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Mechanical Agitation (mechanical + agitation)
Selected AbstractsThe preparation of periapical lesions for flow cytometryINTERNATIONAL ENDODONTIC JOURNAL, Issue 2 2000K. Fernando Aim To devise an optimal protocol and to analyse the leucocyte composition of periapical (PA) lesions by flow cytometry. Methodology PA lesions were mechanically agitated, with and without proteolysis. This was with either 0.2% collagenase alone, or in combination with 0.02% DNA-ase in serial incubations until all tissue was digested. The efficacy of each method was assessed by counting total cell yield and cell viability. Phenotype stability was gauged by the percentage of peripheral blood leucocytes (PBL) which expressed CD45RB, CD3, CD20, CD4 and CD8 before and after mechanical and collagenase treatment. Results Disaggregation of PA lesions was superior if collagenase was present, but cell clumping was problematic unless the DNA-ase was also added, and serial digestion with this combination produced optimal cell yield and viability. Nevertheless, the total number of cells released rarely exceeded 105, though viability was in excess of 80%. Mechanical agitation and proteolysis adversely affected PBL phenotypes, but collagenase digestion limited to 10 min caused least damage. Flow cytometric analysis of disaggregated PA lesions failed to identify more than 7.9% (mean, range 6,10%) CD45RB + cells. Conclusions Because of the necessity for single cell suspensions, flow cytometry is not easily applied to the analysis of leucocytes in PA lesions, and further refinements in tissue disaggregation and cell preparation are required. [source] Proteolysis During the Fermentation of Ethanol-Supplemented MisoJOURNAL OF FOOD SCIENCE, Issue 8 2001R.Y.-Y. ABSTRACT: Steam-cooked soybeans mixed with rice koji (2:1, w/w) were ground into a fine paste, combined with NaCl (0 to 12.5%) or sucrose (0 to 25%), and supplemented with 15% ethanol for fermentation. The proteolytic activities decreased with NaCl or sucrose; the dose-response effect of NaCl was much more effective than that of sucrose. When fermented with 15% ethanol and 12.5% sucrose at various moisture contents from 30.6 to 53.0%, proteolysis increased proportionally to the increase of moisture content. Mechanical agitation enhanced proteolysis. After 4 w of fermentation, free amino acid contents were higher in products fermented without pH control than in products fermented with pH control. [source] Peracetic acid as an alternative wastewater disinfectant to chlorine dioxideJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2002S. Stampi Aims: The aim of this study was to compare the efficiency of peracetic acid with that of chlorine dioxide in the disinfection of wastewater from a sewage treatment plant (serving about 650 000 inhabitants) that has been using peracetic acid as a disinfectant since 1998. Methods and Results: A total of 23 samplings were made, each consisting of three samples: from secondary effluent, effluent disinfected with 2 mg l,1 of peracetic acid and effluent disinfected with 2·2 mg l,1 of chlorine dioxide (contact time 20 min). For each sample, measurements were made of the heterotrophic plate count at 36°C, total and faecal coliforms, Escherichia coli, enterococci, pH, suspended solids and chemical oxygen demand (COD). During the first phase of the experiment the peracetic acid was seen to be less efficient than chlorine dioxide. To improve the disinfectant action a system of mechanical agitation was added which led to a greater efficiency in the inactivation of bacteria of faecal origin. Conclusions: Both products were found to be influenced by the level of microbial contamination, the amount of suspended solids and COD but not by the pH of the effluent before disinfection. The immediate mixing of the wastewater and disinfectant caused a greater reduction in enterococci. Significance and Impact of the Study: Since peracetic acid was seen to produce a high abatement of micro-organisms, it can be considered as a valid alternative to chlorine dioxide in the disinfection of wastewaters. [source] Enhanced production of lovastatin in a bubble column by Aspergillus terreus using a two-stage feeding strategyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2007EM Rodríguez Porcel Abstract A two-stage feeding strategy is shown to improve the rate of production of lovastatin by Aspergillus terreus when compared with conventional batch fermentation. The feeding strategy consisted of an initial batch/fed-batch phase and a semi-continuous culture dilution phase with retention of pelleted biomass in a slurry bubble column reactor. The batch phase served only to build up the biomass for producing lovastatin, a secondary metabolite that inhibits its own synthesis in the producing microfungus. The semi-continuous dilution