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91.
José A. Blanco-Aguiar Miguel Delibes-Mateos Beatriz Arroyo Pablo Ferreras Fabián Casas Raimundo Real J. Mario Vargas Rafael Villafuerte Javier Viñuela 《European Journal of Wildlife Research》2012,58(2):433-439
Hyperpredation can be described as a restrictive case of apparent competition where an increased number of primary prey species
indirectly induces the decrease of the secondary prey species through numerical response of predators to the primary prey
dynamics. It has been proposed that rabbit hemorrhagic disease (RHD), which decimated populations of European wild rabbit
(Oryctolagus cuniculus) in Spain, led to prey switching by raptors towards red-legged partridges (Alectoris rufa) causing declines in their populations as a peculiar case of hyperpredation. 相似文献
92.
The cavum septi pellucidi: a fifth ventricle? 总被引:1,自引:0,他引:1
The morphological characteristics of the cavum septi pellucidi (CSP) in the rat are described. This structure is formed by a set of cavities generally located in the midline area of the septal region. Into the lumen of the cavities free cells rooted out from the CSP walls were observed. Several layers could be delimitated from the surface of the CSP to the most inner region consisting of connective cells and fibers, and astrocytes. However, no ependymal cells were visualized. According to the morphological data, the CSP wall could have a function of resistance against mechanical tensions that are produced in this brain region. The term 'fifth ventricle' for the CSP seems to be inappropriate. 相似文献
93.
Structure and assembly of phage phi29. 总被引:1,自引:0,他引:1
E Vi?uela A Camacho F Jiménez J L Carrascosa G Ramírez M Salas 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1976,276(943):29-35
Bacteriophage phi29 is a small, morphologically complex, virus with a DNA of molecular mass 12 X 10(6). The most likely structure of the head of phi29 consists of two fivefold symmetric end-caps based on T = 1 icosahedral symmetry, separated by an equatorial row of 5 hexamers. The eighteen genes identified in phi29 genome have been mapped and, in some cases, the gene products have been identified. Five linked genes, four coding for structural proteins (G, A, E, H) and one coding for a non-structural protein (J), are essential to determine the normal shape of the capsid. Protein pJ may be a scaffolding protein. An account of the effects of mutations in phi29 genes is given. 相似文献
94.
95.
J L Subiza J Gil R Rodríguez J G Ruiz de Morales J E Vi?uela E G de la Concha 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(8):2636-2642
We have shown previously that an IgM mAb (A10) recognizing Ehrlich tumor (ET) cell surface carbohydrates, inhibits in vivo ET growth by a macrophage-dependent mechanism. The inhibition mechanism involving both IgM and macrophages was unclear because receptors for IgM on macrophages are controversial and another monoclonal IgM (E1), also recognizing ET cell surface carbohydrates, was completely unable to show any protective effect. Here we show that A10, but not E1, was able to promote adhesion between macrophages and ET cells by a receptor for IgM-independent mechanism. Immunofluorescence studies showed that A10, but not E1, did react with macrophages if these cells were preincubated with a source of Ag spontaneously released from ET cells. This Ag release appeared to be required for A10-mediated adhesion, because adhesion was not obtained when ET cells fixed with paraformaldehyde were used. Cytostasis studies performed with macrophages stimulated with L-929 conditioned medium and ET cells showed that A10, but not E1 nor unrelated IgM, was able to inhibit ET cell proliferation in vitro by a mechanism involving cell contact between both cell populations. Therefore, IgM inhibition of ET growth, both in vivo and in vitro, could be explained by a lectin-like mechanism, where IgM, recognizing Ag of tumor origin, bridges macrophages to tumor cells. 相似文献
96.
97.
The chinstrap penguin (Pygoscelis antarctica) is the smallest penguin species to be used to study the physiology of fasting. We analysed body-mass change and plasma chemistry of five non-breeding chinstraps during an experimental fasting period in the breeding season. We also analysed the same parameters in six fasting birds under natural conditions (during an incubation shift, which lasts about 10 days). Both groups presented similar patterns of change, showing a rapid increase in urea and uric acid plasma concentrations. Urea surpassed 3 mmol/l after 5 fasting days, while uric acid reached 1 mmol/l after 9 days. Plasma glucose levels decreased after 11 days, whereas cholesterol also showed a clear reduction during fasting. These results as a whole suggest that chinstrap penguins reached phase III after a short period in comparison with other Pygoscelis species. Body size and ecological factors could explain these inter-specific differences. 相似文献
98.
