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Biomedical subjects

D C Clark

Publications and source records attributed to D C Clark.

At least 109 records · Page 6Linked to original sources
PubMed1989

An evaluation of the Saskatchewan pit and fissure sealant program: a longitudinal followup.

The Saskatchewan Health Dental Plan (SHDP) is a publicly funded dental insurance program for children between the ages of five and 16 years residing in the province. In 1981, fissure sealants were added as a covered expense. Until September 1, 1987, sealants and other dental treatments covered under the SHDP were provided to schoolchildren by dental therapists in dental clinics established in elementary schools throughout the province. After September 1, 1987, the provision of dental services was transferred to private practitioners in the province. The objectives of this study were to (1) estimate the retention rates of sealants after one, two, and three years of placement; and (2) conduct a longitudinal followup of sealed and unsealed sound teeth to measure the effectiveness of sealants in reducing dental caries incidence. Relative to the first objective, a cohort of children was identified and comparisons were carried out for the periods of 1982-83, 1982-84, and 1982-85. For the last objective, a longitudinal evaluation of effectiveness was carried out only for children five to seven years of age in 1981. Saskatchewan children, who experienced higher caries prevalence than children in the United States, had the highest caries increments on occlusal surfaces of posterior teeth. About 79 percent of the sealants applied by dental therapists were retained three years after application. Sealed teeth experienced 46 percent less caries than unsealed teeth four years after the application of sealants.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Brucellar and tuberculous spondylitis: comparative imaging features.

Radiographs, scintigrams, computed tomographic scans, and magnetic resonance (MR) images of 17 patients with brucellar spondylitis and 15 with tuberculous spondylitis were analyzed to identify distinguishing features. Characteristic findings of brucellar spondylitis included predilection for the lower lumbar spine (68% of lesions), bone destruction limited to the end plates, disk collapse (16 of 19 disks), and granulation tissue or localized soft-tissue edema (17 of 19 sites). MR imaging showed diffuse increased signal in vertebrae and disks on long repetition time (TR)/echo time (TE) images in four patients and focal increased signal with normal disks in one. Epidural extension was best seen on short TR/TE images in four. Tuberculous spondylitis was characterized by predilection for the midthoracic spine (73%), vertebral destruction with gibbus deformity (60%), disk collapse, and paraspinal abscesses (14 of 15). On MR images signal intensity of affected vertebrae was similar to but more severe than findings in patients with brucellar spondylitis. Scintigraphy was the least helpful in differentiating the two infections. Lesions of tuberculous spondylitis affecting the lower lumbar spine were difficult to differentiate from those of brucellar spondylitis.

Adult↗
PubMed1989

The student survey of problems in the academic environment in Canadian dental faculties.

A survey of problems related to stress encountered by 1,255 Canadian dental students was conducted. Substantial experience with problems was reported infrequently, although most students were affected negatively by at least one problem. Most difficulties concerned students' doubts about harnessing their efforts and abilities to master large amounts of material, which, of necessity, reduced their opportunity to pursue other interests. Few demographic features predicted the level of students' problems, although there was an indication that those who perceived themselves above average academically reported fewer problems.

Adult↗
PubMed1988

Vicissitudes of depressed mood during four years of medical school.

We describe the vicissitudes of depressed mood for one medical school class that was assessed repeatedly overtime, from the first day of medical school until several months short of graduation, using the Beck Depression Inventory (BDI). Using an arbitrarily defined BDI cutoff point of 14 or greater, at least 12% of the class showed considerable depressive symptoms at any assessment during the first three years; the largest fraction (25%) was symptomatic near the end of the second year. The median class BDI score increased almost threefold during the first two years. Students were likely to be in a similar class ranking at all assessments, indicating that for many students dysphoric mood was enduring. Those with BDI scores of 21 or greater were more likely to quit medical school. Students with high scores for dysphoria were not more likely to evidence a family history of major depression or concomitant substance abuse. Women medical students were not more vulnerable to depressed mood than men.

Adult↗
PubMed1988

The secondary structure of peptides derived from caseins: a circular dichroism study.

Three peptides have been formed by proteolytic digestion of individual casein proteins and their secondary structures characterised by far-UV circular dichroism (CD). Peptide alpha s1(1-23), residues 1-23 of alpha s1-casein, was generated by treatment of the parent protein with chymosin. Peptides beta(1-28) and beta(1-52), residues 1-28 and 1-52 of beta-casein, were plasmin- and chymotrypsin-generated fragments, respectively. Analysis of the CD spectra revealed that in aqueous solution all three peptides have secondary structures composed exclusively of beta-sheet and random coil. A limited amount of alpha-helix was formed in two of the three peptides upon treatment with high concentrations (greater than 40% (v/v] of 2,2,2-trifluoroethanol. Partial dephosphorylation (60%) of beta(1-28) and beta(1-52) by treatment with alkaline phosphatase resulted in homogeneous preparations, as judged by polyacrylamide gel electrophoresis, which exhibited increased hydrophobicity. This reduction in the level of phosphorylation of serine residues 15, 17, 18 and 19 led to increased propensity for helix formation in the peptides in the presence of 2,2,2-trifluoroethanol, but no alpha-helical structures were detected in the dephosphorylated peptides in the absence of 2,2,2-trifluoroethanol.

