SciCombinator

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Concept: Red blood cell

368

The ‘Blood-Type’ diet advises individuals to eat according to their ABO blood group to improve their health and decrease risk of chronic diseases such as cardiovascular disease. However, the association between blood type-based dietary patterns and health outcomes has not been examined. The objective of this study was to determine the association between ‘blood-type’ diets and biomarkers of cardiometabolic health and whether an individual’s ABO genotype modifies any associations.

Concepts: Medicine, Epidemiology, Nutrition, Death, Blood, Red blood cell, Blood type, ABO blood group system

240

Current treatment of anemia in chronic kidney disease (CKD) with erythropoiesis-stimulating agents can lead to substantial hemoglobin oscillations above target range and high levels of circulating erythropoietin. Vadadustat (AKB-6548), a novel, titratable, oral hypoxia-inducible factor prolyl hydroxylase inhibitor induces endogenous erythropoietin synthesis and enhances iron mobilization. In this 20-week, double-blind, randomized, placebo-controlled, phase 2b study, we evaluated the efficacy and safety of once-daily vadadustat in patients with stages 3a to 5 non-dialysis-dependent CKD. The primary endpoint was the percentage of patients who, during the last 2 weeks of treatment, achieved or maintained either a mean hemoglobin level of 11.0 g/dl or more or a mean increase in hemoglobin of 1.2 g/dl or more over the predose average. Significantly, the primary endpoint was met in 54.9% of patients on vadadustat and 10.3% of patients on placebo. Significant increases in both reticulocytes and total iron-binding capacity and significant decreases in both serum hepcidin and ferritin levels were observed in patients on vadadustat compared with placebo. The overall incidence of adverse events was comparable between the 2 groups. Serious adverse events occurred in 23.9% and 15.3% of the vadadustat- and placebo-treated patients, respectively. Three deaths occurred in the vadadustat arm. Thus, this phase 2b study demonstrated that vadadustat raised and maintained hemoglobin levels in a predictable and controlled manner while enhancing iron mobilization in patients with nondialysis-dependent CKD.

Concepts: Hemoglobin, Chronic kidney disease, Kidney, Erythropoietin, Red blood cell, Anemia, Transferrin, Ferritin

208

Somatic cell nuclear transfer (SCNT) is a unique technology that produces cloned animals from single cells. It is desirable from a practical viewpoint that donor cells can be collected noninvasively and used readily for nuclear transfer. The present study was undertaken to determine whether peripheral blood cells freshly collected from living mice could be used for SCNT. We collected a drop of peripheral blood (15-45 µl) from the tail of a donor. A nucleated cell (leukocyte) suspension was prepared by lysing the red blood cells. Following SCNT using randomly selected leukocyte nuclei, cloned offspring were born at a 2.8% birth rate. Fluorescence-activated cell sorting revealed that granulocytes/monocytes and lymphocytes could be roughly distinguished by their sizes, the former being significantly larger. We then cloned putative granulocytes/monocytes and lymphocytes separately, and obtained 2.1% and 1.7% birth rates, respectively (P > 0.05). Because the use of lymphocyte nuclei inevitably results in the birth of offspring with DNA rearrangements, we applied granulocyte/monocyte cloning to two genetically modified strains and two recombinant inbred strains. Normal-looking offspring were obtained from all four strains tested. The present study clearly indicated that genetic copies of mice could be produced using a drop of peripheral blood from living donors. This strategy will be applied to the rescue of infertile founder animals or a “last-of-line” animal possessing invaluable genetic resources.

Concepts: DNA, Gene, Genetics, Cell nucleus, Blood, Red blood cell, Cloning, Somatic cell nuclear transfer

