Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002871 (anemia)
 52,094 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the effects of recombinant human erythropoietin (rHuEPO) on anemic W/WV mice which manifested severe anemia accompanied by mutation of the W gene encoding tyrosine kinase type receptor (c-kit gene) of bone marrow hematopoietic cells. Nine-week-old male W/WV mice or normal littermates (+/+) were used. Since serum EPO concentration in W/WV mice increased in proportion to severity of anemia, EPO production in the kidneys of these animals was found to be regulated normally. Hematocrit in +/+ mice increased and a maximal response was also obtained with 2,000 IU/kg of rHuEPO. On the other hand, hematocrit in W/WV mice increased in a dose-responsive manner by administration with 2,000 and 10,000 IU/kg, showing different responses to rHuEPO in these two types of mice. The responsiveness of W/WV mice to rHuEPO was low in terms of increases in erythroblastic precursor cells (CFU-E), and immature cells in the bone marrow. Scatchard analysis of the specific binding of 125I-rHuEPO against bone marrow cells revealed that the different responsiveness to rHuEPO between W/WV and +/+ mice may be correlated with differences in affinity of EPO receptor of bone marrow cells in these mice. From these results, a high dose of rHuEPO is capable of improving the anemia in W/WV mice that had EPO receptors with lowered affinity, indicating the possible effectiveness of rHuEPO in anemic patients with EPO receptor abnormality.
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PMID:Improvement of anemia in W/WV mice by recombinant human erythropoietin (rHuEPO) mediated through EPO receptors with lowered affinity. 765 14

W/Wv and S1/S1d mice with macrocytic anemias are a potential model for human inherited pure red cell anemia, called Diamond-Blackfan anemia (DBA). The W mutation involves the gene for c-kit, and the S1 mutation the gene for the kit ligand, called mast cell growth factor, steel factor, or stem cell factor. Since many children with DBA respond to treatment with corticosteroids, we administered steroids to these genetically anemic mice, to determine whether they might provide a model for the human disease. There was no improvement in the murine anemia, consistent with other evidence suggesting that mutations in kit or steel may not be involved in Diamond-Blackfan anemia.
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PMID:Lack of effect of corticosteroids in W/Wv and S1/S1d mice: these strains are not a model for steroid-responsive Diamond-Blackfan anemia. 768 5

A study of immunological markers was performed in 16 patients with newly diagnosed refractory anaemia with excess of blasts (RAEB) and RAEB in transformation (RAEB-T) and in 12 other patients with acute myeloid leukaemia evolving from RAEB or RAEB-T. Immunocytochemical investigation of bone marrow blasts was done using a modified indirect immunoperoxidase technique. This method permitted accurate morphological identification of blasts and other cells in bone marrow. The monoclonal antibodies used in RAEB and RAEB-T samples were anti-CD34, -c-kit, -HLA-DR and -CD13. The range of CD34 expression of blasts in RAEB samples was 1-14% (mean 6.2%) and in RAEB-T samples 29-48% (mean 35.5%). CD34 positivity was detected in 3-94% (mean 47.4%) of the bone marrow blasts in acute myeloid leukaemia evolving from RAEB and RAEB-T. Expression of c-kit was demonstrated only in a low percentage of blast cells in RAEB, RAEB-T and acute myeloid leukaemia following myelodysplasia. A high percentage (> 30%) of blasts in most patients with RAEB, RAEB-T and acute myeloid leukaemia was HLA-DR and CD13 positive. We observed the transformation from RAEB to acute myeloid leukaemia in three patients. The proportion of CD34 positive blasts increased to 25% and 32% in two patients. The third patient showed an unchanged percentage of CD34 positivity of blasts. These findings indicate that the CD34 positivity of blasts increases with the progression of myelodysplasia to RAEB-T and acute myeloid leukaemia demonstrating the instability of the clonal defect in myelodysplasia.
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PMID:Immunotyping of blasts in refractory anaemia with excess of blasts. 769 Nov 47

The white-spotting (Ws) locus of rats represents a 12-base deletion of the c-kit receptor tyrosine kinase. Homozygous Ws/Ws rats are deficient in melanocytes, mast cells, and erythrocytes. Although mice possessing two mutant alleles at the c-kit (W) locus, such as mice of W/Wv genotype, show severe anemia even in adult age, the anemia of Ws/Ws rats remarkably ameliorated with age. We investigated the mechanism of the age-dependent amelioration. Bone marrow cells of Ws/Ws rats did not form macroscopic colonies in the spleen of irradiated rats, and the concentration of burst-forming unit-erythroid in the marrow of Ws/Ws rats was comparable with that of +/+ rats. Therefore, the increase in morphologically identifiable erythroid precursors in the marrow of Ws/Ws rats was attributed to the increased concentration of colony-forming unit-erythroid (CFU-E). Furthermore, the increase in CFU-E appeared to result from the increased concentration of erythropoietin (EPO). Because injections of relatively low doses of EPO cured the slight anemia that remained in adult Ws/Ws rats, CFU-E and/or its immediate precursors of Ws/Ws rats appeared to be more sensitive to EPO than those of W/Wv mice, in which a huge dose of EPO was necessary to cure the anemia.
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PMID:Age-dependent amelioration of hypoplastic anemia in Ws/Ws rats with a small deletion at the kinase domain of c-kit. 769 80

