BackgroundMetallothioneins are ubiquitous small, cysteine-rich, multifunctional proteins which can bind heavy metals.Methodology/Principal FindingsWe report the results of phylogenetic and gene expression analyses that include two new Tetrahymena thermophila metallothionein genes (MTT3 and MTT5). Sequence alignments of all known Tetrahymena metallothioneins have allowed us to rationalize the structure of these proteins. We now formally subdivide the known metallothioneins from the ciliate genus Tetrahymena into two well defined subfamilies, 7a and 7b, based on phylogenetic analysis, on the pattern of clustering of Cys residues, and on the pattern of inducibility by the heavy metals Cd and Cu. Sequence alignment also reveals a remarkably regular, conserved and hierarchical modular structure of all five subfamily 7a MTs, which include MTT3 and MTT5. The former has three modules, while the latter has only two. Induction levels of the three T. thermophila genes were determined using quantitative real time RT-PCR. Various stressors (including heavy metals) brought about dramatically different fold-inductions for each gene; MTT5 showed the highest fold-induction. Conserved DNA motifs with potential regulatory significance were identified, in an unbiased way, upstream of the start codons of subfamily 7a MTs. EST evidence for alternative splicing in the 3′ UTR of the MTT5 mRNA with potential regulatory activity is reported.Conclusion/SignificanceThe small number and remarkably regular structure of Tetrahymena MTs, coupled with the experimental tractability of this model organism for studies of in vivo function, make it an attractive system for the experimental dissection of the roles, structure/function relationships, regulation of gene expression, and adaptive evolution of these proteins, as well as for the development of biotechnological applications for the environmental monitoring of toxic substances.

Background: Most patients infected with Helicobacter pylori show no clinical symptoms. Nonetheless, approximately 10% to 20% of these patients will develop peptic ulcers and 1% will develop gastric cancer. The International Agency for Cancer Research has classified Helicobacter pylori as a Group 1 carcinogen. Materials and Methods: Drinking water samples from 20 cantons situated in areas of low and high incidence of gastric cancer in Costa Rica were analyzed. Water samples were concentrated and the nitrocellulose filter was cultivated for later molecular identification of Helicobacter pylori using the glmM marker. The tumor necrosis factor-alpha inducing protein (Tipalpha TNF-α) was used as a pathogenicity marker of the strains found followed by the sequencing of two products. Information on water management by aqueduct operators was collected in order to establish statistical relationships. Results: A total of 112 water samples were analyzed. Successful cultivation and molecular identification using the glmM marker was achieved in 39% of samples from areas of high incidence and in 7.5% of samples from areas of low incidence. Two glmM gene PCR products were sequenced and confirmed as true positives. Conclusions: The highest prevalence rate of Helicobacter pylori was found in water from areas with a high incidence of gastric cancer. Additionally, significant statistical correlations were established among environmental conditions, drinking water management and incidence of gastric cancer.

Chronic Kidney Disease (CKD) of unknown origin has caused serious public health problems in specific countries in the word, such as, Sri Lanka, India and Mesoamerica. Particularly in Costa Rica the pathology and linked mortality are concentrated in the north pacific region from the country. Affected people are found predominantly in rural agricultural areas with warm climate and low altitude and to a much lesser extent in hilly elevated areas; however, the full geographic extent of the disease is still unclear. The objective of this research is to determine a scenario of exposure to toxicants in populations with high numbers of cases of CKD. Explanatory variables for the high rate of CKD were determined by means of a Poisson multivariate regression analysis at a national level. The environmental variables included hectares of cultivated and burned sugarcane, atmospheric temperatures, relative humidity, arsenic in water for human consumption, speed and direction of winds, annual average precipitation, and geographical location with respect to alti- tude. Heavy metals, including transition metals and metalloids such as arsenic, cadmium, mercury, lead, vanadium, and silicon, which even at low concentrations have the potential to cause nephrotoxicity via chronic exposure, were quantified in the soils in areas with the highest prevalence of the disease in the country. According to this quantifica- tion and analysis, these metal(loid)s may have causal relevance in the pathology of CKD. The statistical, geographical and laboratory analy- ses determined that population exposure to environmental toxicants is seasonal, occurring under the convergence of annual climatic phenomena.

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Aim: To disclose scientific knowledge about hydroarsenicism in Latin America, as well as to determine the presence of arsenic in water used for human consumption in risk areas of Costa Rica, specifically at the Central, Oreamuno, Paraíso and Alvarado counties of the province of Cartago. Methods: Quantification of inorganic arsenic by hydride generation and flame atomic absorption, according to method 7062 of the US Agency of Environmental Protection. Results:  None of the analyzed samples surpassed the maximum limit of 10 µg/L allowed by the present Costa Rican legislation. Conclusion: Even though sampled areas are of volcanic nature and therefore of arsenic risk, the population consumes water of direct underground origin with a great superficial influence and little or no contact to deeper volcanic rock, thus not contaminated with arsenic.