Effects of phenylhydrazine or recombinant human erythropoietin on deformability and activity of dehydrogenase glucose-6-phosphate and acetylcholinesterase in Wistar rats blood enriched in reticulocytes

Deformability and activity of the enzymes: acetylcholinesterase (AChE) and dehydrogenase glucose-6-phosphate (G-6-PD), were assayed for RBC enriched in immature reticulocytes. Reticulocytosis was evoked by administration of two different drugs: recombinant human erythropoietin (rHuEPO) and phenylhydrazine (PHZ) to two groups of Wistar rats. After treatment with the former compound, a group of animals exhibited 17.33% reticulocytes in blood whereas a group of rats treated with the latter drug reached 57.66% of these cells in blood. A marked decrease in RBC deformability was found in both groups of animals. AChE did not significantly change activity neither in PHZ-treated nor in rHuEPO-treated rats, whereas G-6-PD activity was significantly decreased in the PHZ-treated group.

Five fully automated methods for performing immature reticulocyte fraction: comparison in diagnosis of bone marrow aplasia

We performed a parallel evaluation of 5 automated reticulocyte counters to produce the immature reticulocyte fraction (IRF). We analyzed 225 samples from healthy control subjects, 115 from patients with various diseases, 38 with advanced aplasia, and 22 in early erythropoietic recovery after chemotherapy or bone marrow transplantation. The reference intervals were different for each instrument (ADVIA 120, 0.04-0.25; CELL DYN 4000, 0.15-0.35; GEN-S, 0.20-0.37; SE 9500 RET 0.05-0.21; VEGA RETIC: 0.06-0.23). The imprecision, obtained by 1-way analysis of variance on duplicates, was satisfactory for clinical use for all methods (coefficient of variation, 7.6%-20.5% in healthy subjects), although it was higher than the analytic goal based on biologic variability within subjects. The comparison of different methods shows that agreement is good only between SE 9500 RET CELL DYN 4000, and VEGA RETIC (r2 = 0.72-0.78). The study of diagnostic performance in distinguishing aplasia from early bone marrow recovery shows slightly different results (area under the curve from 0.70 for ADVIA 120 to 0.96 for SE 9500 RET). Even with slight differences, the fluorescence-based methods seem to be more robust than other methods for IRF measurement.

Changes in erythropoiesis assessed by reticulocyte parameters during ultralong distance running

OBJECTIVE

To investigate the possibility of early changes in erythropoiesis during prolonged exercise being reflected in reticulocyte parameters.

DESIGN

This was a case-control field study of hematological variables in a group of ultramarathon runners competing in a 6-day track race.

SETTING

A 6-day ultramarathon in Colac, Australia.

PARTICIPANTS

7 male and 1 female experienced ultramarathon runners.

INTERVENTION

A track race of 6 days' duration.

MAIN OUTCOME MEASURES

A wide range of red cell and reticulocyte parameters.

RESULTS

Resting red cell parameters were within normal clinical limits. However, except for the expected findings typical of hemodilution, red cell parameters were relatively unchanged during and after the event, with the exception of small but statistically significant changes in number and percentage of macrocytic, microcytic, hypochromic, and hyperchromic red cells. No reticulocytosis was found in an event that would have been expected to be associated with significant foot-strike hemolysis; however, an increase in the percentage of reticulocytes with high RNA content late in the event indicates early release from the marrow. Reduction in reticulocyte mean cell volume, which is consistent with functional iron deficiency, was demonstrated during the event. This finding is consistent with changes in some of the iron-related parameters associated with the acute phase response, but the dissociation in time between these changes makes a causal relationship unlikely. Other changes such as those in reticulocyte hemoglobin distribution width, reticulocyte distribution width, cell hemoglobin concentration mean, and lack of change in corpuscular hemoglobin are not typical of true iron deficiency, and the mechanism of these changes is currently unknown.

CONCLUSION

The hematopoietic system demonstrates remarkable stability in the face of very significant exercise stress. No reticulocyte response was demonstrated in this study, but reticulocyte changes both consistent with and contrary to early release from the marrow were demonstrated after several days of strenuous running. The significance of several newly developed ratios of red cell and reticulocyte parameters in conditions of exercise stress requires further investigation.

Autophagy in hepatocytes and erythropoietic cells isolated from the twenty-one day old rat embryo

Liver cells of the twenty-one day old rat embryo are isolated by a modified method and autophagy is studied in them by electron microscopic morphology and morphometry. Immediately after isolation or 2.5 h incubation in nutrient-free medium, embryonic hepatocytes contain high amount of glycogen and only very few autophagic vacuoles. In contrast, all glycogen is lost and 15% of the cytoplasmic volume is occupied by late autophagic vacuoles in hepatocytes after 18 h in the same medium. Presence of 3-methyladenine in the latter case inhibits both the loss of glycogen and the appearance of autophagic vacuoles while enlarging the multivesicular body compartment. Our findings reveal major differences between isolated embryonic and adult hepatocytes concerning autophagy. Several types of autophagic vacuoles are described in the cell types of the erythropoietic cell lineage. This means that autophagy is an integral part of erythropoiesis not only in bone marrow, but also in embryonic liver that is investigated here for the first time from this point of view. The presence of unclosed isolation membranes and the predominance of early autophagic vacuoles in reticulocytes indicates that the molecular machinery of segregation is still active in this functionally and structurally highly reduced cell type.

Reticulocyte analysis by flow cytometry and other techniques

Enumeration of peripheral blood reticulocytes is an essential part of the diagnosis and management of anemic patients, since the number of reticulocytes in the peripheral blood reflects the erythrocytic activity of the bone marrow. Reticulocyte enumeration using flow cytometric methodology is rapidly replacing the inaccurate, imprecise manual counting technique used in the past. This article explores the pathophysiology of the reticulocyte, the various means of counting reticulocytes, and the diverse clinical applications of reticulocyte data.

[Treatment of anemia in rheumatoid arthritis with transplantation of hemopoietic stem cells from human embryonic liver]

The article describes chief links of pathogenesis of anemia in rheumatoid arthritis (RA). These include the blood hyperviscosity syndrome, abnormalities of iron metabolism, blockade of iron in the reticuloendothelial system, hemolysis, depression of erythropoiesis. Indices for the hemoglobin peripheral blood, erythrocytes, reticulocytes, platelets in the group of RA patients were analysed together with their changes under exposure to transplantation of hemopoitic stem cells of human embryional liver.

Carnitine action on red blood cell osmotic resistance in hemodialysis patients

Low red blood cell osmotic resistance (RBCOR) in dialysis patients aggravates anemia and raises EPO needs. We studied RBCOR in 30 stable patients (22 M, 8 F), dialyzed for more than one year, with no systemic illness, blood transfusions, recent infection or treatment by ACE inhibitors. Nineteen were on EPO. Cuprophane dialysis membranes were used in 21, synthetic in the remaining nine. RBCOR was low in 13 patients and these patients received L-carnitine, 20 mg/kg IV, post dialysis, for one year (A); 17 with normal RBCOR served as untreated controls (B). We investigated the relations between RBCOR and membrane material, time on HD (THD), weekly dialysis duration (WHDT), serum total carnitine (TC), acyl carnitine (AC), free carnitine (FC) and AC/FC in all patients, before and after carnitine supplementation. RBCOR changes under carnitine treatment were evaluated. Age, sex, primary renal disease, THD, EPO dose, hematology and biochemistry were similar in treated patients and controls. Patients in group A (dialysed with cuprophane) had lower RBCOR than group B, (dialysed with synthetic and cuprophane membranes) (0.473 +/- 0.02 vs. 0.420 +/- 0.02, P < 0.001). RBCOR remained stable under carnitine in group A, but became abnormally low in controls (especially in 10/17 patients). RBCOR was significantly higher than the pretreatment values in 5/13 group A patients (month 0-M0: 0.48 +/- 0.02, M12: 0.45, +/- 0.02, P < 0.05). Carnitine levels, similar in both groups before treatment, remained stable in group A, but dropped in group B (TC: 52.1 +/- 9.6/31.1 +/- 21.2, FC: 33.1 +/- 8.3/15.6 +/- 19.2 micromol/L, P < 0.002). Patients with shorter WHDT (< or = 12 vs. > 12 h) had higher FC levels (36 +/- 6.9 vs. 30 +/- 6 micromol/L, P < 0.03). Low RBCOR is frequent in stable dialyzed patients. It is related to dialysis membranes and is aggravated by time on hemodialysis. Serum carnitine levels depend on weekly dialysis time and on carnitine supplementation, that normalizes osmotic resistance in some dialysis patients.

