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Biomedical subjects

J A Oosterbaan

Publications and source records attributed to J A Oosterbaan.

9 recordsLinked to original sources
PubMed1993

Ultrastructural changes of the basement membrane zone in benign lesions of the vocal folds.

The basement membrane zone (BMZ) of the epithelium of the vocal folds was investigated electron microscopically in 10 patients suffering from various benign lesions and in 3 controls. Various defects were observed: a thickening by deposition of electron dense material, a loss of normal architecture, and a near absence of normal hemidesmosomes and anchoring fibers. Beside these previously reported phenomena, many vesicles carrying electron dense material were found near the plasma membrane. The vesicles were observed at various stages of fusion with the plasma membrane, on the other side of which their content was discharged. In the cytoplasm an increase of mitochondria was seen. The amount of condensed chromatin decreased while the nucleoli increased in comparison with the controls. These observations are suggestive of a hyperactivity of the basal cells of the epithelium in response to vibratory stress.

Basement Membrane↗
PubMed1992

Dextran-magnetite particles: contrast-enhanced MRI of blood-brain barrier disruption in a rat model.

Dextran-magnetite particles (DMP) were studied for their use as a MR contrast agent to visualize lesions with a blood-brain barrier (bbb) disruption. A freezing injury to the rat cerebral cortex was used as a model of bbb disruption. The biodistribution of iv-injected DMP was studied using atomic absorption spectrophotometry, electron microscopy, and MRI. One hour after injection, focal accumulation of the particles in capillary endothelial cells could be demonstrated in the freezing lesion. Despite the observation that the relaxivity of DMP in vivo appears to be less well pronounced than that in vitro, the MR imaging studies show that DMP can be used to visualize bbb disruption with adequate contrast.

Animals↗
PubMed1992

[Healing of a deep skin wound using a collagen sponge as dressing in the animal experiment].

The high number of available wound dressing materials as well as the scientific reports about the topic indicates that the problem of an ideal wound dressing is not jet solved. In the last thirty years lot of scientific reports about collagen as wound covering has been published. The positive effect of collagen by his application on a wound ist well known. We investigated the effect of a collagen sponge on healing of full thickness skin wound in guinea pig. The animals were divided in two control groups and two experimental groups. In the control group there were air exposed wounds and another wounds covered with paraffin gauze. In the experimental groups were such wounds covered with natural reconstituted collagen sponge as well as wounds covered with chemically prepared collagen sponge with hexamethyldiisocyanat. The results were compared. The air exposed wounds healed in 50 days, the wounds covered with paraffin gauze healed in 48 days. By covering the wounds with collagen sponge the healing was shortened in 24 or 27 days respectively. Not only the healing time was shortened but also the quality of the wound repair by dressing the wounds with collagen sponge was enhanced.

Animals↗
PubMed1991

[Comparative animal experiment studies of the effect of exogenous collagen on healing of a deep skin wound].

The high number of available wound dressings as well as the scientific reports about this topic indicates that the problem of an ideal wound dressing material is not jet solved. In the last 30 years lot of scientific reports about collagen as wound covering has been published. The positive effect of collagen by this application on a wound is well-known. We investigated the effect of a collagen sponge on healing of full thickness wound in rats. The animals were divided in two control and two experimental groups. In the control groups there were air exposed wounds as well as wounds covered with paraffin gauze. In the experimental groups the wounds were covered with natural reconstituted collagen sponge as well as with chemically prepared sponge. All results were compared. The wounds with collagen sponge covering healed significantly faster. Also the quality of the wound healing was better in the experimental groups.

Animals↗
PubMed1989

Improved Epon embedding for biomaterials.

To obtain improved transmission electron microscopy sections for cell biological and interface evaluation of implanted biomaterials we present an improved embedding procedure. Standard problems in preparation and sectioning, like dissolution of the biomaterial, or holes and chatter in the sections can be prevented by introducing butyl-2,3-epoxypropylether as an intermedium between the dehydration series and the Epon resin. Most biomaterials were not affected by this chemical agent. The introduction of butyl-2,3-epoxypropylether resulted in completely homogeneous Epon blocks which enabled us to cut 50 nm sections, free of holes and chatter. The biomaterials did not dislodge during the process of sectioning and the cell-polymer interface remained intact for electron microscopical evaluation.

Biocompatible Materials↗
PubMed1988

Biodegradable hollow fibres for the controlled release of drugs.

Biodegradable hollow fibres of poly-L-lactic acid (PLLA) filled with a suspension of the contraceptive hormone levonorgestrel in castor oil were implanted subcutaneously in rats to study the rate of drug release, rate of biodegradation and tissue reaction caused by the implant. The in vivo drug release was compared with the release in vitro using different release media. Fibres, disinfected with alcohol showed a zero-order release, both in vitro and in vivo, for over 6 months. Fibres, either gamma-sterilized or disinfected with alcohol were harvested at time intervals ranging from 1 d to 6 months after implantation. Molecular weights of PLLA, tensile strengths, and remaining amounts of drug were determined as a function of time. The tissue reaction can be described as a very moderate foreign body reaction with the initial presence of macrophages, which are gradually replaced by fibroblasts which form a collagen capsule. Molecular weight determinations of PLLA showed a decrease from an initial Mw of 1.59 X 10(5) to 5.5 X 10(4) in 4 months (after alcohol sterilization). A gradual decrease in fibre strength with time was observed which did not significantly impair the release rate of levonorgestrel.

Animals↗
PubMed1983

Influence of radial TEM distortion on the accuracy of lattice parameter determinations of apatites: a comparison of four electron microscopes.

Lattice fringe distances of synthetic hydroxyapatite were measured quantitatively in four different TEM microscopes as a function of the position with respect to the optical axis. Using the accurately known "a" value of this apatite from X-ray diffraction, the maximum radial distortion in the image planes can be determined in various positions. For the Philips EM 400, EM 300 (1) and EM 300 (2) and JEOL 200 CX the maximum radial distortion was found to be 1.0%, 0.8%, 1.5% and 0.5%, respectively. In accurate lattice parameter determinations of mineral and mineral phases in biological tissues by means of TEM; this radial distortion is an important parameter to take into account.

Crystallography↗