Mechanical impedance increases aluminium tolerance of soybean (Glycine max) roots

The effect of aluminium (Al) on root elongation was studied in solution culture and sand culture. Compared to solution culture, in sand culture a ten times higher Al supply was necessary to inhibit root elongation to a comparable degree. This was due to a much lower Al uptake into the 5 mm root tips in sand culture. Fe concentrations in root tips were also lower in sand culture. Ca concentrations were higher and less depressed by Al, whereas Mg and K concentrations were not affected by the culture substrate. Regressions of Al concentrations in root tips versus inhibition of root elongation by Al revealed root damage at lower Al concentrations in sand culture. The effect of culture substrate on Al tolerance was independent of N source and could also be shown in flowing solution culture with and without sand. The results indicate that mechanical impedance in sand culture decreased Al uptake. This may be due to enhanced exudation of organic complexors thus reducing activites of monomeric Al species.     

Biphenomycin A production by a mixed culture.

Production of biphenomycin A by Streptomyces griseorubiginosus 43708 was stimulated by a mixed culture with a partner strain, Pseudomonas maltophilia 1928. This stimulatory effect on biphenomycin A accumulation by the mixed culture was caused by the enzyme activity which strain 1928 possessed. It is suggested that in a mixed culture strain 43708 produces a precursor of biphenomycin A in culture broth and that strain 1928 converts the precursor to biphenomycin A.     

Biphenomycin A production by a mixed culture.

Production of biphenomycin A by Streptomyces griseorubiginosus 43708 was stimulated by a mixed culture with a partner strain, Pseudomonas maltophilia 1928. This stimulatory effect on biphenomycin A accumulation by the mixed culture was caused by the enzyme activity which strain 1928 possessed. It is suggested that in a mixed culture strain 43708 produces a precursor of biphenomycin A in culture broth and that strain 1928 converts the precursor to biphenomycin A.     

Enhancement of 1,4-dihydroxy-2-naphthoic acid production by Propionibacterium freudenreichii ET-3 fed-batch culture

The production of 1,4-dihydroxy-2-naphthoic acid (DHNA) was investigated using a fed-batch culture of Propionibacterium freudenreichii ET-3. DHNA is a precursor of menaquinone (MK) and is transformed to MK by combination with an isoprenoid unit. We found that ET-3 stopped MK production and increased DHNA production in an anaerobic fed-batch culture by maintaining the lactose concentration at approximately zero. The maximum DHNA concentration observed in the anaerobic fed-batch culture was markedly higher than the maximum DHNA concentration observed in an anaerobic batch culture. Moreover, MK or DHNA production was affected by the lactose feeding rate; this suggests that lactose metabolism participates in the syntheses of these products. On the other hand, accumulation of propionate was found to inhibit DHNA production in the fed-batch culture. Based on the fact that ET-3 increases DHNA production in an aerobic culture by consuming propionate, we carried out a cultivation experiment in which an anaerobic fed-batch culture was switched to an anaerobic batch culture and found that the DHNA production was increased to a greater extent than the DHNA production in an anaerobic fed-batch culture. These results suggest that DHNA production by ET-3 is markedly influenced by carbon source limitation and the oxygen supply.     

Enhancement of 1,4-Dihydroxy-2-Naphthoic Acid Production by Propionibacterium freudenreichii ET-3 Fed-Batch Culture

The production of 1,4-dihydroxy-2-naphthoic acid (DHNA) was investigated using a fed-batch culture of Propionibacterium freudenreichii ET-3. DHNA is a precursor of menaquinone (MK) and is transformed to MK by combination with an isoprenoid unit. We found that ET-3 stopped MK production and increased DHNA production in an anaerobic fed-batch culture by maintaining the lactose concentration at approximately zero. The maximum DHNA concentration observed in the anaerobic fed-batch culture was markedly higher than the maximum DHNA concentration observed in an anaerobic batch culture. Moreover, MK or DHNA production was affected by the lactose feeding rate; this suggests that lactose metabolism participates in the syntheses of these products. On the other hand, accumulation of propionate was found to inhibit DHNA production in the fed-batch culture. Based on the fact that ET-3 increases DHNA production in an aerobic culture by consuming propionate, we carried out a cultivation experiment in which an anaerobic fed-batch culture was switched to an anaerobic batch culture and found that the DHNA production was increased to a greater extent than the DHNA production in an anaerobic fed-batch culture. These results suggest that DHNA production by ET-3 is markedly influenced by carbon source limitation and the oxygen supply.     

