Seed and seedling predation by vertebrates mediates the effects of adult trees in two temperate tree species.

Specialised natural enemies can locally suppress seeds and seedlings near conspecific adults more than far from them. Whilst this is thought to facilitate species coexistence, the relative contribution of multiple enemies to whether heterospecific seeds and seedlings rather than conspecifics perform better beneath a particular adult species remains less clear, especially in regions with spatially extensive monodominant stands. We designed a field exclusion experiment to separate the effects of fungi, insects and vertebrates on the seedling establishment and early survival of two temperate tree species, Fagus sylvatica and Picea abies, in the adult tree monocultures of these species. Our experiment demonstrates the key role of vertebrates in mediating the effects of adult trees on seeds and seedlings. Due to vertebrates and partly insects, Fagus sylvatica seedlings survived worse beneath conspecific than heterospecific adults and were also outperformed by Picea abies seedlings beneath their own adults. Picea abies seedling establishment was higher beneath conspecific than heterospecific adults, but Fagus sylvatica seedlings outperformed them beneath their own adults. The impact of enemies on Picea abies establishment beneath conspecific adults was less clear. Fungi did not influence seedling establishment and survival. Our findings highlight the need to compare enemy impacts on each seedling species beneath conspecific and heterospecific adults with their impacts on conspecific and heterospecific seedlings beneath a particular adult species. Such evaluations can shed more light on the role of enemies in tree communities by identifying the plant-enemy interactions that facilitate species coexistence and those that promote species monodominance.

Distribution of biomass dynamics in relation to tree size in forests across the world.

Tree size shapes forest carbon dynamics and determines how trees interact with their environment, including a changing climate. Here, we conduct the first global analysis of among-site differences in how aboveground biomass stocks and fluxes are distributed with tree size. We analyzed repeat tree censuses from 25 large-scale (4-52 ha) forest plots spanning a broad climatic range over five continents to characterize how aboveground biomass, woody productivity, and woody mortality vary with tree diameter. We examined how the median, dispersion, and skewness of these size-related distributions vary with mean annual temperature and precipitation. In warmer forests, aboveground biomass, woody productivity, and woody mortality were more broadly distributed with respect to tree size. In warmer and wetter forests, aboveground biomass and woody productivity were more right skewed, with a long tail towards large trees. Small trees (1-10 cm diameter) contributed more to productivity and mortality than to biomass, highlighting the importance of including these trees in analyses of forest dynamics. Our findings provide an improved characterization of climate-driven forest differences in the size structure of aboveground biomass and dynamics of that biomass, as well as refined benchmarks for capturing climate influences in vegetation demographic models.

Beyond direct neighbourhood effects: higher-order interactions improve modelling and predicting tree survival and growth.

It is known that biotic interactions are the key to species coexistence and maintenance of species diversity. Traditional studies focus overwhelmingly on pairwise interactions between organisms, ignoring complex higher-order interactions (HOIs). In this study, we present a novel method of calculating individual-level HOIs for trees, and use this method to test the importance of size- and distance-dependent individual-level HOIs to tree performance in a 25-ha temperate forest dynamic plot. We found that full HOI-inclusive models improved our ability to model and predict the survival and growth of trees, providing empirical evidence that HOIs strongly influence tree performance in this temperate forest. Specifically, assessed HOIs mitigate the competitive direct effects of neighbours on survival and growth of focal trees. Our study lays a foundation for future investigations of the prevalence and relative importance of HOIs in global forests and their impact on species diversity.

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity.

Response to Comment on "Plant diversity increases with the strength of negative density dependence at the global scale".

Hülsmann and Hartig suggest that ecological mechanisms other than specialized natural enemies or intraspecific competition contribute to our estimates of conspecific negative density dependence (CNDD). To address their concern, we show that our results are not the result of a methodological artifact and present a null-model analysis that demonstrates that our original findings-(i) stronger CNDD at tropical relative to temperate latitudes and (ii) a latitudinal shift in the relationship between CNDD and species abundance-persist even after controlling for other processes that might influence spatial relationships between adults and recruits.

Response to Comment on "Plant diversity increases with the strength of negative density dependence at the global scale".

