Ligand spectrum of hemoglobin activity of methemoglobin-reductase and hemolytic resistance of erythrocytes during chronic exposure to nitrates]

It is found that nitrite-ions formed as a result of biotransformation during long term feeding of calves with sodium and potassium nitrates induce changes in some biochemical parameters of blood, including HS-glutathione content in erythrocytes, acid hemolytic resistance of erythrocytes, activity of NAD-dependent methemoglobin-reductase, correlation of ligand forms of hemoglobin and its total content. It is supposed that the observed changes are of an adaptational character and, as a whole, provide for the optimization of both quantitative and qualitative composition of population of erythroid cells at the expense of erythropoiesis intensification.     

On the kinetics of erythroid cell differentiation in fetal mice. I. Microspectrophotometric determination of the hemoglobin content in erythroid cells during gestation

In a microspectrophotometric study, photographic emulsions and a computer are used for measuring the hemoglobin content of a large number (about 50,000) of erythroid cells in fetal mice. Histograms of the hemoglobin content in erythroid cells illustrate the kinetics of erythropoiesis in yolk sac derived nucleated cells in the fetal peripheral blood, in fetal liver, and in fetal spleen. After the occasional extrusion of their nucleus, yolk sac derived erythrocytes remain as “macrocytes” in fetal circulation two or three days longer than the nucleated yolk sac derived erythrocytes do. Erythrocytes in fetal liver have a constant hemoglobin content of 28 pg ² until day 17 of gestation. During further erythropoiesis in liver and then in the spleen, this amount is gradually adapted to the normal hemoglobin content in red blood cells of 16 pg.     

Characteristics of the pathways of erythroid cell differentiation in birds in anemia

A comparative study has been made of erythroid cell development pathways in the peripheral blood of pigeons during severe, moderate and weak forms of anaemia. Three modes of erythrocyte formation from bone marrow precursor are described: 1. A reserve erythropoiesis--the principal process during severe anaemia; the bone marrow precursors are basophylic erythroblasts which are reversibly blocked in phase G2 of the cell cycle; in results the rapid, increase of erythrocyte population above the normal level, although the cells have 25-30 per cent deficiency in haemoglobin content. 2) A mode of erythropoiesis, whose precursors are proliferating polychromatophylic erythroblasts; this is the principal mode of erythropoiesis at the moderate anaemia, leading to restoration of the normal quantity of erythrocytes with a normal haemoglobin content. 3) A mode of erythropoiesis with proliferating orthochromatic erythroblasts being precursors (which do not divide normally); this is the principal mode during the weak anaemia to result in a slow restoration of the number of erythrocytes with an excess in haemoglobin content. It is shown that regulation of the restoration processes during anaemia are characterized by a specific combination of cell proliferation and differentiation.     

THe dynamics of erythropoiesis inhibition in posttransfusion polycythaemia in the rat

The dynamics of erythropoiesis inhibition as the consequence of polycythaemia induced in rats by four to six transfusions of homologous erythrocytes was studied in detail. It was found, that, in rats with polycythaemia elicited by two transfusions of erythrocytes, erythropoiesis inhibition occurs 67h after the first transfusion and it is most pronounced in the period between 115-187 h. The hemopoietic system is not completely free from the inhibitory influence of polycythaemia up to 283 h after the first transfusion. Maintenance of a state of polycythaemia for 17 days by repeated transfusions strongly and durably inhibits the haemopoietic system. The red blood cell system remained for this whole period under the inhibitory effect.     

Bisphosphoglycerate synthase activity in cells of the erythrocytic line of rat

The specific activity of bisphosphoglycerate synthase (EC 2.7.5.4) is significantly higher in rat mature erythrocytes than in reticulocytes from phenylhydrazine treated animals, while 2,3-bisphosphoglycerate levels do not differ between them. The enzyme specific activity and the concentration of 2,3-bisphosphoglycerate are both negligible in the erythroid cell pool from the bone marrow of anaemic animals. Thus, a cellular specialization in the last stages of erythropoiesis is confirmed. Human bisphosphoglycerate synthase shows a lower specific activity than that of rat without a parallel decrease in 2,3-bisphosphoglycerate levels.     

