SummaryThe T cell surface molecule CD28 can provide costimulatory signals that permit the full activation of T cells. Here we demonstrate that stimulation of CD28, either by B7, its natural ligand, or by the anti-CD28 monoclonal antibody 9.3, induces an association between CD28 and phosphatidylinositol 3-kinase (PI3-K) in Jurkat T cells, raising the possibility that an interaction with PI3-K contributes to CD28-mediated signaling. To examine the mechanism of the association, we synthesized tyrosine-phosphorylated oligopeptides corresponding to each of the four tyrosines in the CD28 cytoplasmic domain. When added to lysates of B7-stimulated Jurkat cells, the oligopeptide corresponding to Tyr 173 inhibits the coimmunoprecipitation of PI3-K with CD28; the other oligopeptides have no effect. Tyr 173 is contained within the sequence YMNM, a motif that is also found in the platelet-derived growth factor receptor and that, when phosphorylated, forms a high af~nity binding site for the p85 subunit of PI3-K. These observations suggest that phosphorylation of Tyr 173 may mediate the interaction between CD28 and PI3-K. However, because CD28 is not known to be phosphorylated, it remains possible that CD28 interacts with PI3-K through a mechanism independent of tyrosine phosphorylation.T ceU activation in response to antigen depends upon stimulation of the TCR and upon signals delivered through accessory T cell molecules (1, 2). In the absence of the proper costimulus, TCR signaling can induce a long-lasting anergic state in which appropriate presentation of antigen fails to elicit IL-2 production (3). Recent studies indicate that CD28 functions as a T cell accessory molecule capable of delivering costimulatory signals. CD28 binds B7 (also designated BB1), a molecule expressed by activated B cells, macrophages, and other APCs (4-6). Stimulation of CD28 prevents anergy induction in T cell clones (7). Conversely, disruption of the interaction between CD28 and B7 induces alloantigen-specific hyporesponsiveness in T cells in vitro, and blockade of B7 in vitro prolongs the survival of xenografts and allografts (8-10). Perturbation of CD28 augments TCR-induced production of lymphokines (2). The CD28 signals appear both to influence the transcription of the IL-2 gene and to enhance the stability of IL-2 transcripts (11,12). Under certain conditions, CD28 delivers activation signals to T cells in the absence of TCR ligation. In the presence of PMA, for example, the addition of soluble anti-CD28 mAbs stimulates T cell proliferation (13).The mechanism of transmembrane signaling by CD28 remains uncertain. When T cells have been pretreated with either a TCR mAb or with PMA, stimulation of CD28 leads to the appearance of tyrosine-phosphorylated proteins, suggesting that CD28 interacts with protein tyrosine kinase(s) in these primed T cells (14). The kinase(s) involved has not been identified, and the identities of the tyrosine-phosphorylated proteins are not known. Extensive crosslinking of anti-CD28 mAb elicits polyphosphoinositide turn...

BACKGROUND:The American Board of Internal Medicine (ABIM) has recommended a specific number of procedures be done as a minimum standard for ensuring competence in various medical procedures. These minimum standards were determined by consensus of an expert panel and may not reflect actual procedural comfort or competence.

Programmed cell death or apoptosis leads to the activation of the caspase-activated DNase (CAD), which degrades chromosomal DNA into nucleosomal fragments. Biochemical studies revealed that CAD forms an inactive heterodimer with the inhibitor of caspase-activated DNase (ICAD), or its alternatively spliced variant, ICAD-S, in the cytoplasm. It was initially proposed that proteolytic cleavage of ICAD by activated caspases causes the dissociation of the ICAD/CAD heterodimer and the translocation of active CAD into the nucleus in apoptotic cells. Here, we show that endogenous and heterologously expressed ICAD and CAD reside predominantly in the nucleus in nonapoptotic cells. Deletional mutagenesis and GFP fusion proteins identified a bipartite nuclear localization signal (NLS) in ICAD and verified the function of the NLS in CAD. The two NLSs have an additive effect on the nuclear targeting of the CAD–ICAD complex, whereas ICAD-S, lacking its NLS, appears to have a modulatory role in the nuclear localization of CAD. Staurosporine-induced apoptosis evoked the proteolysis and disappearance of endogenous and exogenous ICAD from the nuclei of HeLa cells, as monitored by immunoblotting and immunofluorescence microscopy. Similar phenomenon was observed in the caspase-3–deficient MCF7 cells upon expressing procaspase-3 transiently. We conclude that a complex mechanism, involving the recognition of the NLSs of both ICAD and CAD, accounts for the constitutive accumulation of CAD/ICAD in the nucleus, where caspase-3–dependent regulation of CAD activity takes place.

Introduction: Effective trauma resuscitation requires the coordinated efforts of an interdisciplinary team. Mental practice (MP) is defined as the mental rehearsal of activity in the absence of gross muscular movements and has been demonstrated to enhance acquiring technical and procedural skills. The role of MP to promote nontechnical, team-based skills for trauma has yet to be investigated. Methods: We randomized anaesthesiology, emergency medicine, and surgery residents to two-member teams randomly assigned to either an MP or control group. The MP group engaged in 20 minutes of MP, and the control group received 20 minutes of Advanced Trauma Life Support (ATLS) training. All teams then participated in a high-fidelity simulated adult trauma resuscitation and received debriefing on communication, leadership, and teamwork. Two blinded raters independently scored video recordings of the simulated resuscitations using the Mayo High Performance Teamwork Scale (MHPTS), a validated team-based behavioural rating scale. The Mann-Whitney U-test was used to assess for between-group differences. Results: Seventy-eight residents provided informed written consent and were recruited. The MP group outperformed the control group with significant effect on teamwork behaviour as assessed using the MHPTS: r = 0.67, p < 0.01. Conclusions: MP leads to improvement in team-based skills compared to traditional simulation-based trauma instruction. We feel that MP may be a useful and inexpensive tool for improving nontechnical skills instruction effectiveness for team-based trauma care.