Biomedical subjects

T Yamazaki

Publications and source records attributed to T Yamazaki.

At least 217 records · Page 12Linked to original sources

PubMed1999

Both Gs and Gi proteins are critically involved in isoproterenol-induced cardiomyocyte hypertrophy.

Activation of beta-adrenoreceptors induces cardiomyocyte hypertrophy. In the present study, we examined isoproterenol-evoked intracellular signal transduction pathways leading to activation of extracellular signal-regulated kinases (ERKs) and cardiomyocyte hypertrophy. Inhibitors for cAMP and protein kinase A (PKA) abolished isoproterenol-evoked ERK activation, suggesting that Gs protein is involved in the activation. Inhibition of Gi protein by pertussis toxin, however, also suppressed isoproterenol-induced ERK activation. Overexpression of the Gbetagamma subunit binding domain of the beta-adrenoreceptor kinase 1 and of COOH-terminal Src kinase, which inhibit functions of Gbetagamma and the Src family tyrosine kinases, respectively, also inhibited isoproterenol-induced ERK activation. Overexpression of dominant-negative mutants of Ras and Raf-1 kinase and of the beta-adrenoreceptor mutant that lacks phosphorylation sites by PKA abolished isoproterenol-stimulated ERK activation. The isoproterenol-induced increase in protein synthesis was also suppressed by inhibitors for PKA, Gi, tyrosine kinases, or Ras. These results suggest that isoproterenol induces ERK activation and cardiomyocyte hypertrophy through two different G proteins, Gs and Gi. cAMP-dependent PKA activation through Gs may phosphorylate the beta-adrenoreceptor, leading to coupling of the receptor from Gs to Gi. Activation of Gi activates ERKs through Gbetagamma, Src family tyrosine kinases, Ras, and Raf-1 kinase.

Animals↗

PubMed1999

Context-dependent transcriptional cooperation mediated by cardiac transcription factors Csx/Nkx-2.5 and GATA-4.

Although the cardiac homeobox gene Csx/Nkx-2.5 is essential for normal heart development, little is known about its regulatory mechanisms. In a search for the downstream target genes of Csx/Nkx-2. 5, we found that the atrial natriuretic peptide (ANP) gene promoter was strongly transactivated by Csx/Nkx-2.5. Deletion and mutational analyses of the ANP promoter revealed that the Csx/Nkx-2.5-binding element (NKE2) located at -240 was required for high level transactivation by Csx/Nkx-2.5. We also found that Csx/Nkx-2.5 and GATA-4 displayed synergistic transcriptional activation of the ANP promoter, and in contrast to previous reports (Durocher, D., Charron, F., Warren, R., Schwartz, R. J., and Nemer, M. (1997) EMBO J. 16, 5687-5696; Lee, Y., Shioi, T., Kasahara, H., Jobe, S. M., Wiese, R. J., Markham, B., and Izumo, S (1998) Mol. Cell. Biol. 18, 3120-3129), this synergism was dependent on binding of Csx/Nkx-2.5 to NKE2, but not on GATA-4-DNA interactions. Although GATA-4 also potentiated the Csx/Nkx-2.5-induced transactivation of the artificial promoter that contains multimerized Csx/Nkx-2.5-binding sites, Csx/Nkx-2.5 reduced the GATA-4-induced transactivation of the GATA-4-dependent promoters. These findings indicate that the cooperative transcriptional regulation mediated by Csx/Nkx-2.5 and GATA-4 is promoter context-dependent and suggest that the complex cis-trans interactions may fine-tune gene expression in cardiac myocytes.

Animals↗

PubMed1999

Rho family small G proteins play critical roles in mechanical stress-induced hypertrophic responses in cardiac myocytes.

