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Biomedical subjects

W T Daems

Publications and source records attributed to W T Daems.

At least 19 recordsLinked to original sources
PubMed1990

Tissue/biomaterial interface characteristics of four elastomers. A transmission electron microscopical study.

The tissue/biomaterial interface reactions of four elastomers--selected as candidates for scaffolding for tympanic membrane tissue in a total alloplastic middle ear prosthesis--were studied at the electron microscopical level after implantation in the rat middle ear. Time-dependent changes in the phagocyte/polymer interface suggested degradation of porous implants made of Estane polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer (HPOE/PBT copolymer), but not of dense Silastic silicone rubber implants. Silastic was always encapsulated in fibrous tissue. Contact between fibrous tissue and HPOE/PBT copolymer or Estane was established in the third month, but fibrous tissue was never seen close to polypropylene oxide. Bone made contact only with Estane and HPOE/PBT copolymer implants. The bone/copolymer interface showed an electron-dense layer morphologically similar to that seen between bone and hydroxyapatite ceramic, suggesting that with respect to bone HPOE/PBT copolymer behaves like a bioactive implant material. The electron-dense layer was absnet at the bone/Estane interface. Estane and especially HPOE/PBT copolymer seem to be suitable as alloplastic tympanic membrane because of their interface behavior with respect to fibrous tissue and bone.

Animals↗
PubMed1990

The behavior of alloplastic tympanic membranes in Staphylococcus aureus-induced middle ear infection. I. Quantitative biocompatibility evaluation.

The biocompatibility of dense Silastic implants and porous implants made of Estane 5714 F1 polyether urethane, polypropylene oxide, and an HPOE/PBT segmented polyether polyester copolymer was evaluated during an induced Staphylococcus aureus middle ear infection. The middle ear response to infection seemed not to be affected by the presence of implants made of either of the polymers. Light microscopical morphometry and transmission electron microscopy showed degradation of the porous implants under study, but not of Silastic implants, which were invariably surrounded by a fibrous capsule. This finding, combined with the degree of porous implant degradation, the composition of the tissues surrounding the implants, and the tissue/biomaterial interface reactions are consistent with the results obtained in the noninfected middle ear. Round-cell infiltrates however, were predominantly associated with implants made of polypropylene oxide and HPOE/PBT copolymer; while the presence of (phagocytosed) microbial debris was associated with copolymer. The present findings indicate that with respect to implant behavior in infected surroundings Estane is the best porous material, whereas the behavior of Silastic implants did not deviate from that in non-infected ears.

Animals↗
PubMed1990

The behavior of alloplastic tympanic membranes in Staphylococcus aureus-induced middle ear infection. II. Morphological study of epithelial reactions.

Epithelial reactions to Silastic, Estane polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer were investigated after implantation in tympanic membranes and submucosa of noninfected and Staphylococcus aureus-infected rat middle ears. Porous implants made of Estane and polypropylene oxide were completely covered by tympanic-membrane connective tissue, epidermis, and epithelium in 2 weeks and those made of copolymer in between 2 and 4 weeks postoperatively. Silastic implants, which were dense, were not enveloped by tympanic-membrane tissue but rejected. Starting in the 6th postoperative month the proliferative activity and structure of both the tympanic membrane epithelium and epidermis became normal except for the presence of iron-containing secretory epithelium near polypropylene oxide. After initial swelling caused by the surgical trauma, neither the proliferative activity nor the composition of the epithelium covering submucosal implants was affected by the presence of any of the biomaterials. Infection of middle ears bearing implants induced epithelial reactions similar to those associated with infected middle ears without an implant.

Animals↗
PubMed1990

Asbestos body formation and iron accumulation in mouse peritoneal granulomas after the introduction of crocidolite asbestos fibers.

