Clinical disorders of the red cell membrane skeleton

[A patient with hereditary spherocystosis and sudden deafness after splenectomy]

We report the case of a 29 year-old male with of hereditary spherocytosis, who developed two episodes of sensorineural hearing loss in his right ear after splenectomy due to repetitive hemolytic crisis. We discuss the eventual altiopathogenic mechanism of this audiological disorder.

Erythrocyte deformability in schizophrenic patients

Erythrocyte deformability as a clinical indicator of microcirculatory disturbance was determined in the erythrocyte of 25 schizophrenic patients and of 18 normal controls. Schizophrenic patients had significantly lower erythrocyte deformability than did the normal controls (P < 0.001). This result suggests that microcirculation in schizophrenic patients is disturbed, and that this disturbance might be involved in the pathophysiological genesis of schizophrenia.

Current problems in haematology. 2: Hereditary spherocytosis

Hereditary spherocytosis is a relatively common haematological disorder and will be encountered by all haematologists. The abundance of new information, dealing principally with molecular and genetic aspects of pathophysiology, is beginning to have implications for its investigation and management. While these advances have not yet exerted a large influence at therapeutic level, the promise of such advents as prenatal diagnosis make this an exciting field to watch.

Reduction in band 3 protein of red cells in sickle cell anaemia

Twelve patients suffering from sickle cell anaemia (Hb less than 75 g/l) with SS-haemoglobin were studied with special regard to Band 3-protein content in their erythrocyte membranes on SDS-PAGE. They were compared in this respect with 7 asymptomatic individuals with AS-haemoglobin and 10 healthy controls with the ordinary adult haemoglobin. A heterogeneity in Band 3-protein content was evident among the 12 patients. Six of them belonged to a low content group while the other 6 belonged to a high content group comparable with the asymptomatic subjects and the controls. No simple relationship seemed to exist between Band 3-protein reduction and the clinical presentation.

The membrane skeleton of erythrocytes. A percolation model

The spectrin network on the cytoplasmic surface of the erythrocyte membrane is modeled as a triangular lattice of spectrin tetramers. This network obstructs lateral diffusion of proteins and provides mechanical reinforcement to the membrane. These effects are treated in a systematic and unified manner in terms of a percolation model. The diffusion coefficient is obtained as a function of the fraction of normal spectrin tetramers for both static and fluctuating barriers. The elasticity of the network is calculated as a function of the fraction of normal spectrin and the ratio of bending to stretching energies. For static barriers, elasticity and lateral diffusion are incompatible: if a network is connected enough to be elastic, it is connected enough to block long-range lateral diffusion. The elasticity and the force required for mechanical breakdown go to zero at the percolation threshold; experimental evidence suggests the existence of a stability threshold at or near the percolation threshold. The model is qualitatively applicable to other cells with membrane skeletons, such as epithelial cells, in which localization of membrane proteins is essential to differentiation.

Erythrocyte rheology

Two main subjects of erythrocyte rheology, deformation and aggregation, are discussed in detail, on the basis of biochemical structure. The close relationship between the life span (or cell aging) and the rheology of individual erythrocytes is also briefly described. A currently important problem is emphasized, that is, the molecular aspect of the dynamic cytoskeletal structure and the mechanism of its regulation. This concerns not only the rheological function and the survival of circulating erythrocytes, but also the pathophysiology of abnormal erythrocytes.

The spectrin network as a barrier to lateral diffusion in erythrocytes. A percolation analysis

The spectrin network on the cytoplasmic surface of an erythrocyte can be modeled as a triangular lattice of spectrin tetramers (Tsuji, A., and S. Ohnishi, 1986. Biochemistry. 25:6133-6139). The tetramers act as barriers to protein diffusion, while dissociated dimer pairs, single dimers, and missing tetramers do not. Diffusion in the presence of these barriers is shown to be equivalent to bond percolation on the honeycomb lattice. Monte Carlo calculations for this system then yield the relative diffusion constant of a mobile integral protein as a function of the fraction of spectrin tetramers. At high concentrations of spectrin tetramer, long-range diffusion is blocked, but short-range diffusion is still possible. Monte Carlo calculations yield the average distance over which short-range diffusion can occur, as a function of the fraction of spectrin tetramers. Applications to erythrocyte development and hereditary hemolytic anemia are discussed.

Partial deficiency of protein 4.1 in hereditary elliptocytosis

Protein 4.1, an important component of the red cell membrane skeleton, was quantitated relative to protein 3 after sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of membranes isolated from red cells of members of 14 kindreds with hereditary elliptocytosis (HE) who reside in South Africa. A partial deficiency of protein 4.1 (mean 30% reduction) was inherited in autosomal dominant fashion in five white kindreds giving a frequency of 0.36 of HE families studied. Immunoblots of membrane proteins separated by SDS-PAGE and probed with a monoclonal antibody to protein 4.1 did not reveal any proteolytic fragments in the 4.1-deficient subjects that could account for the reduction of this protein. These studies draw attention to the relatively high frequency of this condition as a cause of HE in white subjects in this country.