Biomedical subjects

W L Jongebloed

Publications and source records attributed to W L Jongebloed.

At least 37 records · Page 2Linked to original sources

PubMed1992

Rate and mechanism of enamel demineralization in situ.

In this paper, data are presented on the in situ demineralization of human enamel as a function of the demineralization period. To quantify the mineral loss parameters versus time, it is important to obtain information on the kinetics, and thus on the mechanism of dental caries. The results show that for in situ enamel demineralization, the lesion depth as well as the mineral loss parameter both vary linearly with the demineralization time. This is in contrast to in vitro lesion formation where the third power, or the square power of the lesion depth is linearly related to the demineralization time. In in situ demineralization, the rate-determining step of the demineralization process is the inhibitor-controlled dissolution process at the enamel crystallite surfaces, while the inhibitor content (F-, proteins etc.) in the lesion originating from the plaque, saliva and enamel is high. Furthermore, the study indicates that in in situ demineralization, interprismatic mineral loss is very important.

Dental Enamel↗

PubMed1992

[Xerostomia-related dental caries].

The initiation and prevention of xerostomia-related dental caries were studied using an in situ model. The morphology of induced carious lesions was compared with that of natural xerostomia-related dental caries. Both natural and induced xerostomia-related dental caries showed the same patterns of decay. Using the in situ model three preventive procedures were tested: neutral F gel applied every second day or weekly, and a daily rinse with a fluoride mouthwash for a period of six weeks. Application of fluoride gel or the use of the fluoride mouthrinse resulted in significant inhibition of the demineralization process. Of the procedures evaluated fluoride gel applied every second day was the most effective in preventing the onset of xerostomia-related dental caries.

Administration, Topical↗

PubMed1991

Cell-ingrowth in a silicone plombe. Interactions between biomaterial and scleral tissue after 8 years in situ: a SEM and TEM investigation.

A male patients (42 years) who had been treated for retinal detachment by the implantation of a silicone plombe into the sclera, returned to the clinic 8 years after implantation because of inflammation of the tissue and partial protrusion from the sclera. After removal of the plombe this was processed for TEM and SEM and examination of the plombe material after 8 years in situ could be carried out in order to get information about the cell-biomaterial interface. A large proportion of the silicone pores was filled with cellular material, including macrophages, giant cells and erythrocytes thus indicating a foreign body granuloma. The external surface of the pores showed a granular osmiophilic dense amorphous layer including extracellular debris. Engulfing of silicone particles by macrophages and the evidence of long-term tissue response suggest partial biodegradation of the silicone and certainly not complete inertness as was formerly claimed.

Adult↗

PubMed1991

Morphological aspects of human lens capsules. A comparative LM, SEM and TEM examination.

Lens capsules of patients of advanced age, obtained after extracapsular cataract surgery, were carefully prepared for a combined LM, TEM and SEM investigation, after preliminary washing and mounting onto a holder in a buffer solution. After pre-fixation with GA, samples were postfixed for LM/TEM and OsO4/K4Fe)CN)6 and stained with toluidine-blue/basic fuchsin for LM and with uranyl acetate/lead citrate for TEM; for SEM the GA-pre-fixed samples were post-fixed by the Tannin Arginine-OsO4 non-coating technique. At LM-level discrimination between healthy and degenerating cells was possible after toluidine staining. At SEM-level protrusion of the cell nucleus and fibrillation and blebbing of the cell membrane as the result of capsular degeneration could be observed with the TAO-method. At TEM-level protrusion of the cell nucleus, degeneration of the cytoplasm, ballooning of the mitochondria, the presence of microfilaments and the occurrence of vacuoles were visible as the result of capsular degeneration on cataract formation.

Cataract Extraction↗

PubMed1991

A combined scanning and transmission electronmicroscopic investigation of human (secondary) cataract material.

Cataract lenses from patients of advanced age were processed for SEM by standard pre-fixation followed by treatment by the Tannin-Arginine-Osmium-tetroxide (TAO) method and critical point drying, and for TEM by standard pre-fixation followed by vibratomation, standard post-fixation, ultramicrotome sectioning and staining with uranyl acetate/lead citrate. Secondary cataract material was brought onto a Millipore filter, fixed by standard methods, dried in air and sputter-coated with Au. Both SEM and TEM images revealed degeneration processes in lensfibre material, such as swelling of the lensfibre, protrusion of the cytoplasm, fibrillation of the cell membrane, loss of the nucleus, spherical bodies of various sizes between 0.5-1.5 microns, sometimes surrounded by a (double) membrane with different contrast but without cellular evidence, and small and large vacuoles partly filled with granular material both in and at the periphery of the lensfibre-body. The secondary cataract material on the Millipore filter revealed erythrocytes and more or less spherical bodies with high contrast, measuring between 0.5-1.5 microns, often referred to as Elschnig's pearls, besides non-definable organic material. The SEM and TEM micrographs of the cataract lens material strongly suggest that the spherical bodies with sizes of approximately 0.5-1.5 micrometer and high contrast without cellular evidence, are similar to the more or less spherical bodies found in the secondary cataract material on the filter, referred to as Elschnig's pearls.

