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41.
Daniel M. Moraga† Patricio Nuñez‡ Jorge Garrido‡ Ricardo B. Maccioni† 《Journal of neurochemistry》1993,61(3):979-986
Abstract: Much indirect evidence suggests that the interconnections of actin microfilaments with the microtubule system are mediated by microtubule-associated proteins (MAPs). In this study we provide new data to support the interaction of a specific tubulin-binding domain on τ with actin in vitro. In actin polymerization assays, the synthetic peptide VRSKIGSTENLKHQPGGG, corresponding to the first repetitive sequence of τ protein, increased turbidity at 320 nm in a dose-dependent fashion. A salient feature of the τ peptide-induced assembly process is the formation of a large amount of actin filament bundles, as revealed by electron microscopic analysis. An increase in the τ peptide concentration resulted in a proportional increase in the bundling of actin filaments. It is interesting that a gradual decrease of pH within the range 7.6–4.7 resulted in a higher effect of τ peptide in promoting bundles of actin filaments. A similar pH-dependent effect was observed for τ protein-induced bundling. An analysis of the mechanisms that operate in the peptide induction of actin filament bundles suggests the involvement of electrostatic forces, because the neutralization of ɛ-aminolysyl residues by selective carbamoylation resulted in a complete loss of the peptide induction of actin bundles. The data suggest that a τ repetitive sequence (also found in MAP-2 and MAP-4) containing a common tubulin binding motif may constitute a functional domain on τ for the dynamics of the interconnections between actin filaments and microtu-bules. 相似文献
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Andrea Evangelina Arcángel Emiliano Alexis Rodríguez Juan Francisco Saad Paula de la Barra Maite Andrea Narvarte Lorena Pía Storero Patricio Javier Pereyra 《Journal of phycology》2023,59(6):1310-1322
Population dynamics can be influenced by physical and biological factors, particularly in stressful environments. Introduced species usually have great physiological plasticity, resulting in populations with different traits. Undaria pinnatifida, a macroalga originally described from northeast Asia, was introduced in Northern Patagonia, Argentina (San Matías Gulf) around 2010. To describe the spatio-temporal variability in population structure and morphometry of U. pinnatifida, we conducted monthly field samplings for 2 years at the intertidal area of two contrasting sites in the San Matías Gulf. Individuals of U. pinnatifida were classified by developmental stage, and their morpho-gravimetric variables were measured. In both intertidal sites juveniles were found in higher proportion during austral autumn and grew and matured during the autumn-winter months (from May onwards), and individuals senesced during early austral summer (December and January). Conversely, density and biomass were largely different between sites, and individuals showed slight morphological variability between sites. Environmental (e.g., nutrient concentration, available substrate) and biological factors (e.g., facilitation, competition) may explain the observed differences. Since there is not a macroalga with U. pinnatifida morphometrical characteristics in the intertidal environments of San Matías Gulf, studying this recent introduction gives us a better understanding of its potential ecological effects. 相似文献
45.
Serrano Alejandra Kuhn Nathalie Restovic Franko Meyer-Regueiro Carlos Madariaga Mónica Arce-Johnson Patricio 《Journal of Plant Growth Regulation》2023,42(1):365-375
Journal of Plant Growth Regulation - Auxin is a hormone that delays ripening in part by reducing anthocyanin content and impairing color development. Auxin content declines during the ripening... 相似文献
46.
J. Fábregas E. D. Morales N. Polanco M. Patiño A. Otero J. F. Tobar 《World journal of microbiology & biotechnology》1996,12(1):47-49
The marine microalga Phaeodactylum tricornutum was cultivated in semi-continuous culture under mixotrophic conditions with the soluble fractions of potato, rye and wheat flours that had been naturally fermented, at 2% or 4% (w/v). The rye flour produced the highest microalgal cellular density of 90×106 cells.ml-1 when supplemented with NaNO3 and NaH2PO4. The autotrophic control only gave 57×106 cells.ml-1. The value of agricultural surpluses, such as rye flour, can therefore be increased by its use in the production of valuable, microalgal biomass which is rich in protein, pigments and fatty acids. 相似文献
47.
