Contractile ring mechanosensation and its anillin-dependent tuning during early embryogenesis.

Cytokinesis plays crucial roles in morphogenesis. Previous studies have examined how tissue mechanics influences the position and closure direction of the contractile ring. However, the mechanisms by which the ring senses tissue mechanics remain largely elusive. Here, we show the mechanism of contractile ring mechanosensation and its tuning during asymmetric ring closure of Caenorhabditis elegans embryos. Integrative analysis of ring closure and cell cortex dynamics revealed that mechanical suppression of the ring-directed cortical flow is associated with asymmetric ring closure. Consistently, artificial obstruction of ring-directed cortical flow induces asymmetric ring closure in otherwise symmetrically dividing cells. Anillin is vital for mechanosensation. Our genetic analysis suggests that the positive feedback loop among ring-directed cortical flow, myosin enrichment, and ring constriction constitutes a mechanosensitive pathway driving asymmetric ring closure. These findings and developed tools should advance the 4D mechanobiology of cytokinesis in more complex tissues.

An analysis of the mechanical parameters used for finite element compression of a high-resolution 3D breast phantom.

PURPOSE: The authors previously introduced a methodology to generate a realistic three-dimensional (3D), high-resolution, computer-simulated breast phantom based on empirical data. One of the key components of such a phantom is that it provides a means to produce a realistic simulation of clinical breast compression. In the current study, they have evaluated a finite element (FE) model of compression and have demonstrated the effect of a variety of mechanical properties on the model using a dense mesh generated from empirical breast data. While several groups have demonstrated an effective compression simulation with lower density finite element meshes, the presented study offers a mesh density that is able to model the morphology of the inner breast structures more realistically than lower density meshes. This approach may prove beneficial for multimodality breast imaging research, since it provides a high level of anatomical detail throughout the simulation study. METHODS: In this paper, the authors describe methods to improve the high-resolution performance of a FE compression model. In order to create the compressible breast phantom, dedicated breast CT data was segmented and a mesh was generated with 4-noded tetrahedral elements. Using an explicit FE solver to simulate breast compression, several properties were analyzed to evaluate their effect on the compression model including: mesh density, element type, density, and stiffness of various tissue types, friction between the skin and the compression plates, and breast density. Following compression, a simulated projection was generated to demonstrate the ability of the compressible breast phantom to produce realistic simulated mammographic images. RESULTS: Small alterations in the properties of the breast model can change the final distribution of the tissue under compression by more than 1 cm; which ultimately results in different representations of the breast model in the simulated images. The model properties that impact displacement the most are mesh density, friction between the skin and the plates, and the relative stiffness of the different tissue types. CONCLUSIONS: The authors have developed a 3D, FE breast model that can yield high spatial resolution breast deformations under uniaxial compression for imaging research purposes and demonstrated that small changes in the mechanical properties can affect images generated using the phantom.

In Vitro Reconstitution of Spatial Cell Contact Patterns with Isolated Caenorhabditis elegans Embryo Blastomeres and Adhesive Polystyrene Beads.

In multicellular systems, individual cells are surrounded by the various physical and chemical cues coming from neighboring cells and the environment. This tissue complexity confounds the identification of causal link between extrinsic cues and cellular dynamics. A synthetically reconstituted multicellular system overcomes this problem by enabling researchers to test for a specific cue while eliminating others. Here, we present a method to reconstitute cell contact patterns with isolated Caenorhabditis elegans blastomere and adhesive polystyrene beads. The procedures involve eggshell removal, blastomere isolation by disrupting cell-cell adhesion, preparation of adhesive polystyrene beads, and reconstitution of cell-cell or cell-bead contact. Finally, we present the application of this method to investigate the orientation of cellular division axes that contributes to the regulation of spatial cellular patterning and cell fate specification in developing embryos. This robust, reproducible, and versatile in vitro method enables the study of direct relationships between spatial cell contact patterns and cellular responses.

Invasive Fungal Infections While on Voriconazole, Liposomal Amphotericin B, or Micafungin for Antifungal Prophylaxis in Pediatric Stem Cell Transplant Patients.

OBJECTIVE: This study aimed to report the incidence of invasive fungal infections (IFIs) in pediatric hematopoietic stem cell transplant (HSCT) patients who received voriconazole, liposomal amphotericin B (L-AMB), or micafungin for primary antifungal prophylaxis (PAP). METHODS: Using data retrospectively collected from institution's electronic records, this study analyzed the incidence of IFIs in pediatric HSCT patients between November 2012 and November 2016. RESULTS: A total of 103 patients were screened. Of the 84 patients who met inclusion criteria, 76.2%, 29.8%, and 19% patients received voriconazole, L-AMB, and micafungin, respectively. The incidence of overall IFIs was 2.08 per 1000 prophylaxis days. There were 2 mold infections identified in 2 patients. Among 3 antifungal agents, the rates of IFIs were 2.67 per 1000 prophylaxis days in L-AMB group, 2.08 per 1000 prophylaxis days in micafungin group, and 1.17 per 1000 prophylaxis days in voriconazole group. CONCLUSION: Patients who received L-AMB or micafungin had higher rates of IFIs than those who received voriconazole for PAP.

