Phototransduction in Drosophila.

Phototransduction in Drosophila's microvillar photoreceptors is mediated by phospholipase C (PLC) resulting in activation of two distinct Ca(2+)-permeable channels, TRP and TRPL. Here we review recent evidence on the unresolved mechanism of their activation, including the hypothesis that the channels are mechanically activated by physical effects of PIP2 depletion on the membrane, in combination with protons released by PLC. We also review molecularly explicit models indicating how Ca(2+)-dependent positive and negative feedback along with the ultracompartmentalization provided by the microvillar design can account for the ability of fly photoreceptors to respond to single photons 10-100× more rapidly than vertebrate rods, yet still signal under full sunlight.The authors’ own research reviewed in the paper was supported by the Biotechnology and Biological Sciences Research Council (BBSRC Grants BB/D007585/1 and BB/G006865/1 to RCH; BB/H013849/1 to MJ), the State Key Laboratory of Cognitive Neuroscience and Learning open research fund to MJ, Jane and Aatos Erkko Foundation Fellowship to MJ, and the Leverhulme Trust grant (RPG-2012-567 to MJ).This is the accepted manuscript for a paper published in Current Opinion in Neurobiology Volume 34, October 2015, Pages 37–45, DOI: 10.1016/j.conb.2015.01.00

The Rate of Information Transfer of Naturalistic Stimulation by Graded Potentials

We present a method to measure the rate of information transfer for any continuous signals of finite duration without assumptions. After testing the method with simulated responses, we measure the encoding performance of Calliphora photoreceptors. We find that especially for naturalistic stimulation the responses are nonlinear and noise is nonadditive, and show that adaptation mechanisms affect signal and noise differentially depending on the time scale, structure, and speed of the stimulus. Different signaling strategies for short- and long-term and dim and bright light are found for this graded system when stimulated with naturalistic light changes

Random Photon Absorption Model Elucidates How Early Gain Control in Fly Photoreceptors Arises from Quantal Sampling

Many diurnal photoreceptors encode vast real-world light changes effectively, but how this performance originates from photon sampling is unclear. A 4-module biophysically-realistic fly photoreceptor model, in which information capture is limited by the number of its sampling units (microvilli) and their photon-hit recovery time (refractoriness), can accurately simulate real recordings and their information content. However, sublinear summation in quantum bump production (quantum-gain-nonlinearity) may also cause adaptation by reducing the bump/photon gain when multiple photons hit the same microvillus simultaneously. Here, we use a Random Photon Absorption Model (RandPAM), which is the 1st module of the 4-module fly photoreceptor model, to quantify the contribution of quantum-gain-nonlinearity in light adaptation. We show how quantum-gain-nonlinearity already results from photon sampling alone. In the extreme case, when two or more simultaneous photon-hits reduce to a single sublinear value, quantum-gain-nonlinearity is preset before the phototransduction reactions adapt the quantum bump waveform. However, the contribution of quantum-gain-nonlinearity in light adaptation depends upon the likelihood of multi-photon-hits, which is strictly determined by the number of microvilli and light intensity. Specifically, its contribution to light-adaptation is marginal (≤1%) in fly photoreceptors with many thousands of microvilli, because the probability of simultaneous multi-photon-hits on any one microvillus is low even during daylight conditions. However, in cells with fewer sampling units, the impact of quantum-gain-nonlinearity increases with brightening light

Caught in crossfire : health care workers’ experiences of violence in Syria

Health care is attacked in many contemporary conflicts despite the Geneva Conventions. The war in Syria has become notorious for targeted violence against health care. This qualitative study describes health care workers’ experi-ences of violence using semi-structured interviews (n = 25) with professionals who have been working in Syria. The participants were selected using a snow-ball sampling method and interviewed in Turkey and Europe between 2016– 2017. Analysis was conducted using content analysis. Results revealed that the most destructive and horrific forms of violence health care workers have experienced were committed mostly by the Government of Syria and the Islamic State. Non-state armed groups and Kurdish Forces have also committed acts of violence against health care, though their scope and scale were con-sidered to have a lower mortality. The nature of violence has evolved during the conflict: starting from verbal threats and eventually leading to hospital bomb-ings. Health care workers were not only providers of health care to injured demonstrators, they also participated in non- violent anti-government actions. The international community has not taken action to protect health care in Syria. For health workers finding safe environments in which to deliver health care has been impossible.Peer reviewe

I had to leave. I had to leave my clinic, my city, leave everything behind in Syria : Qualitative research of Syrian healthcare workers migrating from the war-torn country

Peer reviewe

I don't leave my people; They need me : Qualitative research of local health care professionals' working motivations in Syria

Background The Syrian conflict has endured for a decade, causing one of the most significant humanitarian crises since World War II. The conflict has inflicted massive damage to civil infrastructure, and not even the health care sector has been spared. On the contrary, health care has been targeted, and as a result, many health professionals have left the country. Despite the life-threatening condition, many health professionals continued to work inside Syria even in the middle of the acute crisis. This qualitative study aims to determine the factors that have motivated Syrian health professionals to work in a conflict-affected country. Methods The research is based on 20 semi-structured interviews of Syrian health care workers. Interviews were conducted in 2016-2017 in Gaziantep, Turkey. A thematic inductive content analysis examined the motivational factors Syrian health care workers expressed for their work in the conflict area. Results Motivating factors for health care workers were intrinsic and extrinsic. Intrinsic reasons included humanitarian principles and medical ethics. Also, different ideological reasons, patriotic, political and religious, were mentioned. Economic and professional reasons were named as extrinsic reasons for continuing work in the war-torn country. Conclusions The study adds information on the effects of the Syrian crisis on health care-from healthcare workers' perspective. It provides a unique insight on motivations why health care workers are continuing their work in Syria. This research underlines that the health care system would collapse totally without local professionals and leave the population without adequate health care.Peer reviewe

Does calcium diffusional global feedback leads to slow light adaptation in Drosophila photoreceptors? - A 3D biophysical modelling approach

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are