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Biomedical subjects

J W Adamson

Publications and source records attributed to J W Adamson.

At least 127 records · Page 7Linked to original sources
PubMed1985

Megakaryocytopoiesis in the rat: response to thrombocytopenia induced by exchange transfusion.

We have studied the megakaryocytopoietic response in rats to acute thrombocytopenia induced by exchange transfusion of platelet-poor blood. Our analysis included serial determinations of peripheral blood counts, the size and number of megakaryocytes in sections of humeral marrow, the numbers of megakaryocytic (CFU-Meg) and granulocyte-macrophage (CFU-GM) colony-forming cells in marrow and spleen, and the proportion of CFU-Meg and CFU-GM in DNA synthesis. With exchange transfusion, the platelet count fell to 11% of the control value (101,000 +/- 49,000/mm3; mean +/- SD) and returned to normal by day 3; rebound thrombocytosis (peak 1,720,000 +/- 246,000/mm3) was observed on days 4 and 5. The average size of marrow megakaryocytes increased significantly on days 2 and 3 compared with normal (p less than 0.01), but the numbers of recognizable megakaryocytes did not change through day 5. The numbers of splenic CFU-Meg and CFU-GM increased significantly (p less than 0.05) on days 2-4 and on day 2, respectively, after the exchange; however, the numbers of marrow progenitors, which account for over 95% of total body progenitors, remained unchanged throughout the duration of the study. The proportion of CFU-Meg in DNA synthesis (mean +/- SD) increased from a baseline value of 17% +/- 4% to 33% +/- 11% (p less than 0.02) and 35% +/- 6% (p less than 0.001) on days 1 and 2, respectively, and returned to control values thereafter. There were no changes in the cell cycle activity of CFU-GM. Thus, acute selective thrombocytopenia induced by exchange transfusion causes an enlargement of marrow megakaryocytes and an increase in the fraction of CFU-Meg in cell cycle. These changes, occurring in the absence of immunologically mediated events, are the direct result of lowered platelet count.

Animals↗
PubMed1984

Human megakaryocytic progenitors (CFU-M) assayed in methylcellulose: physical characteristics and requirements for growth.

The basic culture requirements and several physical characteristics were defined for megakaryocytic colony-forming cells (CFU-M) from normal human marrow growing in methylcellulose. Ficoll-hypaque separated mononuclear cells from human marrow gave rise to megakaryocytic colonies in the presence of normal human plasma and phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). Their identity as megakaryocytic colonies was confirmed by immunofluorescence staining with a monoclonal antibody to human factor VIII antigen and by electron microscopy of individually harvested colonies. Demonstration of the single-cell origin of the colonies was provided by analysis of the glucose-6-phosphate dehydrogenase (G-6-PD) enzyme type of individually harvested colonies grown from a G-6-PD heterozygote. The colonies grew best in heparinized or citrated plasma as opposed to serum. Detailed studies suggested that platelet-release products were responsible for this difference. Tritiated thymidine suicide studies showed that the percentage of CFU-M in DNA synthesis was 23 +/- 8% (n = 10). The modal velocity sedimentation rate of CFU-M was 4.9 +/- 0.6 mm/hr (n = 4) while that of concurrently studied granulocyte/macrophage colony-forming cells (CFU-GM) was 5.7 +/- 0.5 mm/hr. Examination of the PHA-LCM dose-response characteristics suggested the presence in the conditioned medium of an inhibitor to megakaryocyte colony growth which was partially removed by chromatography of the medium on Sephadex G-100. The resulting conditioned medium increased the cloning efficiency for CFU-M compared with that with crude PHA-LCM (15.3 +/- 7.0 and 8.2 +/- 5.3/10(5) marrow cells, respectively).

Blood↗
PubMed1984

Platelet factor-4 excretion in myeloproliferative disease: implications for the aetiology of myelofibrosis.

Experimental evidence suggests that the fibroblastic proliferation often associated with the myeloproliferative disorders is not part of the neoplastic process, but is secondary to an unknown stimulus. This stimulus may be a factor derived from platelets which promotes the proliferation of fibroblasts in vitro (PDGF). Platelet-derived growth factor is localized to platelet alpha-granules together with PF4 and beta-TG. As an indicator of alpha-granule release, we have measured PF4 levels in plasma, platelets and urine in 46 normal subjects and 49 patients with myeloproliferative disorders, secondary thrombocytosis and miscellaneous malignancies. All 11 patients with elevated urinary PF4 excretion exhibited myelofibrosis, whereas 11 of 22 patients with documented myelofibrosis had urinary PF4 excretion in the normal range. No correlation was seen between marrow fibrosis and plasma levels or the platelet content of PF4. The data are consistent with the possibility that release of mitogen(s) from platelet or megakaryocyte alpha-granules in some patients with myeloproliferative disorders is pathogenetically related to the development of marrow fibrosis.

