Root seasonal pattern,spatial distribution,and C:N ratio of matgrass pasture (Nardus stricta L.) in the Lombardy Prealps

Abstract

The aim of the present study was to investigate carbon and nutrient cycling and the role of root dynamics in terrestrial ecosystems such as large abandoned pastures and natural grasslands present in the Prealps, for which below‐ground processes are currently enigmatic. In particular, we quantified root/leaf biomass and C:N ratio throughout two growing seasons. Additionally, root traits such as root length density (RLD), root mass density (RMD), and root diameter classes (RDC) were also investigated with the aim of understanding the spatial distribution of roots in the soil. In our samples, we found that the roots could be divided into three main diameter classes and hence quantified the presence of each class along the soil profile. With regard to total root biomass, we found the occurrence of two peaks of biomass accumulation during the growth season, and when biomass accumulation was compared with climatic data, it was impossible to obtain a clear indication of the root turnover rate. In fact, the strong influence of grazing on the above‐ground biomass could have affected, in turn, root biomass. In future, this possible complication will be avoided by repeating the measurements within enclosures to avoid grazing interference. We found that C:N ratio remained constant, with a single peak, suggesting a lower root decomposition during the warmest period (August 2006). The concentration of nitrogen in roots decreased with depth as a result of a decrease in roots with smaller diameters. The reverse was found for carbon content, which increased with depth, probably due to an increase in roots with larger diameters. This study represents the first attempt to estimate root turnover rates in this prealpine ecosystem, which have been analysed to date only for the above‐ground biomass.     

Predicted distributions and abundances of the sea turtle ‘lost years’ in the western North Atlantic Ocean

Oceanic dispersal characterizes the early juvenile life-stages of numerous marine species of conservation concern. This early stage may be a ‘critical period’ for many species, playing an overriding role in population dynamics. Often, relatively little information is available on their distribution during this period, limiting the effectiveness of efforts to understand environmental and anthropogenic impacts on these species. Here we present a simple model to predict annual variation in the distribution and abundance of oceanic-stage juvenile sea turtles based on species’ reproductive output, movement and mortality. We simulated dispersal of 25 cohorts (1993–2017) of oceanic-stage juveniles by tracking the movements of virtual hatchling sea turtles released in a hindcast ocean circulation model. We then used estimates of annual hatchling production from Kemp's ridley Lepidochelys kempii (n = 3), green Chelonia mydas (n = 8) and loggerhead Caretta caretta (n = 5) nesting areas in the northwestern Atlantic (inclusive of the Gulf of Mexico, Caribbean Sea and eastern seaboard of the U.S.) and their stage-specific mortality rates to weight dispersal predictions. The model's predictions indicate spatial heterogeneity in turtle distribution across their marine range, identify locations of increasing turtle abundance (notably along the U.S. coast), and provide valuable context for temporal variation in the stranding of young sea turtles across the Gulf of Mexico. Further effort to collect demographic, distribution and behavioral data that refine, complement and extend the utility of this modeling approach for sea turtles and other dispersive marine taxa is warranted. Finally, generating these spatially-explicit predictions of turtle abundance required extensive international collaboration among scientists; our findings indicate that continued conservation of these sea turtle populations and the management of the numerous anthropogenic activities that operate in the northwestern Atlantic Ocean will require similar international coordination.     

Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications

ABSTRACT: Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.     

Second-generation thyrotropin receptor antibodies assay and quantitative thyroid scintigraphy in autoimmune hyperthyroidism.

Graves' disease (GD) is characterized by circulating TSH receptor antibodies (TRAb), and so-called hyperthyroid autoimmune thyroiditis (H-AIT) generally shows negative TRAb results with first-generation assays. However, a positive titer was observed in up to 13% of patients with euthyroid or hypothyroid autoimmune thyroiditis (AIT) by second-generation TRAb assays, and a larger increase is expected in hyperfunctioning forms. A thyroid 99mTc-pertechnetate uptake (TcTUs) cutoff of 2% previously was shown to accurately discriminate between GD and H-AIT. Here we evaluated the relationship between second-generation TRAb assays and TcTUs in 139 patients with untreated autoimmune hyperthyroidism. An increase in TRAb levels was found in 114 of 139 patients (82%). All patients with TcTUs >2% and 66% of those with lower values had positive TRAb measurements. When the cutoff was increased to 5.9 U/l, positive TRAb occurred in 92.6% of those having higher TcTUs and in 1.4% of those with lower TcTUs. TRAb levels significantly increased in patients with TcTUs higher than 2% as compared with those having lower values, while no differences occurred in patients with TcTUs ranging from 0 to 1%, from 1.1 to 1.5%, or from 1.6 to 2%. A significant relationship between TRAb and TcTUs (as well as fT3, fT4, and thyroid volume) was found. TcTUs, fT4, fT3, and thyroid volume significantly increased in patients with positive TRAb (cutoff 1.5 U/l) compared with those testing negative. Our data indicate that a large proportion of patients with hyperthyroidism and hypoechoic thyroid, including those previously diagnosed as having H-AIT, actually have circulating TRAb. TRAb levels predicate the degree of iodine uptake (as measured by TcTUs) and thyroid hyperfunction. The role of baseline TRAb measurement by second-generation assays to predict patients' outcome needs to be further evaluated and compared with TcTUs in prospective studies.     