Amino Acids↗
PubMed1988

Platelet monoamine oxidase in alcoholism.

We studied platelet monamine oxidase (MAO) activity using 14C-tyramine as substrate in hospitalized alcoholic patients in the early phases of abstinence and in nonhospitalized normal control volunteers. Platelet MAO was determined in 75 patients (67 men, 8 women) with alcoholism and 123 normal control volunteers (52 men, 71 women). The platelet MAO activity in alcoholic patients was significantly lower than in normal control volunteers. We also observed that the mean platelet MAO activity in male alcoholics was significantly lower than in normal males. The analysis of platelet MAO in alcoholics revealed a mixture of two normal distributions. Alcoholic patients falling into the low MAO component were younger in age, with a lower age of onset of alcoholism, and had higher frequencies of family history of alcoholism. They thus resembled type II alcoholics described by other investigators. Platelet MAO may thus serve as a useful biological marker for subtyping alcoholism and identifying high-risk groups at an early stage. The findings of this study are consistent with previous reports of low platelet MAO activity in alcoholic patients.

Adult↗
PubMed1988

Patterns of psychoactive drug prescriptions by house officers for nonpatients.

Substance abuse may be an occupational hazard for physicians, yet the mechanisms of this hazard remain obscure. The present authors tested the hypothesis that a potential source of psychoactive drugs for the physician trainees and other health professionals is prescription writing by house officers. Furthermore, the hypothesis was advanced that house officers may write significant numbers of psychoactive prescriptions for their family members and friends. Of 565 house officers at a medical center, 339 responded to a questionnaire designed to determine the number of prescriptions each had written for nonpatients in the previous eight months for several categories of psychoactive drugs. The largest number of such prescriptions was written for family members and friends, and the second largest number was for fellow house officers. Narcotics were the most frequently prescribed psychoactive drugs. When compared with their representation in the sample, first-year residents and residents in surgery and surgical subspecialties wrote significantly more psychoactive drug prescriptions than other residents. Implications of these findings for residents are discussed.

Academic Medical Centers↗
PubMed1988

Family history and five-year suicide risk.

Family history was examined to determine whether suicide in index patients is associated with suicidal behaviour or mental disorder in their first-degree relatives. Twenty-seven suicides occurred within 5 1/2 years among 955 affectively disordered probands. Among 5042 proband relatives aged 18 years and older, 44 had committed suicide prior to proband entry to the study; however, only one was the relative of a proband suicide. Only two of the relatives who committed suicide were themselves related. As to attempted suicide of relatives, neither the number of attempts nor the severity of attempt was predictive of suicide in probands. Comparison of diagnosis between groups of relatives showed more drug abuse among relatives of proband suicides; this appears to be related to drug abuse among the proband suicides themselves. In contrast to the clustering of suicides within biological families found in other research, these data do not support the use of family history as a clinically useful indicator of suicidal potential in affectively disordered probands.

Adolescent↗
PubMed1987

Magnesium ion effects on microtubule nucleation in vitro.

Much interest has currently been attached to the length distribution of microtubules polymerized in vitro and the related question of their possible 'dynamic instability'. Fundamental to this question is the mechanism of microtubule nucleation, which controls the rates of assembly and disassembly of microtubule protein in vitro. These kinetics are affected by a number of factors, including both the guanine nucleotides, GTP and GDP, and magnesium ion. Mg2+ exerts complex effects, as indicated by the existence of an optimal Mg2+ concentration for the maximum assembly rate of microtubule protein, and we investigate these effects in this report. At [Mg2+] greater than 0.5 mM, the characteristic lag-phase is substantially increased and the rate of assembly is greatly reduced without affecting the critical concentration significantly. We show that increasing [Mg2+] has two effects on the assembly process: nucleation is less efficient and the intrinsic rate constant for the elongation reaction is reduced. Lowering [Mg2+] (less than 0.5 mM) also inhibits nucleation. These effects of varying [Mg2+] can be explained predominantly in terms of enhanced stability of the microtubule-associated protein-containing oligomeric species present in the microtubule protein preparation. [Mg2+] is thus found to be a further important factor in microtubule nucleation, and hence, in determining length distributions in assembling microtubules.

Animals↗
PubMed1987

Alcohol-use patterns through medical school. A longitudinal study of one class.

