Tritium radiolabelling of PB28, a potent sigma-2 receptor ligand: pharmacokinetic and pharmacodynamic characterization

A potent sigma-2 receptor ligand, known as PB28, was tritium radiolabelled and biologically evaluated. The results showed that [(3)H]PB28 and the corresponding unlabelled PB28 had superimposed pharmacodynamic properties. This radioligand appears as a potential candidate for receptor binding and in living cells assays.     

Archaebacterial lipid membranes as models to study the interaction of 10-N-nonyl acridine orange with phospholipids

The dye 10-N-nonyl acridine orange (NAO) is used to label cardiolipin domains in mitochondria and bacteria. The present work represents the first study on the binding of NAO with archaebacterial lipid membranes. By combining absorption and fluorescence spectroscopy with fluorescence microscopy studies, we investigated the interaction of the dye with (a) authentic standards of archaebacterial cardiolipins, phospholipids and sulfoglycolipids; (b) isolated membranes; (c) living cells of a square-shaped extremely halophilic archaeon. Absorption and fluorescence spectroscopy data indicate that the interaction of NAO with archaebacterial cardiolipin analogues is similar to that occurring with diacidic phospholipids and sulfoglycolipids, suggesting as molecular determinants for NAO binding to archaebacterial lipids the presence of two acidic residues or a combination of acidic and carbohydrate residues. In agreement with absorption spectroscopy data, fluorescence data indicate that NAO fluorescence in archaeal membranes cannot be exclusively attributed to bisphosphatidylglycerol and, therefore, different from mitochondria and bacteria, the dye cannot be used as a cardiolipin specific probe in archaeal microorganisms.     

Factors controlling the colonial structure of <Emphasis Type="Italic">Pediastrum tetras</Emphasis> (Chlorophyceae)

Accounting for morphological plasticity in phytoplankton populations is relevant for taxonomy, systematic/evolutionary, and ecological studies. In this work, the green alga Pediastrum tetras (Ehrenberg) Ralfs was used to describe the variation in population size structure over its growth cycle and to analyze responses to changes in biotic and abiotic factors. Pediastrum cultures reached a final stable concentration in approximately 10 days. This density (8 × 10⁵ cells ml⁻¹) remained stable for at least another 13 days and the intrinsic growth rate was 0.24 ± 0.01 day⁻¹. In the exponential phase, the relative number of single cells and the proportion of large cells (with vesicles inside) within colonies increased. When density peaked, a relative increase of single cells as well as small cells in new colonies took place. Finally, during the stationary phase, the trend reversed: fewer single cells and a larger cell size (without vesicles) were observed. Results indicated that nutrient supply could affect population structure, diminishing the proportion of eight-cell colonies. Daphnia magna Straus significantly reduced the Pediastrum population density due to predation, and this led to a significant decrease in the density of the largest colonies. In addition, info-chemicals induced a slight increase in the density of the largest colonies compared to the control treatment. Our study suggests a possible trade-off in P. tetras colonial size in natural environments: during the stationary growth period in a lake, Pediastrum populations tend to increase in size for efficient use of nutrients, while they decrease in size in the presence of herbivores. Handling editor: J. Padisak     

Oxidosqualene cyclase from Saccharomyces cerevisiae,Trypanosoma cruzi,Pneumocystis carinii and Arabidopsis thaliana expressed in yeast: A model for the development of novel antiparasitic agents

A series of 25 compounds, some of which previously were described as inhibitors of human liver microsomal oxidosqualene cyclase (OSC), were tested as inhibitors of Saccharomyces cerevisiae, Trypanosoma cruzi, Pneumocystis carinii and Arabidopsis thaliana OSCs expressed in an OSC-defective strain of S. cerevisiae. The screening identified three derivatives particularly promising for the development of novel anti-Trypanosoma agents and eight derivatives for the development of novel anti-Pneumocystis agents.     

Molecular Characterization of Microbial Population Dynamics during Sildenafil Citrate Degradation

Little is known about pharmaceutical and personal care products pollutants (PPCPs), but there is a growing interest in how they might impact the environment and microbial communities. The widespread use of Viagra (sildenafil citrate) has attracted great attention because of the high usage rate, the unpredictable disposal and the unknown potential effects on wildlife and the environment. Until now information regarding the impact of Viagra on microbial community in water environment has not been reported. In this research, for the first time, the genetic profile of the microbial community, developing in a Viagra polluted water environment, was evaluated by means of the 16S and 18S rRNA genes, for bacteria and fungi, respectively, amplified by polymerase chain reaction (PCR) and separated using the denaturing gradient gel electrophoresis (DGGE) technique. The DGGE results revealed a complex microbial community structure with most of the population persisting throughout the experimental period. DNA sequences from bands observed in the different denaturing gradient gel electrophoresis profiles exhibited the highest degree of identity to uncultured bacteria and fungi found previously mainly in polluted environmental and treating bioreactors. Biotransformation ability of sildenafil citrate by the microbial pool was studied and the capability of these microorganisms to detoxify a polluted water ecosystem was assessed. The bacterial and fungal population was able to degrade sildenafil citrate entirely. Additionally, assays conducted on Daphnia magna, algal growth inhibition assay and cell viability determination on HepG2 human cells showed that biotransformation products obtained from the bacterial growth was not toxic. The higher removal efficiency for sildenafil citrate and the lack of toxicity by the biotransformation products obtained showed that the microbial community identified here represented a composite population that might have biotechnological relevance to retrieve sildenafil citrate contaminated sites.     

Do Larvae and Ovipositing Chironomus riparius (Diptera: Chironomidae) Females Avoid Copper-Contaminated Environments?

