Pathological and immunological evaluation of different regimens of praziquantel treatment in a mouse model of Schistosoma mansoni infection

BackgroundOne of the considerable challenges of schistosomiasis chemotherapy is the inefficacy of praziquantel (PZQ) at the initial phase of the infection. Immature schistosomes are not susceptible to PZQ at the curative dose. Here, we investigated the efficacy of different PZQ regimens administered during the initial stage of Schistosoma mansoni infection in mice.Methodology/Principal findingsTwo months-old mice were individually infected with 80 S. mansoni cercariae and divided into one infected-untreated control group (IC) and four PZQ-treated groups: PZQ at 100 mg/kg/day for five consecutive days (group PZQ1), PZQ at 100 mg/kg/day for 28 days (group PZQ2), PZQ at 18 mg/kg/day for 28 days (group PZQ3) and a single dose of PZQ at 500 mg/kg (group PZQ4). The treatment started on day one post-infection (p.i), and each group of mice was divided into two subgroups euthanized on day 36 or 56 p.i, respectively. We determined the mortality rate, the parasitological burden, the hepatic and intestinal granulomas, the serum levels of Th-1, Th-2, and Th-17 cytokines, and gene expression. The treatment led to a significant (p < 0.001) reduction of worm burden and egg counts in the intestine and liver in groups PZQ2 and PZQ3. On 56^th day p.i, there was a significant reduction (p < 0.001) of the number and volume of the hepatic granulomas in groups PZQ2 and PZQ3 compared to group PZQ1 or PZQ4. Moreover, in group PZQ3, the serum levels of IFN-γ, TNF-α, IL-13, and IL-17 and their liver mRNA expressions were significantly reduced while IL-10 and TGF-β gene expression significantly increased. The highest mortality rate (81.25%) was recorded in group PZQ2.Conclusion/SignificanceThis study revealed that the administration of PZQ at 18 mg/kg/day for 28 consecutive days was the optimal effective posology for treating S. mansoni infection at the initial stage in a murine model.     

Riboflavin, overproduced during sporulation of Ashbya gossypii, protects its hyaline spores against ultraviolet light

Riboflavin (vitamin B₂), essential in tiny amounts as a precursor for oxidoreductase coenzymes, is a yellow pigment. Although it causes cytotoxicity via photoinduced damage of macromolecules, several microorganisms are striking overproducers. A question, unanswered for decades, is whether riboflavin overproducers can benefit from this property. Here, we report an ultraviolet (UV) protective effect of riboflavin. The spores of Ashbya gossypii , a riboflavin-overproducing fungus, are more sensitive to UV than those of Aspergillus nidulans . The addition of riboflavin to suspensions improves the UV resistance of both spore types. Interestingly, we show that regulation of sporulation and riboflavin overproduction in A. gossypii are linked. In batch culture, both were elevated when growth ceased. At constant growth rates, obtained in a chemostat culture, neither was elevated. Supplementation of cultures by cAMP, a known stress signal, negatively affected sporulation as well as riboflavin overproduction, establishing a second, independent argument for the linkage.     

Chlorophyll fluorescence images demonstrate variable pathways in the effects of plasma membrane excitation on electron flow in chloroplasts of <Emphasis Type=Italic>Chara</Emphasis> cells

