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Biomedical subjects

C Davies

Publications and source records attributed to C Davies.

At least 235 records · Page 13Linked to original sources
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Muscle powered circulatory assist device for diastolic counterpulsator.

A diastolic counterpulsator that uses either skeletal muscle or pneumatic actuation was developed. The unit is positioned between the latissimus dorsi and the chest wall, without interference with collateral blood supply, and is connected in series with the descending aorta. The system was able to generate stroke volumes between 52 and 16 ccs against pressures of 60 and 140 mmHg, respectively. Stroke work at 200 msec stimulation averaged 2.8 X 10(6) ergs. Power output at an afterload of 100 mmHg, and at a rate of 60 bpm, was 0.51 W. Back-up pneumatic actuation provided by an intraaortic balloon pump resulted in a 46% increase in the endocardial viability ratio (EVR).

Animals↗
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A canine model for global control of the reimplanted larynx. A potential avenue for human laryngeal transplantation.

Previous attempts at laryngeal transplantation have failed because the grafted organ could not be dynamically rehabilitated. Nerve-muscle pedicles were used to reinnervate each of the principal intrinsic laryngeal muscles in 20 dogs after autotransplantation with conservation of the essential nutrient vessels. Afferent information obtained by sensors fixed to the chest (a strain gauge and transthoracic impedance electrode) was channeled to an electronic package for coordinated stimulation of pedicles reinnervating the posterior cricoartenoideus (opening), the cricothyroideus (elongation) and the thyroarytenoideus (closure of the vocal cords) by perineural electrodes. Corresponding vocal cord motion was videotaped on the same screen as sensor displacements and stimulating currents (approximately 2 V, 60 Hz, and 4 msec pulse width). Clear responses were recorded in all evaluable animals (n = 8), but contraction was stronger with longer reinnervation time (3-7 weeks). Based on this feasibility study, chronic experiments are planned that will set the ground work for possible future human laryngeal transplantation.

Animals↗
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Hemodynamic changes with posture in calves with total artificial heart.

Hemodynamic changes with posture, sitting versus standing, were analyzed in five Holstein calves with the Cleveland Clinic-Nimbus TAH. This total artificial heart (TAH) has a left master alternate control mode that adjusts the pump rate and consequently pump flow proportional to the pulmonary venous return to the left pump (AUTO period). However, in this series of experiments, the pump reached its maximum beat rate within 1-5 days post operatively, after which pump flow could not increase (MAX period). Hemodynamic parameters (RAP, LAP, PAP, AoP, and pump flow) were obtained every 15-20 min throughout the experiments for as long as 120 days and averaged for each posture for each period. During the AUTO period, the flow while standing was significantly higher than that while sitting (standing: 8.7 +/- 0.2 L/min; sitting: 7.5 +/- 0.4 L/min; p < 0.05), and the systemic vascular resistance (SVR) was significantly lower (standing: 895 +/- 93 dyne.sec.m-5; sitting: 1,041 +/- 124 dyne.sec.m-5; p < 0.05). During the MAX period, the AoP and SVR standing were significantly lower than those sitting (AoP standing: 91 +/- 7 mmHg; AoP sitting: 98 +/- 7 mmHg; p < 0.05; SVR standing: 652 +/- 75 mmHg; SVR sitting: 730 +/- 96 mmHg; p < 0.05). The Cleveland Clinic-Nimbus TAH responded well to these changes in position, increasing pump flow and maintaining the AoP during the AUTO period.

Animals↗
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Structures of prokaryotic ribosomal proteins: implications for RNA binding and evolution.

After a long hiatus, the pace of determination of the structures of ribosomal proteins has accelerated dramatically. We discuss here the structures of five ribosomal proteins from Bacillus stearothermophilus: S5, S17, L6, L9, and L14. These structures represent several new motifs. Each of these structures has revealed new insights, and we have developed criteria for recognizing RNA-binding regions of each protein and correlating the structures with such properties as antibiotic resistance. The information here should also prove invaluable in an eventual high-resolution picture of the intact ribosome.

Bacterial Proteins↗
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Comparison of the metabolic response to a glucose tolerance test and a standardized test meal and the response to serial test meals in normal healthy subjects.

The plasma glucose and insulin response to a standardized meal test breakfast was compared with the time-honored glucose tolerance test in the same normal healthy subjects. The amplitude of glycemic excursion and between-subject variation was less with the more physiologic standardized test meal than with that seen with the glucose tolerance test. The glucose tolerance test's prime function is to amplify any glucose intolerance, thus aiding diagnosis, whereas a standardized meal gives a more clinically relevant metabolic status. The administration of serial test meals during the same day in a smaller group of normal subjects indicated, as seen previously with repeated glucose tolerance tests, a diminishing carbohydrate tolerance during the day.

Adult↗
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Deep mycotic infections in cats.

A review of deep mycotic infections assessed incidence, signalment, clinical presentation, and outcome in 571 feline cases. Pertinent findings included a predisposition in young, male cats for Sporothrix schenckii and Blastomyces dermatitidis. There was an increased incidence of feline leukemia virus infection in cases with histoplasmosis and of feline panleukopenia virus infection in cases with either aspergillosis or mucoralosis. Few other predisposing conditions were identified. Cryptococcosis, coccidioidomycosis, and sporotrichosis had better prognoses for recovery. Blastomycosis, histoplasmosis, and aspergillosis commonly were disseminated infections and were associated with guarded-to-poor prognoses.

Animals↗
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Teaching in practice.

This article describes an action research project designed to develop a teaching programme which would enable students to bridge the theory-practice gap they experienced while on placement in a gynaecology unit.

Clinical Competence↗
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Use of Doppler ultrasound in leg ulcer assessment.

Adequate patient assessment is the most important element of chronic wound management, and the use of holistic techniques enables practitioners to make informed clinical judgements. Doppler ultrasound is integral to the holistic assessment of leg ulcers. This article reviews the procedure for measuring ankle/brachial pressure indices using Doppler ultrasound and outlines various diagnostic tests that employ the Doppler principle.

Data Interpretation, Statistical↗
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Plotting a course.

Explore the source record for details and available documents.

Clinical Competence↗
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Choledochal cysts: heterogeneity of clinical presentation.

Over a 12-year period, 23 children were diagnosed as having choledochal cysts, of which 22 were type I and one was type II. The triad of right upper-quadrant abdominal pain, right upper-quadrant abdominal mass, and cholestatic jaundice was present in only four of 23 (17%). Mean time from the onset of symptoms to establishing the correct diagnosis was 20 months, and in one child the diagnosis was established only at autopsy. Six children had histologic evidence of biliary cirrhosis, and three developed portal hypertension despite surgical intervention. Both ultrasonography of the abdomen and endoscopic retrograde cholangiopancreatography (ERCP) were useful methods in establishing the diagnosis, but both tests did result in false negatives. Choledochal cysts are treatable causes of cholestatic jaundice in infants and children, but the intermittent and variable nature of their presentation renders clinical diagnosis difficult.

Adolescent↗