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T Iwasaki

Publications and source records attributed to T Iwasaki.

At least 145 records · Page 8Linked to original sources
PubMed2000

[Prediction of cardiac sympathetic nerve activity and cardiac functional outcome after treatment in patients with dilated cardiomyopathy: examination using dobutamine gated blood pool scintigraphy].

OBJECTIVES: This study evaluated whether dobutamine gated blood pool scintigraphy can predict improvement of cardiac sympathetic nerve activity and cardiac function. METHODS: Sixteen patients(10 men and 6 women, mean age 59 +/- 13 years) with dilated cardiomyopathy underwent dobutamine gated blood pool scintigraphy to measure left ventricular ejection fraction (LVEF) using tracer at 0, 5, 10 and 15 micrograms/kg/min before treatment. Patients were divided into good responders (LVEF increase > or = 15%) 8 patients(GR Group) and poor responders(LVEF increase < 15%) 8 patients (PR Group) after treatment with beta-blocker or amiodarone with a background treatment of digitalis, diuretics and angiotensin converting enzyme inhibitor. I-123 metaiodobenzylguanidine(MIBG) imaging to evaluate cardiac sympathetic nerve activity and echocardiography were performed before and at one year after treatment. MIBG imaging was obtained 4 hours after tracer injection, and the heart/mediastinum count ratio(H/M ratio) calculated from the anterior planar image and the total defect score(TDS) from the single photon emission computed tomography image. LVEF and left ventricular endo-diastolic dimension (LVDd) were measured by echocardiography and New York Heart Association(NYHA) functional class was evaluated. RESULTS: The GR Group showed TDS decreased from 28 +/- 6 to 17 +/- 12(p < 0.05), H/M ratio increased from 1.79 +/- 0.26 to 2.07 +/- 0.32(p < 0.05), LVEF increased from 29 +/- 8% to 48 +/- 10%(p < 0.01), and LVDd decreased from 65 +/- 4 mm to 58 +/- 5 mm(p < 0.05). In contrast, the PR Group showed no significant changes in TDS, H/M ratio, LVEF and LVDd. NYHA functional class improved in both groups. The improvement was better in the GR Group than in the PR Group. CONCLUSIONS: Dobutamine gated blood pool scintigraphy is useful to predict the improvement of the cardiac sympathetic nerve activity and cardiac function, and symptoms after treatment in patients with dilated cardiomyopathy.

3-Iodobenzylguanidine↗
PubMed2000

Measurement of human plasma phospholipid transfer protein by sandwich ELISA.

BACKGROUND: Plasma phospholipid transfer protein (PLTP) plays a central role in the remodeling of HDLs. Reliable and accurate methods for assaying PLTP concentration are required. METHODS: A sandwich ELISA for PLTP has been developed, using two monoclonal antibodies against recombinant human PLTP (rhPLTP) expressed in Chinese hamster ovary cells. The ELISA allows for the quantification of PLTP in the range 0.625-15.0 ng/assay (1.2-30.0 mg/L). Intra- and interassay CVs were <3.0% and <4.2% respectively. The assay was used to quantify plasma PLTP concentrations in 132 Japanese subjects (75 males and 57 females). RESULTS: PLTP concentrations were 12.0 +/- 3. 0 mg/L (mean +/- SD; range, 4.9-20.5 mg/L). No sex difference was observed. Plasma PLTP concentration was positively correlated with HDL-cholesterol (r = 0.72; P: <0.001), apolipoprotein (apo) A-I (r = 0.62; P: <0.001) and HDL(2)-cholesterol (r = 0.72; P: <0.001), and was negatively correlated with triacylglycerol (r = -0.45; P: <0. 001). There was no correlation with plasma apo A-II. These results agree with other evidence that plasma PLTP is associated with large apo A-I-containing lipoproteins. There was no correlation (r = -0. 01) between plasma PLTP and plasma phosphatidylcholine transfer activity (range, 3.5-10.5 micromol. mL(-1). h(-1)), suggesting that PLTP may exist in active and inactive forms. CONCLUSION: This new ELISA will be of value for further studies of PLTP in health and disease.

Adult↗
PubMed2000

[Comparison of epidural anesthesia and general anesthesia for patients with bronchial asthma].

