Maternal long-chain polyunsaturated fatty acid status during early pregnancy:Association with child behavioral problems and the role of autonomic nervous system activity

Background & aims: The prenatal environment, including availability of critical nutrients, has a profound impact on offspring development. The present study examined the association between maternal long-chain polyunsaturated fatty acid (LC-PUFA) status during pregnancy and later child behavioral problems at the age of 5–6 years. In light of evidence of autonomic nervous system (ANS) dysregulation in some behavioral problems, study further tested if the above association is statistically mediated by cardiac ANS activity. Methods: Data was collected as part of the Amsterdam Born Children and their Development-study and complete data were available for 1717 mothers and their offspring. Maternal LC-PUFA status was assessed during early pregnancy (mean gestation = 12.7, SD = 2.5 weeks) and quantified as levels of docosahexenoic acid (DHA), arachidonic acid (AA), eicosapentaenoic acid (EPA), as well as the ratio of n-6:n-3 fatty acids. Child emotional problems and peer problems (internalizing problems), as well as conduct problems and inattention/hyperactivity (externalizing problems), were assessed using the Strengths and Difficulties Questionnaire as rated by the mother and teacher at 5–6 years. Child cardiac respiratory sinus arrhythmia (RSA), pre-ejection period (PEP), and heart rate (HR) were utilized as measures of ANS activity at 5–6 years. Results: The results confirmed an association between maternal LC-PUFA status and internalizing behavioral problems as rated by the mother, as shown for DHA (β = −0.11;p < 0.01), EPA (β = -0.22;p < 0.05), and n-6:n-3 LC-PUFA (β = 0.17;p < 0.01). Statistical mediation was only demonstrated for HR. No associations were observed between LC-PUFA status and externalizing behavioral problems. Conclusions: The present results are consistent with a role of maternal LC-PUFA status in internalizing behavioral problems as rated by the mother. These results were not observed when problem behavior was rated by the teacher. Analyses did not yield strong evidence supporting ANS activity as a possible mediator in this relationship

Porous iron pellets for AMS C-14 analysis of small samples down to ultra-microscale size (10-25 mu gC)

We developed the use of a porous iron pellet as a catalyst for AMS C-14 analysis of small samples down to ultra-microscale size (10-25 mu gC). It resulted in increased and more stable beam currents through our HVEE 4130 C-14 AMS system, which depend smoothly on the sample size. We find that both the expected decrease of oxalic acid standards and increase of backgrounds with decreasing sample size, due to increasing influence of contamination, are reproducible. Using a mass-dependent background correction for dead (1.0 +/- 0.4 mu gC) and modern (0.25 +/- 0.10 mu gC) contamination, we obtain reliable results for small samples down to 10 mu gC and possibly smaller. Due to our low graphitization yield for ultra-small samples (increases from 40% to 80% on average with sample size), we measured graphite standards as small as 3 mu gC. The standard deviation of the corrected activity is about 5% for a 10-mu gC HOxII standard. Here we report the iron pellet technique, which is new to the best of our knowledge. It is generally applicable for AMS C-14 laboratories that want to measure small samples down to ultra-microscale size. As an illustrative test-case, we analyze C-14 data for IAEA-05, C7 and C8 samples with masses ranging from 15 to 300 mu gC. (C) 2009 Elsevier B.V. All rights reserved

αE-catenin-dependent mechanotransduction is essential for proper convergent extension in zebrafish

Cadherin complexes mediate cell-cell adhesion and are crucial for embryonic development. Besides their structural function, cadherin complexes also transduce tension across the junction-actomyosin axis into proportional biochemical responses. Central to this mechanotransduction is the stretching of the cadherin-F-actin-linker α-catenin, which opens its central domain for binding to effectors such as vinculin. Mechanical unfolding of α -catenin leads to force-dependent reinforcement of cadherin-based junctions as studied in cell culture. The importance of cadherin mechanotransduction for embryonic development has not been studied yet. Here we used TALEN-mediated gene disruption to perturb endogenous αE-catenin in zebrafish development. Zygotic α-catenin mutants fail to maintain their epithelial barrier, resulting in tissue rupturing. We then specifically disrupted mechanotransduction, while maintaining cadherin adhesion, by expressing an αE-catenin construct in which the mechanosensitive domain was perturbed. Expression of either wild-type or mechano-defective α-catenin fully rescues barrier function in α-catenin mutants. Expression of mechano-defective α-catenin, however, also induces convergence and extension defects. Specifically, the polarization of cadherin-dependent, lamellipodia-driven cell migration of the lateral mesoderm was lost. These results indicate that cadherin mechanotransduction is crucial for proper zebrafish morphogenesis and uncover one of the essential processes affected by its perturbation

Stability criteria for a pyramidal shaped asperity ploughing through a plastically deforming substrate

In two body abrasion processes hard asperities plough through a soft surface. If the asperities can resist the forces that act on it, scratches will develop in the soft material. If the asperities cannot withstand these forces, they will break off and not cause direct abrasion damage. The same is the case for galling, where lumps develop on one of the surfaces because of material transfer. These lumps will abrade the counter surface, if the lumps are strong enough to withstand the forces that act on it. In order to describe these phenomena, simple criteria are desired to describe the mechanical stability of asperities and lumps.\ud \ud In this work, an analytical model is presented for the mechanical stability of asperities. In the analysis, a pyramidal asperity shape will be assumed. Given the pyramidal asperity shape, several cases will be studied: the load is carried by a pyramid with a triangular base, a pyramid with a triangular base and an extended backside and the case where a crack has developed. Based on these models stability criteria of ploughing pyramidal asperities will be developed. Important results of the model will be discussed in the context of abrasion and adhesive wear processes

Modelling of a thin soft layer on a self-lubricating ceramic composite

Friction and wear of a self-lubricating ceramic composite under unlubricated sliding contact conditions is dependent on the formation and regeneration of a thin soft surface layer. Experimental observations have shown that a thin soft layer (third body) may be formed depending on the tribological tests conditions. This thin soft layer is a pre-requirement for the occurrence of low friction in the mild wear regime. This paper proposes a physically based model for the process of the formation and removal of the soft layer. The model is developed on the basis of mechanical stresses in the soft second phase and the elastic–plastic contact between a rough surface and a flat surface. Based on the model, the thickness of the soft surface layer on a ceramic substrate is predicted. The results show that the thickness of the soft layer is mainly determined by the mechanical properties of soft phase as well as the applied load

Contribution of viscous shear to friction in cold rolling of low-carbon steel

This work shows that for temperatures, pressures and shear rates that are common in cold rolling of low-carbon steel, viscous shear stress significantly contributes to the total friction force. Experiments were carried out to validate the theory on lubricant film formation and elasto-hydrodynamic lubrication, both with laboratory scale tribometers and a semi-industrial pilot mill facility. These experiments showed that at high shear rates, that are common in cold rolling, the lubricant does not behave as a Newtonian fluid anymore; moreover the viscosity at high pressure cannot accurately be described by a simple exponential law. With the correct relations implemented in a rolling model, both rolling force and forward slip are predicted with good accuracy for hydrodynamically lubricated cold rolling experiments.</p