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Biomedical subjects

R A Thoft

Publications and source records attributed to R A Thoft.

At least 73 records · Page 4Linked to original sources
PubMed1983

Conjunctival goblet cell frequency after alkali injury is not accurately reflected by aqueous tear mucin content.

Goblet cell counts have been used to evaluate the suitability of conjunctiva as a source of ocular surface epithelial cells. However, since tear mucin content can be determined without tissue excision, it seemed that the concentration of those compounds might be a useful indicator of conjunctival vitality. To test the extent to which aqueous tear composition reflects conjunctival goblet cell frequency, goblet cell frequency and aqueous tear mucin content were measured after alkali injury in rabbits. Mild alkali injury (0.1 N NaOH for 30 sec) caused a transient but substantial decrease in goblet cells (to 25% of normal at day 7) with a return to normal by six weeks. Tear mucin content was decreased to a lesser degree, from a normal value of 6.4 +/- 0.47 nmol oligosaccharide per microliter (n = 10) to a minimal value of 4.7 +/- 0.64 (n = 7) (73% of normal) at day 7, returning to normal 4 weeks after injury. Thus, the direction of the change was the same, but the magnitudes were quite different. These results suggest that conjunctival goblet cell frequency is not accurately reflected by aqueous tear mucin content, and therefore, that tear mucin content cannot be used directly as an indicator of conjunctival health.

Animals↗
PubMed1982

Indications for conjunctival transplantation.

Long-term follow-up (two to five years) of 12 unilateral chemical burn patients treated by conjunctival transplantation shows permanent stabilization of the ocular surface. The procedure was used in another group of five patients with unilateral recalcitrant epithelial defects. Regardless of the etiology of the epithelial defect, prompt healing of the surface occurs after conjunctival transplantation with no further stromal loss and long-term stabilization of the surface. Such results suggest that epithelial replacement may be a valuable therapeutic approach to a variety of ocular surface disorders.

Adult↗
PubMed1982

Corneal epithelial changes in diabetic rats.

Electron microscopy of streptozotocin diabetic rat eyes showed increased intracellular levels of tonofilaments and glycogen, thickenings and infoldings of subepithelial basement membrane and basal cell degeneration after 8 months. Glycogen, glucose, sorbitol, and fructose were measured in corneal epithelium from short- and long-term diabetic rats. The small increase in sorbitol pathway products which were found after 8 months of diabetes (less than 1.0 mosm/1 tissue water) confirmed similar findings in rabbits and humans. Thus, the morphologic changes occur in the absence of significant accumulation of sorbitol pathway products. Osmotic damage secondary to corneal epithelial cell accumulation of sorbitol is probably not a significant factor in corneal epithelial diabetic disease.

Animals↗
PubMed1982

Corneal epithelial cell cultures on stromal carriers.

Exposure of denuded rabbit corneal stromal carriers for 24 hr at 37 degrees C to suspensions of rabbit corneal epithelial cells grown in tissue culture resulted in the establishment of a cell layer on the carriers. The cell layers persisted for at least 1 week of incubation and were one to three cells thick. They consisted of healthy-appearing cells with normal intracellular organelles and intercellular desmosomal connections. After 2 to 7 days of incubation the cells were still capable of DNA replication and produced hemidesmosomes and basement membrane. This system is useful for in vitro studies of substrate requirements for hemidesmosome and basement-membrane formation by corneal epithelial cells.

Animals↗
PubMed1982

Limbal epithelium in ocular surface wound healing.

The regenerated epithelium derived from limbal epithelium was histologically and biochemically compared with epithelia regenerated from corneal and bulbar conjunctival epithelia. The histologic results indicated that regenerated epithelium of limbal origin increased in thickness with time after healing and showed no goblet cell appearance on the cornea. This suggests that regenerated epithelium from the limbus is more like regenerated epithelium of corneal origin than that of bulbar conjunctival origin. However, the glycogen content and protein pattern profile showed that regenerated epithelium of limbal origin had characteristics intermediate between those of corneal and bulbar conjunctival origin. Thus it is proposed that there are three distinct types of ocular surface epithelia--corneal, bulbar conjunctival, and limbal--and that limbal epithelium behaves differently from corneal and conjunctival epithelia in ocular surface wound healing.

Animals↗
PubMed1981

Exogenous Nocardia asteroides endophthalmitis associated with malignant glaucoma.

A 42-year-old man sustained a penetrating corneal wound with a soil-contaminated wire and developed Nocardia asteroides endophthalmitis. A month delay in diagnosis occurred while topical and systemic steroids were prescribed for persistent anterior uveitis, but the diagnosis was finally established by separate aqueous and vitreous aspirates. The patient's course was complicated by a form of malignant glaucoma that was relieved by vitreous aspiration and reformation of the anterior chamber. Surgical intervention, followed by intensive topical and systemic sulfonamide therapy, has resulted in potential visual improvement.

Adult↗
PubMed1981

Sex chromatin of donor corneal epithelium in rabbits.

The survival of donor corneal epithelium was investigated in rabbits after they received unilateral 8 mm diameter lamellar keratoplasties with living donor tissue of a different sex from the host. Three weeks, 6 weeks, and 12 weeks postoperatively, cultured corneal epithelia, grown from 5 mm diameter central buttons, the adjacent 0.75 mm wide donor rings, the peripheral 10 to 13 mm diameter rings, and 5 mm diameter central host buttons were used for sex-chromatin analysis. The results indicated that some of the donor corneal epithelium survived up to 12 weeks postoperatively. Even in the absence of overt epithelial rejection, however, a time-dependent decrease of donor corneal epithelium and simultaneous invasion of host corneal epithelium were demonstrated.

