Sigma-1 and sigma-2 sites in rat brain: comparison of regional, ontogenetic, and subcellular patterns

Radioligand binding assay conditions were established for the selective labeling of sigma-1 and sigma-2 sites in membrane homogenates of rat brain. Selective sigma-1 assays were conducted using 5 nM(+)[3H]SKF-10,047 in the presence of 300 nM dizocilpine (MK-801). Selective sigma-2 assays were conducted using 5 nM [3H]DTG in the presence of 1 microM (+)SKF-10,047. Distributions of sigma-1 and sigma-2 binding among brain regions were found to differ. While the brain stem yields the highest level of sigma-1 binding, it yields among the lowest levels of sigma-2 binding. The reverse is true in hippocampal membranes. Different ontogenetic patterns were also observed. Sigma-2 binding decreases substantially during brain development, whereas sigma-1 binding does not vary significantly. Patterns of distribution among subcellular fractions of rat brain homogenates were found to be similar. Both sigma-1 and sigma-2 sites are most enriched in microsomal fractions, and neither is enriched in synaptosomal or mitochondrial fractions. The present results suggest that sigma-1 and sigma-2 sites are distinct entities; they do not appear to be located on a common macromolecule, and they do not represent two different affinity states of a single type of binding site. While the precise subcellular locations of sigma-1 and sigma-2 sites remain to be determined, we conclude that localization of either type of binding site to synaptic regions of plasma membrane or to mitochondria is highly unlikely.     

Environmental factors influencing annual sucker (Catostomus sp.) migration into a Great Lakes tributary

Fish migration in rivers is a growing area of concern as mounting anthropogenic influences, particularly fragmentation from dams and barriers, constitute major threats to global river species diversity. Barriers can impede the movement of fishes between areas critical to the completion of their lifecycle, affecting both population and ecosystem viability. In response, fish passage solutions have been identified as a critical need to maintain fisheries viability in the Laurentian Great Lakes, and around the world. Pivotal to the success of these fish passage solutions is a more complete understanding of the movement phenology and environmental cues that instigate migration. We used a dual-frequency identification sonar (DIDSON) to evaluate environmental triggers of river entry during spring and summer for three size classes of migratory fishes in the Boardman River, a Lake Michigan tributary. Our results indicate that medium size fish (>30 cm and < 50 cm), primarily composed of white sucker Catostomus commersonii and longnose sucker Catostomus catostomus were 21% more likely to enter the river at sunset and 25% less likely at midnight in comparison to midday. Entry rates of medium fish increased 6% for every 1 °C increase in river temperature, 4% for every 1 m³/s increase in river discharge from the day prior, and were reduced by 1% for every 10 cm increase in lake level. Understanding these processes in the tributaries of the Great Lakes is important to inform the fish passage solutions currently being developed for the Boardman River, and to inform management regulations for Great Lakes migratory fishes.     

Infra-red microspectroscopy of hydrated biological systems: design and construction of a new cell with atmospheric control for the study of plant cell walls

A new hydration cell has been constructed that allows wet biological samples, or samples of controlled moisture content, to be analysed in situ using infra-red microspectroscopy. The cell has been used to show that there are minor spectral changes associated with the hydration of pectin and tomato pericarp cell walls and slightly more significant changes in onion and carrot epidermal walls. The cell was also used to show that molecular orientations of polymers, previously observed in dry cell walls, were also to be seen in hydrated walls. For cell walls of onion and carrot epidermis, it was shown that the orientations of cell wall polymers are not affected by hydration. Furthermore, the polymer orientations in cell walls of fully elongated onion epidermal cells are different from those of elongating carrot epidermis. By using the hydration cell, it is now possible to investigate both fresh samples and wet systems routinely. The applications of this to the study of biological materials with infra-red microspectroscopy are discussed.     

Geophysical imaging inside masonry structures

Geophysical techniques offer the capability to non-invasively investigate engineering structures, both in terms of their spatial variability, and the prediction of properties of interest to the engineer from the ‘pixel’ values of the geophysical tomograms. The combined use of different geophysical methods provides a means of identifying the signature of salient engineering conditions. The response of seismic, radar and electrical resistivity tomography to simple targets within masonry structures is demonstrated. The benefits of combining rapid standard radar surveys with more detailed tomography is discussed and strategies for investigating typical structures developed. The response of the three methods, acoustic, electrical and radar to changes in the condition of masonry, such as reduction in strength and ingress of water, are discussed, with particular reference to a case study utilising the Ribblehead viaduct as an example. The corresponding responses to changes in ground conditions are also presented and shown to be important in understanding possible further applications of these methods, such as investigating behind retaining walls.     

Innovation, knowledge spillovers and local labour markets

Abstract.  This article investigates the role played by geography in the promotion of innovation. In order to examine these issues we employ empirical data from Finland in order to test the extent to which the variety and nature of face-to-face contacts affects the innovation performance of the firm. In addition, we then also control for the geographical mobility of the labour employed by the firm. This allows us to identify the different roles that the geography of knowledge spillovers and exchanges and the geography of labour markets play in the innovation process.     

Japanese contributions to regional science

Given the field's interdisciplinary nature, regional scientists come with a wide spectrum of backgrounds. In this paper, we study the contributions to regional science made by scholars from Japan. First, we briefly examine how Japanese regional scientists came to develop a keen sense towards urban problems. Second, we identify the most influential authors and papers via a citation analysis. The results indicate that scholarly outputs in regional science are reaching a wider audience beyond scientists, while maintaining the order of impact among them. Lastly, we focus on the new economic geography where Japanese scholars have made a significant contribution.     

Application of a sliding-mode observer for position and speedestimation in switched reluctance motor drives

A sliding-mode observer is applied toward the operation of a switched reluctance motor (SRM) drive. The sliding-mode observer estimates rotor position and velocity to control the conduction angles of the machine. Conventional on-off control with hysteresis current control is included with the position estimation scheme. The particular case of an automotive brake system motor is considered in detail where the conduction angles are modified with velocity feedback to provide optimum time response to brake system commands. Nonlinear modeling of a SRM is described and a computer simulation is developed based on data from an experimental SRM system. The sliding-mode observer is implemented with fixed-point and floating-point digital signal processors (DSPs) and the discrete-time implementations first examined under locked-rotor conditions. A comparison is also made between the implementation in two different types of DSPs. After confirming the accuracy of the computer simulation with experimental data, the design considerations in selecting observer coefficients with regard to sampling time, convergence rate, and transient stability are discussed. In conclusion, the effects of flux estimation errors on the system time response during a startup transient are examined