Plasma Membrane Integrity and Survival of Melanoma Cells After Nanosecond Laser Pulses

Circulating tumor cells (CTCs) photoacoustic detection systems can aid clinical decision-making in the treatment of cancer. Interaction of melanin within melanoma cells with nanosecond laser pulses generates photoacoustic waves that make its detection possible. This study aims at: (1) determining melanoma cell survival after laser pulses of 6 ns at λ = 355 and 532 nm; (2) comparing the potential enhancement in the photoacoustic signal using λ = 355 nm in contrast with λ = 532 nm; (3) determining the critical laser fluence at which melanin begins to leak out from melanoma cells; and (4) developing a time-resolved imaging (TRI) system to study the intracellular interactions and their effect on the plasma membrane integrity. Monolayers of melanoma cells were grown on tissue culture-treated clusters and irradiated with up to 1.0 J/cm2. Surviving cells were stained with trypan blue and counted using a hemacytometer. The phosphate buffered saline absorbance was measured with a nanodrop spectrophotometer to detect melanin leakage from the melanoma cells post-laser irradiation. Photoacoustic signal magnitude was studied at both wavelengths using piezoelectric sensors. TRI with 6 ns resolution was used to image plasma membrane damage. Cell survival decreased proportionally with increasing laser fluence for both wavelengths, although the decrease is more pronounced for 355 nm radiation than for 532 nm. It was found that melanin leaks from cells equally for both wavelengths. No significant difference in photoacoustic signal was found between wavelengths. TRI showed clear damage to plasma membrane due to laser-induced bubble formation

Colorization and Automated Segmentation of Human T2 MR Brain Images for Characterization of Soft Tissues

Characterization of tissues like brain by using magnetic resonance (MR) images and colorization of the gray scale image has been reported in the literature, along with the advantages and drawbacks. Here, we present two independent methods; (i) a novel colorization method to underscore the variability in brain MR images, indicative of the underlying physical density of bio tissue, (ii) a segmentation method (both hard and soft segmentation) to characterize gray brain MR images. The segmented images are then transformed into color using the above-mentioned colorization method, yielding promising results for manual tracing. Our color transformation incorporates the voxel classification by matching the luminance of voxels of the source MR image and provided color image by measuring the distance between them. The segmentation method is based on single-phase clustering for 2D and 3D image segmentation with a new auto centroid selection method, which divides the image into three distinct regions (gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) using prior anatomical knowledge). Results have been successfully validated on human T2-weighted (T2) brain MR images. The proposed method can be potentially applied to gray-scale images from other imaging modalities, in bringing out additional diagnostic tissue information contained in the colorized image processing approach as described

Meneco, a Topology-Based Gap-Filling Tool Applicable to Degraded Genome-Wide Metabolic Networks

International audienceIncreasing amounts of sequence data are becoming available for a wide range of non-model organisms. Investigating and modelling the metabolic behaviour of those organisms is highly relevant to understand their biology and ecology. As sequences are often incomplete and poorly annotated, draft networks of their metabolism largely suffer from incompleteness. Appropriate gap-filling methods to identify and add missing reactions are therefore required to address this issue. However, current tools rely on phenotypic or taxonomic information, or are very sensitive to the stoichiometric balance of metabolic reactions, especially concerning the co-factors. This type of information is often not available or at least prone to errors for newly-explored organisms. Here we introduce Meneco, a tool dedicated to the topological gap-filling of genome-scale draft metabolic networks. Meneco reformulates gap-filling as a qualitative combinatorial optimization problem, omitting constraints raised by the stoichiometry of a metabolic network considered in other methods, and solves this problem using Answer Set Programming. Run on several artificial test sets gathering 10,800 degraded Escherichia coli networks Meneco was able to efficiently identify essential reactions missing in networks at high degradation rates, outperforming the stoichiometry-based tools in scalability. To demonstrate the utility of Meneco we applied it to two case studies. Its application to recent metabolic networks reconstructed for the brown algal model Ectocarpus siliculosus and an associated bacterium Candidatus Phaeomarinobacter ectocarpi revealed several candidate metabolic pathways for algal-bacterial interactions. Then Meneco was used to reconstruct, from transcriptomic and metabolomic data, the first metabolic network for the microalga Euglena mutabilis. These two case studies show that Meneco is a versatile tool to complete draft genome-scale metabolic networks produced from heterogeneous data, and to suggest relevant reactions that explain the metabolic capacity of a biological system

Effects of Experience on Relational Inferences in Children: The Case of Folk Biology

