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Biomedical subjects

E Bruno

Publications and source records attributed to E Bruno.

At least 127 records · Page 7Linked to original sources
PubMed1986

Terminal cytoplasmic maturation of human megakaryocytes in vitro.

Several studies suggest that serum factors (thrombopoietins) regulate thrombopoiesis by altering the number, size, ploidy, and maturation rate of megakaryocytes (MK). Various in vivo systems have been used to quantitate these events. In this study, an in vitro system was developed to monitor terminal cytoplasmic maturation of isolated human MK. MK enriched by elutriation, which eliminated the MK progenitors, were suspended in culture with serum from either normal donors (NABS) or patients with aplastic anemia (AAS). In cultures composed of small platelet glycoprotein-positive mononuclear cells and morphologically immature MK, development was characterized by sequential shifts in MK through morphologically recognizable maturation stages I, II, III, and IV over eight days of incubation (I and II only; then I, II, III; II, III, IV; III and IV; then IV only). Platelet formation coincided with the appearances of stage IV cells. Cultures composed of a mixture of all stages followed a similar maturation sequence, only at an accelerated rate. AAS resulted in the more rapid appearances of the mature cells in either system. This study indicates that human MK can undergo terminal cytoplasmic maturation in vitro, and that altering culture conditions (AAS for NABS) can accelerate the rate of maturation. Three major events occur during megakaryocytopoiesis: proliferation of the progenitor cells, polyploidization, and cytoplasmic maturation. Now it is possible to study the terminal steps of differentiation independent of proliferative events.

Anemia, Aplastic↗
PubMed1985

Purification and partial characterization of a megakaryocyte colony-stimulating factor from human plasma.

Human plasma obtained from patients with hypomegakaryocytic thrombocytopenia contains a factor that promotes megakaryocyte colony formation by normal human marrow cells. This megakaryocyte colony-stimulating factor was purified from such a plasma specimen. A four-step purification scheme which included ammonium sulfate precipitation, diethylaminoethyl-Sepharose chromatography, affinity chromatography on wheat germ lectin-Sepharose 6MB, and reverse-phase high performance liquid chromatography resulted in a recovery of 16.6% of the initial biological activity and an increase in specific activity by 3,489-fold. The purified protein produced a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Purified megakaryocyte colony-stimulating factor was capable of promoting megakaryocyte colony formation at a concentration of 7.6 X 10(-8) M. Megakaryocyte colony-stimulating factor was shown to be a glycoprotein and had an apparent 46,000 mol wt. Deglycosylation of megakaryocyte colony-stimulating factor by treatment with trifluoromethane-sulfonate resulted in the loss of its ability to promote megakaryocyte colony formation. Megakaryocyte colony-stimulating factor appears to be an important regulator of in vitro human megakaryocytopoiesis at the level of the colony-forming unit megakaryocyte and may be of importance physiologically.

Colony-Stimulating Factors↗
PubMed1985

In vitro hematopoiesis following induction chemotherapy for acute leukemia.

The treatment of acute nonlymphocytic leukemia results in predictable bone marrow hypoplasia and eventual cellular repopulation. In order to study this postchemotherapy repopulation, assays for hematopoietic progenitor cells were performed on bone marrow samples obtained from seven patients with acute nonlymphocytic leukemia who had received similar chemotherapeutic induction regimens. Burst-forming units (erythrocyte), colony-forming units (megakaryocyte), colony-forming units (granulocyte-macrophage), and colony-forming units (granulocyte-erythrocyte-megakaryocyte-macrophage) were cloned from human bone marrow mononuclear cells 5 and/or 10 days following completion of chemotherapy. All patients were pancytopenic and had hypocellular marrows when studied. Assays were performed 7 to 30 days prior to complete remission. Colony-forming units (granulocyte-macrophage) were equivalent to control values 5 days following chemotherapy, while burst-forming units (erythrocyte) and colony-forming units (granulocyte-erythrocyte-megakaryocyte-macrophage) were not assayable at that time. Ten days following chemotherapy, colony-forming units (granulocyte-erythrocyte-megakaryocyte-macrophage) and colony-forming units (granulocyte-macrophage) were 200 and 250% of normal controls, respectively, while burst-forming units (erythrocyte) were 29% of control values. Colony-forming units (macrophage) were 10 to 15 times normal values 10 days following chemotherapy. In contrast to colonies from normal individuals, those grown from marrow obtained following chemotherapy were frequently macroscopic and were composed of thousands of cells. Patient marrow had larger proportions of progenitor cells in S phase of the cell cycle than did normal controls. These studies suggest the presence of a stem cell in human bone marrow which is resistant to chemotherapeutic agents and has a high capacity to regenerate hematopoietic progenitor cells. The period following completion of chemotherapy for acute nonlymphocytic leukemia appears suitable for the study of the hierarchical nature of human hematopoiesis.

