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991.
Jessica Escoffier Morgane Couvet Harold de Pomyers Pierre F. Ray Michel Sève Gérard Lambeau Michel De Waard Christophe Arnoult 《Biochimie》2010
The goal of this study was to identify new compounds from venoms able to modulate sperm physiology and more particularly sperm motility. For this purpose, we screened the effects of 16 snake venoms cleared of molecules higher than 15 kDa on sperm motility. Venoms rich in neurotoxins like those from Oxyuranus scutellatus scutellatus or Daboia russelii, were highly potent inhibitors of sperm motility. In contrast, venoms rich in myotoxins like those from Echis carinatus, Bothrops alternatus and Macrovipera lebetina, were inactive. From the main pharmacologically-active fraction of the Taipan snake O. scutellatus s., a proteomic approach allowed us to identify 16 different proteins, among which OS1 and OS2, two secreted phospholipases A2 (sPLA2). Purified OS1 and OS2 mimicked the inhibitory effect on sperm motility and were likely responsible for the inhibitory effect of the active fraction. OS1 and OS2 triggered sperm acrosome reaction and induced lipid rearrangements of the plasma membrane. The catalytic activity of OS2 was required to modulate sperm physiology since catalytically inactive mutants had no effect. Finally, sperm treated with OS2 were less competent than control sperm to initiate in vitro normal embryo development. This is the first report characterizing sPLA2 toxins that modulate in vitro sperm physiology. 相似文献
992.
993.
Alban Franco Aude Jouaux Michel Mathieu Pascal Sourdaine Christophe Lelong Kristell Kellner Clothilde Heude Berthelin 《Cell and tissue research》2010,340(1):201-210
To understand the processes involved in tissue remodeling associated with the seasonal reproductive cycle of the oyster Crassostrea gigas, we used immunodetection and expression measurements of proliferating cell nuclear antigen (PCNA). The expression of the
PCNA gene was measured by real-time polymerase chain reaction in the whole gonadal area compared with laser microdissected
gonad and storage tissue. Results underlined the advantage of the laser microdissection approach to detect expression, mainly
for early stages of spermatogenesis. In the storage tissue, PCNA expression was reduced in the gonadal tubules, but immunolabeled
hemocytes and vesicular cells were detected when the storage tissue was being restored. In the gonadal tubules, the PCNA gene
was more highly expressed in males than in females. As soon as spermatogenesis was initiated, PCNA expression showed a high
and constant level. In females, the expression level increased gradually until the ripe stage. The immunological approach
established the involvement of peritubular cells in gonadal tubule expansion during early gametogenesis. In both sexes, gonial
mitosis was immunodetected throughout the reproductive cycle. In males, the occurrence of two types of spermatogonia was ascertained
by differential immunolabeling, and intragonadal somatic cell proliferation was noted. As expected, immunolabeling was never
observed from stage II spermatocytes to spermatozoa. In females, positively stained cells were detected from oogonia to growing
oocytes with various labeled intracellular locations. 相似文献
994.
Kathleen Mahias Neveen Ahmed-El-Sayed Cyril Masante Juliette Bitard Cathy Staedel Fabien Darfeuille Michel Ventura Thérèse Astier-Gin 《Nucleic acids research》2010,38(12):4079-4091
The replication of the genomic RNA of the hepatitis C virus (HCV) of positive polarity involves the synthesis of a replication intermediate of negative polarity by the viral RNA-dependent RNA polymerase (NS5B). In vitro and likely in vivo, the NS5B initiates RNA synthesis without primers. This de novo mechanism needs specific interactions between the polymerase and viral RNA elements. Cis-acting elements involved in the initiation of (–) RNA synthesis have been identified in the 3′ non-coding region and in the NS5B coding region of the HCV RNA. However, the detailed contribution of sequences and/or structures of (–) RNA involved in the initiation of (+) RNA synthesis has been less studied. In this report, we identified an RNA element localized between nucleotides 177 and 222 from the 3′-end of the (–) RNA that is necessary for efficient initiation of RNA synthesis by the recombinant NS5B. By site-directed mutagenesis experiments, we demonstrate that the structure rather than the primary sequence of this domain is important for RNA synthesis. We also demonstrate that the intact structure of this RNA element is also needed for efficient RNA synthesis when the viral NS5B functions in association with other viral and cellular proteins in cultured hepatic cells. 相似文献
995.
Yves‐Marie Coïc Charlotte Le Lan Jean‐Michel Neumann Nadège Jamin Françoise Baleux 《Journal of peptide science》2010,16(2):98-104
This work contributes to highlight the benefits of pseudoproline dipeptides introduction in difficult SPPS. We show how a slight modification in the positioning choice conditioned the synthesis achievement of a 54 amino acid long caveolin‐1 peptide encompassing the intramembrane domain. Furthermore, we report a side reaction correlated with the coupling steps and generating truncated fragments with a mass deviation of + 42 Da. Considering the need of structural data for membrane proteins, most of which are considered as prevalent therapeutic targets, chemical synthesis provides an interesting alternative pathway to obtain hydrophobic domains by pushing back the frontiers of conventional RP methods of purification. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
996.
