Contribution of the mitochondrial compartment to the optical properties of the rat liver: a theoretical and practical approach

Abstract

The purpose of this work was to analyze the contribution of the mitochondria to the optical properties, i.e., light absorption and scattering, of the blood-free rat liver. Firstly, a theoretical model of the reduced scattering coefficient of the liver was performed by using the Mie theory, the Rayleigh-Debye-Gans approximation, and the electron microscopy descriptions of the liver ultrastructure. Compared with the hepatocyte volume, the nucleus and the peroxisomes, the mitochondria compartment, accounting for 22% of the liver cell volume, seemed to be the predominant factor for the light scattering of the liver. Second, by using time-resolved spectroscopy and a sample substitution method, we have measured the absorption and reduced scattering coefficients of blood-free perfused rat livers, isolated hepatocyte suspensions, and isolated mitochondria suspensions. A subsequent extrapolation of the isolated mitochondria data to the in vivo mitochondrial content and a comparison with the whole liver measurements lead to the following conclusions: 1) the mitochondria account for about 50% of the liver absorption coefficient at 780 nm (mu a = 0.25 cm-1 extrapolated from isolated mitochondria vs. 0.53 +/- 0.05 cm-1 measured for the liver); and 2) the mitochondrial compartment is the primary factor for the light scattering in the rat liver (mu s' = 15.5 cm-1 extrapolated from the isolated mitochondria versus 15.9 +/- 2.4 cm-1 measured for the liver), demonstrating the relevancy of our preliminary theoretical study.

Concurrent MRI and diffuse optical tomography of breast after indocyanine green enhancement

“…The technique has the capacity to produce quantitative images of intrinsic and extrinsic absorption and scattering (1)(2)(3)(4), as well as fluorophore lifetime and yield (5)(6)(7) in diffuse media such as tissue. These fundamental quantities can then be used to derive tissue oxy-and deoxyhemoglobin concentrations, blood oxygen saturation (8), contrast agent uptake, and organelle concentration (9). Such novel contrast mechanisms are important for practical applications such as the measurement of tissue metabolic state, angiogenesis, and permeability for cancer detection (10)(11)(12), the measurement of functional activity in brain (13) and muscle (14), and the detection of hematomas (15).…”

Noninvasive functional optical spectroscopy of human breast tissue

“…The concentration of significant NIR absorbers [deoxyhemoglobin (Hb), oxyhemoglobin (HbO 2 ), water, and adipose] can be calculated by using measured a values (11,12). Multiple scattering of light in breast tissue occurs as a consequence of spatial variations in refractive index, which are influenced by cellular and extracellular matrix density (13,14). Both a and s Ј provide an understanding of changes in tissue cellularity, metabolic activity, physiology, and host response to cancer.…”

Gold Nanorod-assisted Optical Stimulation of Neuronal Cells

“…However, the detailed mechanisms by which NIR stimulation affects gene transcription and other cellular activities are currently unresolved. Current data suggests the interplay of different effects in the stimulation, including photon absorption within chromophores in the mitochondria (almost 50% of the energy at 780 nm might be absorbed by cytochrome c oxidase) 37,[39][40][41] , changes in membrane permeability to calcium 37 and inhibition of inflammatory activity in the cells 37 .…”