A STUDY ON THE MECHANISM OF INTERCELLULAR ADHESION : Effects of Neuraminidase, Calcium, and Trypsin on the Aggregation of Suspended HeLa Cells

Aggregation of suspended HeLa cells is increased on removal of cell surface sialic acid. Calcium ions promote aggregation whereas magnesium ions have no effect. The calcium effect is abolished by previous treatment of the cells with neuraminidase. Trypsinization of the HeLa cells followed by thorough washing diminishes the rate of mutual cell aggregation. Subsequent incubation with neuraminidase restores the aggregation rate to the original value before trypsin treatment. Cells which had acquired a greater tendency for aggregation after removal of peripheral sialic acid lose this property when subsequently treated with trypsin. Calcium ions have no aggregative effect on trypsinized cells. In contrast to HeLa cells, aggregation of human erythrocytes was not increased after treatment with neuraminidase or on addition of calcium. The results with HeLa cells are interpreted as follows: (a) Trypsin-releasable material confers adhesiveness upon the cells. (b) The adhesive property of this material is counteracted by the presence of cell surface sialic acids. (c) Calcium ions exert their effect by attenuating the adverse effect of sialic acid

Anisotropic composite polymer for high magnetic force in microfluidic systems

International audienceAnisotropic carbonyl iron-PolyDiMethylSiloxane (PDMS) composites were developed and implemented in microfluidic devices to serve as magnetic flux concentrators. These original materials provide technological solutions for heterogeneous integration with PDMS. Besides microfabrication advantages, they offer interesting modular magnetic properties. Applying an external magnetic field during the PDMS reticulation leads to the formation of 1D-agglomerates of magnetic particles, organized in the non-magnetic polymer matrix. This induces an increase of susceptibility as compared to composites with randomly dispersed particles. In this report, we explored the gain in reachable magnetophoretic forces in operating microfluidic devices, from the study of magnetic micro-beads motion injected in the microchannel. We show that even at relatively large distances from the magnetically-functionalized channel wall, the anisotropic composite leads to a factor two increase in the magnetophoretic force. Finally, further investigations based on finite element description suggest that the measured benefit of anisotropic composite polymers does not only rely on the global susceptibility increase but also on the local magnetic field gradients originating from the microstructure

<i>Legionella</i> species: A potential problem associated with rain water harvesting systems?

The risk of Legionella transmission from rain water harvesting (RWH)-fed water toilet flushing was investigated. Experiments monitored RWH tanks to determine Legionella spp. presence which was successfully isolated from three of four of RWH tanks (site 1: 3600 CFU/dm3 in February and 3600 CFU/dm3 in May; site 2: not detected; site 3: 3; site 4: 44,000 GU/dm3), and to determine whether toilets could generate aerosol droplets capable of harbouring bacteria. The concentrations of particles measuring 10 µm or less in diameter (PM10, capable of reaching the alveolar region of the lungs and causing disease) were monitored following flushes. Aerosols were detectable in an enclosed toilet cubicle (PM10 concentration increased in one experiment from 0.038 mg/m3 when t = 1–600 s to 0.057 mg/m3 when t = 600–800 s). Recovery of Lactobacillus plantarum (surrogate for Legionella) from a seeded toilet cistern (108 CFU ml/dm3) indicated that bacteria were expelled, as demonstrated by recovery on MRS plates placed around the toilet unit. Legionella could be dispersed via aerosols from a toilet flushed with water from an RWH system and the effect would be more pronounced in smaller, enclosed areas, but this is unlikely to pose a risk to human health

Seasonal prediction of Horn of Africa long rains using machine learning: the pitfalls of preselecting correlated predictors

The Horn of Africa is highly vulnerable to droughts and floods, and reliable long-term forecasting is a key part of building resilience. However, the prediction of the “long rains” season (March–May) is particularly challenging for dynamical climate prediction models. Meanwhile, the potential for machine learning to improve seasonal precipitation forecasts in the region has yet to be uncovered. Here, we implement and evaluate four data-driven models for prediction of long rains rainfall: ridge and lasso linear regressions, random forests and a single-layer neural network. Predictors are based on SSTs, zonal winds, land state, and climate indices, and the target variables are precipitation totals for each separate month (March, April, and May) in the Horn of Africa drylands, with separate predictions made for lead-times of 1–3 months. Results reveal a tendency for overfitting when predictors are preselected based on correlations to the target variable over the entire historical period, a frequent practice in machine learning-based seasonal forecasting. Using this conventional approach, the data-driven methods—and particularly the lasso and ridge regressions—often outperform dynamical seasonal hindcasts. However, when the selection of predictors is done independently of both the train and test data, by performing this predictor selection within the cross-validation loop, the performance of all four data-driven models is poorer than that of the dynamical hindcasts. These findings should not discourage future applications of machine learning for rainfall forecasting in the region. Yet, they should be seen as a note of caution to prevent optimistically biased results that are not indicative of the true power in operational forecast systems

Nitrate supply routes and impact of internal cycling in the North Atlantic Ocean inferred from nitrate isotopic composition

