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Cecilia Del Casino Yi-Qin Li Alessandra Moscatelli Monica Scali Antonio Tiezzi Mauro Cresti 《Biology of the cell / under the auspices of the European Cell Biology Organization》1993,79(2):125-132
Summary— The distribution of microtubules was investigated in Nicotiana tabacum pollen tubes at different stages of tube growth by immunofluorescence microscopy. Using specific antibodies, the presence of microtubules consisting of different tubulin isoforms was tested. α-, β- and tyrosinated α-tubulin were present within the tube, whereas the acetylated form was lacking. The presence of tubulin subunits in pollen tube extracts was also investigated by immunoblotting analyses. The use of a confocal laser scanning microscope integrated with computer-assisted imaging, allowed a detailed visualization of the microtubule distribution and organization. Cytoplasmic microtubules organized as short bundles with various orientations were detected at the apex of long tubes. 相似文献
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Marcela F. Lopes Vânia Lúcia C. Merquior JoséMauro Peralta Lúcia M. Teixeira 《FEMS immunology and medical microbiology》1995,12(3-4):205-211
Abstract Exosubstances (cohemolysins) produced by Streptococcus agalactiae (CAMP-factor) and Streptococcus uberis (Uberis-factor) showing hemolytic synergism with β-lysin produced by Staphylococcus aureus were compared. Cohemolytic activity was evaluated in the supernatants of bacterial cultures, before and after ammonium sulfate precipitation. Sheep erythrocytes sensitized with β-lysin were used as substrate. The assays were performed in microtiter plates and results were expressed as cohemolytic units/ml. Maximum cohemolytic activity was detected, respectively, after 8 h and 14 h of growth in Columbia broth in S. uberis and S. agalactiae cultures. Cohemolytic activities of both microorganisms showed similarities when submitted to various physical and chemical treatments. They were significantly decreased by heating at 60°C and 100°C, or in presence of trypsin, and were abolished in the presence of Tween 20. Activities were found to be stable in crude supernatants and concentrated preparations maintained at −20°C for 3 months. Differences were related to levels of activity and kinetics of detection during the growth cycle. The results indicate the proteic nature, at least in part, of the Uberis factor. Analysis by PAGE in the presence or absence of SDS allowed us to correlate Uberis activity with a protein band with apparent molecular mass of 42 kDa, while CAMP activity was associated with a protein band of 27 kDa. 相似文献
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Four diploid and three phylogenetically tetraploid Cyprinidae (Ostariophysi) have been characterized as for nuclear DNA content, modal chromosome number and DNA reassociation kinetics (hydroxyapatite chromatography). Among the diploid species nuclear DNA content (10(-12) g DNA/2C) was 1.62 for Tinca tinca, 1.87 for Scardinius erythrophthalmus, 2.53 for Leuciscus cephalus and 2.75 for Alburnus alburnus, while the phylogenetically tetraploid species Carassius auratus, Barbus barbus and Cyprinus carpio attained 3.40, 3.66 and 3.80 respectively. Modal chromosome number was 2n = 48-50 for diploid individuals and 2n = 100-104 for phylogenetically tetraploid ones. In all the species 5--8% of the genome is represented by highly repetitive and foldback DNA. In DNA reassociation kinetics of phylogenetically tetraploid Cyprinidae a distinct plateau separates an intermediate reassociating sequence fraction (about 22% of the genome; with average repetition frequencies between 1,000 and 1,400) from a slow reassociating one (unique DNA; about 72% of the genome). These two genome fractions are not clearly distinguishable from each other in Cot curves of the diploid Cyprinidae, where a similar plateau is not evident. Since simple ploidy changes are not expected to affect DNA reassociation kinetics we suggest a different evolution in the genome organization of the two ploidy groups. Some possible hypotheses are discussed. 相似文献
