Scaling of gas exchange cycle frequency in insects.
Ontology highlight
ABSTRACT:
SUBMITTER: Terblanche JS
PROVIDER: S-EPMC2412941 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The discontinuous gas-exchange cycles (DGCs) observed in many quiescent insects have been a cause of debate for decades, but no consensus on their evolutionary origin or adaptive significance has been achieved. Nevertheless, three main adaptive hypotheses have emerged: (i) the hygric hypothesis suggests that DGCs reduce respiratory water loss; (ii) the chthonic hypothesis suggests that DGCs facilitate gas exchange during environmental hypoxia, hypercapnia, or both; and (iii) the oxidative-damage hypothesis suggests that DGCs minimize oxidative tissue damage. However, most work conducted to date has been based on single-species investigations or nonphylogenetic comparative analyses of few species, despite calls for a strong-inference, phylogenetic approach. Here, we adopt such an approach by using 76 measurements of 40 wild-caught species to examine macrophysiological variation in DGC duration in insects. Potential patterns of trait variation are first identified on the basis of the explicit a priori predictions of each hypothesis, and the best phylogenetic generalized least-squares fit of the candidate models to the data is selected on the basis of Akaike's information criterion. We find a significant positive relationship between DGC duration and habitat temperature and an important interaction between habitat temperature and precipitation. This result supports the hygric hypothesis. We conclude that the DGCs of insects reduce respiratory water loss while ensuring adequate gas exchange.
| S-EPMC1895954 | biostudies-literature
Project description:The earliest description of the discontinuous gas exchange cycle (DGC) in lepidopterous insects supported the hypothesis that the DGC serves to reduce water loss (hygric hypothesis) and facilitate gaseous exchange in hyperoxia/hypoxia (chthonic hypothesis). With technological advances, other insect orders were investigated, and both hypotheses were questioned. Thus, we conducted a meta-analysis to evaluate the merit of both hypotheses. This included 46 insect species in 24 families across nine orders. We also quantified the percent change in metabolic rates per °C change of temperature during the DGC. The DGC reduced water loss (-3.27 ± 0.88; estimate ± 95% confidence limits [95% CI]; p < 0.0001) in insects. However, the DGC does not favor gaseous exchange in hyperoxia (0.21 ± 0.25 [estimate ± 95% CI]; p = 0.12) nor hypoxia, but did favor gaseous exchange in normoxia (0.27 ± 0.26 [estimate ± 95% CI]; p = 0.04). After accounting for variation associated with order, family, and species, a phylogenetic model reflected that metabolic rate exhibited a significant, non-zero increase of 8.13% (± 3.48 95% CI; p < 0.0001) per °C increase in temperature. These data represent the first meta-analytic attempt to resolve the controversies surrounding the merit of adaptive hypotheses in insects.
| S-EPMC8878836 | biostudies-literature
Project description:We explored changes in multiscale brain signal complexity and power-law scaling exponents of electroencephalogram (EEG) frequency spectra across several distinct global states of consciousness induced in the natural physiological context of the human sleep cycle. We specifically aimed to link EEG complexity to a statistically unified representation of the neural power spectrum. Further, by utilizing surrogate-based tests of nonlinearity we also examined whether any of the sleep stage-dependent changes in entropy were separable from the linear stochastic effects contained in the power spectrum. Our results indicate that changes of brain signal entropy throughout the sleep cycle are strongly time-scale dependent. Slow wave sleep was characterized by reduced entropy at short time scales and increased entropy at long time scales. Temporal signal complexity (at short time scales) and the slope of EEG power spectra appear, to a large extent, to capture a common phenomenon of neuronal noise, putatively reflecting cortical balance between excitation and inhibition. Nonlinear dynamical properties of brain signals accounted for a smaller portion of entropy changes, especially in stage 2 sleep.
| S-EPMC6865770 | biostudies-literature
Project description:Background: HIV infection is associated with impaired gas transfer in the lung as indicated by a low diffusing capacity (DLCO). Mechanisms for reduced DLCO in the setting of HIV infection are not well understood. We hypothesized that HIV-associated gas exchange impairment is indicative of system-wide perturbations that could be reflected by alterations in peripheral blood gene expression. Methods: A total of 40 HIV-infected (HIV+) and uninfected (HIV-) men with preserved versus reduced DLCO were selected from a larger cohort study of lung function. All subjects were current smokers and those with acute illness, lung diseases other than COPD or asthma were excluded. Total RNA was extracted from peripheral blood leukocytes (PBLs) and hybridized to whole-genome microarrays. Gene set enrichment analysis (GSEA) was performed between HIV+ vs. HIV- subjects with preserved DLCO and those with impaired DLCO to identify differentially activated pathways. Results: Using pathway-based analyses we found that in subjects with preserved DLCO, HIV infection is associated with activation of processes involved in immunity, cell cycle, and apoptosis. When we applied a similar analysis to subjects with low DLCO, we identified a much broader repertoire of inflammatory and immune-related pathways in HIV+ patients relative to HIV- subjects, with up-regulation of multiple interleukin pathways, interferon signaling, Toll-like receptor signaling, and T cell/B cell receptor signaling. We confirmed elevated circulating levels of IL-6 in HIV+ patients with reduced DLCO relative to the other groups. Conclusions: Our findings reveal that PBLs of subjects with HIV infection and low DLCO are distinguished by widespread enrichment of immuno-inflammatory programs. Activation of these pathways may alter the biology of circulating leukocytes and play a role in the pathogenesis of HIV-associated pulmonary gas exchange impairment. Total RNA was isolated from peripheral blood leukocytes in four subject groups: 1. HIV-, low DLCO (N = 11); 2. HIV+, low DLCO (N = 10); 3. HIV-, preserved DLCO (N = 9); 4. HIV+, preserved DLCO (N = 9). Each sample was hybridized to an Affymetrix PrimeView Human Gene Expression microarray for a total of 39 experiments.
