Overexpression of Tropomyosin Isoform Tpm3.1 Does Not Alter Synaptic Function in Hippocampal Neurons

Tropomyosin (Tpm) has been regarded as the master regulator of actin dynamics. Tpms regulate the binding of the various proteins involved in restructuring actin. The actin cytoskeleton is the predominant cytoskeletal structure in dendritic spines. Its regulation is critical for spine formation and long-term activity-dependent changes in synaptic strength. The Tpm isoform Tpm3.1 is enriched in dendritic spines, but its role in regulating the synapse structure and function is not known. To determine the role of Tpm3.1, we studied the synapse structure and function of cultured hippocampal neurons from transgenic mice overexpressing Tpm3.1. We recorded hippocampal field excitatory postsynaptic potentials (fEPSPs) from brain slices to examine if Tpm3.1 overexpression alters long-term synaptic plasticity. Tpm3.1-overexpressing cultured neurons did not show a significantly altered dendritic spine morphology or synaptic activity. Similarly, we did not observe altered synaptic transmission or plasticity in brain slices. Furthermore, expression of Tpm3.1 at the postsynaptic compartment does not increase the local F-actin levels. The results suggest that although Tpm3.1 localises to dendritic spines in cultured hippocampal neurons, it does not have any apparent impact on dendritic spine morphology or function. This is contrary to the functional role of Tpm3.1 previously observed at the tip of growing neurites, where it increases the F-actin levels and impacts growth cone dynamics.     

Power and conflict resolution in sibling, parent–child, and spousal negotiations.

This study used a within-family observational design to examine conflict strategies (planning, opposition) and resolutions (standoff, win-loss, compromise) across family subsystems, with an emphasis on power differences between parents and children during relatively symmetrical within-generation (spousal, sibling) and relatively asymmetrical between-generation (parent–child) dyadic interactions. Up to six dyads in 67 families (children's ages ranging from 3 to 12 years) discussed an unresolved conflict. Results revealed that within-generation discussions ended more in standoff, whereas between-generation discussions ended with more win-loss resolutions. Multilevel analyses indicated that parents engaged in more planning and opposition than children; however, they opposed more and planned less with their spouses than their children. In general, more planning and less opposition were associated with achieving resolutions rather than failing to resolve differences. Some effects were qualified by within-family differences between mothers versus fathers and older versus younger siblings, as well as between-family differences in younger siblings' age. Implications for theories of power and family relationship dynamics are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of window opening and other occupant behavior on simulated energy performance in residence halls

A poor depiction of occupant behavior in building performance simulation frequently results in substantial divergences between real and simulated results. The problem may be of particular concern with simulation supporting the renovation of older multi-unit residential buildings, buildings whose occupants use windows for temperature control even during heating season. Here, we investigated the impact of window operation models (as well as other occupant behaviors) on simulated energy performance in university residence halls. Based on environmental monitoring, along with information collected from occupant surveys and wearable devices, we estimated air exchange rates and developed a probabilistic window-operation prediction model. The data were collected in 76 dormitory rooms sampled from a pre-renovated historic building and two similar buildings. We then evaluated the window-operation model’s predictive performance in 15 dormitory rooms in the post-renovated building with new occupants. The results of our predictive model were also compared with previously reported window-operation models. We implemented each window-operation model in a calibrated EnergyPlus building performance model, comparing the results of each simulation to metered hourly steam consumption. The impact of the different window operation models on simulated heating energy use was significant (annual error ranging from 0.2% to 10%). Our model demonstrated the highest capability of predicting window state (accuracy=85.8%) and steam use (NMBE=?0.2%); however, some previously published windowoperation models also produced satisfactory performance, implying that such models may be generalizable to some extent. The results suggest that data collected from somewhat ubiquitous indoor environmental quality sensors can glean insights into occupant behavior for building performance simulation. Furthermore, the energy impacts resulting from the variations in occupant behavior studied here were large enough to show that the choice of behavior model can have meaningful implications for real-world applications, such as estimating saving from heating and lighting system upgrades.     

