Utilization of trihalogenated propanes by Agrobacterium radiobacter AD1 through heterologous expression of the haloalkane dehalogenase from Rhodococcus sp strain m15-3

Trihalogenated propanes are toxic and recalcitrant organic compounds. Attempts to obtain pure bacterial cultures able to use these compounds as sole carbon and energy sources were unsuccessful. Both the haloalkane dehalogenase from Xanthobacter autotrophicus GJ10 (DhlA) and that from Rhodococcus sp, strain m15-3 (DhaA) were found to dehalogenate trihalopropanes to 2,3-dihalogenated propanols, but the kinetic properties of the latter enzyme are much better, Broad-host-range dehalogenase expression plasmids, based on RSF1010 derivatives, were constructed with the haloalkane dehalogenase from Rhodococcus sp, strain m15-3 under the control of the heterologous promoters P-lac, P-dhlA, and P-trc. The resulting plasmids yielded functional expression in several gram-negative bacteria. A catabolic pathway for trihalopropanes was designed by introducing these broad-host-range dehalogenase expression plasmids into Agrobacterium radiobacter AD1, which has the ability to utilize dihalogenated propanols for growth. The recombinant strain AD1 (pTB3), expressing the haloalkane dehalogenase gene under the control of the dhlA promoter, was able to utilize both 1,2,3-tribromopropane and 1,2-dibromo-3-chloropropane as sole carbon sources. Moreover, increased expression of the haloalkane dehalogenase resulted in elevated resistance to trihalopropanes.</p

Laser-driven resonance of dye-doped oil-coated microbubbles: A theoretical and numerical study

Microbubbles are used to enhance the contrast in ultrasound imaging. When coated with an optically absorbing material, these bubbles can also provide contrast in photoacoustic imaging. This multimodal aspect is of pronounced interest to the field of medical imaging. The aim of this paper is to provide a theoretical framework to describe the physical phenomena underlying the photoacoustic response. This article presents a model for a spherical gas microbubble suspended in an aqueous environment and coated with an oil layer containing an optically absorbing dye. The model includes heat transfer between the gas core and the surrounding liquids. This framework is suitable for the investigation of both continuous wave and pulsed laser excitation. This work utilizes a combination of finite difference simulations and numerical integration to determine the dependancy on the physical properties, including composition and thickness of the oil layer on the microbubble response. A normalization scheme for a linearized version of the model was derived to facilitate comparison with experimental measurements. The results show that viscosity and thickness of the oil layer determine whether or not microbubble resonance can be excited. This work also examines the use of non-sinusoidal excitation to promote harmonic imaging techniques to further improve the imaging sensitivity

Four-Dimensional Computational Ultrasound Imaging of Brain Haemodynamics

Four-dimensional ultrasound imaging of complex biological systems such as the brain is technically challenging because of the spatiotemporal sampling requirements. We present computational ultrasound imaging (cUSi), a new imaging method that uses complex ultrasound fields that can be generated with simple hardware and a physical wave prediction model to alleviate the sampling constraints. cUSi allows for high-resolution four-dimensional imaging of brain haemodynamics in awake and anesthetized mice

Information-theoretic active contour model for microscopy image segmentation using texture

High throughput technologies have increased the need for automated image analysis in a wide variety of microscopy techniques. Geometric active contour models provide a solution to automated image segmentation by incorporating statistical information in the detection of object boundaries. A statistical active contour may be defined by taking into account the optimisation of an information-theoretic measure between object and background. We focus on a product-type measure of divergence known as Cauchy-Schwartz distance which has numerical advantages over ratio-type measures. By using accurate shape derivation techniques, we define a new geometric active contour model for image segmentation combining Cauchy-Schwartz distance and Gabor energy texture filters. We demonstrate the versatility of this approach on images from the Brodatz dataset and phase-contrast microscopy images of cells