Increased intrinsic stiffness and mineralization in femurs of adult rats after high intensity treadmill running training.

Background: Physical activity plays a tremendous role in determining bone mechanical behavior, which is superimposed to gravidity.

Objective: Compare the geometric and material responses of the rat femur to a high intensity treadmill running training of a relatively short duration, as assessed by 3-point mechanical test.

Methods: Mature male rats (180.

Effect of chronic undernutrition on body mass and mechanical bone quality under normoxic and altitude hypoxic conditions.

Both undernutrition and hypoxia exert a negative influence on both growth pattern and bone mechanical properties in developing rats. The present study explored the effects of chronic food restriction on both variables in growing rats exposed to simulated high-altitude hypoxia. Male rats (n 80) aged 28 d were divided into normoxic (Nx) and hypoxic (Hx) groups.

Structural and Material Mechanical Quality of Femoral Shafts in Rats Exposed to Simulated High Altitude from Infancy to Adulthood.

The growth of the body and bone mass and the mechanical properties of appendicular bone are impaired in immature rats exposed to different simulated high altitudes (SHA) (1850-5450 m) between the 32nd and the 74th days of postnatal life. Now, we report the effects of exposure to 4100 m on the above cited variables in female rats from infancy (age: 1 month) to adulthood (age: 8 months) to define the occurrence of catch up and to establish whether the effects of altitude are transient or permanent. The ex vivo right femur was mechanically tested in three-point bending.

Effect of physical consistency of food on the biomechanical behaviour of the mandible in the growing rat.

This study investigated the effect of a soft diet, given to growing rats, on the biomechanical behaviour of the mandible. Female rats, 30 d of age, received an ordinary diet in the form of pellets (i.e.

Effect of dexamethasone on mandibular bone biomechanics in rats during the growth phase as assessed by bending test and peripheral quantitative computerized tomography.

Long-term glucocorticoid administration to growing rats induces osteopenia and alterations in the biomechanical behavior of the bone. This study was performed to estimate the effects of dexamethasone (DTX), a synthetic steroid with predominant glucocorticoid activity, on the biomechanical properties of the mandible of rats during the growth phase, as assessed by bending test and peripheral quantitative computed tomographic (pQCT) analysis. The data obtained by the two methods will provide more precise information when analyzed together than separately.

Gestational and early postnatal exposure to simulated high altitude does not modify postnatal body mass growth trajectory in the rat.

Postnatal hypoxia blunts body mass growth. It is also known that the quality of the fetal environment can influence the subsequent adult phenotype. The main purpose of the study was to determine whether gestational hypoxia and early postnatal hypoxia are able to blunt growth when the offspring is raised under normoxia.

Static biomechanics in bone from growing rats exposed chronically to simulated high altitudes.

Biomechanical behavior of bone is related to the amount (bone mass) and its architectural distribution, as well as the mechanical quality of bone material. This investigation reports the effects of exposure to different simulated high altitudes (SHA) (1850, 2900, 4100, and 5450 m) on femur biomechanical properties in female growing rats exposed to SHA (22-23 h/d) between the 32° and the 74° days of life. The ex vivo right femur was mechanically tested in three-point bending.

Growth inhibition in rats fed inadequate and incomplete proteins: repercussion on mandibular biomechanics.

This study describes the effects of feeding growing rats with a diet containing inadequate and incomplete proteins on both the morphological and the biomechanical properties of the mandible. Female rats aged 30 d were fed freely with one of two diets, control (CD, 301 Cal/100g) and experimental (ED, 359 Cal/100g). CD was a standard laboratory diet, while ED was a synthetic diet containing cornflower supplemented with vitamins and minerals.

Mechanical testing at the whole-bone level of the femur in immature rats stunted by cornstarch consumption.

Both body weight and somatic muscle forces are the main "mechanical factors" in the determination of bone strength in the "weight-bearing bones". However, other "non-mechanical factors", such as dietary proteins, also exist, which modulate bone physiology. This study was designed to explore the mechanical behavior of the femur in post-weaning female rats stunted by feeding on cornstarch.

Biomechanical properties of the mandible, as assessed by bending test, in rats fed a low-quality protein.

Objective: The present study describes the effects of feeding growing rats with diets containing increasing concentrations of wheat gluten (a low quality protein, G) on both the morphometrical and the biomechanical properties of the mandible.

Design: Female rats were fed one of six diets containing different concentrations (5-30%) of G between the 30th and 90th days of life. Control rats were fed a diet containing 20% casein (C), which allows a normal growth and development of the bone.

