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Biological Cells (biological + cell)
Selected AbstractsEvaluation of Process-Induced Dimensional Changes in the Membrane Structure of Biological Cells Using Impedance MeasurementBIOTECHNOLOGY PROGRESS, Issue 3 2002Alexander Angersbach The impact of high intensity electric field pulses, high hydrostatic pressure, and freezing-thawing on local structural changes of the membrane was determined for potato, sugar beet tissue, and yeast suspensions. On the basis of the electrophysical model of cell systems in biological tissues and suspensions, a method was derived for determining the extent of local damage of cell membranes. The method was characterized by an accurate and rapid on-line determination of frequency-dependent electrical conductivity properties from which information on microscopic events on cellular level may be deduced. Evaluation was based on the measurement of the relative change in the sampleapos;s impedance at characteristically low ( fl) and high ( fh) frequencies within the ,-dispersion range. For plant and animal cells the characteristic frequencies were fl , 5 kHz and fh > 5 MHz and for yeast cells in the range fl , 50 kHz and fh > 25 MHz. The observed phenomena were complex. The identification of the underlying mechanisms required consideration of the time-dependent nature of the processing effects and stress reactions of the biological systems, which ranged from seconds to several hours. A very low but significantly detectable membrane damage (0.004% of the total area) was found after high hydrostatic pressure treatment of potato tissue at 200 MPa. The membrane rupture in plant tissue cells was higher after freezing and subsequent thawing (0.9% of total area for potato cells and 0.05,0.07% for sugar beet cells determined immediately after thawing), which increased substantially during the next 2 h. [source] Impedance Spectroscopy: A Powerful Tool for Rapid Biomolecular Screening and Cell Culture MonitoringELECTROANALYSIS, Issue 23 2005Isaac Abstract Dielectric spectroscopy or Electrochemical impedance spectroscopy (EIS) is traditionally used in corrosion monitoring, coatings evaluation, batteries, and electrodeposition and semiconductor characterization. However, in recent years, it is gaining widespread application in biotechnology, tissue engineering, and characterization of biological cells, disease diagnosis and cell culture monitoring. This article discusses the principles and implementation of dielectric spectroscopy in these bioanalytical applications. It provides examples of EIS as label-free, mediator-free strategies for rapid screening of biocompatible surfaces, monitoring pathogenic bacteria, as well as the analysis of heterogeneous systems, especially biological cells and tissues. Descriptions are given of the application of nanoparticles to improve the analytical sensitivities in EIS. Specific examples are given of the detection of base pair mismatches in the DNA sequence of Hepatitis B disease, TaySach's disease and Microcystis spp. Others include the EIS detection of viable pathogenic bacteria and the influence of nanomaterials in enhancing biosensor performance. Expanding applications in tissue engineering such as adsorption of proteins onto thiolated hexa(ethylene glycol)-terminated (EG6) self-assembled monolayer (SAM) are discussed. [source] Development of microdevices for physioelectrical measurement of biological cellsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 1 2008Takanori Akagi Abstract Electrical characteristics of biological cells are important indices for obtaining information about the state and function of a cell. In this paper, we report the development of microdevices for physioelectrical measurement of cells by applying nano/microfabrication technologies. These devices enable the highly precise measurement of cell membrane potential and zeta potential of individual cells in a minimally invasive manner. Such a fusion of the microdevice technologies and biotechnologies is expected to provide power diagnostic tools for future cell study and cell therapy. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(1): 40, 45, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10027 [source] Single cell manipulation, analytics, and label-free protein detection in microfluidic devices for systems nanobiologyELECTROPHORESIS, Issue 19 2005Wibke Hellmich Abstract Single cell analytics for proteomic analysis is considered a key method in the framework of systems nanobiology which allows a novel proteomics without being subjected to ensemble-averaging, cell-cycle, or cell-population effects. We are currently developing a single cell analytical method for protein fingerprinting combining a structured microfluidic device with latest optical laser technology for single cell manipulation (trapping and steering), free-solution electrophoretical protein separation, and (label-free) protein detection. In this paper we report on first results of this novel analytical device focusing on three main issues. First, single biological cells were trapped, injected, steered, and deposited by means of optical tweezers in a poly(dimethylsiloxane) microfluidic device and consecutively lysed with SDS at a predefined position. Second, separation and detection of fluorescent dyes, amino acids, and proteins were achieved with LIF detection in the visible (VIS) (488,nm) as well as in the deep UV (266,nm) spectral range for label-free, native protein detection. Minute concentrations of 100,fM injected fluorescein could be detected in the VIS and a first protein separation and label-free detection could be achieved in the UV spectral range. Third, first analytical experiments with single Sf9 insect cells (Spodoptera frugiperda) in a tailored microfluidic device exhibiting distinct electropherograms of a green