Specific Inhibition of Lignification in Bryonia dioica: Effects on Thigmomorphogenesis

Rubbing-induced lignification in Bryonia dioica internodes is significantly impaired by N(o-hydroxyphenyl) and N(o-aminophenyl) sulfinamoyl tertiobutyl acetate, specific inhibitors of cinnamyl alcohol dehydrogenase, an enzyme which is strictly associated with lignin monomer synthesis. Along with the reduction of lignification, these inhibitors counteract the inhibition of elongation due to rubbing. These results indicate that lignification participates in the thigmomorphogenetic growth response of Bryonia dioica internodes. In a general way, the data point to the causal role of lignification in the limitation of plant growth.     

The effects of temperature and nutrients on the growth and dynamics of toxic and non-toxic strains of Microcystis during cyanobacteria blooms

In temperate latitudes, toxic cyanobacteria blooms often occur in eutrophied ecosystems during warm months. Many common bloom-forming cyanobacteria have toxic and non-toxic strains which co-occur and are visually indistinguishable but can be quantified molecularly. Toxic Microcystis cells possess a suite of microcystin synthesis genes (mcyA–mcyJ), while non-toxic strains do not. For this study, we assessed the temporal dynamics of toxic and non-toxic strains of Microcystis by quantifying the microcystin synthetase gene (mcyD) and the small subunit ribosomal RNA gene, 16S (an indicator of total Microcystis), from samples collected from four lakes across the Northeast US over a two-year period. Nutrient concentrations and water quality were measured and experiments were conducted which examined the effects of elevated levels of temperatures (+4 °C), nitrogen, and phosphorus on the growth rates of toxic and non-toxic strains of Microcystis. During the study, toxic Microcystis cells comprised between 12% and 100% of the total Microcystis population in Lake Ronkonkoma, NY, and between 0.01% and 6% in three other systems. In all lakes, molecular quantification of toxic (mcyD-possessing) Microcystis was a better predictor of in situ microcystin levels than total cyanobacteria, total Microcystis, chlorophyll a, or other factors, being significantly correlated with the toxin in every lake studied. Experimentally enhanced temperatures yielded significantly increased growth rates of toxic Microcystis in 83% of experiments conducted, but did so for non-toxic Microcystis in only 33% of experiments, suggesting that elevated temperatures yield more toxic Microcystis cells and/or cells with more mcyD copies per cell, with either scenario potentially yielding more toxic blooms. Furthermore, concurrent increases in temperature and P concentrations yielded the highest growth rates of toxic Microcystis cells in most experiments suggesting that future eutrophication and climatic warming may additively promote the growth of toxic, rather than non-toxic, populations of Microcystis, leading to blooms with higher microcystin content.     

Telemetered electromyography of peroneus longus in Varecia variegata and Eulemur rubriventer: implications for the functional significance of a large peroneal process

A foot specialized for grasping small branches with a divergent opposable hallux (hallucal grasping) represents a key adaptive complex characterizing almost all arboreal non-human euprimates. Evolution of such grasping extremities probably allowed members of a lineage leading to the common ancestor of modern primates to access resources available in a small-branch niche, including angiosperm products and insects. A better understanding of the mechanisms by which euprimates use their feet to grasp will help clarify the functional significance of morphological differences between the euprimate grasp complex and features representing specialized grasping in other distantly related groups (e.g., marsupials and carnivorans) and in closely related fossil taxa (e.g., plesiadapiforms). In particular, among specialized graspers euprimates are uniquely characterized by a large peroneal process on the base of the first metatarsal, but the functional significance of this trait is poorly understood. We tested the hypothesis that the large size of the peroneal process corresponds to the pull of the attaching peroneus longus muscle recruited to adduct the hallux during grasping. Using telemetered electromyography on three individuals of Varecia variegata and two of Eulemur rubriventer, we found that peroneus longus does not generally exhibit activity consistent with an important function in hallucal grasping. Instead, extrinsic digital flexor muscles and, sometimes, the intrinsic adductor hallucis are active in ways that indicate a function in grasping with the hallux. Peroneus longus helps evert the foot and resists its inversion. We conclude that the large peroneal tuberosity that characterizes the hallucal metatarsal of prosimian euprimates does not correlate to "powerful" grasping with a divergent hallux in general, and cannot specifically be strongly linked to vertical clinging and climbing on small-diameter supports. Thus, the functional significance of this hallmark, euprimate feature remains to be determined.     

Biodiversity effects on productivity and stability of marine macroalgal communities: the role of environmental context

The influence of biodiversity on ecosystem functioning has been the focus of much recent research, but the role of environmental context and the mechanisms by which it may influence diversity effects on production and stability remain poorly understood. We assembled marine macroalgal communities in two mesocosm experiments that varied nutrient supply, and at four field sites that differed naturally in environmental conditions. Concordant with theory, nutrient addition promoted positive species richness effects on algal growth in the first mesocosm experiment; however, it tended to weaken the positive diversity relationship found under ambient conditions in a second experiment the next year. In the field experiments, species richness increased algal biomass production at two of four sites. Together, these experiments indicate that diversity effects on algal biomass production are strongly influenced by environmental conditions that vary over space and time. In decomposing the net biodiversity effect into its component mechanisms, seven of the eight experimental settings showed positive complementarity effects (suggesting facilitation or complementary resource use) countered by negative selection effects (i.e. enhanced growth in mixture of otherwise slow growing species) to varying degrees. Under no conditions, including nutrient enrichment, did we find evidence of positive selection effects commonly thought to drive positive diversity effects. Species richness enhanced stability of algal community biomass across a range of environmental settings in our field experiments. Hence, while species richness can increase production, enhanced stability is also an important functional outcome of maintaining diverse marine macroalgal communities.     

