Changes in erythropoiesis due to radiation or chemotherapy as studied by flow cytometric determination of peripheral blood reticulocytes

Flow cytometric determination of time dependent changes of numbers of reticulocytes in peripheral blood were investigated as a parameter for changes in erythropoiesis induced by radiation- or chemotherapy. Rats irradiated or treated with drugs (such as e.g. cyclophosphamide 100 mg/kg, vincristin 0.2 mg/kg, or mitomycin C 1.0 mg/kg) showed clear changes in erythropoietic activity. Reticulocyte numbers decreased rapidly until day 3-4 after treatment; this period was followed by a gradual increase and normal control values were seen at day 8-11. Radiation effects of doses as low 0.5 Gy could be detected in such a way. Similar studies were performed with patients with ovarian tumors treated with cis-platinum, a drug that may cause non-immune haemolysis. During prolonged treatment some patients showed increasing numbers of reticulocytes, measured at the first day of each hospitalization period, whereas leucocyte and platelet counts stayed more or less constant. Increasing numbers of reticulocytes generally indicates stimulation of erythropoietic activity of the bone marrow (due to increased blood loss); in this study increasing numbers often preceeded a decrease in hemoglobin values later on. Flow cytometric analysis of reticulocytes is therefore a potentially useful tool to detect changes in erythropoiesis, and considered more sensitive for the early recognition of patients that develop anemia, than hemoglobin measurements only.     

Effect of purified recombinant human erythropoietin on anemia in rats with experimental renal failure induced by five-sixth nephrectomy

Recombinant human erythropoietin (rHuEPO) was purified from the conditioned media of Chinese hamster ovary cells with a transfected human erythropoietin gene. We investigated the effects of the rHuEPO in rats with renal anemia induced by partial nephrectomy. Five-sixth nephrectomy resulted in renal failure with anemia. Twenty-five days after the operation plasma urea nitrogen was increased about 2.5 times, and the red blood cell count, hematocrit, and hemoglobin concentration fell to 85% of normal. The reticulocyte count and plasma erythropoietin level did not change such as they do in patients with anemia due to chronic renal failure. Both total red blood cell volume and the plasma iron turnover rate were depressed in five-sixth nephrectomized rats compared with normal rats.The five-sixth nephrectomized rats were injected with rHuEPO (60 IU/kg) intravenously every second day for a total of six injections. After three injections of rHuEPO, circulation volume of total red blood cells was increased from 9.9 ml to 14.6 ml, and the plasma iron turnover rate was increased from 1.03 mg/kg/day to 2.12 mg/kg/day, and the reticulocyte count was also increased. After six injections, a marked increase of the red blood cell count, hematocrit, and hemoglobin concentration were observed. Plasma urea nitrogen and the creatinine levels as indications for renal function did not change after rHuEPO administration in both normal and five-sixth nephrectomized rats.In conclusion rHuEPO has a potent erythropoietic action and it is possible to cure the anemia caused by renal failure.     

Changes in erythropoiesis due to radiation or chemotherapy as studied by flow cytometric determination of peripheral blood reticulocytes

Summary Flow cytometric determination of time dependent changes of numbers of reticulocytes in peripheral blood were investigated as a parameter for changes in erythropoiesis induced by radiation- or chemotherapy. Rats irradiated or treated with drugs (such as e.g. cyclo-phosphamide 100 mg/kg, vincristin 0.2 mg/kg, or mitomycin C 1.0 mg/kg) showed clear changes in erythropoietic activity. Reticulocyte numbers decreased rapidly until day 3–4 after treatment; this period was followed by a gradual increase and normal control values were seen at day 8–11. Radiation effects of doses as low 0.5 Gy could be detected in such a way.Similar studies were performed with patients with ovarian tumors treated with cis-platinum, a drug that may cause non-immune haemolysis. During prolonged treatment some patients showed increasing numbers of reticulocytes, measured at the first day of each hospitalization period, whereas leucocyte and platelet counts stayed more or less constant. Increasing numbers of reticulocytes generally indicates stimulation of erythropoietic activity of the bone marrow (due to increased blood loss); in this study increasing numbers often preceeded a decrease in hemoglobin values later on.Flow cytometric analysis of reticulocytes is therefore a potentially useful tool to detect changes in erythropoiesis, and considered more sensitive for the early recognition of patients that develop anemia, than hemoglobin measurements only.In honous of Prof. P. van Duijn.     