Recent research suggests that adults utilize thematic relations as well as taxonomic relations for guiding inductive inferences, and that thematic relations grow in salience with experience in a given domain. The present study examines the impact of experience on the salience of thematic versus taxonomic inferences. 151 kindergarten through sixth-grade children from urban, suburban, and rural communities in New England were given a forced choice triad induction task requiring them to project a novel internal substance or disease from a base species to a taxonomically or ecologically related target. Results indicate clear evidence of inductive selectivity; children projected insides taxonomically and disease ecologically, both at above-chance levels. Moreover, ecological projections of disease were more likely for older children and for children from more rural communities. Overall, results suggest that for children, like adults, experience renders non-taxonomic relations salient for selectively guiding inductive inferences

Journal of Biomedical Optics 12 6 064027 064027 SPIE-SOC PHOTOPTICAL INSTRUMENTATION ENGINEERS BELLINGHAM; 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225 USA

Interstitial quantification of the optical properties of tissue is important in biomedicine for both treatment planning of minimally invasive laser therapies and optical spectroscopic characterization of tissues, for example, prostate cancer. In a previous study, we analyzed a method first demonstrated by Dickey et al., [Phys. Med. Biol. 46, 2359 (2001)] to utilize relative interstitial steady-state radiance measurements for recovering the optical properties of turbid media. The uniqueness of point radiance measurements were demonstrated in a forward sense, and strategies were suggested for improving performance under noisy experimental conditions. In this work, we test our previous conclusions by fitting the P3 approximation for radiance to Monte Carlo predictions and experimental data in tissue-simulating phantoms. Fits are performed at: 1. a single sensor position (0.5 or 1 cm), 2. two sensor positions (0.5 and 1 cm), and 3. a single sensor position (0.5 or 1 cm) with input knowledge of the sample's effective attenuation coefficient. The results demonstrate that single sensor radiance measurements can be used to retrieve optical properties to within similar to 20%, provided the transport albedo is greater than similar to 0.9. Furthermore, compared to the single sensor fits, employing radiance data at two sensor positions did not significantly improve the accuracy of recovered optical properties. However, with knowledge of the effective attenuation coefficient of the medium, optical properties can be retrieved experimentally to within similar to 10% for an albedo greater or equal to 0.5. (C) 2007 Society of Photo-Optical Instrumentation Engineers.CR: ALTSCHULER MD, 2005, MED PHYS, V32, P3524, DOI 10.1118/1.2107047 BAJARAS O, 1997, PHYS MED BIOL, V42, P1675 CHANDRASEKHAR S, 1950, RADIATIVE TRANSFER CHIN LC, 2006, APPL OPTICS, V45, P101 CHIN LCL, 2004, OPT LETT, V29, P959 DICKEY DJ, 2001, PHYS MED BIOL, V46, P2359 DIMOFTE A, 2005, PHYS MED BIOL, V50, P2291, DOI 10.1088/0031-9155/50/10/008 FARIS GW, 2005, APPL OPTICS, V44, P2058 FARRELL TJ, 1992, MED PHYS, V19, P879 HAYAKAWA CK, 2004, APPL OPTICS, V43, P4677 HENYEY LG, 1941, ASTROPHYS J, V93, P70 HOLMER C, 2006, COLORECTAL TUMORS HE HULL EL, 1998, PHYS MED BIOL, V43, P3381 HULL EL, 2001, J OPT SOC AM A, V18, P584 IIZUKA MN, 1999, LASER SURG MED, V25, P159 JACQUES SL, 1996, OSA TOPS ADV OPTICAL, V2, P364 LIEBERT A, 2003, APPL OPTICS, V42, P5795 LILGE L, 2004, PHYS MED BIOL, V49, P3209, DOI 10.1088/0031-9155/49/14/014 MARIJNISSEN JPA, 1996, PHYS MED BIOL, V41, P1191 MARIJNISSEN JPA, 2002, PHYS MED BIOL, V47, P2049 MARTELLI F, 2000, PHYS MED BIOL, V45, P1359 MENON S, 2005, PHYS REV LETT, V94, ARTN 153904 PUCCINI S, 2003, MAGNET RESON MED, V49, P351, DOI 10.1002/mrm.10357 RINZEMA K, 1998, J OPT SOC AM A, V15, P2078 VANSTAVEREN HJ, 1991, APPL OPTICS, V30, P4507 VENUGOPALAN V, 1998, PHYS REV E B, V58, P2395 WEERSINK RA, 2005, J PHOTOCH PHOTOBIO B, V79, P211, DOI 10.1016/j.jphotobiol.2005.01.008 WYMAN DR, 1989, APPL OPTICS, V28, P5243 XU HP, 2006, OPT EXPRESS, V14, P6485 YOU JS, 2005, PHYS REV E 1, V72, ARTN 021903 ZHU TC, 2005, J PHOTOCH PHOTOBIO B, V79, P231, DOI 10.1016/j.jphotobiol.2004.09.01