Animals↗
PubMed1981

Corneal re-epithelialization from the conjunctiva.

After debridement of the entire corneal epithelium, epithelial cells of conjunctival origin cover the exposed corneal surface. Four to five weeks later, these cells undergo a morphologic transformation to normal-appearing corneal epithelium. To study this transformation the entire corneal epithelium was removed from rabbits with the use of n-heptanol, after which the histologic appearance of and the number of goblet cells in the regenerated epithelium were noted. Five stages of transformation were seen. Immediately after healing, the epithelium consisted of one to two squamous cell layers with no goblet cells apparent at the light microscope level (stage 1). In the following weeks goblet cells appeared at the limbal edge of the cornea (stage 2), reached a uniform distribution across the cornea (stage 3), and subsequently receded toward the limbus (stage 4), leaving an epithelium with normal corneal morphologic appearance (stage 5). To see if there was an ongoing centripetal cell migration from the conjunctiva across the cornea after initial healing, the central corneal epithelium was isolated from the periphery by a ring of glue. Such isolation resulted in a thinning of the central epithelium and a thickening of the peripheral epithelium. These studies suggest that (1) the transformation into corneal epithelium lags behind defect closure by 4 to 5 weeks, (2) goblet cells do not initially migrate as recognizable cells, and (3) there is a continuous centripetal cell motion even after the initial defect closure is accomplished.

Animals↗
PubMed1981

Diabetes mellitus and the rabbit corneal epithelium.

Diabetes mellitus has been shown to be a factor in the development of corneal epithelial abnormalities in stressed human eyes, but the biochemical basis for this is not known. To see if sorbitol pathway activation might be involved, ocular surface epithelial healing rates and metabolites of the glycolytic and sorbitol pathways were measured in alloxan-diabetic rabbits. As in humans, corneal epithelial healing rates were not decreased in the diabetic rabbits, suggesting that the rabbit may be an appropriate model for human disease. Increased levels of glucose, glycogen, and sorbitol were found in the diabetic corneal epithelium compared with normal. However, the sorbitol accumulation only mounted to 1.0 mOsm/L of tissue water, which implies that osmotic damage secondary to corneal epithelial cell sorbitol accumulation might not be a significant factor in corneal epithelial abnormalities of diabetes.

Animals↗
PubMed1980

Similar epithelial healing rates of the corneas of diabetic and nondiabetic patients.

We developed a reliable method for measuring corneal regeneration in humans with noninvasive, readily available photographic techniques. We then used this method prospectively to compare the rates of primary corneal regeneration after surgery in a series of 27 diabetic and nondiabetic patients. The rates of corneal epithelial regeneration were not significantly different when diabetic patients were compared with nondiabetic patients. A tendency toward recurrent epithelial defects was confirmed in the diabetic patients, however.

Adult↗
PubMed1980

Insulin sensitivity and sorbitol production of the normal rabbit corneal epithelium in vitro.

Insulin-depleted, normal rabbit corneal epithelium was incubated in vitro in tissue culture medium containing high concentrations of glucose (35 mM). These short-term incubations showed that the epithelium took up glucose equally whether or not insulin had been added to the medium, indicating that corneal epithelium is an insulin-insensitive tissue. Sorbitol accumulation showed that the normal corneal epithelium has a sorbitol pathway which can be activated in the presence of high intracellular glucose. The low level of sorbitol accumulation in these normal epithelia is probably not osmotically significant.

Animals↗
PubMed1979

Factors related to corneal epithelial complications after closed vitrectomy in diabetics.

In a series of 30 vitrectomy patients, postoperative corneal complications developed in 14 (47%). Thirteen (92%) of the 14 patients with complications were diabetic. Other factors that were positively correlated with the development of corneal complications included decreased corneal sensitivity, intraoperative lensectomy, and intraoperative epithelial debridement. The corneal complications involved the epithelium in 11 (78%) of the 14 complicated cases, with involvement of the endothelium (as manifested by stromal edema) in five (35%) cases. The diabetic human corneal epithelium contains considerable levels of sorbitol and fructose, which indicates the probable presence of the sorbitol pathway. As in the lens, this pathway may lead to osmotic changes that make the diabetic corneal epithelium more vulnerable to damage intraoperatively. Postoperatively, reepithelialization is delayed because of a probable failure of adhesion of cells to the underlying basement membrane.

Cornea↗
PubMed1979

Conjunctival transplantation as an alternative to keratoplasty.

Rehabilitation of the ocular surface is frequently desired following severe chemical and thermal injury. While keratoplasty, both lamellar and penetrating, has been the usual mode of therapy, chronic healing deficits and graft rejections as a result of heavy vascularization often lead to an unsatisfactory result. In unilateral injury, conjunctival transplantation from the opposite, uninvolved eye offers an alternative therapy which avoids both intraocular surgery and the introduction of immunologically foreign tissue. Seven of ten cases of unilateral chemical or thermal injury showed marked reduction in vascularization and scarring following conjunctival transplantation. The characteristic early vascularization of the peripheral conjunctival grafts showed marked regression one to four months postoperatively. At the same time, the central cornea, whose superficial vessels and scarring were removed by keratectomy, showed reepithelialization and smoothing, without attendant vascularization. Three cases were optical failures partially as a result of deep scarring that could not be adequately excised with keratectomy. Preoperative evaluation must be directed primarily toward evaluation of the corneal thickness and the extent of deep vascularization to select those patients most likely to be improved by conjunctival transplantation.

Adult↗