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1.
PLoS One ; 15(3): e0229142, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32134934

RESUMO

Migratory birds can detect the direction of the Earth's magnetic field using the magnetic compass sense. However, the sensory basis of the magnetic compass still remains a puzzle. A large body of indirect evidence suggests that magnetic compass in birds is localized in the retina. To confirm this point, an evidence of visual signals modulation by magnetic field (MF) should be obtained. In a previous study we showed that MF inclination impacts the amplitude of ex vivo electroretinogram (ERG) recorded from isolated pigeon retina. Here we present the results of an analysis of putative MF effect on one component of ERG, the photoreceptor's response, isolated from the total ERG by adding sodium aspartate and barium chloride to the perfusion solution. Photoresponses were recorded from isolated retinae of domestic pigeons Columba livia. The retinal samples were placed in MF that was modulated by three pairs of orthogonal Helmholtz coils. Light stimuli (blue and red) were applied under two inclinations of MF, 0° and 90°. In all the experiments, preparations from two parts of retina were used, red field (with dominant red-sensitive cones) and yellow field (with relatively uniform distribution of cone color types). In contrast to the whole retinal ERG, we did not observe any effect of MF inclination on either amplitude or kinetics of pharmacologically isolated photoreceptor responses to blue or red half-saturating flashes. A possible explanations of these results could be that magnetic compass sense is localized in retinal cells other than photoreceptors, or that photoreceptors do participate in magnetoreception, but require some processing of compass information in other retinal layers, so that only whole retina signal can reflect the response to changing MF.


Assuntos
Migração Animal/fisiologia , Columbidae/anatomia & histologia , Campos Magnéticos , Orientação Espacial/fisiologia , Células Fotorreceptoras de Vertebrados/fisiologia , Retina/anatomia & histologia , Resposta Táctica/fisiologia , Animais , Cor , Eletrorretinografia/veterinária , Fundo de Olho , Luz , Magnetismo , Estimulação Luminosa , Células Fotorreceptoras de Vertebrados/citologia , Retina/citologia , Retina/diagnóstico por imagem , Células Fotorreceptoras Retinianas Cones/citologia , Células Fotorreceptoras Retinianas Cones/fisiologia
2.
PLoS Comput Biol ; 16(1): e1006919, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31986145

RESUMO

During angiogenesis, new blood vessels sprout and grow from existing ones. This process plays a crucial role in organ development and repair, in wound healing and in numerous pathological processes such as cancer progression or diabetes. Here, we present a mathematical model of early stage angiogenesis that permits exploration of the relative importance of mechanical, chemical and cellular cues. Endothelial cells proliferate and move over an extracellular matrix by following external gradients of Vessel Endothelial Growth Factor, adhesion and stiffness, which are incorporated to a Cellular Potts model with a finite element description of elasticity. The dynamics of Notch signaling involving Delta-4 and Jagged-1 ligands determines tip cell selection and vessel branching. Through their production rates, competing Jagged-Notch and Delta-Notch dynamics determine the influence of lateral inhibition and lateral induction on the selection of cellular phenotypes, branching of blood vessels, anastomosis (fusion of blood vessels) and angiogenesis velocity. Anastomosis may be favored or impeded depending on the mechanical configuration of strain vectors in the ECM near tip cells. Numerical simulations demonstrate that increasing Jagged production results in pathological vasculatures with thinner and more abundant vessels, which can be compensated by augmenting the production of Delta ligands.


