Horn core

The essential genetic material ofthe original vegetative bacterium is retained in the core or protoplast around this lies the thick cortex which contains the murein or peptidoglycan already encountered as a cell wall component (see Fig. 1.2). The outer coats which are protein in composition are distinguished by their high cysteine content. In this respect they resemble keratin, the protein of hair and horn. 

Antler is the name of the bony material that makes up a deciduous pair of protrusions shed every year known as "antlers" on the heads of animals of the deer family, for example, reindeer, elk, and fallow deer. Antler has a composition similar to that of horn. Like bone, antler is made up of a hard and compact outer layer surrounding a core of spongy tissue. Since it is regularly shed from the body of the animal, it differs morphologically from horn, which is not shed (O Connor et al. 1987). 

FIGURE 1-8 A dendrite (D) emerging from a motor neuron in the anterior horn of a rat spinal cord is contacted by four axonal terminals terminal 1 contains clear, spherical synaptic vesicles terminals 2 and 3 contain both clear, spherical and dense-core vesicles (arrow) and terminal 4 contains many clear, flattened (inhibitory) synaptic vesicles. Note also the synaptic thickenings and, within the dendrite, the mitochondria, neurofilaments and neurotubules. x33,000. 

FIGURE 1-10 An axonal terminal at the surface of a neuron from the dorsal horn of a rabbit spinal cord contains both dense-core and clear, spherical synaptic vesicles lying above the membrane thickenings. A subsurface cisterna (arrow) is also seen. x68,000. 

Cammenga, J., Horn, S., Bergholz, U., Sommer, G., Besmer, P., Fiedler, W. and Stocking, C. (2005) Extracellular KIT receptor mutants, commonly found in core binding factor AML, are constitutively active and respond to imatinib mesylate. Blood 106, 3958-3961. 

The Method of Explicit Core-Valence Orthogonality.—Horn and Murrell19 have proposed an approximate method for introducing core-valence orthogonality in performing valence-electron calculations, and this has been implemented in a number of papers.48-51 The outline of their scheme is as follows ... 

Tilgen, N., Zorzato, F., Halliger-Keller, B., Muntoni, F., Sewry, C., Palmucci, L. M., Schneider, C., Hauser, E., Lehmann-Horn, F., Muller, C. R., and Treves, S. (2001). Identification of four Novel Mutations in the C-Terminal Membrane Spanning Domain of the Ryanodine Receptor 1 Association with Central Core Disease and Alteration of Calcium Homeostasis. Hum Mol Genet 10(25) 2879-87. 

M. Tecle, F. Booy, M. C. Brahimi-Horn, C. Coutelle, N. R. Lemoine, E. W. Alton, and A. D. Miller, Characterisation of LMD virus-like nanoparticles self-assembled from cationic liposomes, adenovirus core peptide mu and plasmid DNA, Gene Ther., 9 (2002) 564-576. 

The experiments were carried out in the set-up shown in Fig. 1. The cores that were used for the experiments were cylindrically shaped Berea sandstone samples. The length of the cores was 20 cm and the diameter 7.62 cm. The porosity was about 0.25. The initial permeability was 100-300 mD for all samples. During an experiment a core was placed in a rubber sleeve to keep it fixed during the experiment. It was then placed in a steel vessel in which downhole reservoir conditions of up to 150 bars and 100°C were simulated. An acoustic horn was placed at one end of the core (see Fig. 1). The high pressure in the vessel made it possible to avoid cavitation. For pressures lower than 100 bars the influence of cavitation becomes noticeable. The space between the vessel and sleeve, which was filled with water, was pressurized to 180 bars to make the rubber sleeve completely seal off. 

Horns are the hard protuberances that extend from the heads of some animals (Figure 6.22). In most cases, horns have a core of bone that is part of... 

Rhinoceros horns are composed of densely compressed hair-like fibers over a stubby bone core that is part of the skull. They are composed of a dense growth of epidermal cells and dermal papillae, which are similar to thick hair. These are not really true hairs, since they do not grow from a follicle in the skin. Unlike the sheath-like horns of cattle and buffalo, rhino horns are mosdy solid. 

In more recent times, while bone lost favour and became a cheap substitute for ivory, antler became more valued in its own right. The attractive, ridged, outer surface of the material was usually incorporated in, or used as, part of the decoration. With the iimer core hollowed out, antler was made into powder horns, or pieces of it were mounted on gun butts, where they gave a good grip at the same time as being decorative. 

Horn fi om the rhino is different firom other types of hom, as it is composed entirely of compacted strands of keratin, so that it is solid with no bony core. Other types of hom are thin sheaths of homy material covering a bony core. Rhinos horns grow throughout the animals lives, and can regrow if broken or damaged. They grow om the skin on the animals noses (Fig. 6.1). 

There is one other bone which could be useful to geochemists interested in assessing environmental exposures. Antlers, but not horns, are shed annually. Both these organs have a bony core but horn is covered with dead keratinous tissues while antlers are covered initially by velvet, an epidermal tissue with separate blood and neural supply. Once the velvet has been rubbed off, the bony super-stmcrnre that has formed and mineralized very rapidly provides the animal with a remarkable headdress. After the breeding season osteoclasts resorb at the base where the antler is attached to the frontal bone of the skull and antlers may be relatively easily obtained for analyses. Male deer, reindeer, and caribou regrow their membranous bone excrescences each year with an increase in the complexity and size of these unique structures... 

Many grades of urushi are used, depending on the different applications or decorative effects desired. (A detailed description of materials and methods may be found in Reference 8.) The sap, after removal of some water and careful filtration and cleaning, is most often coated onto a prepared core. This core is usually made of wood, but examples of leather, basketry, cloth, paper, metal, pottery, shell, horn, and fish skin may be found. Normally, many lacquer layers are built up on the core, with polishing occurring after each layer has hardened. 

Figure 6.11 Horning-crown macrocycle (derived from isoaromatization of 25) inclusion complexes with oc-methylphenethylamine and propylenedia-mine contain ball-like structures (left) and sheath/core structures (right), respectively.

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