Biomedical subjects

M Inagaki

Publications and source records attributed to M Inagaki.

At least 109 records · Page 6Linked to original sources

PubMed1999

A novel human nucleoside diphosphate (NDP) kinase, Nm23-H6, localizes in mitochondria and affects cytokinesis.

Nucleoside diphosphate kinases (NDP kinases) are enzymes known to be conserved throughout evolution and have been shown to be involved in various biological events, in addition to the "housekeeping" phosphotransferase activity. We present the molecular cloning of a novel human NDP kinase gene, termed Nm23-H6. Nm23-H6 gene has been mapped at chromosome 3p21.3 and is highly expressed in heart, placenta, skeletal muscle, and some of the cancer cell lines. Recombinant Nm23-H6 protein has been identified to exhibit functional NDP kinase activity. Immunolocalization studies showed that both endogenous and inducibly expressed Nm23-H6 proteins were present as short, filament-like, perinuclear radical arrays and that they colocalized with mitochondria. Cell fractionation study also demonstrated the presence of Nm23-H6 protein in a mitochondria-rich fraction. Moreover, induction of overexpression of Nm23-H6 in SAOS2 cells, using the Cre-loxP gene activation system, resulted in growth suppression and generation of multinucleated cells. Flow cytometric analysis also demonstrated that the proportion of cells with more than 4N DNA content increased to 28.1% after induction of Nm23-H6, coinciding with the appearance of multinucleated cells. These observations suggest that Nm23-H6, a new member of the NDP kinase family, resides in mitochondria and plays a role in regulation of cell growth and cell cycle progression.

Amino Acid Sequence↗

PubMed1999

Metastatic seeding of bile duct carcinoma in the transhepatic catheter tract: report of a case.

We describe herein the case of a 51-year-old woman in whom metastatic tumor seeding of the percutanenous transhepatic biliary drainage tract occurred following a pancreatoduodenectomy for carcinoma of the distal common bile duct. An abdominal computed tomography scan done 6 months after the initial operation detected a hepatic lesion located at the site of the previous percutaneous transhepatic biliary drainage tract. Implantation of bile duct carcinoma in the drainage tract was diagnosed, and the recurrent tumor was successfully resected by performing a subsegmentectomy of segment 3 and removal of the adjacent abdominal wall. At present, 5 years and 4 months after the second resection, the patient is in good health without any signs of recurrence. This case report demonstrates that an aggressive surgical approach should be performed for tumor seeding of a transhepatic biliary catheter tract.

Carcinoma, Squamous Cell↗

PubMed1999

Aortic dissection in an elderly patient with atrial septal defect.

We report a case of acute aortic dissection that occurred in the late course of surgically untreated atrial septal defect. A 60-year-old man with acute aortic dissection and atrial septal defect was operated on successfully, and we discuss the causal relationship between these two unusual conditions.

Aortic Dissection↗

PubMed1999

Mucin-producing tumors of the pancreas: clinicopathological features, surgical treatment, and outcome.

Mucin-producing tumors (MPTs) of the pancreas are increasingly being recognized. To evaluate the appropriate surgical treatment and predict the prognosis of MPTs, we performed a retrospective clinicopathological study in 51 patients, 27 with benign tumors and 24 with borderline/malignant tumors. Three of the malignant tumors showed stromal invasion and lymph node metastasis on histological examination. Of the 24 patients with borderline/malignant tumors, 2 died of MPTs and 4 died of other diseases. At the last follow-up, 35 patients were alive and well. The 5-year postoperative survival rate was 90% for patients with benign tumors, and 78% of these with borderline/malignant tumors. Five of the patients with borderline/malignant tumors had multicentric tumors. Three of these patients underwent resection of the rest of the pancreas, 5, 6, and 8 years, respectively, after the first operation. Extended radical resection is required for malignant MPT with invasion of the pancreatic stroma. We prefer to perform pancreatogastrostomy or Imanaga's procedure to allow examination of the body and tail of the pancreas by endoscopic retrograde pancreatography after resection of the pancreatic head. Careful follow-up for a long period may be the most prudent approach for detecting multiple MPTs in the residual pancreas after surgical treatment.

Adenocarcinoma, Mucinous↗

PubMed1999

Papillary adenoma of the distal common bile duct.

