Nicholas Dainiak

Serial Assessment of Doxorubicin Cardiotoxicity with Quantitative Radionuclide Angiocardiography

We measured cardiac performance sequentially, using quantitative radionuclide angiocardiography to estimate left ventricular ejection fraction in 55 patients receiving doxorubicin for treatment of cancer. With final doxorubicin dosages greater than 350 mg per square meter, the lowest ejection fraction measured was significantly less than the initial determination. Five patients had severe cardiotoxicity (congestive heart failure). All had an ejection fraction of less than 30 per cent at the time of heart failure, and demonstrated moderate cardiotoxicity (a decline in ejection fraction by at least 15 per cent to a final value of less than 45 per cent) before clinical manifestations. Six patients with moderate toxicity in whom doxorubicin was discontinued did not have heart failure or a further decline in ejection fraction during the follow-up period. Moderate toxicity was continued, but mild toxicity (decline of ejection fraction by greater than 10 per cent, noted in 11 patients) was not well predicted. The assessment of radionuclide left ventricular ejection fraction during doxorubicin therapy may make it possible to avoid congestive heart failure.

3′-Azido-3′-deoxythymidine (AZT) inhibits proliferation in vitro of human haematopoietic progenitor cells

Peripheral blood cytopenias are a serious, dose‐limiting toxicity of AZT therapy in patients infected by HIV. To evaluate the mechanism by which cytopenias develop, AZT effects of haematopoietic differentiation and growth were measured in serum‐free, nucleoside‐depleted cultures of normal human bone marrow. In contrast to native thymidine, AZT suppressed the proliferation of erythroid, granulocyte/macrophage and primitive haematopoietic stem cells in a dose‐related and time‐dependent fashion. Relative progenitor sensitivity varied, with half‐maximal concentrations of 1–5 μM and 20–40 μM AZT for inhibition of erythroid and nonerythroid progenitor cell growth, respectively. Inhibition was observed over full ranges of concentrations of haematopoietic tissue‐specific regulators (human erythropoietin, colony‐stimulating activity, interleukin‐3 and lymphocyte conditioned medium) and of platelet‐derived growth factor (PDGF), an agent that enhances erythropoiesis in vitro via accessory marrow stromal elements. Furthermore, suppression was similar in cultures of marrow cells that were depleted of accessory populations, suggesting that its action is directed at progenitors. Finally, when deoxythymidine was added in increasing amounts to cultures with a half‐maximal concentration of AZT, inhibition was abrogated. We conclude that AZT is a potent inhibitor of haematopoiesis in vitro, and that erythroid progenitors are particularly sensitive to its action. These results may explain the marrow hypoplasia that occurs during AZT administration in vivo.

Antibody-Mediated Aplastic Anemia and Diffuse Fasciitis

IT has been suggested that aplastic anemia may be due to either a deficiency of hematopoietic stem cells or an adverse interaction between stem cells and factors in the marrow microenvironment.1 Th...

Structurally distinct plasma membrane regions give rise to extracellular membrane vesicles in normal and transformed lymphocytes

Shedding of extracellular membranes from the cell surface may be one of the means through which cells communicate with one another. In an attempt to elucidate whether cell surface exfoliation is a directed or random process, we investigated the membrane lipid and protein composition and membrane lipid order of shed extracellular membranes and of plasma membranes from which they arose in normal circulating lymphocytes and in the B-lymphoblastoid cell lines Raji, WI HF2 729 and the T-lymphoblastoid cell line Jurkat. Extracellular membranes derived from transformed cell lines were more rigid as assessed by steady state polarization of 1,6-diphenylhexatriene (DPH) and were highly enriched in cholesterol when compared with the corresponding plasma membrane. The extracellular membranes from normal lymphocytes, on the other hand, were more fluid and contained more polyunsaturated acyl chains than did the plasma membranes from these cells. Our results suggest that extracellular membranes are shed from specialized regions of the lymphocyte plasma membrane and that membrane exfoliation is likely to be a directed event.

Acetylated lipoproteins impair erythroid growth factor release from endothelial cells.

