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71.
Phenotypic plasticity in oysters (Crassostrea virginica) mediated by chemical signals from predators and injured prey 下载免费PDF全文
Avery E. Scherer Jessica Lunt Alex M. Draper Delbert L. Smee 《Invertebrate Biology》2016,135(2):97-107
Prey organisms reduce predation risk by altering their behavior, morphology, or life history. Avoiding or deterring predators often incurs costs, such as reductions in growth or fecundity. Prey minimize costs by limiting predator avoidance or deterrence to situations that pose significant risk of injury or death, requiring them to gather information regarding the relative threat potential predators pose. Chemical cues are often used for risk evaluation, and we investigated morphological responses of oysters (Crassostrea virginica) to chemical cues from injured conspecifics, from heterospecifics, and from predatory blue crabs (Callinectes sapidus) reared on different diets. Previous studies found newly settled oysters reacted to crab predators by growing heavier, stronger shells, but that adult oysters did not. We exposed oysters at two size classes (newly settled oyster spat and juveniles ~2.0 cm) to predation risk cue treatments including predator or injured prey exudates and to seawater controls. Since both of the size classes tested can be eaten by blue crabs, we hypothesized that both would react to crab exudates by producing heavier, stronger shells. Oyster spat grew heavier shells that required significantly more force to break, an effective measure against predatory crabs, when exposed to chemical exudates from blue crabs as compared to controls. When exposed to chemical cues from injured conspecifics or from injured clams (Mercenaria mercenaria), a sympatric bivalve, shell mass and force were intermediate between predator treatments and controls, indicating that oysters react to injured prey cues but not as strongly as to cues released by predators. Juvenile oysters of ~ 2.0 cm did not significantly alter their shell morphology in any of the treatments. Thus, newly settled oysters can differentiate between predatory threats and adjust their responses accordingly, with the strongest responses being to exudates released by predators, but oysters of 2.0 cm and larger do not react morphologically to predatory threats. 相似文献
72.
Sylvia M. Dobbs R. John Dobbs Clive Weller André Charlett Ingvar T. Bjarnason Andrew J. Lawson Darren Letley Lucy Harbin Ashley B. Price Mohammad A. A. Ibrahim Norman L. Oxlade James Bowthorpe Daniel Leckstroem Cori Smee J. Malcolm Plant Dale W. Peterson 《Helicobacter》2010,15(4):279-294
Background: We examine the effect of eradicating Helicobacter in idiopathic parkinsonism (IP). Marked deterioration, where eradication‐therapy failed, prompted an interim report in the first 20 probands to reach de‐blinding. The null‐hypothesis, “eradication has no effect on principal outcome, mean stride length at free‐walking speed,” was rejected. We report on study completion in all 30 who had commenced post‐treatment assessments. Methods: This is a randomized, placebo‐controlled, parallel‐group efficacy study of eradicating biopsy‐proven (culture and/or organism on histopathology) Helicobacter pylori infection on the time course of facets of IP, in probands taking no, or stable long‐t½, anti‐parkinsonian medication. Persistent infection at de‐blinding (scheduled 1‐year post‐treatment) led to open active eradication‐treatment. Results: Stride length improved (73 (95% CI 14–131) mm/year, p = .01) in favor of “successful” blinded active over placebo, irrespective of anti‐parkinsonian medication, and despite worsening upper limb flexor rigidity (237 (57–416) Nm × 10?3/year, p = .01). This differential effect was echoed following open active, post‐placebo. Gait did not deteriorate in year 2 and 3 post‐eradication. Anti‐nuclear antibody was present in all four proven (two by molecular microbiology only) eradication failures. In the remainder, it marked poorer response during the year after eradication therapy, possibly indicating residual “low‐density” infection. We illustrate the importance of eradicating low‐density infection, detected only by molecular microbiology, in a proband not receiving anti‐parkinsonian medication. Stride length improved (424 (379–468) mm for 15 months post‐eradication, p = .001), correction of deficit continuing to 3.4 years. Flexor rigidity increased before hydrogen‐breath‐test positivity for small intestinal bacterial overgrowth (208 (28–388) Nm × 10?3, p = .02), increased further during (171 (67–274), p = .001) (15–31 months), and decreased (136 (6–267), p = .04) after restoration of negativity (32–41 months). Conclusion: Helicobacter is an arbiter of progression, independent of infection‐load. 相似文献
73.
