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Biomedical subjects

M Chvapil

Publications and source records attributed to M Chvapil.

At least 109 records · Page 6Linked to original sources
PubMed1980

Collagen biosynthesis in healing wounds of the spinal cord and surrounding membranes.

Kinetics of collagen synthesis and deposition were studied in the canine spinal cord, pia mater, and dura mater and in wounds of these tissues over the first 8 weeks. Little collagen is present in unwounded spinal cord compared with surrounding mesenchymal membranes. Collagen synthetic potential was found within the spinal cord, a tissue of neurectodermal origin. Rate of collagen synthesis per collagen content in the unwounded spinal cord was high. This synthetic rate was as high as that of wounds at their maximum collagen synthetic rates. Substantial deposition of collagen followed spinal cord wounding. Wounding the spinal cord, pia mater, and dura mater caused substantial elevations in rates of collagen synthesis in each tissue. These synthetic rates remained at maximum levels throughout the 8-week study, a prolonged period when compared with other wounded tissues previously studied. The role of mesenchymal tissue physiology in central nervous system wound healing is discussed. The potential value of these findings for further studies and for experimental manipulation of the healing process in spinal cord and central nervous system wounds is presented. Implications of these findings on the hypothetical relationship of scar to spinal cord and central nervous system regeneration are noted.

Animals↗
PubMed1980

Preliminary testing of the contraceptive collagen sponge.

The results of 3 years of developing the collagen sponge as an intravaginal contraceptive are presented. Postcoital tests were used to evaluate the efficacy of the sponge as a mechanical barrier. Results with the collagen sponge alone were compared to those of the sponge with spermicidal cream or spermicidal solution (acid buffer and zinc) and of spermicidal cream alone. The presence of any motile spermatozoa in the cervical mucus was considered a failure of the barrier method. The collagen sponge alone or with acid and zinc and spermicidal cream alone had failure rates of 22, 20, and 14%, respectively, whereas the collagen sponge with spermicidal cream had a 6% failure rate. The authors conclude that the combination of a mechanical and a chemical barrier is a more effective contraceptive method than a mechanical barrier or chemical agent alone.

Adolescent↗
PubMed1980

Ultrastructural changes in the architecture of collagen in the human cervix treated with urea.

Injection of a solution of 30% urea in acetate buffer at pH 4.0 into the stroma of the uterine cervix results in a marked change in the mechanical properties of the tissue with subsequent easy dilatation. This study analyzes the changes in the collagenous matrix of the cervix by ultrastructural and biochemical methods. Collagen fibrils in urea-treated sections of the cervix are swollen and unravelled, showing spiral configuration of subunits in both cross-sections and longitudinal sections. The regular localization of ruthenium-red-positive material is absent in urea-treated tissues. Chemical analysis of incubated cervical tissues shows a reduction of the total glycosaminoglycans and of dermatan sulfate with release of the latter into the medium. It is suggested that urea dissociates intercollagen linkages by solubilizing a certain glycosaminoglycan, possibly dermatan sulfate. After this solubilization the collagen fibril is prompted to unwind, resolving the collagen microfibrils, which appear to be organized in a spiral fashion.

Cervix Uteri↗
PubMed1979

Reaction of vaginal tissue of rabbits to inserted sponges made of various materials.

Sponges of the same size made of collagen (CS), polyurethane (PU), polyvinylalcohol (PVA) and acetylcellulose (AC) were inserted for 10 days in the vaginas of 22 rabbits. Light and scanning electron microscopy of the vaginal wall and its mucosal lining showed signs of cytotoxicity only with PU and AC while CS and PVA picture did not differ from sham controls. In order to explain the reasons for the toxic effects, all sponges were extracted into aqueous or organic solvent media and analyzed by gas liquid chromatography. Only several minute peaks in organic solvents were found. Extracts of all sponges tested for cytotoxicity in fibroblast cultures showed significant inhibition of H3-thymidine uptake. Nevertheless, extract of collagen sponge was significantly less cytotoxic than the extracts of all other sponges.

