Metabolic flux analysis of HEK-293 cells in perfusion cultures for the production of adenoviral vectors

To meet increasing needs of adenovirus vectors for gene therapy programs, development of efficient and reproducible production processes is required. Perfusion cultures were employed to allow infection at greater cell concentrations. In an effort to define culture conditions resulting in enhanced productivities, experiments performed at different feed rates and infected at various cell densities were compared using metabolic flux analysis. The highest specific product yields were achieved in experiments performed at high perfusion rates and/or low cell concentrations. The intracellular flux analysis revealed that these experiments exhibited greater glycolytic fluxes, slightly higher TCA fluxes, and greater ATP production rates at the time of infection. In contrast, cultures infected at high cell density and/or low medium renewal rates were characterized by a more efficient utilization of glucose at the time of infection, but the specific product yields achieved were lower. The intracellular flux analysis provided a rational basis for the implementation of a feeding strategy that allowed successful infection at a density of 5x10(6)cells/ml.     

Effects of temperature and food supply on the growth of whitefish Coregonus lavaretus larvae in an oligotrophic peri‐alpine lake

The relative roles of temperature and food availability on the seasonal and daily growth of whitefish Coregonus lavaretus larvae were investigated in the oligotrophic peri‐alpine Lake Annecy, France. During the spring from 2004 to 2007, surface water temperature and density of potential zooplankton prey were monitored, and 2688 larvae were caught and measured. In addition, the daily growth of 130 larvae was estimated retrospectively by investigating the microstructure of their otoliths. Temperature played the predominant role in controlling both seasonal and daily growth of early larvae. In contrast, the abundance of Mesocyclops leuckarti and larval density was only slightly correlated to larval growth, suggesting no food limitation nor strong interindividual competition over the study period. Overall, these findings run counter to concerns about potential food limitation, but sound a warning about the potential impact of climate change on fish ecology and fisheries management.     

Full-length prion protein aggregates to amyloid fibrils and spherical particles by distinct pathways

As limited structural information is available on prion protein (PrP) misfolding and aggregation, a causative link between the specific (supra)molecular structure of PrP and transmissible spongiform encephalopathies remains to be elucidated. In this study, high pressure was utilized, as an approach to perturb protein structure, to characterize different morphological and structural PrP aggregates. It was shown that full-length recombinant PrP undergoes beta-sheet aggregation on high-pressure-induced destabilization. By tuning the physicochemical conditions, the assembly process evolves through two distinct pathways leading to the irreversible formation of spherical particles or amyloid fibrils, respectively. When the PrP aggregation propensity is enhanced, high pressure induces the formation of a partially unfolded aggregated protein, Agg(HP), which relaxes at ambient pressure to form amorphous aggregates. The latter largely retain the native secondary structure. On prolonged incubation at high pressure, followed by depressurization, Agg(HP) transforms to a monodisperse population of spherical particles of about 20 nm in diameter, characterized by an essentially beta-sheet secondary structure. When the PrP aggregation propensity is decreased, an oligomeric reaction intermediate, I(HP), is formed under high pressure. After pressure release, I(HP) relaxes to the original native structure. However, on prolonged incubation at high pressure and subsequent depressurization, it transforms to amyloid fibrils. Structural evaluation, using optical spectroscopic methods, demonstrates that the conformation adopted by the subfibrillar oligomeric intermediate, I(HP), constitutes a necessary prerequisite for the formation of amyloids. The use of high-pressure perturbation thus provides an insight into the molecular mechanism of the first stages of PrP misfolding into amyloids.     

Somaclonal variation rate evolution in plant tissue culture: Contribution to understanding through a statistical approach

Summary In order to better understand somaclonal variant rate evolution in plant tissue culture, a statistical approach has been adopted. According to this approach, the variant percentage could be calculated by: %V=[1−(1−p) ⁿ ]×100, where %V is the percentage of variant, p the probability of variation and n the number of multiplication cycles. A numerical estimation was performed to characterize the variance of this function. It has been demonstrated that a wide scale of variance is associated with ‘%V’, due to the occurrence of variations after a variable number of multiplication cycles in the different lines of culture. Two main conclusions can be drawn from this model: (1) a variant rate increase can be expected as an exponential function of the number of multiplication cycles; (2) after a given number of multiplication cycles, variable off-types percentages can be expected. Due to the complexity of biological systems, this statistical approach could obviously not be applied directly for the calculation and forecasting of variant rates in tissue culture. However, this approach results in a better understanding of two apparently confusing experimental features often reported in tissue culture: the increase of the variant rate as a function of the length of the culture period on the one hand, and, on the other hand, the observations of different variant rates among lines cultured for the same lengths of time under strietly identical culture conditions. This approach also underlined that the comparison of somaclonal variant percentage between batches of plants from different in vitro treatments could be, in some cases, insufficient for ascertaining a difference of variability generated by tissue culture.     

Effect of L-adrenaline on extracellular space in rabbit aorta and pulmonary artery]

Adrenaline causes an increase of extra-cellular fluid space in aorta and pulmonary artery of the rabbit. The effect is parallel in both tissues and the relative increase is about 20% of the normal value. The results confirm the oedematous reaction of the arterial wall to adrenaline; this action of adrenaline appears to be very long.     

The discovery of rofecoxib, [MK 966, Vioxx, 4-(4'-methylsulfonylphenyl)-3-phenyl-2(5H)-furanone], an orally active cyclooxygenase-2-inhibitor.

The development of a COX-2 inhibitor rofecoxib (MK 966, Vioxx) is described. It is essentially equipotent to indomethacin both in vitro and in vivo but without the ulcerogenic side effect due to COX-1 inhibition.