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Biomedical subjects

D C Clark

Publications and source records attributed to D C Clark.

At least 127 records · Page 7Linked to original sources
PubMed1987

Model for quantifying the drug involvement of medical students.

We have applied a two-parameter normal item-response model to analyze data on "drugs ever used" by freshman medical students, then used the result to predict their subsequent drug use patterns over the first 18 months of medical school. Our results provide strong evidence for the existence of a single latent dimension of "drug involvement," and they demonstrate that a student's initial position on this dimension predicts subsequent drug use well. The model applies to male and female students equally well, suggesting the dimension is not sex specific. Students' drug use is cumulative in the sense that an individual tends to add new drugs to all previous drugs, rather than "graduating" from a previous to a new drug, as he/she becomes more "drug involved." Greater "drug involvement" is also associated with more frequent use of most drug categories.

Adult↗
PubMed1986

Natural history of untreated inferior vena cava injury and assessment of venous access.

Conventional policy mandates exploration of retroperitoneal hematomas presumed to contain penetrating injuries of the inferior vena cava (IVC). In clinical practice this maneuver frequently results in torrential blood loss, suggesting the injury may be best managed without exploration and IVC suturing. The present study was undertaken to define the natural history of untreated IVC perforations, and to assess venous access with such injuries. Twelve adolescent Hampshire pigs (20-25 kg) underwent halothane anesthesia and laparotomy. The infrarenal IVC was isolated temporarily and a posterior cruciate incision, equivalent to 50% of the IVC circumference, made via anterior venotomy. Animals were resuscitated with Ringer's lactate. Technetium sulfur colloid was injected 20 min postlaparotomy closure via either a jugular or femoral venous cannula, and count activity measured over the IVC injury site using a mobile gamma camera. The procedure was repeated via the counterpart limb. Background from the first injection was subtracted, and count ratios integrated from 16 to 19 min postinjection. Extravasation following lower extremity infusion was not significantly different from that following central venous administration. One pig succumbed to cryptogenic peritonitis one wk postinjury. The remaining animals were killed at periods ranging from 3 to 12 wk. No animal had clinical evidence of delayed bleeding, pulmonary embolus, or other venous sequelae during the observation period. At autopsy all vena cavae were normal caliber without evidence or pseudoaneurysm of thrombosis. This swine study confirms the efficacy of lower extremity venous access with contained IVC injury, and suggests that isolated retroperitoneal IVC injuries may be treated nonoperatively in very selected patients.

Animals↗
PubMed1985

The assembly of microtubule protein in vitro. The kinetic role in microtubule elongation of oligomeric fragments containing microtubule-associated proteins.

The kinetics of assembly were studied for bovine and pig microtubule protein in vitro over a range of conditions of pH, temperature, nucleotide and protein concentration. The kinetics are in general biphasic with two major processes of similar amplitude but separated in rate by one order of magnitude. Rates and amplitudes are complex functions of solution conditions. The rates of the fast phase and the slow phase attain limiting values as a function of increasing protein concentration, and are more stringently limited at pH 6.5 than pH 6.95. Such behaviour indicates that mechanisms other than the condensation polymerization of tubulin dimer become rate-limiting at higher protein concentration. The constancy of the wavelength-dependence of light-scattering and ultrastructural criteria indicate that microtubules of normal morphology are formed in both phases of the assembly process. Electrophoretic analysis of assembling microtubule protein shows that MAP- (microtubule-associated-protein-)rich microtubules are formed during the fast phase. The rate of dissociation of oligomeric species on dilution of microtubule protein closely parallels the fast-phase rate in magnitude and temperature-dependence. We propose that the rate of this process constitutes an upper limit to the rate of the fast phase of assembly. The kinetics of redistribution of MAPs from MAP-rich microtubules may be a factor limiting the slow-phase rate. A working model is derived for the self-assembly of microtubule protein incorporating the dissociation and redistribution mechanisms that impose upper limits to the rates of assembly attainable by bimolecular addition reactions. Key roles are assigned to MAP-containing fragments in both phases of microtubule elongation. Variations in kinetic behaviour with solution conditions are inferred to derive from the nature and properties of fragments formed from oligomeric species after the rapid temperature jump. The model accounts for the limiting rate behaviour and indicates experimental criteria to be applied in evaluating the relative contributions of alternative pathways.

