The Src-homology domain 2-bearing protein tyrosine phosphatase-1 inhibits antigen receptor-induced apoptosis of activated peripheral T cells.

Restimulation of Ag receptors on peripheral T lymphocytes induces tyrosine phosphorylation-based signaling cascades that evoke Fas ligand expression and induction of Fas-mediated programmed cell death. In view of the role for the Src homology domain 2-bearing protein tyrosine phosphatase-1 (SHP-1) in modulating TCR signaling, we investigated the influence of SHP-1 on TCR-mediated apoptosis by assaying the sensitivity of peripheral T cells from SHP-1-deficient viable motheaten (mev) mice to cell death following TCR restimulation. The results of these studies revealed mev peripheral T cells to be markedly more sensitive than wild-type cells to induction of cell death following TCR stimulation. By contrast, PMA/ionophore and anti-Fas Ab-induced apoptotic responses were no different in mev compared with wild-type activated cells. Enhanced apoptosis of TCR-restimulated mev lymphocytes was associated with marked increases in Fas ligand expression as compared with wild-type cells, but was almost abrogated in both mev and wild-type cells by Fas-Fc treatment. Thus, the increased sensitivity of mev T cells to apoptosis following TCR restimulation appears to reflect a TCR-driven phenomenon mediated through up-regulation of Fas-Fas ligand interaction and induction of the Fas signaling cascade. These findings, together with the hyperproliferative responses of mev peripheral T cells to initial TCR stimulation, indicate that SHP-1 modulation of TCR signaling translates to the inhibition of both T cell proliferation and activation and, as such, is likely to play a pivotal role in regulating the expansion of Ag-stimulated T cells during an immune response.     

Effects of the Escherichia coli SSB protein on the binding of Escherichia coli RecA protein to single-stranded DNA. Demonstration of competitive binding and the lack of a specific protein-protein interaction

The effect of the Escherichia coli single-stranded DNA binding (SSB) protein on the stability of complexes of E. coli RecA protein with single-stranded DNA has been investigated through direct DNA binding experiments. The effect of each protein on the binding of the other to single-stranded DNA, and the effect of SSB protein on the transfer rate of RecA protein from one single-stranded DNA molecule to another, were studied. The binding of SSB protein and RecA protein to single-stranded phage M13 DNA is found to be competitive and, therefore, mutually exclusive. In the absence of a nucleotide cofactor, SSB protein binds more tightly to single-stranded DNA than does RecA protein, whereas in the presence of ATP-gamma-S, RecA protein binds more tightly than SSB protein. In the presence of ATP, an intermediate result is obtained that depends on the type of DNA used, the temperature, and the magnesium ion concentration. When complexes of RecA protein, SSB protein and single-stranded M13 DNA are formed under conditions of slight molar excess of single-stranded DNA, no effect of RecA protein on the equilibrium stability of the SSB protein-single-stranded DNA complex is observed. Under similar conditions, SSB protein has no observed effect on the stability of the RecA protein-etheno M13 DNA complex. Finally, measurements of the rate of RecA protein transfer from RecA protein-single-stranded DNA complexes to competing single-stranded DNA show that there is no kinetic stabilization of the RecA protein-etheno M13 DNA complex by SSB protein, but that a tenfold stabilization is observed when single-stranded M13 DNA is used to form the complex. However, this apparent stabilizing effect of SSB protein can be mimicked by pre-incubation of the RecA protein-single-stranded M13 DNA complex in low magnesium ion concentration, suggesting that this effect of SSB protein is indirect and is mediated through changes in the secondary structure of the DNA. Since no direct effect of SSB protein is observed on either the equilibrium or dissociation properties of the RecA protein-single-stranded DNA complex, it is concluded that the likely effect of SSB protein in the strand assimilation reaction is on a slow step in the association of RecA protein with single-stranded DNA. Direct evidence for this conclusion is presented in the accompanying paper.     

Differences between the biliary excretion of tri[14C]methyl-1-(3-hydroxyphenyl)ammonium iodide in Wistar and Gunn rats

1. The biliary excretion of [¹⁴C]trimophonium iodide [tri[¹⁴C]methyl(3-hydroxyphenyl)ammonium iodide] was studied in normal Wistar animals and in jaundiced homozygous Gunn rats. 2. In normal Wistar rats small amounts of radioactivity (approx. 3% of the dose in 4h) were excreted in bile as two glucuronide conjugates, i.e. [¹⁴C]trimophonium glucuronide [tri[¹⁴C]methyl-(3-oxyphenyl)ammonium glucuronide] (85%) and 3-di[¹⁴C]methylaminophenyl glucuronide (10–15%). Only minor amounts of the unchanged drug were detected in bile. 3. In the homozygous jaundiced Gunn rat large amounts of radioactivity (26% of the dose in 4h) were eliminated in bile as [¹⁴C]trimophonium glucuronide alone. The quantitative excretion of this metabolite in Gunn rat bile was about ten times that in normal animals. 4. It is proposed that the biochemical lesion in the homozygous Gunn rat may indirectly affect the biliary transport of exogenous glucuronides across the canalicular membrane.     

