Tyramine-Mediated Hyperactivity Modulates the Dietary Habits in Helicoverpa armigera.

Helicoverpa armigera exhibits extensive variability in feeding habits and food selection. Neuronal regulation of H. armigera feeding behavior is primarily influenced by biogenic amines such as Tyramine (TA) and Octopamine (OA). The molecular responses of H. armigera to dietary challenges in the presence of TA or OA have yet to be studied. This investigation dissects the impact of OA and TA on H. armigera feeding choices and behaviors under non-host nutritional stress. It has been observed that feeding behavior remains unaltered during the exogenous administration of OA and TA through an artificial diet (AD). Ingestion of higher OA or TA concentrations leads to increased mortality. OA and TA treatment in combination with host and non-host diets results in the induction of feeding and higher locomotion toward food, particularly in the case of TA treatment. Increased expression of markers, prominin-like, and tachykinin-related peptide receptor-like transcripts further assessed increased locomotion activity. Insects subjected to a non-host diet with TA treatment exhibited increased feeding and overexpression of the feeding indicator, the Neuropeptide F receptor, and the feeding regulator, Sulfakinin, compared with other conditions. Expression of sensation and biogenic amine synthesis genesis elevated in insects fed a non-host diet in combination with OA or TA. Metabolomics analysis revealed a decreased concentration of the feeding behavior elicitor, dopamine, in insects fed a non-host diet containing TA. This work highlights the complex interplay between biogenic amine functions during dietary stress and suggests the role of tyramine in feeding promotion under stressed conditions.

Developing a Feeding Assay System for Evaluating the Insecticidal Effect of Phytochemicals on Helicoverpa armigera.

Helicoverpa armigera, a lepidopteran insect, is a polyphagous pest with a worldwide distribution. This herbivorous insect is a threat to plants and agricultural productivity. In response, plants produce several phytochemicals that negatively impact the insect's growth and survival. This protocol demonstrates an obligate feeding assay method to evaluate the effect of a phytochemical (quercetin) on insect growth, development, and survival. Under controlled conditions, the neonates were maintained until the second instar on a pre-defined artificial diet. These second-instar larvae were allowed to feed on a control and quercetin-containing artificial diet for 10 days. The insects' body weight, developmental stage, frass weight, and mortality were recorded on alternate days. The change in body weight, the difference in feeding pattern, and developmental phenotypes were evaluated throughout the assay time. The described obligatory feeding assay simulates a natural mode of ingestion and can be scaled up to a large number of insects. It permits one to analyze phytochemicals' effect on the growth dynamics, developmental transition, and overall fitness of H. armigera. Furthermore, this setup can also be utilized to evaluate alterations in nutritional parameters and digestive physiology processes. This article provides a detailed methodology for feeding assay systems, which may have applications in toxicological studies, insecticidal molecule screening, and understanding chemical effects in plant-insect interactions.

Prodigiosin from Serratia rubidaea MJ 24 impedes Helicoverpa armigera development by the dysregulation of Juvenile hormone-dopamine system.

Prodigiosin pigment is a secondary metabolite produced by many bacterial species and is known for its medicinal properties. A few of these prodigiosin-producing bacteria are also reported to be entomopathogenic. It is intriguing to unravel the role of prodigiosin in insecticidal activities and its mode of action. In this study, we have shown the production and characterization of prodigiosin from the Serratia rubidaea MJ 24 isolated from the soil of the Western Ghats, India. Further, we assessed the effect of this pigment on the lepidopteran agricultural pest, Helicoverpa armigera. Prodigiosin-fed H. armigera indicated defective development of insect growth upon treatment. Due to defective early development, about 50% mortality and 40% reduction in body weight were observed in insects fed on a 500 ppm prodigiosin-containing diet. The transcriptomic analysis of these insects indicated significant dysregulation of Juvenile hormone synthesis and response related genes. In addition, dopamine related processes and their resultant melanization and sclerotization processes were also found to be affected. The changes in the expression levels of the key transcripts were further validated using real-time quantitative PCR. The metabolome data confirmed the developmental dysregulation of precursors and products of differentially regulated genes due to prodigiosin. Therefore, the corroborated data suggests that prodigiosin majorly affects H. armigera development through dysregulation of the Juvenile hormone-dopamine system and can be considered as a bioactive scaffold to design insect-pest management compounds. This study provides the first report of in-depth analysis of insecticidal system dynamics in H. armigera insects upon prodigiosin feeding via gene expression and metabolic change via omics approach.