Determining the validity of the AMA guide: A historical cohort analysis of the Assessment of Driving Related Skills and crash rate among older drivers

Background

Chronic health conditions associated with ageing can lead to changes in driving ability. The Canadian Driving Research Initiative for Vehicular Safety in the Elderly (Candrive II) is a 5-year prospective study funded by the Canadian Institutes of Health Research aiming to develop an in-office screening tool that will help clinicians identify potentially at-risk older drivers. Currently, no tools exist to directly predict the risk of motor vehicle collision (MVC) in this population. The American Medical Association (AMA), in collaboration with the National Highway Traffic Safety Association, has designed an opinion-based guide for assessing medical fitness to drive in older adults and recommends that physicians use the Assessment of Driving Related Skills (ADReS) as a test battery to measure vision, cognition and motor/somatosensory functions related to driving. The ADReS consists of the Snellen visual acuity test, visual fields by confrontation test, Trail Making Test part B, clock drawing test, Rapid Pace Walk, and manual tests of range of motion and motor strength. We used baseline data from the Candrive/Ozcandrive common cohort of older drivers to evaluate the validity of the ADReS subtests. We hypothesized that participants who crashed in the 2 years before the baseline assessment would have poorer scores on the ADReS subtests than participants who had not crashed.

Methods

In the Candrive/Ozcandrive study, 1230 participants aged 70 years or older were recruited from 7 Canadian cities, 1 Australian city and 1 New Zealand city, all of whom completed a comprehensive clinical assessment at study entry. The assessment included all tests selected as part of the ADReS. For this historical cohort study, data on all crashes (at-fault and non-at-fault) that occurred within 2 years preceding the baseline assessment were obtained from the respective licensing jurisdictions. Those who crashed were compared to those who had not crashed on their ADReS subtest scores using Pearson's chi-squared test and Student's t-test.

Results

Sixty-three of the 1230 participants (5.1%) were involved in an MVC within the 2 years preceding the baseline assessment. Contrary to our hypothesis, there were no statistically significant associations between abnormal performance on the tests constituting the ADReS and history of crash in the previous 2 years (p > 0.01).

Discussion

We found that a history of crash in the previous 2 years was not associated with abnormalities on the subtests comprising the ADReS. This suggests the need for prospective analyses of risk factors over time to establish sensitive, valid predictors of crash that can be incorporated in clinical practice guidelines.     

It is premature to test older drivers with the SIMARD-MD

Background

A new tool, the SIMARD-MD, has been proposed to help physicians identify cognitively impaired drivers who may be unfit to drive, but little empirical evidence is available to justify its use. We analyzed data from a cohort of older Canadian drivers who had undergone cognitive testing to: (1) correlate the SIMARD-MD with other tools that measure cognition (e.g., trail-making test), (2) identify how many drivers, using published cut-offs on the SIMARD-MD, would be recommended to lose their license, or be considered fit to drive, or be required to undergo further driving assessment, and (3) determine if the SIMARD-MD is biased by level of education as many cognitive tools are.

Methods

Cross-sectional data from 841 drivers aged 70 and over from seven Canadian sites who are enrolled in a 5-year cohort study were used for the analyses. Scores on the SIMARD-MD were correlated with scores on the other cognitive measures. The recommendations that would be made based on the SIMARD-MD scores were based on published cut-off values suggested by the authors of the tool. The impact of education status was examined using linear regression controlling for age.

Results

Correlations between the SIMARD-MD and other cognitive measures ranged from .15 to .86. Using published cut-off scores, 21 participants (2.5%) would have been recommended to relinquish their licenses, 428 (50.9%) would have been deemed fit to drive, and 392 (46.6%) would have been required to undergo further testing. We found a difference of 8.19 points (95% CI = 4.99, 11.40, p < .001) in favor of drivers with post-secondary education versus those without, representing over 11% of the mean score.

Discussion

The SIMARD-MD is unlikely to be valuable to clinicians because it lacks sufficient precision to provide clear recommendations about fitness-to-drive. Recommendations based solely on the SIMARD-MD may place many seniors at risk of losing their transportation mobility or incurring unnecessary stress and costs to prove they are safe to drive. Furthermore, the education bias may create an unwanted structural inequity. Hence, adoption of the SIMARD-MD as a tool to determine fitness-to-drive appears premature.     

