Growth kinetics of glucose-limited petunia hybrida cells in chemostat cultures: Determination of experimental values for growth and maintenance parameters

With glucose-limited continuous cultures of Petunia hybrida six steady states were obtained at specific growth rates varying from 0.0035 to 0.012 h(-1) (corresponding with culture residence times varying from 285 to 85 h). The macromolecular and the elemental biomass composition which were determined in four steady states showed no major differences over the range of growth rates examined. During all six steady states specific subtrate and oxygen consumption as well as biomass and extracellular product formation rates were monitored. Moreover the specific activities of the mitochondrial cytochrome and alternative pathway were determined and used to estimate specific adenosine triphosphate (ATP) production rates. Data thus obtained were used in the determination of maintenance and true growth yield parameters. For the maintenance on glucose and ATP values of 0.0070 C-mol/C-mol/h and 0.034 mol/C-mol/h were obtained, respectively. True yields of biomass on glucose and ATP were 0.50 C-mol/C-mol and 0.28 C-mol/mol, respectively. (c) 1995 John Wiley & Sons, Inc.     

Embryogenesis and cardenolide formation in tissue cultures of Digitalis lanata

Digitalis lanata strain VII from filament callus grew in small cell colonies in nutrient media with high auxin activity. Upon increasing the cytoki     

Nitrate assimilatory properties of barley grown under long-term N limitation: Effects of local nitrate supply in split-root cultures

The effect of nitrate availability on characteristics of the nitrate assimilatory system was investigated in N-limited barley (Hordeum valgare L. cv. Golf), grown with the seminal root system split into initially equal-sized halves. The cultures were continuously supplied with nitrate-N at a relative addition rate (RA) of 0.09 day^?1, which resulted in relative growth rates (RG) that were ca 85% of those observed under surplus nitrate nutrition. The total N addition was divided between the subroots in ratios of 100:0, 80:20, 70:30, 60:40, and 50:50. For comparison, standard cultures were grown at RAs ranging from 0.03 to 0.18 day^?1. Initially, biomass and N partitioning to the subroots responded strongly and proportionally to the nitrate distribution ratio. After 12-14 days no further effect was observed. The V_max for net nitrate uptake and in vitro nitrate reductase (NR) activity were measured in acclimated plants, i.e., after > 14 days under a certain nitrate regime. In subroots fed from 20 to 100% of the total N addition, V_max for net nitrate uptake increased slightly, whereas NR activity was unaffected. Uptake and NR activities were insignificant in the 0%-subroot. Uneven nitrate supply to individual subroots had negligible effect on the whole-plant ability for nitrate uptake, and the relative V_max (unit N taken up per unit N in whole plant tissue and time) remained about 7-fold in excess of the demand set by growth. Balancing nitrate concentrations (the resulting external nitrate concentrations at a certain RA) generally ranged between 2 and 10 μM at growth-limiting RA, both when predicted from uptake kinetics and when actually measured. When comparing split root and standard cultures when acclimated, it appears that uptake and NR activities in roots respond more strongly to over-all nitrate availability than to nitrate availability to individual subroots.     

Production of higher levels of trigonelline by cell cultures of Trigonella foenum-graecum than by the differentiated plant

Callus cultures of Trigonella foenum-graecum contained 3 to 4 times more trigonelline than the seeds of this plant and 12 to 13 times more than the roots and shoots. Even higher levels of this alkaloid were produced by suspension cultures. This high productivity was maintained during successive subculturing of calli and cell suspensions for eight months. Thus, trigonelline is to be added to the group of the few metabolites whose synthesis in cell cultures exceeds its production in the differentiated plants. Media that had supported the growth of suspension cultures contained one third or more of the total alkaloid, whereas media of callus cultures contained about one tenth of this substance. Trigonelline accumulated in callus and suspension cultures with aging. Raising the level of nicotinic acid in the nutrient medium resulted in some increase of trigonelline production by the culture.Abbreviations 2.4 D 2.4-dichlorophenoxyacetic acid - IAA indoleacetic acid - IPA indolepropionic acid - NAA -naphthaleneacetic acid - GA Gibberellic acid - K kinetin     

Mixed immunotherapy and chemotherapy of tumors: feedback design and model updating schemes

In this paper, a recently developed model governing the cancer growth on a cell population level with combination of immune and chemotherapy is used to develop a reactive (feedback) mixed treatment strategy. The feedback design proposed here is based on nonlinear constrained model predictive control together with an adaptation scheme that enables the effects of unavoidable modeling uncertainties to be compensated. The effectiveness of the proposed strategy is shown under realistic human data showing the advantage of treatment in feedback form as well as the relevance of the adaptation strategy in handling uncertainties and modeling errors. A new treatment strategy defined by an original optimal control problem formulation is also proposed. This new formulation shows particularly interesting possibilities since it may lead to tumor regression under better health indicator profile.     

