Anisotropic lattice distortions in the mollusk-made aragonite: a widespread phenomenon

In this paper, we present experimental results demonstrating systematic structural distinctions between biogenic and non-biogenic calcium carbonate. Specifically we show, by high-resolution X-ray powder diffraction on dedicated synchrotron beam lines, that the orthorhombic unit cell of the mollusk-made aragonite is anisotropically distorted as compared with that one of geological aragonite. In all investigated shells, belonging to different classes (bivalve, gastropod, and cephalopod) and taken from different habitat origins (sea, fresh water, and land), the maximum elongation of about 0.1-0.2% was found along the c-axis. The lattice distortions along the a-axis were also of the positive sign (elongation) but lower than those along the c-axis, whereas lattice distortions along the b-axis were always negative (contraction). Supporting experiments, including structural analysis after a bleach procedure, measurements of temperature-dependent lattice relaxation, measurements of the CO(2) release at elevated temperatures, signify that the observed structural distinctions are most probably caused by the organic molecules intercalating into the aragonite lattice during biomineralization. Our findings show that in some sense organisms control the atomic structure of the crystals. Deeper understanding of this phenomenon will aid in the development of new approaches to grow biomimetic composites and tailor their properties on a molecular level.     

Public information for the assessment of quality: a widespread social phenomenon

We propose that the use of public information about the quality of environmental resources, obtained by monitoring the sampling behaviour of others, may be a widespread social phenomenon allowing individuals to make faster, more accurate assessments of their environment. To demonstrate this (i) we define public information and distinguish it from other kinds of social information; (ii) we review empirical work demonstrating the benefits and costs of using public information to estimate food patch quality; (iii) we examine recent work showing that individuals may also be using public information to improve their estimates of the quality of such disparate environmental parameters as breeding patches, opponents and mates; and finally (iv) we suggest avenues of future work to better understand the nature of public information use and when it might be used or ignored. Such work should lead to a more complete understanding of the behaviour of individuals in social aggregations.     

Fossil Record and Age of the Asteridae

The Asteridae is a group of some 80,000 species of flowering plants characterized by their fused corollas and iridoid compounds. Recent phylogenetic analyses have helped delimit the group and have identified four main clades within it; Cornales, Ericales, Lamiids and Campanulids, with the last two collectively known as the Euasteridae. A search for the oldest fossils representing asterids yielded a total of 261 records. Each of these fossils was evaluated as to the reliability of its identification. The oldest accepted fossils for each clade were used to estimate minimum ages for the whole of the Asteridae. The results suggest that the Asteridae dates back to at least the Turonian, Late Cretaceous (89.3 mya) and that by the Late Santonian-Early Campanian (83.5 mya) its four main clades were already represented in the fossil record.     

Mitochondrial targeting of farnesyl diphosphate synthase is a widespread phenomenon in eukaryotes

Cellular internalization of cell-penetrating peptide HIV-1 Tat basic domain (RKKRRQRRR) was studied in Triticale cv AC Alta mesophyll protoplasts. Fluorescently labeled monomer (Tat) and dimer (Tat(2)) of Tat basic domain efficiently translocated through the plasma membrane of mesophyll protoplast and showed distinct nuclear accumulation within 10 min of incubation. Substitution of first arginine residue with alanine in Tat basic domain (M-Tat) severely reduced cellular uptake of the peptide (3.8 times less than Tat). Tat(2) showed greater cellular internalization than Tat (1.6 times higher). However, characteristics of cellular uptake remained same for Tat and Tat(2). Cellular internalization of Tat and Tat(2) was concentration dependent and non-saturable whereas no significant change in cellular uptake was observed even at higher concentrations of M-Tat. Low temperature (4 degrees C) remarkably increased cellular internalization of Tat as well as Tat(2) but M-Tat showed no enhanced uptake. Viability test showed that peptide treatment had no cytotoxic effect on protoplasts further indicating involvement of a common mechanism of peptide uptake at all the temperatures. Endocytic inhibitors nocodazole (10 muM), chloroquine (100 muM) and sodium azide (5 mM) did not show any significant inhibitory effect on cellular internalization of either Tat or Tat(2). These results along with stimulated cellular uptake at low temperature indicate that Tat peptide is internalized in the plant protoplasts in a non-endocytic and energy-independent manner. Competition experiments showed that non-labeled peptide did not inhibit or alter nuclear accumulation of fluorescent Tat or Tat(2) suggesting active transport to the nucleus was not involved. Studies in mesophyll protoplasts show that internalization pattern of Tat peptide is apparently similar to that observed in mammalian cell lines.     

