Physical and functional interactions between Stat5 and the tyrosine- phosphorylated receptors for erythropoietin and interleukin-3

Erythropoietin (Epo) and interleukin-3 (IL-3) stimulate activation of the Jak2 tyrosine kinase and induce tyrosine phosphorylation and activation of Stat5. In the present study, we have shown that Epo or IL- 3 stimulation induces binding of Stat5 to the tyrosine-phosphorylated Epo receptor (EpoR) or IL-3 receptor beta subunit (betaIL3), respectively, in IL-3-dependent 32D cells expressing the EpoR. The binding of Stat5 to these cytokine receptors was shown to be rapid and transient, occurring within 1 minute of stimulation of cells and significantly decreasing after 5 minutes of cell treatment. In vivo binding experiments in COS cells showed that binding of Stat5 to the EpoR was mediated through the Stat5 Src homology 2 (SH2) domain. In vitro binding studies further showed that Stat5, but not other Stats examined, bound specifically to tyrosine-phosphorylated recombinant EpoR fusion proteins. In these in vivo and in vitro binding studies, Stat5 bound, albeit to a lesser degree, to truncated EpoR mutants in which all the intracellular tyrosines except Y-343 were removed. Furthermore, EpoR-derived synthetic phosphotyrosine peptides corresponding to Y-343, Y-401, Y-431, and Y-479 inhibited the in vitro binding of Stat5. When expressed in 32D cells, a mutant EpoR in which all the intracellular tyrosines were removed by carboxy-terminal truncation showed a significantly impaired ability to induce tyrosine phosphorylation of Stat5, particularly at low concentrations of Epo, but exhibited an increased sensitivity to Epo for growth signaling as compared with the wild-type EpoR. These results indicate that Stat5 specifically and transiently binds to the EpoR through the interaction between the Stat5 SH2 domain and specific phosphorylated tyrosines, including Y-343, in the EpoR cytoplasmic domain. It was implied that betaIL3 may also have similar Stat5 docking sites. The Stat5 docking sites in the EpoR were shown to facilitate specific activation of Stat5, which, however, may not be required for the EpoR-mediated growth signaling.     

High-dose etoposide and cyclophosphamide without bone marrow transplantation for resistant hematologic malignancy

Seventy-five patients with resistant acute leukemia or lymphoma received high-dose cyclophosphamide and etoposide to explore the activity of this combination in resistant hematologic malignancies, and to determine the maximum doses of these drugs that can be combined without bone marrow transplantation. Etoposide was administered over 29 to 69 hours by continuous infusion corresponding to total doses of 1.8 g/m2 to 4.8 g/m2. Cyclophosphamide, 50 mg/kg/d, was administered on 3 or 4 consecutive days total 150 to 200 mg/kg ideal body weight). At all dose levels myelosuppression was severe but reversible. Mucosal toxicity was dose-limiting with the maximum tolerated dose level combining etoposide 4.2 g/m2 with cyclophosphamide 200 mg/kg. Continuous etoposide infusion produced stable plasma levels that were lower than would be achieved after administration by short intravenous infusion, and this could explain our ability to escalate etoposide above the previously reported maximum tolerated dose. There were 28 complete (35%) and 12 partial (16%) responses. Median duration of complete response (CR) was 3.5 months (range 1.1 to 20+). Seventeen of 40 patients (42%) with acute myelogenous leukemia (AML) achieved CR, including 6 of 20 (30%) with high-dose cytosine arabinoside resistance. We conclude that bone marrow transplantation is not required after maximum tolerated doses of etoposide and cyclophosphamide. This regimen is active in resistant hematologic neoplasms, and the occurrence of CR in patients with high-dose cytosine arabinoside-resistant AML indicates a lack of complete cross-resistance between these regimens.     

Temporal Trends Between 2010 and 2015 in Intensity of Care at End-of-Life for Patients With Chronic Illness: Influence of Age Under vs. Over 65 Years

Context

Recent analyses of Medicare data show decreases over time in intensity of end-of-life care. Few studies exist regarding trends in intensity of end-of-life care for those under 65 years of age.

Characterization and expression of the murine CD3-epsilon gene.

The receptor for antigen on the surface of T lymphocytes consists of a variable disulfide-bridged hetero-dimer (TCR-alpha/beta or -gamma/delta) associated with invariant CD3 proteins (CD3-gamma, -delta, -epsilon, and -zeta). The genes coding for the CD3 proteins are expressed in the earliest recognizable thymocytes, preceding the rearrangement and expression of the TCR genes. The isolation, characterization, and in vitro expression of the murine CD3-epsilon gene, as reported here, represent obligatory steps toward our understanding of the complex rules that govern T-cell-specific gene expression. The CD3-epsilon gene was transcribed from a non-TATA promoter and consisted of eight exons, two of which were unusually small (18 and 15 base pairs). The transmembrane exon was found to be homologous to the transmembrane exons of the CD3-gamma and CD3-delta genes. In transient-transfection experiments, a genomic fragment comprising 4 kilobases of upstream sequence and extending into the second exon sufficient to drive the expression of a reporter gene in murine T cells.     

Giant Mitochondria in a Cardiomyopathic Heart

Giant mitochondria (megamitochondria) measuring up to 14 µm in length and 3 µm in width are sporadically present in an exclusively interfibrillar position in the cardiomyocytes of a patient with restrictive cardiomyopathy. The number of cristae is augmented in the megamitochondria; these internal membranes are for the most part irregularly arrayed, but in certain giant mitochondria they run a parallel, zigzag course imparting a paracrystalline appearance to such organelles. Many of the giant mitochondria have one or several lucent, single membrane-bound inclusions that contain either &#102 - or &#103 -glycogen particles. Megamitochondria probably originate at least in part by fusion of adjacent organelles.     

