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Biomedical subjects

M Chvapil

Publications and source records attributed to M Chvapil.

At least 37 records · Page 2Linked to original sources
PubMed1989

Transport of beta-aminopropionitrile through intact skin or scar tissue.

A lathyrogen, [C14]aminopropionitrile (beta APN), was administered to 34 rats either in K-Y jelly or saline vehicles onto intact shaven skin or onto a healed splinted deep excision wound. The dynamics of beta APN transport and content in the skin or repair tissue was observed after 2, 5, 8, and 24 hr of topical administration. The repair tissue quickly absorbed the lathyrogen and reached maximum at the 2-hr sampling. The content of beta APN in the repair tissue was twice as high as that in K-Y jelly vehicle and remained high and stable for at least 24 hr only when beta APN was administered through a saline vehicle. The transport of beta APN through intact skin, irrespective of the vehicle tested, was slow and continuously increased. The study showed that almost 20% of the beta APN administered onto the wounded skin area was transported into the repair tissue within 2 hr. We suggest that, due to the absence of epidermal stratum corneum from the repair tissue, drugs, such as beta APN, penetrate quickly into the wound.

Absorption↗
PubMed1989

The organ distribution of liposome-encapsulated and free cobalt in rats. Liposomes decrease the cardiac uptake of the metal.

Rats were administered intravenously liposome-encapsulated or free cobalt, and the organ distribution of the metal was explored using Co57 tracer. Two hours after administration, the cobalt level in the heart was about 40% of the control when given in sphingomyelin (SM)/cholesterol (CH) (1:1 mole ratio) liposomes. These vesicles also tended to decrease the uptake of cobalt in the kidney and the carcass, and to increase it in the spleen and the bones. Liposomes prepared from soybean phosphatidylcholine (SPC)/CH (1:1) had no effect on the uptake of cobalt in the heart, whereas increased its level in the spleen, liver and lung. The time-course of cobalt deposition in the organs displayed substantial variation with the different preparations. Most importantly, no buildup of cobalt level was observed in the heart when the metal was administered in SM/CH vesicles. While confirming known effects of liposomes on the organ-distribution of entrapped drugs, our findings suggest that administration of cobalt in SM/CH liposome-encapsulated form may result in decreased cardiotoxicity and thus increased safety of cobalt-treatment in some anemias.

Animals↗
PubMed1989

Effects of extracorporeal shock wave lithotripsy on the structure and function of rabbit kidney.

An animal model was developed to investigate the effect of extracorporeal shock wave lithotripsy (ESWL) on a normal kidney. Rabbits were treated with 3,000 shock waves at 18 kV to each kidney. Blood and urine samples were collected daily before and after shock wave treatment. Serum levels of hemoglobin, creatinine, lactic dehydrogenase (LDH), creatinine phosphokinase (CPK), and total protein were determined. Urine determination of volume, total protein, hemoglobin, and creatinine were also made. All kidneys, after sacrifice, were subjected to histologic analysis. The average pre-treatment creatinine clearance of our rabbits was 8.3 ml./min. After the treatment, a significant (p less than 0.01) reduction in creatinine clearance was noted for four days. The reduction was to 0.61 ml./min. on day one, 0.87 on day two, 1.04 on day three, and so forth. Urine hemoglobin rose significantly (p less than 0.01) for the first three days from 0.0 to 1.5 gm./dl. Histologic examination at seven days showed focal subcapsular hemorrhage, tubular dilation, and interstitial hemorrhage. Histologic evaluation at two months revealed focal interstitial fibrosis. In conclusion, this study reveals that shock waves to the kidney have short term physiologic effects on renal function and permanent focal histologic effects, which do not effect long term physiologic function. Further research on the effects of ESWL on renal function and structure could be facilitated with the use of this model.

Animals↗
PubMed1989

Use of cross-linked bovine pericardium as a disc replacement in the rabbit temporomandibular joint.

Chemically purified bovine pericardial membrane, highly cross-linked with monomeric glutaraldehyde, was implanted in the TMJ area in ten adult rabbits in place of partially excised discs. Sham controls had the temporal aspect of the TMJ scraped with a scalpel. After 3 months, the whole TMJ area was processed for morphologic and scanning electron micrographic (SEM) evaluation. Evidence was found of the disintegration of the implanted pericardium, which was extensively infiltrated by inflammatory cells. The collagen matrix of the membrane was distended and dissociated, showing signs of degradation by its stainability with trichrome stain. It was concluded that cross-linking of a collagenous structure such as pericardium does not prevent it from being resorbed. It is suggested that the cytotoxic residues of polymeric glutaraldehyde within the implant may render the implant more resistant to cellular degradation.