Endothelial cells are a known source of hematopoietic growth-enhancing factors, including platelet-derived growth factor (PDGF). In addition, endothelium interacts directly with plasma lipoproteins which have been shown to modulate hematopoiesis. To determine the relationship of these properties, we measured the release of an erythroid growth-enhancing factor from bovine endothelial cells under lipid-loaded and control conditions. Human bone marrow cells cultured under serum-free conditions form more erythroid, granulocyte/macrophage, and mixed hematopoietic colonies when supplemented with endothelial cell-conditioned medium (ECCM) than do controls (P less than 0.05). The activity is expressed over a wide range of erythropoietin, lymphocyte-conditioned medium (LCM), recombinant human interleukin-3, and colony-stimulating factor (CSF) concentrations, and is related to ECCM dose. In contrast, enhancing activity in ECCM prepared with 0-400 micrograms/ml acetylated low density lipoproteins (AcLDL) or native LDL is diminished to 0% in a dose-dependent fashion (relative to ECCM from unexposed cells or from cells incubated with very low density lipoproteins, P less than 0.05). Upon dilution, medium prepared from cells incubated with LDL shows a rightward shift in the dose-response curve for erythroid colony formation, while that prepared from AcLDL loaded cells demonstrates a downward shift, indicating that the inhibitory activities are kinetically distinct. Delipidation of ECCM prior to addition to marrow culture removes the inhibitory action of native LDL (P less than 0.05) but not that of AcLDL (P greater than 0.10). Immunochemical analysis suggests that the erythropoietic activity in ECCM is unrelated to that of PDGF, recombinant human CSF, and erythroid burst-promoting activity (BPA) present in LCM. This conclusion is supported by Northern blot analysis of endothelial cells using a cDNA probe for the v-sis homologue of the PDGF beta chain and by immunoprecipitation of metabolically labeled PDGF. The relative amounts of c-sis transcripts and of secreted PDGF were similar in endothelial cells incubated with or without AcLDL. We conclude that AcLDL impair the synthesis or release of an erythropoietic growth-enhancing factor(s) which is biologically distinct from PDGF and BPA present in LCM.

Heterogeneity of erythropoietin‐dependent erythrocytosis: case report in a child and synopsis of primary erythrocytosis syndromes

To investigate the pathogenesis of polycythaemia in a child with isolated, primary erythrocytosis, we measured serum erythropoietin activity and in vitro erythroid progenitor cell responsiveness to erythropoietin. Unstimulated erythropoietin activity was markedly elevated (1.8 IU/ml), and isovolaemic phlebotomy induced a four‐fold increment above this level. In contrast to findings in our index case with this syndrome, normal erythroid colony growth patterns were present in patient marrow cultures. The primary mechanism of polycythaemia in this individual is similar to that reported in the index case: an inappropriately elevated regulatory set point for erythropoietin production. Since an additional defect of progenitor cell hypersensitivity to erythropoietin is not always present, we conclude that abnormalities at single or multiple sites of the erythropoietic regulatory axis may occur in primary erythropoietin‐dependent erythrocytosis.

Chromosome analysis of isolated colony erythroblasts in chronic myelogenous leukaemia

Summary. To isolate and karyotype the progeny of erythroid progenitors, we applied colony erythroblasts derived from plasma clot marrow cultures from two healthy adults and two patients with newly diagnosed Ph1+ chronic myelogenous leukaemia (CML) to discontinuous Stractan density gradients. Erythroid colony proliferation by patient cells was increased relative to that of normal donor cells (P<0.01). ‘Endogenous’colonies appeared in patient but not in normal donor marrow cultures. Greater than 95% of nucleated cells equilibrating at 1.071 were basophilic proerythroblasts. While analysis of chromosome spreads of normal donor cells in this fraction showed normal karyotypes, cells from patient marrow cultures were Ph1+, whether cultured in the presence or absence of added erythropoietin. These findings suggest that chromosome abnormalities of erythroid progenitors may be expressed by their progeny in tissue culture, and that Stractan may be a useful supporting medium for separating colony erythroblasts for chromosome analysis.