title: Ultrastructural characterization of normal Merkel cells in the dog.
abstract: BACKGROUND
  Involvement of Merkel cells (MKs) in different cutaneous diseases as well as in the growth, differentiation and homeostasis of the skin has been previously documented.
  
  
  OBJECTIVE
  The aim was to assess the ultrastructural features of MKs in canine skin, including morphometrics, highlighting their similarities with and differences from those described for other mammals.
  
  
  METHODS
  Hard palate, nasal planum, lower lip and whisker pad samples were taken from two healthy young dogs destined for academic purposes.
  
  
  METHODS
  Ultrathin sections of samples fixed in osmium tetroxide and embedded in Epon 812 resin were stained with uranyl acetate and lead citrate and examined using a JEOL JEM 2010 transmission electron microscope.
  
  
  RESULTS
  Ultrastructural characteristics included the following: (i) arrangement in clusters in the basal layer of the epidermis, oral mucosa and external follicular root sheath; (ii) inconstant link with nerve terminal; (iii) oval (10.27 ± 1.64 μm major axis) cell shape with large lobulated nuclei (5.98 ± 1.16 μm major axis); (iv) spine-like and thick cytoplasmic processes interdigitating with surrounding keratinocytes; (v) presence of desmosomes in the cell body or at the base of spine-like processes attaching to neighbouring keratinocytes; and (vi) cytoplasm containing loosely arranged intermediate filaments (10.04 ± 1.17 nm) and numerous dense-core granules (100.1 ± 17.12 nm) arranged in the basal portion of the cytoplasm.
  
  
  CONCLUSIONS
  This study provides the first complete description of the ultrastructural characteristics of MKs in the dog, enhancing our knowledge of the skin structure in this species and providing a basis for future physiological and pathological studies of the role of these cells in normal and damaged canine tissues.
authors.affiliation: Unit of Histology and Veterinary Pathology, Institute for Animal Health, Veterinary College, University of Las Palmas de Gran Canaria, Campus Universitario Cardones, Arucas, Las Palmas, 45413, Spain.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Ramírez
authors.affiliation: Unit of Histology and Veterinary Pathology, Institute for Animal Health, Veterinary College, University of Las Palmas de Gran Canaria, Campus Universitario Cardones, Arucas, Las Palmas, 45413, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Rodríguez
authors.affiliation: Unit of Histology and Veterinary Pathology, Institute for Animal Health, Veterinary College, University of Las Palmas de Gran Canaria, Campus Universitario Cardones, Arucas, Las Palmas, 45413, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Herráez
authors.affiliation: Unit of Histology and Veterinary Pathology, Institute for Animal Health, Veterinary College, University of Las Palmas de Gran Canaria, Campus Universitario Cardones, Arucas, Las Palmas, 45413, Spain.
authors.forename: Ayoze
authors.initials: A
authors.lastname: Castro-Alonso
authors.affiliation: Unit of Histology and Veterinary Pathology, Institute for Animal Health, Veterinary College, University of Las Palmas de Gran Canaria, Campus Universitario Cardones, Arucas, Las Palmas, 45413, Spain.
authors.forename: Marisa
authors.initials: M
authors.lastname: Andrada
authors.affiliation: Unit of Histology and Veterinary Pathology, Institute for Animal Health, Veterinary College, University of Las Palmas de Gran Canaria, Campus Universitario Cardones, Arucas, Las Palmas, 45413, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Espinosa-de-los-Monteros
mesh_terms: D000818:Animals; D004285:Dogs / Q000033:anatomy & histology*; D008046:Lip / Q000166:cytology / Q000648:ultrastructure; D018862:Merkel Cells / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission / Q000662:veterinary; D009666:Nose / Q000166:cytology / Q000648:ultrastructure; D021362:Palate, Hard / Q000166:cytology / Q000648:ultrastructure; D012867:Skin / Q000166:cytology / Q000648:ultrastructure