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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Diffusive flux in a model of stochastically gated oxygen transport in insect respiration

Oxygen delivery to insect tissues is controlled by transport through a branched tubular network that is connected to the atmosphere by valve-like gates, known as spiracles. In certain physiological regimes, the spiracles appear to be randomly switching between open and closed states. Quantitative analysis of this regime leads a reaction-diffusion problem with stochastically switching boundary condition. We derive an expression for the diffusive flux at long times in this problem. Our approach starts with the derivation of the passage probability for a single particle that diffuses between a stochastically gated boundary, which models the opening and closing spiracle, and the perfectly absorbing boundary, which models oxygen absorption by the tissue. This passage probability is then used to derive an expression giving the diffusive flux as a function of the geometric parameters of the tube and characteristic time scales of diffusion and gate dynamics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

In situ detection of ferric reductase activity in the intestinal lumen of an insect

The rise of atmospheric oxygen as a result of photosynthesis in cyanobacteria and chloroplasts has transformed most environmental iron into the ferric state. In contrast, cells within organisms maintain a reducing internal milieu and utilize predominantly ferrous iron. Ferric reductases are enzymes that transfer electrons to ferric ions, either extracellularly or within endocytic vesicles, enabling cellular ferrous iron uptake through Divalent Metal Transporter 1. In mammals, duodenal cytochrome b is a ferric reductase of the intestinal epithelium, but how insects reduce and absorb dietary iron remains unknown. Here we provide indirect evidence of extracellular ferric reductase activity in a small subset of Drosophila melanogaster intestinal epithelial cells, positioned at the neck of the midgut’s anterior region. Dietary-supplemented bathophenanthroline sulphate (BPS) captures locally generated ferrous iron and precipitates into pink granules, whose chemical identity was probed combining in situ X-ray absorption near edge structure and electron paramagnetic resonance spectroscopies. An increased presence of manganese ions upon BPS feeding was also found. Control animals were fed with ferric ammonium citrate, which is accumulated into ferritin iron in distinct intestinal subregions suggesting iron trafficking between different cells inside the animal. Spectroscopic signals from the biological samples were compared to purified Drosophila and horse spleen ferritin and to chemically synthesized BPS-iron and BPS-manganese complexes. The results corroborated the presence of BPS-iron in a newly identified ferric iron reductase region of the intestine, which we propose constitutes the major site of iron absorption in this organism.

EPR↗
DOE OSTI2017

Scaling up our understanding of non-consumptive effects in insect systems

Here, non-consumptive effects (NCEs) of predators on prey is an important topic in insect ecology with potential applications for pest management. NCEs are changes in prey behavior and physiology that aid in predation avoidance. While NCEs can have positive outcomes for prey survival there may also be negative consequences including increased stress and reduced growth. These effects can cascade through trophic systems influencing ecosystem function. Most NCEs have been studied at small spatial and temporal scales. However, recent studies show promise for the potential to manipulate NCEs for pest management. We suggest the next frontier for NCE studies includes manipulating the landscape of fear to improve pest control, which requires scaling-up to field and landscape levels, over ecologically relevant time frames.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Activity, structure, and diversity of Type II proline-rich antimicrobial peptides from insects

Abstract Apidaecin 1b (Api), the first characterized Type II Proline-rich antimicrobial peptide (PrAMP), is encoded in the honey bee genome. It inhibits bacterial growth by binding in the nascent peptide exit tunnel of the ribosome after the release of the completed protein and trapping the release factors. By genome mining, we have identified 71 PrAMPs encoded in insect genomes as pre-pro-polyproteins. Having chemically synthesized and tested the activity of 26 peptides, we demonstrate that despite significant sequence variation in the N-terminal sequence, the majority of the PrAMPs that retain the conserved C-terminal sequence of Api are able to trap the ribosome at the stop codons and induce stop codon readthrough—all hallmarks of Type II PrAMP mode of action. Some of the characterized PrAMPs exhibit superior antibacterial activity in comparison with Api. The newly solved crystallographic structures of the ribosome complexed with Api and with the more active peptide Fva1 from the stingless bee demonstrate the universal placement of the PrAMPs’ C-terminal pharmacophore in the post-release ribosome despite variations in their N-terminal sequence.

