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Biomedical subjects

A Nakano

Publications and source records attributed to A Nakano.

At least 73 records · Page 4Linked to original sources
PubMed2000

Evidence for recycling of cytochrome P450 sterol 14-demethylase from the cis-Golgi compartment to the endoplasmic reticulum (ER) upon saturation of the ER-retention mechanism.

Cytochrome P450 sterol 14-demethylase (P450-CYP51) is the enzyme that catalyzes 14alpha demethylation of lanosterol, a step in ergosterol biosynthesis, on the cytoplasmic side of the endoplasmic reticulum (ER) in Saccharomyces cerevisiae. To investigate its localization and the localization mechanism(s), we constructed a chimera by inserting a 30-residue segment, Leu(283)-Leu(312) of P450-CYP51 containing a potential N-glycosylation site in the cytoplasmic region, into the N-terminus of the same protein and tagging the C-terminus with three repeats of a hemagglutinin epitope. This chimera complements gene disruption on a single-copy vector and undergoes N-glycosylation, showing that it functions normally in vivo. Indirect immunofluorescence microscopy revealed that this chimera is localized exclusively to the ER when it is expressed on either a single-copy or multicopy vector. We carried out pulse-chase experiments and found that this chimera, when expressed on a multicopy plasmid, gradually undergoes alpha1-->6 glycosylation, a cis-Golgi-specific modification, but not alpha1-->;3 glycosylation, a medial Golgi-specific modification. In contrast, a single-copy expression of this chimera does not lead to the cis-Golgi-specific modification. These findings suggest that, when expressed on a multicopy plasmid, a fraction of this chimera is transported from the ER to the cis-Golgi compartment and subsequently recycled to the ER, but when expressed on a single-copy plasmid, no significant transport of this protein from the ER takes place. We thus suggest the possibility that cytochrome P450 is retained in the ER by a saturable static mechanism.

Aspartic Acid Endopeptidases↗
PubMed2000

Role of p38 mitogen-activated protein kinase in neointimal hyperplasia after vascular injury.

p38 mitogen-activated protein kinase (MAPK) is involved in intracellular signals that regulate a variety of cellular responses during inflammation. However, the role of p38 MAPK in atherosclerosis, a chronic inflammatory disorder, remains uncertain. The aim of the present study was to examine the role of p38 MAPK in the development of neointimal hyperplasia in balloon-injured rat carotid arteries. Immunohistochemical studies indicated that p38 MAPK was rapidly activated in the majority of medial cells in injured arterial walls. Rats treated with FR167653, a selective inhibitor of p38 MAPK, at a dosage of 10 mg x kg(-1) x d(-1), had a 29.4% lower intima-to-media ratio than the untreated controls at 14 days after balloon injury (P:<0.05). The percentage of proliferating nuclear antigen-positive cells in the media at 48 hours was significantly lower in the FR167653-treated group than in the control group. Quantitative competitive reverse transcription-polymerase chain reaction analysis revealed that interleukin-1beta mRNA expression in arteries was significantly inhibited by FR167653 (to 18.1% of control, P:<0.05) at 8 hours after balloon injury. Moreover, p38 MAPK activation and interleukin-1beta production by lipopolysaccharide-stimulated vascular smooth muscle cells were inhibited by FR167653 in a concentration-dependent manner in vitro. These results indicate that p38 MAPK is activated in vascular walls after injury and promotes neointimal formation and suggest that selective inhibition of p38 MAPK may be effective in the prevention of restenosis after percutaneous transluminal coronary angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed2000

Overexpression of PRA2, a Rab/Ypt-family small GTPase from Pea Pisum sativum, aggravates the growth defect of yeast ypt mutants.

