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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.
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
4.
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
5.
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
6.
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
7.
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
8.
The brain organization of butterflyfishes 总被引:2,自引:0,他引:2
Roland Bauchot Jean-Marc Ridet Marie-Louise Bauchot 《Environmental Biology of Fishes》1989,25(1-3):205-219
Synopsis The encephalization indices of angelfishes (Pomacanthidae) and butterflyfishes (Chaetodontidae) are typical of advanced perciform
fishes: both families lie in the upper part of the polygon of teleost indices. The chaetodontids seem to be a little more
encephalized than pomacanthids. The general morphology of the brains in both families is very similar: small olfactory bulbs,
large optic tectum and a cerebellum which covers the brain structures in front of it like a cap. This morphology is shared
by another family of the coral reef biotope, the Acanthuridae. The histological architecture is also typical of advanced teleosts,
with a cortex-like pallium, a laminated nucleus geniculatus (= pretectalis superficialis), a complex valvula cerebelli and
a corpus glomerulosum with a clear neuropile centre. The quantitative analysis of the main subdivisions of the brain, either
from relative volumes or from indices, shows small olfactory bulbs (microsmy) but important telencephalic and diencephalic
centres, large tectal centres (vision) and large cerebellum (precise locomotion). Many of these peculiarities are shared by
other fishes inhabiting coral reefs. The differences between the two families seem to be primarily correlated with food habits:
the angelfishes, which are sponge-feeders and may have an overweight due to the ballast of the sponge-skeleton in their digestive
tract, and which do not need either such good vision or such precise locomotion to pick up their prey, could be a little less
encephalized than the butterflyfishes. 相似文献
9.
Identification and expression of water stress- and abscisic acid-regulated genes in a drought-tolerant sunflower genotype 总被引:17,自引:0,他引:17
10.
Drosophila melanogaster acetylcholinesterase: Identification and expression of two mutations responsible for cold- and heat-sensitive phenotypes 总被引:2,自引:0,他引:2
Annick Mutero Jean-Marc Bride Madeleine Pralavorio Didier Fournier 《Molecular & general genetics : MGG》1994,243(6):699-705
Ace
IJ29 and Ac
IJ40 are cold- and heat-sensitive variants of the gene coding for acetylcholinesterase in Drosophila melanogaster. In the homozygous condition, these mutations are lethal when animals are raised at restrictive temperatures, i.e., below 23° C for Ace
IJ29 or above 25° C for Ace
IJ40. The coding regions of the gene in these mutants were sequenced and mutations changing Ser374 to Phe in Ace
IJ29 and Pro75 to Leu in Ace
IJ40 were found. Acetylcholinesterases bearing these mutations were expressed in Xenopus oocytes and we found that these mutations decrease the secretion rate of the protein most probably by affecting its folding. This phenomenon is exacerbated at restrictive temperatures decreasing the amount of secreted acetylcholinesterase below the lethality threshold. In parallel, the substitution of the conserved Asp248 by an Asn residue completely inhibits the activity of the enzyme and its secretion, preventing the correct folding of the protein in a non-conditional manner. 相似文献