Comparison of C-reactive protein and white blood cell count with differential in neonates at risk for septicaemia.

We prospectively compared the diagnostic value of C-reactive protein (CRP) and white blood cell counts for detection of neonatal septicaemia. Sensitivity and specifity in receiver operating characteristics, and positive and negative predictive value of CRP and white blood cell count were compared in 195 critically ill preterm and term newborns clinically suspected of infection. Blood cultures were positive in 33 cases. During the first 3 days after birth CRP elevation (sensitivity 75%, specifity 86%), leukopenia (67%/90%), neutropenia (78%/80%) and immature to total neutrophil count (I/T) ratio (78%/73%) were good diagnostic parameters, as opposed to band forms with absolute count (84%/66%) or percentage (79%/71%), thrombocytopenia (65%/57%) and toxic granulations (44%/94%). Beyond 3 days of age elevated CRP (88%/87%) was the best parameter. Increased total (84%/66%) or percentage band count (79%/71%) were also useful. Leukocytosis (74%/56%), increased neutrophils (67%/65%), I/T ratio (79%/47%), thrombocytopenia (65%/57%) and toxic granulations had a low specifity. The positive predictive value of CRP was 32% before and 37% after 3 days of age, that of leukopenia was 37% in the first 3 days. CONCLUSION: During the first 3 days of life CRP, leukopenia and neutropenia were comparably good tests while after 3 days of life CRP was the best single test in early detection of neonatal septicaemia. Serial CRP estimations confirm the diagnosis, monitor the course of infection and the efficacy of antibiotic treatment.

Seventy-five genetic loci influencing the human red blood cell.

Anaemia is a chief determinant of global ill health, contributing to cognitive impairment, growth retardation and impaired physical capacity. To understand further the genetic factors influencing red blood cells, we carried out a genome-wide association study of haemoglobin concentration and related parameters in up to 135,367 individuals. Here we identify 75 independent genetic loci associated with one or more red blood cell phenotypes at P < 10(-8), which together explain 4-9% of the phenotypic variance per trait. Using expression quantitative trait loci and bioinformatic strategies, we identify 121 candidate genes enriched in functions relevant to red blood cell biology. The candidate genes are expressed preferentially in red blood cell precursors, and 43 have haematopoietic phenotypes in Mus musculus or Drosophila melanogaster. Through open-chromatin and coding-variant analyses we identify potential causal genetic variants at 41 loci. Our findings provide extensive new insights into genetic mechanisms and biological pathways controlling red blood cell formation and function.

Red blood cell-derived microparticles isolated from blood units initiate and propagate thrombin generation.

BACKGROUND: Red blood cell-derived microparticles (RMPs) are small phospholipid vesicles shed from RBCs in blood units, where they accumulate during storage. Because microparticles are bioactive, it could be suggested that RMPs are mediators of posttransfusion complications or, on the contrary, constitute a potential hemostatic agent. STUDY DESIGN AND METHODS: This study was performed to establish the impact on coagulation of RMPs isolated from blood units. Using calibrated automated thrombography, we investigated whether RMPs affect thrombin generation (TG) in plasma. RESULTS: We found that RMPs were not only able to increase TG in plasma in the presence of a low exogenous tissue factor (TF) concentration, but also to initiate TG in plasma in absence of exogenous TF. TG induced by RMPs in the absence of exogenous TF was neither affected by the presence of blocking anti-TF nor by the absence of Factor (F)VII. It was significantly reduced in plasma deficient in FVIII or F IX and abolished in FII-, FV-, FX-, or FXI-deficient plasma. TG was also totally abolished when anti-XI 01A6 was added in the sample. Finally, neither Western blotting, flow cytometry, nor immunogold labeling allowed the detection of traces of TF antigen. In addition, RMPs did not comprise polyphosphate, an important modulator of coagulation. CONCLUSIONS: Taken together, our data show that RMPs have FXI-dependent procoagulant properties and are able to initiate and propagate TG. The anionic surface of RMPs might be the site of FXI-mediated TG amplification and intrinsic tenase and prothrombinase complex assembly.

