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Biomedical subjects

K Sakamoto

Publications and source records attributed to K Sakamoto.

At least 469 records · Page 26Linked to original sources
PubMed1994

Characterization of the secondary structure of an oligonucleotide corresponding to the autocleavage site of a precursor RNA from bacteriophage T4.

We studied the secondary structure of an RNA fragment (GUUUCGUACAAAC) (R1) having the sequence corresponding to the self-cleavage domain in a precursor RNA molecule from bacteriophage T4 infected Escherichia coli cells (p2Sp1 RNA). We synthesized an oligoribonucleotide (CAAACGUACAAAC) (R3) which contained the sequence (CGUACA) proposed for the p2Sp1 RNA self-cleavage site but did not form the hairpin loop structure. The self-cleavage ability of the single stranded RNA (R3) is significantly lower than that of R1. We have also designed a modified RNA fragment (R2), which contained a noncleavable RNA with 2'-O-methylcytidine or 2-O-methyluridine. R3 did not exhibit cleavage. To further investigate the structural requirements in the cleavage reaction, we synthesized mutant RNAs which contained different bases within consensus sequences and the cleavage sites were tested for self-cleavage. Guanosine and adenosine 3'-phosphates seemed not to be susceptible to transesterification at the cleavage site. The data from native gel electrophoresis, the CD spectra and the Tm suggested that the hairpin structure is necessary for the cleavage.

Bacteriophage T4↗
PubMed1994

[CT and MR imaging findings of sphenoidal masses].

CT and MR imaging findings of 57 sphenoidal masses were retrospectively reviewed to assess the possibility of differential diagnosis between them. Various kinds of masses such as pituitary adenoma, epipharyngeal cancer, mucocele, chordoma, chondroma, chondrosarcoma, distant metastasis, multiple myeloma, fibrous dysplasia, craniopharyngioma, hemangiopericytoma, giant cell tumor, primary sphenoidal cancer, malignant melanoma, leukemia, histiocytosis X, and giant cell tumor were included in this series. CT scanning was performed in all cases, while MR images were obtained in 48 cases using a spin-echo pulse sequence. The relative density of the masses, bony changes and calcification were evaluated on CT, and on MR images, signal intensity of the masses relative to the normal gray matter, contrast enhancement and extension/contour were evaluated. Although no single feature appeared to be specific to the masses, detection of calcification on CT, identification of the normal pituitary gland as deformed or displaced on T1-weighted images, signal intensity on T2-weighted images, and extension of the masses seemed to be useful and should be examined in terms of their ability to assist in differential diagnosis. Finally, accommodative classification of sphenoidal masses primarily based on presumed origin or mode of extension was attempted.

Adolescent↗
PubMed1994

[A case of pulmonary sarcoidosis associated with severe hypercalcemia].

A 71-year-old man with a history of sarcoidosis was admitted to our hospital because of polyuria and polydipsia. On admission, the serum calcium concentration was elevated to 12.7mg/dl, and the creatinine clearance was 28.3ml/min. The initial serum 1,25-dihydroxyvitamin D concentration was 55.0pg/ml, while angiotensin-converting enzyme activity and serum PTH-rP concentration were within the normal range. Radiological studies revealed enlargement of bilateral hilar lymph nodes and a nodular lesion in the right lower lung field. Transbronchial lung biopsy showed noncaseous granuloma consistent with pulmonary sarcoidosis. After oral administration of 20mg prednisolone daily, the serum calcium and 1,25-dihydroxyvitamin D concentration returned to normal, and creatinine clearance was raised to 55ml/min. In conclusion, low dose glucocorticoid administration successfully reduced serum 1,25-dihydroxyvitamin D level with a prompt decrease in serum calcium level in a patient with sarcoidosis.

Aged↗
PubMed1994

Molecular cloning of the human histamine H1 receptor gene.

