Polyhedral Cells Research Articles

Malignant primary nerve sheath tumor of the cauda equina in a patient without Von Recklinghausen disease

Malignant peripheral nerve sheath tumor (MPNST) is a rare variety of soft-tissue sarcoma of ecto-mesenchymal origin. Various sites have been mentioned, but it is rare in cauda equina. Only five cases of MPNST of cauda equina are reported till date. A 42-year-old male presented with complaints of weakness in lower limbs for last 5 months with bladder and bowel dysfunction. On magnetic resonance imaging, an isointense lesion on T1 and a hyperintense on T2 imaging was found at terminal spinal cord level. The lesion was excised following laminectomy and showed varied cellularity with thin oval, polyhedral and spindle-shaped cells arranged in bundles on microscopic examination suggesting MPNST. MPNST of cauda equina is rare and is associated with Neurofibromatosis Type-1 or radiation exposure, but is rarer without these risk factors. Prognosis is favorable in these cases.

In-Vitro Culture Morphology of Spermatogonial Stem Cells (SSCs) in Mice

Spermatogonial Stem Cells (SSCs) from pre and post-pubertal age groups of mice were isolated by two step enzymatic digestion method and cultured in six-well plates. The in-vitro culture morphology of the SSCs was observed upto passage 2. In primary culture (P0), on day two, the cells were single and transparent. On day 4, the colony forming unit consisted of four to five cells. Three dimensional colonies were observed on day seven post incubation. From day eight onwards, the cells had spindle shape and showed varied morphology till twelve days post incubation. Double nucleolus is prominent in cells on day eight post incubation. In passage 1, though the cells exhibited different morphology viz., round, stellate, polyhedral, and triangular, the stellate cells were found to be more. In passage 2, the spindle-shaped cells with prominent nucleoli were often observed. Other cell morphology like round, stellate, polyhedral and triangular cells were also observed.

Micro-Morphological investigation of the Skin of the Larval and Adult Stages of the African Catfish (Clarias gariepinus)

The current study aimed to explore the skin sructure at the larval and adult stages of the African catfish. Of the previous studies on the skin morphology of fish, none has researched the detailed skin differentiation at the larval and adult stages of the African catfish. Here by light microscopic investigation, the skin of the larva after hatching consisted of two layers of simple squamous epithelium. The skin of the 5-6 day old larva consisted of more than one layer of flattened to oval cells, continuous layer of melanocytes and club cells showed up. The skin of the 15-days old larva distinguished into epidermis, dermis and hypodermis. While the skin of the adult catfish, the epidermis consisted of three layers a basal layer of cuboidal or columnar cells, middle layer of polyhedral cells and surface layer of flattened cells. Its mucous cells were oval in shape having foamy cytoplasm. Its club cells had acidophilic cytoplasm and some cells were binucleated. At the lateral line, a group of elongated neuromasts viewed between the club cells. Langerhans like cell showed a positive reaction with CD 1a. The dermis divided into stratum spongiusm and stratum compactum. At lateral line beneath the hypodermis, the neuromast canal detected. By SEM, no any evidence of taste buds pores and neuromast detected at the newly hatched larva. Different forms of neuromast appeared on the surface as small epidermal protrusions at the 6-day old larva. In addition, the neuromast at the epidermal protrusion appeared with long and short hair bundles. While, the skin the adult catfish, the surface epithelium showed many projections, the broken epidermis showed a large club cells, melanocytes with cytoplasmic processes and pores. By TEM of the adult catfish, the surface cells had (microridges), desmosomes distinguished between the neighboring epidermal surface cells. The club cells cytoplasm had scanty organelles, two types of club cells identified; the first type with no vesicular secretion and the second type with fibrillar cytoplasm. The plasma membrane showed many invaginations. The study recorded two types of neuromast; superficial neuromast and canal neuromast set in the dermis. No neurmast detected at the 1st day larva afterthat it appeared and incresead in number and its shape changed from simillar hair cells to long and short hair bundles.

Unilateral luteoma of the ovary in a pregnant Risso's dolphin (Grampus griseus).

A white, lobular mass was found in the right ovary of a pregnant Risso’s dolphin (Grampus griseus) at necropsy. The mass was unilateral and occupied most of the pre-existing ovarian tissue. Histologically, the mass was composed of diffuse sheets of polyhedral cells with abundant eosinophilic cytoplasm and oval nuclei, separated by fibrous connective tissue. Only a few ovarian follicles were observed at the periphery of the mass. Immunohistochemically, the large eosinophilic cells were positive for vimentin and negative for pan-cytokeratins. Based on the histopathological features, the present case was diagnosed as luteoma. In human medicine, luteoma of pregnancy, a tumor-like proliferative lesion occurring in pregnant women, is well described. In veterinary medicine, luteoma associated with pregnancy has never been described. The present study would provide useful information for understanding the characteristics of luteoma in animals.

