Patterns of Development and Nitrogen Reserves Mobilization during Regrowth of Defoliated Clover

Contribution of nitrogen reserves to regrowth following defoliation was studied in white clover plants (Trifolium repens) according to the morphological pattern of differentiation of the aerial parts during the same period. Low temperature and short day lengths were used as a pre-treatment in order to increase branching and enhance new sites of leaf production during a further 25 d period of regrowth. Pre-treated plants exhibited a large reduction in leaf area largely counterbalanced with a high increase in leaf pool size during the first 10 d of regrowth. The mobilization of nitrogen reserves during regrowth of defoliated clover was intimately linked to the pattern of differentiation of the newly developed organs. It thus appeared that regrowth of pretreated plants was less supported by endogenous N during the first 10 d as compared to control plants continously grown in standard conditions. It is assumed that regrowth of dwarf plants is less dependent upon the mobilization rate of soluble proteins previously accumulated in roots and uncut stolons

Discretization of hyperbolic type Darboux integrable equations preserving integrability

A method of integrable discretization of the Liouville type nonlinear partial differential equations is suggested based on integrals. New examples of discrete Liouville type models are presented.Comment: 16 page

Modelling Nitrogen Uptake in Winter Oilseed Rape by Using Influx Kinetics of Nitrate Transport Systems

A mechanistic model was proposed in order to predict nitrogen uptake by a culture of oilseed rape (Brassica napus L.), using independently measured characteristics of plants growing in hydroponic or under field conditions. Uptake kinetics of the different components (Constitutive and Inducible) of the Low and High Affinity Transport Systems of nitrate (CLATS, ILATS, CHATS and IHATS, respectively) were determined by 15NO3- labelling in controlled conditions. The use of kinetic equations of transport systems and the experimental field data from the INRA-Châlons rape databank allowed to model NO3- uptake during the plant growth cycle. The study of different factors such as root temperature, day/night cycle and ontogenetic stages on NO3- uptake rate has been undertaken in order to improve the model prediction. Model outputs show that the high affinity transport system (HATS) accounted for about 90 % of total NO3- uptake (20 and 70 % for CHATS and IHATS without fertilization, respectively). The low affinity transport system (LATS) accounted for a minor proportion of total N uptake, and its activity was restricted to the early phase of the growth cycle. However, N autumnal fertilization increased the duration of its contribution (from 67 to 100 days) to total N uptake

Brain Tumors: Convection-Enhanced Delivery of Drugs (Method)

Delivery of therapeutic agents into the brain has been an ongoing challenge for many years. The poor prognosis for patient with primary malignant brain tumors treated with conventional techniques (surgery, radiotherapy and chemotherapy) has motivated the development of new strategies to deliver drugs into the brain. Local intracranial delivery of antineoplastic agents has appeared to be the most effective drug delivery technique into the central nervous system by circumventing the limitations imposed by the blood brain barrier (BBB). Convection-enhanced delivery (CED) is an alternative strategy to directly infuse drugs into brain tissue. This approach is based on continuous injection of the therapeutic agent under positive pressure via a catheter implanted into the brain. Convective transport driven by pressure gradient allows a widespread distribution of small and large drugs within the brain. In vivo experiments in rodents, cats and primates proved the efficacy of CED to deliver drugs into a targeted zone. However, clinical trials have reported frequent leakage phenomenon leading to mixed results for this delivery technique. A better optimization of operational parameters including infusion rate, catheter design, catheter placement and drug pharmacological formulation should allow achieving accurate and efficient delivery. In conjunction with CED, the use of nanocarriers to enhance drug pharmacokinetic behavior may help to achieve higher therapeutic index against tumor cells over healthy tissues. Additionally, the development of computer simulation to predict drug distribution and the real-time imaging for immediate assessment of convection efficiency may contribute to the CED improvement

Characterization of the TRBP domain required for Dicer interaction and function in RNA interference

<p>Abstract</p> <p>Background</p> <p>Dicer, Ago2 and TRBP are the minimum components of the human RNA-induced silencing complex (RISC). While Dicer and Ago2 are RNases, TRBP is the double-stranded RNA binding protein (dsRBP) that loads small interfering RNA into the RISC. TRBP binds directly to Dicer through its C-terminal domain.</p> <p>Results</p> <p>We show that the TRBP binding site in Dicer is a 165 amino acid (aa) region located between the ATPase and the helicase domains. The binding site in TRBP is a 69 aa domain, called C4, located at the C-terminal end of TRBP. The TRBP1 and TRBP2 isoforms, but not TRBPs lacking the C4 site (TRBPsΔC4), co-immunoprecipitated with Dicer. The C4 domain is therefore necessary to bind Dicer, irrespective of the presence of RNA. Immunofluorescence shows that while full-length TRBPs colocalize with Dicer, TRBPsΔC4 do not. <it>tarbp2</it>^-/-cells, which do not express TRBP, do not support RNA interference (RNAi) mediated by short hairpin or micro RNAs against EGFP. Both TRBPs, but not TRBPsΔC4, were able to rescue RNAi function. In human cells with low RNAi activity, addition of TRBP1 or 2, but not TRBPsΔC4, rescued RNAi function.</p> <p>Conclusion</p> <p>The mapping of the interaction sites between TRBP and Dicer show unique domains that are required for their binding. Since TRBPsΔC4 do not interact or colocalize with Dicer, we suggest that TRBP and Dicer, both dsRBPs, do not interact through bound dsRNA. TRBPs, but not TRBPsΔC4, rescue RNAi activity in RNAi-compromised cells, indicating that the binding of Dicer to TRBP is critical for RNAi function.</p