排序方式: 共有116条查询结果,搜索用时 31 毫秒
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Selene Báez Agustina Malizia Julieta Carilla Cecilia Blundo Manuel Aguilar Nikolay Aguirre Zhofre Aquirre Esteban álvarez Francisco Cuesta álvaro Duque William Farfán-Ríos Karina García-Cabrera Ricardo Grau Jürgen Homeier Reynaldo Linares-Palomino Lucio R. Malizia Omar Melo Cruz Oriana Osinaga Oliver L. Phillips Carlos Reynel Miles R. Silman Kenneth J. Feeley 《PloS one》2015,10(5)
General patterns of forest dynamics and productivity in the Andes Mountains are poorly characterized. Here we present the first large-scale study of Andean forest dynamics using a set of 63 permanent forest plots assembled over the past two decades. In the North-Central Andes tree turnover (mortality and recruitment) and tree growth declined with increasing elevation and decreasing temperature. In addition, basal area increased in Lower Montane Moist Forests but did not change in Higher Montane Humid Forests. However, at higher elevations the lack of net basal area change and excess of mortality over recruitment suggests negative environmental impacts. In North-Western Argentina, forest dynamics appear to be influenced by land use history in addition to environmental variation. Taken together, our results indicate that combinations of abiotic and biotic factors that vary across elevation gradients are important determinants of tree turnover and productivity in the Andes. More extensive and longer-term monitoring and analyses of forest dynamics in permanent plots will be necessary to understand how demographic processes and woody biomass are responding to changing environmental conditions along elevation gradients through this century. 相似文献
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Cell wall lytic enzymes are valuable tools for the biotechnologist, with many applications in medicine, the food industry,
and agriculture, and for recovering of intracellular products from yeast or bacteria. The diversity of potential applications
has conducted to the development of lytic enzyme systems with specific characteristics, suitable for satisfying the requirements
of each particular application. Since the first time the lytic enzyme of excellence, lysozyme, was discovered, many investigations
have contributed to the understanding of the action mechanisms and other basic aspects of these interesting enzymes. Today,
recombinant production and protein engineering have improved and expanded the area of potential applications. In this review,
some of the recent advances in specific enzyme systems for bacteria and yeast cells rupture and other applications are examined.
Emphasis is focused in biotechnological aspects of these enzymes. 相似文献
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Barboni B Russo V Cecconi S Curini V Colosimo A Garofalo ML Capacchietti G Di Giacinto O Mattioli M 《PloS one》2011,6(11):e27550
Background
Assisted reproductive technologies allow to utilize a limited number of fully grown oocytes despite the presence in the ovary of a large pool of meiotically incompetent gametes potentially able to produce live births. In vitro folliculogenesis could be useful to recruit these oocytes by promoting their growth and differentiation.Methodology/Principal Findings
In vitro folliculogenesis was performed starting from sheep preantral (PA) follicles to evaluate oocyte nuclear/epigenetic maturation. Chromatin configuration, quantification of global DNA methylation, and epigenetic remodelling enzymes were evaluated with immunocytochemistry, telomere elongation was assessed with the Q-FISH technique, while the DNA methylation status at the DMRs of maternally IGF2R and BEGAIN, and paternally H19 methylated imprinted genes was determined by bisulfite sequencing and COBRA. Specifically, 70% of PA underwent early antrum (EA) differentiation and supported in culture oocyte global DNA methylation, telomere elongation, TERT and Dnmt3a redistribution thus mimicking the physiological events that involve the oocyte during the transition from secondary to tertiary follicle. Dnmt1 anticipated cytoplasmic translocation in in vitro grown oocytes did not impair global and single gene DNA methylation. Indeed, the in vitro grown oocytes acquired a methylation profile of IGF2R and BEGAIN compatible with the follicle/oocyte stage reached, and maintained an unmethylated status of H19. In addition, the percentage of oocytes displaying a condensed chromatin configuration resulted lower in in vitro grown oocytes, however, their ability to undergo meiosis and early embryo development after IVF and parthenogenetic activation was similar to that recorded in EA follicle in vivo grown oocytes.Conclusions/Significance
In conclusion, the in vitro folliculogenesis was able to support the intracellular/nuclear mechanisms leading the oocytes to acquire a meiotic and developmental competence. Thus, the in vitro culture may increase the availability of fertilizable oocytes in sheep, and become an in vitro translational model to investigate the mechanisms governing nuclear/epigenetic oocyte maturation. 相似文献5.