Animals↗
PubMed1988

An optimal morphometric method for quantitating wound epithelization.

A new, inexpensive method for quantitative evaluation of reepithelization of shallow split thickness wounds in piglets is described. Wounds, 2.2 X 2.2 cm and 0.4 mm depth are inflicted by an electro-keratome knife in domestic piglets. At a specific time after wounding, the wound area is excised and processed for histology. A computer simulation, based on a randomized systematic sectioning of an entire wound, was used to conclude that only eight sections from the 2.2 X 2.2 cm wound are needed for the final evaluation. The results showed that the above method allows for determination of the epithelization magnitude within +/- 5% at a 95% confidence limit. It was found that in 15 kg piglets 50% epithelization of the above wounds was achieved in 65 hr; however, there exists a great interindividual variability. The rate of epithelization is age dependent and significantly faster in 7 kg body weight piglets than in those weighing 40 kg. The epithelization rate was the same at both the wound edge and the center of the wound, stressing the importance of hair follicles as a source of epithelization.

Animals↗
PubMed1988

Topical beta-aminopropionitrile and biochemistry of granuloma tissue.

The changes of connective tissue in granuloma development were studied up to 20 days following subcutaneous implantation of polyvinyl alcohol (PVA) sponges in rats. The total protein and collagen content were found to increase from the 4th to 12th days of implantation while the content of DNA continuously decreased with the age of the granuloma. Administration of beta-aminopropionitrile (beta APN) fumarate on the intact skin overlying the implanted PVA sponge in the presence and absence of dimethyl sulfoxide (DMSO) during the growth phase of granuloma development (4th through 12th days after implantation) was accompanied by significant inhibition of collagen polymerization. This was documented by a significant increase of collagen extractable into 1 N NaCl, by a significantly reduced content of aldehydes in collagens extractable into neutral salt solution, and by a significant increase of alpha subunits and alpha/beta ratio. Topical beta APN administration had no effect on the content of DNA, noncollagenous proteins, or total hydroxyproline. We conclude that topically administered beta APN fumarate onto the intact skin penetrates the stratum corneum and effectively inhibits collagen crosslinking in the underlying granuloma tissue. The extent of the effectiveness was found to be significantly greater in the presence of DMSO.

Administration, Cutaneous↗
PubMed1988

Changes in the fatty acid profile of lung, liver and serum of rats intratracheally given silica.

The esterified (E) and nonesterified (NE) fatty acid level and profile in the lung, serum, and liver of rats are significantly altered after intratracheal administration of silica. The changes include a silica-specific increase of the total long chain (C16-C20:4) fatty acid content in the lung, and a decrease in the serum and liver of both groups of rats intratracheally given silica and/or saline. In the silicotic lung, arachidonate and palmitate accumulated at the highest rate. A heat-labile, high-molecular weight component from lung homogenates increases lipogenesis in isolated hepatocytes in vitro. These findings, taken together with evidence indicating increased lipogenesis in the liver of rats treated with silica under identical conditions, suggest a lung-liver communication mechanism which coordinates lipid uptake by the lung and lipid synthesis and release by the liver. The stimulatory factor identified in lung homogenates might play an important regulatory role-for hepatic lipogenesis in rats developing silicotic lungs.

Animals↗
PubMed1988

Collagen based biomaterials: an ideal way of increasing their resistance to infection.

Collagen and gelatin containing biomaterials are relatively more susceptible to bacterial infection. Systemic administration or local delivery of antibiotics after implantation does not seem to solve the problem either effectively or easily. Antibiotics may be incorporated in the implant; but many, being water soluble, are quickly absorbed and not effective for adequate time periods. Resorcinol monoacetate (RMA) is a relatively water insoluble antibacterial agent which partially crosslinks collagen and has the potential to be an intrinsic antibiotic in collagenous bioprostheses. This study confirms the efficacy of RMA as a chemical that: (a) mildly crosslinks collagen at pH 3.5-4.5; (b) releases very slowly from the pretreated collagen sponge when washed in aqueous medium; (c) inhibits bacterial growth on the pretreated collagen sponges, at 2% (w/w) concentration, for at least 12 days; (d) remains biocompatible under treated conditions.

Animals↗
PubMed1988

Effect of topically applied beta-aminopropionitrile on granuloma tissue biochemistry.

