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991.
Eftimie R Dushoff J Bridle BW Bramson JL Earn DJ 《Bulletin of mathematical biology》2011,73(12):2932-2961
Recent advances in virology, gene therapy, and molecular and cell biology have provided insight into the mechanisms through
which viruses can boost the anti-tumor immune response, or can infect and directly kill tumor cells. A recent experimental
report (Bridle et al. in Molec. Ther. 18(8):1430–1439, 2010) showed that a sequential treatment approach that involves two viruses that carry the same tumor antigen leads to an improved
anti-tumor response compared to the effect of each virus alone. In this article, we derive a mathematical model to investigate
the anti-tumor effect of two viruses, and their interactions with the immune cells. We discuss the conditions necessary for
permanent tumor elimination and, in this context, we stress the importance of investigating the long-term effect of non-linear
interactions. In particular, we discuss multi-stability and multi-instability, two complex phenomena that can cause abrupt
transitions between different states in biological and physical systems. In the context of cancer immunotherapies, the transitions
between a tumor-free and a tumor-present state have so far been associated with the multi-stability phenomenon. Here, we show
that multi-instability can also cause the system to switch from one state to the other. In addition, we show that the multi-stability
is driven by the immune response, while the multi-instability is driven by the presence of the virus. 相似文献
992.
993.
Hélène Pereira Jean-François Martin Charlotte Joly Jean-Louis Sébédio Estelle Pujos-Guillot 《Metabolomics : Official journal of the Metabolomic Society》2010,6(2):207-218
In order to study the effect of a diet on metabolites found in body fluids such as plasma, we have developed and validated
a UPLC/MS method. While methods using NMR have been well established to analyse different biological tissues, recent studies
have described robust untargeted UPLC-MS methods for plasma analysis. One major concern when profiling plasma is the presence
of an important quantity of proteins which have to be precipitated without any loss of metabolites prior to LC/MS analysis.
The utilization of untargeted approaches in nutritional metabolomics still suffers from the lack of identification of specific
biomarkers. We therefore suggest an alternative method still using a global approach but focusing at the same time on metabolites
previously described in human plasma in order to detect biomarkers of metabolic dysregulations. Thus, to fulfil our objectives,
analytical parameters were tested (i) the anticoagulant type for sample collection, (ii) the protein precipitation method
and (iii) UPLC/MS analytical conditions. Three protein precipitation methods and two anticoagulants were tested and compared.
The method utilizing blood collection on heparin and methanol precipitation was chosen for giving the most reproducible results
while keeping the complexity of the sample. Finally, a validation was proposed to evaluate the stability of this analytical
method applied to a large batch of samples for nutritional metabolomic studies. 相似文献
994.
ATP-binding cassette (ABC) transporters serve as importers and exporters for a wide variety of solutes in both prokaryotes
and eukaryotes, and are implicated in microbial drug resistance and a number of significant human genetic disorders. Initial
crystal structures of the soluble nucleotide binding domains (NBDs) of ABC transporters, while a significant step towards
understanding the coupling of ATP binding and hydrolysis to transport, presented researchers with important questions surrounding
the role of the signature sequence residues, the composition of the nucleotide binding sites, and the mode of NBD dimerization
during the transport reaction cycle. Recent studies have begun to address these concerns. This mini-review summarizes the
biochemical and structural characterizations of two archaebacterial NBDs from Methanocaldococcus jannaschii, MJ0796 and MJ1267, and offers current perspectives on the functional mechanism of ABC transporters. 相似文献
995.
用Lowry法测定冻干注射用胸腺肽中多肽含量时,由于冻干前所加赋形剂甘露醇的干扰,其测定结果明显偏高(P<0.0005)。本文经试验证明,用等量于检品中的甘露醇作空白对照,可以消除这种干扰。 相似文献
996.
Previous work has shown that bacterial isolates from the sheep rumen are capable of detoxifying 2,4,6-trinitrotoluene (TNT)
into polar constituents. In this study, the dietary effects of TNT on the sheep rumen microbial community were evaluated using
molecular microbiology ecology tools. Rumen samples were collected from sheep fed with and without TNT added to their diet,
genomic DNA was extracted, and the 16S rRNA-V3 gene marker was used to quantify changes in the microbial population in the
rumen. Control and treatment samples yielded 533 sequences. Phylogenetic analyses were performed to determine the microbial
changes between the two conditions. Results indicated the predominant bacterial populations present in the rumen were comprised
of the phyla Firmicutes and Bacteroidetes, irrespective of presence/absence of TNT in the diet. Significant differences (P < 0.001) were found between the community structure of the bacteria under TNT (−) and TNT (+) diets. Examination of the TNT
(+) diet showed an increase in the clones belonging to family Ruminococcaceae, which have previously been shown to degrade
TNT in pure culture experiments. 相似文献
997.
