**1. Introduction**

100 Blood Cell – An Overview of Studies in Hematology

1996;87:1862-1872.

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[63] Introna M, Alles VV, Castellano M, Picardi G, De Gioia L, et al. Cloning of mouse ptx3, a new member of the pentraxin gene family expressed at extrahepatic sites. Blood

> Microarray techniques allow to detect genome-wide perturbations during various treatments and to measure various responses by multitude of gene probes. Toxicogenomics, in which microarray techniques are specifically used in toxicology test, has been widely recognized as one of standard safety procedures for chemicals [1-3]. Gene expression microarrays have been used particularly for screening of genes involved in specific biological processes of interest, such as diseases or responses to environmental stimuli. Such experiments adopt the "healthy state" as a control, and identify highly expressed or suppressed genes. However, few studies deal with the features of gene expression and its variation at the "healthy state" to be influenced by species, age, sex, and individual variability. In measuring the state of disease and drug response, minimally invasive blood sampling, which allows for direct measurement of immune-responsive blood cells, excels other invasive biopsy techniques upon disease diagnostics and assessment of drug response, as well as health monitoring. Blood RNA contains an enormous amount of information on expression of messenger RNA and non coding functional RNA which remains without being translated into protein. Thus, blood RNA offers an opportunity to detect subtle change in physiological state. In this chapter, we discuss the potential of the RNA diagnosis using whole blood, showing a series of whole blood microarray experiments to evaluate variations of correlation among individuals and ages [4], dietary-induced hyperlipidemia, and other stresses using specific pathogen-free (SPF) miniature pigs.
