Cells Of Various Sizes Research Articles

A computational study of VEGF production by patterned retinal epithelial cell colonies as a model for neovascular macular degeneration

BackgroundThe configuration of necrotic areas within the retinal pigmented epithelium is an important element in the progression of age-related macular degeneration (AMD). In the exudative (wet) and non-exudative (dry) forms of the disease, retinal pigment epithelial (RPE) cells respond to adjacent atrophied regions by secreting vascular endothelial growth factor (VEGF) that in turn recruits new blood vessels which lead to a further reduction in retinal function and vision. In vitro models exist for studying VEGF expression in wet AMD (Vargis et al., Biomaterials 35(13):3999–4004, 2014), but are limited in the patterns of necrotic and intact RPE epithelium they can produce and in their ability to finely resolve VEGF expression dynamics.ResultsIn this work, an in silico hybrid agent-based model was developed and validated using the results of this cell culture model of VEGF expression in AMD. The computational model was used to extend the cell culture investigation to explore the dynamics of VEGF expression in different sized patches of RPE cells and the role of negative feedback in VEGF expression. Results of the simulation and the cell culture studies were in excellent qualitative agreement, and close quantitative agreement.ConclusionsThe model indicated that the configuration of necrotic and RPE cell-containing regions have a major impact on VEGF expression dynamics and made precise predictions of VEGF expression dynamics by groups of RPE cells of various sizes and configurations. Coupled with biological studies, this model may give insights into key molecular mechanisms of AMD progression and open routes to more effective treatments.

Primary hepatic angiomyolipoma: immunohistochemistry and electron microscopic observations: a case report

BackgroundHepatic angiomyolipomas are a rare, benign group of mesenchymal tumors in the liver. Hepatic angiomyolipoma is sometimes misdiagnosed as hepatocellular carcinoma, and there is the possibility of a malignant transformation. Hence, the accurate diagnosis of this disorder is necessary.Case presentationA 64-year-old Japanese man was observed to have a space-occupying lesion of 15-mm diameter in the liver during a follow-up examination for a previously resected cecal carcinoma. He underwent lateral segmentectomy of the liver with a provisional diagnosis of hepatic metastatic recurrence of the carcinoma based on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging and diffusion-weighted imaging.ConclusionsWe have explored the combination of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging and histological examination to confirm our diagnosis of hepatic angiomyolipoma comprising an intimate mixture of numerous abnormal blood vessels, adipocytes, and epithelioid spindle cells of various sizes. Immunohistochemical examination revealed characteristic pathological findings associated with positive qualitative immunoreactions for human melanoma black 45 and desmin. Electron microscopic findings revealed the presence of melanosomes in the epithelioid cells. Diffusion-weighted imaging provides a more accurate diagnostic image with the characteristic macroscopic appearance of hepatic angiomyolipoma. Through immunohistochemistry and electron microscopy, we also show that this benign tumor comprises tissue elements.

Absorbed dose evaluation of Auger electron-emitting radionuclides: impact of input decay spectra on dose point kernels and S-values

The aim of this study was to investigate the impact of decay data provided by the newly developed stochastic atomic relaxation model BrIccEmis on dose point kernels (DPKs - radial dose distribution around a unit point source) and S-values (absorbed dose per unit cumulated activity) of 14 Auger electron (AE) emitting radionuclides, namely 67Ga, 80mBr, 89Zr, 90Nb, 99mTc, 111In, 117mSn, 119Sb, 123I, 124I, 125I, 135La, 195mPt and 201Tl.Radiation spectra were based on the nuclear decay data from the medical internal radiation dose (MIRD) RADTABS program and the BrIccEmis code, assuming both an isolated-atom and condensed-phase approach. DPKs were simulated with the PENELOPE Monte Carlo (MC) code using event-by-event electron and photon transport. S-values for concentric spherical cells of various sizes were derived from these DPKs using appropriate geometric reduction factors.The number of Auger and Coster–Kronig (CK) electrons and x-ray photons released per nuclear decay (yield) from MIRD-RADTABS were consistently higher than those calculated using BrIccEmis. DPKs for the electron spectra from BrIccEmis were considerably different from MIRD-RADTABS in the first few hundred nanometres from a point source where most of the Auger electrons are stopped. S-values were, however, not significantly impacted as the differences in DPKs in the sub-micrometre dimension were quickly diminished in larger dimensions.Overestimation in the total AE energy output by MIRD-RADTABS leads to higher predicted energy deposition by AE emitting radionuclides, especially in the immediate vicinity of the decaying radionuclides. This should be taken into account when MIRD-RADTABS data are used to simulate biological damage at nanoscale dimensions.

