Torgeir Vegge

An epithelial blood-aqueous barrier to horseradish peroxidase in the ciliary processes of the vervet monkey (Cercopithecus aethiops).

SummaryVervet monkeys were given horseradish peroxidase intravenously. Subsequent studies with the electron microscope showed:1.The peroxidase molecules penetrated the capillary walls of the ciliary processes and “filled” the stroma and the intercellular spaces as far as the basal junctional complex of the superficial epithelial cells.2.The ciliary channels filled rapidly with peroxidase molecules.3.No peroxidase penetrated beyond the basal junctional complex of the superficial cells.

Electron microscopy of the trabecular meshwork in eyes with exfoliation syndrome (pseudoexfoliation of the lens capsule)

The trabecular meshwork of three human eyes involved with the exfoliation syndrome were studied. The intraocular tension in the eyes represented successive stages. Exfoliation material was found in all three eyes: In Eye 1 (no glaucoma) only in intertrabecular spaces, in Eyes 2 and 3 also within trabecular beams and in the juxtacanalicular tissue. In addition, abnormal basement membranes were revealed. In Eye 3 (uncontrollable glaucoma), the disorganized trabecular meshwork contained increased amounts of connective tissue elements as well as small vessels. The concept is advanced that the accumulation of exfoliation material in the meshwork impedes aqueous outflow and thus is a pathogenetic factor of importance in glaucoma capsulare.

Ultrastructure of the wall of human iris vessels

Summary1.The walls of iris vessels in five human eyes were studied.2.No fenestrae are present in capillary endothelium.3.A several thousand Å thick basement membrane is found in practically all vessels. The basement membrane is often multi-layered and its external limit irregular.4.A distinct zone of thin collagen fibrils is present between the “inner” and “outer tube” in almost all vessels.5.Membrane-bounded, moderately dense bodies about 0.3 μ in diameter are concentrated among the extracellular components of vessel walls.6.Muscular tissue is scanty.7.No elastic fibres are found.

An electron microscopic study of the permeability of iris capillaries to horseradish peroxidase in the vervet monkey (Cercopithecus aethiops)

SummaryAnesthetized vervets were given intravenous injections of horseradish peroxidase. Subsequent studies of iris capillaries with the electron microscope showed peroxidase reaction product within the lumen of the vessels and in endothelial vesicles, but no peroxidase had penetrated the vascular endothelium. The normal ultrastructure of the vascular wall was retained.

A study of the ultrastructure of the small iris vessels in the vervet monkey (Cercopithecus aethiops)

SummaryEyes of vervets were fixed by several methods, and the iris capillaries were studied by electron microscopy.The capillaries have a continuous endothelium without fenestrae. Tight junctions are always present in intercellular clefts of the endothelium, and marginal folds are frequent. A rather thick basement membrane is present, similar to what is found in the human iris. Pericytes are frequent, and specialized areas of membrane contact between endothelium and pericytes are described. Peculiar marginal vacuoles are found in the endothelium after perfusion with hypertonic fixative.

ULTRASTRUCTURE OF NORMAL HUMAN TRABECULAR ENDOTHELIUM1

Despite the numerous investigations carried out on the tissues in the aqueous area and on other subjects related to intrabulbar tension, we still do not know the mechanism or mechanisms of aqueous flow from the anterior chamber into the aqueous veins. The interest of morphologists, as well as of other scientists, in this area is therefore not only still justified, but indeed needed. The trabecular meshwork of the normal human eye as seen with the light microscope was particularly well described by Salzmann (1912). Later, other workers have added to his description. (For references, see Ashton et al., 1956). Early studies on the ultrastructure of the tissues of the anterior chamber angle are those of Garron, Feeney, Hogan and McEwen (1958), Garron and Feeney (1959) and Holmberg (1959). None of these papers deal with the details of endothelial cells. Recently, Spelsberg and Chapman (1962) presented important new information on the ultrastructure of the trabecular meshwork (based on the findings in one eye), including the fine structure of the endothelial cell cytoplasm. For details, see below. The present paper confirms some of the findings of earlier authors and gives additional information on the endothelial cells. A preliminary report has been given previously (Vegge, 1963).

Vascular reactions to horseradish peroxidase in the guinea pig.

SummaryAlbino guinea pigs were given intradermal injections of the protein tracer horseradish peroxidase. In a 0.1 mM concentration the tracer did not increase vascular permeability to Evans blue-labelled plasma proteins. In a 1 mM concentration, however, the peroxidase induced a local vascular leakage. This leakage was almost totally inhibited by pretreating the animals with acetylsalicylic acid, while antihistamine had only a weak inhibitory effect. We therefore believe that prostaglandins are important mediators in this HRP-induced vascular reaction.

The fine structure of the trabeculum cribriforme and the inner wall of Schlemm's canal in the normal human eye

SummaryThe tissue in the area of the inner wall of Schlemms canal was examined in four human eyes.1.Flocculent material was found within some of the giant cytoplasmic vacuoles of the Schlemm canal endothelium.2.In a few cases, gaps were seen in the endothelial lining of the inner wall. In each case, a non-endothelial cell was interposed in the gap.3.Collagen fibrils with regular periodicity was found immediately beneath the inner wall endothelium.4.Erythrocytes were observed in the cribriform area among the extracellular tissue components.5.The extracellular compartment of the cribriform area is continuous with the cores of the corneoscleral trabeculae.

Horseradish peroxidase in plasma studied by gel filtration

SummaryThe problem whether the molecular size of horseradish peroxidase is significantly altered when the enzyme is injected into the blood stream in tracer studies, has been studied by molecular sieve chromatography (gel filtration). The results obtained rule out the possibility that the horseradish peroxidase molecule (containing about 20% carbohydrates) is significantly degraded by carbohydrate-splitting enzymes or by proteases in the circulation into a smaller active unit. Furthermore, significant binding of peroxidase to plasma proteins or polymerization of the enzyme, has not been detected. It is concluded, therefore, that conclusions about the size of functional pores based on the known molecular weight (40000 daltons) are permitted, when the enzyme is used in permeability studies.

Ultrastructure and distribution of intercellular junctions in corneal endothelium.

The intercellular junctions of the corneal endothelium has been studied in rabbit, monkey and human eyes. A union of apposing outer leaflets (tight junction) is usually found near the apical end of the intercellular clefts. However, evidence from lanthanum tracer studies indicates that the tight junctions do not seal the intercellular clefts completely. In addition to tight junctions, the presence of gap junctions or nexuses is demonstrated in all three species studied.