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Littérature scientifique sur le sujet « White matter maturation »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 1 février 2022

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Articles de revues sur le sujet "White matter maturation"

Millichap, J. Gordon. « White Matter Maturation in Holoprosencephaly ». Pediatric Neurology Briefs 17, n^o 1 (1 janvier 2003) : 2. http://dx.doi.org/10.15844/pedneurbriefs-17-1-2.

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Yu, Qinlin, Yun Peng, Huiying Kang, Qinmu Peng, Minhui Ouyang, Michelle Slinger, Di Hu, Haochang Shou, Fang Fang et Hao Huang. « Differential White Matter Maturation from Birth to 8 Years of Age ». Cerebral Cortex 30, n^o 4 (9 décembre 2019) : 2674–90. http://dx.doi.org/10.1093/cercor/bhz268.

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Abstract Comprehensive delineation of white matter (WM) microstructural maturation from birth to childhood is critical for understanding spatiotemporally differential circuit formation. Without a relatively large sample of datasets and coverage of critical developmental periods of both infancy and early childhood, differential maturational charts across WM tracts cannot be delineated. With diffusion tensor imaging (DTI) of 118 typically developing (TD) children aged 0–8 years and 31 children with autistic spectrum disorder (ASD) aged 2–7 years, the microstructure of every major WM tract and tract group was measured with DTI metrics to delineate differential WM maturation. The exponential model of microstructural maturation of all WM was identified. The WM developmental curves were separated into fast, intermediate, and slow phases in 0–8 years with distinctive time period of each phase across the tracts. Shorter periods of the fast and intermediate phases in certain tracts, such as the commissural tracts, indicated faster earlier development. With TD WM maturational curves as the reference, higher residual variance of WM microstructure was found in children with ASD. The presented comprehensive and differential charts of TD WM microstructural maturation of all major tracts and tract groups in 0–8 years provide reference standards for biomarker detection of neuropsychiatric disorders.

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Bugiani, Marianna, Ilja Boor, Barbara van Kollenburg, Nienke Postma, Emiel Polder, Carola van Berkel, Ronald E. van Kesteren et al. « Defective Glial Maturation in Vanishing White Matter Disease ». Journal of Neuropathology & ; Experimental Neurology 70, n^o 1 (janvier 2011) : 69–82. http://dx.doi.org/10.1097/nen.0b013e318203ae74.

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Bells, Sonya, Jérémie Lefebvre, Giulia Longoni, Sridar Narayanan, Douglas L. Arnold, Eleun Ann Yeh et Donald J. Mabbott. « White matter plasticity and maturation in human cognition ». Glia 67, n^o 11 (24 juin 2019) : 2020–37. http://dx.doi.org/10.1002/glia.23661.

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Bava, Sunita, Rachel Thayer, Joanna Jacobus, Megan Ward, Terry L. Jernigan et Susan F. Tapert. « Longitudinal characterization of white matter maturation during adolescence ». Brain Research 1327 (avril 2010) : 38–46. http://dx.doi.org/10.1016/j.brainres.2010.02.066.

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Kulikova, S., L. Hertz-Pannier, G. Dehaene-Lambertz, A. Buzmakov, C. Poupon et J. Dubois. « Multi-parametric evaluation of the white matter maturation ». Brain Structure and Function 220, n^o 6 (3 septembre 2014) : 3657–72. http://dx.doi.org/10.1007/s00429-014-0881-y.

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Herting, Megan M., Robert Kim, Kristina A. Uban, Eric Kan, Andrea Binley et Elizabeth R. Sowell. « Longitudinal changes in pubertal maturation and white matter microstructure ». Psychoneuroendocrinology 81 (juillet 2017) : 70–79. http://dx.doi.org/10.1016/j.psyneuen.2017.03.017.

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Barkovich, A. J., E. M. Simon, O. A. Glenn, N. J. Clegg, S. L. Kinsman, M. Delgado et J. S. Hahn. « MRI shows abnormal white matter maturation in classical holoprosencephaly ». Neurology 59, n^o 12 (24 décembre 2002) : 1968–71. http://dx.doi.org/10.1212/01.wnl.0000038354.10891.0e.

