Determinants of midterm outcome of partial left ventriculectomy in dilated cardiomyopathy

The objective of this study was to test the hypothesis that maternal CRH concentrations are elevated in women experiencing threatened preterm labor who subsequently give birth within 24 h compared to those in women who do not. We also characterized the changes in maternal plasma cortisol, ACTH, corticosteroid binding capacity (CBC), and CRH concentrations in 28 healthy pregnant women between 20-38 weeks gestation. Overall, maternal plasma CRH concentrations were significantly greater (P < 0.05) in those women giving birth within 24 h (1343.3 +/- 143.9 pg/mL; n = 81) compared to those in women who did not (714.5 +/- 64.8 pg/mL; n = 144) or those in normal subjects. This difference was present between 28-36 weeks, but not 24-28 weeks gestation. The ratio of maternal cortisol to CBC was also significantly greater (P < 0.05; 0.65 +/- 0.04; n = 82) in women giving birth within 24 h than in those who did not (0.55 +/- 0.02; n = 136). This difference was significant at all gestational ages studied. Elevated CRH concentrations and bioavailability of free cortisol may both be implicated in the pathogenesis of preterm labor in some women. Further prospective clinical trials are warranted to determine the positive and negative predictive values of maternal CRH concentrations and/or the ratio of cortisol/CBC for identifying women with threatened preterm labor destined to give birth within 24 h.     

A NEW METHOD FOR PREDICTING FATIGUE LIFE IN NOTCHED GEOMETRIES

The objective of this paper is to develop a notch crack closure model, called NCCM, based on plasticity-induced effects and short fatigue crack growth in the vicinity of the notch, and to predict the fatigue failure life of notched geometries. By using this model the regime for non-propagating cracks (n.p.c.) and the relationship between the fatigue strength reduction factor, Kf , and the elastic stress concentration factor, Kt , under mean stress conditions, can be determined quantitatively. A crack closure model is assumed to apply in the notch regime based on an approach developed to explain the crack growth retardation behavior observed in smooth specimen geometries after an overload. Notch plasticity effects are also applied in the NCCM model. Fatigue failure life is calculated from both short fatigue crack growth in the notch region where elastic–plastic fracture mechanics (EPFM) is applied and from long fatigue crack growth remote from the notch where linear elastic fracture mechanics (LEFM) occurs. This prediction is obtained using a quantity called the effective plasticity-corrected pseudo-stress. The NCCM can be used to account quantitatively for various observed notch phenomena, including both the relationship between Kf and Kt and n.p.c. The effects of the tensile mean stress on the Kf versus Kt relationship is investigated and leads to the little recognized but technologically important observation that mean stress conditions exist where Kf can be greater than Kt . The role of notch radius and tensile mean stress on n.p.c. behavior is also explored. The model is verified using experimental data for notch geometries of aluminum alloy 2024-T3, alloy steel SAE 4130 and mild steel specimens tested at zero and tensile mean stress.     

Effect of bacterial association on the phenotype and genotype of an Entamoeba histolytica clonal population

A several-times-cloned population of Entamoeba histolytica trophozoites (clone MAVIII) was cultured under axenic (MAVIIIax), monoxenic (MAVIIImx) and polyxenic (MAVIIIpx) conditions. Clones MAVIIIax and MAVIIImx presented similar virulence in vitro, but differed in their virulence in vivo, whereas MAVIIIpx trophozoites were neither virulent in vitro or in vivo. The MAVIII clones maintained their zymodeme and exhibited three unusual glucose phosphate isomerase bands, absent in other E. histolytica strains studied. Similar patterns were shown by the three MAVIII clones in the signature of a 482-bp DNA fragment from the M17 gene (which encodes for a variable immunodominant antigen), obtained by low stringency single specific primer PCR technique. However, MAVIII clones displayed genotypic variability in the patterns obtained by the random amplified polymorphic DNA technique using total DNA as template. Results suggest that monomorphism is kept in certain regions of the genome, mainly in those carrying protein encoding genes, but a high polymorphism is present in total DNA of cloned trophozoites cultured under different conditions, confirming the plasticity of the E. histolytica genome.     

A precise interchromosomal reciprocal exchange between hot spots for cleavable complex formation by topoisomerase II in amsacrine-treated Chinese hamster ovary cells

Among the aprt mutations induced in confluence-arrested Chinese hamster ovary D422 cells by the topoisomerase II poison amsacrine, there was a reciprocal exchange between the aprt gene and an unrelated sequence, accompanied by a chromosomal translocation at the aprt locus. The breakpoints in both parental sequences were hot spots for amsacrine-stimulated DNA cleavage in vitro, and the novel junctions formed were precisely as expected for a mechanism involving reciprocal exchange of topoisomerase II subunits followed by resealing of the breaks and correction of mismatches in the cohesive ends. The results are consistent with a role for direct subunit exchange in the production of chromosomal translocations by topoisomerase poisons, although more complex models involving double-strand breakage and repair could produce reciprocal exchanges of similar specificity.     

Urorectal septum malformation sequence: report of thirteen additional cases and review of the literature

We present the findings of 13 additional cases of the urorectal septum malformation (URSM) sequence, and review the literature. The URSM sequence consists of ambiguous genitalia concurrent with absence of perineal and anal openings. The sex ratio of the 13 new cases was 7 males to 6 females and from the literature 21 males and 28 females. In addition, 11 of the 13 new cases had anorectal atresia with 5 of the cases also having partial agenesis of the colon. Bilateral renal agenesis was present in 3 of the 13 cases, unilateral renal agenesis occurred in 6, and dysplastic kidneys were found in 10. The URSM sequence is a lethal condition with long-term survival reported in only 3 of a total of 62 literature and new cases. Recurrence of this condition has not been reported.