Arp2/3 Complex Regulates Asymmetric Division and Cytokinesis in Mouse Oocytes

Mammalian oocyte meiotic maturation involves oocyte polarization and a unique asymmetric division, but until now, the underlying mechanisms have been poorly understood. Arp2/3 complex has been shown to regulate actin nucleation and is widely involved in a diverse range of processes such as cell locomotion, phagocytosis and the establishment of cell polarity. Whether Arp2/3 complex participates in oocyte polarization and asymmetric division is unknown. The present study investigated the expression and functions of Arp2/3 complex during mouse oocyte meiotic maturation. Immunofluorescent staining showed that the Arp2/3 complex was restricted to the cortex, with a thickened cap above the meiotic apparatus, and that this localization pattern was depended on actin. Disruption of Arp2/3 complex by a newly-found specific inhibitor CK666, as well as by Arpc2 and Arpc3 RNAi, resulted in a range of effects. These included the failure of asymmetric division, spindle migration, and the formation and completion of oocyte cytokinesis. The formation of the actin cap and cortical granule-free domain (CGFD) was also disrupted, which further confirmed the disruption of spindle migration. Our data suggest that the Arp2/3 complex probably regulates oocyte polarization through its effect on spindle migration, asymmetric division and cytokinesis during mouse oocyte meiotic maturation

Postoperative abdominal wound infection – epidemiology, risk factors, identification, and management

Saïd C Azoury,1 Norma Elizabeth Farrow,2 Qing L Hu,2 Kevin C Soares,1 Caitlin W Hicks,1 Faris Azar,1 Nelson Rodriguez-Unda,3 Katherine E Poruk,1 Peter Cornell,1 Karen K Burce,1 Carisa M Cooney,3 Hien T Nguyen,1 Frederic E Eckhauser1 1Department of Surgery, The Johns Hopkins Hospital, Baltimore, MD, USA; 2School of Medicine, Johns Hopkins University, Baltimore, MD, USA; 3Department of Plastic and Reconstructive Surgery, The Johns Hopkins Hospital, Baltimore, MD, USA Abstract: Surgical site infections (SSIs) complicate the postoperative course of a significant proportion of general abdominal surgical patients and are associated with excessive health care costs. SSIs increase postoperative morbidity and mortality, and may require hospital admission, intravenous antibiotics, and even surgical reintervention. Risks associated with SSIs are related to both host and perioperative factors. However, a vast majority of these infections are preventable. More recently, quality initiative programs such as American College of Surgeons National Surgical Quality Improvement Program are expanding their roles to help better monitor adherence to improvement measures. Indeed, standardizing preoperative antibiotic prophylaxis timing is perhaps the most persuasive example and this has been integral to reducing postoperative SSI rates. Herein, the authors provide an update on the epidemiology, risk factors, identification, and management of wound infections following abdominal surgery. Keywords: surgical site infection, diagnosis, treatment, preventio

A soft cortex is essential for asymmetric spindle positioning in mouse oocytes

At mitosis onset, cortical tension increases and cells round up, ensuring correct spindle morphogenesis and orientation. Thus, cortical tension sets up the geometric requirements of cell division. On the contrary, cortical tension decreases during meiotic divisions in mouse oocytes, a puzzling observation because oocytes are round cells, stable in shape, that actively position their spindles. We investigated the pathway leading to reduction in cortical tension and its significance for spindle positioning. We document a previously uncharacterized Arp2/3-dependent thickening of the cortical F-actin essential for first meiotic spindle migration to the cortex. Using micropipette aspiration, we show that cortical tension decreases during meiosis I, resulting from myosin-II exclusion from the cortex, and that cortical F-actin thickening promotes cortical plasticity. These events soften and relax the cortex. They are triggered by the Mos-MAPK pathway and coordinated temporally. Artificial cortex stiffening and theoretical modelling demonstrate that a soft cortex is essential for meiotic spindle positioning