Fixed interval and fixed time treadle pressing in the pigeon: A comparison with FI and FT keypecking

Experiment I used non-naive pigeons having previously performed on both keypecking and treadlepressing Fixed Interval schedules. In condition IT, treadlepressing was reinforced on successive Fixed Interval 60 seconds, Fixed Time 60 seconds and Fixed Interval 60 seconds schedules. Subsequently (condition IK), the same subjects pecked a key on an identical schedule sequence (FI60, FT60, FI60). In Experiment II, separate groups of naïve subjects were assigned either to treadlepressing (condition IIT) or keypecking (condition IIK) and to the same schedule sequence (FI60, FT60, FI60). Treadle pressing and keypecking decreased greatly in Fixed Time schedules. Curvature indices, pauses and running rates were less sensitive than response rates to the switching from one schedule to the other. Experiments I and II yielded similar results, experimental history accounting only for minor differences. The results were discussed in relation to interspecies differences in the temporal regulation of behavior and operant versus respondent control of the response and schedule-induced behaviour.     

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 locus involved in kanamycin, chloramphenicol and L-serine resistance is located in the bglY-galU region of the Escherichia coli K12 chromosome

Summary Spontaneous mutants of Escherichia coli K12 displaying an increased level of the kanamycin resistance conferred by plasmid pGR71 were selected. Several mutants obtained in this way apparently carry large chromosomal deletions extending into galU and/or bglY (27 min). This positive selection of deletions allowed detection of a new locus located between galU and bglY. Deletions of this locus are responsible for increased resistance to kanamycin (Irk), decreased resistance to l-serine in minimal medium (Drs) and decreased resistance to chloramphenicol (Drc) when a cat gene is present in the bacteria.     

Structure of the gene of tum- transplantation antigen P91A: the mutated exon encodes a peptide recognized with Ld by cytolytic T cells

Mutagen treatment of mouse P815 tumor cells produces immunogenic mutants that express new transplantation antigens (tum- antigens) recognized by cytolytic T cells. We found that the gene conferring expression of tum- antigen P91A contains 12 exons, encoding a 60 kd protein lacking a typical N-terminal signal sequence. The sequence shows no significant similarity with sequences in current data bases. A mutation that causes expression of the antigen is located in exon 4; it is the only apparent difference between the normal and the antigenic alleles. A short synthetic peptide corresponding to a region of exon 4 located around this mutation makes P815 cells sensitive to lysis by anti-P91A cytolytic T cells. The mutation creates a strong aggretope enabling the peptide to bind the H-2 Ld molecule. Several secondary tumor cell variants that no longer express tum- antigen P91A were found to carry deletions in the gene.     

A spectrophotometric assay for the cyclization activity of cyclomaltohexaose (alpha-cyclodextrin) glucanotransferase

A cyclomaltohexaose (alpha-cyclodextrin) determination method which is both highly reproducible and selective is described. It involves the formation of an inclusion complex between the cyclodextrin and methyl orange under conditions of low pH (1.2) and low temperature (16 degrees C) and is useful for the assay of cyclodextrin glucanotransferase activity. The formation of the inclusion complex causes a decrease in absorbance of the methyl orange solution and this is monitored at a wavelength of 505 nm. The decrease in absorbance is linearly correlated with the cyclomaltohexaose concentration in the range of 0.25 optical density unit and 0.30 mM cyclomaltohexaose. The specificity of the test for cyclomaltohexaose is high, with only limited interference by linear oligosaccharides and other cyclodextrins: cyclomaltoheptaose and cyclomaltooctaose cause absorbance variations of 16 and 5%, respectively, of the response of maltohexaose. The formation of the complex is instantaneous and the complex is stable in time, provided the temperature is constant. The presence of methyl orange does not hinder enzymatic activity determination. The reaction is stopped by acidification and absorbance is measured at the fixed temperature of 16 degrees C. Possible interferences inherent to the composition of the sample itself can be suppressed by running appropriate controls and calculating a corrected optical density. This colorimetric method is simple and should be versatile in assaying diverse cyclomaltohexaose glucanotransferase enzymes.     

Soluble and particulate inositol 1,4,5-trisphosphate 5-phosphatases show common antigenic determinants

Inositol 1,4,5-trisphosphate 5-phosphatase catalyses the dephosphorylation of the phosphate in the 5-position from inositol 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate. One particulate and two soluble enzymes were previously described in bovine brain. In this study, we have obtained a precipitating antiserum against soluble type I inositol 1,4,5-trisphosphate 5-phosphatase. The particulate, but not the soluble type II enzyme, was immunoprecipitated by the serum. Inositol 1,4,5-triphosphate 5-phosphatase activity from crude extracts of rat brain, human platelets and rat liver were immmunoprecipitated by the same antibodies, suggesting the existence of common antigenic determinant among inositol 1,4,5-trisphosphate 5-phosphatases of diverse sources.     

Mass-spectrometric determination of O2 and CO2 gas exchange in illuminated higher-plant cells

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 - K_d permeability coefficient The authors thank Drs A. Vermeglio and P. Thibault, Dépt. de Biologie, CEN-Cadarache, St. Paul Lez Durance, France, for helpful discussions.     

Thyroid function and trisomy 21. TSH increase and rT3 deficiency

An excess of thyrotropin (TSH) with normal levels of tetraiodothyronine (T4) and of 3,5,3'-triiodothyronine (T3) was confirmed in the serum of 78 trisomy 21 children. A severe deficiency of 3,3',5'-triiodo-thyronine (rT3 or reverse T3) was observed and the decrease of the rT3/TSH ratio was highly significant. These new facts suggest that the rT3 deficiency plays a peculiar role in trisomy 21 (maybe through the regulation of one or few steps of monocarbons' metabolism). A systematic control of thyroid function (including the patient's rT3 level) is mandatory for the follow-up of every trisomy 21 patient.