Outbreak of aplastic crises in sickle cell anaemia associated with parvovirus-like agent

Since 1952, 112 children with sickle cell anaemia (SCA) in Jamaica have had an aplastic crisis. Outbreaks occurred in 1956, 1960, 1065-67, 1971-73, and 1979-80. Most cases occurred in children under 10 years of age, and an aplastic crisis in a patient over the age of 15 years is rare. There were 38 cases in 1979-80 and stored serum specimens from 28 of these were available for virus studies. Evidence for infection with a parvovirus-like agent was found in 24 of these 28 cases. Viral antigen was detected in 2 patients, both of whom demonstrated seroconversion. Seroconversion during 1980 was detected in a further 7, increasing amounts of antibody during the convalescent period were found in 5, antibody was found in 2 of 4 patients from whom only an acute phase specimen was available and the remaining 10 were antibody positive in the only convalescent phase sample available for testing. Antibody was found in 4 of 94 controls with the SS genotype (in retrospect 2 of these may have had an aplastic crisis) and in 17% of 48 controls with a normal haemoglobin (AA) genotype. The results accord with the possibility that the parvovirus-like agent is the principal cause of aplastic crisis in SCA.

Exosomes from Plasmodium yoelii-infected reticulocytes protect mice from lethal infections

Exosomes are 30-100-nm membrane vesicles of endocytic origin that are released after the fusion of multivesicular bodies (MVBs) with the plasma membrane. While initial studies suggested that the role of exosomes was limited to the removal of proteins during the maturation of reticulocytes to erythrocytes, recent studies indicate that they are produced by different types of cells and are involved in promoting inter-cellular communication and antigen presentation. Here, we describe the isolation and characterization of exosomes from peripheral blood of BALB/c mice infected with the reticulocyte-prone non-lethal Plasmodium yoelii 17X strain. Importantly, proteomic analysis revealed the presence of parasite proteins in these vesicles. Moreover, immunization of mice with purified exosomes elicited IgG antibodies capable of recognizing P. yoelii-infected red blood cells. Furthermore, lethal challenge of immunized mice with the normocyte-prone lethal P. yoelii 17XL strain caused a significant attenuation in the course of parasitaemia, increased survival time, and altered the cell tropism to reticulocytes. These results were obtained also when the exosomes were isolated from a P. yoelii-infected reticulocyte culture indicating that reticulocyte-derived exosomes carry antigens and are involved in immune modulation. Moreover, inclusion of CpG ODN 1826 in exosome immunizations elicited IgG2a and IgG2b antibodies and promoted survival, clearance of parasites and subsequent sterile protection of 83% of the animals challenged with P. yoelli 17XL. To our knowledge, this is the first report of immune responses elicited by exosomes derived from reticulocytes opening new avenues for the modulation of anti-malaria responses.

Conditional deletion of the Bcl-x gene from erythroid cells results in hemolytic anemia and profound splenomegaly

Bcl-x is a member of the Bcl2 family and has been suggested to be important for the survival and maturation of various cell types including the erythroid lineage. To define the consequences of Bcl-x loss in erythroid cells and other adult tissues, we have generated mice conditionally deficient in the Bcl-x gene using the Cre-loxP recombination system. The temporal and spatial excision of the floxed Bcl-x locus was achieved by expressing the Cre recombinase gene under control of the MMTV-LTR. By the age of five weeks, Bcl-x conditional mutant mice exhibited hyperproliferation of megakaryocytes and a decline in the number of circulating platelets. Three-month-old animals suffered from severe hemolytic anemia, hyperplasia of immature erythroid cells and profound enlargement of the spleen. We demonstrate that Bcl-x is only required for the survival of erythroid cells at the end of maturation, which includes enucleated reticulocytes in circulation. The extensive proliferation of immature erythroid cells in the spleen and bone marrow might be the result of a fast turnover of late red blood cell precursors and accelerated erythropoiesis in response to tissue hypoxia. The increase in cell death of late erythroid cells is independent from the proapoptotic factor Bax, as demonstrated in conditional double mutant mice for Bcl-x and Bax. Mice conditionally deficient in Bcl-x permitted us for the first time to study the effects of Bcl-x deficiency on cell proliferation, maturation and survival under physiological conditions in an adult animal.

