A single pair of pharyngeal neurons functions as a commander to reject high salt in Drosophila melanogaster.

Salt (NaCl), is an essential nutrient for survival, while excessive salt can be detrimental. In the fruit fly, Drosophila melanogaster, internal taste organs in the pharynx are critical gatekeepers impacting the decision to accept or reject a food. Currently, our understanding of the mechanism through which pharyngeal gustatory receptor neurons (GRNs) sense high salt are rudimentary. Here, we found that a member of the ionotropic receptor family, Ir60b, is expressed exclusively in a pair of GRNs activated by high salt. Using a two-way choice assay (DrosoX) to measure ingestion volume, we demonstrate that IR60b and two co-receptors IR25a and IR76b are required to prevent high salt consumption. Mutants lacking external taste organs but retaining the internal taste organs in the pharynx exhibit much higher salt avoidance than flies with all taste organs but missing the three IRs. Our findings highlight the vital role for IRs in a pharyngeal GRN to control ingestion of high salt.

Avoiding cantharidin through ionotropic receptors.

The discernment and aversion of noxious gustatory stimuli profoundly influence homeostasis maintenance and survival of fauna. Cantharidin, a purported aphrodisiac, is a monoterpenoid compound secreted by many species of blister beetle, particularly by the Spanish fly, Lytta vesicatoria. Although the various advantageous functions of cantharidin have been described, its taste analysis and toxic properties in animalshave been rarely explored. Our study using Drosophila melanogaster examines the taste properties of cantharidin along with its potential hazardous effect in the internal organs of animals. Here, we find that cantharidin activates bitter taste receptors. Our findings show that specific ionotropic receptors (IR7g, IR51b, and IR94f) in labellar bitter-sensing neurons, along with co-receptors IR25a and IR76b, are responsible for detecting cantharidin. By introducing the IR7g and IR51b in sweet and bitter neurons, naturally expressing IR76b and IR25a, we show that these genes are sufficient for cantharidin perception. Moreover, we witness the deleterious ramifications of cantharidin on survival and visceral integrities, shedding light on its hazardous effect.

A single pair of pharyngeal neurons functions as a commander to reject high salt in Drosophila melanogaster.

Salt is an essential nutrient for survival, while excessive NaCl can be detrimental. In the fruit fly, Drosophila melanogaster, internal taste organs in the pharynx are critical gatekeepers impacting the decision to accept or reject a food. Currently, our understanding of the mechanism through which pharyngeal gustatory receptor neurons (GRNs) sense high salt are rudimentary. Here, we found that a member of the ionotropic receptor family, Ir60b, is expressed exclusively in a pair of GRNs activated by high salt. Using a two-way choice assay (DrosoX) to measure ingestion volume, we demonstrate that IR60b and two coreceptors IR25a and IR76b, are required to prevent high salt consumption. Mutants lacking external taste organs but retaining the internal taste organs in the pharynx exhibit much higher salt avoidance than flies with all taste organs but missing the three IRs. Our findings highlight the vital role for IRs in a pharyngeal GRN to control ingestion of high salt.

Pulmonary Cavitary Sarcoidosis: A Case Report.

Sarcoidosis is a granulomatous disease characterized by a non-caseating granuloma formation in different organs of the body. However, the presence of cavitary lesions is rare. We present a case report of a 38-year-old male who presented with a three-month history of cough, dyspnea, and weight loss. Computed tomography of the chest demonstrated enlarged mediastinal and bilateral hilar lymphadenopathy with bilateral perihilar consolidation and cavitation in the upper lobes of both lungs. Later, the patient underwent bronchoscopy with bronchoalveolar lavage and endobronchial biopsy which showed well-formed and non-necrotizing granulomas which were also embedded in the dense hyaline sclerosis. This finding is consistent with sarcoidosis. Treatment with systemic corticosteroids was initiated, resulting in significant improvement in the patient's symptoms. This case report highlights the uncommon manifestation of pulmonary cavitary sarcoidosis and emphasizes the significance of accurate diagnosis and appropriate management of this complex disease.

Acid and Alkali Taste Sensation.

