On the purinergic system in rat duodenum: existence of P1 and P2 receptors on the smooth muscle.

In rat duodenum, in vitro, in the presence of atropine and guanethidine, ATP administration caused a tetrodotoxin-insensitive relaxation followed by a rebound contraction. A similar response was obtained also after electrical field stimulation (EFS) of non-adrenergic, non-cholinergic (NANC) nerves. alpha, beta-methylene-TP and theophylline antagonized the response to ATP, but they failed to affect the noradrenaline- and EFS-induced relaxation. These results suggest that P1 and P2 receptors are present in rat duodenum, but their activation is not responsible for the inhibitor effects due to the NANC nerves.     

Evidence for the mannosylation of a non-histone protein in monkey liver chromatin

Summary Mannose is incorporated in monkey liver chromatin by the means of a nuclear membrane mannosyl-transferase.¹⁴C-labelled chromatin is dissociated either by sulfuric acid or 6 M urea and 0.4 M GuCl. The fractions then enriched in non-histone¹⁴C-labelled proteins are excluded from Ultro-gel AcA 202, their analysis in SDS-polyacrylamide gel electrophoresis shows that radioactivity fits with one major protein band, confirming the presence of at least a non-histone protein labelled with mannose in monkey liver chromatin, with an apparent molecular weight of 13 000.     

In vitro stimulation of human granulopoiesis by purified protein derivative (PPD)

Summary The effect of purified protein derivative (PPD) on human granulopoiesis was studied in an in vitro semisolid culture system of human bone marrow in which PPD was incorporated into the leukocyte feeder layers. We observed that preincubation of the feeder layers with PPD was necessary to induce a significant rise of agar culture colony-forming units (CFU-c) with a maximum of 3 days' preincubation and a dose of 200 g for 10 ⁶ leukocytes. A similar effect was obtained when a conditioned medium from PPD-stimulated leukocytes was used instead of feeder layers. We have found a significant correlation between the skin test response of the leukocyte donors to PPD and the colony-stimulating activity of their leukocytes exposed to PPD: these results suggest that PPD could stimulate human granulopoiesis by an indirect effect on CSF-producing mononuclear cells.     

Differential mitotic rates and patterns of growth in compartments in the Drosophila wing

In the wing disks of Drosophila slowly dividing cells of Minute mutations are progressively eliminated from Minute/Minute⁺ mosaic compartments by a process known as cell competition. From a study of two different Minutes we show here that the intensity of competition is greater in the more extreme Minute with the slowest rate of cell division. The way in which the more rapidly growing Minute⁺ clones grow and overcome the surrounding Minute cells is described and cell competition is shown to be a result of local interactions between slow- and faster-growing cells.     

Structural studies of the apoprotein of the Folch-Pi bovine brain myelin proteolipid : characterization of the CNBr-fragments and of a long C-terminal sequence.

The action of cyanogen bromide on the quite insoluble bovine proteolipid apoprotein allowed the determination of four peptide fragments: two of them constituted a 19 amino acid long C-terminal sequence of the apoprotein. Our results were in favour of the existence of only one subunit presenting a molecular weight closely related to 25,000 for which a schematic representation is given.     

Properties of succinylated wheat-germ agglutinin.

The physicochemical and binding properties of succinylated wheat germ agglutinin are described in comparison with these of unmodified wheat germ agglutinin. Succinylated wheat germ agglutinin is an acidic protein with a pI of 4.0 +/- 0.2 while the native lectin is basic, pI of 8.5. The solubility of succinylated wheat germ agglutinin is about 100 times higher than that of the unmodified lectin at neutral pH. Both lectins are dimeric at pH down to 5, and the dissociation occurs at pH lower than 4.5. The binding of oligosaccharides of N-acetylglucosamine to both lectins is very similar on the basis of fluorescence and phosphorescence studies. The minimal concentration required to agglutinate rabbit red blood cells is about 2 microgram/ml with both lectins and the concentrations of N-acetylglucosamine and di-N-acetylchitobiose which inhibit agglutination are similar with both lectins. The number of succinylated wheat germ agglutinin molecules bound to the surface of mouse thymocytes was ten times lower than that of the unmodified lectin although the apparent binding constant was only slightly different between the two lectins. The dramatic decrease of the apparent number of cell surface receptors upon succinylation of the lectin is discussed on the basis of the decrease of the isoelectric point and of the acidic properties of the cell surface.     

Autoradiographic studies of a glucocorticoid agonist and antagonist: Localization of 3H-corticosterone and 3H-cortexolone in mouse brain

Summary The localization in the mouse brain of corticosterone, the natural glucocorticoid in the mouse, and cortexolone, reported to be a glucocorticoid antagonist, was studied by autoradiography 30 min after in vivo administration of the tritiated compounds.After ³H-corticosterone (³HB) injection, radioactivity was preferentially concentrated in cell nuclei of several structures within the limbic system, and in nuclei of certain neurones of the cerebral cortex and medulla oblongata. This nuclear concentration was abolished after injection of ³H-corticosterone with an excess of unlabelled corticosterone. After ³H-cortexolone (³HS) injection, a diffuse radioactivity was observed throughout the brain. However, a higher concentration of grains was present in the ventral nucleus arcuatus and in the infundibulum. When excess unlabelled cortexolone was administered with ³H-cortexolone this preferential accumulation of grains was abolished.The accumulation of ³H-cortexolone in the medial basal hypothalamic region suggests that cortexolone concentrates preferentially in dexamethasone (DM) target regions, and in addition the autoradiographic results show that the cortexolone-receptor complex does not accumulate in the cell nucleus.

