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Biomedical subjects

D C Clark

Publications and source records attributed to D C Clark.

At least 91 records · Page 5Linked to original sources
PubMed1991

Clinical documentation and occurrence of putative periodontopathic bacteria in human immunodeficiency virus-associated periodontal disease.

Human immunodeficiency virus (HIV)-associated gingivitis (HIV-G) and HIV-associated periodontitis (HIV-P) are two intraoral lesions manifested by patients with HIV infection. Periodontal indices were measured for 87 subjects in 5 study groups: HIV-seropositive patients with healthy periodontium (HIV-H), with HIV-G, or with HIV-P; and non-HIV-infected subjects with healthy periodontium (H) or with adult chronic periodontitis (P). The quantitative clinical parameters were compared and statistically significant intergroup differences were noted. The mean scores on PI and PD do not discriminate between HIV-seropositive and non-HIV-infected seronegative cohorts, but a significant difference in the GI between HIV-H and H was noted. When categories of PD and AL are examined, some differences become apparent. Generally, the PD and AL of HIV-P are not as great as those of P. PI correlates well with GI (r = 0.86) in P, but does not (r = 0.33) in HIV-P. In addition, the occurrence of selected putative periodontopathic bacteria (Porphyromonas gingivalis, spirochetes, and motile eubacteria) in these lesions was determined by brightfield (after staining), darkfield and immunofluorescent microscopy. No difference in microbiological profile in the bacterial groups monitored was found between P and HIV-P. Spirochetes were found to be more abundant than P. gingivalis in the lesions of P and HIV-P. In marked contrast, P. gingivalis was found to be in highest numbers in samples from the gingival crevice of H as determined by indirect immunofluorescence.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The assessment and management of the suicidal patient.

This chapter will be oriented toward the problem faced by the clinician in attempting to prevent suicide in patients under treatment. It will focus on the clinician's difficult task of assessing suicide potential and initiating interventions to prevent suicide in patients at high risk. Specifically, the state of the art in identifying the suicidal patient will be reviewed, and various interventions available to the clinician will be discussed.

Anxiety Disorders↗
PubMed1991

Current research in preventive dentistry and its impact on the future of dental care.

To my mind, preventive dentistry has not changed all that much in the last 10 to 15 years. No miracle drug has come on the scene to prevent periodontal disease. There is no caries vaccine to eliminate dental caries. Interestingly, it has been the traditional technologies that have, given the advantage of time, proven their potential. The reality seems to have surpassed even our most optimistic expectations. But while we have learned how to effectively implement these technologies in many instances, the promotion of water fluoridation has lagged. Nevertheless, the improvements in oral health speak well of the work of our predecessors, who shaped the world of modern dental care. It is up to the profession to use existing preventive technologies to their best advantage and to devise even better preventive measures for the 20 per cent to 30 per cent of the population who are at highest risk of caries and periodontal disease. This paper has focused on some points of interest that have been published in the dental literature on preventive dentistry. Other issues represent concerns of the author. I invite comment and discussion on the topics and issues that were raised. Dialogue is healthy.

Adolescent↗
PubMed1990

De novo design and structure-activity relationships of peptide emulsifiers and foaming agents.

A series of eight amphipathic peptides (8, 11, 15, 2 x 18, 22, 26, 29 amino acids in length) were designed to investigate the effects of amino acid composition, peptide length and secondary structure on surface activity assessed as emulsification and foaming activity. The potential for alpha-helix formation at the hydrophobic/hydrophilic interface was maximized through the use of helix-forming amino acids, a relatively large hydrophobic surface of 200 degrees of arc and ion pairs between basic and acidic amino acids on the hydrophilic surface. Emulsification activity increased rapidly between 11 and 22 residues as alpha-helicity in aqueous solution increased. Despite their small size, the peptides produced exceptionally stable emulsions, compared with proteins. Foaming activity was enhanced by the presence of aromatic amino acids and the activity of the best peptide examined was superior to that of bovine serum albumin and beta-lactoglobulin.

Amino Acid Sequence↗
PubMed1990

A norm-referenced longitudinal study of medical student drinking patterns.

The alcohol consumption patterns of a single class of 121 medical students was assessed at six points over the course of 4 years of medical school training, along with other measures of drinking-related impairment, family history of alcoholism, personality, and psychosocial functioning. Research Diagnostic Criteria were applied to make diagnoses of alcoholism. Eleven percent of the class reported drinking at a level considered "heavy" by class social norms, most transiently. Eighteen percent of the class met criteria for alcohol abuse by virtue of drinking-related impairment during medical school; they were likely to evidence a prior history of alcohol abuse and a family history of alcoholism. Half the excessive drinkers abused alcohol, but two-thirds of the abusers were not excessive drinkers. Alcohol abusers describe themselves as less warm, kind, gentle, and emotionally expressive than their classmates, and were more preoccupied with themes of power in spontaneous fantasy productions. These findings suggest that interpersonal strategies to intervene with alcohol abusing medical students may encounter predictable resistances, and suggest another intervention approach better suited to their psychological concerns.

