Biology subjects

Oliveira, A. G.

Publications and source records attributed to Oliveira, A. G..

6 recordsLinked to original sources

bioRxiv2025

High-throughput microplate luminometry of Pyrocystis lunula bioluminescence for metal toxicity assessment

Dinoflagellates are major contributors to marine phytoplankton, and many species emit blue bioluminescence from specialized organelles called scintillons in response to mechanical stimulation and transient intracellular acidification. Because pollutants can disrupt this pathway, changes in light output provide a sensitive proxy for environmental stress. We utilized the bioluminescence of dinoflagellate Pyrocystis lunula to develop a rapid, high-throughput toxicity assay. Cultures aged 30-40 days were exposed to a range of metal concentrations for 24 hours, and stimulus-evoked emission was quantified in 96-well plates using a microplate luminometer. All metals tested produced dose-dependent inhibition of bioluminescence, with sensitivity varying by contaminant. Non-essential metals showed the strongest inhibitory effects: Cd2+ (half-maximal inhibitory concentration, IC50, 24 h = 0.014 mg L-1) and Pb2+ (IC50, 24 h = 0.016 mg L-1). Essential metals, Cu2+ and Zn2+, also reduced emission but at higher concentrations; differences were significant by one-way analysis of variance with Tukeys post hoc test. This assay is rapid, low-cost, and scalable, offering a practical tool for monitoring trace-metal contamination and supporting ecotoxicological assessments.

biochemistry↗

bioRxiv2024

Velamins: the first green-light emitting class of wild-type Ca2+-regulated photoproteins isolated from the ctenophore Velamen parallelum

Ca2+-regulated photoproteins (CaPhs) consist of single-chain globular proteins to which coelenterazine, a widely distributed marine luminogenic substrate (the luciferin), binds along with molecular oxygen, producing a stable peroxide. Upon Ca2+ addition, CaPhs undergo conformational changes leading to the cyclization of the peroxide and the formation of a high-energy intermediate. Subsequently, its decomposition yields coelenteramide in an excited state and results in the emission of a flash of light. To date, all CaPhs reported produce blue light ({lambda}max 465-495 nm). Here, we report the cloning and functional characterization of a novel class of wild-type CaPhs capable of emitting green light: velamins, isolated from the bioluminescent ctenophore Velamen parallelum. Ten unique photoprotein-like sequences were recovered and grouped in three main clusters. Representative sequences were cloned, expressed, purified, and regenerated into the active His-tagged -, {beta}-, and {gamma}-velamins. Upon injection of a calcium-containing buffer into the velamin, a flash of green light ({lambda}max 500-508 nm) was observed across pH values ranging from 7 to 9. Whilst -velamin isoforms exhibited the highest light emission activity, {beta}- and {gamma}-velamins were found to be more thermostable at higher temperatures. Velamins are the only known wild-type Ca2+-regulated photoproteins that exhibit the longest wavelength in light emission, making them a promising model for studying spectral modulation. As a result, velamins hold potential for enhancing the sensitivity of signal detection in analytical systems, particularly when dealing with complex biological matrices.

biochemistry↗

bioRxiv2024

Waves of light at the bottom of the ocean: insights into the luminous systems of three Pennatuloidea (Anthozoa)

Bioluminescence is the production of visible light by living organisms. It occurs through the oxidation of a luciferin substrate catalysed by luciferase enzymes. Auxiliary proteins, such as fluorescent proteins and luciferin-binding proteins, can modify the light emitted wavelength or stabilize reactive luciferin molecules, respectively. Additionally, calcium ions are crucial for the luminescence across various species. Despite the large phylogenetic distribution of bioluminescent organisms, only a few systems have been comprehensively studied. Notably, cnidarian species of the Renilla genus utilize a coelenterazine-dependent luciferase, a calcium-dependent coelenterazine-binding protein and a green fluorescent protein. We investigated the bioluminescence of three sea pen species: Pennatula phosphorea, Anthoptilum murrayi and Funiculina quadrangularis (Pennatuloidea, Anthozoa). Their light-emission spectra reveal peaks at 510, 513 and 485 nm, respectively. A coelenterazine-based reaction was demonstrated in all three species. Using transcriptome analyses, we identified predicted transcripts coding for luciferases, green fluorescent proteins and coelenterazine-binding proteins for P. phosphorea and A. murrayi. Immunodetection confirmed the expression of luciferase in P. phosphorea and F. quadrangularis. We also expressed recombinant luciferase of A. murrayi, confirming its activity. We highlighted the role of calcium ions in bioluminescence, possibly associated with the mechanism of substrate release at the level of coelenterazine-binding proteins. The study proposes a model for anthozoan bioluminescence, offering new avenues for future ecological and functional research on these luminous organisms.