-Mechanical stress induces a variety of hypertrophic responses, such as activation of protein kinases, reprogramming of gene expression, and an increase in protein synthesis. In the present study, to elucidate how mechanical stress induces such events, we examined the role of Rho family small GTP-binding proteins (G proteins) in mechanical stress-induced cardiac hypertrophy. Treatment of neonatal rat cardiomyocytes with the C3 exoenzyme, which abrogates Rho functions, suppressed stretch-induced activation of extracellular signal-regulated protein kinases (ERKs). Overexpression of the Rho GDP dissociation inhibitor (Rho-GDI), dominant-negative mutants of RhoA (DNRhoA), or DNRac1 significantly inhibited stretch-induced activation of transfected ERK2. Overexpression of constitutively active mutants of RhoA slightly activated ERK2 in cardiac myocytes. Overexpression of C-terminal Src kinase, which inhibits functions of the Src family of tyrosine kinases, or overexpression of DNRas had no effect on stretch-induced activation of transfected ERK2. The promoter activity of skeletal alpha-actin and c-fos genes was increased by stretch, and these increases were completely inhibited by either cotransfection of Rho-GDI or pretreatment with C3 exoenzyme. Mechanical stretch increased phenylalanine incorporation into cardiac myocytes by approximately 1.5-fold compared with control, and this increase was also significantly suppressed by pretreatment with C3 exoenzyme. Overexpression of Rho-GDI or DNRhoA did not affect angiotensin II-induced activation of ERK. ERKs were activated by culture media conditioned by stretch of cardiomyocytes without any treatment, but not of cardiomyocytes with pretreatment by C3 exoenzyme. These results suggest that the Rho family of small G proteins plays critical roles in mechanical stress-induced hypertrophic responses.

Angiotensin II↗

PubMed1999

Liver fatty acid-binding protein is a new prognostic factor for hepatic resection of colorectal cancer metastases.

BACKGROUND AND OBJECTIVES: Liver fatty acid-binding protein (L-FABP) is reported as a biological marker for enterocytic differentiation. We evaluated the prognostic value of L-FABP expression for patients undergoing hepatic resection of colorectal cancer metastases. METHODS: The study group comprised 68 patients who underwent hepatic resection for colorectal cancer metastases between 1982 and 1996 at Niigata University Medical Hospital, Niigata, Japan. L-FABP expression was immunohistochemically studied in metastatic liver tumors and their primary colorectal cancers. The relationship between L-FABP expression and patient prognoses was statistically analyzed. RESULTS: L-FABP was positively stained in 56% (38/68) of liver metastases from colorectal cancers and in 56% (38/68) of their primary tumors. Of 68 cases, 54 (79%) showed similar immunohistochemical findings between primary and metastatic tumors. Patients with L-FABP-positive liver metastases showed better prognosis than patients with L-FABP-negative metastases (P = 0.046). L-FABP expression in primary colorectal cancers more significantly (P = 0.009) affected long-term survival after hepatic surgery. Multivariate analysis revealed that the prognostic effect of L-FABP expression in primary colorectal cancers was exerted independently and that its impact was larger than conventional pathological prognosticators. CONCLUSIONS: L-FABP expression is suitable for use as a new presurgical prognostic factor for patients undergoing hepatic surgery for colorectal cancer metastases.

Adult↗

PubMed1999

Sigmoid colon cancer presenting as complete rectal prolapse: report of a case.

We describe herein the unusual case of a 76-year-old woman who was diagnosed as having sigmoid colon cancer after presenting with complete rectal prolapse. The rectal prolapse was considered to have been caused by constipation accelerated by the colon cancer. The relationship between colorectal cancer and rectal prolapse has not yet been clarified; however, this case report suggests that rectal prolapse can present as a symptom of colorectal cancer. Thus, patients with a sudden onset of rectal prolapse should be screened for colorectal cancer.

Aged↗

PubMed1999

Effect of Tween-80 on cell killing by etoposide in human lung adenocarcinoma cells.

