Redescription of Papilloma luteum and description of a new Praon species (Hymenoptera: Braconidae; Aphidiinae) parasitic on Kurisakia querciphila (Homoptera: Aphididae: Thelaxinae) in Japan,with notes on synonymy and life cycle of P. luteum

Two aphidiine species were found to be associated with a thelaxine aphid, Kurisakia querciphila on Quercus serrata and Q. acutissima in Japan. One of them is identified as Papilloma luteum and redescribed, and the other is described as a new species, Praon kurisakiae. Sinoaphidius zhejiangensis is synonymized with P. luteum. Papilloma luteum aestivated within a unique shaped and black “diapausing mummy”. Aestivating adults of P. luteum emerging from “diapausing mummies” in the autumn were darker and smaller than non‐aestivating ones. The aphidiine parasitoids of Thelaxinae are reviewed; the systematic position of Papilloma and life cycles of K. querciphila and P. luteum are discussed.     

A Single Amino Acid in the M1 Protein Responsible for the Different Pathogenic Potentials of H5N1 Highly Pathogenic Avian Influenza Virus Strains

Two highly pathogenic avian influenza virus strains, A/duck/Hokkaido/WZ83/2010 (H5N1) (WZ83) and A/duck/Hokkaido/WZ101/2010 (H5N1) (WZ101), which were isolated from wild ducks in Japan, were found to be genetically similar, with only two amino acid differences in their M1 and PB1 proteins at positions 43 and 317, respectively. We found that both WZ83 and WZ101 caused lethal infection in chickens but WZ101 killed them more rapidly than WZ83. Interestingly, ducks experimentally infected with WZ83 showed no or only mild clinical symptoms, whereas WZ101 was highly lethal. We then generated reassortants between these viruses and found that exchange of the M gene segment completely switched the pathogenic phenotype in both chickens and ducks, indicating that the difference in the pathogenicity for these avian species between WZ83 and WZ101 was determined by only a single amino acid in the M1 protein. It was also found that WZ101 showed higher pathogenicity than WZ83 in mice and that WZ83, whose M gene was replaced with that of WZ101, showed higher pathogenicity than wild-type WZ83, although this reassortant virus was not fully pathogenic compared to wild-type WZ101. These results suggest that the amino acid at position 43 of the M1 protein is one of the factors contributing to the pathogenicity of H5N1 highly pathogenic avian influenza viruses in both avian and mammalian hosts.     

The Structure of Mycoplasma pneumoniae as Determined by the Freeze-Substitution Technique

The ultrastructure of Mycoplasma pneumoniae FH was examined by a mild fixation method, the freeze-substitution technique, for thin-section transmission electron microscopy and the following new findings were obtained. In the cytoplasm, no nuclear region could be clearly identified. The cytoplasm was filled with many ribosome-like particles, fine fibers and electron-dense particles. The electron-dense particles appeared to be similar to the particles found in the nucleoid region of Pseudomonas aeruginosa and might therefore possibly be a kind of DNA binding protein. The cell surface was completely enveloped with a thin opaque layer. The presence of this surface layer prevented any direct contact of the cell surface with that of the two M. pneumoniae cells.     

Characterization of cross-reactive polysaccharide antigen with serotype a and d strains from Streptococcus sobrinus 6715.

The polysaccharide antigen (designated SI) from Streptococcus sobrinus 6715 (serotype g) which cross-reacts with serotype a and d strains was purified by a specific anti-cross-reactive g-a antibody-Sepharose 4B affinity column. By a double immunodiffusion analysis, the SI antigen was found to lack the serotype-specific g site, but contained the cross-reactive sites g-a, g-d and g-(a-d) on a single molecule. Polysaccharide SI was composed of galactose, glucose and rhamnose in a molar ratio of 4.79:1.52:1. The results of the test on the inhibition of the precipitin reaction and methylation analysis suggested that the cross-reactive site g-a of the SI antigen appeared to have two regions, one containing galactose residues and the other, beta-linked glucose residues.     

Interaction between collagen and the alpha(2) I-domain of integrin alpha(2)beta(1). Critical role of conserved residues in the metal ion-dependent adhesion site (MIDAS) region.

