title: Secretory glands and microvascular systems imaged in aqueous solution by atmospheric scanning electron microscopy (ASEM).
abstract: Exocrine glands, e.g., salivary and pancreatic glands, play an important role in digestive enzyme secretion, while endocrine glands, e.g., pancreatic islets, secrete hormones that regulate blood glucose levels. The dysfunction of these secretory organs immediately leads to various diseases, such as diabetes or Sjögren's syndrome, by poorly understood mechanisms. Gland-related diseases have been studied by optical microscopy (OM), and at higher resolution by transmission electron microscopy (TEM) of Epon embedded samples, which necessitates hydrophobic sample pretreatment. Here, we report the direct observation of tissue in aqueous solution by atmospheric scanning electron microscopy (ASEM). Salivary glands, lacrimal glands, and pancreas were fixed, sectioned into slabs, stained with phosphotungstic acid (PTA), and inspected in radical scavenger d-glucose solution from below by an inverted scanning electron microscopy (SEM), guided by optical microscopy from above to target the tissue substructures. A 2- to 3-µm specimen thickness was visualized by the SEM. In secretory cells, cytoplasmic vesicles and other organelles were clearly imaged at high resolution, and the former could be classified according to the degree of PTA staining. In islets of Langerhans, the microvascular system used as an outlet by the secretory cells was also clearly observed. Microvascular system is also critically involved in the onset of diabetic complications and was clearly visible in subcutaneous tissue imaged by ASEM. The results suggest the use of in-solution ASEM for histology and to study vesicle secretion systems. Further, the high-throughput of ASEM makes it a potential tool for the diagnosis of exocrine and endocrine-related diseases.
authors.affiliation: Department of Molecular Physiology, The Jikei University School of Medicine, Minato-ku, Tokyo, 105-8461, Japan.
authors.forename: Toshiko
authors.initials: T
authors.lastname: Yamazawa
authors.affiliation: Department of Statistical Genetics, Center for Genomic Medicine, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
authors.forename: Naotoshi
authors.initials: N
authors.lastname: Nakamura
authors.affiliation: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8568, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Sato
authors.affiliation: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8568, Japan.
authors.forename: Chikara
authors.initials: C
authors.lastname: Sato
mesh_terms: D000818:Animals; D005260:Female; D006243:Harderian Gland / Q000166:cytology / Q000000981:diagnostic imaging / Q000648:ultrastructure; D007150:Immunohistochemistry; D051379:Mice; D008813:Mice, Inbred ICR; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D010179:Pancreas / Q000166:cytology / Q000000981:diagnostic imaging / Q000648:ultrastructure; D012469:Salivary Glands / Q000166:cytology / Q000000981:diagnostic imaging / Q000648:ultrastructure; D040521:Subcutaneous Tissue / Q000098:blood supply / Q000000981:diagnostic imaging / Q000648:ultrastructure
keywords: ASEM; endocrine organ; exocrine organ; scanning electron microscope