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Biomedical subjects

F Dijk

Publications and source records attributed to F Dijk.

At least 37 records · Page 2Linked to original sources
PubMed1993

Healing of microvenous PTFE prostheses implanted into the rat femoral vein.

44 PTFE prostheses (Gore-Tex; ID 1 mm) were implanted into rats' femoral veins by means of the sleeve anastomotic technique and were evaluated at regular intervals from 1 h up till 24 weeks after implantation by means of light and electron microscopy to study in detail their healing process. All prostheses, except one at 1 week and one at 24 weeks after implantation, were patent at the time of removal. Upon implantation, the luminal surface of the prostheses became covered with a thin clot layer. From 1 week onwards, endothelial cells originating from the anastomotic sides grew in across the anastomoses. In addition, small capillary-like orifices were present at the anastomotic sites, from which endothelial cells also seemed to originate. At 2 weeks, in several areas in the mid-region of the prostheses, the fronts of regenerating endothelial cells had reached each other, and about 80% of the luminal surface was covered by endothelium and at 3 weeks, the prostheses were completely covered by an endothelial layer. These results demonstrate that PTFE microvenous prostheses heal exclusively by means of rapid ingrowth of endothelial cells originating from both sides at the anastomoses.

Animals↗
PubMed1993

Biodeterioration of medical-grade silicone rubber used for voice prostheses: a SEM study.

Silicone voice prostheses used for rehabilitation of speech after total laryngectomy are inserted in an non-sterile habitat. Deposits on explanted Groningen Button voice prostheses revealed a biofilm, due to heavy colonization of the silicone surface by bacteria and yeasts. Furthermore, it was demonstrated by scanning electron microscopy on sectioned explants that the silicone material was deteriorated by filamentous and vegetative yeast cells. The different explants showed a variety of sharp-edged, discrete yeast colonies. The yeasts grew just under the silicone surface and up to 700 microns into the silicone material. Finally, nine different types of defects in the silicone material created by the yeasts are described. This deterioration of the silicone by yeasts seems to be the main reason for the failure and the frequent replacement of the prostheses. The mechanisms of silicone deterioration are still hypothetical.

Bacterial Adhesion↗
PubMed1992

Mersilene (polyester), a new suture for penetrating keratoplasty.

Mersilene (polyester monofilament) seems to be suitable for penetrating keratoplasty because it is strong, shows no degradation by ultraviolet light, is insoluble, so that it can be left in situ, and offers the possibility of regulating postoperative astigmatism by suture adjustment. In 12 patients penetrating keratoplasty was performed with the combined interrupted/running suturing technique, using eight interrupted nylon 10-0 sutures and one running Mersilene 11-0 suture. The results were compared with those of 25 patients in whom eight interrupted nylon 10-0 sutures and one running nylon 11-0 suture were used. Six months after penetrating keratoplasty, no differences could be found between the two groups in keratometric astigmatism, visual acuity or slitlamp findings. In three patients postoperative adjustment of the running Mersilene suture reduced astigmatism by 50, 90 and 100% respectively. In an animal study the behaviour of Mersilene in the cornea was evaluated by slitlamp examination, histology and electron-microscopy. The tissue response to Mersilene was minimal. Considering the resemblance to nylon in clinical findings, minimal tissue response, lack of biodegradation and possibility of regulating postoperative astigmatism by suture adjustment, Mersilene seems to be a suitable material for penetrating keratoplasty.

Animals↗
PubMed1991

Experimental microvenous reconstructions with Gore-Tex polytetrafluoroethylene prosthesis implanted by means of the sleeve anastomotic technique.

