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91.
At altitudes between 1300 m to 2100 m in the Etna massif (Sicily), an endemic species of theBetula genus,Betula aetnensis Rafin, grows in a well-defined microclimatical context. Aboveground biomass and nutrient content studies within one stand revealed no significant differences from the otherBetula species, normally found in colder more temperate climate regions.Throughout the studied sites, biomass production, nutrient cycling and various structural or physiological characteristics (leaf area index) varied very little.Other researches indicate that the originality ofBetula aetnensis lies more in the histological or anatomical characteristics of its water conducting system which enables the species to adapt to Mediterranean-climate summer droughts in the Etna massif.
Riassunto Sull'Etna, tra 1300 e 2100 m d'altitudine, in una zona microclimaticamente ben definita del versante nordorientale, si rinviene laBetula aetnensis Rafin.Dallo studio della fitomassa e della mineralomassa aerea del bosco di Monte Baracca, è emerso che non vi sono differenze notevoli con le altre specie indagate del genereBetula, più caratteristiche dei climi temperati e freddi.La produzione di biomassa, cosi come la gestione degli elementi nutritivi, è molto simile ai diversi popolamenti già indagati, cosi come certe caratteistiche strutturali e fisiologiche (leaf area index).L'originalità dellaBetula aetnensis è da ricercarsi nel vantaggio che ne ricava, a livello endogeno, sfruttando le caratteristiche istologiche ed anatomiche del suo apparato conduttore, che le consentono un efficace ed eccellente adattamento alle condizioni di siccità estive particolari del clima mediterraneo del vulcano.
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92.
Morphine-6-beta-d-glucuronide (M6G) is an active metabolite of morphine with high analgesic potency despite a low blood-brain barrier (BBB) permeability. The aim of the study was to elucidate its transport mechanism across the BBB. We first checked if M6G was effluxed by the P-glycoprotein (P-gp), as previously reported by others. Second, we investigated the role of anionic transporters like the multidrug resistance-associated protein mrp1 and the glucose transporter GLUT-1. The brain uptake of [14C]M6G was measured by the in situ brain perfusion technique in wild-type and deficient mice [mdr1a(-/-) and mrp1(-/-)], with and without probenecid, digoxin, PSC833 or d-glucose. No difference was found between P-gp and mrp1 competent and deficient mice. The brain uptake of [14C]M6G co-perfused with probenecid in wild-type mice was not significantly different from that found in group perfused with [14C]M6G alone. The co-perfusion of [14C]M6G with digoxin or PSC833 was responsible of a threefold decrease of its uptake in mdr1a competent and deficient mice, suggesting that another transporter than P-gp and sensitive to digoxin and PSC833, may be involved. The co-perfusion of [14C]M6G with d-glucose revealed a threefold decrease in M6G uptake. In conclusion, P-gp and mrp1 are not involved in the transport of M6G at the BBB level in contrast to GLUT-1 and a digoxin-sensitive transporter (probably oatp2), which can actively transport M6G but with a weak capacity.  相似文献   
93.
In response to a wound, astrocytes in culture extend microtubule‐rich processes and polarize, orienting their centrosomes and Golgi apparatus woundside. β1 Integrin null astrocytes fail to extend processes toward the wound, and are disoriented, and often migrate away orthogonal, to the wound. The centrosome is unusually fragmented in β1 integrin null astrocytes. Expression of a β1 integrin cDNA in the null background yields cells with intact centrosomes that polarize and extend processes normally. Fragmented centrosomes rapidly assemble following integrin ligation and cell attachment. However, several experiments indicated that cell adhesion is not necessary. For example, astrocytes in suspension expressing a chimeric β1 subunit that can be activated by an antibody assemble centrosomes suggesting that β1 activation is sufficient to cause centrosome assembly in the absence of cell adhesion. siRNA knockdown of PCM1, a major centrosomal protein, inhibits cell polarization, consistent with the notion that centrosomes are necessary for polarity and that integrins regulate polarity via centrosome integrity. Screening inhibitors of molecules downstream of integrins indicate that neither FAK nor ILK is involved in regulation of centrosome integrity. In contrast, blebbistatin, a specific inhibitor of non‐muscle myosin II (NMII), mimics the response of β1 integrin null astrocytes by disrupting centrosome integrity and cell polarization. Blebbistatin also inhibits integrin‐mediated centrosome assembly in astrocytes attaching to fibronectin, consistent with the hypothesis that NMII functions downstream of integrins in regulating centrosome integrity. © 2012 Wiley Periodicals, Inc. Develop Neurobiol 73: 333–353, 2013.  相似文献   
94.
