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Biomedical subjects

H F Edelhauser

Publications and source records attributed to H F Edelhauser.

At least 19 recordsLinked to original sources
PubMed1992

Corneal endothelial cytoskeletal changes in F-actin with aging, diabetes, and after cytochalasin exposure.

We investigated the changes in endothelial cytoskeletal F-actin that occur with aging, diabetes, and exposure to cytochalasin D. Rabbit corneas, human donor corneas (with or without polymegethism), and corneas of diabetic individuals were studied. Endothelial F-actin was stained using nitrobenzoxadiazole-phallacidin. Results of these experiments demonstrated that F-actin of the rabbit and human corneal endothelium was arranged in linear circumferential strands that formed a hexagonal array. After in vitro perfusion of cytochalasin D to the corneal endothelium, the F-actin became randomly distributed throughout the cytoplasm, the hexagonal shape of the endothelial cell was disrupted, and endothelial permeability to carboxyfluorescein increased. Changes in F-actin were also observed in the endothelium of the human corneas with polymegethism, and in donor tissue having had previous posterior chamber intraocular lens implantation. The corneas of diabetic individuals also showed marked irregular F-actin fibers crossing the endothelial cell cytoplasm. These abnormal patterns of F-actin may contribute in part to the polymegethism observed in the corneal endothelial cells and may be the result of constant stress in cell volume regulation, particularly in the corneas of diabetic individuals.

Actins↗
PubMed1992

Correlation of histologic corneal endothelial cell counts with specular microscopic cell density.

The central endothelia of 48 eye bank corneas from donors ranging in age from 5 weeks to 88 years were photographed using in vitro specular microscopy. Computer-assisted morphometric analysis of the size and shape of endothelial cells was performed, and cell density was calculated. Histologic examination of the corneas after specular microscopy determined endothelial cell counts using x40 objective magnification. The mean endothelial cell counts from five different high-power fields were calculated. Results showed that there is a direct correlation between cell number and specular microscopy cell density (r = .91 and Spearman rank correlation, 0.69; both significant at P less than .01). A nomogram was developed to estimate corneal endothelial cell density from high-power field cell counts of pathologic specimens.

Adolescent↗
PubMed1992

Sodium activity in the aqueous humor and corneal stroma of the rabbit.

The present study examined the free sodium concentration of the aqueous humor and corneal stroma of both transparent and non-transparent corneas to assess the transendothelial activity gradient for sodium. In the transparent cornea of the adult rabbit, the sodium activity was higher in the aqueous humor than the stroma. This difference in sodium activity would cause water to diffuse down its concentration gradient from stroma to aqueous humor. In this way corneal transparency and the deturgesced state are maintained. Removal of the corneal endothelium in the adult rabbit produced an opaque swollen cornea. Under these conditions the sodium activity was higher in the stroma than the aqueous humor. However, an osmotic gradient was not produced by the Na+ activity gradient because the endothelium was not present to act as a semi-permeable membrane. The corneal endothelium was no longer present to establish and sustain the activity gradient for sodium that is necessary for corneal transparency in the mature rabbit. The transendothelial sodium activity gradient was also measured in 13-day-old rabbits. At this age, the cornea was not yet transparent, nevertheless the free sodium concentration of the aqueous humor was higher than that of the stroma, similar to the adult transparent cornea. This suggests that forces other than the establishment of the proper transendothelial sodium gradient are responsible for the lack of corneal transparency in the young rabbit.

Animals↗
PubMed1992

Comparison of corneal preservation media for corneal hydration and stromal proteoglycan loss.

Changes in the composition of stromal proteoglycans (PGs) have been previously demonstrated in corneal edema, wound healing, and disease. To examine if PGs are lost during corneal preservation, rabbit corneal PGs were radiolabeled in situ with 35S-sulfate and 3H-glucosamine, excised and stored in either modified McCarey-Kaufman medium (MMK), K-Sol (Coopervision-Cilco, Bellevue, WA, U.S.A.), corneal storage medium (CSM), or Dexsol (Chiron Ophthalmics, Irvine, CA, U.S.A.) for up to 14 days. The percentage of total radio-label lost was significantly greater from de-epithelialized corneas (p less than 0.05) and from corneas stored in CSM (p less than 0.05) or K-Sol (p less than 0.05). Corneas stored in CSM for 4 and 7 days were significantly more hydrated than corneas stored in MMK, K-Sol, or Dexsol. After 14 days of storage, all corneas were hydrated above control values with the Dexsol-stored cornea showing the least hydration. Results suggest that loss of stromal PGs during corneal storage is reduced with epithelial integrity and with preservation media containing dextran.