Polytetrafluoroethylene (PTFE) prostheses (Gore-Tex; ID, 1 mm; length, 5-7 mm; wall thickness, 0.2 mm; fibril length, 30 microns, n = 28) were implanted into the rat femoral vein by means of the sleeve anastomotic technique to enhance the patency rate. In the control group, PTFE prostheses (n = 8) were implanted by means of the end-to-end technique. In the experimental group patency and healing of the PTFE prostheses were evaluated at 1 day (n = 4), 1 week (n = 6), 3 weeks (n = 6), 6 weeks (n = 6), and 12 weeks (n = 6) after implantation by means of macroscopic inspection and routine light and scanning electron microscopy. All prostheses, except one at 1 week after implantation, were patent at the time of removal. All of the microvenous prostheses were completely covered by an endothelial layer at 3, 6, and 12 weeks after implantation. Occasionally some smooth muscle-like cells could be found underneath this endothelial layer, but stenosis was never observed at the anastomotic sites. Only scarce tissue ingrowth was observed in the wall of the PTFE prostheses. In the control group, all prostheses, except one prosthesis after 3 weeks, were found to be occluded. An occlusive mural thrombus was found firmly attached at the anastomoses at 1 day, and an organized thrombus at 3 weeks after implantation. The patent prosthesis demonstrated complete endothelial healing. These results demonstrate the importance of the sleeve anastomotic technique and the potential of PTFE prostheses as a microvenous conduit when implanted by means of the sleeve anastomotic technique in experimental reconstructive microvascular procedures.

Anastomosis, Surgical↗
PubMed1990

Morphology of donor lens-capsule material studied by SEM.

The lens capsule of a 70-year-old male donor with a cataractous lens was carefully prepared for SEM by first washing the capsule with buffer solution to remove lens-fibres and subsequently attaching it to silicon rubber. During the fixation and drying stages of the preparation procedure the capsule stayed attached to the rubber substratum. In the equatorial zone germinating cells were found with knob-shaped microvilli, closely connected to lens-fibres. Large units of pathological capsule epithelial cells were found, only slightly inter connected by a few pseudopodia. In addition, single pathological epithelial cells with pseudopodia, arranged on top of the cell in a rosette-like configuration, were found at certain locations. Both types are probably related to the original lens-cataract.

Aged↗
PubMed1990

Secondary cataract material collected with a glass cannula. A SEM study.

Secondary cataract material from three patients, collected with a glass cannula approx. 18, 24 and 30 months respectively after operation, was prepared for SEM examination. For the soft samples this was done by filtration through a millipore filter followed by fixation and drying. The more solid material was suspended in a fixation solution, followed by centrifuging, suspension in 70% ethanol and drying on a specimen-holder. The short residence samples (18 months) showed mainly erythrocytes, some (inflammatory) cells and degenerated lens-fibre material. Most of the more solid material, which was collected more than 20 months after operation, showed fragments of (regenerated) capsule epithelium and pieces of solid lens-fibre material with fragments of capsule epithelium attached.

Cataract↗
PubMed1990

Vacuum cell seeding: a new method for the fast application of an evenly distributed cell layer on porous vascular grafts.

The study was to develop a method to induce rapid endothelial coverage of vascular prostheses by cell seeding. The method uses vacuum pressure and is therefore called vacuum cell seeding. A special seeding device was constructed, in which grafts of different length and/or inner diameter could be positioned. Microporosity of the grafts was a prerequisite for this method. Two types of commercially available microporous grafts were tested. The ePTFE graft routinely used clinically needed pretreatment to enable the method, whilst a polyurethane-based graft could be seeded as received. Vacuum cell seeding applied cells from a suspension in culture medium within 10 min in an evenly distributed cell layer on to the luminal graft surface. The adhering cells immediately started flattening, thereby completely covering the luminal surface. It was concluded that the vacuum cell seeding method rapidly introduced a confluent layer of seeded cells on porous vascular grafts in a simple way, which in the clinical setting could easily be performed on the operating table.

Animals↗
PubMed1989

Keratoconus morphology and cell dystrophy: a SEM study.

The SEM-pictures represent a keratoconus in a 59-year-old patient with a Descemet rupture, which had led to a so-called Kammerwassereinbruch, where the failure of the endothelial structure has become manifest in the epithelium. In the Descemet-rupture the onset of stromal pathology is observable, while outside the rupture severe degradation of endothelial cells is seen. This is manifested as cell-membrane perforation, loss of cell contents and oedema formation in general. On the epithelial side the pathology is expressed as cell-membrane degradation and the presence of very irregularly shaped, sometimes swollen and in other cases shrunken, epithelial cells, in particular in the areas of the surface depressions. The topographical correspondence of these pathological phenomena on the endothelial and the epithelial sides is stressed.

