Dielectrophoresis based discrimination of human embryonic stem cells from differentiating derivatives

Assessment of the dielectrophoresis(DEP) cross-over frequency (f xo), cell diameter, and derivative membranecapacitance (C m) values for a group of undifferentiated human embryonic stem cell (hESC) lines (H1, H9, RCM1, RH1), and for a transgenic subclone of H1 (T8) revealed that hESC lines could not be discriminated on their mean f xo and C m values, the latter of which ranged from 14 to 20 mF/m2. Differentiation of H1 and H9 to a mesenchymal stem cell-like phenotype resulted in similar significant increases in mean C m values to 41–49 mF/m2 in both lines (p < 0.0001). BMP4-induced differentiation of RCM1 to a trophoblast cell-like phenotype also resulted in a distinct and significant increase in mean C m value to 28 mF/m2 (p < 0.0001). The progressive transition to a higher membranecapacitance was also evident after each passage of cell culture as H9 cells transitioned to a mesenchymal stem cell-like state induced by growth on a substrate of hyaluronan. These findings confirm the existence of distinctive parameters between undifferentiated and differentiating cells on which future application of dielectrophoresis in the context of hESC manufacturing can be based

Microfluidic Impedance Spectroscopy as a Tool for Quantitative Biology and Biotechnology

A microfluidic device that is able to perform dielectric spectroscopy is developed. The device consists of a measurement chamber that is 250 μm thick and 750 μm radius. Around 1000 cells fit inside the chamber assuming average quantities for cell radius and volume fraction. This number is about 1000 folds lower than the capacity of conventional fixtures. A T-cell leukemia cell line Jurkat is tested using the microfluidic device. Measurements of deionized water and salt solutions are utilized to determine parasitic effects and geometric capacitance of the device. Physical models, including Maxwell-Wagner mixture and double shell models, are used to derive quantities for sub-cellular units. Clausius-Mossotti factor of Jurkat cells is extracted from the impedance spectrum. Effects of cellular heterogeneity are discussed and parameterized. Jurkat cells are also tested with a time domain reflectometry system for verification of the microfluidic device. Results indicate good agreement of values obtained with both techniques. The device can be used as a unique cell diagnostic tool to yield information on sub-cellular units. (C) 2012 American Institute of Physics

Dielectric relaxation of DNA aqueous solutions

We report on a detailed characterization of complex dielectric response of Na-DNA aqueous solutions by means of low-frequency dielectric spectroscopy (40 Hz - 110 MHz). Results reveal two broad relaxation modes of strength 20<\Delta\epsilon_LF<100 and 5<\Delta\epsilon_HF<20, centered at 0.5 kHz<\nu_LF<70 kHz and 0.1 MHz<\nu_HF<15 MHz. The characteristic length scale of the LF process, 50<L_LF<750nm, scales with DNA concentration as c_DNA^{-0.29\pm0.04} and is independent of the ionic strength in the low added salt regime. Conversely, the measured length scale of the LF process does not vary with DNA concentration but depends on the ionic strength of the added salt as I_s^{-1} in the high added salt regime. On the other hand, the characteristic length scale of the HF process, 3<L_HF<50 nm, varyes with DNA concentration as c_DNA^{-0.5} for intermediate and large DNA concentrations. At low DNA concentrations and in the low added salt limit the characteristic length scale of the HF process scales as c_DNA^{-0.33}. We put these results in perspective regarding the integrity of the double stranded form of DNA at low salt conditions as well as regarding the role of different types of counterions in different regimes of dielectric dispersion. We argue that the free DNA counterions are primarily active in the HF relaxation, while the condensed counterions play a role only in the LF relaxation. We also suggest theoretical interpretations for all these length scales in the whole regime of DNA and salt concentrations and discuss their ramifications and limitations.Comment: 15 pages, 9 figure

Single stage repair of a complex pathology: end stage ischaemic cardiomyopathy, ascending aortic aneurysm and thoracic coarctation

The not uncommon combination of ascending aortic pathology with late presenting coarctation is a difficult surgical challenge. The two stage approach is usually adopted. The necessity for cardiac transplantation adds to the complexity: a trans-sternal approach and single stage repair become mandatory

Single-stage repair of adult aortic coarctation and concomitant cardiovascular pathologies: a new alternative surgical approach

