RESUMO
Tarantulas represent some of the heaviest and most famous spiders. However, there is little information about the embryonic development of these spiders or their relatives (infraorder Mygalomorphae) and time-lapse recording of the embryonic development is entirely missing. I here describe the complete development of the Brazilian white knee tarantula, Acanthoscurria geniculata, in fixed and live embryos. The establishment of the blastoderm, the formation, migration and signalling of the cumulus and the shape changes that occur in the segment addition zone are analysed in detail. In addition, I show that there might be differences in the contraction process of early embryos of different theraphosid spider species. A new embryonic reference transcriptome was generated for this study and was used to clone and analyse the expression of several important developmental genes. Finally, I show that embryos of A. geniculata are amenable to tissue transplantation and bead insertion experiments. Using these functional approaches, I induced axis duplication in embryos via cumulus transplantation and ectopic activation of BMP signalling. Overall, the mygalomorph spider A. geniculata is a useful laboratory system to analyse evolutionary developmental questions, and the availability of such a system will help understanding conserved and divergent aspects of spider/chelicerate development.
Assuntos
Blastoderma/embriologia , Embrião não Mamífero/metabolismo , Aranhas/embriologia , Transcriptoma/genética , Animais , Proteína Morfogenética Óssea 4/genética , Proteína Morfogenética Óssea 4/metabolismo , Movimento Celular , Células do Cúmulo/metabolismo , Células do Cúmulo/fisiologia , Desenvolvimento Embrionário/genética , Larva/citologia , Larva/crescimento & desenvolvimento , Larva/metabolismo , Músculos/embriologia , Músculos/metabolismo , Filogenia , Pigmentação , Transdução de Sinais/genética , Aranhas/genética , Transplante de TecidosRESUMO
Embryonic muscular activity (EMA) is involved in the development of several distinctive traits of birds. Modern avian diversity and the fossil record of the dinosaur-bird transition allow special insight into their evolution. Traits shaped by EMA result from mechanical forces acting at post-morphogenetic stages, such that genes often play a very indirect role. Their origin seldom suggests direct selection for the trait, but a side-effect of other changes such as musculo-skeletal rearrangements, heterochrony in skeletal maturation, or increased incubation temperature (which increases EMA). EMA-shaped traits like sesamoids may be inconstant, highly conserved, or even disappear and then reappear in evolution. Some sesamoids may become increasingly influenced in evolution by genetic-molecular mechanisms (genetic assimilation). There is also ample evidence of evolutionary transitions from sesamoids to bony eminences at tendon insertion sites, and vice-versa. This can be explained by newfound similarities in the earliest development of both kinds of structures, which suggest these transitions are likely triggered by EMA. Other traits that require EMA for their formation will not necessarily undergo genetic assimilation, but still be conserved over tens and hundreds of millions of years, allowing evolutionary reduction and loss of other skeletal elements. Upon their origin, EMA-shaped traits may not be directly genetic, nor immediately adaptive. Nevertheless, EMA can play a key role in evolutionary innovation, and have consequences for the subsequent direction of evolutionary change. Its role may be more important and ubiquitous than currently suspected.
Assuntos
Evolução Biológica , Aves/crescimento & desenvolvimento , Osso e Ossos/embriologia , Dinossauros/crescimento & desenvolvimento , Músculos/embriologia , Animais , Aves/embriologia , Desenvolvimento Ósseo , Dinossauros/embriologia , Desenvolvimento MuscularRESUMO
The Brazilian africanized Apis mellifera is currently considered as one of the most important pollinators threatened by the use of insecticides due to its frequent exposition to their toxic action while foraging in the crops it pollinated. Among the insecticides, the most used in the control of insect pragues has as active agent the pyriproxyfen, analogous to the juvenile hormone (JH). Unfortunately the insecticides used in agriculture affect not only the target insects but also beneficial nontarget ones as bees compromising therefore, the growth rate of their colonies at the boundaries of crop fields. Workers that forage for provisions in contaminated areas can introduce contaminated pollen or/and nectar inside the beehives. As analogous to JH the insecticide pyriproxyfen acts in the bee's larval growth and differentiation during pupation or metamorphosis timing. The flighty muscle is not present in the larvae wingless organisms, but differentiates during pupation/metamorphosis. This work aimed to investigate the effect of pyriproxyfen insecticide on differentiation of such musculature in workers of Brazilian africanized honey bees fed with artificial diet containing the pesticide. The results show that the bees fed with contaminated diet, independent of the insecticide concentration used, show a delay in flight muscle differentiation when compared to the control.
