Objective To evaluate the association of subretinal hyper-reflective material (SHRM) with visual acuity (VA), geographic atrophy (GA) and scar in the Comparison of Age related Macular Degeneration Treatments Trials (CATT) Design Prospective cohort study within a randomized clinical trial. Participants The 1185 participants in CATT. Methods Participants were randomly assigned to ranibizumab or bevacizumab treatment monthly or as-needed. Masked readers graded scar and GA on fundus photography and fluorescein angiography images, SHRM on time domain (TD) and spectral domain (SD) optical coherence tomography (OCT) throughout 104 weeks. Measurements of SHRM height and width in the fovea, within the center 1mm2, or outside the center 1mm2 were obtained on SD-OCT images at 56 (n=76) and 104 (n=66) weeks. VA was measured by certified examiners. Main Outcome Measures SHRM presence, location and size, and associations with VA, scar, and GA. Results Among all CATT participants, the percentage with SHRM at enrollment was 77%, decreasing to 68% at 4 weeks after treatment and 54% at 104 weeks. At 104 weeks, scar was present more often in eyes with persistent SHRM than eyes with SHRM that resolved (64% vs. 31%; p<0.0001). Among eyes with detailed evaluation of SHRM at weeks 56 (n=76) and 104 (n=66), mean [SE] VA letter score was 73.5 [2.8], 73.1 [3.4], 65.3 [3.5], and 63.9 [3.7] when SHRM was absent, present outside the central 1mm2, present within the central 1mm2 but not the foveal center, or present at the foveal center (p=0.02). SHRM was present at the foveal center in 43 (30%), within the central 1mm2 in 21 (15%) and outside the central 1mm2 in 19 (13%). When SHRM was present, the median maximum height in microns under the fovea, within the central 1 mm2 including the fovea and anywhere within the scan was 86; 120; and 122, respectively. VA was decreased with greater SHRM height and width (p<0.05). Conclusions SHRM is common in eyes with NVAMD and often persists after anti-VEGF treatment. At 2 years, eyes with scar were more likely to have SHRM than other eyes. Greater SHRM height and width were associated with worse VA. SHRM is an important morphological biomarker in eyes with NVAMD.

DNA molecules isolated from bacteriophage P4 are mostly linear with cohesive ends capable of forming circular and concatemeric structures. In contrast, almost all DNA molecules isolated form P4 tailless capsids (heads) are monomeric DNA circles with their cohesive ends hydrogen-bonded. Different form simple DNA circles, such P4 head DNA circles contain topological knots. Gel electrophoretic and electronmicroscopic analyses of P4 head DNA indicate that the topological knots are highly complex and heterogeneous. Resolution of such complex knots has been studied with various DNA topoisomerases. The conversion of highly knotted P4 DNA to its simple circular form is demonstrated by type II DNA topoisomerases which catalyze the topological passing of two crossing double-stranded DNA segments [Liu, L. F., Liu, C. C. & Alberts, B. M. (1980) Cell, 19, 697-707]. The knotted P4 head DNA can be used in a sensitive assay for the detection of a type II DNA topoisomerase even in the presence of excess type I DNA topoisomerases.

Eukaryotic DNA topoisomerase I introduces transient single-stranded breaks on double-stranded DNA and spontaneously breaks down single-stranded DNA. The cleavage sites on both single and double-stranded SV40 DNA have been determined by DNA sequencing. Consistent with other reports, the eukaryotic enzymes, in contrast to prokaryotic type I topoisomerases, links to the 3'-end of the cleaved DNA and generates a free 5'-hydroxyl end on the other half of the broken DNA strand. Both human and calf enzymes cleave SV40 DNA at the identical and specific sites. From 827 nucleotides sequenced, 68 cleavage sites were mapped. The majority of the cleavage sites were present on both double and single-stranded DNA at exactly the same nucleotide positions, suggesting that the DNA sequence is essential for enzyme recognition. By analyzing all the cleavage sequences, certain nucleotides are found to be less favored at the cleavage sites. There is a high probability to exclude G from positions -4, -2, -1 and +1, T from position -3, and A from position -1. These five positions (-4 to +1 oriented in the 5' to 3' direction) around the cleavage sites must interact intimately with topo I and thus are essential for enzyme recognition. One topo I cleavage site which shows atypical cleavage sequence maps in the middle of a palindromic sequence near the origin of SV40 DNA replication. It occurs only on single-stranded SV40 DNA, suggesting that the DNA hairpin can alter the cleavage specificity. The strongest cleavage site maps near the origin of SV40 DNA replication at nucleotide 31-32 and has a pentanucleotide sequence of 5'-TGACT-3'.

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