Chisholm and Fung claim that our method of estimating conspecific negative density dependence (CNDD) in recruitment is systematically biased, and present an alternative method that shows no latitudinal pattern in CNDD. We demonstrate that their approach produces strongly biased estimates of CNDD, explaining why they do not detect a latitudinal pattern. We also address their methodological concerns using an alternative distance-weighted approach, which supports our original findings of a latitudinal gradient in CNDD and a latitudinal shift in the relationship between CNDD and species abundance.

Plant diversity increases with the strength of negative density dependence at the global scale.

Theory predicts that higher biodiversity in the tropics is maintained by specialized interactions among plants and their natural enemies that result in conspecific negative density dependence (CNDD). By using more than 3000 species and nearly 2.4 million trees across 24 forest plots worldwide, we show that global patterns in tree species diversity reflect not only stronger CNDD at tropical versus temperate latitudes but also a latitudinal shift in the relationship between CNDD and species abundance. CNDD was stronger for rare species at tropical versus temperate latitudes, potentially causing the persistence of greater numbers of rare species in the tropics. Our study reveals fundamental differences in the nature of local-scale biotic interactions that contribute to the maintenance of species diversity across temperate and tropical communities.

Expanded conventional first trimester screening.

OBJECTIVE: The study aims to determine the performance of a five (5) serum marker plus ultrasound screening protocol for T21, T18 and T13. METHOD: Specimens from 331 unaffected, 34 T21, 19 T18 and 8 T13 cases were analyzed for free Beta human chorionic gonadotropin, pregnancy-associated plasma protein A, alpha-fetoprotein, placental growth factor and dimeric inhibin A. Gaussian distributions of multiples of the median values were used to estimate modeled false positive and detection rates (DR). RESULTS: For T21, at a 1/300 risk cut-off, DR of screening with all five serum markers along with nuchal translucency and nasal bone was 98% at a 1.2% false positive rate (FPR). Using a 1/1000 cut-off, the DR was 99% with a 2.6% FPR. For T18/13 with free Beta human chorionic gonadotropin, pregnancy-associated plasma protein A, placental growth factor and nuchal translucency at a 1/150 cut-off, DR was 95% at a 0.5% FPR while at a 1/500 risk cut-off, DR was 97% at a 1.2% FPR. CONCLUSION: An expanded conventional screening test can achieve very high DRs with low FPRs. Such screening fits well with proposed contingency protocols utilizing cell-free DNA as a secondary or reflex but also provides the advantages of identification of pregnancies at risk for other adverse outcomes such as early-onset preeclampsia. © 2017 Eurofins NTD, LLC. Prenatal Diagnosis published by John Wiley & Sons, Ltd.

Incorporation of dried blood alpha fetoprotein into traditional first trimester Down syndrome screening service.

OBJECTIVE: The aim of this study was to determine whether incorporation of dried blood alpha fetoprotein (AFP) into first trimester screening using the biochemical markers free Beta human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein A (PAPP-A) can improve screening performance. METHODS: A retrospective study of 34 Down syndrome and 1185 unaffected dried blood specimens. First trimester dried blood AFP was performed using in-house immunofluorometric time-resolved assay. False positive and detection rates were determined from modeling. RESULTS: The multiple of the median in Down syndrome cases was 0.73. At a fixed 5% false positive rate, incorporating AFP into a free Beta hCG, PAPP-A, and nuchal translucency protocol adds 2% detection resulting in detection rates of 92% to 94% depending on the gestational age of the blood draw. At a fixed 90% detection rate, AFP reduced the false positive rate by 1.0 to 1.6 percentage points depending on gestational age. Using a cutoff of 1/1000, the combination of free beta hCG, PAPP-A, AFP, and nuchal translucency achieved a detection rate of 96% with a false positive rate of 8.4% to 9.9%. Adding in nasal bone increased detection to 98% while reducing false positive rates to 4.1% to 4.7%. CONCLUSION: Inclusion of dried blood AFP into traditional first trimester screening improves detection while optimizing contingent protocols so that cell-free fetal DNA testing may be offered in a more cost effective manner.

Staphylococcal Enterotoxin B (SEB) Induces Memory CD4 T Cell Anergy in vivo and Impairs Recall Immunity to Unrelated Antigens.

