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PubMed1979

Effect of sodium azide on the ultrastructural preservation of tissues.

An electron microscopic study was carried out to examine the quality of ultrastructural preservation of parenchymatous and mesenchymatous tissues and isolated cells fixed in glutaraldehyde with sodium azide (NaN3) as an additive. The dense tissues fixed with conventional glutaraldehyde containing calcium chloride demonstrated only a narrow zone of good tissue preservation on the surface of the specimens. Addition of azide at a concentration of 0.1% greatly improved the cellular preservation in the deeper region of tissues, in particular with respect to the mitochondrial morphology. There was no adverse effect on other cell organelles. The improvement in mitochondrial preservation and the enhancement of penetration of the fixative is presumably due to selective and instantaneous inhibition of mitochondrial metabolic activity by the azide, thus retarding anoxic degenerative effects on cellular structures until permanent fixation is completed by the comparatively slow-acting aldehyde. However, the addition of azide offers no significant improvement in the ultrastructural preservation of isolated lymphocytes and liver cells, or fibroblasts maintained in culture.

Animals↗
PubMed1975

Fixation of foetal pig liver for electron microscopy. I. The effect of various aldehydrs and of delayed fixation.

Light and electron microscopic investigations of the ability of various fixatives to preserve foetal pig liver tissue (immersion fixed 5 min, 20 min, and 40 min after the death of the mother) gave the following results: 1) Fixation with 4% formaldehyde gives, in all circumstances, an unacceptable tissue presevation. 2)Fixation with 2.5% glutaraldehyde gives fair tissue preservation in a ca. 130 mu thick zone below the surface. 3) Fixation with a fixative mixture containing 2% formaldehyde and 1.25% glutaraldehyde or 2% formaldehyde, 1% glutaraldehyde and 1% acrolein gives good tissue preservation in a ca. 500 mu thick zone under the surface. 4) The addition of DMSO does not improve tissue preservation. 5) Delayed fixation of liver tissue removed from the foetus after the uterus has been placed in an incubator for 40 min has only a slight effect on tissue preservation.

Acrolein↗
PubMed1989

Optimization of immunohistochemical techniques to detect extracellular matrix proteins in fixed skin specimens.

Complete antigen visualization in the context of well-preserved tissue architecture is the goal of all immunohistochemical techniques. Frozen tissue section techniques achieve optimal antigen visualization but preserve tissue architecture poorly. On the other hand, formalin-fixed tissue section techniques preserve tissue architecture very well but result in antigen masking. Enzymatic digestion or salt extraction of formalin-fixed sections has been used to reestablish antigen expression. Recently acid-alcohol-fixed tissue has been used as a successful compromise between tissue architecture preservation and the visualization of cytoskeletal antigens. In an attempt to find an improved immunohistochemical process for non-cytoskeletal antigens, we compared avidin-biotin immunofluorescence staining in frozen, formalin-fixed, and acid-alcohol-fixed tissues. The fixed tissues were either untreated or treated with enzyme digestion or salt extraction. For this study, we examined healing cutaneous wounds in Yorkshire pigs with antibodies to fibronectin, laminin, von Willebrand factor VIII, and keratin. Although tissue architecture was poor, frozen sections provided the best antigen visualization and were therefore used as the standard for complete antigen expression. Formalin-fixed tissues had excellent tissue architecture, but most antigens were completely masked. Pre-treatment technique only partially overcame the antigen masking caused by formalin. In contrast, acid-alcohol fixation preserved tissue architecture almost as well as formalin and sometimes allowed complete antigen visualization; however, laminin and fibronectin were partially masked. Total recovery of the expression of these antigens could be obtained by pre-treating the acid-alcohol-fixed tissue with either hyaluronidase or 1 M NaCl. Therefore, acid-alcohol-fixed tissue appears best for extracellular matrix (ECM) protein immunostaining as well as for cytoskeletal staining. However, certain ECM antigens require hyaluronidase or 1 M NaCl treatment for optimal visualization.

Acetates↗
PubMed1983

Epikeratophakia: existing limitations and future modifications.

