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Biomedical subjects

M J Kahn

Publications and source records attributed to M J Kahn.

At least 37 records · Page 2Linked to original sources
PubMed1997

Hepatosplenic gammadelta T-cell lymphoma: ultrastructural, immunophenotypic, and functional evidence for cytotoxic T lymphocyte differentiation.

Hepatosplenic gammadelta T cell lymphoma (TCL) is a rare, aggressive subset of peripheral TCL that presents with hepatosplenomegaly and cytopenias. Detailed clinicopathological, ultrastructural, and cytogenetic analyses of these lymphomas are limited; functional characteristics of these lymphomas are unknown. We have undertaken a clinicopathological, immunophenotypic, ultrastructural, cytogenetic, and functional analysis of three hepatosplenic gammadelta TCLs. All patients presented with massive hepatosplenomegaly and anemia, thrombocytopenia, or severe neutropenia; terminal blastlike transformation occurred in one patient. Combination chemotherapy had no response in two patients, but induced complete remission in one. gammadelta T cell receptor (TCR) expression and clonal TCRdelta gene rearrangements were documented in each case. Two different subsets of gammadelta TCL were identified based on delta chain variable region usage; two lymphomas were Vdelta1+, whereas the third was negative for both Vdelta1 and Vdelta2. Cytogenetic analysis was performed on two lymphomas; isochromosome 7q and probable trisomy 8 was shown in one of the Vdelta1+ lymphomas, whereas the Vdelta1 negative lymphoma had 14p+ with t(1;14)(q21;p13). NK cell-associated antigens (CD11c, CD16, or CD56) and cytotoxic T lymphocyte (CTL) effector proteins (perforin, granzyme B, TIA-1, and Fas ligand) were expressed by each lymphoma; dense core cytolytic granules were observed by electron microscopy in both lymphomas studied. Functional studies performed in two cases showed TCR-mediated cytolysis of P815 x 2 FcR+ cells induced by anti-CD3 in a redirected cytolysis assay in one of the CD56+, Vdelta1+ lymphomas, whereas IFNgamma secretion was induced by anti-CD3 in the CD56-, Vdelta1 negative lymphoma. These studies show that hepatosplenic gammadelta TCLs have CTL differentiation, retain functional activity in vitro, and are derived from at least two gammadelta T cell subsets.

Adolescent↗
PubMed1997

Chemoprevention for colorectal carcinoma.

The literature on chemoprevention for colorectal carcinoma can be summarized as follows: (1) Aspirin and NSAIDs usage can decrease polyp formation and promote polyp regression and have a strong epidemiologic link to colorectal cancer prevention. (2) Fiber intake is strongly associated with a decreased incidence of colorectal carcinoma. Whether supplemental fiber can prevent colorectal neoplasia is not yet clear. (3) Calcium and vitamin D intake is inversely proportional to the risk of developing colorectal carcinoma. Prospective trials make the role of supplemental calcium as a chemoprotective agent unclear: (4) Chemoprevention is an exciting area of research. More work needs to be done to establish the precise steps necessary for neoplastic transformation of cells so that pharmaceuticals can be developed to target carcinogenesis at several levels.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Controlled trial of fluorouracil and low-dose leucovorin given for 6 months as postoperative adjuvant therapy for colon cancer.

PURPOSE: The goal of this study was to determine the efficacy of intensive-course fluorouracil (5FU) plus low-dose leucovorin given for 6 months following potentially curative resection of colon cancer. PATIENTS AND METHODS: Three hundred seventeen patients with high-risk stage II or stage III colon cancer were randomly assigned 3 to 4 weeks following surgery to receive either (1) chemotherapy with six cycles of 5FU (425 mg/m2) plus leucovorin (20 mg/m2) by rapid intravenous injection daily for 5 consecutive days every 4 to 5 weeks, or (2) observation. RESULTS: The median follow-up duration is 72 months for patients still alive. Patients who received postoperative 5FU plus leucovorin experienced significant improvement in time to relapse (P < .01) and survival (P = .02) compared with control patients treated with surgery alone. Stomatitis, diarrhea, and leukopenia were the predominant chemotherapy toxicities. There were no treatment-related deaths. CONCLUSION: These results indicate that intensive-course 5FU plus low-dose leucovorin is effective in preventing tumor relapse and improving survival in patients with high-risk colon cancer. These benefits were seen with only six cycles of treatment, using low-dose leucovorin in combination with 5FU on a schedule convenient for outpatient administration.

Adult↗
PubMed1997

Carcinoid tumors and sarcoidosis--does a link exist?

