Biology subjects

Schaefer, R.

Publications and source records attributed to Schaefer, R..

4 recordsLinked to original sources

bioRxiv2024

Influence of salinity on the thermal tolerance of aquatic organisms

Aquatic organisms are challenged by changes in the external environment, such as temperature and salinity fluctuations. The response of an organism to temperature changes can be modified by salinity, thus pointing at the potential interaction of both variables. In the present study, we tested this assumption for freshwater, brackish, and marine organisms, including algae, macrophytes, heterotrophic protists, parasites, invertebrates, and fish. We reviewed the existing body of literature on potential interactions between temperature and salinity and performed a meta-analysis that compared the thermal tolerance (characterized by the temperature optima, lower and upper temperature limits, and thermal breadths). The final database includes 90 relevant publications (algae: 15; heterotrophic protists: 1; invertebrates: 43; and fish: 31). Relevant publications for microphytes and parasites were not available. Overall, our results show that decreasing salinity significantly increased the lower temperature limits and decreased the upper temperature limits irrespective of the organism groups. These findings mainly reflect the response to salinity changes in brackish and marine systems that dominate our database. Although the number of studies on freshwater species was limited, they showed negative, although statistically nonsignificant, effects of an increased salinity on the thermal tolerance of these species (i.e. increased lower limits and decreased upper limits). In addition, our meta-analysis shows nonsignificant differences in the responsiveness of thermal tolerance to salinity changes among different groups of organisms, but the sensitivity of thermal tolerance to salinity changes generally followed the order: algae > invertebrates > fish. Facing the impact of climate change, our findings point at adverse effects of salinity changes on the temperature tolerance of aquatic organisms. Further studies that investigate the thermal performance of freshwater species at various salinity gradients are required to broaden the evidence for interactions between salinity and temperature tolerance. This also applies to the influence of parasitic infections, which have been found to modulate the temperature tolerance of aquatic invertebrates and fish.

ecology↗

bioRxiv2023

Antigenic and genetic diversity of H1 and H3 influenza A viruses in swine in Brazil

BackgroundInfluenza A virus (IAV) circulates within human and swine populations, and pigs are considered intermediate hosts for the generation of IAV with pandemic potential. Surveillance and characterization of IAVs circulating in pig populations are crucial to strain match vaccines to control IAV transmission in pigs and quantify pandemic potential to humans. MethodsHere, we characterized the genetic and antigenic diversity of IAVs circulating in Brazilian swine between 2010-2018. Phylogenetic maximum-likelihood trees were generated for 84 Brazilian hemagglutinin (HA) gene segments. Hemagglutination inhibition (HI) assay data was used with antigenic cartography to quantify the antigenic differences among representative H1 and H3 swine viruses and relative cross-reactivity between these viruses and human seasonal vaccine strains. ResultsWe identified two genetic lineages of H1 viruses derived from separate human-to-swine transmission events (H1 1B lineage, clades 1B.2.3 and 1B.2.4), an H3 lineage that has diversified into two genetic clades (H3 1990.5.1 and 1990.5.2), and HA genes associated with the 2009 H1N1 pandemic. There was limited cross-reactivity between circulating swine lineages and significant antigenic variation within lineage. ConclusionsThe antigenic diversity among endemic IAV in swine indicates a need for regional strain-specific vaccination strategies in Brazil. Our data supports the need for systematic genomic surveillance and characterization in Brazil to improve the efficacy of swine vaccines and quantify the pandemic potential of endemic swine influenza A viruses.

microbiology↗

bioRxiv2023

Dosimetric and biologic intercomparison between electron and proton FLASH beams

Background and purposeThe FLASH effect has been validated in different preclinical experiments with electrons (eFLASH) and protons (pFLASH) operating at a mean dose rate above 40 Gy/s. However, no systematic intercomparison of the FLASH effect produced by e vs. pFLASH has yet been performed and constitutes the aim of the present study. Materials and methodsThe electron eRT6/Oriatron/CHUV/5.5 MeV and proton Gantry1/PSI/170 MeV were used to deliver conventional (0.1 Gy/s eCONV and pCONV) and FLASH ([≥]100 Gy/s eFLASH and pFLASH) irradiation. Protons were delivered in transmission. Dosimetric and biologic intercomparisons were performed with previously validated models. ResultsDoses measured at Gantry1 were in agreement ({+/-} 2.5%) with reference dosimeters calibrated at CHUV/IRA. The neurocognitive capacity of e and pFLASH irradiated mice was indistinguishable from the control while both e and pCONV irradiated cohorts showed cognitive decrements. Complete tumor response was obtained with the two beams and was similar between e and pFLASH vs. e and pCONV. Tumor rejection was similar indicating that T-cell memory response is beam-type and dose-rate independent. ConclusionDespite major differences in the temporal microstructure, this study shows that dosimetric standards can be established. The sparing of brain function and tumor control produced by the two beams were similar, suggesting that the most important physical parameter driving the FLASH effect is the overall time of exposure which should be in the range of hundreds of milliseconds for WBI in mice. In addition, we observed that immunological memory response is similar between electron and proton beams and is independent off the dose rate.

cancer biology↗

bioRxiv2022

Beat encoding at mistuned octaves within single sensory neurons

Beats are periodic amplitude modulations resulting from the superposition of two spectrally close periodic signals, where the difference between the two signal frequencies defines the frequency of the beat. Such amplitude modulations are known to be well encoded in corresponding firing rate modulations in auditory fibers as well as in electrosensory afferents. In a field study we showed the behavioral relevance of beat-like amplitude modulations exceeding spectrally close interactions in electric fish. Thus, we here study the encoding of beat-like waveforms over a wide range of difference frequencies in the electrosensory system of Apteronotus leptorhynchus. Contrary to expectations from the previously measured beat tuning, the activity of p-type electroreceptor afferents follows a repetitive pattern with slow modulations of their firing rate reoccurring around multiples of the frequency of the carrier signal. Mathematical reasoning supported by simulations of modified integrate-and-fire models reveals that neither Hilbert transform, squaring, harmonics of the carrier, half-wave rectification, nor the threshold-non-linearity of a spike generator are sufficient to extract slow beating signal envelopes around the octave of the carrier. Rather, a threshold operation smoothed out by exponentiation with a power of three is needed prior to spike generation to explain the repetitive occurrence of slow signal envelopes and electroreceptor responses. Our insights suggest the synapses of inner hair cells as candidate mechanisms underlying the perception of beats at mistuned octaves that has been described by Georg Simon Ohm, Hermann Helmholtz, and others already in the 19th century.

neuroscience↗