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Biomedical subjects

W Chou

Publications and source records attributed to W Chou.

At least 19 recordsLinked to original sources
PubMed2001

Distinct gene expression profiles of human type 1 and type 2 T helper cells.

BACKGROUND: The development and activation of CD4+ helper T cell (Th) subsets with distinct patterns of unbalanced production of cytokines play an important part in infectious, allergic and autoimmune diseases. Human neonatal cord blood CD4+ Th cells can be polarized into type 1 or type 2-like effector cells in vitro by culturing them in the presence of interleukin (IL)-12 or IL-4, respectively. We have exploited this experimental system to identify marker genes that are differentially expressed by polarized Th1 and Th2 cells. An oligonucleotide microarray specifically designed to screen for inflammation-related candidate genes was used and the differential expression was further validated with a quantitative real-time RT-PCR method. RESULTS: In addition to the previously described marker genes of Th cells, we report subtle changes in the expression of several other genes that represent growth factors, receptors and other signaling molecules in polarized Th1 and Th2 cell subsets. Additionally, we describe a novel set of genes as Th1/Th2 differentiation markers for cells activated by anti-CD3 and anti-CD28 antibodies. CONCLUSIONS: This study demonstrates the power of the targeted use of microarrays in combination with quantitative real-time RT-PCR in identifying and validating new marker genes for gene expression studies.

CD4 Antigens↗
PubMed2001

Soft-decision array decoding for volume holographic memory systems.

We study the use of soft-decision array decoding in a volume holographic memory (VHM) system that is corrupted by interpixel interference (IPI) and detector noise. Soft-decision methods can unify equalization and error decoding. A highly parallel array decoder is presented in the context of two-dimensional low-pass channel mitigation and error correction. The new decoding algorithm is motivated by iterative turbo-decoding methods and is capable of incorporating a priori knowledge of the corrupting IPI channel during decoding. The resulting joint detection decoding algorithm is shown to offer VHM capacity and density performance superior to that of hard-decision n = 255 Reed-Solomon codes in concatenation with a Wiener filter.

Journal Article↗
PubMed2001

Modulation of lens cell adhesion molecules by particle beams.

Cell adhesion molecules (CAMs) are proteins which anchor cells to each other and to the extracellular matrix (ECM), but whose functions also include signal transduction, differentiation, and apoptosis. We are testing a hypothesis that particle radiations modulate CAM expression and this contributes to radiation-induced lens opacification. We observed dose-dependent changes in the expression of beta 1-integrin and ICAM-1 in exponentially-growing and confluent cells of a differentiating human lens epithelial cell model after exposure to particle beams. Human lens epithelial (HLE) cells, less than 10 passages after their initial culture from fetal tissue, were grown on bovine corneal endothelial cell-derived ECM in medium containing 15% fetal bovine serum and supplemented with 5 ng/ml basic fibroblast growth factor (FGF-2). Multiple cell populations at three different stages of differentiation were prepared for experiment: cells in exponential growth, and cells at 5 and 10 days post-confluence. The differentiation status of cells was characterized morphologically by digital image analysis, and biochemically by Western blotting using lens epithelial and fiber cell-specific markers. Cultures were irradiated with single doses (4, 8 or 12 Gy) of 55 MeV protons and, along with unirradiated control samples, were fixed using -20 degrees C methanol at 6 hours after exposure. Replicate experiments and similar experiments with helium ions are in progress. The intracellular localization of beta 1-integrin and ICAM-1 was detected by immunofluorescence using monoclonal antibodies specific for each CAM. Cells known to express each CAM were also processed as positive controls. Both exponentially-growing and confluent, differentiating cells demonstrated a dramatic proton-dose-dependent modulation (upregulation for exponential cells, downregulation for confluent cells) and a change in the intracellular distribution of the beta 1-integrin, compared to unirradiated controls. In contrast, there was a dose-dependent increase in ICAM-1 immunofluorescence in confluent, but not exponentially-growing cells. These results suggest that proton irradiation downregulates beta 1-integrin and upregulates ICAM-1, potentially contributing to cell death or to aberrant differentiation via modulation of anchorage and/or signal transduction functions. Quantification of the expression levels of the CAMs by Western analysis is in progress.

Cell Adhesion↗
PubMed1994

The fundamental motor of the human neutrophil is not random: evidence for local non-Markov movement in neutrophils.

The search for a fundamental mechano-chemical process that results in net cell motion has led investigators to fit neutrophil tracking data to well described physical models in hopes of understanding the functional form of the driving force. The Ornstein-Uhlenbeck (OU) equation for mean square displacement describes a locally persistent and globally random process and is often used as a starting point for analysis of neutrophil displacements. Based upon the apparently close fit of neutrophil tracking data to this equation and the nature of its derivation, biologists have inferred that the motor of the neutrophil is best represented as a random process. However, 24 of 37 neutrophil paths that we investigated preferentially display programmatic rather than Markov short term correlations between displacements or turn angles. These correlations reflect a bimodal rather than a uniform distribution of subpath correlations in the two variables, and are strongly sampling rate-dependent. Significant periodic components of neutrophil shape change are also detected at the same time scale using either Fourier or elliptical Fourier transform-based descriptors of the neutrophil perimeter. Oscillations in neutrophil velocity have the same period. Taken together, these data suggest a nonstochastic, and perhaps periodic, component to the process driving neutrophil movement.

Biophysical Phenomena↗
PubMed1993

Development of a shape vector that identifies critical forms assumed by human polymorphonuclear neutrophils during chemotaxis.

Human polymorphonuclear neutrophils undergo characteristic shape changes that are critical to their ability to move and ingest their targets. We present here the construction of a simple shape vector, calculated from the coordinates of the cell perimeter, that can identify critical forms that a neutrophil assumes during the course of ameboid movement. The vector can be used to find neutrophils of a specific shape from the image analyzer data produced during a typical neutrophil tracking experiment.

Amanitins↗
PubMed1991

Chemosensitivity of medullary neurons in explant tissue cultures.

To determine whether cultured medulla contains chemosensitive neurons which are excited by CO2 and fixed acid and whether this function is specific to the ventral medulla, tissue explants of ventral and dorsal medulla were prepared from neonatal rats and incubated for two to three weeks. Cultures were superfused with artificial cerebrospinal fluid, maintained at 37 degrees C, and pH of the superfusate was varied either with PCO2 (14-71 Torr) at constant HCO3- (22 mM) or HCO3- (10-30 mM) at constant PCO2 (35 Torr). Spontaneous action potentials were recorded extracellularly in 51 ventral and 23 dorsal medullary neurons. Ventral medullary neurons exhibited a steady baseline firing frequency of 4 +/- 0.8 Hz. In contrast, dorsal medullary neurons exhibited two different patterns of spontaneous activity: 11 fired continuously (7.2 +/- 1.4 Hz) while 12 fired with a bursting pattern. Burst duration was 0.80 +/- 0.14 min and cycle time was 1.74 +/- 0.43 min. Decreasing pH with CO2 caused an increase in the activity of 10 of 27 ventral medullary neurons and two of six dorsal medullary neurons with a mean response of 7.5 Hz/pH unit. Varying pH by changing HCO3- had no effect on firing frequency. These results demonstrate that: (i) chemosensitive neurons are present in both ventral and dorsal medullary explant cultures; (ii) these cells only respond to changes in pH induced with CO2; and (iii) about half of the dorsal medullary neurons fire spontaneously with a regular bursting pattern of activity.

Action Potentials↗