University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

Genetic Diversification and Dispersal of Taro (Colocasia esculenta (L.) Schott).

Abstract: Taro (Colocasia esculenta (L.) Schott) is widely distributed in tropical and sub-tropical areas. However, its origin, diversification and dispersal remain unclear. While taro genetic diversity has been documented at the country and regional levels in Asia and the Pacific, few reports are available from Americas and Africa where it has been introduced through human migrations. We used eleven microsatellite markers to investigate the diversity and diversification of taro accessions from nineteen countries in Asia, the Pacific, Africa and America. The highest genetic diversity and number of private alleles were observed in Asian accessions, mainly from India. While taro has been diversified in Asia and the Pacific mostly via sexual reproduction, clonal reproduction with mutation appeared predominant in African and American countries investigated. Bayesian clustering revealed a first genetic group of diploids from the Asia-Pacific region and to a second diploid-triploid group mainly from India. Admixed cultivars between the two genetic pools were also found. In West Africa, most cultivars were found to have originated from India. Only one multi-locus lineage was assigned to the Asian pool, while cultivars in Madagascar originated from India and Indonesia. The South African cultivars shared lineages with Japan. The Caribbean Islands cultivars were found to have originated from the Pacific, while in Costa Rica they were from India or admixed between Indian and Asian groups. Taro dispersal in the different areas of Africa and America is thus discussed in the light of available records of voyages and settlements.

Composition and Gene Expression of the cag Pathogenicity Island in Helicobacter pylori Strains Isolated from Gastric Carcinoma and Gastritis Patients in Costa Rica

Abstract: The composition and in vitro expression of the cag pathogenicity island genes in a group of Helicobacter pylori strains obtained from patients suffering from chronic gastritis-associated dyspepsia (n 5 26) or gastric carcinoma (n 5 17) were analyzed. No significant difference in the distribution of the 10 studied regions was found between the cases and the controls. Nine strains did not harbor any of the selected regions: eight (30.8%) isolated from patients with gastritis only and one (5.9%) from a patient with gastric carcinoma. No association was found between the number of repeated sequences at the 3* end of the cagA gene or the presence of tyrosine phosphorylation motifs and the clinical origin of the strains. The virB10 homolog gene was the sole gene studied to be significantly expressed more often in cancer strains than in gastritis strains (P 5 0.03).

The first dirhodium tetracarboxylate molecule without axial ligation: new insight into the electronic structures of molecules with importance in catalysis and other reactions.

Abstract: The first crystalline tetracarboxylato dirhodium paddlewheel complex with no axial ligation has been synthesized and structurally characterized. The compound, tetrakis(2,4,6-triisopropylbenzoato)dirhodium(II,II), Rh2(TiPB)4, exhibits a Rh−Rh bond length of 2.3498(4) A. Interestingly, this is only ca. 0.02 A shorter than that in the corresponding bis-acetone adduct, 2.3700(4) A. The electronic spectrum exhibits two bands in the visible region; the low-energy band A has been previously attributed to a π*(Rh2)→σ*(Rh2) transition in various bis-adducts. The spectrum of Rh2(TiPB)4(acetone)2 shows this band at 610 nm, while that of Rh2(TiPB)4 is greatly displaced to 760 nm. This is very persuasive evidence that the assignment for this transition is correct.

Chirality and field activity of rhynchophorol, the aggregation pheromone of the American palm weevil

Abstract: The American palm weevil, Rhynchophoruspalmarum (L.) (Coleoptera: Curculionidae), is the major vector of Rhadinaphelenchus cocophilus, a nematode which causes red ring disease in oil and coconut palms throughout Central and South America [1]. Losses to this disease are significant, and its incidence has been correlated with weevil population density [1]. Trapping with insecticide-treated pieces of palm is practiced but traps lose their attractancy after a few days [2]. Therefore, the availability of a stable semiochemical to enhance trap attractancy would be of significant value in control of this pest. Recently, Rochat et al. [3] reported the identification and laboratory activity of a male-produced aggregation pheromone, 6-methyl-2(E)-hepten-4-ol (1) for this weevil. Weevils were collected on sawn sections of oil palm trunk in the Palma Tica plantations at Quepos and Coto 47, Costa Rica. They were maintained in laboratory cultures on fresh sugarcane or apples. Volatiles were collected by drawing air over 20 25 male or female R. palmarum in a Nalgene desiccator fitted with a charcoal filter at the inlet and a Porapak Q trap at the outlet. Aerations were carried out for 2 4 days at a flow rate of 85 1/h [4]. Trapped volatiles were extracted from the Porapak Q with pentane which was concentrated by distillation [4]. Gas chromatographic analysis conducted