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21.
MH Bowie J Klimaszewski CJ Vink S Hodge SD Wratten 《New Zealand journal of zoology.》2013,40(4):268-284
Pitfall traps were used to monitor predatory arthropod numbers along two types of field boundary, a post and wire fence line and a Cupressus macrocarpa hedge, along the same paddock margin in Canterbury, New Zealand, over 24 months. The seven most abundant predator groups recorded were: Araneae > Phalangiidae > Staphylinidae > Coccinellidae > Chilopoda > Hemerobiidae > Carabidae. Araneae, Phalangiidae, Staphylinidae, Chilopoda and Hemerobiidae were found in larger numbers at the wire fence than at the hedge site, whereas the numbers of Carabidae and Coccinellidae adults exhibited no field margin preference. However, more species of Araneae and Staphylinidae were caught at the hedge site, whereas species richness of carabid beetles was greatest at the wire fence. Principal component analysis clearly separated the samples collected from the two habitats based on the assemblages of Araneae, Staphylinidae and Carabidae, and certain species in each of these taxonomic groups appeared to be particularly associated with one boundary type or the other. All the main taxonomic groups exhibited clear seasonal patterns, with distinct peaks in abundance occurring at certain times of the year. The results of the study reinforce the idea that management of field boundaries can be used to manipulate the type and abundance of particular groups of predatory arthropods, and that seasonal patterns should be taken into account in schemes of integrated pest management so that any adverse effects of biocide application on these beneficial species may be minimised. 相似文献
22.
Karim M ElSawy Chandra S Verma David P Lane Leo SD Caves 《Cell cycle (Georgetown, Tex.)》2013,12(24):3727-3735
The stereoselective affinity of small-molecule binding to proteins is typically broadly explained in terms of the thermodynamics of the final bound complex. Using Brownian dynamics simulations, we show that the preferential binding of the MDM2 protein to the geometrical isomers of Nutlin-3, an effective anticancer lead that works by inhibiting the interaction between the proteins p53 and MDM2, can be explained by kinetic arguments related to the formation of the MDM2:Nutlin-3 encounter complex. This is a diffusively bound state that forms prior to the final bound complex. We find that the MDM2 protein stereoselectivity for the Nutlin-3a enantiomer stems largely from the destabilization of the encounter complex of its mirror image enantiomer Nutlin-3b, by the K70 residue that is located away from the binding site. On the other hand, the trans-Nutlin-3a diastereoisomer exhibits a shorter residence time in the vicinity of MDM2 compared with Nutlin-3a due to destabilization of its encounter complex by the collective interaction of pairs of charged residues on either side of the binding site: Glu25 and Lys51 on one side, and Lys94 and Arg97 on the other side. This destabilization is largely due to the electrostatic potential of the trans-Nutlin-3a isomer being largely positive over extended continuous regions around its structure, which are otherwise well-identified into positive and negative regions in the case of the Nutlin-3a isomer. Such rich insight into the binding processes underlying biological selectivity complements the static view derived from the traditional thermodynamic analysis of the final bound complex. This approach, based on an explicit consideration of the dynamics of molecular association, suggests new avenues for kinetics-based anticancer drug development and discovery. 相似文献
23.