[Autoimmune hemolytic anemia]

Autoimmune hemolytic anemia (AIHA) is subclassified according to the character of the autoantibodies, however, its clinical pictures are highly heterogenous even in a given subclass. In this article, we reviewed pathogenesis, clinical and laboratory characteristics of AIHA, exemplifying data of 26 patients with autoimmune hemolysis with warm-type autoantibodies (13 AIHA, 10 Evans' syndrome, 3 systemic lupus erythematosus), and recent advances in this field. White blood cell and platelet counts varied among patients at presentation. Six of 13 AIHA patients had low reticulocyte production index (RPI) indicative of inappropriate reticulocyte response with considerable erythroblasts in the bone marrow, suggesting that ineffective erythropoiesis contributes the pathogenesis of warm-type AIHA. Ten patients were judged to require red cell transfusion. Their RPI did not differ from that of patients who did not require transfusion, indicating that the degree of hemolysis is the major determinant of the severity of the disease. No significant side effects of transfusion were observed.

Role of reticulocytes on gametocytogenesis in chickens infected with Leucocytozoon caulleryi

Reticulocytes, known as late polychromatic erythrocytes, were induced in blood of chickens infected with Leucocytozoon caulleryi by bleeding when the second-generation merozoites were released into the blood from the second-generation schizonts. The second-generation merozoites preferentially invaded into reticulocytes and developed to stage II gametocytes. Enhanced development of stage II gametocytes to mature gametocytes was observed in the reticulocytes in vivo and in vitro in the bleeding group. Nevertheless, invasion of reticulocytes by the second-generation merozoites was not considered to be absolutely necessary for the development of gametocytes.

Cord blood transferrin receptors to assess fetal iron status

OBJECTIVE

To study iron status at different gestational ages using cord blood serum transferrin receptors (STfRs).

METHODS

STfRs, iron, ferritin, total iron binding capacity, haemoglobin, and reticulocytes were measured in 144 cord blood samples. The babies were divided into three groups according to gestation (26 very preterm (24-29 weeks); 50 preterm (30-36 weeks); 68 term (37-41 weeks)).

RESULTS

Serum iron, ferritin, and total iron binding capacity were highest at term, whereas reticulocytes were highest in the very preterm. STfR levels were not influenced by gestation. Haemoglobin (r = 0.46; p < 0.0001) and reticulocytes (r = 0.42; p < 0.0001) were the only indices that independently correlated with STfR levels.

CONCLUSIONS

STfR levels in cord blood are not directly influenced by gestation and probably reflect the iron requirements of the fetus for erythropoiesis.

Reticulocyte subpopulations and reticulocyte maturity index (RMI) rise as body iron status falls

To investigate the influence of body iron status on reticulocyte subpopulations and reticulocyte maturity index (RMI), we measured serum iron markers, fluorescent intensity of reticulocytes, and serum transferrin receptor (sTfR) concentrations in 374 females aged 14-19 years. Reticulocyte subpopulations were analyzed by flow cytometry, and sTfR concentration was measured by enzyme immunoassay. There were no significant differences in the values of reticulocyte subpopulations and RMI between ferritin alone-depleted group and healthy controls. However, middle- and high-fluorescence reticulocytes and RMI were significantly higher in both the serum iron- and serum ferritin-depleted groups than in the ferritin alone-depleted group. Middle-fluorescence reticulocytes and RMI increased gradually as the body iron store was depleted and were 3.4- and 3.6-fold higher, respectively, than normal controls, when the subjects attained a frank iron-deficiency anemia. There were no significant changes in the values of red blood cells or total reticulocyte counts during iron-depleted states. The mean value of sTfR (3.98 mg/l) in the subjects with RMI > or = 1.5% was significantly higher than that (2.26 mg/l) in the subjects with RMI < 1.5% (P < 0.01). The sTfR concentration correlated significantly with RMI (r = 0.61, P < 0.01) and middle-fluorescence reticulocytes (r = 0.59, P < 0.01). In short, body iron depletion induces elevation of immature reticulocyte fractions and RMI.

Cation transport and cell volume changes in maturing rat reticulocytes

During maturation, reticulocytes lose membrane material, including transporters, and this is accompanied by a loss of cell water and volume. Here we determined a possible role of ion transport in adjusting cell volume during maturation. Reticulocytes and red blood cells of different ages were prepared from erythropoietin-treated rats by density gradient fractionation. Cell volume and ion transport were measured in freshly prepared cells and in reticulocytes during in vitro maturation. Reticulocytes had an increased K content and cell volume, whereas intracellular Na was decreased. All parameters approached whole blood values after 2 days in culture. Na-K pump was elevated in reticulocytes and decreased during maturation. Na-K-2Cl cotransport (NKCC) activity was lower in reticulocytes and was activated 8- and 20-fold by shrinkage and okadaic acid, respectively, whereas stimulation was barely detectable in high-buoyant density red blood cells. The ouabain- and bumetanide-insensitive Na flux in reticulocytes decreased on maturation. Most of it was inhibited by amiloride, indicating the presence of Na/proton exchange. Our results show that, although the Na-K-pump activity in reticulocytes is very much increased, the enhanced capacity of NKCC is essentially cryptic until stimulated. Both types of capacities (activities) decrease during maturation, indicating a possible loss of transport protein. The decrease was constrained to the period of reticulocyte maturation. Loss of transport capacity appears to exceed the loss of membrane surface area. Reticulocyte age-related changes in the net electrochemical driving force indicate that the increasing NKCC activity might contribute to the reduction in cell water.

A pharmacodynamic analysis of erythropoietin-stimulated reticulocyte response in phlebotomized sheep

The pharmacodynamics (PD) of the reticulocyte response resulting from phlebotomy-induced erythropoietin (EPO) was investigated in adult sheep. The anemia caused by the controlled phlebotomy (Hb < 4 g/dl, t = 0) resulted in a rapid increase in EPO with peak concentrations from 200 to 1400 mU/ml at 0.5 to 3 days generating a delayed reticulocyte response with peak levels from 9.3 to 14.1% at 2.5 to 5.1 days. The PD EPO-reticulocyte relationship is well described by a simple kinetic model involving 3 relevant physiologic parameters: T(1) = lag-time (0.73 +/- 0.32 days, mean +/- S.D.), T(2) = reticulocyte maturation time (5.61 +/- 1.41 days), and k = EPO efficacy coefficient (0.052 +/- 0.048% g/dl mU/ml/day). Accordingly, 0.52% reticulocytes at 10 g/dl Hb level are generated per day at an EPO concentration of 100 mU/ml. The difference between the T(2) parameter in this study and the maturation time reported for humans may be due to interspecies differences or different technique and experimental conditions. The PD transduction appears largely linear in the observed EPO concentration range, indicating a full utilization of EPO without any significant PD saturation. Also, the EPO concentration versus time profiles resulting from the phlebotomy were similar to exogenous EPO profiles resulting from s.c. therapeutic dosing. This study supports the hypothesis that s.c. EPO dosing is more efficacious than i.v. dosing.