PURPOSE: The non-ionic detergent Tween-80, a surface-active agent, has been shown to modulate the cytocidal effect of certain antitumor agents. In the present study, we sought to determine whether or not Tween-80 could enhance the antitumor effect of etoposide (VP16) in human lung cancer cells in vitro. METHODS: Survival fractions were measured by growth inhibiton assays of PC14, H69, KB, and PC14/CDDP (the corresponding cisplatin-resistant subline of PC14) cells. An in vitro clonogenic assay of PC14 and PC14/CDDP cells was undertaken after incubation for 10-12 days in RPMI-1640 medium with 20% fetal calf serum and 1.72% methyl cellulose, plus continuous exposure to VP16 with Tween-80. We also investigated the direct toxicity of Tween-80 to PC14 and PC14/CDDP cells using a clonal assay. The intracellular accumulation of VP16 was further analyzed using [3H]VP16 in PC14, PC14/CDDP, A549, KB and H69 cells, and compared with that of daunorubicin (DNR), a hydrophilic anti-cancer agent, using [3H]DNR in PC14, A549 and KB cells. RESULTS: It was found that PC14/CDDP had collateral sensitivity to VP16 and Tween-80 markedly enhanced the killing effect of VP16 not only of PC14 cells but also of PC14/CDDP cells while exerting little cytotoxic effect. Moreover, Tween-80 increased the intracellular accumulation of VP16 in PC14, PC14/CDDP and A549 cells, and not in KB and H69 cells. Tween-80 did not increase the intracellular DNR levels in PC14, A549 and KB cells. CONCLUSIONS: Tween-80 was shown to potentiate the cytotoxicity of VP16 against several human lung adenocarcinoma cells by increasing the accumulation of VP16 in vitro. Tween-80-mediated sensitization of lung adenocarcinoma cells to VP16 is considered to be related to both the characteristics of the cell membrane in adenocarcinoma cells and the lipotropic properties of VP16. These results suggest that this combination might have the potential to improve the therapeutic index of VP16 in human lung adenocarcinoma.

Adenocarcinoma↗

PubMed1999

Colocutaneous fistula after percutaneous endoscopic gastrostomy in a remnant stomach.

An 82-year-old woman underwent percutaneous endoscopic gastrostomy (PEG) 5 years after partial gastrectomy for cancer. Four months after PEG insertion, a colocutaneous fistula was noted at exchange of the PEG tube. Colocutaneous fistula is a rare and major complication of PEG with 10 reported cases to date. In eight of the 11 reported cases, including this case, fistulas appeared late (>6 weeks) after PEG insertion. This complication may heal after removal of the PEG alone, if the fistula has formed completely; otherwise a surgical approach is necessary for the treatment. Since five of the 11 reported patients had previously undergone abdominal surgery, prior abdominal surgery may increase the risk of a colonic injury after PEG. Open surgical gastrostomy is a wiser option when performing gastrostomy in patients with prior abdominal surgery.

Aged↗

PubMed1999

Local coagulofibrinolysis in the postsurgical recovery of patients with chronic subdural haematoma.

Postoperative recovery of patients with chronic subdural haematoma (CSH) was investigated by comparing pre- and postoperative coagulant and fibrinolytic activity in the haematoma contents of 15 patients with SCH. Patients in this study were treated draining the haematoma cavity without irrigation, a procedure dubbed the closed drainage. Haematomas were collected during, and 24 hrs after, surgery. Postoperative fibrinolytic activity was lower than that observed pre-operatively. In particular, levels of tissue plasminogen activator activity (TPA), and fibrin and fibrinogen degradation products (FDP) all decreased. In contrast, coagulant activity increased postoperatively. This paper will discuss the role of local coagulofibrinolysis in the postoperative recovery of CSH patients.

Aged↗

PubMed1999

Stable expression in Chinese hamster ovary cells of mutated tau genes causing frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17).

Extensive neuronal loss and aggregation of tau as cytoplasmic inclusions in neurons and glial cells in selected cortical and subcortical regions is the most striking characteristic of frontotemporal dementia and parkinsonism linked to chromosome 17, which is caused by exonic or intronic mutations in the tau gene. Here, we examined the effects of four exonic mutations in four-repeat tau using stably transfected Chinese hamster ovary cells. The proportion of polymerized tubulin was the largest in the P301L transfectant. G272V and P301L transfectants showed greater instability of microtubules in the presence of Colcemid than wild-type tau, V337M, or R406W transfectants. Thus no distinct phenotypes were shared by the mutant tau transfectants with regard to microtubule assembly and stability. Unexpectedly, R406W showed low and negligible levels of phosphorylation at Thr 231 and Ser 396, respectively, in the transfectant. This presents a sharp contrast to the observation that tau aggregates in R406W-affected brains are heavily phosphorylated at these two sites. This result suggests that hyperphosphorylation at these sites cannot occur in the tau R406W bound to microtubules, and thus that the hyperphosphorylated species of tau may be generated only after disruption of microtubules.

