Direct Observation of Strand Passage by DNA-Topoisomerase and Its Limited Processivity

Type-II DNA topoisomerases resolve DNA entanglements such as supercoils, knots and catenanes by passing one segment of DNA duplex through a transient enzyme-bridged double-stranded break in another segment. The ATP-dependent passage reaction has previously been demonstrated at the single-molecule level, showing apparent processivity at saturating ATP. Here we directly observed the strand passage by human topoisomerase IIα, after winding a pair of fluorescently stained DNA molecules with optical tweezers for 30 turns into an X-shaped braid. On average 0.51±0.33 µm (11±6 turns) of a braid was unlinked in a burst of reactions taking 8±4 s, the unlinked length being essentially independent of the enzyme concentration between 0.25–37 pM. The time elapsed before the start of processive unlinking decreased with the enzyme concentration, being ∼100 s at 3.7 pM. These results are consistent with a scenario where the enzyme binds to one DNA for a period of ∼10 s, waiting for multiple diffusional encounters with the other DNA to transport it across the break ∼10 times, and then dissociates from the binding site without waiting for the exhaustion of transportable DNA segments

Complete Genomic Structure of the Bloom-forming Toxic Cyanobacterium Microcystis aeruginosa NIES-843

The nucleotide sequence of the complete genome of a cyanobacterium, Microcystis aeruginosa NIES-843, was determined. The genome of M. aeruginosa is a single, circular chromosome of 5 842 795 base pairs (bp) in length, with an average GC content of 42.3%. The chromosome comprises 6312 putative protein-encoding genes, two sets of rRNA genes, 42 tRNA genes representing 41 tRNA species, and genes for tmRNA, the B subunit of RNase P, SRP RNA, and 6Sa RNA. Forty-five percent of the putative protein-encoding sequences showed sequence similarity to genes of known function, 32% were similar to hypothetical genes, and the remaining 23% had no apparent similarity to reported genes. A total of 688 kb of the genome, equivalent to 11.8% of the entire genome, were composed of both insertion sequences and miniature inverted-repeat transposable elements. This is indicative of a plasticity of the M. aeruginosa genome, through a mechanism that involves homologous recombination mediated by repetitive DNA elements. In addition to known gene clusters related to the synthesis of microcystin and cyanopeptolin, novel gene clusters that may be involved in the synthesis and modification of toxic small polypeptides were identified. Compared with other cyanobacteria, a relatively small number of genes for two component systems and a large number of genes for restriction-modification systems were notable characteristics of the M. aeruginosa genome

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

Several double-bundle anterior cruciate ligament (ACL) reconstruction procedures were reported in the 1980s and 1990s. However, no significant differences were found in the clinical results between these double-bundle procedures and single-bundle procedures because the double-bundle procedures appeared to reconstruct only the anteromedial bundle with two bundles. In the early 2000s, the authors proposed a new concept of anatomic reconstruction of the anteromedial and posterolateral bundles, in which 4 independent tunnels were created through the center of each anatomic attachment of the 2 bundles. We named it "anatomic" double-bundle ACL reconstruction. Biomechanical studies have shown that the anatomic double-bundle ACL reconstruction can restore knee stability significantly closer to the normal level than the conventional single-bundle reconstruction. Recent intraoperative measurement studies have showed that the clinically available anatomic double-bundle procedures can reconstruct knee stability significantly better and improve knee function close to the normal level at the time immediately after surgery than the conventional single-bundle procedures. However, the greatest criticism of the anatomic double-bundle reconstruction is whether the clinical results of anatomic double-bundle reconstruction are better than the results of single-bundle reconstruction. Currently, 10 prospective comparative clinical trials (Level I or II) and 1 meta-analysis have been reported to date (January, 2010) that compare single-bundle and anatomic double-bundle reconstructions using hamstring tendons. In 8 of the 10 studies, the anterior and/or rotatory stability of the knee was significantly better in the anatomic double-bundle ACL reconstruction than the conventional single-bundle reconstruction. However, 1 original trial and the meta-analysis found that there were no differences in the results between the 2 types of reconstructions. Thus, the utility of the anatomic double-bundle reconstruction has not yet been established. Our systematic review shows how much evidence exists as to the benefits of double-bundle ACL reconstruction at the present time

A Pilot Study of Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction With Ligament Remnant Tissue Preservation