Effects of recombinant human erythropoietin in infants with the anemia of prematurity: a pilot study

In an attempt to stimulate endogenous erythrocyte production and thereby provide an alternative to erythrocyte transfusions, we administered recombinant human erythropoietin (rHuEpo) in doses of 75 to 300 units/kg/wk to seven infants with the anemia of prematurity. Treatment was started between 21 and 33 days of life, maintained for 4 weeks, and was well tolerated. All the patients had low baseline serum erythropoietin levels. After rHuEpo therapy, the number of reticulocytes increased from a mean baseline count of 75 x 10(9)/L to 95, 141, and 165 x 10(9)/L on days 7, 10, and 14 of therapy, respectively. Correction or stabilization of the anemia was observed in six of seven patients, whose estimated total erythrocyte volume increased by 49% during therapy (vs a predicted increment of 18% in the absence of rHuEpo). In one patient, however, the hematocrit declined during the treatment, and in three of the responders a secondary fall in hematocrit was noted either during therapy or after its discontinuation. Serum iron and ferritin levels rapidly decreased after the initiation of rHuEpo therapy, and in most patients transient early thrombocytosis and late neutropenia were observed. These data suggest that rHuEpo may correct or stabilize the anemia of prematurity. Its effects, however, may be limited by a variety of factors, among which iron availability probably plays an important role. Controlled studies will be needed to confirm these preliminary observations.

A mathematical model of hematopoiesis—I. Periodic chronic myelogenous leukemia

Periodic chronic myelogenous leukemia (PCML) is an interesting dynamical disease of the hematopoietic system in which oscillating levels of circulating leukocytes, platelets and/or reticulocytes are observed. Typically all of these three differentiated cell types have the same oscillation period, but the relation of the oscillation mean and amplitude to the normal levels is variable. Given the appearance of the abnormal Philadelphia chromosome in all of the nucleated progeny of the hematopoietic stem cells (HSCs), the most parsimonious conclusion is that chronic myelogenous leukemia, and its periodic variant, arise from derangements partially involving the dynamics of the stem cells. Here, we have synthesized several previous mathematical models of HSC dynamics, and models for the regulation of neutrophils, platelets and erythrocytes into a comprehensive model for the regulation of the hematopoietic system. Based on estimates of parameters for a typical normal human, we have systematically explored the changes in some of these parameters necessary to account for the quantitative data on leukocyte, platelet and reticulocyte cycling in 11 patients with PCML. Our results indicate that the critical model parameter changes required to simulate the PCML patient data are an increase in the amplification in the leukocyte line, an increase in the differentiation rate from the stem cell compartment into the leukocyte line, and the rate of apoptosis in the stem cell compartment. Our model system is particularly sensitive to changes in stem cell apoptosis rates, suggesting that changes in the numbers of proliferating stem cells may be important in generating PCML.

Sickle cell disease in Orissa State, India

A study of 131 patients with homozygous sickle cell (SS) disease in Orissa State, India, indicated that, compared with Jamaican patients, Indian patients have higher frequencies of alpha thalassaemia, higher fetal haemoglobin, total haemoglobin, and red cell counts, and lower mean cell volume, mean cell haemoglobin concentration, and reticulocyte counts. Indian patients have a greater frequency and later peak incidence of splenomegaly, and hypersplenism is common. Painful crises and dactylitis are not uncommon in Indian patients but chronic leg ulceration is rare. Homozygous sickle cell disease in Orissa is similar to that in the Eastern Province of Saudi Arabia and is very different from that in populations of West African origin.

Effect of high doses of human recombinant erythropoietin on the need for blood transfusions in preterm infants

To determine whether prophylactic treatment with recombinant human erythropoietin (rHuEPO) and iron would reduce the need for blood transfusions, we randomly assigned 22 premature infants with gestational ages less than or equal to 32 weeks and birth weights less than or equal to 1.75 kg to receive rHuEPO, 400 IU/kg three times a week, plus iron, 20 mg/wk intravenously, from the second day of life (11 infants), or no rHuEPO and no iron (11 infants). The two groups had similar birth weights and clinical variables. The treated infants required fewer blood transfusions (0.8 +/- 1.5 vs 3.1 +/- 2.1; p = 0.01) and less volume of packed erythrocytes (14.2 +/- 25.9 vs 48.4 +/- 34.0 ml/kg; p = 0.02). The amounts of blood sampled were not different (19.5 +/- 21.1 vs 27.8 +/- 19.1 ml/kg; p = 0.35). Reticulocyte and hematocrit values were higher in the treated group (4.46% +/- 0.8% vs 1.49% +/- 1.1% (p = 0.0001) and 48.1% +/- 7.3% vs 43.8% +/- 4.7% (p = 0.004), respectively). No side effects of either rHuEPO or intravenously administered iron were noted. These data indicate that rHuEPO, in combination with iron supplementation, is effective in reducing the need for blood transfusions in the premature infant. More information is needed on dosage, timing, and iron and vitamin supplementation.