The effects of the percutaneous transport of vehicles and the transport of beta-amino-propionitrile (beta APN) in vehicles were studied in rats. The bioavailability of topically administered beta APN was determined by measuring the degree of collagen cross-linking inhibition in the underlying granuloma tissue. Granulomas were induced by subcutaneous implantation of polyvinylalcohol sponges. From the 4th to 12th days postimplantation, a 20 mg/cm2 dose of beta APN fumarate was applied. Vehicles employed included dimethylsulfoxide (DMSO), urea, and occlusion. DMSO significantly enhanced the effect of beta APN in reducing the cross-linking of collagen. beta APN administered onto urea-pretreated skin and followed by occlusion in the granuloma tissue was more effective than beta APN in 30% DMSO, but only in the parameter reflecting extractibility of collagen into urea or thiocyanate solutions. The results suggest that beta APN administered topically in an appropriate vehicle penetrates the granuloma tissue and affects collagen polymerization. Though beta APN was topically administered, a systemic effect from the drug was evident, as documented by lower body weight of treated rats.

Aminopropionitrile↗
PubMed1988

The effect of zinc on iron-induced lipid peroxidation in different lipid systems including liposomes and micelles.

The effect of zinc on FeSO4/ascorbic acid-induced lipid peroxidation was measured by the thiobarbituric acid assay in various lipid systems including small unilamellar liposomes prepared from egg phosphatidylcholine (EPC), ionic micelles prepared from arachidonic acid (C20:4), non-ionic monocomponent micelles prepared from EPC-derived, methylated fatty acids, and an eicosatetrene emulsion. With the exception of C20:4 micelles, zinc inhibited lipid peroxidation in each of the above systems in a similar dose-related fashion, with 0.5 mM zinc having maximal effect. Gas-chromatographic fatty acid analysis too indicated a protective effect of zinc against FeCl3-induced lipid peroxidation in soybean PC vesicles, which do not contain C20:4 moieties. These findings, in particular the inhibition of lipid peroxidation in eicosatetrene emulsion, suggest that the presence of uncharged polar head groups, or packing of lipid molecules into ordered self-assemblages (membranes and micelles) have no critical influence on the antioxidant effect of zinc. The results with Fe2+ are compatible with the concept that zinc interferes with the formation of Fe2+-oxygen-enoic complexes. This mechanism, however, cannot account for the inhibition by zinc of the Fe#+-induced lipid peroxidation, suggesting the involvement of other types of zinc effects in these systems.

Ascorbic Acid↗
PubMed1987

Use of chemically purified and cross-linked bovine pericardium as a ligament substitute.

This study tested the reaction of a periarticular tissue to implanted pericardial membrane, substituting a segment of patellar ligament. Bovine pericardium was chemically purified and cross-linked with monomeric glutaraldehyde under pH, temperature and time conditions minimizing the polymerization of the cross-linking agent. Eight rats had both knee joint patellar ligaments excised. One side served as a control (simple suture), the other dissected ligament was replaced with a strip of pericardium. After 18 days and 12 weeks the dissected ligaments were analyzed by morphological methods. An unexpected fast ingrowth of cells and vessels was observed at 18 days. At 12 weeks new collagen deposits within pericardial patch were seen with striking biodegradation of the implant. Thus, using a new method of cross-linking the collagenous matrix with glutaraldehyde we see no evidence of glutaraldehyde cytotoxicity, as documented by our previous work.

Animals↗
PubMed1987

Effect of topical beta APN application on evoked potential conduction in rat sciatic nerve and spinal cord.

The purpose of this study is to evaluate possible toxic effects of beta-aminopropionitrile fumarate (beta APN), a lathyrogenic agent that inhibits fibrosis. This drug has been considered for use as an adjunct to surgical repair after topical application upon peripheral and central nervous system structures. In vivo and in vitro studies were done using rats to study the dose dependent neurotoxicity of this water soluble chemical. The results indicate that when the neural sheaths are removed the amplitude of the evoked sciatic nerve potential is irreversibly suppressed from 1 to 10 mM concentrations of beta APN. Nerve conduction velocities are relatively less affected with reduction from 43 to 35 m/sec by beta APN immersion. Similarly, the spinal cord studies show that when the dura and arachnoid are opened and damaged, 0.1 mM beta APN causes increased latency (from 9.9 to 14.5 msec) and decreased amplitude (from 79.4 to 56.8 microV) of cortical somatosensory evoked potentials. Possible mechanisms for the neurotoxic effects of beta APN are discussed.

Aminopropionitrile↗
PubMed1987

Pulmonary phospholipidosis in rats respiring air containing diesel particulates.

