chi sequences switch the RecBCD helicase-nuclease complex from degradative to replicative modes during the completion of DNA replication.

Accurately completing DNA replication when two forks converge is essential to genomic stability. The RecBCD helicase-nuclease complex plays a central role in completion by promoting resection and joining of the excess DNA created when replisomes converge. chi sequences alter RecBCD activity and localize with crossover hotspots during sexual events in bacteria, yet their functional role during chromosome replication remains unknown. Here, we use two-dimensional agarose gel analysis to show that chi induces replication on substrates containing convergent forks. The induced replication is processive but uncoupled with respect to leading and lagging strand synthesis and can be suppressed by ter sites which limit replisome progression. Our observations demonstrate that convergent replisomes create a substrate that is processed by RecBCD and that chi, when encountered, switches RecBCD from a degradative to replicative function. We propose that chi serves to functionally differentiate DNA ends created during completion, which require degradation, from those created by chromosomal double-strand breaks, which require resynthesis.

RecBCD, SbcCD and ExoI process a substrate created by convergent replisomes to complete DNA replication.

The accurate completion of DNA replication on the chromosome requires RecBCD and structure specific SbcCD and ExoI nucleases. However, the substrates and mechanism by which this reaction occurs remains unknown. Here we show that these completion enzymes operate on plasmid substrates containing two replisomes, but are not required for plasmids containing one replisome. Completion on the two-replisome plasmids requires RecBCD, but does not require RecA and no broken intermediates accumulate in its absence, indicating that the completion reaction occurs normally in the absence of any double-strand breaks. Further, similar to the chromosome, we show that when the normal completion reaction is prevented, an aberrant RecA-mediated recombination process leads to amplifications that drive most of the instabilities associated with the two-replisome substrates. The observations imply that the substrate SbcCD, ExoI and RecBCD act upon in vivo is created specifically by two convergent replisomes, and demonstrate that the function of RecBCD in completing replication is independent of double-strand break repair, and likely promotes joining of the strands of the convergent replication forks.

Waterjet hydrodissection: first experiences and short-term outcomes of a novel approach to bladder tumor resection.

INTRODUCTION: TURB is the standard approach to bladder tumors but suffers from several disadvantages. Waterjet hydrodissection is a new technology for removing superficial tumors in the GI tract promising to preserve the histological structures of biopsy specimens with favorable long-term results as recent studies have shown. The aim of this study was to show the feasibility and applicability of waterjet hydrodissection for removing papillary superficial bladder tumors. MATERIALS AND METHODS: In five patients diagnosed with superficial papillary bladder tumor, transurethral submucosal dissection was conducted using the T-type I-Jet HybridKnife (Erbe, Tuebingen). The resection edges were labeled by means of electrical coagulation with the HybridKnife. Subsequently, a submucosal fluid cushion specific to the tissue layer was formed by the waterjet implementation function of the HybridKnife, thereby elevating the tumorous tissue. The tumor was endoscopically extracted with a retrieval bag. Biopsy specimens of the tumor edges and base were subsequently collected. RESULTS: All tumors could be resected en bloc, and the lamina propria was intact in all specimens, allowing the pathologist to distinguish between superficial and invasive tumors. Pathological analysis confirmed R0 resection in all samples. CONCLUSION: These initial results prove the feasibility of waterjet hydrodissection for removing bladder tumors. In contrast to conventional TURB, this new technique allows the pathologist to assess the entire lamina propria and the resection edges due to the en-bloc resection and to determine invasiveness as well as R0 versus R1 resection. These first results are promising, long-term oncological follow-up, and prospective randomized surveys investigating the recurrence rate have to be evaluated.

Occurrence and fate of pharmaceutically active compounds in the environment, a case study: Höje River in Sweden.

