pH-dependent effects of procaine on equine gamete activation

Procaine directly triggers pH-dependent cytokinesis in equine oocytes and induces hypermotility in stallion spermatozoa, an important event during capacitation. However, procaine-induced hyperactivated motility is abolished when sperm is washed to remove the procaine prior to sperm-oocyte co-incubation. To understand how procaine exerts its effects, the external Ca2+ and Na+ and weak base activity dependency of procaine-induced hyperactivation in stallion spermatozoa was assessed using computer-assisted sperm analysis. Percoll-washed stallion spermatozoa exposed to Ca2+-depleted (+2 mM EGTA) procaine-supplemented capacitating medium (CM) still demonstrated hyperactivated motility, whereas CM without NaCl or Na+ did not. Both procaine and NH4Cl, another weak base, were shown to trigger a cytoplasmic pH increase (BCECF-acetoxymethyl (AM)), which is primarily induced by a pH rise in acidic cell organelles (Lysosensor green dnd-189), accompanied by hypermotility in stallion sperm. As for procaine, 25 mM NH4Cl also induced oocyte cytokinesis. Interestingly, hyperactivated motility was reliably induced by 2.5-10 mM procaine, whereas a significant cytoplasmic cAMP increase and tail-associated protein tyrosine phosphorylation were only observed at 10 mM. Moreover, 25 mM NH4Cl did not support the latter capacitation characteristics. Additionally, cAMP levels were more than 10x higher in boar than stallion sperm incubated under similar capacitating conditions. Finally, stallion sperm preincubated with 10 mM procaine did not fertilize equine oocytes. In conclusion, 10 mM procaine causes a cytoplasmic and acidic sperm cell organelle pH rise that simultaneously induces hyperactivated motility, increased levels of cAMP and tail-associated protein tyrosine phosphorylation in stallion spermatozoa. However, procaine-induced hypermotility is independent of the cAMP/protein tyrosine phosphorylation pathway

Interactions of Tollmien-Schlichting waves and Dean vortices. Comparison of direct numerical simulation and a weakly nonlinear theory

Direct numerical simulation is used to evaluate a weakly nonlinear theory describing the interaction of Tollmien-Schlichting waves with Dean vortices in curved channel flow. The theory and the simulation agree for certain combinations of parameters, but the two approaches give conflicting results for other combinations. Some possibilities for these discrepancies are discussed

Technology Diffusion and Postwar Growth

In the aftermath of World War II, the world's economies exhibited very different rates of economic recovery. We provide evidence that those countries that caught up the most with the U.S. in the postwar period are those that also saw an acceleration in the speed of adoption of new technologies. This acceleration is correlated with the incidence of U.S. economic aid and technical assistance in the same period. We interpret this as supportive of the interpretation that technology transfers from the U.S. to Western European countries and Japan were an important factor in driving growth in these recipient countries during the postwar decades.wars, economic growth, technology adoption, cross-country studies.

Rice Price Stabilization in Madagascar: Price and Welfare Implications of Variable Tariffs

Given the large share of major staples in the budgets of the poor, governments in many developing countries intervene in food markets to limit variation in the prices of staple foods. This paper examines the recent experience of Madagascar in stabilizing prices through international trade and the implications of adjustments in tariff rates. Using a partial equilibrium model, we quantify the overall costs and benefits of a change in import duties for various household groups, and compare this intervention to a policy of targeted food transfers or security stocks.Food Policy, Price Stabilization, Trade, sub-Saharan Africa, Crop Production/Industries, International Relations/Trade, Q11, Q17,

The CHAT Dataset

This note accompanies the Cross?country Historical Adoption of Technology (CHAT) dataset. CHAT is an unbalanced panel dataset with information on the adoption of over 100 technologies in more than 150 countries since 1800. The data is available for download at: http://www.nber.org/data/chat. We discuss the main aim of CHAT, its scope and limitations, as well as several ways in which we have used the data so far and ways to potentially use the data for other research. Suggested acknowledgment: If you use the CHAT dataset for your research, please include the following citation: "Our technology measures come from the CHAT data set which is an extension of the data set described in Comin and Hobijn (2004)"