Flow structure in a flat channel with honeycomb surfaces

This paper deals with the experimental study of the gas flow structure at longitudinal flow around a honeycomb surface with hexagonal cells of various sizes and depths. The measurements were carried out using the PIV system for the developed flow in a flat channel with the cross-section 21 × 150 mm and length of 1000 mm. The flow was visualized and the velocity and turbulence components were measured in a smooth channel and in the presence of honeycomb surfaces. It is shown that a boundary layer with high gradient of velocity and turbulent pulsations is formed near the honeycomb.

Automated leukocyte processing by microfluidic deterministic lateral displacement.

We previously developed a Deterministic Lateral Displacement (DLD) microfluidic method in silicon to separate cells of various sizes from blood (Davis et al., Proc Natl Acad Sci 2006;103:14779-14784; Huang et al., Science 2004;304:987-990). Here, we present the reduction-to-practice of this technology with a commercially produced, high precision plastic microfluidic chip-based device designed for automated preparation of human leukocytes (white blood cells; WBCs) for flow cytometry, without centrifugation or manual handling of samples. After a human blood sample was incubated with fluorochrome-conjugated monoclonal antibodies (mAbs), the mixture was input to a DLD microfluidic chip (microchip) where it was driven through a micropost array designed to deflect WBCs via DLD on the basis of cell size from the Input flow stream into a buffer stream, thus separating WBCs and any larger cells from smaller cells and particles and washing them simultaneously. We developed a microfluidic cell processing protocol that recovered 88% (average) of input WBCs and removed 99.985% (average) of Input erythrocytes (red blood cells) and >99% of unbound mAb in 18 min (average). Flow cytometric evaluation of the microchip Product, with no further processing, lysis or centrifugation, revealed excellent forward and side light scattering and fluorescence characteristics of immunolabeled WBCs. These results indicate that cost-effective plastic DLD microchips can speed and automate leukocyte processing for high quality flow cytometry analysis, and suggest their utility for multiple other research and clinical applications involving enrichment or depletion of common or rare cell types from blood or tissue samples. © 2016 International Society for Advancement of Cytometry.

Study on the evaluation of pterygium activity with in vivo confocal microscopy

Objective: To observe the characteristics of pterygium with in vivo confocal microscopy (IVCM) and understand pterygium activity with the density of inflammatory cells, formation of new blood vessels, and the number of activated keratocytes within the stroma. Methods: A prospective case-controlled study. Thirty-six pterygia from 28 patients were analyzed in this study. A pterygium activity score was obtained by summing four scores of ocular discomfort, pterygium hyperemia, keratitis, and the presence of Fuchs patches. Among them, the low activity of pterygium (PAS score less than 3 points) appeared in 12 eyes and high activity of pterygium (PAS score ≥ 4 points) in 24 eyes. All Patients underwent pterygium IVCM quantitative analysis by observing the boundaries between the pterygium and the adjacent cornea, the density of goblet cells and dendritiform inflammatory cells and Fuchs patches. The correlation of pterygium activity between IVCM and PAS with slit lamp was analyzed with Spearman correlation analysis. Results: The presence of inflammatory cells, numerous blood vessels, and irregular boundary between the cornea and the pterygium with infiltration of hyper-reflective cells in the adjacent corneal epithelium were signs observed with IVCM associated with pterygium activity. With IVCM technique, epithelial cells, goblet cells, and dendritiform inflammatory cells of various sizes were observed within the pterygium epithelium.The active (PAS ≥4) pterygium showed irregular boundaries between the pterygium and the adjacent cornea (score, 0.84±0.51) comparing with inactive subjects (score 0.23±0.12, t=2.68, P=0.009). Fuchs patches were observed as islets of hyper-reflective polygonal cells in front of the pterygium head with blurred boundary. The score (0.75±0.25) in active group showed significant changes as compared with normal subjects (0.23±0.12, t=3.79, P=0.001). The score of dendritiform inflammatory cells, activated keratocytes, and goblet cells in active group were 2.75±0.76, 1.92±0.68, and 2.08±0.42, which were significantly higher than those in inactive group (1.25±0.55, 0.50±0.25, 1.15±0.32, P=0.035, 0.030, <0.01). There was significant positive correlation between IVCM activity and traditional slit lamp PAS. Conclusion: Quantitative analysis of dendritiform inflammatory cells, vascular proliferation and activated keratocytes of pterygium by IVCM may be a reliable evaluation method to evaluate the activity of pterygium.(Chin J Ophthalmol, 2016, 52: 755-763).

