Bursts of activity in collective cell migration

Dense monolayers of living cells display intriguing relaxation dynamics, reminiscent of soft and glassy materials close to the jamming transition, and migrate collectively when space is available, as in wound healing or in cancer invasion. Here we show that collective cell migration occurs in bursts that are similar to those recorded in the propagation of cracks, fluid fronts in porous media and ferromagnetic domain walls. In analogy with these systems, the distribution of activity bursts displays scaling laws that are universal in different cell types and for cells moving on different substrates. The main features of the invasion dynamics are quantitatively captured by a model of interacting active particles moving in a disordered landscape. Our results illustrate that collective motion of living cells is analogous to the corresponding dynamics in driven, but inanimate, systems

Luminescent conjugates between dinuclear rhenium complexes and 17α-ethynylestradiol: synthesis, photophysical characterization, and cell imaging

Three new luminescent conjugates between dinuclear rhenium complexes and an estradiol, namely E2-Re, are described. The derivatives have the general formula [Re2(\u3bc-Cl)2(CO)6(\u3bc-R-pydz-17\u3b1-ethynylestradiol)] (R-pydz = functionalized 1,2-pyridazine), where the estradiol moiety is covalently bound to the \u3b2 position of the pyridazine ligand. Different synthetic pathways are investigated, including the inverse-type [4 + 2] Diels Alder cycloaddition reaction between the electron poor 1,2,4,5-tetrazine and 17\u3b1-ethynylestradiol for the synthesis of E2-Re1. The three E2-Re conjugates are purified on silica gel and isolated in a spectroscopically pure form in moderate to good yields (28-50%). All the E2-Re conjugates are comprehensively characterized from the spectroscopic and photophysical points of view. Cellular internalization experiments on human MCF-7 and 231 cells are also reported, displaying interesting staining differences depending on the nature of the spacer linking the estradiol unit to the organometallic fragment. Furthermore, the suitability of these conjugates to also stain simple multicellular organisms, i.e. Ciona intestinalis embryos and larvae at different stages of development, is reported here for the first time

Postnatal Changes in K+/Cl- Cotransporter-2 Expression in the Forebrain of Mice Bearing a Mutant Nicotinic Subunit Linked to Sleep-Related Epilepsy

ABSTRACT The Na+/K+/Cl- cotransporter-1 (NKCC1) and the K+/Cl- cotransporter-2 (KCC2) set the transmembrane Cl- gradient in the brain, and are implicated in epileptogenesis. We studied the postnatal distribution of NKCC1 and KCC2 in wild-type (WT) mice, and in a mouse model of sleep-related epilepsy, carrying the mutant \u3b22-V287L subunit of the nicotinic acetylcholine receptor (nAChR). In WT neocortex, immunohistochemistry showed a wide distribution of NKCC1 in neurons and astrocytes. At birth, KCC2 was localized in neuronal somata, whereas at subsequent stages it was mainly found in the somatodendritic compartment. The cotransporters\u2019 expression was quantified by densitometry in the transgenic strain. KCC2 expression increased during the first postnatal weeks, while the NKCC1 amount remained stable, after birth. In mice expressing \u3b22-V287L, the KCC2 amount in layer V of prefrontal cortex (PFC) was lower than in the control littermates at postnatal day 8 (P8), with no concomitant change in NKCC1. Consistently, the GABAergic excitatory to inhibitory switch was delayed in PFC layer V of mice carrying \u3b22-V287L. At P60, the amount of KCC2 was instead higher in mice bearing the transgene. Irrespective of genotype, NKCC1 and KCC2 were abundantly expressed in the neuropil of most thalamic nuclei since birth. However, KCC2 expression decreased by P60 in the reticular nucleus, and more so in mice expressing \u3b22-V287L. Therefore, a complex regulatory interplay occurs between heteromeric nAChRs and KCC2 in postnatal forebrain. The pathogenetic effect of \u3b22-V287L may depend on altered KCC2 amounts in PFC during synaptogenesis, as well as in mature thalamocortical circuits

The imbalance between dynamic and stable microtubules underlies neurodegeneration induced by 2,5-hexanedione

