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Biomedical subjects

A B Cohen

Publications and source records attributed to A B Cohen.

At least 19 recordsLinked to original sources
PubMed1992

Young physicians most and least likely to have second thoughts about a career in medicine.

To identify factors associated with apparent disaffection with medicine as a career, the authors analyzed data for 4,931 young physicians surveyed in 1987. Using survey responses, the authors classified 932 of the physicians (18.9%) as most likely to have second thoughts about their career choices and 1,094 (22.2%) as least likely to have second thoughts. The group with the greatest reservations included significantly higher proportions of white women, blacks, and Hispanics. This group reported significantly lower incomes, higher educational debt, and more hours and patients' visits per week. Among employee physicians, those most disaffected were significantly more likely to report inappropriate use of tests and procedures and lack of autonomy in their practices. The authors conclude that it is important to reexamine the heavy reliance on debt financing of medical education, especially for minority students, and to explore the equality of career opportunities for women and minorities in medicine.

Adult↗
PubMed1992

Generation of the neutrophil-activating peptide-2 by cathepsin G and cathepsin G-treated human platelets.

The neutrophil-activating peptide-2 (NAP-2) is a cytokine that is generated by the proteolytic cleavage of a precursor protein and that causes neutrophil degranulation and chemotaxis. NAP-2 precursors are produced in platelets and are normally found in the circulation. We showed that NAP-2 is generated by the action of neutrophil cathepsin G on two of the precursors, the connective tissue-activating peptide-III (CTAP-III) and beta-thromboglobulin (beta-TG). However, neutrophil elastase degraded the precursors to inactive peptides. The specific binding of cathepsin G to platelets caused the platelets to secrete NAP-2, and cathepsin G bound to the platelets could still generate NAP-2 from its precursor proteins. In addition, activated neutrophils in the presence of platelets generated NAP-2 from its precursors and caused platelets to secrete NAP-2. These studies demonstrate a unique mechanism for the activation of neutrophils through the interaction of neutrophils, platelets, and NAP-2 precursors that are released either by activated platelets or are present in circulation. It is therefore possible that NAP-2 may be generated at sites where aggregations of neutrophils and platelets occur in vessels such as pulmonary capillaries in patients with the adult respiratory distress syndrome and coronary arteries in patients with evolving myocardial infarctions.

Blood Platelets↗
PubMed1992

Elevated levels of NAP-1/interleukin-8 are present in the airspaces of patients with the adult respiratory distress syndrome and are associated with increased mortality.

The adult respiratory distress syndrome (ARDS) is characterized by increased neutrophils within the airspaces of the lungs. In order to determine if neutrophil activating protein (NAP)-1/interleukin-8 (NAP-1/IL-8) could be an important cause of neutrophil influx and activation in ARDS, we examined fluid, which was either directly aspirated or lavaged with saline from the lungs of patients with ARDS. NAP-1/IL-8 was present in significantly higher concentrations in the fluids of patients with ARDS compared with control subjects. There was a significant correlation between the percentage of neutrophils in the lavage fluids and the NAP-1/IL-8 concentration (r2 = 0.74). Furthermore, the NAP-1/IL-8 concentration of the pulmonary edema fluid was equivalent to the optimal concentration required to induce neutrophil chemotaxis in vitro. Although not all of the chemotactic activity of the edema fluid was removed by an anti-NAP-1/IL-8 affinity column, the data established that NAP-1/IL-8 is an important neutrophil chemotaxin in the airspaces of patients with ARDS. In addition, those patients with very high concentrations of NAP-1/IL-8 in their bronchoalveolar lavage fluids had a higher mortality rate than those patients with lower concentrations of NAP-1/IL-8. The correlation between NAP-1/IL-8 concentration and mortality is not paralleled by total protein concentration and mortality.

Adolescent↗
PubMed1992

Administrative costs in the U.S. health care system: the problem or the solution?

The estimates of potential savings as a result of reductions in administrative costs have generated considerable controversy. In response to this debate, the Robert Wood Johnson Foundation sponsored an invitational workshop for policymakers, health services researchers, and key stakeholders in the health care system. The workshop, conducted by the Alpha Center in February this year, provided a framework for identifying, measuring, and weighing the value of administrative costs and served as a vehicle for discussion of these issues. This article summarizes the presentations, the issues raised, and questions for further research. Overall, the papers and presentations emphasized that while the focus of attention has been on the controversy over whether particular aggregate estimates of administrative costs and potential savings are correct, the fundamental underlying issue is how the health care system might best be managed.

