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Biomedical subjects

R E Clark

Publications and source records attributed to R E Clark.

At least 91 records · Page 5Linked to original sources
PubMed1997

Multiple acral syringomata with uniform involvement of the hands and feet.

We present a case of a 43-year-old black woman with multiple syringomata located on the dorsa of the hands and feet. Although syringoma is a common adnexal tumor, acral presentation is very rare. Symmetrical involvement of the distal lower extremities has not been reported previously. This interesting clinical presentation should be included in the differential diagnosis of a papular eruption of the hands and feet.

Adult↗
PubMed1997

The use of antidesmoglein stains in Mohs micrographic surgery. A potential aid for the differentiation of basal cell carcinoma from horizontal sections of the hair follicle and folliculocentric basaloid proliferation.

BACKGROUND: Histopathologic differentiation between benign and malignant tissue is of utmost importance for the Mohs surgeon. Folliculocentric basaloid proliferation (FBP) shares many histologic features with basal cell carcinoma (BCC). It is most commonly associated with tumors of areas with abundant hair follicles such as nasal and perinasal skin. Residual BCC incorrectly identified as a horizontally sectioned hair follicle undoubtedly increases the risk of tumor recurrence. Excision of additional layers of normal tissue to remove "funny looking follicles" may have profound impacts on tissue conservation, preservation of function, and cosmesis. Electron microscope studies of BCC revealed a significant reduction of desmosomes compared with normal basal cells and hair follicle keratinocytes. OBJECTIVE: This study has assessed the potential of rapid staining with monoclonal antidesmoglein antibody (33-3D) to discriminate between BCC, horizontally sectioned hair follicles, and FBP. METHODS: A rapid immunoperoxidase technique with 33-3D antidesmoglein antibody was performed on Mohs frozen sections. We selected 18 patients with BCC of nasal and perinasal locations where histologic discrimination between residual tumor and tumor-free margins with FBP or horizontally sectioned hair follicle was equivocal. RESULTS: Fourteen sections disclosed the preservation of desmoglein marker delineating the cell membranes ("perimembranous" pattern) consistent with normal hair follicles. The sections were identified as tumor-free and no additional stages were performed. The remaining four sections revealed absent perimembranous pattern but presence of diffuse cytoplasmic staining. These were diagnosed as positive for residual BCC requiring the excision of another layer of tissue to obtain tumor-free margins. A follow-up period ranging from 6 to 24 months revealed no instance of recurrent disease. CONCLUSION: Rapid detection of desmoglein with 33-3D antibody is a promising tool for discrimination between residual BCC and FBP or horizontally sectioned hair follicles. It may enhance the sensitivity of Mohs surgery by disclosing the hidden foci of BCC, thus preventing tumor recurrence and unnecessary excision of normal tissue.

Aged↗
PubMed1996

Spine update: understanding cost-effectiveness.

Although most people are familiar with the idea of cost-effectiveness, many wonder how--or whether--it should be applied to health care. This article discusses the concept of cost-effectiveness, techniques for measuring it, and the pitfalls and benefits of applying cost-effectiveness analysis to health care.

Cost-Benefit Analysis↗
PubMed1996

Outcome as a function of annual coronary artery bypass graft volume. The Ad Hoc Committee on Cardiac Surgery Credentialing of The Society of Thoracic Surgeons.