Blood Platelets↗
PubMed1984

Adrenergic modulation of erythropoiesis: in vitro studies of colony-forming cells in normal and polycythaemic man.

The effect of hormonal interactions on human erythroid colony growth has been studied using the beta adrenergic agonist, isoproterenol. The growth of colonies derived from both erythroid burst-forming cells (BFU-E) and erythroid colony-forming cells (CFU-E) was enhanced in the presence of isoproterenol. While isoproterenol was effective at all concentrations of erythropoietin (Ep) in cultures of marrow cells, an increase in BFU-E-derived colonies in peripheral blood cultures could be detected only at suboptimal levels of Ep concentrations. The isoproterenol effect was blocked by an agent with beta 2 receptor specificity (butoxamine), and L-isomeric configuration (L-propranolol). The stimulatory effect appeared to be mediated by a receptor different from that for Ep or for phytohaemagglutinin-stimulated leucocyte conditioned medium. Circulating BFU-E from eight patients with polycythaemia vera were also studied. Those colonies which grew in the absence of added Ep increased with isoproterenol; in cultures from normal subjects and in patients with secondary erythrocytosis, agonist stimulation was seen only in the presence of Ep. These studies provide evidence that the growth of both normal and neoplastic erythroid progenitors may be modulated by hormonal interactions.

Butoxamine↗
PubMed1984

The anaemia of chronic renal failure in sheep: studies in vitro.

The presence of inhibitors which accumulate during uraemia has been postulated as a significant factor in the development of anaemia in chronic renal failure (CRF). To determine whether factors in uraemic serum depress erythropoiesis, samples were obtained from sheep prior to and after surgical induction of CRF. The sera were tested in vitro for their effect on erythroid colony growth. The sheep sera were substituted for fetal calf serum (30% concentration) in cultures of serotype-matched or autologous sheep marrow cells at optimal doses of erythropoietin (Ep). Forty-two paired sera from five animals were tested against normal (22) and uraemic marrow (20). In 7/42 random pairs, erythroid colony growth was decreased by 20% in the presence of uraemic serum when compared to a normal sample from the same animal. In the remainder of the cultures, uraemic sera stimulated or supported erythroid colony growth as well as normal sera. When the results were analysed individually, serum from only one of five animals showed minimal (10%) in vitro inhibition of erythroid colony growth. This study, performed in a prospective manner utilizing compatible target cells, disputes the hypothesis that uraemic toxins significantly inhibit in vitro erythropoiesis. These data correlate with the in vivo response to Ep in this sheep model, and suggest Ep would be effective in treating the anaemia of CRF.

Anemia↗
PubMed1984

Pancytopenia as a clonal disorder of a multipotent hematopoietic stem cell.

Hematopoiesis was investigated in a 14-yr-old girl who had a 2-yr history of stable asymptomatic pancytopenia and who was also heterozygous at the structural locus for glucose-6-phosphate dehydrogenase (G-6-PD). There was no morphologic or cytogenetic evidence for preleukemia and no suggestion of Fanconi anemia. In the skin and sheep erythrocytes-rosetted T lymphocytes, the ratio of G-6-PD A/B activities was 1:1. However, only type B activity was found in peripheral blood erythrocytes, granulocytes, and platelets. Most erythroid bursts and all granulocyte/macrophage colonies formed in methylcellulose culture were derived from the abnormal clone. These findings demonstrate that (a) some cases of pancytopenia are stem cell diseases that apparently develop clonally; (b) circulating differentiated cells originate from this clone; (c) despite a hypoproliferative anemia, the in vivo expression of presumably normal (nonclonal) progenitors is suppressed. In this patient, the relationship between clonal dominance and possible malignancy may be assessed prospectively.

Bone Marrow↗
PubMed1984

The anemia of chronic renal failure in sheep. Response to erythropoietin-rich plasma in vivo.

The hypoproliferative anemia in chronic renal failure has been assumed to be the result of decreased erythropoietin (Ep) production by the damaged kidney and of the shortening of erythrocyte survival. However, many in vitro studies suggest that erythropoietic inhibitors in uremic plasma may contribute to the anemia. To determine the in vivo relevance of uremic inhibitors, increasing amounts of Ep as Ep-rich plasma were infused into six uremic sheep, and their erythropoietic responses were compared with those of nine normal sheep receiving similar amounts of Ep-rich plasma. Three sheep were studied in both normal and uremic states. Ep-rich plasma was obtained from phenylhydrazine- and phlebotomy-induced anemic sheep. Stable uremia was created by subtotal nephrectomy. Erythropoiesis was quantitated by reticulocyte response, ferrokinetics (plasma iron turnover and marrow transit time), and by hemoglobin C synthesis. Ep-rich plasma stimulated erythropoiesis similarly in uremic and normal sheep, regardless of the degree of uremia. Nondialyzed uremic sheep responded as well as dialyzed animals. The anemia was corrected in the uremic dialyzed animals. The anemia was corrected in the uremic sheep after 15-40 daily infusions of Ep-rich plasma, the total dosage depending on the severity of the anemia. Polycythemia was induced when the infusions were continued. Reticulocytes, plasma iron turnover, and erythrocyte mass changes increased as the amount of Ep-rich plasma was increased. These dose-response effects, coupled with the identical erythropoietic response in normal and uremic sheep given the same amount of Ep-rich plasma, imply that there are no physiologically significant erythropoietic inhibitors in uremia.

