Biomedical subjects
R W Turner
Publications and source records attributed to R W Turner.
Butter: the natural choice?
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Does control of risk factors prevent coronary heart disease?
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Calcium-induced long-term potentiation in the hippocampus.
The effect of a transient increase in extracellular calcium concentration on the Schaffer collateral-commissural evoked excitatory postsynaptic potential and population spike responses of CAI pyramidal neurons was investigated using the rat in vitro hippocampal slice preparation. Brief exposure of slices (5-10 min) to twice the normal concentration of calcium (4 mM) induced a marked potentiation of both the excitatory postsynaptic potential and population spike that could persist for at least 3 h. No long-term changes were observed in either the presynaptic fiber volley of antidromically evoked CAI population spike, indicating that the potentiation could not be attributed to an increase in the number of fibers activated or a generalized increase in cellular excitability. The response of CAI pyramidal neurons to the iontophoretic application of L-glutamate in the apical dendritic zone was also unaffected after exposure to high calcium perfusate, suggesting a lack of alteration in membrane excitability or receptor sensitivity restricted to the region of synaptic input. In addition, total intracellular calcium content of individual slices, measured by atomic absorption spectrophotometry, was significantly increased for at least 1 h following return to the control medium. These data indicate that brief exposure of in vitro hippocampal slices to a high extracellular calcium concentration results in a long-term increase in synaptic efficacy which is similar in many respects to long-term potentiation induced by tetanic stimulation of hippocampal excitatory afferents. The results further suggest that the mechanisms underlying calcium-induced long-term potentiation may reside in presynaptic components and involve an enhanced transmitter release.
Effects of extracellular calcium on low frequency induced potentiation and habituation in the in vitro hippocampal slice preparation.
The electrophysiological characteristics of frequency potentiation and habituation were investigated in two afferent systems of the in vitro hippocampal slice preparation. Low frequency stimulation (1 Hz) of the Schaffer collateral - commissural (Sch-comm) fibers results in a short-term potentiation of the amplitude and rate of rise of the EPSP and population spike responses recorded in the CA1 region. In contrast, 1-Hz stimulation of the perforant path (PP) evokes a short-term, habituation-like depression of the dentate granule cell EPSP and population spike. An inverse relationship was observed between stimulus intensity and the magnitude of frequency potentiation or habituation. Changes in afferent fiber volleys or general excitability of postsynaptic membranes did not contribute significantly to the development of either of these forms of short-term plasticity. Perfusion with a medium containing a high calcium - low magnesium concentration (4 mM Ca+2 and 1 mM Mg+2) produced a differential effect on CA1 and dentate evoked potentials. Following a 20-min exposure to this medium, the amplitude of CA1 potentials was increased while dentate responses were decreased. Frequency potentiation of CA1 responses and habituation of dentate responses were depressed or eliminated by the high calcium medium. The opposing influence of extracellular calcium on CA1 and dentate evoked potentials indicates a fundamental difference in the process of transmitter release in these systems, a characteristic that may contribute to the production of frequency potentiation and habituation.
Dietary fats and heart disease.
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Fats and heart disease: points for controversy.
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Atherogenicity and the supermarket shelf.
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Coronary heart disease. The size and nature of the problem.
In the U.K., coronary heart disease has reached epidemic proportions. It is the commonest cause of death after the age of 35 years and the fastest rate of increase is in early middle age. The epidemic is due mainly to our way of life. The most important factors are dietary, with smoking, physical inactivity and stress also contributing. Twenty independent working parties from different countries have reviewed the dietary evidence and reached a strong consensus on dietary recommendations. Little action has been taken in the U.K. The Coronary Prevention Group has been formed to consider the reasons for this inaction and also the implication for research, the government, the Ministry of Agriculture, Fisheries and Food, the Department of Health and Social Security, the food and agriculture industries, caterers, nutrition education and for individuals, of the dietary recommendations.
Plague in Central Java, Indonesia.
Plague in man occurred from 1968 to 1970 in mountain villages of the Boyolali Regency in Central Java. Infected fleas, infected rats, and seropositive rats were collected in villages with human plague cases. Subsequent isolations of Yersinia pestis and seropositive rodents, detected during investigations of rodent plague undertaken by the Government of Indonesia and the WHO, attested to the persistence of plague in the region from 1972 to 1974.Since 1968, the incidence of both rodent and human plague has been greatest from December to May at elevations over 1000 m. Isolations of Y. pestis were obtained from the fleas Xenopsylla cheopis and Stivalius cognatus and the rats Rattus rattus diardii and R. exulans ephippium. The major risk to man has been fleas infected with Y. pestis of unique electrophoretic phenotype. Infected fleas were collected most often in houses.Introduced in 1920, rodent plague had persisted in the Boyolali Regency for at least 54 years. The recent data support specific requirements for continued plague surveillance.
