The development of the lamprey pattern generator for locomotion

The life cycle of the lamprey includes a larval stage that can last for several years. The motor behavior of the larval lamprey, the ammocoete, has been only minimally studied and little is known of the neural correlates of that behavior. Comparison of known larval behavior to that of adults leaves unclear whether there are large or small changes in the spinal nervous system during transformation. The motor output of isolated larval and transforming spinal cords when stimulated to "swim" with D-glutamate has some differences from that of comparable adult preparations, but shares many important features with adults. Primarily, the fictive swimming is less well regulated and less stable than adults of the same species. We propose that a major difference in the structure and organization of the central pattern generator for locomotion between adults and ammocoetes is a relative lack or immaturity of some cell types that participate in the coordination of the segments and the generation of the rhythm of the periodic bursting.     

Modified model of potato virus X coat protein structure

We propose the modified model of the structure of coat protein (CP) subunits in filamentous virions of potato virus X (PVX). The model is similar to the one proposed by us in 2001 for the CP of another helical plant virus (potato virus A) belonging to other (potyvirus) group. In this model the PVX CP molecule consist of two main domains--a bundle of four alpha-helices located close to the virion long axis and a so-called RNP-fold (or abCd-fold) located near the virion surface. Basing on this model we suggest possible mechanism of described by J.G. Atabekov and colleagues structural transition ("remodeling") of the PVX virions resulting from their interaction with virus-specific TGB-1 protein.     

Intrinsically unstructured regions in the C domain of the influenza virus M1 protein

The M1 matrix protein of the influenza virus is one of the main structural components of the virion that performs several different functions in the infected cell. X-ray analysis (with 2.08 Å resolution) has been performed for the N-terminal part of the M1 protein (residues 2–158) but not for its C-terminal domain (159–252). In the present study, we analyzed the structure of the M1 protein of the influenza virus A/Puerto Rico/8/34 (H1N1) strain in acidic solution using tritium planigraphy. The incorporation of tritium label into the domains of the M1 protein were studied; the C domain and the interdomain loops are preferentially accessible to tritium. Analytical centrifugation and dynamic laser light scattering demonstrated anomalous hydrodynamic parameters and low structuredness of the M1 protein, which has also been confirmed by circular dichroism data. Bioinformatic analysis of the M1 protein sequence revealed intrinsically unstructured segments that were concentrated in the C domain and interdomain loops between the N-, M-, and C domains. We suggest that the multifunctionality of the M1 protein in a cell is determined by the plasticity of its tertiary structure, which is caused by the presence of intrinsically unstructured segments.     

Two types of structural organization of double-stranded DNA in phage particles

Structural arrangement of linear unmodified duplex DNA in phage particles FI5 and SB1 was studied by the techniques of absorption spectrum, CD, scanning microcalorimetry. Hyperchromism is not registered for SB1 DNA in situ at 260 nm, in contrast to FI5 and other phages, but is visible at 260-290 nm. Phage SB1 had an unusual CD spectrum: intensity of the positive band at 280 nm was, practically, identical to the free SB1 DNA intensity. However, the character of SB1 DNA in situ melting in 1.5% HCHO corresponds to FI5 (and other phages) melting in situ in the presence of HCHO. Analysis of these spectral studies and calorimetry permitted one to identify the peaks on the thermograms of phages FI5 and SB1. Variability of heat capacity in the zone of phage particles destruction is supposed to be connected with DNA rearrangements.     

A test of biotic interactions among two alpine plant species in Australia

This study examines the extent to which interactions among two common alpine/subalpine plant species and their neighbours at the Bogong High Plains in southern Australia are characterized by competition or facilitation. The two target species were Celmisia pugioniformis (Asteraceae) and Carex breviculmis (Cyperaceae). Biotic interactions were examined using vegetation removal manipulations over three growing seasons at five sites across the altitudinal range of tall alpine herbfield communities. Observations recorded growth and mortality. Results for C. pugioniformis clearly indicated facilitation as a dominant process across all sites and seasons. Plants that had their neighbours removed tended to perform worse than plants that had their neighbours left intact. Growth observations for Ca. breviculmis were less clear, but again suggested facilitation. Mortality was distinctly higher among Ca. breviculmis individuals that had their neighbours removed relative to those with neighbours left intact. Results collectively suggest the removal of neighbours acts to reduce growth and increase mortality in C. pugioniformis and Ca. breviculmis throughout the altitudinal range of tall alpine herbfields at the Bogong High Plains. Facilitative and competitive interactions need to be recognized in efforts aimed at mitigating climate change‐associated impacts on the ecology of alpine plant communities. The extent to which biotic interactions may exacerbate or buffer abiotic change is difficult to predict, emphasizing the need for ecological monitoring.     

