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Biomedical subjects

T Johnson

Publications and source records attributed to T Johnson.

At least 235 records · Page 13Linked to original sources
PubMed1986

Potential methods for predicting tumor radiocurability.

Several predictors of tumor radiocurability are already integrated into clinical practice, for example, tumor size, gross morphology (that is, infiltrative or exophytic), histologic type and grade. These are nonspecific and relatively imprecise. The aim of research into predictive assays is not only to refine the discrimination of existing predictors, but also to suggest specific experimental approaches for overcoming tumor radioresistance in individual patients. Two broad categories of predictive assays can be defined: direct and indirect measurement of tumor cell survival and/or repair capability following irradiation, and measurement of cellular and extracellular parameters affecting radiosensitivity. The ongoing research at The University of Texas M. D. Anderson Hospital is overviewed to illustrate potential methods for predicting radiocurability.

Animals↗
PubMed1985

Predicting radiocurability.

Several predictors of tumor radiocurability are already integrated into clinical practice, e.g., tumor size, gross morphologic features (i.e., infiltrative or exophytic), histologic type, and grade. These are relatively imprecise, however, and none is specific. The aim of research into predictive assays is not only to refine the discrimination of existing predictors but also to suggest specific experimental approaches for overcoming tumor radioresistance in individual patients. Two broad categories of predictive assays can be defined: direct and indirect measurements of tumor cell survival and/or repair capability following irradiation and measurement of cellular and extracellular parameters affecting radiosensitivity. Examples from ongoing research at the University of Texas M. D. Anderson Hospital using one technique from each category (the micronucleus assay and flow cytometric analysis of tumor cell proliferation kinetics and ploidy) are used to illustrate potential methods of selecting patients for fast neutron radiotherapy.

Animals↗
PubMed1985

Detection of an abdominal aneurysm by indium-111 platelet imaging.

The authors report a case in which In-111 platelet imaging provided uniquely useful information in the discovery of an abdominal aortic aneurysm. This case illustrates the potential usefulness of this procedure in the detection of unsuspected sites of thrombogenic vascular disease.

Aorta, Abdominal↗
PubMed1984

Methylprednisolone sodium succinate (Solu-Medrol) in the treatment of typhoid perforation (a preliminary report).

It is now universally accepted that treatment of typhoid perforation must be surgical. In spite of this and the use of antibiotics, the mortality rate is still high. Previous observations that some patients with typhoid perforation present with features suggestive of septicaemia and septic shock made us conduct a clinical trial with methylprednisolone sodium succinate (Solu-Medrol) in treating this disease. Our data show that use of this drug in addition to antibiotics and early surgical intervention reduces the mortality rate in typhoid perforation.

Adolescent↗
PubMed1984

Venous pressures during simulated Bier's block.

Venous pressures in the forearm veins during the simulated performance of intravenous regional analgesia were measured. Pressures obtained equalled or exceeded the recommended occluding pressure of the tourniquet. This finding is proposed as one of the possible reasons for the occasional observation that convulsions may occur during Bier's block despite the presence of an intact tourniquet system.

Anesthesia, Conduction↗
PubMed1984

Nasal carriage and antibiotic susceptibility of Staphylococcus aureus in general practice.

The incidence of nasal carriage of Staphylococcus aureus and the in vitro susceptibility of isolates to fusidic acid, penicillin, erythromycin, methicillin and tetracycline was determined in 204 patients who had been treated previously with a short course of a topical preparation of Fucidin for acute skin sepsis, and in an equal number of control subjects. Staphylococcus aureus was isolated from 36 per cent and 34 per cent of patients in the Fucidin and control groups respectively. Only one of the 144 isolates was resistant to fusidic acid. Short, single courses of topical therapy in general practice are unlikely to be epidemiologically hazardous in the long term. Evidence of possible cross-infection in general practice was obtained.

Administration, Topical↗
PubMed1983

Simultaneous three color and electronic cell volume analysis with a single UV excitation source.

We have adapted an Ortho ICP-22 flow cytometer (Ortho Instruments, Westwood MA) for the simultaneous measurement of three independent fluorochromes and cell volume. This has been accomplished by the addition of a third photomultiplier tube and the development of a new electronic cell volume (ECV) flow cell. Cells are first analyzed as they pass through the 100 U ECV aperture and are then excited approximately 15 musec later by the 365 nm mercury are beam reflected by a 400 nm dicroic mirror. Independent blue, green and red signals can be associated by a delay circuit to the ECV signal from the same cell. We have developed this system as an aid in the analysis of tumor cell and macrophage heterogeneity and differentiation. The choice of stain combinations to be used is extremely flexible and permits the analysis of a wide range of enzyme activities in conjunction with DNA/RNA and phagocytic probes. Data presented indicates the value of this approach in identifying the presence of plasminogen activator-like activity in both tumor and inflammatory cells within a malignant effusion as well as the quantitative expression of a number of markers of macrophage differentiation. Although the described techniques have been developed on a mercury arc instrument, they can be used equally well with cell sorters.