Mutations of c-kit, which encodes a transmembrane receptor tyrosine kinase, have been identified in mice by abnormal coat color, anemia, and germ cell defects. Mice heterozygous for mutations of c-kit have a white forehead blaze and a white ventral spot, leading these mutants to be termed dominant White spotting (W). We have previously demonstrated that the membrane-associated isoform of human stem cell factor (hSCF220, the ligand for c-kit) is inefficiently processed in murine stromal cell transfectants. Thus, in murine cell lines analyzed in vitro, hSCF220 transfectants present SCF as a membrane restricted protein in contrast to the murine SCF220 cDNA protein product, which is slowly cleaved and secreted. We show here that transgenic mice expressing the human SCF220 isoform in vivo display a phenotype indistinguishable from some alleles of W. Specifically, hSCF220-expressing transgenic mice display a prominent forehead blaze and a white ventral spot. Generations of doubly heterozygous animals that carry both a mutated c-kit allele and the hSCF220 transgene display a more severe coat color abnormality. This phenotype appears to be due to occupancy of murine c-kit by human SCF and diminished cell surface expression of endogenous murine SCF. Normal signaling events that lead to cell survival or proliferation appear to be disrupted in vivo in these transgenic mice.
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PMID:Xenogeneic expression of human stem cell factor in transgenic mice mimics codominant c-kit mutations. 860 35

W/c-kit mutant mice accept engraftment by small numbers of normal hematopoietic stem cells without the necessity for myeloablation. One explanation for this observation is that a deficiency of Kit receptors reduces the number of primitive hematopoietic stem cells and increases the number of available "niches" or "space" in the marrow. As a test of this model, we transplanted a series of unirradiated W mutant mice with donor marrow cells of the identical mutant genotype. Despite the intrinsic anemia and hematopoietic defect of severely affected W(X)/W(V) and mildly affected W(V)/+ hosts, donor-derived red blood cells (RBC) were not detected for up to 6 months after transplantation with 1-4 x 10(7) marrow cells of the same W(X)/W(V) and W(V)/+ genotypes, respectively. In contrast, both genotypes were engrafted, as judged by sustained proliferation of donor-derived RBC, after a second transplant with equal numbers of +/+ cells. The inability of W(X)/W(V) marrow to proliferate in W(X)/W(V) hosts was not due to an absence of transplantable stem cells, however, as W(X)/W(V) cells were capable of sustained engraftment and proliferation in irradiated W(X)/W(V) recipients. We conclude that when donor and host are equivalent for Kit receptor function, W mutant mice do not accept marrow grafts more readily than wild-type mice. The results suggest that a deficiency of host Kit receptor function promotes engraftment of normal stem cells not by increasing marrow space, but by providing an advantage to donor cells in competition for marrow stroma or for self-renewal and differentiation.
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PMID:Engraftment of W/c-kit mutant mice is determined by stem cell competition, not by increased marrow 'space'. 864 43

The expression of c-myc was analyzed in murine and human erythroblasts throughout their differentiation in vitro into reticulocytes. The murine cells were splenic erythroblasts from animals infected with the anemia strain of Friend virus (FVA cells). In FVA cells cultured without EPO, the c-myc mRNA and protein levels decrease sharply within 3 to 4 h, showing that continual EPO stimulation is required to maintain c-myc expression. When cultured with EPO, the c-myc mRNA level of FVA cells is raised within 30 min of exposure. The c-myc mRNA and protein reach maxima at 1 to 3 h, then decline slowly to very low levels by 18 h. In contrast, c-fos and c-jun mRNA levels are not regulated by EPO in FVA cells. The human cells analyzed were colony-forming units-erythroid, CFU-E, derived in vitro by the culture of peripheral blood burst-forming units-erythroid (BFU-E). When grown in EPO and insulin-like growth factor 1 (IGF-1) these cells differentiate into reticulocytes over 6 days rather than the 2 days required for murine cells, but the c-myc mRNA kinetics and response to EPO parallel those of mouse cells at similar stages of differentiation. Both IGF-1 and c-kit ligand (SCF) cause an additive increase in c-myc mRNA in human CFU-E in conjunction with EPO. These additive effects suggest that EPO, IGF-1, and SCF affect c-myc mRNA accumulation by distinct mechanisms. Addition of an antisense oligonucleotide to c-myc in cultures of human CFU-E specifically inhibited cell proliferation but did not affect erythroid cell differentiation or apoptosis. When human cells were grown in high SCF concentrations, an environment which enhances proliferation and retards differentiation, antisense oligonucleotide to c-myc strongly inhibited proliferation, but such inhibition did not induce differentiation. This latter result indicates that differentiation requires signals other than depression of c-Myc and resultant depression of proliferation.
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PMID:C-myc expression affects proliferation but not terminal differentiation or survival of explanted erythroid progenitor cells. 870 61

