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Biomedical subjects

Y Yokota

Publications and source records attributed to Y Yokota.

At least 73 records · Page 4Linked to original sources
PubMed1998

Molecular analysis of carbon ion-induced mutations in Arabidopsis thaliana.

In order to elucidate the characteristics of the mutations induced by ion particles at the molecular level in plants, mutated loci in carbon ion-induced mutants of Arabidopsis were investigated by PCR and Southern blot analyses. In the present study, two lines of gl1 mutant and two lines of tt4 mutant were isolated after carbon ion-irradiation. Out of four mutants, one had a deletion, other two contained rearrangements, and one had a point-like mutation. From the present result, it was suggested that ion particles induced different kinds of alterations of the DNA and therefore they could produce various types of mutant alleles in plants.

Arabidopsis↗
PubMed1998

Nucleotide sequence of the GLABROUS1 gene of Arabidopsis thaliana ecotype Columbia.

The GLABROUS1 (GL1) gene from Arabidopsis thaliana ecotype Columbia was isolated and sequenced. Comparison of the nucleotide sequence with that of the gl1-2allele revealed that two sites were changed in gl1-2. One was a 14-bp deletion in exon 3, which seemed most likely to be the cause of the mutated phenotype. The other was a change from TC to CT in the 5' untranslated region. Since the 5' upstream sequence required for the GL1 gene expression has not been clearly specified, one cannot rule out the possibility that this change may contribute to the phenotype of gl1-2. A comparison was also made with the GL1 gene of ecotype Wassilewskija and revealed some lack of sequence conservation. The changes observed may have little influence on the function or the expression of the GL1 gene product.

5' Untranslated Regions↗
PubMed1997

Resistance to endotoxic shock in phospholipase A2 receptor-deficient mice.

Mammals possess various types of secretory phospholipase A2, which differ in the primary structure and tissue distribution. The phosholipase A2 receptor (PLA2R) recognizes group IB phospholipase A2 (PLA2-IB) and mediates the PLA2-IB-induced biological responses in non-digestive organs, including eicosanoid production and contraction of airway smooth muscles. In this study, we generated PLA2R-deficient mice to define its biological roles further. These mice are viable, fertile, and without evident histopathological abnormalities. There was no difference in the clearance of circulating PLA2-IB between wild-type and mutant mice. After challenge with bacterial lipopolysaccharide (LPS), PLA2R-deficient mice exhibited longer survival than wild-type mice. The mutant mice were also resistant to lethal effects of exogenous PLA2-IB after sensitization with sublethal dose of LPS. The plasma levels of tumor necrosis factor-alpha and interleukin-1beta elevated after LPS treatment were significantly reduced in mutant mice compared with wild-type mice. These findings suggest a potential role of PLA2R in the progression of endotoxic shock.

Animals↗
PubMed1997

Disruption of the splicing enhancer sequence within exon 27 of the dystrophin gene by a nonsense mutation induces partial skipping of the exon and is responsible for Becker muscular dystrophy.

The mechanism of exon skipping induced by nonsense mutations has not been well elucidated. We now report results of in vitro splicing studies which disclosed that a particular example of exon skipping is due to disruption of a splicing enhancer sequence located within the exon. A nonsense mutation (E1211X) due to a G to T transversion at the 28th nucleotide of exon 27 (G3839T) was identified in the dystrophin gene of a Japanese Becker muscular dystrophy case. Partial skipping of the exon resulted in the production of truncated dystrophin mRNA, although the consensus sequences for splicing at both ends of exon 27 were unaltered. To determine how E1211X induced exon 27 skipping, the splicing enhancer activity of purine-rich region within exon 27 was examined in an in vitro splicing system using chimeric doublesex gene pre-mRNA. The mutant sequence containing G3839T abolished splicing enhancer activity of the wild-type purine-rich sequence for the upstream intron in this chimeric pre-mRNA. An artificial polypurine oligonucleotide mimicking the purine-rich sequence of exon 27 also showed enhancer activity that was suppressed by the introduction of a T nucleotide. Furthermore, the splicing enhancer activity was more markedly inhibited when a nonsense codon was created by the inserted T residue. This is the first evidence that partial skipping of an exon harboring a nonsense mutation is due to disruption of a splicing enhancer sequence.

Adult↗
PubMed1997

Paired-related murine homeobox gene expressed in the developing sclerotome, kidney, and nervous system.