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Kansagra, Akash P., Marc C. Mabray, Donna M. Ferriero, A. James Barkovich, Duan Xu et Christopher P. Hess. « Microstructural maturation of white matter tracts in encephalopathic neonates ». Clinical Imaging 40, n^o 5 (septembre 2016) : 1009–13. http://dx.doi.org/10.1016/j.clinimag.2016.05.009.

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Scantlebury, Nadia, Todd Cunningham, Colleen Dockstader, Suzanne Laughlin, William Gaetz, Conrad Rockel, Jolynn Dickson et Donald Mabbott. « Relations between White Matter Maturation and Reaction Time in Childhood ». Journal of the International Neuropsychological Society 20, n^o 1 (29 octobre 2013) : 99–112. http://dx.doi.org/10.1017/s1355617713001148.

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AbstractWhite matter matures with age and is important for the efficient transmission of neuronal signals. Consequently, white matter growth may underlie the development of cognitive processes important for learning, including the speed of information processing. To dissect the relationship between white matter structure and information processing speed, we administered a reaction time task (finger abduction in response to visual cue) to 27 typically developing, right-handed children aged 4 to 13. Magnetoencephalography and Diffusion Tensor Imaging were used to delineate white matter connections implicated in visual-motor information processing. Fractional anisotropy (FA) and radial diffusivity (RD) of the optic radiation in the left hemisphere, and FA and mean diffusivity (MD) of the optic radiation in the right hemisphere changed significantly with age. MD and RD decreased with age in the right inferior fronto-occipital fasciculus, and bilaterally in the cortico-spinal tracts. No age-related changes were evident in the inferior longitudinal fasciculus. FA of the cortico-spinal tract in the left hemisphere and MD of the inferior fronto-occipital fasciculus of the right hemisphere contributed uniquely beyond the effect of age in accounting for reaction time performance of the right hand. Our findings support the role of white matter maturation in the development of information processing speed. (JINS, 2013, 19, 1–14)

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Thèses sur le sujet "White matter maturation"

Grosse, Wiesmann Charlotte. « The Emergence of Theory of Mind : Cognitive and Neural Basis of False Belief Understanding in Preschool Age ». 2017. https://ul.qucosa.de/id/qucosa%3A21070.