Assuntos
Modelos Biológicos , Neovascularização Patológica/fisiopatologia , Receptores Notch/metabolismo , Transdução de Sinais/fisiologia , Resposta Táctica/fisiologia , Algoritmos , Animais , Biologia Computacional , Simulação por Computador , Neovascularização Fisiológica/fisiologia
3.
Proc Natl Acad Sci U S A ; 117(3): 1638-1647, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31911469

RESUMO

Presynaptic plasticity is known to modulate the strength of synaptic transmission. However, it remains unknown whether regulation in presynaptic neurons can evoke excitatory and inhibitory postsynaptic responses. We report here that the Caenorhabditis elegans homologs of MAST kinase, Stomatin, and Diacylglycerol kinase act in a thermosensory neuron to elicit in its postsynaptic neuron an excitatory or inhibitory response that correlates with the valence of thermal stimuli. By monitoring neural activity of the valence-coding interneuron in freely behaving animals, we show that the alteration between excitatory and inhibitory responses of the interneuron is mediated by controlling the balance of two opposing signals released from the presynaptic neuron. These alternative transmissions further generate opposing behavioral outputs necessary for the navigation on thermal gradients. Our findings suggest that valence-encoding interneuronal activity is determined by a presynaptic mechanism whereby MAST kinase, Stomatin, and Diacylglycerol kinase influence presynaptic outputs.


Assuntos
Caenorhabditis elegans/metabolismo , Neurônios/fisiologia , Transmissão Sináptica/fisiologia , Resposta Táctica/fisiologia , Animais , Comportamento Animal , Proteínas de Caenorhabditis elegans/metabolismo , Diacilglicerol Quinase/metabolismo , Ácido Glutâmico/metabolismo , Interneurônios/fisiologia , Proteínas Associadas aos Microtúbulos/metabolismo , Neuropeptídeos/metabolismo
4.
FEMS Microbiol Lett ; 366(22)2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31855240

RESUMO

Magnetotactic bacteria (MTB) are a group of microorganisms that have the ability to synthesize intracellular magnetic crystals (magnetosomes). They prefer microaerobic or anaerobic aquatic sediments. Thus, there is growing interest in their ecological roles in various habitats. In this study we found co-occurrence of a large rod-shaped deltaproteobacterial magnetotactic bacterium (tentatively named LR-1) in the sediment of a brackish lagoon with algal bloom. Electron microscopy observations showed that they were ovoid to slightly curved rods having a mean length of 6.3 ± 1.1 µm and a mean width of 4.1 ± 0.4 µm. Each cell had a single polar flagellum. They contained hundreds of bullet-shaped intracellular magnetite magnetosomes. Phylogenetic analysis revealed that they were most closely related to Desulfamplus magnetovallimortis strain BW-1, and belonged to the Deltaproteobacteria. Our findings indicate that LR-1 may be a new species of MTB. We propose that deltaproteobacterial MTB may play an important role in iron cycling and so may represent a reservoir of iron, and be an indicator species for monitoring algal blooms in such eutrophic ecosystems. These observations provide new clues to the cultivation of magnetotactic Deltaproteobacteria and the control of algal blooms, although further studies are needed.


Assuntos
Deltaproteobacteria/classificação , Deltaproteobacteria/isolamento & purificação , Eutrofização , Sedimentos Geológicos/microbiologia , Magnetismo , Filogenia , Resposta Táctica , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Deltaproteobacteria/genética , Deltaproteobacteria/ultraestrutura , Flagelos/ultraestrutura , Magnetossomos/ultraestrutura , Microscopia Eletrônica , RNA Ribossômico 16S/genética , Análise de Sequência de DNA
5.
Nat Commun ; 10(1): 5082, 2019 11 08.
Artigo em Inglês | MEDLINE | ID: mdl-31705050

RESUMO

From intracellular protein trafficking to large-scale motion of animal groups, the physical concepts driving the self-organization of living systems are still largely unraveled. Self-organization of active entities, leading to novel phases and emergent macroscopic properties, recently shed new light on these complex dynamical processes. Here we show that under the application of a constant magnetic field, motile magnetotactic bacteria confined in water-in-oil droplets self-assemble into a rotary motor exerting a torque on the external oil phase. A collective motion in the form of a large-scale vortex, reversable by inverting the field direction, builds up in the droplet with a vorticity perpendicular to the magnetic field. We study this collective organization at different concentrations, magnetic fields and droplet radii and reveal the formation of two torque-generating areas close to the droplet interface. We characterize quantitatively the mechanical energy extractable from this new biological and self-assembled motor.


