Production of gramicidin S in batch and continuous culture

A mathematical model for the production of gramicidin S in batch and continuous culture is proposed. It is based on the division of the age of a cell into two phases—an immature and a mature one. A nongrowth associated product, such as an antibiotic, is assumed to be produced when the organism is in the older of these two phases, the mature state. The parameters describing the model were evaluated from batch and single stage transient continuous culture of Bacillus brevis, which produces the antibiotic gramicidin S. The predictive value of the model was studied in steady-state single stage continuous culture and in a transient two stage system. Good agreement between the theoretical curves and the experimental results was found in the transient response of both the first and second stage systems, although at high dilution rates (0.34 hr^?1) in the first stage, deviations from the predicted response were observed in the second stage. These may have been due to chemostat instability at dilution rates close to washout, lags in cell growth, and a metabolic lag on going from stage one to stage two.     

Purification of human antibodies from transgenic corn using aqueous two‐phase systems

A recombinant human antibody expressed in corn was purified using aqueous two‐phase extraction. The antibody was an immunoglobulin G fully unglycosylated. Using systems of different compositions and/or pHs in each of one or two partitioning stages followed by one more stage in which the antibody was precipitated at the liquid/liquid interface facilitated the removal of different impurities in each stage. The best system yields a product 72% pure (22‐fold purification) with a yield of 49%. The optimum extraction was done in two partitioning stages followed by an interfacial precipitation stage using poly(ethylene)glycol/potassium phosphate systems. NaCl was added to the first stage to eliminate large molecular weight impurities. The pH in the first stage was kept at 6 but a pH of 8 was used in the second stage and in the precipitation stage. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Observation of wind-induced two-layer dynamics in Lake Nakaumi, a coastal lagoon in Japan

A response in movement of a two-layered water body in Lake Nakaumi to a strong wind, which suddenly rose and continued for 15 h with nearly constant speed and direction, was observed using the current and salinity meters situated at two points in the lake. At the initial stage of water movement, large fluctuations in current velocity in reverse directions were observed in the upper and lower layers, accompanied by mixing between the two layers. At the stationary stage following the initial stage, current velocities in the upper and lower layers were kept constant, as was salinity. It was considered that a slab-type flow, which enhanced mixing between the two layers, occurred at the initial stage in water movement, then changed into a steady circulation flow at the stationary stage with completion of the set up in the two-layered structure. Received: July 3, 2000 / Accepted: February 8, 2001     

Immunological properties of the cell surface haemagglutinins (sHAs) of Helicobacter pylori strain NCTC 11637

Abstract Rabbits were immunised with stage 1 and stage 2 soluble haemagglutinins (sHA) of Helicobacter pylori strain NCTC 11637 and with rabbit erythrocytes coated with stage 1 sHA. After adsorption of stage 1 sHA on erythrocytes, SDS-PAGE analysis showed that 4 major protein bands were removed from the preparation. The anti-sHA coated erythrocyte serum had the highest HA inhibition titre of 16. Crossed immunoelectrophoresis of the stage 1 sHA, against stage 1 and 2 antisera showed multiple precipitin arcs; however, the anti-sHA coated erythrocyte serum produced only two arcs. One arc produced by the anti-stage 2 serum was absent with the anti-stage 1 serum. This arc could have been produced against a 20 kDa polypeptide which was absent in the stage 1 sHA. The other arc was stronger when compared with that produced by anti-stage 1 serum. These two arcs corresponded to the two arcs produced by the anti-sHA coated erythrocyte serum, which had the highest inhibition titre. The two arcs were markedly reduced in crossed immunoelectrophoresis with an adsorbed stage 1 sHA preparation, which indicates that these arcs were produced against the sHAs.     