Descemet Membrane↗
PubMed1989

Kinetics of cell spreading on protein precoated substrata: a study of interfacial aspects.

In this paper, interfacial aspects of spreading and adhesion of human skin fibroblasts on solid substrata after protein precoating have been studied. Three solid substrata were used with different surface free energy (gamma s): Tissue Culture Polystyrene (TCPS) with gamma s = 70 erg.cm-2, Polyvinylfluoride (PVF) with gamma s = 56 erg.cm-2 and Fluoroethylenepropylene (FEP) copolymer with gamma s = 18 erg.cm-2. The substrata were precoated with fetal calf serum, bovine fibronectin or bovine serum albumin. Cell spreading was evaluated by means of light microscopy and scanning electron microscopy (SEM). Adhesion sites were studied by transmission electron microscopy (TEM). In general, spreading was lowest on FEP and highest on TCPS. Although protein precoating markedly increased cell spreading, the relative order in which the cells spread on the protein precoated substrata remained identical to that on the bare substrata. Analysis of the kinetics of spreading demonstrated that spreading was fastest on the high-energy substratum and slowest on the low-energy substratum. In the presence of all three types of protein precoating, the average distance between a cell and a substratum after spreading was smaller (20-50 nm) than without a coating (greater than 100 nm).

Albumins↗
PubMed1987

Sequential studies of arterial wall regeneration in microporous, compliant, biodegradable small-caliber vascular grafts in rats.

Microporous, compliant, biodegradable vascular grafts prepared from a mixture of polyurethane (95% weight) and poly-L-lactic acid (5% weight) can function as a temporary scaffold for the regeneration of the arterial wall in small-caliber arteries. This study was undertaken to document the sequential events leading to this regeneration. Therefore, polyurethane/poly-L-lactic acid vascular grafts were implanted into the abdominal aorta of rats (N = 28) and were harvested at regular intervals from 1 hour up to 12 weeks after implantation. The implants were evaluated by means of light and electron microscopy. At each time of harvesting, the implants were patent and showed arterial pulsations. No stenosis or dilatation was observed. Endothelial cells grew from the adjacent aortic intima across the anastomoses, from day 6 onward, to form an almost complete neointima after 6 weeks of implantation. Smooth muscle cells also grew from the adjacent aortic media over the graft lattice through the platelet-fibrin coagulum from day 6 onward. The smooth muscle cells, predominantly longitudinally arranged at week 6, but also circularly arranged in some areas at week 12, formed a neomedia in which elastic laminae regenerated. Polymorphonuclear leukocytes and monocytes initially invaded the graft lattices. Fibroblasts, histiocytes, and capillaries grew from the perigraft tissue into the polyurethane/poly-L-lactic acid lattices from day 6 onward, which resulted in the formation of a neoadventitia. The polyurethane/poly-L-lactic acid lattices started to disintegrate from day 12 onward. The regenerative processes in the disintegrating polyurethane/poly-L-lactic acid grafts resulted in the formation of neoarteries, which were of sufficient strength, compliance, and thromboresistance to function as small-caliber arterial substitutes.

Animals↗
PubMed1985

Regeneration of the arterial wall in microporous, compliant, biodegradable vascular grafts after implantation into the rat abdominal aorta. Ultrastructural observations.

The ultrastructure of a new type of vascular graft, prepared from a mixture of polyurethane (95 weight %) and poly-L-lactic acid (5 weight %), was examined six weeks after implantation into the abdominal aorta of rats. These microporous, compliant, biodegradable, vascular grafts function as temporary scaffolds for the regeneration of the arterial wall. Smooth muscle cells, covering the grafts, regenerated a neo-media underneath an almost completely regenerated endothelial layer (neo-intima). These smooth muscle cells varied in morphology from normal smooth muscle cells to myofibroblasts. They were surrounded by elastic laminae and collagen fibers. Macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries were present in the disintegrating graft lattices. The epithelioid cells and multinucleated giant cells engulfed polymer particles of the disintegrating grafts. The regeneration of the endothelial and smooth muscle cells is similar to the natural response of arterial tissue upon injury. The presence of macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries in the graft lattices resembles the natural response of tissue against foreign body implants. Both of these responses result in the formation of a neo-artery that possesses sufficient strength, compliance and thromboresistance to function as a small caliber arterial substitute.

