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Biomedical subjects

R A Harrison

Publications and source records attributed to R A Harrison.

209 records · Page 12Linked to original sources
PubMed1971

Glycolytic enzymes in mammalian spermatozoa. Activities and stabilities of hexokinase and phosphofructokinase in various fractions from sperm homogenates.

1. Methods of homogenizing suspensions of washed mammalian spermatozoa were studied. The most useful methods were those using sonication and those using a French press. 2. Hexokinase, phosphofructokinase, glucose phosphate isomerase and adenosine triphosphatase activities in ram, bull and boar spermatozoa were investigated by using these two homogenization methods. Glucose phosphate isomerase, representative of soluble cytoplasmic material, was very readily extracted and remained entirely in the supernatant after centrifugation at 145000g for 60min. In contrast, the other three activities were less easily extracted and were sedimented in various proportions under the described conditions of centrifugation. 3. Attempts to obtain subcellular fractions from sperm homogenates by ;classical' methods failed, owing apparently to the inhomogeneity of subcellular particles in the homogenates. It is concluded that, after removal of sperm heads, the only meaningful fractionation is a separation of spermatozoal material which sediments at 145000g during 60min from that which does not. 4. The stabilities of hexokinase and phosphofructokinase activities in bull, boar and ram sperm homogenates were investigated. Hexokinases showed very little dependence on the various environments tested, whereas the optimum conditions for phosphofructokinase stability were: a minimum of sonication, the presence of phosphate ions and of a thiol-group protectant, and a pH7.5. Activities of hexokinase, phosphofructokinase and glucose phosphate isomerase per sperm cell were compared with published data on rates of fructolysis by spermatozoa; the potential catalytic activities were shown to be considerably in excess of these rates. However, phosphofructokinase may be the rate-limiting enzyme of glycolysis in vivo in bull and ram spermatozoa.

Adenosine Triphosphatases↗
PubMedDate not supplied

Immunization of baboons with attenuated schistosomula of Schistosoma haematobium: levels of protection induced by immunization with larvae irradiated with 20 and 60 krad.

We have shown previously that baboons (Papio anubis) develop high levels (greater than 80%) of protection against challenge infection following immunization with Schistosoma haematobium cercariae irradiated with 20 krad. In the present study baboons were immunized with schistosomula irradiated with either 20 krad or 60 krad, with variations in the timing and number of larvae comprising each vaccination. Baboons immunized 2 or 3 times with schistosomula irradiated with 20 krad were significantly more protected (85-90%) against challenge infection than baboons similarly immunized with larvae receiving 60 krad (56-50% protection). Baboons immunized with schistosomula irradiated with 20 krad were better protected against challenge infection at 8 weeks after immunization than at 28 weeks after immunization. Protection was manifest by a reduction in worm numbers, tissue and excreta egg counts, gross pathology and, to a lesser extent, by stability of body weight and haematological indices following challenge. Enzyme-linked immunosorbent assay (ELISA) results of selected baboon sera showed few differences related to irradiation dose alone, but titres were higher in baboons receiving booster immunizations, and there was a significant correlation between titres immediately preceding challenge and the degree of resistance. Examination of responses to individual schistosomular surface antigens by immunoprecipitation and sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed no correlation between the pattern of antigens recognized and resistance status. As with the ELISA assay, an anamnestic response was detected after vaccination, while the amount of antibody present declined markedly with increasing time after individual immunizations.

Animals↗
PubMedDate not supplied

Reassessment of the assumed A-V oxygen content difference in the shunt calculation.

A study was undertaken in 15 patients to compare measured and assumed arteriovenous oxygen (A-V O2) content differences and their effects on resultant shunt calculations. All patients were on volume ventilators and demonstrated a stable cardiovascular state. Simultaneous measurements of the O2 content of a pulmonary artery (PA) and of a superior vena cava (SVC) sample were compared. A mean A-V 02 content difference of 3.5 plus or minus 0.8 volumes percent was obtained from the PA and 2.6 plus or minus 1.1 volumes percent from the SVC. The resultant shunt calculations derived from measured A-V 02 content differences were compared with the calculation based on an assumed A-V O2 content difference of 5 volumes percent. A method for extrapolating a "true" A-V 02 content difference from an SVC blood sample was obtained. The extrapolated value resulted in a more representative "true shunt" calculation in 13 of the 15 patients.

Aged↗
PubMedDate not supplied

Portable ramps for wheelchair users--an appraisal.

This paper describes a study to establish values for gradients which could be achieved by wheelchair users whilst using two different lengths of otherwise identical portable ramps. Sixty subjects each tested gradients of between 1:14 and 1:6 on portable ramps of 1 metre and 1.8 metres length. The results demonstrated that the majority of attendant-propelled, self-propelling, and powered wheelchair users could negotiate gradients of 1:8 and 1:6 on the shorter ramp with varying degrees of effort. A gradient of 1:10 on a short ramp presented few difficulties for the majority of wheelchair users. Although this work relates specifically to portable ramps, there is little to suggest that the results could not be applied to permanent ramps, including those used in the home.

Activities of Daily Living↗
PubMedDate not supplied

Breast cancer screening knowledge, attitudes, and practices among Korean American women.

PURPOSE/OBJECTIVES: To describe the knowledge and beliefs about breast cancer and breast cancer screening and practices of clinical breast examination (CBE) and mammography of Korean American women. DESIGN: Cross-sectional survey. SETTING: Two Korean churches in a mid-sized Southeastern U.S. city. SAMPLE: A convenience sample of 107 Korean women ages 40 and older. METHODS: Data were collected using Champion's Health Belief Model instrument (susceptibility, seriousness, benefits, and barriers) and the Breast Cancer Knowledge test through mailed questionnaires. MAIN RESEARCH VARIABLES: Knowledge and beliefs about breast cancer screening and practices of CBE and mammography. FINDINGS: The percentages of Korean American women who ever had a CBE and mammography were 67 and 58, respectively. Among the Health Belief Model variables, women who never had a CBE had significantly lower knowledge scores and higher perceived barriers to CBE than those who had. Women who never had a mammogram reported significantly higher perceived barriers to mammography. Logistic regression analyses demonstrated that husband's nationality, regular checkups, and encouragement from family members and physicians were significant predictors of CBE and mammography use. CONCLUSIONS: The frequency of breast cancer screening practices among Korean American women is below national objectives. IMPLICATIONS FOR NURSING PRACTICE: As healthcare professionals in a culturally diverse nation, nurses need to increase their awareness of cultural variations and provide culturally and linguistically appropriate breast health education. Additional studies with women from a variety of settings are needed to validate present study findings.

Adult↗