Finite element stress analysis of a new design of synthetic leaflet heart valve

This paper presents a parametric finite element analysis of the stresses in the leaflets of a new design of polyurethane heart valve in the closed position. The alpharabola geometry of the valve has previously been reported by Leat and Fisher (1) and has been shown to demonstrate good opening characteristics. The effects of variations in leaflet offset parameter, g, length, h, and local thickening have been determined for a valve where the frame is assumed rigid. A spherical leaflet geometry has also been analysed for comparative purposes. Results have shown that the alpharabola leaflet geometry can reduce the maximum principal tensile stress to 60 per cent of that for a spherical valve of the same mesh density.     

Gene Transfer Systems and Molecular Cloning in Group N Streptococci: A Review

Plasmid deoxyribonucleic acid of group N streptococci codes for a wide variety of important metabolic properties associated with dairy fermentations. The increasing knowledge of the genetics of these bacteria has created exciting possibilities for genetically constructing improved starter strains. A review of current literature is presented on the genetics of group N streptococci, especially the development and implications of gene transfer and molecular cloning systems for further genetic studies and for strain improvement. Functional properties of plasmid deoxyribonucleic acid and gene transfer systems, which include transduction, conjugation, transformation, and protoplast fusion, are reviewed and followed by a discussion of recent advances in gene cloning.     

A novel zinc finger cDNA with a polymorphic pentanucleotide repeat (ATTTT)n maps on human chromosome 19p

PURPOSE: To evaluate the therapeutic effectiveness of a combined chemoradiotherapy program, followed by surgery in selected cases, in Stage III non-small cell lung cancer. METHODS AND MATERIALS: Between August 1988 and February 1990, 43 patients Staged IIIa-b (UICC 1987, 58% IIIb) have been treated with concomitant chemotherapy (cisplatin 15 mg/m2 and VP16 75 mg/m2, 5 days a week on week 1 and 5) and radiotherapy (40 Gy split course, 2 Gy/day on week 1, 2, 5, and 6), followed by attempted curative thoracotomy or more cycles of full dose chemotherapy with the same two drugs. RESULTS: Planned chemoradiotherapy has been given to 91% of patients; 13/43 patients have been operated, with 12 complete resections and three (7%) pathological complete responses. Toxicity was significant, with two postoperative deaths and two fatal radiation pneumonitis. Crude progression-free survival rate is 21% at 30 months, with nine patients (21%) alive and free from progression at follow-up times ranging from 31 to 49 months. Subset survival analysis showed a possibly greater therapeutic effect for non-squamous histology as compared to squamous carcinoma. CONCLUSION: These results are encouraging in a cohort of patients with quite advanced disease (58% Stage IIIb).     

Polymerase chain reaction amplification analyses of clonality in T-cell malignancy including peripheral T-cell lymphoma

Clonality in T-cell malignancy was investigated using T-cell receptor (TcR) V beta 1-20 family primers and polymerase chain reaction amplification (PCR) of cDNA prepared from tissue biopsies and blood involved with tumour. Secondary PCR amplification of the VDJ joints of primary PCR products was performed to distinguish clonal from polyclonal products, and clonal V beta gene products were confirmed by direct PCR sequencing in the majority of cases. In eight T-cell malignancies including T-cell acute lymphoblastic leukaemia (T-ALL) and T-cell chronic lymphocytic leukaemia (T-CLL) shown to be clonal by Southern blot analysis, one or two primary PCR products were identified and shown to be clonal. In five cases of peripheral T-cell lymphoma (PTCL) all V beta 1-20 families were identified after primary PCR amplification, and clonal products were identified in two cases after secondary amplification; TcR V beta clonal families could not be demonstrated in the remaining three cases. These data were in agreement with previous Southern blot analysis of these cases, and confirmed the presence of reactive T cells in PTCL as well as providing further evidence for the genotypic heterogeneity of this entity. In the remaining case, a blood lymphocytosis, primary PCR amplification produced predominant TcR V beta 6 and V beta 12 family products, of which the V beta 6 family proved clonal after secondary PCR amplification. There was no evidence for overrepresentation of TCR V beta families by the tumour populations in this study, furthermore the data confirm the involvement of reactive cells in T-cell malignancy and the genetic heterogeneity of PTCL.     

The geographic variation of cancer incidence in Ontario

OBJECTIVES: Our objectives were (1) to describe an analysis of the spatial pattern of cancer incidence in Ontario and (2) to discuss the quality of data in the Ontario Cancer Registry with respect to the accuracy of local cancer rates. METHODS: Cancer incidence rates were calculated for 22 cancer sites in 49 counties of Ontario during 1976 to 1986. Capture-recapture methods were used to estimate completeness of case registration, and completeness of residence information was also assessed. Spatial autocorrelation was used in measuring the geographic pattern of incidence rates. Comparisons were also made between sexes and with earlier data from 1966 to 1975. RESULTS: The quality of the geographic data in the registry appeared good, and corrections for incomplete or inaccurate registration had little impact. About one third of the sex-site combinations showed some evidence of spatial patterning in the cancer rate. Particularly strong regional variation was noted for cancers of the stomach, lung, uterus, and prostate. CONCLUSIONS: The analysis revealed a number of cancers with significant spatial patterning of risk. Further work is needed to relate the cancer data to other information on potential life-style and environmental factors.