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Biomedical subjects

Y Takagi

Publications and source records attributed to Y Takagi.

At least 289 records · Page 16Linked to original sources
PubMed1995

Molecular analysis of the Cip1/Waf1 (p21) gene in diverse types of human tumors.

We have screened for mutations in the Cip1/Waf1 gene using Southern blot analysis and the polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) method in diverse human tumors. Seven of 102 (7%) human tumor samples were identified to have point mutations within the coding region of the Cip1/Waf1 gene. Two of the seven mutated cases showed gene rearrangements. These results suggest that the frequency of genetic alterations in the Cip1/Waf1 gene is relatively low in comparison with several known tumor suppressor genes.

Base Sequence↗
PubMed1995

Structural basis of G protein specificity of human endothelin receptors. A study with endothelinA/B chimeras.

The endothelin (ET) family of peptides acts via two subtypes of guanine nucleotide-binding regulatory protein (G protein)-coupled receptors termed ETA and ETB. ET-1 stimulated cAMP formation in Chinese hamster ovary (CHO) cells stably expressing human wild-type ETA (CHO/hETA cells) while it inhibited cAMP formation in CHO cells expressing human wild-type ETB (CHO/hETB cells), and pharmacological evidence indicated that the opposite effects were due to the selective coupling of each receptor subtype with G alpha s/G alpha i. To find out a receptor domain(s) that determined the selective coupling, a series of chimeric receptors between hETA and hETB was expressed on CHO cells, and the effect of ET-1 on cAMP formation in each cell line was tested. hETA with the replacement of second and/or third intracellular loop (ICLII and/or -III) to the corresponding region(s) of hETB failed to transmit the stimulatory effect of ET-1. hETB with the replacement of ICLIII to the corresponding region of hETA failed to transmit the inhibitory effect of ET-1. A chimeric receptor with ICLII of hETB and with ICLIII of hETA failed to transmit both effects. In cells expressing chimeric receptors with ICLII of hETA and with ICLIII of hETB, ET-1 inhibited cAMP formation while it stimulated cAMP formation when cells were pretreated with pertussis toxin. These results indicated the roles of ICLII and -III of hETR as a major determinant of the selective coupling of hETA and hETB with G alpha s/G alpha i, respectively. We also demonstrated that each receptor subtype expressed on the same cell could work independently, i.e. for hETA to activate G alpha s and for hETB to activate G alpha i, resulting in dose-dependent dual effects of ET-1 on cAMP formation.

Animals↗
PubMed1995

Temperature-dependent change in the rate-determining step in a reaction catalyzed by a hammerhead ribozyme.

To characterize the reaction catalyzed by a hammerhead ribozyme, the dependence on temperature of the reaction was examined. An Arrhenius plot revealed a transition that indicated a temperature-dependent change in the activation energy at around 25 degrees C. Thermodynamic parameters of the reaction were estimated at 10 and 35 degrees C. The analyses led to the following conclusions. At 25-50 degrees C, the chemical cleavage step (kcleav) was the rate-determining step, and the cleaved fragments dissociated from the ribozyme at a higher rate than the rate of the chemical reaction. When the temperature was below 25 degrees C, the cleaved fragments adhered to the ribozyme more tightly and the product dissociation step became the rate-determining step. Above 50 degrees C, the rate of the reaction decreased because, at such high temperatures, the formation of the Michaelis-Menten complex (duplex formation) was hampered by thermal melting. A conformational change in the ribozyme-substrate complex was not the rate-determining step at any of the temperatures examined.

Base Sequence↗
PubMed1995

Transmenopausal change of trabecular bone density and structural pattern assessed by peripheral quantitative computed tomography in Japanese women.

Trabecular bone pattern, related to connectivity, was analyzed along with a separate measurement of cortical and trabecular bone mineral density (BMD) at the distal radius by peripheral quantitative computed tomography (pQCT) in 48 perimenopausal women, consisting of 25 premenopausal women aged 41 to 52 (mean 46.6 +/- 2.9 years) and 23 early postmenopausal women aged 46 to 59 (mean 53.2 +/- 3.2 years) within 5 years of the menopause (mean 2.7 +/- 1.5 years). No significant difference was found in either cortical or trabecular bone density between premenopausal and postmenopausal women despite a significant difference in age (premenopause vs postmenopausal: 46.7 +/- 2.9 years vs 53.2 +/- 3.1 years, p < 0.00001), including a slow change of BMD, if any, before and within 5 years of the menopause. However, analysis of trabecular fragments and perforation revealed a significant increase of the number of perforations in postmenopausal compared with premenopausal women (premenopausal vs postmenopausal: 0.9 +/- 1.6 vs 2.9 +/- 2.3, p < 0.002), indicating that disconnectivity has already increased before a significant reduction of BMD. Furthermore, chi-square analysis showed that even postmenopausal women with trabecular BMD more than 160 mg/cm3 were about 11 times more likely to have three or more perforations than premenopausal ones (odds ratio: 11.42, F = 0.030). These data suggest that trabecular bone connectivity is more sensitive that BMD in the detection of the early changes of postmenopausal osteoporosis.

