Abstract: In technology acceptance literature, few have studied end users’ post-adoption attitude of technologies within organizational contexts before end-users start using the technology- the pre-implementation stage. This research proposes that perceived usefulness, appropriateness, and perceived behavioral control have influences on post-adoption attitudes toward web based content management systems. The proposed model was empirically tested using the Partial Least Squares technique with the 148 web based content management system end-users’ data collected from a large organization in a field setting. As theorized, all three variables were found to be significant determinants of system users’ post-adoption attitude in the pre-implementation stage. Furthermore, appropriateness was found to be the strongest determinant of systems users’ post-adoption attitude. The study findings provide important insights on enhancing system users’ post-adoption attitude in the pre-implementation stage.

Metallothioneins (MTs) are very particular proteins with a molar mass between 6-7 kDa, rich in cysteine (30%) and absence of aromatic amino acids. They undertake the maintenance of homeostasis of Cu and Zn and the detoxification of non-bioessential metals as Cd and Hg, and they are scavengers of free radicals, mainly of free hydroxyl and superoxides. These proteins are involved in a large number of physiological processes that have been studied in detail in vertebrate organisms. However, in invertebrates the study has not advanced at the same rate. Studies of MTs in bivalve mollusks have increased as a physiological response to heavy metal exposure. These invertebrates have been used widely as biomarkers of heavy metals, which supported their use as a tool to determine contaminated environments. More recently, isoforms of the MTs on bivalve mollusks have been isolated and characterized. Different functions of these isoforms have been proposed at different stages of the life cycle. Additionally environmental and xenobiotic factors modulate the expression and function of these proteins. The studies have demonstrated that there is a great polymorphism of MTs in bivalves, Some MTs can be induced by heavy metals, other are only associated with physiological processes. This revision deals about the characteristics and function of MTs, starting from the wide available knowledge in vertebrates and less knowledge in invertebrates.

Las metalotioneínas (MTs) son proteínas muy particulares con masa molar entre 6-7 kDa, alto contenido de cisteínas (30%) y ausencia de aminoácidos aromáticos. Se encargan de mantener la homeostasis del Zn y Cu e intervienen en la desintoxicación de metales no esenciales, como Cd y Hg. Son barredores de radicales libres, principalmente de hidroxilos libres y superóxidos. Estas proteínas participan en una gran cantidad de procesos fisiológicos que han sido estudiados detalladamente en organismos vertebrados. Sin embargo, en invertebrados el estudio no ha avanzado a la misma velocidad. En los moluscos bivalvos, los estudios de estas proteínas surgen como una respuesta fisiológica ante la exposición a metales pesados, por lo que han sido utilizados ampliamente como biomarcadores de metales pesados, lo cual sustentó su validación como herramienta para determinar ambientes contaminados. Más recientemente, se han aislado y caracterizado isoformas de las MTs en moluscos bivalvos. En algunas especies se ha determinado la función de cada una de ellas en diferentes etapas del ciclo de vida y se han establecido asociaciones entre la inducción de MTs y factores ambientales. Los estudios han demostrado que en bivalvos existe gran polimorfismo de las MTs y mientras algunas pueden ser inducidas por metales pesados, otras sólo se asocian a procesos fisiológicos. Esta revisión trata las características y funciones de las MTs partiendo del amplio conocimiento que se tiene en vertebrados y los alcances en los estudios realizados en bivalvos.

Abstract Increased serum CA 19-9 levels in patients with nonmalignant diseases have been investigated in previous reports. This study evaluates the clinical significance of serum CA 19-9 elevation in pulmonary nontuberculous mycobacterial disease and pulmonary tuberculosis. The median CA 19-9 level was higher in patients with pulmonary nontuberculous mycobacterial disease than in patients with pulmonary tuberculosis (pulmonary nontuberculous mycobacterial disease: 13.80, tuberculosis: 5.85, p < 0.001). A multivariate logistic regression analysis performed in this study showed that Mycobacterium abscessus (OR 9.97, 95% CI: 1.58, 62.80; p = 0.014) and active phase of pulmonary nontuberculous mycobacterial disease (OR 12.18, 95% CI: 1.07, 138.36, p = 0.044) were found to be risk factors for serum CA 19-9 elevation in pulmonary nontuberculous mycobacterial disease. The serum CA 19-9 levels showed a tendency to decrease during successful treatment of pulmonary nontuberculous mycobacterial disease but not in pulmonary tuberculosis. These findings suggest that CA 19-9 may be a useful marker for monitoring therapeutic responses in pulmonary nontuberculous mycobacterial disease, although it is not pulmonary nontuberculous mycobacterial disease-specific marker.

