Multivesicular bodies and autophagy in erythrocyte maturation

During reticulocyte maturation, hematopoietic progenitors undergo numerous changes to reach the final functional stage which concludes with the release of reticulocytes and erythrocytes into circulation. During this process some proteins, which are not required in the mature stage, are sequestered in the internal vesicles present in multivesicular bodies (MVBs). These small vesicles are known as exosomes because they are released into the extracellular medium by fusion of the MVB with the plasma membrane. Interestingly, during this maturation process some organelles, such as mitochondria and endoplasmic reticulum, are wrapped in double membrane vacuoles and degraded via autophagy. We have demonstrated in human leukemic K562 cells a role for calcium and Rab11 in the biogenesis of MVBs and exosome release. Here we discuss evidence indicating that K562 cells present a high basal level of autophagy, and that there is an association between MVBs and autophagosomes, suggesting a role for the autophagic pathway in the maturation process of this cell type.

[On the biophysics characteristics of reticulocytes]

This paper reports an in vivo study on the biophysics characteristics of reticulocytes. Anemia was induced by injection of phenylhydrazine in rabbits. The measurements, including electrophoresis rate, hematolytic rate, fluorescent polarization and the changing anisotropic value, were performed in vivo for 72 hours in the process of reticulocytes growing into erythrocytes. It was shown that there were obvious changes in the biophysics characteristics of reticulocytes in this course. Therefore, the findings are of significance to basic, theoretical and clinical studies.

Is it more effective for highly trained swimmers to live and train at 1200 m than at 1850 m in terms of performance and haematological benefits?

OBJECTIVES

The effects of living and training have not been compared at different altitudes in well trained subjects.

METHODS

Nine international swimmers lived and trained for 13 days similarly at 1200 m (T1200) and 1850 m (T1850). The two altitude training periods were separated by six weeks of sea level training. Before and after each training trip, subjects performed, at an altitude of 1200 m, an incremental exercise test to exhaustion of 5 x 200 m swims and a maximal test over 2000 m.

RESULTS

There was no difference in Vo(2)max after each training trip: the before values were 58.5 (5.6) and 60.4 (6.7) ml/kg/min and the after values were 56.2 (5.2) and 57.1 (4.7) ml/kg/min for T1200 and T1850 respectively. The 2000 m performance had improved during T1200 (1476 (34) to 1448 (45) seconds) but not during T1850 (1458 (35) v 1450 (33) seconds). Mean cell volume increased during T1850 (86.6 (2.8) to 88.7 (2.9) microm(3)) but did not change during T1200 (85.6 (2.9) v 85.7 (2.9) microm(3)). The proportion of reticulocytes decreased during T1200 (15.2 (3.8)% to 10.3 (3.4)%) and increased during T1850 (9.3 (1.6)% to 11.9 (3.5)%).

CONCLUSIONS

The short term effects of 13 days of training at 1200 m on swimming performance appear to be greater than the same type of training for the same length of time at 1850 m. As mean cell volume and proportion of reticulocytes only increased during training at 1850 m, the benefits of training at this altitude may be delayed and appear later on.

Studies on the biomechanical properties of maturing reticulocytes

We investigated the biomechanical properties of reticulocytes obtained from an animal model of hemolytic anemia induced by antibody injection. The hemorheological indices, membrane viscoelasticity, membrane fluidity, and the secondary structure of membrane proteins of the reticulocytes were monitored continuously during the course of their maturation into erythrocytes. The results indicate that reticulocytes had lower deformability, lower membrane fluidity, greater viscoelastic modulus and lesser proportions of alpha-helices and beta-sheets in protein secondary structures than mature erythrocytes. All these indices approached to the level of normal erythrocytes when reticulocytes transformed during maturation. The results help to enhance our understanding of the biomechanical properties of the reticulocytes in their maturing process with clinical diagnosis significances.

