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T Ohsato

Publications and source records attributed to T Ohsato.

12 recordsLinked to original sources
PubMed2000

The D-loop structure of human mtDNA is destabilized directly by 1-methyl-4-phenylpyridinium ion (MPP+), a parkinsonism-causing toxin.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine has been reported to cause parkinsonism via its neurotoxic form, 1-methyl-4-phenylpyridinium ion (MPP+), which inhibits complex I of the mitochondrial respiratory chain. Its parkinsonism-causing mechanisms attract a great deal of interest as a model of the disease. Recently, we reported that MPP+ strongly decreases the amount of mtDNA independent of the inhibition of complex I. Maintenance of a proper amount of mtDNA is essential for the normal function of mitochondria as exemplified in many mitochondrial diseases. The most characteristic feature in vertebral mtDNA replication is that H-strand synthesis proceeds displacing the parental H-strand as a long single strand. It forms the D-loop, a triplex replication intermediate composed of the parental L-strand, nascent H-strand and displaced H-strand. Here we show that MPP+ does not inhibit DNA synthesis by DNA polymerase gamma, but rather releases the nascent H-strands from mtDNA both in organello and in vitro. This indicates that MPP+ directly destabilizes the D-loop structure, thereby inhibiting replication. This study raises a new mechanism, i.e. destabilization of replication intermediates, for depletion of mtDNA.

1-Methyl-4-phenylpyridinium↗
PubMed1999

R-Loop in the replication origin of human mitochondrial DNA is resolved by RecG, a Holliday junction-specific helicase.

Stable RNA-DNA hybrids (R-loops) prime the initiation of replication in Escherichia coli cells. The R-loops are resolved by Escherichia coli RecG protein, a Holliday junction specific helicase. A stable RNA-DNA hybrid formation in the mitochondrial D-loop region is also implicated in priming the replication of mitochondrial DNA. Consistent with this hypothesis, the 3' ends of the mitochondrial R-loop formed by in vitro transcription are located close to the initiation sites of the mitochondrial DNA replication. This mitochondrial R-loop is resolved by RecG in a dose-dependent manner. Since the resolution by RecG requires ATP, the resolution is dependent on the helicase activity of RecG. A linear RNA-DNA heteroduplex is not resolved by RecG, suggesting that RecG specifically recognizes the higher structure of the mitochondrial R-loop. This is the first example that R-loops of an eukaryotic origin is sensitive to a junction-specific helicase. The resolution of the mitochondrial R-loop by RecG suggests that the replication-priming R-loops have a common structural feature recognized by RecG.

Bacterial Proteins↗
PubMed1996

Clinico-pathological findings of asymptomatic intrahepatic cholangiocellular carcinoma: report of two cases and review of the literature.

The prognosis of intrahepatic bile duct carcinoma (cholangiocellular carcinoma: CCC) is extremely poor unless detected at an early and curable stage. However, little is known about the clinico-pathological features of CCC resected at a symptom-free stage. We herein report the clinico-pathological findings in two asymptomatic patients who underwent resection. Their liver function tests showed elevated levels of gamma-glutamyl transpeptidase. An intrahepatic mass was first detected by ultrasonography, and subsequent direct cholangiography and cytological examination revealed the presence of carcinoma in both patients. Left or right hepatic lobectomy with caudate lobectomy and lymph node dissection with or without resection of the extrahepatic bile duct was carried out. The lesions were 2.5 and 2.8 cm in maximal size, originating from the intrahepatic bile duct of segment IV and I, respectively. Both were free from extrahepatic bile duct involvement, intrahepatic and lymph node metastases. However, even in a symptom-free stage, perineural invasion, vascular or lymphatic involvements were histologically proved in both cases, which may be an indication of poor prognosis after surgery alone.

Aged↗
PubMed1994

[An experimental study of balloon angioplasty of the canine basilar artery].

Balloon angioplasty has recently been applied to cerebral arteries but its influences on cerebral vessels are still unknown in detail. Balloon angioplasty was performed on 20 canine basilar arteries. Each artery was subjected to either one (six dogs), three (eight dogs) or ten (six dogs) balloon inflations of one-minute at three atmospheres using a 1.5 French balloon catheter. Angiograms were performed immediately after, one hour, two weeks and four weeks after angioplasty. Specimens were obtained from both angioplasty segments and non-angioplasty segments of the basilar arteries after perfusion fixation two hours (six dogs), two weeks (eight dogs) and four weeks (six dogs) after angioplasty. In addition to histological observations, the arterial diameter was measured on the angiograms and number of endothelial cells and smooth muscle cells were counted. Then, area of the vascular lumen (AL), area of the median (AM) and thickness rate of the media (TM) on the cross section were analyzed morphometrically. Stenoses of the basilar artery were frequently observed on angiograms. Histological and morphometrical findings of angioplasty segments at two hours revealed wall irregularity, medial split, slight platelet deposition and decrease in the number of endothelial cells (p < 0.01). At two weeks, smooth muscle cells were decreased (p < 0.03) and were replaced by fibrosis, but endothelial cells had regenerated to the baseline. AL was decreased (p < 0.01) and TM was increased (p < 0.01). At four weeks, fibrotic change, decrease in smooth muscle cells (p < 0.002) and increase in TM (p < 0.03) remained. Marked mural thrombus was observed in two cases at two weeks and four weeks. Balloon angioplasty caused various unfavorable changes on the canine basilar arteries both in acute and in chronic stage. This should be taken into consideration on balloon angioplasty on cerebral vessels.

