Internal Structure Of Cells Research Articles

Functional optical coherence tomography (fOCT) biospeckle imaging to investigate response of plant leaves to ultra-short term exposure of Ozone

In this study, response of leaves of Chinese chives (Allium tuberosum) to ozone stress was investigated using functional optical coherence tomography (fOCT) based on biospeckle. The biospeckles arising out of dynamic motion of organelles can reflect the biological activities of plant. The fOCT biospeckle image was obtained by calculating the standard deviation (SD) of the fOCT temporal signal (biospeckle signal) at each and every point from the successively acquired OCT images. Plant leaves were subjected to treatment under different concentrations of O3, and imaging data were acquired from back and front surfaces of the leaves. The internal cell structure within the Chinese chives leaves could be clearly visualized in the functional OCT biospeckle image, which was not clearly visible in conventional OCT cross-sectional image. The SDs were found to be increasing significantly, especially in the surface layers of both front and back sides of the leaf with ozone exposure. Thus, the fOCT based on biospeckle is found to be suitable for fast, non-destructive monitoring environmental stresses on plants, which can potentially lead to significant time saving, for which conventional techniques require a few days to a few weeks time.

Sealable Femtoliter Chamber Arrays for Cell-free Biology

Cell-free systems provide a flexible platform for probing specific networks of biological reactions isolated from the complex resource sharing (e.g., global gene expression, cell division) encountered within living cells. However, such systems, used in conventional macro-scale bulk reactors, often fail to exhibit the dynamic behaviors and efficiencies characteristic of their living micro-scale counterparts. Understanding the impact of internal cell structure and scale on reaction dynamics is crucial to understanding complex gene networks. Here we report a microfabricated device that confines cell-free reactions in cellular scale volumes while allowing flexible characterization of the enclosed molecular system. This multilayered poly(dimethylsiloxane) (PDMS) device contains femtoliter-scale reaction chambers on an elastomeric membrane which can be actuated (open and closed). When actuated, the chambers confine Cell-Free Protein Synthesis (CFPS) reactions expressing a fluorescent protein, allowing for the visualization of the reaction kinetics over time using time-lapse fluorescent microscopy. Here we demonstrate how this device may be used to measure the noise structure of CFPS reactions in a manner that is directly analogous to those used to characterize cellular systems, thereby enabling the use of noise biology techniques used in cellular systems to characterize CFPS gene circuits and their interactions with the cell-free environment.

Sealable femtoliter chamber arrays for cell-free biology.

Cell-free systems provide a flexible platform for probing specific networks of biological reactions isolated from the complex resource sharing (e.g., global gene expression, cell division) encountered within living cells. However, such systems, used in conventional macro-scale bulk reactors, often fail to exhibit the dynamic behaviors and efficiencies characteristic of their living micro-scale counterparts. Understanding the impact of internal cell structure and scale on reaction dynamics is crucial to understanding complex gene networks. Here we report a microfabricated device that confines cell-free reactions in cellular scale volumes while allowing flexible characterization of the enclosed molecular system. This multilayered poly(dimethylsiloxane) (PDMS) device contains femtoliter-scale reaction chambers on an elastomeric membrane which can be actuated (open and closed). When actuated, the chambers confine Cell-Free Protein Synthesis (CFPS) reactions expressing a fluorescent protein, allowing for the visualization of the reaction kinetics over time using time-lapse fluorescent microscopy. Here we demonstrate how this device may be used to measure the noise structure of CFPS reactions in a manner that is directly analogous to those used to characterize cellular systems, thereby enabling the use of noise biology techniques used in cellular systems to characterize CFPS gene circuits and their interactions with the cell-free environment.

Achievement of Superresolution in Optical-Thickness Measurement and Statistical Localization of Fluorophores in Holographic and Fluorescent Microscopy

We present the concept of combining the holographic and localization fluorescent microscopy. The ways to optimize the optical schemes and image recording regimes in the process of combining such interferometric and statistical methods are developed, which makes it possible to study the dynamics of the internal cell structure with transverse and longitudinal superresolution.

