Evolutionary changes in the structures of the cox2 and atp6 loci in the mitochondrial genome of soybean involving recombination across small interspersed sequences

Mitochondrial DNA (mtDNA) fragments that contained cox2 or atp6 loci were cloned from three accessions of wild soybean (Glycine soja) in order to understand the evolutionary changes of mitochondrial genomes in the genus Glycine subgenus Soja. Cox2 was cloned as a single configuration, while atp6 was cloned as either one or two configurations from each accession. Structural variations were detected in the 5′ upstream region of cox2 and in both the 5′ upstream and 3′ downstream regions of atp6. These variations appeared to be the results of recombination events. A comparison of the mtDNA fragments previously cloned from a cultivated soybean (G. max) and a wild soybean revealed various sites of recombination, as well as various combinations of the 5′ and 3′ regions, at the cox2 and atp6 loci. Some of the cloned fragments were found to contain a set of repeated sequences, namely 299-bp and 23-bp repeats in the 5′ region of cox2 or atp6, which were interspersed in the mitochondrial genome in the subgenus Soja. Recombination events involving the 299-bp or 23-bp repeated sequences were shown to account for the generation of structural variations in the 5′ regions of these loci. Received: 21 March / 4 August 1998     

Histological studies on the ontogeny of bovine gut-associated lymphoid tissue: appearance of T cells and development of IgG+ and IgA+ cells in lymphoid follicles

The development and distribution of lymphocyte subsets in bovine gut-associated lymphoid tissues (ileal and jejunal Peyer's patches (PP)) were examined. Before birth, the composition of lymphocyte subsets in both PP follicles did not differ except for the dimensions of the interfollicular area and the dome region. Many IgM+ cells were observed in these follicles, but very few CD3+, IgG+, and IgA+ cells could be found. At neonatal period, the IgG+ cells, which did not produce IgG mRNA, were dominant within both PP follicles. From 1 month after birth, many CD3+ cells, IgG mRNA expression, and IgA mRNA expression were detected within the jejunal PP follicles, but very few were in the ileal PP follicles. These data suggest that the characteristics of the jejunal PP follicles metamorphose into secondary lymphoid tissue such as germinal centers at around 1 month after birth, whereas the characteristics of ileal PP follicles were distinct from those of germinal centers.     

Pseudotype hepatitis C virus enters immature myeloid dendritic cells through the interaction with lectin

Dendritic cells (DC) are the most potent antigen-presenting cells that regulate immune responses. One of the mechanisms for hepatitis C virus (HCV) persistence is the ability of HCV to suppress DC function. Direct HCV infection to blood DC has been implicated for DC dysfunction. To clarify the susceptibility of each DC subset to HCV, we used pseudotype vesicular stomatitis virus (VSV) coated with chimeric HCV envelope glycoproteins (E1 and E2). We demonstrate that pseudotype VSV enters myeloid DC (MDC) but not plasmacytoid DC (PDC). The highest efficiency of pseudotype VSV entry to MDC was observed when MDC were cultured with GM-CSF. Such efficiency decreased when MDC are matured with the treatment of IL-4, CpG oligodeoxynucleotide, or CD40 ligand. Mannan inhibited pseudotype VSV entry to MDC, but Ca(2+) chelators failed to do so. These results show that pseudotype VSV possessing HCV-E1 and E2 enters immature MDC through the interaction with lectins in a Ca(2+)-independent manner.     