Animals↗

PubMed1999

Protective effects of ONO-5046*Na, a specific neutrophil elastase inhibitor, on postperfusion lung injury.

BACKGROUND: Polymorphonuclear neutrophil elastase might contribute to postperfusion lung injury, so we evaluated the protective effect of ONO-5046*Na, a specific inhibitor of polymorphonuclear neutrophil elastase, against such an injury. METHODS: The study was done using 8 mongrel dogs that received ONO-5046*Na (15 mg/kg per hour) (group O) and 8 control dogs (group C), all of which had 1 hour of partial bypass and 5 hours of observation. RESULTS: The respiratory index showed no significant changes in group O, but increased significant in group C (1.4+/-2.0 versus 5.1+/-4.7, p = 0.0047). Pulmonary extravascular water volume increased markedly in group C but only slightly in group O (group C 20.6+/-8.7, group O 11.2+/- 2.7 mL/kg; p = 0.0005). Blood concentrations of polymorphonuclear neutrophil elastase and interleukin-6 showed more than a tenfold increase in group C (PMN elastase, group C 12.9+/-12.8, group O 2.4+/-1.3 ng/mL; IL-b, group C 11.0+/-9.3, group O 2.9+/-3.8 pg/mL; p < 0.05) but were only slightly higher in group O. Histologic examination revealed interstitial and intraalveolar edema in group C, but group O was virtually normal. CONCLUSIONS: ONO-5046*Na inhibits polymorphonuclear neutrophil elastase and maintains better pulmonary function, so it should reduce postperfusion lung injury.

Animals↗

PubMed1999

Effects of long-term supplementation of eicosapentanoic and docosahexanoic acid on the 2-, 3-series prostacyclin production by endothelial cells.

We studied the effects of polyunsaturated fatty, acids such as arachidonic acid [20:4 (n-6)], eicosapentanoic acid [EPA, 20:5 (n-3)], and docosahexanoic acid [DHA, 22:6 (n-3)] on the changes of lipid profiles and prostacyclin production by cultured bovine aortic endothelial cells. The amounts of 6-keto-prostaglandin F1alpha(6-keto-PGF1alpha) and delta17-6-keto-PGF1alpha, non-enzymatic metabolites of prostacyclin (PGI2 and PGI3) in culture medium were measured by gas chromatography/selected ion monitoring. Endothelial cells were supplemented for five passages with arachidonic acid, EPA, or DHA, and the fatty acids of cell lipids and prostacyclin production in cultured medium were quantified. From the fatty acid analysis, the amounts of docosapentaenoic acid [22:5 (n-3)] were significantly increased in EPA-grown cells. In DHA-grown cells, the amounts of EPA were slightly increased compared to control cells. These cells produced similar amounts of PGI2 as the controls, but larger amounts of PGI3 under basal conditions. These findings suggest that EPA, docosapentaenoic acid, and DHA are interconverted to each other, and anti-aggregatory effects of EPA or DHA may be partially due to the stimulation of prostacyclin formation in endothelial cells.

Animals↗

PubMed1999

Urinary thromboxane A2/prostacyclin balance reflects the pathological state of a diabetic.

Levels of the stable urinary metabolites of thromboxane A2 and prostacyclin, 11-dehydro-thromboxane B2 (11-dehydro-TXB2) and 2,3-dinor-6-keto-prostaglandin F1alpha (2,3-dinor-6-keto-PGF1alpha) were measured in diabetics to elucidate the relation between the thromboxane A2/prostacyclin (TX/PGI) balance and pathological states of diabetes mellitus. 11-Dehydro-TXB2 and 2,3-dinor-6-keto-PGF1alpha were derivatized to methyl ester-propylamide-dimethylisopropylsilyl ether and methyl ester-methoxime-dimethylisopropylsilyl ether derivatives, respectively, and applied to a gas chromatography/selected ion monitoring. The TX/PGI ratios of diabetics were higher than those of healthy volunteers, suggesting the hypercoagulative states of this disease. The ratios showed positive correlations with the levels of blood glucose. The levels of hemoglobin A1c and triglyceride were correlated weakly with the ratio. Some of the patients who had relatively low levels of blood glucose also showed high TX/PGI ratios. Furthermore, the ratio increased in the order of the groups 1, 2, and 3; group 1 contained patients who did not take medicine for diabetes, group 2 contained those who took oral hypoglycemic agents, and group 3 contained those who received insulin therapy. These observations indicate that the TX/PGI ratio reflects the pathological conditions of diabetes and is a useful marker, having few different features from other markers that are presently used.

