Antiglobulin serum mediated phagocytosis of normal senescent and oxidized RBC: role of anti-IgM immunoglobulins in phagocytic recognition

Acarbose Mitigates Age-Dependent Alterations in Erythrocyte Membrane Transporters During Aging in Rats

Acarbose (ACA), a well-studied and effective inhibitor of α-amylase and α-glucosidase, is a postprandial-acting antidiabetic medicine. The membrane of the erythrocyte is an excellent tool for analyzing different physiological and biochemical activities since it experiences a range of metabolic alterations throughout aging. It is uncertain if ACA modulates erythrocyte membrane activities in an age-dependent manner. As a result, the current study was conducted to explore the influence of ACA on age-dependent deteriorated functions of transporters/exchangers, disrupted levels of various biomarkers such as lipid hydroperoxides (LHs), protein carbonyl (PCO), sialic acid (SA), total thiol (-SH), and erythrocyte membrane osmotic fragility. In addition to a concurrent increase in Na+/H+ exchanger activity and concentration of LH, PCO, and osmotic fragility, we also detected a considerable decrease in membrane-linked activities of Ca2+-ATPase (PMCA) and Na+/K+-ATPase (NKA), as well as concentrations of SA and -SH in old-aged rats. The aging-induced impairment of the activities of membrane-bound ATPases and the changed levels of redox biomarkers were shown to be effectively restored by ACA treatment.

Enhanced oxidative cross-linking of hemoglobin E with spectrin and loss of erythrocyte membrane asymmetry in hemoglobin Ebeta-thalassemia

Oxidative stress to the erythrocytes is associated with formation of large molecular complexes of hemoglobin and the skeletal protein, spectrin. In this work, such complexes are formed with hemoglobin mixtures isolated from patients suffering from HbEbeta-thalassemia with elevated levels of the HbE and purified erythroid spectrin in the presence of hydrogen peroxide. The complexes are separated on 4% SDS-PAGE and analyzed by densitometry. The results indicate enhanced formation of complexes with higher amounts of HbE, the most common hemoglobin variant prevalent in Southeast Asia. The binding affinity of spectrin with hemoglobin, in the absence of hydrogen peroxide, was found to increase with hemoglobin mixtures enriched with HbE. The presence of ATP was also found to decrease the overall yield of such complexes. Flow cytometric measurements of phosphatidylserine on the red cell surface also showed a lower degree of membrane asymmetry in HbEbeta-thalassemic patients than in normal subjects. The present work shows enhanced formation of high molecular weight cross-linked complexes of hemoglobin derivatives with erythroid spectrin in HbEbeta-thalassemia.

Time course of hemoglobin concentrations in nonbleeding intensive care unit patients

OBJECTIVES

To evaluate the time course of hemoglobin concentrations in nonbleeding intensive care unit patients.

DESIGN

Prospective, observational study.

SETTING

Multidisciplinary (medicosurgical) department of intensive care.

PATIENTS

Ninety-one patients with no evidence of recent or active blood loss, no history of hematologic disease or chronic renal failure, and no need for extracorporeal epuration techniques.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data collection included primary diagnoses, Acute Physiology and Chronic Health Evaluation II and sepsis-related organ failure assessment scores, signs of sepsis, 24-hr fluid balance, and hemoglobin concentrations. For the entire intensive care unit stay, the fall in hemoglobin concentrations (calculated from the mean of individual slopes of hemoglobin concentrations over time) averaged 0.52 +/- 0.69 g/dL/day. For the 33 patients who stayed in the intensive care unit for >3 days, this decline was larger for the first 3 days than for subsequent days (0.66 +/- 0.84 g/dL/day vs. 0.12 +/- 0.29 g/dL/day; p<.01). After the third intensive care unit day, the change in hemoglobin concentrations was inversely related to the severity of the disease, as reflected by the Acute Physiology and Chronic Health Evaluation II and the sepsis-related organ failure assessment scores. Hemoglobin concentrations decreased by 0.44 +/- 0.70 g/dL/day in the nonseptic and 0.68 +/- 0.66 g/dL/day in the septic patients (p =.13). After the third intensive care unit day, hemoglobin concentrations continued to decrease in the septic patients but not in the nonseptic patients (-0.29 +/- 0.19 vs. 0.006 +/- 0.3 g/dL/day; p=.0016). The fall in hemoglobin concentrations was not significantly related to the fluid balance. The volume of blood drawn daily for laboratory studies was 40.3 +/- 15.4 mL: 49.0 +/- 11.3 mL in the septic patients and 36.7 +/- 14.9 mL in the nonseptic patients (p =.04).

CONCLUSIONS

Hemoglobin concentrations typically decline by >0.5 g/dL/day during the first days of intensive care unit stay in nonbleeding patients. Beyond the third day, hemoglobin concentrations can remain relatively constant in nonseptic patients but continue to decrease in septic patients, as well as patients with high sepsis-related organ failure assessment or Acute Physiology and Chronic Health Evaluation II scores. These observations may help in the interpretation of hemoglobin concentrations in critically ill patients.

Role of linkage specific 9-O-acetylated sialoglycoconjugates in activation of the alternate complement pathway in mammalian erythrocytes

Substitution of the -OH group at C-9 of sialic acid by an O-acetyl ester has been suggested to modify various biological phenomena that are regulated by sialic acids. Amongst them, enhancement of erythrocyte lysis by 9-O-acetylated sialic acid determinants through modulation of the alternate pathway of complement has been extensively studied on murine erythrocytes [1]. A variable expression of linkage specific 9-O-acetylated sialoglycoconjugates as defined by the lectinogenic epitope of Achatinin-H namely 9-O-acetylated sialic acid alpha2-->6Gal NAc was identified on rabbit, guinea pig, hamster, rat, mouse and human erythrocytes. This differential expression of linkage specific 9-O-acetylated sialoglycoconjugates strongly correlated with the susceptibility of mammalian erythrocytes to lysis by the alternate pathway of complement. Additionally, low levels of antibodies directed against O-acetylated sialic acids in these mammalian species suggested that these constitutively present determinants have low immunogenicity. Taken together, our results indicate that complement mediated hemolysis depends not simply upon the extent of surface 9-O-acetylated sialic acids present but more importantly upon the specific linkage.