Biomedical subjects

I Stokroos

Publications and source records attributed to I Stokroos.

24 records · Page 2Linked to original sources

PubMed1984

Quantitative cement solubility experiments in vivo.

The dissolution and dissolution rate of dental luting cements was measured longitudinally. Cement samples in enamel were placed in a full prosthesis and worn in the mouth for up to 6 months. At given intervals, replicas of the cement surfaces were made and quantified by means of SEM stereographic photographs. With a stereometer the distance between cement surface and original enamel surface can be determined quantitatively. The results show in vivo solubility rates for zinc-phosphate and glass-ionomer cement of about 80 microns week-1 and 2 microns week-1 respectively.

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↗

PubMed1978

Morphology and origin of arachnoid cysts. Scanning and transmission electron microscopy of three cases.

Three surgically removed primary arachnoidal cysts were studied with scanning electron microscopy (SEM) and two of the cases with transmission electron microscopy (TEM). The cells lining the cyst cavity had microvilli at the surface, true cilia were absent. In the cytoplasm multivesicular bodies, many pinocytotic vesicles, some large vacuoles and strands of tonofilaments were prominent features. The cells were interconnected by desmosome-like junctions and were separated from the surrounding tissue by a distinct but sometimes incomplete basal membrane. Based on these findings it is concluded that arachnoid cysts are derived from the outer arachnoid cells (subdural neurothelium), the formation of the cysts being attributabel to secretory capacity of the subdural neurothelium.

Adult↗

PubMed1976

Changes of ventricular ependyma and choroid plexus in experimental hydrocephalus, as observed by scanning electron microscopy.

Hydrocephalus was induced in rats by the injection of silicone oil or kaolin suspension into the cisterna magna. One to 5 weeks later the walls of the lateral ventricles were studied with the scanning electron microscope after killing the animals by perfusion fixation. In contrast to controls, the hydrocephalic animals killed 1 or 2 weeks after injection showed degeneration of ependymal cilia and infestation of the ependymal and choroid plexus surface with reactive cells, which presumably may be identified as Kolmer phagocytic cells by their ultrastructural features as studied by the transmission electron microscope. A coating of debris on the surface of the choroid plexus in the hydrocephalic animals possibly bears upon the ciliary degeneration with consequent deficiency of the clearing effect of ciliary movement. In the longer surviving hydrocephalic animals regeneration of cilia seemed to have occurred.

Animals↗

PubMedDate not supplied

The remineralization of EDTA-treated human dentine.

The remineralization of whole human dentine treated with a neutral EDTA solution was investigated: the treatment periods were 15, 30 and 120 min. From the literature it is known that EDTA removes noncollagenous proteins (NCPs) from dentine powders. In order to extract more phosphoproteins from dentine lesions, in part of this work samples were also treated with 1 M NaCl or 4 M guanidine chloride solutions. All the dentine samples after the treatments mentioned were immersed subsequently in a remineralizing solution without fluoride for 2 weeks and microradiographed. To investigate the effects of fluoride, samples treated with EDTA for 120 min were also remineralized with 2 ppm fluoride in solution. The results presented show that: (1) Measurable remineralization did not occur when fluoride was free in the remineralizing solution. Because remineralization occurred neither at the lesion front nor in the nonmineral part of the surface-softened tissue, presumably the NCPs (inhibitors) of underlying dentine diffused into the tissue during the remineralization period. (2) 2 ppm fluoride caused remineralization at the lesion front. In this case we assume fluoride either acted as nucleating agent or overcame the NCP effects at the lesion front.

Analysis of Variance↗

PubMedDate not supplied

The glycocalyx and stereociliary interconnections of the vestibular sensory epithelia of the guinea pig. A freeze-fracture, low-voltage cryo-SEM, SEM and TEM study.

In this study freeze fracture, low-voltage cryo-SEM, SEM and TEM were used to characterise the glycocalyx and stereociliary interconnections in the hair cell bundle of the vestibular sensory epithelia of the guinea pig. The glycocalyx resembles a shell-like structure separately surrounding each stereocilium and kinocilium over its entire length. The lateral interciliary connections emerge from the glycocalyx layer, forming an extensive extracellular network maintaining the stereocilia as a bundle. These connections are morphologically similar to the glycocalyx, and grossly oriented in the same direction, indicative of a role in the mechanical transduction system. The matrix material around the glycocalyx also appears to be morphologically similar to the glycocalyx, suggesting the glycocalyx to be even more important in the mechanical transduction system. The tip-links are covered with a layer, which is a continuation of the glycocalyx covering the stereocilia.

Animals↗