Home About us Contact
|
Home About us Contact | ||
|
|
||
Independent Experiments (independent + experiment)
Selected AbstractsModeling and simulation of the formation and utilization of microbial products in aerobic granular sludgeAICHE JOURNAL, Issue 2 2010Bing-Jie Ni Abstract A mathematical model is established to simulate the formation of extracellular polymeric substances (EPS), soluble microbial products (SMP), and internal storage products (XSTO) in aerobic granular sludge. The sensitivity of these microbial products concentrations toward the key model parameters is analyzed. Independent experiments are conducted to find required parameter values and to test its predictive ability. The model is evaluated by using one-cycle operating experimental results of a lab-scale aerobic granule-based sequencing batch reactor (SBR) and batch experimental results. Results show that the model is able to describe the microbial product dynamics in aerobic granules and provide further insights into a granule-based SBR. The effect of the initial substrate and biomass concentrations on the formation of microbial products in aerobic granular sludge can therefore be analyzed by model simulation. A higher substrate concentration results in a greater concentration of EPS, SMP, and XSTO. An accumulation of biomass in the bioreactor leads to an increased production rate of EPS, SMP, and XSTO. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Genotoxicity of inorganic lead salts and disturbance of microtubule functionENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 4 2005Daniela Bonacker Abstract Lead compounds are known genotoxicants, principally affecting the integrity of chromosomes. Lead chloride and lead acetate induced concentration-dependent increases in micronucleus frequency in V79 cells, starting at 1.1 ,M lead chloride and 0.05 ,M lead acetate. The difference between the lead salts, which was expected based on their relative abilities to form complex acetato-cations, was confirmed in an independent experiment. CREST analyses of the micronuclei verified that lead chloride and acetate were predominantly aneugenic (CREST-positive response), which was consistent with the morphology of the micronuclei (larger micronuclei, compared with micronuclei induced by a clastogenic mechanism). The effects of high concentrations of lead salts on the microtubule network of V79 cells were also examined using immunofluorescence staining. The dose effects of these responses were consistent with the cytotoxicity of lead(II), as visualized in the neutral-red uptake assay. In a cell-free system, 20,60 ,M lead salts inhibited tubulin assembly dose-dependently. The no-observed-effect concentration of lead(II) in this assay was 10 ,M. This inhibitory effect was interpreted as a shift of the assembly/disassembly steady-state toward disassembly, e.g., by reducing the concentration of assembly-competent tubulin dimers. The effects of lead salts on microtubule-associated motor-protein functions were studied using a kinesin-gliding assay that mimics intracellular transport processes in vitro by quantifying the movement of paclitaxel-stabilized microtubules across a kinesin-coated glass surface. There was a dose-dependent effect of lead nitrate on microtubule motility. Lead nitrate affected the gliding velocities of microtubules starting at concentrations above 10 ,M and reached half-maximal inhibition of motility at about 50 ,M. The processes reported here point to relevant interactions of lead with tubulin and kinesin at low dose levels. Environ. Mol. Mutagen., 2005. © 2005 Wiley-Liss, Inc. [source] Social context affects testosterone-induced singing and the volume of song control nuclei in male canaries (Serinus canaria)DEVELOPMENTAL NEUROBIOLOGY, Issue 10 2006Géraldine Boseret Abstract The contribution of social factors to seasonal plasticity in singing behavior and forebrain nuclei controlling song, and their interplay with gonadal steroid hormones are still poorly understood. In many songbird species, testosterone (T) enhances singing behavior but elevated plasma T concentrations are not absolutely required for singing to occur. Singing is generally produced either to defend a territory or to attract a mate and it is therefore not surprising that singing rate can be influenced by the sex and behavior of the social partner. We investigated, based on two independent experiments, the effect of the presence of a male or female partner on the rate of song produced by male canaries. In the first experiment, song rate was measured in dyads composed of one male and one female (M-F) or two males (M-M). Birds were implanted with T-filled Silastic capsules or with empty capsules as control. The number of complete song bouts produced by all males was recorded during 240 min on week 1, 2, 4, and 8 after implantation. On the day following each recording session, brains from approximately one-fourth of the birds were collected and the volumes of the song control nuclei HVC and RA were measured. T increased the singing rate and volume of HVC and RA but these effects were affected by the social context. Singing rates were higher in the M-M than in the M-F dyads. Also, in the M-M dyads a dominance-subordination relationship soon became