1,721,500 research outputs found
Effects of abiotic stress on photosystem II proteins
No full textPhotosystem II (PSII) represents the most vulnerable component of the photosynthetic machinery and its response in plants subjected to abiotic stress has been widely studied over many years. PSII is a thylakoid membrane-located multiprotein pigment complex that catalyses the light-induced electron transfer from water to plastoquinone with the concomitant production of oxygen. PSII is rich in intrinsic (PsbA and PsbD, namely D1 and D2, CP47 or PsbB and CP43 or PsbC) but also extrinsic proteins. The first ones are more largely conserved from cyanobacteria to higher plants while the extrinsic proteins are different among species. It has been found that extrinsic proteins involved in oxygen evolution change dramatically the PSII efficiency and PSII repair systems. However, little information is available on the effects of abiotic stress on their function and structure
Antioxidant defenses in plants: A dated topic of current interest
No full text: Plants have been challenged against oxidative stress since their appearance on land [...]
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
TREM1 predicts response to anti-tumor necrosis factor in inflammatory bowel diseases: Towards precision medicine
No full textEndonuclear bacterial symbionts in two termite species: an ultrastructural study.
No full textIntracellular symbionts (endosymbiotic bacteria), either isolated or in clusters, were found within the cytoplasm and the nucleus of female germ cells and of trophocytes in nymphs and reproductives of two termite species, Kalotermes flavicollis (Isoptera: Kalotermitidae) and Reticulitermes lucifugus (Isoptera: Rhinotermitidae) , collected in the wild. This finding represents the first record of endonuclear symbiotic bacteria in a metazoan species. The bacteria reach the host ovarian cells by crossing the tunica propria. The ultrastructural morphology of the bacteria closely resembles that of cytoplasmic symbionts found in other insect orders (such as Dictyoptera and Homoptera) and their presence does not appear to be correlated with bacteriocytes (or mycetocytes) as in the more primitive termite Mastotermes darwiniensis (Isoptera: Mastotermitidae). The endonuclear symbionts, as well as the cytoplasmic ones, are enveloped by a plasma membrane, by a cell wall typical of Gram-negative bacteria and by a perisymbiotic membrane, the last two separated by an outer periplasmic space. In some of the endonuclear symbionts, however, the perisymbiotic membrane is lacking. Different kinds of inclusions, apparently unrelated to mesosomes, are visible within the endonuclear symbionts. A wide array of vesicles is found in the outer periplasmic space and inside the host chromatin, in close proximity to bacteria. Some vesicles apparently originate tram the outer layer of bacterial cell wall and are freed in the host chromatin by a further process of budding and vesiculation of the perisymbiotic membrane. These observations support the hypothesis of product exchanges between endosymbionts and the host cell. The presence of endonucIear symbionts (also seen in the act of dividing within the nucleus) does not apparently affect the meiotic processes or cause host cell degenerations, although a less dense chromatin, aggregates of granular material, thin cylindroid bodies and bundles of microfibrils are indeed observed within the nucleoplasm. A continuity between the perisymbiotic membrane and the RER is often detected in the cytoplasm and some endosymbionts appear to be closely associated with mitochondria
Chlorophyll fluorescence, photoinhibition and abiotic stress: does it make any difference the fact to be a C3 or C4 species?
Full text linkChlorophyll fluorescence analysis is one of the most powerful and widely used techniques to study the effect of stresses on the photosynthetic process. From the first utilization, the Fv/Fm ratio has been largely used as a sensitive indicator of plant photosynthetic performance. Decreases of this index are indicative of the reduction of photosystem II (PSII) efficiency, namely photoinhibition. In the last 20 years, application of chlorophyll fluorescence has been largely improved, and many other informative parameters have been established to detect PSII photochemical efficiency and the partitioning of light energy to alternative dissipative mechanisms (qE, energy-dependent quenching; qZ, zeaxanthin-dependent quenching and qI, photoinhibitory quenching; qH, sustained photoprotective antenna quenching; qM, quenching dependent to chloroplast movement; qT, light harvesting complexes II–I state-transition) such as the recently developed “photoprotective power” of non-photochemical quenching (pNPQ). This review reports a brief description of the main chlorophyll fluorescence parameters and a wide analysis of the current bibliography on the use of different parameters which are useful to detect events of PSII photoinhibition. In addition, in view of the inherent differences in morpho-anatomical, physiological and biochemical features between C3 and C4 metabolism, possible differences in terms of photoinhibition between C3 and C4 plant species under stress conditions are proposed. The attempt is to highlight the limits of their comparison in terms of susceptibility to photoinhibition and to propose direction of future research which, assisted by chlorophyll fluorescence, should improve the knowledge of the different sensitivity of C3 and C4 to abiotic stressors
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Nutritional and antioxidant value of horticulturae products
No full textThe recent growing interest towards the nutraceutical and antioxidant value of fruit and vegetables has arisen from their content of phytochemicals, which provide desirable health benefits, beyond basic nutrition, to reduce the risk of major chronic diseases [1]. For this reason, it is necessary for the human diet to contain a good proportion of plant antioxidant compounds. Therefore, horticultural science must dedicate more attention to satisfy the expectations of consumers who are demanding more and more high-quality functional foods.
The Special Issue on the “Nutritional and Antioxidant Value of Horticultural Products” has provided readers with novel insights into some ‘unusual’ types of foods. In fact, the articles published included information about edible flowers, Italian green tea, and stinging nettle, along with potato and sweet potato.
Demasi et al. [2] investigated the sensory profile of 17 edible flowers (Figure 1) at harvest, and their shelf life and bioactive compound dynamics during cold storage, providing the characteristics and requirements of the different flowers. The authors evaluated the aroma of the flower with 10 sensory descriptors (intensity of sweet, sour, bitter, salt, smell, specific flower aroma, and herbaceous aroma; spiciness, chewiness, and astringency), and, both at harvest and during 14 d of storage at 4 °C, the flower visual quality, polyphenol and anthocyanin content, and antioxidant activity were evaluated. The paper presents a lot of information concerning flowers’ sensory profiles, phytochemical characteristics, and shelf life, which are very useful to select suitable species for the edible flower market; for example, a strong aroma was revealed for Allium ursinum, Dianthus carthusianorum, Lavandula angustifolia, and Leucanthemum vulgare, while the flowers with the longest shelf life were Rosa pendulina (14 days) and Rosa canina (10 days)
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