Analysis of cubic and orthorhombic C3A hydration in presence of gypsum and lime.

Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) have been used to study the microstructural changes and phase development that take place during the hydration of cubic (pure) and orthorhombic (Na-doped) tricalcium aluminate (C3A) and gypsum in the absence and presence of lime. The results demonstrate that important differences occur in the hydration of each C3A polymorph and gypsum when no lime is added; orthorhombic C3A reacts faster with gypsum than the cubic phase, forming longer ettringite needles; however, the presence of lime slows down the formation of ettringite in the orthorhombic sample. Additional rheometric tests showed the possible effects on the setting time in these cementitious mixes.

Mouse models in oncogenesis and cancer therapy.

Animal models have been critical in the study of the molecular mechanisms of cancer and in the development of new antitumor agents; nevertheless, there is still much room for improvement. The relevance of each particular model depends on how close it replicates the histology, physiological effects, biochemical pathways and metastatic pattern observed in the same human tumor type. Metastases are especially important because they are the main determinants of the clinical course of the disease and patient survival, and are the target of systemic therapy. The generation of clinically relevant models using the mouse requires their humanization, since differences exist in transformation and oncogenesis between human and mouse. Although genetically modified (GM) mice have been instrumental in understanding the molecular mechanisms involved in tumor initiation, they have been less successful in replicating advanced cancer. Moreover, a particular genetic alteration frequently leads to different tumor types in human and mouse and to lower metastastatic rates in GM mice than in humans. These findings question the capacity of current GM mouse carcinoma models to predict clinical response to therapy. On the other hand, orthotopic (ORT) xenografts of human tumors, or tumor cell lines, in nude mice reproduce the histology and metastatic pattern of most human tumors at advanced stage. Using ex vivo genetic manipulation of human tumor cells, ORT models can be used to molecularly dissect the metastatic process and to evaluate in vivo tumor response to therapy, using non-invasive procedures. Nevertheless, this approach is not useful in the study of the initial stages of tumorigenesis or the contribution of the immune system in this process. Despite ORT models are more promising than the most commonly used subcutaneous xenografts in preclinical drug development, their capacity to predict clinical response to antitumor agents remains to be studied. Humanizing mouse models of cancer will most likely require the combined use of currently available methodologies.

Enteroparasitosis en escolares de dos unidades educativas rurales del Municipio La Cañada, Estado Zulia Venezuela / Enteroparasitosis in school children from two educatives rurals units of the Municipality La Cañada, Zulia State Venezuela

El objetivo de la presente investigación fue determinar la prevalencia de la parasitosis intestinales, en los escolares de las unidades educativas rurales "Cacique Mara" y "Puerto Páez", ubicadas en la Parroquia Potreritos, Municipio La Cañada de Urdaneta del Estado Zulia. Se procesaron un total de 84 muestras de heces correspondientes entre 7 y 12 años, las cuales fueron sometidas a los métodos coproparasitológicos de: examen al fresco con solución salina fisiológica y lugol, técnica de concentración con formol-acetato de etilo y técnica de recuento de huevos de kato-kats. Los resultados obtenidos demuestran una elevada prevalencia de enteroparásitos (74,6 por ciento para Cacique Mara y 92,0 por ciento para Puerto Páez); así como un marcado predominio del poliparasitismo sobre el monoparasitismo. No se observó diferencia significativa de susceptibilidad a las parasitosis por edad o por sexo dentro de cada escuela o entre ambas unidades educativas. Las especies de enteroparásitos patógenos más frecuentes en los escolares de Cacique Mara y Puerto Páez fueron: T.trichiura (32,2 por ciento y 80,0 por ciento); A.lumbricoides (5,1 por ciento y 52,0 por ciento); G.lamblia (22,0 por ciento y 36,0 por ciento) y E.histolytica 85,1 por ciento y 16,0 por ciento). Al analizar la intensidad de infestación por geohelmintos, se observó que el mayor por centaje de los casos de Trichuriasis y Ascaridiasis se correspondían con cuadros "leves", restando sólo unos pocos casos "moderados" o "severos"; lo que confirma la tesis de que las cargas parasitarias de helmintos en los individuos ocurre en forma de agregados

Anodontites trapesialis: a biological monitor of organochlorine pesticides.

The mussel Anodontites trapesialis (Lam, 1819) was used as an indicator of organochlorine pollutants in the Pardo River, located in the municipality of Ribeirão Preto (21 degrees 07'S and 47 degrees 45'W), State of São Paulo, Brazil. Biological monitoring was performed for one year at the site of a sugar cane grove on the left bank of the river. Forty-three animals were placed in two aluminum enclosures on the river bottom at this site and 4 animals of each enclosure were sacrificed for pesticide analysis at 3-month intervals, each collection corresponding to one season of the year. The animals were found to have been exposed to DDT, lindane, heptachlor, aldrin and dieldrin. Endrin was not detected in any of the analyses.

Organochlorine pesticide residues in human milk in the Ribeirão Preto region, state of São Paulo, Brazil.

Thirty-seven samples of human milk (colostrum) from donors living in the Ribeirão Preto region were analyzed to determine the levels of organochlorine pesticide residues. Donors were classified into two groups, i.e., occupationally exposed and non-exposed to pesticides. Other factors such as age, previous lactations, race, smoking habit, occupation, family income and educational level were also considered. Analysis was performed by preliminary lipid extraction followed by fractional partition on a column and finally by gas chromatography with an electron capture detector. Lindane was found in 32% of the samples in amounts of less than 0.001 mg/kg; heptachlor was found in 65% of the samples at mean levels of 0.001 mg/kg, i.e., a level five-fold lower than that established by FAO/WHO (1970) for cow's milk. Aldrin and endrin were not detected in any of the samples. Dieldrin was detected in only one sample at a level of 0.038 mg/kg, which is considered high. DDT and DDE amounts are reported as total DDT and at least one of these compounds was present in every sample. Amounts detected in donors occupationally exposed to pesticides ranged from 0.008 to 0.455 mg/kg (mean, 0.149 mg/kg), i.e., three times the limit established by FAO/WHO (1970), while values for donors who had not been exposed ranged from 0.002 to 0.072 mg/kg (mean, 0.025 mg/kg), i.e., half the limit. Considering the level of acceptable daily intake proposed by FAO/WHO (1973), lactents ingested 1% of the acceptable intake of lindane (all donors), 30% of the acceptable intake of heptachlor (all donors), 60% of the acceptable intake of DDT (non-exposed donors), and 3.7 times the acceptable intake of DDT (exposed donors).(ABSTRACT TRUNCATED AT 250 WORDS)

Biological monitoring of organochlorides using the limnic bivalves Anodontites trapesialis (Lam., 1819).

The mussel Anodontites trapesialis (Lam, 1819) was used as an indicator of organochloride pollutants in the Canoas River, located in the municipality of Mococa (21 degrees 25'08''S and 47 degrees W), State of São Paulo, Brazil. Biological monitoring was performed for one year at the site of an orange grove on the left bank of the river. Forty-five animals were placed in aluminum enclosures on the river bottom at this site and 4 animals were sacrificed for pesticide analysis at 3-month intervals, each corresponding to one season of the year. Pesticides were extracted by the method of Bedford et al., (1968), modified, and the analyses were performed by gas phase chromatography equipped with an electron capture detector. The animals were found to have been exposed to DDT, Lindane and Heptachlor. Variation in Aldrin and Dieldrin levels was not significant enough to permit inferences. Endrin was not detected in any of the analyses.