Vegan diet and health.
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Behavioral treatment for depression: an evaluation of therapeutic components.
Designed study to determine the "active ingredients" in Lewinsohn's behavioral treatment for depression. Fifty-six men and women were screened for significant depression and were assigned to four experimental treatment groups: (1) an activities-increase group instructed to increment participation in reinforcing activities; (2) an expectancy-control group that participated in a fitness program; (3) a self-monitoring control that simply recorded activities and mood daily; and (4) an attention-control group. Consistent with an operant model of depression, the resulted indicated that increases in activities that Ss had rated as pleasureable alleviated depressed mood over a 30--day time period. While all Ss evidenced some improvement in mood, the activities-increase group showed significantly greater improvement than Ss in groups that did not increase their activity levels. Correlational analyses of daily activity and Depression Adjective Check List Scores proved additional support for the behavioral model of depression. The outcome for the four experimental groups was not different on a measure of belief in internal vs. external control of reinforcement.
Urgent care in the HMO: evolution of a system in Washington, D.C.
In 1961, Group Health Association, a large, non-hospital based, prepaid group practice in Washington, D.C. established an after-hours walk-in clinic on its premises for the care of medical problems requiring prompt attention. Within a year, this clinic's operation was extended to daytime hours for the use of the consumer-member at his own discretion. After 10 years, in the plan's main health center, the volume of adult visits to the acute care/walk-in center exceeded the number seen in the Department of Internal Medicine; most were of a routine rather than urgent nature. More visits to the acute care service were made during the day, when the full range of ambulatory services were available by appointment, than were made after hours. The choic of immediate first-come, first-served care over the conventional care-by-appointment by so many members was felt to have resulted in discontinuous suboptimal care, segregation of the membership along socioeconomic lines, as well as unnecessary and very costly duplications of service. The background of organizational behavior and community medical practices contribuing to this pattern of utilization are explored. Compared to traditional fee-for-service medicine, demands for outpatient services in the HMO tend to be greater. Acceptable alternatives to off-line channeling of patients with unexpected or acute conditions can be designed. In the general community today, utilization of medical services is strongly influenced by imbalances in available resources and by financial factors which are under no central control. In the HMO, all costs are prepaid and services are planned for a membership of known size. Even so, consumers' use of services in prepaid plans tends to follow the patterns seen in the community. More appropriate distribution of demands requires an active and ongoing system of patient education. A commitment by the HMO's providers and managers toward this goal is indispensable.
Perspectives in coronary prevention.
The seeds of premature coronary heart disease are often sown in childhood and it is the developing arteries of children which are the most susceptible. Paediatricians and all who work with them have the earliest and most promising opportunities for prevention. Coronary protection can be added to the potential advantages of breast feeding and to ensure appropriate fatty acid balance throughout weaning. It is reasonable to accept the strong consensus of opinion on diet reflected in the reports of the eighteen national committees. They are: to reduce total fat intake to 30-35% of the energy, to restrict consumption of saturated fat, cholesterol, sugar, and salt, to increase unrefined carbohydrate and polyunsaturated fat, and to maintain a P/S balance of 1.0-1.5:1. Food is the fundamental coronary risk factor, but others may add insult to injury. Smoking, hypertension, obesity, lack of exercise, and stress, each of which is related to behaviour, may start in childhood. Smoking doubles the overall risk CHD and increases it ten times in males under 45 years old. Good habits, including food preferences and eating patterns learned early, are those most likely to be continued. School meals require and should match revised nutritional education. The co-operation of the food industry is essential and can be anticipated, but it requires a clear lead by paediatricians. The nutritional advice should come from the medical profession. Every contact with children and their parents provides an opportunity for enquiry and giving advice.
Experience with Devine-Horton dermal patch graft for Peyronie's disease.
Peyronie's disease is a malady frequently seen by the urologist. Many conservative treatment modalities have yeilded successful alleviation of symptoms in a significant number of these patients. A number, however, do not respond and are left with penile curvature and pain on erection such that intercourse is severely impaired. Devine and Horton have proposed resection of the plaque with replacement of the defect with a full-thickness dermal graft. They reported excellent results with minimal complications. Five patients were treated by this technique with successful penile straightening and alleviation of pain. To date, follow-up results have been gratifying, and the Devine-Horton dermal graft technique is suggested for use in treatment of patients with disabling Peyronie's disease.