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Biomedical subjects

S B Krantz

Publications and source records attributed to S B Krantz.

At least 91 records · Page 5Linked to original sources
PubMed1987

Identification of the receptor for erythropoietin by cross-linking to Friend virus-infected erythroid cells.

Erythropoietin (Epo) is a glycoprotein hormone that regulates erythroid development and interacts with surface receptors on developing erythroid cells. In this laboratory, a cell system with a relatively pure population of erythroid cells that respond to Epo has been developed. Immature erythroid cells are obtained from the spleens of mice infected with the anemia strain of Friend virus. The binding of 125I-labeled Epo (125I-Epo) to plasma membranes from these cells was studied in this investigation. 125I-Epo binding reached equilibrium within 20 min at 37 degrees C. Twenty percent of the receptors bound 125I-Epo with a Kd of 0.08 X 10(-9) M, while the remaining receptors bound the hormone with a Kd of 0.6 X 10(-9) M. In this study, a receptor for Epo was identified by cross-linking 125I-Epo to the receptor in intact cells and plasma membrane preparations using disuccinimidyl suberate. Polyacrylamide gel electrophoresis revealed two labeled bands of 100 and 85 kDa. The 85-kDa band was more heavily labeled (65%) than the 100-kDa band. Both bands were equally decreased when increasing amounts of unlabeled Epo were included in the binding mixture, indicating a specific interaction of 125I-Epo with the receptor.

Animals↗
PubMed1987

Variable differentiation patterns of acute myelogenous leukaemia blasts in liquid suspension cultures.

To study the ability of acute myelogenous leukaemia blasts to spontaneously differentiate in vitro, bone marrow and/or blood mononuclear cells from 63 patients with acute myelogenous leukaemia were incubated in liquid suspension cultures containing human serum, without addition of chemical inducers of differentiation. Cultures were examined weekly for disappearance or persistence of blasts, and for appearance of morphologically recognizable granulocytes and macrophages. Culture outcomes were extremely variable, ranging from lack of appearance of differentiated cells to complete disappearance of blasts with replacement by mature cells. In 50 cases an increase (25-185%) in the absolute number of differentiated cells in culture was noted during the culture period. Full differentiation was seen exclusively in cultures from 13/48 (27.1%) patients studied at diagnosis, as compared to 0/20 patients studied at relapse (P less than 0.01). The ability to fully or partially differentiate in culture was lost to a significant degree at relapse (13/20 patients) as compared to diagnosis (48/48 patients, P = 0.0001). At diagnosis full differentiation in culture was associated with a significantly higher remission rate than partial differentiation (89% versus 40%, P less than 0.02). Origination of mature cells from leukaemic rather than normal precursors was suggested by the appearance of Auer rods in mature cells in seven cases, by the correlation of types of differentiated cells seen in culture with the FAB class of leukaemia and by cytogenetic data in one case.

Adult↗
PubMed1987

Blunted erythropoietin response to anaemia in rheumatoid arthritis.

The relationship of serum immunoreactive erythropoietin to haemoglobin concentration was defined for 54 patients with rheumatoid arthritis (RA) and 41 patients with anaemia of varying aetiology (excluding pregnancy and renal insufficiency), not associated with RA. Significant inverse correlations between the logarithm of serum immunoreactive erythropoietin and the haemoglobin concentration were noted for the anaemic patients in both groups. The regression line for the RA patients had a similar slope, but a significantly lower y-intercept as compared to that for the non-RA patients. Erythropoietin levels were also significantly lower for the group of RA patients than for the group of non-RA patients when matched for comparable haemoglobin concentrations. These studies suggest that the erythropoietin response to anaemia in RA is intact but blunted relative to that for anaemia of other aetiologies. Lower levels of serum erythropoietin in anaemic RA patients may contribute to the pathogenesis of their anaemia.

Adolescent↗
PubMed1987

Purification of human erythroid colony-forming units and demonstration of specific binding of erythropoietin.

