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At least 487 records · Page 27Linked to original sources
PubMed2001

Fixation-related autolysis and bioprosthetic aortic wall calcification.

BACKGROUND AND AIM OF THE STUDY: It has been established previously that immediate fixation and increased glutaraldehyde (GA) concentrations are required to prevent severe autolytic tissue damage during bioprosthetic aortic root production. The study aim was to verify that structure-preserving fixation also reduces aortic wall calcification. METHODS: Porcine aortic roots were fixed either instantly or after being kept on ice for 48 h (phosphate-buffered saline, PBS). Two concentrations of GA (0.2% and 3.0%) were chosen (4 degrees C, seven days, PBS). Discs of aortic wall tissue (1.2 cm diameter) were implanted subcutaneously in rats for 60 days (n = 10 per group), while aortic roots were implanted in the distal aortic arch of sheep for six weeks (n = 3 per group) and six months (n = 4 per group). Calcification was assessed by atomic absorption spectrophotometry and light microscopy. Fixation-related tissue damage was determined by transmission electron microscopy, and correlated with calcification. RESULTS: No significant difference in calcification was found between immediate and delayed fixation if tissue was fixed with 0.2% GA. In the 3.0% GA group, both animal models showed a significantly lower level of calcification if tissue was immediately fixed. In the subcutaneous rat model, immediate fixation reduced calcification by 26% (p <0.0001). In the circulatory sheep model immediate fixation did not affect calcification in the short-term six-week implants, but markedly lowered it by 37% (p = 0.035) after six months. Ultrastructurally, there was a significant correlation between membrane damage, vacuolization and vesicle shedding on the one hand, and calcification on the other. CONCLUSION: Coincidental fixation-related ultrastructural damage and increased calcification was demonstrated in bioprosthetic aortic wall tissue.

Animals↗
PubMed1975

Epithelial autolysis during implantation of the mouse blastocyst: an ultrastructural study.

An ultrastructural investigation was made of cell death in the uterine epithelium during the implantation of the mouse blastocyst. Cell death occurs in two phases: (i) early individual cell death, and (ii) later general cell death. Individual dead epithelial cells are phagocytosed and digested by trophoblast cells. At 95 h post coitum (p.c.) there are 1-4 dead cells; at 105 h and 113 h, 6-8 dead cells, and at 116 h, 2-3 dead cells. No lysosomal involvement could be identified in the death of these cells. The general breakdown of the uterine epithelium around the implanting blastocyst is first recognizable at the ultrastructural level at 113 h p.c., and continues until the adjacent deteriorated epithelium has been phagocytosed by the trophoblast cells at 119 h p.c. Ultrastructurally, from 113 h p.c. cytoplasmic portions of epithelial cells are trapped within cytosegrosomes, and there is an increase in size of the dense lysosomal bodies found in viable epithelial cells at 105 h p.c. The dense bodies, which are positively stained for acid phosphatase enzyme at 105 h p.c., increase in diameter approximately 3-5 times between 105 h p.c. and 119 h p.c. These results provide evidence of intracellular digestion of small portions of the cytoplasm possibly through the formation of cytosegrosomes which then fuse with residual bodies already present. Thus the evidence favours a process of autolytic breakdown of the uterine epithelium around the implanting blastocyst.

Animals↗
PubMedDate not supplied

[Change in the alpha-glucosidase activity of cattle muscle tissue during slow autolysis].

Changes in the alpha-glucosidase activity of the cattle muscular tissue (oxen eye muscle of loin) were evaluated during storage at 2 degrees. Under these conditions both lysosomal and extralysosomal alpha-glucosidase activities underwent no significant changes during a long period of time (12 days). Activity of lysosome-bound alpha-glucosidase was about 10% of total enzyme activity in the homogenate; the remaining part of alpha-glucosidase was contained outside lysosomes.

Animals↗
PubMed1975

[Accumulation of basic amino acid residues, rate of autolysis and relative length of gut during trypsin evolution (author's transl)].

The study of six trypsins (crayfish, dogfish, horse, pig, sheep, bovine) showed that among these the highest lysine + arginine content and the highest inactivation rate occur in specialized herbivorous animals with extreme length of gut. Since the autocatalytic degradation in trypsins can take place only at lysine or arginine residues, an accumulation of basic amino acids, the increase of the autocatalytic inactivation rate and the relative length of gut might be correlated during the evolution of mammalian trypsins.

Amino Acids↗