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91.
Monique L'Hostis Henri Dumon Bertrand Dorchies Florence Boisdron André Gorenflot 《Experimental & applied acarology》1995,19(4):211-220
A longitudinal survey was carried out during a 2 year period in Western France to assess the infestation level of grazing pastures byIxodes ricinus ticks. Four farms were visited once a month and each of the grazing pastures was sampled in the centre and at the border using the blanket dragging method. A total of 3562I. ricinus (34 adults, 900 nymphs and 2628 larvae) were collected and the infestation was significantly higher during the first year (p<0.0001). The infestation level byI. ricinus varied between grazing pastures and farms. Grazing pastures in the vicinity of forest were more infested than the others, all through the study. The seasonal distribution of ticks showed peaks, with low fluctuations between farms, years and stages. Tick abundance could not be related to vegetation, but only to the vicinity of woods. 相似文献
92.
93.
Artificial crosses between Helianthus annuus and H. petiolaris using 1:9, 1:1, and 9:1 mixtures of intraspecific: interspecific pollen were conducted to determine the role of interspecific pollen competition as a reproductive barrier in Helianthus. Of 1,245 achenes analyzed from the pollen competition experiments, only 49 were hybrids. The number of hybrids observed was significantly less than expectations for all three pollen mixtures, regardless of the identity of maternal parent (P < 0.01). Stigma age and pollen ratio had no significant impact on hybrid frequency. However, hybrids were significantly more frequent with H. annuus than with H. petiolaris as the maternal parent (P < 0.01). Analysis of pollen tube growth rates revealed no differences in the rate of growth of intraspecific vs. interspecific pollen. Likewise, pollinations with either intraspecific or interspecific pollen or with different pollen ratios did not affect the percentage of filled achenes. Thus, the mechanism responsible for selective fertilization by intraspecific pollen in mixed pollen loads remains unclear. Nonetheless, these findings suggest that interspecific pollen competition plays an important role in controlling the formation of hybrids between H. annuus and H. petiolaris and may partially account for patterns or differential cytoplasmic vs. nuclear introgression in Helianthus. 相似文献
94.
Bertrand Dommée Andrée Biascamano Nicole Denelle Jean-Louis Bompar John D. Thompson 《American journal of botany》1995,82(6):734-740
Natural populations of Thymelaea hirsuta have previously been shown to comprise four distinct sexual morphs: males, females, protogynous individuals, i.e., first female then male, and protandrous individuals, i.e., first male then female. The objective of the present study has been to confirm the genetic basis of this sexual tetramorphism by quantifying morph ratios in the open-pollinated progeny of the four sexual phenotypes growing in a natural population. All four phenotypes were recovered in the progeny of each morph. All observed plants displayed a single sexual phenotype, thus confirming the genetic basis of the tetramorphism. The progeny sex ratios indicate that the genetic determination of sex in this species may be influenced by cytoplasmic factors, while the observed levels of functional female fertility suggest a near-dioecious system. The evolutionary significance of this tetramorphism as a transitional stage in the evolution of dioecy is discussed. 相似文献
95.
Miklós Fári István Nagy Márta Csányi Judit Mitykó András Andrásfalvy 《Plant cell reports》1995,15(1-2):82-86
Summary Novel and efficient protocols for plant regeneration and genetic transformation from longitudinally-halved cotyledons ofin vitro raised seedlings in eggplant (Solanum melongena L.) are described. After co-cultivation withAgrobacterium vectors harboring neomycin phosphotransferase (nptll) as selectable marker, transgenic plantlets were regenerated on selective media containing 100 mg/l kanamycin. Transformants were recovered from embryogenic calli induced by 4 mg/l-naphthaleneacetic acid (NAA), and from organogenic calli induced by the addition of 2 mg/l zeatin plus 0.01 mg/l NAA. Nineteen independent transgenic lines were grown to maturity. The structural integrity, expression and sexual transmission of the introduced genes for neomycin phosphotransferase and ß-glucuronidase (gus) were investigated. 相似文献
96.
Klaus Kayser Sabine André Gerhard Böhm Sonia Donaldo-Jacinto Peter Fritz Herbert Kaltner Gian Kayser Wolf-Peter Kunze Andreas Nehrlich Fu-Yue Zeng Hans-Joachim Gabius 《Development genes and evolution》1995,204(5):344-349
Protein-carbohydrate interactions are supposed to play key roles in the mechanisms of cell adhesion, biosignalling and intracellular routing, warranting the analysis of the developmental course of expression of epitopes of this system. Thus, a panel of carrier-immobilized carbohydrate ligands was used as probes, namely lactose,N-acetylgalactosamine,N-acetylglucosamine, mannose, fucose and maltose. Additionally, an antibody to an endogenous -galactoside-binding lectin (anti-galectin-1), the biotinylated lectin and two further human lectins, namely the macrophage migration inhibitory factor-binding sarcolectin and serum amyloid P component (SAP) that displays selectivity for sulphated sugars and mannose-6-phosphate, were included. They enabled us to assess the extent of the presence of respective binding sites in fixed sections from human lungs (pulmonary epithelial cells), livers (hepatocytes) and hearts (myocard cells) of 10–50 weeks gestation. Invariably, specific binding was detected in the three organ types, at least in certain stages. In most of the cases, the intensity of staining exhibited developmental regulation. The apparent patterns reveal similarities between the different cell types, as seen with immobilizedN-acetylglucosamine as well as with labelled galectin-1 and sarcolectin. However, drastic differences among such patterns with nearly opposite developmental courses do also occur, as detected for carrier-attached mannose and maltose residues. These results point to a potential importance for the detected glycohistochemical features in human development and substantiate the possibility of differential regulation of the presence of binding sites for distinct sugars within a certain organ and between the individual cell types of the monitored organs. 相似文献
97.