This report describes the cell biology of the development of asbestos bodies after a single intraperitoneal injection of a suspension of crocidolite asbestos fibers into the mouse peritoneal cavity. The majority of the infected fibers were found in aggregates of peritoneal macrophages, exudate cells, and fibrous tissue. These aggregates developed into granulomas containing not only numerous asbestos fibers, but also cells of various types, including macrophages, multinucleated giant cells, fibroblasts, plasma cells, granulocytes, and mast cells. Cytoplasmic ferritin was abundantly present in macrophages and giant cells. In addition, iron-rich inclusion bodies were detected. The results of this study show that asbestos body formation can occur outside the pleural cavity. Asbestos body formation occurred in the granulomas after periods of 1 month and longer. On the basis of morphologic criteria, various types of asbestos body were distinguished. X-ray microanalysis showed that variations in the density of the coat could attributed to the presence of chemical elements in various concentrations. Evidence is presented that asbestos body formation is an extracellular phenomenon.

Animals↗
PubMed1990

The formation of asbestos bodies by mouse peritoneal macrophages. An in vitro study.

For studies on the mechanism of asbestos body formation, Union Internationale Contre Cancer (UICC) crocidolite asbestos fibers were added to a culture of mouse peritoneal macrophages. Small asbestos fibers were totally ingested by the macrophages, but fibers too long to be taken up completely remained as a consequence extracellular. These long asbestos fibers became the basis for asbestos body formation. The basic mechanism underlying asbestos body formation was found to be the exocytotic activity of macrophages. The number of iron-rich inclusion bodies was dependent on the availability of iron in the culture media, and the same holds for the amount of iron in the asbestos body coat. This means that asbestos body formation is a phenomenon that occurs accidentally when macrophages come into contact with long fibers in an iron-rich environment. A time-dependent increase in the number, average size, and rate of segmentation of the asbestos bodies was observed. The present report is the first to describe asbestos body formation in vitro.

Acid Phosphatase↗
PubMed1989

Ultrastructural electron probe X-ray microanalytical reaction product identification of three different enzymes in the same mouse resident peritoneal macrophage.

Simultaneous cytochemical enzyme localization procedures for peroxidase (PO) plus acid phosphatase (AcP-ase) and/or aryl sulphatase (AS) have been investigated at the ultrastructural (EM) level. Electron probe X-ray microanalysis (EPMA) will identify and differentiate the reaction products. Dual reaction product localization of PO plus AcP-ase or alternatively PO plus AS have been obtained in the same mouse resident peritoneal macrophage. This has been acquired by first performing a PO-reaction followed by AcP-ase or followed by AS. In both cases PO-related reaction products (PODAB/Os or PODAB/Pt) were localized in nuclear envelope (NE) and rough endoplasmic reticulum (RER). Cells were identified by this reaction product as resident macrophages. Reaction products from the AcP-ase related cerium (AcP-aseCe), localized in lysosomes have been identified and differentiated from the PO-related osmium containing products. Similarly AS related barium (ASBa), localized in lysosomal structures and (R)ER was identified and differentiated. Triple reaction product localization of PO followed by AcP-ase plus AS could also be obtained. In this case, PO-related platinum containing reaction products (PODAB/Pt or PODAB/Os) in NE and RER has been identified and differentiated from the AcP-ase related lysosomal cerium (AcP-aseCe) and the AS related barium localized in lysosomal and (R)ER structures. Reversing the sequences in both dual cytochemical procedures: AcP-aseCe or ASBa followed by PODAB/Os (or PODAB/Pt) resulted in AcP-aseCe or ASBa activity related reaction products only. Reversing the sequence in the triple reaction procedures (ASBa followed by AcP-aseCe) resulted in the absence of the barium containing reaction products. By application of OsO4 postfixation with aminotriazole (ATR) additives the detrimental effects upon the various precipitates have been confirmed. In LM studies, using rat intestine and non-metal identification reactions for two of the enzymes (pararosaniline for AcP-ase, DAB for peroxidase), the influences of the metal ions used in EM were tested on the appearance of the coloured reaction products. Cerium ions used in EM for detection of AcP-aseCe activity have been shown to influence the PODAB visibility in LM and EM experiments. From the AS reaction media components neither barium ions nor p-nitro catachol sulphate influenced the LM visibility of the PO reaction.

