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51.
Starvation-Induced Stress Resistance in Lactococcus lactis subsp. lactis IL1403 总被引:2,自引:1,他引:1 下载免费PDF全文
Axel Hartke Sandrine Bouche Xavier Gansel Philippe Boutibonnes Yanick Auffray 《Applied microbiology》1994,60(9):3474-3478
Carbohydrate-starved cultures of Lactococcus lactis subsp. lactis IL1403 showed enhanced resistance to heat, ethanol, acid, osmotic, and oxidative stresses. This cross-protection seems to be established progressively during the transitional growth phase, with maximum resistance occurring when cells enter the stationary phase. Chloramphenicol or rifamycin treatment does not abolish the development of a tolerant cell state but, on the contrary, seems to provoke this response in L. lactis subsp. lactis. 相似文献
52.
Murielle Rinaldi-Carmona Francis Barth Michel Haulme David Shire Bernard Calandra Christian Congy Serge Martinez Jeanne Maruani Gervais Nliat Daniel Caput Pascual Ferrara Philippe Soubri Jean Claude Brelire Grard Le Fur 《FEBS letters》1994,350(2-3):240-244
SR141716A is the first selective and orally active antagonist of the brain cannabinoid receptor. This compound displays nanomolar affinity for the central cannabinoid receptor but is not active on the peripheral cannabinoid receptor. In vitro, SR141716A antagonises the inhibitory effects of cannabinoid receptor agonists on both mouse vas deferens contractions and adenylyl cyclase activity in rat brain membranes. After intraperitoneal or oral administration SR141716A antagonises classical pharmacological and behavioural effects of cannabinoid receptor agonists. This compound should prove to be a powerful tool for investigating the in vivo functions of the anandamide/cannabinoid system. 相似文献
53.
A cytogenetic map of chromosome 5 from the Mediterranean fruit fly, Ceratitis capitata, was constructed. Six mutations were located by translocation, transposition or deletion mapping. This knowledge allowed alignment and orientation of the existing linkage map with the polytene chromosomes. In addition, mapping of mutations used as selectable markers in genetic sex-separation strains is an essential prerequisite for the improvement of genetic stability during mass-rearing. 相似文献
54.
The effect of exogenous abscisic acid, provided to somatic embryos during the maturation step, on endogenous abscisic acid and its main conjugated form (abscisic acid glucose ester), germination and conversion frequencies is presented in this paper. Abscisic acid measurements were obtained after a methanolic extraction, a fractionation through high performance liquid chromatography, quantitation with an immunoassay and identification of the quantitated compound using gas chromatography-mass spectrometry. Results show that endogenous abscisic acid and abscisic acid glucose ester levels are clearly correlated with the exogenous abscisic acid concentration provided to the embryos. Maturation was clearly enhanced by exogenous abscisic acid, but no correlation was found between abscisic acid concentration and germination frequency. Conversely, development of the aerial part of the germinated somatic embryos was dependent upon the abscisic acid concentration in the culture medium and results suggest that this dependence could be related to the endogenous abscisic acid content. 相似文献
55.
Changes in carbon storage in temperate humic loamy soils after forest clearing and continuous corn cropping in France 总被引:3,自引:0,他引:3
Soil samples from forest and agricultural sites in three areas of southwest France were collected to determine the effect
of forest conversion to continuous intensive corn cropping with no organic matter management on soil organic carbon (C) content.
Soils were humic loamy soils and site characteristics that may affect soil C were as uniform as possible (slope, elevation,
texture, soil type, vegetation).
Three areas were selected, with adjacent sites of various ages of cultivation (3 to 35 yr), and paired control forest sites.
The ploughed horizon (0-Dt cm) and the Dt-50 cm layer were collected at each agricultural site. In forest sites, each 10 cm
layer was collected systematically down to 1 meter depth. Carbon concentrations were converted to total content to a given
depth as the product of concentration, depth of sample and bulk density, and expressed in units of kg m-2. For each site and each sampled layer, the mineral mass of soil was calculated, in order to base comparisons on the same
soil mass rather than the same depth.