192

While intermittent hypoxic training (IHT) has been reported to evoke cellular responses via hypoxia inducible factors (HIFs) but without substantial performance benefits in endurance athletes, we hypothesized that repeated sprint training in hypoxia could enhance repeated sprint ability (RSA) performed in normoxia via improved glycolysis and O(2) utilization. 40 trained subjects completed 8 cycling repeated sprint sessions in hypoxia (RSH, 3000 m) or normoxia (RSN, 485 m). Before (Pre-) and after (Post-) training, muscular levels of selected mRNAs were analyzed from resting muscle biopsies and RSA tested until exhaustion (10-s sprint, work-to-rest ratio 1∶2) with muscle perfusion assessed by near-infrared spectroscopy. From Pre- to Post-, the average power output of all sprints in RSA was increased (p<0.01) to the same extent (6% vs 7%, NS) in RSH and in RSN but the number of sprints to exhaustion was increased in RSH (9.4±4.8 vs. 13.0±6.2 sprints, p<0.01) but not in RSN (9.3±4.2 vs. 8.9±3.5). mRNA concentrations of HIF-1α (+55%), carbonic anhydrase III (+35%) and monocarboxylate transporter-4 (+20%) were augmented (p<0.05) whereas mitochondrial transcription factor A (-40%), peroxisome proliferator-activated receptor gamma coactivator 1α (-23%) and monocarboxylate transporter-1 (-36%) were decreased (p<0.01) in RSH only. Besides, the changes in total hemoglobin variations (Δ[tHb]) during sprints throughout RSA test increased to a greater extent (p<0.01) in RSH. Our findings show larger improvement in repeated sprint performance in RSH than in RSN with significant molecular adaptations and larger blood perfusion variations in active muscles.

Concepts: Hemoglobin, Oxygen, Carbon dioxide, Peroxisome proliferator-activated receptor, Red blood cell, Muscle, Muscular system, Carbonic anhydrase

191

Chironex fleckeri (Australian box jellyfish) stings can cause acute cardiovascular collapse and death. We developed methods to recover venom with high specific activity, and evaluated the effects of both total venom and constituent porins at doses equivalent to lethal envenomation. Marked potassium release occurred within 5 min and hemolysis within 20 min in human red blood cells (RBC) exposed to venom or purified venom porin. Electron microscopy revealed abundant ∼12-nm transmembrane pores in RBC exposed to purified venom porins. C57BL/6 mice injected with venom showed rapid decline in ejection fraction with progression to electromechanical dissociation and electrocardiographic findings consistent with acute hyperkalemia. Recognizing that porin assembly can be inhibited by zinc, we found that zinc gluconate inhibited potassium efflux from RBC exposed to total venom or purified porin, and prolonged survival time in mice following venom injection. These findings suggest that hyperkalemia is the critical event following Chironex fleckeri envenomation and that rapid administration of zinc could be life saving in human sting victims.

Concepts: Blood, Red blood cell, Cnidaria, Potassium chloride, Box jellyfish, Chironex fleckeri, Cubozoa, Chirodropidae

173

Marchioli et al.(1) report in the Journal that a hematocrit target of less than 45% for therapeutic phlebotomy reduces the risk of thrombosis in patients with polycythemia vera. In the genomic era, readers may question attention given to a measurement as mundane as the hematocrit, but this study resolves a half-century of debate about the role of phlebotomy in polycythemia vera and has ramifications for diagnosis and management. Polycythemia vera is a unique myeloproliferative disorder in which there is overproduction of morphologically normal erythrocytes, granulocytes, and platelets, a phenotype that is caused by a mutation (V617F) in JAK2, encoding . . .

Concepts: Blood, Red blood cell, Hematology, Hematocrit, Polycythemia vera

172

Children with neurofibromatosis type 1 (NF1) are predisposed to juvenile myelomonocytic leukemia (JMML), an aggressive myeloproliferative neoplasm (MPN) that is refractory to conventional chemotherapy. Conditional inactivation of the Nf1 tumor suppressor in hematopoietic cells of mice causes a progressive MPN that accurately models JMML and chronic myelomonocytic leukemia (CMML). We characterized the effects of Nf1 loss on immature hematopoietic populations and investigated treatment with the MEK inhibitor PD0325901 (hereafter called 901). Somatic Nf1 inactivation resulted in a marked expansion of immature and lineage-committed myelo-erythroid progenitors and ineffective erythropoiesis. Treatment with 901 induced a durable drop in leukocyte counts, enhanced erythropoietic function, and markedly reduced spleen sizes in mice with MPN. MEK inhibition also restored a normal pattern of erythroid differentiation and greatly reduced extramedullary hematopoiesis. Remarkably, genetic analysis revealed the persistence of Nf1-deficient hematopoietic cells, indicating that MEK inhibition modulates the proliferation and differentiation of Nf1 mutant cells in vivo rather than eliminating them. These data provide a rationale for performing clinical trials of MEK inhibitors in patients with JMML and CMML.

