Biology Open最新文献

Mechanically stimulated bioluminescence (MSL) is present in most planktonic clades and marine ecosystems. The first flash kinetic parameters (FFKPs) and spectral properties are often species specific, making MSL a powerful tool for in situ ID and biodiversity assessments. The peak intensity (PI) of mechanically stimulated bioluminescence was measured for five species of dinoflagellates: Alexandrium monilatum, Lingulodinium polyedra, Pyrocystis fusiformis, Pyrocystis noctiluca and Pyrodinium bahamense. Peak intensity was assessed with respect to organism cell surface area and volume, building upon Seliger's rule, where previously a relationship was found linking cell surface area and total mechanically stimulated light (TMSL) ( Buskey and Swift, 1990). These dinoflagellate species were chosen to cover a wide range of peak intensities (108 to 1010 photons/s) and surface area (104 to 106μm2). Individual cells were isolated and individually photographed under a compound microscope, where cell size was measured. They were then dark-adapted and first flash emission from mechanical stimulation was measured with the Underwater Bioluminescence Assessment Tool (UBAT) from Seabird Scientific (www.seabird.com). Distributions of PI and surface area across all species were compared using non-parametric ANOVAs and a linear regression model, uncovering a strong positive correlation and strength of fit across all species between peak intensity and both cell surface area and volume. This study provides insight into understanding and potentially predicting the bioluminescence of organisms often responsible for significant primary and secondary productivity in marine waters with subsequent global impacts on fisheries and ecology. Bioluminescence measurements may also be a powerful tool for understanding plankton composition, ecology, and diversity.

Immune signals coordinate the repair of damaged epithelia by intestinal stem cells. However, it is unclear if immune pathways act autonomously within the stem cell to direct the damage response pathway. We consider this an important question, as stem cell dynamics are essential for formation and maintenance of the entire epithelium. We used Drosophila to determine the impact of stem cell-specific loss of NF-κB on tissue regeneration upon chemical injury. We found that loss of NF-κB enhanced cell death, impaired enterocyte renewal and increased mortality. Mechanistically, we showed that inhibition of stem cell apoptosis is essential for NF-κB-dependent maintenance of cell viability and tissue repair. Combined, our data demonstrate that stem cell-intrinsic NF-κB activity is essential for an orderly repair of damaged intestinal epithelia.

Goldfish (Carassius auratus) were first introduced to the Laurentian Great Lakes when it was first introduced into Lake Ontario in the 1800s. In the past 15 years, there have been dramatic increases in both goldfish abundance and geographic spread across North America, including the Great Lakes, raising concerns about its potential for negative impacts on aquatic ecosystems. Climate studies suggest that habitat ranges suitable for goldfish will continue to expand in the future as water temperatures rise towards its thermal optima. We explore whether warmer temperatures are physiologically suitable for a population of wild, invasive goldfish (Hamilton, ON, Canada) by testing aerobic scope (AS) at current (26°C) and predicted (30°C) peak summer water temperatures. Goldfish were first acclimated to a common-garden average summer pond temperature (22°C), then their AS was estimated by calculating the difference between routine and maximum metabolic rates (RMR and MMR) at the two test temperatures. Our results demonstrate that wild goldfish sustain their AS through increases in both RMR and MMR from 26°C to 30°C (mass-standardized means of 1.07 versus 1.17 mgO2h-1 at 26°C versus 30°C, respectively). This ability to sustain aerobic energy budget at high peak water temperatures could offer physiological benefits to this invasive population in a warming climate.

Feather regeneration is vital for birds' thermoregulation, courtship, breeding, camouflage, and locomotion, with strategies reflecting life history. Little penguins (Eudyptula minor) undergo catastrophic moult, replacing all feathers within a short timeframe while on land and not foraging. This study examined the 2015 and 2016 moult seasons on Phillip Island to explore factors influencing moult timing, duration, and mass. Moult started 9.6 days earlier in 2016 (∼Feb. 15) than in 2015 (∼Feb. 24), and year was found to be the only significant predictor of this moult start date. Moult duration was similar between years (medians: 18.0 days in 2015, 17.5 in 2016) and only slightly reduced with later start dates (-0.04 days per day delay; ∼58 min). Average daily mass loss during moult were best explained by moult duration and starting mass, with longer moult and greater starting mass leading to greater mass loss. The timing and duration of little penguins' moult, along with the need for significant pre-moult mass gain, are likely influenced by external factors like local prey availability. Moult plasticity likely benefits little penguin survival.

The principal organization of mammalian neuromuscular junctions (NMJs) shares essential features across species. However, human NMJs (hNMJs) exhibit distinct structural and physiological properties. While recent advances in stem-cell-based systems have significantly improved in vitro modeling of hNMJs, the extent to which these models recapitulate in vivo development remains unclear. Here, we performed temporal transcriptomic analysis of human three-dimensional (3D) neuromuscular co-cultures, composed of iPSC-derived motoneurons and skeletal muscle engineered from primary myoblasts. We found that the expression pattern follows a temporally coordinated gene expression program underlying NMJ maturation. The model recapitulates transcriptional features of NMJ development, including early myoblast fusion and presynaptic development, followed by a late-stage upregulation of postsynaptic markers and embryonic AChR subunits. Importantly, comparable transcriptional dynamics across two independent hiPSC lines confirm the reproducibility and robustness of this system. This study confirms on a transcriptional level that human 3D neuromuscular co-cultures are a robust and physiologically relevant model for investigating hNMJ development and function.

