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In this paper, we investigate the Casimir effect within a virus RNA, particularizing the study to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Then, we discuss the possibility of occurring damage or mutation in its genome due to the presence of quantum vacuum fluctuations inside and around the RNA ribbon. For this, we consider the geometry and the nontrivial topology of the viral RNA as having a simple helical structure. We initially compute the non-thermal Casimir energy associated to that geometry, considering boundary conditions that constrain the zero point oscillations of a massless scalar field to the cylindrical cavity containing a helix pitch of RNA ribbon. Then we extend the obtained result to the electromagnetic field and, following, we calculate the probability of occurring damage or mutation in RNA by using the normalized inverse exponential distribution, which suppresses very low energies, and consider cutoff (threshold) energies corresponding to UV-A and UV-C rays, surely responsible by mutations. Then, by taking into account UV-A, we arrive at a mutation rate per base per infection cycle, which in the case of the SARS-CoV-2 is non-negligible. We find a maximum value of this mutation rate for an RNA ribbon radius, applying it for SARS-CoV-2, in particular. We also calculate a characteristic longitudinal oscillation frequency for the helix pitch value corresponding to the local minimum of the Casimir energy. Finally, we consider thermal fluctuations of classical and quantum nature and show that the corresponding probability of mutation is completely negligible for that virus. Therefore, we conclude that only the nontrivial topology and the geometric attributes of the RNA molecule contribute to the possible mutations caused by quantum vacuum fluctuations in the viral genome.

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Our study aimed to evaluate the frame size as a genetic selection criterion as well as the association of scores with carcass characteristics measured via ultrasound to the genetic improvement of carcass quality in Nellore cattle. The variance components were estimated using the restricted maximum likelihood method for the thoracic perimeter (TP), frame size score (FRAME), yearling weight (YW), visual scores of body structure (BS), muscularity (MUSC), and precocity (PREC). The carcass traits included loin eye area (REA), backfat thickness (BF), rump fat (FR), and intramuscular fat (IF). The estimated heritabilities ranged from moderate to high. The FRAME showed a positive genetic correlation with YW (0.82 ± 0.07), TP (0.58 ± 0.09), and BS score (0.62 ± 0.07), but it had a negative correlation with the MUSC and PREC visual scores (- 0.34 ± 0.09 and - 0.50 ± 0.08, respectively). The genetic correlation between FRAME and REA was positive (0.26 ± 0.09). However, FRAME presented a correlation close to zero with BF, RF, and IF. TP had a positive genetic correlation with body size traits such as YW (0.76 ± 0.05) and BS score (0.55 ± 0.08) and with muscularity traits such as REA (0.44 ± 0.01). Frame size has the potential to be used as a parameter in the selection of precocious beef cattle, but a study of its use is necessary to determine the ideal biotype for each production system.

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The objective of this study was to contribute to genetic improvement for carcass quality in Nellore cattle by estimating genetic parameters for carcass characteristics measured by traditional and novel ultrasound adjusted for body weight. Records of 19,910 Nellore breed animals born between 2001 and 2015 as part of a genetic improvement program were evaluated for this purpose. The (co)variance components and genetic parameters for yearling weight (YW), slaughter conformation at yearling age (SCY), ribeye area (REA), REA adjusted for 100 kg of body weight (REA100), REA adjusted for 450 kg of body weight (REA450), subcutaneous fat thickness over the loin (SFTL) and the rump (SFTR), intramuscular fat (IF), and height × width ratio of the sirloin steak (RATIO) were estimated using the restricted maximum likelihood (REML) method and the three-trait animal model. The estimated heritability values were 0.39 (YW), 0.33 (SCY), 0.31 (REA), 0.42 (REA100), 0.38 (REA450), 0.31 (RATIO), 0.17 (SFTL), 0.27 (SFTR), and 0.41 (MAR). The genetic correlations between REA and YW (0.43) and SCY and YW (0.78), respectively, suggested that selecting for REA or SCY could result in an increase in body weight. Because of its moderate and negative correlation with YW, REA100 was ineffective as a muscling indicator (- 0.38). The indicators REA450 and RATIO had a - 0.12 and 0.11 low correlation with YW, respectively. Thus, it is concluded that REA450 and RATIO were the best indicators of muscling, with heritability of medium magnitude, making the selection viable, as well as having a low correlation with body weight.

