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排序方式: 共有193条查询结果,搜索用时 140 毫秒
1.
W. Rossi B. Corrias P. Arduino R. Cianchi L. Bullini 《Plant Systematics and Evolution》1992,179(1-2):43-58
Data are presented on genetic variation at 27 enzyme loci of the Green-Winged orchid,Orchis morio, in 18 population samples from Italy. The existence in Italy of two subspecies, i.e. subspp.morio andpicta, is not supported by allozyme data. No genetic heterogeneity was found betweenmorio-like andpicta-like samples and specimens. Moreover, morphological transition between the two forms was observed in different Italian populations. The parameters of genetic variability estimated forO. morio populations are consistent with those found among monocotyledon plants, and among those outcrossing, animal-pollinated and with wind-dispersed seeds. Genetic diversity of ItalianO. morio is mostly within populations. Correspondingly, low values of interpopulational genetic distance were found. This appears to be due to high levels of gene flow, which were estimated with different methods. The lack ofO. longicornu from Italian samples, as well as of any hybrid withO. morio (F1, backcrossed or recombinant individuals) is demonstrated on the basis of genetic data. It is concluded that recurrent reports ofO. longicornu from Italy are due to confusion withO. morio or with otherOrchis species. 相似文献
2.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
3.
Arduino Arduini Natalia Denisova† Ashraf Virmani Natascia Avrova† Giorgio Federici† Edoardo Arrigoni-Martelli 《Journal of neurochemistry》1994,62(4):1530-1538
Abstract: This study focuses on the potential involvement of carnitine palmitoyltransferase (CRT) on the phospholipid and triglyceride fatty acid turnover in neurons. This category of enzymes, which has been identified in several rat brain tissues, is well known for its role in modulating cellular fatty acid oxidation. Neuronal cell cultures from rat brain cortex incorporated radioactive palmitate or oleate into phospholipids and triglycerides. The largest fraction of radioactive fatty acids was recovered in phosphatidyl- choline followed by triglycerides and, to a lesser extent, phosphatidylethanolamine. CPT activity measured in neuronal lysates obtained from neurons treated with 40 μ M 2-tetradecylglycidic acid (TDGA) was almost completely abolished. Furthermore, between 2 and 10 μ M TDGA CPT activity dropped more rapidly than between 10 and 40 μ M. When the cells were pretreated with TDGA, the incorporation process of either radioactive fatty acid into triglycerides was dose-dependently suppressed. Radioactive fatty acid incorporation into phosphatidylcholine was significantly decreased in cells treated with TDGA. In contrast, phosphatidylethanolamine reacylation was essentially not affected by the CpT inhibitor. Similar results on the fatty acid incorporation into triglycerides and phospholipids were observed with neurons treated with palmitoyl- dl - aminocarnitine (PAC), a reversible CPT inhibitor, which does not consume free CoA. These effects do not seem to be the result of an inhibitory activity toward one of the steps involved in the acylation-deacylation process of triglycerides or phospholipids, as cellular lysates from TDGA-treated cells or lysates containing PAC incorporated radioactive fatty acids at rates comparable to controls. Our results suggest that CRT may be an important partner in the pathway of phospholipid and triglyceride fatty acid turnover in neurons. 相似文献
4.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
5.
Selecting pedigrees for linkage analysis of a quantitative trait: the expected number of informative meioses. 总被引:1,自引:1,他引:0 下载免费PDF全文
With evidence of segregation at a major locus for a quantitative trait having been found, a logical next step is to select a subset of the pedigrees to include in a linkage study to map the major locus. Ideally this subset should include much of the linkage information in the sample but include only a fraction of the pedigrees. We previously described a strategy for selecting pedigrees for linkage analysis of a quantitative trait on the basis of a pedigree likelihood-ratio statistic. For quantitative traits controlled by a major locus with a rare dominant allele, the likelihood-ratio strategy extracted nearly all the information for linkage while typically requiring marker data on only about one-third of the pedigrees. Here, we describe a new strategy to select pedigrees for linkage analysis on the basis of the expected number of potentially informative meioses in each pedigree. We demonstrate that this informative-meioses strategy provides an efficient and more general means to select pedigrees for a linkage study of a quantitative trait. 相似文献
6.
