Strength training prior to muscle injury potentiates low-level laser therapy (LLLT)-induced muscle regeneration.

We evaluated whether strength training (ST) performed prior to skeletal muscle cryolesion would act as a preconditioning, improving skeletal muscle regeneration and responsiveness to low-level laser therapy (LLLT). Wistar rats were randomly assigned into non-exercised (NE), NE plus muscle lesion (NE + LE), NE + LE plus LLLT (NE + LE + LLLT), strength training (ST), ST + LE, and ST + LE + LLLT. The animals performed 10 weeks of ST (climbing ladder; 3× week; 80% overload). Forty-eight hours after the last ST session, tibialis anterior (TA) cryolesion was induced and LLLT (InGaAlP, 660 nm, 0.035 W, 4.9 J/cm2/point, 3 points, spot light 0.028 cm2, 14 J/cm2) initiated and conducted daily for 14 consecutive days. The difference between intergroups was assessed using Student's t test and intragroups by two-way analysis of variance. Cryolesion induced massive muscle degeneration associated with inflammatory infiltrate. Prior ST improved skeletal regeneration 14-days after cryolesion and potentiated the regenerative response to LLLT. Cryolesion induced increased TNF-α levels in both NE + LE and ST + LE groups. Both isolated ST and LLLT reduced TNF-α to control group levels; however, prior ST potentiated LLLT response. Both isolated ST and LLLT increased IL-10 levels with no additional effect. In contrast, increased TA IL-6 levels were restricted to ST and ST + LE + LLLT groups. TA myogenin mRNA levels were not changed by neither prior ST or ST + LLLT. Both prior ST and LLLT therapies increased MyoD mRNA levels and, interestingly, combined therapies potentiated this response. Myf5 mRNA levels were increased only in ST groups. Taken together, our data provides evidences for prior ST potentiating LLLT efficacy in promoting skeletal muscle regeneration.

Effects of neonatal castration and androgenization on sexual dimorphism in bone, leptin and corticosterone secretion.

This study investigated the role of neonatal sex steroids in rats on sexual dimorphism in bone, as well as on leptin and corticosterone concentrations throughout the lifespan. Castration of males and androgenization of females were used as models to investigate the role of sex steroids shortly after birth. Newborn Wistar rats were divided into four groups, two male groups and two female groups. Male pups were cryoanesthetized and submitted to castration or sham-operation procedures within 24 h after birth. Female pups received a subcutaneous dose of testosterone propionate (100 µg) or vehicle. Rats were euthanized at 20, 40, or 120 postnatal days. Body weight was also measured at 20, 40, and 120 days of age, and blood samples and femurs were collected. The length and thickness of the femurs were measured and the areal bone mineral density (areal BMD) was determined by dual-energy X-ray absorptiometry (DEXA). Biomechanical three-point bending testing was used to evaluate bone breaking strength, energy to fracture, and extrinsic stiffness. Blood samples were submitted to a biochemical assay to estimate calcium, phosphorus, alkaline phosphatase, leptin, and corticosterone levels. Weight gain, areal BMD and bone biomechanical properties increased rapidly with respect to age in all groups. In control animals, skeletal sexual dimorphism, leptin concentration, and dimorphic corticosterone concentration patterns were evident after puberty. However, androgen treatment induced changes in growth, areal BMD, and bone mass properties in neonatal animals. In addition, neonatally-castrated males had bone development and mechanical properties similar to those of control females. These results suggest that the exposure to neonatal androgens may represent at least one covariate that mediates dimorphic variation in leptin and corticosterone secretions. The study indicates that manipulation of the androgen environment during the critical period of sexual differentiation of the brain causes long-lasting changes in bone development, as well as serum leptin and corticosterone concentrations. In addition, this study provides useful models for the investigation of bone disorders induced by hypothalamic hypogonadism.

Efeitos da timectomia neonatal sobre o dimorfismo sexual esquelético e concentrações plasmáticas de leptina em ratos / Effects of neonatal thymectomy on skeletal sexual dimorphism and plasma leptin concentration in rats

