Use of zebrafish ( Danio rerio ) embryos as a model to assess effects of mercury on developing skeletal muscle: a morphometric and immunohistochemical study / Uso de embriones de pez cebra ( Danio rerio ) como modelo para evaluar los efectos del mercurio en el desarrollo del músculo esquelético: un estudio morfométrico e inmunohistoquímico

Exposure to mercury in the environment continues to be a significant worldwide concern, especially for developing embryos and fetuses. While extensive research effort has focused on the effects of mercury on the developing nervous system, much less is known concerning adverse effects of mercury on other organ systems, including the development of skeletal muscle. We exposed developing zebrafish embryos to a range of concentrations of mercuric chloride (100 to 400 µg/liter or ppb) and compared them to control embryos (0 µg/L mercuric chloride). Embryos were examined at 48 hours post fertilization (hpf) for morphometry and morphological deformities of skeletal muscle fibers in the trunk and tail. Embryos exposed to 400 ppb mercuric chloride showed decreased trunk and tail areas compared to control embryos. A dose-dependent reduction in muscle fiber length was observed, and exposure to all concentrations of mercuric chloride used in this study resulted in decreased muscle fiber immunohistochemical staining with anti-myosin antibodies. Irregular muscle fiber diameters, twisted muscle fibers, and degenerated muscle fibers were observed in sections of embryos stained with eosin at the higher exposure concentrations. Evidence presented in this study suggests that exposure to even low concentrations of mercuric chloride adversely affects skeletal muscle fiber development or muscle fiber integrity, or both.

La exposición al mercurio en el medio ambiente sigue siendo una preocupación mundial importante, especialmente para el desarrollo de embriones y fetos. Si bien un amplio esfuerzo de investigación se ha centrado en los efectos del mercurio en el sistema nervioso en desarrollo, se sabe mucho menos sobre los efectos adversos en otros sistemas orgánicos, incluido el desarrollo del músculo esquelético. Expusimos embriones de pez cebra en desarrollo a un rango de concentraciones de cloruro de mercurio (100 a 400 mg / l o ppb) y los comparamos con embriones de control (0 mg / L de cloruro de mercurio). Los embriones se examinaron a las 48 horas después de la fertilización (HPF) pararealizar la morfometría y verificar las deformidades morfológicas de las fibras del músculo esquelético en el tronco y la cola. Los embriones expuestos a 400 ppb de cloruro de mercurio mostraron una disminución de las áreas del tronco y la cola en comparación con los embriones de control. Se observó una reducción dependiente de la dosis en la longitud de la fibra muscular, y la exposición a todas las concentraciones de cloruro de mercurio utilizadas en este estudio, dio como resultado una tinción inmunohistoquímica de fibra muscular disminuida con anticuerpos anti-miosina. Se observaron diámetros irregulares de fibras musculares, fibras musculares retorcidas y fibras musculares degeneradas en secciones de embriones teñidos con eosina en las concentraciones de exposición más altas. La evidencia presentada en este estudio sugiere que la exposición incluso a bajas concentraciones de cloruro mercúrico afecta negativamente el desarrollo de la fibra del músculo esquelético o la integridad de la fibra muscular, o ambas.

Rol protector del 17ß-Estradiol y la testosterona en la apoptosis del músculo esquelético / Protective role of 17ß-Estradiol and testosterone in apoptosis of skeletal muscle

La sarcopenia, pérdida de masa y fuerza del músculo esqueléico, es una condición frecuente durante el envejecimiento. Conduce a incapacidad motora resultando en internación y mortalidad. Puesto que los niveles de estrógenos y/o testosterona disminuyen con la edad, la sarcopenia se ha asociado al déficit de estas hormonas. Aunque los mecanismos moleculares involucrados en esta patología no están totalmente dilucidados, existen evidencias indicando que la apoptosis es en parte responsable de la pérdida de miocitos en la adultez. Previamente demostramos que el 17ß-estradiol (E2) inhibe la apoptosis en la línea celular C2C12 de músculo esquelético a través de PI3K/Akt, MAPKs, HSP27 y receptores estrogénicos (ERs) con localización no clásica. Usando siRNAs específicos para silenciar las isoformas del ER, comprobamos que el E2 activa ERK involucrando a ERa, mientras que la activación de p38 MAPK es independiente de ERs. Confirmamos que el E2 puede inhibir la apoptosis a través de las MAPKs en cultivos primarios de músculo esquelético de ratón. Al igual que la E2, la testosterona bloquea la apoptosis. Las alteraciones morfológicas típicas de la apoptosis como fragmentación nuclear, desorganización del citoesqueleto, reorganización/disfunción mitocondrial y liberación de citocromo c, inducidos por H2O2 fueron suprimidas al preincubar las células con testosterona. Se requieren investigaciones adicionales para establecer un paralelismo entre los mecanismos de acción de ambas hormonas, que podrían estar implicados en patologías musculares asociadas a apoptosis. Los datos presentados en este estudio profundizan el conocimiento de las bases moleculares de la sarcopenia relacionada con estados de déficit de hormonas sexuales.

