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. Both diets had the same physical characteristics. Control (C) and experimental (E) animals were divided into 4 groups of 10 animals each. C40 and E40 rats were fed CD and ED, respectively, for 40 d; C105 were fed the CD for 105 d; and E105 were fed the ED for 40 d and then the CD for the remainder of the experimental period (65 d). Mandibular growth was estimated directly on excised and cleaned bones by taking measurements between anatomical points. Mechanical properties of the right hemimandible were estimated by using a 3-point bending test to estimate the structural properties of the bone. Geometric properties of both the entire bone and the cross-section were determined. Bone material properties were calculated from structural and geometric properties. The left hemimandibles were ashed and the ash weight obtained. Rats fed the ED failed to achieve normal body weight gain. Complete catch-up was observed at the end of nutritional rehabilitation. Mandibular weight and length were negatively affected by the ED, as were the cross-sectional area, the mineralized cortical area, and the cross-sectional moment of inertia. All of these parameters showed incomplete catch-up. The structural bone mechanical properties indicative of strength and stiffness were negatively affected. Intrinsic material properties, as assessed by the modulus of elasticity and maximal elastic stress, were within normal values. In summary, the experimental bone was weaker than the control and structurally incompetent. The bone considered was smaller than the control bone, showing a significant reduction in the cross-sectional area and the moment of inertia. However, material properties as well as the ash fraction and degree of mineralization were similar in E and C bones. Therefore, the E bone was weaker than the C bone because of its smaller bone mass, which appears to have been negatively influenced by the ED in relation to its effects on overall body massFil: Bozzini, Clarisa. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina;Fil: Champin, Graciela Monica. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina;Fil: Bozzini, Carlos Eduardo Jose. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina;Fil: Alippi, Rosa Maria. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina

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. Hypobaric hypoxia was induced in simulated high altitude (SHA) chambers in which air was maintained at 380 mmHg (5450 m). Mature Sprague-Dawley rats of both sexes were divided in normoxic (NX) and hypoxic (HX) groups and, in the case of the HX group, maintained for 1 month at 5450 m. Mating was then allowed under NX or HX conditions. Offspring were NX-NX, NX-HX, HX-HX, or HX-NX: the first term indicates NX or HX during both gestation and the first 30 days of life; the second term indicates NX or HX during postnatal life between days 30 and 133. Body mass (g) was measured periodically and body mass growth rate (BMGR, g/d) was estimated between days 33 and 65 of postnatal life. Results can be summarized as follows: 1) BM was significantly higher in NX than in HX rats at weaning; 2) BMGR was not significantly different between NX-NX and HX-NX rats, and between HX-HX and NX-HX animals; and 3) BMGR was significantly higher in rats living under NX conditions than in those living under HX conditions during postnatal life. Data suggest that that hypobaric hypoxia during gestational and early postnatal development of rats does not alter the regulation of body mass growth in rats when compared to that seen under sea-level conditions.Fil: Bozzini, Carlos Eduardo Jose. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Champin, Graciela Monica. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bozzini, Clarisa. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Alippi, Rosa Maria. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

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 PGE2 signaling and other bone regulatory molecules, such as OPG and RANKL, involved in tooth extraction socket healing. Male Wistar rats, 70 g body weight, were assigned to an experimental (subjected to SMx) or a control group (sham operated). One week later, the animals in both groups underwent bilateral extraction of the first mandibular molars. The effect of SMx on different stages of socket healing after tooth extraction (7, 14, and 30 days) was studied by evaluating some parameters of inflammation, including PGE2 and its receptors, and of bone metabolism, as well as by performing bone biomechanical studies. SMx increased TNFα and PGE2 content as well as cyclooxygenase-II (COX-II) expression in tooth socket tissue at almost all the studied time points. SMx also had an effect on mRNA expression of PGE2 receptors at the different time points, but did not significantly alter osteoprotegerin (OPG) and RANKL mRNA expression at any of the studied time points. In addition, an increase in bone mass density was observed in SMx rats compared with matched controls, and the structural and mechanical bone properties of the mandibular socket bone were also affected by SMx. Our results suggest that the SMG/SLG complex regulates cellular activation and differentiation by modulating the production of molecules intervening in tooth extraction socket repair, including the PGE2 signaling system, which would therefore account for the higher density and resistance of the newly formed bone in SMx rat.Fil: Mohn, Claudia Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Troncoso, Gastón Rodolfo. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Bozzini, Clarisa. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Conti, María Inés. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Fernández Solari, José Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Elverdín, Juan Carlos. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin

