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181.
182.
183.
Zilli L Beirão J Schiavone R Herraez MP Cabrita E Storelli C Vilella S 《Theriogenology》2011,76(4):737-744
Our previous studies demonstrated that osmolality is the key signal in sperm motility activation in Sparus aurata spermatozoa. In particular, we have proposed that the hyper-osmotic shock triggers water efflux from spermatozoa via aquaporins. This water efflux determines the cell volume reduction and, in turn, the rise in the intracellular concentration of ions. This increase could lead to the activation of adenylyl cyclase and of the cAMP-signaling pathway, causing the phosphorylation of sperm proteins and then the initiation of sperm motility. This study confirms the important role of sea bream AQPs (Aqp1a and Aqp10b) in the beginning of sperm motility. In fact, when these proteins are inhibited by HgCl2, the phosphorylation of some proteins (174 kDa protein of head; 147, 97 and 33 kDa proteins of flagella), following the hyper-osmotic shock, was inhibited (totally or partially). However, our results also suggest that more than one transduction pathways could be activated when sea bream spermatozoa were ejaculated in seawater, since numerous proteins showed an HgCl2(AQPs)-independent phosphorylation state after motility activation. The role played by each different signal transduction pathways need to be clarified. 相似文献
184.
We extend the existing work on the time-optimal control of the basic SIR epidemic model with mass action contact rate. Previous
results have focused on minimizing an objective function that is a linear combination of the cost associated with using control
and either the outbreak size or the infectious burden. We instead, provide analytic solutions for the control that minimizes
the outbreak size (or infectious burden) under the assumption that there are limited control resources. We provide optimal
control policies for an isolation only model, a vaccination only model and a combined isolation–vaccination model (or mixed
model). The optimal policies described here contain many interesting features especially when compared to previous analyses.
For example, under certain circumstances the optimal isolation only policy is not unique. Furthermore the optimal mixed policy
is not simply a combination of the optimal isolation only policy and the optimal vaccination only policy. The results presented
here also highlight a number of areas that warrant further study and emphasize that time-optimal control of the basic SIR
model is still not fully understood. 相似文献
185.
Fernandes JC Borges M Nascimento H Bronze-da-Rocha E Ramos OS Pintado ME Malcata FX Santos-Silva A 《International journal of biological macromolecules》2011,49(3):433-438
Two COS mixtures and a low molecular weight chitosan (LMWC) were tested for potential cytotoxicity and genotoxicity upon human lymphocytes. Genotoxicity was evaluated in vitro by cytokinesis-blocked micronucleus and alkaline comet assays, while cytotoxicity was assessed by flow cytometry analysis. Our results suggest that COS do not exhibit any genotoxicity upon human lymphocytes, independently of MW or concentration. However, above 0.07 mg/mL COS induced strong cytotoxic effects. According to the concentration used, such cytotoxicity will induce cell death, essentially by necrosis (>0.10 mg/mL) and/or apoptosis (<0.10 mg/mL). The level of necrosis/apoptosis induced by high COS concentrations, suggests a promising use as apoptosis inducers in specific cancer situations. 相似文献
186.
Blanca P. Martínez-Bonfil Guadalupe Salcedo-Morales Alma R. López-Laredo Elsa Ventura-Zapata Silvia Evangelista-Lozano Gabriela Trejo-Tapia 《Plant Cell, Tissue and Organ Culture》2011,107(2):195-203
Castilleja tenuiflora is a medicinal plant that grows in pine–oak woods primarily in southern and central Mexico. It is highly valued for its medicinal
properties, which have been attributed to aucubin-like iridoids. In the present study, we developed an efficient protocol
for in vitro shoot proliferation and ex vitro rooting of C. tenuiflora. Using a colorimetric method, we determined total iridoid contents of various different tissues of propagated plants. The
shoots were induced from nodal explants cultured on Murashige and Skoog (MS) (1962) medium supplemented with indole-3-butyric
acid (IBA) (0 and 0.5 μM) and different concentrations of thidiazuron (TDZ), 6-benzyladenine (BA), or kinetin (KIN) (0–20 μM).
Of the cytokinins tested, KIN was more effective for shoot induction than TDZ or BA, and the highest shoot proliferation rate
was achieved with 5 μM KIN (4 shoots per explant). Plantlets were rooted on MS medium, nutrient solution, or potting mix,
alone or in combination with auxins. The best responses (100% rooting efficiency) were obtained by dipping shoots in half-strength
MS medium containing 7.5 μM IBA before transfer to potting mix. On average, each shoot formed 9 roots of 39.3 ± 3.8 mm in
length after 21 days. These roots appeared to be more functional than those that developed in nutrient solution, and were
associated with a high survival rate (95%) during acclimatization and cultivation in a greenhouse, where flowering occurred
after 4 months. Propagated plants accumulated iridoids, thus representing a potential source of pharmacologically useful compounds. 相似文献
187.
