Differential epithelial and stromal protein profiles in keratoconus and normal human corneas

The purpose of the study was to identify epithelial and stromal proteins that exhibit up- or down-regulation in keratoconus (KC) vs. normal human corneas. Because previous proteomic studies utilized whole human corneas or epithelium alone, thereby diluted the specificity of the proteome of each tissue, we selectively analyzed the epithelium and stromal proteins. Individual preparations of epithelial and stromal proteins from KC and age-matched normal corneas were analyzed by two independent methods, i.e., a shotgun proteomic using a Nano-Electrospray Ionization Liquid Chromatography Tandem Mass Spectrometry [Nano-ESI-LC-MS (MS)(2)] and two-dimensional-difference gel electrophoresis (2D-DIGE) coupled with mass spectrometric methods. The label-free Nano-ESI-LC-MS (MS)(2) method identified 104 epithelial and 44 stromal proteins from both normal and KC corneas, and also quantified relative changes in levels of selected proteins, in both the tissues using spectral counts in a proteomic dataset. Relative to normal corneal epithelial proteins, six KC epithelial proteins (lamin-A/C, keratin type I cytoskeletal 14, tubulin beta chain, heat shock cognate 71 kDa protein, keratin type I cytoskeletal 16 and protein S100-A4) exhibited up-regulation and five proteins (transketolase, pyruvate kinase, 14-3-3 sigma isoform, phosphoglycerate kinase 1, and NADPH dehydrogenase (quinone) 1) showed down-regulation. A similar relative analysis showed that three KC stromal proteins (decorin, vimentin and keratocan) were up-regulated and five stromal proteins (TGF-betaig h3 (Bigh3), serotransferrin, MAM domain-containing protein 2 and isoforms 2C2A of collagen alpha-2[VI] chain) were down-regulated. The 2D-DIGE-mass spectrometry followed by Decyder software analysis showed that relative to normal corneas, the KC corneal epithelium exhibited up-regulation of four proteins (serum albumin, keratin 5, L-lactate dehydrogenase and annexin A8) and down-regulation of four proteins (FTH1 [Ferritin heavy chain protein 1], calpain small subunit 1, heat shock protein beta 1 and annexin A2). A similar relative analysis of stroma by this method also showed up-regulation of aldehyde dehydrogenase 3A1 (ALDH3A1), keratin 12, apolipoprotein A-IV precursor, haptoglobin precursor, prolipoprotein and lipoprotein Gln in KC corneas. Together, the results suggested that the Nano-ESI-LC-MS(MS)(2) method was superior than the 2D-DIGE method as it identified a greater number of proteins with altered levels in KC corneas. Further, the epithelial and stromal structural proteins of KC corneas exhibited altered levels compared to normal corneas, suggesting that they are affected due to structural remodeling during KC development and progression. Additionally, because several epithelial and stromal enzymes exhibited up- or down-regulation in the KC corneas relative to normal corneas, the two layers of KC corneas were under metabolic stress to adjust their remodeling.

Clinical measures to promote corneal epithelial healing

It is necessary to know the specific pathobiology of a persistent epithelial defect to determine the strategy to be employed to assist in its repair. Lid position and function must be normal and any deficiency in the quantity and quality of the tears enhanced by tear preparations and closure of the lacrimal canaliculi. Adverse drug effects must be eliminated. Multiple corneal punctures and excision of reduplicated basal lamina have virtually eliminated the problem of recurrent corneal erosions. Control of any inflammatory process also speeds healing. Vitamin supplements, especially A, reverse defects associated with xerophthalmia. In any of these diseases, mechanical treatments consisting of soft contact lenses for persistent epithelial defects and collagen shields for the delivery of antibiotics or steroids to the eye may be employed. Tarsorrhaphy relieves the problem of persistent epithelial defects in neurotrophic keratitis and a variety of other conditions characterized by persistent surface breakdown. Preliminary data from open label studies of epidermal growth factors and fibronectin are encouraging but not yet conclusive.

Inhibitory effect of a complementary peptide on ulceration in the alkali-injured rabbit cornea

PURPOSE

Two tripeptide chemoattractants, acetyl-proline-glycine-proline (Ac-PGP) and methyl-proline-glycine-proline (Me-PGP), are the primary triggers for early neutrophil invasion into the alkali-injured cornea. In the present study the effectiveness of a complementary peptide designed to inhibit the PGP chemoattractants (arginine-threonine-arginine [RTR] tetrameric peptide) and an apo A-1 mimicking peptide (5F) was investigated in the alkali-injured rabbit eye.

METHODS

(L)-RTR tetramer, (D)-RTR tetramer, and 5F were tested in vitro for their effects on neutrophil polarization. Synthetic 5F was also tested in vitro for its effect on the neutrophil respiratory burst. In the alkali-injured rabbit eye model, the right corneas of 48 rabbits were exposed to 1 N NaOH for 35 seconds. Sixteen animals were randomly assigned to each of three groups: phosphate-buffered saline (PBS) control; 800 microM RTR (dextrorotatory) tetramer in PBS alternating each hour with 1.5 mM RTR (levorotatory) tetramer in PBS; and 12 microM 5F in PBS. One topical drop of each substance was administered hourly (14 times per day) for 33 days. The experiment was continued until day 42 with no additional drops administered.

RESULTS

(L)-RTR tetramer and (D)-RTR tetramer inhibited neutrophil polarization activated by the PGP chemoattractants in vitro. Synthetic 5F did not inhibit neutrophil polarization in the presence of Ac-PGP or the respiratory burst of neutrophils in the presence of a metabolic stimulant derived from alkali-degraded corneas. During the entire animal experiment, statistically fewer ulcers occurred in the RTR tetramer group than in the PBS control group (43.8% vs. 87.5%, P = 0.0046). The frequency of ulceration in the 5F group (68.8%) was not significantly different from the PBS control group.

CONCLUSIONS

The reduction in the frequency of corneal ulceration by the RTR tetramer possibly resulted from its complementary binding to Ac-PGP and Me-PGP in the cornea shortly after alkali injury, leading to a reduction in the early and late infiltration of neutrophils. RTR tetramer appears to hold enough promise to warrant additional study as a therapeutic drug for the alkali-injured eye.

