Ultrastructural studies of the bone marrow in sickle cell anaemia. II. The morphology of erythropoietic cells and their response to deoxygenation in vitro

Electron microscopic studies of bone marrow aspirates obtained from patients with homozygous sickle cell anaemia (HbSS) were fixed immediately without attempts to deoxygenate the samples. Erythroblasts and normoblasts in these preparations were devoid of haemoglobin polymers or other indications of sickling. Furthermore, the nucleated erythroid cells from sickle-cell patients presented an ultrastructural morphology indistinguishable from that of identically-processed erythroid cells in marrow samples from normal human volunteers. This report presents a description of the ultrastructural features of pronormoblasts and normoblasts in normal and sickle-cell marrows and stresses the essentially normal appearance of nucleated erythroid elements in sickle cell anaemia. Exposure of sickle-cell marrow aspirates to nitrogen at 37 degrees C for 30 min resulted in haemoglobin polymerization in most erythrocytes and reticulocytes but only in 10-20% of the nucleated erythroid cells. Haemoglobin polymers in the form of intertwining fibre meshworks were observed in reticulocytes, orthochromatic and polychromatophilic normoblasts, but were absent in basophilic normoblasts and pronormoblasts. The results suggest that the concentration of haemoglobin in intramedullary normoblasts may be the limiting factor determining the predisposition of these cells to undergo sickling as well as the pattern of haemoglobin aggregation. Under the physiological conditions prevailing in the marrow, haemoglobin concentration in normoblasts may be insufficient to result in aggregation and polymerization.

Congenital dyserythropoietic anaemia with features of both type I and TYPE II

A 13 year old girl with the typical clinical and haematological picture of congenital dyserythropoietic anaemia (CDA) is reported. The bone marrow is highly cellular with 70 per cent erythroid cells, and 28% bi- and multinuclear cells among the orthochromatic and polychromatic erythroblasts. Moderate megaloblastoid changes are present. On light microscopy the findings are in agreement with those described in CDA type II. On electron microscopy both the cytoplasmatic changes described as typical of CDA type II, and the nuclear changes found in type I can be demonstrated. The acidified serum test (Ham test) is negative with normal sera. The patient's red blood cells show increased agglutinability with anti-I and and anti-I antibodies, but no haemolysis. Total serum lipids are about 50% of the normal average. All lipoprotein classes are lowered to about the same extent. The total phospholipid content of the erythrocytes is slightly reduced, with a moderate, relative increase of the lecithin fraction and a decrease of the sphingomyelin fraction. Doubts can be raised about the tenability of the current classification of CDA based on morphological and serological criteria, especially about the distinction between types I and II.

Congenital dyserythropoietic anaemia with peculiar nuclear abnormality

A patient with clinical and haematological findings compatible with congenital dyserythropoietic anaemia (CDA) most porbably type II is described. In contradistinction to previous observations, electron microscope examination of the erythroid cells in the bone marrow showed the concomitant appearance of nuclei at different maturation stages in a single cell. In addition, a marked tendency toward multinuclearity of the megakaryocytes was found. The mature erythroblasts showed an increased uptake of 3H-thymidine less than is normally found in these cells. Thes findings suggest an impairment in RNA and DNA synthesis.

Clinical and ultrastructural observations in primary acquired sideroblastic anemia

The clinical and laboratory findings in three patients with primary acquired sideroblastic anemia (PASA) are described. The results demonstrate that what seems to be a well defined entity of the large group of sideroblastic anemias, is in itself a heterogeneous subgroup, with differences capable of detection by more extensive studies. Electron microscopic examination of erythroid cell precursors confirmed previously described features such as deposition of large amounts of iron, mainly in the mitochondria. The precipitated serum proteins revealed an increased content of ferritin molecules only in the patients and not in control individuals, suggesting an increased supply of iron to the erythroid precursors. This finding could serve as an additional mechanism for the accumulation of iron in the erythroid precursors, considering also the defect in heme synthesis and increased permeability of the erythroid membrane for iron, described in this condition.

