Dysfunctional cGMP Signaling Leads to Age-Related Retinal Vascular Alterations and Astrocyte Remodeling in Mice

The nitric oxide–guanylyl cyclase-1–cyclic guanylate monophosphate (NO–GC-1–cGMP) pathway is integral to the control of vascular tone and morphology. Mice lacking the alpha catalytic domain of guanylate cyclase (GC1^−/−) develop retinal ganglion cell (RGC) degeneration with age, with only modest fluctuations in intraocular pressure (IOP). Increasing the bioavailability of cGMP in GC1^−/− mice prevents neurodegeneration independently of IOP, suggesting alternative mechanisms of retinal neurodegeneration. In continuation to these studies, we explored the hypothesis that dysfunctional cGMP signaling leads to changes in the neurovascular unit that may contribute to RGC degeneration. We assessed retinal vasculature and astrocyte morphology in young and aged GC1^−/− and wild type mice. GC1^−/− mice exhibit increased peripheral retinal vessel dilation and shorter retinal vessel branching with increasing age compared to Wt mice. Astrocyte cell morphology is aberrant, and glial fibrillary acidic protein (GFAP) density is increased in young and aged GC1^−/− mice, with areas of dense astrocyte matting around blood vessels. Our results suggest that proper cGMP signaling is essential to retinal vessel morphology with increasing age. Vascular changed are preceded by alterations in astrocyte morphology which may together contribute to retinal neurodegeneration and loss of visual acuity observed in GC1^−/− mice.     

The effect of microstructure on the permeability of metallic foams

Pressure drop was measured across complex and simple structure metallic foams at different velocity ranges using air as working fluid. Darcian and non-Darcian permeability parameters, K and C, were determined by fitting experimental data with widely accepted quadratic model of Hazen-Dupuit-Darcy. Generally, the experimental results are in good agreement with the model. The differences in K and C values between the two types of metallic foams are due to the different microstructure. For the simple structure specimens, permeability K increased whereas non-Darcian permeability C decreased with increasing pore diameter. The effect of pore size on the permeability of complex structure metallic foams seems to be opposite to that observed with the simple structure specimens and to results reported by other researchers on other porous medium. This discrepancy mainly stems from the differences in window concentration in addition to some heterogeneity in the foam that impeded the gas flow on one side of the specimens. The difference in pressure drop observed in the different metallic foams is due to combined effect of K and C. However, for simple structure foams, K and C could be predicted by Ergun-like model using appropriate values for the empirical constants. The permeability K is significantly affected by pore size and porosity. The quadratic term of Hazen-Dupuit-Darcy equation is mainly due to the inertia of the flow and partially to the drag exerted by the microstructure of the metallic foam. For both foams, as the porosity increases, pressure drop decreases and permeability, K, increases. The introduction of the open cross sectional area term enabled better understanding of the permeability of metallic foams with intricate morphologies.     

Antecedents of computer self-efficacy: A study of the role of personality traits and gender

Empirical evidence suggests that computer self-efficacy plays an important role in one’s acceptance and use of new information technology. Little is however known about the antecedents of computer self-efficacy. This paper reports on a study of 143 non-users of a self-checkout library system available at a large Canadian university which was conducted to investigate the relationships between stable personality traits and gender with computer self-efficacy. Results indicate that four of the five stable personality traits, as measured by the Big-5 factors of personality, contribute to explain computer self-efficacy. Taking gender into account, results show that the traits of neuroticism, extraversion, and agreeableness are significantly related to computer self-efficacy for women but not for men. Implications for research and practice are discussed.     

Translumbar placement of inferior vena caval catheters: a solution for challenging hemodialysis access

Access to the central venous circulation for hemodialysis has traditionally been achieved via the subclavian or jugular venous routes. With ongoing improvements in medical management, many hemodialysis recipients develop exhaustion of these routes and require alternative means of central venous access. Inferior vena caval (IVC) catheters have been placed with a percutaneous translumbar approach to allow central venous access for chemotherapy, harvesting of stem cells, and total parenteral nutrition. Translumbar placement of IVC catheters has become accepted by some as a useful and reliable alternative in patients who require long-term hemodialysis but have exhausted traditional access sites. IVC catheters have been placed in patients with IVC filters, and IVC filters have been placed in patients with IVC catheters. Complications include those associated with central venous catheters, for example, sepsis, fibrin sheaths, and thrombosis. A complication specific to placement of IVC hemodialysis catheters is migration of the catheter into the subcutaneous soft tissues, retroperitoneum, or iliac veins. Translumbar placement of IVC catheters is performed only in patients considered to have few or no other medical options and is not intended as a primary means of central venous access.     

