Regulation of the bovine retinal rod Na-Ca+K exchanger

MEASUREMENTS OF RETINAL FLUID BY OPTICAL COHERENCE TOMOGRAPHY LEAKAGE IN DIABETIC MACULAR EDEMA: A Biomarker of Visual Acuity Response to Treatment

PURPOSE

To evaluate the effects of anti-vascular endothelial growth factor treatment on retinal fluid in patients with diabetic macular edema by using optical coherence tomography leakage (OCT-L), a new method of quantifying sites of lower than normal optical reflectivity (LOR) in OCT, and to correlate these findings with best-corrected visual acuity (BCVA) response.

METHODS

Prospective analysis of 21 eyes with diabetic macular edema, naive to anti-vascular endothelial growth factor treatment. Macular cube 512 × 128 and OCT angiography 6 × 6-mm scans (CIRRUS AngioPlex; ZEISS, Dublin, CA) were acquired in all eyes before the first ranibizumab injection (V1) and 1 week after treatment (V2). Optical coherence tomography leakage analysis was performed with Angioplex raw scan data used to calculate LOR map ratios. Lower optical reflectivity ratios at baseline and differences from V1 to V2 and other OCT morphological features such as central retinal thickness measurements, disorganization of the inner retinal layers, and disruption of ellipsoid zone were compared with BCVA response 1 month after the first intravitreal injection.

RESULTS

After the first intravitreal injection of ranibizumab, eight patients (38%) were identified as good responders, 5 (24%) as moderate, and 8 (38%) as poor. There were no significant BCVA differences at baseline. Significant differences were found in LOR ratio changes between the different treatment response groups after 1 week of treatment, especially in outer segment and outer plexiform layer (outer segment-good responders: -53%, responders: -12%, and poor responders: 7% [P = 0.026]; outer plexiform layer-good responders: -49%, responders: 18%, and poor responders: 5% [P = 0.010]). Lower optical reflectivity ratios differences after 1 week of treatment predict better the BCVA treatment response at 1 month than changes of central retinal thickness, disorganization of the inner retinal layer, and ellipsoid zone disruption, especially in the outer segment and outer plexiform layer (area under the curve = 0.82 and 0.73, respectively).

CONCLUSION

Optical coherence tomography leakage changes after anti-vascular endothelial growth factor treatment of diabetic macular edema, identifying the degree of decrease in retinal fluid in the outer layers of the retina is a more robust biomarker of BCVA recovery than central retinal thickness, disorganization of the inner retinal layer, or ellipsoid zone disruption changes.

Vertebrate photoreceptors

The basis of the duplex theory of vision is examined in view of the dazzling array of data on visual pigment sequences and the pigments they form, on the microspectrophotometry measurements of single photoreceptor cells, on the kinds of photoreceptor cascade enzymes, and on the electrophysiological properties of photoreceptors. The implications of the existence of five distinct visual pigment families are explored, especially with regard to what pigments are in what types of photoreceptors, if there are different phototransduction enzymes associated with different types of photoreceptors, and if there are electrophysiological differences between different types of cones.

Alternatively spliced isoforms of the rat eye sodium/calcium+potassium exchanger NCKX1

We have investigated the structure, function, and expression of the rat eye sodium/calcium+potassium exchanger NCKX1. The sequence of independent rat NCKX1 clones and the analysis of rat eye mRNA by RT-PCR revealed a region of alternative splicing that comprised four exons and encoded a stretch of 113 amino acids near the beginning of the large cytosolic loop. In comparison with other NCKX1 molecules and the rat NCKX2 protein, rat NCKX1 was highly conserved within the hydrophobic regions but was quite divergent in the two large hydrophilic loops. The only exception was the region of the cytosolic loop encoded by the second alternatively spliced exon, which was approximately 60% identical. Similar to bovine, but different from human, rat NCKX1 possessed an acidic motif that was repeated 14 times in the cytoplasmic loop. Analysis of NCKX1 expression in different rat tissues by Northern blot revealed a very high level of expression of a 7-kb transcript in the eye but also lower levels of transcripts of various lengths in other tissues. The recombinant rat NCKX1 protein was tagged in the extracellular loop with the FLAG epitope and expressed in HEK-293 cells. Surface delivery and potassium-dependent sodium/calcium exchange activity were observed for each spliced variant.