The red blood cells in growing guinea pigs. (Cavia cobaya). II. Communication: erythropoiesis and red blood cells in the postnatal development period

Bone-marrow smears of 175 guinea pigs aged 1-27 days and venous blood samples of 351 animals aged 1-25 days were prepared for cell counting. A significant increase of erythroblasts were found between life day 1 and 2; normoblasts increased in number synchronously with a decrease of erythroblasts after the 5th day. The percentage of the erythroid bone marrow increased from 10 to 14 during the developmental period. Beyond the perinatal period the red blood picture is characterized by the following changes: a decrease of erythrocyte count, hematocrit, hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin; a constant mean corpuscular hemoglobin concentration; an increase of the reticulocyte count. The decrease of the red cell count is compensated by a decreasing oxygen affinity attained by an important increase of 2,3-DPG. Nevertheless, the stimulus for a raising erythropoiesis remains constant which can be shown by the growing percentage of erythroid cells and reticulocytes. The difference between the human postnatal development and that of the guinea pig becomes obvious. Cell counts in dependence of body masses in postnatally growing guinea pigs, veil the perinatal finding of the increase in erythrocytes up to the 5th day and the decrease of the mean corpuscular volume after the 3rd day.     

Effect of Trypanosoma brucei brucei on erythropoiesis in infected rats

Anemia generated from African trypanosome infection is considered an important symptom in humans and in domestic animals. In order to recover from anemia, the process of erythropoiesis is essential. Erythropoiesis is affected by erythropoietin (EPO), an erythropoietic hormone, supplying iron and inflammatory and proinflammatory cytokines. However, the role of these factors in erythropoiesis during African trypanosome infection remains unclear. In the present study, we analyze how erythropoiesis is altered in anemic Trypanosoma brucei brucei (interleukin-tat 1.4 strain [ILS])-infected rats. We report that the packed cell volume (PCV) of blood from ILS-infected rats was significantly lower 4 days after infection, whereas the number of reticulocytes, as an index of erythropoiesis, did not increase. The level of EPO mRNA in ILS-infected rats did not increase from the third day to the sixth day after infection, the same time that the PCV decreased. Kidney cells of uninfected rats cultured with ILS trypanosome strain for 8 hr in vitro decreased EPO mRNA levels. Treatment of both ILS and cobalt chloride mimicked hypoxia, which restrained the EPO-production-promoting effect of the cobalt. Messenger RNA levels of β-globin and transferrin receptor, as markers of erythropoiesis in the bone marrow, also decreased in ILS-infected rats. Levels of hepcidin mRNA, which controls the supply of iron to the marrow in liver, were increased in ILS-infected rats; however, the concentration of serum iron did not change. Furthermore, mRNA levels of interleukin-12, interferon-γ, tumor necrosis factor-α, and macrophage migration inhibitory factor in the spleen, factors that have the potential to restrain erythropoiesis in bone marrow, were elevated in the ILS-infected rats. These results suggest that ILS infection in rats affect erythropoiesis, which responds by decreasing EPO production and restraining its function in the bone marrow.     

Peripheral blood reticulocytes and their reference range values for percentage, absolute count, and immature fraction in children, measured with flow cytometry

Reticulocyte count by manual method has been the assay traditionally used to evaluate the status of erythropoiesis in hematological disorders with disturbances in erythropoietic activity. However, due to its variability, it is rather a semiquantitative method. Automated reticulocyte counting based on flow cytometry has provided more objective and exact measure of reticulocytes. Besides traditional parameters, such as percentage and absolute number of reticulocytes, automatic reticulocyte counters can detect differences in the amounts of cellular RNA present in immature erythrocytes that reflect their maturational stages and evaluate indices of reticulocyte maturation such as RMI, HFR, IRF. These parameters can be used as the earliest signs of marrow engraftment after autologous or allogeneic bone marrow transplantation. Currently there is no strict agreement between various automated methods of reticulocyte evaluation. Additionally, lack of standardization and quality control materials for this assay compels determination of own, interlaboratory ranges of reference values for new proposed parameters. A group of 102 children aged from 3 months to 18 years with normal hematological parameters was examined. Samples of blood stained supravitally with thiazole orange were analyzed in a flow cytometer. Results for percentage, absolute number and immature reticulocyte fraction expressed as a mean +/- 2SD were: 2.00 +/- 1.56%, 88.8 +/- 68.94 x 10(3)/microliter, and 0.22 +/- 0.16, respectively. A poor correlation was found between IRF and other parameters, suggesting its independent role as a marker of erythropoietic activity. Automated reticulocyte counting will probably improve the diagnosis and monitoring of many hematological diseases.     