Concepts: Cancer, Oncology, Red blood cell, Hematology, Leukemia, Spleen, Erythropoiesis, Juvenile myelomonocytic leukemia

166

The quantity of circulating reticulocytes is an important indicator of erythropoietic activity in response to a wide range of haematological pathologies. While most modern laboratories use flow cytometry to quantify reticulocytes, most field laboratories still rely on ‘subvital’ staining. The specialist ‘subvital’ stains, New Methylene Blue (NMB) and Brilliant Crésyl Blue are often difficult to procure, toxic, and show inconsistencies between batches. Here we demonstrate the utility of Giemsa’s stain (commonly used microbiology and parasitology) in a ‘subvital’ manner to provide an accurate method to visualize and count reticulocytes in blood samples from normal and malaria-infected individuals.

Concepts: Biology, Red blood cell, Anemia, Hematology, Flow cytometry, Stain, Reticulocyte, New methylene blue

166

Dietary iron absorption is regulated by hepcidin, an iron regulatory protein produced by the liver. Hepcidin production is regulated by iron stores, erythropoiesis and inflammation, but its physiology has not been characterized when repeated blood loss occurs. Hepcidin was measured in plasma samples obtained from 114 first-time/reactivated (no blood donations in prior 2 years) female donors and 34 frequent (≥3 red blood cell donations in prior 12 months) male donors as they were phlebotomized ≥4 or more times over 18-24 months. Hepcidin was compared to ferritin and hemoglobin using multivariable repeated measures regression models. Hepcidin, ferritin and hemoglobin declined with increasing frequency of donation in the first-time/reactivated females. Hepcidin and ferritin correlated well with each other (Spearman correlation of 0.74), but on average hepcidin varied more between donations for a given donor relative to ferritin. In a multivariable repeated measures regression model the predicted inter-donation decline in hemoglobin varied as a function of hepcidin and ferritin; hemoglobin was 0.51 g/dL lower for subjects with low (≤45.7 ng/ml) or decreasing hepcidin and low ferritin (≤26 ng/ml), and was essentially zero for other subjects including those with high (>45.7 ng/ml) or increasing hepcidin and low ferritin (≤26 ng/ml) (p<0.001). Hepcidin rapidly changes in response to dietary iron needed for erythropoiesis. The dynamic regulation of hepcidin in the presence of low ferritin suggests that plasma hepcidin may provide clinically useful information about an individual's iron status (and hence capacity to tolerate repeated blood donations) beyond that of ferritin alone.

Concepts: Hemoglobin, Blood, Red blood cell, Spearman's rank correlation coefficient, Liver, Anemia, Hematology, Iron deficiency anemia

164

Recent studies suggest that leukocytes and erythrocytes play a role in coagulation. However, whether leukocytes, erythrocytes and other hematological variables are associated with risk of venous thrombosis is not well known. To study this, we used data from 2473 venous thrombosis patients and 2935 controls. The variables assessed were: total leukocytes, granulocytes, lymphocytes, monocytes, hematocrit, hemoglobin, erythrocytes and red cell indices (mean corpuscular volume, mean hemoglobin volume, mean corpuscular hemoglobin volume and red cell distribution width). We found a strong dose-response relation for higher red cell distribution width and monocytes with risk of venous thrombosis, with odds ratios of 3.1 (95% confidence interval, 2.0-4.8) and 2.8 (95% confidence interval, 1.3-5.8), respectively, after adjustment for age, sex, C-reactive protein, malignancy and co-morbidities. Monocyte count and red cell distribution width were associated with venous thrombosis even within reference ranges. A low monocyte count (< 0.12x109/L) was associated with a lower venous thrombosis risk after full adjustment (odds ratios 0.6; 95% confidence interval, 0.4-0.8). In summary, high red cell distribution width and blood monocytes, two unexpensive and easily obtainable tests were clearly associated with an increased risk of venous thrombosis. Future studies should evaluate the underlying mechanism and the use of these variables in prediction models for first and recurrent thrombosis.

Concepts: Immune system, White blood cell, Monocyte, Blood, Red blood cell, Hematology, Complete blood count, Mean corpuscular volume