Regulation of heptaspanning-membrane-receptor function by dimerization and clustering

G-protein-coupled receptors form homomers and heteromers; agonist-induced conformational changes within interacting receptors of the oligomer modify their pharmacology, signalling and/or trafficking. When these receptors are activated, the oligomers rearrange and cluster and a novel mechanism of receptor-operation regulation by oligomer intercommunication is possible. This intercommunication would be assisted by components of the plasma membrane and by scaffolding proteins. Receptor cross-sensitization, cross-desensitization and novel, integrated receptor responses can then develop between oligomeric receptor complexes of the cluster without direct contact between them. This concept gives a new perspective to the understanding of neurotransmission and neuronal plasticity.     

STRUCTURE AND FUNCTION OF BENTHIC ALGAL COMMUNITIES IN AN EXTREMELY ACID RIVER1

The composition of algal species and pigments and the structural and functional characteristics of the algal community were investigated in an acid stream of southwestern Spain, the Río Tinto. The algal community had low diversity and showed few seasonal differences. It was mainly made up of Klebsormidium flaccidum Kütz. (Silva, Mattox & Blackwell) that produced long greenish or purplish filaments, Pinnularia acoricola Hust. (producing brown patches) and Euglena mutabilis Schmitz. The algal filaments made up a consistent biofilm that also included fungal hyphae, iron bacterial sheaths, diatoms, and mineral particles. HPLC analyses on Río Tinto samples showed that undegraded chl accounted for 67% of the total chl in the filamentous patches but were a minority in the brown patch (2.6%). The brown patch had a concentration of carotenoids eight times lower than that observed in the green patch. When chl concentrations were weighted for the proportion of the different patches on the streambed, undegraded chl a accounted for 89.2 mg chl a·m ^{? 2} of stream surface area (5.4 g C·m ^{? 2}). This high algal biomass was supported by relatively high nutrient concentrations and by a high phosphatase activity (V_max = 137.7 nmol methylumbelliferyl substrate·cm ^{? 2}·h ^{? 1} 1 Received 15 July 2002. Accepted 17 February 2003. , K_m = 0.0045 μM). The remarkable algal biomass in Río Tinto potentially contributed to the bacterial–fungal community and to the macroinvertebrate community and emphasizes the role that the algae may have in the organic matter cycling and energy flow in extreme systems dominated by heterotrophic microorganisms.     

Effects of copper on algal communities at different current velocities

This study examines the influence of current velocity in the toxiceffect of copper in diatom-dominated biofilms grown in artificial channels.Effects on community structure, algal biomass and photosynthesis (carbonincorporation) caused by 15 g L^–1 of copperwere tested at contrasting (1 and 15 cm s^–1)velocities. Moreover, a possible threshold on the effect of copper on algalbiomass and photosynthesis related to current velocity was examined by usingprogressively increasing current velocity (1 to 50 cms^–1) at 15 g L^–1 Cu.Chlorophyll-a decreased ca. 50% as a result of addition of15 g L^–1 Cu. Chlorophyll decrease occurredearlier at 15 cm s^–1 than at 1 cms^–1 when adding 15 g L^–1Cu. Copper also caused a remarkable decrease in carbon incorporation(from 30 to ca. 50%), which was produced earlier at 15 cms^–1 (three days) than at 1 cms^–1 (seven days). Some taxa were affected by thecombination of copper and current velocity. Both Achnanthesminutissima and Stigeoclonium tenue becomedominant at 15 cm s^–1 in the presence of copper.Significant inhibition of algal growth in 15 g L^–1Cu occurred at low (1 cm s^–1) and highvelocities (50 cm s^–1), but not at intermediatevelocity (20 cm s^–1). The experiments indicatethat current velocity triggers the effect that copper has on diatom-dominatedbiofilms, and that the effect is more remarkable at low and high than atintermediate current velocities.     