Morphological and biochemical studies of human colony-forming units-erythroid (CFU-E) have been hindered by their extreme rarity. Since burst-forming units-erythroid (BFU-E) develop into CFU-E, we used normal human blood BFU-E to generate large numbers of highly purified CFU-E in vitro. Using density centrifugation, sheep erythrocyte rosetting, surface immunoglobulin-positive cell depletion, adherence to plastic, and negative panning with monoclonal antibodies, human blood BFU-E were purified from 0.017 to 0.368%, a 22-fold purification with a 43% yield. The panned cells were cultured in methylcellulose with recombinant erythropoietin (rEp) and conditioned medium for 9 d. These cells were then collected and CFU-E were further purified using adherence and density centrifugation. This yielded almost 10(7) erythroid colony forming cells with a purity of 70 +/- 18%. Analysis of these cells by light and electron microscopy showed 94% erythroid cells. The prominent cell was a primitive blast with high nuclear/cytoplasmic ratio, dispersed nuclear chromatin and a distinct large nucleolus. The relation between the number of erythroid colonies and the number of day 9 cells plated in plasma clots was a straight line through the origin with a maximum number of erythroid colonies at 1 U/ml of rEp and no erythroid colonies without rEp. Specific binding with 125I-rEp showed that 60% of the binding was inhibited by excess pure erythropoietin (Ep), but not by albumin, fetal calf serum, and a variety of growth factors or glycoproteins. By days 12-13 of cell culture, when the progenitor cells matured to late erythroblasts, specific binding markedly declined. In this study, human CFU-E have been isolated in sufficient purity to characterize the morphology of these rare cells and in sufficient numbers to measure specific binding of Ep.

Antibodies, Monoclonal↗
PubMed1986

Transferrin receptor number, synthesis, and endocytosis during erythropoietin-induced maturation of Friend virus-infected erythroid cells.

Erythropoietin (EP) responsive Friend virus-infected erythroid cells had 200,000 steady-state binding sites for transferrin at 37 degrees C when isolated from the spleens of Friend virus-infected mice. Upon culture of these cells with EP, the synthesis of transferrin receptors increased 4- to 7-fold and the number of transferrin-binding sites per cell doubled after 24 h. However, the rate of uptake of 59Fe from transferrin remained constant at approximately 35,000 atoms of 59Fe per minute per cell during this period in culture. The amount of 125I-transferrin internalized during the steady-state binding did not change during this culture period while the transferrin bound to the surface increased 3-fold. At all stages of erythroid maturation, the maximum rate of endocytosis was determined to be 18,000 molecules of transferrin per minute per cell, and the interval that 125I-transferrin remains in the interior of the cell was calculated to be 6.9 min. After 48 h of culture with EP, the number of steady-state transferrin-binding sites was reduced in part due to the sequestration of surface receptors within the cell. The uptake of iron from transferrin was limited by the level of endocytosis of transferrin during the initial phase of culture and the number of transferrin receptors at the cell surface during the latter stages of erythroid maturation of these cells.

Animals↗
PubMed1986

Malignant histiocytoses developing in patients with B-cell lymphomas. Report of two cases.

Two patients with indolent B-cell lymphomas (small B-cell and small cleaved cell) developed a coexistent malignant histiocytosis 3 and 6 years after diagnosis of their lymphomas. In both patients, malignant histiocytosis presented as new onset of fever, weight loss, and rapidly progressive bulky disease super-imposed on a previously stable clinical course without constitutional symptoms. Both patients failed to respond to combination chemotherapy. The terminal aggressive phase of indolent B-cell lymphomas usually represents transformation of the original neoplasm to a large non-cleaved or immunoblastic B-cell histology. Malignant histiocytosis has not previously been reported as a second neoplasm in patients with B-cell lymphomas.

Adult↗
PubMed1986

Effects of ethanol on cultured human megakaryocytic progenitors.

Ethanol intoxication may result in the suppression of platelet production in human beings through direct toxicity to the bone marrow. To determine whether this suppression is due in part to a toxic effect on megakaryocytic progenitors, human bone marrow was cultured for 15 days in plasma clots, and megakaryocytic colonies were enumerated. Addition of ethanol to cultures at the beginning of incubation resulted in a reduction in megakaryocytic colonies only when the initial ethanol concentration exceeded 1 g/dl, well above physiologically tolerated levels. However, when cultures were treated with lower concentrations of ethanol (0.5 g/dl) after seven days of incubation, a reduction of megakaryocytic colony formation also occurred. These results suggest that development of a human cell more differentiated than the megakaryocytic progenitor is sensitive to ethanol toxicity at or near concentrations observed in vivo and is in accord with clinical features of the reversible alcohol-induced thrombocytopenic syndrome.

Cell Differentiation↗
PubMed1985

Primary refractory anemia: clinical and laboratory study of erythropoiesis in 16 patients.

