Mitochondrial DNA divergence in populations of the tapeworm Diphyllobothrium nihonkaiense and its phylogenetic relationship with Diphyllobothrium klebanovskii

Diphyllobothrium nihonkaiense [Y. Yamane, H. Kamo, G. Bylund, J.P. Wilkgren. Diphyllobothrium nihonkaiense sp. nov (Cestoda: Diphyllobothriidae)- revised identification of Japanese broad tapeworm. Shimane J Med Sci 1986;10:29-48.] and Diphyllobothrium klebanovskii [I.V. Muratov, P.S. Posokhov. Causative agent of human diphyllobothriasis - Diphyllobothrium klebanovskii sp. n. Parazitologiia. 1988;22:165-170.] are two major species of human diphyllobothriasis in Japan and Far East Russia, respectively, but their taxonomical relationship remains unclear. In this study, we analysed the DNA sequences of 16 clinical isolates of D. nihonkaiense from Japanese people, 3 isolates of D. klebanovskii from a bear in Kamchatka, and 4 clinical isolates of D. klebanovskii from native Udygeyci people in Russia, as well as 4 plerocercoids from Oncorhynchus spp. 18S rDNA and internal transcribed spacer 1 (ITS1) sequences from D. nihonkaiense and D. klebanovskii showed a high level of similarity, indicating synonymy of the two species. Analyses of mitochondrial DNA (mtDNA) sequence polymorphisms in the cox1 and nad3 genes of D. nihonkaiense (D. klebanovskii) revealed two deeply divergent lineages, A and B, with genetic distances (Kimura-2 parameter) of 0.018-0.022. Furthermore, the distinct monophyletic groupings of cox1 haplotypes corresponded to the distinct monophyletic groupings of nad3 haplotypes. The two lineages were neither distinguished by morphological features nor defined by the localities of the samples. These results suggest that the two morphologically cryptic lineages have diverged and coexisted over a long period of time.     

Studies on the role of HtpG in the tetrapyrrole biosynthesis pathway of the cyanobacterium Synechococcus elongatus PCC 7942

In cyanobacterium Synechococcus elongatus PCC 7942, we observed that htpG-overexpression caused remarkable growth inhibition. In addition, subcellular fractionation experiments showed that HtpG was localized in the membrane fraction. To understand its function in cyanobacteria, we carried out yeast two-hybrid screening to identify specific proteins interacting with HtpG, and found out, HemE, uroporphyrinogen decarboxylase. When compared to the wild-type strain, the htpG-null mutant and -overexpressing strains exhibited higher and lower cytosolic HemE activity, based on the coproporphyrin production, respectively. These results strongly suggest that HtpG is involved in the regulation of tetrapyrrole biosynthesis through interacting with HemE protein.     

Site-specific protein dynamics in communication pathway from sensor to signaling domain of oxygen sensor protein, HemAT-Bs: Time-resolved Ultraviolet Resonance Raman Study

HemAT-Bs is a heme-based signal transducer protein responsible for aerotaxis. Time-resolved ultraviolet resonance Raman (UVRR) studies of wild-type and Y70F mutant of the full-length HemAT-Bs and the truncated sensor domain were performed to determine the site-specific protein dynamics following carbon monoxide (CO) photodissociation. The UVRR spectra indicated two phases of intensity changes for Trp, Tyr, and Phe bands of both full-length and sensor domain proteins. The W16 and W3 Raman bands of Trp, the F8a band of Phe, and the Y8a band of Tyr increased in intensity at hundreds of nanoseconds after CO photodissociation, and this was followed by recovery in ～50 μs. These changes were assigned to Trp-132 (G-helix), Tyr-70 (B-helix), and Phe-69 (B-helix) and/or Phe-137 (G-helix), suggesting that the change in the heme structure drives the displacement of B- and G-helices. The UVRR difference spectra of the sensor domain displayed a positive peak for amide I in hundreds of nanoseconds after photolysis, which was followed by recovery in ～50 μs. This difference band was absent in the spectra of the full-length protein, suggesting that the isolated sensor domain undergoes conformational changes of the protein backbone upon CO photolysis and that the changes are restrained by the signaling domain. The time-resolved difference spectrum at 200 μs exhibited a pattern similar to that of the static (reduced - CO) difference spectrum, although the peak intensities were much weaker. Thus, the rearrangements of the protein moiety toward the equilibrium ligand-free structure occur in a time range of hundreds of microseconds.     