Chlorophyll fluorescence Imaging and Microscopy PAM fluorometry were applied to study spatial dynamics of photosystem II quantum yield ( DF/F_m￠ ) left( {Delta F/F_m^prime } right) and non-photochemical quenching (NPQ) in resting and electrically stimulated Chara corallina cells in the absence and presence of the hydrophilic electron acceptor methyl viologen (MV) in the external medium. Electrical excitation of the plasma membrane temporarily enhanced the heterogeneity of photosynthetic patterns under physiological conditions (in the absence of MV), but irreversibly eliminated these patterns in the presence of MV. These findings suggest that the action potential (AP) of the excitable plant cell affects the spatial patterns of photosynthesis and chlorophyll fluorescence through different pathways operated in the absence and presence of MV. Based on the extent of NPQ as an indicator of MV-dependent electron flow, it is supposed that MV cannot permeate into the chloroplasts of photosynthetically active “acid cell regions” but gains an immediate access to the stroma of these chloroplasts after triggering of an AP. The AP-triggered MV-dependent non-photochemical quenching in the chloroplasts of acidic cell regions was routinely observed at 0.1 mM Ca²⁺ in the medium but not at elevated (2 mM) external Ca²⁺ concentration. The results are interpreted in terms of competition between two permeant divalent ion species, Ca²⁺ and MV²⁺, for their passage through the voltage-gated calcium channels of the plasma membrane. It is proposed that the herbicidal activity of MV in characean cells, here serving as model object, can be manipulated by triggering AP and varying Ca²⁺ concentration in the environmental medium.     

Borrelia burgdorferi binds fibronectin through a tandem beta-zipper, a common mechanism of fibronectin binding in staphylococci, streptococci, and spirochetes

BBK32 is a fibronectin-binding protein from the Lyme disease-causing spirochete Borrelia burgdorferi. In this study, we show that BBK32 shares sequence similarity with fibronectin module-binding motifs previously identified in proteins from Streptococcus pyogenes and Staphylococcus aureus. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetry are used to confirm the binding sites of BBK32 peptides within the N-terminal domain of fibronectin and to measure the affinities of the interactions. Comparison of chemical shift perturbations in fibronectin F1 modules on binding of peptides from BBK32, FnBPA from S. aureus, and SfbI from S. pyogenes provides further evidence for a shared mechanism of binding. Despite the different locations of the bacterial attachment sites in BBK32 compared with SfbI from S. pyogenes and FnBPA from S. aureus, an antiparallel orientation is observed for binding of the N-terminal domain of fibronectin to each of the pathogens. Thus, these phylogenetically and morphologically distinct bacterial pathogens have similar mechanisms for binding to human fibronectin.     

Cyclohexane-1,2-dione hydrolase from denitrifying Azoarcus sp. strain 22Lin, a novel member of the thiamine diphosphate enzyme family

Alicyclic compounds with hydroxyl groups represent common structures in numerous natural compounds, such as terpenes and steroids. Their degradation by microorganisms in the absence of dioxygen may involve a C-C bond ring cleavage to form an aliphatic intermediate that can be further oxidized. The cyclohexane-1,2-dione hydrolase (CDH) (EC 3.7.1.11) from denitrifying Azoarcus sp. strain 22Lin, grown on cyclohexane-1,2-diol as a sole electron donor and carbon source, is the first thiamine diphosphate (ThDP)-dependent enzyme characterized to date that cleaves a cyclic aliphatic compound. The degradation of cyclohexane-1,2-dione (CDO) to 6-oxohexanoate comprises the cleavage of a C-C bond adjacent to a carbonyl group, a typical feature of reactions catalyzed by ThDP-dependent enzymes. In the subsequent NAD(+)-dependent reaction, 6-oxohexanoate is oxidized to adipate. CDH has been purified to homogeneity by the criteria of gel electrophoresis (a single band at ～59 kDa; calculated molecular mass, 64.5 kDa); in solution, the enzyme is a homodimer (～105 kDa; gel filtration). As isolated, CDH contains 0.8 ± 0.05 ThDP, 1.0 ± 0.02 Mg(2+), and 1.0 ± 0.015 flavin adenine dinucleotide (FAD) per monomer as a second organic cofactor, the role of which remains unclear. Strong reductants, Ti(III)-citrate, Na(+)-dithionite, and the photochemical 5-deazaflavin/oxalate system, led to a partial reduction of the FAD chromophore. The cleavage product of CDO, 6-oxohexanoate, was also a substrate; the corresponding cyclic 1,3- and 1,4-diones did not react with CDH, nor did the cis- and trans-cyclohexane diols. The enzymes acetohydroxyacid synthase (AHAS) from Saccharomyces cerevisiae, pyruvate oxidase (POX) from Lactobacillus plantarum, benzoylformate decarboxylase from Pseudomonas putida, and pyruvate decarboxylase from Zymomonas mobilis were identified as the closest relatives of CDH by comparative amino acid sequence analysis, and a ThDP binding motif and a 2-fold Rossmann fold for FAD binding could be localized at the C-terminal end and central region of CDH, respectively. A first mechanism for the ring cleavage of CDO is presented, and it is suggested that the FAD cofactor in CDH is an evolutionary relict.     

