Browsing by Subject "Light"

Now showing 1 - 11 of 11
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    B12-based photoreceptors: from structure and function to applications in optogenetics and synthetic biology
    (2019-08) Padmanabhan, S; Pérez-Castaño, Ricardo; Elías Arnanz, Montserrat; Genética y Microbiología
    Vitamin B12-based photoreceptor proteins sense ultraviolet (UV), blue or green light using 5´-deoxyadenosylcobalamin (AdoCbl). The prototype of this widespread bacterial photoreceptor family, CarH, controls light-dependent gene expression in photoprotective cellular responses. It represses transcription in the dark by binding to operator DNA as an AdoCbl-bound tetramer, whose disruption by light relieves operator binding to allow transcription. Structures of the "dark" (free and DNA-bound) and "light" CarH states and studies on the unusual AdoCbl photochemistry have provided fundamental insights into these photoreceptors. We highlight these, the plasticity within a conserved mode of action among CarH homologs, their distribution, and their promising applications in optogenetics and synthetic biology.
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    Correlated color temperature and light intensity: complementary features in non-visual light field
    (Public Library of Science (PLoS), 2021-07-12) Arguelles Prieto, Raquel; Madrid, Juan Antonio; Rol de Lama, María de los Ángeles; Bonmatí Carrión, María de los Ángeles; Fisiología
    An appropriate exposure to the light-dark cycle, with high irradiances during the day and darkness during the night is essential to keep our physiology on time. However, considering the increasing exposure to artificial light at night and its potential harmful effects on health (i.e. chronodisruption and associated health conditions), it is essential to understand the non-visual effects of light in humans. Melatonin suppression is considered the gold standard for nocturnal light effects, and the activation of intrinsically photosensitive retinal ganglion cells (ipRGCs) through the assessment of pupillary light reflex (PLR) has been recently gaining attention. Also, some theoretical models for melatonin suppression and retinal photoreceptors activation have been proposed. Our aim in this study was to determine the influence of correlated color temperature (CCT) on melatonin suppression and PLR, considering two commercial light sources, as well as to explore the possible correlation between both processes. Also, the contribution of irradiance (associated to CCT) was explored through mathematical modelling on a wider range of light sources. For that, melatonin suppression and PLR were experimentally assessed on 16 healthy and young volunteers under two light conditions (warmer, CCT 3000 K; and cooler, CCT 5700 K, at ~5·1018 photons/cm2/sec). Our experimental results yielded greater post-stimulus constriction under the cooler (5700 K, 13.3 ± 1.9%) than under the warmer light (3000 K, 8.7 ± 1.2%) (p < 0.01), although no significant differences were found between both conditions in terms of melatonin suppression. Interestingly, we failed to demonstrate correlation between PLR and melatonin suppression. Although methodological limitations cannot be discarded, this could be due to the existence of different subpopulations of Type 1 ipRGCs differentially contributing to PLR and melatonin suppression, which opens the way for further research on ipRGCs projection in humans. The application of theoretical modelling suggested that CCT should not be considered separately from irradiance when designing nocturnal/diurnal illumination systems. Further experimental studies on wider ranges of CCTs and light intensities are needed to confirm these conclusions.
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    Detection of factors influencing circadian rhythms on Intensive Care inpatients and hospitalization: protocol for an observational study
    (Wiley, 2020-09-30) Padilla Martínez, Julia M.; Abad Corpa, Eva; Gea Sánchez, Montserrat; Casado Ramírez, Elvira; Rol de Lama, María de los Ángeles; Madrid, Juan Antonio; Moreno Casbas, María T.; Fisiología
    Aims Identify the prevalence of circadian health disorders in ICU and hospitalized patients. Stablish the relationship of the circadian system with light, temperature, noise and nursing activities. Background Commonly, self-assessment through subjective questionnaires is used for research about sleep quality. However, more reliable and valid measures should be applied objectively to find out the real prevalence of the problem. There is a negative relationship between circadian rhythms and hospitalization. In this study, we will analyse sleep patterns and hospital environments to implement measures to improve the quality of care related to sleep. Design Descriptive observational study. It is estimated that 975 patients from 13 hospitals need to be recruited from ICU and hospitalization units. The sample should meet the following criteria: Patients over 18 admitted to ICU and medical units, length of stay between 96–148 hr, with no visual, hearing or moderate-severe cognitive impairment. Variables: Sleep variables are collected with an electronic device (named Kronowise® and Kronobed®), circadian and infrared light exposure, environmental noise, temperature, unit structural characteristics, nursing care (from 0 to 6 a.m.) and, characteristics of hospitalization period. The study, registered on Clinical Trials, initiated in December 2019 and it will continue up to December 2022. Discussion Using objective and subjective measures of sleep and circadian rhythms, this study will shed light on the factors that negatively affect the hospitalized patients’ sleep quality and circadian health. The ultimate goal is to design hospital guidelines to minimize the adverse effects on the dependent variables studied. Arguably, these guidelines will contribute to reducing the risk of these alterations and it will also serve to improve the nursing activities. Conclusion We expect to obtain adequate results for the creation of a protocol to improve the circadian health, quality of care and health outcomes related to sleep in patients.