An analysis of extended and exponentially-fed-batch cultures.

Under certain conditions it is shown that an extended culture is equivalent to an exponentially-fed-batch culture, that an exponentially-fed-batch culture (and an extended culture) can be maintained at a steady state and that an exponentially-fed-batch culture may be mimicked by a continuous-flow culture with a constant dilution rate. Operational conditions required to maintain steady states are specified.     

The functional regeneration of syncytiotrophoblast in cultured explants of term placenta

We have investigated the functional characteristics of term human placental villous explants kept in long-term (7-11 days) culture. Fragments of placental villous tissue (approximately 5-10 mg wet wt) were cultured in supplemented CMRL-1066 culture medium for up to 11 days. After the first day of culture, the syncytiotrophoblast appeared vacuolated and eventually degenerated. However, a new syncytiotrophoblast developed by day 4, being indistinguishable from that of a fresh placenta by 11 days. Release of human chorionic gonadotrophin increased and activity of lactate dehydrogenase in culture medium decreased with culture time. Transport variables were measured over the first 7 days of culture. Basal (86)Rb efflux was reduced with time in culture and was inhibited by Ba2+, suggesting the efflux was mediated by K+ channels. At all stages of culture, (86)Rb efflux was stimulated by ATP, hyposmotic medium, and ANG II. A complex pattern of efflux changes with culture time and type of stimulator was observed, suggesting that several compartments of the tissue contributed to stimulated efflux. This culture system provides opportunities for studies of chronic regulation of placental function.     

Comparison of cultures from rectoanal-junction mucosal swabs and feces for detection of Escherichia coli O157 in dairy heifers

Fecal culture for Escherichia coli O157:H7 was compared to rectoanal mucosal swab (RAMS) culture in dairy heifers over a 1-year period. RAMS enrichment culture was as sensitive as fecal culture using immunomagnetic separation (IMS) (P = 0.98, as determined by a chi-square test). RAMS culture is less costly than fecal IMS culture and can yield quantitative data.     

Production of Polyvinyl Alcohol Oxidase by a Symbiotic Mixed Culture

Production of polyvinly alcohol (PVA) oxidase by Pseudomonas sp. strain VM15C, a PVA degrader of a symbiotic PVA-utilizing mixed culture, was examined in various cultures. Despite the absence of PVA in the culture in nutrient broth, VM15C showed approximately the same productivity of PVA oxidase activity as that in the culture with PVA as the sole carbon source, whereas the productivity in the culture with glucose was lower than that of either the nutrient broth or the PVA culture. PVA oxidase activity produced in the nutrient broth culture was predominantly present in the cells, and most of the activity appeared to be in the cytoplasm. In contrast, in the culture with PVA as the sole carbon source, the activity was present in the culture fluid in a larger ratio than in the nutrient broth culture. Thus, production of PVA oxidase activity by this strain was constitutive and repressible, although localization of the produced activity was changed by growth conditions.     

Enhanced hyaluronic acid production by a two-stage culture strategy based on the modeling of batch and fed-batch cultivation of Streptococcus zooepidemicus

This study aimed to enhance hyaluronic acid (HA) production by a two-stage culture strategy based on the modeling of batch and fed-batch culture of Streptococcus zooepidemicus. Batch culture had higher specific HA synthesis rate while fed-batch culture had higher specific cell growth rate. The lower specific HA synthesis rate in fed-batch culture resulted from the competition of cell growth for the common precursors at a low substrate concentration. Based on the modeling of batch and fed-batch culture of S. zooepidemicus, a two-stage culture strategy was proposed to enhance HA production. S. zooepidemicus were cultured in a fed-batch mode with sucrose concentration maintained at 1.0+/-0.2g/L during 0-8h and then batch culture was performed during 8-20h with an initial sucrose concentration of 15g/L. With the proposed two-stage culture strategy, HA production was increased to 6.6g/L compared with 5.0g/L in batch culture with the same total sucrose. The enhanced HA production by the proposed two-stage culture strategy resulted from the decreased inhibition of cell growth and the increased transformation rate of sucrose to HA.     

Plating efficiency measurements and the experimental control of ageing of adult human skin fibroblasts in vitro.

