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Query: UMLS:C0026986 (myelodysplastic syndrome)
 14,926 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Somatic cell genetic approaches utilizing the cellular mosaicism present in women heterozygous for glucose-6-phosphate dehydrogenase (G6PD) have provided information relevant to the pathogenesis of some neoplastic disorders. With these techniques, we studied a 61-year-old woman with a myelodysplastic syndrome. GdB/GdA heterozygosity was demonstrated in skin and cultured T lymphocytes, which exhibited both A and B type G6PD. In contrast, erythrocytes, platelets, granulocytes, and marrow nucleated cells displayed almost exclusively G6PD type B. In addition, 21 of 24 Epstein-Barr virus-transformed B lymphoblastoid lines that expressed a single immunoglobulin light chain showed only type B G6PD, suggesting that the stem cells involved by this disease were clonal and could differentiate to B lymphocytes as well as to mature granulocytes, erythrocytes , and platelets. Cultured skin fibroblasts and phytohemagglutinin-stimulated lymphocytes were karyotypically normal, but two independent abnormalities were found in marrow--47,XX, +8 and 46,XX,del(11)(q23). None of 14 type B G6PD lymphoblastoid lines analyzed in detail contained these karyotypic abnormalities, which strongly suggests that a visible chromosomal alteration is not the sole step in the development of this disease. We hypothesize that at least two events are involved in the pathogenesis of this patient's myelodysplasia: one causing proliferation of a clone of genetically unstable pluripotent stem cells and another inducing chromosomal abnormalities in its descendants.
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PMID:Evidence for a multistep pathogenesis of a myelodysplastic syndrome. 632 94

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.
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PMID:Pancytopenia as a clonal disorder of a multipotent hematopoietic stem cell. 669 Apr 81

The kinetics of hematopoietic stem cells were investigated in glucose-6-phosphate dehydrogenase (G-6-PD) heterozygous cats treated with dimethylbusulfan. Because of X-chromosome inactivation during embryogenesis, each somatic cell from these animals contains either maternal- or paternal-type G-6-PD. Therefore, all hematopoietic progenitor cells carry the G-6-PD phenotype of the most primitive cell (stem cell) from which they originate. For up to 6.5 years after dimethylbusulfan therapy, we determined the percentages of erythroid and granulocyte/macrophage progenitor cells with each G-6-PD phenotype. Significant variations were seen in studies from five of six cats, showing that the population of stem cells contributing to hematopoiesis was neither large nor constant. With mathematical analyses, we estimated that the proliferative potential of residual stem cells was much less than that of normal stem cells reduced in number by autologous transplantation (Abkowitz et al, Proc Natl Acad Sci USA 87:9062, 1990). There was no evidence for the regeneration of a normal stem cell reserve over time; rather, damage was most pronounced years after dimethylbusulfan exposure. These data may help explain the high clinical incidence of aplastic anemia and myelodysplasia after alkylating agent therapies.
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PMID:Behavior of feline hematopoietic stem cells years after busulfan exposure. 840 Feb 59

Clonality in myelodysplastic syndromes (MDS) has been studied with various techniques including glucose-6-phosphate dehydrogenase (G6PD) isoenzyme and cytogenetic analyses, and with molecular techniques such as gene deletion studies and the analysis of restriction fragment-length polymorphisms (RFLP) of X-linked genes. In this study, we investigated the use of fluorescence in situ hybridization (FISH) with a chromosome-specific probe to examine cytogenetic clonality in peripheral blood (PB) cells from three patients with MDS. In each case, trisomy 8 was shown by conventional cytogenetic analysis at the time of the initial diagnosis. By using FISH with a probe for the centromere of chromosome 8, we identified the trisomy in individual PB cells from Wright-stained smears. With this technique, we could determine the cell lineage involved by the trisomy, and through serial analyses we could assess the response of the clonal and nonclonal cells to growth-factor therapy, and the expansion of the trisomic clone over time. In each of the three cases, various proportions of granulocytes, monocytes, eosinophils, and basophils showed trisomy 8 by FISH analysis. In none of the cases did we detect trisomy 8 in lymphocytes. By analysis of PB cells before and during therapy with recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF), we found that GM-CSF stimulated both trisomic and disomic cells. During a 1-year period of sequential study, we detected an abrupt increase in the percentage of trisomic cells in one patient, a stable percentage in another, and a slowly increasing percentage in the third. The abrupt increase in the first patient preceded a transformation to a more acute phase by 2 months. We conclude that FISH analysis of PB cells of patients with MDS offers an additional approach to the study of clonality in this disorder. In some cases this analysis may provide a useful and simple means of assessing response to therapy and progression of disease.
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PMID:Cytogenetic clonality in myelodysplastic syndromes studied with fluorescence in situ hybridization: lineage, response to growth factor therapy, and clone expansion. 845 4

