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

Developmental changes in OSN spontaneous activity patterns depend upon OR function.

<p>(A) Five-minute representative trace recordings overlaid with individual OSN units as identified with Spikepy. Top trace control 15 h AEL, middle trace control first instar larvae, and bottom trace Orco mutant first instar larva. OSNs at early stages (15 h and 16 h AEL) often fire in bursts, unlike OSNs at later stages (18.5 h and first instar larvae). OSNs in Orco mutants show throughout development and even in first instar larva stages bursty activity patterns. (B) Coefficient of variation of the interspike intervals (CV) at different developmental stages in controls (blue) and <i>Orco</i> mutants (red). CV is significantly higher in 16 h AEL embryos and first instar <i>Orco</i> mutants than in controls, which demonstrates that at least part of the reduction in spike train variability as development proceeds is due to OR expression. (C) Firing rate at different developmental stages in controls (blue) and <i>Orco</i> mutants (red). The firing rate at 16 h AEL is similar in <i>Orco</i> mutants and controls, but there is a significant difference between controls and <i>Orco</i> mutants in first instar larvae. (B–C) Error bars represent SEM. A single asterisk (*) indicates <i>p</i>≤0.05. <i>N.S.</i> indicates <i>p</i>>0.05.</p

Optogenetics.

<p><b>A</b>. Experimental configuration suitable for optogenetic stimulation of an individual zebrafish larva suspended in a drop of E3 (Methods). <b>B</b>. Spectrum and peak power of the three light-emitting diodes (LEDs) embedded at each ring position. Spectral filters can be used to limit excitation light reaching the camera (Rosco Supergel No. 19, ‘Fire’). <b>C</b>. Zebrafish larva (3 days postfertilisation [<i>dpf</i>]) expressing ChR2 broadly in neurons (<i>Et(E1b</i>:<i>Gal4)s1101t</i>, <i>Tg(UAS</i>::<i>Cr</i>.<i>ChR2_H134R-mCherry)s1985t</i>, <i>nacre-/-</i>). <b>D</b>. The animal exhibits pectoral fin burst motor patterns upon activation of blue LEDs (cf. <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2002702#pbio.2002702.s010" target="_blank">S8 Video</a>). <b>E, F</b>. <i>Drosophila</i> larvae expressing ChR2 in all neurons (elav-GAL4/+; UAS-shibre^ts; UAS-ChR2/+; UAS-ChR2/+) crawling on ink-stained agar reliably contract when blue LEDs are active. <b>G</b>, <b>H</b>. Proboscis extension reflex (PER) in adult <i>Drosophila</i> expressing CsChrimson in the gustatory circuit (w; +; GMR86A08-GAL4/UAS-CSChrimson; the GMR86A08-GAL4 is part of the Janelia Farm Flightlight collection [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2002702#pbio.2002702.ref032" target="_blank">32</a>]; its effect on PER is a personal communication from Olivia Schwarz and Jan Pielage, University of Kaiserslautern, Germany, who observed this phenotype as part of behavioural screen [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2002702#pbio.2002702.ref033" target="_blank">33</a>]) is reliably elicited by activation of red LEDs.</p