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101.
A high-performance liquid chromatography (HPLC) method has been developed to quantify the major and modified nucleoside composition of total, unfractionated transfer RNA. The method is rapid and sensitive and offers a high degree of chromatographic resolution suitable for quantifying both stable and unstable modified nucleosides. It is nondestructive and allows the recovery of nucleosides for further characterization. We apply the method in the analysis of the 29 modified nucleosides in tRNA from Salmonella typhimurium (and Escherichia coli) and show it to be useful in examining changes in the modified nucleoside content of tRNA. Such changes may be important in regulation. 相似文献
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Kemp S Wheate NJ Buck DP Nikac M Collins JG Aldrich-Wright JR 《Journal of inorganic biochemistry》2007,101(7):1049-1058
Fifteen platinum(II)-based metallointercalators have been synthesised that utilise substituted 1,10-phenanthroline (phen) ligands, including 5-chloro-1,10-phenanthroline (5-Cl-phen), 5-methyl-1,10-phenanthroline (5-CH3-phen), 5-amino-1,10-phenanthroline (5-NH2-phen), 5-nitro-1,10-phenanthroline (5-NO2-phen) and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), and achiral ethylenediamine (en) and the chiral ancillary ligands 1S,2S-diaminocyclohexane (S,S-dach) and 1R,2R-diaminocyclohexane (R,R-dach). Their cytotoxicity in the L1210 murine leukaemia cell line was determined using growth inhibition assays. The most cytotoxic metal complexes are those that contain S,S-dach ancillary ligands and 5-CH3-phen intercalating ligands. One metallointercalator [Pt(5-CH3-phen)(S,S-dach)]Cl2 (5MESS), displays a 5-10-fold increase in cytotoxicity compared to the clinical agent cisplatin. From DNA binding experiments there appears to be no significant difference between any of the metal complexes, indicating that neither DNA binding affinity nor the mode of binding/DNA adduct formed is the sole determinant of the cytotoxicity of this family of platinum(II)-based metallointercalators. 相似文献
104.
Effects of nutritional restriction on nitrogen and carbon stable isotopes in growing seabirds 总被引:4,自引:0,他引:4
When using stable isotopes as dietary tracers it is essential to consider effects of nutritional state on isotopic fractionation.
While starvation is known to induce enrichment of 15N in body tissues, effects of moderate food restriction on isotope signatures have rarely been tested. We conducted two experiments
to investigate effects of a 50–55% reduction in food intake on δ15N and δ13C values in blood cells and whole blood of tufted puffin chicks, a species that exhibits a variety of adaptive responses to
nutritional deficits. We found that blood from puffin chicks fed ad libitum became enriched in 15N and 13C compared to food-restricted chicks. Our results show that 15N enrichment is not always associated with food deprivation and argue effects of growth on diet–tissue fractionation of nitrogen
stable isotopes (Δ15N) need to be considered in stable isotope studies. The decrease in δ13C of whole blood and blood cells in restricted birds is likely due to incorporation of carbon from 13C-depleted lipids into proteins. Effects of nutritional restriction on δ15N and δ13C values were relatively small in both experiments (δ15N: 0.77 and 0.41‰, δ13C: 0.20 and 0.25‰) compared to effects of ecological processes, indicating physiological effects do not preclude the use of
carbon and nitrogen stable isotopes in studies of seabird ecology. Nevertheless, our results demonstrate that physiological
processes affect nitrogen and carbon stable isotopes in growing birds and we caution isotope ecologists to consider these
effects to avoid drawing spurious conclusions. 相似文献
105.
Marker-free transgenic plants through genetically programmed auto-excision 总被引:4,自引:0,他引:4 下载免费PDF全文
We present here a vector system to obtain homozygous marker-free transgenic plants without the need of extra handling and within the same time frame as compared to transformation methods in which the marker is not removed. By introducing a germline-specific auto-excision vector containing a cre recombinase gene under the control of a germline-specific promoter, transgenic plants become genetically programmed to lose the marker when its presence is no longer required (i.e. after the initial selection of primary transformants). Using promoters with different germline functionality, two modules of this genetic program were developed. In the first module, the promoter, placed upstream of the cre gene, confers CRE functionality in both the male and the female germline or in the common germline (e.g. floral meristem cells). In the second module, a promoter conferring single germline-specific CRE functionality was introduced upstream of the cre gene. Promoter sequences used in this work are derived from the APETALA1 and SOLO DANCERS genes from Arabidopsis (Arabidopsis thaliana) Columbia-0 conferring common germline and single germline functionality, respectively. Introduction of the genetic program did not reduce transformation efficiency. Marker-free homozygous progeny plants were efficiently obtained, regardless of which promoter was used. In addition, simplification of complex transgene loci was observed. 相似文献
106.