Adult human skin fibroblasts were serially cultured by means of eleven protocols differing in inoculum size, duration of culture between passage and the ability of the medium to support cell division. Each protocol was terminated only when there were too few cells for further subculturing. The fraction of the cells of an inoculum adhering to the growth surface was unaffected by serial subculturing or by differences in protocol. The final cell count at the end of a period of culture and the plating efficiency for the next culture diminished progressively with serial subculturing. Nevertheless, the computed number of cell generations per culture period of those cells which divided was unaffected by serial passaging. The total number of cell doublings accruing during an entire protocol depended only on the duration of the period of culture between successive passages which was characteristic of that protocol. The observations can be accounted for quantitatively by the following assumptions. A cell which loses its ability to divide after a given period of culture nevertheless continues to grow in size during the next period of culture. The increase in volume of cell substance during any such period is the same whether or not a cell divides. The second postulate is that the probability of a cell being able to divide at the start of a period of culture is proportional to the probability that it will not lose this ability by the following period of culture.     

基于对立价值构架的医院文化建设实证研究

??????? 目的 了解医院现有和员工期望的文化类型,找到优势文化,为医院文化建设提供参考。方法 使用组织文化评价量表（OCAI）对山西省某医院230名员工进行问卷调查。结果 文化类型现状得分,团队支持型、创新变革型、市场绩效型和层级规范型依次为30.51、22.55、23.41、23.53分;上述文化类型期望得分依次是32.24、24.80、21.06、21.90分。结论 医院的优势文化为团队支持型和层级规范型,员工期望的优势文化是团队支持型和创新变革型。     

一种细胞培养微芯片的制作及应用

细胞培养是细胞研究的基础, 微系统技术的发展给细胞培养提供了新的方法。在微系统平台上进行细胞研究,能够充分利用微流体和微结构的性质, 对细胞进行操控, 在细胞生物学、组织工程学、药物筛选等领域有广泛应用。介绍了一种利用SU-8负性光刻胶模具制作双层细胞培养微芯片的方法, 该芯片通过狭缝将细胞培养区和微通道区隔离, 既保证细胞培养区域的相对独立, 又可以利用微流体的特性调节细胞外基质的性质, 给基于微芯片进行细胞研究提供了一种新的平台。     

A culture apparatus for maintaining H2 at sub-nanomolar concentrations

We devised a microbial culture apparatus capable of maintaining sub-nanomolar H2 concentrations. This apparatus provides a method for study of interspecies hydrogen transfer by externally fulfilling the thermodynamic requirement for low H2 concentrations, thereby obviating the need for use of cocultures to study some forms of metabolism. The culture vessel is constructed of glass and operates by sparging a liquid culture with purified gases, thereby removing H2 as it is produced. We used the culture apparatus to decouple a syntrophic association in an ethanol-consuming, methanogenic enrichment culture, allowing ethanol oxidation to dominate methane production. We also used the culture apparatus to grow pure cultures of the ethanol-oxidizing, proton-reducing Pelobacter acetylenicus (WoAcy 1), and to study the bioenergetics of growth.     

Simultaneous production of hydrogen and bioflocculant by Enterobacter sp. BY-29

Hydrogen and a bioflocculant could be produced simultaneously by anaerobic culture of Enterobacter sp. BY-29. For production of hydrogen and the bioflocculant by cell culture of the bacterium in batch cultures, cultivation at 37 °C in a medium containing glucose as a carbon source and Polypepton as a nitrogen source was found to be suitable. In continuous production of hydrogen and the bioflocculant by cell culture or immobilized cells of the bacterium, the hydrogen production rate and hydrogen yield by the immobilized cells on porous glass beads in stirred and column reactors were higher than those by the cell culture in a stirred reactor. However, production of the bioflocculant by the cell culture was superior to that by the immobilized cells in continuous production.     

The Effect of the Microgravity Rotating Culture System on the Chondrogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

We investigated the influence of the microgravity rotating culture system on the chondrogenic differentiation of bone marrow mesenchymal stem cells (MSCs). During chondrogenic induction, MSCs combined with polyglycolic acid (PGA) were cultured by static culture or microgravity rotating culture and chondrocyte formation was confirmed by toluidine blue staining. Furthermore, the mRNA and protein expressions of a specific cartilage extracellular matrix protein (collagen type II and Aggrecan) were evaluated by real-time RT-PCR and western blot, respectively. Toluidine blue staining indicated the OD values of proteoglycans semi-determination were higher in the microgravity rotating culture group than the static culture group. Following chondrogenic induction, mRNA and proteins of collagen type II and Aggrecan were more significantly expressed in cells of the microgravity rotating culture group compared with the controls. Compared with routine three-dimensional static culture, the microgravity rotating culture system was more effective for the construction of tissue-engineered cartilage in vitro.     

