Search PubMed⌕ Search

Biomedical subjects

J W Adamson

Publications and source records attributed to J W Adamson.

At least 109 records · Page 6Linked to original sources
PubMed1987

Mechanisms of thrombocytopenia in chronic autoimmune thrombocytopenic purpura. Evidence of both impaired platelet production and increased platelet clearance.

Mechanisms of thrombocytopenia were studied in 38 patients with mild to moderately severe chronic autoimmune thrombocytopenia (AITP). 51Cr and 111In-labeled autologous platelet turnover studies and in vitro analysis of committed megakaryocyte progenitors (CFU-Meg) were used as independent measures of platelet production. Autologous 111In-labeled platelet localization studies were performed to assess platelet clearance. Although there was no increase in the frequency of marrow CFU-Meg, a specific increase in the CFU-Meg [3H]TdR suicide rate was seen which was inversely correlated with the platelet count (P less than 0.001). Platelet turnover studies showed significant numbers of patients had inappropriate thrombopoietic responses to their reduced platelet counts. Platelet-associated antibody levels correlated inversely with platelet turnover suggesting that antiplatelet antibody impairs platelet production. The circulating platelet count was best predicted by an index relating platelet production (i.e., turnover) to the spleen-liver platelet clearance that correlated directly with platelet survival (P less than 0.001). In summary, both depressed platelet production and increased platelet clearance by the liver and spleen contribute to the thrombocytopenia of AITP.

Autoantibodies↗
PubMed1986

Pure red cell aplasia: response to therapy with anti-thymocyte globulin.

Pure red cell aplasia (PRCA) results from the failure of erythrocyte differentiation and may respond to immunosuppressive therapies. We have treated nine patients with PRCA refractory to steroids and/or cyclophosphamide with anti-thymocyte globulin (ATG). Six patients had normal numbers of erythroid bursts (from erythroid burst-forming units) or erythroid colonies (from erythroid colony-forming units) detectable in vitro, and all responded to therapy with ATG. In vitro studies suggested T-cell inhibition of erythropoiesis in four of these six patients and humorally mediated erythroid suppression in one. In three individuals, virtually no erythroid progenitors were detected in marrow culture. None of these patients responded to ATG. Myelofibrosis, 5q- chromosomal abnormality, or the subsequent development of thrombocytopenia in these individuals suggested that PRCA resulted from an intrinsic stem cell disorder. Our studies demonstrate that ATG is effective therapy for PRCA, and it may be especially useful in children or other patients in whom alkylating agents are not appropriate. We also confirm that erythroid growth in marrow culture predicts those patients who will respond to ATG or other immunosuppressive therapies.

Adolescent↗
PubMed1986

Hematopoiesis in the rat: quantitation of hematopoietic progenitors and the response to iron deficiency anemia.

To determine the quantitative effects of iron deficiency on erythropoiesis and to assess the response of erythroid progenitors to sustained anemia, we developed quantitative assays for various hematopoietic progenitors in the adult, Sprague-Dawley rat including erythroid colony- and burst-forming cells (CFU-E and BFU-E), granulocyte/macrophage colony-forming cells (CFU-GM), and megakaryocytic colony-forming cells (CFU-Meg). CFU-E were cultured in methylcellulose and grew best in the presence of fetal calf serum. CFU-GM, BFU-E, and CFU-Meg grew better in normal rat plasma and required the presence of pokeweed mitogen-stimulated rat spleen cell conditioned medium. The numbers of progenitors and nucleated erythroblasts in total marrow were estimated by the ratios of radioactivity in the humerus to the total skeleton as determined by radioiron dilution. The numbers of progenitors and erythroblasts in the spleen were measured by simple dilution. Sustained anemia was brought about through chronic iron deficiency. The response to iron deficiency anemia (IDA) was monitored by the numbers of the various progenitors and their cell cycle characteristics as measured by the tritiated thymidine suicide technique. With IDA, the number of CFU-F in the body (marrow plus spleen) was increased to 3.5 times control, whereas the numbers of BFU-E and CFU-GM were unchanged. There was no difference in the percentage of CFU-E, BFU-E, and CFU-GM in DNA synthesis (68%, 19.4%, and 18.8%, respectively). With iron therapy of IDA, CFU-E numbers in marrow began to decrease by day 1 and fell in a manner reciprocal to changes in the hematocrit. Marrow and spleen erythroblasts, 1.7 times control in IDA, increased further to 3.9 times control by the fourth day after iron administration. There was no change in BFU-E or CFU-GM numbers in response to iron repletion, although the fraction of progenitors increased in the spleen. Thus, IDA does not limit the increase in CFU-E seen with anemia, but does restrict erythroid maturation. Furthermore, the increase in CFU-E and the state of chronic anemia occur without detectable changes in the number of cell cycle state of the more primitive BFU-E.

