Leveraging open hardware to alleviate the burden of COVID-19 on global health systems.

With the current rapid spread of COVID-19, global health systems are increasingly overburdened by the sheer number of people that need diagnosis, isolation and treatment. Shortcomings are evident across the board, from staffing, facilities for rapid and reliable testing to availability of hospital beds and key medical-grade equipment. The scale and breadth of the problem calls for an equally substantive response not only from frontline workers such as medical staff and scientists, but from skilled members of the public who have the time, facilities and knowledge to meaningfully contribute to a consolidated global response. Here, we summarise community-driven approaches based on Free and Open Source scientific and medical Hardware (FOSH) as well as personal protective equipment (PPE) currently being developed and deployed to support the global response for COVID-19 prevention, patient treatment and diagnostics

Tsetse flies ( Glossina morsitans morsitans ) choose birthing sites guided by substrate cues with no evidence for a role of pheromones

Tsetse flies significantly impact public health and economic development in sub-Saharan African countries by transmitting the fatal disease African trypanosomiasis. Unusually, instead of laying eggs, tsetse birth a single larva that immediately burrows into the soil to pupate. Where the female chooses to larviposit is, therefore, crucial for offspring survival. Previous laboratory studies suggested that a putative larval pheromone, n-pentadecane, attracts gravid female Glossina morsitans morsitans to appropriate larviposition sites. However, this attraction could not be reproduced in field experiments. Here, we resolve this disparity by designing naturalistic laboratory experiments that closely mimic the physical characteristics found in the wild. We show that gravid G. m. morsitans were neither attracted to the putative pheromone nor, interestingly, to pupae placed in the soil. By contrast, females appear to choose larviposition sites based on environmental substrate cues. We conclude that, among the many cues that likely contribute to larviposition choice in nature, substrate features are a main determinant, while we failed to find evidence for a role of pheromones

Open labware: 3-D printing your own lab equipment

The introduction of affordable, consumer-oriented 3-D printers is a milestone in the current “maker movement,” which has been heralded as the next industrial revolution. Combined with free and open sharing of detailed design blueprints and accessible development tools, rapid prototypes of complex products can now be assembled in one’s own garage—a game-changer reminiscent of the early days of personal computing. At the same time, 3-D printing has also allowed the scientific and engineering community to build the “little things” that help a lab get up and running much faster and easier than ever before

Embryonic Origin of Olfactory Circuitry in <em>Drosophila</em>: Contact and Activity-Mediated Interactions Pattern Connectivity in the Antennal Lobe

<div><p>Olfactory neuropiles across different phyla organize into glomerular structures where afferents from a single olfactory receptor class synapse with uniglomerular projecting interneurons. In adult <em>Drosophila</em>, olfactory projection interneurons, partially instructed by the larval olfactory system laid down during embryogenesis, pattern the developing antennal lobe prior to the ingrowth of afferents. In vertebrates it is the afferents that initiate and regulate the development of the first olfactory neuropile. Here we investigate for the first time the embryonic assembly of the <em>Drosophila</em> olfactory network. We use dye injection and genetic labelling to show that during embryogenesis, afferent ingrowth pioneers the development of the olfactory lobe. With a combination of laser ablation experiments and electrophysiological recording from living embryos, we show that olfactory lobe development depends sequentially on contact-mediated and activity-dependent interactions and reveal an unpredicted degree of similarity between the olfactory system development of vertebrates and that of the <em>Drosophila</em> embryo. Our electrophysiological investigation is also the first systematic study of the onset and developmental maturation of normal patterns of spontaneous activity in olfactory sensory neurons, and we uncover some of the mechanisms regulating its dynamics. We find that as development proceeds, activity patterns change, in a way that favours information transfer, and that this change is in part driven by the expression of olfactory receptors. Our findings show an unexpected similarity between the early development of olfactory networks in <em>Drosophila</em> and vertebrates and demonstrate developmental mechanisms that can lead to an improved coding capacity in olfactory neurons.</p> </div

Recurrent olfactory stimulation reduces the 70–80 Hz response to odours.

<p>(A) Diagram illustrating the protocol. Flies were exposed to 6 consecutive 500 ms odour pulses spaced 25 s. (B) A sample power spectrum of brain frequencies (1–100 Hz) in response to the first odour presentation (green), compared to the sixth odour presentation (yellow), and unstimulated periods before and after the protocol (blue). The arrow points to the 70–80 Hz response to the first olfactory stimulation, and its specific reduction during the sixth exposure. (C) Average 70–80 Hz RCI (±SEM) during the presentation of the first two odour puffs (1+2, light green) compared to the response to the last two odour puffs (5+6, dark green). (D) The baseline response does not change during the protocol. Significance was assessed by two-tailed t-test; a single asterisk (*) indicates <i>p</i><0.05, and <i>N.S</i> indicates <i>p</i>>0.05.</p

Response to odours.