NMR conformational analysis of cis and trans proline isomers in the neutrophil chemoattractant, N-acetyl-proline-glycine-proline

Alkaline hydrolysis of corneal proteins in the alkali-injured eye releases N-acetyl-proline-glycine-proline (Ac-Pro-Gly-Pro-OH) among other peptides. It has been shown that this tripeptide is a neutrophil chemoattractant. Existing data suggest that the release of this peptide is the catalytic event for early neutrophil invasion of the cornea leading to corneal ulcers. In order to design inhibitors of this tripeptide chemoattractant that would block neutrophil invasion and diminish corneal ulcers, we studied the solution properties of this tripeptide by NMR spectroscopy and compared this peptide to Ac-Pro-Gly-OH (a weaker chemoattractant), and to Ac-Pro-OH (inactive). The NMR data were consistent with Ac-Pro-Gly-Pro-OH existing in solution as a mixture of four isomers with different cis and trans conformations about the two X-proline amide bonds. The isomer with two trans conformations (trans-trans) was the most dominant (41%) in aqueous solution. This was followed by the isomers with mixed cis and trans conformations (trans-cis, 26% and cis-trans, 20%). The isomer with two cis conformations (cis-cis) was the least favored (13%). The populations of these isomers were investigated in DMSO and they were similar to those reported in aqueous solutions except that the ordering of the trans-cis and cis-trans isomers were reversed. NMR NH temperature coefficients and nuclear Overhauser effect (NOE) measurements as well as CD spectroscopy were used to demonstrate that the four isomers exist primarily in an extended conformation with little hydrogen bonding. The available (NOE) information was used with molecular dynamics calculations to construct a dominant solution conformation for each isomer of the tripeptide. This information will serve as a model for the design of peptide and nonpeptide inhibitors of the chemoattractant.

Synthetic complementary peptides inhibit a neutrophil chemoattractant found in the alkali-injured cornea

PURPOSE

We have previously presented evidence that the neutrophil chemoattractant, N-acetyl-proline-glycine-proline (N-acetyl-PGP), triggers the initial polymorphonuclear leukocyte (PMN) invasion into the alkali-injured eye. In this study, sense-antisense methodology was used to develop novel complementary peptides to be potential inhibitors of N-acetyl-PGP.

METHODS

The polarization assay was used to measure the potential chemotactic response of PMNs to synthetic N-acetyl-PGP, the ultrafiltered tripeptide chemoattractants obtained from alkali-degraded rabbit corneas, or leukotriene B4 (LTB4). Inhibition was expressed as the peptide concentration producing 50% inhibition (ID50) of polarization. Five complementary peptides were tested as potential inhibitors of N-acetyl-PGP: arginine-threonine-arginine (RTR), RTR-glycine-glycine (RTRGG), RTR dimer, RTR tetramer, and alanine-serine-alanine (ASA) tetramer. In addition, the RTR tetramer and both monomeric peptides (RTR and RTRGG) were separately tested for inhibition of the ultrafiltered tripeptide chemoattractants or LTB4.

RESULTS

The complementary RTR tetrameric peptide was a powerful antagonist of N-acetyl-PGP-induced PMN polarization (ID50 of 200 nM). The RTR dimer was much less potent (ID50 of 105 microM). Both monomeric peptides, RTR and RTRGG, were only antagonistic at millimolar concentrations. The ASA tetramer showed no capacity to inhibit N-acetyl-PGP. The RTR tetramer also inhibited PMN activation by the ultrafiltered tripeptide chemoattractants (ID50 of 30 microM) but had no effect on LTB4.

CONCLUSIONS

A complementary peptide (RTR) was designed which is an effective inhibitor of the neutrophil chemoattractant, N-acetyl-PGP. The potency of the RTR complementary peptide is dramatically enhanced by tetramerization. Inhibition of N-acetyl-PGP by complementary peptides offers great promise for control of the inflammatory response in the alkali-injured eye.

Bioactivity of peptide analogs of the neutrophil chemoattractant, N-acetyl-proline-glycine-proline

PURPOSE

The release of N-acetyl-proline-glycine-proline (PGP), a chemoattractant resulting from direct alkaline hydrolysis of corneal proteins, is believed to be the initial trigger for neutrophil invasion into the alkali-injured cornea. The purpose of this study is twofold: (1) to compare the activity of N-acetyl-PGP with the bioactivities of other similar synthetic peptides in an effort to uncover information about this chemoattractant molecule, and (2) to test these peptide analogs as potential antagonists of N-acetyl-PGP.

METHODS

The polarization assay was used to measure the potential chemotactic response of human neutrophils to peptides. Bioactivity was expressed as the peptide concentration required to produce 50% neutrophil polarization (EC50). Antagonist activity was expressed as the peptide concentration required to produce 50% inhibition (ID50) of polarization activated by N-acetyl-PGP.

RESULTS

Peptide bioactivities (EC50) were ranked as follows: APGPR (0.34 mM) > N-acetyl-PGP (0.5 mM) > N-(PGP)4-PGLG (3 mM) = t-Boc-PGP (3 mM) > N-acetyl-PG (3.4 mM) > N-methyl-PGP (15 mM) = PGP (15 mM) > peptides without detectable activity (t-Boc-PGP-OMe, N-acetyl-P, PG, PGG, GP, GG and gly-pro-hyp). Peptides with no detectable bioactivity were tested as potential antagonists of neutrophil polarization induced by N-acetyl-PGP. Gly-Pro-Hyp inhibited N-acetyl-PGP activation of polarization at 20 mM (ID50). No other synthetic peptide demonstrated a capacity for inhibition.

CONCLUSIONS

The minimum requirement to elicit bioactivity was the presence of PGP alone or derivatives of PG in which the N-terminal proline is blocked. Using this approach, active and inactive mimetic peptides of N-acetyl-PGP were produced. The most active peptide, APGPR, was equal to or slightly greater than N-acetyl-PGP, suggesting that more potent analogs might be designed. Gly-pro-hyp was the only inactive peptide analog to inhibit the chemoattractant.

Injection of chemoattractants into normal cornea: a model of inflammation after alkali injury

PURPOSE

The objective of this study was to establish and characterize the invasion of polymorphonuclear leukocytes (PMNs) into a normal cornea after intrastromal injection of the tripeptide chemoattractants generated from alkali-degraded corneas.

METHODS

The following samples were injected into the midstroma of normal rabbit corneas: ultrafiltered tripeptide chemoattractants (N-acetyl-proline-glycine-proline and N-methyl-proline-glycine-proline) generated from alkali-degraded corneas, synthetic N-acetyl-PGP, positive control (leukotriene B4 [LTB4]), or negative control (Hanks' balanced salt solution [HBSS]). Timed responses of PMN infiltration were established for effective concentrations of LTB4 or the ultrafiltered chemoattractants.

RESULTS

All intrastromal injections resulted in the immediate development of an edematous disc that was 10 mm in diameter. The lesion essentially had cleared in the HBSS-injected eyes by 8 hours, and histologic sections revealed minimal numbers of PMNs in the cornea or limbal tissue. The injection of LTB4 or the ultrafiltered tripeptide chemoattractants induced peak numbers of PMNs within the stroma at 8 hours, subsiding by 16 hours. Seventy units of ultrafiltered chemoattractants yielded a strong PMN response, similar to 1 X 10(-5) M LTB4. The highest concentration of ultrafiltered chemoattractants (350 U) produced a severe PMN response that was characterized by a solid sheet of neutrophils surrounding the injection site. The injection of synthetic N-acetyl-PGP (2 X 10(-4) M) produced a marked PMN response.

