Cellular Shape Research Articles

Turnover versus treadmilling in actin network assembly and remodeling.

Actin networks are highly dynamic cytoskeletal structures that continuously undergo structural remodeling. One prominent way to probe these processes is via Fluorescence Recovery After Photobleaching (FRAP), which can be used to estimate the rate of turnover for filamentous actin monomers. It is thought that head-to-tail treadmilling and de novo filament nucleation constitute two primary mechanisms underlying turnover kinetics. More generally, these self-assembly activities are responsible for many important cellular functions such as force generation, cellular shape dynamics, and cellular motility. In what relative proportions filament treadmilling and de novo filament nucleation contribute to actin network turnover is still not fully understood. We used an advanced stochastic reaction-diffusion model in three dimensions, MEDYAN, to study turnover dynamics of actin networks containing Arp2/3, formin and capping protein at experimentally meaningful length- and time-scales. Our results reveal that, most commonly, treadmilling of older filaments is the main contributor to actin network turnover. On the other hand, although turnover and treadmilling are often used interchangeably, we show clear instances where this assumption would not be justified, for example, finding that rapid turnover is accompanied by slow treadmilling in highly dendritic Arp2/3 networks.

An RNAi screen unravels the complexities of Rho GTPase networks in skin morphogenesis.

During mammalian embryogenesis, extensive cellular remodeling is needed for tissue morphogenesis. As effectors of cytoskeletal dynamics, Rho GTPases and their regulators are likely involved, but their daunting complexity has hindered progress in dissecting their functions. We overcome this hurdle by employing high throughput in utero RNAi-mediated screening to identify key Rho regulators of skin morphogenesis. Our screen unveiled hitherto unrecognized roles for Rho-mediated cytoskeletal remodeling events that impact hair follicle specification, differentiation, downgrowth and planar cell polarity. Coupling our top hit with gain/loss-of-function genetics, interactome proteomics and tissue imaging, we show that RHOU, an atypical Rho, governs the cytoskeletal-junction dynamics that establish columnar shape and planar cell polarity in epidermal progenitors. Conversely, RHOU downregulation is required to remodel to a conical cellular shape that enables hair bud invagination and downgrowth. Our findings underscore the power of coupling screens with proteomics to unravel the physiological significance of complex gene families.

Malignant phyllodes tumors of the breast: A comprehensive literature review.

Malignant phyllodes tumors (MPT) have always been a great deal of controversy among fibroepithelial tumors of the breast. Genetics, histopathology, and tumor behavior on the cellular scale shape their extent of aggressiveness. Diagnosis is based on radiological and pathological findings. Cure is surgical excision. This article reveals the most common clinical indices, which should raise the surgeon's concerns on a benign-looking tumor to further investigate its nature, and the importance of an adequate surgical intervention, preferably done by an oncoplastic breast surgeon, in order to accomplish the ideal outcome for the patient.

Shapes and distributions of soft tissue scatterers

What causes scattering of ultrasound from normal soft tissues such as the liver, thyroid, and prostate? Commonly, the answer is formulated around the properties of spherical scatterers, related to cellular shapes and sizes. However, an alternative view is that the closely packed cells forming the tissue parenchyma create the reference media, and the long cylindrical-shaped fluid vessels serve as the scattering sites. Under a weak scattering or Born approximation for the extracellular fluid in the vessels, and assuming an isotropic distribution of cylindrical channels across a wide range of diameters, consistent with a fractal branching pattern, some simple predictions can be made about the nature of backscatter as a function of frequency in soft tissues. Specifically, a number of plausible shapes would predict that backscatter increases as a power law of frequency, where the power law is determined by the function governing the number density of the vessels versus diameter. These results are compared with some historical models developed over the last 100 years in scattering theory and point to the need for higher spatial resolution and higher bandwidths to obtain more precise measures of the key parameters in normal tissues, and to better identify the dominant structures responsible for backscatter in everyday clinical imaging.