Acute retinal necrosis in a neonate.

PURPOSE: To report an unusual case of dizygotic twins, in whom one neonate developed acute retinal necrosis from herpes simplex virus (HSV) type 2. METHODS: Retrospective chart review. RESULTS: A 29-week-old premature infant from in vitro fertilization donor egg with negative maternal and fetal history for HSV-1 and HSV-2 developed vesiculopapular rash upon birth. Fundus examination revealed vitritis with retinal hemorrhages, suggestive of retinitis; the twin, however, had a normal funduscopic examination. A presumptive diagnosis of HSV infection was made, and the patient was started on intravenous acyclovir. Polymerase chain reaction of the anterior chamber fluid was positive for HSV-2; serology of both mother and child was HSV-2 IgG(+), IgM(-). Acute retinal necrosis was managed with 360° of bilateral peripheral laser cerclage. A subsequent rhegmatogenous retinal detachment in one eye was successfully treated with a scleral buckle. Retinal reattachment, macular pigmentary disturbances, and mild optic atrophy were noted at 6 months of follow-up. CONCLUSION: The authors report a case of isolated congenital acute retinal necrosis in an otherwise healthy neonate, and product of a dichorionic, diamniotic in vitro fertilization pregnancy. Clinicians should consider possible HSV transmission from in vitro fertilization donor egg in the differential diagnosis, despite the negative fetal and maternal histories for HSV infection.

Generation of a suite of 3D computer-generated breast phantoms from a limited set of human subject data.

PURPOSE: The authors previously reported on a three-dimensional computer-generated breast phantom, based on empirical human image data, including a realistic finite-element based compression model that was capable of simulating multimodality imaging data. The computerized breast phantoms are a hybrid of two phantom generation techniques, combining empirical breast CT (bCT) data with flexible computer graphics techniques. However, to date, these phantoms have been based on single human subjects. In this paper, the authors report on a new method to generate multiple phantoms, simulating additional subjects from the limited set of original dedicated breast CT data. The authors developed an image morphing technique to construct new phantoms by gradually transitioning between two human subject datasets, with the potential to generate hundreds of additional pseudoindependent phantoms from the limited bCT cases. The authors conducted a preliminary subjective assessment with a limited number of observers (n = 4) to illustrate how realistic the simulated images generated with the pseudoindependent phantoms appeared. METHODS: Several mesh-based geometric transformations were developed to generate distorted breast datasets from the original human subject data. Segmented bCT data from two different human subjects were used as the "base" and "target" for morphing. Several combinations of transformations were applied to morph between the "base' and "target" datasets such as changing the breast shape, rotating the glandular data, and changing the distribution of the glandular tissue. Following the morphing, regions of skin and fat were assigned to the morphed dataset in order to appropriately assign mechanical properties during the compression simulation. The resulting morphed breast was compressed using a finite element algorithm and simulated mammograms were generated using techniques described previously. Sixty-two simulated mammograms, generated from morphing three human subject datasets, were used in a preliminary observer evaluation where four board certified breast radiologists with varying amounts of experience ranked the level of realism (from 1 = "fake" to 10 = "real") of the simulated images. RESULTS: The morphing technique was able to successfully generate new and unique morphed datasets from the original human subject data. The radiologists evaluated the realism of simulated mammograms generated from the morphed and unmorphed human subject datasets and scored the realism with an average ranking of 5.87 ± 1.99, confirming that overall the phantom image datasets appeared more "real" than "fake." Moreover, there was not a significant difference (p > 0.1) between the realism of the unmorphed datasets (6.0 ± 1.95) compared to the morphed datasets (5.86 ± 1.99). Three of the four observers had overall average rankings of 6.89 ± 0.89, 6.9 ± 1.24, 6.76 ± 1.22, whereas the fourth observer ranked them noticeably lower at 2.94 ± 0.7. CONCLUSIONS: This work presents a technique that can be used to generate a suite of realistic computerized breast phantoms from a limited number of human subjects. This suite of flexible breast phantoms can be used for multimodality imaging research to provide a known truth while concurrently producing realistic simulated imaging data.

CSX/Nkx2.5 modulates differentiation of skeletal myoblasts and promotes differentiation into neuronal cells in vitro.

CSX/Nkx2.5 transcription factor plays a pivotal role in cardiac development; however, its role in development and differentiation of other organs has not been investigated. In this study, we used C2C12 myoblasts and human fetal primary myoblasts to investigate the function of Nkx2.5 in skeletal myogenesis. The expression levels of Nkx2.5 decreased as C2C12 myoblasts elongated and fused to form myotubes. The expression of human NKX2.5 in C2C12 myoblasts inhibited myocyte differentiation and myotube formation, and up-regulated Gata4 and Tbx5 expression. The expression of NKX2.5 in terminally differentiated C2C12 myotubes resulted in a change in morphology and breakdown into smaller myotubes. Furthermore, overexpression of NKX2.5 in C2C12 cells and primary cultures of human fetal myoblasts led to differentiation of myoblasts into neuron-like cells and expression of neuronal markers. This study sheds light on the previously unknown non-cardiac functions of Nkx2.5 transcription factor.