Selective modulation of the erythropoietic and tissue-protective effects of erythropoietin: time to reach the full therapeutic potential of erythropoietin

Erythropoietin (EPO) has been used clinically both as an erythropoietic stimulating agent in the treatment of anemia and as a tissue-protective agent in diverse clinical settings including stroke, multiple sclerosis, acute myocardial infarction and others. However, use of EPO or EPO-analogues leads to simultaneous targeting of both the erythropoietic and tissue-protective properties of EPO, and this strategy has been associated with several problems. Specifically, the benefit of correction of cancer-related anemia can be offset by the tissue-protective effects of EPO, which may lead to stimulation of cancer cell proliferation. Conversely, the benefit of tissue-protection in patients with stroke or myocardial infarction can be offset by adverse effects associated with the erythropoietic effects of EPO such as elevation of red blood cell mass, hypertension and prothrombotic phenomena. The finding that the erythropoietic and tissue-protective properties of EPO are conferred via two distinct receptor systems raises the interesting possibility of discovering novel drugs that selectively stimulate either the erythropoietic or the tissue-protective activities of EPO. This article reviews the current status of the clinical use of EPO and EPO-analogues in the treatment of cancer-related anemia and for tissue protection, outlines the distinct molecular biology of the tissue-protective and erythropoietic effects of EPO and discusses strategies of selective targeting of these activities with the goal of exploiting the full therapeutic potential of EPO.     

A relative morphological evaluation of hemoglobin biosynthesis in peripheral blood reticulocytes of normal and anemic rabbits

1. Peripheral blood reiculocytes of normal and bled rabbits and of rabbits with phenylhydrazine-induced anemia, were morphologically analysed, through silver sections, for a relative evaluation of hemoglobin (Hb) biosynthesis activity. 2. Reticulocytes of maturation degrees within the range of 35-60 polysomes/microns2, were compared as to their mean numbers of hemosomes (sites of heme integration into the globin chains), and mitochondria (indirect precursors for hemosome formation). 3. The results on the mean numbers of hemosomes per reticulocyte section, correlated to several physiological data under those three conditions, suggested a close relationship between Hb biosynthesis activity and hemosome frequency. 4. In bled rabbits, reticulocytes showing a low mean number of hemosomes (means hB/section = 0.32), as compared to reticulocytes of normal rabbits (means hN/section = 0.70) and to reticulocytes of rabbits with hemolytic anemia (means hH/section = 2.10), gave rise to a new erythrocyte population characterized by a low Hb content. 5. Hb concentration differences were verified by confronting hematological data before bleeding with those obtained after the regression of anemia.     

Low red cell production may protect against severe anemia during a malaria infection—Insights from modeling

The malaria parasite causes lysis of red blood cells, resulting in anemia, a major cause of mortality and morbidity. Intuitively, one would expect the production of red blood cells to increase in order to compensate for this loss. However, it has been observed that this response is weaker than would be expected. Furthermore, iron supplementation for iron deficient children in malaria endemic regions can paradoxically adversely affect the clinical outcome of malaria infection. A possible explanation may lie in the preference that some malaria parasites show for infecting immature red blood cells (reticulocytes). In the presence of a parasite preference for immature red cells, a rise in red cell production can ‘fuel the fire’ of infection by increasing the availability of the parasite's preferred target cell.We present a mathematical model of red blood cell production and infection in order to explore this hypothesis. We assess the effect of varying the reticulocyte replacement rate and preference of the parasite for reticulocytes on four key outcome measures assessing anemia and parasitemia.For a given level of parasite preference for reticulocytes we uncover an optimal erythropoietic response which minimizes disease severity. Increasing red blood cell production much above this optimum confers no benefit to the patient, and in fact can increase the degree of anemia and parasitemia. These conclusions are consistent with epidemiological studies demonstrating that both iron deficiency and anemia are protective against severe malaria, whilst iron supplementation in malaria endemic regions is with an increased number of malaria related adverse effects. Thus, suppression of red blood cell production, rather than being an unfortunate side effect of inflammation, may be a host protective effect against severe malarial anemia.     

