Survival and senescence of human young red cells in vitro.

Background: A number of experimental investigations in vivo suggest that in humans a decrease of circulating erythrocyte number ensues whenever erythropoietin (EPO) plasma level decreases. Since the process seems to selectively eliminate young red cells (neocytes), it has been named neocytolysis. The experimental models in vivo have revealed and documented multiple forms of neocytolysis but have not fully elucidated the specificity of the target red cells and the relation with EPO level changes.

Neocytolysis: none, one or many? A reappraisal and future perspectives.

Neocytolysis is the hypothesis formulated to explain experimental evidence of selective lysis of young red blood cells (RBCs) (neocytes) associated with decreased plasma levels of erythropoietin (EPO). In humans, it appears to take place whenever a fast RBC mass reduction is required, i.e.

Freely turning over palmitate in erythrocyte membrane proteins is not responsible for the anchoring of lipid rafts to the spectrin skeleton: a study with bio-orthogonal chemical probes.

Erythrocyte lipid rafts are anchored to the underlying spectrin membrane skeleton [A. Ciana, C. Achilli, C.

Expression of fetal hemoglobin in adult humans exposed to high altitude hypoxia.

In humans, acute erythroid expansion can lead to maturation of red blood cell (RBC) precursors containing fetal hemoglobin (F red cells). This can occur in patients after recovery from bone marrow transplantation, or in individuals affected by sickle cell or thalassemic syndromes. An accelerated erythroid lineage expansion is also a hallmark of the adaptive response to high altitude hypoxia.

Application of gelatin zymography for evaluating low levels of contaminating neutrophils in red blood cell samples.

Supposedly "homogeneous" red blood cell (RBC) samples are commonly obtained by "washing" whole blood free of plasma, platelets, and white cells with physiological solutions, a procedure that does not result, however, in sufficient removal of polymorphonuclear neutrophils (PMNs), leading to possible artifactual results. Pure RBC samples can be obtained only by leukodepletion procedures. Proposed here is a version of gelatin zymography adapted to detect matrix metalloproteinase 9 (MMP-9), selectively expressed by PMNs, in heterogeneous mixtures of RBCs and PMNs that can reveal contamination at levels as low as 1 PMN/10⁶ RBCs.

Fragmentation of human erythrocyte actin following exposure to hypoxia.

In a comparative study on erythrocytes (RBCs) drawn from mountaineers before and after a high-altitude stay, we observed that upon returning to sea level, their RBCs displayed a senescent-like phenotype as indicated by their density and the partial loss of membrane proteins which are shed by ageing RBCs. The aim of this study was to investigate possible changes in the membrane skeleton of these RBCs and to compare them with pathological RBCs. We analysed the proteins of RBC ghosts obtained from our subjects before and after returning to sea level by two-dimensional electrophoresis and mass spectrometry.

Red blood cell senescence and neocytolysis in humans after high altitude acclimatization.

A selective lysis of relatively young erythrocytes (neocytolysis), together with a decrease of erythropoietin (EPO) production, has been described in polycythemic, high altitude acclimatized climbers, after descent to sea level, and in astronauts, soon after exposure to weightlessness (Alfrey CP, Rice L, Udden MM, Driscoll TB. Neocytolysis may represent the physiological down-regulation of red-cell mass. Lancet 349 (1997) 1389-90).

Activation of human T lymphocytes under conditions similar to those that occur during exposure to microgravity: a proteomics study.

A number of experiments, conducted under microgravity conditions, i.e. in space shuttle biolaboratories or in ground based systems simulating the conditions occurring in microgravity, show that in hypogravity, in vitro human lymphocyte activation is severely impaired.

BMAP-28, an antibiotic peptide of innate immunity, induces cell death through opening of the mitochondrial permeability transition pore.

BMAP-28, a bovine antimicrobial peptide of the cathelicidin family, induces membrane permeabilization and death in human tumor cell lines and in activated, but not resting, human lymphocytes. In addition, we found that BMAP-28 causes depolarization of the inner mitochondrial membrane in single cells and in isolated mitochondria. The effect of the peptide was synergistic with that of Ca(2+) and inhibited by cyclosporine, suggesting that depolarization depends on opening of the mitochondrial permeability transition pore.

Antigene effect in K562 cells of a PEG-conjugated triplex-forming oligonucleotide targeted to the bcr/abl oncogene.

Triplex-forming oligonucleotides are able to modulate gene expression by site-specific binding to genomic DNA. Their use as therapeutic agents is limited by inefficient cellular uptake, scarce nuclear internalization, and oligonucleotide self-aggregation. In this study, we demonstrate that a 13-mer AG motif oligonucleotide covalently linked to a high-molecular mass (9000 Da) polyethylene glycol (PEG ODN(13)) exhibits uptake and biological properties that are superior to those of the nonconjugated isosequence analogue (free ODN(13)).