Spike timing dependent plasticity finds the start of repeating patterns in continuous spike trains

Experimental studies have observed Long Term synaptic Potentiation (LTP) when a presynaptic neuron fires shortly before a postsynaptic neuron, and Long Term Depression (LTD) when the presynaptic neuron fires shortly after, a phenomenon known as Spike Timing Dependent Plasticity (STDP). When a neuron is presented successively with discrete volleys of input spikes STDP has been shown to learn 'early spike patterns', that is to concentrate synaptic weights on afferents that consistently fire early, with the result that the postsynaptic spike latency decreases, until it reaches a minimal and stable value. Here, we show that these results still stand in a continuous regime where afferents fire continuously with a constant population rate. As such, STDP is able to solve a very difficult computational problem: to localize a repeating spatio-temporal spike pattern embedded in equally dense 'distractor' spike trains. STDP thus enables some form of temporal coding, even in the absence of an explicit time reference. Given that the mechanism exposed here is simple and cheap it is hard to believe that the brain did not evolve to use it.     

Zika virus induces massive cytoplasmic vacuolization and paraptosis‐like death in infected cells

The cytopathic effects of Zika virus (ZIKV) are poorly characterized. Innate immunity controls ZIKV infection and disease in most infected patients through mechanisms that remain to be understood. Here, we studied the morphological cellular changes induced by ZIKV and addressed the role of interferon‐induced transmembrane proteins (IFITM), a family of broad‐spectrum antiviral factors, during viral replication. We report that ZIKV induces massive vacuolization followed by “implosive” cell death in human epithelial cells, primary skin fibroblasts and astrocytes, a phenomenon which is exacerbated when IFITM3 levels are low. It is reminiscent of paraptosis, a caspase‐independent, non‐apoptotic form of cell death associated with the formation of large cytoplasmic vacuoles. We further show that ZIKV‐induced vacuoles are derived from the endoplasmic reticulum (ER) and dependent on the PI3K/Akt signaling axis. Inhibiting the Sec61 ER translocon in ZIKV‐infected cells blocked vacuole formation and viral production. Our results provide mechanistic insight behind the ZIKV‐induced cytopathic effect and indicate that IFITM3, by acting as a gatekeeper for incoming virus, restricts virus takeover of the ER and subsequent cell death.     

Recurrence of COVID-19 after recovery ? A case series in health care workers,France

We describe 3 cases of coronavirus disease 2019 in health care workers in France involving presumed clinical and microbiological recurrence after recovery. All patients were immunocompetent with clinical mild form. These cases highlight the possibility of coronavirus disease–recurrence.     

How many can you catch? Factors influencing the occurrence of multi-prey loading in provisioning Greater Crested Terns§

Seabirds use several methods to transport food to their chicks; most species carry food in their stomachs or crops, but some terns and auks carry prey in their bills. Terns usually only carry one prey item at a time, limiting the rate at which they can provision their chicks, and restricting their effective foraging range. However, some terns do occasionally carry multiple prey, which should offer a selective advantage, but there are very few studies investigating the factors influencing the occurrence of multi-prey loading. We investigated the occurrence of multi-prey loads in provisioning Greater Crested Terns (Swift Tern) Thalasseus bergii bergii breeding on Robben Island, South Africa. Of 24 173 loads photographed, 1.3% comprised multiple prey items. Up to 11 fish were carried at once, but most multi-prey loads contained two Anchovies Engraulis encrasicolus, the most common prey item for this population of terns. Mixed species prey were recorded for the first time in a tern. Multi-prey loads occurred more frequently during mid- and late-provisioning, presumably because large chicks can cope with multiple prey, and have higher energetic requirements than small chicks. Mean standard length of Anchovies in multi-prey prey loads was less than Anchovies in single loads, possibly suggesting terns compensate for smaller prey sizes by bringing multiple prey back to their chick. The orientation of multiple Anchovies in a tern’s bill tended to be the same, suggesting that they were captured from polarised fish schools. At least some multi-prey loads were caught in a single dive.     

Quantitative Outcomes of a One Health approach to Study Global Health Challenges

Having gained momentum in the last decade, the One Health initiative promotes a holistic approach to address complex global health issues. Before recommending its adoption to stakeholders, however, it is paramount to first compile quantitative evidence of the benefit of such an approach. The aim of this scoping review was to identify and summarize primary research that describes monetary and non-monetary outcomes following adoption of a One Health approach. An extensive literature search yielded a total of 42,167 references, of which 85 were included in the final analysis. The top two biotic health issues addressed in these studies were rabies and malaria; the top abiotic health issue was air pollution. Most studies described collaborations between human and animal (n = 42), or human and environmental disciplines (n = 41); commonly reported interventions included vector control and animal vaccination. Monetary outcomes were commonly expressed as cost–benefit or cost–utility ratios; non-monetary outcomes were described using disease frequency or disease burden measurements. The majority of the studies reported positive or partially positive outcomes. This paper illustrates the variety of health challenges that can be addressed using a One Health approach, and provides tangible quantitative measures that can be used to evaluate future implementations of the One Health approach.     

