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Assessing Prenatal and Neonatal Gonadal Steroid Exposure for Studies of Human Development: Methodological and Theoretical Challenges

Authors: --- ---
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889196074 Year: Pages: 80 DOI: 10.3389/978-2-88919-607-4 Language: English
Publisher: Frontiers Media SA
Subject: Medicine (General) --- Internal medicine
Added to DOAB on : 2016-08-16 10:34:25
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There is extensive evidence from animal models that gonadal steroids, produced in fetal and neonatal life, act on the developing organism to produce sex differences far beyond the reproductive system. That early gonadal steroid exposure also plays an important role in human development is supported by studies of individuals with disorders of sex determination and differentiation. It is much less clear whether normal variation in gonadal steroid exposure predicts sexually dimorphic health outcomes or within-sex variation. This is largely due to challenges related to the assessment of gonadal steroid exposure in the developing fetus and neonate. Regarding the prenatal period, serial measurements of serum hormone levels in the fetus, for use in studies of later development, are not possible for ethical reasons. Researchers have measured hormones in maternal blood, umbilical cord blood, and amniotic fluid; used putative anthropometric indices such as the relative lengths of the 2nd and 4th digits (2D:4D); evaluated common variants in genes related to hormone production, transport, and metabolism; and examined development in opposite sex twins and the offspring of mothers with hyperandrogeny. Each of these approaches has particular strengths and notable weaknesses. Regarding the neonatal period, serial measurements in serum are often impractical for studies of typical development. Salivary hormone assays, frequently used in studies of older children and adults, have not been extensively investigated in neonates. The most appropriate timing for testing is also open to debate. Early work suggested that testosterone levels in males begin to rise after the first postnatal week, peak around the 3rd to 4th months of life, and then drop back to very low levels by 1 year. However a more recent study of 138 infants did not demonstrate this pattern. Testosterone was highest on the day of birth and gradually dropped over the first 6 months. Even less is known about patterns of early estrogen exposure, though highly sensitive bioassays indicated that sex differences are present in early childhood. In addition, the design and interpretation of studies may be impacted by widespread acceptance of conceptual frameworks that are not well-supported empirically. For example, many researchers presume that the free hormone hypothesis, which states that unbound hormone is more readily diffusible into tissues and thus a better measure of actual exposure, is true. However this hypothesis has been challenged on multiple grounds. A second example: it is generally accepted that masculinization of the human brain is primarily mediated by the androgen receptor (in contrast to rodents where the estrogen receptor plays a major role), in part because chromosomal males with complete androgen insensitivity generally espouse a female gender identity. However this is not always the case, and other sexually dimorphic outcomes have not been carefully assessed in CAIS. The aim of this research topic is to gather together experimental and review papers which address the diverse challenges in assessing prenatal and neonatal gonadal steroid exposure for studies of human development with the expectation that this will allow more critical appraisal of existing studies, identify critical research gaps, and improve the design of future studies.

Twin Studies: Research in Genes, Teeth and Faces

Authors: --- --- --- --- et al.
ISBN: 9781925261158 Year: Pages: 199 DOI: 10.20851/twin-studies Language: English
Publisher: University of Adelaide Press
Subject: Biology --- Medicine (General)
Added to DOAB on : 2015-10-09 11:01:11
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This volume is about an ongoing long-term research initiative led by researchers from the School of Dentistry at the University of Adelaide. The aim of this book is to provide an overview of the studies of the teeth and faces of Australian twins and their families that have extended over more than thirty years.

New Directions in Dental Anthropology: Paradigms, methodologies and outcomes

Authors: --- ---
ISBN: 9780987171870 Year: Pages: 147 DOI: 10.1017/9780987171870 Language: English
Publisher: University of Adelaide Press
Subject: Medicine (General) --- Anthropology
Added to DOAB on : 2012-05-14 07:35:12
License: University of Adelaide Press

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This book contains papers arising from a symposium held during a combined meeting of The International Union of Anthropological and Ethnological Sciences (IUAES), The Australian Anthropological Society (AAS) and The Association of Social Anthropologists of Aotearoa New Zealand at the University of Western Australia from July 5-8th, 2011. It follows on from a recently published Special Issue Supplement of Archives of Oral Biology, Volume 54, December 2009 that contains papers from an International Workshop on Oral Growth and Development held in Liverpool in 2007 and edited by Professor Alan Brook. Together, these two publications provide a comprehensive overview of state-of-the-art approaches to study dental development and variation, and open up opportunities for future collaborative research initiatives, a key aim of the International Collaborating Network in Oro-facial Genetics and Development that was founded in Liverpool in 2007.

The aim of the symposium held at The University of Western Australia in 2011 was to emphasise some of the powerful new strategies offered by the science of dental anthropology to elucidate the historical lineage of human groups and also to reconstruct environmental factors that have acted on the teeth by analysing dental morphological features. In recent years, migration, as well as increases and decreases in the size of different human populations, have been evident as a result of globalisation. Dental features are also changing associated with changes in nutritional status, different economic or social circumstances, and intermarriage between peoples. Dental anthropological studies have explored these changes with the use of advanced techniques and refined methodologies. New paradigms are also evolving in the field of dental anthropology.

