ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<1::AID-MRDD1>3.0.CO;2-J

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

摘要:

AbstractNeural tube defects (NTD) remain a major cause of morbidity in spite of the reduction in liveborn incidence with periconceptional folic acid. However, the etiology remains unknown. This article reviews studies that address causation and potential treatment of NTD in humans and in animal models that resemble aspects of the common human NTD. Studies of nutritional markers of vitamin B12 and folic acid support a defect in homocysteine metabolism; a thermolabile variant of methylene tetrahydrofolate reductase, an enzyme that remethylates homocysteine to methionine, correlates with a risk of NTD in some human populations. Numerous mouse mutant models of NTD exist, attesting to the ease of disruption of neurulation, and a genetic basis for this malformation. Of these models, thecurly tailmouse mutant most closely resembles the common human NTD. Folic acid does not prevent NTD in this model; however inositol supplementation does result in a significant reduction in incidence. Recent advances in fetal surgery, and evidence from mechanically created myelomeningocele in large animals amenable to surgical intervention suggest that the handicaps associated with myelomeningocele and associated Chiari Type II malformation may be prevented by in utero NTD closure. Success will depend on preservation of neurological tissue until such intervention is possible. Further research in animal models at the genetic and cellular levels, together with technological surgical advances, provide hope that prevention of more NTD and the associated handicaps may be possible. MRDD Research Reviews 6:6–14, 2000. © 2000 Wiley‐Liss,

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<6::AID-MRDD2>3.0.CO;2-B

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

摘要:

AbstractHoloprosencephaly (HPE) is the most common major developmental defect of the forebrain in humans. Clinical expression is variable, ranging from a small brain with a single cerebral ventricle and cyclopia to clinically unaffected carriers in familial HPE. Significant etiologic heterogeneity exists in HPE and includes both genetic and environmental causes. Defects in the cell signaling pathway involving theSonic Hedgehog(SHH) gene, as well as defects in the cholesterol biosynthesis have been shown to cause HPE in humans. More recently, HPE genes from additional signaling pathways have been identified. These discoveries and current genetic approaches serve as a paradigm for studying normal and abnormal brain morphogenesis. MRDD Research Reviews 6:15–21, 2000. © 2000 Wiley‐Liss,

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<15::AID-MRDD3>3.0.CO;2-8

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

摘要:

AbstractVariations in the structure of the neocortex induced by single gene mutations may be extreme or subtle. They differ from variations in neocortical structure encountered across and within species in that these “normal” structural variations are adaptive (both structurally and behaviorally), whereas those associated with disorders of development are not. Here we propose that they also differ in principle in that they represent disruptions of molecular mechanisms that are not normally regulatory to variations in the histogenetic sequence. We propose an algorithm for the operation of the neuronogenetic sequence in relation to the overall neocortical histogenetic sequence and highlight the restriction point of the G1 phase of the cell cycle as the master regulatory control point for normal coordinate structural variation across species and importantly within species. From considerations based on the anatomic evidence from neocortical malformation in humans, we illustrate in principle how this overall sequence appears to be disrupted by molecular biological linkages operating principally outside the control mechanisms responsible for the normal structural variation of the neocortex. MRDD Research Reviews 6:22–33, 2000. © 2000 Wiley‐L

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<22::AID-MRDD4>3.0.CO;2-5

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

摘要:

AbstractThe development of the cerebral cortex requires large‐scale movement of neurons from areas of proliferation to areas of differentiation and adult function in the cortex proper, and the patterns of this neuronal migration are surprisingly complex. The migration of neurons is affected by several naturally occurring genetic defects in humans and mice; identification of the genes responsible for some of these conditions has recently yielded new insights into the mechanisms that regulate migration. Other key genes have been identified via the creation of induced mutations that can also cause dramatic disorders of neuronal migration. However, our understanding of the physiological and biochemical links between these genes is still relatively spotty. A number of molecules have also been studied in mice (Reelin, mDab1, and the VLDL and ApoE2 receptors) that appear to represent part of a coherent signaling pathway that regulates migration, because multiple genes cause an indistinguishable phenotype when mutated. On the other hand, two human genes that cause lissencephaly (LIS1,DCX) encode proteins that have recently been implicated as regulators or microtubule dynamics. This article reviews some of the mutant phenotypes in light of the mechanisms of neuronal migration. MRDD Research Reviews 6:34–40, 2000. © 2000 Wiley‐Lis

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<34::AID-MRDD5>3.0.CO;2-Y

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

摘要:

AbstractDifferentiation of neurons within the central nervous system occurs by the combined effects of intrinsic genetic programs and epigenetic stimuli. Disorders causing mental retardation and other abnormalities of higher cortical function arise by disturbances of the normal developmental sequence. MRDD Research Reviews 6:41–46, 2000. © 2000 Wiley‐Liss,

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<41::AID-MRDD6>3.0.CO;2-V

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<47::AID-MRDD7>3.0.CO;2-M

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

摘要:

AbstractUnderstanding of the morphological development of the human brain has largely come from neuropathological studies obtained postmortem. Magnetic resonance (MR) techniques have recently allowed the provision of detailed structural, metabolic, and functional information in vivo on the human brain. These techniques have been utilized in studies from premature infants to adults and have provided invaluable data on the sequence of normal human brain development. This article will focus on MR techniques including conventional structural MR imaging techniques, quantitative morphometric MR techniques, diffusion weighted MR techniques, and MR spectroscopy. In order to understand the potential applications and limitations of MR techniques, relevant physical and biological principles for each of the MR techniques are first reviewed. This is followed by a review of the understanding of the sequence of normal brain development utilizing these techniques. MRDD Research Reviews 6:59–67, 2000. © 2000 Wiley‐Liss,

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<59::AID-MRDD8>3.0.CO;2-E

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY

摘要:

AbstractCognitive and motor development in children remain fascinating processes that are uniquely human. Progress has been made in recent years in elucidating the prenatal process of human brain development. In addition, much information exists regarding the behavioral aspects of postnatal human development. However, little is known about the relationship between anatomic postnatal central nervous system development and the accretion of functional milestones observed in children from the neonatal period through adolescence. Recently, powerful qualitative and quantitative magnetic resonance techniques have been developed that will permit detailed inquiry into the connection between the developing brain and the developing mind. In this review, first, the steps of prenatal and postnatal brain development are reviewed briefly. Subsequently, recent magnetic resonance imaging data related to human brain development during the fetal, neonatal, and later childhood periods are presented. Finally, functional magnetic resonance imaging (fMRI) is discussed. Specific examples of its usefulness are provided. Magnetic resonance imaging techniques such as quantitative MRI, volumetric MRI, diffusion tensor imaging, and functional magnetic resonance imaging (fMRI) when combined with neurologic and neuropsychologic evaluation, will provide new insights into the cognitive development of children. MRDD Research Reviews 6:68–80, 2000. © 2000 Wiley‐Liss,

ISSN:1080-4013    

DOI:10.1002/(SICI)1098-2779(2000)6:1<68::AID-MRDD9>3.0.CO;2-9

出版商:John Wiley&Sons, Inc.    

年代:2000

数据来源: WILEY