Animals↗
PubMed1985

Application of modern psychometric theory in psychiatric research.

This paper describes the general statistical theory of item-response modeling as developed in the fields of statistics and education. Generalization of these procedures for application in the analysis of psychiatric rating scales is the focus of this paper. Questions of unidimensionality vs multidimensionality and choice of distributional transform (logistic vs normal) are both discussed and statistically examined using data on the Beck Depression Inventory (BDI). Application of these models to the BDI revealed two subscales that maximally differentiate high and low levels of depression in psychiatric and medically ill patients respectively. There was considerable but not complete overlap between the two subscales. These statistical models are found to have desirable properties when used to analyze psychiatric rating scales and provide a refinement over existing techniques of classical test theory and factor analysis.

Adult↗
PubMed1985

Personality indicators of psychosocial adjustment in first-year medical students.

One aspect of the Rush Medical College Longitudinal Study is concerned with the identification of personality traits that predict various kinds of psychosocial adjustments and impairments among medical students and physicians. Two orthogonal traits, masculinity and femininity, were selected for study as independent variables because of their implications for mental health and their relevance to the work of physicians. Ninety percent (N = 106) of a class of first-year medical students completed measures of masculinity and femininity during orientation and, 8 months later, completed a broad array of dependent measures of psychological well-being, interpersonal satisfaction, humanistic attitudes and alcohol consumption. Analyses of the data revealed strong and consistent main effects of masculinity on depression, confidence, pleasure capacity, extraversion, locus of control, neuroticism and interpersonal satisfaction. Femininity was associated with depression, pleasure capacity, extraversion, neuroticism, interpersonal satisfaction, concern for the opinion of others and humane attitudes toward patient care. Low femininity was also associated with high alcohol consumption. These results suggest that masculinity and femininity scores may help to identify at the outset medical students at risk for impairment, and that androgynous individuals (who are high in both masculinity and femininity) may be especially well-suited to assume the demanding and varied roles that physicians are called on to play.

Adaptation, Psychological↗
PubMed1985

Unbiased criteria for severity of depression in alcoholic inpatients.

The internal consistency of the Beck Depression Inventory (BDI) is assessed in 106 inpatient alcoholics by using a latent trait model. The analysis confirms that the BDI measures a single underlying dimension of depressive severity among alcoholics. Seven symptoms discriminate well for severity of depression. These seven--work inhibition, guilt, self-disgust, irritability, indecision, dissatisfaction, and loss of social interest--may represent criteria for depressive severity that are not confounded by chronic drinking, physical withdrawal, unique personality organization, or life circumstances of alcoholics. Three of the symptoms--dissatisfaction, loss of social interest, indecision--may represent core criteria for depressive severity by virtue of their previously demonstrated ability to discriminate well for severity of depression among both psychiatric and medical inpatients.

Adult↗
PubMed1985

Results of the Sherbrooke-Lac Mégantic fluoride varnish study after 20 months.

The purpose of this study was to demonstrate the effectiveness of two fluoride varnishes (Duraphat and Fluor Protector) in the prevention of dental caries in children residing in a non-fluoridated community. At baseline, 787 grade one children (6-7-yr old) were examined and randomly allocated into a control and two treatment groups. At 20 months, 703 children remained in the study. The mean baseline caries experience and the mean number of permanent teeth present at 20 months were not significantly different among the treatment and control groups. The mean DMFS increments after 20 months were 1.70, 1.73 and 2.02 for Fluor-Protector, Duraphat and control groups respectively (% reductions of 15.8 and 14.4 for Fluor-Protector and Duraphat groups). The mean dfs increments for primary molars after 20 months were 1.56, 1.62 and 1.74 for Fluor-Protector, Duraphat and control groups respectively (% reductions of 10 for Fluor-Protector and 7 for Duraphat).