Schistosomiasis vector snails are subjected to extreme seasonal changes, particularly in ephemeral rivers and lentic waterbodies. In the tropics, aestivation is one of the adaptive strategies for survival and is used by snails in times of extremely high temperatures and desiccation. Aestivation therefore plays an important role in maintaining the transmission of schistosomiasis. This review assesses the possible impacts of climate change on the temporal and spatial distribution of schistosomiasis-transmitting snails with special emphasis on aestivation, and discusses the effect of schistosome infection on aestivation ability. The impacts of parasite development on snails, as well as physiological changes, are discussed with reference to schistosomiasis transmission. This review shows that schistosome-infected snails have lower survival rates during aestivation, and that those that survive manage to get rid of the infection. In general, snail aestivation ability is poor and survival chances diminish with time. Longer dry periods result in fewer, as well as uninfected, snails. However, the ability of the surviving snails to repopulate the habitats is high. 相似文献
7.
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase 下载免费PDF全文
Sharon C Mithoe Christina Ludwig Michiel JC Pel Mara Cucinotta Alberto Casartelli Malick Mbengue Jan Sklenar Paul Derbyshire Silke Robatzek Corné MJ Pieterse Ruedi Aebersold Frank LH Menke 《EMBO reports》2016,17(3):441-454
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex. 相似文献
8.
1-Thio-beta-D-galactofuranosides: synthesis and evaluation as beta-D- galactofuranosidase inhibitors
Marino C; Marino K; Miletti L; Manso Alves MJ; Colli W; de Lederkremer RM 《Glycobiology》1998,8(9):901-904
Beta-D-galactofuranosidase is a good chemotherapeutic target for the design
of inhibitors, since beta-D-galactofuranose is a constituent of important
parasite glycoconjugates but is not present in the host mammals. With this
aim, we have synthesized for the first time alkyl, benzyl and aryl
1-thio-beta-D-galactofuranosides by condensation of
penta-O-benzoyl-alpha,beta-D-galactofuranose with the corresponding thiols,
in the presence of SnCl4as catalyst. The complete chemical and
spectroscopical characterization of these compounds showed that the
reaction was stereoselective. Debenzoylation with sodium methoxide afforded
the beta-S-galactofuranosides in high yield. The thioglycosides were tested
as inhibitors of the beta-D- galactofuranosidase of Penicillium fellutanum,
using for the first time 4-nitrophenyl-beta-D-galactofuranoside as
chromogenic substrate. The 4- aminophenyl-1-thio-beta-D-galactofuranoside,
obtained by catalytic hydrogenation of the nitrophenyl derivative, was the
best inhibitor being then an adequate ligand for the preparation of an
affinity phase aimed at the isolation of beta-d-galactofuranosidases from
different sources. Also the inhibitory activity of d-galactono-1, 4-lactone
was shown.
相似文献
9.
M Alonso N Alonso Rodriguez C Garzelli M Martínez Lirola M Herranz S Samper MJ Ruiz Serrano E Bouza D García de Viedma 《BMC microbiology》2010,10(1):151
Background
The Beijing lineage of Mycobacterium tuberculosis is causing concern due to its global distribution and its involvement in severe outbreaks. Studies focused on this lineage are mainly restricted to geographical settings where its prevalence is high, whereas those in other areas are scarce. In this study, we analyze Beijing isolates in the Mediterranean area, where this lineage is not prevalent and is mainly associated with immigrant cases. 相似文献10.
Jason A Roberts Michael S Roberts Andrew Semark Andrew A Udy Carl MJ Kirkpatrick David L Paterson Matthew J Roberts Peter Kruger Jeffrey Lipman 《BMC anesthesiology》2011,11(1):1-7