In and out: Effects of shoot- vs. rooted-presence sampling methods on plant diversity measures in mountain grasslands

Plant diversity measures (e.g., alpha- and beta-diversity) provide the basis for a number of ecological indication and monitoring methods. These measures are based on species counts in sampling units (plots or quadrats). However, there are two alternative conventions for defining a vascular plant species as “present” in a plot, i.e. “shoot presence” (a species is recorded if the vertical projection of any above-ground part falls within the plot) and “rooted presence” (a species is recorded only when an individual is rooted inside the plot). Very few studies addressed the effects of the two sampling conventions on species richness and diversity indices. We sampled mountain dry grasslands in Italy across different plot sizes and vegetation types to assess how large is the difference in alpha- and beta-diversity values and in sample-based rarefaction curves between the two methods. We found that the difference is greatly dependent on plot size, being more relevant, both in absolute and percentage values, at smaller grain; it is also dependent on habitat type, being larger in shallow-soil communities, as they have a sparser vegetation structure and host life-form types with a larger lateral spread. At fine spatial scales (<1 m²) the difference is large enough to bias statistical inference, and we conclude that at such scales one should not attempt to compare plant diversity indices if they were not obtained with the same sampling convention.     

The role of histidine residues in the alpha toxin of Clostridium perfringens

The α -toxin (phospholipase C) of Clostridium perfringens has been reported to contain catalytically essential zinc ions We report here that histidine residues are essential for the co-ordination of these ion(s). Incubation of alpha toxin with diethylpyrocarbonate, a histidine modifying reagent, did not result in the loss of phospholipase C activity unless the protein was first incubated with EDTA, suggesting that zinc ions normally protect the susceptible histidine residues. When the amino acid sequences of three phospholipase C's were aligned, essential zinc binding histidine residues in the non-toxic B. cereus phospholipase C were found in similar positions in the toxic C. perfringens enzyme and the weakly toxic C. bifermentans phospholipase C.     

Genetic diversity of dispersed seeds is highly variable among leks of the long-wattled umbrellabird

Frugivorous animals frequently generate clumped distributions of seeds away from source trees, but genetic consequences of this phenomenon remain poorly resolved. Seed dispersal of the palm Oenocarpus bataua by long-wattled umbrellabirds Cephalopterus penduliger generates high seed densities in leks (i.e., multi-male display sites), providing a suitable venue to investigate how dispersal by this frugivore may influence seed source diversity and genetic structure at local and landscape levels. We found moderate levels of maternal seed source diversity in primary seed rain across five leks in northwest Ecuador (unweighted mean alpha diversity α = 9.52, weighted mean α_r = 3.52), with considerable variation among leks (α_r range: 1.81–24.55). Qualitatively similar findings were obtained for allelic diversity and heterozygosity. Higher densities of O. bataua adults around leks were associated with higher values of α_r and heterozygosity (non-significant trends) and allelic diversity (significant correlation). Seed source overlap between different leks was not common but did occur at low frequency, providing evidence for long-distance seed dispersal by umbrellabirds into leks. Our findings are consistent with the idea that seed pool diversity within leks may be shaped by the interaction between density of local trees, which can vary considerably between leks, and umbrellabird foraging ecology, particularly a lack of territorial defense of fruiting trees. Taken as a whole, this work adds to our growing appreciation of the ways resource distribution and associated frugivore foraging behaviors mechanistically shape seed dispersal outcomes and the distribution of plant genotypes across the landscape.     

AFP蛋白芯片技术的检测流程优化

目的:通过优化现有的蛋白芯片检测过程,在保证检测准确性的同时缩短甲胎蛋白(Alpha Fetal protein,AFP)的检测时间,提高检测效率,为原发性肝癌的筛查提供经济、便捷、省时、有效的检测方法。方法:本研究在传统蛋白芯片检测流程(1-1.5小时)的基础上,通过优化检测流程将检测时间缩短至18分钟,并且通过和传统方法进行比较,评价该优化方法的检测效能。结果:与传统蛋白芯片检测方法相比,本优化方法的检测时间缩短至18分钟。重复检测同一样本,传统方法 AFP水平为16.50±1.172ng/m L,优化方法 AFP水平为18.33±1.029 ng/m L,结果无明显统计学差异(P=0.251)。结论:本研究成功地优化了AFP的蛋白芯片检测流程,在缩短检测时间的同时,保证了检测的准确率,是一种经济省时易操作的AFP检测方法。     

Do U.S. county data disprove linear no‐threshold predictions of lung cancer risk for residential radon?‐A preliminary assessment of biological plausibility