phase provided nutrients to sustain the fungus, but prevented biomass growth by limiting the supply of essential nitrogen. (Synthesis of lovastatin does not require nitrogen.) The preferred pelleted growth morphology that favors lovastatin synthesis was readily obtained and maintained in the 20 L bubble column used. In contrast, a stirred tank fermentation had a substantially lower production of lovastatin because mechanical agitation damaged the fungal pellets. The two-stage feeding method increased lovastatin production rate by more than 50% in comparison with the conventional batch operation. Rheological data for the fungal broth are presented. Copyright © 2007 Society of Chemical Industry [source] Freezing-sensitive tomato has a functional CBF cold response pathway, but a CBF regulon that differs from that of freezing-tolerant ArabidopsisTHE PLANT JOURNAL, Issue 6 2004Xin Zhang Summary Many plants increase in freezing tolerance in response to low temperature, a process known as cold acclimation. In Arabidopsis, cold acclimation involves action of the CBF cold response pathway. Key components of the pathway include rapid cold-induced expression of three homologous genes encoding transcriptional activators, CBF1, 2 and 3 (also known as DREB1b, c and a, respectively), followed by expression of CBF-targeted genes, the CBF regulon, that increase freezing tolerance. Unlike Arabidopsis, tomato cannot cold acclimate raising the question of whether it has a functional CBF cold response pathway. Here we show that tomato, like Arabidopsis, encodes three CBF homologs, LeCBF1,3 (Lycopersicon esculentum CBF1,3), that are present in tandem array in the genome. Only the tomato LeCBF1 gene, however, was found to be cold-inducible. As is the case for Arabidopsis CBF1,3, transcripts for LeCBF1,3 did accumulate in response to mechanical agitation, but not in response to drought, ABA or high salinity. Constitutive overexpression of LeCBF1 in transgenic Arabidopsis plants induced expression of CBF-targeted genes and increased freezing tolerance indicating that LeCBF1 encodes a functional homolog of the Arabidopsis CBF1,3 proteins. However, constitutive overexpression of either LeCBF1 or AtCBF3 in transgenic tomato plants did not increase freezing tolerance. Gene expression studies, including the use of a cDNA microarray representing approximately 8000 tomato genes, identified only four genes that were induced 2.5-fold or more in the LeCBF1 or AtCBF3 overexpressing plants, three of which were putative members of the tomato CBF regulon as they were also upregulated in response to low temperature. Additional experiments indicated that of eight tomato genes that were likely orthologs of Arabidopsis CBF regulon genes, none were responsive to CBF overexpression in tomato. From these results, we conclude that tomato has a complete CBF cold response pathway, but that the tomato CBF regulon differs from that of Arabidopsis and appears to be considerably smaller and less diverse in function. [source] Emission to air of volatile organotins from tributyltin-contaminated harbour sedimentsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2002Alfred J. Vella Abstract An analytical method for determining the presence in air of volatile forms (e.g. chlorides) of tributyltin (TBT) and that of methylbutyltins MenBu(4,n)Sn (n,=,1,3) was developed and used to establish whether dredged harbour sediments contaminated with TBT served as sources of air pollution with respect to organotin compounds. The method was based on active sampling of the air being analysed and sorption of analytes onto Poropak-N. Sorbed methylbutyltins were extracted with dichloromethane and analysed by gas chromatography using flame photometric detection. Other butyltins were converted into butyltin hydrides prior to analysis by gas chromatography. It was shown that TBT-contaminated sediments from Marsamxett Harbour, Malta, placed in 0.5 l chambers through which air was displaced by continuous pumping for 11 days released mainly methylbutyltins, with concentrations (as tin) reaching maximum 48,h mean values of 8.7 (Me3BuSn), 22.1 (Me2Bu2Sn) and 93.0,ng m,3(MeBu3Sn) being measured. Other volatile forms of TBT, dibutyltin and monobutyltin were detected in the headspace air, but very infrequently and at much lower tin concentrations (<2,ng m,3). It was also shown that methylbutyltins dissolved in sea-water ([Sn],=,0.2 to 400,ng l,1) were very difficult to exsolve from this medium, even on prolonged evaporation of the solutions using mechanical agitation and active ventilation. The results suggest that emission of methylbutyltins from contaminated sediments probably occurs only from the surface of the material. The environmental implications of these findings in the management of TBT-polluted harbour sediments are discussed. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||