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211.
Gabriel E. Bertolesi John Zhijia Zhang Sarah McFarlane 《Pigment cell & melanoma research》2019,32(4):510-527
Different camouflages work best with some background matching colour. Our understanding of the evolution of skin colour is based mainly on the genetics of pigmentation (“background matching”), with little known about the evolution of the neuroendocrine systems that facilitate “background adaptation” through colour phenotypic plasticity. To address the latter, we studied the evolution in vertebrates of three genes, pomc, pmch and pmchl, that code for α‐MSH and two melanin‐concentrating hormones (MCH and MCHL). These hormones induce either dispersion/aggregation or the synthesis of pigments. We find that α‐MSH is highly conserved during evolution, as is its role in dispersing/synthesizing pigments. Also conserved is the three‐exon pmch gene that encodes MCH, which participates in feeding behaviours. In contrast, pmchl (known previously as pmch), is a teleost‐specific intron‐less gene. Our data indicate that in zebrafish, pmchl‐expressing neurons extend axons to the pituitary, supportive of an MCHL hormonal role, whereas zebrafish and Xenopus pmch+ neurons send axons dorsally in the brain. The evolution of these genes and acquisition of hormonal status for MCHL explain different mechanisms used by vertebrates to background‐adapt. 相似文献
212.
Gabriel Birzu Sakib Matin Oskar Hallatschek Kirill S. Korolev 《Ecology letters》2019,22(11):1817-1827
Theory predicts rapid genetic drift during invasions, yet many expanding populations maintain high genetic diversity. We find that genetic drift is dramatically suppressed when dispersal rates increase with the population density because many more migrants from the diverse, high‐density regions arrive at the expansion edge. When density dependence is weak or negative, the effective population size of the front scales only logarithmically with the carrying capacity. The dependence, however, switches to a sublinear power law and then to a linear increase as the density dependence becomes strongly positive. We develop a unified framework revealing that the transitions between different regimes of diversity loss are controlled by a single, universal quantity: the ratio of the expansion velocity to the geometric mean of dispersal and growth rates at expansion edge. Our results suggest that positive density dependence could dramatically alter evolution in expanding populations even when its contribution to the expansion velocity is small. 相似文献
213.
Michael J. Fanous Yanfen Li Mikhail E. Kandel Amr A. Abdeen Kristopher A. Kilian Gabriel Popescu 《Journal of biophotonics》2019,12(12)
The development of three‐dimensional (3D) cellular architectures during development and pathological processes involves intricate migratory patterns that are modulated by genetics and the surrounding microenvironment. The substrate composition of cell cultures has been demonstrated to influence growth, proliferation and migration in 2D. Here, we study the growth and dynamics of mouse embryonic fibroblast cultures patterned in a tissue sheet which then exhibits 3D growth. Using gradient light interference microscopy (GLIM), a label‐free quantitative phase imaging approach, we explored the influence of geometry on cell growth patterns and rotational dynamics. We apply, for the first time to our knowledge, dispersion‐relation phase spectroscopy (DPS) in polar coordinates to generate the radial and rotational cell mass‐transport. Our data show that cells cultured on engineered substrates undergo rotational transport in a radially independent manner and exhibit faster vertical growth than the control, unpatterned cells. The use of GLIM and polar DPS provides a novel quantitative approach to studying the effects of spatially patterned substrates on cell motility and growth. 相似文献
214.
Shamira Sridharan Weaver Yanfen Li Louis Foucard Hassaan Majeed Basanta Bhaduri Alex J. Levine Kristopher A. Kilian Gabriel Popescu 《Journal of biophotonics》2019,12(3)
Characterizing the effects of force fields generated by cells on proliferation, migration and differentiation processes is challenging due to limited availability of nondestructive imaging modalities. Here, we integrate a new real‐time traction stress imaging modality, Hilbert phase dynamometry (HPD), with spatial light interference microscopy (SLIM) for simultaneous monitoring of cell growth during differentiation processes. HPD uses holographic principles to extract displacement fields from chemically patterned fluorescent grid on deformable substrates. This is converted into forces by solving an elasticity inverse problem. Since HPD uses the epi‐fluorescence channel of an inverted microscope, cellular behavior can be concurrently studied in transmission with SLIM. We studied the differentiation of mesenchymal stem cells (MSCs) and found that cells undergoing osteogenesis and adipogenesis exerted larger and more dynamic stresses than their precursors, with MSCs developing the smallest forces and growth rates. Thus, we develop a powerful means to study mechanotransduction during dynamic processes where the matrix provides context to guide cells toward a physiological or pathological outcome. 相似文献
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Denise P. Silva Gustavo Duarte Helena D.M. Villela Henrique F. Santos Phillipe M. Rosado Joo Gabriel Rosado Alexandre S. Rosado Edir M. Ferreira Adriana U. Soriano Raquel S. Peixoto 《Ecology and evolution》2019,9(9):5172-5185
Although numerous studies have been carried out on the impacts of oil spills on coral physiology, most have relied on laboratory assays. This scarcity is partly explained by the difficulty of reproducing realistic conditions in a laboratory setting or of performing experiments with toxic compounds in the field. Mesocosm systems provide the opportunity to carry out such studies with safe handling of contaminants while reproducing natural conditions required by living organisms. The mesocosm design is crucial and can lead to the development of innovative technologies to mitigate environmental impacts. Therefore, this study aimed to develop a mesocosm system for studies simulating oil spills with several key advantages, including true replication and the use of gravity to control flow‐through that reduces reliance on pumps that can clog thereby decreasing errors and costs. This adaptable system can be configured to (a) have continuous flow‐through; (b) operate as an open or closed system; (c) be fed by gravity; (d) have separate mesocosm sections that can be used for individual and simultaneous experiments; and (e) simulate the migration of oil from ocean oil spills to the nearby reefs. The mesocosm performance was assessed with two experiments using the hydrocoral Millepora alcicornis and different configurations to simulate two magnitudes of oil spills. With few exceptions, physical and chemical parameters remained stable within replicates and within treatments throughout the experiments. Physical and chemical parameters that expressed change during the experiment were still within the range of natural conditions observed in Brazilian marine environments. The photosynthetic potential (Fv/Fm) of the algae associated with M. alcicornis decreased in response to an 1% crude‐oil contamination, suggesting a successful delivery of the toxic contaminant to the targeted replicates. This mesocosm is customizable and adjustable for several types of experiments and proved to be effective for studies of oil spills. 相似文献
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