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Biomedical subjects

M Bagnara

Publications and source records attributed to M Bagnara.

11 recordsLinked to original sources
PubMed1994

Interaction of antiarrhythmic drugs with model membranes.

Several hypotheses link the molecular mechanism of action of the antiarrhythmic drugs (AAD) that belong to class I to nonspecific interactions with phospholipids sited in the neighborhood of the sodium channels in the membrane of the myocard. The interactions of asocainol (ASOC), procainamide (PROC) and quinidine (QUIN) with: (a) multibilayers of dimyristoylphosphatidylcholine (DMPC) and of dimyristoylphosphatidylethanolamine (DMPE), in both a hydrophobic and a hydrophilic medium, and (b) DMPC vesicles, were studied, respectively, by X-ray diffraction and fluorescence spectroscopy. It was found that the three AAD interacted with the lipid bilayers. However, the extension of these interactions depended on the nature and concentration of the lipids and AAD as well as on the medium where the interactions were performed. The different capacity of ASOC and PROC to perturb the bilayer structures, mainly that of DMPC, indicated that the interactions were strongly dependent on the lipophilicity of these drugs. The fact that QUIN did not completely interact in accordance to its lipophilicity suggested that other factors also play a role in these interactions. It is concluded that it may be valid the suggested molecular mechanisms of action of class I AAD involving their interaction with the membrane phospholipids.

Anti-Arrhythmia Agents↗
PubMed1994

Differential sensitivity to cryopreservation of clonogenic progenitor cells and stromal precursors from leukemic and normal bone marrow.

The survival of human leukemic and normal progenitor cells was determined after cryopreservation. Thirteen marrows from patients with acute myeloid leukemia (AML) were studied as fresh and eight as cryopreserved samples. Marrows from five normal donors were studied as both fresh and cryopreserved samples. Although the number of bone marrow mononuclear cells (BMMC) recovered after cryopreservation was always lower than that originally stored, no significant difference was observed between the clonogenic potential of fresh and cryopreserved BMMC from either the leukemic or the normal samples. When grown in long-term bone marrow culture (LTBMC), the cultures initiated with cryopreserved BMMC failed to form a confluent stroma, and the duration of nonadherent and progenitor cell production was significantly lower than that from fresh samples. However, when these cryopreserved samples were recharged onto preformed irradiated stroma, the duration of the cultures improved significantly. We conclude that it is the bone marrow stromal cells rather than the clonogenic progenitors which are sensitive to the effects of cryopreservation. Thus cryopreservation does not appear to influence the activity of AML progenitor cells. Our results also indicate that frozen marrow can be used for LTBMC experiments if cultured on a preformed stromal layer.

Adolescent↗
PubMed1994

Persistence of an activating N-RAS oncogene mutation in clonogenic progenitor cells from an acute myeloid leukaemia patient in remission.

A patient with acute myeloid leukaemia (AML) with an activating N-RAS oncogene mutation was studied in a haemopoietic clonogenic progenitor cell assay. Individual colonies and clusters were analysed by polymerase chain reaction and oligonucleotide hybridization for the original mutation. The mutation was detected in a majority of leukaemic clusters, but also in almost half of the differentiated colonies. After chemotherapy the patient entered clinical remission. However, the mutation could still be detected in the bone marrow. Only differentiated colonies and no leukaemic clusters were grown from the remission bone marrow, but the original mutation was still detectable in almost half of the colonies.

Aged↗
PubMed1994

Haemopoietic progenitor cells are reduced in aplastic anaemia.

We investigated the frequencies of early populations of progenitors in aplastic anaemia (AA) bone marrow, from patients with a range of disease severity, compared with normal. Double-colour immunofluorescent staining for CD34 and CD33 was carried out on bone marrow mononuclear cells (BMMC) and analysed using fluorescence activated cell sorting (FACS). AA CD34+ cells were reduced by 68% compared to normal. In addition, AA CD33+ cells and the three progenitor subsets (CD34+/CD33-, CD34+/CD33+ and CD34-/CD33+) were reduced by 44-80%. Our data lend further support for an early stem cell deficiency in AA.

Adolescent↗
PubMed1992

Transbilayer asymmetry of pyrene mobility in human spherocytic red cell membranes.

The diffusion-dependent formation of pyrene excimers (excited dimers) was studied in normal and spherocytic red cell membranes. Pyrene emission was alternatively quenched in either bilayer half by non radiative energy transfer to haemoglobin. Pyrene excimer to monomer fluorescence intensity ratio, I'/I, was 0.35 +/- 0.03 (S.E.) in washed red blood cells obtained from normal donors (n = 8) and 0.45 + 0.03 (n = 13) in the corresponding isolated, haemoglobin-free resealed membranes (P less than 0.02). In the spherocytic condition the respective values were 0.28 +/- 0.01 (n = 9) and 0.53 +/- 0.03 (n = 9), P less than 0.001. In contrast to the decrease of I'/I in red cells as compared to isolated membranes, being 22% in normal cells and 47% in spherocytic ones, haemoglobin added to the exofacial side of isolated membranes, respectively, reduced I'/I by 18% and 5%. In normal red cell membranes, pyrene mobility appears to be higher in the inner monolayer than in the outer one. In spherocytic membranes our results indicate an enhanced transmembrane asymmetry in lipid monolayer fluidity, probably due to a defect of the membrane protein skeleton organization.

