PubMed Health⌕ Search

Biomedical subjects

T R Knapp

Publications and source records attributed to T R Knapp.

15 recordsLinked to original sources
PubMed1991

The multitrait-multimethod approach to construct validity.

The multitrait-multimethod matrix approach as proposed by Campbell and Fiske (1959) was an important contribution to our understanding of the nature of validation procedures. There are, however, problems encountered when using the Campbell and Fiske (1959) approach. The purpose of this article is to discuss the method and selected problems, and to propose an alternate approach to address those problems.

Analysis of Variance↗
PubMed1991

More on MTMM: the role of confirmatory factor analysis.

This article is the second of two on the use of confirmatory factor analysis (CFA) as a method to assess construct validity. The construct validation criteria required by the conventional MTMM approach are satisfied only by certain ideal data sets, such as those in which the method variance of measures is very low. The CFA approach to multitrait-multimethod (MTMM) data is more general, in that violations of those stringent criteria can be managed. Another limitation of the conventional MTMM approach is that only a relatively small number of indicators can be examined by bivariate analysis. The economy of the CFA approach permits the analysis of a much larger number of indicators. In this article, a data set is analyzed using the CFA approach. Results are presented that illustrate the application of this statistical method.

Electromyography↗
PubMed1991

Coefficient alpha: conceptualizations and anomalies.

In this article distinctions are made among some of the different conceptualizations of, and formulas for, Cronbach's coefficient alpha as it is applied to dichotomous or nondichotomous, standardized or unstandardized, and weighted or unweighted data. Issues regarding the statistical significance of alpha and the occasionally encountered anomalies of artificially high alpha and negative values of alpha are given particular attention.

Data Interpretation, Statistical↗
PubMed1991

Ovarian steroid production in vitro during gonadal regression in the turkey. I. Changes associated with incubation behavior.

The mechanism regulating ovarian regression during incubation behavior in the domestic turkey has not been elucidated. This study was designed to determine whether ovarian steroidogenic potential is depressed during gonadal regression associated with the onset of incubation behavior. Hens were housed in floor pens equipped with trap nests that were checked 7 times per day. Hens were grouped, according to nesting frequency and egg production, into the following classifications: laying (laid an egg every day and trapped in the nest only once/day); transitional (laid an egg every day but trapped in the nest 4 or more times/day); and Day 1, Day 3, and Day 5 incubating (no egg for 2, 4, or 6 days, respectively, while trapped in the nest at least 4 times/day). Follicular atresia was evident in the largest preovulatory follicle (F1) in transitional hens, extensive in F1 through the third largest follicle (F3) in Day 1 incubating hens, and extensive in F1 through F7in Day 3 incubating hens. Levels of circulating LH, progesterone (P), androgen (A), and estradiol (E) decreased in transitional hens relative to concentrations in laying hens and remained low thereafter. In contrast, levels of prolactin were greater in Day 3 and Day 5 incubating hens than in laying, transitional, or Day 1 incubating hens. Basal production of P by F1 granulosa cells was lower from Day 1 incubating hens than from the other groups. Production of P in response to porcine-luteinizing hormone (pLH) was greater by cells from transitional and Day 1 incubating hens than from those of laying hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗
PubMed1989

Age, cohort, and time-period confounds in aging research.

1. Cross-sectional studies of age-related changes or developmental patterns contain the inherent confound of age and cohort. 2. Longitudinal studies of age-related changes or developmental patterns contain the inherent confound of age and time-period. 3. Many complex research designs and decision rules have been developed in an attempt to disentangle these confounds. These designs and decision rules are only useful if their assumptions are met. 4. It is important to logically determine when the age, cohort, and time-period confounds discussed in this article are important to resolve in a nursing study and when the confounds do not directly relate to the clinical or theoretical merit of a study.

Aged↗
PubMed1988

Gonadal steroid modulation of basal and vasoactive intestinal polypeptide-stimulated prolactin release by turkey anterior pituitary cells.

