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At least 19 recordsLinked to original sources
PubMed1991

Megaloblastic hematopoiesis in vitro. Interaction of anti-folate receptor antibodies with hematopoietic progenitor cells leads to a proliferative response independent of megaloblastic changes.

We tested the hypothesis that anti-placental folate receptor (PFR) antiserum-mediated effects on hematopoietic progenitor cells in vitro of increased cell proliferation and megaloblastic morphology were independent responses. We determined that (a) purified IgG from anti-PFR antiserum reacted with purified apo- and holo-PFR and specifically immunoprecipitated a single (44-kD) iodinated moiety on cell surfaces of low density mononuclear cells (LDMNC); (b) when retained in culture during in vitro hematopoiesis, anti-PFR IgG (in contrast to PFR-neutralized anti-PFR IgG and nonimmune IgG) consistently led to increased cloning efficiency of colony forming unit-erythroid (CFU-E), burst forming unit-E (BFU-E), CFU-granulocyte macrophage (CFU-GM), and CFU-GEM megakaryocyte (CFU-GEMM), and objectively defined megaloblastic changes in orthochromatic normoblasts from CFU-E- and BFU-E-derived colonies; (c) when anti-PFR antiserum was removed after initial (less than 1 h) incubation with LDMNC, a cell proliferation response was induced, but megaloblastic changes were not evident. (d) Conversely, delay at 4 degrees C for 24 h before long-term plating with antiserum resulted in megaloblastosis without increased cell proliferation; (e) however, 500-fold molar excess extracellular folate concentrations completely abrogated the expected anti-PFR antiserum-induced megaloblastic changes, without altering cell proliferative responses. Thus, although cell proliferative and megaloblastic changes are induced after short-term and prolonged interaction of antibody with folate receptors on hematopoietic progenitors, respectively, they are independent effects.

Animals↗
PubMed1983

The changing pattern of megaloblastic anemia: megaloblastic anemia in Israel.

The causes of megaloblastic anemia were studied in a survey of patients admitted to six Israeli hospitals over a period of 15 yr. Among the 203 patients identified, 69% had pernicious anemia, 12% had gastrointestinal disease, 9% had primary nutritional deficiency of whom only 1% were associated with pregnancy, and 7% had selective vitamin B12 malabsorption with albuminuria. Comparison with previously published surveys showed, that in contrast with earlier studies where primary nutritional deficiency was the cause of megaloblastic anemia in about 70% of cases and pernicious anemia in only 20%, in more recent studies the proportion of cases with primary nutritional anemia in general and those associated with pregnancy in particular was much lower. This is most probably the result of improved standards of living and a national program of preventive folate supplementation at maternity clinics. A potential hazard of such preventive programs is the aggravation of neurological complications in patients with undiagnosed vitamin B12 deficiency. Early recognition of pernicious anemia and other forms of selective B12 malabsorption is a new challenge created by the changing pattern of megaloblastic anemias.

Adolescent↗
PubMed2006

Incidence of megaloblastic anaemia and its correction in leishmaniasis--a prospective study at BPKIHS hospital, Nepal.

Fifty (50) cases of Leishmaniasis were included in a prospective study after making the diagnosis based on the demonstration of L D Bodies on bone marrow aspirate. Hemoglobin (Hb) and total leucocyte count (TLC) were less than 10 gm/dl and 4000 per/ml respectively in 22 out of 50 cases. Among 50 cases, 30 showed macrocytic red cell and hypersegmented neutrophils on peripheral blood smear as features of megaloblastic anemia. Out of 30 cases of leishmaniasis with megaloblastic anemia, 10 cases showed decreased reticulocyte count. Bone marrow aspiration cytology showed megaloblastic maturation in erythroid series and giant metamyelocytes in myeloid series in all 30 cases of leishmaniasis with megaloblastic changes. Bone marrow iron was also increased in these cases. However megakaryocyte was normal in all. Among 30 cases of leishmaniasis with megaloblastic changes, 15 cases were treated with sodium antimony gluconate (SAG) only and other 15 with SAG, folic acid and Vit. B12. Rest 20 cases of leishmaniasis without megaloblastic changes were also treated with SAG only. After treatment with SAG alone as well as with SAG, folic acid and vit. B12, hemoglobin and TLC improved in all 50 cases. Of 15 cases of leishmaniasis with megaloblastic changes, who were treated with SAG, folic acid and vit. B12, the reticulocyte count reached at peak on the 7th day and normalized at the end of 4th week. Red blood cells (RBC) also became normocytic normochromic and neutrophils became normal on peripheral blood smear. But no change was observed in reticulocyte count, RBC and white blood cell (WBC) morphology on peripheral blood smear in cases of leishmaniasis without megaloblastic changes and other 15 cases of leishmaniasis with megaloblastic changes, who received SAG only.