Discovery and identification of a male-killing agent in the Japanese ladybird <Emphasis Type="Italic">Propylea japonica</Emphasis> (Coleoptera: Coccinellidae)

Background  

Endosymbionts that manipulate the reproduction of their hosts have been reported widely in invertebrates. One such group of endosymbionts is the male-killers. To date all male-killers reported are bacterial in nature, but comprise a diverse group. Ladybirds have been described as a model system for the study of male-killing, which has been reported in multiple species from widespread geographic locations. Whilst criteria of low egg hatch-rate and female-biased progenic sex ratio have been used to identify female hosts of male-killers, variation in vertical transmission efficiency and host genetic factors may result in variation in these phenotypic indicators of male-killer presence. Molecular identification of bacteria and screening for bacterial presence provide us with a more accurate method than breeding data alone to link the presence of the bacteria to the male-killing phenotype. In addition, by identifying the bacteria responsible we may find evidence for horizontal transfer between endosymbiont hosts and can gain insight into the evolutionary origins of male-killing. Phylogenetic placement of male-killing bacteria will allow us to address the question of whether male-killing is a potential strategy for only some, or all, maternally inherited bacteria. Together, phenotypic and molecular characterisation of male-killers will allow a deeper insight into the interactions between host and endosymbiont, which ultimately may lead to an understanding of how male-killers identify and kill male-hosts.     

Characterization of adenylate cyclase fromEscherichia coli

Adenylate cyclase activity was detected and characterized in cell-free preparations of different strains ofEscherichia coli; it was localized not only in the membrane fraction but also in the cytoplasm, the localization differing from strain to strain. The adenylate cyclase activity is highly dependent on the method used for disintegration of cells. The best results were obtained when using vortexing of the cell suspension with ballotini beads. The pH optimum of adenylate cyclase in cell-free preparations was found to be 9.0 –9.5. The enzyme has an absolute requirement for Mg²⁺ and is inhibited by sodium fluoride and inorganic diphosphate. Release of adenylate cyclase from the membrane leads to an immediate loss of the activity; it was found that adenylate cyclase is quite labile and hence it could not yet been purified. The method used to determine adenylate cyclase activity and cyclic AMP is described.     

Culic 3', 5', -adenosine monophosphate and catabolic repression in Escherichia coli.

Several strains of $\text{E. coli}$ were grown on different sources of carbon and β-galactosidase activity as well as intracellular and extracellular concentrations of c-AMP were determined. There was a good (inverse) correlation between extracellular concentrations of c-AMP and the intensity of catabolite repression, whereas the relationship between intracellular c-AMP levels and catabolite repression was not clear-cut.     

Disordered regions in C-domain structure of influenza virus M1 protein

Influenza virus matrix M1 protein is one of the main structural components of the virion performing also many different functions in infected cell. X-ray analysis data with 2.08 angstrom resolution were obtained only for the N-terminal part of M1 protein molecule (residues 2-158) but not for its C-terminal domain (159-252). In the present work M1 protein of A/Puerto Rico/8/34 (H1N1) virus strain in acidic solution was investigated with the help of tritium bombardment. Tritium label incorporation into M1 protein domains preferentially labeled the C-domain and inter-domain loops. Analytical centrifugation and dynamic light scattering experiments demonstrated increased hydrodynamic parameters (diameter) that may be explained by low degree of M1 structural organization. Computational analysis of M1 protein by intrinsic disorder predictions methods also demonstrated the presence of unfolded regions mostly in the C-domain and inter-domain loops. It is suggested, that influenza virus M1 polyfunctionality in infected cell is determined by its tertiary structure plasticity which in its turn results from the presence of unstructured regions.