Biology subjects

Amaral, C.

Publications and source records attributed to Amaral, C..

7 recordsLinked to original sources

bioRxiv2026

Functional relevance of mobile and clustered CaV2.1 channels in central synapses

Reliable neurotransmitter release critically depends on the spatial relationship between voltage- gated calcium channels (VGCCs) and presynaptic release sites. Single particle tracking of endogenous CaV2.1 channels at glutamatergic synapses of hippocampal neurons revealed that apart from CaV2.1 channels aggregated in stable nanodomain clusters, a substantial fraction of Cav2.1 channels remained mobile, raising the question of whether these dispersed channels contribute to synaptic function. Mathematical modelling predicted that dispersed Cav2.1 channels cooperatively enhance release reliability. Upon repetitive stimulation, mobile CaV2.1 channels enable alternative use of release sites and thereby reduce the probability of failed presynaptic release. Both optogenetic immobilisation of CaV2.1 channels per se or activation of GABAB receptors (GABABRs) alone increase the failure rate and can lead to synaptic silencing. However, optogenetic clustering CaV2.1 channels prior to GABABR activation increases the fraction of synapses that remain active even in presence of GABABR agonist. The contribution of mobile channels to reliable neurotransmitter release is frequency-dependent and is minor at stimulation frequencies 1 Hz but becomes strong at frequencies over 10 Hz. These results demonstrate that mobile presynaptic CaV2.1 channels increase the frequency range of synaptic transmission but are particularly sensitive to metabotropic GABABR-mediated inhibition in glutamatergic hippocampal synapses.

neuroscience↗

bioRxiv2024

Caspofungin binding to iron compromises its antifungal efficacy against Candida albicans

Echinocandin drugs, such as caspofungin, inhibit the synthesis of {beta}-1,3-D-glucans, which are essential components of the fungal cell wall. These drugs are often the preferred option for treating invasive fungal infections (IFIs) caused by Candida spp. due to their superior efficacy compared to other antifungal agents. Iron overload conditions, which exacerbate fungal burden, are well-documented as significant risk factors for the progression of IFIs. Recent in vitro studies have suggested that iron overload may also reduce the efficacy of cell wall-perturbing agents, such as echinocandins, against Candida albicans, by altering the composition of the fungal cell wall. Here, we show that iron loading conditions which do not interfere with the cell wall composition are still capable of recapitulating the caspofungin-resistant phenotype induced by iron in C. albicans. Spectroscopic analyses provided evidence that caspofungin binds to iron through its ethylenediamine moiety and two amide groups. Consistent with the in vitro activity of {beta}-1,3-D-glucan synthase, molecular dynamics simulations revealed that, when bound to iron, caspofungin undergoes conformational changes that may reduce its ability to inhibit the enzyme. Importantly, the in vivo antifungal efficacy of caspofungin is compromised in a Galleria mellonella model of IFI caused by C. albicans simulating a context of iron overload. This effect may extend beyond C. albicans infections, as the antagonism between iron and caspofungin was also observed in other medically important fungi causing IFIs.

microbiology↗

bioRxiv2024

Neuroimage Denoiser for removing noise from transient fluorescent signals in functional imaging.

We developed Neuroimage Denoiser, a novel U-Net-based model that effectively removes noise from microscopic recordings of transient local fluorescent signals. The model makes the denoising process independent of the recording frequency and the kinetics of the sensor used. The framework is easy to use for denoising and training and has minimal hardware requirements, thus, making it accessible for an average laboratory to create a custom version specific to their experimental setup. Neuroimage Denoiser significantly enhances the quality of functional microscopy recordings by effectively removing noise, thereby facilitating a more accurate and reliable analysis of neural activity. Highlights- Neuroimage Denoiser is a deep learning framework to remove noise from functional microscopic recordings, particularly trained and tested for glutamate imaging - Neuroimage Denoiser balances the removal of noise while preserving the amplitude of responses - Neuroimage Denoiser operates without re-training for different sensors (when the localization is similar) and recording frequencies MotivationAccurate measurements of neuronal activity through functional imaging are critical in understanding mechanisms of synaptic plasticity and learning concerning changes in the molecular composition of single synapses. Traditional denoising methods, such as Gaussian or Median filters, indiscriminately smooth entire recordings, reducing temporal and spatial resolutions considerably. Existing frameworks are not suited to remove noise from glutamate recordings due to the fast dynamics of the sensor. Therefore, a specialized tool for the challenges imposed by glutamate recordings, i.e. faster dynamics, and synaptic localization, is needed.

bioinformatics↗

bioRxiv2022

Drivers of mangrove vulnerability and resilience to tropical cyclones in the North Atlantic Basin

The North Atlantic Basin (NAB) is seeing a significant increase in the frequency and intensity of tropical cyclones since the 1980s, with record-breaking seasons such as 2017 and 2020. However, little is known about how coastal ecosystems, particularly mangroves in the Gulf of Mexico and the Caribbean, are responding to these new "climate normals" at regional and subregional scales. Wind speed, rainfall, pre-cyclone forest structure, and hydro-geomorphology are known to influence mangrove damage and recovery following cyclones in the NAB. However, these studies have focused on site-specific responses and individual cyclonic events. Here, we analyze 25 years (1996-2020) of mangrove vulnerability (damage after a cyclone) and short-term resilience (recovery after damage) for the entire NAB and its subregions, using multi-annual, remote sensing-derived databases. We applied machine learning to characterize the influence of 22 potential drivers that include previously researched variables and new ones such as human development and long-term climate trends. The characteristics of the cyclones mainly drive vulnerability at the regional level, while resilience is largely driven by site-specific conditions. These include long-term climate conditions, such as air temperature and drought trends, pre-cyclone habitat conditions, such as canopy cover and height and soil organic carbon stock, and human interventions on the land. Rates and drivers of mangrove vulnerability and resilience vary across subregions in the NAB, and hotspots for restoration and conservation actions are highlighted within subregions. The impacts of increasing cyclone activity need to be framed in the context of climate change compound effects and heavy human influences in the region. There is an urgent need to value the restoration and conservation of mangroves as fundamental Nature-based Solutions against cyclone impacts in the NAB.

