Peripheral and Central Determinants of a Nociceptive Reaction: An Approach to Psychophysics in the Rat

BACKGROUND: The quantitative end-point for many behavioral tests of nociception is the reaction time, i.e. the time lapse between the beginning of the application of a stimulus, e.g. heat, and the evoked response. Since it is technically impossible to heat the skin instantaneously by conventional means, the question of the significance of the reaction time to radiant heat remains open. We developed a theoretical framework, a related experimental paradigm and a model to analyze in psychophysical terms the "tail-flick" responses of rats to random variations of noxious radiant heat. METHODOLOGY/PRINCIPAL FINDINGS: A CO(2) laser was used to avoid the drawbacks associated with standard methods of thermal stimulation. Heating of the skin was recorded with an infrared camera and was stopped by the reaction of the animal. For the first time, we define and determine two key descriptors of the behavioral response, namely the behavioral threshold (Tbeta) and the behavioral latency (Lbeta). By employing more than one site of stimulation, the paradigm allows determination of the conduction velocity of the peripheral fibers that trigger the response (V) and an estimation of the latency (Ld) of the central decision-making process. Ld (approximately 130 ms) is unaffected by ambient or skin temperature changes that affect the behavioral threshold (approximately 42.2-44.9 degrees C in the 20-30 degrees C range), behavioral latency (<500 ms), and the conduction velocity of the peripheral fibers that trigger the response (approximately 0.35-0.76 m/s in the 20-30 degrees C range). We propose a simple model that is verified experimentally and that computes the variations in the so-called "tail-flick latency" (TFL) caused by changes in either the power of the radiant heat source, the initial temperature of the skin, or the site of stimulation along the tail. CONCLUSIONS/SIGNIFICANCE: This approach enables the behavioral determinations of latent psychophysical (Tbeta, Lbeta, Ld) and neurophysiological (V) variables that have been previously inaccessible with conventional methods. Such an approach satisfies the repeated requests for improving nociceptive tests and offers a potentially heuristic progress for studying nociceptive behavior on more firm physiological and psychophysical grounds. The validity of using a reaction time of a behavioral response to an increasing heat stimulus as a "pain index" is challenged. This is illustrated by the predicted temperature-dependent variations of the behavioral TFL elicited by spontaneous variations of the temperature of the tail for thermoregulation

Sustainable livelihoods to adaptive capabilities: a global learning journey in a small state, Zanzibar

This thesis takes global learning out of the formal setting of a Northern classroom to a rural community setting in the Global South as a social learning process. It begins with a critical reflection of a large EU project to develop a global learning programme as a Global North South initiative. The focus narrows to Zanzibar, a small island state, to critically reflect on the delivery of the programme. And then further to focus on the global social learning and change that occurred in a rural community setting in the north of the island. Through participatory action research, I investigate the relevance of global learning as a social learning process, how norms and rules are shaped within a community setting and how these enable social change towards sustainable livelihoods. The thesis splices the intersection between critical and social theories of learning and engagement, to include critical social theories of Habermas (1984) and Wals (2007); critical race theories of Giroux (1997) and Said (1994) and distributive justice and entitlements theories of Sen (1997) and Moser (1998). It demonstrates the importance of dissonance and a safe space for deliberative dialogue, to be able to consider the global pressures and forces on local realities as the precursor to social change towards sustainability. I conclude by relating the learning from this small island state to the wider world and the current discourse on quality of education in a community development context

Pancytopenia and megaloblastic erythropoiesis reveal a novel GIF mutation

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Rivers of the Hadramawt watershed (Yemen) during the Holocene: Clues of late functioning

International audienceRecent geoarchaeological investigations have been carried out in the thick silty alluvial formations of the northern Hadramawt basin (Yemen). Field data was combined with a compilation of palaeoenvironmental records published from Arabia and its margins. Research performed on palaeolakes and other geoarchives indicates that the wet early-mid Holocene has little in common with the continuously arid period after 5.2 ka BP. The data sets allowed the authors to propose new perspectives for the Holocene palaeohydrological evolution of Southern Arabia, which was more variable and contrasting than previously thought. Furthermore, these data provide the opportunity to go deeper into the Holocene and to present a new precise palaeohydrological framework for the Late Holocene (7.0e2.0 ka BP). River functioning, fluvial aquifer dynamics and types of sedimentation are closely related to the rainfall regime, length and intensity (monsoonal or Mediterranean), and to the landscape conditions in the upper watersheds. The development of fluvial palaeosols in the Hadramawt valleys, often associated with high levels of the aquifers, is clearly in phase with humid periods until the beginning of the first millennium BC (5.9e5.3, 4.8e4.5 and 4.0e2.7 ka). River behaviour also impacted Neolithic and early Bronze Age settlement systems in this lowland area, as phases of floodplain stability favour site location. The hyperarid 4.2 ka event is associated with an unprecedented fluvial detrital phase with high energy discharges in the entire Hadramawt basin

Rivers of the Hadramawt watershed (Yemen) during the Holocene: Clues of late functioning

International audienceRecent geoarchaeological investigations have been carried out in the thick silty alluvial formations of the northern Hadramawt basin (Yemen). Field data was combined with a compilation of palaeoenvironmental records published from Arabia and its margins. Research performed on palaeolakes and other geoarchives indicates that the wet early-mid Holocene has little in common with the continuously arid period after 5.2 ka BP. The data sets allowed the authors to propose new perspectives for the Holocene palaeohydrological evolution of Southern Arabia, which was more variable and contrasting than previously thought. Furthermore, these data provide the opportunity to go deeper into the Holocene and to present a new precise palaeohydrological framework for the Late Holocene (7.0e2.0 ka BP). River functioning, fluvial aquifer dynamics and types of sedimentation are closely related to the rainfall regime, length and intensity (monsoonal or Mediterranean), and to the landscape conditions in the upper watersheds. The development of fluvial palaeosols in the Hadramawt valleys, often associated with high levels of the aquifers, is clearly in phase with humid periods until the beginning of the first millennium BC (5.9e5.3, 4.8e4.5 and 4.0e2.7 ka). River behaviour also impacted Neolithic and early Bronze Age settlement systems in this lowland area, as phases of floodplain stability favour site location. The hyperarid 4.2 ka event is associated with an unprecedented fluvial detrital phase with high energy discharges in the entire Hadramawt basin