established and dominant males sang at higher rates than subordinates in T-treated but not in control pairs. The differences in song production were not reflected in the size of the song control nuclei: HVC was larger in M-F than in M-M males and within the M-M dyads, no difference in HVC or RA size could be detected between dominant and subordinate males. At the individual level, the song rate with was positively correlated with RA and to a lower degree HVC volume, but this relationship was observed only in M-M dyads, specifically in dominant males. A second experiment, carried out with castrated males that were all treated with T and exposed either to another T-treated castrate or to an estradiol-implanted female, confirmed that song rate was higher in the M-M than in the M-F condition and that HVC volume was larger in heterosexual than in same-sex dyads. The effects of T on singing rate and on the volume of the song control nuclei are thus modulated by the social environment, including the presence/absence of a potential mate and dominance status among males. 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Linking environmental warming to the fitness of the invasive clam Corbicula flumineaGLOBAL CHANGE BIOLOGY, Issue 12 2009MARKUS WEITERE Abstract Climate warming is discussed as a factor that can favour the success of invasive species. In the present study, we analysed potential fitness gains of moderate warming (3 °C above field temperature) on the invasive clam Corbicula fluminea during summer and winter. The experiments were conducted under seminatural conditions in a bypass-system of a large river (Rhine, Germany). We showed that warming in late summer results in a significant decrease in the clams' growth rates (body mass and shell length increase) and an increase in mortality rate. The addition of planktonic food dampens the negative effect of warming on the growth rates. This suggests that the reason for the negative growth effect of temperature increase in late summer is a negative energetic balance caused by an enhanced metabolic rate at limited food levels. Warming during early summer revealed contrasting effects with respect of body mass (no warming effect) and shell length (increased shell growth with warming). This differential control of both parameters further enhances the loss of the relative (size-specific) body mass with warming. In contrast, warming in winter had a consistently positive effect on the clams' growth rate as demonstrated in two independent experiments. Furthermore, the reproduction success (as measured by the average number of larvae per clam) during the main breeding period (April) was strongly enhanced by experimental warming during winter, i.e. by eight times during the relatively cold winter 2005/2006 and by 2.6 times during the relatively warm winter 2007/2008. This strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere. However, warm summer events might counteract the positive winter warming effect, which could balance out the fitness gains. [source] Proteome analysis of rat hepatic stellate cellsHEPATOLOGY, Issue 2 2000Dan Bach Kristensen Proteome analysis was performed on cellular and secreted proteins of normal (quiescent) and activated rat hepatic stellate cells. The stellate cells were activated either in vitro by cultivating quiescent stellate cells for 9 days or in vivo by injecting rats with carbon tetrachloride for 8 weeks. A total of 43 proteins/polypeptides were identified, which altered their expression levels when the cells were activated in vivo and/or in vitro. Twenty-seven of them showed similar changes in vivo and in vitro, including up-regulated proteins such as calcyclin, calgizzarin, and galectin-1 as well as down-regulated proteins such as liver carboxylesterase 10 and serine protease inhibitor 3. Sixteen of them showed different expression levels between in vivo and in vitro activated stellate cells. These results were reproducibly obtained in 3 independent experiments. The up-regulation of calcyclin, calgizzarin, and galectin-1, as well as the down-regulation of liver carboxylesterase 10 were directly confirmed in fibrotic liver tissues. Northern blots confirmed up-regulation of the messenger RNAs (mRNAs) of calcyclin, calgizzarin, and galectin-1 in activated stellate cells, indicating that these changes were controlled at the mRNA level. In addition a list compiling over 150 stellate cell proteins is presented. The data presented here thus provide a significant new protein-level insight into the activation of hepatic stellate cells, a key event in liver fibrogenesis. [source] Germ-line transformation of the South American malaria vector, Anopheles albimanus, with a piggyBac/EGFP transposon vector is routine and highly efficientINSECT MOLECULAR BIOLOGY, Issue 4 2002O. P. Perera Abstract Stable and efficient germ-line transformation was achieved in the South American malaria vector, Anopheles albimanus, using a piggyBac vector marked with an enhanced green fluorescent protein gene regulated by the Drosophila melanogaster polyubiquitin promoter. Transgenic mosquitoes were identified from four independent experiments at frequencies ranging from 20 to 43% per fertile G0. Fluorescence was observable throughout the body