The nitric oxide-cGMP pathway may mediate communication between sensory afferents and projection neurons in the antennal lobe of Manduca sexta

The nitric oxide (NO)-cGMP signaling system is thought to play important roles in the function of the olfactory system in both vertebrates and invertebrates. One way of studying the role of NO in the nervous system is to study the distribution and properties of NO synthase (NOS), as well as the soluble guanylyl cyclases (sGCs), which are the best characterized targets of NO. We study NOS and sGC in the relatively simple and well characterized insect olfactory system of the hawkmoth, Manduca sexta. We have cloned Manduca sexta nitric oxide synthase (MsNOS) and two sGCs (MsGCalpha1 and MsGCbeta1), characterized their basic biochemical properties, and studied their expression in the olfactory system. The sequences of the Manduca genes are highly similar to their mammalian homologs and show similar biochemical properties when expressed in COS-7 cells. In particular, we find that MsGC functions as an obligate heterodimer that is stimulated significantly by NO. We also find that MsNOS has a Ca2+-sensitive NO-producing activity similar to that of mammalian neuronal NOS. Northern and in situ hybridization analyses show that MsNOS and the MsGCs are expressed in a complementary pattern, with MsNOS expressed at high levels in the antennae and the MsGCs expressed at high levels in a subset of antennal lobe neurons. The expression patterns of these genes suggest that the NO-sGC signaling system may play a role in mediating communication between olfactory receptor neurons and projection neurons in the glomeruli of the antennal lobe.     

Photoconductivity in p-i-n Quantum Well Optical Modulators

Abstract

We have studied the temperature dependence of the current due to photoexcited carriers in p-i-n single quantum-well optical modulators, in order to ascertain the dominant transport mechanisms involved. A model describing the photocurrent is presented which includes the temperature and field dependence of the thermal emission, the tunnelling, the mobility and the recombination rate. A comparison between the experimental results and the model is also presented, outlining the probable transport processes.     

Characterizing user navigation through complex data structures

As part of the general study of user navigation through interactive databases, a set of indices is proposed to characterise users' search sequences. These indices are presented as an attempt to capture some of the psychologically significant aspects of the movement of users within interactive data-bases. An example of the use of the indices is given in reference to an experiment to compare front-ends to a data-base program. Their strengths and weaknesses are discussed in the light of this experiment. Their potential as a basis for the precise definition of search strategies such as browsing and scanning is also considered.     

The role of external validity in evidence-based practice for rehabilitation.

Objective: To advance a methodological convention that balances concern for rigor (i.e., internal validity) with equal concern for relevance (i.e., external validity). Method: Conceptual. Results: A rating format for relevance is derived, determined, and applied to cognitive rehabilitation. Implications: The evidentiary base for applying research to practice can be properly determined through expert analysis of multidimensional criteria. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Zurek-Kibble Causality Bounds in Time-Dependent Ginzburg-Landau Theory and Quantum Field Theory

Zurek's and Kibble's causal constraints for defect production at continuous transitions are encoded in the field equations that condensed matter systems and quantum fields satisfy. In this article we highlight some of the properties of the solutions to the equations and show to what extent they support the original ideas.     

High tolerances for a low-voltage, high-contrast, low-insertion-loss asymmetric Fabry-Perot modulator

The authors report on the reduction of the operating voltage of a GaAs/AlGaAs multiple-quantum-well asymmetric Fabry-Perot modulator to approximately 4.2 V for a high-contrast ( approximately 15 dB), low-insertion-loss ( approximately 3 dB) device. This improvement on modulator performance makes the device suitable for a practical system and has been accomplished by an increase of the front reflectivity to approximately 43%. The authors discuss general design issues and show that the higher finesse cavity does not have to lead to low fabrication and environmental tolerances. On the contrary, this device's tolerance to fabrication and environmental factors is expected to have been improved.<>     

Synchrotron Radiation for Detecting Movement of a Volatile Soil Liquid

Heat and volatile liquid transport in soils are physically coupled processes. Soil water movement driven by thermal gradients has received considerable attention both experimentally and via models. This is appropriate since the thermal regime of underground electric power cables, pipelines, agricultural soils, and nuclear-waste repositories influences their ability to function effectively. However, available experimental liquid concentration data are of relatively low resolution, generally about one measurement per cm. By using synchrotron x rays we were able to nondestructively obtain high (50 μm) spatial resolution, time-lapsed data for the thermally driven movement of dibromomethane (DBM) in soil. Under repeated temperature cycling during a 22 h period, DBM movement within a sealed, 25-mm-long quartz sand (D50 = 0.25?mm) soil column was highly repeatable. About four complete scans of the column were completed each hour. Average DBM vol?% within the column as a whole was 4.0 and the porosity was 0.31. Measurements of DBM concentration at the same position and equivalent times during different cycles usually differed by less than 0.2 vol?%. Experimental data of this precision will permit better comparison with detailed model predictions.     

Volatile anesthetic agents and vascular communication in the microcirculation of the hamster cheek pouch

BACKGROUND: There is communication between tissue and the vascular network involved in regulating distribution of blood flow. Signals generated by the tissue are communicated upstream to create a coordinated network response in unison with other controllers of blood flow, such as myogenic and flow-dependent responses. METHODS: This vascular communication was modeled with the microapplication of methacholine (10(-4) M) or potassium chloride solution (KCl; 100 mM) to arterioles (40-60 microm in diameter) of the cheek pouch of anesthetized hamsters and viewed with videomicroscopy. Local and conducted (500 microm upstream) responses were measured. Halothane or isoflurane (1%, 2%, and 3%) was equilibrated with the superfusion solution and applied to the entire tissue. Responses to KCl and methacholine were then repeated in the presence of an anesthetic agent. RESULTS: Halothane and isoflurane increased the resting diameter of the arterioles. They also decreased the methacholine-initiated dilations. To test for the effects of increased resting diameter on the dilations, 0%, 5% and 10% oxygen alone was applied to the pouch to alter the tone, and the methacholine responses were repeated. The dilations decreased with oxygen-induced increases in resting diameter, but the conducted dilation decreased to a lesser extent than was seen with the volatile anesthetic agents. Neither halothane nor isoflurane decreased constrictions caused by KCl. CONCLUSIONS: Decreased methacholine-initiated conducted dilations caused by halothane and isoflurane were not due to decreases in cell-cell communication because KCl conducted responses persisted. Therefore, cell-cell vascular communication appears intact in the presence of clinical concentrations of halothane and isoflurane.