Comparative erythropoietic effects of three vanadium compounds

The biotoxic effects of vanadium are variable depending upon a number of factors including the oxidation state of the test compound. This study reports the effects of three vanadium compounds on peripheral erythrocytes. On day 0 female ICR mice received a single injection of vanadium chloride (V-III), vanadyl sulfate (V-IV), or sodium orthovandate (V-V). At scheduled intervals post-injection, the number of circulating erythrocytes [red blood cells per millimeter cubed (RBC/mm3)], reticulocyte percentages, and radioiron uptake percentages were determined and compared to mice receiving saline only. Data show that all three test substances promoted a significant lowering of RBC/mm3 beginning on day 1 for V-IV and V-V and on day 2 for V-III through day 4. The reticulocyte percentages increase followed the same time course as that of the peripheral RBC decrease. Peak reticulocytosis was noted on days 2 and 4 for all three vanadium-treated groups; for V-IV and V-V the increase continued to day 6. Radioiron data showed an erythropoietic stimulation by a significant increase in uptake percentages on days 4-6 after vanadium injections compared to saline-treated controls.

Different reticulocyte volume in diabetes mellitus patients with and without hypercholesterolemia and/or hypertriglyceridemia

Red cells and reticulocytes from patients with diabetes mellitus (DM) were analysed using laser and computer technology of H*3 hematology analyzer. Four groups of diabetes mellitus patients: diabetes with normolipemia (DM) (n = 12) and DM patients with excess triglyceride (DM-T) (n = 7) or cholesterol (DM-C) (n = 21) or both (DM-TC) (n = 21) were studied. Mean corpuscular volume of mature red cells (Mean +/- SD = 93.6 +/- 5.5 fl) and reticulocyte (119.1 +/- 12.3 fl) of patients with DM-T was not significantly increased from normal (red cell, 90.0 +/- 3.5 fl; reticulocyte, 115.2 +/- 7.3 fl). Plasma triglyceride levels had no significant correlation with red cell MCV, reticulocyte MCV and %Hb A1c. This suggests that high triglyceride levels in DM are not dose-dependent in producing increased MCV of red cells and reticulocytes. Comparing between DM-T and DM-C, red cells and reticulocytes from DM-C patients had significantly decreased MCV (red cell, 85.5 +/- 6.1 fL; reticulocyte, 103.8 +/- 7.4 fL). Plasma cholesterol levels were inversely correlated with MCV of red cells (r = -0.377, p = 0.003) and also MCV of reticulocytes (r = -0.418, p = 0.001). In addition, cholesterol levels showed considerable correlation with Hb A1c (r = 0.572, p = 0.004). The red cell volume change in DM-C patients may be partly due to the shift in balance of cholesterol exchange between red cell membranes and serum lipoproteins.

The cause of the predilection of Babesia gibsoni for reticulocytes

This study was conducted to determine why Babesia gibsoni replicates well in reticulocytes. First, B. gibsoni was cultivated in resealed erythrocyte ghosts loaded with either erythrocyte or reticulocyte lysate, and in reticulocyte ghosts loaded with either erythrocyte or reticulocyte lysate. The parasites multiplied well in the erythrocyte or reticulocyte ghosts loaded with reticulocyte lysate compared to the other resealed cells loaded with erythrocyte lysate. Second, the parasites were cultivated in erythrocytes in culture medium supplemented with either erythrocyte or reticulocyte lysate. The parasites multiplied better in reticulocyte lysate-containing cultures than in erythrocyte lysate-containing cultures. Finally, the parasites were cultivated in erythrocytes in culture medium supplemented with glutamate, aspartate, asparagine, glycine, isoleucine, proline, taurine or GSH, which were present in higher concentrations in reticulocytes than in erythrocytes. Supplementation of the culture medium with glutamate and GSH resulted in enhancement of the multiplication of the parasites, while the other amino acids did not enhance the multiplication. These results indicated that the high levels of the multiplication of B. gibsoni in reticulocytes are partly due to the high concentrations of glutamate and GSH in reticulocytes.

Erythropoietic activity and soluble transferrin receptor level in neonates and maternal blood

Serum transferrin receptor (sTfR) concentration reflects functional iron status and erythropoietic activity. The aims of this study were to examine gender differences of erythropoiesis in newborns and to evaluate the influences of maternal anaemia or iron deficiency on foetal cord blood parameters for iron status and sTfR. In total, 527 newborns and their mothers were examined. Reticulocytes were analysed by flow cytometry and sTfR was measured by an immunoenzymometric method. There were no sex differences in haematological or iron parameters. However, the reticulocyte maturity index (RMI) of male neonates was 37.45%, significantly higher than the 26.81% in female neonates (p <0.01). The high fluorescence reticulocytes (HFR) and middle fluorescence reticulocytes (MFR) of male neonates were 4.91% and 22.36%, respectively, while those of female neonates were 3.31% and 17.83%, respectively (p < 0.01 for each gender). The sTfR concentrations of male and female neonates were 6.27 mg/l and 5.09 mg/l, respectively (p < 0.01). Values for serum iron, ferritin and reticulocyte subpopulations were significantly lower in the newborns of anaemic mothers. However, newborns of iron-deficient mothers showed no differences in iron parameters from those of non-iron-deficient mothers.

CONCLUSIONS

The higher values of RMI and sTfR observed in male neonates indicate that erythropoietic activity is higher in this group. Iron transport to the foetus appears to be independent of maternal iron deficiency. However, iron transport and erythropoiesis in newborns seems to decline from the time that the mothers acquire frank iron deficiency anaemia.

Reticulocyte analysis in iron deficiency anemia and hemolytic anemia

Reticulocyte analysis was studied in 28 anemic patients, 15 with iron deficiency anemia (IDA), and 13 with hemolytic anemia including 9 glucose 6 phosphate dehydrogenase deficiency (G6PD def.), and 4 with G6PD def. combined with HbE trait or alpha thalassemia trait (alpha thal trait). The reticulocyte analysis among these patients showed the increased number of reticulocyte percentage with low degree of maturation in both IDA and G6PD def. patients. The significantly decreased reticulocyte hemoglobin content (CHr) was found in IDA (CHr = 21.74 +/- 4.61 pg in IDA vs 28.41 +/- 1.34 pg in normal; p-value = < 0.0001), whereas, increased CHr was found in G6PD def. patients. In addition, the G6PD def. patients also showed a significant increase in mean corpuscular reticulocyte volume (MCVr) when compared to normal (MCVr = 132.0 +/- 8.39 fl. in G6PD def. vs 110.39 +/- 5.09 in normal; p-value = < 0.0001). However, a significant decrease in MCVr was found in IDA patients (MCVr = 95.89 +/- 8.57 fl.; p-value = < 0.0001 vs normal). From this study, we can suggest that the reticulocyte hemoglobin content (CHr) and mean corpuscular reticulocyte volume (MCVr) are the important defects in patients with iron deficiency anemia.

