First derivative of NIR light diffuse reflectance spectra as an approach to analyze muscle tissue chromophores and light pathlength

Diffuse reflectance was applied to the biomedical studies (muscles, cardiac tissues etc.) in a form of either a direct pseudo-optical spectrum or its second derivative. The first derivative adopts advantages of both direct spectrum (high signal-to-noise ratio) and its second derivative (simplifying the consideration of light scattering contribution, S). In contrast to spectrophotometry of solutions, diffuse reflectance application to the analysis of turbid medium chromophores leads to non-trivial problems of contribution of light scattering, the choice of reference, and light pathlength. Under certain conditions, the first approximation of the Taylor series of S results in the known linear dependence of S on wavelength in the 650-1050 nm wavelength range. Then the light scattering contribution to the first derivative becomes a wavelength-independent offset. In contrast to the second derivative, the information on light scattering inside the tissue is not lost. Effect of reference on the measured spectra becomes negligible. Application of the first derivative allowed (i) determination of NIR light pathlength in muscle tissue, and (ii) quantification of hemoglobin myoglobin absolute concentration (in mM) in cardiac tissue during open-heart surgery. The first derivative approach may in general be applied to any chromophores in turbid (biological) media.Peer reviewed: YesNRC publication: Ye

Circularly Polarized Luminescence (CPL) of Proteins and Protein Complexes

Peer reviewed: NoNRC publication: Ye

On the emission intensity of fluorescent microspheres in cardiac tissue images

Formulations for the total fluorescence intensity of fluorescent microspheres in slabs of cardiac tissue were determined experimentally and theoretically. The tissue depth, at which the slab can be considered as a semi-infinite turbid medium, and critical layer thickness, which accounts for the most emission intensity were evaluated to be 8\u20139 and 3\u20135 mm, respectively, for the cardiac tissue. When fluorescent microspheres are linearly distributed across the slab depth, the mean absorption of them is proportional to the sum of their normalized total emissions in the slab excited from both sides. The formulations may be used for the fluorescence images analysis of cardiac and other biological tissues.Peer reviewed: YesNRC publication: Ye

Non-invasive measurements of hemoglobin + myoglobin, their oxygenation and NIR light pathlength in heart in vivo by diffuse reflectance spectroscopy

The existing non-invasive optical methods of the hemoglobin (Hb) and myoglobin (Mb) estimation in cardiac tissues imply knowledge of the light pathlength (L) when various modifications of Lambert-Beer law for either spectrophotometry or light diffuse reflectance is applied. For Hb and/or Mb quantification in tissue, a few invasive (biochemical) approaches were applied. For L (differential pathlength factor; DPF) determination in tissue, special optical methods were used. No approaches have been proposed to simultaneously and non-invasively determine Hb/Mb and L in cardiac or other muscle tissues. In the present study, the first derivative of the NIR diffuse reflectance spectrum is shown to be effective in simultaneous determination of Hb+Mb concentration (in mM) and L (in mm) in cardiac tissue in vivo. The results showed that measured in a few minutes in a normal pig heart in vivo the total Hb+Mb concentration was 0.9-1.2 mM of heme, tissue oxygen saturation parameter (OSP) was approximately 65%, and DPF at 700-965 nm was of 2.7-2.8. At the experimental ischemia, total [Hb+Mb] decreased by 25%, OSP reduced to zero, while DPF did not change. These results correlated with the previously published. The method may be applied during open-heart surgery, heart studies ex vivo or to any muscle tissue to continuously and non-invasively monitor the [Hb+Mb] content and oxygenation as well as L, which may reflect the changes in tissue structurePeer reviewed: YesNRC publication: Ye

Fluorescence imaging to quantify the fluorescent microspheres in cardiac tissue

To quantify the fluorescent microsphere (FM) content in cardiac tissue, which is an indicative of blood flow, fluorescence imaging of both sides of the pig heart slice was employed. Despite the light scattering inside the tissue and contributions from multiple tissue layers to the total emission, it is shown that the fluorescence intensity at any pixel is proportional to the FM content and the fluorescence image may be transformed to the image of the FM concentration. A convenient standard for the emission-FM concentration transformation is proposed. The approach has several advantages in comparison with the traditional \u201cdigestion & extraction\u201d method such as: non-destructiveness, high spatial resolution, high throughput, repeatability and simplicity of operation.Peer reviewed: YesNRC publication: Ye