997.
998.
Loïc Lesobre Frédéric Lacroix Eric Le Nuz Yves Hingrat Toni Chalah Michel Saint Jaime 《Journal of avian biology》2010,41(2):117-127
Behavioural studies have led to the perception that lekking species experience a high male reproductive skew as a consequence of females’ selective mate choice. In addition, observations suggest that females copulate only once and therefore polyandry seems unlikely as females are supposed to choose the best male available. In order to analyse the mating strategy of the Houbara bustard, an endangered lekking species under reinforcement in eastern Morocco, we used microsatellite data to perform paternity analyses. None of our observations followed common expectations under a lek mating system: we found no male reproductive skew suggesting no apparent selective female mate choice and no apparent male benefit from lekking. In contrast, a high level of polyandry (60 % of the nests) was recorded suggesting that sperm competition may operate. In addition, we present another case of conspecific brood parasitism in a lekking species and this was an unexpected alternative strategy for a species presenting high parental cost and low fecundity. The increasing number of studies contradicting common assumptions on lekking species suggests that alternative breeding strategies such as males pursuing an off‐lek mating strategy, female polyandry and even conspecific brood parasitism might be more widespread in lekking species than previously thought. 相似文献
999.
Jožica Dolenc John H. Missimer Michel O. Steinmetz Wilfred F. van Gunsteren 《Journal of biomolecular NMR》2010,47(3):221-235
The C-terminal trigger sequence is essential in the coiled-coil formation of GCN4-p1; its conformational properties are thus
of importance for understanding this process at the atomic level. A solution NMR model structure of a peptide, GCN4p16–31,
encompassing the GCN4-p1 trigger sequence was proposed a few years ago. Derived using a standard single-structure refinement
protocol based on 172 nuclear Overhauser effect (NOE) distance restraints, 14 hydrogen-bond and 11 ϕ torsional-angle restraints,
the resulting set of 20 NMR model structures exhibits regular α-helical structure. However, the set slightly violates some
measured NOE bounds and does not reproduce all 15 measured 3J(HN-HCα)-coupling constants, indicating that different conformers of GCN4p16–31 might be present in solution. With the aim to resolve
structures compatible with all NOE upper distance bounds and 3J-coupling constants, we executed several structure refinement protocols employing unrestrained and restrained molecular dynamics
(MD) simulations with two force fields. We find that only configurational ensembles obtained by applying simultaneously time-averaged
NOE distance and 3J-coupling constant restraining with either force field reproduce all the experimental data. Additionally, analyses of the
simulated ensembles show that the conformational variability of GCN4p16–31 in solution admitted by the available set of 187
measured NMR data is larger than represented by the set of the NMR model structures. The conformations of GCN4p16–31 in solution
differ in the orientation not only of the side-chains but also of the backbone. The inconsistencies between the NMR model
structures and the measured NMR data are due to the neglect of averaging effects and the inclusion of hydrogen-bond and torsional-angle
restraints that have little basis in the primary, i.e. measured NMR data. 相似文献
1000.
Michel Besserve Bernhard Schölkopf Nikos K. Logothetis Stefano Panzeri 《Journal of computational neuroscience》2010,29(3):547-566
Characterizing how different cortical rhythms interact and how their interaction changes with sensory stimulation is important
to gather insights into how these rhythms are generated and what sensory function they may play. Concepts from information
theory, such as Transfer Entropy (TE), offer principled ways to quantify the amount of causation between different frequency
bands of the signal recorded from extracellular electrodes; yet these techniques are hard to apply to real data. To address
the above issues, in this study we develop a method to compute fast and reliably the amount of TE from experimental time series
of extracellular potentials. The method consisted in adapting efficiently the calculation of TE to analog signals and in providing
appropriate sampling bias corrections. We then used this method to quantify the strength and significance of causal interaction
between frequency bands of field potentials and spikes recorded from primary visual cortex of anaesthetized macaques, both
during spontaneous activity and during binocular presentation of naturalistic color movies. Causal interactions between different
frequency bands were prominent when considering the signals at a fine (ms) temporal resolution, and happened with a very short
(ms-scale) delay. The interactions were much less prominent and significant at coarser temporal resolutions. At high temporal
resolution, we found strong bidirectional causal interactions between gamma-band (40–100 Hz) and slower field potentials when
considering signals recorded within a distance of 2 mm. The interactions involving gamma bands signals were stronger during
movie presentation than in absence of stimuli, suggesting a strong role of the gamma cycle in processing naturalistic stimuli.
Moreover, the phase of gamma oscillations was playing a stronger role than their amplitude in increasing causations with slower
field potentials and spikes during stimulation. The dominant direction of causality was mainly found in the direction from
MUA or gamma frequency band signals to lower frequency signals, suggesting that hierarchical correlations between lower and
higher frequency cortical rhythms are originated by the faster rhythms. 相似文献