Many woody plants respond to intense clipping through an increase in growth parameters and nutritive value. However, optimal clipping intensities that result in peak plant growth and nutritive value ...have not been determined. We studied the response of Ziziphus mucronata and Acacia nilotica saplings to four clipping intensities. Parts of the main stem and each lateral branch were removed to simulate 0%, 30%, 60%, and 90% clipping intensity. After four months of resprouting five sapling growth parameters were determined viz. height, basal stem diameter, length of the longest shoot, root length, and number of new shoots. In addition, foliar crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), total phenolic (TP), and condensed tannin (CT) concentrations were determined. Shoot clipping did not stimulate sapling height and basal diameter growth, while shoot length responded to an increase in clipping intensity with a weak hump-shape in both species. Ziziphus mucronata increased root growth in response to increasing clipping intensity, while A. nilotica showed no clear trend. The largest number of new shoots was produced at 60% and 30% clipping intensities for Z. mucronata and A. nilotica respectively. Ziziphus mucronata produced more new shoots than A. nilotica. The most severe (90%) clipping intensity produced the highest CP and lowest NDF content in the two species, reduced TP and CT content in A. nilotica, but not in Z. mucronata. We conclude that an increase in clipping intensity produced varying responses in sapling growth parameters and nutritive values in Z. mucronata and A. nilotica.
Establishment of neuronal polarity depends on local microtubule (MT) reorganization. The endoplasmic reticulum (ER) consists of cisternae and tubules and, like MTs, forms an extensive network ...throughout the entire cell. How the two networks interact and control neuronal development is an outstanding question. Here we show that the interplay between MTs and the ER is essential for neuronal polarity. ER tubules localize within the axon, whereas ER cisternae are retained in the somatodendritic domain. MTs are essential for axonal ER tubule stabilization, and, reciprocally, the ER is required for stabilizing and organizing axonal MTs. Recruitment of ER tubules into one minor neurite initiates axon formation, whereas ER retention in the perinuclear area or disruption of ER tubules prevent neuronal polarization. The ER-shaping protein P180, present in axonal ER tubules, controls axon specification by regulating local MT remodeling. We propose a model in which feedback-driven regulation between the ER and MTs instructs neuronal polarity.
•ER tubules localize to the axon, and ER cisternae are retained in the soma•Localization of axonal ER depends on ER-shaping proteins and the MT cytoskeleton•ER-MT crosstalk stabilizes both ER tubules and MTs in the axon•ER-MT crosstalk is critical for neuronal polarity
Farías et al. report that the localization of the endoplasmic reticulum (ER) in the axon is controlled by the interaction between ER-shaping proteins and the microtubule cytoskeleton. Local ER and microtubule crosstalk promotes ER tubule-microtubule stabilization and drives neuronal polarity.
Neuron morphology and function are highly dependent on proper organization of the cytoskeleton. In neurons, the centrosome is inactivated early in development, and acentrosomal microtubules ...are generated by mechanisms that are poorly understood. Here, we show that neuronal migration, development, and polarization depend on the multi-subunit protein HAUS/augmin complex, previously described to be required for mitotic spindle assembly in dividing cells. The HAUS complex is essential for neuronal microtubule organization by ensuring uniform microtubule polarity in axons and regulation of microtubule density in dendrites. Using live-cell imaging and high-resolution microscopy, we found that distinct HAUS clusters are distributed throughout neurons and colocalize with γ-TuRC, suggesting local microtubule nucleation events. We propose that the HAUS complex locally regulates microtubule nucleation events to control proper neuronal development.
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•The HAUS/augmin complex regulates migration and polarization in vivo•Axonal and dendritic development are regulated by HAUS/augmin complex•HAUS/augmin regulates microtubule density in dendrites and polarity in axons•Discrete clusters of HAUS/augmin regulate local microtubule nucleation in neurons
Cunha-Ferreira et al. report that the HAUS/augmin complex regulates neuronal migration, polarization, and development. In neurons, the HAUS complex is distributed as discrete clusters regulating local microtubule nucleation. These findings shed light into how microtubules are generated in developing neurons after centrosome inactivation in early development.
