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Biomedical subjects

T Shibata

Publications and source records attributed to T Shibata.

At least 667 records · Page 37Linked to original sources
PubMed1991

DNA sequence recognition by a eukaryotic sequence-specific endonuclease, Endo.SceI, from Saccharomyces cerevisiae.

A eukaryotic sequence-specific endonuclease, Endo.SceI, causes sequence-specific double-stranded scission of double-stranded DNA to produce cohesive ends with four bases protruding at the 3' termini. Unlike in the case of restriction enzymes, an asymmetric 26-base pair consensus sequence was found around the cleavage site for Endo.SceI instead of a common sequence. We analyzed the base pairs that interacted with Endo.SceI on the recognition of its cleavage sites. A region comprising -10 through +16 base pairs from the center of the cleavage site was shown to be essential and sufficient for the sequence-specific cutting with Endo.SceI by experiments involving synthesized DNAs. Methylation interference experiments indicate that bases in the region comprising the +7 through +14 base pairs is involved in close contact with Endo.SceI in its recognition of the cleavage site. This +7 through +14-base pair region overlaps the most stringently conserved sequence in the consensus sequence for the cleavage site, suggesting that this region constitutes the core for the recognition by Endo.SceI.

Base Sequence↗
PubMed1991

A maturase-like subunit of the sequence-specific endonuclease endo.SceI from yeast mitochondria.

Some yeast strains possess a sequence-specific endonuclease, Endo.SceI, which is a heterodimeric enzyme localized in mitochondria. The larger subunit (75 kDa) of Endo.SceI, encoded by a nuclear gene (ENS1), is transported from the cytosol into the mitochondria. In this study, we determined the partial amino acid sequence of the smaller subunit (50 kDa) of Endo.SceI. The determined sequence matched well the partial sequence deduced from a mitochondrial open reading frame (RF3). The RF3 locus is known to exhibit polymorphism since this reading frame in some yeast strains is supposed to encode a maturase-like protein, whereas in other strains, the frame is interrupted by GC clusters, which thus break the frame. Southern blot analysis of various yeast strains showed that the continuity of RF3 is correlated with the presence of Endo.SceI activity. These data indicate that the continuous RF3 sequence is a functional gene (ENS2) coding for the smaller subunit of Endo.SceI. The results of cytoduction, by which the continuous RF3 sequence was transferred into a yeast strain lacking mitochondrial DNA, confirmed this conclusion. This study suggests the involvement of Endo.SceI in genetic recombination of mitochondrial DNA.

Amino Acid Sequence↗
PubMed1991

Recurrent hepatocellular carcinoma: usefulness of ultrasonography compared with computed tomography and AFP assay.

Follow-up studies using monitoring with alpha1-feto protein (AFP), ultrasonography (US), and computed tomography (CT) were carried out in 75 patients who had prior partial hepatectomy for hepatocellular carcinoma (HCC). Recurrence in the remaining liver was confirmed in 31 patients (41.3%) during the 4 month to 3 years 7 month period. Ultrasonography detected recurrence in 29 cases (sensitivity: 93.5%), CT in 26 (83.9%), and AFP assay in 12 (38.7%). In 4 patients, ultrasonography detected four recurrent nodules that CT missed. In 1 patient, two subphrenic nodules were detected with CT but not with ultrasonography. The specificity of US, CT, and AFP assay was 90.9%, 95.5%, and 93.2% respectively. Frequent follow-up study with ultrasonography in combination with CT and AFP assay should be recommended for the early detection of recurrent HCC. Ultrasonography is mandatory for the follow-up of patients with a prior hepatectomy for HCC.

Adult↗
PubMed1991

Immunoregulatory cytokine release in rat spleen cell cultures after treatment with bleomycin and its analogues in vivo.

We have studied the immunological effects that accompany a change in the chemical structure of a group of antineoplastic antibiotics by comparing the immunoregulatory cytokine release during mitogen-stimulated spleen cell culture after in vivo drug treatment. Whereas bleomycin and peplomycin increased cytokine levels in culture supernatants when compared with supernatants from untreated control rat spleen cell cultures, liblomycin generally reduced cytokine levels under the same culture conditions. We then compared these results with the antitumor effects of equivalent doses of the three drugs against a highly antigenic rat fibrosarcoma, KMT-17, both in vivo and in vitro. The results suggest that the immunoaugmenting effects of these antitumor antibiotics are essential for an optimal antitumor effect in vivo, and that these effects can be drastically altered by modification of the chemical structure of the drugs employed.

