Charles C. Tseng

2.45 GHz radiofrequency fields alter gene expression in cultured human cells

The biological effect of radiofrequency (RF) fields remains controversial. We address this issue by examining whether RF fields can cause changes in gene expression. We used the pulsed RF fields at a frequency of 2.45 GHz that is commonly used in telecommunication to expose cultured human HL‐60 cells. We used the serial analysis of gene expression (SAGE) method to measure the RF effect on gene expression at the genome level. We observed that 221 genes altered their expression after a 2‐h exposure. The number of affected genes increased to 759 after a 6‐h exposure. Functional classification of the affected genes reveals that apoptosis‐related genes were among the upregulated ones and the cell cycle genes among the downregulated ones. We observed no significant increase in the expression of heat shock genes. These results indicate that the RF fields at 2.45 GHz can alter gene expression in cultured human cells through non‐thermal mechanism.

Consistent deregulation of gene expression between human and murine MLL rearrangement leukemias.

Important biological and pathologic properties are often conserved across species. Although several mouse leukemia models have been well established, the genes deregulated in both human and murine leukemia cells have not been studied systematically. We performed a serial analysis of gene expression in both human and murine MLL-ELL or MLL-ENL leukemia cells and identified 88 genes that seemed to be significantly deregulated in both types of leukemia cells, including 57 genes not reported previously as being deregulated in MLL-associated leukemias. These changes were validated by quantitative PCR. The most up-regulated genes include several HOX genes (e.g., HOX A5, HOXA9, and HOXA10) and MEIS1, which are the typical hallmark of MLL rearrangement leukemia. The most down-regulated genes include LTF, LCN2, MMP9, S100A8, S100A9, PADI4, TGFBI, and CYBB. Notably, the up-regulated genes are enriched in gene ontology terms, such as gene expression and transcription, whereas the down-regulated genes are enriched in signal transduction and apoptosis. We showed that the CpG islands of the down-regulated genes are hypermethylated. We also showed that seven individual microRNAs (miRNA) from the mir-17-92 cluster, which are overexpressed in human MLL rearrangement leukemias, are also consistently overexpressed in mouse MLL rearrangement leukemia cells. Nineteen possible targets of these miRNAs were identified, and two of them (i.e., APP and RASSF2) were confirmed further by luciferase reporter and mutagenesis assays. The identification and validation of consistent changes of gene expression in human and murine MLL rearrangement leukemias provide important insights into the genetic base for MLL-associated leukemogenesis.

Determining a Pulse Coupling to Subcellular Components With a Frequency-Domain Transfer Function

This paper describes the theoretical analysis of an external rectangular time-varying electric field pulse to subcellular components in a two-shell model using published parameters. The methods use a linear analysis that provides a fourth-order solution in the frequency domain. The fourth-order model provides increased accuracy over a lower order model to calculate responses to submicrosecond pulses and susceptibility to parameter variations. The time response of a pulsed 50-ns extracellular electrical field to a nucleoplasm provides a means of comparing cell parameter estimates

Effect of subcooling on convective melting of a particle

We consider convective melting of a spherical particle. The study is intended to provide understanding of how both subcooling and convection of heat and mass affect the melting process. Since part of heat transferred to the particle is used to increase its sensible energy during melting by internal heat conduction, the heat transfer rate across the melting interface determines the melting rate. Subcooling of a particle affects the melting rate; therefore, if the effect of subcooling can be neglected during melting in calculating the melting rate, the Stefan number and heating rate must satisfy certain criteria that are described in this contribution. In addition, the effect of mass convection is also discussed