CONCLUSIONS

PMN invasion of the normal cornea after the injection of the ultrafiltered tripeptide chemoattractants or the synthetic N-acetyl-PGP mimicked early PMN infiltration in the alkali-injured eye, confirming the importance of this chemoattractant as an inflammatory mediator.

A new classification system predicting keratomalacia after trauma in vitamin A deficiency: sodium citrate does not prevent disease progression

PURPOSE

The purpose of this study was to develop a classification system to predict keratomalacia after trauma in vitamin A-deficient eyes and to determine whether citrate impedes polymorphonuclear leukocyte infiltration into the cornea, thus preventing keratomalacia.

METHODS

Preliminary classification studies showed that a 7.0-mm corneal epithelial scrape, before clinical findings of corneal xerosis, did not induce keratomalacia. Primary studies were conducted concurrently on the same animals to develop the classification system and test the effect of citrate in vitamin A deficiency. A 7.0-mm corneal epithelial scrape was performed on vitamin A-deficient eyes in various stages of corneal xerosis and treated as follows. Experiment 1: group 1, 10% citrate drops; group 2, phosphate buffer solution (PBS) drops; experiment II: group 3, drops and subconjunctival injection of 10% citrate; group 4, drops and subconjunctival injection of PBS.

RESULTS

Corneal abrasion in eyes with 2+ corneal xerosis yielded keratomalacia in 50% of cases; the remainder healed with xerotic epithelium. Eighty-three percent of eyes with > 2+ xerosis developed keratomalacia after corneal abrasion, whereas only 7.1% of eyes with < 2+ xerosis advanced to this stage. In experiment I, 27% of citrate-treated eyes and 38% of PBS-treated eyes developed keratomalacia (not significant). In experiment II, two of six citrate-treated eyes perforated and one eye developed keratomalacia. One of six control PBS eyes perforated and four developed keratomalacia.

CONCLUSION

We correlated the degree of corneal xerosis with the occurrence of keratomalacia after corneal trauma. This led to the development of a classification scale that is of research and clinical significance. Additionally, citrate did not significantly reduce keratomalacia or perforation in the vitamin. A-deficient eye.

Effect of synthetic metalloproteinase inhibitor or citrate on neutrophil chemotaxis and the respiratory burst

PURPOSE

A topical synthetic metalloproteinase inhibitor (SIMP) has been reported to reduce the incidence of corneal ulcerations in the alkali-injured eye by the putative mechanism of collagenase inhibition. The current study was performed to determine whether SIMP has a direct inhibitory effect on the activation of neutrophils and to compare any such effect with that of citrate, a known inhibitor of polymorphonuclear leukocyte (PMNL) activity.

METHODS

The effect of SIMP or citrate was tested on chemotaxis of PMNL and the respiratory burst in vitro.

RESULTS

Synthetic metalloproteinase inhibitor (1 mM) or citrate (12 mM) produced significant inhibition of chemotaxis of PMNL and the accompanying behavioral characteristics of motility. Synthetic metalloproteinase inhibitor, but not citrate, generated a dramatic respiratory burst when incubated with resting PMNL. Both SIMP and citrate inhibited the respiratory burst of PMNL in the presence of opsonized zymosan. For a brief, initial period each substance enhanced the respiratory burst generated by the metabolic stimulant from alkali-degraded corneas, followed by a rapid decline in activity that was associated with cell death.

CONCLUSIONS

Although SIMP has been shown to exhibit powerful collagenase inhibition, its inhibitory effect on chemotaxis of PMNL might be the primary mechanism in reducing the incidence of ulceration in the alkali-injured cornea. Very significant reduction in the accumulation of PMNL in SIMP-treated corneas supports this conviction. Activation by SIMP of the respiratory burst in resting PMNL is of concern, but overall its beneficial effect is favorable, as demonstrated in prior alkali-injured animal models. The dual effect of inhibition of chemotaxis of PMNL and activity of collagenase makes SIMP a potential drug for combating ulceration in the alkali-injured cornea.

An excess of topical calcium and magnesium reverses the therapeutic effect of citrate on the development of corneal ulcers after alkali injury

Our purpose was to determine whether chelation of Ca2+ and Mg2+ is the mechanism by which sodium citrate inhibits corneal ulceration in the alkali-injured rabbit eye. The right eyes of 60 albino rabbits (2-2.5 kg) were alkali-injured by filling a 12-mm-diameter plastic well placed on the corneal surface with 0.4 ml of 1 N NaOH. After 35 s the alkali was aspirated, and the well was rinsed with physiological saline. Animals were randomly distributed to three treatment groups of equal size. Two drops of the following topical medications were administered on the hour (14 times per day) for 35 days: physiological saline, 10% citrate in saline, and 346 mM Ca2+, 346 mM Mg2+, and 10% citrate in saline. During the experiment, significantly fewer ulcerations occurred in the citrate-treated eyes (five of 20, 25%) than in the saline-treated eyes (13 of 20, 65%) or in the calcium-magnesium-citrate-treated eyes (15 of 20, 75%). When ulcerations did develop in the citrate group, they occurred significantly later and were less severe than those in the saline and calcium-magnesium-citrate groups. There was a significant increase in the number of eyes with signs of band keratopathy and translucent areas in the calcium-magnesium-citrate group when compared with the other two groups. As in previous studies, sodium citrate significantly inhibited the development of corneal ulcers after alkali injury. The annullment of the favorable effect of citrate on ulceration in the alkali-injured eye by the addition of calcium and magnesium shows that the mechanism of action of citrate is the chelation of these divalent cations.

A neutrophil chemoattractant is released from cellular and extracellular components of the alkali-degraded cornea and blood

PURPOSE

A tripeptide chemoattractant(s) for neutrophils has been shown to release from alkali-degraded cornea. This study is designed to determine the source of the chemoattractant(s).

METHODS

Whole corneas were degraded in 1 N NaOH for 10 minutes, 30 minutes, 1 hour, 4, 8, 24, and 48 hours to determine an optimal duration of alkali exposure for production of the chemoattractant. Whole cornea, cornea minus epithelium, cornea minus endothelium, and stroma alone were degraded in 1 N NaOH for 4 hours to determine the relative contribution of each corneal layer. In a separate experiment, epithelium alone, endothelium alone, cultured keratocytes alone, or bovine corneal collagen were treated separately in 1 N NaOH for 4 hours. Finally, human plasma, platelets, polymorphonuclear leukocytes (PMNL), and red blood cells were treated separately in 1 N NaOH for 4 hours to determine if a similar chemoattractant was released from alkali-treated noncorneal tissue. Neutralized suspensions of all samples were ultrafiltered and dialyzed. The chemotactic potential of each sample was determined in the polarization assay.

