Mammary gland development is marked by numerous cellular changes that begin in the embryo, continue postnatally, are modified at puberty, and come to full fruition during the adult cycles of pregnancy, lactation, and involution. These changes are initiated by hormones produced at distant ...

During early craniofacial development, cranial neural crest cells emigrate from seg-mentally distinct divisions of the hindbrain (rhombomeres) to populate the various branchial arches and subsequently differentiate into multiple neuronal and non-neu-ronal cell linea ...

All the bones of the craniofacial skeleton are united by the fibrous sutures, and those of the neurocranium are lined additionally by the dura mater. The sutures and dura mater are not only integral structural elements of the formed skeleton, but during morphogenesis they also are sites of apposi ...

The formation of a skeleton with its numerous bones of various shapes and sizes and the growth of these bones from embryonic to adult size is a complex process involving a multitude of genes. The complexity of the process is reflected by the large number of inherited diseases with skeletal phenotypes ...

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 ...