Antidiabetic activity of N-(6-substituted-1,3-benzothiazol-2-yl)benzenesulfonamides

N-(6-Substituted-1,3-benzothiazol-2-yl)benzenesulfonamide derivatives 1–8 were synthesized and evaluated for their in vivo antidiabetic activity in a non-insulin-dependent diabetes mellitus rat model. Several compounds synthesized showed significant lowering of plasma glucose level in this model. As a possible mode of action, the compounds were in vitro evaluated as 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitors. The most active compounds (3 and 4) were docked into the crystal structure of 11β-HSD1. Docking results indicate potential hydrogen bond interactions with catalytic amino acid residues.     

Mannitol biosynthesis is required for plant pathogenicity by Alternaria alternata

Mannitol has been hypothesized to play a role in antioxidant defense. In previous work, we confirmed the presence of the two mannitol biosynthetic enzymes, mannitol dehydrogenase (MtDH) and mannitol 1-phosphate 5-dehydrogenase (MPDH), in the fungus Alternaria alternata and created disruption mutants for both enzymes. These mutants were used to investigate the role of mannitol in pathogenicity of A. alternata on its host, tobacco. Conidia of all mutants were viable and germinated normally. GC-MS analysis demonstrated elevated levels of trehalose in the mutants, suggesting that trehalose may substitute for mannitol as a storage compound for germination. Tobacco inoculation showed no reduction in lesion severity caused by the MtDH mutant as compared with wild type; however, the MPDH mutant and a mutant in both enzymes caused significantly less disease. Microscopy analysis indicated that the double mutant was unaffected in the ability to germinate and produce appressoria on tobacco leaves and elicited a defense response from the host, indicating that it was able to penetrate and infect the host. We conclude that mannitol biosynthesis is required for pathogenesis of A. alternata on tobacco, but is not required for spore germination either in vitro or in planta or for initial infection.     

A first-principles study of Ni<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>Pd<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (n = 1 − 5) clusters

A first-principle investigation of structures and properties of Ni _n Pd _n (n=1-5) clusters is presented. For this study, the linear combination of Gaussian-type orbitals auxiliary density functional theory (LCGTO-ADFT) method has been employed. In order to determine the lowest energy structures, several isomers in different spin multiplicities were studied, for each cluster size. Initial structures, for which successive geometry optimization was computed without any constrain, were taken along Born–Oppenheimer molecular dynamics (BOMD) trajectories. To discriminate between minima and transition state structures, harmonic frequency analyses were performed at the optimized structures. Ground state structures, bond lengths, harmonic frequencies, dissociation energy, ionization potential, electron affinity and spin density plots are presented. This work demonstrates, that the Pd atoms prefer to allocate on the surface of the cluster structures whose core is formed by the 3d TM atoms type. Moreover, it has been observed that the ground-state structure spin multiplicity increases as the system size grows. The results of this study contribute to gain insight into how structures and energy properties change with cluster size in bimetallic Pd-based alloys.     

Functional specialization of Chlamydomonas reinhardtii cytosolic thioredoxin h1 in the response to alkylation-induced DNA damage

DNA damage occurs as a by-product of intrinsic cellular processes, like DNA replication, or as a consequence of exposure to genotoxic agents. Organisms have evolved multiple mechanisms to avoid, tolerate, or repair DNA lesions. To gain insight into these processes, we have isolated mutants hypersensitive to DNA-damaging agents in the green alga Chlamydomonas reinhardtii. One mutant, Ble-1, showed decreased survival when it was treated with methyl methanesulfonate (MMS), bleomycin, or hydrogen peroxide (H2O2) but behaved like the wild type when it was exposed to UVC irradiation. Ble-1 carries an extensive chromosomal deletion that includes the gene encoding cytosolic thioredoxin h1 (Trxh1). Transformation of Ble-1 with a wild-type copy of Trxh1 fully corrected the MMS hypersensitivity and partly restored the tolerance to bleomycin. Trxh1 also complemented a defect in the repair of MMS-induced DNA strand breaks and alkali-labile sites. In addition, a Trxh1-beta-glucuronidase fusion protein translocated to the nucleus in response to treatment with MMS. However, somewhat surprisingly, Trxh1 failed to correct the Ble-1 hypersensitivity to H2O2. Moreover, Trxh1 suppression by RNA interference in a wild-type strain resulted in enhanced sensitivity to MMS and DNA repair defects but no increased cytotoxicity to H2O2. Thioredoxins have been implicated in oxidative-stress responses in many organisms. Yet our results indicate a specific role of Chlamydomonas Trxh1 in the repair of MMS-induced DNA damage, whereas it is dispensable for the response to H2O2. These observations also suggest functional specialization among cytosolic thioredoxins since another Chlamydomonas isoform (Trxh2) does not compensate for the lack of Trxh1.     