Acid Phosphatase↗
PubMed1989

Immunoelectron microscopic visualization of the transcytosis of low density lipoproteins in perfused rat arteries.

A postembedding labeling technique was employed to visualize human native low density lipoproteins (LDL) during transcytosis in rat arterial endothelium. For this purpose human LDL was perfused through rat vasculature before fixation and processing for immunoelectron microscopy. The LDL particles were located on sections by anti-human apolipoprotein B-100 (LDL) antibodies and secondary antibodies or protein-A conjugated to 10-nm colloidal gold. LDL molecules were seen in plasmalemmal vesicles as well as in the subendothelial space. No colloidal gold was found in the intercellular junctions. Perfusion with reductively methylated LDL, which cannot bind to the LDL receptor, gave a similar labeling pattern, indicating that transcytosis of LDL via plasmalemmal vesicles is most likely receptor independent. Furthermore, the passage of LDL through intact vascular endothelium is a vesicular transport rather than an intercellular diffusion process.

Animals↗
PubMed1988

Biocompatibility of six elastomers in vitro.

The biocompatibility of two silicone rubbers, Silastic and Dow Corning Elastomer, and of a polyether and a polyester urethane, a polyether polyester copolymer, and polypropylene oxide was assessed in vitro. These elastomers were selected for assessment as a possible alloplastic tympanic membrane. For these studies use was made of rat middle ear mucosa explants and serially cultured epithelium. The quantitative results were based on epithelial growth curves, the morphological picture was based on the findings in epithelium, and the aging of a biomaterial was simulated. Epithelium morphology was investigated by scanning and transmission electron microscopy and x-ray microanalysis. Quantitative results showed that on Dow Corning Elastomer and polypropylene oxide, cell proliferation was significantly lower compared to normal growth curves. The morphological findings were negative for polypropylene oxide, and did not discriminate between the other biomaterials under study. The simulation results indicated better biocompatibility for the polyurethanes and the polyether polyester copolymer compared with that of polypropylene oxide and both silicone rubbers. Under the simulation conditions, cells exposed to Silastic showed silicon-containing inclusions. These in vitro results suggest that the biocompatibility of the polyurethanes and the polyether polyester copolymer is better than that of both silicone rubbers and polypropylene oxide.

Animals↗
PubMed1987

Cell surface characteristics and DNA content of macrophages in murine bone marrow cultures. A study using simultaneous scanning electron microscopy and fluorescence microscopy.

An instrument combining scanning electron microscopy (SEM) and light microscopy (LM) was used to study the cell surface characteristics and DNA content of macrophages in murine bone marrow cultures. After a quantitative Feulgen DNA staining, the DNA content of the individual macrophages was measured and their cell surface morphology was studied immediately thereafter with the SEM part of the instrument. The cells were divided into six groups according to the number of microvilli and/or microridges present on their surface. A proportion of macrophages showed a DNA content more than occurs in diploid cells, which could indicate a future division. No special surface morphology could be detected in this cell type.

Animals↗
PubMed1986

The biological performance of calcium phosphate ceramics in an infected implantation site: I. Biological performance of hydroxyapatite during Staphylococcus aureus infection.

In the present study the biological performance of macroporous and dense hydroxyapatite after implantation in the rat middle ear was evaluated during an induced Staphylococcus aureus middle ear infection. The course of the infection was similar to that in the absence of an implant. Hydroxyapatite was frequently integrated with fibrous ingrowths in the middle ear lumen, originating solely from the infection. Good epithelial covering of the implant with all types of epithelial cells of importance for middle ear defence, was found. Increase of the exudate in the pores due to the infection was relatively small, and most of the exudate was restricted to pores on the implant surface. The bony tissue in the pores was not influenced significantly by the induced infection. Degradation of hydroxyapatite was consistent with earlier results obtained in the non-infected middle ear. The results obtained so far suggest that hydroxyapatite is highly suitable for middle ear implantation.