2016-04-01 | E-GEOD-76403 | biostudies-arrayexpress
Project description:Development time is a critical life-history trait that has profound effects on organism fitness and on population growth rates. For ectotherms, development time is strongly influenced by temperature and is predicted to scale with body mass to the quarter power based on 1) the ontogenetic growth model of the metabolic theory of ecology which describes a bioenergetic balance between tissue maintenance and growth given the scaling relationship between metabolism and body size, and 2) numerous studies, primarily of vertebrate endotherms, that largely support this prediction. However, few studies have investigated the allometry of development time among invertebrates, including insects. Abundant data on development of diverse insects provides an ideal opportunity to better understand the scaling of development time in this ecologically and economically important group. Insects develop more quickly at warmer temperatures until reaching a minimum development time at some optimal temperature, after which development slows. We evaluated the allometry of insect development time by compiling estimates of minimum development time and optimal developmental temperature for 361 insect species from 16 orders with body mass varying over nearly 6 orders of magnitude. Allometric scaling exponents varied with the statistical approach: standardized major axis regression supported the predicted quarter-power scaling relationship, but ordinary and phylogenetic generalized least squares did not. Regardless of the statistical approach, body size alone explained less than 28% of the variation in development time. Models that also included optimal temperature explained over 50% of the variation in development time. Warm-adapted insects developed more quickly, regardless of body size, supporting the "hotter is better" hypothesis that posits that ectotherms have a limited ability to evolutionarily compensate for the depressing effects of low temperatures on rates of biological processes. The remaining unexplained variation in development time likely reflects additional ecological and evolutionary differences among insect species.
| S-EPMC3877264 | biostudies-literature
Project description:Chronic lower respiratory disease is highly prevalent in the United States, and there remains a need for alternatives to lung transplant for patients who progress to end-stage lung disease. Portable or implantable gas oxygenators based on microfluidic technologies can address this need, provided they operate both efficiently and biocompatibly. Incorporating biomimetic materials into such devices can help replicate native gas exchange function and additionally support cellular components. In this work, we have developed microfluidic devices that enable blood gas exchange across ultra-thin collagen membranes (as thin as 2 μm). Endothelial, stromal, and parenchymal cells readily adhere to these membranes, and long-term culture with cellular components results in remodeling, reflected by reduced membrane thickness. Functionally, acellular collagen-membrane lung devices can mediate effective gas exchange up to ∼288 mL/min/m(2) of oxygen and ∼685 mL/min/m(2) of carbon dioxide, approaching the gas exchange efficiency noted in the native lung. Testing several configurations of lung devices to explore various physical parameters of the device design, we concluded that thinner membranes and longer gas exchange distances result in improved hemoglobin saturation and increases in pO2. However, in the design space tested, these effects are relatively small compared to the improvement in overall oxygen and carbon dioxide transfer by increasing the blood flow rate. Finally, devices cultured with endothelial and parenchymal cells achieved similar gas exchange rates compared with acellular devices. Biomimetic blood oxygenator design opens the possibility of creating portable or implantable microfluidic devices that achieve efficient gas transfer while also maintaining physiologic conditions.
| S-EPMC4529054 | biostudies-literature
Project description:Although interspecific body size frequency distributions are well documented for many taxa, including the insects, intraspecific body size frequency distributions (IaBSFDs) are more poorly known, and their variation among mass-based and linear estimates of size has not been widely explored. Here we provide IaBSFDs for 16 species of insects based on both mass and linear estimates and large sample sizes (n ? 100). In addition, we review the published IaBSFDs for insects, though doing so is complicated by their under-emphasis in the literature. The form of IaBSFDs can differ substantially between mass-based and linear measures. Nonetheless, in non-social insects they tend to be normally distributed (18 of 27 species) or in fewer instances positively skewed. Negatively skewed distributions are infrequently reported and log transformation readily removes the positive skew. Sexual size dimorphism does not generally cause bimodality in IaBSFDs. The available information on IaBSFDs in the social insects suggests that these distributions are usually positively skewed or bimodal (24 of 30 species). However, only c. 15% of ant genera are polymorphic, suggesting that normal distributions are probably more common, but less frequently investigated. Although only 57 species, representing seven of the 29 orders of insects, have been considered here, it appears that whilst IaBSFDs are usually normal, other distribution shapes can be found in several species, though most notably among the social insects. By contrast, the interspecific body size frequency distribution is typically right-skewed in insects and in most other taxa.