Erythropoiesis was studied in vitro in 16 selected patients with primary refractory anemia without excess of blasts who have been followed for an average of 4.8 years. The number of erythroid colonies and bursts grown in vitro from the patients' marrows did not correlate with any parameter of their disease or their prognosis. The response of marrow erythroid precursor cells to erythropoietin was found to be normal. In no case was a serum or IgG inhibitor of erythropoiesis detected either by quantitation of heme synthesized by marrow cells or by the erythroblast cytotoxicity assay. A clinically significant response of the anemia to corticosteroids was noted in three out of 14 patients. Ten patients died during the followup period, eight of them as a consequence of their hematologic disorder. Bone marrow aplasia with pancytopenia developed in six cases, increased number of marrow blasts in two cases, myelofibrosis with myeloid metaplasia in one case and a spontaneous remission in another case. Refractory anemia without excess of blasts is a heterogeneous disorder with variable natural history including evolution into marrow aplasia.

Adult↗
PubMed1985

The Fv-2 gene controls induction of erythroid burst formation by Friend virus infection in vitro: studies of growth regulators and viral replication.

When infected in vitro with Friend virus complex, the bone marrow cells of susceptible mice form large colonies (bursts) of erythroblasts after 5 days of culture in semi-solid medium. This virus-induced burst growth occurs without the addition of erythropoietin (EP) which is normally required for erythroid progenitor growth in vitro. Erythroid progenitor cells from C57BL/6 mice infected in vitro with Friend virus are resistant to virus-induced burst growth, while cells from the B6.S mouse strain, which is congenic with C57BL/6 but possesses the 'Friend virus sensitivity' alleles at the Fv-2 locus, are susceptible. This susceptibility of the B6.S cells demonstrates that virus-induced burst growth is regulated by the Fv-2 gene. Two mechanisms by which the Fv-2 locus could control virus resistance were analysed. The possible modulation of the erythroproliferative effect of the virus by soluble substances which either promote burst growth in the sensitive strains or inhibit growth in the resistant strain was examined. Also, the possible restriction of virus infection or replication in resistant (Fv-2rr) haemopoietic cells was investigated. In a variety of experimental conditions designed to test the effects of soluble growth promoters on bone marrow cells infected in vitro, the resistance of C57BL/6 cells to erythroid burst formation could not be overcome. Neither could resistance be transferred to co-cultured sensitive cells by any soluble substances produced in culture by C57BL/6 cells. Use of haemopoietic cells from C57BL/6 animals in various physiological states of haemopoiesis also did not overcome the resistance to virus-induced burst growth. Quantification of several parameters of viral replication in whole marrow cultures or in erythroblasts from bursts of the Fv-2 sensitive and Fv-2 resistant congenic mouse strains showed that haemopoietic cells of both strains support virus growth equally well. These data suggest that Fv-2rr-mediated resistance to the erythroproliferative effect of Friend virus infection in vitro is an inherent property of an erythroid progenitor target cell and is not determined by external factors. The resistance is also not due to restriction of virus replication.

Animals↗
PubMed1985

Diphenylhydantoin-induced pure red cell aplasia.

The pathogenesis of diphenylhydantoin-induced pure red cell aplasia was investigated in the case of a 32-year-old man who developed pure red cell aplasia while he was under treatment with diphenylhydantoin. The patient's serum IgG purified from serum drawn at the time of diagnosis suppressed normal allogeneic marrow colony-forming (CFU-E) and burst-forming (BFU-E) and autologous blood BFU-E growth in vitro only in the presence of diphenylhydantoin. This IgG-diphenylhydantoin complex had no effect on CFU-GM growth in vitro. Normal IgG or patient's IgG purified from serum drawn after the remission of red cell aplasia had no effect on erythroid colony formation in vitro in the presence of diphenylhydantoin. The IgG-diphenylhydantoin complex exerted no direct cytotoxic effect on normal marrow erythroblasts, CFU-E, and BFU-E, nor did it interfere with the action of erythropoietin on marrow erythroblasts. These studies suggest that diphenylhydantoin-induced red cell aplasia is immunologically mediated through an IgG inhibitor, which requires the presence of the drug to suppress erythroid colony formation in vitro. This inhibitor seems to exert its effect on erythroid progenitors at or beyond the stage of differentiation of CFU-E, but not on erythroblasts.

Adult↗
PubMed1984

Erythropoietin stimulates 45Ca2+ uptake in Friend virus-infected erythroid cells.