Copolymerization of elemental sulfur with styrene

Copolymerization of elemental sulfur with styrene in the presence and absence of metallic sodium was studied at 120°C and 138°C. Propagation of the reaction was followed by gel permeation chromatography (GPC). Glass transition temperatures of all samples were obtained by differential scanning calorimetry (DSC). Reaction products were fractionated with a preparative-type GPC, and each fraction was characterized by DSC, vapor pressure osmometry, infrared spectrophotometry, and both proton and carbon-13 nuclear magnetic resonance spectrometry. Results indicate that the product is a true copolymer of styrene and sulfur. Kinetics of the copolymerization were studied using GPC to monitor styrene and sulfur concentrations. The initial rate of copolymerization (as followed by the consumption of styrene and sulfur) decreases with increasing initial styrene to sulfur ratio. From kinetic analyses, ratios of the rate constants of homo- and copolymerization were determined. Copolymerization of the reactants is more spontaneous than homopolymerization. The reactivity ratios obtained are 0.2 for styrene and 0.6 for sulfur.     

Evolution of porosity, shrinkage and density of pasta fortified with pea protein concentrate during drying

The aim of this work was to study the impact of fortification with commercial pea protein concentrate on the evolution of the moisture content, density, shrinkage and porosity of pasta made from durum wheat semolina during drying. Pasta were processed from durum wheat semolina enriched with pea protein concentrate at 0, 5, 10 and 15 g 100-g-dry matter⁻¹ and dried at low (40 °C) and high (80 °C) temperature. Moisture content, density, shrinkage and porosity and effective moisture diffusivity coefficients were linked through theoretical development. It enabled to study the behaviour of the properties as a function of drying time. The results showed that drying temperature has a greater effect on the studied properties than enrichment with pea protein concentrate. Drying at 80 °C increased radial and total shrinkage compared to drying at 40 °C, but no differences were observed for longitudinal shrinkage. Pasta dried at 80 °C were denser and overall less porous, but had greater internal porosity. The volumetric percentage of water lost during drying replaced by air within the pasta matrix was lower at 80 °C. Scanning electron microscopy analysis showed that the gluten network of pasta dried at 80 °C seems denser and more continuous. Effective moisture diffusivity coefficients of pasta dried at 80 °C were higher at 5 and 10 g 100-g-dry matter⁻¹ enrichment level compared to the control.     

Effects of disclosure of comprehensive pretherapy information on clients at a university counseling center.

This experimental study examined the effects of comprehensive versus partial written pretherapy disclosure on the behavior and perceptions of university counseling center clients. Although all clients received information on services provided, confidentiality, length of sessions, and right to terminate therapy, only the treatment group received additional information that included personalized data on therapists, what to expect in therapy, and risks and alternatives to therapy. The one statistically significant difference between clients who received partial versus comprehensive disclosure favored the comprehensive disclosure group. The results support previous research, which also concluded that there is no evidence that pretherapy disclosure adversely affects therapy, and add substantially to this conclusion because of several methodological improvements and additions in the current research design compared with prior research designs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increases in food web cadmium following reductions in atmospheric inputs to some lakes

We measured the toxic metal cadmium (Cd) over a 13-year interval in lakes located near two metal smelters to determine whether reductions in atmospheric Cd emissions have led to reductions in the Cd present in aquatic food webs. Although Cd in the lake water consistently declined over time, Cd in animals increased in some lakes. This apparent contradiction was explained when we considered the simultaneous reductions that have occurred in lake water acidity; under these conditions, animal Cd can increase if there are insufficient hydrogen ions to out-compete Cd ions at biological uptake sites. We conclude that the risk to organisms from metals has increased in some lakes recovering from smelter emissions.