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Biomedical subjects

C R Walker

Publications and source records attributed to C R Walker.

35 records · Page 2Linked to original sources
PubMed1981

Evaluation of an information retrieval system for assessment of toxicological effects of chemicals on fish, wildlife, and ecosystem components.

A user-oriented information retrieval system is needed for assessment of materials hazardous to fish, wildlife, food chain organisms, and other organisms essential to the maintenance to ecosystem processes and functions. Critical evaluation of data also requires rigorous documentation of test conditions, precision of methods used, and the sensitivity of the test organism. Particular emphasis of the evaluation was in developing practical criteria that aid in the use and interpretation of data with respect to need for further testing in a scoring exercise performed for the Toxic Substances Control Act Interagency Testing Committee. Recommendations are made for the integration of information on physical and chemical properties, health effects, ecotoxicology, and environmental concentration or exposure level.

Animal Population Groups↗
PubMed1980

Treatment of phenytoin-induced gingival hyperplasia by electrosurgery.

Many medications and combinations of medications are available for the control of epilepsy, but phenytoin continues to be the most effective agent for most patients. A common side effect of this drug is the development of moderate to severe gingival hyperplasia in tooth-bearing areas, which can contribute to problems of function, oral hygiene, appearance, and, eventually, loss of teeth. Excision by conventional means is technically difficult, time-consuming, may be associated with considerable loss of blood, and requires postoperative care, such as periodontal packing, that is impractical if not impossible for many patients, especially the severely mentally handicapped. We have described a technique of gingivectomy using an electrosurgical device in the hospital with the patient under general anesthesia that has produced good results for more than 15 years. This procedure has virtually eliminated the problems of conventional surgical excision with little or no postoperative sequelae.

Connective Tissue↗
PubMed1978

Diazepam inhibits myoblast fusion and expression of muscle specific protein synthesis.

The presence of diazepam in culutres of chicken embryo myoblasts arrests normal muscle cell differentiation. High concentrations of the drug reversibly prevent myoblasts from fusing to form multinucleated myotubes. Lower concentrations of diazepam allow cell fusion to occur, but inhibit the synthesis and accumulation of myosin heavy chain, implying that cell fusion does not obligate myoblasts to synthesize and accumulate large quantities of muscle specific protein. The effect of diazepam on muscle cells in culture is direct and specific.

Animals↗
PubMed1976

Regulation of acetylcholinesterase in cultured muscle by chemical agents and electrical stimulation.

Cultures of 11 day old chick embryo pectoral muscle were used to study the effects of direct electrical stimulation and neurochemicals such as acetylcholine, acetyl-beta-methylcholine, tetrodotoxin, and d-tubocurarine on the acetylcholinesterase levels of muscle. The results suggest that excitation-contraction is an important factor in regulation of muscle acetylcholinesterase. Tetrodotoxin, acetylcholine and its analog acetyl-beta-methylcholine increased acetylcholinesterase levels and reduced spontaneous contractions. D-tubocurarine blocked the increase in acetylcholinesterase and the decrease in spontaneous contractions caused by acetyl-beta-methylcholine. Electrical stimulation decreased acetylcholinesterase and increased muscle contractions in normal and in diisopropylfluorophosphate treated cultures. Tetrodotoxin also affected the morphology of the muscle cells, as if it adversely affected normal growth and differentiation. Electrical stimulation did not increase muscle creatine kinase.

Acetylcholine↗
PubMed1976

Regulation of acetylcholinesterase in chick muscle cultures after treatment with diisopropylphosphorofluoridate: ribonucleic acid and protein synthesis.

Previous studies have established that short treatments with diisoprophylphosphorofluoridate of chick embryo muscle cultures irreversibly inhibit the enzyme acetylcholinesterase and that the enzyme's levels in the cells rapidly recover due to synthesis of new protein. In addition, it has been shown that acetylcholine, acetyl-beta-methylcholine and choline increase the acetylcholinesterase content of the cultures. In the experiments presented here, actinomycin D and cycloheximide were used to study the relationships between the synthesis of ribonucleic acid and of protein, the recovery of acetylcholinesterase levels after diisopropylphosphorofluoridate treatment and the increase of acetylcholinesterase levels evoked by choline and its esters. Both recovery of acetylcholinesterase and the increase in its activity with acetyl-beta-methylcholine occurred in the absence of ribonucleic acid synthesis but required protein synthesis. The results suggest that transcription of desoxyribonucleic acid and a change in the degradation rate of acetylcholinesterase are not involved. An additional finding was that the level of newly synthesized acetylcholinesterase activity continued to increase for a short period of time after synthesis of protein had ceased, as if some previously synthesized protein was being transformed into active enzyme.

Acetylcholinesterase↗
PubMed1974

Regulation of newly synthesized acetylcholinesterase in muscle cultures treated with diisopropylfluorophosphate.

Brief treatment with 0.1 mM diisopropylfluorophosphate inhibited an average of 89% of the acetylcholinesterase (EC 3.1.1.7; acetylcholine hydrolase) activity of cultures of chick embryo muscle. As long as protein synthesis occurred, an average of 78% of the activity returned within 4 hr. Newly synthesized acetylcholinesterase did not stain cytochemically, was rapidly and extensively degraded or released in the presence of 10 muM cycloheximide, and consisted mainly of low-molecular-weight forms. Acetylcholinesterase activity first appeared around the nucleus, about 4 hr after treatment with diisopropylfluorophosphate, and then spread to the rest of the cell about the time release of acetylcholinesterase was detected in the medium. With time, more and more of the enzyme was retained in the cells after treatment with cycloheximide, and the proportions of low-molecular-weight forms decreased and high-molecular-weight forms increased. The results suggest that newly synthesized acetylcholinesterase undergoes an orderly process of binding, movement, and assembly in diisopropylfluorophosphate treated, and probably also in untreated, embryo muscle fibers.

Acetylcholinesterase↗
PubMedDate not supplied

Discharge of mothers and babies from hospital after birth of a healthy full-term infant: developing criteria through a community-wide consensus process.

OBJECTIVE: To ensure safe care of mothers and babies after birth, irrespective of length of hospital stay, and to ensure effective links between hospital and community postnatal services. METHODS: Program aimed toward consumers and professionals working with them in Ottawa-Carleton (750,000 persons.) All pregnant women in the community included. Program developed by professionals, institutions and community agencies. Information on current practices elsewhere and early discharge literature studied. New provincial survey on practice changes performed in Ontario. Emergency room utilization data analyzed. Discharge and post-discharge criteria, and a common prenatal education curriculum, developed. RESULTS: Multidisciplinary, multi-sectoral committees, institutions and agencies have developed programs for appropriate discharge practice and improved postnatal follow-up. Professionals have supported flexible discharge guidelines. CONCLUSIONS: Provided discharge criteria and follow-up are available, flexible discharge timing and safety appear compatible. The Ottawa-Carleton process to develop criteria and programs has allowed a collaborative, consensus-based approach to 'early' newborn discharge.

Community Participation↗