6-Ketoprostaglandin F1 alpha↗

PubMed1999

Monitoring of the thromboxane A2/prostacyclin ratio in the urine of patients with retinal vascular occlusion through the low-dose-aspirin therapy using the gas chromatography/selected ion monitoring method.

We determined the levels of the stable urinary metabolites of thromboxane A2 and prostacyclin, 11-dehydro-thromboxane B2 (11-dehydro-TXB2) and 2,3-dinor-6-keto-prostaglandin F1alpha (2,3-dinor-6-keto-PGF1alpha) in patients with retinal vascular occlusion (RVO) to elucidate the change of the thromboxane A2/prostacyclin (TX/PGI) ratio with this disease and the effect of low-dose-aspirin therapy. 11-Dehydro-TXB2 and 2,3-dinor-6-keto-PGF1alpha were converted to 1-methyl ester-propylamide-9,12,15-tris-dimethylisopropylsilyl ether derivative and 1-methyl ester-6-methoxime-9,12,15-tris-dimethylisopropylsilyl ether derivative, respectively, and applied to a gas chromatography/selected ion monitoring. The average level of 11-dehydro-TXB2 in 30 patients with RVO was 1038 +/- 958 pg/mg creatinine. It was significantly higher than that of 27 healthy volunteers, which was 616 +/- 294 pg/mg creatinine (p < 0.05 with unpaired t-test). However, 2,3-dinor-6-keto-PGF1alpha levels were not significantly different between these two groups. The average ratio of TX/PGI in the RVO patients was 32 +/- 26 and it was significantly higher than that of healthy volunteers, 17 +/- 10 (p < 0.01). Patients with central retinal artery occlusion or branch retinal artery occlusion showed greatly high 11-dehydro-TXB2 levels and TX/PGI ratios, although the number of patients was limited in the current study. After the administration of low-dose aspirin (40 mg/day) for about 1 month, the TX/PGI ratio decreased to around the normal level. Following the levels for up to 10 months, they also remained at the normal level. These observations suggested that the 11-dehydro-TXB2 levels and the TX/PGI ratio reflect the pathological conditions of RVO and are useful markers of the treatment.

6-Ketoprostaglandin F1 alpha↗

PubMed1999

Acute myeloid leukemia with hypergranular cytoplasm accompanied by t(X;11)(q24;q23) and rearrangement of the MLL gene.

This report describes a unique case of acute myeloid leukemia with hypergranular cytoplasm and t(X;11)(q24;q23). The breakpoint on 11q23 was identified within the MLL gene. The hypergranular cytoplasm of leukemic cells and the associated coagulopathy resembled a characteristic of acute promyelocytic leukemia, despite the absence of RARalpha gene rearrangement in this case. The Xq24 site possibly played a role in this atypical blast phenotype.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1999

Effects of ouabain on in situ cardiac sympathetic nerve endings.

Using dialysis technique, the effects of ouabain on in situ cardiac sympathetic nerve endings were examined in anesthetized cats. Dialysis probes were implanted in the left ventricular myocardium, and the concentration of dialysate norepinephrine (NE) was used as an indicator of NE output at the cardiac sympathetic nerve ending. Locally applied ouabain dose-dependently (1, 10, 100 microM) increased dialysate NE levels. This finding suggested that ouabain causes an increase in NE efflux without any requirement for prior mobilization of NE from vesicular stores. Transection of sympathetic nerves innervating the heart, was without effect on the ouabain (100 microM)-induced increase in NE efflux. Pretreatment with a Ca2+-channel blocker, omega-conotoxin GVIA (10 microg/kg i.v.) suppressed the ouabain-induced NE efflux. These data suggested that ouabain opened N-type calcium channels coupled to NE release without centrally mediated neural transmission. Furthermore, ouabain-induced NE efflux was suppressed by pretreatment with desipramine (neuronal NE uptake inhibitor, 100 microM). Our data suggest that the two mechanisms (exocytosis and carrier-mediated outward transport), to the same extent, contributed to the amount of NE efflux evoked by ouabain in in situ cardiac sympathetic nerve endings.

