Effects of Species, Density, Patch-type, and Season on Post-dispersal Seed Predation in a Puerto Rican Pasture1

An experimental study of seed removal of four woody species in an abandoned pasture revealed significant main effects of species, density (higher densities survived more than lower densities), and patch‐type (seeds under shrub patches survived more than in grass patches), but no effects of season. Rates of seed loss decreased with seed size across species. Significant interactions between species and density and between species and patch‐type were also observed.     

Development of motavizumab, an ultra-potent antibody for the prevention of respiratory syncytial virus infection in the upper and lower respiratory tract

Respiratory syncytial virus (RSV) is the leading cause of viral bronchiolitis and pneumonia in infants and children. Currently, palivizumab is the only approved monoclonal antibody (mAb) for prophylaxis of RSV. However, a small percentage of patients are not protected by palivizumab; in addition, palivizumab does not inhibit RSV replication effectively in the upper respiratory tract. We report here the development and characterization of motavizumab, an ultra-potent, affinity-matured, humanized mAb derived from palivizumab. Several palivizumab variants that enhanced the neutralization of RSV in vitro by up to 44-fold were generated; however, in vivo prophylaxis of cotton rats with these antibodies conferred only about a twofold improvement in potency over palivizumab. This unexpected small increase of in vivo potency was caused by poor serum pharmacokinetics and lung bio-availability that resulted from unexpectedly broad tissue binding. Subsequent analyses revealed that changes at three amino acids arising from the affinity maturation markedly increased the non-specific binding to various tissues. Our results suggested that k(on)-driven mutations are more likely to initiate non-specific binding events than k(off)-driven mutations. Reversion of these three residues to the original sequences greatly diminished the tissue binding. The resulting mAb, motavizumab, binds to RSV F protein 70-fold better than palivizumab, and exhibits about a 20-fold improvement in neutralization of RSV in vitro. In cotton rats, at equivalent concentrations, motavizumab reduced pulmonary RSV titers to up to 100-fold lower levels than did palivizumab and, unlike palivizumab, motavizumab very potently inhibited viral replication in the upper respiratory tract. This affinity-enhanced mAb is being investigated in pivotal clinical trials. Importantly, our engineering process offers precious insights into the improvement of other therapeutic mAbs.     

Variability in the bioluminescence response of the dinoflagellate Pyrocystis lunula

Light emission in dinoflagellates is induced by water motions. But although it is known that mechanical stimulations of these organisms trigger the bioluminescent response, the exact mechanism that involves some cell membrane excitations by fluid motions is not yet fully understood and is still controversial. We show in this experimental study that the accelerated shear flow, created by abrupt rotations of one or both co-axial cylinders of a Couette shearing chamber excites the light emission from cultured dinoflagellates Pyrocystis lunula. Following our first results published earlier that state that pure laminar shear does not excite the main bioluminescent response in dinoflagellates, our present experiments show that both shear and acceleration in the flow are needed to trigger the bioluminescent response. Besides, the probability to stimulate this bioluminescent response under acceleration and shear is deduced from the response curves. This response follows a Gaussian distribution that traduces a heterogeneity in individual cell thresholds for the stimulation of bioluminescence in a dinoflagellate population. All these results will have a repercussion in the possible applications of dinoflagellate bioluminescence in flow visualizations and measurements. Moreover, this study opens a new way in studying mechanically-induced stimulus thresholds at the cell level.     

Red-Headed Woodpecker Nest-Habitat Thresholds in Restored Savannas

Abstract: The red-headed woodpecker (Melanerpes erythrocephalus) is a widespread, adaptable species that continues to decline across North America. We examined stand, nest-tree, and cavity characteristics of red-headed woodpeckers in restored savannas within the Necedah National Wildlife Refuge, Wisconsin, USA, during 2002 and 2003. Based on availability, red-headed woodpeckers selected snags and trees with greater dead limb length. Red-headed woodpeckers nested in areas with greater basal area, cavity density, snag density, limb-tree density, and total dead limb length. Red-headed woodpeckers exhibited a decadent-tree threshold that was most accurately measured by the number of trees with dead limbs around (0.04 ha) nests. We found that the probability of a red-headed woodpecker nest being present greatly increased above the decadent-tree threshold. Woodland managers throughout the red-headed woodpecker's extensive breeding range can use our results and recommendations to guide decadent-tree retention for this species.     

