Functional and molecular characterization of the conserved Arabidopsis PUMILIO protein,APUM9

Plant Molecular Biology - Here we demonstrate that the APUM9 RNA-binding protein and its co-factors play a role in mRNA destabilization and how this activity might regulate early plant development....     

A predominant idiotype on rabbit anti-VH a1 allotype antibodies: sharing by both major and minor VH subgroups

In every rabbit examined, greater than or equal to 80% of antibodies directed against the VH allotypic marker, a1, bears a predominant idiotype (IdX-a1). The IdX-a1 marker is site-associated and expressed on H chains, but not L chains, of anti-a1 antibody. Experiments using rabbits suppressed for the VH a subgroup demonstrated that IdX-a1 can be associated with both major (a+) and minor (a-) VH subgroup gene products and that a1 rabbits contain IdX-a1 within their genetic repertoire. The genetic and regulatory implications of our results are discussed.     

C-Glycosylflavonoids. The chemistry of aspalathin

1. The isolation of aspalathin, the principal phenolic constituent in the leaves of Aspalathus linearis, is described and its properties are discussed. 2. The compound has been identified as 3'-C-beta-d-glucopyranosyl-2',3,4,4',6'-pentahydroxydihydrochalcone by the preparation and analysis of various derivatives, by photochemical oxidation to 2,3-dihydroiso-orientin and by nuclear-magnetic-resonance studies.     

Ultrastructure of Weddellomyces epicallopisma (Dothideales, Dacampiaceae, Ascomycota), especially of its ascospores]

An ultrastructural study of Weddellomyces epicallopisma (ascomata wall, asci, ascospores and vegetative hyphae), the first done on the family Dacampiaceae, confirms most of the observations made in light microscopy. Moreover it shows that ascospores are provided with an endospore (not visible in light microscope) and that the structure of the ascospore septum is more complex. The similarity of the wall structure between the ascospore and the hyphoid appendages, developed on the upper part of the ascoma, is emphasized.     

Expression and subcellular localization of a 35-kDa carbonic anhydrase IV in a human pancreatic ductal cell line (Capan-1).

The high intraluminal concentrations of HCO(3)(-) in the human pancreatic ducts have suggested the existence of a membrane protein supplying the Cl(-)/HCO(3)(-) exchanger. Membrane-bound carbonic anhydrase IV (CA IV) is one of the potential candidates for this protein. The difficulties in isolating human pancreatic ducts have led the authors to study the molecular mechanisms of HCO(3)(-) secretion in cancerous cell lines. In this work, we have characterized the CA IV expressed in Capan-1 cells. A 35-kDa CA IV was detected in cell homogenates and purified plasma membranes. Treatment of purified plasma membranes with phosphatidylinositol-phospholipase-C indicated that this CA IV was not anchored by a glycosylphosphatidylinositol (GPI). In contrast, its detection on purified plasma membranes by an antibody specifically directed against the carboxyl terminus of human immature GPI-anchored CA IV indicated that it was anchored by a C-terminal hydrophobic segment. Immunoelectron microscopy and double-labeling immunofluorescence revealed that this CA IV was present on apical plasma membranes, and in the rough endoplasmic reticulum, the endoplasmic reticulum-Golgi intermediate compartment, the Golgi complex, and secretory granules, suggesting its transport via the classical biosynthesis/secretory pathway. The expression in Capan-1 cells of a 35-kDa CA IV anchored in the apical plasma membrane through a hydrophobic segment, as is the case in the healthy human pancreas, should make the study of its role in pancreatic HCO(3)(-) secretion easier.     

Circumferential analysis of digitalized gamma angiocardiography by assessment of regional left ventricular contraction

After acquisition of a digital equilibrium gamma-angiocardiographie, circumferential analysis of end-diastolic and end-systolic frames gives 120 points diastolic and systolic curves. Their difference represents systolic volume and leads to regional left ventricular ejection fraction assessment at the considered radius level. The circumferential analysis evolute gives the regional left ventricular ejection fraction representative curves which allows especially differential diagnosis between left ventricular akinesia and dyskinesia.     

Enhanced release and synthesis of lipoprotein lipase in rat heart cell cultures exposed to high concentrations of Hepes

While attempting to optimize conditions for synthesis of lipoprotein lipase by cultured heart cells, we encountered an unexpected rise in enzyme activity when media were supplemented inadvertently with 100 mM Hepes buffer (4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid). This finding was further investigated and optimal results were obtained at pH 7.0-7.2. The increase in lipoprotein lipase activity was time dependent; after 3-6 h there was a rise in medium activity but cellular activity increased only after 24 h. The increased enzyme activity was defined as lipoprotein lipase by inhibition with antiserum to rat adipose tissue lipoprotein lipase. A 72-h exposure to Hepes resulted in a 30% increase in the incorporation of [35S]methionine into cellular proteins and a 2-fold increase into heparin-releasable proteins. Using heparin Sepharose chromatography and stepwise elution, a lipoprotein lipase enriched fraction was recovered with 2 M NaCl. The amount of [35S]methionine and [3H]galactose incorporated into protein of this fraction derived from Hepes-treated cells was 2-6-fold that of controls. A 4-fold increase in cellular lipoprotein lipase mass in Hepes-treated cells was shown by immunoblotting. Results obtained with Hepes-conditioned medium suggest the presence of cell-derived compounds that enhance release and subsequent synthesis of lipoprotein lipase. The effect of Hepes-conditioned medium on lipoprotein lipase resembled to some extent that of the addition of heparin. Therefore, it appears that when Hepes is first added to the culture medium, it might promote a release of heparan sulfate or related compounds, possibly by virtue of its negatively charged sulfonic acid residue. The accumulated heparan sulfate could then promote a sustained release of lipoprotein lipase into the culture medium which in turn leads to increased enzyme synthesis.     

Calcium requirement of phytochrome-mediated fern-spore germination: No direct phytochrome-calcium interaction in the phytochrome-initiated transduction chain

Phytochrome-mediated germination of fern spores of Dryopteris paleacea Sw. was initiated by a saturating red-light (R) irradiation after 20 h of imbibition. For its realization external Ca²⁺ was required, with a threshold at a submicromolar concentration, and an optimum was reached around 10^-4 M. At concentrations 10^-1 M only a reduced response was obtained, based probably on an unspecific osmotic or ionic effect. The germination response was inhibited by La³⁺, an antagonist of Ca²⁺. From these results it is concluded that Ca²⁺ influx from the medium into the spores may be an important event in phytochrome-mediated germination. In the absence of Ca²⁺ the R-stimulated system remained capable of responding to Ca²⁺, added as late as 40 h after R. Moreover, Ca²⁺ was effective even if added after the active form of phytochrome, Pfr, had been abolished by far-red (FR) 24 h after R. Thus, the primary effect of Pfr, that initiates the transduction chain, does not require calcium. Coupling of Pfr to subsequent dark reactions has been investigated by R-FR irradiations with various dark intervals. The resulting escape kinetics were characterized by a lag phase (6 h) and half-maximal escape from FR reversibility (19 h). These kinetics were not significantly changed by the presence or absence of calcium. Thus, direct interaction of Pfr and calcium is not a step in the transduction chain initiated by the active form of photochrome.Abbreviations EGTA ethyleneglycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid - FR far-red light - Pr red-light-absorbing form of phytochrome - Pfr far red-light-absorbing form of phytochrome - Pipes piperazine-1,4-bis(2-ethanesulfonic acid) - R red light A preliminary report of this work was presented at the XIV Int. Bot. Congr., Berlin (West), Germany, Book of Abstracts, 2-116a-5 (1987)