RESUMO
INTRODUCTION: A balanced maternal diet is a determining factor in normal fetal development. The objective of this study was to evaluate the effects of maternal protein restriction during pregnancy and lactation on muscle fiber and neuromuscular junction (NMJ) morphology of rat offspring at 21 days of age. METHODS: Wistar rats were divided into a control group (CG), offspring of mothers fed a normal protein diet (17%), and a restricted group (RG), offspring of mothers fed a low-protein diet (6%). After a period of lactation, the animals were euthanized, and soleus muscles were obtained from pups for analysis. RESULTS: The soleus muscles of the RG exhibited an increase of 133% in the number of fibers and of 79% in the amount of nuclei. Moreover, the number of NMJs was lower in the restricted group than in the CG. CONCLUSIONS: Maternal protein restriction alters the normal development of the neuromuscular system. Muscle Nerve 55: 109-115, 2017.
Assuntos
Dieta com Restrição de Proteínas , Lactação/fisiologia , Junção Neuromuscular , Efeitos Tardios da Exposição Pré-Natal/fisiopatologia , Animais , Peso Corporal , Feminino , Masculino , Microscopia Eletrônica , Fibras Musculares Esqueléticas/patologia , Fibras Musculares Esqueléticas/ultraestrutura , Junção Neuromuscular/embriologia , Junção Neuromuscular/crescimento & desenvolvimento , Junção Neuromuscular/fisiologia , Junção Neuromuscular/ultraestrutura , Gravidez , Ratos , Ratos WistarRESUMO
Wnt proteins play prominent roles in different aspects of neuronal development culminating with the formation of complex neuronal circuits. Here, we discuss new studies addressing the function of Wnt signalling at the peripheral neuromuscular junction (NMJ). In both, invertebrate and vertebrate organisms, Wnt signalling promotes and also inhibits the assembly of the neuromuscular synapse. Here, we focus our attention on recent studies at the vertebrate NMJ that demonstrate that some Wnt proteins collaborate with the Agrin-MuSK signalling to induce post-synaptic differentiation. In contrast, Wnts that activate the Wnt/ß-catenin signalling inhibit post-synaptic differentiation. The dual function of different Wnts might finely modulate the proper apposition of the pre- and post-synaptic terminals during NMJ formation and growth.
Assuntos
Junção Neuromuscular/embriologia , Proteínas Wnt/metabolismo , Via de Sinalização Wnt/fisiologia , Agrina/metabolismo , Animais , Diferenciação Celular , Receptores Frizzled/metabolismo , Humanos , Junção Neuromuscular/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Sinapses/fisiologia , beta Catenina/metabolismoRESUMO
OBJECTIVES: The aim of the present investigation is to examine if the histological maturation of the neuromuscular junction in the masseters of human fetuses has already begun by the 12-th week of gestation or not. MATERIAL AND METHODS: Twenty-four masseter muscles from 14 human fetuses at gestational age 12 weeks were divided into two groups. In the first group, muscle sections were stained with Bielschowsky and Holzer stains for examination of neurofibrils and glial cells respectively. In the second group, rhodamine and fluorescein conjugated alpha-bungarotoxin were used to detect nicotinic receptors and anti-GAD for neuronal terminals. RESULTS: It was observed the presence of one axon for each end-plate and glial cells spread over a branched axon. The nicotinic receptors clustered in the neuromuscular junction, neuronal terminals and large oval nucleus were detected. CONCLUSIONS: These observations suggest that the maturation of the neuromuscular junctions of the masseter muscles in the human fetuses has already begun at the 12-th week of gestation.
Assuntos
Diferenciação Celular , Feto/citologia , Músculo Masseter/citologia , Músculo Masseter/embriologia , Junção Neuromuscular/citologia , Junção Neuromuscular/embriologia , Axônios/metabolismo , Núcleo Celular/metabolismo , Humanos , Miofibrilas/metabolismo , Neurofibrilas/metabolismo , Neuroglia/citologia , Neuroglia/metabolismo , Receptores Nicotínicos/metabolismo , Coloração e RotulagemRESUMO
Function of dystrophin Dp71 isoforms is unknown but seems related to neurite outgrowth and synapse formation. To evaluate Dp71 role in myoneural synapses, we established a coculture model using PC12 cells and L6 myotubes and analyzed expression and localization of Dp71 and related proteins, utrophin and beta-dystroglycan, in PC12 cells. Confocal microscopy showed Dp71d isoform in PC12 nuclei, golgi-complex-like and endoplasmic reticulum-like structures, whereas Dp71ab concentrates at neurite tips and cytoplasm, colocalizing with beta-dystroglycan, utrophin, synaptophysin and acetylcholine receptors. Evidences suggest that Dp71ab isoform, unlike Dp71d, may take part in neurite-related processes. This is the first work on Dp and members of Dp-associated protein complex roles in a cell-line based coculturing system, which may be useful in determining Dp71 isoforms associations.