Evolutionary relationship between the T3 chains of the T-cell receptor complex and the immunoglobulin supergene family.

Antigen receptors on the surface of the thymus-derived (T) lymphocytes are associated with small integral membrane proteins called the T3 (CD3) gamma, delta, epsilon, and zeta chains. After interaction of the T-cell receptor with antigen, the T3 proteins are believed to transfer an activation signal to the intracellular compartment. In previous studies, the human gamma, epsilon, and delta chains have been cloned along with the mouse delta chain, but a relationship between these sequences and known molecular families has not been established. We now report the molecular cloning and characterization of the murine T3-epsilon protein and a sequence and structural analysis of the relationships between all the T3 chains and the immunoglobulin superfamily. It is established that the T3 chains are immunoglobulin-related and a particular relationship to the neural cell adhesion molecule (N-CAM) is noted. This sequence relationship adds interest to previous findings that the T3 chains are genetically linked to N-CAM and Thy-1 antigen on band q23 of human chromosome 11.     

Acceptability of Smartphone Application-Based HIV Prevention Among Young Men Who Have Sex With Men

Young men who have sex with men (YMSM) are increasingly using mobile smartphone applications (“apps”), such as Grindr, to meet sex partners. A probability sample of 195 Grindr-using YMSM in Southern California were administered an anonymous online survey to assess patterns of and motivations for Grindr use in order to inform development and tailoring of smartphone-based HIV prevention for YMSM. The number one reason for using Grindr (29 %) was to meet “hook ups.” Among those participants who used both Grindr and online dating sites, a statistically significantly greater percentage used online dating sites for “hook ups” (42 %) compared to Grindr (30 %). Seventy percent of YMSM expressed a willingness to participate in a smartphone app-based HIV prevention program. Development and testing of smartphone apps for HIV prevention delivery has the potential to engage YMSM in HIV prevention programming, which can be tailored based on use patterns and motivations for use.     

Experimental evolution of prepared learning

Animals learn some things more easily than others. To explain this so-called prepared learning, investigators commonly appeal to the evolutionary history of stimulus–consequence relationships experienced by a population or species. We offer a simple model that formalizes this long-standing hypothesis. The key variable in our model is the statistical reliability of the association between stimulus, action, and consequence. We use experimental evolution to test this hypothesis in populations of Drosophila. We systematically manipulated the reliability of two types of experience (the pairing of the aversive chemical quinine with color or with odor). Following 40 generations of evolution, data from learning assays support our basic prediction: Changes in learning abilities track the reliability of associations during a population’s selective history. In populations where, for example, quinine–color pairings were unreliable but quinine–odor pairings were reliable, we find increased sensitivity to learning the quinine–odor experience and reduced sensitivity to learning quinine–color. To the best of our knowledge this is the first experimental demonstration of the evolution of prepared learning.For animals to learn, they must form associations among various stimuli. However, in a world full of potential stimuli, why does a special relationship form between a given stimulus and consequence in a way that actually allows the animal to predict future events? Animals seem to solve this problem by being born better able to learn some things than others. The most notable example of this special learning is the Garcia effect, published in one of the most influential papers in the history of animal learning (1). This paper showed that rats are prepared to learn some associations (e.g., taste and gastric illness) and less well prepared to learn others (e.g., light–sound combinations and gastric illness). In its day, this evidence was seen as both important and controversial, because it challenged the prevailing claims about the generality of the learning process [specifically the idea of equipotentiality (e.g., 2–6)]. We now have many examples of preparedness in learning (e.g., 5–8), although the terms used to describe this phenomenon have varied widely. Investigators have called this “belongingness” (9), species-specific defense reactions (10), biological constraints (e.g., 5, 11), adaptive specializations (8), and “preparedness” (4, 12). In response, learning theorists have advocated more general theories of learning that acknowledge an element of biological preparedness in nearly all learning (13–17).Investigators seem to agree that the explanation of preparedness must flow from evolution. Evolution by natural selection, the argument goes, has prepared animals to learn from some associations better than others because these associations had predictive power in the animal’s evolutionary past. However, within this agreed framework, explanations of specific examples of prepared learning tend to be post hoc and glib, in that we identify the “predictive power” of specific associations only after investigators have identified an example of prepared learning. Taste obviously predicts the onset of gastric illness more reliably than flashing lights, after we have Garcia''s result in hand. In response to this unsatisfying situation, several authors have argued that the study of preparedness needs a clear-cut predictive theory (3, 18, 19). Without such a predictive theory to guide them, investigators seem to have lost interest in further empirical studies of preparedness (see refs. 20–23 for possible exceptions to this pattern).Even with an agreed conceptual framework in hand, studies of the evolution of preparedness face a significant empirical hurdle. The problem is that any model of the evolution of preparedness will flow from properties of the environment that the animal’s ancestors experienced during the course of evolution. How can we know empirically whether tastes have reliably predicted gastric illness since the Paleozoic? A meaningful test of claims like this would seem to require a time machine.This paper addresses these two problems directly. First, it offers a simple model that formalizes existing ideas about the evolution of prepared learning in terms of measureable and experimentally accessible variables. Second, and most important, it uses the techniques of experimental evolution to create a selective environment in which stimuli, actions, and consequences have specific and controlled statistical relationships as our model of preparedness requires.