In this study we report full‐depth water column profiles for nitrogen and oxygen isotopic composition (δ15N and δ18O) of nitrate (NO3‐) during the GEOTRACES GA01 cruise (2014). This transect intersects the double gyre system of the subtropical and subpolar regions of the North Atlantic separated by a strong transition zone, the North Atlantic Current. The distribution of NO3‐ δ15N and δ18O shows that assimilation by phytoplankton is the main process controlling the NO3‐ isotopic composition in the upper 150 m, with values increasing in a NO3‐ δ18O versus δ15N space along a line with a slope of one towards the surface. In the subpolar gyre, a single relationship between the degree of NO3‐ consumption and residual NO3‐ δ15N supports the view that NO3‐ is supplied via Ekman upwelling and deep winter convection, and progressively consumed during the Ekman transport of surface water southward. The co‐occurrence of partial NO3‐ assimilation and nitrification in the deep mixed layer of the subpolar gyre elevates subsurface NO3‐ δ18O in comparison to deep oceanic values. This signal propagates through isopycnal exchanges to greater depths at lower latitudes. With recirculation in the subtropical gyre, cycles of quantitative consumption‐nitrification progressively decrease subsurface NO3‐ δ18O toward the δ18O of regenerated NO3‐. The low NO3‐ δ15N observed south of the Subarctic Front is mostly explained by N2 fixation, although a contribution from the Mediterranean outflow is required to explain the lower NO3‐ δ15N signal observed between 600 and 1500 m depth close to the Iberian margin

Perceptions of climate change and willingness to save energy related to flood experience

One of the reasons that people may not take action to mitigate climate change is that they lack first-hand experience of its potential consequences. From this perspective, individuals who have direct experience of phenomena that may be linked to climate change would be more likely to be concerned by the issue and thus more inclined to undertake sustainable be- haviours. So far, the evidence available to test this hypothesis is limited, and in part contradictory1–4. Here we use national survey data collected from 1,822 individuals across the UK in 2010, to examine the links between direct flooding experience, perceptions of climate change and preparedness to reduce energy use. We show that those who report experience of flooding express more concern over climate change, see it as less uncertain and feel more confident that their actions will have an effect on climate change. Importantly, these perceptual differences also translate into a greater willingness to save energy to mitigate climate change. Highlighting links between local weather events and climate change is therefore likely to be a useful strategy for increasing concern and action

Acatalasemic mice are mildly susceptible to adriamycin nephropathy and exhibit increased albuminuria and glomerulosclerosis

Background: Catalase is an important antioxidant enzyme that regulates the level of intracellular hydrogen peroxide and hydroxyl radicals. The effects of catalase deficiency on albuminuria and progressive glomerulosclerosis have not yet been fully elucidated. The adriamycin (ADR) nephropathy model is considered to be an experimental model of focal segmental glomerulosclerosis. A functional catalase deficiency was hypothesized to exacerbate albuminuria and the progression of glomerulosclerosis in this model. Methods: ADR was intravenously administered to both homozygous acatalasemic mutant mice (C3H/AnLCs(b)Cs(b)) and control wild-type mice (C3H/AnLCs(a)Cs(a)). The functional and morphological alterations of the kidneys, including albuminuria, renal function, podocytic, glomerular and tubulointerstitial injuries, and the activities of catalase were then compared between the two groups up to 8 weeks after disease induction. Moreover, the presence of a mutation of the toll-like receptor 4 (tlr4) gene, which was previously reported in the C3H/HeJ strain, was investigated in both groups. Results: The ADR-treated mice developed significant albuminuria and glomerulosclerosis, and the degree of these conditions in the ADR-treated acatalasemic mice was higher than that in the wild-type mice. ADR induced progressive renal fibrosis, renal atrophy and lipid peroxide accumulation only in the acatalasemic mice. In addition, the level of catalase activity was significantly lower in the kidneys of the acatalasemic mice than in the wild-type mice during the experimental period. The catalase activity increased after ADR injection in wild-type mice, but the acatalasemic mice did not have the ability to increase their catalase activity under oxidative stress. The C3H/AnL strain was found to be negative for the tlr4 gene mutation. Conclusions: These data indicate that catalase deficiency plays an important role in the progression of renal injury in the ADR nephropathy model

The seeds of commerce: a network analysis-based approach to the Romano-British transport system

Communication routes are an important subject in the study of the human past. They allowed interactions between communities and the dispersal of goods and ideas. Their study, therefore, can shed light on the way in which communities inhabited the landscape, related to each other and were affected by macro-regional trends. Many methods, such as archaeomorphological analysis and Least Cost Route modelling (LCR), have been devised and are routinely employed for the reconstruction of ancient routes. Their analysis in terms of communication, trade or historical significance, however, has usually been left unexplored. This is probably due to the connected nature of routes, which form communication networks: these are shaped by interconnected nodes and extend over territories surpassing the regional scale in such a way that even a change in a single node or link can affect the whole network. Consequently, the partial reconstruction of communication networks provided by the aforementioned methods does not usually allow a holistic analysis. In this paper the relatively well understood British Roman road network is employed to explore the analytical possibilities offered by a combination of Social Network Analysis, Spatial Network Analysis and spatial interpolation-based distribution analysis. The British road network has been reconstructed using published data but also a variation of LCR in which cost surfaces are derived from cultural data obtained from large-scale cultural inventories. The distribution of introduced food plants during the Roman period serve as an excellent proxy for the study of trade along the network and its historical consequences. This multi-period archaeobotanical dataset has some evident advantages to other types of material remains: archaeobotanical remains are not reused as, for example, amphorae and, accordingly, they reflect a distribution pattern based on consumption or commerce. Some of them are imported (as they cannot be produced locally) and, consequently, their distribution would be applied through usage of the main routes. The results suggest a continuous inflow of exotics but highlight their changing transport routes, their differential access and the particular weight of certain nodal sites in the development of this commerce with direct impact on urbanisation and the overall economy of Britannia. The Roman road network acted as a major factor in the distribution of sites, their political and economic importance and their permanence or disappearance as global economic trends changed over time