Assuntos
Hidrodinâmica , Campos Magnéticos , Magnetospirillum/fisiologia , Óleos , Rotação , Resposta Táctica/fisiologia , Torque , Água , Alcanos , Emulsões
6.
Microbiology ; 165(12): 1331-1344, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31639075

RESUMO

Chemotaxis allows bacteria to sense gradients in their environment and respond by directing their swimming. Aer is a receptor that, instead of responding to a specific chemoattractant, allows bacteria to sense cellular energy levels and move towards favourable environments. In Pseudomonas, the number of apparent Aer homologues differs between the only two species it has been characterized in, Pseudomonas aeruginosa and Pseudomonas putida. Here we combined bioinformatic approaches with deletional mutagenesis in Pseudomonas pseudoalcaligenes KF707 to further characterize Aer. It was determined that the number of Aer homologues varies between zero and four throughout the genus Pseudomonas, and they were phylogenetically classified into five subgroups. We also used sequence analysis to show that these homologous receptors differ in their HAMP signal transduction domains. Genetic analysis also indicated that some Aer homologues have likely been subject to horizontal transfer. P. pseudoalcaligenes KF707 was unique among strains for having three Aer homologues as well as the receptors CttP and McpB. Phenotypic characterization in this strain showed that the most prevalent homologue of Aer was key, but not essential, for energy taxis. This study demonstrates that energy taxis in Pseudomonas varies between species and provides a new naming convention and associated phylogenetic details for Aer chemoreceptors.


Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Membrana/metabolismo , Filogenia , Pseudomonas pseudoalcaligenes/classificação , Pseudomonas pseudoalcaligenes/fisiologia , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Transferência Genética Horizontal , Variação Genética , Proteínas de Membrana/química , Proteínas de Membrana/genética , Fenótipo , Pseudomonas/classificação , Pseudomonas/genética , Pseudomonas/fisiologia , Pseudomonas pseudoalcaligenes/genética , Transdução de Sinais/genética , Especificidade da Espécie , Resposta Táctica
7.
Anal Sci ; 35(12): 1367-1373, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31474659

RESUMO

C. elegans exhibits a directional migration toward a remembered temperature setpoint (Ts) by activating thermo-sensorimotor neurons. While cryophilic thermotaxis is well reproduced, thermophilic thermotaxis requires very stringent temperature regulations - otherwise, worms exhibit random migration in colder side of Ts. Here, we introduce a thermal stimulus device developed to control worms with different thermotactic behaviors on both colder and warmer sides of the Ts. On a linear gradient, the worm population displayed a Gaussian distribution near Ts but in a skewed shape with a peak shifted to the colder side due to their atactic motion in colder temperature than Ts. By repetitive application of thermal gradient-reversals, we found that their population density became higher near Ts because the speed at which the worms accumulate toward Ts was much faster than that of the dispersion by diffusion to the cold side, resulting in forced aggregation of worms at the desired temperature.


Assuntos
Bioensaio/instrumentação , Caenorhabditis elegans/fisiologia , Resposta Táctica , Temperatura , Animais , Caenorhabditis elegans/citologia , Desenho de Equipamento , Neurônios/citologia
8.
Microbiology ; 165(10): 1061-1074, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31436522

