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Biomedical subjects

C A Paterson

Publications and source records attributed to C A Paterson.

At least 109 records · Page 6Linked to original sources
PubMed1982

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.

Administration, Topical↗
PubMed1981

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.

Alkalies↗
PubMed1981

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.

Acetylcysteine↗
PubMed1980

Ascorbic acid in the treatment of alkali burns of the eye.

Severe ocular alkali burns in rabbits result in a decrease in aqueous humor ascorbate levels to one-third normal levels. If this deficiency is reversed by immediate treatment with parenteral or topical ascorbate, there is a significantly decreased incidence of subsequent corneal ulceration and perforation. The morphologic changes in these ulcerating corneas are typical of those noted in scorbutus (scurvy). It is concluded that alkali injury to the ciliary epithelial transport processes or ciliary body vasculature results in localized deficiency of ascorbic acid in the aqueous humor and cornea. The development of corneal ulceration is thought to be based on this deficiency which results in the failure of fibroblasts to produce sufficient collagen for repair. A randomized clinical trial of ascorbic acid in the treatment of human alkali burned eyes is now underway.

Alkalies↗
PubMed1980

Characteristics of voltage-dependent conductance in the membranes of a non-excitable tissue: the amphibian lens.

1. The electrical conductance of the frog lens membranes was observed to increase when the lens was depolarized by current, and to decrease when the lens was hyperpolarized. 2. The total lens conductance (GT) could be described by a voltage-dependent component (GH) together with a voltage-insensitive component (GO). 3. Conductance measured at the resting potential increased from 9.7 to 14.4 x 10(-5) S when the lens was depolarized by 9.1 mV in 10(-4) M-ouabain. The increase of conductance could be explained by an increase of GH which resulted from the depolarization alone. 4. Potassium-rich solutions influenced the conductance by increasing GH as the result of depolarization and by decreasing (blocking) GO. Small increases in the external potassium concentration (from 2.5 to 5 mM), which did not depolarize the lens, resulted in a decrease in resting conductance due to the blockade of GO. 5. Conductance-voltage relationships established in 2.5 (control), 5, 12.5 and 25 mM external potassium could each be fitted to a single mathematical model by assuming that GO had been reduced for 5.0 (control) to 4.5, 3 and 1 x 10(-5) S respectively by those increased potassium concentrations. 6. Barium (2 mM) depolarized the lens by 14.3 mV and decreased the resting conductance by 39%. When the lens was depolarized by a step current pulse in the presence of barium, the conductance increased with time after the onset of the current. Hyperpolarization elicited less time dependence of the conductance. 7. Barium reduced the extent to which lens conductance was dependent on voltage.

Animals↗
PubMed1980

The effect of ascorbic acid on experimental acid burns of the rabbit cornea.

The corneas of albino rabbits were subjected to 45 sec, 12 mm, 2.3N hydrochloric acid burns. Of 18 eyes in nine rabbits receiving no treatment (controls), 11 (61%) developed ulceration sometimes progressing to descemetoceles and perforation. Of 17 eyes in nine rabbits receiving a daily subcutaneous injection of ascorbic acid (0.5 gm/kg), only one eye (5.9%) developed an anterior stromal ulcer. The difference in incidence of ulceration between the control and ascorbate-treated eyes was statistically significant (p less than 0.01). The aqueous humor level of ascorbate in untreated animals was 6.0 +/- 0.6 mg/dl compared to 33.0 +/- 2.7 in the treated group. This study therefore demonstrates that subcutaneous administration of ascorbic acid significantly raises the aqueous humor level of ascorbic acid in severely acid-burned eyes, thereby largely preventing the characteristic development of corneal ulceration. The mechanism of this effect is presumably the same as previously described for alkali-burned eyes.

Animals↗
PubMed1980

The efficacy of ascorbate treatment after severe experimental alkali burns depends upon the route of administration.

Rabbit eyes were subjected to severe alkali burns (35 sec, 12 mm, 1N sodium hydroxide). In one experiment, rabbits in the treated group received a daily subcutaneous injection of neutralized ascorbic acid solution (0.5 gm/kg body weight), while control animals received no treatment. At the termination of the experiment (30 days), 11 of 16 eyes (68.8%) in the control group had ulcerated or formed descemetoceles, and in the experimental (treated) group, 15 of 20 eyes (75%) had ulcerated, formed descemetoceles, or perforated. In a second experiment, burned rabbits received topical 10% ascorbic acid while control eyes were given the vehicle only. At the termination of the experiment (34 days), 16 of 20 eyes (80%) in the control group had ulcerated or perforated, compared to five of 18 eyes (27.8%) in the ascorbate treated groups. The failure of systemic administration of ascorbic acid to prevent corneal ulceration could be explained on the basis of inadequate penetration of ascorbic acid into the anterior segment of severely burned rabbit eyes. On the other hand, immediate topical treatment of identically burned rabbit eyes achieved greatly elevated aqueous humor ascorbate levels and provided substantial protection from corneal ulceration and perforation.

Administration, Topical↗
PubMed1979

The influence of calcium on lens ATPase activity.

The activities of ouabain-sensitive (Na-5-) and ouabain-insensitive ATPases were determined in 3.6 mM calcium-containing and calcium-free media. Three lens tissue segments were studied: the epithelium/capsule segment, the anterior cortical segment and the posterior cortical segment. In the presence of calcium, the Na-K-ATPase activity in each segment was reduced, whereas the ouabain-insensitive ATPase activity in each segment was increased.

Adenosine Triphosphatases↗
PubMed1979

The ocular hypertensive response following experimental acid burns in the rabbit eye.

Following application of 50 microliter of 2N hydrochloric acid to the rabbit cornea, the intraocular pressure rapidly increases and remains markedly elevated for up to 3 hr. The initial rapid increase in intraocular pressure appears to be the result of acid-induced shrinkage of the outer collagenous coats of the eye. The sustained rise in intraocular pressure is mediated in part by prostaglandin release. Increased prostaglandin-like activity, determined in the aqueous after an acid burn, was greatly inhibited by pretreatment of rabbits with indomethacin and to a much lesser extent by pretreatment with imidazole. Both indomethacin and imidazole essentially abolished the sustained elevation of intraocular pressure after an acid burn. Analysis of changes in pH and protein level in the aqueous implies that the stimulus for prostaglanding release within the eye is the penetration of hydrogen ions into the aqueous humor, with resultant intraocular trauma.

Animals↗
PubMed1978

The influence of calcium-free EGTA solution upon membrane permeability in the crystalline lens of the frog.

Potential difference, resistance, cation content, and 86Rb efflux were measured in frog lenses maintained in normal or calcium-free EGTA Ringer's solution. Exposure of the lens to calcium-free solution resulted in a rapid fall in potential and resistance, together with a twofold increase in 86Rb efflux rate. These rapid changes were not due to an alteration in cation distribution between the lens and its environment. However, the alteration in 86Rb efflux rate could be explained on the basis of the fall in potential. These findings suggested that removal of calcium from the bathing medium caused a rapid increase in sodium permeability alone. This suggestion was substantiated by the results of experiments where the response of the lens to low calcium solution was determined in a medium in which 90% of the sodium had been replaced by sucrose.

Animals↗