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Human social interaction crucially depends on the ability to attribute thoughts and beliefs to other individuals. This ability is referred to as Theory of Mind (ToM), and understanding that other people can have false beliefs about the world is considered to be a critical test of ToM. In childhood, a developmental breakthrough is achieved around the age of 4 years, when children start explicitly reasoning about others’ false beliefs. The cognitive and neural developments that lead to this milestone of human cognition, however, are currently unknown. Moreover, recently, novel im- plicit paradigms have shown that, already before the age of 2 years, infants display correct expectations of the actions of an agent with a false belief. The processes that underlie these expectations and their relation to the later-developing explicit false belief reasoning, however, are unclear. The current thesis addresses these open issues in three studies. The first study investigates the developmental trajectory and robustness of an implicit false belief task longitudinally from the age of 2 to 4 years. We find that children only perform above chance by the age of 4 years, but not at 2 and 3 years. This indicates that early success on implicit false belief tasks is fragile. The second study examines the correlation of implicit and explicit false belief tasks with each other and with co-developing cognitive abilities. This shows a dissociation of implicit and explicit false belief tasks in that performance on the two task types does not correlate, and that explicit false belief tasks correlate with syntactic and executive functions, whereas implicit false be- lief tasks do not. Finally, the third study shows that the maturation of white matter in brain regions that support false belief reasoning in adultsand of their dorsal connectivity to the inferior frontal gyrus, suggested to support hierarchical processing, is associated with the emergence of explicit false belief reasoning in 3- and 4-year-old children. These associations are independent of implicit false belief-related action anticipation and of developments in other cognitive domains. Taken together, our results speak for a dissociation of the processes underlying implicit and explicit false belief tasks. We suggest that the developmental breakthrough in explicit false belief reasoning around the age of 4 years might result from improved belief processing, emerging hierarchical processing abilities, and the maturation of the connection between the relevant brain regions. Furthermore, I speculate on processes that might underlie early success on implicit false belief tasks in infancy.:Acknowledgements iii Summary xi Deutsche Zusammenfassung xvii 1 General Introduction 1.1 Theory of Mind . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1 Precursors of ToM in Infancy . . . . . . . . . . . . . 3 1.1.2 False Belief Understanding . . . . . . . . . . . . . . . 4 1.1.3 Relation between Implicit and Explicit False Belief Tasks . . . . . . . 8 1.1.4 Theoretical Accounts of the Emergence of ToM . . . 14 1.2 Relation to Other Cognitive Domains . . . . . . . . . . . . . 20 1.2.1 Executive Function . . . . . . . . . . . . . . . . . . . 25 1.2.2 Language . . . . . . . . . . . . . . . . . . . . . . . . 26 1.2.3 Correlations with Implicit False Belief Tasks . . . . . 29 1.3 Neural Basis of ToM . . . . . . . . . . . . . . . . . . . . . . 31 1.3.1 Neural Basis of ToM in Adults . . . . . . . . . . . . . 31 1.3.2 Neural Basis of ToM in Development . . . . . . . . . 35 1.3.3 Structural Brain Development in Early Childhood . . 36 1.4 Research Questions and Hypotheses . . . . . . . . . . . . . . 38 2 Study 1: Longitudinal evidence for 4-year-olds’ but not 2- and 3-year-olds’ false belief-related action anticipation . . . . . . . . . . . .45 3 Study 2: Implicit and explicit false belief development in preschool children . . . . . . . . . . . .73 4 Study 3: White matter maturation is associated with the emergence of Theory of Mind in early childhood . . . . . . . . . . . .91 5 General Discussion 5.1 Is there a continuity from early-developing to later explicit false belief abilities? . . . . . . . . . . . . . . . . . . . . . . . 106 5.2 What is the relation of implicit and explicit false belief tasks to other cognitive domains? . . . . . . . . . . . . . . . . . . 109 5.3 What is the neural basis of the emergence of ToM? And what does this tell us about the underlying cognitive processes? . . . . 114 5.4 What processes underlie implicit false belief tasks?. . . . . 118 5.5 Future Research and Limitations . . . . . . . . . . . . . . . 120 5.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 References . . . . . . . 128 A Supplements Study 1 . . . . . . . 161 B Supplements Study 2 . . . . . . . 163 C Supplements Study 3 . . . . . . . .181 Abbreviations . . . . . . . . 187 List of Figures . . . . . . . . 191 List of Tables . . . . . . . . 193

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Chapitres de livres sur le sujet "White matter maturation"

Mengotti, Paola, et Paolo Brambilla. « Developmental Trajectory of White Matter and Connectivity Maturation in Autism ». Dans Comprehensive Guide to Autism, 911–27. New York, NY : Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-4788-7_47.

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« White Matter Maturation and Cognitive Development during Childhood ». Dans Handbook of Developmental Cognitive Neuroscience. The MIT Press, 2008. http://dx.doi.org/10.7551/mitpress/7437.003.0018.

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Friederici, Angela D., et Noam Chomsky. « Ontogeny of the Neural Language Network ». Dans Language in Our Brain. The MIT Press, 2017. http://dx.doi.org/10.7551/mitpress/9780262036924.003.0007.