We prospectively investigated the incidence of asthmatic attacks in 94 patients (1.5%) who were diagnosed as definite asthma. We separated the patients into three groups: epidural anesthesia (n = 10) including combined spinal/epidural anesthesia (n = 7), combined epidural and general anesthesia (n = 23), and general anesthesia (n = 54). General anesthesia was induced with propofol or midazolam and maintained with N2O and O2 with sevoflurane in adults. Patients who underwent epidural anesthesia and combined spinal and epidural anesthesia showed no asthmatic attacks. The incidence of bronchospasm with combined epidural and general anesthesia was 2/23. The incidence of bronchospasm with general anesthesia was 4/54. Bronchoconstriction occurred after tracheal intubation in 5 patients except in one patient, in whom it occurred after induction of anesthesia with midazolam. All episodes of bronchospasm in the operative period were treated successfully. The frequency of bronchospasm did not depend on the severity of asthmatic symptoms or the chronic use of bronchodilators before operation. These findings suggest that tracheal intubation, not the choice of anesthetic, plays an important role in the pathogenesis of bronchospasm.

Adult↗
PubMed2000

[Long-term effects of non-supervised home exercise therapy on quality of life in patients with myocardial infarction].

OBJECTIVES: Improvement in exercise tolerance is an important goal in cardiac rehabilitation, but improvement in quality of life (QOL) must also be considered. Therefore, we planned a non-supervised walking exercise program at home for 1 year in patients in the convalescent phase of myocardial infarction to study the exercise tolerance and QOL. METHODS: Thirty-two patients (mean age 60.3 +/- 10 years, 23 men and 9 women) performed our non-supervised home exercise program in which the exercise prescription was based on the rating of perceived exertion. Before discharge, 1 month and 1 year after discharge, exercise tolerance was measured by the cardiopulmonary treadmill exercise test, and QOL was investigated by questionnaire. RESULTS: Anaerobic threshold increased from 15.8 +/- 3.4 ml/kg/min before discharge to 17.5 +/- 3.0 ml/kg/min 1 month after (p < 0.05) and to 18.3 +/- 3.0 ml/min/kg 1 year after (p < 0.05 vs at discharge), and peak oxygen consumption increased from 22.2 +/- 4.3 to 25.2 +/- 5.1 ml/kg/min (p < 0.05) and to 26.4 +/- 5.2 ml/kg/min (p < 0.05 vs at discharge), respectively. QOL score by questionnaire was maintained in 13 patients (improved in 3, same in 10) and decreased in 19 of 32 patients from discharge to 1 month, and the score was maintained in 18 patients (improved in 13, same in 5) and decreased in 14 of 32 patients from 1 month to 1 year after discharge. CONCLUSIONS: In patients with myocardial infarction in the convalescent phase, our non-supervised home exercise program resulted in improvement in exercise tolerance, but QOL score decreased gradually. Therefore, we should not only prescribe an exercise program, but also must give more psychosocial support to the patients. The reasons for the decreased QOL by cardiac rehabilitation must be further investigated.

Anaerobic Threshold↗
PubMed2000

[Phase I study of super high-dose chemotherapy for liver cancer with percutaneous isolated hepatic perfusion (PIHP) and peripheral blood stem cell transplantation (PBSCT)].

The aim of this study was to evaluate the phase I aspects of super high-dose chemotherapy for advanced liver cancer with combined use of PIHP and PBSCT. In 4 patients with HCC and 1 patient with colonic liver metastases, peripheral blood stem cells (PBSC) were mobilized by either i.v. infusion of ETP (180 mg/m2/day for 3 days) or i.a. infusion of doxorubicin (100-120 mg/m2). In 3 (60%) of 5 patients, PBSC for PBSCT were harvested in effective quantities (CFU-GM > or = 2 x 10(5)/kg or CD 34 positive cells > or = 2 x 10(6)/kg). In these 3 patients, a repeated PIHP with either doxorubicin, 5-fluorouracil, or CDDP was carried out 4 weeks after the 1st PIHP. Thereafter, auto-PBSCT was intravenously administered 2 days after PIHP. In the repeated PIHP treatments, although anti-cancer drugs were administered at doses equivalent to or even higher than those administered at the 1st PIHP, bone marrow suppressions were transient and well tolerated. Fatal complications were not observed in any patients. These results indicate that with the combined use of PIHP and PBSCT, high-dose regional chemotherapy of the liver can be safely repeated without systemic toxicities.

Adolescent↗
PubMed2000

[Clinical characteristics of ventricular tachycardia and ventricular fibrillation in exercise stress testing].