Bone marrow cell differential counts obtained by multidimensional flow cytometry.

Five-dimensional flow cytometric analysis of normal bone marrow aspirates was utilized to determine the frequency of neutrophils, eosinophils, monocytes, lymphocytes, nucleated erythrocytes, reticulocytes, platelets, and a cell population that included blasts of each of the cell lineages, megakaryocytes, plasma cells, and basophils. Each of these bone marrow cell populations had unique features with respect to forward light scatter, orthogonal light scatter, and staining with Thiazole-Orange, LDS-751, and CD45 labeled with Phycoerythrin (PE). The identity of the cell populations was verified by sorting each of the cell populations and subsequent light microscopic examination of the cells. The frequencies of the nucleated bone marrow cell subpopulations of 50 normal donors were for neutrophils, mean 72.3%; SD +/- 5.1; 95% limits, 70.9-73.8%; eosinophils, mean 1.8%; SD +/- 1.3; 95% limits, 1.4-2.1%; monocytes, mean, 2.8%; SD +/- 1.2; 95% limits, 2.5-3.1%; lymphocytes, mean 12.1%; SD +/- 3.6; 95% limits 11.1-13.2%; nucleated erythrocytes, mean 8.9%; SD +/- 3.9; 95% limits, 7.8-10.1%; and the cell population that included blasts of each of the cell lineages, megakaryocytes, plasma cells, and basophils, mean 1.6%; SD +/- 1.2; 95% limits, 1.3-1.9%. The percentage of reticulocytes in bone marrow aspirates from 50 normal donors correlated with the reticulocyte frequency in the peripheral blood of these donors. However, the mean frequency of reticulocytes was significantly greater (p < 0.0001) in bone marrow (mean 2.19%; SD +/- 0.88) than in peripheral blood (mean 1.71%; SD +/- 0.88). The technique could discriminate between immature and mature reticulocytes based on the brighter staining with both Thiazole-Orange and LDS-751 of the immature reticulocytes. This was confirmed by cell sorting of both reticulocyte populations, which revealed larger clumps of New Methylene Blue staining material in the brighter Thiazole-Orange and LDS-751 stained reticulocytes. The immature reticulocytes were present in normal bone marrow, but not in normal peripheral blood. As expected, a significantly greater frequency of nucleated cells was found in bone marrow aspirates (mean 0.85%; SD +/- 0.59) than in peripheral blood (mean 0.20%; SD +/- 0.11). The frequency of platelets was significantly lower in bone marrow (mean 1.24%; SD +/- 0.69) than in peripheral blood (mean 2.94%, SD +/- 1.14). Flow cytometric bone marrow analysis can provide clinical laboratories with a technique that generates quantitative bone marrow cell differentials and potentially can reduce the need for light microscopic examination of bone marrow smears.     

Clinical use of recombinant human hematopoietic growth factors (GM-CSF, IL-3, EPO) in patients with myelodysplastic syndrome.

We have conducted several phase I/II clinical studies in a total of 65 MDS patients utilizing recombinant human hematopoietic growth factors including GM-CSF, IL-3, and EPO. Twenty-seven patients with MDS were treated with either continuous i.v. infusion or single daily s.c. injection of rhGM-CSF at dosages from 15 micrograms/m2 to 1000 micrograms/m2. All of them exhibited white cell responses during the treatment cycles, but no sustained rise in reticulocytes or platelets was recorded. In four of the patients, all with > or = 15% blast cells in the bone marrow, the percentage of circulating blast cells increased during treatment with rhGM-CSF (at dosages of 500 micrograms/m2 and 1000 micrograms/m2, respectively), although no leukemic conversion occurred. Of 9 patients treated so far with rhIL-3 at single daily s.c. dosages of 60 micrograms/m2, all exhibited white cell responses; 8 exhibited significant improved platelet and reticulocyte counts. Nineteen further patients received rhEPO for a period of 14 weeks by s.c. (10,000 U five times weekly) or i.v. bolus administration (150-450 U/kg). None of these patients experienced an increase in white cell and platelet counts. A significant increase of the reticulocyte count was recorded in 3 patients only. Another strategy involves the recruitment of leukemic cells into the cell cycle by hematopoietic growth factors followed by treatment with cycle-specific cytostatic agents. Therefore in 10 patients administration of rhGM-CSF (250 g/m2/day x 14, s.c.) was combined with Ara-C treatment (20 mg/m2/day x 14; s.c.). Initial results of this pilot study available in 5 patients indicated that this approach may control leukemic cell proliferation and may increase number of mature myeloid cells in both bone marrow and peripheral blood. A similar approach utilizing rhIL-3 in conjunction with Ara-C is on-going.     

