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1.
This study investigated the toxic effects of essential oils isolated from Siparuna guianensis against Aedes aegypti, Culex quinquefasciatus (eggs, larvae, pupae, and adult) and Aedes albopictus (C6/36) cells. The oviposition-deterring activity, egg viability, and repellence activity in the presence of different essential oils concentrations were determined. The essential oils showed high toxicity to all developmental stages of A. aegypti and C. quinquefasciatus. Furthermore, the oils also showed high repellent activity towards the adult stage of mosquitoes (0.025 to 0.550 μg/cm2 skin conferred 100% repellence up to 120 min) and in contact with cultured insect cells (C6/36) induced death possibly by necrosis. The results presented in this work show the potential of S. guianensis essential oils for the development of an alternative and effective method for the natural control of mosquitoes in homes and urban areas.  相似文献   
2.
We present an algorithm for counting glycan topologies of order \(n\) that improves on previously described algorithms by a factor \(n\) in both time and space. More generally, we provide such an algorithm for counting rooted or unrooted \(d\) -ary trees with labels or masses assigned to the vertices, and we give a “recipe” to estimate the asymptotic growth of the resulting sequences. We provide constants for the asymptotic growth of \(d\) -ary trees and labeled quaternary trees (glycan topologies). Finally, we show how a classical result from enumeration theory can be used to count glycan structures where edges are labeled by bond types. Our method also improves time bounds for counting alkanes.  相似文献   
3.
A good deal of data support a role for probiotic intestinal bacteria in the prophylaxis and therapy of candidiasis. Candida spp. are highly infectious eukaryotes that can colonize and infect humans and other warm-blooded mammals, worldwide. Although most humans manifest antibody- and cell-mediated immune responses to Candida antigens a large percentage of the human population is colonized with Candida spp. in their alimentary and vaginal tracts. The bacterial flora plays a very important probiotic role in the prophylaxis of candidiasis by suppressing the growth of Candida spp. on mucosal and cutaneous surfaces; however, the specific bacteria and the mechanisms they use to inhibit Candida spp. and candidiasis are still poorly understood. The increased incidence of Candida infections, their increasing resistance to antifungal antibiotics and the fact that vaccines to protect against candidiasis are not yet available (and may not work in immunodeficient, Candida-susceptible, patients) provides a strong impetus for new research efforts to explore the use of probiotic, anti- Candida intestinal bacteria for the prophylaxis and therapy of candidiasis.  相似文献   
4.
Diane Wagner 《Oecologia》1993,96(2):276-281
The transfer of nutrients between organisms is a common feature of mutualism. The production of these food rewards is often assumed to be costly. Estimation of the costs of producing food rewards is important for understanding the overall effects of the interaction on fitness. When food rewards are harvested by several species differing in foraging behavior, costs to the producer may differ. The larvae of many species in the butterfly family Lycaenidae produce secretions consumed by tending ants. Here I report that three North American ant species, Formica perpilosa, Dorymyrmex sp. (smithi complex), and Forelius foetida, had no negative effect on the duration of development and adult size of the lycaenid Hemiargus isola. Moreover, tending by the ant Formica perpilosa significantly enhanced larval growth, resulting in butterflies that were 20% heavier than their untended counterparts. Tending by the ants Dorymyrmex sp. (smithi complex) and Forelius foetida had no effect on butterfly weight. Tended, nonfeeding larvae lost 69% more weight than untended, nonfeeding larvae. Taken together, the results suggest that, although ant tending imposes a physiological cost, H. isola larvae use behavioral or physiological mechanisms to compensate or overcompensate for nutrients lost to ants.  相似文献   
5.
Specific antigen/antibody interactions measured by force microscopy.   总被引:11,自引:2,他引:9       下载免费PDF全文
Molecular recognition between biotinylated bovine serum albumin and polyclonal, biotin-directed IG antibodies has been measured directly under various buffer conditions using an atomic force microscope (AFM). It was found that even highly structured molecules such as IgG antibodies preserve their specific affinity to their antigens when probed with an AFM in the force mode. We could measure the rupture force between individual antibody-antigen complexes. The potential and limitations of this new approach for the measurement of individual antigen/antibody interactions and some possible applications are discussed.  相似文献   
6.
