Fibrinogen Baltimore II: congenital hypodysfibrinogenemia with delayed release of fibrinopeptide B and decreased rate of fibrinogen synthesis.

A congenital hypodysfibrinogenemia, fibrinogen Baltimore II, was found in a young asymptomatic Caucasian female. Prothrombin, partial thromboplastin, and euglobulin lysis times were normal, as were platelet function and coagulation factor assays. Subnormal plasma fibrinogen levels were found using chronometric, rate-independent, and immunologic assay methods. Kinetic analysis of fibrinopeptide release revealed a delay in the thrombin-catalyzed release of fibrinopeptide B from the abnormal protein. Proteolysis of fibrinopeptide A by thrombin or Arvin, fibrin monomer polymerization, and fibrin polymer ligation occurred at normal rates. Catabolism of radiolabeled autologous and homologous fibrinogen was also normal, but the fibrinogen synthetic rate was less than half the normal value. Comparison of the coagulation characteristics of fibrinogen Baltimore II with those of other abnormal fibrinogens indicates that it represents a unique example of hypodysfibrinogenemia.     

Alloimmunization to platelets in heavily transfused patients with sickle cell disease

Bone marrow transplantation (BMT) is now an option for some patients with sickle cell disease (SCD). Many SCD patients are multiply transfused with red blood cells (RBCs), and may be immunized to alloantigens other than erythrocyte antigens. Because platelet refractoriness is a significant complication during BMT, we wished to determine the prevalence of alloimmunization to platelets in transfused SCD patients. Sera collected from 47 transfused and 14 untransfused SCD patients were screened for HLA and platelet-specific antibodies. Transfusion and RBC antibody histories were reviewed. A subset of the patients were rescreened 1 year later. Eighty-five percent of patients with at least 50 RBC transfusions (22 of 26), 48% of patients with less than 50 transfusions (10 of 21), and none of 14 untransfused patients demonstrated platelet alloimmunization (P < .05). Platelet alloimmunization was more prevalent than RBC alloimmunization (20% to 30%). Half of the platelet reactivity was chloroquine-elutable. Eighteen of 22 patients (82%) on chronic RBC transfusion remained platelet-alloimmunized 11 to 22 months after initial testing. In summary, 85% of heavily transfused SCD patients are alloimmunized to HLA and/or platelet-specific antigens. These patients may be refractory to platelet transfusion, a condition that would increase their risk during BMT. Leukodepletion in the transfusion support of SCD patients should be considered to prevent platelet alloimmunization.     

Endogenous soluble receptor for advanced glycation endproducts is increased in preeclampsia

OBJECTIVE: Preeclampsia is a serious complication in pregnancy with an increased future cardiovascular risk for both mother and newborn. Recently, low levels of endogenous soluble receptor for advanced glycation endproducts (esRAGE) have been associated with increased cardiovascular risk. In the current study, we investigated esRAGE serum levels in patients with preeclampsia as compared to healthy gestational age-matched controls. METHODS: esRAGE was quantified by enzyme-linked immunosorbent assay in controls and patients with preeclampsia during pregnancy (control: n = 20, preeclampsia: n = 16) and 6 months after delivery (control: n = 19, preeclampsia: n = 15). Furthermore, esRAGE was correlated to clinical and biochemical measures of renal function, glucose and lipid metabolism, as well as inflammation. RESULTS: During pregnancy, median maternal serum esRAGE concentrations were more than three-fold higher in patients with preeclampsia (200 ng/l) than in controls (63 ng/l) (P < 0.01). Furthermore, esRAGE levels positively correlated with age, blood pressure, creatinine, adiponectin, and C-reactive protein, whereas a negative correlation existed with fasting insulin and the homeostasis model assessment of insulin resistance index. In multivariate analyses, homeostasis model assessment of insulin resistance and C-reactive protein independently predicted esRAGE serum levels and explained 44% of the variation in esRAGE concentrations. Surprisingly, median esRAGE concentrations 6 months after delivery were significantly lower in former patients with preeclampsia (270 ng/l) than in controls (342 ng/l) in contrast to the results obtained during pregnancy. CONCLUSION: We showed that maternal esRAGE concentrations are significantly increased in patients with preeclampsia during pregnancy. Here, insulin sensitivity and inflammatory status independently predict serum esRAGE levels.     

Immunologic status of hemophilia patients treated with cryoprecipitate or lyophilized concentrate

We evaluated 37 patients with moderate or severe hemophilia A and six patients with severe factor IX deficiency for clinical or laboratory evidence of immune abnormalities. Patients were assigned to one of four groups according to the type of clotting factor replacement. Twenty patients had received only cryoprecipitate during the two years preceding the evaluation (group I); 11 additional patients were treated predominantly with cryoprecipitate but had also received up to nine bottles of factor VIII concentrate (group II); six patients received factor VIII concentrate (group III); six patients received factor IX concentrate (group IV). There was no clinical or laboratory evidence of immunodeficiency among the 43 patients. The mean absolute number of Th cells was normal in all patient groups, but the mean absolute number of Ts cells was increased compared with controls, both in patients treated with cryoprecipitate and in patients treated with factor VIII or factor IX concentrate. There was no correlation between the Th/Ts ratio and patient age, alanine aminotransferase level, hepatitis serology, in vitro lymphocyte function, or amount of clotting factor administered. Our observations demonstrate that the volunteer or commercial origin of clotting factor replacement cannot fully explain the alterations in lymphocyte subset distribution previously described in patients with hemophilia A.     