Studies on the avoidance behavior of aquatic organisms to contaminants have confirmed that such behavior can be relevant in field situations. However, almost all toxicity tests involve the forced exposure of organisms to toxicants. In particular, despite the importance of Chironomus riparius Meigen larvae in sediment toxicity testing, only a few studies on avoidance behavior have been performed. This study investigated the ability of different life stages of C. riparius, including ovipositing females, first-, second-, and fourth-instar larvae, to avoid copper-contaminated environments. Ovipositing females were given a choice between a control and copper solution (1.3 mg Cu l^{? 1}). First-instar larvae were provided with a choice between a control and a copper (2.0 mg Cu l^{? 1})-spiked sediment. Both second- and fourth-instars were exposed to a copper gradient (0.38–3.4 mg Cu l^{? 1}) in a flow-through system. None of the life stages avoided copper, even though the highest concentrations caused lethal effects on midges. The avoidance behavior of C. riparius is not a sensitive endpoint to assess copper sublethal toxicity.     

PKR activity is required for acute leukemic cell maintenance and growth: A role for PKR‐mediated phosphatase activity to regulate GSK‐3 phosphorylation

Recent reports demonstrate that PKR is constitutively active in a variety of tumors and is required for tumor maintenance and growth. Here we report acute leukemia cell lines contain elevated levels of p‐T451 PKR and PKR activity as compared to normal controls. Inhibition of PKR with a specific inhibitor, as well as overexpression of a dominant‐negative PKR, inhibited cell proliferation and induced cell death. Interestingly, PKR inhibition using the specific inhibitor resulted in a time‐dependent augmentation of AKT S473 and GSK‐3α S21 phosphorylation, which was confirmed in patient samples. Increased phosphorylation of AKT and GSK‐3α was not dependent on PI3K activity. PKR inhibition augmented levels of p‐S473 AKT and p‐S21/9 GSK‐3α/β in the presence of the PI3K inhibitor, LY294002, but was unable to augment GSK‐3α or β phosphorylation in the presence of the AKT inhibitor, A443654. Pre‐treatment with the PKR inhibitor blocked the ability of A443654 and LY294002 to promote phosphorylation of eIF2α, indicating the mechanism leading to AKT phosphorylation and activation did not require eIF2α phosphorylation. The effects of PKR inhibition on AKT and GSK‐3 phosphorylation were found to be, in part, PP2A‐dependent. These data indicate that, in acute leukemia cell lines, constitutive basal activity of PKR is required for leukemic cell homeostasis and growth and functions as a negative regulator of AKT, thereby increasing the pool of potentially active GSK‐3. J. Cell. Physiol. 221: 232–241, 2009. © 2009 Wiley‐Liss, Inc     

Eukaryotic Initiation Factors (eIF) 2�� and 4E Expression, Localization, and Phosphorylation in Brain Tumors

Increased protein synthesis is regulated, in part, by two eukaryotic translation initiation factors (eIFs): eIF4E and eIF2α. One or both of these factors are often overexpressed in several types of cancer cells; however, no data are available at present regarding eIF4E and eIF2α levels in brain tumors. In this study, we analyzed the expression, subcellular localization and phosphorylation states of eIF4E and eIF2α in 64 brain tumors (26 meningiomas, 16 oligodendroglial tumors, and 22 astrocytomas) and investigated the correlation with the expression of MIB-1, p53, and cyclin D1 proteins as well. There are significant differences in the phosphorylated eIF4E levels between the tumors studied, being the highest in meningiomas and the lowest in the oligodendroglial tumors. Relative to subcellular localization, eIF4E is frequently found in the nucleus of the oligodendroglial tumors and rarely in the same compartment of the meningiomas, whereas eIF2α showed an inverse pattern. Finally, cyclin D1 levels directly correlate with the phosphorylation status of both factors. The different expression, phosphorylation, or/and subcellular distribution of eIF2α and eIF4E within the brain types of tumors studied could indicate that different pathways are activated for promoting cell cycle proliferation, for instance, leading to increased cyclin D1 expression. (J Histochem Cytochem 57:503–512, 2009)     

Six Years after the Commercial Introduction of Bt Maize in Spain: Field Evaluation, Impact and Future Prospects

We carried out a 6-year-field evaluation to assess potential hazards of growing Compa, a transgenic Bt maize variety based on the transformation event CG 00256-176. Two categories of hazards were investigated: the potential of the target corn borer Sesamia nonagrioides to evolve resistance to Bt maize and effects on non-target organisms. In order to address the first hazard, dispersal capacity of the corn borer was measured and our results indicated that larvae move to plants other than those onto which the female oviposited - even to plants in adjacent rows - in remarkable numbers and they do so mostly at a mature age, suggesting that mixing Bt and non-Bt seeds in the same field would not be a very useful deployment strategy to delay/prevent resistance. In addition, adults move among fields to mate and males may do so for up to 400 m. Three different aspects of potential non-target effects were investigated: sub-lethal effects on the target S. nonagrioides, effects on non-target maize pests, and effects on maize-dwelling predators. Larvae collected in Bt fields at later growth stages, in which event 176 Bt maize expresses Bt toxin at sub-lethal concentrations, had longer diapause and post-diapause development than larvae collected in non-Bt fields, a feature that might lead to a certain isolation between populations in both type of fields and accelerate Bt resistance evolution. Transgenic maize did not have a negative impact on non-target pests in the field; more aphids and leafhoppers but similar numbers of cutworms and wireworms were counted in Bt versus non-Bt fields; in any case differences in damage or yield were recorded. We observed no difference in the numbers of the most relevant predators in fields containing transgenic or no transgenic maize.