Biomedical subjects

R D Gibbons

Publications and source records attributed to R D Gibbons.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Exactly what does the Hamilton Depression Rating Scale measure?

The purpose of this study is to evaluate empirical criticism of the psychometric properties of the Hamilton Depression Rating Scale (HDRS) by undertaking an "internal construct validity" evaluation. Individual symptom responses for the HDRS were obtained from 370 patients meeting Research Diagnostic Criteria for major depression. A multidimensional normal item response theory (IRT) model was used to assess the dimensionality of the HDRS and estimate corresponding item parameters which were then expressed as factor loadings and item thresholds. The analysis yielded a five-dimensional solution. The first dimension (depressed mood, guilt, suicide, work and interests, agitation, psychic anxiety, somatic anxiety, and loss of libido) appeared to define global depression severity. These results are consistent with other published factor analytic studies and provide further justification for thinking that the HDRS total score is a weak index of depressive syndrome severity. The findings provide a benchmark by which the adequacy of future results may be judged, because the multidimensional IRT model does not suffer from the statistical limitations that arise when applying traditional factor analytic methods to discrete symptom ratings.

Adolescent↗

PubMedDate not supplied

The effect of diethylstilbestrol as measured by host resistance and tumor susceptibility assays in mice.

As part of a program to develop and validate methodology to measure chemically induced immunotoxicity, the effect of DES on resistance of adult B6C3F1 female mice to various microorganisms and to challenge with syngeneic tumor cells was evaluated. The mice received sc injections of 50 microliter corn oil alone or of corn oil containing the equivalent of 0.2, 1, and 4 mg DES/kg X d for 14 d. Three days later they were challenged with Listeria monocytogenes, Streptococcus sp. influenza virus, herpes virus, Trichinella spiralis, or B16-F10 tumor cells. Host resistance parameters were mortality for the bacterial and viral systems, expulsion of adult parasites from the gut for T. spiralis, and lung weights for the B16-F10 tumor-cell model. Host resistance to L. monocytogenes, herpes virus, and T. spiralis was significantly decreased following DES exposure. Resistance to Streptococcus sp. was decreased, but not at a statistically significant level following these doses of DES. However a dose of DES at 8 mg/kg X d resulted in a highly significant decrease in resistance to the organism. Resistance to influenza virus was unaffected by the DES. In contrast to the above, host resistance to iv-administered B16-F10 tumor cells was significantly increased as a consequence of DES exposure. These model systems for measuring alterations in host resistance have been indicated to hold potential for the routine screening of drugs, chemicals, and environmental agents for their possible immune effects, both adverse and potentiating. The results indicate the importance of selecting the appropriate assay for evaluating a particular agent. They also stress the necessity for including host resistance assays along with assays to measure specific immune aspects, in order to assess in the intact animal the overall effect of complex immune interactions following exposure to a test agent.

Animals↗

PubMedDate not supplied

Automatic bone age measurement using computerized image analysis.

In 1992 we described a computer-assisted method for assigning Tanner-Whitehouse RUS skeletal maturity scores to hand-wrist radiographs. An operator positions each epiphysis in turn beneath a video camera, views the image on the computer screen and corrects the position of the radiograph by matching to templates of the TW stages displayed on the screen. The process is then automatic; the computer, not the operator, rates the bone. The image is digitized and then represented by a large number of mathematical coefficients. These coefficients are then compared to those generated by each stage of the TW standards, and the closest match is sought. Since the comparison is quantitative the system produces continuous stage scores instead of the old discrete ones such as B, C, D, etc. Thus in longitudinal data a much smoother progression of skeletal maturity scores with age is achieved. The reliability of the computer-assisted skeletal age score (CASAS) is considerably greater than that of the usual manual method. Differences between duplicate readings of a bone by a single observer average about 0.25 stage, and reach 1.0 stage or more only in about 3% of instances, compared with 15-20% characteristic of manual ratings.

Age Determination by Skeleton↗