The human histamine H1 receptor gene, an intron-lacking gene, was isolated with bovine H1 receptor cDNA [Yamashita, M., Fukui, H., Sugama, K., Horio, Y., Ito, S., Mizuguchi, H., and Wada, H. (1991) Proc. Natl. Acad. Sci. USA 88, 11515-11519] used as a probe. The receptor protein deduced from the nucleotide sequence of this gene was composed of 487 amino acid residues with a calculated Mr of 55,781 and possessed characteristic properties of GTP binding protein-coupled receptors. At the 5' flanking region of the human H1 receptor gene, we located potential TATA box and CACCC sequences, AP1 binding site-like sequences, glucocorticoid responsive element-like sequences, and other binding sequences for inducers. Northern blot analysis showed that H1 receptor mRNAs visualized as two bands with 3.0-kilobase and 3.5-kilobase nucleotides were expressed in peripheral tissues such as placenta, lung, skeletal muscle, and kidney and that only one species with 3.5-kilobase nucleotides was present in the brain. H1 receptor mRNA was most abundant in the placenta. The human H1 receptor gene was mapped to the chromosome 3p25 by the fluorescence in situ hybridization method.

Amino Acid Sequence↗
PubMed1994

Prostaglandin F2 alpha receptor is coupled to Gq in cDNA-transfected Chinese hamster ovary cells.

We examined intracellular signal transduction of prostaglandin F2 alpha (PGF2 alpha) receptors by transfection and stable expression of the receptor cDNA in Chinese hamster ovary (CHO-PGF2 alpha) cells. The binding to the membrane was specific for PGF2 alpha, and the Scatchard plot analysis showed a single high-affinity binding site (Kd = 25.2 nM). PGF2 alpha gradually elevated intracellular Ca2+ and stimulated phosphoinositide metabolism in CHO-PGF2 alpha cells. In whole-cell clamp recordings, PGF2 alpha induced an outward current in the presence of external Ca2+, but it induced a long-lasting inward Ca2+ current in a Na(+)-free solution containing K+ channel blockers. Gq alpha antibody applied intracellularly blocked both outward and inward currents induced by 1 microM PGF2 alpha. These results demonstrate that the PGF2 alpha receptor is coupled to phosphoinositide metabolism in CHO-PGF2 alpha cells via Gq.

Animals↗
PubMed1994

Aclarubicin inhibits phosphatidylinositol hydrolysis and contraction of rat aorta.

The effects of aclarubicin on phosphatidylinositol hydrolysis and contractile responses were investigated in isolated rat aorta. In the aclarubicin-pretreated aorta, the basal level of [3H]inositol monophosphate accumulation was significantly lower whereas [3H]phosphoinositide formation was significantly higher than in the saline-pretreated control aorta. Phenylephrine-, 5-hydroxytryptamine- and sodium fluoride-stimulated increases in [3H]inositol monophosphate accumulation were also significantly reduced in the aclarubicin-treated aorta compared to the control. Contractile forces induced by 5-hydroxytryptamine and sodium fluoride were markedly diminished in the aclarubicin-treated aorta. These results suggest that aclarubicin inhibits phosphatidylinositol hydrolysis at a level of phospholipase C activation, which is involved in the reduction of agonist-induced contraction of rat aorta.

Aclarubicin↗
PubMed1994

Localization of sequences for the basal and insulin-like growth factor-I inducible activity of the fatty acid synthase promoter in 3T3-L1 fibroblasts.

