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S Horai

Publications and source records attributed to S Horai.

At least 73 records · Page 4Linked to original sources
PubMed1990

Intraspecific nucleotide sequence differences in the major noncoding region of human mitochondrial DNA.

Nucleotide sequences of the major noncoding region of human mitochondrial DNA (mtDNA) from 95 human placentas have been determined. These sequences include at least a 482-bp-long region encompassing most of the D-loop-forming region. Comparisons of these sequences with those previously determined have revealed remarkable features of nucleotide substitutions and insertion/deletion events. The nucleotide diversity among the sequences is estimated as 1.45%, which is three- to fourfold higher than the corresponding value estimated from restriction-enzyme analysis of whole mtDNA genome. A hypervariable region has also been defined. In this 14-bp region, 17 different sequences were detected. More than 97% of the base changes are transitions. A significantly nonrandom distribution of nucleotide substitutions and sequence length variations were also noted. The phylogenetic analysis indicates that diversity among the negroids is much larger than that among the caucasoids or the mongoloids. In fact, part of the negroids first diverged from other humans in the phylogenetic tree. A striking finding in the phylogenetic analysis is that the mongoloids can be separated into two distinct groups. Divergence of part of the mongoloids follows the earliest divergence of part of the negroids. The remainder of the mongoloids subsequently diverged together with the caucasoids. This observation confirmed our earlier study, which clearly demonstrated, by the restriction-enzyme analysis, existence of two distinct groups in the Japanese.

Base Sequence↗
PubMed1989

Specific amplification of deleted mitochondrial DNA from a myopathic patient and analysis of deleted region with S1 nuclease.

Heteroplasmy of the normal-sized and the deleted mitochondrial genome has been observed in mitochondrial myopathy. The deleted region of the genome in the skeletal muscle of a patient was analyzed both by the conventional Southern blot method and by the novel method of employing the combination of polymerase chain reaction and S1 nuclease digestion. The results obtained by these methods were compared. Southern hybridization using various mitochondrial DNA fragments localized the deletion from at least position 9020 to 14,955, but regions of uncertainty of 1 kb remained on both ends of the deletion. Using the polymerase chain reaction, a fragment from the deleted genome was specifically amplified by choosing a pair of primers surrounding the deletion, and two fragments adjacent to the starting and end of the deletion were amplified from the normal-sized genome. S1 nuclease analysis of the heteroduplexes formed among these fragments demonstrated that the deletion extended from positions 8650 +/- 50 to 15,660 +/- 60. This method does not require radioisotopes and, moreover, can determine the deleted region within 5 h, in contrast to the 2 days required by the conventional Southern blot analysis. These results indicate that the novel method is faster and more accurate than the conventional method for the determination of the deleted region of genome.

Adult↗
PubMed1989

Increased level of mitochondrial gene expression in polyps of familial polyposis coli patients.

To elucidate the mechanism of polyp formation in familial polyposis coli patients, cDNA clones, expressed differently between normal colonic mucosae and polyps, were screened. Three polyp-derived cDNA clones showed increased levels of transcription under neoplastic conditions. Among them, clone P6 was determined to be derived from the mtDNA encoding parts of subunit 1 of NADH dehydrogenase and 16S rRNA. The number of copies and restriction enzyme patterns of the mtDNA did not vary in either normal or neoplastic tissues, and a level of different mitochondrial mRNA was increased in the same proportion, suggesting a change in the rate of synthesis and/or degradation of the mtRNA. No cDNA clone which was expressed higher in normal colonic mucosae than in polyps was isolated from the cDNA library derived from normal mucosae.

Adenomatous Polyposis Coli↗
PubMed1989

Pleiotropic molecular defects in energy-transducing complexes in mitochondrial encephalomyopathy (MELAS).

The extent of molecular defects in the mitochondrial energy-transducing system was examined in autopsied tissues of a 14-year-old male with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) in order to elucidate the underlying molecular and genetic abnormalities. The patient also had other multiorganic disorders: hypertrophic cardiomyopathy, nephrotic syndrome, and pseudohypoparathyroidism. Enzymic activities of complex I and IV were severely decreased, and those of complex III and V were mildly decreased in the mitochondria isolated from various tissues, but the severity of the deficiencies varied from tissue to tissue. In contrast, complex II and citrate synthase activities were normal or were decreased to a lesser extent than the enzymic activities of other complexes in all the tissues examined. These results suggest that the energy-transducing complexes, namely complexes, I, III, IV, and V, that contain mitochondrially synthesized subunits, were selectively affected. Immunoblot analysis demonstrated that the decreased enzymic activities were based on decreased contents of subunits in these complexes. The multiorganic manifestation of the disorder may result from wide and uneven distribution of abnormal mitochondria that have pleiotropic molecular defects in the energy-transducing complexes among the organs of the patient.

