Метод определения скрытых параметров синаптической передачи на основе данных ингибиторного анализа

Nowadays neuroscience strongly demands application of the mathematical methods for description of many neurophysiological and neurochemical processes among which the synaptic transmission outstands. One of the main problems in synaptic transmission modelling is the lack of the accurate values of dynamic parameters of biomolecules and complexes taking part in this process.The goal of this study is to elaborate the method for evaluation of synaptic transmission parameters that cannot be measured directly (so-called hidden parameters) and apply its results for investigation of the main stages of synaptic transmission in neuronets of hippocampus.The method is based on the parametric identification of the synaptic transmission deterministic model, which includes equations for description of inhibitors action on the main biochemical participants. We used three inhibitors: cilnidipine, 1.2-        bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA-AM), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). The parametric identification was performed by minimization of deviation of modeled field excitatory postsynaptic potential from those measured in rat hippocampus slices with microelectrode technique when inhibitors were applied.The results of the parametric identification of proposed model show that the model can adequately describe the generation of field excitatory postsynaptic potentials and their inhibition. The elaborated method afforded to evaluate the numerical meanings of eleven synaptic transmission hidden parameters. Using these parameters we have modelled the key synaptic transmission stages and got the time courses of the main biochemical participants: calcium ions in presynaptic bouton, SNARE complexes, synaptic vesicles in different states, glutamate in the synaptic cleft and open channels of AMPA receptor on the postsynaptic membrane. Thus, we propose method of hidden parameters evaluation that can be applied for different synaptic contacts in the brain of mammalians.Математическое описание передачи сигнала в синапсах открывает широкие перспективы в изучении деятельности головного мозга, позволяя собрать результаты многочисленных экспериментальных исследований в единую модель. Существенные затруднения при таком подходе возникают вследствие не только многоэтапности синаптической передачи, но и отсутствия точных численных характеристик динамики многих ее участников.Цель работы - разработать метод определения параметров синаптической передачи, недоступных для прямого измерения (скрытых параметров), и апробировать его в процессе изучения динамики основных этапов данного процесса в нейронных сетях гиппокампа.Предлагаемый в данной работе метод основан на построении детерминистической модели, описывающей генерацию полевого возбуждающего постсинаптического потенциала в условиях действия ингибиторов (цилнидипина, 1.2-  бис(2-аминофенокси) этан- N,N,N′,N′ тетрауксусной кислоты тетракис(ацетоксиметилового эфира), 6-циано-7-ни-трокиноксалин-2,3-диона), и параметрической идентификации данной модели на зарегистрированных с помощью микроэлектродной техники полевых возбуждающих постсинаптических потенциалах в срезах гиппокампа крысы. Параметрическая идентификация проводилась путем минимизации отклонения моделируемого сигнала от экспериментально зарегистрированного. Для минимизации целевой функции использовали генетический алгоритм.В результате проведенного исследования было показано, что параметрическая идентификация модели позволяет с высокой степенью соответствия воспроизводить формирование полевых возбуждающих постсинаптических потенциалов и оказываемое на них действие ингибиторов. Установлены численные значения одиннадцати скрытых параметров синаптической передачи. С помощью данных значений получены временные зависимости содержания ключевых участников синаптической передачи: ионов Ca2+ в пресинаптическом окончании, SNARE-комплексов, синаптических везикул в различных состояниях, глутамата в синаптической щели, доли открытых каналов АМРА-рецепторов на постсинаптической мембране. Таким образом, предложен метод, который целесообразно использовать для определения скрытых параметров различных типов синаптических контактов в головном мозге млекопитающих

Hawk Eyes II: Diurnal Raptors Differ in Head Movement Strategies When Scanning from Perches

Background Relatively little is known about the degree of inter-specific variability in visual scanning strategies in species with laterally placed eyes (e.g., birds). This is relevant because many species detect prey while perching; therefore, head movement behavior may be an indicator of prey detection rate, a central parameter in foraging models. We studied head movement strategies in three diurnal raptors belonging to the Accipitridae and Falconidae families. Methodology/Principal Findings We used behavioral recording of individuals under field and captive conditions to calculate the rate of two types of head movements and the interval between consecutive head movements. Cooper\u27s Hawks had the highest rate of regular head movements, which can facilitate tracking prey items in the visually cluttered environment they inhabit (e.g., forested habitats). On the other hand, Red-tailed Hawks showed long intervals between consecutive head movements, which is consistent with prey searching in less visually obstructed environments (e.g., open habitats) and with detecting prey movement from a distance with their central foveae. Finally, American Kestrels have the highest rates of translational head movements (vertical or frontal displacements of the head keeping the bill in the same direction), which have been associated with depth perception through motion parallax. Higher translational head movement rates may be a strategy to compensate for the reduced degree of eye movement of this species. Conclusions Cooper\u27s Hawks, Red-tailed Hawks, and American Kestrels use both regular and translational head movements, but to different extents. We conclude that these diurnal raptors have species-specific strategies to gather visual information while perching. These strategies may optimize prey search and detection with different visual systems in habitat types with different degrees of visual obstruction

