Search PubMed⌕ Search

Biomedical subjects

J Feijen

Publications and source records attributed to J Feijen.

159 records · Page 9Linked to original sources
PubMed1983

Adhesion of coagulase-negative staphylococci to biomaterials.

The adhesion of two Staphylococcus epidermidis strains and one Staphylococcus saprophyticus strain on to poly(tetrafluorethylene-co-hexafluorpropylene) (FEP)-fluorocarbon and cellulose acetate was studied in vitro. Both S. epidermidis strains showed a more hydrophobic character than the encapsulated S. saprophyticus as determined by the bacterial affinity towards xylene. Staphylococcus epidermidis showed a significantly higher adhesion on to the hydrophobic FEP than S. saprophyticus. The adhesion of staphylococci on to the more hydrophilic cellulose acetate was always low. Treatment of S. epidermidis with pepsin or extraction with aqueous phenol yielded cells with a decreased hydrophobicity, which resulted in a decreased adhesion on to FEP. Cells with a decreased hydrophobicity showed a lower rate of reaggregation in suspension. The hydrophobicity and the adhesion on the FEP of S. epidermidis were not affected by exposure to a subminimal inhibitory concentration of penicillin. The strong interaction between S. epidermidis and FEP, which appeared not to be influenced by the age or the metabolic stage of the bacteria, is mainly caused by hydrophobic bonding.

Adhesiveness↗
PubMed1982

In vitro adsorption of oxalic acid and glyoxylic acid onto activated charcoal, resins and hydrous zirconium oxide.

Patients suffering from primary hyperoxaluria show elevated plasma concentrations of oxalic acid and glyoxylic acid. The in vitro adsorption of these compounds into activated charcoal, a series of neutral and ion exchange resins and onto hydrous zirconium oxide has been investigated. Hydrous zirconium oxide was the most effective sorbent studied for the removal of both oxalic acid and glyoxylic acid. In batch experiments, the zirconium oxide was capable of binding 5.5 mu mol oxalic acid and 8 mu mol glyoxylic acid per gram sorbent using 0.5 gram sorbent and 50 ml of solutions with initial concentrations of 100 mu mol . L-1 and an ionic composition resembling that of plasma. Recirculation of 2 L of the same solutions through 12 gram of a mixture of hydrous zirconium oxide and alumina for 6 hours at a flow rate of 12 ml . min-1, resulted in a final concentration of 70 mu mol . L-1 of oxalic acid and 50 mu mol . L-/ of glyoxylic acid.

Adsorption↗
PubMed1980

Experimental myringoplasty.

Artificial eardrums made from biodegradable poly(D,L-lactic acid), poly(glycolic acid) and poly(beta-benzyl-L-aspartate-co-L-leucine) 50/50, and made from the microporous poly(tetrafluoroethylene) and bisphenol-A poly(carbonate) membranes were implanted into the ear and as a reference subcutaneously in rats. The implants were histologically examined for periods up to one year. From the biodegradable polymers studied the poly(beta-benzyl-L-aspartate-co-L-leucine) 50/50 evoked the least tissue reaction and the newly formed tympanic membranes are the best in terms of thickness and overall integrity. The microporous poly(tetrafluoroethylene) membrane can be considered as a valuable support for the formation of a reinforced tympanic membrane.

Animals↗
PubMed1979

Progestin permeation through polymer membranes IV: Mechanism of steroid permeation and functional group contributions to diffusion through hydrogel films.

Hydrogel films were prepared from hydroxyethyl methacrylate, both with (Film II) and withouth (Film I) 5.25 mole% of ethylene glycol dimethacrylate. Permeation, diffusion, and partition coefficients for progesterone, testosterone, nandrolone, norethindrone, 17 alpha-hydroxyprogesterone, estradiol, and hydrocortisone were determined. A solute permeation model was proposed based on the separation of a domain (B) composed of "bulk-like" water and a doman (A) composed of polymer, interfacial water, and bound water present in the films. The separate contributions from the "pore" and "solution-diffusion" mechanisms to the total permeability were calculated from the model. Steroid permeabilities through Films I and II were analyzed in accordance with this model. Permeation of Film II occurred via the solution-diffusion mechanism. Permeation of Film I occurred predominately by the pore mechanism with a small contribution (approximate 20%) from the solution-diffusion mechanism. The latter contribution was dependent on the solubility of the solute within the A domains of the hydrogel film. Functional group contributions to permeation of Film II were ascribed to either steric or hydrogen bonding effects.

Diffusion↗
PubMed1979

A hemoperfusion column based on activated carbon granules coated with an ultrathin membrane of cellulose acetate.

A hemoperfusion system has been developed which makes use of activated carbon encapsulated with cellulose acetate. Studies have revealed that there are no stagnant flow regions in the column, there is minimal particle release and the coating is 30 A thick. The relationships between pore size, pore volume and surface area have been examined. Twenty-five patients in grade IV coma have been treated with the column for treatment of drug overdose or agricultural chemical poisoning; the clinical course of one meprobamate-poisoned patient is described in detail.

Acetates↗
PubMed1978

Experimental myringoplasty.

Different materials were compared as implants in performing a myringoplasty on rats immediately after making a total perforation, (autologous fascia, homologous tympanic membrane, homologous collagen, heterologous collagen, heterologous amnion and proplast). As a reference one group of rats had no myringoplasty done after perforating their drums. The animals were examined regularly, then killed after 40 and 64 weeks. Macroscopically and microscopically proplast and homologous collagen were very inferior to homograft tympanic membrane and autologous fascia. The best results were obtained both macroscopically and histologically with heterologous collagen and heterologous amnion.