PAI-1 contributes to homocysteine-induced cellular senescence

Cellular Senescence is associated with organismal aging and related pathologies. Previously, we reported that plasminogen activator inhibitor-1 (PAI-1) is an essential mediator of senescence and a potential therapeutic target for preventing aging-related pathologies. In this study, we investigate the efficacies of PAI-1 inhibitors in both in vitro and in vivo models of homocysteine (Hcy)-induced cardiovascular aging. Elevated Hcy, a known risk factor of cardiovascular diseases, induces endothelial senescence as evidenced by increased senescence-associated β-Gal positivity (SA-β-Gal), flattened cellular morphology, and cylindrical appearance of cellular nuclei. Importantly, inhibition of PAI-1 by small molecule inhibitors reduces the number of SA-β-Gal positive cells, normalizes cellular morphology and nuclear shape. Furthermore, while Hcy induces the levels of senescence regulators PAI-1, p16, p53 and integrin β3, and suppresses catalase expression, treatment with PAI-1 inhibitors blocks the Hcy-induced stimulation of senescence cadres, and reverses the Hcy-induced suppression of catalase, indicating that PAI-1 specific small molecule inhibitors are efficient to prevent Hcy-induced cellular senescence. Our in vivo study shows that the levels of integrin β3, a recently identified potential regulator of cellular senescence, and its interaction with PAI-1 are significantly elevated in Hcy-treated heart tissues. In contrast, Hcy suppresses antioxidant gene regulator Nrf2 expression in hearts. However, co-treatment with PAI-1 inhibitor completely blocks the stimulation of Hcy-induced induction of integrin β3 and reverses Nrf2 expression. Collectively these in vitro and in vivo studies indicate that pharmacological inhibition of PAI-1 improves endothelial and cardiac health by suppressing the pro-senescence effects of hyperhomocysteinemia through suppression of Hcy-induced master regulators of cellular senescence PAI-1 and integrin β3. Therefore, PAI-1 inhibitors are promising drugs for amelioration of hyperhomocysteinemia-induced vascular aging and aging-related disease.

Effect of In-Situ Post Heating on Repairing STS316L Built by Laser Powder Bed Fusion Using Direct Energy Deposition

The repairing parts were fabricated by PBF (powder bed fusion) using direct energy deposition (DED), interfacial cracks can occur at the interface between the substrate and the area to be repaired. Such interfacial defects are due to the thermal stress induced by the temperature gradient which results from repeated melting and solidification during the powder deposition by laser. These cracks degrade the mechanical properties of the repaired parts. Therefore, in this study, in-situ post heating is proposed to lower the cooling rate of deposited layers directly after repairing, in which several layers are additionally deposited onto the repair zone. To investigate the effect of the in-situ post heating, we have studied the microhardness, microstructure, and tensile properties according to the post heating, as well as the occurrence of cracks. The experimental results showed the formation of macro-scale cracks in the absence of post heating, whereas only micro-scale cracks (10 μm or less) were observed in the repaired sample with a low repair depth in the presence of post heating. Meanwhile, regardless of the use of in-situ post heating, complex dendritic structures (columnar and cellular shapes) were found on the deposited layer, which also appeared in the substrate built by PBF. Similar to the microstructure, no hardness changes were observed in the deposited layer; however, the hardness of the DED repaired zone tended to be slightly lower compared to that of the PBF substrate. For a specimen with a repair depth 1 mm, the tensile strength and elongation of the specimen repaired with the in-situ post heating increased by 8 and 13%, respectively, compared to the specimen repaired without the in-situ post heating. However, in the specimen with a large repair depth (2mm), macro-scale cracks occurred, which led to degradation of tensile properties. Key words: direct energy deposition (DED), crack, post heating, microhardness, tensile test

The Tricellular Junction Protein Sidekick Regulates Vertex Dynamics to Promote Bicellular Junction Extension

Remodeling of cell-cell junctions drives cell intercalation that causes tissue movement during morphogenesis through the shortening and growth of bicellular junctions. The growth of new junctions is essential for continuing and then completing cellular dynamics and tissue shape sculpting; however, the mechanism underlying junction growth remains obscure. We investigated Drosophila genitalia rotation where continuous cell intercalation occurs to show that myosin II accumulating at the vertices of a new junction is required for the junction growth. This myosin II accumulation requires the adhesive transmembrane protein Sidekick (Sdk), which localizes to the adherens junctions (AJs) of tricellular contacts (tAJs). Sdk also localizes to and blocks the accumulation of E-Cadherin at newly formed growing junctions, which maintains the growth rate. We propose that Sdk facilitates tAJ movement by mediating myosin II-driven contraction and altering the adhesive properties at the tAJs, leading to cell-cell junction extension during persistent junction remodeling.

