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We demonstrate the transfer of a cesium frequency standard steered to UTC(NIST) over 20 km of dark telecom optical fiber. Our dissemination scheme uses an active stabilization technique with a phase-locked voltage-controlled oscillator. Out-of-loop characterization of the optical fiber link performance is done with dual-fiber and single-fiber transfer schemes. We observe a fractional frequency instability of 1.5 × 10-12 and 2 × 10-15 at averaging intervals of 1 s and 105 s, respectively, for the link. Both schemes are sufficient to transfer the cesium clock reference without degrading the signal, with nearly an order of magnitude lower fractional frequency instability than the cesium clocks over all time scales. The simplicity of the two-fiber technique may be useful in future long-distance applications where higher stability requirements are not paramount, as it avoids technical complications involved with the single-fiber scheme.
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The inadequate vascularization seen in fast-growing solid tumors gives rise to hypoxic areas, fostering specific changes in gene expression that bolster tumor cell survival and metastasis, ultimately leading to unfavorable clinical prognoses across different cancer types. Hypoxia-inducible factors (HIF-1 and HIF-2) emerge as druggable pivotal players orchestrating tumor metastasis and angiogenesis, thus positioning them as prime targets for cancer treatment. A range of HIF inhibitors, notably natural compounds originating from marine organisms, exhibit encouraging anticancer properties, underscoring their significance as promising therapeutic options. Bioprospection of the marine environment is now a well-settled approach to the discovery and development of anticancer agents that might have their medicinal chemistry developed into clinical candidates. However, despite the massive increase in the number of marine natural products classified as 'anticancer leads,' most of which correspond to general cytotoxic agents, and only a few have been characterized regarding their molecular targets and mechanisms of action. The current review presents a critical analysis of inhibitors of HIF-1 and HIF-2 and hypoxia-selective compounds that have been sourced from marine organisms and that might act as new chemotherapeutic candidates or serve as templates for the development of structurally similar derivatives with improved anticancer efficacy.
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Antineoplásicos , Organismos Aquáticos , Produtos Biológicos , Fator 1 Induzível por Hipóxia , Neoplasias , Animais , Humanos , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Organismos Aquáticos/química , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/antagonistas & inibidores , Produtos Biológicos/farmacologia , Produtos Biológicos/química , Produtos Biológicos/uso terapêutico , Fator 1 Induzível por Hipóxia/antagonistas & inibidores , Neoplasias/tratamento farmacológico , Neoplasias/patologia , Transdução de Sinais/efeitos dos fármacosRESUMO
Studies of eco-evolutionary dynamics have integrated evolution with ecological processes at multiple scales (populations, communities and ecosystems) and with multiple interspecific interactions (antagonistic, mutualistic and competitive). However, evolution has often been conceptualised as a simple process: short-term directional adaptation that increases population growth. Here we argue that diverse other evolutionary processes, well studied in population genetics and evolutionary ecology, should also be considered to explore the full spectrum of feedback between ecological and evolutionary processes. Relevant but underappreciated processes include (1) drift and mutation, (2) disruptive selection causing lineage diversification or speciation reversal and (3) evolution driven by relative fitness differences that may decrease population growth. Because eco-evolutionary dynamics have often been studied by population and community ecologists, it will be important to incorporate a variety of concepts in population genetics and evolutionary ecology to better understand and predict eco-evolutionary dynamics in nature.
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Evolução Biológica , Ecossistema , Dinâmica Populacional , Genética Populacional , Crescimento DemográficoRESUMO
BACKGROUND: Despite evidence supporting its use, many Enhanced Recovery After Surgery (ERAS) recommendations remain poorly adhered to and barriers to ERAS implementation persist. In this second updated ERAS® Society guideline, a consensus for optimal perioperative care in gynecologic oncology surgery is presented, with a specific emphasis on implementation challenges. METHODS: Based on the gaps identified by clinician stakeholder groups, nine implementation challenge topics were prioritized for review. A database search of publications using Embase and PubMed was performed (2018-2023). Studies on each topic were selected with emphasis on meta-analyses, randomized controlled trials, and large prospective cohort studies. These studies were then reviewed and graded by an international panel according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. RESULTS: All recommendations on ERAS implementation challenge topics are based on best available evidence. The level of evidence for each item is presented accordingly. CONCLUSIONS: The updated evidence base and recommendations for stakeholder derived ERAS implementation challenges in gynecologic oncology are presented by the ERAS® Society in this consensus review.