A mathematical model of hematopoiesis: II. Cyclical neutropenia

Cyclical neutropenia is a dynamical disease of the hematopoietic system marked by an oscillation in circulating leukocyte (e.g. neutrophil) numbers to near zero levels and then back to normal. This oscillation is also mirrored in the platelets and reticulocytes which oscillate with the same period. Cyclical neutropenia has an animal counterpart in the grey collie. Using the mathematical model of the hematopoietic system of Colijn and Mackey [A mathematical model of hematopoiesis: I. Periodic chronic myelogenous leukemia. Companion paper to the present paper.] we have determined what parameters are necessary to mimic laboratory and clinical data on untreated grey collies and humans, and also what changes in these parameters are necessary to fit data during treatment with granulocyte colony stimulating factor (G-CSF). Compared to the normal steady-state values, we found that the major parameter changes that mimic untreated cyclical neutropenia correspond to a decreased amplification (increased apoptosis) within the proliferating neutrophil precursor compartment, and a decrease in the maximal rate of re-entry into the proliferative phase of the stem cell compartment. For the data obtained during G-CSF treatment, good fits were obtained only when parameters were altered that would imply that G-CSF led to higher amplification (lower rate of apoptosis) in the proliferating neutrophil precursors, and a elevated rate of differentiation into the neutrophil line.

Failure of red blood cell maturation in mice with defects in the high-density lipoprotein receptor SR-BI

Mammalian erythrocytes undergo a unique maturation process in which they discard their nuclei and organelles and assume a flexible biconcave shape. We found that altered plasma lipoprotein metabolism can profoundly influence these events. Abnormal erythrocyte morphology was observed in hypercholesterolemic mice lacking the high-density lipoprotein receptor SR-BI. This was exacerbated by feeding mice a high-cholesterol diet or, more dramatically, by inactivating the apolipoprotein E gene. Erythrocytes from SR-BI(-/-)/apolipoprotein E(-/-) mice and SR-BI(-/-) mice that were fed cholesterol had markedly increased membrane cholesterol. Their morphology appeared immature, with macrocytosis, irregular shape, and large autophagolysosomes. Autophagolysosomes from SR-BI(-/-)/apolipoprotein E(-/-) erythrocytes were expelled when the erythrocytes were transfused into wild-type animals or incubated in vitro with normolipidemic serum or the cholesterol-sequestering agent methyl cyclodextrin. We propose that autophagocytosis and phagolysosome expulsion are essential steps in erythroid maturation and that expulsion is inhibited in the presence of markedly increased cellular cholesterol.

Antimutagenic effect of Agaricus blazei Murrill mushroom on the genotoxicity induced by cyclophosphamide

Agaricus blazei Murrill extracts have previously been shown to have anticarcinogenic and antimutagenic properties. These results suggest that antimutagenic activity, besides the modulation of the immune system, might be involved in the anticarcinogenic action of A. blazei. To investigate the possible antimutagenic effect of A. blazei in vivo, we evaluated its effect on clastogenicity induced by cyclophosphamide (CP) in mice, using the micronucleus test in bone marrow (MNPCE) and in peripheral blood (MNRET). Male Swiss mice were treated with CP (25 or 50mg/kg i.p.) or with CP plus mushroom solution at three different temperatures: 4, 21, and 60 degrees C. Aqueous solution of a mixture from various lineages of the mushroom inhibited induction of micronuclei by CP in bone marrow and in peripheral blood of mice. In contrast to the mixture of lineages, a single isolated lineage did not lead to a reduction of CP-induced MN frequencies in either bone marrow or blood cells of mice. The results suggest that under certain circumstances these mushrooms exhibit antimutagenic activities that might contribute to an anticarcinogenic effect.

