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Biomedical subjects

Roy Chen

Publications and source records attributed to Roy Chen.

5 recordsLinked to original sources
PubMed2025

Exploring endothelial cell environments across organs in spatially resolved omics data.

Endothelial cells are ubiquitously present in the human body and line the luminal surface of blood and lymphatic vessels. The oxygen-dependence of cells impacts their proximity to blood vessels, and consequently, to endothelial cells depending on their functional properties and priorities. This paper presents cell-to-nearest-endothelial-cell distance distributions for various cell types using 399 spatially resolved omics datasets from 14 studies comprising 12 tissue types with a total of 47,349,496 cells. Additionally, we developed an open-source web-based interactive tool, Cell Distance Explorer, that allows researchers to interactively visualize cell graphs and linkages in 2D and 3D datasets. Finally, we present a hierarchical neighborhood analysis focused on the endothelial cell neighborhoods in small and large intestine datasets. This paper provides an open-access resource (datasets, tools, and analyses) to characterize and compare cell distances and cell neighborhoods in spatially resolved omics data.

Journal Article↗
PubMed2005

Sandwich type ELISA and a fluorescent cytometric microbead assay for quantitative determination of hepatitis B virus X antigen level in human sera.

The hepatitis B virus X protein (HBxAg) is responsible for severe complications of HBV infections including primary hepatocellular carcinoma. A sandwich type ELISA and a flow cytometric microbead assay for quantitative determination of serum levels of Hbx-Ag are introduced. We have previously developed monoclonal antibody families against well-conserved epitopes on HbxAg, characterized by different immunohistochemical and immunoserological techniques. Special selection of the antibody pairs provided highly sensitive and highly specific tools for quantitative immunoassay development. The resulting assays were tested on human sera (208 samples) collected from patients suffering from different clinical forms of HBV infection. The sensitivity range of the sandwich type ELISA was between 4 and 2000 ng/ml as measured on both the recombinant antigen and the sera of chronic hepatitis patients. A further flow cytometric microbead assay was established and tested in parallel with the ELISA. The quantitative results of these two immunoserological techniques were in strong correlation and they were found to be highly specific and sensitive on clinical samples. The HBxAg ELISA technique is applicable for routine clinical laboratory measurements, and our HBxAg microbead technique is recommended for complex multiparametric measurements combined with other markers.

Amino Acid Sequence↗
PubMed2004

Cytometric bead array: a multiplexed assay platform with applications in various areas of biology.

The introduction of flow cytometric bead-based technology has added a new approach for investigators to simultaneously measure multiple analytes in biological and environmental samples. This new technology allows for (1) evaluation of multiple analytes in a single sample; (2) utilization of minimal sample volumes to glean data; (3) reproducibility and results comparative with previous experiments; (4) direct comparison with existing assays; and (5) a more rapid evaluation of multiple samples in a single platform. The cytometric bead array (CBA) system enables simultaneous measurement of multiple analytes in sample volumes too small for traditional immunoassays. Results have been presented for the analysis of a variety of human cytokines. In addition, the technology allows for the design and creation of assays to measure a variety of analytes including inflammatory mediators, chemokines, immunoglobulin isotypes, intracellular signaling molecules, apoptotic mediators, adhesion molecules, and antibodies. New initiatives put forward by the Human Genome Project and the FDA require the development and use of assays for the rapid simultaneous quantitation of multiple analytes. The CBA technology provides the ability to quantify multiple proteins within a given sample, with precision and consistency.

Anaphylatoxins↗
PubMed2004

A new simple whole blood flow cytometry-based method for simultaneous identification of activated cells and quantitative evaluation of cytokines released during activation.

The multiple cellular and soluble elements of the immune system respond in a coordinated way, orchestrated by cytokines, to preserve the integrity of the organism. In this study, we describe a new and unique whole blood method that, with minimal sample manipulation, allows an overall evaluation of immune responses by simultaneously measuring cell activation and cytokine secretion. The identification of cells actively secreting cytokines is based on the stabilization of tumor necrosis factor alpha (TNFalpha) at the cell surface through the use of a specific inhibitor of the TNFalpha-converting enzyme. This inhibitor does not affect the release of cytokines other than TNFalpha and makes it possible to assess, in the same measurement, the phenotype of TNFalpha(+)-secreting cells and quantify multiple secreted cytokines by using a specific and highly sensitive flow cytometry-based bead immunoassay. Upon stimulation of normal peripheral blood samples with either phorbol 12-myristate 13 acetate (PMA) plus ionomycin or lipopolysaccharide (LPS), both the number of TNFalpha+ cells and the amount of secreted cytokines progressively increased, the former becoming detectable first. After stimulation for 3 h with PMA plus ionomycin, cellular responses were associated with surface TNFalpha expression on the majority of CD3+ T cells and secretion of Th1-associated cytokines: interferon gamma, interleukin (IL)-2, and to a lesser extent IL4. In turn, stimulation with LPS induced a response mainly by inflammatory cells. After 4 h of LPS-stimulation, the majority of CD14+ monocytes showed surface TNFalpha expression; in parallel, high amounts of soluble IL1beta, IL6, and IL8 became detectable. Likewise, stimulation of blood samples with cytomegalovirus (CMV) lysates induced viral-specific immune responses detectable in seropositive but not seronegative volunteers; such responses were associated with the detection of increased numbers of TNFalpha+ monocytes, TNFalpha+/CD8+ T cells and TNFalpha+/CD8- T lymphocytes in association with an increased secretion of IFNgamma, IL6 and TNFalpha.

Adult↗