Acute Disease↗
PubMed1984

Isolation of human megakaryocytes by density centrifugation and counterflow centrigual elutriation.

Density centrifugation and counterflow centrifugal elutriation were utilized to prepare enriched fractions of megakaryocytes from human bone marrow aspirates. This separation method enriched megakaryocytes in initial marrow aspirates by 116- to 463-fold. Approximately 63% of megakaryocytes were recovered from the initial samples, composing 18.7% of the nucleated cells in the final preparations. Mean megakaryocyte diameters of 51.6 micron and 33.8 micron were obtained from fixed and unfixed cellular specimens, respectively. Smaller platelet glycoprotein-positive mononuclear cells with a mean diameter of 20.5 micron were found in the highest concentrations in this final fraction. These cells presumably represent immature megakaryocytic forms. Counterflow centrifugal elutriation provides a means of isolating enriched populations of marrow megakaryocytes. This accessibility to viable populations of human megakaryocytes will allow additional investigation of the terminal events of megakaryocyte development.

Bone Marrow↗
PubMed1983

In vitro studies of megakaryocytopoiesis in thrombocytotic disorders of man.

Increased numbers of bone marrow megakaryocytes and thrombocytosis are frequently observed in patients with myeloproliferative disorders (MPD). Increased marrow megakaryocytes and thrombocytosis are also noted in a variety of inflammatory and neoplastic disease leading to the phenomenon of reactive thrombocytosis (RT). The pathogenesis of this finding remains incompletely understood. Using methodology developed in our laboratory, we investigated the causative role of megakaryocyte colony-stimulating activity (Meg-CSA) in generating this phenomenon. We also examined the cloning efficiency of colony-forming units-megakaryocyte (CFU-M) and their responsiveness to an exogenous source of Meg-CSA in patients with these diseases. The results of our investigations suggest that: (1) increased production of Meg-CSA is not responsible for the megakaryocyte hyperplasia and thrombocytosis noted in these patients; (2) the intrinsic stem cell defect described in MPD appears to affect the CFU-M of these patients as well, resulting in an effective expansion of the CFU-M pool with consequent megakaryocyte hyperplasia and thrombocytosis; (3) the CFU-M of patients with MPD remain responsive to an exogenous source of Meg-CSA, suggesting that this megakaryocyte hyperplasia may not be entirely autonomous of its effects; and (4) the CFU-M pool in RT is normal both in size and responsiveness to Meg-CSA, suggesting that in these disorders, the stimulus leading to megakaryocyte hyperplasia and thrombocytosis is active at the post-CFU-M level of megakaryocyte differentiation.

Cells, Cultured↗
PubMed1982

Acquired amegakaryocytic thrombocytopenic purpura: a syndrome of diverse etiologies.

The possible pathogenetic mechanisms responsible for the production of acquired amegakaryocytic thrombocytopenic purpura (AATP) were investigated in a group of patients with this disorder. Absence of megakaryocytes and small platelet glycoprotein-bearing mononuclear cells, as determined by immunochemical staining of patient marrows with an antisera to platelet glycoproteins, suggested that the defect in AATP occurs in an early progenitor cell of the megakaryocytic lineage. Using an in vitro clonal assay system for negakaryocytic progenitor cells or megakaryocyte colony-forming units (CFU-M), the proliferative capacity of AATP marrow cells was then assessed. Bone marrow cells from three of four patients formed virtually no megakaryocyte colonies, suggesting that in these individuals the AATP was due to an intrinsic defect in the CFU-M. Bone marrow cells from an additional patient, however, formed 12% of the normal numbers of colonies, providing evidence for at least partial integrity of the CFU-M compartment in this patient. Serum specimens from all six patients were screened for their capacity to alter in vitro megakaryocyte colony formation. Five of six sera enhanced colony formation in a stepwise fashion, demonstrating appropriately elevated levels of megakaryocyte colony-stimulating activity. The serum of the patient with partial integrity of the CFU-M compartment, however, stimulated colony formation only at low concentrations. At higher concentrations, this patient's serum actually inhibited the number of colonies cloned, suggesting the presence of a humoral inhibitor to CFU-M. Serum samples from all patients were further screened for such humoral inhibitors of megakaryocyte colony formation using a cytotoxicity assay. The patient whose serum was inhibitory to CFU-M at high concentrations was indeed found to have a complement-dependent serum IgG inhibitor that was cytotoxic to allogeneic and autologous marrow CFU-M but did not alter erythroid colony formation. These-studies suggest that AATP can be due to at least two mechanisms: either an intrinsic effect at the level of the CFU-M or a circulating cytotoxic autoantibody directed against the CFU-M.