A large number of Rab/Ypt-family small GTPases have been identified from higher plants. While some of them can complement yeast ypt mutants, the expression of Arabidopsis Ara4 protein aggravated the growth defect of a subset of ypt mutants, probably because of the titration of common regulator(s) of yeast Ypt proteins [Ueda, T. et al. (1996) Plant Cell, 8: 2079-20911. PRA2 from pea Pisum sativum encodes an interesting Rab GTPase whose expression is regulated by light [Yoshida, K. et al. (1993) Proc. Natl. Acad. Sci. USA, 90: 6636-6640]. We examined whether PRA2 complements any of the yeast ypt mutants and found again that PRA2 does not complement but rather confers the growth defect to some of the ypt mutants. No growth defect was observed when PRA2 was expressed in the wild-type yeast cells. Unlike the case of Ara4, neither Arabidopsis nor yeast GDI remedied the growth defect by Pra2, indicating that the mechanism of the exacerbation is different. Mutational analysis of PRA2 suggests that the growth inhibition can be ascribed to unidentified factor(s) which prefers the GTP-bound form of Pra2. This yeast system will be useful for identifying such putative regulatory factor(s) from yeast and plants and analyzing their interactions with Pra2.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Serum atrial natriuretic peptide concentration is a useful predictor of atrial standstill in patients with heart failure.

Two cases of atrial standstill are presented, one with cardiac amyloidosis, the other with idiopathic dilated cardiomyopathy. The plasma atrial natriuretic peptide (ANP) concentration was normal to slightly elevated in both patients, despite a marked elevation of the plasma brain natriuretic peptide (BNP) concentration. In the patient with amyloidosis (ANP: 170 pg/ml, BNP: 1220 pg/ml), a dual chamber pacemaker was successfully implanted for the treatment of sinus arrest. However, loss of atrial capture occurred 1 month later. In the patient with dilated cardiomyopathy (ANP: 47 pg/ml, BNP: 422 pg/ml), an electrophysiologic study confirmed persistent atrial standstill and failure to pace from either the right atrium or the coronary sinus. The hypothesis is that the attenuated increase in plasma ANP concentration relative to the increase in the BNP concentration may be a sensitive and useful marker to confirm atrial standstill in the setting of congestive heart failure.

Atrial Function↗
PubMed2000

Distribution of sarcophytol A in soft coral of the Sarcophyton genus.

The distribution of sarcophytol-A in the Sarcophyton genus was investigated in seven samples belonging to S. glaucum (3 samples), S. infundibulifurme (2 samples), S. crassocaule (1 sample) and S. trocheliophorum (1 sample) that were collected on Ishigaki Island in Okinawa Prefecture. Sarcophytol-A was present in one sample each of S. glaucum and S. infundibulifurme. This study indicates that the composition of cembranoids in the Sarcophyton genus is not related with the respective species, but with the individual samples collected.

Animals↗
PubMed2000

beta-blockers reduce the incidence of cardiac events in post-myocardial infarction patients.

The capacity of beta-blockers to prevent cardiac events in post-myocardial infarction (MI) patients was investigated. Among 1,483 study participants, a beta-blocker was included in the therapeutic regimens of 833 (beta-blocker group) and was omitted from the regimens of 650 (control group). The incidence of cardiac events (recurrent MI, sudden death and death by congestive heart failure) during a follow up period of 17.4 +/- 20.9 months was retrospectively compared between the two groups. Cardiac events occurred in 27 (3.2%) members of the beta-blocker group and in 44 (6.8%) controls, which represents a significant decline in the incidence of cardiac events among patients administered beta-blockers (p < 0.01, odds ratio 0.46, 95 % confidence intervals 0.28-0.75). Subgroup and multivariate analyses showed beta-blockers to be as efficacious in Japanese post-MI patients as was previously shown in Western patients. While these findings are compelling, it is clear that confirmation in a large, multicenter, placebo - controlled, randomized clinical trial, analogous to those that have been carried out in Western countries, is necessary.

Adrenergic beta-Antagonists↗
PubMed2000

Endothelium-dependent coronary response is impaired in the myocardium at an early phase of post-infarct remodeling.