Ana Benítez-López Javier Viñuela François Mougeot Jesús T. García 《Biodiversity and Conservation》2017,26(1):63-83
Habitat selection is an inherently scale-sensitive process in which detected selection patterns frequently depend on the scale of analysis employed. We used a multi-scale modelling approach to identify how the distributions of two sympatric birds are shaped by differential selection at the landscape, land use and microhabitat scales and by human infrastructures as possible sources of disturbance. We studied two threatened steppe birds, the pin-tailed sandgrouse (PTS) and black-bellied sandgrouse (BBS) in central Spain. Land use gradients explained most of the variation in PTS and BBS occurrence, but there was cross-scale interdependence between the lower (microhabitat) and upper (landscape) spatial scales for the PTS. Synergies between the three scales highlighted the importance of integrating habitat scales in a single modelling framework. The process of habitat selection was also modulated by human disturbance. Both species selected ploughs of large size distant from houses, tracks and other infrastructures, although BBS exhibited broader habitat tolerance than the PTS, and was more sensitive to human disturbance. At microhabitat scale, PTS selected ploughs with greater green vegetation cover and insect abundance and fallows with lower dry vegetation cover and height but greater stone cover. This might reflect a trade-off between camouflage (vegetation and stone cover for concealment) and visibility for predator detection and escape. Ploughs and fallows should be maintained by means of traditional 2-year rotations and low management during the breeding season. Ongoing urbanization trends and infrastructure development inside protected areas should be limited. Multi-scale models were key to identify scale-specific factors that determine sandgrouse habitat preferences and conservation requirements at appropriate levels, and are recommended to better guide regional and local conservation efforts of threatened species. 相似文献
99.
Polo V Veiga JP Cordero PJ Viñuela J Monaghan P 《Proceedings. Biological sciences / The Royal Society》2004,271(1551):1929-1933
Adjustment of offspring sex ratios should be favoured by natural selection when parents are capable of facultatively altering brood sex ratios and of recognizing the circumstances that predict the probable fitness benefit of producing sons and daughters. Although experimental studies have shown that female birds may adjust offspring sex ratios in response to changes in their own condition and in the external appearance of their mate, and male attributes other than his external morphology are also thought to act as signals of male quality, it is not known whether females will respond to changes in such signals, in the absence of any change in the appearance of the male himself. Here, we experimentally manipulated a male courtship display, the green plants carried to the nest by male spotless starlings (Sturnus unicolor), without changing any physical attributes of the male himself, and examined whether this influenced female decisions on offspring sex ratio. We found that in an environment in which female starlings were producing more daughters than sons, experimental enhancement of the green nesting material caused females to significantly increase the number of male eggs produced and thereby removed the female bias. This effect was consistent in 2 years and at two localities. This demonstrates that the green material, whose function has long puzzled biologists, conveys important information to the female and that she facultatively adjusts offspring production accordingly. 相似文献
100.
Targeted isolation,sequence analysis,and physical mapping of nonTIR NBS-LRR genes in soybean 总被引:2,自引:0,他引:2
Peñuela S Danesh D Young ND 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,104(2-3):261-272
Most cloned plant disease resistance genes (R-genes) code for proteins belonging to the nucleotide binding site (NBS) leucine-rich
repeat (LRR) superfamily. NBS-LRRs can be divided into two classes based on the presence of a TIR domain (Toll and interleukin receptor-like sequence) or a coiled coil motif (nonTIR) in their N-terminus. We used conserved motifs specific
to nonTIR-NBS-LRR sequences in a targeted PCR approach to generate nearly 50 genomic soybean sequences with strong homology
to known resistance gene analogs (RGAs) of the nonTIR class. Phylogenetic analysis classified these sequences into four main
subclasses. A representative clone from each subclass was used for genetic mapping, bacterial artificial chromosome (BAC)
library screening, and construction of RGA-containing BAC contigs. Of the 14 RGAs that could be mapped genetically, 12 localized
to a 25-cM region of soybean linkage group F already known to contain several classical disease resistance loci. A majority
of the genomic region encompassing the RGAs was physically isolated in eight BAC contigs, together spanning more than 1 Mb
of genomic sequence with at least 12 RGA copies. Phylogenetic and sequence analysis, together with genetic and physical mapping,
provided insights into the genome organization and evolution of this large cluster of soybean RGAs.
Received: 8 May 2001 / Accepted: 30 June 2001 相似文献