Animals↗

PubMed1999

The origin of hypsarrhythmia and tonic spasms in West syndrome: evidence from a case of porencephaly and hydrocephalus with focal hypsarrhythmia.

We report on a 3-year-old girl with West syndrome and with focal hypsarrhythmia. The left hemisphere of the patient was virtually completely defective and continuous hypsarrhythmia was only seen in the residual right frontal cortex, where an interictal single photon emission computed tomography (SPECT) showed hyperperfusion. Despite a focal epileptic pattern, the tonic spasms were quite symmetrical. In our patient, spasms might not require the sensorimotor cortex, but the brainstem containing the descending pathways that control spinal reflexes and other infratentorial structures seem to be essential for the occurrence of spasms. This is in accordance with the result of an ictal SPECT that showed hyperperfusion of the brainstem and cerebellum. These findings suggest that hypsarrhythmia originates from cortical lesions, while subcortical structures may be primarily responsible for the tonic spasms in this patient.

Brain↗

PubMed1999

Morphological onset and early diagnosis in apical hypertrophic cardiomyopathy: a long term analysis with nuclear magnetic resonance imaging.

OBJECTIVES: A long-term follow-up study with nuclear magnetic resonance (NMR) imaging was undertaken to detect the morphological onset and to establish the early diagnosis in apical hypertrophic cardiomyopathy (HCM). BACKGROUND: A spadelike configuration on left ventriculogram (LVG) is regarded as a diagnostic criterion for the classical apical HCM. There also exists a segmented hypertrophy at the apical level without indicating the spadelike features (a nonspade configuration). To detect the hypertrophied myocardium of the nonspade configuration, circumferential scrutiny of the apex is required. Although both configurations can be underlying causes of giant negative T waves, etiological relationship between the two is not clarified. METHODS: The criteria for the spadelike configuration defined on left ventricular short-axis NMR images were as follows: (apical maximal thickness > or = 15 mm), (apical anterior thickness over basal anterior thickness > or = 1.3) and (apical posterior thickness over basal posterior thickness > or =1.3). Thirteen patients who had predominant hypertrophy (> or = 15 mm) at the apical level without the spadelike configuration underwent NMR imaging twice before and after 54+/-10 months' follow-up. RESULTS: Apical hypertrophy that had been confined to the lateral wall in four, the anterior-lateral wall in two, and the septal-anterior wall in one developed to become circumferential hypertrophy that fulfilled the criteria for the spadelike configuration after the follow-up period. CONCLUSIONS: The spadelike configuration can begin with the nonspade configuration and therefore, both can constitute a single disease entity of apical HCM. The early diagnosis of apical HCM can be achieved by identifying the hypertrophy frequently confined to the lateral wall at the apical level.

Adult↗

PubMed1999

Improved segmental isotope labeling of proteins and application to a larger protein.

A new isotope labeling technique for peptide segments in a protein sample was recently established using the protein splicing element intein [Yamazaki et al. (1998) J. Am. Chem. Soc., 120, 5591-5592]. This method makes it possible to observe signals of a selected amino (N-) or carboxyl (C-) terminal region along a peptide chain. However, there is a problem with the yield of the segmentally labeled protein. In this paper, we report an increase in the yield of the protein that enables the production of sufficient amounts of segmentally 13C/15N-labeled protein samples. This was achieved by improvement of the expression level of the N-terminal fragment in cells and the efficiency of refolding into the active splicing conformation. The N-terminal fragment was expressed as a fused protein with the cellulose binding domain at its N-terminus, which was expressed as an insoluble peptide in cells and the expression level was increased. Incubation with 2.5 M urea and 50% glycerol increased the efficiency of the refolding greatly, thereby raising the final yields of the ligated proteins. The feasibility of application of the method to a high-molecular-weight protein was demonstrated by the results for a maltose binding protein consisting of 370 amino acids. All four examined joints in the maltose binding protein were successfully ligated to produce segmentally labeled protein samples.

ATP-Binding Cassette Transporters↗