Protein transport in Archaea: Sec and twin arginine translocation pathways

The transport of proteins into and across hydrophobic membranes is an essential cellular process. The majority of proteins that are translocated in an unfolded conformation traverse the membrane by way of the universally conserved Sec pathway, whereas the twin arginine translocation pathway is responsible for the transport of folded proteins across the membrane. Structural, biochemical and genetic analyses of these processes in Archaea have revealed unique archaeal features, and have also provided a better understanding of these pathways in organisms of all domains. Further study of these pathways in Archaea might elucidate fundamental principles involved in each type of transport and could help determine their relative costs and benefits as well as evolutionary adaptations in protein secretion strategies.     

Seed germination of high mountain Mediterranean species: altitudinal,interpopulation and interannual variability

The germination response of 20 species from high altitude Mediterranean climates, most of them rare endemics, was studied. Our main goal was to model the germination response of a complete set of Iberian high mountain species. The effect of temperature and other parameters, such as spatial and temporal short gradients, on germination were also evaluated. Some seed features (mass and size) were also related to the germination response. Finally, we tested the effect of cold-wet stratification pretreatment when germination was low under natural conditions. Seeds were collected at four locations from 1,900 to 2,400 m a.s.l. in the Sierra de Guadarrama (Spanish Central Range) over two consecutive growing seasons (2001–2002) and submitted to different temperatures and a constant photoperiod of 16 h light/8 h darkness. Most plants readily germinate without treatment, reaching an optimum at relatively high temperatures in contrast to lowland Mediterranean species. Seeds seem to be physiologically prepared for rapid germination even though these plants usually face very intense summer droughts after ripening and dispersal. Germination was also highly variable among altitudes, populations and years, but results were inconsistent among species. Such flexibility could be interpreted as an efficient survival strategy for species growing under unpredictable environments, such as the Mediterranean climate. Finally cold-wet stratification increased germination capacity in five of nine dormant species, as widely reported for many arctic, boreal and alpine species. In conclusion, high mountain Mediterranean species do not differ from alpine species except that a relatively high number of species are ready to germinate without any treatment.     

Expression of functional recombinant mussel adhesive protein type 3A in Escherichia coli

Mussel adhesive proteins, including the 20-plus variants of foot protein type 3 (fp-3), have been suggested as potential environmentally friendly adhesives for use in aqueous conditions and in medicine. Here we report the novel production of a recombinant Mytilus galloprovincialis foot protein type 3 variant A (Mgfp-3A) fused with a hexahistidine affinity ligand in Escherichia coli and its approximately 99% purification with affinity chromatography. Recombinant Mgfp-3A showed a superior purification yield and better apparent solubility in 5% acetic acid (prerequisites for large-scale production and practical use) compared to those of the previously reported recombinant M. galloprovincialis foot protein type 5 (Mgfp-5). The adsorption abilities and adhesion forces of purified recombinant Mgfp-3A were compared with those of Cell-Tak (a commercial mussel extract adhesive) and recombinant Mgfp-5 using quartz crystal microbalance analysis and modified atomic force microscopy, respectively. These assays showed that the adhesive ability of recombinant Mgfp-3A was comparable to that of Cell-Tak but lower than that of recombinant Mgfp-5. Collectively, these results indicate that recombinant Mgfp-3A may be useful as a commercial bioadhesive or an adhesive ingredient in medical or underwater environments.     

Self-assembly of monoglycerides in beta-lactoglobulin adsorbed films at the air-water interface. Structural, topographical, and rheological consequences

In this work, we have analyzed the structural, topographical, and surface dilatational characteristics of pure beta-lactoglobulin adsorbed films and the effect of the self-assembly of monoglycerides (monopalmitin or monoolein) in beta-lactoglobulin films at the air-water interface. Measurements were performed in a single device that incorporates a Wilhelmy-type film balance, Brewster angle microscopy, and interfacial dilatational rheology. The structural and topographical characteristics of beta-lactoglobulin adsorbed and spread films are similar. However, the surface dilatational modulus of beta-lactoglobulin films shows a complex behavior depending on film formation. The self-assembly of monoglyceride in a beta-lactoglobulin adsorbed film has an effect on the structural, topographical, and dilatational properties of the mixed films, depending on the interfacial composition and the surface pressure (pi). At low pi, a mixed film of monoglyceride and beta-lactoglobulin may exist. At high pi (after the collapse of beta-lactoglobulin), the mixed films are dominated by monoglyceride molecules. However, the small amounts of collapsed beta-lactoglobulin have a significant effect on the surface dilatational properties of the mixed films. Protein displacement by monoglyceride is higher for monopalmitin than for monoolein. However, some degree of interaction exists between proteins and monoglycerides, and these interactions are more evident in adsorbed films than in spread films.     