OBJECTIVE: To attempt to determine whether a relationship exists between carcinoid tumors and sarcoidosis. MATERIAL AND METHODS: We present a series of seven case reports and discuss hypotheses about possible disease associations. RESULTS: Certain malignant lesions have tended to occur in patients with sarcoidosis. Seven patients who were encountered at Mayo Clinic Rochester between 1950 and 1994 had both sarcoidosis and carcinoid tumors. These patients ranged in age from 31 to 66 years, and three of the patients had a history of benign thyroid disorders. Malignant tumors have been thought to be related to sarcoidosis in one of two ways: (1) immunologic abnormalities in sarcoidosis may promote the development of neoplasms or (2) malignant disease may promote the onset of sarcoidosis either by causing local sarcoid reactions that progress or by directly initiating the manifestations of systemic sarcoidosis. Because the chronology of events differed in our seven cases, various mechanisms of action may have a role in the manifestations of these two disease entities. Our cases emphasize the importance of avoiding the diagnosis of disseminated malignant disease in patients with cancer and associated hilar and mediastinal lymphadenopathy without biopsy confirmation of metastatic disease. CONCLUSION: Application of the knowledge gained about the mechanisms of disease in sarcoidosis will perhaps facilitate identification of the pathogenesis of carcinoid tumors and other neuroendocrine tumors.

Adult↗
PubMed1996

Effect of mutagenesis of GPIIb amino acid 273 on the expression and conformation of the platelet integrin GPIIb-IIIa.

A G273D mutation immediately proximal to the first calcium binding domain of platelet GPIIb impairs the export of GPIIb-IIIa heterodimers to the platelet surface. To examine how this mutation might alter the structure of GPIIb, G273 was replaced by other amino acids and the resulting mutants were coexpressed with GPIIIa in COS-1 cells. Although replacement with Ala or Val had no effect on GPIIb-IIIa expression, replacement with Glu, Lys, Pro, or Asn caused intracellular retention of GPIIb-IIIa. Concurrently, the consequences of these replacements were examined by comparative modeling by introducing them into the analogous position of the first helix-loop-helix (HLH) motif of calmodulin, based on homology between the calcium binding domains of GPIIb and the calcium binding loops of HLH-containing proteins. The modeling revealed that as the side chain of the introduced amino acid increased in size, it progressively interfered with hydrophobic interactions between the incoming and outgoing helices of the motif. To test whether this observation also applies to GPIIb, V286, located immediately distal to the first GPIIb calcium binding domain, was replaced by Asp and Phe. Expression of these mutants in COS-1 cells also resulted in the intracellular retention of GPIIb-IIIa, suggesting that interactions between sequences that flank the first calcium binding domain of GPIIb affect its folding. Finally, the endoplasmic reticulum chaperone BiP was detected in immunoprecipitates of GPIIb-IIIa containing GPIIb with Ala, Val, Lys, or Pro, but not Gly, at position 273. This suggests that although BiP binding is a sensitive indication of the fidelity of GPIIb-IIIa folding, it is not sufficient to account for the intracellular retention of the heterodimer.

Amino Acid Sequence↗
PubMed1996

Teaching efficacy of a medical education module on genetic testing for cancer.

BACKGROUND: With the identification of the breast cancer susceptibility genes BRCA1 and BRCA2, clinical testing for detection of the mutated genes may be available in the near future. Primary care physicians increasingly serve as full-service providers and gatekeepers and must be aware of presymptomatic testing in order to counsel their patients appropriately. To address this educational need, a new module was incorporated into the genetics course taken by first-year medical students at the Medical College of Virginia. METHODS: The module used small groups, led by genetics faculty and members of the Virginia Breast Cancer Foundation, for discussion of case examples. The medical students' knowledge of and attitudes toward cancer and predictive genetic testing were assessed by a pretest and a posttest. RESULTS: After the module, knowledge scores increased by 27%, and significant changes were seen in the students' attitudes toward issues such as the regulation of testing availability and the psychological effect of testing. Most students consistently felt that predictive genetic testing is beneficial, that they would have the testing themselves, that genetic counseling should be required for testing, and that insurers' access to genetic testing results should be limited. Overall, the module was received favorably by all participants. CONCLUSIONS: Small-group discussion of relevant case examples increases knowledge and awareness of issues regarding presymptomatic genetic testing for breast cancer.

Breast Neoplasms↗
PubMed1996

Lupus aortitis: a case report and review of the literature.

