The relation of Helicobacter pylori with dysplasia and stomach neoplasms in Costa Rica]

Occurrence of the bacterium Helicobacter pylori was compared for two Costa Rican sites with contrasting levels of gastric cancer incidence, Poás (incidence 15.13%) and Puriscal (83.53%). A sample of 185 adults of similar age and sex proportions was studied in each site, using both H. pylori antiserum tests and gastroscopy to collect two biopsies per case. No clear association between H. pylori and gastric cancer was found.     

Volatile isoprenoid emission potentials are correlated with essential isoprenoid concentrations in five plant species

This study offers new insight and data in support of the “opportunist hypothesis”, which suggests that there might be a relationship between carotenoid and volatile isoprenoid production. Five species of volatile isoprenoid-emitting plants (Eucalyptus globulus, Eucalyptus gunnii, Mucuna pruriens, Lycopersicon esculentum and Quercus ilex) were exposed to a range of imposed and natural stress conditions over a period of a few weeks in order to generate different levels of isoprenoid production potential. Volatile isoprenoid emission potentials and carotenoid concentrations were measured in all species, and dimethylallyl diphosphate (DMAPP) concentrations were measured in E. globulus, E. gunnii, M. pruriens and L. esculentum. Generally, instantaneously emitted isoprenoid emission potentials were positively correlated with carotenoid concentrations, and were negatively correlated with DMAPP concentrations. In contrast, emission potentials of monoterpenes stored in tissue pools were negatively correlated with carotenoid concentrations, and positively correlated with DMAPP concentrations. Our results support the possibility of a link (either direct, e.g. via substrate availability, or indirect, e.g. via complementary functionality) between emission potential of the volatile isoprenoid compounds studied here, and carotenoid synthesis at time scales of days to weeks.     

Electrochemical potential and ion transport in vesicles of yeast plasma membrane

Vesicles from yeast plasma membrane were prepared according to Franzusoff and Cirillo [1983) J. Biol. Chem. 258, 3608), with slight modifications. When Mg-ATP was added, this preparation was able to generate a membrane potential, that was sensitive to inhibitors of the yeast H+-ATPase and uncouplers, and could be decreased by the addition of permeant anions, as measured by the fluorescence changes of the dye oxonol V. The addition of ATP could also generate a pH gradient, detectable by the fluorescence changes of the monitor aminochloromethoxyacridine. This gradient was sensitive to inhibitors of ATPase and uncouplers, and could be increased by the addition of permeant anions to the incubation mixture. When the vesicles were loaded with KCl, an increased rate of K+ efflux was produced upon the addition of ATP. Cytochrome oxidase from bovine heart could be reconstituted into the vesicles and was shown to generate a membrane potential difference, negative inside, evidenced by the fluorescence quenching of the cyanide dipropylthiacarbocyanine and the uptake of tetraphenylphosphonium. Besides, in these vesicles, K+ and Rb+, but not Na+ or NH+4 could decrease the quenching of fluorescence and the uptake of tetraphenylphosphonium produced when the electron-donor system was present. In the vesicles in which cytochrome oxidase was incorporated, upon the addition of cytochrome c and ascorbate, the uptake of 86Rb+ could be demonstrated also. This uptake was found to be saturable and inhibited by K+, and to a lesser degree by Na+. The results obtained indicate that these vesicles are reasonably sealed and capable of generating and maintaining a membrane potential. The membrane potential could be used to drive ions across the membrane of the vesicles, indicating the presence and functionality of the monovalent cation carrier. The vesicles, in general terms seem to be suitable for studying transport of ions and metabolites in yeast.     

