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排序方式: 共有164条查询结果,搜索用时 15 毫秒
61.
Anne E. McManis James A. Powell Barbara J. Bentz 《Entomologia Experimentalis et Applicata》2019,167(5):457-466
Mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae), is a significant forest disturbance agent with a widespread distribution in western North America. Population success is influenced by temperatures that drive phenology and ultimately the adult emergence synchrony required to mass attack and kill host trees during outbreaks. In addition to lifestage‐specific developmental rates and thresholds, oviposition timing can be a source of variance in adult emergence synchrony, and is a critical aspect of mountain pine beetle phenology. Adaptation to local climates has resulted in longer generation times in southern compared to northern populations in common gardens, and the role of oviposition rate in these differences is unclear. Oviposition rates and fecundity in a northern population have been described, although data are lacking for southern populations. We assessed southern mountain pine beetle oviposition rates and fecundity in a range of temperatures using a non‐destructive technique that included frequent X‐ray imaging. We found that oviposition rate and fecundity vary independently such that a female with high oviposition rate did not necessarily have high fecundity and vice versa. Observed fecundity within the 30‐day experimental period was lowest at the lowest temperature, although estimated potential fecundity did not differ among temperatures. Females at varying temperatures have the potential to lay similar numbers of eggs, although it will take longer at lower temperatures. Southern mountain pine beetle reared in Pinus strobiformis Engelm. (Pinaceae) had a higher upper threshold for oviposition, a similar lower threshold, and slightly greater potential fecundity compared to a northern population reared in Pinus contorta Douglas. A comparison of modeled oviposition rates between the two populations, which could be influenced by host tree, suggests that differences in oviposition rate do not explain observed differences in total generation time. Our oviposition model will facilitate development of a phenology model for southern mountain pine beetle populations. 相似文献
62.
In the search for new antioxidants, flavan structures called our attention, as substructures of many important natural compounds,
including catechins (flavan-3-ols), simple and dimeric proanthocyanidins, and condensed tannins. In this work the conformational
space of the Z-isomers of (4α→6′′, 2α→O→1′′)-phenylflavans substituted with R = H, OH and OCH3 was scanned in aqueous solution, simulating the solvent by the polarizable continuum model (PCM). Geometry optimizations
were performed at B3LYP/6-31 G** level. Electronic distributions were analyzed at a better calculation level, thus improving
the basis set (6-311++G**). A topological study based on Bader′s theory (atoms in molecules) and natural bond orbital (NBO)
framework was performed. Furthermore, molecular electrostatic potential maps (MEPs) were obtained and thoroughly analyzed.
The stereochemistry was discussed, and the effect of the solvent was addressed. Moreover, intrinsic properties were identified,
focusing on factors that may be related to their antioxidant properties. Hyperconjugative and inductive effects were described.
The coordinated NBO/AIM analysis allowed us to rationalize the changes of MEPs in a polar solvent. To investigate the molecular
and structural properties of these compounds in biological media, the polarizabilities and dipolar moments were predicted
which were further used to enlighten stability and reactivity properties. All conformers were taken into account. Relevant
stereoelectronic aspects were described for understanding the stabilization and antioxidant function of these structures. 相似文献
63.
A genome survey of Moniliophthora perniciosa gives new insights into Witches' Broom Disease of cacao
Jorge MC Mondego Marcelo F Carazzolle Gustavo GL Costa Eduardo F Formighieri Lucas P Parizzi Johana Rincones Carolina Cotomacci Dirce M Carraro Anderson F Cunha Helaine Carrer Ramon O Vidal Raíssa C Estrela Odalys García Daniela PT Thomazella Bruno V de Oliveira Acássia BL Pires Carolina S Maria Rio Marcos Renato R Araújo Marcos H de Moraes Luis AB Castro Karina P Gramacho Marilda S Gonçalves José P Moura Neto Aristóteles Góes Neto Luciana V Barbosa Mark J Guiltinan Bryan A Bailey Lyndel W Meinhardt Julio CM Cascardo Gonçalo AG Pereira 《BMC genomics》2008,9(1):1-25
64.
