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Biomedical subjects

H F Edelhauser

Publications and source records attributed to H F Edelhauser.

At least 55 records · Page 3Linked to original sources
PubMed1994

Long-term observation of morphologic and functional features of cat corneal endothelium after wounding.

PURPOSE: (1) To test the hypothesis that corneas with enlarged endothelial cells (and thus less intercellular space) have decreased endothelial permeability to small polar solutes. (2) To measure corneal endothelial ouabain binding (Na+/K+ ATPase "pump site" density) and Descemet's membrane production after endothelial wounding. METHODS: Bilateral specular microscopy and anterior segment fluorophotometry were performed at 2-month intervals for 1 year in ten cats after mechanically damaging the corneal endothelium in one eye of each. The measurements were repeated at 2 years in four cats and at 3 years in two cats. Eighteen months after wounding, endothelial ouabain binding was measured in both eyes of six cats. Transmission electron micrographs of Descemet's membrane were analyzed in both eyes of six cats at 18 months, two cats at 2 years, and two cats at 3 years after wounding. RESULTS: From 6 to 12 months after wounding, the endothelial permeability to carboxyfluorescein was significantly decreased (P < 0.05), and the mean endothelial cell size was significantly increased (P < 0.001) in the damaged eyes. The enlarged endothelial cells persisted in the few cats observed 2 and 3 years after wounding. There was no significant difference in endothelial ouabain binding between the damaged and control corneas in six cats tested 18 months after wounding. On subsequent histologic examination, a layer of abnormal Descemet's membrane was present in all ten wounded eyes, with additional normal Descemet's membrane posterior to it, between the abnormal layer and the endothelial cells. CONCLUSIONS: The results are consistent with the hypothesis that corneal endothelial permeability to small polar solutes varies directly with the amount of intercellular space available for diffusion across the monolayer. The results also confirm clinical reports of decreased endothelial permeability in corneas with enlarged endothelial cells. In histopathologic specimens, a layer of abnormal Descemet's membrane can be a historical marker for a period of endothelial damage and corneal decompensation.

Animals↗
PubMed1993

Swelling in the isolated perfused cornea induced by 12(R)hydroxyeicosatetraenoic acid.

PURPOSE: To evaluate the effect of 12(R)hydroxyeicosatetraenoic acid (12(R)HETE) on corneal swelling when directly perfused to human and rabbit corneal endothelium. METHOD: Excised rabbit and human corneas were mounted in the in vitro specular microscope and the endothelium was perfused with 12(R)HETE at 10(-5), 10(-6), and 10(-7) mol/l. Both 12(R)HETE and 12(S)HETE were compared at equal molar (10(-6) mol/l) concentrations. The reversal of 12(R)HETE and ouabain corneal swelling was also compared. Endothelial permeability to carboxyfluorescein was measured after 12(R)HETE perfusion. High-performance liquid chromatographic analysis confirmed that 12(R)HETE remained in the perfusion media. RESULTS: 12(R)HETE caused a dose-dependent corneal swelling of 25 +/- 2, 24 +/- 1, and 14 +/- 0.5 microns/hr at 10(-5), 10(-6), and 10(-7) mol/l, respectively. Equal molar concentrations (10(-6) mol/l) of 12(S)HETE did not cause corneal swelling. Removal of the 12(R)HETE from the perfusion media resulted in reversal of corneal swelling whereas corneal swelling induced by ouabain did not reverse after ouabain removal. 12(R)HETE (10(-6) mol/l) perfused to the human corneal endothelium inhibited temperature reversal corneal thinning when compared to the paired corneal endothelium perfused with BSS Plus (Alcon Laboratories, Inc., Fort Worth, TX). Na/K adenosine triphosphatase activity was inhibited by 10(-6) mol/l ouabain by 35%, 10(-6) mol/l 12(R)HETE by 54%, and 10(-6) mol/l 12(S)HETE by 0.5%. Endothelial permeability to carboxyfluorescein was unaffected by 12(R)HETE. CONCLUSION: 12(R)HETE causes corneal swelling by inhibiting endothelial pump function. This inhibition of transport appears to be at least partly mediated by inhibition of endothelial Na/K adenosine triphosphatase.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
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

Effect of gas-permeable contact lenses on the endothelium of corneal transplants.

