Evaluation of lignin contents in tropical forages using different analytical methods and their correlations with degradation of insoluble fiber

We compared the lignin contents of tropical forages by different analytical methods and evaluated their correlations with parameters related to the degradation of neutral detergent fiber (NDF). The lignin content was evaluated by five methods: cellulose solubilization in sulfuric acid [Lignin (sa)], oxidation with potassium permanganate [Lignin (pm)], the Klason lignin method (KL), solubilization in acetyl bromide from acid detergent fiber (ABLadf) and solubilization in acetyl bromide from the cell wall (ABLcw). Samples from ten grasses and ten legumes were used. The lignin content values obtained by gravimetric methods were also corrected for protein contamination, and the corrected values were referred to as Lignin (sa)p, Lignin (pm)p and KLp. The indigestible fraction of NDF (iNDF), the discrete lag (LAG) and the fractional rate of degradation (kd) of NDF were estimated using an in vitro assay. Correcting for protein resulted in reductions (P < 0.05) in the lignin contents as measured by the Lignin (sa), Lignin (pm) and, especially, the KL methods. There was an interaction (P < 0.05) of analytical method and forage group for lignin content. In general, LKp method provided the higher (P < 0.05) lignin contents. The estimates of lignin content obtained by the Lignin (sa)p, Lignin (pm)p and LKp methods were associated (P > 0.05) with all of the NDF degradation parameters. However, the strongest correlation coefficients for all methods evaluated were obtained with Lignin (pm)p and KLp. The lignin content estimated by the ABLcw method did not correlate (P > 0.05) with any parameters of NDF degradation. There was a correlation (P < 0.05) between the lignin content estimated by the ABLadf method and iNDF content. Nonetheless, this correlation was weaker than those found with gravimetric methods. From these results, we concluded that the gravimetric methods produce residues that are contaminated by nitrogenous compounds. Adjustment for these contaminants is suggested, particularly for the KL method, to express lignin content with greater accuracy. The relationships between lignin content measurements and NDF degradation parameters can be better determined using KLp and Lignin (pm)p methods. (C) 2011 Elsevier B.V. All rights reserved.

Analytical solution and numerical model for the interface in a stratified long wave system

For a two layered long wave propagation, linearized governing equations, which were derived earlier from the Euler equations of mass and momentum assuming negligible friction and interfacial mixing are solved analytically using Fourier transform. For the solution, variations of upper layer water level is assumed to be sinosoidal having known amplitude and variations of interface level is solved. As the governing equations are too complex to solve it analytically, density of upper layer fluid is assumed as very close to the density of lower layer fluid to simplify the lower layer equation. A numerical model is developed using the staggered leap-forg scheme for computation of water level and discharge in one dimensional propagation having known amplitude for the variations of upper layer water level and interface level to be solved. For the numerical model, water levels (upper layer and interface) at both the boundaries are assumed to be known from analytical solution. Results of numerical model are verified by comparing with the analytical solutions for different time period. Good agreements between analytical solution and numerical model are found for the stated boundary condition. The reliability of the developed numerical model is discussed, using it for different a (ratio of density of fluid in the upper layer to that in the lower layer) and p (ratio of water depth in the lower layer to that in the upper layer) values. It is found that as ‘CX’ increases amplification of interface also increases for same upper layer amplitude. Again for a constant lower layer depth, as ‘p’ increases amplification of interface. also increases for same upper layer amplitude.

Prevalence and diagnostic workup of primary aldosteronism: new knowledge and new approaches

No Abstract

A potential role for the analytical ultracentrifuge in the experimental measurement of protein valence

A method is described whereby sedimentation velocity is combined with equilibrium dialysis to determine the net charge (valence) of a protein by using chromate as an indicator ion for assessing the extent of the Donnan redistribution of small ions. The procedure has been used in experiments on bovine serum albumin under slightly alkaline conditions (pH 8.0, I 0.05) to illustrate its application to a system in which the indicator ion and protein both bear net negative charge and on lysozyme under slightly acidic conditions (pH 5.0, I 0.10) to illustrate the situation where chromate is a counterion. (C) 2001 Elsevier Science.

Analytical validation for a series of marker compounds used to assess renal drug elimination processes

Renal drug elimination is determined by glomerular filtration, tubular secretion, and tubular reabsorption. Changes in the integrity of these processes influence renal drug clearance, and these changes may not be detected by conventional measures of renal function such as creatinine clearance. The aim of the current study was to examine the analytic issues needed to develop a cocktail of marker drugs (fluconazole, rac-pindolol, para-aminohippuric acid, sinistrin) to measure simultaneously the mechanisms contributing to renal clearance. High-performance liquid chromatographic methods of analysis for fluconazole, pindolol, para-aminohippuric acid, and creatinine and an enzymatic assay for sinistrin were developed or modified and then validated to allow determination of each of the compounds in both plasma and urine in the presence of all other marker drugs. A pilot clinical study in one volunteer was conducted to ensure that the assays were suitable for quantitating all the marker drugs to the sensitivity and specificity needed to allow accurate determination of individual renal clearances. The performance of all assays (plasma and urine) complied with published validation criteria. All standard curves displayed linearity over the concentration ranges required, with coefficients of correlation greater than 0.99. The precision of the interday and intraday variabilities of quality controls for each marker in plasma and urine were all less than 11.9% for each marker. Recoveries of markers (and internal standards) in plasma and urine were all at least 90%. All markers investigated were shown to be stable when plasma or urine was frozen and thawed. For all the assays developed, there were no interferences from other markers or endogenous substances. In a pilot clinical study, concentrations of all markers could be accurately and reproducibly determined for a sufficient duration of time after administration to calculate accurate renal clearance for each marker. This article presents details of the analytic techniques developed for measuring concentrations of marker drugs for different renal elimination processes administered as a single dose to define the processes contributing to renal drug elimination.