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Rennet milk curds were prepared under 4 different temperature and acidity conditions. The development of different types of inter-protein chemical bonds (disulfide, hydrophobic, electrostatic, hydrogen, and calcium bridges) was monitored for 60 min after curd cutting. Hydrophobic inter-protein interactions originally present in casein micelles in milk were substituted by electrostatic, hydrogen, and calcium bonds throughout the curd curing period. Disulfide bonds were not disturbed by the experimental conditions employed in the study, remaining at a constant level in all studied treatments. Acidification of curds increased the availability of soluble ionic calcium, increasing the relative proportion of calcium bridges at the expense of electrostatic-hydrogen bonds. Although pH defined the nature of the interactions established among proteins in curd, temperature modified the rate at which such bonds were formed.

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Abstract In aquatic environments, dams are considered one of the main threats to fish species, acting as an environmental filter for certain functional traits. Although there is some predictability in the composition of the functional traits in reservoirs, it is hypothesized that the environmental filters imposed by evolutionary processes, linked to the characteristics of the basins, are determinant for the functional composition of the traits in reservoirs. For this we performed a PCoA using the functional traits composition matrix of the reservoirs. We used PERMANOVA to test the difference in functional composition between basins. We performed the same process for the species composition matrix to compare the patterns. In this study, there were taxonomic and functional differences among reservoirs inserted in different basins. It was observed that the basin is a determining factor for the functional structure of fish assemblage in reservoirs. When compared, functional and taxonomic structures follow the same pattern, although functionally the reservoir tends to be more similar. These results reinforce the idea that reservoirs act as filters for functional traits (e.g., related with reproduction, feeding and habitat use), although there is a great influence of evolutionary processes related to the basin's characteristics and origin of the ichthyofaunistic province.

Resumo Em ambientes aquáticos, a construção de barragens é considerada uma das principais ameaças para as espécies de peixes, atuando como filtro ambiental para determinados traços funcionais. Assim, embora exista certa previsibilidade na composição dos traços funcionais em reservatórios, é hipotetizado que os filtros ambientais impostos pelos processos evolutivos, ligados as características das bacias, são determinantes para a composição funcional dos traços nos reservatórios. Para isso realizamos uma PCoA utilizando a matriz de composição de traços funcionais dos reservatórios. Utilizamos a PERMANOVA para testar a diferença da composição funcional entre as bacias. Realizamos o mesmo processo para a matriz de composição de espécies para comparar os padrões. Foi possível observar que a bacia hidrográfica é um fator determinante para a estruturação funcional da assembleia de peixe em reservatórios. Quando comparadas, a estrutura funcional e taxonômica, ambas seguem o mesmo padrão, embora funcionalmente os ambientes tendem a ser mais semelhantes. Esses resultados reforçam a ideia de que reservatórios atuam como filtros para determinados traços funcionais (e.g., relacionados à reprodução, alimentação e uso de habitat), embora exista uma grande influência dos processos evolutivos ligados a característica da bacia e da origem da província ictiofaunística.

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The composition of the diet of two species of characids (Knodus heteresthes and Moenkhausia lepidura) was evaluated in the Teles Pires and Juruena Rivers, sampled in September and October 2016. We analyzed 226 stomachs of K. heteresthes and 425 of M. lepidura. The analysis of the stomach contents was based on volumetric and frequency of occurrence methods, applying the food importance index. For the similarity of the diets between the species we calculated the niche overlap with Pianka's index. Both species in the Juruena River have a dietary preference for arthropods (IAi > 0.95). In the Teles Pires River the diet is concentrated in three sources for both species: arthropods (IAi > 0.52), vegetables (IAi > 0.33) and fish (IAi > 0.12). The diet was dissimilar when compared to environments (ANOSIM, R ≥ 0.57, p < 0.001) with high trophic niche overlap (α > 0.97), regardless of the sampled environment. In the Teles Pires River, both species were classified as omnivorous with an insectivorous tendency and in the Juruena River the insectivorous behaviour occurs.

