In vitro induction of androgenic plantlets inAesculus hippocastanum

Summary Horsechestnut anthers were isolated from flower buds in various stages of development and cultivated in the presence of auxin and kinetin. The anthers showed the capacity for androgenesis and evidence is presented that the plantlets developed from single microspores. Haploid karyotypes were observed in the root menstem cells in three plantlets.     

Effect of static magnetic fields on bioelectric properties of the Br and N1 neurons of snail Helix pomatia

The effects of 2.7 mT and 10 mT static magnetic fields were investigated on two identified neurons with different bioelectric properties of the snail Helix pomatia. Membrane resting potential, amplitude, spiking frequency, and duration of action potential were measured. The two neurons of H. pomatia, parabolic burster Br and silent N₁, showed different responses to a static magnetic field. The magnetic field of 2.7 mT intensity caused changes in the amplitude and duration of action potential of the Br neuron, whereas the 10 mT magnetic field changed the resting potential, amplitude spike, firing frequency, and duration of action potential of the Br neuron. Bioelectric parameters measured on the N₁ neuron did not change significantly in these magnetic fields.     

Tetanus toxoid purification: chromatographic procedures as an alternative to ammonium-sulphate precipitation

Given an existing demand to establish a process of tetanus vaccine production in a way that allows its complete validation and standardization, this paper focuses on tetanus toxoid purification step. More precisely, we were looking at a possibility to replace the widely used ammonium-sulphate precipitation by a chromatographic method. Based on the tetanus toxin's biochemical characteristics, we have decided to examine the possibility of tetanus toxoid purification by hydrophobic chromatography, and by chromatographic techniques based on interaction with immobilized metal ions, i.e. chelating chromatography and immobilized metal affinity chromatography. We used samples obtained from differently fragmented crude tetanus toxins by formaldehyde treatment (assigned as TTd-A and TTd-B) as starting material for tetanus toxoid purification. Obtained results imply that purification of tetanus toxoid by hydrophobic chromatography represents a good alternative to ammonium-sulphate precipitation. Tetanus toxoid preparations obtained by hydrophobic chromatography were similar to those obtained by ammonium-sulphate precipitation in respect to yield, purity and immunogenicity. In addition, their immunogenicity was similar to standard tetanus toxoid preparation (NIBSC, Potters Bar, UK). Furthermore, the characteristics of crude tetanus toxin preparations had the lowest impact on the final purification product when hydrophobic chromatography was the applied method of tetanus toxoid purification. On the other hand, purifications of tetanus toxoid by chelating chromatography or immobilized metal affinity chromatography generally resulted in a very low yield due to not satisfactory tetanus toxoid binding to the column, and immunogenicity of the obtained tetanus toxoid-containing preparations was poor.     

In Silico Study of the Structurally Similar ORL1 Receptor Agonist and Antagonist Pairs Reveal Possible Mechanism of Receptor Activation

An opioid receptor like (ORL1) receptor is a member of a family of G-protein coupled receptors. It is a new pharmaceutical target with broad therapeutic potential in the regulation of important biological functions such as nociception, mood disorders, drug abuse, learning or cardiovascular control. The crystal structure of this receptor in complex with an antagonist was determined recently (PDB ID: 4EA3). By removing the ligand and subjecting the empty receptor to molecular dynamics simulation in a solvated lipid membrane we obtained an optimized ORL1 receptor structure which could be used in a subsequent docking study of two structurally similar agonist–antagonist ligand pairs. Ligands were docked to the empty ORL1 receptor (with and without the third intracellular loop, IC3) in different orientations, and the resulting complexes were monitored during molecular dynamics simulation in order to see how the subtle differences in structure of agonists and antagonists might affect ligand–receptor interactions and trigger receptor activation. It was established that agonists and antagonists bound to the same, relatively large, binding site in the receptor, created by residues from transmembrane helices TM2, TM3, TM5, TM6 and TM7 and close to the extra cellular end of the receptor bundle. The key difference between these two types of ligands is interaction with residue Val283^6.55 and a flexibility of ligand molecules. Ligands that cannot easily avoid this interaction will initiate movement of the intracellular end of TM6 (by a mechanism which involves Met134^3.36 and several aminoacids of TM5) and possibly activate the receptor when assisted by G-protein.     

Phylogeography of the Vipera ursinii complex (Viperidae): mitochondrial markers reveal an east–west disjunction in the Palaearctic region

