Effects of starvation on the fighting ability of invasive and autochthonous ants

Ants are widespread in all terrestrial habitats, and competitive interactions between species are common. Although redistribution of food within a colony may buffer the negative effects of temporary resource shortages, colony functionality can be compromised when famine is prolonged. One of the possible effects of famine is impairment of the fighting ability of species, with cascade effects on community. Here, we investigated whether food shortage alters the fighting ability of workers of three dominant species in the Mediterranean area: the invasive alien species, Lasius neglectus and Linepithema humile, and one highly polydomous autochthonous species belonging to the Tapinoma nigerrimum complex. We performed laboratory tests of interspecific one-on-one aggression and pairwise group contests between species, with all possible combinations of artificially satiated and starved groups. Results showed that starvation had a scarce effect on the individual aggressiveness in all three species. Similarly, the outcomes of the group fights were only lightly affected, but with an important exception. The positions of species in the fighting hierarchies were in most cases clear and linear, with L. neglectus at the top. However, we found that L. humile and L. neglectus showed equal mortality when one of the two species was starved and the other satiated. Although we investigated only one aspect of competition, that is, fighting ability, our results provide a piece of the complex jigsaw of competitive interactions of ants, and suggest that food deprivation can be a determinant that alters the relationships between ants and promotes or hampers the coexistence of dominant species.     

Soil fertility promotes decomposition rate of nutrient poor,but not nutrient rich litter through nitrogen transfer

Plant and Soil - Litter decomposition is a critical process in terrestrial ecosystems and understanding the effects of soil fertility on the litter decay rate is of great ecological relevance. Here...     

Effects of a high lipidic diet on murine energetic reserves in food deprivation

Female mice were fed for one month either control or cafeteria diets. Then they were subjected to food deprivation for up to 36 hours and their weight loss, tissue lipid, glycogen and protein were determined together with their plasma glycose, amino acids, urea, lipoproteins and ketone bodies. Cafeteria mice were able to cope with prolonged starvation with altered plasma composition and important loss of lipids and protein, sparing to a certain degree their glucose and amino acids. Control-fed mice, however, showed a intense ketosis and significant losses of nitrogen. The results obtained showed a higher ability of cafeteria mice to handle and use lipids, that evolves in a better suitability to resist food deprivation with less extensive alterations in their fuel and nitrogen homeostasis.     

Synthesis and biological evaluation of new [Tc(N)(PS)]-based mixed-ligand compounds useful in the design of target-specific radiopharmaceuticals: the 2-methoxyphenylpiperazine dithiocarbamate derivatives as an example

This study presents the first application of a general procedure based on the use of the [Tc(N)Cl(PS)(PPh₃)] species (PS is an alkyl phosphinothiolate ligand) for the preparation of Tc(N) target-specific compounds. [Tc(N)Cl(PS)(PPh₃)] selectively reacts with an appropriate dithiocarbamate ligand (S^∧Y) to give [Tc(N)(PS)(S^∧Y)] compounds. 1-(2-Methoxyphenyl)piperazine, which displays a potent and specific affinity for 5HT_1A receptors, was selected as a functional group and conjugated to the dithiocarbamate unit through different spacers (L ⁿ ). [^99mTc(N)(PS)(L ⁿ )] complexes were prepared in high yield (more than 90%). The chemical identity of ^99mTc complexes was determined by high performance liquid chromatography comparison with the corresponding ^99gTc complexes. All complexes were found to be inert toward transchelation with an excess of glutathione and cysteine. No notable biotransformation of the native compound into different species by the in vitro action of the serum and liver enzymes was shown. Nanomolar affinity for the 5HT_1A receptor was obtained for [^99mTc(N)(PSiso)L³] (IC₅₀ = 1.5 nM); a reduction of the affinity was observed for the other complexes as a function of the shortening of the alkyl chain interposed between the dithiocarbamate and the pharmacophore. Negligible brain uptake was found from in vivo distribution data of [^99mTc(N)(PSiso)L³]. The key finding of this study is that the complexes maintained good affinity and selectivity for 5HT_1A receptors, and the IC₅₀ value for [^99gTc(N)(PSiso)L³] being comparable to the IC₅₀ value found for WAY 100635. This result confirmed the possibility of preparing [^99mTc(N)(PS)]-based target-specific compounds without affecting the affinity and selectivity of the bioactive molecules for the corresponding receptors.     

Reconsidering anion inhibitors in the general context of drug design studies of modulators of activity of the classical enzyme carbonic anhydrase

Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a non-coordinating CA inhibitor but those erroneous results were subsequently corrected by another group. We review the anion CA inhibitors (CAIs) in the more general context of drug design studies and the discovery of a large number of inhibitor classes and inhibition mechanisms, including zinc binders (sulphonamides and isosteres, dithiocabamates and isosteres, thiols, selenols, benzoxaboroles, ninhydrins, etc.); inhibitors anchoring to the zinc-coordinated water molecule (phenols, polyamines, sulfocoumarins, thioxocoumarins, catechols); CAIs occluding the entrance to the active site (coumarins and derivatives, lacosamide), as well as compounds that bind outside the active site. All these new chemotypes integrated with a general procedure for obtaining isoform-selective compounds (the tail approach) has resulted, through the guidance of rigorous X-ray crystallography experiments, in the development of highly selective CAIs for all human CA isoforms with many pharmacological applications.     

Synthesis of an acridine orange sulfonamide derivative with potent carbonic anhydrase IX inhibitory action

Acridine orange (AO) a fluorescent cationic dye used for the management of human musculoskeletal sarcomas, due to its strong tumoricidal action and accumulation in the acidic environment typical of hypoxic tumors, was used for the preparation of a primary sulfonamide derivative. The rationale behind the drug design is the fact that hypoxic, acidic tumors overexpress carbonic anhydrase (CA, EC 4.2.1.1) isoforms, such as CA IX, which is involved in pH regulation, proliferation, cell migration and invasion, and this enzyme is strongly inhibited by primary sulfonamides. The AO-sulfonamide derivative was indeed a potent, low nanomolar CA IX inhibitor whereas its inhibition of the cytosolic isoforms CA I and II was in the micromolar range. A second transmembrane, tumor-associated isoform, CA XII, was also effectively inhibited by the AO-sulfonamide derivative, making this compound an interesting theranostic agent for the management of hypoxic tumors.