Diurnal normobaric moderate hypoxia raises serum erythropoietin concentration but does not stimulate accelerated erythrocyte production

This study was performed to examine the effect of diurnal normobaric hypoxia on hematological parameters. Eleven healthy male volunteers were randomly selected to be in either the hypoxic group (n=6) or the control group (n=5). The hypoxic group was exposed to 8 h of normobaric hypoxia in hypoxic tent systems that elicited a target peripheral O(2) saturation of 81+/-2% on three consecutive days. The control group spent three consecutive 8-h days in modified tent systems that delivered normoxic air into the tent. Venous blood samples were collected before the exposure (days -5, 0), after each day of the exposure (days 1, 2, 3), and for 3 weeks after the exposure (days 7, 10, 13, 17, 24). Serum erythropoietin concentration significantly increased from 9.1+/-3.3 U.L(-1) to 30.7+/-8.6 U.L(-1) in the hypoxic group. Although there were significant increases in hematocrit (4%), hemoglobin concentration (5%), red blood cell count (4%) on day 7 in the hypoxic group, these observations were likely due to dehydration or biological variation over time. There was no significant change in early erythropoietic markers (reticulocyte counts or serum ferritin concentration), which provided inconclusive evidence of accelerated erythroid differentiation and proliferation. The results suggest that the degree of hypoxia was sufficient to stimulate increased erythropoietin production and release. However, the duration of hypoxic exposure was insufficient to propagate the erythropoietic cascade.

Changes in erythropoiesis, iron metabolism and oxidative stress after half-marathon

OBJECTIVE

In marathon runners changes in red blood cell count, haematocrit and haemoglobin in relation to haemodilution have been reported. Moreover, it has been hypothesized that strenuous exercise induces oxidant stress through several different mechanisms. This study investigated the haematological variables, iron status and oxidative indices before, immediately and 48 h after a race in 8 healthy trained males aged 33-44 years running a 21-km marathon in 79 +/- 3 min.

METHODS

The haematological parameters were determined by standard procedures. Erythropoietin and soluble-transferrin receptor were evaluated immunoenzymatically. Nontransferrin-bound iron (NTBI) was assayed by high-performance liquid chromatography after nitrilotriacetic acid chelation. Malonyldialdehyde (MDA) concentration was assayed colorimetrically.

RESULTS

The total number of reticulocytes rose significantly after the run with a significant increase in the high-RNA-content fraction (14 +/- 5, p < 0.0006). Erythropoietin rose by 26% (15.0 +/- 2.8 mU/ml, p < 0.004) and by 25% (14.9 +/- 2.13 mU/ml, p < 0.02) immediately and 48 h after the race, respectively. Serum iron and serum ferritin remained unchanged but NTBI and serum MDA increased significantly immediately after running (1.16 +/- 0.40 mmol/l, p < 0.0008; 0.76 +/- 0.16 mmol/l, p < 0.0001). Significant positive correlations at any time between MDA and polymorphonuclear neutrophils (p = 0.0005), MDA and NTBI (p = 0.0018), polymorphonuclear neutrophils and NTBI (p = 0.0008) and between lactate dehydrogenase and NTBI (p = 0.0212) were observed.

CONCLUSIONS

The erythropoietic changes observed in marathon runners are the results of several interacting mechanisms that involve either the haemopoietic system per se or erythrocyte haemolysis and oxidative stress.

