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

Glutaraldehyde-preserved porcine mitral leaflet tissue has been subjected to extended accelerated fatigue loading in Ringer's solution containing 0.15% glutaraldehyde. Five tissue test pieces were subjected to cyclic tensile stresses of 50 and 200 Gm. per square millimeter and to 300 million to 800 million accumulated fatigue cycles. Tissue disruption occurred in each of the fatigued test pieces. Tensile loading, apart from reducing the acuteness of the collagen waveform and thereby decreasing tissue compliance, does not contribute significantly to the disruption process nor its rate of occurrence. Compressive flexure occurring during the unloading half of the fatigue cycle, however, does induce damage in the tissue. Mechanisms involved in the disruptive processes have been identified by conducting simultaneous morphologic and stress/strain observations on both the fatigued and unfatigued tissues in their wet functional condition. This vulnerability of the preserved tissue to compressive flexure could well affect the long-term durability of the glutaraldehyde-preserved heterograft valve, and this possibility is discussed in relation to the clinical use of these valves.
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PMID:Fatigue-induced damage in glutaraldehyde-preserved heart valve tissue. 9 72

To maintain optimum mechanical properties in glutaraldehyde-treated heart-valve tissue the full collagen crimp geometry originally present in the relaxed fresh tissue should be retained. By varying the pressure at which glutaraldehyde fixation is carried out, considerable alterations to this crimp geometry can be achieved. The mechanical stiffness of the preserved tissue is consequently affected, and this in turn has a striking influence on both the opening behaviour of the valve and the degree of strain localisation in the leaflet tissue. A pressure of 100 mmHg eliminated the collagen crimp geometry entirely, and this resulted in the formation of sites of local strain or kinks in the valve leaflets during opening. It is expected that this strain localisation phenomenon will influence the long-term fatigue durability of the treated tissue. Pressures even as low as 4 mmHg result in significant reductions of crimp geometry. Fresh valves should therefore be fixed under a positive head of pressure sufficient only to ensure that the leaflets seal along their coapting free margins. A pressure of less than 1 mmHg was sufficient to achieve this. Leaflets of the commercially available Hancock valve show features similar to valves fixed in glutaraldehyde at about 100 mmHg pressure.
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PMID:Influence of fixation conditions on the performance of glutaraldehyde-treated porcine aortic valves: towards a more scientific basis. 11 99

Two Hancock Model 242 prostheses, tissue anulus diameter 21 mm., were tested in a closed, low-volume, accelerated fatigue tester. The fluid media was sterils fresh-frozen plasma. The normal human aortic root was simulated. The cyclic rate was 20 Hz at 37 degrees C. The prostheses developed severe fatigue at 77 million cycles. Fraying of the free edges was found after 2 million cycles. Small tears near the commissures and then holes between collagen bundles at the base of the leaflets appeared at 7 million cycles. At 71 million cycles the leaflets began to tear and complete prolapse, with gross valvular insufficiency occurring at 77 million cycles. The accelerated wear of Hancock procine prosthesis is frequency dependent and independent of media and the flow geometry of the testing device.
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PMID:In vitro durability of Hancock Model 242 porcine heart valve. 57 54

The tensile fatigue properties of the collagen fibre meshwork in normal human articular cartilage were measured by subjecting isolated specimens of post-mortem femoral head cartilage to cyclic tensile stress. The results of the study showed (1) that the collagen fibre meshwork is fatigue prone and (2) that its fatigue strength decreases rapidly with age. Extrapolation of the data to physiologically possible stress levels suggests that tensile fatigue failure of the collagen meshwork could occur in life.
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PMID:A second study of tensile fatigue properties of human articular cartilage. 62 5

The dorsal cortex of the equine third metacarpal mid-diaphyseal bone was characterised during growth by the histological and microradiographic examination of specimens from 30 horses ranging in age from 2 months to 8 y. Bone from horses aged less than 6 months was characterised by rapid periosteal apposition of circumferential trabeculae of woven bone that were next connected by radial trabeculae to the parent cortex. Deposition of lamellar bone on the inner trabecular surfaces resulted in rows of primary osteons. Replacement of primary bone occurred only after 4 months of age and preferentially in the woven interstitial bone separating rows of primary osteons formed in the postnatal periosteal cortex. Resorption cavities and incompletely filled secondary osteons characterised bone of 1 and 2-y-old horses. Bone from horses older than 3 y contained several generations of secondary osteons, fewer resorption spaces and incompletely filled osteons, and had a greater portion of circumferentially oriented collagen fibres than bone from younger horses. Bone from horses older than 5 y had large resorption cavities characterised by irregular boundaries. We propose that the process of periosteal bone tissue apposition observed in growing foals be called 'saltatory primary osteonal bone formation' and that this process results in faster cortical expansion and larger total surface area for bone deposition than circumferential lamellar, simple primary osteonal, and plexiform mechanisms of periosteal bone formation. We speculate that bone from 1 and 2-y-old horses would be more susceptible to fatigue microdamage resulting from compressive loads because of high porosity, few completed secondary osteons and low proportion of circumferentially oriented collagen fibres.
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PMID:Histological features of the dorsal cortex of the third metacarpal bone mid-diaphysis during postnatal growth in thoroughbred horses. 130 84

