Hepatic venous pressure gradient correlates with advanced hepatic fibrosis: a retrospective review.

PURPOSE: To determine if hepatic venous pressure gradient (HVPG) correlates with advanced hepatic fibrosis, as a complement to transjugular (transvenous) core needle liver biopsy. MATERIALS AND METHODS: After institutional review board approval, a retrospective review was conducted on 340 patients who underwent transjugular (transvenous) core needle liver biopsy with concurrent pressure measurements between 6/1/2007 and 6/1/2013. Spearman correlation and linear regression were performed. A receiver operating characteristic (ROC) curve was created and sensitivity, specificity, predictive values and likelihood ratios were calculated. RESULTS: Indications included hepatitis C, abnormal liver function tests, non-alcoholic steatohepatitis, autoimmune hepatitis, and cirrhosis, among others. Biopsies showed stage 1 or 2 fibrosis in 15.6% each, stage 3 fibrosis in 21.6%, stage 4 fibrosis in 40.7%, and no fibrosis in 6.5%. Mean HVPG was 6.5 mm Hg (SD 5.0) with a range of 0-26 mm Hg. Spearman correlation coefficient for association between HVPG and fibrosis stage was 0.561 (p < 0.001). R2 on linear regression was 0.247 (p < 0.001). ROC curve for the prediction of stage 4 fibrosis had an area under the curve of 0.79 (95% CI 0.73-0.85). HVPG of ≥6 mm Hg had a sensitivity of 71.3%, specificity of 79.6%, positive predictive value of 70.5%, negative predictive value of 80.2%, positive likelihood ratio of 3.49 (95% CI 2.45-4.97) and negative likelihood ratio of 0.36 (95% CI 0.26-0.50) for diagnosis of stage 4 fibrosis. CONCLUSIONS: HVPG correlates with stage 4 (advanced) hepatic fibrosis.

A pulsed field gradient NMR diffusion investigation of enkephalin peptide-sodium dodecyl sulfate micelle association.

Pulsed field gradient NMR (PFG-NMR) diffusion experiments were used to investigate the binding of leucine and methionine enkephalin peptides to anionic sodium dodecyl sulfate (SDS) micelles. The study was undertaken to investigate the mechanism of interaction between enkephalin peptides and SDS micelles and to determine if NMR-derived association constants, K(eq), can predict the elution order in electrokinetic chromatography (EKC). In EKC, peptides are separated on the basis of their interactions with micelles. The Leu-enkephalin peptide-micelle association constant increased from 130 +/- 8 to 1459 +/- 57 and 1744 +/- 64 M(-1), respectively, when an Arg or Lys was added to the C-terminus. The association constant of Leu-enkephalinamide was approximately equal to that of Leu-enkephalin-Arg. Substitution of Phe4 with a Trp or Gly2 with an Ala in the Leu-enkephalin peptides also increased the micelle binding affinity. These results confirm that the interaction of Leu-enkephalin peptides with SDS micelles is largely electrostatic and that the non-polar amino acid side chains interact with the hydrophobic micelle core. The peptide-micelle association constants for the cationic Met-enkephalin peptides were also greater than their zwitterionic counterparts. For example, the Met-enkephalin K(eq) value was 162 +/- 9 M(-1), while the association constants for Met-enkephalin-Arg, Met-enkephalin-Lys, and Met-enkephalinamide were, respectively, 674 +/- 31, 426 +/- 23, and 453 +/- 27 M(-1). In both Met-enkephalin and Met-enkephalinamide, replacing Gly2 with an Ala did not significantly increase the association constant. These results confirm that with the Met-enkephalin peptides, there was little or no interaction of the amino acid side chains with the micelle core. For both the Leu-enkephalin and Met-enkephalin peptides, the association constants were consistent with EKC results, in that the peptides with smaller K(eq) values were found to elute before those with larger association constants.

Six-dimensional quantum dynamics of dissociative chemisorption of H2 on Ru(0001).

Six-dimensional quantum dynamics calculations on dissociative chemisorption of H(2) on Ru(0001) are performed. The six-dimensional potential energy surface is generated using density functional theory. Two different generalized gradient approximations are used, i.e., RPBE and PW91, to allow the results to be compared. The dissociation probability for normally incident H(2) on a clean Ru(0001) surface is calculated. Large differences between the reaction probabilities calculated using the RPBE and PW91 are seen, with the PW91 results showing a much narrower reaction probability curve and a much higher reactivity. Using the reaction probabilities and assuming normal energy scaling reaction rates are generated for temperatures between 300 and 800 K. The rate generated using the PW91 results is higher by about a factor 5 than the rate based on the RPBE results in the range of temperatures relevant to ammonia production.