Prior bleeding enhances the sensitivity of the in vivo micronucleus test

It has been reported that the sensitivity of the in vivo mouse bone marrow micronucleus test can be increased by inducing erythropoiesis with exogenous erythropoietin prior to treatment (Suzuki et al., 1989). In these studies we demonstrate that removing approximately 0.5 ml of blood from an adult male BDF1 mouse, another method for increasing the rate of erythropoiesis, synergistically increased the frequency of bone marrow micronucleated polychromatic erythrocytes induced by mitomycin C, with maximal enhancement occurring when the mutagen was given 24 h after bleeding. This enhancement response was also demonstrated for benzo[a]pyrene and dimethylnitrosamine but not for 2-acetylaminofluorene. These results indicate that bleeding mice prior to chemical treatment is a simple method for increasing the sensitivity of the micronucleus assay.     

The mechanism of inactivation of the bird erythrocyte genome. III. Pathways of terminal differentiation of erythrocytes]

Under the conditions of acute phenylhydrazine anemia in pigeons, early erythroblasts develop in reticulocytes with basophilic cytoplasm directly by passing the stages of polychromatophilic and ortochromic erythroblasts. During the maximum activity of bone marrow erythropoiesis stimulated by anemia over 80% of reticulocytes develop in such a way. A hypothesis is put forward to the effect that there exist in birds two alternative pathways of erythropoiesis: the main pathway which ensures the slow repopulation of blood by erythrocytes under normal conditions and the reserve pathway which opens for a short time under anemia and ensures rapid increase of the erythrocyte titer in blood up to its normal value.     

On the kinetics of erythroid cell differentiation in fetal mice. II. DNA and hemoglobin measurements of individual erythroblasts during gestation

Microspectrophotometric absorption measurements were used to determine the hemoglobin content of erythroid cells derived from the yolk sac during gestation of fetal C3H mice, from day 9 to day 15. Using the DNA content as a marker for the mitotic state between 2C and 4C phase, five successive cell generations and their mean hemoglobin contents were distinguished: 12 pg (pg, picogram = 10^?12 gm). 22.2 pg, 37 pg, 50 pg and 56 pg. In the final state, nucleated erythrocytes contained 98 ± 22 pg hemoglobin. Erythroid cells derived from the liver were measured on day 15 of fetal gestation. The hemoglobin content of proerythroblasts was below 0.3 pg. The two cell generations in the basophilic state had 0.6 pg and 1.7 pg respectively. Polychromatic erythroblasts yielded a hemoglobin content of 5.1 pg in the first cell generation and 7.5 pg in the second one. Orthochromatic erythroblasts contained 8 pg, reticulocytes 12 pg and mature erythrocytes 28 ± 7 pg hemoglobin. Calculations based on these data suggest that the rate of total hemoglobin synthesis is similar in both yolk sac and liver erythropoiesis. The difference between the final hemoglobin content in nucleated erythrocytes of yolk sac origin and that in hepatic erythrocytes can be explained by the different cell generation times.     

Isotopic evidence of unaccounted for Fe and Cu erythropoietic pathways

Despite its potential importance for understanding perturbations in the Fe-Cu homeostatic pathways, the natural isotopic variability of these metals in the human body remains unexplored. We measured the Fe, Cu, and Zn isotope compositions of total blood, serum, and red blood cells of ~50 young blood donors by multiple-collector ICP-MS after separation and purification by anion exchange chromatography. Zinc shows much less overall isotopic variability than Fe and Cu, which indicates that isotope fractionation depends more on redox conditions than on ligand coordination. On average, Fe in erythrocytes is isotopically light with respect to serum, whereas Cu is heavy. Iron and Cu isotope compositions clearly separate erythrocytes of men and women. Fe and Cu from B-type men erythrocytes are visibly more fractionated than all the other blood types. Isotope compositions provide an original method for evaluating metal mass balance and homeostasis. Natural isotope variability shows that the current models of Fe and Cu erythropoiesis violate mass balance requirements. It unveils unsuspected major pathways for Fe, with erythropoietic production of isotopically heavy ferritin and hemosiderin, and for Cu, with isotopically light Cu being largely channeled into blood and lymphatic circulation rather than into superoxide dismutase-laden erythrocytes. Iron isotopes provide an intrinsic measuring rod of the erythropoietic yield, while Cu isotopes seem to gauge the relative activity of erythropoiesis and lymphatics.     

