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BIOL 370 – Developmental Biology Topic #10 More on the Amphibians and Fish: Early Development and Axis Formation Lange Standardized Color Scheme: Ectoderm – outer germ layer… will become nervous system, tooth enamel, epidermis, lining of the mouth, anus, nostrils, sweat glands, hair and nails. Mesoderm – middle germ layer… will become the muscle (smooth, cardiac and skeletal), connective tissues, dermis, hypodermis (subcutaneous layer of the skin), bone, cartilage, red blood cells, white blood cells, kidneys, and the adrenal cortex. Endoderm – inner germ layer… will become a variety of epithelia including the alimentary canal (excluding specialized parts of the mouth, pharynx & rectum), the lining cells of all the glands, trachea, bronchi, and alveoli of the lungs, endocrine glands, auditory tube, urinary bladder and parts of the urethra. Figure 7.23 Vegetal induction of mesoderm Induction in this case is related to the activation of genes in the vegital region that will guide development of the mesoderm. Figure 7.23 Vegetal induction of mesoderm (Part 1) Figure 7.23 Vegetal induction of mesoderm (Part 2) Figure 7.25 The soluble protein Noggin dorsalizes the amphibian embryo Figure 7.27 Model for the action of the organizer Figure 7.29 Regional and temporal specificity of induction Figure 7.30 Paracrine factor antagonists from the organizer are able to block specific paracrine factors to distinguish head from tail Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Figure 7.30 Paracrine factor antagonists from the organizer are able to block specific paracrine factors to distinguish head from tail (Part 1) • BMPs were originally discovered through their ability to induce the formation of bone and cartilage • BMPs are now considered to constitute a group of pivotal morphogenetic signals, orchestrating tissue architecture throughout the body Figure 7.30 Paracrine factor antagonists from the organizer are able to block specific paracrine factors to distinguish head from tail (Part 2) Figure 7.31 Cerberus mRNA injected into a single D4 blastomere of a 32-cell Xenopus embryo induces head structures as well as a duplicated heart and liver Figure 7.33 Insulin-like growth factors enhance anterior neural development Figure 7.35 Model of organizer function and axis specification in the Xenopus gastrula Figure 7.36 Pitx2 determines the direction of heart looping and gut coiling Figure 7.37 Zebrafish development occurs very rapidly Figure 7.37 Zebrafish development occurs very rapidly (Part 1) Figure 7.37 Zebrafish development occurs very rapidly (Part 2) Figure 7.38 Screening protocol for identifying mutations of zebrafish development Figure 7.38 Screening protocol for identifying mutations of zebrafish development (Part 1) Figure 7.38 Screening protocol for identifying mutations of zebrafish development (Part 2) Figure 7.39 The gene for green fluorescent protein was fused to the regulatory region of a zebrafish sonic hedgehog gene Figure 7.40 Discoidal meroblastic cleavage in a zebrafish egg Figure 7.41 Fish blastula Figure 7.41 Fish blastula (Part 1) Figure 7.41 Fish blastula (Part 2) End.