Cervical Spinal Cord Atrophy Profile in Adult SMN1-Linked SMA

PurposeThe mechanisms underlying the topography of motor deficits in spinal muscular atrophy (SMA) remain unknown. We investigated the profile of spinal cord atrophy (SCA) in SMN1-linked SMA, and its correlation with the topography of muscle weakness.ResultsCSA measurements revealed a significant cord atrophy gradient mainly located between C3 and C6 vertebral levels with a SCA rate ranging from 5.4% to 23% in SMA patients compared to controls. RD was significantly lower in SMA patients compared to controls in the anterior-posterior direction with a maximum along C4 and C5 vertebral levels (p-values < 10⁻⁵). There were no correlations between atrophy measurements, strength and disability scores.ConclusionsSpinal cord atrophy in adult SMN1-linked SMA predominates in the segments innervating the proximal muscles. Additional factors such as neuromuscular junction or intrinsic skeletal muscle defects may play a role in more complex mechanisms underlying weakness in these patients.     

Synthetic datasets and community tools for the rapid testing of ecological hypotheses

The increased availability of both open ecological data, and software to interact with it, allows the fast collection and integration of information at all spatial and taxonomic scales. This offers the opportunity to address macroecological questions in a cost‐effective way. In this contribution, we illustrate this approach by forecasting the structure of a stream food web at the global scale. In so doing, we highlight the most salient issues needing to be addressed before this approach can be used with a high degree of confidence.     

Beyond species: why ecological interaction networks vary through space and time

Community ecology is tasked with the considerable challenge of predicting the structure, and properties, of emerging ecosystems. It requires the ability to understand how and why species interact, as this will allow the development of mechanism‐based predictive models, and as such to better characterize how ecological mechanisms act locally on the existence of inter‐specific interactions. Here we argue that the current conceptualization of species interaction networks is ill‐suited for this task. Instead, we propose that future research must start to account for the intrinsic variability of species interactions, then scale up from here onto complex networks. This can be accomplished simply by recognizing that there exists intra‐specific variability, in traits or properties related to the establishment of species interactions. By shifting the scale towards population‐based processes, we show that this new approach will improve our predictive ability and mechanistic understanding of how species interact over large spatial or temporal scales. Synthesis Although species interactions are the backbone of ecological communities, we have little insights on how (and why) they vary through space and time. In this article, we build on existing empirical literature to show that the same species may happen to interact in different ways when their local abundances vary, their trait distribution changes, or when the environment affects either of these factors. We discuss how these findings can be integrated in existing frameworks for the analysis and simulation of species interactions.     

A Continuum of Specialists and Generalists in Empirical Communities

Understanding the persistence of specialists and generalists within ecological communities is a topical research question, with far-reaching consequences for the maintenance of functional diversity. Although theoretical studies indicate that restricted conditions may be necessary to achieve co-occurrence of specialists and generalists, analyses of larger empirical (and species-rich) communities reveal the pervasiveness of coexistence. In this paper, we analyze 175 ecological bipartite networks of three interaction types (animal hosts–parasite, plant–herbivore and plant–pollinator), and measure the extent to which these communities are composed of species with different levels of specificity in their biotic interactions. We find a continuum from specialism to generalism. Furthermore, we demonstrate that diversity tends to be greatest in networks with intermediate connectance, and argue this is because of physical constraints in the filling of networks.     

EFFECTS OF NITROGEN SOURCES ON P-LIMITED GROWTH OF ANABAENA FLOS-AQUAE1

The effects of N₂, nitrate and ammonia as N sources were investigated in P-limited and nutrient-sufficient cultures of Anabaena flos-aquae (Lyngb.) Bréb. The maximum growth rate (μ_m) was highest at 1.34 d^?1 with ammonia, compared to 1.18 with nitrate and 0.95 d^?1 with N₂. There was no difference in P requirement between N₂ and nitrate cultures. Under P-limited conditions, the increase in cell P with growth rate (μ) was identical. With N₂ as the N source, cell-N concentrations in P-limited cells increased with μ as did cell P, and the cellular N:P ratio remained the same (14) within the range of μ examined. With nitrate, however, cell N concentrations were high and independent of n, except at a low μ. It appears that this organism fixes atmospheric N₂ only at the minimum concentration required to maintain a μ. The acetylene reduction rate increased with μ in both N_2- and nitrate-grown cells, but the rate was lower in nitrate. Under P-limitation, there was no difference in net C-fixation rate per cell between N₂ and nitrate cultures at a given μ. However, the rate per unit of chlorophyll a (chl a) was higher in N₂ than in nitrate cultures, and the rate was independent of μ with N₂ but was a linear function of nitrate supplied. The maximum C-fixation rate in nutrient sufficient cells was highest with ammonia, followed by nitrate and N₂. The cellular chl a concentration was correlated with the total cell-N concentrations regardless of H and the source of N.