Mika Omote

Immature platelet fraction for prediction of platelet engraftment after allogeneic stem cell transplantation.

Platelet regeneration represents an important and separate element in the engraftment process for allogeneic stem cell transplantation. Fully automated flow cytometry using blood cell counters now allows reliable quantification of reticulated platelets, expressed as the immature platelet fraction (IPF). We studied the kinetics of IPF in six patients grafted with allogeneic peripheral blood stem cell transplantation (PBSCT), 12 patients with bone marrow transplantation (BMT) and seven patients with cord blood transplantation (CBT). Preconditioning therapy caused an immediate and rapid fall in tri-lineage hematopoiesis. IPF rose transiently above 3% after a mean duration of 11 days post-PBSCT, 18 days post-BMT and 19 days post-CBT. This was 1, 4 and 13 days earlier than platelet engraftment, respectively. A linear correlation model showed a close association between the rise of IPF and tri-lineage engraftment after transplantation. IPF counting may thus provide an accessible measure of thrombopoietic activity, leading to early evaluation of marrow function and allowing monitoring of platelet regeneration.

Aberrant increase in the immature platelet fraction in patients with myelodysplastic syndrome: a marker of karyotypic abnormalities associated with poor prognosis

Objectives:  Some patients with myelodysplastic syndrome (MDS) show a marked increase in the percentage of immature platelet fraction (IPF%) despite the absence of severe thrombocytopenia. To determine the significance of such an unbalanced increase in the IPF%, we investigated the IPF% and other laboratory findings of 51 patients recently diagnosed with MDS.

Changes in molecular markers of hemostatic and fibrinolytic activation under various sampling conditions using vacuum tube samples from healthy volunteers

Molecular makers such as thrombin-antithrombin complex (TAT), prothrombin fragment 1+2 (F1+2), soluble fibrin (SF), and D-dimer, are useful markers in the diagnosis and assessment of various thrombotic conditions. These markers are measured in plasma after blood sampling. Difficult blood sampling is known to falsely elevate plasma TAT levels. However, it is not known exactly why this occurs. In the present study, we examined how levels of molecular markers of haemostatic and fibrinolytic activation change under various sampling conditions using vacuum tube samples from healthy volunteers. When blood was sampled continuously by taking 10 consecutive vacuum tube samples following application of a tourniquet, blood sampling resulted in an accurate assessment of these molecular makers. When blood was sampled continuously by taking vacuum tube samples every one minute over a total of 9 minutes to investigate possible changes in the levels of the molecular markers over time, plasma levels of TAT, SF, and F1+2 gradually increased with time. Plasma levels of TAT, F1+2, and SF increased beyond the normal range over the course of nine minutes. When blood was sampled using three alternative methods, which varied in terms of the duration of needle puncture (sampling B), duration of tourniquet use (sampling C), or both (sampling A), plasma TAT and SF levels were significantly increased with all three methods, compared to control samples. Plasma F1+2 levels were significantly increased with sampling methods A and B, compared to control samples, but not with sampling method C. On the other hand, plasma D-dimer levels were not significantly altered by any of the sampling methods. In conclusion, the results suggest that molecular markers of haemostatic and fibrinolytic activation, except for D-dimer, may be affected by sampling method, particularly the duration of needle puncturing. Therefore, care needs to be taken when using TAT, F1+2, and SF levels to diagnose and estimate activation of the coagulation system.

Beneficial effects of urokinase on lipopolysaccharide-induced disseminated intravascular coagulation in rats: focus on organ function and endothelin levels.

In a rat model of lipopolysaccharide (LPS)-induced disseminated intravascular coagulation (DIC), we used urokinase (UK) in an attempt to clarify the role of fibrinolysis and to investigate changes in plasma endothelin levels. Two kinds of experiment were performed. The first one: experimental DIC was induced by sustained infusion of 30 mg/kg LPS for 4 h via the tail vein, and two doses of UK (2.0 or 10.0 IU/g/4.5 h) were administered to rats 30 min before infusion of LPS, after which UK infusion was continued for a further 4 h. The second one: experimental DIC was induced by sustained infusion of 1 mg/kg/10 min LPS for 10 min, and two doses of UK (2.0 or 10.0 IU/g/4 h) were administered to rats at 30 min after LPS infusion. The parameters described below were determined at 4 h in the first experiment, at 4 h and 8 h in the second one. The similar results were observed in both kinds of experiment. There were no significant differences in plasma thrombin-antithrombin complex, fibrinogen or platelet number among the three DIC groups, in both kinds of experiment. Plasma levels of D-dimer were significantly increased in the LPS + higher dose of UK group when compared with the LPS group. The increased plasma plasminogen activator inhibitor (PAI) activity seen in the LPS group was significantly suppressed in the groups receiving UK (especially higher dose of UK). In addition, the increased plasma levels of creatinine and alanine aminotransferase seen in the LPS group were significantly suppressed in the groups receiving UK (especially higher dose of UK). Plasma levels of endothelin, known to be a potent vasoconstrictive agent, were markedly elevated by LPS infusion, and were significantly suppressed in the groups receiving UK of both kinds of experiment, in a dose-dependent fashion compared with LPS group. Glomerular fibrin deposition was significantly suppressed in the groups receiving UK when compared with the LPS group. No manifestations of bleeding were observed in any of the groups. Enhanced fibrinolysis and depressed endothelin induced by UK thus appear to play an important role in preventing the development of organ failure in the LPS-induced DIC model.