Biomechanical properties of the mid-shaft femur in middle-aged hypophysectomized rats as assessed by bending test.

Both stiffness and strength of bones are thought to be controlled by the "bone mechanostat". Its natural stimuli would be the strains of bone tissue (sensed by osteocytes) that are induced by both gravitational forces (body weight) and contraction of regional muscles. Body weight and muscle mass increase with age.

Growth-dependent effects of dietary protein concentration and quality on the biomechanical properties of the diaphyseal rat femur.

Objectives: This study compares the effects of feeding growing rats with increasing concentrations of casein (C) and wheat gluten (G), proteins that show different biological qualities, on the morphometrical and biomechanical properties of the femoral diaphysis.

Materials And Methods: Female rats were fed with one of ten diets containing different concentrations (5-30%) of C and G between the 30th and 90th days of life (Control=C-20%). Biomechanical structural properties of the right femur middiaphysis were estimated using a 3-point bending mechanical test with calculation of some indicators of bone material properties.

Bone mineral density and bone strength from the mandible of chronically protein restricted rats.

Unlabelled: The present investigation was performed to assess the biomechanical repercussion of protein malnutrition imposed on rats between the 26th and 135th days of postnatal life on the mandible, which is not a weight-bearing bone but supports the loads related to the masticatory activity. Female Wistar rats aged 26 d (n = 14) were placed on either a 4%-protein diet (ICN 960254, P4 group) or a 20%-protein diet (ICN 960260, P20 group) and killed 111 d later. Both body weight and length were recorded regularly.

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.

Improved bone status by the beta-blocker propranolol in an animal model of nutritional growth retardation.

The aim of the present research was to study if the beta-blocker propranolol, which is known to increase bone mass, could reverse the adverse skeletal effects of mild chronic food restriction in weanling rats. Male Wistar rats were divided into four groups: control, control+propranolol (CP), nutritional growth retardation (NGR) and nutritional growth retardation+propranolol (NGRP). Control and CP rats were fed freely with the standard diet.

Long-term exposure to hypobaric hypoxia in rat affects femur cross-sectional geometry and bone tissue material properties.

Hypoxia leads to an increase in erythropoiesis, which induces hypertrophy of the erythropoietic marrow and may induce bone resorption. This study investigates the effect of chronic hypobaric hypoxia (simulated high altitude, SHA) on the biomechanics of rat femurs by mechanical tests of diaphyseal stiffness and strength and calculation of some indicators of bone material properties. Adult female rats were exposed to SHA (5500 m, 23.

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.

Mandibular bone stiffening and increased bone calcium mass in rats permanently stunted by hypophysectomy.

Objective: This investigation was designed to obtain information on the changes induced by hypophysectomy on biometric parameters, bone calcium mass, and material and architectural properties during ontogenesis of the rat mandible.

Design: Female Sprague-Dawley rats were hypophysectomised (HX) at 30 days of age. A "basal control group" (BC) was sacrificed on the same day surgery was performed.

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.

Bone status in an animal model of chronic sub-optimal nutrition: a morphometric, densitometric and mechanical study.

In children, inappropriate eating habits can induce a disease known as nutritional dwarfing (ND). Due to the link between nutritional condition and bone growth, the effects induced by a 20 % reduction of food intake on bone competence were assessed in an animal model of ND. Bone status during catch-up growth was also analysed.

The development of bone mass and bone strength in the mandible of the female rat.

The present study provides baseline data for a number of mandibular growth dimensions, specially on bone mass and bone strength, that were collected between the 21st and the 180th days of postnatal life, which are intended as a reference for researchers designing experimental studies, specially on mandibular catch-up growth, and as an aid for clinicians who must evaluate results from published animal studies for validity and potential extrapolation to the human clinical situation. Fifty weanling female Wistar (Hsd:Wi) rats were fed ad libitum a diet previously shown to allow normal, undeformed mandibular growth. Five of them were randomly selected at different times between 21 and 180 d of life.

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.

Effect of protein-energy malnutrition in early life on the dimensions and bone quality of the adult rat mandible.

Morphological and biomechanical features of the mandible are negatively affected by protein-energy malnutrition, whose effects are apparently dependent on the time of life of application. The aim here was to investigate, in neonatal rats nursed by dams put on a protein-free diet to depress milk production and thus create a state of protein-energy malnutrition in the offspring, subsequent growth and long-term effects by analyzing mandibular dimensions and bone quality in adulthood. Pregnant Wistar rats were fed a 20% protein diet (control) or a protein-free diet (malnourished) to obtain normal or subnormal milk production, respectively.