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11.
Rebecca C Mueller Fabiana S Paula Babur S Mirza Jorge LM Rodrigues Klaus Nüsslein Brendan JM Bohannan 《The ISME journal》2014,8(7):1548-1550
Understanding the interactions among microbial communities, plant communities and soil properties following deforestation could provide insights into the long-term effects of land-use change on ecosystem functions, and may help identify approaches that promote the recovery of degraded sites. We combined high-throughput sequencing of fungal rDNA and molecular barcoding of plant roots to estimate fungal and plant community composition in soil sampled across a chronosequence of deforestation. We found significant effects of land-use change on fungal community composition, which was more closely correlated to plant community composition than to changes in soil properties or geographic distance, providing evidence for strong links between above- and below-ground communities in tropical forests. 相似文献
12.
Bat hibernacula with high numbers of bats can become high-risk areas, as they attract flying and non-flying predators. In order to protect hibernating bats effectively, more knowledge about mortality factors is needed. During the winters of 2003–2015, we found 214 dead bats in 12 hibernacula in The Netherlands province of Zuid-Holland. Most bat remains were found in December and January, with a second peak in April. Their remains showed a typical pattern of lesions consistent with those caused by predation by the wood mouse (Apodemus sylvaticus). Trail camera surveys showed that wood mice actively searched for bats. Predation pressure seemed to vary between winters, with a peak in the winters of 2004, 2011 and 2015. The annual mortality (relative to the maximum winter population size) caused by wood mouse predation varied between 0.1 and 8.8 %, with a maximum local effect of 83.6 %. The years with high wood mouse predation pressure were characterized by a long frost period and a low mast production of common oak in the preceding autumn. The size of a hibernaculum and the population density of its bats had an effect on predation-dependent mortality. The highest predation risk occurred near the entrance of bunkers. From these results we tentatively conclude that predation is not incidental and that wood mice actively search for and kill hibernating bats or scavenge for weakened individuals. 相似文献
13.
Three satellite DNA families were identified in three species of burying
beetles, Nicrophorus orbicollis, N. marginatus, and N. americanus. Southern
hybridization and nucleotide sequence analysis of individual randomly
cloned repeats shows that these satellite DNA families are highly abundant
in the genome, are composed of unique repeats, and are species-specific.
The repeats do not have identifiable core elements or substructures that
are similar in all three families, and most interspecific sequence
similarity is confined to homopolymeric runs of A and T. Satellite DNA from
N. marginatus and N. americanus show single-base-pair indels among repeats,
but single-nucleotide substitutions characterize most of the repeat
variability. Although the repeat units are of similar lengths (342, 350,
and 354 bp) and A + T composition (65%, 71%, and 71%, respectively), the
average nucleotide divergence among sequenced repeats is very low (0.18%,
1.22%, and 0.71%, respectively). Transition/transversion ratios from the
consensus sequence are 0.20, 0.69, and 0.70, respectively.
相似文献
14.
Membrane resistance change of the frog taste cells in response to water and Nacl 总被引:2,自引:0,他引:2 下载免费PDF全文
The electrical properties of the frog taste cells during gustatory stimulations with distilled water and varying concentrations of NaCl were studied with intracellular microelectrodes. Under the Ringer adaptation of the tongue, two types of taste cells were distinguished by the gustatory stimuli. One type, termed NaCl-sensitive (NS) cells, responded to water with hyperpolarizations and responded to concentrated NaCl with depolarizations. In contrast, the other type of cells, termed water-sensitive (WS) cells, responded to water depolarizations and responded to concentrated NaCl with hyperpolarizations. The membrane resistance of both taste cell types increased during the hyperpolarizing receptor potentials and decreased during the depolarizing receptor potentials, Reversal potentials for the depolarizing and hyperpolarizing responses in each cell type were a few millivolts positive above the zero membrane potential. When the tongue was adapted with Na-free Ringer solution for 30 min, the amplitude of the depolarizing responses in the NS cells reduced to 50% of the control value under normal Ringer adaptation. On the basis of the present results, it is concluded (a) that the depolarizing responses of the NS and WS cells under the Ringer adaptation are produced by the permeability increase in some ions, mainly Na+ ions across the taste cell membranes, and (b) that the hyperpolarizing responses of both types of taste cells are produced by a decrease in the cell membrane permeability to some ions, probably Na+ ions, which is slightly enhanced during the Ringer adaptation. 相似文献
15.