Human cytogenetic biomonitoring using flow-cytometric analysis of micronuclei in transferrin-positive immature peripheral blood reticulocytes

We have developed a method to isolate and analyze nascent human reticulocytes in peripheral blood for the presence of micronuclei (MN). For a very short time peripheral reticulocytes show residual expression of the transferrin receptor. Using immunomagnetic separation of cells expressing the transferrin receptor, a population of immature reticulocytes (Trf-Ret) was isolated from peripheral blood. In humans, the spleen actively removes micronucleated erythrocytes but during the short lifetime of the isolated Trf-Ret only a fraction (less than about 20%) of the MN-containing reticulocytes will have been eliminated. Cells were stained with the fluorescent dyes Thiazole Orange for RNA and Hoechst 33342 for DNA and analyzed by flow cytometry and fluorescence microscopy. Baseline frequencies of MN-Trf-Ret on a group of healthy donors were found to be 1.1% for males and 1.4% for females; however, the gender difference was not significant. The frequency of MN-Trf-Ret in the studied group increased with age, and was dependent on blood group. In three donors studied over 4 months, the baseline level remained stable. In cancer patients treated with radiation or chemotherapy, the frequency of MN-Trf-Ret increased 10- to 20-fold after 1-4 days, depending on the treatment. A high correlation between flow and manual analysis of MN-Trf-Ret was seen. We believe the method has a high potential as a sensitive and rapid method for biological monitoring in presumed exposed groups and individuals.

Exosomes released during reticulocyte maturation bind to fibronectin via integrin alpha4beta1

Exosomes are vesicles formed in the endosomal compartment and released in the extracellular medium during reticulocyte maturation into erythrocytes. They have a clearing function because of their enrichment with some proteins known to decrease or disappear from the cell surface during maturation, e.g. acetylcholinesterase and transferrin receptor. We show here that integrin alpha4beta1, present on the surface of erythroid precursors but absent from the mature red cell membrane, is at least partly cleared from the reticulocyte plasma membrane by the exosomal pathway. Using flow cytometry, we found that the alpha4 subunit disappears from the reticulocyte surface during in vitro maturation. Two different monoclonal antibodies (B-5G10 and HP 2/1) were used to demonstrate the presence of the alpha4 chain on the exosome surface. Moreover, membrane acetylcholinesterase and lumenal peroxidase-like (i.e. hemoglobin) enzymatic activities were assayed to demonstrate exosome binding to plates coated with increasing fibronectin (FN) concentrations. This interaction was dependent on divalent cations (MnCl2 > MgCl2 > CaCl2). Similarly, vesicles bound to plates coated with the chymotryptic 40 K fragment (FN-40) containing the heparin-binding region of FN. This binding was inhibited by exosome preincubation with fibronectin CS1 peptide and with a monoclonal antibody (HP 2/1) against the integrin alpha4-chain, confirming an alpha4beta1-induced interaction. The importance of the exosome clearance function is highlighted here, since the presence of VLA-4 on reticulocytes often leads to blood circulation complications in some diseases. Moreover, the presence of alpha4beta1 on the exosome surface, by allowing binding to endothelial cells through vascular cell adhesion molecule 1 (VCAM-1), might confer another physiological function to the secreted vesicles.

Kinetic dissection of fundamental processes of eukaryotic translation initiation in vitro

Approaches have been developed for the kinetic dissection of eukaryotic translation initiation in vitro using rabbit reticulocyte ribosomes and a crude preparation of initiation factors. These new approaches have allowed the kinetics of formation of the 43S and 80S ribosomal complexes to be followed and have substantially improved the ability to follow formation of the first peptide bond. The results suggest the existence of a new step on the initiation pathway that appears to require at least one additional factor and the hydrolysis of GTP and may prepare the 80S complex for the formation of the first peptide bond. The initial kinetic framework and methods developed herein will allow the properties of individual species along the initiation pathway to be probed further and will facilitate dissection of the mechanistic roles of individual translation factors and their interplay with RNA structural elements.

TOP mRNAs are translationally inhibited by a titratable repressor in both wheat germ extract and reticulocyte lysate

Vertebrate TOP mRNAs contain a 5' terminal oligopyrimidine tract (5' TOP), which is subject to selective translational repression in non-growing cells or in cell-free translation systems. In the present study, we monitored in vitro the effect of increasing amounts of a 16 nucleotides long oligoribonucleotide representing the 5' terminus of mouse ribosomal protein S16 mRNA on the translation of TOP and non-TOP mRNAs. Our results demonstrate that the wild-type sequence (but not its mutant counterparts) derepresses the translation of mRNAs containing 5' TOP motifs, but failed to stimulate the translation of non-TOP mRNAs, even if the latter differed only by a single nucleotide from their 5' TOP-containing counterparts. Similar results have been obtained with both wheat germ extract and rabbit reticulocyte lysate. It appears, therefore, that translational repression of TOP mRNAs is achieved in vitro by the accumulation of a titratable repressor rather than by the loss of an activator and that this repressor recognizes multiple TOP mRNAs with a diverse set of 5' TOP motifs.

Complement receptor 1 (CD35) on human reticulocytes: normal expression in systemic lupus erythematosus and HIV-infected patients

The low levels of complement receptor 1 (CR1) on erythrocytes in autoimmune diseases and AIDS may be due to accelerated loss in the circulation, or to a diminished expression of CR1 on the red cell lineage. Therefore, we analyzed the expression of CR1 on reticulocytes (R) vs erythrocytes (E). Healthy subjects had a significant higher CR1 number per cell on R (919 +/- 99 CR1/cell) than on E (279 +/- 30 CR1/cell, n = 23), which corresponded to a 3. 5- +/- 1.3-fold loss of CR1. This intravascular loss was confirmed by FACS analysis, which showed that all R expressed CR1, whereas a large fraction of E was negative. The systemic lupus erythematosus (SLE), HIV-infected, and cold hemolytic Ab disease (CHAD) patients had a CR1 number on R identical to the healthy subjects, contrasting with a lower CR1 on their E. The data indicated a significantly higher loss of CR1 in the three diseases, i.e., 7.0- +/- 3.8-, 6.1- +/- 2.9-, and 9.6- +/- 5.6-fold, respectively. The intravascular loss was best exemplified in a patient with factor I deficiency whose CR1 dropped from 520 CR1/R to 28 CR1/E, i.e., 18.6-fold loss. In one SLE patient and in the factor I-deficient patient, the FACS data were consistent with a loss of CR1 already on some R. In conclusion, CR1 is lost progressively from normal E during in vivo aging so that old E are almost devoid of CR1. The low CR1 of RBC in autoimmune diseases and HIV-infection is due to a loss occurring in the circulation by an active process that remains to be defined.

Failure to demonstrate postpartum functional iron deficiency using quantitative red blood cell analysis

OBJECTIVE

The aim of this prospective study was to assess erythropoiesis and test for functional iron deficiency in the postpartum period using quantitative red blood cell analysis.

STUDY DESIGN

Parameters were determined on admission for delivery and postpartum from 82 obstetric patients at Zurich University Hospital: full blood count, hypochromic and microcytic red cells, reticulocyte count (including subsets), reticulocyte mean corpuscular volume, reticulocyte mean hemoglobin content and reticulocyte mean corpuscular hemoglobin concentration.

RESULTS

Microcytic cells increased from 0.9% prepartum to 1.4% on day 42 postpartum; hypochromic cells decreased from 4.3 to 1.9%; reticulocyte mean corpuscular volume decreased from 134 to 125 fl; reticulocyte mean hemoglobin content was unchanged.

CONCLUSION

To our knowledge, this is the first medium scale application of quantitative red blood cell analysis to normal pre- and postpartum women. Our data show no evidence of functional iron deficiency or increased erythropoiesis in the postpartum period.