Martin Schebeck E. Matthew Hansen Axel Schopf Gregory J. Ragland Christian Stauffer Barbara J. Bentz 《Physiological Entomology》2017,42(3):200-210
Diapause, a strategy to endure unfavourable conditions (e.g. cold winters) is commonly found in ectothermic organisms and is characterized by an arrest of development and reproduction, a reduction of metabolic rate, and an increased resistance to adversity. Diapause, in addition to adaptations for surviving low winter temperatures, significantly influences phenology, voltinism and ultimately population growth. We review the literature on diapause and overwintering behaviour of two bark beetle species that affect spruce‐dominated forests in the northern hemisphere, and describe and compare how these strategies can influence population dynamics. The European spruce bark beetle Ips typographus (L.) (Coleoptera, Curculionidae) is the most important forest pest of Norway spruce in Europe. It enters an adult reproductive diapause that might be either facultative or obligate. Obligate diapausing beetles are considered strictly univoltine, entering this dormancy type regardless of environmental cues. Facultative diapausing individuals enter diapause induced by photoperiod, modified by temperature, thus being potentially multivoltine. The spruce beetle Dendroctonus rufipennis (Kirby) (Coleoptera: Curculionidae) infests all spruce species in its natural range in North America. A facultative prepupal diapause is averted by relatively warm temperatures, resulting in a univoltine life cycle, whereas cool temperatures induce prepupal diapause leading to a semivoltine cycle. An adult obligate diapause in D. rufipennis could limit bi‐ or multivoltinism. We discuss and compare the influence of diapause and overwinter survival on voltinism and population dynamics of these two species in a changing climate and provide an outlook on future research. 相似文献
65.
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67.
Kinetics of Ca2+-induced fusion of phosphatidylserine vesicles is studiied for lipid concentrations varying from 1 μM to 100 μM. Fusion is monitored by mixing of aqueous vesicle contents and by explicitly accounting for leakage. The analysis provides separately rates of aggregation and fusion. The rate of fusion per se decreases steeply with vesicle size. 相似文献
68.
The binding of mono-, di- and trivalent cations to negatively charged surfaces is studied within the framework of a modified
Gouy-Chapman equation. For any given combination of ions of the above valences, the existence and uniqueness of the solution
for the surface potential is shown. The treatment provides the surface potential and charge density. For a system containing
only monovalent and divalent ions, analytical solutions are given. When trivalent ions are also present, a procedure based
on numerical integration is described. The distance dependence of the electrostatic potential for planar surfaces is given.
The calculations provide the amount of cations tightly bound and the amount trapped in the double layer region. The competition
between cations for binding to surfaces is elucidated. 相似文献
69.
Mangru S Bentz BL Davis TJ Desai N Stabile PJ Schmidt JJ Millard CB Bavari S Kodukula K 《Journal of biomolecular screening》2005,10(8):788-794
A microfluidic assay was developed for screening botulinum neurotoxin serotype A (BoNT-A) by using a fluorescent resonance energy transfer (FRET) assay. Molded silicone microdevices with integral valves, pumps, and reagent reservoirs were designed and fabricated. Electrical and pneumatic control hardware were constructed, and software was written to automate the assay protocol and data acquisition. Detection was accomplished by fluorescence microscopy. The system was validated with a peptide inhibitor, running 2 parallel assays, as a feasibility demonstration. The small footprint of each bioreactor cell (0.5 cm2) and scalable fluidic architecture enabled many parallel assays on a single chip. The chip is programmable to run a dilution series in each lane, generating concentration-response data for multiple inhibitors. The assay results showed good agreement with the corresponding experiments done at a macroscale level. Although the system has been developed for BoNT-A screening, a wide variety of assays can be performed on the microfluidic chip with little or no modification. 相似文献
70.
Cartilage-inducing factor-B is a unique protein structurally and functionally related to transforming growth factor-beta 总被引:24,自引:0,他引:24
S M Seyedin P R Segarini D M Rosen A Y Thompson H Bentz J Graycar 《The Journal of biological chemistry》1987,262(5):1946-1949
Cartilage-inducing factors-A (CIF-A) and -B (CIF-B), purified from bovine bone on the basis of their ability to induce the cartilage phenotype in vitro, are proteins with molecular weights of 26,000 composed of two apparently identical disulfide-linked chains. CIF-A is apparently identical to TGF-beta from human platelets (Seyedin S. M., Thompson, A. Y., Bentz, H., Rosen, D. M., McPherson, J. M., Conti, A., Siegel, N. R., Galluppi, G. R., and Piez, K. A. (1986) J. Biol. Chem. 261, 5693-5695). We have now found that, like CIF-A and TGF-beta, CIF-B induces anchorage-independent proliferation of NRK-49F cells when these cells are simultaneously treated with epidermal growth factor. Furthermore, CIF-B competes with CIF-A for the same cell membrane receptors in NRK-49F cells. Partial amino acid sequencing reveals that CIF-B is a distinct molecule with extensive homology to CIF-A/TGF-beta. These results show that CIF-B and TGF-beta are structurally and functionally similar molecules, but differ more from each other than does TGF-beta from different species. 相似文献