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981.
Exposure to nitrogen–oxygen mixture at high pressure induces narcosis, which can be considered as a first step toward general
anaesthesia. Narcotic potencies of inert gases are attributed to their lipid solubility. Nitrogen narcosis induces cognitive
and motor disturbances that occur from 0.3 MPa in man and from 1 MPa in rats. Neurochemical studies performed in rats up to
3 MPa have shown that nitrogen pressure decreases striatal dopamine release like argon, another inert gas, or nitrous oxide,
an anaesthetic gas. Striatal dopamine release is under glutamatergic and other amino acid neurotransmission regulations. The
aim of this work was to study the effects of nitrogen at 3 MPa on striatal amino acid levels and to compare to those of 3 MPa
of helium which is not narcotic at this pressure, by using a new technique of microdialysis samples extraction under hyperbaric
conditions, in freely moving rats. Amino acids were analysed by HPLC coupled to fluorimetric detection in order to appreciate
glutamate, aspartate, glutamine and asparagine levels. Nitrogen–oxygen mixture exposure at 3 MPa decreased glutamate, glutamine
and asparagine concentrations. In contrast, with helium–oxygen mixture, glutamate and aspartate levels were increased during
the compression phase but not during the stay at maximal pressure. Comparison between nitrogen and helium highlighted the
narcotic effects of nitrogen at pressure. As a matter of fact, nitrogen induces a reduction in glutamate and in other amino
acids that could partly explain the decrease in striatal dopamine level as well as the motor and cognitive disturbances reported
in nitrogen narcosis. 相似文献
982.
Continuous and intermittent 50 Hz, 1.5 mT magnetic field with the exposure period of 4 h/day for 4 days was used to investigate
its possible effect on adult guinea pigs. Tissues and plasma specimens were assessed by biochemical parameters. Malondialdehyde
(MDA), glutathione (GSH), nitric oxide (NO) levels and myeloperoxidase activity (MPO) were examined in plasma, liver and brain
tissues. All parameters were determined by spectrophotometer. While intermittent magnetic field was effective on plasma lipid
peroxidation, continuous magnetic field was found to be effective on plasma MPO activity and NO levels. Augmentation of lipid
peroxidation was also observed in liver tissue both intermittent and continuous magnetic field exposures. These results indicate
that both the intermittent and continuous magnetic field exposures affect various tissues in a distinct manner because of
having different tissue antioxidant status and responses. 相似文献
983.
Marie-Pierre Forquin Hugo Duvergey Caroline Proux Valentin Loux Jerome Mounier Sophie Landaud Jean-Yves Coppée Jean-Fran?ois Gibrat Pascal Bonnarme Isabelle Martin-Verstraete Tatiana Vallaeys 《Applied and environmental microbiology》2009,75(19):6406-6409
Multilocus sequence typing with nine selected genes is shown to be a promising new tool for accurate identifications of Brevibacteriaceae at the species level. A developed microarray also allows intraspecific diversity investigations of Brevibacterium aurantiacum showing that 13% to 15% of the genes of strain ATCC 9174 were absent or divergent in strain BL2 or ATCC 9175.Brevibacteriaceae play a major part in the cheese smear community (6, 11). The classification and typing of cheese-related Brevibacteriaceae have been based mainly on molecular methods such as amplified ribosomal DNA restriction enzyme analysis, pulsed-field gel electrophoresis, and ribotyping (8, 10, 12). Recently, the original Brevibacterium linens group was split into two species on the basis of their physiological and biochemical characteristics, the sugar and polyol composition of their teichoic acids, and their 16S rRNA sequence and DNA-DNA hybridization levels. One species remains B. linens and is represented by type strain ATCC 9172. The other, represented by type strain ATCC 9175, has been renamed Brevibacterium aurantiacum. Regarding this new classification, the taxonomic position of cheese-related isolates has to be revisited and potential relationships between phylogenetic affiliation and the potential occurrence of given metabolic characteristics redefined (7). The unfinished genome sequence of B. aurantiacum ATCC 9174 has recently been released by the Joint Genome Institute (http://genome.jgi-psf.org/draft_microbes/breli/breli.home.html). The development of focused phylogenetic approaches using multiple markers in conjunction with whole-genome screening techniques such as comparative genomic hybridization (CGH) has proven to be useful for the detailed characterization of pathogenic species, including food pathogens (3, 5, 9). However, only a few technological species have been investigated at an intraspecies level (2). Our intention was thus to develop modern tools to facilitate the typing of strains of technological interest, for which Brevibacteriaceae could be used as a case study. 相似文献
984.