Classic MIKC-type MADS-box genes (MIKCc) play diverse and crucial roles in angiosperm development, the most studied and best understood of which is the specification of floral organ identities. To shed light on how the flower evolved, phylogenetic and functional analyses of genes involved in its ontogeny, such as the MIKCc genes, must be undertaken in as broad a selection as possible of plants with disparate ancestries. Since little is known about the functions of these genes in non-seed plants, we investigated the developmental roles of a subset of the MIKCc genes present in the moss, Physcomitrella patens, which is positioned informatively near the base of the land plant evolutionary tree. We observed that transgenic lines possessing an antisense copy of a MIKCc gene characteristically displayed knocked-down expression of the corresponding native MIKCc gene as well as multiple diverse phenotypic alterations to the haploid gametophytic and diploid sporophytic generations of the life cycle.1 In this addendum, we re-examine our findings in the light of recent pertinent literature and provide additional data concerning the effects of simultaneously knocking out multiple MIKCc genes in this moss.Key words: Physcomitrella, moss, MADS-box gene functions, gene knock-down, gene knockout, gene expression, evo-devoThe moss, Physcomitrella patens, is the only non-seed plant that is amenable to an investigation of MADS-box gene function comparable to that achieved in angiosperms. P. patens possesses six MIKCc genes which cluster into two distinct phylogenetic clades.2 We recently reported a functional genetic analysis of the three genes (PPM1, PPM2 and PpMADS1) within the PPM2-like clade as an initial contribution towards gaining an understanding of the role(s) of MIKCc genes in this moss.1By fusing the respective MIKCc promoters to a GUS reporter gene, we found that both PPM1 and PpMADS1 exhibited fairly ubiquitous expression patterns in both gametophytic and sporophytic tissues. The levels of PPM1 expression were generally higher than those of PpMADS1, and PpMADS1 was not expressed in antheridia, suggesting subtle differences in the functions of these genes. The observed patterns of widespread expression resemble those characterising the majority of vascular, non-seed plant MIKCc genes3–7 and accord with RT-PCR results of Quodt and coworkers.2 Our in situ GUS expression and RT-PCR results1 showed that PPM2 was not expressed or was expressed at levels too low to be detected by these methods. Conversely, the original isolation of PPM2 cDNA8 and data from more recent expression studies2 indicated that PPM2 is expressed (albeit inconsistently and weakly) ubiquitously with elevated levels of expression sometimes observed in gametangia, sporophytic feet and basal portions of sporophytic setae.2 The contradictory expression data for PPM2 may derive from differences between the PPM2-reporter gene constructs used by the respective research groups1,2 or perhaps from variations in moss culture conditions.We also employed an antisense approach designed to knock down expression of PPM1, and perhaps closely related MIKCc genes, in order to discern MADS-box gene function in P. patens. Knocked-down strains displayed a complex mutant phenotype comprising delayed gametangia formation and sporophyte production, diminished sporophyte yields, and morphological abnormalities in both leaves and sporophytes, findings that are generally consistent with the ubiquitous expression pattern of PPM11 and PPM2''s expression as described by Quodt et al.2The phenotypes of strains with single gene knockouts of PPM1, PPM2 or PpMADS1 appeared to be perfectly normal, not displaying any of the phenotypic alterations observed in PPM1 gene knock-down mutants. While it is possible that subtle, transient or conditional phenotypic changes went unnoticed, it seems more probable that genetic redundancy is responsible for these results since the PPM2-like genes exhibit a very high level of sequence similarity. In an effort to circumvent the problem of functional redundancy, we generated all double knockout combinations for PPM1, PPM2 and PpMADS1. However, the double mutants were also phenotypically unchanged. Finally we attempted to produce triple mutants by co-transforming single PPM2 knockout lines with PPM1 and PpMADS1 linear knockout constructs. Of the 31 stable transformants from two transformation experiments, 55% were shown to be double mutants in which the original PPM2 knockout was accompanied by a second gene knockout in either PPM1 or PpMADS1. However, no triple knockouts were obtained. Given the knockout frequencies generally observed in batch transformation experiments in our laboratory and those of others,9 between two and five of the transformants had been expected to be triple mutants. These preliminary data, albeit involving a relatively small sample of transformants, suggest that PPM1, PPM2 and PpMADS1 triple knockouts may be lethal.We have related compelling evidence that functionally redundant PPM2-like MIKCc genes are involved in several aspects of the moss developmental program. It has been argued that broad expression patterns like theirs represent the ancestral state of MADS-box genes in land plants, and that the sporophytic- and organ-specific expression patterns that characterise many MIKCc genes in extant spermatophytes, including those that specify floral organ identity, correspond to a derived condition that evolved in the spermatophyte lineage following its separation from lineages that led to bryophytes and ferns and fern allies.10 Nevertheless, it is the apparent participation of PPM2-like genes in the formation of gametangia (the differentiation of reproductive organs from non-reproductive tissues at the gametophore apex) that is particularly interesting and assumes a special significance because of its analogy to the proposed role for ancestors of seed plant C-function MADS-box genes (identifying those regions of the vegetative SAM that will become reproductive organs).11 Furthermore, expression studies of MIKCc genes in two charophycean algae, the presumed progenitors of all terrestrial plants,12–14 suggest that they too are involved in haploid reproductive cell differentiation.15 While these functional similarities do not infer orthology and may be coincidental, we should not discount yet the admittedly controversial hypothesis that some MIKCc genes in non-seed plants, for example PPM2-like genes of Physcomitrella, are homologous to spermatophyte class C genes and that the ancient role proposed for ancestral class C genes11 has been conserved, in some form, in all major terrestrial plant taxa. 相似文献
24.
