Ethical statement
Animals were housed in a Home Office (UK authority) accredited facility and in compliance with the Animal Scientific Procedure Act 1986 and the European Directive 2010/63/EU. Newcastle University Animal Welfare and Ethic Review Body and the Home Office approved research protocols. The procedure was performed under the United Kingdom Veterinary Surgeon’s Act 1969 with the agreement of the principal investigator and the Home Office.
Animals and husbandry
This report is based on treatment of 258 male mice C3H/HeNHsd (from Harlan Laboratories, UK) involved in a study of the effect of several diets on the formation of liver fibrosis. Animals were aged from 6 to 10 weeks at the start of the study and the first signs of gland inflammation were noted between 18 and 20 weeks of age. In total, 56 mice (21.7 %) developed at least one gland abscess. The mice were housed in Individually Ventilated Cages (580 cm2, 226 mm × 419 mm × 147 mm, Arrowmight, UK), with 20 air cycles per hour. The day-night cycle was 12–12 h and the temperature was maintained at 22+/− 2 °C. During the study, an increasing number of mice presented with inflammation of their preputial glands. Because of the large number of affected animals, and because medical management of similar cases had proved unsuccessful, surgical removal of the gland was proposed.
Surgical procedure and perioperative cares
Anaesthesia was induced with 5 % and maintained with 2.5 % of isoflurane (IsoFlo 100 % w/w Inhalation Vapour, Abbott Laboratories, Maidenhead, UK), in 100 % oxygen. Anaesthesia was maintained for no more than 10 min. Body temperature was maintained with a heat pad set at 38 °C (Homeothermic Blanket system, Harvard Apparatus, Cambridge, UK). Meloxicam (5 mg/g s/c) (Metacam, Boehringer Ingelheim Limited, Bracknell, UK) was administered 10 min prior to surgery for pain relief and enrofloxacin (10 mg/kg s/c)(Baytril 2.5 % solution for injection, Bayer plc, Newbury, UK) as prophylactic antibiotic therapy. The preputial region was prepared for aseptic surgery (http://www.procedureswithcare.org.uk/aseptic-technique-in-rodent-surgery/). A 15 mm transverse skin incision was made cranial to the prepuce using a number 11 scalpel blade. The subcutaneous tissues were gently dissected forward to the prepuce with Metzenbaum scissors and Debakey forceps, without touching the penis. The healthy gland appeared as a flattened circular structure with a cream to light brown colouration (Fig. 1). In contrast the infected gland appeared larger and thin walled with a yellow-red colouration [15]. When a gland was infected, pus was often visible in one lobe of the gland or disseminated throughout. Some glands were embedded in fatty tissue, necessitating its isolation by gentle manipulation with a sterile cotton bud or a swap. Each gland was removed using a hemostat is placed on the ventral side of its duct, followed by cutting proximally with a scalpel blade 11. In animals with abscessation of the gland, adhesions with the skin necessitated very careful dissection before removal. If the gland ruptured during this dissection the surgical wound was thoroughly flushed with sterile saline and an additional dose of enrofloxacin administered at 24 h post-surgery. The skin was closed with polyglactin 910, 4/0 suture (Coated VicrylEthicon, Johnson&Johnson international, Diegrem, Belgium) with an interrupted pattern and skin glue (Indermil xfine, Henkel, Dublin, Ireland) to reinforce the closure (Fig. 2).