Serum erythropoietic activity in acute anemia--an animal model

Serum erythropoietic activity and reticulocyte response to anemia were investigated using a rabbit model. In hemolytic anemia, induced by injections of phenylhydrazine on Day 0 the hemoglobin reached a nadir (mean, 6.23 g/dl) on Day 4 when SEA was maximal (mean, 765 mU/ml). In animals venesected on Day 0 and Day 1 to produce anemia of equal severity, the SEA was maximal (mean 235 mU/ml) on Day 2. In both groups the reticulocyte response peaked on Day 7--at 34% for the hemolytic group and 21% for the venesected group. The 2,3-diphosphoglycerate, measured on Day 4, was significantly reduced in the PHZ-treated group. In the venesected group the 2,3-DPG increased between Day 0 and Day 4. There were no concurrent changes in acid-base balance. These results imply that the degree of anemia is only one of the factors which influence the level of circulating SEA.     

The activity of erythrocyte enzymes in rats subjected to running exercises

The studies were carried out on male Wistar rats subjected to running within an electric rotating drum. The animals were divided into four experimental groups, differing one from another as to the duration of training. Each training session lasted 30 days. In the first group the daily run lasted 3 min, in the second group 5 min; in the third group, a 1 min run on the first day, and one min longer on each successive day; in the fourth group a 2 min run on the first day and for two min longer on each successive day. The determinations made prior to and after training included the peripheral blood erythrocyte (Er) and reticulocyte (Ret.) count, the hemoglobin concentration (Hb) and packed cell volume (PCV) and, determined by spectrophotometric methods, the activity of pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G6PD) and glutathione reductase (GR). Training induced an improvement of all enzymatic activities. The heavier the physical exertion, the more intensive was the enzymatic activity of red blood cells, due to the intensification of bone marrow erythropoetic activity under physical exertion and the appearance of young red cells in peripheral blood. All the experimental groups revealed a drop in erythrocyte count (Er), hemoglobin concentration (Hb), and hematocrit values (PCV), as well as an increase in the reticulocytes count (Ret) and in the activity of all the enzymes investigated. In the fourth group anemia was detected: prolonged endurance training decreased the RBC by 24.2%, Hb by 31.1%, PCV by 26.2% and increased the reticulocyte count by 881.6%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Study of maturation of membrane transport function in red blood cells by X-ray microanalysis

Summary Red blood cells of certain species of animals, such as dogs and cats, contain low potassium and high sodium, whereas the erythropoietic stem cells giving rise to these cells are of high potassium type. This paper examines the sequence of membrane transport changes during erythropoiesis by analyzing the K, Na and Fe in single bone marrow cells, reticulocytes and mature red blood cells with X-ray microanalysis. The relationship between K/Na ratios and Fe/(K+Na) ratios were examined by X-ray microanalysis. The K/Na ratios give a measure of the membrane cation transport function. The Fe/(K+Na), which is analogous to hemoglobin concentration, gives an index of maturation stage. The relationships between K/Na and Fe/(K+Na) in the marrow cells of normal adult dog and those of a phenylhydrazine-injected dog with accelerated erythropoiesis show that the modification of cation composition occurs after the initiation of hemoglobin synthesis but before its completion. Similar relationships in the reticulocytes obtained from phenylhydrazine-injected dogs as well as from newborn dogs show a consistent decrease in K/Na with increased Hb, indicating a drastic change in cation composition during the maturation of the reticulocytes. Therefore the modification in membrane transport function must have occurred before or during the formation of reticulocytes.     