The distribution of serine proteinase inhibitors in seeds of the Asteridae

The Asteridae is one of the most successful clades of flowering plants comprising some 80,000 species. Despite this diversity, analysis of seeds from 398 species (representing 8 orders, 32 families and 181 genera) showed just two major types of serine proteinase inhibitors (PI). PIs of the potato inhibitor I family were widely distributed. These had M(r) of 7000-7500 and were inhibitory to subtilisin and one or more other proteinases (but only rarely elastase). The second major group was TI related to the well-characterised Bowman-Birk inhibitors of legume seeds but these varied widely in their sequences and structure. In addition to these two groups of inhibitors, seeds of the Solanaceae also often contained PI of the potato inhibitor II family while some other asterids contained inhibitors whose relationships were not established.     

Nodding Capitula in Superpáramo Asteraceae: An Adaptation to Unpredictable Environment1

Nodding capitula are a striking feature in several Asteraceae species of the Andean superpáramo. In this study, the thermal environment of the nodding inflorescence in Culcitium canescens Humb. & Bonpl. was surveyed by a short-term microclimatic measurement. Temperatures of the nodding inflorescences were higher than temperatures of the surrounding air during the day, while the respective temperatures were comparable during the night. Also, compared to other parts of the plant, the nodding inflorescence provided favorable temperature conditions. An experiment showed that the radiation reflected from the substratum explained most of the variability in the inflorescence temperature. It is suggested that the nodding capitula have evolved to protect the flowers from snow and rain while at the same time ensuring sufficient temperatures for floral development.     

Structural analysis of xyloglucans in the primary cell walls of plants in the subclass Asteridae

The structures of xyloglucans from several plants in the subclass Asteridae were examined to determine how their structures vary in different taxonomic orders. Xyloglucans, solubilized from plant cell walls by a sequential (enzymatic and chemical) extraction procedure, were isolated, and their structures were characterized by NMR spectroscopy and mass spectrometry. All campanulids examined, including Lactuca sativa (lettuce, order Asterales), Tenacetum ptarmiciflorum (dusty miller, order Asterales), and Daucus carota (carrot, order Apiales), produce typical xyloglucans that have an XXXG-type branching pattern and contain alpha-d-Xylp-, beta-D-Galp-(1-->2)-alpha-D-Xylp-, and alpha-L-Fucp-(1-->2)-beta-D-Galp-(1-->2)-alpha-D-Xylp- side chains. However, the lamiids produce atypical xyloglucans. For example, previous analyses showed that Capsicum annum (pepper) and Lycopersicon esculentum (tomato), two species in the order Solanales, and Olea europaea (olive, order Lamiales) produce xyloglucans that contain arabinosyl and galactosyl residues, but lack fucosyl residues. The XXGG-type xyloglucans produced by Solanaceous species are less branched than the XXXG-type xyloglucan produced by Olea europaea. This study shows that Ipomoea pupurea (morning glory, order Solanales), Ocimum basilicum (basil, order Lamiales), and Plantago major (plantain, order Lamiales) all produce xyloglucans that lack fucosyl residues and have an unusual XXGGG-type branching pattern in which the basic repeating core contains five glucose subunits in the backbone. Furthermore, Neruim oleander (order Gentianales) produces an XXXG-type xyloglucan that contains arabinosyl, galactosyl, and fucosyl residues. The appearance of this intermediate xyloglucan structure in oleander has implications regarding the evolutionary development of xyloglucan structure and its role in primary plant cell walls.     