Remarkable structural transformations of actin bundles are driven by their initial polarity, motor activity, crosslinking, and filament treadmilling.

Bundled actin structures play a key role in maintaining cellular shape, in aiding force transmission to and from extracellular substrates, and in affecting cellular motility. Recent studies have also brought to light new details on stress generation, force transmission and contractility of actin bundles. In this work, we are primarily interested in the question of what determines the stability of actin bundles and what network geometries do unstable bundles eventually transition to. To address this problem, we used the MEDYAN mechano-chemical force field, modeling several micron-long actin bundles in 3D, while accounting for a comprehensive set of chemical, mechanical and transport processes. We developed a hierarchical clustering algorithm for classification of the different long time scale morphologies in our study. Our main finding is that initially unipolar bundles are significantly more stable compared with an apolar initial configuration. Filaments within the latter bundles slide easily with respect to each other due to myosin activity, producing a loose network that can be subsequently severely distorted. At high myosin concentrations, a morphological transition to aster-like geometries was observed. We also investigated how actin treadmilling rates influence bundle dynamics, and found that enhanced treadmilling leads to network fragmentation and disintegration, while this process is opposed by myosin and crosslinking activities. Interestingly, treadmilling bundles with an initial apolar geometry eventually evolve to a whole gamut of network morphologies based on relative positions of filament ends, such as sarcomere-like organization. We found that apolar bundles show a remarkable sensitivity to environmental conditions, which may be important in enabling rapid cytoskeletal structural reorganization and adaptation in response to intracellular and extracellular cues.

Abstract 2019: Enhancing the effect of immunotherapy by inhibiting tumor promoting effect of HDAC6

Abstract Histone deacetylases (HDAC) are recognized for diverse functions beyond remodeling of chromatin landscape. It may range from regulating the cellular-health to immune-diseases like cancer, positioning the HDAC inhibitors (HDACi) at a crucial junction of immunotherapy. The toxicity among pan-HDACi has led to the development of selective inhibitors, which helped to understand the roles of specific HDACs in immune responses. For example, HDAC6 is reported to promote the pro-tumorigenic STAT3 pathway. By using specific HDAC6i, the downstream immune-modulatory pathways of STAT3, such as PDL1, could be targeted. HDAC6 has been associated with numerous structural functions, including cellular motility, shape, antigen processing, and intracellular transport through the acetylation of tubulin and cortactin, among others. This function suggests that HDAC6 could also a regulator of cellular processes involved in metastasis. In this respect, we found that the selective HDAC6i NextA was able to reduce the primary tumor growth and the appearance of spontaneously metastatic nodules in the murine Triple Negative Breast Cancer (TNBC) tumor model 4T1. Additionally, the in vitro use of NextA in multiple murine and human breast cancer cell lines was found to reduce invasion and modulate multiple EMT-specific genes without exhibiting excessive cytotoxicity. PDL1 expression was also reduced, as described previously in melanoma models. Given that 4T1 is a TIL-infiltrated tumor, we tested the efficacy of αPD-1 immune checkpoint inhibitors (ICI) and found a lower dose of αPD-1 to be more effective than the higher doses to reduce primary and secondary tumor growth. However, the expression of IFNγ & PD-L1 were enhanced with the monotherapy. In an in vitro setting, we were able to nullify the upregulation of PD-L1 by αPD-1 with either NextA or IFNγ neutralization. To apply this insight in vivo, we tested the combination of NextA and αPD-1 to find a significant reduction in tumor growth, both in primary & secondary nodules. Analysis of the effector molecules revealed a reduction in intra-tumoral PD-L1 and IDO1 along with a moderate level of IFNγ, as well as a reduction in several key EMT signature genes, including cMYC, MMP9, vimentin, and twist. We also identified E-cadherin, a negative regulator of the metastatic process, as a novel target of NextA that was found to be upregulated in vivo. This was corroborated by the in vitro observations in several murine and human breast cancer cell lines, irrespective of hormonal receptor status. In conclusion, we propose that combining HDAC6i along with ICI such as αPD-1 may offer a novel avenue to enhance the efficacy of immunotherapy, as well as alter the tumor-intricate physiology, without incurring unnecessary toxicity. Note: This abstract was not presented at the meeting. Citation Format: Debarati Banik, Melissa Beaty, Erical Palmer, Maria Del Mar Gracia Hernandez, Satish K. Noonepalle, Prathima Vembu, Alan P. Kozikowski, Alejandro Villagra. Enhancing the effect of immunotherapy by inhibiting tumor promoting effect of HDAC6 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2019.

