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101.
Biotechnological applications of diatoms are still in development. Further development at the industrial scale will depend on optimisation of the culture process with the aim of reducing costs. Because of the photoautotrophic status of the majority of diatoms, microalgal cultures suffer from the limitation of light diffusion, which requires the development of suitable photobioreactors. Thus, genetically engineered microalgae that may be cultivated in heterotrophic conditions present a new opportunity. Other limiting factors, such as nutrients (phosphate, nitrogen, silicon), pH, temperature, bioturbation and many more must be taken into account. Most of the time, metabolic stress conditions lead to an overproduction of the products of interest, with a decrease in biomass production as a consequence. Outdoor cultures in open ponds are usually devoted to aquaculture for the feeding of shrimps and bivalve molluscs (commercial production), while closed axenic indoor/outdoor photobioreactors are used for biotechnological compounds of homogeneous composition (still at the laboratory scale). In addition to the optimum culture conditions that have to be taken into account for photobioreactor design, the localisation of produced metabolites (intra- or extracellular) may also be taken into account when choosing the design. Microalgal cell immobilisation may be a suitable technique for application to benthic diatoms, which are usually sensitive to bioturbation and/or metabolites which may be overexpressed. 相似文献
102.
103.
It is commonly assumed that spontaneous activity of striatal output neurons is characterized by a two-state behavior. This assumption is mainly based on in vivo intracellular recordings under urethane and/or ketamine-xylazine anesthesia showing that striatal neurons oscillate between two preferred membrane potentials, a Down state (hyperpolarized level), resulting from an inwardly rectifying potassium conductance, and an Up state (depolarized level) caused by complex interactions between a barrage of cortical synaptic excitation and voltage-dependent potassium conductances. However, a recent comparative study using different anesthetics showed that striatal neurons can exhibit various shapes of synaptic activity depending on the temporal structure and the degree of synchronization of their cortico-striatal afferents. These new data demonstrate that the "classical" Up and Down states do not provide the unique spontaneous activity that can be encountered in striatal neurons in vivo. Rather we propose that striatal neurons should exhibit various synaptic activities and firing patterns depending on the states of vigilance. This hypothesis would be validated in further experiments in which the intracellular activity of striatal neurons will be recorded during the natural sleep-wake cycle. 相似文献
104.
Ndd, the Bacteriophage T4 Protein That Disrupts the Escherichia coli Nucleoid, Has a DNA Binding Activity
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Early in a bacteriophage T4 infection, the phage ndd gene causes the rapid destruction of the structure of the Escherichia coli nucleoid. Even at very low levels, the Ndd protein is extremely toxic to cells. In uninfected E. coli, overexpression of the cloned ndd gene induces disruption of the nucleoid that is indistinguishable from that observed after T4 infection. A preliminary characterization of this protein indicates that it has a double-stranded DNA binding activity with a preference for bacterial DNA rather than phage T4 DNA. The targets of Ndd action may be the chromosomal sequences that determine the structure of the nucleoid. 相似文献
105.
Alois Honk Vojtch Jaroik Laurent Lapchin Jean-Michel Rabasse 《Entomologia Experimentalis et Applicata》1998,87(2):191-200
The effect of simulated plant stress and parasitism by Aphelinus abdominalis (Dalman) on the mobility of four species of aphids was investigated. The aphids were placed on water stressed potted plants or on excised leaf segments on dry or moist filter-paper in Petri dishes. Winter wheat (Triticum aestivum) was infested with Metopolophium dirhodum (Walker), Sitobion avenae (F.) and Rhopalosiphum padi (L.) (segments only), aubergine (Solanum melongena) leaf segments with Macrosiphum euphorbiae (Thomas). The aphids that moved off the plants were removed and their development stage determined at 24-h (drought-stressed plants) or 3-h (leaf segments) intervals. On intact plants, aphid larvae were reluctant to move, and only moved after moulting into adults. On cut leaves, young 1st and 2nd instar larvae were more reluctant to move than 3rd and 4th instar larvae and adults. The numbers moving were initially positively correlated with aphid population density, and in M. euphorbiae occurred mainly during the night. Depending on aphid species and parasitoid age, parasitism by A. abdominalis retarded or accelerated movement, but the differences between young and old larvae and adults persisted after parasitism. A. abdominalis lays male eggs in small hosts and female eggs in large hosts. Consequently, its sex ratio was affected by differential movement of the host aphids of the male and female parasitoids. Old larvae and adult aphids readily moved and carried off female parasitoids, while the small aphids were more likely to remain and give rise to male-biased sex ratios. 相似文献
106.
