Biomedical subjects

T A Hall

Publications and source records attributed to T A Hall.

94 records · Page 6Linked to original sources

PubMedDate not supplied

Localised concentrations of elements in hamster cardiomyopathy. Electron microscopic x-ray microanalysis of normal and sick myocardia.

Localized elemental concentrations of Ca, P, Cl, S, and Zn were detected by X-ray microanalysis during viewing of ultrathin myocardial sections. Cardiomyopathic hamsters were compared with a healthy strain of the same age. Significant increases in calcium and chlorine concentrations were found in sick animals. These were highest in the hypertrophic stage of the disease. Phosphorus and zinc were more variable. Ratios between elements (especially P/Ca) in the same cells and of the same elements in different cell types were found to offer numerical criteria for estimating the degree of pathological change.

Animals↗

PubMedDate not supplied

Use of global positioning system technology to track subject's location during environmental exposure sampling.

Global positioning system (GPS) data recorders were worn by subjects in the Oklahoma Urban Air Toxics Study (OUATS) for automatic logging of their location as they went about their normal daily activities. The location information obtained by the GPS units had an uncertainty of about 10-20 m, which was sufficiently precise to track subjects' movements on trips outside the immediate vicinity of their homes. Due to instrument problems, primarily related to reduced battery life, the units operated for only about 30% of the total monitoring time attempted in 25 trials. The GPS data were compared to time-activity diaries kept by the subjects. In almost all cases, the GPS data confirmed all travel events reported in the subjects' diaries. Additionally, in five out of five trials in which the logging period covered most or all of the subjects' daytime activities, at least one travel event that was not recorded in the diary was detected by GPS. Notwithstanding the limitations of present technology, GPS was found to be a promising means for tracking of research subjects in community-based exposure assessment studies.

Adult↗

PubMedDate not supplied

Posterior disk displacement: morphologic assessment and measurement reliability--cervical spine.

BACKGROUND: Magnetic resonance imaging (MRI) is often used to assess for disk displacement after manipulation, but limited information about the true incidence of iatrogenic herniations exists. Preliminary data must be obtained concerning the size of different types of displacement to further assess this relationship. The reliability of chiropractic radiologists in assessing disks, and a comparison of measuring devices should be evaluated. OBJECTIVE: To identify average measurements for normal and displaced disks and to assess the reliability of measurements by chiropractic radiologists. STUDY DESIGN: Intraobserver and interobserver reliability study assessing cervical disk displacement on MRI scans. METHODS: Three evaluators assessed the disks on 106 MRI scans. Six categories were assessed and compared. Thirty-seven scans were reassessed for intraobserver comparisons. Interobserver and intraobserver variations and measurement-device correlations were determined. RESULTS: Interexaminer measurement reliability for the 2 devices was 0.80 to 0.84. Intraexaminer reliability ranged from 0.58 to 0.94. Interexaminer and intraexaminer agreement for the presence of disk displacement was 86% (kappa = 0.69) and 78% to 85% (kappa = 0.50-0.67), respectively; for the presence of osteophytes, 92% (kappa = 0.54) and 86% to 95% (kappa = 0.60-0.80); and for the classification of disk displacements, 76% (kappa = 0.53) and 73% to 80% (kappa 0.44-0.61). Distinguishing between normal versus bulged disks demonstrated the greatest classification disagreement. Clear size differences between the types of disk displacement were noted. The ruler and digitizer correlation coefficient was 0.96. CONCLUSIONS: Interexaminer and intraexaminer agreement were good to very good concerning measurements and fair to good concerning disk assessments. Different disk displacement types demonstrated obvious mean size differences. No significant mean difference in measurements between the ruler and the digitizer was noted.

Adolescent↗

PubMedDate not supplied

An investigation of secondary exposure misclassification effects of lifelong occupational history in exposure estimation.

The effects of exposure misclassification on the interpretation of results of occupational epidemiological studies has been widely investigated and reported. Usually, only the direct effects of misclassification have been considered or simple estimates of misclassification rates have been assigned to various types of exposure estimation processes. Lifelong job profile data obtained from a previously published case-control study provided complete or nearly complete job histories of 511 decedents. An analysis of these work histories and the comparison of exposures related to longest-held job to estimated total lifetime exposures suggest that single job-based exposure estimates may lead to significant exposure misclassification rates. In addition, the appearance of shorter duration jobs in a study population occurring predominantly early in the work history may exacerbate problems associated with exposure misclassification. While few specific suggestions emerge from this analysis, the inclusion of extensive recording of the work history of study subjects emerges as a reasonable basis for the investigation and potential reduction of secondary misclassification of exposures in occupational epidemiological studies.

Aged↗