The pattern of C accumulation in forest soils showed an exponential decrease with depth. Results suggested that soil organic
carbon declined rapidly during the first years of cultivation, and at a slower rate thereafter. This pattern of decrease can
be fitted by a bi-exponential model assuming that initial soil organic carbon can be separated into two parts, a very labile
pool reduced during the first rapid decline and more refractory fractions oxidizing at a slower rate. Sampling to shallow
depths (0-Dt cm) resulted in over-estimation of the rate of carbon release in proportion to the initial amount of C, and in
under-estimation of the total loss of C with age. The results for the 0–50 cm horizon indicated that losses of total carbon
average about 50% in these soils, ranging in initial carbon content from 19 to 32.5 kg m-2. Carbon release to the atmosphere averaged 0.8 kg m-2 yr-1 to 50 cm depth during the first 10 years of cultivation. The results demonstrate that temperate soils may also be an important
source of atmospheric carbon, when they are initially high in carbon content and then cultivated intensively with no organic
matter management. 相似文献
56.
Alain Delbarre Philippe Muller Viviane Imhoff Jean-Louis Morgat Hélène Barbier-Brygoo 《Planta》1994,195(2):159-167
Uptake and metabolism of exogenous naphthalene-1-acetic acid (NAA) and indole-3-acetic acid (IAA) have been studied in tobacco (Nicotiana tabacum L. cv. Xanthi) mesophyll protoplasts. Both auxins entered protoplasts by diffusion under the action of the transmembrane pH gradient without any detectable participation of an influx carrier. Molecules were accumulated by an anion-trapping mechanism and most of them were metabolized within hours, essentially as glucose-ester and amino-acid conjugates. Protoplasts were equipped with a functional auxin-efflux carrier as evidenced by the inhibitory effect of naphthylphtalamic acid on IAA efflux. Basically, similar mechanisms of NAA and IAA uptake occurred in protoplasts. However, the two auxins differed in their levels of accumulation, due to different membrane-transport characteristics, and the nature of the metabolites produced. This shows the need to estimate the accumulation and the metabolism of auxins when analyzing their effects in a given cell system. The internal auxin concentration could be modulated by changing the transmembrane pH gradient, giving an interesting perspective for discriminating between the effects of intra- and extracellular auxin on physiological processes.Abbreviations BA
benzoic acid
- Ci/Ce
accumulation ratio of auxin
- IAAasp
N-[3-indolylacetyl]-dl-aspartic acid
- NAA
naphthalene-1-acetic acid
- NAAasp
N-[1-naphthylacetyl]-l-aspartic acid
- NPA
N-1-naphthylphthalamic acid
The authors thank Dr. M. Caboche (I.N.R.A, Versailles, France) for his generous gifts of some amide derivatives of 1-NAA, Mr. P. Varennes and Dr. B. Das (I.C.S.N., C.N.R.S., Gif-sur-Yvette, France) for recording and interpreting the mass spectra of NAA glucose ester, and Prof. P. Manigault (Institut des Sciences Végétales, Gif-sur-Yvette) for microscopy measurements of protoplast dimensions. This work was supported by funds from the C.N.R.S, I.N.R.A, and E.E.C. 相似文献
57.
Mainul Hassan Philippe J. Blanc Alain Pareilleux Gérard Goma 《Biotechnology letters》1994,16(8):819-824
Summary A search was carried out for mutants, defective in the conversion of stearic acid to oleic acid in effort to improve the quality of lipids produced by Cryptococcus curvatus ATCC, 20509. Mutants were selected as unsaturated fatty acid (Ufa) auxotrophs. After treatment of parent organism with Ethyl methanesulfonate (EMS), 11 oleate-requiring auxotrophs were isolated. Only 3 of them were real unsaturated fatty acid (Ufa) mutants, while the other 8 were designated as fatty acid synthetase (Fas) mutants. The amount of saturated fatty acid (SFA) was about 65.2 % in the lipids extracted from an Ufa mutant named UfaM3 and it was significantly higher than that of the wild-type (WT) (46.6 %) and similar to that of cocoa butter (60.4 %). 相似文献
58.
The soil fauna: the other last biotic frontier 总被引:4,自引:0,他引:4
Different approaches to biodiversity yield global totals as small as 3 million or as large as 80 million species. Erwin's calculation and estimation leads to an estimate of ca 30 million species and relies on four assumptions of which one concerns the ratio between the number of canopy insects and those found elsewhere, especially in the soil. A short survey of the microarthropods living in coastal sand dunes and collected with a new flotation method yielded amazing results. In spite of the severity of the habitat (low organic matter content and extreme dryness), the density of microarthropods varied between 175 000 and 1 400 000 individuals per square metre, i.e., densities 3 to 10 times higher than densities usually observed in any other type of soil. A total of 31 species was recorded, most undescribed and smaller than 200 m. The consequences of these findings on the estimation of the number of species are discussed. It is suggested that the soil, including the deepest horizons and the rhizosphere, might constitute a huge reservoir for biodiversity. 相似文献
59.
60.