Animals↗
PubMed1986

The biological performance of calcium phosphate ceramics in an infected implantation site: II. Biological evaluation of hydroxyapatite during short-term infection.

Macroporous hydroxyapatite was implanted submucosally in the rat middle ear and studied after intratympanic injection of a Staphylococcus aureus suspension. The middle ear infection was induced 1 week after the implantation, and the effects of infection on the middle ear and the implant material were evaluated after 1, 3, 7, and 14 days by light and electron microscopy. The findings in the infected middle ear with an implant corresponded well with those described for the infected middle ear cavity without an implant. The reactions of the tissue over the implant were similar to those of the original mucosa of the middle ear. Bone was deposited on the implant and in its pores in relatively large quantities. Biodegradation, due at least partially to phagocytic activity of macrophages and multinucleated cells, was more prominent than previously found. This higher degree of biodegradation may be attributed to the use of the mucosal implantation technique, because this was the only point of divergence with respect to material or methods from earlier work reported by our group. The present results, together with those published earlier, suggest that this material has promising features for use as a bone substitute in reconstructive middle ear surgery. Definitive conclusions on biological performance and biofunctionality will, however, have to await long term clinical trials.

Animals↗
PubMed1986

Ultrastructural localization of peroxidase activity in developing neutrophil granulocytes from human bone marrow.

Developing neutrophil granulocytes of normal human bone marrow were investigated with the diaminobenzidine technique to determine the ultrastructural localization of peroxidase activity. Neutrophil granulocytes have three types of granule: nucleated, azurophil, and specific granules. These granules are produced consecutively during the eomyelocyte stage, the promyelocyte stage, and the myelocyte stage, respectively. The organelles involved in the production of granules, i.e., the nuclear envelope, rough endoplasmic reticulum, and Golgi apparatus, are peroxidase positive during the eomyelocyte and promyelocyte stages and peroxidase negative thereafter. This pattern differs for the granules themselves: nucleated granules are negative in the eomyelocyte and become positive in the promyelocyte. Azurophil granules become positive in the promyelocyte. Specific granules are negative. Our observations highly suggest that small Golgi-derived peroxidase-positive vesicles are involved in the maturation of both nucleated granules and azurophil granules.

Bone Marrow Cells↗
PubMed1986

Pt-staining of peroxidatic reaction products at the ultrastructural level.

The use of H2PtCl6 is proposed for the selective visualization of the poly-DAB reaction product created, in aldehyde-fixed tissue, with the cytochemical reaction according to Graham and Karnovsky (1966) or to Hoefsmit (1975). At sites known to contain peroxidatic activity, at the ultrastructural level, an electron-dense reaction product is acquired in otherwise unstained ultrathin sections. The presence of the element platinum in these sites has been demonstrated by X-ray microanalysis, for both the endogenous peroxidase and peroxidase conjugated to antibodies. The absolute platinum concentration has been established in erythrocytes and the granules in eosinophils and monocytes by co-embedded, Pt-containing Chelex ion-exchange beads next to the cells. By the application of the method of integrated morphometrical and chemical analysis (de Bruijn and Zeelen 1984; de Bruijn 1985; de Bruijn and Cleton 1985), both the elemental concentration and the area occupied have been calculated for eosinophil granules. The mean Pt net-intensity values of the cytoplasmic areas, known not to contain the enzyme peroxidase has been measured, and compared to the mean net-intensity Pt values of the granules. It was noted that the cytoplasmic Pt net-intensity values were not zero. The two sets of values are expressed as a mean Pt granule/cytoplasm ratio, this ratio creates a value for the "selectivity" of the reaction. The application of a postfixation reaction with OsO4- containing media, at pH 7.4, in addition to the H2PtCl6 reaction, resulted in a contrasted poly-DAB reaction product at all sites known to contain peroxidatic activity. However, X-ray microanalysis revealed that in addition to platinum, osmium was present.(ABSTRACT TRUNCATED AT 250 WORDS)

3,3'-Diaminobenzidine↗
PubMed1986

DNA measurements of cervical epithelial cells in combination with scanning electron microscopy.