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Recuperação Pós-Cirúrgica Melhorada , Neoplasias dos Genitais Femininos , Feminino , Humanos , Neoplasias dos Genitais Femininos/cirurgia , Estudos Prospectivos , Assistência Perioperatória , Procedimentos Cirúrgicos em GinecologiaRESUMO
The inflammatory response is a vital mechanism for repairing damage induced by aberrant health states or external insults; however, persistent activation can be linked to numerous chronic diseases. The nuclear factor kappa ß (NF-κB) inflammatory pathway and its associated mediators have emerged as critical targets for therapeutic interventions aimed at modulating inflammation, necessitating ongoing drug development. Previous studies have reported the inhibitory effect of a hydroethanol extract derived from Parinari excelsa Sabine (Chrysobalanaceae) on tumour necrosis factor-alpha (TNF-α), but the phytoconstituents and mechanisms of action remained elusive. The primary objective of this study was to elucidate the phytochemical composition of P. excelsa stem bark and its role in the mechanisms underpinning its biological activity. Two compounds were detected via HPLC-DAD-ESI(Ion Trap)-MS2 analysis. The predominant compound was isolated and identified as naringenin-8-sulphonate (1), while the identity of the second compound (compound 2) could not be determined. Both compound 1 and the extract were assessed for anti-inflammatory properties using a cell-based inflammation model, in which THP-1-derived macrophages were stimulated with LPS to examine the treatments' effects on various stages of the NF-κB pathway. Compound 1, whose biological activity is reported here for the first time, demonstrated inhibition of NF-κB activity, reduction in interleukin 6 (IL-6), TNF-α, and interleukin 1 beta (IL-1ß) production, as well as a decrease in p65 nuclear translocation in THP-1 cells, thus highlighting the potential role of sulphur substituents in the activity of naringenin (3). To explore the influence of sulphation on the anti-inflammatory properties of naringenin derivatives, we synthesized naringenin-4'-O-sulphate (4) and naringenin-7-O-sulphate (5) and evaluated their anti-inflammatory effects. Naringenin derivatives 4 and 5 did not display potent anti-inflammatory activities; however, compound 4 reduced IL-1ß production, and compound 5 diminished p65 translocation, with both exhibiting the capacity to inhibit TNF-α and IL-6 production. Collectively, the findings demonstrated that the P. excelsa extract was more efficacious than all tested compounds, while providing insights into the role of sulphation in the anti-inflammatory activity of naringenin derivatives.
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Chrysobalanaceae , NF-kappa B , Humanos , NF-kappa B/metabolismo , Interleucina-6/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Chrysobalanaceae/metabolismo , Casca de Planta/metabolismo , Anti-Inflamatórios/uso terapêutico , Inflamação/metabolismo , Extratos Vegetais/farmacologia , Extratos Vegetais/uso terapêutico , Lipopolissacarídeos/farmacologiaRESUMO
Riboswitches are structural RNA elements that are generally located in the 5' untranslated region of messenger RNA. During regulation of gene expression, ligand binding to the aptamer domain of a riboswitch triggers a signal to the downstream expression platform. A complete understanding of the structural basis of this mechanism requires the ability to study structural changes over time. Here we use femtosecond X-ray free electron laser (XFEL) pulses to obtain structural measurements from crystals so small that diffusion of a ligand can be timed to initiate a reaction before diffraction. We demonstrate this approach by determining four structures of the adenine riboswitch aptamer domain during the course of a reaction, involving two unbound apo structures, one ligand-bound intermediate, and the final ligand-bound conformation. These structures support a reaction mechanism model with at least four states and illustrate the structural basis of signal transmission. The three-way junction and the P1 switch helix of the two apo conformers are notably different from those in the ligand-bound conformation. Our time-resolved crystallographic measurements with a 10-second delay captured the structure of an intermediate with changes in the binding pocket that accommodate the ligand. With at least a 10-minute delay, the RNA molecules were fully converted to the ligand-bound state, in which the substantial conformational changes resulted in conversion of the space group. Such notable changes in crystallo highlight the important opportunities that micro- and nanocrystals may offer in these and similar time-resolved diffraction studies. Together, these results demonstrate the potential of 'mix-and-inject' time-resolved serial crystallography to study biochemically important interactions between biomacromolecules and ligands, including those that involve large conformational changes.