Algorithms for modeling structural changes in human chromosomes

Human cytogenetics is the study of chromosomes (typically at mitotic metaphase). The study of chromosomes has recently become integrated with molecular biology and genomics. Thus, it is an important part of genetics education. However, it is time consuming to train students and clinical technologists to recognize patterns of G-banded human chromosomes because of the dynamic nature of G-band resolutions in different metaphase spreads. Moreover, there are limited resources to obtain the images of abnormal chromosomes. We present in this paper an advanced version of computer based interactive tutorial program capable of simulating chromosome abnormalities, altering chromosome shapes, and manipulating G-band resolutions for human cytogenetic seduction. By simulating chromosomes using digital image processing and pattern recognition, the versatile software, together with various strategies such as website links and dialogs, will provide students with a virtual learning environment for self-practicing and testing, thus transforming the traditionally dry and ineffective approach into an exciting and efficient learning process.

Laser imaging for rapid Microbial Source Tracking

DNA fingerprinting, PCR and other genomic technologies have recently been used to determine sources of fecal bacteria in waterways. Here, we report on the development of a simple and automated optical method for potential use in Microbial Source Tracking (MST) of E. coli. The method employs laser imaging of bacterial colonies and high-resolution optical scattering image analysis for information extraction and classification. Cross validation is used to statistically evaluate the robustness of the classifiers. The entire image analysis procedure can be fully automated, making this a potentially useful tool for future MST studies.

Analytical and Experimental Dosimetry of a Cell Culture in T-25 Flask Housed in a Thermally Controlled Waveguide

This paper describes the dosimetry of a 2.45-GHz thermally controlled waveguide exposure system containing a T-25 cell culture flask used for gene expression studies. The bottom surface of the flask is maintained at 37 degC while the remaining surfaces of the flask are at a lower temperature determined by air convection currents. Thermal gradients are set up in the cell culture medium that creates convection currents that affect cell position and exposure. The finite-element commercial software high-frequency structure simulator (HFSS) by Ansoft Corporation is used to analyze the three-dimensional distribution of electric field. The data from HFSS are exported to the finite element computational fluid dynamics (CFD) software FLUENT. The results from HFSS and CFD software agree with experimental data

Simulation of Human Abnormal Chromosomes: An Innovative Tool for Teaching

Human chromosome structural changes are associated with many genetic diseases including cancers. The ability to identify different abnormal chromosomes is therefore important in genetics education. In this paper, we describe new algorithms for generating abnormal chromosomes to enrich the teaching resources.

VISUALIZING HOMOLOGOUS RECOMBINATION WITH INTERACTIVE COMPUTER PROGRAM

Homologous recombination is important for DNA repair and for increasing genetic variation, whereby it enriches the gene pool and keeps populations viable. In eukaryotes, genetic recombination takes place during meiosis. For genes on different chromosomes, mixing of paternal and maternal genes is achieved through the random formation of different chromosome configurations at metaphase I of meiosis. This process accounts for the genetic principle of the independent assortment of unlinked genes. Recombination of paternal and maternal genes on different members of the homologous chromosome pair, on the other hand, can only be achieved through the exchange of genetic material between nonsister chromatids, resulting in increased genetic variation. The molecular mechanisms of homologous recombination are complicated and often difficult for students to understand. The objective of this research is to develop an interactive computer program for teaching this important biological process. The software program, along with related computer-based genetics learning programs — for mitosis and meiosis, as well as for a cytogenetics laboratory — will be useful for genetics education at the high school and university levels.

Computer Based Karyotyping

Karyotyping is a fundamental step in chromosome analysis. Since G-banding patterns of any chromosomes in the metaphase spread are changeable, it is difficult and time consuming for students to master the technique of karyotyping. Current methods for leaning karyotyping are ineffective, and therefore it is necessary to develop a software program to help students learn the skill efficiently. Virtual reality is suitable for this purpose because of its inherent simulating ability. By building dynamic chromosome models capable changing shapes, G-band resolutions, and structure, along with creating variable metaphase spreads, a versatile software program was developed to provide students with a virtual learning environment for self practicing and testing, thus transforming the traditionally dry and tedious approach into an exciting and efficient learning process.