Assuntos
Abelhas/efeitos dos fármacos , Inseticidas/toxicidade , Piridinas/toxicidade , Animais , Abelhas/embriologia , Brasil , Músculos/efeitos dos fármacos , Músculos/embriologiaRESUMO
El músculo romboides (m. rhomboideus) forma parte de la sinsarcosis que une la cintura del miembro torácico con el esqueleto axil en los mamíferos domésticos. En estas especies, está integrado por los músculos romboides cervical (m. rhomboideus cervicis) y romboides torácico (m. rhomboideus thoracis), siendo imposible establecer el límite entre ellos, a diferencia de lo que sucede en el Hombre. Los carnívoros en general, el cerdo y el conejo presentan, además de las partes mencionadas, el músculo romboides de la cabeza (m. rhomboideus capitis). En la llama, la porción cefálica está ausente y la cervical pobremente desarrollada. Los autores proponen sumar a las porciones cervical y torácica del músculo romboides de este camélido sudamericano, al músculo romboides supraescapular (m. rhomboideus suprsacapularis), descrito por Lesbre (1903), en el camello y el dromedario. En este trabajo se establecen las inserciones, dimensiones e inervación del músculo romboides supraescapular de la llama, elementos que permiten definirlo como otra porción del complejo muscular romboideo en dicha especie. Además, se postula su acción como elevador de la escápula, dirigiéndola craneal y dorsalmente.
The rhomboideus muscle of the domestic mammals is part of the muscular set that joins the scapular waist to the axial skeleton. In these animals, the forenamed muscle has a cervical portion (m. rhomboideus cervicicis), and a thoracic portion (m. rhomboideus thoracis). Unlike in the man, these parts cannot be separated. In addition, carnivores, pigs and rabbits also have a cephalic portion (m. rhomboideus capitis). In the llamas, the cephalic portion is absent, and the cervical part is poorly developed. The authors propose to add a suprascapular portion (m. rhomboideus suparsacapularis), first described by Lesbre, 1903 in camels, to the Rhomboideus muscular complex of the llama. In this study, the authors describe the length, insertions, and inervation of the Rhomboideus Suprascapular muscle of the llama in order to define it as another portion of the Rhomboideus muscular complex. Moreover, the forenamed muscle is proposed as a scapular elevator.
Assuntos
Animais , Dorso/anatomia & histologia , Dorso/embriologia , Escápula/anatomia & histologia , Escápula/crescimento & desenvolvimento , Escápula/inervação , Músculos/anatomia & histologia , Músculos/embriologia , Músculos/inervação , Anatomia Comparada/métodos , Camelídeos Americanos/anatomia & histologia , Camelídeos Americanos/embriologia , Desenvolvimento Musculoesquelético/genética , Extremidade Superior/anatomia & histologia , Extremidade Superior/embriologia , Extremidade Superior/inervação , Ligamentos/anatomia & histologia , Ligamentos/embriologia , Ligamentos/inervaçãoRESUMO
OBJECTIVES: In this study, we aimed at determining whether human immature dental pulp stem cells (hIDPSC) would be able to contribute to different cell types in mouse blastocysts without damaging them. Also, we analysed whether these blastocysts would progress further into embryogenesis when implanted to the uterus of foster mice, and develop human/mouse chimaera with retention of hIDPSC derivates and their differentiation. MATERIALS AND METHODS: hIDPSC and mouse blastocysts were used in this study. Fluorescence staining of hIDPSC and injection into mouse blastocysts, was performed. Histology, immunohistochemistry, fluorescence in situ hybridization and confocal microscopy were carried out. RESULTS AND CONCLUSION: hIDPSC showed biological compatibility with the mouse host environment and could survive, proliferate and contribute to the inner cell mass as well as to the trophoblast cell layer after introduction into early mouse embryos (n = 28), which achieved the hatching stage following 24 and 48 h in culture. When transferred to foster mice (n = 5), these blastocysts with hIDPSC (n = 57) yielded embryos (n = 3) and foetuses (n = 6); demonstrating presence of human cells in various organs, such as brain, liver, intestine and hearts, of the human/mouse chimaeras. We verified whether hIDPSC would also be able to differentiate into specific cell types in the mouse environment. Contribution of hIDPSC in at least two types of tissues (muscles and epithelial), was confirmed. We showed that hIDPSC survived, proliferated and differentiated in mouse developing blastocysts and were capable of producing human/mouse chimaeras.