Molecular evidence for the rapid propagation of mouse t haplotypes from a single, recent, ancestral chromosome 总被引:11,自引:0,他引:11
Silver LM; Hammer M; Fox H; Garrels J; Bucan M; Herrmann B; Frischauf AM; Lehrach H; Winking H; Figueroa F 《Molecular biology and evolution》1987,4(5):473-482
Mouse t haplotypes are variant forms of chromosome 17 that exist at high
frequencies in worldwide populations of two species of commensal mice. To
determine both the relationship of t haplotypes to each other and the
species within which they exist, 35 representative t haplotypes were
analyzed by means of 10 independent molecular probes, including five DNA
clones and five polypeptide spots identified by means of two- dimensional
gel electrophoresis. All of the tested haplotypes were found to share
restriction fragments and polypeptide spots that are absent in mice
carrying wild-type forms of chromosome 17. This observation provides the
first direct evidence that all of the known t haplotypes are descendents of
a single ancestral chromosome. The absence of variation among t haplotypes
could mean that this ancestral chromosome existed relatively recently, in
which case it would be necessary to postulate introgressions of t
haplotypes across species lines to explain their presence in both Mus
domesticus and M. musculus. Alternatively, it is possible that the
ancestral chromosome existed prior to the split between M. domesticus and
M. musculus and that, by chance, our probes fail to detect polymorphisms
that exist among the t haplotypes. A further result of our analysis is the
characterization of a partial t haplotype in a wild population of Israeli
mice.
相似文献
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A parsimony analysis was performed on restriction sites at the Hba-ps4
pseudogene locus within one of four inversions associated with mouse t
haplotypes. The results suggest that all t haplotypes form a monophyletic
group and that the in (17)4 inversion originated before the radiation of
the Mus musculus species complex but after the divergence of the lineages
leading to M. spretus, M. abbotti, and M. hortulanus. A time frame based on
the evolutionary rate of mouse pseudogenes places the origin of this t
haplotype inversion at 1.5 Mya, or approximately 1.5 Myr after the origin
of the more proximal t complex inversion, in (17)2. The accumulated
evidence indicates that complete t haplotypes have been assembled in a
stepwise manner, with each of these inversions occurring on separate
chromosomal lineages and at different evolutionary times. In addition, the
evolutionary relationships of pseudogene sequences resulting from genetic
exchange between wild-type and t haplotype alleles were examined. Analysis
of sequences from the 5' and 3' sides of a putative site of recombination
resulted in cladograms with different topologies. The implications for
hypotheses concerning the evolutionary forces acting on t haplotypes and
their rapid propagation throughout worldwide populations of mice are
discussed.
相似文献
20.
Chronic mitochondrial inhibition induces selective motoneuron death in vitro: a new model for amyotrophic lateral sclerosis 总被引:10,自引:0,他引:10
Kaal EC Vlug AS Versleijen MW Kuilman M Joosten EA Bär PR 《Journal of neurochemistry》2000,74(3):1158-1165
Evidence is increasing that mitochondrial dysfunction is involved in amyotrophic lateral sclerosis, a neurodegenerative disease characterized by selective motoneuron death. To study the role of mitochondrial dysfunction in the pathways leading to motoneuron death, we developed an in vitro model of chronic motoneuron toxicity, based on malonate-induced inhibition of complex II in the mitochondrial electron transport chain. Treatment with malonate resulted in a dose-dependent decrease in cellular ATP levels. We observed that motoneurons were significantly more vulnerable to mitochondrial inhibition than control neurons in the dorsal horn. We could reproduce this dose-dependent phenomenon with the complex IV inhibitor sodium azide. The free radical scavenger alpha-phenyl-N-tert-butylnitrone, the AMPA/kainate receptor blocker 6-cyano-7-nitroquinoxaline-2,3-dione, and riluzole, a drug that is currently used for the treatment of amyotrophic lateral sclerosis, were protective against malonate-induced motoneuron death. Furthermore, the caspase inhibitors N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone and z-Asp-Glu-Val-Asp-fluoromethyl ketone were both protective against malonate toxicity. Our model shows that chronic mitochondrial inhibition leads to selective motoneuron death, which is most likely apoptotic. 相似文献