Kinetic studies of recombinant rabies virus glycoprotein (RVGP) cDNA transcription and mRNA translation in Drosophila melanogaster S2 cell populations.

Recombinant rabies virus glycoprotein (RVGP) was expressed in cell membranes of stably transfected Drosophila S2 cells using constitutive and inducible promoters. Although with quantitative differences of RVGP expression in both systems, the cDNA transcription, as evaluated by relative RVGP mRNA levels measured by qRT-PCR, sustained the amount of RVGP producing cells and the RVGP volumetric (ΠRVGP) productivity. At the transition to the stationary cell growth phase, once the cell culture slowed down its rate of multiplication, an accumulation of RVGP mRNA and RVGP was clearly observed in both cell populations. Nevertheless, cell cultures performed under sub-optimal temperatures indicated that an envisaged increase in the RVGP production is not only dependent on cell growth rate, but essentially on optimal cell metabolic state.

Kinetic response of a Drosophila melanogaster cell line to different medium formulations and culture conditions.

In the past few years, Drosophila melanogaster cells have been employed for recombinant protein production purposes, and a comprehensive knowledge of their metabolism is essential for process optimization. In this work, the kinetic response of a Schneider S2 cell line, grown in shake flasks, in two different culture media, the serum-free SF900-II((R)) and the serum-supplemented TC-100, was evaluated. Cell growth, amino acids and glucose uptake, and lactate synthesis were measured allowing the calculation of kinetic parameters. The results show that S2 cells metabolism was able to adjust to different environmental situations, as determined by medium formulation, as well as by the particular situation resulting from the culture conditions. Cells attained a 163% higher final cell concentration (1.4 x 10(7) cells mL(-1)) in SF900 II((R)) medium, when compared to serum-supplemented TC-100 medium. Also, a maximum specific cell growth rate 52% higher in SF900 II((R) )medium, when compared to serum-supplemented TC-100 one, was observed. Glutamine was the growth limiting factor in SF900 II((R)) medium, while glucose, sometimes associated with glutamine, controlled growth in serum-supplemented TC-100 medium based formulation. The different pattern of lactate production is an example of the versatility of the metabolism of these cells. This by-product was produced only in glutamine limitation, but the amount synthesized depended not only on the excess glucose, but on other medium components. Therefore, in serum-supplemented TC-100 medium a much smaller lactate amount was generated. Besides, glucose was identified not only as a growth limiting factor, but also as a viability limiting factor, since its depletion accelerated cell death.

Uranium incorporation biokinetics in poultry bonesas function of phytase doses

Direct alpha-energy spectroscopy in liquids is possible by placing a chemically selective polymer thin film upon the surface of passivated silicon diodes. By utilizing polymer thin films with high affinity for actinides, we have been able to selectively concentrate actinides of interest upon the diode surface, resulting in a substantial increase in sensitivity relative to a direct measurement. With this film coated diodes, we were able to obtain in-situ alpha spectra with energy resolution comparable to that of conventional alpha-spectroscopy. The response of the thin film coated diode was found to be linear over . The sensitivity and reversibility is a function of the membrane complexation chemistry.

Long-term accumulation and microdistribution of uranium in the bone and marrow of beagle dog.

The accumulation and microdistribution of uranium in the bone and marrow of Beagle dogs were determined by both neutron activation and neutron-fission analysis. The experiment started immediately after the weaning period, lasting till maturity. Two animal groups were fed daily with uranyl nitrate at concentrations of 20 and 100 microg g(-1) food. Of the two measuring techniques, uranium accumulated along the marrow as much as in the bone, contrary to the results obtained with single, acute doses. The role played by this finding for the evaluation of radiobiological long-term risks is discussed. It was demonstrated, by means of a biokinetical approach, that the long-term accumulation of uranium in bone and marrow could be described by a piling up of single dose daily incorporation.

Rabies virus production in high vero cell density cultures on macroporous microcarriers.

The purpose of the study was to investigate the rabies virus multiplication in Vero cell cultures performed on porous microcarriers, MCs (cellulose-Cytopore and gelatin-Cultispher G), which provide higher available surface area compared with solid (nonporous) MCs (DEAE-Cytodex 1). In a set of experiments performed at the same MC concentration (MCs per milliliter), cell densities regularly obtained in porous MC cultures were comparable, but almost twice as high as those in solid MC cultures. In addition, 41.1 +/- 3.9-, 35.2 +/- 2-, and 19.6 +/- 5.8-fold increases in cell concentration, relative to the initial cell number, along with maximum rabies virus titers of 6.3 +/- 0.3 x 10(4), 5 +/- 0.1 x 10(4), and 4.3 +/- 0.2 x 10(4) FFD(50)/mL were observed in Cytopore, Cultispher G, and Cytodex 1 MC cultures, respectively. When higher concentrations of MCs were employed, lower performances of virus production and MC-cell occupation (cells per MC or cells per square millimeter) were observed. Cell attachment to MCs was shown to be faster for Cytopore MCs and Cytodex 1 MCs than for Cultispher G MCs. Concerning the kinetics of cell multiplication on MCs, exponential cell growth, at similar specific cell growth rates, took place on Cytopore, Cultispher G, and Cytodex 1 MCs. In addition, cell densities as high as 2.1 +/- 0.2 x 10(6) cells/mL on Cytopore MCs, 1.8 +/- 0.1 x 10(6) cells/mL on Cultispher G MCs, and 1 +/- 0.3 x 10(6) cells/mL on Cytodex 1 MCs were regularly obtained in batch cultures. Optical as well as scanning and transmission electron microscopy studies carried out to analyze MC structure, MC cell occupation, and cell permissivity to virus infection demonstrated that there was uniform cell distribution in the external and internal areas of the MCs, suggesting an efficiency of virus synthesis. Our results indicate the usefulness of these supports for rabies virus antigen production, as well as possibilities for further optimization.