Assuntos
Células-Tronco Adultas/citologia , Polpa Dentária/citologia , Embrião de Mamíferos/citologia , Desenvolvimento Embrionário/fisiologia , Feto/citologia , Quimeras de Transplante/embriologia , Células-Tronco Adultas/transplante , Estruturas Animais/citologia , Estruturas Animais/embriologia , Estruturas Animais/metabolismo , Animais , Blastocisto/citologia , Diferenciação Celular/fisiologia , Cromossomos Humanos Y/química , Transferência Embrionária , Embrião de Mamíferos/embriologia , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Epitélio/embriologia , Epitélio/metabolismo , Feminino , Feto/embriologia , Feto/metabolismo , Humanos , Hibridização in Situ Fluorescente , Masculino , Camundongos , Camundongos Endogâmicos , Células Musculares/citologia , Células Musculares/metabolismo , Músculos/citologia , Músculos/embriologia , Músculos/metabolismo , Quimeras de Transplante/metabolismoRESUMO
The fate of single somites has not been analyzed from a comparative perspective with modern cell-marking methods. Most of what we know is based on work using quail-chick chimeras. Consequently, to what degree cell fate has been conserved despite the anatomical differences among vertebrates is unknown. We have analyzed the cell fate of the cranialmost somites, with the focus on somite two, in the Mexican axolotl (Ambystoma mexicanum). Somite cells were marked by injection of dextran-fluorescein and detected using immunofluorescence after 2 months of development in paraffin sections. Our data confirm and extend earlier studies based on classical histology in salamanders. We show that somite two contributes to different muscles, skeletal elements, and connective tissues of the head and cranial trunk region. Cells from somites two and three migrate latero-ventrally and contribute to the hypobranchial muscles mm. geniohyoideus and rectus cervicis. We provide evidence that the specific formation of the hypobranchial musculature from ventral processes of the somites might be variable in different classes of vertebrates. We further demonstrate that mm. cucullaris and dilatator laryngis, which were earlier thought to have a branchial origin, arise from somitic material in a manner very similar to the findings in quail-chick chimeras. Our findings indicate that the pattern of somitic derivatives is highly conserved within tetrapods.
