Biomedical subjects

Yuriko Hirai

Publications and source records attributed to Yuriko Hirai.

11 recordsLinked to original sources

PubMed2006

Schistosome egg production is dependent upon the activities of two developmentally regulated tyrosinases.

Egg production is responsible for life cycle progression and host immunopathology during schistosomiasis, with the associated parasite molecules being investigated as potential novel chemotherapeutic targets. Here, we characterize two Schistosoma mansoni products, tyrosinase 1 and tyrosinase 2 (SmTYR1/SmTYR2) and show that their diphenol oxidase enzyme activities are critical for eggshell formation and production. The genes encoding these bifunctional enzymes (monophenol and diphenol oxidases) result from a duplication event that likely occurred before speciation and exist in the parasite's genome as multiple copies, which are linked and localized to chromosomes 4 and W. SmTYR1/SmTYR2 transcription and diphenol oxidase action are developmentally regulated with most enzyme activity localized to the eggshell-producing cells contained within the vitellaria of adult female worms. Importantly, kojic-acid mediated inhibition (IC50=0.5 microM) of SmTYR1/SmTYR2's diphenol oxidase activity during in vitro culture of sexually mature adult worms resulted in a significant decrease in the production of phenotypically normal eggs. Therefore our data suggest that SmTYR1/2 inhibition represents a novel and potentially effective strategy for combating schistosomiasis and furthermore, it may point to new methods for combinatorial control of immunopathology and egg transmission during platyhelminth infection.

Animals↗

PubMed2005

Patterns of C-heterochromatin and telomeric DNA in two representative groups of small apes, the genera Hylobates and Symphalangus.

The course of chromosome evolution in small apes is still not clear, though painting analyses have opened the way for elucidating the puzzle. Even the C-banding pattern of the lar-group of gibbons (the genus Hylobates) is not clarified yet, although our previous studies suggested that lar-group gibbons have a unique C-banding pattern. We therefore made observations to establish C-banded karyotypes of the agile gibbons included in the lar-group. The data were compared with those of siamangs (the genus Symphalangus), which carry distinctive C-bands, to determine the chromosomal patterns in each group. C-banded chromosomes of agile gibbons showed several terminal, interstitial and paracentric bands, whose patterns are specific for each chromosome, whereas the C-bands of siamangs were located only at the terminal and centromeric regions in most chromosomes. Moreover, the C-bands of agile gibbons and siamangs were shown to be G+C-rich and A+T-rich DNA, respectively, by DAPI/C-band sequential staining. Additionally, PRINS labelling with a telomere primer revealed that agile gibbons have telomeric DNA only at chromosome ends where there is no C-band (non-telomeric heterochromatin), whereas the telomeric DNA of siamangs is located in the terminal C-banded regions (telomeric heterochromatin). Although the evolutionary mechanisms in small apes are still unknown, C-banding patterns and distribution of telomeric DNA sequences should provide valuable data to deduce the evolutionary pathways of small apes.

AT Rich Sequence↗

PubMed2005

A multifunctional shuttling protein nucleolin is a macrophage receptor for apoptotic cells.

Early apoptotic Jurkat T cells undergo capping of CD43, and its polylactosaminyl saccharide chains serve as ligands for phagocytosis by macrophages. This suggests the presence of a polylactosaminoglycan-binding receptor on macrophages. Here we show that this receptor is nucleolin, a multifunctional shuttling protein present in nucleus, cytoplasm, and on the surface of some types of cells. Nucleolin was detected at the surface of macrophages, and anti-nucleolin antibody inhibited the binding of the early apoptotic cells to macrophages. Nucleolin-transfected HEK293 cells expressed nucleolin on the cell surface and bound the early apoptotic cells but not phosphatidylserine-exposing late apoptotic cells. This binding was inhibited by anti-nucleolin antibody, by polylactosamine-containing oligosaccharides, and by anti-CD43 antibody. Deletion of the antibody binding region of nucleolin resulted in loss of the apoptotic cell-binding ability. Moreover, truncated recombinant nucleolin in solution containing this region blocked the apoptotic cell binding to macrophages, and the blocking effect was cancelled by the oligosaccharides. These results indicate that nucleolin is a macrophage receptor for apoptotic cells.