With the cancellation of fenamiphos in the near future, alternative nematode management tactics for plant-parasitic nematodes (PPN) on golf courses need to be identified. The use of entomopathogenic nematodes (EPN) has been suggested as one possible alternative. This paper presents the results of 10 experiments evaluating the efficacy of EPN at managing PPN on turfgrasses and improving turf performance. These experiments were conducted at various locations throughout Florida over the course of a decade. In different experiments, different EPN species were tested against different species of PPN. Separate experiments evaluated multiple rates and applications of EPN, compared different EPN species, and compared single EPN species against multiple species of PPN. In a few trials, EPN were associated with reductions in certain plant-parasite species, but in other trials were associated with increases. In most trials, EPN had no effect on plant parasites. Because EPN were so inconsistent in their results, we conclude that EPN are not acceptable alternatives to fenamiphos by most turf managers in Florida at this time. 相似文献
74.
Estimation of the membrane potential of cultured macrophages from the fast potential transient upon microelectrode entry 总被引:3,自引:1,他引:2 下载免费PDF全文
Analysis of membrane potential recordings upon microelectrode impalement of four types of macrophages (cell lines P388D1 and PU5-1.8, cultured mouse peritoneal macrophages, and cultured human monocytes) reveals that these cells have membrane potentials at least two times more negative than sustained potential values (E(s)) frequently reported. Upon microelectrode entry into the cell (P388D1), the recorded potential drops to a peak value (E(p)) (mean -37 mV for 50 cells, range -15 to -70 mV) within 2 ms, after which it decays to a depolarized potential (E(n)) (mean -12 mV) in about 20 ms. Thereafter, the membrane develops one or a series of slow hyperpolarizations before a final sustained membrane potential (E(s)) (mean -14 mV, range -5 to -40) is established. The mean value of the peak of the first hyperpolarization (E(h)) is -30 mV (range -10 to -55 mV). The initial fast peak transient, measured upon microelectrode entry, was first described and analyzed by Lassen et al. (Lassen, U.V., A.M. T. Nielson, L. Pape, and L. O. Simonsen, 1971, J. Membr. Biol. 6:269-288 for other change in the membrane potential from its real value before impalement to a sustained depolarized value. This was shown to be true for macrophages by two-electrode impalements of single cells. Values of E(p), E(n), E(h), E(s), and membrane resistance (R(m)) measured for the other macrophages were similar to those of P388D1. From these results we conclude that E(p) is a better estimate of the true membrane potential of macrophages than E(s), and that the slow hyperpolarizations upon impalement should be regarded as transient repolarizations back to the original membrane potentials. Thus, analysis of the initial fast impalement transient can be a valuable aid in the estimation of the membrane potential of various sorts of small isolated cells by microelectrodes. 相似文献
75.
A nuclear gene for higher level phylogenetics: phosphoenolpyruvate carboxykinase tracks mesozoic-age divergences within Lepidoptera (Insecta) 总被引:3,自引:0,他引:3
The sequence of phosphoenolpyruvate carboxykinase (PEPCK) has been
previously identified as a promising candidate for reconstructing
Mesozoic-age divergences (Friedlander, Regier, and Mitter 1992, 1994). To
test this hypothesis more rigorously, 597 nucleotides of aligned PEPCK
coding sequence (approximately 30% of the coding region) were generated
from 18 species representing Mesozoic-age lineages of moths (Insecta:
Lepidoptera) and outgroup taxa. Relationships among basal Lepidoptera are
well established by morphological analysis, providing a strong test for the
utility of a gene which has not previously been used in systematics.
Parsimony and other phylogenetic analyses were conducted on nucleotides by
codon positions (nt1, nt2, nt3) separately and in combination, and on amino
acids, for comparison to the test phylogeny. The highest concordance was
achieved with nt1 + nt2, for which one of two most-parsimonious trees was
identical to the test phylogeny, and with all nucleotides when nt3 was
down-weighted sevenfold or higher, for which a single most-parsimonious
tree identical to the test phylogeny resulted. Substitutions in nt3
approached saturation in many, but not all, pairwise comparisons and their
exclusion or severe downweighting greatly increased the degree of
concordance with the test phylogeny. Neighbor-joining analysis confirms
this finding. The utility of PEPCK for phylogenetics is demonstrated over a
time span for which few other suitable genes are currently available.
