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1.
The elongation rate, the gradient of the local elongation rate and the surface pH of maize roots were measured over 12 h. A data bank was constituted by storing these values. By sorting these results on the basis of different elongation rates, different classes of root were obtained. Two classes were chosen: the low-growth roots and the high-growth roots. The mean growth of these two root classes was stable with time and differed significantly from one another. The surface pH of the elongation zone was the same for the roots of these two classes, but the roots selected for their higher growth rate had a larger acid efflux in this zone. 相似文献
2.
3.
Raymond L. White Jean-Marc Lalouel G. Mark Lathrop Mark F. Leppert Yusuke Nakamura Peter O'Connell 《The Western journal of medicine》1987,147(4):423-427
Although a number of human genes that cause disease have been traced through the defective product, most genetic defects are recognized only by phenotype. When the biochemical defect is unknown, a gene can be located only through molecular approaches based on coinheritance (genetic linkage) of the disease phenotype with a particular allele of a polymorphic DNA marker that has already been mapped to a specific chromosomal region. Linkage studies in affected families have already localized genes for several important diseases, including cystic fibrosis. Finding a genetic linkage in families in which a disease segregates requires that the human genetic map have a large number of polymorphic markers; when the map is dense enough, any disease gene can be located by linkage to a known marker. Many DNA segments with a high degree of polymorphism are being found and mapped as markers in normal reference pedigrees. Genetic linkage mapping has implications even broader than its application to prenatal diagnosis or therapeutic strategy; analyzing mutations in important genes will illuminate basic mechanisms in molecular biology and the early events that lead to cancer and other disorders. 相似文献
4.
Improvement in stability of an immobilized fungal laccase 总被引:4,自引:0,他引:4
Andrzej Leonowicz Jawed M. Sarkar Jean-Marc Bollag 《Applied microbiology and biotechnology》1988,29(2-3):129-135
Summary A laccase of the basidiomyceteTrametes versicolor was immobilized on porous glass beads that were activated with 3-aminopropyltriethoxysilane and glutaraldehyde. The support immobilized 100% of the enzyme, whereupon 90% of the original activity was retained. After immobilization, the enzyme was active in a wider pH and temperature range, and its heat stability and reuse were greatly improved compared to those of the free laccase. The immobilized enzyme was found reusable in treating different substrates, either recycled alone or in a sequential order. 相似文献
5.
Peter O''Connell G. Mark Lathrop Mark Leppert Yusuke Nakamura Ulrich Müller Jean-Marc Lalouel Ray White 《Genomics》1988,3(4):367-372
We have constructed a primary genetic map of human chromosome 18 consisting of 11 DNA markers and one serological marker (JK). Two of these loci define highly polymorphic VNTR systems. The markers define a continuous genetic linkage map of 97 cM in males and 205 cM in females; female genetic distances in a panel of 59 three-generation families were consistently about twice those observed in males. The high odds in support of the linear order of the markers on this recombination map, and the extent of coverage of chromosome 18, indicate that this map will permit efficient linkage studies of human genetic diseases that may be segregating on chromosome 18 and will provide anchor points for development of high-resolution maps for this chromosome. 相似文献
6.
Recently attempts have been made to establish the presence and to determine the metabolic versatility of microorganisms in
the terrestrial deep subsurface at the Savannah River Plant, Aiken, SC, USA. Sediment samples obtained at 20 different depths
of up to 526 m were examined to determine carbon mineralization under aerobic, sulfate-reducing, and methanogenic conditions.
The evolution of14CO2 from radiolabelled glucose was observed under aerobic conditions in all sediments, whereas pyridine was transformed in 50%
of the 20 sediments and indole was metabolized in 85% of the sediments. Glucose mineralization in certain sediments was comparable
to that in the surface environment. Sulfate was reduced in only five sediments, and two were carbon limited. Methane production
was detected in ten sediments amended with formate only after long-term incubations. The transformation of indole and pyridine
was only rarely observed under sulfate-reducing conditions and was never detected in methanogenic incubations. This study
provides information concerning the metabolic capability of both aerobic and anaerobic microorganisms in the deep subsurface
and may prove useful in determining the feasibility of microbial decontamination of such environments. 相似文献
7.