RESUMO

In radiating populations of Pseudomonas fluorescens SBW25, adaptive wrinkly spreader (WS) mutants are able to gain access to the air-liquid (A-L) interface of static liquid microcosms and achieve a significant competitive fitness advantage over other non-biofilm-forming competitors. Aerotaxis and flagella-based swimming allows SBW25 cells to move into the high-O2 region located at the top of the liquid column and maintain their position by countering the effects of random cell diffusion, convection and disturbance (i.e. physical displacement). However, wild-type cells showed significantly lower levels of enrichment in this region compared to the archetypal WS, indicating that WS cells employ an additional mechanism to transfer to the A-L interface where displacement is no longer an issue and a biofilm can develop at the top of the liquid column. Preliminary experiments suggest that this might be achieved through the expression of an as yet unidentified surface active agent that is weakly associated with WS cells and alters liquid surface tension, as determined by quantitative tensiometry. The effect of physical displacement on the colonization of the high-O2 region and A-L interface was reduced through the addition of agar or polyethylene glycol to increase liquid viscosity, and under these conditions the competitive fitness of the WS was significantly reduced. These observations suggest that the ability to transfer to the A-L interface from the high-O2 region and remain there without further expenditure of energy (through, for example, the deployment of flagella) is a key evolutionary innovation of the WS, as it allows subsequent biofilm development and significant population increase, thereby affording these adaptive mutants a competitive fitness advantage over non-biofilm-forming competitors located within the liquid column.


Assuntos
Biofilmes/crescimento & desenvolvimento , Pseudomonas fluorescens/fisiologia , Aderência Bacteriana/genética , Evolução Biológica , Meio Ambiente , Flagelos/genética , Aptidão Genética , Oxigênio/metabolismo , Fenótipo , Pseudomonas fluorescens/genética , Pseudomonas fluorescens/crescimento & desenvolvimento , Tensão Superficial , Resposta Táctica , Viscosidade
9.
Theriogenology ; 137: 8-14, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31266655

RESUMO

The journey of mammalian sperm through the female genital tract requires the existence of a myriad of mechanisms that allow cells to reach the oviduct in a timely manner from the place of semen deposition. Several biochemical mechanisms such as signaling through molecules like bicarbonate, neurotransmitters or even glycosaminoglycanes are known and have been studied by several relevant groups worldwide. However, biophysical mechanisms for sperm transport are much less studied and understood. Thermotaxis, for example, is a powerful, physical signaling system that is known to direct sperm inside the female genital tract, although the intimate mechanisms by which this effect is launched are yet to be elucidated. This review is focuses on the analysis of thermotaxis and its possible relationship with another phenomenon that has been observed in sperm from a variety of species, namely photostimulation. An overall review on sperm thermotaxis and putative mechanism/s that can be involved in this phenomenon is developed, followed by a description of the most recent findings on the mechanisms underlying sperm photostimulation, highlighting its possible relationship with thermotactic mechanisms. Finally, an overview regarding some practical implications of the phototactic/thermotactic phenomenon has been included in order to evaluate the possible use of techniques based on these phenomena as tools for improving pig reproduction.


Assuntos
Temperatura Alta , Luz , Espermatozoides/efeitos da radiação , Suínos/fisiologia , Resposta Táctica/fisiologia , Animais , Masculino , Espermatozoides/fisiologia
10.
Theriogenology ; 137: 15-22, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31176491

RESUMO

Artificial insemination (AI) is the single most important assisted reproductive technique devised to facilitate the genetic improvement of livestock. In the swine industry, it has broadly replaced natural service over the last number of decades which has been made possible by the high pregnancy rates and litter sizes obtainable with semen extended, up to, and sometimes beyond 5 d. Central to achieving good reproductive performance is the ability of boar studs to monitor semen quality, the basis of which has long been the assessment of sperm motility by subjective and, more recently, by more objective computerised systems. In this review, the literature on the relationship between sperm motility and kinematic parameters and field fertility is summarised. We discuss how this relationship is dependent on factors such as the viscosity of the media and the use of standard operating procedures. Emerging evidence is discussed regarding the importance of sperm rheotaxis and thigmotaxis as long-distance sperm guidance mechanisms, which enable motile functional spermatozoa to avoid the backflow of fluid, mucus and semen from the sow's uterus in the hours post AI, facilitating the establishment of sperm reservoirs in the oviducts. The literature on the use of microfluidics in studying sperm rheotaxis in vitro is also summarised, and we discuss how these systems, when combined with techniques such as lensless microscopy, have the potential to offer more physiological assessments of the swimming patterns of boar spermatozoa. Finally, possible future avenues of further investigation are proposed.