Assuntos
Músculos/embriologia , Crânio/embriologia , Somitos/embriologia , Ambystoma mexicanum/embriologia , Animais , Embrião não Mamífero/embriologia , Embrião não Mamífero/ultraestrutura , Somitos/ultraestruturaRESUMO
Desmin is the intermediate filament (IF) protein occurring exclusively in muscle and endothelial cells. There are other IF proteins in muscle such as nestin, peripherin, and vimentin, besides the ubiquitous lamins, but they are not unique to muscle. Desmin was purified in 1977, the desmin gene was characterized in 1989, and knock-out animals were generated in 1996. Several isoforms have been described. Desmin IFs are present throughout smooth, cardiac and skeletal muscle cells, but can be more concentrated in some particular structures, such as dense bodies, around the nuclei, around the Z-line or in costameres. Desmin is up-regulated in muscle-derived cellular adaptations, including conductive fibers in the heart, electric organs, some myopathies, and experimental treatments with drugs that induce muscle degeneration, like phorbol esters. Many molecules have been reported to associate with desmin, such as other IF proteins (including members of the membrane dystroglycan complex), nebulin, the actin and tubulin binding protein plectin, the molecular motor dynein, the gene regulatory protein MyoD, DNA, the chaperone alphaB-crystallin, and proteases such as calpain and caspase. Desmin has an important medical role, since it is used as a marker of tumors' origin. More recently, several myopathies have been described, with accumulation of desmin deposits. Yet, after almost 30 years since its identification, the function of desmin is still unclear. Suggested functions include myofibrillogenesis, mechanical support for the muscle, mitochondrial localization, gene expression regulation, and intracellular signaling. This review focuses on the biochemical interactions of desmin, with a discussion of its putative functions.
Assuntos
Humanos , Animais , Desmina/fisiologia , Desenvolvimento Muscular , Músculos/embriologia , Desmina/genética , Desmina/metabolismo , Imunofluorescência , Regulação da Expressão Gênica , Músculos/metabolismo , Doenças Musculares/metabolismoRESUMO
Desmin is the intermediate filament (IF) protein occurring exclusively in muscle and endothelial cells. There are other IF proteins in muscle such as nestin, peripherin, and vimentin, besides the ubiquitous lamins, but they are not unique to muscle. Desmin was purified in 1977, the desmin gene was characterized in 1989, and knock-out animals were generated in 1996. Several isoforms have been described. Desmin IFs are present throughout smooth, cardiac and skeletal muscle cells, but can be more concentrated in some particular structures, such as dense bodies, around the nuclei, around the Z-line or in costameres. Desmin is up-regulated in muscle-derived cellular adaptations, including conductive fibers in the heart, electric organs, some myopathies, and experimental treatments with drugs that induce muscle degeneration, like phorbol esters. Many molecules have been reported to associate with desmin, such as other IF proteins (including members of the membrane dystroglycan complex), nebulin, the actin and tubulin binding protein plectin, the molecular motor dynein, the gene regulatory protein MyoD, DNA, the chaperone alphaB-crystallin, and proteases such as calpain and caspase. Desmin has an important medical role, since it is used as a marker of tumors' origin. More recently, several myopathies have been described, with accumulation of desmin deposits. Yet, after almost 30 years since its identification, the function of desmin is still unclear. Suggested functions include myofibrillogenesis, mechanical support for the muscle, mitochondrial localization, gene expression regulation, and intracellular signaling. This review focuses on the biochemical interactions of desmin, with a discussion of its putative functions.
Assuntos
Desmina/fisiologia , Desenvolvimento Muscular , Músculos/embriologia , Animais , Desmina/genética , Desmina/metabolismo , Imunofluorescência , Regulação da Expressão Gênica , Humanos , Músculos/metabolismo , Doenças Musculares/metabolismoRESUMO
The role of cranial neural crest cells in the formation of visceral arch musculature was investigated in the Mexican axolotl, Ambystoma mexicanum. DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine, perchlorate) labeling and green fluorescent protein (GFP) mRNA injections combined with unilateral transplantations of neural folds showed that neural crest cells contribute to the connective tissues but not the myofibers of developing visceral arch muscles in the mandibular, hyoid, and branchial arches. Extirpations of individual cranial neural crest streams demonstrated that neural crest cells are necessary for correct morphogenesis of visceral arch muscles. These do, however, initially develop in their proper positions also in the absence of cranial neural crest. Visceral arch muscles forming in the absence of neural crest cells start to differentiate at their origins but fail to extend toward their insertions and may have a frayed appearance. Our data indicate that visceral arch muscle positioning is controlled by factors that do not have a neural crest origin. We suggest that the cranial neural crest-derived connective tissues provide directional guidance important for the proper extension of the cranial muscles and the subsequent attachment to the insertion on the correct cartilage. In a comparative context, our data from the Mexican axolotl support the view that the cranial neural crest plays a fundamental role in the development of not only the skeleton of the vertebrate head but also in the morphogenesis of the cranial muscles and that this might be a primitive feature of cranial development in vertebrates.