Anemia↗
PubMed1984

Analysis of haemopoiesis: the use of cell markers and in vitro culture techniques in studies of clonal haemopathies in man.

The clonal haemopathies have in common the expansion of a neoplastic stem cell which has retained a variable capacity for differentiation to granulocytes, monocytes, erythrocytes, and platelets. Although normal stem cells are present in such patients, their differentiation is somehow suppressed. However, their presence may be demonstrated either by cell culture studies, employing G6PD as the marker in appropriately selected cases, or by their emergence in patients subjected to marrow ablative chemotherapy. Suppression of normal stem cell growth and development does not require a hyperproliferative marrow, and the current data do not support the notion that normal stem cells are simply reduced in frequency by a vast increase in the numbers of neoplastic progenitors. It is likely, therefore, that such suppression involves cellular signals, operating over short distances (perhaps through cell-to-cell contact), which interfere with normal progenitors. Thus, stem cell culture techniques, in combination with cell markers, have provided a direct and informative way to approach the issues of disease pathogenesis, the kinetics of stem cell differentiation, and the interaction of normal and neoplastic cells in patients with clonal haemopathies.

Cells, Cultured↗
PubMed1984

Human mixed cell colonies: unicellular or multicellular origin--analysis by G-6-PD.

Marrow and peripheral blood cells from normal women heterozygous (GdB/GdA) at the X-chromosome-linked glucose-6-phosphate dehydrogenase (G-6-PD) locus were cultured at cell concentrations ranging from 2 X 10(4)/ml to 4 X 10(5)/ml to test formally the plating conditions necessary for reliable enumeration of multipotent stem cells (CFU-mix). The culture system was rigorously tested by plating cells obtained after velocity sedimentation and the G-6-PD enzyme type of individual colonies was determined. At cell concentrations less than or equal to 7.5 X 10(4)/ml for marrow and less than or equal to 1 X 25 X 10(5)/ml for peripheral blood, mixed-cell colonies had either type A or type B enzyme, but not both. At higher cell concentrations, significant numbers of colonies showed both enzyme types and therefore arose from more than one cell. These studies demonstrate that enumeration of CFU-mix by in vitro colony assay is accurate only at low cell concentrations. Studies of haematopoietic differentiation relying on in vitro colony assays of multipotent stem cells must be carefully analysed in light of these data.

Bone Marrow Cells↗
PubMed1983

High levels of the circulating form of parathyroid hormone do not inhibit in vitro erythropoiesis.

Either primary or secondary hyperparathyroidism may be associated with anemia. The pathogenesis of this anemia remains obscure, but parathyroid hormone may directly suppress erythropoiesis or anemia may result from myelofibrosis. Previously reported in vitro studies of a direct inhibitory effect of PTH on erythroid progenitor growth were carried out with crude hormone preparations and appeared nonspecific. We have studied simultaneously the in vitro effects of pure (greater than 6000 U/mg) and crude (130 U/mg) preparations of PTH on murine and human hematopoietic progenitor growth. Increasing concentrations (2.5 to 20 U/ml) of crude PTH produced a dose-dependent inhibition of early erythroid (BFU-E) and granulocyte/macrophage progenitor (CFU-GM) growth in human and mouse marrow cell cultures. However, the biologically active N-terminal fragment containing amino acids 1-34 and the pure intact molecule of 84 amino acids failed to significantly inhibit hematopoietic colony growth. These observations demonstrate that in vitro inhibitory effects described with parathyroid gland extracts are not specific for erythropoiesis and may not be related to the circulating form of PTH.

Animals↗
PubMed1982

Polycythemia vera: studies of hemopoiesis in continuous long-term culture of human marrow.

