排序方式： 共有9条查询结果，搜索用时 15 毫秒
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Mary Alexandra da Costa Fernanda Pinto‐Ferreira Roblia Pond Amorim de Almeida Felippe Danyel Cardoso Martins Adriene Lino Pires Marcelle Mareze Regina Mitsuka‐Bregan Roberta Lemos Freire Rosalynd Vinicios da Rocha Moreira Juliene Meira Borges Italmar Teodorico Navarro 《Zoonoses and public health》2020,67(2):122-129
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Ectodermal Wnt function as a neural crest inducer 总被引：1，自引：0，他引：1
Neural crest cells, which generate peripheral nervous system and facial skeleton, arise at the neural plate/ectodermal border via an inductive interaction between these tissues. Wnts and bone morphogenetic proteins (BMPs) play roles in neural crest induction in amphibians and zebrafish. Here, we show that, in avians, Wnt6 is localized in ectoderm and in vivo inhibition of Wnt signaling perturbs neural crest formation. Furthermore, Wnts induce neural crest from naive neural plates in vitro in a defined medium without added factors, whereas BMPs require additives. Our data suggest that Wnt molecules are necessary and sufficient to induce neural crest cells in avian embryos. 相似文献
3.
Lo B Chou V Cedars MI Gates E Taylor RN Wagner RM Wolf L Yamamoto KR 《Science (New York, N.Y.)》2003,301(5635):921
As research with human embryos and embryonic stem cells proceeds, the authors of this Policy Forum argue that all donors of biological materials should give informed consent, including oocyte and sperm donors. Informed consent is particularly important because of the diverse opinions and strong emotions that surround such research. Some gamete donors who are willing to help women and couples bear children may object to the use of their genetic materials for certain types of research. 相似文献
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The hypothesis that a relatively high Ca content in the fruit associated with relatively low K/Ca, K/Ca and K + Mg/Ca ratios are indicators of a slow ripening and a delayed senescence has been confirmed by analysing the sound and greenback fruits of two tomato varieties. The elemental changes characterizing a retardation of ripening are associated with the greenback disorder not only in the diseased calyx end of the fruit but also in the apex end where the fruit seems to ripen and colour uniformly. 相似文献
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Siqueira FF Almeida MO Barroca TM Horta CC Carmo AO Silva RO Pires PS Lobato FC Kalapothakis E 《Veterinary microbiology》2012,159(3-4):397-405
Clostridium perfringens phospholipase C (Cp-PLC), also called alpha-toxin, is encoded by the plc gene and has been implicated in several diseases; however, only a few studies have described polymorphisms in this gene. The aim of this study was to analyze polymorphisms in the Cp-PLC nucleotide and amino acid sequences obtained from isolates from different regions and to compare them to Clostridium phospholipase C sequences deposited in the NCBI database. Environmental samples (sediment, poultry feed, sawdust) and stool samples (from poultry, bovine, swine, horse, caprine, bird, dog, rabbit, toucan) were collected from healthy and sick animals. A total of 73 isolates were analyzed with the majority of samples belonging to the toxin type A subtype and possessing the gene encoding for the beta-2 toxin. Comparison of plc gene sequences from respective isolates revealed a high genetic diversity in the nucleotide sequences of mature Cp-PLC. Sequence comparisons identified 30 amino acid substitutions and 34 isoforms including some isoforms with substitutions in amino acids critical to toxin function. Comparison of sequences obtained in this study to Cp-PLC sequences obtained from the NCBI database resulted in the identification of 11 common haplotypes and 22 new isoforms. Phylogenetic analysis of phospholipase C sequences obtained from other Clostridium species identified relationships previously described. This report describes a broad characterization of the genetic diversity in the C. perfringens plc gene resulting in the identification of various isoforms. A better understanding of sequences encoding phospholipase C isoforms may reveal changes associated with protein function and C. perfringens virulence. 相似文献
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Jobin Benoît Beaulieu Jason Grenier Marcelle Bélanger Luc Maisonneuve Charles Bordage Daniel Filion Bernard 《Landscape Ecology》2003,18(6):575-590
Most landscape definitions in the western world are based on soil, climatic, or physiographic features and do not integrate