Living organisms rely on pH levels for a multitude of crucial biological processes, such as the digestion of food and the facilitation of enzymatic reactions. Among these organisms, animals, including insects, possess specialized taste organs that enable them to discern between acidic and alkaline substances present in their food sources. This ability is vital, as the pH of these compounds directly influences both the nutritional value and the overall health impact of the ingested substances. In response to the various chemical properties of naturally occurring compounds, insects have evolved peripheral taste organs. These sensory structures play a pivotal role in identifying and distinguishing between nourishing and potentially harmful foods. In this concise review, we aim to provide an in-depth examination of the molecular mechanisms governing pH-dependent taste responses, encompassing both acidic and alkaline stimuli, within the peripheral taste organs of the fruit fly, Drosophila melanogaster, drawing insights from a comprehensive analysis of existing research articles.

Emergence of Pulmonary Tuberculosis While Recovering From COVID-19 Pneumonia: A Case Report.

COVID-19 can have different presentations; from asymptomatic to multiorgan involvement. This case report is of an elderly gentleman, with known comorbidities of chronic obstructive airway disease and alcoholic liver disease on treatment. He presented with a history of increasing dyspnea and cough for a few days which was present after cold symptoms, and was admitted for the treatment of severe COVID-19 pneumonia. Later, while he was recovering from COVID-19 pneumonia, his respiratory symptoms worsened. After a thorough evaluation, his sputum smear was positive for acid-fast bacilli and also rifampicin sensitive on GeneXpert assay. With timely diagnosis and appropriate treatment, he recovered from both acute conditions and was sent home on the twentieth day of admission.

Molecular Basis of Hexanoic Acid Taste in Drosophila melanogaster.

Animals generally prefer nutrients and avoid toxic and harmful chemicals. Recent behavioral and physiological studies have identified that sweet-sensing gustatory receptor neurons (GRNs) in Drosophila melanogaster mediate appetitive behaviors toward fatty acids. Sweet-sensing GRN activation requires the function of the ionotropic receptors IR25a, IR56d, and IR76b, as well as the gustatory receptor GR64e. However, we reveal that hexanoic acid (HA) is toxic rather than nutritious to D. melanogaster. HA is one of the major components of the fruit Morinda citrifolia (noni). Thus, we analyzed the gustatory responses to one of major noni fatty acids, HA, via electrophysiology and proboscis extension response (PER) assay. Electrophysiological tests show this is reminiscent of arginine-mediated neuronal responses. Here, we determined that a low concentration of HA induced attraction, which was mediated by sweet-sensing GRNs, and a high concentration of HA induced aversion, which was mediated by bitter-sensing GRNs. We also demonstrated that a low concentration of HA elicits attraction mainly mediated by GR64d and IR56d expressed by sweet-sensing GRNs, but a high concentration of HA activates three gustatory receptors (GR32a, GR33a, and GR66a) expressed by bitter-sensing GRNs. The mechanism of sensing HA is biphasic in a dose dependent manner. Furthermore, HA inhibit sugar-mediated activation like other bitter compounds. Taken together, we discovered a binary HA-sensing mechanism that may be evolutionarily meaningful in the foraging niche of insects.

The taste of vitamin C in Drosophila.

Vitamins are essential micronutrients, but the mechanisms of vitamin chemoreception in animals are poorly understood. Here, we provide evidence that vitamin C doubles starvation resistance and induces egg laying in Drosophila melanogaster. Our behavioral analyses of genetically engineered and anatomically ablated flies show that fruit flies sense vitamin C via sweet-sensing gustatory receptor neurons (GRNs) in the labellum. Using a behavioral screen and in vivo electrophysiological analyses of ionotropic receptors (IRs) and sweet-sensing gustatory receptors (GRs), we find that two broadly tuned IRs (i.e., IR25a and IR76b) and five GRs (i.e., GR5a, GR61a, GR64b, GR64c, and GR64e) are essential for vitamin C detection. Thus, vitamin C is directly detected by the fly labellum and requires at least two distinct receptor types. Next, we expand our electrophysiological study to test attractive tastants such as sugars, carboxylic acids, and glycerol. Our analysis elucidates the molecular basis of chemoreception in sweet-sensing GRNs.

