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Biomedical subjects

E D Varnell

Publications and source records attributed to E D Varnell.

16 recordsLinked to original sources
PubMed1992

Vancomycin-enriched corneal storage medium.

Antibiotics in a corneal preservation solution probably have little effect during storage at 4 C, but are effective as the tissue is warmed. The tissue acts as a sponge, soaking up the antibiotic from the solution and releasing it into the eye, where the bactericidal effect is achieved. Currently, high concentrations of gentamicin (relative to the minimal inhibitory concentration) are used in the preserving solution for this purpose. Presumably, proportionately high concentrations of any proposed new antibiotic added to supplement the bactericidal effect of gentamicin, such as the vancomycin used in this study, would be required. However, neither the ability of donor tissue to tolerate high concentrations of vancomycin nor the stability of vancomycin at neutral pH in appropriate storage media has been documented. We evaluated the addition of vancomycin (100 micrograms/ml) to two corneal storage media that contained gentamicin in terms of stability of the antibiotic in solution and the effect on the endothelial cells of donor tissue stored for two weeks at 4 C. Vancomycin was stable in solution at neutral pH (7.2) during the five-month period of the study; the concentration exceeded 90 micrograms/ml for the first five weeks. The endothelial cells from donor tissue stored in the vancomycin-enriched media showed no notable differences from those stored in the same media without vancomycin in terms of cell shape, cell borders, cell swelling, and apical holes. The stability of vancomycin in storage and the absence of endothelial toxicity in vitro support the potential use of this antibiotic as a supplement to gentamicin for the prevention of endophthalmitis in patients receiving corneal transplants.

Aged↗
PubMed1991

Optisol corneal storage medium.

Optisol is an investigational, intermediate-term corneal storage medium containing chondroitin sulfate and dextran to enhance corneal dehydration during storage. We used scanning electron microscopy to grade endothelial cell morphologic characteristics in terms of cell shape, cell borders, cell swelling, and apical holes in pairs of corneas stored in Optisol and Dexsol. Optisolstored corneas showed significantly fewer morphologic changes after 14 days at 4 degrees C than did Dexsol-stored corneas. No significant differences were seen after 1 to 4 days at 26 degrees C. Temperature-reversal analysis showed no significant change in corneal thickness with warming after 2-week storage at 4 degrees C in either medium, although Optisol-stored corneas were significantly thinner than those stored in Dexsol at all times. The results of scanning electron microscopy suggest that preservation at refrigerator temperature for 2 weeks in Optisol is superior to preservation in Dexsol. Both media may be useful in preserving endothelial structure for limited periods at room temperature, which could provide a measure of safety in shipping or storage where refrigeration is unreliable.

Adult↗
PubMed1991

Suppression of ocular herpes recurrences by a thymidine kinase inhibitor in squirrel monkeys.

5'-Ethynylthymidine, an inhibitor of viral thymidine kinase (TK), was given intraperitoneally to squirrel monkeys previously infected by the ocular route with Rodanus strain herpes simplex virus. Spontaneous ocular recurrences were reduced during therapy, compared to saline-treated controls. This is the first in vivo demonstration that a viral TK inhibitor can reduce recurrences of HSV-1. Similar benefit would be expected for HSV-2 and perhaps VZV (varicella zoster virus).

Animals↗
PubMed1989

Endothelial cell damage in human and rabbit corneas stored in K-Sol without antioxidants.

Human and rabbit corneas were stored at 4 degrees C in K-Sol with and without antioxidants (ascorbic acid, reduced glutathione, alpha-tocopherol, and retinol acetate) for two to three weeks. All the corneas were then examined visually and by scanning electron microscopy. They appeared clear and slightly oedematous. Scanning electron micrographs were used to grade corneal endothelial cell morphology in a masked manner in terms of cell shape, cell borders, cell swelling, and apical holes. Corneas stored in K-Sol without antioxidants showed changes in cell shape, cell borders, and apical holes. Human corneas showed more morphological changes than rabbit corneas. The results suggest that antioxidants in K-Sol have an important role in the preservation of endothelial cell morphology.

Animals↗
PubMed1988

K-Sol corneal preservation at room temperature.