Assuntos
Preservação do Sêmen/veterinária , Espermatozoides/fisiologia , Suínos , Resposta Táctica/fisiologia , Animais , Masculino , Análise do Sêmen/métodos , Análise do Sêmen/veterinária , Motilidade Espermática
11.
PLoS Biol ; 17(4): e3000044, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30964858

RESUMO

Many bacterial pathogens hijack macrophages to egress from the port of entry to the lymphatic drainage and/or bloodstream, causing dissemination of life-threatening infections. However, the underlying mechanisms are not well understood. Here, we report that Salmonella infection generates directional electric fields (EFs) in the follicle-associated epithelium of mouse cecum. In vitro application of an EF, mimicking the infection-generated electric field (IGEF), induces directional migration of primary mouse macrophages to the anode, which is reversed to the cathode upon Salmonella infection. This infection-dependent directional switch is independent of the Salmonella pathogenicity island 1 (SPI-1) type III secretion system. The switch is accompanied by a reduction of sialic acids on glycosylated surface components during phagocytosis of bacteria, which is absent in macrophages challenged by microspheres. Moreover, enzymatic cleavage of terminally exposed sialic acids reduces macrophage surface negativity and severely impairs directional migration of macrophages in response to an EF. Based on these findings, we propose that macrophages are attracted to the site of infection by a combination of chemotaxis and galvanotaxis; after phagocytosis of bacteria, surface electrical properties of the macrophage change, and galvanotaxis directs the cells away from the site of infection.


Assuntos
Trato Gastrointestinal/imunologia , Macrófagos/fisiologia , Resposta Táctica/fisiologia , Animais , Proteínas de Bactérias , Movimento Celular/fisiologia , Condutividade Elétrica , Eletricidade , Epitélio/imunologia , Epitélio/metabolismo , Feminino , Macrófagos/microbiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fagocitose , Salmonella/patogenicidade , Infecções por Salmonella/metabolismo , Infecções por Salmonella/fisiopatologia
12.
Curr Biol ; 29(4): 554-566.e4, 2019 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-30744969

RESUMO

Animals use sensory information to move toward more favorable conditions. Drosophila larvae can move up or down gradients of odors (chemotax), light (phototax), and temperature (thermotax) by modulating the probability, direction, and size of turns based on sensory input. Whether larvae can anemotax in gradients of mechanosensory cues is unknown. Further, although many of the sensory neurons that mediate taxis have been described, the central circuits are not well understood. Here, we used high-throughput, quantitative behavioral assays to demonstrate Drosophila larvae anemotax in gradients of wind speeds and to characterize the behavioral strategies involved. We found that larvae modulate the probability, direction, and size of turns to move away from higher wind speeds. This suggests that similar central decision-making mechanisms underlie taxis in somatosensory and other sensory modalities. By silencing the activity of single or very few neuron types in a behavioral screen, we found two sensory (chordotonal and multidendritic class III) and six nerve cord neuron types involved in anemotaxis. We reconstructed the identified neurons in an electron microscopy volume that spans the entire larval nervous system and found they received direct input from the mechanosensory neurons or from each other. In this way, we identified local interneurons and first- and second-order subesophageal zone (SEZ) and brain projection neurons. Finally, silencing a dopaminergic brain neuron type impairs anemotaxis. These findings suggest that anemotaxis involves both nerve cord and brain circuits. The candidate neurons and circuitry identified in our study provide a basis for future detailed mechanistic understanding of the circuit principles of anemotaxis.