Angioplasty, Balloon↗
PubMed1992

Establishment and characterization of a human T-cell lymphoblastic lymphoma cell line (HT-1) carrying an inversion of chromosome 14.

A new human lymphoblastic lymphoma cell line was established (designated HT-1) from the pleural fluid lymphoma cells of a patient with lymphoblastic lymphoma of T-cell type. The HT-1 cells expressed CD1, CD2, CD3, CD4, CD5, CD7, CD8, CD57, and terminal deoxynucleotidyl transferase (TdT) but lacked B-cell-associated antigens and myeloid-associated antigens. In addition, HT-1 cells had rearranged T-cell receptor (TCR) beta-chain gene and gamma-chain gene but retained germlines of immunoglobulin (Ig) heavy chain gene. These findings indicate that HT-1 cell line represents a common thymocyte in the T-cell lineage. Cytogenetic studies revealed that HT-1 cells carry an inversion (inv) of the long arm of chromosome 14. This cell line is the second T-cell line carrying inv(14) chromosome and may be useful for the molecular investigation of the cytogenetic break points of inv(14).

Adult↗
PubMed1991

Acute aggravation of subdural effusion associated with pachymeningitis carcinomatosa: case report.

The authors present a case of acute aggravation of subdural effusion associated with pachymeningitis carcinomatosa. Microscopic examination of a surgical specimen revealed diffuse involvement of the dura mater by a metastatic adenocarcinoma in which the tumor cells invaded venules located in the areolar layer in particular. The rapid increase in capillary transmural pressure resulted in extravasation of plasma components, causing an increase in subdural effusion.

Adenocarcinoma↗
PubMed1990

A newly established human acute lymphoblastic leukemia cell line with characteristics of the earliest B-cell maturation.

A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin (SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line kappa light chain genes and germ-line T-cell receptor beta- and gamma-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage.

B-Lymphocytes↗
PubMed1987

[A case of subtentorial ventricular diverticulum accompanied with choroid plexus papilloma in the lateral ventricle].

Marked non-communicating hydrocephalus may rarely cause ventricular rupture producing either a dilated cystic cavity (ventricular diverticulum) or communication between ventricle system and subarachnoid space (spontaneous ventriculostomy). Ventricular diverticulum has been believed to be collection of cerebrospinal fluid which escaped beneath the pia mater after rupture of ependymal layers and cerebral parenchyma. We proposed herein to report a case of subtentorial ventricular diverticulum which accompanied with choroid plexus papilloma of the lateral ventricle. A nine year-old girl admitted to our hospital complaining of clumsiness of hands and walking, disability of reading, headache and vomiting. The neurological examination revealed alexia, papilledema, anisocoria, righ hemianopsia, weakness of right upper limb, and cerebellar ataxia. CT brain scan showed a large high density area at the trigone of the left lateral ventricle with non-communicating hydrocephalus and an extra-axial low density area in the posterior fossa. The medial space of the left trigone was especially ballooned and is just shifted above incisura tentoria by the tumor. The intraventricular tumor was totally removed by operation and proved to be benign choroid plexus papilloma microscopically. The subtentorial mass was confirmed to be a cyst contiguous to the medial trigone of the lateral ventricle, namely ventricular diverticulum. Three special features were recognized in this case. The first, this was the first example of ventricular rupture accompanied with tumor in the lateral ventricle reviewing all reports of both ventricular diverticulum and spontaneous ventriculostomy. The second, this ventricular diverticulum was not produced merely by hydrocephalus alone but mainly by direct effects of the tumor.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Diseases↗
PubMed1987

[Diagnostic value of digital subtraction angiography (DSA) using Toshiba Digiformer X in the cerebrospinal vascular diseases].

Using TOSHIBA Digiformer X, digital subtraction angiography (DSA) was performed in 286 patients, in whom 229 patients of cerebro-spinal vascular disease was included. The authors emphasize the usefulness of DSA in cerebro-spinal vascular disease in relation to conventional angiography. DSA taken by single small dose injection of contrast medium into the ascending aorta clearly demonstrates not only aortic arch and thoracic major vessels, but also cervical vessels and all intracranial vessels. Therefore, we could rapidly understand gross dynamics of the circulation and obtain useful informations prior to catheterization to the selective artery. This advantage of DSA was particularly useful for occlusive vascular diseases. Gradual injection of small dose of contrast medium obviously reduced recoiling of the catheter tip, which enabled the selective angiography with setting of the tip of the catheter at the entrance of cervical major vessels without its sufficient insertion into the selective vessels. This advantage is particularly beneficial for the patients with severe arteriosclerosis who was found to be difficult for selective catheterization. In our experience, demonstration of a presence of aneurysm by DSA was possible in almost all cases of subarachnoid hemorrhage, although spatial resolution of DSA is said to be inferior to the conventional angiography. Real time display of DSA decreased the time required for examination and enabled repeated angiography. This advantage of DSA is especially useful for the patients with spinal arterio-venous malformation and thoracic outlet syndrome.

Cerebral Angiography↗