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51.
Cécile Duclairoir Poc Anne Groboillot Olivier Lesouhaitier Jean-Paul Morin Nicole Orange Marc JG Feuilloley 《BMC research notes》2011,4(1):503
Background
Low environmental air quality is a significant cause of mortality and morbidity and this question is now emerging as a main concern of governmental authorities. Airborne pollution results from the combination of chemicals, fine particles, and micro-organisms quantitatively or qualitatively dangerous for health or for the environment. Increasing regulations and limitations for outdoor air quality have been decreed in regards to chemicals and particles contrary to micro-organisms. Indeed, pertinent and reliable tests to evaluate this biohazard are scarce. In this work, our purpose was to evaluate the Caenorhaditis elegans killing test, a model considered as an equivalent to the mouse acute toxicity test in pharmaceutical industry, in order to monitor air bacterial quality.Findings
The present study investigates the bacterial population in dust clouds generated during crop ship loading in harbor installations (Rouen harbor, Normandy, France). With a biocollector, airborne bacteria were impacted onto the surface of agar medium. After incubation, a replicate of the colonies on a fresh agar medium was done using a velvet. All the replicated colonies were pooled creating the "Total Air Sample". Meanwhile, all the colonies on the original plate were isolated. Among which, five representative bacterial strains were chosen. The virulence of these representatives was compared to that of the "Total Air Sample" using the Caenorhaditis elegans killing test. The survival kinetic of nematodes fed with the "Total Air Sample" is consistent with the kinetics obtained using the five different representatives strains.Conclusions
Bacterial air quality can now be monitored in a one shot test using the Caenorhaditis elegans killing test.52.
Homologues of glucosephosphate isomerase (GPI, EC 5.3.1.9) were purified to
homogeneity and kinetically characterized from Mytilus edulis and Isognomon
alatus, two bivalve molluscs experiencing contrasting thermal environments.
The enzyme isolated from I. alatus functions at warmer temperatures (25-35
C) than GPI from M. edulis, a species that inhabits colder marine littoral
habitats (5-20 C). The former exhibits apparent first-order (with respect
to substrate) catalytic rate constants (Vmax/KM) in vitro that become
progressively greater than the mussel enzyme as the assay temperature is
raised. Apparent zero-order catalytic rate constants (Vmax) are relatively
less differentiated. Catalytic efficiency, defined as the rate at which a
catalytic event occurs in either reaction direction for reference standard
states (substrate concentrations), is greater for the enzyme from the
tropical species (I. alatus) at all realistic combinations of temperature
and substrate concentration except for the lowest temperatures and highest
substrate concentrations, where the GPI from the boreal/temperate M. edulis
is more efficient. This pattern of catalytic divergence appears to be due
primarily to differentiation in Vmax/KM. These results and other published
data are reviewed and shown to be inconsistent with claims that adaptation
of enzymes to higher cell temperatures requires a loss in catalytic
efficiency.
相似文献
53.
Summary We examined how prey size-distributions influence size-specific foraing rate and food gain, i.e., food intake scaled to metabolic demands, in Jefferson's and small-mouth salamander larvae. Ambystoma jeffersonianum larvae sampled on 17 dates from a farm pond whose fauna was dominated by macrozooplankton and chironomid larvae were rarely gape-limited, and total volume of food in the stomach (VS) showed only a slight tendency to increase with larval size. Although 15 of 17 correlation coefficients of VS with larval size were positive, only 1 of 17 correlations were statistically significant, and body size explained only 8% of the overall variation in VS. Correlation coefficients of food gain and body size were positive in 9 cases and negative in 8, but only 3 were statistically significant.In contrast, Ambystoma texanum larvae in 42 samples taken from five sites dominated by macrozooplankton as well as relatively large isopods and amphipods were almost always gape-limited, and VS tended to increase markedly with larval size. 40 of 42 correlation coefficients of VS and larval size were positive, and 19 correlations were statistically significant. Body size in turn explained about 35% of the overall variation in VS. Correlation coefficients of food gain and larval size were positive in 32 of 42 samples, and 9 of 10 significant correlations were positive.When food is limiting and prey selection is not limited by gape, smaller larvae may grow as fast or in some cases faster than larger larvae because they are nearly as effective foragers, but have lower metabolic demands. Larger larvae may in turn grow faster than smaller larvae in environments which support a broad size spectrum of prey, particularly when gape limitations are highly disproportionate among size classes. The growth rate of larvae in one size class relative to another depends primarily on the extent to which increased foraging rate compensates for higher energy demands as body size increases. Size-specific foraging rate may in turn be strongly influenced by the prey size-distribution within a habitat. These relationships suggest that relative size is not always a good a priori predictor of exploitative competitive ability. 相似文献
54.
