[Acardiac fetus].

Acardiac fetus is a rare lethal fetopathy usually encountered in monozygous pregnancies. Ultrasound prenatal diagnosis has enabled an increasing number of observations and raised the need for an adequate therapeutic approach since the spontaneous prognosis for the healthy twin is unfavorable in half of the cases. An acardiac fetus was identified at 12 weeks gestation in a 36-year-old woman.

Noninvasive measurement of platelet kinetics in normal and hypertensive pregnancies.

Objective: Our purpose was to determine platelet kinetics in pregnancy by means of noninvasive reticulated platelet counts and to examine in a pilot study whether increased reticulated platelet values were associated with preeclampsia and pregnancy-induced hypertension.

Study Design: Nulliparous women had blood samples drawn at enrollment (first prenatal visit) and at 28 and 36 weeks' gestation. The percent of reticulated platelets (an index of marrow platelet release correlating with increased thrombopoiesis), platelet-associated immunoglobulin, and serum antiplatelet antibody were measured and correlated with the clinical course for each patient.

Aspirin does not inhibit adenosine diphosphate-induced platelet alpha-granule release.

The involvement of metabolites of arachidonic acid in platelet-dense granule secretion and secondary platelet-platelet interactions is well characterized. However, their role in heterotypic interactions dependent on alpha-granule secretion is less well understood. Using platelet-surface expression of P-selectin as a marker of alpha-granule secretion, we have shown that: (1) aspirin treatment of platelets at doses that block dense granule secretion does not inhibit alpha-granule secretion to adenosine diphosphate (ADP); (2) synergism between epinephrine and ADP in the induction of P-selectin expression is similarly unaffected by aspirin; and (3) the ability of P-selectin to mediate adhesion of activated platelets to monocytes and polymorphonuclear lymphocytes in whole blood is also unchanged by aspirin treatment.

Reticulated platelets in the evaluation of thrombopoietic disorders.

The laboratory diagnosis of immune platelet destruction has relied predominantly on the presence or absence of megakaryocytes in bone marrow. Recently, examination of peripheral blood platelets for high RNA content (reticulated platelets) or for elevated levels of platelet-associated IgG have been suggested as less invasive diagnostic tests. We used thiazole orange fluorescence labeling to determine the percentage of circulating reticulated platelets and two antibodies with different specificities directed against human IgG to measure platelet-associated IgG by flow cytometry in 59 patients with either immune thrombocytopenic purpura (n = 23) or chemotherapy-induced thrombocytopenia (n = 36).

Determination of the percentage of thiazole orange (TO)-positive, "reticulated" platelets using autologous erythrocyte TO fluorescence as an internal standard.

Determination of the percentage of thiazole orange (TO)-positive or "reticulated" platelets by flow cytometry has been advocated as an aid in the diagnosis of thrombocytopenic disorders. However, a reproducible method for determining control fluorescence and setting threshold values on a routine clinical basis has not been described. We used erythrocyte TO fluorescence in whole blood as an internal standard to set threshold markers for TO fluorescence of autologous, purified platelets.

Activation in stored platelet concentrates: correlation between membrane expression of P-selectin, glycoprotein IIb/IIIa, and beta-thromboglobulin release.

By using two distinct measurements of alpha-degranulation (surface P-selectin [alpha-granule membrane protein-140] expression and beta-thromboglobulin [beta-TG] release) and quantitation of glycoprotein (GP) IIb/IIIa surface density, stored platelet concentrates were evaluated to determine a) which method of measuring platelet alpha-granule release was more sensitive in detecting early platelet activation; b) whether Day 1 levels of activation predicted the extent of activation or cell lysis on Day 5 of storage; and c) whether changes in surface GPIIb/IIIa density were primarily dependent on platelet activation. By using samples from paired and unpaired units stored for 1, 3, and 5 days, four observations could be made. 1) A flow cytometric assay for the percentage of P-selectin-positive platelets was more sensitive for early detection of platelet activation than was measurement of beta-TG release.

Cardiopulmonary bypass induces leukocyte-platelet adhesion.

Cardiopulmonary bypass (CPB) has been demonstrated to activate platelets, producing an increased number of circulating platelets that have undergone alpha-granule release and express granule membrane protein-140 (GMP-140) on their surface. In vitro, GMP-140 mediates activated platelet adhesion to neutrophils (PMN) and monocytes, causing the formation of leukocyte-platelet conjugates. Using a newly developed assay that measures the percentage of circulating leukocyte-platelet conjugates in whole blood, we studied 17 patients undergoing CPB and have determined that (1) monocyte-platelet conjugates increased significantly during CPB, from 18% +/- 1.

Modulation of platelet surface adhesion receptors during cardiopulmonary bypass.

Alterations in platelet receptors critical to adhesion may play a role in the pathogenesis of the qualitative platelet defect associated with cardiopulmonary bypass. Using flow cytometry, we measured changes in the following platelet surface adhesive proteins: the von Willebrand factor receptor, glycoprotein Ib; the fibrinogen receptor, glycoprotein IIb/IIIa; the thrombospondin receptor, glycoprotein IV; the adhesive glycoprotein granule membrane protein 140, whose expression also reflects platelet activation and alpha-granule release; and, as a control, the nonreceptor protein HLA, A,B,C. Glycoprotein Ib decreased during cardiopulmonary bypass (P less than 0.

Activated and unactivated platelet adhesion to monocytes and neutrophils.

To examine the possible receptor-ligand pairs mediating adhesion of activated and "unactivated" platelets to leukocytes and the kinetics of leukocyte-platelet binding, we developed a flow cytometric assay using isolated cell fractions to accurately measure heterotypic cell adhesion, including both total leukocyte-platelet conjugate formation as well as the number of platelets bound per leukocyte. We have shown that (1) activated platelet binding to both polymorphonuclear leukocytes (PMN) and monocytes is dependent on both a specific epitope (blocked by monoclonal antibody G1) of granule membrane protein-140 (GMP-140) and the presence of divalent cations; (2) unactivated platelets bind to 87% of viable, resting monocytes but to only 34% of PMN; (3) the receptor(s) on unactivated platelets that mediate adhesion to PMN and monocytes do not require divalent cations and become nonfunctional after thrombin activation; and (4) the kinetics of platelet adhesion to monocytes and PMN indicate that monocyte adhesion is favored over neutrophil adhesion. We conclude that platelet-heterotypic cell adhesion is a dynamic process reflecting the activation status of the platelet and differential binding abilities of leukocytes.

Dynamics of leukocyte-platelet adhesion in whole blood.

The dynamics of leukocyte-platelet adhesion and platelet-platelet interaction in whole blood are not well understood. Using different platelet agonists, we have studied the whole blood kinetics of these heterotypic and homotypic interactions, the relative abilities of different leukocyte subsets to participate in platelet adhesion, and the ligands responsible for adhesion. When platelet aggregation was inhibited by the Arg-Gly-Asp-Ser (RGDS) peptide, thrombin stimulation of whole blood resulted in platelet expression of granule membrane protein 140 (GMP-140) and, simultaneously, a marked increase in the percentage of monocytes and neutrophils (PMN) binding platelets, as well as an increase in the number of platelets bound per monocyte and PMN.

Sonography of umbilical cord hematoma following genetic amniocentesis.

A case of umbilical cord hematoma, following genetic amniocentesis, is reported. Spontaneous resorption of the hematoma was observed at sonography. A normal infant was born vaginally at term.