Dynamic and static cord-structure: A new dielectrophoretic phenomenon

During the dielectrophoresis of cells or other particles it is observed that unusual distributions of the cells appear on the floor of the test chamber. In certain narrow frequency ranges, the distributions are cord-like, with the “cords” running more or less parallel to the electrode faces, but also developing highly branched structures. It is observed that the cells within the cords form “pearl-chains” along the field lines and across the cords. Within the cords, the cells move actively in spiralized paths. This the dynamic cord-structure is considered to be due to the combined action of negative dielectrophoresis, Brownian motion, and gravity. Outside the conditions requisite for dynamic cord formation, the cells are seen to assume conformations reflective of simple negative dielectrophoresis which merely causes them to amass into regions of low field strength. The theory for the effects is presented, together with experimental evidence for the kinetic behavior of the dynamic cord effect.     

The GD box: A widespread noncontiguous supersecondary structural element

Identification and characterization of recurrent supersecondary structural elements is central to understanding the rules governing protein tertiary structure. Here, we describe the GD box, a widespread noncontiguous supersecondary element, which we initially found in a group of topologically distinct but homologous β‐barrels—the cradle‐loop barrels. The GD box is similar both in sequence and structure and comprises two short unpaired β‐strands connected by an orthogonal type‐II β‐turn and a noncontiguous β‐strand forming hydrogen bonds with the β‐turn. Using structure‐based analysis, we have detected 518 instances of the GD box in a nonredundant subset of the SCOP database comprising 3771 domains. Apart from the cradle‐loop barrels, this motif is also found in a diverse set of nonhomologous folds including other topologically related β‐barrels. Since nonlocal interactions are fundamental in the formation of protein structure, systematic identification and characterization of other noncontiguous supersecondary structural elements is likely to prove valuable to protein structure modeling, validation, and prediction.     

Changes in nectar supply: A possible cause of widespread butterfly decline

Recent studies have documented declining trends of various groups of flower-visiting insects,even common butterfly species.Causes of these declines are still unclear but the loss of habitat quality across the wider countryside is thought to be a major factor.Nectar supply constitutes one of the main resources determining habitat quality.Yet,data on changes in nectar abundance are lacking.In this study,we provide the first analysis of changes in floral nectar abundance on a national scale and link these data to trends in butterfly species richness and abundance.We used transect data from the Dutch Butterfly Monitoring Scheme to compare two time periods:1994-1995 and 2007-2008.The results show that butterfly decline can indeed be linked to a substantial decline in overall flower abundance and specific nectar plants,such as thistles.The decline is as severe in reported flower generalists as in flower specialists.We suggest that eutrophication is a main cause of the decline of nectar sources.     

Bisphenol A: an endocrine disruptor with widespread exposure and multiple effects

Bisphenol A (BPA) is one of the highest volume chemicals produced worldwide. This compound is a building block of polycarbonate plastics often used for food and beverage storage, and BPA is also a component of epoxy resins that are used to line food and beverage containers. Studies have shown that BPA can leach from these and other products in contact with food and drink, and as a result, routine ingestion of BPA is presumed. This compound is also found in an enormous number of other products that we come into contact with daily, and therefore it is not surprising that it has been detected in the majority of individuals examined. BPA is a known endocrine disruptor. Although initially considered to be a weak environmental estrogen, more recent studies have demonstrated that BPA may be similar in potency to estradiol in stimulating some cellular responses. Moreover, emerging evidence suggests that BPA may influence multiple endocrine-related pathways. Studies in rodents have identified adverse effects of BPA at levels at or below the current acceptable daily intake level for this compound. The various reported adverse effects of BPA are reviewed, and potential mechanisms of BPA action are discussed. Much more investigation is needed to understand the potential adverse health effects of BPA exposure in humans and to understand the multiple pathways through which it may act. Although many questions remain to be answered, it is becoming increasingly apparent that exposure to BPA is ubiquitous and that the effects of this endocrine disruptor are complex and wide-ranging.     