of larvae and pupae, and abdominal segments of adults. Transgenic lines analysed by Southern hybridization had one to six germ-line integrations, with most lines having three or more integrations. Hybridized transposon vector fragments and insertion site sequences were consistent with precise piggyBac -mediated integrations, although this was not verified for all lines. The piggyBac/PUbnlsEGFP vector appears to be a robust transformation system for this anopheline species, in contrast to the use of a piggyBac vector in An. gambiae. Further tests are needed to determine if differences in anopheline transformation efficiency are due to the marker systems or to organismal or cellular factors specific to the species. [source] Quantifying Phytophthora medicaginis in Susceptible and Resistant Alfalfa with a Real-Time Fluorescent PCR AssayJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2003G. J. Vandemark Abstract A real-time fluorescent PCR assay using a set of specific primers and a fluorochrome-labelled probe (TaqMan) was developed to quantify the amount of Phytophthora medicaginis DNA in alfalfa plants that were classified as either resistant or susceptible to the pathogen based on visual assessment of disease response. The assay clearly discriminated among three standard check alfalfa populations with different levels of resistance based on the analysis of DNA extracted from the roots of bulked plant samples. In two independent experiments, the Spearman rank correlation between pathogen DNA content and the number of susceptible plants in a bulked sample was greater than 0.89 and highly significant (P<0.0001). Significantly less pathogen DNA was detected in bulked samples of a highly resistant check population than in bulked samples from more susceptible check populations. Analysis of individual plants indicated that significantly less pathogen DNA was detected in resistant plants than in susceptible plants. Applications of the assay are considered for breeding programs and the study of microbial population dynamics in plants simultaneously infected with different pathogens. [source] Effect of temperature on the chromatographic retention of ionizable compounds.JOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2008Abstract We propose a general simple equation for accurately predicting the retention factors of ionizable compounds upon simultaneous changes in mobile phase pH and column temperature at a given hydroorganic solvent composition. Only four independent experiments provide the input data: retention factors measured in two pH buffered mobile phases at extreme acidic and basic pH values (e. g., at least ± 2 pH units far from the analyte pKa) and at two column temperatures. The equations, derived from the basic thermodynamics of the acid,base equilibria, additionally require the knowledge of the solute pKa and enthalpies of acid,base dissociation of both the solute and the buffer components in the hydroorganic solvent mixture. The performance of the predictive model is corroborated with the comparison between theoretical and experimental retention factors of several weak acids and bases of important pharmacological activity, in mobile phases containing different buffer solutions prepared in 25% w/w ACN in water and at several temperatures. [source] Genome-wide analysis of the general stress response in Bacillus subtilisMOLECULAR MICROBIOLOGY, Issue 4 2001Chester W. Price Bacteria respond to diverse growth-limiting stresses by producing a large set of general stress proteins. In Bacillus subtilis and related Gram-positive pathogens, this response is governed by the ,B transcription factor. To establish the range of cellular functions associated with the general stress response, we compared the transcriptional profiles of wild and mutant strains under conditions that induce ,B activity. Macroarrays representing more than 3900 annotated reading frames of the B. subtilis genome were hybridized to 33P-labelled cDNA populations derived from (i) wild-type and sigB mutant strains that had been subjected to ethanol stress; and (ii) a strain in which ,B expression was controlled by an inducible promoter. On the basis of their significant ,B -dependent expression in three independent experiments, we identified 127 genes as prime candidates for members of the ,B regulon. Of these genes, 30 were known previously or inferred to be ,B dependent by other means. To assist in the analysis of the 97 new genes, we constructed hidden Markov models (HMM) that identified possible ,B recognition sequences preceding 21 of them. To test the HMM and to provide an independent validation of the hybridization experiments, we mapped the ,B -dependent messages for seven representative genes. For all seven, the 5, end of the message lay near typical ,B recognition sequences, and these had been predicted correctly by the HMM for five of the seven examples. Lastly, all 127 gene products were assigned to functional groups by considering their similarity to known proteins. Notably, products with a direct protective function were in the minority. Instead, the general stress response increased relative message levels for known or predicted regulatory proteins, for transporters controlling solute influx and efflux, including