Acidosis, Lactic↗
PubMed1988

Maternal inheritance of deleted mitochondrial DNA in a family with mitochondrial myopathy.

Skeletal muscles from a mother and her daughter both with chronic progressive ophthalmoplegia were analyzed. Histological and biochemical analyses of their muscle samples showed typical features of this type of mitochondrial myopathy. Southern blot analysis revealed that, in both patients, there were two species of mitochondrial DNA (mtDNA): normal one and partially deleted one. The sizes of the deletion were different; the mutant mtDNAs from the mother and the daughter had about 2.5- and 5-kilobase deletions, respectively. The two mutant mtDNAs shared a common deleted region of 1.2-kilobase. However, both the start and the end of deletion were different between them, implying a novel mode of inheritance. This is the first report that the mutant mtDNA is responsible for the maternal inheritance of a human disease.

Adolescent↗
PubMed1988

Phylogenetic relationships among Japanese, rhesus, Formosan, and crab-eating monkeys, inferred from restriction-enzyme analysis of mitochondrial DNAs.

Mitochondrial DNA (mtDNA) polymorphisms in four species of macaques, i.e., Japanese monkey (Macaca fuscata), rhesus monkey (M. mulatta), Formosan monkey (M. cyclopis), and crab-eating monkey (M. fascicularis), were analyzed to study phylogenetic relationships. When 17 restriction enzymes of 6-bp recognition were used, 42-49 sites were observed in the samples. The estimated number of nucleotide substitutions per site among Japanese, rhesus, and Formosan monkeys ranges from 0.0318 to 0.0396, and that between the crab-eating monkey and the other monkeys from 0.0577 to 0.0653. These findings suggest that the crab-eating monkey diverged from the other three approximately 1.5-3.0 Myr before the present (Mybp) and that the Japanese, rhesus, and Formosan monkeys diverged approximately 0.9-1.8 Mybp, although the branching order cannot be determined conclusively.

Animals↗
PubMed1988

Molecular phylogeny and evolution of primate mitochondrial DNA.

We determined nucleotide sequences of homologous 0.9-kb fragments of mitochondrial DNAs (mtDNAs) derived from four species of old-world monkeys, one species of new-world monkeys, and two species of prosimians. With these nucleotide sequences and homologous sequences for five species of hominoids, we constructed a phylogenetic tree for the four groups of primates. The phylogeny obtained is generally consistent with evolutionary trees constructed in previous studies. Our results also suggest that the rate of nucleotide substitution for mtDNAs in hominines (human, chimpanzee, and gorilla) may have slowed down compared with that for old-world monkeys. This evolutionary feature of mitochondrial genes is similar to one found in nuclear genes.

Amino Acid Sequence↗
PubMed1987

An apparent discrepancy between chain length and electrophoretic mobility of restriction fragments: a case of human mitochondrial DNA.

DNA sequence analysis and electrophoresis in denaturing gel revealed that a 60 base pair insertion which had been previously postulated on the basis of native polyacrylamide gel electrophoresis of mitochondrial DNA from Japanese (Horai and Matsunaga 1986) did not exist at all. Unusual behavior of certain restriction fragments in native polyacrylamide gels apparently resulted in what appeared to be an insertion. Further study revealed that this behavior is most likely due to secondary structures of the fragments. The results of the present study suggest that adequate care should be taken when assessing molecular weights of restriction fragments by native polyacrylamide gel electrophoresis.

Base Sequence↗
PubMed1986

Mitochondrial DNA polymorphism in Japanese. II. Analysis with restriction enzymes of four or five base pair recognition.

Mitochondrial DNA (mtDNA) from 116 Japanese was analyzed with nine restriction enzymes that recognize a four or five base pair sequence. The sizes of the mtDNA fragments produced by digestion by each enzyme were compared after gel electrophoresis. Double digestion experiments indicated that, in the coding region from URF2 (unidentified reading frame) to tRNAAsn (bp 5274-5691), there is an insertion of about 60 base pairs (bp) compared with the published mtDNA sequence, which is common to all individuals in the present sample. A total of 95 different morphs were detected with the nine enzymes, 60 of which have not been documented previously. Based on a comparison of the cleavage maps of all individuals, 62 different combinations of restriction types were observed. By pairwise comparison of each restriction type, the average number of nucleotide substitutions per nucleotide site (delta) was estimated to be 0.0026. Phylogenetic analysis of the present data indicates that at least two distinct lineages exist in the Japanese population.