RESULTS

Activation of the PMNL polarization response increased with the duration of exposure of corneal tissue to alkali, peaking at 6 hours. Release of the chemoattractant from alkali-degraded corneal tissue showed a significant decrease when the epithelium was removed from the stroma. All tissue layers showed a PMNL polarization response when treated with alkali. The response decreased from epithelium > endothelium > cultured keratocytes > collagen. Alkali degradation of human blood components, including plasma, showed significant polarization responses ranked in the following order: plasma > PMNL > tendon collagen > platelets = red blood cells.

CONCLUSIONS

This study demonstrates that the tripeptide chemoattractant(s) is released from all layers of the cornea after alkali injury. The substance released from blood components is of similar size and biologic activity as that found in the cornea, but its exact molecular composition is yet to be determined. Timed response of alkali degradation determined the optimal conditions for generation of the chemoattractant(s) including clinically relevant time intervals.

Identification and synthesis of chemotactic tripeptides from alkali-degraded whole cornea. A study of N-acetyl-proline-glycine-proline and N-methyl-proline-glycine-proline

PURPOSE

To identify and synthesize the polymorphonuclear leukocyte chemoattractant(s) released from alkali-degraded corneas.

METHODS

Corneas were degraded in 1.0 N NaOH, neutralized, ultrafiltered, and dialyzed. The final active ultrafiltrate was subjected to high-performance liquid chromatography on a Protein PAK I-60 column. The most active fractions were further separated on a mu-Bondapak-C18 and I-60 column in sequence.

RESULTS

Fraction 38 from the final I-60 column associated with a 210-nm absorption peak and elicited a polarization and chemotactic response from polymorphonuclear leukocytes. The loss of polarization activity in fraction 38 after exposure to prolidase suggests that this peptide contains a Pro-X (X = amino acid) peptide bond. The amino acid composition of fraction 38 was 35% glycine and 53% proline. Peptide sequence analysis was unable to establish a primary sequence even though Picotag analysis showed the presence of large amounts of the two amino acids. Mass spectrometry revealed only two molecular species of 312 MWt and 284 MWt. Tripeptides were synthesized using all possible amino acid permutations of 2 Pro and 1 Gly and tested in the polarization and chemotactic assays. These techniques demonstrated that n-acetyl-Pro-Gly-Pro, and to a lesser degree n-methyl-Pro-Gly-Pro, were the only synthetic tripeptides with activity similar to the purified chemoattractant.

CONCLUSIONS

The data show that the chemotactic peptides, purified from alkali-degraded whole cornea and confirmed with identical synthetic tripeptides, are N-acetyl-Pro-Gly-Pro and N-methyl-Pro-Gly-Pro. Although a number of proteins contain the Pro-Gly-Pro sequence, large amounts of collagen in the cornea suggest this as a major source. The small size and hydrophilic nature of these chemoattractants are predictive of a high degree of diffusibility. These chemoattractants are likely to play a major role in the early neutrophil response after an alkali injury.

Characterization of chemical gradients in the collagen gel-visual chemotactic assay

Chemical gradients developing in a collagen gel-visual chemotactic assay (CG-VCA) for PMNs were evaluated by theoretical and experimental methods. First, a video image analysis system was used to establish the diffusion coefficients of bromophenol blue (BPB) through the membrane (D1) and across the collagen gel (D2) in a capillary tube apparatus used only for this purpose. The diffusion coefficients of BPB and the geometry of the CG-VCA system were then used to develop a mathematical model, estimating theoretical gradients in the CG-VCA system. In addition, gradients in the CG-VCA system were characterized experimentally by employing BPB as the source and determining the concentration profiles of BPB in the chemotactic compartment by video image analysis. A relative error of approximately 21% exists between the theoretical and experimental gradients for both 0.5 and 1.0 mM source concentrations of BPB. This favorable comparison demonstrates reliability in predicting chemical gradients for the CG-VCA system. The mathematical model was then used to predict gradients using nanomolar and micromolar concentrations of low molecular weight chemoattractants. Analysis of these specific gradients showed that gradients were steep enough to be detected by PMNs in the collagen gel during the observation period used in previous experiments. The determination of BPB gradients in the CG-VCA system illustrates the utility of this system.

Ventral preputial onlay island flap and proximal flip-flap technique for the repair of epispadias: a case report

Use of the ventral preputial island flap technique for repair of epispadias has yielded satisfying functional and cosmetic results. We report a modification of this technique in a patient with proximal penile epispadias without exstrophy. We used the Duckett modification of the onlay island flap using ventral preputial skin and coupled it with a proximal flip-flap of perimeatal skin without division of the urethral plate. This achieved an excellent result.

Alkali-degraded cornea generates a low molecular weight chemoattractant for polymorphonuclear leukocytes

PURPOSE

The current study was designed to determine if a polymorphonuclear leukocyte (PMN) chemoattractant is derived from alkali-degraded whole cornea and to establish a range for its molecular weight.

METHODS

We utilized a collagen gel-visual chemotactic assay to quantify the directional movement of PMN exposed to alkali-degraded corneas (30 min or 24 hr). In this experiment, the sample to be tested for chemotactic activity passed through a 14,000 molecular weight cutoff membrane into a collagen gel in which resting neutrophils were suspended in a random fashion. Cell movement was videotaped and subsequently tracked by digitizing the centroid of the cells at 30-sec intervals. Computer analysis of these tracks illustrated many behavioral characteristics, including directional movement.

RESULTS

Alkali-degraded whole bovine corneas produced a chemotactic response in neutrophils within 5 min. Dilution of the 24-hr sample to 1:7 yielded a significant chemotactic response. The chemotactic response of both the 30-min and 24-hr samples followed a dose-response curve.

CONCLUSIONS

This agent may be one of the inflammatory mediators that trigger the early neutrophil response after an alkali-injury to the eye.

Alkali-degraded cells generate a respiratory burst stimulant for neutrophils

Alkali treatment of whole cornea produces a high molecular weight polypeptide causing a respiratory burst in neutrophils. The current study was conducted to determine if this stimulant could be elicited from cultured or scraped corneal cells (epithelium, keratocytes, or endothelium). Fresh or previously frozen epithelium, endothelium, and stroma were isolated from bovine eyes, alkali treated, and tested for the presence of the respiratory burst stimulant. The same procedure was performed on cultured bovine epithelium, keratocytes, and endothelium. To determine if the stimulant is specific to corneal cells, the component parts of human blood (cellular and extracellular) were separated, treated with alkali, and tested individually. Activation of the respiratory burst of polymorphonuclear leukocytes (PMNs) was used as a marker for the presence of the stimulant. All alkali-degraded cell samples, except red blood cells, produced a respiratory burst when added to viable PMNs. Alkali-treated plasma induced weak stimulation. Bovine corneal epithelium was alkali-treated and separated by high-performance liquid chromatography (HPLC) according to molecular size. The stimulant was shown to have a high molecular weight by its recovery in HPLC fraction number 7. These results demonstrate that the PMN stimulant originates from cells. This PMN stimulant is proposed as an inflammatory mediator in the alkali-injured cornea.

