Intrauterine growth restriction is associated with structural alterations in human umbilical cord and decreased nitric oxide-induced relaxation of umbilical vein.

INTRODUCTION: Intrauterine growth restriction (IUGR) affects ∼8% of all pregnancies and is associated with major perinatal mortality and morbidity, and with an increased risk to develop cardiovascular diseases in adulthood. Despite identification of several risk factors, the mechanisms implicated in the development of IUGR remain poorly understood. In case of placental insufficiency, reduced delivery of oxygen and/or nutrients to the fetus could be associated with alterations in the umbilical circulation, contributing further to the impairment of maternal-fetal exchanges. We compared the structural and functional properties of umbilical cords from growth-restricted and appropriate for gestational age (AGA) term newborns, with particular attention to the umbilical vein (UV). METHODS: Human umbilical cords were collected at delivery. Morphological changes were investigated by histomorphometry, and UV's reactivity by pharmacological studies. RESULTS: Growth-restricted newborns displayed significantly lower growth parameters, placental weight and umbilical cord diameter than AGA controls. Total cross-section and smooth muscle areas were significantly smaller in UV of growth-restricted neonates than in controls. Maximal vasoconstriction achieved in isolated UV was lower in growth-restricted boys than in controls, whereas nitric oxide-induced relaxation was significantly reduced in UV of growth-restricted girls compared to controls. CONCLUSION: IUGR is associated with structural alterations of the UV in both genders, and with a decreased nitric oxide-induced relaxation in UV of newborn girls, whereas boys display impaired vasoconstriction. Further investigations will allow to better understand the regulation of umbilical circulation in growth-restricted neonates, which could contribute to devise potential novel therapeutic strategies to prevent or limit the development of IUGR

Shear assessment of a reinforced concrete bridge deck slab according to level-of-approximation approach

International Federation for Structural Concrete Reinforced concrete (RC) slabs without shear reinforcement are commonly used for existing bridge structures. For such structures, shear and punching can be the governing failure modes at the ultimate limit state if subjected to large concentrated loads. The aim of this study is to examine a structured approach for the analyses of the RC bridge deck slabs, which make up a considerable proportion of the currently used bridge decks. The method used for analyses is the levels-of-approximation introduced in fib Model Code for Concrete Structures 2010. The different levels include simplified calculation method, linear finite element analysis as well as non-linear finite element analysis. The differences between analysis methods at different levels of analyses were discussed regarding one-way shear and punching shear behavior of the slab