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1.
Ouenzar Bouchra Hartmann Caroline Rode Andre Benslimane Abdelali 《Plant Molecular Biology Reporter》1998,16(3):263-269
We have developed a new mini-procedure for isolation of total cellular DNA from date palm (Phoenix dactylifera L.). The procedure, which does not use liquid nitrogen, has proved useful due to temporary disruptions in supplies of liquid nitrogen that occur in countries where date palm trees are cultivated. DNA suitable for RFLP and PCR analyses is obtained. 相似文献
2.
Glutamate is the main excitatory amino acid, but its presence in the extracellular milieu has deleterious consequences. It
may induce excitotoxicity and also compete with cystine for the use of the cystine–glutamate exchanger, blocking glutathione
neosynthesis and inducing an oxidative stress-induced cell death. Both mechanisms are critical in the brain where up to 20%
of total body oxygen consumption occurs. In normal conditions, the astrocytes ensure that extracellular concentration of glutamate
is kept in the micromolar range, thanks to their coexpression of high-affinity glutamate transporters (EAATs) and glutamine
synthetase (GS). Their protective function is nevertheless sensitive to situations such as oxidative stress or inflammatory
processes. On the other hand, macrophages and microglia do not express EAATs and GS in physiological conditions and are the
principal effector cells of brain inflammation. Since the late 1990s, a number of studies have now shown that both microglia
and macrophages display inducible EAAT and GS expression, but the precise significance of this still remains poorly understood.
Brain macrophages and microglia are sister cells but yet display differences. Both are highly sensitive to their microenvironment
and can perform a variety of functions that may oppose each other. However, in the very particular environment of the healthy
brain, they are maintained in a repressed state. The aim of this review is to present the current state of knowledge on brain
macrophages and microglial cells activation, in order to help clarify their role in the regulation of glutamate under pathological
conditions as well as its outcome. 相似文献
3.
4.
The influence of He-Ne laser radiation (632.8 nm, 56 J/m2, t = 10 s) and phytohaemagglutinin (PHA, 2 micrograms/ml) on chromatin structure in human lymphocytes was studied by electron microscopy using ultrathin cell sections. Morphometric analysis of extranuclear condensed chromatin masses was performed 1 h after the irradiation or after the beginning of PHA treatment. In the irradiated cells the following insignificant changes were revealed: decrease in the relative area of the nucleoplasmic chromatin, increase in the relative area of decondensation zones as well as increase in the number of clumps of nucleoplasmic chromatin and relative length at their boundary with nucleoplasma. The tendency of these morphological changes may be interpreted as functional activation of extranucleolar RNA synthesis in response to irradiation by red laser light. Action of PHA results in significant changes of the surfaces of chromatin clumps, namely increase in relative length of nucleoplasmic chromatin boundary and decrease in relative length of perimembranous chromatin boundary with nucleoplasma as well as some less expressed delamination of the chromatin masses from the nuclear membrane. These essential changes may reflect chromatin activation by proliferative stimulus. Peculiarities of the ultrastructural reorganisation in the condensed chromatin after irradiation and PHA-treatment probably reflect the differences in the processes of gene activation caused by the two agents. 相似文献
5.
Soil and climate are major constituents of the French notion of Terroir. This concept implies that there is a strong relationship
between the composition of the grape, the characteristics of the wine and the territory of production. To study this link,
a new method of characterization of the Terroir, including geological and pedological factors, was investigated. It uses a
field model based on depth and clay content of soil, together with the degree of weathering of the parent rock. Consequently,
for every type of parent rock belonging to a given geologic stage, there are a series of soils that show different stages
of pedological evolution. According to the model, three kinds of soils are distinguished with regards to the weathering intensity
of the parent rock, that are named weakly weathered rock (WWR), moderately weathered rock (MWR) and strongly weathered rock
(SWR). By hypothesis, each soil type is considered as a homogeneous unit for vine production from the viewpoint of ecophysiological
factors. Each terroir unit defined by this method is called a Basic Terroir Unit (BTU). To validate this hypothesis, experimental
plots planted with Chenin and Cabernet Franc vines were studied over three consecutive seasons (2000–2002), in the Anjou vineyard
(Loire Valley – France). The major BTUs developed on the two most important geological systems of Anjou (Brioverian and Ordovician–Devonian),
were studied. Results showed that the berries of vines cultivated in WWR were significantly smaller, richer in sugars and
anthocyanins and had a Total Phenolic Index higher than those of the vines cultivated in SWR. They also had a lower titratable
acidity. Cabernet Franc vines cultivated in MWR had berries with sugar and anthocyanin contents but also total phenolics very
close to those of WWR. With Chenin vines there was a good relationship between the global pool of free aromas of berries and
the BTU type. The study showed significant relationships between the quality of grapes and the measured values of several
ecophysiological variables such as the water supply regime or the timing of budburst. 相似文献
6.