potential drug efflux pumps, and for products implicated in carbon metabolism, envelope function and macromolecular turnover. [source] Use of decreasing foliar carbon isotope discrimination during water limitation as a carbon tracer to study whole plant carbon allocationPLANT CELL & ENVIRONMENT, Issue 5 2002S. K. Arndt Abstract Foliar carbon isotope discrimination (,) of C3 plants decreases in water-deficit situations as discrimination by the photosynthetic primary carboxylation reaction decreases. This diminished , in leaves under water deficit can be used as a tracer to study whole plant carbon allocation patterns. Carbon isotope composition (,13C value) of leaf hot water extracts or leaf tissue sap represents a short-term integral of leaf carbon isotope discrimination and thus represents the ,13C value of source carbon that may be distributed within a plant in water-deficit situations. By plotting the ,13C values of source carbon against the ,13C values of sink tissues, such as roots or stems, it is possible to assess carbon allocation to and incorporation into sink organs in relation to already present biomass. This natural abundance labelling method has been tested in three independent experiments, a one-year field study with the fruit tree species Ziziphus mauritiana and peach (Prunus persica), a medium-term drought stress experiment with Ziziphus rotundifolia trees in the glasshouse, and a short-term drought stress experiment with soybean (Glycine max). The data show that the natural abundance labelling method can be applied to qualitatively assess carbon allocation in drought-stressed plants. Although it is not possible to estimate exact fluxes of assimilated carbon during water deficit the method represents an easy to use tool to study integrated plant adaptations to drought stress. In addition, it is a less laborious method that can be applied in field studies as well as in controlled experiments, with plants from any developmental stage. [source] Novel two-stage screening procedure leads to the identification of a new class of transfection enhancersTHE JOURNAL OF GENE MEDICINE, Issue 6 2006Birgit Neukamm Abstract Background Non-viral gene transfer efficiency is low as compared to viral vector systems. Here we describe the discovery of new drugs that are capable of enhancing non-viral gene transfer into mammalian cells using a novel two-stage screening procedure. Methods First, potential candidates are preselected from a molecular library at various concentrations by a semi-automated yeast transfection screen (YTS). The maximal transfection efficiency of every positive drug is subsequently determined in independent experiments at the optimal concentration and compared to the inhibitory effect of the drug on cell growth (IC50). In a subsequent mammalian cell transfection screen (MTS), the maximal transfection efficiency and the IC50 are determined for all preselected drugs using a human cell line and a luciferase reporter gene construct. Results Employing our novel system we have been able to identify a new class of transfection enhancers, the tricyclic antidepressants (i.e. doxepin, maprotiline, desipramine and amoxapine). All positive drugs enhanced gene transfer in both yeast and human cell lines, but lower concentrations were sufficient for mammalian cells. With a triple combination of doxepin, amoxapine and chloroquine we obtained a transfection efficiency that exceeded that of chloroquine, one of the best-known transfection enhancers of mammalian cells, by nearly one order of magnitude. Conclusions Non-viral gene transfer efficiency can be increased significantly using new transfection enhancers that are identified by a novel, semi-automated two-stage screening system employing yeast cells in the first and specific human target cells in the second round. Copyright © 2006 John Wiley & Sons, Ltd. [source] ORIGINAL ARTICLE: How Should Data on Murine Spontaneous Abortion Rates be Expressed and Analyzed?AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 3 2008David A. Clark Problem, Spontaneous abortions in the CBA × DBA/2 model are normally reported as number of resorptions/total number of implantations (R/T), pooling data from individual mice. The significance of differences between groups has been determined using non-parametric statistics (e.g. chi-square or Fisher's Exact test) based on a priori predictions. Recently, it has been argued that medians with box plots should replace the accepted standard, but this deprives readers of data needed to verify P -values, and leads to inferences incompatible with biological and statistical reality. Method of study, Raw data on 173 individual CBA × DBA/2 matings were analyzed by median and mean, along with R/T data from 18 independent experiments containing 5,10 mice per group. Raw data from 19 CBA × BALB/c matings were similarly analyzed. Results, Individual CBA × DBA/2 mouse resorption rates showed a non-Gaussian distribution, but the mean and median differed by <0.5%. Resorption data from 6 and 12 independent pools of mice were normally distributed. Only the mean enabled a between-group P -value calculation. CBA × BALB/c matings gave a median of 0 and mean of 5.1%; the data were not normally distributed, but that was because