生产疫苗的植物表达系统

综述了近些年来转基因植物作为疫苗表达系统的新进展,比较了植物表达系统相对其他表达系统的优点,介绍了不同介导方式的植物表达系统,包括农杆菌介导的转化和重组植物病毒表达疫苗,讨论了提高表达效率的载体构建策略,对其应用前景提出了展望。     

Evaluation of the sustainability of contrasted pig farming systems: breeding programmes

The sustainability of breeding activities in 15 pig farming systems in five European countries was evaluated. One conventional and two differentiated systems per country were studied. The Conventional systems were the standard systems in their countries. The differentiated systems were of three categories: Adapted Conventional with focus on animal welfare, meat quality or environment (five systems); Traditional with local breeds in small-scale production (three systems) and Organic (two systems). Data were collected with a questionnaire from nine breeding organisations providing animals and semen to the studied farming systems and from, on average, five farmers per farming system. The sustainability assessment of breeding activities was performed in four dimensions. The first dimension described whether the market for the product was well defined, and whether the breeding goal reflected the farming system and the farmers’ demands. The second dimension described recording and selection procedures, together with genetic change in traits that were important in the system. The third dimension described genetic variation, both within and between pig breeds. The fourth dimension described the management of the breeding organisation, including communication, transparency, and technical and human resources. The results show substantial differences in the sustainability of breeding activities, both between farming systems within the same category and between different categories of farming systems. The breeding activities are assessed to be more sustainable for conventional systems than for differentiated systems in three of the four dimensions. In most differentiated farming systems, breeding goals are not related to the system, as these systems use the same genetic material as conventional systems. The breeds used in Traditional farming systems are important for genetic biodiversity, but the small scale of these systems renders them vulnerable. It is hoped that, by reflecting on different aspects of sustainability, this study will encourage sustainable developments in pig production.     

Relations between substrate feeding pattern and development of filamentous bacteria in activated sludge processes

Summary Laboratory scale activated sludge systems were operated under regimes of continuous or intermittent feeding of substrate. It was found that continuously fed systems repeatedly resulted in the development of filamentous bacteria and bulking of the sludge. Intermittently fed systems did form good settling sludges, without filamentous bacteria. The same results were found using different sludge loadings and different concentrations of mixed liquor suspended solids. High dissolved oxygen concentration did not prevent bulking in continuous systems while low dissolved oxygen concentration resulted in bulking with intermittently fed systems. It was found that the substrate removal rate of intermittently operated systems was always higher than for continuously fed systems. The hypothesis is formulated that intermittent feeding leads to higher substrate removal rates by floc forming bacteria and their predominance in intermittently fed systems, which can be compared to plug flow systems.     

Congruence between the courses of the biliary ductal and the hepatic arterial systems

The development of diagnostic methods and new surgical techniques means it is increasingly important to have accurate knowledge of the anatomy of the hepatic arterial and biliary systems, including their variations, at extrahepatic and intrahepatic levels. The aim of this study was to determine how often the biliary and arterial systems run together and branch in the same pattern. Fifty corrosion casts of the liver were used to analyse the origin and branching patterns of arteries and the confluences of bile ducts. In addition, both systems were analysed to determine the frequency of normal arrangements and variations. The congruence of the course of both systems was analysed at the porta hepatis and in the left and right hemilivers down to the segmental level. A congruent course of the arterial and the biliary systems was identified in 38% of cases at the porta hepatis, in 32% of cases in the left hemiliver and in 30% of the right hemiliver. The congruence of both systems at the porta hepatis and in the left hemiliver was identified only if both systems were normal. In the right hemiliver, however, the congruence of both systems was identified even when both systems were variable, but only in 10% of cases. The results of the study show that, on the basis of knowledge of the course and branching of one system, the other system cannot be predicted.     

