Germination responses of an invasive species in native and non-native ranges

Studying germination in the native and non‐native range of a species can provide unique insights into processes of range expansion and adaptation; however, traits related to germination have rarely been compared between native and non‐native populations. In a series of common garden experiments, we explored whether differences in the seasonality of precipitation, specifically, summer drought vs summer rain, and the amount and variation of annual and seasonal precipitation affect the germination responses of populations of an annual ruderal plant, Centaurea solstitialis, from its native range and from two non‐native regions with different climates. We found that seeds from all native populations, irrespective of the precipitation seasonality of the region in which they occurred, and non‐native populations from regions with dry summers displayed similarly high germination proportions and rates. In contrast, genotypes from the non‐native region with predominantly summer rain exhibited much lower germination fractions and rates. Also, percent germination was strongly correlated with variation in precipitation in winter, the season that follows germination for C. solstitialis. Specifically, germination was lower for native and non‐native populations experiencing greater variation in winter precipitation. This correlation, however, was greatly influenced by the non‐native region with summer rain, which also exhibited the greatest variation in winter precipitation among studied regions. These results suggest that rather than general climatic patterns, the degree of risk experienced at early developmental stages could exert an important control over the germination strategy of C. solstitialis populations in both native and non‐native ranges. Also, these findings reveal a largely unique germination response in C. solstitialis genotypes growing in the non‐native region with summer rain and high variation in winter precipitation. Our work raises the possibility that rapid adaptive changes in germination strategies may contribute to the success of globally distributed invaders.     

Cytoprotective Effect of <Emphasis Type="Italic">Valeriana officinalis</Emphasis> Extract on an In Vitro Experimental Model of Parkinson Disease

Parkinson′s disease (PD) is one of the most important neurodegenerative worldwide disorders. The potential cytoprotective effects of aqueous extract of Valeriana officinalis on rotenone-induced apoptosis in human neuroblastoma SH-SY5Y cells were demonstrated. The cytotoxicity, cell viability and analysis of cellular morphology were performed by MTT-tetrazole (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and phase contrast microscopy, respectively. Significant changes in the cellular morphology, and condensation of the cell body could be observed when cells were treated with 300 nM rotenone for 48 h. Three different concentrations of Valeriana officinalis extract were used (0.049, 0.098 and 0.195 mg/mL). These extracts brought about an increase of 7.0 ± 1.3%, 14.5 ± 1.3% and 14.5 ± 3.2% in cell viability. Our results indicated that neuroprotector action of the Valeriana officinalis extract provides support for later studies as they help understanding this drug for the development of cytoprotective various therapies in PD.     

2-Benzoylpyridine-N(4)-tolyl thiosemicarbazones and their palladium(II) complexes: Cytotoxicity against leukemia cells

The palladium(II) complexes [Pd(2Bz4oT)Cl], [Pd(2Bz4mT)Cl], and [Pd(2Bz4pT)Cl] were prepared with N(4)-ortho- (H2Bz4oT) N(4)-meta- (H2Bz4mT) and N(4)-para- (H2Bz4pT) tolyl-thiosemicarbazones derived from 2-benzoylpyridine. The free thiosemicarbazones proved to be highly cytotoxic against Jurkat, HL60 and the resistant HL60.Bcl-X_L leukemia cell lines at nanomolar concentrations, but were much less cytotoxic to HepG2 human hepatoma cells. Upon coordination to palladium(II) the cytotoxic activity against all studied cell lines decreases. However, the high cytotoxicity of the free thiosemicarbazones against leukemia, together with their hepatotoxic profile similar to that of cisplatin suggest that N(4)-tolyl thiosemicarbazones have potential as chemotherapeutic drug candidates.     

New potent 5-nitroindazole derivatives as inhibitors of Trypanosoma cruzi growth: Synthesis,biological evaluation,and mechanism of action studies

New 5-nitroindazole derivatives were developed and their antichagasic properties studied. Eight compounds (14–18, 20, 26 and 28) displayed remarkable in vitro activities against Trypanosoma cruzi (T. cruzi). Its unspecific cytotoxicity against macrophages was evaluated being not toxic at a concentration at least twice that of T. cruzi IC₅₀, for some derivatives. The electrochemical studies, parasite respiration studies and ESR experiment showed that 5-nitroindazole derivatives not be able to yield a redox cycling with molecular oxygen such as occurs with nifurtimox (Nfx). The study on the mechanism of action proves to be related to the production of reduced species of the nitro moiety similar to that observed with benznidazole.     

2-O-β-d-Glucopyranosyl-sn-glycerol based analogues of sulfoquinovosyldiacylglycerols (SQDG) and their role in inhibiting Epstein-Barr virus early antigen activation

New sulfoquinovosyldiacylglycerols derived from 2-O-β-d-glucopyranosyl-sn-glycerol, carrying acyl chains of various length on the glycerol moiety, were prepared through a convenient synthetic procedure in which a sulfonate is introduced at the C-6 position of glucose by oxidation of a thioacetate in the presence of the unprotected secondary hydroxyl groups, and tested for their anti-tumor-promoting activity using a short-term in vitro assay for Epstein-Barr virus early antigen (EBV-EA) activation. Our study has allowed to ascertain the role of the 6′-sulfonate group and the need of a free hydroxyl group on the glycerol moiety in inhibiting the EBV activation promoted by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA).     