K-Sol, a recently developed corneal storage medium that contains purified chondroitin sulphate in tissue culture medium (TC 199), is capable of preserving corneal tissue for 14 days at 4 degrees C. To study the effect of tissue storage in K-Sol at room temperature we preserved rabbit corneas in K-Sol and M-K medium for three or seven days at 25 degrees C. All of the corneal endothelial sheets were intact after three days. At seven days the change in pH of the K-Sol medium was less than that of M-K medium. Corneas preserved in M-K medium showed swelling of mitochondria and a decrease in the number of cytoplasmic organelles. Corneas preserved in K-Sol had organised cytoplasmic organelles and nuclei. Scanning electron micrographs revealed well preserved endothelial sheets. Corneas stored in the two media showed no significant difference in thickness. A pair of human corneas preserved in K-Sol at room temperature for six days maintained about 95% of the endothelial sheet in good condition. Small separations were observed between some of the endothelial cells. However, even in these areas, the cytoplasmic organelles were well preserved. It appeared that K-Sol is more stable than M-K medium at room temperature, and that both rabbit and human corneas can be preserved in good condition in K-Sol for at least six days at 25 degrees C.

Animals↗
PubMed1987

Histological study of corneas preserved in two new media.

A new corneal preserving medium (K-Sol), developed by Kaufman and others, contains purified chondroitin sulphate, TC 199, HEPES buffer, and gentamicin. Another new medium (JM) containing bicarbonate-free glucose-phosphate Ringer solution and dextran 70 has been developed in Japan. New Zealand white rabbit corneas with scleral rims were stored in each medium at 4 degrees C for one or two weeks. The condition of the endothelium was evaluated histologically. Corneas preserved in both media were in good condition at the end of one week. Corneas preserved in K-Sol for two weeks showed fewer endothelial changes than similar tissue stored in JM for two weeks. Corneal swelling was also less in corneas preserved in K-Sol, than in corneas preserved in JM.

Animals↗
PubMed1987

A primate model for acute and recurrent herpetic keratitis.

Twelve squirrel monkeys were inoculated in both eyes with the Rodanus strain of herpes simplex virus type 1 (HSV-1) and were examined for the presence of acute epithelial keratitis. All of the eyes developed dendritic keratitis within 72 hours after inoculation. The twelve monkeys plus two additional similarly infected monkeys were also examined for the presence of clinical recurrences of ocular herpes infections and spontaneous shedding of virus in their tears. Two of the eyes developed stromal disease, and 13 of the monkeys had at least one episode of recurrent clinical epithelial disease. Virus was isolated from two of the eyes with recurrent dendrites.

Animals↗
PubMed1985

K-Sol corneal preservation.

K-Sol, a new cornea preserving solution which contains no calf serum of foreign protein and is used for refrigerated storage of donor tissue, has storage procedures identical to those currently used for tissue preservation in McCarey-Kaufman medium. K-Sol can keep corneas alive and usable for penetrating keratoplasty for at least two weeks. The clinical results in a series of 17 patients indicated that tissue preserved in K-Sol for as long as two weeks, even when used by inexperienced surgeons in difficult or unfavorable cases requiring extensive anterior segment reconstruction, including reoperations or retained intraocular lenses, gave results virtually identical to those obtained with tissue preserved in McCarey-Kaufman medium for only two or three days.

Adult↗
PubMed1985

Effect of the herpes simplex virus genome on the response of infection to corticosteroids.

The type and severity of ocular herpetic disease, as well as the pattern of recurrence, have been shown to be determined by the virus genome. We infected rabbit eyes with two closely related recombinant strains of herpes simplex virus type 1 and treated one half of the eyes in each group with corticosteroids before or immediately after virus inoculation. The severity of disease in the first week was similar in the treated and untreated eyes infected with the F(MP)F strain; however, with F(MP)E infection, the disease in the treated eyes was significantly worse than the disease in the untreated eyes. Cultures of corneal virus showed similar titers in all of the groups, but cultures of trigeminal ganglia indicated that increased severity of disease did not result in an increased tendency toward ganglionic colonization. The results suggest that the response to corticosteroids is another factor that is determined by the genetics of the infecting virus, but that there is no correlation between worsening of disease with corticosteroid treatment and the establishment of virus latency.

