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Biomedical subjects

R Parker

Publications and source records attributed to R Parker.

At least 199 records · Page 11Linked to original sources
PubMed1985

Interpretation of excessive serum concentrations of digoxin in children.

Between January 1981 and April 1984, excessive serum concentrations of digoxin (5 ng/ml or higher) were recorded in 47 children, aged 2 days to 16 years. In 10 patients, the high concentrations were measured 9.25 to 48 hours after death and were significantly higher than antemortem levels in all cases (8.3 +/- 2.4 (+/- standard deviation) postmortem vs 3.3 +/- 1.5 antemortem, less than 0.0001). In 15 patients (40.5% of the living patients) serum concentrations of 5 ng/ml or higher reflected sampling errors; drug levels were monitored too closely to the administration of a dose. None of these children had toxic manifestations of digoxin. In 10 patients, the excessive concentrations were associated with renal failure and a prolonged elimination half-life (T1/2) of digoxin; in 3 of these patients, there were signs of digoxin toxicity. Six cases were caused by digoxin overdose (accidental ingestions, pharmacy error and a suicide attempt). In 6 additional cases, the existence of an endogenous digoxin-like substance (EDLS) was shown to contribute to the excessive levels of the drug. One case could be attributed to digoxin-amiodarone interaction. In 10 of 37 living patients, digoxin toxicity was diagnosed. After excluding the 15 sampling errors and 6 cases with EDLS, this represents 63% of the cases. There was a good correlation between digoxin elimination T1/2 and serum creatine concentrations (r = 0.71, p less than 0.01). The above observations suggest that excessive serum concentrations of digoxin may not necessarily reflect potentially toxic levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

A point mutation in the conserved hexanucleotide at a yeast 5' splice junction uncouples recognition, cleavage, and ligation.

We have constructed an actin-HIS4 gene fusion, such that expression of HIS4 requires proper splicing of the actin intron. Using this chimeric gene in an in vivo screen for splicing mutations, we have isolated a G to A transition in the fifth position of the yeast 5' consensus sequence/GTAPyGT. This mutation still allows the junction to be recognized by the splicing machinery, albeit inefficiently. Surprisingly, the fidelity of the 5' endonucleolytic cleavage is also reduced. This results in an incorrect cleavage 6 nucleotides 5' of the 5' junction, at the dinucleotide/AT. Cleavage at this abnormal site does not lead to the production of mature mRNA, although this species appears to be in a lariat structure. The behavior of this mutant argues that recognition of the 5' junction and subsequent cleavage are separable events and, furthermore, that requirements for 3' endonucleolytic cleavage may be more complex than previously imagined.

Actins↗
PubMed1985

Energy cost index as an estimate of energy expenditure of cerebral-palsied children during assisted ambulation.

The energy expenditure of cerebral-palsied children ambulating with bilateral quad canes and wheeled walkers was estimated, using average heart rate and speed of walking. An energy cost index (average number of heart rates per unit distance walked) was derived to allow for varying speeds among patients. Children were then categorized into those who had a lower energy cost index when using quad canes and those who had a lower index when using walkers. This made it possible to offer treatment recommendations based on objective data.

Canes↗
PubMed1985

Masculinity, femininity, and homosexuality: on the anthropological interpretation of sexual meanings in Brazil.

This essay examines the anthropological interpretation of sexual meanings in Brazil as presented in the recent work of Peter Fry. Following Fry's lead, it places central emphasis on the study of male homosexuality and sexual ideology, suggesting that these cultural domains can be fully understood only when situated within the wider context of sexual meanings in Brazil. With this in mind, it traces the historical development of a series of analytically distinct, though practically interrelated, systems of sexual classification which structure the constitution of meaningful sexual identities in Brazilian life.

Anthropology↗
PubMed1984

Attachment of fibroblasts following hyperthermia and ultrasound.

The rate of cell attachment to the culture substratum is reduced in mouse L cells by hyperthermia at 44 degrees C. The time for 50 per cent attachment of the cells increases rapidly with increasing time of heating immediately before assay. The rate of attachment after 44 degrees C does not show a linear correlation with clonogenic survival, ruling out the use of attachment as a rapid assay of clonogenic survival. The attachment process is less sensitive to heat in cells made thermally tolerant by a prior heat treatment. In contrast, ultrasound irradiation at 37 degrees C and below the cavitational threshold (1.5 MHz, 2.2 W/cm2, 15 min) did not alter the rate of attachment, but at 44 degrees C, ultrasound decreased both clonogenic survival and the rate of attachment to a much greater extent than 44 degrees C alone. As the temperature increase caused by the ultrasound was less than 0.5 degrees C, the data provide evidence of a non-thermal component of ultrasound damage.