Cutaneous Histiocytic Sarcoma with Regional Lymph Node Metastasis in a Netherland Dwarf Rabbit (Oryctolagus cuniculus)

A 10-year-old male Netherland dwarf rabbit (Oryctolagus cuniculus) was presented with a red nodular mass (1cm in diameter) with ulceration and hair loss in the skin of the left upper lip. Cytological examination revealed atypical round cells. The mass was excised surgically. Histologically, the mass was composed of large round to polyhedral neoplastic cells with marked cytological atypia. The neoplastic cells were often binucleated or multinucleated. Immunohistochemically, the neoplastic cells were intensely positive for Iba1 and vimentin, but fewer neoplastic cells expressed E-cadherin. Nuclear immunoreactivity for Ki67 was detected in approximately 41% of the neoplastic cells. Metastasis to the left cervical lymph nodes was detected 6 months after the surgical excision. Based on clinical, histopathological and immunohistochemical findings, the present case was diagnosed as cutaneous histiocytic sarcoma. To the authors' knowledge cutaneous histiocytic disease has not been reported previously in lagomorphs.

A computational method for sharp interface advection

We devise a numerical method for passive advection of a surface, such as the interface between two incompressible fluids, across a computational mesh. The method is called isoAdvector, and is developed for general meshes consisting of arbitrary polyhedral cells. The algorithm is based on the volume of fluid (VOF) idea of calculating the volume of one of the fluids transported across the mesh faces during a time step. The novelty of the isoAdvector concept consists of two parts. First, we exploit an isosurface concept for modelling the interface inside cells in a geometric surface reconstruction step. Second, from the reconstructed surface, we model the motion of the face–interface intersection line for a general polygonal face to obtain the time evolution within a time step of the submerged face area. Integrating this submerged area over the time step leads to an accurate estimate for the total volume of fluid transported across the face. The method was tested on simple two-dimensional and three-dimensional interface advection problems on both structured and unstructured meshes. The results are very satisfactory in terms of volume conservation, boundedness, surface sharpness and efficiency. The isoAdvector method was implemented as an OpenFOAM® extension and is published as open source.

Ovarian clear cell carcinoma with plasma cell‐rich inflammatory stroma

We report a case of clear cell carcinoma (CCC) of the ovary with plasma cell-rich inflammatory stroma, a recently proposed subtype of CCC, and present the cytological findings. The patient was a 48-year-old woman, who was incidentally found to have a right ovarian tumor during the preoperative work-up for an early-stage adenocarcinoma of the uterine cervix. Cytological examination of an imprint smear of the ovarian tumor and peritoneal washing revealed solid cell clusters of irregular, often dendritic shapes, which were intermingled with many inflammatory cells. "Raspberry bodies" were not found. Histopathological examination of the extirpated ovarian tumor showed the features of CCC with plasma cell-rich inflammatory stroma. This subtype of ovarian CCC poses cytological and histological diagnostic problems, and its differentiation from dysgerminoma is often difficult, because it mostly lacks the hyaline or mucoid stroma. Irregularly shaped clusters of large polyhedral cells, coarsely clumped nuclear chromatin, and plasma cell-rich inflammatory infiltrates suggest CCC, but the cytological differences between dysgerminoma and CCC are often subtle, and immunohistochemical examinations for cytokeratin 7 or epithelial membrane antigen may be necessary. Diagn. Cytopathol. 2017;45:128-132. © 2016 Wiley Periodicals, Inc.

Simulated airflow and rigid fiber behavior in a realistic nasal airway model

ABSTRACTParticles may become airborne due to numerous natural and anthropogenic processes. The nose provides protection for the respiratory system through deposition that prevents particles from reaching more sensitive regions. A series of simulations have been conducted to better predict the deposition efficiency within the nasal passages. Computational fluid dynamics coupled with Lagrangian particle tracking have been used to estimate the deposition of both fibrous and spherical particles. MRI data was collected from the left and right passages of an adult male of mass 120.2 kg and height 181.6 cm. The two passages were constructed into separate computational volumes consisting of approximately 950,000 unstructured polyhedral cells each. A steady, incompressible, laminar flow model was used to simulate the inhalation portion of a human breathing cycle. Volumetric flow rates were varied to represent the full range of human nasal breathing. Qualitatively, the simulated airflow field was shown to agree well with previously published in vitro studies on different nasal replicas. An empirical expression for pressure drop as a function of flow rate that takes the form of Rohrer’s equation is proposed based on the measured data. Deposition efficiency was shown to depend on fiber aspect ratio, particle size, and flow rate. Nasal geometry was also identified as a key factor affecting deposition. A modified Stokes number is proposed along with a novel empirical expression for fiber deposition efficiency in the nasal airway.

