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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Crosslinking of collagenous biomaterials currently employs the use of glutaraldehyde. The putative enhancement of glutaraldehyde crosslinking by lysine was investigated in three model systems: bovine pericardium, collagen membranes, and bovine serum albumin. Repetitive sequential treatment of bovine pericardium with glutaraldehyde and lysine and finally with formaldehyde produced a matrix which, by the two criteria used (shrinkage temperature and urea/SDS soluble collagen), was shown to be more highly crosslinked than pericardium fixed in glutaraldehyde alone. Essentially the same results were obtained when membranes prepared from pepsin-soluble pericardial collagen were subjected to sequential glutaraldehyde and lysine treatments, reaching shrinkage temperatures of more than 90 degrees C. Heart valves prepared from lysine-enhanced glutaraldehyde crosslinked bovine pericardium were tested in vitro in an accelerated fatigue tester and have been shown to behave satisfactorily after 300 million cycles. These additional crosslinks proved to be stable in saline at 37 degrees C. Studies on bovine serum albumin attempted to get an insight into the mechanisms of lysine enhancement of glutaraldehyde crosslinking by treating sequentially albumin with glutaraldehyde and lysine and analysis of the products by gel filtration and SDS-PAGE. These studies suggest that free amino groups exposed by proteins are initially reacted with glutaraldehyde and then bridged by the diamino compound (lysine) producing more extensive intermolecular crosslinking than glutaraldehyde alone.
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PMID:Lysine-enhanced glutaraldehyde crosslinking of collagenous biomaterials. 179 97

Structural-metabolic changes of the principle cells in the rat gastric glands have been studied electron-microscopically and cytochemically with subsequent cytophotometry during the process of a disturbed pepsin secretion when thyroxin and hydrocortisone are administered. At the experimentally induced hypo- and hyperthyreosis, the gastric juice proteolytic activity is inhibited owing to a decreased energy potential of the principle cell. As ultrastructural analysis has demonstrated, under the conditions mentioned above not only zymogen transport is disturbed, but the release of the mature secretion is also inhibited. Secretory cycle of the principle cell is changed under the effect of hydrocortisone.
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PMID:[Structural and metabolic changes in the chief gastric glandulocytes in disturbed hormonal balance]. 732 16

Wear debris generated from total joint arthroplasty may elicit a granulomatous and inflammatory response and has also been implicated in the development of osteolysis. Technical difficulty in retrieval and isolation of wear material from tissues has hindered the study of their physicochemical properties. The purpose of this study was to retrieve and analyze metallic wear debris from periprosthetic tissue obtained during revision arthroplasty. Tissue from six osteoarthritic patients was obtained during revision arthroplasty. The tissue was minced and then heated in a sodium dodecyl sulfate solution. Undigested tissue was incubated sequentially with papain and pepsin solutions. Metallic wear debris retrieved from the digestion procedure was analyzed by scanning electron microscopy. Wear fragments were seen as irregularly shaped flakes, splinters and polyhedral structures ranging from 1 to 100 microns in size. These structures appeared to be free from non-metallic surface-adherent material. Energy dispersion spectroscopy verified the presence of cobalt, chrome and molybdenum which comprised the implant alloy. Fatigue lines were observed on the surface suggesting brittle wear. Our technique for isolating metallic fragments facilitates the retrieval and preparation of wear debris for analysis of physicochemical properties and how wear debris interacts with cellular elements in surrounding tissue.
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PMID:Extraction and characterization of metallic wear debris from total joint arthroplasty. 1748 65