Child↗
PubMed1985

The results after 20 months of a study testing the efficacy of a weekly fluoride mouthrinsing program.

The purpose of this study was to determine the efficacy of weekly mouthrinsing with a 0.2 percent NaF solution in first-grade children living in a non-fluoridated community. Children in the control group were also participants in a randomized clinical trial to evaluate the efficacy of semiannual fluoride varnish treatments. Children allocated to the mouthrinse group attended school at three of the 17 area schools where the varnish study was occurring. Random allocation of children into the treatment group was considered impractical because of potential problems of teacher cooperation and compliance. The same two standardized examiners examined all participants, and were blind to group assignment for all children. After two academic years, or approximately 72 weeks of rinsing, 178 and 247 children remained in the treatment and control groups, respectively. The control group experienced a mean caries rate of 2.02 surfaces over 20 months, while the treatment group demonstrated an increment of only 1.33 surfaces, representing a savings of about 0.34 surfaces per year or a reduction in DMFS of 34.2 percent. Surface-specific incremental reductions after 20 months were 0.35, 0.19, and 0.14 for the occlusal, buccal, and lingual surfaces, respectively. The proximal increment was too small to draw any meaningful conclusions. In the primary dentition, the treatment and control dfs increments were 0.74 and 1.74, respectively. This reduction represents a savings of one-half surface increment per year, or a reduction of 57.5 percent.

Child↗
PubMed1984

Is capacity for pleasure associated with executive career success?

Executives with a low capacity for pleasure were examined to determine if they evidence less occupational and social success than those with normal or high capacity. Data on pleasure capacity and depressive symptoms were collected from 88 senior executive officers, and scores were compared with independent ratings of career success. The 11% of executives with serious work-related or personal problems showed significantly higher pleasure scores than the rest. It is hypothesized that the relatively high pleasure scores of the least successful executives reflect a defensive process of denial or reaction formation rather than an excessively joyful personality trait. A longitudinal study of executives is proposed to clarify whether the high pleasure capacity scores of the least successful executives change situationally over time.

Adult↗
PubMed1984

Seven-month clinical outcome of anhedonic and normally hedonic depressed inpatients.

Using a measure of capacity for pleasurable experiences (the Pleasure Scale), the authors compared at admission and 7-month follow-up 74 psychiatric inpatients meeting DSM-III criteria for major depression. Pleasure scores were stable over 7 months despite the fact that two-thirds of the sample recovered from depression. The subgroup of subjects who were most anhedonic at admission were more likely than the remaining subjects to show clinical recovery but persisted in exhibiting a lower pleasure score (even when the comparison was limited to recovered subjects). Pleasure scores were much better predictors of clinical recovery than were neuroticism scores.

Adult↗
PubMed1984

Predictors of depression during the first 6 months of internship.

Fifty-five interns, representing 71% of the medicine, obstetrics-gynecology, surgery, and pediatric interns at one medical center for one year, participated in interviews involving the Schedule for Affective Disorders and Schizophrenia-Research Diagnostic Criteria (RDC) and Family History-RDC and completed symptom and attitudinal scales at 6-month intervals. Fifteen (27%) developed a depressive syndrome during the first 6 months of internship. Parental history of depression and high scores of trait neuroticism were significantly associated with onset of depression, but personal history of psychopathology, low capacity for experiencing pleasure, and workload were not.

Adult↗
PubMed1984

Evaluation of lithium therapy for alcoholism.

The efficacy of lithium therapy for alcoholism was examined in 84 alcoholic volunteers admitted for rehabilitation. Subjects were randomly assigned to a lithium or placebo treatment condition for 18 months, and were reinterviewed monthly to document their compliance, drinking status, and mood. Two separate factors contributed to abstinent outcome: therapeutic serum lithium levels (greater than or equal to 0.4 mEq/L) and medication compliance. Recommendations are proposed for studying compliance effects in future treatment studies.

Adult↗