Color↗
PubMed1982

Age-related differences in isometric and dynamic strength and endurance.

To measure age-related skeletal muscle changes, 30 healthy, moderately active women performed isometric and dynamic strength and endurance tests of their left quadriceps femoris muscle groups. Fifteen of the subjects were ages 20 to 29 years and 15 were ages 50 to 80 years. A cybex II isokinetic dynamometer was used to measure the torque output isometrically with the knee at 90 degrees of flexion on three trials. In addition, each subject performed three trials from 90 degrees of knee flexion to full knee extension and back to 90 degrees of knee flexion with the velocity of the isokinetic dynamometer set at 10 rpms. Endurance time was calculated to be the length of time a torque output of at least 50 percent of the maximal strength could be maintained. The t tests done revealed a significant difference between the two groups on isometric and dynamic strength, while no significant difference was found on isometric or dynamic endurance. Statistically correcting for the extraneous variables, height and weight, through a partial correlation revealed a significant negative correlation between age and strength. The younger subjects had higher torque outputs, both isometrically and dynamically, than the older subjects. The same partial correlation between isometric endurance and age and dynamic endurance and age demonstrated no significant correlation. The fact that endurance did not change in this older population while strength did may be the result of fast-twitch and slow-twitch muscle fibers changing with age.

Adult↗
PubMed1982

Slow late myocardial clearance of thallium: a characteristic phenomenon in coronary artery disease.

We extended the quantitative seven-pinhole method to follow the dynamics of thallium redistribution after exercise. We observed a pattern of slow late thallium clearance that appears to be characteristic of myocardium supplied by obstructed coronary arteries. In 28 subjects, quantitative thallium scintigrams (seven-pinhole tomography, circumferential count profiles) and blood samples for thallium concentration were taken immediately, 2 hours and 4 hours after maximal treadmill exercise. Twenty subjects had coronary artery disease (CAD) and eight were normal. The rate of thallium clearance from the blood (TCB) was compared with the rate of thallium clearance from each segmental region of myocardium (TCM, derived by ratioing corresponding segments of the absolute circumferential count profiles) between the 2- and 4-hour images. In seven of the eight normal subjects, TCM exceeded TCB in all regions of all images (specificity 88%). Seventeen of the 20 CAD patients had at least one region where TCM was less than TCB (sensitivity 85%). Of the 13 patients with multivessel CAD, 11 had multiple regions with TCM less than TCB. Using this criterion, we detected 31 of 39 obstructed coronary arteries. Of the 37 regions that were abnormal by this analysis, 30 corresponded to obstructed coronary arteries. In contrast, while conventional circumferential count profile analysis also was abnormal in 17 of the 20 CAD patients, it diagnosed multivessel CAD in only five of the 13 patients that had it. These results show that slow late thallium clearance from myocardium is characteristic of regions of myocardium supplied by diseased coronary arteries and that observation of this phenomenon may improve diagnostic sensitivity for the presence of multivessel CAD.

Coronary Disease↗
PubMed1982

Single-photon emission tomography with a 12-pinhole collimator.

To assess the advantages of more complete angular sampling and of more views in the tomographic reconstruction process, tomographic imaging with a 12-pinhole (12PH) collimator has been compared with 7-pinhole tomography (7PH). The 12PH system gives a 50% increase in sensitivity but resolution degrades more rapidly with depth. The 7PH and 12PH systems provide similar accuracy of detection of lesions in a myocardial ring phantom. The 7PH images, however, demonstrated more noise and "ripple" artifacts. The 12PH system offers a larger reconstruction volume and generates fewer artifacts when the collimator is misaligned with the myocardial long-axis, thus making patient positioning less critical than with 7PH. A disadvantage is that individual views are minified by the 12PH collimator, and a 256 X 256 image matrix should be used during image acquisition to limit digital sampling errors.

Evaluation Studies as Topic↗
PubMed1981

Faculty supervision of residents in an internal medicine practice.

This study examines the supervision of residents by faculty members in an outpatient internal medicine practice. For the study, the investigators developed a methodology to analyze the cognitive content and the focus of residents' thoughts during conversations between faculty members and residents. The residents also identified characteristics of productive and less productive exchanges with the faculty. The study shows that both residents and faculty members use the majority of their part of conversations to present information. Residents in early training appear to be more challenged by diagnostic issues, while residents later in training are more concerned with therapy and management. The study results suggest that effective supervision may relate more to the ability of faculty members to display their reasoning as they present information to residents than to the quantity and types of questions they pose to residents.

Communication↗