Endopyelotomy associated ureteral necrosis: complete ureteral replacement using the Boari flap

A case of an adolescent who sustained necrosis of the entire ureter after attempted endopyelotomy for congenital ureteropelvic junction obstruction is presented. Successful reconstruction of a neoureter was performed easily with the Boari bladder flap coupled with nephropexy and a psoas hitch. Although repair of upper ureteral injuries with the Boari flap has been described in the literature, to our knowledge its use in the pediatric population has not. Our case exemplifies how the Boari flap repair is particularly suitable in children for bridging significant segments of injured ureters, not just the lower third.

Serious complications of topical mitomycin-C after pterygium surgery

BACKGROUND

The use of topical mitomycin (mitomycin-C) as a medical adjunct to pterygium and glaucoma surgery is increasing.

METHODS

The authors report on a series of 10 patients who experienced serious, vision-threatening complications associated with the use of this drug after pterygium surgery.

RESULTS

Complications included severe secondary glaucoma (4 patients), corneal edema (3 patients), corneal perforation (1 patient), corectopia (2 patients), iritis (8 patients), sudden onset mature cataract (2 patients), scleral calcification (1 patient) and incapacitating photophobia and pain (8 patients). Two patients required penetrating keratoplasties and a third required three lamellar keratoplasties. Another patient underwent four additional surgeries including a conjunctival Z-plasty, scleral patch grafting, and conjunctival autografting before his intractable pain and photophobia resolved 15 months after the original surgery. Because of these complications, 6 patients required a total of 20 return visits to the operating room after their original pterygium surgery. In 5 eyes, visual acuity remained at 20/200 or less. Three of the six patients with the most severe complications had concomitant chronic external diseases (rosacea [3 patients], ichthyosis [1 patient], keratitis sicca [1 patient]).

CONCLUSION

The authors urge extreme caution in the use of mitomycin. If mitomycin is used, the lowest possible concentration should be applied for the shortest time period in an effort to avoid these complications. A prospective multicenter study of the ophthalmic use of this medication is needed.

Subconjunctival injection of purified blood mononuclear cells into alkali-injured rabbit eyes

Monocytes transform into tissue macrophages that scavenge necrotic debris from wounds but also release substances stimulatory to fibroblasts. In an effort to encourage the healing process, monocytes, purified from rabbit blood, were injected subconjunctivally 1 or 2 days and 6 or 7 days after alkali injury to the rabbit eye. The injected monocytes failed to alter the course of the alkali-injured eyes. Specifically, the incidence of corneal ulceration in the experimental group was not statistically different from that of the control group. A byproduct of this study was a presentation of the technique to purify platelet-free mononuclear leukocytes from rabbit peripheral blood.

A visual assay for quantitating neutrophil chemotaxis in a collagen gel matrix. A novel chemotactic chamber

The chemotactic behavior of polymorphonuclear leukocytes (PMNs) suspended in a three-dimensional gel of native collagen fibers was analyzed using a new visual assay aided by computer assisted tracking. Cell behavior was observed in a 7 microliters chamber closed at either end with capillary tubes tipped with dialysis membrane. The chemoattractant, LTB4, was placed in one capillary tube and the control substance in the opposite tube. Under microscopic observation neutrophils were videotaped, their images digitized, and the x and y coordinates of the cell centroids captured at 30 s intervals for 15 min and subsequently analyzed. The data generate a global perspective of neutrophil behavior in a medium simulating a collagenous tissue. The results show that when leukotriene B4 was substituted for HBSS the PMN population underwent chemotactic displacement. PMN chemotaxis was increased greatly when the concentration of LTB4 was increased from 10 nM to 1 microM in separate experiments. This result was partly achieved by movement of an increasing percentage of the PMN population, less frequent stops, and longer durations of motility for individual cells. The most dramatic effect of LTB4 on neutrophil behavior was a large increase in directional movement toward the chemotactic source. The effects of LTB4 fell dramatically when the gradient source concentration was increased to 10 microM. The visual assay described here provides clear evidence that LTB4 induces true neutrophil chemotaxis in a collagenous matrix.

Amino acid composition of a neutrophil respiratory burst stimulant. Evidence for a protein, noncollagenous source

Activation of the neutrophil respiratory burst by the supernatant fraction from an alkali-treated collagen preparations (SAC) was enhanced by longer durations of exposure to alkali (1 N NaOH for 0.5-24 hr). The concentrate obtained from ultrafiltration (greater than 30,000 molecular weight) of SAC (1 N NaOH for 24 hr) retained the stimulatory factor. Fractionation of this ultraconcentrate by high-performance liquid chromatography showed that the stimulatory activity resided in the void volume (highest molecular weight). The amino acid composition of this active fraction revealed that this proteinaceous stimulant was not derived from the collagen molecule. Treatment of the SAC with ultrapure bacterial collagenase increased its stimulatory capacity, confirming its noncollagenous nature. Alkali treatment of whole cornea also released a similar large molecular weight, noncollagenous protein that stimulated the respiratory burst of polymorphonuclear leukocytes. Enhanced stimulation after prolonged NaOH treatment of the collagen preparation or collagenase treatment of SAC suggests that the stimulant might reside between collagen fibrils and then be released as the matrix is degraded.

The combined effect of citrate/ascorbate treatment in alkali-injured rabbit eyes

The incidence of ulceration and perforation in the cornea of alkali-injured eyes is significantly reduced by treatment with trisodium citrate or sodium ascorbate. Topical citrate reduces the inflammatory response in the cornea by inhibiting polymorphonuclear leukocytes. Topical ascorbate elevates the depressed level of this vitamin in the alkali-injured cornea, reversing a scorbutic condition. The purpose of the current study was to determine whether combined treatment with topical citrate and ascorbate has an additional therapeutic value when compared with citrate alone. Adsorbotear without EDTA was used as the vehicle for both medications. Rabbit eyes were injured with 1N NaOH for 35 s using a 12-mm well and were rinsed. Group I (47 eyes) received two drops of 10% citrate every hour on the hour and Adsorbotear on the half-hour for 14 h/day. Group II (48 eyes) received two drops of 10% citrate every hour on the hour and 10% ascorbate every hour on the half-hour for 14 h/day. The citrate/ascorbate group had significantly fewer ulcerations during the experiment than did the group receiving citrate alone (2 of 48 versus 10 of 47, 0.01 less than p less than 0.02). Both anterior ulcers in the citrate/ascorbate group and five ulcers in the citrate group healed to no ulcer by the end of the experiment (0 of 48 versus 5 of 47, 0.02 less than p less than 0.05). The average depth of ulceration was significantly less for the citrate/ascorbate group (p less than 0.001). No descemetoceles or perforations were observed in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

