Bandage contact lens augmentation of 5-fluorouracil treatment in glaucoma filtration surgery.

The use of 5-Fluorouracil (5-FU) to inhibit scarring following filtration surgery has been hampered by corneal epithelial defects and their accompanying inflammation. This toxicity, which occurs during the crucial period in which the risk of bleb failure is highest, has previously been a relative contraindication to further 5-FU use. We have found the early placement of a therapeutic bandage contact lens permits extended administration of 5-FU during this period, minimizing discomfort and inflammation as well as enhancing bleb survival.

Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism: isolation and characterization of a mutant deficient in the activity of phosphoribosylaminoimidazole synthetase.

A new purine-requiring mutant of Chinese hamster ovary cells (CHO-Kl) is described. This mutant, Ade-G, grows on aminoimidazole carboxamide, hypoxanthine, or adenine. It complements all eight of our other previously described Ade- mutants. Biochemical analysis of de novo purine synthesis in whole cells suggests that Ade-G is capable of the first four reactions of de novo purine biosynthesis and that it synthesizes and accumulates phosphoribosylformylglycinamidine (FGAM). Direct enzyme assay in cell-free extracts confirms that Ade-G is defective in phosphoribosylaminoimidazole synthetase activity and does not convert FGAM to phosphoribosylaminoimidazole (AIR), the next intermediate in the de novo biosynthetic pathway.

Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism: characterization of Chinese hamster cell mutants defective in phosphoribosylpyrophosphate amidotransferase and phosphoribosylglycinamide synthetase and an examination of alternatives to the first step of purine biosynthesis.

Activities of the first three enzymes in the de novo purine biosynthetic pathway have been measured in cell-free extracts of the Chinese hamster ovary cell (CHO-K1) and two purine-requiring auxotrophs of this cell. Ade-A has been found to be defective in phosphoribosylpryophosphate (PRPP) amidotransferase while Ade-C has been found to be defective in glycinamide ribonucleotide (GAR) synthetase. Neither enzyme deficiency is due to the presence of an excess of diffusible inhibitor, and mixed extracts of Ade-A and Ade-C are capable of performing both enzymatic steps in a coupled assay. Assays of GAR formyltransferase show that it is present in Ade-A and Ade-C, indicating that these cell types are defective in only one enzyme each of the early purine biosynthetic enzymes. Using the Ade-A mutant, analysis of alternatives to PRPP plus glutamine as substrates for the first step in the purine biosynthetic pathway showed that a common genetic unit must direct the synthesis for both PRPP plus glutamine and PRPP plus ammonia activities. Although ribose-5-phosphate plus ammonia can be used in cell-free extracts to perform the first step in purine biosynthesis, it is shown that this activity is apparently not used by intact CHO-K1 cells.

Synteny between glycinamide ribonucleotide synthetase and superoxide dismutase (soluble).

The auxotrophic mutant ade -C derived from Chinese hamster ovary cell CHO-K1 lacks the enzyme glycinamide ribonucleotide synthetase and requires exogenous supplement of purines for growth. Cells from this mutant were fused with normal human lymphocytes, and the resulting hybrids were isolated in purine-deficient medium. A total of 32 primary clones and 49 secondary clones were analyzed for various isozyme markers. Cytogenetic analysis with chromosome banding was also performed in some hybrid clones. The results provide evidence indicating that glycinamide ribonucleotide synthetase is syntenic with superoxide dismutase (soluble) and is located on human chromosome 21.