Search PubMed⌕ Search

Biomedical subjects

R Sakai

Publications and source records attributed to R Sakai.

At least 163 records · Page 9Linked to original sources
PubMed1989

Flat reversion by okadaic acid of raf and ret-II transformants.

Okadaic acid is a non-phorbol 12-myristate 13-acetate (PMA)-type tumor promoter on mouse skin and known to be a potent inhibitor of serine/threonine protein phosphatases. Contrary to expectation from its tumor-promoting activity, okadaic acid was shown to have a potential to revert the phenotypes of cells transformed by raf and ret-II to that of normal cells. Two to 3 days after addition of 8 ng of okadaic acid per ml to the culture medium, raf and ret-II transformants changed to flat cells and gained contact inhibition. The amount of fibronectin, which was decreased in malignant transformed cells, was increased in the flat revertants. Moreover, okadaic acid caused a dose-dependent loss of ability to grow in soft agar. The morphology of the cells reverted to malignant phenotype within 1 week after removal of okadaic acid. The levels of mRNA and protein of activated c-raf in flat revertants were similar to those in parental transformed cells. The level of mRNA of ret-II was also not changed by flat reversion. No induction of flat reversion was observed with okadaic acid tetramethyl ether, an inactive compound, or a phorbol ester, PMA. As okadaic acid is a potent inhibitor of protein phosphatases 1 and 2A, the possibility that these phosphatases are involved in signal transduction from the raf and ret-II oncogenes is suggested.

Animals↗
PubMed1989

Epidemiologic survey on lung cancer with respect to cigarette smoking and plant diet.

This case-control study of lung cancer was based on a cross-sectional questionnaire survey of inpatients at 5 general hospitals in Okinawa, Japan, from 1982 to 1987. The purpose of the study was to clarify the relations of lung cancer to cigarette smoking and plant diet. Ingestion frequencies of 17 major dietary plants and/or herbs were obtained by means of a questionnaire interview. As eligible subjects for a case-control analysis, there were 673 respondents aged over 30 years with clear smoking history, age, sex and diagnosis. Psychiatric patients were excluded. Odds ratios of newly diagnosed lung cancer were calculated by the Mantel-Haenszel procedure. A pair consisted of a case and two controls which were selected randomly by using multivariate caliper matching. Sixty-four pairs matched for age (+/- 5) and sex showed a significantly high odds ratio of 2.9 (P less than 0.0005). However, three male groups who were categorized by the number of cigarettes smoked did not exhibit dose-dependency of lung cancer on smoking. Lung cancer was more prevalent in ex-smokers than in current smokers. Case-control analyses by male generations revealed that lung cancer incidence was age-dependent, and there was a clear dose-response relationship between smoking and lung cancer in males in their sixties. A case-control analysis of each of 17 edible plants based on 44 pairs who were matched for age (+/- 5), sex and smoking history demonstrated that the odds ratio of aloe (Aloe arborescens Mill var. natalensis Berger) was 0.5 (P less than 0.1), suggesting that the aloe may prevent human carcinogenesis at various sites.

Adult↗
PubMed1989

Correlation between hydrophobicity of N-alkylxanthine derivatives and their biological activities on guinea-pig isolated tracheal smooth muscle.

Cyclic (c) AMP phosphodiesterase (PDE) inhibitory activities of N-alkylxanthine derivatives (3-methyl-,3-ethyl-,3-propyl-,3-butyl-,1,3-dimethyl-,1-methyl-3-ethyl-,1-methyl - 3-propyl- and 1-methyl-3-butyl xanthines) and their relaxant effects on carbachol-induced contraction and on resting tone guinea-pig isolated tracheal smooth muscle have been investigated. The PDE inhibition constant (Ki) and the concentration producing 50% tracheal smooth muscle relaxation in-vitro (EC50) were determined. Significant correlations between the -log Ki values and the -log EC50 values on the carbachol-induced contraction or on the resting tone were found (r = 0.902 and 0.892). The apparent partition coefficient (P) between n-octanol and pH 7.4 phosphate-buffered saline (PBS) was measured as an index of hydrophobicity of the xanthine derivatives. There were significant correlations between log P and both -log EC50 values and between the log P and -log Ki values. These findings suggest that the cAMP PDE inhibitory activity of N-alkylxanthine derivatives contributes to the mechanism of bronchodilatory action, and that an increase in hydrophobicity of the xanthine molecule enhances the biological activity.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

Expression of salt hunger in hypophysectomized rats.

