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S. Grassi D. Bambagioni F. Ottaviani G. Serafini 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,172(4):473-479
The link between stapedius muscle activity and acoustic structure of vocalization was analysed in cocks of age 20–30 to 90–100 days old. The results show that stapedius muscle activation depends on the acoustic structure of vocalization and changes during vocal development. This dependence was observed in spontaneous calls and in vocalizations elicited by stimulating the mesencephalic calling area. In 30-day-old cocks stapedius muscle EMG response is never associated with vocalizations with an acoustic energy content which is always distributed at frequencies higher than 2000 Hz. The coupling between vocalization and stapedius muscle activity begins later, when birds produce vocalizations with acoustic energy shifted towards lower frequencies. Overall, stapedius muscle activity is related to a bird's production of high amplitude low frequencies. These results support the hypothesis that the primary role of the stapedius muscle during normal vocal development is to dampen the amplitude of low frequency energy that reaches the cochlea during vocalization. 相似文献
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We examined reproductive attrition in Fremontodendron decumbens to characterize sexual reproduction in this rare California shrub. Reproductive individuals produced an average of 2,900 flower buds in a season, with no significant difference in bud production between two seasons. Because of intense insect predation, <;2% of initiated flower buds became mature fruits. A threefold decrease in predation of flower buds between seasons resulted in an increase in seed output the second season, indicating that seed production was partially predator-limited. Most seeds (97.8%) were dormant due to an impermeable seed coat. Breaking of the coat, mechanically or by heat, allowed high levels of germination. Chamise charate and ash added to the potting medium resulted in the highest level of germination and emergence. Rodents were more important than birds as seed predators, destroying 90% of seeds under parent shrub canopies within 8–10 months. Seeds already integrated into the seed bank were comparatively safe from predation, relative to newly added seeds. If predation was prevented, seeds were long-lived under field conditions (>;80% survived after 5.75 years). Most seedlings produced in unburned chaparral by planting heat-treated seeds in openings between shrubs were destroyed by predators (rodents and insects). All seedlings that escaped predation died during the summer drought. We concluded that sexual reproduction was limited by (in order of importance): 1) lack of fire, 2) predehiscence predation by insects, and 3) postdehiscence predation by rodents. Size distributions from two populations revealed that, despite the apparent absence of sexual reproduction in unbumed chaparral, two unbumed sites contained a large proportion of individuals in small size classes. Excavation of several small individuals demonstrated they were sprouts from the roots of nearby larger shrubs. Because asexual reproduction by rootsprouting circumvents the high attrition of sexual reproductive effort on unbumed sites, rootsprouting may be a significant reproductive strategy of some ‘sprouter’ species in chaparral. 相似文献
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S Perito L Vecchiarelli P D'Errico S Serafini G Sbaraglia 《Bollettino della Società italiana di biologia sperimentale》1984,60(7):1415-1419
The systemic infection induced by Candida albicans, Candida krusei and Candida viswanathii was studied in an experimental murine system. Candida albicans is able to kill outbred CD1 mice within a few days and at a very low concentration; C. krusei is not pathogenic not even when inoculated at a higher concentration; C. viswanathii is able to kill animals only a a higher concentration. The different resistances do not seem to be under genic control, in as much as the different strains of mice used (hybrid CD2F1 and B6C3HF1, inbred Balb/c) show the same degree of resistance as the CD1 mice to the three species of Candida. The colony forming units (CFU) in the kidneys of CD1 mice inoculated intravenously with 10(5) cells of the three species of Candida, collected at various intervals showed a good correlation with the median survival times: a rapid moltiplication of the C. albicans is evident in the kidneys of the animals 24 hours after the inoculation, while the C. krusei and the C. viswanathii do not moltiply. 相似文献
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M Magnani G Serafini A Antonelli M Malatesta G Gazzanelli 《The Journal of biological chemistry》1991,266(31):21018-21024
