Biomedical subjects

T Kamada

Publications and source records attributed to T Kamada.

At least 253 records · Page 14Linked to original sources

PubMed1995

Activation of Na+/H+ exchanger by hepatocyte growth factor in hepatocytes.

The effect of the hepatocyte growth factor (HGF) on the Na+/H+ exchanger was studied using primary cultured hepatocytes. HGF induced intracellular pH (pHi) elevation of 0.10 pH units in hepatocytes cultured for 4 to 7 hours; the response was lower after other culture periods. Even with the same culture period, intercellular heterogeneity was found in the responsiveness to HGF. This heterogeneity may be partially accounted for by the weak but significant correlation observed between the basal pHi level and the degree of pHi elevation caused by HGF in hepatocytes. The pHi elevation caused by HGF was blocked on pretreatment of the hepatocytes with amiloride, suggesting that HGF activates the Na+/H+ exchanger. This hypothesis was confirmed by the fact that HGF increased the initial rapid rate of cell alkalization of acid-loaded hepatocytes. The tyrosine kinase inhibitor, genistein, also blocked the elevation, consistent with the fact that HGF receptor/c-met has a tyrosine kinase domain. To clarify the signal transduction pathway from tyrosine kinase to the Na+/H+ exchanger, we examined the effects of inhibitors of other kinases (H-7, H-8, and W-7) on the HGF-induced pHi elevation and found that only W-7 blocked it. This pHi elevation was also prevented on preincubation of the hepatocytes with thapsigargin, which blocks the calcium response caused by HGF. These results suggest that HGF activates the Na+/H+ exchanger in hepatocytes through a tyrosine kinase-calcium/calmodulin-dependent pathway.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1995

In vivo transfection of hepatitis C virus complementary DNA into rodent liver by asialoglycoprotein receptor mediated gene delivery.

An in vivo model of hepatitis C virus (HCV) infection is needed to enable investigation of the mechanism of the liver injury that it causes. In this study, we used asialoglycoprotein receptor mediated gene delivery to obtain expression of the complementary DNA (cDNA) coding the core and part of the envelope 1 protein of HCV because selective delivery to the hepatocytes has been reported to be attained with this method. The optimum carrier-DNA ratio was examined using in vitro transfection and found to be important for the efficiency of this method. In transfection in vivo, microautoradiographical examination showed that the transfected plasmids were delivered selectively to the liver parenchymal cells. To obtain an immunohistochemically detectable level of protein expression in rodent liver, some modifications for increasing the in vivo transfection efficiency were performed; a lysosomal enzyme inhibitor, chloroquine, was used and the administration route of the carrier-DNA complex was changed from the tail vein to the portal vein. On the bases of these results, in vivo transfection with expression vector of HCV core/E1 region was performed. In rat liver transfected by intraportal injection with chloroquine, the transcript RNA and the core protein were detected. These results indicated that the HCV core/E1 expression vector was not merely delivered but also successfully expressed in the liver using asialoglycoprotein receptor mediated gene delivery. The number of the HCV core expressing cells in the transfected liver was similar to that in patients with hepatitis C. These in vivo transfected animals should be useful for investigating the role of this region in the liver injury caused by HCV.

Animals↗

PubMed1995

Ethanol induces heterogeneous reduction of cytochrome aa3 within perfused rat liver lobule assessed using microspectroscopy.

The redox state of cytochrome aa3 was measured at microspots (20 microns diameter) within the lobule of perfused rat livers, using reflectance microspectroscopy, and the effect of ethanol infusion on sublobular distribution of the redox states was evaluated. A sigmoidal relationship was observed between oxygen delivery and the reduction of cytochrome aa3 in both the periportal and pericentral regions of the liver lobule when the influent O2 concentration was decreased in a graduated manner. This sigmoidal curve was shifted to the more reduced state by ethanol infusion, with ethanol (25-100 mM) increasing the degree of cytochrome aa3 reduction in a dose-dependent manner according to the distance from the periportal region along a sinusoid. This increase was spatially heterogeneous within a liver lobule. These data indicate that ethanol accelerates cytochrome aa3 reduction, with a distinct gradient of reduction along sinusoids but a heterogeneous distribution within the liver lobule.

Animals↗

PubMed1995

[Progress in particle-beam radiation therapy].

The advantages of particle-beam radiation therapy include its radiobiologic properties and spatial dose distribution. With the recent progress in diagnostic imaging, the cumulative knowledge of radiation biology, and the development of a 3-dimensional treatment planning system, particle-beam radiation therapy could prove clinically effective. Local control of tumors is an essential for the cure. Particle-beam radiation therapy has the potential to provide better local tumor control.

