1,294 research outputs found
Physiological Status Drives Metabolic Rate in Mediterranean Geckos Infected with Pentastomes
Negative effects of parasites on their hosts are well documented, but the proximate mechanisms by which parasites reduce their host's fitness are poorly understood. For example, it has been suggested that parasites might be energetically demanding. However, a recent meta-analysis suggests that they have statistically insignificant effects on host resting metabolic rate (RMR). It is possible, though, that energetic costs associated with parasites are only manifested during and/or following periods of activity. Here, we measured CO2 production (a surrogate for metabolism) in Mediterranean geckos (Hemidactylus turcicus) infected with a lung parasite, the pentastome Raillietiella indica, under two physiological conditions: rested and recently active. In rested geckos, there was a negative, but non-significant association between the number of pentastomes (i.e., infection intensity) and CO2 production. In recently active geckos (chased for 3 minutes), we recorded CO2 production from its maximum value until it declined to a stationary phase. We analyzed this decline as a 3 phase function (initial decline, secondary decline, stationary). Geckos that were recently active showed, in the secondary phase, a significant decrease in CO2 production as pentastome intensity increased. Moreover, duration of the secondary phase showed a significant positive association with the number of pentastomes. These results suggest that the intensity of pentastome load exerts a weak effect on the metabolism of resting geckos, but a strong physiological effect on geckos that have recently been active; we speculate this occurs via mechanical constraints on breathing. Our results provide a potential mechanism by which pentastomes can reduce gecko fitness
Effects of SARS-CoV-2 on Pulmonary Function and Muscle Strength Testing in Military Subjects According to the Period of Infection: Cross-Sectional Study
Background: Pulmonary function can be impaired as a long-term consequence of SARS-CoV-2 infection. The aim of this study was to evaluate the effect of SARS-CoV-2 infection on pulmonary function, exercise tolerance, and muscle strength in healthy middle-aged military outpatients according during the period of infection. Methods: A cross-sectional study was carried out from March 2020 to November 2022 at the Military Hospital "Celio" (Rome, Italy). If someone had a diagnosis of SARS-CoV-2 infection certified by molecular nasal swab and if they performed pulmonary function tests, diffusion of carbon monoxide (DL'co), a six Minute Walk Test (6MWT), a Handgrip (HG) Test, and a One Minute Sit to Stand Test (1 ' STST). The included subjects were divided into two groups, A and B, according to the period of infection: A) from March 2020 to August 2021 and B) from September 2021 to October 2022. Results: One hundred fifty-three subjects were included in the study: 79 in Group A and 74 in Group B. Although the values were within the normal range, Group A had smaller FVC, FEV1, and DL'co compared to Group B. Group A also walked a shorter distance at the 6MWT and performed fewer repetitions in the 1 ' STS test compared to Group B. In both groups, the DL'co (%predicted) correlated with the 6MWT distance (R-2 = 0.107, p < 0.001), the number of repetitions of the 1'STST (R-2 = 0.086, p = 0.001), and the strength at the HG test (R-2 = 0.08, p < 0.001). Conclusions: This study shows that the SARS-CoV-2 infection in healthy middle-aged military outpatients was more severe in the first waves than in the later ones and that, in healthy and physically fit individuals, even a marginal reduction in resting respiratory test values can have a major impact on exercise tolerance and muscles strength. Moreover, it shows that those infected more recently had symptoms related to the upper respiratory tract infection compared to those of the first waves
Disruption of the Key Ca2+ Binding Site in the Selectivity Filter of Neuronal Voltage-Gated Calcium Channels Inhibits Channel Trafficking
Voltage-gated calcium channels are exquisitely Ca2+ selective, conferred primarily by four conserved pore-loop glutamate residues contributing to the selectivity filter. There has been little previous work directly measuring whether the trafficking of calcium channels requires their ability to bind Ca2+ in the selectivity filter or to conduct Ca2+. Here, we examine trafficking of neuronal CaV2.1 and 2.2 channels with mutations in their selectivity filter and find reduced trafficking to the cell surface in cell lines. Furthermore, in hippocampal neurons, there is reduced trafficking to the somatic plasma membrane, into neurites, and to presynaptic terminals. However, the CaV2.2 selectivity filter mutants are still influenced by auxiliary α2δ subunits and, albeit to a reduced extent, by β subunits, indicating the channels are not grossly misfolded. Our results indicate that Ca2+ binding in the pore of CaV2 channels may promote their correct trafficking, in combination with auxiliary subunits. Furthermore, physiological studies utilizing selectivity filter mutant CaV channels should be interpreted with caution
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DIII-D data for modeling the scrape-off-layer plasma
We are in the process of assembling a database of edge and divertor plasma parameters suitable for use in benchmarking tious 2D models of the scrape-off- layer (SOL) plasma. Also, we are using the Braams B2 code to derive transport coefficients for the edge plssma. In parallel, work is starting on an upgrade to the B2 code that includes padlel current flow and EXB drifts. These efforts are directed at increasing the confidence level of models of the tokamak edge plasma so that we can predict the effect of planned upgrades to DIII-D (e.g., the Advanced Divertor Program) and the performance of next generation machines such as CIT or ITER, where initial design studies show that plasma conditions at the divertor targets can have a large impact on the lifetime and cost of the machine. This report summarizes our recent progress in characterizing the DIII-D SOL plasma and in modeling these data with the the B2 code. Section I contains a brief description of the diagnostics available for characterizing the SOL plasma. In Section II we present our measurements of the SOL parameters for H-mode plasmas. This includes data showing how the divertor plasma parameters (n{sub e}(r), T{sub e}(r), and Q(r)) vary from ohmic to L-mode to H-mode, and power balance for quasi-stationary H-mode plasmas. Section III covers divertor-target heat-flux asymmetries for double and single null operation with forward and reversed toroidal field. In Section IV we show the scaling of L-mode parameters with neutral beam power, and Section V concludes with a summary of the results obtained from the Braams B2 SOL simulation code
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Effect of Profiles and Shape on Ideal Stability of Advanced Tokamak Equilibria
OAK-B135 The pressure profile and plasma shape, parameterized by elongation ({kappa}), triangularity ({delta}), and squareness ({zeta}), strongly influence stability. In this study, ideal stability of single null and symmetric, double-null, advanced tokamak (AT) configurations is examined. All the various shapes are bounded by a common envelope and can be realized in the DIII-D tokamak. The calculated AT equilibria are characterized by P{sub 0}/<P> {approx} 2.0-4.5, weak negative central shear, high q{sub min} (> 2.0), high bootstrap fraction, an H-mode pedestal, and varying shape parameters. The pressure profile is modeled by various polynomials together with a hyperbolic tangent pedestal, consistent with experimental observations. Stability is calculated with the DCON code and the resulting stability boundary is corroborated by GATO runs
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