Purpose: The purpose of this pilot study is to clarify the preliminary results of an anatomic double-bundle ACL reconstruction procedure with ligament remnant tissues. Methods: Using the trans-tibial technique, 2 doubled semitendinosus tendons were grafted into 4 tunnels created at the center of each bundle attachment, penetrating the ACL remnant tissue. Forty-four patients (27 men and 17 women) with an isolated ACL injury underwent ACL reconstruction using this procedure. The mean age of subjects was 29 years (range: 17-58). Postoperative clinical evaluations were performed at 16.6 months on average (range: 12-23). Radiologic evaluations were also performed to evaluate the tunnel location in the femur and the tibia. Results: The average operation time was 86 minutes (range: 72-96) in the cases with ACL reconstruction only. Postoperatively, the mean anterior laxity was 0.7 mm. The postoperative pivot-shift test was negative in 81.8% of the patients, while there were no patients evaluated as ++. No patients showed any extension or flexion deficit. There were no patients evaluated as "nearly abnormal" or "abnormal" under the IKDC evaluation. The tunnel angles of the 4 tunnels were identical to those reported in the previous study. Conclusions: The minimal 1-year clinical results of anatomic double-bundle ACL reconstruction with ligament remnant tissue preservation were comparable to the previously reported results of the anatomic double-bundle reconstruction without remnant tissue preservation. Level of Evidence: Level IV, Prospective case series

Diverticular Bleeding of the Colon during Combination Chemotherapy with Bevacizumab and Paclitaxel for Recurrent Breast Cancer

Background: Bevacizumab has been increasingly used in combination chemotherapy with paclitaxel for treatment of metastatic or recurrent breast cancer. The aim of this report is to underline possible risks associated with the new combination chemotherapy. Case Presentation: A 39-year-old woman with recurrent breast cancer was treated with bevacizumab and paclitaxel. Positron emission tomography revealed breast cancer metastasis to the left supraclavicular lymph nodes and right axillary lymph nodes, with no distant metastasis. Results: After the third cycle of bevacizumab and paclitaxel, the patient developed a bloody bowel discharge. Emergent colonoscopy demonstrated diverticular bleeding on one of the multiple diverticula in the ascending colon. The bleeding point was successfully clipped colonoscopically. Conclusion: The factors for diverticular bleeding are believed to be non-steroidal anti-inflammatory drugs, constipation, and bevacizumab. We recommend reviewing anamneses for diverticulitis, multiple prior abdominal surgeries, peritoneal carcinomatosis, and regular use of certain drugs

Clinical results of anterior cruciate ligament reconstruction with ligament remnant tissue preservation: A systematic review

Purpose: To clarify the effects of ACL remnant tissue preservation on the clinical outcome of ACL reconstruction. Methods: This is a systematic review. Results: The majority of the reviewed articles suggested that remnant preservation significantly improved knee stability after ACL reconstruction, although there was some controversy. In addition, it was suggested that the degree of initial graft coverage significantly affected postoperative knee stability. Remnant preservation did not increase the occurrence rate of cyclops lesion. Conclusion: Sufficient coverage of the graft with remnant tissue improves postoperative knee stability without any detrimental effects on the subjective and functional results

Pancreatic Steatosis Evaluated by Automated Volumetric CT Fat Fraction of the Pancreas: Association with Severity in COVID-19 Pneumonia

This study investigated the relationship between the severity of pneumonia based on chest CT findings and that of pancreatic steatosis assessed using an automated volumetric measurement of the CT fat volume fraction (CT-FVF) of the pancreas, using unenhanced three-dimensional CT in polymerase chain reaction (PCR)-confirmed COVID-19 patients. The study population consisted of 128 patients with PCR-confirmed COVID-19 infection who underwent CT examinations. The CT-FVF of the pancreas was calculated using a histogram analysis for the isolation of fat-containing voxels in the pancreas. The CT-FVF (%) of the pancreas had a significantly positive correlation with the lung severity score on CT (ρ = 0.549, p p < 0.01). The area under the curve of CT-FVF (%) of the pancreas in predicting the severity of pneumonia on CT was calculated to be 0.82, with a sensitivity of 88% and a specificity of 68% at a threshold for the severity score of 12.3. The automated volumetric measurement of the CT-FVF of the pancreas using unenhanced CT can help estimate disease severity in patients with COVID-19 pneumonia based on chest CT findings