Organotypic slice co‐cultures reveal that early postnatal hippocampal axons lose the ability to grow along the fimbria,while retaining the ability to invade and arborise in septal neuropil

The failure of cut axons to grow along fibre tracts in the adult CNS contrasts with their ability to do so in development. Organotypic slices culture of a number of areas enables the time of failure to be pinpointed to around the second week of postnatal life in the rat. ‘Heterochronic’ co‐culture of slices above and below this age shows that the failure is due to the inability of the older axons to grow into either the same age or younger targets. Using hippocampo‐septal slices the present experiments show that this failure is due to an inability to recognise the glial pathway of the fimbria, even when this is of a younger age. However, the older hippocampal neurons retain the ability to grow axons into septal target tissue when they are placed in direct contact with it. This exactly mirrors the inability of cut central axons to regenerate along their previous fibre pathways while they retain their ability to reinnervate neuropil.     

How early must an acute Achilles tendon rupture be repaired?

An acute Achilles tendon rupture is the most common tendon rupture of the lower extremities, yet the optimal timing for an early surgical repair is unclear. To identify the optimal time for an early surgical repair with favorable results, we evaluated the isokinetic muscle strength and clinical outcomes of early surgical repairs of acute Achilles tendon ruptures performed at different time points after injury. Between January 2011 and July 2015, a total of 65 patients underwent an acute Achilles tendon rupture repair within 1 week after injury. To compare the outcomes at different time points post-injury, we divided patients into 3 groups: group 1, surgical treatment at ≤24 h; group 2, surgery at ≥24 h and ≤48 h; and group 3, surgery at ≥48 hours and ≤1 week. The isokinetic muscle strength in both ankles were measured using a Cybex dynamometer, and the Achilles tendon total rupture score, the modified Tegner scoring system, the visual analog scale was used to assess clinical outcomes. Kruskal-Wallis and Fisher’s exact tests were used to compare multiple results in the 3 groups. No significant differences were found among the groups in terms of ankle isokinetic muscle strength or clinical outcome scores (P > 0.05). The complication rate was low in all groups. There were no significant differences in isokinetic muscle strength or clinical outcomes following acute Achilles tendon rupture repairs performed within 1 week after injury.     

An end-joining repair mechanism in Escherichia coli

Bridging broken DNA ends via nonhomologous end-joining (NHEJ) contributes to the evolution and stability of eukaryote genomes. Although some bacteria possess a simplified NHEJ mechanism, the human commensal Escherichia coli is thought to rely exclusively on homology-directed mechanisms to repair DNA double-strand breaks (DSBs). We show here that laboratory and pathogenic E. coli strains possess a distinct end-joining activity that repairs DSBs and generates genome rearrangements. This mechanism, named alternative end-joining (A-EJ), does not rely on the key NHEJ proteins Ku and Ligase-D which are absent in E. coli. Differently from classical NHEJ, A-EJ is characterized by extensive end-resection largely due to RecBCD, by overwhelming usage of microhomology and extremely rare DNA synthesis. We also show that A-EJ is dependent on the essential Ligase-A and independent on Ligase-B. Importantly, mutagenic repair requires a functional Ligase-A. Although generally mutagenic, accurate A-EJ also occurs and is frequent in some pathogenic bacteria. Furthermore, we show the acquisition of an antibiotic-resistance gene via A-EJ, refuting the notion that bacteria gain exogenous sequences only by recombination-dependent mechanisms. This finding demonstrates that E. coli can integrate unrelated, nonhomologous exogenous sequences by end-joining and it provides an alternative strategy for horizontal gene transfer in the bacterial genome. Thus, A-EJ contributes to bacterial genome evolution and adaptation to environmental challenges. Interestingly, the key features of A-EJ also appear in A-NHEJ, an alternative end-joining mechanism implicated in chromosomal translocations associated with human malignancies, and we propose that this mutagenic repair might have originated in bacteria.     

Homing endonucleases catalyze double-stranded DNA breaks and somatic transgene excision in Aedes aegypti

Aedes aegypti is a major vector of arthropod-borne viruses such as yellow fever virus and dengue viruses. Efforts to discern the function of genes involved in important behaviours, such as vector competence and host seeking through reverse genetics, would greatly benefit from the ability to generate targeted gene disruptions. Homing endonucleases are selfish elements which catalyze double-stranded DNA (dsDNA) breaks in a sequence-specific manner. In this report we demonstrate that the homing endonucleases I- Ppo I, I- Sce I, I- Cre I and I- Ani I are all able to induce dsDNA breaks in adult female Ae. aegypti chromosomes as well as catalyze the somatic excision of a transgene. These experiments provide evidence that homing endonucleases can be used to manipulate the genome of this important disease vector.     

软骨组织工程的研究进展

目前，软骨组织工程已在基础研究方面取得了令人瞩目的成果，并在临床应用方面进行了初步尝试，为I临床软骨缺损的修复提供了新的思路与途径，已经成为该领域主要的研究方向，但其大规模临床应用尚存在诸多困难。现结合近年的研究成果，就组织工程化软骨的种子细胞、生物支架材料、体内外构建以及临床应用等方面进行综述。     

A case of laparoscopy-assisted vaginal cuff suturing for vaginal cuff dehiscence after total laparoscopic hysterectomy

IntroductionVaginal cuff dehiscence after hysterectomy is a rare complication and occurs in less than 1% of patients. It can present with serious complications, such as bowel evisceration and peritonitis.Presentation of caseA 51-year-old multigravida Korean woman underwent total laparoscopic hysterectomy for leiomyoma. Six months later, she reported lower abdominal pain and vaginal bleeding. Physical examination revealed rebound tenderness in the lower abdomen, and pelvic examination showed a small amount of vaginal bleeding with an evisceration of the small intestine through the vagina that exhibited healthy peristalsis. The eviscerated bowel, which seemed to be a part of the ileum, was carefully manually reduced transvaginally into the abdominal cavity. Laparoscopic observation revealed adhesions between the omentum, small intestine, and the peritoneum. Specifically, the small intestine was adhered around the vaginal cuff. An abdominal abscess was found in the left lower abdominal cavity. An adhesiotomy was performed and the abdominal abscess was removed and irrigated. Complete separation of the anterior and posterior vaginal cuff edges was obtained. The vaginal cuff was closed with interrupted 0-polydioxanone absorbable sutures without bowel injury. A 6-month follow-up examination revealed complete healing of the vaginal cuff.DiscussionIn this case, we were able to make use of both laparoscopic and transvaginal methods to perform a successful repair with a minimally invasive and safe technique.ConclusionLaparoscopically assisted vaginal cuff suturing for vaginal cuff dehiscence after total laparoscopic hysterectomy was found to be effective, safe, and minimally invasive.