We isolated a murine homeobox containing gene, Uncx4.1. The homeodomain sequence exhibits 88% identity to the unc-4 protein at the amino acid level. In situ hybridization analysis revealed that Uncx4.1 is expressed in the paraxial mesoderm, in the developing kidney, and central nervous system. The most intriguing expression domain is the somite, where it is confined to the caudal part of the newly formed somite and subsequently restricted to the caudal domain of the developing sclerotome. In the central nervous system, Uncx4.1 is detected in the developing spinal cord, hindbrain, mesencephalon, and telencephalon. The temporal and spatial expression pattern suggests that Uncx4.1 may play an important role in kidney development and in the differentiation of the sclerotome and the nervous system.

Amino Acid Sequence↗
PubMed1997

Cementum, root dentin and bone extracts stimulate chemotactic behavior in cells from periodontal tissue.

In this paper, we used the extracts from cementum, bone, dentin and enamel, and compared the chemotactic behavior of human periodontal ligament (HPDL) cells, human gingival fibroblasts (HGF) and human alveolar bone (HAB) cells using modified Boyden chambers. The extracts, obtained using 4 M guanidine HCl ("G" extract), from cementum, root dentin, and bone had greater chemotactic effects than all the 4 M guanidine HCl/0.5 M EDTA extracts ("E" extract). HPDL cells and HGF exhibited higher chemotactic behavior than osteoblast-like HAB cells in response to cementum and root dentin "G" extracts. On the other hand, HAB cells showed the highest migratory activity in response to the bone "G" extract. The chemotactic activities of these extracts were reduced by heat- and trypsin-treatment. These results suggest that proteinaceous chemotactic factors exist in the cementum, root dentin and bone, and they appear to regulate the migration and orientation of HPDL cells, HGF and HAB cells during periodontal wound healing.

Alveolar Process↗
PubMed1997

Retinoic acid mediates Pax6 expression during in vitro differentiation of embryonic stem cells.

Neural cells are found rarely during differentiation of embryonic stem (ES) cells in vitro. To increase the yield of neuronal and glial cells from ES cells, we designed a differentiation procedure in which embryoid bodies were grown in medium containing retinoic acid (RA) and a low level (1%) of fetal calf serum. Using this procedure we were able to obtain neurofilament or glial fibrillary acidic protein-positive cells in 90% of outgrowths of embryonic bodies. Differentiation was dependent on the RA concentration, whereas depletion of RA favored the appearance of cardiac muscle cells. Differentiation of ES cells correlated with increased activity of Pax6, a transcription factor involved in central nervous system development. Pax6 was not expressed in undifferentiated ES cells, nor after differentiation by depletion of leukemia inhibitory factor or by overgrowth. After embryoid body formation and subsequent attachment, only infrequently did a few cells express Pax6. Addition of RA resulted in the appearance of Pax6-expressing cells in a concentration-dependent manner, with a peak at 100 nM RA. The presented differentiation procedure can be used for studying the molecular biology of neurogenesis in vitro.

Animals↗
PubMed1997

Analysis of measured values of ejaculation time in healthy males.

Although it has been deemed irrelevant to address ejaculation time in terms of mean values, our study was designed as a preliminary step in determining the normal range of ejaculation time (from the start of stimulation of the erect penis to ejaculation) as a criterion for assessing the degree of ejaculation disorder. Ejaculation experiments were performed with informed and consenting healthy volunteers about 20 years of age, using identical manual stimulation by the same woman, and ejaculation time was measured. The mean +/- standard deviation for the ejaculation time was 156.5 +/- 80.7 seconds, which was shown to be erection time dependent.

Adolescent↗
PubMed1997

Effects of heavy ions on the germination and survival of Arabidopsis thaliana.

Inhibition of germination and reduction in survival of Arabidopsis thaliana were investigated to study the effects of heavy ions on a multicellular system. Dry seeds of Col and Ler ecotypes were exposed to He, C, Ar and Ne ions with linear energy transfer (LET) in the range of 17-549 keV/micron and to electrons (LET = 0.2 keV/micron). The relative biological effectiveness (RBE) for the survival of both ecotypes showed the same pattern of variation with a maximum RBE of 11-12 at 252 keV/micron. For germination, RBE increased with increasing LET in Ler but not in Col, showing different sensitivities between the plant ecotypes. Inactivation cross sections of survival increased linearly in the range of 0.2-17 keV/micron and proceeded more steeply in the range of 113-252 keV/micron. At higher LET, cross sections appeared to reach a plateau at a little less than the size of the cell nucleus. When the value for survival was plotted against LET, it decreased steeply in the range about 113-252 keV/micron, indicating that heavy ions may have similar effects on both the shoulder and slope of the survival curve.

Arabidopsis↗
PubMed1997

Induction of ulceration and severe gastritis in Mongolian gerbil by Helicobacter pylori infection.

