Reaching across Borders: Canadian Girls Reading African Girls’ Stories

Review of: Badoe, Adwoa. Between Sisters. Toronto: Groundwood, 2010. Combres, Élisabeth. Broken Memory: A Novel of Rwanda. Trans. Shelley Tanaka. Toronto: Groundwood, 2009. Joyal, Lisa. Swahili for Beginners: A Young Adult Novel. Toronto: Sumach, 2007. Kent, Trilby. Stones for My Father. Toronto: Tundra, 2011. Mankell, Henning. Shadow of the Leopard. Trans. Anna Paterson. Toronto: Annick, 2009 Oron, Judie. Cry of the Giraffe: Based on a True Story. Richmond Hill: Annick, 2010.   DOI: 10.1353/jeu.2011.001

La crisis del COVID-19 : Una oportunidad para fortalecer las políticas de cuidados en la región

El presente trabajo es una investigación que trata sobre la manera en que nuestra sociedad organiza las tareas de cuidado. La injusta distribución de las responsabilidades de cuidado se construye sobre una idea social a partir de las características biológicas de los sexos. Las políticas de cuidado no son una cuestión de reparaciones tecnocráticas. En consecuencia, en su implementación pueden fomentar la igualdad de género, e incluso mitigar otras dimensiones de la desigualdad, como las de clase, casta y pertenencia étnica; o bien, exacerbarlas. El involucramiento y el apoyo del Estado marcan una diferencia en lo que atañe a empoderar a las mujeres y alcanzar la igualdad de género.Facultad de Trabajo Socia

A contribution to the deterministic modelling of circadian rhythms in cell proliferation activity

This paper presents a deterministic continuous model of proliferative cell activity. The classical series of connected compartments is revisited along with a simple mathematical treatment of two hypotheses: constant transit times and harmonic Ts. Several examples are presented to support these ideas, both taken from previous literature and recent experiences with the fish Carassius auratus, developed at the Junta de Energía Nuclear, Madrid, Spain

An individual based computational model of intestinal crypt fission and its application to predicting unrestrictive growth of the intestinal epithelium.

Intestinal crypt fission is a homeostatic phenomenon, observable in healthy adult mucosa, but which also plays a pathological role as the main mode of growth of some intestinal polyps. Building on our previous individual based model for the small intestinal crypt and on in vitro cultured intestinal organoids, we here model crypt fission as a budding process based on fluid mechanics at the individual cell level and extrapolated predictions for growth of the intestinal epithelium. Budding was always observed in regions of organoids with abundant Paneth cells. Our data support a model in which buds are biomechanically initiated by single stem cells surrounded by Paneth cells which exhibit greater resistance to viscoelastic deformation, a hypothesis supported by atomic force measurements of single cells. Time intervals between consecutive budding events, as simulated by the model and observed in vitro, were 2.84 and 2.62 days, respectively. Predicted cell dynamics was unaffected within the original crypt which retained its full capability of providing cells to the epithelium throughout fission. Mitotic pressure in simulated primary crypts forced upward migration of buds, which simultaneously grew into new protruding crypts at a rate equal to 1.03 days-1 in simulations and 0.99 days-1 in cultured organoids. Simulated crypts reached their final size in 4.6 days, and required 40 6.2 days to migrate to the top of the primary crypt. The growth of the secondary crypt is independent of its migration along the original crypt. Assuming unrestricted crypt fission and multiple budding events, a maximal growth rate of the intestinal epithelium of 0.10 days-1 43 is predicted and thus approximately 22 days are required for a 10-fold increase of polyp size. These predictions are in agreement with the time reported to develop macroscopic adenomas in mice after loss of Apc in intestinal stem cells

Evolución de la calidad de agua en establecimientos de la cuenca lechera de La Pampa