Huang, Weiping (ORCID:0000000273063550)↗
DOE OSTI2024

Plant, insect, and fungi fossils under the center of Greenland’s ice sheet are evidence of ice-free times

The persistence and size of the Greenland Ice Sheet (GrIS) through the Pleistocene is uncertain. This is important because reconstructing changes in the GrIS determines its contribution to sea level rise during prior warm climate periods and informs future projections. To understand better the history of Greenland’s ice, we analyzed glacial till collected in 1993 from below 3 km of ice at Summit, Greenland. The till contains plant fragments, wood, insect parts, fungi, and cosmogenic nuclides showing that the bed of the GrIS at Summit is a long-lived, stable land surface preserving a record of deposition, exposure, and interglacial ecosystems. Knowing that central Greenland was tundra-covered during the Pleistocene informs the understanding of Arctic biosphere response to deglaciation.

58 GEOSCIENCES↗
DOE OSTI2012

A data-driven model of a modal gated ion channel: The inositol 1,4,5-trisphosphate receptor in insect Sf9 cells

The inositol 1,4,5-trisphosphate (IP 3 ) receptor (IP 3 R) channel is crucial for the generation and modulation of intracellular Ca 2+ signals in animal cells. To gain insight into the complicated ligand regulation of this ubiquitous channel, we constructed a simple quantitative continuous-time Markov-chain model from the data. Our model accounts for most experimentally observed gating behaviors of single native IP 3 R channels from insect Sf9 cells. Ligand (Ca 2+ and IP 3 ) dependencies of channel activity established six main ligand-bound channel complexes, where a complex consists of one or more states with the same ligand stoichiometry and open or closed conformation. Channel gating in three distinct modes added one complex and indicated that three complexes gate in multiple modes. This also restricted the connectivity between channel complexes. Finally, latencies of channel responses to abrupt ligand concentration changes defined a model with specific network topology between 9 closed and 3 open states. The model with 28 parameters can closely reproduce the equilibrium gating statistics for all three gating modes over a broad range of ligand concentrations. It also captures the major features of channel response latency distributions. The model can generate falsifiable predictions of IP 3 R channel gating behaviors and provide insights to both guide future experiment development and improve IP 3 R channel gating analysis. Maximum likelihood estimates of the model parameters and of the parameters in the De Young–Keizer model yield strong statistical evidence in favor of our model. Our method is simple and easily applicable to the dynamics of other ion channels and molecules.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Mosquito-Borne Viruses and Insect-Specific Viruses Revealed in Field-Collected Mosquitoes by a Monitoring Tool Adapted from a Microbial Detection Array

Several mosquito-borne diseases affecting humans are emerging or reemerging in the United States. The early detection of pathogens in mosquito populations is essential to prevent and control the spread of these diseases. Here, we tested the potential applicability of the Lawrence Livermore Microbial Detection Array (LLMDA) to enhance biosurveillance by detecting microbes present in Aedes aegypti, Aedes albopictus, and Culex mosquitoes, which are major vector species globally, including in Texas. The sensitivity and reproducibility of the LLMDA were tested in mosquito samples spiked with different concentrations of dengue virus (DENV), revealing a detection limit of >100 but <1,000 PFU/ml. Additionally, field-collected mosquitoes from Chicago, IL, and College Station, TX, of known infection status (West Nile virus [WNV] and Culex flavivirus [CxFLAV] positive) were tested on the LLMDA to confirm its efficiency. Mosquito field samples of unknown infection status, collected in San Antonio, TX, and the Lower Rio Grande Valley (LRGV), TX, were run on the LLMDA and further confirmed by PCR or quantitative PCR (qPCR). The analysis of the field samples with the LLMDA revealed the presence of cell-fusing agent virus (CFAV) in A. aegypti populations. Wolbachia was also detected in several of the field samples (A. albopictus and Culex spp.) by the LLMDA. Our findings demonstrated that the LLMDA can be used to detect multiple arboviruses of public health importance, including viruses that belong to the Flavivirus, Alphavirus, and Orthobunyavirus genera. Additionally, insect-specific viruses and bacteria were also detected in field-collected mosquitoes. Another strength of this array is its ability to detect multiple viruses in the same mosquito pool, allowing for the detection of cocirculating pathogens in an area and the identification of potential ecological associations between different viruses. Finally, this array can aid in the biosurveillance of mosquito-borne viruses circulating in specific geographical areas.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

