Evaluation of the antiprotozoan properties of 5′-norcarbocyclic pyrimidine nucleosides

Carbocyclic nucleoside analogues have a distinguished history as anti-infectious agents, including key antiviral agents. Toxicity was initially a concern but this was reduced by the introduction of 5′-nor variants. Here, we report the result of our preliminary screening of a series of 5′-norcarbocyclic uridine analogues against protozoan parasites, specifically the major pathogens Leishmania mexicana and Trypanosoma brucei. The series displayed antiparasite activity in the low to mid-micromolar range and establishes a preliminary structure-activity relationship, with the 4′,N³-di-(3,5-dimethylbenzoyl)-substituted analogues showing the most prominent activity. Utilizing an array of specially adapted cell lines, it was established that this series of analogues likely act through a common target. Moreover, the strong correlation between the trypanocidal and anti-leishmanial activities indicates that this mechanism is likely shared between the two species. EC₅₀ values were unaffected by the disabling of pyrimidine biosynthesis in T. brucei, showing that these uridine analogues do not act directly on the enzymes of pyrimidine nucleotide metabolism. The lack of cross-resistance with 5-fluorouracil, also establishes that the carbocyclic analogues are not imported through the known uracil transporters, thus offering forth new insights for this class of nucleosides. The lack of cross-resistance with current trypanocides makes this compound class interesting for further exploration.     

Functional analysis of drug resistance‐associated mutations in the Trypanosoma brucei adenosine transporter 1 (TbAT1) and the proposal of a structural model for the protein

The Trypanosoma brucei aminopurine transporter P2/TbAT1 has long been implicated in the transport of, and resistance to, the diamidine and melaminophenyl arsenical classes of drugs that form the backbone of the pharmacopoeia against African trypanosomiasis. Genetic alterations including deletions and single nucleotide polymorphisms (SNPs) have been observed in numerous strains and clinical isolates. Here, we systematically investigate each reported mutation and assess their effects on transporter function after expression in a tbat1^?/? T. brucei line. Out of a set of six reported SNPs from a reported ‘resistance allele’, none significantly impaired sensitivity to pentamidine, diminazene or melarsoprol, relative to the TbAT1‐WT allele, although several combinations, and the deletion of the codon for residue F316, resulted in highly significant impairment. These combinations of SNPs, and ΔF316, also strongly impaired the uptake of [³H]‐adenosine and [³H]‐diminazene, identical to the tbat1^?/? control. The TbAT1 protein model predicted that residues F19, D140 and F316 interact with the substrate of the transporter. Mutation of D140 to alanine resulted in an inactive transporter, whereas the mutation F19A produced a transporter with a slightly increased affinity for [³H]‐diminazene but reduced the uptake rate. The results presented here validate earlier hypotheses of drug binding motifs for TbAT1.     

Pretreatment with Proline or an Organic Bio-stimulant Induces Salt Tolerance in Wheat Plants by Improving Antioxidant Redox State and Enzymatic Activities and Reducing the Oxidative Stress

Journal of Plant Growth Regulation - In this study, the effects of seed soaking in proline (12 mM) or Moringa oleifera leaf extract (MLE; 6%) on the biomass, yield, and the antioxidant...     

New Operational Matrices for Solving Fractional Differential Equations on the Half-Line

In this paper, the fractional-order generalized Laguerre operational matrices (FGLOM) of fractional derivatives and fractional integration are derived. These operational matrices are used together with spectral tau method for solving linear fractional differential equations (FDEs) of order ν (0 < ν < 1) on the half line. An upper bound of the absolute errors is obtained for the approximate and exact solutions. Fractional-order generalized Laguerre pseudo-spectral approximation is investigated for solving nonlinear initial value problem of fractional order ν. The extension of the fractional-order generalized Laguerre pseudo-spectral method is given to solve systems of FDEs. We present the advantages of using the spectral schemes based on fractional-order generalized Laguerre functions and compare them with other methods. Several numerical examples are implemented for FDEs and systems of FDEs including linear and nonlinear terms. We demonstrate the high accuracy and the efficiency of the proposed techniques.     

Ligand-based design and synthesis of N'-Benzylidene-3,4-dimethoxybenzohydrazide derivatives as potential antimicrobial agents; evaluation by in vitro,in vivo,and in silico approaches with SAR studies

Herein, a series of N''-benzylidene-3,4-dimethoxybenzohydrazide derivatives were designed and synthesised to target the multidrug efflux pump (MATE). The antibacterial activities were screened against S. aureus, Acinetobacter, S. typhi, E. coli, and P. aeruginosa, whereas their antifungal activities were screened against C. albicans. Compounds 4a, 4h, and 4i showed the most promising antibacterial and antifungal activities. Moreover, compounds 4h and 4i being the broader and superior members regarding their antimicrobial effects were selected to be further evaluated via in vivo testing using biochemical analysis and liver/kidney histological examination. Additionally, molecular docking was carried out to attain further deep insights into the synthesised compounds'' binding modes. Also, ADMET studies were performed to investigate the physicochemical/pharmacokinetics features and toxicity parameters of the synthesised derivatives. Finally, a structure-antimicrobial activity relationship study was established to facilitate further structural modifications in the future.

