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排序方式: 共有325条查询结果,搜索用时 15 毫秒
61.
Carlo Natale Giuseppe Giachello Federica Premoselli Pier Giorgio Montarolo Mirella Ghirardi 《PloS one》2013,8(2)
Epileptic activity is generally induced in experimental models by local application of epileptogenic drugs, including pentylenetetrazol (PTZ), widely used on both vertebrate and invertebrate neurons. Despite the high prevalence of this neurological disorder and the extensive research on it, the cellular and molecular mechanisms underlying epileptogenesis still remain unclear. In this work, we examined PTZ-induced neuronal changes in Helix monosynaptic circuits formed in vitro, as a simpler experimental model to investigate the effects of epileptiform activity on both basal release and post-tetanic potentiation (PTP), a form of short-term plasticity. We observed a significant enhancement of basal synaptic strength, with kinetics resembling those of previously described use-dependent forms of plasticity, determined by changes in estimated quantal parameters, such as the readily releasable pool and the release probability. Moreover, these neurons exhibited a strong reduction in PTP expression and in its decay time constant, suggesting an impairment in the dynamic reorganization of synaptic vesicle pools following prolonged stimulation of synaptic transmission. In order to explain this imbalance, we determined whether epileptic activity is related to the phosphorylation level of synapsin, which is known to modulate synaptic plasticity. Using western blot and immunocytochemical staining we found a PTZ-dependent increase in synapsin phosphorylation at both PKA/CaMKI/IV and MAPK/Erk sites, both of which are important for modulating synaptic plasticity. Taken together, our findings suggest that prolonged epileptiform activity leads to an increase in the synapsin phosphorylation status, thereby contributing to an alteration of synaptic strength in both basal condition and tetanus-induced potentiation. 相似文献
62.
Marcelo Mueller de Freitas Bruno Henrique Sardinha de Souza Luciano Nogueira Mirella Marconato Di Bello Arlindo Leal Boiça Júnior 《Arthropod-Plant Interactions》2018,12(1):85-96
Plants have evolved a diverse array of defensive mechanisms against biotic and abiotic stresses, which can be either constitutive or inducible. Variation in plant-intrinsic factors such as the genotype and the leaf position coupled with insect herbivory can affect the expression of resistance to insects. We investigated if soybean defense induction triggered by Spodoptera cosmioides herbivory varies in function of the genotype and leaf position. This hypothesis was tested in two bioassays using leaf discs or entire leaflets collected from the upper and lower trifoliates of S. cosmioides-injured and uninjured V3-V4 soybean plants. We used one genotype that was constitutively resistant and one that was constitutively susceptible to S. cosmioides based on previous screening. Third-instar larvae were fed one of the treatments and assayed for leaf consumption, larval growth, and efficiency of conversion of ingested food. Genotype and leaf position significantly interacted with herbivory and affected soybean-induced resistance to S. cosmioides. Negative responses on S. cosmioides larvae consumption and growth rates were only observed when leaf material was originated from the upper soybean trifoliate. The susceptible soybean genotype did not exhibit induced resistance characteristics. Food offered as leaf disc was better at demonstrating induced resistance in previously injured soybean, whereas offering entire leaflet the induced effects were less pronounced. Here we provide new findings on soybean resistance by demonstrating that resistance induction to S. cosmioides herbivory is dependent on the plant genotype and leaf position where injury took place, with negative effects better evinced in bioassays using leaf discs than entire leaflets. 相似文献
63.
Marisa Gariglio Guo-Guang Ying Laura Hertel Mirella Gaboli Roger G. Clerc Santo Landolfo 《Experimental cell research》1997,236(2):472
The high-mobility group protein T160 was isolated by screening a phage library from a murine pre-B-cell line L1210. South–Western experiments have previously shown that this protein binds to V-(D)-J recombination signal sequences, suggesting that it may be a sequence-specific DNA-binding protein. However, neither gel-shift nor footprinting analyses have been successfully employed with the T160 protein, despite an extensive effort. In this study, the T160 protein or truncated forms made soluble through denaturing and renaturing cycles in urea were successfully used in gel-shift experiments showing that T160 binds to cruciform or linear duplex DNA with no apparent sequence specificity. Furthermore, fragments longer than 100 bp efficiently formed covalently closed circular monomers in the presence of T160 and T4 DNA ligase, indicating that the protein is capable of introducing bends into the duplex. Last, tissue distribution by Western blotting analysis showed that the T160 protein is expressed in various murine tissues in addition to those of lymphoid origin. Considering its broad evolutionary conservation (from plants to mammals) also, these results suggest that the functional role of the T160 protein is not limited to V-(D)-J recombination, but might be involved in basic processes such as DNA replication and repairing, where irregular DNA structures are generated and very likely recognized by HMG domain proteins. 相似文献
64.