Animals↗
PubMed1991

The developing corneal endothelium: correlation of morphology, hydration and Na/K ATPase pump site density.

The physiology and anatomy of the cornea of the New Zealand white rabbit were studied from birth to young adulthood (3 months). The main objective of the study was to follow the ontogeny of the corneal endothelium and correlate its maturation with the establishment of stromal transparency. With maturity, central corneal thickness increases as do corneal diameter and surface area. Endothelial morphology undergoes marked changes including an increase in cell hexagonality and cell surface area, along with a decrease in cell density and coefficient of variation of cell area. Corneal hydration decreases from a high value at birth to the adult level by 20 days after birth, the time of the onset of stromal transparency. By transmission electron microscopy, corneas of newborn rabbits exhibit an endothelium of irregular cell height with some overlap at the bases of adjacent cells. Apical junctions are incomplete in the neonates. With time the endothelium thins and cells becomes more regular in height, overlap of adjacent cells diminishes, and apical junctions develop. Descemet's membrane is thin in newborns and thickens and becomes more homogenous in appearance with maturation. The abundance of Na/K ATPase pump sites per endothelial cell, as determined by 3H-ouabain binding, increases progressively with age even after the establishment of corneal transparency at 20 days. Scatchard and LIGAND analyses of 3H-ouabain binding data indicate that there is a progressive increase in Bmax with no change in the KD from 7 days to 3 months.

Age Factors↗
PubMed1990

Toxic effects of detergents on the corneal endothelium.

Eighteen patients developed a toxic endothelial cell destruction syndrome following normal intraocular surgery, caused by a detergent residue originating from irrigating cannulas. The residue occurred after the concentration of a detergent solution has been increased from 0.4% to 4%, in combination with insufficient cleaning of the cannulas. Mass spectrometric analysis revealed the detergent to contain a nonionic ethoxylated fatty alcohol (6% vol/vol). Quantitative endothelial vital staining and in vitro corneal endothelial perfusion demonstrated endothelial toxic effects at the 1% and 0.06% level for the detergent and the pure ethoxylated fatty alcohol, respectively. Permeability studies showed that the toxic effects occurred as a result of endothelial barrier breakdown.

Chemical Phenomena↗
PubMed1979

The effect of phenylephrine on the cornea.

Rabbit corneas were treated with three drops of phenylephrine hydrochloride with the epithelium intact or denuded. Corneal thickness was measured before and after drug treatment, and at various times after treatment the corneas were fixed for scanning and transmission electron microscopic observation. The results of this study show that phenylephrine caused a dramatic increase in corneal thickness (drug-induced edema) and cellular vacuolation within the keratocytes and endothelial cells in the corneas without the epithelium. Corneal thickness did not change and the ultrastructural changes were minimal following drug application in those corneas with the epithelium intact. Results of this study also suggest that phenylephrine has a cytotoxic effect on the corneal endothelium and keratocytes when used in corneas where the epithelium has been removed. In coreas with intact epithelium, the damage was less severe and limited to the epithelium.

Animals↗
PubMed1979

The pH tolerance of rabbit and human corneal endothelium.

The endotheliums of rabbit corneas were perfused in an in vitro perfusion specular microscope up to 3 hr with solutions varying in pH from 3.5 to 10.0. Corneal thickness was monitored throughout the experiment, and at appropriate times the corneas were prepared for SEM and TEM. Analysis of the corneal thickness data and interpretation of the electron micrographs reveals that outside of the pH range of 6.5 to 8.5, structural and functional alterations occur. Direct cellular damage, as well as disruption of junctional complexes, lead to a breakdown in the barrier function of the corneal endothelium. The extent of this breakdown is dependent upon both the magnitude of the pH change and the exposure time. Further experiments on banked human eyes support this finding.

Aged↗
PubMed1979

Effect of phenylephrine on normal and regenerated endothelial cells in cat cornea.