<p>(A) Average (±SEM) of the 70–80 Hz power during baseline (blue), odour (red) and air (green) stimulation in a sample fly. Each line is an average of eleven recordings performed randomly on the same fly. (B) Average 70–80 Hz RCI (±SEM) at baseline (blue) and during olfactory (red) and air (green) stimulation. Olfactory stimulation showed a significant increase in the 70–80 Hz RCI compared to baseline and air stimulation. n = 3 flies, 11 recordings of each condition per fly; Significance was first assessed with an ANOVA <i>p</i> = 0.011. Afterwards a post-hoc two-tailed t-test was performed in between the different conditions; a single asterisk (*) indicates <i>p</i><0.05, and <i>N.S</i> indicates <i>p</i>>0.05.</p

Electric shock stimulation increases the 70–80 Hz response to odours.

<p>(A) Diagram illustrating the protocol: 6 pulses of electric shock spaced 10 s. (B) Average 70–80 Hz RCI (±SEM) to 6 pulses of odour spaced by 10 s after the electric shock protocol (pink), compared to a control before the protocol (bright green), and to post-protocol control after 2 minutes of rest (light green). Significance was first assessed with a Kruskall Wallis test <i>p</i> = 0.027. Afterwards a post-hoc Wilcoxon test was performed in between the different conditions; a single asterisk (*) indicates <i>p</i><0.05, and <i>N.S</i> indicates <i>p</i>>0.05.</p

Development of OSNs and PNs between 16 h and 21 h AEL.

<p>(A–I) Development of OSNs between 16 h and 21 h AEL as revealed by dye injection. (A) Schematic of the injection procedure; as in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001400#pbio-1001400-g001" target="_blank">Figure 1</a>, the square indicates the area shown in the confocal images. Columns show injections at different developmental times. The two rows (B–E) and (F–I) each represent a different example of OSN injection. All figures are at the same scale. Terminals at 21 h AEL (E and I) appear more compact than at earlier stages. Morphologies found at 18.5 h AEL (two examples in D and H) are especially variable, with some showing long filopodia (H) or broad regions of occupancy (D). (J–N′) Development of PNs between 16 h and 21 h AEL as revealed by dye injection. (J) as (A). (K–N′) The two rows show the AL and the MB and LH regions for a representative PN injection at each developmental stage. Red brackets indicate the PN dendrites.</p

Recording from OSNs during development.

<p>(A–D) OSN recording technique. (A) Schematic showing the way in which the recordings were performed. Embryos were dissected to expose the DOG, a suction electrode was placed in contact with the DOG, and suction applied until a seal was made and action potentials were visible on the recording. (B) Example recording trace from a first instar larvae expressing ChR2 in OSNs (<i>Orco-Gal4;UAS-CD8GFP/UAS-ChR2</i>). The blue bar at the bottom indicates the period of time when the UV light was turned on to activate ChR2. In this particular recording three different units were identified using Spikepy. (C) Experimental trace from (B) showing the shape of individual spikes. (D) Clusters separated with Spikepy. Average spike shapes are plotted with their standard deviation at the top left. The other three panels are an overlay of a maximum of 250 individual spikes for each cluster, with the average spike shape plotted in black. (E) Peri-stimulus time histogram (PSTH), Raster plots, and heat maps showing the response to UV light stimulation of 16 units recorded in three different larvae in response to five different stimuli presentations in <i>Orco-Gal4;UAS-CD8GFP/UAS-ChR2</i> animals. PSTH (top panel) shows the average firing rate of the 16 units in 200 ms bins. Raster plots (middle panel) show the raw data for each of the 16 units. Heat maps (bottom panel) show for each unit the firing rate in 1 s bins. For each unit the average firing rate in the 10 s before light stimulation was significantly lower (<i>p</i><0.001) than the average firing rate in the 10 s during the stimulation. (F) Firing rate, example trace, and example spike shape of OSN recordings at four different developmental stages.</p

PNs require presynaptic innervation during development for their survival.

<p>(A) Schematic of the experimental approach. OSNs on one side were laser ablated at stage 14, before OSN axons contact PNs. Animals were left to develop and hatch and PN morphology was examined in mid-first instar larvae. (B) Anterior part of a first instar larva in which OSNs have been unilaterally ablated. All sensory neurons are labelled using <i>PO163-Gal4;UAS-CD8GFP</i>, including taste neurons that appear as the most anteriorly located cluster of PO163 positive cells on both sides. OSNs labelled both with PO163 in green and with α-Orco antibody (magenta) are present on the control side (bottom) but not in the ablated side (top). (C) Quantification of the OSN ablation experiments. Number of PNs in the control (blue dots) and OSN ablated side (pink dots) for each animal are linked by a grey line. (D–D″) Z projection of a brain in which OSNs were unilaterally ablated (right side). PNs visible with <i>GH146-QF;QUAS-mTomato</i> on the control side are missing on the ablated side. The AL, visualized with Nc82 antibody staining in the control side (dashed line), is absent on the ablated side. (E–E″) Z projection of a brain in which OSNs were unilaterally ablated (right side). PNs (<i>GH146-QF;QUAS-mTomato</i>) can be seen innervating the AL in the control side. Some PN of the ablated side are missing, while surviving ones are found innervating the subesophageal ganglion (SOG). The AL, visualized in the control side as a gap with DAPI staining, is missing on the ablated side (see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001400#pbio.1001400.s002" target="_blank">Figure S2</a>).</p