Amnion↗
PubMed1978

The effect of radiolabeling of human fibrinogen on its adsorption behaviour on a polystyrene surface.

Human fibrinogen (HFB) was labeled with different radioactive labels (Technetium -99m and iodine -125) in various ways. Characterization by chromatographic and electrophoretic methods did not show differences between the labeled and the nonlabeled proteins. The effect of the label and the labeling method on the adsorption behaviour of 99mTc and 125I labeled HFB at a polystyrene surface was investigated. In all cases labeled HFB showed preferential adsorption as compared to nonlabeled HFB. The preferential adsorption was expressed in terms of a factor ø (van der Scheer et al. 1978a), which will be 1, when no preferential adsorption occurs. 99mTc - and 125I - HFB showed ø values from 1.48 - 1.88. It is concluded that only meaningful adsorption experiments with labeled proteins can be performed when the possible occurrence of preferential adsorption has been investigated by appropriate methods. The results of prior work on protein adsorption at biomaterials using radiolabeled proteins have to be reconsidered.

Adsorption↗
PubMed1977

Biodegradability and tissue reaction of random copolymers of L-leucine, L-aspartic acid, and L-aspartic acid esters.

A series of copoly(alpha-amino acids) with varying percentages of hydrophilic (L-aspartic acid) and hydrophobic monomers (L-leucine, beta-methyl-L-aspartate, and beta-benzyl-L-aspartate) were implanted subcutaneously in rats and the macroscopic degradation behavior was studied. Three groups of materials (A,B,C) with different ranges of hydrophilicity were distinguished: A) hydrophobic materials showed no degradation after 12 weeks; B) more hydrophilic materials revealed a gradual reduction in size of the samples, but were still present after 12 weeks; and C) hydrophilic copolymers disappeared within 24 hr. The tissue reactions caused by the materials of group A resembled that of silicone rubber, whereas those of group B showed a more cellular reaction.

Animals↗
PubMedDate not supplied

Analysis of the balance between proliferation and apoptosis of cultured vascular smooth muscle cells for tissue-engineering applications.

Tissue homeostasis, the balance between cell proliferation and apoptosis, is an important factor in tissue engineering. We describe a new method to analyze markers of both proliferation and apoptosis in a single assay to monitor growth behavior of cell cultures. Human vascular smooth muscle cells (VSMCs) were cultured either on gelatin-coated tissue culture polystyrene or in three-dimensional porous scaffolds composed of insoluble collagen and elastin. mRNA concentrations of cyclin E, as a marker of proliferation, and of tissue transglutaminase (tTG) as a marker of apoptosis, quantified by a real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and normalized to porphobilinogen deaminase mRNA concentrations, were analyzed. tTG mRNA expression levels were increased when apoptosis was induced by tumor necrosis factor-alpha in combination with cycloheximide or by culturing the cells in serum-free culture medium. Cyclin E mRNA expression levels were less altered in these cell cultures. Results were compared with several reference tests to measure apoptosis including DNA fragmentation, annexin V staining, and light microscopy. This RT-PCR method could be used to characterize cell growth behavior of VSMCs in vitro. In addition, it was shown that this test is suitable to measure the balance between proliferation and apoptosis of VSMCs present in tissue-engineered constructs.

Annexin A5↗
PubMedDate not supplied

Prevention of infection in a porous tracheal prosthesis by omental wrapping.

The ideal tracheal prosthesis has to permit complete incorporation by epithelialization of the luminal surface. This is not possible with the currently available impermeable solid silicone tube. The authors developed a reinforced, porous polyurethane tubular prosthesis which has the potential for complete incorporation. However, because these prostheses are implanted in a contamined area such as the airway, they all become infected. In order to prevent infection, the authors evaluated the effect of omental wrapping in guinea pigs. The authors' tubular prosthesis was implanted subcutaneously in the abdominal area with the ends open to the air. Ten prostheses were wrapped with omentum and 10 prostheses were not. In 4 weeks, all control prostheses were infected and marsupialized. All the wrapped prostheses remained in place and were macroscopically not infected. Microscopically, all wrapped prostheses were well vascularized and were incorporated by granulation tissue, which did not occur in the prostheses of the control group. From these results the authors conclude that omental wrapping would be an effective way to prevent infection of porous tracheal prostheses in an open-to-the-air situation, and allow rapid tissue ingrowth and incorporation in the host.

Animals↗
PubMedDate not supplied

Morphometric study of myocardial changes during puromycin aminonucleoside induced nephropathy in rats.

Puromycin aminonucleoside (PAN)-treated rats developed a severe nephrotic syndrome. Morphometric analysis of the hearts revealed significant differences between treated and control rats regarding nuclear index, reticulin index, nuclear and myocellular transsectional area, capillary number and transsectional area of capillaries. These differences were comparable with those induced by adriamycin. It is suggested that PAN can induce morphometrically measurable abnormalities in hearts of rats comparable to the morphometric changes seen after adriamycin treatment. The question of whether nephropathy, a result of both DOX and PAN treatment of rats, adds to or perhaps even causes doxorubicin - induced cardiomyopathy remains unclear.

Animals↗