Systems biology,emergence and antireductionism

This study explores the conceptual history of systems biology and its impact on philosophical and scientific conceptions of reductionism, antireductionism and emergence. Development of systems biology at the beginning of 21st century transformed biological science. Systems biology is a new holistic approach or strategy how to research biological organisms, developed through three phases. The first phase was completed when molecular biology transformed into systems molecular biology. Prior to the second phase, convergence between applied general systems theory and nonlinear dynamics took place, hence allowing the formation of systems mathematical biology. The second phase happened when systems molecular biology and systems mathematical biology, together, were applied for analysis of biological data. Finally, after successful application in science, medicine and biotechnology, the process of the formation of modern systems biology was completed.Systems and molecular reductionist views on organisms were completely opposed to each other. Implications of systems and molecular biology on reductionist–antireductionist debate were quite different. The analysis of reductionism, antireductionism and emergence issues, in the era of systems biology, revealed the hierarchy between methodological, epistemological and ontological antireductionism. Primarily, methodological antireductionism followed from the systems biology. Only after, epistemological and ontological antireductionism could be supported.     

Investigation of chitosan-phenolics systems as wood adhesives

Chitosan-phenolics systems were investigated as wood adhesives. Adhesion between two pieces of wood veneer developed only when all three components-chitosan, a phenolic compound, and laccase-were present. For the adhesive systems containing a phenolic compound with only one phenolic hydroxyl group, adhesive strengths were highly dependent upon the chemical structures of phenolic compounds used in the system and the relative oxidation rates of the phenolic compounds by laccase. The adhesive strengths were also directly related to the viscosity of the adhesive systems. However, for the adhesive systems containing a phenolic compound with two or three phenolic hydroxyl groups adjacent to each other, no correlations among adhesive strengths, relative oxidation rates of the phenolic compounds by laccase, and viscosities were observed. The adhesion mechanisms of these chitosan-phenolics systems were proposed to be similar to those of mussel adhesive proteins.     

Amylo-1,6-glucosidase/1,4-α-glucan: 1,4-α-glucan 4-α-glycosyltransferase: Specificity toward polysaccharide substrates

The substrate specificities of the glucosidase-transferase debranching enzyme systems from yeast and rabbit muscle were examined by the use of polysaccharide substrates of defined outer chain lengths. The results were consistent with the specificities ascribed to the transferase portion of the debranching enzyme system by previous studies using maltosaccharide substrates. The specificities of the two enzyme systems were also examined in the reversion reaction. The results showed that both systems displayed an inverse specificity to that observed in the hydrolytic reaction. This suggested that the reversion reaction reflects the specificity of the glucosidase portion of the debranching system. The major differences between the specificities of the yeast and rabbit muscle systems were found to lie in the specificity of the transferase and in the ability of the yeast system to debranch native glycogen and amylopectin.     

Factors That Influence Microbial Contamination of Fluids Associated with Hemodialysis Machines

Studies were conducted on the microbiological quality of fluids associated with different types of dialysis systems located in six dialysis centers and 14 homes. Included were (i) single-pass systems employing either parallel flow (Kiil or Gambro) or capillary cartridge dialyzers and (ii) recirculating single-pass and batch recirculating systems using coil dialyzers. Microbiological assays were performed on the water used to prepare dialysis fluid, the concentrated dialysate, and either pre- and postdialyzer dialysate (single-pass systems) or the dialysate contained in storage reservoirs and recirculating cannisters (recirculating systems). The levels of microbial contamination consisting of gram-negative bacteria were directly related to the type of dialysis system, method of water treatment, distribution system, and in some instances, the type of dialyzer. Recirculating single-pass and batch recirculating systems consistently contained significantly higher levels of contamination than single-pass systems. These results were directly related to the design of recirculating systems which permits carbon- and nitrogen-containing waste products dialyzed from the patient to accumulate, be used as nutrients by microorganisms, and subsequently allow for 2- to 4-log increases in contamination levels during a dialysis treatment. In contrast, levels of contamination in single-pass machines were related more to the quality of the water used to prepare dialysis fluid and the adequacy of cleaning and disinfection procedures than to the design of the system.     

Novel polymer-polymer conjugates for recovery of lactic acid by aqueous two-phase extraction