The cytoplasm is a highly complex and heterogeneous medium that is structured by the cytoskeleton. How local transport depends on the heterogeneous organization and dynamics of F-actin and ...microtubules is poorly understood. Here we use a novel delivery and functionalization strategy to utilize quantum dots (QDs) as probes for active and passive intracellular transport. Rapid imaging of non-functionalized QDs reveals two populations with a 100-fold difference in diffusion constant, with the faster fraction increasing upon actin depolymerization. When nanobody-functionalized QDs are targeted to different kinesin motor proteins, their trajectories do not display strong actin-induced transverse displacements, as suggested previously. Only kinesin-1 displays subtle directional fluctuations, because the subset of microtubules used by this motor undergoes prominent undulations. Using actin-targeting agents reveals that F-actin suppresses most microtubule shape remodelling, rather than promoting it. These results demonstrate how the spatial heterogeneity of the cytoskeleton imposes large variations in non-equilibrium intracellular dynamics.
Les parents des nouveau-nés hospitalisés sont soumis à une situation stressante. Il leur est difficile de s’impliquer dans les soins apportés à leur enfant. Leur ressenti après une hospitalisation ...n’a jamais été exploré à grande échelle.
Analyser le ressenti des parents concernant leur participation aux soins.
Une enquête anonyme accessible en ligne a été diffusée dès février 2014 avec analyse en août 2014. Les 222 items étaient à choix multiples ou sous forme de questions ouvertes. L’analyse a été quantitative et qualitative.
Parmi les 1500 parents ayant répondu, 98 % étaient des mères. Les enfants étaient nés en moyenne à 32 semaines d’aménorrhée avec un poids de naissance moyen de 1600 g. La première participation des parents aux soins avait donné lieu à des émotions contradictoires (joie, stress, angoisse). Ils souhaitaient le plus souvent une participation active, même pour des soins complexes (alimentation par sonde, positionnement de la continuous positive airway pressure CPAP…). Le peau à peau avait été proposé après 7 jours de vie pour 20 % des parents et 10 % des parents ne s’étaient pas sentis en confiance. Le besoin d’intimité et d’un accompagnement sécurisant a été mis en avant.
Les parents s’étaient sentis entourés et encouragés par l’équipe soignante mais ils souhaitaient souvent une participation plus active. Le peau à peau avait été apprécié et souhaité, mais il peut être stressant si les conditions optimales ne sont pas réunies.
The experience of becoming the parent of a sick or premature newborn can be particularly distressing for parents. They often encounter challenges to the development of their parenting roles. Perception of the hospital stay has never been analyzed on a large scale.
To analyze parents’ perception of their involvement in the care of their newborn.
An internet-based survey started in France in February 2014 on the basis of a validated questionnaire composed of 222 neonatal care-related items. A quantitative and qualitative analysis was performed on the items dealing with parents’ involvement until August 2014.
The survey was completed by 1500 parents, 98 % of whom were mothers. The infants had a mean GA of 32 weeks and a mean birth weight of 1600g. Parents rated their first care of their infant with mixed emotions (joy, stress, etc.). Parents were willing to practice new skills through guided participation, even for more complex care. Skin-to-skin care was only proposed after 7 days for 20 % of the parents; 10 % of the parents did not feel secure during this practice. The need for privacy and professional guidance was essential for meaningful skin-to-skin contact.
Parents’ perception of participating actively in their infant's care was positive and they felt guided by the nursing team. Most of them would have been more active with guidance. Skin-to-skin care was appreciated and desired, but could become stressful if the conditions were not optimal.
Neuronal development is a complex multistep process that shapes neurons by progressing though several typical stages, including axon outgrowth, dendrite formation, and synaptogenesis. Knowledge of ...the mechanisms of neuronal development is mostly derived from the study of animal models. Advances in stem cell technology now enable us to generate neurons from human induced pluripotent stem cells (iPSCs). Here we provide a mass spectrometry-based quantitative proteomic signature of human iPSC-derived neurons, i.e., iPSC-derived induced glutamatergic neurons and iPSC-derived motor neurons, throughout neuronal differentiation. Tandem mass tag 10-plex labeling was carried out to perform proteomic profiling of cells at different time points. Our analysis reveals significant expression changes (FDR < 0.001) of several key proteins during the differentiation process, e.g., proteins involved in the Wnt and Notch signaling pathways. Overall, our data provide a rich resource of information on protein expression during human iPSC neuron differentiation.