Erythroid marrow activity and hemoglobin H levels in hemoglobin H disease

PURPOSE

To determine serum immunoreactive erythropoietin (Epo) and soluble transferrin receptors (sTfR) levels in patients with hemoglobin H (HbH) disease and the correlation with HbH levels and alpha-globin genotype.

PATIENTS AND METHODS

Twenty patients with HbH disease were studied. Methods applied included cation-exchange high pressure liquid chromatography for HbH levels, chemoluminescence for Epo concentration, immunoassay for sTfR concentration, and DNA analysis for alpha-globin genotype characterization.

RESULTS

Serum Epo and sTfR levels were significantly elevated (46.6+/-26.8 IU/l and 5.6+/-1.8 mg/l, respectively) in patients with HbH disease compared to controls (9.2+/-3.3 IU/l and 1.8+/-0.7 mg/l, respectively). Epo and sTfR levels correlated positively with HbH concentration (r = 0.93 and 0.80, respectively). The highest Epo and sTfR values were observed in three patients with the highest HbH levels who all had nondeletion alpha-thalassemia mutations.

CONCLUSION

Epo and sTfR levels are increased in patients with HbH disease; this increase is directly related to the HbH concentration that usually reflects the degree of globin polypeptide imbalance. The correlation of Epo, sTfR, and reticulocyte production index in these patients indicates that anemia in HbH disease mainly is caused by ineffective erythropoiesis and a mild degree of peripheral hemolysis.

A function for lipoxygenase in programmed organelle degradation

Membrane-enclosed organelles, a defining characteristic of eukaryotic cells, are lost during differentiation of specific cell types such as reticulocytes (an intermediate in differentiation of erythrocytes), central fibre cells of the eye lens, and keratinocytes. The degradation of these organelles must be tightly regulated with respect to both the time of activation and the specificity of membrane degradation. The expression of 15-lipoxygenase (15-LOX) peaks in reticulocytes immediately before organelle degradation. Here we show that 15-LOX integrates into the membranes of various organelles, allowing release of proteins from the organelle lumen and access of proteases to both lumenal and integral membrane proteins. In addition, by sparing the plasma membrane, 15-LOX shows the required specificity for organellar membranes. Thus, the action of 15-LOX provides a mechanism by which the natural degradation process can be explained. This conclusion is supported by our finding that lipoxygenase expression in the eye lens is restricted to the region at which organelle degradation occurs.

Changes in the expression of the heme-regulated eIF-2 alpha kinase and heat shock proteins in rabbit reticulocytes maturing during recovery from anemia

Changes in the expression of the heme-regulated eIF-2 alpha kinase (HRI), heat shock proteins (Hsps, Hsp90, and 70) and their associated cohorts (p60 and p23) were studied in maturing rabbit reticulocytes during recovery from anemia. Reticulocytosis was induced by injection of N-acetylphenylhydrazine or by phlebotomy from the ear vein, and circulating red blood cells were fractionated on histopaque density gradients. Northern and Western blot analyses indicated that HRI and hsps mRNA and protein content gradually decreased during maturation of reticulocytes into erythrocytes. Reduction in levels of hsps and HRI was also observed when cells of same age group (density) were compared as the animals recovered from the anemia. Low hematocrits correlated with high levels of hsps expression and with increasing hematocrits hsps expression decreased. Under the conditions used to quantify these protein levels, Hsc70 and p60 were detected in erythrocytes of fully recovered animals. Maintenance of Hsc70 and p60 suggests important ongoing roles for these hsps in protecting the structure and function of proteins in erythrocytes lacking transcriptional and translational machinery.

Expression of a cDNA encoding Phytolacca insularis antiviral protein confers virus resistance on transgenic potato plants

To develop an antiviral agent and virus-resistant plants, a cDNA clone encoding Phytolacca insularis antiviral protein (PIP) was isolated from a cDNA library constructed with poly(A)+ RNA purified from leaves of P. insularis. The PIP cDNA contains an open reading frame encoding 307 amino acids. The deduced amino acid sequence includes a putative signal sequence of 22 amino acids at the N-terminus. The amino acid sequence of PIP shares 84% homology with that of the pokeweed antiviral protein (PAP). In addition, the mature PIP exhibits the conserved putative active site found in other ribosome-inactivating proteins (RIPs). Recombinant PIP (rPIP) synthesized in Escherichia coli inhibits protein synthesis in vitro in rabbit reticulocyte lysate through the N-glycosidase activity in a similar manner with other RIPs. Local lesion assays with purified rPIP revealed that it inhibits infection of various viruses to plants. Transgenic potato plants expressing the PIP cDNA under the control of the cauliflower mosaic virus 35S promoter are resistant to viruses, such as potato virus X, potato virus Y, and potato leafroll virus. These results suggest that the PIP cDNA could be used for the development of an antiviral agent and transgenic plants resistant against a broad spectrum of plant viruses infecting through both mechanical and aphid transmission.

Aggregation reroutes molecules from a recycling to a vesicle-mediated secretion pathway during reticulocyte maturation

Endocytosis of the Tf/TfR complex is essentially the only pathway active in maturing reticulocytes, while exosomes, formed by invagination of the endosomal membrane, provide a mechanism to eliminate seemingly obsolescent proteins, including the TfR, when their function is completed. In this study, we examined molecular trafficking in the recycling and exosome-directed pathways during endocytosis in maturing reticulocytes. To this end, the flow of two exogenously inserted fluorescent lipid analogs, N-(N-[6-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]caproyl]) sphingomyelin (C6-NBD-SM) and N-(lissamine rhodamine B sulfonyl) phosphatidyl ethanolamine (N-Rh-PE) was monitored and compared to that of the transferrin (Tf)/Tf receptor (TfR) complex. Prior to elimination via exosomes, the TfR actively recycles with a half-time of approx. 2 minutes. The recycling kinetics of C6-NBD-SM, as bulk plasma membrane marker, are identical to those of the apoTf/TfR complex, as shown by fluorescence microscopy and biochemical analysis. By contrast, although efficiently internalized along the same pathway, N-Rh-PE does not return to the cell surface. More specifically, sucrose gradient analysis and immunoisolation experiments demonstrated that N-Rh-PE accumulates in exosomes, which are eventually released into the extracellular medium. Fluorometric measurements showed that exogenously inserted N-Rh-PE is present in the reticulocyte plasma membrane as small molecular clusters. Moreover, a close correlation was observed between the fate of crosslinked proteins, including the TfR and acetylcholinesterase (AChE), and the fate of the clustered lipid N-Rh-PE. Thus antibody-induced aggregation of specific proteins like the TfR and AChE, which are normally sorted into exosomes during reticulocyte maturation, enhances their shedding by the exosomal pathway. Taken together, the results support the hypothesis that aggregation of either proteins or lipids act as a general sorting signal for exosomal processing, thereby inhibiting reentry in a recycling pathway and providing an effective means for clearing molecules from the cell surface and their eventual elimination from the cells.

The effect of intravenous iron on the reticulocyte response to recombinant human erythropoietin

We studied the effect of intravenous (i.v.) administration of 200 mg of iron sucrose following an i.v. bolus injection of recombinant human erythropoietin (r-HuEPO; 300 U/kg body weight) in seven subjects and compared it with seven subjects treated with r-HuEPO alone. Reticulocytes, serum erythropoietin (EPO) and ferritin levels were studied at baseline and daily for the following 8 d. Use of i.v. iron abolished the marked reduction in serum ferritin observed with r-HuEPO administration. Although the total number of reticulocytes was not affected by i.v. iron administration, the reticulocyte Hb content and retHb (a measure in g/l of the Hb contained in all reticulocytes) were increased in the i.v. iron/r-HuEPO group compared with the group who received r-HuEPO alone. Therefore i.v. iron significantly potentiates the haemopoietic response to r-HuEPO in normal subjects.

