Measurement of Contractile Ring Tension Using Two-photon Laser Ablation during Drosophila Cellularization.

Cytokinesis occurs at the final step of cell division and leads to the separation of daughter cells. It requires assembly and constriction of the actomyosin contractile ring. The phases of assembly and constriction of the contractile ring show an increase in tension in the actomyosin complex. The measurement of tension in the contractile ring is of interest to probe the mechanics of contractile ring formation. Drosophila cellularization is a powerful genetic model system to study the mechanisms regulating actomyosin contractility during contractile ring constriction. Cellularization occurs in the interphase of syncytial cycle 14, where the plasma membrane extends around individual nuclei and forms complete cells with the help of a contractile ring at the bottom. The contractile ring forms at the furrow tip during the extension around individual nuclei and its assembly requires the coordinated action of cytoskeletal and plasma membrane-associated proteins. Laser ablation of the contractile ring enables the measurement of the contractility of the actomyosin network during cytokinesis. This protocol outlines the method used for estimating the contractility at the actomyosin ring during cellularization by laser ablation, in both control and mutant embryos for a Rho guanosine triphosphatase activating protein (RhoGAP) containing protein called GRAF (GTPase regulator associated with focal adhesion kinase-1). Physical cutting of the contractile ring by a two-photon laser at 800 nm leads to the displacement of the actomyosin ring edges, at a rate dependent upon the tension. This can be carried out at distinct steps of the contractile ring assembly during furrow extension in cellularization. Quantification of the extent of displacement and recoil velocity of movement of the edges at different stages of cellularization provides a quantitative measure of contractility in the system. This protocol describes the experimental procedure containing the preparation of live embryos, optimization of laser power, acquisition settings, and post-acquisition analysis of actomyosin contractility during Drosophila cellularization.

CT examination anatomical features and clinical significance of paraesophageal vein in portal hypertension / 中华消化外科杂志

Objective:To investigate the computed tomography (CT) examination anato-mical features and clinical significance of paraesophageal vein (PEV) in portal hypertension.Methods:The retrospective and descriptive study was conducted. The clinical data of 173 patients with portal hypertension who were admitted to the People's Hospital of Ningxia Hui Autonomous Region from January 2018 to June 2021 were collected. There were 124 males and 49 females, aged from 22 to 71 years, with a median age of 47 years. Observation indicators: (1) preoperative CT examinations; (2) surgical situations; (3) follow-up. Follow-up was conducted using outpatient examination to detect surgical effects once every 3 months within postoperative 6 months and once every 6 months after postoperative 6 months. The follow-up was up to June 2021. Measurement data with skewed distribution were represented as M(range) and count data were described as absolute numbers. Results:(1) Preoperative CT examinations. The CT detection rate of PEV in the 173 portal hyper-tension patients was 52.60%(91/173). Of 173 patients, 82 cases were negative with PEV and 91 cases were positive with PEV. Of the 91 patients who were positive with PEV, there were 46 cases with paraesophageal varices, 24 cases with thick PEV, 21 cases with thin PEV, 8 cases without esophageal varices and 83 cases accompanied with esophageal varices. Of the 83 patients who were accom-panied with esophageal varices, there were 44 cases with PEV converged alone with azygos vein or semiazygos vein, 39 cases with paraesophageal varices formed above the diaphragm confluent with esophageal varices into azygos vein. (2) Surgical situations. All the 173 patients underwent surgery successfully, including 8 cases undergoing splenectomy, 86 cases undergoing splenectomy combined with modified complete devascularization, 35 cases undergoing splenectomy combined with spontaneous gastrorenal shunt reconstructing devascularization, 41 cases undergoing splenectomy combined with PEV preserving devascularization and 3 cases undergoing splenectomy combined with PEV ring constriction. None of 173 patients had surgical relative death, 67 cases had complica-tions, including 3 cases undergoing splenectomy, 29 cases undergoing splenectomy combined with modified complete devascularization, 11 cases undergoing splenectomy combined with spontaneous gastrorenal shunt reconstructing devascularization, 23 cases undergoing splenectomy combined with PEV preserving devascularization and 1 case undergoing splenectomy combined with PEV ring constriction underwent complications. (3) Follow-up. Of the 173 patients, 159 cases were followed up for 6 to 42 months, with a median follow-up time of 28 months. In the 7 cases undergoing splenectomy who were followed up, there were 6 cases without esophageal varices and 1 case with recurrence of esophageal varices. In the 79 cases undergoing splenectomy combined with modified complete devascularization who were followed up, there were 5 cases without esophageal varices, 67 cases with mild to moderate residual of esophageal varices, 5 cases with severe residual of esophageal varices, 1 case with recurrence of esophageal varices and 1 case with recurrence of esophageal varices hemorrhage. In the 34 cases undergoing splenectomy combined with sponta-neous gastrorenal shunt reconstructing devascularization who were followed up, there were 7 cases without esophageal varices and 27 cases with mild to moderate residual of esophageal varices. In the 36 cases undergoing splenectomy combined with PEV preserving devascularization who were followed up, there were 4 cases without esophageal varices, 21 cases with mild to moderate residual of esophageal varices, 5 cases with severe residual of esophageal varices, 4 cases with recurrence of esophageal varices and 2 cases with recurrence of esophageal varices hemorrhage. In the 3 cases undergoing splenectomy combined with PEV ring constriction who were followed up, there were 2 cases with mild to moderate residual of esophageal varices, 1 case with severe residual of esophageal varices.Conclusions:The CT detection rate of PEV in portal hypertension patients is >50% and the internal diameter and distribution of blood vessels are different in patients. CT examination anatomical features of PEV can be used to guide the formula-tion of surgical methods.