Anemia, Megaloblastic↗
PubMed1991

Natural autoantibodies may play a role in ineffective erythropoiesis during megaloblastic haemopoiesis.

Marrow aspirates from 11 patients with megaloblastic haemopoiesis and from 14 healthy individuals with normoblastic haemopoiesis were studied for antibodies associated with polychromatic/orthochromatic erythroblasts, using an 125I-labelled anti-human immunoglobulin reagent and autoradiography. In addition, the expression on these cells of receptors for FcIgG (FcR) and of the type I receptor for fragments of the third complement component (CR1) were investigated with receptor-specific monoclonal antibodies, 125I-labelled anti-mouse immunoglobulin and autoradiography. The percentages of immunoglobulin-positive erythroblasts were significantly greater in the megaloblastic than in the normoblastic marrows. Abnormally high percentages of labelled erythroblasts were present in patients without any manifestations of an autoimmune disorder. The percentage of labelled erythroblasts in the marrows of the patients correlated well with the degree of anaemia. FcR were absent on the majority of megaloblasts or normoblasts while the expression of CR1 was similar in both types of cell. The difference between the percentage labelling of megaloblasts and normoblasts was therefore unlikely to be due to greater binding of immune complexes with or without associated complement to megaloblasts than normoblasts. The megaloblast-bound immunoglobulin is, therefore, likely to have recognized abnormally expressed epitopes on the surface of megaloblasts. The results suggest that natural autoantibodies play a role in the destruction of erythroblasts during megaloblastic haemopoiesis.

Antibodies, Monoclonal↗
PubMed2004

Role of myeloperoxidase index in differentiation of megaloblastic and aplastic anemia.

BACKGROUND: Elevated neutrophil myeloperoxidase may have a role in the diagnosis of megaloblastic erythropoiesis. AIMS: To study the differentiating role of myeloperoxidase index in megaloblastic and aplastic anemia. SETTINGS AND DESIGN: The myeloperoxidase index (MPXI) was studied in 96 patients with megaloblastic and aplastic anemia diagnosed on bone marrow aspiration and biopsy examinations. METHODS AND MATERIALS: MPXI was measured with Technicon H1 (Bayer) automated analyzer. Nonparametric Mann-Whitney statistical test was used to compare the MPXI values between groups. RESULTS: The mean MPXI in megaloblastics and aplastic anemia was 18.3 and 1.8 (p< 0.001) respectively. MPXI> 20 denoted megaloblastic and MPXI <-11.6 denoted aplastic anemia. CONCLUSION: MPXI measurement may assist differentiation of megaloblastic from aplastic anemia, while MPXI> 20 rules out aplastic and MPXI <-11.6 rules out megaloblastic anemia.

Adolescent↗
PubMed1989

Thymidylate synthesis and utilization via the de novo pathway in normal and megaloblastic human bone marrow cells.

We have measured the thymidylate synthetase activity of intact bone marrow cells using a 3H2O release assay. The mean thymidylate synthetase activity of vitamin B12- or folate-deficient megaloblastic marrow cells was reduced only in severely anaemic patients. There was a correlation between thymidylate synthetase activity and RBC in patients with megaloblastic haemopoiesis. The mean rate of incorporation into DNA of 6-3H deoxyuridine was similar in megaloblastic and normoblastic marrows. The rate of thymidylate synthesis exceeded its incorporation into DNA in all marrows, and the mean ratio between synthesis and incorporation was similar in normoblastic and megaloblastic patients, being independent of both thymidylate synthetase activity and RBC. Thus de novo thymine nucleotides were not utilized more efficiently in megaloblastic marrow cells. These data suggest that impaired thymidylate synthesis may not be the central defect in megaloblastic haemopoiesis, and that there is only a single pool of thymidine triphosphate in human bone marrow cells.

Anemia, Macrocytic↗