An in-core grid index for transferring finite element data across dissimilar meshes

The simulation of a manufacturing process chain with the finite element method requires the selection of an appropriate finite element solver, element type and mesh density for each process of the chain. When the simulation results of one step are needed in a subsequent one, they have to be interpolated and transferred to another model. This paper presents an in-core grid index that can be created on a mesh represented by a list of nodes/elements. Finite element data can thus be transferred across different models in a process chain by mapping nodes or elements in indexed meshes. For each nodal or integration point of the target mesh, the index on the source mesh is searched for a specific node or element satisfying certain conditions, based on the mapping method. The underlying space of an indexed mesh is decomposed into a grid of variable-sized cells. The index allows local searches to be performed in a small subset of the cells, instead of linear searches in the entire mesh which are computationally expensive. This work focuses on the implementation and computational efficiency of indexing, searching and mapping. An experimental evaluation on medium-sized meshes suggests that the combination of index creation and mapping using the index is much faster than mapping through sequential searches.

Macro fat and micro fat: insulin sensitivity and gender dependent response of adipose tissue to isocaloric diet change

The adipose cell-size distribution is a quantitative characterization of adipose tissue morphology. At a population level, the adipose cell-size distribution is insulin-sensitivity dependent, and the observed correlation between obesity and insulin resistance is believed to play a key role in the metabolic syndrome. Changes in fat mass can be induced by altered energy intake or even diet composition. These macroscopic changes must manifest themselves as dynamic adipose cell-size distribution alterations at the microscopic level. The dynamic relationship between these 2 independent measurements of body fat is unknown. In this study, we investigate adipose tissue dynamics in response to various isocaloric diet compositions, comparing gender- and insulin sensitivity-dependent differences. A body composition model is used to predict fat mass changes in response to changes in diet composition for 28 individuals, separated into 4 subgroups according to gender and insulin sensitivity/resistance. Adipose cell-size distribution changes in each individual are simulated with a dynamic model and parameters corresponding to lipid turnover and cell growth rates are determined for each subgroup to match the relative change of fat mass for each diet composition, respectively. We find that adipose cell-size dynamics are associated with different modulations dependent on gender and insulin resistance. Larger turnover and growth/shrinkage rates in insulin resistant individuals suggest they may be more sensitive to changes in energy intake and diet composition than insulin sensitive subjects. The different cell-size distribution changes of adipose cells of various sizes in different subject groups further suggest distinct modulations of adipose cell dynamics.

Hailing cloud empowered radio access networks

Radio access networks empowered by CRAN is a new design paradigm that is drawing the attention of many researchers today to tackle the growing complexity of provisioning broadband wireless services. Because of the need to provide high data rates and better coverage simultaneously, operators are maintaining heterogeneous networks with cells of various sizes, ranging from femtocells to macrocells. Moving the provisioning of wireless network services for all users in collective cells to a central cloud can reduce the otherwise embedded costs and improve processing power performance by dynamically scaling up and down . For interference mitigation, cognitive radio technology can be used to dynamically provide information on spectrum availability over time and space to central processing base station units located in the cloud. In this article, we delve into all these aspects including mobile cloud computing to leverage the concept of cloud empowered radio access networks for future wireless communication needs of 5G networks. We provide an architecture for CRAN. In particular, we discuss in detail the cognitive-radio-based interference mitigation strategy and provide a media access control protocol for the proposed framework that uses this overlay interference mitigation strategy.

