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Biomedical subjects

A Ringvold

Publications and source records attributed to A Ringvold.

At least 91 records · Page 5Linked to original sources
PubMed1980

Demonstration of a diffusional pathway between the subretinal space and the juxtapapillary connective tissue. An in vitro experiment using horseradish peroxidase as a tracer.

A defect in the blood-retina barrier in the optic nerve head region has been demonstrated. In order to show the exact localization of this defect, an in vitro experiment has been performed on rabbit eyes, using horseradish peroxidase as a tracer. From a subretinal depot the tracer diffused between the innermost retinal pigment epithelial cell and the cells of Kuhnt intermediary tissue into the border tissue of Elschnig and the juxtapapillary choroid. The defect in the permeability barrier is thus located to the junction between the retinal pigment epithelium and the Kuhnt intermediary tissue. The role of the junctional complexes in the Kuhnt intermediary tissue in relation to the blood-retina barrier is discussed.

Animals↗
PubMed1979

Choroidal fluorescein angiography in rabbit.

The extreme permeability of the choriocapillaris to sodium fluorescein makes angiography with this tracer unsuitable to show the choroidal vascular bed. In order to prevent this profuse leakage, the choroidal circulation is visualized with fundus angiography after injection of fluorescein isothiocyanate (FITC) labelled dextrans of different molecular weight: 20 000, 40 000, 70 000, and 150 000. It is shown that the two first dextrans leak out of the choriocapillaris rather rapidly, whereas the last two dextrans remain intravascularly long enough to enable good demonstration of choroidal vessels. The practical application of these findings is discussed, and it is concluded that the dextran with molecular weight 70 000 should be preferred for use in humans.

Animals↗
PubMed1979

Villous processes from the inner segments of cones in the human macula lutea.

The cones of the human macula lutea were examined by scanning electron microscopy. It was found that each inner segment had about 15 thread-like processes which projected from the cell surface. They were arranged in a longitudinal straight line along the photoreceptor, and were directed away from or towards the fovea contralis. The villous processes may be analogous with the lateral fins of the inner segments of certain vertebrates. They may perhaps bridge the space between neighbouring photoreceptors and may establish contact and interaction between them.

Adult↗
PubMed1978

A study on the postulated transoptic regulation of the intraocular pressure.

The possibility that fibers regulating the intraocular pressure originate in the hypothalamus and course in the optic nerve, has been investigated in albino rabbits with different techniques. By means of horseradish perixodase tracing-technique, oculohypothalamic but no hypothalamoocular connections were observed. The water-loading effect on the intraocular pressure was studied after unilateral optic nerve transection. The transection was performed in three experimental groups in the following way: Intracranial transection of one optic nerve, retrobulbar transection of one optic nerve and sham operation on the other side, retrobulbar transection of one optic nerve without sham operation on the other side. In contrast to previous reports, we found no significant side difference in intraocular pressure after water-loading in any of these groups.

Animals↗
PubMed1978

Actin filaments in trabecular endothelial cells in eyes of the vervet monkey. (Cercopithecus aethiops).

An electron microscopic study was performed on the trabecular meshwork of two monkeys (cercopithecus aethiops). Specimens from one animal revealed numerous cytoplasmic filaments of 45-65 A thickness in endothelial cells both on the trabeculae in the wall of Schlemm's canal after conventional glutaraldehyde and osmium fixation. Using a histochemical technique it was shown in specimens from the other animal that these filaments consist of actin material. This evidence of intracellular actin filaments in the trabecular endothelium indicates that these cells have contractile properties, and the possible significance of this finding for the regulation of outflow facility of aqueous humour is suggested.

Actins↗
PubMed1977

The ciliary body and the suspension of the lens in a monkey (Cercopithecus aethiops). A scanning electron microscopic study.

The zonules of Zinn and their insertion on the ciliary body and the lens in a monkey (Cercopithecus aethiops) have been studied with the scanning electron microscope. The specimens were dissected after drying by the critical point method, and the lens was separated from the ciliary body by simple traction. The pars plana was completely covered by a mat which consisted of meridionally directed zonule-like fibers. Most of these fibers inserted at the base of the posterior end of the ciliary processes, and some of them radiated into the valleys between the processes. About two fibers for each process split off from the mat and became attached to the sides of the processes near their posterior ends. The true zonules spanned from the sides of the processes to the pre- and post-equatorial region of the lens. They were clearly separated into an anterior and a posterior row with no fibers crossing over from one row to the other. Usually four true zonules joined each process, i.e. one zonule of the anterior row and one of the posterior row attached to each side of the single ciliary process.

Animals↗
PubMed1977

Notes on the distribution of pseudo-exfoliation material with particular reference to the uveoscleral route of aqueous humour.

The distribution of pseudo-exfoliation material along the uveoscleral route of aqueous humour has been studied by electron microscopy. It turned out that such material is present only in the very first part of this exit pathway, i.e. in the innermost zone of the connective tissue bordering the anterior chamber angle. No pseudo-exfoliation material was observed between the ciliary muscle cells, in the suprachoroidal space or in the sclera. It is concluded that transport of pseudo-exfoliation material by flow of aqueous humour through the uveoscleral route to the bulbar and palpebral conjunctiva is improbable, and accordingly the pseudo-exfoliation material found in extrascleral tissue most likely arises in loco.

Aged↗
PubMed1975

Distribution of ascorbic acid in the ciliary body of albino rabbit, guinea pig and rat.

The distribution of ascorbic acid in the ciliary body has been demonstrated by means of a silver nitrate technique. It appeared that the basal cells in the pars plana region and in the valleys between the ciliary processes contain great amounts of ascorbic acid, in contrast to the basal cells over the processes proper which showed only traces. Rabbit and guinea pig revealed mainly the same findings, and quantitative differences occurred before and after intracardial injection of ascorbic acid. On the other hand, ascorbic acid was absent in the ciliary body of untreated rats, whereas only traces were found after intracardial injection of this substance. These species differences are in keeping with previous reports showing high concentration of ascorbic acid in the aqueous humour from rabbit/guinea pig, and no ascorbic acid at all in aqueous humour from rats.

Animals↗