New insights into the evolution of metazoan tyrosinase gene family   总被引:1,自引:0,他引:1  
Tyrosinases, widely distributed among animals, plants and fungi, are involved in the biosynthesis of melanin, a pigment that has been exploited, in the course of evolution, to serve different functions. We conducted a deep evolutionary analysis of tyrosinase family amongst metazoa, thanks to the availability of new sequenced genomes, assessing that tyrosinases (tyr) represent a distinctive feature of all the organisms included in our study and, interestingly, they show an independent expansion in most of the analyzed phyla. Tyrosinase-related proteins (tyrp), which derive from tyr but show distinct key residues in the catalytic domain, constitute an invention of chordate lineage. In addition we here reported a detailed study of the expression territories of the ascidian Ciona intestinalis tyr and tyrps. Furthermore, we put efforts in the identification of the regulatory sequences responsible for their expression in pigment cell lineage. Collectively, the results reported here enlarge our knowledge about the tyrosinase gene family as valuable resource for understanding the genetic components involved in pigment cells evolution and development.  相似文献   
95.
96.
Human Mental Retardation (MR) is a common and highly heterogeneous pediatric disorder affecting around 3% of the general population; at least 215 X-linked MR (XLMR) conditions have been described, and mutations have been identified in 83 different genes, encoding proteins with a variety of function, such as chromatin remodeling, synaptic function, and intracellular trafficking. The small GTPases of the RAB family, which play an essential role in intracellular vesicular trafficking, have been shown to be involved in MR. We report here the identification of mutations in the small GTPase RAB39B gene in two male patients. One mutation in family X (D-23) introduced a stop codon seven amino acids after the start codon (c.21C > A; p.Y7X). A second mutation, in the MRX72 family, altered the 5′ splice site (c.215+1G > A) and normal splicing. Neither instance produced a protein. Mutations segregate with the disease in the families, and in some family members intellectual disabilities were associated with autism spectrum disorder, epileptic seizures, and macrocephaly. We show that RAB39B, a novel RAB GTPase of unknown function, is a neuronal-specific protein that is localized to the Golgi compartment. Its downregulation leads to an alteration in the number and morphology of neurite growth cones and a significant reduction in presynaptic buttons, suggesting that RAB39B is required for synapse formation and maintenance. Our results demonstrate developmental and functional neuronal alteration as a consequence of downregulation of RAB39B and emphasize the critical role of vesicular trafficking in the development of neurons and human intellectual abilities.  相似文献   
97.
CdSe nanocrystals (NCs) can be used as an electron acceptor in solar cells, employing organic ligands to passivate their surface and make them processable from solution. The nature and abundance of impurities present after NC ligand exchange from oleic acid to n‐butylamine are identified. A further purification step using hexane as a selective solvent is described, which excludes NC aggregates from solution. The influence of NC aggregates on photovoltaic device performance is studied in a CdSe:poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylene vinylene] (MDMO‐PPV) bulk heterojunction solar cell. The exclusion of NC aggregates leads to a four‐fold increase in device power conversion efficiency (PCE) in optimized devices. A superior blend morphology leading to improved charge generation and a better NC percolation network is identified as the main causes of this increased solar cell performance.  相似文献   
98.
The structure of pyrenocine C, a new metabolite isolated from onion pink root fungus, Pyrenochaeta terrestris (Hansen) has been elucidated as (±)-(2′E)-5-(1′-hydroxybut-2′-enyl)-4-methoxy-6-methyl-2-pyrone by spectroscopic methods and chemical correlation with pyrenocine A.  相似文献   
99.
100.
Epac1 is a cAMP-stimulated guanine exchange factor that activates Rap1. The protein product of the T cell leukemia 1 (TCL1) proto-oncogene binds to Akt enhancing its kinase activity. TCL1 and Epac promote cellular proliferation because of their activating effects on Akt. Employing macrophages, we have studied the mechanisms whereby these proteins function in the regulation of Akt kinase activity. Cells were treated with 8-CPT-2-O-Me-cAMP, a cAMP analog which acts selectively and specifically via Epac1. Epac1 co-immunoprecipitated with TCL1 in plasma membrane and nuclear fractions of 8-CPT-2-O-Me-cAMP-stimulated macrophages. Interaction of TCL1 and Epac1 was also observed in a [125I]GST-Epac1 pulldown assay. A two-threefold increase in Akt Thr-308 and Akt Ser-473 protein kinase activities and their phosphoprotein levels was observed in TCL1 immunoprecipitates of plasma membranes and nuclei of the treated cells. Elevated Akt Thr-308 protein kinase activity and its phosphoprotein levels were significantly reduced in TCL1 immunoprecipitates of plasma membranes of 8-CPT-2-O-Me-cAMP-treated cells where Epac1 gene expression was silenced. In contrast, Akt Ser-473 protein kinase activity and its phosphoprotein levels were reduced only in plasma membranes. Our studies suggest that a ternary complex of TCL1, Epac1, and Akt forms in activated macrophages both promoting Akt activation and regulating intracellular distribution of Akt.  相似文献   
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