Adult↗
PubMed1995

Rapid turnover proteins as a prognostic indicator in cancer patients.

We investigated the relation between the plasma levels of various proteins, especially rapid turnover proteins (RTPs), and the prognosis in advanced cancer patients receiving total parenteral nutrition (TPN). In the patients with benign disease (n = 40), RTPs increased abruptly following TPN, but in patients with malignant disease, they rose slowly. Patients with malignant disease were divided into two different groups according to the outcome; group A, surviving 3 months or more after TPN and group B, who died within 3 months after TPN initiation. Whereas the RTP levels were elevated significantly in group A, they did not show any noticeable increase in group B. There was a close correlation between the plasma protein levels at 2 weeks and the survival time after TPN initiation. Thus, using the estimated critical values of RTPs with prognostic significance, the correct prognosis rate in 37 newly treated cases was: transferrin 75.7%, prealbumin: 91.9%, retinol-binding protein: 86.5%. These results clearly indicate that the TPN-induced changes in RTPs, notably in the PA value, can be a good prognostic indicator of survival in advanced cancer patients.

Adult↗
PubMed1995

Report on the first annual survey of home parenteral nutrition in Japan.

An annual survey of the current national status of home parenteral nutrition (HPN) in Japan was begun in 1991, with a total of 231 registered patients from 142 institutions providing adequate data for evaluation and analysis. HPN was given for an average of 683 +/- 764 days to 93 patients with malignant diseases and 138 with benign disease, including 53 with inflammatory bowel disease and 79 with short bowel syndrome, 107 (46.3%) of whom were successfully rehabilitated. By the end of 1990, 61% of the patients investigated were still on HPN, 7% had already completed HPN, and 26% had died, the deceased accounting for 54% of the patients with malignant diseases and 7% of those with benign diseases. A total of 321 catheters had been used by all 231 patients, the most common being the subcutaneously implanted type, accounting for 33% of all catheters. By the end of 1990, 32% of these 321 catheters were still in place, 18% had been removed on the termination of HPN and 44% had been removed due to complications of total parenteral nutrition, including 20% for catheter fever. Rehospitalization was required in 62% of the patients, the cause being HPN-related in 21% of the total patients. Metabolic complications were experienced by 60% of the patients, but none of these were severe although 6% required hospitalization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Surgical treatment of renal cell carcinoma metastases: prognostic significance.

Between January 1980 and March 1993, 166 patients with renal cell carcinoma were treated at Nagoya University Hospital. Among them 16 (9.6%) underwent surgical removal of 21 metastatic lesions: 12 patients had distant metastases at diagnosis and the other 4 demonstrated new distant metastases during their clinical course after nephrectomy. The metastatic lesions involved the brain in 6 patients, bone in 4, lung in 2, contralateral adrenal glands in 2, soft tissues in 2, lymph nodes in 2, pleura in 1, pancreas in 1, and contralateral renal pelvis in 1. All of the 16 patients underwent nephrectomy and 15 of them (93%) received interferon-alpha therapy. Patients with lesions which were completely resected had significantly longer survival than those with lesions which were palliatively treated and those with metastatic lesions at other sites (p = 0.02). Improvement of performance status was observed in 5 of 6 (83%) patients undergoing palliative surgical treatment. The present study suggests that surgical removal of metastatic lesions prolongs survival in a limited number of renal cell carcinoma patients and that it improves performance status in those symptoms related to metastasis.

Bone Neoplasms↗
PubMed1995

Insulin-specific activation of S6 kinase and its desensitization in cultured rat vascular smooth muscle cells.

To elucidate the role of hyperinsulinemia in the development of atherosclerosis, we evaluated insulin-specific signaling in cultured vascular smooth muscle cells (SMCs) and its desensitization by continuous exposure to insulin. The concentration of unlabeled insulin that inhibited specific [A14-125I]-insulin binding by 50% (IC50) was 0.33 +/- 0.02 nM, which was 100 times less than the IC50 of unlabeled IGF-I. For [125I]-IGF-I binding, the IC50 of unlabeled IGF-I was found to be 6.6 +/- 0.88 nM, which was 100 times less than the IC50 of unlabeled insulin. The binding capacities for insulin and IGF-I were found to be 1.28 +/- 0.86 and 1200 +/- 170 fmol/0.5 mg protein, respectively. Autophosphorylation of the beta-subunit of the insulin receptor was stimulated at above 0.17 nM (24 microU/ml) insulin. Insulin concentrations exceeding 1 nM significantly activated the S6 kinase in a dose-dependent manner. In contrast, 10 nM insulin did not activate MAP kinase nor [3H]thymidine incorporation into DNA, while both were activated by 38% and 44% with 1 microM insulin and by 52% and 67% with 10 nM IGF-I, respectively. By pre-exposing cells to 10 nM insulin for 12 h, the binding capacity for insulin decreased by 34% (P < 0.05), and activation of S6 kinase by insulin almost disappeared, while both IGF-I binding and the activation of S6 kinase by IGF-I were not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Differential effects of hypoxia on ligand binding properties of nicotinic and muscarinic acetylcholine receptors on cultured bovine adrenal chromaffin cells.