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    Effects of white light on the pineal gland of the chick embryo
    (Murcia : F. Hernández, 1992) Aige-Gil, Vicente; Murillo-Ferrol, Narciso
    Chick embryos were directly exposed to a source of white light during incubation and sacrificed before hatching. The light caused a number of teratological effects such as high mortality, delay in development, celosomy, hepatomegaly, auricular dilation and micrognatia. The pineal gland of the illuminated embryos showed an increase in number and size of the intracytoplasmic lipid droplets of the follicular pinealocytes. These findings suggest that the pineal gland of the chick embryo is sensitive to light.
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    Light-induced rhythmic changes in thermotolerance in stationary-phase cells of Candida utilis
    (International microbiology : the official journal of the Spanish Society for Microbiology., 2006) Lapeña, Miguel A.; Vicente, Jero; Soto, Teresa; Madrid, Marisa; Núñez, Andrés; García, Encarnación; Cansado Vizoso, José; Gacto, Mariano; Genética y Microbiología
    In synchronized light-dark cycles, stationary-phase cultures of the budding yeast Candida utilis were able to survive heat treatment at 50ºC with an apparent circadian-like rhythm related to the onset of light. However, in continuous darkness this pattern did not run freely and was markedly dampened. We discuss these findings in terms of the potential circadian control of heat tolerance, which has been described in the fission yeast Schizosaccharomyces pombe. Our results suggest that the resistance pattern observed in C. utilis is most likely an adaptive response to the light-induced generation of reactive oxygen species rather than the occurrence of a truly endogenous circadian rhythm
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    La noción de cuerpo y alma como centro en el Bruno de F.W.J. Schelling
    (Universidad de Murcia. Servicio de Publicaciones, 2016) Ramírez Cordón, Miguel Ángel
    Cuerpo y alma son conceptos antinómicos que permiten establecer un juego de analogías donde decir cuerpo supone también decir lo real, ser, finitud, lo mortal, o el trabajo del entendimiento, mientras alma denota a su vez lo ideal, pensar, la infinitud, la inmortalidad, o el órgano de la razón. Con todo, seguir esta pista, la de ver grados distintos de conceptos opuestos recíprocamente, es tanto como conformarse con ver en el vínculo de los términos correlativos una «turbia unidad» meramente analítica. La cuestión por tanto es si ha de haber una unidad absoluta que pueda extraerse de la inseparabilidad de estos conceptos. A partir de este punto se deja introducir el concepto de centro. Sólo cuanto más se habita este centro, el hombre logra quedar incluido en esta unidad absoluta, y ser más auténticamente hombre.
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    El nombre “luz” en la poesía de Fernando de Herrera. Una lectura desde el neoplatonismo renacentista
    (2019-02-18) Torres Salinas, Ginés
    Uno de los rasgos más característicos de la poesía amorosa de Fernando de Herrera es el nombre propio que en ella recibe su dama: Luz. En este artículo pretendemos demostrar cómo el uso de dicho nombre, más que una mera alusión a Leonor de Milán, debe entenderse según ciertos aspectos doctrinales del neoplatonismo renacentista. El estudio de la teoría neoplatónica del nombre, a partir de fray Luis de León, y de la metafísica ficiniana de la luz ponen de manifiesto cómo el nombre que Herrera da a su dama conlleva unas implicaciones que la sitúan en un espacio privilegiado dentro del imaginario de la lírica renacentista.
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    Photoresponsive metal-organic frameworks as adjustable scaffolds in reticular chemistry
    (Multidisciplinary Digital Publishing Institute, 2022-06-27) Saura Sanmartín, Adrián; Saura Sanmartín, Adrián; Química Orgánica
    The easy and remote switching of light makes this stimulus an ideal candidate for a large number of applications, among which the preparation of photoresponsive materials stands out. The interest of several scientists in this area in order to achieve improved functionalities has increase parallel to the growth of the structural complexity of these materials. Thus, metal-organic frameworks (MOFs) turned out to be ideal scaffolds for light-responsive ligands. This review is focused on the integration of photoresponsive organic ligands inside MOF crystalline arrays to prepare enhanced functional materials. Besides the summary of the preparation, properties and applications of these materials, an overview of the future outlook of this research area is provided.