Study on Maximum Power Point Tracking for Photovoltaic Arrays Based on Fuzzy-Control Strategy

The equivalent circuit diagram was established based on the internal structure of the photovoltaic cells, and a simulation model of the photovoltaic cells was built in Matlab/Simulink, which could simulate the output characteristics of the cells under different temperatures and light conditions. According to the separate simulation of the perturbation & observation and fuzzy-control algorithms, the results show that fuzzy control has better performance when dealing with this non-line system.

Biological applications of cryo-soft X-ray tomography.

X-rays are used for imaging many different types of biological specimen, ranging from live organisms to the individual cells and proteins from which they are made. The level of detail achieved as a result of the imaging varies depending on both the sample and the technique used. One of the most recent technical developments in X-ray imaging is that of the soft X-ray microscope, designed to allow the internal structure of individual biological cells to be explored. With a field of view of ∼10-20 × ∼10-20 μm, a penetration depth of ∼10 μm and a resolution of ∼40 nm(3), the soft X-ray microscope neatly fits between the imaging capabilities of light and electron microscopes.

Antifungal activity of oligochitosans (short chain chitosans) against some Candida species and clinical isolates of Candida albicans: Molecular weight–activity relationship

A series of oligochitosans (short chain chitosans) prepared by acidic hydrolysis of chitosan and characterized by their molecular weight, polydispersity and degree of deacetylation were used to determine their anticandidal activities. This study has demonstrated that oligochitosans show a high fungistatic activity (MIC 8–512 μg/ml) against Candida species and clinical isolates of Candida albicans, which are resistant to a series of classic antibiotics. Flow cytometry analysis showed that oligochitosan possessed a high fungicidal activity as well. For the first time it was shown that even sub-MIC oligochitosan concentration suppressed the formation of C. albicans hyphal structures, cause severe cell wall alterations, and altered internal cell structure. These results indicate that oligochitosan should be considered as a possible alternative/additive to known anti-yeast agents in pharmaceutical compositions.

Jet Noise Reduction via Fluidic Injection

In this study, a method for reducing the jet noise of a high-speed jet is presented. An array of microjets was immersed within the centerline of an underexpanded Mach 1.6 jet in an effort to reduce the overall sound pressure level and alter its spectral composition. Based on the mass flux through the microjets and the location of the microjets along the centerline of the jet, reductions of up to 5.81 dB with respect to the downstream direction and 7.99 dB with respect to the perpendicular direction can be achieved. An interesting phenomenon is discovered whereby the maximum noise reduction in the downstream direction is found with injection activated, whereas the maximum noise reduction in the perpendicular direction is found with injection deactivated. Placement of the injection tube within the flow is shown to eradicate distinct tones while flow visualizations depicted a strong augmentation in the jet plume via a modification of the shear layer and the internal shock cell structure.

Imaging and elemental mapping of biological specimens with a dual-EDS dedicated scanning transmission electron microscope

A dedicated analytical scanning transmission electron microscope (STEM) with dual energy dispersive spectroscopy (EDS) detectors has been designed for complementary high performance imaging as well as high sensitivity elemental analysis and mapping of biological structures. The performance of this new design, based on a Hitachi HD-2300A model, was evaluated using a variety of biological specimens. With three imaging detectors, both the surface and internal structure of cells can be examined simultaneously. The whole-cell elemental mapping, especially of heavier metal species that have low cross-section for electron energy loss spectroscopy (EELS), can be faithfully obtained. Optimization of STEM imaging conditions is applied to thick sections as well as thin sections of biological cells under low-dose conditions at room and cryogenic temperatures. Such multimodal capabilities applied to soft/biological structures usher a new era for analytical studies in biological systems.

Preparation and Adsorption Performance of GF/EPDM/LLDPE Foaming Composite for Petrol

In our study, a new kind of material for petrol adsorption was prepared by melt blending and molding foaming with EPDM and LLDPE as the matrix and modified glass fiber (GF) as the filler. LLDPE as the second matrix can improve the matrix reinforcement, the composite cross-linked network density was reduced, but the oil absorption rate was increasing. After recycling three times, the oil absorption rate GF/EPDM foaming composite and GF / LLDPE / EPDM foam composite were changed little, the internal cell structure can exist for a long time and showed good recycling performance.