Animals↗
PubMed1985

Membrane specializations and their relation to HRP transport in the medial habenular nucleus of the rat.

In the medial habenular nucleus of the rat, ependymal and endothelial membrane specializations were studied with TEM and freeze-fracturing. They comprise ependymal adherent junctions - not manifest in freeze-fracture replicas-, gap junctions, and membrane-associated orthogonal particle complexes ("assemblies") - not identifiable in thin-sectioned material. Ependymal tight junctions being absent, no brain-liquor barrier exists. The capillary endothelium is provided with tight junctions only. Intraventricularly injected HRP was transported in large amounts through the ependyma, mainly through the intercellular spaces and additionally by way of massive pinocytosis through the cytoplasm of particular ependymal cells only, and finally through the parenchymal intercellular compartments towards habenular capillaries. Following intravenous injection of HRP, considerable transport of the enzyme took place by means of transendothelial pinocytosis, followed by some pinocytotic transport through diverse parenchymal elements and markedly profuse incorporation and lysis within pericytes. The habenular blood-brain barrier appeared to be considerably leaky with respect to HRP.

Animals↗
PubMed1984

Monocytes and radiation-induced atheromatosis in rabbits.

Previous experiments have shown that local irradiation of the carotid arteries of hypercholesterolemic rabbits results in the development of atheromatosis in the irradiated areas of the arteries. The process starts with the adherence of monocytes to the endothelial layer, their entrance into the subendothelial space, and their subsequent transformation into lipophages (foam cells). Prevention of this type of plaque formation can be achieved by prednisolone (in a lower concentration than previously used) (Vos et al. 1981) and by VP16-213 (Vepesid). Differential blood cell counts demonstrated that the animals subjected to treatment with prednisolone developed a moderate relative lymphocytopenia, whereas treatment with Vepesid resulted in a severe monocytopenia. Since prednisolone treatment only partially prevented plaque formation, whereas Vepesid seemed to fully inhibit the development of plaques, we conclude that although a role of the lymphocyte in the process of plaque formation cannot be excluded, the monocyte seems to play a crucial role in the pathogenesis of radiation-induced atheromatosis.

Animals↗
PubMed1983

On the cellular origin and development of atheromatous plaques. A light and electron microscopic study of combined X-ray and hypercholesterolemia-induced atheromatosis in the carotid artery of the rabbit.

The cellular origin and development of radiation-induced atheromatous plaques in the carotid artery of the hypercholesterolemic rabbit have been studied morphologically from a few hours post-irradiation up to several weeks later. As early as 8 h following local X-irradiation (500 or 1,000 rad) mononuclear cells, presumably blood monocytes, enter the subendothelial space. The cells have disappeared again 10 days post-irradiation in normocholesterolemic animals. In irradiated hypercholesterolemic animals, however, the invading mononuclear cells transform into lipophages and become so-called foam cells, visible from the second day post-irradiation. The number of lipophages increases with time resulting in plaques of about 5-10 cell layers after 20 days. From 20 days post-irradiation onwards smooth muscle cells enter the plaque by migrating from the tunica media through the fenestrations of the lamina elastica interna. Smooth muscle cells are found to contain less lipid vacuoles than monocyte-derived lipophages. At 30 days post-irradiation the smooth muscle cells have formed parallel layers in the luminal side of the plaque encapsulating an inner core of foam cells and other material. The morphology of the plaque at 30 days post-irradiation is similar to that reported for advanced plaques developing in rabbits by mere cholesterol feeding over a relatively long period. In irradiated normocholesterolemic and in non-irradiated hypercholesterolemic rabbits plaques are not observed in the carotid arteries during the experimental period. The early involvement of blood monocytes has been separated from the later role of medial smooth muscle cells in radiation-induced plaque formation. The results suggest that the underlying process in this lesion may be understood in terms of a sterile inflammation, complicated by an immediate fatty degeneration and followed by repair phenomena. The combination of hypercholesterolemia and ionizing radiation may serve as a useful experimental model for further studies in various animal species on why and how plaques originate, develop or regress and how they could possibly be prevented. The relevance of the results to radiotherapy in humans is mentioned briefly.

Animals↗