The effects of betaine treatment on rats fed an acute bolus of ethanol at 3 and 12 h post bolus: a microarray analysis

Betaine, a methyl donor active in methionine metabolism, is effective in preventing and reversing experimental alcohol liver disease. The metabolic and molecular biologic mechanisms involved in this prevention are only partially known. To further investigate how betaine modifies the effects of ethanol on the liver, rats were given an acute ethanol bolus with or without betaine and the results were compared to isocaloric dextrose-fed controls. Livers were subjected to microarray analysis, and functional pathways and individual gene expression changes were analyzed. Experimental groups were compared by Venn diagrams showing that both ethanol and betaine caused a change in the expression of a large number of genes indicating that the changes were global. The bio-informatic analysis showed that all the KEGG functional pathways were affected and mainly down regulated at 3 h post bolus when ethanol plus betaine were compared with ethanol-fed rats. The most profound effect of betaine was on the metabolic pathways both at 3 and 12 h post bolus. At 3 h, the changes in gene expression were mostly down regulated, but at 12 h, the changes were regulated equally up and down. This hypothesis-driven analysis showed that the effects of betaine on the effects of ethanol were partly transient.     

Hydrodynamics of bolus flow—An analytical approach to blood flow in capillaries

A model which was used by Prothero and Burton to simulate a particular configuration in capillary blood vessels is investigated from a hydrodynamic point of view. In this model, the erythrocytes are approximated by rigid pistons, and plasma is assumed to be an incompressible Newtonian fluid. An order of magnitude analysis using the physiologically realistic values for various parameters reduces the exact equations of motion to an equation describing the creeping motion of the fluid. An analytical approach to the solution of the equation is proposed and some results are reported here. The solution of the flow field is given in terms of a stream function which is represented by two infinite series composed of known functions. Two coupled infinite systems of algebraic equations determining the coefficients of the two series have been derived. This method of solution is proposed as an alternative to the entirely numerical procedure of solving the similar problem proposed by Bugliarelloet al. A limiting case of large aspect ratio (the ratio of the axial spacing of the two successive erythrocytes to the capillary diameter) is studied and the solution, valid away from the erythrocyte surface, has been obtained in simple form. It resembles the classical Poisenille flow, but the pressure gradient is related to the erythrocyte speed.