The objective of this study was to determine the water quality evolution in dairy farms of the Province of La Pampa, Argentina. The hypothesis that mega-dairy farms, because of their high animal population (400-700 cows), could cause water salinisation, due to an excessive use of ground water, and ground water contamination, as a result of accumulation of waste, was posed. We decided to compare then with medium dairy farms (lOO to 250 cows) to evaluate the impact of both models on water quality. We worked with 8 dairy farms in each category. During 3 consecutive years, samples of water were obtained every 6 months. Chemical (pR, total Salinity, Rardness, Sulfates, Chloride, Nitrates, Nitrites, Ammoniac, Calcium, Magnesium, Fluorine and Arsenium) and bacteriological analyses were performed in each sample. A statistically significant increase of the water Total Salinity could not be demonstrated in neither of the two groups. Rowever, in a few dairy farms, evidence of salinisation was found. A number of coliform bacteria above the tolerated values for human consumption, and belonging to a certain percentage of samples, was found within the first sampling. After corrective procedures were carried out, the results were negative in the sucessive samplings, without evidence of fecal contamination. In both groups, an important percentage of samples with Total Salinity, Sulfates, Fluorine and Arsenium levels above the advisable limits for dairy cattle was found.El objetivo de este trabajo fue determinar la evolución de la calidad del agua en establecimientos de la cuenca lechera de La Pampa. Se planteó la hipótesis de que los megatambos, debido a su alto número de animales (400 a 700 vacas), podrían causar una salinización del agua de bebida, por un uso excesivo de las napas, y la contaminación de las mismas, por la gran acumulación de efluentes. Se decidió compararlos con tambos medianos (lOO a 250 vacas) para evaluar el impacto de ambos modelos sobre la calidad del agua. Se trabajó con un total de 8 tambos en cada categoría. Las muestras de agua se obtuvieron semestralmente, durante 3 años consecutivos, y sobre ellas se realizaron análisis químicos (pR, Sales Totales, Dureza, Sulfatos, Cloruros, Nitratos, Nitritos, Amoníaco, Calcio, Magnesio, Flúor y Arsénico) y bacteriológicos. No pudo demostrarse, en ninguno de los dos grupos, un incremento estadísticamente significativo de la salinidad total del agua durante el período de estudio, aún cuando en algunos megatambos hubo evidencias de este proceso. En el primer muestreo se encontró, en un cierto porcentaje de muestras, un número de bacterias coliformes por encima de los valores permitidos para consumo humano. Al implementarse medidas correctivas, en los sucesivos muestreos los resultados fueron negativos, sin evidencias de contaminación fecal. En ambos grupos, se halló un porcentaje importante de muestras con tenores de Sales Totales, Sulfatos, Flúor y Arsénico por encima de los límites recomendados para bovinos lechero

A Multicellular Model of Intestinal Crypt Buckling and Fission

Crypt fission is an in vivo tissue deformation process that is involved in both intestinal homeostasis and colorectal tumourigenesis. Despite its importance, the mechanics underlying crypt fission are currently poorly understood. Recent experimental development of organoids, organ-like buds cultured from crypt stem cells in vitro, has shown promise in shedding light on crypt fission. Drawing inspiration from observations of organoid growth and fission in vivo, we develop a computational model of a deformable epithelial tissue layer. Results from in silico experiments show the stiffness of cells and the proportions of cell subpopulations affect the nature of deformation in the epithelial layer. In particular, we find that increasing the proportion of stiffer cells in the layer increases the likelihood of crypt fission occurring. This is in agreement with and helps explain recent experimental work

Expansion of Intestinal Epithelial Stem Cells during Murine Development

Murine small intestinal crypt development is initiated during the first postnatal week. Soon after formation, overall increases in the number of crypts occurs through a bifurcating process called crypt fission, which is believed to be driven by developmental increases in the number of intestinal stem cells (ISCs). Recent evidence suggests that a heterogeneous population of ISCs exists within the adult intestine. Actively cycling ISCs are labeled by Lgr5, Ascl2 and Olfm4; whereas slowly cycling or quiescent ISC are marked by Bmi1 and mTert. The goal of this study was to correlate the expression of these markers with indirect measures of ISC expansion during development, including quantification of crypt fission and side population (SP) sorting. Significant changes were observed in the percent of crypt fission and SP cells consistent with ISC expansion between postnatal day 14 and 21. Quantitative real-time polymerase chain reaction (RT-PCR) for the various ISC marker mRNAs demonstrated divergent patterns of expression. mTert surged earliest, during the first week of life as crypts are initially being formed, whereas Lgr5 and Bmi1 peaked on day 14. Olfm4 and Ascl2 had variable expression patterns. To assess the number and location of Lgr5-expressing cells during this period, histologic sections from intestines of Lgr5-EGFP mice were subjected to quantitative analysis. There was attenuated Lgr5-EGFP expression at birth and through the first week of life. Once crypts were formed, the overall number and percent of Lgr5-EGFP positive cells per crypt remain stable throughout development and into adulthood. These data were supported by Lgr5 in situ hybridization in wild-type mice. We conclude that heterogeneous populations of ISCs are expanding as measured by SP sorting and mRNA expression at distinct developmental time points