The aim of the present study was to characterize endothelium-dependent and -independent coronary functions in remodeling hearts after infarction. First, echocardiography showed that the left ventricular diastolic dimension and thickness of the non-ischemic region were increased by 25% and 20%, respectively, at 2 weeks after coronary ligation in the rabbit heart. In the second series of experiments, 2 weeks after coronary ligation or a sham operation, the heart was isolated and perfused with modified Krebs-Henseleit buffer at 75 mmHg, and effluent from the pulmonary artery was measured as total coronary flow (CF). Regional CF analysis by microspheres indicated that flow to the infarcted region as a percentage of total CF is negligibly small. There was no significant difference between CF responses to sodium nitroprusside (10(-9)-10(-5) mole/l) in the sham-operated and remodeling hearts. However, the increase in CF after acetylcholine (ACh: 10(-8)-10(-5) mole/l) injection was significantly reduced by approximately 50% in the remodeling hearts compared to that in the sham-operated hearts. Furthermore, the percent increase in CF by ACh (10(-5) mole/l) was inversely correlated with weight of the remodeling myocardium (r = -0.630, p < 0.05). These results suggest that endothelium-dependent vasodilatory function is impaired in the myocardium at the early stage of post-infarct remodeling and that this endothelial dysfunction is closely related to the degree of hypertrophy of the remodeling myocardium.

Acetylcholine↗
PubMed2000

[Potential exposure to inorganic mercury in people living near a sewage sludge dumping site: urinary excretion of mercury, subjective symptoms and renal function].

OBJECTIVE: The purpose of this study was to evaluate the presence of exposure to inorganic mercury and its health effects among people living near a sewage sludge dumping site in Nagasaki Prefecture, Japan. In this area, sewage sludge and industrial waste have been dumped since 1975, and total mercury levels exceeding the water quality standards (0.0006-0.0020 mg/l) have been detected in seeping water and river water since July 1997. METHODS: The population for the present study comprised 48 subjects (aged 11-91 years) living near a sewage sludge dumping site and 49 subjects (aged 10-82 years) living in a non-polluted area. In November and December 1998, subjective symptoms of inorganic mercury exposure, history of occupational exposure to inorganic mercury, frequency of fish intake, sources of drinking water and other health habits were inquired by a self-administered questionnaire. Total mercury and total protein levels and N-acetyl-beta-D-glucosaminidase (NAG) activity in morning urine specimens were also measured. RESULTS: Among males, the proportion of subjects who complained of tremor in the hands (P = 0.02) and increased irritability (P = 0.10) was higher in the polluted area than in the control area. In addition, the proportion of those who did not report being easily fatigued was lower in the polluted area than in the control area (P = 0.07). Among females there was no significant difference in the prevalence of self-reported symptoms related to the central nervous system disturbance between the two areas. After adjustment for gender and age using logistic regression analysis, the prevalence of increased irritability was significantly higher (P = 0.05) and the proportion of those who did not report being easily fatigued was significantly lower (P = 0.03) in the polluted area than in the control area. However, there was no significant difference in the geometric mean of urinary total mercury concentration (microgram/g creatinine) between the polluted area (0.66, 95% confidence interval [CI] 0.48-0.91 for men and 0.96, 95% CI 0.70-1.33 for women) and the control area (0.81, 95% CI 0.60-1.09 for men and 0.83, 95% CI 0.57-1.22 for women). There was no individual whose total mercury concentration in urine exceeded 30 micrograms/g creatinine, at which level of urinary total mercury toxic effects on the central nervous system have been reported in industrial workers. There was also no significant difference in the geometric means of urinary total protein level and NAG activity. CONCLUSION: There was no evidence of excessive exposure to inorganic mercury among residents in the polluted area. Thus, we concluded that the difference in the prevalence of subjective symptoms was not due to the direct effect of exposure to inorganic mercury. To prevent the contamination of water by taking measures against pollution sources, monitoring of the quality of drinking water, and finally to secure safe water supply by public waterworks are required.

Adolescent↗
PubMed2000

[Treatment of renal cell carcinoma extending into the right atrium with extra-corporeal circulation using high-grade hypothermia: a case report].

A 68-year-old woman underwent surgical treatment for renal cell carcinoma associated with tumor thrombus extending into the right atrium. Although the tumor thrombus reached the level of the right atrium, there were no other apparent metastases. Combination therapy with interferon alfa plus tegafur/uracil (UFT) was attempted with the expectation of reducing the tumor thrombus, but there was no change. Successful management was achieved with right radical nephrectomy, right auriculotomy, and partial cavectomy using cardiopulmonary bypass under high-grade hypothermia. After removal of the tumor and thrombus, blood loss was 13,900 ml during the patient's recovery. She had mild heart failure for about two weeks after the operation, but recovered. She was discharged on the 40th day after the operation. Proper preparation for blood transfusion is the key point of this operation.

