10-Year Overview of the Hospital-Based Prevalence and Treatment of Congenital Cataracts: The CCPMOH Experience

A review of 6 years of hospitalization charts from Zhongshan Ophthalmic Center (ZOC) revealed that congenital cataracts (CC) accounted for 2.39% of all cataract in-patient cases and that the age at surgery was decreasing before the establishment of the Childhood Cataract Program of the Chinese Ministry of Health (CCPMOH) in December 2010. We aimed to investigate data from the 4 years (January 2011 to December 2014) following the establishment of the CCPMOH, compared, and combined with data from the previous study period (January 2005 to December 2010) to generate a 10-year overview of the hospital-based prevalence and treatment of CC. In the 4-year period after CCPMOH establishment, the prevalence of CC was 2.01% in all hospitalizations, and was 2.78% in all cataract in-patients. Most of the eligible CC in-patients (71%) lived in south China. The ratio of boys to girls was 1.42:1. Nearly 2/3 of the patients underwent cataract extraction with primary intraocular lens (IOL) implantation at a mean age of 78.40±51.45 months, and cataract extraction surgeries without IOL implantation were performed in the remaining 1/3 of patients at a mean age of 10.03±15.92 months. After CCPMOH establishment, an increased incidence of CC was revealed, and the CC in-patients were younger than the patients in the previous period. The 10-year overview (2421 CC in-patients from 206630 hospitalizations) revealed upward trends in both the number and the prevalence of CC and a further reduction in age at surgery. In conclusion, the data from 4-year period after CCPMOH establishment and the 10-year overview showed upward trends in the hospital-based prevalence of CC cases and a further reduction in age at surgery, likely reflecting the effects of the CCPMOH establishment and providing useful information for further CC studies and a valuable foundation for the prevention and treatment of this cause of childhood blindness.     

The use of a drug resistance cartridge for in vitro insertion and deletion mutagenesis of a cosmid clone

A drug-resistant cartridge was employed in the construction of families of insertion mutants of a cosmid clone. The cartridge contains a cml gene and has identical restriction enzyme sites, EcoRI, BamHI, SalI, and PstI, on both ends. The families of mutants were made by ligation of the cartridge to the cosmid, which was linearized or partially digested, followed by in vitro packaging and transduction. From these families we selected cosmid derivatives which either have a unique BamHI site at a predetermined site in the cosmid or have deletions covering different portions of the original clone. The extent of a large gene cluster cloned into the original cosmid was identified by confirming the gene function in some of the deletion mutants. The possibility for further and various uses of this cartridge is discussed.     

Improved two‐stage group sequential procedures for testing a secondary endpoint after the primary endpoint achieves significance

In two‐stage group sequential trials with a primary and a secondary endpoint, the overall type I error rate for the primary endpoint is often controlled by an α‐level boundary, such as an O'Brien‐Fleming or Pocock boundary. Following a hierarchical testing sequence, the secondary endpoint is tested only if the primary endpoint achieves statistical significance either at an interim analysis or at the final analysis. To control the type I error rate for the secondary endpoint, this is tested using a Bonferroni procedure or any α‐level group sequential method. In comparison with marginal testing, there is an overall power loss for the test of the secondary endpoint since a claim of a positive result depends on the significance of the primary endpoint in the hierarchical testing sequence. We propose two group sequential testing procedures with improved secondary power: the improved Bonferroni procedure and the improved Pocock procedure. The proposed procedures use the correlation between the interim and final statistics for the secondary endpoint while applying graphical approaches to transfer the significance level from the primary endpoint to the secondary endpoint. The procedures control the familywise error rate (FWER) strongly by construction and this is confirmed via simulation. We also compare the proposed procedures with other commonly used group sequential procedures in terms of control of the FWER and the power of rejecting the secondary hypothesis. An example is provided to illustrate the procedures.     

Removal of the RecA C-terminus results in a conformational change in the RecA-DNA filament

The Escherichia coli RecA protein catalyzes homologous recombination of DNA molecules, and the active form of the protein is a helical polymer that it forms around DNA. Previous image analysis of electron micrographs has revealed the RecA protein to be organized into two domains or lobes within the RecA-DNA filament. We have now been able to show that a small modification of the RecA protein by proteolysis results in a significant shift in the internal mass in the RecA filament. We have cleaved approximately 18 residues from the C-terminus of the RecA protein, producing a roughly 36K MW RecA core protein that binds DNA and polymerizes normally. A three-dimensional reconstruction of this complex has been computed, and has been compared with a previous reconstruction of the intact protein. The main difference is consistent with a 15 A outward movement of the lobe that was at an inner radius in the wild-type protein. These observations yield additional evidence about the conformational flexibility of the RecA filament, and will aid in understanding the structural mechanics and dynamics of the RecA filament.