98.
Distribution and properties of pea (Pisum sativum L.) cells, competent forAgrobacterium-mediated transformation were analysed byin situ histochemical detection of GUS (-glucuronidase) activity, 4 d after inoculation with engineeredAgrobacterium tumefaciens. The vector system consisted of the hypervirulent disarmed strain EHA101 and the binary plasmid pIBGUS, carrying an intron-containing, 35S-promotor drivengusA (oruidA) gene and two selectable marker genes. Cells competent for transformation were mainly restricted to the dedifferentiating cells neighbouring the vascular system of cotyledon and epicotyl explants. A standardized assay was developed, allowing determination and quantification of factors influencing number and distribution of competent cells. In etiolated seedlings, competence for transformation decreased with the distance of the epicotyl explant from the shoot apex and was specifically induced by the exogenous application of auxins. Transient expression ofgusA afterAgrobacterium-mediated DNA transfer was dramatically reduced upon application of cell-cycle and DNA replication inhibitors aphidicolin, colchicine and nalidixic acid. GUS expression after direct DNA transfer of double-stranded plasmid DNA (via PEG into protoplasts or via particle bombardment of epicotyl segments) was independent of cell-division/DNA replication.A GUS-positive mutant of EHA101 was constructed to allowin situ analysis of attaching bacteria within the plant tissue. Attachment and invasion was inhibited by well-developed cuticula but was restored after chloroform treatment of the tissue surface. Moreover, no correlation was found between distribution of attaching bacteria and the pattern of transformation-competent cells. 相似文献
99.
André W. Schram Marianne Dreissen Johan Bastiaannet Wilma E. Donker-Koopman Elisabeth M. Brouwer-Kelder Gabriele Weitz John A. Barranger Konrad Sandhoff Joseph M. Tager 《Bioscience reports》1984,4(12):1051-1057
The immunoblotting technique was used to identify sphingomyeJinase protein in samples of tissue and urine after subjection to poIyacrylamide-gel etectrophoresis in the presence of sodium dodecyl sulphate. In a sphingomyelinase preparation purified from control urine a prominent band was seen with an Mr of 28 000 Da. Glycoprotein fractions from urine and placenta, a membrane extract from spleen, and a partially purified sphingomyelinase preparation from placenta contained the 28 000-Da band plus additional, higher-Mr bands. The 28 000-Da band was detectable in urine from a patient with Niemann-Pick disease type C, but not in urine from patients with Niemann-Pick disease types A and B. It is concluded t h a t sphingomyeJinase is composed of at least one polypeptide with an Mr of 28 000 Da and that this polypeptide is deficient in the urine of patients with Niemann-Pick disease types A and B. 相似文献
100.
N Ellfolk M R?nnberg R Aasa L E Andréasson T V?nng?rd 《Biochimica et biophysica acta》1984,784(1):62-67
The anion-binding characteristics of resting and half-reduced Pseudomonas cytochrome c peroxidase (ferrocytochrome c-551: hydrogen peroxide oxidoreductase, EC 1.11.1.5) have been examined by EPR and optical spectroscopy with cyanide, azide and fluoride as ligands. The resting enzyme was found to be essentially inaccessible for ligation, which indicates that it has a closed conformation. In contrast, the half-reduced enzyme has a conformation in which the low-potential heme is easily accessible for ligands, a behavior parallel to that towards the substrate hydrogen peroxide (R?nnberg, M., Araiso, T., Ellfolk, N. and Dunford, H.B. (1981) Arch. Biochem. Biophys. 207, 197-204). Cyanide and azide caused distinct changes in the low-potential heme c moiety, and the gz values of the two low-spin derivatives were 3.14 and 3.22, respectively. Fluoride binds to the same heme, giving rise to a high-spin signal at g = 6. The dissociation constants of the anions differ widely from each other, the values for the cyanide, azide and fluoride being 23 microM, 2.5 mM and 0.13 M, respectively. In addition, a partial shift of the low-spin peak at g = 2.84 of the half-reduced species to 3.24 was observed even at low concentrations of fluoride. 相似文献