Adult↗
PubMed1981

Assay of an activity in the serum of patients with disorders of thrombopoiesis that stimulates formation of megakaryocytic colonies.

We have recently described an in vitro clonal assay system for human megakaryocyte-progenitor cells or megakaryocytic colony-forming units (CFU-M). Serum specimens from patients with quantitative platelet disorders were screened for the capacity to alter in vitro megakaryocyte-colony formation. Serum from 11 patients with hypomegakaryocytic thrombocytopenia significantly enhanced the formation of CFU-M-derived colonies (200 to 1840 per cent). Neither serum from eight patients with thrombocytopenia and normal or increased numbers of marrow megakaryocytes nor serum from 11 patients with thrombocytosis altered colony formation. This stimulatory activity has been termed megakaryocytic-colony-stimulating activity (Meg-CSA). The number of megakaryocytic colonies formed was directly proportional to the quantity of stimulatory serum added. Meg-CSA levels appeared to be inversely related to marrow megakaryocyte numbers. The variations in Meg-CSA levels that were detected in different disease states suggest that alterations in the production of this stem-cell regulator have physiologic importance.

Blood Platelet Disorders↗
PubMed1981

Regulation of human megakaryocytopoiesis. An in vito analysis.

We have recently described an assay system for human peripheral blood megakaryocyte colony-forming unit cells (CFU-M) using an anti-platelet glycoprotein antiserum probe to define megakaryocyte colonies grown in vitro. This system was applied to study the nature and regulation of human bone marrow CFU-M. In the absence of a specific megakaryocyte growth-promoting factor, 12.4 +/- 3.0 (means +/- SEM) megakaryocyte colonies were cloned per 5 X 10(5) cells cultured. Colonies were present after 6 d of incubation reaching peak numbers between days 10 and 14 and slowly decreasing thereafter. Erythropoietin in concentrations of up to 4 U/ml failed to augment colony numbers. Also failing to enhance megakaryocyte colony plating efficiency were media containing burst-promoting activity and colony-stimulating activity. A medium conditioned by human embryonic kidney cells, which has been previously demonstrated to contain thrombopoietin, also had no effect on megakaryocyte colony numbers. In contrast, sera from three patients with severe aplastic anemia produced significant enhancement of CFU-M-derived colony formation in vitro. Both the number of megakaryocyte colonies present and the number of megakaryocytes per colony were increased in proportion to the final concentration of aplastic anemia serum. In the presence of 10% aplastic anemia serum, cultured megakaryocyte colony numbers were linear with respect to the number of bone marrow mononuclear cells plated suggesting a clonal origin of each of the colonies. This in vitro assay for bone marrow CFU-M is a reliable means by which to study the regulation of human megakaryocytopoiesis. Initial data suggest that megakaryocyte production is stimulated by a factor detectable in aplastic anemia serum that may be distinct from other known hematopoietic stem cell regulators.

Anemia, Aplastic↗
PubMed1981

Immunofluorescent identification of human megakaryocyte colonies using an antiplatelet glycoprotein antiserum.

The development of a satisfactory in vitro assay system for human megakaryocyte colony forming progenitor cells has been delayed by the lack of a suitable marker for cells of human megakaryocyte lineage. For this purpose we raised an antiserum directed against a purified human platelet glycoprotein preparation. In conjunction with indirect immunofluorescent staining of human bone marrow, this antiserum labeled only platelets, megakaryocytes, and an infrequent population of small mononuclear cells. These small mononuclear cells, not otherwise identifiable as members of the megakaryocyte series, constituted 22.9% of the total fluorescein positive nucleated bone marrow cells. This antiserum was also used to label colonies cultured from human peripheral blood mononuclear cells using a modified plasma clot technique. A mean of 123 fluorescein-labeled colonies were cloned per 10(6) mononuclear cells cultured. Granulocyte-macrophage and erythroid burst colonies did not label using this method. No augmentation of colony numbers was found with varying concentrations of erythropoietin, human embryonic kidney cell conditioned media (a source of thrombopoietin), or media conditioned by a human T lymphoblast cell line (a source of both colony stimulating and burst promoting activities). Immunofluorescent labeling for platelet glycoproteins is a convenient phenotypic marker for cells of human megakaryocyte lineage useful in the study of in vitro human megakaryocytopoiesis.

Antibody Specificity↗