Adrenal Cortex Hormones↗
PubMed1978

Effect of 9-(2-hydroxyethoxymethyl)guanine on herpesvirus-induced keratitis and iritis in rabbits.

Drugs used for the inhibition of DNA viruses, such as iododeoxyuridine, adenine arabinoside, or trifluorothymidine, are not biochemically selective in their action and also interfere with normal cellular functions. The recently reported 9-(2-hydroxyethoxymethyl)guanine (acycloguanosine) is selectively phosphorylated by viral thymidine kinase but not by normal cellular thymidine kinase. Our present studies show that the acycloguanosine is as effective in treating herpetic keratitis in the rabbit as iododeoxyuridine and trifluorothymidine when given topically as an ointment. It is also effective when given intravenously for the treatment of herpetic iritis and is effective in preventing death from encephalitis in rabbits.

Animals↗
PubMed1977

Lack of levamisole effect on experimental herpes keratitis.

Levamisole, which is an anthelminthic, can restore depressed cell-mediated immunity (CMI) under some circumstances. In a controlled trial of experimental herpetic keratis in rabbits, levamisole was found to have no significant effect on acute herpetic keratitis or its recurrence rate. This is consistent with previous findings that other nonspecific CMI stimulation had no effect on recurrences of experimental herpes keratitis. Because of the known tendency of levamisole to produce agranulocytosis, we believe it should not be used in man unless proven effective in a carefully controlled double-blind study.

Animals↗
PubMed1976

Effect of 9-beta-D-arabinofuranosyladenine 5'-monophosphate and 9-beta-D-arabinofuranosylhypoxanthine 5'-monophosphate on experimental herpes simplex keratitis.

Treatment of established experimental keratitis caused by herpes simplex virus with 9-beta-d-arabinofuranosyladenine 5'-monophosphate (Ara-AMP) or 9-beta-d-arabinofuranosylhypoxanthine 5'-monophosphate (Ara-HxMP) showed that the Ara-AMP, in a concentration of 2 or 20%, had a significant effect on the keratitis but that 0.4% Ara-HxMP showed only minimal activity. Ara-AMP was also effective in the treatment of idoxuridine-resistant keratitis. No local toxicity with a high concentration (20%) of Ara-AMP was seen, but the duration of therapy was brief.

Animals↗
PubMed1976

Phosphonoacetic acid in the treatment of experimental ocular herpes simplex infections.

Phosphonoacetic acid had a significant antiviral effect when applied topically, both in liquid and ointment preparations, on superficial herpetic keratitis in rabbits and was equally as effective as idoxuridine. It was also effective in the treatment of idoxuridine-resistant herpetic keratitis. Phosphonoacetic acid was not effective in the treatment of experimental herpetic iritis when applied topically but was significantly effective when administered intravenously and subconjunctivally. No significant local or systemic toxicity was encountered.

Acetates↗
PubMed1975

The effect of nonspecific immune stimulation on the recurrence rate of herpetic keratitis in rabbits.

Cellular immunity is of primary importance in resistance to virus infection. In this study, 75 rabbits were immunized with live BCG, 75 rabbits were immunized with Staphylococcus aureus, and 75 rabbits were injected with saline. Two weeks after immunization the corneal epithelium of both eyes was infected with McKrae strain herpes virus, and five weeks after immunization the rabbits were skin tested with old tuberculin or staphylococcus to ascertain their immune status. The corneas were observed under the slit lamp for recurrent epithelial herpes from day 52 through day 84 after immunization. During the second week of observation the group immunized with BCG had statistically significantly fewer recurrences than the saline-injected control group. The data for the BCG group during the remainder of the observation period, and for the SPL immunized group, were not statistically distinguishable from the control group. These experiments indicate that nonspecific immune stimulation provides little protection against recurrent herpetic infection. It is possible that manipulation of dosage and timing could enhance this effect.

Animals↗
PubMed1973

Photodynamic inactivation with proflavine: quantitative comparison with iodo-deoxyuridine.

Photodynamic inactivation utilizing proflavine and light was quantitatively compared with the therapeutic antiviral effect of iodo-deoxyuridine in experimental herpetic keratitis in the rabbit. This rabbit model, which has been shown to be highly predictive for antiviral therapy in man, indicates that the photodynamic effect, though definite, is minimal.

Animals↗