Differential cellular contractility as a mechanism for stiffness sensing

The ability of cells to sense and respond to the mechanical properties of their environments is fundamental to a range of cellular behaviours, with substrate stiffness increasingly being found to be a key signalling factor. Although active contractility of the cytoskeleton is clearly necessary for stiffness sensing in cells, the physical mechanisms connecting contractility with mechanosensing and molecular conformational change are not well understood. Here we present a contractility-driven mechanism for linking changes in substrate stiffness with internal conformational changes. Cellular contractility is often assumed to imply an associated compressive strain. We show, however, that where the contractility is non-uniform, localized areas of internal stretch can be generated as stiffer substrates are encountered. This suggests a physical mechanism for the stretch-activation of mechanotransductive molecules on stiffer substrates. Importantly, the areas of internal stretch occur deep within the cell and not near the cellular perimeter, which region is more traditionally associated with stiffness sensing through e.g. focal adhesions. This supports recent experimental results on whole-cell mechanically-driven mechanotransduction. Considering cellular shape we show that aspect ratio acts as an additional control parameter, so that the onset of positive strain moves to higher stiffness values in elliptical cells.

Three-dimensional architecture of the acetabular labrum in the human hip joint.

The acetabular labrum is frequently damaged with advancing age. As collagen fibers are the main sources of strength, knowledge of their ultrastructure is important to determine the cause of age-induced changes. We aimed to investigate the ultrastructure of collagen fibers constituting the acetabular labrum using scanning electron microscopy (SEM). Acetabular labrum samples obtained during total hip arthroplasty were studied. The samples were specially prepared to observe the steric construction of collagen fibrils constituting the acetabular labrum under light microscopy followed by SEM. The acetabular labrum was mostly composed of cartilage tissue, consisting of chondrocytes and collagen type II, with a layer of collagen type I. In adults, chondrocytes with a rich cytoplasm were surrounded by a dense network of fine type II collagen fibrils, and small bundles of type I collagen fibrils were interposed in the cartilage layer. In elderly individuals, the chondrocytes atrophied and both type I and II collagen fibrils were sparse. We suggest that cartilage has three to five layers, consisting of type I and type II collagen fibrils with a solid cartilage substrate. In elderly individuals, the density of chondrocytes decreases and the cellular shape and architecture of collagen fibrils also changes.

Cardiac Troponins are Among Targets of Doxorubicin-Induced Cardiotoxicity in hiPCS-CMs.

