Chromosomes of Temnocephala minor,an ectosymbiotic turbellarian on Australian crayfish found in Kagoshima Prefecture,with karyological notes on exotic turbellarians found in Japan

Records of exotic turbellarian species found in Japan are reviewed from taxonomic and karyological viewpoints. Temnocephala minor Haswell, 1888, an ectocommensal on a freshwater crayfish of Australia, was found from culture ponds of Cherax tenuimanus (introduced from W. Australia) in Kagoshima Prefecture. T. minor had the chromosome number of 2x = 18 (2sm + 2m + 2m + 2sm + 2m + 2m + 2m + 2sm + 2m). The following 3 species of exotic freshwater triclads were recorded from tanks and ponds used for tropical fish culture: Dugesia austroasiatica Kawakatsu, 1985 (2x = 16), Dugesia tigrina (Girard, 1850) (2x = 16) and Rhodax? sp. (3x = 24; 3x = 24 &; 3x + 1LB + 1SB = 25 + 1SB). The following 3 species of exotic terrestrial triclads were recorded: Bipalium nobile Kawakatsu et Makino, 1982 (2x = 10), Bipalium kewense Moseley, 1878 (2x = 18), and Platydemus manokwari de Beauchamp, 1962 (n = 6, 2x = 12). An extensive occurrence of P. manokwari in the Southwest Islands of Japan may be due to an unexpected introduction of the animal in very recent years.     

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Organizers of the Sixth International Symposium on the Biology of the Turbellaria     

Karyology of four land-planarian species of the genus Bipalium from Japan

We have employed a new scale for characterizing chromosomal forms in the karyotypes of four species of Bipalium from five localities in Japan. Specimens of Bipalium nobile Kawakatsu et Makino, 1982, from Yokohama had a diploid chromosome number of 2x = 10 (2m + 2sm + 2sm + st & sm + 2sm); specimens of the same species from Toyonaka had this number as well but with slightly different chromosomal form (2m + 2sm + sm & st + 2st + m & sm). An undescribed species from Sanjô, Bipalium sp. 2, with two dorsal stripes and a yellow head crescent, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m); and another undescribed species from Chichijima Island, Bipalium sp. 3, with five dorsal stripes, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m). A non-sexual bipaliid tentatively identified as Bipalium kewense Moseley, 1878, from Chichijima Island had 2x = 18 (2m + 2m + 2m + 2sm + 2st + 2sm + 2sm + 2sm + 2sm).     

Presence of transplantable T-lymphoid cells in C57BL/6 mice infected with murine AIDS virus.

The Duplan strain of murine leukemia virus induces murine AIDS in C57BL/6 mice. When spleen cells from C57BL/6 mice infected with the virus were transplanted into nude mice, subcutaneous solid tumors at the transplanted sites were formed and splenomegaly and lymphadenopathy were induced. These transplantable cells were Thy-1- CD4+ alpha-beta T-cell receptor-positive T cells and integrated with the pathogenic defective viral genome. These results indicate that neoplastic cells of T-cell lineage were induced by infecting C57BL/6 mice with murine AIDS virus.     

Chromosomes of Phagocata kawakatsui and Bdellocephala annandalei from Lake Biwa-ko in Honshú, central Japan

Two lake-dwelling species of paludicolen triclads from Lake Biwa-ko (Honshû, Japan) were studied taxonomically and karyologically. (1) Phagocata kawakatsui Okugawa, 1956, is an epigean species usually inhabiting shallow springs and spring-fed streams in Central Japan. In Lake Biwa-ko, animals were obtained from several bottom stations of the littoral area in the southern part of the northern basin (3–70 m in depth). Chromosome numbers and karyotype: 2x=24 (2m+2sm+2sm+2m+2sm+2m+2sm+2m+2m+2sm+2m+2m). The first pair of metacentric chromosomes is very large in size. (2) Bdellocephala annandalei Ijima et Kaburaki, 1916, an endemic species, is distributed widely in the deep areas of the northern basin (30 to over 100 m in depth). Chromosome numbers and karyotype: 2x=28 (2m+2sm+2sm+2sm+2sm+2m+2m+2m+2m+2m+2m+2m+2m+2m) with the first pair of metacentric chromosomes very long.     

Fine structure of a virus-encoded helper T-cell epitope expressed on FBL-3 tumor cells.

Antigen peptide fn20 representing Friend murine leukemia virus env122-141 (DEPLTSLTPRCNTAWNRLKL) is recognized by two independent Friend virus-induced, FBL-3 tumor-specific helper T-cell (Th) clones. We isolated more Th clones from mice immunized with fn20 peptide. We examined the fine structure of the peptide required to activate a large group of fn20-specific Th clones. A systematic analysis of peptides of decreasing lengths eliciting Th proliferation defined the minimum core length as 13 amino acids (LTSLTPRCNTAWN). Functional proliferation and competition assays with variant peptides with alanine substitutions permitted the assignment of five peptide residues in two major histocompatibility complex-interacting and three T-cell-receptor-interacting sites. Th clones were different in their reactivities toward peptides of various lengths and the variant peptides.     