Base Sequence↗
PubMed1984

Differential enzyme activities in human esterase D phenotypes.

Red cell ESD activities have been determined in 78 individuals with ESD-1 phenotype, in 94 with ESD2-1 and in 28 with ESD-2 phenotype. The mean activities of these three groups were 276.7, 216.6 and 171.5 expressed as 10(-7) M methylumbelliferone produced/h/g Hb, respectively. The activities associated with a single ESD*1 gene are estimated to be 60% higher than ESD*2.

Alleles↗
PubMed1984

Mitochondrial DNA polymorphism in Japanese. I. Analysis with restriction enzymes of six base pair recognition.

The mitochondrial DNA (mtDNA) from 120 Japanese was analysed with 15 restriction enzymes that recognize six base pairs, of which 11 enzymes showed at least one atypical cleavage pattern. Digestion patterns with Hinc II and Hae II were highly polymorphic. The observed restriction enzyme morphs were classified into 22 types of distinct cleavage patterns. By pairwise comparison of each restriction type, the average number of nucleotide substitutions per nucleotide site (delta) was estimated at 0.00417, which agreed with the values obtained from other human populations in previous studies. There were 11 site gains, of which seven were transitions and four were transversions. Phylogenetic analysis of the present data suggested that the Japanese population conceals a considerably high degree of mtDNA diversity.

Base Composition↗
PubMed1982

Differential recognition of the serologically defined HLA-A2 antigen by allogeneic cytotoxic T cells. I. Population studies.

Human alloimmune cytotoxic T cells, sensitized selectively against the HLA-A2 antigen, were tested on a panel of selected target cells. Five HLA-A2 positive outlier cells could be identified. These outlier cells were only weakly lysed by HLA-A2 specific CTLs, although they were serologically indistinguishable from the other HLA-A2 positive, strongly lysed target cells. Furthermore, it was found that the outlier cells were poor cold target inhibitors in contrast to the other HLA-A2 positive target cells, which showed adequate inhibition of specific lysis of HLA-A2 positive target cells. Population studies indicate that the frequency of such HLA-A2 outlier cells may be approximately 10%.

Epitopes↗
PubMed1982

Cytotoxic T lymphocytes directed against HLA-Bw 35-linked target determinants show differences in sensitivity toward antibiotics during sensitization period.

Recently, we demonstrated that the outcome of human CML was influenced by the presence of antibiotics in the culture medium, In earlier studies we had found that cytotoxic T lymphocytes could recognize HLA-Bw 35-linked target determinants. These so-called Bw35 a and b determinants showed mendelian segregation. We describe in this article a difference between the Bw35 a and b cytotoxic T cells in their sensitivity toward antibiotics. The lysis against the Bw35 b cytotoxic determinant was not influenced by either the presence or the absence of antibiotics during the sensitization period, whereas the lysis against the Bw35 a cytotoxic determinant was drastically diminished when the effector cells were cultured in the absence of antibiotics during the sensitization period.

Anti-Bacterial Agents↗
PubMed1982

The outcome of cell mediated lympholysis is influenced by the antibiotics in the culture medium.

Recently we could demonstrate that antibiotics can interact with polymorphic membrane determinants. As a result, these determinants can no longer react with their corresponding antisera (Claas et al. 1981, 1982). In the present experiments it was found that allogeneic cytotoxic T cells (CTLs), which were cultured in the presence of antibiotics, induced significantly stronger lysis against the specific target than CTLs which were cultured in the absence of antibiotics. In some cases the CML assay was only positive according to the European Workshop criteria when penicillin was added to the cultures, whereas the assay was negative in the absence of penicillin. On the other hand when CTLs were induced in an MLC culture without penicillin, lysis was higher against the target cell in the absence of penicillin than in the presence of penicillin. By adding penicillin to the effector phase, inhibition of lysis was observed. No difference in 3H-thymidine-incorporation was observed between MLC cultures with and without antibiotics. We conclude that antibiotics in the culture medium can influence the outcome of CML experiments.

Culture Media↗