Hypoxia is known to disturb neuronal signal transmission at the synapse. Presynaptically, hypoxia is reported to suppress the release of neurotransmitters, but its postsynaptic effects, especially on the function of neurotransmitter receptors, have not yet been elucidated. To clarify the postsynaptic effects, we used cultured bovine adrenal chromaffin cells as a model of postsynaptic neurons and examined specific binding of L-[3H]nicotine (an agonist for nicotinic acetylcholine receptors: nAChRs) and 22Na+ flux under control and hypoxic conditions. Experiments were performed in media preequilibrated with a gas mixture of either 21% O2/79% N2 (control) or 100% N2 (hypoxia). Scatchard analysis of the specific binding to the cells revealed that the KD under hypoxic conditions was twice as large as that under control conditions, whereas the Bmax was unchanged. When the specific [3H]nicotine binding was kinetically analyzed, the association constant (k1) but not the dissociation constant (k-1) was decreased to 40% of the control value by hypoxia. When the binding assay was performed using the membrane fraction, these changes were not observed. Nicotine-evoked 22Na+ flux into the cells was suppressed by hypoxia. In contrast, specific [3H]quinuclidinyl benzilate binding to the intact cells was unaffected by hypoxia. These results demonstrate that hypoxia specifically suppresses the function of nAChRs (and hence, neuronal signal transmission through nAChRs), primarily by acting intracellularly.

Adrenal Glands↗
PubMed1995

Characterization of a dopamine-releasing action of 6R-L-erythro-tetrahydrobiopterin: comparison with a 6S-form.

6R-L-erythro-Tetrahydrobiopterin (6R-BH4) is a cofactor for aromatic L-amino acid hydroxylases and nitric oxide synthase. Recently, we have reported that independently of its cofactor activities, 6R-BH4 acts from the outside of neurons in the brain to enhance the release of monoamine neurotransmitters such as dopamine. To characterize the pharmacological properties of the action, we examined the effects of 6S-BH4, a diastereoisomer of 6R-BH4, on dopamine release in the rat striatum by using brain microdialysis and compared its effects with those of 6R-BH4. Perfusion of 6S-BH4 or 6R-BH4 through the dialysis probe increased extracellular dopamine levels (an index of in vivo dopamine release) concentration dependently; the maximal increase by 6S-BH4, was one-sixth of that by 6R-BH4. 6S-BH4 increased extracellular DOPA levels in the presence of NSD 1015, an inhibitor of aromatic L-amino acid decarboxylase (an index of in vivo tyrosine hydroxylase activity), to an extent similar to the increase induced by 6R-BH4. The increase in the DOPA levels induced by either of the pteridines was abolished after pretreatment of rats with alpha-methyl-p-tyrosine (an inhibitor of tyrosine hydroxylase). Under the same conditions, the 6S-BH4-induced dopamine release was abolished, but most of the 6R-BH4-induced increase persisted. Coadministration of 6S-BH4 with 6R-BH4 inhibited the increase in dopamine release induced by 6R-BH4 alone. These results show that 6R-BH4 stimulates dopamine release by acting at the specific recognition site on the neuronal membrane, and that 6S-BH4 acts as an antagonist of 6R-BH4 at this site, although it has cofactor activities.

Animals↗
PubMed1995

Magnesium status, serum HDL cholesterol, and apolipoprotein A-1 levels.

To determine the relationship between low magnesium status and lipids, we divided 27 patients with microscopic hematuria and normal renal function into two groups according to magnesium retention, as measured by a magnesium-loading test, and compared their serum lipid and apolipoproteins. Patients with low magnesium status (n = 7) had significantly lower levels of cholesterol, HDL cholesterol, and apolipoprotein A-1 than those with normal magnesium status (n = 20); however, there were no significant differences between the groups in serum concentrations of magnesium and apolipoprotein B. These data suggest that magnesium deficiencies are associated with low serum concentration of HDL cholesterol and apolipoprotein A-1.

Adolescent↗
PubMed1995

Plasma endothelin-1 levels of children with cirrhosis.

