Evolution and the Expression of Biases: Situational Value Changes the Endowment Effect

Cognitive and behavioral biases, which are widespread among humans, have recently been demonstrated in other primates, suggesting a common origin. Here we examine whether the expression of one shared bias, the endowment effect, varies as a function of context. We tested whether objects lacking inherent value elicited a stronger endowment effect (or preference for keeping the object) in a context in which the objects had immediate instrumental value for obtaining valuable resources (food). Chimpanzee subjects had opportunities to trade tools when food was not present, visible but unobtainable, and obtainable using the tools. We found that the endowment effect for these tools existed only when they were useful, showing that the effect varies as a function of context-specific utility. Such context-specific variation suggests that the variation seen in some human biases may trace predictably to behaviors that evolved to maximize gains in specific circumstances

Chimpanzees (Pan troglodytes) do not Develop Contingent Reciprocity in an Experimental Task

Chimpanzees provide help to unrelated individuals in a broad range of situations. The pattern of helping within pairs suggests that contingent reciprocity may have been an important mechanism in the evolution of altruism in chimpanzees. However, correlational analyses of the cumulative pattern of interactions over time do not demonstrate that helping is contingent upon previous acts of altruism, as required by the theory of reciprocal altruism. Experimental studies provide a controlled approach to examine the importance of contingency in helping interactions. In this study, we evaluated whether chimpanzees would be more likely to provide food to a social partner from their home group if their partner had previously provided food for them. The chimpanzees manipulated a barpull apparatus in which actors could deliver rewards either to themselves and their partners or only to themselves. Our findings indicate that the chimpanzees’ responses were not consistently influenced by the behavior of their partners in previous rounds. Only one of the 11 dyads that we tested demonstrated positive reciprocity. We conclude that contingent reciprocity does not spontaneously arise in experimental settings, despite the fact patterns of behavior in the field indicate that individuals cooperate preferentially with reciprocating partners

Outcome after steroid withdrawal in pediatric renal transplant patients receiving tacrolimus-based immunosuppression

Background. Corticosteroids have always been an integral part of immunosuppressive regimens in renal transplantation. The primary goal of this analysis was to assess the safety of steroid withdrawal in our pediatric renal transplant recipients receiving tacrolimus-based immunosuppression. Methods. Between December 1989 and December 1996, 82 renal transplantations were performed in pediatric patients receiving tacrolimus-based immunosuppression. Two of these patients lost their grafts within 3 weeks of transplantation (and were still on steroids at the time of graft loss), and were excluded from further analysis. Seventy-four patients (92.5%) were taken off prednisone a median of 5.7 months after transplantation. Of these 74, 56 (70%) remained off prednisone (OFF), and 18 (22.5%) were restarted on prednisone a median of 14.8 months after discontinuing steroids (OFF → ON). 6(7.5%) were never taken off prednisone (ON). The mean follow-up was 59±23 months. Results. The 1-, 3-, and 5-year actuarial patient survival rates in the OFF group were 100%, 98%, and 96%, respectively; in the OFF → ON group, they were 100%, 100%, and 100%, and in the ON group, they were 100%, 83%, and 83%. The 1-, 3-, and 5- year actuarial graft survival rates in the OFF group were 100%, 95%, and 82%, respectively; in the OFF → ON group, they were 100%, 89%, and 83%; and in the ON group, they were 100%, 50%, and 33%. Two of the six graft losses in the OFF group, three out of four in the OFF → ON Group, and two out of five in the ON group, were to chronic rejection. A time-dependent Cox regression analysis showed that the hazard for graft failure for those who came and stayed off prednisone was 0.178 relative to those who were never withdrawn from prednisone (P=0.005). Patients who were 10 years of age or younger were withdrawn from prednisone earlier (median: 5 months) than those older than 10 years (median: 7.3 months, P=0.02). In addition, patients who never had acute rejection were withdrawn from steroids earlier (median: 5 months) than those who had one or more episodes of acute rejection (median: 7.6 months, P=0.001). There was no effect of donor age, race, sex, recipient race, sex, cadaveric versus living donor, 48-hr graft function, panel reactive antibody, and total HLA mismatches or matches on the likelihood of being weaned off steroids. Serum creatinine at most recent follow-up in the OFF group was 1.2±0.5 mg/dl; in the OFF → ON group, it was 1.8±0.9 mg/dl, and in the ON group it was 2.0 mg/dl (P<0.003). The incidence of rejection in the OFF, OFF → ON, and ON groups was 39%, 77%, and 100%, respectively (P<0.05). Conclusion. These data suggest that steroid withdrawal in pediatric renal transplant patients receiving tacrolimus-based immunosuppression is associated with reasonable short- and medium-term patient and graft survival, and acceptable renal function. Patients who discontinue and then resume steroids had patient and graft survival rates comparable with those in patients who discontinue and stay off steroids, but had a higher serum creatinine and a higher incidence of rejection