Ulrike Korn Thomas Müller Andreas Ulrich Marina Elsa Herta Müller 《Mycotoxin Research》2011,27(3):195-206
Plant-associated isolates from Fusarium graminearum and F. culmorum were inoculated on wheat in field experiments in 2007 and 2008 to ascertain their influence on fungal colonization of the
ears, as well as mycotoxin contamination (deoxynivalenol, DON; nivalenol, NIV; zearalenone, ZEA) and yield parameters in the
mature crop after inoculation with or without irrigation. The isolates were assigned to four different groups of aggressiveness
on the basis of pathogenic symptom development and mycotoxin production in vitro. Increased levels of trichothecene-producing
Fusarium DNA in the ears indicated a successful inoculation of the plants, which resulted in increased DON content in the wheat kernels
in 2007. Dry conditions at anthesis markedly suppressed fungal colonization as well as mycotoxin accumulation. However, due
to precipitation during the ripening period, yield and thousand-kernel weight were similar whether or not irrigation was applied
at the time of inoculation. The level of aggressiveness among the isolates as determined in vitro was not reflected in the
field experiment. The activity of the extracellular invertase in developing ears increased as a plant response to pathogen
infection, especially when the plants were irrigated at the time of inoculation. In 2008, the Fusarium inoculation of wheat heads did not cause fungal growth and mycotoxin contamination in the grain, because of the dry weather
conditions that occurred over the entire period of anthesis and ripening. The risk of future mycotoxin contamination in grains
was discussed based on climate change prognosis. 相似文献
188.
Miñano-Molina AJ España J Martín E Barneda-Zahonero B Fadó R Solé M Trullás R Saura CA Rodríguez-Alvarez J 《The Journal of biological chemistry》2011,286(31):27311-27321
β-Amyloid (Aβ), a peptide generated from the amyloid precursor protein, is widely believed to underlie the pathophysiology of Alzheimer disease (AD). Emerging evidences suggest that soluble Aβ oligomers adversely affect synaptic function, leading to cognitive failure associated with AD. The Aβ-induced synaptic dysfunction has been attributed to the synaptic removal of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors (AMPARs). However, the molecular mechanisms underlying the loss of AMPAR induced by Aβ at synapses are largely unknown. In this study we have examined the effect of Aβ oligomers on phosphorylated GluA1 at serine 845, a residue that plays an essential role in the trafficking of AMPARs toward extrasynaptic sites and the subsequent delivery to synapses during synaptic plasticity events. We found that Aβ oligomers reduce basal levels of Ser-845 phosphorylation and surface expression of AMPARs affecting AMPAR subunit composition. Aβ-induced GluA1 dephosphorylation and reduced receptor surface levels are mediated by an increase in calcium influx into neurons through ionotropic glutamate receptors and activation of the calcium-dependent phosphatase calcineurin. Moreover, Aβ oligomers block the extrasynaptic delivery of AMPARs induced by chemical synaptic potentiation. In addition, reduced levels of total and phosphorylated GluA1 are associated with initial spatial memory deficits in a transgenic mouse model of AD. These findings indicate that Aβ oligomers could act as a synaptic depressor affecting the mechanisms involved in the targeting of AMPARs to the synapses during early stages of the disease. 相似文献
189.
Champ S Puvirajesinghe TM Perrody E Menouni R Genevaux P Ansaldi M 《The Journal of biological chemistry》2011,286(45):38876-38885
Temperate bacteriophage lytic development is intrinsically related to the stress response in particular at the DNA replication and virion maturation steps. Alternatively, temperate phages become lysogenic and integrate their genome into the host chromosome. Under stressful conditions, the prophage resumes a lytic development program, and the phage DNA is excised before being replicated. The KplE1 defective prophage of Escherichia coli K12 constitutes a model system because it is fully competent for integrative as well as excisive recombination and presents an atypical recombination module, which is conserved in various phage genomes. In this work, we identified the host-encoded stress-responsive molecular chaperone DnaJ (Hsp40) as an active participant in KplE1 prophage excision. We first show that the recombination directionality factor TorI of KplE1 specifically interacts with DnaJ. In addition, we found that DnaJ dramatically enhances both TorI binding to its DNA target and excisive recombination in vitro. Remarkably, such stimulatory effect by DnaJ was performed independently of its DnaK chaperone partner and did not require a functional DnaJ J-domain. Taken together, our results underline a novel and unsuspected functional interaction between the generic host stress-regulated chaperone and temperate bacteriophage lysogenic development. 相似文献
190.
Abdalbaset A. A. Bugila José Carlos Franco Elsa Borges da Silva Manuela Branco 《Journal of Insect Behavior》2014,27(4):439-453
The host behavioral and immune (encapsulation) defenses against the parasitoid Anagyrus sp. nr. pseudococci were compared for five mealybug species with different phylogenetic relationships and geographical origins: i) a Mediterranean native mealybug species, Planococcus ficus, with a long co-evolutionary history with the parasitoid; ii) three alien mealybugs species, Planococcus citri, Pseudococcus calceolariae and Pseudococcus viburni, with a more recent co-evolutionary history; and iii) a fourth alien mealybug species, Phenacoccus peruvianus, with no previous common history with the parasitoid. Three host defense behaviors were registered: abdominal flipping, reflex bleeding and walking away. The native host Pl. ficus and its congener Pl. citri exhibited the lowest probability of defense behavior (0.11?±?0.01 and 0.09?±?0.01 respectively), whereas the highest value was observed in P. viburni (0.31?±?0.02). Intermediate levels of defense behavior were registered for Ps. calceolariae, and Ph. peruvianus. The probability of parasitoid encapsulation was lowest and highest for two alien host species, Ph. peruvianus (0.20?±?0.07) and Ps. viburni (0.86?±?0.05), respectively. The native host Pl. ficus, its congener Pl. citri and Ps. calceolariae showed intermediate values (0.43?±?0.07, 0.52?±?0.06, and 0.45?±?0.09, respectively). The results are relevant with respect to biological control and to understand possible evolutionary processes involved in host range of A. sp. nr. pseudococci. 相似文献