Central nervous system regulation of mammalian hibernation: implications for metabolic suppression and ischemia tolerance 总被引:1,自引:0,他引:1
Drew KL Buck CL Barnes BM Christian SL Rasley BT Harris MB 《Journal of neurochemistry》2007,102(6):1713-1726
Torpor during hibernation defines the nadir of mammalian metabolism where whole animal rates of metabolism are decreased to as low as 2% of basal metabolic rate. This capacity to decrease profoundly the metabolic demand of organs and tissues has the potential to translate into novel therapies for the treatment of ischemia associated with stroke, cardiac arrest or trauma where delivery of oxygen and nutrients fails to meet demand. If metabolic demand could be arrested in a regulated way, cell and tissue injury could be attenuated. Metabolic suppression achieved during hibernation is regulated, in part, by the central nervous system through indirect and possibly direct means. In this study, we review recent evidence for mechanisms of central nervous system control of torpor in hibernating rodents including evidence of a permissive, hibernation protein complex, a role for A1 adenosine receptors, mu opiate receptors, glutamate and thyrotropin-releasing hormone. Central sites for regulation of torpor include the hippocampus, hypothalamus and nuclei of the autonomic nervous system. In addition, we discuss evidence that hibernation phenotypes can be translated to non-hibernating species by H(2)S and 3-iodothyronamine with the caveat that the hypothermia, bradycardia, and metabolic suppression induced by these compounds may or may not be identical to mechanisms employed in true hibernation. 相似文献
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108.
Van Coillie E Goris J Cleenwerck I Grijspeerdt K Botteldoorn N Van Immerseel F De Buck J Vancanneyt M Swings J Herman L Heyndrickx M 《Journal of applied microbiology》2007,102(4):1095-1106
AIMS: To select Lactobacillus strains from laying hens for potential use as probiotic to control Salmonella Enteritidis infection. METHODS AND RESULTS: One hundred and eighty-six lactobacilli were isolated from the cloaca and vagina of laying hens, and identified at the species level by a polyphasic taxonomic approach. All isolates belonged to the Lactobacillus acidophilus, Lactobacillus reuteri or Lactobacillus salivarius phylogenetic groups, with the L. reuteri group being the most predominant group. Based on genetic diversity, about 50 representative strains were selected and tested for in vitro properties that could be predictive for probiotic activity in laying hens. Salmonella inhibition was shown to be species dependent, and correlated to some extent with the production of lactic acid. A selection of strains was evaluated in a S. Enteritidis challenge experiment. Two strains, L. reuteri R-17485 and Lactobacillus johnsonii R-17504 significantly decreased the colonization of chicks by S. Enteritidis in caeca, liver and spleen. CONCLUSIONS: Lactobacilli isolated from laying hens were observed to inhibit Salmonella growth in vitro, most probably through production of lactic acid, and to decrease in vivo the S. Enteritidis colonization of chicks. SIGNIFICANCE AND IMPACT OF THE STUDY: The data demonstrate that Lactobacillus isolates from laying hens may have probiotic potential in reducing S. Enteritidis infection. 相似文献
109.
Auxotrophy and intrapopulation complementary in the ‘interactome’ of a cultivated freshwater model community 下载免费PDF全文
Sarahi L. Garcia Moritz Buck Katherine D. McMahon Hans‐Peter Grossart Alexander Eiler Falk Warnecke 《Molecular ecology》2015,24(17):4449-4459
Microorganisms are usually studied either in highly complex natural communities or in isolation as monoclonal model populations that we manage to grow in the laboratory. Here, we uncover the biology of some of the most common and yet‐uncultured bacteria in freshwater environments using a mixed culture from Lake Grosse Fuchskuhle. From a single shotgun metagenome of a freshwater mixed culture of low complexity, we recovered four high‐quality metagenome‐assembled genomes (MAGs) for metabolic reconstruction. This analysis revealed the metabolic interconnectedness and niche partitioning of these naturally dominant bacteria. In particular, vitamin‐ and amino acid biosynthetic pathways were distributed unequally with a member of Crenarchaeota most likely being the sole producer of vitamin B12 in the mixed culture. Using coverage‐based partitioning of the genes recovered from a single MAG intrapopulation metabolic complementarity was revealed pointing to ‘social’ interactions for the common good of populations dominating freshwater plankton. As such, our MAGs highlight the power of mixed cultures to extract naturally occurring ‘interactomes’ and to overcome our inability to isolate and grow the microbes dominating in nature. 相似文献
110.