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Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

Pituitary and autonomic responses to cold exposures in man

ACTA PHYSIOLOGICA, Issue 4 2005
J. Leppäluoto
Abstract This review presents hormonal responses to various cold exposures and their calorigenic effects in man and some animals. Previous studies in rats have shown that cold exposures activate the hypothalamic-pituitary-thyroid axis. Increased thyroid hormone concentrations lead to heat production via general stimulation of metabolism (obligatory thermogenesis) and possibly via activation of thyroid hormone receptors and uncoupling protein 1 (UCP 1) and deiodinase enzyme genes in the brown adipose tissue (BAT). In human subjects long-term cold exposures do not seem to activate the pituitary-thyroid axis, but rather accelerate the elimination of triiodothyronine (T3), leading to low serum concentrations of free T3 hormone. In corollary to this a hypothyreotic condition with increased serum thyroid-stimulating hormone and impaired mood and cognitive performance can be observed after long-term cold exposures such as wintering. During cold exposures the sympathetic nerve system is activated and noradrenaline is released to blood circulation and to BAT, where it leads to production of cAMP, lipolysis and free fatty acids. Free fatty acids open the mitochondrial proton channel protein in BAT. Protons enter the mitochondria and inhibit ATP synthesis (uncoupling). By this way energy is transformed into heat (facultatory or adaptive thermogenesis). In adult human subjects the amount of BAT is small and adaptive thermogenesis (non-shivering thermogenesis) has a smaller role. UCP 1 with other uncoupling proteins may have other functions in the control of body weight, sugar balance and formation of reactive oxygen species. [source]

The New Keynesian Phillips Curve: From Sticky Inflation to Sticky Prices

JOURNAL OF MONEY, CREDIT AND BANKING, Issue 4 2008
CHENGSI ZHANG
New Keynesian Phillips Curve; inflation survey forecasts; sticky prices; structural breaks; monetary policy The New Keynesian Phillips Curve (NKPC) model of inflation dynamics based on forward-looking expectations is of great theoretical significance in monetary policy analysis. Empirical studies, however, often find that backward-looking inflation inertia dominates the dynamics of the short-run aggregate supply curve. This inconsistency is examined by investigating multiple structural changes in the NKPC for the U.S. between 1960 and 2005, employing both inflation expectations survey data and a rational expectations approximation. We find that forward-looking behavior plays a smaller role during the high and volatile inflation regime to 1981 than in the subsequent period of moderate inflation, providing empirical support for sticky price models over the last two decades. A break in the intercept of the NKPC is also identified around 2001 and this may be associated with U.S. monetary policy in that period. [source]

Murine in vitro whole bladder model: A method for assessing phenotypic responses to pharmacologic stimuli and hypoxia

NEUROUROLOGY AND URODYNAMICS, Issue 4 2004
Joel C. Hutcheson
Abstract Aims Recent advances in genetic manipulation have allowed for over expression or deletion of selective genes in mice. This offers urologic investigators new means of understanding bladder function in the context of normal development or the response to outlet obstruction. It is important to correlate any genetic manipulations in mice with specific phenotypic properties such as voiding patterns, or muscle strip physiology. We describe a simple in vivo whole bladder preparation that may be used to study the phenotypic changes in bladder function. Methods Murine bladders were mounted on a 30 gauge needle and mounted in an organ chamber containing a physiologic buffer solution. Passive bladder properties were assessed with cystometry, and active contractile responses were measured in response to electrical field stimulation and agonists. The effects of hypoxia were also studied. Results Compliance in the murine bladder is dependent upon actin myosin interactions, and increased in the presence of calcium free buffer and EGTA. The sarcoplasmic reticulum plays a smaller role in the contraction of murine bladder than in other species. Murine bladder smooth muscle demonstrated a remarkable ability to withstand hypoxia. Conclusions This simple model can be adapted to help study the murine bladder smooth muscle phenotype under highly controlled circumstances. © 2004 Wiley-Liss, Inc. [source]

Orthodontically stressed periodontium of transgenic mouse as a model for studying mechanical response in bone: The effect on the number of osteoblasts

ORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 2 2000
Dubravko Pavlin
A better understanding of cellular and molecular mechanisms involved in response to mechanical stress is a prerequisite for future improvements in orthodontic treatment. To expand the application of molecular biology techniques in this area of research, we developed and characterized a mouse tooth movement model. The aim of this study was to biomechanically characterize this model and to evaluate the effect of orthodontic stress on the proliferation of periodontal osteoblasts. We used an orthodontic coil spring appliance with a low force/deflection rate, which produced an average force of 10,12 g. This design provided a predictable tipping movement of the molar with the center of rotation at the level of root apices. Histological observations of paradental tissues revealed a response favoring a fast onset of tooth movement and deposition of new osteoid starting after 3 days of treatment. The effect of treatment on the histomorpometric parameter of the number of osteoclasts per unit bone perimeter was determined after 1, 2, 3, 4, 6, and 12 days of treatment. Starting with day 2, the osteoblast number showed a modest but consistent increase in treated periodontal sites at all time-points, ranging from 14 to 39% and becoming significant only at day 6. Only a moderate increase in the number of osteoblasts in the areas of otherwise intense bone matrix synthesis suggests that, during bone formation, proliferation of cells has a smaller role compared to a marked increase in differentiation of individual cells. The mouse model, which allows for a controlled, reproducible, orthodontic mechanical loading, can be applied to both wild-type and transgenic animals and should enhance the research of the transduction of mechanical orthodontic signal into a biological response. [source]

Elites and the Diffusion of Foreign Models in Russia

POLITICAL STUDIES, Issue 1 2004
Sharon Werning Rivera
Globalization has sparked renewed interest in the diffusion of ideas and norms across boundaries. Although much work has focused on diffusion at the macro-level and on the groups that transmit ideas, few researchers have studied the cognitive processes of political elites as they weigh the merits of various foreign-inspired models. Drawing on a series of original, in-depth interviews with Russian parliamentarians and high-ranking bureaucrats conducted in 1996, this paper makes two contributions to the study of individual-level borrowing in the Russian context. First, the openness of Russian elites to foreign borrowing is investigated; despite the public rhetoric about Russia's uniqueness, a substantial number of Russian elites are willing to borrow from foreign experience , particularly from models of European welfare capitalism. Second, three explanations of why policy-makers prefer to emulate some countries rather than others are tested , because they are similar to their own country either geographically, historically or culturally (comparability); because they have geostrategic prominence (prestige); or because they excel economically and/or politically (performance). Comparability and prestige are found to be of lesser importance than performance to Russian elites when considering the merits of various foreign models. Given that Russia closely approximates a most-likely case for validating explanations stressing comparability, this suggests that the array of foreign ideas that could become part and parcel of Russia's transition process is probably wider than is usually assumed. It also implies that, in general, the regional dimension of diffusion plays a smaller role than previously theorized. [source]