Delayed effects on plasma concentration of testosterone and testicular morphology by intramuscular low-dose di(2-ethylhexyl)phthalate or oestradiol benzoate in the prepubertal boar

The immediate and delayed effects of prepubertal exposure to di(2-ethylhexyl)phthalate (DEHP) or oestradiol benzoate on the plasma concentrations of testosterone, oestradiol and LH, as well as testicular morphology were examined in prepubertal boars. In a split litter design experiment, prepubertal boars were intramuscularly exposed to DEHP, oestradiol or vehicle during five weeks, starting at six weeks of age. The dose of DEHP was 50mg/kg of bodyweight twice weekly, which is in the same range as recently used oral doses in rodents. Oestradiol-benzoate was administered at 0.25mg/kg of bodyweight twice weekly. One set of animals was examined immediately after the exposure, and the other set was examined at an age of 7.5 months. During the exposure period concentrations of LH in plasma were lower (p=0.02) in the oestradiol-treated animals than in the control group. In the group exposed to oestradiol, the relative to the body weight of the testicles tended to be lower (p=0.07) than control immediately after five weeks of exposure, and the relative to the body weight of the seminal vesicles tended to be lower (p=0.05) than control at 7.5 months of age. In the DEHP-exposed group an elevated (p=0.005) concentration of testosterone and increased (p=0.04) area of the Leydig cells in the testicles compared to the control group were seen at 7.5 months of age. These data suggest that DEHP early in life causes delayed effects on the reproductive system in the adult.     

Synthesis of NSC 106084 and NSC 14778 and evaluation of their DNMT inhibitory activity

DNA methylation is an epigenetic modification that is performed by DNA methyltransferases (DNMTs) and that leads to the transfer of a methyl group from S-adenosylmethionine (SAM) to the C5 position of cytosine. This transformation results in hypermethylation and silencing of genes such as tumor suppressor genes. Aberrant DNA methylation has been associated with the development of many diseases, including cancer. Inhibition of DNMTs promotes the demethylation and reactivation of epigenetically silenced genes. NSC 106084 and 14778 have been reported to inhibit DNMTs in the micromolar range. We report herein the synthesis of NSC 106084 and 14778 and the evaluation of their DNMT inhibitory activity. Our results indicate that while commercial NSC 14778 is moderately active against DNMT1, 3A/3L and 3B/3L, resynthesized NSC 14778 is inactive under our assay conditions. Resynthesized 106084 was also found to be inactive.     

Cryo-scanning electron microscopy (Cryo-SEM) of boar semen frozen in medium-straws and MiniFlatPacks