A new family of polymer conjugates is proposed to overcome constraints in the applicability of aqueous two-phase systems for the recovery of lactic acid. Polyethylene glycol-polyethylenimine (PEI) conjugates and ethylene oxide propylene oxide-PEI (EOPO-PEI) conjugates were synthesized. Aqueous two-phase systems were generated when the conjugates were mixed with fractionated dextran or crude hydrolyzed starch. With 2% phosphate buffer in the systems, phase diagrams with critical points of 3.9% EOPO-PEI-3.8% dextran (DEX) and 3.5% EOPO-PEI-7.9% crude starch were obtained. The phase separation temperature of 10% EOPO-PEI solutions titrated with lactic acid to pH 6 was 35 degrees C at 5% phosphate, and increased linearly to 63 degrees C at 2% phosphate. Lactic acid partitioned to the top conjugate-rich phase of the new aqueous two-phase systems. In particular, the lactic acid partition coefficient was 2.1 in 10% EOPO-PEI-8% DEX systems containing 2% phosphate. In the same systems, the partitioning of the lactic acid bacterium, Lactococcus lactis subsp. lactis, was 0.45. The partitioning of propionic, succinic, and citric acids was also determined in the new aqueous two-phase systems.     

Blood groups and serum protein polymorphisms in the Pitman-Moore and Ohmini strains of miniature pigs

The variations of blood groups and biochemical polymorphisms in the populations of the two miniature pig strains reared in Japan were investigated in this report. The variations in eight blood group systems were investigated by using serological techniques, and five serum protein systems by using starch gel electrophoresis. The Pitman-Moore strain showed no variations in K, O, Tf, Cp and Am systems, but showed plymorphisms in A, E, F, G, H, L, Pa and Hpx systems. The Ohmini strain showed no or little variations in E, F, G, Tf, Pa and Cp systems, but showed polymorphisms in A, H, K, L, O, Hpx and Am systems. From the results of investigation of genetic similarities among nine pig populations including various breeds, it was made clear that the two miniature pig strains were very different genetically, and the Pitman-Moore strain was genetically closer to European large pig breeds than to East Asian native pigs, while the Ohmini strain was close to Thai and Philippine natives.     

Community dynamics and heterogeneities in mixed bacterial communities subjected to nutrient periodicities

Sixteen replicate microcosms were inoculated with a mixed assemblage of heterotrophic bacteria and provided with discrete pulses of protein as carbon and energy source. The dynamics of community structure were monitored by 16S rRNA gene polymerase chain reaction denaturant gradient gel electrophoresis (PCR-DGGE). The results were consistent with a strong role for biological interactions in maintaining diversity. Replicate microcosms developed different microbial communities. For systems exposed to nutrient pulses every 7 days, the number of DGGE bands averaged 13 +/- 4 (mean +/- SD) and the Dice similarity coefficient between pairs ranged from 0.08 to 0.67. In each of 16 systems provided protein once each day, there were dynamic changes over the first 30 days but community composition was stable over the next 20 days. However, most systems differed from each other; two-thirds of the pairwise comparisons had similarity coefficients in the range of 0.35-0.63. These 16 systems contained 10 +/- 2 phylotypes (mean +/- SD) and in aggregate 34 phylotypes were found in the 16 systems. Most phylotypes were found in < 25% of the systems, and there were not strong networks of association among phylotypes.     

北方农牧过渡带农户农业生产系统模式的生态评价和改良研究

农牧过渡带 (或农牧交错带、半农半牧区 )是指我国传统种植业区和传统畜牧业区的镶嵌结合地带。近世纪以来 ,由于人口剧增 ,垦草种粮面积不断扩大 ,滥垦、过牧、滥樵 ,使草地植被大面积消失 ,沙漠化和荒漠化日趋严重。据报道 ,目前我国北方农牧过渡带荒漠化土地面积已达 1 6 7×10 5ｈａ ,占土地总面积的 5 2 73% ,年增长率约为1 39% [3] 。赤峰市是我国北方农牧过渡带较典型、分布面积较大的地区。该地区资源类型丰富 ,互补优势明显 ,特别是农牧结合的潜力巨大。但长期以来这里区域生态环境恶化加剧 ,导致严重的贫困化。解决这一问题的关…     

Parsimony Analysis of Endemicity (PAE) of Mexican hydrological basins based on helminth parasites of freshwater fishes