Trendtests with adaptive scoring

The concept of adaptive two‐stage designs is applied to the problem of testing the equality of several normal means against an ordered (monotone) alternative. The likelihood‐ratio‐test proposed by Bartholomew is known to have favorable power properties when testing against a monotonic trend. Tests based on contrasts provide a flexible way to incorporate available information regarding the pattern of the unknown true means through appropriate specification of the scores. The basic idea of the presented concept is the combination of Bartholomew 's test (first stage) with an “adaptive score test” (second stage) which utilizes the information resulting from isotonic regression estimation at the first stage. In a Monte Carlo simulation study the adaptive scoring procedure is compared to the non‐adaptive two‐stage procedure using the Bartholomew test at both stages. We found that adaptive scoring may improve the power of the two stage design, in particular if the sample size at the first stage is considerably larger than at the second stage.     

A Robust Test for Two‐Stage Design in Genome‐Wide Association Studies

Summary A two‐stage design is cost‐effective for genome‐wide association studies (GWAS) testing hundreds of thousands of single nucleotide polymorphisms (SNPs). In this design, each SNP is genotyped in stage 1 using a fraction of case–control samples. Top‐ranked SNPs are selected and genotyped in stage 2 using additional samples. A joint analysis, combining statistics from both stages, is applied in the second stage. Follow‐up studies can be regarded as a two‐stage design. Once some potential SNPs are identified, independent samples are further genotyped and analyzed separately or jointly with previous data to confirm the findings. When the underlying genetic model is known, an asymptotically optimal trend test (TT) can be used at each analysis. In practice, however, genetic models for SNPs with true associations are usually unknown. In this case, the existing methods for analysis of the two‐stage design and follow‐up studies are not robust across different genetic models. We propose a simple robust procedure with genetic model selection to the two‐stage GWAS. Our results show that, if the optimal TT has about 80% power when the genetic model is known, then the existing methods for analysis of the two‐stage design have minimum powers about 20% across the four common genetic models (when the true model is unknown), while our robust procedure has minimum powers about 70% across the same genetic models. The results can be also applied to follow‐up and replication studies with a joint analysis.     

Relationship between leaf stages and epistasis for resistance to Stagonospora nodorum in durum wheat

Ten varieties and eight generations (2F1, 2F2, 2B1 and 2B2) of durum wheat derived from two crosses were evaluated for resistance to natural infection by Stagonospora nodorum blotch (SNB) at the 2-3 and 6-7 leaf stages at two sites over two years. There were significant differences in the incidence of SNB between leaf stages in most of the wheat varieties, with resistance being most evident at the 6-7 leaf stage. Separate analyses of the mean values for each generation showed that the genetic mechanism of defense against the pathogen depended upon the leaf stage. At the 2-3 leaf stage, only additive and dominance effects were implicated in the control of SNB for the two crosses at the two sites and for the two replications. For the 6-7 leaf stage, inheritance was more complicated and an epistatic effect was involved. Narrow-sense heritability values (range: 0.63-0.67) were consistent between crosses and leaf stages. These findings indicate a lack of resistance to SNB at the 2-3 leaf stage whereas resistance was observed at the 6-7 leaf stage and involved the genetic mechanisms of plant defense such as epistasis.     

Comparison of the performance of one stage and two stage sequential anaerobic-aerobic biological processes for the treatment of reactive-azo-dye-containing synthetic wastewaters

In the present study the performance of anaerobic-aerobic one and two stage processes for the biological treatment of synthetic wastewaters containing Reactive Black 5 (RB5) were studied and compared with each other. In both processes the majority of colour removal by biodegradation occurred under anaerobic environment. The colour change under aerobic conditions was correlated with extent of anaerobic decolourisation in the preceding phase/stage of the process. Partial mineralisation of the anaerobic dye metabolites, roughly to the same extent, was achieved aerobically in both one stage and two stage processes. The majority of COD was removed in the anaerobic stage for two stage processes and aerobic stage in one stage processes. In one stage processes, the exposure of anaerobic sludge to alternating anaerobic-aerobic environment decreased anaerobic decolourisation efficiency and COD removal; when employing activated sludge, the same exposure enhanced anaerobic substrate utilisation whereas the effect on the anaerobic decolourisation efficiency depended on RB5 concentration. The comparative performance of one and two stage processes in terms of overall dye decolourisation depended on RB5 concentration. Both types of processes brought about similar overall COD removal. Increase in RB5 concentration, in the range studied, resulted in decrease in overall COD removal for both processes.     

