Search PubMed⌕ Search

Biomedical subjects

E Heilmann

Publications and source records attributed to E Heilmann.

At least 19 recordsLinked to original sources
PubMed1992

A defect of platelet aggregation associated with an abnormal distribution of glycoprotein IIb-IIIa complexes within the platelet: the cause of a lifelong bleeding disorder.

A young Italian man (A.P.) has a lifelong history of bleeding from gums and mucocutaneous tissue. Electron microscopy showed a wide diversity of platelet size including giant forms. In citrated platelet-rich plasma (PRP), platelet aggregation induced by adenosine diphosphate (ADP) and other agonists was much reduced. Both secretion and clot retraction were normal. The aggregation of washed platelets with ADP was improved but remained subnormal, as was aggregation with collagen and thrombin. Fibrinogen-binding was analyzed by flow cytometry using platelets in whole blood or PRP and was markedly decreased. Crossed immunoelectrophoresis of Triton X-100 extracts of (A.P.) platelets showed that GP IIb-IIIa levels were 40% to 50% of normal. Glycoprotein (GP) IIb and GP IIIa were of usual migration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but their labeling was much reduced during lactoperoxidase-catalyzed iodination. Binding to (A.P.) platelets of four different 125I-labeled monoclonal antibodies to GP IIb-IIIa complexes was reduced to 12% to 20% of normal levels. However, when the patient's platelets were stimulated with alpha-thrombin, monoclonal antibody binding showed the same increase (approximately 20,000 sites) as normal platelets. Both flow cytometry and immunocytochemical studies showed that the distribution of residual surface GP IIb-IIIa within the total (A.P.) platelet population was heterogeneous and not related to platelet size. Staining of ultrathin sections confirmed the presence of an internal pool of GP IIb-IIIa. Monoclonal antibodies to other membrane glycoproteins bound normally to (A.P.) platelets. The patient has a selective deficiency of the surface pool of GP IIb-IIIa complexes that is manifested clinically by a mild Glanzmann's thrombasthenia-like syndrome.

Adenosine Diphosphate↗
PubMed1992

von Willebrand factor bound to glycoprotein Ib is cleared from the platelet surface after platelet activation by thrombin.

We recently reported that after activation of human platelets by thrombin, glycoprotein (GP) Ib-IX complexes are translocated to the surface-connected canalicular system (SCCS) (Blood 76:1503, 1990). As GPIb is a major receptor for von Willebrand factor (vWF) in platelet adhesion, we have now examined the consequences of thrombin activation on the organization of vWF bound to GPIb on the platelet surface. Studies were performed using monoclonal or polyclonal antibodies in either immunogold staining and electron microscopy (Au-EM) or in flow cytometry. When unstirred platelet-rich plasma was incubated with ristocetin, bound vWF was located by Au-EM as discrete masses regularly distributed over the cell surface. Platelets from a patient with Glanzmann's thrombasthenia, lacking GPIIb-IIIa complexes, gave a similar pattern, confirming that this represented binding to GPIb. That ristocetin was not precipitating vWF before their binding to the platelets was shown by the detection of similar masses on the surface of platelets of a patient with type IIB von Willebrand disease. Experiments were continued using washed normal platelets incubated in Tyrode-EDTA, the purpose of the EDTA being to limit the surface expression of endogenous vWF after platelet stimulation. Under these conditions, platelets were treated with ristocetin for 5 minutes at 37 degrees C in the presence of increasing amounts of purified vWF. This was followed by incubation with thrombin (0.5 U/mL) for periods of up to 10 minutes. Flow cytometry showed a time-dependent loss in the surface expression of vWF bound to GPIb and these changes were confirmed by Au-EM. In particular, immunogold staining performed on ultrathin sections showed that the bulk of the vWF was being cleared to internal membrane systems. Surface clearance of vWF during thrombin-induced platelet activation is a potential mechanism for regulating platelet adhesivity.

Antibodies↗
PubMed1990

Thrombin induces a rapid redistribution of glycoprotein Ib-IX complexes within the membrane systems of activated human platelets.

Previous studies have shown a decreased binding of monoclonal antibodies (MoAbs) to glycoprotein (GP) Ib-IX complexes on thrombin-stimulated platelets, but the reason for this is poorly understood. We have used (1) immunofluorescence procedures and flow cytometry, and (2) immunogold staining and electron microscopy to investigate this phenomenon. Washed platelets were incubated with alpha-thrombin, adenosine diphosphate, or ionophore A23187 for increasing lengths of time. For alpha-thrombin, but not the other agonists, flow cytometry confirmed a dose- and time-dependent decrease in the binding of MoAbs specific for GP Ib alpha (AP-1, Bx-1), GP IX (FMC 25), or to the complex itself (SZ 1). Immunoglold staining performed using standard transmission or scanning electron microscopy high-lighted surface areas devoid of bound antibody. However, a quantitatively normal immunofluorescence was restored if paraformaldehyde-fixed, thrombin-stimulated platelets were permeabilized with Triton X-100 (Sigma Chemical Co, St Louis, MO) before MoAb addition, while immunogold staining was now seen to be concentrated within the interior of the platelet. Glutaraldehyde-fixed samples were then embedded in the resin Lowicryl K4M (Taab Laboratories Equipment Ltd, Aldermaston, England) and immunogold staining performed on thin sections using a polyclonal antibody to glycocalicin. An increased presence of GP Ib-IX complexes within surface-connected membrane systems of the thrombin-stimulated platelets was confirmed. Interestingly, GP Ib-IX movement was opposite to the thrombin-induced externalization of internal pools of GP IIb-IIIa complexes and of the alpha-granule membrane GP, GMP-140.

Adenosine Diphosphate↗
PubMed1985

[Serum factors in chronic myeloid leukemia].

Mononuclear cells from the peripheral blood of healthy test persons were cultivated in a methylcellulose medium with serum samples taken from 13 patients with chronic myeloid leukemia (CML) and with osteomyelosclerosis (OMS) as well as with serum samples of 6 healthy test persons. From evaluating the proliferation of granulopoietic cells quantitatively, conclusions were made concerning the concentrations of granulopoietic stimulating substances in these sera. In all cultures with the serum of patients the number of granulopoietic cell colonies was greater than that in cultures with the serum of normal persons. The stronger proliferation of granulopoietic precursor cells in cultures with serum of patients is seen to be due to an enhanced production of the granulocyte-macrophage colony stimulating factor (GM-CSF) by leukemic cells. The differential hemograms and curves indicating the course of leukocytes in patients are compared with the corresponding results of cultures. In patients with CML an increased output of GM-CSF will apparently influence the increase in size of the granulopoietic stem cell pool, which is evident in the steep increase of those curves indicating the course of leukocytes. In patients with OMS, however, there is a discrepancy between granulopoietic serum activity and proliferation in vivo. From these investigations the hypothesis is derived that an increased synthesis of GM-CSF in patients with CML may be one of the causes underlying hyperplastic granulopoiesis. A direct advantage of leukemic cells in proliferation cannot be derived from it.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

[Investigations of iron and folate levels in serum after implantation of heart valve prostheses (author's transl)].

In 90 patients with prosthetic heart valves, the presence of iron and folate deficiencies was assessed in a double-blind study. Anemia was found in 18 cases. Average serum iron levels were below the normal range and could be incremented significantly through the administration of 193 mg Fe++ daily during a 4-week period. No evidence of folate deficiency was found.

Anemia, Hypochromic↗