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Biomedical subjects

A M Tonjum

Publications and source records attributed to A M Tonjum.

At least 19 recordsLinked to original sources
PubMed1987

Risk factors for intraoperative complications in 1000 extracapsular cataract cases.

A prospective study of the risk factors in extracapsular surgery was carried out between October 1984 and April 1986. One thousand extracapsular cataract extractions were performed by seven physicians. Decreasing pupil size was the only statistically significant risk factor for vitreous loss (P = 0.0002). Zonular breaks occurred more commonly with pseudoexfoliation syndrome (PX) (P less than 0.0001), with decreasing pupil size (P less than 0.0001), and with one surgeon who used the Simcoe aspirating needle (Storz) exclusively (P = 0.0001). It is acknowledged that it is very difficult to standardize what constitutes a small zonular break; hence, the increase in zonular breaks recorded by this surgeon may have been due only to his using less stringent criteria than the others. Capsule breaks had no significant risk factors at the 0.01 level. High myopia, advanced cataract, glaucoma, advanced age, and diabetes mellitus were not found to be risk factors for vitreous loss, zonular breaks, or capsular breaks.

Adult↗
PubMed1977

Movement of horseradish peroxidase in the cornea, sclera and the anterior uvea.

The anterior chambers of rabbit, monkey and human eyes were perfused with horseradish peroxidase. The perfusion was started immediately after enucleation of the monkey and human eyes, while the rabbit eyes were perfused in situ after the animals had been killed. Comparative results were obtained after 1 h or perfusion and were mainly based on frozen sections. Intensive staining was found in the Descemet's membrane, the sclera and the iridial stroma, considerably more than in the corneal stroma and in the ciliary body base. In the vervet monkey and human eyes only traces of peroxidase reaction products were seen in the stroma of the ciliary body base. The movement of the protein tracer from the anterior chamber into the corneal stroma is probably dependent upon vesicular transport across the corneal endothelium. The Discemet's membrane was interpreted to be more porous than the corneal stroma. A transcorneal and a corneo-scleral movement appeared to be more efficient than the uveo-scleral one, at least in the vervet monkey and the human eyes.

Animals↗
PubMed1977

The permeability of the human ciliary and iridial epithelium to horseradish peroxidase. An in vitro study.

The permeability of the human ciliary epithelium to horseradish peroxidase (PO) has been studied in vitro with the electron microscope. Ciliary body and iris specimens were obtained from freshly enucleated eyes. PO was applied at the stromal side of the epithelium, and was left for 120 min. The movement of PO through the intercellular spaces of the human ciliary epithelium was blocked apically in the lateral intercellular spaces of the non-pigmented epithelial cells, indicating that these cells are girdled by zonulae occludentes. In the iridial epithelium, the same distribution pattern of peroxidase reaction products (PORP) was found, i.e. the progression of PO was blocked apically in the lateral intercellular spaces of the posterior epithelial cells. The study indicates that the human ciliary and iridial epithelium contains a system of zonulae occludentes, which represents a diffusion barrier to high molecular, water soluble substances. This is consistent with previous studies in several species of animals.

Adult↗
PubMed1975

Permeability of rabbit corneal epithelium to horseradish peroxidase after the influence of benzalkonium chloride.

A tight barrier against permeation of horseradish peroxidase into the corneal epithelium exists at the corneal surface adjacent to the tear film. The present light and transmission electron microscopic study reveals that the cationic surfactant, benzalkonium chloride, which is commonly added to eye drops as a preservative, breaks down this barrier. Lysis of the cell membranes was demonstrated, resulting in a leakage of the tracer into and underneath the superficial cells. The grade of cellular destruction caused by benzalkonium chloride was dependent upon the concentration and exposure time of the drug.

Animals↗
PubMed1975

The effect of benzalkonium chloride on the electropotential of the rabbit cornea.

The effect of benzalkonium chloride on the electropotenial of the cornea has been examined. The anterior surface of the in vivo or in vitro cornea was exposed to various concentrations of the surfactant, from 0.005% to 0.02%, for either 1 or 2 min. The initial effect is a hyperpolarization lasting up to 30 sec, followed by a rapid fall in potential difference with a subsequent recovery. The degree of potential difference decrease and the recovery rate was dependent upon both the concentration of the detergent, and the exposure time. There is excellent correlation between the previous anatomical and physiological studies on tracer penetration across the in vivo and in vitro cornea and our present work. The data indicate that benzalkonium chloride acts by breaking down the physiological and anatomical diffusion barrier to solute and solvent which is located in the outer layer of the epithelium.

Animals↗
PubMed1975

Effects of benzalkonium chloride upon the corneal epithelium studied with scanning electron microscopy.

The corneal surface of rabbits and vervet monkeys was studied by means of scanning electron microscopy after the influence of the cationic surfactant, benzalkonium chloride. The concentration of the drug was 0.02% or 0.01% and the exposure time was 2 or 4 min. The corneas treated with the drug had characteristic changes with small holes or more extensive lesions of the superficial cell membranes, and loss of microvilli or microplicae. The damage was considered to be due to the lytic effect of benzalkonium chloride upon the plasma membranes.

Animals↗
PubMed1975

In vitro studies on peroxidase movement in the epithelium of prostaglandin-treated rabbit ciliary bodies.

The movement of horseradish peroxidase (HRP) in the epithelium of isolated rabbit iris/ciliary body preparations, has been studied with the electron microscope. HRP was applied at the stromal side of the epithelium, and was left for 60 and 120 min. The distribution pattern of HRP found in the epithelium of the iridial and ciliary processes is consistent with in vivo studies, i.e. the progression of HRP is blocked at the site of the zonula occludens of the superficial epithelium. The HRP distribution pattern found in the iris epithelium indicates that also the superficial epithelial cells of this epithelium are girdled by zonulae occludentes. Specimens treated with prostaglandins E1, E2, and F2alpha, showed no change in the epithelial distribution pattern of HRP, and the occluding zonules were found to be intact.

Animals↗