Assuntos
Drosophila/fisiologia , Resposta Táctica/fisiologia , Vento , Movimentos do Ar , Animais , Drosophila/crescimento & desenvolvimento , Larva/fisiologia , Células Receptoras Sensoriais/fisiologia
13.
J Theor Biol ; 460: 227-242, 2019 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-30336156

RESUMO

Navigation of cells and organisms is typically achieved by detecting and processing orienteering cues. Occasionally, a cue may be assessed over a much larger range than the individual's body size, as in visual scanning for landmarks. In this paper we formulate models that account for orientation in response to short- or long-range cue evaluation. Starting from an underlying random walk movement model, where a generic cue is evaluated locally or nonlocally to determine a preferred direction, we state corresponding macroscopic partial differential equations to describe population movements. Under certain approximations, these models reduce to well-known local and nonlocal biological transport equations, including those of Keller-Segel type. We consider a case-study application: "hilltopping" in Lepidoptera and other insects, a phenomenon in which populations accumulate at summits to improve encounter/mating rates. Nonlocal responses are shown to efficiently filter out the natural noisiness (or roughness) of typical landscapes and allow the population to preferentially accumulate at a subset of hilltopping locations, in line with field studies. Moreover, according to the timescale of movement, optimal responses may occur for different perceptual ranges.


Assuntos
Locomoção/fisiologia , Percepção Visual/fisiologia , Animais , Comportamento Animal , Sinais (Psicologia) , Lepidópteros/fisiologia , Densidade Demográfica , Resposta Táctica
14.
Electrophoresis ; 40(3): 431-436, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30039534

RESUMO

C. elegans is a popular model organism with a well-developed neural network. Approximately 60% of the genes in C. elegans have genomic counterparts in humans, including those involved in building neural circuits. Therefore, we can extend the study of human neural network mechanisms to C. elegans which is easy to genetically manipulate. C. elegans shows behavioural responses to various external physical and chemical stimuli. Electrotaxis is one of its distinct behavioural responses, which is defined as movement towards the cathode in an electric field. In this study, we developed an effective microfluidic trap system for analysing electrotaxis in C. elegans. In addition, two mutant strains (unc-54(s74) and unc-6(e78)) from wild-type (N2) worms were screened using the system. Wild-type (N2) worms and the two mutant strains clearly showed different behavioural responses to the applied electric field, thus enabling the effective screening of the mutant worms from the wild type (N2). This microfluidic system can be utilized as a platform for the study of behavioural responses, and for the sorting and mutant screening of C. elegans.


Assuntos
Caenorhabditis elegans , Técnicas Analíticas Microfluídicas , Resposta Táctica , Animais , Caenorhabditis elegans/fisiologia , Caenorhabditis elegans/efeitos da radiação , Eletricidade , Eletrofisiologia , Desenho de Equipamento , Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Mutação/fisiologia , Resposta Táctica/fisiologia , Resposta Táctica/efeitos da radiação
15.
Sci Total Environ ; 658: 95-104, 2019 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-30572219

RESUMO

Biochar widely applied to soil can influence microbial community composition and participate in extracellular electron transfer (EET). However, little is known about the cotransport behaviors of bacteria and biochar in aquifer and soil-water environments, which can affect the fate and application performance of biochar. In this study, we found that in comparison to their individual transport behaviors, the mobilities of cotransporting Shewanella oneidensis MR-1 and biochar colloid (BC) were significantly inhibited. The decreasing colloidal mobilities at higher ionic strengths signified the importance of electrostatic interaction between cell and BC in cotransport. Moreover, the less suppressed cotransport of BC and mutants defective of EET and the elevated inhibition effects on cotransport by adding exogenous electron donor suggested the importance of EET. Difference in cotransport behavior was also observed with BC having different redox states. Compared with oxidized BC, reduced BC with higher hydrophobicity led to easier aggregation with cell and higher retention in column. More importantly, MR-1 exhibited EET-dependent taxis towards biochar, which also contributed to the enhanced heteroaggregation and decreased mobilities of cell and biochar. Our results highlight that metabolic activities of microbes towards abiotic colloids cannot be neglected when assessing their transport behaviors, especially in subsurface environments abounded with redox-active inorganic particles and microbes performing extracellular respiration.