Dietary bioaccumulation of perfluorophosphonates and perfluorophosphinates in juvenile rainbow trout: evidence of metabolism of perfluorophosphinates

The perfluorophosphonates (PFPAs) and perfluorophosphinates (PFPiAs) are high production volume chemicals that have been observed in Canadian surface waters and wastewater environments. To examine whether their occurrence would result in contamination of organisms in aquatic ecosystems, juvenile rainbow trout (Oncorhynchus mykiss) were separately exposed to a mixture of C6, C8, and C10 monoalkylated PFPAs and a mixture of C6/C6, C6/C8, and C8/C8 dialkylated PFPiAs in the diet for 31 days, followed by 32 days of depuration. Tissue distribution indicated preferential partitioning to blood and liver. Depuration half-lives ranged from 3 to 43 days and increased with the number of perfluorinated carbons present in the chemical. The assimilation efficiencies (α, 7-34%) and biomagnification factors (BMFs, 0.007-0.189) calculated here for PFPAs and PFPiAs were lower than those previously observed for the perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs) in the same test organism. Bioaccumulation was observed to decreased in the order of PFSAs > PFCAs > PFPAs of equal perfluorocarbon chain length and was dependent on the charge of the polar headgroup. Bioaccumulation of the PFPiAs was observed to be low due to their rapid elimination via metabolism to the corresponding PFPAs. Here, we report the first observation of an in vivo cleavage of the carbon-phosphorus bond in fish, as well as, the first in vivo biotransformation of a perfluoroalkyl acid (PFAA). As was previously observed for PFCAs and PFSAs, none of the BMFs determined here for the PFPAs and PFPiAs were greater than one, which suggests PFAAs do not biomagnify from dietary exposure in juvenile rainbow trout.     

Structure–property quantification of corrosion pitting under immersion and salt-spray environments on an extruded AZ61 magnesium alloy

Extruded AZ61 magnesium coupons were exposed to immersion and cyclical salt spray environments over 60 h in order to characterize their corrosion rates. The characteristics of general corrosion, pitting corrosion, and intergranular corrosion were quantified at various intervals. General corrosion was more prevalent on the immersion surface. In addition, more pits formed on the immersion surface due the continuous exposure to water and chloride ions. However, the pits on the salt spray surface showed larger surface areas, larger volumes, and covered more area on the micrographs as compared to the pits on the immersion surface, due to the dried pit debris that trapped chloride ions within the pits.     

Soy flour dispersibility and performance as wood adhesive

Soy flour adhesives using polyamidoamine-epichlorohydrin (PAE) resin as the curing agent are being used commercially to make bonded wood products. The original studies on the soy-PAE adhesives used purified soy protein isolate, but the much lower cost soy flour is now used commercially. We examined the performance of commercially available soy flours that have their proteins either mainly in their native (90 protein dispersibility index (PDI)) or denatured (70 and 20 PDI) states. We expected that the more native state soy proteins with their better dispersibility would provide better adhesion to wood surfaces and enhanced reaction with PAE resin. Small-scale wood bonding tests showed that neither of these effects was observed without and with a low level of PAE. In these tests, the solids content of the soy formulations had a large influence on adhesive viscosity but little influence on bond strength. Additionally, little difference was observed in any of the adhesive or viscosity properties between the soy flours having either a 0.152 or 0.075?mm (100 or 200 mesh) particle size.     

Career development in adolescence as a family project.

This study conceptualizes and investigates career-relevant parent–child conversations and other actions over time as a family project. Dyads composed of a parent and an adolescent from 20 families participated in a videotaped career-related conversation to determine a family career-development project that was subsequently monitored for a 6-month period and followed up with a 2nd videotaped conversation. On the basis of a systematic qualitative analysis, several dimensions were identified as facilitating the family career-development project, including joint goals, communication, goals-steps congruence, and individuation. These family career-development projects were organized as part of broader relationship, identity, parenting, and cultural projects that also played a decisive role in the success of the family career-development projects themselves. (PsycINFO Database Record (c) 2010 APA, all rights reserved)