The intraocular changes of anterior segment necrosis

Anterior segment necrosis is an acute or chronic process occasioned by embarrassment of the blood supply of the anterior segment of the eye. In the acute form this vascular obstruction leads to severe corneal oedema, necrosis of anterior uvea, hypotony and cataract formation. Depression of aqueous humour formation accounts for severe reduction of glucose levels in corneal stroma and aqueous humour lasting for two days after cautery of the long posterior ciliary arteries (LPCA) in rabbits. Lactate levels are initially significantly elevated but return to normal after one week. Stromal hydration was elevated for one week but then returned to normal. Corneal epithelial glycogen was diminished at one and two days after surgery but then returned to normal. Although unproven, oxygen deprivation probably plays a major role in endothelial ischaemia and therefore corneal oedema. It is concluded that the abnormalities seen in anterior segment necrosis stem from changes in aqueous metabolic components resulting from severely reduced aqueous turnover. Hyperbaric oxygen and intracameral metabolite substitution are unproven treatments but merit further experimental study.

Sorption of sodium hydroxide by type I collagen and bovine corneas

There are no quantitative studies on the uptake of alkali into corneal tissues. To study this phenomenon, both type I collagen and bovine corneas were incubated in sodium hydroxide (NaOH) under varying conditions for periods up to 27.5 h. The sorption (absorption or adsorption) of the alkali to protein and tissue was measured as the quantity of NaOH no longer available for titration to neutrality with hydrochloric acid. Sorption was found to be dependent on the concentration of NaOH (0.01-1 N) but independent of the incubation temperature (4-35 degrees C). In whole cornea, sorption of 1 N NaOH began immediately and increased with time up to 6 h. After 6 h, sorption decreased, together with the observed degradation and solubilization of the tissue. Stripping of the corneal endothelium alone or of the endothelium and epithelium increased sorption in a similar manner when compared to whole corneas for periods up to 4 h. These observations are compatible with ionic and nonionic bonding of hydroxide ions to collagen (including that of the cornea) and the subsequent release of hydroxide ions during hydrolysis of the protein itself. Indirect evidence also suggests the inclusion of quantities of unbound hydroxide ions in hydrated gels of glycosaminoglycans. It is proposed that in a chemical burn of the cornea, alkali is both stored in the tissue (by sorption) and reacted with it (by hydrolysis), without any net consumption of alkali taking place.

Topical citrate inhibits the adherence of neutrophils to postcapillary venules

The high incidence of corneal ulceration in the alkali-injured rabbit eye can be reduced by topical citrate drops. Citrate interferes with polymorphonuclear leukocyte (PMN) accumulation in the corneal stroma after alkali injury. It inhibits the adherence, locomotion, respiratory burst, phagocytosis, and degranulation of human PMNs in vitro. The objective of this research was to determine if PMN adherence to the vascular endothelium could be inhibited by superfused citrate in vivo. PMN adherence to the endothelium of postcapillary venules in the hamster cheek pouch was greatly enhanced and maintained by addition of leukotriene B4 (LTB4) to the superfusate. Superfusion of the pouch with 24 mM citrate for 5 min, before addition of LTB4, inhibited PMN adherence to the endothelium. The free calcium level in the superfusate was reduced from approximately 650 to 33 microM in the presence of 24 mM citrate. When LTB4-augmented PMN adherence was allowed to occur, followed by citrate treatment (24 mM), it was reversed. Simultaneous addition of CaCl2 and MgCl2 to the superfusate raised the free Ca2+ level to 786 microM and reversed the citrate-induced inhibition of LTB4-augmented adherence. From this and other research, we conclude that citrate probably inhibits adherence of PMNs to pericorneal and conjunctival vessels in the eye, preventing their accumulation in the corneal stroma.

The efficacy of topical citrate after alkali injury is dependent on the period of time it is administered

The neutrophilic response in the alkali-injured rabbit cornea can be separated into two peaks: the first from 12-24 hr and the second at 21 days. In the experiments detailed here, alkali-injured rabbit eyes were treated for 0-7 days (early peak), 6-35 days (late peak), or 0-35 days (both peaks) with 6.5% or 10% topical citrate. Clinical evaluation of these eyes showed that treatment with 10% citrate (0-35 days) significantly reduced the incidence and severity of corneal ulceration from the control level. When 10% citrate was administered to block the early neutrophilic peak, the incidence of corneal ulceration was also significantly reduced (33.3% from 72.2%). The average ulcer depth increased gradually, reaching an intermediate level well below the control group by day 35. In contrast, 10% citrate treatment of the late peak had no significant effect on the incidence of ulceration; however, these ulcers were less severe than those in the control. When 6.5% topical citrate (0-35 days) was used, there was a significant reduction in the severity but not the incidence of ulceration. In addition, the beneficial effects obtained from separate treatment of the early and late PMN peaks were mostly lost. These experiments suggest that both the early and late peak of the PMN response after alkali injury are important to the development of corneal ulcers. We hypothesize that the early use of 10% citrate diminishes the initial peak of PMNs, interfering with the release of self-perpetuating inflammatory mediators, thereby decreasing the later accumulation of PMNs that cause ulceration.

Citrate or ascorbate/citrate treatment of established corneal ulcers in the alkali-injured rabbit eye

Immediate treatment of alkali-injured eyes with citrate or ascorbate has previously been shown to prevent corneal ulceration and perforation in the rabbit. Other experiments showed that while ascorbate treatment of established ulcers did not appear to lead to significant healing it did reduce perforations by prolonging the presence of descemetoceles. In the present experiment with established ulcers, alkali injuries were created with 1 N NaOH in a 12 mm corneal well for 35 seconds. Eyes were entered into the study with anterior, middle or posterior ulcers. When compared to controls, 10% citrate (q1/2 hr) significantly reduced the deepening of anterior stromal ulcers while 10% ascorbate/10% citrate (q1 hr/q1 hr-30 min apart) showed only a trend toward reduction of these ulcers (14 hr of dropping). The demonstration of healing (total vascularization or no ulcer) is significant when comparing the control group (8.3%) to the citrate treated group (58.3%, 0.01 less than P less than 0.009), but not the ascorbate/citrate group (18.2%). Sixty-seven percent of anterior stromal ulcers in the control group progressed to descemetocele or perforation, compared to 8.3% in the citrate treated (0.003 less than P less than 0.004), and 45.5% in the ascorbate/citrate treated group (not significant). While the numbers of ulcers entered as middle stromal were too few to analyze statistically, the reduced numbers of perforations and increased stability prior to perforation in both treatment groups suggest a positive effect by both citrate and ascorbate/citrate. Treatment of posterior stromal ulcers did not prevent the development of descemetoceles and perforations in either treatment group; however, the numbers in this category were too few to analyze.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of citrate on the adherence of neutrophils to nylon fibers in vitro