Core erythropoietin receptor signals for late erythroblast development

Critical signals for erythroblast formation are transduced by activated, tyrosine-phosphorylated erythropoietin receptor (EpoR) complexes. Nonetheless, steady-state erythropoiesis is supported effectively by EpoR alleles that are deficient in cytoplasmic phosphotyrosine sites. To better define core EpoR action mechanisms, signaling capacities of minimal PY-null (EpoR-HM) and PY343-retaining (EpoR-H) alleles were analyzed for the first time in bone marrow-derived erythroblasts. Jak2 activation via each allele was comparable. Stat5 (and several Stat5-response genes) were induced via EpoR-H but not via EpoR-HM. Stat1 and Stat3 activation was nominal for all EpoR forms. For both EpoR-HM and EpoR-H, Akt and p70S6-kinase activation was decreased multifold, and JNK activation was minimal. ERKs, however, were hyperactivated uniquely via EpoR-HM. In vivo, Epo expression in EpoR-HM mice was elevated, while Epo-induced reticulocyte production was diminished. In vitro, EpoR-HM erythroblast maturation also was attenuated (based on DNA content, forward-angle light scatter, and hemoglobinization). These EpoR-HM-specific defects were corrected not only upon PY343 site restoration in EpoR-H, but also upon MEK1,2 inhibition. Core EpoR PY site-independent signals for erythroblast formation therefore appear to be Stat5, Stat1, Stat3, p70S6-kinase, and JNK independent, but ERK dependent. Wild-type signaling capacities, however, depend further upon signals provided via an EpoR/PY343/Stat5 axis.

Four-base codon-mediated incorporation of non-natural amino acids into proteins in a eukaryotic cell-free translation system

Various four-base codons have been shown to work for the introduction of non-natural amino acids into proteins in an Escherichia coli cell-free translation system. Here, a four-base codon-mediated non-natural mutagenesis was applied to a eukaryotic rabbit reticulocyte cell-free translation system. Mutated streptavidin mRNAs containing four-base codons were prepared and added to a rabbit reticulocyte lysate in the presence of tRNAs that were aminoacylated with a non-natural amino acid and had the corresponding four-base anticodons. A Western blot analysis of translation products indicated that the four-base codons CGGU, CGCU, CCCU, CUCU, CUAU, and GGGU were efficiently decoded by the aminoacyl-tRNAs having the corresponding four-base anticodons. In contrast, the four-base codons AGGU, AGAU, CGAU, UUGU, UCGU, and ACGU were not decoded. The stop codon-derived four-base codons UAGU, UAAU, and UGAU were found to be inefficient, whereas the amber codon UAG and opal codon UGA were efficient for the incorporation of non-natural amino acids. The application of the expanded genetic code in a eukaryotic cell-free system opens the possibility of a four-base codon-mediated incorporation of non-natural amino acids into proteins in living eukaryotic cells.

Supramaximal exercise mobilizes hematopoietic progenitors and reticulocytes in athletes

Marathon runners show increased circulating CD34+ cell counts and postexercise release of interleukin-6 (IL-6), granulocyte-colony stimulating factor (G-CSF) and flt3-ligand (Bonsignore MR, Morici G, Santoro A, Pegano M, Cascio L, Bonnano A, Abate P, Mirabella F, Profita M, Insalaco G, Gioia M, Vignola AM, Majolino I, Testa U, and Hogg JC. J Appl Physiol 93: 1691–1697, 2002). In the present study we hypothesized that supramaximal (“all-out”) exercise may acutely affect circulating progenitors and reticulocytes and investigated possible mechanisms involved. Progenitor release was measured by flow cytometry ( n = 20) and clonogenic assays ( n = 6) in 20 young competitive rowers (13 M, 7 F, age ± SD: 17.1 ± 2.1 yr, peak O2consumption: 56.5 ± 11.4 ml·min−1·kg−1) at rest and shortly after 1,000 m “all-out.” Release of reticulocytes, cortisol, muscle enzymes, neutrophil elastase, and several cytokines/growth factors was measured. Supramaximal exercise doubled circulating CD34+ cells (rest: 7.6 ± 3.0, all-out: 16.3 ± 9.1 cells/μl, P < 0.001), and increased immature reticulocyte fractions; AC133+ cells doubled, suggesting release of angiogenetic precursors. Erythrocyte burst forming units and colony forming units for granulocytes-monocytes and all blood series increased postexercise by 3.4-, 5.5-, and 4.8-fold, respectively ( P < 0.01 for all). All-out rowing acutely increased plasma cortisol, neutrophil elastase, flt3-ligand, hepatocyte growth factor, VEGF, and transforming growth factor-β1, and decreased erythropoietin; K-ligand, stromal-derived factor-1, IL-6, and G-CSF were unchanged. Therefore, all-out exercise is a physiological stimulus for progenitor release in athletes. Release of reticulocytes and proangiogenetic cells and mediators suggests tissue hypoxia as possibly involved in progenitor mobilization.