Humans↗

PubMed1995

[SH/TA-508 clinical phase II study: dose evaluation of SH/TA-508 in echocardiography].

A cooperative study was conducted at 18 institutions to evaluate the safety and usefulness of SH/TA-508, a contrast medium for ultrasound diagnosis, and to find its optimum dose. One hundred and one patients with confirmed or suspected ischemic heart disease were examined with two-dimensional echocardiography, and 95 patients with mild mitral insufficiency were studied with the color Doppler method. The contrast medium was administered at low-dose (1.5-1.6g galactose) and high-dose (3.0-3.2 g galactose) levels at concentrations of 200, 300 and 400 mg/ml. The contrast effect was evaluated into five grades by two-dimensional echocardiography: - (ineffective), + (weak), 2+ (moderate), 3+ (good), 4+ (excessive effect) and into four grades with the color Doppler method, - (ineffective), + (weak), 2+ (optimum), 3+ (excessive effect). The two-dimensional echocardiographic studies showed effects graded at 2+ and above in most patients (83-93%). These findings were significantly more common in patients who had received the 300 and 400 mg/ml concentrations than in those who received the 200 mg/ml concentration. Statistical analysis found no significant differences between the high-dose and low-dose groups. Color Doppler echocardiography found signal enhancement graded at 2+ and above in 80-93% of cases. There were no significant differences in enhancement effect attributable to concentration or total dose. However, since excessive signal intensity was seen quite frequently, the dose levels in the present study were considered to be a little too high. Side effects includes transient feelings of warmth or cold, and the incidence of side effects was higher at higher doses and concentrations. The results show that the optimum concentration for two-dimensional echocardiography is 300 mg/ml and for color Doppler 200 mg/ml. No particular safety problems were seen with SH/TA-508, and this contrast medium is useful in echocardiography of the left ventricle and in enhancing mitral regurgitation signals in color Doppler examinations. Therefore, a phase III multicenter trial should be performed.

Adult↗

PubMed1995

Three-dimensional display of surface cortical perfusion by SPECT: application in assessing Alzheimer's disease.

UNLABELLED: To better understand cortical perfusion, we developed a method for a three-dimensional display technique with 99mTc-hexamethylpropyleneamine oxime (HMPAO) SPECT. METHODS: Twelve patients with higher cortical dysfunction due to Alzheimer's disease and 18 age-matched controls were examined. Data acquisition was performed after intravenous injection of 740 MBq of 99mTc-HMPAO. After reconstructing the transaxial images, the three-dimensional images were obtained by modified volume rendering, where the surfaces were displayed in the corresponding colors as the maximum cortical value within a depth of 2 cm. RESULTS: In the control studies, almost all surface cortices were over 60% of the maximum cerebellar value. In Alzheimer's disease patients, areas of perfusion below 60% were detected in the temporo-parietal lesions and frontal lobe lesions in 6 of 12. These findings correlated with the neurological dysfunction. CONCLUSION: This method provides realistic three-dimensional information about surface cortical perfusion, which was found to be useful in clinical investigations of higher cortical dysfunction due to degenerative or cerebrovascular diseases.

Alzheimer Disease↗

PubMed1995

[An outbreak of tuberculosis involving foreign workers from South America].

A twenty-four year old male Peruvian of Japanese origin, who came to Japan in September 1990 and had been working in a minor factory in a rural area, was admitted to a hospital in March '91 with severe cough. Smear examination of his sputum smear was positive for acid-fast bacilli and his chest X-ray showed multiple cavities (Index case). Subsequent contact examination identified further four patients with pulmonary tuberculosis among his colleagues in the factory, all of whom lived in the same house with the index case. During following three years, further six patients with mycobacteriosis, two Peruvians and four Japanese, were found among the employee of that factory. M. tuberculosis was cultured from the sputa obtained from seven of these eleven patients. Another patient was diagnosed as non-tuberculous mycobacteriosis. Restriction fragment length polymorphism (RFLP) analysis carried out with five strains of M. tuberculosis isolated from these patients revealed the identical RFLP pattern which is uncommon in Japan. Still more, an isolate from another patient was subjected to RFLP analysis by chance, and was found to show the same RFLP pattern. Later epidemiological study revealed that the last patient, a 53 year-old saleswoman of boxlunch, might have some contact with the index case at her booth. Though RFLP analysis was not done for the isolate from the index case, from the identity of RFLP patterns of other isolates, clinical course and epidemiological study, it is considered that six patients were certainly, and two others were probably infected from the index case.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

[Experimental techniques for developing new drugs acting on dementia (9)--Brain ischemia models].