Fatty acid synthase (FAS) plays a central role in fatty acid synthesis and its expression is under nutritional and hormonal control. We have investigated insulin-like growth factor-I (IGF-I) regulation of FAS by transfecting into 3T3-L1 fibroblasts chimeric genes comprising the 5'-flanking region of the FAS gene linked to a luciferase (LUC) reporter gene. First, the basal promoter activity of the 5' serial deletions from nucleotides -318 to -19 of the FAS gene were compared. Deletions of the promoter sequences from -136 to -19 resulted in a step-wise decrease in the promoter activity, with the -67 LUC and -19 LUC plasmids retaining 40% and 16% of the luciferase activity of -136 LUC. Regulatory sequences important for the FAS basal promoter activity in 3T3-L1 fibroblasts are, therefore, located within the -136 to -19 region. Treatment with 10 mM IGF-I also increased luciferase activity 1.8 +/- 0.2-, 1.8 +/- 0.3- and 2.5 +/- 0.1-fold in 3T3-L1 fibroblasts transiently transfected with -136 LUC, -110 LUC and -67 LUC plasmids, respectively. Deletion of sequences from -67 to -19 resulted in the loss of responsiveness to IGF-I. Physiological doses of insulin (10 nM), however, did not increase luciferase activity in 3T3-L1 fibroblasts transfected with any of the above plasmids. Only upon treatment with pharmacological doses of insulin (1 microM), probably through IGF-I receptor, did luciferase activity increase 4.3 +/- 0.4-, 3.2 +/- 0.4- and 3.5 +/- 0.5-fold when transfected with -136 LUC, -110 LUC and -67 LUC plasmids, respectively; there was no increase with -19 LUC. The half-maximal effect of IGF-I on FAS promoter activity was observed at 3 nM and a maximal effect was reached at 10 nM. These results indicate that the increased promoter activities observed are probably mediated through the IGF-I receptor. Furthermore, sequences responsible for IGF-I regulation of the FAS gene are located within the proximal promoter between nucleotides -67 and -19 of the FAS gene.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Group II phospholipase A2 in invasive gastric cancer cell line is induced by interleukin 6.

To investigate the role of group II phospholipase A2(PLA2) in cancer, we examined the expression and secretion of group II PLA2 in response to the stimulation of interleukin 6(IL-6) in human gastric cancer cells in vitro. Group II PLA2 determined by a specific radioimmunoassay was constitutively produced in culture supernatant of KATO III (signet ring cell carcinoma) and MKN28 (well differentiated adenocarcinoma). This production in KATO III significantly increased with a treatment of IL-6, whereas that in MKN28 remained at a same level. Moreover, the quantitation by reverse transcription-polymerase chain reaction(RT-PCR) demonstrated the IL-6 inducible overexpression of group II PLA2 mRNA in KATO III. This transcription was mediated by NF-IL6, the same as in hepatocytes. These results suggest two possible mechanisms of group II PLA2 production by cancer cells in vivo, that is, cytokine-induced production and constitutive production.

Adenocarcinoma↗
PubMed1994

Molecular cloning and expression of a cDNA of the bovine prostaglandin F2 alpha receptor.

Capitalizing on the significant sequence homology comprising the transmembrane motif regions of known prostanoid receptor family, we targeted the cloning of a cDNA clone for prostaglandin (PG) F2 alpha receptor from a bovine corpus luteum cDNA library. By using several pairs of degenerated primers created from a common motif of transmembrane domains, polymerase chain reaction gave a clone SN463 carrying the homologous sequence, which covered transmembrane motif IV-VI of the thromboxane (TX) A2 receptor. This polymerase chain reaction product was used as a DNA probe for the following cross-hybridization, and a clone BC2211 carrying a 2.2-kilobase pair DNA insert was isolated. This clone encodes a protein of 362 amino acid residues (M(r) = 40,983) with seven potential transmembrane domains and represented significant overall sequence homology to human TXA2 receptor protein (34% in amino acid). Injection of the mRNA synthesized in vitro from the cloned cDNA into a Xenopus oocyte elicited electrophysiological response to PGF2 alpha. Ligand binding displacement in membranes of mammalian COS-7 cells transfected with the cDNA indicated the rank order of affinity of the receptor to PGs: PGF2 alpha > PGD2 > PGE2 > STA2, a TXA2 agonist. PGF2 alpha activated inositol phosphate formation in COS-7 cells transfected with receptor cDNA. Northern blot analysis and in situ hybridization indicated that the PGF2 alpha receptor mRNA is highly expressed and accumulated in corpus luteum. This is the first report on a successful cloning of functional receptor cDNA for PGF2 alpha.

Amino Acid Sequence↗
PubMed1994

The anterior choroidal artery syndrome. I. Microangiography of the anterior choroidal artery.

The distribution of the anterior choroidal artery (AChA) was analysed on coronal, sagittal and axial microangiograms of cadaver brains. On axial sections, the territory of the AChA was confined to an arcuate zone between the striatum anterolaterally and the thalamus posteromedially. On sagittal sections, fine vessels from the cisternal part of the AChA were seen to extend upwards and somewhat posteriorly into the region of the posterior limb of the internal capsule. On coronal sections, ascending branches of the AChA coursed laterally and then upwards to penetrate the globus pallidus and the inferior portion of the posterior limb of the internal capsule, apparently terminating at the lateral border of the thalamus. Determining the distribution of this artery on multiplanar sections was helpful for interpreting pathological changes, including infarcts, occurring in this region on multiplanar CT and/or MR images.