相似文献
76.
Stable expression of mammalian beta 1,4-galactosyltransferase extends the N-glycosylation pathway in insect cells 总被引:5,自引:2,他引:3
An established lepidopteran insect cell line (Sf9) was cotransfected with
expression plasmids encoding neomycin phosphotransferase and bovine beta
1,4-galactosyltransferase. Neomycin-resistant transformants were selected,
assayed for beta 1,4-galactosyltransferase activity, and the transformant
with the highest level of enzymatic activity was characterized. Southern
blots indicated that this transformed Sf9 cell derivative contained
multiple copies of the galactosyltransferase- encoding expression plasmid
integrated at a single site in its genome. One-step growth curves showed
that these cells supported normal levels of baculovirus replication.
Baculovirus infection of the transformed cells stimulated beta
1,4-galactosyltransferase activity almost 5-fold by 12 h postinfection.
This was followed by a gradual decline in activity, but the infected cells
still had about as much activity as uninfected controls as late as 48 h
after infection and they were able to produce a beta 1,4-galactosylated
virion glycoprotein during infection. Infection of the transformed cells
with a conventional recombinant baculovirus expression vector encoding
human tissue plasminogen activator also resulted in the production of a
galactosylated end-product. These results demonstrate that stable
transformation can be used to add a functional mammalian
glycosyltransferase to lepidopteran insect cells and extend their N-
glycosylation pathway. Furthermore, stably-transformed insect cells can be
used as modified hosts for conventional baculovirus expression vectors to
produce foreign glycoproteins with "mammalianized" glycans which more
closely resemble those produced by higher eucaryotes.
相似文献
77.
The impact of gender and/or hormone variations on a wide variety of neural functions makes the choice between studying males or females (or both) of a given species difficult. Although female rats are widely used experimentally, few studies control for the stage of estrus. More detailed information about how to distinguish the various stages of the estrous cycle is needed. For the present study, vaginal smears were obtained once a day and stained using an adaptation of the Papanicolaou (PAP) procedure. Images are provided of unstained “wet” samples and the corresponding PAP stained smears illustrating the cellular profile for each stage of the cycle as well as post-ovariectomy. The different cell populations across the cycle were quantified and ratios determined to show trends between the predominant and other cell types in each stage of the estrous cycle. Both stained and unstained images and cell quantification data provide valuable guidelines for distinguishing the stages of the estrous cycle. 相似文献
78.
Many studies have shown that nonlethal predator effects such as trait-mediated interactions (TMIs) can have significant impacts
on the structure and function of communities, but the role that environmental conditions play in modulating the scale and
magnitude of these effects has not been carefully investigated. TMIs occur when prey exhibit behavioral or physiological responses
to predators and may be more prevalent when abiotic conditions increase prey reactions to consumers. The purpose of this study
was to determine if turbulence would alter the distance over which prey in aquatic systems respond to chemical cues emitted
by predators in nature, thus changing the scales over which nonlethal predator effects occur. Using hard clams and blue crabs
as a model predator–prey system, we investigated the effects of turbulence on clam reactive distance to predatory blue crabs
in the field. Results suggest that turbulence diminishes clam reactions to predators and that the environmental context must
be considered when predicting the extent of indirect predator effects in natural systems. 相似文献
79.
Angell RM Angell TD Bamborough P Bamford MJ Chung CW Cockerill SG Flack SS Jones KL Laine DI Longstaff T Ludbrook S Pearson R Smith KJ Smee PA Somers DO Walker AL 《Bioorganic & medicinal chemistry letters》2008,18(15):4433-4437
The biphenyl amides (BPAs) are a series of p38α MAP kinase inhibitors. Compounds are able to bind to the kinase in either the DFG-in or DFG-out conformation, depending on substituents. X-ray, binding, kinetic and cellular data are shown, providing the most detailed comparison to date between potent compounds from the same chemical series that bind to different p38α conformations. DFG-out-binding compounds could be made more potent than DFG-in-binding compounds by increasing their size. Unexpectedly, compounds that bound to the DGF-out conformation showed diminished selectivity. The kinetics of binding to the isolated enzyme and the effects of compounds on cells were largely unaffected by the kinase conformation bound. 相似文献