Assuntos
Distroglicanas/metabolismo , Distrofina/metabolismo , Fibras Musculares Esqueléticas/metabolismo , Junção Neuromuscular/embriologia , Neurônios/metabolismo , Utrofina/metabolismo , Animais , Diferenciação Celular/fisiologia , Técnicas de Cocultura , Distroglicanas/genética , Distrofina/genética , Microscopia Confocal , Fibras Musculares Esqueléticas/ultraestrutura , Músculo Esquelético/embriologia , Músculo Esquelético/inervação , Músculo Esquelético/metabolismo , Neuritos/metabolismo , Neuritos/ultraestrutura , Junção Neuromuscular/citologia , Junção Neuromuscular/metabolismo , Neurônios/ultraestrutura , Organelas/metabolismo , Organelas/ultraestrutura , Células PC12 , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Ratos , Receptores Colinérgicos/metabolismo , Membranas Sinápticas/metabolismo , Membranas Sinápticas/ultraestrutura , Sinaptofisina/metabolismo , Utrofina/genéticaRESUMO
The pattern of innervation of the vertebrate neuromuscular junction is established during early development, when junctions go from multiple to single innervation in the phenomenon of synapse elimination, suggesting that changes at the molecular level in the postsynaptic cell lead to the removal of nerve terminals. The mdx mouse is deficient in dystrophin and associated proteins that are part of the postsynaptic cytoskeleton. We used rhodamine-alpha-bungarotoxin and anti-neurofilament IgG-FITC to stain acetylcholine receptors and nerve terminals of the sternomastoid muscle during postnatal development in mdx and control C57BL/10 mice. Using fluorescence confocal microscopy, we observed that, 7 days after birth, 86.7% of the endplates of mdx mice were monoinnervated (n = 200) compared with 41.4% in control mice (n = 200). By the end of the second postnatal week, all endplates were innervated singly (100% mdx and 94.7% controls, n = 200 per group). These results show that dystrophic fibers achieve single innervation earlier, perhaps because dystrophin or a normal cytoskeletal complex is implicated in this phenomenon.
Assuntos
Distrofina/deficiência , Junção Neuromuscular/química , Junção Neuromuscular/crescimento & desenvolvimento , Receptores Colinérgicos/análise , Sinapses/química , Animais , Animais Recém-Nascidos , Distrofina/genética , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Junção Neuromuscular/embriologia , Receptores Colinérgicos/fisiologia , Sinapses/fisiologiaRESUMO
The Drosophila Rel transcription factor Dorsal and its inhibitor Cactus participate in a signal transduction pathway involved in several biologic processes, including embryonic pattern formation, immunity, and muscle development. In contrast with embryonic muscle, where Dorsal is reportedly absent, this protein and Cactus accumulates in the neuromuscular junctions in the muscle of both larvae and adults. The phenotype of homozygous dorsal mutant larvae suggested that Dorsal and Cactus maybe necessary for normal function and maintenance of the neuromuscular system. Here we investigate if these proteins can respond to synaptic activity. Using larval body wall preparations and antibodies specific for Dorsal or Cactus we show that the amount of these proteins at the neuromuscular junction is substantially decreased after electrical stimulation of the nerves or incubation in glutamate, the principal transmitter in this type of synapse. The specificity of the response was tested with a glutamate receptor antagonist (argiotoxin 636). Because the effect can be reproduced using a calcium ionophore (ionomycin treatment) as well as blocked by the inhibition of the muscle ryanodine receptor (tetracaine treatment), the involvement of calcium in this process seems likely. We also observed that the inhibition of the calcium dependent protein phosphatase calcineurin prevents the effect of glutamate on the fluorescence for Dorsal and Cactus, suggesting its participation in a signal transduction cascade that may activate Dorsal in the muscle independently of Toll. Our results are consistent with a novel function of the Rel factor Dorsal in a molecular pathway turned on by neural activity and/or contractile activity.