A 73-year-old man with a papillary adenoma located in the distal common bile duct is reported. He underwent pylorus-preserving pancreatoduodenectomy. The lesion in the common bile duct featured papillary proliferation of the epithelium and fibrous elements with diffuse infiltration by inflammatory cells. Positive staining for MIB-1 (Ki-67) and p53 was identified in the nuclei of the proliferative epithelium. These findings suggested the malignant potential of this lesion. Further progress in imaging diagnostic techniques should increase the frequency with which such lesions are discovered. Even now, if mural irregularities and defects are found in the extrahepatic biliary system, especially the distal common bile duct, the possibility of such borderline biliary adenoma should be taken into consideration when making a diagnosis.

Adenoma, Bile Duct↗

PubMed1999

Effect of acute and chronic administration of dehydroepiandrosterone on (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane-induced wet dog shaking behavior in rats.

It has been reported that dehydroepiandrosterone (DHEA) or dehydroepiandrosterone sulfate (DHEA-S) is associated with affective disorders and that pathology of affective disorders are related with dysfunction of serotonin(5-HT)-2A receptor-mediated responses. In this study, we investigated the effect of DHEA on (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2 aminopropane (DOI), 5-HT-2A receptor agonist, -induced wet dog shaking behavior (WDS) in rats. Acute treatment with DHEA inhibited the DOI-induced WDSs dose dependently. This inhibition was recovered by opioid receptor antagonist, naltrexone. 5-HT-2A receptor-mediated WDSs were desensitized after chronic treatment with DOI, however chronic treatment with DHEA had no effect on this desensitization. Chronic treatment with DHEA had no facilitating effect of chronic dexamethasone treatment on DOI-induced WDSs. These findings may lead the possibility that DHEA has the inhibitory effect of 5-HT-2A mediated signaling pathway via non-genomic action.

Amphetamines↗

PubMed1999

Specific interaction of fused H protein of bacteriophage phiX174 with receptor lipopolysaccharides.

The DNA fragment encoding the spike H protein of bacteriophage phiX174 was amplified by polymerase chain reaction. The fragment was sub-cloned into pQE-30 to yield pQE-H. The histidine-tagged H protein (HisH) was obtained from the cell extract of Escherichia coli M15 (pREP4) harboring pQE-H and purified by nickel chelating and anion-exchange chromatographies. HisH was shown to bind dose-dependently to the lipopolysaccharides (LPSs) isolated from phiX174-sensitive strains, E. coli C or Salmonella typhimurium TV119 (Ra mutant). In sharp contrast, HisH did not bind to the LPSs from insensitive strains, E. coli F583 (Rd2 mutant) or E. coli O111:B4 (smooth strain). Since the same selectivity was observed in the plaque counting assay for in vitro inactivation of phiX174, the spike H protein was shown to recognize receptor LPS.

Bacteriophage phi X 174↗

PubMed1999

Abortive synaptogenesis as a factor in the inner hair cell degeneration in the Bronx Waltzer (bv) mutant mouse.

The Bronx Waltzer (vb) mutation in the mouse results in the degeneration of most but not all of the primary auditory receptors, the inner hair cells, and their afferent neurons. We analyzed the ultrastructure of 94 inner hair cells in the intact postnatal mutant mouse and in neonatal cochleas in culture to understand the pathogenesis of hair cell death and to detect factors that may prevent it. The vb spiral neurons of the Bronx Waltzer display two distinctive features: some of them continue to divide mitotically for at least seven postnatal days, and the type I radial fibers that innervate inner hair cells display a deficiency in immunoexpression of GAD. The growing endings of spiral neurons converge around the inner hair cells or, in their absence, invade the outer hair cell region. Their profuse sprouting among inner spiral sulcus cells contributes to the characteristic ultrastructural picture of the bv cochlea. During the first three days after birth, 40% of the inner hair cells appear normal and innervated, 40% are mostly denervated and degenerating, and 20% are immature, with minimal or no neuronal appositions. However, in mutants 6 days and older only a few inner hair cells survive, and these show either normal or superfluous afferent innervation and axosomatic GABAergic efferent innervation. Degeneration of inner hair cells begins with a distention of the nuclear envelope and the ribosomal endoplasmic reticulum. The outer nuclear membrane eventually breaks, and exudate fills the cell interior. The cellular edema leads to cell death. We propose that success or failure in synaptic acquisition is a decisive factor in the survival or decline of the mutant inner hair cells. We also suggest that the developmental delay in maturation of the spiral ganglion neurons (type I) and the failure in their synaptogenesis may be caused by an impairment in neurotrophin (NT3/BDNF) synthesis by their mutant receptor cells.