Molecular sensors in the taste system of Drosophila.

BACKGROUND: Most animals, including humans and insects, consume foods based on their senses. Feeding is mostly regulated by taste and smell. Recent insect studies shed insight into the cross-talk between taste and smell, sweetness and temperature, sweetness and texture, and other sensory modality pairings. Five canonical tastes include sweet, umami, bitter, salty, and sour. Furthermore, other receptors that mediate the detection of noncanonical sensory attributes encoded by taste stimuli, such as Ca2+, Zn2+, Cu2+, lipid, and carbonation, have been characterized. Deorphanizing receptors and interactions among different modalities are expanding the taste field. METHODS: Our study explores the taste system of Drosophila melanogaster and perception processing in insects to broaden the neuroscience of taste. Attractive and aversive taste cues and their chemoreceptors are categorized as tables. In addition, we summarize the recent progress in animal behavior as affected by the integration of multisensory information in relation to different gustatory receptor neuronal activations, olfaction, texture, and temperature. We mainly focus on peripheral responses and insect decision-making. CONCLUSION: Drosophila is an excellent model animal to study the cellular and molecular mechanism of the taste system. Despite the divergence in the receptors to detect chemicals, taste research in the fruit fly can offer new insights into the many different taste sensors of animals and how to test the interaction among different sensory modalities.

Protocol for binary food choice assays using Drosophila melanogaster.

Food preference is a fundamental behavior for animals to choose nutritious foods while rejecting foods containing toxins. Here, we describe binary food choice assays using Drosophila melanogaster, which are straightforward approaches for the characterization of two-way choice tastants. We detail the preparation of flies and dye-containing food, followed by the binary-choice feeding assays and the determination of the preference index (PI). This protocol is simple, sensitive, and reproducible in qualitatively detecting attractive or aversive characteristics toward any two-way choice tastants. For complete details on the use and execution of this protocol, please refer to Aryal et al. (2022).

Molecular and neuronal mechanisms for amino acid taste perception in the Drosophila labellum.

Amino acids are essential nutrients that act as building blocks for protein synthesis. Recent studies in Drosophila have demonstrated that glycine, phenylalanine, and threonine elicit attraction, whereas tryptophan elicits aversion at ecologically relevant concentrations. Here, we demonstrated that eight amino acids, including arginine, glycine, alanine, serine, phenylalanine, threonine, cysteine, and proline, differentially stimulate feeding behavior by activating sweet-sensing gustatory receptor neurons (GRNs) in L-type and S-type sensilla. In turn, this process is mediated by three GRs (GR5a, GR61a, and GR64f), as well as two broadly required ionotropic receptors (IRs), IR25a and IR76b. However, GR5a, GR61a, and GR64f are only required for sensing amino acids in the sweet-sensing GRNs of L-type sensilla. This suggests that amino acid sensing in different type sensilla occurs through dual mechanisms. Furthermore, our findings indicated that ecologically relevant high concentrations of arginine, lysine, proline, valine, tryptophan, isoleucine, and leucine elicit aversive responses via bitter-sensing GRNs, which are mediated by three IRs (IR25a, IR51b, and IR76b). More importantly, our results demonstrate that arginine, lysine, and proline induce biphasic responses in a concentration-dependent manner. Therefore, amino acid detection in Drosophila occurs through two classes of receptors that activate two sets of sensory neurons in physiologically distinct pathways, which ultimately mediates attraction or aversion behaviors.

Cellular and molecular basis of IR3535 perception in Drosophila.