The occupation of adjacent, non‐overlapping positions along environmental gradients by closely related and ecologically similar species has drawn considerable attention from ecologists over the past decades. Condition‐specific competition, wherein competitive superiority varies with the abiotic environmental gradient, has been proposed as the major structuring force behind such distributions. These concepts, however, are generally applied to explain the contemporary distribution of organisms that share an evolutionary history. Our aim was to apply these concepts to the naive interactions between native and introduced fishes. In 1990 yellowfin shiner ( Notropis lutipinnis ) were introduced into the headwaters of the Little Tennessee River of western North Carolina, U.S.A. where it exhibits microhabitat preferences that overlap significantly with those of a threatened native minnow, the smokey dace ( Clinostomus funduloides raneyi ). Previous research has established that these drift‐feeding minnows: (1) differ in their average ability to intercept drifting prey as a function of water velocity; (2) generally occupy focal‐point velocities that maximize the rate of prey capture; and, (3) occasionally defend the forward positions in foraging aggregations that form in high quality patches. We present the results of a series of experiments designed to: (1) evaluate the role of aggression in the establishment and maintenance of preferred foraging positions in drift‐feeding minnows; (2) test the effects of prey availability, group size, and velocity on dominance rank, spatial position in groups, and feeding rates of individuals; and, (3) evaluate the potential for condition‐specific competition to establish competitive refugia for the native within the natural heterogeneity of mountain streams.  相似文献   
7.
Plants from the Brazilian flora were evaluated for the inhibition of 5-lipoxygenase. The species were selected based on their traditional use and on a chemosystematic approach. In total, 19 species belonging to 13 families have been investigated. Hedychium coronarium J. Koenig (Zingiberaceae), Xylopia frutescens Aubl. (Annonaceae) and Hymenaea courbaril L. (Leguminosae) presented a high 5-lipoxygenase inhibitory activity. Some hypothesis about the nature of the active compounds are discussed, based on reports of the chemical constitution of these species or other species from the same botanical family.  相似文献   
8.
Modulation of the malate content of tomato (Solanum lycopersicum) fruit by altering the expression of mitochondrially localized enzymes of the tricarboxylic acid cycle resulted in enhanced transitory starch accumulation and subsequent effects on postharvest fruit physiology. In this study, we assessed whether such a manipulation would similarly affect starch biosynthesis in an organ that displays a linear, as opposed to a transient, kinetic of starch accumulation. For this purpose, we used RNA interference to down-regulate the expression of fumarase in potato (Solanum tuberosum) under the control of the tuber-specific B33 promoter. Despite displaying similar reductions in both fumarase activity and malate content as observed in tomato fruit expressing the same construct, the resultant transformants were neither characterized by an increased flux to, or accumulation of, starch, nor by alteration in yield parameters. Since the effect in tomato was mechanistically linked to derepression of the reaction catalyzed by ADP-glucose pyrophosphorylase, we evaluated whether the lack of effect on starch biosynthesis was due to differences in enzymatic properties of the enzyme from potato and tomato or rather due to differential subcellular compartmentation of reductant in the different organs. The results are discussed in the context both of current models of metabolic compartmentation and engineering.Starch is the most important carbohydrate used for food and feed purposes and represents the major resource for our diet (Smith, 2008). The total yield of starch in rice (Oryza sativa), corn (Zea mays), wheat (Triticum aestivum), and potato (Solanum tuberosum) exceeds 109 tons per year (Kossmann and Lloyd, 2000; Slattery et al., 2000). In addition to its use in a nonprocessed form, extracted starch is processed in many different ways, for instance as a high-Fru syrup, as a food additive, or for various technical purposes. As a result of this considerable importance, increasing the starch content of plant tissues has been a major goal for many years, with both classical breeding and biotechnological approaches being taken extensively over the last few decades (Martin and Smith, 1995; Regierer et al., 2002).The pathway by which carbon is converted from Suc to starch in the potato tuber is well established (Kruger, 1997; Fernie et al., 2002; Geigenberger et al., 2004; Geigenberger, 2011). Imported Suc is cleaved in the cytosol by Suc synthase, resulting in the formation of UDP-Glc and Fru; the UDP-Glc is subsequently converted to Glc-1-P by UDP-Glc pyrophosphorylase. The second product of the Suc synthase reaction, Fru, is efficiently phosphorylated to Fru-6-P by fructokinase (Renz et al., 1993; Davies et al., 2005). Fru-6-P is freely converted to Glc-6-P, in which form it normally enters the amyloplast (Kammerer et al., 1998; Tauberger et al., 2000; Zhang et al., 2008), and once in the plastid, it is converted to starch via the concerted action of plastidial phosphoglucomutase, ADP-Glc