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Biomedical subjects

K A Kang

Publications and source records attributed to K A Kang.

28 records · Page 2Linked to original sources
PubMed1990

Membrane resistance to oxygen transport inside hybridoma cells in suspension culture.

We have examined oxygen transport from media to a single hybridoma cell for different dissolved oxygen concentrations in media and oxygen consumption rates of cells. Intracellular oxygen concentration profiles inside the cell were simulated using currently available parameters. From the simulation, it was found that mass transfer resistance at the boundary layer does not seem to be significant. Intracellular oxygen concentrations did not differ very much from outside media concentration and the concentration gradients were relatively low for all five different media DOC's (from 0.1 to 100% air saturation). From these results, it is suspected that either hybridoma cells have better tolerance to high intracellular oxygen concentrations than normal cells or that the cell membrane has a certain mechanism for limiting oxygen transport into the cell to avoid the oxidative damage.

Animals↗
PubMed1989

Structured modeling and simulation of oxygen transport to hybridoma cell in a suspension culture: theoretical analysis.

The importance of the consideration of micro-anatomical and cytological observation for the oxygen utilization by hybridoma cells are emphasized. Tumor cells have considerably lower content of mitochondria and that cells metabolize much of their carbon source by anaerobic pathway, therefore, consumes much less oxygen. Because of the fact that hybridoma cells are derived from a myeloma cell, which is a type of tumor cell, there may be possibility that the oxygen demand could be closely related to mitochondrial content of the resulting cell. Possible correlation between the optimum DOT and mitochondrial content of the hybridoma cells is hypothesized. By simulating oxygen transport inside of a single hybridoma cells for the cases of three different mitochondrial contents, possible differences in the optimum DOT according to the mitochondrial contents were studied and the results reported.

Animals↗
PubMed1988

A computer simulation of simultaneous heat and oxygen transport during heterogeneous three dimensional tumor hyperthermia.

Hyperthermia is a developing modelity for the treatment of cancer. This therapy is occasionally used by itself, however, usually it is used as an adjuvate with chemo or radiation therapy. The mechanism for this treatment is based on the fact that cancer cells are heated preferentially by heat application due to lower vascularity in the tumor tissue as compared with the surrounding normal tissue and that, when used with radiation therapy or chemo therapy, higher oxygen partial pressure in the tumor results in increased tumor cell damage. Appropriate mathematical models and their real time prediction of oxygen and temperature profiles could be very helpful in achieving optimal results via hyperthermia and to avoid possible danger which might occur during the treatment. Because of the complexity and the heterogeneous nature of physiological system, it is necessary to include heterogeneous properties in the mathematical models for them to be useful for biomedical calculations. Of course, it is much more difficult to solve mathematically the heterogeneous system than the homogeneous one. In this paper, the importance of the implementation of heterogeneities in the heat and mass transport for biological system mathematical modelling is discussed. Results of a three dimensional computer simulation of mass and heat transfer in tumor tissue with different capillary geometries during hyperthermia are demonstrated. The method used for the computer simulation is a deterministic/probabilistic technique, Williford-Bruley calculational strategy.

Animals↗
PubMedDate not supplied

Highly scattering optical system identification via frequency response analysis of NIR-TRS spectra.

Frequency response analysis via pulse testing is often used for the characterization of engineering systems. Near infrared-time resolved spectroscopy (NIR-TRS) is a frequently used technique for the analysis of biological system properties. Since the TRS input is a very sharp photon pulse, a well designed TRS input pulse can produce a multi-frequency response over the useful frequency range for the system identification. This new approach for analyzing NIR-TRS provides new optical system parameters (e.g., magnitude ratio and phase shift at multi-frequencies, system time constant, system order, and steady state gain) that are not available by traditional TRS spectra analysis. In this paper, the basic theory of pulse reduction is introduced for the multi-modulation frequency response of TRS spectra. Homogeneous system response with various absorption and scattering properties were analyzed for the multi-system parameters. In heterogeneous systems, the position of the localized absorber is correlated with the multi-parameters, which can ultimately be used to enhance medical imaging.

Absorption↗
PubMedDate not supplied

Studies on scale-up parameters of an immunoglobulin separation system using protein A affinity chromatography.

Effects of operational and system parameters on process scale-up of murine immunoglobulin (IgG2a kappa) purification using Protein A affinity chromatography are investigated. Parameters studied are those related to sample application, elution, ligand concentration on support, and column size change. Between sample application velocities of 0.004 and 0.030 cm/s (16-108 cm/h), the product concentration profiles in eluate did not show significant differences. With given system parameters, the retention time and bandwidth of the peak could be predicted by moment theory. The mean equilibrium constant during elution showed a strong effect of pH between 2 and 4. Within the range of protein A concentrations studied, 0.15-1.22 mg/mL of gel, the column capacity shows a linear relationship with the concentration of protein A immobilized. Dimensional scale-up of the column in the radial direction increased the total purification capacity linearly as the cross-sectional area increased without increasing pressure drop; however, the product concentration was diluted. Scale-up of the column dimension in the axial direction enables higher concentrations of product in the eluate, although the retention time increases linearly as the gel height increases.