A docking model of the alpha(2) I-domain and collagen has been proposed based on their crystal structures (Emsley, J., King, S., Bergelson, J., and Liddington, R. C. (1997) J. Biol. Chem. 272, 28512-28517). In this model, several amino acid residues in the I-domain make direct contact with collagen (Asn-154, Asp-219, Leu-220, Glu-256, His-258, Tyr-285, Asn-289, Leu-291, Asn-295, and Lys-298), and the protruding C-helix of alpha(2) (residues 284-288) determines ligand specificity. Because most of the proposed critical residues are not conserved, different I-domains are predicted to bind to collagen differently. We found that deleting the entire C-helix or mutating the predicted critical residues had no effect on collagen binding to whole alpha(2)beta(1), with the exception that mutating Asn-154, Asp-219, and His-258 had a moderate effect. We performed further studies and found that mutating the conserved surface-exposed residues in the metal ion-dependent adhesion site (MIDAS) (Tyr-157 and Gln-215) significantly blocks collagen binding. We have revised the docking model based on the mutagenesis data. In the revised model, conserved Tyr-157 makes contact with collagen in addition to the previously proposed Asn-154, Asp-219, His-258, and Tyr-285 residues. These results suggest that the collagen-binding I-domains (e.g. alpha(1), alpha(2), and alpha(10)) bind to collagen in a similar fashion.     

ADP-ribosylarginine hydrolases

ADP-ribosylation is a reversible post-translational modification of proteins involving the addition of the ADP-ribose moiety of NAD to an acceptor protein or amino acid. NAD: arginine ADP-ribosyltransferase, purified from numerous animal tissues, catalyzes the transfer of ADP-ribose to an arginine residue in proteins. The reverse reaction, catalyzed by ADP-ribosylarginine hydrolase, removes ADP-ribose, regenerating free arginine. An ADP-ribosylarginine hydrolase, purified extensively from turkey erythrocytes, was a 39-kDa monomeric protein under denaturing and non-denaturing conditions, and was activated by Mg²⁺ and dithiothreitol. The ADP-ribose moiety was critical for substrate recognition; the enzyme hydrolyzed ADP-ribosylarginine and (2-phospho-ADP-ribosyl)arginine but not phosphoribosylarginine or ribosylarginine. The hydrolase cDNA was cloned from rat and subsequently from mouse and human brain. The rat hydrolase gene contained a 1086-base pair open reading frame, with deduced amino acid sequences identical to those obtained by amino terminal sequencing of the protein or of HPLC-purified tryptic peptides. Deduced amino acid sequences from the mouse and human hydrolase cDNAs were 94% and 83% identical, respectively to the rat. Anti-rat brain hydrolase polyclonal antibodies reacted with turkey erythrocyte, mouse and bovine brain hydrolase. The rat hydrolase, expressed inE. coli, demonstrated enhanced activity in the presence of Mg²⁺ and thiol, whereas the recombinant human hydrolase was stimulated by Mg²⁺ but was thiol-independent. In the rat and mouse enzymes, there are five cysteines in identical positions; four of the cysteines are conserved in the human hydrolase. Replacement of cysteine 108 in the rat hydrolase (not present in the human enzyme) resulted in a thiol-independent hydrolase without altering specific activity. Rabbit anti-rat brain hydrolase antibodies reacted on immunoblot with the wild-type rat hydrolase and only weakly with the mutant hydrolase. There was no immunoreactivity with either the wild-type or mutant human enzyme. Cysteine 108 in the rat and mouse hydrolase may be responsible in part for thiol-dependence as wall as antibody recognition. Based on these studies, the mammalian and avian ADP-ribosylarginine hydrolases exhibit considerable conservation in structure and function.     

Environmental parameters and estivation of Rhyacodrilus (Tubificidae, Oligochaeta) in Lake Suwa, Japan

We confirmed that Rhyacodrilus spp of Yasuda and Okino (1987) (Tubificidae, Oligochaeta) migrated entirely downward below 15 cm into the sediment from June to September m Lake Suwa, a shallow eutrophic lake in Japan In October, Rhyacodrilus spp began to return to the upper layer and immediately attained sexual maturity They tended to show reduced body weight and respiratory activity during summer The results indicate that an oligochaete of Rhyacodrilus spp estivated in the deeper layer during summer The estivation ostensibly occurred at 15°C and the species died off at 20°C, so it is evident that they must migrate from the surface to the deeper layer of sediment during summer in order to escape high temperature Furthermore, physiological experiment suggested that this behavior is accelerated by low oxygen concentration with high temperature