INTRODUCTION: Naïve and memory T cells can utilize unique regulatory pathways to promote protection but prevent self-reactivity. A bacterial superantigen SEB exploits unique TCR proximal signaling processes in memory CD4 T cells to induce clonal anergy. The aim of this study was to determine if SEB could antagonize memory CD4 T cells in vivo and whether there would be consequences on recall immune responses. We evaluated Ab responses to a T-dependent antigen as a measurement of memory T cell helper function. METHOD: BALB/c mice were primed with TNP-RGG to elicit memory B cells and also immunized with an ovalbumin peptide to elicit memory helper T cells. Another group of TNP-RGG immunized mice were used as adoptive transfer recipients of exogenous DO11.10 memory T cells. Mice were challenged with TNP-OVA with or without prior administration of SEB. B cells secreting IgM or IgG TNP-specific Ab were enumerated by ELISPOT as indicators of primary versus secondary humoral immunity. RESULTS: Comparing the SEB and non-SEB-treated groups, the SEB-treated group failed to produce TNP-specific IgG in response to challenge with TNP-OVA, even if they were previously immunized with OVA. All groups produced IgM, indicating that the primary Ab responses and naïve helper T cells were not impacted by SEB. SEB had no negative impact when DO11.10 × Fyn-/- memory T cells were used as donor cells. CONCLUSION: The present study indicated that SEB selectively targeted memory CD4 T cells in vivo and prevented helper function. Consequently, recall humoral immunity was lost. The data are most consistent with in vivo T cell anergy as opposed to indirect suppression as elimination of Fyn kinase restored helper function. These data suggest that bacterial superantigens can impair post-vaccination memory cell responses to unrelated antigens via their ability to target Vb families and antagonize memory cell activation.

Maternal Serum Screening Markers and Adverse Outcome: A New Perspective.

There have been a number of studies evaluating the association of aneuploidy serum markers with adverse pregnancy outcome. More recently, the development of potential treatments for these adverse outcomes as well as the introduction of cell-free fetal DNA (cffDNA) screening for aneuploidy necessitates a re-evaluation of the benefit of serum markers in the identification of adverse outcomes. Analysis of the literature indicates that the serum markers tend to perform better in identifying pregnancies at risk for the more severe but less frequent form of individual pregnancy complications rather than the more frequent but milder forms of the condition. As a result, studies which evaluate the association of biomarkers with a broad definition of a given condition may underestimate the ability of such markers to identify pregnancies that are destined to develop the more severe form of the condition. Consideration of general population screening using cffDNA solely must be weighed against the fact that traditional screening using serum markers enables detection of severe pregnancy complications, not detectable with cffDNA, of which many may be amenable to treatment options.

Superantigen-induced CD4 memory T cell anergy. I. Staphylococcal enterotoxin B induces Fyn-mediated negative signaling.

Memory CD4 T cells must provide robust protection for an organism while still maintaining self-tolerance. Superantigens reveal a memory cell-specific regulatory pathway, by which signaling through the TCR can lead to clonal tolerance (anergy). Here we show that the src kinase Fyn is a critical regulator of anergy in murine memory CD4 T cells induced by the bacterial superantigen staphylococcal enterotoxin B (SEB). Exposure to SEB results in impaired TCR signaling due to failed CD3/ZAP-70 complex formation. Further, signal transduction through the TCR remains similarly blocked when anergic memory cells are subsequently exposed to agonist peptide antigen. Pharmacological inhibition or genetic elimination of Fyn kinase reverses memory cell anergy, resulting in SEB-induced cell proliferation. The mechanism underlying impaired TCR signaling and subsequent memory cell anergy must involve a Fyn signaling pathway given that the suppression of Fyn activity restores CD3/ZAP-70 complex formation and TCR proximal signaling.

A microsphere-based assay for mutation analysis of the biotinidase gene using dried blood spots.