Modern diagnostic strategies for early recognition of cancer therapeutics-related cardiac dysfunction involve cardiac troponins measurement. Still, the role of other markers of cardiotoxicity is still unclear. The present study was designed to investigate dynamics of response of human cardiomyocytes derived from induced pluripotent stem cells (hiPCS-CMs) to doxorubicin with the special emphasis on their morphological changes in relation to expression and organization of troponins. The hiPCS-CMs were treated with doxorubicin concentrations (1 and 0.3 µM) for 48 h and followed for next up to 6 days. Exposure of hiPCS-CMs to 1 µM doxorubicininduced suppression of both cardiac troponin T (cTnT) and cardiac troponin I (cTnI) gene expression. Conversely, lower 0.3 µM doxorubicin concentration produced no significant changes in the expression of aforementioned genes. However, the intracellular topography, arrangement, and abundance of cardiac troponin proteins markedly changed after both doxorubicin concentrations. In particular, at 48 h of treatment, both cTnT and cTnI bundles started to reorganize, with some of them forming compacted shapes extending outwards and protruding outside the cells. At later intervals (72 h and onwards), the whole troponin network collapsed and became highly disorganized following, to some degree, overall changes in the cellular shape. Moreover, membrane permeability of cardiomyocytes was increased, and intracellular mitochondrial network rearranged and hypofunctional. Together, our results demonstrate complex effects of clinically relevant doxorubicin concentrations on hiPCS-CM cells including changes in cTnT and cTnI, but also in other cellular compartments contributing to the overall cytotoxicity of this class of cytostatics.

Microtubule number and length determine cellular shape and function in Plasmodium

Microtubules are cytoskeletal filaments essential for many cellular processes, including establishment and maintenance of polarity, intracellular transport, division and migration. In most metazoan cells, the number and length of microtubules are highly variable, while they can be precisely defined in some protozoan organisms. However, in either case the significance of these two key parameters for cells is not known. Here, we quantitatively studied the impact of modulating microtubule number and length in Plasmodium, the protozoan parasite causing malaria. Using a gene deletion and replacement strategy targeting one out of two α‐tubulin genes, we show that chromosome segregation proceeds in the oocysts even in the absence of microtubules. However, fewer and shorter microtubules severely impaired the formation, motility and infectivity of Plasmodium sporozoites, the forms transmitted by the mosquito, which usually contain 16 microtubules. We found that α‐tubulin expression levels directly determined the number of microtubules, suggesting a high nucleation barrier as supported by a mathematical model. Infectious sporozoites were only formed in parasite lines featuring at least 10 microtubules, while parasites with 9 or fewer microtubules failed to transmit.

Development and implementation of an effective constitutive model for architected cellular iron-based shape memory alloys: Pressure dependency and transformation-plasticity interaction

Using architected cellular iron-based shape memory alloys (AC Fe-SMAs) can help compensate the relatively higher density of the base material compared to NiTi-based and Cu-based shape memory alloys, while providing good shape recovery, lower production cost, and greater energy dissipation. This article is dedicated to the development of an effective and pressure-dependent constitutive model that predicts the thermomechanical response of AC Fe-SMAs. We first simulate the behavior of the cellular material using the dense model that was previously developed by the authors, along with different unit cells (UCs) subject to periodic boundary. The shape memory effect is simulated by compressing the UCs by 2% of their height, followed by mechanical unloading, and heating above the austenite finish temperature. The results highlight stress concentration, maximum phase transformation, and maximum plastic deformation at the geometry discontinuities or strands necks. Post-processing the ABAQUS ODB files with Python scripts shows that the bending-dominated unit cell with the highest maximum local values of state variables exhibits the lowest volume-averaged outputs. Comparison of the unit cell to cubic multi-cell structures points out an asymptotic vanishing of the effects of the free boundaries as the number of cells in the multi-cell structure increases. The results of the unit cells are used to calibrate the parameters of the pressure-dependent effective model. The ratios of the inelastic hydrostatic strains to the equivalent total inelastic strains indicate higher pressure effects in the bending-dominated cellular lattice than in the stretch-dominated structures. The force-displacement and “dissipated energy”-temperature curves of the cellular beam and its equivalent bulk structure obtained by simulations of 4-point bending tests are found to be close enough that the effective model can be considered as an efficient design tool for architected cellular iron-based shape memory alloy structures.

