Necessary Sequencing Depth and Clustering Method to Obtain Relatively Stable Diversity Patterns in Studying Fish Gut Microbiota

The 16S rRNA gene is one of the most commonly used molecular markers for estimating bacterial diversity during the past decades. However, there is no consistency about the sequencing depth (from thousand to millions of sequences per sample), and the clustering methods used to generate OTUs may also be different among studies. These inconsistent premises make effective comparisons among studies difficult or unreliable. This study aims to examine the necessary sequencing depth and clustering method that would be needed to ensure a stable diversity patterns for studying fish gut microbiota. A total number of 42 samples dataset of Siniperca chuatsi (carnivorous fish) gut microbiota were used to test how the sequencing depth and clustering may affect the alpha and beta diversity patterns of fish intestinal microbiota. Interestingly, we found that the sequencing depth (resampling 1000-11,000 per sample) and the clustering methods (UPARSE and UCLUST) did not bias the estimates of the diversity patterns during the fish development from larva to adult. Although we should acknowledge that a suitable sequencing depth may differ case by case, our finding indicates that a shallow sequencing such as 1000 sequences per sample may be also enough to reflect the general diversity patterns of fish gut microbiota. However, we have shown in the present study that strict pre-processing of the original sequences is required to ensure reliable results. This study provides evidences to help making a strong scientific choice of the sequencing depth and clustering method for future studies on fish gut microbiota patterns, but at the same time reducing as much as possible the costs related to the analysis.</p

Effect of a standardized meal on the threshold of exercise-induced myocardial ischemia in patients with stable angina

AbstractObjectives. This study was undertaken to determine the effect of a standardized meal on the ischemie threshold and exercise capacity in a series of 20 patients with stable angina, exerciseinduced ischemia and reversible exercise-induced perfusion defects.Background. It is generally accepted that exercise tolerance in patients with angina is reduced after a meal. However, studies that have addressed this phenomenon have yielded results that are contradictory and inconclusive.Methods. Two exercise tests using the Brace protocol with technetium-99m (99mTc)-sestamibi were performed on consecutive days in a randomized order. One test was performed in the fasting state and the other 30 min after a 1,000-calorle meal.Results. In the postprandial state, exercise time to ischemia was reduced by 20% from 248 ± 93 s to 197 ±87 s (p = 0.0007), time to angina by 15% from 340 ± 82 s to 287 ± 94 s (p = 0.002) and exercise tolerance by 9% from 376 ± 65 s to 344 ± 86 s (p = 0.002). Rate-pressure products at these exercise test end points were not significantly different in the fasting and postprandial tests, and the quantitative 99mTc-sestamibi ischemia score was unchanged.Conclusions. In patients with stable angina, a 1,000-calorie meal significantly reduced tine to ischemia, time to angina and exercise tolerance because of a more rapid increase in myocardial oxygen demand with exercise. The extent and severity of exerciseinduced ischemia were unchanged

Nitrogen resorption in Acer platanoides and Acer saccharum : influence of light exposure and leaf pigmentation