Normal and disordered reticulocyte maturation

PURPOSE OF REVIEW

Reticulocyte remodeling has emerged as an important model for the understanding of vesicular trafficking and selective autophagy in mammalian cells. This review covers recent advances in our understanding of these processes in reticulocytes and the role of these processes in erythroid development.

RECENT FINDINGS

Enucleation is caused by the coalescence of vesicles at the nuclear-cytoplasmic junction and microfilament contraction. Mitochondrial elimination is achieved through selective autophagy, in which mitochondria are targeted to autophagosomes, and undergo subsequent degradation and exocytosis. The mechanism involves an integral mitochondrial outer membrane protein and general autophagy pathways. Plasma membrane remodeling, and the elimination of certain intracellular organelles occur through the exosomal pathway.

SUMMARY

Vesicular trafficking and selective autophagy have emerged as central processes in cellular remodeling. In reticulocytes, this includes enucleation and the elimination of all membrane-bound organelles and ribosomes. Ubiquitin-like conjugation pathways, which are required for autophagy in yeast, are not essential for mitochondrial clearance in reticulocytes. Thus, in higher eukaryotes, there appears to be redundancy between these pathways and other processes, such as vesicular nucleation. Future studies will address the relationship between autophagy and vesicular trafficking, and the significance of both for cellular remodeling.

New quantitative parameters on a recently introduced automated blood cell counter--the XE 2100

The XE 2100 (Sysmex Corporation) is a cell counter that furthers the technology of fluorescent flow cytometry developed from the earlier range of Sysmex analysers. The new diagnostic features are a nucleated red cell count (NRBC), the ability to measure platelets by impedance as well as an 'optical' platelet count using a fluorescence dye and an immature granulocyte (IG) count. The NRBC count was highly correlated (r = 0.97) with the manual reference count. For counts below 100 x 109/l the 'optical' method and the immunocount gave good a correlation (r = 0.97) optical and impedance counts were also well correlated (r = 0.89). The use of the 'optical' platelet count significantly improves the reliability of low platelet counts. The IG count correlated with visual counts (r = 0.81) and allows the detection of immature cells at an earlier stage in the laboratory process. The introduction of fluorescent flow cytometric analysis allows extended quantification of additional cell populations and so potentially improves screening and monitoring of various pathological conditions.

Spindle cell neoplasms of lymph nodes of probable reticulum cell lineage. True reticulum cell sarcoma?

Primary spindle cell neoplasms involving hematolymphoid organs are extremely rare. We present four cases of spindle cell neoplasms of unusual phenotype arising within lymph nodes. Two of the four cases showed morphologic and immunophenotypic features suggestive of interdigitating reticulum cell lineage; these cases expressed several macrophage antigens and S-100 protein but not CD1. The other two cases showed evidence suggestive of dendritic reticulum cell lineage. Both cases expressed HLA-DR, several macrophage antigens, complement receptors C3b and C3d; one case expressed R4/23; both showed the presence of desmosomes on ultrastructural examination. A germline configuration for the immunoglobulin heavy chain and beta-T--cell receptor genes was detected in all four cases. Of the two patients in the first group, one had local recurrence of tumor; the other died of widespread metastases. Of the two patients in the second group, both are alive and well at 12 and 27 months follow-up, respectively.

Mitochondria in the programmed death phenomena; a principle of biology: "it is better to die than to be wrong"

The very fact that mitochondria participate in amplification of the cell suicide signals has stimulated interest in the mechanism of this and related phenomena. It seems probable that mitochondria possess an autonomic system that allows them to commit suicide. This mitoptosis is mediated by reactive oxygen species (ROS), causing opening of the permeability transition pores (PTP) in the inner mitochondrial membrane. Mitoptosis can purify the mitochondrial population in a cell from the ROS-overproducing organelles. Massive mitoptosis can result in apoptosis (programmed cell death) because of the release of proapoptotic proteins from the mitochondrial intermembrane space, a mechanism purifying tissues from the ROS-overproducing and other unwanted cells. Large-scale apoptosis can be used by organisms to eliminate some organs during ontogenesis (organoptosis). In adult organisms, organoptosis of organs of vital importance may entail a programmed death of individuals (phenoptosis). This mechanism might purify kins, communities, and populations from individuals becoming dangerous because of, for example, heavy infection (septic shock). It is hypothesized that aging represents a slow ROS-linked phenoptosis that eliminates individuals with damaged genomes and gives reproductive advantage to those who succeeded in a better preservation of their genomes from damage.

