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Results for “Tissue Preservation”

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At least 109 records · Page 6Linked to original sources
PubMed2005

Bioprosthetic tissue preservation by filling with a poly(acrylamide) hydrogel.

Glutaraldehyde (GA) fixation has been used for more than 40 years as the preferred treatment to suppress immunogenicity and increase durability of bioprosthetic tissues (BPT) used in heart valve prostheses. This fixative and its reaction products have, however, been implicated in the calcific degeneration and long-term failure of these devices. The current study investigates stabilization of BPT and the mitigation/prevention of calcification by filling aortic wall samples with a synthetic poly(acrylamide) (pAAm) hydrogel, with and without pre-treatment with GA. Histological and gravimetric analysis showed full penetration of the acrylamide (AAm) into the fresh tissue, while only partial filling could be achieved with GA pre-fixed tissue. The observed decrease in amino-group content (0.157+/-0.012-0.123+/-0.021 micromol/mg, p<0.03) and corresponding increase in shrinkage temperature (67.2+/-0.8-78.1+/-1.8 degrees C, p<0.0001) when fresh tissue was filled, indicate the participation of tissue-amines in a process that leads to BPT crosslinking. These effects were much less pronounced when the tissue was pre-fixed with GA. Filling increased the tensile stiffness of fresh tissue (to levels half that of 0.2% GA fixed tissue), but decreased the stiffness of GA pre-fixed tissue. When compared to standard 0.2% GA fixed samples, fresh tissue filled with AAm showed 88% (p<0.0001) less calcification while exhibiting similar resistance toward degradation by protease. Filling did not result in significant decreases in calcification when the tissue was pre-fixed with GA.

Acrylic Resins↗
PubMed2006

Polymethylmethacrylate (PMMA) as an embedding medium preserving tissues and foreign materials encroaching in endovascular devices.

Problems of displacement, poor healing, degradation of the polymers and corrosion of the metallic frame in endovascular devices still require in-depth investigations. As the tissues and the foreign materials are in close contact, it is of paramount importance to efficiently investigate the interfaces between them. Inclusion in polymethymethacrylate (PMMA) permits us to obtain thin slides and preserve the capacity to perform the appropriate stainings. An AneuRx prosthesis was harvested in bloc with the surrounding tissues at the autopsy of a patient 25 months post deployment in a 5.7 cm diameter AAA and sectioned in the direction of the blood flow in two halves. A cross-section of the encapsulated distal segment together with the surrounding aneuryshmal sac was embedded in polymethylmethacrylate (PMMA). Further to complete polymerization, slices of the specimen were cut on a precision banding saw under coolant. They were affixed onto methacrylate slides with a UV cured adhesive. Binding and polishing were done on a numeric grinder and slices 25 to 30 microm in thickness were stained with toluidine blue prior to observation in light microscopy. Additional slices were prepared for scanning electron microscopy and X-ray energy dispersive spectrometry for determination of the elemental composition of the Nitinol stent. The aortic wall did not demonstrate complete integrity along with its circumference. Some areas of rupture were noted. The content of the sac was heavily shrunk and was mostly acellular. The walls of the device were very well encapsulated. The PMMA embedding permitted the polyester wall, the Nitinol wire and the collagen to keep in close contact. Scanning electron microscopy involved backscattered electrons and confirmed the corrosion the Nitinol wire at the boundary with living tissues. Based upon the results obtained, we believe that PMMA embedding is the most appropriate method to process endovascular devices for histological and material investigation. Needless to say, that paraffin embedding would have not been feasible for such a big size specimen involving different materials.

Aged↗
PubMed1995

Corneal grafting of donor tissue preserved for longer than 4 weeks in organ-culture medium.

In vitro viability of the endothelium of corneas stored in organ-culture medium is longer than in other storage techniques. This article reports on the clinical results of 20 penetrating keratoplasties performed using corneas stored for > 4 weeks in organ culture. Seventeen of the procedures were elective and three were emergencies. Mean preservation time was 35.6 +/- 7 days (mean +/- SD) and mean follow-up was 16.2 months. During preservation, an endothelial cell loss of 10% was noted. Seventeen grafts remained transparent, and three failed between 3 and 24 months postoperatively. Mean endothelial cell density was 2,153 +/- 372/mm2 at 4 months and 1,854 +/- 390/mm2 at 12 months. Central pachymetry was 548 +/- 53 microns at 4 months and 528 +/- 57 microns at 12 months after surgery. Corneas stored for up to 48 days in organ culture can be used in elective as well as in emergency procedures.

Adolescent↗
PubMed1990

Transplant of embryonal nervous tissue preserves the responses of rat retinal ganglion cells after section of the optic nerve.

