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Langmuir : the ACS Journal of Surfaces... Nov 2023Aspirin has been used for broad therapeutic treatment, including secondary prevention of cardiovascular disease associated with increased cholesterol levels. Aspirin and...
Aspirin has been used for broad therapeutic treatment, including secondary prevention of cardiovascular disease associated with increased cholesterol levels. Aspirin and other nonsteroidal anti-inflammatory drugs have been shown to interact with lipid membranes and change their biophysical properties. In this study, mixed lipid model bilayers made from 1-palmitoyl-2-oleoyl--glycero-3-phosphatidylcholine (POPC) or 1,2-dioleoyl--glycero-3-phosphatidylcholine (DOPC) comprising varying concentrations of cholesterol (10:1, 4:1, and 1:1 mole ratio of lipid:chol), prepared by the droplet interface bilayer method, were used to examine the effects of aspirin at various pH on transbilayer water permeability. The presence of aspirin increases the water permeability of POPC bilayers in a concentration-dependent manner, with a greater magnitude of increase at pH 3 compared to pH 7. In the presence of cholesterol, aspirin is similarly shown to increase water permeability; however, the extent of the increase depends on both the concentration of cholesterol and the pH, with the least pronounced enhancement in water permeability at high cholesterol levels at pH 7. A fusion of data from differential scanning calorimetry, confocal Raman microspectrophotometry, and interfacial tensiometric measurements demonstrates that aspirin can promote significant thermal, structural, and interfacial property perturbations in the mixed-lipid POPC or DOPC membranes containing cholesterol, indicating a disordering effect on the lipid membranes. Our findings suggest that aspirin fluidizes phosphocholine membranes in both cholesterol-free and cholesterol-enriched states and that the overall effect is greater when aspirin is in a neutral state. These results confer a deeper comprehension of the divergent effects of aspirin on biological membranes having heterogeneous compositions, under varying physiological pH and different cholesterol compositions, with implications for a better understanding of the gastrointestinal toxicity induced by the long term use of this important nonsteroidal anti-inflammatory molecule.
Topics: Aspirin; Phosphatidylcholines; Cholesterol; Lipid Bilayers; Water; Anti-Inflammatory Agents; Hydrogen-Ion Concentration
PubMed: 37939382
DOI: 10.1021/acs.langmuir.3c02242 -
Scientific Reports Jul 2023Dystrophic muscle is characterized by necrosis/regeneration cycles, inflammation, and fibro-adipogenic development. Conventional histological stainings provide essential...
Dystrophic muscle is characterized by necrosis/regeneration cycles, inflammation, and fibro-adipogenic development. Conventional histological stainings provide essential topographical data of this remodeling but may be limited to discriminate closely related pathophysiological contexts. They fail to mention microarchitecture changes linked to the nature and spatial distribution of tissue compartment components. We investigated whether label-free tissue autofluorescence revealed by Synchrotron deep ultraviolet (DUV) radiation could serve as an additional tool for monitoring dystrophic muscle remodeling. Using widefield microscopy with specific emission fluorescence filters and microspectroscopy defined by high spectral resolution, we analyzed samples from healthy dogs and two groups of dystrophic dogs: naïve (severely affected) and MuStem cell-transplanted (clinically stabilized) animals. Multivariate statistical analysis and machine learning approaches demonstrated that autofluorescence emitted at 420-480 nm by the Biceps femoris muscle effectively discriminates between healthy, dystrophic, and transplanted dog samples. Microspectroscopy showed that dystrophic dog muscle displays higher and lower autofluorescence due to collagen cross-linking and NADH respectively than that of healthy and transplanted dogs, defining biomarkers to evaluate the impact of cell transplantation. Our findings demonstrate that DUV radiation is a sensitive, label-free method to assess the histopathological status of dystrophic muscle using small amounts of tissue, with potential applications in regenerative medicine.
Topics: Animals; Dogs; Random Forest; Support Vector Machine; Muscular Dystrophies; Ultraviolet Rays; Microspectrophotometry; Microscopy; Stem Cell Transplantation; Male; Biopsy
PubMed: 37402811
DOI: 10.1038/s41598-023-37762-1 -
The Journal of Experimental Biology Apr 2024In many animals, ultraviolet (UV) vision guides navigation, foraging, and communication, but few studies have addressed the contribution of UV signals to colour vision,...
In many animals, ultraviolet (UV) vision guides navigation, foraging, and communication, but few studies have addressed the contribution of UV signals to colour vision, or measured UV discrimination thresholds using behavioural experiments. Here, we tested UV colour vision in an anemonefish (Amphiprion ocellaris) using a five-channel (RGB-V-UV) LED display. We first determined that the maximal sensitivity of the A. ocellaris UV cone was ∼386 nm using microspectrophotometry. Three additional cone spectral sensitivities had maxima at ∼497, 515 and ∼535 nm. We then behaviourally measured colour discrimination thresholds by training anemonefish to distinguish a coloured target pixel from grey distractor pixels of varying intensity. Thresholds were calculated for nine sets of colours with and without UV signals. Using a tetrachromatic vision model, we found that anemonefish were better (i.e. discrimination thresholds were lower) at discriminating colours when target pixels had higher UV chromatic contrast. These colours caused a greater stimulation of the UV cone relative to other cone types. These findings imply that a UV component of colour signals and cues improves their detectability, which likely increases the prominence of anemonefish body patterns for communication and the silhouette of zooplankton prey.