Cerebral Angiography↗
PubMed1994

The anterior choroidal artery syndrome. II. CT and/or MR in angiographically verified cases.

We reviewed 12 cases of infarcts in the territory of the anterior choroidal artery (AChA) on CT and/or MRI. In each case vascular occlusion in the region was verified angiographically. Although the extent of the lesion on CT/MR images was variable, all were located on the axial images within an arcuate zone between the striatum anterolaterally and the thalamus posteromedially. The distribution of the lesions on mutiplanar MRI conformed well to the territory of the AChA demonstrated microangiographically. The variability of the extent of the infarcts may be explained by variations in the degree of occlusive changes in the AChA or the development of collateral circulation through anastomoses between the AChA and the posterior communicating and posterior cerebral arteries. The extent of the lesion appeared to be closely related to the degree of neurological deficit.

Adolescent↗
PubMed1994

Rapid detection of African horsesickness virus by the reverse transcriptase polymerase chain reaction (RT-PCR) using the amplimer for segment 3 (VP3 gene).

The complete sequence of the major core protein (VP3) gene of African horsesickness virus serotype 4 (AHSV-4; vaccine strain) was determined by analysis of a complete cDNA clone representing segment 3. The RNA was 2,789 bp long and a comparison of its sequence with that of bluetongue virus serotype 10 (BTV-10) revealed 58% nucleotide similarity. Based on these data, the reverse transcriptase-polymerase chain reaction (RT-PCR) technique was applied to the specific detection of AHSV using a pair of primers designed for AHSV-4 VP3 gene. Approximately 230 bp of PCR products were amplified by RT-PCR from the total RNA extracts (mRNA and dsRNA) of Vero cells infected with eight serotypes of AHSV. No product was observed analogous to other orbiviruses. The supernatant of the infected cell culture fluid without any RNA purification was also suitable as a template for RT-PCR after being denatured at 94 degrees C for 5 min. The sensitivity of this method was between 10(0) and 10(1) TCID50 when viral RNA from the supernatant of infected cell culture was subjected to RT-PCR. The whole procedure for detecting the virus RNA by RT-PCR could be carried out within 5 h. The RT-PCR with AHSV VP3 gene as a target was found to be a simple, highly specific and sensitive assay for AHSV.

African Horse Sickness Virus↗
PubMed1994

Intestinal and extraintestinal complications of Crohn's disease: predictors and cumulative probability of complications.

Of 238 patients with Crohn's disease seen at our clinics from April 1973 to August 1988, 203 patients were selected for this study, since they fulfilled the following criteria: they had been followed up for more than 6 months as outpatients or had been treated as inpatients for more than 1 month. They were studied to elucidate: (a) the different types and incidence of various complications, (b) the factors related to complications present at the time of diagnosis, (c) predictors of new complications arising after diagnosis, and (d) the cumulative incidence of complications occurring during the course of the disease from the times of onset and diagnosis. Of the intestinal complications, perianal fistula was most common (33%), followed by strictures with dilatations of the proximal bowel (21%), and internal fistula (14%). Of the extraintestinal complications, menstrual disturbance was the most common (18% of the female patients), followed by arthritis (10%), and aphthous stomatitis (10%). As for the factors influencing complications present at the time of diagnosis, the pattern of bowel involvement was significantly correlated with the presence of intestinal stricture, while the erythrocyte sedimentation rate was significantly correlated with the presence of perianal fistula. A significant predictor of new complications arising after diagnosis was the general well-being of patients at the time of diagnosis. Patients who, at diagnosis, already have complications such as stricture, abdominal abscess, internal or external fistula, massive hemorrhage, and free perforation or anal lesions are more likely to develop new complications in addition to those present at diagnosis, compared with patients without any complications at diagnosis (P = 0.055).

Adult↗