Mandibular biomechanical behavior of rats submitted to chronic intermittent or continuous hypoxia and periodontitis.

Background: The aim of this study was to investigate the effects of exposure to continuous (CH) and intermittent (IH) hypoxia on biomechanical properties of the mandible and periodontal tissue of animals submitted to experimental periodontitis (EP) when applying loads in a hypoxic environment.

Methods: Adult female Wistar rats were exposed during 90 days to IH or CH (simulated high altitude of 4200 m above sea level). Fourteen days prior to the euthanasia, EP was induced to half of the animals of each group.

The Process of Acclimation to Chronic Hypoxia Leads to Submandibular Gland and Periodontal Alterations: An Insight on the Role of Inflammatory Mediators.

The exposition to hypoxia is a stressful stimulus, and the organism develops acclimation mechanisms to ensure homeostasis, but if this fails, it leads to the development of pathological processes. Considering the large number of people under hypoxic conditions, it is of utmost importance to study the mechanisms implicated in hypoxic acclimation in oral tissues and the possible alteration of some important inflammatory markers that regulate salivary and periodontal function. It is the aim of the present study to analyze submandibular (SMG) and periodontal status of animals chronically exposed to continuous (CCH) or intermittent (CIH) hypoxia in order to elucidate the underlying molecular mechanisms that may lead to hypoxic acclimation.

Changes in PGE2 signaling after submandibulectomy alter post-tooth extraction socket healing.

Saliva is very important to oral health, and a salivary deficit has been shown to bring serious problems to oral health. There is scant information about the mechanisms through which salivary glands participate in post-tooth extraction socket healing. Therefore, the aim of the present study was to investigate the effect of submandibulectomy (SMx), consisting of the ablation of submandibular and sublingual glands (SMG and SLG, respectively), on PGE signaling and other bone regulatory molecules, such as OPG and RANKL, involved in tooth extraction socket healing.

Deleterious effect of chronic continuous hypoxia on oral health.

Objective: To evaluate the effect of chronic continuous hypoxia (CCH) in alveolar bone and its correlation with the inflammatory markers which play a key role in the development of periodontitis.

Material And Methods: Wistar rats were exposed to CCH (600mbar, 3 months). Macroscopic and histological analyses of alveolar bone were performed, together with measurement of oxidative stress and inflammatory parameters in gums and submandibular glands (SMG).

Chronic lead poisoning magnifies bone detrimental effects in an ovariectomized rat model of postmenopausal osteoporosis.

Lead (Pb) is a persistent environmental contaminant that is mainly stored in bones being an important source of endogenous lead exposure during periods of increased bone resorption as occurs in menopause. As no evidence exists of which bone biomechanical properties are impaired in those elderly women who had been exposed to Pb during their lifetime, the aim of the present study is to discern whether chronic lead poisoning magnifies the deterioration of bone biology that occurs in later stages of life. We investigated the effect of Pb in the femora of ovariectomized (OVX) female Wistar rats who had been intoxicated with 1000 ppm of Pb acetate in drinking water for 8 months.

Lead intoxication under environmental hypoxia impairs oral health.

We have reported that chronic lead intoxication under hypoxic environment induces alveolar bone loss that can lead to periodontal damage with the subsequent loss of teeth. The aim of the present study was to assess the modification of oral inflammatory parameters involved in the pathogenesis of periodontitis in the same experimental model. In gingival tissue, hypoxia increased inducible nitric oxid synthase (iNOS) activity (p < .

Alveolar bone loss associated to periodontal disease in lead intoxicated rats under environmental hypoxia.

Previously reported studies from this laboratory revealed that rats chronically intoxicated with lead (Pb) under hypoxic conditions (HX) impaired growth parameters and induced damages on femoral and mandibular bones predisposing to fractures. We also described periodontal inflammatory processes under such experimental conditions. Periodontitis is characterised by inflammation of supporting tissues of the teeth that result in alveolar bone loss.

Lead bone toxicity in growing rats exposed to chronic intermittent hypoxia.

Lead chronic intoxication under hypoxic conditions revealed growth retardation in growing rats and damages on femoral and mandibular bones that predispose to fractures. These findings aimed us to investigate if bone material and geometric properties, bone mass in terms of histomorphometry or antioxidant capacity are also impaired in such experimental model. Combined treatments significantly reduced hemimandible cross sectional geometry and intrinsic stiffness (-16% and -34%); tibia and hemimandible bone volume (-45% and -40%) and growth plate cartilage thickness (-19%).