Assuntos
Carvão Vegetal/química , Shewanella/metabolismo , Coloides/química , Elétrons , Água Subterrânea/química , Concentração Osmolar , Oxirredução , Shewanella/fisiologia , Solo/química , Eletricidade Estática , Resposta Táctica
16.
PLoS One ; 13(12): e0208428, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30586408

RESUMO

Urban and suburban landscapes can be refuges for biodiversity of bees and other pollinators. Public awareness of declining pollinator populations has increased interest in growing plants that provide floral resources for bees. Various publications and websites list "bee-friendly" plants, but such lists are rarely based on empirical data, nor do they emphasize flowering trees and shrubs, which are a major component of urban landscapes. We quantified bee visitation to 72 species of flowering woody landscape plants across 373 urban and suburban sites in Kentucky and southern Ohio, USA, sampling and identifying the bee assemblages associated with 45 of the most bee-attractive species. We found strong plant species effects and variation in seasonal activity of particular bee taxa, but no overall differences in extent of bee visitation or bee genus diversity between native and non-native species, trees and shrubs, or early-, mid-, and late-season blooming plants. Horticulturally-modified varieties of Hydrangea, Prunus, and Rosa with double petals or clusters of showy sterile sepals attracted few bees compared to related plants with more accessible floral rewards. Some of the non-native woody plant species bloomed when floral resources from native plants were scarce and were highly bee-attractive, so their use in landscapes could help extend the flowering season for bees. These data will help city foresters, landscape managers, and the public make informed decisions to create bee-friendly urban and suburban landscapes.


Assuntos
Abelhas , Conservação dos Recursos Naturais/métodos , Flores/fisiologia , Magnoliopsida , Resposta Táctica/fisiologia , Árvores , Animais , Abelhas/fisiologia , Biodiversidade , Cidades , Demografia , Monitoramento Ambiental/métodos , Kentucky , Magnoliopsida/fisiologia , Ohio , Polinização , Estações do Ano , Árvores/fisiologia
17.
Sci Rep ; 8(1): 16114, 2018 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-30382191

RESUMO

Temperature is physiologically critical for all living organisms, which cope with temperature stress using metabolic and behavioral responses. In unicellular and some multicellular organisms, thermotaxis is a behavioral response to avoid stressful thermal environments and promote accumulation in an optimal thermal environment. In this study, we examined whether Chlamydomonas reinhardtii, a unicellular green alga, demonstrated thermotaxis. We found that between 10 °C and 30 °C, Chlamydomonas cells migrated toward lower temperatures independent of cultivation temperature. Interestingly, when we applied reagents to change intracellular reduction-oxidation (redox) conditions, we saw that thermotaxis was enhanced, suppressed, or reversed, depending on the redox conditions and cultivation temperature. Thermotaxis was almost absent in ppr2 and ppr3 mutants, which cannot swim backward because of a defect in generating calcium current in flagella. The frequency of spontaneous backward swimming was lower at more favorable temperature, suggesting a pivotal role of spontaneous backward swimming generated by flagellar membrane excitation.


