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51.
Aurélie Dery Virginie Guibourt Ana I. Catarino Philippe Compère Philippe Dubois 《Invertebrate Biology》2014,133(2):188-199
Cidaroid sea urchins are the sister clade to all other extant echinoids and have numerous unique features, including unusual primary spines. These lack an epidermis when mature, exposing their high‐magnesium calcite skeleton to seawater and allowing the settlement of numerous epibionts. Cidaroid spines are made of an inner core of classical monocrystalline skeleton and an outer layer of polycrystalline magnesium calcite. Interestingly, cidaroids survived the Permian‐Triassic crisis, which was characterized by severe acidification of the ocean. Currently, numerous members of this group inhabit the deep ocean, below the saturation horizon for their magnesium calcite skeleton. This suggests that members of this taxon may have characteristics that may allow them to resist ongoing ocean acidification linked to global change. We compared the effect of acidified seawater (pH 7.2, 7.6, or 8.2) on mature spines with a fully developed cortex to that on young, growing spines, in which only the stereom core was developed. The cortex of mature spines was much more resistant to etching than the stereom of young spines. We then examined the properties of the cortex that might be responsible for its resistance compared to the underlying stereomic layers, namely morphology, intramineral organic material, magnesium concentration, intrinsic solubility of the mineral, and density. Our results indicate that the acidification resistance of the cortex is probably due to its lower magnesium concentration and higher density, the latter reducing the amount of surface area in contact with acidified seawater. The biofilm and epibionts covering the cortex of mature spines may also reduce its exposure to seawater. 相似文献
52.
Small cryptic plasmids of molecular weights ranging from 1 to 3 Mdal were detected by electron microscopy in Salmonella typhimurium strain LT2 (ColIb). They were divided into different size classes. Two of the cryptic plasmids were transferred simultaneously with ColIb to Escherichia coli.List of Abbreviations TES buffer
0.05 M tris-HCl pH 8.0, 0.05 M NaCl, 0.005 M Na2 EDTA
- TCG medium
tris-casamino acid-glucose medium
- cpm
counts per min 相似文献
53.
Strains of Rhizoctonia solani, a common soil-borne, pathogenic fungus of plants, are assigned to one of 11 anastomosis groups (AGs) based on the occurrence of imperfect fusions (anastomoses) between hyphae of a non-typed strain and a tester strain of one of the 11 AG's. Imperfect fusion is characterized by the death of one or more cells in each of the hyphae involved in the fusion. Although hyphae from branches of the same strain of JR. solani may fuse with each other (self-fusion), cell death does not occur. Cell death is accompanied by nuclear degradation and granulation, or plasmolysis of the cytoplasm, which often is not visible using bright-field microscopy. When the DNA-binding fluorochrome DAPI (4', 6-diamidino-2-phenylindole) is used and the hyphal fusions viewed under fluorescence microscopy, no nuclei are observed in fused hyphal cells from two strains of the same AG of R. solani Because DAPI reacts only with living nuclei, lack of staining is presumptive evidence that the fused cells are dead as a result of imperfect fusion. The use of DAPI reduces the time required for making AG determinations compared to standard methods because it eliminates the need to assess cell wall dissolution and cytoplasmic fusion. Also, it is not necessary to trace the hyphae involved in the fusion to their respective origins to ensure that self-fusion has not occurred. 相似文献
54.
Jinong Feng Zhifang Zhang Xiwei Wu Allen Mao Frances Chang Xutao Deng Harry Gao Ching Ouyang Kenneth J. Dery Keith Le Jeffrey Longmate Claudia Marek R. Paul St. Amand Theodore G. Krontiris John E. Shively 《PloS one》2013,8(6)
Fibromyalgia syndrome (FMS) is a chronic musculoskeletal pain disorder affecting 2% to 5% of the general population. Both genetic and environmental factors may be involved. To ascertain in an unbiased manner which genes play a role in the disorder, we performed complete exome sequencing on a subset of FMS patients. Out of 150 nuclear families (trios) DNA from 19 probands was subjected to complete exome sequencing. Since >80,000 SNPs were found per proband, the data were further filtered, including analysis of those with stop codons, a rare frequency (<2.5%) in the 1000 Genomes database, and presence in at least 2/19 probands sequenced. Two nonsense mutations, W32X in C11orf40 and Q100X in ZNF77 among 150 FMS trios had a significantly elevated frequency of transmission to affected probands (p = 0.026 and p = 0.032, respectively) and were present in a subset of 13% and 11% of FMS patients, respectively. Among 9 patients bearing more than one of the variants we have described, 4 had onset of symptoms between the ages of 10 and 18. The subset with the C11orf40 mutation had elevated plasma levels of the inflammatory cytokines, MCP-1 and IP-10, compared with unaffected controls or FMS patients with the wild-type allele. Similarly, patients with the ZNF77 mutation have elevated levels of the inflammatory cytokine, IL-12, compared with controls or patients with the wild type allele. Our results strongly implicate an inflammatory basis for FMS, as well as specific cytokine dysregulation, in at least 35% of our FMS cohort. 相似文献
55.