Hypophysectomized and pituitary-intact rats were tested for their expression of salt hunger under a variety of experimental conditions. The results show that hypophysectomized rats ingest less salt in response to salt hunger induced by sodium depletion, captopril or angiotensin in comparison to pituitary-intact rats. In contrast, both groups ingest the same amount of salt in response to mineralocorticoid-induced salt hunger. While sodium excretion and plasma sodium levels were comparable in the two groups, the angiotensinogen mRNA was reduced by hypophysectomy in several limbic brain regions as well as in the liver. These results suggest that reduced salt intake in response to manipulations of the body sodium and renin-angiotensin system in hypophysectomized rats may result from decreased angiotensinogen mRNA levels.

Angiotensin II↗
PubMed1989

[Fundamental studies, reference values and relationship to menstrual cycle of prolactin RIA BEAD II].

We have tried fundamental studies, reference values and relationship to menstrual cycle on Prolactin RIA BEAD II kit which has a method of IRMA using monoclonal antibody. On clinical studies, we investigated change of serum prolactin level during the menstrual cycle and relationship to other hormones (LH, FSH, estradiol, progesterone). It was the result that prolactin level of follicular phase was lower than that of preovulatory phase and luteal phase. We conclude that change of prolactin level during the menstrual cycle is related with change of estradiol level.

Adult↗
PubMed1989

Role of protein phosphatases in malignant transformation.

Many oncogene products are protein kinases and signals are transduced via phosphorylation of proteins. Similarly, protein-dephosphorylation may play a critical role in malignant cell transformation. We have cloned two catalytic subunits of ser/thr protein phosphatase (PP) type 2A, PP2A alpha, and PP2A beta, from a rat liver cDNA library. Both cDNAs encode peptides of 309 amino acids with a difference of only 8 amino acids between the two. All primary hepatocellular hyperplastic nodules or carcinomas, which were induced by a food carcinogen, 2-amino-3-methylimidazo[4,5-f]quinoline, showed up-regulation of expression of the mRNAs of both PP2A alpha and PP2A beta. NIH3T3 cell transformants obtained by introducing activated c-raf, ret-II or Ki-ras oncogenes also showed high levels of PP2A alpha transcripts. Okadaic acid, a non-TPA type tumor promoter, was found to be a potent inhibitor of PP1 and PP2A. Its IC50 for PP1 was much higher than that for PP2A with phosphorylase a as a substrate. When raf and ret-II transformants were cultured with okadaic acid at 8 ng/ml for 2 days, both transformants became flattened and showed strict contact inhibitions. This flat cell morphology was stable for at least one month in the presence of okadaic acid, but in its absence, the cells reverted to their original transformed shape within 7-10 days. Colony formation by raf and ret-II transformants in soft agar was inhibited dose-dependently by okadaic acid; very few colonies grew in the presence of the acid at 8 ng/ml. Okadaic acid had less effect on a transformant of the Ha-ras gene, causing only 50% inhibition of colony formation at 8 ng/ml. The role of protein phosphatases in cellular transformation by certain oncogenes is suggested.

Animals↗
PubMed1988

Molecular cloning of rat phosphoprotein phosphatase 2A beta cDNA and increased expressions of phosphatase 2A alpha and 2A beta in rat liver tumors.

A cDNA clone coding for an isotype of the catalytic subunit of rat phosphoprotein phosphatase 2A was isolated. The deduced amino acid sequence of the clone was different at 8 positions from that of rat phosphatase 2A alpha determined in a previous study. The deduced amino acid sequence of the clone was, however, identical to that of human phosphatase 2A beta and differed only at one position from that of rabbit 2A beta. Thus, the isolated cDNA was identified as a clone coding for rat phosphatase 2A beta. Using a 2A beta specific probe, two kinds of transcripts were detected in rat liver: a major 2.0 kb mRNA transcript and a minor 1.4 kb mRNA transcript. These transcripts were both greatly increased in rat liver tumors induced by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) regardless of the carcinoma or hyperplastic nodule.