Pharmaceutically active compounds (PhACs) in the environment lately have been acknowledged to constitute a health risk for humans and terrestrial and aquatic ecosystems. Human and veterinary applications are the main sources of PhACs in the environment and the major pathways are excretion and discharge to the environment through sewage treatment plants (STPs). In this study, the occurrence and fate of selected human PhACs belonging to different therapeutic classes (non-steroidal anti-inflammatory drugs, lipid regulators, anti-epileptics, antibiotics and beta-blockers) were investigated in a small river in the very south of Sweden. The objectives of the study were to evaluate the impact of a high and rather constant load in sewage influent on downstream concentrations and whether substances that are metabolized to a high degree in humans also show a low persistency in a natural aquatic environment. Water samples were collected from the influent and effluent of the STP, in a series of dammed reservoirs leading to discharge into the Höje River in Sweden, and at several locations in the river downstream of the outfall. After enrichment by solid-phase extraction, the compounds were analyzed using GC-MS (methylated derivatives) or LC-MS/MS. In addition to the targeted pharmaceuticals, GC-MS analysis of the samples revealed the presence of other sewage-related pollutants (triclosan, caffeine, flame-retardants, antioxidants) and these results where included for comparison. Removal efficiencies were calculated in the STP and found to display a wide range with numerous species surviving treatment at greater than half their influent concentrations, including diclofenac, the anti-epileptic carbamazepine, a beta-blocker (propanolol), and antibiotics trimetoprim and sulfamethoxazole. Low removals were also observed for Tris(2-chloroisopropyl)phosphate (flame retardant), BHT-aldehyde (oxidation product of BHT) and synthetic musk (HHCB). The concentrations of chloride (Cl(-)) and boron (B) were used as natural inert tracers to estimate the relative extent of dilution of PhACs measured in the effluent of the STP on concentrations measured further downstream. Based on spatial trends of concentrations (recalculated to reflect a hypothetical scenario with no dilution), ibuprofen, ketoprofen, naproxen and dicofenac were shown to be subject to significant abiotic or biotic transformations or physical sequestration in the river. The beta-blockers atenolol, metoprolol and propanolol, the antibiotics trimetoprim and sulfametoxazole, and carbamazepine demonstrated a high degree of persistence. Fluctuations in the concentration of carbamazepine and gemfibrozil were observed along the series of reservoirs and within the river and are hypothesized to be due to release of parent compound from glucuronides. Several of the investigated substances (metaprolol, propanolol and carbamazepin) that exhibit low excretion rates as parent compounds demonstrate a surprising persistence in the aquatic environment. It is concluded that pharmaceutical substances with a high metabolic rate in humans (low excretion rate) do not necessarily induce a short lifetime in aquatic environments. Results from this study emphasize the need for a broader view on the concept of persistence that accounts for loading rates, in addition to removal mechanisms (e.g., transformation, volatility and physical sequestration by solids), under a variety of spatial and temporal scales.

Imaging strategies in the pregnant cancer patient.

This review summarizes the pertinent issues of radiation exposure to the developing fetus and the existing imaging techniques available to detect neoplastic disease spread of the common malignancies in women of reproductive age (breast cancer, cervical carcinoma, Hodgkin's disease, and melanoma). The standard radiologic work-up for assessing disease extent is reviewed and the pros and cons of these various imaging modalities are discussed with regard to the potential deleterious effects on the mother and fetus. Reasonable alternatives to the standard protocols for documenting extent of disease for these neoplasms are proposed. Usually a pregnant cancer patient can be safely and reasonably staged with imaging. Magnetic resonance (MR) imaging will most often be the procedure of choice because it does not use ionizing radiation. Specialized, focused questions such as sentinel lymph node detection may require limited exposure to ionizing radiation, which will not expose the fetus to a significant dose. While a standard chest x-ray does involve ionizing radiation, it does not expose the fetus to significant radiation.

Anatomy of the left upper quadrant for cannula insertion.

STUDY OBJECTIVE: To determine the anatomy of the left upper quadrant (LUQ) of the abdomen in women with different body mass indexes. DESIGN: Review of computed tomographic (CT) scans and medical records (Canadian Task Force classification II-2). SETTING: Large tertiary care medical center. PATIENTS: Sixty-three women over age 18 years who had scans performed for any indication. Nine women were excluded because of contraindication to LUQ laparoscopic cannula insertion and five because of incomplete records. Intervention. None. MEASUREMENTS AND MAIN RESULTS: The closest organs to the LUQ insertion site were the liver and stomach. There was significantly more subcutaneous fat at the umbilicus than at the insertion site. A positive correlation was found between body mass index and distance between structures and the site. CONCLUSION: Cannulas should not be inserted in the LUQ in women with hepatomegaly or splenomegaly. Because the stomach is so close to the insertion site, gastric drainage should be performed before cannula insertion. The site is likely safe in obese women whose abdominal organs are far away from it, and who have less subcutaneous fat there than at the umbilicus.