zoology↗

bioRxiv2023

Vagus nerve mediated liver-brain axis is a major regulator of the metabolic landscape in the liver

BackgroundThe liver serves as a major energetic reservoir for other tissues and its metabolic function is controlled by humoral and neural factors. The vagus nerve innervating the gastrointestinal tract plays an important role in regulating peripheral metabolism and energy expenditure. Although the liver receives vagus nerve fibers, the impact of this circuitry in the regulation of hepatic metabolism is still poorly understood. MethodsHerein, we used a combination of quantitative proteomics and in vivo imaging techniques to investigate the impact of the vagus nerve on liver metabolism. ResultsVagus nerve shapes the metabolic framework of the liver, as surgical ablation (vagotomy; VNX) of this circuitry led to a significant alteration of the hepatic proteome landscape. Differential protein expression and pathway enrichment analyses showed that glycolytic and fatty acid biosynthesis were increased following VNX, whereas {beta}-oxidation was decreased. This metabolic shift facilitated lipid accumulation in hepatocytes. Furthermore, VNX worsened liver steatosis following high-carbohydrate or high-fat dietary challenges. ConclusionsThis study describes the liver-brain axis mediated by the vagus nerve as an important regulator of the hepatic metabolic landscape. HighlightsO_LIVagus nerve is a novel regulator of the hepatic metabolic landscape. C_LIO_LIAblation of vagus nerve neural circuit by vagotomy resulted in a metabolic shift towards glycolysis and fatty acid biosynthesis. C_LIO_LILipid accumulation was increased in vagotomized mice fed with a standard diet. C_LIO_LILiver steatosis was increased following dietary challenges with high-carbohydrate or high-fat diets. C_LIO_LIVagus nerve can be a promising new target for NAFLD treatment. C_LI

physiology↗

bioRxiv2023

Asymmetric control of food intake by left and right vagal sensory neurons

We investigated the lateralization of gut-innervating vagal sensory neurons and their roles in feeding behavior. Using genetic, anatomical, and behavioral analyses, we discovered a subset of highly lateralized vagal sensory neurons with distinct sensory responses to intestinal stimuli. Our results demonstrated that left vagal sensory neurons (LNG) are crucial for distension-induced satiety, while right vagal sensory neurons (RNG) mediate preference for nutritive foods. Furthermore, these lateralized neurons engage different central circuits, with LNG neurons recruiting brain regions associated with energy balance and RNG neurons activating areas related to salience, memory, and reward. Altogether, our findings unveil the diverse roles of asymmetrical gut-vagal-brain circuits in feeding behavior, offering new insights for potential therapeutic interventions targeting vagal nerve stimulation in metabolic and neuropsychiatric diseases. One Sentence SummaryLateralized gut-brain circuits respond to different sensory modalities and control distinct feeding behaviors.

neuroscience↗

bioRxiv2021

Landscape dynamics promoted the evolution of mega-diversity in South American freshwater fishes

Landscape dynamics and river network rearrangements are widely thought to shape the diversity of Neotropical freshwater fishes, the most species-rich continental vertebrate fauna on Earth. Yet the effects of hydrogeographic changes on fish dispersal and diversification remain poorly understood. Here we integrate an unprecedented occurrence dataset of 4,967 South American freshwater fish species with a species-dense phylogeny to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Three abrupt shifts in diversification rates occurred during the Paleogene (between 63 and 23 Ma) in association with major landscape evolution events, and net diversification accelerated from the Miocene to the Recent (c. 20 - 0 Ma). The Western Amazon exhibited the highest rates of in situ diversification and was also the most important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including Early Miocene (c. 20 Ma) uplift of the Serra do Mar, and Late Miocene (c. 10 Ma) uplift of the Northern Andes and formation of the modern transcontinental Amazon River. Reciprocal mass dispersal of fishes between the Western and Eastern Amazon coincided with this phase of Andean uplift. The Western Amazon has the highest contemporary levels of species richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics were constrained by the history of drainage basin connections, strongly affecting the assembly and diversification of basin-wide fish faunas. Significance StatementDespite progress in mapping geographic distributions and genealogical relationships, scientists have few clear answers about the origins of South American freshwater fishes, the most diverse vertebrate fauna on Earth. Here we used the most complete dataset of geographic distributions and evolutionary relationships of South American fishes to track how the geological history of river dynamics influenced the origin, extinction, and interchange of species over the past 100 Ma. We found abrupt increases of species origination between 66 and 23 Ma, coinciding with repeated uplifts of the Andes. The Western Amazon region served as source of freshwater fishes to other regions, as a place where species tended to persist over longer historical periods, and where species originations occurred with higher frequency.

ecology↗