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排序方式: 共有385条查询结果,搜索用时 15 毫秒
1.
Andrew F. Feldman Daniel J. Short Gianotti Jianzhi Dong Isabel F. Trigo Guido D. Salvucci Dara Entekhabi 《Global Change Biology》2023,29(1):110-125
Vegetation cover creates competing effects on land surface temperature: it typically cools through enhancing energy dissipation and warms via decreasing surface albedo. Global vegetation has been previously found to overall net cool land surfaces with cooling contributions from temperate and tropical vegetation and warming contributions from boreal vegetation. Recent studies suggest that dryland vegetation across the tropics strongly contributes to this global net cooling feedback. However, observation-based vegetation-temperature interaction studies have been limited in the tropics, especially in their widespread drylands. Theoretical considerations also call into question the ability of dryland vegetation to strongly cool the surface under low water availability. Here, we use satellite observations to investigate how tropical vegetation cover influences the surface energy balance. We find that while increased vegetation cover would impart net cooling feedbacks across the tropics, net vegetal cooling effects are subdued in drylands. Using observations, we determine that dryland plants have less ability to cool the surface due to their cooling pathways being reduced by aridity, overall less efficient dissipation of turbulent energy, and their tendency to strongly increase solar radiation absorption. As a result, while proportional greening across the tropics would create an overall biophysical cooling feedback, dryland tropical vegetation reduces the overall tropical surface cooling magnitude by at least 14%, instead of enhancing cooling as suggested by previous global studies. 相似文献
2.
Pili of Pasteurella multocida of porcine origin 总被引:1,自引:0,他引:1
Abstract Using electron microscopy, pili with at least two distinct morphologies were observed on strains of Pasteurella multocida isolated from pigs with atrophic rhinitis. Rigid pili were found on 60–80% of all cells observed. These pili had a strong tendency to lie flat along the side of the outer cell membrane of P. multocida and as a result frequently were difficult to see. After growth in vitro, piliated P. multocida cells produced few pili (approx. 3–5 per cell). Heavily piliated cells were occasionally observed. The second type of pili were curly and also were difficult to visualize. Cells from cultures containing piliated cells failed to attach to red blood cells and to immobilized mucus. 相似文献
3.
4.
Fabio Orlandi Herminia Garcia-Mozo Carmen Galán Bruno Romano Consuelo Diaz de la Guardia Luis Ruiz Maria del Mar Trigo Eugenio Dominguez-Vilches Marco Fornaciari 《International journal of biometeorology》2010,54(2):151-163
The aim of this study was to investigate the main climatic and biological trends related to olive flowering in central-southern
Italy compared to those in Andalusia, Spain. Results since 1982 were compared for the two long-series monitoring areas of
Cordoba and Perugia, and since 1992–1999 for the short-series areas. The relationship between climatic trends and the biological
response of the olive, a widespread culture in the Mediterranean basin, were investigated. An aerobiological method involving
capturing pollen released into the atmosphere was utilised as a bioindicator of flowering phenology. The study results confirm
the strong relationship between flowering periods and spring temperature trends for the olive. Temperature during March, April
and May was the parameter most related to flowering date in the study areas, particularly in Italy. In some cases we found
a significant correlation between flowering and past autumn temperatures, probably due to their effect on floral bud dormancy
induction, but this phenomenon appeared to be of minor importance in the studied areas. The phenological trend results show
the continuous advance of flowering dates to the late 1990s, followed by a relatively stationary time series related to a
short-term temperature fluctuation in the Mediterranean area. This latter period probably represents a mesoscale event forced
by a macroscale event—the North Atlantic Oscillation. The results reveal that the trend towards increased temperatures, and
the consequent flowering advance of some species, indicated some years ago is nowadays not as clear as was expected and should
be confirmed over the next few years in the Mediterranean areas under investigation. 相似文献
5.
Conidial spores are often used as the infectious agent during insect biocontrol applications of entomopathogenic fungi. Here we show differential virulence of conidia derived from Metarhizium anisopliae strain EAMa 01/58-Su depending upon the solid substrata used for cultivation, where LC50 values differed by up to ~10-fold (5.3×106?4.5×105 conidia/ml) and LT50 values by ~40% (9.8?7.1 d). This fungal strain is also known to secrete proteins that are toxic towards adult Mediterranean fruit flies, Ceratitis capitata, and the Greater wax moth, Galleria mellonella, larvae. In vitro production and intrahemoceol injection using G. mellonella as the host was used to test fractions during purification of the protein toxins, demonstrating that they elicited defence-related responses including melanisation and tissue necrosis. Production of these proteins/peptides along with a number of potential cuticle degrading enzymes was confirmed both in vitro and during the infection process (in vivo). Two-dimensional gel electrophoresis, followed by gel elution and bioassay, was used to identify at least three proteins or peptides (molecular mass=11, 15 and 15 kDa) as mediating the observed insect toxicity. These data demonstrate that in vitro screening for insect toxins can mimic in vivo (i.e. during the infection process) secretion and applies the use of proteomics to invertebrate pathology. 相似文献
6.