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Résumé La localisation au niveau du cerveau de souris de la corticostérone, qui est le glucocorticoide naturel chez la souris, et de la cortexolone, démontrée comme étant un antagoniste des glucocorticoides, est étudiée par autoradiographie 30 min après injection in vivo des composés tritiés.Après injection de ³H-corticosterone (³HB), la radioactivité se concentre préférentiellement dans des noyaux cellulaires de plusieurs structures du système limbique et dans les noyaux de certains neurones du cortex cérébral et du bulbe rachidien. Cette concentration nucléaire est abolie après injection de ³H-corticostérone en présence d'un excès de corticostérone non radioactive. Après injection de ³H-cortexolone (³HS), une distribution diffuse de la radioactivité est observée dans tout le cerveau, cependant, une concentration plus élevée de grains d'argent est présente dans la partie ventrale du nucleus arcuatus et dans l'infundibulum. Après injection de ³H-cortexolone en présence d'un excès de cortexolone non radioactive, cette accumulation préférentielle des grains est abolie.L'accumulation de la ³H-cortexolone dans la région hypothalamique suggère que la cortexolone se concentre préférentiellement dans la région cérébrale qui contient les sites de liaison de la dexaméthasone et de plus, les résultats autoradiographiques montrent que le complexe cortexolone-récepteur ne s'accumule pas dans le noyau cellulaire.

     

Autoradiographic localization of 3H-glucocorticoids and 3H-cortexolone in mouse pituitary

Summary Autoradiograms of mouse pituitaries were prepared 30 min after injection of ³H-dexamethasone (³HDM), ³H-corticosterone (³HB) and ³H cortexolone (³HS) either alone or in the presence of competing unlabelled steroids. ³H-dexamethasone accumulated in cell nuclei of both the pars distalis and the pars nervosa but not in those of the pars intermedia. This preferential accumulation (nuclear/cytoplasmic grain density, 41) was abolished by the concurrent administration of excess dexamethasone. ³H-corticosterone, to a much less marked extent than ³H-dexamethasone, accumulated in cell nuclei of the pars distalis but not in those of the pars intermedia and the pars nervosa. Excess unlabelled corticosterone diminished nuclear grain density in the pars distalis. After ³H-cortexolone injection, preferential nuclear uptake was not observed. In a second series of experiments, excess dexamethasone (10 x, 100 x), corticosterone (100 x, 300 x) and cortexolone (100 x, 300 x) administered with ³H-dexamethasone were without effect on cytoplasmic grain density but totally abolished preferential nuclear accumulation. Parallel biochemical studies on kidney cytoplasmic preparations from the same animals showed no differences in total cytoplasmic radioactivity between treatments but marked differences in cytoplasmic bound ³H-dexamethasone. The results demonstrate: i) that dexamethasone binds specifically to cell nuclei of the pars distalis and the pars nervosa and that this nuclear concentration is abolished by competing corticosterone and cortexolone as well as dexamethasone; ii) that corticosterone localizes in cell nuclei of the pars distalis but much less markedly than dexamethasone; iii) that cortexolone fullfils the criteria of a glucocorticoid antagonist at the pituitary cell level.

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Résumé La localisation au niveau de l'hypophyse de souris de la ³H-dexaméthasone (³HDM), de la ³H-corticostérone (³HB) et de la ³H-cortexolone (³HS) est étudiée par autoradiographie 30 min après l'injection des composés tritiés seuls ou en présence de stéroides compétiteurs non radioactifs. La ³H-dexaméthasone s'accumule dans des noyaux cellulaires de la pars distalis et de la pars nervosa mais pas dans des noyaux de la pars intermédia. Cette accumulation préférentielle (densité des grains d'argent nucléaire/cytoplasmique: 4/1) est abolie par l'injection de ³H-dexaméthasone en présence de dexaméthasone non radioactive. La ³H-corticostérone se concentre avec une intensité beaucoup plus faible que la ³H-dexaméthasone uniquement dans certains noyaux de la pars distalis. Un excès de corticostérone non radioactive diminue la densité nucléaire des grains d'argent des cellules de la pars distalis. Après injection de ³H-cortexolone, aucune accumulation préférentielle de grains d'argent n'est observée dans les noyaux cellulaires. Dans une seconde série d'expériences, la ³H-dexaméthasone est injectée soit en présence d'excès de dexaméthasone (10x, 100x) ou de corticostérone (100x, 300x) ou de cortexolone (100 x, 300 x). Dans ces conditions, la densité cytoplasmique des grains d'argent n'est pas différente de celle observée après injection de ³H-dexaméthasone seule mais l'accumulation préférentielle de la radioactivité dans les noyaux cellulaires est abolie. Des études biochimiques parallèles effectuées sur des préparations cytoplasmiques de rein des mêmes animaux montrent que la radioactivité cytoplasmique totale ne varie pas tandis que la liaison cytoplasmique de la ³H-dexaméthasone diffère suivant les traitements. Ces résultats montrent i) que la dexaméthasone se fixe spécifiquement dans des noyaux cellulaires de la pars distalis et de la pars nervosa et que cette fixation nucléaire est abolie aussi bien par des excés de corticostérone ou de cortexolone que par des excès de dexaméthasone, ii) que la corticostérone se localise dans des noyaux cellulaires de la pars distalis mais beaucoup moins intensément que la dexaméthasone, iii) que la cortexolone se comporte comme un antagoniste des glucocorticoides au niveau de la cellule hypophysaire.