Recruitment of the RNA helicase RHAU to stress granules via a unique RNA-binding domain

In response to environmental stress, the translation machinery of cells is reprogrammed. The majority of actively translated mRNAs are released from polysomes and driven to specific cytoplasmic foci called stress granules (SGs) where dynamic changes in protein-RNA interaction determine the subsequent fate of mRNAs. Here we show that the DEAH box RNA helicase RHAU is a novel SG-associated protein. Although RHAU protein was originally identified as an AU-rich element-associated protein involved in urokinase-type plasminogen activator mRNA decay, it was not clear whether RHAU could directly interact with RNA. We have demonstrated that RHAU physically interacts with RNA in vitro and in vivo through a newly identified N-terminal RNA-binding domain, which was found to be both essential and sufficient for RHAU localization in SGs. We have also shown that the ATPase activity of RHAU plays a role in the RNA interaction and in the regulation of protein retention in SGs. Thus, our results show that RHAU is the fourth RNA helicase detected in SGs, after rck/p54, DDX3, and eIF4A, and that its association with SGs is dynamic and mediated by an RHAU-specific RNA-binding domain.     

Experimental study and constitutive modelling of the passive mechanical properties of the ovine infrarenal vena cava tissue

The passive mechanical properties of the ovine infrarenal vena cava are analysed in this paper. In vivo stretch from 15 venae was measured in order to get data from the physiological situation before harvesting the vessel. Vena cava strips (n=64) both in longitudinal and circumferential directions were cut and subjected to simple tension tests. Results showed the strongly marked anisotropic character of the caval tissue. The maximal stretch ranges reached in both directions were very different, with the longitudinal range being much higher than the circumferential range in all cases. Three anisotropic constitutive models were used to fit the data obtained from the experiments. Advantages and drawbacks of each of these models are also discussed.     

Serological and molecular detection of <Emphasis Type="Italic">Borrelia burgdorferi</Emphasis> sensu lato and <Emphasis Type="Italic">Anaplasmataceae</Emphasis> in rodents

The presence of Anaplasma spp. and Borrelia burgdorferi sensu lato in rodents from Eastern Slovakia were followed by serological and molecular methods. The seroprevalence for Borrelia was detected in 16.6 %, for Anaplasmataceae (APT) in 13.2 % and co-occurrence of Borrelia and APT in 7.5 %. Out of 110 ear biopsies of rodents, 5 were B. afzelii-positive. Five biopsies tested positive with the Ehr521-Ehr747 primers amplifying all the members of the family APT. A. phagocytophilum was detected in 1.8 %, 2.7 % were infected with Anaplasma-like organisms. Co-occurrence of Borrelia and Anaplasma in ear biopsies was found in 1.8 %. The circulation of both Borrelia and Anaplasma in the region of Eastern Slovakia was confirmed.     

Nitrogen and Carbon Concentrations, and Stable Isotope Ratios in Mediterranean Shrubs Growing in the Proximity of a CO2 spring

Seasonal changes in foliage nitrogen (N) and carbon (C) concentrations and δ¹⁵N and δ¹³C ratios were monitored during a year in Erica arborea, Myrtus communis and Juniperus communis co-occurring at a natural CO₂ spring (elevated [CO₂], about 700 μmol mol⁻¹) and at a nearby control site (ambient [CO₂], 360 μmol mol⁻¹) in a Mediterranean environment. Leaf N concentration was lower in elevated [CO₂] than in ambient [CO₂] for M. communis, higher for J. communis, and dependent on the season for E. arborea. Leaf C concentration was negatively affected by atmospheric CO₂ enrichment, regardless of the species. C/N ratio varied concomitantly to N. Leaves in elevated [CO₂] showed lower δ¹³C, and therefore likely lower water use efficiencies than leaves at the control site, regardless of the species, suggesting substantial photosynthetic acclimation under long-term CO₂-enriched atmosphere. Leaves of E. arborea showed lower values of δ¹⁵N under elevated [CO₂], but this was not the case of M. communis and J. communis foliage. The use of the resources and leaf chemical composition are affected by elevated [CO₂], but such an effect varies during the year, and is species-dependent. The seasonal dependency and species specificity suggest that plants are able to exploit different available water and N resources within Mediterranean sites. This revised version was published online in July 2006 with corrections to the Cover Date.     

