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101.
Maurice Arissian Dominique Perrissin-Fabert André Blouet Jean-Louis Morel Armand Guckert 《Journal of Plant Growth Regulation》1991,10(1-4):1-4
The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)14C-chlormequat chloride, (2) CYCOCEL* CL containing14C-chlormequat chloride, and (3) CYCOCEL* CL containing14C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the14C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant. 相似文献
102.
103.
Bernard Flouret Dominique Mengin-Lecreulx Jean van Heijenoort 《Analytical biochemistry》1981,114(1):59-63
A series of seven different UDP-N-acetylmuramyl peptide precursors of bacterial cell wall peptidoglycan was examined by reverse-phase high-pressure liquid chromatography. Mixtures of these compounds were successfully and rapidly analyzed by using a Waters μBondapak C18 column as a stationary phase and isocratic elutions with 0.05 m ammonium phosphate or formate buffers of appopriate pH. Furthermore, their accurate quantitation could also be readily achieved by reverse-phase high-pressure liquid chromatography. All these techniques should be extremely useful for the purification of these compounds and for a wide range of biochemical studies concerning the cytoplasmic steps of the biosynthesis of peptidoglycan. 相似文献
104.
The effect of Concanavalin A (Con A), or bacterial lipopolysaccharide (LPS) on mouse spleen cell populations was investigated. The membrane fluorescence changes of activated splenic lymphocytes were studied during two weeks after the injection of polyclonal immunogens. Experiments were performed with the hydrophobic fluorescent probe: 1-anilino-8-naphthalene sulphonate (ANS). The kinetic studies further indicated that the course of fluorescence changes may considerably vary depending on both immunogens. These fluorescence intensity changes would be in direct relation to the electrokinetic surface potential changes of activated lymphocytes, as assessed by the electrophoretic mobility analysis. By comparison with the inverse relationship observed in our previous study, it would be concluded that the relation (direct or inverse) between ANS fluorescence and electrokinetic potential depends on the net electrical charge of the antigens used. 相似文献
105.
Genetic Diversity and Temporal Variation in the E. COLI Population of a Human Host 总被引:34,自引:0,他引:34
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Electrophoretic techniques were employed to study variation in chromosomal genes encoding enzymes and in the distribution of cryptic plasmids in the E. coli population of a human host over an 11-month period. Thirteen of the 15 enzymes studied were polymorphic, and mean genetic diversity per locus was 0.39. Among 550 clones isolated from fecal samples, protein electrophoresis revealed 53 distinct electrophoretic types (ETs). Most ETs appeared on only one or a few days and were considered transients, but two (ET-12 and ET-13) were observed many times over extended periods and represented residents. Complete turnover in the transient ETs in the population occurred in periods of from two weeks to a month. ETs appearing in one month showed no particular genetic similarity to those of the previous month. — All but 4 of the 53 ETs carried one or more "cryptic" plasmids with molecular weights ranging from 1 to 80 megadaltons. With few exceptions, the plasmid composition of each ET was unique. In the course of the 11-month sampling period, there were changes in the plasmid profiles of the resident strains ET-12 and ET-13, and also in the profile of a recurrent strain, ET-2, which was isolated on four days. Modification of the plasmid profile of ET-12 involved the sequential addition of relatively high molecular weight bands. For ET-2 and ET-13, the changes in the plasmid profiles were radical, suggesting invasions of new cell types rather than merely the addition and deletion of plasmids. — The results of this study provide three lines of evidence that recombination plays a minor role in the generation of genetic diversity in the E. coli population of a single host. (1) Several pairs of loci were in strong linkage disequilibrium; compared to a randomly generated array of genotypes, the sample of ETs contained an excess of pairs differing at one or two loci and too many pairs with highly distinctive combinations of electromorphs. (2) In most cases where pairs of ETs differed at a single locus and, therefore, could reasonably have been generated by phage- or plasmid-mobilized gene transfer, the plasmid profiles of the pair members were radically different and/or the potentially transmitted alleles were not present in other ETs in the population. (3) Although ET-12 was abundant, being represented by 252 of the 550 clones sampled, the electrophoretic type most similar to ET-12 different from it at six loci, and ET-12 carried two unique alleles. We conclude that most of the genetic diversity observed in this human host is a consequence of successive invasions of E. coli genotypes. 相似文献
106.
Hybrids between a tumorigenic Chinese hamster cell line (DC3F-aza) and normal mouse thymus cells very rapidly lost most of their mouse chromosomes, whereas hybrids between tumorigenic mouse cell lines (either Cl.1D of L cell line origin, or PCC4-aza1 teratocarcinoma cells) and normal Chinese hamster thymus cells lost most of their hamster chromosomes. From three such fusion experiments, 20 cell lines were developed which all followed the same evolution, namely, the elimination of the majority of the chromosomes contributed by the normal thymus cell. In some hybrids, the elimination process resulted in the total absence of intact chromosomes contributed by the thymus cell parent. Such hybrids were distinguished from revertant parental cells growing in the selective hybrids were distinguished from revertant parental cells growing in the selective medium by the presence of at least one enzyme in their cell extracts which displayed the electrophoretic mobility of the enzyme of the thymus cell parent. These observations, together with data from other reports, suggest that, as a rule, interspecific cell hybrids which develop upon fusion between normal diploid cells and tumorigenic cell lines maintain the chromosomes of the latter and eliminate preferentially many or most of the chromosomes contributed by the normal cell parents, independent of the respective species of the parental cells. 相似文献
107.
108.