Assuntos
Ambystoma mexicanum , Cabeça , Morfogênese , Músculos/embriologia , Crista Neural , Ambystoma mexicanum/anatomia & histologia , Ambystoma mexicanum/embriologia , Animais , Padronização Corporal , Linhagem da Célula , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Cabeça/anatomia & histologia , Cabeça/embriologia , Imuno-Histoquímica , Músculos/anatomia & histologia , Crista Neural/citologia , Crista Neural/fisiologiaAssuntos
Humanos , Anatomia/educação , Osso e Ossos/anatomia & histologia , Osso e Ossos/embriologia , Osso e Ossos/fisiologia , Desenvolvimento Ósseo/fisiologia , Cabelo/anatomia & histologia , Desenvolvimento Humano , Articulações/anatomia & histologia , Articulações/embriologia , Articulações/crescimento & desenvolvimento , Articulações/fisiologia , Músculos/anatomia & histologia , Músculos/embriologia , Músculos/fisiologia , Sistema Nervoso/anatomia & histologia , Pele/anatomia & histologia , Unhas/anatomia & histologia , Fraturas Ósseas/classificação , Fraturas Ósseas/terapia , Osteogênese/fisiologia , EsqueletoAssuntos
Humanos , Elementos de DNA Transponíveis/fisiologia , Fáscia/anatomia & histologia , Fáscia/fisiologia , Fibras Musculares Esqueléticas , Tono Muscular/fisiologia , Músculos/anatomia & histologia , Músculos/embriologia , Músculos/fisiologia , Parassimpatectomia , Reflexo/fisiologia , Tendões/anatomia & histologia , Tendões/fisiologia , Vasos Sanguíneos/anatomia & histologiaRESUMO
While present in the surface membrane of embryonic muscle fibers, in adult normal muscle fibers, utrophin is restricted to the motor endplate and cells of blood vessel walls. However, the observation that utrophin is maintained in the extrajunctional plasma membrane in Duchenne (DMD) and in mdx muscle fibers has led to the suggestion that excess utrophin might compensate for dystrophin deficiency in the Xp21 muscular dystrophies. In order to detect an inverse correlation of utrophin presence and clinical severity, we have assessed utrophin distribution and quantity in DMD and Becker (BMD) patients of different ages and stages of clinical severity. All patients showed a positive discontinuous immunolabeling of utrophin on the sarcolemma, staining equally small and large muscle fibers, indicating that immature characteristics are maintained in such fibers. On Western blot, utrophin bands with concentrations 2- to 10-fold greater than in normal controls were detected in all DMD/BMD patients. However, no negative correlation was found between the amount of utrophin and the severity of clinical course, implying that the detectable utrophin levels in these patients did not compensate for dystrophin deficiency. In a DMD patient with growth hormone (GH) deficiency and a BMD-like clinical course, utrophin levels were comparable to the other typical DMD cases, which reinforces the hypothesis that the observed increase in utrophin is apparently not responsible for a milder clinical course in some patients with Xp21 muscular dystrophies.