Long-term cultures of marrow cells from ten normal subjects and three patients with polycythemia vera were established to compare normal and neoplastic hemopoiesis in vitro. Suspended cells were removed periodically from the cultures and assayed from their content of various colony-forming cells, including erythroid colony- and burst-forming cells (CFU-E and BFU-E), granulocyte/macrophage colony-forming (CFU-C), and "mixed cell" colony progenitors (CFU-GEMM). To determine if mixed cell colonies arise from a single progenitor, we used the cellular mosaicism conferred by X-chromosome inactivation. The isoenzymes of glucose-6-phosphate dehydrogenase (G-6-PD) were used as markers of the mosaicism. Preliminary results suggest that these colonies are clonal only at low plating densities. The G-6-PD system was also used to determine whether selection or "drift" occurs in continuous long-term cultures. The ratios of G-6-PD isoenzyme types in pooled colonies from cultures of two normal heterozygotes remained similar, indicating stable cultures. Long-term cultures of normal marrow and marrow from the patients with polycythemia vera maintained BFU-E for a mean of 8.7 (+/- 0.6) and 12.5 (+/- 0.5) weeks (P = 0.03), respectively. The fractions of total BFU-E detected as endogenous erythroid colonies remained similar over the culture period. These results demonstrate that 1) hemopoiesis in polycythemia vera can be analyzed in long-term culture; 2) polycythemia vera marrow grows as well or better than normal in long-term culture; and 3) the proportion of the neoplastic clone in polycythemia vera represented by endogenous erythroid colony growth is unchanged over time, suggesting no reemergence of normal stem cell progeny in this system.

Bone Marrow↗
PubMed1982

Canine cyclic haematopoiesis: the effect of endotoxin on erythropoiesis.

We have examined the effects of chronic endotoxin treatment on erythropoiesis in six grey collies with cyclic haematopoiesis. Blood reticulocytes, bone marrow erythroid colony (EC) forming cells, serum iron and erythropoietin (ESF) values showed regular periodic fluctuations in untreated grey collies. Daily endotoxin injections eliminated the cyclic fluctuations of reticulocytes and EC. The mean serum iron values were increased and recurrent hypoferraemia eliminated, while the mean serum ESF values were reduced. The cyclic fluctuations of serum ESF values were no longer apparent in the endotoxin treated grey collies. Tritiated thymidine suicide of the marrow EC forming cells failed to show cyclic changes either in untreated or endotoxin treated dogs. The ESF sensitivity of EC in the grey collie was unchanged during endotoxin treatment and was not different from normal dogs. Endotoxin appears to alter periodic erythropoiesis by stabilizing the flux of cells into the committed erythroid precursor cell pool from a more primitive stem cell compartment.

Animals↗
PubMed1982

Characteristics of circulating erythroid colony-forming cells in normal and polycythaemic man.

Circulating erythroid progenitors from 10 patients with polycythaemia vera, nine with secondary polycythaemia and 10 normal subjects were studied in culture to determine their frequency, requirements for erythropoietin (ESF) and physical characteristics. Increased numbers of erythroid progenitors were detected in circulation from the patients with polycythaemia vera when compared to patients with secondary polycythaemia or normals, and 19 +/- 3% of these progenitors formed endogenous colonies without added ESF. Velocity sedimentation analysis showed that the majority of ESF-dependent erythroid progenitors in all study groups sedimented at 6.46 mm/h. The circulating endogenous erythroid colony-forming cells in polycythaemia vera patients sedimented more rapidly. Tritiated thymidine suicide experiments failed to detect significant differences between the percentages of endogenous and ESF-dependent progenitors in DNA synthesis in polycythaemia patients and normals. Thus, differences in cell cycle state were not responsible for the more rapid sedimentation of endogenous colony-forming cells. These results further define characteristics of circulating erythroid progenitors in polycythaemia vera and normal subjects and suggest that simple culture of peripheral blood cells may be useful in the differential diagnosis of polycythaemia.

Blood Sedimentation↗
PubMed1982

Immunologic stimulation of early murine hematopoiesis and its abrogation by cyclosporin A.

Mice injected chronically with antiplatelet serum develop an increase in the number of megakaryocytic progenitor cells compared to animals given normal rabbit serum. To examine the specificity of this response, progenitor cells giving rise to megakaryocyte, granulocyte-macrophage, erythroid, and mixed-cell colonies were assayed after injection of various heterosera or saline. All four colony types increased in the serum-treated groups. Since the in vitro proliferation of hematopoietic progenitor cells is promoted by supernatants of mitogen-stimulated spleen cells, we hypothesized that the immune response following antiserum administration resulted in the in vivo activation of T lymphocytes which produced or led to the production of colony stimulating activities. To test this hypothesis, cyclosporin A, a preferential inhibitor of T lymphocyte function, was given to mice concurrently with antiserum and also added to spleen cell cultures in the presence of pokeweed mitogen. Cyclosporin A abrogated the antiserum-related increases in progenitor cell numbers in vivo and the production of colony stimulating activity in vitro. The results suggest that the immune response related to antiserum administration results in the in vivo production of hematopoietic colony stimulating activities that may be identical to those produced in vitro by mitogen-stimulation of spleen cells.

Animals↗