We investigated the effects of leaf color change in the fall on photosynthetic production and nitrogen resorption. Seedlings of Acer platanoides L. and A. saccharum Marsh. were grown in a shade house for 5 months in either 21 % (intermediate light, M) or 4.9 % (low light, L) of incident irradiance. After this period, a subset of the intermediate-light grown seedlings was transferred to a high-light stress treatment (H). Gas exchange, chlorophyll fluorescence, pigments, antioxidant activity, and nitrogen (N) resorption were examined at three leaf senescence stages during September and October. Our results show that plants of both species produce more anthocyanins in the H treatment. In comparison with plants grown in the L and M treatments, plants of both species in the H treatments had lower chlorophyll, carotenoid and chlorophyll fluorescence parameters (F (v)/F (m), I broken vertical bar (PSII), NPQ and ETR) at the third sampling date (October 12-18), and indicating higher levels of photoinhibition in the seedlings exposed to high light. Our results imply that autumn leaf redness is inducible and closely linked to photo-oxidative stress. However, anthocyanins did not enhance antioxidant capacity in red leaves in either species, when exposed to high light. For both species, our results showed a higher N-resorption for high-light stressed plants. We also observed that the number of abscised leaves at the second sampling dates (September 10) was higher than at the third sampling dates. The intra-leaf distribution of anthocyanin, the association between anthocyanin production and the high-light environments, the retention of red leaves, the substantial physiological gain of photosynthetic activity, as well as the links between anthocyanins and increased N resorption led us to assume that one primary role of autumn anthocyanin could be to protect the photosynthetic apparatus from photo-oxidative damage as light filters rather than as antioxidant. Another major role is to extend carbon capture and help supply the energy needed for N resorption from senescing leaves in both A. saccharum and A. Platanoides during high-light stress. Nevertheless, photoprotective capacity of anthocyanins was not able to fully compensate for photoinhibitory stress as the anthocyanins are not optimally located to efficiently reduce light within the leaves.Peer reviewe

Le déficit de l’attention / hyperactivité (TDA/H) et les comportements violents des jeunes en milieu scolaire : L’état de la question

Cet article vise, d’une part, à faire le point sur l’état des connaissances actuelles en regard de ce qu’il est convenu d’appeler le trouble relatif au déficit de l’attention avec ou sans hyperactivité (TDA/H), et d’autre part, à examiner dans quelle mesure les élèves qui en sont atteints manifestent des comportements violents et s’il existe des types d’intervention aptes à contribuer à les réduire. Bien qu’il soit le trouble de comportement le plus commun diagnostiqué au cours de l’enfance, le TDA/H est plutôt mal connu et difficile à identifier et à diagnostiquer. Compte tenu de l’ampleur du phénomène, des conséquences observées sur le comportement des élèves qui en sont atteints, il s’avère important d’en connaître les symptômes et les conséquences, plus particulièrement en ce qui concerne les comportements violents. Les études tendent à montrer que les élèves ayant un TDA/H sont significativement plus nombreux que les autres à manifester des comportements colériques, agressifs, voire violents envers leurs pairs. De tels comportements entraînent des situations de conflit, d’impopularité et de rejet de la part de leurs pairs et plus d’attention négative de leur enseignant. Les interventions qui font appel à des moyens qui aident les individus à contrôler leurs comportements apparaissent particulièrement appropriées pour amener les jeunes atteints de ce syndrome à réduire leurs comportements agressifs et violents et à développer leurs compétences sociales.This article attempts to clarify what is currently known about problems related to attention deficit disorder with or without hyperactivity. (ADD/H), to examine to what extent affected students manifest violent behaviour and whether there are interventions that could contribute to reducing these behaviours. Although it is the most common behavioural problem diagnosed in childhood, ADD/H is poorly understood and difficult to identify and diagnose. Considering the scale of the phenomenon and the consequences observed on the behaviour of affected children, it is important to understand its symptoms and consequences, particularly in terms of violent behaviour. Studies tend to demonstrate that students with ADD/H are significantly more likely than the others to manifest angry, aggressive, even violent behaviour towards their peers. Such behaviour leads to situations of conflict, unpopularity, rejection by peers, and more negative attention from their teachers. Interventions giving that provide students with ways of controlling their behaviour seem particularly appropriate for helping those with ADD to reduce their aggressive and violent behaviour and to develop social skills.Este artículo pretende, por una parte, hacer balance de los conocimientos actuales sobre lo que se ha convenido en llamar el trastorno relativo al déficit de la atención con o sin hiperactividad (TDA/H), y por otra parte, examinar en qué medida los alumnos que sufren dicho déficit manifiestan comportamientos violentos y si existen tipos de intervención que pueden contribuir a su reducción. Aunque es el trastorno del comportamiento más frecuentemente diagnosticado durante la infancia, el TDA/H es relativamente mal conocido y su identificación y diagnóstico es difícil. Teniendo en cuenta la magnitud del fenómeno y las consecuencias observadas sobre el comportamiento de los alumnos que son afectados, resulta importante conocer los síntomas y las consecuencias, particularmente en lo que concierne los comportamientos violentos. Los estudios tienden a demostrar que los alumnos que sufren de TDA/H presentan una tendencia importante en la demostración de comportamientos coléricos, agresivos, incluso violentos hacia sus pares. Dicho tipo de comportamiento provoca situaciones de conflicto, impopularidad y rechazo de la parte de los pares y atención negativa de la parte del maestro. Las intervenciones que utilizan medios que ayudan a los individuos a controlar sus comportamientos se presentan como particularmente apropiadas para ayudar a los jóvenes afectados por dicho síndrome a reducir los comportamientos agresivos y violentos y desarrollar sus habilidades sociales