Census timing alters stage duration distributions in matrix population models

Matrix population models are widely used to study the dynamics of stage‐structured populations. A census in these models is an event monitoring the number of individuals in each stage and occurs at discrete time intervals. The two most common methods used in building matrix population models are the prebreeding census and postbreeding census. Models using the prebreeding and postbreeding censuses assume that breeding occurs immediately before or immediately after the censuses, respectively. In some models such as age‐structured models, the results are identical regardless of the method used, rendering the choice of method a matter of preference. However, in stage‐structured models, where the duration of the first stage of life varies among newborns, a choice between the prebreeding and postbreeding censuses may result in different conclusions. This is attributed to the different first‐stage duration distributions assumed by the two methods. This study investigated the difference emerging in the structures of these models and its consequence on conclusions of eigenvalue and elasticity analyses using two‐stage models. Considerations required in choosing a modeling method are also discussed.     

Effects of embryotrophic factors on the embryogenesis and organogenesis of mouse embryos in vitro

In order to study embryogenesis and organogenesis in vitro, two cell mouse embryos were cultured with alpha-MEM supplemented 10% FCS and embryotrophic factors (ETFs). The ETFs were separated from the conditioned medium of a SKG-II-SF cell line derived from a human uterine cervical epidermoid carcinoma. IL-1 beta, IL-6, IL-8, EGF, GH, PDGF-AB, basic FGF, VEGF were also detected in the conditioned media of this cell line. Using ETFs and a 10% FCS supplemented culture medium, 23% of the mouse two cell stage embryos developed to the bilaminar disc stage, 13% to the trilaminar germ disc stage, 9% were observed with blood islets in the yolk sac, and the heart beat was noted in 7% (28 embryos) of the embryos. Furthermore, primordial organs, such as the liver, heart, kidney, notochord, retina-like structure, etc. were observed. Usually, structures associated with the primordial streak stage (bilaminar germ disc embryo) developed in vitro using ETFs from two cell stage embryos. These closely resemble structures found at the same stage in the normal embryo in vivo. After the primordial streak stage, the cultured embryos showed no resemblance to the same stage in normal embryos. None of the external appearances of these embryos appeared normal. On the other hand, trilaminar disc stage embryos never developed when using only a 10% FCS supplemented culture system.     

A Pachytene map of the mouse oocyte

A map of the mouse oocyte has been constructed utilizing early and mid/late pachytene stages. Each bivalent was clearly identified. At the mid/late stage 195 chromomeres corresponded directly to precursor chromomeres in the early stage, whilst 84 chromomeres were derived from two chromomeres from the early stage. The X and 13 bivalents were found to have a single chromomere in the early stage which later yielded two sites. There were approximately twice as many total chromomeres as mitotic bands, with good correspondence between pachytene chromomeres and major mitotic bands. Application of the use of mapping to a previously reported bivalent bearing a pleiomorphic region is noted.     

Ethanol addition on inactivation of Saccharomyces pastorianus by a two‐stage system with low‐pressure carbon dioxide microbubbles can accelerate the cell membrane injury

The effect of ethanol on the inactivation of Saccharomyces pastorianus by a two‐stage system with low‐pressure carbon dioxide microbubbles (two‐stage MBCO₂) was investigated. Zero and >5 log reductions of S. pastorianus populations suspended in physiological saline (PS) containing 0% and 10% ethanol, respectively, occurred by the two‐stage MBCO₂ at a mixing vessel pressure of 1 MPa and a heating coil temperature of 40°C. Conversely, the detected number of surviving S. pastorianus cells in PS containing 5% ethanol was higher in yeast and mold agar (YMA, an optimum agar) than YMA with 2.5% sodium chloride, followed by yeast nitrogen base agar (YNBA, a minimum agar). The fluorescence polarization of S. pastorianus in PS containing 5% and 10% ethanol increased similarly with exposure time in the heating coil of two‐stage MBCO₂ and was correlated with the surviving cell number measured in YNBA. The intracellular pH (pH_in) of S. pastorianus in PS containing 5% ethanol decreased linearly with exposure time in the heating coil of two‐stage MBCO₂. Also, the pH_in‐lowering of S. pastorianus in PS containing 10% ethanol was drastically caused by two‐stage MBCO₂ at 1 min exposure time in the heating coil but then stayed constant until 5 min, agreeing with the inactivation efficiency. Therefore, ethanol in S. pastorianus suspension was suggested to accelerate the cell membrane injury caused by two‐stage MBCO₂. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:282–286, 2018     