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In aquatic environments, dams are considered one of the main threats to fish species, acting as an environmental filter for certain functional traits. Although there is some predictability in the composition of the functional traits in reservoirs, it is hypothesized that the environmental filters imposed by evolutionary processes, linked to the characteristics of the basins, are determinant for the functional composition of the traits in reservoirs. For this we performed a PCoA using the functional traits composition matrix of the reservoirs. We used PERMANOVA to test the difference in functional composition between basins. We performed the same process for the species composition matrix to compare the patterns. In this study, there were taxonomic and functional differences among reservoirs inserted in different basins. It was observed that the basin is a determining factor for the functional structure of fish assemblage in reservoirs. When compared, functional and taxonomic structures follow the same pattern, although functionally the reservoir tends to be more similar. These results reinforce the idea that reservoirs act as filters for functional traits (e.g., related with reproduction, feeding and habitat use), although there is a great influence of evolutionary processes related to the basin's characteristics and origin of the ichthyofaunistic province.

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The composition of the diet of two species of characids (Knodus heteresthes and Moenkhausia lepidura) was evaluated in the Teles Pires and Juruena Rivers, sampled in September and October 2016. We analyzed 226 stomachs of K. heteresthes and 425 of M. lepidura. The analysis of the stomach contents was based on volumetric and frequency of occurrence methods, applying the food importance index. For the similarity of the diets between the species we calculated the niche overlap with Pianka's index. Both species in the Juruena River have a dietary preference for arthropods (IAi > 0.95). In the Teles Pires River the diet is concentrated in three sources for both species: arthropods (IAi > 0.52), vegetables (IAi > 0.33) and fish (IAi > 0.12). The diet was dissimilar when compared to environments (ANOSIM, R ≥ 0.57, p < 0.001) with high trophic niche overlap (α > 0.97), regardless of the sampled environment. In the Teles Pires River, both species were classified as omnivorous with an insectivorous tendency and in the Juruena River the insectivorous behaviour occurs.

Foram avaliadas a composição da dieta de duas espécies de Characideos (Knodus heteresthes e Moenkhausia lepidura) nos rios Teles Pires e Juruena, amostrados em setembro e outubro de 2016. Analisamos 226 estômagos de K. heteresthes e 425 de M. lepidura, sendo utilizados os métodos volumétrico e frequência de ocorrência, aplicando-se o índice de importância alimentar. Para a similaridade das dietas entre as espécies calculamos a sobreposição de nicho com índice de Pianka. Ambas as espécies no rio Juruena têm preferência alimentar por artrópodes (IAi > 0,95), no rio Teles Pires a dieta concentra-se em três fontes para ambas espécies: artrópodes (IAi > 0,52), vegetais (IAi > 0,33) e peixes (IAi > 0,12). A dieta é dissimilar quando comparados os ambientes (ANOSIM, R ≥ 0,57; p < 0,001), com alta sobreposição de nicho trófico (α > 0,97), independente do ambiente amostrado. No rio Teles Pires, ambas as espécies foram classificadas como onívoras com tendência insetívora e no rio Juruena ocorre o comportamento insetívoro.

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RESUMEN Introducción: La depresión representa un problema de salud que repercute de manera importante en la estabilidad mental y calidad de vida de las personas. Estudiar los dominios culturales relacionados con esta patología es relevante para diferenciarla, pues suele confundirse con otros estados emocionales. Objetivo: Analizar los dominios culturales relacionados con la depresión en mujeres y hombres adultos. Material y métodos: Estudio mixto de consenso cultural realizado en San Luis Potosí, México, que incluyó a 163 participantes. La recolección de datos se efectuó por muestreo a conveniencia mediante listados libres, entrevistas estructuradas y sorteos por montones. Se identificaron 20 elementos categorizados en áreas temáticas, se organizaron en conjuntos jerárquicos para observar la distribución y dimensiones de los dominios culturales. Resultados: Las personas tienen nociones en común respecto a lo que implica la depresión. Los elementos relacionados con mayor frecuencia fueron: tristeza, desánimo y soledad, a su vez, la agrupación de estos mostró dos dimensiones principales: consecuencias y atención. Discusión: La literatura reporta que hay diferencias subjetivas entre la depresión y otros padecimientos, también indica que existen contrastes por sexo y que las condiciones sociales desfavorables se relacionan con malestares emocionales; sin embargo, en las dimensiones culturales no están presentes la promoción ni la prevención de esta enfermedad. Conclusiones: Considerar los dominios culturales de la población adulta con respecto a la depresión posibilita la creación de programas dirigidos a promocionar la salud y prevenir la enfermedad, así como facilitar la práctica clínica fundamentada en el contexto social y cultural de las personas.

