Effects on red blood cell choline transport induced by different sulfhydryl compounds.

The uptake of choline was studied in different types of paroxysmal nocturnal hemoglobinuria (PNH)-like RBC obtained from normal human erythrocytes by the action of different sulfhydryl compounds. The results were compared with the uptake of choline in true PNH cells and in normal reticulocytes. The PNH-like cells which better mimicked true PNH were those prepared using acetylcysteine. Indeed these erythrocytes displayed a capacity to incorporate choline against a concentration gradient exactly as PNH cells exposed to either acetylcholine or choline. The uptake of choline by by the other PNH-like cells differed from that of PNH erythrocytes in several ways. The results suggest that every sulfhydryl compound induces a different damage on RBC membrane.

[Ataxia telangiectasia. Description of a case with multiple cerebral hemorrhages and liver cirrhosis]. / Atassia-teleangiectasia. Descrizione di un caso con emorragie cerebrali multiple e cirrosi epatica.

Clinical history and morbid anatomy findings of a new case of ataxia-telangiectasia are reported. A 26 years old man, with overt signs of the disease since the age of 8, died for decompensated cirrhosis; in the last year he suffered for cerebral haemorrhage; post-mortem examination showed venous angiectasias in cerebral white matter that caused two macroscopical areas of haemorrhagic infarction and multiple pin-pointed haemorrhages. We suggest that longer survival of patients with A.T., due to better management of infectious complications, permits the appearance of vascular abnormality not only in skin and mucosae, but also in deep organs, generally protected from environmental damages.

Alternative pathway for complement activation triggered by human liver plasma membranes.

Liver plasma membranes (LPM) prepared from normal hepatocytes by centrifugation in sucrose discontinuous gradient, are capable of haemolysing PNH-like cells in the presence of complement or complement plus EGTA or MG2+ ions. In contrast, EDTA or Ca2+ ions inhibit the lysis. The total complement lytic activity is reduced by some 40% when fresh serum is incubated with LPM, whereas the total amount of C4 remains constant. The cross-immunoelectrophoresis studies of fresh serum incubated with LPM demonstrate the appearance of C3 breakdown products, which suggests the activation of the alternative complement pathway. In contrast, the sucrose test, which proceeds mainly through the classical complement pathway, is inhibited by LPM. The possible role of complement in liver disease is discussed.

In vitro production of PNH-like red blood cells by 2-mercaptopropionylglycine.

2-Mercaptopropionylglycine (2-MPG) transformed normal red blood cells (RBCs) into paroxysmal nocturnal haemoglobinuria (PNH)-like RBCs in vitro, depending on the concentration, pH and time of incubation. The incorporation of radioactive choline in the presence of acetylcholine was reduced, as in RBCs treated with aminoethylisothiouronium salt (AET). In contrast, the uptake in the presence of choline differed when the RBCs were incubated with the two compounds, being reduced in AET-treated RBCs and increased in 2-MPG-treated ones. As true PNH RBCs incorporated to a higher extent the radioactivity in the presence of both acetylcholine and choline, 2-MPG-treated RBCs seemed to resemble the PNH RBCs better than the AET-treated ones. Present results suggest the possibility of modifying selectively the activity of acetylcholinesterase and the transport of choline through the cell membrane.

Partial characterization of cytosol and membrane-bound protein kinases in hereditary spherocytosis erythrocytes.

The protein kinase activity located in the cytosol of hereditary spherocytosis erythrocytes is due to multiple forms which can be resolved by Sepharose 6B filtration at high ionic strength into two fractions phosphorylating the whole casein on different sites. The membrane-bound protein kinases, solubilized by 0.7 M NaCl, display an elution volume from Sepharose column and a phosphorylation behaviour towards casein quite similar to those of the more retarded fraction of hemolysate. When compared with the multiple protein kinase forms from normal human erythrocytes, no significant difference has been found.

Activation of complement by stroma from normal and paroxysmal nocturnal haemoglobinuria red cells.

Stroma from normal, AET-treated and PNH red cells and their KC1-extracts (partially purified on Sephadex G-200) are able to trigger the activation of the alternative complement pathway. This fact has been demonstrated by: 1 - the lysis of PNH cells incubated in serum treated with stroma from normal or PHN-RBC or with their extracts; the addition of Mg2+ or Ca2+ or of their chelators (EDTA, EGTA) to the extract-treated serum enhances or abolishes the lysis 2 - the reduction of complement acitvity in fresh serum incubated for 60' with PNH-extract 3 - the appearance of C3 breakdown products in serum incubated with PNH-extract, demonstrated by crossed immunoelectrophoresis. In contrast, the same stroma (or extract) inhibits the sucrose lysis test, in which the lysis takes place through the classical complement pathway. No differences on the complement activation were observed between PNH and normal RBC stroma and between their chromatographic extracts. These findings may suggest the possible role of diurnal variation of Mg2+ and Ca2+ concentration in precipitating haemolytic attacks and the possibility that small amount of circulating red cell stroma might maintain the haemolysis on PNH RBC.

Endogenous phosphorylation of membrane proteins in normal and in hereditary spherocytosis erythrocytes.

The phosphorylation state of the proteins in hereditary spherocytosis erythrocyte membranes, incubated in the presence of [gamma-32P]ATP, appears to be different from that in normal ones. This is indicated by the finding that in the two types of erythrocyte membranes the ratios between the 32P-labeling of their phosphorylserine and phosphorylthreonine residues were different.

Increased potassium permeability by calcium in hypochromic red blood cells.

The red blood cell (RBC) content of Na+ and K+ were measured both on fresh cells from normal, heterozygous beta-thalassaemic and iron-deficiency-anaemic subjects, and on the same cells incubated for 24 h, at 37 degrees C, either in presence or in absence of Calcium (Ca2+). Ca2+ did not increase membrane permeability to Na+, but increased the K+ loss, both from normal cells and to a greater degree much more from hypochromic cells. Glucose largely prevented the K+ loss from hypochromic cells incubated either in absence or in presence of Ca2+, probably maintaining an adequate level of ATP during the incubation. EDTA only partially decreased the permeability to K+ in hypochromic cells incubated for 24 h at 37 degrees C, possibly removing Ca2+ bound to the cell membrane. The results suggest that Ca2+ does not represent the primary cause of K+ leak in hypochromic cells, but it is able to enhance a pre-existing peculiar abnormality of the cell membrane when the ATP level slows down.

Increased potassium permeability induced in vitro by menadione in normal human red cells.

Normal red blood cells, preincubated for 75 min with 1.15 mM menadione sodium bisulfite lose potassium and water on subsequent incubation at 37 degrees C for 24 h without menadione. The potassium loss is increased by addition of calcium and prevented by addition of glucose. Since normal red cells treated with menadione behave like untreated hypochromic cells, both from beta-thalassaemia or iron deficiency anaemia in respect to membrane permeability to potassium, it may be supposed that menadione induces in normal red cells an abnormality similar to that naturally occurring in hypochromic cells.