Plasma homocysteine and vitamin B12 serum levels, red blood cell folate concentrations, C677T methylenetetrahydrofolate reductase gene mutation and risk of recurrent miscarriage: a case-control study in Spain.

Background: Hyperhomocysteinemia and methylenetetrahydrofolate reductase (MTHFR) gene mutation have been postulated as a possible cause of recurrent miscarriage (RM). There is a wide variation in the prevalence of MTHFR polymorphisms and homocysteine (Hcy) plasma levels among populations around the world. The present study was undertaken to investigate the possible association between hyperhomocysteinemia and its causative genetic or acquired factors and RM in Catalonia, a Mediterranean region in Spain. Methods: Sixty consecutive patients with ≥ 3 unexplained RM and 30 healthy control women having at least one child but no previous miscarriage were included. Plasma Hcy levels, MTHFR gene mutation, red blood cell (RBC) folate and vitamin B12 serum levels were measured in all subjects. Results: No significant differences were observed neither in plasma Hcy levels, RBC folate and vitamin B12 serum levels nor in the prevalence of homozygous and heterozygous MTHFR gene mutation between the two groups studied. Conclusions: In the present study RM is not associated with hyperhomocysteinemia, and/or the MTHFR gene mutation.

Microparticles from stored red blood cells induce thrombin generation

Background: Microparticles are small phospholipid vesicles of <1 lm shed in blood flow by various cell types including red blood cells. Erythrocyte-derived microparticles (EMPs) accumulate in erythrocyte concentrates (ECs) during their storage time. EMPs are considered as part of storage lesion and as their exact role is not elucidated, they could be involved in these clinical outcomes. Aims: The aim of this study is to evaluate the impact and implication of EMPs isolate from ECs on coagulation. Methods: EMPs were first isolated from erythrocyte concentrates by centrifugation and counted by flow cytometry. Using a calibrated automated thrombogram, EMPs were then added to different type of plasmas in order to evaluate the potential of thrombin generation. Results: We demonstrate that EMPs isolated from ECs are capable to accelerate and amplify thrombin generation in presence of a low exogenous tissue factor concentration, thanks to their negatively charged membrane necessary for the assembly of coagulation complexes. Interestingly, in the absence of exogenous tissue factor, EMPs are also able to trigger thrombin generation. In addition, thrombin generation induced by EMPs is not affected by the presence of anti-TF antibodies. Finally, thrombin generation induced by EMPs is not affected by using plasma samples deficient in factor VII, XI or XII. However, thrombin generation is reduced in plasma deficient in factor VIII or IX and is completely abolished in plasma deficient in factor X, V or II. No thrombin generation was observed in plasma samples without EMPs. Summary/conclusion: Several studies have shown a link between storage time of blood products and post transfusion complications. We provide evidence that EMPs accumulated during storage of erythrocyte concentrates were not only able to accelerate and support thrombin generation in plasma in presence of a low exogenous tissue-factor concentration, but also to trigger thrombin generation in absence of exogenous TF. The impact of those transfused EMs is unknown on recipients, nevertheless it could be hypothesized that under certain circumstances, transfused EMPs could be involved in thrombin generation and could be linked to adverse clinical outcome. Further work is needed to determine whether procoagulant EMPs transfused with erythrocyte concentrate may account for some of the complications occurring after red blood cell transfusion, and more particularly after transfusion of ''older''stored blood, rich in EMPs.

Detection and quantification of Duffy antigen on bovine red blood cell membranes using a polyclonal antibody

Babesiosis is one of the most important diseases affecting livestock agriculture worldwide. Animals from the subspecies Bos taurus indicus are more resistant to babesiosis than those from Bos taurus taurus. The genera Babesia and Plasmodium are Apicomplexa hemoparasites and share features such as invasion of red blood cells (RBC). The glycoprotein Duffy is the only human erythrocyte receptor for Pasmodium vivax and a mutation which abolishes expression of this glycoprotein on erythrocyte surfaces is responsible for making the majority of people originating from the indigenous populations of West Africa resistant to P. vivax. The current work detected and quantified the Duffy antigen on Bos taurus indicus and Bos taurus taurus erythrocyte surfaces using a polyclonal antibody in order to investigate if differences in susceptibility to Babesia are due to different levels of Duffy antigen expression on the RBCs of these animals, as is known to be the case in human beings for interactions of Plasmodium vivax-Duffy antigen. ELISA tests showed that the antibody that was raised against Duffy antigens detected the presence of Duffy antigen in both subspecies and that the amount of this antigen on those erythrocyte membranes was similar. These results indicate that the greater resistance of B. taurus indicus to babesiosis cannot be explained by the absence or lower expression of Duffy antigen on RBC surfaces.

