title: Ultrasonographic evaluation of gastrocnemius muscle in a rat model of N-methyl-N-nitrosourea-induced mammary tumor.
abstract: OBJECTIVE
  Ultrasonography is frequently used to study body tissues. Our aim was to evaluate by ultrasonography, gastrocnemius muscle wasting induced by cancer in a rat model of chemically-induced mammary tumor, muscular response to exercise.
  
  
  METHODS
  Female Sprague-Dawley rats were divided into as well as four groups. Groups I and II were injected with N-methyl-N-nitrosourea (MNU). Groups I and III performed endurance training on a treadmill. Gastrocnemius muscles were palpated for tonus evaluation. Gastrocnemius muscle and fibrous tissue between muscle and tibia were examined by ultrasonography. At necropsy, muscle was collected and weighed. Myostatin was assessed by immunoblotting.
  
  
  RESULTS
  The final body weight, gastrocnemius weight, length and width were similar among groups. Tone of muscle was higher in exercised animals. Myostatin was higher in MNU-treated groups. Echogenicity of muscle and fibrous tissue in group IV was higher than in other groups (p<0.05). Echogenicity of fibrous tissue was higher than echogenicity of muscle in all groups.
  
  
  CONCLUSIONS
  Our results showed that muscle ultrasonography is a useful tool to identify alterations in muscle structure. More studies are necessary for researchers to understand the influence of fat location in muscle ultrasonographic imaging.
authors.affiliation: Department of Veterinary Sciences, University of Trás-os-Montes and Alto Douro, 5001-801 Vila Real, Portugal. mginja@utad.pt.
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Faustino-Rocha
authors.forename: Paula A
authors.initials: PA
authors.lastname: Oliveira
authors.forename: José Alberto
authors.initials: JA
authors.lastname: Duarte
authors.forename: Rita
authors.initials: R
authors.lastname: Ferreira
authors.forename: Mário
authors.initials: M
authors.lastname: Ginja
mesh_terms: D000818:Animals; D021461:Animals, Outbred Strains; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000150:complications / Q000000981:diagnostic imaging*; D008770:Methylnitrosourea; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D009133:Muscular Atrophy / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D055435:Myostatin / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014463:Ultrasonography
chemical_list: C525913:Mstn protein, rat; D055435:Myostatin; D008770:Methylnitrosourea
keywords: MNU; Ultrasonography; exercise; gastrocnemius muscle; mammary tumor; rat