BACKGROUND: Recent changes in health care financing have raised the specter of operation-specific, volume credentialing for cardiac surgeons. To meet this challenge, the leadership of The Society of Thoracic Surgeons formed an Ad Hoc Committee to study the question of the relationship of case volume to outcome. One product of the committee's work in this analysis of data from The Society of Thoracic Surgery National Cardiac Database. METHODS: We examined data for all types of coronary artery bypass graft-only operations (n = 124,793) from more than 1,200 surgeons working in more than 600 hospitals for the years 1991 through 1993. All in-hospital and 30-day out-of-hospital mortality, both observed and expected as predicted by The Society of Thoracic Surgeons risk stratification method, was plotted against annualized group practice volume. Both patient-based and practice-based sampling techniques were used. RESULTS: The data show that observed mortality ranged from 2.0% to 3.6% for practices of more than 100 cases through practices with more than 900 cases per year. Those practices with less than 100 cases (n = 18) had a mean mortality of 5%. Expected mortalities ranged from 2.4% to 3.9% and did not vary as a function of volume. No practice volume category had an observed/expected ratio of less than 0.8 and none had a ratio greater than 1.2, if annual volume was more than 100. Practices of less than 100 cases/year had an observed/expected ratio of 1.6% to 1.7%. There was great variation in observed and expected mortalities in the lower volume categories and less variation when volume was greater (more than 600 cases/year). CONCLUSIONS: Although the data are practice-group-specific only, there was no clinically relevant correlation of volume to outcome except at extremely low annual volume (less than 100 cases per year). Variability of outcome was significant in lower volume practices (less than 600 cases/year) and varied little at more than 600 cases per year. There were no differences in expected mortality regardless of the size of the practice.

Coronary Artery Bypass↗
PubMed1996

Volume requirements for cardiac surgery credentialing: a critical examination. The Ad Hoc Committee on Cardiac Surgery Credentialing of The Society of Thoracic Surgeons.

New volume requirements for coronary artery bypass grafting are being imposed on cardiac surgeons by hospitals, managed care groups, and others. The rationale for this is unclear. The available literature as well as additional sources relating volume and outcomes in cardiac surgery were extensively reviewed and reexamined. There are no data to conclusively indicate that outcomes of cardiac operations are related to a specific minimum number of cases performed annually by a cardiac surgeon. Each cardiothoracic surgeon should participate in a national database that permits comparison of his or her outcomes on a risk-adjusted basis with other surgeons. Until conclusive data become available that link volume to outcome, volume should not be used as a criterion for credentialing of cardiac surgeons by hospitals, managed care groups, or others. Instead, each surgeon should be evaluated on his or her individual results.

Cardiac Surgical Procedures↗
PubMed1996

Small, low-cost implantable centrifugal pump for short-term circulatory assistance.

BACKGROUND: In 1991, Allegheny General Hospital and Allegheny-Singer Research Institute purchased a centrifugal pump, then a 2-year-old technology, from Medtronic Bio-Medicus, as part of its research program for novel treatments of acute and chronic heart failure. During a 4-year development program, we then established and met goals of durability, performance, thromboresistance, and low cost. METHODS: In vitro testing involved extensive hydraulic characterizations using Penn State mock loops. Calorimetry was used to determine efficiency. Durability studies used heated (37 degrees C) seawater for 28 to 45 days. In vivo studies used 46 sheep to test performance and engineering changes and to determine myocardial oxygen consumption, thromboresistance, and long-term durability. A left atrium-to-aorta circuit was used in all. RESULTS: Hydraulic testing showed no preload sensitivity but moderate afterload sensitivity at all impeller speeds (2,000 to 6,000 rpm). The heat load was low, and overall efficiency was 13% to 15%. Bench durability studies showed no electrical malfunction of the stator or console without degradation of the biomaterials used. Acute in vitro studies showed a near-linear relationship of myocardial oxygen consumption and left ventricular stroke work, pump flow, and pump speed. At speeds of 2 to 3 L/min (50% bypass), left ventricular stroke work and myocardial oxygen consumption were decreased approximately 50%. Additionally, 5 animals have had implants for 28 to 154 days with no macroemboli or microemboli detected in any animal. Hematologic and biochemical studies became normal 3 to 7 days after implantation. Hemolysis was low at less than 10 mg/dL. Clinical costs of the device are estimated to be 80% less than those of currently available devices. CONCLUSIONS: We conclude that an old technology has been made into new technology by application of sound engineering design principles, microchips, and new biomaterials. Qualifying trails for a Food and Drug Agency investigational device exemption application are in progress.

Animals↗
PubMed1996

Calculating risk and outcome: The Society of Thoracic Surgeons database.

Various approaches to the calculation of medical risk are reviewed, including univariate analysis, additive methods, use of Bayes' theorem by The Society of Thoracic Surgeons, logistic regression, and neural networks. Strengths and weaknesses of the various approaches are evaluated. The use and importance of observed/expected ratios, the C statistic, and receiver operating curves are discussed. Specific requirements for the building of useful risk-calculation models are discussed, including the importance of the model set/test set method and the role of both numbers of patients and time frames in model building.