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Cristalografia por Raios X/métodos , Nanotecnologia/métodos , Conformação de Ácido Nucleico , RNA Bacteriano/química , Riboswitch , Regiões 5' não Traduzidas/genética , Aptâmeros de Nucleotídeos/química , Cristalização , Difusão , Elétrons , Cinética , Lasers , Ligantes , Modelos Moleculares , Dobramento de RNA , RNA Bacteriano/genética , Fatores de Tempo , Vibrio vulnificus/genéticaRESUMO
Ecological studies require quality data to describe the nature of ecological processes and to advance understanding of ecosystem change. Increasing access to big data has magnified both the burden and the complexity of ensuring quality data. The costs of errors in ecology include low use of data, increased time spent cleaning data, and poor reproducibility that can result in a misunderstanding of ecosystem processes and dynamics, all of which can erode the efficacy of and trust in ecological research. Although conceptual and technological advances have improved ecological data access and management, a cultural shift is needed to embed data quality as a cultural practice. We present a comprehensive data quality framework to evoke this cultural shift. The data quality framework flexibly supports different collaboration models, supports all types of ecological data, and can be used to describe data quality within both short- and long-term ecological studies.
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OBJECTIVE: To assess the benefit of Enhanced Recovery After Surgery (ERAS) on length of stay (LOS), postoperative complications, 30-day readmission, and cost in gynecologic oncology. METHODS: A systematic literature search was performed in MEDLINE, EMBASE, Cochrane Register of Controlled Trials, and Web of Science for all peer-reviewed cohort studies and controlled trials on ERAS involving gynecologic oncology patients. Abstracts, commentaries, non-controlled studies, and studies without specific data on gynecologic oncology patients were excluded. Meta-analysis was performed on the primary endpoint of LOS. Subgroup analyses were performed based on risk of bias of the studies included, number of ERAS elements, and ERAS compliance. Secondary endpoints were readmission rate, complications, and cost. RESULTS: A total of 31 studies (6703 patients) were included: 5 randomized controlled trials, and 26 cohort studies. Meta-analysis of 27 studies (6345 patients) demonstrated a decrease in LOS of 1.6 days (95% confidence interval, CI 1.2-2.1) with ERAS implementation. Meta-analysis of 21 studies (4974 patients) demonstrated a 32% reduction in complications (OR 0.68, 95% CI 0.55-0.83) and a 20% reduction in readmission (OR 0.80, 95% CI 0.64-0.99) for ERAS patients. There was no difference in 30-day postoperative mortality (OR 0.61, 95% CI 0.23-1.6) for ERAS patients compared to controls. No difference in the odds of complications or reduction in LOS was observed based on number of included ERAS elements or reported compliance with ERAS interventions. The mean cost savings for ERAS patients was $2129 USD (95% CI $712 - $3544). CONCLUSIONS: ERAS protocols decrease LOS, complications, and cost without increasing rates of readmission or mortality in gynecologic oncology surgery. This evidence supports implementation of ERAS as standard of care in gynecologic oncology.