Secretion of stem cell factor and granulocyte-macrophage colony-stimulating factor by mouse embryos in culture: influence of group culture

Previous studies showed that the addition of a growth factor to the culture medium could modulate embryo development. The possible secretion of different factors to the culture medium by the embryo itself, however, has been poorly evaluated. The present study was designed to investigate: (1) the influence of single or group culture on the development of 2-cell mouse embryos (strain CD-1) to the blastocyst stage; (2) the release of granulocyte-macrophage colony-stimulating factor (GM-CSF) and stem cell factor (SCF) into the culture medium by the embryo; and (3) the levels of GM-CSF and SCF in the culture medium from both single and group embryos. Two-cell CD-1 mouse embryos were cultured for 96 h singly or in groups of five embryos per drop. GM-CSF and SCF were assayed by ELISA in the complete culture medium. It was found that embryos cultured in groups gave a higher percentage of total blastocyst formation and hatched blastocyst when compared with single embryo culture. The mouse embryos secreted GM-CSF and SCF to the culture medium. The concentration of these cytokines is significantly higher in the group cultures than the level found in single cultures. In conclusion, mouse embryos in culture secrete GM-CSF and SCF to the culture medium and the concentration of these cytokines increases during communal culture. These factors may be operating in both autocrine and paracrine pathways to modulate embryo development during in vitro culture.     

Ethanol production from starch by a coimmobilized mixed culture system of Aspergillus awamori and Zymomonas mobilis

The production of ethanol from starch by a coimmobilized mixed culture system of aerobic and anaerobic microorganisms in Ca-alginate gel beads was investigated. The mold Aspergillus awamori was used as an aerobic amylolytic microorganism and an anaerobic bacterium, Zymomonas mobilis, as an ethanol producer. By controlling the mixing ratio of the microorganisms in the inoculum size, a desirable coimmobilized mixed culture system, in which the aerobic mycelia grew on and near the oxygen-rich surface of the gel beads while the anaerobic bacterial cells mainly grew in the oxygen-deficient central part of the gel beads, was naturally established under the aerobic culture conditions, and ethanol could be directly produced from starch by the system. The ethanol productivity by the system in flask culture was particularly affected by the shear stress (dependent on the shaking speed) which controlled the mycelial growth on the surface of the gel beads. Under optimum culture conditions in the flask culture, the glucose produced was instantly consumed, and was not observed in the culture broth; the final concentration of ethanol produced from 100 g/L starch was 25 g/L and the yield coefficient for ethanol, Y(pls), was 0.38. The ethanol productivity by the coimmobilized mixed culture system was compared with those by other various culture systems and the advantages of the system were clarified.     

Role of distant cellular communications in regulation of Pseudomonas fluorescens adhesion

The effects of long-range interactions (LRI) and culture air on the adhesion of Pseudomonas fluorescens cells were studied. One P. fluorescens culture was found to diminish the adhesion of cells of another, glass-screened, P. fluorescens culture by 30%. This effect was interpreted to be due to penetrating LRI. Under the combined action of LRI and culture air (the latter alone reduced cell adhesion by only several percent), the amount of unattached cells increased 2- to 30-fold (on the average, by a factor of nine). Such a great reduction of cell adhesion indicated the synergistic action of LRI and culture air.     

Forensic culture as epistemic culture: The sociology of forensic science

This paper explores whether we can interpret the notion of ‘forensic culture’ as something akin to what Knorr-Cetina called an ‘epistemic culture’. Can we speak of a ‘forensic culture’, and, if so, how is it similar to, or different from, other epistemic cultures that exist in what is conventionally called ‘science’? This question has important policy implications given the National Academy Science’s (NAS) recent identification of ‘culture’ as one of the problems at the root of what it identified as ‘serious deficiencies’ in U.S. forensic science and ‘scientific culture’ as an antidote to those problems. Finding the NAS’s characterisation of ‘scientific culture’ overly general and naïve, this paper offers a preliminary exploration of what might be called a ‘forensic culture’. Specifically, the paper explores the way in which few of the empirical findings accumulated by sociologists of science about research science seem to apply to forensic science. Instead, forensic science seems to have developed a distinct culture for which a sociological analysis will require new explanatory tools. Faithful sociological analysis of ‘forensic culture’ will be a necessary prerequisite for the kind of culture change prescribed by external reformist bodies like the NAS.