Bayes Theorem↗
PubMed1996

Guidelines for reporting morbidity and mortality after cardiac valvular operations. The American Association for Thoracic Surgery, Ad Hoc Liaison Committee for Standardizing Definitions of Prosthetic Heart Valve Morbidity.

At the request of the Councils of The Society of Thoracic Surgeons (STS) and The American Association for Thoracic Surgery (AATS) the Ad Hoc Liaison Committee for Standardizing Definitions of Prosthetic Heart Valve Morbidity "revisited" the "Guidelines" published in September 1988 [1-3]. The purpose of the review was to update and clarify definitions within the guidelines and to consider recommendations made by others [4, 5]. The variety of cardiac valvular procedures has expanded since 1988; therefore, in this document the term "operated valve" indicates prosthetic and bioprosthetic heart valves of all types: operated or repaired native valves and allograft and autograft valves. The term "operated valve" includes any cardiac valve altered by a surgeon during an operation. Much morbidity and mortality is a direct consequence of the interaction between the patient and operated valve(s), although patient variables (e.g., age, degree of coronary arterial disease, follow-up care) may be more responsible for outcomes than an operated valve. However, no set of guidelines can identify all possible patient factors that may affect morbidity and mortality. General agreement regarding the following definitions of terms and suggestions for reporting data do not preclude more detailed analyses or constructive recommendations and investigators are encouraged to identify relevant patient factors in addition to factors related to operated valves.

Documentation↗
PubMed1996

Guidelines for reporting morbidity and mortality after cardiac valvular operations.

At the request of the Councils of the Society of Thoracic Surgeons (STS) and the American Association of Thoracic Surgery (AATS) the Ad Hoc Liaison Committee for Standardizing Definitions of Prosthetic Heart Valve Morbidity reviewed the "Guidelines" published in September 1988 [3, 7, 8]. The purpose of the review was to update and clarify definitions within the guidelines and to consider recommendations made by other [2, 11]. The variety of cardiac valvular procedures has expanded since 1988; therefore, in this document the term "operated valve" indicates prosthetic and bioprosthetic heart valves of all types, operated or repaired native valves and allograft and autograft valves. The term "operated valve" includes any cardiac valve altered by a surgeon during an operation. Much morbidity and mortality is a direct consequence of the interaction between the patient and operated valve(s), although patient variables (e.g., age, degree of coronary arterial disease, follow-up care, etc.) may be more responsible for outcomes than an operated valve. However, no set of guidelines can identify all possible patient factors that may affect morbidity and mortality. General agreement regarding the following definitions of terms and suggestions for reporting data do not preclude more detailed analyses or constructive recommendations and investigators are encouraged to identify relevant patient factors in addition to factors related to operated valves. Purpose The purpose of these guidelines is to facilitate the analysis and reporting of results of operations on diseased cardiac valves. The definitions and recommendations that follow are guidelines, not standards, and are designed to facilitate comparisons between the experiences of different surgeons who treat different cohorts of patients at different times with different techniques and materials.

Data Collection↗
PubMed1996

The New Hampshire study of supported employment for people with severe mental illness.

This study compared supported employment services in 2 contrasting programs: (a) Group Skills Training, a professional rehabilitation agency outside of the mental health center that provided pre-employment skills training and support in obtaining and maintaining jobs, or (b) the Individual Placement and Support (IPS) model, which integrated clinical and vocational services within the mental health center. People with severe mental disorders who expressed interest in competitive employment (N = 143) were randomly assigned to 1 of these 2 programs. Results showed that clients in the IPS program were more likely to be competitively employed throughout most of the 18-month follow-up. Among those who obtained jobs, there were few group differences, although workers in the IPS program did work more total hours and earn more total wages during the 18-month follow-up. There were no group differences on nonvocational outcomes.

Adult↗
PubMed1996

Neural unit activity in the trigeminal complex with interpositus or red nucleus inactivation during classical eyeblink conditioning.