ecology↗

bioRxiv2022

Multi-scale observations of mangrove blue carbon fluxes; the NASA Carbon Monitoring System BlueFlux field campaign

The BlueFlux field campaign is supported by NASAs Carbon Monitoring System (CMS) and will develop prototype blue carbon products to inform coastal carbon management. Blue carbon is included in carbon-dioxide removal actions proposed to reduce atmospheric CO2 concentrations to mitigate climate change. Due to their high productivity and carbon storage, combined with historic losses and a wide-range of beneficial ecosystem services, the restoration and conservation of mangrove ecosystems features prominently in blue-carbon planning. The goal of BlueFlux is to carry out multi-scale measurements of CO2 and CH4 fluxes using chambers, flux towers, and aircraft and scale these to gridded products using space-based observations of forest structure and surface reflectance. The measurements cover gradients in disturbance, mainly from the history of hurricanes in the region that drive the dieback of mangroves and the formation of ghost forests. The fluxes of CH4 emissions will be contrasted with CO2 uptake to provide a more complete budget of radiative forcing and to understand the net climate benefits of blue carbon. BlueFlux demonstrates that quantifying the removals of CO2 and emissions of CH4 using a multi-scale approach can provide increased confidence in regional greenhouse-gas accounting, contribute to process-understanding, and help inform restoration and conservation efforts in the context of climate mitigation.

ecology↗

bioRxiv2021

Copper Acts Synergistically with Fluconazole in Candida glabrata by Compromising Drug Efflux, Sterol Metabolism, and Zinc Homeostasis

The synergistic combinations of drugs are promising strategies to boost the effectiveness of current antifungals and thus prevent the emergence of resistance. In this work, we show that copper and the antifungal fluconazole act synergistically against Candida glabrata, an opportunistic pathogenic yeast intrinsically tolerant to fluconazole. Analyses of the transcriptomic profile of C. glabrata after the combination of copper and fluconazole showed that the expression of the multidrug transporter gene CDR1 was decreased, suggesting that fluconazole efflux could be affected. In agreement, we observed that copper inhibits the transactivation of Pdr1, the transcription regulator of multidrug transporters and leads to the intracellular accumulation of fluconazole. Copper also decreases the transcriptional induction of ergosterol biosynthesis (ERG) genes by fluconazole, which culminates in the accumulation of toxic sterols. Co-treatment of cells with copper and fluconazole should affect the function of proteins located in the plasma membrane, as several ultrastructural alterations, including irregular cell wall and plasma membrane and loss of cell wall integrity, were observed. Finally, we show that the combination of copper and fluconazole downregulates the expression of the gene encoding the zinc-responsive transcription regulator Zap1, which possibly, together with the membrane transporters malfunction, generates zinc depletion. Supplementation with zinc reverts the toxic effect of combining copper with fluconazole, underscoring the importance of this metal in the observed synergistic effect. Overall, this work, while unveiling the molecular basis that supports the use of copper to enhance the effectiveness of fluconazole, paves the way for the development of new metal-based antifungal strategies.

microbiology↗

bioRxiv2020

Estrogen withdrawal alters oxytocin signaling in the paraventricular hypothalamus and dorsal raphe nucleus to increase postpartum anxiety

BackgroundEstrogen increases dramatically during pregnancy, but quickly drops below pre-pregnancy levels at birth and remains suppressed during the postpartum period. Clinical and rodent work suggests that this postpartum drop in estrogen results in an "estrogen withdrawal" state that is related to changes in affect, mood, and behavior. Most studies examining the effect of estrogen withdrawal on the brain have focused solely on the hippocampus. MethodsWe used a hormone-simulated pseudopregnancy model in Syrian hamsters, a first for this species. Ovariectomized females were given daily injections to approximate hormone levels during gestation and then withdrawn from estrogen to simulate postpartum estrogen withdrawal. Subjects were tested for behavioral assays of anxiety and anhedonia during estrogen withdrawal. Following sacrifice, neuroplasticity in oxytocin-producing neurons in the paraventricular nucleus of the hypothalamus (PVH) and its efferent targets was measured. ResultsEstrogen-withdrawn females had increased anxiety-like behaviors in the elevated plus and open field, but did not differ from controls in sucrose preference. Furthermore, estrogen-withdrawn females had more oxytocin-immunoreactive cells and oxytocin mRNA in the PVH, as well as an increase in oxytocin receptor density in the dorsal raphe nucleus (DRN). Finally, blocking oxytocin receptors in the DRN during estrogen withdrawal prevented the high-anxiety behavioral phenotype in estrogen-withdrawn females. ConclusionsEstrogen withdrawal alters oxytocin signaling in the PVH and DRN to increase anxiety-like behavior during the postpartum period. More broadly, these experiments suggest Syrian hamsters as a novel organism in which to model the effects of postpartum estrogen withdrawal on the brain and anxiety-like behavior.

neuroscience↗