Comparison of photoacclimation in twelve freshwater photoautotrophs (chlorophyte, bacillaryophyte, cryptophyte and cyanophyte) isolated from a natural community.

Different representative of algae and cyanobacteria were isolated from a freshwater habitat and cultivated in laboratory to compare their photoacclimation capacity when exposed to a wide range of light intensity and to understand if this factor may modify natural community dominance. All species successfully acclimated to all light intensities and the response of phytoplankton to increased light intensity was similar and included a decrease of most photosynthetic pigments accompanied by an increase in photoprotective pigment content relative to Chl a. Most species also decreased their light absorption efficiency on a biovolume basis. This decrease not only resulted in a lower fraction of energy absorbed by the cell, but also to a lower transfer of energy to PSII and PSI. Furthermore, energy funnelled to PSII or PSI was also rearranged in favour of PSII. High light acclimated organisms also corresponded to high non-photochemical quenching and photosynthetic electron transport reduction state and to a low Φ'M. Thus photoacclimation processes work toward reducing the excitation pressure in high light environment through a reduction of light absorption efficiency, but also by lowering conversion efficiency. Interestingly, all species of our study followed that tendency despite being of different functional groups (colonial, flagellated, different sizes) and of different phylogeny demonstrating the great plasticity and adaptation ability of freshwater phytoplankton to their light environment. These adjustments may explain the decoupling between growth rate and photosynthesis observed above photosynthesis light saturation point for all species. Even if some species did reach higher growth rate in our conditions and thus, should dominate in natural environment with respect to light intensity, we cannot exclude that other environmental factors also influence the population dynamic and make the outcome harder to predict

Temperature and Light Modulation of Herbicide Toxicity on Algal and Cyanobacterial Physiology

HIGHLIGHTSWe reviewed the interaction between light, temperature and herbicides on algal and cyanobacterial physiology.Temperature is the main factor affecting herbicide toxicity to algae and cyanobacteria.Changes in light environment may modulate the effects of photosynthesis-targeting herbicides.Important interactions between climatic parameters and herbicide toxicity have been discussed in the literature. As climate changes are expected to influence the growth conditions of aquatic photosynthetic organisms over the next century by modifying the physicochemical parameters of the environment (such as temperature and incident light characteristics), the following questions arise: How will variations in climatic conditions influence herbicide toxicity in algae and cyanobacteria? Are these coupled effects on aquatic photosynthetic organism physiology antagonistic, additive, or synergistic? We discuss here the physiological responses of algae and cyanobacteria to the combined effects of environmental changes (temperature and light) and herbicide exposure. Both temperature and light are proposed to influence herbicide toxicity through acclimation processes that are mainly related to cell size and photosynthesis. Algal and cyanobacterial responses to interactions between light, temperature, and herbicides are species-specific, making it difficult today to establish a single model of how climate changes will affect toxicity of herbicides. Acclimation processes could assure the maintenance of primary production but total biodiversity should decrease in communities exposed to herbicides under changing temperature and light conditions. The inclusion of considerations on the impacts of environmental changes on toxicity of herbicides in water quality guidelines directed toward protecting aquatic life is now urgently needed