Boolean operations on arbitrary polygonal and polyhedral meshes

A linearithmic floating-point arithmetic algorithm designed for solving usual boolean operations (intersection, union, and difference) on arbitrary polygonal and polyhedral meshes is described in this paper. This method does not dis-feature the inputs which can be two volume meshes, two surface meshes or one of each. It provides conformal meshes upon exit. It can be used in many pre- and post-processing applications in computational physics (e.g. cut-cell volume mesh generation or conservative remapping). The core idea is to consider any configuration as a polygonal cloud. The polygons are first triangulated, the intersections are solved, the polyhedral cells are then reconstructed from the conformal triangles cloud and finally their triangular faces are re-aggregated to polygons. This approach offers great flexibility regarding the admissible topologies: non-planar faces, concave faces or cells and some non-manifoldness are handled. The algorithm is described in detail and some current results are shown.

Three-dimensional bonded-cell model for grain fragmentation

We present a three-dimensional numerical method for the simulation of particle crushing in 3D. This model is capable of producing irregular angular fragments upon particle fragmentation while conserving the total volume. The particle is modeled as a cluster of rigid polyhedral cells generated by a Voronoi tessellation. The cells are bonded along their faces by a cohesive Tresca law with independent tensile and shear strengths and simulated by the contact dynamics method. Using this model, we analyze the mechanical response of a single particle subjected to diametral compression for varying number of cells, their degree of disorder, and intercell tensile and shear strength. In particular, we identify the functional dependence of particle strength on the intercell strengths. We find that two different regimes can be distinguished depending on whether intercell shear strength is below or above its tensile strength. In both regimes, we observe a power-law dependence of particle strength on both intercell strengths but with different exponents. The strong effect of intercell shear strength on the particle strength reflects an interlocking effect between cells. In fact, even at low tensile strength, the particle global strength can still considerably increase with intercell shear strength. We finally show that the Weibull statistics describes well the particle strength variability.

Age-Related Changes in the Histological Structure of Rabbit Testes and the Prophylactic Role of Vitamin E.

The present investigation is planned to compare between the histological structure of rabbit testes of different ages and the prophylactic role of vitamin E on senescent animals. Male NewZeland rabbits were divided into four groups according to age. Group I: represented the young rabbits (one month age, weighing 1 ± 0.4 kg), group II: adult rabbits (6 months age, weighing 4 ± 0.5 kg), group III: aged animals (24 month age, weighing 7.5 ± 0.5 kg and group (IV) aged rabbits treated daily with the therapeutic dose of vitamin E orally at a dose of 10 mg/kg b.w / day for 60 days. The testes of young rabbits revealed a small form of seminiferous tubules with regular outline with spermatogonia and Sertoli cells, and the lumen appeared empty from spermatozoa. The interstitium is made up of loose connective tissue with large polyhedral interstitial Leydig cells. In adult studied animals, testes demonstrated with all spermatogenic cells and the lumen filled with spermatozoa. In aged rabbits, the histological studies of testis demonstrated atrophied irregular tubules, disarrangement of vacuolated spermatogenic cells, and sloughing of germ cells into the tubular lumen with reduction and degeneration of spermatozoa. The interstitium between the tubules was widen and filled with degenerated and reduced Leydig cells. Administration of vitamin E to aged animals group revealed an obvious improvement of spermatogenic cells, and the spermatozoa appeared in the lumen of many seminiferous tubules.