Migration Behavior of Rodent Granule Neurons in the Presence of Antibody to the 4C5 Antigen

Abstract: We have reported the production of monoclonal antibody 4C5, which recognizes a cell surface antigen, the 4C5 antigen, involved in granule cell migration processes. In the present study, we investigated in a more precise manner the role of the 4C5 antigen in the different types of granule cell migrations that take place during cerebellar development. When cerebellar explant cultures derived from 10-day-old rats were performed for 2 days in the presence of monoclonal antibody 4C5, vertical granule cell migration, occurring in the presence of glia, was not significantly inhibited. In contrast, when monoclonal antibody 4C5 was included in the medium of microexplant cultures derived from 4-day-old mice and maintained for 4 days in vitro, granule cell migrations that occurred both parallel and perpendicular to the neurite bundles that were free of glia were inhibited. Moreover, a stronger inhibitory effect of the antibody was observed on migration perpendicular to the neurite bundles compared with the parallel type of migration. Our results indicate that the 4C5 antigen differentially affects the different developmental stages and types of granule cell migration during rodent cerebellar development.     

Excitable properties of insect neurones in culture: A developmental study

The passive and excitable electrical properties of cockroach neurones growing in vitro have been investigated using intracellular recording techniques. The resting membrane potentials of the neurones are similar to those of their in vivo counterparts but the input resistances and membrane capacitive properties are more typical of embryonic insect neurones. During the first 12 days of growth in vitro the neurones exhibit delayed rectification in response to the injection of depolarising current steps. After this period “all or none” action potentials can be evoked by depolarising pulses in approximately half of the neurones tested. These spikes are abolised by 1 μM tetrodotoxin but are unaffected by 5 mM Co²⁺. Spontaneous excitatory activity develops in approx 25% of the neurones after 3 weeks in culture.     

Fertile plant regeneration from cell suspension and protoplast cultures of barley (t Hordeum vulgare cv. Schooner)

Fertile plants were regenerated from both cell suspension and protoplast-derived cultures of the two-row barley, Hordeum vulgare L. cv. Schooner. Embryogenic calluses, derived from immature embryos, were used to establish suspension cultures. More than 100 plants, with variable seed set, have been regenerated from six embryogenic cell suspension cultures. Protoplasts isolated from three suspension cultures divided and when the resultant embryogenic proto-calluses were transferred to regeneration medium both green and albino shoots were produced. The green shoots were transferred to growth regulator-free medium and plantlets that developed strong root systems were potted in soil and grown to maturity in the glasshouse. Root tip analysis of plants regenerated from cell suspension cultures revealed the expected 2N = 14 complement of chromosomes. However, chromosomal analysis of protoplast-derived plants showed numerical variation among a proportion of the regenerants. This revised version was published online in June 2006 with corrections to the Cover Date.     

High rate treatment of terephthalic acid production wastewater in a two-stage anaerobic bioreactor

The feasibility was studied of anaerobic treatment of wastewater generated during purified terephthalic acid (PTA) production in two-stage upflow anaerobic sludge blanket (UASB) reactor system. The artificial influent of the system contained the main organic substrates of PTA-wastewater: acetate, benzoate, and terephthalate. Three parallel operated reactors were used for the second stage, and seeded with a suspended terephthalate degrading culture, with and without additional methanogenic granular sludge (two different types). The first stage UASB-reactor was seeded with methanogenic granular sludge. Reactors were operated at 37 degrees C and pH 7. During the first 300 days of operation a clear distinction between the biomass grown in both reactor stages was obtained. In the first stage, acetate and benzoate were degraded at a volumetric loading rate of 40 g-COD/L . day at a COD-removal efficiency of 95% within the first 25 days of operation. No degradation of terephthalate was obtained in the first stage during the first 300 days of operation despite operation of the reactor at a decreased volumetric loading rate with acetate and benzoate of 9 g-COD/L . day from day 150. Batch incubation of biomass from the reactor with terephthalate showed that the lag-phase prior to terephthalate degradation remained largely unchanged, indicating that no net growth of terephthalate degrading biomass occurred in the first stage reactor. From day 300, however, terephthalate degradation was observed in the first stage, and the biomass in this reactor could successfully be enriched with terephthalate degrading biomass, resulting in terephthalate removal capacities of 15 g-COD/L . day. Even though no single reason could be identified why (suddenly) terephthalate degradation was obtained after such a long period of operation, it is suggested that the solid retention time as well the prevailing reactor concentrations acetate and benzoate may have played an important role. From day 1 of operation, terephthalate was degraded in the second stage. In presence of methanogenic granular biomass, high terephthalate removal capacities were obtained in these reactors (15 g-COD/L . day) after approximately 125 days of operation. From the results obtained it is concluded that terephthalate degradation is the bottleneck during anaerobic treatment of PTA-wastewater. Pre-removal of acetate and benzoate in staged bioreactor reduces the lag-phase prior to terephthalate degradation in latter stages, and enables high rate treatment of PTA-wastewater.