Dopaje genético: transferencia génica y su posible detección molecular / Gene doping: gene transfer and possible molecular detection

El uso de sustancias prohibidas en el deporte con el propósito de incrementar el rendimiento en las competencias deportivas ha provocado que los organismos internacionales en el ámbito deportivo, como el COI y la WADA, traten de tomar medidas en contra del dopaje. Uno de los métodos más recientes de dopaje es el denominado dopaje genético, definido como el uso no terapéutico de genes, elementos genéticos y/o células que tienen la capacidad de incrementar el rendimiento atlético. Ahora bien, el dopaje genético no es fácil de detectar y puede tener consecuencias graves. Es necesario usar técnicas de biología molecular para conocer la diferencia entre un genoma “normal” y un genoma “alterado”, desarrollar métodos analíticos y moleculares en los laboratorios de control del dopaje y trabajar en políticas apropiadas para evitar el uso no terapéutico de genes.

The use of illegal substances in sports to enhance athletic performance during competition has caused international sports organizations such as the COI and WADA to take anti doping measures. A new doping method know as gene doping is defined as [quot ]the non-therapeutic use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance[quot ]. However, gene doping in sports is not easily identified and can cause serious consequences. Molecular biology techniques are needed in order to distinguish the difference between a [quot ]normal[quot ] and an [quot ]altered[quot ] genome. Further, we need to develop new analytic methods and biological molecular techniques in anti-doping laboratories, and design programs that avoid the non therapeutic use of genes.

Postnatal growth and development of skeletal muscle fibers in albino rat. A histological and histochemical study

This work was done to study the postnatal development of the skeletal muscle fibers, which have received little attention in the few last decades, regarding their morphological and histochemical features. The gastocnemius muscle of fifty albino rats of different ages were examined histologically using H and E and Van Gieson's stain to study the morphological features of the developing skeletal muscle. This reveals that the skeletal muscle fibers, since birth, were enclosed by three levels of connective tissue containing blood vessels and nerves, which increase in amount with the advance of age. The nuclei were distributed irregularly throughout the skeletal muscle fiber during the first week of life, and then they take a peripheral position. The transverse striations of the skeletal muscle fibers couldn't be seen until 14[th] days of age of albino rat. The histochemistry of the developing skeletal muscle was investigated using Periodic acid Schiff reagent, Nitroblue tetrazolium technique for the detection of succinic dehydrogenage activity and Tetrazolium reductase linked staining technique for the detection of alpha-glycerophosphate dehydrogenase activity. This revealed that the gastrocnemius muscle displayed increasingly glycolytic fast fibers profile with the advance of age. According to succinic dehydrogenase activity the muscle could be differentiated since birth into 2 types of fibers: Type 1 [slow oxidative fibers] and Type II [fast glycolytic fibers]. From 14[th] days postnatally a third type of fibers, Type III [fast oxidative glycolytic fibers] could be recognized. Differentiation of both types of skeletal muscle fibers [slow and fast twitch] according to alpha-glycorophosphate dehydrogenase enzyme activity could be made from the beginning of the first week of life, whereas the appearance of the third type of fibers[fast oxidative glycolytic fibers] was delayed till the third week of life. As regard the glycogen content, the skeletal muscle fibers in younger age groups contained more glycogen than in adults and differentiation between fast and slow twitch fibers based on this point could be made at the end of the first week postnatally. It is concluded that the skeletal muscle in albino rat was undeveloped at birth and its growth and differentiation was a gradual process including major changes in both morphological and histochemical features

The Union between gracilis and sartorius muscles in leontopithecus: morphofunctional analysis