Las metalotioninas (Mts) se han utilizado como biomarcadores debido a que metales tóxicos como Hg, Cd, Cu pueden inducir su síntesis; sin embargo, los factores ambientales y la presencia de otros xenobioticos pueden determinar la magnitud de la respuesta en futuras exposiciones a iones metálicos. En el presente trabajo se evaluó la concentración de Mts en el tejido blando de ejemplares juveniles de Perna viridis preexpuestos a Cu y luego a Cd (Cu/Cd) durante 21 días, para lo cual se establecieron tres grupos experimentales: expuestos a Cd, preexpuestos a Cu y expuestos a Cd y el grupo control (sin metal). La acumulación de Cd en los tejidos fue significativamente mayor en los organismos preexpuestos a Cu, con un valor promedio de 6,64 ± 1,90 μg/g, mientras que en los expuestos a Cd, fue de 4,74 ± 2,33 μg/g. Las concentraciones de Mts también fueron mayores en el grupo Cu/Cd con un valor de 1,36 ± 0,52 μg/g con relación a los expuestos a Cd con un valor de 0,79 ± 0,47 μg/g durante los 21 días de exposición. La relación entre los niveles de Mts y la bioacumulación de Cd resultó ser lineal y significativa en el grupo expuesto a Cd, pero no en el expuesto a Cu/Cd. Estos resultados sugieren que el Cu posiblemente actuó como un inductor de Mts en el organismo, lo que propició un aumento de la acumulación de Cd en P. viridis y un incremento en la concentración de la Mts, lo que determina que la tolerancia y la bioacumulación de Cd en P. viridis está determinado por exposiciones previas y por ende su respuesta en los niveles de MTs también depende de ésto.

The metallothioneins (Mts) have been used as biomarkers because toxic metals such as Hg, Cd, Cu can induce their synthesis; however, environmental factors and the presence of other xenobiotics can determine the magnitude of the response in future exposures to metal ions. Metallothionein concentration was determinate in the soft tissue of Perna viridis juveniles pre-exposed to Cu and exposed to Cd (Cu/Cd) for 21 days. For this, three experimental groups were established: exposed to Cd, pre-exposed to Cu and exposed to Cd and the control group (no metal). Cadmium accumulation in tissues of P. viridis was significantly higher in pre-exposed organisms to Cu, with an average value of 6.6 ± 1.9 mg/g, while in those exposed to Cd, was 4.7 ± 2.4 mg/g. Mts concentrations were also higher in the Cu/Cd experimental group, with a value of 1.36 ± 0.52 mg/g in relation to those exposed to Cd which had a value of 0.79 ± 0.47 mg/g. The relationship between Mts and bioaccumulation of Cd was significant in the group exposed to Cd, but not in the exposed Cu/Cd. These results suggest that Cu possibly acted as an inducer of Mts in the body, which led to increased accumulation of Cd in P. viridis and increase in Mts concentration. Tolerance and bioaccumulation of Cd in P. viridis was determined by previous exposure of the organism and hence its response on levels of MTs also depends on it.

The concentration of Hg, Cu, Cd, Cr and Ni was estimated in fish and invertebrates captured in the Gulf of Paria coastal zone, Venezuela. The results show that invertebrates have a higher bioaccumulation of metals in relation to fish, particularly C. virginica that had the highest concentrations of Hg, Cu and Cd and the snail A. deflorata with the highest values of Cr, Ni and Pb. In relation to fishes, C. spixii (catfish) presented the highest values of all metals tested. The metals tested in the species do not exceed the maximum permissible values indicated by the WHO for human consumption. However, heavy metals are present in the Gulf of Paria.