Changes in red blood cell osmotic fragility induced by total plasma and plasma fractions obtained from rats bearing progressive and regressive variants of the Walker 256 tumor

Two variants (A and B) of the widely employed Walker 256 rat tumor cells are known. When inoculated sc, the A variant produces solid, invasive, highly metastasizing tumors that cause severe systemic effects and death. We have obtained a regressive variant (AR) whose sc growth is slower, resulting in 70-80% regression followed by development of immunity against A and AR variants. Simultaneously with the beginning of tumor regression, a temporary anemia developed (~8 days duration), accompanied by marked splenomegaly (~300%) and changes in red blood cell osmotic fragility, with mean corpuscular fragility increasing from 4.1 to 6.5 g/l NaCl. The possibility was raised that plasma factors associated with the immune response induced these changes. In the present study, we identify and compare the osmotic fragility increasing activity of plasma fractions obtained from A and AR tumor bearers at different stages of tumor development. The results showed that by day 4 compounds precipitating in 60% (NH4)2SO4 and able to increase red blood cell osmotic fragility appeared in the plasma of A and AR tumor bearers. Later, these compounds disappeared from the plasma of A tumor bearers but slightly increased in the plasma of AR tumor bearers. Furthermore, by day 10, compounds precipitating between 60 and 80% (NH4)2SO4 and with similar effects appeared only in plasma of AR tumor bearers. The salt solubility, production kinetics and hemolytic activity of these compounds resemble those of the immunoglobulins. This, together with their preferential increase in rats bearing the AR variant, suggest their association with an immune response against this tumor.

Melatonin and N-acetyl-serotonin cross the red blood cell membrane and evoke calcium mobilization in malarial parasites

The duration of the intraerythrocytic cycle of Plasmodium is a key factor in the pathogenicity of this parasite. The simultaneous attack of the host red blood cells by the parasites depends on the synchronicity of their development. Unraveling the signals at the basis of this synchronicity represents a challenging biological question and may be very important to develop alternative strategies for therapeutic approaches. Recently, we reported that the synchrony of Plasmodium is modulated by melatonin, a host hormone that is synthesized only during the dark phases. Here we report that N-acetyl-serotonin, a melatonin precursor, also releases Ca2+ from isolated P. chabaudi parasites at micro- and nanomolar concentrations and that the release is blocked by 250 mM luzindole, an antagonist of melatonin receptors, and 20 mM U73122, a phospholipase C inhibitor. On the basis of confocal microscopy, we also report the ability of 0.1 µM melatonin and 0.1 µM N-acetyl-serotonin to cross the red blood cell membrane and to mobilize intracellular calcium in parasites previously loaded with the fluorescent calcium indicator Fluo-3 AM. The present data represent a step forward into the understanding of the signal transduction process in the host-parasite relationship by supporting the idea that the host hormone melatonin and N-acetyl-serotonin generate IP3 and therefore mobilize intracellular Ca2+ in Plasmodium inside red blood cells.