Anemia, Hypochromic↗
PubMed1986

Multilineage, non-species specific hematopoietic growth factor(s) elaborated by a feline fibroblast cell line: enhancement by virus infection.

In studies designed to determine the role of feline leukemia virus (FeLV) in the pathogenesis of marrow failure in the cat, we tested medium conditioned by uninfected and FeLV-infected feline embryonic fibroblasts (FEA) for its effect on hematopoietic colony growth in culture. As opposed to an inhibitory effect, we found that the conditioned medium (CM) from FEA or FEA/FeLV increased the in vitro growth of multiple hematopoietic progenitor cell types including erythroid burst-forming cells (BFU-E), granulocyte/macrophage colony-forming cells, megakaryocytic colony-forming cells, and mixed-cell colony-forming cells. Furthermore, CM enhanced the growth of progenitors in cultures of mouse or human marrow cells, as well as cat marrow cells. Stimulation of feline BFU-E was most marked with an increment in growth of 400% over control. The human burst promoting activity (BPA) of the CM was equivalent or better than other CM available in our laboratory. The evidence suggest that the growth-promoting activity is a constitutive product(s) released by FEA which was enhanced eightfold with virus infection. Studies with non-adherent and T-lymphocyte-depleted human marrow cells and human peripheral blood cells suggest that the growth factor(s) acts directly on progenitor cells and not through readily identified accessory cells. These findings are consistent with the concept that mesenchymal cells such as fibroblasts have the capacity to release hematopoietic growth factor(s) capable of acting on primitive hematopoietic progenitors. The results provide an example of how injury of such cells, through virus infection, may enhance growth factor(s) release and influence the hematopoietic microenvironment.

Animals↗
PubMed1986

Hematopoietic inhibitors in chronic renal failure: lack of in vitro specificity.

To assess the potential role of retained inhibitors in the pathogenesis of the anemia of chronic renal failure, we have studied simultaneously the effects of increasing concentrations of normal or uremic sera on the growth of erythroid colonies (from CFU-E), granulocyte-macrophage colonies (from CFU-GM), and megakaryocytic colonies (from CFU-Meg) in mouse marrow cell cultures. As compared to normal human serum, increasing concentrations of uremic sera induced a dose-dependent inhibition in the growth of all colony types. Significant correlations (P less than 0.001) were found between the ability of any individual uremic serum to support CFU-E, CFU-GM, and CFU-Meg growth, and, whenever significant inhibition was seen, all three progenitor types were affected. The inhibitory effect on CFU-E growth was significantly greater (P less than 0.01) in patients with serum creatinine concentrations greater than or equal to 7 mg/dl, but no correlation was found between CFU-E inhibition and hematocrit. Likewise, inhibition of CFU-GM and CFU-Meg growth was not associated with leukopenia or thrombocytopenia, respectively. Sera from patients undergoing chronic intermittent hemodialysis were assayed before and after one hemodialysis session. In each case, the degree of inhibition of CFU-E and CFU-GM growth decreased after hemodialysis, but improvement in CFU-Meg growth was more variable. These data indicate that uremic sera contain dialyzable inhibitors of in vitro hematopoiesis which increase with the severity of renal dysfunction, but these inhibitors lack specificity. If uremic inhibitors of erythropoiesis are of pathophysiologic significance in vivo, there must be unrecognized repair mechanisms for granulopoiesis and thrombopoiesis.