Spurious counts and spurious results on haematology analysers: a review. Part II: white blood cells, red blood cells, haemoglobin, red cell indices and reticulocytes

Haematology analysers provide quick and accurate results in most situations. However, spurious results, related either to platelets (part I of this report) or to other parameters from the cell blood count (CBC) may be observed in several instances. Spuriously low white blood cell (WBC) counts may be observed because of agglutination in the presence of ethylenediamine tetra-acetic acid (EDTA). Cryoglobulins, lipids, insufficiently lysed red blood cells (RBC), erythroblasts and platelet aggregates are common situations increasing WBC counts. In most of these instances flagging and/or an abnormal WBC differential scattergram will alert the operator. Several situations lead to abnormal haemoglobin measurement or to abnormal RBC count, including lipids, agglutinins, cryoglobulins and elevated WBC counts. Mean (red) cell volume (MCV) may be also subject to spurious determination, because of agglutinins, excess of glucose or salts and technological considerations. In turn, abnormality related to one measured parameter will lead to abnormal calculated RBC indices: mean cell haemoglobin content (MCHC) is certainly the most important RBC indices to consider, as it is as important as flags generated by the haematology analysers (HA) in alerting the user to a spurious result. In many circumstances, several of the measured parameters from CBC may be altered, and the discovery of a spurious change on one parameter frequently means that the validity of other parameters should be considered. Sensitive flags now allow the identification of several spurious counts, but only the most sophisticated HA have optimal flagging and more simple HA, especially those without a WBC differential scattergram, do not possess the same sensitivity for detecting anomalous results. Reticulocytes are integrated now into the CBC in many HA, and several situations may lead to abnormal counts.

Resistance to Plasmodium chabaudi in B10 mice: influence of the H-2 complex and testosterone

Resistance to Plasmodium chabaudi has been examined in different inbred mouse strains bearing identical H-2 haplotypes on different genetic backgrounds as well as in H-2-congenic mouse strains on B10 background. Resistance is expressed in terms of percent survival after a challenge with 10(6) P. chabaudi-infected erythrocytes. We can show that murine resistance to P. chabaudi is under complex polygenic control involving a non-H-2 gene(s) as well as genes in both I-A and I-E subregions of the H-2 complex. Our data indicate in particular that malaria protective antigens can be presented in context with I-Ab molecules but not in context with I-Ak molecules. Resistance controlled by I-Ab does not become apparent when I-Ek molecules are coincidentally expressed. Moreover, testosterone abrogates I-Ab-controlled resistance to P. chabaudi.

Comparative scoring of micronucleated reticulocytes in rat peripheral blood by flow cytometry and microscopy

A flow cytometric technique for scoring the incidence of micronucleated reticulocytes in rat peripheral blood was compared to a standard microscopy-based procedure. For these studies, groups of five male Sprague-Dawley rats were treated with vehicle or a broad range of chemical genotoxicants: 6-thioguanine, N-methyl-N'-nitro-N-nitrosoguanidine, vincristine, methylaziridine, acetaldehyde, methyl methanesulfonate, benzene, monocrotaline, and azathioprine. Animals were treated once a day for up to 2 days, and peripheral blood was collected between 24 and 48 h after the final administration. These samples were processed for flow cytometric scoring and microscopy-based analysis using supravital acridine orange staining, and the percentage of reticulocytes and micronucleated reticulocytes was determined for each sample. The resulting data demonstrate good agreement between these scoring methodologies, although careful execution of the flow cytometric method was found to enhance the micronucleus assay by reducing both scoring time and scoring error. These data add further support to the premise that the peripheral blood compartment of rats can be used effectively to detect genotoxicant-induced micronuclei.

