title: Noise-induced gastric lesions: a light and electron microscopy study of the rat gastric wall exposed to low frequency noise.
abstract: BACKGROUND
  Only a few studies evaluated the digestive alterations caused by low frequency noise (LFN) and most focused only on mucosal alterations.
  
  
  OBJECTIVE
  To investigate the morphological injury of LFN-exposed gastric wall, beyond the epithelial layer.
  
  
  METHODS
  Wistar rats were exposed to low frequency noise (LFN), during increasing periods, 1 to 13 weeks. A control group was kept in silence. Gastric specimens were studied using: (i) light microscopy with hematoxylin-eosin and immunostaining for collagens; (ii) transmission electron microscopy; (iii) morphometry allowing statistical analysis.
  
  
  RESULTS
  Submucosa of all LFN-exposed animals exhibit increased thickness with fibrous proliferation. Transmission electron microscopy showed massive collagen deposition. Immunostaining identified collagen IV as responsible for the increased thickness. Morphometry allowed the demonstration of a significant difference of thickness between control and exposed groups. Vascular alterations included: i) intima proliferation and thickening, rupture of the internal elastic lamina, thrombotic changes; ii) thickening of the media; iii) after 9 weeks of LFN-exposure, we found new formed vessel presenting tortuous and twisted. There is a significant difference of arterial wall thickness between control and exposed groups.
  
  
  CONCLUSIONS
  Deeper layers of gastric wall undergo alterations, including fibrosis of the submucosa caused by collagen IV deposition, an early marker of neoangiogenesis. Vascular alterations included thickening and thrombotic phenomena, but also images of newly formed vessels. This study suggests that, at least in the stomach, LFN-induced fibrosis could be linked with neoangiogenesis.
authors.affiliation: Instituto Superior de Ciências da Saúde Egas Moniz, Almada, Portugal. jorgedafonseca@hotmail.com
authors.forename: Jorge
authors.initials: J
authors.lastname: Fonseca
authors.forename: José
authors.initials: J
authors.lastname: Martins-dos-Santos
authors.forename: Pedro
authors.initials: P
authors.lastname: Oliveira
authors.forename: Nuno
authors.initials: N
authors.lastname: Laranjeira
authors.forename: Artur
authors.initials: A
authors.lastname: Aguas
authors.forename: Nuno
authors.initials: N
authors.lastname: Castelo-Branco
mesh_terms: D000818:Animals; D005260:Female; D005753:Gastric Mucosa / Q000473:pathology* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D009622:Noise / Q000009:adverse effects*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors