RESUMO
The crocodilian naris is regulated by smooth muscle. The morphology of this system was investigated using a combination of gross, light microscopic, and micro-CT analyses, while the mechanics of narial regulation were examined using a combination of Hall Effect sensors, narial manometry, and electromyography. Alligator mississippiensis, like other crocodilians, routinely switches among multiple ventilatory mechanics and does not occlude the nares during any portion of the ventilatory cycle. In a complex that is unique among vertebrates, a single block of smooth muscle functions in dilation when active, and in constriction when passive. The alligator nares may include one of the best examples of a muscle that functions in "pushing" as well as "pulling." The central muscle for narial regulation, the dilator naris, can legitimately be viewed as its own antagonist.
Assuntos
Jacarés e Crocodilos/anatomia & histologia , Músculos/anatomia & histologia , Animais , Eletromiografia , Fenômenos Eletrofisiológicos , Nariz/anatomia & histologia , Costelas/anatomia & histologiaRESUMO
While the signals and complexes that coordinate the heartbeat are well established, how the heart maintains its electromechanical rhythm over a lifetime remains an open question with significant implications to human health. Reasoning that this homeostatic challenge confronts all pulsatile organs, we developed a high resolution imaging and analysis toolset for measuring cardiac function in intact, unanesthetized Drosophila melanogaster. We demonstrate that, as in humans, normal aging primarily manifests as defects in relaxation (diastole) while preserving contractile performance. Using this approach, we discovered that a pair of two-pore potassium channel (K2P) subunits, largely dispensable early in life, are necessary for terminating contraction (systole) in aged animals, where their loss culminates in fibrillatory cardiac arrest. As the pumping function of its heart is acutely dispensable for survival, Drosophila represents a uniquely accessible model for understanding the signaling networks maintaining cardiac performance during normal aging.
Assuntos
Drosophila melanogaster , Insuficiência Cardíaca Diastólica/fisiopatologia , Animais , Modelos Animais de Doenças , HumanosRESUMO
Fluorescent proteins (FPs) are powerful tools for cell and molecular biology. Here based on structural analysis, a blue-shifted mutant of a recently engineered monomeric infrared fluorescent protein (mIFP) has been rationally designed. This variant, named iBlueberry, bears a single mutation that shifts both excitation and emission spectra by approximately 40 nm. Furthermore, iBlueberry is four times more photostable than mIFP, rendering it more advantageous for imaging protein dynamics. By tagging iBlueberry to centrin, it has been demonstrated that the fusion protein labels the centrosome in the developing zebrafish embryo. Together with GFP-labeled nucleus and tdTomato-labeled plasma membrane, time-lapse imaging to visualize the dynamics of centrosomes in radial glia neural progenitors in the intact zebrafish brain has been demonstrated. It is further shown that iBlueberry can be used together with mIFP in two-color protein labeling in living cells and in two-color tumor labeling in mice.
Assuntos
Corantes Fluorescentes/análise , Proteínas Luminescentes/análise , Imagem Óptica/métodos , Animais , Linhagem Celular Tumoral , Drosophila/ultraestrutura , Feminino , Corantes Fluorescentes/metabolismo , Células HEK293 , Humanos , Proteínas Luminescentes/genética , Camundongos , Camundongos Endogâmicos BALB C , Modelos Moleculares , Mutagênese Sítio-Dirigida , Mutação , Neoplasias/diagnóstico , Fotodegradação , Conformação Proteica , Estabilidade Proteica , Peixe-Zebra/embriologia , Proteína Vermelha FluorescenteRESUMO
Infrared fluorescent proteins (IFPs) provide an additional color to GFP and its homologs in protein labeling. Drawing on structural analysis of the dimer interface, we identified a bacteriophytochrome in the sequence database that is monomeric in truncated form and engineered it into a naturally monomeric IFP (mIFP). We demonstrate that mIFP correctly labels proteins in live cells, Drosophila and zebrafish. It should be useful in molecular, cell and developmental biology.