Animals↗
PubMed1986

Genomic cloning, characterization, and multilineage growth-promoting activity of human granulocyte-macrophage colony-stimulating factor.

Through the use of long single-sequence oligonucleotide probes, the complete gene for human granulocyte-macrophage colony-stimulating factor (hGM-CSF) has been cloned from a human genomic library. The gene is 2.5 kilobases in length, contains three introns, and is present as a single copy in the human genome. When subcloned into the mammalian expression vector pD3, the gene directs the synthesis of authentic hGM-CSF. In addition to its stimulation of in vitro granulopoiesis and monopoiesis, recombinant hGM-CSF stimulates in vitro erythropoiesis and megakaryopoiesis.

Base Sequence↗
PubMed1986

Human erythropoietin gene: high level expression in stably transfected mammalian cells and chromosome localization.

The glycoprotein hormone erythropoietin plays a major role in regulating erythropoiesis and deficiencies of erythropoietin result in anemia. Detailed studies of the hormone and attempts at replacement therapy have been difficult due to the scarcity of purified material. We used a cloned human erythropoietin gene to develop stably transfected mammalian cell lines that secrete large amounts of the hormone with potent biological activity. These cell lines were produced by cotransfection of mammalian cells with a plasmid containing a selectable marker and plasmid constructions containing a cloned human erythropoietin gene inserted next to a strong promoter. The protein secreted by these cells stimulated the proliferation and differentiation of erythroid progenitor cells and, with increased selection, several of these cell lines secrete up to 80 mg of the protein per liter of supernatant. Hybridization analysis of DNA from human chromosomes isolated by high resolution dual laser sorting provides evidence that the gene for human erythropoietin is located on human chromosome 7.

Animals↗
PubMed1986

Tumor necrosis factor type alpha stimulates human endothelial cells to produce granulocyte/macrophage colony-stimulating factor.

Tumor necrosis factor type alpha (TNF-alpha) is produced by monocytes and has been purified, sequenced, and cloned from the HL-60 cell line. Soluble products of monocytes stimulate endothelial cells to release multilineage hematopoietic colony-stimulating activity. To determine whether TNF-alpha could stimulate endothelial cells to produce these activities, we added recombinant human TNF-alpha to cultured human umbilical vein endothelial cells. Untreated endothelial cell conditioned medium and TNF-alpha-stimulated endothelial cell conditioned medium were tested for hematopoietic colony stimulating activity in colony-forming assays in methylcellulose. TNF-alpha stimulated growth factor production by endothelial cells. Fifth-passage human endothelial cells and multiply-passaged bovine aortic endothelial cells responded similarly to first-passage endothelial cells, indicating that the action of TNF-alpha on endothelial cells is direct and not due to contaminating lymphocytes or monocytes present in the first-passage cultures. To investigate the molecular basis for these findings, polyadenylylated RNA was prepared from the TNF-alpha-stimulated endothelial cells and probed for granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor mRNA. Granulocyte-macrophage colony-stimulating factor, but not granulocyte colony-stimulating factor, message was detected. This finding suggests that at least some of the hematopoietic colony-stimulating activity released by the TNF-alpha-stimulated endothelial cells is granulocyte-macrophage colony-stimulating factor. These results demonstrate that a purified monocyte product can stimulate endothelial cells to produce the multilineage growth factor granulocyte-macrophage colony-stimulating factor and extend the role of this immunoregulatory protein to the regulation of hematopoiesis in vitro.

Cells, Cultured↗
PubMed1986

Pure red cell aplasia: lymphocyte inhibition of erythropoiesis.

