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971.
Phase shift of the circannual reproductive rhythm in European hamsters by 2 days of long photoperiod
OBJECTIVEs AND DESIGN: In European hamsters a circannual clock drives the seasonal changes in the reproductive state. Its resetting by photoperiod is clearly phase dependent. In mid subjective winter a 1-month pulse of long photoperiod (LP) advances the onset of the reproductive phase of animals maintained in constant short photoperiod (SP) by up to 1.5 months. The present study investigated whether shorter pulses, i.e. 8, 4 or 2 days LP-pulses are still effective to phase shift the circannual rhythm. MAIN FINDINGS: All pulses induced gonadal development after a similar time relative to the offset of the pulse and earlier than in the control group. Thus, they all shared a similar effectiveness. CONCLUSIONS: In European hamsters a very brief LP-pulse can phase shift the reproductive rhythm but its strength is not determined by its duration at least not in the tested range. 相似文献
972.
973.
The adrenal medullary tissue contributes to maintain body homeostasis in reaction to stressful environmental changes via the
release of catecholamines into the blood circulation in response to splanchnic nerve activation. Accordingly, chromaffin cell
stimulus-secretion coupling undergoes temporally restricted periods of anatomo-functional remodeling in response to prevailing
hormonal requirements of the organism. The postnatal development of the adrenal medulla and response to stress are remarkable
physiological situations in which the stimulus-secretion coupling is critically affected. Catecholamine secretion from rat
chromaffin cells is under a dual control involving an incoming initial command arising from the sympathetic nervous system
that releases acetylcholine at the splanchnic nerve terminal-chromaffin cell synapses and a local gap junction-mediated intercellular
communication. Interestingly, these two communication pathways are functionally interconnected within the gland and exhibit
coordinated plasticity mechanisms. This article reviews the physiological and molecular evidence that the adrenal medullary
tissue displays anatomical and functional adaptative remodeling of cell–cell communications upon physiological (postnatal
development) and/or physiopathological (stress) situations associated with specific needs in circulating catecholamine levels. 相似文献
974.
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
975.
976.
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
977.
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
978.
979.
980.
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