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Biomedical subjects

A Walker

Publications and source records attributed to A Walker.

At least 289 records · Page 16Linked to original sources
PubMed1983

Dental microwear in adult and still-born guinea pigs (Cavia porcellus).

Scanning electron microscope analyses of dental microwear showed that (1) microscopic striations are not caused by tooth-tooth contact, and (2) the model of striation formation used by Ryan (1979a, J. dent. Res. 58, 525-530; 1979b, Am. J. phys. Anthrop. 50, 155-168) to make directional interpretations of jaw movement is incorrect.

Animals↗
PubMed1983

Experimental condition and the acute reaction of mouse skin to ionizing radiation.

The acute reactions of skin of the thigh-leg of normal young adult C3Hf/Sed mice following five equal radiation doses (60Co) were studied in mice irradiated at various leg skin temperatures and while respiring various gas mixtures in control or anesthetized condition (sodium pentobarbital, 0.05 mg/g-1 body wt.) At 25 and 35 degrees C, anesthesia reduced the RD50 (2.5+ reaction) by 4-5%. An increase of temperature from 25 to 35 degrees C resulted in a decrease in RD50 by 10-12% for subjects respiring air or 5% for subjects respiring O2 at 1 or at 3 ATA. The major modifier of radiation response was to change from respiration of air to O2 at 1 or 3 ATA. Enhancement ratios for RD50 Air/O2 1 ATA were 1.4-1.5 for 25 and 35 degrees C. The ratios O2 1 ATA/3 ATA were 1-1.05.

Anesthesia↗
PubMed1982

Clinical trial of Corynebacterium parvum (intra-lymph-node and intravenous) and radiation therapy in the treatment of head and neck carcinoma.

Fifty-seven patients with previously untreated squamous cell carcinoma of the head and neck region of all clinical stages were entered a trial to evaluate the effectiveness of Corynebacterium parvum combined with radiation therapy in improving local and survival results. Twenty-nine patients were randomized to receive radiation therapy alone, and 28 patients were randomized to receive radiation therapy combined with C. parvum. The C. parvum was administered into the tumor-bearing lymph nodes of the neck or into the cervical node region in non-node-positive patients (4 mg/m2) and by intravenous routes (at 2, 2, 4, 4 and 4 mg/M2) at days -10, -7, and -3 before, and at +7 and +14 days after the start of radiation therapy. The study began in July 1975 and was terminated after 2 1/2 years of patient accession. The statistical analysis showed that those receiving C. parvum were not doing better than controls and, in fact, in some subgroups there was concern that they might be doing less well. Pertinently, analysis showed that those receiving C. parvum would not experience the 25% point improvement in disease-free survival frequency which had been stipulated in the design of the protocol.

Aged↗
PubMed1982

Function of the future respiratory system in the growth retarded fetal sheep.

The development of the future air breathing respiratory system was investigated in eight carunclectomised fetal sheep and five control fetal animals over the last third of gestation (approximately day 100-day 145). Carunclectomy resulted in the test fetal animals being hypoxaemic, hypercapnic, hypoglycaemic and acidotic. All fetal animals were chronically instrumented with diaphragmatic electromyographic leads, fetal jugular vein and carotid artery catheters, an amniotic fluid catheter and small electrocardiographic leads placed on the chest wall. There was evidence of a significant, but small, reduced relative lung size in the carunclectomised animals by day 140 without corresponding relative changes in the weight of the brain, liver, or heart. Diaphragmatic electromyograph (EMG) was analysed in detail over the last third of gestation. In both groups of animals, the normal reduction in fetal 'breathing' rate, and the normal increase in fetal apnoea was noted with increasing periods of diaphragmatic silence as fetal apnoea was noted with increasing periods of diaphragmatic silence as gestation advanced. Linear regression analyses revealed that fetal breathing rate was significantly reduced over the last third of gestation, whilst fetal apnoea significantly increased in the carunclectomised animals. Average total integrated diaphragmatic activity was reduced prior to 120 days. This reduction was evident in the strength of each diaphragmatic contraction before 110 days. In three test and three control animals, histochemical analyses were undertaken to fibre type the muscles of the diaphragm. Fatigue resistant fibres were significantly reduced in the carunclectomised fetuses, and fibre diameters were diminished. Centroid analyses of the power spectrum of the diaphragmatic EMG did not however support the concept of increased muscle fatigue in the test animals.

Animals↗
PubMed1981

Diet and teeth. Dietary hypotheses and human evolution.

Hypotheses concerning the diet of early hominids have played an important role in discussions on human evolution. Three investigations have helped define the extent to which dietary hypotheses may be taken and still be testable. Comparative anatomy is a fairly coarse approach, which despite convergences allows only the most specialized diets to be ruled out. A biomechanical analysis makes it clear that the changes in jaw and tooth form are subtle and outside the resolution given by present understanding of cranial function. Analysis of the microscopic tooth wear of extant species has been carried out. Major dietary types can be distinguished by their microwear. The microwear on fossil hominids appears to rule out certain diets that have been proposed for them.

Animals↗
PubMed1981

Community care and the elderly in Great Britain: theory and practice.

Analysis of the postwar record in Great Britain shows that the state's response to the needs of the elderly has been increasingly centered on the provision of care in the community, or in the family. This community care policy is examined in relation both to some of the implicit functions of this policy and to performance of the policy in practice, particularly in relation to its effects on the sexual division of labor within the family. Also discussed are the processes which create dependency, and the possible conflict between increasing dependency and other social changes, specifically the changing status and aspirations of women. The article concludes with some tentative remarks about the future of community care.

Aged↗
PubMed1980

Fecal lead excretion in young children as related to sources of lead in their environments.

Fecal lead excretion (PbF) was studied in young children with elevated lead exposure. PbB was generally 40-70 microgram/dl. The children's home environments were classified as to lead-base paint hazard and traffic density. There was a significant correlation between paint hazard classification and PbF but not between traffic density and PbF. There also was a correlation of PbB with paint hazard classification. Long-term fecal collections were instituted using 10 children who lived in high hazard homes and three children with low PbB's, whose PbF's were considered normal. Among the children living in high hazard homes, median fecal lead excretion generally was only moderately elevated. Grossly elevated amounts of led were found only occasionally and only in a few of the children. Movement of two children from a high hazard home to a low hazard home resulted in prompt and substantial reduction in PbF. By contrast, PbB fell only very slowly.

Child↗