The pathogenesis of pure red cell aplasia (PRCA) was studied in a patient who had no evidence of malignancy. In marrow culture, no erythroid colonies (from late erythroid progenitors [CFU-E]) but normal numbers of well-haemoglobinized erythroid bursts (from early erythroid progenitors [BFU-E]) were found, indicating that BFU-E existed in the patient but that their subsequent in vivo differentiation was inhibited. Autologous coculture studies suggested that inhibition was mediated by the patient's ER + lymphocytes. After remission was induced with cyclophosphamide, autologous ER + cells no longer suppressed in vitro erythropoiesis. However, cryopreserved ER + cells, obtained with anaemia, suppressed BFU-E growth from remission marrow. An expanded population of large granular lymphocytes (LGL) with ER +, Fc gamma +, T3+, T8+, HNK-1+, Ia-, M1 -- phenotype and no functional natural killer (NK) cell activity was noted during PRCA that reverted to normal with remission. For this patient, both in vivo and in vitro evidence demonstrates a cellular inhibition of erythropoiesis at the level of differentiation between BFU-E and CFU-E.

Bone Marrow↗
PubMed1986

Quantitative studies of erythropoiesis in the clinically normal, phlebotomized, and feline leukemia virus-infected cat.

Erythropoiesis was evaluated in 5 cats at base line with normal PCV and then in the same cats with anemia induced by phlebotomy and in 5 other cats with nonregenerative anemia from community-acquired feline leukemia virus (FeLV) infection. The hematologic evaluation included complete blood cell and reticulocyte counts, marrow morphologic features, determination of serum erythropoietin concentrations by radioimmunoassay, ferrokinetic studies, and in vitro marrow culture of early erythroid progenitors (erythroid burst-forming units; BFU-E) and late erythroid progenitors (erythroid colony-forming units; CFU-E). Phlebotomized cats developed marrow erythroid hyperplasia and an increased reticulocyte count. Ferrokinetic studies revealed an increase in plasma iron turnover from 1.4 to 3.8 mg of Fe/dl of blood/day and RBC use from 50.4% to 78.5%. The mean CFU-E number and CFU-E/BFU-E ratio increased after phlebotomy, but the increase was not significant (P greater than 0.05). Serum erythropoietin values did increase significantly. In FeLV-infected cats, a nonregenerative anemia was demonstrated by marrow erythroid hypoplasia and a low total reticulocyte count. An increased percentage of rubriblasts and prorubricytes was observed in 4 of the 5 cats. Although serum erythropoietin values were high (321 +/- 123 mU/ml vs normal 14 +/- 1 mU/ml), ferrokinetic data revealed decreased erythropoiesis. Marrow culture studies in the FeLV-infected cats also revealed low numbers of BFU-E and CFU-E, but normal numbers of granulocyte-macrophage progenitors remained. Seemingly, the FeLV infection impaired the ability of feline marrow to respond physiologically to anemia.

Anemia↗
PubMed1985

Feline glucose-6-phosphate dehydrogenase cellular mosaicism. Application to the study of retrovirus-induced pure red cell aplasia.

Neoplasms result from the uncontrolled proliferation of abnormal or transformed cells. The early stages of this process are difficult to study because of the lack of sensitive and specific markers of clonal evolution in an experimental system. We have developed a cat model using cellular mosaicism for glucose-6-phosphate dehydrogenase (G-6-PD). Our findings confirm that the structural locus for feline G-6-PD is on the X-chromosome and demonstrate that it is randomly inactivated in somatic cells. Heterozygous cats have balanced ratios of G-6-PD enzyme types in peripheral blood cells and hematopoietic progenitors that remain stable over time. In our initial studies, we used the model to analyze the events surrounding marrow failure experimentally induced by selected strains of feline leukemia virus (FeLV). Two G-6-PD heterozygous cats, one F1 male hybrid and one domestic cat were infected with FeLV (C or KT) and developed pure red cell aplasia (PRCA). Colonies arising from the more mature erythroid colony-forming cell were not detected in marrow culture of anemic animals although erythroid bursts persisted, suggesting that the differentiation of early erythroid progenitors (BFU-E) was inhibited in vivo. The ratio of G-6-PD types in hematopoietic progenitors and peripheral blood cells from the heterozygous cats did not change when the animals developed PRCA. Thus, the anemia did not result from the clonal expansion of a transformed myeloid stem cell. With this experimental approach, one may prospectively assess clonal evolution and cellular interactions in other FeLV-induced diseases.

