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991.
M. J. Puertas R. Carmona 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1976,47(1):41-43
Summary To contribute to knowledge on the significance of B chromosomes in rye populations, a component of fertility has been estimated by a comparative study of germination and growth of pollen tubes in plants with and without B chromosomes. The highest percentage germination of pollen and mean speed of pollen tube growth was shown by 14 + 2B plants, followed by normal plants.Observations of first pollen mitosis indicated that in most cases the chromatid constitution of the tube nucleus was the same in 14, 14 + 1 and 14 + 2B plants. In contrast, the mean growth rate of pollen tubes differed significantly among the three cases. From these data it seems that the determination of germination ability and pollen tube growth depends on the sporophyte and is related to the number of Bs carried by the plant. 相似文献
992.
Risk Assessment Studies: Detailed Host Range Testing of Wild-Type Cabbage Moth, Mamestra brassicae (Lepidoptera: Noctuidae), Nuclear Polyhedrosis Virus 总被引:2,自引:0,他引:2 下载免费PDF全文
Cathy J. Doyle Mark L. Hirst Jenny S. Cory Philip F. Entwistle 《Applied microbiology》1990,56(9):2704-2710
The host range of a multiply enveloped nuclear polyhedrosis virus (NPV) (Baculoviridae) isolated from the cabbage moth, Mamestra brassicae (Lepidoptera: Noctuidae), was determined by challenging a wide range of insect species with high (106 polyhedral inclusion bodies) and low (103 polyhedral inclusion bodies) doses of the virus. The identity of the progeny virus was confirmed by dot blotting. Analysis of 50% lethal dose was carried out on selected species, and the progeny virus was identified by using restriction enzyme analysis and Southern blotting. Other than the Lepidoptera, none of the species tested was susceptible to M. brassicae NPV. Within the Lepidoptera, M. brassicae NPV was infective to members of four families (Noctuidae, Geometridae, Yponomeutidae, and Nymphalidae). Of 66 lepidopterous species tested, M. brassicae NPV was cross-infective to 32 of them; however, 91% of the susceptible species were in the Noctuidae. The relevance of host range data in risk assessment studies is discussed. 相似文献
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995.
Egg production by the calanoid copepods Calanoides carinatusand Calanus agulhensis fed excess Thalassiosira weissflogiiwas monitored in the laboratory following starvation periodsof 1, 3, 5, 7 and 9 days. Following short (13 day) periodsof starvation, egg production by C.agulhensis returned to thesatiated rate (51.1 eggs {female} day1) more rapidly(after 0.92.4 days of excess food) than that of Ca. carinatus(after 2.83.1 days). However, following longer (59day) periods of starvation, Ca. carinatus regained satiatedlevels of egg production (55.8 eggs {female}1 day1)more rapidly (after 3.14.0 days of excess food) thanC. agulhensis (after 3.85.2 days of feeding following57 days of starvation). Moreover, many C. agulhensisfemales did not regain normal rates of egg production after9 days of starvation. For both species, the time required foregg production to recover was proportional to the starvationperiod, although only up to 7 days for C. agulhensis, and wasthe same following 4.25 days of starvation. Previously fed Ca.carinatus terminated egg production more rapidly than C. agulhensiswhen starved. The ability of Ca. carinatus to tolerate, andrecover rapidly from, prolonged periods of starvation, combinedwith a comparatively fast development time and high rate ofegg production, provides this species with a strong competitiveadvantage over C. agulhensis in the highly pulsed food environmentof the southern Benguela upwelling region. 相似文献
996.
Louise?C.?KennyEmail author Warwick?B.?Dunn David?I.?Ellis Jenny?Myers Philip?N.?Baker GOPEC Consortium Douglas?B.?KellEmail author 《Metabolomics : Official journal of the Metabolomic Society》2005,1(3):227-234
Pre-eclampsia is a multi-system disorder of pregnancy with major maternal and perinatal implications. Emerging therapeutic
strategies are most likely to be maximally effective if commenced weeks or even months prior to the clinical presentation
of the disease. Although widespread plasma alterations precede the clinical onset of pre-eclampsia, no single plasma constituent
has emerged as a sensitive or specific predictor of risk. Consequently, currently available methods of identifying the condition
prior to clinical presentation are of limited clinical use. We have exploited genetic programming, a powerful data mining
method, to identify patterns of metabolites that distinguish plasma from patients with pre-eclampsia from that taken from
healthy, matched controls. High-resolution gas chromatography time-of-flight mass spectrometry (GC-tof-MS) was performed on
87 plasma samples from women with pre-eclampsia and 87 matched controls. Normalised peak intensity data were fed into the
Genetic Programming (GP) system which was set up to produce a model that gave an output of 1 for patients and 0 for controls.
