Biomedical subjects
Publications and source records attributed to C Pichon.
Evidence for an azafulvene intermediate in the enzymatic formation of Uroporphyrinogen III has been obtained. Using conditions to slow down the enzyme activity (high pH, low temperature), the transient species was trapped with ammonium ions as aminomethylbilane and with sodium borohydride as methylbilane, and observed by 13C-NMR.
A novel hydroxymethylbilane analog, 19-Br-HMB (11), has been synthesized. Its activity with the enzyme Uro'gen III synthase shows competitive inhibition.
The extracellular and intracellular domains of the human thyrotropin receptor were expressed in Escherichia coli and the proteins were used to produce monoclonal anti-receptor antibodies. Immunoblot studies and immunoaffinity purification showed that the receptor is composed of two subunits linked by disulfide bridges and probably derived by proteolytic cleavage of a single 90-kDa precursor. The extracellular alpha subunit (hormone binding) had an apparent molecular mass of 53 kDa (35 kDa after deglycosylation with N-glycosidase F). The membrane-spanning beta subunit seemed heterogeneous and had an apparent molecular mass of 33-42 kDa. Human thyroid membranes contained a 2.5- to 3-fold excess of beta subunits over alpha subunits. Immunocytochemistry showed the presence of both subunits in all the follicular thyroid cells, and both subunits were restricted to the basolateral region of the cell membrane.
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A 1H NMR study of urocanic acid dissolved in water/dimethyl sulfoxide mixtures together with potentiometric determinations of its two successive acidities in the same solutions reveal that a proton is transferred from the imidazolium ring to the carboxylate group when the amount of dimethyl sulfoxide is increased. An analysis of the potentiometric data by means of the classical Hammett linear relationship allowed the four microscopic acidity constants to be determined. At 20 degrees C, there are equal fractions of the tautomeric species, i.e. urocanic acid (AH0) and its zwitterion (AH+-) in the mixture containing 34% dimethyl sulfoxide by weight (congruent to 0.1 in mole fraction), while 50% dimethyl sulfoxide by weight (congruent to 0.2 in mole fraction) is necessary to completely bias the equilibrium: AH+- in equilibrium AH0 toward the molecular form AH0.
A case of mandibular osteitis is reported, showing histologically, an important pseudo peitheliomatous hyperplasia. A possible histological explanation of this observation is that the inflammatory process may be responsible for an odontogenic cell rest (of Malassez) hyperplasia derived from the dental lamina.
BACKGROUND: We recently designed a cationic polymer called histidylated polylysine made of polylysine partially substituted with histidyl residues which become protonated at slightly acidic pH. This polymer is thought to induce the leakage of acidic vesicles containing plasmid/histidylated polylysine complexes. METHODS: and results Here, we have analyzed the ability of histidylated polylysine to transfer reporter or CFTR genes into immortalized cystic fibrosis airway surface epithelial cells (sigmaCFTE29o- cells) and airway gland serous cells (CF-KM4 cells) which are both important targets for cystic fibrosis gene therapy. The luciferase reporter gene expression measured after gene transfer with histidylated polylysine into both cell lines was quite high and similar to that obtained with commercially available vectors. In addition, the level of expression was not dependent on the presence of a membrane disrupting agent such as chloroquine. Histidylated complexes were present in slightly acidic non-lysosomal cellular compartments as shown by a cytological approach using biotinylated plasmid, lysosome-specific antibodies and confocal microscopy. Histidylated complexes appeared to be of small size when prepared at low ionic strength and formed aggregates upon increasing the ionic strength. However, aggregate formation was prevented by the addition of 10% fetal bovine serum. Gene transfer efficiency varied with the size of the complexes and decreased when small particles were used. CONCLUSIONS: These results suggest that histidylated polylysine may be an efficient non-viral vector for gene transfer into cystic fibrosis airway surface epithelial cells and airway gland serous cells.