Risk factors for alloimmunization by patients with sickle cell disease

Blood transfusion in patients with sickle cell disease (SCD) is limited by the development of alloantibodies to erythrocytes. In the present study, the frequency and risk factors for alloimmunization were determined. Transfusion records and medical charts of 828 SCD patients who had been transfused and followed at the Belo Horizonte Blood Center, Belo Horizonte, MG, Brazil, were retrospectively reviewed. Alloimmunization frequency was 9.9% (95% CI: 7.9 to 11.9%) and 125 alloantibodies were detected, 79% of which belonged to the Rhesus and Kell systems. Female patients developed alloimmunization more frequently (P = 0.03). The median age of the alloimmunized group was 23.3 years, compared to 14.6 years for the non-alloimmunized group (P < 0.0001). Multivariate analyses were applied to the data for 608 hemoglobin (Hb) SS or SC patients whose number of transfusions was recorded accurately. Number of transfusions (P = 0.00006), older age (P = 0.056) and Hb SC (P = 0.02) showed independent statistical associations with alloimmunization. Hb SC patients older than 14 years faced a 2.8-fold higher (95% CI: 1.3 to 6.0) risk of alloimmunization than Hb SS patients. Female Hb SC patients had the highest risk of developing alloantibodies. In patients younger than 14 years, only the number of transfusions was significant. We conclude that an increased risk of alloimmunization was associated with older patients with Hb SC, specially females, even after adjustments were made for the number of transfusions received, the most significant variable.

Acute effects of resistance exercise and intermittent intense aerobic exercise on blood cell count and oxidative stress in trained middle-aged women

The aim of this study was to compare the effect of an intermittent intense aerobic exercise session and a resistance exercise session on blood cell counts and oxidative stress parameters in middle-aged women. Thirty-four women were selected and divided into three groups: RE group (performing 60 min of resistance exercises, N = 12), spinning group (performing 60 min of spinning, N = 12), and control group (not exercising regularly, N = 10). In both exercise groups, lymphocytes and monocytes decreased after 1-h recuperation (post-exercise) compared to immediately after exercise (P < 0.05). Immediately after exercise, in both exercised groups, a significant increase in TBARS (from 16.5 ± 2 to 25 ± 2 for the spinning group and from 18.6 ± 1 to 28.2 ± 3 nmol MDA/mL serum for the RE group) and protein carbonyl (from 1.0 ± 0.3 to 1.6 ± 0.2 for the spinning group and from 0.9 ± 0.2 to 1.5 ± 0.2 nmol/mg protein for the RE group) was observed (P < 0.05). A decrease in antioxidant activities (non-protein sulfhydryl, superoxide dismutase, catalase) was also demonstrated with a negative correlation between damage markers and antioxidant body defenses (P < 0.05). These results indicate that an acute bout of intermittent or anaerobic exercise induces immune suppression and increases the production of reactive oxygen species, causing oxidative stress in middle-aged and trained women. Furthermore, we demonstrated that trained women show improved antioxidant capacity and lower oxidative damage than sedentary ones, demonstrating the benefits of chronic regular physical activity.

Preparation, characterization, and rheological properties of star-shaped poly(ethylene glycol) with a cholane core and study of its effect on red blood cell aggregation

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

In vitro and in vivo evaluation of a primaquine prodrug without red blood cell membrane destabilization property

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Detection and quantification of Duffy antigen on bovine red blood cell membranes using a polyclonal antibody

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

CHARACTERISTICS OF ZINC-BINDING TO HUMAN RED-BLOOD-CELL MEMBRANES

The objective of the present study was to standardize the analysis of zinc binding on human red blood cell (RBC) membranes in 20 normal adults. The displacement studies revealed that at the maximal stable zinc concentration tested (600 muM), 57% (mean) of the bound Zn-65 was displaced and to displace half maximal Zn-65, the stable zinc concentration was 300 muM. Scatchard plots revealed two classes of binding sites for zinc on RBC membranes: one with higher affinity, Kd = 1.20 x 10(-5) M (site I), and the other with lower affinity, Kd = 2.77 x 10(-4) M (site II). Binding sites occupancy was 97% means and 58.5% means for sites I and 11, respectively. The displacement was affected by temperature, membrane protein concentration, freezing, thawing, and dialysis. Other metal cations, including Co++, Fe++, and Mn++, had very little effect on Zn-65 displacement, in contrast copper displaced Zn-65 from its binding sites on RBC membranes. Zinc binding to RBC membranes was rapid and readily reversible in a dynamic equilibrium with its binding sites. It is anticipated that this method will be applicable to studies of a wide variety of diseases specifically related to zinc metabolism in humans as well as in animals. (C) 1994 Wiley-Liss, Inc.