On the curvature in logarithmic plots of rate coefficients for chemical reactions

In terms of the reduced potential energy barrier ζ = ΔuTS/kT, the rate coefficients for chemical reactions are usually expressed as proportional to e-ζ. The coupling between vibrational modes of the medium to the reaction coordinate leads to a proportionality of the regularized gamma function of Euler Q(a,ζ) = Γ(a,ζ)/Γ(a), with a being the number of modes coupled to the reaction coordinate. In this work, the experimental rate coefficients at various temperatures for several chemical reactions were fitted to the theoretical expression in terms of Q(a,ζ) to determine the extent of its validity and generality. The new expression affords lower deviations from the experimental points in 29 cases out of 38 and it accounts for the curvature in the logarithmic plots of rate coefficients versus inverse temperature. In the absence of tunneling, conventional theories predict the curvature of these plots to be identically zero

Interaction between polymorphisms of the Human Leukocyte Antigen and HPV-16 Variants on the risk of invasive cervical cancer

<p>Abstract</p> <p>Background</p> <p>Persistent infection with oncogenic types of human papillomavirus (HPV) is the major risk factor for invasive cervical cancer (ICC), and non-European variants of HPV-16 are associated with an increased risk of persistence and ICC. HLA class II polymorphisms are also associated with genetic susceptibility to ICC. Our aim is to verify if these associations are influenced by HPV-16 variability.</p> <p>Methods</p> <p>We characterized HPV-16 variants by PCR in 107 ICC cases, which were typed for <it>HLA-DQA1</it>, <it>DRB1 </it>and <it>DQB1 </it>genes and compared to 257 controls. We measured the magnitude of associations by logistic regression analysis.</p> <p>Results</p> <p>European (E), Asian-American (AA) and African (Af) variants were identified. Here we show that inverse association between <it>DQB1*05 </it>(adjusted odds ratio [OR] = 0.66; 95% confidence interval [CI]: 0.39–1.12]) and HPV-16 positive ICC in our previous report was mostly attributable to AA variant carriers (OR = 0.27; 95%CI: 0.10–0.75). We observed similar proportions of <it>HLA DRB1*1302 </it>carriers in E-P positive cases and controls, but interestingly, this allele was not found in AA cases (p = 0.03, Fisher exact test). A positive association with <it>DRB1*15 </it>was observed in both groups of women harboring either E (OR = 2.99; 95% CI: 1.13–7.86) or AA variants (OR = 2.34; 95% CI: 1.00–5.46). There was an inverse association between <it>DRB1*04 </it>and ICC among women with HPV-16 carrying the 350T [83L] single nucleotide polymorphism in the <it>E6 </it>gene (OR = 0.27; 95% CI: 0.08–0.96). An inverse association between <it>DQB1*05 </it>and cases carrying 350G (83V) variants was also found (OR = 0.37; 95% CI: 0.15–0.89).</p> <p>Conclusion</p> <p>Our results suggest that the association between HLA polymorphism and risk of ICC might be influenced by the distribution of HPV-16 variants.</p

The expression of FHIT, PCNA and EGFR in benign and malignant breast lesions

Immunohistochemical staining for FHIT and PCNA proteins was carried out in 451 breast lesions showing nonproliferative benign breast disease (BBD) (n=263), proliferative BBD without atypia (n=128), proliferative BBD with atypia (n=11), carcinoma in situ (n=15) or invasive carcinoma (n=34) and for EGFR protein in a subset of 71 of these cases. FHIT underexpression was not detected in nonproliferative lesions, but occurred in 2% of proliferative BBD without atypia, 10% proliferative BBD with atypia, 27% of carcinoma in situ and 41% of invasive carcinoma, which suggests that it could be useful in assessing those carcinoma in situ lesions (ductal, DCIS and lobular, LCIS) that are more likely to progress to malignancy. Preliminary microarray comparisons on DCIS and invasive carcinoma samples dissected from formalin-fixed paraffin sections showed a consistent downregulation of two previously identified FHIT-related genes, caspase 1 and BRCA1 in lesions underexpressing FHIT

Evidence for nonregulatory trehalase activity in Dictyostelium discoideum

An in vitro activation treatment, stimulatory to the regulatory cytoplasmic trehalase of Saccharomyces cerevisiae , had no effect on the lysosomal trehalase of Dictyostelium discoideum . Concentrations of cAMP that produced a 19 to 22-fold increase in trehalase activity in S. cerevisiae extracts did not stimulate trehalase activity in D. discoideum extracts.. cGMP and 5′-AMP were also not effective in activating the enzyme. Dictyostelium discoideum trehalase exhibits characteristics typical of nonregulatory trehalases, in agreement with its lysosomal localization. The data are consistent with the hypothesis that changes in compartmentation regulate trehalose mobilization in D. discoideum .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41332/1/284_2005_Article_BF01588179.pd