Conjugate ubiquitin was previously found in the nucleus, cytoplasm, and membranes of eukaryotic cells while the enzymes of the ubiquitin-conjugating system appear to be cytoplasmic. We have prepared the mitochondrial fraction from rabbit brain by discontinuous density gradient ultracentrifugation and by Western blotting, using a specific antibody against conjugate ubiquitin, showing that it contains ubiquitin conjugates in a very wide molecular weight range. Electron microscopy and measurement of specific enzyme markers show that this fraction not only contains mitochondria but also some endoplasmic reticulum vesicles. Immunostaining with anti-ubiquitin IgG followed by immunodecoration with colloidal gold particles provides evidence for the presence of conjugate ubiquitin both in mitochondria and in the endoplasmic reticulum. Furthermore, this "mitochondrial fraction" shows a pronounced ATP-dependent ability to conjugate 125I-ubiquitin into a number of endogenous proteins as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Addition of E1, E2, and E3, the enzymes of the ubiquitin conjugating system purified from rabbit reticulocytes, does not further increase this ubiquitination nor incorporate 125I-ubiquitin into additional protein bands. The same mitochondrial fraction is not able to carry out any ATP-dependent degradation of 125I-albumin; however, it contains an isopeptidase activity able to release the covalently incorporated 125I-ubiquitin and is also able to conjugate 125I-ubiquitin to exogenous proteins as oxidized RNase. By affinity chromatography on ubiquitin-agarose of fraction II of a crude Triton X-100 extract of the mitochondrial fraction, several proteins corresponding in Mr to the E1 and E2s enzymes were obtained. These proteins were also able to form specific ubiquitin-thiol ester bounds on sodium dodecyl sulfate-polyacrylamide gels and to support 125I-ubiquitin conjugation to oxidized RNase. Detergent fractionation of the mitochondrial fraction provided evidence for a possible localization of the ubiquitin conjugating activity in the mitochondrial external membrane and endoplasmic reticulum. The presence of an active ubiquitin protein conjugating system in mitochondria and endoplasmic reticulum may be related to the turnover of organelle proteins as well as to specific cell functions such as import of proteins into mitochondria and ubiquitination of externally oriented membrane-bound proteins. 相似文献
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As water and nutrient uptake should be related in the response of plants to salinity, the aim of this paper is to establish whether or not aquaporin functionality is related to H+ -ATPase activity in root cells of pepper ( Capsicum annuum L.) plants. Thus, H+ -ATPase activity was measured in plasma membrane vesicles isolated from roots and aquaporin functionality was measured using a cell pressure probe in intact roots. Salinity was applied as 60 m M NaCl or 60 m M KCl, to determine which ion (Na+ , K+ or Cl− ) is producing the effects. We also investigated whether the effects of both salts were ameliorated by Ca2+ . Similar results were obtained for cell hydraulic conductivity, Lpc , and H+ -ATPase activity, large reductions in the presence at NaCl or KCl and an ameliorative effect of Ca2+ . However, fusicoccin (an activator of H+ -ATPase) did not alter osmotic water permeability of protoplasts isolated from roots. Addition of Hg2+ inhibited both ATPase and aquaporins, but ATPase also contains Hg-binding sites. Therefore, the results indicate that H+ -ATPase and aquaporin activities may not be related in pepper plants. 相似文献
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M. Carmen Martínez-Ballesta Luis López-Pérez Mercedes Hernández Carmen López-Berenguer Nieves Fernández-García Micaela Carvajal 《Phytochemistry Reviews》2008,7(2):251-260
Phytochemicals in vegetables are known to be responsible for protective effects against many human diseases, including cardiovascular
diseases and different types of cancer. Environmental conditions and physiological factors may modify the amounts of these
compounds present in vegetables and fruits, but also crop management strategies could increase the production of phytochemicals.
Therefore, the effects of mineral nutrition, soil composition and water content on the production of phytochemicals have been
considered in the development of different fertilisation strategies, efficient water management and techniques such as grafting.
Finally, the contents of health-promoting compounds in vegetables and fruits depend both quantitatively and qualitatively
on their genetic bases. Thus, conventional breeding and genetic modification have been developed as new methodologies to enhance
the nutritional properties of plants.
M. C. Martínez-Ballesta, L. López-Pérez, M. Hernández, C. López-Berenguer, N. Fernández-García contributed equally. 相似文献
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