humans as an integral part of the landscape. We present an approach where landscape types have been delineated in southern
Québec, Canada based on current land use where anthropogenic and agricultural activities are concentrated as a practical application
of the holistic approach in landscape definition. Landsat-TM satellite images were classified and the 27 habitat classes were
regrouped into 5 general land cover classes (cash crop, dairy farming, forest, anthropogenic, wetlands) and overlaid onto
soil landscape polygons to characterize natural boundary units. Cluster analyses were used to aggregate these polygons into
seven agricultural types of land scape forming a gradient from urban and high-intensity cash crop farming activities to landscapes
dominated by a mosaic of agriculture and forested areas. Multivariate analyses of raw data and of socio-economic and farming
practices variables were used to describe the defined types of landscape and these were projected over three established land
classification systems of southern Québec (Canadian ecoregions, North American Bird Conservation Initiative regions and Corn
Heat Unit regions) to compare their similarity in terms of land cover and for planning of future ecological studies. Because
agricultural landscapes are highly dynamic, they are bound to undergo changes in the near future. Our landscape delineation
may serve as an experimental setup where land scape dynamics and wildlife populations and community structures could be monitored.
Because the information we used to delineate and characterize agricultural landscape types is readily available in other countries,
our approach could easily be adapted to similar data sources under and a wide variety of landscape types.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Luara Castilho Pereira Leonardo Balbinot Marcelle Teodoro Lima Julieta Bramorski Kelly Cristina Tonello 《林业研究》2022,(2):543-552
Although forests play important roles in the hydrological cycle, there is little information that relates the water retention capacity of litter in areas under ... 相似文献
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Quantifying remaining forest cover and understanding how thefragmentation process operates with respect to the various land-use practicesare important steps when working to preserve the biodiversity associated withwoodlots in agricultural landscapes. We used LANDSAT satellite imagery, soiltypes, and boundaries of regional county municipalities (RCM) as the samplingunit of a 6 million-ha territory located in southern Québec (Canada), to provide a picture of the forest situation in the St. Lawrence Valley.We assessed the effect of human population densities and various types ofagricultural production on the fragmentation process. On average, 45% of thetotal land area of RCMs is forested. However, in 8 of the 59 RCMs studied 20%orless of the total area is still forest habitat. As agricultural use of landincreased, the density of woodlots also increased but their average sizedecreased. An overall fragmentation effect seems to occur where less than 50%ofthe territory is forested, as it is the case for 31 of the 59 studied RCMs.Fragmentation increased along a gradient from traditional dairyagriculture to more intensive cash crop agriculture. Finally, we foundthat the forest discontinuity index, mean woodlot area, and woodlot densitywerethe best indicators of the ongoing forest fragmentation process, but overallhuman population density is the most useful predictive variable.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
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Lipoxygenase activity (LOX), levels of 1-aminocyclopropane-1-carboxylic acid (ACC) and of 1-malonyl-aminocyclopropane-1-carboxylic acid (MACC) and the capacity of isolated fruit disks to evolve ethylene were examined during storage of apples having different fruit mineral content. The internal ethylene concentration (IEC) of the whole fruit was also measured before removing discs of tissue. The results show that all these activities depend on the fruit mineral content and confirm general knowledge on the relations between minerals and fruit storage. For instance, fruits rich in calcium and/or phosphorus presented a lower LOX activity, a lower ACC content and a lower ethylene emission while fruits rich in potassium and/or with a relatively high K/Ca presented a higher LOX activity, a higher ACC level and a higher ethylene emission. Results are discussed in an attempt to explain the effects of minerals on storage quality. 相似文献
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