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.     

Two dimensional Doppler echocardiographic/M mode echocardiographic and phonocardiographic method for study of extracardiac heterograft valved conduits in the right ventricular outflow tract position

Significant concern exists over the long-term results of right ventricular outflow tract repair using heterograft valved conduits. Because these conduits and valves are difficult to image using ultrasound, a serially applicable two dimensional Doppler echocardiographic, M mode echocardiographic and phonocardiographic method for noninvasive investigation was developed and applied in 15 children. The method provides two dimensional echocardiographic imaging of valve contour and motion, as well as M mode and phonocardiographic analysis and quantitative range-gated Doppler information about the timing of flow through the conduit. Conduit diameter in two dimensional echocardiographic images correlated well with known conduit size (r = +0.96). A thickened and stenosed heterograft valve was predicted in two patients before hemodynamic investigation. This new method provides serially obtainable information to aid in the management of children and infants with a valved conduit placed for repair of congenital heart malformations and aids in planning the timing of hemodynamic follow-up studies.     

Antiplatelet or anticoagulant therapy after coronary artery bypass surgery. A meta-analysis of clinical trials

PURPOSE: To determine the efficacy of antiplatelet or anti-coagulant therapy in preventing graft occlusions after coronary artery bypass surgery. DATA IDENTIFICATION: Studies published from 1966 to 1988 were identified through a computerized search using MEDLINE, by searching the bibliographies of all identified articles, and by consulting with the cardiologists and cardiothoracic surgeons in the Veterans Administration Cooperative Study Group on Antiplatelet Therapy After Coronary Artery Bypass Surgery. STUDY SELECTION: All studies selected were randomized, controlled clinical trials comparing at least one active drug with a placebo or nonplacebo control group. DATA EXTRACTION: Key data were extracted from each article, including the percentage of patients in each treatment group with one or more grafts occluded, the percentage of patients with completed postoperative catheterizations, timing of postoperative catheterization, and timing of start of treatment. These data were easily obtained from each article and did not require multiple observers. RESULTS OF DATA ANALYSIS: All studies had positive treatment-effect sizes in favor of active treatment, although some studies did not achieve statistical significance. A meta-analysis combining all treatment effects clearly shows that active treatment is beneficial (overall effect size = 0.30; CI, 0.21 to 0.38). Efficacy improves with early initiation of treatment. CONCLUSIONS: Early initiation of antiplatelet or anticoagulant drugs reduces the incidence of graft occlusions after coronary artery bypass surgery.     

MRI volume of the medial frontal cortex predicts financial capacity in patients with mild Alzheimer’s disease

Persons with mild Alzheimer’s disease (AD) have significant deficits in financial abilities. This study examined the relationship between brain structure volumes, cognition, and financial capacity in patients with mild AD. Sixteen mild AD patients and 16 older adult comparisons completed the Financial Capacity Instrument (FCI), a psychometric measure of financial abilities, and also underwent magnetic resonance imaging (MRI) to obtain volumes of the bilateral hippocampi, angular gyri, precunei, and medial and dorsolateral frontal cortices. Mild AD patients performed significantly below comparisons on the FCI and had significantly smaller hippocampi. Among mild AD patients, FCI performance was moderately correlated with frontal (medial and dorsolateral frontal cortex) and posterior (angular gyri and precunei) cortical volumes. Stepwise regression demonstrated that medial frontal cortex volume predicted FCI score. The relationship between medial frontal cortex volume and overall FCI score was partially mediated by two measures of simple attention (DRS Attention, DRS Construction). The findings suggest that medial frontal cortex atrophy and associated declines in simple attention play an increasingly important role in declining financial skills in patients with mild AD.     

Posttraumatic stress disorder and odds of major invasive procedures among U.S. Veterans Affairs patients

Objectives

Although individuals with posttraumatic stress disorder (PTSD) are at heightened risk for several serious health conditions, research has not examined how having PTSD impacts receipt of invasive procedures that may alleviate these problems. We examined whether PTSD, after controlling for major depression, was associated with odds of receiving common types of major invasive procedures, and whether race, ethnicity, and gender was associated with odds of procedures.

Methods

Veterans Health Administration patients with PTSD and/or depression were age-matched with patients without these disorders. The odds of invasive hip/knee, digestive system, coronary artery bypass graft/percutaneous coronary intervention (CABG/PCI), and vascular procedures during FY2006–2009 were modeled for the full sample of 501,489 patients and for at-risk subsamples with medical conditions alleviated by the procedures examined.

Results

Adjusting for demographic covariates and medical comorbidity, PTSD without depression was associated with decreased odds of all types of procedures (odds ratios [OR] range 0.74–0.82), as was depression without PTSD (OR range 0.59–0.77). In analyses of at-risk patients, those with PTSD only were less likely to undergo hip/knee (OR = 0.78) and vascular procedures (OR = 0.73) but not CABG/PCI. African-Americans and women at-risk patients were less likely to undergo hip/knee, vascular, and CABG/PCI procedures (OR range 0.31–0.82).

Conclusion

With the exception of CABG/PCI among at-risk patients, Veterans with PTSD and/or depression were less likely to undergo all types of procedures examined. Future studies should examine the reasons for this disparity and whether it is associated with subsequent adverse outcomes.