Konishi MA Fukuoka T Shimane Y Mori K Nagano Y Ohta Y Kitamoto D Hatada Y 《Biotechnology letters》2011,33(1):139-145
Purpose of work
To explore a novel glycolipid, we performed biochemical reactions using a recombinant α-glucosidase from Geobacillus sp. which shows excellent transglycosylation reaction to hydroxyl groups in a variety of compounds. 相似文献998.
The microbial population of geothermally heated sediments in a shallow bay of Vulcano Island (Italy) was characterized with
respect to metabolic activities and the putatively catalyzing hyperthermophiles. Site-specific anoxic culturing media, most
of which were amended with combinations of electron donors (glucose or carboxylic acids) and acceptors (sulfate), were used
for selective enrichment of metabolically defined subpopulations. The mostly archaeal chemoautotrophs produced formate at
rates of 3.25 and 0.46 fmol cell−1 day−1 with and without sulfate, respectively. The glucose fermenting heterotrophs produced acetate (18 fmol cell−1 day−1) and lactate (2.6 fmol cell−1 day−1) and were identified as predominantly Thermus sp. and coccoid archaea. These archaeal cells also metabolized lactate (5.6 fmol cell−1 day−1), but neither formate nor acetate. The heterotrophic culture enriched on formate/acetate/propionate/sulfate utilized mainly
formate (27 fmol cell−1 day−1) and lactate (89–195 fmol cell−1 day−1), and consumed sulfate (38–68 fmol cell−1 day−1). These formate or lactate consuming sulfate reducers were dominated by Archaeoglobales (7% in situ) and unidentified Archaea.
The in situ benthic community comprised 15% Crenarchaeota, a significant group only in the autotrophic cultures, and 3% Thermus sp., the putatively predominant group involved in fermentative metabolism. The role of Thermoccales (4% in situ) remained
undisclosed in our experiments. This first comprehensive data set established plausible links between several groups of hyperthermophiles
in shallow marine hydrothermal systems, their metabolic function within the benthic microbial community, and biogeochemical
turnover rates. 相似文献
999.
We introduce a novel computational approach to predict effective genome size (EGS; a measure that includes multiple plasmid copies, inserted sequences, and associated phages and viruses) from short sequencing reads of environmental genomics (or metagenomics) projects. We observe considerable EGS differences between environments and link this with ecologic complexity as well as species composition (for instance, the presence of eukaryotes). For example, we estimate EGS in a complex, organism-dense farm soil sample at about 6.3 megabases (Mb) whereas that of the bacteria therein is only 4.7 Mb; for bacteria in a nutrient-poor, organism-sparse ocean surface water sample, EGS is as low as 1.6 Mb. The method also permits evaluation of completion status and assembly bias in single-genome sequencing projects. 相似文献
1000.
Inventory and monitoring of wine microbial consortia 总被引:2,自引:0,他引:2
The evolution of the wine microbial ecosystem is generally restricted to Saccharomyces cerevisiae and Oenococcus oeni, which are the two main agents in the transformation of grape must into wine by acting during alcoholic and malolactic fermentation,
respectively. But others species like the yeast Brettanomyces bruxellensis and certain ropy strains of Pediococcus parvulus can spoil the wine. The aim of this study was to address the composition of the system more precisely, identifying other
components. The advantages of the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) approach to
wine microbial ecology studies are illustrated by bacteria and yeast species identification and their monitoring at each stage
of wine production. After direct DNA extraction, PCR-DGGE was used to make the most exhaustive possible inventory of bacteria
and yeast species found in a wine environment. Phylogenetic neighbor-joining trees were built to illustrate microbial diversity.
PCR-DGGE was also combined with population enumeration in selective media to monitor microbial changes at all stages of production.
Moreover, enrichment media helped to detect the appearance of spoilage species. The genetic diversity of the wine microbial
community and its dynamics during winemaking were also described. Most importantly, our study provides a better understanding
of the complexity and diversity of the wine microbial consortium at all stages of the winemaking process: on grape berries,
in must during fermentation, and in wine during aging. On grapes, 52 different yeast species and 40 bacteria could be identified.
The diversity was dramatically reduced during winemaking then during aging. Yeast and lactic acid bacteria were also isolated
from very old vintages. B. bruxellensis and O. oeni were the most frequent. 相似文献