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J Bolard

Publications and source records attributed to J Bolard.

78 records · Page 5Linked to original sources
PubMed1978

Complexes of cobalt (II) and manganese (II) with adenosine 5'-diphosphate and adenosine 5'-triphosphate. A circular dichroism study.

For studies of interactions between Co2+ and adenosine 5'-diphosphate or adenosine 5'-triphosphate (ADPH4+ and ATPH5+ in strongly acidic medium) visible circular dichroism (d-d transitions of Co2+) and ultraviolet circular dichroism (adenine transitions) have proven to be very sensitive to structural changes. Drastic variation of spectra as a function of pH and concentration enabled us to show the existence of various species, to state their stoichiometry and eventually, their self-association. With ATPH22-, C.D. results are in agreement with recent N.M.R. results. With ligands bearing three negative charges, complexes (1 metal:2 nucleotides)n are formed in which bases of the two nucleotides of the molecule are self-associated. With ADP3-, the visible C.D. spectrum of this complex is intense and hides the spectra of the complexes formed with other protonated species of ADP; this self-associated complex is detected up to a lower limit of 5 X 10(-4) M concentration. With ATPH3-, a complex exhibiting the same characteristics as the one with ADP3- is formed but in about twenty times less amount which explains why it was not detected by potentiometry. With 0.1 M ATP4-, dimeric (or polymeric) complexes, of 1:2 and 1:1 stoichiometry are observed. With 0.01 M ATP4-, 1:1 monomeric and 2:1 dimeric (or polymeric) complexes are detected. The interactions between Mn2+ ions and ADP or ATP have been studied by C.D. on the UV range. The same species as with Co2+ ions have been found but the 1:2 complex formation with ADP3- was shown to occur to a lesser extent and was not observed below a 10(-2) M ADP concentration.

Adenosine Diphosphate↗
PubMedDate not supplied

Membrane effects of the polyene antibiotic amphotericin B and of some of its derivatives on lymphocytes.

Amphotericin B (AmB) exhibits immunomodulating properties in mice. In vitro studies on lymphocytes, in relation with these properties, are reported here with AmB and two of its derivatives: the N-Fructosyl (N-Fru AmB) and the N-thiopropionyl (AmBSH) derivatives. Interactions of these molecules with thymocytes, a sensitive cell type, demonstrated that the extent of binding is not a toxicity parameter. In contrast, membrane fluidity changes have been observed and appeared to be related to toxicity. Experiments performed with normal B lymphocytes have shown that Amphotericin B derivatives were more potent polyclonal B cell activators than the parent compound. To go further in the understanding of these events, we have investigated in a B cell line WEHI 231, the changes in intracellular Ca2+ and membrane potential induced by AmB and AmBSH. The two polyenes were shown to induce membrane depolarization but no intracellular Ca2+ increase.

Amphotericin B↗
PubMedDate not supplied

Delivery systems for antisense oligonucleotides.

In vitro, the efficacy of the antisense approach is strongly increased by systems delivering oligodeoxyribonucleotides (ODNs) to cells. Up to now, most of the developed vectors favor ODN entrance by a mechanism based on endocytosis. Such is the case for particulate systems, including liposomes (cationic or non-cationic), cationic polyelectrolytes, and delivery systems targeted to specific receptors. Under these conditions, endosomal compartments may represent a dead end for ODNs. Current research attempts to develop conditions for escaping from these compartments. A new class of vectors acts by passive permeabilization of the plasma membrane. It includes peptides, streptolysin O, and cationic derivatives of polyene antibiotics. In vivo, the interest of a delivery system, up to now, has appeared limited. Development of vectors insensitive to the presence of serum seems to be a prerequisite for future improvements.

Amphotericin B↗