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排序方式: 共有279条查询结果,搜索用时 15 毫秒
271.
Ionic content of haemolymph in the cockroach, Periplaneta americana. A critical analysis 总被引:1,自引:0,他引:1
Y Pichon 《The Journal of experimental biology》1970,53(1):195-209
272.
Bruno Pichon Laurence Mousson Claude Figureau François Rodhain Claudine Perez-Eid 《Experimental & applied acarology》1999,23(3):267-275
The Rambouillet Forest, a Lyme disease-endemic area near Paris, France, was surveyed from September 1994 to October 1995 to determine the risk periods and zones for humans. Firstly, during the period of Ixodes ricinus activity, abundance of nymphs is greater in spring than in autumn. Secondly, we observed significant variation in nymphal abundance between zones according to the density of cervids. The polymerase chain reaction (PCR) was used to detect DNA of Borrelia burgdorferi sensu lato in 461 unfed nymphs. DNA was detected in 38 nymphs (8.2%). By genospecific PCR based on the OspA gene, we detected the three pathogenic spirochetes with occurrences of 10.3, 31.1 and 58.6 for B. burgdorferi s.s., Borrelia garinii and Borrelia afzelii, respectively, indicating that B. afzelii is probably the main Borrelia species in the Rambouillet Forest. Finally, 11.5% of positive nymphs exhibited a double infection. Infection rates of I. ricinus nymphs by B. burgdorferi s.l. were not significantly different throughout the year for a given area, indicating that the risk periods of acquiring Lyme disease are mainly linked to nymph activity and correspond to spring and autumn. Likewise infection rates of nymphs were not significantly different between zones with a high density of deer (more than 100 animals per 100 ha) and zones with lower deer density (less than 20 animals per 100 ha). In addition to the role of deer as an amplifier of tick populations, these data indicate that zones with a high density of cervids should be considered as higher risk areas. © Rapid Science Ltd. 1998 相似文献
273.
274.
Seed limitation can narrow down the number of coexisting plant species, limit plant community productivity, and also constrain community responses to changing environmental and biotic conditions. In a 10-year full-factorial experiment of seed addition, fertilisation, warming and herbivore exclusion, we tested how seed addition alters community richness and biomass, and how its effects depend on seed origin and biotic and abiotic context. We found that seed addition increased species richness in all treatments, and increased plant community biomass depending on nutrient addition and warming. Novel species, originally absent from the communities, increased biomass the most, especially in fertilised plots and in the absence of herbivores, while adding seeds of local species did not affect biomass. Our results show that seed limitation constrains both community richness and biomass, and highlight the importance of considering trophic interactions and soil nutrients when assessing novel species immigrations and their effects on community biomass. 相似文献
275.
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277.
Periaxonal K+ regulation in the small squid Alloteuthis. Studies on isolated and in situ axons.
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A novel giant axon preparation from the squid Alloteuthis is described. Properties of in situ and isolated axons are similar. Periaxonal K+ accumulation is a function of the physiological state of the animal and of the axon and its sheathing layers. Carefully dissected isolated axons, and axons in situ in a healthy mantle, show much less K+ accumulation than previously reported in squid. It is suggested that the Schwann cells are involved in the observed K+ regulation. 相似文献
278.
Pierre Poutrain Gr��gory Guirimand Ga?lle Gl��varec Vincent Courdavault Olivier Pichon 《Journal of Plant Growth Regulation》2011,30(2):235-241
In Catharanthus roseus cells, auxins are known to negatively regulate the biosynthesis of monoterpenoid indole alkaloids (MIA), a class of valuable
secondary metabolites. Despite extensive studies of this regulation, no protein of the auxin signaling pathway has been isolated
to date in this plant. We therefore decided to clone and characterize a C. roseus Aux/IAA protein that belongs to a family of gene expression repressors mediating auxin effects. Using PCR, a cDNA encoding
the first C. roseus Aux/IAA was cloned and named CrIAA1. The deduced amino acid sequence has four highly conserved domains that are typical of the Aux/IAA protein family and has
high homology to the Aux/IAA isoforms of Arabidopsis (>67%). The CrIAA1 gene expression, monitored by real-time PCR, was found to be dramatically induced by auxin treatment in C. roseus cells. Using GFP imagery and a bimolecular fluorescence complementation assay, we found that CrIAA1 can form oligomers in
the nucleus. We also found that CrIAA1 is quickly degraded following auxin treatments, suggesting that auxin regulates CrIAA1
availability via a feedback mechanism. These results should help to elucidate the molecular nature of the processes responsible
for the auxin-mediated regulation of MIA biosynthesis in C. roseus. 相似文献
279.
A 31P nuclear magnetic resonance study of the hydrothermal vent tube worm Riftia pachyptila. 总被引:1,自引:0,他引:1
M T Thébault N Kervarec R Pichon G Nonnotte Y Le Gal 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1999,322(7):537-541
31P nuclear magnetic resonance (NMR) was used to study the major phosphorylated compounds visible in perchloric extracts of three body regions of the vestimentiferan worm Riftia pachyptila: winged vestimentum, trunk and segmented posterior opisthosome. Two phosphagens (PGs) were present in vestimentum and opisthosome. The major resonance corresponded to those of phosphoarginine and phosphotaurocyamine, which cannot be discriminated on 31P NMR spectra. We have identified four distinct phosphodiesters (PDEs) in these tissues: glycerophosphorylethanolamine (GPE), serine ethanolamine phosphodiester (SEP), glycero-phosphorylcholine (GPC) and threonine ethanolamine phosphodiester (TEP). Three phosphonates or derivates (PAs) were observed in the three body regions. The minor one was identified as 2-aminoethyl phosphonate (2-AEP). The phosphorus profile of the trunk was appreciably different: one additional resonance in the PDE region and only one phosphagen peak were observed. 相似文献