Assuntos
Proteínas do Citoesqueleto/fisiologia , Epistasia Genética , Proteínas de Membrana , Distrofias Musculares/genética , Adolescente , Adulto , Pré-Escolar , Proteínas do Citoesqueleto/análise , Proteínas do Citoesqueleto/genética , Distrofina/análise , Distrofina/deficiência , Distrofina/genética , Humanos , Masculino , Desenvolvimento Muscular , Fibras Musculares Esqueléticas/química , Músculos/embriologia , Sarcolema/química , Deleção de Sequência , Índice de Gravidade de Doença , Utrofina , Cromossomo XRESUMO
1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) rapidly stimulates the biphasic formation of diacylglycerol (DAG) in chick myoblasts. Neomycin (0.5 mM), an inhibitor of phosphoinositide hydrolysis, abolished the first phase (1 min) but had no effect on the second 1,25(OH)2D3-induced DAG peak (5 min). In myoblasts prelabeled with [3H]choline, 1,25(OH)2D3 increased the release of [3H]choline (maximally at 5 min), with a concomitant decrease in phosphatidylcholine and the absence of significant changes in phosphocholine. 1,25(OH)2D3 caused a significant increase in phosphatidylethanol (PEt) formation in myoblasts in the presence of 1.5% ethanol. The effects of 1,25(OH)2D3 were time- and dose-dependent (10(-11) to 10(-8) M) and specific as 25OHD3 and 24,25(OH)2D3 failed to accumulate PEt. 12-O-Tetradecanoylphorbol-13-acetate failed to accumulate PEt. 12-O-Tetradecanoylphorbol-13-acetate also stimulated PEt formation. The combination of 1,25(OH)2D3 and 12-O-tetradecanoylphorbol-13- acetate was more effective than either compound alone. Neither the PKC inhibitor H7 nor PKC down-regulation blocked the hormone-induced increase in PEt. The effects of 1,25(OH)2D3 were, however, inhibited in the absence of extracellular Ca2+ (+EGTA) and by nifedipine and verapamil, whereas the Ca2+ ionophore A23187 also increased PEt generation. The data support the notion that 1,25(OH)2D3 triggers the hydrolysis of phosphatidylcholine in myoblasts through a Ca(2+)-dependent, PKC-independent, phospholipase D-catalyzed mechanism.
Assuntos
Calcitriol/fisiologia , Músculos/fisiologia , Fosfatidilcolinas/metabolismo , Fosfolipase D/metabolismo , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Células Cultivadas , Embrião de Galinha , Diglicerídeos/metabolismo , Ativação Enzimática , Etanol/farmacologia , Técnicas In Vitro , Isoquinolinas/farmacologia , Músculos/embriologia , Neomicina/farmacologia , Fosfatidiletanolaminas/metabolismo , Piperazinas/farmacologia , Transdução de Sinais , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
1,25-Dihydroxyvitamin D-3 (1,25(OH)2D3) which activates the phospholipase C (PLC)-protein kinase C (PKC) signalling pathway, induces within 1 min a dose-dependent (10(-11)-10(-7) M) increase in the release of [3H]arachidonic acid ([3H]AA) from prelabeled embryonic chick myoblasts. The response is dependent on extracellular calcium, since it is suppressed by EGTA and nifedipine, a Ca(2+)-channel blocker, and is mimicked by the calcium ionophore A23187. 1,25(OH)2D3-induced release of [3H]AA is not affected by neomycin (0.5 mM), an inhibitor of phosphoinositide hydrolysis. 12-o-tetradecanoylphorbol-13-acetate (TPA), a PKC activator, induces an extracellular Ca(2+)-independent release of [3H]AA and amplifies the release of AA stimulated by 1,25(OH)2D3. 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H7), a PKC inhibitor, markedly suppressed TPA as well as 1,25(OH)2D3-induced [3H]AA release. Down-regulation of cellular PKC abolishes the effect of the phorbol ester, and partially inhibits 1,25(OH)2D3-induced [3H]AA release. Temporally correlated with AA liberation, the hormone increases the formation of lysophosphatidylcholine (lysoPC) and lysophosphatidylethanolamine (lysoPE) and decreases the cellular content of PC and PE. These results indicate that part of AA release by 1,25(OH)2D3 derives from PLA2 activation and that the effects of the hormone are mediated by PKC in a mode independent of phosphoinositide hydrolysis by PLC.