Assuntos
Proteínas de Fluorescência Verde/química , Raios Infravermelhos , Sequência de Aminoácidos , Animais , Animais Geneticamente Modificados , DNA/química , Biologia do Desenvolvimento , Drosophila melanogaster , Corantes Fluorescentes/química , Células HeLa , Histidina/química , Humanos , Proteínas Luminescentes/química , Camundongos , Dados de Sequência Molecular , Mutação , Neurônios/metabolismo , Plasmídeos/metabolismo , Conformação Proteica , Multimerização Proteica , Proteínas Recombinantes de Fusão/química , Transfecção , Peixe-ZebraRESUMO
RATIONALE AND OBJECTIVES: The objective of this study was to compare reader accuracy and time efficiency between coronal reformats of abdominopelvic computed tomography (CT) and axial images, by means of a visual search task. MATERIALS AND METHODS: In this experimental crossover study, a novel visual search task, containing targets placed on actual CT images, was constructed to assess reader performance on both planes. Six trials were shown to participants in each plane, at a fixed time of 0.5 seconds per slice. The task was presented to 43 junior doctors. On each trial, participants were assessed for accuracy and confidence in finding the target on a five-point scale. Statistical analysis was performed using the Wilcoxon signed rank test, and Fleiss kappa. RESULTS: Coronal images took 40% less time to view overall. No significant difference was found in reader accuracy or reader confidence between the two planes. Interrater agreement was observed as fair, across a very large number of raters (43). CONCLUSIONS: Target identification in the coronal plane is extremely similar to the axial plane on abdominopelvic CT in this study and offers a substantial time benefit. A perceptual limit to visual processing of CT images may contribute to this similarity. Greater use of coronal reformats in day-to-day practice could substantially improve radiologist workflow.
Assuntos
Reconhecimento Visual de Modelos/fisiologia , Pelve/diagnóstico por imagem , Radiografia Abdominal/métodos , Análise e Desempenho de Tarefas , Tomografia Computadorizada por Raios X/métodos , Humanos , Variações Dependentes do Observador , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estudos de Tempo e MovimentoRESUMO
Environmental stress triggers substantial alterations in animal physiology and, in some cases, brain structure. Using the nematode Caenorhabditis elegans, a new study reports that unfavorable conditions lead to dramatic dendrite remodeling in neurons that mediate an adaptive dispersal behavior.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/fisiologia , Furina/genética , AnimaisRESUMO
Presynaptic assembly requires the packaging of requisite proteins into vesicular cargoes in the cell soma, their long-distance microtubule-dependent transport down the axon, and, finally, their reconstitution into functional complexes at prespecified sites. Despite the identification of several molecules that contribute to these events, the regulatory mechanisms defining such discrete states remain elusive. We report the characterization of an Arf-like small G protein, ARL-8, required during this process. arl-8 mutants prematurely accumulate presynaptic cargoes within the proximal axon of several neuronal classes, with a corresponding failure to assemble presynapses distally. This proximal accumulation requires the activity of several molecules known to catalyze presynaptic assembly. Dynamic imaging studies reveal that arl-8 mutant vesicles exhibit an increased tendency to form immotile aggregates during transport. Together, these results suggest that arl-8 promotes a trafficking identity for presynaptic cargoes, facilitating their efficient transport by repressing premature self-association.