Three-color labeling method for flow cytometric measurement of cytogenetic damage in rodent and human blood

Experiments described herein were designed to evaluate the performance characteristics of a flow cytometry-based system that scores the incidence of peripheral blood micronucleated reticulocytes (MN-RETs). These procedures represent the continued refinement of a previously reported anti-CD71-based method (Dertinger et al. [1996]: Mutat Res 371:283-292), with the following modifications: incorporation of a third fluorescent label to exclude platelets from the MN-RET region, and use of a CD71-associated fluorescence thresholding technique to increase data acquisition rates. Mouse, rat, and human blood samples were analyzed using both the previously described two-color procedure (anti-CD71-FITC and propidium iodide) and a newly developed three-color technique (which adds an antiplatelet-PE antibody). The rodent specimens were also evaluated by standard microscopy procedures (acridine orange staining). Mouse blood was collected via heart puncture of vehicle- and 5-fluorouracil-treated CD-1 mice; blood samples from saline-treated Sprague-Dawley rats were collected from the tail vein and via heart puncture. Rodent blood samples were analyzed by both the two- and three-color methods. Human blood specimens, obtained via arm venipuncture from cancer patients undergoing radiation therapy, were analyzed for MN-RETs using the two-color method. Subsequently, blood samples from a single chemotherapy patient were analyzed by both the two- and three-color methods. Finally, the chemotherapy patient blood samples and blood samples from 15 healthy volunteers were evaluated at very high densities in conjunction with a CD71-associated fluorescence thresholding technique. Results of these investigations showed that data from mouse blood analyzed by the two- and three-color procedures correlated well with microscopy data (r values = 0.917 and 0.937 for the two- and three-color methods, respectively); all three methods confirmed the genotoxicity of 5-FU. Data from rat tail vein samples showed improved reproducibility with the three-color technique, but no significant difference between the two techniques was seen with the heart puncture specimens. Human blood analyzed according to the two-color procedure produced unreliable results, as platelets and platelet aggregates impacted the rare MN-RET scoring region. The three-color technique effectively overcame this problem and produced reproducible measurements that fell within expected ranges. For human blood analyses, the high cell density/CD71-thresholding technique provided significant improvements over the low-density technique, as it allowed data acquisition to occur approximately six times faster with no loss of sensitivity.

Sox6 cell-autonomously stimulates erythroid cell survival, proliferation, and terminal maturation and is thereby an important enhancer of definitive erythropoiesis during mouse development

Erythropoiesis, the essential process of hematopoietic stem cell development into erythrocytes, is controlled by lineage-specific transcription factors that determine cell fate and differentiation and by the hormone erythropoietin that stimulates cell survival and proliferation. Here we identify the Sry-related high-mobility-group (HMG) box transcription factor Sox6 as an important enhancer of definitive erythropoiesis. Sox6 is highly expressed in proerythroblasts and erythroblasts in the fetal liver, neonatal spleen, and bone marrow. Mouse fetuses and pups lacking Sox6 develop erythroid cells slowly and feature misshapen, short-lived erythrocytes. They compensate for anemia by elevating the serum level of erythropoietin and progressively enlarging their erythropoietic tissues. Erythroid-specific inactivation of Sox6 causes the same phenotype, demonstrating cell-autonomous roles for Sox6 in erythroid cells. Sox6 potentiates the ability of erythropoietin signaling to promote proerythroblast survival and has an effect additive to that of erythropoietin in stimulating proerythroblast and erythroblast proliferation. Sox6 also critically facilitates erythroblast and reticulocyte maturation, including hemoglobinization, cell condensation, and enucleation, and ensures erythrocyte cytoskeleton long-term stability. It does not control adult globin and erythrocyte cytoskeleton genes but acts by stabilizing filamentous actin (F-actin) levels. Sox6 thus enhances erythroid cell development at multiple levels and thereby ensures adequate production and quality of red blood cells.

The hematopoietic stroma

The stroma of the hematopoietic tissues includes a number of diverse cell types, i.e., bone-lining cells and related capsular and trabecular structures, epithelial-reticular cells and other epithelial cells, reticular cells, macrophages, and antigen-presenting cells. These stromal cells possess a variety of mechanical and metabolic functions. They support and confine the hematopoietic tissues and their vasculature. They regulate the migrations of blood and hematopoietic cells. Stromal cells contribute to the microenvironment that induces the differentiation of stem cells into the several blood-cell lines. The nature of the interactions of stromal and hematopoietic cells depends upon long- and short-range humoral factors, and upon such cell-surface compounds as immunoglobulins and major histocompatability antigens. Blood cells themselves, as neutrophils and lymphocytes, play regulatory roles in hematopoiesis along with stromal cells. Moreover, certain stromal cells, such as macrophages, originate as blood cells and have migratory phases. Distinctions between blood cells, their derivatives, and stromal cells may therefore be difficult to draw.