In vitro assays of substrate degradation induced by high-risk HPV E6 oncoproteins

The high-risk mucosal human papillomavirus E6 proteins were the first viral proteins that were shown to use the ubiquitin proteasome pathway for the inactivation of their cellular target proteins. The first substrate to be identified was the p53 tumor suppressor protein, and since then many other substrates for E6-induced degradation have been described. All of these require the presence of high-risk mucosal E6 together with the E1, E2, and E3 enzymes of the ubiquitin pathway. This activity of E6, although complex, is nonetheless amenable to in vitro analysis. Many different protocols have been described over the years for performing these assays. In this chapter we describe the most easily used and robust procedure that is routinely used in our laboratory.

Changes in the mutagenic and estrogenic activities of bisphenol A upon treatment with nitrite

Bisphenol A (4,4'isopropylidenediphenol: BPA), an endocrine-disrupting chemical, is contained in food-packaging and can-coating agents as well as in dental sealants. Nitrite is present in vegetables, fish and tap water as an ingredient or contaminant, and also in human saliva. Here, we explored the possible generation of genotoxicity from the reactions of BPA and nitrite under acidic conditions, a situation simulating the stomach. We determined the changes in the mutagenic and estrogenic activities of BPA before and after nitrite treatment. Untreated BPA did not exhibit any mutagenicity. However, the mixture of BPA and sodium nitrite after incubation at pH 3.0 showed strong mutagenic activity toward Salmonella typhimurium strains TA 100 and TA 98 either with or without a metabolic activation system (S9 mix). The clastogenic properties of nitrite-treated and untreated BPA were analyzed by a micronucleus test with male ICR mice. A single gastric intubation of nitrite-treated BPA induced a significantly higher frequency of micronucleated reticulocytes (MNRETs) in mice. The results of analysis of electron spin resonance (ESR) suggest that the expression of the mutagenic activity of nitrite-treated BPA is related to the generation of radicals in the reaction mixture. By applying 1H and 13C NMR, AB-MS and APCI/LC/MS, we identified two compounds 3-nitrobisphenol A and 3,3'-dinitro-bisphenol A. These compounds were synthesized by the reaction of BPA with nitric acid. 3,3'-Dinitro-bisphenol induced a significantly greater frequency of MNRETs in male ICR mice. By applying a green fluorescent protein (GFP)-reporter expression system and an estrogen R(alpha) competitor screening kit, we found that nitrite-treated BPA and 3,3'-dinitro-bisphenol A showed weak estrogenic activity compared to that of untreated BPA.

Pharmacodynamic Analysis of Changes in Reticulocyte Subtype Distribution in Phlebotomy-Induced Stress Erythropoiesis

Changes in the reticulocyte subtype distribution (high, medium and low reticulocytes count (HR, MR, LR)) measured by flow cytometry following phlebotomy-induced stress erythropoiesis (abruptly dropping hemoglobin to 3-4 g/dl over 4-5 hr) and the pharmacodynamic (PD) relationship to the stimulated erythropoietin (EPO) was investigated in sheep. A PD model was developed that describes the relationship between EPO and the reticulocyte maturity distribution fractions (r=0.95+/-0.02, mean +/- SD). The lag-time between EPO activation of erythroid progenitor cells and the subsequent increase in the least mature HR fraction in the peripheral circulation was 0.72 +/- 0.08 days. The mean transition times (in days) for all three reticulocyte fractions changed at baseline from, T(HR) : 0.09 +/- 0.06, T(MR) : 0.06 +/- 0.04, and T(LR) : 0.46 +/- 0.24 to T(HR) : 0.13 +/- 0.08, T(MR) : 0.29 +/- 0.15, and T(LR) : 2.3 +/- 0.24 under stress erythropoiesis. The total mean residence time for a reticulocyte in the peripheral circulation, T(total) (T(HR) + T(MR) + T(LR)), increased from 0.60 +/- 0.33 days under basal to 2.8 +/- 0.09 days during stress erythropoiesis. The statistically significant increase observed for T(LR) and T(total) supports the hypothesis that stress erythropoiesis perturbs the mean reticulocyte transition times. A correlation analysis between various new, proposed metrics involving the HR, MR and LR fractions and the total reticulocyte count, with the latter indicative of stress erythropoiesis at higher total counts, revealed a highly significant correlation indicating these new metrics may be a valuable adjunct to the reticulocyte maturation index (RMI) and the immature reticulocyte fractions index (IRF) previously used in assessing erythropoietic activity in response to anemia.