Nucleolar changes in maturing avian erythroblasts and erythrocytes

Maturing erythroblasts and erythrocytes were studied in chickens and adult hens to provide more information on the presence and frequency of various nucleolar types in these cells. Nucleoli were present at all stages of erythroblastic and erythrocytic development except in the case of a few reticulocytes and the mature erythrocytes. The number of nucleoli per cell (expressed as the nucleolar coefficient) reached a maximum at the stage of the polychromatic erythroblast. Early erythroblasts were characterized by the presence of compact nucleoli or nucleoli with nucleolonemata. Rings shaped nucleoli and micronucleoli increased in number with further maturation. Cells of the final erythroblast stage (orthochromatic erythroblasts) contained mostly micronucleoli, and micronucleoli alone were present in reticulocytes and mature erythrocytes.

Light and electron microscopic studies of the bone marrow and blood cells in chronic panmyelosis including polycythemia vera and primary thrombocythemia

Both bone marrow and peripheral blood was investigated light and electron microscopically in 3 cases with polycythemia vera, 2 cases with primary thrombocythemia and 1 case with panmyelosis. In 5 cases the peripheral blood showed persistent increase in cells of two or three hematopoietic systems. Giant thrombocytes in the peripheral blood were seen in 3 cases. Erythroblasts, granulocytic young forms, and megakaryocytes were often observed in the blood. Histologic bone marrow examination showed prominent proliferation of all 3 hematopoietic cells in every case. Cytological and electron microscopical examinations of the bone marrow revealed many mitotic figures, morphological abnormalities, and unbalanced nucleocytoplasmic maturation in various hematopoietic cells. These findings suggested that the proliferation of all 3 hematopoietic cells in the bone marrow was not simply reactive in nature, but an idiopathic progressive process. It is considered that these disorders and primary myelosclerosis represent no separate entities and must be unified as "chronic panmyelosis".

Observations on the ultrastructure of erythropoietic cells and reticulum cells in the bone marrow of patients with homozygous beta-thalassaemia

An electron microscopic study of marrow fragments from patients with homozygous beta-thalassaemia has shown that 3% of early polychromatic erythroblast profiles and 20% of late polychromatic erythroblast profiles contain intracytoplasmic alpha-chain precipitates. Various nuclear abnormalities were found including the loss of parts of the nuclear membrane and the presence of intranuclear alpha-chain precipitates, and these abnormalities were virtually confined to the non-dividing, late polychromatic erythroblasts. As most profiles of the proliferating early polychromatic erythroblasts did not contain intracytoplasmic or intranuclear alpha-chain precipitates, it is suggested that the arrest of many of these cells in the G1 phase of the cell cycle may be related to the presence of an excess of free alpha-chains rather than to the presence of alpha-chain precipitates within them. The cytoplasm of the bone marrow reticulum cells contained early and late polychromatic erythroblasts at various stages of degradation, providing direct evidence of ineffective erythropoiesis.

Congential dyserythropoietic anemia--type IV

Congenital dyserythropoietic anemia is characterized by ineffective erythropoiesis and increased numbers of multinucleated red cell precursors in the marrow. This syndrome has been subclassified on the basis of morphologic differences in the red cell precursors. Type I is characterized by megaloblastoid erythropoiesis and macrocytosis; Type II, by normoblastic multinuclearity and normocytosis; and Type III, by frequent giant multinucleated erythroblasts and macrocytes. Type II is further distinguished from the other types by serologic and ultrastructural abnormalities. The patient presented in this report does not fit any of the above categories; her red cells are similar to Type II congenital dyserythropoietic anemia cells, but no characteristic ultrastructural or serologic abnormalities are present. It is suggested that this patient may represent an additional variant of congenital dyserythropoietic anemia, Type IV.