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This chapter reviews the neural underpinning of normal language acquisition and asks not only at which age certain milestones in language acquisition are achieved, but moreover to what extent is this achievement dependent on the maturation of particular brain structures. In our recent model, the neural basis of the developing language system is described to reflect two major phases. The available data provide consistent evidence that very early on an infant is able to extract language-relevant information from the acoustic input. This first phase covers the first three years of life when language processing is largely input-driven and supported by the temporal cortex and the ventral part of the network. A second phase extends beyond age 3, when top-down processes come into play, and the left inferior frontal cortex and the dorsal part of the language network are recruited to a larger extent. Development towards full language performance beyond age 3 is dependent on maturational changes in the gray and white matter. An increased language ability is correlated with an increase in structural and functional connectivity between language-related brain regions in the left hemisphere, the inferior frontal gyrus and the posterior superior temporal gyrus/superior temporal sulcus.

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Harris, James C. « A Life Span Developmental Approach ». Dans Intellectual Disability. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195178852.003.0011.

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Intellectual disability is a neurodevelopmental disorder that continues throughout the life span of the affected person. It is essential to understand how persons with intellectual disability progress throughout their life span from infancy to old age. The maturation of the brain, their environmental experiences, and the mastery of developmental challenges and tasks must all be considered. A focus on brain development is in keeping with neuroscience research indicating that progressive brain maturation is accompanied by successive synaptic reorganization as one moves from one developmental stage to the next. Anatomical Magnetic Resonance Imaging Studies are playing a major role in understanding the developmental trajectories of normal brain development (Durston et al., 2001; Giedd et al., 1999). Understanding the developmental trajectories of normal brain development is crucial to the interpretation of brain development in neurodevelopmental disabilities. During normal development, white matter volume increases with age, and although gray matter volumes increase during childhood, they decrease before adulthood. These changes in the brain are accompanied by changes in cognitive processing; for example, executive functioning shows a progressive emergence from the preschool years (Espy et al., 1999) into the adolescent years. Working memory and inhibitory processes may be measured during the preschool years. By adolescence, abstract reasoning, anticipatory planning, and mental judgment have emerged and may be measured. Cognitive abilities in adolescence are qualitatively different from those of young children as a result of the reorganization of the prefrontal cortex during maturation. How genetic background and environment interact in producing these changes is the object of ongoing study, yet investigators are beginning to understand how physiological processes of synaptic development, circuits, and neuronal network formation relate to processes of cognitive development (Fossella et al., 2003). The development of persons with intellectual disability is now being evaluated systematically, and developmental trajectories are being established for known neurogenetic syndromes. These studies are making up for a surprising lack of application of a developmental perspective to persons with intellectual disability. Developmental theorists have, for the most part, monitored and measured development in normally intelligent persons in establishing developmental landmarks.

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Friederici, Angela D., et Noam Chomsky. « The Brain’s Critical Period for Language Acquisition ». Dans Language in Our Brain. The MIT Press, 2017. http://dx.doi.org/10.7551/mitpress/9780262036924.003.0006.

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Whether a critical period for language learning exists (or not) is at the heart of ongoing debates over why second language learning appears to be easy early in life but much more difficult as we age. Neurocognitive studies on second language learning suggest that a unitary neural system is involved when processing more than one language, and the earlier a second language is learned, the more similar the neural language networks for the two languages will be. There appears to be a close relation between the developmental trajectory of white matter maturation and behavioral language skills. By looking at individuals coming from very different language backgrounds, such as native signers and hearing individuals, we find data that point towards a universal neural language system that is largely independent of input modality, but can be modulated slightly by the lifelong use of a given language.

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Sondheimer, Adrian, Niranjan Karnik et Peter Jensen. « Child and adolescent psychiatry ». Dans Psychiatric Ethics, sous la direction de Sidney Bloch et Stephen A. Green, 469–98. Oxford University Press, 2021. http://dx.doi.org/10.1093/med/9780198839262.003.0020.

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Ethical dilemmas unique to child and adolescent psychiatry are consequences of the child psychiatrist’s duty to serve as advocate for child patients while simultaneously having professional responsibilities to the parents and guardians of the children, as well as to child-related institutions inclusive of schools, juvenile justice systems, and childcare agencies. In addition, awareness of developmental differences is paramount, as continuous maturation occurs from ages zero through eighteen years and beyond. With this in mind, the chapter first reviews ethical principles and reasoning and the influence of context on such ever-present matters as assent/consent/dissent, agency, assessment, treatments, and confidentiality, and then hones in on current and future dilemmas posed by the needs of transitional age youth and the impacts of social media, marijuana decriminalization, alternative sexual and gender expressions, minority vulnerabilities, and casualties of global conflicts. A separate section focuses on ethical considerations relevant to research performed with child subjects.

