Postmenopausal osteoporosis represents a failure of the response by which bone cells adapt bone mass and architecture to be sufficiently strong to withstand loading without fracture. To address why this failure should be associated with oestrogen withdrawal, we investigated the ulna's adaptive response to mechanical loading in adult female mice lacking oestrogen receptor-(ER / ), those lacking oestrogen receptor-(ER / ) and their wild-type littermates. In wild-type mice, short periods of physiologic cyclic compressive loading of the ulna in vivo over a 2-week period stimulates new bone formation. In ER -/-and ER -/-mice this osteogenic response was respectively threefold and twofold less (P<0·05). In vitro, primary cultures of osteoblast-like cells derived from these mice were subjected to a single short period of mechanical strain. Twenty-four hours after strain the number of wild-type cells was 61 25% higher than in unstrained controls (P<0·05), whereas in ER / cells there was no strain-related increase in cell number. However, the strain-related response of ER / cells could be partially rescued by transfection with functional human ER (P<0·05). ER / cells showed a 125 40% increase in cell number following strain. This was significantly greater than in wild types (P<0·05).These data support previous findings that functional ER is required for the full osteogenic response to mechanical loading and particularly the stage of this response, which involves an increase in osteoblast number. ER appears to depress the ER -mediated strain-related increase in osteoblast number in vitro, but in female transgenic mice in vivo the constitutive absence of either ER or ER appears to diminish the osteogenic response to loading.
In dogs with non-perforated ulcers, survey radiography was usually negative whereas ultrasonography and CT frequently enabled detection of the site of the ulcer; in dogs with perforated ulcers, radiography was frequently positive for peritoneal gas and CT was a sensitive modality for both the ulcer and signs of perforation.
An 11-week-old, female, Japanese shiba inu, weighing 1.3 kg, was presented with a history of intermittent regurgitation since birth. An oesophagram showed a partial obstruction of the caudal cervical oesophagus associated with a narrow, transverse tissue band. Following surgical resection, the regurgitation resolved and the dog attained a normal bodyweight. Histological examination revealed focally hyperplastic epithelium with dense fibrous underlying connective tissue forming the band. The diagnosis was a congenital oesophageal stricture.
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