Spectrin changes occur in erythrocytes from patients with Fanconi's anemia and their parents

Fanconi's anemia (FA) is a clinically and genetically heterogeneous disease which has been hypothesized to be defective in the detoxification of reactive oxygen species. In this work we report the results obtained by morphometric analyses on the red blood cells (RBCs) from FA patients and their parents. We found that a high rate of erythrocytes from both homozygous and heterozygous subjects was significantly altered. RBCs underwent in fact cytoskeleton-dependent modifications, in particular of spectrin molecule, leading to cell shrinking and blebbing. We hypothesize that these changes may be the result of an oxidative imbalance that probably lead to alterations of RBC plasticity- and deformation-associated functions. Moreover, our results also suggest the possibility to identify FA carriers by the existence of RBC abnormalities.     

Serum leptin levels in patients with sideropenic and pernicious anemia: the influence of anemia treatment

Leptin is a 16 kDa protein hormone involved in food intake, energy expenditure regulation and numerous other physiological processes. Recently, leptin has been demonstrated to stimulate hematopoietic stem cells in vitro. The aim of our study was to measure serum leptin and erythropoietin levels in patients with sideropenic (n = 18) and pernicious anemia (n=7) before and during anemia treatment. Blood samples for the blood count, leptin and erythropoietin determinations were obtained by venepunction at the time of the diagnosis of anemia and after partial and complete anemia recovery. The relationships of serum leptin levels to erythropoietin levels and blood count parameters were also studied. No significant differences in serum leptin levels between the groups studied were found. The serum leptin levels in none of groups were modified by treatment of anemia (basal levels, the levels during treatment and after anemia recovery were 13.1+/-14.5 vs 12.8+/-15.6 vs 12.0+/-14.8 ng/ml in patients with sideropenic anemia and 7.8+/-8.5 vs 9.5+/-10.0 vs 8.9+/-6.6 ng/ml in patients with pernicious anemia). The erythropoietin levels were higher at the time of anemia in both groups and decreased significantly after partial or complete recovery. Serum leptin levels in both groups correlated positively with the body mass index. No significant relationships were found between serum leptin levels and erythropoietin values or various parameters of the peripheral blood count. We conclude that serum leptin levels in patients with sideropenic and pernicious anemia positively correlate with the body mass index but are not influenced by the treatment of anemia.     

Detergent-resistant membranes in human erythrocytes and their connection to the membrane-skeleton

In cell membranes, local inhomogeneity in the lateral distribution of lipids and proteins is thought to existin vivo in the form of lipid ‘rafts’, microdomains enriched in cholesterol and sphingolipids, and in specific classes of proteins, that appear to play specialized roles for signal transduction, cell-cell recognition, parasite or virus infection, and vesicular trafficking. These structures are operationally defined as membranes resistant to solubilization by nonionic detergents at 4°C (detergent-resistant membranes, DRMs). This definition appears to be necessary and sufficient, although additional manoeuvres, not always described with sufficient detail, may be needed to ensure isolation of DRMs, like mechanical homogenization, and changes in the pH and/or ionic strength of the solubilization medium. We show here for the human erythrocyte that the different conditions adopted may lead to the isolation of qualitatively and quantitatively different DRM fractions, thus contributing to the complexity of the notion itself of lipid raft. A significant portion of erythrocyte DRMs enriched in reported lipid raft markers, such as flotillin-1, flotillin-2 and GM₁, is anchored to the spectrin membrane-skeleton via electrostatic interactions that can be disrupted by the simultaneous increase in pH and ionic strength of the solubilization medium. An erratum to this article is available at .     

Mechanisms of the structural changes in erythrocyte membranes under the action of a shift in pH]

The effect of pH shifts (5--10) on erythrocyte "ghosts" has been studied using the IR spectroscopy. The process of regulation has been shown to take place within pH 7.15--8 range involving both protein (transition testified by absorption band changes 1520, 1540, 1635, 1645, 1585, 1696, 3305 CM-1) and lipid membrane components testified by absorption band splits 1745, 1470, 1380, 720 AND 1242 cm-1. The transition from a lesser to a higher regulating state of membrane structure happens unevenly, since the above changes take place within the narrow pH 7.15--8 interval, near the homeostase limit, being never observed at pH 5--7.15 or 8--10. It is supposed that the increase in regulation of both protein, phospholipid and lipid membrane fields is of phasic nature which presumably constitutes the basis for pH action mechanism as a regulation factor.     

Mechanisms of age‐related changes in forest production: the influence of physiological and successional changes

Net primary production (NPP) declines as forests age, but the causal role of decreased gross primary production (GPP), or increased autotrophic respiration (R_a) is still a matter of debate. This uncertainty complicates predicted responses to future climate, as higher atmospheric carbon dioxide (CO₂) concentrations may amplify the carbon (C)‐sink in temperate forests if GPP controls the decline in NPP, but increased temperatures may decrease this C‐sink if R_a controls the NPP decline. We quantified NPP in forests dominated by loblolly pine (Pinus taeda) in North Carolina, USA that varied from 14 to 115 years old. We used a sap‐flow approach to quantify summer canopy photosynthesis by pines and later‐successional hardwood trees, and measured wood CO₂ efflux to investigate age‐related changes in pine R_a. Despite increasing production by later‐successional hardwoods, an 80% decline in pine NPP caused ecosystem NPP to decline with age by ～40%. The decline in pine NPP was explained by reduced stomatal conductance and photosynthesis, supporting the hypothesis that increasing hydraulic limitation and declining GPP drove the age‐related decline of NPP in this species. The difference between GPP and NPP indicated that pine R_a also declined with age; this was corroborated by measurements of reduced stem CO₂ efflux with increasing age. These results indicate that C cycling in these successional temperate forests is controlled by C input from GPP, and elements of global change that increase GPP may increase the C‐sink in aging warm‐temperate pine forests.     