Highlights

• A series of new N''-benzylidene-3,4-dimethoxybenzohydrazide derivatives were designed and synthesised targeting the multidrug efflux pump (MATE) guided by the pharmacophoric features of the co-crystallized native inhibitor of the target protein.
• The newly synthesised compounds were assessed through in vitro, in vivo, and in silico approaches.
• Using the agar well diffusion assay, the antibacterial activities of the synthesised compounds were screened against S. aureus, Acinetobacter, S. typhi, E. coli, and P. aeruginosa, whereas, their antifungal activities were screened against C. albicans.
• The minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of the synthesised compounds were investigated on variable microbial species.
• Compounds (4h and 4i) -as the broader and superior members regarding their antimicrobial effects- were further evaluated via in vivo testing using bio-chemical analysis and liver/kidney histological examination.
• A molecular docking study and ADMET in silico studies were performed.
• A structure-antimicrobial activity relationship study was established to facilitate further structural modifications in the future.

     

Mutations in Critical Domains Confer the Human mTOR Gene Strong Tumorigenicity

Mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that regulates cell growth, proliferation, and survival. mTOR is frequently activated in human cancers and is a commonly sought anticancer therapeutic target. However, whether the human mTOR gene itself is a proto-oncogene possessing tumorigenicity has not been firmly established. To answer this question, we mutated evolutionarily conserved amino acids, generated eight mutants in the HEAT repeats (M938T) and the FAT (W1456R and G1479N) and kinase (P2273S, V2284M, V2291I, T2294I, and E2288K) domains of mTOR, and studied their oncogenicity. On transient expression in HEK293T cells, these mTOR mutants displayed elevated protein kinase activities accompanied by activated mTOR/p70S6K signaling at varying levels, demonstrating the gain of function of the mTOR gene with these mutations. We selected P2273S and E2288K, the two most catalytically active mutants, to further examine their oncogenicity and tumorigenicity. Stable expression of the two mTOR mutants in NIH3T3 cells strongly activated mTOR/p70S6K signaling, induced cell transformation and invasion, and remarkably, caused rapid tumor formation and growth in athymic nude mice after subcutaneous inoculation of the transfected cells. This study confirms the oncogenic potential of mTOR suggested previously and demonstrates for the first time its tumorigenicity. Thus, beyond the pivotal position of mTOR to relay the oncogenic signals from the upstream phosphatidylinositol 3-kinase/Akt pathway in human cancer, mTOR is capable potentially of playing a direct role in human tumorigenesis if mutated. These results also further support the conclusion that mTOR is a major therapeutic target in human cancers.     

Quantity of supplementary LED lightings regulates photosynthetic apparatus,improves photosynthetic capacity and enhances productivity of Cos lettuce grown in a tropical greenhouse

Photosynthesis Research - Although cooling their rootzone allows year-round (temperate) vegetable production in Singapore's warm climate, these crops have frequently experienced increasingly...     

On mechanically driven biological stimulus for bone remodeling as a diffusive phenomenon

Biomechanics and Modeling in Mechanobiology - In the past years, many attempts have been made in order to model the process of bone remodeling. This process is complex, as it is governed by not yet...     

Soil survival of Escherichia coli O157:H7 acquired by a child from garden soil recently fertilized with cattle manure

AIMS: This investigation was conducted to determine the survival of a naturally occurring Escherichia coli O157:H7 in garden soil linked to a sporadic case of E. coli O157 infection in Minnesota. METHODS AND RESULTS: The presence and viability of E. coli O157:H7 was monitored in manure-contaminated garden soil for several weeks. Bacterial isolates were characterized using PCR and pulsed-field gel electrophoresis (PFGE). Isolates obtained from the patient and the garden plots during this investigation had indistinguishable PFGE patterns and had the same virulence factors (stx1, stx2, eaeA, ehxA). The E. coli O157:H7 levels obtained from the garden plots declined gradually for a period of 2 months, and on day 69 only one garden plot of four had detectable levels of pathogen. All plots were negative on day 92. The rate of decline in the soil samples stored at 4 degrees C was faster compared with soil samples that remained in ambient conditions, and in refrigerated storage E. coli O157:H7 could not be detected after 10 days. CONCLUSIONS: E. coli O157:H7 strains can survive on manure-amended soil for more than 2 months, and this survival could be reduced by low temperature. SIGNIFICANCE AND IMPACT OF THE STUDY: This is one of the few reports that have investigated the survival of a proven virulent strain in naturally contaminated soil samples. This case stresses the importance of avoiding the use of raw cattle manure to amend soil for cultivation of foods, including soils in residential garden plots.