Norian-Rhaetian reefs in Argolis Peninsula,Greece 总被引:2,自引:0,他引:2
PD Dr. Baba Senowbari-Daryan Dr. Dionissios Matarangas Dr. Myrsini Vartis-Matarangas 《Facies》1996,34(1):77-82
Summary Upper Triassic to Lower Jurassic shallow-water carbonate sequences of the ‘Pantokrator limestones’ are widely distributed
in the Argolis Peninsula, southern Greece. Within this sequence are some reef or reefal structures. In the Mavrovouni Mountains,
near Sarmeika, 6 km SE of the ancient theatre of Epidavros (Argolis Peninsula), a Norian-Rhaetian reef complex has been identified.
This is the first well-documented Norian-Rhaetian reef in Greece. The main reef builders are coralline sponges (‘sphinctozoans,’
‘inozoans’, and sclerosponges), followed by dendroid, cerioid, and solitary corals, and algae. The reef type corresponds to
a ‘sponge-coral reef’. 相似文献
56.
57.
Molecular clocks are routinely tested for linearity using a relative rate
test and routinely calibrated against the geological time scale using a
single or average paleontologically determined time of divergence between
living taxa. The relative rate test is a test of parallel rate equality,
not a test of rate constancy. Temporal scaling provides a test of rates,
where scaling coefficients of 1.0 (isochrony) represent stochastic rate
constancy. The fossil record of primates and other mammals is now known in
sufficient detail to provide several independent divergence times for major
taxonomic groups. Molecular difference should scale negatively or
isochronically (scaling coefficients less than 1.0) with divergence time:
where two or more divergence times are available, molecular difference
appears to scale positively (scaling coefficient greater than 1.0). A
minimum of four divergence times are required for adequate statistical
power in testing the linear model: scaling is significantly nonlinear and
positive in six of 11 published investigations meeting this criterion. All
groups studied show some slowdown in rates of molecular change over
Cenozoic time. The break from constant or increasing rates during the
Mesozoic to decreasing rates during the Cenozoic appears to coincide with
extraordinary diversification of placental mammals at the beginning of this
era. High rates of selectively neutral molecular change may be concentrated
in such discrete events of evolutionary diversification.
相似文献
58.
Rhizobium trifolii AR182, a mutant resistant to rhizobiophages lysing the parental strain AR5, formed abortive nodules on the clover plant roots. The polyacrylamide gel electrophoresis of the isolated lipopolysaccharide revealed only one band. On the other hand, the lipopolysaccharide isolated from the non-mucoid mutant R. trifolii AR16 showed several, regularly spaced bands in the high molecular weight region. The results suggest that R. trifolii AR182 is a rough (R)-mutant.Abbreviations LPS
lipopolysaccharide
- EPS
exopolysaccharide
- CPS
capsular polysaccharide
- DOC
sodium deoxycholate
- PAGE
polyacrylamide gel electrophoresis
- GC-MS
gas liquid chromatography-mass spectrometry
- KDO
2-keto-3-deoxy-octonic acid
- Rha
rhamnose
- Fuc
fucose
- Man
mannose
- Gal
galactose
- Glc
glucose
- UA
uronic acid 相似文献
59.
Summary Several strains ofRhizobium trifolii were tested for their ability to synthesize and utilize phenolate or hydroxamate types of siderophores. None of the nodulating strains ofR. trifolii was able to produce detectable amounts of siderophores. Only the non-nodulating strainR. trifolii AR6 formed a phenolate siderophore, which stimulated the growth of the siderophore-negative mutant AR65. Other strains ofR. trifolii could not utilize iron from exogenously supplied Desferal, pseudobactin or citrate. The siderophore fromR. trifolii AR6 and 2,3-dihydroxybenzoic acid slightly stimulated the growth of someR. trifolii strains. 相似文献
60.