Significance of Decreased Plasma D-Dimer Levels following Lipopolysaccharide-Induced Disseminated Intravascular Coagulation in Rats

Plasma D-dimer (DD) is considered to be one of the most useful markers in the diagnosis and assessment of disseminated intravascular coagulation (DIC). The present study was performed to clarify the role of DD in a rat model of lipopolysac-charide (LPS)-induced DIC in which low—molecular-weight heparin (LMWH) and tranexamic acid (TA) were used. We investigated whether a relationship exists between plasma DD levels and severity of DIC. Experimental DIC was induced in rats by a sustained 4-hour infusion of 30 mg/kg LPS administered via the tail vein (LPS group). Rats received either LPS alone (LPS group) or LPS combined with 200 U/kg LMWH (LPS+LMWH group) or 50 mg/kg TA (LPS+TA group) from-30 minutes to 4 hours. Blood was drawn from each rat at 4, 8, and 12 hours. Plasma levels of thrombin-antithrombin complex (TAT) and creatinine were suppressed in the LPS+LMWH group, and less glomerular fibrin deposition was observed compared with the LPS group. On the other hand, an increased level of creatinine and increased glomerular fibrin deposition were observed in the LPS+TA group compared with the LPS group. LMWH demonstrated a protective effect against LPS-induced DIC, resulting in increased survival at 12 hours, whereas TA had the opposite effect. From these results, it appears that LMWH protects against LPS-induced DIC, but TA exacerbates LPS-induced DIC. It was interesting that plasma levels of DD were almost completely suppressed by concurrent administration of either TA or LMWH in this LPS-induced DIC model. This finding suggested that plasma levels of DD were suppressed by inhibition of coagulation (reduced deposition of fibrin) in the LPS+LMWH group and that DD levels were also suppressed by inhibition of fibrinolysis (reduced degradation of fibrin by plasmin) in the LPS+TA group. Thus care should be taken when evaluating the significance of plasma DD levels, because suppressed levels can occur with progressive fibrin deposition and worsening organ dysfunction or improvement in the course of DIC.

Antithrombotic role of nitric oxide in rats under physiological conditions.

Although sepsis-induced release of nitric oxide (NO) is known to have an antithrombotic effect, it is unknown if NO exerts this same effect under physiological conditions. We have there-fore attempted to determine whether or not NO protects against thrombus formation in normal Wistar rats injected with various amounts (0.8, 4.0, 20.0 and 100 mg/kg/4 hr) of L-NAME (N (omega)-nitro-l-arginine methyl ester), an NO synthase inhibitor, via the tail vein. Plasma levels of D-dimer fragments of fibrin were significantly increased in rats receiving L-NAME (0.21+/-0.04, 0.22+/-0.05, 0.26+/-0.07, 0.59+/-0.17 micro g/mL, means+/-SE; p<0.05, 0.05, 0.05, 0.01: L-NAME 0.8, 4, 20, 100, respectively, compared with control levels: <0.06 micro g/mL), and thrombin-anti-thrombin complex (TAT) levels were significantly increased in rats receiving 20mg/kg/4 hr or greater doses of L-NAME (4.5+/-1.1, 4.7+/-1.4, 18.7+/-4.9, 42.5+/-4.0 ng/mL, NS, NS, p<0.05, 0.01, respectively, compared with control levels: 3.8+/-1.2 ng/mL). Glomerular fibrin deposition was increased in a dose-dependent manner in rats receiving L-NAME (6.8+/-1.5, 13.9+/-1.6, 32.4+/-2.6, 49.2+/-5.2%, p<0.05, 0.05, 0.01, 0.01, respectively, com-pared with control levels: 0.0+/-0.0%). Renal dysfunction and hepatic dysfunction were observed in rats receiving 20mg/kg/4 hr or greater, or 100mg/kg/4 hr, doses of L-NAME, respectively. Mean blood pressure was also elevated in rats receiving L-NAME in a dose-dependent manner. These findings suggest that NO, in addition to regulating blood pressure, is involved in prevention of thrombus formation under physiological circumstances.

Two case reports of inherited antithrombin deficiency: a novel frameshift mutation and a large deletion including all seven exons detected using two methods.

An inherited antithrombin deficiency is an autosomal dominant thrombotic disorder. We identified two pedigrees of inherited type I antithrombin deficiency and two responsible mutations in each. A novel 21–22delAA appeared to have caused a frameshift with a premature termination at amino acid +63 in one patient and a large deletion including all seven exons was identified by multiplex ligation-dependent probe amplification in the other. Some asymptomatic relatives of the second patient had the same mutation. The present findings support the value of using more than one method of gene analysis and of studying the families of probands with inherited thrombotic disorders.