Trypanosoma evansi: Hematologic changes in experimentally infected cats

This study aimed at evaluating hemogram and erythropoietic changes in cats experimentally infected with Trypanosoma evansi. Thirteen adult female non-breeding Felix catus were separated into two groups: seven animals were infected with 10⁸ trypomastigotes each, and six animals were used as negative controls. Animals were kept in air-conditioned rooms and blood smears were performed daily for 49 days. Blood samples were collected from the jugular vein at days 0, 7, 21, 35 and 49 and stored in blood-collecting tubes containing anticoagulant. Bone marrow was collected from the proximal epiphysis of the right femur at days 14 and 42 post-inoculation (PI). Total erythrocyte count, hematocrit and hemoglobin showed statistical differences among groups from the seventh day PI onwards (P < 0.05). The mean corpuscular volume and the mean corpuscular hemoglobin concentration remained normal, characterizing a normocytic-normochromic anemia. Reticulocyte count increased in the infected group from the 21st day onwards, but remained near normal values suggesting a mild regenerative anemia. Moreover, the myeloid:erythroid ratio significantly reduced at day 42 PI, evidencing a bone marrow hematopoietic response. Based on these results we conclude that cats infected with T. evansi have normocytic, normochromic, regenerative anemia.     

Preferential invasion of reticulocytes during late-stage Plasmodium berghei infection accounts for reduced circulating reticulocyte levels

Insufficient circulating reticulocytes have been observed during severe malarial anaemia in both human and murine infection, and are often attributed to reduced production of red cell precursors. However, a number of Plasmodium species display a preference for invading reticulocytes rather than erythrocytes. Thus, the reduction in circulating reticulocyte numbers may arise as a result both of increased parasitization and lysis of reticulocytes, as well as decreased production. We have analysed both circulating reticulocyte numbers and the percentage of infected reticulocytes during murine Plasmodium berghei infection. We found a large reduction in circulating numbers when compared with an equivalent chemically induced anaemia. However, mathematical analysis of parasite and red cell numbers revealed the preference of P. berghei for reticulocytes to be approximately 150-fold over that for erythrocytes, leading to increased destruction of reticulocytes. Although erythropoietic suppression is evident during the first week of P. berghei infection, this preferential infection and destruction of reticulocytes is sufficient to mediate ongoing reduced levels of circulating reticulocytes during the latter stages of infection, following compensatory erythropoiesis in response to haemolytic anaemia.     

Quantitative Analysis of Mechanisms That Govern Red Blood Cell Age Structure and Dynamics during Anaemia

Mathematical modelling has proven an important tool in elucidating and quantifying mechanisms that govern the age structure and population dynamics of red blood cells (RBCs). Here we synthesise ideas from previous experimental data and the mathematical modelling literature with new data in order to test hypotheses and generate new predictions about these mechanisms. The result is a set of competing hypotheses about three intrinsic mechanisms: the feedback from circulating RBC concentration to production rate of immature RBCs (reticulocytes) in bone marrow, the release of reticulocytes from bone marrow into the circulation, and their subsequent ageing and clearance. In addition we examine two mechanisms specific to our experimental system: the effect of phenylhydrazine (PHZ) and blood sampling on RBC dynamics. We performed a set of experiments to quantify the dynamics of reticulocyte proportion, RBC concentration, and erythropoietin concentration in PHZ-induced anaemic mice. By quantifying experimental error we are able to fit and assess each hypothesis against our data and recover parameter estimates using Markov chain Monte Carlo based Bayesian inference. We find that, under normal conditions, about 3% of reticulocytes are released early from bone marrow and upon maturation all cells are released immediately. In the circulation, RBCs undergo random clearance but have a maximum lifespan of about 50 days. Under anaemic conditions reticulocyte production rate is linearly correlated with the difference between normal and anaemic RBC concentrations, and their release rate is exponentially correlated with the same. PHZ appears to age rather than kill RBCs, and younger RBCs are affected more than older RBCs. Blood sampling caused short aperiodic spikes in the proportion of reticulocytes which appear to have a different developmental pathway than normal reticulocytes. We also provide evidence of large diurnal oscillations in serum erythropoietin levels during anaemia.     