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

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 (180.0±30 g) were assigned (7 rats/group) to no exercise (NE) or treadmill exercise (EX). After preconditioning period, the running speed was set at 45 cm.seg−1 during 2 wks, frequency 5 d/wk, 2-hour sessions/day. Body weight and weight of the crural quadriceps were registered at euthanasia. The right femur was mechanically tested through 3-point bending. The left femur was ashed to estimate bone mineral content. Geometric and material bone properties were estimated directly or calculated by appropriate equations. RESULTS: Final body weight was 14% reduced in EX rats, while the crural quadriceps was 47% increased. Yield and fracture loads, and structural stiffness were significantly higher in the EX rats, as were the apparent elastic modulus, the bone mineral content and the degree of mineralization. Geometric properties were not affected. CONCLUSIONS: High intensity treadmill running training increases bone strength and stiffness by increasing material stiffness and mineralization, without affecting geometric bone parameters

Unexpected hypoxia-dependent erythropoietin secretion during experimental conditions not affecting tissue oxygen supply/demand ratio

Unexpected hypoxia-dependent erythropoietin secretion during experimental conditions not affecting tissue oxygen supply/demand ratio. Although a great deal of evidence supports the hypothesis that plasma erythropoietin (EPO) levels of mammals are related to the oxygen supply to the tissues relative to their oxygen needs, several observations millitate against its inherent simplicity. This study presents our results obtained from in vivo experiments that suggest that hypoxia-dependent EPO production can be altered by conditions which apparently do not modify the tissue oxygen supply/demand ratio. Hypoxia-dependent EPO production rate (EPO-PR), derived from plasma EPO titers and plasma EPO half-lives, were estimated in both transfused-polycythemic and normocy-themic mouse models subjected to different treatments. From calculations of the o2 carrying capacity of blood and body o2 consumption, it was assumed that the tissue supply/demand ratios were similar in both experimental and control mice of the same model at the time of induction of EPO production. The following observations were worth noting: (1) EPO-PRs in transfused polycythemic mice whose erythropoietic rates were stimulated by intermittent exposure to hypobaria (0·5 atm, 18 hr/day × 3 weeks), phenylhydrazine administration (40 mg/kg at weekly intervals × 3 weeks) or repeated rh-EPO injections (1500 U/kg 3 times a week × 3 weeks) before transfusion were more than five times higher than in comparabily polycythemic mice whose erythropoietic rates were not stimulated previously; and (2) EPO-PR in response to hypobaric hypoxia was 2·08 times normal in normocythemic mice with cyclophosphamide (100 mg/kg) induced depression of erythropoiesis, and 0·33 times normal in normocythemic mice with rh-EPO (400 U/kg × 2) induced enhancement of erythropoiesis. Although the results obtained in polycythemic mice are difficult to explain, those from normocythemic mice suggest the existence of a feedback mechanism between EPO-responsive cells and EPO-producing cells. Both demonstrate the existence of experimental conditions in which modulation of the hypoxia-dependent expression of the EPO gene appears to occur. This modulation would be dependent on factors other than oxygen

Absorción mineral y retención ósea en un modelo de crecimiento normal: efecto del consumo de una dieta a base de yogur experimental reducido en lactosa que contiene galactooligosacáridos (GOS)

