The CD28 and CTLA-4 receptors associate with the serine/threonine phosphatase PP2A.

CD28 and CTLA-4 are related members of a family of T lymphocyte cell surface receptors that function to regulate T cell activation. We have found that the cytoplasmic domains of both CTLA-4 and CD28 can associate with members of the PP2A family of serine/threonine phosphatases. The association of PP2A with CD28 was negatively regulated by tyrosine phosphorylation of the CD28 cytoplasmic domain. Inhibition of PP2A activity in Jurkat leukemia T cells by treatment with okadaic acid or by expression of a dominant-negative mutant enhanced T cell activation induced by CD28 engagement. Interactions between cell surface receptors such as CTLA-4 and CD28 and serine/threonine phosphatases may represent a novel mechanism for modulating the intracellular signal transduction pathways associated with cell activation.

Regulation of cytotoxic T lymphocyte-associated molecule-4 by Src kinases.

Cytotoxic T lymphocyte-associated molecule-4 (CTLA-4) is a cell surface receptor expressed on activated T cells that can inhibit T cell responses induced by activation of the TCR and CD28. Studies with phosphorylated peptides based on the CTLA-4 intracellular domain have suggested that tyrosine phosphorylation of CTLA-4 may regulate its interactions with cytoplasmic proteins that could determine its intracellular trafficking and/or signal transduction. However, the kinase(s) that phosphorylate CTLA-4 remain uncharacterized. In this report, we show that CTLA-4 can associate with the Src kinases Fyn and Lck and that transfection of Fyn or Lck, but not the unrelated kinase ZAP70, can induce tyrosine phosphorylation of CTLA-4 on residues Y201 and Y218. A similar pattern of tyrosine phosphorylation was found in pervanadate-treated Jurkat T cells stably expressing CTLA-4. Phosphorylation of CTLA-4 Y201 in Jurkat cells correlated with cell surface accumulation of CTLA-4. CTLA-4 phosphorylation induced the association of CTLA-4 with the tyrosine phosphatase SHP-2, but not with phosphatidylinositol 3-kinase. In contrast, Lck-induced phosphorylation of CD28 resulted in the recruitment of phosphatidylinositol 3-kinase, but not SHP-2. These findings suggest that phosphorylation of CD28 and CTLA-4 by Lck activates distinct intracellular signaling pathways. The association of CTLA-4 with Src kinases and with SHP-2 results in the formation of a CTLA-4 complex with the potential to regulate T cell activation.

Ion transport processes of crustacean epithelial cells.

Epithelial cells of the gut, antennal glands, integument, and gills of crustaceans regulate the movements of ions into and across these structures and thereby influence the concentrations of ions in the hemolymph. Specific transport proteins serving cations and anions are found on apical and basolateral cell membranes of epithelia in these tissues. In recent years, a considerable research effort has been directed at elucidating their physiological and molecular properties and relating these characteristics to the overall biology of the organisms. Efforts to describe ion transport in crustaceans have focused on the membrane transfer properties of Na+/H+ exchange, calcium uptake as it relates to the molt cycle, heavy metal sequestration and detoxification, and anion movements into and across epithelial cells. In addition to defining the properties and mechanisms of cation movements across specific cell borders, work over the past 5 yr has also centered on defining the molecular nature of certain transport proteins such as the Na+/H+ exchanger in gill and gut tissues. Monovalent anion transport proteins of the gills and gut have received attention as they relate to osmotic and ionic balance in euryhaline species. Divalent anion secretion events of the gut have been defined relative to potential roles they may have in hyporegulation of the blood and in hepatopancreatic detoxification events involving complexation with cationic metals.

Effectiveness of the California 1990-1991 tobacco education media campaign.

The California Department of Health Services conducted a $28,600,000 tobacco education media campaign in 1990 and 1991. An independent evaluation of the media campaign featured four waves of data-gathering, one prior to the campaign's beginning and three at intervals thereafter. In all, 29,264 students in grades 4-12 and 6,785 adult smokers provided data for the evaluation. Through telephone interviews for adults and written questionnaires for students, these participants supplied information so that each person could be classified as exposed or unexposed to the media campaign's advertisements. Five criterion variables were used in the evaluation: campaign awareness, tobacco use, smokers' intention to quit, nonsmokers' intention to start, and attitudes toward smoking. Based chiefly on the differences between the results of waves 1 and 4, we believe the media campaign had a number of positive effects on California students. For adult smokers, the results were mixed.

An analysis of pH tolerance and substrate preference of isolated skeletal muscle mitochondria from Bufo marinus and Rana catesbeiana.

1. The effects of varying pH and substrate on isolated skeletal muscle mitochondria from Bufo marinus and Rana catesbeiana were investigated. 2. For both species, VO2 max significantly decreased at all pH < 7.3 (P < 0.05), while maximum values were observed at a pH range of 7.3-7.6 with B. marinus maintaining a greater VO2 max than R. catesbeiana. 3. Respiratory control values (RCR) decreased significantly at all pH < 6.9 for both species (P < 0.05). 4. Isolated mitochondria from both species were maintained at pH = 7.2 and O2 consumption measured under five separate substrate conditions. 5. A rank preference was established based upon state 3 and RCR values. 6. Substrate preference was identical for both species and interspecific comparisons revealed differences in state 3 respiration and coupling.

Do anti-smoking media campaigns help smokers quit?

As part of an evaluation of the 1990-91 anti-tobacco media campaign carried out by the California Department of Health Services, a study was conducted among 417 regular smokers who had quit during the period of the media campaign. In brief telephone interviews, all respondents identified up to three events or experiences that had influenced them to quit. In response to uncued questions, 6.7 percent of those interviewed indicated that they had been influenced to quit by an advertisement they had seen or heard on radio, television, or billboards. In response to direct questions about the media campaign, 34.3 percent of the respondents indicated that the media campaign's advertisement had played a part in their decision to quit. Applying the 6.7 percentage to the number of Californians who quit smoking in 1990-91, it can be estimated that for 33,000 former smokers, the anti-tobacco media advertisements were an important stimulus in their quit decision. Multiplying the 34.3 percent by the number of former California smokers who quit in 1990-91, the estimate of former smokers for whom the media campaign's advertisements played at least some part in their decision to quit rises to 173,000 persons. While causal attributions from such investigations should be made with caution, the evidence suggests that the 1990-91 campaign did influence substantial number of smokers in California to quit.

Chemically modified and unmodified anti-D (Rho) reagents in the micro Du procedure.

The ability of anti-D (Rho) reagents containing chemically modified and unmodified IgG molecules to detect fetal-maternal hemorrhages was compared using mixtures of Rh negative adult red blood cells and Rh positive cord red blood cells. No significant differences among reagents were observed in this small study. These results do confirm the reported lack of sensitivity of the micro Du method as a fetal red blood cell screening test.