Assuntos
Fatores de Ribosilação do ADP/fisiologia , Transporte Axonal/fisiologia , Proteínas de Membrana/fisiologia , Terminações Pré-Sinápticas/metabolismo , Vesículas Sinápticas/metabolismo , Proteínas Vesiculares de Transporte de Neurotransmissores/antagonistas & inibidores , Fatores de Ribosilação do ADP/genética , Animais , Transporte Axonal/genética , Caenorhabditis elegans , Proteínas de Membrana/genética , Complexos Multiproteicos/antagonistas & inibidores , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Terminações Pré-Sinápticas/ultraestrutura , Transporte Proteico/genética , Vesículas Sinápticas/genética , Vesículas Sinápticas/ultraestrutura , Proteínas Vesiculares de Transporte de Neurotransmissores/genética , Proteínas Vesiculares de Transporte de Neurotransmissores/metabolismoRESUMO
BACKGROUND: Wnts are secreted glycoproteins that regulate diverse aspects of development, including cell proliferation, cell fate specification and differentiation. More recently, Wnts have been shown to direct axon guidance in vertebrates, flies and worms. However, little is known about the intracellular signaling pathways downstream of Wnts in axon guidance. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that the posterior C. elegans Wnt protein LIN-44 repels the axons of the adjacent D-type motor neurons by activating its receptor LIN-17/Frizzled on the neurons. Moreover, mutations in mig-5/Disheveled, gsk-3, pry-1/Axin, bar-1/beta-catenin and pop-1/TCF, also cause disrupted D-type axon pathfinding. Reduced BAR-1/beta-catenin activity in D-type axons leads to undergrowth of axons, while stabilization of BAR-1/beta-catenin in a lin-23/SCF(beta-TrCP) mutant results in an overextension phenotype. CONCLUSIONS/SIGNIFICANCE: Together, our data provide evidence that Wnt-mediated axon guidance can be transduced through a beta-catenin-dependent pathway.
Assuntos
Axônios , Caenorhabditis elegans/citologia , Neurônios Motores/citologia , Proteínas Wnt/fisiologia , beta Catenina/fisiologia , Animais , Animais Geneticamente Modificados , Proteínas de Caenorhabditis elegans/fisiologia , Microscopia de Fluorescência , Mutação , Receptores Acoplados a Proteínas G/fisiologia , Proteínas Wnt/genéticaRESUMO
Calcium/calmodulin-dependent kinase II has been suggested to produce input-specific long-term potentiation of synaptic strength. This idea has been complicated by results from Rose, Jin, and Craig demonstrating that spatiotemporally restricted NMDA receptor excitation at contiguous synapses can result in the translocation of activated CaMKII throughout the dendritic arbor.
Assuntos
Encéfalo/enzimologia , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapses/enzimologia , Transmissão Sináptica/fisiologia , Animais , Encéfalo/ultraestrutura , Sinalização do Cálcio/fisiologia , Humanos , Potenciação de Longa Duração/fisiologia , Transporte Proteico/fisiologia , Sinapses/ultraestruturaRESUMO
Polarity is an essential feature of many cell types, including neurons that receive information from local inputs within their dendrites and propagate nerve impulses to distant targets through a single axon. It is generally believed that intrinsic structural differences between axons and dendrites dictate the polarized localization of axonal and dendritic proteins. However, whether extracellular cues also instruct this process in vivo has not been explored. Here we show that the axon guidance cue UNC-6/netrin and its receptor UNC-5 act throughout development to exclude synaptic vesicle and active zone proteins from the dendrite of the Caenorhabditis elegans motor neuron DA9, which is proximal to a source of UNC-6/netrin. In unc-6/netrin and unc-5 loss-of-function mutants, presynaptic components mislocalize to the DA9 dendrite. In addition, ectopically expressed UNC-6/netrin, acting through UNC-5, is sufficient to exclude endogenous synapses from adjacent subcellular domains within the DA9 axon. Furthermore, this anti-synaptogenic activity is interchangeable with that of LIN-44/Wnt despite being transduced through different receptors, suggesting that extracellular cues such as netrin and Wnts not only guide axon navigation but also regulate the polarized accumulation of presynaptic components through local exclusion.