Adult↗
PubMed1990

A statistical method for evaluating suicide clusters and implementing cluster surveillance.

The absence of any standard definition of suicide cluster events hinders understanding of the prevalence of the problem, hinders the development of appropriate public health responses to observed clusters, and ultimately hinders investigation of the mechanisms underlying contagious communication of suicidal behavior. The authors introduce a Poisson mixture model for assessing potential clusters of adolescent suicide, apply that model to the monthly incidence rates of adolescent suicide for one populous US county over the last 11 years, and generate 99% tolerance limits with 95% confidence for the number of suicides which may occur by chance within specific intervals of time in that county. The suicide incidence data showed a remarkable fit to a single Poisson distribution, suggesting it is not unreasonable to consider the cases as randomly-distributed and independent events. The authors conclude that there is no evidence that adolescent suicides occurred in clusters in the place and in the time frame under study, and recommend the Poisson mixture model for ascertaining clusters as well as implementing cluster surveillance.

Adolescent↗
PubMed1990

Physical recklessness in adolescence. Trait or byproduct of depressive/suicidal states?

The authors assessed adolescents (264 psychiatric inpatients and 742 high school students) with a new instrument (the Sommerfeldt-Clark Adolescent Recklessness Scale) to test whether adolescents show individual differences on a dimension ranging from physical caution to physical recklessness. The three dimensions that emerged reflect an interest in weapons and military dangers, which we have tentatively labeled "foolhardiness"; the combination of dangerous driving and substance abuse; and involvement with smoking, drug use, and "bad company." The personality traits of "venturesomeness" and "impulsiveness" were significantly correlated with all three recklessness factors. The first two factors showed no significant relationship with patient status, diagnosis of mood disorder, or history of suicidal behavior; the third factor was associated with inpatient status and a history of suicide attempts.

Adolescent↗
PubMed1990

Validation of flow cytometry for rapid enumeration of bacterial concentrations in pure cultures.

Flow cytometry was investigated as a rapid detection and counting method for bacteria in pure cultures. A simple two-parameter detection scheme was employed: particle size was measured by forward angle light scatter and nucleic acid content by fluorescence of the DNA/RNA-binding dye ethidium bromide. The technique gave results that correlated exceptionally well with conventional plate counting for four species of bacteria, and concentrations in the range 10(2) to 10(7) cfu/ml. Cytometric counts were obtained in a few minutes, as compared with 2 d required for the plate counts. Under ideal conditions, each bacterial species examined exhibited a characteristic 'signature' on the cytometer, which could be explained by its known properties and morphology.

Aeromonas↗
PubMed1990

Availability of knowledgeable informants for a psychological autopsy study of suicides committed by elderly people.

Psychological autopsy methodology has not been applied in studies of elderly suicides, despite the fact that the elderly are associated with a higher rate of suicide than any other age group. One school of thought argues that older adults who die by suicide are socially isolated and/or estranged for a long period of time before death, so that knowledgeable informants are difficult or impossible to obtain. In the present retrospective study we examine the number and availability of knowledgeable informants for 145 older people who committed suicide. We believe that the ability to access several motivated informants per case is essential to any psychological autopsy study by modern standards. The stereotype of the "average expectable" elderly suicide victim as socially isolated and living alone or in an institutional setting was not supported by our findings; an unexpectedly high percentage of subjects were married at the time of their death. There was at least one knowledgeable informant in 90% of cases and two or more in almost 50%. In 46%, the subject had expressed despondency over illness. In a prospective study involving interviews with informants for eight subjects, all eight had at least two knowledgeable and willing informants. Two cases of the eight are presented to illustrate the role of delirium and an ominous diagnosis (cancer) as causes of suicide. We conclude that it is feasible to do a psychological autopsy study of elderly suicides.

Aged↗
PubMed1990

Granulomatous spinal infections: MR imaging.

The value of magnetic resonance (MR) imaging in evaluating granulomatous spinal infection was retrospectively assessed in 81 patients with proved disease; 27 were reexamined after administration of gadolinium diethylenetriaminepentaacetic acid, and 25 underwent follow-up studies. Blinded interpretations were correlated with clinical, microbiologic, and surgical findings. MR imaging enabled prediction of the presence of neurologic complications in 93% of patients and diagnosis of the type of infection in 94%, and correlated well with surgical findings in 24 of 27 patients. Vertebral intraosseous abscesses, meningeal involvement, subligamentous spread, and paraspinal abscess location were best identified on contrast-enhanced studies and were seen most frequently in tuberculous spondylitis. High signal intensity on T1-weighted images of previously affected vertebrae suggested healing and correlated well with symptoms. The authors conclude that MR imaging may be useful as the method of first choice for the initial assessment and posttherapy follow-up of patients with granulomatous spinal infection.

Adult↗
PubMed1990

Time-related predictors of suicide in major affective disorder.

