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Biomedical subjects

M Ohki

Publications and source records attributed to M Ohki.

At least 127 records · Page 7Linked to original sources
PubMed1993

Sequence-tagged NotI sites of human chromosome 21: sequence analysis and mapping.

We isolated and analyzed 19 NotI site-containing clones specific for human chromosome 21. The overall process consisted of selective isolation of NotI site-containing clones from flow-sorted chromosome 21 libraries, selection of independent clones by their restriction patterns and nucleotide sequences, and assignment of the clones to chromosome 21. Sequence analysis showed that the regions around the NotI sites had features typical of CpG islands, such as extremely high GC content, high-frequency appearance of CpG dinucleotide sequences, and lack of methylation of these CpGs. PCR conditions for these extremely G + C-rich templates were optimized to establish these NotI sites as sequence-tagged sites.

Base Sequence↗
PubMed1993

Bone mineral and other bone components in vertebrae evaluated by QCT and MRI.

To evaluate the usefulness of assessing bone components using magnetic resonance imaging (MRI), the contributions of bone components, including mineral, fat and collagen, to bone mineral density (BMD) and T1 relaxation time (T1) were studied using phantoms. Excised human vertebrae were also evaluated by quantitative computed tomography (QCT) and MRI. T1 was shortened with increasing quantities of fat and collagen. In water, T1 was significantly affected by bone density, while in oil, T1 became slightly longer as bone density increased. The presence of fat and collagen caused under- and overestimations of BMD, respectively. There was good correlation between T1 and BMD in osteoporotic vertebrae and the vertebrae with long T1 showed an increased content of hematopoietic marrow and/or abnormally increased bone mineral. It was concluded that the experimental data showed that MRI can contribute to the assessment of bone quality.

Adipose Tissue↗
PubMed1993

A NotI restriction map of the entire long arm of human chromosome 21.

A variety of maps of the human genome have been constructed, including cloned DNA maps. We have isolated 40 of the 42 NotI sites that exist on the long arm of human chromosome 21, as NotI linking clones and constructed a complete NotI restriction map spanning the entire region. This map, which provides the most reliable ordering and distance estimation in the region from a pericentromeric locus to the terminus, demonstrates the usefulness of linking clone mapping for analysing human chromosomes.

Animals↗
PubMed1993

Extinction of T cell receptor alpha-chain gene expression accompanied by loss of the lymphoid enhancer-binding factor 1 (LEF-1) in murine somatic cell hybrids.

To investigate the presence of a negative regulatory factor(s) suppressing T-cell receptor alpha-chain (TCR alpha) gene expression in non-T cells, 10 independent cell hybrid clones were generated between mouse T-cell lymphoma EL4 cells (TCR alpha+/beta+) and mouse fibroblast B82 cells. These cell hybrids showed a typical fibroblastic morphology and retained an approximate sum of chromosome numbers derived from both parental cells. No transcripts of the TCR alpha gene were detected in the cell hybrids, although the presence of the rearranged TCR alpha allele from EL4 cells was confirmed. The possibility of involvement of nuclear proteins responsible for the activity of the TCR alpha gene enhancer in the extinction of TCR alpha gene expression in the cell hybrids was examined. Nuclear proteins which bind to the lymphoid enhancer-binding factor 1 (LEF-1) binding motif present in EL4 cells disappeared in the hybrid clones, whereas no significant change was observed in DNA-binding activity of nuclear proteins to a consensus cyclic AMP response element (CRE) and the Ets-1 binding motif between the parental cells and the cell hybrids. No transcripts of the LEF-1 gene were detected in the cell hybrids, despite the retention of the LEF-1 gene and murine chromosomes 3, on which the LEF-1 allele is located, from both parental cells. These results suggest that a trans-acting negative regulatory factor(s) present in fibroblasts suppresses LEF-1 gene expression and that suppression of LEF-1 may lead to the extinction of TCR alpha gene expression in the cell hybrids.

Animals↗
PubMed1993

Molecular basis of the t(8;21) translocation in acute myeloid leukaemia.

The t(8;21) translocation is one of the most frequent chromosomal abnormalities in acute myeloid leukaemia and results in gene fusion between AML1 on chromosome 21 and MTG8 (= ETO or CDR) on chromosome 8. AML1 contains a region of sequence homology to the Drosophila runt gene and the mouse polyomavirus enhancer binding protein PEBP2 alpha gene. The rearrangement occurs within a specific intron of the AML1 gene and results in the formation of a chimaeric protein with the consistent feature that the region of sequence homology of AML1 is fused with almost the entire MTG8 protein. MTG8 (ETO, CDR) is predicted to be a transcription activation factor from its sequence with zinc-finger motifs and proline-rich domains. Thus the rearrangement is a fusion between two probable transcription activation factors.

