Although the mechanism of neuronal death

The genotype of Blastocystis isolated from humans and animals is highly polymorphic. Therefore, it is important to compare the genotypes of Blastocystis isolates from humans and animals to determine the zoonotic potential of animal isolates. PCR-based genotype classification using known sequence-tagged site (STS) primers allows identification of zoonotic isolates of animal origin. To this end, 51 isolates from monkeys, cattle, pigs, chickens, quails and pheasants were subjected to genotype analysis using seven kinds of STS primers. Out of the 51 isolates, 39 were identified as one of the known genotypes, four showed mixed genotypes, and eight were unknown genotypes as these were negative for all STS primers. When these results were combined with previous studies on 41 isolates from animals and compared with the diversity of genotypes of 102 human Blastocystis hominis isolates, 67?4 % (62/92) of isolates from mammals and birds were identical to human B. hominis genotypes. Since the unknown genotype of human origin had been placed into an additional clade in the small-subunit rRNA gene phylogeny, further molecular study on the eight isolates of unknown genotype from the present study will facilitate our understanding of their zoonotic potential. INTRODUCTIONBlastocystis hominis was first reported as a yeast in human faecal samples in 1912samples in (Brumpt, 1912, and now this organism is accepted as a common protozoan parasite of the human intestinal tract (Windsor et al., 2002). The species name B. hominis is generally used for human isolates, while many B. hominis-like organisms have been isolated from various animals, especially from many species of mammals and birds (Abe et al., 2002; Burden et al., 1978 Burden et al., / 1979Chen et al., 1997;Pakandl, 1991;Quílez et al., 1995). These isolates have been classified as B. hominis, Blastocystis sp. or newly proposed species, because there was no consensus for species designation of newly isolated Blastocystis from non-human hosts. So far, six and five isolates from different mammalian and avian species, respectively, have been proposed as new Blastocystis species, based on the differences in host origin, morphology, in vitro culture characteristics and/or karyotype (Belova, 1991(Belova, , 1995Belova & Kostenko, 1990;Chen et al., 1997;Krylov & Belova, 1997). However, Blastocystis is now recognized as a morphologically and genetically polymorphic organism and some non-human isolates have been demonstrated to be genotypically identical to B. hominis (Abe et al., 2003a, b, c;Arisue et al., 2003;Clark, 1997; Noël et al., 2003;Thathaisong et al., 2003;Yoshikawa et al., 1996 Yoshikawa et al., , 1998 Yoshikawa et al., , 2000Yoshikawa et al., , 2003Yoshikawa et al., , 2004. Therefore, if Blastocystis is a widely transmissible parasite between humans and mammals or birds, it is important to determine whether newly isolated non-human isolates are zoonotic. Recently we developed several sequence-tagged site (STS) primers derived from random amplified polymorphic DNAs (...

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The semaphorin family contains a large number of secreted and transmembrane proteins, some of which are known to act as repulsive axon guidance cues during development or to be involved in immune function. We report here on the identification of semaphorin K1 (sema K1), the first semaphorin known to be associated with cell surfaces via a glycosylphosphatidylinositol linkage. Sema K1 is highly homologous to a viral semaphorin and can interact with specific immune cells, suggesting that like its viral counterpart, sema K1 could play an important role in regulating immune function. Sema K1 does not bind to neuropilin-1 or neuropilin-2, the two receptors implicated in mediating the repulsive action of several secreted semaphorins, and thus it likely acts through a novel receptor. In contrast to most previously described semaphorins, sema K1 is only weakly expressed during development but is present at high levels in postnatal and adult tissues, particularly brain and spinal cord.The semaphorins constitute a large family of evolutionally conserved glycoproteins that are defined by a characteristic semaphorin domain of approximately 500 amino acids (1-3). The first vertebrate semaphorin, collapsin-1 in chick, was identified by its ability to induce growth cone collapse (4). Consistent with this function, its mammalian homologue, sema III, has been shown to repel specific subsets of sensory axons (5). As a result of these and other studies, Coll-1/sema III/D has been implicated in the patterning of sensory axon projections into the ventral spinal cord and cranial nerve projections into the periphery (6 -11).Several other semaphorins have also been implicated as repulsive and/or attractive cues in axon guidance, axon fasciculation, and synapse formation (1,(12)(13)(14)(15)(16)(17). In addition, members of the semaphorin family have been implicated in functions outside the nervous system, including bone skeleton and heart formation (9), immune function (18, 19), tumor suppression (20 -22), and conferring drug resistance to cells (23).Recent studies have identified the first semaphorin receptor as a member of the neuropilin family. Neuropilin-1 is a high affinity receptor for sema III, E, and IV, whereas neuropilin-2 binds differentially to the subfamily of secreted semaphorins (24 -27).The vertebrate semaphorin family can be classified into several phylogenetically distinct subfamilies (Ref. 15, Fig. 1B). Each subfamily has a unique structural arrangement of protein domains. The secreted members of the semaphorin family contain a characteristic semaphorin domain at the NH 2 terminus, followed by an immunoglobulin (Ig) domain and a stretch of basic amino acids in the carboxyl-terminal region. Between the NH 2 -terminal semaphorin domain and the transmembrane spanning region, the transmembrane semaphorins contain several alternative structural motifs, including either an Ig domain, a stretch of thrombospondin repeats, or a sequence with no obvious domain homology. Interestingly, semaphorin-like sequences have been identifi...