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    Quete et Enjeux de l'Eden dans la poésie de Saint-John Perse
    (2016-11-18) Kouakou Aho, Bernard
    In the poetry of Saint-John Perse, the man is in the center of the concerns of the poet. The Eden translates the place of delights that underlies the human exis- tence by the infinite enjoyment which bases it. Any life cannot understand only by its conquest translating, from the fact, from the imperceptible and insatiable desire of the being. The problem which arouses this quest of such a place is also, at the poet, that of the poetic writing connected to the bright structure of the universe, stemming from the bioluminescence and taken on an aura multicolored and wonderful colors; it could so offer the enjoyment of an existence which insures the sea as microcosm of the Eden, such are the real stakes in the notion in its poetic functioning. The objective of the work is to show that by launching in the conquest of such a space of plenitude, Perse embodies the symbolism of the light and is established as the wise man. This edenic world appears as an universe which, leads to the essential truth, illuminates things.
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    Relationship between human pupillary light reflex and circadian system status
    (Public Library of Science, 2016-09-16) Hild, Konstanze; Isherwood, Cheryl; Sweeney, Stephen J.; Revell, Victoria L.; Skene, Debra J.; Rol, Maria Ángeles; Madrid, Juan Antonio; Bonmatí Carrión, María de los Ángeles; Anatomía Humana y Psicobiología
    Intrinsically photosensitive retinal ganglion cells (ipRGCs), whose photopigment melanopsin has a peak of sensitivity in the short wavelength range of the spectrum, constitute a common light input pathway to the olivary pretectal nucleus (OPN), the pupillary light reflex (PLR) regulatory centre, and to the suprachiasmatic nuclei (SCN), the major pacemaker of the circadian system. Thus, evaluating PLR under short wavelength light (λmax 500 nm) and creating an integrated PLR parameter, as a possible tool to indirectly assess the status of the circadian system, becomes of interest. Nine monochromatic, photon-matched light stimuli (300 s), in 10 nm increments from λmax 420 to 500 nm were administered to 15 healthy young participants (8 females), analyzing: i) the PLR; ii) wrist temperature (WT) and motor activity rhythms (WA), iii) light exposure (L) pattern and iv) diurnal preference (HorneÖstberg), sleep quality (Pittsburgh) and daytime sleepiness (Epworth). Linear correlations between the different PLR parameters and circadian status index obtained from WT, WA and L recordings and scores from questionnaires were calculated. In summary, we found markers of robust circadian rhythms, namely high stability, reduced fragmentation, high amplitude, phase advance and low internal desynchronization, were correlated with a reduced PLR to 460–490 nm wavelengths. Integrated circadian (CSI) and PLR (cp-PLR) parameters are proposed, that also showed an inverse correlation. These results demonstrate, for the first time, the existence of a close relationship between the circadian system robustness and the pupillary reflex response, two non-visual functions primarily under melanopsin-ipRGC input.
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    El silencio del corazón y la negrura del no saber. Resonancias del pensamiento de Ibn ʿArabī en la obra de Bill Viola
    (Universidad de Murcia, Servicio de Publicaciones., 2018) Crespo, Ana
    Bill Viola se asoma al universo de Ibn ʿArabī, bebe de la belleza de sus paradojas y las concreta, a su vez, en enigmáticas paradojas visuales. En este artículo presentamos una reflexión sobre la cualidad simbólica del negro en la obra de Viola y su rela- ción con el silencio del corazón. Como, desde este silencio interno, se penetra en una dimensión lucida de la conciencia, en el intermundo del barzaḫ (mundo imaginal). Las formas de Viola nacen y se diluyen en un Negro maravilloso, Noche de Luz, Negro de la sabiduría que todo lo contiene y en el que se disuelven los colores cambiantes de los estados. Mediante el uso paradójico del tiempo, la luz y el espacio, la obra de Viola induce a una experiencia contem- plativa, a un conocimiento por degustación, que en el sufismo se denomina saboreo (ḏawq). La temporalidad de sus imágenes produce un distanciamiento del tiempo cuantitativo y nos conduce a un silencio interno, lo que Ibn ʿArabī denomina silencio del corazón. Las imágenes de Viola nos llevan a habitar esa intensidad luminosa e inabarcable de la Luz negra.