Aim The distributional patterns of helminthological fauna of freshwater fishes were analysed to postulate a general hypothesis on the relationships of some Mexican hydrological systems. Location Eight hydrological systems of central and eastern Mexico were studied and compared with records from Nicaragua. Methods A Parsimony Analysis of Endemicity (PAE) was applied to the presence/absence of ninety‐two helminth parasite taxa (Monogeneans, Digeneans, Cestodes, Acanthocephalans and Nematodes) of freshwater fishes, from eight Mexican hydrological systems, using the Hennig86 program. Results The results represent the first attempt for a biogeographical analysis through application of the PAE method to the distributional patterns of helminth parasites of freshwater fishes in Mexico. A single most parsimonious cladogram was obtained, which grouped all the Neotropical systems in accordance with previous proposals based on other plant and animal taxa. Main conclusions The most basal systems were Santiago and Lerma basins, which exhibited Nearctic affinities. The remaining areas of the cladogram showed Neotropical affinities. All the southeastern systems were grouped in a clade with the Nicaragua system, providing support for a ‘Mesoamerican province’ based on helminth parasites of cichlids. The cladogram also suggests that the treatment of the Lerma‐Santiago basin as a single biogeographical unit is inaccurate and that they should be treated as separate systems.     

Source of energy for the Escherichia coli galactose transport systems induced by galactose

The beta-methyl-galactoside- and galactose-specific transport systems of Escherichia coli were shown by experiments involving inhibitors and the use of an adenosine triphosphatase mutant strain to utilize adenosine 5'-triphosphate or a related compound to drive active transport. These systems were shown to be unable to use the activated-membrane state. The galactose-specific transport system was shown to behave most like a member of the binding-protein class of transport systems by its response to osmotic shock and vesicle formation. These results extended to two sugar transport systems: the correlation between the source of energy and class of transport system found by Berger (1973) for amino acid transport systems. That is, binding-protein systems utilized adenosine 5'-triphosphate whereas membrane-bound systems utilized the activated-membrane state to drive active transport.     

Development and application of bio-economic modelling to compare silvoarable, arable, and forestry systems in three European countries

Silvoarable agroforestry could promote use of trees on farms in Europe, but its likely effect on production, farm profitability, and environmental services is poorly understood. Hence, from 2001 to 2005, the Silvoarable Agroforestry for Europe project developed a systematic process to evaluate the biophysical and economic performance of arable, forestry, and silvoarable systems in Spain, France, and The Netherlands. A biophysical model called “Yield-SAFE” was developed to predict long-term yields for the different systems and local statistics and expert opinion were used to derive their revenue, costs, and pre- and post-2005 grant regimes. These data were then used in an economic model called “Farm-SAFE” to predict plot- and farm-scale profitability. Land equivalent ratios were greater than one, showing Yield-SAFE predicted that growing trees and crops in silvoarable systems was more productive than growing them separately. Pre-2005 grants in Spain and The Netherlands penalised silvoarable systems, but post-2005 grants were more equitable. In France, walnut and poplar silvoarable systems were consistently the most profitable system under both grant regimes. In Spain, holm oak and stone pine silvoarable systems were the least profitable system under pre-2005 grants, but only marginally less profitable than arable systems under post-2005 grants. In The Netherlands, low timber values and the opportunity cost of losing arable land for slurry manure application made silvoarable and forestry systems uncompetitive with arable systems under both grant regimes.     

Relationship between population genetic structure and riparian habitat as revealed by RAPD analysis of the rheophyte Acorus gramineus Soland. (Araceae) in Taiwan

Acorus gramineus Soland. (Araceae) is a rheophyte and is distributed in southeastern Asia. Its populations are restricted to riparian habitats. The discontinuous distribution might result in high genetic diversification among plants of different river systems. In the present study, leaf samples were collected from populations along six river systems in western Taiwan and the genetic variation was investigated by employing RAPD markers. A total of 255 samples from 17 sampling sites was studied. Eighty random 10-mer primers were screened and six of them, which showed better amplification results, were selected to analyse all of the samples. Data of 34 high-intensity and highly reproducible polymorphic fragments were used in statistical analyses. The results of AMOVA analyses indicated that, of the total variation, 46.84% was attributable to differences among river systems, 16.88% to differences among sampling sites within river systems, and 36.28% to differences among individuals within sampling sites. The results of cluster analysis and principal coordinate analysis revealed that sampling sites of each river system formed distinct clusters and the sampling sites of six river systems were clustered into three main groups according to latitudinal relationships. The results of the present study indicated that the population genetic structure of the plants of different river systems is highly diversified, which seems to imply that the gene flow among them is very limited.     