RESUMEN: El Tití León Dorado, (Leontopithecus rosalia) es un primate (especie de los Tamarinos y Titíes) de la foresta atlántica brasileña en serio riesgo de extinción. Poco se conoce acerca de su anatomía, específicamente de las uniones musculares. Debido a ello, con el objetivo de comprender la locomoción de éste y otros primates, estudiamos la morfología y morfometría de los músculos grácil y sartorio y la relación entre ellos, en 3 especies de Leontopithecus rosalia. Se examinaron 18 animales adultos, de ambos sexos, sin anormalidades físicas en la región estudiada. El material pertenece a la colección del Centro de Primatología de Rio de Janeiro, Brasil. Los miembros posteriores fueron disecados hasta el nivel de los músculos grácil y sartorio, donde se efectuó la morfometría, obteniéndose, entre los músculos mencionados un área para su análisis histológico. Describimos la morfología de los músculos grácil y sartorio. Se obtuvieron valores promedio de la morfometría muscular y se estudió histológicamente la unión entre esos músculos. El análisis morfológico y morfométrico permite sugerir parámetros descriptivos de esos músculos. El análisis histológico permite concluir que las fibras del músculo grácil y del músculo sartorio no están fusionadas sino que se mantienen juntas a través de tejido conjuntivo, así, se insertan en el lado medial de la tibia. Funcionalmente, creemos que los músculos grácil y sartorio contribuyen a una activa contención de la articulación de la rodilla y sobre la biomecánica de los miembros posteriores de esos primates, conocidos como corredores.

Ectopic development of skeletal muscle induced by subcutaneous transplant of rat satellite cells

The present study analyzes the ectopic development of the rat skeletal muscle originated from transplanted satellite cells. Satellite cells (10(6) cells) obtained from hindlimb muscles of newborn female 2BAW Wistar rats were injected subcutaneously into the dorsal area of adult male rats. After 3, 7, and 14 days, the transplanted tissues (N = 4-5) were processed for histochemical analysis of peripheral nerves, inactive X-chromosome and acetylcholinesterase. Nicotinic acetylcholine receptors (nAChRs) were also labeled with tetramethylrhodamine-labeled alpha-bungarotoxin. The development of ectopic muscles was successful in 86 percent of the implantation sites. By day 3, the transplanted cells were organized as multinucleated fibers containing multiple clusters of nAChRs (N = 2-4), resembling those from non-innervated cultured skeletal muscle fibers. After 7 days, the transplanted cells appeared as a highly vascularized tissue formed by bundles of fibers containing peripheral nuclei. The presence of X chromatin body indicated that subcutaneously developed fibers originated from female donor satellite cells. Differently from the extensor digitorum longus muscle of adult male rat (87.9 ± 1.0 æm; N = 213), the diameter of ectopic fibers (59.1 æm; N = 213) did not obey a Gaussian distribution and had a higher coefficient of variation. After 7 and 14 days, the organization of the nAChR clusters was similar to that of clusters from adult innervated extensor digitorum longus muscle. These findings indicate the histocompatibility of rats from 2BAW colony and that satellite cells transplanted into the subcutaneous space of adult animals are able to develop and fuse to form differentiated skeletal muscle fibers.

Heritability estimates for carcass traits of cattle: a review

We present estimates of heritability for carcass traits of cattle published in the scientific literature. Seventy-two papers published from 1962 to 2004, which reported estimates of heritability for carcass traits, were reviewed. The unweighted means of estimates of heritability for 14 carcass traits by slaughter end point (age, weight, and fat depth) were calculated. Among the three end points, carcass weight, backfat thickness, longissimus muscle area, and marbling score were the carcass traits with the most estimates of heritability (56 is less than or equal to "n", and "n" is less than or equal to 66). The averages for these traits indicate that they are similarly and moderately heritable (0.40, 0.36, 0.40, and 0.37, respectively). However, heritability estimates for most traits varied greatly, which could be due to differences in breed groups, methods of estimation, effects in the model, number of records, measurement errors, sex, and management. Few studies have compared heritability estimates for carcass traits adjusted to different end points. Results from such studies have been inconsistent, although some studies revealed that heritability estimates for several carcass traits are sensitive to the covariate included in the model for the end point, implying that direct response to selection would be different for some traits depending on slaughter end point. The effect of different end points on estimates of heritability for many carcass traits has not been studied.