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951.
Innate immunity in plants: a continuum of layered defenses 总被引:1,自引:0,他引:1
Plant responses to pathogenic invaders result from recognition of nonself elicitors. Host surveillance proteins activate distinct signaling pathways that induce partially overlapping defensive responses. Pathogen virulence is promoted by inhibition of these pathways. This evolutionary struggle has produced plant immune systems that rely on a continuum of layered defenses. 相似文献
952.
A ribosomal RNA gene intergenic spacer based PCR and DGGE fingerprinting method for the analysis of specific rhizobial communities in soil 总被引:5,自引:0,他引:5
de Oliveira VM Manfio GP da Costa Coutinho HL Keijzer-Wolters AC van Elsas JD 《Journal of microbiological methods》2006,64(3):366-379
A direct molecular method for assessing the diversity of specific populations of rhizobia in soil, based on nested PCR amplification of 16S-23S ribosomal RNA gene (rDNA) intergenic spacer (IGS) sequences, was developed. Initial generic amplification of bacterial rDNA IGS sequences from soil DNA was followed by specific amplification of (1) sequences affiliated with Rhizobium leguminosarum "sensu lato" and (2) R. tropici. Using analysis of the amplified sequences in clone libraries obtained on the basis of soil DNA, this two-sided method was shown to be very specific for rhizobial subpopulations in soil. It was then further validated as a direct fingerprinting tool of the target rhizobia based on denaturing gradient gel electrophoresis (DGGE). The PCR-DGGE approach was applied to soils from fields in Brazil cultivated with common bean (Phaseolus vulgaris) under conventional or no-tillage practices. The community fingerprints obtained allowed the direct analysis of the respective rhizobial community structures in soil samples from the two contrasting agricultural practices. Data obtained with both primer sets revealed clustering of the community structures of the target rhizobial types along treatment. Moreover, the DGGE profiles obtained with the R. tropici primer set indicated that the abundance and diversity of these organisms were favoured under NT practices. These results suggest that the R. leguminosarum-as well as R. tropici-targeted IGS-based nested PCR and DGGE are useful tools for monitoring the effect of agricultural practices on these and related rhizobial subpopulations in soils. 相似文献
953.
This study describes a novel isolation procedure for major glycolipids from Bifidobacterium adolescentis 94 BIM. The procedure consists of the use of supercritical carbon dioxide (scCO(2)) with hydro-methanolic solution as co-solvent. The major glycolipids were isolated using the following operating conditions: pressure, 30 MPa, co-solvent concentration, 10% (9:1, methanol/water, v/v), CO(2) flow rate, 5 g/min, extraction time and temperature, 2h and 55 degrees C, respectively. The reference glycolipids sample was prepared by classical organic solvent extraction followed by chromatographic purification. All isolates were characterized by TLC and the major glycolipids additionally by enzyme linked immunosorbent (ELISA). Sixty milligrams of glycolipids with similar immunoreactivity as the reference glycolipids were isolated from 1g of freeze-dried biomass (6% of yield). 相似文献
954.
955.
Patrícia A. de Campos Braga Márcio Santos Soares M. Fátima das G.F. da Silva Paulo C. Vieira João B. Fernandes Antônio L. Pinheiro 《Biochemical Systematics and Ecology》2006
The stem of Cabralea canjerana (Vell.) Mart. yielded three new dammarane triterpenes 20S,24S-epoxy-7β,25-dihydroxy-3,4-secodammar-4(28)-en-3-oic acid, 20S,24S-epoxy-7β,15α,25-trihydroxy-3,4-secodammar-4(28)-en-3-oic acid and 20S,24R-epoxy-7β,22ξ,25-trihydroxy-3,4-secodammar-4(28)-en-3-oic acid, which were identified on the basis of spectroscopic methods. The known dammarane triterpenes ocotillone, eichlerianic acid, shoreic acid and the sterols sitosterol, campesterol, stigmasterol, sitostenone and stigmast-5-en-3-one were also isolated and identified. The branches yielded the above three known dammaranes and eichlerialactone. The dammaranes in C. canjerana display strong similarities with Trichilieae tribe, which contains several dammaranes. The data reported herein thus provide firm support for placing Cabralea within the subfamily Melioideae, Trichilieae tribe. 相似文献
956.
957.
Lukácová N Kolesárová M Kuchárová K Pavel J Kolesár D Radonák J Marsala M Chalimoniuk M Langfort J Marsala J 《Cellular and molecular neurobiology》2006,26(7-8):1365-1383
1. The present study was designed to examine the nitric oxide synthase activities (constitutive and inducible) in the site of injury in response to Th10-Th11 spinal cord hemisection and, to determine whether unilateral disconnection of the spinal cord influences the NOS pools on the contra- and ipsilateral sides in segments located far away from the epicentre of injury.2. A radioassay detection was used to determine Ca2+-dependent and inducible nitric oxide synthase activities. Somal, axonal and neuropil neuronal nitric oxide synthase was assessed by immunocytochemical study. A quantitative assessment of neuronal nitric oxide synthase immunoreactivity was made by an image analyser. The level of neuronal nitric oxide synthase protein was measured by the Western blot analysis.3. Our data show the increase of inducible nitric oxide synthase activity and a decrease of Ca2+-dependent nitric oxide synthase activity in the injured site analysed 1 and 7 days after surgery. In segments remote from the epicentre of injury the inducible nitric oxide synthase activity was increased at both time points. Ca2+-dependent nitric oxide synthase activity had decreased in L5-S1 segments in a group of animals surviving for 7 days. A hemisection performed at thoracic level did not cause significant difference in the nitric oxide synthase activities and in the level of neuronal nitric oxide synthase protein between the contra- and ipsilateral sides in C6-Th1 and L5-S1 segments taken as a whole. Significant differences were observed, but only when the spinal cord was analysed segment by segment, and/or was divided into dorsal and ventral parts. The cell counts in the cervicothoracic (C7-Th1) and lumbosacral (L5-S1) enlargements revealed changes in neuronal nitric oxide synthase immunoreactivity on the ipsilateral side of the injury. The densitometric area measurements confirmed the reduction of somal, neuropil and axonal neuronal nitric oxide synthase immunoreactive staining in the ventral part of rostrally oriented segments.4. Our findings provide evidence that the changes in nitric oxide synthase pools are limited not only to impact zone, but spread outside the original lesion. The regional distribution of nitric oxide synthase activity and neuronal nitric oxide synthase immunoreactivity, measured segment by segment shows that nitric oxide may play a significant role in the stepping cycle in the quadrupeds. 相似文献
958.