Daniela Virgintino Paul Monaghan David Robertson Mariella Errede Mirella Bertossi Glauco Ambrosi Luisa Roncali 《Journal of molecular histology》1997,29(9):655-660
In this study, astrocytes and microvessels of the human cerebral cortex were analysed morphometrically with the aim of acquiring
quantitative information on the glio-vascular relationships, considered to be of great importance in the formation and functioning
of the blood--brain barrier. Immunohistochemistry for the astrocytic marker, glial fibrillary acidic protein, was used with
a computerized image analysis system. The brain tissue was embedded using the progressive lowering of temperature method,
and the image analyser was applied to semithin sections subjected to immunogold--silver staining and viewed by epipolarization
microscopy. The results show that, in the human cerebral cortex, astrocytes cover 11.4% of the cortex area and that their
perivascular processes are nearly as extensive as the vascular bed (0.8% versus 1.72% of the cortex area). These processes
form a virtually continuous sheath around the vascular walls, only 11% of the vessel perimeter lacking this astrocytic glia
covering. The present results, compared with previous unpublished data obtained by conventional immunocytochemical procedures
on wax sections, indicate that low-temperature methods combined with gold--silver immunolabelling on semithin sections significantly
improve the detection of immunoreactivity and the performance of the image analyser.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
65.
Roberto Della Pergola Alessandro Fumagalli Carlo Manassero Mirella Sansoni 《Inorganica chimica acta》2008,361(6):1763-1769
The two clusters [HFe5NiN(CO)14]2− (1) and [HFe4Ni2N(CO)13]2− (2) were obtained by reaction of [Fe4N(CO)12]− and [Ni6(CO)12]2− in refluxing MeCN and EtCN, respectively, along with other Fe-Ni mixed metal clusters. Their solid state structures were determined on the [PPh4]+ salts, and both have an octahedral metal cage, containing an interstitial nitrogen atom. The two Ni atoms in 2 are cis, with a Ni-Ni separation of 2.724(1) Å. The two anions have different stereochemistry of the carbonyl ligands: in 1, five CO’s are semi-bridging, and the remaining nine are terminal; in 2 there are three asymmetric bridging and ten terminal ligands (two for each iron and one for each nickel). The hydride ligands were located in the final difference maps, both bridging a Ni-Fe edge of the clusters but, thanks to the better quality of the diffraction data, the metal-hydrogen distances were refined only in 2. In this cluster, the Fe-H and Ni-H bond lengths are 1.77(2) and 1.79(2) Å, respectively. 相似文献
66.
Christian Cortés-Rojo Elizabeth Calderón-Cortés Mónica Clemente-Guerrero Mirella Estrada-Villagómez Salvador Manzo-Avalos Ricardo Mejía-Zepeda Istvan Boldogh Alfredo Saavedra-Molina 《Journal of bioenergetics and biomembranes》2009,41(1):15-28
Lipoperoxidative damage to the respiratory chain proteins may account for disruption in mitochondrial electron transport chain
(ETC) function and could lead to an augment in the production of reactive oxygen species (ROS). To test this hypothesis, we
investigated the effects of lipoperoxidation on ETC function and cytochromes spectra of Saccharomyces cerevisiae mitochondria. We compared the effects of Fe2+ treatment on mitochondria isolated from yeast with native (lipoperoxidation-resistant) and modified (lipoperoxidation-sensitive)
fatty acid composition. Augmented sensitivity to oxidative stress was observed in the complex III-complex IV segment of the
ETC. Lipoperoxidation did not alter the cytochromes content. Under lipoperoxidative conditions, cytochrome c reduction by succinate was almost totally eliminated by superoxide dismutase and stigmatellin. Our results suggest that lipoperoxidation
impairs electron transfer mainly at cytochrome b in complex III, which leads to increased resistance to antimycin A and ROS generation due to an electron leak at the level
of the QO site of complex III. 相似文献
67.