ABSTRACT Introduction: Depression represents a health problem which has important impacts on the mental stability and quality of life. Therefore, studying the related cultural domains becomes relevant in order to differentiate this pathology from other emotional states. Objective: To analyze the cultural domains related to depression in adults. Materials and methods: This is a mixed study with cultural consensus carried out in the state of San Luis Potosi, Mexico, which included 163 participants. Data collection was based on sampling by convenience using free listings, structured interviews, and lots. Twenty elements related to the thematic areas were identified, and organized in hierarchical sets in order to observe the distributions and dimensions of the cultural domains. Results: Participants showed common notions regarding what depression implies. The most cited related elements were sadness, discouragement, and loneliness, which were grouped in two main dimensions: consequences and attention. Discussion: The literature reports the existance of subjective differences between depression and other emotional pathologies, and that these differences are influenced by sex and social conditions. Nevertheless, the related cultural dimensions are not always considered, in particular regarding the prevention of the illness. Conclusions: The precise consideration of the cultural domains which are associated with adults suffering from depression can allow the design and implementation of programs aimed at promoting health and preventing illness, as well as at fostering a clinical practice based on the social and cultural context of these persons.

RESUMO Introdução: A depressão representa um problema de saúde que reverbera de maneira importante na estabilidade mental e qualidade de vida das pessoas; estudar os domínios culturais relacionados com esta patologia é relevante para diferenciá-la, já que geralmente confunde-se com outros estados emocionais. Objetivo: Analisar os domínios culturais relacionados com a depressão em mulheres e homens adultos. Material e métodos: Estudo misto de consenso cultural realizado em San Luis Potosí, México; que incluía 163 participantes, a coleta de dados efetuou-se por amostragem a conveniência mediante listados livres, entrevistas estruturadas e classificação da pilha, identificaram-se 20 elementos categorizados por áreas temáticas, organizaram-se em conjuntos hierárquicos para observar a distribuição e dimensões dos domínios culturais. Resultados: As pessoas têm noções em comum ao respeito do que envolve a depressão. Os elementos relacionados com maior frequência foram: tristeza, desânimo e solidão; enquanto a agrupação deles mostrou duas dimensões principais: consequências e atenção. Discussão: A literatura relata que existem diferenças subjetivas entre a depressão e outras doenças, indica também que existem contrastes por sexo e que as condições sociais desfavoráveis se relacionam ao desconforto emocional, porém, nas dimensões culturais não estão presentes a promoção nem a prevenção desta doença. Conclusões: Considerar os domínios culturais da população adulta ao respeito da depressão, possibilita a criação de programas dirigidos a promover a saúde e prevenir a doença, assim como facilitar a prática clínica fundamentada no contexto social e cultural das pessoas.

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Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO2) emissions from these sediments are too scarce to upscale emissions for global estimates or to understand their fundamental drivers. Here, we present the results of a global survey covering 196 dry inland waters across diverse ecosystem types and climate zones. We show that their CO2 emissions share fundamental drivers and constitute a substantial fraction of the carbon cycled by inland waters. CO2 emissions were consistent across ecosystem types and climate zones, with local characteristics explaining much of the variability. Accounting for such emissions increases global estimates of carbon emissions from inland waters by 6% (~0.12 Pg C y-1). Our results indicate that emissions from dry inland waters represent a significant and likely increasing component of the inland waters carbon cycle.

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Milk curds are a semisolid structure resulting from the enzymatic coagulation of milk, consisting mainly of paracasein micelles, fat globules, and whey. This gel undergoes a series of changes in its composition and structure during setting and curing, affecting curd density. The present study investigated the composition and density of inoculated and noninoculated milk curds during a 60-min curing period conducted at 30, 35, and 40°C. The purpose of the study was to determine the density changes occurring in the protein phase of curds during curing under different conditions of temperature and pH to understand the nature of the structural changes happening in the paracasein matrix. Noninoculated curd density values oscillated between 1.0247 and 1.0294 g/cm3 after 60 min of curing, whereas inoculated treatments showed values between 1.0222 and 1.0321 g/cm3. This small difference in density between the studied samples was surprising because the whey content of samples differed greatly. Density of the protein phase reached values of 1.8002 and 1.4388 g/cm3 for noninoculated and inoculated curds, respectively, after 60 min of curing. Two independent mechanisms involved in the development of the protein-based structure of curds were identified upon comparison of the development of protein phase density in inoculated and noninoculated curds. Although the larger increase in protein phase density observed in noninoculated curds was probably due to the concurrent action of calcium-mediated electrostatic bonds and temperature-dependent hydrophobic bonds, inoculated curds showed a lower protein phase density caused by calcium solubilization and by a decrease in the net charge of paracasein micelles induced by pH reduction.