of a bimodal distribution. One group of mice had 0 abortions, and the second a mean of 13.9% abortions, and the data from the latter group were normally distributed. Conclusion, Although it is possible to compare individual mice, and even individual implantation sites, in resorption (abortion) studies, as the relevant question is the significance of differences between treatment groups of mice, and reproducibility, the established classical method of reporting R/T should continue to be provided. In CBA × BALB/c matings, where abortion rates are low, using the median is misleading and may obscure the existence of two distinct populations. [source] Limitations of the Human-PBL-SCID Mouse Model for Vaginal Transmission of HIV-1AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 5 2007Osmond J. D'Cruz Problem SCID mice reconstituted with human peripheral blood lymphocytes (PBL) are amenable to vaginal transmission of HIV-1. We investigated the effectiveness of this model to establish systemic HIV-1 infection. Method of study Eighty progesterone-primed C.B-17 SCID mice were reconstituted with human-PBLs and intravaginally inoculated with CCR5 HIV-1 (BaL or 92BR09) infected human-PBLs in the presence of human semen. After two weeks, viral RNA load in spleen, peritoneal lavage (PL), and serum was quantitated by the nucleic acid sequence-based amplification method. Results In five independent experiments, spleen from 8/60 (13.3%), PL from 7/60 (11.6%), and serum from 16/56 (28.5%) mice were positive for BaL HIV-1 infection. Similarly, spleen from 4/20 (20%), PL from 1/20 (5%) and serum from 5/20 (25%) mice vaginally inoculated with 92BR09-infected human-PBLs were positive for HIV-1. A one-sided power analysis using normal approximation revealed that at 5% significance level, the overall response rate need to increase form 0.29 to 0.9 and 80% of the control groups needs to achieve a response rate between 6/10 and 9/10 to make the assay feasible. Conclusion The incidence of vaginal transmission of CCR5 HIV-1 in the human-PBL-SCID mouse was low and variable, which constitutes a major disadvantage for preclinical evaluation of vaginal microbicides. [source] Growth performance, feed efficiency and fatty acid composition of juvenile Murray cod, Maccullochella peelii peelii, fed graded levels of canola and linseed oilAQUACULTURE NUTRITION, Issue 5 2007D.S. FRANCIS Abstract In two independent experiments, the effects of dietary inclusion of canola and linseed oil were evaluated in juvenile Murray cod (Maccullochella peelii peelii, Mitchell) over a 112-day period. In each experiment, fish received one of five semi-purified diets in which the dietary fish oil was replaced with canola oil (Experiment A) or linseed oil (Experiment B) in graded increments of 25% (0,100%). Murray cod receiving the graded canola and linseed oil diets ranged in final weight from 112.7 ± 7.6 to 73.8 ± 9.9 g and 93.9 ± 3.6 to 74.6 ± 2.2 g, respectively, and exhibited a negative trend in growth as the inclusion level increased. The fatty acid composition of the fillet and liver were modified extensively to reflect the fatty acid composition of the respective diets. Levels of oleic acid (18:1 n-9) and linoleic acid (18:2 n-6) increased with each level of canola oil inclusion while levels of , -linolenic acid (18:3 n-3) increased with each level of linseed oil inclusion. The concentration of n-3 highly unsaturated fatty acids in the fillet and liver decreased as the amount of vegetable oil in the diets increased. It is shown that the replacement of fish oil with vegetable oils in low fish meal diets for Murray cod is possible to a limited extent. Moreover, this study reaffirms the suggestion for the need to conduct ingredient substitution studies for longer periods and where possible to base the conclusions on regression analysis in addition to anova. [source] GSM modulated radiofrequency radiation does not affect 6-sulfatoxymelatonin excretion of ratsBIOELECTROMAGNETICS, Issue 8 2003József Bakos Abstract In this study, the effect of exposure to 900 and 1800 MHz GSM-like radiofrequency radiation upon the urinary 6-sulfatoxymelatonin (6SM) excretion of adult male Wistar rats was studied. Seventy-two rats were used in six independent experiments, three of which were done with 900 MHz and the other three with 1800 MHz. The exposures were performed in a gigahertz transverse electromagnetic mode (GTEM) cell. The power densities of radiation were 100 and 20 ,W/cm2 at 900 and 1800 MHz frequency, respectively. The carrier frequency was modulated with 218 Hz, as in the GSM signal. The animals were exposed for 2 h between 8:00 AM and noon daily during the 14 day exposure period. The urine of rats was collected from 12:00 AM to 8:00 AM, collecting from exposed and control animal groups on alternate days. The urinary 6SM concentration was measured by 125I radioimmunoassay and was referred to creatinine. The combined results of three experiments done with the same frequency were statistically analyzed. Statistically significant changes in the 6SM excretion of exposed rats (n,=,18) compared to control group (n,=,18) were not found either at 900 or 1800 MHz. Bioelectromagnetics 24:531,534, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||||||||