Wednesday, 1 August 2012

Types Of Dogs

Types Of Dogs Biography
Dog types are broad categories of dogs based on function,[1] with dogs identified primarily by specific function or style of work rather than by lineage or appearance.
In contrast, modern dog breeds are particular breed standards,[note 1] [2] sharing a common set of heritable characteristics,[3] determined by the kennel club that recognizes the breed.
Dog types include ancestral forms (or landraces) that arose undocumented over a long period of time.
A dog type can be referred to broadly, as in Bird dog, or more specifically, as in Spaniel. Dogs raised and trained for a specific working ability rather than appearance may not closely resemble other dogs doing the same work, or any of the dogs of the analogous breed group of purebred dogs.

With the beginnings of agriculture, approximately 12,000 years ago, humans began making use of dogs in various ways. Molecular biologist and founder of the Canine Genome Project Elaine Ostrander comments, "When we became an agricultural society, what we needed dogs for changed enormously, and a further and irrevocable division [between dogs and wolves] occurred at that point."[5] There is a great deal of speculation about the early uses of dogs, but recent genetic analysis shows that the earliest ancestors of modern breeds (those with the least genetic divergence from the ancestral wolf) include lap dog types (Pekingese, Shih Tzu) along with hunting dog and working dog types.

The effect of the synthetic extracellular matrix (ECM) in a diffusion chamber for a bioartificial endocrine pancreas (Bio-AEP) on pancreatic endocrine cells in vitro and its biocompatibility in dogs were investigated. Two different types of ECM were used: type I collagen treated with low antigen (type I LA), and reconstituted basement membrane matrix (Matrigel) derived from Englbreth-Holm-Swarm (EHS) mouse sarcoma. Matrigel contains growth and differentiation factors and cell adhesion molecules such as laminin, heparan sulfate proteoglycan, and entactin. Purified porcine pancreatic endocrine (PE) cells were suspended in type I LA or Matrigel and then placed into a 12-well culture plate (4 x 10(7) cells/ml gel/well). The insulin accumulation from PE cells in Matrigel was significantly greater than that in type I LA (9.3 +/- 3.6 mU/well vs. 2.3 +/- 1.3 mU/well). When Bio-AEP with Matrigel and PE cells was implanted into the abdominal cavity of a pancreatectomized diabetic dog, the exogenous insulin requirement for maintaining normoglycemia was reduced for the first 4 weeks. However, after 6 weeks of implantation, fasting blood glucose levels suddenly increased. Laparotomy revealed encapsulated Bio-AEP with thick fibrous tissue. Following removal of the Bio-AEP from the abdominal cavity, another Bio-AEP containing type I LA and PE cells was implanted into the same dog. The exogenous insulin requirement was gradually decreased to almost half that of preimplantation levels. Bio-AEPs containing type I LA or Matrigel, but not PE cells, were implanted into the abdominal cavities of four healthy dogs. After 4 weeks of implantation, the Bio-AEP with Matrigel was encapsulated with fibrous tissue similar to that in the diabetic dog, but the Bio-AEP with type I LA was not. These results indicate that Matrigel may be incompatible with dogs and that the type I LA is more suitable for Bio-AEP.
PMID: 11549077 [PubMed - indexed for MEDLINE]
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Types Of Dogs
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Types Of Dogs
Types Of Dogs
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1 comment:

  1. This is the type of information I’ve long been trying to find. Thank you for writing this information.

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