Mechanical Cell-Cell Communication in Fibrous Networks: The Importance of Network Geometry.

Cells contracting in extracellular matrix (ECM) can transmit stress over long distances, communicating their position and orientation to cells many tens of micrometres away. Such phenomena are not observed when cells are seeded on substrates with linear elastic properties, such as polyacrylamide (PA) gel. The ability for fibrous substrates to support far reaching stress and strain fields has implications for many physiological processes, while the mechanical properties of ECM are central to several pathological processes, including tumour invasion and fibrosis. Theoretical models have investigated the properties of ECM in a variety of network geometries. However, the effects of network architecture on mechanical cell-cell communication have received little attention. This work investigates the effects of geometry on network mechanics, and thus the ability for cells to communicate mechanically through different networks. Cell-derived displacement fields are quantified for various network geometries while controlling for network topology, cross-link density and micromechanical properties. We find that the heterogeneity of response, fibre alignment, and substrate displacement fields are sensitive to network choice. Further, we show that certain geometries support mechanical communication over longer distances than others. As such, we predict that the choice of network geometry is important in fundamental modelling of cell-cell interactions in fibrous substrates, as well as in experimental settings, where mechanical signalling at the cellular scale plays an important role. This work thus informs the construction of theoretical models for substrate mechanics and experimental explorations of mechanical cell-cell communication.

Using Positive Deviance to Understand the Uptake of Optimal Infant and Young Child Feeding Practices by Mothers in an Urban Slum of Mumbai.

Objectives Positive deviance research seeks out well-nourished children living in disadvantaged contexts to understand local growth-promoting behaviors. This study explored the factors that influence the uptake of infant and young child feeding behaviors among mothers. Methods Children with a height-for-age z-score (HAZ) > 0 (n = 10) or a HAZ < -2.0 (n = 12) were purposefully selected from households enrolled in a community management of acute malnutrition (CMAM) program in an urban slum of Mumbai, India. Qualitative methods were employed by means of semi-structured key informant interviews with positive and non-positive deviant mothers. Eligibility was restricted to households with limited resources and more than one child. A 24-h dietary recall and anthropometric measurements were taken for the index child. An observation checklist assessed household hygiene. Data analysis was based on the Grounded Theory of qualitative research. Results Positive deviant mothers (those with children with a HAZ > 0) largely exhibited optimal infant and young child feeding practices explained by maternal information seeking behaviors; mothers acknowledging the importance of maternal health; and social support. The relationship between mother and health worker seemed to influence how well they listened to the health workers' recommendations. Across all households, the daily consumption of high-energy, processed foods was apparent. Conclusions Practical considerations include exploring how to tailor CMAM programs to include social support and counseling training for health workers to engage more closely with mothers; exploring the feasibility of a women's social group for mothers to share information on child rearing; and teaching mothers about healthy eating and the link between nutrition and health.

The use of human faeces for fertilizer is associated with increased intensity of hookworm infection in Vietnamese women.

To investigate different factors associated with hookworm infections we conducted 2 studies in a commune in northern Viet Nam. The first was part of a larger study on anaemia and covered 213 women (15-49 years of age) and their 92 children (6 months to 5 years of age) in one commune; 90% of the families reported using human faeces for fertilizer. Women who reported using fresh human faeces as fertilizer had significantly higher hookworm egg counts than women who either used treated human faeces or who did not use human faeces as fertilizer. The second study examined how human faeces were used for fertilizer in 30 selected families. Women participated in preparation and application of human faeces to crops in 81% of the families using human faeces for fertilizer. Two methods of preparing the faeces were described: 48% of the families mixed the faeces with ash before applying them to the field; 18% mixed the faeces with water; 33% used both methods.