Specific pathogen-free Mongolian gerbils were infected orally with Helicobacter pylori to establish a new small animal model of severe gastritis H. pylori was recovered by culture from both antrum and body over a 16-week period after a single inoculation. The number of H. pylori colonising the antrum was about 100-fold higher than in the body, and this was consistent throughout the experiment. Histological examination showed that all animals developed severe inflammation with infiltration of polymorphonuclear leucocytes and mononuclear cells into the lamina propria and submucosa of the antrum from 4 weeks after infection. From 8 weeks after infection, multifocal lymphoid follicles appeared in the lamina propria and submucosa, and micro-erosions were also observed in the epithelial layer. At 16 weeks after infection, ulceration with disruption of the lamina muscularis mucosae was observed in the antral mucosa. To determine whether H. pylori caused gastritis or not, infected gerbils were treated with amoxycillin. After the treatment, gastritis could not be seen in the gastric mucosa. Therefore, the Mongolian gerbil is a useful small animal model to study the pathogenesis of H. pylori in gastric ulceration and severe gastritis and to assess anti-H. pylori treatment.

Amoxicillin↗
PubMed1997

Leukocytapheresis with leukocyte removal filter as new therapy for ulcerative colitis.

Leukocytapheresis (LCAP) with a leukocyte removal filter column was administered for 45 patients with ulcerative colitis (UC). We evaluated changes in the leukocyte count and the differential percentages during LCAP. Cytokine production was assessed from each patient's peripheral mononuclear cells or monocytes. Flow cytometry was performed to assess the removal rates of activated cells and adhesion molecule positive cells by LCAP. Clinical improvement was recognized in 35 of 45 patients during intensive LCAP therapy, and it continued throughout maintenance therapy in 32 patients (71.1%). The leukocyte count was decreased to about 40% during the first 30 min, but it increased to approximately 170% at 20 min after the completion of LCAP. The concentration of tumor necrosis factor (TNF)alpha before LCAP in the effective group was higher than it was in either the ineffective group or the control group. Its level decreased to near normal range after LCAP. In the effective group, the concentrations of interleukin (IL)-1beta, IL-2, interferon (IFN)gamma, and IL-8 were near the normal upper limits before LCAP; however, they had decreased after LCAP. The concentration of IL-4 increased after LCAP. In the ineffective group, in contrast, the concentrations had been at or near normal before the initial LCAP treatment. Flow cytometry study revealed that LCAP could remove the activated cells and adhesion molecule positive cells more effectively. The clinical improvement and the changes observed before and after LCAP therapy suggest that LCAP is able to intervene in the causal mechanism(s) of UC.

Blood Cell Count↗
PubMed1997

Appearance of a metronidazole-resistant Helicobacter pylori strain in an infected-ICR-mouse model and difference in eradication of metronidazole-resistant and -sensitive strains.

We tested whether antibiotic-resistant strains appeared in vivo after the failure of treatment using the Helicobacter pylori-infected euthymic mouse model. The numbers of colonies isolated from 56 ICR mice 2 weeks after 4 days of treatment with metronidazole (3.2, 10, or 32 mg/kg of body weight) or amoxicillin (1, 3.2 or 10 mg/kg), with treatment started 4 days after H. pylori CPY2052 inoculation, were counted, and the isolated strains were tested for their sensitivities to two antibiotics to rule out the presence of antibiotic-resistant strains. One metronidazole-resistant strain was detected in a mouse treated with 10 mg of metronidazole per kg, and the MIC of metronidazole for this strain was 25 microg/ml, compared to a MIC of 1.56 microg/ml for the original strain. However, no resistant strain was detected in the amoxicillin treatment group. After the examination described above, mice challenged with a metronidazole-resistant or -sensitive strain isolated from the stomach of a mouse were treated with metronidazole or amoxicillin. The metronidazole-resistant strain was more difficult to eradicate in vivo than the sensitive strain after treatment with metronidazole but not after treatment with amoxicillin. Thus, a metronidazole-resistant H. pylori strain was selected by insufficient treatment, but no resistant strain was selected with amoxicillin. Eradication of a metronidazole-resistant H. pylori strain in vivo required a higher dosage than eradication of a metronidazole-sensitive H. pylori strain. These results may explain one of the reasons for H. pylori treatment failure.

Amoxicillin↗
PubMed1997

The mechanisms of transient hypothyroxinemia in infants born to mothers with Graves' disease.

