Relative quantification in imaging of a peptide on a mouse brain tissue by matrix-assisted laser desorption ionization.

It is well-known that the number of analyte ions generated by matrix-assisted laser desorption ionization (MALDI) is not directly proportional to the analyte concentration at the irradiated spot. This is an obstacle to acquiring quantitatively meaningful maps for materials in a tissue by MALDI imaging. The problem worsens as the matrix suppression due to contaminants in the sample increases. In this work, we use a peptide as an example and show that we can overcome this problem by utilizing three guidelines derived from our recent studies on the generation of reproducible MALDI spectra. First is to acquire MALDI spectra under a temperature-controlled condition. Second is to keep the matrix suppression below an experimentally determined limit, and the third is to construct the image map using the peptide-to-matrix ion abundance ratio rather than the peptide ion abundance. The strategy works well for contaminated tissue samples and generates quantitatively meaningful maps. Also, it is demonstrated that a preposterous map can be generated when the peptide ion abundance is used in the construction of the map.

CT scans in young people in Northern England: trends and patterns 1993-2002.

BACKGROUND: Although CT can be greatly beneficial, its relatively high radiation doses have caused public health concerns. OBJECTIVE: To assess patterns in CT usage among patients aged less than 22 years in Northern England during the period 1993-2002. MATERIALS AND METHODS: Electronic data were obtained from radiology information systems of all nine National Health Service trusts in the region. RESULTS: A total of 38,681 scans had been performed in 20,483 patients aged less than 22 years. The number of CT examinations rose, with the steepest increase between 1997 and 2000. The number of patients scanned per year increased less dramatically, with 2.24/1,000 population aged less than 22 years having one scan or more in 1993 compared to 3.54/1,000 in 2002. This reflects an increase in the median number of scans per patient, which rose from 1 in 1993 to 2 by 1999. More than 70% of CT examinations were of the head, with the number of head examinations varying with time and patient age. CONCLUSION: The frequency of CT scans in this population more than doubled during the study period. This is partly, but not wholly, explained by an increase in the number of scans per patient.

CD22 is a functional ligand for SH2 domain-containing protein-tyrosine phosphatase-1 in primary T cells.

The intracellular Src homology 2 (SH2) domain-containing protein-tyrosine phosphatase (SHP-1) has been characterized as a negative regulator of T cell function, contributing to the definition of T cell receptor signaling thresholds in developing and peripheral mouse T lymphocytes. The activation of SHP-1 is achieved through the engagement of its tandem SH2 domains by tyrosine-phosphorylated proteins; however, the identity of the activating ligand(s) for SHP-1, within mouse primary T cells, is presently unresolved. The identification of SHP-1 ligand(s) in primary T cells would provide crucial insight into the molecular mechanisms by which SHP-1 contributes to in vivo thresholds for T cell activation. Here we present a combination of biochemical and yeast genetic analyses indicating CD22 to be a T cell ligand for the SHP-1 SH2 domains. Based on these observations we have confirmed that CD22 is indeed expressed on mouse primary T cells and capable of associating with SHP-1. Significantly, CD22-deficient T cells demonstrate enhanced proliferation in response to anti-CD3 or allogeneic stimulation. Furthermore, the co-engagement of CD3 and CD22 results in a raising of TCR signaling thresholds hence demonstrating a previously unsuspected functional role for CD22 in primary T cells.