Rats chronically exposed to diesel particulates (dp) or given intratracheally a single dose of dp show increased levels of phospholipids in the lungs and in pulmonary lavage fluid. Pulmonary phospholipidosis is accompanied by increased lecithin levels and by increased palmitate content in lecithin of both lungs and pulmonary lavage fluid. A de novo increase of pulmonary and hepatic phospholipid (PL) formation was detected 5 days after rats were treated with dp. We hypothesize that a dp-stressed lung releases a pulmonary lipogenic factor (PLF), which stimulates hepatic lipogenesis. This was further tested by an in vitro study in which primary cultures of free hepatocytes were incubated with [2-14C]acetate and various molecular weight fractions of a pulmonary homogenate from rats. The results from these studies indicated that in rat lung homogenates a PLF exists of greater than 100,000 Da molecular mass. The results also indicate that respired air containing a dp concentration of greater than 750 micrograms dp/m3 of air would result in a mild phospholipidosis in the lung, whereas a dp dose in respired air of 250 micrograms dp/m3 of air for 2 years did not alter pulmonary PL content in rats.

Acetates↗
PubMed1987

Comparative study of four wound dressings on epithelization of partial-thickness wounds in pigs.

Sixteen shallow wounds were inflicted in each of five Yorkshire white female piglets, 18-20 kg body weight, by a 2-cm diameter, fast-rotating abrasive disc. The injury is similar to a second-degree burn. The wounds were dressed with one of four dressings: Duoderm (Squibb), Op-Site (Smith & Nephew) [corrected], and collagen sponge, covered with either occlusive or semiocclusive polyurethane film (Datascope Corp.). The last two dressings were moistened with saline before application. The rate of epithelization by planimetric quantitation after 3 to 5 days was the same regardless of the dressing used, although the epithelium layer was thicker in wounds treated with Duoderm. Wounds dressed by either of the collagen sponge materials showed a better appearance when visually scored. Wounds dressed with Duoderm or Op-Site were often macerated; Duoderm's paste-like material remained on the wound and was difficult to remove without inflicting discomfort to the patient. Duoderm, and also Op-Site, adhered much more strongly to the intact skin than either type of collagen sponge dressing.

Animals↗
PubMed1987

Increasing the breaking strength of wounds exposed to preoperative irradiation using vitamin E supplementation.

This study investigated if the prophylactic administration of vitamin E, an antioxidant, normalizes the healing of wounds exposed to preoperative ionizing radiation. Vitamin E was given intraperitoneally to three experimental groups of rats every other day at doses of 10, 20 or 40 International Units (IU) until a total dose of 30, 60 or 120 IU respectively was administered. There were three control groups: non-irradiated control, irradiated, non-supplemented control and irradiated, sesame oil-supplemented control. Two days following the last vitamin E or sesame oil injection 600 Rads of local radiation was delivered to the area of wounding. Two hours following the radiation treatment five centimeter long incisions were made in the area of radiation. There was no difference in the growth of the rats. Radiation exposure significantly reduced the breaking strength (g/5 mm wound) of the wounds compared to non-irradiated controls. With increasing levels of vitamin E there was an increase in the breaking strength of wounds (Y = 360.0 + 0.64 X, SE = 0.27, p less than 0.01). This study provides evidence suggesting that vitamin E may help normalize the breaking strength of wounds that receive preoperative irradiation.

Animals↗
PubMed1986

Development of a "leak-proof," knitted Dacron vascular prosthesis.

We have developed a technique to render knitted Dacron prostheses totally impervious to blood leak by impregnating the cloth with collagen. These grafts were prepared by the manufacturer, sterilized, and have an indefinite shelf life. The objective of this study was to determine whether collagen impregnation has a deleterious effect on surface thrombogenicity and graft healing. The infrarenal aortas of 30 mongrel dogs were replaced with 6 cm X 6 mm Dacron grafts (15 collagen-impregnated and 15 control). The collagen-impregnated prostheses were visibly indistinguishable from the control. After blood flow was restored, no interstitial bleeding occurred in the collagen grafts, in contrast to the control grafts that initially leaked profusely. When they recovered, the dogs were divided into three groups: group I (five collagen, five control), group II (five collagen, four control), and group III (five collagen, three control). The grafts were harvested at 3, 6, and 9 months, respectively. Retroperitoneal healing response, capsular thickness and adherence, completeness of neointimal healing, surface fibrinolytic activator activity, and sections taken for light and scanning electron microscopy were studied and compared in a blinded fashion. In a separate set of experiments, experimental and control grafts were compared for in vivo surface thrombogenicity. The healing data were identical in the experimental and control prostheses in all parameters. Of particular interest was that initial capsule adherence was better and surface thrombogenicity less in the collagen-impregnated prosthesis. We conclude that collagen impregnation of a knitted Dacron prosthesis has no deleterious effect for the term of observation of this experiment.

Animals↗