Hawk Eyes I: Diurnal Raptors Differ in Visual Fields and Degree of Eye Movement

BACKGROUND: Different strategies to search and detect prey may place specific demands on sensory modalities. We studied visual field configuration, degree of eye movement, and orbit orientation in three diurnal raptors belonging to the Accipitridae and Falconidae families. METHODOLOGY/PRINCIPAL FINDINGS: We used an ophthalmoscopic reflex technique and an integrated 3D digitizer system. We found inter-specific variation in visual field configuration and degree of eye movement, but not in orbit orientation. Red-tailed Hawks have relatively small binocular areas (∼33°) and wide blind areas (∼82°), but intermediate degree of eye movement (∼5°), which underscores the importance of lateral vision rather than binocular vision to scan for distant prey in open areas. Cooper's Hawks' have relatively wide binocular fields (∼36°), small blind areas (∼60°), and high degree of eye movement (∼8°), which may increase visual coverage and enhance prey detection in closed habitats. Additionally, we found that Cooper's Hawks can visually inspect the items held in the tip of the bill, which may facilitate food handling. American Kestrels have intermediate-sized binocular and lateral areas that may be used in prey detection at different distances through stereopsis and motion parallax; whereas the low degree eye movement (∼1°) may help stabilize the image when hovering above prey before an attack. CONCLUSIONS: We conclude that: (a) there are between-species differences in visual field configuration in these diurnal raptors; (b) these differences are consistent with prey searching strategies and degree of visual obstruction in the environment (e.g., open and closed habitats); (c) variations in the degree of eye movement between species appear associated with foraging strategies; and (d) the size of the binocular and blind areas in hawks can vary substantially due to eye movements. Inter-specific variation in visual fields and eye movements can influence behavioral strategies to visually search for and track prey while perching

Political Capitalism: The Interaction between Income Inequality, Economic Freedom and Democracy

In this contribution we study the relationship between income inequality and economic freedom for a panel of 100 countries for the 1971-2010 period. From a panel causality study we find that income inequality has a negative causal effect on economic freedom, while causation does not run in the opposite direction. We argue that the negative effect of inequality on economic liberty is due to the elite’s political power stemming from its disproportionate control over a country’s economic resources. The elite uses this power to curtail economic freedom to defend its economic interests by discouraging innovation, competition and protecting its rents. Running a series of dynamic panel estimations, we show that the negative effect of income inequality on economic freedom is robust to different sets of controls and estimation techniques. Finally, we show that the dynamics of the inequality-freedom nexus are to some extent conditional upon a country’s political regime. When inequality is low, democracies enjoy comparatively higher levels of economic liberty, in line with the interests of a large middle-class. By contrast, economic freedom is lower in democracies (compared to strongly autocratic regimes with the same income distribution) when inequality is high. We argue that the latter finding corresponds to a system of political capitalism or captured democracy, where a powerful economic elite cooperates with politicians and bureaucrats for their mutual benefit

Environmentalism in the EU-28 context: the impact of governance quality on environmental energy efficiency

Environmental policies are a significant cornerstone of a developed economy, but the question that arises is whether such policies lead to a sustainable growth path. It is clear that the energy sector plays a pivotal role in environmental policies, and although the current literature has focused on examining the link between energy consumption and economic growth through an abundance of studies, it does not explicitly consider the role of institutional or governance quality variables in the process. Both globalization and democracy are important drivers of sustainability, while environmentalism is essential for the objective of gaining a “better world.” Governance quality is expected to be the key, not only for economic purposes but also for the efficiency of environmental policies. To that end, the analysis in this paper explores the link between governance quality and energy efficiency for the EU-28 countries, spanning the period 1995 to 2014. The findings document that there is a nexus between energy efficiency and income they move together: the most efficient countries are in the group with higher GDP per capita. Furthermore, the results show that governance quality is an important driver of energy efficiency and, hence, of environmental policies.University of Granad