Evaluation of quantification methods for real-time PCR minor groove binding hybridization probe assays

Real-time PCR data analysis for quantification has been the subject of many studies aimed at the identification of new and improved quantification methods. Several analysis methods have been proposed as superior alternatives to the common variations of the threshold crossing method. Notably, sigmoidal and exponential curve fit methods have been proposed. However, these studies have primarily analyzed real-time PCR with intercalating dyes such as SYBR Green. Clinical real-time PCR assays, in contrast, often employ fluorescent probes whose real-time amplification fluorescence curves differ from those of intercalating dyes. In the current study, we compared four analysis methods related to recent literature: two versions of the threshold crossing method, a second derivative maximum method, and a sigmoidal curve fit method. These methods were applied to a clinically relevant real-time human herpes virus type 6 (HHV6) PCR assay that used a minor groove binding (MGB) Eclipse hybridization probe as well as an Epstein-Barr virus (EBV) PCR assay that used an MGB Pleiades hybridization probe. We found that the crossing threshold method yielded more precise results when analyzing the HHV6 assay, which was characterized by lower signal/noise and less developed amplification curve plateaus. In contrast, the EBV assay, characterized by greater signal/noise and amplification curves with plateau regions similar to those observed with intercalating dyes, gave results with statistically similar precision by all four analysis methods.     

内蒙古呼伦贝尔草甸草原的草地退化等级数量分析

采用样方取样方法实地调查内蒙古呼伦贝尔草甸草原的植物群落特征,利用植被和土壤数据,应用系统聚类分析方法对其草地退化等级进行定量划分.结果表明:(1)植被指标聚类可将草地划分为3个等级,即轻度退化、中度退化和重度退化草地,而利用土壤指标聚类则划分为2个等级,其中轻度退化和中度退化草地的土壤状况相似合为一个等级,重度退化草地为另一个等级;(2)随着放牧梯度的变化,植被和土壤都发生了变化,中度退化草地植被变化大,而土壤变化不大;(3)内蒙古呼伦贝尔草甸草原为同一草地利用单元,所划分的草地退化等级系列是由放牧引起的.     

三种群互惠模型抛物系统解的整体存在与爆破

研究了三种群互惠模型的抛物系统,用上下解方法研究解的整体存在性与爆破问题,并给出了相应的条件.结果表明当种群自身的竞争强时解整体存在,反之则有可能爆破.     

混合拟单调系统行波解的存在性

运用单调迭代方法,证明了混合拟单调系统的行波解的存在性．当反应扩散系。统的反应函数是混合拟单调函数时,如果选取一对合适的耦合上下解作为迭代初值,则迭代序列将收敛到一对拟解．而且在这对拟解之间存在系统的行波解．     

A periodic analysis of longitudinal binary responses: a case study of clinical mastitis in Norwegian Red cows

A Bayesian procedure for analyzing longitudinal binary responses using a periodic cosine function was developed. It was assumed that, after adjustment for "seasonal" effects, the oscillation of the underlying latent variables for longitudinal binary responses was a stationary series. Based on this assumption, a single dimension sinusoidal analysis of longitudinal binary responses using the Gibbs sampling and Metropolis algorithms was implemented in a study of clinical mastitis records of Norwegian Red cows taken over five lactations.     

Genetic relationship of discrete-time survival with fertility and production in dairy cattle using bivariate models

Bivariate analyses of functional longevity in dairy cattle measured as survival to next lactation (SURV) with milk yield and fertility traits were carried out. A sequential threshold-linear censored model was implemented for the analyses of SURV. Records on 96 642 lactations from 41 170 cows were used to estimate genetic parameters, using animal models, for longevity, 305 d-standardized milk production (MY305), days open (DO) and number of inseminations to conception (INS) in the Spanish Holstein population; 31% and 30% of lactations were censored for DO and INS, respectively. Heritability estimates for SURV and MY305 were 0.11 and 0.27 respectively; while heritability estimates for fertility traits were lower (0.07 for DO and 0.03 for INS). Antagonist genetic correlations were estimated between SURV and fertility (-0.78 and -0.54 for DO and INS, respectively) or production (-0.53 for MY305), suggesting reduced functional longevity with impaired fertility and increased milk production. Longer days open seems to affect survival more than increased INS. Also, high productive cows were more problematic, less functional and more liable to being culled. The results suggest that the sequential threshold model is a method that might be considered at evaluating genetic relationship between discrete-time survival and other traits, due to its flexibility.