Akt and STAT5 mediate na\xefve human CD4+ T-cell early metabolic response to TCR stimulation

Metabolic pathways that regulate T-cell function show promise as therapeutic targets in diverse diseases. Here, we show that at rest cultured human effector memory and central memory CD4+ T-cells have elevated levels of glycolysis and oxidative phosphorylation (OXPHOS), in comparison to naïve T-cells. Despite having low resting metabolic rates, naive T-cells respond to TCR stimulation with robust and rapid increases in glycolysis and OXPHOS. This early metabolic switch requires Akt activity to support increased rates of glycolysis and STAT5 activity for amino acid biosynthesis and TCA cycle anaplerosis. Importantly, both STAT5 inhibition and disruption of TCA cycle anaplerosis are associated with reduced IL-2 production, demonstrating the functional importance of this early metabolic program. Our results define STAT5 as a key node in modulating the early metabolic program following activation in naive CD4+ T-cells and in turn provide greater understanding of how cellular metabolism shapes T-cell responses.

3DMMS: robust 3D Membrane Morphological Segmentation of C. elegans embryo

BackgroundUnderstanding the cellular architecture is a fundamental problem in various biological studies. C. elegans is widely used as a model organism in these studies because of its unique fate determinations. In recent years, researchers have worked extensively on C. elegans to excavate the regulations of genes and proteins on cell mobility and communication. Although various algorithms have been proposed to analyze nucleus, cell shape features are not yet well recorded. This paper proposes a method to systematically analyze three-dimensional morphological cellular features.ResultsThree-dimensional Membrane Morphological Segmentation (3DMMS) makes use of several novel techniques, such as statistical intensity normalization, and region filters, to pre-process the cell images. We then segment membrane stacks based on watershed algorithms. 3DMMS achieves high robustness and precision over different time points (development stages). It is compared with two state-of-the-art algorithms, RACE and BCOMS. Quantitative analysis shows 3DMMS performs best with the average Dice ratio of 97.7% at six time points. In addition, 3DMMS also provides time series of internal and external shape features of C. elegans.ConclusionWe have developed the 3DMMS based technique for embryonic shape reconstruction at the single-cell level. With cells accurately segmented, 3DMMS makes it possible to study cellular shapes and bridge morphological features and biological expression in embryo research.

Mechanical Stress and Alteration of Cellular Morphology Influences O‐GlcNAc Modification

Protein O‐linked N‐acetylglucosamine modification (O‐GlcNAc) is the result of a post‐translational modification that involves the reversible transfer of an N‐acetyl‐glucosamine molecule to Ser/Thr OH‐group of intracellular proteins. O‐GlcNAc modification is increasingly recognized as a key regulatory element, capable to modify the functionality and the life‐cycle of hundreds of proteins. O‐GlcNAc's participation in stress adaptation processes was evidenced after several environmental challenges such as heat shock, hypoxia or oxidative stress. However, intracellular O‐GlcNAc modification was not yet studied under mechanical stress, despite the fact that physical stress is a constant challenge for many cells in our body.In our present work, we used human periodontal ligament (PDL) cells isolated from teeth extracted for orthodontic indications. PDL cells were cultivated under standard cell culture conditions and exposed to various amount of compression force for 12 hours.We have analyzed cell survival by flow‐cytometry and protein O‐GlcNAc by Western‐blot. Since cytoskeletal filaments are essential to the structural integrity of the cells both in normal condition and under mechanical stress, we also studied the intracellular distribution of O‐GlcNAc in relation to actin, alpha‐tubulin, vimentin and the cellular shape. We have found that O‐GlcNAc elevated under moderate mechanical load (1.5 – 3 g/cm2) but did not changed significantly under higher load ( ≥ 7 g/cm2). Intracellular distribution of O‐GlcNAc in non‐loaded cell demonstrated an accumulation at several membrane protrusion sites which showed the most overlap with tubulin and no overlap at all with vimentin. Under mechanical stress, the cells retracted these protrusions and O‐GlcNAc distribution became more centralized as well.In conclusion, we found that O‐GlcNAc regulation responds to mechanical challenges and our data suggest that O‐GlcNAc is coupled to cellular morphology.Support or Funding InformationThis work was funded by the Research Fund of the University of Pécs, Faculty of Medicine (grant No.: AOK‐KA 2/2015 (06.30)) and the EU founded Hungarian project GINOP 2.3.2. –15 (grant No.: 2.3.2. –15‐2016‐00050).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Molecular Signatures of Fusion Proteins in Cancer.