Chaperonin-mediated folding in the eukaryotic cytosol proceeds through rounds of release of native and nonnative forms

The eukaryotic cytosolic chaperonin, CCT, plays an essential role in mediating ATP-dependent folding of actin and tubulin. There is debate about whether it mediates folding through a single round of association followed by release of native forms, or through cycles of binding and full release in which only a fraction of released molecules reaches native form in any cycle. We examine the fate of newly synthesized substrate proteins bound to CCT in reticulocyte lysate or intact Xenopus oocytes. When a chaperonin "trap," able to bind but not release substrate protein, is introduced, production of the native state is strongly inhibited, associated with transfer to trap. While predominantly nonnative forms of actin, tubulin, and a newly identified substrate, G(alpha)-transducin, are released from CCT, a small fraction reaches native form with each round of release, inaccessible to trap. This overall mechanism resembles that of the bacterial chaperonin, GroEL.

Reticulocyte maturity index reflects erythropoietin effects in hemodialysis patients

Flow cytometric reticulocyte analysis is widely utilized because of its sensitivity, precision, and high throughput of analysis as compared to manual reticulocyte counting. With this automated method reticulocytes can be classified into three groups according to the fluorescence intensity that reflects maturity of reticulocytes. In this study, changes in red cell parameters, reticulocyte percentage, absolute reticulocyte count, and reticulocyte maturity index were evaluated 13 hemodialysis patients with renal anemia after single administration of recombinant human erythropoietin. The reticulocyte count and reticulocyte maturity index were elevated significantly (P < .01) 2 days after the single bolus of erythropoietin, and they reached the maximum value vn the fourth day, but other red cell indices could not detect the effects of erythropoietin during this early period. These results suggested that the reticulocyte maturity index could be an early indicator of the effect of erythropoietin in hemodialysis patients.

Surface area and volume changes during maturation of reticulocytes in the circulation of the baboon

Changes in the surface area and volume of reticulocytes were measured in vivo during late stage maturation. Baboons were treated with erythropoietin to produce mild reticulocytosis. Reticulocyte-rich cohorts of cells were obtained from whole blood by density gradient centrifugation. The cohorts were labeled with biotin, reinfused into the animal, and recovered from whole blood samples by panning on avidin supports. Changes in the surface area, volume, and membrane deformability were measured using micropipettes during the 2 to 6 weeks subsequent to reinfusion. For the entire cohort, the membrane area decreased by 10% to 15% and the cell volume decreased by approximately 8.5%, mostly within 24 hours after reinfusion. Estimates of the cellular dimensions of the reticulocyte subpopulation within this cohort indicated larger reductions in the mean cell area (12% to 30%) and mean cell volume (approximately 15%) of the reticulocytes themselves. Two weeks after reinfusion, the distribution of cell size for the cohort was indistinguishable from that of whole blood. There was evidence of slightly elevated membrane shear rigidity in some reticulocytes before reinfusion, but this slight increase disappeared within 24 hours after reinfusion. These are the first direct measurements of changes in the membrane physical properties of an identifiable cohort of reticulocytes as they mature in vivo.

Micronucleus induction in germ and somatic cells of the mouse after exposure to the butadiene metabolites diepoxybutane and epoxybutene

The genotoxicity of diepoxibutane (DEB) and epoxybutene (EB), two of the main metabolites of 1,3-butadiene, was tested in the germ and somatic cells of the mouse by applying an MN assay in early spermatids, and in peripheral blood reticulocytes of a subgroup of the same animals. DEB (0.17 and 0.35 mmol/kg) and EB (0.35, 0.70 and 1.04 mmol/kg) were administered i.p. In the germ cell assay, significant increases of MN were observed after treatment of premeiotic S-phase cells with both butadiene metabolites, but DEB was shown to be more powerful than EB in the induction of chromosomal damage. A weak effect of the same compounds was also found after treatment of late spermatocytes, approaching the meiotic divisions. From the MN assay in peripheral blood reticulocytes, a statistically significant increase of the frequency of MN was detected at each dose tested for both chemicals. However, the results have again shown that DEB is much more efficient than EB in inducing chromosome damage.

Phorbol ester stimulation increases sickle erythrocyte adherence to endothelium: a novel pathway involving alpha 4 beta 1 integrin receptors on sickle reticulocytes and fibronectin

Sickle-cell adherence to endothelium has been hypothesized to initiate or contribute to microvascular occlusion and pain episodes. Adherence involves plasma proteins, endothelial-cell adhesion molecules, and receptors on sickle erythrocytes. It has previously been reported that sickle reticulocytes express the alpha 4 beta 1 integrin receptor and bind to cytokine-activated endothelium via an alpha 4 beta 1/vascular-cell adhesion molecule-1 (VCAM-1) interaction. To elucidate other roles for alpha 4 beta 1 in sickle-cell adherence, the ability of activated alpha 4 beta 1 to promote adhesion to endothelium via a ligand different than VCAM-1 was explored. Adherence assays were performed under dynamic conditions at a shear stress of 1 dyne/cm2. Preincubation of sickle erythrocytes with phorbol 12,13-dibutyrate (PDBu) increased adherence of sickle cells eightfold as compared with untreated sickle cells. Normal erythrocytes, whether treated with PDBu or not, did not adhere to the endothelium. Activating anti-beta 1 antibodies 4B4 and 8A2 also increased the adhesion of sickle, but not normal, red blood cell (RBC) adhesion to endothelium. Anti-alpha 4 antibodies HP1/2 and HP2/1, inhibitory antibody 4B5, or an RGD peptide inhibited sickle-cell adherence induced by PDBu. Additional studies were undertaken to examine if fibronectin, a ligand for activated alpha 4 beta 1, was involved in PDBu-induced sickle erythrocyte adherence. Adherence of PDBu-treated sickle cells was completely inhibited by the CS-1 peptide of fibronectin. Fibronectin was detected on the surface of washed endothelium using an antifibronectin antibody in enzyme-linked immunosorbent assays. Antifibronectin antibody pretreatment of endothelial cells inhibited PDBu-induced adherence by 79% +/- 17%. Incubation of sickle RBCs with exogenous fibronectin after PDBu treatment inhibited adherence 86% +/- 8%. Taken together, these data suggest that endothelial-bound fibronectin mediates adherence of PDBu-treated sickle cells. Interleukin-8 (IL-8), a chemokine released in response to bacterial infection, viral infection, or other injurious agents, and known to activate integrins, also increased adherence of sickle erythrocytes to endothelial cells via fibronectin. This novel adherence pathway involving sickle-cell alpha 4 beta 1 activated by PDBu or IL-8 may therefore be relevant in vivo at vascular sites that produce IL-8 or similar agonists in response to vascular injury or immune activation. These observations describe ways in which inflammation and immune responses cause vasoocclusive complications in sickle-cell disease.

