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排序方式: 共有515条查询结果,搜索用时 281 毫秒
101.
Paula?Andrea?Giraldo Carly?Elliott Pieter?Badenhorst Gavin?Kearney German?C.?Spangenberg Noel?O.?I.?Cogan Kevin?F.?SmithEmail authorView authors OrcID profile 《Transgenic research》2018,27(5):397-407
Alkaloid concentration of perennial ryegrass herbage is affected by endophyte strain and host plant genotype. However, previous studies suggest that associations between host and endophyte also depends on environmental conditions, especially those affecting nutrient reserves and that water-soluble carbohydrate (WSC) concentration of perennial ryegrass plants may influence grass-endophyte associations. In this study a single transgenic event, with altered expression of fructosyltransferase genes to produce high WSC and biomass, has been crossed into a range of cultivar backgrounds with varying Epichloë endophyte strains. The effect of the association between the transgenic trait and alkaloid production was assessed and compared with transgene free control populations. In the vast-majority of comparisons there was no significant difference between alkaloid concentrations of transgenic and non-transgenic plants within the same cultivar and endophyte backgrounds. There was no significant difference between GOI+?(gene of interest positive) and GOI? (gene of interest negative) populations in Janthritrem response. Peramine concentration was not different between GOI+?and GOI? for 10 of the 12 endophytes-cultivar combinations. Cultivar Trojan infected with NEA6 and Alto with SE (standard endophyte) exhibited higher peramine and lolitrem B (only for Alto SE) concentration, in the control GOI? compared with GOI+. Similarly, cultivar Trojan infected with NEA6 and Alto with NEA3 presented higher ergovaline concentration in GOI?. Differences in alkaloid concentration may be attributable to an indirect effect in the modulation of fungal biomass. These results conclude that the presence of this transgenic insertion, does not alter the risk (toxicity) of the endophyte–grass associations. Endophyte–host interactions are complex and further research into associations with high WSC plant should be performed in a case by case basis. 相似文献
102.
Short-Term In Vitro Culture and Molecular Analysis of the Microsporidian, Enterocytozoon bieneusi 总被引:2,自引:0,他引:2
GOVINDA S. VISVESVARA GORDON J. LEITCH NORMAN J. PIENIAZEK ALEXANDRE J. DA SILVA SARA WALLACE SUSAN B. SLEMENDA RAINER WEBER DAVID A. SCHWARTZ LEO GORELKIN C. MEL WILCOX RALPH T. BRYAN 《The Journal of eukaryotic microbiology》1995,42(5):506-510
ABSTRACT. The microsporidium, Enterocytozoon bieneusi , causes a severe, debilitating, chronic diarrhea in patients with the acquired immunodeficiency syndrome. Specific diagnosis of intestinal microsporidiosis, especially due to Enterocytozoon , is difficult and there is no known therapy that can completely eradicate this parasite. Preliminary studies indicate that a short term (about 6 months) in vitro culture of this parasite yielding low numbers of spores, may be established by inoculating human lung fibroblasts and/or monkey kidney cell cultures with duodenal aspirates and or biopsy from infected patients. The cultures may subsequently be used for the isolation and molecular analysis of parasite DNA. 相似文献
103.
Gram-Chromotrope: a New Technique that Enhances Detection of Microsporidial Spores in Clinical Samples 总被引:3,自引:0,他引:3
HERCULES MOURA JORGE L. NUNES DA SILVA FERNANDO C. SODRÉ PATRICIA BRASIL KRISTY WALLMO SUSANNE WAHLQUIST SARA WALLACE GIAN P. CROPPO GOVINDA S. VISVESVARA 《The Journal of eukaryotic microbiology》1996,43(5):94S-95S
We have developed a new staining procedure that combines the traditional Gram staining for bacteria and the Weber's chromotrope staining method, the standard technique for the detection of microsporidia spores in clinical Specimens. This “Gram-chromotrope” staining technique enhances the staining characteristics of microsporidia spores and facilitates the easy detection and differentiation of spores from other microorganisms that are found in clinical specimens, especially stool samples. This new technique is fast, reliable, and simple to perform, and can be easily adapted for use in clinical laboratories. 相似文献
104.
105.
Hierarchical genetic structure and gene flow in three sympatric species of Amazonian rodents 总被引:2,自引:0,他引:2
The population genetic structure of three species of Amazonian rodents ( Oligoryzomys microtis, Oryzomys capito , and Mesomys hispidus ) is examined for mtDNA sequence haplotypes of the cytochrome b gene by hierarchical analysis of variance and gene flow estimates based on fixation indices ( N ST ) and coalescence methods. Species samples are from the same localities along 1000 km of the Rio Juruá in western Amazonian Brazil, but each species differs in important life history traits such as population size and reproductive rate. Average haplotype differentiation, hierarchical haplotype apportionment, and gene flow estimates are contrasted in discussing the current and past population structure. Two species exhibit isolation by distance patterns wherein gene flow is largely limited to geographically adjacent localities. Mesomys exhibits this pattern throughout its range along the river. More than 75% of haplotype variation is apportioned among localities and regions, and estimates of Nm for pair-wise comparisons are nearly always less than 1. Oligoryzomys shows weak isolation by distance, but only over the largest geographical distances. Nm values for this species are nearly always above 1 and most (about 80%) of haplotype variation is contained within local populations. In contrast, Oryzomys exhibits no genetic structure throughout its entire distribution; Nm values average 17 and nearly 90% of the total haplotype variance is contained within local populations. Although gene flow estimates are high, the pattern of Nm as a function of geographical distance suggests that this species experienced a more recent invasion of the region and is still in genetic disequilibrium under its current demographic conditions. 相似文献
106.