fluorescent protein-construct proved the validity of the concept. Thus, the presented microfluidic concept allows novel and fascinating single cell experiments for systems nanobiology in the future. [source] Time-resolved Acoustic MicroscopyIMAGING & MICROSCOPY (ELECTRONIC), Issue 3 2007Dynamical Processes in Cell Biology Recent growth of interest in the mechanical properties of cells demands for the development of new techniques for the assessement of these atributes. Acoustic microscopy equipped with time-resolved signal analysis provides unique possibilities for the determination of dynamical processes in biological cells and allows probing biological specimen with submicrometre resolution. [source] The network behind spatio-temporal patterns: building low-complexity retinal models in CNN based on morphology, pharmacology and physiologyINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 2 2001Csaba Rekeczky Abstract In this paper, a vertebrate retina model is described based on a cellular neural network (CNN) architecture. Though largely built on the experience of previous studies, the CNN computational framework is considerably simplified: first-order RC cells are used with space-invariant nearest-neighbour interactions only. All non-linear synaptic connections are monotonic continuous functions of the pre-synaptic voltage. Time delays in the interactions are continuous represented by additional first-order cells. The modelling approach is neuromorphic in its spirit relying on both morphological and pharmacological information. However, the primary motivation lies in fitting the spatio-temporal output of the model to the data recorded from biological cells (tiger salamander). In order to meet a low-complexity (VLSI) implementation framework some structural simplifications have been made. Large-neighbourhood interaction (neurons with large processes), furthermore inter-layer signal propagation are modelled through diffusion and wave phenomena. This work presents novel CNN models for the outer and some partial models for the inner (light adapted) retina. It describes an approach that focuses on efficient parameter tuning and also makes it possible to discuss adaptation, sensitivity and robustness issues on retinal ,image processing' from an engineering point of view. Copyright © 2001 John Wiley & Sons, Ltd. [source] Flocculation of biological cells: Experiment vs. theoryAICHE JOURNAL, Issue 7 2003Binbing Han Flocculation of biological cells is important in the biotechnology industry, as it could lead to improved efficiencies for bioreactor harvesting operations such as microfiltration. Experimental studies for flocculation of yeast and CHO cells using cationic polyelectrolytes suggest the existence of a steady-state, self-similar floc size distribution. The experimentally determined floc size distributions were modeled using a population balance approach. For flocculated yeast suspensions, the variation of the floc volume fraction with dimensionless particle diameter is predicted by the population balance model assuming a binary breakage distribution function. However, the variation of floc number fraction with dimensionless particle diameter is better predicted assuming a log normal fragment distribution function probably due to the presence of submicron-sized yeast cell debris. For CHO cell flocs, the floc volume and number fractions are predicted using a log normal fragment distribution function. CHO cells are far more fragile than yeast cells. Thus, individual CHO cells in a CHO cell floc can lyse leading to the formation of a number of small particles. [source] Non-homogeneous infinitely many sites discrete-time model with exact coalescentMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2010Adam Bobrowski Abstract Kingman's coalescent is among the most fertile concepts in mathematical population genetics. However, it only approximates the exact coalescent process associated with the Wright,Fisher model, in which the ancestry of a sample does not have to be a binary tree. The distinction between the approximate and exact coalescent becomes important when population size is small and time has to be measured in discrete units (generations). In the present paper, we explore the exact coalescent, with mutations following the infinitely many sites model. The methods used involve random point processes and generating functionals. This allows obtaining joint distributions of segregating sites in arbitrary intervals or collections of intervals, and generally in arbitrary Borel subsets of two or more chromosomes. Using this framework it is possible to find the moments of the numbers of segregating sites on pairs of chromosomes, as well as the moments of the average of the number of pairwise differences, in the form that is more general than usually. In addition, we demonstrate limit properties of the first two moments under a range of demographic scenarios, including different patterns of population growth. This latter part complements results obtained earlier for Kingman's coalescent. Finally, we discuss various applications, including the analysis of fluctuation experiments, from which mutation rates of biological cells can be inferred. Copyright © 2009 John Wiley & Sons, Ltd. [source] Microsystems for Optical Cell Detection: Near versus Far FieldPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 1 2008Stefan Kostner Abstract Optical flow cytometry is a process where physical and (bio-) chemical parameters of single biological cells can be obtained in a flow-through setup by optical measurement techniques. Unlike conventional systems, where measurements are conducted in the optical far field, the proposed system senses the cell's optical projection in the near field by using integrated photodiodes. This allows for the attainment of additional parameters, e.g., size and shape, which