Summary In this study, immunohistochemistry for neuronal nitric oxide synthase (bNOS-IR), nicotinamide adenine dinucleotide phosphate
diaphorase histochemistry (NADPHd) and nitric oxide synthase radioassay were used to study the occurrence, number and distribution
pattern of nitric oxide synthesizing neurons in the lumbar (L1–L7) and sacral (S1–S3) dorsal root ganglia of the dog. Nitric
oxide synthase immunolabelling was present in a large number of small- (area <1000 μm2) and medium-sized (area 1000–2000 μm2) as well as in a limited number of large-sized (area >2000 μm2) neurons. Although neuronal nitric oxide synthase immunolabelling and histochemical staining provided intense staining of
multiple small- and medium-sized neurons in all lumbar and sacral dorsal root ganglia, immunolabelled or histochemically stained
somata exhibited little topographic distribution in individual dorsal root ganglia. Great heterogeneity was noticed in the
immunolabelling of medium-sized nitric oxide synthase immunopositive neurons ranging from lightly immunolabelled somata to
heavily immunoreactive ones with completely obscured nuclei. Both staining procedures proved to be highly effective in visualizing
intraganglionic fibers of various diameters. In general, the largest fibers revealed at the peripheral end of lumbar and sacral
dorsal root ganglia were larger, 6.49–9.35 μm in diameter, while those running centrally and proceeding into the dorsal roots
were about 30% reduced, ranging between 5.32 and 8.67 μm in diameter. Peripherally, the occurrence of nitric oxide synthase
detected in axonal profiles, and confirmed histochemically, in the specimens of the femoral and sciatic nerves, is the first
indication of the presence of nitric oxide synthase in the peripheral processes of somata located in L4–S2 dorsal root ganglia.
Large and thin central nitric oxide synthase immunoreactive processes of L1–S3 dorsal root ganglion neurons segregate shortly
before entering the spinal cord, the former making a massive medial bundle in the dorsal root accompanied by a slim lateral
bundle penetrating Lissauer's tract. Quantitative assessment of the distribution of bNOS-IR and/or NADPHd-stained neurons
showed a peculiar pattern in relation to spinal levels. Apparent incongruity was found in the total number of NADPHd-stained
versus bNOS-IR neurons, demonstrating a clear prevalence of small bNOS-IR somata in all lumbar ganglia, while medium-sized
NADPHd-stained somata clearly prevailed all along the rostrocaudal axis with a peak in L5 ganglion. While the number of small
bNOS-IR neurons clearly outnumbered NADPHd-stained and NADPHd-unstained somata in S1–S3 ganglia, an inverse relation appeared
comparing the total number of medium-sized NADPHd-stained and NADPHd-unstained somata compared with the number of moderate
and intense bNOS-IR neurons. Densitometry of bNOS-IR and NADPHd-stained neurons in lumbar and sacral ganglia revealed two
distinct subsets of densitometric profiles, one relating to more often found medium-sized bNOS immunolabelled and the other,
characteristic for moderately bNOS immunoreactive somata of the same cell size. Considerable differences in catalytic nitric
oxide synthase activity, determined by conversion of [3H]arginine to [3H]citrulline were obtained in lumbosacral dorsal root ganglia all along the lumbosacral intumescence, the lowest (0.898± 0.2
dpm/min/μg protein) being in the L4 dorsal root ganglion and the highest (4.194± 0.2 dpm/min/μg protein) in the S2 dorsal
root ganglion. 相似文献
959.
960.
Kinetics of double-chain reversals bridging contiguous quartets in tetramolecular quadruplexes
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Repetitive 5'GGXGG DNA segments abound in, or near, regulatory regions of the genome and may form unusual structures called G-quadruplexes. Using NMR spectroscopy, we demonstrate that a family of 5'GCGGXGGY sequences adopts a folding topology containing double-chain reversals. The topology is composed of two bistranded quadruplex monomeric units linked by formation of G:C:G:C tetrads. We provide a complete thermodynamic and kinetic analysis of 13 different sequences using absorbance spectroscopy and DSC, and compare their kinetics with a canonical tetrameric parallel-stranded quadruplex formed by TG4T. We demonstrate large differences (up to 10(5)-fold) in the association constants of these quadruplexes depending on primary sequence; the fastest samples exhibiting association rate equal or higher than the canonical TG4T quadruplex. In contrast, all sequences studied here unfold at a lower temperature than this quadruplex. Some sequences have thermodynamic stability comparable to the canonical TG4T tetramolecular quadruplex, but with faster association and dissociation. Sequence effects on the dissociation processes are discussed in light of structural data. 相似文献