We describe the histopathologic changes of skin, muscle, vessels, and fascia in 11 patients with eosinophilia myalgia syndrome, a newly described entity that has been linked to the ingestion of L-tryptophan. This syndrome is defined clinically by severe incapacitating myalgias and a peripheral eosinophilia. Arthralgias, edema of the extremities, morbilliform rashes, skin induration, weakness, fatigue, and respiratory weakness may be present as well. The earliest apparent histologic changes were observed at the septa between subcutaneous fat lobules and in the deep dermis or fascia. The septa and fascia were infiltrated with a sparse mixture of lymphocytes and histiocytes. In the deep fascia, in addition to inflammatory cells, there were distinctive, reactive mesenchymal cells that showed features of both histiocytes and fibrocytes. Minimal tissue eosinophilia was seen despite the extent of blood eosinophilia. Dermal thickening and homogenization of collagen bundles occurred with replacement of fat and adnexa (changes indistinguishable from scleroderma or morphea). Vessel walls in the dermis and fascia showed thickening and endothelial swelling, but no overt vasculitis was noted. Skeletal muscle biopsies showed a perimysial, epimysial, and/or fascial inflammatory infiltrate of lymphocytes and distinctive reactive mesenchymal cells with some eosinophils. Minimal myofiber atrophy, regeneration, or necrosis was seen despite the clinical history of severe myalgias in almost all patients. This syndrome should help gain insight into the mechanisms of fibrosis in environmental-induced, scleroderma-like syndromes and in idiopathic, scleroderma-like disorders as well.
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PMID:Pathologic manifestations of the eosinophilia myalgia syndrome: analysis of 11 cases. 156 45

The feasibility of one whole liver chemoembolization (CE) procedure with Angiostat, a vasoocclusive collagen, mitomycin, doxorubicin, and cisplatin was evaluated in eight patients with unresectable colorectal carcinoma metastatic to the liver and good performance status. One heavily pretreated patient showed a partial response in the liver lasting 188 days. Five patients had stabilization of the disease for 85-150 days. The side effects of the treatment were considerable with a fatigue syndrome lasting up to eight weeks, chemical and ischemic hepatitis, severe thrombopenia (WHO grade 4 in 2 pts) and icterus being the most disturbing toxicities. We recommend to restrict CE to patients with a life expectancy of more than 4-6 months confined to protocols, which evaluate efficacy, toxicity and influence on quality of life of CE with various cytotoxic drugs. We further suggest to perform staged unilobar CE at 4- to 6-week intervals rather than whole liver CE.
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PMID:Considerable side effects of chemoembolization for colorectal carcinoma metastatic to the liver. 160 81

A 38-year-old man presented with a cavernous hemangioma in the liver. Transarterial embolization (TAE) using a gelatin sponge was carried out 14 days prior to surgical resection of the tumor. Granulomatous arteritis with massive infiltration by eosinophilic leukocytes and histiocytes was present at the periphery of the hemangioma, and transient eosinophilia in the peripheral blood occurred six days after resection. Granulomatous arteritis was evident in medium-sized arteries and there was narrowing or occlusion of the vascular lumen. In the granulomatous cellular infiltrates in the arteries, giant cells of the foreign body type were numerous. An eosinophilic substance differing from fibrin was present in some of the vascular lumina. As this showed staining for collagen, it was considered likely to be fragments of the gelatin sponge. The patient had no symptoms of fever, chills or general fatigue. The clinical course and pathologic findings suggest a causative role of the gelatin sponge in this case of granulomatous arteritis. Vascular change, a rare complication of TAE therapy, may be induced by a hypersensitivity reaction against the intra-arterial gelatin sponge.
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PMID:Granulomatous arteritis with massive eosinophilic leukocyte infiltration and transient peripheral eosinophilia subsequent to transarterial embolization therapy with a gelatin sponge. 175 Mar 58

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

The effects of mechanical stimuli on preserving muscle mass while transforming them into slow, fatigue resistant muscles have been studied in the rabbit. When combined, stretching and electrical stimulation (10 Hz) induce rapid and marked growth of muscles. This procedure also more rapidly activates the transformation process(es) than when either stretching or electrical stimulation (10 Hz) are used alone. Stretch by itself is also anabolic causing useful lengthening of muscles and preventing collagen accumulation. In contrast, muscle inactivity leads to rapid atrophy, fiber shortening and reduced muscle compliance. We believe these findings have important implications to cardiomyoplasty.
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PMID:The role of passive stretch and repetitive electrical stimulation in preventing skeletal muscle atrophy while reprogramming gene expression to improve fatigue resistance. 180 7


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