Porcine vasoactive intestinal polypeptide (VIP; 10(-9) to 10(-7) M) was a potent stimulator of prolactin (PRL) release by anterior pituitary cells from immature and laying turkey hens. Basal and VIP-induced PRL release of cells from laying hens were diminished (P less than 0.05) when the cells were cultured for 48 hr in the presence of charcoal-stripped laying hen serum, but not when the cells were cultured in the presence of whole laying hen serum. This change in VIP-induced PRL release was not evident when cells were derived from immature hens. Basal PRL release by cells from laying hens was not altered by the presence of estradiol (E2; 10(-12) to 10(-5) M), although such release was generally enhanced in cultures of cells from immature hens containing E2. The presence of E2 enhanced (P less than 0.05) the magnitude of the VIP-induced PRL release by cultures of cells from laying hens and diminished (P less than 0.05) the magnitude of this release in cultures of cells from immature hens. Cells from immature and laying hens exposed to progesterone (P4; 10(-5) M) for 96 hr exhibited enhanced basal PRL release, though lower P4 concentrations had no effect. Utilizing cells from laying hens, P4 exposure for 24 hr resulted in diminished (P less than 0.05) VIP-induced PRL release, while P4 exposure for 96 hr resulted in markedly enhanced (P less than 0.05) VIP-induced PRL release. Basal PRL release was generally not altered by the presence of testosterone (T). The VIP-induced PRL release by cells derived from immature and laying hens was diminished (P less than 0.05) by the presence of T. Prolactin release in the turkey is likely modulated by gonadal steroids acting directly on the cells of the anterior pituitary.

Animals↗
PubMed1988

Nurses' attitudes toward conventional and automated vital signs measurement methods.

The acceptance and assimilation of new medical technologies into the health-care arena is a complex process involving financial, humanistic, and clinical considerations. This experimental research compared nurses' attitudes regarding the clinical acceptability of conventional methods of measuring vital signs with their attitudes toward a new, automated method, using the IVAC Model 4000 Vital-Check. Two studies were conducted, at different university-affiliated hospitals, involving different nursing-care-delivery models. The 102 nurses who participated in the studies generally favored the automated method with respect to provider convenience, patient acceptance, and the opportunity to simultaneously perform other nursing assessments. Conventional techniques were preferred for patients on isolation precautions and in some very specific clinical situations such as those requiring detection of abnormalities in the heart rhythm. Interviews of patients were also conducted at both sites and their comments supplemented and supported the quantitative findings for the nurses. Patients seemed to adapt very well to the new technology. They were particularly interested in being better able to monitor their own measurements with the automated process.

Attitude of Health Personnel↗
PubMed1977

Pathologic scar formation. Morphologic and biochemical correlates.

Morphologic and biochemical analyses were performed to compare normal skin and mature scars to hypertrophic scar and keloid. Correlation of morphologic findings with biochemical profiles of the skin and scar samples proved feasible and enlightening. Scanning electron microscopy (SEM) was used to characterize the architectural arrangement of collagen fibers in skin and scars. Cultured fibroblasts from each specimen were also examined with the SEM. A biochemical profile of each tissue specimen was constructed, characterizing the collagen component of the specimen by sequential molecular sieve and ion exchange chromatography to determine a) the degree of intermolecular crosslinking, b) amino acid analysis, and c) levels of lysyl oxidase activity. Results indicate that collagen fibers and fiber bundles display a decreasing level of organization as the clinical degree of scar abnormality increases, and this structural gradient correlates with the gradient of intermolecular crosslinking in the same tissue--normal skin and mature scar being highly crosslinked, hypertrophic and keloid successively less so. Surprisingly, the level of the crosslinking enzyme lysyl oxidase is normal or elevated in hypertrophic scar and keloid despite the relative lack of crosslinking. Amino acid content was uniform for all specimens. Scanning electron microscopy examination of cultured fibroblasts from the tissue specimens demonstrated three phenotypically distinctive fibroblasts whose numerical and volumetric proportions correlated with the tissue of origin.

Amino Acids↗
PubMed1977

Injectable collagen for soft tissue augmentation.

Collagen from allogenic and xenogeneic sources has been made soluble by controlled proteolytic digestion. The monomeric, telopeptide-poor collagen so prepared forms a cohesive mass when warmed to body temperature (upon injection), creating a structural basis for new soft connective tissue. We have treated 28 patients with human and/or bovine collagen injections for the correction of soft tissue contour defects, and we have followed them for 3 to 18 months. In most instances, there has been lasting and substantial correction of the defects treated. The complications have been few and transient.

Acne Keloid↗