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The oligomerization of glycerol to preferentially di-and triglycerol is reviewed, with primary focus on the use of heterogeneous acidic and basic catalysts. Low molecular-weight oligomers have found a wide field of applications in cosmetics, food industry and polymer production. The growing market intensified research work on the selective catalytic oligomerization of glycerol. Performing the reaction of glycerol in the presence of microporous and mesoporous solid catalysts aims at exerting shape-selective effects on the reaction, suppressing the abundant formation of cyclic isomers and cutting further polymerization of the target products. Enhanced selectivity to diglycerol is observed over some type of catalysts, but the solids suffer from leaching of active alkaline cations from the solid, severe deterioration of crystallinity of zeolites and even dissolution of the solids in the hot glycerol during batch reaction at temperatures in the range of 240-2608C. In those cases it is difficult to separate homogeneous and heterogenous reaction routes, and the shape-selective effects are levelled off. The oligomerization is a consecutive reaction, and complete conversion of glycerol favours formation of high molecular-weight glycerol oligo-and polymers. To achieve maximum yield of diglycerol, the reaction has to be interrupted at glycerol conversions of ca. 50%. Alternative reaction engineering is required to overcome the inherent disadvantages of a batch reaction. Examples will be given for a selective glycerol oligomerization under reduced pressure in a so-called fall-film reactor using super-acidic polymers as catalysts.

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Gap junctions (GJ) are important determinants of cardiac conduction and the evidence has recently emerged that altered distribution of these junctions and changes in the expression of their constituent connexins (Cx) may lead to abnormal coupling between cardiomyocytes and likely contribute to arrhythmogenesis. However, it is largely unknown whether changes in the expression and distribution of the major cardiac GJ protein, Cx43, is a general feature of diverse chronic myocardial diseases or is confined to some particular pathophysiological settings. In the present study, we therefore set out to investigate qualitatively and quantitatively the distribution and expression of Cx43 in normal human myocardium and in patients with dilated (DCM), ischemic (ICM), and inflammatory cardiomyopathies (MYO). Left ventricular tissue samples were obtained at the time of cardiac transplantation and investigated with immunoconfocal and electron microscopy. As compared with the control group, Cx43 labeling in myocytes bordering regions of healed myocardial infarction (ICM), small areas of replacement fibrosis (DCM) and myocardial inflammation (MYO) was found to be highly disrupted instead of being confined to the intercalated discs. In all groups, myocardium distant from these regions showed an apparently normal Cx43 distribution at the intercalated discs. Quantitative immunoconfocal analysis of Cx43 in the latter myocytes revealed that the Cx43 area per myocyte area or per myocyte volume is significantly decreased by respectively 30 and 55% in DCM, 23 and 48% in ICM, and by 21 and 40% in MYO as compared with normal human myocardium. In conclusion, focal disorganization of GJ distribution and down-regulation of Cx43 are typical features of myocardial remodeling that may play an important role in the development of an arrhythmogenic substrate in human cardiomyopathies.