We measured plasma concentration of endothelin-1 in three children with Byler's disease, five with biliary atresia after portoenterostomy, and nine controls. No patients had ascites or hepatorenal syndrome. Plasma endothelin-1 levels were significantly higher in patients with Byler's disease than in the controls (5.19 +/- 0.90 versus 1.81 +/- 0.19 pg/ml, respectively; p < 0.01), but were normal in operated biliary atresia. Urinary concentrations of N-acetyl-beta-D-glucosaminidase (NAG) were significantly higher in the patients with Byler's disease than in controls. Plasma endothelin-1 level correlated significantly with serum concentration of bile acid (r = 0.91; p < 0.01) and urinary concentration of NAG (r = 0.92; p < 0.01). We conclude that plasma endothelin-1 levels are high in patients with severe biliary cirrhosis and that endothelin-1 may partially contribute to development of renal injury in cirrhosis.

Acetylglucosaminidase↗
PubMed1995

Molecular and epidemiological analyses of abnormal expression of aromatase in breast cancer.

One-third of human breast cancers exhibit estrogen-dependent proliferation. It appears that estrogen functions as a mitogenic factor in these carcinomas. As aromatase is the rate-limiting enzyme in estrogen biosynthesis. It could play an important role in the pathogenesis of estrogen-dependent breast cancer. The aromatase gene consists of at least six exons 1, each containing a promoter, and the tissue-specific expression is regulated by alternative use of these multiple promoters. The expression of aromatase in the breast and abdominal adipose tissues is regulated by a promoter flanking exon 1b. Molecular and epidemiological analyses of tissue-specific utilization of multiple exons 1 and promoters revealed a switching from use of the adipose-specific exon 1b to exon 1c in adipose tissues adjacent to the carcinomas in most breast cancer patients. Exon 1c has been shown to be specific for the ovary. Aromatase mRNA in adipose tissues distal to the tumour of the same patients was normally transcribed from exon 1b as was breast tissue in healthy controls. It is noteworthy that a switching from exon 1b to exon 1c was often observed in breast cancer patients having metastatic lymph nodes. These data suggest that switching from an adipose-specific exon 1b to exon 1c could cause a deviation from strict regulation of tissue-specific expression of the adipose aromatase leading to over-expression of the adipose aromatase. Consequently overproduction of local estrogen may promote carcinogenesis or proliferation of breast cancer cells.

Adipose Tissue↗
PubMed1995

Mass screening for prostate carcinoma: a study in Hokkaido, Japan.

Although there has been controversy about the early detection of prostate carcinoma by mass screening, we carried out an investigational study of such screening, using digital rectal examination (DRE) and serum prostate-specific antigen (PSA) determination in Hokkaido, Japan. We determined the detection rate and some profiles of the carcinoma detected by screening in Japanese men 50 years old and older. The detection rate of carcinoma was 1.10% in 1,639 participants. The rate linearly increased with aging from 0.25% for men in their fifties to 2.29% for those in their seventies. Two thirds of the carcinomas were T1(c) or T2, the frequency of which seemed to be higher than that of patients who visited medical institutions. The simultaneous use of both DRE and serum PSA determination showed a higher positive predictive value than either alone. Our current results indicated that the detection rate of carcinoma was higher than we previously anticipated for Japanese men, and that simultaneous use of DRE and serum PSA determination yielded a higher positive predictive value than either alone.

Aged↗
PubMed1995

Effect of a hematopoietic promoting factor derived from porcine kidney on the proliferation of mouse hematopoietic progenitor cells in liquid culture.

We have partially purified a factor from porcine kidney, hematopoietic-promoting factor (HPF), which enhances granulocyte-macrophage colony-forming units (CFU-GM) and erythropoietic burst-forming unit (BFU-E) colony formation in the presence of various exogenous colony-stimulating factors (CSF) or erythropoietin (Epo) from mouse bone marrow cells. In this paper we examine the combined effects of HPF and/or stem cell factor (SCF) with interleukin-3 (IL-3) and interleukin-6 (IL-6) on the proliferation of primitive hemopoietic progenitor cells in liquid cultures for 7 or 14d. The combination of IL-3+IL-6+HPF could not increase the number of CFU-GM, BFU-E, and day-8 colony forming units in spleen (CFU-S) in cultures of unfractionated bone marrow cells, while this combination resulted in a marked increase of progenitors in cultures of c-kit+ enriched cells. In contrast, expansion of progenitors was observed by IL-3+IL-6+SCF or IL-3+IL-6+SCF+HPF in the culture of both unfractionated bone marrow cells and c-kit(+)-enriched cells after 7d. The number of CFU-GM and BFU-E in the combination of IL-3+IL-6+SCF+HPF for c-kit+ cells showed the largest increase, 109-fold and 38-fold respectively after 14d. These results show that HPF has promoting activity on hematopoietic stem cells and acts synergistically with SCF in early stages of hematopoiesis.

Animals↗