The hamster adrenal cytochrome P450C11 has equipotent 11beta-hydroxylase and 19-hydroxylase activities, but no aldosterone synthase activity

We have isolated a hamster adrenal P45OC11 cDNA which shared 90 and 84% homology, respectively, with the nucleotide sequence and the amino acid sequence of the hamster adrenal P450aldo. Both P450C11 and P450aldo cDNA coding sequences were inserted in the plasmid pBluescript SK, transcribed and then translated using a rabbit reticulocyte system in the presence of [35S]methionine. The reaction products were immunoprecipitated with an anti-bovine P450C11 antibody for P450C11 and with an anti-hamster P450aldo for P450aldo. Immunoprecipitated proteins were analyzed by polyacrylamide gel electrophoresis. A single 35S-labeled protein band was detected for P450C11 and for P450aldo, respectively. P450C11 and P450aldo cDNAs were then both inserted into the expression vector pCMV5 containing a viral sequence specific for the attachment of ribosomes to mRNA. These constructions were transfected in COS-1 cells. 24 h after transfection, the presence of P450C11 and P450aldo mRNAs was determined by Northern blot analysis. In a time study experiment we found that P450C11 transformed the labeled-steroid into [14C]corticosterone, [14C]19-OH-deoxycorticosterone and [14C]18-OH-deoxycorticosterone in ratios of 1:1.11:0.07, after 2 h of incubation; no [14C]aldosterone could be detected. Cells transfected with plasmids harboring the P450aldo cDNA transformed [14C]deoxycorticosterone to [14C]corticosterone, [14C]aldosterone, [14C]18-OH-corticosterone, [14C]18-OH-deoxycorticosterone, [14C]19-OH-deoxycorticosterone and [14C]11-dehydrocorticosterone in ratios of 1:0.25:0.45:0.04:0.04:0.04 after 12 h of incubation. These results indicate that one P450 catalyzes the ultimate step of glucocorticoid formation and a separate P450 is involved in the final steps of aldosterone formation in hamster adrenals. The capacity of the hamster adrenal P450C11 to hydroxylate at positions 11beta and 19 in nearly equal ratio makes this animal an excellent model to study the mechanism of synthesis and inhibition of 19-OH-deoxycorticosterone, the precursor of 19-nor-deoxycorticosterone, a very potent mineralocorticoid involved in the development of essential hypertension.

Criteria for marrow engraftment: comparison of reticulocyte maturity index with conventional parameters

Reticulocyte maturity index (RMI) has recently been proposed as an early indicator of marrow engraftment. We compared the RMI with conventional bone marrow engraftment criteria including total leukocyte count (WBC), absolute neutrophil count (ANC), reticulocyte count (RC) and the day of last platelet transfusion required to maintain the platelet count (PC) > or = 20 x 10(9)/l in 37 patients undergoing allo- or autologous BMT. There was no discrepancy in predicting engraftment between RMI, ANC, WBC and RC. RMI indicated engraftment earlier (median day 17, range 10-63 days) than the ANC (median day 19, range 8-63 days), WBC (median day 19, 9-71), RC (median day 19, 11-125) or PC (median day 29, 11-237). RMI heralded engraftment preceded ANC, WBC, RC or PC in 22, 21, 34 and 32 patients, respectively. RMI signal occurred 6 days prior to the rise in ANC in patients who engrafted later than 25 days (n = 7). Trend analysis showed that ANC fluctuated more frequently (6/37 patients) than RMI (1/37). Combined use of ANC and RMI (whichever increased first) predicted engraftment earlier (median 15 days) and more confidently (no false starts) than either used alone.

Flow cytometric analysis of punctate and aggregate reticulocyte responses in phlebotomized cats

Five cats were made anemic by one-time phlebotomy, and their reticulocyte responses were monitored daily for 20 days, using manual enumeration and a standardized feline reticulocyte protocol developed and validated in our laboratory. The reticulocyte responses of 38 clinically normal client-owned cats also were analyzed manually and cytometrically to determine clinical reference ranges. Increases in the percentage of aggregate reticulocytes over the reference range were detected in 5 of 5 phlebotomized cats, using the cytometric protocol. Only 4 of the 5 cats had an increase by results of manual enumeration. Manual aggregate counts had considerable daily variation and often fluctuated in and out of reference range, whereas cytometric aggregate counts remained consistently increased for distinct periods. Increased numbers of aggregate cells could also be detected for longer periods when evaluated by flow cytometry. Increased numbers of punctate reticulocytes were detected in 4 of 5 cats, using the cytometric protocol. None of the cats had increased numbers of punctate cells when evaluated by use of the manual technique. Aggregate reticulocytes in the 38 clinically normal cats ranged from 0.1 to 0.5%, which corresponded to 8,487 to 42,120 cells/microliter. Punctate reticulocytes ranged from 2 to 17%, which corresponded to 225,400 to 1,268,584 cells/microliter. Flow cytometry, using a standardized analysis protocol, was a more reliable and sensitive technique for detection and evaluation of feline reticulocytosis than was manual enumeration. The sensitivity of the flow cytometer to small amounts of intracellular nucleoprotein makes this assay especially valuable for detection of punctate reticulocytosis and low degrees of aggregate reticulocytosis in cats.

m7GpppG cap dependence for efficient translation of Drosophila 70-kDa heat-shock-protein (Hsp70) mRNA

To investigate whether preferential translation of the heat-shock mRNAs occurs via cap-independent translation, the requirement for the m7GpppG cap structure for efficient translation of 70-kDa heat-shock-protein (Hsp70) mRNA was quantified by in vitro translation and by in vivo translation following electroporation. Hsp70 mRNA was transcribed in vitro with and without a cap structure. Translation in the rabbit reticulocyte or wheat germ lysate was reduced about 70% when the cap was absent. For comparison, translation of uncapped encephalomyocarditis virus 5'-untranslated-region-containing mRNA was equal to or greater than capped mRNA, whereas translation of several non-heat-shock mRNAs was reduced by 85-95% when capping was omitted. Cap-dependent translational stimulation of Hsp70 is not due to increased stability, is not a kinetic effect, and requires the methylated GpppG. To confirm the in vitro analyses, capped and uncapped mRNA were introduced into Drosophila tissue culture cells by electroporation, followed by heat shock. Paralleling the in vitro results, uncapped Hsp70 mRNA translation was 70-80% reduced relative to the capped form. Complementary experiments in which eIF-4 was inactivated in vitro using either m7GTP cap analogue or foot-and-mouth-disease virus L protease expression likewise indicated that the cap-dependent translation pathway is required for optimal Hsp mRNA translation. Since cellular Hsp70 mRNA translation during heat shock is very efficient, it is unlikely that translation via a cap-independent pathway is the principal basis for preferential translation.

Gene therapy for long-term expression of erythropoietin in rats

The injection of recombinant erythropoietin (Epo) is now widely used for long-term treatment of anemia associated with chronic renal failure, cancer, and human immunodeficiency virus infections. The ability to deliver this hormone by gene therapy rather than by repeated injections could provide substantial clinical and economic benefits. As a preliminary approach, we investigated in rats the expression and biological effects of transplanting autologous vascular smooth muscle cells transduced with a retroviral vector encoding rat Epo cDNA. Vector-derived Epo secretion caused increases in reticulocytes, with peak levels of 7.8-9.6% around day 10 after implantation. The initial elevation in reticulocytes was followed by clinically significant increases in hematocrit and hemoglobin for up to 11 weeks. Ten control and treated animals showed mean hematocrits of 44.9 +/- 0.4% and 58.7 +/- 3.1%, respectively (P < 0.001), and hemoglobin values of 15.6 +/- 0.1 g/dl and 19.8 +/- 0.9 g/dl, respectively (P < 0.001). There were no significant differences between control and treated animals in the number of white blood cells and platelets. Kidney and to a lesser extent liver are specific organs that synthesize Epo in response to tissue oxygenation. In the treated animals, endogenous Epo mRNA was largely down regulated in kidney and absent from liver. These results indicate that vascular smooth muscle cells can be genetically modified to provide treatment of anemias due to Epo deficiency and suggest that this cell type may be targeted in the treatment of other diseases requiring systemic therapeutic protein delivery.

