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Biomedical subjects

J Hopkins

Publications and source records attributed to J Hopkins.

At least 181 records · Page 10Linked to original sources
PubMed1983

Differential responses of nascent DNA synthesis and chain elongation in V79 and V79/79 cells exposed to u.v. light and chemical mutagens.

DNA repair after u.v., N-methyl-N-nitrosourea (MNU) and ethylmethane sulphonate (EMS) in Chinese hamster V79 cells and the mutagen sensitive derivative V79/79 was investigated by measurement of five parameters: production of strand breaks in template DNA, incorporation of [3H]TdR, semi-conservative and repair synthesis, molecular weights of pulse labelled DNA after mutagen exposure (nascent synthesis) and molecular weights of DNA pulse labelled and chased after mutagen exposure (elongation and ligation). Equal template strand breakage was evident in both cell lines immediately after MNU and EMS exposure and by 4-5 h after MNU the extent of fragmentation was greater in V79/79 cells. After u.v. irradiation template fragmentation was evident in V79/79 but not in V79 cells, even though V79/79 cells failed to excise cyclobutane dimers and repair synthesis was demonstrable in V79 cells but not in V79/79 cells after exposure to all three mutagens. The rate of incorporation of [3H]TdR during semi-conservative DNA synthesis was inhibited equally in a dose dependent manner after u.v. and MNU exposure; incorporation by V79/79 cells was inhibited to a greater extent than by V79 cells after EMS exposure. Nascent DNA synthesis was suppressed more in V79/79 cells than in V79 cells after u.v. but to similar extents in both cell lines after MNU and EMS treatment. Pulse chase experiments indicated a lower rate of elongation of nascent DNA in V79/79 cells after MNU and u.v. exposure but little difference was detectable after EMS.

Animals↗
PubMed1982

Noninvasive detection and localization of coronary stenoses in patients: comparison of resting dipyridamole and exercise thallium-201 myocardial perfusion imaging.

Two noninvasive tests to detect and localize coronary stenoses were compared in a fully blinded protocol. Thallium201 myocardial perfusion imaging (MPI) following maximal treadmill exercise and pharmacologic coronary vasodilation with intravenous dipyridamole (DP) was performed in 33 patients. Thallium201 imaging defects in six myocardial perfusion regions were correlated with stenoses in their respective vascular distributions. Disease severity was determined with coronary arteriograms using a computer-assisted method. 198 myocardial regions were evaluated; 101 were supplied by at least one major artery with a greater than or equal to 50% stenosis (luminal diameter narrowing). The sensitivity and specificity for detecting a greater than or equal to 50% stenosis were 85% and 64% (p less than 0.005), respectively, for DP and 84% and 68% (p less than 0.005) for exercise-thallium201 imaging. A particular combination of anterior and septal imaging defects was useful in detecting left anterior descending artery stenoses proximal to its first septal branch. DP administration was safe in this group of patients; however, 42% experienced transient chest pain. Although the overall sensitivity and specificity of the two methods were not significantly different, DP-MPI appeared more sensitive than exercise-MPI (70% vs 52%, p less than 0.01) in detecting coronary stenoses in the 40% to 60% range. DP-thallium201 MPI provides a useful alternative test for potential coronary disease patients unable to perform maximal exercise.

Adult↗
PubMed1982

Total pinealectomy by an occipital parasagittal approach in sheep.

A reliable method of total pinealectomy in sheep without a resulting significant neurological deficit has been developed and is described. The known effect of light on sheep gonadotropin levels helps validate these studies of its pineal gland. Special attention is given to delineation of the surgical anatomy of the gland and its relationship under magnification to the central draining veins of the brain. In this large mammal this relationship differs considerably from that of humans. The application of an intrahemispheric occipital exposure using magnification, as well as the preoperative administration of steroids and osmotic agents, helped to minimize the effects of retraction and resultant cerebral edema. We have thus been able to increase the rate of successful pinealectomy to 83%, allowing the development of groups of animals suitable for studies of the neuroendocrine function of the pineal and pituitary glands.

Animals↗
PubMed1981

Specific selection of antigen-reactive lymphocytes into antigenically stimulated lymph nodes in sheep.

Sheep were primed to a variety of antigens and the efferent lymphatic from a popliteal lymph node was cannulated. The cannulated node was challenged repeatedly with PPD and all the lymph and cells removed from the animal. During this time the PBL were monitored for reactivity to all antigens (purified protein derivative of tuberculin [PPD], johnin, and keyhole limpet hemocyanin [KLH]) by the vitro transformation assay. The response of these cells to PPD was found to be gradually eliminated after repeated challenge of the cannulated node with that antigen. The response to the other antigens was unimpaired. No depletion of this response to PPD occurred in cannulated sheep when the antigen was given into a noncannulated node. In vivo delayed-type hypersensitivity skin test and helper T cell assays confirmed that there is a specific selection of antigen-reactive cells from the recirculating lymphocyte pool into antigen-stimulated lymph nodes.

Animals↗
PubMed1981

Expectations and outcome of total hip replacement.

The preoperative function, expectations of pain relief and expectations of improvement in activities of daily living were compared with the results nine months after total hip replacement in 145 patients with osteoarthrosis or rheumatoid arthritis. patients improved functionally and their expectations generally were met. They were most satisfied with improvements in pain relief and mobility but 28% still expressed disappointment because specific expectations were not fulfilled. The expectations of doctors were higher than those of occupational therapists.

Activities of Daily Living↗
PubMed1981

Behavioral and cardiorespiratory responses to 4-aminopyridine in healthy awake horses.

4-Aminopyridine was administered in incremental IV doses to healthy horses to evaluate cardiorespiratory and behavioral effects. Doses of 100 micrograms/kg produced apparent sensory discomfort, manifested by wiggling or curling of the lips and tongue, arching or stretching the neck, snorting, squealing, and coughing. At cumulative dosages of 300 to 500 micrograms/kg, muscle tremors, a stilted gait, and signs of excitement occurred. Once signs of excitement occurred, additional administration of 4-aminopyridine resulted in prolonged excitement consisting of severe muscle tremors and exaggerated responses to external stimuli. Heavy sedation with xylazine provided nearly complete relief from these effects. 4-Aminopyridine could be a useful adjunct to treatment of botulism in horses; however, administration of doses in excess of 300 to 500 micrograms/kg may cause severe CNS excitatory effects.

4-Aminopyridine↗
PubMed1981

Lymphocyte traffic through antigen-stimulated lymph nodes. II. Role of Prostaglandin E2 as a mediator of cell shutdown.

Prostaglandin E2 (PGE2) can mediate changes in lymphocyte traffic through lymph nodes. By measuring PGE2 levels in efferent lymph from cannulated sheep lymph nodes it was shown that increased synthesis of PGE2 always correlated with cell shutdown; infusion of PGE2 alone induced cell shutdown and inhibition of PGE2 synthesis by the node abolished cell shutdown induced by antigen.

Animals↗
PubMed1980

Carrageenan.

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Animals↗