Aim The aim of this study was to elucidate the phylogeographical pattern of taxa composing the Vipera ursinii complex, for which the taxonomic status and the dating of splitting events have been the subject of much debate. The objectives were to delimit potential refugia and to date splitting events in order to suggest a scenario that explains the diversification of this species complex. Location Western Europe to Central Asia. Methods Sequences of the mitochondrial cytochrome b and NADH dehydrogenase subunit 4 (ND4) genes were analysed for 125 individuals from 46 locations throughout the distribution range of the complex. The phylogeographical structure was investigated using Bayesian and maximum likelihood methods. Molecular dating was performed using three calibration points to estimate the timing of diversification. Results Eighty‐nine haplotypes were observed from the concatenation of the two genes. Phylogenetic inferences supported two main groups, referred to in this study as the ‘ursinii clade’ and the ‘renardi clade’, within which several subclades were identified. Samples from Greece (Vipera ursinii graeca) represented the first split within the V. ursinii complex. In addition, three main periods of diversification were revealed, mainly during the Pleistocene (2.4–2.0 Ma, 1.4 Ma and 1.0–0.6 Ma). Main conclusions The present distribution of the V. ursinii complex seems to have been shaped by Quaternary climatic fluctuations, and the Balkan, Caucasus and Carpathian regions are identified in this study as probable refugia. Our results support a south–north pattern of colonization, in contrast to the north–south colonization previously proposed for this complex. The biogeographical history of the V. ursinii complex corroborates other biogeographical studies that have revealed an east–west disjunction (situated near the Black Sea) within a species complex distributed throughout the Palaearctic region.     

High Spatial Resolution Infrared Micro-Spectroscopy Reveals the Mechanism of Leaf Lignin Decomposition by Aquatic Fungi

Organic carbon is a critical component of aquatic systems, providing energy storage and transfer between organisms. Fungi are a major decomposer group in the aquatic carbon cycle, and are one of few groups thought to be capable of breaking down woody (lignified) tissue. In this work we have used high spatial resolution (synchrotron light source) infrared micro-spectroscopy to study the interaction between aquatic fungi and lignified leaf vein material (xylem) from River Redgum trees (E. camaldulensis) endemic to the lowland rivers of South-Eastern Australia. The work provides spatially explicit evidence that fungal colonisation of leaf litter involves the oxidative breakdown of lignin immediately adjacent to the fungal tissue and depletion of the lignin-bound cellulose. Cellulose depletion occurs over relatively short length scales (5–15 µm) and highlights the likely importance of mechanical breakdown in accessing the carbohydrate content of this resource. Low bioavailability compounds (oxidized lignin and polyphenols of plant origin) remain in colonised leaves, even after fungal activity diminishes, and suggests a possible pathway for the sequestration of carbon in wetlands. The work shows that fungi likely have a critical role in the partitioning of lignified material into a biodegradable fraction that can re-enter the aquatic carbon cycle, and a recalcitrant fraction that enters long-term storage in sediments or contribute to the formation of dissolved organic carbon in the water column.     

Relationship between plant life forms and ecological indices in a lacustrine ecosystem

This study is the first to analyze the relationship between ecological indices (substrate moisture, nutrient content, substrate dispersion/aeration, substrate pH and humus content) and life forms of the vascular flora in and around Lake Provala; these relationships may serve as reliable indicators of the ecological conditions prevailing in this ecosystem. Since the development of certain life forms, in addition to climatic conditions, depends on plant requirements for several major environmental factors expressed as ecological indices, we established the relationship between the ecological index and life form of vascular plants collected over an eight year period in this system using correspondence analysis. We found a significant correlation between the development of certain life forms and levels of substrate moisture, nutrient content and substrate dispersion/aeration. These relationships help explain the predominance of hemicryptophytes and hydro-helophytes in the riparian zone of the lake, as these forms are perfectly adapted to water-saturated or aquatic environments rich in nutrients and relatively well aerated. There was no significant relationship between life forms and substrate pH or the content of organo-mineral compounds (humus) in the soil.     

True bugs (Hemiptera,Heteroptera) as psyllid predators (Hemiptera,Psylloidea)

Data on natural enemies of psyllids are rare and can usually be found in papers about economically significant species. During an investigation of psyllid fauna in Serbia, natural enemies were investigated, too. True bugs were the most numerous among them. From 28 psyllid species, 21 species of true bugs from families Anthocoridae and Miridae were reared. Seven species of Anthocoridae were identified: Anthocoris amplicollis (Horváth, 1839), Anthocoris confusus Reuter, 1884, Anthocoris nemoralis (Fabricius, 1794), Anthocoris nemorum (Linnaeus, 1761), Orius majusculus Reuter, 1884, Orius minutus (Linnaeus, 1758) and Orius niger Wolff, 1811. The following 14 species of Miridae were identified: Atractotomus mali Meyer-Dür, 1843, Campylomma verbasci (Meyer-Dür, 1843), Deraeocoris flavilinea (A. Costa, 1862), Deraeocoris ruber (Linnaeus, 1758), Deraeocoris lutescens (Schilling, 1836), Heterocordylus genistae (Scopoli, 1763), Hypseloecus visci (Puton, 1888), Malacocoris chlorizans Panzer, 1794, Miris striatus (Linnaeus, 1758), Orthotylus marginalis Reuter, 1884, Psallus assimilis Stichel, 1956, Psallus quercus Kirschbaum, 1856, Psallus flavellus Stichel, 1933 and Pseudoloxops coccinea (Meyer-Dür, 1843). The aim of the research was to provide list of true bugs recorded as predators of psyllids in order to preserve their diversity and significance, especially on cultivated plants.