When considered together with the recent special issue of Archives of Oral Biology that highlighted the importance of research approaches focused at both the molecular and phenotypic levels, it is clear that we have now reached a very exciting stage in our ability to address key questions and issues about the normal and abnormal development of the dentition, as well as the diseases that commonly affect our teeth and gums.

Genetic Determinants of Human Longevity

Authors: --- ---
ISBN: 9783039216789 / 9783039216796 Year: Pages: 118 DOI: 10.3390/books978-3-03921-679-6 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Biology --- Genetics
Added to DOAB on : 2019-12-09 11:49:16
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In the last two decades, due to the continuous increase of lifespans in Westernsocieties, and the consequent growing of the elderly population, have witnessedan increase in the number of studies on biological and molecular factors able topromote healthy aging and reach longevity. The study of the genetic componentof human longevity demonstrated that it accounts for 25% of intra populationphenotype variance. The efforts made to characterize the genetic determinantssuggested that the maintenance of cellular integrity, inflammation, oxidativestress response, DNA repair, as well as the use of nutrients, represent the mostimportant pathways correlated with a longer lifespan. However, although aplethora of variants were indicated to be associated with human longevity, onlyvery few were successfully replicated in different populations, probably becauseof population specificity, missing heritability as well as a complex interactionamong genetic factors with lifestyle and cultural factors, which modulate theindividual chance of living longer. Thus, many challenges remain to be addressedin the search for the genetic components of human longevity. This Special Issue isaimed to unify the progress in the analysis of the genetic determinants of humanlongevity, to take stock of the situation and point to future directions of the field.We invite submissions for reviews, research articles, short-communicationsdealing with genetic association studies in human longevity, including all types ofgenetic variation, as well as the characterization of longevity-related genes.

Microstructure and Mechanical Properties of Structural Metals and Alloys

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ISBN: 9783038975052 / 9783038975069 Year: Pages: 272 DOI: 10.3390/books978-3-03897-506-9 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Technology (General) --- Chemical Engineering
Added to DOAB on : 2019-06-26 08:44:06
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The papers collected in this special issue clearly reflect the modern research trends in materials science. These fields of specific attention are high-Mn TWIP steels, high-Cr heat resistant steels, aluminum alloys, ultrafine grained materials including those developed by severe plastic deformation, and high-entropy alloys. The major portion of the collected papers is focused on the mechanisms of microstructure evolution and the mechanical properties of metallic materials subjected to various thermo-mechanical, deformation or heat treatments. Another large portion of the studies is aimed on the elaboration of alloying design of advanced steels and alloys. The changes in phase content, transformation and particle precipitation and their effect on the properties are also broadly presented in this collection, including the microstructure/property changes caused by irradiation.

Keywords

Mg–Sm–Zn–Zr --- dynamic precipitation --- microstructure --- mechanical property --- bimodal ferrite steel --- ultrafine-grained microstructure --- mechanical properties --- corrosion resistance --- abnormal grain growth --- grain boundary engineering --- electron backscattered diffraction --- growth rate --- Al metal matrix composites --- microstructure --- mechanical properties --- strengthening mechanism --- hot compression --- dynamic recovery --- dynamic recrystallization --- texture --- aluminum alloys --- Al-Fe-Si-Zr system --- microstructure --- hardness --- electrical conductivity --- metal–matrix composite --- high-pressure torsion --- microstructure evolution --- microhardness --- shape memory alloy --- columnar grain --- Cu-Al-Mn --- elastocaloric effect --- strain rate --- measuring temperature --- creep --- lead-free solder --- Sb solder --- Sn-8.0Sb-3.0Ag --- solder microstructure --- martensitic steels --- creep --- precipitation --- electron microscopy --- high-Mn TWIP steel --- cold rolling --- annealing --- recovery --- recrystallization --- strengthening --- austenitic 304 stainless steels --- sub-merged arc welding --- post-weld heat treatment --- aluminum alloys --- aging --- precipitation --- electrical resistivity --- mechanical properties --- ferritic steel --- irradiation --- nanoindentation --- hardness --- transmission electron microscopy (TEM) --- microstructure --- high-entropy alloys --- high-pressure torsion --- microstructure evolution --- twinning --- mechanical properties --- welded rotor --- weld metal --- impact toughness --- PWHT --- microstructure evolution --- Cu-Cr-Zr --- precipitation --- orientation relationship --- recrystallization --- annealing twins --- structural steel plate --- nonmetallic inclusions --- rare earth control --- M23C6 --- ion irradiation --- M6C --- amorphization --- RAFM steels --- hot stamping --- press hardening --- martensitic expansion --- force peak --- cycle time --- high-Mn steel --- deformation twinning --- dynamic recrystallization --- grain refinement --- work hardening --- in situ tensile testing --- super duplex stainless steel --- SDSS --- low-temperature --- ?-phase --- SEM --- EBSD --- microstructure analysis --- n/a

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