Red blood cell mannoses as phagocytic ligands mediating both sickle cell anaemia and malaria resistance

In both sickle cell disease and malaria, red blood cells (RBCs) are phagocytosed in the spleen, but receptor-ligand pairs mediating uptake have not been identified. Here, we report that patches of high mannose N-glycans (Man_5-9GlcNAc₂), expressed on diseased or oxidized RBC surfaces, bind the mannose receptor (CD206) on phagocytes to mediate clearance. We find that extravascular hemolysis in sickle cell disease correlates with high mannose glycan levels on RBCs. Furthermore, Plasmodium falciparum-infected RBCs expose surface mannose N-glycans, which occur at significantly higher levels on infected RBCs from sickle cell trait subjects compared to those lacking hemoglobin S. The glycans are associated with high molecular weight complexes and protease-resistant, lower molecular weight fragments containing spectrin. Recognition of surface N-linked high mannose glycans as a response to cellular stress is a molecular mechanism common to both the pathogenesis of sickle cell disease and resistance to severe malaria in sickle cell trait.

Identification of psychosocial factors which influence patient adherence with antihypertensive medication

Focal points

The influence of depression and perceived health competence on adherence in patients with heart disease

Focal points

Changes in QT dispersion during adenosine infusion

BACKGROUND

QT dispersion (QTd) measurement during treadmill stress testing has been to shown to improve the accuracy of exercise electrocardiogram (ECG) in the detection of significant coronary artery disease (CAD).

HYPOTHESIS

The aim of this study was to determine whether adenosine-induced changes in QTd could predict significant CAD and to assess its efficacy as a diagnostic index in patients undergoing adenosine stress test.

METHODS

QT interval measurements were made in 57 consecutive patients undergoing adenosine sestamibi stress test. Patients with an abnormal stress test underwent coronary angiography. Patients with significant disease by coronary angiography (> 70% stenosis) were classified as having CAD (Group 1), and those with normal stress images and/or normal coronaries by angiography were classified as having no CAD (Group 2).

RESULTS

QT dispersion increased from 28.2 +/- 4.5 to 43.8 +/- 4.5 ms with a delta QTd of 15.53 +/- 3.68 in Group 1 (p = 0.001) and from 28.4 +/- 2.6 to 34.8 +/- 2.8 ms with a delta QTd of 6.58 +/- 2.21 ms in Group 2 (p = 0.006). Patients in Group 1 had a significantly higher increase in QTd (delta QTd) than the patients in Group 2 (p < 0.03). Addition of delta QTd (> 10 ms) to the ST depression during adenosine infusion would increase the sensitivity of the ECG from 23 to 65% and decrease the specificity from 91 to 70% for diagnosis of significant CAD.

CONCLUSIONS

delta QTd is significantly more prolonged in patients with CAD during adenosine infusion. It increases the sensitivity of the stress ECG in diagnosis of CAD during adenosine infusion when used as an adjuvant index.

In vitro modulation of the expression of 15-hydroxy-prostaglandin dehydrogenase by trophoblast differentiation

OBJECTIVE

Our goal was to determine the expression and activity of 15-hydroxy-prostaglandin dehydrogenase, a prostaglandin-metabolizing enzyme, in differentiating trophoblasts in vitro.

STUDY DESIGN

Cytotrophoblasts from placentas of term healthy women were cultured in either Ham's-Waymouth medium, which hinders the process of cytotrophoblast differentiation, or medium 199, which facilitates differentiation into syncytiotrophoblasts. 15-Hydroxy-prostaglandin dehydrogenase expression was determined with Western immunoblotting, and activity was measured by a specific enzyme immunoassay of 13, 14-dihydro-15-keto prostaglandin F2 alpha, an inactive product of 15-hydroxy-prostaglandin dehydrogenase activity.

RESULTS

The expression and activity of 15-hydroxy-prostaglandin dehydrogenase were enhanced during trophoblast differentiation and were higher in cells grown in medium 199 than in those grown in Ham's-Waymouth medium. 8-Bromo-cyclic adenosine monophosphate, which stimulates prostaglandin H synthase-2 expression, diminished the expression and activity of 15-hydroxy-prostaglandin dehydrogenase in concentration- and time-dependent manners.

CONCLUSIONS

15-Hydroxy-prostaglandin dehydrogenase expression and activity are regulated during trophoblast differentiation and by cyclic adenosine monophosphate. Coordinated expression of l5-hydroxy-prostaglandin dehydrogenase and prostaglandin H synthase-2 contributes to the regulation of prostaglandin release from trophoblasts.

Protein-calorie malnutrition does not predict subtle vitamin K depletion in hospitalized patients

OBJECTIVE

Recent studies suggest that subtle vitamin K depletion has far-reaching consequences. As this entity is not associated with prothrombin time elevation, it is important to determine whether alternate methods can help identify it. We investigated subtle vitamin K depletion in a hospital setting and determined whether protein calorie malnutrition predicts its presence.

DESIGN, SETTING, SUBJECTS

Using a high-pressure liquid chromatography (HPLC) assay of plasma phylloquinone and a food frequency questionnaire for phylloquinone intake, we examined the phylloquinone status of 27 hospitalized patients with normal coagulation parameters, no liver disease, and no recent warfarin use. We assessed protein-calorie nutritional status with Reilly's criteria and anthropometrics.

RESULTS

51% of patients (95% CI = 31% to 70%) had evidence of subtle vitamin K depletion as defined by a subnormal plasma phylloquinone concentration. Patients whose phylloquinone intake was less than the Recommended Daily Allowance (RDA) over the preceding year had lower plasma phylloquinone concentrations when compared to other patients: median (range) 0.106 nmol/l (0.022-0.461) versus 0.301 nmol/l (0.067-3.928), respectively (P = 0.023). Plasma phylloquinone concentrations were no different, however, between well-nourished and malnourished patients: median (range) 0.245 nmol/l (0.022-0.522) versus 0.188 nmol/l (0.067-3.928), respectively (P=0.782).

CONCLUSIONS

Subtle vitamin K depletion is common among hospitalized patients and protein-calorie malnutrition does not predict its presence.

The vitamin K content of intravenous lipid emulsions

Commercially available intravenous lipid emulsions are largely derived from vegetable oils, a natural source of phylloquinone (vitamin K1). We therefore examined the concentration of vitamin K1 in two widely used intravenous lipid emulsions by using a previously validated high performance liquid chromatography technique. The vitamin K1 concentrations of 10% emulsions of Intralipid and Liposyn II were 30.8 and 13.2 micrograms/dL, respectively. The concentration of vitamin K1 in the 20% emulsions of these products was essentially double that in the 10% emulsions. The coefficients of variation between the vitamin K1 content in three different lots of each product were consistently less than 7.0%. The observed concentrations of the vitamin in these lipid emulsions paralleled the predicted content on the basis of the type of vegetable oil(s) used to make the product. The type of vegetable oil used for production therefore seems to be a major determinant of the final vitamin K1 content. The vitamin K1 contained in these intravenous lipid emulsions is substantial and may have great impact on the vitamin K status of the recipient.