Distinction between cultivated and wild chicory gene pools using AFLP markers

The cultivation area of industrial chicory, Cichorium intybus L. cv Sativum, coincides with the natural distribution area of its wild relative, C. intybus L., which could lead to gene flow between wild and cultivated types. The genetic diversity within and between the two types has therefore been studied using AFLP genotyping of samples from 12 wild populations collected in Belgium and ten commercial varieties. The genotyping of 233 individuals allowed the identification of 254 AFLP markers. Similar levels of genetic diversity were observed within wild populations and cultivated varieties, suggesting the absence of any strong bottleneck in the history of the cultivated types. The phylogenetic analysis pointed to a monophyletic origin of cultivated varieties as compared to the local wild populations studied, hence the two types of chicory form two separate gene pools. The genotyping of some individuals sampled in ruderal sites clearly showed that they belong to the cultivated gene pool, which suggests the existence of feral or weedy types. The low differentiation observed among wild populations indicates that gene flow might be important in this species.     

Somatic motoneurone specification in the hindbrain: the influence of somite-derived signals,retinoic acid and Hoxa3

We have investigated the mechanisms involved in generating hindbrain motoneurone subtypes, focusing on somatic motoneurones, which are confined to the caudal hindbrain within rhombomeres 5-8. Following heterotopic transplantation of rhombomeres along the rostrocaudal axis at various developmental stages, we have found that the capacity of rhombomeres to generate somatic motoneurones is labile at the neural plate stage but becomes fixed just after neural tube closure, at stage 10-11. Grafting of somites or retinoic acid-loaded beads beneath the rostral hindbrain induced the formation of somatic motoneurones in rhombomere 4 only, and Hox genes normally expressed more caudally (Hoxa3, Hoxd4) were induced in this region. Targeted overexpression of Hoxa3 in the rostral hindbrain led to the generation of ectopic somatic motoneurones in ventral rhombomeres 1-4, and was accompanied by the repression of the dorsoventral patterning gene Irx3. Taken together, these observations suggest that the somites, retinoic acid and Hox genes play a role in patterning somatic motoneurones in vivo.     

Mechanisms governing the accumulation of estrogen receptor alpha in MCF-7 breast cancer cells treated with hydroxytamoxifen and related antiestrogens

This study aimed at a better understanding of estrogen receptor alpha (ER) up regulation induced by partial estrogen antagonists. Effect of treatment with hydroxytamoxifen (OH-Tam) on ER level in MCF-7 cells was investigated by an approach combining ER measurement (enzyme immunoassay) and morphological demonstration (immunofluorescence). Furthermore, the influence of drug exposure on the rates of ER synthesis and degradation was assessed by determining [35S]methionine incorporated into the receptor in different experimental conditions (measurement of synthesis or pulse-chase experiments). ER up regulation was already induced by a 1-h pulse treatment with OH-Tam, thus a continuous exposure was not required. This process appeared reversible (i.e. ER accumulation due to OH-Tam rapidly vanished upon subsequent exposure to 17beta-estradiol (E2) or the pure antiestrogen RU 58668). While OH-Tam did not affect the rate of [35S]methionine incorporation into ER, it clearly caused an impairment of ER degradation (pulse-chase experiments) indicating that up regulation results from a stabilization of the receptor associated with the maintenance of its synthesis. Various tamoxifen derivatives, as well as a few related partial antiestrogens, were compared on the basis of binding ability and propensity to induce ER up regulation. A close relationship was found between both properties. Structure-activity analysis revealed that the capacity of these compounds to induce ER up regulation is associated with characteristics of their aminoalkyle side-chain, similar to those required for antiestrogenicity.     

Forecasting Physicochemical Variables by a Classification Tree Method. Application to the Berre Lagoon (South France)

The dynamics of the "Etang de Berre", a brackish lagoon situated close to the French Mediterranean sea coast, is strongly disturbed by freshwater inputs coming from an hydroelectric power station. The system dynamics has been described as a sequence of daily typical states from a set of physicochemical variables such as temperature, salinity and dissolved oxygen rates collected over three years by an automatic sampling station. Each daily pattern summarizes the evolution, hour by hour of the physicochemical variables. This article presents results of forecasts of the states of the system subjected to the simultaneous effects of meteorological conditions and freshwater releases. We recall the main step of the classification tree method used to build up the predictive model (Classification and Regression Trees, Breiman et al., 1984) and we propose a transfer procedure in order to test the stability of the model. Results obtained on the Etang de Berre data set allow us to describe and predict the effects of the environmental variables on the system dynamics with a margin of error. The transfer procedure applied after the tree building process gives a maximum gain in prediction accuracy of about 15%.     

