Carol Schwartz

Nitric oxide coordinates metabolism, growth, and development via the nuclear receptor E75.

Nitric oxide gas acts as a short-range signaling molecule in a vast array of important physiological processes, many of which include major changes in gene expression. How these genomic responses are induced, however, is poorly understood. Here, using genetic and chemical manipulations, we show that nitric oxide is produced in the Drosophila prothoracic gland, where it acts via the nuclear receptor ecdysone-induced protein 75 (E75), reversing its ability to interfere with its heterodimer partner, Drosophila hormone receptor 3 (DHR3). Manipulation of these interactions leads to gross alterations in feeding behavior, fat deposition, and developmental timing. These neuroendocrine interactions and consequences appear to be conserved in vertebrates.

FTZ-Factor1 and Fushi tarazu interact via conserved nuclear receptor and coactivator motifs

To activate transcription, most nuclear receptor proteins require coactivators that bind to their ligand‐binding domains (LBDs). The Drosophila FTZ‐Factor1 (FTZ‐F1) protein is a conserved member of the nuclear receptor superfamily, but was previously thought to lack an AF2 motif, a motif that is required for ligand and coactivator binding. Here we show that FTZ‐F1 does have an AF2 motif and that it is required to bind a coactivator, the homeodomain‐containing protein Fushi tarazu (FTZ). We also show that FTZ contains an AF2‐interacting nuclear receptor box, the first to be found in a homeodomain protein. Both interaction motifs are shown to be necessary for physical interactions in vitro and for functional interactions in developing embryos. These unexpected findings have important implications for the conserved homologs of the two proteins.

Antibiotic Resistance of Ocular Surface Flora With Repeated Use of a Topical Antibiotic After Intravitreal Injection

IMPORTANCE Treatment with intravitreal (IVT) injections has increased during the last several years as evidence has accumulated demonstrating the efficacy of anti-vascular endothelial growth factor agents in the treatment of neovascular age-related macular degeneration (AMD) and various retinal vascular diseases. Although IVT injections are generally safe, infectious endophthalmitis is a rare but devastating complication, and the risk of morbidity and vision loss from endophthalmitis is high. OBJECTIVE To examine the change in antibiotic resistance of ocular surface flora with repeated prophylactic use of antibiotics after IVT injection for AMD. DESIGN AND SETTING Prospective, nonrandomized cohort study in 2 tertiary academic hospitals. PARTICIPANTS Patients 65 years and older with newly diagnosed AMD were recruited by 7 retinal specialists from July 1, 2010, through December 31, 2011. INTERVENTION The study group received topical moxifloxacin hydrochloride for 3 days after each monthly IVT injection. MAIN OUTCOME MEASURE Resistance to moxifloxacin and ceftazidime in cultured isolates at baseline and monthly for 3 months by change in minimal inhibitory concentration (MIC) of culture isolates was studied. RESULTS The study group consisted of 84 patients, and the control group had 94 patients. In the study group, the baseline adjusted MIC increased (from 1.04 to 1.25 μg/mL; P = .01) as did the MIC for 50% of isolates (MIC50) (from 0.64 to 1.00 μg/mL) and the MIC for 90% of isolates (MIC90) (from 0.94 to 4.00 μg/mL). In both groups, the culture-positive rate did not change significantly when adjusted for baseline. No significant change was found in the MIC level, culture-positive rate, MIC50 level, and MIC90 level in the control group. Subgroup analysis found diabetes mellitus to be noncontributory to both the MIC and culture-positive rate. No endophthalmitis or adverse events were reported. CONCLUSIONS AND RELEVANCE Repeated use of topical moxifloxacin after IVT injection significantly increases antibiotic resistance of ocular surface flora. We recommend that routine use of prophylactic antibiotics after IVT injection be discouraged. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01181713.

FLP Recombinase of the 2 μm circle plasmid of Saccharomyces cerevisiae bends its DNA target: Isolation of FLP mutants defective in DNA bending☆

The FLP recombinase is encoded by the yeast plasmid 2 microns circle and catalyses a site-specific recombination reaction that results in inversion of a segment of the 2 micron plasmid. We describe a method for the isolation of inactivating mutations in the FLP gene. The analysis of the recombination and binding activity of defective FLP proteins in vitro resulted in the identification of two classes of mutations: those that completely abolish FLP function by interfering with DNA binding and others that block recombination after the binding step. We have shown that FLP-mediated recombination is accompanied by bending of the DNA target and that mutations in the FLP recombinase that block bending also eliminate recombination.

FLP protein of 2 μ circle plasmid of yeast induces multiple bends in the FLP recognition target site

The FLP recombinase of the 2 mu plasmid of Saccharomyces cerevisiae binds to a target containing three 13 base-pair symmetry elements called a, b and c. The symmetry elements b and c are in direct orientation while the a element is in inverted orientation with respect to b and c on the opposite side of an eight base-pair core region. Each symmetry element acts as a binding site for the FLP protein. The FLP protein can form three different complexes with the FLP recognition target (FRT site) according to the number of elements within the site that are occupied by the FLP protein. Binding of FLP to the FRT site induces DNA bending. We have measured the angles of bends caused by the binding of the FLP protein to full and partial FRT sites. We find that FLP induces three types of bend in the FRT-containing DNA. The type I bend is approximately 60 degrees and results from a molecule of FLP bound to one symmetry element. The type II bend is greater than 144 degrees and results from FLP molecules bound to symmetry elements a and b. The type III bend is approximately 65 degrees and results from FLP proteins bound to symmetry elements b and c. Certain FLP proteins that are defective in recombination can generate the type I and type III bends but are impaired in their ability to induce the type II bend. We discuss the role of bending in FLP-mediated recombination.

Age-related macular degeneration: Is polypoidal choroidal vasculopathy recognized and treated?

OBJECTIVE To assess how polypoidal choroidal vasculopathy (PCV) is recognized and treated, and to assess whether treatment outcomes are different between Chinese and Caucasian Canadian patients with age-related macular degeneration (AMD). DESIGN Retrospective chart review. PARTICIPANTS 154 eyes from 135 Chinese patients and 2291 eyes from 1792 Caucasian patients who were newly diagnosed with either AMD or PCV and had more than 1 year of follow-up were included. METHODS All newly diagnosed AMD patients presenting to the Retina Service of 3 Toronto University Hospitals, between March 25, 2008, to September 30, 2014, were reviewed. RESULTS 10/154 eyes (6.5%) in Chinese Canadians and 16/2291 eyes (0.7%) in Caucasian Canadians were diagnosed as having PCV. Indocyanine green angiography (ICGA) was used to diagnose PCV in 20% of Chinese Canadians and 8.8% of Caucasian Canadians. Clinical practices with a larger percentage of Chinese patients were more likely to diagnose PCV in both Chinese (p = 0.004) and Caucasian patients (p = 0.03), were more likely to use photodynamic therapy (PDT) (p < 0.01), and had significantly greater central retinal thickness decrease (p < 0.001). CONCLUSION Our study has shown that PCV is under-recognized in a Canadian population, and ICGA is underutilized. In clinical practices with a greater portion of Chinese patients, PCV is more often recognized and PDT is used more liberally.