Isolation and characterization of a novel glycosyl-phosphatidylinositol-anchored glycoconjugate expressed by developing neurons.

In search of new markers for studying thymic and nervous system ontogeny, we raised rat monoclonal antibodies against glycosyl-phosphatidylinositol-anchored molecules among which larger groupings have been shown to be ectoenzymes and adhesion molecules. Two of these monoclonal antibodies (H193-4 and H194-563, IgG) were found to recognize glycosyl-phosphatidylinositol-anchored glycoconjugates of 28-33 kDa (P31) and 50-70 kDa in developing mouse brain and thymus respectively, when these tissues were analysed by immunoblot experiments. P31 antigen was found to be transiently expressed by neurons in neural primary cultures [Rougon, G., Alterman, L., Dennis, K., Guo, X. J. & Kinnon, K. (1991) Eur. J. Immunol. 21, 1397-1402]. We show in this report that, in developing mouse brain, a maximal expression occurred between embryonic day 17 and post-natal day 5, a period that corresponds to the formation of neuronal networks. P31 antigen was immunopurified and found to possess the following properties: (a) it was soluble in alkaline solvents; (b) it bound to DEAE-cellulose and was eluted by a salt gradient of 0-1 M NaCl; (c) it was sensitive to endoglycosidase F digestion; (d) it was insensitive to heparinase, hyaluronidase, chondroitinase ABC, endo-beta-galactosidase and sialidase treatment; (e) it was labile to mild acid hydrolysis without loss of immunoreactivity; (f) it contained phosphate; (g) it lost its immunoreactivity after treatment with phosphatidylinositol phospholipase C and treatment. These characteristics combine to suggest that P31 is an anionic glycoconjugate sharing similarities with Leishmania donovani lipophosphoglycan and with the heat-stable antigen recognized by J11d antibody on murine hematopo?etic cells. This last hypothesis was further confirmed by the observation that oligonucleotide probes derived from the heat-stable antigen-encoding cDNA detect, in developing brain, a 1.8-kb mRNA species similar in size to that reported for the heat-stable antigen mRNA and following the same developmental expression as P31 antigen.     

Isoform purification of gastric lipases. Towards crystallization.

Several isoforms of rabbit and human gastric lipases have been purified. These isoforms have the same apparent molecular weight (Mr approximately 50,000), but very different isoelectric points. Some of these isoforms were purified: pI 7.2 and 6.5 in the case of rabbit gastric lipase; and pI 7.4 and 7.2 in that of human gastric lipase. All the purified isoforms were found to have the same specific lipase activity (around 1200 units per mg of protein, measured on tributyrin as substrate). The isoforms of dog gastric lipase are more closely related, and could not be separated. Partial enzymatic deglycosylation of human gastric lipase reduced the apparent molecular weight from Mr approximately 50,000 to Mr approximately 43,000 and induced a change in the isoelectrofocusing pattern and the emergence of a new isoform (pI 7.3). It is concluded that the charge heterogeneity of gastric lipases is at least partly due to the glycan moiety of the molecule, which amounts to approximately 14% of the total molecular weight. Several crystallization trials on purified native preparations of rabbit and human gastric lipases were unsuccessful, whereas crystals were obtained from native dog gastric lipase and all the purified isoforms of rabbit and human gastric lipases, some of which were crystallographically characterized.     

Photometric or fluorometric assay of cathepsin B, L and H and papain using substrates with an aminotrifluoromethylcoumarin leaving group

N-trifluoromethylcoumarinylamide derivatives of benzyloxycarbonyl-Arg-Arg, benzyloxycarbonyl-Phe-Arg and Arg are convenient chromogenic and fluorogenic substrates of cathepsin B, L and H, respectively. Benzyloxycarbonyl-Phe-Arg-N-trifluoromethylcoumarinylamide is also a highly sensitive substrate for papain.     

A microfluorometric method for alkaline phosphatase: Application to the various segments of the nephron

A microtechnique has been developed for the measurement of alkaline phosphatase in minute amounts of renal tissue. This microtechnique utilizes the known fluorescent property of 4-methylumbelliferyl phosphate following enzymatic hydrolysis. The reaction is sensitive and reproducible and is inhibited by l-bromotetramisole, a specific alkaline phosphatase inhibitor. The microdetermination of alkaline phosphatase activity in the various segments of the mouse nephron allowed the localization of the enzyme in the glomeruli, and in the proximal convoluted tubule where the activity progressively decreases from the capsule of Bowman to the more distal segments. The enzyme was absent from the pars recta or S3 and from the rest of the nephron. This technique is applicable to very small amounts (0.1 μg of protein) of any tissue containing alkaline phosphatase.     

Nutritional, cardiac and adrenergic changes induced by swimming training in rats (author's transl)

The effects of training were investigated in male Sprague Dawley rats group (N), fed ad libitum, by measuring the weight increase and food intake of the animals, biochemical parameters (myocardial triglycerides and glycogen levels), mechanical and metabolic properties of the heart, and adrenergic reactions to swimming stress. An other group of rats remaining sedentary served as control (T). Conditioned rats had been submitted to a one hour test swim 6 days a week for 9 weeks. Gradually additional weights were fixed to the thorax. At the end of training, the load reached 6% of the body weight. Both groups were sacrified by decapitation at the same time, thirty hours after the last swimming session. The study of mechanical performances and metabolic properties was achieved with isolated working heart preparation. Adrenergic reactions of swimming stress were evaluated from plasma, heart and adrenal catecholamine concentrations.     

Inhibition of lymphocyte transformation: effect of soy bean trypsin inhibitor and synthetic anti-proteases.

Soybean trypsin inhibitor (SBI) was found to inhibit transformation of human lymphocytes induced by mitogens (leucoagglutinin, concanavalin A, NaIO4) or in mixed lymphocyte reaction (MLR). SBI covalently cross-linked to Sepharose beads inhibited the MLR and mitogen stimulation virtually completely. We have confirmed the work of others which showed that the synthetic anti-proteases epilson-aminocaproic acid and tosyl-L-lysyl-chloromethane (TLCK) also inhibited mitogen-induced blastogenesis and we have shown that phenylmethylsulfonylfluride was effective also; all of these agents were found to inhibit the MLR as well. SBI and TLCK were most inhibitory when added along with mitogen or when mixing allogeneic cells in a MLR; significant decrease in inhibition was noted when TLCK was added 1 h after mitogen. These data support the hypothesis that protease action at a cell surface is an essential early event common to all types of lymphocyte transformation.