Spontaneous lesions in the respiratory epithelium of the Syrian golden hamster as seen by scanning electron microscopy

The respiratory epithelium of 8, 12.5, and 17.5-month-old Syrian golden hamsters was investigated by scanning electron microscopy (SEM) and routine light microscopy (LM) of paraplast sections. In selected cases, SEM-specimens were embedded in Epon after SEM evaluation. The samples were cut in semithin sections and examined by light microscopy. The density of ciliated cells in the respiratory ephithelium differs from hamster to hamster. Care must, therefore, be taken when diagnosing simple metaplasia by SEM alone unless a sufficient number of damaged cilia are present. Only one animal (8 months old) exhibited squamous metaplasia of the tracheal mucosa. However, surface polymorphism resembling squamous metaplasia was seen in almost every specimen. The polymorphism was caused by either submucosal calcifications or by cystic changes of hyperthropic submucosal glands. In addition, variously formed aggregations of mucus were seen protruding from duct openings of hypertrophic submucosal gland s. To avoid false positive or negative diagnosis which can occur when screening is done by SEM alone, light-microscopical examination of sections cut from SEM identified lesions appears necessary.