A Simple and Low-Cost, but Naturalistic Method for Introducing Students to Action Potentials

Abstract Current trends in science education recommend the complementary use of virtual and hands-on methods of teaching. In neurobiology, for instance, there is a plethora of virtual laboratories and simulators that can be readily combined with traditional physical labs. Unfortunately, physical laboratories are almost unaffordable for many institutions due to the high cost of equipment. In this paper, we present a simple and low-cost in vivo method for demonstrating some of the basic biophysical properties of neural action potentials. The method involves the following steps: a) dissection of the ventral nerve cord of earthworm; b) electrical stimulation; c) amplification and visualization of the medial and lateral giant fibers' action potentials; and d) recording. The system showed stability, expected amplification, high signal-to-noise ratio, and an estimated total cost of US$ 5.662. We provide guidelines for assembling the system and discus its utility as a teaching alternative for low budget institutions.

Medios de cultivo económicos para la producción de un biocatalizador a células enteras para el tratamiento de aguas residuales que contienen Cr(VI) / Economical fermentation media for the production of a whole cell catalyst for the treatment of Cr(VI)-containing wastewaters

The biotechnology sector is continually seeking sustainable and more economical bioprocesses. Fermentation media produced with cheap components or wastes reduce production costs. Moreover, if wastes are used, they contribute to avoid environmental pollution. In this work, microbial growth media based on molasses or acidified glycerol as carbon sources and fertilizer as nitrogen source were tested for the production of a whole-cell catalyst that could be used in Cr(VI)-containing wastewater treatments. Results showed that the highest biomass production yield was obtained with a medium containing acidified glycerol 5% v/v and fertilizer 0.6% v/v. The biomass produced using this medium was immobilized in calcium alginate beads and used as catalyst in the biotransformation of Cr(VI) into Cr(III). The catalyst could be efficiently used for 5 reduction cycles of 40 mg/l Cr(VI) each. Cr(III) retention assays were performed to determine whether Cr(III) could be retained by the catalyst avoiding its solubilization in the supernatants. The retention capacity of the catalyst at 32 °C and pH 3.0 was 3 mg Cr(III)/g. Both an alternative and economical fermentation medium is here proposed for the optimization of Cr(VI)-containing wastewater treatment.

El sector industrial biotecnológico continuamente busca bioprocesos más económicos y sustentables. El uso de medios de cultivo producidos con componentes de bajo costo o con residuos reduce el presupuesto global del proceso y, particularmente si se utilizan residuos, se contribuye, además, a evitar la contaminación ambiental. En este trabajo se probaron medios de cultivo basados en melaza de caña o glicerol ácido como fuentes de carbono y energía, y fertilizante como fuente de nitrógeno, para la producción de un biocatalizador que podría ser usado para el tratamiento de aguas residuales que contienen Cr(VI). Los resultados mostraron que el mayor rendimiento de producción de biomasa se obtuvo con un medio que contenía 5% v/v de glicerol ácido y 0,6% v/v de fertilizante. Utilizando este medio se produjo la biomasa suficiente para la biotransformación de Cr(VI) a Cr(III), luego de ser inmovilizada en alginato de calcio. El proceso pudo ser aplicado eficientemente durante 5 ciclos de reducción de 40 mg/l de Cr(VI) cada uno. Además, se realizaron ensayos de retención de Cr(III) para determinar si esta especie química podría ser removida de la solución por interacción con el biocatalizador. La capacidad de retención obtenida por el biocatalizador a 32 °C y pH 3 fue de 3 mg de Cr(III)/g. De esta manera, se propone un medio de cultivo alternativo y económico para la efectivización de un tratamiento de aguas residuales que contengan Cr(VI).

Safe drinking water. Who is willing to pay the price?

Treating water can reduce the prevalence of diarrhoea by up to 70 percent. Although there are several inexpensive water treatment technologies available, statistics show that every 15 seconds a child dies due to waterborne diseases. Over 700 million people still lack access to safe drinking water. While there is a lot of research on the effectiveness of water treatment technologies, we urgently need to build on our understanding of the factors that contribute to the demand for and adoption of these products. The second issue of the 3ie-IDS brief Evidence Matters addresses crucial questions related to this development conundrum - Are people willing to pay for clean water? Is pricing the only factor influencing how people view its benefits? This brief distills policy relevant messages from a recent 3ie systematic review by Null, C., Kremer, M., Miguel, E., Garcia Hombrados J., Meeks R., and Zwane Alix to answer these questions. The evidence cited here is drawn from research in Bangladesh, Ghana, Kenya and Zambia. Key policy messages: 1- Many people are not willing to pay for safe drinking water. Even paying a small fee puts people off using water treatment technologies. 2- Understanding why people are not keen to pay and how much they might pay if they had the right information could help overcome these barriers. 3- Subsidising the costs of water treatment technologies can improve their uptake, but large subsidies are required. 4- Cheaper and innovative technologies and distribution models may encourage people to change their behaviour and start using water treatment technologies which would improve their health.