Dendritic spines are protrusions along neuronal dendrites that harbor the majority of excitatory postsynapses. Their distinct morphology, often featuring a bulbous head and small neck that connects ...to the dendritic shaft, has been shown to facilitate compartmentalization of electrical and cytoplasmic signaling stimuli elicited at the synapse. The extent to which spine morphology also forms a barrier for membrane-bound diffusion has remained unclear. Recent simulations suggested that especially the diameter of the spine neck plays a limiting role in this process. Here, we examine the connection between spine morphology and membrane-bound diffusion through a combination of photoconversion, live-cell superresolution experiments, and numerical simulations. Local photoconversion was used to obtain the timescale of diffusive equilibration in spines and followed by global sparse photoconversion to determine spine morphologies with nanoscopic resolution. These morphologies were subsequently used to assess the role of morphology on the diffusive equilibration. From the simulations, we could determine a robust relation between the equilibration timescale and a generalized shape factor calculated using both spine neck width and neck length, as well as spine head size. Experimentally, we found that diffusive equilibration was often slower, but rarely faster than predicted from the simulations, indicating that other biological confounders further reduce membrane-bound diffusion in these spines. This shape-dependent membrane-bound diffusion in mature spines may contribute to spine-specific compartmentalization of neurotransmitter receptors and signaling molecules and thereby support long-term plasticity of synaptic contacts.
Microtubules are polymeric protein structures and components of the cytoskeleton. Their dynamic polymerization is important for diverse cellular functions. The centrosome is the classical site of ...microtubule nucleation and is thought to be essential for axon growth and neuronal differentiation--processes that require microtubule assembly. We found that the centrosome loses its function as a microtubule organizing center during development of rodent hippocampal neurons. Axons still extended and regenerated through acentrosomal microtubule nucleation, and axons continued to grow after laser ablation of the centrosome in early neuronal development. Thus, decentralized microtubule assembly enables axon extension and regeneration, and, after axon initiation, acentrosomal microtubule nucleation arranges the cytoskeleton, which is the source of the sophisticated morphology of neurons.
The specific organization of the neuronal microtubule cytoskeleton in axons and dendrites is an evolutionarily conserved determinant of neuronal polarity that allows for selective cargo sorting. ...However, how dendritic microtubules are organized and whether local differences influence cargo transport remains largely unknown. Here, we use live-cell imaging to systematically probe the microtubule organization in
neurons, and demonstrate the contribution of distinct mechanisms in the organization of dendritic microtubules. We found that most non-ciliated neurons depend on
(kinesin-1),
(CRMP) and
(ankyrin) for correct microtubule organization and polarized cargo transport, as previously reported. Ciliated neurons and the URX neuron, however, use an additional pathway to nucleate microtubules at the tip of the dendrite, from the base of the cilium in ciliated neurons. Since inhibition of distal microtubule nucleation affects distal dendritic transport, we propose a model in which the presence of a microtubule-organizing center at the dendrite tip ensures correct dendritic cargo transport.
Despite causing considerable damage to host tissue during the onset of parasitism, nematodes establish remarkably persistent infections in both animals and plants. It is thought that an elaborate ...repertoire of effector proteins in nematode secretions suppresses damage-triggered immune responses of the host. However, the nature and mode of action of most immunomodulatory compounds in nematode secretions are not well understood. Here, we show that venom allergen-like proteins of plant-parasitic nematodes selectively suppress host immunity mediated by surface-localized immune receptors. Venom allergen-like proteins are uniquely conserved in secretions of all animal- and plant-parasitic nematodes studied to date, but their role during the onset of parasitism has thus far remained elusive. Knocking-down the expression of the venom allergen-like protein Gr-VAP1 severely hampered the infectivity of the potato cyst nematode Globodera rostochiensis. By contrast, heterologous expression of Gr-VAP1 and two other venom allergen-like proteins from the beet cyst nematode Heterodera schachtii in plants resulted in the loss of basal immunity to multiple unrelated pathogens. The modulation of basal immunity by ectopic venom allergen-like proteins in Arabidopsis thaliana involved extracellular protease-based host defenses and non-photochemical quenching in chloroplasts. Non-photochemical quenching regulates the initiation of the defense-related programmed cell death, the onset of which was commonly suppressed by venom allergen-like proteins from G. rostochiensis, H. schachtii, and the root-knot nematode Meloidogyne incognita. Surprisingly, these venom allergen-like proteins only affected the programmed cell death mediated by surface-localized immune receptors. Furthermore, the delivery of venom allergen-like proteins into host tissue coincides with the enzymatic breakdown of plant cell walls by migratory nematodes. We, therefore, conclude that parasitic nematodes most likely utilize venom allergen-like proteins to suppress the activation of defenses by immunogenic breakdown products in damaged host tissue.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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