Septate-like junctions in abnormal erythroblasts: cytochemical, ultrastructural and freeze-etch studies

Ultrastructural studies of the bone marrow of a patient with refractory anemia revealed aberrant erythroblasts with unique cell junctions. Periodic structures linked adjacent processes on the same cell as well as surfaces of neighboring erythroblasts. Inclusions circumscribed by similar complexes were also present in the cytoplasm. The junction appeared in cross sections as two rigidly parallel unit membranes separated by 250-300 A interspace with two regular arrays of facing 70 A particles at intervals of 160-200 A. These intracellular specializations were present between erythroblasts at various stages of maturation and between, mono, bi or multinucleated erythroblasts. Junctions were permeable to lanthanum and many that appeared to be intracellular were demonstrated to be continuous with the extracellular space. The fact that others were not penetrated by lanthanum indicates that detachment of the interdigitating processes from cells of origin could have occurred. In freeze-etched replicas, distribution of membrane particles was random in areas of septate-like junctions, although parallel rows were sometimes observed both on A and B inner hydrophobic faces of the membrane leaflets. Junctional complexes in tissue culture appeared to have been disrupted and were not reestablished; however, inclusions resembling internalized junctions were observed associated with multivesicular bodies. Ineffective erythropoiesis and the resulting refractory anemia appear to be associated with the presence of the described anomalous junctional complexes.

Dyserythropoiesis and annulate lamellae

Cytoplasmic and intranuclear annulate lamellae in the erythroblasts from patients with dyserythropoietic anaemia (megaloblastic anaemia, dysplastic anaemia and erythroleukaemia) are described. Annulate lamellae have mainly been observed in oocytes, in embryonic tissues and in malignant cells. Their occurrence in dyserythropoietic anaemia may be related to the reappearance of fetal characteristics in the erythroblasts and erythrocytes.

[Ultrastructure of human yolk sac]

The yolk-sac of a 15 mm and 20 mm long human embryo was investigated by the aid of electron microscope. Ultrastructure of the yolk-sac and that of the precursors of haemopoietic cells is described. The latter have been found to have a close correlation with endodermal cells.

Fine structural and cytochemical identification of microperoxisomes in developing human erythrocytic cells

An alkaline diaminobenzidine (DAB) medium has been used to identify peroxidase activity in small granules (0.09 to 0.2 mu in diameter) present in all forms of maturing erythrocytic cells with the exception of erythrocytes. These granules, which were more frequent in proerythroblasts (from two to seven by thin section), were distinct from pleomorphic granules present in the close proximity to the Golgi apparatus. They were also distinct from ferritin molecules which were seen as aggregates in siderosomes of polychromatophilic erythroblasts. They often appeared in close association with the smooth membrane of the nuclear envelope. Optimal conditions for the visualization of these granules by incubation in alkaline DAB were obtained when the peroxidase activity of hemoglobin was reduced by addition of low concentrations of potassium cyanide. Lack of hydrogen peroxide in the incubation media completely inhibited the staining reaction of hemoglobin, while the positive reaction persisted in the granules. Aminotriazole in the incubation media prevented the staining of these organelles. These findings suggest that small granules seen in maturing erythroblasts contain catalase and that they correspond to microperoxisomes described in other tissues. The mechanism of their disappearance during reticulocyte maturation is unknown. The relationship between particulate catalase of erythroblasts and soluble erythrocytic catalase has not been elucidated.

Selective eradication of rat bone marrow erythroid cells by administration of cytosine arabinoside. Observations on resumption phase of erythropoiesis

The in vivo effect of a single i.p. injection of cytosine arabinoside (250 mg/kg body weight) on the rat bone marrow is reported. Cytosine arabinoside (ara-C), a potent inhibitor of DNA-synthesis, was seen to produce selective necrosis of fast cycling bone marrow erythroblasts. The depleted erythroid marrow is replenished by stem cells which are members of the lymphoid-transitional cells compartment. An indirect correlation between the degree of erythroid cell depletion and the extent of marrow lymphocytosis was noted 6-12 h after the administration of ara-C. At 24-48 h, however, the marrow returned to its normal activity. The rat bone marrow 6-12 h following a single injection of ara-C is suggested as an experimental model for providing stem cells committed to the erythroid line.