Texture of Bread Crust: Puncturing Settings Effect and Its Relationship to Microstructure

AbstractThe effect of the puncturing settings (crosshead speed and punch cross‐section) on the crust mechanical parameters was investigated using breads with two different crust thickness. Results showed that, greater punch cross‐section was associated to compression behavior, which reduced the sensibility to detect changes in the crust structure. Moreover, low crosshead speed (0.5 mm/s) puncture test provided information about the cellular structure of the crust. The relationship between the puncturing parameters and the water activity and moisture content together with the crust microstructure analysis revealed that for obtaining reliable information about the structural ruptures related to crispiness texture, it is necessary to use low crosshead speeds (0.5 mm/s) and low punch cross‐section (3 mm2). Crust microstructure observations indicate that the crust layers and the size and shape of the air cells are responsible of the puncturing behavior.Practical ApplicationsTexture of the bread crust is an important parameter used to define the quality of crispy breads and their freshness. Consequently, the extension of crust crispiness is still a priority for the baking industry. Different methods have been proposed for assessing the mechanical properties of the bread crust, although punching is a common feature in all of them. However, there is no information about the incidence of punching settings on the bread crust mechanical parameters. Water activity and moisture content of the crust, besides scanning electron microscopy of the crust section, were used to confirm the reliability of the mechanical parameters. The study allows defining the best conditions to study the crust's mechanical properties providing information about the internal cell structure. Results could be very useful at research level and also for the baking industry when investigating crust freshness.

Imaging cells and sub-cellular structures with ultrahigh resolution full-field X-ray microscopy

Our experimental results demonstrate that full-field hard-X-ray microscopy is finally able to investigate the internal structure of cells in tissues. This result was made possible by three main factors: the use of a coherent (synchrotron) source of X-rays, the exploitation of contrast mechanisms based on the real part of the refractive index and the magnification provided by high-resolution Fresnel zone-plate objectives. We specifically obtained high-quality microradiographs of human and mouse cells with 29nm Rayleigh spatial resolution and verified that tomographic reconstruction could be implemented with a final resolution level suitable for subcellular features. We also demonstrated that a phase retrieval method based on a wave propagation algorithm could yield good subcellular images starting from a series of defocused microradiographs. The concluding discussion compares cellular and subcellular hard-X-ray microradiology with other techniques and evaluates its potential impact on biomedical research.

Patterned Monolayer Self-Assembly Programmed by Side Chain Shape: Four-Component Gratings

A molecular recognition strategy based on alkadiyne side chain shape is used to self-assemble a four-component, 1D-patterned monolayer at the solution-HOPG interface. The designed monolayer unit cell contains six molecules and spans 23 nm × 1 nm. The unit cell's internal structure and packing are driven by complementary shapes and lengths of six different alkadiyne side chains. A solution of the four compounds on HOPG self-assembles monolayers (i) comprised, almost entirely, of the intended unit cell, (ii) exhibiting patterned domains spanning 10(4) nm(2), and (iii) which are sufficiently robust that patterned domains survive solvent rinsing and drying. The patterned monolayer affords 1D-feature spacings ranging from 3.3 to 23 nm. The results demonstrate the remarkable selectivity afforded by molecular recognition based on alkadiyne side chain shape and the ability to program highly complex 1D-patterns in self-assembled monolayers.

Flow distortion in an S-duct inlet with simulated icing effect and heat transfer

AbstractA diffusing S-duct aircraft intake system is computationally studied for the effects of inlet icing and wall heat transfer on engine face distortion. A Reynolds-Averaged Navier-Stokes (RANS) code with k -ω SST turbulence model is used to simulate the compressible viscous flow in the duct. The glaze ice accretion on the inlet lip is simulated as a fixed protrusion from NASA LEWICE3D code. The shape and size of the ice on the inlet lip are assumed to remain constant even in the case of the heated wall. The case of zero external heat transfer is modeled by the adiabatic wall boundary condition, and constant-wall temperature is used to simulate the heated wall effect. The freestream Mach number of 0·85 and glaze ice condition on the inlet lip produce massive flow separation at the lip and internal shock cell structure in the S-duct. The heated wall creates additional vorticity and thus increases the engine face distortion level. The area-averaged total pressure distortion at the engine face in a freestream Mach number of 0·85 is increased by ~7% in the heated wall case as compared to the adiabatic flow.