Circadian remodeling of neuronal circuits involved in rhythmic behavior

Clock output pathways are central to convey timing information from the circadian clock to a diversity of physiological systems, ranging from cell-autonomous processes to behavior. While the molecular mechanisms that generate and sustain rhythmicity at the cellular level are well understood, it is unclear how this information is further structured to control specific behavioral outputs. Rhythmic release of pigment dispersing factor (PDF) has been proposed to propagate the time of day information from core pacemaker cells to downstream targets underlying rhythmic locomotor activity. Indeed, such circadian changes in PDF intensity represent the only known mechanism through which the PDF circuit could communicate with its output. Here we describe a novel circadian phenomenon involving extensive remodeling in the axonal terminals of the PDF circuit, which display higher complexity during the day and significantly lower complexity at nighttime, both under daily cycles and constant conditions. In support to its circadian nature, cycling is lost in bona fide clockless mutants. We propose this clock-controlled structural plasticity as a candidate mechanism contributing to the transmission of the information downstream of pacemaker cells.     

Differences in potential and content of the mucus in the stomach of the rat with avitaminosis A

Vitamin A (vit. A) acts in the synthesis of glycoproteins and in cell surface phenomena of epithelia. Since the glycoproteins of gastric mucus and the integrity of gastric cell membranes are components of gastric barrier (GB), vit. A could play a role in GB. Five groups of rats were used: I) rats fed on vit. A deficient diet; II) rats pair-fed plus a daily oral dose of 45 micrograms vit. A; III) normal rats; IV) rats recovered from avitaminosis A (avit. A) after 20 days of daily oral dose of 300 micrograms vit. A; V) rats pair-fed plus a daily oral dose of 45 micrograms vit. A. We measured: 1) transparietal gastric potential difference (PD) in vivo (by means of agar-KCl electrodes); 2) mucus (by binding of Alcian blue): in gastric mucosa; adherent to gastric mucosa; in gastric lumen; 3) dry weight of the stomach. Avit. A induced: i) a decrease of PD and mucus in mucosa and lumen; ii) an increase of mucus adherent to mucosa; iii) an increase of the percentage of dry weight on wet weight. All parameters were normal after recovery from avit. A. Results suggest that avit. A could reduce either mucus synthesis or its erosion. Moreover avit. A might modify mucus structure and sterical configuration of mucosal cells. The alteration of mucosal cell membranes could decrease PD. In conclusion the modifications of some components of rat GB seem specifically caused by avit. A and suggest a protective role of vit. A.     

Identifying population thresholds for flowering plant reproductive success: the marsh gentian (<Emphasis Type="Italic">Gentiana pneumonanthe</Emphasis>) as a flagship species of humid meadows and heathland

The threshold below which population declines impact the effectiveness of plant reproduction is essential for the identification of populations that can no longer spontaneously recover following habitat management or restoration, below the minimum viable population (MVP) size. We hypothesized that risk of reproductive limitation can be evaluated from combined analysis of pollen activity, ovule fertilization and germination in the context of population demographics and fragmentation. The marsh gentian (Gentiana pneumonanthe), a rare emblematic species of European heathland and fen, was investigated at the southern limit of its range in eighteen populations encompassing one to several hundred thousand individuals, spanning small fragments to extensive well-preserved areas. An index of habitat fragmentation was determined from GIS; field surveys determined the ratio of juvenile to reproductive age states; fluorescence microscopy of pistils determined, for each population, the proportion of flowers exhibiting active pollen tube growth. Analysis of seed lots determined the ovule fertilization rate and seed germination capacity. Some of the small populations occupying restricted habitat fragments showed high rates of pollination (100%) and ‘normal’ age state demographics. However, reproductive characters all exhibited exponential rise to maximum relationships with population size, indicating clear tipping points (for pollination, at a threshold of 7 reproductive adults, and for ovule fertilization rate and germination at 42 reproductive adults). Thus although small populations may set seed, exhibit a ‘normal’ age state structure, and may appear viable, reproductive effectiveness declines when population size falls below 42 generative individuals and < 7 is an indicator of strong limitation. Although many remnant populations of G. pneumonanthe are in the order of 50–150 individuals these should be not be considered as MVPs; they are on the brink of calamity.