The c-KIT proto-oncogene encodes for a transmembrane receptor and is associated with maturation of several cell types, including germ cells. The ligand of the receptor has been identified as stem cell factor (SCF). Loss or alteration of the expression of either of these factors leads to anemia, albinism, and/or sterility in mice. We examined the expression of c-KIT and SCF by immunohistochemistry in specimens from normal and infertile human testis. All specimens were obtained in the evaluation of male subfertility. We were able to demonstrate staining for c-KIT in Leydig cells in all specimens. Normal testis stained for c-KIT in the cytoplasm of early spermatogenic cells, as well as the acrosomal granules of the round spermatids and the acrosome of testicular spermatozoa. However, staining in testis demonstrating maturation arrest failed to demonstrate acrosomal staining, and Sertoli-only specimens demonstrated staining for c-KIT in Leydig cells only. The results for SCF demonstrated an overall uniform staining of Leydig cells in all specimens. The intensity of staining of Sertoli cells increased from normal to maturation arrest to Sertoli-only specimens. Germ cell staining was consistently negative. We hypothesize that these staining patterns for SCF are due to either lack of staining of the receptor-ligand complex or overexpression of the kit ligand in tissue that does not express the kit receptor. It appears that the c-kit receptor is expressed in the acrosome of developing germ cells, as well as in Leydig cells and early spermatogenic cells, suggesting a role in the acrosome reaction, as well as germ cell maturation and differentiation.
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PMID:Expression of c-KIT and its ligand, stem cell factor, in normal and subfertile human testicular tissue. 888 3

Deoxyspergualin (DSG) is an immunosuppresive agent of proven effectiveness in the prevention and treatment of transplant rejection; its most frequent side effect is reversible bone marrow suppression. To clarify the mechanisms of bone marrow suppression induced by DSG, we monitored the numbers of peripheral blood and marrow stem cells in C3H/HeN mice receiving 14 days of DSG injections at a highly immunosuppressive dose of 10 mg/kg/day. In the peripheral blood cells, DSG induced severe anemia and mild leukopenia because of a decrease in granulocyte counts, although these phenomena were reversible. During DSG administration, nucleated cell counts in the femur also markedly decreased, whereas the absolute numbers of various stem cells and progenitor cells, except for erythroid colony-forming units (CFU-E), remained normal or increased; CD34- or c-kit-positive and lineage-negative cell levels markedly increased on the day DSG administration ceased. These findings indicate that DSG-induced anemia and leukopenia are not initiated by a generalized killing of these stem cells, but rather by a transient suppression of their ability to mature. Significantly, the severe anemia induced by DSG resembles pure red cell aplasia in humans, because there were marked decreases in peripheral reticulocytes, marrow CFU-E, and erythroblasts, with no decrease in renal erythropoietin mRNA expression. Furthermore, DSG-induced anemia was completely ameliorated by treatment with human recombinant erythropoietin.
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PMID:Unique action of an immunosuppressive agent, deoxyspergualin, on hematopoiesis in mice. 940 93

Mutations of the receptor tyrosine kinase c-kit or its ligand stem cell factor (SCF), which is encoded as a soluble and membrane-associated protein by the Steel gene in mice, lead to deficiencies of germ cells, melanocytes, and hematopoiesis, including the erythroid lineage. In the present study, we have used genetic methods to study the role of membrane or soluble presentation of SCF in hematopoiesis. Bone marrow-derived stromal cells expressing only a membrane-restricted (MR) isoform of SCF induced an elevated and sustained tyrosine phosphorylation of both c-kit and erythropoietin receptor (EPO-R) and significantly greater proliferation of an erythrocytic progenitor cell line compared with stromal cells expressing soluble SCF. Transgene expression of MR-SCF in Steel-dickie (Sld) mutants resulted in a significant improvement in the production of red blood cells, bone marrow hypoplasia, and runting. In contrast, overexpression of the full-length soluble form of SCF transgene had no effect on either red blood cell production or runting but corrected the myeloid progenitor cell deficiency seen in these mutants. These data provide the first evidence of differential functions of SCF isoforms in vivo and suggest an abnormal signaling mechanism as the cause of the severe anemia seen in mutants of the Sl gene.
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PMID:Signaling through the interaction of membrane-restricted stem cell factor and c-kit receptor tyrosine kinase: genetic evidence for a differential role in erythropoiesis. 944 48


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