Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: HUMANGGP:031673 (collagen)
 124,196 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.
J Thorac Cardiovasc Surg 1978 Aug
PMID:Fatigue-induced damage in glutaraldehyde-preserved heart valve tissue. 9 72

A tubular prosthesis was initially made of silicone rubber, spot-bonded on the inside and outside to a layer of knitted Dacron. This was covered on the outside by a loose layer of knitted Dacron, attached to the rubber only at the two ends, to allow incorporation by fibrous tissue and fixation of the prosthesis. Anastomoses were made with one layer of continuous sutures. There was initial incorporation of the graft. After 29 to 44 days the tube became loose and migrated, leaving a stricture. The prosthesis was redesigned with two loose layers of wider mesh. Incorporation occurred early with abundant fibrous reaction. Separation of the tube started at 40 days and was complete within 72 to 152 days. When the sutures became disengaged, bacteria entered the space between rubber and incorporated fabric, resulting in collagen lysis and separation of the tube. There were no anastomotic leaks in the entire series.
J Thorac Cardiovasc Surg 1975 Oct
PMID:Prosthetic replacement of the esophagus. 12 37

Estimates of the collagen concentration in human ventricles have been made from measurements of the hydroxyproline concentration. In the normal heart the concentration of collagen was higher in the right ventricle than in the left ventricle. Age had no effect on the ventricular concentration of collagen. Hypertrophy in the absence of a valvar lesion was not associated with an increased concentration of collagen but, owing to the increased size of the ventricle, there was an increase in the estimated total mass of ventricular collagen. The concentration of collagen in the left ventricle of patients with aortic stenosis was higher than normal. Ventricular hypertrophy seems to be accompanied by an increase in the total mass of collagen whatever the cause. Whether the concentration changes or not depends on the proportion in which the mass of collagen increases relative to the mass of muscle cells.
Cardiovasc Res 1977 Nov
PMID:Collagen in the normal and hypertrophied human ventricle. 14 67

Right ventricular hypertrophy induced by hypobaric conditions was accompanied by an increased collagen mass. Left ventricular collagen was unaffected. Right ventricular mass remained unchanged after involution of right ventricular hypertrophy on return to normobaric conditions. Dietary restriction limited the size and collagen mass of both ventricles.
Cardiovasc Res 1978 Mar
PMID:Myocardial collagen, the effects of right ventricular hypertrophy and its involution induced by changes in atmospheric pressure. 14 22

It is generally agreed that cardiac hypertrophy is accompanied by the hyperplasia of connective tissue cells. In the present work, collagen metabolism was studied in the heart of nondigitalised and digitalised rats after the constriction of the aorta. The activity of prolyl hydroxylase was maximally increased 2 days after the operation. The incorporation of proline into collagen hydroxyproline increased without any increase in the specific radioactivity of free intracellular proline, the peak labelling of collagen occurring at 4 days. Although the treatment of the rats with digitoxin prevented the development of cardiac hypertrophy and an increase in collagen labelling, an increase in the activity of prolyl hydroxylase was observed. The intracellular free proline pool and its specific radioactivity were significantly lower in digitalised rats as compared with non-digitalised rats. The results indicate that constriction of the aorta is accompanied by an activation of connective tissue cells leading to increased synthesis of collagen. However, digitoxin treatment can prevent the increase in collagen labelling, possibly by inhibiting the amino acid transport, but it is unable to remove the stimulus for hypertrophy.
Cardiovasc Res 1977 Jul
PMID:Collagen metabolism in experimental cardiac hypertrophy in the rat and the effect of digitoxin treatment. 19 55

Porcine pulmonary and aortic heart valve leaflets have been examined as wet whole mounts with the Nomarski differential-contrast imaging technique. The fibrous components, collagen and elastin, which comprise the load-bearing components of the tissue are imaged readily as a function of location on the leaflets as well as of depth through their section. The response of the collagen and elastin structures to applied stress was observed directly with a simple straining device fitted to the microscope stage. I believe that the method has considerable advantages over standard histologic or scanning electron microscope techniques in that detailed structural studies can be related easily to the gross leaflet structure and that there is no interference with the biologic properties of the tissue.
J Thorac Cardiovasc Surg 1978 Jan
PMID:The observation of collagen and elastin structures in wet whole mounts of pulmonary and aortic leaflets. 33 2

Heterograft porcine valves have gained wide acceptance in replacement of diseased cardiac valves, and their clinical performance in adults has been very satisfactory over follow-up periods of up to 8 years. Valve replacement in children is relatively infrequent and experience with porcine xenografts is necessarily small. Our combined experience at three university hospitals has been with 25 children, 17 months to 16 years of age, who have been followed for 10 to 54 months (mean follow-up 33 months). Porcine valves were used to replace the aortic valve in nine, the mitral valve in seven, both valves in two, the tricuspid valve in two, and the pulmonary valve in five patients. Severe bioprosthetic valve dysfunction has occurred in five (20%) of these patients so far and necessitated replacement because of severe stenosis in mitral (two) or aortic (three) valve prostheses at 18 to 45 months after implantation; one postoperative death occurred among the five reoperations. Pathological examination showed extensive fragmentation of collagen with focal heavy calcification and degeneration. In addition we have encountered deterioration and calcification of two porcine valves in 23 valved conduits followed for 12 to 70 months (mean 43 months), requiring removal and replacement of the valves 65 and 67 months after implantation. This experience indicates a disquietingly high incidence of relatively early failure of porcine xenograft valves in children. This is significantly higher than the failure rate observed in adult patients. The failure rate is not consistently related to the small size of an implanted valve which becomes relatively narrow with the growth of the patient, leading to excessive turbulence and trauma to the prosthesis. Other factors, including increased turnover of calcium and accelerated rejection in growing children, may contribute to these failures and should be examined in order to improve long-term results. A satisfactory performance would make heterografts the ideal valvular prosthesis in children, since anticoagulation is avoided.
J Thorac Cardiovasc Surg 1979 Sep
PMID:Late failure of porcine valve heterografts in children. 47 Apr 16

The long-term behaviour of the aortic-valve allograft seems to be dependent on the maintenance of its matrix. Protein and collagen synthesis was studied in rat aortic-valves. Quantitative and qualitative methods proved the production of at least two protein pools. One protein pool is localised intracellularily with a 'turn-over' time of about 2 weeks, and a second pool is localised extracellularly with a 'turn-over' time of at least 8 weeks. The latter protein pool mainly consists of collagen.
Cardiovasc Res 1979 Mar
PMID:Fibroblast function and the maintenance of the aortic-valve matrix. 47 44

Visceral artery aneurysms have been reported which involve most major visceral arteries. However, these are usually isolated and limited to one or, at most, two visceral vessels or are related to specific systemic disorders such as the collagen vascular diseases. we have identified a patient who presented with an asymptomatic upper abdominal mass which proved upon angiography to be a splenic artery aneurysm. The patient also proved to have aneurysms of the superior mesenteric artery, the left and right hepatic arteries and the gastroduodenal artery. Histologic examination revealed normal and elastic tissue content of the vessels. Review of the literature has not revealed a similar type of case of multiple aneurysmal degeneration of visceral arteries as domonstrated by this case.
J Cardiovasc Surg (Torino)
PMID:Visceral artery aneurysmosis. Case report. 51 22

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.
J Thorac Cardiovasc Surg 1979 Aug
PMID:In vitro durability of Hancock Model 242 porcine heart valve. 57 54


1 2 3 4 5 6 7 8 9 10 Next >>