Biology subjects

Lines, J.

Publications and source records attributed to Lines, J..

5 recordsLinked to original sources

bioRxiv2023

A spatial threshold for astrocyte calcium surge

Astrocytes are active cells involved in brain function through the bidirectional communication with neurons, in which the astrocyte calcium signal plays a crucial role. Synaptically-evoked calcium increases can be localized to independent subcellular domains or expand to the entire cell, i.e., calcium surge. In turn, astrocytes may regulate individual synapses by calcium-dependent release of gliotransmitters. Because a single astrocyte may contact [~]100,000 synapses, the control of the intracellular calcium signal propagation may have relevant consequences on brain function by regulating the spatial range of astrocyte neuromodulation of synapses. Yet, the properties governing the spatial dynamics of the astrocyte calcium signal remains poorly defined. Imaging subcellular responses of cortical astrocytes to sensory stimulation in mice, we show that sensory-evoked astrocyte calcium responses originated and remained localized in domains of the astrocytic arborization, but eventually propagated to the entire cell if a spatial threshold of >23% of the arborization being activated was surpassed. Using transgenic IP3R2-/- mice, we found that type-2 IP3 receptors were necessary for the generation of the astrocyte calcium surge. We finally show using in situ electrophysiological recordings that the spatial threshold of the astrocyte calcium signal consequently determined the gliotransmitter release. Present results reveal a fundamental property of astrocyte calcium physiology, i.e., a spatial threshold for the astrocyte intracellular calcium signal propagation, which depends on astrocyte intrinsic properties and governs the astrocyte integration of local synaptic activity and the subsequent neuromodulation. One-Sentence SummaryThere is a spatial threshold for the astrocyte intracellular calcium signal propagation that is determined by astrocyte intrinsic properties and controls gliotransmission.

neuroscience↗

bioRxiv2023

Building the vector in? Construction practices contribute to the invasion and persistence of Anopheles stephensi in Jigjiga, Ethiopia

Anopheles stephensi is a major vector of malaria in Asia and the Arabian Peninsula, and its recent invasion into Africa poses a significant threat to malaria control and elimination efforts on the continent. The mosquito is well-adapted to urban environments, and its presence in Africa could potentially lead to an increase in malaria transmission in cities. Most of the knowledge about An. stephensi ecology in Africa has been generated from studies conducted during the rainy season, when vectors are most abundant. Here, we provide evidence from the peak of the dry season in the city of Jigjiga, Ethiopia, and report the finding of An. stephensi immature stages infesting predominantly water reservoirs made to support construction operations (in construction sites or associated with brick manufacturing businesses). Political and economic changes in Ethiopia (and particularly the Somali Region) have fueled an unprecedented construction boom since 2018 that, in our opinion, has been instrumental in the establishment, persistence and propagation of An. stephensi via the year-round availability of perennial larval habitats associated with construction. We argue that larval source management during the dry season may provide a unique opportunity for focused control of An. stephensi in Jigjiga and similar areas.

ecology↗

bioRxiv2023

Visually evoked neuronal ensembles reactivate during sleep

Neuronal ensembles, defined as groups of coactive neurons, dominate cortical activity and are causally related to perceptual states and behavior. Interestingly, ensembles occur spontaneously in the absence of sensory stimulation. To better understand the function of ensembles in spontaneous activity, we explored if ensembles also occur during different brain states, including sleep, using two-photon calcium imaging from mouse primary visual cortex. We find that ensembles are present during all wake and sleep states, with different characteristics depending on the exact sleep stage. Moreover, visually evoked ensembles are reactivated during subsequent slow wave sleep cycles. Our results are consistent with the hypothesis that repeated sensory stimulation can reconfigure cortical circuits and imprint neuronal ensembles that are reactivated during sleep for potential processing or memory consolidation. One-Sentence SummaryCortical neuronal ensembles are present across wake and sleep states, and visually evoked ensembles are reactivated in subsequent slow-wave sleep.

neuroscience↗

bioRxiv2022

Towards environmental detection, quantification, and molecular characterization of Anopheles stephensi and Aedes aegypti from larval breeding sites

The invasion and establishment of An. stephensi mosquitoes in the Horn of Africa represents a significant regional threat, which may jeopardise malaria control, particularly in urban areas which were formally free from disease transmission. Novel vector surveillance methods are urgently needed, both agnostic to mosquito larval morphology, and simple to implement at the sampling stage. Using new multiplex TaqMan assays, specifically targeting An. stephensi and Ae. aegypti, we validated the use of environmental DNA (eDNA) for simultaneous vector detection in shared artificial breeding sites. Study findings demonstrated that An. stephensi and Ae. aegypti eDNA deposited by as few as one second instar larva in 1L of water was detectable. Characterization of molecular insecticide resistance mechanisms, using novel amplicon-sequencing panels for both vector species, was possible from eDNA shed by as few as 32 second instar larvae in 50ml of water. An. stephensi eDNA, derived from emergent pupae for 24 hours, was remarkably stable, and still detectable ~2 weeks later. eDNA surveillance has the potential to be implemented in local endemic communities and points of country entry, to monitor the spread of invasive vector species. Further studies are required to validate the feasibility of this technique under field conditions.

molecular biology↗

bioRxiv2020

Determination of the amount of insecticide picked up by mosquitoes from treated nets

BackgroundInsecticides used in vector control mostly rely on vectors being exposed through contact with treated surfaces, yet little is known about the amount picked up by the insect. Measuring this amount is relevant not only for determining the actual doses that are lethal to the mosquito, but also for understanding effects on the physiology and vector competence of mosquitoes. Insecticides at sub-lethal doses can affect both parasites developing inside mosquitoes and mosquito microbiota, hence it is important to understand the processes by which parasites are exposed to insecticide inside the insect. These doses will inevitably depend on the amount of insecticide that mosquitoes pick up when they come into contact with treated nets. MethodsThree to five days old non-blood fed female Anopheles coluzzii mosquitoes were exposed to a long-lasting insecticidal net (PermaNet 2.0 containing 55 mg/m2 deltamethrin), using a wire ball frame, for 0.5-5.0 minutes. Our in-house developed colorimetric test was used to visually detect the amount of deltamethrin on different parts of the mosquito (legs, heads, thoraxes, abdomens) following exposure to the net. The amount of insecticide picked up by mosquitoes from the net over a range of exposure times was measured using a high-performance liquid chromatography with diode array detection (HPLC-DAD). ResultsThe colorimetric test, designed to only detect the type 2 pyrethroids (i.e deltamethrin, -cypermethrin and {lambda}-cyhalothrin) on fabrics (e.g. ITNs) and sprayed walls, was successfully used for the first time to detect deltamethrin on mosquitoes following exposure to the net. The confirmatory HPLC-DAD analysis determined that after 2 min exposure up to 12 ng of deltamethrin adhered to mosquitoes following exposure to PermaNet 2.0 (mean = 5.2 ng/mosquito, SE = 1.9) and that the final dose depends on the length of exposure time. ConclusionsThis study demonstrated the potential of a screening (type 2 pyrethroid colorimetric test) and a confirmatory test (HPLC-DAD) to determine the amount of insecticide that adheres to mosquitoes on contact with treated surfaces. This has implications for a precise lethal dose determination and detection of specific insecticide that causes the greatest mosquito mortality in circumstances where mixtures of insecticides may be used to maximise effectiveness of interventions.

biochemistry↗