A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Resistance of photoreceptors in the C57BL/6-c2J, C57BL/6J, and BALB/cJ mouse strains to oxygen stress: Evidence of an oxygen phenotype

Purpose. To assess the vulnerability of retinal photoreceptors in the BALB/cJ, C57BL/6J, and C57BL/6-c2J (c2J) mouse strains to hypoxic and hyperoxic stress. Methods. Mice were raised in dim cyclic light. Pups aged postnatal day 7 (P7) were exposed to hypoxia (11-12% oxygen) for periods up to 23 days. Adult mice were exposed to either hypoxia (12% oxygen) or to hyperoxia (75% oxygen) for up to 2 weeks. Using the TUNEL (terminal dUTP-mediated nick end labeling) technique retinas were examined for cell death. Results. In juvenile mice, hypoxia induced a robust increase in photoreceptor death in the C57BL/6J strain and a weaker increase in the C57BL/6-c2J strains. In the adult, hypoxia was associated with a small reduction in photoreceptor death in the C57BL/6-c2J strains. Hyperoxia caused substantial photoreceptor death in both the C57BL/6-c2J and C57BL/6J strains. The BALB/cJ strain was more resistant to oxygen stress than the C57BL strains. Conclusions. The difference in oxygen vulnerability between C57BL/6J and BALB/c strains may provide a useful starting point for the analysis of genetic regulation of this vulnerability. The resistance of the C57BL/6-c2J substrains to hypoxia may reflect their degenerative status

Photoreceptor degeneration and loss of retinal function in the C57BL/6-C(2J) mouse

PURPOSE. The C57BL/6-c2J (c2J) mouse strain has been shown in earlier studies to be highly resistant to light damage. Subsequent studies related this resistance to an amino acid substitution (leu450met) in a pigment epithelial enzyme (RPE65), which slowed the rate of rhodopsin regeneration. The present study was conducted to examine patterns of photoreceptor death, electrophysiological function (the ERG) and trophic factor expression over the life of the C57BL/6-c2J retina. METHODS. Observations were made on two C57BL/6J-c2J substrains, one albino (Tyr/Tyr) and one pigmented (Tyr/+), and two nondegenerative strains, one albino (BALB/cJ) and one pigmented (C57BL/6J). Mice were raised in dim cyclic light (12 hours at 5 lux, 12 hours in the dark), and a developmental series of retinas of each strain was taken between postnatal day (P)4 and (P365+). Retinas were examined for cell death by using the TUNEL technique, stress-induced protein expression (FGF-2 and GFAP), and measures of retinal thickness. The dark-adapted ERG was recorded in dark-adapted conditions in early adulthood (13-15 weeks) and late adulthood (>1 year). RESULTS. In both C57BL/6-c2J substrains, the retina showed marked degenerative features when compared with two control strains, BALB/cJ (leucine at codon 450 in RPE65) and C57BL/6J (methionine). During development and into young adulthood, photoreceptor death rates were abnormally high, levels of two stress-inducible proteins (FGF-2 and GFAP) were abnormally high, and the ERG (electroretinogram) was significantly reduced in amplitude (<50% of values in BALB/cJ or C57BL/6J). The rate of photoreceptor death remained abnormally high into young adulthood (2-3 months) but decreased to control levels by 1 year. Accordingly, the thickness of the outer nuclear layer and the ERG were stable over the same period. CONCLUSIONS. Results suggest that a still-unidentified stress increases photoreceptor death in the C57BL/6-c2J retina during the critical period of photoreceptor development and into young adulthood, upregulates stress-inducible factors, and markedly limits the amplitude of the ERG, These degenerative changes do not continue after early adulthood, the retina remaining stable in structure and function into late adulthood. The degenerative changes were apparent in both albino and pigmented C57BL/6-c2J substrains. Their genetic cause remains unknown