The effects of gas-permeable contact lens wear on the density and morphologic characteristics of corneal endothelial cells were prospectively studied by wide-field specular microscopy in 18 eyes that had undergone keratoplasty at least 14 months previously. Daily-wear rigid gas-permeable lenses were fitted to allow as much movement and tear exchange as possible. There was no evidence of morphologic instability of the endothelial cells during the course of the study, with a mean duration of lens wear of 9.8 months. Although there is concern over adverse effects associated with polymethylmethacrylate contact lens wear, this study suggests that the endothelium of a corneal transplant tolerates rigid gas-permeable lens wear without adverse effect during a limited period of follow-up.

Contact Lenses↗
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↗
PubMed1991

Human corneal storage in modified McCarey-Kaufman and K-Sol media: effect on endothelial Na+/K+ ATPase pump site density and permeability.

Endothelial permeability (Pac) to carboxyfluorescein and Na+/K+ ATPase pump site density were determined in human corneas following storage for 4 or 7 days at 4 degrees C in either modified McCarey-Kaufman (mMK) or K-Sol media. Following 4 days of storage, Pac values for mMK- and K-Sol-preserved corneas were not significantly different from those of their prestorage mates. After 7 days of storage, however, corneas stored in K-Sol media showed a significant increase in Pac compared to their prestorage mates, whereas the mMK-stored corneas showed no change in Pac. Na+/K+ ATPase pump site density determined using [3H]ouabain was similar to a control group in the K-Sol-stored tissue but higher in the mMK-stored tissue following 7 days of storage. These studies suggest that mMK medium maintains endothelial barrier function and Na+/K+ ATPase pump site density at least as well as K-Sol medium through 7 days of corneal storage.

Adult↗
PubMed1991

Maturation of the corneal endothelial tight junction.

Apical tight junctional formation of the rabbit corneal endothelium was examined by freeze-fracture analysis and measurement of paracellular permeability to 5(6)-carboxyfluorescein. Freeze-fracture analysis indicated that apical tight junction formation of the rabbit corneal endothelium is a dynamic process. At birth, there are few tight junctional strands present and a minimal barrier for paracellular diffusion. As the rabbit matures, a more complex network of anastomosing tight junctional strands begins to encircle the cell perimeter under the apical folds. However, even in the mature animal (3 months), there are discontinuities and free ends in the network, thus suggesting that the barrier is not complete even at this stage. Paracellular permeability measurements using 5(6)-carboxyfluorescein as a tracer corroborate these anatomic findings. Endothelial paracellular flux measurements steadily decrease as the rabbit matures from birth to young adult. This indicates that the tight junctional network is increasing in complexity and progressively limiting the flow of substances through the intercellular space.

Animals↗
PubMed1990

A bisulfite-free intraocular epinephrine solution.

We evaluated a preservative-free, sulfite-free epinephrine solution for potential corneal toxicity, which has been described for sulfite-containing epinephrine solutions. The preservative-free, sulfite-free epinephrine solution did not exhibit endothelial toxicity in three-hour paired human corneal endothelial perfusion at two and four times the concentration of the 1:1,000,000 dilution currently recommended for anterior chamber intraocular irrigating solutions. When epinephrine at a dilution of 1:1,000 was injected directly into the anterior chamber of New Zealand white rabbits, there was markedly less corneal edema induced than there was in previous studies with sulfite-containing solutions of comparably low pH but higher buffer capacities. Although potential toxicity exists for any irrigating solution with a pH outside of the 6.5 to 8.5 pH range, the endothelial toxicity of this solution has been reduced by its low buffer capacity, lack of preservatives, and lack of sulfite, offering an extra margin of safety for intraocular use.

Aged↗
PubMed1990

Toxic endothelial cell destruction of the cornea after routine extracapsular cataract surgery.

