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991.
The influence of light level on the functional response of a zooplanktonivorous fish 总被引:1,自引:1,他引:0
Summary Light and vision are clearly of significance in foraging behaviour by underyearling common bream [Abramis brama (L.)]. These fish are effective predators at 1.25 Lux but they were also shown to be capable of taking prey, at a reduced rate, at a much lower light intensity (less than 5x10-3 Lux). In the latter case they may have been using sensory modes other than vision, perhaps involving tactile and/or olfactory stimuli.We investigated the influence of light level on the functional response of bream to Daphnia magna prey. At 1.25 Lux the predator showed a typical type II response. However, the relatively unfavourable conditions in the lower light intensity appear to have been responsible for generating a sigmoid type III functional response. Observations, using infra-red sensitive equipment, suggested a behavioural basis for this result. Thus, the predator's attack rate was not constant, but increased with prey density. The significance of the type III functional response is discussed, both in terms of predator energetics and predator-prey population stability. 相似文献
992.
The morphology of cilia in sponge larvae 总被引:1,自引:0,他引:1
Patricia R. Bergquist Colin R. Green Mary E. Sinclair Heather Silyn Roberts 《Tissue & cell》1977,9(1):179-184
Sponge larvae possess cilia with unusual terminal expansions which are curled or biconcave in shape externally, as seen by scanning electron microscopy. Thin sections, passing through the point where the ciliary shaft enters the expanded area reveal the ciliary axoneme to be surrounded by many membranous folds, some of which are vesicular. The ‘club footed’ cilia occur in disparate groups of Demospongiae and most frequently, all larval cilia are of this type. There is no immediately obvious correlation between the type of movement displayed by the larvae and the occurrence of terminally expanded cilia. 相似文献
993.
Julie A. Hawkins Laura White Olascoaga Colin E. Hughes José-Luis R. Contreras Jiménez Pedro Mercado Ruaro 《Plant Systematics and Evolution》1999,216(1-2):49-68
Morphometric, cytogenetic, geographical and ecological evidence for hybridization betweenParkinsonia aculeata andCercidium praecox is presented. Morphometric investigation using the character count procedure and cytogenetic observations confirm hybrid status. All diagnostic morphometric characters were intermediate in the hybrid. Both parents (2n = 28) show regular tetrad formation and pollen fertility greater than 94%. Hybrids have a chromosome number of 2n = 28 or 2n = 30, and display meiotic abnormalities including lagging chromosomes and micronucleus formation; less than 21% of hybrid pollen was fertile. Ecological and geographical information suggests that hybridization is occurring at increasing frequency due to the expanding range ofP. aculeata associated with cultivation as an ornamental, coupled with ecological disturbance and weediness, and the cultivation ofC. praecox and hybrids as fodder, ornamental and shade trees. Hybrid fertility and phenological observations, in conjunction with F-weighted principal component analysis, suggest that the progeny of F1 hybrids are established. The hybrid is formally described asP. ×carterae. 相似文献
994.
Petros Papagerakis Dominique Hotton Frederic Lezot Steve Brookes William Bonass Colin Robinson Nadine Forest Ariane Berdal 《Journal of cellular biochemistry》2000,76(2):194-205
The unique hereditary enamel defect clearly related to the disturbance of one enamel matrix protein is X‐linked amelogenesis imperfecta (AI), in which several mutations of amelogenin gene have been identified. The clinical phenotype of many of these subjects shows similarities with enamel defects related to rickets. Therefore, we hypothesized that rachitic dental dysplasia is related to disturbances in the amelogenin pathway. In order to test this hypothesis, combined qualitative and quantitative studies in experimental vitamin D‐deficient (−D) rat model systems were performed. First, Western blot analysis of microdissected enamel matrix (secretion and maturation stages) showed no clear evidence of dysregulation of amelogenin protein processing in −D rats as compared with the controls. Second, the ultrastructural investigation permitted identification of the internal tissular defect of rachitic enamel, the irregular absence of intraprismatic enamel observed in −D animals, suggesting a possible link between prism morphogenesis and vitamin D. In addition, the steady‐state levels of amelogenin mRNAs measured in microdissected dental cells was decreased in −D rats and up‐regulated by an unique injection of 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3). The present study shows evidences that amelogenin expression is regulated by vitamin D. This is the first study of an hormonal regulation of tooth‐specific genes. J. Cell. Biochem. 76:194–205, 1999. © 1999 Wiley‐Liss, Inc. 相似文献
995.
Allele specific timing of replication is believed to be a hallmark of imprinted genes, however recent evidence suggests that this might not be the case for the insulin-like growth factor 2 (Igf2) and H19 locus. In this report, we assayed the timing of replication of Igf2 and H19 in two mouse embryonic cell lines expressing both H19 and Igf2, and one cell line maternally disomic for the Igf2/H19 mouse locus which expresses H19 but not Igf2. In all cell lines, Igf2 and H19 were replicated early in the S phase of the cell cycle, and both alleles replicated at the same time. This indicates that any differences in the timing of replication at the Igf2/H19 locus are of a lesser magnitude than those found in other imprinted regions. Dev Genet 20:29–35, 1997. © 1997 Wiley-Liss, Inc. 相似文献
996.