Cadmium exposure modifies lactotrophs activity associated to genomic and morphological changes in rat pituitary anterior lobe

Cadmium (Cd) is widely used in industrial applications and is an important contaminant of agricultural products. As an endocrine disruptor, Cd modifies the hormone release of pituitary anterior lobe (PAL). This work was undertaken to evaluate a possible association between phospholipase D (PLD) and prolactin mRNA expressions and the activity of lactotrophs and folliculostellate cells (FSC) in PAL of Cd exposed adult male Wistar rats (Cd, 0.133 mM per liter for 2 months). The PALs were submitted to immunohistochemical and morphometric analysis to determine the percentage of lactotrophs (PRL-ir) and FSC (S-100-ir). Cultured PAL cells were stained with Hoechst 33258 to determine the presence of alterations in nuclear morphology consistent with apoptosis. The expressions of PLD and prolactin mRNA were assessed by RT-PCR. Cd treated rats showed a decrease of PLD mRNA levels that can be associated to both high number of apoptotic cells and increase of S-100 protein expression in FSC. Cd decreased prolactin mRNA expression, number of lactotrophs and percentage of PRL-ir suggesting a low availability of prolactin to be secreted from PAL. Cd modifies the lactotrophs activity of pituitary gland through biochemical, genomic and morphological changes and contributes directly or indirectly to the levels of serum prolactin.     

Anti-Trypanosoma activity of some natural stilbenoids and synthetic related heterocyclic compounds

We report the anti-Chagasic activity of the natural dihydrostilbenoid isonotholaenic acid and several simple derivatives, as well as that of some representative compounds of related synthetic series, with basic structures of benzalphthalides, dihydrostilbamides, isoindoles, phthalazin-1-ones, imidazo[2,1-a]isoindoles and pyrimido[2,1-a]isoindoles. The evaluation was performed in vitro on cultures of epimastigote and trypomastigote forms of Trypanosoma cruzi. Some of the tested compounds resulted to be as potent as benznidazole (epimastigotes), and others were shown to be more active than gentian violet (trypomastigotes), used as reference drugs.     

Nucleolar Organizer ultrastructure in Allium cepa

The Nuoleolar Organizer Region (NOR) was studied in Allium cepa. The cells analyzed were: meristematic root tip cells, cells from the layers of the anther (exothecium, intermediate layer cells, endothecium and tapetum) and meiocytes from preleptotene to diptotene. Conventional electron microscope techniques and serial section were used in the study. Ultracytochemical tests, using preferential techniques for nucleic acids were also applied. The results show that: a) Although the NOR may have a very variable form in the different cells analyzed, in each case its fine structure is similar, being constituted of chromatin differentiated in high and low density zones. b) In each case, its cytochemical characteristics are similar; highly positively to EDTA (preferential stain for RNP) being observed in the low density zones. As scattered chromatin these would constitute the active regions of the NOR. c) In certain cases a clear relationship is seen between NOR volume and the size of the nucleolus. d) The chromatin associated to the NOR always appears as very dense zones. e) The NOR-Nucleolus relationships are established exclusively with the latter's fibrillar pars. f) The nucleolar segregation phenomenon takes place sometimes as a result of a NOR contraction and in other cases depends on the position of the NOR in relation to the nucleolus. g) In preleptotene, the NOR shows its characteristic morphology and is positive to EDTA, while from zygotene to diplotene the structure of the NOR presents no differences from the rest of the chromatin and only the lateral elements of the synaptonemal complex or its remnants are positive to EDTA. h) The synaptonemal complex runs through the NOR with no differentiation and on occasions its lateral elements show associations with the nucleolus.     

C957T polymorphism of the dopamine D2 receptor gene is associated with motor learning and heart rate

Genetic variants that are related to the dopaminergic system have been frequently found to be associated with various neurological and mental disorders. Here, we studied the relationships between some of these genetic variants and some cognitive and psychophysiological processes that are implicated in such disorders. Two single nucleotide polymorphisms were chosen: one in the dopamine D2 receptor gene (rs6277-C957T) and one in the catechol-O-methyltransferase gene (rs4680-Val158Met), which is involved in the metabolic degradation of dopamine. The performance of participants on two long-term memory tasks was assessed: free recall (declarative memory) and mirror drawing (procedural motor learning). Heart rate (HR) was also monitored during the initial trials of the mirror-drawing task, which is considered to be a laboratory middle-stress generator (moderate stress), and during a rest period (low stress). Data were collected from 213 healthy Caucasian university students. The C957T C homozygous participants showed more rapid learning than the T allele carriers in the procedural motor learning task and smaller differences in HR between the moderate- and the low-stress conditions. These results provide useful information regarding phenotypic variance in both healthy individuals and patients.