Evaluation of the reticulocyte micronucleus assay in patients treated with radioiodine for thyroid cancer

In the case of accidental radiation exposure, biological dosimetry has an important role. Previous studies have indicated that the flow cytometric micronucleus (MN) assay in human transferrin receptor positive reticulocytes (Tf-Ret) in blood could be a sensitive biomarker for chromosome damage. In the present investigation, the utility and sensitivity of this method was studied in 44 young patients from Belarus, who were treated with 131I for thyroid cancer. Red marrow (RM) is the critical organ in radioiodine therapy (RIT). In our patients, it was exposed to 100-700 mSv low-dose rate irradiation within 2-4 days. About 3 days after 131I administration, the frequency of micronucleated-Tf-Ret (f(MN-Tf-Ret)) increases within 1 day to a maximum and declines in the following 2-5 days to its value before treatment. A total dose of 100 mSv was easily detectable. The sensitivity of the assay after acute irradiation may be 50 mSv. The method should be useful for monitoring individuals after a radiation accident, provided blood samples can be obtained within a few days after exposure. The time-course of f(MN-Tf-Ret) is interpreted using a model, which considers the exponential exposure of red marrow in RIT as well as the kinetics of erythroblast maturation and reticulocyte migration into the peripheral circulation. Similar modelling was done on published data of MN in immature mouse erythrocytes. Striking similarities in the kinetic and in the yield of MN-induction were found between these two species. This lends support for the use of the mouse as a model for the MN-induction in humans.     

Flow cytometric analysis of micronucleated reticulocytes in mouse bone marrow

This laboratory has previously reported a flow cytometric procedure for quantitatively analyzing mouse peripheral blood reticulocytes for micronucleus content. The current study extends this line of investigation by evaluating whether these same flow cytometric scoring procedures can be applied to the analysis of mouse bone marrow samples. To validate the method, three groups of male BALB/c mice were treated with 100 mg/kg b.wt. methyl methanesulfonate. Bone marrow samples were collected 20, 40 or 60 h after administration. A set of 5 untreated animals was included to provide an indication of spontaneous micronucleus frequencies. The cells were fixed with ultracold methanol, treated with ribonuclease, and labeled with anti-CD71 antibody (FITC conjugate) and propidium iodide. This fixing and labeling procedure resulted in the resolution of the micronucleated reticulocyte population and facilitated high-speed acquisition and enumeration via flow cytometry. The number of micronucleated reticulocytes was determined flow cytometrically by the analysis of 10?000 total reticulocytes per bone marrow sample. In addition to these automated measurements, slides stained with acridine orange were prepared and the number of micronuclei per 1000 reticulocytes was determined microscopically for each sample. The resulting data demonstrate that flow cytometry can effectively enumerate micronucleated reticulocytes in mouse bone marrow. The advantages associated with an objective, high throughput scoring methodology are also clearly indicated.     

Erythrocyte-based Pig-a gene mutation assay: demonstration of cross-species potential

Glycosylphosphatidylinositol (GPI) anchors attach specific proteins to the cell surface of hematopoietic cells. Of the genes required to form GPI anchors, only Pig-a is located on the X-chromosome. Prior work with rats suggests that the GPI anchor deficient phenotype is a reliable indicator of Pig-a mutation [Bryce et al., Environ. Mol. Mutagen., 49 (2008) 256-264]. The current report extends this line of investigation by describing simplified blood handling procedures, and by testing the assay principle in a second species, Mus musculus. With this method, erythrocytes are isolated, incubated with anti-CD24-PE, and stained with SYTO 13. Flow cytometric analyses quantify GPI anchor-deficient erythrocytes and reticulocytes. After reconstruction experiments with mutant-mimicking cells demonstrated that the analytical performance of the method is high, CD-1 mice were treated on three occasions with 7,12-dimethyl-1,2-benz[a]anthracene (DMBA, 75 mg/kg/day) or ethyl-N-nitrosourea (ENU, 40 mg/kg/day). Two weeks after the final treatment, DMBA-treated mice were found to exhibit markedly elevated frequencies of GPI anchor deficient erythrocytes and reticulocytes. For the ENU experiment, blood specimens were collected at weekly intervals over a 5-week period. Whereas the frequencies of mutant reticulocytes were significantly elevated 1 week after the last administration, the erythrocyte population was unchanged until the second week. Thereafter, both populations exhibited persistently elevated frequencies for the duration of the experiment (mean frequency at termination=310x10(-6) and 523x10(-6) for erythrocyte and reticulocyte populations, respectively). These data provide evidence that Pig-a mutation does not convey an appreciable positive or negative cell survival advantage to affected erythroid progenitors, although they do suggest that affected erythrocytes have a reduced lifespan in circulation. Collectively, accumulated data support the hypothesis that flow cytometric enumeration of GPI anchor deficient erythrocytes and/or reticulocytes represents an effective in vivo mutation assay that is applicable across species of toxicological interest.