Jacqueline A. Greenwooda James Millsa Colin W. Jonesa 《FEMS microbiology letters》1997,153(1):167-171
A major outer-membrane protein was purified and partially characterised from the methylotrophic bacterium Methylophilus methylotrophus. The protein had a subunit Mr of 38 000 and was similar in terms of its biochemical properties to the recently characterised amide-urea porin (FmdC) from the same organism. Expression of the protein, as determined by SDS-PAGE and Western blotting of cells grown in continuous culture under various nutrient limitations, varied in a similar manner to that of methanol dehydrogenase and was maximal under methanol limitation. It was concluded that the protein is probably an outer-membrane porin for methanol. 相似文献
997.
The particulate methane monooxygenase gene pmoA and its use as a functional gene probe for methanotrophs 总被引:4,自引:0,他引:4
The particulate methane monooxygenase gene pmoA, encoding the 27 kDa polypeptide of the membrane-bound particulate methane monooxygenase, was amplified by PCR from DNA isolated from a blanket peat bog and from enrichment cultures established, from the same environment, using methane as sole carbon and energy source. The resulting 525 bp PCR products were cloned and a representative number of clones were sequenced. Phylogenetic analysis of the derived amino acid sequences of the pmoA clones retrieved directly from environmental DNA samples revealed that they form a distinct cluster within representative PmoA sequences from type II methanotrophs and may originate from a novel group of acidophilic methanotrophs. The study also demonstrated the utility of the pmoA gene as a phylogenetic marker for identifying methanotroph-specific DNA sequences in the environment. 相似文献
998.
Genome sequencing is an increasingly common component of infectious disease outbreak investigations. However, the relationship between pathogen transmission and observed genetic data is complex, and dependent on several uncertain factors. As such, simulation of pathogen dynamics is an important tool for interpreting observed genomic data in an infectious disease outbreak setting, in order to test hypotheses and to explore the range of outcomes consistent with a given set of parameters. We introduce ‘seedy’, an R package for the simulation of evolutionary and epidemiological dynamics (http://cran.r-project.org/web/packages/seedy/). Our software implements stochastic models for the accumulation of mutations within hosts, as well as individual-level disease transmission. By allowing variables such as the transmission bottleneck size, within-host effective population size and population mixing rates to be specified by the user, our package offers a flexible framework to investigate evolutionary dynamics during disease outbreaks. Furthermore, our software provides theoretical pairwise genetic distance distributions to provide a likelihood of person-to-person transmission based on genomic observations, and using this framework, implements transmission route assessment for genomic data collected during an outbreak. Our open source software provides an accessible platform for users to explore pathogen evolution and outbreak dynamics via simulation, and offers tools to assess observed genomic data in this context. 相似文献
999.
Cell density and airspace patterning in the leaf can be manipulated to increase leaf photosynthetic capacity
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Andrew Mathers Jen Sloan Marion Bauch Alice Mitchell Chandra Bellasio Adam Green Daniel Bouyer Arp Schnittger Craig Sturrock Colin P. Osborne Stephen Rolfe Sacha Mooney Andrew J. Fleming 《The Plant journal : for cell and molecular biology》2017,92(6):981-994
The pattern of cell division, growth and separation during leaf development determines the pattern and volume of airspace in a leaf. The resulting balance of cellular material and airspace is expected to significantly influence the primary function of the leaf, photosynthesis, and yet the manner and degree to which cell division patterns affect airspace networks and photosynthesis remains largely unexplored. In this paper we investigate the relationship of cell size and patterning, airspace and photosynthesis by promoting and repressing the expression of cell cycle genes in the leaf mesophyll. Using microCT imaging to quantify leaf cellular architecture and fluorescence/gas exchange analysis to measure leaf function, we show that increased cell density in the mesophyll of Arabidopsis can be used to increase leaf photosynthetic capacity. Our analysis suggests that this occurs both by increasing tissue density (decreasing the relative volume of airspace) and by altering the pattern of airspace distribution within the leaf. Our results indicate that cell division patterns influence the photosynthetic performance of a leaf, and that it is possible to engineer improved photosynthesis via this approach. 相似文献
1000.
Xiao Ding Xuedong Dai Kai Long Cheng Peng Daniele Andreotti Paul Bamborough Andrew J. Eatherton Colin Edge Karamjit S. Jandu Paula L. Nichols Oliver J. Philps Luigi Piero Stasi Zehong Wan Jia-Ning Xiang Kelly Dong Pamela Dossang Ming-Hsun Ho Yi Li Feng Ren 《Bioorganic & medicinal chemistry letters》2017,27(17):4034-4038
Leucine-rich repeat kinase 2 (LRRK2) has been suggested as a potential therapeutic target for Parkinson’s disease. Herein we report the discovery of 5-substituent-N-arylbenzamide derivatives as novel LRRK2 inhibitors. Extensive SAR study led to the discovery of compounds 8e, which demonstrated potent LRRK2 inhibition activity, high selectivity across the kinome, good brain exposure, and high oral bioavailability. 相似文献