Correlation of chromatin composition with metabolic changes in nuclei of primitive erythroid cells from chicken embryos

Changes in levels of biosynthesis of DNA, RNA, and histones were compared with relative proportions of each histone class during primitive erythropoiesis in embryonic chicks. We confirmed that erythrocyte-specific histone 5 (H5) was substantial in the earliest accessible, erythroblast-enriched stage and that it doubled in relative amount between polychromatic and orthochromatic stages to about 1 mol per 2 mol of each nucleosomal histone, still considerable less than in adult definitive erythrocytes. No other histones changed during primitive erythropoiesis, but the molar proportion of histone 1 (H1) always exceeded that of H5 in these cells, unlike definitive erythrocytes. The increase in content of H5 was accompanied by continued decline in synthesis of the other histones and DNA. The accumulation of H5 during development appears to occur in steps corresponding to the maturation of the primitive and definitive erythroid cell lines. Lysine-rich histones were more easily extracted from nuclei of the erythrosynthesis in whole cells and in isolated nuclei.     

Onset of hepatic erythropoiesis after malarial infection in mice

Plasmodium yoelii-infected erythrocytes were injected into mice with or without 6.5 Gy irradiation. This irradiation suppressed erythropoiesis and induced severe immunosuppression. However, these mice showed a rather delayed infection, suggesting that fresh erythrocytes may become malarial targets. In other words, malarial infection did not persist without newly generated erythrocytes in mice. We then examined erythropoiesis in the liver and bone marrow of mice with malaria. Surprisingly, erythropoiesis began in the liver. At this time, the serum level of erythropoietin (EPO) was prominently elevated and the EPO mRNA also became detectable in the kidney. Many clusters of red blood cells appeared de novo in the parenchymal space of the liver. These results revealed that malarial infection had a potential to induce the onset of hepatic erythropoiesis in mice.     

Blood and Bone Marrow Studies in Cattle Feeding on Brassica Species

Daily administration of 40—60 kg rape for 9 weeks to 8 cows produced no changes in the red blood picture. On the other hand a reduction of the myeloid: erythroid ratio and the maturity ratio of the erythroid cells of the bone marrow was found. This is interpreted as a sign of increased erythropoiesis. The Brassica-induced anaemia found in other investigations is assumed on several grounds to be haemolytic. The present study confirms this assumption, the increased breakdown of erythrocytes being entirely compensated by an increased erythropoiesis. The difference between the present and earlier reports, in which anaemia was found after a shorter time of feeding on roughly the same quantities of rape, is discussed, one possible explanation being that differences exist in rhodanid content between Brassica species.     

Erythrocyte ferritin in patients with normal and abnormal iron metabolism

Erythrocyte and serum ferritin was determined in 36 patients with different pictures of diseases and under bleeding therapy in idiopathic haemochromatosis (IH). With latent iron deficiency there was no significant difference in the ferritin content of erythrocytes in comparison with the control group. The intraerythrocyte ferritin content in idiopathic haemochromatosis is always increased and will normalize under bleeding therapy as well serum ferritin. After disrupting the therapy the ferritin content in erythrocytes will more rapidly increase again than in the serum. Increased erythrocyte ferritin could be identified in patients with anaemia due to ineffective erythropoiesis.     

The effect of various stage maturity of erythrocytes upon proliferatio rate of erythroid cells in "crown" of erythroblastic islands

Joint cultivation of small amounts of young and mature erythrocytes with bone marrow erythroblastic islands during 24 hours in liquid culture system results in erythropoiesis stimulation due to increase of number of cells in the state of mitosis in island's "crown". Prolonged joint cultivation and/or joint cultivation with plenty of premature and mature erythrocytes leads to inhibition of the erythropoiesis in the state of mitosis in the island's "crown". The maximum of the inhibitory effect was shown by erythrocytes from polycythemia rats.     

Effect of erythrocytes from intact, polycythemic, and anemic rats on erythropoiesis in erythroblastic island culture

Comparison of influence of erythrocytes of different stages of maturity, and their amount on erythropoiesis in erythroblastic island culture revealed their dose-dependent and maturity-dependent inhibiting effect on erythropoiesis. Erythrocytes of polycythemic rats inhibit maturing and formation of erythroblastic islands more intensively than erythrocytes of normal on anemic rats.     