Functional ultrastructure of the parenchymatic capsules of the cestode Thysanotaenia congolensis (Cyclophyllidea, Anoplocephalidae, Inermicapsiferinae).

Proglottids from adult Thysanotaenia congolensis from naturally infected black rats Rattus rattus from Santiago Island, Cape Verde, were examined by transmission electron microscopy (TEM). The uterus in mature proglottids is composed of an ephemeral transverse tube or sac that breaks down, releasing eggs into the parenchyma where they are sequestered in groups and encapsulated by parenchymatous layers. In gravid proglottids, eggs accumulate in groups of 6-12 at the distal end of sac-like uterine ducts. As eggs accumulate, the end of the uterine ducts expands until it pinches off, releasing groups of eggs into the parenchyma surrounded by remnants of uterine epithelium. These epithelium-bound groups of eggs remain in the parenchyma until they are encapsulated with several parenchymatous layers, forming parenchymatic egg capsules, typical for mature and gravid proglottids of Inermicapsiferinae. The parenchymatic capsules originate from the medullary parenchyma of immature proglottids, which undergoes differentiation into the three layers of gravid proglottids: (1) an outer connective tissue layer composed of long delicate filaments of unknown chemical nature embedded in a granular extracellular matrix; (2) a middle layer appearing as an accumulation of large closely packed PAS-positive mucous goblets that are intensely metachromatic after toluidine blue staining and (3) an inner compact layer composed of lipid-containing cells, muscle cells with elongated muscle fibres and cells of various sizes and shapes forming or containing calcareous corpuscles. The mature hexacanths of T. congolensis are surrounded by reduced oncospheral envelopes consisting of remnants of a very thin membranous layer of degenerating embryophore with long, irregularly shaped cytoplasmic processes and by remnants of uterine epithelium extending as numerous apical microlamellae into the parenchymatic capsule lumen.

Numerical study of a macroscopic finite pulse model of the diffusion MRI signal

Diffusion magnetic resonance imaging (dMRI) is an imaging modality that probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. The dMRI signal from a heterogeneous sample includes the contribution of the water proton magnetization from all spatial positions in a voxel. If the voxel can be spatially divided into different Gaussian diffusion compartments with inter-compartment exchange governed by linear kinetics, then the dMRI signal can be approximated using the macroscopic Karger model, which is a system of coupled ordinary differential equations (ODEs), under the assumption that the duration of the diffusion-encoding gradient pulses is short compared to the diffusion time (the narrow pulse assumption). Recently, a new macroscopic model of the dMRI signal, without the narrow pulse restriction, was derived from the Bloch–Torrey partial differential equation (PDE) using periodic homogenization techniques. When restricted to narrow pulses, this new homogenized model has the same form as the Karger model.We conduct a numerical study of the new homogenized model for voxels that are made up of periodic copies of a representative volume that contains spherical and cylindrical cells of various sizes and orientations and show that the signal predicted by the new model approaches the reference signal obtained by solving the full Bloch–Torrey PDE in O(ε2), where ε is the ratio between the size of the representative volume and a measure of the diffusion length. When the narrow gradient pulse assumption is not satisfied, the new homogenized model offers a much better approximation of the full PDE signal than the Karger model. Finally, preliminary results of applying the new model to a voxel that is not made up of periodic copies of a representative volume are shown and discussed.