In vitro-primed human lymphocytes proliferate in a secondary mixed lymphocyte reaction (MLR) under the control of MLR-S specificities. HL-A antigens are unable to induce a secondary Proliferation. In familial haploidentical combinations, the secondary proliferation is specific for the priming MLR-S specificity, i.e., as early as 24 to 48 hours after the re-stimulation, a clearcut response is observed toward the sensitizing MLR-S specificity. The secondary response is reflected in acceleration of the reaction rather than in the peak of (3H) TdR uptake. However, when either haploidentical familial primed responding cells or unrelated cells primed toward MLR-S homozygous cells were used, no early typing response was observed against unrelated cells. The level of (3H) TdR incorporation toward cells which possessed and those which did not possess the priming specificity was identical until day 3–4. Noneless, the peak response toward cells possessing the priming MLR-S specificity occurs regularly 24 to 48 hours prior to the peak response toward the cells negative for the priming specificity (day 3–4 as opposed to day 5). Technical improvements are therefore needed before such a technique will provide a clearcut MLR-S typing methodology. 相似文献
109.
Dominique A. Cowart Stefano Schiaparelli Maria Chiara Alvaro Matteo Cecchetto AnneSophie Le Port Didier Jollivet Stephane Hourdez 《Ecology and evolution》2022,12(7)
The Antarctic marine environment hosts diversified and highly endemic benthos owing to its unique geologic and climatic history. Current warming trends have increased the urgency of understanding Antarctic species history to predict how environmental changes will impact ecosystem functioning. Antarctic benthic lineages have traditionally been examined under three hypotheses: (1) high endemism and local radiation, (2) emergence of deep‐sea taxa through thermohaline circulation, and (3) species migrations across the Polar Front. In this study, we investigated which hypotheses best describe benthic invertebrate origins by examining Antarctic scale worms (Polynoidae). We amassed 691 polynoid sequences from the Southern Ocean and neighboring areas: the Kerguelen and Tierra del Fuego (South America) archipelagos, the Indian Ocean, and waters around New Zealand. We performed phylogenetic reconstructions to identify lineages across geographic regions, aided by mitochondrial markers cytochrome c oxidase subunit I (Cox1) and 16S ribosomal RNA (16S). Additionally, we produced haplotype networks at the species scale to examine genetic diversity, biogeographic separations, and past demography. The Cox1 dataset provided the most illuminating insights into the evolution of polynoids, with a total of 36 lineages identified. Eunoe sp. was present at Tierra del Fuego and Kerguelen, in favor of the latter acting as a migration crossroads. Harmothoe fuligineum, widespread around the Antarctic continent, was also present but isolated at Kerguelen, possibly resulting from historical freeze–thaw cycles. The genus Polyeunoa appears to have diversified prior to colonizing the continent, leading to the co‐occurrence of at least three cryptic species around the Southern and Indian Oceans. Analyses identified that nearly all populations are presently expanding following a bottleneck event, possibly caused by habitat reduction from the last glacial episodes. Findings support multiple origins for contemporary Antarctic polynoids, and some species investigated here provide information on ancestral scenarios of (re)colonization. First, it is apparent that species collected from the Antarctic continent are endemic, as the absence of closely related species in the Kerguelen and Tierra del Fuego datasets for most lineages argues in favor of Hypothesis 1 of local origin. Next, Eunoe sp. and H. fuligineum, however, support the possibility of Kerguelen and other sub‐Antarctic islands acting as a crossroads for larvae of some species, in support of Hypothesis 3. Finally, the genus Polyeunoa, conversely, is found at depths greater than 150 m and may have a deep origin, in line with Hypothesis 2. These “non endemic” groups, nevertheless, have a distribution that is either north or south of the Antarctic Polar Front, indicating that there is still a barrier to dispersal, even in the deep sea. 相似文献
110.
Blanche Collard Philippe Tixier Dominique Carval Claire Lavigne Thomas Delattre 《Ecology and evolution》2022,12(7)
Understanding the effect of ground types on foraging movements of ground‐dwelling arthropods is a key step to managing their spatial distribution as required for successful conservation biological control. Indeed, fine movements at the centimeter scale can strongly influence the foraging ability of pest predators. However, because radio frequency identification or harmonic tracking techniques are not yet suitable for small species and video tracking focuses on uniform and light backgrounds, foraging movements have rarely been studied in relation to ground types. We present a method to track a ground‐dwelling arthropod (the earwig Euborellia caraibea) at night, walking on two contrasted ground types: bare soil and soil partly covered with a stratum of banana plant residues allowing individuals to hide periodically. The tracking of individuals within these ground types was achieved by infrared light, tagging individuals, video treatments, and semi‐automatic cleaning of trajectories. We tested different procedures to obtain segments with identical durations to quantify speeds and sinuosities. These procedures were characterized by the junction time gap between trajectory fragments, the rediscretization time of trajectories, and whether or not to use interpolation to fill in missing points in the trajectories. Earwigs exhibited significantly slower and more sinuous movements on soil with banana plant residues than on bare soil. Long time gaps for trajectory junction, extended rediscretization times, and interpolation were complementary means to integrate concealed movements in the trajectories. The highest slowdown in plant residues was detected when the procedure could account for longer periods under the residues. These results suggest that earwigs spent a significant amount of time concealed by the residues. Additionally, the residues strongly decreased the earwigs'' movement. Since the technical solutions presented in this study are inexpensive, easy to set up, and replicate, they represent valuable contributions to the emerging field of video monitoring. 相似文献