Positive associations between the cushion plant Azorella monantha (Apiaceae) and alpine plant species in the Chilean Patagonian Andes

Low growing, compact cushion plants are a common and often dominant life form in temperate and subpolar alpine habitats. The cushion life-form can modify wind patterns, temperature and water availability and thus cushion species could be expected to act as nurse-plants facilitating the establishment of other alpine plant species on their surfaces. It has been suggested that the nurse effect should be most pronounced under more stressful environmental conditions, as found with increasing elevation in the alpine. One of the approaches used to detect the nurses has been the study of spatial associations among species, in which extreme clumping within or beneath one species has been interpreted as evidence of nursing. We characterized microclimatic conditions (soil and air temperature) within and outside cushions of Azorella monantha at two elevations (700 m a.s.l., corresponding to an elevation just above treeline, and 900 m a.s.l., corresponding to the upper limit of the cushion belt zone) on Cerro Diente in the Patagonian alpine of southern South America (50° S) and recorded all plant species growing upon cushions of various sizes and for paired sampling areas of equivalent sizes outside cushions. At 5 cm depth, soil temperature was slightly higher under cushions than under bare ground, but only significantly so at 900 m. Air temperature at ground level was significantly higher in the cushion microhabitat at both 700 m and 900 m, with the difference being more exaggerated at the highest elevation. At 700 m, a total of 27 species were recorded growing within cushions as compared to 29 outside cushions. At 900 m the corresponding numbers were 34 and 18. At the highest elevation, significantly more species grow within cushions than for equal areas outside cushions. Here moreover, 17 (48.6%) species grew preferentially within cushions, with eight of the latter being limited to the cushion microhabitat at this elevation. However, at 700 m there was no significant difference in species richness in the two microhabitats, and only one species (3.1%) grew preferentially on cushions. Considering individual species, nine occurring at both elevations showed non-preferential recruitment on cushions at 700 m, but significantly higher frequencies on cushions at 900 m. Results suggest striking altitudinal variation in the association with Azorella monantha on Cerro Diente, ranging from a very strong at 900 m to near absence at 700 m. Milder air and soil temperatures, shelter from wind, and greater water availability within cushions as opposed to outside cushions are discussed as possible factors favoring strong plant recruitment on cushions at higher elevations in the harsh Patagonian alpine environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Enhancing the early performance of the leguminous shrub Retama sphaerocarpa (L.) Boiss.: fertilisation versus Rhizobium inoculation

We have investigated the effect on growth of fertilisation versus biological nitrogen fixation by rhizobial nodules in Retama sphaerocarpa(L.) Boiss, a leafless leguminous shrub native to the Iberian Peninsula and North-West Africa that has generated interest for revegation of dry Mediterranean habitats. Our main objective was to optimise the formation of root nodules under nursery conditions and to evaluate their influence on the first year of seedling growth in comparison with standard fertilisation. Seedlings of R. sphaerocarpa from two Spanish localities were grown under two levels of fertilisation, and half of each were inoculated with rhizobia isolated from adult Retama, Cytisus and Adenocarpusplants in the field. Although some promiscuity was observed, nodulation was significantly successful with specific rhizobia. At the end of the experiment, highly fertilised plants were taller and heavier and exhibited larger photosynthetic rates than either nodulated or non-nodulated plants under low fertilisation. High fertilisation enhanced seedling growth but inhibited both the nodulation and the nitrogenase activity of the nodules. Thus, physiological differences between nodulated and non-nodulated plants were observed in the low but not in the high fertilisation treatment. Nitrogen uptake and use was enhanced by root nodules, which translated into enhanced photosynthesis and growth. Since inoculation is simple, environmentally friendly and cheap, and nodulated plants are more likely to overcome transplant stress than non-nodulated ones, our results suggest that inoculation together with low, background fertilisation (instead of high fertilisation) should be used when producing high quality seedlings of this autochthonous Mediterranean shrub.