Ultrastructural localization of rRNA shows defective nuclear export of preribosomes in mutants of the Nup82p complex.

To study the nuclear export of preribosomes, ribosomal RNAs were detected by in situ hybridization using fluorescence and EM, in the yeast Saccharomyces cerevisiae. In wild-type cells, semiquantitative analysis shows that the distributions of pre-40S and pre-60S particles in the nucleolus and the nucleoplasm are distinct, indicating uncoordinated transport of the two subunits within the nucleus. In cells defective for the activity of the GTPase Gsp1p/Ran, ribosomal precursors accumulate in the whole nucleus. This phenotype is reproduced with pre-60S particles in cells defective in pre-rRNA processing, whereas pre-40S particles only accumulate in the nucleolus, suggesting a tight control of the exit of the small subunit from the nucleolus. Examination of nucleoporin mutants reveals that preribosome nuclear export requires the Nup82p-Nup159p-Nsp1p complex. In contrast, mutations in the nucleoporins forming the Nup84p complex yield very mild or no nuclear accumulation of preribosome. Interestingly, domains of Nup159p required for mRNP trafficking are not necessary for preribosome export. Furthermore, the RNA helicase Dbp5p and the protein Gle1p, which interact with Nup159p and are involved in mRNP trafficking, are dispensable for ribosomal transport. Thus, the Nup82p-Nup159p-Nsp1p nucleoporin complex is part of the nuclear export pathways of preribosomes and mRNPs, but with distinct functions in these two processes.

Cell cycle redistribution of U3 snRNA and fibrillarin. Presence in the cytoplasmic nucleolus remnant and in the prenucleolar bodies at telophase.

The distribution of the U3 small nuclear RNA during the cell cycle of the CHO cell line was studied by in situ hybridization using digoxigenin-labelled oligonucleotide probes. The location of the hybrids by immunofluorescence microscopy and at the ultrastructural level was correlated with the distribution of two nucleolar proteins, nucleolin and fibrillarin. The U3 snRNA molecules persist throughout mitosis in close association with the nucleolar remnant. U3 snRNA is present in the prenucleolar bodies (PNBs) and could participate in nucleologenesis in association with several nucleolar proteins such as nucleolin and fibrillarin. The interaction of U3 snRNP with the 5' external spacer of pre-RNA newly synthesized by active NORs is proposed to be the promoting event of nucleologenesis.

Fate of specific nucleolar perichromosomal proteins during mitosis: cellular distribution and association with U3 snoRNA.

In mammalian cells, the nucleoli disintegrate during mitosis and some nucleolar proteins disperse at the periphery of all chromosomes forming a novel class of chromosomal passenger proteins. The nucleolar components which participate in the formation of this perichromosomal layer have been investigated to elucidate the role of these perichromosomal proteins in the assembly and disassembly of the nucleoli. i) Electron microscopy immunolabelling reveals that these proteins are predominantly located in the granular component of the nucleoli during interphase. ii) Immunoprecipitation data suggest that they are distributed at the chromosome periphery in association with U3 small nucleolar RNA (snoRNA). In addition, the distribution of U3 snoRNA visualized by in situ hybridization, is similar to that observed for the perichromosomal proteins. iii) In cells which possess a nucleolar remnant during mitosis, U3 snoRNA and perichromosomal proteins were found both in the perichromosomal layer and in the nucleolar remnant. iv) Some of these proteins are conserved from yeast to man such as fibrillarin and a protein of 52 kDa. v) The location of these proteins observed in yeast by confocal microscopy shows that they are not dispersed during mitosis. Their partition between the two daughter cells is performed by scission of nucleolar structures forming a rod during the budding process. Therefore RNP complexes related to the processing steps of ribosome biogenesis in mammalian cells quit the nucleolus in late G2 and associate with the chromosome periphery until late telophase. They associate in the perichromosomal layer in human and PtK1 cells and both in the perichromosomal layer and the nucleolar remnant in CHO cells.

Location of ribosomal genes in CHO cells; in situ hybridization with a non-isotopic DNA probe on G-banded chromosomes.

A novel in situ hybridization technique using sulfonated probes is described. This non-radioactive approach, which employs chemically modified DNA and immunocytochemical procedures, is compatible with pre-G-banding and allows a rapid localization of the hybridized sequences on chromosomal spreads with a high spatial resolution. Using this technique we have localised the Chinese hamster ribosomal genes in the telomeric region of ten chromosomes, and among them in the subtelomeric q region of the Z5 chromosome. These results are discussed, the genetic markers confirming and locating the origin of Z group chromosomes by rearrangements of Chinese hamster chromosomes.

[Structure-activity relationship of various ephedrine isomers on noradrenaline uptake by the isolated perfused rabbit heart]. / Relation structure-acitivité de différents isomères de l'éphédrine sur la captation de la noradrénaline par le coeur isolé et perfusé de lapin.

(-)Ephedrine, (+) Ephedrine, (-) psi ephedrine and (+) psi ephedrine inhibit both the neuronal and extraneuronal uptakes of noradrenaline in isolated Rabbit heart. (-) ephedrine is the most active isomer for the inhibition of both neuronal and extraneuronal uptakes. The relative inhibition potential of the three other isomers is not the same when applied to one or other uptake.

[Modulator role of prostaglandins (Pg) in adrenergic neurotransmission in carotid sinus]. / Rôle modulateur des prostaglandines (Pg) dans la neurotransmission adrénergique au niveau des sinus carotidiens.

In Rabbit carotid sinus, the presence of sympathetic nerve endings capable of releasing noradrenaline has been demonstrated. The release of NA in response to sympathetic nerve stimulation was decreased by PgE2 and a precursor of Pg (arachidonic acid) but was strongly increased by an inhibitor of Pg biosynthesis (indomethacin). The experiments carried out demonstrated that freshly synthesized Pg acts in the same way as exogenous Pg and suggested that Pg could have a regulating effect on adrenergic neurotransmission in carotid sinus. The role of this regulating mechanism in the physiology of carotid sinus has been discussed.

[Role of alpha and beta adrenoceptors in the regulation of adrenergic neurotransmission in the carotid sinus]. / Rôle des alpha et des bêta adrénocepteurs dans la régulation de la neurotransmission adrénergique au niveau du sinus carotidien.

The experiments carried out showed the presence- in sympathetic nerve endings ot the carotid sinus- of alpha and beta adrenoceptors which by means of respective negative and positive feedback processes, modulated NA release induced by a sympathetic nerve stimulation. Similarly, Pgs acted by means of a negative feedback mechanism to regulated adrenergic neuro-transmission in carotid sinus but they could not be considered as the chemical mediators of either alpha or beta adrenoceptors.

[Action of synthetic substance P (SP) on the respiration, general metabolism and systemic hemodynamics of the anesthetized dog]. / Etude de l'action de la substance P (SP) synthétique sur la respiration et le métabolisme général et sur l'hémodynanique systémique du chien anesthésié

In the anaesthetized Dog, synthetic substance P in one dose (0.5 mug/kg i.v.) induced a quick hypotensive but short-lasting action and a respiratory analeptic activity which only appeared with some delay and lasted more than one hour. The possibility of a rapid metabolization of synthetic SP is discussed.