Amino Acid Sequence↗
PubMed1988

[Triiodothyronine(T3) autoantibodies in a woman with nonthyroidal disorder: a study on preparation of serum IgG fraction employing protein A column chromatography].

A 48-year-old non-goitrous woman, who had undergone cardiac surgery for mitral stenosis under the extracorporeal circulation, showed high levels of serum T3 and free T3 in a recent follow-up study, employing antibody coated-bead RIA for T3 and -Amerlex M particle RIA for free T3. However, other thyroid function tests (T4, free T4, TSH and TBG) were normal. We suspected that thyroid hormone autoantibodies (THAA) in her serum interfered with T3 and free T3 analyses. The presence of THAA was demonstrated by the use of various procedures as follows. Firstly, the patient's serum was directly incubated with 125I-T3 or -T4 analog which did not bind to TBG, followed by B/F separation with polyethyleneglycol, counting the precipitates. Secondly, after the serum was treated with an acid-charcoal solution to remove circulating thyroid hormone, the measurement of THAA was made as stated above. Normal sera were used as controls. Both the non- and acid-charcoal-treated sera showed much higher percentages of 125I-T3 analog precipitation as compared with controls. In the case of 125I-T4 analog, there was no difference between them. In the third study, the presence of IgG antibodies that bound T3 but not T4 was investigated. The IgG fraction of the patient's serum was separated employing a Protein A-Sepharose CL-4B column chromatography. Then, the prepared IgG fraction was purified by a technique of gel filtration chromatography (Sephacryl S 200). Non-purified and purified-IgG fractions both revealed higher binding percentages of 125I-T3 analog than the control IgG fraction and non-IgG fraction of the patient. Furthermore, a good dose response was observed between the binding percentage of 125I-T3 analog and each dose of the patient's serum or IgG fraction. From these observations, it was clarified that this woman had anti-T3 IgG autoantibodies using a Protein A column chromatography with confirmation of gel filtration chromatography.

Autoantibodies↗
PubMed1988

Lack of effect of gamma-globulin infusion on circulating immune complexes in patients with Kawasaki syndrome.

Previous studies have demonstrated circulating immune complexes (CICs) in sera of 70% of Kawasaki syndrome (KS) patients but the pathogenic role of these complexes in the illness is unknown. Infusions of gamma-globulin (GG) have been shown recently to reduce the prevalence of coronary artery aneurysms in KS patients. One of the proposed mechanisms of action of GG therapy is through an effect on CICs. We analyzed paired sera for CICs from 29 patients with KS, 19 of whom were treated with aspirin and GG and 10 of whom received aspirin only. Assay systems used for CIC detection were Raji-mu enzyme immunoassay, C1q solid phase assay-enzyme immunoassay and F(ab')2-anti-C3-mu enzyme immunoassay. Overall 20 of 29 patients had CICs detected by at least two of three assays used. Of the 19 GG-treated patients 14 had CICs detected: 5 in both paired sera; 2 in pretherapy sera; and 7 posttherapy specimens. There was no correlation between duration of fever, presence of myocarditis or the development of coronary artery aneurysms and the presence of CICs in the serum of KS patients. Although CICs can be found frequently in the sera of KS patients there seems to be no association between the presence of CICs and the duration of fever or the development of coronary artery aneurysms.

Antibodies↗
PubMed1988

A case of lung infection caused by an unusual strain of Nocardia farcinica.

A case of lung infection caused by an unusual strain of Nocardia farcinica is reported. This is the third case of the N. farcinica infection in this country. The strain failed to utilize rhamnose as sole carbon source, but could be identified by a numerical identification method. The mycolic acids contained 1-3 double bonds and the numbers of the carbon atoms of the mycolic acids were 50 to 60, average 56.