Pediatric renal transplantation under tacrolimus-based immunosuppression

Background. Tacrolimus has been used as a primary immunosuppressive agent in adult and pediatric renal transplant recipients, with reasonable outcomes. Methods. Between December 14, 1989 and December 31, 1996, 82 pediatric renal transplantations alone were performed under tacrolimus-based immunosuppression without induction anti-lymphocyte antibody therapy. Patients undergoing concomitant or prior liver and/or intestinal transplantation were not included in the analysis. The mean recipient age was 10.6±5.2 years (range: 0.7-17.9). Eighteen (22%) cases were repeat transplantations, and 6 (7%) were in patients with panel-reactive antibody levels over 40%. Thirty-four (41%) cases were with living donors, and 48 (59%) were with cadaveric donors. The mean donor age was 27.3±14.6 years (range: 0.7-50), and the mean cold ischemia time in the cadaveric cases was 26.5±8.8 hr. The mean number of HLA matches and mismatches was 2.8±1.2 and 2.9±1.3; there were five (6%) O-Ag mismatches. The mean follow-up was 4.0±0.2 years. Results. The 1- and 4-year actuarial patient survival was 99% and 94%. The 1- and 4-year actuarial graft survival was 98% and 84%. The mean serum creatinine was 1.1±0.5 mg/all, and the corresponding calculated creatinine clearance was 88±25 ml/min/1.73 m2. A total of 66% of successfully transplanted patients were withdrawn from prednisone. In children who were withdrawn from steroids, the mean standard deviation height scores (Z-score) at the time of transplantation and at 1 and 4 years were - 2.3±2.0, -1.7±1.0, and +0.36±1.5. Eighty-six percent of successfully transplanted patients were not taking anti-hypertensive medications. The incidence of acute rejection was 44%; between December 1989 and December 1993, it was 63%, and between January 1994 and December 1996, it was 23% (P=0.0003). The incidence of steroid-resistant rejection was 5%. The incidence of delayed graft function was 5%, and 2% of patients required dialysis within 1 week of transplantation. The incidence of cytomegalovirus was 13%; between December 1989 and December 1992, it was 17%, and between January 1993 and December 1996, it was 12%. The incidence of early Epstein- Barr virus-related posttransplant lymphoproliferative disorder (PTLD) was 9%; between December 1989 and December 1992, it was 17%, and between January 1993 and December 1996, it was 4%. All of the early PTLD cases were treated successfully with temporary cessation of immunosuppression and institution of antiviral therapy, without patient or graft loss. Conclusions. These data demonstrate the short- and medium-term efficacy of tacrolimus-based immunosuppression in pediatric renal transplant recipients, with reasonable patient and graft survival, routine achievement of steroid and anti- hypertensive medication withdrawal, gratifying increases in growth, and, with further experience, a decreasing incidence of both rejection and PTLD

Draft Genome Sequences of 10 Strains of the Genus Exiguobacterium

High-quality draft genome sequences were determined for 10 Exiguobacterium strains in order to provide insight into their evolutionary strategies for speciation and environmental adaptation. The selected genomes include psychrotrophic and thermophilic species from a range of habitats, which will allow for a comparison of metabolic pathways and stress response genes

Platelet factor XIII-A regulates platelet function and promotes clot retraction and stability.

Factor XIII (FXIII) is an important proenzyme in the hemostatic system. The plasma-derived enzyme activated FXIII cross-links fibrin fibers within thrombi to increase their mechanical strength and cross-links fibrin to fibrinolytic inhibitors, specifically α2-antiplasmin, to increase resistance to fibrinolysis. We have previously shown that cellular FXIII (factor XIII-A [FXIII-A]), which is abundant in the platelet cytoplasm, is externalized onto the activated membrane and cross-links extracellular substrates. The contribution of cellular FXIII-A to platelet activation and platelet function has not been extensively studied. This study aims to identify the role of platelet FXIII-A in platelet function. We used normal healthy platelets with a cell permeable FXIII inhibitor and platelets from FXIII-deficient patients as a FXIII-free platelet model in a range of platelet function and clotting tests. Our data demonstrate that platelet FXIII-A enhances fibrinogen binding to the platelet surface upon agonist stimulation and improves the binding of platelets to fibrinogen and aggregation under flow in a whole-blood thrombus formation assay. In the absence of FXIII-A, platelets show reduced sensitivity to agonist stimulation, including decreased P-selectin exposure and fibrinogen binding. We show that FXIII-A is involved in platelet spreading where a lack of FXIII-A reduces the ability of platelets to fully spread on fibrinogen and collagen. Our data demonstrate that platelet FXIII-A is important for clot retraction where clots formed in its absence retracted to a lesser extent. Overall, this study shows that platelet FXIII-A functions during thrombus formation by aiding platelet activation and thrombus retraction in addition to its antifibrinolytic roles

Hsp90 orchestrates transcriptional regulation by Hsf1 and cell wall remodelling by MAPK signalling during thermal adaptation in a pathogenic yeast

Acknowledgments We thank Rebecca Shapiro for creating CaLC1819, CaLC1855 and CaLC1875, Gillian Milne for help with EM, Aaron Mitchell for generously providing the transposon insertion mutant library, Jesus Pla for generously providing the hog1 hst7 mutant, and Cathy Collins for technical assistance.Peer reviewedPublisher PD

Discovery of a novel member of the histamine receptor family

We report the discovery, tissue distribution and pharmacological characterization of a novel receptor, which we have named H4. Like the three histamine receptors reported previously (H1, H2, and H3), the H4 receptor is a G protein-coupled receptor and is most closely related to the H3 receptor, sharing 58% identity in the transmembrane regions. The gene encoding the H4 receptor was discovered initially in a search of the GenBank databases as sequence fragments retrieved in a partially sequenced human genomic contig mapped to chromosome 18. These sequences were used to retrieve a partial cDNA clone and, in combination with genomic fragments, were used to determine the full-length open reading frame of 390 amino acids. Northern analysis revealed a 3.0-kb transcript in rat testis and intestine. Radioligand binding studies indicated that the H4 receptor has a unique pharmacology and binds [3H]histamine (K d = 44 nM) and [3H]pyrilamine (K d = 32 nM) and several psychoactive compounds (amitriptyline, chlorpromazine, cyproheptadine, mianserin) with moderate affinity (K i range of 33–750 nM). Additionally, histamine induced a rapid internalization of HA-tagged H4 receptors in transfected human embryonic kidney 293 cells