Victoria E. Santos Almudena Alcón Ana B. Martín Emilio Gómez Felix Garcia-Ochoa 《Biocatalysis and Biotransformation》2013,31(2-4):286-294
The influence of operational conditions (pH, temperature and oxygen transfer rate) on the initial reaction rates of the four reactions involved in the 4S biodesulfurization route of dibenzothiophenes (DBT) has been studied. The bioprocess was carried out using a genetically modified organism, Pseudomonas putida CECT 5279. The rates of the four reactions were calculated from the rates of production of different compounds involved in the 4S pathway, by matrix manipulation. The initial (zero time) reaction rates showed a slight dependence on oxygen transfer rate. Temperature and pH were optimal at 30°C and 9, respectively, temperature being the most important variable. This study also identifies the last reaction as the limiting step in the pathway. 相似文献
7.
Nadia Aboulaich Lamiaa Achmakh Hassan Bouziane M. Mar Trigo Marta Recio Mohamed Kadiri Baltasar Cabezudo Hassane Riadi Mohamed Kazzaz 《International journal of biometeorology》2013,57(2):197-205
Poaceae pollen is one of the most prevalent aeroallergens causing allergenic reactions. The aim of this study was to characterise the grass pollen season in Tetouan during the years 2008–2010, to analyse the effect of some meteorological parameters on the incidence of the airborne Poaceae pollen, and to establish forecasting variables for daily pollen concentrations. Aerobiological sampling was undertaken over three seasons using the volumetric method. The pollen season started in April and showed the highest pollen index in May and June, when the maximum temperature ranged from 23 to 27 °C, respectively. The annual pollen score recorded varied from year to year between 2,588 and 5,404. The main pollen season lasted 114–173 days, with peak days occurring mainly in May; the highest concentration reached 308 pollen grains/m3. Air temperature was the most important meteorological parameter and correlated positively to daily pollen concentration increase. An increase in relative humidity and precipitation was usually related to a decrease in airborne pollen content. External validation of the models performed using data from 2011 showed that Poaceae pollen concentration can be highly predicted (64.2–78.6 %) from the maximum temperature, its mean concentration for the same day in other years, and its concentration recorded on the previous day. Sensitive patients suffering allergy to Poaceae pollen are at moderate to highest risk of manifesting allergic symptoms to grass pollen over 33–42 days. The results obtained provide new information on the quantitative contribution of the Poaceae pollen to the airborne pollen of Tetouan and on its temporal distribution. Airborne pollen can be surveyed and forecast in order to warn the atopic population. 相似文献
8.
Marta Corton Koji M. Nishiguchi Almudena Avila-Fernández Konstantinos Nikopoulos Rosa Riveiro-Alvarez Sorina D. Tatu Carmen Ayuso Carlo Rivolta 《PloS one》2013,8(6)
Background
Retinal dystrophies (RD) are a group of hereditary diseases that lead to debilitating visual impairment and are usually transmitted as a Mendelian trait. Pathogenic mutations can occur in any of the 100 or more disease genes identified so far, making molecular diagnosis a rather laborious process. In this work we explored the use of whole exome sequencing (WES) as a tool for identification of RD mutations, with the aim of assessing its applicability in a diagnostic context.Methodology/Principal Findings
We ascertained 12 Spanish families with seemingly recessive RD. All of the index patients underwent mutational pre-screening by chip-based sequence hybridization and resulted to be negative for known RD mutations. With the exception of one pedigree, to simulate a standard diagnostic scenario we processed by WES only the DNA from the index patient of each family, followed by in silico data analysis. We successfully identified causative mutations in patients from 10 different families, which were later verified by Sanger sequencing and co-segregation analyses. Specifically, we detected pathogenic DNA variants (∼50% novel mutations) in the genes RP1, USH2A, CNGB3, NMNAT1, CHM, and ABCA4, responsible for retinitis pigmentosa, Usher syndrome, achromatopsia, Leber congenital amaurosis, choroideremia, or recessive Stargardt/cone-rod dystrophy cases.Conclusions/Significance
Despite the absence of genetic information from other family members that could help excluding nonpathogenic DNA variants, we could detect causative mutations in a variety of genes known to represent a wide spectrum of clinical phenotypes in 83% of the patients analyzed. Considering the constant drop in costs for human exome sequencing and the relative simplicity of the analyses made, this technique could represent a valuable tool for molecular diagnostics or genetic research, even in cases for which no genotypes from family members are available. 相似文献9.