Modifications of lipid structure and their influence on mesomorphism in model membranes: the influence of hydrocarbon chains

The influence of hydrocarbon chains on the temperature (TG-LC) of the gel to liquid-crystalline phase transition of model membranes has been investigated over an extensive variety of phosphatidylcholines (PC). The TG-LC is dependent upon the length of the hydrocarbon chains, on whether or not the chains are saturated or have been modified in some way, and on the position of any modification along the chain. For PC having two different acyl chains (heteroacid PC) in the sn-1 and sn-2 positions, the TG-LC is dependent on the chain position and on the inequivalence of chain penetration into the bilayer. Positional isomers of PC have different TG-LC. The first two double bonds introduced in each chain of a PC cause a much greater reduction in TG-LC and in the enthalpy change of the transition than does the subsequent introduction of additional double bonds. Dipolyunsaturated PC have uncooperative (broad) transitions that occur at low temperatures and have small enthalpy changes. While each PC has unique transitional characteristics, there are a number of patterns in the TG-LC which emerge on consideration of all the available data. One such pattern may be useful in predicting TG-LC from analytical data on the composition and positions of acyl chains of various lipids.     

Fluidity of erythrocyte membranes from patients with Duchenne muscular dystrophy: studies in intact erythrocytes and in ghosts

We have studied the alterations of fluidity in intact erythrocytes and in erythrocyte membranes from patients with Duchenne muscular dystrophy. The interest of this study was to comparison directly two types of results; these demonstrate an increase of fluidity in the erythrocytic membranes, no changes are present when the label is incorporated in intact erythrocytes. It might be inferred that hypotonic haemolysis removes components that are more weakly bound in Duchenne membranes, and that exert an immobilizing effect on the membrane lipids.     

Enzymatic modification of the L and M antigens in LK and HK sheep erythrocytes and their membranes

Summary This paper reports on the effect of two hydrolytic enzymes, neuraminidase and trypsin, on the interaction of blood group L-positive low-potassium-type (LK) and blood group M-positive high-potassium-type (HK) sheep red cells with their respective isoimmune antisera. It was found that treatment of LK and HK red cells with neuraminidase did not change the interaction of these cells with their homologous antibodies as measured by K⁺-pump flux, complement-mediated immune hemolysis and absorption of antibody. Similarly, trypsin pretreatment of LK and HK red cells did not interfere with the hemolytic action of anti-L and anti-M antibodies, respectively. In striking contrast, however, it was observed that pretreatment of LK cells with trypsin rendered these cells insensitive to the K⁺-pump stimulating antibody present in the anti-L serum.     

Methods of measuring volume changes in erythrocytes under hypoosmotic stress: a comparison

OBJECTIVE: To compare methods of analyzing changes in red blood cell volume when exposed to osmotic challenge. STUDY DESIGN: The sensitivity of different methods was tested using fish erythrocytes under hypoosmotic stress (80% and 60% saline): hematocrit ratio, Hcto(exp)/ Hcto(ctr); cellular hemoglobin mean concentration; optical density (OD400); water content; surface area estimation; mean corpuscular volume (MCV); and mean cellular hemoglobin (MCH). RESULTS: Cells exposed to both solutions demonstrated a volume increase via hematocrit ratio of 16 +/- 2% and 30 +/- 3% (p < 0.001) when exposed to 80% and 60% saline, respectively. Cellular volume estimation by OD400 revealed a change in volume only at 60% saline (26% increase). Surface area estimation suggested a difference in volume at 60% saline. MCV revealed differences in volume at < 60% saline exposure with a 33% increase and indicated a 19% increase at 80% saline. MCH showed an increase of 48% with exposure to 80% saline. CONCLUSION: The results reveal that Hcto(ctr)/Hcto(exp), MCV, OD400 and MCH yield significant volume changes and that Hcto(ctr)/Hcto(exp) is the most sensitive assay.     

Isolation and characterization of poly-N-acetyllactosaminylceramides accumulated in the erythrocytes of congenital dyserythropoietic anemia type II patients

Congenital dyserythropoietic anemia type II or hereditary erythroblastic polynuclearity with positive acidified serum test (HEMPAS) is a rare genetic disease inherited by a recessive mode. Previous studies on HEMPAS erythrocytes have shown that Band 3 and Band 4.5 glycoproteins were not glycosylated by lactosaminoglycans, while polylactosaminyl carbohydrates are accumulated as glycolipids (P. Scartezzini et al., Br J. Haematol., 51 (1982) 569; M.N. Fukuda et al., Br. J. Haematol., 56 (1984)55). Presently, we have isolated polylactosaminyl lipids from HEMPAS blood cells and analyzed their structures by fast atom bombardment-mass spectrometry (FAB-MS), methylation analysis, endo-beta-galactosidase digestion. The results indicate that polylactosaminyl lipids accumulated in HEMPAS erythrocytes are a species of poly-N-acetyllactosaminylceramides which are also present in normal erythrocytes, but at 7 approximately 9 times lower level. Isolated polylactosaminylceramides exhibit I-, i-, H- and Lex antigenic activities which suggest that the polylactosaminylceramides are derived from both erythrocytes and granulocytes.