Porous polymers for fixed bed adsorption of aroma compounds in fermentation processes

Summary Deionized water as well as simulated and genuine fermentation media, which contained varying concentrations of benzaldehyde and 4-decanolide, were used to investigate the applicability of selected styrene-divinylbenzene resins for low pressure downflow adsorption of aroma compounds in a fixed bed. The effects of flow rate and matrix on the respective breakthrough curve slopes were examined using the LUB-and the MTZ-model.     

Electron Flow to the Intersystem Chain from Stromal Components and Cyclic Electron Flow in Maize Chloroplasts, as Detected in Intact Leaves by Monitoring Redox Change of P700 and Chlorophyll Fluorescence

The functional pool size of electrons in the intersystem chainof the chloroplasts of maize was estimated to be about 25 perP700 by the redox change in P700 with single- and multiple-turnoverlights under far-red light in intact leaves. This is about twicethe pool size observed in C₃ plants. Furthermore, the stromalpool size of electrons that can be donated to P700⁺ after actinicillumination was larger in maize leaves than in leaves of C₃plants, giving a maximum value of 225 electrons per P700. Maizeleaves showed an increase in the yield of modulated Chl fluorescenceafter turning off of actinic light, which confirms the donationof electrons in the dark to the intersystem chain from the stromaldonors that accumulated during actinic illumination. We proposethat the mesophyll chloroplasts are responsible for a high levelof electron-donating activity to the intersystem chain fromstromal donors such as triose phosphates and malate with NADPHas an intermediate. The level of P700⁺ under strong far-redlight was decreased after actinic illumination, suggesting theoperation of an actinic light-triggered cyclic electron flowin chloroplasts of the bundle sheath cells. (Received August 14, 1992; Accepted October 13, 1992)     

A Dual Role for Corneal Dendritic Cells in Herpes Simplex Keratitis: Local Suppression of Corneal Damage and Promotion of Systemic Viral Dissemination

The cornea is the shield to the foreign world and thus, a primary site for peripheral infections. However, transparency and vision are incompatible with inflammation and scarring that may result from infections. Thus, the cornea is required to perform a delicate balance between fighting infections and preserving vision. To date, little is known about the specific role of antigen-presenting cells in viral keratitis. In this study, utilizing an established murine model of primary acute herpes simplex virus (HSV)-1 keratitis, we demonstrate that primary HSV keratitis results in increased conventional dendritic cells (cDCs) and macrophages within 24 hours after infection. Local depletion of cDCs in CD11c-DTR mice by subconjuntival diphtheria toxin injections, led to increased viral proliferation, and influx of inflammatory cells, resulting in increased scarring and clinical keratitis. In addition, while HSV infection resulted in significant corneal nerve destruction, local depletion of cDCs resulted in a much more severe loss of corneal nerves. Further, local cDC depletion resulted in decreased corneal nerve infection, and subsequently decreased and delayed systemic viral transmission in the trigeminal ganglion and draining lymph node, resulting in decreased mortality of mice. In contrast, sham depletion or depletion of macrophages through local injection of clodronate liposomes had neither a significant impact on the cornea, nor an effect on systemic viral transmission. In conclusion, we demonstrate that corneal cDCs may play a primary role in local corneal defense during viral keratitis and preserve vision, at the cost of inducing systemic viral dissemination, leading to increased mortality.