Cataract↗

PubMed1991

Acute irradiation effects on morphology and function of rat submandibular glands.

In this study the morphologic and functional changes were compared after irradiation (single dose, 15 Gy) of rat submandibular salivary glands. Before and 1-10 days after local irradiation of the gland region, samples of submandibular saliva were collected after stimulation by pilocarpine. At the same time-points and also 3 h postirradiation submandibular glands were carefully extirpated and prepared for histocytologic examination (LM, TEM). Maximal increase of the lag phase and decrease of the flow rate were observed 3 days after irradiation, while [K+] and [Na+] increased and decreased, respectively, from days 1 and 3 after irradiation. Morphologic changes were observed from the third hour after irradiation, were maximal 3 days after irradiation and had partially recovered by day 10. Three hours and 1 day after irradiation degranulation of convoluted granulated tubes (CGT) was observed. Three days after irradiation the most striking morphologic changes in serous and mucous cells were distension of the cisternae of the RER, degeneration of mitochondria and vacuolization of the cytoplasm. Fibril-like condensations of electron dense material in the mucous granules were observed 3 h, 1 and 6 days after irradiation. Regranulation of CGT cells was observed from day 6. From this study it is concluded that changes in salivary gland function can be observed before major morphologic changes occur. Functional changes persist after the morphologic changes seem to have virtually returned to normal.

Animals↗

PubMed1990

Amount and surface structure of albumin adsorbed to solid substrata with different wettabilities in a parallel plate flow cell.

In this article we studied the adsorption of serum albumin to substrata with a broad range of wettabilities from solutions with protein concentrations between 0.03 and 3.00 mg.mL-1 in a parallel-plate flow cell. Wall shear rates were varied between 20 and 2000 s-1. The amount of albumin adsorbed in a stationary state was always highest on PTFE, the most hydrophobic material employed and decreased with increasing wettability of the substrata. Increasing stationary amounts of adsorbed albumin were observed with increasing wall shear rates at the lowest protein concentration. Inverse observations were made at the highest protein concentration. Transmission electron micrographs of replicas from the albumin-coated substrata showed that proteins were mostly adsorbed in islandlike structures on the hydrophobic substrata. The tendency to form islandlike structures was shear rate- and concentration-dependent and disappeared gradually going to more hydrophilic substrata. On glass, the most hydrophilic material employed, a homogeneous, well distributed, fine knotted, reticulated structure was found. In conclusion, this study demonstrates that both the amount of adsorbed albumin as well as the surface structure of the adsorbed proteins are regulated by the substratum wettability. This observation may well account for the fact that substratum properties can be transferred by an adsorbed protein film to the interface with adhering cells or microorganisms.

Adsorption↗

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

Reaction of the rabbit corneal endothelium to nylon sutures. A SEM study.

Nylon and stainless steel sutures separately placed deeply into rabbit corneas by splitting the stroma for a few millimeters, without closing sutures, remained in the cornea for two, four and six weeks respectively. In contrast to the stainless steel sutures an extensive tissue reaction could be observed clinically around the nylon sutures within a few days and was still present after 4-6 weeks. On the endothelial side, covering of the nylon with fibroblast cells took place very slowly, this in contrast with stainless steel. Irritation of the tissue and an oedematous appearance of the endothelium around the nylon suture was the result. At first a kind of collagen network, often mixed with inflammatory cells, was deposited on the nylon material before fibroblast cells could grow in. Covering of the stainless steel started quite soon after implantation, without preliminary deposition of collagen material. The reason for this phenomenon must be sought in the high free surface energy of the stainless steel, which attracts cells, in contrast to nylon which has a very low free surface energy.

Animals↗

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

The Gonioseton, a surgical treatment for chronic glaucoma.

A new and simple technique for glaucoma filtering surgery is presented. It is based on the introduction of a stainless steel microspiral or gonioseton into a goniopuncture by way of an ab interno procedure, minimising surgical trauma to the filtration area. Preliminary results are presented.

Adult↗

PubMed1990

Remineralization of human dentine in vitro.

