To counter the global threat caused by Plasmodium falciparum malaria, new drugs and vaccines are urgently needed. However, there are no practical animal models because P. falciparum infects human erythrocytes almost exclusively. Here we describe a reliable falciparum murine model of malaria by generating strains of P. falciparum in vivo that can infect immunodeficient mice engrafted with human erythrocytes. We infected NODscid/β2m−/− mice engrafted with human erythrocytes with P. falciparum obtained from in vitro cultures. After apparent clearance, we obtained isolates of P. falciparum able to grow in peripheral blood of engrafted NODscid/β2m−/− mice. Of the isolates obtained, we expanded in vivo and established the isolate Pf3D70087/N9 as a reference strain for model development. Pf3D70087/N9 caused productive persistent infections in 100% of engrafted mice infected intravenously. The infection caused a relative anemia due to selective elimination of human erythrocytes by a mechanism dependent on parasite density in peripheral blood. Using this model, we implemented and validated a reproducible assay of antimalarial activity useful for drug discovery. Thus, our results demonstrate that P. falciparum contains clones able to grow reproducibly in mice engrafted with human erythrocytes without the use of myeloablative methods.

A series of diaryl ether substituted 4-pyridones have been identified as having potent antimalarial activity superior to that of chloroquine against Plasmodium falciparum in vitro and murine Plasmodium yoelii in vivo. These were derived from the anticoccidial drug clopidol through a systematic study of the effects of varying the side chain on activity. Relative to clopidol the most active compounds show >500-fold improvement in IC50 for inhibition of P. falciparum in vitro and about 100-fold improvement with respect to ED50 against P. yoelii in mice. These compounds have been shown elsewhere to act selectively by inhibition of mitochondrial electron transport at the cytochrome bc1 complex.

Plasmodium falciparum, the causative agent of malaria, relies extensively on glycolysis coupled with homolactic fermentation during its blood-borne stages for energy production. Selective inhibitors of the parasite lactate dehydrogenase (LDH), central to NAD ؉ regeneration, therefore potentially provide a route to new antimalarial drugs directed against a novel molecular target. A series of heterocyclic, azole-based compounds are described that preferentially inhibit P. falciparum LDH at sub-micromolar concentrations, typically at concentrations about 100-fold lower than required for human lactate dehydrogenase inhibition. Crystal structures show these competitive inhibitors form a network of interactions with amino acids within the active site of the enzyme, stacking alongside the nicotinamide ring of the NAD ؉ cofactor. These compounds display modest activity against parasitized erythrocytes, including parasite strains with known resistance to existing anti-malarials and against Plasmodium berghei in BALB/c mice. Initial toxicity data suggest the azole derivatives have generally low cytotoxicity, and preliminary pharmocokinetic data show favorable bioavailability and circulation times. These encouraging results suggest that further enhancement of these structures may yield candidates suitable for consideration as new therapeutics for the treatment of malaria. In combination these studies also provide strong support for the validity of targeting the Plasmodium glycolytic pathway and, in particular, LDH in the search for novel anti-malarials.Plasmodium parasites are believed to lack a functional Krebs (citric acid) cycle for at least part of their life cycle and hence rely extensively on ATP generation via the anaerobic fermentation of glucose (see Ref. 1 for review). The energy requirement of the parasitized erythrocyte is such that utilization of glucose is up to 100 times greater than in nonparasitized erythrocytes (2, 3), and virtually all glucose can be accounted for by production of lactate (2). Lactate dehydrogenase (LDH), 1 the last enzyme in the glycolytic pathway in Plasmodium falciparum, is a 2-hydroxy acid oxidoreductase that converts pyruvate to lactate and simultaneously the conversion of NADH to NAD ϩ . As a constant supply of NADH is a prerequisite for glycolysis, and LDH acts as the primary source in Plasmodium for the regeneration of NADH from NAD ϩ , inhibition of LDH is expected to stop production of ATP, with subsequent P. falciparum cell death. Any compound that blocks the LDH enzyme is a potentially potent antimalarial with a different mode of action to existing drugs. As such, P. falciparum lactate dehydrogenase (pfLDH) has been suggested as a drug target by several authors (4 -6). One well recognized difficulty is that the drug must potently inhibit pfLDH yet show much less activity against the three human LDH (hsLDH) isoforms.A comparison of the crystal structures of both P. falciparum and human LDH (7,8) shows the following two key differences: namely positioning of the NADH factor, re...

