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1.
Different extracellular matrix (ECM) molecules, when presented to hippocampal neurons in culture in a substrate-bound form, exert strikingly similar effects on the establishment of neuronal polarity, i.e., the growth of axon-like major neurites is favored, whereas extension of dendrite-like minor neurites is inhibited. To gain insight into the underlying signal transduction processes, we have investigated the effects of modulators of protein kinase activity on the morphology of neurons cultured on tenascin-R, tenascin-C, and laminin-entactin substrates. We found differential effects of broad-spectrum protein kinase inhibitors: H-7 promoted the growth of minor neurites, whereas H-8 reduced the growth of major neurites on ECM but not control substrates. In contrast, chelerythrine, a specific inhibitor of protein kinase C, selectively affected growth of both minor and major neurites on control, but not on ECM substrates. Finally, reagents which elevate intracellular cAMP levels facilitated growth of minor neurites and inhibited growth of major neurites and thus interfered with the establishment of a polarized phenotype on both ECM and control substrates. Our results suggest that protein kinases mediate the effects of ECM molecules on neuronal polarity and that different kinases control extension of axons and dendrites. 相似文献
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Toma S.; Campagnoli S.; Gregoriis E.De; Gianna R.; Margarit I.; Zamai M.; Grandi G. 《Protein engineering, design & selection : PEDS》1989,2(5):359-364
On the basis of the homology with the Bacillus thermoproteolyticuszinc endopeptidase thermotysin, we hypothesized that Glu-143and His-231 are the key residues for the catalytic activityof the Bacillus subtilis neutral protease. To test this possibilityby site-directed mutagenesis, we substituted these two residueswith Ala, Ser, Trp and Arg, and Leu, Val and Cys respectively.All these substitutions dramatically affected the amount ofsecreted mutant proteins, as determined by immunological methods,and their catalytic activities. No appreciable secretion wasobserved with the three Glu mutants Trp, Ser and Arg, whereasthe GluAla mutant enzyme was secreted at a level of afew hundred micrograms per litre of culture. The His mutantswere all secreted at higher levels (in the order of a few milligramsper litre) and their residual catalytic activity could be determinedusing Z-Ala-Leu-Ala as substrate. Our results confirm the keyrole played by Glu-143 and His-231 in catalysis and moreoversuggest the existence of a relationship between the catalyticactivity of the enzyme and the extent of its secretion. In thiscontext, we present data suggesting an autoproteolytic mechanismof cleavage of the precursor form of the enzyme, analogous tothe one previously reported for the B.subtilis subtilisin. 相似文献
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Riccardo Matera Simone Gabbanini Gina Rosalinda De Nicola Renato Iori Gianna Petrillo Luca Valgimigli 《Food chemistry》2012
The freeze-dried sprouts’ juice of Raphanus sativus (L.) cv. Sango was prepared and analysed for the first time. HPLC analysis of total isothiocyanates, after protein displacement, resulted in 77.8 ± 3.0 μmol/g of dry juice while GC–MS analysis of hexane and acetone extracts showed E- and Z-raphasatin (8.9 and 0.11 μmol/g, respectively) and sulforaphene (11.7 μmol/g), summing up to 20.7 ± 1.7 μmol/g of free isothiocyanates. Sprouts’ juice contained an unprecedented wealth of anthocyanins and a new fractionation methodology allowed us to isolate 34 mg/g of acylated anthocyanins (28.3 ± 1.9 μmol/g), belonging selectively to the cyanidin family. Analysis was performed by HPLC–PDA–ESI–MSn and extended to deacylated anthocyanins and aglycones, obtained, respectively, by alkaline and acid hydrolysis. This study identified 70 anthocyanins, 19 of which have never been described before and 32 of which are reported here in R. sativus for the first time. Sango radish sprouts are exceptional dietary sources of heath-promoting micronutrients. 相似文献
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Schommer Marlene; Calvert Christy; Gariglietti Gianna; Bajaj Amit 《Canadian Metallurgical Quarterly》1997,89(1):37
This article is the continuation of M. Schommer's (1993) study, in which the development of secondary students' beliefs about the nature of knowledge and learning, or epistemological beliefs, was examined. High school students (N?=?69) completed an epistemological questionnaire as freshmen in 1992 and as seniors in 1995. Repeated-measures analyses revealed that their beliefs in fixed ability to learn, simple knowledge, quick learning, and certain knowledge changed as they neared the end of their 4th year in high school. In addition, the less students believed in quick learning, the better grade point average they earned. These results are consistent with a cross-sectional study (M. Schommer, 1993) establishing substantial differences in students' epistemological beliefs across the high school years and thus strengthen the case that there is development of epistemological beliefs related to learning during high school. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
Gianna Stefani 《Systems & Control Letters》1985,6(2):123-125
An example of a locally controllable nonlinear system on R3 is given. The system is of the type
with f, g analytic vector fields and u bounded. The fields f and g are such that the dimension of the vector space spanned at x0 by the Lie brackets which contain g an odd number of times is 2. 相似文献
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Silvia Francesca Storti Emanuela Formaggio Deborah Moretto Alessandra Bertoldo Francesca Benedetta Pizzini Alberto Beltramello Antonio Fiaschi Gianna Maria Toffolo Paolo Manganotti 《Magma (New York, N.Y.)》2014,27(2):171-184