Flexural properties of Ti6Al4V rhombic dodecahedron open cellular structures fabricated with electron beam melting

Open cellular structures fabricated in Ti6Al4V using the electron beam melting (EBM) process have been proposed for tissue scaffolds and low stiffness implants that approximate the properties of bone. The properties of these structures, regardless of cell geometry, have often been determined through compressive testing, and very few of these studies have investigated the flexural properties. For certain types of implants that are designed to fill very large segmental defects in appendicular bones, such as those used in limb sparing, compression testing does not provide the necessary insight into the complex loading states typical of bending. In this study, EBM-fabricated Ti6Al4V prismatic bars, populated with rhombic dodecahedron unit cells of various sizes and relative densities, were subjected to four-point flexure tests. While the results generally follow the power scaling models of Gibson and Ashby, the use of these models as a design tool is limited by machine resolution, particularly when producing structures with small pore sizes required for bone ingrowth.

Parameters estimation from the diffusion MRI signal using a macroscopic model

Diffusion magnetic resonance imaging (dMRI) probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. The dMRI signal from a heterogeneous sample includes the water proton magnetization from all spatial positions in a voxel. If the voxel consists of different diffusion compartments with weak exchange, while the duration of the diffusion-encoding gradient pulses is short compared to the diffusion time (the narrow pulse approximation), the dMRI signal can be approximated by the Karger model. A new macroscopic ODE model for the dMRI signal was recently derived mathematically from the microscopic multiple compartments Bloch-Torrey partial differential equation (PDE) without the narrow pulse restriction. We illustrate by numerical simulations that this ODE model accurately approximates the dMRI signal in a domain containing spherical cells of various sizes, and show preliminary results on solving the inverse problem to estimate the cellular volume fraction and surface area.

The case for random access in OFDMA femtocells

Data services in current cellular networks are growing exponentially, due to the proliferation of high-end mobile devices (smartphones, tablets, ereaders) supporting ever increasing multimedia applications. Clearly, availing of new spectrum (as with 4G allocations) is a necessary part of meeting this challenge, but so are improved network architectures that achieve enhanced spatial spectral efficiency (bits per second per Hertz per area). 4G network operators are moving toward a heterogeneous architecture consisting of overlaid cells of various sizes. A variety of low-power, small-cell base stations and relays are being deployed to increase capacity around local, typically indoor hotspots. The primary concern in such scenarios is understanding the nature and impact of inter-cell interference in dense deployments of such unmanaged small cells, and arriving at solutions for its mitigation. Resource allocation in traditional wide-area cellular networks usually assume a fully loaded network (i.e. many simultaneous active users in a cell) where the system performance is insensitive to the activity of a single user. This assumption is not suitable for femtocells which are designed to serve very few (indoor) users and thus lacks the presumed traffic aggregation. This article provides a fresh look at the femtocell interference problem from a multiple access perspective. It first compares the multi-channel features inherent to OFDMA with traditional multi-channel MAC designs for wireless LANs and highlights how the ability to schedule users in both time and frequency as afforded by OFDMA, can be exploited to achieve more effective (distributed) random access. A simplified MAC model that hides the complexity of LTE protocol stack is proposed to facilitate the design and analysis of random access MAC algorithms in the context of OFDMA femtocells.

Early intrauterine embryonic development of the bothriocephalidean cestode Clestobothrium crassiceps (Rudolphi, 1819), a parasite of the teleost Merluccius merluccius (L., 1758) (Gadiformes: Merlucciidae)

The early intrauterine embryonic development of the bothriocephalidean cestode Clestobothrium crassiceps (Rudolphi, 1819), a parasite of the teleost Merluccius merluccius (L., 1758), was studied by means of light (LM) and transmission electron microscopy (TEM). Contrary to the generic diagnosis given in the CABI Keys to the cestode parasites of vertebrates, the eggs of C. crassiceps, the type of species of Clestobothrium Lühe, 1899, are operculate and embryonated. Our LM and TEM results provide direct evidence that an operculum is present and that the eggs exhibit various stages of intrauterine embryonic development, and in fact represent a good example of early ovoviviparity. The intrauterine eggs of this species are polylecithal and contain numerous vitellocytes, generally∼30, which are pushed to the periphery and remain close to the eggshell, whereas the dividing zygote and later the early embryo remain in the egg centre. During early intrauterine embryonic development, several cleavage divisions take place, which result in the formation of three types of blastomeres, i.e. macro-, meso- and micromeres. These can be readily differentiated at the TEM level, not only by their size, but also by the ultrastructural characteristics of their nuclei and cytoplasmic organelles. The total number of blastomeres in these early embryos, enclosed within the electron-dense eggshells, can be up to∼20 cells of various sizes and characteristics. Mitotic divisions of early blastomeres were frequently observed at both LM and TEM levels. Simultaneously with the mitotic cleavage divisions leading to blastomere multiplication and their rapid differentiation, there is also a deterioration of some blastomeres, mainly micromeres. A similar degeneration of vitellocytes begins even earlier. Both processes show a progressive degeneration of both vitellocytes and micromeres, and are good examples of apoptosis, a process that provides nutritive substances, including lipids, for the developing embryo.