Topics: Animals; Color; Color Vision; Retinal Cone Photoreceptor Cells; Color Perception; Perciformes; Ultraviolet Rays
PubMed: 38586934
DOI: 10.1242/jeb.247425 -
Insects Aug 2023Quantifying the growth of entomopathogenic fungi is crucial for understanding their virulence and pathogenic potential. Traditional methods for determining growth, such...
Quantifying the growth of entomopathogenic fungi is crucial for understanding their virulence and pathogenic potential. Traditional methods for determining growth, such as biomass determination or colony growth area, are time-consuming and quantitatively and spatially limited in scope. In this study, we introduce a high-throughput method for rapidly measuring fungal growth using spectrophotometry in small-volume, liquid media cultures in 96-well microplates. Optical density (OD) changes were directly correlated with dry weight of samples for six isolates from three species of the genus to validate spectrophotometric growth measurements, and investigate species- and isolate-specific effects. We quantified fungal biomass from the microcultures by extracting, drying, and weighing mycelial mats. From the relationship established between OD and biomass, we generated standard curves for predicting biomass based on the OD values. The OD measurements clearly distinguished growth patterns among six isolates from three species. The logistic growth phase, as captured by the OD measurements, could be accurately assessed within a span of 80 h. Using isolates of , , and , this technique was demonstrated to be an effective, reproducible, and simple method for rapidly measuring filamentous fungal growth with high precision. This technique offers a valuable tool for studying the growth dynamics of entomopathogenic fungi and investigating the factors that influence their growth.
PubMed: 37623413
DOI: 10.3390/insects14080703 -
Journal of the American Chemical Society Jul 2023Single-molecule localization microscopy (SMLM) at cryogenic temperature opens new avenues to investigate intact biological samples at the nanoscale and perform...
Single-molecule localization microscopy (SMLM) at cryogenic temperature opens new avenues to investigate intact biological samples at the nanoscale and perform cryo-correlative studies. Genetically encoded fluorescent proteins (FPs) are markers of choice for cryo-SMLM, but their reduced conformational flexibility below the glass-transition temperature hampers efficient cryo-photoswitching. We investigated cryo-switching of rsEGFP2, one of the most efficient reversibly switchable fluorescent proteins at ambient temperature due to facile isomerization of the chromophore. UV-visible microspectrophotometry and X-ray crystallography revealed a completely different switching mechanism at ∼110 K. At this cryogenic temperature, on-off photoswitching involves the formation of two off-states in conformation with blue-shifted absorption relative to that of the protonated chromophore populated at ambient temperature. Only one of these off-states can be switched back to the fluorescent on-state by 405 nm light, while both of them are sensitive to UV light at 355 nm. Superior recovery to the fluorescent on-state by 355 nm light was confirmed at the single-molecule level. This suggests, as also shown by simulations, that employing 355 nm light in cryo-SMLM experiments using rsEGFP2 and possibly other FPs could improve the effective labeling efficiency achievable with this technique. The rsEGFP2 photoswitching mechanism discovered in this work adds to the panoply of known switching mechanisms in fluorescent proteins.
Topics: Temperature; Luminescent Proteins; Isomerism; Protein Conformation; Ultraviolet Rays
PubMed: 37389576
DOI: 10.1021/jacs.3c01500 -
Molecular Biology and Evolution Apr 2024Visual systems adapt to different light environments through several avenues including optical changes to the eye and neurological changes in how light signals are...
Visual systems adapt to different light environments through several avenues including optical changes to the eye and neurological changes in how light signals are processed and interpreted. Spectral sensitivity can evolve via changes to visual pigments housed in the retinal photoreceptors through gene duplication and loss, differential and coexpression, and sequence evolution. Frogs provide an excellent, yet understudied, system for visual evolution research due to their diversity of ecologies (including biphasic aquatic-terrestrial life cycles) that we hypothesize imposed different selective pressures leading to adaptive evolution of the visual system, notably the opsins that encode the protein component of the visual pigments responsible for the first step in visual perception. Here, we analyze the diversity and evolution of visual opsin genes from 93 new eye transcriptomes plus published data for a combined dataset spanning 122 frog species and 34 families. We find that most species express the four visual opsins previously identified in frogs but show evidence for gene loss in two lineages. Further, we present evidence of positive selection in three opsins and shifts in selective pressures associated with differences in habitat and life history, but not activity pattern. We identify substantial novel variation in the visual opsins and, using microspectrophotometry, find highly variable spectral sensitivities, expanding known ranges for all frog visual pigments. Mutations at spectral-tuning sites only partially account for this variation, suggesting that frogs have used tuning pathways that are unique among vertebrates. These results support the hypothesis of adaptive evolution in photoreceptor physiology across the frog tree of life in response to varying environmental and ecological factors and further our growing understanding of vertebrate visual evolution.
Topics: Humans; Animals; Opsins; Retinal Pigments; Anura; Gene Duplication; Microspectrophotometry
PubMed: 38573520
DOI: 10.1093/molbev/msae049