Chromosomal DNA from 23 closely related, pathogenic strains of Escherichia
coli was digested and probed for the insertion sequences IS1, IS2, IS4,
IS5, and IS30. Under the assumption that elements residing in DNA
restriction fragments of the same apparent length are identical by descent,
parsimony analysis of these characters yielded a unique phylogenetic tree.
This analysis not only distinguished among bacterial strains that were
otherwise identical in their biochemical characteristics and enzyme
electrophoretic mobilities, but certain aspects of the topology of the tree
were consistent across several unrelated insertion elements. The
distribution of IS elements was then reexamined in light of the inferred
phylogenetic relationships to investigate the biological properties of the
elements, such as rates of insertion and deletion, and to discover apparent
recombinational events. The analysis shows that the pattern of distribution
of insertion elements in the bacterial genome is sufficiently stable for
epidemiological studies. Although the rate of recombination by conjugation
has been postulated to be low, at least two such events appear to have
taken place.
相似文献
55.
56.
Jayadev S Petranka JG Cheran SK Biermann JA Barrett JC Murphy E 《The Journal of biological chemistry》1999,274(12):8261-8268
A preneoplastic variant of Syrian hamster embryo cells, sup(+), exhibits decreased endoplasmic reticulum calcium levels and subsequently undergoes apoptosis in low serum conditions (Preston, G. A., Barrett, J. C., Biermann, J. A., and Murphy, E. (1997) Cancer Res. 57, 537-542). This decrease in endoplasmic reticulum calcium appears to be due, at least in part, to reduced capacitative calcium entry at the plasma membrane. Thus we investigated whether inhibition of capacitative calcium entry per se could reduce endoplasmic reticulum calcium and induce apoptosis of cells. We find that treatment with either SKF96365 (30-100 microM) or cell-impermeant 1,2-bis(o-amino-5-bromophenoxy)ethane-N,N,N', N'-tetraacetic acid (5-10 mM) is able to induce apoptosis of cells in conditions where apoptosis does not normally occur. Because previous work has implicated vesicular trafficking as a mechanism of regulating capacitative calcium entry, we investigated whether disruption of vesicular trafficking could lead to decreased capacitative calcium entry and subsequent apoptosis of cells. Coincident with low serum-induced apoptosis, we observed an accumulation of vesicles within the cell, suggesting deregulated vesicle trafficking. Treatment of cells with bafilomycin (30-100 nM), an inhibitor of the endosomal proton ATPase, produced an accumulation of vesicles, decreased capacitative entry, and induced apoptosis. These data suggest that deregulation of vesicular transport results in reduced capacitative calcium entry which in turn results in apoptosis. 相似文献
57.
58.
With rare exceptions, anuran larvae have traditionally been considered to occupy lower trophic levels in aquatic communities
where they function as microphagous suspension feeders. This view is being challenged by studies showing that tadpoles with
generalized morphology often function as macrophagous predators. Here, we review the literature concerning macrophagy by tadpoles
and provide two additional examples involving generalized tadpoles. In the first, we demonstrate with laboratory and field
experiments that wood frog (Rana sylvatica) tadpoles are major predators of macroinvertebrates in ponds. In the second, we show that green frog (R. clamitans) tadpoles can cause catastrophic reproductive failure of the wood frog via egg predation. These results and data from other
studies challenge the assumption that generalized tadpoles function as filter-feeding omnivores, and question the general
applicability of community organization models which assume that predation risk increases with pond permanence. We suggest
that predation risk is greater in temporary ponds than in more permanent ponds for many organisms that are vulnerable to predation
by tadpoles. This being so, a conditional model based upon interactions that are species-specific, life-stage-specific, and
context-dependent may better explain community organization along hydrological gradients than models which assume that temporary
ponds have few or no predators.
Received: 30 November 1998 / Accepted: 2 May 1999 相似文献
59.
This study focuses on the cytotoxic effects of fumonisin B1 (FB1) on both immortalised and immortalised and subsequently transfected normal human bronchial epithelial (NHBE) cells of human
origin using four bioassays. While the MTT, Neutral Red and hexosaminidase colorimetric assays showed little difference between
the toxic effects on the two related cell lines, the clonogenic assay, measuring cell survival and proliferation, indicated
that FB1 had a more toxic effect on the nontransfected cells. This kind ofin vitro approach using cells which retain many characteristics of normal cell growth and differentiation can go some way to developing
evaluation models for food safety in the case of mycotoxin contamination without resorting totally to whole animal testing.
Nevertheless, one or two cytotoxicity tests may be inadequate for a complete appraisal of toxic potential: rather, as wide
a range of methodologies as feasible should be employed initially before meaningful conclusions may be drawn. 相似文献
60.