In this paper the in vitro remineralization of human dentine with 0, 0.5, 2 and 10 ppm F in the remineralization solution is presented and analyzed by microradiography. Furthermore, the remineralization data of human and bovine dentine are quantitatively compared. The main results of this paper are: (1) the efficacy of human (and bovine) remineralization is about proportional to the square root of the F level in the remineralizing solution, and (2) the amount of mineral effectively deposited in the dentine is most likely controlled by the diffusion of fluoride into the tissue. This study shows furthermore that although numerical differences exist in the remineralization of human and bovine dentine, the general remineralization behaviour is quite similar. The presence of F- in the parts per million range is essential for the remineralization efficacy in vitro and also for the 'overremineralization' of the outer dentine surface.

Adolescent↗

PubMed1989

Comparison of the reaction of the cornea to nylon and stainless steel sutures: an animal study.

In 11 rabbits a comparison was made between the reactions of the cornea to nylon and to stainless steel sutures, macroscopically and by means of scanning electron-microscopy (SEM). Macroscopically, the wounds sutured with steel thread showed much less reaction than the wounds sutured with nylon. Vascularization was never encountered in the wounds sutured with steel thread. SEM examination also showed clear differences, which became noticeable within a short time. Both on the suture and round the opening in the cornea extensive deposits of material are seen within a short time (1 week) in the case of nylon, in the case of stainless steel this reaction is much less marked. A few weeks later deposits also appear on the steel thread, but these have a different composition and contain no material suggestive of an inflammatory reaction.

Alloys↗

PubMed1989

Air-injection of the corneal stroma: a SEM study.

The corneal stroma is supposed to be a homogeneous structure both from an optical and an anatomical point of view. Intrastromal injection of glutaraldehyde as a fixative causes local swelling and opacification of the corneal tissue. Local injections of small volumes of air superficially and more deeply into the corneal stroma produce similar swellings and formation of opaque areas. SEM investigation of these areas shows the existence of stromal canals, partly pre-existing, partly caused by the internal 'explosions' due to the air-injection. This suggests an anatomically non-homogeneous, although optically homogeneous, cornea.

Air↗

PubMed1989

Lens-capsule material of human and animal origin, studied by SEM.

Lens-capsule material from healthy and cataractous human lenses and from rabbits was collected with specially designed forceps. Subsequently the capsule fragments were fastened, after short pre-fixation, onto a rubber substrate with small stainless steel tacks, to prevent rolling-up of the fragments during the fixation and drying procedure for the SEM. Finally the capsule fragments were studied by SEM. Marked morphological changes, e.g., irregular swelling (like blebs) of the nuclei, formation of deep grooves at the cell borders and complete loss of epithelial cells, were found in the lens capsules obtained from certain cataractous lenses. Differences in capsule thickness were found in pathological capsule material. The imprints (attachment-lines) of the lens-fibres on the epithelial cells were often difficult to visualize.

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

Glass-metal keratoprosthesis: light and electron microscopical evaluation of experimental surgery on rabbit eyes.

A keratoprosthesis (KP) is the last and only surgical resort to regain some visual acuity in eyes with severely damaged corneae. Corneal blindness represents an important percentage of the blind in the economically poor countries. Commercially available KP's, e.g. those made of PMMA, which are difficult to sterilize and vulnerable to surface damage, are too expensive in these countries. To overcome these disadvantages, we developed a new KP, made of a glass core melted into a platinum cylinder with flange. They were implanted unilaterally in eyes of ten Hollander rabbits intralamellarly. They were fixated by two stainless steel traction threads passed around the whole eyeball. We investigated this type of KP in the rabbit cornea, its acceptance by stroma, epi- and endothelium, and its hydro-mechanical dynamics in situ. No signs of infection or extrusion were observed. No epithelial downgrowth, nor adverse tissue reaction could be detected. LM and SEM showed endothelialization of the newly formed stroma around the central column of the KP. We conclude that this type of KP (although optically still to be optimized) has been accepted by the rabbit cornea and a clinical trial on cornea-blind patients is justified.

Animals↗

PubMed1989

A transmission electron microscopy study of the adsorption patterns of early developing artificial pellicles on human enamel.

Adsorption patterns of pellicles formed in a flow cell system under a moderate shear rate of 21 s-1, were studied with a replica technique. Characteristic features of the bare enamel surface disappeared within seconds after exposure to reconstituted saliva, indicating the adsorption of a homogeneous film. After that, three to four distinct homogeneous films were adsorbed on top of each other within 10 s and an uneven, knotted structure developed with stalky projections on the outer surface. This heterogeneous adsorption pattern determined the structure of the pellicle surface for at least 2 h.

Adsorption↗