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« Biology and Management of Dogfish Sharks ». Dans Biology and Management of Dogfish Sharks, sous la direction de Steven E. Campana, Warren Joyce et David W. Kulka. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874073.ch18.

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Abstract.—As part of an intensive study of spiny dogfish Squalus acanthias off the Atlantic coast of Canada, we studied the sexual maturation and growth of dogfish collected on research surveys and as part of the commercial fishery. Sexually mature and pregnant females were distributed throughout the waters of southwest Nova Scotia during the summer and fall but moved offshore to deeper waters in the winter. Juveniles were most abundant off Georges Bank and near the edge of the Scotian Shelf during the winter. The fork length at 50% maturity for males was 55.5 cm at age 10, while that for females was 72.5 cm at age 16. Free embryos were observed in 62% of all pregnant females (n = 1,491), the number of embryos increasing with the size of the female. Free embryos first became apparent in June at a fork length of 16 cm and would be expected to reach their birth size of 22–25 cm during the winter. Validated ages based on spine growth bands indicated a longevity of 31 years (n = 525). Males and females grew at similar rates until the size and age of male maturity, after which male growth rate slowed considerably. Two-parameter von Bertalanffy growth equations using a fixed size at birth gave L∞ = 78.0 and K = 0.099 for the males and L∞ = 119.5 and K = 0.042 for the females. Atlantic dogfish appear to grow more quickly and die at a younger age than do Northeast Pacific dogfish. Small amounts of offshore pupping in southern Nova Scotia waters probably represent the northern limits of an extended distribution centered in U.S. waters. Although they probably originate from the same population, dogfish living in the Gulf of St. Lawrence and off Newfoundland may be functionally isolated from dogfish found further south. Our results and published tagging studies suggest that both resident and migratory components of the Northwest Atlantic population occupy Canadian waters.

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Atkinson, Martin E. « Embryonic development—the first few weeks ». Dans Anatomy for Dental Students. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199234462.003.0014.

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Embryology is a fascinating subject and is the foundation of the development, growth, and maturation of all the cells, organs, and tissues of the body. Strictly, embryology is the study of the early processes of development beginning at fertilization and following the processes that turn a single cell into a multicellular organism. It is all about generation of the building blocks required to make a human body. Developmental anatomy is the study of how these building blocks are turned into specific cells, tissues, and organs as well as the general growth of the body. As you will soon appreciate in the following paragraphs, all organs and systems do not develop at the same rate so there is a degree of overlap between embryology and developmental anatomy. For example, the heart and circulatory system must develop and be functioning very early in development to ensure adequate supplies of nutrients to the developing fetal tissues. Teeth, on the other hand, are not going to be used until about six months after birth at the earliest; while the heart is already beating away, each developing tooth is merely a tiny group of cells bearing little resemblance to a fully formed tooth. Human gestation is considered to take nine months; more accurately, it usually lasts for 38 to 39 weeks from fertilization to birth. Clinically, it is divided into three trimesters of three months each. In this chapter, we will focus on events in the first few weeks. During the first two and a half weeks after fertilization, the very basic building blocks are formed from the single fertilized cell; this is the pre-embryonic period. The embryonic period covers the next five and half weeks during which these basic building blocks develop into the cells, tissues, and organs. As already indicated, some of these may be in a very rudimentary state at the end of the embryonic period. The remaining 30 or so weeks is the fetal period when the tissues and organs of the body grow and develop and the fetus grows considerably. We are not fully mature organisms at birth and have another 20 years a-growing.