Adsorption↗
PubMedDate not supplied

Application of near-IR time-resolved spectroscopy and frequency response analysis for deep vein thrombosis detection.

Frequency response analysis is applied to analyze NIR-TRS spectra in a tissue model with a simulated thrombus. The value changes in parameters obtained from frequency response analysis are correlated with heterogeneity position in three dimensions. The goal of this research is to noninvasively localize deep vein thrombosis in the human leg through the use of this novel combination.

Humans↗
PubMedDate not supplied

Localization of a fluorescent object in highly scattering media via frequency response analysis of near infrared-time resolved spectroscopy spectra.

Frequency response analysis via pulse testing for engineering systems and near infrared (NIR) time resolved spectroscopy (TRS) for biological system characterization involve identical principles: the system of interest is disturbed by an input pulse and the output response is observed. Since a sharp pulse, such as the Dirac delta function, contains the information of multimodulation frequencies (theoretically from 0 to infinity in frequency) a narrow pulse TRS input can produce a wide range frequency response for identifying any system of interest. Currently used NIR-TRS spectral analyses either fit the spectra with a known theoretical solution or use photon mean time-of-flight. Transforming the system time domain representation to the frequency domain generates five system parameters that can be valuable for process identification utility: steady state gain, time constant, system order, and magnitude ratio and phase shift over a wide frequency range. Optical contrast agents or fluorescent agents can be used to enhance the capability of optical instruments in detecting biological heterogeneities. In this article, magnitude ratio, phase shift, and other system parameters derived from the transfer function of systems with both a fluorescent absorber and a regular absorber are correlated with the position of the absorber. This technique is important in that ultimately it can be used to enhance optical medical imaging.

Artifacts↗
PubMedDate not supplied

A feasibility study of multispectral image analysis of skin tumors.

To develop a noninvasive, early-detection method for skin cancers, a feasibility study of multispectral image analysis was investigated. The three most frequently occurring skin cancer types, ten basal-cell carcinomas (BCCs), ten squamous-cell carcinomas (SCCs) and five malignant melanomas (MMs) were studied, along with ten normal moles. Images were acquired by a charge-coupled device camera using eight narrow-band filters ranging from 450 nm to 800 nm, at 50-nm intervals. To extract main features of these tumors, principal components analysis (PCA) was performed, because it projects the multidimensional (here, eight-dimensional) data in the direction of maximum data variance. Then, the primary PCA components for red, green, and blue subset images were analyzed in terms of hue-saturation-intensity (HSI). By hue distributions, the BCCs and SCCs were differentiated from the MMs and normal moles. Texture information was used to further classify tumor types after the HSI analysis. The texture analysis, performed using a spatial gray-level co-occurrence matrix (SGCM), could separate MMs from normal moles. The BCCs and SCCs were further studied by Fisher's linear discriminant analysis. Distribution was described as a Gaussian mixture model. By this classification procedure, seven BCCs, eight SCCs, five MMs, and ten NMs were correctly classified. Three BCCs and two SCCs were unseparable. Thus, multispectral skin cancer image analysis has potential to diagnose skin cancers.

Algorithms↗
PubMedDate not supplied

Feasibility study of a single- and multiple-source near-infrared phase-modulation device for characterizing biologic systems.

Near-infrared (NIR) spectroscopy is an inexpensive and noninvasive optical method to characterize biologic and physiologic systems. Measurements of oxygen saturation in various organs, cytochrome oxidase concentration, and glucose concentration in tissue are examples of NIR spectroscopy applications. This instrument also has potential for diagnostic imaging by comparing the optical properties of a given point in tissue with those of the surrounding areas, e.g., tumor localization, hematoma detection, or deep vein thrombosis detection. Currently, NIR spectroscopy is available in three modalities: time-resolved spectroscopy (TRS), continuous-wave spectroscopy (CWS), and a phase-modulation device. This paper describes a single-source phase-modulation device and a multiple-source (in- and anti-phased) device and their application to system identification. The phase and intensity information for homogeneous systems is correlated with system and instrumental parameters. Phase and intensity changes resulting from the presence of one and two absorbers are illustrated. The sensitivity of in- and anti-phased phase-modulation devices (phased arrays) is demonstrated. The use of amplitude-modulated phased array for heterogeneity detection is described.

Computer Simulation↗