Amino Acid Sequence↗
PubMed1993

[A basic study on a highly sensitive automated method for hypercoagulable state in plasma, fluorogenic prothrombin time (FPT) method].

A highly sensitive automated method, fluorogenic prothrombin time (FPT) method, was developed by a combination of a fluorogenic peptide substrate for thrombin and a centrifugal autoanalyzer (Cobas Bio). Using plasmas from stroke patients, we showed that the second reagent containing fluorogenic peptide substrate should be mixed after the first reagent containing tissue factor and plasma were mixed, that is, two steps method, in order to detect hypercoagulable state. When the first and the second reagent were mixed with plasma at the same time, that is, one step method, FPT was not sensitive to hypercoagulable state. We also showed that patient plasmas should be stored at -80 degrees C and subjected to FPT analysis immediately after thawing, not leaving at 4 degrees C or room temperature. Good correlation was observed on FPT of stroke patients using human tissue factor and bovine tissue factor. Another fluorogenic method was developed by the same principle for the evaluation of factors X and VII concentrations in plasma using deficient plasma of factor X or factor VII. Good correlation was observed on factors X and VII concentrations of stroke patients using human tissue factor and bovine tissue factor.

Blood Coagulation Tests↗
PubMed1993

[Physical mapping of human chromosomes with linking clones and jumping clones].

Physical maps facilitate the correlation of genetic linkage maps and actual genome structure, and contribute to the immediate access to disease genes in question. The introduction of pulsed-field gel electrophoresis (PFGE) made it possible to construct restriction maps in Mb order with rare-cutting enzymes. Linking clones and jumping clones are useful tools for constructing long-range and accurate maps. The linking clones are used to identify adjacent restriction fragments and the jumping clones are to identify neighboring restriction sites. The general strategy for physical mapping using these clones and our application to NotI restriction mapping of human chromosome 21 are described.

Animals↗
PubMed1993

[Effectiveness of a community-based education program on blood pressure reduction for cardiovascular disease prevention].

To evaluate the effectiveness of lifestyle modification community-based programs on blood pressure reduction, blood pressure changes were examined according to frequency of attendance at these adult classes. The subjects were 1,017 men and women aged 40-69 who participated in a survey from 1985 to 1987, whose blood pressure was > = 140 mmHg for systolic, and/or > = 90 mmHg for diastolic and/or with antihypertensive medication use in the earlier 1981-1984 surveys. Adult classes were conducted eleven times between 1982 and 1987, emphasizing primarily reduction of salt intake, weight control if necessary, and alcohol modification. Blood pressure changes between 1981-1984 and 1985-1988 were examined in relation to the number of classes attended, stratified by antihypertensive medication use. In the group with no medication use in both surveys (n = 347), there was a significantly larger decline in systolic and diastolic blood pressures with an increase in the number of classes attended (p < 0.001). A similar trend was observed in other groups: a starting medication group (n = 198), a quitting medication group (n = 100) and a continuous medication group (n = 372). The blood pressure trend in the no medication group remained significant after controlling for age, initial blood pressure, follow-up years and the number of follow-up screenings attended. For the no medication group, there was no significant association between the number of classes attended and changes in relative weight index and alcohol intake. The proportion of persons reporting dietary modification of reduction in salt was larger, and mean 24-hour urine sodium excretion was smaller, with increasing number of classes attended in the 1985-1988 surveys. Furthermore, the proportion of persons who were able to reduce salt intake between the two survey periods was higher with an increase in the number of classes attended. Mean urine sodium excretion was smaller in those who reported reduction of salt intake than those who did not. Although this study is not a randomized controlled trial, these results suggest that a community-based education program of adult classes can be effective in reduction of blood pressure levels through modification of diet.

Adult↗
PubMed1992

Consistent disruption of the AML1 gene occurs within a single intron in the t(8;21) chromosomal translocation.

The AML1 gene on chromosome 21 was rearranged by the t(8;21) chromosomal translocation in acute myeloid leukemia (AML). Southern blot analysis of 21 AML patients with t(8;21), including three with complex translocations, t(8;V;21), demonstrated that all the breakpoints occurred at random within a single intron between two coding exons of AML1. Clustering of the breakpoints in the restricted intron suggests the formation of a unique fusion gene between the AML1 gene and a presumable counterpart gene on chromosome 8. Nucleotide sequencing of the breakpoint region revealed that the translocation event was accompanied by deletion of a short stretch of nucleotides.

Base Sequence↗
PubMed1992

Escherichia coli dnaJ deletion mutation results in loss of stability of a positive regulator, CRP.