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High-performance permanent magnets (PM) are compounds with outstanding intrinsic magnetic properties. Most PMs are obtained from a favorable combination of rare earth metals (RE = Nd, Pr, Ce) with transition metals (TM = Fe, Co). Amongst them, CeFe11Ti claims considerable attention due to its large Curie temperature, saturation magnetization, and significant magnetocrystalline anisotropic energy. CeFe11Ti has several potential applications, in particular, in the development of electric motors for future automatic electrification. In this work, we shed some light on the mictrostructure of this compound by performing periodic hybrid-exchange density functional theory (DFT) calculations. We use a combined approach of atom-centered local orbitals, plane waves and full-potential linear muffin-tin orbital (LMTO) for our computations. The electronic configuration of the atoms involved in different steps of formation of the crystal structure of CeFe11Ti gives an explanation on the effect of Ce and Ti on its magnetic properties. While Ti stabilizes the structure, atomic orbitals of Ce hybridizes with Fe atomic orbitals to a significant extent and alters the electronic bands. Our calculations confirm a valence of 3+ for Ce, which has been deemed crucial to obtain a large magnetocrystalline anisotropy. In addition, we analyze several spin configurations, with the ferromagnetic configuration being most stable. We compare and contrast our data to those available and provide an insight for further development of optimized high-performance PMs. Moreover, we compute the Magnetocrystalline Anisotropy of this compound by means of two approaches: the Force Theorem and a full-potential LMTO method.

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Foliar uptake of dew is likely an important mechanism of water acquisition for plants from tropical dry environments. However, there is still limited experimental evidence describing the anatomical pathways involved in this process and the effects of this water subsidy on the maintenance of gas exchange and leaf lifespan of species from seasonally dry tropical vegetation such as the Brazilian caatinga. We performed scanning electron, bright-field and confocal microscopic analyses and used apoplastic tracers to examine the foliar water uptake (FWU) routes in four woody species with different foliar phenology and widely distributed in the caatinga. Leaves of plants subjected to water stress were exposed to dew simulation to evaluate the effects of the FWU on leaf water potentials, gas exchange and leaf lifespan. All species absorbed water through their leaf cuticles and/or peltate trichomes but FWU capacity differed among species. Leaf wetting by dew increased leaf lifespan duration up to 36 days compared to plants in the drought treatment. A positive effect on leaf gas exchange and new leaf production was only observed in the anisohydric and evergreen species. We showed that leaf wetting by dew is relevant for the physiology and leaf lifespan of plants from seasonally dry tropical vegetation, especially for evergreen species.

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Eutrophication is a water enrichment in nutrients (mainly phosphorus) that generally leads to symptomatic changes and deterioration of water quality and all its uses in general, when the production of algae and other aquatic vegetations are increased. In this sense, eutrophication has caused a variety of impacts, such as high levels of Chlorophyll a (Chl-a). Consequently, anticipate its presence is a matter of importance to prevent future risks. The aim of this study was to obtain a predictive model able to perform an early detection of the eutrophication in water bodies such as lakes. This study presents a novel hybrid algorithm, based on support vector machines (SVM) approach in combination with the particle swarm optimization (PSO) technique, for predicting the eutrophication from biological and physical-chemical input parameters determined experimentally through sampling and subsequent analysis in a certificate laboratory. This optimization technique involves hyperparameter setting in the SVM training procedure, which significantly influences the regression accuracy. The results of the present study are twofold. In the first place, the significance of each biological and physical-chemical variables on the eutrophication is presented through the model. Secondly, a model for forecasting eutrophication is obtained with success. Indeed, regression with optimal hyperparameters was performed and coefficients of determination equal to 0.90 for the Total phosphorus estimation and 0.92 for the Chlorophyll concentration were obtained when this hybrid PSO-SVM-based model was applied to the experimental dataset, respectively. The agreement between experimental data and the model confirmed the good performance of the latter.