O presente trabalho avaliou os efeitos da timectomia neonatal sobre o dimorfismo sexual esquelético e qualidade óssea, bem como, determinou se as alterações causadas por este modelo podem influenciar as secreções de leptina em animais pré- púberes, púberes e adultos-jovens. Para isso, Ratos Wistar, neonatos foram divididos em grupo controle e grupo timectomizado, de ambos os sexos, totalizando quatro grupos experimentais (n = 06-08 por grupo). Os animais foram timectomizados no terceiro dia pós-natal. Os grupos foram eutanasiados aos 20, 40 e 120 dias pós-natais, que correspondem, respectivamente, às fases pré-púbere, púbere e adultos-jovens. Foram coletados sangue e ambos os fêmures. Os fêmures esquerdos foram usados para determinação do comprimento, realizado com auxílio de um paquímetro. Avaliação das propriedades biofísicas do fêmur foram determinadas por meio do teste de densitometria óssea, e o comportamento biomecânico avaliado por meio do o ensaio mecânico de compressão da cabeça do fêmur. Os fêmures direitos foram usados para avaliação histométrica da base do colo femoral. As amostras sanguíneas foram utilizadas para determinar as concentrações plasmáticas de leptina. Em conjunto os dados do presente trabalho demonstram que em animais controle, as diferenças sexualmente dimórficas em relação ao desenvolvimento corporal e esquelético, bem como na secreção de leptina, existem durante o período pré-púbere, mas são consolidadas após a puberdade. Demonstram ainda, que a timectomia neonatal causa alterações sexo- e tempo-dependentes no desenvolvimento corporal, propriedades estruturais e biomecânicas do tecido ósseo, além de modular a secreção plasmática de leptina, sugerindo uma comunicação bidirecional entre o Timo e esse hormônio. Estes resultados fornecem uma nova visão sobre a complexidade dinâmica da homeostase da massa óssea e sugerem que a presença do Timo durante o período perinatal é importante para o desenvolvimento esquelético normal.

This study evaluates the effects of neonatal thymectomy on skeletal sexual dimorphism and bone quality. In addition, we verified whether the changes caused by this model may influence the leptin secretion in prepubertal, puberty and adulthood. For this, Wistar, newborns were divided into control group and thymectomized group, of both sexes, totaling four experimental groups (n = 08 per group). The animals were thymectomized at the third postnatal day. The groups were euthanized at 20, 40 and 120 days’ postnatal life, which correspond respectively to the prepuberty, puberty and adulthood periods. Blood and both femurs were collected. The left femurs were used to determine the length, conducted with the aid of a caliper. The biophysical properties of the femur were evaluated using dual-energy x-ray absorptiometry, and the biomechanical properties assessed by the mechanical compression of the femoral head. In the right femurs, the base of the femoral neck was used to quantitative histometric analysis. The blood samples were used to determine plasma concentrations of leptin. Taken together, the data of the present study demonstrates that control animals, sexually dimorphic differences in relation to body and skeletal development as well as the secretion of leptin, there during the prepubertal period but are consolidated after puberty. Demonstrate further that the neonatal thymectomy causes changes sex- and time-dependent on body development, structural and biomechanical properties of bone tissue, as well as plasma leptin secretion, suggesting a cross-talk between Thymus and this hormone. These findings provide new insight into the dynamic complexity of bone homeostasis and suggest that the presence of Thymus during the perinatal period is important for normal skeletal development.

Efeitos da timectomia neonatal sobre o dimorfismo sexual esquelético e concentrações plasmáticas de leptina em ratos / Effects of neonatal thymectomy on skeletal sexual dimorphism and plasma leptin concentration in rats

O presente trabalho avaliou os efeitos da timectomia neonatal sobre o dimorfismo sexual esquelético e qualidade óssea, bem como, determinou se as alterações causadas por este modelo podem influenciar as secreções de leptina em animais pré- púberes, púberes e adultos-jovens. Para isso, Ratos Wistar, neonatos foram divididos em grupo controle e grupo timectomizado, de ambos os sexos, totalizando quatro grupos experimentais (n = 06-08 por grupo). Os animais foram timectomizados no terceiro dia pós-natal. Os grupos foram eutanasiados aos 20, 40 e 120 dias pós-natais, que correspondem, respectivamente, às fases pré-púbere, púbere e adultos-jovens. Foram coletados sangue e ambos os fêmures. Os fêmures esquerdos foram usados para determinação do comprimento, realizado com auxílio de um paquímetro. Avaliação das propriedades biofísicas do fêmur foram determinadas por meio do teste de densitometria óssea, e o comportamento biomecânico avaliado por meio do o ensaio mecânico de compressão da cabeça do fêmur. Os fêmures direitos foram usados para avaliação histométrica da base do colo femoral. As amostras sanguíneas foram utilizadas para determinar as concentrações plasmáticas de leptina. Em conjunto os dados do presente trabalho demonstram que em animais controle, as diferenças sexualmente dimórficas em relação ao desenvolvimento corporal e esquelético, bem como na secreção de leptina, existem durante o período pré-púbere, mas são consolidadas após a puberdade. Demonstram ainda, que a timectomia neonatal causa alterações sexo- e tempo-dependentes no desenvolvimento corporal, propriedades estruturais e biomecânicas do tecido ósseo, além de modular a secreção plasmática de leptina, sugerindo uma comunicação bidirecional entre o Timo e esse hormônio. Estes resultados fornecem uma nova visão sobre a complexidade dinâmica da homeostase da massa óssea e sugerem que a presença do Timo durante o período perinatal é importante para o desenvolvimento esquelético normal