Biotinidase deficiency is an autosomal recessive syndrome caused by defects in the biotinidase gene, the product of which affects biotin metabolism. Newborn screening (NBS) for biotinidase deficiency can identify affected infants prior to onset of symptoms; biotin supplementation can resolve or prevent the clinical features. In NBS, dry blood spots (DBS) are usually tested for biotinidase enzyme activity by colorimetric analysis. By taking advantage of the multiplexing capabilities of the Luminex platform, we have developed a microsphere-based array genotyping method for the simultaneous detection of six disease causing mutations in the biotinidase gene, thereby permitting a second tier of molecular analysis. Genomic DNA was extracted from 3.2 mm DBS. Biotinidase gene sequences, containing the mutations of interest, were amplified by multiplexed polymerase chain reaction, followed by multiplexed allele-specific primer extension using universally tagged genotyping primers. The products were then hybridized to anti-tag carrying xTAG microspheres and detected on the Luminex platform. Genotypes were verified by sequencing. Genotyping results of 22 known biotinidase deficient samples by our xTAG biotinidase assay was in concordance with the results obtained from DNA sequencing, for all 6 mutations used in our panel. These results indicate that genotyping by an xTAG microsphere-based array is accurate, flexible, and can be adapted for high-throughput. Since NBS for biotinidase deficiency is by enzymatic assay, less than optimal quality of the DBS itself can compromise enzyme activity, while the DNA from these samples mostly remains unaffected. This assay warrants evaluation as a viable complement to the biotinidase semi-quantitative colorimetric assay.

A multiplex immunoassay using the Guthrie specimen to detect T-cell deficiencies including severe combined immunodeficiency disease.

BACKGROUND: Severe combined immunodeficiency (SCID) fulfills many of the requirements for addition to a newborn screening panel. Two newborn screening SCID pilot studies are now underway using the T-cell receptor excision circle (TREC) assay, a molecular technique. Here we describe an immunoassay with CD3 as a marker for T cells and CD45 as a marker for total leukocytes that can be used with the Guthrie specimen. METHODS: The multiplexing capabilities of the Luminex platform were used. Antibody pairs were used to capture and detect CD3 and CD45 from a single 3-mm punch of the Guthrie specimen. The assay for each biomarker was developed separately in identical buffers and then combined to create a multiplex assay. RESULTS: Using calibrators made from known amounts of leukocytes, a detection limit of 0.25 x 10(6) cells/mL for CD3 and 0.125 x 10(6) cells/mL for CD45 was obtained. Affinity tests showed no cross-reactivity between the antibodies to CD3 and CD45. The multiplex assay was validated against 8 coded specimens of known clinical status and linked to results from the TREC assay that had identified them. All were correctly identified by the CD345 assay. CONCLUSIONS: The performance parameters of the CD345 assay met the performance characteristics generally accepted for immunoassays. Our assay classifications of positive specimens concur with previous TREC results. This CD345 assay warrants evaluation as a viable alternative or complement to the TREC assay as a primary screening tool for detecting T-cell immunodeficiencies, including SCID, in Guthrie specimens.

Laterally spreading tumors--experience based on 138 consecutive cases.

BACKGROUND/AIMS: Laterally spreading tumors (LST) are flat elevated neoplastic lesions with diameters equal to or greater than 10 mm. The treatment results of 138 lesions in 131 patients are presented here as a part of a retrospective analysis. METHODOLOGY: Two gastroenterology centers participated in the study in the period from 1/2002-12/2006. During colonoscopy, each superficial lesion was classified according to the Paris endoscopic classification. Endoscopic mucosal resection (EMR) lift and cut was employed. Treatment was considered successful when both endoscopic and histo-pathological criteria of complete resection were fulfilled. RESULTS: A total of 138 LST in 131 patients were diagnosed. Average LST diameter was 25 mm. A total of 5 (3.6%) lesions in 4 patients were referred for primary surgery. One patient was treated with argon plasma coagulation only. EMR was attempted for 132/138 (95.7%) of all LST and was successful in 125 (90.6%) cases. Complications occured in 16/132 (12.1%) patients. Severe complications, defined as decession, emergency surgery, emergency endoscopy and transfusion of eryhrocyte concentrate occured in 5/132 (3.8%). One (0.7%) 69 year-old-male patient died on the third day following EMR due to complications of acute myocardial infarction. CONCLUSION: LST lesions could be efficiently treated with EMR lift and cut method with a reasonable rate of complications.