Although gene fusions are recognized as driver mutations in a wide variety of cancers, the general molecular mechanisms underlying oncogenic fusion proteins are insufficiently understood. Here, we employ large-scale data integration and machine learning and (1) identify three functionally distinct subgroups of gene fusions and their molecular signatures; (2) characterize the cellular pathways rewired by fusion events across different cancers; and (3) analyze the relative importance of over 100 structural, functional, and regulatory features of ∼2200 gene fusions. We report subgroups of fusions that likely act as driver mutations and find that gene fusions disproportionately affect pathways regulating cellular shape and movement. Although fusion proteins are similar across different cancer types, they affect cancer type-specific pathways. Key indicators of fusion-forming proteins include high and nontissue specific expression, numerous splice sites, and higher centrality in protein-interaction networks. Together, these findings provide unifying and cancer type-specific trends across diverse oncogenic fusion proteins.

Insights into the molecular basis of immunosuppression and increasing pathogen infection severity of ammonia toxicity by transcriptome analysis in pacific white shrimp Litopenaeus vannamei

The high concentration of ammonia resulting from intensive culture system and environmental pollution could cause disease occurrence in shrimp, but little information is available on its molecular mechanisms. In this study, we performed comparative transcriptome analysis among WSSV-infected shrimp under ammonia stress (LAV), WSSV-infected shrimp under normal water (LV), and normal shrimp under ammonia stress (LA) groups to identify the key genes and pathways involved in immunosuppression and increasing pathogen infection severity caused by ammonia toxicity in Litopenaeus vannamei. Totally, 526 significantly differential expressed genes (DEGs) were identified in LAV group compared to LV and LA groups, among which 270 genes were lost expressed and 67 genes uniquely expressed in the LAV group. According to the public functional reports for the annotated DEGs, they potentially involved in the following functions: (1) accelerating pathogen adhesion, invasion and multiplication; (2) reducing the ability for pathogen defense and immune response; (3) inhibiting positive regulation of apoptotic and antioxidant defense for host homeostasis; (4) inhibiting transcription and protein transport; (5) and increasing protein methylation and ubiquitination, etc. A total of 13 pathways were obtained mainly involving in this process, which mainly led to the following changes: (1) increasing the immunosuppression, anemia, endocrine dysfunction, neurotoxic effect and neuroinvasion, atherosclerosis and thrombogenesis, blood-brain barrier penetration, thyroid disorder, necrosis, inflammation, and circadian disturbance; (2) reducing the ability of vascular remodeling, angiogenesis, cell survival, migration, apoptosis, and lymph transferred to blood stream; (3) leading to cell hypertrophy, cellular shape changes, and mesangial matrix expansion. The present results firstly supplied molecular mechanisms for the ammonia toxicity inhibiting the immune system and increasing pathogen infection severity in shrimp, which is a prerequisite for better understanding the pathogenesis caused by ammonia toxicity.

Deformation of cellular components of bone forming cells when exposed to a magnetic field

It has been suggested that alignment control of biological macromolecules and structures is possible when the diamagnetic energy is sufficient to overcome the thermal energy. Strong magnetic fields of several Tesla (T) have previously been shown to enable the observation of the magnetic orientations of protein fibers and suspended or adherent cells. In the present study, the fine structure of a bone-forming osteoblast cell line was observed in real-time under strong static magnetic fields of up to 5 T. The magnetic field was applied normal to the adhering surface, and induced slight deformation of cellular shape under bright field illumination. A newly developed dark field observation method presented more precise analysis of the inner structures of the cells in strong magnetic fields. Specifically, structures with a round appearance were clearly visualized around the cell nucleus using the electromagnetic illumination. In addition to the magnetically induced swelling of the round structures—which showed differences in diameter of several micrometers—color changes for these intracellular components were also detected using this technique. A high-resolution analysis of fine cellular structure based on the magnetic orientation of intracellular components including microtubules is proposed.