Litter Overlap in Gambusia hubbsi: Superfetation Revisited

The frequency of litter overlap, the simultaneous presence of two litters at different stages of development within a single female, varies among populations of Gambusia hubbsi in different habitats on Andros, Bahamas. In freshwater bluehole and shallow water populations, less than 2% of the females carried two litters, independent of the difference in developmental stage between the litters. In well field populations, 2% of the females carried two litters composed of immature and mature oocytes, whereas 10% carried developing oocytes and late stage embryos, and 16% carried mature oocytes (or older) and late stage embryos. Among females from populations that we introduced into unoccupied well fields 2% carried two litters composed of immature and mature oocytes, about 14% carried developing oocytes and late stage embryos, and less than 6% carried mature oocytes (or older) and late stage embryos. When two litters composed developing oocytes and late stage embryos were present, the two litters were of equal size, and the total number of offspring was 1.5 times larger than expected on the basis of female body length. When two litters composed mature oocytes (or older stages) and late stage embryos were present, the two litters were also of equal size, and the total number of offspring was as expected on the basis of female body length. Litter overlap was independent of female size. A comparison of the consequences of litter overlap for strictly lecithotrophic and strictly matrotrophic modes of reproduction with the patterns of litter overlap observed in G. hubbsi, suggests that litter overlap in G. hubbsi reduces the cost of reproduction, but does not increase the rate of offspring production.     

The statistical analysis of insect phenology

We introduce two simple methods for the statistical comparison of the temporal pattern of life-cycle events between two populations. The methods are based on a translation of stage-frequency data into individual 'times in stage'. For example, if the stage-k individuals in a set of samples consist of three individuals counted at time t(1) and two counted at time t(2), the observed times in stage k would be (t(1), t(1), t(1), t(2), t(2)). Times in stage then can be compared between two populations by performing stage-specific t-tests or by testing for equality of regression lines of time versus stage between the two populations. Simulations show that our methods perform at close to the nominal level, have good power against a range of alternatives, and have much better operating characteristics than a widely-used phenology model from the literature.     

On a two urn model of Polya-type

A two urn Polya-type scheme is considered in whichr black balls (corresponding to the stable form of an element) are added to urn one at every stage and the same number of balls are removed at random at every stage from the same urn. In between these two operations, which form a stage or iteration, a fixed number of balls is exchanged at random between urns one and two. Urn one has a given initial number of white balls (corresponding to a radioactive form of the same element). The problem of interest is to study the stochastic aspect of the number of white balls remaining in urn one (and/or urn two) aftern iterations.     

Estimation of the individual number entering each development stage in an insect population

A method for estimating the number entering each development stage from data obtained by regular sampling through one generation of an insect population was described. This method is consisted of the following two procedures: The provisional estimates are calculated on the assumption that each stage has a common mortality in a sampling interval. Then these estimates are corrected on another assumption that the mortality is different in each stage but constant during a stage. The result of testing its validity with two laboratory populations of the common cabbage butterfly, Pieris rapae crucivora, showed the availability of the present method.     

单叶省藤苗期的生长规律

通过有序样品聚类分析单叶省藤生长规律,将苗木生长分为5个阶段:出苗期4月4日～5月21日,生长速生期5月22日～6月22日,二次速生期6月23日～7月22日,生长后期7月23日～11月22日,生长停止期11月23日～2月22日。其生长阶段缺少生长初期,而是直接进入速生期,并且有一个二次速生期。除了在两个速生期加强水肥管理外,在生长后期适当管理也能增加其生长量。