Animals↗
PubMed1985

Evidence for the involvement of B lymphoid cells in polycythemia vera and essential thrombocythemia.

Previous studies with the X-chromosome-linked glucose-6-phosphate dehydrogenase (G6PD) as a marker of cellular mosaicism demonstrated that polycythemia vera (PV) and essential thrombocythemia (ET) are clonal disorders of hematopoietic stem cells that can differentiate to erythrocytes, granulocytes, and platelets. To determine if the involved stem cells could also differentiate along the B-lymphoid pathway, we studied one woman with PV and one woman with ET. Of 117 Epstein-Barr virus-transformed B-lymphoblastoid lines expressing a single G6PD derived from the patient with PV, 108 expressed G6PD type A, the type characteristic of the abnormal clone. The ratio of 108:9 was significantly different from the one to one ratio predicted for this patient, which suggested that at least some circulating progenitors for B-lymphoid cell lines differentiate from the stem cell involved by the disease. Results obtained from the patient with ET were similar--104 of the 109 lymphoblastoid lines monotypic for G6PD expression displayed the enzyme type found in the abnormal clone of marrow cells. Therefore, in these patients, PV and ET, like chronic myelogenous leukemia, involve a stem cell pluripotent for the lymphoid as well as the myeloid series.

Adult↗
PubMed1985

Erythropoietin kinetics in normal and uremic sheep.

Homologous erythropoietin (Ep)-rich plasma was infused into sheep to determine the kinetics of this hormone in a large animal model. Ep levels after infusion were measured by radioimmunoassay using a sheep standard. Twenty-seven infusions into normal (14), subtotally nephrectomized (11), and anephric (two) animals were analyzed according to a single-compartment model. The volume of distribution was also calculated, and compared with values obtained indirectly from measurement of chromium 51-labeled red blood cells. The data showed that the t1/2 of the infused hormone was approximately 9 hours and was independent of renal function. After multiple infusions, the t1/2 appeared to shorten. The volume of distribution for this hormone corresponded to the plasma volume of the animals. These studies suggest that Ep, if administered to patients with chronic renal failure, could be given infrequently with little dependence on renal function.

Anemia↗
PubMed1985

Hematopoietic growth factors in human serum. erythroid burst-promoting activity in normal subjects and in patients with severe aplastic anemia.

The activity capable of promoting the growth of human erythroid burst-forming cells (BFU-E) in culture was measured in the sera from 39 patients with aplastic anemia (AA) and compared with similar activity in patients with various other hematologic disorders and 31 normal subjects. Burst-promoting activity (BPA) was determined by its ability to support erythroid burst growth from adherent cell-depleted normal human marrow cells. The results were expressed as the percentage of burst growth supported by test serum compared with cultures established in the presence of 20% test serum and 2.5% phytohemagglutinin-stimulated lymphocyte conditioned medium. The mean BPA level in normal serum was 18.5% (1.5 +/- SEM) and was not significantly different from BPA levels in patients with various forms of nonhypoplastic anemia or polycythemia (10.2% +/- 1.2%). In contrast, 15 of the 39 patients with AA had elevated BPA levels, ranging from 40.0% to 106.0%. These elevated levels did not correlate with serum erythropoietin or hematocrit values, white blood cell count, platelet count, time from diagnosis, or the presence or numbers of BFU-E in circulation. The BPA was shown not to be T cell growth factor (interleukin-2), and the effect was not blocked by the addition of cyclosporine to culture, consistent with a direct effect of this activity on BFU-E. When the 39 patients with AA were treated with antithymocyte globulin, 20 obtained a complete or partial remission. BPA levels determined from sera obtained before treatment did not correlate with response or duration of survival but did correlate with granulocyte-macrophage colony-stimulating activity (GM-CSA).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