Isolation and characterization of a glucose/mannose/rhamnose-specific lectin from the knife bean Canavalia gladiata

A lectin with specificity toward mannose, glucose, and rhamnose has been isolated from the legumes of the knife bean Canavalia gladiata. The lectin is composed of two identical 30-kDa subunits with substantial N-terminal sequence similarity to Concanavalin A (Con A). It was purified by affinity chromatography on Affi-gel blue gel, ion exchange chromatography on Mono S, and gel filtration by fast protein liquid chromatography on Superdex 200. Compared with Con A, knife bean lectin started to stimulate [methyl-(3)H]thymidine uptake by mouse splenocytes at a lower concentration, and more potently inhibited proliferation of L1210 leukemia cells. In contrast to Con A, the mitogenic activity of knife bean lectin toward mouse splenocytes, but not its antiproliferative activity toward tumor cells, could be abrogated by 250 mM glucose. Both mitogenic and antiproliferative activities of Con A were abolished by glucose. The lectin inhibited HIV-1 reverse transcriptase with an IC(50) of 35 microM and cell-free translation in a rabbit reticulocyte lysate system with an IC(50) of 2.08 microM. The lectin did not exhibit antifungal activity.

Effect of blood reticulocyte concentration on electrophoretic mobility of erythrocytes in rats

In intact rats electrokinetic characteristics of erythrocytes weakly depended on the intensity of erythropoiesis. This dependence became significant when the degree of erythropoiesis approached the upper limit of variations. Electrophoretic mobility of erythrocytes progressively decreased with increasing blood reticulocyte count. Subpopulations of erythrocytes with low mobility in electric field accumulated in the blood. Our results indicate that erythrocytes whose electrokinetic potential is similar to the mean mobility of circulating cells migrate from the bone marrow into the circulation under normal conditions.

Pilot study for comparison of reticulocyte-micronulei with lymphocyte-micronuclei in human biomonitoring

Biomonitoring tries to determine the consequences for humans of exposures to environmental or pharmaceutical agents. Different end points have been employed to assess the burden of genomic damage. This is the first report comparing a recently introduced new end point, the reticulocyte-micronuclei analyzed by flow cytometry with the widely used lymphocyte-micronucleus assay, applied to two exposure scenarios leading to enhanced genomic damage. Radioiodine therapy was chosen to represent a short time exposure and hemodialysis treatment in end-stage renal failure was chosen to represent a chronic exposure. The results show that iodine radiation induced measurable genomic damage in the lymphocyte-micronucleus assay as well as in the reticulocyte-micronucleus test. Of two groups of patients under hemodialysis treatment, a reduced genomic damage was found with the lymphocyte-micronucleus test, but not with the reticulocyte-micronucleus test in the group undergoing daily hemodialysis, which removes uremic toxins more efficiently as compared to conventional hemodialysis, the treatment applied in the other group. The limited life-span of reticulocytes may make them less suitable for accumulation of chronic low level damage than lymphocytes. In conclusion, the lymphocyte-micronucleus test may be applicable to more exposure situations (including low chronic exposure), but the reticulocyte-micronucleus assay may be easier to perform in a clinical setting. The latter reflects a more rapid reduction of genomic damage after an acute exposure.