It has been shown previously in this laboratory that in vitro infection of mouse bone marrow cells with the anemia strain of Friend leukemia virus leads to growth of large bursts of erythroid cells which are arrested in development prior to hemoglobin synthesis but can respond to erythropoietin (EP) to complete the late stage of erythroblast differentiation. In this study, the effect of EP on the metabolism of 45Ca2+ in these cells was examined. At 4 degrees C, an increased rate of 45Ca2+ uptake and efflux as well as an increase in the steady state level of 45Ca2+ in treated cells was observed. Exchange of 45Ca2+ from preloaded cells at 4 degrees C indicated that treatment with EP increased the size of a rapidly exchanging pool of 45Ca2+ from 5 to 12% of total 45Ca2+ in the cell. The effect of treatment with EP can be seen as increased exchange of extracellular 45Ca2+ with cellular Ca2+; however, an effect of EP on the net level of Ca2+ in these cells cannot be excluded. This investigation demonstrates one of the earliest effects of EP on erythroid cells and suggests that alterations in Ca2+ metabolism may contribute to the progression of erythroid cells to their final development.

Animals↗
PubMed1984

Specific binding of erythropoietin to spleen cells infected with the anemia strain of Friend virus.

Tritiated erythropoietin with full biological activity has been prepared, and a relatively homogeneous population of enriched progenitor cells that respond to the hormone has been generated by infection of mice with the Friend virus that produces anemia. These cells, obtained from the spleens of infected mice, develop into mature erythroblasts and erythrocytes in the presence of erythropoietin. We have measured the binding of erythropoietin to these target cells; 62% of the binding was inhibited by excess unlabeled erythropoietin, but no inhibition occurred with albumin, serum, or a variety of growth factors and glycoproteins. Apparent equilibrium was reached by 2 hr at 37 degrees C and by 3.5-4 hr at 10 degrees C. The extent of specific binding increased linearly with cell concentration. In binding experiments at 10 degrees C, apparent saturation of specific binding occurred at approximately equal to 8.7 nM. Scatchard analysis showed a single class of binding sites. The dissociation constant is 5.2 nM with an average of 660 binding sites per cell. At 0.06 nM, where most of the cells are induced to terminally differentiate in vitro, an average of only 8 erythropoietin molecules bound per cell. These studies indicate that erythropoietin attaches to specific binding sites, which are most likely receptors since they manifest high affinity and specificity, and that the biologic effect of the hormone may be produced by attachment of a very small number of erythropoietin molecules.

Anemia↗
PubMed1984

Effect of pure erythropoietin on DNA-synthesis by human marrow day 15 erythroid burst forming units in short-term liquid culture.

The effect of pure erythropoietin (EP) on human marrow day 15 burst-forming units-erythroid (BFU-E) was studied using a short-term liquid culture system containing 30% human serum. Non-adherent marrow cells were cultured in liquid medium for 0-48 h and then the number of BFU-E was assayed by the use of the plasma clot method. The addition of 1 U/ml of EP into the liquid culture medium resulted in maintenance of the number of BFU-E assayed after 24-48 h of incubation. The number of BFU-E recovered after 24-48 h culture was directly proportional to the concentration of EP present in the liquid medium. In addition, the proliferative status of BFU-E before and after exposure to EP was studied by 3H-thymidine and hydroxyurea suicide. It was found that EP doubles the percentage of BFU-E in DNA synthesis after 24-48 h of incubation in the liquid medium. This effect of EP on DNA synthesis by bone marrow day 15 BFU-E is detectable as early as 6 h after the onset of incubation and at EP concentrations as low as 0.2 U/ml of medium, a concentration present in the serum of moderately anaemic patients. The human marrow day 15 BFU-E is an EP-responsive cell and pure EP can induce it into DNA synthesis.

Adult↗
PubMed1984

Rheumatoid arthritis and pure red cell aplasia.

Three patients with severe, deforming, and long-standing rheumatoid arthritis developed pure red cell aplasia that did not remit after withdrawal of medications, ran a chronic course, and in two patients remitted only after cytotoxic immunosuppressive treatment. An IgG inhibitor of autologous erythroid colony-forming and burst-forming unit growth in vitro was found in the serum of one patient. This specific erythropoietic inhibitor persisted in lower titer in the patient's serum even after an azathioprine-induced remission of pure red cell aplasia, indicating the possible need for maintenance immunosuppressive therapy. Chronic pure red cell aplasia may be another extra-articular manifestation of rheumatoid arthritis and should be considered when severe anemia develops in the absence of blood loss or hemolysis.

Aged↗