Exposure to environmental toxins, including hydrocarbon solvents, increases the risk of developing Parkinson's disease. An emergent hypothesis considers microtubule dysfunction as one of the crucial events in triggering neuronal degeneration in Parkinson's disease. Here, we used 2,5-hexanedione (2,5-HD), the toxic metabolite of n-hexane, to analyse the early effects of toxin-induced neurodegeneration on the cytoskeleton in multiple model systems. In PC12 cells differentiated with nerve growth factor for 5 days, we found that 2,5-HD treatment affected all the cytoskeletal components. Moreover, we observed alterations in microtubule distribution and stability, in addition to the imbalance of post-translational modifications of \u3b1-tubulin. Similar defects were also found in vivo in 2,5-HD-intoxicated mice. Interestingly, we also found that 2,5-HD exposure induced significant changes in microtubule stability in human skin fibroblasts obtained from Parkinson's disease patients harbouring mutations in PRKN gene, whereas it was ineffective in healthy donor fibroblasts, suggesting that the genetic background may really make the difference in microtubule susceptibility to this environmental Parkinson's disease-related toxin. In conclusion, by showing the imbalance between dynamic and stable microtubules in hydrocarbon-induced parkinsonism, our data support the crucial role of microtubule defects in triggering neurodegeneration

Metamaterial architecture from a self-shaping carnivorous plant

As meticulously observed and recorded by Darwin, the leaves of the carnivorous plant Drosera capensis L. slowly fold around insects trapped on their sticky surface in order to ensure their digestion. While the biochemical signaling driving leaf closure has been associated with plant growth hormones, how mechanical forces actuate the process is still unknown. Here, we combine experimental tests of leaf mechanics with quantitative measurements of the leaf microstructure and biochemistry to demonstrate that the closure mechanism is programmed into the cellular architecture of D. capensis leaves, which converts a homogeneous biochemical signal into an asymmetric response. Inspired by the leaf closure mechanism, we devise and test a mechanical metamaterial, which curls under homogeneous mechanical stimuli. This kind of metamaterial could find possible applications as a component in soft robotics and provides an example of bio-inspired design

Polymer-interaction driven diffusionof eyeshadow in soft contact lenses

Soft contact lenses used for the correction of ametropia are often made of hydrogel and silicone-hydrogel materials. Since they are placed directly on the surface of the eye and they are hydrated by tears, eye cosmetics can compromise the lens performance and, even worse, can be transported from an external environment to the ocular surface through the contact lens. The diffusion of the dye component of a purple eyeshadow in soft contact lenses of different materials is here evaluated. Diffusivity is found to be typically higher in silicone-hydrogels than in hydrogels. In hydrogels, diffusivity is greater in the case of lower oxygen transmissibility. Despite differences between materials, absorbed mass of dye is much larger (10-100 times) than the expected mass by simple hydration and swelling of the contact lens. The most contaminated materials are also resistant to cleaning solutions. The results indicate that, notwithstanding the complexity of contact lens networks, diffusion of dye is found to follow Fick's law and it is driven by polymer-dye interaction, which governs lens hydration and swelling

Polymer-interaction driven diffusionof eyeshadow in soft contact lenses

Soft contact lenses used for the correction of ametropia are often made of hydrogel and silicone-hydrogel materials. Since they are placed directly on the surface of the eye and they are hydrated by tears, eye cosmetics can compromise the lens performance and, even worse, can be transported from an external environment to the ocular surface through the contact lens. The diffusion of the dye component of a purple eyeshadow in soft contact lenses of different materials is here evaluated. Diffusivity is found to be typically higher in silicone-hydrogels than in hydrogels. In hydrogels, diffusivity is greater in the case of lower oxygen transmissibility. Despite differences between materials, absorbed mass of dye is much larger (10-100 times) than the expected mass by simple hydration and swelling of the contact lens. The most contaminated materials are also resistant to cleaning solutions. The results indicate that, notwithstanding the complexity of contact lens networks, diffusion of dye is found to follow Fick's law and it is driven by polymer-dye interaction, which governs lens hydration and swelling

Wear effects on microscopic morphology and hyaluronan uptake in siloxane-hydrogel contact lenses

The purpose of this study was a comparison between new and worn siloxane-hydrogel contact lenses in terms of microscopic structure, surface morphology, and loading of hyaluronan. The analyses were performed by scanning electron microscopy, with the support of the freeze-drying technique, and by fluorescence confocal microscopy. Along the depth profile of new lenses, a thin porous top layer was observed, which corresponds to the region of hyaluronan penetration inside well-defined channels. The time evolution was followed from one day to two weeks of daily wear, when a completely different scenario was found. Clear experimental evidence of a buggy surface was observed with several crests and regions of swelling, which could be filled by the hyaluronan solution. The modifications are attributed to the progressive relaxation of the structure of the polymeric network

Morphological characterization of a murine model of autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE)