The predictability of optical correction has been a problem for all forms of refractive corneal surgery in epikeratophakia, changes in graft dimensions and surgical technique improved accuracy, but several problems still exist in cryolathing preserved corneal tissue. Preserved corneal tissue is quite oedematous and when frozen on the cryolathe, assumes an irregular shape. A mechanical technique to dehydrate tissue was developed which yields corneal tissue which behaves in a predictable fashion. The use of donor corneal tissue in refractive surgery has certain inherent limitations. There is no way of measuring the power of the lathed corneal lens prior to surgery; the power is a function of the shape the lens will take in vivo. The ability to supply large numbers of donor corneal buttons may be an impractical task should this type of surgery become widely used. The use of alloplastic lenses should overcome most of these difficulties.

Cornea↗
PubMed1996

[Future of bone allografts in massive bone resection for tumor].

Currently cryopreservation offers the best means of preserving bone tissue for allografts. At -196 degrees C all enzyme activity is halted and tissue preservation is unlimited. Perfect sterilization, adapted cryoprotection and controlled freezing and thawing are now part of the well-controlled process of bone preservation in bone banks. At implantation, the mechanical properties of cryopreserved bone is as good as or better than fresh bone, although the diaphyseal cortical bone is more fragile. Anatomic and physiologic reconstruction of the graft area is a major factor in graft resistance. It takes approximately three weeks for vessels to penetrate cancellous allografts and at least one month for total revascularization. The delay may reach several years for cortical bone. The immune response of the host is determined by the antigenic properties of the leukocytes in the bone marrow as well as the blood vessels and nerves. The protein-mineral complex itself has little antigenic effect. A certain number of non-specific immune reactions result from transfusions almost always performed with bone grafting. At the present time, there is no artificial material capable of providing a mechanically acceptable substitute for allograft bone in limb reconstruction. Allograft bone currently stocked in bone banks provides a biologically and clinically acceptable means of reconstruction after major bone loss. Other factors such as public acceptance and administrative authorizations will also play an important role in the future of massive reconstruction with bone allografts.

Bone Neoplasms↗
PubMed2000

Homogenous implant in rat tibias of matrix preserved in 98% glycerin: histomorphologic study.

As a chemical medium for preservation of tissues, glycerin has shown good results because it maintains the cellular integrity despite the tissue dehydration it causes. Taking advantage of the osteoinducing properties of the osseous matrix and glycerin as a proper medium for tissue preservation, osseous matrix was implanted in rat tibias. Twenty-four rats were used, each receiving two surgical wounds. In one of the wounds an osseous matrix preserved in 98% glycerin was implanted and the other received a matrix without preservatives. Six animals were sacrificed on days 10, 20, 30 and 60 post-implant. After routine histological processing, the specimens were stained in hematoxylin-eosin and Masson's trichrome. The results showed that the matrixes preserved in glycerin presented faster resorption with replacement by newly formed tissue.

Animals↗
PubMed1999

Immunocytochemistry of lipids: chemical fixatives have dramatic effects on the preservation of tissue lipids.

We report here the effects of chemical fixatives on lipids studied under conditions simulating the immunogold labelling of phosphatidylserine. Using anti-phosphatidylserine antibodies, it is shown that the labelling intensity of a phosphatidylserine/phosphatidylcholine coating depends largely on the conditions of fixation. In fact, the usual aldehydic fixatives washed out most of the phostphatidylserine, thus preventing the binding of anti-phosphatidylserine antibodies. This was confirmed on biological samples such as rat liver and brain by measuring the loss of radiolabelled lipids during the fixation procedure. Furthermore, the complete procedure of tissue preparation for electron microscopical observation was investigated. The loss of (radiolabelled) lipids was studied in tissue samples during fixation and resin embedding. The results showed that the classical procedure (glutaraldehyde fixation followed by epoxy resin embedding) results in the loss of 73-91% of the tissue lipids whereas in unfixed, freeze-substituted samples, more than 76% of the tissue lipids are preserved.

Animals↗
PubMed1978

Tissue culture preservation and intramuscular transplantation of pancreatic islets.

Pancreatic tissue from neonatal rats was cultured for 6 days and then transplanted into isologous animals made diabetic with streptozotocin. The cultured pancreatic tissue was implanted either into the peritoneal cavity or into muscle pockets and showed survival by functional and morphological studies for longer than 40 weeks. Pancreatic tissue from a patient subjected to subtotal pancreatectomy for chronic pancreatitis was maintained in culture for 7 days, with evidence for insulin release into medium, sterility, and histological viability of islets. Autotransplantation of this tissue into muscle pockets of the forearm was tolerated well. Glucose tolerance improved following transplantation, but evidence for function of the graft (insulin, C-peptide) remains inconclusive, 4 months after transplantation.

Animals↗