Erythroblastosis and reticulocytosis in anemic fetuses

The fetal blood erythroblast and reticulocyte counts were determined in umbilical cord samples obtained at 17 to 36 weeks' gestation from 127 pregnancies complicated by red blood cell isoimmunization. The reticulocyte count increased linearly with fetal anemia, and the erythroblast count increased exponentially. Significant erythroblastosis was observed only when the hemoglobin concentration deficit was greater than 7 gm/dl. Of the 52 fetuses with a hemoglobin concentration deficit greater than 7 gm/dl, 35 had ultrasonographic evidence of hydrops. These data suggest that medullary hematopoiesis is stimulated by mild anemia and that recruitment of extramedullary sites occurs when anemia is severe. Extensive hepatic erythropoiesis may be the cause of fetal hydrops in red blood cell isoimmunization.

Early prediction of response to intravenous iron supplementation by reticulocyte haemoglobin content and high-fluorescence reticulocyte count in haemodialysis patients

BACKGROUND

Optimal response to recombinant human erythropoietin (rHuEpo) in haemodialysis (HD) patients requires provision of sufficient available iron. However, a balance between iron requirements and supplements remains a challenge in clinical practice. Reticulocyte parameters, i.e. reticulocyte haemoglobin content (CHr) and reticulocytes in a high-fluorescence intensity region (HFR), have been shown to be accurate predictors of iron-deficient erythropoiesis as compared with traditional markers. Therefore, the aim of this study was to appraise the diagnostic power of these two parameters in the early prediction of response to intravenous iron (IVFE) medications in HD patients receiving rHuEpo.

METHODS

Sixty-five HD patients with a serum ferritin level of <500 microg/l and on rHuEpo therapy for >6 months were enrolled for IVFE supplementation (100 mg iron saccharate three times a week for 4 weeks, then 100 mg every 2 weeks for 5 months). Haemoglobin, haematocrit, serum ferritin, transferrin saturation, reticulocyte count, percentage of hypochromic red cells, CHr and HFR were measured before and following iron supplementation. Response was defined as a rise in haematocrit of >3% and/or a reduction in rHuEpo dose of >30% over the baseline values at the end of the study.

RESULTS

Forty-two patients had a dramatic response to IVFE therapy with a 13.5% increase in mean haematocrit and a 38% reduction in rHuEpo dose at the end of the study (P<0.001). This paralleled a statistically significant rise in CHr and HFR (P<0.001). Univariate analyses showed that ferritin (P<0.010) and CHr (P<0.001) at baseline, changes in CHr (DeltaCHr(2W), P<0.001) and HFR (DeltaHFR(2W), P<0.010) at 2 weeks, as well as changes in CHr (DeltaCHr(4W), P<0.001) and HFR (DeltaHFR(4W), P<0.001) at 4 weeks, strongly correlated with response to IVFE supplementation. Stepwise discriminant analysis disclosed that DeltaCHr(4W) in conjunction with DeltaHFR(4W) exhibited an r(2) value of 0.531 (P<0.001) to predict response to IVFE therapy. Analyses by receiver operating characteristic curves and logistic regression further revealed that DeltaCHr(4W) at a cut-off value of >1.2 pg and DeltaHFR(4W) of >500/microl were more specific to the status of iron-deficient erythropoiesis following IVFE medications. Combined use of the two cut-off values allowed for the highest accuracy in the early prediction of the response to IVFE therapy, with a sensitivity of 96% and a specificity of 100%.

CONCLUSIONS

Our study shows that changes in CHr and HFR at either 2 or 4 weeks are superior to the conventional erythrocyte and iron metabolism indices and may serve as reliable parameters to detect iron-deficient erythropoiesis in HD patients undergoing rHuEpo therapy. During aggressive IVFE treatment, early identification of non-responsiveness and subsequent discontinuation of treatment can avoid the inadvertent iron-related toxicity due to over-treatment.

