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Biomedical subjects

R W Nash

Publications and source records attributed to R W Nash.

At least 19 recordsLinked to original sources
PubMed1995

Comparison of scleral tensile strength after transscleral retinal cryopexy, diathermy, and diode laser photocoagulation.

OBJECTIVES: To determine the effect of transscleral diode photocoagulation on the tensile strength of sclera in an experimental rabbit model and to compare it with that of transscleral cryotherapy and diathermy. METHODS: Twenty-four Dutch-belted rabbits received one of the following three treatment modalities in one eye: (1) transscleral cryotherapy, (2) transscleral diathermy, or (3) transscleral diode laser photocoagulation. The opposite eye served as a paired control. Tensile strength measurements of scleral strips excised from areas of treatment were obtained 6 weeks later. RESULTS: No statistically significant difference in mean tensile strength was observed between eyes receiving transscleral cryopexy (n = 7) or transscleral diode photocoagulation (n = 8) and their corresponding, paired, control eyes. In contrast, transscleral diathermy reduced mean scleral tensile strength to 26% of that of the paired control eyes (n = 8, P = .0001). CONCLUSIONS: In this rabbit model, scleral weakening is significant following transscleral diathermy while transscleral cryopexy or transscleral diode photocoagulation produces no significant weakening relative to paired, untreated controls.

Animals↗
PubMed1994

Freehand composite veneering--the direct option.

Freehand bonding of direct composite resin veneers is one of the new techniques developed during the past decade. This article discusses the clinical procedure of this technique, with indications and contraindications, and a new composite resin material used in this technique. The learning objective of this article is to expand the expertise of freehand bonding of direct composite veneers into a larger segment of clinicians.

Composite Resins↗
PubMed1994

The response of cultured human retinal pigment epithelium to hypoxia: a comparison to other cell types.

PURPOSE: To characterize the response of cultured human retinal pigment epithelial (RPE) cells to lowered environmental oxygen. METHODS: The response of cultured RPE cells to lowered oxygen environments was compared to that of cell types of presumed high (Madin-Darby canine kidney [MDCK] cells, an epithelial cell line) and low (CSF, corneal stromal fibroblasts) aerobic requirements. Cultures in a range of densities were exposed for 7 days to 3%, 8%, or 20% O2 with measurements of adenosine triphosphate (ATP), cell number, and cytochrome oxidase (CO) activity (an enzyme marker of aerobic metabolism). RESULTS: RPE cells had levels of CO activity and total cellular ATP intermediate between those of CSF (low) and MDCK (high) in all oxygen environments. Hypoxia led to modestly lowered ATP pools and CO activity for RPE cells over a wide range of culture densities. Hypoxia induced a greater cell loss in MDCK cells than in RPE cells, and the effects of hypoxia were greater in dense cultures of both epithelial cell types. Hypoxia had little effect on cell number for CSF. CONCLUSIONS: The data suggest that cultured RPE cells, though aerobically active, are not as dependent upon oxidative phosphorylation and are more resistant to hypoxia than MDCK cells, a cell type derived from another well-perfused tissue. The authors conclude that RPE cells are unlikely to suffer from hypoxic injury in situ because of a moderate aerobic demand and an abundant oxygen supply.

Adenosine Triphosphate↗
PubMed1993

Freehand composite veneering-the direct option.

Freehand bonding of direct composite resin veneers is one of the new techniques developed during the past decade. This article discusses the clinical procedure of this technique, with indications and contraindications, and a new composite resin material used in this technique.

Composite Resins↗
PubMed1991

An evaluation of saline irrigation and comparison of povidone-iodine and antibiotic in the surface decontamination of donor eyes.

We evaluated the effect of saline irrigation on 38 pairs of donor eyes and determined the relative efficacy of antibiotic rinse/storage (neomycin-polymyxin B-gramicidin) and povidone-iodine immersion. Microbial growth was found in 49 (64.5%) of 76 eyes from which cultures were taken before irrigation, and only four (8.2%) became culture negative after irrigation. Of 27 eyes culture negative before irrigation, 15 (55.6%) became positive after irrigation. One eye of each pair was then assigned randomly to antibiotic rinse/storage and the other eye to 3-minute immersion in 1% povidone-iodine. Both antimicrobial treatments decreased the numbers of positive cultures, with povidone-iodine showing an advantage that did not reach significance. These results demonstrate that saline irrigation of donor eyes in situ does not reduce surface contamination and that povidone-iodine immersion should be considered as an alternative for donor eye decontamination.

Anti-Bacterial Agents↗