Membrane alterations leading to red cell destruction☆

Arsine is one of the highly toxic forms of arsenic and one of the leading causes of pollution worldwide. The persistent rise of this toxic matter in the atmosphere can create various toxic effects such as hemolysis, loss of blood, and liver and kidney function disturbance. This chapter discusses findings that define the toxicological and environmental issues encountered postexposure of arsine. Also, the chapter gives an account of studies associated with the progress of risk assessment, as well as management of toxic matter while handling and storing the gas.

In both man and the dog, anaemia resulting from natural leishmaniasis is often severe and mainly associated with a shortened life span of erythrocytes. Lipid fluidity of erythrocyte membranes from 17 dogs with anaemia caused by visceral leishmaniasis was investigated by means of fluorescence polarization. Results were compared with those from three groups of control animals (10 healthy dogs, seven dogs with visceral leishmaniasis but no anaemia, and 10 dogs with anaemia unrelated to leishmaniasis). Fluorescence polarization values recorded for animals with leishmaniasis-associated anaemia were elevated—indicating reduced erythrocyte membrane fluidity—and significantly higher than in the control groups. Mechanical sequestration by the spleen due to increased cell rigidity, or alterations in receptor/ligand erythrocyte cytoadherence mechanisms, or both, may result from decreased membrane fluidity and hence contribute to the anaemia ofLeishmania -infected dogs.

Human red blood cells (RBCs) have a life-span of 120 days in circulation, after they are phagocytized by resident macrophages. Extensive studies have been undertaken by many investigators in order to elucidate the cellular and molecular mechanisms of the erythrophagocytosis. The critical questions addressed by physiologists, clinicians and biochemists are: which of the many traumatic blemishes that appear on the erythrocyte surface as it winds its way through the circulation is the primary signal for clearance of the effete RBC from the circulation?, or ‘What is the critical signal that it, and it alone, will activate the resident macrophage to adhere to and engulf it?’. Numerous, and often conflicting, hypotheses have been proposed. Each investigator focusing on but one of the many modifications that afflict the cell surface of the ageing erythrocyte, viz changes in either or both the carbohydrate or peptidic moieties of glycoproteins; abolishment of the pre-existing asymmetry in the lipid bilayer with the exposure of phosphatidylserine residues: or alterations in spectrin, to mention but a few. Many of these investigators also have invoked an intermediary role for auto-immune antibodies that recognise the change(s) on the erythrocyute surface and thereby serve as opinion as a prelude to the erythrophagocytosis. The objective of the present review is to evaluate the data in support of the various hypotheses, and to submit some of our own recent observations involving the use of flow cytometric procedures that: i) provide evidence that the cell surface sialic acid serves as a determinant of the life-span: ii) characterise the senescent erythrocyte population that is specifically captured and phagocytized by macrophages (utilising the rapid and sensitive procedure we developed for quantification of in vivo erythrophagocytosis); and finally iii) provide evidence for the existence of an alternative pathway that is independent of immunoglobulins.

Erythrocyte aging, accompanied by reduced deformability and low ATP level, is considered to be among the factors limiting the survival of old erythrocytes. The aim of this study was to observe the effect of reversible erythrocyte shape changes of discocyte-echinocyte-discocyte, following ATP-depletion and repletion with adenosine of normal human erythrocytes, on the cytoskeletal network. The effect becomes evident from electron microscopical observations on Triton-treated erythrocyte membranes. The two-dimensional lattice of spectrin-actin junction polygons increases in size in ATP-depleted erythrocytes. This may be due to the spectrin elasticity permitting an expansion of the skeletal lattice. The observations demonstrate alterations in the configuration of the filamentous units visualized in the cytoskeleton during the process of reversible erythrocyte shape changes, a capacity which is limited in aged human erythrocytes.

Objectives. The aims of this study were to define the hydrodynamic mechanisms involved in the occurrence of hemolysis in prosthetic mitral valve regurgitation and to reproduce them in a numeric simulation model in order to estimate peak shear stress.

Background. Although in vitro studies have demonstrated that shear stresses >3,000 dynes/cm²are associated with significant erythrocyte destruction, it is not known whether these values can occur in vivo in conditions of abnormal prosthetic regurgitant flow.

Methods. We studied 27 patients undergoing reperattion for significant mitral prosthetic regurgitation, 16 with and 11 without hemolysis. We classified the origin and geometry of the regurgitant jets by using transesophageal echocardiography. By using the physical and morphologic characteristics defined, several hydrodynamic patterns were simulated numerically to determine shear rates.

Results. Eight (50%) of the 16 patients with hemolysis had paravalvular leaks and the other 8 had a jet with central origin, in contrast to 2 (18%) and 9 (82%), respectively, of the 11 patients without hemolysis (p = 0.12, power 0.38). Patients with hemolysis had patterns of flow fragmentation (n = 2), collision (n = 11) or rapid acceleration (n = 3), whereas those without hemolysis had either free jets (n = 7) or slow deceleration (n = 4) (p < 0.001, power 0.99). Numeric simulation demonstrated peak shear rates of 6,000, 4,500, 4,500, 925 and^a50 dynes/cm²in these five models, respectively.

Conclusions. The distinct patterns of regurgitant flow seen in these patients with mitral prosthetic hemolysis were associated with rapid acceleration and deceleration or high peak shear rates, or both. The nature of the flow disturbance produced by the prosthetic regurgitant lesion and the resultant increase in shear stress are more important than the site of origin of the flow disturbance in producing clinical hemolysis.

The effects of primaquine (PQ), its enantiomers [(+)PQ,(−)PQ] and hydroxy metabolites [5-hydroxyprimaquine (5HPQ) and 6-desmethyl-5-hydroxyprimaquine (6D5HPQ)] on cell membranes of glucose-6-phosphate dehydrogenase (G-6-PD) deficient red cells were studied in vitro. There was no significant effect of PQ on the malonyldialdehyde (MDA) content of normal and heterozygous red cells, but it caused a significant increase in MDA in G-6-PD deficient red cells (P < 0.05). There was no noticeable difference between the effects of the two enantiomers on this variable (P > 0.05). Compared to PQ, the hydroxy metabolites produced a significantly greater increase in MDA in all the groups studied (P < 0.001). Of the two hydroxy metabolites, 6D5HPQ was more toxic than 5HPQ. Staining with MC 540 showed that exposure to PQ, its enantiomers and two putative metabolites produced significant fluorescence, indicating that the drug produces marked alterations in membrane fluidity. Although the fluorescence was seen both in normal and heterozygous cells, the effect was marked in hemizygous deficient red cells (P < 0.001). Scanning electron microscopic (SEM) studies revealed that PQ enantiomers had a stomatocytic effect on red cells of normal, heterozygous and hemizygous G-6-PD deficient red cells, whereas the putative metabolites had an echinocytic effect. The effects were most pronounced in G-6-PD deficient red cells.