Role of Myo/Nog Cells in Neuroprotection: Evidence from the Light Damaged Retina

PURPOSE: To identify Myo/Nog cells in the adult retina and test their role in protecting retinal photoreceptors from light damage. METHODS: Light damage was induced by exposing albino rats raised in dim cyclic light to 1000 lux light for 24 hours. In one group of rats, Myo/Nog cells were purified from rat brain tissue by magnetic cell sorting following binding of the G8 monoclonal antibody (mAb). These cells were injected into the vitreous humour of the eye within 2 hours following bright light exposure. Retinal function was assessed using full-field, flash electroretinogram (ERG) before and after treatment. The numbers of Myo/Nog cells, apoptotic photoreceptors, and the expression of glial fibrillary acidic protein (GFAP) in Muller cells were assessed by immunohistochemistry. RESULTS: Myo/Nog cells were present in the undamaged retina in low numbers. Light induced damage increased their numbers, particularly in the choroid, ganglion cell layer and outer plexiform layer. Intravitreal injection of G8-positive (G8+) cells harvested from brain mitigated all the effects of light damage examined, i.e. loss of retinal function (ERG), death of photoreceptors and the stress-induced expression of GFAP in Muller cells. Some of the transplanted G8+ cells were integrated into the retina from the vitreous. CONCLUSIONS: Myo/Nog cells are a subpopulation of cells that are present in the adult retina. They increase in number in response to light induced stress. Intravitreal injection of Myo/Nog cells was protective to the retina, in part, by reducing retinal stress as measured by the Muller cell response. These results suggest that Myo/Nog cells, or the factors they produce, are neuroprotective and may be therapeutic in neurodegenerative retinal diseases

Relationship between mitochondrial DNA damage and photoreceptor death in developing and adult retina, assessed in normal and degenerative rat strains

In this study, we used Real-Time PCR to study the correlation of mtDNA deletions and photoreceptor death by apoptosis in one normal (SD) and two different degenerative (RCS and P23H) rat strains. Our results show that, in the SD and RCS strains, mtDNA deletion frequency increased and fell during neonatal life, correlating with rates of photoreceptor death during the critical period of photoreceptor development, and into adulthood. Results suggest that mitochondrial damage occurs in close association with photoreceptor death, in the normal (SD) and fast degenerative (RCS) retinas. The lack of a similar association was observed in the slowly degenerative P23H-3 strain

Neuroprotective effect of Myo/Nog cells in the stressed retina

Myo/Nog cells are essential for eye development in the chick embryo and respond to injury in adult tissues. These cells express mRNA for the skeletal muscle specific transcription factor MyoD, the bone morphogenetic protein (BMP) inhibitor Noggin and the cell surface protein recognized by the G8 monoclonal antibody (mAb). In this study, we determined that Myo/Nog cells are present in low numbers in the retina of the mouse eye. G8-positive Myo/Nog cells were distinguished from neuronal, Müller and microglial cells that were identified with antibodies to calretinin, Chx10, glial fibrillary acidic protein and ionized calcium binding adaptor molecule 1, respectively. In the neonatal retina, the number of Myo/Nog cells increased in parallel with cell death induced by transient exposure to hyperoxia. In this model of retinopathy of prematurity, depletion of Myo/Nog cells by intravitreal injection of the G8 mAb and complement increased cell death. These findings demonstrate that Myo/Nog cells are a distinct population of cells, not previously described in the retina, which increases in response to retinal damage and mitigate hypoxia-induced cell death

Deletion of GLUT1 in Mouse Lens Epithelium Leads to Cataract Formation

The primary energy substrate of the lens is glucose and uptake of glucose from the aqueous humor is dependent on glucose transporters. GLUT1, the facilitated glucose transporter encoded by Slc2a1 is expressed in the epithelium of bovine, human and rat lenses. In the current study, we examined the expression of GLUT1 in the mouse lens and determined its role in maintaining lens transparency by studying effects of postnatal deletion of Slc2a1. In situ hybridization and immunofluorescence labeling were used to determine the expression and subcellular distribution of GLUT1 in the lens. Slc2a1 was knocked out of the lens epithelium by crossing transgenic mice expressing Cre recombinase under control of the GFAP promoter with Slc2a