Topical commercial phenylephrine HCl (Neo-Synephrine 10%) has been shown to cause an increase in corneal thickness and reversible vacuolization of corneal endothelial cells in rabbits. Using an in vivo model of regenerated corneal endothelial cells in the cat, we compared the cytotoxicity of phenylephrine-HCl 10% to regenerated and to normal, nonregenerated cells. Following removal of the epithelium, topical application of the drug causes the appearance of anterior and posterior bands of stromal edema and reversible vacuolization in both normal and regenerated endothelial cells. Phenylephrine was not more damaging to the regenerated cells. Polymorphonuclear leukocytes infiltrated between the regenerating cells 24 hr after treatment but did not appear to destroy them. Phenylephrine may therefore be implicated as a causative factor of corneal edema and postoperative inflammation.

Animals↗
PubMed1978

The pentose phosphate pathway in developing chick cornea.

Embryonic chick corneas at different stages of development were evaluated for activity of the pentose phosphate pathway. The appearance of activity was concurrent with the onset of corneal transperancy (stage 40). Highest values were found after complete transparency is achieved (stage 45 and after hatching). Phenazine methosulfate, an artificial electron acceptor, increased activity at all stages studied even before endogenous activity was measurable; however, no increase in glucose uptake was observed. Thus, the enzymes for the pathway are present at early stages (i.e., stage 38 and 40) although in latent form. The pathway probably functions in the developing cornea to generate NADPH rather than sugar moieties for macromolecular incorporation.

Age Factors↗
PubMed1978

Intraocular sulfur hexafluoride and octofluorocyclobutane. Effects on intraocular pressure and vitreous volume.

Partial vitrectomies were performed on rabbits and the amount of vitreous removed was replaced with either 100% sulfur hexafluoride (SF6), 100% octofluorocyclobutane (freon-C318), 40% SF6, or air. Intraocular pressure and vitreous volume were determined. Replacing 40% of the initial vitreous volume with either 100% SF6 or 100% octofluorocyclobutane caused an increase over 20 mm Hg in the IOP with an associated loss of the remaining vitreous, whereas replacement with 40% SF6 or air caused no significant increase in IOP. Replacement with 40% SF6 caused a significant loss of the remaining vitreous, whereas the air replacement did not result in a vitreous loss. The experiments were repeated substituting only 20% of initial vitreous volume with 100% SF6 and 100% octofluorocyclobutane. Using this amount of SF6 and octofluorocyclobutane, the IOP did not increase but an associated vitreous loss occurred equal to twice the amount of SF6 injected and three times the amount of octofluorocyclobutane injected.

Air↗
PubMed1978

Intraocular irrigating solutions. A comparative study of BSS Plus and lactated Ringer's solution.

Isolated human corneas maintained normal corneal thickness and endothelial ultrastructural integrity throughout a three-to four-hour period of perfusion of BSS plus to the endothelial surface. By comparison, only one of six human corneas perfused with lactated Ringer's solution was able to maintain normal thickness and ultrastructural integrity. The other five corneas perfused with lactated Ringer's solution showed various degrees of endothelial cell breakdown and corneal swelling during three hours of perfusion. The results of these studies suggest that BSS plus is a better solution for maintenance of human corneal endothelium during long-term (one- to three-hour) surgical procedures.

Cornea↗
PubMed1978

Endothelial degeneration and posterior collagenous proliferation in aphakic bullous keratopathy.

In series of 39 corneal grafts, aphakic bullous keratopathy comprised 13 (33%) of the cases. By scanning and transmission electron microscopy, endothelial degeneration and posterior collagenous proliferation were consistent features. In all 13 cases, the patchy loss of endothelial cells occurred diffusely over the entire posterior corneal surface. The remaining endothelial cells had become extremely attenuated to increase their surface area. In nine cases, acellular proliferations of collagenous tissue were interposed between the endothelial cells and Descemet's membrane. These posterior collagenous layers were composed of collagen fibrils and basement membrane material, randomly arrayed in a feltwork of uniform thickness; they appeared ultrastructurally identical to those encountered in a variety of conditions involving endothelial distress.

Aphakia, Postcataract↗
PubMed1978

Glutathione in rabbit corneal endothelia: the effects of selected perfusion fluids.