NIR spectroscopic imaging to map hemoglobin + myoglobin oxygenation, their concentration and optical pathlength across a beating pig heart during surgery

The purpose of this paper is to demonstrate that near-infrared (NIR) spectroscopic imaging can provide spatial distribution (maps) of the absolute concentration of hemoglobin + myoglobin, oxygen saturation parameter and optical pathlength, reporting on the biochemico-physiological status of a beating heart in vivo. The method is based on processing the NIR spectroscopic images employing a first-derivative approach. Blood-pressure-controlled gating compensated the effect of heart motion on the imaging. All the maps are available simultaneously and noninvasively at a spatial resolution in the submillimeter range and can be obtained in a couple of minutes. The equipment has no mechanical contact with the tissue, thereby leaving the heart unaffected during the measurementPeer reviewed: YesNRC publication: Ye

Mapping the myoglobin concentration, oxygenation, and optical pathlength in heart ex vivo using near-infrared imaging

A method that provides maps of absolute concentrations of oxygenated and deoxygenated myoglobin (Mb), its oxygenation, and its near-infrared (NIR) optical pathlength in cardiac tissue was developed. These parameters are available simultaneously. The method is based on NIR diffuse reflectance spectroscopic imaging and specific processing of the NIR images, which included a first derivative of the diffuse reflectance spectrum. Mb oxygenation, total Mb concentration, and NIR light pathlength were found to be in the range of 92%, 0.3 mM, and 12.5 mm, respectively, in beating isolated buffer-perfused and arrested pig hearts. The charge-coupled device camera enables sub-millimeter spatial resolution and spectroscopic imaging in 1.5 to 2.0 min. The technique is noninvasive and nondestructive. The equipment has no mechanical contact with the tissue of interest, leaving it undisturbed.Peer reviewed: YesNRC publication: Ye

Cryoinjury to pig heart : Near-infrared spectroscopic (NIRS) imaging study.

NRC publication: Ye

Differential Expression of Secretory Phospholipases A2 in Normal and Malignant Prostate Cell Lines: Regulation by Cytokines, Cell Signaling Pathways, and Epigenetic Mechanisms

Upregulation of group IIA phospholipase A2 (sPLA2-IIA) correlates with prostate tumor progression suggesting prooncogenic properties of this protein. Here, we report data on expression of three different sPLA2 isozymes (groups IIA, V, and X) in normal (PrEC) and malignant (DU-145, PC-3, and LNCaP) human prostate cell lines. All studied cell lines constitutively expressed sPLA2-X, whereas sPLA2-V transcripts were identified only in malignant cells. In contrast, no expression of sPLA2-IIA was found in PrEC and DU-145 cells, but it was constitutively expressed in LNCaP and PC-3 cells. Expression of sPLA2-IIA is upregulated in PC-3 and in PrEC cells by IFN-γ in a signal transducer and activator of transcription-1-dependent manner, but not in LNCaP cells. Additional signaling pathways regulating sPLA2-IIA expression include cAMP/protein kinase A, p38 mitogen-activated protein kinase, protein kinase C, Rho-kinase, and mitogen-activated/extracellular response protein kinase / extracellular signal-regulated kinase. No deletions were revealed in the sPLA2-IIA gene from DU-145 cells lacking the expression of sPLA2-IIA. Reexpression of sPLA2-IIA was induced by 5-aza-2′-deoxycytidine demonstrating that DNA methylation is implicated in the regulation of sPLA2-II. Together, these data suggest that sPLA2-IIA and sPLA2-V, but not sPLA2-X, are differentially expressed in normal and malignant prostate cells under the control of proinflammatory cytokines; epigenetic mechanisms appear involved in the regulation of sPLA2-IIA expression, at least in DU-145 cells