High-level expression of a tobacco chitinase gene in Nicotiana sylvestris. Susceptibility of transgenic plants to Cercospora nicotianae infection 总被引:12,自引:0,他引:12
Jean-Marc Neuhaus Patricia Ahl-Goy Ursula Hinz Susan Flores Frederick Meins Jr. 《Plant molecular biology》1991,16(1):141-151
Endochitinases (E.C. 3.2.14, chitinase) are believed to be important in the biochemical defense of plants against chitin-containing fungal pathogens. We introduced a gene for class I (basic) tobacco chitinase regulated by Cauliflower Mosaic Virus 35S-RNA expression signals into Nicotiana sylvestris. The gene was expressed to give mature, enzymatically active chitinase targeted to the intracellular compartment of leaves. Most transformants accumulated extremely high levels of chitinase-up to 120-fold that of non-transformed plants in comparable tissues. Unexpectedly, some transformants exhibited chitinase levels lower than in non-transformed plants suggesting that the transgene inhibited expression of the homologous host gene. Progeny tests indicate this effect is not permanent. High levels of chitinase in transformants did not substantially increase resistance to the chitin-containing fungus Cercospora nicotiana, which causes Frog Eye disease. Therefore class I chitinase does not appear to be the limiting factor in the defense reaction to this pathogen. 相似文献
8.
Jean-Marc Gilli Paolo Mariani Franco Rustichelli Bin Yang Hervé Delacroix 《Molecular Engineering》1992,2(2):177-188
We recently showed that a side-chain industrial co-oligosiloxane presents a quenchable enlarged blue phase behaviour at the cholesteric-isotropic phase transition. In this paper, we present the results of a structural study based on X-ray diffraction, differential scanning calorimetry and optical measurements. In particular, the smectic A organisation is demonstrated in the lower temperature domain, which was hitherto understood as a cholesteric phase. A structural model for this phase is proposed on the basis of the analysis of the anisotropic scattering of stretched fibers. Our results also suggest that the observed glass transition is indeed a rather complex phenomenon, which seems to involve not only the freezing of the main chains, but also smectic correlations at the side-chain level. Moreover, the calorimetric study indicates that, notwithstanding the conservation of the processed film's optical properties, low kinetic reorganisations occur at room temperature. 相似文献
9.
Synergism between gangliosides and basic fibroblastic growth factor in favouring survival, growth, and motility of capillary endothelium 总被引:1,自引:0,他引:1
G De Cristan L Morbidelli G Alessandri M Ziche A P Cappa P M Gullino 《Journal of cellular physiology》1990,144(3):505-510
The experiments reported were motivated by the observation that in vivo gangliosides promoted angiogenesis when the dose of the angiogenic factor was too low to be effective (Ziche et al.: Laboratory Investigation 61:629-634, 1989). As an approach to understanding the mechanism of this modulatory effect, we analysed the influence that gangliosides have on survival, growth, and migration of capillary endothelium when an angiogenesis factor like basic fibroblast growth factor (bFGF) was present in the culture medium. Clones of bovine capillary endothelium were cultivated in media unable to sustain survival over a 72 h period. With this experimental approach, cell survival was evaluated after addition of either bFGF or gangliosides or both to the medium. The Boyden chamber procedure was utilized to measure the influence of bFGF or gangliosides on cell mobilization across a micropore filter. Low doses of both molecules, ineffective when added singly to the culture media, improved all three parameters when added in combination. A synergic effect between bFGF and the gangliosides (GM1, GD1b, GT1b) was observed for the improvement of survival or growth and for the acceleration of endothelial cell migration. The removal of sialic acid from the ganglioside molecule prevented any effect on all three parameters. The addition of sialic acid alone to cultures was also totally ineffective. In the adult organism most angiogenic events occur under conditions of tissue damage. The synergism between gangliosides and bFGF can be interpreted as the initial phase of a process for which endothelial cell survival is the indispensable first step in the formation of a new vascular network. 相似文献
10.
M. Rosa Pinol Urs Kägi Claus W. Heizmann Brigitte Vogel Jean-Marc Séquier Werner Haas Willi Hunziker 《Journal of neurochemistry》1990,54(6):1827-1833
Many processes in the CNS depend on calcium. The calcium signal is transduced into an intracellular response via Ca2(+)-binding proteins, including calbindin D-28K. In many laboratories, polyclonal antibodies against chicken intestinal calbindin D-28K have been used to study its localization in the brain (normal and degenerated) of various species, including humans, but some of these antisera cross-reacted with other proteins, including calretinin. We purified recombinant rat brain calbindin D-28K to raise antisera in rabbits and purified a recombinant rat-chicken calbindin D-28K hybrid protein to immunize mice for the generation of monoclonal antibodies. These antisera were highly specific for calbindin D-28K, as demonstrated by two-dimensional Western blotting analysis. Immunohistochemical analyses combined with in situ hybridization studies demonstrated that calbindin D-28K in the Purkinje cells of the cerebellum is independent of vitamin D. The antibodies described here will be important tools for studying the regulation of expression of calbindin D-28K and its biological function in the brain and in the PNS. 相似文献