Multiscale Simulation of Polymer Flooding with Shear Effects

Multiscale methods have been developed as an alternative approach to upscaling and to accelerate reservoir simulation. The key idea of all these methods is to construct a set of prolongation operators that map between unknowns associated with cells in a fine grid holding petrophysical properties and unknowns on a coarser grid used for dynamic simulation. Herein, we extend one such method—the multiscale restricted-smoothed basis (MsRSB) method—to polymer flooding including shear-thinning (and thickening) effects, which gives highly nonlinear fluid models that are challenging to simulate. To this end, we first formulate a sequentially implicit solution procedure for polymer models with non-Newtonian rheology. By treating the implicit velocity dependence of the viscosities in an inner iteration loop, we obtain a formulation that appears to be more robust and stable than the standard fully-implicit approach. We then use a general algebraic multiscale framework to formulate an efficient and versatile multiscale solver. The unique feature of the MsRSB method is how the prolongation operators are constructed. By using restricted smoothing much in the same way as in smoothed aggregation multigrid methods, one gets a robust and flexible method that enables coarse partitions and prolongation operators to be constructed in an semi-automated manner even for highly complex geo-cellular models with high media contrasts and unstructured cell connections. By setting iterative tolerances appropriately, the resulting iterative multiscale solver can be set to compute mass-conservative approximations to the sequential or fully-implicit solution to arbitrary accuracy and hence be used to trade accuracy for efficiency. We first verify the sequential solution procedure and multiscale solver against a well-established commercial simulator on a test case with simple geometry, highly heterogeneous media properties, and strongly nonlinear fluid behavior. Next, the sequential fine-scale and multiscale solvers are validated on a synthetic simulation model of a shallow-marine reservoir. Here, the computational time is dominated by the pressure solves, and 5–8 times speedup is observed when replacing the fine-scale pressure solver by the iterative multiscale method. We also demonstrate the flexibility of the method by applying it to model with unstructured polyhedral cells that adapt to well positions and faults.

Centroidal Voronoi tessellation based polycube construction for adaptive all-hexahedral mesh generation

This paper presents a novel automatic polycube construction algorithm using centroidal Voronoi tessellation (CVT) based surface segmentation. Given a smooth surface triangle mesh, we segment triangles into six clusters in the surface normal space while satisfying the constraints of polycube construction. A bijective mapping between the input mesh and polycube surfaces is then built via a planar domain parameterization. We develop a new harmonic boundary-enhanced centroidal Voronoi tessellation (HBECVT) method by including local neighbouring information in the energy function. Improving upon the classic CVT method, the HBECVT algorithm can not only overcome the sensitivity to the initialization and noise, but also improve the segmentation results and the resulting polycubes by reducing non-monotone boundaries. Based on the constructed polycube, we then generate quality all-hexahedral (all-hex) meshes. The uniform all-hex mesh and volumetric T-mesh can be obtained through the octree subdivision and mapping. We can also generate adaptive all-hex meshes by extracting the dual mesh from a hybrid octree, which consists of polyhedral cells and each grid point is always shared by eight cells. Several examples are presented in this paper to show the robustness of our algorithms.

Direct Numerical Simulations in Solid Mechanics for Quantifying the Macroscale Effects of Microstructure and Material Model-Form Error

Two fundamental approximations in macroscale solid-mechanics modeling are (1) the assumption of scale separation in homogenization theory and (2) the use of a macroscopic plasticity material model that represents, in a mean sense, the multitude of inelastic processes occurring at the microscale. With the goal of quantifying the errors induced by these approximations on engineering quantities of interest, we perform a set of direct numerical simulations (DNS) in which polycrystalline microstructures are embedded throughout a macroscale structure. The largest simulations model over 50,000 grains. The microstructure is idealized using a randomly close-packed Voronoi tessellation in which each polyhedral Voronoi cell represents a grain. An face centered cubic crystal-plasticity model is used to model the mechanical response of each grain. The overall grain structure is equiaxed, and each grain is randomly oriented with no overall texture. The detailed results from the DNS simulations are compared to results obtained from conventional macroscale simulations that use homogeneous isotropic plasticity models. The macroscale plasticity models are calibrated using a representative volume element of the idealized microstructure. Ultimately, we envision that DNS modeling will be used to gain new insights into the mechanics of material deformation and failure.

Hidradenocarcinoma presenting as soft tissue mass: Case report with cytomorphologic description, histologic correlation, and differential diagnosis

Hidradenocarcinoma (HAC) is a rare adenexal tumor with a propensity for the head and neck region and extremities. We report a case of hidradenocarcinnoma in a 56-year-old woman with a mass on her right palm sampled by fine-needle aspiration and later confirmed on histological examination. Fine-needle aspiration cytology revealed a dual population of cells including polyhedral eosinophilic cells and glycogen containing cells with pale/clear cytoplasm. The nuclei were pleomorphic with prominent nucleoli. Occassional papillary structures were identified on the cell block material. A series of immunohistochemical stains were performed and an adnexal neoplasm was suggested. The mass was resected. On histologic sections, infiltration into the adjacent soft tissue was identified. After an additional series of immunohistochemical stains, the diagnosis was confirmed as a HAC. Herein, we present our findings and discuss the differential diagnoses.