Luis Alberto Henríquez-Hernández Almudena Valenciano Palmira Foro-Arnalot María Jesús álvarez-Cubero José Manuel Cozar José Francisco Suárez-Novo Manel Castells-Esteve Adriana Ayala-Gil Pablo Fernández-Gonzalo Montse Ferrer Ferrán Guedea Gemma Sancho-Pardo Jordi Craven-Bartle María José Ortiz-Gordillo Patricia Cabrera-Roldán Estefanía Herrera-Ramos Pedro C. Lara 《PloS one》2013,8(7)
Background
Differences in the distribution of genotypes between individuals of the same ethnicity are an important confounder factor commonly undervalued in typical association studies conducted in radiogenomics.Objective
To evaluate the genotypic distribution of SNPs in a wide set of Spanish prostate cancer patients for determine the homogeneity of the population and to disclose potential bias.Design, Setting, and Participants
A total of 601 prostate cancer patients from Andalusia, Basque Country, Canary and Catalonia were genotyped for 10 SNPs located in 6 different genes associated to DNA repair: XRCC1 (rs25487, rs25489, rs1799782), ERCC2 (rs13181), ERCC1 (rs11615), LIG4 (rs1805388, rs1805386), ATM (rs17503908, rs1800057) and P53 (rs1042522). The SNP genotyping was made in a Biotrove OpenArray® NT Cycler.Outcome Measurements and Statistical Analysis
Comparisons of genotypic and allelic frequencies among populations, as well as haplotype analyses were determined using the web-based environment SNPator. Principal component analysis was made using the SnpMatrix and XSnpMatrix classes and methods implemented as an R package. Non-supervised hierarchical cluster of SNP was made using MultiExperiment Viewer.Results and Limitations
We observed that genotype distribution of 4 out 10 SNPs was statistically different among the studied populations, showing the greatest differences between Andalusia and Catalonia. These observations were confirmed in cluster analysis, principal component analysis and in the differential distribution of haplotypes among the populations. Because tumor characteristics have not been taken into account, it is possible that some polymorphisms may influence tumor characteristics in the same way that it may pose a risk factor for other disease characteristics.Conclusion
Differences in distribution of genotypes within different populations of the same ethnicity could be an important confounding factor responsible for the lack of validation of SNPs associated with radiation-induced toxicity, especially when extensive meta-analysis with subjects from different countries are carried out. 相似文献10.
Competition between spermatozoa of rival males to gain fertilizations has led to a wide array of modifications in sperm structure and function. Sperm cells of most muroid rodents have hook‐shaped extensions in the apical–ventral tip of the head, but the function of this structure is largely unknown. These ‘hooks’ may facilitate aggregation of spermatozoa in so‐called ‘trains’, as an adaptation to sperm competition, because sperm in trains may swim faster than free‐swimming cells. However, there is controversy regarding the role of the hook in train formation, and in relation to whether it is selected by sperm competition. We examined spermatozoa from muroid rodents with varying levels of sperm competition to assess whether (i) sperm aggregates are common in these taxa, (ii) presence of a hook relates to the formation of sperm aggregations, and (iii) formation of sperm aggregations is explained by sperm competition. Our analyses in 25 muroid species revealed that > 92% of spermatozoa swim individually in all species, with the exception of the wood mouse, Apodemus sylvaticus, which has ~50% spermatozoa swimming freely. Species with hooked spermatozoa had higher sperm competition levels and longer sperm than species whose sperm lack a hook. Neither the presence of hook nor sperm competition levels were related to the percentage of sperm in aggregations. Thus, (i) sperm aggregates in muroid rodents are an exceptional trait found only in a few species, (ii) evolution of the sperm hook is associated to sperm competition levels, but (iii) the hook is unlikely to be related to the formation of sperm aggregates. The evolutionary significance of the sperm head hook thus remains elusive, and future studies should examine potential roles of this pervasive structure in sperm's hydrodynamic efficiency and sperm–female tract interactions. 相似文献