Cholesterol↗
PubMed1992

Interaction of granulocyte-macrophage colony-stimulating factor and interleukin 3 in human long-term bone marrow culture.

Granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 3 (IL-3), or a combination of both growth factors were added weekly to normal human long-term bone marrow cultures (LTBMC). GM-CSF had a greater effect on the total nonadherent cell population than the committed progenitor cells (granulocyte-macrophage colony-forming units, CFUgm), whereas IL-3 had the opposite effect and stimulated the expansion of greater numbers of CFUgm than GM-CSF. The combination of both factors had an additive effect on CFUgm. The longevity of the growth factor-treated cultures was not reduced. These data indicate that IL-3 stimulates an earlier progenitor cell population than GM-CSF and that a combination of the two factors should be more effective in vivo and could be applied to the expansion of bone marrow progenitor cells in culture before bone marrow transplantation.

Bone Marrow↗
PubMed1989

[Therapy and iron supplements with ferritin iron during pregnancy. Randomized prospective study of 458 cases].

A randomized polycentric study was programmed to establish the effects of daily administration of ferritin iron from early pregnancy to puerperium. 254 women with normal iron balance at the beginning of their pregnancy were randomized receiving no supplements or 40 mg iron daily. At the end of pregnancy iron balance was still normal only in one third of the pregnant women of the first group versus two third of the second group. 204 women who were iron-deficient received daily 40 or 120 mg of iron; in this group anemia developed less frequently (13% versus 29%) and iron balance normalized in one subject on four; the great majority of these women remained iron-deficient. Unwanted effects of minimal or mild relevance, and almost always sporadic were observed in 6.5% of cases and with the reduction or withdraw of the treatment in only 1.4% of cases. These results showed that daily administration of ferritin iron during pregnancy is effective and well tolerated; furthermore they suggest that the treatment must be done with at least 60 mg daily in women with normal iron balance and protracted also after the puerperium in iron deficient subjects.

Anemia, Hypochromic↗
PubMedDate not supplied

X-ray and fluorescence studies on phospholipid bilayers. IX. Interactions with pentachlorophenol.

Pentachlorophenol (PCP) is a widely used and highly toxic fungicide. Its toxicity is mainly expressed at the cell membrane level. It is, therefore, of interest to test its ability to alter the lipid bilayer organization. The present study was performed by X-ray diffraction techniques on dimyristoylphosphatidylethanolamine (DMPE) and dimyristoylphosphatidylcholine (DMPC) bilayers and by fluorescence on DMPC liposomes. These two phospholipids are respectively found at the inner and outer monolayers of human erythrocyte membranes. Each type of phospholipid was made to interact with different concentrations of the sodium form of PCP in absence and in presence of water. It was found that PCP significantly affected the structure of both phospholipids, being the damage much higher in DMPC bilayers.

Chlorophenols↗
PubMedDate not supplied

Interaction of the antiarrhythmic drug procainamide with phospholipid bilayers.

Several hypotheses link the molecular mechanism of action of the antiarrhythmic drugs (AAD) that belong to class I to non-specific interactions with phospholipids sited in the neighborhood of sodium channels in the membrane of the myocardium. Procainamide (PROC), one of the least lipophilic drugs of this group, was induced to interact with bilayers of dimyristoylphosphatidylcholine (DMPC) and dimirystoylphosphatidylethanolamine (DMPE), liposomes of DMPC and human erythrocytes. The perturbing effects of PROC upon these systems were respectively determined by X-ray diffraction, fluorescence spectroscopy and scanning electron microscopy. It was found that PROC exerted very little effect upon DMPC and DMPE even at such a high concentration as 10 mM. However, at therapeutical plasma concentrations, PROC induced shape changes in vitro to red cells.

Dimyristoylphosphatidylcholine↗
PubMedDate not supplied

Molecular interactions of quinidine with phospholipid bilayers.

Quinidine (QUIN) is one of the most important and efficient antiarrhythmic drugs (AAD). It belongs to class I, which are the drugs that exert their action at the level of the sodium channels in the membrane of the myocard. Several hypotheses support the idea that the molecular mechanism of action of the AAD is via nonspecific interactions with phospholipids sited in the neighborhood of the channels. In order to probe the validity of these hypotheses, QUIN was made to interact with the phospholipids dimyristoylphosphadidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE). These interactions were performed in a hydrophobic and a hydrophilic medium under a wide range of molar ratios. The resulting products were analyzed by X-ray diffraction. QUIN solutions were also made to interact with DMPC liposomes, which were studied by fluorescent spectroscopy. Finally, human erythrocytes which were incubated with QUIN solutions were observed by scanning electron microscopy. The results of these experiments proved that QUIN indeed interacted with phospholipid bilayers.

Anti-Arrhythmia Agents↗