Assuntos
Ácido Araquidônico/metabolismo , Calcitriol/farmacologia , Músculos/efeitos dos fármacos , Animais , Cálcio/metabolismo , Células Cultivadas/efeitos dos fármacos , Embrião de Galinha , Relação Dose-Resposta a Droga , Ativação Enzimática/efeitos dos fármacos , Lisofosfolipídeos/análise , Músculos/embriologia , Fosfolipases A/metabolismo , Fosfolipases A2 , Fosfolipídeos/análise , Proteína Quinase C/metabolismo , Trítio , Fosfolipases Tipo C/metabolismoRESUMO
The single channel activity of nicotinic acetylcholine receptor (AChR) channels from Xenopus laevis embryonic myotomes in culture, was studied with the patch clamp technique. Two types of single channel activity were observed at low agonist concentration (100 nM ACh-Cl), which were distinguished by their conductance (60 and 40 pS, approximately). Both channel types were recorded simultaneously and therefore to carry out the kinetic analysis, we separate them by using a program exploiting the difference in amplitude of the channels. By using the program CLASS the stationary kinetic characteristics of both types of channels can be obtained separately and evaluated.
Assuntos
Músculos/embriologia , Receptores Nicotínicos/fisiologia , Xenopus laevis/embriologia , Animais , Condutividade Elétrica , Eletrofisiologia , Cinética , Músculos/metabolismo , SoftwareRESUMO
En este trabajo se emplea la técnica de control de voltaje en pequeños parches de membrana, para evaluar la actividad eléctrica unitaria del receptor-canal nicotínico para acetilcolina (AChR) en miotomos extraídos de embriones de Xenopus laevis. Dos patrones de actividad unitaria del receptor nicotínico para la acetilcolina, se distinguen por su conductancia, 60 y 40 pS. Regularmente, la actividad de ambos tipos de canales aparece en los registros y las complicaciones del análisis cinético estacionario producidas por la mezcla de los dos tipos de actividad se superaron a través del uso del programa de separación "CLASS"
Assuntos
Animais , Músculos/embriologia , Receptores Nicotínicos/fisiologia , Xenopus laevis/embriologia , Condutividade Elétrica , Eletrofisiologia , Cinética , Músculos/metabolismoRESUMO
Biphasic effects of 1,25-dihydroxyvitamin D-3 on DNA synthesis were shown in primary cultured (24 h) chick embryo myoblasts exposed to physiological concentrations of the hormone. The sterol stimulated [3H]thymidine incorporation into DNA in proliferating myoblasts, e.g., at early stages of culture prior to cell fusion or in high serum-treated cells. The opposite effects were observed during the subsequent stage of myoblast differentiation in low-serum media. The mitogenic effect of 1,25-dihydroxyvitamin D-3 was correlated with an increase in c-myc mRNA and a decrease in c-fos mRNA levels, whereas its inhibitory action on DNA synthesis was accompanied by increased myofibrillar and microsomal protein synthesis and an elevation of creatine kinase activity, the latter suggesting a stimulation of muscle cell differentiation by the sterol. These data are in agreement with the results of previous morphological studies. Treatment of myoblasts with the calcium ionophore X-537 A or the phorbol ester TPA caused only a transient stimulation of [3H]thymidine incorporation into DNA, which occurred earlier than the response elicited by 1,25-dihydroxyvitamin D-3, suggesting that changes in intracellular Ca2+ and kinase C activity are not major mediators of the hormone effects. A similar temporal profile of changes in calmodulin mRNA levels as that of [3H]thymidine incorporation into DNA was observed after treatment of myoblasts with the sterol, in accordance with the role of calmodulin in the regulation of cell proliferation. 1,25-dihydroxyvitamin D-3 may play a function in embryonic muscle growth and differentiation.