BACKGROUND: Coarctation of the aorta in the adulthood is sometimes associated with additional cardiovascular pathologies that require intervention. Ideal approach in such patients is uncertain. Anatomic left-sided short aortic bypass from the arcus aorta to descending aorta via median sternotomy allows simultaneuos repair of both complex aortic coarctation and concomitant cardiac operation. MATERIALS: Four adult patients were underwent Anatomic left-sided short aortic bypass operation for complex aortic coarctation through median sternotomy using deep hypothermic circulatory arrest. Concomitant cardiac operations were Bentall procedure for annuloaortic ectasia in one patient, coronary artery bypass grafting for three vessel disease in two patient, and patch closure of ventricular septal defect in one patient. RESULTS: All patients survived the operation and were alive with patent bypass at a mean follow-up of 36 months. No graft-related complications occurred, and there were no instances of stroke or paraplegia. CONCLUSION: We conclude that single-stage repair of adult aortic coarctation with concomitant cardiovascular lesions can be performed safely using this newest technique

Two stage hybrid approach for complex aortic coarctation repair

<p>Abstract</p> <p>Background</p> <p>Management of an adult patient with aortic coarctation and an associated cardiac pathology poses a great surgical challenge since there are no standard guidelines for the therapy of such complex pathology. Debate exists not only on which lesion should be corrected first, but also upon the type and timing of the procedure. Surgery can be one- or two-staged. Both of these strategies are accomplice with elevate morbidity and mortality.</p> <p>Case report</p> <p>In the face of such an extended surgical approach, balloon dilatation seems preferable for treatment of severe aortic coarctation.</p> <p>We present an adult male patient with aortic coarctation combined with ascending aorta aneurysm and concomitant aortic valve regurgitation. The aortic coarctation was corrected first, using percutaneous balloon dilatation; and in a second stage the aortic regurgitation and ascending aorta aneurysm was treated by Bentall procedure. The patients' postoperative period was uneventful. Three years after the operation he continues to do well.</p

Altered Chromosomal Positioning, Compaction, and Gene Expression with a Lamin A/C Gene Mutation

Lamins A and C, encoded by the LMNA gene, are filamentous proteins that form the core scaffold of the nuclear lamina. Dominant LMNA gene mutations cause multiple human diseases including cardiac and skeletal myopathies. The nuclear lamina is thought to regulate gene expression by its direct interaction with chromatin. LMNA gene mutations may mediate disease by disrupting normal gene expression.To investigate the hypothesis that mutant lamin A/C changes the lamina's ability to interact with chromatin, we studied gene misexpression resulting from the cardiomyopathic LMNA E161K mutation and correlated this with changes in chromosome positioning. We identified clusters of misexpressed genes and examined the nuclear positioning of two such genomic clusters, each harboring genes relevant to striated muscle disease including LMO7 and MBNL2. Both gene clusters were found to be more centrally positioned in LMNA-mutant nuclei. Additionally, these loci were less compacted. In LMNA mutant heart and fibroblasts, we found that chromosome 13 had a disproportionately high fraction of misexpressed genes. Using three-dimensional fluorescence in situ hybridization we found that the entire territory of chromosome 13 was displaced towards the center of the nucleus in LMNA mutant fibroblasts. Additional cardiomyopathic LMNA gene mutations were also shown to have abnormal positioning of chromosome 13, although in the opposite direction.These data support a model in which LMNA mutations perturb the intranuclear positioning and compaction of chromosomal domains and provide a mechanism by which gene expression may be altered

Eco-efficiency measurement and material balance principle:an application in power plants Malmquist Luenberger Index

Incorporating Material Balance Principle (MBP) in industrial and agricultural performance measurement systems with pollutant factors has been on the rise in recent years. Many conventional methods of performance measurement have proven incompatible with the material flow conditions. This study will address the issue of eco-efficiency measurement adjusted for pollution, taking into account materials flow conditions and the MBP requirements, in order to provide ‘real’ measures of performance that can serve as guides when making policies. We develop a new approach by integrating slacks-based measure to enhance the Malmquist Luenberger Index by a material balance condition that reflects the conservation of matter. This model is compared with a similar model, which incorporates MBP using the trade-off approach to measure productivity and eco-efficiency trends of power plants. Results reveal similar findings for both models substantiating robustness and applicability of the proposed model in this paper