Jason Greenwald Mirella Nader Hervé Celia Christelle Gruffaz Valérie Geoffroy Jean-Marie Meyer Isabelle J. Schalk Franc Pattus 《Molecular microbiology》2009,72(5):1246-1259
The first step in the specific uptake of iron via siderophores in Gram-negative bacteria is the recognition and binding of a ferric siderophore by its cognate receptor. We investigated the molecular basis of this event through structural and biochemical approaches. FpvA, the pyoverdine–Fe transporter from Pseudomonas aeruginosa ATCC 15692 (PAO1 strain), is able to transport ferric–pyoverdines originating from other species, whereas most fluorescent pseudomonads are only able to use the one they produce among the more than 100 known different pyoverdines. We solved the structure of FpvA bound to non-cognate pyoverdines of high- or low-affinity and found a close correlation between receptor–ligand structure and the measured affinities. The structure of the first amino acid residues of the pyoverdine chain distinguished the high- and low-affinity binders while the C-terminal portion of the pyoverdines, often cyclic, does not appear to contribute extensively to the interaction between the siderophore and its transporter. The specificity of the ferric–pyoverdine binding site of FpvA is conferred by the structural elements common to all ferric–pyoverdines, i.e. the chromophore, iron, and its chelating groups. 相似文献
68.
Jeronymo Dalapicolla Ronnie Alves Rodolfo Jaff Santelmo Vasconcelos Eder Soares Pires Gisele Lopes Nunes Jovani Bernardino de Souza Pereira Jos Tasso F. Guimares Mariana C. Dias Taís Nogueira Fernandes Daniela Scherer Fernando Marino Gomes dos Santos Alexandre Castilho Mirella Pupo Santos Emiliano Nicolas Caldern Rodrigo Lemes Martins Rodrigo Nunes da Fonseca Francisco de Assis Esteves Cecílio Frois Caldeira Guilherme Oliveira 《Ecology and evolution》2021,11(15):10119
The quillwort Isoëtes cangae is a critically endangered species occurring in a single lake in Serra dos Carajás, Eastern Amazon. Low genetic diversity and small effective population sizes (N e) are expected for narrow endemic species (NES). Conservation biology studies centered in a single species show some limitations, but they are still useful considering the limited time and resources available for protection of species at risk of extinction. Here, we evaluated the genetic diversity, population structure, N e, and minimum viable population (MVP) of I. cangae to provide information for effective conservation programs. Our analyses were based on 55 individuals collected from the Amendoim Lake and 35,638 neutral SNPs. Our results indicated a single panmictic population, moderate levels of genetic diversity, and N e in the order of thousands, contrasting the expected for NES. Negative FIS values were also found, suggesting that I. cangae is not under risk of inbreeding depression. Our findings imply that I. cangae contains enough genetic diversity to ensure evolutionary potential and that all individuals should be treated as one demographic unit. These results provide essential information to optimize ex situ conservation efforts and genetic diversity monitoring, which are currently applied to guide I. cangae conservation plans. 相似文献
69.
To get access to iron, Pseudomonas aeruginosa produces the siderophore pyoverdine (PVD), composed of a fluorescent chromophore linked to an octapeptide, and its corresponding outer membrane transporter FpvA. This transporter is composed of three domains: a β-barrel inserted into the membrane, a plug that closes the channel formed by the barrel, and a signaling domain in the periplasm. The plug and the signaling domain are separated by a sequence of five residues called the TonB box, which is necessary for the interaction of FpvA with the inner membrane TonB protein. Genetic deletion of the plug domain resulted in the presence of a β-barrel in the outer membrane unable to bind and transport PVD-Fe. Expression of the soluble plug domain with the TonB box inhibited PVD-(55)Fe uptake most likely through interaction with TonB in the periplasm. A reconstituted FpvA in the bacterial outer membrane was obtained by the coexpression of separately encoded plug and β-barrel domains, each endowed with a signal sequence and a signaling domain. This resulted in polypeptide complementation after secretion across the cytoplasmic membrane. The reconstituted FpvA bound PVD-Fe with the same affinity as wild-type FpvA, indicating that the resulting transporter is correctly folded and reconstituted in the outer membrane. PVD-Fe uptake was TonB-dependent but 75% less efficient compared to wild-type FpvA. These data are consistent with a gated mechanism in which no open channel with a complete removal of the plug domain for PVD-Fe diffusion is formed in FpvA at any point during the uptake cycle. 相似文献
70.
Three new chiral ligands bearing an O,O′,N donor set (OmethoxyOhydroxyNpyridine) were synthesised and coordinated to FeIII, FeII, NiII, CuII and ZnII to yield complexes with the general formula [M(OON)Clx]y. While the pyridine N and the hydroxy O atoms coordinate strongly to all applied metal ions, the methoxy donor seems not to be involved in coordination, although some evidence for a weak interaction between OMe and the ZnII were found in NMR spectra. In the bidentate O′,N coordination mode the new ligands exhibit several coordination geometries as analysed in the solid compounds by XRD, EXAFS and EPR and in solution by UV-Vis absorption, cyclic voltammetry, EXAFS, EPR or NMR spectroscopy. 相似文献