En el presente trabajo se evaluó la concentración de Hg, Cu, Cd, Cr, Ni en peces e invertebrados capturados en la zona costera del Golfo de Paria, Venezuela. Los resultados muestran que los invertebrados tienen mayor bioacumulación de metales en relación a peces, particularmente C. virginica presentó la mayor concentración de Hg, Cu y Cd y el caracol A. deflorata que presentó las mayores concentraciones de Cr, Ni y Pb. En peces el bagre C. spixii presentó los más elevados valores de los metales analizados. Los metales evaluados en las especies no superen los valores máximos permisibles señalados por la Organización Mundial de la Salud para consumo humano, sin embargo se determina la presencia de los metales en el Golfo de Paria.

Las metalotioninas (Mts) son proteínas de baja masa molecular que juegan un rol importante en la detoxificación de metales, en vista de su papel ecotoxicológico se evaluaron las metalotioneínas (MTs) en 350 ejemplares del bivalvo Perna viridis en dos localidades de la costa norte del estado Sucre, desde febrero hasta diciembre 2003. Se determinaron los índices biométricos: índice de condición (IC), rendimiento de carne (RC) y relación peso seco-talla (PSL). Las Mts fueron separadas por cromatografía de exclusión molecular, Sephadex G-50 y se cuantificaron por saturación con cadmio. Los índices biométricos (RC y PSL) mostraron variaciones estacionales, entre localidades y estados de madurez, con la excepción del CI. No se encontraron diferencias significativas entre sexos. Las Mts mostraron variaciones estacionales, con concentraciones más elevadas entre febrero y marzo y mínimos entre septiembre y diciembre, que coincidieron con los períodos de alta y baja productividad en el área, respectivamente. Los mejillones de Río Caribe presentaron una mayor concentración de Mts que los de Chacopata. Los mejillones inmaduros mostraron la mayor concentración de Mts y la más baja en los desovados. Se encontró una relación negativa y significativa entre Mts y CI. Los resultados demuestran que las Mts de Perna viridis están influidas por el índice de condición y la condición reproductiva, asi como también pot los factores físico-químicos del ambiente marino.

Metallothionein is a cytosolic protein found in a variety of tissues and have been involved in the regulation of essential trace metals such as copper and zinc, and in the detoxification of essential and nonessential metals. With the aim to study their seasonal variation and their possible role in reproductive behavior, we evaluated metallothioneins (Mts) in Perna viridis, taken from Rio Caribe and Chacopata localities in the North coast of Sucre state, Venezuela. A total of 325 samples were obtained from February to December 2003. We determined the following biometric indices in bivalves: Condition Index (CI), meat yield (RC) and dry weight-length relationship (PSL). Besides, Mts in whole tissue were separated by molecular exclusion chromatography, Sephadex G-50 and quantified by saturation with cadmium. Our results showed that the biometric indices (RC and PSL) had seasonal variations between localities and maturity stages, with the exception of IC. No significant differences were found between sexes. Mts showed seasonal variations between localities, with the highest concentrations between February and March, and minimum ones between September and December, coinciding with the respectively high and low productivity periods in the area. The mussels from Rio Caribe had higher Mts concentration than those from Chacopata. Furthermore, immature mussels showed the highest Mts concentration while the lowest was found in spawned specimens. We found a significant negative relationship between Mts and CI. Our results demonstrated that MTs in Perna viridis are influenced by the condition index and reproductive status, as well as physicochemical factors in the marine environment.

Physiological response of tropical organisms to salinity changes was studied for some marine, estuarine and freshwater fishes (Astyanax bimaculatus, Petenia karussii, Cyprinodon dearborni, and Oreochromis mossambicus), marine and freshwater crustaceans (Penaeus brasiliensis, Penaeus schmitti and Macrobrachium carcinus), and marine bivalves (Perna perna, Crassostrea rhizophorae, and Arca zebra) collected from Northeast Venezuela. They were acclimated for four weeks at various salinities, and (1) placed at high salinities to determine mean lethal salinity, (2) tested by increasing salinity 5 ‰ per day to define upper lethal salinity tolerance limit, or (3) observed in a saline gradient tank to determine salinity preference. Acclimation level was the most significant factor. This phenomenon is important for tropical aquatic organisms in shallow waters, where they can adapt to high salinity during the dry season and cannot lose their acclimation level at low salinity during abrupt rain. For saline adaptation of tropical organisms, this behavior will contribute to their proliferation and distribution in fluctuating salinity environments.