Search

Background: Recent genome-wide association studies (GWAS) have identified a large number of genetic risk factors for schizophrenia (SCZ) featuring ion channels and calcium transporters. For some of these risk factors, independent prior investigations have examined the effects of genetic alterations on the cellular electrical excitability and calcium homeostasis. In the present proof-of-concept study, we harnessed these experimental results for modeling of computational properties on layer V cortical pyramidal cell and identify possible common alterations in behavior across SCZ-related genes. Methods: We applied a biophysically detailed multi-compartmental model to study the excitability of a layer V pyramidal cell. We reviewed the literature on functional genomics for variants of genes associated with SCZ, and used changes in neuron model parameters to represent the effects of these variants. Results: We present and apply a framework for examining the effects of subtle single nucleotide polymorphisms in ion channel and Ca2+ transporter-encoding genes on neuron excitability. Our analysis indicates that most of the considered SCZ- related genetic variants affect the spiking behavior and intracellular calcium dynamics resulting from summation of inputs across the dendritic tree. Conclusions: Our results suggest that alteration in the ability of a single neuron to integrate the inputs and scale its excitability may constitute a fundamental mechanistic contributor to mental disease, alongside with the previously proposed deficits in synaptic communication and network behavior.

This study assessed the impact of the HORIZONS Student Support Program on participating college freshmen at Purdue University (Indiana). HORIZONS is a federally funded program designed to increase retention of first generation, low income, or physically disabled students. The cornerstone of the project and the vehicle through which most services are delivered is the freshman orientation course, "Strategies for Effective Academic Performance," which addresses cognitive and affective needs. Students meet for 3 hours per week in a classroom to address the cognitive portion of the course and for 2 hours per week in a "Community Building/Personal Growth Laboratory" to work on the affective portion of the course. This study compared all 47 freshmen who entered the program in fall 1990 with a matched group of those who did not. Results showed that participation in HORIZONS had a dramatic impact on student retention and rate of graduation. The HORIZONS group retained 85 percent through 10 semesters while the control group retained only 47 percent. The increase in retention and graduation rates resulted from the delivery of a comprehensive set of services. Students evaluated the services and indicated that belonging to a support network, instruction in effective study methods, and tutoring were the most important services. (JB)

Reflectance data derived from Viking Lander multispectral data were used to characterize the types of soils and blocks exposed at the landing sites and to search for evidence of relatively unaltered igneous rocks. A comprehensive effort was mounted to examine multispectral data that combines testing of camera radiometric calibrations, explicitly removing the effects of atmospheric attenuation and skylight, and quantitatively comparing the corrected data to reflectance data from laboratory materials. Bi-directional reflectances for blue, green and red channels were determined for 31 block and soil exposures at Viking landing sites.

The use of Viking Lander 6 channel (0.4 to 1.1 microns) images to identify igneous materials is discussed. Movies of synthetic image cubes demonstrate that there are a number of contrast reversals between soils and certain rocks. Typically, large, angular rocks are brighter than the surrounding soils in the shortest wavelengths, and much darker than the soils at longest wavelengths. These results, which seem difficult to explain solely on the basis of photometric effects related to local lighting and viewing, are consistent with the presence of Fe+2 bearing silicates at the rock surfaces, producing relatively moderate absorptions in the blue and green parts of the spectrum, but more significant absorptions near about 1.0 micrometer (e.g., Fe+2 bearing pyroxenes). The soils, on the other hand, have signatures consistent with strong Fe+3 related absorptions at shorter wavelengths (e.g., Fe+3 bearing oxides or hydroxides).

Proof pressure, functional, dielectric, humidity, temperature, vibration, life cycle, and impact tests for qualifying Saturn S-IB stage LOX REPLENISHING ball valve