Structural basis for distinct roles of Lys63- and Lys48-linked polyubiquitin chains

Ubiquitination, a modification in which single or multiple ubiquitin molecules are attached to a protein, serves as a signalling function that controls a wide variety of cellular processes. To date, two major forms of polyubiquitin chain have been functionally characterized, in which the isopeptide bond linkages involve Lys48 or Lys63. Lys48-linked polyubiquitin tagging is mostly used to target proteins for degradation by the proteasome, whereas Lys63-linked polyubiquitination has been linked to numerous cellular events that do not rely on degradative signalling via the proteasome. Apparently linkage-specific conformations of polyubiquitin chains are important for these cellular functions, but the structural bases distinguishing Lys48- and Lys63-linked chains remain elusive. Here, we report NMR and small-angle X-ray scattering (SAXS) studies on the intersubunit interfaces and conformations of Lys63- and Lys48-linked di- and tetraubiquitin chains. Our results indicate that, in marked contrast to Lys48-linked chains, Lys63-linked chains are elongated molecules with no stable non-covalent intersubunit interfaces and thus adopt a radically different conformation from that of Lys48-linked chains.     

Changes in the somatosensory N250 and P300 by the variation of reaction time

We investigated the relationship between somatosensory event-related potentials (ERP) and the variation of reaction time (RT). For this purpose, we recorded the ERPs (N250 and P300) in fast- and slow-reaction trials during a somatosensory discrimination task. Strong, standard, and weak target electrical stimuli were randomly delivered to the left median nerve at the wrist with a random interstimulus interval (900–1,100 ms). All the subjects were instructed to respond by pressing a button with their right thumb as fast as possible whenever a target stimulus was presented. We divided all the trials into fast- and slow-RT trials and averaged the data. N250 latency tended to be delayed when the RT was slow, but not significantly. P300 latency was delayed significantly when the RT was slow, but to a much lesser extent than the RT delay, so we concluded that the change of RT was not fully determined by the processes reflected by the somatosensory N250 or P300. Furthermore, the larger and earlier P300 in the fast-RT trials implied that when larger amounts of attentional resources were allocated to a given task, the speed of stimulus evaluation somewhat increased and RT was shortened to a great extent. N250 amplitude did not significantly vary in the two RT clusters. In conclusion, the somatosensory N250 reflects active target detection, which is relatively independent of the modulation of the response speed, whereas the somatosensory P300 could change without manipulation of either the stimulus or the response processing demand. Electronic Publication     

Construction of a standard rating scale to estimate sleep onset and the analysis of influencing factors

In this study, we developed a ratings scale for estimating sleep onset that would be capable of providing quantitative evaluations of the quality of the sleep onset process. We also examined factors affecting sleep onset using a questionnaire consisting of two separate clusters of items: the first, consisting of 9 items, related to the quality of sleep onset; and the second, consisting of 56 items, related to factors with apparent effects on sleep onset. The questionnaire was administered to 515 day-workers (range: 25-44 years old) for standardization. Each item was weighted based on the distribution of subject responses to determine discrimination. The reliability coefficient alpha for the questionnaire was high, exceeding 0.8. Of 41 items set out as potential factors affecting sleep onset, the results of the questionnaire indicated that five factors consisting of 26 items could be isolated as most likely affecting sleep onset. Path analysis indicated that sleep onset is more commonly affected by factors present at bedtime than factors related to sleep quality the previous night, or to daytime activities.     

Anionic copolymerization of β-lactones in correlation with the mode of fission. studies on the syntheses of aliphatic polyesters. XI

The copolymerization behavior of β-propiolactone (PL) and α.α-bischloromethyl β-propiolactone (α-BCPL) is correlated with the mode of fission. With sodium acetate as catalyst, the formation of β-acetoxy propionic acid at the initiation reaction was observed and α-BCPL was more than five times as reactive as PL in copolymerization. Thus propagation by carboxylate anion through alkyl-oxygen fission was presumed in the case of pyridine and the acetate of Na, Li, and Mg as catalyst. On the other hand, the formation of ethyl β-hydroxy propionate and the decreased reactivity of α-BCPL in copolymerization was observed with magnesium and aluminum ethoxide as catalyst. In the case of the ethoxide of Na, Li, and Al, and Et₂Mg or Et₃Al as catalyst, propagation by alkoxide anions through acyl-oxygen fission of the coordinated lactones was presumed.