Transient hypothyroxinemia in infants born to mothers with Graves' disease is a unique disorder first reported by us in 1988. Most mothers of these infants have had no treatment, are diagnosed as having thyrotoxicosis during the last trimester, or were not well controlled during pregnancy. These infants are believed to have transient central hypothyroidism, the mechanisms of which have not been elucidated. We measured TSH-receptor antibody activities in maternal serum and blood thyroxine (T4) (free thyroxine, FT4) and TSH levels in blood dried on filter paper at 1, 3, and 5 d of age in 114 infants born to mothers with Graves' disease. The 114 infants were retrospectively divided into three groups according to the clinical course and thyroid function data: group G, neonatal thyrotoxicosis; group T, transient hypothyroxinemia; and group E, euthyroid. In group T, the dried blood T4 (FT4) level from cord blood and/or 1 d of age blood was 6.0 +/- 2.3 microg/dL (0.92 +/- 0.52 ng/dL), a value significantly higher than that at 5 d of age (3.6 +/- 1.0 microg/dL; 0.38 +/- 0.18 ng/dL) (p = 0.025 in T4, p = 0.042 in FT4). In contrast, these levels were significantly lower at birth relative to 5 d in group G (p = 0.0001 in T4) and not significantly changed in group E. The TSH level of cord blood and/or 1-d-old blood in group T was significantly lower than that of group E (p = 0.0006). Moreover, the TSH levels in response to thyrotropin-releasing hormone were blunted in most infants in group T. Bone maturation was not delayed in group T, compared with euthyroid infants. The higher blood T4 (FT4) levels at birth, relative to 5 d in group T, suggested that the fetal T4 level was higher than that of the newborn period. The fetal T4 level might have been elevated owing to transfer of T4 from mother to fetus during the last trimester when the mother's thyroid function was elevated and consequently the fetal pituitary-thyroid axis was suppressed. Although the serum T4 (FT4) levels were decreased after birth, TSH levels were not elevated, probably because the pituitary-thyroid axis was suppressed. This may be the reason for the transient hypothyroxinemia with a normal TSH level in infants born to mothers with poorly controlled Graves' disease. Weak maternal thyroid-stimulating antibody activities and differences in sensitivity of the thyroid gland to TSH-receptor antibodies may contribute to this unique disorder.

Bone Development↗
PubMed1997

A new Arabidopsis mutant induced by ion beams affects flavonoid synthesis with spotted pigmentation in testa.

A new stable mutant of Arabidopsis thaliana with a spotted pigment in the seed coat, named anthocyanin spotted testa (ast), was induced by carbon ion irradiation. The spotted pigmentation of ast mutant was observed in immature seeds from 1-2 days after flowering (DAF), at the integument of the ovule, and spread as the seed coat formed. Anthocyanin accumulation was about 6 times higher in ast mutant than in the wild-type at 6 DAF of the immature seeds, but was almost the same in mature dry seeds. A higher anthocyanin accumulation was not observed in the seedlings, leaves or floral buds of ast mutant compared with the wild-type, which suggests that a high accumulation of anthocyanins is specific to the seed coat of the immature ast seeds. Reciprocal crosses between ast mutant and the wild-type indicated that ast is a single recessive gene mutation and segregates as a delayed inheritance. The results of crossing with tt7 and ttg mutants also confirmed that the AST gene is probably a regulatory locus that controls flavonoid biosynthesis. A mapping analysis revealed that the gene is located on chromosome I and is closely linked to the SSLP DNA marker nga280 with a distance of 3.2 cM. AST has been registered as a new mutant of Arabidopsis.

Anthocyanins↗
PubMed1997

[Two patients with pulmonary hemorrhage associated with myeloperoxidase-antineutrophil cytoplasmic antibody].

We encountered two patients with pulmonary hemorrhage who had high levels of myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA). Patient 1 was a 69-year-old woman. Both were admitted to our hospital complaining of hemoptysis. Microscopic hematuria was detected in patient 1, and proteinuria and renal insufficiency were detected in patient 2. Chest X-ray films showed bilateral patchy infiltrates in patient 1, and right middle-lower infiltrates in patient 2. In both patients the levels of MPO-ANCA were high and the results of tests for anti-basement membrane antibodies were negative. These patients were suspected to have pulmonary-renal vasculitic syndrome with a high level of MPO-ANCA. In patient 1, because the level of MPO-ANCA decreased after treatment with steroid therapy, we believe that measuring the level of MPO-ANCA was useful in the management of the disease. Rapidly progressive glomerulonephritis developed in patient 2, and was exacerbated despite hemodialysis, steroid therapy, and plasma exchange therapy. Use of the term microscopic polyangiitis (MPA) was first proposed by yhe Chapel Hill Consensus Conference in 1993. MPA, which was formerly called microscopic polyarteritis nodosa, connotes pauci-immune necrotizing vasculitis affecting arterioles, venules, or capillaries, and this condition is strongly associated with ANCA. Patients with pulmonary-renal vasculitic syndrome who have MPO-ANCA may be given a diagnosis of MPA. Therefore, we diagnosed MPA in these two patients. Testing for ANCA may be useful in patients with pulmonary hemorrhage and renal involvement.

Aged↗