In vivo effects of interleukin-11 and stem cell factor in combination with erythropoietin in the regulation of erythropoiesis

In this study we evaluated the in vivo effects of interleukin-11 (IL-11) and stem cell factor (SCF), in combination with erythropoietin (EPO) on murine erythropoiesis. Mice were treated for 7 d with IL-11. SCF and EPO, each at three dose levels. In total, 27 different dose combinations were tested. IL-11 as well as SCF could only marginally stimulate erythroid progenitor cell numbers, but IL-11 in combination with SCF was able to increase BFU-E and CFU-E numbers 4-fold, in the absence of exogenous EPO. This resulted in an increased reticulocyte count. In contrast with the stimulatory effect on immature erythroid cell stages, IL-11 treatment induced a mild anaemia, which probably resulted from a plasma volume expansion. The additional treatment with EPO resulted in strong synergistic effects on CFU-E numbers. The combination of high-dose IL-11 and high-dose SCF was able to increase the overall efficiency of EPO-induced erythroid amplification, which was reflected by a left-shift of the in vivo EPO dose-response curve. The stimulating effects of IL-11 and SCF were further demonstrated when the effects on the reticulocyte count of a single high-dose EPO injection were assessed in normal and SCF+IL-11 treated mice. Whereas a single EPO dose increased the reticulocyte count by a factor of 3, IL-11 + SCF pretreatment increased this to a factor of 7. This study shows that in vivo SCF and IL-11 are important modulators of red blood cell production. First, these factors probably increase the input from the stem cell compartment into the erythroid lineage, where subsequently EPO is required for further amplification. Additionally, however, IL-11 and SCF increase the overall efficiency of EPO-induced amplification, probably due to a stimulatory effect on late-stage erythroid cells and to a redistribution of cells from marrow to spleen.

Intricate combinatorial patterns of exon splicing generate multiple Rh-related isoforms in human erythroid cells

The Rhesus (Rh) blood group system shows complex polymorphisms in the human. Some of the heterogeneity may be generated by alternative RNA splicing. For a systematic analysis of Rh-related mRNA isoforms expressed in reticulocytes, we isolated mRNA, which was then reverse transcribed and amplified by the polymerase chain reaction (PCR) to give Rh-related cDNAs of two segments of 704 bp and 975 bp. The PCR amplification of the 5'-region yielded a single PCR product, whereas a complex electrophoretic pattern of PCR bands was derived from the 3'-region. A highly reproducible ladder of multiple additional bands migrated below the PCR products corresponding to the full-size cDNAs for RhPI and RhPII and encoding two different Rh polypeptides. Eleven and five truncated isoforms of the RhPI and RhPII cDNAs, respectively, were identified in the PCR products. These isoforms appear to be generated by combinatorial splicing of six RhPI and three RhPII exons. Our results suggest that the Rh-related polypeptides consist of a mixture of RhPI and RhPII polypeptide isoforms differing at the C terminus. Multiple RNA splicing pathways are thus operative in the two Rh-related genes even within a single cell lineage of human erythroid cells.

Fidelity of translation initiation of mRNA for the precursor of rat mitochondrial serine:pyruvate/alanine:glyoxylate aminotransferase

Serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT) of rat liver is localized in both mitochondria and peroxisomes. The rat SPT/AGT gene is single, but there are two species of mRNA which differ at their 5' termini due to transcription from two alternative initiation sites. The longer mRNA is translated from the first AUG codon and thereby directs synthesis of the 45 kDa precursor of mitochondrial SPT/AGT, which includes a mitochondria-targeting N-terminal signal sequence. Peroxisomal SPT/AGT is synthesized as a product of mature size (43 kDa) from the shorter mRNA, which starts 3' to the first AUG codon and thus is translated from a downstream AUG codon. In our previous immunocytochemical study, SPT/AGT was found to be localized only in peroxisomes, when a cDNA encoding 43 kDa SPT/AGT was expressed in COS cells. When a cDNA encoding the 45 kDa precursor was expressed, on the other hand, SPT/AGT was localized mostly in mitochondria, but a small number of peroxisomes were also positively stained [Yokota, S., Funai, T., and Ichiyama, A. (1991) Biomed. Res. 12, 53-59]. We show in this paper that 43 kDa SPT/AGT is also synthesized from the longer mRNA in an in vitro translation system through a leaky scanning mechanism. Although the first AUG initiator codon is in a suboptimal context, the amount of 43 kDa SPT/AGT synthesized from the longer mRNA was small, probably because a downstream stem-loop structure facilitates recognition of the first AUG initiator codon.

The simian virus 40 large T antigen does not inhibit translation of the 14-kDa myelin basic protein mRNA in reticulocyte lysates or in transfected cells

Viral T antigens are transcription factors that have been suspected of inhibiting expression of the myelin basic protein (MBP) mRNA at the translational level in vitro and in vivo. The effect of simian virus 40 (SV40) large T antigen (T-ag) was examined on the translation of the 14-kDa MBP mRNA in reticulocyte lysates and on MBP expression after transfection into cells that express SV40 T-ag. SV40 T-ag did not inhibit translation of 14-kDa MBP cRNAs in cell-free translations even at 30 microM (approximately 600 micrograms/ml) T-ag. Permanent transfection of COS-1 cells (which endogenously express SV40 T-ag) with the 14-kDa MBP cDNA resulted in the expression of the 14-kDa MBP as determined by western blot analysis. Permanent transfection of N20.1 cells, an oligodendrocyte line immortalized with a temperature-sensitive SV40 T-ag, with the 14-kDa MBP cDNA construct also resulted in the expression of the 14-kDa MBP under conditions in which the cells expressed functional SV40 T-ag. These results indicate that SV40 T-ag does not prevent expression of the MBP gene at the translational level and that in those immortalized oligodendrocyte lines that express MBP mRNA, but not MBP protein, some factor other than the SV40 large T-ag is responsible for the posttranscriptional regulation.

Flow cytometric reticulocyte analysis. Multiinstitutional interlaboratory correlation study

Reticulocyte analysis by flow cytometry offers precision and sensitivity greater than those of conventional morphologic methods and permits derivation of a reticulocyte maturity index. However, interlaboratory variability has not yet been reported. The authors analyzed 310 samples at eight sites using 11 instruments over a 4-month period to examine intermethod and interlaboratory variabilities. Stains included thiazole orange, ethidium bromide, and auramine O. Instruments included models by Coulter, Becton Dickinson, TOA Medical Electronics, and Ortho Diagnostics. The coefficient of variation (CV) among all sites and methods on these samples varied as a function of the reticulocyte percentage, ranging from a mean CV of 69% for samples with < .5% reticulocytes to 24.1% for those with > 2.5% reticulocytes. The best performance was observed with the TOA R-1000 dedicated reticulocyte analyzers, with a mean CV of 18.4% for samples with < .5% reticulocytes and 4.6% for samples with > 2.5% reticulocytes. The reticulocyte maturity index showed comparable intersite precision, with a mean CV of 16% for samples with > 2.5% reticulocytes with multipurpose flow cytometers and a mean CV of 7.3% with the TOA R-1000 instruments. Interclass correlations among all sites ranged from .79 to .99 for the reticulocyte counts and .41 to .88 for the reticulocyte maturity index. The authors conclude that flow cytometric reticulocyte analysis is more precise than manual reticulocyte analysis. With greater automation of this methodology, further interlaboratory standardization of reticulocyte counts and the reticulocyte maturity index can be achieved.