The dnaJ deletion mutant K7052(lambda dnaK) has a temperature-sensitive defect in the synthesis of beta-galactosidase. We confirmed this operon-specific and temperature-sensitive defect in cell-free extracts prepared from the mutant cells and found that the missing factor was CRP. In the mutant, the cellular concentration of CRP was too low to allow the expression of the lac operon at a nonpermissive temperature. Introduction of a CRP over-producing plasmid into the dnaJ deletion mutant suppressed the defect of beta-galactosidase synthesis. The lower content of CRP in the mutant was found to result from extreme instability of the protein. These results strongly suggested that the heat shock protein dnaJ is involved in the stabilization (or degradation) of CRP.

Autoradiography↗
PubMed1992

Quantitative evaluation of sialograms.

RATIONALE AND OBJECTIVES: The authors developed and evaluated a quantitative analytic method for interpreting clinical sialograms. METHODS: Images were obtained by digital subtraction sialography and transformed into binary form. The duct width of the image was calculated and represented as a normalized histogram. The effects of the volume of contrast medium injected and of the inclination angle of the objects on the histogram were examined. RESULTS: In model studies, the normalized histogram was affected insignificantly by these factors. Clinical sialograms of 18 patients with normal results, 12 patients with parotitis, and 5 patients with Sjögren syndrome were preliminarily analyzed by the histogram method and four representative parameters of the histogram. Discriminant analysis showed a relatively high correct-predictive rate in the distinction between patients with normal and abnormal results. CONCLUSIONS: This method reduces the effect of observer variation in diagnosing sialograms, and improves diagnostic accuracy for assessing the presence of inflammatory diseases of the parotid gland.

Animals↗
PubMed1992

[Application of the limulus amebocyte lysate test to measurement of endotoxin in therapeutic human plasma protein fraction. Comparison with the rabbit pyrogen test].

We applied the limulus amebocyte lysate (LAL) test to the detection of bacterial endotoxins in therapeutic human plasma protein fraction (PPF) and compared the LAL-test with the rabbit pyrogen test. Two endotoxin-specific LAL-reagents were used for the colorimetric method and turbidimetric kinetic method. The amounts of added endotoxin to the PPF were correctly estimated by either method. The results of four independent assays for the 53 samples of PPF corresponded well with each other (correlation coefficient: 0.851-0.959, regression coefficient: 0.898-1.151). The amounts of endotoxin in the PPF estimated by the LAL-test significantly correlated with the rise of body temperature in rabbits (correlation coefficient: 0.547-0.642, and 0.911-0.934 for the endotoxin added samples). These results suggest that the LAL-test could be used as an alternative method for the rabbit pyrogen test to PPF.

Animals↗
PubMed1992

Standardized lateral oblique projection of the mandible for digital subtraction radiography.

A special apparatus was developed for standardization of the lateral oblique projection of the mandible (LOPM) in order to apply the digital subtraction method. Geometric reproducibility was examined over an 8-week period using a dry skull. Angulation errors were determined by the relation to image noise in the subtraction image. It was found that the relation between image noise and angulation error was approximated by a second-order polynomial. Geometric reproducibility was within 1 degree over the experimental period. These results suggest that this standardized LOPM is satisfactory for clinical application of digital subtraction. Two cases are presented where this technique was used to demonstrate longitudinal changes in bone density.

Adult↗
PubMed1991

t(8;21) breakpoints on chromosome 21 in acute myeloid leukemia are clustered within a limited region of a single gene, AML1.

The t(8;21)(q22;q22) translocation is a non-random chromosomal abnormality frequently found in patients with acute myeloid leukemia (AML) with maturation (M2 subtype). We report here the cloning of a gene, named AML1, on chromosome 21 that was found to be rearranged in the leukemic cell DNAs from t(8;21) AML patients. The breakpoints in 16 out of 21 patients were clustered within a limited region of AML1, and detailed analysis in 3 patients revealed that the breakpoints occurred in the same intron of the gene. Sequencing of cDNA clones identified a long open reading frame encoding a 250-amino acid protein. Northern blot analysis detected four constant mRNA species in t(8;21) leukemic and normal cells; the largest species was more abundant in the leukemic cells than in normal cells. In addition, two mRNA species limited to the leukemic cells were found. These findings indicate that the AML1 gene may be involved in neoplastic transformation of AML with the t(8;21) translocation.

Acute Disease↗
PubMed1991

Molecular assignment of a translocation breakpoint in acute myeloid leukemia with t(8;21).

An 8;21 translocation is a common chromosome abnormality associated with acute myeloblastic leukemia with maturation (M2 of French-American-British (FAB) classification). We have isolated chromosome 21 Notl linking clones; pulsed field gel electrophoresis analysis with one clone (LL263) detected an altered fragment of Notl-digested leukemic cell DNA carrying t(8;21). The altered fragment was shown to be produced by the 8;21 translocation. The breakpoint in chromosome 21 was located about 13 kb to 100 kb proximal to the LL263 Notl site. Because the LL263 clone has a CpG island and is a short distance from the breakpoint, the clone itself may be considered as a candidate for part of the t(8;21) associated gene.

Acute Disease↗