| S-EPMC3068144 | biostudies-literature
Project description:Background: HIV infection is associated with impaired gas transfer in the lung as indicated by a low diffusing capacity (DLCO). Mechanisms for reduced DLCO in the setting of HIV infection are not well understood. We hypothesized that HIV-associated gas exchange impairment is indicative of system-wide perturbations that could be reflected by alterations in peripheral blood gene expression. Methods: A total of 40 HIV-infected (HIV+) and uninfected (HIV-) men with preserved versus reduced DLCO were selected from a larger cohort study of lung function. All subjects were current smokers and those with acute illness, lung diseases other than COPD or asthma were excluded. Total RNA was extracted from peripheral blood leukocytes (PBLs) and hybridized to whole-genome microarrays. Gene set enrichment analysis (GSEA) was performed between HIV+ vs. HIV- subjects with preserved DLCO and those with impaired DLCO to identify differentially activated pathways. Results: Using pathway-based analyses we found that in subjects with preserved DLCO, HIV infection is associated with activation of processes involved in immunity, cell cycle, and apoptosis. When we applied a similar analysis to subjects with low DLCO, we identified a much broader repertoire of inflammatory and immune-related pathways in HIV+ patients relative to HIV- subjects, with up-regulation of multiple interleukin pathways, interferon signaling, Toll-like receptor signaling, and T cell/B cell receptor signaling. We confirmed elevated circulating levels of IL-6 in HIV+ patients with reduced DLCO relative to the other groups. Conclusions: Our findings reveal that PBLs of subjects with HIV infection and low DLCO are distinguished by widespread enrichment of immuno-inflammatory programs. Activation of these pathways may alter the biology of circulating leukocytes and play a role in the pathogenesis of HIV-associated pulmonary gas exchange impairment.
2016-04-01 | GSE76403 | GEO
Project description:Limiting fluid in lung is critical for efficient gas exchange. Here we discovered a mechanism of neuropeptidergic control of lung fluid balance by pulmonary neuroendocrine cells (PNECs), potent sensors of chemical and mechanical cues. We studied the first animal model of neuroendocrine cell hyperplasia of infancy (NEHI), which faithfully recapitulated patient phenotypes including PNEC hyperplasia and impaired gas exchange. Double mutants showed that increased PNECs and excess PNEC products such as CGRP are responsible for poor gas exchange, acting through downregulating endothelial junctions, increasing vessel leakage and fluid accumulation. Endothelium-specific inactivation of CGRP receptor, or treatment with CGRP receptor antagonist reduced fluid and improved gas exchange. In lungs with acute respiratory distress syndrome (ARDS), including those caused by COVID-19, there was a striking increase of CGRP-expressing PNECs. These findings raise the possibility that increased neuropeptides would contribute to excess extravascular lung fluid and antagonizing their function may improve gas exchange.
2022-02-18 | GSE171907 | GEO
Project description:The mean state of the atmosphere and ocean is set through a balance between external forcing (radiation, winds, heat and freshwater fluxes) and the emergent turbulence, which transfers energy to dissipative structures. The forcing gives rise to jets in the atmosphere and currents in the ocean, which spontaneously develop turbulent eddies through the baroclinic instability. A critical step in the development of a theory of climate is to properly include the eddy-induced turbulent transport of properties like heat, moisture, and carbon. In the linear stages, baroclinic instability generates flow structures at the Rossby deformation radius, a length scale of order 1,000 km in the atmosphere and 100 km in the ocean, smaller than the planetary scale and the typical extent of ocean basins, respectively. There is, therefore, a separation of scales between the large-scale gradient of properties like temperature and the smaller eddies that advect it randomly, inducing effective diffusion. Numerical solutions show that such scale separation remains in the strongly nonlinear turbulent regime, provided there is sufficient drag at the bottom of the atmosphere and ocean. We compute the scaling laws governing the eddy-driven transport associated with baroclinic turbulence. First, we provide a theoretical underpinning for empirical scaling laws reported in previous studies, for different formulations of the bottom drag law. Second, these scaling laws are shown to provide an important first step toward an accurate local closure to predict the impact of baroclinic turbulence in setting the large-scale temperature profiles in the atmosphere and ocean.
| S-EPMC7060697 | biostudies-literature