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Biomedical subjects

R Thomas

Publications and source records attributed to R Thomas.

At least 559 records · Page 31Linked to original sources
PubMed1988

Effects of repeated days of intensified training on muscle glycogen and swimming performance.

Twelve, highly trained male swimmers were studied before, during, and after 10 successive days of increased training in an attempt to determine the physical effects of training over-load. Their average training distance was increased from 4,266 to 8,970 m.d-1, while swimming intensity was maintained at 94% (SE +/- 2%) of their maximal oxygen uptake, resulting in an average caloric cost during training of 2,293 kcal.d-1 (+/- 74). As a result of the intensified training regimen, the swimmers experienced local muscular fatigue and difficulty in completing the training sessions. Nevertheless, their swimming power, sprinting (s.22.86 m-1), endurance (s.365.8 m-1) performance, aerobic capacity, and muscle (m. deltoid) citrate synthase were unchanged as a consequence of the 10-d training regimen. Four of the 12 swimmers were, however, unable to tolerate the heavier training demands, and were forced to swim at significantly slower (P less than 0.05) speeds during the training sessions. These men were found to have significantly reduced muscle glycogen values, which was the result of their abnormally low carbohydrate intake. The findings of this research suggest that some swimmers may experience chronic muscular fatigue as a result of their failure to ingest sufficient carbohydrate to match the energy demands of heavy training.

Adult↗
PubMed1988

Cardiac transplantation without cardiopulmonary bypass: experimental model to study growth of the transplanted heart.

An experimental model using surface-induced (20 degrees C) deep hypothermia and total circulatory arrest instead of cardiopulmonary bypass was developed for the study of growth of the transplanted heart. Autotransplantation of the heart was performed in 42 young dogs weighing from 4.4 to 9.0 kg (mean, 6.9 kg). Time of ischemia ranged from 26.0 to 60 minutes (mean, 43.4 minutes). Return of satisfactory cardiac function occurred in all but one animal. An early high mortality rate was due primarily to pulmonary complications, but with modifications to the technique, long-term survival increased to 70%. Early deaths (5 days to 13 weeks) of five dogs during preliminary trials were due to pleural effusion (2), sepsis (1), endocarditis (1), and ascites (1). There have been 14 long-term survivors (range, 194 to 498 days; mean, 264 days). Long-term survivors appear well, are active, and show satisfactory growth. This experimental model eliminates the need for heparinization and reduces the potential for complications associated with cardiopulmonary bypass in the dog. It avoids cannulations that might impinge on anastomotic sites. This model appears to be suited for studying growth of the transplanted heart.

Animals↗
PubMed1988

Ischemic myocardial protection. Comparison of nonoxygenated crystalloid, oxygenated crystalloid, and oxygenated fluorocarbon cardioplegic solutions.

This study was designed to compare myocardial protection with a nonoxygenated crystalloid solution, an oxygenated crystalloid solution, and an oxygenated fluorocarbon cardioplegic solution. Postischemic ventricular performance was studied in three equal (N = 7) groups of dogs subjected to 120 minutes of global ischemia induced at an average myocardial temperature of 18.5 degrees +/- 1.4 degrees C (range 17.0 degrees to 21.0 degrees C). Left ventricular global and regional function was evaluated by sonomicrometry and micromanometers before ischemia and at 45 and 60 minutes after ischemia. Stroke volume index, left ventricular pressure-minor external diameter loop area, percent shortening, first derivative of left ventricular pressure, mean velocity of circumferential fiber shortening, and the slope of the end-systolic pressure were used to evaluate myocardial contractility. In vitro oxygen content of the three cardioplegic solutions was measured at a mean injection temperature of 8.3 degrees +/- 0.6 degrees C: 0.8 +/- 0.1 vol% (nonoxygenated crystalloid cardioplegia), 3.2 +/- 0.2 vol% (oxygenated crystalloid cardioplegia), and 6.2 +/- 0.2 vol% (oxygenated fluorocarbon cardioplegia). Recovery of global and regional function was significantly (p less than 0.05) better with both oxygenated solutions than with the nonoxygenated solution. Differences between the oxygenated crystalloid and fluorocarbon groups were not significant. We conclude: (1) Compared to nonoxygenated crystalloid cardioplegia, oxygenated crystalloid and oxygenated fluorocarbon cardioplegic solutions gave superior myocardial protection during 2 hours of ischemic arrest; (2) no difference was found in protective effects between an oxygenated crystalloid and an oxygenated fluorocarbon solution.

Animals↗
PubMed1987

Model analysis of the bases of multistationarity in the humoral immune response.