Amino Acid Sequence↗

PubMed2005

Synthesis and properties of the aromatic clusters arrayed along DNA strands.

Functional groups arrayed along DNA strands have been expected to show unique properties that are different from those monomers. Oligonucleotides carrying multi-pyrene groups arrayed along DNA strands showed strong excimer fluorescence emission intensities. The oligonucleotides carrying pyrene groups are surmised to be in single stranded forms in solutions. On the other hand, oligonucleotides carrying methyl red groups formed double stranded forms in which methyl red groups were tightly stacked. The structural factors which control the single strand-double strand equilibriums will be discussed.

Azo Compounds↗

PubMed2005

Preparation of modified oligonucleotides by the post-synthetic modification on resin method.

We report the novel method that accomplishes many processes such as synthesis, modification, deprotection, washing, on the solid support. Using polymers with a novel linker, oligonucleotides has been synthesized on a DNA synthesizer by the established procedures, then the polymer was treated in alkaline solutions for removing the protection groups. Since the linker is stable in alkaline solutions, oligonucleotides were still connected to the polymers. After washing out the chemical impurities, the oligonucleotides were released from the polymer by light irradiations.

Biochemistry↗

PubMed2004

Transcriptional repression mechanisms of nucleolus organizer regions (NORs) in humans and chimpanzees.

Polymorphisms related to transcriptional inactivation of nucleolus organizer regions (NORs) have long been described in many animals, particularly humans. However, the precise aetiology of such variations is not always clear. We conducted analyses to investigate the repression mechanisms in humans and chimpanzees using FISH (fluorescence in situ hybridisation) with 18S rDNA, Ag-NOR (silver nitrate) staining, C-banding, and the in situ nick translation technique with the HpaII restriction enzyme. Examination of 48 humans and 46 chimpanzees suggested that there are at least three different mechanisms that produce inactivation of NORs. These include: (1) elimination of rDNA; (2) DNA methylation: (3) gene silencing due to position effects induced by heterochromatin (C-bands) and/or telomeres.

Animals↗

PubMed2004

FISH mapping for helminth genome.

Basic techniques for fluorescence in situ hybridization (FISH) mapping that have been used in genome projects on schistosomes and filariae are introduced. The chapter shows techniques specific for bacterial artificial chromosome (BAC) and yeast artificial chromosome (YAC) clones and includes experiences of chromosome preparation, DNA labeling, hybridization, microscopy, and localization of BAC clones.

Animals↗

PubMed2003

The amelogenin loci span an ancient pseudoautosomal boundary in diverse mammalian species.

The mammalian amelogenin (AMEL) genes are found on both the X and Y chromosomes (gametologous). Comparison of the genomic AMEL sequences in five primates and three other mammals reveals that the 5' portion of the gametologous AMEL loci began to differentiate in the common ancestor of extant mammals, whereas the 3' portion differentiated independently within species of different mammals. The boundary is marked by a transposon insertion in intron 2 and is shared by all species examined. In addition, 540-kb DNA sequences from the short arm of the human X chromosome are aligned with their Y gametologous sequences. The pattern and extent of sequence differences in the 5' portion of the AMEL loci extend to a proximal region that contains the ZFX locus, and those in the 3' portion extend all the way down to the pseudoautosomal boundary (PAB)1. We concluded that the AMEL locus spans an ancient PAB, and that both the ancient and present PABs were determined by chance events during the evolution of mammals and primates. Sex chromosome differentiation likely took place in a region that contains the male-determining loci by suppressing homologous recombination.

Amelogenin↗

PubMed2003

A probe generated by chromosome microdissection, useful for analyzing Y chromosome evolution in Old World monkeys.

