Clinical observations in thrombocytopenia:

We investigated clinical and laboratory aspects in three different situations of thrombocytopenia in which an immune mechanism is active, i.e. thrombocytopenia caused by autoantibodies (thrombocytopenia induced by the anticoagulant drug heparin (HITT) and immune thrombocytopenic purpura (ITP), thrombocytopenia and platelet alloimmunization and a platelet consumption type of thrombocytopenia (thrombotic thrombocytopenic purpura (TTP). First, we prospectively studied the incidence of HITT using new, will- defined criteria of a proportional fall in the platelet count in combination with the presence of HITT antibodies, in 358 patients with cardiac or neurological complaints. The observed incidence was 0.3%. Secondly, in an evaluation of the predictive value of HLA-antibody testing for the outcome of the first HLA-matched platelet transfusion in thrombocytopenic patients who were refractory to random donor platelet transfusions and who always had received non-leukodepleted blood products in case of transfusion, we found that almost 90% of the patients with a positive HLA test can be treated with HLA matched platelets. Third, in studying ITP patients we found a strong indication that intensive immunosuppressive treatment cannot prevent but only postpone splenectomy as the standard second-line therapy. In addition, the study of serum thrombopoietin levels and platelet kinetics, pointed to an impaired regulation of thrombo- and megakaryopoiesis in ITP. Finally, it was found that splenectomy could be effective in inducing durable remissions and in the prevention of relapse in patients with TTP

Prospective multicentre cohort study of heparin-induced thrombocytopenia in acute ischaemic stroke patients

Acute ischaemic stroke patients sometimes receive heparin for treatment and/or prophylaxis of thromboembolic complications. This study was designed to elucidate the incidence and clinical features of heparin-induced thrombocytopenia (HIT) in acute stroke patients treated with heparin. We conducted a prospective multicentre cohort study of 267 patients who were admitted to three stroke centres within 7 d after stroke onset. We examined clinical data until discharge and collected blood samples on days 1 and 14 of hospitalization to test anti-platelet factor 4/heparin antibodies (anti-PF4/H Abs) using an enzyme-linked immunosorbent assay (ELISA); platelet-activating antibodies were identified by serotonin-release assay (SRA). Patients with a 4Ts score ≥4 points, positive-ELISA, and positive-SRA were diagnosed as definite HIT. Heparin was administered to 172 patients (64·4%: heparin group). Anti-PF4/H Abs were detected by ELISA in 22 cases (12·8%) in the heparin group. Seven patients had 4Ts ≥ 4 points. Among them, three patients (1·7% overall) were also positive by both ELISA and SRA. National Institutes of Health Stroke Scale score on admission was high (range, 16–23) and in-hospital mortality was very high (66·7%) in definite HIT patients. In this study, the incidence of definite HIT in acute ischaemic stroke patients treated with heparin was 1·7% (95% confidence interval: 0·4–5·0). The clinical severity and outcome of definite HIT were unfavourable

Trombotische trombocytopenische purpura in 13 Nederlandse centra: behandeling en beloop

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Cloning and identification of uts2^+ gene, involved in ubiquitin-proteasome system in fission yeast

紫外線照射により, 細胞ではDNAの損傷とその修復, 細胞周期の変化, アポトーシスなど多様な現象が引き起こされるが, 紫外線に対する細胞応答の機構には未だ不明な点が多い。我々は, 分裂酵母をモデル系として研究を行い, 短波長紫外線に対して超感受性を示すと共に温度感受性も示す変異株 (uts2-1) を得た。uts2-1は紫外線, 温度以外にも, methyl-methanesulfonate, カルシウムイオン, 重金属, 酸化ストレスなど多様なストレスに対して感受性を示した。Uts2のアミノ酸配列を解析した結果, Uts2はWD40反復構造を含む新規遺伝子であることが判明した。さらに, uts2-1の温度感受性を部分的に相補する遺伝子としてポリユビキチンをコードするubi4^+が得られた。また, uts2遺伝子破壊株は野生株に比べて細胞内ユビキチン量が著しく減少していること, およびuts2^+の導入にてプロテアソームの機能に異常をもつ変異株の表現型が相補されることが判明した。これらの結果から, Uts2はユビキチン-プロテアソーム系において, ユビキチンの供給, 消費に強い影響を与えることが示唆された。 / Ubiquitin-mediated proteolysis controls intracellular levels of various regulatory proteins. However, the underlying regulatory mechanisms controlling ubiquitin level have remained obscure. In an attempt to identify genes involved in the stress response, we screened for fission yeast mutants that showed increased sensitivity to the ultraviolet light and high temperature, and isolated a mutant, uts2-1. uts2^+ encodes a highly conserved WD protein. Disruption of uts2^+ gene caused defects, including increased sensitivity to various stresses such as heavy metals, hydrogen peroxide, methyl methanesulfonate, and high temperature, as well as reduced mating frequency. The level of mono- and poly-ubiquitin was very low in the uts2 mutant or disruptant. Consistently, the polyubiquitin gene ubi4^+ suppressed all defects associated with loss uts2^+ gene. Overexpression of C-terminal half of Uts2 resulted in aberrant elongated cell morphologies, and increased intracellular ubiquitin level. These results suggest that shortage of ubiquitin caused the pleiotropic defects of uts2 mutant and that Uts2 functions as a key regulator of ubiquitin metabolism