Rapid imaging of mycoplasma in solution using Atmospheric Scanning Electron Microscopy (ASEM)

Mycoplasma is a genus of bacterial pathogen that causes disease in vertebrates. In humans, the species Mycoplasma pneumoniae causes 15% or more of community-acquired pneumonia. Because this bacterium is tiny, corresponding in size to a large virus, diagnosis using optical microscopy is not easy. In current methods, chest X-rays are usually the first action, followed by serology, PCR amplification, and/or culture, but all of these are particularly difficult at an early stage of the disease. Using Mycoplasma mobile as a model species, we directly observed mycoplasma in buffer with the newly developed Atmospheric Scanning Electron Microscope (ASEM). This microscope features an open sample dish with a pressure-resistant thin film window in its base, through which the SEM beam scans samples in solution, from below. Because of its 2–3μm-deep scanning capability, it can observe the whole internal structure of mycoplasma cells stained with metal solutions. Characteristic protein localizations were visualized using immuno-labeling. Cells were observed at low concentrations, because suspended cells concentrate in the observable zone by attaching to sialic acid on the silicon nitride (SiN) film surface within minutes. These results suggest the applicability of the ASEM for the study of mycoplasmas as well as for early-stage mycoplasma infection diagnosis.

Downregulation of keratins 8, 18 and 19 influences invasiveness of human cultured squamous cell carcinoma and adenocarcinoma cells

Keratin (K) expression index has been reported to be related to cell invasion activity in adenocarcinoma. In a previous study, we observed a negative correlation between K expression and cell invasion activity; i.e., when many Ks are expressed in the cells, the cell activity is low. To further elucidate the correlation between Ks and invasion activity, RNA interference experiments of K8, K18 and K19 were carried out to clarify the essential role of Ks using T24 and HEC-1 as typical squamous cell carcinoma and adenocarcinoma cells, respectively. K8 small interfering RNA (siRNA) was most effective against K18 and K19 expression and demonstrated the strongest effect on relative invasion activity among the siRNAs used. These results suggest that K8/K18 or K8/K19 filaments may play roles in internal cell structure and invasion activity. Moreover, K18 and K19 were capable of substituting for each other, and K18 or K19 formed filaments with K8. In addition, cells treated with K8 siRNA demonstrated high invasion activity, which was approximately double that observed with control siRNA in HEC-1 cells. The order of effects was K8>K19>K18 in the two cell lines. The above results suggest that K8 may play a signifiant role in invasive functions in epithelial and metastatic cells.

Determining the infection process of Phoma macrostoma that leads to bioherbicidal activity on broadleaved weeds

Isolates of the fungus Phoma macrostoma cause intense photobleaching and mortality of Canada thistle (Cirsium arvense), dandelion (Taraxacum officinale) and other broadleaved weeds when applied to the soil. The symptoms are caused by the production of macrocidins which have been extracted from cultured mycelium and the growth medium broth. The objective of this study was to determine the pathway of infection that leads to plant damage resulting in bioherbicidal activity. This was accomplished by first determining which infective unit (i.e., conidia and/or mycelium) resulted in plant damage when applied to a host. Then the infection process was microscopically observed from infested granules placed in the soil through the various stages of colonization and penetration in a resistant and a susceptible host. Conidia were ineffective as infective units because there was no plant damage when target weeds were inoculated using either a foliar spray of a conidial suspension or granules containing conidia placed in the soil. Only mycelium of the fungus applied either pre-emergently to soil ahead of weed seed emergence or post-emergently to soil containing established weeds resulted in significant plant damage. Microscopic observations showed that P. macrostoma 94-44B mycelium germinated from formulated granules in soil, colonizing roots of dandelion (susceptible) and barley (resistant) within 7days of application. The fungus entered the hosts at sites proximal to root hairs where wounding of the cells was most likely, and growing intercellularly towards the root core. In dandelion, the mycelium proliferated around the vascular trachea disrupting the competence of neighboring cells. In barley, proliferation was less obvious being restricted to the outer layers and there was no disruption of the internal cell structure. P. macrostoma boasts potential as a bioherbicide to control susceptible broadleaved weeds but not harm resistant nontarget hosts.