BACKGROUND: IR3535 is among the most widely used synthetic insect repellents, particularly for the mitigation of mosquito-borne diseases such as malaria, yellow fever, dengue and Zika, as well as to control flies, ticks, fleas, lice and mites. These insects are well-known vectors of deadly diseases that affect humans, livestock and crops. Moreover, global warming could increase the populations of these vectors. RESULTS: Here, we performed IR3535 dose-response analyses on Drosophila melanogaster, a well-known insect model organism, using electrophysiology and binary food choice assays. Our findings indicated that bitter-sensing gustatory receptor neurons (GRNs) are indispensable to detect IR3535. Further, potential candidate gustatory receptors were screened, among which GR47a was identified as a key molecular sensor. IR3535 concentrations in the range 0.1-0.4% affected larval development and mortality. In addition, N,N-diethyl-m-toluamide (DEET, another commonly used insecticide) was found to exert synergistic effects when co-administered with IR3535. CONCLUSION: Our findings confirmed that IR3535 directly activates bitter-sensing GRNs, which are mediated by GR47a. This relatively safe and highly potent insecticide can be largely used in combination with DEET to increase its efficiency to protect livestock and crops. Collectively, our findings suggest that the molecular sensors elucidated herein could be used as targets for the development of alternative insecticides. © 2021 Society of Chemical Industry.

Study on the Synthesis of ZnO Nanoparticles Using Azadirachta indica Extracts for the Fabrication of a Gas Sensor.

This paper compared the effects of A. indica plant proteins over chemical methods in the morphology of zinc oxide nanoparticles (ZnO NPs) prepared by a co-precipitation method, and ethanol sensing performance of prepared thin films deposited over a fluorene-doped tin oxide (FTO) bind glass substrate using spray pyrolysis technique. The average crystallite sizes and diameters of the grain-sized cluster ZnO NPs were 25 and (701.79 ± 176.21) nm for an undoped sample and 20 and (489.99 ± 112.96) nm for A. india dye-doped sample. The fourier transform infrared spectroscopy (FTIR) analysis confirmed the formation of the Zn-O bond at 450 cm-1, and also showed the presence of plant proteins due to A. indica dye extracts. ZnO NPs films exhibited good response (up to 51 and 72% for without and with A. indica dye-doped extracts, respectively) toward ethanol vapors with quick response-recovery characteristics at a temperature of 250 °C for undoped and 225 °C for A. indica dye-doped ZnO thin films. The interaction of A. indica dye extracts helps to decrease the operating temperature and increased the response and recovery rates of the sensor, which may be due to an increase in the specific surface area, resulting in adsorption of more oxygen and hence high response results.

Mechanisms of Carboxylic Acid Attraction in Drosophila melanogaster.

Sour is one of the fundamental taste modalities that enable taste perception in animals. Chemoreceptors embedded in taste organs are pivotal to discriminate between different chemicals to ensure survival. Animals generally prefer slightly acidic food and avoid highly acidic alternatives. We recently proposed that all acids are aversive at high concentrations, a response that is mediated by low pH as well as specific anions in Drosophila melanogaster. Particularly, some carboxylic acids such as glycolic acid, citric acid, and lactic acid are highly attractive to Drosophila compared with acetic acid. The present study determined that attractive carboxylic acids were mediated by broadly expressed Ir25a and Ir76b, as demonstrated by a candidate mutant library screen. The mutant deficits were completely recovered via wild-type cDNA expression in sweet-sensing gustatory receptor neurons. Furthermore, sweet gustatory receptors such as Gr5a, Gr61a, and Gr64a-f modulate attractive responses. These genetic defects were confirmed using binary food choice assays as well as electrophysiology in the labellum. Taken together, our findings demonstrate that at least two different kinds of receptors are required to discriminate attractive carboxylic acids from other acids.

Low-Temperature Plasma-Assisted Nitrogen Fixation for Corn Plant Growth and Development.

Nitrogen fixation is crucial for plants as it is utilized for the biosynthesis of almost all biomolecules. Most of our atmosphere consists of nitrogen, but plants cannot straightforwardly assimilate this from the air, and natural nitrogen fixation is inadequate to meet the extreme necessities of global nutrition. In this study, nitrogen fixation in water was achieved by an AC-driven non-thermal atmospheric pressure nitrogen plasma jet. In addition, Mg, Al, or Zn was immersed in the water, which neutralized the plasma-treated water and increased the rate of nitrogen reduction to ammonia due to the additional hydrogen generated by the reaction between the plasma-generated acid and metal. The effect of the plasma-activated water, with and without metal ions, on germination and growth in corn plants (Zea Mays) was investigated. The germination rate was found to be higher with plasma-treated water and more efficient in the presence of metal ions. Stem lengths and germination rates were significantly increased with respect to those produced by DI water irrigation. The plants responded to the abundance of nitrogen by producing intensely green leaves because of their increased chlorophyll and protein contents. Based on this report, non-thermal plasma reactors could be used to substantially enhance seed germination and seedling growth.