The model was trained on 50% of the data generated and tested on a separate hold-out set of 50%. The model generated by GP
from the GC-tof-MS data identified a metabolomic pattern that could be used to produce two simple rules that together discriminate
pre-eclampsia from normal pregnant controls using just 3 of the metabolite peak variables, with a sensitivity of 100% and
a specificity of 98%. Thus, pre-eclampsia can be diagnosed at the level of small-molecule metabolism in blood plasma. These
findings justify a prospective assessment of metabolomic technology as a screening tool for pre-eclampsia, while identification
of the metabolites involved may lead to an improved understanding of the aetiological basis of pre-eclampsia and thus the
development of targeted therapies. 相似文献
997.
A phylogeny of the species of the nase genus Chondrostoma was constructed from a complete mitochondrial cytochrome b gene (1140 bp). Molecular phylogeny was used to revise the current systematics of this group, and to infer a biogeographical model of the Mediterranean area during the Cenozoic period. We confirmed the monophyly of the genus Chondrostoma, and defined seven different lineages within it: Polylepis, Arcasii, Lemmingii, Toxostoma, Nasus, C. genei, and C. soetta. The separation of main lineages within Chondrostoma occurred in the Middle-Upper Miocene, approximately 11 million years ago, while the greatest species radiation took place in the Pliocene close to the time the current drainages system were created. It is unlikely that this genus experienced an extensive dispersal during the Messinian, in the Lago-Mare Phase. Given the level of current knowledge, a biogeographical model constructed on the basis of vicariant events seems more realistic than does a dispersalist model. 相似文献
998.
Planar cell polarity (PCP) in the Drosophila eye is established by the distinct fate specifications of photoreceptors R3 and R4, and is regulated by the Frizzled (Fz)/PCP signaling pathway. Before the PCP proteins become asymmetrically localized to opposite poles of the cell in response to Fz/PCP signaling, they are uniformly apically colocalized. Little is known about how the apical localization is maintained. We provide evidence that the PCP protein Diego (Dgo) promotes the maintenance of apical localization of Flamingo (Fmi), an atypical Cadherin-family member, which itself is required for the apical localization of the other PCP factors. This function of Dgo is redundant with Prickle (Pk) and Strabismus (Stbm), and only appreciable in double mutant tissue. We show that the initial membrane association of Dgo depends on Fz, and that Dgo physically interacts with Stbm and Pk through its Ankyrin repeats, providing evidence for a PCP multiprotein complex. These interactions suggest a positive feedback loop initiated by Fz that results in the apical maintenance of other PCP factors through Fmi. 相似文献
999.
1000.
Smith JG Latiolais JA Guanga GP Pennington JD Silversmith RE Bourret RB 《Molecular microbiology》2004,51(3):887-901
Two-component regulatory systems, typically composed of a sensor kinase to detect a stimulus and a response regulator to execute a response, are widely used by microorganisms for signal transduction. Response regulators exhibit a high degree of structural similarity and undergo analogous activating conformational changes upon phosphorylation. The activity of particular response regulators can be increased by specific amino acid substitutions, which either prolong the lifetime or mimic key features of the phosphorylated state. We probed the universality of response regulator activation by amino acid substitution. Thirty-six mutations that activate 11 different response regulators were identified from the literature. To determine whether the activated phenotypes would be retained in the context of a different response regulator, we recreated 51 analogous amino acid substitutions at corresponding positions of CheY. About 55% of the tested substitutions completely or partially inactivated CheY, approximately 30% were phenotypically silent, and approximately 15% activated CheY. Three previously uncharacterized activated CheY mutants were found. The 94NS (and presumably 94NT) substitutions resulted in resistance to CheZ-mediated dephosphorylation. The 113AP substitution led to enhanced autophosphorylation and may increase the fraction of non-phosphorylated CheY molecules that populate the activated conformation. The locations of activating substitutions on the response regulator three-dimensional structure are generally consistent with current understanding of the activation mechanism. The best candidates for potentially universal activating substitutions of response regulators identified in this study were 13DK and 113AP. 相似文献