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Recuperação Pós-Cirúrgica Melhorada , Neoplasias dos Genitais Femininos/cirurgia , Procedimentos Cirúrgicos de Citorredução/métodos , Procedimentos Cirúrgicos de Citorredução/normas , Feminino , Procedimentos Cirúrgicos em Ginecologia/métodos , Procedimentos Cirúrgicos em Ginecologia/normas , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto , Resultado do TratamentoRESUMO
The mode-mismatched dual-beam thermal lens technique is widely applied in the characterization of optical and thermo-physical properties of solids and liquids. The technique has also been used to investigate transient acoustic waves induced by pulsed laser excitation at the nanosecond time scale. In this paper, we developed a semi-analytical model to describe the transient acoustic wave that allows a fitting procedure to get the physical properties of fluid samples. The method was used to investigate samples with different mixtures of ethanol and water, and quantitative information of piezo-optic coefficient and sound speed are evaluated for the fluid mixtures.
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We use the thermal lens technique in the nanosecond time scale to describe the acoustic wave effect in liquids and the corresponding correlation with the speed of sound in the fluid, volumetric thermal expansion, and piezo-optic coefficient. These physical properties are found to be directly correlated to the anomalous effects observed in the transients at the nanosecond time scale, where acoustic waves dominate the thermal lens signal inducing an oscillating transient. Our results suggest the application of the thermal lens to study the generation and the detection of thermo-acoustic waves in liquids, which makes this method interesting for all-optoacoustic ultrasound detection and imaging.
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Commonly used to treat skin injuries in Asia, several Homalium spp. have been found to promote skin regeneration and wound healing. While ethnobotanical surveys report the use of H. bhamoense trunk bark as a wound salve, there are no studies covering bioactive properties. As impaired cutaneous healing is characterized by excessive inflammation, a series of inflammatory mediators involved in wound healing were targeted with a methanol extract obtained from H. bhamoense trunk bark. Results showed concentration-dependent inhibition of hyaluronidase and 5-lipoxygenase upon exposure to the extract, with IC50 values of 396.9 ± 25.7 and 29.0 ± 2.3 µg mL-1, respectively. H. bhamoense trunk bark extract also exerted anti-inflammatory activity by significantly suppressing the overproduction of interleukin 6 (IL-6) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages at concentrations ranging from 125 to 1000 µg mL-1, while leading to a biphasic effect on nitric oxide (NO) and tumor necrosis factor alpha (TNF-α) levels. The phenolic profile was elucidated by HPLC-DAD, being characterized by the occurrence of ellagic acid as the main constituent, in addition to a series of methylated derivatives, which might underlie the observed anti-inflammatory effects. Our findings provide in vitro data on anti-inflammatory ability of H. bhamoense trunk bark, disclosing also potential cutaneous toxicity as assessed in HaCaT keratinocytes.
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Anti-Inflamatórios/farmacologia , Interleucina-6/efeitos adversos , Lipopolissacarídeos/efeitos adversos , Macrófagos/efeitos dos fármacos , Medicina Tradicional/métodos , Nephropidae/química , Extratos Vegetais/farmacologia , Animais , Araquidonato 5-Lipoxigenase/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Citocinas/metabolismo , Medicina Herbária , Hialuronoglucosaminidase/efeitos dos fármacos , Hidroxibenzoatos , Mediadores da Inflamação/farmacologia , Concentração Inibidora 50 , Interleucina-6/metabolismo , Queratinócitos , Lipopolissacarídeos/metabolismo , Camundongos , Óxido Nítrico/metabolismo , Células RAW 264.7 , Fator de Necrose Tumoral alfaRESUMO
Population genetics largely rests on a 'standard model' in which random genetic drift is the dominant force, selective sweeps occur infrequently, and deleterious mutations are purged from the population by purifying selection. Studies of phenotypic evolution in nature reveal a very different picture, with strong selection and rapid heritable trait changes being common. The time-rate scaling of phenotypic evolution suggests that selection on phenotypes is often fluctuating in direction, allowing phenotypes to respond rapidly to environmental fluctuations while remaining within relatively constant bounds over longer periods. Whether such rapid phenotypic evolution undermines the standard model will depend on how many genomic loci typically contribute to strongly selected traits and how phenotypic evolution impacts the dynamics of genetic variation in a population. Population-level sequencing will allow us to dissect the genetic basis of phenotypic evolution and study the evolutionary dynamics of genetic variation through direct measurement of polymorphism trajectories over time.
