Quantification and image-derived phenotyping of retinal ganglion cell nuclei in the nee mouse model of congenital glaucoma

The nee mouse model exhibits characteristic features of congenital glaucoma, a common cause of childhood blindness. The current study of nee mice had two components. First, the time course of neurodegeneration in nee retinal flat-mounts was studied over time using a retinal ganglion cell (RGC)-marker, BRN3A; a pan-nuclear marker, TO-PRO-3; and H&E staining. Based on segmentation of nuclei using ImageJ and RetFM-J, this analysis identified a rapid loss of BRN3A⁺ nuclei from 4 to 15 weeks of age, with the first statistically significant difference in average density compared to age-matched controls detected in 8-week-old cohorts (49% reduction in nee). Consistent with a model of glaucoma, no reductions in BRN3A^- nuclei were detected, but the combined analysis indicated that some RGCs lost BRN3A marker expression prior to actual cell loss. These results have a practical application in the design of experiments using nee mice to study mechanisms or potential therapies for congenital glaucoma. The second component of the study pertains to a discovery-based analysis of the large amount of image data with 748,782 segmented retinal nuclei. Using the automatedly collected region of interest feature data captured by ImageJ, we tested whether RGC density of glaucomatous mice was significantly correlated to average nuclear area, perimeter, Feret diameter, or MinFeret diameter. These results pointed to two events influencing nuclear size. For variations in RGC density above approximately 3000 nuclei/mm² apparent spreading was observed, in which BRN3A^- nuclei-regardless of genotype-became slightly larger as RGC density decreased. This same spreading occurred in BRN3A⁺ nuclei of wild-type mice. For variation in RGC density below 3000 nuclei/mm², which only occurred in glaucomatous nee mutants, BRN3A⁺ nuclei became smaller as disease was progressively severe. These observations have relevance to defining RGCs of relatively higher sensitivity to glaucomatous cell death and the nuclear dynamics occurring during their demise.

Therapeutic responses of piglets to experimentally induced colibacillosis

The purpose of these experiments was to determine the effects of prior exposure to antimicrobials on subsequent treatment of artificially induced colibacillosis in pigs. One- to two-week-old piglets were given 10(7) multiple antibiotic resistant Escherichia coli orally. Two groups of the piglets received priming doses at different levels of the antimicrobial preparation, ASP-250 before challenge. The remaining group received no antimicrobial. Piglets ill as a result of the challenge were treated with chloramphenicol of chlortetracycline, or received no treatment. Chloramphenicol was significantly more effective than chlortetracycline in terminating colibacillosis in the primed and unprimed groups. There were fewer deaths and relapse cases in those groups which received chloramphenicol treatment. Results in piglets treated with chlortetracycline were not significantly better than those which received no treatment.