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Actes de conférences sur le sujet "White matter maturation"

Rouchdy, Youssef, Christos Davatzikos et Ragini Verma. « Connectivity-based analysis : Application to white matter maturation in mouse brain ». Dans 2012 IEEE 9th International Symposium on Biomedical Imaging (ISBI 2012). IEEE, 2012. http://dx.doi.org/10.1109/isbi.2012.6235482.

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Prastawa, Marcel, Neda Sadeghi, John H. Gilmore, Weili Lin et Guido Gerig. « A new framework for analyzing white matter maturation in early brain development ». Dans 2010 IEEE International Symposium on Biomedical Imaging : From Nano to Macro. IEEE, 2010. http://dx.doi.org/10.1109/isbi.2010.5490404.

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Jackson, C. W., N. K. Hutson et S. A. Steward. « CHANGES IN PROTEIN SYNTHESIS PROFILES OF MEGAKARYOCYTES (MK) DURING MATURATION ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643545.

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Several key differentiation events occur within the recognizable MK compartment; however, little is known about the macromolecular changes responsible for these events. In this study, protein synthesis profiles of morphologically immature and mature guinea pig MK populations have been analyzed by twodimensional gel electrophoresis after in vivo labeling with 35S-methionine. MK were enriched by a bovine plasma aggregation enrichment procedure (Blood 69:173, 1987) and then fractionated into immature and mature populations based on differences in their respective buoyant densities (Brit. J. Haematol. 64:33, 1986). With this protocol, immature and mature MK populations were obtained in which MK constituted 95% of the cell mass. Ninety percent of the MK in the immature population had basophilic, immature morphology while ≥90% of those in the mature population had acidophilic, mature staining characteristics after Wright's staining. Protease inhibitors were used throughout the isolation procedure. The cells were solubilized and proteins subjected to two-dimensional electrophoresis according to O'Farrell (J. Biol. Chem. 250:4007, 1975). To examine basic proteins, proteins were electrophoresed in the first dimension under nonequilibrium conditions in a pH gradient as described by O'Farrell et al. (Cell 12:1133, 1977). Analyses of fluorograms revealed both qualitative and quantitative differences in synthesis profiles between these two MK populations. Among acidic proteins whose synthesis was readily detected in immature but not mature MK were ones whose MW and pi were respectively: 120K, 6.4; 7OK, 5.9; 70K, 6.9; 65K, 6.8; 55K, 6.2; 55K, 6.0; 53K, 5.8; 53K, 6.5; 52K, 6.7; 50K, 6.8; 41K, 5.5 and 33K, 6.7. Acidic and neutral proteins prominently synthesized in mature but not immature MK were found at MW and PI of: 110K, 5.7; 110K, 5.8 and 80K, 7.2. Basic proteins prominently synthesized in immature but not mature MK were found at MWs of: 110K; 70K; 52K; 48K; 39K and 18K. Basic proteins actively synthesized by mature but not immature MK had MWs of: 83K; 43K and 17K. These findings demonstrate that differences in protein synthesis patterns can be readily detected between immature and mature MK and provide baseline data with which to explore the role of these proteins in MK differentiation

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Young, Jennifer L., Kyle Kretchmer et Adam J. Engler. « Temporally-Stiffening Hydrogel Regulates Cardiac Differentiation via Mechanosensitive Signaling ». Dans ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14674.

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Stiffness of the extracellular matrix (ECM) surrounding cells plays an integral role in affecting how a cell spreads, migrates, and differentiates, in the case of stem cells. For mature cardiomyocytes, stiffness regulates myofibril striation, beating rate, and fiber alignment, but does not induce de-differentiation [1,2]. Despite improved myocyte function on materials which mimic the ∼10 kPa heart stiffness, the heart does not begin as a contractile ∼10 kPa material, but instead undergoes ∼10-fold myocardial stiffening during development [3]. Thiolated hyaluronic acid (HA) hydrogels have been used to mimic these stiffening dynamics by varying hydrogel functionality and component parameters. Recently, we have shown that pre-cardiac mesodermal cells plated on top of these stiffening HA hydrogels improves cardiomyocyte maturation compared to static, compliant polyacrylamide (PA) hydrogels [3]. While active mechanosensing causes maturation, the specific mechanisms responsible for responding to time-dependent stiffness remain unknown. Here we examined protein kinase signaling and mechanics in response to dynamic vs. static stiffness during the commitment process from embryonic stem cells (ESCs) through cardiomyocytes to better understand how developmentally-appropriate temporal changes in stiffness regulate cell commitment.