Assignment of the CD45-AP Gene to the Centromeric End of Mouse Chromosome 19 and Human Chromosome 11q13.1–q13.3

CD45-AP is a recently identified phosphorylated protein that specifically associates with the leukocyte-specific transmembrane glycoprotein CD45. The gene for CD45-AP,Ptprcap(protein tyrosine phosphatase, receptor type c polypeptide associated protein), was mapped in mouse by typing the progeny of two multilocus crosses using the mouse CD45-AP cDNA as a Southern hybridization probe. The CD45-AP gene mapped to the centromeric region of Chr 19 proximal to the genesFth, Cd5,andPcna-rs.The gene for the human CD45-AP homologue,PTPRCAP,was localized to chromosome band 11q13.1–q13.3 by fluorescencein situhybridization using human genomic CD45-AP DNA as a hybridization probe. The genetic mapping of thePtprcap/PTPRCAPgenes extends the previously defined synteny conservation of various genes that have been assigned to these regions of the mouse and the human chromosomes.     

Monoclonal antibody to shiga toxin 1, which blocks receptor binding and neutralizes cytotoxicity

A monoclonal antibody, 5-5B, which neutralizes Shiga toxin 1 (Stx1) cytotoxicity of Escherichia coli, was constructed. An epitope analysis indicated that Asn55 in Stx1 B subunit was an important residue. This result and our previous results using an anti-Stx2 monoclonal antibody indicate that the region around the cysteine residue of the disulfide bond might be important for the neutralization of Stx cytotoxicity, making it a potential vaccination candidate.     

Photosynthetic Characteristics of Photoautotrophically Cultured Cells of Tobacco

The photosynthetic characteristics of photoautotrophically culturedcells of tobacco (Nicotiana tabacum cv. Samsun NN) as well asthose of photomixotrophically cultured cells and green leaveswere investigated. Analyses revealed that on a fresh weightbasis cultured tobacco cells had lower chlorophyll contentsthan cells of green leaves. The chlorophyll content per chloro-plast,however, was almost the same in both types of cell, and thechloroplast number per cell accounted for only small differencesin the cellular chlorophyll content. This indicates that thelarger cell volume of cultured cells is the main factor in thedifference in the chlorophyll content of these cells. Photosynthetic activity measurements also showed differencesin the chloroplasts of cultured and leaf cells. The maximumactivities of photosystem I and the Hill reaction for the culturedcells were about half those for leaf cells on a per unit chlorophyllbasis. Moreover, photo-autotrophic cells had relatively constantphotosystem I and Hill reaction activities during growth; whereas,on a fresh weight basis these activities in leaf cells reflecteddevelopmental changes in the chlorophyll content. Lithium dodecyl sulfate-polyacrylamide gel electrophoresis showedqualitatively similar thylakoid polypeptide compositions forcultured and leaf cells at all stages of growth even thoughthere were quantitative decreases in the contents of severalpolypeptides in the cultured green cells (especially in photomixotrophiccells) in comparison to the polypeptide contents of tobaccoleaves. We speculate that the lower photosynthetic activityof the cultured cells may be caused by this reduction in thecontents of certain thylakoid polypeptides. (Received November 14, 1988; Accepted June 19, 1989)     

Gamma-ray exposure from neutron-induced radionuclides in soil in Hiroshima and Nagasaki based on DS02 calculations

As a result of joint efforts by Japanese, US and German scientists, the Dosimetry System 2002 (DS02) was developed as a new dosimetry system, to evaluate individual radiation dose to atomic bomb survivors in Hiroshima and Nagasaki. Although the atomic bomb radiation consisted of initial radiation and residual radiation, only initial radiation was reevaluated in DS02 because, for most survivors in the life span study group, the residual dose was negligible compared to the initial dose. It was reported, however, that there were individuals who entered the city at the early stage after the explosion and experienced hemorrhage, diarrhea, etc., which were symptoms of acute radiation syndrome. In this study, external exposure due to radionuclides induced in soil by atomic bomb neutrons was reevaluated based on DS02 calculations, as a function of both the distance from the hypocenters and the elapsed time after the explosions. As a result, exposure rates of 6 and 4 Gy h(-1) were estimated at the hypocenter at 1 min after the explosion in Hiroshima and Nagasaki, respectively. These exposure rates decreased rapidly by a factor of 1,000 1 day later, and by a factor of 1 million 1 week later. Maximum cumulative exposure from the time of explosion was 1.2 and 0.6 Gy at the hypocenters in Hiroshima and Nagasaki, respectively. Induced radiation decreased also with distance from the hypocenters, by a factor of about 10 at 500 m and a factor of three to four hundreds at 1,000 m. Consequently, a significant exposure due to induced radiation is considered feasible to those who entered the area closer to a distance of 1,000 m from the hypocenters, within one week after the bombing.     

Microbial communities associated with acetate-rich gas-petroleum reservoir surface facilities

We evaluated the microbial communities in acetate-rich production waters from separators of a high-temperature gas-petroleum reservoir in Higashi-Niigata, Japan. Bacterial and archaeal 16S rRNA gene libraries constructed from these waters were dominated by Acetobacterium-, Methanofollis-, and Methanosarcina-related sequences. The libraries constructed from enrichment cultures of the production waters were dominated by sequences related to the Acetobacterium- and Methanofollis-related sequences.