Monitoring the content of reticulocyte hemoglobin (CHr) as the progression of anemia in nondialysis chronic renal failure (CRF) patients

BACKGROUND

We previously showed that the content of reticulocyte hemoglobin (CHr) is a reliable measure of iron status in chronic dialysis patients with erythrocytopoiesis. The CHr was significantly correlated with conventional parameters of iron deficiency in dialysis patients. We attempted to utilize the measurement of CHr levels to monitor iron status and clarify the changes in iron levels that occur as renal anemia progresses in patients with chronic renal failure (CRF).

METHODS

We measured CHr, iron parameters, and the intrinsic erythropoietin (EPO) concentration in nondialysis CRF patients who visited our outpatient clinic (n=211). Iron deficiency was defined according to the transferrin saturation (TSAT) and ferritin levels. Conventional red blood cell parameters and CHr levels were measured using an ADVIA120 autoanalyzer (Bayer Medical, USA).

RESULTS

The mean CHr value of the nondialysis CRF patients (creatinine clearance less than 70 mL/min) was 32.3 pg, which was not significantly different from that of the dialysis patients. Significant correlations were found between CHr and ferritin levels (r=0.042, p<0.0403) and CHr and TSAT levels (r=0.040, p<0.0157). A positive correlation was observed between the CHr and serum creatinine levels. Nondialysis CRF patients treated with recombinant human EPO (rHuEPO) at a dose of 24,000 U/month exhibited lower CHr levels, compared with those of other patients who received less than 24,000 U/month.

CONCLUSION

CHr is an easily measurable and trustworthy marker of iron status in nondialysis CRF patients. Moreover, the CHr level was also sensitive to iron alterations in nondialysis CRF patients receiving rHuEPO treatment, and thus, the CHr value could likely provide useful information regarding the need for iron supplementation.

Analysis of human reticulocyte genes reveals altered erythropoiesis: potential use to detect recombinant human erythropoietin doping

BACKGROUND AND OBJECTIVES

Enhancement of oxygen delivery to tissues is associated with improved sporting performance. One way of enhancing oxygen delivery is to take recombinant human erythropoietin (rHuEpo), which is an unethical and potentially dangerous practice. However, detection of the use of rHuEpo remains difficult in situations such as: i) several days after the end of treatment ii) when a treatment with low doses is conducted iii) if the rHuEpo effect is increased by other substances. In an attempt to detect rHuEpo abuse, we selected erythroid gene markers from a SAGE library and analyzed the effects of rHuEpo administration on expression of the HBB, FTL and OAZ genes.

DESIGN AND METHODS

Ten athletes were assigned to the rHuEpo or placebo group. The rHuEpo group received subcutaneous injections of rHuEpo (50 UI/kg three times a week, 4 weeks; 20 UI/kg three times a week, 2 weeks). HBB, FTL and OAZ gene profiles were monitored by real time-polymerase chain reaction (PCR) quantification during and for 3 weeks after drug administration.

RESULTS

The global analysis of these targeted genes detected in whole blood samples showed a characteristic profile of subjects misusing rHuEpo with a increase above the threshold levels. The individual analysis of OAZ mRNA seemed indicative of rHuEpo treatment.

INTERPRETATION AND CONCLUSIONS

The performance-enhancing effect of rHuEpo treatment is greater than the duration of hematologic changes associated with rHuEpo misuse. Although direct electrophoretic methods to detect rHuEpo have been developed, recombinant isoforms of rHuEpo are not detectable some days after the last subcutaneous injection. To overcome these limitations indirect OFF models have been developed. Our data suggest that, in the near future, it will be possible to consolidate results achievable with the OFF models by analyzing selected erythroid gene markers as a supplement to indirect methods.