Growth, lipid accumulation, and fatty acid composition in obligate psychrophilic, facultative psychrophilic, and mesophilic yeasts

Obligate psychrophilic, facultative psychrophilic, and mesophilic yeasts were cultured in a carbon-rich medium at different temperatures to investigate whether growth parameters, lipid accumulation, and fatty acid (FA) composition were adaptive and/or acclimatory responses. Acclimation of facultative psychrophiles and mesophiles to a lower temperature decreased their specific growth rate, but did not affect their biomass yield (Y_X/S). Obligate and facultative psychrophiles exhibited the highest Y_X/S. Acclimation to lower temperature decreased the lipid yield (Y_L/X) in mesophilic yeasts, but did not affect Y_L/X in facultative psychrophilic ones. Similar Y_L/X were found in both groups of psychrophiles, suggesting that lipid accumulation is not a distinctive characteristic of adaptation to permanently cold environments. The unsaturation of FAs was one major adaptive feature of the yeasts colonizing permanently cold ecosystems. Remarkable amounts of α-linolenic acid were found in obligate psychrophiles at the expense of linoleic acid, whereas it was scarce or absent in all the other strains. Increased unsaturation of FAs was also a general acclimatory response of facultative psychrophiles to a lower temperature. These results improve the knowledge of the responses enabling psychrophilic yeasts to cope with the cold and may be of support for potential biotechnological exploitation of these strains.     

An ER‐resident membrane protein complex regulates nicotinic acetylcholine receptor subunit composition at the synapse

Nicotinic acetylcholine receptors (nAChRs) are homo‐ or heteropentameric ligand‐gated ion channels mediating excitatory neurotransmission and muscle activation. Regulation of nAChR subunit assembly and transfer of correctly assembled pentamers to the cell surface is only partially understood. Here, we characterize an ER transmembrane (TM) protein complex that influences nAChR cell‐surface expression and functional properties in Caenorhabditis elegans muscle. Loss of either type I TM protein, NRA‐2 or NRA‐4 (n icotinic r eceptor a ssociated), affects two different types of muscle nAChRs and causes in vivo resistance to cholinergic agonists. Sensitivity to subtype‐specific agonists of these nAChRs is altered differently, as demonstrated by whole‐cell voltage‐clamp of dissected adult muscle, when applying exogenous agonists or after photo‐evoked, channelrhodopsin‐2 (ChR2) mediated acetylcholine (ACh) release, as well as in single‐channel recordings in cultured embryonic muscle. These data suggest that nAChRs desensitize faster in nra‐2 mutants. Cell‐surface expression of different subunits of the ‘levamisole‐sensitive’ nAChR (L‐AChR) is differentially affected in the absence of NRA‐2 or NRA‐4, suggesting that they control nAChR subunit composition or allow only certain receptor assemblies to leave the ER.     

Structural studies in solution and in the solid state on the zinc chelate of 2-hydroxy-(4-methylthio)butanoic acid, an effective mineral supplement in animal feeding

The bis-chelate complex of Zn²⁺ with 2-hydroxy-(4-methylthio)butanoate (MHA_-H the anion derived from the so-called methionine hydroxy-analogue, MHA) is an effective, bioavailable mineral supplement for animal feeding. It can be obtained in two solid forms: the anhydrous [Zn(OC(O)CH₂CH(OH)CH₂CH₂SCH₃)₂] and the corresponding dihydrate species, both well distinguishable by IR spectroscopy and powder X-ray diffraction. The crystal and molecular structure of the dihydrate form has been solved by single-crystal X-ray diffraction. It consists of dinuclear bis-chelate species with a bridging carboxylate group, both zinc atoms displaying hexacoordination involving all the hydroxyl and carboxyl groups from the four MHA_-H anions and three oxygens from different water molecules. The fourth water molecule does not participate in coordination. Therefore, the dihydrate complex must be formulated as [Zn₂(OC(O)CH₂CH(OH)CH₂CH₂SCH₃)₄(H₂O)₃] · H₂O (1). A molecular computational analysis has been carried out by density functional theory (DFT) on three possible MHA_-H zinc chelates, i.e. the dinuclear bis-chelate observed in the solid state, the mononuclear bis-chelate diaquo-complex, and the monochelate tetraaquo-complex. Calculations have suggested that between the dinuclear and mononuclear bis-chelates, the preferred form in aqueous solution may be the second one. Moreover, both ¹H (chemical shifts and relaxation rates) and ¹³C NMR data provide further evidence for the formation of Zn/MHA_-H chelates in solution.