Immunological characterization of tumor-rejection antigens on ultraviolet-light-induced tumors originating in the CB6F1 mouse

Six ultraviolet-light(UV)-induced tumors of (BALB/c×C57BL/6)F₁ (H-2^d/b) mouse origin were analyzed for the effector T cell subsets involved in tumor rejection the MHC class I to which cytolytic T lymphocytes (CTL) are restricted, and the effect of UV radiation on tumor rejection, to characterize their tumor-rejection antigens (TRA) recognized by CTL. All tumors were rejected in syngeneic normal mice but grew progressively in nude mice. CD8⁺ T cells mediated the antitumor responses for all tumors and CD4⁺ T cells could also do so for one tumor 6.1B. Each tumor induced potent CTL that recognized the specific TRA in preferential association with MHC class I haplotypes not from H-2^b but from H-2^d; that is, K^d, D^d or L^d. Profiles of TRA expression on two tumors were obtained by the analyses of their antigen-loss variants. 1A codominantly expressed at least four distinct TRA associated with K^d, all of which induced CTL. On the other hand, UV 1 had at least two distinct TRA, one of which, associated with K^d, exclusively induced CTL. However, in the absence of the dominant TRA, another TRA associated with L^d on R95C, a variant of UV, 1, induced CTL. Unlike other tumors, R95C grew progressively in short-term-UV-irradiated syngeneic mice. Nude mice reconstituted with a combination of CD4⁺ T cells from short-term-UV-irradiated mice and CD8⁺ T cells from normal mice did not reject R95C. An increase in the former T cell population led the reconstituted mice to reject the tumor. These findings suggest some functional defects of CD4⁺ T cells rather than the generation of suppressor cells in short-term-UV-irradiated mice. The UV-induced tumors used in the present study provide a unique system for analyzing the preferential sorting of TRA as well as for elucidation of the TRA itself.     

CD4(+) T cells and gamma interferon in the long-term control of persistent friend retrovirus infection

We have used the Friend virus model to determine the basic mechanisms by which the immune system can control persistent retroviral infections. Previously we showed that CD4(+) T cells play an essential role in keeping persistent retrovirus in check. The present in vitro experiments with a Friend virus-specific CD4(+) T-cell clone revealed that these cells produce gamma interferon (IFN-gamma), which acts with two distinct mechanisms of antiviral activity. First, IFN-gamma had a direct inhibitory effect on virus production. This inhibitory effect was noncytolytic and, interestingly, was not associated with decreased cell surface expression of viral antigens. The second mechanism of IFN-gamma-mediated antiviral activity was an enhancement of CD4(+) T-cell-mediated cytolytic activity. We also found an in vivo role for IFN-gamma in the control of persistent Friend virus infections. Neutralization of IFN-gamma in persistently infected mice resulted in significantly increased levels of virus in the spleen, and a significant percentage of IFN-gamma-deficient mice were unable to maintain long-term control over Friend virus infections.     

Isolation of a major genetic interaction associated with an extreme phenotype using assorted F2 populations in rice

Detection of quantitative trait loci (QTLs) is dependent on the materials used in the analysis, as different combinations of parental materials may lead to different outcomes in QTLs for the same trait. On the other hand, an extreme phenotype associated with a given trait implies the potential involvement of a particular allele in various allelic interactions. A genetic factor associated with such an extreme phenotype may frequently be identified from various genetic populations consisting of different parental combinations. In this study, we attempted to uncover the genetic factor associated with extremely early heading date in rice, using various F2 populations. Heading date in rice has been characterized by at least 19 QTLs, from which 12 genes have been identified. A58, a rice strain with an extremely early heading date, is adapted to Hokkaido, the northernmost limit of rice cultivation. Six F2 populations derived from crosses of A58 with six other strains displayed a range of heading dates. Genotyping using 19 QTL markers indicated that the A58 allele of the Ghd7 locus was present in most F2 individuals exhibiting extremely early heading dates. This analysis also demonstrated that when the wild-type Ehd1 allele was present, the Ghd7 allele from A58 accelerated floral induction. The results of this study demonstrate that assorted F2 populations are valuable materials for comprehensive genotyping to explore major genetic factors for extreme phenotypes, and that this methodology is broadly applicable to other unknown traits.     

Features of dnaK operon genes of the obligate thermophile Bacillus thermoglucosidasius KP1006

The dnaK gene was cloned from the obligate thermophile Bacillus thermoglucosidasius KP1006, together with the grpE and dnaJ genes in the same operon. The dnaK, grpE and dnaJ genes showed high identity with those of other bacterial strains, particularly with those of Bacillus stearothermophilus NUB36, despite an extremely low homology for the corresponding total genomic DNA. There were significant differences in the proline content of the DnaK operon proteins which is closely correlated with the thermostability of enzyme proteins. The proline content was higher in the GrpE, DnaK and DnaJ proteins of the thermophilic as opposed to the mesophilic strains. The overexpression of the B. thermoglucosidasius DnaK protein in Escherichia coli MV1184 results in extreme filamentation without inhibition on cell growth. The B. thermoglucosidasius DnaK protein seemed to exclusively disturb septation in E. coli cells which suggests that it interacts with key protein(s) involved in cell septation.