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Biomedical subjects

M Chvapil

Publications and source records attributed to M Chvapil.

At least 91 records · Page 5Linked to original sources
PubMed1981

A quantitative microassay for in-vitro toxicity testing of biomaterials.

A quantitative tissue culture method is described for toxicity testing of biomaterials. The material to be evaluated, or in the case of insoluble materials--an extract of the material, is incubated on a monolayer of fibroblasts in 24 well culture plates. The activity of the fibroblasts is ascertained by measuring the rate of mitosis (3H-thymidine incorporation), the synthesis of glycosaminoglycans (35SO4= incorporation) or production of total protein (3H-tryptophan incorporation). By proper choice of label, the effect of the biomaterial on cellular proliferation or production of macromolecules or both may be assessed. Materials with a cytotoxic effect cause inhibition of incorporation of radioactive label in the above assays. The cell monolayers can also be inspected microscopically for evidence of cytotoxicity. The method is quantitative, simple, reproducible, rapid, and suitable for screening of a large number of samples.

Animals↗
PubMed1981

Experimental and clinical experiences with collagen fleece as a hemostatic agent.

We report on our laboratory and clinical experience with a new hemostatic agent made of collagen fibers and existing in the form of a loose or compressed fleece. This material was tested in two independent bleeding models on eight dogs and 21 patients. Partially compressed collagen fleece showed significantly higher hemostatic effectiveness when compared to loose fleece. This was demonstrated by gravimetric determinations of blood loss in dogs with split-thickness skin excisions and by measuring the blood loss and time of bleeding after an excision 0.5 cm deep and 4 cm wide of the edge of the spleen. The handling of partially compressed hemostatic fleece was found superior to loose or fully compressed fleece. Clinical cases included patients with liver lacerations and retroperitoneal bleeding. Collagen fleece, partially compressed, proved to be an effective topical hemostatic agent when applied directly with pressure to a bleeding surface and when folded and sutured against a bleeding surface. Postoperative injection rate was not increased nor was foreign body reaction demonstrated. The material was extremely easy to apply, did not adhere to gloves or instruments, and could be cut or molded to any desired shape.

Adolescent↗
PubMed1981

Comparison of newer synthetic and biological wound dressings.

In 18 piglets, weighing 10-15 kg, third-degree burns or full-thickness skin excisions of 4 X 4 cm were inflicted. The effect of five dressing materials on adhesiveness to the wounds, appearance, conformability, wound contraction, bacterial count, and morphology of the wound was studied at the end of the seventh and fourteenth days without dressing changes. In 11 piglets with a burn wound, the most adherent dressing was collagen sponge(CS), followed by polyurethane sponge (PU), pigskin xenograph (PS), and xeroform. CS more effectively debrided the wound from coagulated necrotic tissue than the other dressings. Wound contraction was maximal with CS dressing (52%), followed by PU (44%), xeroform (32%), and PS (27%). In another seven piglets with full-thickness excised wounds, a velour dressing made of polytetrafluoroethylene (PTFE) or PU adhered significantly more than CS or PS. Wound contraction was greater with CS (37%) or PTFE (35%) than with PS (23%) or PU (18%). The bacterial counts were similar in wounds dressed with CS, PU, or PTFE. PS dressing showed significantly higher bacterial counts. The results of this study support those of a previous report on the effect of similar dressing materials on rabbit second-degree burns (8).

Animals↗
PubMed1980

Biological effects of residual glutaraldehyde in glutaraldehyde-tanned collagen biomaterials.

Glutaraldehyde is commonly used to control physical and biological properties of collagen structure by means of intramolecular and/or intermolecular crosslinking of collagen molecules. Solubility, antigenicity, and biodegradation of naturally occurring or reconstituted collagenous matrices are effectively reduced by glutaraldehyde treatment. Adverse biological reactions to glutaraldehyde have been limited to infrequent contact dermatitis and to biocidal effects which are exploited in chemical sterilization media. In the present study of glutaraldehyde-tanned collagen sponge, the presence of glutaraldehyde was correlated with cytotoxic effects upon fibroblasts in tissue culture and foreign body giant cell reaction to bioimplants of the sponge. Fibroblast growth in tissue culture is 99% inhibited at media concentrations of 3.0 ppm glutaraldehyde. Extracts of glutaraldehyde collagen sponge in aqueous media at pH 7 and 4.5 yielded 6 micrograms and 65 micrograms glutaraldehyde per gram of collagen sponge, respectively. The yield increased tenfold at pH 4.5. Observations indicate that leaching of the glutaraldehyde from glutaraldehyde-tanned collagen sponge is sufficient to produce potentially adverse cellular effects both in vivo and in vitro.

Aldehydes↗
PubMed1980

Interaction of zinc ions with electron carrying coenzymes NADPH and NADH.

Evidence is presented that the substrate for the drug oxidizing system, NADPH, binds to zinc ions. Zinc ions bind selectively to NADPH but not to NADH. By using equilibrium gel filtration and acid titrations of Zn2+ and NADPH, the molar ratio of metal to nucleotide was determined at 2 : 1, as well as the formation constant of 10(6.75). Results from 31P-nuclear magnetic resonance (NMR), ultraviolet and fluorescence spectra of the complex indicated the possible binding sites of zinc to NADPH. In previous studies we have shown that zinc ions inhibit the metabolism of drugs by mixed function oxidases in liver microsomes. The formation of the Zn2+-NADPH complex suggests the mechanism by which zinc ions may inhibit the drug oxidizing system.

