title: The ultrastructure and distribution of fibrinogen, von Willebrand factor, and glycoprotein IIb/IIIa complex in platelet alpha-granules by cryo-ultramicrotomy.
abstract: Transformation upon mild stimulation and the ultrastructure of blood platelet alpha-granules were examined using cryo-ultramicrotomy. An ultrastructural study found not only round, but also elongated and drumstick-shaped alpha-granules and rod-like structures protruding from round alpha-granules. Some elongated alpha-granules showed distinctive cross-striations in the short axis with a periodicity in the order of 19-22 nm. Gold particle-labeled fibrinogen (Fbg) was observed on elongated alpha-granules having cross-striations. Electron-dense nucleoids were observed on some round alpha-granules. An electron-dense nucleoid, intermediate zone, and an electron-lucent matrix were noted in round alpha-granules by gold particle-labeled Fbg in the intermediate zone. Gold particle-labeled von Willebrand factor (vWF) was observed in alpha-granules except in nucleoid zones. Labeling for Fbg was also observed in rod-like structures protruding from round alpha-granules. Gold particle-labeled glycoprotein (GP)IIb/IIIa complex was observed on the inner face of alpha-granule membranes. A few elongated and drumstick-like alpha-granules were found on freshly fixed platelets. Elongated alpha-granules were only found in a small percentage of washed and collagen-stimulated platelets. Cryo-ultramicrotomy is useful for examination of the distribution of intracellular antigens.
authors.affiliation: First Department of Internal Medicine, Kansai Medical University, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ohga
authors.forename: K
authors.initials: K
authors.lastname: Hamamoto
authors.forename: H
authors.initials: H
authors.lastname: Kitajima
authors.forename: H
authors.initials: H
authors.lastname: Nagata
authors.forename: S
authors.initials: S
authors.lastname: Nomura
authors.forename: T
authors.initials: T
authors.lastname: Kimura
authors.forename: H
authors.initials: H
authors.lastname: Fujitake
authors.forename: T
authors.initials: T
authors.lastname: Kokawa
authors.forename: K
authors.initials: K
authors.lastname: Yasunaga
mesh_terms: D001792:Blood Platelets / Q000737:chemistry / Q000648:ultrastructure*; D003094:Collagen / Q000494:pharmacology; D016616:Cryoultramicrotomy; D003594:Cytoplasmic Granules / Q000737:chemistry; D005340:Fibrinogen / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D015539:Platelet Activation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins / Q000032:analysis*; D014841:von Willebrand Factor / Q000032:analysis*
chemical_list: D010980:Platelet Membrane Glycoproteins; D014841:von Willebrand Factor; D005340:Fibrinogen; D003094:Collagen