Deficiency in glucose-6-phosphate dehydrogenase (G6PD), an X-linked recessive red cell enzymopathy, is endemic in Southern Chinese. Universal screening of newborn is done in Hong Kong, Taiwan and Singapore, among other places. In Hong Kong, 4.8% of males are affected and seven common G6PD alleles account for over 99% of all defects. Male hemizygotes suffer from severe deficiency, while female heterozygotes may also be affected. Deficiency of G6PD may affect haematopoietic stem cell transplantation (HSCT) recipients and donors, before and after HSCT. Female patients with clonal erythropoiesis (eg myelodysplasia/myeloproliferative diseases) will have the male population incidence of G6PD. Quantitative enzyme level screening is prudent for donors and recipients, and should be repeated after engraftment. Cotrimoxazole prophylaxis should be avoided in known male and female carriers, including those with low-normal G6PD enzyme levels. Our experience suggested that G6PD-deficient marrow, stem cell and cord blood donor units have no engraftment problems. Post-engraftment G6PD levels correlate with those in donors. An acquired change in G6PD status may serve as a surrogate marker for engraftment. For female heterozygote donors with normal G6PD levels, skewing of lyonized X-chromosome ratio during engraftment may result in over-expression of the deficient allele. This can result in unexpected significant G6PD deficiency. Hence, a repeat G6PD screening at stable engraftment is recommended, especially before commencement of oxidative medications.
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PMID:Glucose-6-phosphate-dehydrogenase deficiency and haematopoietic stem cell transplantation in Chinese patients. 1949 95

Similar to nucleated cells, erythrocytes may undergo suicidal death or eryptosis, which is characterized by cell shrinkage, cell membrane blebbing and cell membrane phospholipid scrambling. Eryptotic cells are removed and thus prevented from undergoing hemolysis. Eryptosis is stimulated by Ca(2+) following Ca(2+) entry through unspecific cation channels. Ca(2+) sensitivity is enhanced by ceramide, a product of acid sphingomyelinase. Eryptosis is triggered by hyperosmolarity, oxidative stress, energy depletion, hyperthermia and a wide variety of xenobiotics and endogenous substances. Eryptosis is inhibited by nitric oxide, catecholamines and a variety of further small molecules. Erythropoietin counteracts eryptosis in part by inhibiting the Ca(2+)-permeable cation channels but by the same token may foster formation of erythrocytes, which are particularly sensitive to eryptotic stimuli. Eryptosis is triggered in several clinical conditions such as iron deficiency, diabetes, renal insufficiency, myelodysplastic syndrome, phosphate depletion, sepsis, haemolytic uremic syndrome, mycoplasma infection, malaria, sickle-cell anemia, beta-thalassemia, glucose-6-phosphate dehydrogenase-(G6PD)-deficiency, hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria, and Wilson's disease. Enhanced eryptosis is observed in mice with deficient annexin 7, cGMP-dependent protein kinase type I (cGKI), AMP-activated protein kinase AMPK, anion exchanger AE1, adenomatous polyposis coli APC and Klotho as well as in mouse models of sickle cell anemia and thalassemia. Eryptosis is decreased in mice with deficient phosphoinositide dependent kinase PDK1, platelet activating factor receptor, transient receptor potential channel TRPC6, janus kinase JAK3 or taurine transporter TAUT. If accelerated eryptosis is not compensated by enhanced erythropoiesis, clinically relevant anemia develops. Eryptotic erythrocytes may further bind to endothelial cells and thus impede microcirculation.
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PMID:Killing me softly - suicidal erythrocyte death. 2256 48

Prior to senescence, erythrocytes may experience injury, which compromises their integrity and thus triggers suicidal erythrocyte death or eryptosis. This mechanism is characterised by cell shrinkage, cell membrane blebbing, and cell membrane phospholipid scrambling after phosphatidylserine exposure on the cell surface that is identified by macrophages, which engulf and degrade the eryptotic cells. The term eryptosis also includes typical mechanisms, which contribute to the triggering of this process, such as oxidative stress, Ca2+ entry with an increase in cytosolic Ca2+ activity ([Ca ]i) and the activation of p38 kinase, which is a kinase expressed in human erythrocytes and activated after hyperosmotic shock. Enhanced eryptosis has been observed in several clinical conditions such as diabetes, renal insufficiency, haemolytic uremic syndrome, sepsis, mycoplasma infection, malaria, iron deficiency, sickle cell anaemia, beta-thalassemia, glucose-6-phosphate dehydrogenase-(G6PD) deficiency, hereditary spherocytosis, paroxysmal nocturnal haemoglobinuria, Wilson's disease, myelodysplastic syndrome, and phosphate depletion. Therefore, eryptosis may be considered as a useful mechanism of removal of defective erythrocytes to prevent haemolysis. Moreover, the clearance of infected erythrocytes in diseases such as malaria may counteract parasitemia. Indeed it is known that sickle-cell trait, beta-thalassemia trait, glucose-6-phosphate dehydrogenase (G6PD)- deficiency and iron deficiency confer some protection against a severe course of malaria. Importantly, strategies to control Plasmodium infection by inducing eryptosis are not expected to generate resistance of the pathogen, as the proteins involved in suicidal death of the host cell are not encoded by the pathogen and thus cannot be modified by mutations of its genes. However, excessive eryptosis could compromise microcirculation and lead to anemia.
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PMID:Eryptosis: Ally or Enemy. 2785 17