Transglutaminases: widespread cross-linking enzymes in plants

BACKGROUND: Transglutaminases have been studied in plants since 1987 in investigations aimed at interpreting some of the molecular mechanisms by which polyamines affect growth and differentiation. Transglutaminases are a widely distributed enzyme family catalysing a myriad of biological reactions in animals. In plants, the post-translational modification of proteins by polyamines forming inter- or intra-molecular cross-links has been the main transglutaminase reaction studied. CHARACTERISTICS OF PLANT TRANSGLUTAMINASES: The few plant transglutaminases sequenced so far have little sequence homology with the best-known animal enzymes, except for the catalytic triad; however, they share a possible structural homology. Proofs of their catalytic activity are: (a) their ability to produce glutamyl-polyamine derivatives; (b) their recognition by animal transglutaminase antibodies; and (c) biochemical features such as calcium-dependency, etc. However, many of their fundamental biochemical and physiological properties still remain elusive. TRANSGLUTAMINASE ACTIVITY IS UBIQUITOUS: It has been detected in algae and in angiosperms in different organs and sub-cellular compartments, chloroplasts being the best-studied organelles. POSSIBLE ROLES: Possible roles concern the structural modification of specific protein substrates. In chloroplasts, transglutaminases appear to stabilize the photosynthetic complexes and Rubisco, being regulated by light and other factors, and possibly exerting a positive effect on photosynthesis and photo-protection. In the cytosol, they modify cytoskeletal proteins. Preliminary reports suggest an involvement in the cell wall construction/organization. Other roles appear to be related to fertilization, abiotic and biotic stresses, senescence and programmed cell death, including the hypersensitive reaction. CONCLUSIONS: The widespread occurrence of transglutaminases activity in all organs and cell compartments studied suggests a relevance for their still incompletely defined physiological roles. At present, it is not possible to classify this enzyme family in plants owing to the scarcity of information on genes encoding them.     

Origin and Development of Secondary Capitula in Calendula officinalis L. in Response to Gibberellic Acid

Foliar application of gibberellic acid greatly enhanced theformation of secondary capitula. The proportion of primary capitulashowing this feature increased from 6% in the controls to 28,58, and 54% at 100, 250, and 500 parts 10^–6 GA₃, respectively.Secondary capitula were initiated either along the peripheryor in the centre of the receptacle or from both; their totalnumbers for 15 plants per treatment were 53, 215, 660, and 404in response to 0, 100, 250, and 500 parts 10^–6 GA₃, respectively.Secondary capitula were smaller and had fewer disc florets andfruits, particularly of the ‘wingless and small’type. Tertiary capitula, not observed in nature, formed on 2.72and 3.21% of the secondary capitula on plants sprayed with 250and 500 parts 10^–6 GA₃.The formation of a secondary inflorescencemeristem in treated plants in place of a floret primordium canbe detected histologically early in its development, and itspattern of development resembles that of the primary capitulum.     

Droplet sedimentation: A physical description and qualitative explanation of the phenomenon

Experiments with very simple geometric configurations and dynamic conditions were conducted to observe the formation of filaments and droplets from buoyant layers containing dense macromolecules. The development of the droplets into small vortex rings, and their motions were followed. The observations are described. These experiments were conducted in an effort to understand and to predict streaming, or tumbling, or droplet sedimentation in centrifuges. A sequence of physical processes composing the phenomenon of droplet sedimentation is proposed and discussed.     

Pacemaker lead endocarditis: A rare diagnosis with a varied presentation

We present a patient with a pacemaker lead endocarditis who showed no signs of pocket infection but with high fever and signs of infection in the routine laboratory tests. A diagnosis of pacemaker lead endocarditis must be considered in all patients with fever and infection parameters who have a pacemaker inserted, not only in the first weeks after implantation but also late after implantation, as long as no other cause of infection has been found. Transthoracal echocardiography alone is not sensitive enough to establish the correct diagnosis. Transoesophageal echocardiography (TEE) is mandatory to demonstrate the presence or absence of a vegetation on a pacemaker lead.