The authors studied 954 psychiatric patients with major affective disorders and found that nine clinical features were associated with suicide. Six of these--panic attacks, severe psychic anxiety, diminished concentration, global insomnia, moderate alcohol abuse, and severe loss of interest or pleasure (anhedonia)--were associated with suicide within 1 year, and three others--severe hopelessness, suicidal ideation, and history of previous suicide attempts--were associated with suicide occurring after 1 year. These findings draw attention to the importance of 1) standardized prospective data for studies of suicide, 2) assessment of short-term suicide risk factors, and 3) anxiety symptoms as modifiable suicide risk factors within a clinically relevant period.

Adolescent↗
PubMed1990

Measurement of hope in a community-based older population.

This study conceptually and empirically examined two hope scales with a community-based sample of older adults. These findings suggest that the two hope scales used in this study measure Global Hope and Interactive Hope. However, these results also suggest unique characteristics of hope that should be incorporated into future studies of hope with older adults.

Aged↗
PubMed1990

MR imaging of thoracic and abdominal wall infections: comparison with other imaging procedures.

Infections of the chest and abdominal wall are rare but potentially fatal disorders that can occur spontaneously or in association with diabetes mellitus, immunosuppression, or trauma. The condition (either in the form of necrotizing fasciitis and/or pyomyositis) is difficult to diagnose clinically because of poor localizing signs. Prognosis depends on early recognition, extent of disease, and type of causative organism. Pathologically, the infections can manifest as cellulitis, abscess, and/or granulation tissue formation. To determine the value of MR imaging in the assessment of these infections, we compared the findings of MR with those of CT, sonography, scintigraphy, and plain radiography in 13 patients with proved thoracic and/or abdominal wall infection. The imaging findings were correlated with microbiological, pathologic, and/or surgical data. The isolated pathogens were Staphylococcus aureus (n = 6), Klebsiella pneumoniae (n = 1), Mycobacterium tuberculosis (n = 4), and Streptomyces somaliensis (n = 2). In 10 of 13 patients, MR imaging and CT were comparable and proved accurate in detecting the nature and extent of the inflammatory process. In seven of the patients, CT also was useful in guiding percutaneous biopsy and/or partial drainage procedures. Coronal and sagittal MR images were helpful for planning surgery. Rib osteomyelitis was missed with both techniques in one patient; in two other patients who did not have CT, MR imaging missed osteomyelitis of the ribs, the spinous process of a vertebral body, and the iliac bone. Sonography underestimated the extent of the disease in all 13 patients, but detected fluid collections in six. Findings on scintigraphy and plain radiography were the least contributory to the diagnosis and treatment of these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1990

The influence of frequent ingestion of acids in the diet on treatment for dentin sensitivity.

For many patients with severe and persistent pain from dentin sensitivity, therapeutic interventions often produce unsatisfactory results. Eighteen patients with persistent dentin sensitivity following a two-month clinical trial of a desensitizing dentifrice and a two-week treatment of four applications of a topical fluoride varnish participated in post-hoc evaluation of the association between the frequency of acid ingestions in the diet and the persistence of pain. A specific food frequency assessment was performed and tested for association against longitudinal, clinical and subjective patient assessments. There was a negative association (r = 0.49) between the frequency of ingestion of specific acid foods and beverages and the persistence of dentin sensitivity. Findings suggest that nutritional counselling should be part of the treatment offered for patients with these problems.

Acids↗
PubMed1989

Does lithium carbonate therapy for alcoholism deter relapse drinking?

In order to test the efficacy of lithium therapy for alcoholism, to test whether lithium therapy reduces depressive symptoms among alcoholics, and to test whether any positive lithium treatment effects are associated with an antidepressant action, we undertook a double-blind placebo-controlled study of 122 patients meeting DSM-III criteria for alcohol dependence and hospitalized for alcoholism rehabilitation. We used survival analysis to examine the cumulative proportion of each treatment group that remained abstinent (i.e., "survived") over the course of 18 months, using complete abstinence from alcohol as the principal outcome measure. Our findings add support to the hypothesis that lithium carbonate promotes abstinence from alcohol and delays the time to first drink. Patients treated with lithium were much less likely to be rehospitalized for alcoholism rehabilitation during the 18-month follow-up. These effects did not appear to be related to the treatment of concomitant or underlying affective symptoms. We found no support, on the other hand, for the hypothesis that lithium therapy reduces the frequency of drinking for relapse drinkers.

Alcohol Drinking↗
PubMed1989

What is the mechanism by which suicide attempts predispose to later suicide attempts? A mathematical model.

A state dependence model of serial behavior suggests that each occurrence increases the subsequent likelihood of that behavior being repeated. A heterogeneity model, by contrast, suggests that the likelihood of a behavior occurring is predetermined, and uninfluenced by intervening occurrences. We have applied the random-effects probit model of Gibbons and Bock (1987) to examine the fit of the state dependence and heterogeneity models to longitudinal data on suicide attempts by 928 patients with affective disorder. Heterogeneity but not state dependence was required to model these data. The findings suggest that when considering patients with moderate to severe major affective disorder, the clinician should not interpret the absence of any recent suicide attempts to mean that the patient is at relatively low risk for attempting suicide in the future. An implication of the heterogeneity model is that suicide attempts made many years ago may have equal value to recent attempts when estimating an individual's "predisposition" to nonlethal attempts in the future.

Adolescent↗