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Fibrous dysplasia has been regarded as a developmental skeletal disorder characterized by replacement of normal bone with benign cellular fibrous connective tissue. It has now become evident that fibrous dysplasia is a genetic disease caused by somatic activating mutation of the Gsα subunit of G protein-coupled receptor resulting in upregulation of cAMP. This leads to defects in differentiation of osteoblasts with subsequent production of abnormal bone in an abundant fibrous stroma. In addition there is an increased production of IL-6 by mutated stromal fibrous dysplastic cells that induce osteoclastic bone resorption.

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Nine cases with glandular odontogenic cysts (GOC's) are presented bringing the total number reported in the literature to 54. Our study confirmed that most GOC's occur in the mandible, whereas maxillary lesions present only in the globulo-maxillary region. The radiological features were found to be non-distinctive and presented as well-defined radiolucencies with uni- and multilocular appearances. Most of the mandibular GOC's were unilocular, involved the symphysis region and only one extended into the ramus. All GOC's larger than 6 cm in diameter showed perforated margins radiologically. Our two multilocular GOC's demonstrated microscopic features supporting their infiltrative radiological appearance. The invasive clinical and radiological features of GOC support the notion of a possible histo-pathologic overlap between GOC and low-grade central mucoepidermoid carcinoma of the jaw.

Longitudinal studies have revealed how variation in resource use within consumer populations can impact their dynamics and functional significance in communities. Here, we investigate multi-decadal diet variations within individuals of a keystone megaherbivore species, the African elephant (Loxodonta africana), using serial stable isotope analysis of tusks from the Kruger National Park, South Africa. These records, representing the longest continuous diet histories documented for any extant species, reveal extensive seasonal and annual variations in isotopic-and hence dietary-niches of individuals, but little variation between them. Lack of niche distinction across individuals contrasts several recent studies, which found relatively high levels of individual niche specialization in various taxa. Our result is consistent with theory that individual mammal herbivores are nutritionally constrained to maintain broad diet niches. Individual diet specialization would also be a costly strategy for large-bodied taxa foraging over wide areas in spatio-temporally heterogeneous environments. High levels of within-individual diet variability occurred within and across seasons, and persisted despite an overall increase in inferred C 4 grass consumption through the twentieth century. We suggest that switching between C 3 browsing and C 4 grazing over extended time scales facilitates elephant survival through environmental change, and could even allow recovery of overused resources.

Mutations in the p53 gene have been reported in head and neck carcinomas. We determined the p53 mutation profile in 55 oral squamous cell carcinomas (OSCCs) from a black African population sample. DNA from all the patients were investigated using PCR amplification of the p53 gene (exons 5–9), followed by heteroduplex single‐stranded conformational polymorphism (HEX‐SSCP) analysis on the PCR products. Direct sequencing was performed on cases where mutations were identified. The results showed mutations in 13 of 55 (23.6%) tumours. Eleven of 13 (85%) were single base pair substitutions (9 transitions and 2 transversions), and 2 were deletions. Two novel mutations were identified: a large 63‐base pair deletion, and a single base pair substitution. The mutations in our study occurred outside the head and neck tumour hot spot region (codons 238–248). Hum Mutat 11:39–44, 1998. © 1998 Wiley‐Liss, Inc.

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