A statistical analysis of murine stem cell suicide techniques

The clinical application of soft agar cloning techniques for granulocyte-macrophage stem cells (CFU-C) has resulted in a number of contradictory reports that may in part be due to an inadequate data base. Growth of murine CFU-C is more reproducible and less variable than that of human CFU-C. We utilized in vivo hydroxyurea suicide of murine marrow CFU-C to address the question of how many experiments are needed to detect a specific difference with a p of less than 0.05. In 66 experiments the mean marrow CFU-C hydroxyurea kill was 23.3%; 6-9 separate experiments were necessary to detaect differences of 25%-30%. In order to be sure that a 25%-30% difference is not present, 15-21 experiments were required. Using a Dec-20 computer, 1000 samples of sample size 3, 4, or 10 were drawn from the 66 experiments; it was found that with 3 experiments and a true value of 23%, the actually observed value was below 10%, 17% of the time, and was over 40% in 10% of the samplings. In a smaller number of experiments similar results were obtained analyzing 3HTdR suicide of pluripotent stem cells and CFU- C. These data could provide a base from which to judge the validity of studies utilizing the CFU-C technique.     

Distinct roles for long-term hematopoietic stem cells and erythroid precursor cells in a murine model of Jak2V617F-mediated polycythemia vera

In the current model of the pathogenesis of polycythemia vera (PV), the JAK2V617F mutation arises in hematopoietic stem cells (HSCs) that maintain the disease, while erythroid precursor populations expand, resulting in excessive red blood cell production. We examined the role of these specific cell populations using a conditional Jak2V617F knockin murine model. We demonstrate that the most immature long-term (LT) HSCs are solely responsible for initiating and maintaining the disease in vivo and that Jak2V617F mutant LT-HSCs dominate hematopoiesis over time. When we induced Jak2V617F expression in erythropoietin receptor expressing precursor cells, the mice developed elevated hematocrit, expanded erythroid precursors, and suppressed erythropoietin levels. However, the disease phenotype was significantly attenuated compared with mice expressing Jak2V617F in LT-HSCs. In addition to developing a PV phenotype, all mice transplanted with Jak2V617F LT-HSCs underwent myelofibrotic transformation over time. These findings recapitulate the development of post-PV myelofibrosis in human myeloproliferative neoplasms. In aggregate, these results demonstrate the distinct roles of LT-HSCs and erythroid precursors in the pathogenesis of PV.     

L-leucine improves the anemia and developmental defects associated with Diamond-Blackfan anemia and del(5q) MDS by activating the mTOR pathway

Haploinsufficiency of ribosomal proteins (RPs) has been proposed to be the common basis for the anemia observed in Diamond-Blackfan anemia (DBA) and myelodysplastic syndrome with loss of chromosome 5q [del(5q) MDS]. We have modeled DBA and del(5q) MDS in zebrafish using antisense morpholinos to rps19 and rps14, respectively, and have demonstrated that, as in humans, haploinsufficient levels of these proteins lead to a profound anemia. To address the hypothesis that RP loss results in impaired mRNA translation, we treated Rps19 and Rps14-deficient embryos with the amino acid L-leucine, a known activator of mRNA translation. This resulted in a striking improvement of the anemia associated with RP loss. We confirmed our findings in primary human CD34(+) cells, after shRNA knockdown of RPS19 and RPS14. Furthermore, we showed that loss of Rps19 or Rps14 activates the mTOR pathway, and this is accentuated by L-leucine in both Rps19 and Rps14 morphants. This effect could be abrogated by rapamycin suggesting that mTOR signaling may be responsible for the improvement in anemia associated with L-leucine. Our studies support the rationale for ongoing clinical trials of L-leucine as a therapeutic agent for DBA, and potentially for patients with del(5q) MDS.     

Mild cognitive impairment and everyday functioning in older adults

The relations between mild cognitive impairment without dementia (MCI/CIND) and everyday functional abilities were examined using data from the Canadian Study of Health and Aging (CSHA). Individuals were identified with MCI/CIND if both caregiver report and clinician judgment agreed on the presence of cognitive impairment in the absence of dementia. Cross-sectional and longitudinal comparisons indicated that individuals with MCI/CIND demonstrated a broad range of impairment in instrumental activities of daily living (IADL) compared to individuals with no cognitive impairment (NCI). In cross-sectional analyses, neuropsychological measures of memory and psychomotor speed were significantly related to impairment in eight areas of functioning. In addition, poorer memory performance was significantly predictive of future impairment in money management.