Calcineurin is required to release Xenopus egg extracts from meiotic M phase

Fertilization induces a transient increase in cytoplasmic Ca2+ concentration in animal eggs that releases them from cell cycle arrest in the second meiotic metaphase. In frog eggs, Ca2+ activates Ca2+/calmodulin-activated kinase, which inactivates cytostatic factor, allowing the anaphase-promoting factor to turn on and ubiquitinate cyclins and securin, which returns the cell cycle to interphase. Here we show that the calcium-activated protein phosphatase calcineurin is also important in this process. Calcineurin is transiently activated after adding Ca2+ to egg extracts, and inhibitors of calcineurin such as cyclosporin A (ref. 8) delay the destruction of cyclins, the global dephosphorylation of M-phase-specific phosphoproteins and the re-formation of a fully functional nuclear envelope. We found that a second wave of phosphatase activity directed at mitotic phosphoproteins appears after the spike of calcineurin activity. This activity disappeared the next time the extract entered M phase and reappeared at the end of mitosis. We surmise that inhibition of this second phosphatase activity is important in allowing cells to enter mitosis, and, conversely, that its activation is required for a timely return to interphase. Calcineurin is required to break the deep cell cycle arrest imposed by the Mos-MAP (mitogen-activated protein) kinase pathway, and we show that Fizzy/Cdc20, a key regulator of the anaphase-promoting factor, is an excellent substrate for this phosphatase.     

Action Research: Its Foundations in Open Systems Thinking and Relationship to the Scientific Method

This paper considers those interpretations of action research that can be traced to Kurt Lewin at the Research Center for Group Dynamics at the University of Michigan, and the work in social ecology by Emery and Trist at the Tavistock Institute. It locates the logical basis of these interpretations in the philosophy of pragmatism, particularly as it relates to Peirce’s inferential logic and inquiry system. Drawing on this argument, and on the significant developments in approaches to systemic thinking over the past 40–50 years, a normative set of criteria is established for action research. The paper concludes that both positivist science (which relates to closed systems thinking) and action research (which relates to open systems thinking) are essential to any complete scientific approach.     

Impacts of Atlantic sea surface temperature anomalies on Indo-East Asian summer monsoon-ENSO relationship

Science Bulletin - In this study, the effect of the tropical North Atlantic (TNA) sea surface temperature (SST) variation in inducing the circulation anomaly in the Indo-East Asian monsoon (IEAM)...