The Specification of Geometric Edges by a Plant Rab GTPase Is an Essential Cell-Patterning Principle During Organogenesis in Arabidopsis

SummaryPlant organogenesis requires control over division planes and anisotropic cell wall growth, which each require spatial patterning of cells. Polyhedral plant cells can display complex patterning in which individual faces are established as biochemically distinct domains by endomembrane trafficking. We now show that, during organogenesis, the Arabidopsis endomembrane system specifies an important additional cellular spatial domain: the geometric edges. Previously unidentified membrane vesicles lying immediately beneath the plasma membrane at cell edges were revealed through localization of RAB-A5c, a plant GTPase of the Rab family of membrane-trafficking regulators. Specific inhibition of RAB-A5c activity grossly perturbed cell geometry in developing lateral organs by interfering independently with growth anisotropy and cytokinesis without disrupting default membrane trafficking. The initial loss of normal cell geometry can be explained by a failure to maintain wall stiffness specifically at geometric edges. RAB-A5c thus meets a requirement to specify this cellular spatial domain during organogenesis.

Immunohistochemical and pathological studies on granulosa cell tumour in Guinea fowl (Numida meleagris)-A case report

A two year old female guinea fowl was presented for post mortem examination in the Department of Veterinary Pathology, Tirupati. Grossly, the bird revealed distended abdomen with straw coloured fluid filled in the entire abdominal cavity. Large greyish-white, multinodular growths with few cystic areas were seen arising from the ovary. The cytological examination revealed eosinophilic, polyhedral cells with prominent nucleoli along with infiltration of pleomorphic lymphoblasts and lymphocytes. Histopathologically, the irregular accumulation of polyhedral cells forming the tubular and rosette structures was found. Based on histopathological features, the tumour was diagnosed as granulosa cell tumourwhich was further confirmed by positive immunostaining for alpha inhibin marker.

12 Year Pediatric Patient Having Pindborg Tumour an Intraosseous Variant: A Rare Case Presentation Affecting the Maxilla

Pindborg tumor is a rare benign epithelial odontogenic tumor occurring most frequently in the posterior part of the lower jaw. I herein report a case of a 12 year old pediatric male patient with a painless swelling of the left maxilla of 5 months duration. Radio graphically, a well circumscribed unilocular radiolucency containing radiopaque foci associated with impacted tooth was seen, along with cortical bone expansion. Histopathology showed sheets of polyhedral epithelial cells in a fibrous stroma. Cells showed distinct cellular outlines with prominent intercellular bridges. Large areas of amorphous, eosinophilic, hyalinized material seen and calcifications within the amyloid-like material (Liesegang ring calcifications) were evident, confirming a diagnosis of Pindborg tumour (Calcifying Epithelial Odontogenic Tumor). The patient was treated by surgical excision of the tumor.

Tumor trofoblástico del lecho placentario. Presentación de un caso y revisión de la literatura

Placental site trophoblastic tumour is rare, being one of the gestational trophoblastic neoplasms that comprises a group of tumours with potential for local invasion and metastases. We report a case of placental site trophoblastic tumour in a 33 year-old woman. Macroscopically the uterine wall showed a 3.5×2.5cm haemorrhagic soft tumour that occupied almost the entire wall with a perforation point in the fundus. Histologically there was diffuse infiltration of large, polyhedral cells with large, irregular nuclei and occasionally bi- and multinucleated cells. They occurred either individually or in sheets dissecting muscle fibres. Immunohistochemistry revealed CK AE1/AE3, placental lactogen and inhibine but not hCG and p63 expression. Adverse prognostic factors are discussed and the relevant literature is reviewed.

A 3D GCL compatible cell-centered Lagrangian scheme for solving gas dynamics equations

Solving the gas dynamics equations under the Lagrangian formalism enables to simulate complex flows with strong shock waves. This formulation is well suited to the simulation of multi-material compressible fluid flows such as those encountered in the domain of High Energy Density Physics (HEDP). These types of flows are characterized by complex 3D structures such as hydrodynamic instabilities (Richtmyer-Meshkov, Rayleigh-Taylor, etc.). Recently, the 3D extension of different Lagrangian schemes has been proposed and appears to be challenging. More precisely, the definition of the cell geometry in the 3D space through the treatment of its non-planar faces and the limiting of a reconstructed field in 3D in the case of a second-order extension are of great interest. This paper proposes two new methods to solve these problems. A systematic and symmetric geometrical decomposition of polyhedral cells is presented. This method enables to define a discrete divergence operator leading to the respect of the Geometric Conservation Law (GCL). Moreover, a multi-dimensional minmod limiter is proposed. This new limiter constructs, from nodal gradients, a cell gradient which enables to ensure the monotonicity of the numerical solution even in presence of strong discontinuity. These new ingredients are employed into a cell-centered Lagrangian scheme. Robustness and accuracy are assessed against various representative test cases.