In this study we demonstrate, in the frozen state, the architecture of frozen boar spermatozoa collected from the sperm-rich fraction of ejaculates (n=13) from four fertile boars packed and split-frozen in medium-straws (MS) and MiniFlatPacks (MFP), cross-sectioned in the frozen state and evaluated by image analysis on images obtained by use of cryo-scanning electron microscopy (Cryo-SEM). The tested hypothesis was that the degree of in situ dehydration and levels of homogeneity of boar semen either frozen in MSs or MFPs packages differ between them, with MFPs allowing for a more uniform dehydration of the spermatozoa and a higher cryosurvival, monitored by computer assisted sperm analysis (CASA) as proportion of linearly motile spermatozoa, compared to semen packaged and processed in MSs. The organization and relative surface of biological material (veins; e.g., frozen extender, bound water, solutes and spermatozoa) as well as free water (lakes) was measured as the degree of dehydration of the samples. The apparent organization of lakes and veins differed between packages, with the MFPs depicting larger lakes than the MSs. The sizes of the lakes in the latter appeared, moreover, highly asymmetrical depending on their position of the section. The relative surface of these lakes per section, respectively veins differed between packages (P<0.05), indicating a larger amount of free-water (lakes; 81.73+/-2.07% vs. 77.91+/-1.57%) in the MFPs and, consequently, thinner veins than in MSs. In conclusion, MFPs seem to allow for a more homogenous dehydration of the spermatozoa/frozen extender compared to MSs, which might account for their somewhat better sperm quality post-thaw.     

Molecular modeling of some 1H-benzimidazole derivatives with biological activity against Entamoeba histolytica: a comparative molecular field analysis study

Comparative molecular field analysis (CoMFA) was performed on a set of 1H-benzimidazole derivatives. Molecular modeling and 3D-QSAR were employed to determine the tautomeric form that would probably fit a target receptor in Entamoeba histolytica. CoMFA results suggest that the antiamoebic activity is favored with steric bulk at position 5 of the benzimidazole ring and low electron density on the group at position 2. To the best of our knowledge this is the first 3D-QSAR study performed for benzimidazoles as antiamoebic agents. The CoMFA models derived will be very valuable to design new and more potent compounds against E. histolytica.     

DNA damage-induced nuclear translocation of Apaf-1 is mediated by nucleoporin Nup107

Beside its central role in the mitochondria-dependent cell death pathway, the apoptotic protease activating factor 1 (Apaf-1) is involved in the DNA damage response through cell-cycle arrest induced by genotoxic stress. This non-apoptotic function requires a nuclear translocation of Apaf-1 during the G1-to-S transition. However, the mechanisms that trigger the nuclear accumulation of Apaf-1 upon DNA damage remain to be investigated. Here we show that the main 4 isoforms of Apaf-1 can undergo nuclear translocation and restore Apaf-1 deficient MEFs cell cycle arrest in the S phase following genotoxic stress through activation of Chk-1. Interestingly, DNA damage-dependent nuclear accumulation of Apaf-1 occurs independently of p53 and the retinoblastoma (pRb) pathway. We demonstrated that Apaf-1 associates with the nucleoporin Nup107 and this association is necessary for Apaf-1 nuclear import. The CED-4 domain of Apaf-1 directly binds to the central domain of Nup107 in an ATR-regulated, phosphorylation-dependent manner. Interestingly, expression of the Apaf-1-interacting domain of Nup107 interfered with Apaf-1 nuclear translocation upon genotoxic stress, resulting in a marked reduction of Chk-1 activation and cell cycle arrest. Thus, our results confirm the crucial role of Apaf-1 nuclear relocalization in mediating cell-cycle arrest induced by genotoxic stress and implicate Nup107 as a critical regulator of the DNA damage-induced intra-S phase checkpoint response.     

MtDNA metagenomics reveals large‐scale invasion of belowground arthropod communities by introduced species

Using a series of standardized sampling plots within forest ecosystems in remote oceanic islands, we reveal fundamental differences between the structuring of aboveground and belowground arthropod biodiversity that are likely due to large‐scale species introductions by humans. Species of beetle and spider were sampled almost exclusively from single islands, while soil‐dwelling Collembola exhibited more than tenfold higher species sharing among islands. Comparison of Collembola mitochondrial metagenomic data to a database of more than 80 000 Collembola barcode sequences revealed almost 30% of sampled island species are genetically identical, or near identical, to individuals sampled from often very distant geographic regions of the world. Patterns of mtDNA relatedness among Collembola implicate human‐mediated species introductions, with minimum estimates for the proportion of introduced species on the sampled islands ranging from 45% to 88%. Our results call for more attention to soil mesofauna to understand the global extent and ecological consequences of species introductions.