The effect of iron supplementation on the level of haemoglobin after lower limb arthroplasty

We randomised 120 patients who were undergoing either primary total hip or knee arthroplasty to receive either ferrous sulphate or a placebo for three weeks after surgery. The level of haemoglobin and absolute reticulocyte count were measured at one and five days, and three and six weeks after operation. Ninety-nine patients (ferrous sulphate 50, placebo 49) completed the study. The two groups differed only in the treatment administered.

Recovery of level of haemoglobin was similar at five days and three weeks and returned to 85% of the pre-operative level, irrespective of the treatment group. A small, albeit greater recovery in the level of haemoglobin was identified at six weeks in the ferrous sulphate group in both men (ferrous sulphate 5%, placebo 1.5%) and women (ferrous sulphate 6%, placebo 3%). The clinical significance of this is questionable and may be outweighed by the high incidence of reported side effects of oral iron and the cost of the medication. Administration of iron supplements after elective total hip or total knee arthroplasty does not appear to be worthwhile.

Assessment of the in vivo genotoxicity of vanadate: Analysis of micronuclei and DNA damage induced in mice by oral exposure

Vanadium compounds are able to interact with living cells exerting a variety of biological effects. The pentavalent form is the most stable and toxic form of the element. In systems in vitro pentavalent vanadium is an effective genotoxic agent, inducing DNA damage and chromosome malsegregation at low doses. On the other hand, no adequate in vivo data are available for the characterization of the genotoxic hazard following oral intake, the most relevant route of human exposure. In this study, the genotoxic effects produced by the oral intake of sodium ortho-vanadate (Na(3)VO(4)) were investigated. Male CD-1 mice were treated for 5 weeks with a range of concentrations of Na(3)VO(4) in drinking water (0.75-1500 mg/l). Both micronuclei and primary DNA lesions as detected by comet assay were assessed in several tissues. Statistically significant increases of micronuclei in bone marrow were observed in mice receiving the two highest concentrations of Na(3)VO(4) (750 and 1500 mg/l). A significant increase of comet tail length was observed in splenocytes of mice receiving Na(3)VO(4) at 1500 mg/l, whereas no effect was observed in bone marrow and testis cells. No treatment-related effect on sperm chromatin structure or on testis cell population was observed. The determination of vanadium content in mouse tissues at the end of treatment highlighted a very low internal exposure, especially in soft tissues. Overall, the results obtained indicate that the genotoxic activity of pentavalent vanadium is expressed in vivo only following high dose exposure, possibly as a consequence of the poor bioavailability of the element.

Quantitative analysis of Howell-Jolly bodies in children with sickle cell disease

OBJECTIVES

Although functional asplenia in sickle cell disease (SCD) begins early in life and has important clinical consequences, quantitative measurement of splenic function is not readily available. A novel high-throughput flow cytometric method for quantitating Howell-Jolly bodies (HJB) has been developed which isolates HJB-containing CD71(+) and CD71(-) erythrocytes. Analysis of these cell populations allows quantitative measurement of splenic filtrative function and possible chromosomal damage.

METHODS

Blood specimens from 147 children with SCD were analyzed using a high-throughput flow cytometric method. Enumeration of the following populations was accomplished: 1) CD71(+) reticulocytes among total erythrocytes, identifying the youngest erythroid cell population; 2) HJB-containing CD71(+) reticulocytes, which isolate young erythrocytes containing micronuclei as an index of cytogenetic damage; and 3) HJB-containing CD71(-) erythrocytes, identifying older erythrocytes containing micronuclei, indirectly measuring splenic function.

RESULTS

Children with HbSC (n = 24) had slightly elevated HJB frequencies, while children with HbSS (n = 125) had highly elevated frequencies within CD71(+) cells (0.44% +/- 0.40%, normal 0.12% +/- 0.06%, p < 0.001) and CD71(-) cells (2493 +/- 2303 per million RBC, normal 20 +/- 11, p < 0.001). Using a multiple regression model, the frequency of HbSS CD71(+) reticulocytes containing HJB was significantly influenced by hydroxyurea use (p < 0.0001), age (p = 0.0288), and splenectomy (p = 0.0498). Similarly, mature CD71(-) erythrocytes containing HJB were positively correlated with hydroxyurea (p = 0.0001), age (p < 0.0001), and splenectomy (p = 0.0104).

CONCLUSIONS

HJB quantitation by flow cytometry is a novel assay for measuring splenic function and may be valuable for investigating the efficacy and safety of therapeutic options for children with SCD.