Aged↗
PubMed1999

Identification and characterization of human MT5-MMP, a new membrane-bound activator of progelatinase a overexpressed in brain tumors.

A cDNA encoding a new member of the membrane-type (MT) matrix metalloproteinase (MMP) family has been identified and cloned from a human brain cDNA library. The isolated cDNA encodes a polypeptide of 645 amino acids that displays a similar domain organization as other MMPs, including a predomain with the activation locus, a zinc-binding site, and a hemopexin domain. The deduced amino acid sequence contains a COOH-terminal extension, rich in hydrophobic residues and similar in size to the equivalent domains identified in MT-MMPs. Immunofluorescence and Western blot analysis of COS-7 cells transfected with the isolated cDNA revealed that the encoded protein is localized in the plasma membrane. On the basis of these features, this novel human MMP has been called MT5-MMP because it represents the fifth member of the MT-MMP subfamily of MMPs. Fluorescent in situ hybridization experiments showed that the human MT5-MMP gene (MMP-24) maps to 20q11.2, a region frequently amplified in tumors from diverse sources. Northern blot analysis demonstrated that MT5-MMP is predominantly expressed in brain, kidney, pancreas, and lung. In addition, MT5-MMP transcripts were detected at high levels compared to normal brain tissue in a series of brain tumors, including astrocytomas and glioblastomas. The catalytic domain of MT5-MMP, produced in Escherichia coli as a fusion protein with glutathione S-transferase, exhibits a potent proteolytic activity against progelatinase A, leading to the generation of the Mr 62,000 active form of this enzyme. These data suggest that MT5-MMP may contribute to the activation of progelatinase A in tumor tissues, in which it is overexpressed, thereby facilitating tumor progression.

Amino Acid Sequence↗
PubMed1999

Expression of highly polysialylated neural cell adhesion molecule in pancreatic cancer neural invasive lesion.

Neurotropism of pancreatic cancer is one of the hypotheses explaining neural invasion, which is one of the characteristics of pancreatic cancer. In these studies, we immunohistochemically examined neural cell adhesion molecules (NCAM), homophilic adhesion molecules expressed on the nerve cells, as a factor of neurotropism, in 15 pancreatic cancer operatively obtained, especially in neural invasive lesions. We also investigated the role of polysialic acid (PSA), which is attached to NCAM and related to the malignant potential of cancers. NCAM was detected in 66.7% of pancreatic cancers, and in all 9 cases with massive perineural invasion. In neural invasive lesions, however, there were perineurium and endoneurium, which do not express NCAM, between the cancer and nerve cells. PSA was also detected in the pancreatic cancers expressing NCAM. Moreover, PSA expression was stronger in the perineural invasive lesions than in the main tumor and was related to the cancer cell proliferation investigated by Ki-67 staining. It is unlikely therefore, that NCAM plays an important role in neurotropism. However, the NCAM expressed on the pancreatic cancer was attached to PSA, which itself plays an important role in the malignant potential of this disease.

Aged↗
PubMed1999

The inactive form of a yeast casein kinase I suppresses the secretory defect of the sec12 mutant. Implication of negative regulation by the Hrr25 kinase in the vesicle budding from the endoplasmic reticulum.

Sec12p is the guanine nucleotide exchange factor of Sar1 GTPase and functions at the very upstream in the vesicle budding reactions from the endoplasmic reticulum (ER). We previously identified three yeast loci, RST1, RST2, and RST3, whose mutations suppressed the temperature-sensitive growth of the sec12-4 mutant (Nakano, A. (1996) J. Biochem. (Tokyo) 120, 642-646). In the present study, we cloned the wild-type RST2 gene by complementation of the cold-sensitive phenotype of the rst2-1 mutant. RST2 turned out to be identical to HRR25, a gene encoding a dual-specificity casein kinase I in yeast. The rst2-1 mutation, which is now renamed hrr25-2, was due to the T176I amino acid replacement in the kinase domain. This mutation remedied not only the temperature-sensitive growth but also the defect of ER-to-Golgi protein transport of sec12. Immunoprecipitation of the hemagglutinin-tagged Hrr25-2 protein and a subsequent protein kinase assay showed that the kinase activity of the mutant protein was markedly reduced. The overproduction of another kinase-minus mutant of Hrr25p (Hrr25p K38A) slightly suppressed the growth defect of sec12-4 as well. These observations suggest that the reduction of the kinase activity in the mutant protein is important for the suppression of sec12. We propose that Hrr25p negatively regulates the vesicle budding from the ER.

