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St. John's, Canada

Memorial University of Newfoundland, is a comprehensive university located primarily in St. John's, Newfoundland and Labrador, Canada. With historical strengths in education, engineering, business, geology, and medicine, it is one of the top comprehensive universities in Canada. With over 17,500 students, it is also the largest university in Atlantic Canada. MUN's four main campuses are served by more than 900 faculty and 2,300 staff members. Wikipedia.

Mineral and bone metabolism are regulated differently in utero compared with the adult. The fetal kidneys, intestines, and skeleton are not dominant sources of mineral supply for the fetus. Instead, the placenta meets the fetal need for mineral by actively transporting calcium, phosphorus, and magnesium from the maternal circulation. These minerals are maintained in the fetal circulation at higher concentrations than in the mother and normal adult, and such high levels appear necessary for the developing skeleton to accrete a normal amount of mineral by term. Parathyroid hormone (PTH) and calcitriol circulate at low concentrations in the fetal circulation. Fetal bone development and the regulation of serum minerals are critically dependent on PTH and PTH-related protein, but not vitamin D/calcitriol, fibroblast growth factor-23, calcitonin, or the sex steroids. After birth, the serum calcium falls and phosphorus rises before gradually reaching adult values over the subsequent 24-48 h. The intestines are the main source of mineral for the neonate, while the kidneys reabsorb mineral, and bone turnover contributes mineral to the circulation. This switch in the regulation of mineral homeostasis is triggered by loss of the placenta and a postnatal fall in serum calcium, and is followed in sequence by a rise in PTH and then an increase in calcitriol. Intestinal calcium absorption is initially a passive process facilitated by lactose, but later becomes active and calcitriol-dependent. However, calcitriol's role can be bypassed by increasing the calcium content of the diet, or by parenteral administration of calcium. Copyright © 2014 the American Physiological Society. Source

Kovacs C.S.,Memorial University of Newfoundland
Annual Review of Nutrition

Maternal adaptations during pregnancy and lactation appear to provide calcium to fetus and neonate without relying on vitamin D or calcitriol. Consequently, the blood calcium, calciotropic hormones, and skeleton appear normal at birth in the offspring of mothers who are severely vitamin D deficient or who lack calcitriol or its receptor. It remains unclear whether skeletal or extraskeletal problems will develop postnatally from exposure to vitamin D deficiency in utero. During the neonatal period, calcitriol-stimulated intestinal calcium absorption becomes the dominant mechanism of calcium delivery. The vitamin Ddeficient neonate is at risk to develop hypocalcemia, rickets, and possibly extraskeletal disorders (e.g., type 1 diabetes). Breastfed babies are at higher risk of vitamin D deficiency because normally little vitamin D or 25-hydroxyvitamin D passes into breast milk. Dosing recommendations during pregnancy and lactation should ensure that the baby is born vitamin D sufficient and maintained that way during infancy and beyond. Copyright ©2012 by Annual Reviews. All rights reserved. Source

Booth I.,Memorial University of Newfoundland
Physical Review D - Particles, Fields, Gravitation and Cosmology

We study the near-horizon spacetime for isolated and dynamical trapping horizons (equivalently marginally outer trapped tubes). The metric is expanded relative to an ingoing Gaussian null coordinate and the terms of that expansion are explicitly calculated to second order. For the spacelike case, knowledge of the intrinsic and extrinsic geometry of the (dynamical) horizon is sufficient to determine the near-horizon spacetime, while for the null case (an isolated horizon) more information is needed. In both cases spacetime is allowed to be of arbitrary dimension and the formalism accommodates both general relativity as well as more general field equations. The formalism is demonstrated for two applications. First, spacetime is considered near an isolated horizon and the construction is both checked against the Kerr-Newman solution and compared to the well-known near-horizon limit for stationary extremal black hole spacetimes. Second, spacetime is examined in the vicinity of a slowly evolving horizon and it is demonstrated that there is always an event horizon candidate in this region. The geometry and other properties of this null surface match those of the slowly evolving horizon to leading order and in this approximation the candidate evolves in a locally determined way. This generalizes known results for Vaidya as well as certain spacetimes known from studies of the fluid-gravity correspondence. © 2013 American Physical Society. Source

Kovacs C.S.,Memorial University of Newfoundland
Endocrinology and Metabolism Clinics of North America

Pregnancy and lactation cause a substantial increase in demand for calcium that is met by different maternal adaptations within each period. Intestinal calcium absorption more than doubles during pregnancy, whereas the maternal skeleton resorbs to provide most of the calcium content of breast milk during lactation. These maternal adaptations also affect the presentation, diagnosis, and management of disorders of calcium and bone metabolism. Although some women may experience fragility fractures as a consequence of pregnancy or lactation, for most women, parity and lactation do not affect the long-term risks of low bone density, osteoporosis, or fracture. © 2011 Elsevier Inc. Source

This is a review of two bodies of research conducted by myself and my colleagues that is relevant to child witness issues, namely childhood amnesia and children's eyewitness memory for stressful events. Although considerable research over the years has investigated the phenomenon of childhood amnesia in adults, only recently has it begun to be investigated in children. For them, the age of earliest memory is a moving target over their early years. However, there is nonetheless both variation between children in how early their first memories are as well as variation between memories in terms of likelihood of being retained, and some factors influencing both are explored. In terms of eyewitness memory for stressful events, 2-13-year-old children who had been injured seriously enough to require emergency room medical treatment were interviewed. Long-term memory for these stressful events was traced, and factors influencing that retention were investigated. The findings from both areas of research have implications for developmental forensic psychology. © 2012 Elsevier Inc. Source

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