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Biomedical subjects

Min Gu

Publications and source records attributed to Min Gu.

42 records · Page 3Linked to original sources
PubMed2002

Image reconstruction through turbid media under a transmission-mode microscope.

In this paper, image enhancement and reconstruction through a turbid medium by utilizing polarization gating and mathematical image reconstruction methods in a microscopic imaging system are investigated. A Monte Carlo simulation model based on Mie theory and the concept of the effective point spread function (EPSF) is adopted to study image formation under a transmission-mode microscope. The results show that polarization gating methods, and particularly the differential polarization gating method, can be efficient in suppressing highly scattered light, which leads to a significant enhancement of image quality. An image reconstruction method based on the concept of the EPSF is demonstrated to be efficient in further improving image quality.

Biophysical Phenomena↗
PubMed2002

Nuclear transport of parathyroid hormone (PTH)-related protein is dependent on microtubules.

PTH-related protein (PTHrP) was first discovered as a circulating factor secreted by certain cancers and is responsible for the syndrome of humoral hypercalcemia of malignancy induced by various tumors. The similarity of its N terminus to that of PTH enables PTHrP to share the signaling properties of PTH, but the rest of the molecule possesses distinct functions, including a role in the nucleus/nucleolus in reducing apoptosis and enhancing cell proliferation. PTHrP nuclear import is mediated by importin beta1. In this study we use the technique of fluorescence recovery after photobleaching to demonstrate the ability of PTHrP to shuttle between cytoplasm and nucleus and to visualize directly the transport of PTHrP into the nucleus in living cells. Endogenous and transfected PTHrP was demonstrated to colocalize with microtubule structures in situ using various high-resolution microscopic approaches, as well as in in vitro binding studies, where importin beta1, but not importin alpha, enhanced the microtubular association of PTHrP with microtubules. Significantly, the dependence of PTHrP nuclear import on microtubules was shown by the inhibitory effect of pretreatment with the microtubule-disrupting agent nocodazole on nuclear-cytoplasmic flux. These results indicate that PTHrP nuclear/nucleolar import is dependent on microtubule integrity and are consistent with a direct role for the cytoskeleton in protein transport to the nucleus.

Active Transport, Cell Nucleus↗
PubMedDate not supplied

Second-harmonic generation from biological tissues: effect of excitation wavelength.

We report on the measurement of second-harmonic signals from hyperplastic parenchyma and stroma in malignant human prostate tissue under femtosecond pulsed illumination in the wavelength range from 730 to 870 nm. In particular, the relationship of the second-harmonic generation to the excitation wavelength is measured. The result in these two regions behaves considerably differently and thus provides a possible indicator for identifying tissue components and malignancy.

Humans↗
PubMedDate not supplied

Spectra and lifetimes of fluorescence resonance energy transfer fluorophores under two-photon excitation.

We show two-photon spectra and lifetimes acquired using conventional confocal microscopes equipped with an ultra-short pulsed laser and a time-gated intensified charge coupled device. We report on the two-photon spectra and lifetimes of Alexa350, enhanced green fluorescent protein (EGFP), EGFP-CD46, and Cy3 labelled antibodies. Cellular and extracellular EGFP two-photon spectra and lifetimes are compared.

Acetates↗
PubMedDate not supplied

Surface stress on the erythrocyte under laser irradiation with finite-difference time-domain calculation.

The surface stress on the real shape (biconcave disklike) of an erythrocyte under laser irradiation is theoretically studied according to the finite-difference time-domain (FDTD) method. The distribution of the surface stresses depends on the orientation of erythrocytes in the laser beam. Typically when the erythrocyte was irradiated from the side direction (the laser beam was perpendicular to the normal of the erythrocyte plane), the surface stresses were so asymmetrical and nonuniform that the magnitude of the surface stress on the back surface was three times higher than that on the front surface, and the highest-to-lowest ratio of the stress reached 16 times. For comparison, the surface stress was also calculated according to the ray optics (RO) method. The tendency of the stress distribution from the RO calculation was roughly similar to that of the FDTD method. However the RO calculation produced some unphysical results, such as the infinite stress on some surface region and the zero stress on the most parts of the erythrocyte surface, which is due to the neglecting of light diffraction. The results obtained from the FDTD calculation are believed quantitatively reliable, because the FDTD method automatically takes into account of the diffraction and interference effects of the light wave. Thus, the FDTD method is more suitable than the RO method for the stress study of erythrocytes.

Animals↗