Amino Acid Sequence↗
PubMed1999

Proteasome inhibitors induce mitochondria-independent apoptosis in human glioma cells.

The proteasome inhibitors lactacystin and AcLLNal induced p53-independent apoptosis in two human glioma cell lines, and the apoptosis was accompanied by up-regulation of immunoreactive wild-type p53, p21Waf1, Mdm2, and p27Kip1. Pretreatment with cycloheximide decreased the induction of cell death independently of p53 protein status, suggesting that the up-regulation of short-lived proteins is associated with proteasome inhibitor-induced apoptosis. Caspase-3-like proteases were activated in the proteasome inhibitor-mediated apoptosis, and the induction of cell death was inhibited more effectively in the presence of z-VAD.fmk than in the presence of Ac-DEVD.fmk, suggesting that caspases other than caspase-3 are involved. Nonetheless, there were no significant alterations in levels of immunoreactive Bcl-2, Bcl-X(L), Bax, Bad, and Bak, nor any evidence of cytochrome c release into cytosol and dissipation of delta(psi)m. Thus, the proteasome inhibitor-induced apoptosis is mediated by a mitochondria-independent mechanism, and the once activated caspase-3 does not cause the cytochrome c release and the delta(psi)m disruption.

Animals↗
PubMed1999

A trial for the quantification of regional myocardial blood flow with continuous infusion of Tc-99m MIBI and dynamic SPECT.

UNLABELLED: We propose a new method to quantify regional myocardial blood flow (rMBF) by continuous infusion of Tc-99m MIBI and dynamic SPECT. METHODS: Five patients with old myocardial infarction were studied. During continuous infusion of MIBI (approximately 740 MBq) with a syringe pump in 10 min, dynamic SPECT scan was performed every minute and lasted 20 min after the start of infusion to identify myocardial uptake of MIBI. Input function was obtained from the radioactivity in the left ventricle (LV) in dynamic SPECT images. Spillover fraction between LV and myocardium (M) was corrected with phantom data. The influx constant (Ku) was calculated by Patlak plot graphical analysis, and compared with rMBF measured by PET (F) with N-13 ammonia based on Patlak plot analysis with correction for the extraction fraction. To correct the limited first-pass extraction of MIBI, linearization correction by means of the permeability-surface area (PS) product value was also applied. RESULTS: Spillover fractions of MIBI were 0.169+/-0.056 from LV to M, and 0.042+/-0.021 from M to LV. Ku was well correlated with F (Ku = 0.057 + 0.220F, r = 0.83, p < 0.01) and the slope and correlation were improved after linearizaiton (F(MIBI) = -0.131+0.858F, r = 0.94, p < 0.01). CONCLUSION: The proposed method has the potential to be a clinically feasible tool for quantitative measurement of rMBF.

Aged↗
PubMed1999

Characterization of two fungal-elicitor-induced rice cDNAs encoding functional homologues of the rab-specific GDP-dissociation inhibitor.

By using the mRNA differential display approach to isolate defense signaling genes active at the early stage of fungal infection two cDNA fragments with high sequence homology to rab-specific GDP-dissociation inhibitors (GDIs) were identified in rice (Oryza sativa L.) suspension cells. Using polymerase-chain-reaction products as probes, two full-length cDNA clones were isolated from a cDNA library of fungal-elicitor-treated rice, and designated as OsGDI1 and OsGDI2. The deduced amino acid sequences of the isolated cDNAs exhibited substantial homology to Arabidopsis rab-GDIs. Northern analysis revealed that transcripts detected with the 3'-gene-specific DNA probes accumulated to high levels within 30 min after treatment with a fungal elicitor derived from Magnaporthe grisea. The functionality of the OsGDIs was demonstrated by their ability to rescue the Sec19 mutant of Saccharomyces cerevisiae which is defective in vesicle transport. The proteins, expressed in Escherchia coli, cross-reacted with a polyclonal antibody prepared against bovine rab-GDI. Like bovine rab-GDI, the OsGDI proteins efficiently dissociated rab3A from bovine synaptic membranes. Using the two-hybrid system, it was shown that the OsGDIs specifically interact with the small GTP-binding proteins belonging to the rab subfamily. The specific interaction was also demonstrated in vitro by glutathione S-transferase resin pull-down assay.