The therapeutic effect of citrate on alkali-burned eyes is thought to be the result of inhibition of PMN activities while ascorbate apparently stimulates the production of new collagen by scorbutic fibroblasts. Attachment of PMNs to the vascular endothelium is the initial PMN response to mediators and must occur before diapedesis and chemotaxis can produce a tissue infiltrate. The present study was undertaken to test the effects of citrate or ascorbate on the in vitro adherence of resting and leukotriene B4 (LTB4)-treated PMNs. Citrate preincubation of resting or LTB4-treated PMNs inhibited adherence in a dose-dependent manner. Inhibition of LTB4 augmented adherence by 12 mM citrate was effectively reversed by the addition of Ca2+ and Mg2+ (6 mM each). Ascorbate had no significant effect on the adherence of resting or LTB4 treated PMNs. In addition we wished to test the effectiveness of the breakdown product(s) from alkali burned collagen (Type 1) as an augmentor of adherence because of its effectiveness as a locomotory and respiratory burst stimulant. These break-down product(s) had no effect on the adherence of resting or LTB4-treated PMNs unless bovine serum albumin (BSA) was omitted from the incubation mixture. In the absence of BSA, these breakdown products inhibited both types of adherence in a dose-dependent manner with dilutions from 1:10 to 1:1000. This inhibition is probably not clinically meaningful since PMN adherence takes place in the vasculature where BSA would always be present. As a consequence of citrate inhibition of adherence in vivo, PMNs would be denied access to the injury site, trapping them in a resting state within the circulatory system.

Preliminary characterization of a polymorphonuclear leukocyte stimulant isolated from alkali-treated collagen

This study reports the preliminary characterization of a stimulant released from alkali-treated collagen which activates the respiratory burst of PMNs. The supernatant fraction from alkali-treated collagen (SATC) was precipitated with ammonium sulfate, resuspended, and centrifuged through a sucrose gradient (10-30%, W/V). Proteins were detected throughout the gradient but PMN stimulatory activity was found mainly in fractions 1 and 2 (bottom of gradient), indicating a very high molecular weight. When SATC was layered on a denser sucrose gradient (20-85%, W/V), protein was spread over the upper half of the gradient. The peak of PMN stimulatory activity was found in the middle of the gradient (fractions 8 and 9), indicating a molecular weight similar to the 200,000 dalton standard. High pressure liquid chromatography (HPLC) of fractions from this heavier sucrose gradient showed a small peak, followed by a much higher main peak. The small peak, with the highest molecular weight peptide, is responsible for stimulation of the respiratory burst of PMNs (fraction 8 and 9). The source of this stimulant is yet to be determined.

Alkali-burned collagen produces a locomotory and metabolic stimulant to neutrophils

Polymorphonuclear leukocytes (PMNs) invade the cornea following an alkali burn apparently undergoing a respiratory burst and degranulation, which is thought to lead to corneal ulceration. The supernatant obtained from burned Sigma collagen (Miller type 1) or from bovine cornea produced a significant locomotory stimulus to PMNs. Citrate inhibited this locomotory stimulus by 69.5% and 98%, respectively. PMNs were stimulated to undergo a respiratory burst without the concomitant release of beta-glucuronidase when exposed to the supernatant from alkali-burned commercial collagens, or from bovine or porcine corneas. This stimulation is reduced by 72% (Sigma collagen) or 89% (bovine cornea) when the supernatant is dialyzed against distilled water and reinstated when the osmolality is increased. The degree of the respiratory burst is partially dependent on the volume of the supernatant, the duration of alkali exposure, and/or the concentration of NaOH used. The respiratory burst of PMNs stimulated by alkali-burned Sigma collagen supernatant is inhibited by trifluoperazine but not by citrate or EDTA. Light and electron microscopy of these stimulated PMNs show many large blebs and hairlike projections. The authors hypothesize that collagen breakdown product(s) from alkali burning might be the initial, or one of the initial stimuli, for PMN invasion into the cornea and the subsequent activation of the respiratory burst.

Evaluating the undescended testis

This problem is often associated with other anomalies which, if present, are usually evident on the initial examination. Therapy before age two is mandatory to preserve fertility. The malignant potential of undescended testes is well established. Placement of the testes into the scrotum facilitates frequent examinations. All postpubertal patients with intra-abdominal testes, as well as patients who have inguinal testes and are between puberty and age 50, should be referred for orchiectomy.

Urethral duplication and complete bladder exstrophy

Urethral duplication is a rare anomaly that has been classified into epispadiac, hypospadiac, spindle, Y-duplications and collateral varieties. We report a case of an accessory urethra associated with complete bladder exstrophy in which the accessory urethra was integrated into the epispadias repair. To our knowledge this is the first case reported of urethral duplication associated with bladder exstrophy.

Polymorphonuclear leukocytic inhibition by citrate, other metal chelators, and trifluoperazine. Evidence to support calcium binding protein involvement

Corneal ulceration after severe alkali burns of the eye is thought to result principally from collagen breakdown as a consequence of local polymorphonuclear leukocyte (PMN) activities. The favorable effect of topical citrate on such burns suggested a direct effect on these inflammatory cells. These in vitro studies show that the stimulation of human PMN by opsonized zymosan can be inhibited by citrate, EDTA, and EGTA. These compounds interfere with opsonized zymosan attachment to PMN, preventing the respiratory burst, phagocytosis, and degranulation. Reversal of this inhibition by calcium and/or magnesium suggests that mechanism is calcium chelation. Trifluoperazine (TFP) inhibition of opsonized zymosan attachment and phagocytosis implicates the involvement of calmodulin. We propose that citrate, EDTA, and EGTA interfere with the receptor mediated attachment of opsonized zymosan to the PMN cell membrane, leaving the PMN in a resting, granulated state. Inhibition of the receptor system by calcium depletion may be the result of interference with calcium-calmodulin modulated microfilament and/or microtubule interfaces in the PMN plasma membrane. It is postulated that comparable events occur in the citrate treated alkali burned cornea. Citrate inhibition of PMN may be useful in other eye and systemic diseases.

Stage D1 adenocarcinoma of prostate

The natural history of Stage D1 adenocarcinoma of the prostate remains unclear. In a series of 50 patients with positive pelvic lymph nodes at the time of staging lymphadenectomy, metastatic disease developed in 43 per cent of the patients treated for cure within the period of time of follow-up. Several series from the literature confirm those findings. Positive pelvic lymph nodes most probably represent systemic disease, and the patients are incurable by current surgical and radiotherapeutic modalities.

