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At least 433 records · Page 24Linked to original sources
PubMed1988

Differential autolysis of human plasmin at various pH levels.

Denaturation of human plasmin in solutions of various pH levels was studied. The denaturation and loss of catalytic activity of plasmin in solutions of between pH 3.5 and 10.5 is a second-order kinetics. In alkaline solutions of pH levels greater than 11.5, plasmin undergoes a first-order denaturation. The second-order denaturation of plasmin is mainly due to the autolytic reactions between plasmin molecules. Two autolytic processes of human plasmin in aqueous solution were observed. In a slightly acidic solution (pH 6.5) the light (B) chain was found to be cleaved faster than the heavy (A) chain of plasmin. On the other hand, the heavy (A) chain was cleaved in an alkaline solution of pH near 11.0. A cleaved heavy (A) chain of molecular weight 58,000 was observed. Both the heavy (A) chain and the light (B) chain were found to be cleaved at pH levels between 6.5 and 11.0. The loss of the esterase activity of plasmin samples in the autolytic process is in parallel with the decline of intact light (B) chain. The autolytic cleavage of the heavy (A) chain led to the formation of a new type of catalytically active plasmin.

Autolysis↗
PubMed1986

Autolysis in the tail muscles of metamorphosing tadpoles.

Degradation of muscle homogenate from the metamorphosing tadpole tail of bullfrog, Rana catesbeiana, was examined at acid and neutral pHs. More rapid and complete degradation was observed at acid pH. Proteinases working at acid pH were not inhibited by pepstatin but were inhibited by leupeptin. However, the inhibition by leupeptin was enhanced by pepstatin. These results show that lysosomal proteinases, a thiol proteinase(s) rather than cathepsin D, are involved in the degradation of tail muscle proteins.

Animals↗
PubMed1995

Effect of postmortem autolysis on Na,K-ATPase activity and antigenicity in the gerbil cochlea.

Alterations in the enzymatic activity and antigenicity of Na,K-ATPase as well as changes in cochlear morphology were assessed in gerbil inner ears harvested at selected time intervals up to 18 h postmortem. Na,K-ATPase activity was assayed biochemically in one cochlea from each animal and the other cochlea was fixed and embedded in paraffin for evaluation by light microscopy. Na,K-ATPase antigenicity was assessed by immunostaining with a broad-spectrum antiserum reactive with all known isoforms of the enzyme, and structural preservation was evaluated on adjacent sections stained with hematoxylin and eosin. The results showed a downward trend in enzymatic activity of Na,K-ATPase in lateral wall tissues within 1 h of death. In contrast, Na,K-ATPase immunoreactivity was fairly well preserved with postmortem fixation delays up to 12 h, despite the considerable structural degradation of cochlear tissues which began 2-3 h postmortem. It is concluded that under controlled environmental conditions, cochleas collected up to 4 h postmortem are suitable for morphological and immunohistochemical study of Na,K-ATPase by light microscopy. Cochleas collected more than 5 h postmortem were useful only for relatively gross immunohistochemical studies. It is suggested that cochleas intended for biochemical assays of Na,K-ATPase and probably most other enzymes should be collected within 1 h of death.

Animals↗
PubMed2004

Ultrastructural changes during in situ early postmortem autolysis in kidney, pancreas, liver, heart and skeletal muscle of rats.

Many morphological studies of the postmortem interval were carried out under conditions in which the tissue was incubated in vitro after extirpation. However, the extirpation affects cell viability. We examined the ultrastructural changes in the kidney, pancreas, liver, heart and skeletal muscle of male Wistar rats occurring postmortem in situ. In each organ, cell edema (cell swelling), appearance of amorphous dense deposits in the mitochondria, loss of glycogen granules, dilation of the endoplasmic reticulum, clumping and margination of nuclear chromatin, and/or condensation of nuclear chromatin were observed, but the duration of the period of ultrastructural change was organ specific. Most of the ultrastructural changes occurred earlier in kidney. In hepatocytes, the morphological degeneration occurred later than in the renal tubule epithelium and earlier than that in the myocardium. Of the five organs we examined, skeletal muscle showed the greatest delay in postmortem change. In the distal tubule epithelium and pancreatic acinar cells, two forms of nuclear change were seen: one resembled necrotic change and the other resembled apoptotic change. The effect of lysosomes and hydrolytic enzymes was not as great as previous findings.

Animals↗
PubMed1996

Immunohistochemical detection of rinderpest virus: effects of autolysis and period of fixation.

Samples of eyelid, tongue, soft palate and palatine tonsil were collected from calves infected experimentally with rinderpest virus. The tissues were fixed in 10 per cent neutral buffered formalin immediately, 24 or 48 hours post mortem. Then, after three days, 10 days, 28 days or three months in formalin, they were processed into paraffin blocks and examined immunohistochemically for rinderpest viral antigen. The tonsil was the best of the four tissues in providing a consistently positive immunohistochemical signal for the presence of virus, despite autolytic changes and/or prolonged fixation.

Animals↗
PubMed1990

Malignant cell autolysis caused by intracytoplasmic liberation of lysosomal enzymes.

An ultrastructural study of the action of peptidoglycans on malignant lymphocytes was made. Glycans acted upon lysosomes labilizing and rupturing the lysosomal membrane. Lysosomal enzymes were discharged directly into the cell cytoplasm. Nucleus, mitochondria and all organelles were digested in situ, resulting in a completely structureless cell. Finally, cancerous cells disintegrated by the detachment of cytoplasmic fragments.

Animals↗
PubMed2000

Autolysis and related proteolysis in Swiss cheese for two Lactobacillus helveticus strains.

Intracellular peptidases of Lactobacillus helveticus may play a major role in the proteolysis of Swiss cheeses, provided that they are released through bacterial lysis. Experimental Swiss cheeses were manufactured on a small scale from thermized and microfiltered milk using as starters (in addition to Streptococcus thermophilus and Propionibacterium freudenreichii) one of two Lb. helveticus strains, ITGLH1 and ITGLH77, which undergo lysis to different extents in vitro. All the cheeses were biochemically identical after pressing. The viability of Lb. helveticus ITGLH1 and ITGLH77 decreased to a similar extent (96-98%) while in the cold room, but the concomitant release of intracellular lactate dehydrogenase in cheeses made with strain ITGLH1 was 5-7-fold that in cheeses made with ITGLH77. Protein profiles and immunoblot detection of the dipeptidase PepD confirmed a greater degree of lysis of the ITGLH1 strain. Free active peptidases were detected in aqueous extracts of cheese for both strains, and proteolysis occurred principally in the warm room. Reversed-phase HPLC revealed a more extensive peptide hydrolysis for ITGLH1, which was confirmed by the greater release of free NH2 groups (+33%) and free amino acids (+75%) compared with ITGLH77. As the intracellular peptidase activities of ITGLH1 and ITGLH77 have previously been shown to be similar, our results indicated that the extent of lysis of Lb. helveticus could have a direct impact on the degree of proteolysis in Swiss cheeses.

Autolysis↗