细胞功能测定

Altering the spatial relationships of embryonic or postembryonic tissues is one of the oldest and most valuable techniques for investigating mechanisms of development. Urodele amphibians (salamanders and newts) are unique among vertebrates in their ability to regenerate seve ...

The process of neurulation results in the formation of the neural tube, the rudiment of the adult central nervous system. Neurulation occurs in two phases in vertebrate embryos, called primary and secondary neurulation. Primary neurulation, the formation of the neural plate and subsequ ...

The purpose of this chapter is to summarize some technical approaches and aspects of interpretation that are important when studying the process of neurulation and the origin of neural tube defects in mouse embryos. The techniques are not exclusive to studies of neurulation, so few protocols ...

We start with a quote by Rupert Willis (1), who said “Malformations of every conceivable kind, degree, and combination occur, and no two of them are ever alike,”to emphasize the difficulty of what we attempt to do in this chapter: provide a simplified, useful scheme for classifying neural tube defects. T ...

The morphology of the early embryonic vertebrate neural tube differs significantly in the brain and spinal cord anlages. Although both are hollow, the early embryonic brain has a larger cavity volume than tissue volume, whereas the spinal cord consists mostly of tissue and a reduced cavity. Gr ...

The brain of the early chick embryo initially grows by expansion of its fluid-filled cavity much as a balloon expands (1-3). Such expansion occurs rapidly over 3-4 d, beginning at around 43 h of development (1,3), and is under the direct control of internal fluid pressure, as shown from brain intubation ex ...

Placental development, also known as placentation, is orchestrated by precise molecular and cellular interactions between extraembryonic cells and cells of the pregnant uterus. The major extraembryonic cell type of the placenta is the trophoblast cell, which arises from the troph ...

Clefts of the secondary palate are among the most frequent birth defects in live-born human infants. Across the United States between 1981 and 1995, a compilation of data from states with birth defects monitoring programs shows the incidence of cleft palate without cleft lip to range from 2.01 to 14 ...

The formation of the secondary palate requires coordinated expression of genes involved in processes such as cell proliferation, differentiation, and production of extracellular matrix proteins. In order to study the mechanisms through which teratogenic agents induce cleft p ...

Elongation along the proximal distal axis of the limb, from either the pectoral or pelvic girdle to the distal tips of the digits, is regulated from the early stages of limb morphogenesis by the formation of a specialized epithelial structure at the limb bud apex, the apical ectodermal ridge (AER). The ...

How the left-right body axis is established during development and how abnormal sidedness of asymmetric body structures i.e., laterality defects or situs inversus (see Note 1), is induced during development have been questions of great interest in the history of science. A recent discovery ...

Although the phenotypes of situs inversus totalis, isolated malposition of the heart (e.g., isolated dextrocardia), and heterotaxy syndrome have been familiar to physicians for decades Fig. 1), the question of how left-right positional information within an embryo is assigned at a molec ...

In this chapter, we will provide the developmental biologist, interested in cardiac development, a schematic description of heart development. This chapter is not intended to describe in detail every aspect of cardiac morphogenesis in the vertebrate heart or to elaborate extensively ...

Risk assessment is a process conducted by regulatory agencies to safeguard public health from the harmful effects of natural and man-made substances. Thus, a goal of risk assessors is to provide a numerical value of exposure to these substances, below which adverse effects to human health are as ...

A genetic disease gene can be identified by three approaches: (1) Functional cloning in which a disease gene is identified based on biological background of a disease and the gene function without knowledge of chromosomal position of the gene, for example, identification of the globin gene mut ...

The identification of novel, developmentally regulated genes whose products play roles in the differentiation of specific vertebrate tissues and organs can be accomplished using a method called gene trapping (1-9). This technique involves inserting a marker gene, such as β-galacto ...

RNA localization is an important cellular mechanism for restricting the activities of regulatory proteins to cytoplasmic domains in oocytes and embryos (1). Cloning of these localized RNAs is obviously the first step in determining the functions of the encoded proteins. However, loca ...

Differential gene expression is an essential mechanism for the development of a single-celled zygote into a patterned multicellular organism with differentiated cell types and tissues. Therefore, the identification of differentially expressed genes provides an important ...

Preimplantation-stage mammalian embryos are very simple morphologically, being composed of mostly round cells that exhibit only a limited range of changes in cell shape, namely those associated with compaction and formation of the trophectoderm cell lineage. This morphological ...

Analysis of the genetic and molecular mechanisms of embryogenesis requires effective methods to find and isolate genes that are differentially expressed in normal and altered conditions. Comparative genomic screens can lead to the discovery of known or novel transcripts that chan ...