Linkage relationships of the Wiskott-Aldrich syndrome to 10 loci in the pericentromeric region of the human X chromosome

Twelve families with Wiskott-Aldrich syndrome (WAS) were studied by linkage analysis using 10 polymorphic marker loci from the X-chromosome pericentromeric region. The results confirm close linkage of WAS to the DXS14, DXS7, TIMP, and DXZ1 loci and are consistent with previous data suggesting that WAS maps to the proximal Xp and is flanked by the DXS14 and DXS7 loci. The strongest linkage (Z = 10.19 at theta = 0.00) was found to be between WAS and the hypervariable DXS255 locus, a marker locus already mapped between DXS7 and DXS14 and which was informative for all meioses included in this analysis. Linkage of the WAS to two pericentromeric Xq loci, DXS1 and PGK1, was also established. On the basis of these results, accurate predictive testing should now be feasible in the majority of WAS families.     

Grid cellware: the first grid-enabled tool for modelling and simulating cellular processes

Modelling and simulation of complex cellular transactions involve development of platforms that understand diverse mathematical representations and are capable of handling large backend computations. Grid Cellware, an integrated modelling and simulation tool, has been developed to precisely address these niche requirements of the modelling community. Grid Cellware implements various pathway simulation algorithms along with adaptive Swarm algorithm for parameter estimation. For enchanced computational productivity Grid Cellware uses grid technology with Globus as the middleware.     

Interaction of physical training and chronic nitroglycerin treatment on blood pressure and plasma oxidant/antioxidant systems in rats

Many individuals with cardiovascular diseases undergo periodic physical conditioning with or without medication. Therefore, this study investigated the interaction of exercise training and chronic nitroglycerin treatment on blood pressure (BP) and alterations in nitric oxide (NO), glutathione (GSH), antioxidant enzyme activities and lipid peroxidation in rats. Fisher 344 rats were divided into four groups: (1) sedentary control, (2) exercise training for 8 weeks, (3) nitroglycerin (15 mg/kg, s.c. for 8 weeks) and (4) training + nitroglycerin for 8 weeks. BP, heart rate (HR) and respiratory exchange ratio (RER) were monitored weekly for 8 weeks using tail-cuff method and oxygen/carbon dioxide analyzer, respectively. The animals were sacrificed 24 h after last treatments and plasma isolated and analyzed using HPLC, ELISA and UV-VIS spectrophotometric techniques. The results show that exercise conditioning significantly enhanced NO production (p < 0.001), GSH levels (p < 0.001), GSH/GSSG ratio (p < 0.05) and the up-regulation of the activities of catalase (CAT) (p < 0.05), glutathione peroxidase (GSH-Px) (p < 0.001), and glutathione reductase (GR) (p < 0.05), and depression of lactate levels (p < 0.001) in the plasma of the rat. These biochemical changes were accompanied by a significant increase in RER (p < 0.001) without a significant change in BP and HR. Chronic nitroglycerin administration significantly increased NO levels (p < 0.05), GSH levels (p < 0.001), superoxide dismutase (SOD) activity (p < 0.05), GST activity (p < 0.05), and decreased MDA levels (p < 0.05). These biochemical changes were accompanied by a significant decrease in BP (p < 0.05) and without any significant changes in HR and RER. Interaction of exercise training and chronic nitroglycerin treatment resulted in normalization of plasma NO, MDA, lactate levels, and CAT activity. The combination of exercise and nitroglycerin significantly enhanced GSH levels (p < 0.05), and the up-regulation of SOD (p < 0.001), GSH-Px (p < 0.05), GR (p < 0.05) and GST (p < 0.001) activities. These biochemical changes were accompanied by normalization of BP and a significant increased in RER (p < 0.001). The data suggest that the interaction of physical training and chronic nitroglycerin treatment resulted in the maintenance of BP and the up-regulation of plasma antioxidant enzyme activities and GSH levels in the rat.     

Physical microenvironment of platelet membrane in acute myocardial infarction

Patients with acute myocardial infarction have more reactive platelets than those from normal population. These pathological platelets had more viscous plasma membrane, as inferred from fluorescence polarisation studies, and a lower fusion activation energy (delta E) of the membrane, reflecting a higher degree of order within lipid-lipid interactions.