We describe the patterns of alcohol use of one medical school class assessed repeatedly over time from the first day of medical school to a point several months short of graduation. Although male students consistently drank more than their female counterparts during the preclinical years, the men reduced their alcohol intake during the clinical years to converge on the lower, more consistent intake rates of their female classmates. Over the four years of medical school, 11% of the students met criteria for excessive drinking for at least one six-month period and 18% were identified as alcohol abusers by Research Diagnostic Criteria during the first two years. More than half of the excessive drinkers met abuse criteria, whereas only one third of the alcohol abusers were also excessive drinkers. Alcohol abusers had better first-year grades and better overall scores on the National Board of Medical Examiners, part I, test than their classmates. The implications of these findings for designing and implementing alcoholism intervention/prevention programs in medical schools are discussed herein.

Adult↗
PubMed1987

A double-blind, placebo-controlled trial of lithium carbonate therapy for alcoholism.

The efficacy of lithium carbonate as a treatment for alcoholism was examined in a double-blind, placebo-controlled study of 104 men and women meeting DSM-III criteria for alcohol dependence. Subjects entered the study during inpatient treatment and were subsequently followed up for 12 months. Survival analysis disclosed essentially three categories of treatment response: one for noncompliant subjects (0% to 7% abstinent), one for compliant subjects not attaining therapeutic serum lithium levels (31% to 44% abstinent), and one for compliant subjects with therapeutic serum levels (67% abstinent). Two findings led us to believe that therapeutic serum levels of lithium were associated with better outcome over and above a behavioral compliance effect. First, in a dose-response analysis, serum lithium levels and abstinence rates were not linearly associated. Second, all subjects who started lithium carbonate therapy as inpatients were significantly less likely to relapse to drinking during the first month than were placebo-compliant subjects. There was no evidence that depressed alcoholics showed a better treatment response than nondepressed alcoholics or that lithium had any significant impact on the mood or social adjustment of alcoholics. Although the sample size and the difficulties of ascertaining placebo compliance caution against drawing firm conclusions, the data add further support to the hypothesis that lithium has an effect on drinking behavior not related to the treatment of affective symptoms.

Adult↗
PubMed1987

A field test of Motto's risk estimator for suicide.

The authors undertook a field test of Motto and colleagues' Risk Estimator for Suicide by selecting a subset (N = 593) of psychiatric patients with major or chronic affective disorder that corresponded to Motto's sample. They rated each subject on Motto's scale, using standardized data collected at hospital admission. Fourteen patients (2.4%) in their sample and 136 (4.9%) in Motto's sample died by suicide within 2 years. The authors tested the null hypothesis of a uniform suicide risk across all 10 deciles of risk scores by comparing observed and expected frequencies of suicide using the variance test for homogeneity of the binomial distribution. Their findings raise questions about Motto's risk scale but do not definitively invalidate it.

Adolescent↗
PubMed1987

Masculinity, femininity, and psychosocial adjustment in medical students: a 2-year follow-up.

As part of a longitudinal study of medical students, relations between masculinity and femininity and psychosocial well-being were investigated over a 21-month interval. Of a class of medical students, 82% (N = 99) completed measures of masculinity and femininity during orientation and, 21 months later, completed a broad array of measures of psychological well-being, interpersonal functioning, humanistic attitudes toward patient care, and alcohol consumption. Hierarchical multiple regression analyses with interaction terms revealed main effects of masculinity on self-esteem, extraversion, and confidence, and main effects of femininity on hedonic capacity, interpersonal satisfaction, sharing of personal problems, and alcohol consumption. Little evidence for additive or balance androgyny formulations was found. Findings for masculinity were consistent with earlier findings from this study and others, but they were weaker in magnitude. Findings for femininity were surprisingly robust and enrich the construct validity of this measure. Measures of impaired mood and of alcohol and drug impairment were also studied in relation to masculinity and femininity. Both variables contribute to the prediction of depressed mood; femininity also contributes to the prediction of drug involvement. Neither scale has sufficient sensitivity or specificity to be used by itself as a test of impairment.

Adult↗
PubMed1987

Reliability of attachment level measurements using the cementoenamel junction and a plastic stent.

Repeated measurements of attachment level appear to be important assessments in periodontal clinical trials, yet the lack of reliability for this assessment creates measurement error which in turn demands increased sample sizes or reduces the power of the test. A plastic occlusal stent has been developed as a fixed reference point to assess changes in probing depths over time and thus reflect differences in attachment levels. The advantages of this system over traditional methods have not been measured. The purpose of this study was to determine intra- and interexaminer reliability for probing depths from the stent and the CEJ. Paired measurements of attachment level using the stent produced correlation coefficients for inter- and intraexaminer readings of 0.84 and 0.76, respectively. For subgingival cementoenamel (CEJ) measurements, lower coefficients of 0.71 and 0.59 were found for inter- and intraexaminer paired readings, respectively. Thus, measurements using the stent appear to be more reliable than subgingival CEJ readings.

Dental Cementum↗