Animals↗
PubMed1979

Effects of zinc chloride on guinea pig complement component activity in vitro: concentration-dependent inhibition and enhancement.

We have studied the in vitro effects of zinc chloride on the hemolytic activity of each component of the guinea pig classical complement pathway over a wide range (25 to 500 muM) of zinc concentrations. At high concentrations (>200 muM) the activity of all components was strongly inhibited by this metal. Concentrations of 500 muM inhibited C1 and C5 by 80 and 65%, respectively, whereas all other components were inhibited by more than 94%. Zinc chloride at 25 muM produced more varied effects, with C2, C3, and C6 inhibited by 36, 35, and 55%. C7 and C8 were inhibited by approximately 25%, whereas C1, C4, and C9 were not appreciably affected. The activity of the fifth component, on the other hand, was strongly enhanced by the presence of zinc. Concentrations of 25, 50, and 100 muM zinc chloride produced increases of 92, 44, and 18%, respectively, in C5 titers when present during the activation-binding step of this component. Further studies indicated that the activities of cell-bound complement components were unaffected by zinc treatment after activation and/or binding to the sheep erythrocyte surface had occurred. In addition, zinc did not appear to inhibit by causing irreversible denaturation of either total complement proteins or its various components. Rather, it appears that zinc must be present as a reactant during the activation and/or binding step of each component for inhibition or enhancement to occur.

Animals↗
PubMed1979

The importance of liver in normal and silicotic lung-lipid homeostasis: 3. Triacylglycerols.

Early lung silicosis in rats activates the liver for triacylglycerol (TG) biosynthesis. The newly formed liver TG seems mobilized to the silicotic lung, as indicated by increased lung TG content and specific activity. These TG changes are associated with decreased TG content and increased TG specific activity in the liver. Serum TGs are also decreased at the study times of 6, 24, 72, and 144 h post intrapulmonary silica treatment.

Acute Disease↗
PubMed1979

Enhancement of healing in osteochondral defects by collagen sponge implants.

Implants of porous, highly cross-linked collagen sponge (CS) were tested for their capacity to enhance the healing of osteochondral defects in rabbits. Comparison was made to the healing of similar defects with polyvinyl alcohol sponge (PVAS) implants and with no implants (CONT). Evaluation was carried out up to 44 weeks following implantation and included observation of host cellular response, biodegradability of implant, gross appearance of restored joint surface, collagenous architecture of repair tissue, and properties of the junctions of implants and host articular cartilage, subchondral bone, and medullary bone. Collagen sponge proved most effective in promoting healing of osteochondral defects with fibrous and fibrocartilaginous tissue over restored subchondral bone. Collagen sponge showed many desirable properties as a potential material for biologic resurfacing of damaged joints. These properties included porosity, biodegradability, biocompatability, ability to mechanically protect cells and matrix while directing cell ingrowth, and an available chemical technology for modifying its biomechanical and biological properties. Comparative analysis of results of healing of CS, PVAS, and CONT osteochondral defects suggest rational design criteria for implant materials to improve their effectiveness in restoration of articular surfaces.

Animals↗
PubMed1978

Urea and dilatation of the cervix.

The minimal elasticity of the uterine cervix has been related to its high collagen content. By interfering with cohesive forces that hold the collagen fiber bundle together, it is possible to diminish the physical strength of collagen. Urea has been used in collagen chemistry to dissociate collagen by interfering with hydrophobic linkages and hydrogen bonds. This results in a change of mechanical properties such as a decrease in tensile strength and an increase in elasticity. Basic studies of rat tail tendon demonstrated the additive effects of pH, concentration of urea, and temperature on the mechanical characteristics of collagen fibers. In vitro testing was performed using an injection of 30 per cent urea at pH 4. Serial measurements with a spring gauge instrument showed a reduction in cervical resistance. A cervical injection technique has been developed and toxicity of urea studied.

Animals↗