JOSEPH R. MENDELSON III HELIO R. DA SILVA ANNE M. MAGLIA 《Zoological Journal of the Linnean Society》2000,128(2):125-148
We reassess the phylogenetic relationships of genera of hemiphractine hylid frogs (Marsupial Treefrogs) and discuss the evolution of several distinctive characters within this group using parsimony analysis. Fifty-one morphological and life-history characters were sampled from two species of Cryptobatrachus , three species of Flectonotus , 17 species of Gastrotheca , all five species of Hemiphractus , and one species of Stefania as the ingroup and three hyline, one phyllomedusine, and one pelodryadine species as outgroups. Our results support the mon-ophyly of Flectonotus, Cryptobatrachus , and Hemiphractus. Gastrotheca is paraphyletic with respect to Hemiphractus , dorsal pouches were lost in the ancestor of Hemiphractus. Direct development is a synapomorphy for Hemiphractinae and tadpoles were regained independently several times. These results stand in stark contrast to the prevailing paradigm regarding marsupial frog relationships. 相似文献
107.
PATRÍCIA F. M. NOGUEIRA MARIA DA G. G. MELÃO ANA T. LOMBARDI ARMANDO A. H. VIEIRA 《Freshwater Biology》2005,50(9):1560-1567
1. This work investigated the consumption of a microalgal (Anabaena spiroides) exopolysaccharide by the cladoceran Simocephalus serrulatus (Cladocera, Daphnidae) and its effect on copper toxicity. 2. Total organic carbon concentration was used to quantify the microalgal exopolysaccharide. Both copper‐complexed exopolysaccharides and copper‐free exopolysaccharides were taken up by S. serrulatus. 3. A reduction of free copper ions was obtained in the presence of A. spiroides exopolysaccharide. Copper toxicity (EC50) and zooplankton concentrations were inversely correlated to exopolysaccharide concentration in experimental media. 4. An increase of free copper ions in experimental media was obtained after exopolysaccharide consumption, suggesting that S. serrulatus excreted copper to the surrounding environment. 相似文献
108.
109.
锁阳和肉苁蓉都是中医药里重要的补益类药材,但由于过度采挖和采挖方式不当,目前它们的野生资源已濒临枯竭。肉苁蓉和锁阳分别是我国濒危和易危珍稀植物,研究二者寄生方式的特点与区别不仅可以促进锁阳和肉苁蓉的人工栽培,从而使野生药材得到一定的保护,而且对了解寄生植物在荒漠地区等极端严酷环境中的适应机制具有重要的生态学意义。该研究采用形态学观察结合常规石蜡切片法,对锁阳和肉苁蓉分别在各自寄主植物上的寄生方式进行了研究。结果表明:(1)锁阳的营养繁殖体在寄主植物根部呈串状分布,与寄主植物的连接方式属于非末端寄生;锁阳的吸器侵入寄主根系韧皮部和木质部的一部分区域,但是韧皮部和木质部大部分区域未被锁阳吸器占据,即有部分营养物质被锁阳“截取”。(2)肉苁蓉在其肉质茎基部长出新的芽体,与寄主植物的连接方式属于末端寄生;肉苁蓉的吸器侵入寄主根韧皮部和木质部全部区域。因此,锁阳寄生后,被寄生的寄主根依然能够向前生长,具有正常的功能;肉苁蓉寄生后,寄生点的寄主根失去根系的正常功能,成为一个为肉苁蓉生长发育提供营养物质的“输送通道( Transport channel)”。 相似文献
110.
The teleost Fundulus heteroclitus (L.) possesses two loci, Gpi-A and Gpi-B,
for the glycolytic enzyme, glucose-phosphate isomerase (GPI; D-
glucose-6-phosphate ketol-isomerase; E.C. 5.3.1.9). The Gpi-B locus is
polymorphic in Fundulus, with two common alleles, Gpi-Bb and Gpi-Bc,
distributed in a clinal manner in populations along the east coast of North
America. Since this clinal distribution is strongly correlated with a
temperature gradient, we asked whether the GPI-B2 allozymes were
functionally adapted to the thermal environment in which a given phenotype
predominated. The two major GPI-B2 allozymes were purified to homogeneity
and were characterized as to molecular weight, isoelectric pH, thermal
denaturation, and kinetic parameters. Both GPI-Bb2 and GPI- Bc2 allozymes
have molecular masses of 110 kD, and they have isoelectric pHs of 6.4 and
6.6, respectively. The GPI-Bb2 allozyme was more stable to thermal
denaturation than was the GPI-Bc2 enzyme. Kinetic properties of the allelic
isozymes were investigated both as a function of pH and as a function of
temperature. At 25 degrees C, over the pH range considered, there were no
significant differences between allozymes, either in Km for
fructose-6-phosphate or in Ki for 6- phosphogluconate, but apparent Vmax
values differed between pH 7.5 and pH 8.5. All steady-state kinetic
parameters showed strong temperature dependence, but the allozymes differed
only in the Ki for 6- phosphogluconate at temperatures greater than 30
degrees C. On the basis of the observed structural and functional
differences alluded to above, the hypothesis that the major allelic
isozymes of the Gpi-B locus were functionally equivalent was rejected.
However, it is not yet known whether these structural and functional
differences have any significance at higher levels of biological
organization.
相似文献