Assuntos
Calcitriol/farmacologia , DNA/biossíntese , Músculos/metabolismo , Animais , Sangue , Calmodulina/genética , Diferenciação Celular , Divisão Celular , Células Cultivadas , Embrião de Galinha , Lasalocida/farmacologia , Proteínas Musculares/biossíntese , Músculos/efeitos dos fármacos , Músculos/embriologia , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-fos , Proteínas Proto-Oncogênicas c-myc , RNA Mensageiro/metabolismo , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
The presence in myoblasts of an intracellular receptor specific for 1,25-dihydroxyvitamin D-3 [1,25(OH)2D3) and 1,25(OH)2D3-dependent changes in myoblast Ca2+ transport and phospholipid metabolism which are suppressed by RNA and protein synthesis inhibitors have been shown. In agreement with these observations, incubation of chick embryo myoblasts, precultured for 24 h in a medium containing low levels of vitamin D-3 metabolites, with 1,25(OH)2D3 at conditions which induce maximum cell responses (10(-10) M, 24 h) markedly stimulated the incorporation of [3H]leucine into total cell proteins and this effect was abolished when sterol treatment was performed in the presence of cycloheximide or puromycin. To investigate whether 1,25(OH)2D3 selectively stimulates the de novo synthesis of muscle cell proteins, mixtures of myoblast proteins from control and sterol-treated cultures labelled with [14C]leucine and [3H]leucine, respectively, were separated by SDS-polyacrylamide gel electrophoresis and isoelectric focussing. Examination of 3H/14C ratios in gel fractions revealed that 1,25-(OH)2D3 stimulates the production of proteins of molecular masses (isoelectric points) of 9 kDa (4.1 and 8.5), 17 kDa (7.5), 30 kDa (7.2), 40 kDa (5.5), 55 kDa (4.5) and 100 kDa (8.6). Cell fractionation studies showed the following subcellular distribution: 9 kDa (85% cytosol, 15% microsomes); 17 and 100 kDa (100%, 1200 X g pellet); 30 kDa (65% cytosol, 35% mitochondria); 40 kDa (100% microsomes); 55 kDa (65% microsomes, 35% mitochondria). Marker enzyme data indicated that this distribution is not due to cross-contamination between fractions. Affinity chromatography of double-labelled myoblast proteins on an immobilized lectin showed that the 55 kDa protein contains carbohydrate. Labelling of myoblast proteins with 45CaCl2 after their separation on SDS-polyacrylamide gels showed in addition that the 1,25(OH)2D3-dependent proteins of 9, 17, 40 and 100 kDa are major Ca2+-binding components of the cells. Synthesis of these proteins may mediate the effects of the sterol on myoblast calcium metabolism.
Assuntos
Calcitriol/farmacologia , Proteínas Musculares/biossíntese , Músculos/metabolismo , Animais , Cálcio/metabolismo , Células Cultivadas , Embrião de Galinha , Cicloeximida/farmacologia , Citosol/metabolismo , Eletroforese em Gel de Poliacrilamida , Glicoproteínas/biossíntese , Ponto Isoelétrico , Microssomos/metabolismo , Mitocôndrias/metabolismo , Peso Molecular , Músculos/efeitos dos fármacos , Músculos/embriologia , Fosfatidilcolinas/biossíntese , Puromicina/farmacologiaAssuntos
Humanos , Embriologia/educação , Doenças da Boca/embriologia , Doenças da Boca/etiologia , Doenças da Boca/genética , Anormalidades Dentárias/embriologia , Desenvolvimento Ósseo , Sistema Cardiovascular/embriologia , Sistema Digestório/embriologia , Cabeça/embriologia , Morfogênese/genética , Músculos/embriologia , Pescoço/embriologia , Sistema Nervoso/embriologia , Odontogênese/genética , Osteogênese/genética , Região Branquial/embriologia , Sistema Respiratório/embriologiaRESUMO
In the embryonic chick limb, multiple mechanisms are believed to be responsible for a precise guidance of motoneuron axons to their appropriate targets from the earliest stages of axon outgrowth. In this report, I discuss one of these guidance mechanisms; a mechanism which appears to depend on a prelabeling of motoneurons prior to axon outgrowth. By focusing on the development of axonal projections to two specific muscles, I review the evidence that motoneurons destined for each muscle actively recognize environmental cues, and discuss recent experiments designed to identify the source of these cues.