Animals↗
PubMed1991

Spontaneous rupture of intrahepatic artery aneurysm with complicated vascular anomalies.

An 18-year-old man developed a sudden onset of upper abdominal pain with vomiting. Ultrasound and computed tomographic (CT) scans revealed the spontaneous rupture of an intrahepatic artery aneurysm with subcapsular hematoma. A celiac arteriogram demonstrated a ruptured intrahepatic artery aneurysm in the right lobe of the liver, right extrahepatic artery aneurysm, obliteration of gastroduodenal artery, and abnormal flow pattern of the splenic artery. Portal vein phase, using superior mesenteric arteriography, showed portal vein varices and obliteration of the portal trunk. A right hepatic lobectomy was performed. The cut surface of the resected liver revealed a ruptured intrahepatic artery aneurysm with massive hematoma.

Adolescent↗
PubMed1991

The diagnostic value of serum pancreatic phospholipase A2 (PLA2) in pancreatic diseases.

The diagnostic significance of serum immunoreactive pancreatic phospholipase A2 (PLA2) was studied in 119 patients with pancreatic disease, 200 with various non-pancreatic disease, and 203 healthy controls using radioimmunoassay (RIA) specific to human pancreatic PLA2. This newly developed RIA using monoclonal antibody was satisfactorily sensitive and reliable. Serum PLA2 was elevated in all six patients with acute pancreatitis. Frequency of abnormal serum PLA2 levels was 60% in chronic pancreatitis (n = 52) and 67% in pancreatic cancer (n = 61). Serum PLA2 levels were low in chronic pancreatitis with severe exocrine insufficiency and advanced pancreatic cancer. In chronic pancreatitis, patients with low serum PLA2 level showed lower enzyme output in secretin test than patients with normal or high serum PLA2 level. Frequency of abnormal PLA2 levels was 27% in non-pancreatic disease and, in particular, patients with renal failure showed high PLA2 levels. Sensitivity (62%) and efficiency (69%) of serum PLA2 assay in pancreatic disease were superior to those of amylase. In conclusion, serum PLA2 determination using RIA was useful for the diagnosis of acute pancreatitis by high serum PLA2 levels and the diagnosis of severe exocrine pancreatic insufficiency by low serum PLA2 levels.

Amylases↗
PubMed1991

Aberrant pancreas is not susceptible to alcoholic pancreatitis.

Three cases of chronic alcoholic pancreatitis associated with aberrant pancreas are reported. All three patients underwent laparotomy, and an aberrant pancreas was found in the jejunum of each of the three patients. Microscopic examination of the aberrant pancreas did not show any changes suggestive of chronic pancreatitis, despite severe chronic pancreatitis in the main pancreas.

Adult↗
PubMed1991

Harmful effects of inotropic agents on myocardial protection.

Using an isolated working rat heart model, the pretreatment effects of positive inotropic agents on ischemia-reperfusion injury were investigated. The experiment consisted of (1) working control perfusion; (2) working perfusion with isoproterenol (I), milrinone (M), a combination of these drugs (I + M) and dibutyl-cyclic adenosine monophosphate (DB) followed by ischemic arrest for 33 minutes at 37 degrees C or 150 minutes at 20 degrees C and Langendorff reperfusion; and (3) working perfusion. Under conditions of normothermic ischemia, percent recoveries of postischemic cardiac output (mean +/- standard error of the mean) in the I, M, I + M, and DB groups were 37.8% +/- 12.7%, 61.3% +/- 3.1%, 0%, and 53.1% +/- 5.2%, respectively. Under conditions of hypothermic ischemia, the percent recoveries in I + M and DB groups were 10.9% +/- 7.9% and 29.8% +/- 9.5%; they were all significantly lower than that in the control group. The addition of diltiazem or ryanodine at several concentrations and lowering of the Ca2+ concentration in the St. Thomas' cardioplegic solution did not prevent I + M-induced injury. Our data suggest that pretreatment by I + M aggravated ischemia-reperfusion injury, and adjustments in Ca2+ concentration were not sufficient to prevent that injury.

Animals↗
PubMed1991

Signal-averaged body surface mapping for the assessment of low-amplitude potentials. Detailed maps during early ventricular activation in normal subjects.