Animals↗
PubMed1984

Effect of simultaneous prenatal exposure to ochratoxin A and citrinin in the rat.

Ochratoxin A (OA) and citrinin (CT) are food-borne mycotoxins produced by several fungal species of the genera Aspergillus and Penicillium. Both are teratogenic in the rat. To determine the prenatal effects of simultaneous exposure to these toxins, pregnant Sprague-Dawley rats were injected either with a single individual subthreshold teratogenic dose of OA (1 mg/kg) or CT (30 mg/kg) or with both toxins. Toxins were dissolved in 5% sodium bicarbonate and administered subcutaneously on one of gestation d 5, 6, 7, 8, 10, 11, or 14. Maternal body weight gain of animals in the combination group was similar to other treatment groups and the control. Approximately 22-40% mortality in dams occurred on gestation d 5, 6, 7, and 14. Other than d 7, there was no significant effect on the number of implants. Treatment on d 5 or 7 resulted in increased fetal resorptions. Fetal body weights were not decreased significantly. OA and CT in combination resulted in a significant increase in gross malformations on d 6 and 7, visceral anomalies on d 5, 7, 8, and 10, and skeletal defects on d 5, 6, 7, 8, 10, and 14. When administered individually, OA and CT resulted in very few fetal resorptions. Fetal body weights were not significantly different except on d 8 of gestation following CT treatment. Individual toxin treatment resulted in minimal malformations on all gestation days. These results suggest that OA and CT, when administered concurrently, may interact to enhance prenatal toxicity and teratogenicity, and these results have focussed attention on the public health hazards of contamination of food with these mycotoxins.

Abnormalities, Drug-Induced↗
PubMed1984

Ochratoxin A-induced teratogenesis in rats: partial protection by phenylalanine.

Ochratoxin A (OA), an important foodborne mycotoxin, is a potent teratogenic and nephrotoxic agent produced by several species of Aspergillus and Penicillium. OA is a known inhibitor of protein synthesis via competition with phenylalanine (Phe) in the phenylalanyl-tRNA synthetase-catalyzed reaction. It also has been reported that a variety of toxic effects of OA can be prevented by Phe. This study was designed to determine whether Phe could prevent or diminish the teratogenic effects of OA in rats. Pregnant Sprague-Dawley rats were injected with a single individual dose of OA (1.75 mg/kg) alone or in combination with a single dose of Phe (20 mg/kg) or in combination with either a single or daily dose of Phe (25 mg/kg). OA dissolved in 5% sodium bicarbonate and Phe dissolved in normal saline were administered subcutaneously on gestation day 7 to rats. The incidences of OA-induced fetal malformations (gross and skeletal) were significantly diminished in the presence of added Phe. These results indicate that coadministered Phe provides partial prenatal protection from the teratogenic effects of OA.

Abnormalities, Drug-Induced↗
PubMed1983

Measurement of selected hip, knee, and ankle joint motions in newborns.

As clinicians become more involved in preventative screening, assessment, and treatment of newborns and infants, an increasing need exists for quantitative, normal joint range-of-motion data for this population. We used a goniometer to assess in 40 healthy, full-term newborns the following passive ranges of motion: hip extension, knee extension, ankle plantar flexion, ankle dorsiflexion, and the popliteal angle. Every infant except one lacked full extension at both the hip and the knee. Plantar flexion was generally limited, but dorsiflexion was unlimited. Popliteal angle measurements showed the greatest amount of variation among the infants. Pearson correlation coefficients indicated that those infants with greater dorsiflexion tended to have less plantar flexion, and those with a greater limitation of knee extension measured with the hip extended tended also to have a smaller popliteal angle. Intrauterine position and newborn flexor tone are discussed as possible contributing factors to the results obtained in this study.

Ankle Joint↗
PubMed1982

Analysis of membrane lipid composition of mammalian cells during the development of thermotolerance.