On-line monitoring of physiological parameters of insect cell cultures during the growth and infection process

On-line monitoring of insect cell cultures used for the production of recombinant proteins with the baculovirus expression vector system (BEVS) provides valuable tools for the optimization, operation, and control of the production process. The relative permittivity (epsilon') and CO(2) evolution rates (CER) were measured on-line using the biomass monitor and the infrared CO(2) analyzer, respectively. The growth and infection phases of two different cell lines, Spodoptera frugiperda (Sf-9) and Trichoplusia ni(High-5), were monitored using the above measurements. These in turn were correlated to the progress of the culture by using the off-line measurements of protein produced, virus titer, and biovolume, which is the product of viable cell density and mean cell volume. The epsilon', CER, and the biovolume profiles were closely matched during the growth phase of cells when grown in a batch or fed batch culture. The relationship became more complex when the cultures were either in stationary phase or in the postinfection phase. The epsilon' profile was found to be a good indicator of the process of synchronous baculoviral infection, showing a plateau between 18 and 24 h postinfection (hpi), the period during which budded virus is produced, and a peak at approximately 48 hpi correlated to the onset of accelerated cell lysis. The CER profile continues to increase after the growth period with a peak around the 24 hpi period, after which there is a decline in the profile corresponding to release of virus as seen from virus titer determinations. This was examined for Sf-9 cultures under conditions of cell densities from 3 to 50 x 10(6) cells/mL and MOI values ranging from 0.001 to 1000. The profiles were found to be similar also in the case of the High-5 cells. Thus both measurements give reliable information regarding the physiological status of the cells as seen from their correlation to virus and protein production. A further combination of these with the off-line measured parameters such as the biovolume and metabolite concentrations can give a more detailed understanding of the process and help in the better design and automation of these processes.     

Time-resolved electron transfer at the donor side of Rhodopseudomonas viridis photosynthetic reaction centers in whole cells

We have studied the electron transfer reactions from the tetraheme cytochrome of Rhodopseudomonas viridis to the oxidized primary donor in whole cells with a new high sensitivity spectrophotometer. In this apparatus the monochromatic detecting flashes are provided by a YAG pumped Optical Parametric Oscillator, allowing a 10 ns time resolution. When four hemes are reduced the observed electron transfer reaction sequence is the following: first the low-potential c552 heme (the number refers to the maximum absorption wavelength in the alpha-band region) is oxidized with a half time of 130 ns, in agreement with previous reports of measurements performed with purified reaction centers. Then, the electron hole is transferred to the low potential c554 heme with a half time of 2.6 µs. When only the two high potential hemes are reduced the observed electron transfer sequence is the following: oxidation of the high potential c559 heme in the hundreds of ns time range (410 ns), reduction of this heme by the high potential c556 heme in the µs time range (2.7 µs). This confirms the first steps of electron transfer observed in isolated reaction centers. However, in the microsecond time domain, the overall amount of oxidized hemes increases suggesting that, in vivo, the equilibrium constant between the P⁺/P and the c559^ox/c559^red couples is significantly lower than expected from the difference in their midpoint potentials.     

Behavioral Cost & Overdominance in Anopheles gambiae

In response to the widespread use of control strategies such as Insecticide Treated Nets (ITN), Anopheles mosquitoes have evolved various resistance mechanisms. Kdr is a mutation that provides physiological resistance to the pyrethroid insecticides family (PYR). In the present study, we investigated the effect of the Kdr mutation on the ability of female An. gambiae to locate and penetrate a 1cm-diameter hole in a piece of netting, either treated with insecticide or untreated, to reach a bait in a wind tunnel. Kdr homozygous, PYR-resistant mosquitoes were the least efficient at penetrating an untreated damaged net, with about 51% [39-63] success rate compared to 80% [70-90] and 78% [65-91] for homozygous susceptible and heterozygous respectively. This reduced efficiency, likely due to reduced host-seeking activity, as revealed by mosquito video-tracking, is evidence of a recessive behavioral cost of the mutation. Kdr heterozygous mosquitoes were the most efficient at penetrating nets treated with PYR insecticide, thus providing evidence for overdominance, the rarely-described case of heterozygote advantage conveyed by a single locus. The study also highlights the remarkable capacity of female mosquitoes, whether PYR-resistant or not, to locate holes in bed-nets.