OBJECTIVES: Ventricular tachycardia (VT) and ventricular fibrillation (Vf) induced in exercise stress testing should be treated urgently, although the occurrence of arrhythmia is rare. The conditions for the onset of arrhythmia and the clinical characteristics of VT and Vf patients in exercise stress testing were studied. METHODS: Fifty-nine patients (mean age 54 +/- 17 years, 41 males, 18 females) with VT (succession of 3 or more ventricular premature beats) or Vf induced in exercise stress testing were selected from 7,594 patients with consecutive treadmill stress testing in our hospital from January 1993 to February 1998. RESULTS: The incidence of exercise-induced VT or Vf was 0.8%, and there were no fatal accidents in all tests. Among the 59 patients with exercise-induced VT or Vf, 52 patients had non-sustained VT, 5 had sustained VT, and 2 had Vf. Of the 59 patients, 23 had rhythm or conduction disturbances, 14 had coronary artery disease, 13 had cardiomyopathy, and 9 had valvular heart disease. The VT or Vf incidence in coronary artery disease was 0.2%, and in valvular heart disease was 10.8%. VT or Vf occurred at over 80% of maximum heart rate exercise intensity in 40 patients, including 4 with sustained VT and 2 with Vf, of the 59 patients. Also, in 9 VT patients including the 4 sustained VT patients, VT occurred in the exercise recovery period within 2 min after the exercise. Although VT disappeared spontaneously in 52 non-sustained VT and 3 sustained VT patients, intravenous injection of lidocaine was needed in 2 sustained VT patients and direct current defibrillator was needed in 2 Vf patients. Furthermore, only one non-cardiac death was observed in the follow-up period of average 42 months. CONCLUSIONS: Our results showed clinical characteristics and incidence of VT or Vf similar to past reports. Furthermore, all sustained VT and Vf patients, who should be treated urgently, had a past history of ventricular premature beats or VT. Our data suggest that VT and Vf could occur during the recovery period, especially in patients with documented ventricular tachyarrhythmias when the stress intensity has reached the critical level in the exercise tolerance test.

Aged↗
PubMed2000

Functional dissociation of striatal and hippocampal cholinergic systems in egocentric and allocentric localization: effect of overtraining.

The effects of overtraining on the retention of egocentric localization (EL) and allocentric localization (AL) tasks using rats injected with 1.8 nmol/12 microliters of ethylcholine mustard aziridinium ion (AF64A) in the striatum or hippocampus were examined. In the EL task, an arm positioning at in same direction of a randomly selected start arm was baited throughout trials. In the AL task, a baited arm was fixed throughout trials regardless of the position of the start arm. The performance of EL retention was disrupted only by intrastriatal AF64A injection. The overtrained striatal lesioned animals showed better performance compared to the non-overtrained striatal lesioned animals. In contrast, hippocampal AF64A injection selectively impaired AL retention. Unlike the effect of overtraining on EL retention in striatal lesioned animals, however, the AL performance of hippocampal lesioned animals was not significantly affected by overtraining. The results support the idea of functional dissociation of striatal and hippocampal cholinergic systems in EL and AL learning and provide further evidence that the striatal cholinergic system may be involved in the memory (consolidation or retrieval) process of EL learning, and the hippocampal cholinergic system in the processing of specific cues necessary for efficient performance in AL learning rather than memory.

Acetylcholine↗
PubMed2000

[Four cases of the anomalous origin of the left coronary artery from the pulmonary artery].

We report perioperative management of 4 patients with anomalous origin of the left coronary artery from the pulmonary artery. This report involves with 3 infant cases and an adult. Two infants underwent coronary reimplantation procedure and Takeuchi's method was performed on the other infant. In all infant cases, mitral valve plasty was performed to correct mitral regurgitation secondary to papillary muscle dysfunction. The adult patient underwent CABG with ligation of LCA. General anesthesia was performed with high doses of fentanyl in all cases. We employed a relatively high PaCO2 and low FIO2 in order to maintain a high pulmonary vascular resistance. It aims to decrease the incidence of left to right shunt. We used epinephrine to wean one infant and the adult from cardiopulmonary bypass. Perioperative course was uneventful with the use of catecholamines and high doses of vasodilators for left ventricular dysfunction and coronary perfusion under mechanical ventilation.

Anesthesia, General↗
PubMed1999

Effect of graft-versus-host disease (GVHD) on host hematopoietic progenitor cells is mediated by Fas-Fas ligand interactions but this does not explain the effect of GVHD on donor cells.