Acetylcholinesterase↗

PubMed1999

The circadian pattern of the development of ventricular fibrillation in patients with Brugada syndrome.

AIMS: Brugada syndrome is considered to be a distinctive subgroup of idiopathic ventricular fibrillation. Identification of the circadian pattern of ventricular fibrillation would contribute to the elucidation of its underlying pathophysiology, but this pattern remains unknown in patients with Brugada syndrome. METHODS: and Results A total of 12 consecutive Brugada syndrome patients (46+/-14 years, all male) who underwent implantation of an implantable cardioverter defibrillator were studied. The distribution of the time of ventricular fibrillation detection was examined and classified into four 6-hour time periods of the day. The mean follow-up period following implantation was 777+/-535 days. In six out of the 12 patients, ventricular fibrillation occurred during follow-up. The data logs revealed that ventricular fibrillation was detected 30 times (range, 3-9). Ventricular fibrillation was observed more frequently at night ( 1800 h to 0600 h) than in the day (0600 h to 1800 h) (93.3% [28/30] vs 6.7%[2/30], P<0.001), and during sleep than while awake (86.7% [26/30] vs 13.3%[4/30], P<0.001). Ventricular fibrillation occurred most frequently between midnight and 0600 h in patients with ventricular fibrillation episodes during sleep (76.9% [20/26] vs 23.1%[6/26], P<0.01). CONCLUSION: These results suggest that increased nocturnal vagal activity and withdrawal sympathetic activity may play an important role in the arrhythmogenesis of the Brugada syndrome.

Adult↗

PubMed1999

In vitro inducible nitric oxide synthesis inhibitory active constituents from Fraxinus rhynchophylla.

Bioassay-guided fractionation of an H2O extract of the barks of Fraxinus rhynchophylla has furnished two inducible nitric oxide synthase (iNOS) inhibitory compounds, ferulaldehyde (1) and scopoletin (3) together with a coumarin, fraxidin (2). Compounds 1 and 3 showed inhibition of nitric oxide (NO) synthesis in a dose-dependent manner by murine macrophage-like RAW 264.7 cells stimulated with interferon-gamma (IFN-gamma) plus lipopolysaccharide (LPS). The inhibition of NO synthesis of 1 was reflected in the decreased amount of iNOS protein, as determined by Western blotting.

Acrolein↗

PubMed1999

Protein phosphatase 2A inhibitors, phoslactomycins. Effects on the cytoskeleton in NIH/3T3 cells.

Protein phosphorylation is a key regulatory mechanism of the organization and dynamics of the actin cytoskeleton during cell motility, differentiation, and cytokinesis. The level of protein phosphorylation is dependent on the relative activities of both protein kinases and protein phosphatases. In this paper, we examined the effect of phoslactomycins (PLMs) on the regulation of the cytoskeleton of NIH/3T3 fibroblasts. Treatment of cells with PLM-F (10 microM) induced actin filament depolymerization after 4 h. This effect was reversible and actin filaments were reformed 1 h after removal of the inhibitors. As PLM-F had no effect at all on polymerization of purified actin in vitro, it is thought that PLMs induce actin depolymerization through an indirect mechanism. An in vitro assay showed PLMs inhibited protein phosphatase 2A at lower concentrations (IC50 4.7 microM) than protein phosphatase 1. An in situ phosphorylation assay also revealed that PLM-F treatment stimulated the phosphorylation of intracellular vimentin. These results suggest that phoslactomycins are protein phosphatase 2A-specific inhibitors and that protein phosphatase 2A is involved in regulation of the organization of the actin cytoskeleton.

3T3 Cells↗

PubMed1999

Activation process of dipteran-specific insecticidal protein produced by Bacillus thuringiensis subsp. israelensis.

