Andreea Iordan - Academia.edu (original) (raw)

Papers by Andreea Iordan

The force contraction dipole ellipses of , B, are presented in animated sequences in video files ... more The force contraction dipole ellipses of , B, are presented in animated sequences in video files SA1 and SA4, respectively. For a given time instant the ellipses (red) are plotted over the stress fibers (SFs) distribution (black lines).

B29. THE LUNG ON THE BORDER BETWEEN ORDER AND CHAOS, 2012

Cellular and Molecular Bioengineering, 2010

Uniaxial cyclic substrate stretching results in a concerted change of cytoskeletal organization s... more Uniaxial cyclic substrate stretching results in a concerted change of cytoskeletal organization such that stress fibers (SFs) realign away from the direction of stretching. Recent experiments revealed that brief transient stretch promptly ablates cellular contractile stress by means of cytoskeletal fluidization, followed by a slow stress recovery by means of resolidification. This, in turn, suggests that fluidization, resolidification and SF realignment may be linked together during stretching. We propose a mathematical model that simulates the effects of fluidization and resolidification on cytoskeletal contractile stress in order to investigate how these phenomena affect cytoskeletal realignment in response to pure uniaxial stretching of the substrate. The model comprises of individual elastic SFs anchored at the endpoints to an elastic substrate. Employing the global stability convention, the model predicts that in response to repeated stretch-unstretch cycles, SFs tend to realign in the direction perpendicular to stretching, consistent with data from the literature. The model is used to develop a computational scheme for predicting changes in cell orientation and polarity during stretching and how they relate to the underlying alterations in the cytoskeletal organization. We conclude that depletion of cytoskeletal contractile stress by means of fluidization and subsequent stress recovery by means of resolidification may play a key role in reorganization of cytoskeletal SFs in response to uniaxial stretching of the substrate.

ASME 2012 Summer Bioengineering Conference, Parts A and B, 2012

ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Associat... more ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006

To better understand the role of zinc in bone mineralization we studied the distribution of Ca an... more To better understand the role of zinc in bone mineralization we studied the distribution of Ca and Zn by microbeam particle-induced X-ray emission (l-PIXE) profiling and mapping, and of Zn by histochemical mapping and profiling in cortical bovine bone. For l-PIXE, measurements were carried out at the Rossendorf nuclear microprobe with a 3.1 MeV proton beam focused to a spot of 3 lm, at 4-8 lm effective resolution. Maps, unique scans and side-to-side scan sequences were done for Ca and Zn. The noise in Zn profiles was filtered by Fast Fourier Transform (FFT). For histochemistry, Zn was stained in thick sections by the sulphide-silver reaction. Both l-PIXE and histochemistry showed that Zn was localized mainly at the surfaces of various structures in bone tissue.

The affinity constants, the rate constants and the optimal time to achieve a chemical equilibrium... more The affinity constants, the rate constants and the optimal time to achieve a chemical equilibrium represent the essential immunogenic properties of the antibody-antigen systems required to define optimal conditions for ELISA (Enzyme Linked ImmunoSorbent Assay) analyses. Our paper evaluate the affinity constant of the 8OHdG (8-hydroxy-2-deoxyguanosine) antigen, covalently bounded on the glass tube surface, for alkaline phosphatase labeled anti-8OHdG antibody conjugate in the presence or absence of free 8OHdG antigen.

Analytical and Bioanalytical Chemistry, 2004

The particle-induced X-ray emission (PIXE) of thick biomineral targets provides pertinent surface... more The particle-induced X-ray emission (PIXE) of thick biomineral targets provides pertinent surface analysis, but if good reference materials are missing then complementary approaches are required to handle the matrix effects. This is illustrated by our results from qualitative and semiquantitative analysis of biomaterials and calcified tissues in which PIXE usually detected up to 20 elements with Z > 14 per sample, many at trace levels. Relative concentrations allow the classification of dental composites according to the mean Z and by multivariate statistics. In femur bones from streptozotocin-induced diabetic rats, trace element changes showed high individual variability but correlated to each other, and multivariate statistics improved discrimination of abnormal pathology. Changes on the in vitro demineralization of dental enamel suggested that a dissolution of Ca compounds in the outermost layer results in the uncovering of deeper layers containing higher trace element levels. Thus, in spite of significant limitations, standardless PIXE analysis of thick biomineral samples together with proper additional procedures can provide relevant information in biomedical research.

AJP: Cell Physiology, 2012

stretch plays an important role in regulating shape and orientation of the vascular endothelial c... more stretch plays an important role in regulating shape and orientation of the vascular endothelial cell. This morphological response to stretch is basic to angiogenesis, neovascularization, and vascular homeostasis, but mechanism remains unclear. To elucidate mechanisms, we used cell mapping rheometry to measure traction forces in primary human umbilical vein endothelial cells subjected to periodic uniaxial stretches. Onset of periodic stretch of 10% strain amplitude caused a fluidization response typified by attenuation of traction forces almost to zero. As periodic stretch continued, the prompt fluidization response was followed by a slow resolidification response typified by recovery of the traction forces, but now aligned along the axis perpendicular to the imposed stretch. Reorientation of the cell body lagged reorientation of the traction forces, however. Together, these observations demonstrate that cellular reorientation in response to periodic stretch is preceded by traction attenuation by means of cytoskeletal fluidization and subsequent traction recovery transverse to the stretch direction by means of cytoskeletal resolidification.

Physical Review E, 2008

Results on the rheological behavior of novel CHO cell suspensions in a large range of concentrati... more Results on the rheological behavior of novel CHO cell suspensions in a large range of concentrations are reported. The concentration-dependent yield stress and elastic plateau modulus are formalized in the context of fractal aggregates under shear, and quite different exponents are found as compared to the case of red blood cell suspensions. This is explained in terms of intrinsic microscopic parameters such as the cell-cell adhesion energy and cell elasticity but also the cell's individual dynamic properties, found to correlate well with viscoelastic data at large concentrations (φ ≥ 0.5).

Biorheology, 2010

Collagen model tissues, consisting of cells embedded in a collagen matrix at different concentrat... more Collagen model tissues, consisting of cells embedded in a collagen matrix at different concentrations (of cells and collagen) were analyzed. Rheological properties were measured and complementary confocal microscopy analysis carried out. An important feature, corresponding to the breakdown of the collagen network (i.e., decrease in network elasticity) was observed at high collagen concentrations, due to the presence of cells. Thanks to confocal microscopy, we showed that cells elongated within the gel and could remodel it, this being a concentration-dependent feature. A careful analysis of the remodeling process showed that cells can attract collagen in their close neighborhood, this being an irreversible process and that migrating cells create collagen-depleted regions behind them.

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