Baruch MC Warburton DE Bredin SS Cote A Gerdt DW Adkins CM 《Nonlinear biomedical physics》2011,5(1):1-15
Background
Markers of temporal changes in central blood volume are required to non-invasively detect hemorrhage and the onset of hemorrhagic shock. Recent work suggests that pulse pressure may be such a marker. A new approach to tracking blood pressure, and pulse pressure specifically is presented that is based on a new form of pulse pressure wave analysis called Pulse Decomposition Analysis (PDA). The premise of the PDA model is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses, the first of which is due to the left ventricular ejection from the heart while the remaining component pressure pulses are reflections and re-reflections that originate from only two reflection sites within the central arteries. The hypothesis examined here is that the PDA parameter T13, the timing delay between the first and third component pulses, correlates with pulse pressure. T13 was monitored along with blood pressure, as determined by an automatic cuff and another continuous blood pressure monitor, during the course of lower body negative pressure (LBNP) sessions involving four stages, -15 mmHg, -30 mmHg, -45 mmHg, and -60 mmHg, in fifteen subjects (average age: 24.4 years, SD: 3.0 years; average height: 168.6 cm, SD: 8.0 cm; average weight: 64.0 kg, SD: 9.1 kg).Results
Statistically significant correlations between T13 and pulse pressure as well as the ability of T13 to resolve the effects of different LBNP stages were established. Experimental T13 values were compared with predictions of the PDA model. These interventions resulted in pulse pressure changes of up to 7.8 mmHg (SE = 3.49 mmHg) as determined by the automatic cuff. Corresponding changes in T13 were a shortening by -72 milliseconds (SE = 4.17 milliseconds). In contrast to the other two methodologies, T13 was able to resolve the effects of the two least negative pressure stages with significance set at p < 0.01.Conclusions
The agreement of observations and measurements provides a preliminary validation of the PDA model regarding the origin of the arterial pressure pulse reflections. The proposed physical picture of the PDA model is attractive because it identifies the contributions of distinct reflecting arterial tree components to the peripheral pressure pulse envelope. Since the importance of arterial pressure reflections to cardiovascular health is well known, the PDA pulse analysis could provide, beyond the tracking of blood pressure, an assessment tool of those reflections as well as the health of the sites that give rise to them. 相似文献25.
Murphy E Robertson GT Parent M Hagius SD Roop RM Elzer PH Baldwin CL 《FEMS immunology and medical microbiology》2002,33(3):191-200
Immune responses appropriate for control of an intracellular pathogen are generated in mice infected with Brucella abortus, shown by the ability of T cells to adoptively transfer resistance to naive mice. The infection nevertheless persists for months. It was hypothesized that one factor in maintaining the infection despite the presence of immune T cells was suboptimal expression of major histocompatibility complex (MHC) molecules on macrophages containing brucellae. This would allow B. abortus to elude detection by the host's immune system. To test this, B. abortus organisms expressing green fluorescent protein (GFP-Brucella) were constructed and three-color flow cytometry used to evaluate MHC expression on macrophages following in vitro or in vivo infection. When infected in vitro, the levels of MHC class I and class II expression on J774 macrophages containing GFP-Brucella were the same or higher than on macrophages without GFP-Brucella in the same cultures. Similarly, the MHC expression was higher on GFP(+) peritoneal exudate cells following infection or phagocytosis of heat-killed GFP-Brucella than it was on uninfected peritoneal exudate cells. Following in vivo infection of mice the level of MHC class I and II expression on GFP(+) cells in their spleens (the main site of infection) also tended to be as high as or higher than that on the GFP-negative cells. The only in vivo GFP(+) cells that showed a decreased MHC expression was a population of splenic Mac1(+) cells recovered from interferon-gamma gene-disrupted mice at the time of their death due to an overwhelming number of bacteria per spleen. Overall, it was concluded that decreased MHC expression is not a general principle associated with brucella infection of macrophages and thus not likely to contribute to maintenance of the chronic infection. 相似文献