EAAT expression by macrophages and microglia: still more questions than answers

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.     

Characterization of Viticultural Terroirs using a Simple Field Model Based on Soil Depth – II. Validation of the Grape Yield and Berry Quality in the Anjou Vineyard (France)

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.     

A predominant idiotype on rabbit anti-VH a1 allotype antibodies: sharing by both major and minor VH subgroups

In every rabbit examined, greater than or equal to 80% of antibodies directed against the VH allotypic marker, a1, bears a predominant idiotype (IdX-a1). The IdX-a1 marker is site-associated and expressed on H chains, but not L chains, of anti-a1 antibody. Experiments using rabbits suppressed for the VH a subgroup demonstrated that IdX-a1 can be associated with both major (a+) and minor (a-) VH subgroup gene products and that a1 rabbits contain IdX-a1 within their genetic repertoire. The genetic and regulatory implications of our results are discussed.     

C-Glycosylflavonoids. The chemistry of aspalathin

1. The isolation of aspalathin, the principal phenolic constituent in the leaves of Aspalathus linearis, is described and its properties are discussed. 2. The compound has been identified as 3'-C-beta-d-glucopyranosyl-2',3,4,4',6'-pentahydroxydihydrochalcone by the preparation and analysis of various derivatives, by photochemical oxidation to 2,3-dihydroiso-orientin and by nuclear-magnetic-resonance studies.     

Ultrastructure of Weddellomyces epicallopisma (Dothideales, Dacampiaceae, Ascomycota), especially of its ascospores]

An ultrastructural study of Weddellomyces epicallopisma (ascomata wall, asci, ascospores and vegetative hyphae), the first done on the family Dacampiaceae, confirms most of the observations made in light microscopy. Moreover it shows that ascospores are provided with an endospore (not visible in light microscope) and that the structure of the ascospore septum is more complex. The similarity of the wall structure between the ascospore and the hyphoid appendages, developed on the upper part of the ascoma, is emphasized.     

Calcium requirement of phytochrome-mediated fern-spore germination: No direct phytochrome-calcium interaction in the phytochrome-initiated transduction chain

Phytochrome-mediated germination of fern spores of Dryopteris paleacea Sw. was initiated by a saturating red-light (R) irradiation after 20 h of imbibition. For its realization external Ca²⁺ was required, with a threshold at a submicromolar concentration, and an optimum was reached around 10^-4 M. At concentrations 10^-1 M only a reduced response was obtained, based probably on an unspecific osmotic or ionic effect. The germination response was inhibited by La³⁺, an antagonist of Ca²⁺. From these results it is concluded that Ca²⁺ influx from the medium into the spores may be an important event in phytochrome-mediated germination. In the absence of Ca²⁺ the R-stimulated system remained capable of responding to Ca²⁺, added as late as 40 h after R. Moreover, Ca²⁺ was effective even if added after the active form of phytochrome, Pfr, had been abolished by far-red (FR) 24 h after R. Thus, the primary effect of Pfr, that initiates the transduction chain, does not require calcium. Coupling of Pfr to subsequent dark reactions has been investigated by R-FR irradiations with various dark intervals. The resulting escape kinetics were characterized by a lag phase (6 h) and half-maximal escape from FR reversibility (19 h). These kinetics were not significantly changed by the presence or absence of calcium. Thus, direct interaction of Pfr and calcium is not a step in the transduction chain initiated by the active form of photochrome.Abbreviations EGTA ethyleneglycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid - FR far-red light - Pr red-light-absorbing form of phytochrome - Pfr far red-light-absorbing form of phytochrome - Pipes piperazine-1,4-bis(2-ethanesulfonic acid) - R red light A preliminary report of this work was presented at the XIV Int. Bot. Congr., Berlin (West), Germany, Book of Abstracts, 2-116a-5 (1987)