Tissue endodermal

Several different tissue types - epidermis, endodermis, laticifers, idioblasts, pericycle, and cortex — have now been implicated in the biosynthesis and/or accumulation of various alkaloids in plants. Recently, we have localized berberine in the endodermis of Thalictrum flavum roots at the onset of secondary growth.150 Rather than being sloughed off, the endodermis was found to undergo extensive anticlinal division leading to an expanding cellular cylinder that ultimately displaced all external tissues. Endodermal-specific berberine accumulation continued throughout root development, but was extended to include 3 to 4 layers of smaller pericycle cells in the oldest roots near the base of the stem. The cell type-specific accumulation of an antimicrobial alkaloid and the unusual development of the endodermis and pericycle in T. flavum roots are consistent with the putative role of berberine in plant defense. 

According to the accepted definition SC, resulting in only one type of the differentiated cells, are named unipotential (or monopotential), two - bipotential. Those cells which give the beginning to a few types of different specialized cells are named pluripotential or multipotential. Totipotential is the ability of cell to differentiate in all the types of cells and tissues of organism (in any of 350 specialized lines derivative of ectoderm, mesoderm and endoderm). 

Figure 8.3 Specialized cells and tissues in our body develop in stages. The embryo inner cell mass develops into three layers the outer layer, or ectoderm, that will become skin, eyes, and nerves the inner cell layer, the endoderm, that develops into the lungs, liver, and the lining of our digestive system and the middle layer, the mesoderm, that develops into bones, muscle, and blood.

Individuals of the next most complex major phylum, Cnidaria (formerly Coelenterata), are radially symmetric with two distinct cell layers, the endoderm and ectoderm. Many species exist both as a polyp or hydra form (Fig. 1-13) and as a medusa or jellyfish. The jellyfish apparently has no brain but the ways in which its neurons interconnect in a primitive radial net are of interest. The Cnidaria have a very simple body form with remarkable regenerative powers. The freshwater hydra, a creature about 1 cm long (Fig. 1-13), contains a total of -105 cells. A complete hydra can be regenerated from a small piece of tissue if the latter contains some of both the inner and the outer cell layers.121 122... 

The blastocyst is a hollow, fluid-filled ball of approximately 1000 cells. The cells that form the outer layer are referred to as trophoblasts and will ultimately develop as extraembryonic tissues (e.g., placenta), while the cells of the inner cell mass are omnipotent (i.e., stem cells) and form the embryo. Depending on the species, the blastocyst arrives at the uterus within 5-10 days of fertilization, whereupon it hatches from the zona pellucida and implants into the uterine wall, which has been preconditioned by ovarian-derived steroid hormones (see Chapter 33). Shortly after implantation, the inner cell mass undergoes gastrulation to form a trilaminar embryo composed of three primary germ layers, the ectoderm, mesoderm, and endoderm. 

Intramembranous ossification is the transformation of the mesenchyme, cells of an embryo into bone. During early development of vertebrate animals, the embryo consists of three primary cell layers ectoderm on the outside, mesoderm in the middle, and endoderm on the inside. Mesenchyme cells constitute part of the embryo s mesoderm and develop into connective tissue such as bone and blood. The bones of the skull derive directly from mesenchyme cells by intramembranous ossification. 

Hescheler J, Fleischmann BK, Wartenberg M et al (1999) Establishment of ionic channels and signalling cascades in the embryonic stem cell-derived primitive endoderm and cardiovascular system. Cells Tissues Organs 165(3—4) 153-164... 

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