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Evolução Molecular , Genética Populacional , Seleção Genética/genética , Deriva Genética , Fenótipo , Polimorfismo Genético , Deleção de Sequência/genéticaRESUMO
To disclose the mechanisms surrounding obesity, we selected microRNAs (miRNAs) that target genes involved in adipogenesis, angiogenesis, and inflammation and compared their expression levels in the subcutaneous adipose tissue of 40 obese and nonobese women. Mature miRNAs were extracted from subcutaneous adipose tissue samples that were collected during surgery and quantified by real-time polymerase chain reaction. miR-16 was overexpressed in the nonobese group (n-expression ratio = - 151.1; P < 0.001). Furthermore, the expression levels of two other miRNAs were significantly correlated with waist circumference in nonobese women (miR-27b, r = 0.453; P = 0.027 and miR-424-5p, r = 0.502, P = 0.014). Central and total subcutaneous adipose tissue thicknesses were correlated with miR-424-5p levels (r = 0.506, P = 0.034 and r = 0.475, P = 0.046, respectively) in the nonobese group. In the obese group, miR-424-5p expression was correlated with body mass index (r = 0.582, P = 0.018). miR-16 and miR-424 have shown correlations with body-fat-mass-related parameters. Because these miRNAs have vascular endothelial growth factor (VEGF) and its receptors as target genes, they may be involved in the alterations of angiogenesis observed in obesity. In addition, higher levels of miR-27 and miR-424 were correlated with higher fat depot measurements in nonobese women. These results highlight the importance of miRNA expression in subcutaneous adipose tissue and encourage further investigation of miRNAs as prognostic markers.
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Adipogenia/genética , Perfilação da Expressão Gênica , MicroRNAs/genética , Neovascularização Fisiológica/genética , Obesidade/genética , Gordura Subcutânea/metabolismo , Adulto , Feminino , Humanos , MicroRNAs/metabolismoRESUMO
While several marine natural products bearing the 2,5-diketopiperazine ring have been reported to date, the unique chemistry of dimeric frameworks appears to remain neglected. Frequently reported from marine-derived strains of fungi, many naturally occurring diketopiperazine dimers have been shown to display a wide spectrum of pharmacological properties, particularly within the field of cancer and antimicrobial therapy. While their structures illustrate the unmatched power of marine biosynthetic machinery, often exhibiting unsymmetrical connections with rare linkage frameworks, enhanced binding ability to a variety of pharmacologically relevant receptors has been also witnessed. The existence of a bifunctional linker to anchor two substrates, resulting in a higher concentration of pharmacophores in proximity to recognition sites of several receptors involved in human diseases, portrays this group of metabolites as privileged lead structures for advanced pre-clinical and clinical studies. Despite the structural novelty of various marine diketopiperazine dimers and their relevant bioactive properties in several models of disease, to our knowledge, this attractive subclass of compounds is reviewed here for the first time.
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Organismos Aquáticos/química , Produtos Biológicos/química , Dicetopiperazinas/química , Fungos/química , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Antineoplásicos/química , Antineoplásicos/farmacologia , Produtos Biológicos/farmacologia , Dicetopiperazinas/farmacologia , Dimerização , Humanos , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
The role of the marine environment in the development of anticancer drugs has been widely reviewed, particularly in recent years. However, the innovation in terms of clinical benefits has not been duly emphasized, although there are important breakthroughs associated with the use of marine-derived anticancer agents that have altered the current paradigm in chemotherapy. In addition, the discovery and development of marine drugs has been extremely rewarding with significant scientific gains, such as the discovery of new anticancer mechanisms of action as well as novel molecular targets. Approximately 50 years since the approval of cytarabine, the marine-derived anticancer pharmaceutical pipeline includes four approved drugs and eighteen agents in clinical trials, six of which are in late development. Thus, the dynamic pharmaceutical pipeline consisting of approved and developmental marine-derived anticancer agents offers new hopes and new tools in the treatment of patients afflicted with previously intractable types of cancer.