Diagnóstico y manejo de sindrome de brida amniótica

Síndrome de bridas amnióticas (SBA), una anomalía congènita caracterizada por constricciones y/o amputaciones completas de extremidades a causa de las bridas amnióticas durante el embarazo. En los casos más graves las amputaciones completas están asociadas con otras malformaciones como las craneofaciales. La patogenia del SBA es controversial con baja incidencia. El diagnóstico prenatal oscila entre el 29% a 50% de los casos. Presentamos el caso de una paciente con brida amniótica diagnosticada en la semana 33 de gestación, atendida en nuestro Servicio de Ginecología y Obstetricia del Hospital Obrero N°2 de la Caja Nacional de Salud de Cochabamba, Bolivia.

Amniotic band syndrome (ABS) is a congenital anomaly characterized by constrictions and/or complete amputations of limbs due to amniotic bands during pregnancy. In the most severe cases, complete amputations are associated with other malformations such as craniofacial abnormalities. The pathogenesis of ABS is controversial and has a low incidence. Prenatal diagnosis ranges from 29% to 50% of cases. We present the case of a patient with an amniotic band diagnosed at week 33 of pregnancy, treated in our Gynecology and Obstetrics Service of Hospital Obrero N°2 of the National Health Fund of Cochabamba, Bolivia.

A novel checkpoint pathway controls actomyosin ring constriction trigger in fission yeast.

In fission yeast, the septation initiation network (SIN) ensures temporal coordination between actomyosin ring (CAR) constriction with membrane ingression and septum synthesis. However, questions remain about CAR regulation under stress conditions. We show that Rgf1p (Rho1p GEF), participates in a delay of cytokinesis under cell wall stress (blankophor, BP). BP did not interfere with CAR assembly or the rate of CAR constriction, but did delay the onset of constriction in the wild type cells but not in the rgf1Δ cells. This delay was also abolished in the absence of Pmk1p, the MAPK of the cell integrity pathway (CIP), leading to premature abscission and a multi-septated phenotype. Moreover, cytokinesis delay correlates with maintained SIN signaling and depends on the SIN to be achieved. Thus, we propose that the CIP participates in a checkpoint, capable of triggering a CAR constriction delay through the SIN pathway to ensure that cytokinesis terminates successfully.

Amniotic Band Syndrome Associated with Exencephaly: A Case Report and Literature Review.

Amniotic band syndrome (ABS) is a rare congenital disease with variable manifestations ranging from simple constriction rings at the extremities to major defects such as exencephaly. Here we report the case of a female baby born full term (39 weeks) from a 35-year-old primiparous mother by cesarean section. In addition to the constriction rings at the extremities (fingers), the newborn presented facial malformations and a cranial anomaly suggestive of exencephaly. Supportive treatment was chosen because of the poor prognosis, and the child died 5 months later. Depending on the anomaly associated with ABS and its complexity, as in our case, genetic studies should be performed whenever possible, and the parents should be informed about the possibility of recurrences and incompatibility with life.

FtsZ Constriction Force - Curved Protofilaments Bending Membranes.

FtsZ assembles in vitro into protofilaments (pfs) that are one subunit thick and ~50 subunits long. In vivo these pfs assemble further into the Z ring, which, along with accessory division proteins, constricts to divide the cell. We have reconstituted Z rings in liposomes in vitro, using pure FtsZ that was modified with a membrane targeting sequence to directly bind the membrane. This FtsZ-mts assembled Z rings and constricted the liposomes without any accessory proteins. We proposed that the force for constriction was generated by a conformational change from straight to curved pfs. Evidence supporting this mechanism came from switching the membrane tether to the opposite side of the pf. These switched-tether pfs assembled "inside-out" Z rings, and squeezed the liposomes from the outside, as expected for the bending model. We propose three steps for the full process of cytokinesis: (a) pf bending generates a constriction force on the inner membrane, but the rigid peptidoglycan wall initially prevents any invagination; (b) downstream proteins associate to the Z ring and remodel the peptidoglycan, permitting it to follow the constricting FtsZ to a diameter of ~250 nm; the final steps of closure of the septum and membrane fusion are achieved by excess membrane synthesis and membrane fluctuations.

A case report of umbilical ring constriction with application of amnioinfusion.

This is a case report of a pregnant 38-year-old primigravida woman. Due to severe fetal growth restriction and oligohydramnios, she was referred to our tertiary perinatal center at 24 weeks' gestation. To rule out chromosomal abnormalities and facilitate ultrasound evaluation of fetal morphology, we performed amniocentesis and subsequent amnioinfusion. Thereafter, a precise ultrasound examination revealed no obvious fetal morphological abnormalities except for a hyper-coiled cord and marginal placenta previa. During expectant management, the amount of amniotic fluid was maintained at 20-26 mm for a few days; however, the pregnancy resulted in intrauterine fetal death after 26 weeks + 5 days of gestation. The stillborn infant weighed 530 g (-3.3 SD) and had no obvious external abnormalities apart from umbilical ring constriction. Although a postmortem autopsy was not performed, it is suspected that the fetal growth restriction and the intrauterine fetal death were associated with the hyper-coiled cord and the umbilical ring constriction. It is thought that umbilical ring constriction might therefore be an irreversible fatal condition in cases with a hyper-coiled cord.