Cost Allocation↗
PubMed1991

Medical educators' views on medical education reform.

To determine whether medical educators perceive a need for change in medical student education, we analyzed data from a 1989 survey of 1369 respondents from all US schools of allopathic medicine. Except for basic sciences faculty, a majority of educators stated that "fundamental changes" are needed in medical student education in the United States. Nearly three fourths of deans and associated deans reported the need for "fundamental changes" or "thorough reform." At least 79% of educators voiced support for six specific reforms, such as rewarding teaching excellence and increasing clinical education in ambulatory and community settings. While slight majorities supported reducing class size and centralizing governance, substantial proportions stated that they would "work against" such reforms. Most educators reported that a broad base of support within the school would be essential for change. The survey suggests a restlessness among the leaders of medical education.

Attitude of Health Personnel↗
PubMed1991

Sensorimotor myeloradiculoneuropathy in thymoma.

This is the first report describing the clinical, electrophysiological, and neuropathological findings in a patient with thymoma and sensorimotor myeloradiculoneuropathy. Degeneration of the Clarke's nucleus and posterior horns were noted in addition to segmental demyelination and variable axonal loss of the anterior and posterior roots. The segmental demyelination was more severe in the anterior roots of the lower thoracic and lumbosacral regions. A possible rare association between paraneoplastic myeloradiculoneuropathy and thymoma is suggested.

Aged↗
PubMed1991

Use of antibodies in the study of protein structure and function in lung diseases.

Proteins normally fold in a variety of three-dimensional structures. This variety of forms accounts for a multiplicity of functions. One of the major undertakings of modern biochemistry is to determine the structure of a given protein and in doing so learn about its function. Much of the effort in the field of protein chemistry is currently focused on defining areas or domains within the molecule that are responsible for its function. Antibodies specific for functional domains on a protein have been powerful tools in these studies and have provided a great deal of the current knowledge related to the location and function of well-defined structural areas within the protein molecules. The use of antibodies in the study of proteins has considerably advanced our knowledge of both the structure of proteins and their interaction with other molecules. In reviewing the use of antibodies for structure and/or function analysis, we have tried not only to review the techniques and applications involving antibodies but also to show how useful antibody reagents may be designed and prepared. In this review, some of the newer uses of antibodies in modern biology will be described, and a few illustrations of each will be provided.

Amino Acid Sequence↗
PubMed1991

A controlled trial of colchicine to reduce the elastase load in the lungs of ex-cigarette smokers with chronic obstructive pulmonary disease.

A great deal of experimental evidence suggests that emphysema in smokers is caused by the action of neutrophil elastase on lung elastin. In order to test this hypothesis, it is necessary to find a drug that reduces the load of neutrophil elastase in the lungs of patients with emphysema. In a previous study we treated smokers with emphysema with colchicine, a drug that prevents neutrophil elastase secretion, to determine if it would reduce the elastase burden in the lungs. Colchicine was unable to reduce the elastase load while the stimulus of smoking continued. In this study we treated ex-smokers with emphysema to determine if colchicine could reduce the elastase burden in the lungs. The objective of the study was to determine if colchicine can reduce the elastase load and putative indicators of elastase load in the lungs of patients with chronic obstructive pulmonary disease. The study was a prospective, double-blind, randomized, and placebo-controlled clinical trial. The subjects were outpatients seeking treatment at the University of Texas Health Center at Tyler. We studied 16 ex-cigarette smokers between 45 and 75 yr of age with lung disease defined by FEV1 less than 70% of predicted but greater than 1.2 L whose airflow obstruction was less than 20% reversible with bronchodilators. Colchicine or placebo was taken by mouth in disguised capsules, 0.6 mg three times per day. Volunteers were placed on a baseline bronchodilator regimen of theodur by mouth and albuterol by inhalation. Blood, urine, and bronchoalveolar lavage fluids were obtained after 1 wk of stabilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Synthesis and secretion of high- and low-molecular-weight forms of the enzyme-releasing peptide (ERP) from the macrophage-like cell line THP-1.

