CD40 ligand gene defects responsible for X-linked hyper-IgM syndrome

The ligand for CD40 (CD40L) is a membrane glycoprotein on activated T cells that induces B cell proliferation and immunoglobulin secretion. Abnormalities in the CD40L gene were associated with an X-linked immunodeficiency in humans [hyper-IgM (immunoglobulin M) syndrome]. This disease is characterized by elevated concentrations of serum IgM and decreased amounts of all other isotypes. CD40L complementary DNAs from three of four patients with this syndrome contained distinct point mutations. Recombinant expression of two of the mutant CD40L complementary DNAs resulted in proteins incapable of binding to CD40 and unable to induce proliferation or IgE secretion from normal B cells. Activated T cells from the four affected patients failed to express wild-type CD40L, although their B cells responded normally to wild-type CD40L. Thus, these CD40L defects lead to a T cell abnormality that results in the failure of patient B cells to undergo immunoglobulin class switching.     

The Transplant Evaluation Rating Scale. A revision of the psychosocial levels system for evaluating organ transplant candidates

Psychosocial criteria play an important role in evaluating organ transplant candidates. The Transplant Evaluation Rating Scale (TERS) classifies patients' level of adjustment in 10 aspects of psychosocial functioning that are thought to be important in adjusting to transplantation. On the basis of pretransplant psychiatric consultations, 35 liver transplant recipients received retrospective TERS ratings. Results showed significant correlations between TERS scores and visual analogue scale ratings of five outcome variables at 1-3 years posttransplant. Significant interrater reliability was also found. The TERS represents a promising instrument for transplant candidate selection as well as a valuable tool for further research.     

Characterization of lymphokine-activated killing by human peripheral blood mononuclear cells stimulated with interleukin 2 (IL-2) analogs specific for the intermediate affinity IL-2 receptor

Interleukin 2-stimulated human peripheral blood mononuclear cells (PBMC) generate lymphokine-activated killing (LAK). Using the IL-2 analogs R38A and F42K, which interact primarily with the beta and gamma subunits of the IL-2 receptor, we assessed the roles of IL-2R beta gamma and the high-affinity IL-2 receptor complex in LAK activation. Although the kinetics of LAK activation were identical, lytic activity was approximately 30% lower and proliferation was up to 55% lower in those PBMC stimulated by R38A or F42K than in those exposed to wild-type IL-2. The percentage of cells expressing cell-surface markers such as CD3, CD4, CD8, and CD16 was not significantly different after treatment with wild-type IL-2, R38A, or F42K; however, the proportion of cells expressing IL-2R alpha increased dramatically in response to stimulation by F42K (30%) compared to stimulation by either rIL-2 or R38A (15%). In addition, by Day 7 the concentration of soluble IL-2R alpha in analog-stimulated LAK culture supernatants was 50-75% less than that from wild-type IL-2-cultured cells. These findings suggest that interaction of IL-2 with IL-2R beta gamma alone is sufficient for both proliferation and the generation of LAK, and that stimulation with subunit-specific IL-2 analogs results in differential regulation of the IL-2R alpha on human LAK cells.     

32P-postlabelling studies of target tissues and bile from patients with familial adenomatous polyposis and from unaffected controls

Patients with the inherited form of colon cancer, familial adenomatous polyposis (FAP), are at high risk of developing duodenal adenomas and carcinomas. The periampullary clustering of these neoplasms suggests that bile plays a role in their development. We investigated this theory using 32P-postlabelling to detect DNA adducts. We found significantly higher adduct levels in duodenum of FAP patients than in unaffected controls, and higher levels in duodenum than stomach. Levels of adducts were significantly higher in the small bowel of rats gavaged with FAP gallbladder bile than in the small bowel of those that received control gallbladder bile. We found that bile from FAP gallbladder produced significantly more DNA adducts than control gallbladder bile when incubated with salmon sperm DNA in vitro. These results support the hypothesis that the bile of FAP patients may be involved in the development of duodenal adenomas in these patients.     

Molecular recognition of the inhibitor AG-1343 by HIV-1 protease: conformationally flexible docking by evolutionary programming

This article describes a technique for fabricating a custom acrylic resin shell that will ensure a properly designed amalgam core for the coronally debilitated, endodontically treated posterior tooth. A few simple procedures result in a core foundation for root protection, an ideal crown preparation, and a more predictable final restoration.     

A single amino acid change in Raf-1 inhibits Ras binding and alters Raf-1 function

Ras and Raf-1 are key proteins involved in the transmission of developmental and proliferative signals generated by receptor and nonreceptor tyrosine kinases. Genetic and biochemical studies demonstrate that Raf-1 functions downstream of Ras in many signaling pathways. Although Raf-1 directly associates with GTP-bound Ras, an effect of this interaction on Raf-1 activity in vivo has not been established. To examine the biological consequence of the Ras/Raf-1 interaction in vivo, we set out to identify key residues of Raf-1 required for Ras binding. In this report, we show that a single amino acid mutation in Raf-1 (Arg89 to Leu) disrupted the interaction with Ras in vitro and in the yeast two-hybrid system. This mutation prevented Ras-mediated but not tyrosine kinase-mediated enzymatic activation of Raf-1 in the baculovirus/Sf9 expression system. Furthermore, kinase-defective Raf-1 proteins containing the Arg89-->Leu mutation were no longer dominant-inhibitory or capable of blocking Ras-mediated signal transduction in Xenopus laevis oocytes. These results demonstrate that the association of Raf-1 and Ras modulates both the kinase activity and the biological function of Raf-1 and identify Arg89 as a critical residue involved in this interaction. In addition, the finding that tyrosine kinases can stimulate the enzymatic activity of Raf-1 proteins containing a mutation at the Ras-interaction site suggests that Raf-1 can be activated by Ras-independent pathways.     

Endothelin-1 levels in ischaemia, reperfusion, and haemorrhagic shock in the canine infrarenal aortic revascularisation model

Endothelin-1 (ET-1) is a potent vasoconstrictive polypeptide produced from vascular endothelial cells. The effects of ischaemia, reperfusion, and exsanguination on plasma ET-1 levels were studied and compared in the mongrel dog after infrarenal aortic cross clamping. Ischaemia produced a trend toward increased ET-1 serum levels (p < 0.07 with Bonferroni correction) that did not reach significance. Plasma ET-1 levels were significantly increased during reperfusion and even further elevations were found following exsanguination. We found a 2-3 fold increase in ET-1 levels following reperfusion (Initial 3.19 +/- 0.27 pg/ml vs. Reperfusion maximum 6.32 +/- 0.72 pg/ml, Bonferroni p < 0.01). Haemorrhagic shock was associated with a 3-4 fold increase in ET-1 levels (Initial 3.19 +/- 0.27 pg/ml vs. Exsanguination maximum 8.37 +/- 0.97 pg/ml Bonferroni p < 0.001). These data reveal that ET-1 is released during reperfusion and exsanguination and may mediate remote vascular events associated with infrarenal aortic cross clamping and acute blood loss.