Effects of lead exposure on growth and bone biology in growing rats exposed to simulated high altitude.

The existence of children living at high altitude suffering from lead (Pb) poisoning prompted us to investigate the long term effects of this pollutant on growth and bone biology in growing rats maintained at simulated high altitude (SHA). Pb and hypoxia (HX) significantly reduced body weight (-9.4 % and -24 %; p < 0.

Aluminum bone toxicity in immature rats exposed to simulated high altitude.

Aluminum (Al) is an element to which humans are widely exposed. Chronic administration induces a negative effect on bone tissue, affecting collagen synthesis and matrix mineralization. Its toxic effects are cumulative.

Biomechanical performance of diaphyseal shafts and bone tissue of femurs from hypothyroid rats.

The bone changes in hypothyroidism are characterized by a low bone turnover with a reduced osteoid apposition and bone mineralization rate, and a decreased osteoclastic resorption in cortical bone. These changes could affect the mechanical performance of bone. The evaluation of such changes was the object of the present investigation.

Permanent reduction of mandibular size and bone stiffness induced in post-weaning rats by cyclophosphamide.

It has been previously reported that several doses of cyclophosphamide (CPA) reduce body weight gain, diaphyseal torsional strength and longitudinal femoral growth in the growing rat. The present study was thus designed to estimate both the initial and the possible long-term effects of CPA treatment, by analyzing mandibular dimensions and biomechanical performance of the bone in adulthood in rats treated with the drug around weaning. Female Sprague-Dawley rats (N=20), 26 d of age, received 100mg/kg of CPA by the intraperitoneal route during days 0, 7 and 21 of the experimental period.

Evidence from catch-up growth and hoarding behavior of rats that exposure to hypobaric air lowers the body-mass set point.

The depression of body growth rate and the reduction of body mass for chronological age and gender in growing experimental animals exposed to hypobaric air (simulated high altitude = SHA) have been associated with hypophagia because of reduced appetite. Catch-up growth during protein recovery after a short period of protein restriction only occurs if food intake becomes super-normal, which should not be possible under hypoxic conditions if the set-point for appetite is adjusted by the level of SHA. The present investigation was designed to test the hypothesis that growth retardation during exposure to SHA is due to an alteration of the neural mechanism for setting body mass size rather than a primary alteration of the central set-point for appetite.

Enhanced erythropoietin production during hypobaric hypoxia in mice under treatments to keep the erythrocyte mass from rising: implications for the adaptive role of polycythemia.

Stress erythropoiesis is usually considered as a compensatory effort to counteract tissue hypoxia. Its homeostatic importance in anemic hypoxia has not been questioned, but researchers, clinicians, and mountain climbers have had second thoughts on polycythemia as to its appropriateness for hypoxic or altitude hypoxia (HA). Therefore, polycythemia, one of the responses to HA seen in nongenetically adapted mammals, could or could not be considered beneficial.

Enhanced hypoxia-stimulated erythropoietin production in mice with depression of erythropoiesis induced by hyperoxia.

Current evidence suggests that a modulatory action on O(2)-dependent EPO secretion is exerted by the erythroid/precursor cell population in the erythropoietic organs through a negative feedback system. The hypothesis is based on studies of stimulated-EPO secretion performed in mice in whom the erythropoietic rates were either enhanced or depressed in the presence of normal plasma EPO half-lives. Since erythropoietic depression was elicited by cyclophosphamide administration, which could have altered EPO production directly, the aim of the present investigation was to estimate hypoxia-stimulated EPO secretion in a mouse model of functional depressed erythropoiesis induced by exposure to normobaric hyperoxia.

Failure of polycythemia-induced increase in arterial oxygen content to suppress the anorexic effect of simulated high altitude in the adult rat.

The anorexic effect of exposure to high altitude may be related to the reduction in the arterial oxygen content (Ca(O2)) induced by hypoxemia and possibly the associated decreased convective oxygen transport (COT). This study was then performed to evaluate the effects of either transfusion-induced polycythemia or previous acclimation to hypobaria with endogenously induced polycythemia on the anorexic effect of simulated high altitude (SHA) in adult female rats. Food consumption, expressed in g/d/100 g body weight, was reduced by 40% in rats exposed to 506 mbar for 4 d, as compared to control rats maintained in room air.