Optimizing Human Synovial Fluid Preparation for Two-Dimensional Gel Electrophoresis

Background

Prenatal screening for Down Syndrome (DS) would benefit from an increased number of biomarkers to improve sensitivity and specificity. Improving sensitivity and specificity would decrease the need for potentially risky invasive diagnostic procedures.

Results

We have performed an in depth two-dimensional difference gel electrophoresis (2D DIGE) study to identify potential biomarkers. We have used maternal plasma samples obtained from first and second trimesters from mothers carrying DS affected fetuses compared with mothers carrying normal fetuses. Plasma samples were albumin/IgG depleted and expanded pH ranges of pH 4.5 - 5.5, pH 5.3 - 6.5 and pH 6 - 9 were used for two-dimensional gel electrophoresis (2DE). We found no differentially expressed proteins in the first trimester between the two groups. Significant up-regulation of ceruloplasmin, inter-alpha-trypsin inhibitor heavy chain H4, complement proteins C1s subcomponent, C4-A, C5, and C9 and kininogen 1 were detected in the second trimester in maternal plasma samples where a DS affected fetus was being carried. However, ceruloplasmin could not be confirmed as being consistently up-regulated in DS affected pregnancies by Western blotting.

Conclusions

Despite the in depth 2DE approach used in this study the results underline the deficiencies of gel-based proteomics for detection of plasma biomarkers. Gel-free approaches may be more productive to increase the number of plasma biomarkers for DS for non-invasive prenatal screening and diagnosis.     

Sterol composition of Aureoumbra lagunensis, the Texas brown tide alga

Aureoumbra lagunensis, the alga responsible for the "Texas brown tide", contains (E)-24-propylidenecholesterol (35.7% of total sterols) as its dominant sterol, in common with other members of the Pelagophyceae. Other major sterols are stigmasterol (22.2%), sitosterol (19.2%), cholesterol (14.1%), and (24R)-24-propylcholesterol (5.2%). Trace amounts of 24-methylenecholesterol, crinosterol, clerosterol, campesterol, dihydrobrassicasterol, and 24-isopropylcholesterol were also detected.     

In vitro analysis of complement-dependent HIV-1 cell infection using a model system

Previous studies based on the use of human serum as a source of C have provided evidence for the C-dependent enhancement of cell infection by HIV-1. The present study was undertaken to distinguish C from other serum factors and to identify the proteins and the mechanisms involved in C-dependent cell infection by HIV-1. The classical C activation pathway was reconstituted from the proteins C1q, C1r, C1s, C4, C2, C3, factor H, and factor I; each were purified to homogeneity. A mixture of these proteins at physiological concentrations was shown to reproduce the ability of normal human serum to enhance the infection of MT2 cells by HIV-1 at low doses of virus. This enhancing effect was abolished when heat-inactivated serum and C2- or C3-depleted serum were used, and was restored upon addition of the corresponding purified proteins. A mixture of two synthetic peptides corresponding to positions 10-15 and 90-97 of human C receptor type 2 (CD21) as well as soluble CD4 both inhibited the C-dependent infection process. These data provide unambiguous evidence that HIV-1 triggers a direct activation of the classical C pathway in vitro and thereby facilitates the infection of MT2 cells at low doses of virus. These findings are consistent with a mechanism involving increased interaction between the virus opsonized by C3b-derived fragment(s) and the CD21 cell receptors and subsequent virus entry through CD4 receptors.     

Biochemical, genetic and physiological characterization of venom components from two species of scorpions: Centruroides exilicauda Wood and Centruroides sculpturatus Ewing

Current literature concerning the taxonomic names of two possibly distinct species of scorpions from the genus Centruroides (sculpturatus and/or exilicauda) is controversial. This communication reports the results of biochemical, genetic and electrophysiological experiments conducted with C. exilicauda Wood of Baja California (Mexico) and C. sculpturatus Ewing of Arizona (USA). The chromatographic profile fractionation of the soluble venom from both species of scorpions is different. The N-terminal amino acid sequence for nine toxins of C. exilicauda was determined and compared with those from C. sculpturatus. Lethality tests conducted in mice support the idea that C. exilicauda venom should be expected to be medically less important than C. sculpturatus. Thirteen genes from the venomous glands of the scorpion C. exilicauda were obtained and compared with previously published sequences from genes of the species C. sculpturatus. Genes coding for cytochrome oxidase I and II of both species were also sequenced. A phylogenetic tree was generated with this information showing important differences between them. Additionally, the results of electrophysiological assays conducted with the venom from both species on the Ca(2+)-dependent K(+)-channels, showed significant differences. These results strongly support the conclusion that C. exilicauda and C. sculpturatus are in fact two distinct species of scorpions.