Sarcomatoid renal cell carcinoma with scant epithelial components in an Angora cat

CASE HISTORY: A 6-year-old, neutered, female Angora cat presented with a history of lethargy and anorexia for 2 months and a clinically palpable and gradually enlarging, solid mass in the abdominal cavity extending from the last costal arch to the pelvic cavity.CLINICAL FINDINGS: Examination of the cat revealed jaundice, dehydration and hypothermia. Haematological manifestations included lymphopenia and substantial decrease in haematocrit value. Biochemical analysis of the blood revealed hypoglycaemia, three-fold elevated blood urea nitrogen values, increased level of serum aspartate aminotransferase and increased total bilirubin while the creatinine level was normal. Ultrasonographic examination of the abdomen showed a disrupted and large hypoechoic area around the left kidney. The cat was anaesthetised and the left kidney was removed, but the cat died following surgery.PATHOLOGICAL FINDINGS: On post-mortem examination, the left kidney was markedly enlarged and both the cortical and medullary parenchyma were replaced by confluent, multilobulated, pale tan-white, firm nodular masses protruding above the capsular surface. Metastasis was not observed. Cytological examination revealed a population of spindle-shaped cells of variable size, with abundant coarse chromatin and occasionally prominent nucleoli. Initial sections of the kidney were indicative of undifferentiated sarcoma confirmed by immunohistochemistry revealing vimentin-positive and cytokeratin-negative results in all tumour tissues. Additional sections showed very small amounts of both cytokeratin-positive and vimentin-positive areas.DIAGNOSIS: Sarcomatoid renal cell carcinoma (SRCC) with scant epithelial components originating from left kidney.CLINICAL RELEVANCE: Clinical and pathological features were similar to those of human SRCC, even though there was no evidence of metastases. Immunohistochemistry for vimentin and cytokeratin may be useful for definitive diagnosis of renal cell carcinoma with sarcomatoid differentiation, although staining of sections from several different parts of the tumour may be necessary. When a primary renal tumour is presented, SRCC should be considered as this diagnosis may influence treatment protocols and the clinical outcome.

Fully conservative leak-proof treatment of thin solid structures immersed in compressible fluids

We propose a novel high resolution conservative advection scheme that is suitable for thin, embedded moving solid structures. The scheme works by coupling together a high order flux-based method with a conservative semi-Lagrangian solver that is similar in spirit to that of Lentine et al. [26], but modified to treat the cut cells and partial volumes that arise near a thin solid structure. The conservative semi-Lagrangian scheme is unconditionally stable, and so unlike previous methods no cell merging is required to compensate for the small cell volumes that arise. Furthermore, as the semi-Lagrangian scheme works via tracing characteristic curves, no special treatment is required either to enforce non-penetration through thin, moving solid structures, or to populate swept or uncovered degrees of freedom. For the flux-based solver, we use finite-difference ENO with Lax–Friedrich’s diffusion (although any flux-based scheme works), and in doing so we found that a modification to the diffusion calculation leads to improved stability in its third order accurate variant. We integrate this novel hybrid advection scheme into a semi-implicit compressible flow solver, and modify the implicit pressure solver to work with cells of variable size. In addition, we propose an improvement to the semi-implicit compressible flow solver via a new method for computing a post-advected pressure. Finally, this hybrid conservative advection scheme is integrated into a semi-implicit fluid–structure solver, and a number of one-dimensional and two-dimensional examples are considered—in particular, showing that we can handle thin solid structures moving through the grid in a fully conservative manner, preventing fluid from leaking from one side of the structure to the other and without the need for cell merging or other special treatment of cut cells and partial volumes.