The acute graft-versus-host disease (GVHD) generated in BDF1 mice by the injection of spleen cells from the C57BL/6 parental strain induces a direct cell-mediated attack on host lymphohematopoietic populations, resulting in the reconstitution of the host with donor hematopoietic stem cells. We examined the effect of GVHD on the donor and host hematopoiesis in parental-induced acute GVHD. The bone marrow was hypoplastic and the number of hematopoietic progenitor cells significantly decreased at 4 weeks after GVHD induction. However, extramedullary splenic hematopoiesis was present and the number of hematopoietic progenitor cells in the spleen significantly increased at this time. Fas expression on the host spleen cells and bone marrow cells significantly increased during weeks 2 to 8 of GVHD. Host cell incubation with anti-Fas Ab induced apoptosis, and the number of hematopoietic progenitor cells decreased during these weeks. A significant correlation between the augmented Fas expression on host bone marrow cells and the decreased number of host bone marrow cells by acute GVHD was observed. Furthermore, the injection of Fas ligand (FasL)-deficient B6/gld spleen cells failed to affect host bone marrow cells. Although Fas expression on repopulating donor cells also increased, Fas-induced apoptosis by the repopulating donor cells was not remarkable until 12 weeks, when more than 90% of the cells were donor cells. The number of hematopoietic progenitor cells in the bone marrow and the spleen by the repopulating donor cells, however, decreased over an extended time during acute GVHD. This suggests that Fas-FasL interactions may regulate suppression of host hematopoietic cells but not of donor hematopoietic cells. Hematopoietic dysfunctions caused by the reconstituted donor cells are independent to Fas-FasL interactions and persisted for a long time during parental-induced acute GVHD.

Animals↗
PubMed1999

Structural conservation of the isolated zinc site in archaeal zinc-containing ferredoxins as revealed by x-ray absorption spectroscopic analysis and its evolutionary implications.

The zfx gene encoding a zinc-containing ferredoxin from Thermoplasma acidophilum strain HO-62 was cloned and sequenced. It is located upstream of two genes encoding an archaeal homolog of nascent polypeptide-associated complex alpha subunit and a tRNA nucleotidyltransferase. This gene organization is not conserved in several euryarchaeoteal genomes. The multiple sequence alignments of the zfx gene product suggest significant sequence similarity of the ferredoxin core fold to that of a low potential 8Fe-containing dicluster ferredoxin without a zinc center. The tightly bound zinc site of zinc-containing ferredoxins from two phylogenetically distantly related Archaea, T. acidophilum HO-62 and Sulfolobus sp. strain 7, was further investigated by x-ray absorption spectroscopy. The zinc K-edge x-ray absorption spectra of both archaeal ferredoxins are strikingly similar, demonstrating that the same zinc site is found in T. acidophilum ferredoxin as in Sulfolobus sp. ferredoxin, which suggests the structural conservation of isolated zinc binding sites among archaeal zinc-containing ferredoxins. The sequence and spectroscopic data provide the common structural features of the archaeal zinc-containing ferredoxin family.

Amino Acid Sequence↗
PubMed1999

A Combined X-Ray Photoelectron and Auger Electron Spectroscopic Study of Cesium in Variable-Charge Montmorillonites.

A combined X-ray photoelectron and Auger electron spectroscopic investigation of sorption and characterization of bonding states of Cs in montmorillonite (M) and in four reduced-charge montmorillonites (RCMs) were carried out. The nondestructive analysis of sorption of Cs in variable-charge montmorillonites obtained by XPS is consistent within 4-8% to those obtained by solution analysis using AAS. The core-level Cs 3d5/2 photoelectron binding energy was observed to be enhanced with the reduction of electron population from higher to lower charge montmorillonite. The charge potential model has been used to interpret such core-level short-range chemical shifts. However, a larger shift in the Auger Cs-M4N4,5N4,5 line was observed and Cs-Auger kinetic energy was found to decrease from higher charge RCM to lower charge RCM, which may be attributed to the effect of extra-atomic relaxation from surrounding oxygen atoms; this effect implies that the flow of electronic charge to the Cs ion is larger for higher charge RCM than for lower charge RCM. However, this effect is enhanced by the extra contribution of Li that has migrated. A comparison of Cs 3d binding energies and Cs-Auger kinetic energies in a two-dimensional chemical state plot indicates multiple bonding states of Cs in variable-charge montmorillonites. The extra-atomic relaxation energy (DeltaEr) value of each of the Cs-montmorillonites was unique, which indicates that this is dependent on the chemical environment and on the availability of electron density in montmorillonites. Also, the binding energy value of Cs 3d5/2 was found to be nearer to CsOH than to CsCl, which reflects that the bonding state of Cs is not as ionic as CsCl. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Characterization of mouse nNOS2, a natural variant of neuronal nitric-oxide synthase produced in the central nervous system by selective alternative splicing.