pyrophosphorylase (AGPase), and the various isoforms of starch synthase (Martin and Smith, 1995; Geigenberger, 2011). Of these reactions, although some of the control of starch synthesis resides in the plastidial phosphoglucomutase reaction (Fernie et al., 2001b), the AGPase reaction harbors the highest proportion of control within the linear pathway (Sweetlove et al., 1999; Geigenberger et al., 1999, 2004). In addition, considerable control resides in both the Glc-6-P phosphate antiporter (Zhang et al., 2008) and the amyloplastidial adenylate transporter (Tjaden et al., 1998; Zhang et al., 2008) as well as in reactions external to the pathways, such as the amyloplastidial adenylate kinase (Regierer et al., 2002), cytosolic UMP synthase (Geigenberger et al., 2005), and mitochondrial NAD-malic enzyme (Jenner et al., 2001).As part of our ongoing study of the constituent enzymes of the tricarboxylic acid (TCA) cycle, we made an initially surprising observation that increasing or decreasing the content of malate via a fruit-specific expression of antisense constructs targeted against the mitochondrial malate dehydrogenase or fumarase, respectively, resulted in opposing changes in the levels of starch (Centeno et al., 2011). We were able to demonstrate that these plants were characterized by an altered cellular redox balance and that this led to changes in the activation state of the AGPase reaction. Given that starch only accumulates transiently in tomato (Solanum lycopersicum; Beckles et al., 2001) as a consequence of this activation, the fruits were characterized by altered sugar content at ripening, a fact that dramatically altered their postharvest characteristics (Centeno et al., 2011). Here, we chose to express the antisense fumarase construct in potato in order to ascertain the effect of the manipulation in an organ that linearly accumulates starch across its development. The results obtained are compared and contrasted with those of the tomato fruit and within the context of current models of subcellular redox regulation.  相似文献   
9.
ANO1, a calcium-activated chloride channel, is highly expressed and amplified in human cancers and is a critical survival factor in these cancers. The ANO1 inhibitor CaCCinh-A01 decreases proliferation of ANO1-amplified cell lines; however, the mechanism of action remains elusive. We explored the mechanism behind the inhibitory effect of CaCCinh-A01 on cell proliferation using a combined experimental and in silico approach. We show that inhibition of ANO1 function is not sufficient to diminish proliferation of ANO1-dependent cancer cells. We report that CaCCinh-A01 reduces ANO1 protein levels by facilitating endoplasmic reticulum-associated, proteasomal turnover of ANO1. Washout of CaCCinh-A01 rescued ANO1 protein levels and resumed cell proliferation. Proliferation of newly derived CaCCinh-A01-resistant cell pools was not affected by CaCCinh-A01 as compared with the parental cells. Consistently, CaCCinh-A01 failed to reduce ANO1 protein levels in these cells, whereas ANO1 currents were still inhibited by CaCCinh-A01, indicating that CaCCinh-A01 inhibits cell proliferation by reducing ANO1 protein levels. Furthermore, we employed in silico methods to elucidate novel biological functions of ANO1 inhibitors. Specifically, we derived a pharmacophore model to describe inhibitors capable of promoting ANO1 degradation and report new inhibitors of ANO1-dependent cell proliferation. In summary, our data demonstrate that inhibition of the channel activity of ANO1 is not sufficient to inhibit ANO1-dependent cell proliferation, indicating that the role of ANO1 in cancer only partially depends on its function as a channel. Our results provide an impetus for gaining a deeper understanding of ANO1 modulation in cells and introduce a new targeting approach for antitumor therapy in ANO1-amplified cancers.  相似文献   
10.
Development introduces structured correlations among traits that may constrain or bias the distribution of phenotypes produced. Moreover, when suitable heritable variation exists, natural selection may alter such constraints and correlations, affecting the phenotypic variation available to subsequent selection. However, exactly how the distribution of phenotypes produced by complex developmental systems can be shaped by past selective environments is poorly understood. Here we investigate the evolution of a network of recurrent nonlinear ontogenetic interactions, such as a gene regulation network, in various selective scenarios. We find that evolved networks of this type can exhibit several phenomena that are familiar in cognitive learning systems. These include formation of a distributed associative memory that can “store” and “recall” multiple phenotypes that have been selected in the past, recreate complete adult phenotypic patterns accurately from partial or corrupted embryonic phenotypes, and “generalize” (by exploiting evolved developmental modules) to produce new combinations of phenotypic features. We show that these surprising behaviors follow from an equivalence between the action of natural selection on phenotypic correlations and associative learning, well‐understood in the context of neural networks. This helps to explain how development facilitates the evolution of high‐fitness phenotypes and how this ability changes over evolutionary time.  相似文献   
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