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Antineoplásicos/química , Organismos Aquáticos/química , Descoberta de Drogas/tendências , Antineoplásicos/uso terapêutico , Sistemas de Liberação de Medicamentos , Humanos , Neoplasias/tratamento farmacológicoRESUMO
The feasibility of thermography as a technique for plant screening aiming at drought-tolerance has been proven by its relationship with gas exchange, biomass, and yield. In this study, unlike most of the previous, thermography was applied for phenotyping contrasting maize genotypes whose classification for drought tolerance had already been established in the field. Our objective was to determine whether thermography-based classification would discriminate the maize genotypes in a similar way as the field selection in which just grain yield was taken into account as a criterion. We evaluated gas exchange, daily water consumption, leaf relative water content, aboveground biomass, and grain yield. Indeed, the screening of maize genotypes based on canopy temperature showed similar results to traditional methods. Nevertheless, canopy temperature only partially reflected gas exchange rates and daily water consumption in plants under drought. Part of the explanation may lie in the changes that drought had caused in plant leaves and canopy structure, altering absorption and dissipation of energy, photosynthesis, transpiration, and partitioning rates. Accordingly, although there was a negative relationship between grain yield and plant canopy temperature, it does not necessarily mean that plants whose canopies were maintained cooler under drought achieved the highest yield.
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Secas , Estresse Fisiológico/genética , Termografia/métodos , Zea mays/metabolismo , Grão Comestível/genética , Grão Comestível/crescimento & desenvolvimento , Grão Comestível/metabolismo , Genótipo , Fotossíntese/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Temperatura , Água/metabolismo , Zea mays/genética , Zea mays/crescimento & desenvolvimentoRESUMO
Predominantly spread in West Tropical Africa, the shrub Salacia senegalensis (Lam.) DC. is known because of its medicinal properties, the leaves being used in the treatment of skin diseases. Prompted by the ethnomedicinal use, a hydroethanolic extract obtained from the leaves of the plant was screened against a panel of microbial strains, the majority of which involved in superficial infections. The extract was found to be active against the dermatophytes Trichophyton rubrum and Epidermophyton floccosum. Notable results were also recorded regarding the attenuation of the inflammatory response, namely the inhibitory effects observed against soybean 5-lipoxygenase (IC50 = 71.14 µg mL-1), no interference being recorded in the cellular viability of RAW 264.7 macrophages and NO levels. Relevantly, the extract did not lead to detrimental effects against the keratinocyte cell line HaCaT, at concentrations displaying antidermatophytic and anti-inflammatory effects. Flavonoid profiling of S. senegalensis leaves was achieved for the first time, allowing the identification and quantitation of myricitrin, three 3-O-substituted quercetin derivatives, and three other flavonoid derivatives, which may contribute, at least partially, to the observed antidermatophytic and anti-inflammatory effects. In the current study, the plant S. senegalensis is assessed concerning its antidermatophytic and anti-inflammatory properties.
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Anti-Inflamatórios/farmacologia , Antifúngicos/farmacologia , Arthrodermataceae/efeitos dos fármacos , Flavonoides/farmacologia , Extratos Vegetais/farmacologia , Folhas de Planta/química , Salacia/química , Animais , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Anti-Inflamatórios/química , Antifúngicos/química , Sobrevivência Celular/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Relação Dose-Resposta a Droga , Flavonoides/química , Humanos , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Macrófagos/metabolismo , Camundongos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Compostos Fitoquímicos/química , Extratos Vegetais/química , Células RAW 264.7 , Análise EspectralRESUMO
Light is a fundamental driver of ecosystem dynamics, affecting the rate of photosynthesis and primary production. In spite of its importance, less is known about its community-scale effects on aquatic ecosystems compared with those of nutrient loading. Understanding light limitation is also important for ecosystem management, as human activities have been rapidly altering light availability to aquatic ecosystems. Here we show that decreasing light can paradoxically increase phytoplankton abundance in shallow lakes. Our results, based on field manipulation experiments, field observations and models, suggest that, under competition for light and nutrients between phytoplankton and submersed macrophytes, alternative stable states are possible under high-light supply. In a macrophyte-dominated state, as light decreases phytoplankton density increases, because macrophytes (which effectively compete for nutrients released from the sediment) are more severely affected by light reduction. Our results demonstrate how species interactions with spatial heterogeneity can cause an unexpected outcome in complex ecosystems. An implication of our findings is that partial surface shading for controlling harmful algal bloom may, counterintuitively, increase phytoplankton abundance by decreasing macrophytes. Therefore, to predict how shallow lake ecosystems respond to environmental perturbations, it is essential to consider effects of light on the interactions between pelagic and benthic producers.
