Near-infrared, wavelength, and illumination scanning holographic tomography

We present a holographic tomography technique in which the projections are acquired using both wavelength and illumination scanning in the near-infrared region. We show how to process the acquired data to obtain correct values of three-dimensional refractive index distributions in both single-wavelength and multi-wavelength data acquisition schemes and how to properly account for the dispersion of the sample. We perform numerical and experimental comparisons of different illumination scenarios to determine the most efficient measurement protocol. We show that the multi-wavelength protocol is advantageous in terms of signal-to-noise ratio and contrast-to-noise ratio over single-wavelength protocols, even for the same number of projections used for reconstructions. Finally, we show that this approach is suitable for providing high-quality refractive index distributions of relatively thick colon cancer samples.

Realistic simulation and experiment reveals the importance of scatterer microstructure in optical coherence tomography image formation

Realistic simulation of image formation in optical coherence tomography, based on Maxwell's equations, has recently been demonstrated for sample volumes of practical significance. Yet, there remains a limitation whereby reducing the size of cells used to construct a computational grid, thus allowing for a more realistic representation of scatterer microstructure, necessarily reduces the overall sample size that can be modelled. This is a significant problem since, as is well known, the microstructure of a scatterer significantly influences its scattering properties. Here we demonstrate that an optimized scatterer design can overcome this problem resulting in good agreement between simulated and experimental images for a structured phantom. This approach to OCT image simulation allows for image formation for biological tissues to be simulated with unprecedented realism.

Classification of biological micro-objects using optical coherence tomography: in silico study

We report on the development of a technique for differentiating between biological micro-objects using a rigorous, full-wave model of OCT image formation. We model an existing experimental prototype which uses OCT to interrogate a microfluidic chip containing the blood cells. A full-wave model is required since the technique uses light back-scattered by a scattering substrate, rather than by the cells directly. The light back-scattered by the substrate is perturbed upon propagation through the cells, which flow between the substrate and imaging system's objective lens. We present the key elements of the 3D, Maxwell equation-based computational model, the key findings of the computational study and a comparison with experimental results.

Differentiation of morphotic elements in human blood using optical coherence tomography and a microfluidic setup

We demonstrate a novel optical method for the detection and differentiation between erythrocytes and leukocytes that uses amplitude and phase information provided by optical coherence tomography (OCT). Biological cells can introduce significant phase modulation with substantial scattering anisotropy and dominant forward-scattered light. Such physical properties may favor the use of a trans-illumination imaging technique. However, an epi-illumination mode may be more practical and robust in many applications. This study describes a new way of measuring the phase modulation introduced by flowing microobjects. The novel part of this invention is that it uses the backscattered signal from the substrate located below the flowing/moving objects. The identification of cells is based on phase-sensitive OCT signals. To differentiate single cells, a custom-designed microfluidic device with a highly scattering substrate is introduced. The microchannels are molded in polydimethylsiloxane (PDMS) mixed with titanium dioxide (TiO2) to ensure high scattering properties. The statistical parameters of the measured signal depend on the cells' features, such as their size, shape, and internal structure.

Apolipoprotein E4 allele is associated with substantial changes in the plasma lipids and hyaluronic acid content in patients with nonalcoholic fatty liver disease

Fat may affect progression of liver damage in patients with non-alcoholic fatty liver disease (NAFLD). In this study we characterize the state of lipid metabolism in 22 patients with NAFLD and different Apo-E variants. Total concentration of plasma total fatty acids was quantified by gas chromatography, while their derivatives by liquid chromatography/tandem mass spectrometry (LC ESI MS/MS). The ratio of plasma saturated fatty acid to monounsaturated fatty acid increased, whereas the ratio of polyunsaturated fatty acids to saturated fatty acids was reduced in Apo-E4 carriers. Simultaneously, the levels of individual plasma linoleic, arachidonic, and alpha linolenic acids significantly increased in subjects with the Apo-E4 allele. The 15-lipoxygenase metabolite, 13-hydroxyoctadecadienoic acid, was significantly higher in Apo-E3 carriers (p<0.006). 5-oxo-6,8,11,14-eicosatetraenoic acid was significantly elevated in Apo-E4 carriers (p<0.009). A significant difference in hyaluronic acid concentration (p<0.0016) as well as predicted advanced fibrosis (using the BARD scoring system) was found in Apo-E4 carriers (p<0.01). We suggest that a distinct mechanism of fibrosis between Apo E alleles. In Apo-E4 carriers, an elevation in 5-oxo-6,8,11,14-eicosatetraenoic acid synthesis and fatty acid dysfunction may induce fibrosis, while an inflammatory process may be the main cause of fibrosis in Apo-E3 carriers.

Comparison of the structures and elicitor activities of a synthetic and a mycelial-wall-derived hexa(beta-D-glucopyranosyl)-D-glucitol

The elicitor activity and structural characteristics of chemically synthesized hepta- and octa-beta-D-glucopyranosides were compared with the same properties of an elicitor-active mycelial-wall-derived hexa(beta-D-glucopyranosyl)-D-glucitol. The specific elicitor activities, retention times on reversed-phase liquid chromatography columns, glycosyl-linkage compositions, 1H NMR analyses, and glycosyl-sequence analyses of the synthetic and mycelial-wall-derived hexa(beta-D-glucopyranosyl)-D-glucitols were indistinguishable. This work provided conclusive proof that elicitor activity was associated with the structure proposed (Sharp, J. K., McNeil, M., and Albersheim, P. (1984) J. Biol. Chem. 259, 11321-11336) for the elicitor-active mycelial-wall-derived hexa(beta-D-glucopyranosyl)-D-glucitol.

Synthesis of a glucoheptaose and a glucooctaose that elicit phytoalexin accumulation in soybean

The glucoheptaose 1 and the glucooctaose 2 have been synthesized using unambiguous methods. The former is identical with an elicitor-active heptasaccharide obtained from partially hydrolyzed mycelium of Phytophthora megasperma f. sp. glycinea. The octasaccharide is also elicitor active, although to a lesser extent than the heptasaccharide. 1:R = H; 2:R = beta-D-Glcp. (Formula: see text)