An adaptive Cartesian cut-cell/level-set method to simulate incompressible two-phase flows with embedded moving solid boundaries

In this paper, a Cartesian grid method has been developed to simulate two dimensional unsteady viscous incompressible two-phase flows with embedded moving solid boundaries. The solid boundary is treated by a cut cell approach. The fluid–fluid interface is captured and treated by the level set method. A collocated finite volume method with nominally second-order accurate schemes in space is used for discretization. A pressure-free projection method is used to solve the equations governing incompressible flows. Adaptive mesh refinement is applied to efficiently deploy mesh cells of various sizes. The present method proposes an outer-iteration solution procedure to solve two-phase flows with partially submerged moving bodies and physically treats issues on newly exposed cells. Various test examples were computed and validated against previous analytical solutions, simulations, or experiments to prove the accuracy and effectiveness of the present method. We observed first-order spatial accuracy in a specific validating problem. In brief, the major contribution of the present work is the first-time announcement of a well validated level set method based on the cut-cell approach in moving-body problems.

Relationship between tumour development and detection of Marek’s disease virus in the feather follicular epithelium of older chickens

To demonstrate the relationship between tumour development and virus replication, eight specific-pathogen-free pullets of line P2 (Group P; 14 weeks old) and five adult chickens (Group A; 96 weeks old) were inoculated with virulent Marek's disease virus (vMDV). Five chickens of Group P died or were euthanised due to moribund condition following the development of neoplastic lesions between days 53 and 91. On histopathological examination, these lesions were characterised by the proliferation of lymphoid cells of variable size. On analysis by polymerase chain reaction (PCR), the MDV meq gene was detected in Group P from day 21, and it was continuously identified in five chickens until they died or were euthanised. Abnormal signs and histopathological changes were not observed in chickens of Group A. The MDV meq gene was temporarily detected in some chickens of Group A, but it remained almost undetectable throughout the experimental period. In older chickens inoculated with vMDV, the onset of MD lymphoma development tended to be delayed as compared with the young chicks. The relationship between MD lymphoma development and virus replication in older chickens has been suggested. Our data might indicate the underlying existence of an age-related resistance to vMDV challenge.

Essentials of Functional MRI

1496 Objectives Dose point kernels (DPKs) provide information on the spatial pattern of energy deposition around the site of decay of the radionuclide. This information could inform on the choice of radionuclide used with a specific cancer cell targeting strategy. In this work, DPKs are presented for some Auger electron emitting isotopes used for targeted radiotherapy, namely 125I, 123I, 119Sb, 111In, and 67Ga. Methods The DPKs of the aforementioned radionuclides were calculated with the Monte Carlo code PENELOPE. To this end, point sources were placed in an infinite medium and the absorbed dose produced by the emitted electrons (Auger, Coster-Kronig and internal-conversion electrons) and photons (gammas and characteristic x-rays) was scored in spherical shells. Simulations were done in tissue equivalent material as well as liquid water. The generated DPKs were then employed to calculate C←C, C←CS, N←N and N←CS S-values for spherical cells of various sizes. The S-values so obtained are compared to those tabulated by the Medical Internal Radiation Dose (MIRD). Results Summary of S-values (Gy/Bqs) for RC = 10 µm and RN = 5 µm in liquid water (Table 1). Conclusions Cellular S-values can be used to estimate the absorbed dose at the cellular level from intracellularly localized radionuclides. The contribution of photons is much smaller than that of electrons and can be neglected. S-values are comparable with the MIRD data when the source and target regions strongly overlap, e.g. for the C←C and N←N configurations. But discrepancies become visible when the source is far from the target, in the N←CS case. This could be ascribed to MIRD S-values being based on approximate DPKs evaluated from the collision stopping power (i.e. assuming straight trajectories of the electrons and neglecting energy straggling). Research Support This research was supported by Cancer Research UK (CRUK), the Medical Research Council (MRC), and the Nuffield Oxford Trust