This study evaluates the effects of neonatal thymectomy on skeletal sexual dimorphism and bone quality. In addition, we verified whether the changes caused by this model may influence the leptin secretion in prepubertal, puberty and adulthood. For this, Wistar, newborns were divided into control group and thymectomized group, of both sexes, totaling four experimental groups (n = 08 per group). The animals were thymectomized at the third postnatal day. The groups were euthanized at 20, 40 and 120 days’ postnatal life, which correspond respectively to the prepuberty, puberty and adulthood periods. Blood and both femurs were collected. The left femurs were used to determine the length, conducted with the aid of a caliper. The biophysical properties of the femur were evaluated using dual-energy x-ray absorptiometry, and the biomechanical properties assessed by the mechanical compression of the femoral head. In the right femurs, the base of the femoral neck was used to quantitative histometric analysis. The blood samples were used to determine plasma concentrations of leptin. Taken together, the data of the present study demonstrates that control animals, sexually dimorphic differences in relation to body and skeletal development as well as the secretion of leptin, there during the prepubertal period but are consolidated after puberty. Demonstrate further that the neonatal thymectomy causes changes sex- and time-dependent on body development, structural and biomechanical properties of bone tissue, as well as plasma leptin secretion, suggesting a cross-talk between Thymus and this hormone. These findings provide new insight into the dynamic complexity of bone homeostasis and suggest that the presence of Thymus during the perinatal period is important for normal skeletal development

Efeitos da castração e androgenização neonatal sobre o dimorfismo sexual esquelético e secreção de leptina e corticosterona em ratos / Effects of neonatal castration and androgenization on sexual dimorphism in bone, and leptin and corticosterone secretion

Para estudar os efeitos da castração e androgenização neonatal sobre o dimorfismo sexual esquelético, bem como, secreções de leptina e corticosterona. Ratos Wistar, neonatos foram divididos em quatro grupos do mesmo sexo (n = 06-08 por grupo). Os machos foram castrados ou sham-operados nas primeiras 24h de nascimento. As fêmeas receberam injeções subcutâneas diárias de 100mg de propianato de testosterona em 50μl de óleo de milho, ou somente o veículo durante 05 dias. Os animais foram pesados semanalmente para acompanhar a evolução da massa corporal e eutanasiados aos 20, 40 e 120 dias, onde foram coletados sangue e os fêmures para determinação do comprimento e espessura, realizadas com auxílio de um paquímetro. A densidade mineral óssea areal (DMO areal) foi determinada por meio de um densitômetro de dupla emissão de raios-X e, o ensaio mecânico de flexão foi realizado para a aquisição e cálculo das propriedades estruturais: força máxima, rigidez e tenacidade. As amostras sanguíneas foram utilizadas para determinar as concentrações plasmáticas de cálcio, fósforo e fosfatase alcalina, bem como as concentrações plasmáticas de leptina e corticosterona. Os resultados evidenciam que o ganho de massa corpórea, DMO areal e propriedades biofísicas aumentaram rapidamente com o envelhecimento em todos os grupos, confirmando que em animais controle, o dimorfismo sexual esquelético e o padrão dimórfico de secreção da leptina e corticosterona são evidenciados após a puberdade. No entanto, a exposição neonatal a andrógenos induz alterações no crescimento, com DMO areal e qualidade óssea aumentadas em fêmeas androgenizadas, levando a um padrão masculinizado no desenvolvimento. Por outro lado, machos castrados no período neonatal apresentaram fragilidade óssea, com tenacidade e força máxima reduzidas em todas as fases comparados com machos sham-castrados. Estes resultados sugerem ainda, que a exposição ou ausência de andrógenos no período neonatal pode ser uma das...

To study the effects of neonatal castration and androgenization on sexual dimorphism in bone, and leptin and corticosterone secretion, Wistar rats, newborns, were divided into four groups (n = 06-08 per group) of the same sex. Male pups were cryoanesthetized and castrated or sham/castrated by 24 hours after birth; female pups from separate litters were injected SC with testosterone propionate 100 μg in 50μL corn oil or oil vehicle 50μL during 05 days and were euthanized by 20, 40, and 120 postnatal day. Were collected blood samples, and femurs. The animals were weighed weekly to monitor the evolution of body mass, and the length and thickness of the femurs were performed with aid of a caliper. The Areal Bone Mineral Density (areal BMD) was determinate by Dual-energy X-ray Absorptiometry and, Biomechanical Three-Point Bending Testing; these data were used for the acquisition and calculation of the structural properties: Ultimate Strength, Toughness, and Stiffness. The blood samples were subjected to a biochemical assay to estimate the serum levels of calcium, phosphorus and alkaline phosphatase; and serum leptin and corticosterone concentration. The results showed that weight gain, areal BMD and biomechanical properties increased rapidly with aging in all groups, and confirm that in control animals, skeletal sexual dimorphism, and serum leptin concentration, and a dimorphic pattern in serum corticosterone concentration evidenced after puberty. However, the neonatal exposed to androgen induced changes in growth, areal BMD and bone mass quality in androgenized females, leading to a masculinization pattern in development. On the other hand, neonatally castrated males had the bone development and quality of the mechanical properties similar to those control females. These results suggest that the presence or absence of exposure to neonatal androgen may represent at least one covariate that mediates the dimorphic variation in leptin and corticosterone secretion...