A light and scanning electron microscope study of epithelial thickenings and rete ridges in the adult hamster cheek pouch

Structural and ultrastructural studies on the developing vomeronasal sensory epithelium in the grass snake Natrix natrix (Squamata: Colubroidea)

The sensory olfactory epithelium and the vomeronasal sensory epithelium (VSE) are characterized by continuous turnover of the receptor cells during postnatal life and are capable of regeneration after injury. The VSE, like the entire vomeronasal organ, is generally well developed in squamates and is crucial for detection of pheromones and prey odors. Despite the numerous studies on embryonic development of the VSE in squamates, especially in snakes, an ultrastructural analysis, as far as we know, has never been performed. Therefore, we investigated the embryology of the VSE of the grass snake (Natrix natrix) using electron microscopy (SEM and TEM) and light microscopy. As was shown for adult snakes, the hypertrophied ophidian VSE may provide great resolution of changes in neuron morphology located at various epithelial levels. The results of this study suggest that different populations of stem/progenitor cells occur at the base of the ophidian VSE during embryonic development. One of them may be radial glia-like cells, described previously in mouse. The various structure and ultrastructure of neurons located at different parts of the VSE provide evidence for neuronal maturation and aging. Based on these results, a few nonmutually exclusive hypotheses explaining the formation of the peculiar columnar organization of the VSE in snakes were proposed.

Sunitinib Improves Some Clinical Aspects and Reverts DMBA-Induced Hyperplasic Lesions in Hamster Buccal Pouch

Oral squamous cell carcinoma (OSCC) is a public health problem. The hamster buccal pouch model is ideal for analyzing the development of OSCC. This research analysed the effects of sunitinib (tyrosine kinase inhibitor) in precancerous lesions induced by 7,12-dimethylbenz(a)anthracene (DMBA) in this model. Thirty-four male hamsters, divided into six groups: control—C (n = 7), acetone—A (n = 12), carbamide peroxide—CP (n = 5 ), acetone and CP—A+CP (n = 8), 1% DMBA in acetone and CP—DA+CP (n = 6), and 1% DMBA in acetone and CP and 4-week treatment with sunitinib—DA+CP+S (n = 7). The aspects evaluated were anatomopathological features (peribuccal area, paws, nose, and fur), histological sections of the hamster buccal pouches (qualitatively analyzed), epithelium thickness, and the rete ridge density (estimated). Sunitinib was unable to attenuate the decrease in weight gain induced by DMBA; no increase in volume was detected in the pouch and/or ulceration, observed in 43% of the animals in the DA+CP group. DA+CP groups presented a significant increase in rete ridge density compared to the control groups (P < 0.01) which was reverted by sunitinib in the DA+CP+S group. Sunitinib seems to have important benefits in early stage carcinogenesis and may be useful in chemoprevention.

The effect of intraperitoneal N-methyl-N-nitrosourea on hamster palatal gingiva and intermolar mucosa

Fifty 4- to 6-week-old male random-bred golden hamsters were injected intraperitoneally with a weight-related dose (12.5 mg/kg body weight) of N-methyl-N-nitrosourea (NMU) three times a week for 4 weeks. Groups of seven animals were killed 10, 16 and 22 weeks after the first injection. The palatal gingiva from six animals and the intermolar mucosa from 21 animals was examined. Seven male age-matched untreated control animals were killed at each period. Although all NMU-treated hamsters showed dysplastic and neoplastic changes similar to those in human oral squamous-cell carcinoma, other changes such as acantholytic dyskeratosis, invading cysts, duct-like structures and basaloid islands and cords were not. The extent and severity of the changes increased with time so that by 22 weeks there was extensive involvement of the palatal bone and marrow spaces, the molar periodontal ligament and the greater palatine neurovascular bundle by neoplastic epithelium. The invading epithelium was derived from the junctional, crevicular and palatal gingival and intermolar epithelium. The latent period for the crevicular and junctional epithelia was shorter than that for the palatal gingival and intermolar epithelium. The invasive changes from the latter epithelium were often preceded by exophytic changes such as epithelial projections, papillae and papillomas. Such changes were infrequent for the gingival, crevicular and junctional epithelia. The study shows that intraperitoneal NMU acts as a complete carcinogen on the palatal gingival and intermolar epithelium in hamsters.

Effects of chronic Candida albicans in the hamster cheek pouch

Sixty-four adult male hamsters had a suspension of either C. albicans (UO1) or C. albicans (ATCC 10261) placed in their cheek pouches once a week for up to 9 months. Four hamsters from both experimental groups, along with two untreated control hamsters, were killed at monthly intervals after the initial inoculation. Sections taken from the hamsters and examined in the light microscope showed that all experimental pouches had some or all of the following localized changes: inflammation and increased vascularity of the connective tissue; epithelial inflammation and microabscesses; hyperkeratosis; and isolated rete ridges similar to those in control pouches. C. albicans, usually the yeast form, was present on the exposed surface and between hyperplastic keratin squames. There was no hyphal invasion of the epithelium. Rather than being a true long-term study of chronic infection by C. albicans, the changes seen were probably the result of repetitive, more short-term responses after multiple inoculations.

A scanning electron microscopic study of rete ridges in the cheek pouch of normal young, adult and aged Syrian hamsters

Cheek pouches were removed from BIO 87.20 male hamsters 4 weeks, 8 months or 18 months of age. One pouch from each animal was routinely processed for light microscopy. The epithelium and connective tissue of the remaining pouches were separated with EDTA and routinely processed for scanning electron microscopy. Two types of rete ridge were found: simple, consisting of a single epithelial ridge or blunt projection and complex, made up of multiple interconnecting ridges. The simple type predominated at 4 weeks (90%) but the complex type predominated at 8 (58%) and 18 months (73%). Although the 8- and 18-month pouches were significantly larger than the 4-week ones, the total number of rete ridges was similar at all ages. This, taken in association with the shift in type with age, suggests that the simple rete ridges develop into the complex ones. With increasing age more of the complex rete ridges took on the characteristics of touch domes. These changes in the shape of the rete ridges with age need to be taken into account in studies on experimentally altered cheek pouches so that they are not mistaken as pathological changes.