Systemic lupus erythematosus is a complex immunological and rheumatological disease that has numerous complications. Central to the pathogenesis of systemic lupus erythematosus is immune complex formation and deposition in blood vessels and end organs. This is a case report of an autopsy of a patient with systemic lupus erythematosus, end stage renal disease, peripheral vascular occlusive disease, pancreatitis, and aortitis. The aortitis was found to be immune complex mediated with deposition of IgG, C3, as well as fibrinogen in the wall of the aorta as shown by immunofluorescence. The hypercoagulable state of the patient is discussed with particular emphasis on the role of anticardiolipin antibodies, antiphospholipid antibodies, and anti-beta-2-glycoprotein I in the pathogenesis. This case is unique in that the immune complex mediated aortitis has not been described in the literature over the past 25 years. We recommend that the diagnosis of immune complex mediated aortitis be considered in the differential diagnosis of aortitis, particularly in the background of a patient with systemic lupus erythematosus.

Adult↗
PubMed1995

Informed consent for genetic research on stored tissue samples.

OBJECTIVE: To develop recommendations for obtaining adequate informed consent in the future when gathering tissue samples that may be used for genetic studies and defining the circumstances under which it is necessary to obtain further consent if tissue samples already in hand are to be used for such research. PARTICIPANTS: Scientists, ethicists, lawyers, and consumers selected by the National Center for Human Genome Research and the Centers for Disease Control and Prevention to represent a wide array of opinions. EVIDENCE: Statutes, regulations, and cases and articles on law and ethics. CONSENSUS PROCESS: Initial workshop, followed by circulation of several drafts of this document with opportunities for comment by workshop participants and others as well as smaller meetings involving participants with widely differing views. CONCLUSION: Genetic research using stored tissue samples poses an array of benefits and risks to individuals, researchers, and society. As a result, the workshop participants conclude that (1) informed consent is required for all genetic research using linkable samples unless conditions for limitation or waiver are met; (2) informed consent is not required for genetic research using anonymous samples but may be considered if identifiers are to be removed from currently linkable samples; (3) institutional review boards could usefully review all protocols that propose to use samples for genetic research; and (4) further work regarding these issues is warranted.

Anonymous Testing↗
PubMed1991

Factors affecting the coming out process for lesbians.

Cass' model (1979) of identity development and her Stage Allocation Measure (1984a) were assessed to determine their utility in describing the subjective experience of coming out as a lesbian and whether proposed stages could be tied to behavioral correlates of the Openness Questionnaire (Graham, Rawlings, & Girten, 1985). The process was considered in terms of a woman's differentiation from her family, sex-role attitudes, and levels of internalized homophobia. Eighty-one lesbians anonymously completed questionnaires. The results suggest that subjective labeling and behavior are congruent, but that rate of progression through stages does not imply integration of behavior. Four patterns of identity development were identified which suggest that relevant stages, speed of development, and stage attainment are characteristic of certain women. Intergenerational intimidation was significantly related to stage development, sex-role attitudes, openness behavior, and levels of internalized homophobia.

Adult↗
PubMed1990

Gallstone composition in relation to buoyancy at oral cholecystography.

Although it is recognized that some gallstones float at oral cholecystography, the reasons for this are not known. To determine how stone type and composition are related to stone buoyancy, the authors analyzed gallstones from 90 patients in the National Cooperative Gallstone Study. Seventeen patients had floating and 73 had nonfloating radiolucent stones at oral cholecystography. Stone analysis showed that all 17 floating stones were cholesterol stones; 64 of the nonfloating stones were cholesterol stones, while nine were pigment stones. The cholesterol contents of floating and nonfloating cholesterol stones were similar, 90.4% +/- 1.7 and 87.0% +/- 1.2 of stone weight, respectively. The calcium salt content of the nonfloating cholesterol stones was 3.2% +/- 0.6, while that of the floating cholesterol stones was only 1.1% +/- 0.4 (P = .02). The results indicate that floating gallstones are cholesterol stones with a significantly lower calcium salt content than that of nonfloating cholesterol stones.

Cholecystography↗
PubMed1977

The contribution of alpha1-antitrypsin to the total antitrypsin activity of human serum. A study of two phenotype PI OO individuals.

Comparison of the levels of alpha1-AT, alpha2-M, inter alpha-AT, C1 inactivator and antiplasmin and global antitrypsin activity in a group of normal phenotype PI MM individuals, a group of normal individuals with phenotypes with intermediate alpha1 AT activities and alpha2-AT-deficient persons show that alpha1-AT contributes more than 90 percent of the total antitrypsin activity of normal plasma. AT III and fast reacting antiplasmin are shown to contribute to the remaining activity. It can be assumed that due to test conditions the antitrypsin activity of alpha2-M is not assessed. C1 inactivator and inter alpha1-AT do not contribute to a perceptible extent to the overall antitrypsin activity estimated according to the method of Eriksson (Eriksson, S. (1965) Acta Med. Scand. 177, 1).

Adult↗