Grete Helen Meisfjord Jrgensen Linn Borsheim Cecilie Marie Mejdell Eva Sndergaard Knut Egil Be 《Applied animal behaviour science》2009,120(1-2):94-99
Many horse owners tend to group horses according to gender, in an attempt to reduce aggressive interactions and the risk of injuries. The aim of our experiment was to test the effects of such gender separation on injuries, social interactions and individual distance in domestic horses. A total of 66 horses were recruited from 4 different farms in Norway and Denmark and divided into six batches. Within each batch, horses were allotted into one mare group, one gelding group and one mixed gender group, with most groups consisting of three or four animals. After 4–6 weeks of acclimatisation, a trained observer recorded all social interactions using direct, continuous observation 1 h in the morning and 1 h in the afternoon for three consecutive days. Recordings of the nearest neighbour of each horse were performed using instantaneous sampling every 10 min. The horses were inspected for injuries before grouping, day 1 after grouping and after 4–6 weeks. No significant effect of gender composition was found on social interactions (P > 0.05), spacing (P > 0.07) or injuries (P > 0.23). Eighty percent of all aggressive interactions recorded were threats, not involving physical contact. Horses with the smallest space allowance showed the highest mean number of aggressive interactions (28.6 ± 6.1 interactions per 6 h) compared to the mean of all the other batches (8.3 ± 1.0 interactions per 6 h). Very few injuries were found and most were superficial. In conclusion, gender composition does not seem to have any effect on aggression level, spacing or injuries. However, the early social experience of horses, management of feeding and space allowance probably represents more important factors for successful group housing of domestic horses. 相似文献
985.
986.
Soil moisture surpasses elevated CO2 and temperature as a control on soil carbon dynamics in a multi-factor climate change experiment 总被引:1,自引:0,他引:1
Some single-factor experiments suggest that elevated CO2 concentrations can increase soil carbon, but few experiments have examined the effects of interacting environmental factors on soil carbon dynamics. We undertook studies of soil carbon and nitrogen in a multi-factor (CO2 × temperature × soil moisture) climate change experiment on a constructed old-field ecosystem. After four growing seasons, elevated CO2 had no measurable effect on carbon and nitrogen concentrations in whole soil, particulate organic matter (POM), and mineral-associated organic matter (MOM). Analysis of stable carbon isotopes, under elevated CO2, indicated between 14 and 19% new soil carbon under two different watering treatments with as much as 48% new carbon in POM. Despite significant belowground inputs of new organic matter, soil carbon concentrations and stocks in POM declined over four years under soil moisture conditions that corresponded to prevailing precipitation inputs (1,300 mm yr?1). Changes over time in soil carbon and nitrogen under a drought treatment (approximately 20% lower soil water content) were not statistically significant. Reduced soil moisture lowered soil CO2 efflux and slowed soil carbon cycling in the POM pool. In this experiment, soil moisture (produced by different watering treatments) was more important than elevated CO2 and temperature as a control on soil carbon dynamics. 相似文献
987.
988.
