Effect of membrane length, membrane resistance, and filtration conditions on the fractionation of milk proteins by microfiltration.

We investigated the fractionation of casein micelles and the whey protein ß-lactoglobulin (ß-LG) of skim milk by crossflow microfiltration (0.1 µm) for the first time by a novel approach as a function of membrane length and membrane resistance. A special module was constructed with 4 sections and used to assess the effects of membrane length by measuring flux and ß-LG permeation (or transmission) as a function of transmembrane pressure and membrane length. Depending on the position, the membranes were partly controlled by a deposit layer. A maximum for ß-LG mass flow through the various membrane sections was found, depending on the position along the membrane. To study the effect of convective flow toward the membrane, membranes with 4 different intrinsic permeation resistances were assessed in terms of the permeation and fouling effects along the flow channel. From these findings, we derived a ratio between transmembrane pressure and membrane resistance, which was useful in reducing the effect of deposit formation and, thus, to optimize the protein permeation. In addition, the fouling effect was investigated in terms of reversible and irreversible fouling and, in addition, by differentiation between pressure-induced fouling and adsorption-induced (pressure-independent) fouling, again as a function of membrane length.

[Inflammation and subcutaneous calcification of venous origins]. / Inflammation et calcifications sous-cutanees d'origine veineuse.

There have been few descriptions up to now of calcifications in chronic venous insufficiency, other than in cases where venous insufficiency is complicated be severe trophic disorders and in particular ulcers. It was therefore felt to be of interest to assess the presence of calcifications in venous insufficiency without trophic disorders. This study was based upon 40 cases recruited in the phlebology out-patient clinic of the Notre Dame de Bon Secours Hospital. Calcifications of the lower limbs were found in 7 patients, either by palpation, routine X-rays or ultrasonography. The etiopathogenic mechanisms of this occurrence not having been elucidated, a number of hypotheses are put forward on the basis of acquired data concerning: the process of formation of ectopic calcifications, changes in subcutaneous tissue, the ultimate consequences of venous stasis and of raised venous pressure, due essentially to anoxia and inflammation. One hypothesis can thus be put forward: that of inflammation. The release of cells and mediators of inflammation, the production of free radicals, causing damage to the cells of connective tissue and to the organic framework (collagen fibres) and changes in the chemical environment could combine to result in the formation of calcifications in subcutaneous tissue. However, inflammation has not been proven to be the primary etiological factor.