Vegetation Cover,Tidal Amplitude and Land Area Predict Short-Term Marsh Vulnerability in Coastal Louisiana

The loss of coastal marshes is a topic of great concern, because these habitats provide tangible ecosystem services and are at risk from sea-level rise and human activities. In recent years, a significant effort has gone into understanding and modeling the relationships between the biological and physical factors that contribute to marsh stability. Simulation-based process models suggest that marsh stability is the product of a complex feedback between sediment supply, flooding regime and vegetation response, resulting in elevation gains sufficient to match the combination of relative sea-level rise and losses from erosion. However, there have been few direct, empirical tests of these models, because long-term datasets that have captured sufficient numbers of marsh loss events in the context of a rigorous monitoring program are rare. We use a multi-year dataset collected by the Coastwide Reference Monitoring System that includes transitions of monitored vegetation plots to open water to build and test a predictive model of near-term marsh vulnerability. We found that despite the conclusions of previous process models, elevation change had no ability to predict the transition of vegetated marsh to open water. However, we found that the processes that drive elevation change were significant predictors of transitions. Specifically, vegetation cover in prior year, land area in the surrounding 1 km² (an estimate of marsh fragmentation) and the interaction of tidal amplitude and position in tidal frame were all significant factors predicting marsh loss. This suggests that (1) elevation change is likely better a predictor of marsh loss at timescales longer than we consider in this study and (2) the significant predictive factors affect marsh vulnerability through pathways other than elevation change, such as resistance to erosion. In addition, we found that, while sensitivity of marsh vulnerability to the predictive factors varied spatially across coastal Louisiana, vegetation cover in prior year was the best single predictor of subsequent loss in most sites followed by changes in percent land and tidal amplitude. The model’s predicted land loss rates correlated well with land loss rates derived from satellite data, although agreement was spatially variable. These results indicate (1) monitoring the loss of small-scale vegetation plots can inform patterns of land loss at larger scales, (2) the drivers of land loss vary spatially across coastal Louisiana, and (3) relatively simple models have potential as highly informative tools for bioassessment, directing future research and management planning.     

Sperm aneuploidy and DNA fragmentation in unexplained recurrent pregnancy loss: a multicenter case-control study

Background

Recurrent pregnancy loss (RPL) is defined as the loss of at least three pregnancies in the first trimester. Although the most common cause is embryo aneuploidy, and despite female checkup and couple karyotyping, in about 50% of cases RPL remain unexplained. Male implication has little been investigated and results are discordant. In this context, we conducted a multi-center prospective case-control study to investigate male gamete implication in unexplained RPL.

Methods

A total of 33 cases and 27 controls were included from three university hospitals. We investigated environmental and family factors with a detailed questionnaire and andrological examination, sperm characteristics, sperm DNA/chromatin status using the sperm chromatin structure assay (SCSA) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and sperm aneuploidy using fluorescence in situ hybridization (FISH). The Mann-Whitney test and the Wilcoxon or Fisher exact tests were used. A non-parametric Spearman correlation was performed in order to analyze the relationship between various sperm parameters and FISH and sperm DNA fragmentation results.

Results

We found significant differences between cases and controls in time to conceive, body mass index (BMI), family history of infertility and living environment. In cases, total sperm motility and the percentage of morphologically normal spermatozoa were significantly decreased. No difference was found between cases and controls in sperm DNA fragmentation or chromatin integrity. In cases, spermatozoa with aneuploidy, hyperhaploidy and chromosome 18 disomy were significantly increased.

Conclusions

This prospective case-control study is one of the largest to examine environmental factors, sperm characteristics, sperm DNA fragmentation and chromatin, and chromosome anomalies in spermatozoa in relation to unexplained recurrent pregnancy loss. The originality of our study lies in the comprehensive andrological examination and search for risk factors and fertility history. Further studies are needed to confirm the links between unexplained RPL and a male family history of infertility or miscarriages. The increased sperm aneuploidy observed in unexplained RPL supports a male etiology. These data pave the way for further studies to demonstrate the value of preimplantation genetic screening in men with increased sperm aneuploidy whose partners experience unexplained RPL.

     

Denaturation of β-sheet structure

A two-dimensional Ising model is used to study the thermal denaturation of parallel β-sheet structures in biomolecules.The fraction of intact hydrogen bonds and the excess heat capacity are evaluated as a function of the temperature.     

Viability of Homozygous Deficiencies in Somatic Cells of DROSOPHILA MELANOGASTER

The viability of cells made homozygous for different deficiencies by induced mitotic recombination was examined. The deficiencies varied in length from two to 30 polytene chromosome bands and were distributed over the five major chromosome arms. Among a sample of 30, ten deficiencies were cell viable. Our results show that 12% of the genome is necessary for cell survival, supporting previous estimates of about 5,000 genes in the genome of Drosophila.     

The effect of 2-oxoglutarate and biotin in the release of amino acids by Citrobacter intermedius C3

Excretion of amino acids by Citrobacter intermedius C3 was assayed in a mineral medium with glucose as carbon source. Glutamic acid is the main amino acid excreted in liquid medium and it is also detected at the colonial level in solid medium. Mutants with different behaviour with respect to the excretion of amino acids are studied. The presence of 2-oxoglutarate in the medium induced excretion in all strains. On the other hand when biotin was added to the culture media amino acid excretion was partially reduced.     

Behavior of Somatic Cells Homozygous for Zygotic Lethals in DROSOPHILA MELANOGASTER

The behavior in genetic mosaics of 86 EMS-induced sex-linked lethals has been studied. Seventy-five percent of them are autonomous in gynandromorphs. Forty-three lethals nonviable in sex mosaics have been analyzed in X-ray-induced spots in the abdominal tergites and the imaginal wing derivatives. Of the lethals, 90.7% are homozygous viable in mosaic spots, and only 9.3% have been classified as epidermal cell lethal. Thus, the fraction of the Drosophila genome essential for cell viability has been estimated to be about 420 genes. The phenotypes at the cellular level of some cell-viable mutations altering cell parameters (mitotic orientation, differentiation, etc.) are described.     

Pharmacological Evidence for Calcium Involvement in the Long-Term Processing of Abiotic Stimuli in Plants

Information about abiotic conditions is stored for long periods in plants and, in flax seedlings, can lead to the production of meristems. To investigate the underlying mechanism, flax seedlings were given abiotic stimuli that included a mechanical stimulus (by manipulation), one or two cold shocks, a slow cold treatment and a drought stress and, if these seedlings were then subjected to a temporary (1 to 3 days) depletion of calcium, epidermal meristems were produced in the seedling hypocotyls. This production was inhibited by the addition to the nutrient media of EGTA, ruthenium red, lanthanum or gadolinium that affect calcium availability or calcium transport. Use of these agents revealed a period of vulnerability in information processing that was less than two min for mechanical stimuli and over five min for other abiotic stimuli, consistent with information about mechanical stimuli being stored particularly fast. We propose that external calcium is needed for the transduction/storage of the information for meristem production whilst a temporary depletion of external calcium is needed for the actual production of meristems. Such roles for calcium would be consistent with a mechanism based on ion condensation on charged polymers.Key Words: memory, environmental signals, calcium, pharmacological agents, meristems, bud growth, plants