A formal analysis of the regulation of antibody production has been developed. It comprises two complementary approaches: a logical analysis in terms of discrete (boolean) variables and functions and a more classical analysis in terms of differential equations. A first paper dealt mostly with the logical description which provided global information on how complex the network needs to be in order to account for some main aspects of the immune response, without having to specify the details of the cellular interactions or to introduce a great number of parameters. Here we present the continuous approach and, in particular, a detailed study of the steady states and a discussion of their role in the dynamics of the immune response. The model subject to this analysis is a minimal one, which takes into account a small number of well-established facts concerning lymphocyte interactions and some reasonable assumptions. The core of the model is a negative feedback loop between the helper (TH) and suppressor (TS) T lymphocytes on which autocatalytic loops of the TH and TS populations on themselves are grafted. The salient feature of this minimal scheme is the prediction, for given environmental and parametrical conditions, of a multiplicity of steady states. This multistationarity occurs both in the absence of antigen or for constant antigen levels. Variations in the external constraints provoke switches among the steady states which might be related to the various modes of the humoral immune response, and depend on the doses of antigen injected and on the previous antigenic history of the system. In particular, high and low dose paralysis appear to be associated with two distinct steady state branches.

B-Lymphocytes↗
PubMed1987

Diagnostic ultrasound in the urologist's office.

The clinical value of diagnostic ultrasound in the management of urologic patients is now firmly established. The use of real time diagnostic ultrasound equipment in the solo office practice of a urologist was evaluated by retrospective office record review covering a period of at least one year. The appropriate use of this equipment in daily office practice is shown to be clinically useful, cost-effective, and easily performed by a urologist. The routine use of diagnostic ultrasound by urologists is recommended.

Costs and Cost Analysis↗
PubMed1987

Plasma and cerebrospinal fluid pharmacokinetics of 3'-azido-3'-deoxythymidine: a novel pyrimidine analog with potential application for the treatment of patients with AIDS and related diseases.

We investigated the clinical pharmacokinetics of azidothymidine (N3TdR) as part of a phase I/II trial in the treatment of acquired immunodeficiency syndrome and related diseases. During the 6-week course of therapy, drug levels in plasma, cerebrospinal fluid, and urine were determined by HLPC. The plasma half-life of N3TdR was 1.1 hour. The total body clearance was 1.3 L/kg/hr. At intravenous doses of 5 mg/kg or oral doses of 10 mg/kg, plasma levels were continuously maintained above the target level of 1 mumol/L. Oral bioavailability was 63% +/- 13%. Substantial penetration of N3TdR into cerebrospinal fluid was demonstrated. At doses of 5 mg/kg intravenously or 10 mg/kg orally, cerebrospinal fluid drug levels exceeded and were maintained close to 1 mumol/L. Nineteen percent of the administered dose was excreted unchanged into the urine. Renal clearance was 0.23 L/kg/hr. N3TdR possesses pharmacokinetic properties that would facilitate the long-term treatment of patients with acquired immunodeficiency syndrome: it can be given orally and it penetrates the central nervous system.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Massive hemoptysis from iatrogenic balloon catheter rupture of pulmonary artery: successful early management by balloon tamponade.

Cessation of massive hemoptysis after iatrogenic balloon catheter rupture of the pulmonary artery was observed after a 2-ml inflation of the balloon. A wedge angiogram showed a small cavity near the rupture. Secondary lobectomy was performed; however, the patient died 1 month later. Therapeutic approaches of this life-threatening complication are presented.

Aged↗
PubMed1987

Training and evaluating teams of simulated patients.

The purpose of this study was to train and evaluate teams of standardized (simulated) patients as part of a required course in family medicine for second-year medical students. During three hours of training, six women were trained to play the same person. These standardized teams played four roles during the 12-week course. Each simulator was interviewed by three student interviewers who were part of six groups of ten to 12 students, each group led by a physician. All sessions were audiotaped, and a coding system was developed. The completeness of response, new unscripted items, and accuracy of information provided by the simulators were measured using the audiotape sessions as sources of data. In addition, the degree of accuracy of the affect of each simulator was assessed by faculty and students in written case histories. The results of the study show that multiple simulators are an effective way of promoting active learning and of teaching basic clinical concepts and skills. Teams of standardized patients give students a consistent learning experience when there are constraints of student group size, time, and scheduling simulations within a traditional curriculum.

Clinical Competence↗
PubMed1987

Parameters for neodymium-YAG laser trabeculotomy: an in-vitro study.

A Biophysic Médical Nanolas Q-Switched pulsed neodymium-YAG laser has been used to produce lesions in human trabecular meshwork in vitro. Sectors of corneoscleral tissue containing trabecular meshwork were suspended in a waterbath which had had a Trokel gonioscopic contact lens mounted into one side by means of a watertight seal. The laser was used to produce lesions in the trabecular meshwork on either side of each specimen. The energy levels delivered ranged from 0.5 to 7.0 mJ, and convergence angles of 10 degrees and 18 degrees were employed. The energy levels required to produce discrete lesions into the canal of Schlemm without perforating the underlying sclera were 3.0-5.0 mJ at the 10 degrees convergence angle and 4.0-6.0 mJ at the 18 degrees convergence angle setting. It is recommended that such data be determined for each type of laser prior to attempting short-pulsed laser internal trabeculotomy in patients with glaucoma.

Humans↗