Associations between serum transferrin receptor concentrations and erythropoietic activities according to body iron status

This study investigated the associations between serum transferrin receptor (sTfR) concentrations and erythropoietic activities during 3 stages of iron deficiency in humans. Serum iron markers, fluorescent intensity of reticulocytes, and sTfR concentrations were measured in 227 prepubescent children, age 9 to 12 yr. Reticulocyte subpopulations were analyzed by flow cytometry and sTfR concentrations were measured by enzyme immunoassay. Mean values of middle-fluorescence reticulocytes (MFR), reticulocyte maturity index (RMI), and sTfR concentrations were significantly higher in iron-deficiency anemia subjects than in healthy controls. Reticulocyte subpopulations increased gradually, as body iron status diminished; the mean values of MFR and RMI in subjects with serum ferritin concentrations < 4.0 microg/L were 3-fold higher than those in healthy controls (p < 0.01). Correlation coefficients of MFR and RMI vs log ferritin values (r = 0.43 and r = 0.42) were higher than those of MFR and RMI vs sTfR concentrations (r = 0.24 and r = 0.27) in iron-deficiency anemia subjects. In summary, iron deficiency leads to increased production of immature reticulocytes. Erythropoietic activity is more closely associated with log ferritin values than with sTfR concentrations in iron-deficiency anemia.

Time and temperature dependant changes in red blood cell analytes used for testing recombinant erythropoietin abuse in sports

There has been a long debate since the introduction of blood analysis prior to major sports events, to find out whether blood samples should be analysed right away on the site of competition or whether they should be transported and analysed in an anti-doping laboratory. Therefore, it was necessary to measure blood samples and compare the results obtained right after the blood withdrawal with those obtained after a few hours delay. Furthermore, it was interesting to determine the effect of temperature on the possible deterioration of red blood cell analytes used for testing recombinant erythropoietin abuse. Healthy volunteers were asked to give two blood samples and one of these was kept at room temperature whereas the second one was put into a refrigerator. On a regular basis, the samples were rolled for homogenisation and temperature stabilisation and were analysed with the same haematological apparatus. The results confirmed that blood controls prior to competition should be performed as soon as possible with standardised pre-analytical conditions to avoid too many variations notably on the haematocrit and the reticulocyte count. These recommendations should ideally also be applied to the all the blood controls compulsory for the medical follow up, otherwise unexplainable values could be misinterpreted and could for instance lead to a period of incapacity.

What determines whether mammalian ribosomes resume scanning after translation of a short upstream open reading frame?

If the 5'-proximal AUG triplet in a mammalian mRNA is followed by a short open reading frame (sORF), a significant fraction of ribosomes resume scanning after termination of sORF translation, and reinitiate at a downstream AUG. To examine the underlying mechanism, we examined reinitiation in vitro using a series of mRNAs that differed only in the 5'-untranslated region (UTR). Efficient reinitiation was found to occur only if the eIF4F complex, or at a minimum the central one-third fragment of eIF4G, participated in the primary initiation event at the sORF initiation codon. It did not occur, however, when sORF translation was driven by the classical swine fever virus or cricket paralysis virus internal ribosome entry sites (IRESs), which do not use eIF4A, 4B, 4E, or 4G. A critical test was provided by an mRNA with an unstructured 5'-UTR, which is translated by scanning but does not absolutely need eIF4G and eIF4A: There was efficient reinitiation in a standard reticulocyte lysate, when initiation would be largely driven by eIF4F, but no reinitiation in an eIF4G-depleted lysate. These results suggest that resumption of scanning may depend on the interaction between eIF4F (or the eIF4G central domain) and the ribosome being maintained while the ribosome translates the sORF.