Mouse neuronal nitric-oxide synthase 2 (nNOS2) is a unique natural variant of constitutive neuronal nitric-oxide synthase (nNOS) specifically expressed in the central nervous system having a 105-amino acid deletion in the heme-binding domain as a result of in-frame mutation by specific alternative splicing. The mouse nNOS2 cDNA gene was heterologously expressed in Escherichia coli, and the resultant product was characterized spectroscopically in detail. Purified recombinant nNOS2 contained heme but showed no L-arginine- and NADPH-dependent citrulline-forming activity in the presence of Ca2+-promoted calmodulin, elicited a sharp electron paramagnetic resonance (EPR) signal at g = 6.0 indicating the presence of a high spin ferriheme as isolated and showed a peak at around 420 nm in the CO difference spectrum, instead of a 443-nm peak detected with the recombinant wild-type nNOS1 enzyme. Thus, although the heme domain of nNOS2 is capable of binding heme, the heme coordination geometry is highly abnormal in that it probably has a proximal non-cysteine thiolate ligand both in the ferric and ferrous states. Moreover, negligible spectral perturbation of the nNOS2 ferriheme was detected upon addition of either L-arginine or imidazole. These provide a possible rational explanation for the inability of nNOS2 to catalyze the cytochrome P450-type monooxygenase reaction.

Alternative Splicing↗
PubMed1999

Inhibition of tumor invasion and metastasis by a novel lysophosphatidic acid (cyclic LPA).

Fetal calf serum (FCS) and 1-oleoyl lysophosphatidic acid (LPA) were previously found to be potent inducers of invasion (transcellular migration) in an in vitro system. A novel LPA, composed of cyclic phosphate and cyclopropane-containing hexadecanoic acid (PHYLPA), first isolated from myxoamoebae of Physarum polycephalum, and its synthetic derivatives (cLPA) were tested for their ability to inhibit tumor cell invasion and metastasis. Amoung these, Pal-cLPA, which has a palmitoyl moiety, was most potent in inhibiting invasion, with 93.8% inhibition at the concentration of 25 microM. Invasion in vitro by mouse melanoma cells (B16), human pancreatic adenocarcinoma cells (PSN-1), human lung cancer cells (OC-10) and human fibrosarcoma cells (HT-1080) was also inhibited by Pal-cLPA. The stimulation of MMI cells with LPA triggered F-actin formation, which was impaired by the addition of Pal-cLPA at invasion-inhibitory concentration. Pal-cLPA induced a rapid increase in adenosine 3',5'-cyclic monophosphate (cAMP) concentration in MMI cells. The addition of dibutyryl cAMP significantly abrogated LPA-induced invasion by MM1 cells and actin polymerization in the cells. The inhibition of MM1 cell invasion by Pal-cLPA may be ascribed to an increased level of cAMP. Pal-cLPA also suppressed invasion in vitro by MM1 cells induced by FCS dose dependently, without affecting proliferation. It also suppressed the pulmonary metastasis of B16 mouse melanoma cells injected into the tail vein of C57BL/6 mice. Thus, Pal-cLPA is effective in inhibiting invasion and metastasis of a variety of tumor cells.

Actins↗
PubMed1999

Evidence for the involvement of a Src-related tyrosine kinase in Xenopus egg activation.

Recently, we have purified a Src-related tyrosine kinase, named Xenopus tyrosine kinase (Xyk), from oocytes of Xenopus laevis and found that the enzyme is activated within 1 min following fertilization [Sato et al. (1996) J. Biol. Chem. 271, 13250-13257]. A concomitant translocation of a part of the activated enzyme from the membrane fraction to the cytosolic fraction was also observed. In the present study, we show that parthenogenetic egg activation by a synthetic RGDS peptide [Y. Iwao and T. Fujimura, T. (1996) Dev. Biol. 177, 558-567], an integrin-interacting peptide, but not by electrical shock or the calcium ionophore A23187 causes the kinase activation, tyrosine phosphorylation, and translocation of Xyk. A synthetic tyrosine kinase-specific inhibitor peptide was employed to analyze the importance of the Xyk activity in egg activation. We found that the peptide inhibits the kinase activity of purified Xyk at IC50 of 8 microM. Further, egg activation induced by sperm or RGDS peptide but not by A23187 was inhibited by microinjection of the peptide. In the peptide-microinjected eggs, penetration of the sperm nucleus into the egg cytoplasm and meiotic resumption in the egg were blocked. Indirect immunofluorescence study demonstrates that Xyk is exclusively localized to the cortex of Xenopus eggs, indicating that Xyk can function in close proximity to the sperm-egg or RGDS peptide-egg interaction site. Taken together, these data suggest that the tyrosine kinase Xyk plays an important role in the early events of Xenopus egg activation in a manner independent or upstream of calcium signaling.