The mechanism by which cells develop thermotolerance is unknown but some previous results suggest that membranes are involved in the process. The lipid composition of membranes from Ehrlich ascites cells grown in tissue culture was analysed at times up to 24 hours after heat treatments at 42 to 44 degrees C known to induce thermotolerance. No changes were observed in the levels of free cholesterol and phospholipids in the cells, nor in the fatty acid composition of the phospholipids. In addition, no changes were observed in the level of cholesterol esters. When cells were fractionated into crude nuclear, mitochondrial and microsomal fractions by differential centrifugation, there was still no heat-induced change in the free cholesterol or phospholipid levels of these fractions. It is concluded that thermotolerance is not mediated through a compositional change in the membranes to a more thermostable form.

Adaptation, Physiological↗
PubMed1982

Epidemiologic features of Strongyloides stercoralis infection in an endemic area of the United States.

The epidemiologic features of Strongyloides stercoralis infection in Kentucky were studied by an analysis of clinical cases at the University of Kentucky Medical Center (UKMC); by an analysis of parasitologic records of the Kentucky Bureau for Health Services (KBHS); and by a prospective stool survey of school children in Clay County, located in southeastern Kentucky, an area of the state previously found to be highly endemic for intestinal parasites. S. stercoralis was the most common parasitic infection diagnosed at UKMC. The patients were predominantly white male adults who were over 50 years old, had an associated chronic or debilitating medical illness, were of low socioeconomic background, and resided in southeastern Kentucky. S. stercoralis was a common parasitic infection at KBHS ad the patients showed a similar geographic distribution. Of 561 Clay County children surveyed, 23.7% harbored one or more intestinal parasite pathogens and 3.0% had S. stercoralis. Thus, S. stercoralis remains highly endemic in Kentucky and may cause disease even in geriatric patients.

Adolescent↗
PubMed1982

Induction of resistance to tuberculosis in mice with defined components of Mycobacteria and with some unrelated materials.

Factors contributing to protection against experimental tuberculosis have been studied with refined and well-characterized fractions from mycobacteria and with certain unrelated antigens. Mice were vaccinated intravenously with various combinations of materials presented on minute oil droplets in saline emulsion and were later challenged by aerosol. The minimal composition of an effective vaccine was P3 (a trehalose mycolate similar to cord factor) plus an antigen, which could be tuberculo-protein, or a low-molecular-weight tuberculin-active peptide, or unrelated antigen such as bovine serum albumin or bacterial endotoxin. Development of a hypersensitivity granuloma in the lungs appeared to be essential to protection in this laboratory model.

Animals↗
PubMed1982

Induction of resistance to tuberculosis in mice with defined components of mycobacteria and with some unrelated materials.

Factors contributing to protection against experimental tuberculosis have been studied with refined and well characterized fractions from mycobacteria and with certain unrelated antigens. Mice were vaccinated intravenously with various combinations of materials presented on minute oil droplets in saline emulsions and were later challenged by aerosol. The minimal composition of an effective vaccine was P3 (a trehalose mycolate similar to cord factor) plus an antigen, which could be tuberculoprotein, or a low-molecular-weight tuberculin-active peptide, or unrelated antigen such as bovine serum albumin or bacterial endotoxin. Development of a hypersensitivity granuloma in the lungs appeared to be essential to protection in this laboratory model.

Animals↗
PubMed1981

Immediate ambulation after planned extra-capsular cataract extraction and implant of intra-ocular lens.

Day-case or outpatient cataract surgery has been reported many times over the past thirty years or so and the modern micro-surgical techniques were deemed safe enough to allow immediate ambulation and return to the home environment even with the additional step of an intra-ocular lens provided the lens were of the type designed for positive fixation. The trend also toward the planned extra-capsular method of cataract removal was thought to be a further safeguard to the patient, particularly the elderly age-group of patients for whom implants are strongly indicated and for whom also early ambulation and avoidance of general anaesthesia are important in reduction of morbidity. Consequently, a study began in November, 1976, to follow those patients who had the indication and the desire to have their implant surgery on a Day-case basis and this presentation gives the results on 100 cases collected over the 3 1/2 year period. Local anaesthesia was used in all cases and planned extra-capsular surgery was performed with irrigating micro-instruments. Irido-capsular lenses of Binkhorst design were used mostly and the visual results, low complication rate and patient satisfaction appear equal to reports of similar series on In-patient cases.

Aged↗