Los GOS son prebióticos naturales de la leche materna que aumentan la absorción de Ca.Pueden generarse in situ por acción enzimática sobre la lactosa durante la manufactura de alimentos lácteos fermentados (yogures), generando un alimento reducido en lactosa. Objetivo: comparar las ventajas de consumir durante el crecimiento normal? yogur que contiene GOS y reducido en lactosa (YE), respecto de un yogur regular sin GOS (YC), ambos desarrollados por el Instituto de Lactología Industrial (UNL/CONICET, Santa Fe). Ratas recién destetadas (n=10/grupo) recibieron durante 30 días una dieta control preparada según AIN?93-G (C), una dieta a base de yogur regular sin GOS (YC) o una dieta a base del yogur reducido en lactosa que contenía GOS (YE). Se determinó: consumo de alimentos, peso corporal (PC), desarrollo de lactobacilos (LB), absorción de Ca y Pi (%AbsCa por el método de balance); pH, nivel de ácidos grasos cadena corta (AGCC) (por HPLC-IR) en el contenido cecal y profundidad de criptas intestinales (CI) (µm); DMO y CMO del esqueleto total (Et), columna lumbar (Cl) y tibia proximal (Tp) (por densitometría); porcentaje de volumen óseo por histología (VO) (%) y cartílagos epi!sario (GPC.Th) e hipertró!co (HpZ.Th) (µm); longitud del fémur (LF) (cm); parámetros de biomecánica como fuerza máxima de fractura (N), módulo de elasticidad (Mpa) y rigidez ósea (N/mm). Se aplicó test de normalidad Shapiro-Wilk y de Levene, y se realizó ANOVA para determinar diferencias entre grupos mediante programa SPSS 19.0® para Windows, considerando signi!cativo un p<0,05. Resultados (media ± DE): el consumo de alimentos y los PCs inicial y !nal no fueron signi!cativamente diferentes entre los grupos. YE mostró mayores valores en el peso del ciego, en el número de colonias de LB (p<0,05); en la concentración de AGCC fundamentalmente butirato y propionato (p<0,001) y en la profundidad de las CI (p<0,0001) y menor pH cecal (p<0,01) tanto de YC como del grupo C. La AbsCa en mg/d como porcentual también fue mayor vs. YC y C (p<0,05), lo cual se acompañó por mayor Abs%Pi. La AbsMg fue mayor que YC sin diferencias respecto de C. El YE mostró niveles de CTX similares a C y menores que YC (p<0,05). YE mayor DMO que YC en Et, Cl y Tp (p<0,05) sin diferencias respecto de dichos valores en el grupo C. El CMO Et fue similar en los 3 grupos. El grupo YE mostró mayor VO que los grupos C y YC (p<0,05) mientras que la LF y contenido de Ca y Pi en fémur fue mayor respecto de YC y sin diferencias respecto de C. YE presentó valores signi!cativamente menores en GPC.Th y HpZ.Th vs. C (p<0,05), pero signi!cativamente mayor que YC (p<0,05). YE mostró mayores valores de todos los parámetros de biomecánica respecto de YC (p<0,01) sin diferencias respecto de C. Conclusión: los datos obtenidos con!rman que esta matriz alimentaria simbiótica sería de utilidad en una etapa de la vida crítica para la adquisición de masa ósea como el crecimiento, fundamentalmente en individuos con intolerancia a la lactosa.Fil: Seijo, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Bonanno, Marina Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Vénica, Claudia Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Lactología Industrial. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Lactología Industrial; ArgentinaFil: Pita Martín de Portela, María Luz. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Bozzini, Clarisa. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Bergamini, Carina Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Lactología Industrial. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Lactología Industrial; ArgentinaFil: Wolf, Irma Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Lactología Industrial. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Lactología Industrial; ArgentinaFil: Perotti, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Lactología Industrial. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Lactología Industrial; ArgentinaFil: Zeni, Susana Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; Argentina4to Congreso Argentino de OsteologíaCiudad de Buenos AiresArgentinaAsociación Argentina de Osteología y Metabolismo Minera

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. Mandibular growth was estimated directly on excised and cleaned bones by taking measurements between anatomical points. Mechanical properties of the right hemimandibles were determined by using a three-point bending mechanical test to obtain a load/deformation curve and estimate the structural properties of the bone. Bone material properties were calculated from structural and geometric properties. The left hemimandibles were ashed and the ash weight obtained. Calcium content was determined by atomic energy absorption. Results were summarised as means SEM. Comparisons between parameters were performed by ANOVA and post-test. Results: None of the G-fed groups could achieve a normal growth performance as compared to the C-fed control group. Like body size, age-related increments in mandibular weight, length, height and area (index of mandibular size) were negatively affected by the G diets, as was the posterior part of the bone (posterior to molar III). The cross-sectional geometry of the mandible (cross-sectional area and rectangular moment of inertia) as well as its structural properties (yielding load, fracture load, and stiffness) were also severely affected by the G diets. However, material properties (Young?s modulus and maximum elastic stress) and calcium concentration in ashes and the degree of mineralisation were unaffected. Conclusions: The differences in strength and stiffness between treated and control rats seemed to be the result of an induced loss of gain in bone growth and mass, in the absence of changes in the quality of the bone mineralised material.Fil: Bozzini, Carlos Eduardo Jose. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Champin, Graciela Monica. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alippi, Rosa Maria. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bozzini, Clarisa. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentin

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. The left femur was ashed at 600°C and the ash weight obtained. Final body weight and structural (loads at yielding and fracture, stiffness, and elastic energy absorption) and architectural (diaphyseal cross-sectional area, cortical area, and cross-sectional moment of inertia) were negatively affected in the animals exposed to the two highest SHA. Material properties of the mineralized tissue (Young's modulus and limit elastic stress) and the degree of mineralization were unaffected. In conclusion, hypoxic bone is weaker than normoxic one because of its smaller bone mass, which appear to have been negatively influenced by SHA in relation to its effects on overall body mass.Fil: Bozzini, Clarisa. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; ArgentinaFil: Champin, Graciela Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad de Buenos Aires; ArgentinaFil: Alippi, Rosa Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad de Buenos Aires; ArgentinaFil: Bozzini, Carlos Eduardo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad de Buenos Aires; Argentin