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Huang, Alice H., Brendon M. Baker, Gerard A. Ateshian et Robert L. Mauck. « Sliding Contact Loading Improves the Tensile Properties of MSC-Based Engineered Cartilage ». Dans ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19292.

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Articular cartilage is a load-bearing surface whose mechanical function arises from its unique properties. The structural and mechanical properties of mature cartilage are inhomogeneous through the depth and anisotropic. Tissue maturation is directed by mechanical forces; loading induces remodeling of the immature matrix, leading to increases in compressive and tensile properties and the development of tissue anisotropy [1, 2]. Limitations in cartilage repair strategies have engendered numerous efforts to engineer functional replacements. As mesenchymal stem cells (MSCs) undergo chondrogenesis in 3D culture, this cell type has been increasingly utilized in these efforts [3]. Despite their initial promise however, generating MSC-based constructs with the mechanical complexity and integrity of cartilage remains a challenge; the properties of MSC-seeded hydrogels are consistently lower than those of the native tissue [4, 5]. As mechanical stimulation is critical to cartilage development and maturation, bioreactor systems that simulate the native mechanical environment of cartilage may bridge these functional disparities. Indeed, dynamic axial compression enhances the compressive properties of both chondrocyte- and MSC-based engineered cartilage, though collagen content remains low [6, 7]. While promising, these studies were not designed to generate either depth-dependence or constructs with improved tensile properties. We therefore developed a new sliding contact bioreactor system that can better recapitulate the mechanical stimuli arising from joint motion (two contacting cartilage layers). In previous experiments using this system, we demonstrated improved expression of chondrogenic genes with short-term sliding contact of MSC-seeded agarose; these changes in gene expression were dependent on both axial strain and TGF-β supplementation [8]. Furthermore, FEM analysis of sliding contact showed that tensile strains (parallel to the sliding direction) and fluid efflux/influx were depth-dependent and highest in the region closest to the construct surface [8]. In the current study, we applied long-term sliding contact to MSC-seeded agarose constructs using the optimized parameters previously determined. We hypothesized that sliding contact would improve tensile properties and direct depth-dependent matrix remodeling.

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Rapports d'organisations sur le sujet "White matter maturation"

Berkowitz, Jacob. Quantifying functional increases across a large-scale wetland restoration chronosequence. Engineer Research and Development Center (U.S.), août 2021. http://dx.doi.org/10.21079/11681/41500.

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Over 300,000 ha of forested wetlands have undergone restoration within the Mississippi Alluvial Valley region. Restored forest successional stage varies, providing opportunities to document wetland functional increases across a large-scale restoration chronosequence using the Hydrogeomorphic (HGM) approach. Results from >600 restored study sites spanning a 25-year chronosequence indicate that: 1) wetland functional assessment variables increased toward reference conditions; 2) restored wetlands generally follow expected recovery trajectories; and 3) wetland functions display significant improvements across the restoration chronosequence. A functional lag between restored areas and mature reference wetlands persists in most instances. However, a subset of restored sites have attained mature reference wetland conditions in areas approaching or exceeding tree diameter and canopy closure thresholds. Study results highlight the importance of site selection and the benefits of evaluating a suite of wetland functions in order to identify appropriate restoration success milestones and design monitoring programs. For example, wetland functions associated with detention of precipitation (a largely physical process) rapidly increased under post restoration conditions, while improvements in wetland habitat functions (associated with forest establishment and maturation) required additional time. As the wetland science community transitions towards larger scale restoration efforts, effectively quantifying restoration functional improvements will become increasingly important.

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