We isolated a DNA probe, designated MMDYZ1, using a chromosome microdissection technique from the Y chromosome of the Rhesus monkey. The probe obtained from eight whole Y chromosomes shows higher specificity for the Y short arm of the Rhesus monkey, which consists totally of constitutive heterochromatin. Two microclones (MMY#3 and MMY#4) were constructed from the Y-specific primary PCR products. Sequence analysis of these two microclones revealed that both were essentially identical to each other and the sizes were 870 and 686 bp, respectively. From alignment analysis using the Genbank database of primates, the alphoid DNA has the highest affinity with the probe. However, the total composition of this probe has extremely high homology with the Y short arm of the Rhesus monkey, as demonstrated by fluorescence in-situ hybridization (FISH). Comparative FISH-mapping disclosed that this DNA-sequence cluster was located at extremely different sites on the Y chromosome in several species of the Old World monkey. Accordingly, this probe seems to be a high-quality tool, now established for the first time, for investigating Y chromosome evolution of the Old World monkey.

Animals↗

PubMed2002

Adenylosuccinate lyase of Schistosoma mansoni: gene structure, mRNA expression, and analysis of the predicted peptide structure of a potential chemotherapeutic target.

Adenylosuccinate lyase is an enzyme used in parasite nucleotide salvage pathways that cleaves adenylosuccinate into adenosine 5'-monophosphate and fumarate. A cDNA encoding adenylosuccinate lyase from the trematode parasite Schistosoma mansoni has been cloned for analysis. Sequencing of the cDNA revealed an open reading frame of 1454 nucleotides that codes for a protein with a predicted mass of about 54.5 kDa. Comparative analysis of the predicted protein sequence shows that S. mansoni adenylosuccinate lyase has a lot of similarity with human adenylosuccinate lyase. Genomic analysis using S. mansoni adenylosuccinate lyase-containing bacterial artificial chromosome (BAC) clones revealed a gene of approximately 19.4 kb consisting of eight exons and seven introns. Intron 6 was found to contain a novel 2.9 kb long terminal repeat retrotransposon with direct terminal repeats of 500 nucleotides. Fluorescence in situ hybridisation mapping localised S. mansoni adenylosuccinate lyase to the Z and W chromosomes. Analysis of S. mansoni adenylosuccinate lyase mRNA expression levels using real time reverse transcriptase (RT)-PCR showed that S. mansoni adenylosuccinate lyase is expressed at higher levels in the female worms than in the male worms and is expressed at different levels than other purine nucleotide salvage enzymes. Male homogenate showed a specific activity of 10.3 units/mg protein while the female showed a specific activity of 24.2 units/mg protein. These data indicate that S. mansoni adenylosuccinate lyase is an important parasite enzyme and should be examined as a potential chemotherapeutic target.

Adenylosuccinate Lyase↗

PubMed2002

Cytogenetic differentiation of two sympatric tree shrew taxa found in the southern part of the Isthmus of Kra.

Sympatric populations of the genus Tupaia encompassing two cytotypes (cyt60, 2n = 60 and cyt62, 2n = 62) were found in the southern part of the Isthmus of Kra (the middle region of the Malay Peninsula, Thailand). C-bands, location of rDNA, and location of non-essential telomeric repeats (TRs) were investigated in detail for 23 animals captured in the area. Such chromosomal traits definitely reveal that two distinct cytotypes exist in the sympatric population, though the external morphological traits are similar. Hybrid cytotypes were not observed; thus, these two cytotypes appear to be genetically isolated sibling species. Chromosomal results compared with previous data, geographic distribution and morphological data observed with new insight suggest that, in the sympatric population, 'cyt60' represents members of Tupaia glis, while 'cyt62' identifies individuals of Tupaia belangeri. The cytogenetic information discovered in the present study offers new insight to morphological classification and, further, may provide substantial diagnostic characteristics for the distinction of tree shrew species.

Animals↗