Animals↗
PubMed1999

Reciprocal ST-segment depression associated with exercise-induced ST-segment elevation indicates residual viability after myocardial infarction.

OBJECTIVES: We evaluated the clinical significance of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability within the infarcted area. BACKGROUND: Although the relation between residual viability and exercise-induced ST-segment elevation has been described, there are no reports focusing on the relation between myocardial viability and reciprocal ST-segment depression associated with exercise-induced ST-segment elevation. METHODS: We evaluated regional blood flow and glucose utilization using N-13 ammonia (NH3) and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in 30 patients with a previous Q-wave myocardial infarction (anterior in 15, inferior in 15). All subjects had single-vessel disease and had exercise-induced ST-segment elevations (> or =1 mm) in electrocardiographic leads. RESULTS: Reciprocal ST-segment depression (> or =1 mm) was present in 16 patients (Group A; anterior in 6, inferior in 10) but not in the remaining 14 patients (Group B). The degree of exercise-induced ST-segment elevation (1.8+/-0.2 vs. 2.0+/-0.2 mm) and the time from the onset of infarction to the study (75+/-49 vs. 74+/-52 days) did not differ between groups. There were no significant differences between groups in the severity of left ventricular dysfunction and the residual luminal narrowing in the infarct-related artery (45+/-21 vs. 48+/-25%). The presence and site of infarction were confirmed by NH3-PET in all patients. FDG-PET demonstrated residual tissue viability within infarct-related area in all patients in Group A and in 3 (21%) of 14 patients in Group B (p < 0.01). The sensitivity, specificity and accuracy of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability were 84%, 100% and 90%, respectively. CONCLUSIONS: The occurrence of reciprocal ST-segment depression associated with exercise-induced ST segment elevation in patients with a previous Q-wave infarction who had single-vessel disease indicates residual tissue viability within the infarct-related area.

Aged↗
PubMed1999

The Arabidopsis thaliana RER1 gene family: its potential role in the endoplasmic reticulum localization of membrane proteins.

Many endoplasmic reticulum (ER) proteins are known to be localized to the ER by a mechanism called retrieval, which returns the molecules that are exported from the ER to the Golgi apparatus back to the ER. Signals are required to be recognized by this retrieval system. In the work on yeast Saccharomyces cerevisiae, we have demonstrated that transmembrane domains of a subset of ER membrane proteins including Sec12p, Sec71p and Sec63p contain novel ER retrieval signals. For the retrieval of these proteins, a Golgi membrane protein, Rer1p, is essential (Sato et al., Mol. Biol. Cell 6 (1995) 1459-1477; Proc. Natl. Acad. Sci. USA 94 (1997) 9693-9698). To address the role of Rer1p in higher eukaryotes, we searched for homologues of yeast RER1 from Arabidopsis thaliana. We identified three cDNAs encoding Arabidopsis counterparts of Rer1p with an amino acid sequence identity of 39-46% to yeast Rer1p and named AtRER1A, AtRER1B, and AtRER1C1. AtRer1Ap and AtRer1Bp are homologous to each other (85% identity), whereas AtRer1C1p is less similar to AtRer1Ap and AtRer1Bp (about 50%). Genomic DNA gel blot analysis indicates that there are several other AtRER1-related genes, implying that Arabidopsis RER1 constitutes a large gene family. The expression of these three AtRER1 genes is ubiquitous in various tissues but is significantly higher in roots, floral buds and a suspension culture in which secretory activity is probably high. All the three AtRER1 cDNAs complement the yeast rer1 mutant and remedy the defect of Sec12p mislocalization. However, the degree of complementation differs among the three with that of AtRER1C1 being the lowest, again suggesting a divergent role of AtRer1C1p.

Amino Acid Sequence↗