Visualization and mechanism of assembly of a glucocorticoid receptor.Hsp70 complex that is primed for subsequent Hsp90-dependent opening of the steroid binding cleft

A minimal system of five proteins, hsp90, hsp70, Hop, hsp40, and p23, assembles glucocorticoid receptor (GR).hsp90 heterocomplexes and causes the simultaneous opening of the steroid binding cleft to access by steroid. The first step in assembly is the ATP-dependent and hsp40 (YDJ-1)-dependent formation of a GR.hsp70 complex that primes the receptor for subsequent ATP-dependent activation by hsp90, Hop, and p23. This study focuses on three aspects of the GR priming reaction with hsp70. First, we have visualized the primed GR.hsp70 complexes by atomic force microscopy, and we find the most common stoichiometry to be 1:1, with some complexes of a size approximately 1:2 and a few complexes of larger size. Second, in a recent study of progesterone receptor priming, it was shown that hsp40 binds first, leading to the notion that it targets hsp70 to the receptor. We show here that hsp40 does not perform such a targeting function in priming the GR. Third, we focus on a short amino-terminal segment of the ligand binding domain that is required for GR.hsp90 heterocomplex assembly. By using two glutathione S-transferase (GST)/ligand binding domain fusions with (GST/520C) and without (GST/554C) hsp90 binding and steroid binding activity, we show that the priming step with hsp70 occurs with GST/554C, and it is the subsequent assembly step with hsp90 that is defective.

Determination of the elastic shear modulus of cultured human red blood cells

In this study we investigated the mechanical properties of in vitro cultured red blood cells (RBCs) in a liquid system. We used human umbilical cord blood as a highly efficient source of hematopoietic stem cells (HS). Our first goal was to establish an optimal medium composition in order to yield finally differentiated RBCs, i.e. enucleated and hemoglobin-filled cells. Different stages of cell differentiation were distinguished based on morphological observations and flow cytometry measurements. By means of the micropipette aspiration technique we estimated the deformability characteristics of the cultured cells. Up to the stage of oxiphilic normoblasts they readily deformed. Reticulocytes and mature RBCs showed an enhanced stiffness as compared to RBCs obtained from donors.

Soluble transferrin receptor and immature reticulocytes are not useful for distinguishing iron-deficiency anemia from heterozygous beta-thalassemia

Iron deficiency and heterozygous beta-thalassemia are important causes of hypochromic-microcytic anemia. Two laboratory parameters are suggested for the differentiation of such anemia. High-fluorescence reticulocyte counts and soluble transferrin receptor levels were determined in iron-deficiency anemia patients (n = 49) and heterozygous beta-thalassemia patients (n = 43). There was no significant difference in high-fluorescence reticulocyte and soluble transferrin receptor values between the two groups, but a correlation was observed between high-fluorescence reticulocytes and soluble transferrin receptors in iron-deficiency anemia, probably due to increased receptor synthesis as a response to decreased iron content in erythrocytes.

[Evolutionary and bone marrow recovery indicators in bone marrow transplantation after total body irradiation]

Oxidative stress and reticulocyte maturity index (RMI) were studied in 27 patients who underwent bone marrow transplantation (BMT). Plasmatic lipoperoxide levels of those patients with unfavorable evolution were significantly increased on days 12-14 post-transplant (median 1.83 microM, range 0.78-5.82) compared with preconditioning levels (median 1.05 microM, range 0.36-1.84) (p < 0.05). Patients with favorable evolution revealed significantly higher lipoperoxide levels during conditioning regime (median 1.42 microM, range 0.31-4.50) (p < 0.05). Starting from the 3rd post-transplant week a significant and continuous decrease was observed, with a median of 0.77 microM (range 0.21-1.48 p < 0.05) for the 3rd, and a median of 0.60 microM (range 0.11-1.48 for the 4th week (p < 0.01). A significant increase in total antioxidant activity was observed in the three patients who died up to the 35 days post-transplant. Recovery of bone marrow function was detected by RMI after a median time of 17 days (range 11-24) post-allogeneic transplantation. The threshold established for absolute neutrophil count was achieved after a median of 21 days (range 14-28) (p < 0.001). An increase of plasma lipoperoxides on days 12-14 post-transplant may be a predictive value of unfavourable evolution. RMI was the earlier indicator of engraftment in allogeneic BMT.