Animals↗
PubMed1999

ZIP kinase identified as a novel myosin regulatory light chain kinase in HeLa cells.

A novel myosin light chain kinase (MLCK) cDNA was isolated from a HeLa cell cDNA library. The deduced amino acid sequence was identical to that of a zipper-interacting protein kinase (ZIPK) which mediates apoptosis [Kawai et al. (1998) Mol. Cell. Biol. 18, 1642-1651]. Here we found that HeLa ZIPK phosphorylated the regulatory light chain of myosin II (MRLC) at both serine 19 and threonine 18 in a Ca2+/calmodulin independent manner. Phosphorylation of myosin II by HeLa ZIPK resulted in activation of actin-activated MgATPase activity of myosin II. HeLa ZIPK is the first non-muscle MLCK that phosphorylates MRLC at two sites.

Amino Acid Sequence↗
PubMed1999

A 58-kDa Shc protein is present in Xenopus eggs and is phosphorylated on tyrosine residues upon egg activation.

A 58-kDa protein was detected in Xenopus egg lysate by SDS-PAGE and immunoblotting with an antibody raised against adaptor protein Shc, a well known tyrosine kinase substrate in numerous biological events. Tyrosine phosphorylation of the Xenopus Shc protein (p58 xShc) was found to increase 2.3 +/- 0.4-fold (n = 3) upon fertilization. Pretreatment of eggs with the tyrosine kinase inhibitor genistein effectively blocked the fertilization-dependent phosphorylation. Tyrosine phosphorylation of p58 xShc was also observed when eggs were activated parthenogenetically by an integrin-interacting RGDS-peptide which is known to cause egg activation accompanied by intracellular calcium release. On the other hand, other egg-activating treatments such as electrical shock and calcium ionophore, which directly induce the elevation of intracellular calcium, did not show such an effect. It is also suggested that the phosphorylated p58 xShc may play a role unique to the egg activation process because we found that there was no increase of Shc-Grb2 complex after fertilization. These results demonstrate that p58 xShc is a substrate of egg tyrosine kinases which may be activated by sperm-egg interaction and suggest that the phosphorylated p58 xShc may act upstream of the calcium-dependent pathway of egg activation.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Dedifferentiation of adenocarcinomas by activation of phosphatidylinositol 3-kinase.

Signet ring cell carcinoma is a malignant type of poorly differentiated adenocarcinomas in stomach, which is characterized by the occasional presence of signet ring-like cancer cells. We found that expression of constitutively active phosphatidylinositol 3-kinase (PI 3-kinase) in well differentiated adenocarcinoma cell lines induced the loss of cell-cell contact and some of the cells changed their shapes to signet ring cell-like, characterized by appearance of mucus droplets in the cytoplasm with well developed endplasmic reticulum and Golgi complexes. The active PI 3-kinase-expressing cells formed poorly differentiated tumors in nude mice, which were clearly different from those of the original cell lines. The PI 3-kinase activities detected in anti-phosphotyrosine immunoprecipitates were higher in several signet ring cell carcinoma-derived cell lines than in other adenocarcinoma cell lines. In addition, PI 3-kinase was found to be associated with a 200-kDa protein phosphorylated in tyrosine in 4 of 6 signet ring cells but not in other cell lines, suggesting that PI 3-kinase is possibly activated in these cells by binding to the 200-kDa protein. The 200-kDa protein-PI 3-kinase complex was exclusively fractionated in the membrane fractions. The specific activity of the PI 3-kinase immunoprecipitated with anti-phosphotyrosine antibody was approximately 3-fold higher than that with anti-PI 3-kinase antibody. These results suggest that PI 3-kinase in signet ring cell carcinoma is recruited to the membrane and activated by the binding to the 200-kDa protein.

Adenocarcinoma↗