Carbon dioxide (CO 2 ) is one of the prominent sensory cues used by mosquitoes to find hosts for blood-feeding. CO 2 is detected on the maxillary palps by capitate peg sensory neurons, whose axons project to the antennal lobe in the brain. Behavioral studies have shown that mosquitoes prefer non-homogenous plumes of CO 2 over homogenous plumes and CO 2 greatly enhances the attractiveness of lactic acid, a skin volatile. However, the neural mechanisms underlying these behavioral preferences are not known. Using in vivo intracellular recordings from projection neurons and local neurons in the antennal lobe, along with single sensillum recordings from the maxillary palps, we checked the representations of CO 2 in the first two layers of the Aedes aegypti olfactory system. We found that the preference to non-homogeneous plumes of CO 2 and its synergistic attraction with lactic acid are encoded in the PN population responses. Our results provide a foundation for understanding CO 2 -mediated host-attraction in mosquitoes.

ABSTRACT Under normal physiological conditions, the mammalian brain contains very little glycogen, most of which is stored in astrocytes. However, the aging brain and the subareas of the brain in patients with neurodegenerative disorders tend to accumulate glycogen, the cause and significance of which remain largely unexplored. Using cellular models, we have recently demonstrated a neuroprotective role for neuronal glycogen and glycogen synthase in the context of Huntington's disease. To gain insight into the role of brain glycogen in regulating proteotoxicity, we utilized a Drosophila model of Huntington's disease, in which glycogen synthase is either knocked down or expressed ectopically. Enhancing glycogen synthesis in the brains of flies with Huntington's disease decreased mutant Huntingtin aggregation and reduced oxidative stress by activating auto-lysosomal functions. Further, overexpression of glycogen synthase in the brain rescues photoreceptor degeneration, improves locomotor deficits and increases fitness traits in this Huntington's disease model. We, thus, provide in vivo evidence for the neuroprotective functions of glycogen synthase and glycogen in neurodegenerative conditions, and their role in the neuronal autophagy process.

Among the cues that a mosquito uses to find a host for blood-feeding, the smell of the host plays an important role. Previous studies have shown that host odors contain hundreds of chemical odorants, which are detected by different receptors on the peripheral sensory organs of mosquitoes. But how individual odorants are encoded by downstream neurons in the mosquito brain is not known. We developed an in vivo preparation for patch-clamp electrophysiology to record from projection neurons and local neurons in the antennal lobe of Aedes aegypti. Combining intracellular recordings with dye-fills, morphological reconstructions, and immunohistochemistry, we identify different sub-classes of antennal lobe neurons and their putative interactions. Our recordings show that an odorant can activate multiple neurons innervating different glomeruli, and that the stimulus identity and its behavioral preference are represented in the population activity of the projection neurons. Our results provide a detailed description of the second-order olfactory neurons in the central nervous system of mosquitoes and lay a foundation for understanding the neural basis of their olfactory behaviors.

A closed cylindrical pipe with an inner partition wall forms two one-dimensional cavities. These each exhibit acoustic modes at certain well-defined frequencies. A partial transmission through the partition leads to interactions between the two cavities' modes, and hence to avoided crossings between modes' frequencies. This acoustic system is analogous to a quantum system that has two multi-level interacting sub-systems and, thus, exhibits multiple avoided crossings. Such an acoustic analog is realized and studied by measuring sound transmission as a function of frequency through a pipe with a partially transmitting and movable partition. An excellent agreement is obtained between the experimental results and a simple model based on wave transmission and reflection at different interfaces.

Many experimental studies have examined behavioral and electrophysiological responses of mosquitoes to odors. However, the differences across studies in data collection, processing, and reporting make it difficult to perform large-scale analyses combining data from multiple studies. Here we extract and standardize data for 12 mosquito species, along with Drosophila melanogaster for comparison, from over 170 studies and curate the Mosquito Olfactory Response Ensemble (MORE), publicly available at https://neuralsystems.github.io/MORE. We demonstrate the ability of MORE in generating biological insights by finding patterns across studies. Our analyses reveal that ORs are tuned to specific ranges of several physicochemical properties of odorants; the empty-neuron recording technique for measuring OR responses is more sensitive than the Xenopus oocyte technique; there are systematic differences in the behavioral preferences reported by different types of assays; and odorants tend to become less attractive or more aversive at higher concentrations.

Effective outcome from dynamic live-cell-imaging requires utilization of a probe with high emission intensity and low photobleaching. It would be preferable to achieve such properties at a low power of the applied laser to avoid any probable damage to biological cells or tissue. Most of the used small-molecule fluorophores have been reported to show significant photobleaching in a time-dependent manner and require high laser power to gain significant intensity for bioimaging. Carbon nanoparticles have recently been successfully used for cell imaging with low bleaching characteristics but require high laser power and lack optical nonlinearity at low power levels. Here, we report the preparation, characterization, and application of a Nanoscale Carbon (NC) which, on being surface decorated with crescent-shaped poly-lysine (PLNC), provides two-photon fluorescence (TPF) and low bleaching properties. PLNC was found to stain the cytoplasm of C2C12 muscle cells in the first four-hours of incubation with high TPF in the infrared range and can be useful for deep tissue imaging with further improvements.