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Zebu and Holstein x Zebu crossbred have low incidence of uterine infection when compared to Holstein cows. Resistance to uterine infections may be associated with the ability to recognize invading microorganisms. Endometrial transcription of microbial molecular patterns receptors has been investigated in the postpartum period of Holstein cows, but it is completely unknown in Zebu or Holstein x Zebu cows. In this study, 9 Gyr and 12 F1 Holstein x Gyr cows were submitted to endometrial biopsies at the first and seventh days postpartum, with the objective to measure transcription levels of toll-like receptors (TLRs) 1/6, 2, 4, 5, and 9; nucleotide-binding oligomerization domain (NOD)-like receptors 1 and 2; and coreceptors cluster of differentiation 14 (CD14) and myeloid differentiation protein-2 (MD-2). There was a significant (P<0.05) decrease in transcription of TLR5 in Gyr, and an increase in transcription of TLR9 in F1 cows, between the first and seventh day postpartum. Both groups had low incidences of uterine infections up to 42 days postpartum. Uterine involution completed at 27.7 ± 10.1 and 25.1 ± 4.7 days postpartum for Gyr and F1 cows, respectively. In Gyr cows, higher transcription levels of TLR1/6 and NOD1 correlated to a longer period required for uterine involution. In F1 cows, lower levels of TLR1/6, TLR2 and NOD2 correlated to a longer period required for uterine involution. In conclusion, some pathogen recognition receptors associated significantly with the time required for uterine involution in Gyr and F1 cows.(AU)

Vacas Zebu e mestiças Holandês x Zebu apresentam baixas incidências de infecções uterinas quando comparadas às Holandesas. A resistência às infecções uterinas pode estar relacionada com a capacidade de reconhecimento dos microrganismos invasores. A transcrição endometrial de receptores de padrões moleculares microbianos tem sido investigada em vacas Holandesas recém-paridas, porém ainda é desconhecida em vacas Zebu e mestiças Holandês x Zebu. No presente estudo, nove vacas Gir e 12 F1 Holandês x Gir foram submetidas a biópsias endometriais no primeiro e no sétimo dia após o parto, com o objetivo de mensurar os níveis de transcrição gênica dos receptores tipo Toll (TLRs) 1/6, 2, 4, 5 e 9; receptores tipo NOD 1 e 2; e dos coreceptores CD14 e MD-2. Houve diminuição significativa (P < 0,05) do nível de transcrição de TLR5 em vacas Gir e aumento da transcrição de TLR9 em vacas F1, entre o primeiro e o sétimo dia após o parto. Os dois grupos apresentaram baixas incidências de infecções uterinas até 42 dias pós-parto. O período de involução uterina foi de 27,7 ± 10,1 e 25,1 ± 4,7 dias pós-parto, para vacas Gir e F1, respectivamente. No grupo de vacas Gir, altos níveis de transcrição de TLR1/6 e NOD1 tiveram correlação significativa com o prolongamento do período de involução uterina. No grupo de vacas F1, baixos níveis de transcrição de TLR1/6, TLR2 e NOD2 foram associados a maiores períodos de involução uterina. Portanto, os níveis de transcrição endometrial de alguns receptores de padrões moleculares microbianos na primeira semana após o parto podem estar relacionados com o tempo requerido para ocorrência da involução uterina em vacas Gir e F1.(AU)

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Naturalists Fritz and Hermann Müller hypothesised that heteranthery often leads to a division of labour into 'feeding' and 'pollinating' stamens; the latter often being as long as the pistil so as to promote successful pollination on the bees' back. In many buzz-pollinated species of Senna, however, the so-called pollinating stamens are short and not level with the stigma, raising the question of how pollen is shed on the bees' back. Here we explore a mechanism called 'ricochet pollination'. We test whether division of labour is achieved through the interaction between short lower stamens and strongly concave 'deflector petals'. We studied the arrangement and morphology of the floral organs involved in the ricochet pollination, functioning of the flowers through artificial sonication and observed the interactions between bees and flowers in the field. The middle stamens are adapted to eject pollen downwards, which can be readily collected on the bee mid legs. Most of the pollen is ejected towards the deflector petal(s). Pollen from this set of stamens is more likely to contribute to pollination. The pollen grains seem to ricochet multiple times against the deflector petals to eventually reach the bee's back. The pollen ricochet mechanism promotes a division of labour by involving additional floral organs, such as petals, reinforcing the Müllers' division-of-labour hypothesis. However, alternative, non-multiexclusive hypotheses could be explored in genus Senna and other angiosperm species.

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