Emerging delivery systems to reduce doxorubicin cardiotoxicity and improve therapeutic index: focus on liposomes.

Anthracyclines are powerful anticancer agents and among the most important tools in the chemotherapy armamentarium of medical oncologists. They are approved for use in the treatment of a broad variety of solid and hematologic neoplasms. However, the usefulness of these agents, particularly doxorubicin, the most widely used anthracycline, is limited by considerable toxicity, especially damage to the cardiac muscle, which is cumulative and mostly irreversible, restricting extended use of this drug. In the last 30 years, extensive research with a variety of drug-delivery systems has attempted to overcome this limitation, with clinical success mostly confined to liposome formulations. Liposomal doxorubicin, and particularly pegylated liposomal doxorubicin, has shown significant pharmacologic advantages and an added clinical value over doxorubicin. Here, we review the mechanisms of action and toxicity of doxorubicin, and ways to reduce toxicity, with a focus on liposome-based drug-delivery systems.

Novel methods for liposome preparation.

Liposomes are bilayer vesicles which have found use, among other applications, as drug delivery vehicles. Conventional techniques for liposome preparation and size reduction remain popular as these are simple to implement and do not require sophisticated equipment. However, issues related to scale-up for industrial production and scale-down for point-of-care applications have motivated improvements to conventional processes and have also led to the development of novel routes to liposome formation. In this article, these modified and new methods for liposome preparation have been reviewed and classified with the objective of updating the reader to recent developments in liposome production technology.

Isolation of giant unilamellar vesicles from electroformed vesicle suspensions and their extrusion through nano-pores.

Liposomes required for drug delivery are commonly obtained by extrusion of phospholipid vesicle suspensions through track-etched membranes. The effects of trans-membrane pressure, membrane pore size and bilayer composition on extruded liposome size are well-studied. Vesicle suspensions used in these extrusion studies are highly polydisperse, ranging from 20 nm to 100 µm. Vesicle sub-populations smaller than membrane pore size do not undergo extrusion-mediated size reduction and contribute significantly to the mean radius of extruded liposomes. In the present work, giant unilamellar vesicles (GUVs) are isolated by subjecting electroformed vesicle suspensions to low-pressure filtration. The isolated GUVs are extruded through track-etched polycarbonate membranes with pore radii ranging from 25 to 200 nm. We show that, when vesicles larger than the membrane pore size are extruded, the minimum attainable value of mean radius of resulting liposomes is independent of initial vesicle size as well as the number of extrusion cycles. We also show that bilayer composition significantly influences the extruded liposome size. These results provide new insights into the possible mechanisms of vesicle size reduction during extrusion process.

Extrusion of electroformed giant unilamellar vesicles through track-etched membranes.

Unilamellar vesicle populations having a narrow size distribution and mean radius below 100 nm are preferred for drug delivery applications. In the present work, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was used to prepare giant unilamellar vesicles (GUVs) by electroformation and multilamellar vesicles (MLVs) by thin film hydration. Our experiments show that in contrast to MLVs, a single-pass extrusion of GUVs through track-etched polycarbonate membranes at moderate pressure differences is sufficient to produce small liposomes having low polydispersity index. Moreover, we observe that the drug encapsulating potential of extruded liposomes obtained from GUVs is significantly higher compared to liposomes prepared by extrusion of MLVs. Furthermore, our experiments carried out for varying membrane pore diameters and extrusion pressures suggest that the size of extruded liposomes is a function of the velocity of GUV suspensions in the membrane pore.