Collagen is one of the most useful biomaterials. The medical application of collagen tissues requires specific fixation procedures. Dye-mediated photooxidation is a method of the new collagen crosslink formation. In this study, the influence of sorbitol on the extent of porcine pericardial collagen crosslinking was investigated. The collagen modification was estimated on the basis of pericardial susceptibility to pepsin digestion. The hydrolysate components were characterized electrophoretically. The significant collagen crosslinking was found in all photooxidized samples, in comparison with the untreated ones. However, the most enhanced collagen modification was observed for pericardium photooxidized with 0,5% and 0,9% sorbitol, as compared to the samples fixed without sorbitol.
This review presents studies of the induction of meiosis undertaken on the ciliate Paramecium, a unicellular model eukaryotic organism. Meiosis in Paramecium, preceding the process of fertilization, appears in starved cells after passing a defined number of divisions (cell generations), starting from the last fertilization. Investigations were performed on clones of cells entering autogamy, a self-fertilization process. Genetic as well as epigenetic factors, i.e. endo- and exogenous factors, affecting the induction of meiosis and changing the duration of the interautogamous interval (IAI), were analyzed. The results show that: (1) Meiosis induction is controlled genetically by the somatic macronucleus. However, besides the nuclear factors, the cytoplasmic protein immaturin also affects this process (HAGA & HIWATASHI 1981); (2) Epigenetic factors, such as non-genetically disturbed cytoskeleton structures and changes in the cell architecture observed in doublet Paramecium cells, exert internal mechanical stress (INGBER 2003), which constitutes the endogenous impulse accelerating meiosis; (3) Mild osmotic stress, acting as an exogenous factor, can initiate the specific MAP kinases signaling pathway resulting in earlier meiosis induction, as in other unicellular eukaryotes (SEET & PAWSON 2004).
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