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Luz , Fitoplâncton/crescimento & desenvolvimento , Biomassa , Chara/crescimento & desenvolvimento , Chara/efeitos da radiação , Ecossistema , Modelos Teóricos , Fotossíntese , Fitoplâncton/efeitos da radiação , Densidade Demográfica , Dinâmica PopulacionalRESUMO
Predators can alter nutrient cycles simply by inducing stress in prey. This stress accelerates prey's protein catabolism, nitrogen waste production, and nitrogen cycling. Yet predators also reduce the feeding rates of their prey, inducing food deprivation that is expected to slow protein catabolism and nitrogen cycling. The physiology of prey under predation risk thus balances the influences of predation risk and food deprivation, and this balance is central to understanding the role of predators in nutrient cycles. We explored the separate and combined effects of predation risk and food deprivation on prey physiology and nutrient cycling by exposing guppies (Poecilia reticulata) to predation risk and food deprivation in a 2 × 2 design. We simulated predation risk using chemical cues from a natural predator of guppies, and we created food deprivation by rationing food availability. We measured guppy response as food consumption, growth, tissue energy density, tissue carbon:nitrogen, and nitrogen (N) excretion and assimilation. We found that N-linked physiological processes (N consumption, assimilation, excretion) were strongly affected by predation risk, independent of food consumption. Guppies excreted substantially less under predation risk than they did under food deprivation or control conditions. These results suggest that predation risk, per se, triggers physiological changes in guppies that increase N retention and decrease N excretion. We suggest that slower N metabolism under predation risk is an adaptive response that minimizes protein loss in the face of predictable, predator-induced food restriction. Notably, N metabolism shares common hormonal control with food seeking behavior, and we speculate that increased N retention is a direct and immediate result of reduced food seeking under predation risk. Contrary to predation-stress-based hypotheses for how predators affect nutrient cycling by prey, our result indicates that even short-term exposure to predators may decelerate, rather than accelerate, the speed of N cycling by suppressing N turnover by prey.
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Cadeia Alimentar , Privação de Alimentos , Animais , Jejum , Medo , Nitrogênio , Comportamento PredatórioRESUMO
Hospital infections allied to bacterial resistance to antibiotics have become a major worldwide problem. In this context, antimicrobial peptides (AMPs) are presented as an alternative in the control of these resistant organisms. Besides antimicrobial effects, these molecules play a crucial role in immunity by acting as immunomodulators. These peptides can activate inflammatory cells to produce pro- and anti-inflammatory mediators. In this study we will show the activity against multi-drug resistant bacteria (MDRB) of two cathelicidins from South American pit vipers Bothrops atrox and Crotalus durissus terrificus, named batroxicidin and crotalicidin. It was observed that both peptides showed activity against MDRB and presented no hemolytic or cytotoxic activity. In addition, the ability of peptides to modulate the production of cytokines TNF-α, IL-10 and IL-6 was analyzed using Raw 264.7 cells in the presence of IFN-γ stimuli, and multi-resistant E. coli and K. pneumoniae antigens. An up-expression or down-expression of TNF-α, as well as the IL-10 mediator, was observed. The cytokine IL-6, on the other hand, presented only a down-regulation for Raw 264.7 cell groups. In conclusion, the results demonstrate that both peptides presented a predominantly proinflammatory characteristic to the inflammatory mediators dosed. Overall, even presenting a proinflammatory characteristic, these peptides are still promising for future research and development of new potential antimicrobial molecules.