Crystalline ice as a cryoprotectant: theoretical calculation of cooling speed in capillary tubes

It is generally assumed that vitrification of both cells and the surrounding medium provides the best preservation of ultrastructure of biological material for study by electron microscopy. At the same time it is known that the cell cytoplasm may provide substantial cryoprotection for internal cell structure even when the medium crystallizes. Thus, vitrification of the medium is not essential for good structural preservation. By contrast, a high cooling rate is an essential factor for good cryopreservation because it limits phase separation and movement of cellular components during freezing, thus preserving the native-like state. Here we present calculations of freezing rates that incorporate the effect of medium crystallization, using finite difference methods. We demonstrate that crystallization of the medium in capillary tubes may increase the cooling rate of suspended cells by a factor of 25-300 depending on the distance from the centre. We conclude that crystallization of the medium, for example due to low cryoprotectant content, may actually improve cryopreservation of some samples in a near native state.

Effect of uniaxial stretch on morphology and cytoskeleton of human mesenchymal stem cells: static vs. dynamic loading

Abstract Human mesenchymal stem cells (hMSCs) are capable of self-renewal and differentiation into various cell lineages. Mechanical stimuli have been shown to regulate function of stem cells through alteration in morphology and structure. The aim of this study was to evaluate and compare effects of uniaxial static stretch and combined static-dynamic stretch on the orientation, regulation and cytoskeletal structure of hMSCs. Mean values of topological were calculated before and after loadings. Moreover, fractal dimension (FD) was employed to quantify alterations in shape complexity of the cells. Internal cytoskeletal structure of cells was observed by actin filament staining. Results demonstrated a statistically significant change in cell topology and FD due to 10% static-dynamic stretch after 24 h. Static stretch was not as influential as dynamic loading. Whereas for combined static-dynamic stretch systemic alignment of cells was detected, in the static test group local alignment of actin fibers was observed, although the entire cell network was not totally aligned in a specific direction. It was concluded that dynamic stretch leads to cytoskeletal alignment and repolarization of hMSCs, whereas static stretch does not. Under static stretch hMSCs proliferated more than under dynamic stretch. Results can be applied in tissue engineering when functionalization of stem cells is required.

Baker's Yeast Transformation Studies by Atomic Force Microscopy

The baker’s yeast cells (Saccharomyces cerevisiae) are widely used in industry for fermentation control of food and drinks, and as a leavening agent in baking. They are widely available and rapidly reproducible. As an object for investigation the yeast cells distinguish ease of handling and manipulation. The baker’s yeast cells have complex internal cell structure and are well suited as a model organism for scientific studies. Most recent topics of yeast application in industry is related to generation of green-electricity1–3 by microbial fuel cells,4 5 and ethanol production in biofuel technology.6 For this reason baker’s yeasts are very popular among the scientific community for versatile applications. To improve the characteristics of living cells foreign components are introduced into the cell through membrane/wall holes opened by transformations, which are induced by: (i) chemical compounds, (ii) strong magnetic field7 or (iii) electrical discharge. Electrical discharge based method is known as electroporation. The electroporation is usually applied for modification of living cells by introducing into the cell foreign components such as genes, proteins, and other macromolecules8 9 or even specialized nanoparticles,10 which are used for modification of natural chemical processes inside the living cell. Nowadays various nanoparticles offers number of interesting options including fluorescence (e.g., Q-dots)11–14 catalytic ability15–18 and magnetic properties19–23 which could have been artificially added to the cells. Due to mentioned properties very interesting topic is how to introduce them into the cell and one of possible way to solve this problem is application of electroporation. The success of the electroporation usually is controlled by observation