The prevalence of metabolic disease is increased in congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. However, the underlying molecular mechanisms causing these problems are not fully understood. We aimed to elucidate the metabolic phenotype and conduct a transcriptomic analysis of a 21-hydroxylase-deficient zebrafish model, to unravel the molecular mechanisms underlying the metabolic pathophysiology of CAH. The morphology, anatomy and transcriptomic analysis of whole larvae, adult liver tissue from 18-month-old cyp21a2-/- zebrafish were compared to those of wild-type siblings. Our main phenotypical finding was that adult mutants were larger, with increased fat deposition compared to controls, in-keeping with the transcriptomic analysis showing the dysregulation of several biological processes involved in lipid metabolism. Importantly, we found that ATP synthesis and provision of energy precursors were included among the most significantly suppressed processes in both larvae and adult livers. We conclude that cortisol deficiency in cyp21a2-/- mutants causes growth and body fat abnormalities at adult stages, as well as transcriptomic dysregulation of metabolic processes, energy homeostasis and inflammatory responses in both larvae and adults. These findings reveal how GC deficiency in zebrafish contributes to the development of the metabolic comorbidities that are similar to those observed in patients with CAH.

Tricellular tight junctions (tTJs) seal the space between three or more cells in epithelial monolayers. These specialized tight junctions have distinct protein components, including a transmembrane protein tricellulin. However, the mechanisms by which tricellulin localizes specifically to tTJs are incompletely understood. We demonstrate that tricellulin undergoes rapid lateral diffusion along bicellular junctions but is a very stable component of tTJs. BioID proteomics identified several proximity partners of tricellulin, and knockout studies on angulin-1/LSR, occludin and afadin provided evidence that these proteins control tricellulin accumulation to tTJs to different extents and mechanisms. Tricellulin localization was disrupted in afadin and angulin-1/LSR knockout cells, although these proteins did not display similar accumulation to tTJs, suggesting that they contribute to tricellulin localization through indirect or context-dependent mechanisms. Importantly, experiments on mixed cultures revealed that defects of tricellulin localization in occludin knockout cells were affected by the proximity of wild-type cells, and treatment of monolayers with myosin-II inhibitor resulted in displacement of tricellulin from tTJs. These results suggest that, in addition to protein-protein interactions, proper epithelial monolayer mechanics are essential for stabilizing tricellulin at tTJs.

Voice deficits are common in Parkinson's disease (PD) and significantly impact quality of life by increasing stress, social isolation, and caregiver burden. However, despite this impact, there are currently no treatments that target the underlying pathophysiology of PD in the vocalization system. The goal of this study was to examine the effect of one possible underlying mechanism responsible for the complex voice deficits that exist in PD; overexpression of the protein alpha-synuclein. Results show that overexpression of alpha-synuclein, prior to the development of alpha-synuclein aggregate pathology, does not result in significant vocalization deficits. A small but statistically significant increase in the total number of complex vocalizations was found in mice overexpressing alpha-synuclein compared to wild-type mice, but there were no differences in complexity ratio or any of the other specific vocalization parameters tested. Results provide a critical foundational understanding of the impact of overexpression versus aggregation of alpha-synuclein on voice deficits in PD. Future work will focus on manipulation of alpha-synuclein aggregate pathology, and not overexpression alone, to reduce or eliminate the burden of PD specific voice disorders.

Global warming threatens biodiversity, particularly affecting ectothermic animals, which must seek refuge to avoid overheating when ambient temperatures exceed their critical thresholds. Extended shelter use limits the time for essential activities such as foraging, social interactions, and reproduction, potentially reducing survival and increasing local extinction risk. Viviparous Liolaemids inhabiting cold-temperate Andean regions are considered vulnerable to rising temperatures and are predicted to experience local extinctions this century. We evaluated the effects of thermal restriction on pregnancy outcomes and offspring in the viviparous lizard Liolaemus pictus under two conditions. One group of pregnant females experienced simulated future thermal restrictions (restriction group, RG; n=12), while another group experienced identical laboratory conditions without thermal restrictions (no-restriction group, NRG; n=14). In RG females, 41.7% were removed due to feeding cessation or spontaneous abortions (versus 12.3% in NRG), reflecting the consequences of thermal restriction. The remaining RG females selected lower preferred body temperatures after 2 weeks of experimentation and maintained a stable body condition throughout pregnancy. However, both groups of offspring showed similar body condition and locomotor performance, suggesting physiological compensation by RG females. This physiological plasticity of L. pictus may help buffer the adverse effects of global warming on reproductive success.

Vitamin B12 is an essential micronutrient produced only by prokaryotes, and animals must acquire it from their diet. Vitamin B12 is critical for the synthesis of methionine and propionyl-CoA metabolism. In humans, vitamin B12 deficiency has been linked to many disorders, including infertility and developmental abnormalities. The growing trend towards plant-based diets and ageing populations increases the risk of vitamin B12 deficiency, and, therefore, there is an increasing interest in understanding vitamin B12 biology. Accurate approaches for detecting and quantifying vitamin B12 are essential in studying its complex biology, from its biogenesis in Bacteria and Archaea to its effects in complex organisms. Here, we present an approach using the commonly available E. coli methionine auxotroph strain B834 (DE3) and a multi-well spectrophotometer to detect and estimate the levels of vitamin B12 from biological samples at picomolar concentrations. We further show that our method is sufficient to reveal important differences in the production of vitamin B12 from vitamin B12-synthesising bacteria commonly found in the microbiome of wild Caenorhabditis elegans isolates. Our results establish a high-throughput and simple assay platform for detecting and estimating vitamin B12 levels using the E. coli B834 (DE3) strain.