Hedgehog structure

Fig. 18.11 Structure of the hedgehog dScalion. ((PhjPAufoC]2 The inferred Au—An bends are not shown. (From Schertwum. F. Grohmann. A. Huber. B. Kruger. C. Schmidbaur. H. Angew. Cheat. h . J- Engl. 198. 27. 1544-1546. Reproduced with permssion.]...

C., Sonic hedgehog a key mediator of anterior-posterior patterning of the limb and dorso-ventral patterning of axial embryonic structures, Biochem. Soc. Trans. 22, 569-574, 1994 Bumcrot, D.A. and McMahon, A.R., Somite differentiation. Sonic signals somites, Curr. Biol. 5, 612-614, 1995 Lum, L. and Beachy, R.A., The Hedgehog response network sensors, switches, and routers. Science 304, 1755-1759, 2004 Ishibashi, M., Saitsu, H., Komada, M., and Shiota, K., Signaling cascade coordinating... 

Lopez-Mascaraque L, de Carlos JA, Valverde E 1990. Structure of the olfactory bulb of the hedgehog (Erinaceus europaeus) A Golgi study of the intrinsic organization of the superficial layers. J Comp Neurol 301 243-261. 

In addition to Its structural role In membranes, discussed In Chapter 5, cholesterol Is the precursor for several Important bloactive molecules. They Include bile acids (see Figure 18-6), which are made In the liver and help emulsify dietary fats for digestion and absorption In the Intestines, steroid hormones produced by endocrine cells (e.g., adrenal gland, ovary, testes), and vitamin D produced In the skin and kidneys. Arthropods need cholesterol or other sterols to produce membranes and ecdysterold hormones, which control development however, they cannot make the precursor sterols themselves and must obtain these compounds In their diet. Another critical function of cholesterol Is Its covalent addition to Hedgehog protein, a key signaling molecule In embryonic development (Chapter 15). 

Fig. 6-8 Target identification of an inhibitor of Hedgehog signaling, (a) Structure of the alkaloid cyclopamine.

Until recently, cholesterol has been known to serve primarily as a precursor in steroid hormone and bile component biosynthesis and as an important structural component of biological membranes in animals [82]. A fourth major function for cholesterol in animals is suggested by its formation of a covalent linkage to amino-terminal Sonic hedgehog fragment and its modulation of spatial and subcellular distribution that affects mammalian patterning activities [79]. 

Fig. 6.1 Artist s drawing of a crayfish showing some locations for important chemosensory sensilla. Above the crayfish the antennule is where the unimodal (olfactory) chemosensory aesthetascs are situated. To the left of the crayfish on the tips of the walking legs, bimodal chemo- and mechanosensory sensilla may be present e.g., as hedgehog hairs (above left) and smooth, squamose setae (below left). Bimodal sensilla show a considerable structural variety and can also be found e.g., on the mouthparts of the animal (not shown). Drawing by artist Jorge A. Varela Ramos...

The cuticular hair can be of varying length and thickness, and usually has a smooth surface, but the cuticular structure depends on the type of chemosensory sensillum some have cuticular superficial structures. For example, the hedgehog hairs of II. americanus are fringed (Fig. 6.2) (Derby 1982), whereas the hooded sensilla of Panulirus argus have leaf-like setules (Cate and Derby 2002). 

Fig. 3.5.10. Singular points in droplets (a) spherically symmetric radial (hedgehog) configuration with the director normal to the surface (b) bipolar structure with the director tangential to the surface (c) singular points in a capillary.

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