Aged↗
PubMed1988

[Stimulative effect of chlordanes on guinea pig polymorphonuclear leukocytes].

To investigate the toxicity of chlordane, an organochlorine insecticide, effects of cis-Chlordane, trans-Chlordane, Heptachlor and Heptachlor epoxide were examined on stimulus responses of guinea pig polymorphonuclear leukocytes (PMNs). Results obtained were as follows. These chlordane-related compounds stimulated superoxide (O2-) generation, altered membrane potential and increased intracellular Ca2+ concentration ((Ca2+]i). As a significant tendency was not found in the stimulating effects of these compounds, the relationship between the effect and molecular structure of these substances remains unknown. Of these response reactions of PMN stimulated by chlordanes, stimulation of O2- generation lagged behind the others. Increase in [Ca2+]i was due to both acceleration of extracellular Ca2+ influx and Ca2+ release from intracellular pool. These results indicate that these chlordane-related compounds stimulate PMN and suggest a causal relationship between the stimulation of O2- generation by these substances and their toxicity.

Animals↗
PubMed1988

[Studies on aldosterone RIA kit using the two antibody method].

Two antibody method of aldosterone RIA kit was investigated. This kit was measured directly without extracting the aldosterone. On fundamental studies, stability of standard curve, reproductivity, recovery test and dilution test were obtained good results. On clinical studies, the diurnal variation of serum aldosterone concentration in normal child and adult was correlated well to that of concentration of cortisol and ACTH. The concentration of three hormones was the highest in the early morning and it was the lowest in midnight.

Adrenocorticotropic Hormone↗
PubMed1988

Identification of a transforming activity suppressing sequence in the c-raf oncogene.

Our previous study revealed that the rat c-raf was activated by a rearrangement leading to replacement of the amino-terminal half of the product. Therefore, we suggested that some sequences present in the amino-terminal half might prevent c-raf from becoming an active oncogene. To examine this possibility, we constructed a series of deletion mutants of c-raf cDNA by the random linker insertion method. By transfection of NIH3T3 cells with these mutants, a region whose deletion resulted in activation of c-raf was identified. This region is located at amino acid residues 245 to 261, immediate upstream of the kinase domain of the c-raf product and is rich in serine and threonine residues. This region includes a sequence of six amino acids, RSTSTP, which is conserved in the products of normal raf gene families of various species. This sequence is the best candidate for suppressing transforming activity of c-raf.

3T3 Cells↗
PubMed1988

Identification by a random linker insertion method of a region which suppresses the transforming activity of the raf oncogene.

Activation mechanism of raf oncogene was studied by applying in vitro mutagenesis to its cDNA. Previous studies suggested the presence of an activation suppressing sequence in the amino-terminal half of c-raf product. Loss of the sequence by genetic rearrangement was presumed to convert c-raf to possess transforming activity. To identify such sequence, we prepared cDNA mutants by random linker insertion. Synthetic oligonucleotide linker was inserted into the plasmid containing cDNA at a single and random site. Coupling two different mutants, in-frame deletion mutants were constructed systematically. Analysis of these deletion mutants revealed a region, the loss of which made c-raf activated.

Animals↗
PubMed1988

[Cytokinetic effects of carboplatin and cisplatin on a human ovarian cancer cell line].

The cytokinetic effects of carboplatin(CBDCA) on a human ovarian cancer cell line(KF-1) were examined by means of cell survival rate and flow cytometry in comparison with cisplatin(CDDP). CBDCA and CDDP exhibited dose dependent cytotoxicity on KF-1, and CBDCA showed compatible cell growth inhibition to that of 15 times concentration of CDDP in comparison with IC50 of 72 hrs after drug addition. From the analysis of cell cycle, CBDCA and CDDP inhibited cell cycle progression at G2 + M phase. CBDCA exhibited G2 + M phase block to that of 15 to 20 times the concentration of CDDP. We suggested that CBDCA had potential therapeutic activity against ovarian cancer, but should be evaluated carefully in the clinical use.

Carboplatin↗