A study on the nuclear extrusion of mammalian erythroblast

A study was carried out to clarify the mechanism of nuclear extrusion of mammalian erythroid cells by observing erythroblasts of rabbit under various conditions in vitro. The animals were made anemic by phenylhydrazine injection and erythroblasts were obtained from the peripheral blood and observed morphologically after a certain time of incubation. After two hour incubation at 37 degrees C, about 50% of erythroblasts were denucleated. The nuclear extrusion was remarkably suppressed by the inhibitor for electron transport system or by uncouplers for oxidative phosphorylation. It was also arrested by the inhibitor of cell movement, like cytochalasin B. In contrast, monoiodo-acetic acid, ouabain and colchicine hardly inhibited the nuclear extrusion. The observations indicated that the nuclear extrusion of mammalian erythroblast is an energy-dependent process in connection with the function of contractile microfilamentous system susceptible to cytochalasin B.

Hematopoiesis in the embryonic mouse spleen. II. Alterations after phenylhydrazine administration to the mothers

The effect of phenylhydrazine (PHZ) on the hematopoietic events in the embryonic spleen of C57Bl/6J mice was examined by light and electron microscopy. Following PHZ in injections to the mothers, the embryonic spleen revealed a marked increase in erythroid precursors, with a shift to mature cells. This phenomenon was part of a more generalized stimulation of erythorpoiesis, expressed by a shift to mature red cell precursors in the embryonic livers and an increase in the percentage of non-nucleated cells in the embryonic peripheral blood. Concomitantly stimulation of phagocytosis in the spleen of embryos in the early gestational days and increased vascularity were observed, and a later effect of granulocytopoietic stimulation. The effect on erythropoiesis in the embryonic spleen might be a sequence of erythropoietin stimulation, either in the mothers or the fetuses, due to anemia and hypoxia following PHZ injections.

The ultrastructure of dyserythropoiesis in aplastic anaemia

Electron microscopy of erythropoiesis in aplastic anaemia has demonstrated some unique features of dyserythropoiesis at the ultrastructural level, which contribute to understanding of the morphological features which are seen in the light microscope. The findings provide further evidence for the presence of qualitative defects in erythropoiesis in aplastic conditions. The alterations seen included bi- and multinucleated cells, intercellular bridges containing microtubules, internuclear chromatin bridges, irregular nuclear shapes, juxta-nuclear and peripheral cisternal structures, ringed sideroblasts, a diversity of intranuclear inclusions, nuclear clefts in both eu- and heterochromatin, and a variety of anomalies of the nuclear membrane. The significance of the occurrence of these anomalies in aplastic anaemia is considered and the role of the nuclear membrane and of endoplasmic reticulum in the pathogenesis of aplastic anaemia is discussed.

[Isolation of erythroblastic islands. Study by optical and scanning electron microscopy (author's transl)]

1. A simple technique is described for isolation and estimation of number of erythroblastic islands (EBI) in rat bone marrow. The number of EBI decreases during hypertransfusion polycythemia, and increases during experimentally-induced hemolytic anemia. It has also been possible to maintain EBI in vitro, under culture conditions, for up to 36 hours. 2. Each EBI contains a central cell having the character of a macrophage-histiocyte which adheres to glass and spreads, while still retaining its connections with the erythroblasts. 3. In an EBI the erythroblasts are arranged in the form of concentric rings, with the outer cells being more mature than the inner. The outermost layer is frequently made up of reticulocytes even in the isolated island. The erythroblasts of a single ring appear to be at the same stage of maturation which suggests that they are derived from the same stem cell. 4. Using a coordinate reference system, studies of nuclear expulsion were made, by both optical microscopy and scanning electron microscopy.

Ultrastructural study of the erythropoietic events in human embryonic livers

The ultrastructural features of the erythropoietic events in 5- to 9-week embryonic livers are described. By the 5th week of gestation, the human embryonic liver becomes an active site of erythropoiesis represented by the formation of reticular-mesenchyme cells and hemocytoblasts. At the 6--7th week, the first proerythroblasts and islands of polychromatophilic and orthochromatic erythroblasts can be detected. From this stage, by the 8th week of embryonic development, the liver assumes its function as a fully developed embryonic organ. In the embryonic livers studied there were no signs of granuloor lymphopoiesis. Although megakaryocytes were found in the 8-week embryonic liver, there is no evidence that these cells are produced in the liver. Macrophages were found in the 5-week embryonic liver.