Selective alkylation and acylation of alpha and epsilon amino groups with PEG in a somatostatin analogue: tailored chemistry for optimized bioconjugates

The effects of the type and location of polymer grafting on the biological activity of different mono-PEG derivatives of the somatostatin analogue RC160 were evaluated. A chemical strategy to obtain mono-PEG alkylation or acylation of the peptide's alpha-terminal or lysil-epsilon primary amines was devised. Selective BOC protection of the two available primary amines, followed by reaction with two different PEG reagents and removal of the protecting group, was carried out. Chemical characterization, structural studies, and the evaluation of the biological activity of the bioconjugates synthesized allowed the identification of the one having characteristics more suitable for therapeutic application. This corresponds to the mono-epsilon-lysil-pegylated form, obtained by reductive alkylation, where the amine's positive charge is preserved. The results obtained suggest the importance of preliminary studies in the development of new polymer-peptide conjugates with improved pharmacological properties.     

Development of specific fluorescent oligonucleotide probes for in situ identification of wine lactic acid bacteria

A rapid method for the identification of lactic acid bacteria (LAB) from wine has been developed. This method is based on fluorescence in situ hybridisation (FISH), using fluorescent oligonucleotide probes, homologous to 16S rDNA of those species of LAB commonly found in wines. The protocol for the specific detection of these bacteria was established through the hybridisation of 36 reference strains. The specificity of the probes was evaluated by using pure cultures. Probes were used to identify species in different wines, making it evident that direct identification and quantification from natural samples without culturing is also possible. The results show that FISH is a promising technique for the rapid identification of LAB, allowing positive identification in a few hours (4-16 h).     

Ataxia-telangiectasia: identification and detection of founder-effect mutations in the ATM gene in ethnic populations.

To facilitate the evaluation of ATM heterozygotes for susceptibility to other diseases, such as breast cancer, we have attempted to define the most common mutations and their frequencies in ataxia-telangiectasia (A-T) homozygotes from 10 ethnic populations. Both genomic mutations and their effects on cDNA were characterized. Protein-truncation testing of the entire ATM cDNA detected 92 (66%) truncating mutations in 140 mutant alleles screened. The haplotyping of patients with identical mutations indicates that almost all of these represent common ancestry and that very few spontaneously recurring ATM mutations exist. Assays requiring minimal amounts of genomic DNA were designed to allow rapid screening for common ethnic mutations. These rapid assays detected mutations in 76% of Costa Rican patients (3), 50% of Norwegian patients (1), 25% of Polish patients (4), and 14% of Italian patients (1), as well as in patients of Amish/Mennonite and Irish English backgrounds. Additional mutations were observed in Japanese, Utah Mormon, and African American patients. These assays should facilitate screening for A-T heterozygotes in the populations studied.     

Electronic Tagging of Atlantic Bluefin Tuna (Thunnus thynnus,L.) Reveals Habitat Use and Behaviors in the Mediterranean Sea

We analyzed the movements of Atlantic tuna (Thunnus thynnus L.) in the Mediterranean Sea using data from 2 archival tags and 37 pop-up satellite archival tags (PAT). Bluefin tuna ranging in size from 12 to 248 kg were tagged on board recreational boats in the western Mediterranean and the Adriatic Sea between May and September during two different periods (2000 to 2001 and 2008 to 2012). Although tuna migrations between the Mediterranean Sea and the Atlantic Ocean have been well reported, our results indicate that part of the bluefin tuna population remains in the Mediterranean basin for much of the year, revealing a more complex population structure. In this study we demonstrate links between the western Mediterranean, the Adriatic and the Gulf of Sidra (Libya) using over 4336 recorded days of location and behavior data from tagged bluefin tuna with a maximum track length of 394 days. We described the oceanographic preferences and horizontal behaviors during the spawning season for 4 adult bluefin tuna. We also analyzed the time series data that reveals the vertical behavior of one pop-up satellite tag recovered, which was attached to a 43.9 kg tuna. This fish displayed a unique diving pattern within 16 days of the spawning season, suggesting a use of the thermocline as a thermoregulatory mechanism compatible with spawning. The results obtained hereby confirm that the Mediterranean is clearly an important habitat for this species, not only as spawning ground, but also as an overwintering foraging ground.