Often we must balance being prepared to act quickly with being prepared to suddenly stop. The stop signal task (SST) is widely used to study inhibitory control, and provides a measure of the speed of the stop process that is robust to changes in subjects’ response strategy. Previous studies have shown that preparation affects inhibition. We used fMRI to separate activity that occurs after a brief (500 ms) warning stimulus (warning-phase) from activity that occurs during responses that follow (response-phase). Both of these phases could contribute to the preparedness to stop because they both precede stop signals. Warning stimuli activated posterior networks that signal the need for top-down control, whereas response phases engaged prefrontal and subcortical networks that implement top-down control. Regression analyses revealed that both of these phases affect inhibitory control in different ways. Warning-phase activity in the cerebellum and posterior cingulate predicted stop latency and accuracy, respectively. By contrast, response-phase activity in fronto-temporal areas and left striatum predicted go speed and stop accuracy, in pre-supplementary motor area affected stop accuracy, and in right striatum predicted stop latency and accuracy. The ability to separate hidden contributions to inhibitory control during warning-phases from those during response-phases can aid in the study of models of preparation and inhibitory control, and of disorders marked by poor top-down control. 相似文献
7.
8.
Nelson Duran Jaime Rodriguez Andre Ferraz Victoriano Campos 《Biotechnology letters》1987,9(5):357-360
Summary
C. sitophila strain TFB-27441 showed 2–3 times higher lignolytic activity thanPhanerochaete chrysosporium (BKM-F-1767 strain). Lignin had a marked effect on the ligninase activity indicating that some induction or activation mechanism is involved in lignin degradation byC. sitophila. 相似文献
9.
All measurements of photorespiration and gross photosynthesis in leaves, whether using isotopes or not, are underestimated because of the recycling of O2 or CO2. On the basis of a simple diffusion model, we propose a method for the calculation of the recycling and the corresponding underestimation of the measurements. This procedure can be applied when the stomatal resistance is known, and allows for a correction of certain results in the literature. It is found that measurements of the photorespiratory CO2 release are usually underestimated by 20 to 100%, which sets the estimated rate of CO2 photorespired at 30 to 50% of the net photosynthesis in C3 plants under normal conditions. In water stress studies, the correction of the photorespiration is still more important (1.5-3.3) because the stomata are closed more. Analysis of the diffusion of O2 shows that its recycling is low and that the underestimation of photorespiration with 18O2 is negligible. 相似文献
10.
Marie-Hélène Avelange Jean M. Thiéry Frédéric Sarrey Pierre Gans Fabrice Rébeillé 《Planta》1991,183(2):150-157
In order to estimate photosynthetic and respiratory rates in illuminated photoautotrophic cells of carnation (Dianthus caryophyllus L.), simultaneous measurements of CO2 and O2 gas exchange were performed using 18O2, 13CO2 and a mass-spectrometry technique. This method allowed the determination, and thus the comparison, of unidirectional fluxes of O2 and CO2. In optimum photosynthetic conditions (i.e. in the presence of high light and a saturating level of CO2), the rate of CO2 influx represented 75±5% of the rate of gross O2 evolution. After a dark-to-light transition, the rate of CO2 efflux was inhibited by 50% whereas the O2-uptake rate was little affected. The effect of a recycling of respiratory CO2 through photosynthesis on the exchange of CO2 gas was investigated using a mathematical model. The confliction of the experimental data with the simulated gas-exchange rates strongly supported the view that CO2 recycling was a minor event in these cells and could not be responsible for the observed inhibition of CO2 efflux. On the basis of this assumption it was concluded that illumination of carnation cells resulted in a decrease of substrate decarboxylations, and that CO2 efflux and O2 uptake were not as tightly coupled in the light as in the dark. Furthermore, it could be calculated from the rate of gross photosynthesis that the chloroplastic electron-transport chain produced enough ATP in the light to account for the measured CO2-uptake rate without involving cyclic transfer of electrons around PS I or mitochondrial supplementation.Abbreviations Chl
chlorophyll
- Kd
permeability coefficient
The authors thank Drs A. Vermeglio and P. Thibault, Dépt. de Biologie, CEN-Cadarache, St. Paul Lez Durance, France, for helpful discussions. 相似文献