Assuntos
Membrana Celular/fisiologia , Chlamydomonas reinhardtii/fisiologia , Flagelos/fisiologia , Resposta Táctica/fisiologia , Oxirredução , Temperatura
18.
Sci Rep ; 8(1): 15719, 2018 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-30356085

RESUMO

The development of the radical pair mechanism has allowed for theoretical explanation of the fact that magnetic fields are observed to have an effect on chemical reactions. The mechanism describes how an external magnetic field can alter chemical yields by interacting with the spin state of a pair of radicals. In the field of quantum biology, there has been some interest in the application of the mechanism to biological systems. This paper takes an open quantum systems approach to a model of the radical pair mechanism in order to derive a master equation in the Born-Markov approximation for the case of two electrons, each interacting with an environment of nuclear spins as well as the external magnetic field, then placed in a dissipative bosonic bath. This model is used to investigate two different cases relating to radical pair dynamics. The first uses a collective coupling approach to simplify calculations for larger numbers of nuclei interacting with the radical pair. The second looks at the effects of different hyperfine configurations of the radical pair model, for instance the case in which one of the electrons interact with two nuclei with different hyperfine coupling constants. The results of these investigations are analysed to see if they offer any insights into the biological application of the radical pair mechanism in avian magnetoreception.


Assuntos
Campos Magnéticos , Teoria Quântica , Animais , Aves , Criptocromos/fisiologia , Elétrons , Resposta Táctica
19.
Biomed Res Int ; 2018: 2534625, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30186854

RESUMO

Galvanotaxis, or electrotaxis, plays an essential role in wound healing, embryogenesis, and nerve regeneration. Up until now great efforts have been made to identify the underlying mechanism related to galvanotaxis in various cells under direct current electric field (DCEF) in laboratory studies. However, abundant clinical research shows that non-DCEFs including monopolar or bipolar electric field may also contribute to wound healing and regeneration, although the mechanism remains elusive. Here, we designed a novel electric stimulator and applied DCEF, pulsed DCEF (pDCEF), and bipolar pulse electric field (bpEF) to the cells of Dictyostelium discoideum. The cells had better directional performance under asymmetric 90% duty cycle pDCEF and 80% duty cycle bpEF compared to DCEF, with 10 Hz frequency electric fields eliciting a better cell response than 5 Hz. Interestingly, electrically neutral 50% duty cycle bpEF triggered the highest migration speed, albeit in random directions. The results suggest that electric pulses are vital to galvanotaxis and non-DCEF is promising in both basic and clinical researches.


Assuntos
Dictyostelium/fisiologia , Estimulação Elétrica , Resposta Táctica , Movimento Celular , Eletricidade , Cicatrização
20.
PLoS One ; 13(9): e0204065, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30235275

RESUMO

BACKGROUND: Bactrocera cucurbitae (Coquillett) is an important pest of cucurbit crops and certain vegetables in Asia, the Middle East, Africa and Hawaii. Most studies on B. cucurbitae have focussed on the effects of prolonged high temperature and very few have examined the effects of short-term exposures to high-temperature on behaviour. RESULTS: In this study, short-term of high-temperature treatments of 33°C, 37°C, 41°C and 45°C were maintained for 1-3hr, and long-term, variable high-temperature treatments were established that consisted of experienced one, two and three times high temperatures stages to 31°C, 33°C, 34°C, 35°C, 36°C, 37°C, 41°C and 45°C for 7hr. We compared the effects of the different high temperatures regimes changes treatments on the mating, oviposition and thermotactic taxis of the flies. The results showed that exposure to a 45°C/1hr treatment, delayed both initiation of mating and oviposition for 8 hr relative to the control but mating and was observed 41 times and oviposition 47 times. By comparison, in the control, mating commenced immediately and was observed 38.3 times and oviposition was observed 41.3 times. Under the other treatments, all the indices for the flies declined with the increase in temperature and duration of exposure. CONCLUSION: Results showed that 1hr of exposure to 45°C significantly stimulated mating, oviposition and thermotactic behaviour of the flies. These results could improve our understanding of the mechanisms responsible for the population dynamics of B. cucurbitae during the high-temperature season.


Assuntos
Temperatura Alta , Oviposição/fisiologia , Comportamento Sexual Animal/fisiologia , Resposta Táctica/fisiologia , Tephritidae/fisiologia , Animais , Feminino , Masculino
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