Dipteran-specific insecticidal protein Cry4A is produced as a protoxin of 130 kDa in Bacillus thuringiensis subsp. israelensis. Here we performed the in vitro processing of Cry4A and showed that the 130-kDa protoxin of Cry4A was processed into the two protease-resistant fragments of 20 and 45 kDa through the intramolecular cleavage of a 60-kDa intermediate. The processing into these two fragments was also observed in vivo. To investigate functional properties of the two fragments, GST (glutathione S-transferase) fusion proteins of the 60-kDa intermediate and the 20- and 45-kDa fragments were constructed. Neither the GST-20-kDa fusion protein (GST-20) nor the GST-45-kDa fusion protein (GST-45) was actively toxic against mosquito larvae of Culex pipiens, whereas the GST-60-kDa intermediate fusion protein (GST-60) exhibited significant toxicity. However, when the two fusion proteins GST-20 and GST-45 coexisted, significant toxicity was observed. The coprecipitation experiment demonstrated that the two fragments associated with each other. Therefore, it is strongly suggested that the two fragments formed an active complex of apparently 60 kDa. A mutant of the 60-kDa protein which was apparently resistant to the intramolecular cleavage with the midgut extract of C. pipiens larvae had toxicity slightly lower than that of GST-60.

Amino Acid Sequence↗

PubMed1999

PDK1 homologs activate the Pkc1-mitogen-activated protein kinase pathway in yeast.

PDK1 (phosphoinositide-dependent kinase 1) is a mammalian growth factor-regulated serine/threonine kinase. Using a genetic selection based on a mutant form of the yeast MAP kinase kinase Ste7, we isolated a gene, PKH2, encoding a structurally and functionally conserved yeast homolog of PDK1. Yeast cells lacking both PKH2 and PKH1, encoding another PDK1 homolog, were nonviable, indicating that Pkh1 and Pkh2 share an essential function. A temperature-sensitive mutant, pkh1(D398G) pkh2, was phenotypically similar to mutants defective in the Pkc1-mitogen-activated protein kinase (MAPK) pathway. Genetic epistasis analyses, the phosphorylation of Pkc1 by Pkh2 in vitro, and reduced Pkc1 activity in the pkh1(D398G) pkh2 mutant indicate that Pkh functions upstream of Pkc1. The Pkh2 phosphorylation site in Pkc1 (Thr-983) is part of a conserved PDK1 target motif and essential for Pkc1 function. Thus, the yeast PDK1 homologs activate Pkc1 and the Pkc1-effector MAPK pathway.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed1999

New simple methods for isolating baroreceptor regions of carotid sinus and aortic depressor nerves in rats.

We developed new methods for isolating in situ baroreceptor regions of carotid sinus and aortic depressor nerves in halothane-anesthetized rats. After ligation of the root of the external carotid artery, the internal carotid and pterygopalatine arteries were embolized with two ball bearings of 0.8 mm in diameter. Bilateral carotid sinus pressures were changed between 60 and 180 mmHg in 20-mmHg steps lasting 1 min each. The sigmoidal steady-state relationship between aortic and carotid sinus pressures in 11 rats indicated the maximum gain of the carotid sinus baroreflex to be -2. 99 +/- 0.75 at 120 +/- 5 mmHg. An in situ isolation of the baroreceptor area of the right aortic depressor nerve could be made by ligation of the innominate, common carotid, and subclavian arteries in 9 rats. Pressure imposed on the subclavian baroreceptor was altered between 40 and 180 mmHg in 20-mmHg steps lasting 1 min each. The sigmoidal steady-state relationship between the aortic depressor nerve activity and imposed pressure showed that the baroreceptor gain peaked at 118 +/- 4 mmHg. We established an easy approach to the rat baroreflex and baroreceptor research.

Animals↗

PubMed1999

New analytic framework for understanding sympathetic baroreflex control of arterial pressure.