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Microporous carbon materials having a negligible contribution of mesopores have been synthesized by cyclic oxidation/desorption of grape seeds char using air, ozone and HNO3 as oxidant agents. By adequate selection of the operating conditions (oxidation procedure and number of cycles) it is possible to tune the volume and pore size distribution of carbon materials and therefore determine the influence of carbon textural properties on the electrochemical behaviour of carbon-carbon symmetric supercapacitors operating in different aqueous electrolytes. The results confirm that although energy density can be improved using neutral electrolytes in reason of their higher stability potential window compared to acidic or basic ones, it is important to adapt the textural properties of the carbon materials to improve the ions diffusion inside 2 the porosity for assuring the charging of the double layer at high current densities to reach high power densities. 1. Introduction Electric double-layer capacitors (EDLC), often known as "supercapacitors", have recently received much attention in high power electrochemical technology research. The behavior of double-layer charging at the distributed interface of high specific surface materials-such as activated carbon (AC) powders, carbon nanotubes (CNT)or carbon gels, fullerenes, etc.-has been widely studied [1]. The energy storage mechanism in supercapacitor is based on an electrostatic attraction between charges along the double layer formed at the electrode/electrolyte interface. Since this phenomenon is controlled by the surface area of the interface, ACs are the most extensively used electrode materials for EDLC.In addition to their high specific surface area (SSA), ACs have other advantages such as availability, easy process ability and relatively low cost of most of precursors and production technologies [2, 3]. To usethese materials as electrodes for supercapacitors certain conditions are needed, such as a high conductivity ensuring a high power density, and an adequate pore size distribution (PSD), mainly with an average pore size smaller than 1nm. Moreover, a large quantity of surface functionalities can be a source of additional capacitance, called pseudo-capacitance, as some particular functionalities could undergo fast redox reactions with the electrolyte when working in aqueous solutions such as H2SO4 or KOH [4]. When a supercapacitor is connected to a voltage source, the surface of the electrodes is charged and attracts the ions of opposite charge. The ions are stored at the surface of

During recovery from intensive chemotherapy with cyclophosphamide (CTX), mice suffer a severe but transitory impairment in spleen cell proliferation to T-cell mitogens (Con A or anti-CD3 plus IL-2). Although CTX treatment reduced spleen T-cell cellularity, this cannot fully account for T-cell unresponsiveness. The results showed that CTX induces the colonization of spleen by an immature myeloid CD11b+Ly-6G+CD31+ population. Its presence closely correlated with the maximum inhibition of T-cell proliferation. Moreover, this suppressive activity was dependent on nitric oxide (NO) production in cultures since (1) higher amounts of nitric oxide and inducible nitric oxide synthase (iNOS) mRNA were produced in CTX spleen cells (CTX-SC) than in control splenocyte cultures and (2) NOS inhibitors greatly improved the proliferation of T lymphocytes. Nitric oxide production and suppressive activity were also dependent on endogenous interferon-γ (IFN-γ) production since anti–IFN-γ abrogated both effects. Finally, iNOS protein expression was restricted to a heterogeneous population of CD31+cells in which CD11b+Ly-6G+ cells were required to suppress T-cell proliferation. These results indicated that CTX might also cause immunosuppression by a mechanism involving the presence of immature myeloid cells with suppressor activity. This may have implications in clinical praxis since inappropriate immunotherapies in patients treated with intensive chemotherapy could lead to deleterious T-cell responses. (Blood. 2000;95:212-220)

This work studies the influence of the operating conditions used in the pyrolysis of grape seeds on the morphology and textural properties of the chars resulting. Flash and conventional (283 Kmin-1 heating rate) pyrolysis have been used within a wide range of temperature (300-1000 ºC). The effect of a pretreatment for oil extraction has also been studied. The porous structure of the chars was characterized by adsorption of N2 at 77 K, Ar at 77 K and 87 K, and CO2 at 273 K and mercury intrusion porosimetry. The morphology was analyzed by scanning electron microscopy. All the materials prepared revealed an essentially microporous structure, with a poor or even negligible contribution of mesopores. Increasing pyrolysis temperature led to higher specific surface areas and lower pore size. The highest specific surface area values occurred within 700-800 ºC, reaching up to 500 m 2 g-1 with pore sizes in the 0.4-1.1 nm range. No significant morphological changes were observed upon carbonization so that the resulting chars were granular materials of similar size than the starting grape seeds. The hollow core structure of the chars, with most of the material allocated at the periphery of 2 the granules can help to overcome the mass transfer limitations of most common (solid or massive) granular activated carbons. The chars showed a good mechanical strength during attrition tests. These chars can be potential candidates for the preparation of granular carbons molecular sieve or activated carbons raw materials.