are usually hidden in the far field. In addition, parameters such as refractive index and absorption of the cell influence the sensor signal. Additionally, with another setup, a different approach is followed to measure similar parameters with external detection using a DVD laser pickup head and a microchannel equipped with a mirror. This low-cost setup does not measure in the near field, and therefore, is dedicated to different parameters. In this contribution, results from measurements with polystyrene particles and biological cells (yeast and Chinese hamster ovary) are presented and the advantages and limitations of both systems are outlined. [source] High-throughput single molecule screening of DNA and proteinsTHE CHEMICAL RECORD, Issue 2 2001Edward S. Yeung Abstract We report a novel imaging technology for real time comprehensive analysis of molecular alterations in cells and tissues appropriate for automation and adaptation to high-throughput applications. With these techniques it should eventually be possible to perform simultaneous analysis of the entire contents of individual biological cells with a sensitivity and selectivity sufficient to determine the presence or absence of a single copy of a targeted analyte (e.g., DNA region, RNA region, protein), and to do so at a relatively low cost. The technology is suitable for DNA and RNA through sizing or through fluorescent hybridization probes, and for proteins and small molecules through fluorescence immunoassays. This combination of the lowest possible detection limit and the broadest applicability to biomolecules represents the final frontier in bioanalysis. The general scheme is based on novel concepts for single molecule detection (SMD) and characterization recently demonstrated in our laboratory. Since minimal manipulation is involved, it should be possible to screen large numbers of cells in a short time to facilitate practical applications. This opens up the possibility of finding single copies of DNA or proteins within single biological cells for disease markers without performing polymerase chain reaction or other biological amplification. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:123,139, 2001 [source] Building artificial cells and protocell models: Experimental approaches with lipid vesiclesBIOESSAYS, Issue 4 2010Peter Walde Abstract Lipid vesicles are often used as compartment structures for preparing cell-like systems and models of protocells, the hypothetical precursor structures of the first cells at the origin of life. Although the various artificially made vesicle systems are already remarkably complex, they are still very different from and much simpler than any known living cell. Nevertheless, the preparation and study of the structure and the dynamics of functionalized vesicle systems may contribute to a better understanding of biological cells, in particular of the essential features of a living cell that are not found in the non-living form of matter. The study of protocell models may possibly lead to a better understanding of the origin of the first cells. To avoid misunderstanding in this field of research, it would be useful if generally accepted definitions of terms like "artificial cells," "synthetic cells," "minimal cells," "protocells," and "primitive cells" exist. , Editor's suggested further reading in BioEssays Synthetic cells and organelles: compartmentalization strategiesAbstract [source] Giant Vesicles: Preparations and ApplicationsCHEMBIOCHEM, Issue 7 2010Peter Walde Prof. Dr. Abstract There is considerable interest in preparing cell-sized giant unilamellar vesicles from natural or nonnatural amphiphiles because a giant vesicle membrane resembles the self-closed lipid matrix of the plasma membrane of all biological cells. Currently, giant vesicles are applied to investigate certain aspects of biomembranes. Examples include lateral lipid heterogeneities, membrane budding and fission, activities of reconstituted membrane proteins, or membrane permeabilization caused by added chemical compounds. One of the challenging applications of giant vesicles include gene expressions inside the vesicles with the ultimate goal of constructing a dynamic artificial cell-like system that is endowed with all those essential features of living cells that distinguish them from the nonliving form of matter. Although this goal still seems to be far away and currently difficult to reach, it is expected that progress in this and other fields of giant vesicle research strongly depend on whether reliable methods for the reproducible preparation of giant vesicles are available. The key concepts of currently known methods for preparing giant unilamellar vesicles are summarized, and advantages and disadvantages of the main methods are compared and critically discussed. [source] Classification of Fine Particles in High-Speed CentrifugesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2010L. E. Spelter Abstract The classification of dispersed particles below 1,,m is a difficult task due to the high surface area-to-volume ratio. Tubular-bowl centrifuges offer high centrifugal numbers, which enable the separation and classification of fine particles, biological cells and cell debris. This work presents the classification of two fine products with a mean particle size below 1,,m. Polydisperse silica and polystyrene were split successfully into a fine and a coarse fraction by a semi-continuous tubular-bowl centrifuge. The fine fractions exhibited narrow particle size distributions. An optimization of the process could be achieved by a comprehensive understanding of the flow patterns, which are accessible with computational fluid dynamics. The axial and tangential velocity profiles were calculated for rotational speeds up to 40,000 rpm and throughputs ranging from 0.1 to 2,L/min. [source] | ||||||||||||||||