The sympathetic baroreflex is an important feedback system in stabilization of arterial pressure. This system can be decomposed into the controlling element (mechanoneural arc) and the controlled element (neuromechanical arc). We hypothesized that the intersection of the two operational curves representing their respective functions on an equilibrium diagram should define the operating point of the arterial baroreflex. Both carotid sinuses were isolated in 16 halothane-anesthetized rats. The vagi and aortic depressor nerves were cut bilaterally. Carotid sinus pressure (CSP) was sequentially altered in 10-mmHg increments from 80 to 160 mmHg while sympathetic efferent nerve activity (SNA) and systemic arterial pressure (SAP) were recorded simultaneously under various hemorrhagic conditions. The mechanoneural arc was characterized by the response of SNA to CSP and the neuromechanical arc by the response of SAP to SNA. We parametrically analyzed the relationship between input and output for each arc using a four-parameter logistic equation model. In baseline states, the two arcs intersected each other at the point at which the instantaneous gain of each arc attained its maximum. Severe hemorrhage lowered the gain and offset of the neuromechanical arc and moved the operating point, whereas the mechanoneural arc remained unchanged. The operating points measured under the closed-loop conditions were indistinguishable from those estimated from the intersections of the two arc curves on the equilibrium diagram. The average root mean square errors of estimate for arterial pressure and SNA were 2 and 3%, respectively. Such an analytic approach could explain a mechanism for the determination of the operating point of the sympathetic baroreflex system and thus helps us integratively understand its function.

Animals↗

PubMed1999

Summation of dynamic transfer characteristics of left and right carotid sinus baroreflexes in rabbits.

Although interactions among parallel negative-feedback baroreflex systems have been extensively investigated with respect to their steady-state responses, the dynamic interactions remain unknown. In anesthetized, vagotomized, and aortic-denervated rabbits, we perturbed isolated intracarotid sinus pressure (CSP) unilaterally or bilaterally around the physiological operating pressure according to binary white noise. The neural arc transfer function from CSP to cardiac sympathetic nerve activity (SNA) and the peripheral arc transfer function from SNA to aortic pressure were estimated. The gain values of the neural arc at 0.01 Hz estimated by the left (L) and right (R) CSP perturbations were 0.94 +/- 0.31 and 0.96 +/- 0.25, respectively. The gain value increased to 2.17 +/- 0.97 during the bilateral identical CSP perturbation and was not significantly different from L + R. The phase values of the neural arc did not differ among protocols. No significant differences were observed in the peripheral arc transfer functions among protocols. We conclude that summation of the dynamic transfer characteristics of the bilateral carotid sinus baroreflexes around the physiological operating pressure approximates simple addition.

Animals↗

PubMed1999

Dynamic counterbalance between direct and indirect vagal controls of atrioventricular conduction in cats.

The vagal system regulates the atrioventricular conduction time (TAV) via two opposing mechanisms: a direct effect on the atrioventricular node and an indirect effect through changes in heart period (TAA). To evaluate how dynamic vagal activation affects TAV, we stimulated the vagal nerve with frequency-modulated Gaussian white noise and estimated the transfer function from vagal stimulation to the TAV response under conditions of no pacing and constant pacing in anesthetized cats. The effect of changes in TAA on TAV was estimated by a random-pacing protocol. The transfer function from vagal stimulation to TAV has low-pass filter characteristics. Constant pacing increased the maximum step response in TAV (2.4 +/- 1.2 vs. 6.3 +/- 2.2 ms/Hz, P < 0.01). The time constant did not differ between the vagal effect on TAV and that on TAA (2.9 +/- 1.2 vs. 2.3 +/- 0.5 s). Because changes in TAA reciprocally affected TAV without significant delay, the direct and indirect effects were dynamically counterbalanced and exerted stable TAV transient response during vagal stimulation under normal sinus rhythm.

Acoustic Stimulation↗

PubMed1999

Neuronal uptake affects dynamic characteristics of heart rate response to sympathetic stimulation.

Recently, studies in our laboratory involving the use of a Gaussian white noise technique demonstrated that the transfer function from sympathetic stimulation frequency to heart rate (HR) response showed dynamic characteristics of a second-order low-pass filter. However, determinants for the characteristics remain to be established. We examined the effect of an increase in mean sympathetic stimulation frequency and that of a blockade of the neuronal uptake mechanism on the transfer function in anesthetized rabbits. We found that increasing mean sympathetic stimulation frequency from 1 to 4 Hz significantly (P < 0.01) decreased the dynamic gain of the transfer function without affecting other parameters, such as the natural frequency, lag time, or damping coefficient. In contrast, the administration of desipramine (0.3 mg/kg iv), a neuronal uptake blocking agent, significantly (P < 0.01) decreased both the dynamic gain and the natural frequency and prolonged the lag time. These results suggest that the removal rate of norepinephrine at the neuroeffector junction, rather than the amount of available norepinephrine, plays an important role in determining the low-pass filter characteristics of the HR response to sympathetic stimulation.

Adrenergic Uptake Inhibitors↗