the possibility of revealing positive outcomes.

Education, Nursing↗
PubMedDate not supplied

Prenatal exposure to a maternal low protein diet shortens life span in rats.

BACKGROUND: Postweaning diet restriction is associated with prolongation of life span, reduced age-related disease and slower ageing. The effects of diet restriction imposed prior to weaning have not been so well characterised, but studies suggest an opposite effect with increased age-related diseases occurring in offspring exposed to undernutrition in prenatal life. It remains unclear whether life span is similarly adversely affected by early diet restriction. OBJECTIVE: The present study in rats aimed to evaluate the impact of a maternal low protein diet upon the life span of the resulting offspring. METHODS: Rat dams were fed either a 180-gram casein/kg control diet or a 90-gram casein/kg low protein diet from conception until the end of pregnancy. The offspring were then maintained with minimal handling until death from natural causes or distress-necessitated euthanasia. RESULTS: The average life span of female rats exposed to low protein diets in utero was reduced by 11% (p = 0.044, Kaplan-Meier analysis). There was a similar but non- significant trend in the male offspring (control 76 +/- 3 weeks, low protein 73 +/- 3 weeks). In addition the rats exposed to a prenatal low protein diet had significantly higher systolic blood pressure at 4 weeks of age and tended to be smaller than control animals in postnatal life. CONCLUSION: The results suggest that intrauterine diet restriction reduces life span in rats and contrasts with the well-recognised increase in life span produced by postweaning diet restriction. The timing of the nutritional intervention appears to be critical and recognition of this is relevant to understanding the mechanisms underlying the effects of diet restriction on ageing and life span.

Animal Nutritional Physiological Phenomena↗