Biofilms and microbially influenced cuprosolvency in domestic copper plumbing systems

AIMS: To survey biofilm accumulation within domestic copper plumbing pipes in South Australian drinking water distribution systems and examine its role in copper solvation (cuprosolvency). METHODS AND RESULTS: Cold water copper pipes were sampled from two different plumbing systems receiving filtered and unfiltered potable water respectively. Biomass was quantified by total organic carbon measurements and viable cell counts and microbial activity by respirometry. Biofilm accumulation was related to water chemistry within the systems, particularly nutrients, alkalinity and conductivity, as well as water turbulence. Laboratory coupon experiments were used to determine the effect of extracted biofilm on copper solvation. Biofilms were shown to be capable of both increasing and decreasing aqueous copper concentrations in comparison to sterile controls. CONCLUSIONS: The results suggest that water quality may influence the accumulation of biofilms in copper plumbing systems, as well as potential cuprosolvency activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of biofilms in copper plumbing systems and their ability to influence aqueous copper concentrations has implications for both public health and the management of distribution systems.     

Protein secretion systems of Pseudomonas aeruginosa and P fluorescens

Gram-negative bacteria have evolved numerous systems for the export of proteins across their dual-membrane envelopes. Three of these systems (types I, III and IV) secrete proteins across both membranes in a single energy-coupled step. Four systems (Sec, Tat, MscL and Holins) secrete only across the inner membrane, and four systems [the main terminal branch (MTB), fimbrial usher porin (FUP), autotransporter (AT) and two-partner secretion families (TPS)] secrete only across the outer membrane. We have examined the genome sequences of Pseudomonas aeruginosa PAO1 and Pseudomonas fluorescens Pf0-1 for these systems. All systems except type IV were found in P. aeruginosa, and all except types III and IV were found in P. fluorescens. The numbers of each such system were variable depending on the system and species examined. Biochemical and physiological functions were assigned to these systems when possible, and the structural constituents were analyzed. Available information regarding the mechanisms of transport and energy coupling as well as physiological functions is summarized. This report serves to identify and characterize protein secretion systems in two divergent pseudomonads, one an opportunistic human pathogen, the other a plant symbiont.     

Within-host competition selects for plasmid-encoded toxin–antitoxin systems

Toxin–antitoxin (TA) systems are commonly found on bacterial plasmids. The antitoxin inhibits toxin activity unless the system is lost from the cell. Then the shorter lived antitoxin degrades and the cell becomes susceptible to the toxin. Selection for plasmid-encoded TA systems was initially thought to result from their reducing the number of plasmid-free cells arising during growth in monoculture. However, modelling and experiments have shown that this mechanism can only explain the success of plasmid TA systems under a restricted set of conditions. Previously, we have proposed and tested an alternative model explaining the success of plasmid TA systems as a consequence of competition occurring between plasmids during co-infection of bacterial hosts. Here, we test a further prediction of this model, that competition between plasmids will lead to the biased accumulation of TA systems on plasmids relative to chromosomes. Transposon-encoded TA systems were added to populations of plasmid-containing cells, such that TA systems could insert into either plasmids or chromosomes. These populations were enriched for transposon-containing cells and then incubated in environments that did, or did not, allow effective within-host plasmid competition to occur. Changes in the ratio of plasmid- to chromosome-encoded TA systems were monitored. In agreement with our model, we found that plasmid-encoded TA systems had a competitive advantage, but only when host cells were sensitive to the effect of TA systems. This result demonstrates that within-host competition between plasmids can select for TA systems.     

Taking the example of computer systems engineering for the analysis of biological cell systems

In this paper, we discuss the potential for the use of engineering methods that were originally developed for the design of embedded computer systems, to analyse biological cell systems. For embedded systems as well as for biological cell systems, design is a feature that defines their identity. The assembly of different components in designs of both systems can vary widely. In contrast to the biology domain, the computer engineering domain has the opportunity to quickly evaluate design options and consequences of its systems by methods for computer aided design and in particular design space exploration. We argue that there are enough concrete similarities between the two systems to assume that the engineering methodology from the computer systems domain, and in particular that related to embedded systems, can be applied to the domain of cellular systems. This will help to understand the myriad of different design options cellular systems have. First we compare computer systems with cellular systems. Then, we discuss exactly what features of engineering methods could aid researchers with the analysis of cellular systems, and what benefits could be gained.