Body surface isopotential maps around early ventricular activation were investigated in 30 normal subjects by the use of the authors' signal-averaged body surface mapping system. The number of beats averaged was 96-154 (mean, 127). Two distinct patterns were recognized in the appearance of a maximum at the onset of ventricular activation: the maximum in the first type (n = 16) was located on the right anterior chest; the maximum in the second type (n = 14) was on the central or left anterior chest. The site of the earliest ventricular activation was considered to be different in each of these types. During early ventricular activation, 25 subjects (83%) had two minima: one was on the left lateral chest and the other was on the left back. The two minima probably reflect two different receding activation fronts in the ventricles. The data in the present study are important to the understanding of the early ventricular activation process, as well as the diagnosis of heart diseases in which this process is disturbed.

Adolescent↗
PubMed1991

Cystic papillary carcinoma of the thyroid gland: a new sonographic sign.

Cystic thyroid lesions are generally considered to be benign and managed by repeated aspiration and/or biopsy. We report characteristic sonographic signs in eight cases of cystic papillary carcinomas of the thyroid gland. In all eight cases, ultrasonography (US) revealed mostly cystic lesions with solid excrescences protruding into the cyst. These nodules contained multiple punctate echogenic foci suggesting calcification. In three of these cases the initial fine needle aspiration biopsy was negative. The 'calcified nodule in cyst' sign was found to be very specific for cystic thyroid carcinoma in a review of the ultrasound findings in 115 patients with nodular thyroid lesions. Careful evaluation and/or surgery should be recommended in patients who have such characteristic sonographic findings even if the fine needle aspiration result is negative.

Adult↗
PubMed1991

Developmental lingual bone defect of the mandible. Report of a case.

The case of a patient with a lingual bone defect of the mandible accompanied by spontaneous pain is described. This report presents the development of the lesion, and its disappearance 26 months after removal of the submandibular gland. Pain was relieved after the operation. We regard the development of this lesion related to the pressure exerted by the submandibular gland on the corical bone.

Humans↗
PubMed1991

Differential growth inhibition of isoquinolinesulfonamides H-8 and H-7 towards multidrug-resistant P388 murine leukaemia cells.

The effects of N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H-8) and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) on the growth of P388 and its multidrug-resistant (MDR) variants were examined with the objective of assessing the possible changes in cyclic nucleotide-dependent protein kinases and protein kinase C-mediated pathways associated with MDR. H-8, an inhibitor of cyclic nucleotide-dependent protein kinases, inhibited the growth of the parental P388 murine leukaemic cells, but not that of MDR variants up to 200 microM. However the growth of both drug-sensitive and resistant cell lines were uniformly inhibited by H-7. Both the cytotoxic and cytokinetic results revealed that the growth-inhibition by H-8 of P388 cells is mainly due to a blockade of cell-cycle progression rather than due to a killing of cells. The degree of resistance to H-8 was directly proportional to their extent of resistance to vincristine, adriamycin, and 4'-demethylepipodophyllotoxin-9-(4,6-O-ethylidene)-beta-D-gluco pyr anoside (VP-16) and to that of the expression of P-glycoprotein. These findings raised the possibility that P-glycoprotein might play a role in the cross-resistance to H-8. To test the hypothesis, we examined the effect of H-8 on the binding of 3H-vincristine to membrane fraction isolated from P388/VCR-600 cells and on the enhancement of cytotoxicity to anticancer drugs in MDR cells. H-8 did not have any influences on these reactions. Thus, the cross-resistance to H-8 may be mediated through a mechanism different from an overexpression of P-glycoprotein.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Characterization of endothelin receptor subtypes.

Scatchard-plot analysis of [125I]ET-1 and [125I]ET-3 binding to rat lung membranes exhibited almost the same Kd values whereas the concentration of the binding sites of ET-1 is approximately four times higher than that of ET-3. This result suggests the presence of at least two distinct subtypes of ET receptors: an ET-1-specific type and an ET-3-specific or ET-1 and ET-3 nonselective type. On the other hand, in rat brain membranes, a curvilinear Scatchard plot was obtained for [125I]ET-3 in contrast to a linear plot for [125I]ET-1. This finding also demonstrates the existence of the two different receptor subtypes having the same affinity for ET-1, but one of which has a high affinity and the other has a low affinity for ET-3. Moreover, these data indicate that an ET receptor subtype exists in rat brain different from the subtype in rat lung. To obtain the bases for a further detailed characterization of the receptor, we have purified the rat lung ET receptor to homogeneity by ET-1-affinity chromatography. The purified receptor exhibits a molecular mass of 45 kDa, in good agreement with that estimated from the affinity labeling.

Animals↗