Although the ameliorating effect of glutathione on corneal deturgescence is known, its chemical mechanism is not understood. An endeavor toward the latter was made by perfusing freshly excised rabbit corneas with selected perfusion fluids, measuring corneal thickness, and assaying the endothelial cells for reduced and oxidized glutathione after 2 and 5 hr of perfusion. Ringer's solution, containing either lactate or bicarbonate, caused significant decreases in both forms of glutathione after perfusion. The corneas increased in thickness considerably during these periods. When 5 mM glucose was added to bicarbonate-Ringer's solution, the corneas swelled about half as much as before. However, glutathione levels were as depressed as with simple Ringer's fluid. Adenosine (0.5 mM) in the presence of glucose (bicarbonate-Ringer's) caused a further swelling decrease so that the corneas were maintained at near normal thickness. The levels of glutathione were 84% of control values compared to 35% to 45% for Ringer's solutions (+/- glucose). The addition of glutathione to glucose (bicarbonate-Ringer's) caused intracellular glutathione levels to be higher than control values while allowing minimal tissue swelling. Glutathione in combination with adenosine, glucose, and bicarbonate produced the highest intracellular glutathione levels and a slight corneal deswelling. After oxidation of intracellular glutathione with t-butyl hydroperoxide in glucose (bicarbonate-Ringer's), endothelial cells were destroyed within 1 hr. The oxidant, however, may have had a direct effect upon the endothelial cell membranes.

Adenosine↗
PubMed1977

The corneal penetration of trifluorothymidine, adenine arabinoside, and idoxuridine: a comparative study.

Trifluorothymidine (F3TdR) and idoxuridine (IDU) were observed to penetrate through the cornea from the epithelial side at a greater rate than adenine arabinoside (ARA-A) during in vitro corneal perfusions. Removal of the epithelium increased the rate of penetration of F3TdR and IDU by about twofold and the rate of ARA-A penetration by fivefold. The kinetics of antiviral penetration did not display saturation points at high antiviral concentrations, thus indicating that these three antiviral drugs penetrate the cornea by nonfacilitated diffusion. The sole breakdown product detected following F3TdR penetration in vitro, in situ, and in controls was 5 carboxy-2'-deoxyuridine (5-COOH-2'-dUd). The sole breakdown product isolated during ARA-A penetration experiments was hypoxanthine arabinoside (ARA-HX), and control experiments indicated that ARA-A was stable at pH 7.6. IDU was degraded to 2'-deoxyuridine (dUd) in control experiments, but during corneal penetration experiments IDU was degraded to a mixture of dUd and iodouracil (IU).

Animals↗
PubMed1977

Oxygen consumption in the developing chick cornea.

Embryonic chick corneas at different stages of development were evaluated for O2 consumption. Some embryos were treated with thyroxine or thiouracil. In untreated animals, corneal QO2 (oxygen consumption/hr./mg. dry weight) decreased from 3.60 at stage 38 to 1.58 after hatching. The temperature coefficient Q10 increased from 1.55 at stage 40 to 2.03 after hatching. If O2 consumption is calculated as microliters of O2 consumed per hour per corneal pair, it increases between stage 38 (3.20) and hatched chicks (6.20) with a plateau between stages 40 and 45. Thiouracil treatment reduced O2 consumption by the cornea at stages 42 and 45, and thyroxine treatment elevated it at stage 40.

Age Factors↗
PubMed1977

The role of thyroid hormone in the development of the chick corneal endothelium and epithelium.

Previous studies have established that thyroxine or thiouracil treatments affect the development of corneal transparency in the chick. The effects of these drugs on chick corneal epithelial and endothelial development were investigated because in the adult the integrity of these cell layers is necessary for the maintenance of corneal transparency. Chick embryos were treated with thiouracil or thyroxine at stage 36 or 38; the corneas were excised 2 to 12 days after treatment (between stages 38 and 45), and prepared for electron microscopy. The colloidal tracer ruthenium red was added during fixation to study epithelial and endothelial permeability and to stain the intercellular endothelial spaces. At all stages studied, the epithelium was impermeable to ruthenium red and this property was not affected by drug treatment. The epithelial barrier to this tracer is located in the outermost cell layer. The ease of penetration of ruthenium red through the endothelial intercellular spaces indicated the lack of zonular tight functions and the presence of gap functions in this cell layer. Thiouracil treatment delayed the development of the corneal epithelium so that at stage 45 it resembled epithelium from a normal embryo 3 stages younger. In normal animals, chick corneal endothelial development is characterized by an increasing degree of interdigitation of the lateral plasma membranes of adjacent endothelial cells with advancing embryonic age. Thiouracil treatment delayed this progressive development of adjacent cell membrane interdigitation. In contrast, thyroxine treatment accelerated the development of the lateral borders of the endothelial cells. It also appears that thyroid hormone can affect the development of the cell membranes of apposed cells in epithelium as well as the endothelium of the embryonic chick cornea.

Animals↗