We have investigated the effectiveness of embryonal tectal tissue transplants in preserving the physiological activity of lesioned ganglion cells by recording the visual responses from the adult rat retina after section of the optic nerve, with or without transplants of embryonal nervous tissue on the stump. We have found that transplant of embryonal nervous tissue at the level of the optic nerve section has dramatic effects in preserving visual retinal responses to patterned stimuli for times as long as five months after surgery. By this time retinal responses to patterned stimuli have almost completely disappeared in control animals with optic nerve section alone.

Action Potentials↗
PubMed1979

Immunofluorescence of deparaffinized, trypsin-treated renal tissues. Preservation of antigens as an adjunct to diagnosis of disease.

The present study compares formalin-fixed, deparaffinized and trypsin-treated (DTT) renal tissue sections with frozen sections for detecting immune complex deposition. Both DTT and frozen sections from 52 renal biopsies were stained directly with fluorescein isothiocyanate-conjugated antihuman IgG, IgM, IgA, fibrinogen, and C3. DTT sections alone were stained indirectly for C3 using a double conjugate technique. Antigen presence or absence on DTT section was accurately detected in 90 per cent of biopsies for immunoglobulins and fibrinogen and in 75 per cent for C3 when compared to frozen section. Furthermore, antigen deposition was found in 21 per cent of biopsies only on DTT sections (usually because frozen tissue lacked glomeruli). Frozen sections alone were treated with reagents of the fixation-embedding process and directly stained for IgM and C3 to determine antigen stability. Alkaline or neutral formalin pH helped maximize antigen preservation. DTT sections are a valuable tissue source for adjunctive diagnosis of renal disease.

Antigen-Antibody Complex↗
PubMed1999

Effects of hypothermosol, an experimental acellular solution for tissue preservation and cardiopulmonary bypass, on isolated newborn lamb coronary vessels subjected to ultra profound hypothermia and anoxia.

Ultra profound hypothermia (4 to 10 degrees C) is an experimental method aiming at safely prolonging organ and total body preservation. For this purpose, Hypothermosol (HTS), an investigational acellular solution for blood substitution, was demonstrated to be beneficial in animal models undergoing cardiopulmonary bypass. We investigated the beneficial versus deleterious effects of cold preservation and the role of HTS on isolated coronary arteries (CA) during cold exposure, rewarming, and post-rewarming exposure to anoxia. Newborn lamb CA rings were studied using a tissue bath technique. CA were subjected to cold (7 degrees C for 3 h) and treated with either Krebs' buffer (Krebs/hypothermia) or HTS (HTS/hypothermia) (n = 15 each). A third group maintained at 37 degrees C (Krebs/normothermia) (n = 18) served as a time control. After rewarming (37 degrees C), precontracted CA were exposed to anoxia. In Krebs/hypothermia a substantial hypercontraction (g) occurred during rewarming (1.21+/-0.07) (mean +/- SEM) but not in HTS/hypothermia (0.79+/-0.03); P<0.05. Precontraction force generated by indomethacin/U46619 was identical in all three groups. However, Krebs/hypothermia vessels demonstrated a significantly higher relative vasoconstriction (percentage) in the early (approximately 10 min) and late (30 min) anoxia exposure than the HTS/hypothermia and time control (119.5%+/- 3.7 vs. 109.5%+/-4.4 and 101.5%+/-3, and 71%+/-7.6 vs. 38.9%+/-7 and 51.5%+/-5.9, respectively; P<0.05). In conclusion, Ultra profound hypothermia promotes coronary vasoconstriction upon rewarming, which is detrimental to relaxant response to hypoxia. Both phenomena are alleviated by performing ultra profound hypothermia under HTS protection.

Animals↗
PubMed1992

Prevention of stress gastritis with tissue preservation solution.

Stress gastritis frequently occurs in association with shock or sepsis. Gastric mucosal ischemia appears to be a key feature in these critically ill patients. The University of Wisconsin cold preservation solution (UWS) is an isoosmolar, nonglucose-based perfusate that minimizes hypothermia-induced cell swelling and prevents intracellular acidosis and oxygen-free radical injury, while providing high energy substrates for donor organs. In a prospective, single-blind study, 18 similar Sprague-Dawley rats were randomly divided to receive only 5 per cent dextrose and water (D5W) (Group 1) or a 50 per cent solution of D5W+UWS (Group 2) for 72 hours. At the end of 72 hours the animals were stressed by the cold-restraint model. The mean number of ulcers for Group 2 was nearly half that of Group 1. Also, Group 2 had a significantly lower mean total ulcer length (P less than 0.005) and ulcer index (P less than 0.05). Most of Group 2 had mild gastritis changes (grade 0 to 1), while more than half of Group 1 had severe gastritis (grade 3). Gastric mucosal pH was similar for both groups. Topically applied UWS appears to reduce the severity and incidence of stress gastritis in this experimental model. Because mucosal pH values were similar, it is thought that UWS may alter the effects of gastric mucosal ischemia at a cellular level.

Adenosine↗