A method is described in which the surface morphology of benign and malignant cervical cells is investigated with a combined light microscope-scanning electron microscope, after the measurement of the DNA content of each individual cell in the same instrument. The suspect cells can thus be identified by an increased aneuploid DNA content (greater than 5C) and not primarily by morphology. The DNA content was measured, after a quantitative acriflavine-Feulgen staining, by using a microphotometer attached to the combined microscope. It was found that the suspect cells show a different surface morphology compared to normal cells from a benign specimen.

Aneuploidy↗
PubMed1986

Macropore tissue ingrowth: a quantitative and qualitative study on hydroxyapatite ceramic.

The aim of this study was to obtain more information about macropore tissue ingrowth into the pores of sintered hydroxyapatite implanted in the rat middle ear, for the assessment of the usefulness of this material in reconstructive middle-ear surgery. The exudate filing the pores during the early post-operative period was gradually replaced by equal amounts of fibrous tissue and bone. The percentage of the macropore area occupied by bone was directly correlated with the macropore size. Bone was deposited not only from the pore wall towards the pore centre, but also in the opposite direction. Bonding osteogenesis was demonstrated. At sites of mechanical irritation, the presence of multinucleated cells and proliferatively active mononuclear phagocytes persisted for as long as a year. Under appropriate conditions hydroxyapatite seems to be a promising material for bone substitution in reconstructive middle-ear surgery.

Animals↗
PubMed1986

Quantitative DNA measurements in an instrument combining scanning electron microscopy and light microscopy.

An instrument for combined scanning electron microscopy (SEM) and light microscopy (LM) to which a photometer unit is attached is described. A special stage in the vacuum chamber of a scanning electron microscope incorporates light microscope optics (objective and condenser) designed for transmission and epi-illumination fluorescence LM. An optical bridge connects these optics to a light microscope, without objective and condenser. The possibility of performing quantitative DNA measurements in this combined microscope (the LM/SEM) was tested using preparations of either chicken erythrocytes, human lymphocytes, or mouse liver cells. The cells were fixed, brought on a cover-glass, quantitatively stained for DNA, dehydrated, and critical point dried (CPD). After mounting the cells were coated with gold. The specimens were brought into the vacuum chamber of the combined microscope and individual cells were studied with SEM and LM. Simultaneously DNA measurements were performed by means of the photometer unit attached to the microscope. It is shown in this study that DNA measurements of cells in the combined microscope give similar results when compared to DNA measurements of embedded cells performed with a conventional fluorescence microscope. Furthermore, it is shown that although the gold layer covering the LM/SEM specimens weakens the fluorescence signal, it does not interfere with the DNA measurements.

Animals↗
PubMed1986

The endocytosis of asbestos by mouse peritoneal macrophages and its long-term effect on iron accumulation and labyrinth formation.

The effect of a single intraperitoneal injection of crocidolite asbestos fibres on the peritoneal cell population were studied. Attention was paid to the changes in the proportions taken by the various types of cell in this population after peritoneal stimulation as well as the handling of asbestos fibres by the peritoneal cells and the formation of asbestos bodies. Intraperitoneal administration of crocidolite led to an influx of inflammatory cells into the peritoneal cavity. The asbestos fibres were phagocytosed and gradually cleared from the peritoneal cavity. Long before this clearance was completed, the peritoneal cell population had returned to the steady state. The stimulated peritoneal macrophages showed increasing concentrations of iron in both lysosomes and the cytoplasm. At later time points, residual bodies containing iron and asbestos fibres were seen frequently in macrophages, but asbestos bodies were not found. As a reaction to the administration of crocidolite asbestos, macrophages from the peritoneal cavity develop tubular systems (labyrinths) that increase in number and size.

Animals↗