MMTV-trBrca 1 mice display strain-dependent abnormalities in vaginal development

The breast cancer susceptibility gene Brca1 encodes a large multi-functional protein which is implicated as a caretaker of the genome, through its role in regulation of DNA damage response pathways, including apoptosis. Here we show that in mice expressing a dominant-negative Brca1 transgene on a BALB/c background, vaginal entrance remodeling is inhibited, and that the incidence of this phenotype is increased on a p53 +/- genotype. Given that this developmental process is mediated primarily by apoptosis, we hypothesized that disruption of BRCA1 may confer a resistance to apoptosis in normal epithelial cells. Consistent with this, we show that expression of this transgene in vitro leads to resistance to ionizing radiation induced cell killing in mammary epithelial cells. This is the first time that BRCA1 has been implicated in an apoptosis-mediated normal developmental process.

Determining the age of adult wild dogs (Canis lupus dingo, C-l. domesticus and their hybrids). I. Pulp cavity: tooth width ratios

In order to determine the age of adult wild dogs, we compared two methods ( that of Thomson and Rose (TR method) and that of Knowlton and Whittemore (KW method)) of measuring and calculating pulp cavity : tooth width ratios on upper and lower canine teeth from 68 mixed-sex, known-age wild dogs of 9 months to 13 years of age reared at two localities. Although significant relationships ( P = 0.0001) were found between age and pulp cavity ratios by both methods, the TR ratio calculation and measurement showed heteroscedasity in error variance whereas the KW ratios had a more stable error variance and were normally distributed. The KW method also found significant differences between pulp cavity ratios between teeth of the upper and lower jaws ( P < 0.0001) and sex ( P = 0.01) but not geographic origin ( P = 0.1). Regressions and formulae for fitted curves are presented separately for male and female wild dogs. Males show greater variability in pulp cavity decrements with age than do females, suggesting a physiological difference between the sexes. We conclude that the KW method of using pulp cavity as a proportion of tooth width, measured 15 mm from the root tip and averaged over both upper canines, is the more accurate method of estimating the age of adult wild dogs.

Tooth wear: diet analysis and advice

Diet analysis and advice for patients with tooth wear is potentially the most logical intervention to arrest attrition, erosion and abrasion. It is saliva that protects the teeth against corrosion by the acids which soften enamel and make it susceptible to wear. Thus the lifestyles and diet of patients at risk need to be analysed for sources of acid and reasons for lost salivary protection. Medical conditions which put patients at risk of tooth wear are principally: asthma, bulimia nervosa, caffeine addiction, diabetes mellitus, exercise dehydration, functional depression, gastroesophageal reflux in alcoholism, hypertension and syndromes with salivary hypofunction. The sources of acid are various, but loss of salivary protection is the common theme. In healthy young Australians, soft drinks are the main source of acid, and exercise dehydration the main reason for loss of salivary protection. In the medically compromised, diet acids and gastroesophageal reflux are the sources, but medications are the main reasons for lost salivary protection. Diet advice for patients with tooth wear must: promote a healthy lifestyle and diet strategy that conserves the teeth by natural means of salivary stimulation; and address the specific needs of the patients' oral and medical conditions. Individualised, patient-empowering erosion WATCH strategies; on Water, Acid, Taste, Calcium and Health, are urgently required to combat the emerging epidemic of tooth wear currently being experienced in westernised societies.

Eating disorders and oral health: A review of the literature

This article is a review of the recent literature pertaining to the oral sequelae of eating disorders (EDs). Dentists are recognized as being some of the first health care professionals to whom a previously undiagnosed eating disorder patient (EDP) may present. However, despite the prevalence (up to 4 per cent) of such conditions in teenage girls and young adult females, there is relatively little published in the recent literature regarding the oral sequelae of EDs. This compares unfavourably with the attention given recently in the dental literature to conditions such as diabetes mellitus, which have a similar prevalence in the adult population. The incidence of EDs is increasing and it would be expected that dentists who treat patients in the affected age groups would encounter more individuals exhibiting EDs. Most of the reports in the literature concentrate on the obvious clinical features of dental destruction (perimolysis), parotid swelling and biochemical abnormalities particularly related to salivary and pancreatic amylase. However, there is no consistency in explanation of the oral phenomena and epiphenomena seen in EDs. Many EDPs are nutritionally challenged; there is a relative lack of information pertaining to non-dental, oral lesions associated with nutritional deficiencies.

Tetanus in an adult dog originating from a tooth root abscess

A three-and-a-half-year-old entire male Staffordshire Bull Terrier was presented with a cough and difficulty in swallowing. Two days later the dog was re-presented and a diagnosis of tetanus was made. An abscessed canine tooth was extracted and submitted for culture. Clostridium tetani was cultured from the pulp chamber of the tooth. The dog was treated with tetanus antitoxin, antibiotics and supportive care and made a complete recovery.

Microstructure of Pharyngeal Tooth Enameloid in the Parrotfish Scarus rivulatus (Pisces:Scaridae)

The microstructure of parrotfish pharyngeal teeth was examined using scanning electron microscopy to infer possible mechanical properties of the dentition with respect to their function. Parrotfish tooth enameloid is formed from fluorapatite crystals grouped into bundles. In the upper and lower pharyngeal jaw, the majority of the crystal bundles are orientated either perpendicularly or vertically to the enameloid surface. The only exception is in the trailing apical enameloid in which the majority of bundles are orientated perpendicularly or horizontally to the trailing surface. A distinct transition occurs through the middle of the apex between the leading and trailing enameloid in teeth of the lower pharyngeal jaw. This transition appears less distinct in the teeth of the upper pharyngeal jaw. Enameloid microstructure indicates that shear forces predominate at the apex of the teeth. In the remainder of the enameloid, the microstructure indicates that wear is predominant, and the shear forces are of less importance.

Orthodontic tooth movement in the prednisolone-treated rat

Adverse effects of corticosteroids on bone metabolism raise concerns as to whether steroid treatment may influence orthodontic movement. This study examined the effect of prednisolone on orthodontic movement using an established rat model. The corticosteroid treated group (N = 6) was administered prednisolone (1 mg/kg) daily, for a 12-day induction period; the control group (N = 6) received equivalent volumes of saline. On day 12, an orthodontic appliance was placed which exerted 30 g of mesial force to the maxillary first molar. Animals were sacrificed on day 24 and tooth movement was measured. Sagittal sections of the molars were stained with haematoxylin and eosin, and for tartrate-resistant acid phosphatase (TRAP) activity. While there were no significant differences in the magnitude of tooth movement between the 2 groups, steroid-treated rats displayed significantly less root resorption on the compression side and fewer TRAP-positive cells within the PDL space on the same side. This suggests steroid treatment suppressed elastic activity.