Summary. Background: Drugs that block platelet-platelet and platelet-fibrin interactions via the a IIb b 3 (glycoprotein IIb/IIIa) receptor are used daily in patients undergoing percutaneous coronary interventions. Along with expected increases in spontaneous bleeding, clinical trials have revealed a surprising increase in thrombosis when these drugs are used without other anticoagulants. A better understanding of their mechanisms can minimize these risks. Objectives: This study tested the hypothesis that interventions designed to block fibrinogen binding inevitably leave the a IIb b 3 receptor in an activated state. It compared the effects on platelet function and a IIb b 3 conformation of the orally active compounds orbofiban and roxifiban, the i.v. agents eptifibatide and tirofiban, and echistatin, an arginine-glycine-aspartate (RGD) disintegrin. Methods: The integrin antagonist concentrations required to saturate platelets and to block plateletplatelet and platelet-fibrin interactions were determined by flow cytometery, aggregometry, and clot-based adhesion assays, respectively. Analytical ultracentrifugation measured each antagonist's effects on the solution structure of a IIb b 3 . Fluorescence anisotropy provided equilibrium and kinetic data for integrin:antagonist interactions. Results: Both orally active drugs bound more tightly and inhibited platelet aggregation and adhesion to fibrin more effectively than echistatin. Analytical ultracentrifugation yielded this order for perturbing a IIb b 3 conformation (priming) and promoting oligomerization (clustering):echistatin > eptifibatide > orbofiban > tirofiban > roxifiban. Roxifiban was also most effective at disrupting the rapidly forming/slowly dissociating a IIb b 3 :echistatin complex. Conclusions: Our results suggest that the same molecular mechanisms that enable glycoprotein IIb/IIIa inhibitors to bind tightly to the a IIb b 3 receptor and block fibrinogen binding contribute to their ability to perturb the resting integrin's conformation, thus limiting the safety and efficacy of both oral and i.v. integrin antagonists.

Recent studies have suggested that the presence of iron overload prior to stem cell transplantation is associated with decreased survival. Within these studies, the criteria used to define iron overload have varied considerably. Given the lack of consensus regarding the definition of iron overload in the transplant setting, we sought to methodically examine iron status among transplant patients. We studied 78 consecutive patients at risk for transfusion-related iron overload (diagnoses included AML, ALL, MDS, and aplastic anemia) who received either autologous or allogeneic stem cell transplant. Multiple measures of iron status were collected prior to transplantation and examined for their association with survival. Using this data, three potentially prognostic iron measures were identified and incorporated into a rational and unified scoring system. The resulting Transplant Iron Score assigns a point for each of the following variables: (1) greater than 25 red cell units transfused prior to transplantation; (2) serum ferritin > 1000 ng/ml; and (3) a semiquantitative bone marrow iron stain of 6+. In our cohort, the score (range 0 to 3) was more closely associated with survival than any available single iron parameter. In multivariate analysis, we observed an independent effect of iron overload on transplant survival (p = 0.01) primarily attributable to an increase in early treatment-related deaths (p = 0.02) and lethal infections. In subgroup analysis, the predictive power of the iron score was most pronounced among allogeneic transplant patients, where a high score (≥ 2) was associated with a 50% absolute decrease in survival at one year. In summary, our results lend further credence to the notion that iron overload prior to transplant is detrimental and suggest iron overload may predispose to a higher rate of lethal infections.

The processus vaginalis (PV) is a peritoneal diverticulum which forms to allow descent of the fetal testis to the scrotum. During human development fusion and obliteration of the PV often fails to occur with the result that inguinal hernias are the most prevalent congenital abnormality requiring surgery in childhood. Androgen is proposed to regulate testicular descent via the genitofemoral nerve which releases the neuropeptide calcitonin gene-related peptide (CGRP). It is possible that subsequent fusion of the PV and tissue remodelling following descent is indirectly controlled by androgen via CGRP action. An organ culture assay was developed to assess fusion of the PV taken from inguinal herniotomy in infants. Fusion was induced in vitro by CGRP but not by CGRP 8–37, CGRP 27–37 or dihydrotestosterone in equimolar concentrations. Fusion was accompanied by transformation of the epithelium, as shown by staining of intermediate filament proteins, cytokeratin and vimentin. Localization studies for CGRP receptors on 25 specimens indicated CGRP acts on mesenchymal fibroblasts but not directly on PV epithelium suggesting an indirect pathway. Hepatocyte growth factor/scatter factor was found to induce fusion of PV and may be involved as an intermediate molecule in the fusion cascade. This study represents the first approach to understanding the humoral control and underlying mechanism by which the PV fuses.

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Transfusional iron overload is common in survivors of acute leukemia and hematopoietic stem cell transplantation and might cause long-term liver dysfunction. Routine evaluation for iron overload in such patients is recommended because excess iron can be readily removed from the body via phlebotomy or chelation. Iron overload might be associated with worse survival after stem cell transplantation in these diseases. We were interested in determining whether levels of the iron binding protein ferritin or the serum transferrin receptor (TfR) were predictive for survival. In a prospective study, we examined the correlation between iron parameters at the time of transplantation and overall survival. Serum ferritin, transferrin saturation, and TfR were measured before preparative regimen on patients who underwent hematopoietic stem cell transplantation between 1999 and 2004 for the diagnosis of aplastic anemia, MDS or acute leukemia (n=79). We used the number of transfusions before transplantation as a measure of iron load. Among these iron markers, serum ferritin correlated the most with the number of transfusions, regardless of remission status. High ferritin (>1,500 ng/ml), low TfR (≤4 μg/ml) and low TfR/log ferritin ratio (≤2) were associated with shorter survival (p=0.005, 0.04, and 0.001 respectively)(Figure 1). Among acute leukemia patients in remission, there was no difference in overall survival between patients with high or low iron markers. Markers of iron excess (serum ferritin >1,500 ng/ml, TfR/log ferritin ratio ≤2) at the time of stem cell transplantation is associated with shorter survival in MDS, aplastic anemia and acute leukemia with active disease. These results demonstrate that knowledge of patient ferritin and TfR levels can aid in risk stratification. The results also suggest that patients with high levels of ferritin may benefit from iron chelation before treatment. Figure 1: Overall Survival based on iron parameters (A) Serum Ferritin (B) Serum Transferrin Receptor (C) TfR (mcg/ml) divided by log ferritin (ng/ml) Figure 1:. Overall Survival based on iron parameters (A) Serum Ferritin (B) Serum Transferrin Receptor (C) TfR (mcg/ml) divided by log ferritin (ng/ml)