Neutrophil enzymes have been implicated as a source of lung injury in patients with the adult respiratory distress syndrome (ARDS) and with emphysema. We studied a human alveolar macrophage-derived peptide messenger, the enzyme-releasing peptide (ERP), which causes neutrophils to secrete their enzymes. The secretion and synthesis of ERP was studied in human alveolar macrophages and in the macrophage-like cell lines THP-1, HL-60, and U937. All four cell types secrete an ERP-like peptide. THP-1 cells secrete a higher concentration of the peptide than do macrophages. The secretion of ERP by THP-1 is suppressed by the protein synthesis inhibitors actinomycin D and cycloheximide. While the macrophages secrete ERP, they do not synthesize it. These studies suggest that ERP is synthesized by an alveolar macrophage precursor and stored in the mature macrophage for later release. 12-O-tetradecanoylphorbol-13-acetate (TPA) suppresses ERP secretion by THP-1 cells, but it does not modify secretion in macrophages. Escherichia coli-derived lipopolysaccharide and dimethyl sulfoxide do not modify secretion in either cell type. The THP-1 cells secrete a high- and low-mass-ratio (Mr) form of ERP-like proteins. The low Mr but not the high Mr form stimulates neutrophils to secrete their granule enzymes. We conclude that human alveolar macrophages secrete ERP but do not synthesize it. It is likely that ERP is made by an alveolar macrophage precursor in a high Mr form that is cleaved prior to secretion by the macrophages.

Antibodies, Monoclonal↗
PubMed1990

Liberation of a neutrophil enzyme-releasing peptide from the surface of human alveolar macrophages.

The human alveolar macrophage product, enzyme-releasing peptide (ERP), has a molecular mass of 8,000 Da, and releases azurophilic and specific granule constituents from neutrophils. A murine monoclonal anti-ERP antibody (12E10H), previously used to show a lack of antigenic identity between ERP and C5a, interleukin 1, tumor necrosis factor, and gamma-interferon, showed no cross-reactivity with interleukin 8. 12E10H and a fluorescein-labeled second antibody were used to visualize ERP on the macrophage surface. ERP was removed from alveolar macrophages by a 3-min incubation with 5 X 10(-7) M bovine pancreatic trypsin at 37 degrees C. The washed trypsinized cells could readhere to plastic and exclude trypan blue. Dilution of the trypsin-derived ERP released myeloperoxidase from cytochalasin-B-treated neutrophils dose dependently. The enzyme-releasing ability of the trypsin-derived material was removed by immunoprecipitation using antibody 12E10H bound to Staphylococcal protein A Sepharose 4B. The estimated molecular mass of the trypsin-derived ERP (by molecular sieve chromatography on HPLC) was approximately 8,500 Da. Other proteases (plasmin, thrombin, and cathepsin G) also released ERP from the cell surface, but the ERP was not an active secretagogue for neutrophils. However, macrophages cultured with protease inhibitors did not show decreased ERP accumulation in the medium. Our data indicate that ERP exists on the surface of human alveolar macrophages and can be released by proteases found within the lung environment in some disease states.

Antibodies, Monoclonal↗
PubMed1990

A modified bronchoalveolar lavage procedure that allows measurement of lung epithelial lining fluid volume.

We replaced the standard serial bronchoalveolar lavage technique with a new "rewash" lavage procedure to allow estimation of the volume and protein concentration of the epithelial lining fluid (ELF) in anesthetized sheep. A bronchoscope 6.0 mm in diameter wedged in an airway was used to lavage a segment of lung with four cycles of instillation and aspiration of the lavage solution containing a radioactive tracer (technetium pertechnetate, 99mTcO4-). Errors caused by the fall in concentration of the tracer during the lavage were minimized by extrapolating the tracer concentration back to time zero when the lavage solution had mixed with the ELF, but had not had time to be affected by loss of the tracer or influx of fluid from the interstitium. In control sheep, the ELF of these lavaged segments had a mean volume of 1.6 +/- 1.0 ml and a mean protein concentration that was 26 +/- 19% of the protein concentration measured in the plasma. Increasing the left atrial pressure 19 +/- 5 cm H2O to cause "cardiac lung edema" had no significant effect on the ELF volume, but it increased the mean protein concentration to 57 +/- 30% of the plasma value (p less than 0.01). Lung injury caused by intravenous oleic acid caused lung edema, increased the mean ELF volume to 6.8 +/- 2.2 ml, and increased the mean ELF protein concentration to 86 +/- 26% of the plasma value (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