Acid phosphatase: its influence on the management of carcinoma of the prostate

Of 343 patients who underwent pelvic lymph node dissection during treatment for carcinoma of the prostate 25 had persistently elevated serum enzymatic acid phosphatase levels preoperatively: 15 (60 per cent) had metastases to the pelvic lymph nodes and 10 (40 per cent) had negative nodes. Bone metastases occurred in 10 of 12 (83 per cent) and 5 of 7 patients (71 per cent), respectively, who were followed for a minimum of 2 years. Of the 318 patients with normal serum enzymatic phosphatase levels 70 (22 per cent) had positive nodes. A persistently elevated serum enzymatic acid phosphatase level in patients with proved carcinoma of the prostate, with elimination of infrequent causes of enzyme elevation, indicates metastases and has significant implications regarding staging and, thus, therapy of this disease.

The effects of citrate on fMLP-induced polymorphonuclear leukocyte stimulation and locomotion

Citrate reduces the incidence of corneal ulceration and perforation in alkali burned eyes and prevents polymorphonuclear leukocyte (PMN) accumulation in certain inflamed ocular tissues. Chelation of Ca2+ and Mg2+ by citrate appears to be the mechanism causing strong inhibition of in vitro PMN stimulation by opsonized zymosan. It is important to know if other activating agents of PMNs, with differing sensitivity to divalent cations, are inhibited by citrate. Citrate (12 mM) partially inhibits fMLP stimulation of the respiratory burst (50%) and degranulation (65%) of PMNs in a divalent cation free media, while having no effect or only a small effect in the presence of 1 mm Ca2+. Citrate also caused significant inhibition of fMLP (12 mM = 50%) induced locomotion of PMN when incubated in media containing 500 microM Ca2+ and 600 microM Mg2+ in a modified Boyden chamber. When used together, Ca2+ (6 mM) and Mg2+ (6 mM) reduced this inhibition to only 20%. Citrate apparently inhibits fMLP-induced stimulation in cation free media by chelating CA2+ effluxed from intracellular storage sites. In the chemotactic studies, citrate probably chelates extracellular Ca2+ and Mg2+. The divalent cation requirements of the activating agents and/or the PMN function may determine the degree of inhibition by citrate. It is therefore important to identify the mediators in alkali burned corneas as well as other inflammatory conditions.

Chemical injuries of the eye

This overview of the biochemical and pathophysiologic events after chemical burns of the eye is intended to act as a guide for appropriate therapy. Effective emergency measures must be instituted immediately followed by careful clinical evaluation to recognize and then treat problems at their inception. When and how to use the variety of drugs and devices is detailed. When these new methods and technology are applied successfully the clinical course may be improved and visual rehabilitation secured. The early results of conjunctival transplantation and hormonal therapy offer promise from experimental procedures. Exciting new treatments employing the foodstuffs ascorbate or citrate (orthomolecular therapy) are currently under investigation. The National Eye Institute sponsors our ongoing randomized clinical trial of these compounds in the treatment of the alkali burned eye. The outcome may change our thinking and our expectations after chemical burns of the eye.

Aphakic refractive penetrating keratoplasty using newborn donor corneas. A preliminary report on an alternative approach to refractive correction

Eyes with corneal disease receiving transplants from premature, full gestational newborns or postnatal donors yield refractive results with a myopic shift. When the donor cornea is from a newborn (40-41 week gestation) this myopic shift was sufficient to correct 5 of 7 aphakic eyes to an average postsurgical refraction of -1.0 diopter (spher equiv). One premature cornea gave -6.0 diopters while six postnatal infant corneas gave an average correction of +8.6 diopters (spher equiv). The steep corneal curvature resulting from surgery explains the additional refractive power noted. The surgical difficulties encountered and the unknown long-term results auger for a slow and controlled introduction of this concept into our everyday practices.

The effects of chemical injury on the ocular surface

Chemical burns of the eye may destroy all of the corneal epithelium and large portions of conjunctival epithelium into the fornices. Restoration of the ocular surface after a chemical burn depends on the centritedal movement of conjunctival epithelial cells and their adherence to the altered corneal stroma. Epithelial movement after a corneal burn is normal for 72 hours after a burn, but persistent epithelial defects thereafter commonly are not resolved until total corneal vascularization occurs. Although this fresh epithelium may be protected by a bandage soft contact lens, more promising and far-reaching approaches may follow epithelial supplementation and even replacement. The link between the health and integrity of the epithelial layer as it relates to the corneal substratum and its cellular constituents remains to be forged.

Effects of topical 10% ascorbate solution on established corneal ulcers after severe alkali burns

When established corneal ulcers induced by alkali burning were treated with 10% ascorbate drops, no perforation occurred, in contrast to a 25% incidence in the control group. If perforations and descemetoceles were grouped together, these difference became insignificant (i.e., 14.2% ascorbate-treated vs. 25% control). Prolongation of descemetocele presence without perforation in the ascorbate-treated group indicated some therapeutic effect. We conclude that topical ascorbate does not substantially alter the outcome of established corneal ulcers.

Sodium citrate reduces the incidence of corneal ulcerations and perforations in extreme alkali-burned eyes--acetylcysteine and ascorbate have no favorable effect

Alkali-burned eyes (45 sec, 12 mm, 4N NaOH) were subjected to topical treatment with 10% ascorbate, 20% acetylcysteine, 10% ascorbate together with 20% acetylcysteine, 10% citrate, or Adsorbotear vehicle. Only citrate-treated eyes showed a significant decrease in corneal ulcerations and perforations (17%) compared with ascorbate (88%), acetylcysteine (81%), ascorbate/acetyl-cysteine (100%), or Adsorbotear (75%). In the citrate-treated eyes there was a significantly reduced incidence of band keratopathy (17%) but an increased incidence of hyphema (100%). Both groups receiving acetylcysteine developed acellular corneal caps, the result of peripheral ulceration undermining the central cornea. Polymorphonuclear neutrophils (PMN) were substantially increased at the base of the cap in the acetylcysteine- and acetylcysteine/ascorbate-treated eyes at day 56. At the end of the experiment, citrate-treated eyes showed substantially fewer stromal PMN than any other group. These results show that topical citrate has a most favorable effect on the incidence of corneal ulceration and perforation after alkali burning.

The influence of parenteral ascorbate on the strength of corneal wounds

Rabbits receiving subcutaneous ascorbate after corneal wounding showed significant elevation of aqueous humor ascorbate levels but no enhancement of wound breaking strength when compared to controls. In a second group of rabbits, perilimbal alkali burning reduced aqueous humor ascorbate levels one-half to one-third normal. In these perilimbally burned eyes with wounds in clear cornea, subcutaneous ascorbate significantly raised the aqueous humor ascorbate level and enhanced breaking wound strength compared to controls. We conclude that parenterally administered ascorbate has no salutory effect on the breaking strength of corneal wounds in the normal rabbit eye. In contrast, subcutaneous ascorbate has a very favorable effect on the breaking strengths of corneal wounds in those eye with depressed aqueous humor ascorbate.