Isolation and Characterization of Potential Antibiotic-Producing Actinomycetes from Water and Soil Sediments of Different Regions of Nepal.

INTRODUCTION: The actinomycetes are diversely distributed microorganisms in nature. The geographical diversity of Nepal is suitable for adaptation of various species of actinomycetes. The distribution of the actinomycetes is dependent upon the altitude and nature of the soil and water. METHODS: A total of 22 water and soil samples were collected from different regions of Nepal and were processed. Different isolates were characterized by observing colony characteristics and microscopic characteristics. Screening of the antimicrobial property was based upon perpendicular line streaking and submerged-state fermentation for antibiotic production. RESULTS: From the identification tool used, 12 were found to be Micromonospora, 9 were Nocardia, and 7 were Streptomyces. Out of total samples, 8 isolates of actinomycetes were tested effective against the tested bacteria by primary screening using the well diffusion method. Among the primarily screened, all isolates were subjected to submerged-state fermentation methods to produce crude extracts and 4 were found to be effective against the tested bacterial group. The actinomycetes identified from a water source showed better antimicrobial property towards the tested bacteria than the soil sample. Most isolates were found to be Micromonospora followed by Nocardia and Streptomyces with higher antimicrobial activities. CONCLUSION: The water source and soil sediments of Nepal provide suitable environments for actinomycetes towards obtaining a novel antimicrobial agent. The study of actinomycetes from various unexploited areas of Nepal is necessary. Thus, exploitation of various regions of Nepal for the discovery of an effective antimicrobial agent is helpful in providing a solution to the cost-effective therapy and action against antibiotic resistance.

Mechanisms of DEET gustation in Drosophila.

DEET is the most widely used active ingredient in insect repellents and offers protection against insect bites. We previously reported that DEET suppresses the feeding behavior of Drosophila, which is guided by gustatory receptors (GRs) in bitter-sensing gustatory receptor neurons. Here, we sought to identify new candidates using egg-laying assays. Upon screening all GR mutants, GR89a was identified as a potential DEET receptor. Gr89a mutants exhibited reduced oviposition avoidance, feeding avoidance, and electrophysiological responses compared to Gr32a, Gr33a, and Gr66a mutants. However, GR89a was found to modulate DEET avoidance, as demonstrated by genetic and RNA interference assays. Furthermore, we found that DEET ingestion severely affected larval and pupal development and survival, and therefore may act as an effective larvicide.

Cellular and molecular mechanisms of DEET toxicity and disease-carrying insect vectors: a review.

BACKGROUND: Several insects such as mosquitoes, flies, ticks, fleas, lice, and mites are known to serve as vectors for a vast number of pathogens. Many such vectors are hematophagous, and therefore introduce pathogens directly into the host's bloodstream. Importantly, the capacity of these vectors to spread disease can lead to serious global health crises. Furthermore, crop damage can be exacerbated by pathogen infection and increased insect foraging due to recent global warming. METHODS: Our study categorized insect-associated damage into three groups: animal infection, plant infection, and direct crop damage due to insect foraging. To manage these problems, insect repellents and pesticides have been developed, among which DEET is the most broadly used and studied pest control agent. This review discusses the mode of action and possible mechanisms of DEET action, including olfactory and gustatory mechanisms and central nervous system impairment. CONCLUSION: To protect humans from malaria, yellow fever, dengue fever, zika, and filariasis, as well as to reduce economic losses associated with crop damage, considerably more efforts are needed to characterize the interactions between insects and insect repellents/pesticides to develop more potent pest control agents.