The switch from larval to adult globin gene expression in Xenopus laevis is mediated by erythroid cells from distinct compartments

The transition of hemoglobins during metamorphosis of Xenopus laevis involves replacement of the larval erythrocytes by adult ones, suggesting that the developmental control of this event depends upon the growth characteristics of the precursor cells. To identify the erythroid precursor cells and to investigate their developmental fate, we analyzed the distribution of stage-specific globin mRNAs by northern blotting in dorsal and ventral fragments of stage 32 embryos after in vitro culture as well as presumptive erythropoietic tissues of tadpoles during metamorphosis. The histological analysis shows that erythrocytes differentiate only in ventral fragments, suggesting that the ventral blood islands and most likely also the dorsolateral mesoderm are the primary sites of erythropoiesis. We also demonstrate that the first generations of erythrocytes, already express the predominating larval-specific alpha-globin mRNAs. The globin mRNA patterns obtained from presumptive erythropoietic tissues suggest an important role of circulating precursor cells in larval erythropoiesis, whereas the liver appears to be the main site of formation and maturation of the adult erythrocytes. Tentatively we propose that anuran erythropoiesis is dependent upon a self-perpetuating stem-cell line and that the larval and the adult erythrocytes are derived from successive generations of erythroid precursors, whose commitment may be imposed by the erythropoietic sites.     

The ferritin content of human red blood cells during the replacement of embryonic cells by fetal cells

Mature human embryonic erythrocytes (hemoglobin is ≥ 90% of the cellular protein) contained at least 20 times as much ferritin as human adult erythrocytes, suggesting the possibility that the embryonic red cells participate in iron storage as they do in other embryonic or larval vertebrates. The ferritin content of mature red cells in the circulation declined when fetal red cells replaced embryonic red cells; the cell replacement was monitored by the disappearance of embryonic ε-chains and the appearance of the fetal globin chains, γ^A and γ^G. A constant ratio of 0.67 was obtained for $\text{γ}{}^{\mathrm{<mtext>G</mtext>}}\text{γ}{}^{\mathrm{<mtext>A</mtext>}}\text{+ γ}{}^{\mathrm{<mtext>G</mtext>}}$ from the first detectable appearance (4 weeks after conception) until 13 weeks, a value which is similar to the value previously obtained at 20 weeks gestation and birth but higher than that observable in adults; thus, both γ^G and γ^A chains are produced in similar amounts throughout gestation. The high levels of ferritin in normal human embryonic erythrocytes emphasize the similarity of erythropoiesis in human embryos and other vertebrates. In addition, the results show that red cell ferritin can be used as a marker for studying the mechanism of induction of embryonic erythropoiesis in cultured cell lines, such as K562 from human chronic myelocytic leukemia, and that ferritin content may also serve as a marker for cellular transformations involving reversions to embryonic erythropoiesis.     

Adding self-renewal in committed erythroid progenitors improves the biological relevance of a mathematical model of erythropoiesis

We propose a new mathematical model of erythropoiesis that takes a positive feedback of erythrocytes on progenitor apoptosis into account, and incorporates a negative feedback of erythrocytes on progenitor self-renewal. The resulting model is a system of age-structured equations that reduces to a system of delay differential equations where the delays account for progenitor compartment duration and cell cycle length. We compare this model with experimental data on an induced-anemia in mice that exhibit damped oscillations of the hematocrit before it returns to equilibrium. When we assume no self-renewal of progenitors, we obtain an inaccurate fitting of the model with experimental data. Adding self-renewal in the progenitor compartment gives better approximations, with the main features of experimental data correctly fitted. Our results indicate the importance of progenitor self-renewal in the modelling of erythropoiesis. Moreover, the model makes testable predictions on the lifespan of erythrocytes confronted to a severe anemia, and on the progenitors behavior.     

Characteristics of physico-chemical properties of circulating erythrocytes in the post-anoxia period

The normobarometric hypoxic hypoxia stimulates different alterations in the fundamental parameters of physicochemical properties of the peripheric blood erythrocytes and has a stimulating effect on the system of the erythropoiesis in post-hypoxia period.