Palazon Javier; Bonfill Mercedes; Cusido Rosa M.; Pinol M.T.; Morales Carmen 《Plant & cell physiology》1995,36(2):247-252
Pieces of callus obtained from seedlings of Digitalis purpureawere grown on solid Murashige-Skoog's medium supplemented with1 mg liter1 BA and 0.1 mg liter1 IAA or NAA, withor without phenobarbital (40 mg liter1). The replacementof the natural auxin IAA by the synthetic auxin NAA increasedcallus growth and inhibited organogenesis, whereas the additionof phenobarbital had the opposite effect. Morphometric measurementsrevealed a high ratio of vacuole to cytoplasm (v/v) in calluscells. This ratio was affected by the different treatments inthe same way as the fresh weight. The activity of mitochondrialcytochrome P450scc (the enzyme that provides the precursor,pregnenolone, for the biosynthesis of cardenolide in foxgloveplants) was detected in the relevant fraction of callus grownunder all experimental conditions, and its activity was increasedby the addition of phenobarbital. The different treatments testedincreased the cardenolide content and quantifiable amounts ofdigitoxin were detected in all callus tissues. It is of specialinterest that phenobarbital added to the culture medium increasedthe accumulation of digitoxin. The mechanism affecting the developmentand production of cardenolide in callus tissues of D. purpureaby phenobarbital and the replacement of IAA by NAA is discussed. (Received July 18, 1994; Accepted December 14, 1994) 相似文献
48.
Fa´bregas J. Morales E.D. Lamela T. Cabezas B. Otero A. 《World journal of microbiology & biotechnology》1997,13(3):349-351
The marine microalga Phaeodactylum tricornutum was cultured semi-continuously with the soluble fractions of wheat, rye and boiled potato flours. Fifteen percent of the culture volume was renewed every 3 d. The cell productivities were 0.9×109 cells/l/d, 1.1×109 cells/l/d and 2.6×109 cells/l/d for wheat, rye and potato respectively. The productivity of the autotrophic control was 1.0×109 cell/l/d. When a soluble fraction of raw potato was added, the productivity was enhanced to 4.1×109 cells/l/d, 2.4 times higher than the autotrophic culture. The high productivity of P. tricornutum with the soluble fractions of Solanum tuberosum suggests its usefulness as a source of nutrients for the production of microalgal biomass. 相似文献
49.
A. Falconi M. Borde A. Hernández-Cruz F. R. Morales 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,176(5):679-689
Stimulation of the spinal cord of the electric fish Gymnotus carapo, evoked an abrupt increase in the discharge rate of the electric organ. At the maximum of this response, the rate increased an average of 26 ± 11.8%. The duration of the response was 4.9 ± 2.12 s; its latency was 10.4 ± 1.1 ms. Activation of the Mauthner axon played a decisive role in this phenomenon as indicated by the following: (1) recordings from the axon cap of the Mauthner cell demonstrated that the response was evoked if the Mauthner axon was antidromically activated and (2) a response that was similar to that produced by spinal cord stimulation, was elicited by intracellular stimulation of either Mauthner cell. Stimulation of the eighth nerve could also increase the discharge rate of the electric organ. The effect was greater if a Mauthner cell action potential was elicited. The findings described in the present report, indicate the existence of a functional connection between the Mauthner cell and the electromotor system in Gymnotus carapo. This connection may function to enhance the electrolocative sampling of the environment during Mauthner-cell mediated behaviors. This is a novel function for the Mauthner cell.Abbreviations
EHP
extrinsic hyperpolarizing potential
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EOD
electric organ discharge
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M-AIR
Mauthner initiated abrupt increase in rate
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M-cell
Mauthner cell
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M-axon
Mauthner axon
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PM
pacemaker nucleus
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PM-cell
pacemaker cell
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PPn
prepacemaker nucleus
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SPPn
sublemniscal prepacemaker nucleus 相似文献
50.