Background and gender effects on survival in the TgN(SOD1-G93A)1Gur mouse model of ALS.

Amyotrophic lateral sclerosis (ALS) is a progressive neuromuscular disorder. While most cases of ALS are sporadic, 10-15% are familial, and of these 15-20% possess a mutation in the gene that codes for the enzyme Cu/Zn superoxide dismutase (SOD1). In families of ALS patients with specific SOD1 mutations, affected members demonstrate significant heterogeneity of disease and a large variation in age of onset and severity, suggesting that there are genetic modifiers of disease expression. Transgenic mice expressing mutant forms of SOD1 demonstrate symptoms similar to those seen in patients with ALS. We have observed in our colony of G93A SOD1 transgenic mice a milder phenotype in mice in a C57BL/6J background than the C57BL/6JxSJL/J hybrid background used by Jackson Laboratories to maintain their colony. To investigate the effect of genetic background on phenotype, we have constructed congenic lines on two genetic backgrounds, C57BL/6J (B6) and SJL/J (SJL). We report the influence of background and gender on the survival of these congenic lines compared to the hybrid C57BL/6JxSJL/J background. The mean survival of G93A SOD1 mice in the hybrid B6/SJL background was 130 days, with females surviving significantly longer than males. When compared to the hybrid B6/SJL background, the survival of mice in the SJL background significantly decreased, and the gender difference in survival was maintained. On the other hand, mean survival in the B6 background significantly increased, and in contrast to the B6/SJL and SJL backgrounds, there was no difference in survival between males and females. Transgene copy numbers were verified in all animals to ensure that any phenotypic differences observed were not due to alterations in copy number. This is the first report of a shortened lifespan when the G93A SOD1 transgene is placed on the SJL/J background and an increased survival with the loss of gender influences when the transgene is placed on the C57BL/6J background.

Repair of the tarsoligamentous sling in New Zealand white rabbits using polytetrafluoroethylene graft material.

Repair of large full-thickness lower lid defects requires reconstruction of the tarsoligamentous sling. This may necessitate either a tarsus sharing technique or a skin flap with a free cartilage graft. Obtaining tarsus or cartilage in these procedures has the disadvantage of requiring a second surgical site, which may cause further scarring and deformity. Polytetrafluoroethylene (PTFE) is a nonantigenic, inert, highly biocompatible, mechanically strong synthetic material that has been successfully utilized as a vascular and soft tissue patch since the 1970's. PTFE has been used in ophthalmic surgery to wrap orbital implants and as an interpositional graft for the correction of lower lid retraction. We evaluated the usefulness of PTFE in the reconstruction of the tarsoligamentous sling in 24 lids of 12 New Zealand white rabbits. PTFE with internodal spacings of 10 and 30 microns were used initially. Despite a lack of tissue inflammation, the PTFE grafts were uniformly extruded by 2 weeks postoperatively. Four additional lids were reconstructed using PTFE (30 and 60 microns) coated with a biological substrate. This graft material was also extruded. These results suggest that PTFE material may not be satisfactory for reconstruction of the tarsoligamentous sling.