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W.David Ollis Brian T. Redman Richard J. Roberts Ian O. Sutherland Otto R. Gottlieb Mauro T. Magalhaães 《Phytochemistry》1978,17(8):1383-1388
The trunkwood of Machaerium kuhlmannii contains methyl palmitate, 3-O-acetyloleanolic acid and sitosterol; the benzene derivatives 2,3-dimethoxyphenol, 2,6-dimethoxyphenol, 2-hydroxy-3-methoxyphenol, 2,3-dimethoxybenzaldehyde and methyl 3-(2-hydroxy-4-methoxyphenyl)-propionate; the isoflavonoids formononetin and (6aS,11aS)-medicarpin; the neoflavonoids (R)-3,4-dimethoxydalbergione, (R)-3,4-dimethoxydalbergiquinol, kuhlmanniquinol [(R)-3-(4-hydroxyphenyl)-3-(5-hydroxy-2,3,4-trimethoxyphenyl)-propene], dalbergin, kuhlmannin (6-hydroxy-7,8-dimethoxy-4-phenylcoumarin) and kuhlmannene (6-hydroxy-7,8-dimethoxy-4-phenylchrom-3-ene), as well as the cinnamylphenol kuhlmannistyrene [Z-1-(5-hydroxy-2,3,4-trimethoxybenzyl)-2-(2-hydroxyphenyl)-ethylene]. Five of these compounds, in addition to (R)-4′-hydroxy-3,4-dimethoxydalbergione, were also isolated from a trunkwood extract of M. nictitans. Structural assignments were confirmed by chemical interconversion and by the synthesis of (±)-kuhlmanniquinol. 相似文献
17.
Structure of the chicken neuron-glia cell adhesion molecule, Ng-CAM: origin of the polypeptides and relation to the Ig superfamily 总被引:16,自引:9,他引:7 下载免费PDF全文
M P Burgoon M Grumet V Mauro G M Edelman B A Cunningham 《The Journal of cell biology》1991,112(5):1017-1029
The neuron-glia cell adhesion molecule (Ng-CAM) mediates both neuron-neuron and neuron-glia adhesion; it is detected on SDS-PAGE as a predominant 135-kD glycoprotein, with minor components of 80, 190, and 210 kD. We have isolated cDNA clones encoding the entire sequence of chicken Ng-CAM. The predicted extracellular region includes six immunoglobulin-like domains followed by five fibronectin-type III repeats, structural features that are characteristic of several neural CAMs of the N-CAM superfamily. The amino acid sequence of chicken Ng-CAM is most similar to that of mouse L1 but the overall identity is only 40% and Ng-CAM contains a short fibronectin-like segment with an RGD sequence that has no counterpart in L1. These findings suggest that Ng-CAM and L1 may not be equivalent molecules in chicken and mouse. The amino-terminal sequences of the 210-, 190-, and 135-kD components of Ng-CAM are all the same as the predicted amino terminus of the molecule, whereas the 80-kD component begins within the third fibronectin repeat. The cDNA sequence is continuous across the junction between the 135- and 80-kD components, and a single 170-kD Ng-CAM polypeptide was isolated from tunicamycin-treated cells. In addition, all cDNA probes hybridized on Northern blots to a 6-kb RNA, and most hybridized to single bands on Southern blots. These results indicate that the Ng-CAM components are derived from a single polypeptide encoded by a single gene, and that the 135- and 80-kD components are generated from the 210/190-kD species by proteolytic cleavage. The 135-kD component contains most of the extracellular region including all of the immunoglobulin-like domains. It has no transmembrane segment, but it is tightly associated with the membrane. The 80-kD component contains two and a half type III repeats plus the RGD-containing segment, as well as the single transmembrane and cytoplasmic domains. These structural features of Ng-CAM provide a framework for understanding its multiple functions in neuron-neuron interactions, neurite fasciculation, and neuron-glia interactions. 相似文献
18.
S B Scholnick P A Caruso J Klemencic G S Mastick C Mauro M Rotenberg 《Developmental biology》1991,146(2):423-437
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Summary The fermentation of grape must by Candida utilis ISS 28 was studied at different substrate concentrations, pH values, and nutrient supplementation in a shaken-flask fermenter, by using a composite design experiment.The experimental biomass yields were fitted to the only statistically significant factors with a mean standard error less than 8%, by using multiple regression analysis.Optimal conditions for maximum cell yield were established by plotting a series of loci at constant biomass yield and then verified experimentally, thus confirming the remarkable accuracy of the model 相似文献