Chemical Phenomena↗
PubMed1980

Studies on Nonoxynol-9. II. Intravaginal absorption, distribution, metabolism and excretion in rats and rabbits.

Some pharmacological aspects of Igepal CO-630, used by some pharmaceutical companies as the source of nonylphenoxypoly (ethyleneoxy) ethanol (Nonoxynol-9, N-9) in various spermicidal formulations, were studied. It was found that Igepal CO-630 contains at least 13 components, 70% having molecular weights near that of N-9. After intravaginal administration, the detergent is rapidly and quantitatively absorbed through the vaginal wall into the systemic circulation. The rate of vaginal absorption of N-9 depends on the vehicle in which the detergent is carried. Once in the blood, N-9 is excreted by liver-bile-feces and the kidney-urine routes, the first being more effective in rats, the latter in rabbits. Following intravaginal or intraperitoneal injection of radioactive N-9, the highest content of radioactivity was found in the liver and kidney. The detergent was detected in the milk of lactating rats and the serum of their pups within two hours after the intravaginal dose.

Absorption↗
PubMed1980

Reversible stabilization of liver lysosomes by zinc ions.

The effect of zinc ions on the stability of rat liver lysosomes was studied. Zinc was added by several methods: feeding the animals a high-zinc diet; infusion of zinc into the liver through the portal vein, or by adding zinc to the lysosomal fraction either before or after isolation of this fraction from rat liver homogenates. By all techniques, addition of zinc reduced the release of beta-glucuronidase from liver lysosomes. Lysosomes and lysosomal membranes from rats fed a high-zinc diet were found to be relatively high in zinc. These lysosomes were less fragile than lysosomes from the liver of control animals. The stabilizing effect of zinc ions could be reversed by treatment of lysosomes with phosphate buffer. We concluded that increasing the zinc content in the liver by any of these methods results in stabilization of liver lysosomes.

Animals↗
PubMed1980

Complementation of predigested proteins: a nutritionally and economically advantageous method of by-products utilization.

Proteins were isolated from four animal by-products: bovine skin trimmings, sheep wool, whole bovine blood and inedible chicken carcass. These waste protein sources were digested and solubilized with nonspecific bacterial proteases. Commercial casein and isolated soybean protein were treated similarly. Partially digested proteins were characterized by some physical measurements, lipid content and complete amino acid composition. The protein quality of individual proteins as well as their combinations was tested on the growth of Tetrahymena pyriformis. We found that the nutritional value of high quality proteins (casein, soy) could be significantly enhanced by mixing with low nutritional value protein(s). At the same time, the cost of the protein mixture was substantially reduced. We suggest that complementation of proteins isolated from animal by-products is a nutritionally and economically advantageous method.

Amino Acids, Essential↗
PubMed1980

Collagen fibers as a fleece hemostatic agent.

The hemostatic efficacy of collagen fibers as a fleece hemostatic agent (CFH) is compared with the efficacy of three commercially available agents: collagen powder (Avitene), absorbable gelatin sponge, and oxidized cellulose. Identical quantities of the four materials were applied to identical multiple spleen incisions in five dogs; CFH and collagen powder proved three times as effective as the other two mateials. CFH and collagen powder were then compared with regard to hemostatic efficacy, handling characteristics, and tissue reaction. Different weights of the materials were applied to multiple spleen lacerations in 12 dogs and spleen avulsions in 12 dogs. The hemostatic efficacy of the materials was similar, but CFH was superior with regard to handling characteristics and tissue reaction. Another experiment, with six pigs, showed that CFH can be successfully sutured as a patch to profusely bleeding lacerations of the spleen, liver, and kidney.

Animals↗
PubMed1980

Studies of nonoxynol-9. I. The effect on the vaginas of rabbits and rats.

A standard rabbit vaginal irritation test was used to evaluate the morphologic reaction to an aqueous solution of a nonionic spermicidal detergent, nonoxynol-9 (N-9). Various amounts of N-9, between 2.5 mg and 50 mg, were incorporated into cylindrical collagen sponges which were retained in the vagina for 10 days. Changes in the continuity of the epithelial lining, edema of the submucosal layer, and the inflammatory cell infiltrate of this layer were proportional to the amount of N-9 tested. An increase in semiquantitative score for the inflammatory changes in the vagina was noted for increasing amounts of N-9. In young adult female rats treated vaginally with 5 mg/100 gm body weight/day of aqueous N-9 for 5 to 20 days, the number of cells (DNA) was significantly increased on day 5. The collagen content in the vaginal wall (hydroxyproline) was significantly increased after 15 and 20 daily injections of the detergent. We conclude that both morphologic and chemical changes in the vagina are compatible with the inflammatory reaction induced by the detergent tested.

Animals↗
PubMed1980

Studies on nonoxynol-9. III. Effect on fibroblasts and spermatozoa.

Seven nonionic detergents of the Igepal CO series differing in molecular size and including nonoxynol-9 and a representative anionic (SDS) and cationic (Cepacol) detergent were tested as to their relative cytotoxicity. The biologic effects of these detergents on human W1--38 fibroblasts (DNA and glycosaminoglycans synthesis) and on the motility of human spermatozoa were studied. The relative order of cytotoxicities for both fibroblasts and spermatozoa was cationic greater than nonionic greater than anionic. The concentration of nonoxynol-9-inhibiting fibroblast activity was approximately 30 times less than the amount needed to immobilize spermatozoa. It is concluded that CO-630, used as a source of nonoxynol-9, is the most effective polymer to inhibit spermatozoa and also fibroblasts.

Anions↗