Assuntos
Caenorhabditis elegans/citologia , Caenorhabditis elegans/metabolismo , Dendritos/metabolismo , Proteínas de Membrana/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Terminações Pré-Sinápticas/metabolismo , Receptores de Superfície Celular/metabolismo , Animais , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Glicoproteínas/metabolismo , Proteínas de Membrana/genética , Mutação , Proteínas do Tecido Nervoso/genética , Receptores de Netrina , Netrinas , Receptores de Superfície Celular/genética , Sinapses/metabolismo , Proteínas Wnt/metabolismo , Proteínas rab3 de Ligação ao GTP/genética , Proteínas rab3 de Ligação ao GTP/metabolismoRESUMO
Nervous system function is mediated by a precisely patterned network of synaptic connections. While several cell-adhesion and secreted molecules promote the assembly of synapses, the contribution of signals that negatively regulate synaptogenesis is not well understood. We examined synapse formation in the Caenorhabditis elegans motor neuron DA9, whose presynapses are restricted to a specific segment of its axon. We report that the Wnt lin-44 localizes the Wnt receptor lin-17/Frizzled (Fz) to a subdomain of the DA9 axon that is devoid of presynaptic specializations. When this signaling pathway, composed of the Wnts lin-44 and egl-20, lin-17/Frizzled and dsh-1/Dishevelled, is compromised, synapses develop ectopically in this subdomain. Conversely, overexpression of LIN-44 in cells adjacent to DA9 is sufficient to expand LIN-17 localization within the DA9 axon, thereby inhibiting presynaptic assembly. These results suggest that morphogenetic signals can spatially regulate the patterning of synaptic connections by subdividing an axon into discrete domains.
Assuntos
Caenorhabditis elegans , Junção Neuromuscular/fisiologia , Transdução de Sinais , Sinapses/fisiologia , Proteínas Wnt/metabolismo , Animais , Axônios/fisiologia , Padronização Corporal , Caenorhabditis elegans/anatomia & histologia , Caenorhabditis elegans/embriologia , Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Caenorhabditis elegans/fisiologia , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/isolamento & purificação , Proteínas de Caenorhabditis elegans/metabolismo , Embrião não Mamífero , Receptores Frizzled/genética , Receptores Frizzled/metabolismo , Neurônios Motores/fisiologia , Terminações Pré-Sinápticas/fisiologia , Proteínas Wnt/genéticaRESUMO
Somatosensory information from the face is transmitted to the brain by trigeminal sensory neurons. It was previously unknown whether neurons innervating distinct areas of the face possess molecular differences. We have identified a set of genes differentially expressed along the dorsoventral axis of the embryonic mouse trigeminal ganglion and thus can be considered trigeminal positional identity markers. Interestingly, establishing some of the spatial patterns requires signals from the developing face. We identified bone morphogenetic protein 4 (BMP4) as one of these target-derived factors and showed that spatially defined retrograde BMP signaling controls the differential gene expressions in trigeminal neurons through both Smad4-independent and Smad4-dependent pathways. Mice lacking one of the BMP4-regulated transcription factors, Onecut2 (OC2), have defects in the trigeminal central projections representing the whiskers. Our results provide molecular evidence for both spatial patterning and retrograde regulation of gene expression in sensory neurons during the development of the somatosensory map.
Assuntos
Padronização Corporal/fisiologia , Proteínas Morfogenéticas Ósseas/metabolismo , Face/embriologia , Neurônios Aferentes/fisiologia , Transdução de Sinais/fisiologia , Gânglio Trigeminal/citologia , Animais , Padronização Corporal/genética , Proteína Morfogenética Óssea 4 , Proteínas Morfogenéticas Ósseas/genética , Mapeamento Encefálico , Células Cultivadas , Embrião de Mamíferos , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/metabolismo , Hibridização In Situ , Camundongos , Camundongos Transgênicos , Proteínas do Tecido Nervoso/metabolismo , Transdução de Sinais/genética , Fatores de Transcrição/metabolismo , Gânglio Trigeminal/embriologia , Proteína Wnt1/genéticaRESUMO
The central nervous system (CNS) loses the ability to regenerate early during development, but it is not known why. The retina has long served as a simple model system for study of CNS regeneration. Here we show that amacrine cells signal neonatal rat retinal ganglion cells (RGCs) to undergo a profound and apparently irreversible loss of intrinsic axon growth ability. Concurrently, retinal maturation triggers RGCs to greatly increase their dendritic growth ability. These results suggest that adult CNS neurons fail to regenerate not only because of CNS glial inhibition but also because of a loss of intrinsic axon growth ability.