Atomic force microscopy analysis of progenitor corneal epithelial cells fractionated by a rapid centrifugation isolation technique.

PURPOSE: To investigate the use of atomic force microscopy (AFM) to image the three groups of corneal epithelial cells fractionated by a novel rapid centrifugation isolation technique. METHODS: Epithelial cells harvested from primary cultures of rabbit limbal rings were centrifuged onto uncoated dishes, first at 1400 rpm and then at 1800 rpm. The adherent cells after centrifugation at 1400 rpm (ATC1), the adherent cells at 1800 rpm (ATC2) and the non-adherent cells at 1800 rpm (NAC) were investigated for BrdU retention and were subjected to contact mode AFM and Transmission Electron Microscopy (TEM). RESULTS: Compared with unfractionated cells, the ATC1 group, accounting for about 10% of the whole population, was enriched in BrdU label-retaining cells. There were dramatic overall shape, surface membrane and intra-cellular ultrastructure differences noted among ATC1, ATC2 and NAC populations. The whole cell roughness measurements were 21.1±1.5 nm, 79.5±3.4 nm and 103±4.6 nm for the ATC1, ATC2 and NAC groups, respectively. The mero-nucleus roughness measurements were 34.2±1.7 nm, 13.0±0.8 nm and 8.5±0.5 nm in the ATC1, ATC2 and NAC populations, respectively. CONCLUSIONS: AFM was found to be a good tool for distinguishing among the three groups of cells. BrdU label retention, the AFM parameters and TEM together suggest that the ATC1, ATC2 and NAC populations may be progenitor corneal epithelial cells, transit amplifying cells and terminal differentiation cells, respectively.

Chronic phototoxic maculopathy caused by welding arc in occupational welders.

OBJECTIVE: To investigate whether occupationally-related phototoxicity can occur from welding. DESIGN: Cross-sectional study. PARTICIPANTS: Forty welders from manufacturing enterprise and 40 age-matched nonwelder controls. METHODS: Participants underwent thorough ophthalmologic examination including fundus photography, automatic perimeter examination, and high definition optical coherence tomography (OCT) scan. The clinical history of all subjects was screened carefully before the study. RESULTS: There was no significant difference for best corrected distance visual acuity when comparing welders with nonwelders. Anterior segment, red reflex, Amsler grid test, and perimetric examinations were unremarkable. Fundus photographs revealed a small, round, or oval, dark-yellow macular lesion with an obscure boundary in 19 welder eyes (23.8%). OCT revealed an interruption or defect in the inner segment/outer segment (IS/OS) layer and the inner portion retinal pigment epithelium (RPE) layer in varying degrees in 30 welder eyes (38.0%), revealing a higher prevalence of maculopathy. All control examinations were unremarkable. We have also discovered that OCT is more sensitive than fundus photography in identifying macular lesions. CONCLUSIONS: Occupational welders exposed to a welding arc environment have a higher risk of phototoxic maculopathy than nonwelders, as diagnosed most effectively using OCT.