Tissue defects

Type IE vitamin D-dependent rickets is caused by a target tissue defect in response to l,25(OH)2D. Studies have shown a number of point mutations in the gene for the l,25(OH)2D receptor, which disrupt the functions of this receptor and lead to this syndrome. The serum levels of l,25(OH)2D are very high in type II but not in type I. Treatment with large doses of calcitriol has been claimed to be effective in restoring normocalcemia. Such patients are totally refractory to vitamin D. One recent report indicates a reversal of resistance to calcitriol when 24,25(OH)2D was given. These diseases are rare. 

Caspase-3 Perinatal lethality Excess brain tissue Defective apoptosis in neuronal progenitor cells, forebrain malformation, reduced antigen-induced apoptosis of T cells Normal [61-63]... 

Caspase-9 Perinatal lethality Excess brain tissue Defects in brain apoptosis, defects in cell death in response to UV or 7 irradiation Normal [67, 68]... 

Wound healing Repairs tissue defects Promotes fibrous scar Tissue... 

Purified solubilized bovine collagen is used as biomaterial for the treatment of soft tissue defects and has been used for the treatment of stress urinary incontinence since the late 1980s (1). Injected material precipitates at body temperature, forming a matrix allowing fibroblastic infiltration and formation of new tissue. It has been used for cosmetic purposes by injection in the dermis to correct scars and other contour deformities of the skin. 

Tissue Defect Resulting from Copper Deficiency, Proc. Soc. Exp. Biol. Med. (1961) 108,402-405. 

Granulation phase This phase begins 3-5 days postinjury when necrotic tissue sloughs. Granulation tissue begins to fill in tissue defects and connective tissue begins to form in 10-12 days. 

M. Prentki and B. E. Corkey, Are the beta-cell signaling molecules malonyl-CoA and cytosolic long-chain acyl-CoA implicated in multiple tissue defects of obesity and NIDDM , Diabetes, 1996, 45, 273-283. 

A number of other enzymopathic substances (e.g., pyruvate kinase. Chapter 13 and pyrimidine-5 -nucleotidase. Chapter 27), abnormal hemoglobins (Chapter 28), and abnormalities of the erythrocyte cytoskeleton (Chapter 10) may cause hemolytic anemia. Because many enzymes in the red cell are identical to those in other tissues, defects in these enzymes may have pleiotropic effects. Thus, in addition to hemolytic anemia, triose phosphate isomerase deficiency causes severe neuromuscular disease, and phospho-fructokinase deficiency causes a muscle glycogen storage disease (Chapter 13). Mutations that result in decreased enzyme stability are usually most strongly expressed in erythrocytes because of their inability to synthesize proteins. 

Loh NK, Woerly S, Bunt SM, Wilton SD, Harvey AR. The regrowth of axons within tissue defects in the CNS is promoted by implanted hydrogel matrices that contain BDNF and CNTF producing fibroblasts. Exp Neurol 2001 170 72-84. 

Rare mutations in lysyl hydroxylase genes cause Bruck syndrome and one form of Ehlers-Danlos syndrome. Both disorders are marked by connective-tissue defects, although their clinical symptoms differ. I... 

The physical dimension of a template defines the boundary of regeneration. Thus, the size of the collagen template should match the tissue defect to be repaired. A properly sized meniscal substitute has been found to function better than a substitute which mismatches the physical dimension of the host meniscus [Rodkey et al., 1998 Sommerlath et al., 1991]. For a porous, elastic matrix such as the one designed from collagen for meniscal tissue repair, the shape of the meniscus is further defined in vivo by the space available between the femoral condyles and tibial plateau within the synovial joint. 

In the bulk phase-separation approach, an organic solution of a polymer dissolved in a water-miscible solvent is injected into the tissue defect. After injection, the solvent diffuses away from the injection site, resulting in precipitation of the water-insoluble polymer. Selection of an appropriate solvent, which must be non-cytotoxic and not harmful to host tissue, is a key factor for success of the bulk phase-separation system. Two solvents that meet these criteria are N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). In recent years, improved strategies for removal of the solvent and release of growth factors have been active areas of investigation. However, the requirement of a solvent to induce phase separation of the polymer limits the scale at which this approach can be applied in vivo. Even for relatively biocompatible solvents such as NMP and DMSO, injection of large volumes is anticipated to adversely affect host tissue, as well as the ability to eliminate the solvent from the body. 

In situ polymerizable materials comprise reactive monomers and/or macromers that are injected into the tissue defect in liquid form where they cure in situ to form a solid polymer. The cured polymer or gel forms by crosslinking of reactive monomers and macromer chains to form a polymer network. Depending on the crosslinking mechanism, various classes of materials can be prepared, including photopolymerized gels, chemically crosslinked thermosets, and ion-mediated gels." " Each of these types of biomaterials will be reviewed in this section. 

The polyurethane adhesive KL-3 developed by us does not have any topical or systemic toxic effects. Its polymeric film is porous and of high elasticity, and the highly developed surface of the polymer facilitates rapid healing. KL-3 combines the properties of a medical adhesive and of a filling material. Its use is especially indicated when it is necessary to seal tissue defects of considerable size or for closing pathological cavities. 

Polymer meshes, such as polypropylene and polyester, are used for the repair of hernias and other soft tissue defects. Whereas fre use of me material has lead to a widely accepted improvement in this kind of surgery, their implantation can be associated with serious motion rates. In order to reduce the infection rates of such meshes, their surface properties have to be improved. 

Despite their advantages, PPF and other biodegradable polymers (e.g. oligo polyethylene glycol-fumarate), generally lack the mechanical properties required for regeneration of hard and dense cortical bone, and their utility is limited to soft tissue defects and non-load bearing bone defects. 

The scaffolds maintain their geometry and mechanical properties after 28 days of storage in water, Dulbecco s modified Eagle s medium (dMEM), and phosphate-buffered saline (PBS). According to the conducted tests, the scaffolds are suitable for uniform bone tissue defects. 

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