In Vivo Evidence That the Stromelysin-3 Metalloproteinase Contributes in a Paracrine Manner to Epithelial Cell Malignancy 总被引:8,自引:0,他引:8
Rgis Masson Olivier Lefebvre Agns Noël Mostapha El Fahime Marie-Pierre Chenard Corinne Wendling Florence Kebers Marianne LeMeur Andre Dierich Jean-Michel Foidart Paul Basset Marie-Christine Rio 《The Journal of cell biology》1998,140(6):1535-1541
Stromelysin-3 (ST3; Basset, P., J.P. Bellocq, C. Wolf, I. Stoll, P. Hutin, J.M. Limacher, O.L. Podhajcer, M.P. Chenard, M.C. Rio, P. Chambon. 1990. Nature. 348:699–704) is a matrix metalloproteinase (MMP) expressed in mesenchymal cells located close to epithelial cells, during physiological and pathological tissue remodeling processes. In human carcinomas, high ST3 levels are associated with a poor clinical outcome, suggesting that ST3 plays a role during malignant processes. In this study we report the ST3 gene inactivation by homologous recombination. Although ST3 null mice (ST3−/−) were fertile and did not exhibit obvious alterations in appearance and behavior, the lack of ST3 altered malignant processes. Thus, the suppression of ST3 results in a decreased 7,12-dimethylbenzanthracene-induced tumorigenesis in ST3−/− mice. Moreover, ST3−/− fibroblasts have lost the capacity to promote implantation of MCF7 human malignant epithelial cells in nude mice (P < 0.008). Finally, we show that this ST3 paracrine function requires extracellular matrix (ECM)-associated growth factors. Altogether, these findings give evidence that ST3 promotes, in a paracrine manner, homing of malignant epithelial cells, a key process for both primary tumors and metastases. Therefore, ST3 represents an appropriate target for specific MMP inhibitor(s) in future therapeutical approaches directed against the stromal compartment of human carcinomas. 相似文献
107.
108.
Nassima Chikhi-Chorfi Chuong Pham-Huy Hervé Galons Nathalie Manuel William Lowenstein Jean-Michel Warnet Jean-Roger Claude 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,718(2):98
A rapid gas–liquid chromatographic assay is developed for the quantification of methadone (Mtd) and its major metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), in biological fluids of opiate addicts. After alkaline extraction from samples with lidocaine hydrochloride as internal standard, Mtd and EDDP are separated on SP-2250 column at 220°C and detected with a thermionic detector. The chromatographic time is about 6 min. The relative standard deviations (R.S.D.) of Mtd and EDDP standards are between 1.5 and 5.5%. Most drugs of abuse (morphine, codeine, narcotine, cocaine, benzoylecgonine, cocaethylene, dextropropoxyphene etc) are shown not to interfere with this technique. The method has been applied to study the levels of Mtd and EDDP metabolite in serum, saliva and urine of patients under maintenance treatment for opiate dependence. EDDP levels were found higher than those of Mtd in urine samples from four treated patients, but lower in serum and undetectable in saliva. However, Mtd concentrations were higher in saliva than in serum. 相似文献
109.
Adrian Patrut Karl F. von Reden Pascal Danthu Jean-Michel Leong Pock-Tsy Roxana T. Patrut Daniel A. Lowy 《PloS one》2015,10(3)
We extended our research on the architecture, growth and age of trees belonging to the genus Adansonia, by starting to investigate large individuals of the most widespread Malagasy species. Our research also intends to identify the oldest baobabs of Madagascar. Here we present results of the radiocarbon investigation of the two most representative Adansonia rubrostipa (fony baobab) specimens, which are located in south-western Madagascar, in the Tsimanampetsotse National Park. We found that the fony baobab called “Grandmother” consists of 3 perfectly fused stems of different ages. The radiocarbon date of the oldest sample was found to be 1136 ± 16 BP. We estimated that the oldest part of this tree, which is mainly hollow, has an age close to 1,600 yr. This value is comparable to the age of the oldest Adansonia digitata (African baobab) specimens. By its age, the Grandmother is a major candidate for the oldest baobab of Madagascar. The second investigated specimen, called the “polygamous baobab”, consists of 6 partially fused stems of different ages. According to dating results, this fony baobab is 1,000 yr old. This research is the first investigation of the structure and age of Malagasy baobabs. 相似文献
110.
Maud Gits-Muselli Marie-Noelle Peraldi Nathalie de Castro Véronique Delcey Jean Menotti Nicolas Guigue Samia Hamane Emmanuel Raffoux Anne Bergeron Sandrine Valade Jean-Michel Molina Stéphane Bretagne Alexandre Alanio 《PloS one》2015,10(5)
Pneumocystis pneumonia is a severe opportunistic infection in immunocompromised patients caused by the unusual fungus Pneumocystis jirovecii. Transmission is airborne, with both immunocompromised and immunocompetent individuals acting as a reservoir for the fungus. Numerous reports of outbreaks in renal transplant units demonstrate the need for valid genotyping methods to detect transmission of a given genotype. Here, we developed a short tandem repeat (STR)-based molecular typing method for P. jirovecii. We analyzed the P. jirovecii genome and selected six genomic STR markers located on different contigs of the genome. We then tested these markers in 106 P. jirovecii PCR-positive respiratory samples collected between October 2010 and November 2013 from 91 patients with various underlying medical conditions. Unique (one allele per marker) and multiple (more than one allele per marker) genotypes were observed in 34 (32%) and 72 (68%) samples, respectively. A genotype could be assigned to 55 samples (54 patients) and 61 different genotypes were identified in total with a discriminatory power of 0.992. Analysis of the allelic distribution of the six markers and minimum spanning tree analysis of the 61 genotypes identified a specific genotype (Gt21) in our hospital, which may have been transmitted between 10 patients including six renal transplant recipients. Our STR-based molecular typing method is a quick, cheap and reliable approach to genotype Pneumocystis jirovecii in hospital settings and is sensitive enough to detect minor genotypes, thus enabling the study of the transmission and pathophysiology of Pneumocystis pneumonia. 相似文献