S. Becquevort I. Dumont J.-L. Tison D. Lannuzel M.-L. Sauvée L. Chou V. Schoemann 《Polar Biology》2009,32(6):879-895
Pack ice, brines and seawaters were sampled in October 2003 in the East Antarctic sector to investigate the structure of the
microbial communities (algae, bacteria and protozoa) in relation to the associated physico-chemical conditions (ice structure,
temperature, salinity, inorganic nutrients, chlorophyll a and organic matter). Ice cover ranged between 0.3 and 0.8 m, composed of granular and columnar ice. The brine volume fractions
sharply increased above −4°C in the bottom ice, coinciding with an important increase of algal biomass (up to 3.9 mg C l−1), suggesting a control of the algae growth by the space availability at that period of time. Large accumulation of NH4
+ and PO4
3− was observed in the bottom ice. The high pool of organic matter, especially of transparent exopolymeric particles, likely
led to nutrients retention and limitation of the protozoa grazing pressure, inducing therefore an algal accumulation. In contrast,
the heterotrophs dominated in the underlying seawaters. 相似文献
989.
Marie‐Josée Demers Sonya Thibodeau Dominique Noël Naoya Fujita Takashi Tsuruo Rémy Gauthier Mélina Arguin Pierre H. Vachon 《Journal of cellular biochemistry》2009,107(4):639-654
Herein, we investigated the survival roles of Fak, Src, MEK/Erk, and PI3‐K/Akt‐1 in intestinal epithelial cancer cells (HCT116, HT29, and T84), in comparison to undifferentiated and differentiated intestinal epithelial cells (IECs). We report that: (1) cancer cells display striking anoikis resistance, as opposed to undifferentiated/differentiated IECs; (2) under anoikis conditions and consequent Fak down‐activation, cancer cells nevertheless exhibit sustained Fak–Src interactions and Src/MEK/Erk activation, unlike undifferentiated/differentiated IECs; however, HCT116 and HT29 cells exhibit a PI3‐K/Akt‐1 down‐activation, as undifferentiated/differentiated IECs, whereas T84 cells do not; (3) cancer cells require MEK/Erk for survival, as differentiated (but not undifferentiated) IECs; however, T84 cells do not require Fak and HCT116 cells do not require PI3‐K/Akt‐1, in contrast to the other cells studied; (4) Src acts as a cornerstone in Fak‐mediated signaling to MEK/Erk and PI3‐K/Akt‐1 in T84 cells, as in undifferentiated IECs, whereas PI3‐K/Akt‐1 is Src‐independent in HCT116, HT29 cells, as in differentiated IECs; and (5) EGFR activity inhibition abrogates anoikis resistance in cancer cells through a loss of Fak–Src interactions and down‐activation of Src/MEK/Erk (T84, HCT116, HT29 cells) and PI3‐K/Akt‐1 (T84 cells). Hence, despite distinctions in signaling behavior not necessarily related to undifferentiated or differentiated IECs, intestinal epithelial cancer cells commonly display an EGFR‐mediated sustained activation of Src under anoikis conditions. Furthermore, such sustained Src activation confers anoikis resistance at least in part through a consequent sustenance of Fak–Src interactions and MEK/Erk activation, thus not only overriding Fak‐mediated signaling to MEK/Erk and/or PI3‐K/Akt‐1, but also the requirement of Fak and/or PI3‐K/Akt‐1 for survival. J. Cell. Biochem. 107: 639–654, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
990.
The inhibitory effect of Cd on nitrification was investigated in a continuous-flow system with enriched nitrifying bacteria.
The maximum specific ammonium utilization rate and the half-saturation constant were found as 671 mg NH4–N/g VSS day and 0.48 mg/l, respectively. In the case of continuous Cd input at 1 and 2.5 mg/l, nitrification was inhibited
by 30% and 47%, respectively. Inhibition ranged from 20% to 40% and no further increase in inhibition was exhibited in new
runs except at 10 mg/l influent Cd. At 10 mg/l influent Cd, specific ammonium utilization and nitrate production rates were
inhibited by 90%. On the contrary, a serious nitrite accumulation was not observed during this period. When Cd feeding was
stopped, recovery from inhibition was observed after 37 day which was seen by the improvement in ammonium utilization and
nitrate production rates. A shift in microbial population from the initial Nitrosomonas sp. to the Cd-tolerant Nitrosospira sp. was observed in the recovery period from severe Cd inhibition. After the domination of Nitrosospira species, redosing at 10 mg/l and then at 15 mg/l did not affect the performance as before. 相似文献