During classical conditioning, many neurons in the trigeminal complex of rabbits exhibit activity that is related to the conditioned stimulus (tone), the unconditioned stimulus (airpuff), or to the conditioned response (eyeblink). For these reasons the trigeminal complex has been hypothesized to be a brainstem locus for the neuronal plasticity associated with conditioning. In this experiment, the learning-related activity (unit activity associated with the conditioned response) in the trigeminal is abolished when either the red nucleus or interpositus nucleus of the cerebellum is temporarily inactivated by cooling, but the stimulus-evoked activity is unaffected by cooling. This study and previous results support the suggestion that the learning-related activity seen in the trigeminal is driven by the interpositus by way of the red nucleus.

Animals↗
PubMed1996

The course, treatment, and outcome of substance disorder in persons with severe mental illness.

Individuals with co-occurring substance abuse and severe mental illness are particularly vulnerable to negative outcomes. This paper reviews findings on the longitudinal course of dual disorders in traditional treatment systems, which provide separate mental health and substance-abuse programs; describes the movement toward programs that integrate both types of treatment at the clinical level; reviews evidence related to outcomes in integrated treatment programs; and discusses health-care policy changes that would encourage effective treatments.

Humans↗
PubMed1996

KIT expression reveals a population of precursor melanocytes in human skin.

Human skin is believed to harbor a reservoir population of precursor melanocytes. It has been difficult to identify these putative cells experimentally, because they lack phenotypic features that define mature melanocytes. We have evaluated expression of the KIT tyrosine kinase receptor, which is critical for melanocyte development, as a possible marker of these cells. Sections of human skin were evaluated with single- and double-immunolabeling techniques. KIT-reactive dendritic cells were identified in the basal layer of the epithelia and were most numerous in the follicular infundibula and the rete ridges. These cells were located on the epithelial side of the basement membrane and lacked expression of cytokeratin and mast cell tryptase. The location of the KIT-reactive cells was distinctly different from that of Langerhans cells (identified with anti-CD1a) or Merkel cells (identified with CAM 5.2). Within the epidermis and upper follicular infundibulum the majority of the KIT-reactive dendritic cells also coexpressed TRP-1, a marker present in differentiated melanocytes. In the deeper follicular regions, the coexpression of TRP-1 in the KIT-reactive cells was absent. Throughout the epidermis and follicle, however, the KIT-reactive cells coexpressed BCL-2, a marker known to be increased in melanocytes. Thus, KIT expression reveals a population of intraepithelial cells that have immunophenotypic characteristics of mature melanocytes within the upper epithelial regions, but lack the differentiated melanocytic phenotype within the deeper follicular regions. We propose that these KIT(+), BCL-2(+), and TRP-1(-) cells constitute a precursor melanocyte reservoir of human skin.

Adult↗
PubMed1996

Dermatofibrosarcoma protuberans.

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive soft tissue sarcoma in which recurrences are common. It usually affects middle-aged individuals with the most common location being the trunk. Sex distribution varies among published series. Mohs surgery is the treatment of choice. Immunostaining for CD34 facilitates the diagnosis of DFSP and aids in indicating the surgical margins of the tumor; however, the sensitivity of this marker is variable. MATERIALS AND METHODS: This is a retrospective review of 16 cases of DFSP treated with Mohs surgery at Duke University Medical Center between 1981 and 1994. Clinical and histologic features are analyzed. Immunohistochemical stains for CD34 were performed in one case. RESULTS: Twelve of the 16 patients were women with four younger than 20 years. The most common location was the trunk. No recurrences following Mohs surgery have been documented. The average number of stages during Mohs surgery was 3.3. Surgical wounds were repaired by complex layered closure in 11 cases. Stains for CD34 were negative on the initial biopsy, but were positive on frozen sections. CONCLUSIONS: Both sexes and all age groups are affected by DFSP. Mohs surgery is the treatment of choice and offers a significant improvement in cure rates with the cosmetic advantage of smaller postoperative wounds. Immunostains for CD34 appear to be an important adjunct to facilitate tumor removal, but the variable expression of CD34 antigen by DFSP tumors can lead to variable staining patterns.

Adolescent↗