Lung‐cancer mortality (LCM) is elevated in underground miners who chronically inhaled the mutagenic, cytotoxic α‐decay products of radon gas. Epidemiologie studies of LCM rates vs. residential‐radon concentration levels are generally considered inconclusive. However, Cohen (Health Physics 68, 157–174, 1995) has hypothesized that data on LCM vs. residential radon concentrations at the U.S. county level are clearly inconsistent with a linear no‐threshold (LN) dose‐response model, and rather are consistent with threshold or hormesis model. Cohen's hypothesis has been criticized as “ecological fallacy,”; particularly because LN (but not threshold or hormesis) models are generally considered biologically plausible for agents like α radiation that damage DNA in linear proportion to dose. To assess the biological plausibility of Cohen's hypothesis, a preliminary study was made of whether a biologically realistic, cytodynamic 2‐stage (CD2) cancer model can provide a good, joint fit to Cohen's set of U.S. county data as well as to underground‐miner data. The CD2 model used adapts a widely applied, mechanistic, 2‐stage stochastic model of carcinogenesis to realistically account for interrelated cell killing and mutation (both assumed to have a LN dose‐response), cell turnover, and incomplete exposure of stem cells. A CD2 fit was obtained to combined summary data on LCM vs. radon‐exposure in white males in 1, 601 U.S. counties (from Cohen) and in white male Colorado Plateau (CP) uranium miners (from the National Research Council's “BEIRIV”; report). The CD2 fit is shown to: (i) be consistent with the combined data; (ii) have parameter values all consistent with biological data; and (iii) predict inverse dose‐rate‐effects data for CP and other radon‐exposed miners, despite the fact that optimization had not involved any of these dose‐rate data. The latter data were not predicted by a simplified CD2 model in which all stem cells were presumed to be exposed. It is concluded that this study provides preliminary evidence that Cohen's hypothesis is biologically plausible.     

Heat shock factor 4 regulates lens epithelial cell homeostasis by working with lysosome and anti-apoptosis pathways

Activation of Heat shock factor 4-mediated heat shock response is closely associated with postnatal lens development. HSF4 controls the expression of small heat shock proteins (e.g. HSP25 and CRYAB) in lens epithelial cells. However, their roles in modulating lens epithelium homeostasis remain unclear. In this paper, we find that HSF4 is developmentally expressed in mouse lens epithelium and fiber tissue. HSF4 and alpha B-crystallin can selectively protect lens epithelial cells from cisplatin and H2O2 induced apoptosis by stabilizing mitochondrial membrane potential (ΔY_m) and reducing ROS production. In addition, to our surprise, HSF4 is involved in upregulating lysosome activity. We found mLEC/HA-Hsf4 cells to have increased DLAD expression, lysosome acidity, cathepsin B activity, and degradation of plasmid DNA and GFP-LC3 protein when compared to mLEC/Hsf4-/- cells. Knocking down Cryab from mLEC/HA-Hsf4 cells inhibits HSF4-mediated lysosome acidification, while overexpression of CRYAB can upregulate cathepsin B activity in mLEC/Hsf4-/- cells. CRAYAB can interact with ATP6V1/A the A subunit of the H⁺ pump vacuolar ATPase, and is colocalized to lamp1 and lamp2 in the lysosome. Collectively, these results suggest that in addition to modulating anti-apoptosis, HSF4 is able to regulate lysosome activity by at least controlling alpha B-crystallin expression, shedding light on a novel molecular mechanism of HSF4 in regulating lens epithelial cell homeostasis.     

Fatty Acids and Squalene Carried by Alpha Fetoprotein, and Fetal and Adult Serum Albumin from Chicken. Comparison with These from Mammals

Alpha fetoprotein (C-AFP), serum albumin (C-fSA) from chicken embryos, and SA from hens were purified using gentle chromatographic and electrophoretic methods, and their fatty acids (FAs) and squalene contents were analyzed using gas chromatography and mass spectrometry. In 7-day-old chick embryo, AFP carries 16% and fSA 6% free FAs, the rest being carried as phospholipids, which differs from rat and pig AFP, where all fatty acids are carried like free fatty acids. At this stage C-AFP contains 3.6% arachidonic acid, which falls to 1.7% in 14-day-old embryos. Both of these figures are significantly lower than in humans, rats, calves, and pigs. C-AFP does not transport docosahexaenoic acid, in notable contrast to the mammals mentioned above. The finding of squalene in the two fetal proteins is reported for the first time. During the interval between 7 and 14 days, the proportion of C16:1 n-7 and of C18:2 n-6 increases 10-fold, that of C18:0 quadruples, and that of C18:1 n-9 decreases 3-fold. Squalene increases in this period from 2.2% to 10.0%. The C-fSA of a 7-day-old embryo transports only one FA with more than two unsaturated carbons, arachidonic acid (2.4%). It also contains squalene (1.2%). Similarly, only arachidonic acid (2.5%), but not squalene is found in hen SA. The percentage of saturated and monounsaturated FAs divided by the percentage of polyunsaturated FAs, and the ratios of the percentage of FAs with C14–C18 with respect to those with C20–C22 transported by C-AFP are very different from those of studied mammals.     

The track structures of ionizing particles and their application to radiation biophysics

A new approach to the interpretation of the effects of radiation on cells is described, in which sample particle tracks are constructed using a Monte Carlo computer program and the exposure of cellular targets to these tracks is simulated using a second program known as BIOPHYS. Data on the shapes and DNA contents of the cell nuclei are obtained from the literature. It is assumed that the sensitive material is DNA, and that the target is divided into cubes of approximately 2 nm (the diameter of the DNA helix) per side; the numbers of these cubes containing different numbers of ionizations are derived. Two different methods of analysing the output of BIOPHYS are described. In the first, it is assumed that lethality is caused by the occurrence of a number of ionizations equal to or greater than a certain threshold in one cube; in the second method, it is assumed that only two ionizations are required, in different parts of the cube, but that only some fraction of the cube is sensitive. These models have been applied to the interpretation of the variation of radiosensitivity with a linear energy transfer (LET) of spores of Bacillus subtilis exposed wet and dry, and good fits to the published experimental data were obtained using both models. Fits to experimental data for a range of other cell lines will be presented in a second paper. Received: 5 August 1998 / Accepted in revised form: 28 April 1999