Eighteen patients developed an acute corneal decompensation following normal intraocular surgery (cataract extraction in 17 patients), characterized by star-shaped endothelial folds, a twofold increase in corneal thickness, and a visual acuity of counting fingers during several postoperative days. In some cases, there was an additional iritis and transient hypotony. There was no effect of topical and/or subconjunctival corticosteroids on the course of the decompensation. Endothelial morphometric analysis showed a mean endothelial cell loss of 72%. Endothelial wound healing, as determined by coefficient of variation and percentage hexagonals, stabilized 6 months postoperatively. We coined the term toxic endothelial cell destruction for this syndrome. Epidemiological evaluation revealed the toxic endothelial cell destruction syndrome to be linked with the 10-fold increase of a detergent solution in the ultrasonic bath for cleaning the surgical instruments.

Aged↗
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↗
PubMed1990

A method for the in vitro determination of feline corneal endothelial permeability.

A mounting block for in vitro perfusion of the cat cornea is described. Using this apparatus and the techniques of Araie, the permeability (Pac) of the normal cat corneal endothelium to carboxyfluorescein was determined to be 2.5 +/- 0.2 x 10(-4) cm/min. To assess the sensitivity of this technique in determining changes in Pac associated with alterations in endothelial, morphology, three cats underwent 2 successive unilateral, central, 10 mm diameter circular areas of endothelial debridement 6 weeks apart. Six weeks following the second wounding all 3 animals underwent morphometric analysis and Pac determination. A trend toward an elevation in Pac with extreme reductions in cell density was observed.

Animals↗
PubMed1990

Loss of stromal glycosaminoglycans during corneal edema.

This study tried to determine if glycosaminoglycans (GAGs) are released from the rabbit stroma during corneal edema. The GAGs of rabbit corneas were labeled in situ using anterior-chamber injections of 35S-sulfate and 3H-glucosamine. Labeled corneal pairs were excised and the endothelium perfused in vitro in the specular microscope. Edema was induced in one cornea by perfusion with a calcium-free balanced salt solution; the control cornea was perfused with glutathione bicarbonate Ringer's (GBR). Corneal thickness was measured every 15 minutes during the 3-hour perfusion period, and perfusate fractions were collected from each cornea and analyzed for the presence of GAGs. Edematous corneas swelled from 438 +/- 14.8 microns to 688 +/- 10.6 microns compared with control corneas (427 +/- 4.7 microns to 454 +/- 7.2 microns). Total 3H-glucosamine (4.00 +/- 0.68%) and 35S-sulfate (10.36 +/- 0.92%) released from the edematous corneas during perfusion exceeded that lost by control corneas (1.92 +/- 0.18% for 3H-glucosamine; 3.23 +/- 0.52% for 35S-sulfate). Enzymatic digestion studies showed the presence of keratan sulfate in the edematous perfusates. The results suggest that increased loss of radiolabeled components from edematous corneas represent a loss of stromal GAGs and possibly GAG fragments. Therefore, corneal edema involves loss of GAGs and water uptake.

Animals↗
PubMed1990

Corneal endothelial junctions and the effect of ouabain.

Paired rabbit corneas were perfused in vitro for endothelial permeability (Pac) determination with glutathione bicarbonate Ringer's solution (GBR) and GBR plus ouabain (10(-4) M). Results indicated no difference in Pac between the two groups (3.39 vs 3.67, respectively) despite significantly greater stromal swelling in the group perfused with ouabain. Freeze-fracture microscopy of similarly perfused corneas revealed intact tight junctional complexes in both groups, although the tight junctional complex of perfused corneas appeared less organized than that of freshly enucleated, nonperfused controls. Gap junctions were abundant as observed in freeze-fracture replicas of GBR-perfused endothelium, and appeared to be decreased or absent in ouabain-perfused endothelium. These results indicate that corneal endothelial tight junctions are unaffected by perfusion with ouabain, whereas gap junctions appear to be lost. The permeability and freeze-fracture data reaffirms the importance of tight junctions as permeability barriers and indicates that gap junctions are not of primary importance for maintenance or control of the corneal endothelial barrier.

Animals↗