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Richter SN Gatto B Tabarrini O Fravolini A Palumbo M 《Bioorganic & medicinal chemistry letters》2005,15(19):4247-4251
Structural modifications introduced in 6-amino-quinolones to increase antiviral activity can strongly affect cytotoxicity to host cells. By competition to Tat-TAR complex and binding experiments to viral and cellular DNA and RNA structures, we show that the nature of the substituent at position 7 modifies drug affinity and specificity for the nucleic acid. Interestingly, the basicity of the above substituent modulates chelation of the quinolone template to magnesium ions, which, in turn, critically affects the potency and target selectivity in the antiviral quinolone family. 相似文献
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Trubiani O Salvolini E Santoleri F D'Arcangelo C Spoto G Primio RD Mazzanti L 《The Journal of membrane biology》2005,204(2):77-84
A variety of cellular functions are modulated by the physical properties of the cell membrane, and the modification of intracellular transfer, resulting from loss of membrane integrity, may contribute toward setting the cell onto the pathway of apoptosis. Apoptosis in lymphoid cells can be induced in different ways and biochemical modifications occur at an early phase of cell death, while the morphological features of apoptosis are evident later. We previously reported that DMSO is an efficient apoptosis-inducing factor in the human RPMI-8402 pre-T cell line. The aim of the present study was to verify the effect of DMSO on the plasma membrane fluidity, the intracellular calcium concentration and the phosphodiesterase activity in DMSO-induced apoptosis. Our results show a modification of membrane fluidity associated with an increase of intracellular Ca2+ concentration. Moreover, we demonstrate that these modifications are related to a decrease in the phosphodiesterase (PDE) activity. The correlation between the proceedings of added DMSO and the induction of apoptosis will provide significant information regarding the first part of the apoptotic process. 相似文献
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Brendan P. Kelly Oriana H. Badajos Mervi Kunnasranta John R. Moran Micaela Martinez-Bakker Douglas Wartzok Peter Boveng 《Polar Biology》2010,33(8):1095-1109
Population structure and patterns of habitat use among ringed seals (Phoca hispida) are poorly known, in part because seasonal movements have not been adequately documented. We monitored the movements of
98 ringed seals in the Beaufort and Chukchi seas between 1990 and 2006 using three forms of telemetry. In the winter—spring
period (when the seals were occupying shorefast ice), we used radio and ultra-sonic tags to track movements above and below
the ice, respectively. We used satellite-linked transmitters in summer and fall (when the seals ranged away from their winter
sites) to track at-sea movements. In the shorefast ice habitat, the home ranges of 27 adult males ranged from <1 to 13.9 km2 (median = 0.628) while the home ranges of 28 adult females ranged from <1 to 27.9 km2 (median = 0.652). The 3-dimensional volumes used by 9 seals tracked acoustically under the ice averaged 0.07 (SD = 0.04) km3 for subadults and adult males and 0.13 (SD = 0.04) km3 for adult females. Three of the radio-tracked seals and 9 tracked by satellite ranged up to 1,800 km from their winter/spring
home ranges in summer but returned to the same small (1–2 km2) sites during the ice-bound months in the following year. The restricted movements of ringed seals during the ice-bound season—including
the breeding season—limits their foraging activities for most of the year and may minimize gene flow within the species. 相似文献
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Simonetti O Cirioni O Goteri G Ghiselli R Kamysz W Kamysz E Silvestri C Orlando F Barucca C Scalise A Saba V Scalise G Giacometti A Offidani A 《Peptides》2008,29(4):520-528
We investigated the effect of topical temporin A in the management of methicillin-resistant strain of Staphylococcus aureus (MRSA)-infected experimental surgical wounds in mice. The wound, cut through the panniculus carnosus of BALB/c mice, was inoculated with 5x10(7) colony-forming units of MRSA. Mice were treated with Allevyn, temporin A-soaked Allevyn, Allevyn and daily intraperitoneal teicoplanin (7mg/kg), temporin A-soaked Allevyn and daily intraperitoneal teicoplanin. Main outcome measurements were: quantitative bacterial culture, histological examination with assessment of micro-vessel density and of vascular endothelial growth factor (VEGF) expression in tissue sections, and VEGF plasma levels alike. Treatment with temporin-A associated with teicoplanin injection significantly reduced bacterial load to 0.85 x 10(1)+/-0.1 x 10(1)CFU/ml. Histological examination showed that infected mice receiving temporin A-soaked Allevyn (with or without teicoplanin) had a higher degree of granulation tissue formation and collagen deposition compared to the other treated groups. A significant increase in serum VEGF expression was observed in mice receiving temporin A topically and temporin A topically associated with intraperitoneal teicoplanin. In conclusion our results demonstrated that temporin A is effective in the management of infected wounds, by a significant bacterial growth inhibition and acceleration of wound repair process. 相似文献
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