ADNFLE is a partial epilepsy characterized by clusters of hyperkinetic seizures, often accompanied by sudden arousals, mostly occurring during stage II of NREM sleep. Attacks arise in the frontal lobe, tend to begin in childhood and cognitive and psychological alterations may be present. In 20-30% of the cases, the disease does not respond to antiepileptic drug treatment. About 10\u201315% of the ADNFLE families bear mutations on genes coding for nicotinic acetylcholine receptor (nAChR) subunits. We studied how mutant nAChRs can lead to ADNFLE, by using a murine model of the pathology conditionally expressing the ADNFLE-linked nicotinic \u3b22-V287L mutation (TG), for comparison with control mice (CTRL) in prefrontal cortex (PFC), somatosensory cortex (SS) and thalamus (TH) at different developmental stages (P8, P21, P60). In these mice, \u3b22-V287L needs to be expressed throughout brain development, until the end of the second postnatal week, for seizures to develop. First of all, we measured the cortical thickness, number of synapses, neuronal volume and density in both PFC and SS at P60, but no differences were observed between CTRL and TG mice. Moreover, the total and synaptic expression of \u3b22* nAChR subunit was evaluated by using densitometric analysis. \u3b22-V287L mutation did not alter the overall \u3b22* nAChR surface density and no significant differences were observed in the cortex between CTRL and TG neither at the presynaptic sites. In addition, we analysed the GABAergic system carrying out immunofluorescence and densitometric analysis on PFC, SS and TH by using antibodies against GAD67, GABAA receptor \u3b11 subunit and VGAT, but no significant differences were found between CTRL and TG mice. Also parvalbuminpositive cells were counted both by stereological and cell counting methods, but we observed no significant difference. Next, we took into account the expression of K+/Cl- cotransporter KCC2, the responsible of the \u201cswitch of GABA\u201d effect from excitatory to inhibitory. Alteration in its expression could lead to an excitation/inhibition imbalance and to the pathogenesis of diseases such as epilepsy. Densitometric analysis revealed that in P8 TG mice KCC2 expression significantly decreased in PFC layer V, where a significant increase was instead observed at P60. At this age we revealed a concomitant decrease of this cotransporter in the thalamic reticular nucleus (RT) in TG mice compared to CTRL. Further analyses on the forebrain and mesopontine cholinergic nuclei are being carried out by using stereological and densitometric analyses. Our results demonstrate that \u3b22-V287L mutation has no effect on cortex morphology and distribution of GABAergic markers, not affecting the GABAergic switch. However, it locally alters the expression of KCC2, which may be attributed to a compensatory effect caused by increased excitability in these sensitive regions and in general related to the hyperexcitability of the thalamocortical circuits in ADNFLE

Expression of the K+/CL- cotransporter KCC2 in a conditional murine model of autosomal dominant nocturnal frontal lobe epilepsy

The K+/Cl- cotransporter KCC2 is the main chloride extruder in neurons and it exerts an essential role in determining the polarity of GABAA receptor-mediated chloride currents. The increase of KCC2 expression after birth is responsible of the \u201cswitch of GABA\u201d effect from excitatory to inhibitory. KCC2 also covers a critical role in dendritic spine morphogenesis and in maintenance of glutamatergic synapses. Alteration in its expression could lead to an imbalance between excitation and inhibition and to the pathogenesis of diseases such as epilepsy. We studied KCC2 expression and distribution in a murine model of Autosomal Dominant Nocturnal Frontal Lobe Epilepsy (ADNFLE), conditionally expressing the ADNFLE-linked nicotinic \u3b22V287L mutation (TG), for comparison with control mice (CTRL) in prefrontal cortex (PFC), somatosensory cortex (SS) and thalamus (TH). By immunocytochemical approaches, we carried out densitometric analyses of KCC2 expression at different postnatal ages (P8, P21, P60) and we observed a significant increase of KCC2 expression in PFC layer V and a decrease of this cotransporter in the thalamic reticular nucleus (RT) in TG P60 mice compared to age-matched controls. Further analyses of some GABAergic markers showed no substantial alterations. Next, we estimated GABAA reversal potential (EGABA) by perforated patch-clamp recordings on acute dissociated neurons from TG and CTRL mice during postnatal development. EGABA progressively hyperpolarized up to the second postnatal week, but no difference was found between TG and CTRL mice. On the other hand, in mature (older than P28) cortical slices, a potentiation of both EPSCs and IPSCs stimulation was detected in response to nicotine in TG compared to control neurons and, especially in the case of EPSCs, leading towards excitation. Our results suggest that KCC2 and the GABAergic system could be implicated in the pathogenesis of ADNFLE and that \u3b22V287L mutation could alter the excitatory/inhibitory balance in murine forebrain