In vivo subcellular localization of Mal de Rio Cuarto virus (MRCV) non-structural proteins in insect cells reveals their putative functions

The in vivo subcellular localization of Mal de Rio Cuarto virus (MRCV, Fijivirus, Reoviridae) non-structural proteins fused to GFP was analyzed by confocal microscopy. P5-1 showed a cytoplasmic vesicular-like distribution that was lost upon deleting its PDZ binding TKF motif, suggesting that P5-1 interacts with cellular PDZ proteins. P5-2 located at the nucleus and its nuclear import was affected by the deletion of its basic C-termini. P7-1 and P7-2 also entered the nucleus and therefore, along with P5-2, could function as regulators of host gene expression. P6 located in the cytoplasm and in perinuclear cloud-like inclusions, was driven to P9-1 viroplasm-like structures and co-localized with P7-2, P10 and {alpha}-tubulin, suggesting its involvement in viroplasm formation and viral intracellular movement. Finally, P9-2 was N-glycosylated and located at the plasma membrane in association with filopodia-like protrusions containing actin, suggesting a possible role in virus cell-to-cell movement and spread.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Conservation of Oxidative Protein Stabilization in an Insect Homologue of Parkinsonism-Associated Protein DJ-1

DJ-1 is a conserved, disease-associated protein that protects against oxidative stress and mitochondrial damage in multiple organisms. Human DJ-1 contains a functionally essential cysteine residue (Cys106) whose oxidation is important for regulating protein function by an unknown mechanism. This residue is well-conserved in other DJ-1 homologues, including two (DJ-1{alpha} and DJ-1{beta}) in Drosophila melanogaster. Because D. melanogaster is a powerful model system for studying DJ-1 function, we have determined the crystal structure and impact of cysteine oxidation on Drosophila DJ-1{beta}. The structure of D. melanogaster DJ-1{beta} is similar to that of human DJ-1, although two important residues in the human protein, Met26 and His126, are not conserved in DJ-1{beta}. His126 in human DJ-1 is substituted with a tyrosine in DJ-1{beta}, and this residue is not able to compose a putative catalytic dyad with Cys106 that was proposed to be important in the human protein. The reactive cysteine in DJ-1 is oxidized readily to the cysteine-sulfinic acid in both flies and humans, and this may regulate the cytoprotective function of the protein. We show that the oxidation of this conserved cysteine residue to its sulfinate form (Cys-SO{sub 2{sup -}}) results in considerable thermal stabilization of both Drosophila DJ-1{beta} and human DJ-1. Therefore, protein stabilization is one potential mechanism by which cysteine oxidation may regulate DJ-1 function in vivo. More generally, most close DJ-1 homologues are likely stabilized by cysteine-sulfinic acid formation but destabilized by further oxidation, suggesting that they are biphasically regulated by oxidative modification.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

Persistent reduced ecosystem respiration after insect disturbance in high elevation forests

Amid a worldwide increase in tree mortality, mountain pine beetles (Dendroctonus ponderosae Hopkins) have led to the death of billions of trees from Mexico to Alaska since 2000. This is predicted to have important carbon, water and energy balance feedbacks on the Earth system. Counter to current projections, we show that on a decadal scale, tree mortality causes no increase in ecosystem respiration from scales of several square metres up to an 84 km2 valley. Rather, we found comparable declines in both gross primary productivity and respiration suggesting little change in net flux, with a transitory recovery of respiration 6–7 years after mortality associated with increased incorporation of leaf litter C into soil organic matter, followed by further decline in years 8–10. The mechanism of the impact of tree mortality caused by these biotic disturbances is consistent with reduced input rather than increased output of carbon.

54 ENVIRONMENTAL SCIENCES↗