Cinétique de cristallisation de la gélatine en solution aqueuse. Influence des différents composés moléculaires

The gelation kinetics of gelatin of various molecular structures and also of different molecular components is studied by polarimetry. The gelation phenomenon can be analyzed as a conventional crystallization process assuming predetermined primary nucleation and unidirectional growth. The study of gelation kinetics of the different fractions displayed important alterations induced by the manufacturing process on the molecular structure and on the number of nucleation sites.     

Diagnosis of variants of hyperphenylalaninemia by determination of pterins in urine

Assessment of urinary pterins is proposed as a rapid method for recognition of the variants of hyperphenylalaninemia. This is achieved by means of oxidation of pterins by iodine in acidic and alkaline solutions and then by high performance liquid chromatography on a cation-exchange column with fluorimetric detection.

In biopterin-synthetase deficiency, only neopterin accumulated; in dihydropteridine-reductase (DHPR) deficiency and in phenylketonuria, high levels of pterins are found, but BH₄ levels, absent in the former and high in the latter, allow a differential diagnosis. Phenylalanine loads in the controls also lead to increased elimination of pterins, but with a pattern different from that found in phenylketonuria.

This method can be used before dietary treatment and thus can be proposed for all newly detected hyperphenylalaninemic babies.     

Evidence for Imbalanced Furosemide-Sensitive Na+, K+ Cotransport in Hereditary Stomatocytosis

The red cells from 5 related patients with hereditary stomatocytosis were investigated. Maximal rate constant of Na⁺ passive permeability was increased while that of K⁺ passive permeability was nearly normal. Ouabain-sensitive Na⁺ efflux was elevated. The Na⁺ component of furosemide-sensitive Na⁺, K⁺ cotransport was also increased. However, its K⁺ component, determined in 2 patients, remained within normal limits, thus departing from the strict 1:1 stoichiometry of the Na⁺, K⁺ cotransport system. Yet, intracellular Na⁺ and K⁺ concentrations displayed limited and inconstant changes. A variety of abnormally-shaped cells, including stomatocytes, were observed in scanning electron micrographs. Upon differential centrifugation, reticulocytes usually concentrated in the most dense region of the gradient. Red cell deformability, as studied by ektacytometry, was reduced. Membrane phosphatidylcholines and sphingomyelins were increased and decreased, respectively, whereas fatty acid distribution was unchanged. Membrane microviscosity was normal.     

Evidence for electrophilic properties of N 2 -methyl-9-hydroxy ellipticinium acetate (Celiptium) from human biliary metabolites

Summary The human biliary metabolism of the antitumor agent N ² -methyl-9-hydroxyellipticinium acetate is described. Three major compounds have been identified by high-performance liquid chromatography and comparison with synthetic reference derivatives: the unchanged drug, the O-glucuronide conjugate and the cysteinyl-ellipticinium adduct. The latter one is the expected detoxification compound of an intermediate electrophilic quinone-imine derivative generated in vivo. This result provides a further evidence that hydroxylated forms of ellipticine derivatives might be activated by a biooxidation route.Part of this work was done by J. B. as part of his preparation for the degree of Doctor of Medicine in the Centre Claudius Regaud     

ISOLATION OF A TRYPSIN-LIKE ENZYME FROM. STREPTOMYCES PAROMOMYCINUS (PAROMOTRYPSIN) BY AFFINITY ADSORPTION THROUGH KUNITZ INHIBITOR-SEPHAROSE

A trypsin-like enzyme has been isolated from the filtrate of a Streptomyces rimosus forma paromomycinus culture. Purification involves acetone fractionated precipitation, ultrafiltration on a Diaflo UM 10 membrane and affinity adsorption on to Kunitz pancreatic trypsin inhibitor linked to Sepharose. The trypsin-like enzyme (paromotrypsin) appears homogeneous by zone electrophoresis on gelatinized cellulose acetate. Specific activity toward Tos-Arg-OMe, calculated from amino acid analysis, is about 220 u mg^-1. The overall yield in activity is about 30%. The molecular weight of the trypsin-like enzyme, determined by gel filtration, is around 22,000–25,000 daltons. Electrophoretic migration on cellulose acetate strips indicates an isoelectric point around 8. Amino acid composition has been determined; the protein comprises about 210 residues on the basis of a single histidine residue per molecule. Paromotrypsin is unstable in acidic medium and is not stabilized by calcium ions. Enzymic activity towards Bz-Arg-OEt is not increased by the addition of calcium ion in contrast to the activating effect observed on bovine trypsin. Paromotrypsin is inhibited by TLCK and NPGB; it interacts with naturally occurring bovine trypsin inhibitors such as soya bean and Kunitz pancreatic inhibitors, but not with chicken ovomucoid. Proteolytic specificity, examined by hydrolysis of oxidized Kunitz pancreatic inhibitor and characterization of resulting peptides, seems similar to that of bovine trypsin.     

Consequences of blocking the nerve with a local anaesthetic on the evolution of multiinnervation at the regenerating neuromuscular junction of the rat

A transient multiinnervation is observed in adult rats during reinnervation of the soleus muscle. Chronic blockage of the sciatic nerve with a cuff of the local anaesthetic lidocaine during reinnervation increases the number of multiply innervated muscle fibres. This result indicates that the selective elimination of redundant nerve terminals is regulated by the activity of the innervated muscle.