Many brain ischemia models have so far been developed and used for investigating the pathophysiology of ischemic stroke. Among these stroke models, gerbil models of brain ischemia have been widely used because of several advantages such as easy operability and convenience. In the present paper, we first discuss several subjects related to the use of animal models of brain ischemia for the development of new therapeutic agents against vascular dementia, and the theoretical, technical and clinical implications of gerbil models of brain ischemia have been outlined. Secondly, we describe the detailed procedures for obtaining forebrain ischemia or four different grades of unilateral cerebral ischemia in Mongolian gerbils. The advantages and drawbacks of these models are also discussed and compared with other models for investigation of the pathophysiology of vascular dementia.

Animals↗

PubMed1995

Expression of the hepatitis C virus genome in rat liver after cationic liposome-mediated in vivo gene transfer.

The lack of a small animal model of hepatitis C virus (HCV) infection has impeded elucidation of the pathogenesis of HCV. The aim of this study was to develop an HCV-expressing animal model by means of cationic liposome-mediated in vivo gene transfer. To examine the feasibility of this strategy, pActLacZ, an expression vector composed of the LacZ gene driven by the beta-actin promoter, complexed with lipofectin, was injected retrogradely into the common bile ducts of adult rats. X-Gal histochemical staining clearly showed that the LacZ gene was expressed in hepatocytes, but not in biliary epithelial cells. Maximal expression was observed at a DNA to lipofectin ratio of 1:4. Based on this observation, pAGS3M091, an expression vector containing the full length of HCV complementary DNA (cDNA) preceded by the beta-actin promoter, was evaluated. Two days after in vivo intrabiliary administration of pAGS3M091 complexed with lipofectin, polymerase chain reaction (PCR) amplification of reverse-transcribed liver RNA demonstrated the 5' and 3' portions of HCV transcripts derived from pAGS3M091. Immunohistochemical analysis showed the HCV core protein in a small number of hepatocytes scattered in the hepatic lobules. We conclude that the full-length HCV genome was successfully expressed in adult rat liver by means of cationic liposome-mediated in vivo gene transfer. This model will be useful for determining the immunopathological role of HCV in vivo.

Animals↗

PubMed1995

Super-early iodine-123-iodoamphetamine SPECT imaging of human primary motor cortex.

UNLABELLED: This study was designed to visualize the motor function area related to finger movements in normal human brain using super-early (first 640 sec of acquisition) [123l]iodoamphetamine ([123I]IMP) SPECT. METHODS: Seven healthy male volunteers performed paired, isolated baseline and task sessions. The task was a right thumb-to-fingers opposition task, which was loaded for the initial 11 min of the session. A high-performance, four-head SPECT camera was used. At each session, administration of 222 MBq [123I]IMP was followed by 16 serial 160-sec dynamic SPECT acquisitions. To obtain matched brain anatomical images, MRI was also performed using the same slice formation as in the SPECT study. After image reconstruction, ROIs were set on bilateral sensorimotor hand areas (SMHA), the supplementary motor area (SMA), the frontal, temporal and occipital lobes and the cerebellar hemispheres. The percent increase of ROI activity (%INC) in the task session compared with that in the baseline session was calculated in each ROI after normalization to the global brain radioactivity. RESULTS: There was significant activation of the left SMHA by the task, the amplitude of which was maximal in the initial phase of dynamic images (the super-early phase). This area was located in the left peri-central area identified on the analogous slice in the MR image. The left SMHA showed gradual and statistically significant decrease of %INC during the three phases. CONCLUSION: Super-early [123I]IMP may be used to identify the primary motor cortex and to evaluate its function in some pathological conditions.

Adult↗

PubMed1995

[Ultrasonic assessment of cerebrovascular disease].

The aim of this paper of the symposium of the 36th Scientific Meeting of Japanese Society of Neurology is to clarify the general status of ultrasonic assessment in the imaging modality of cerebrovascular disease (CVD). Although there are many ultrasonic techniques, we want to address the carotid ultrasonography and transcranial ultrasonography. Cervical carotid atherosclerosis is known to be a major cause of brain infarction and Duplex ultrasonography is the best imaging tool. This method made it possible to visualize the living human arterial wall and to visualize the intraplaque characters. This was most advantage among several modalities. Few and really disadvantages of this method are examiner dependent results and narrow visual window. On the basis of these ultrasonic data, many investigations of nature of stroke have been performed. Transcranial ultrasonography have been accepted as a new method for non-invasive intracranial vascular imaging. There are the transcranial Doppler, transcranial tomography and the transcranial color flow imaging. Using these transcranial methods, we can evaluate the intracranial lesions. Transcranial color flow imaging made it possible to obtain real images of major arteries of circle of Willis. In conclusion, ultrasonic modality is a useful tool for assessing the risk of cerebrovascular disease or atherosclerosis, especially in chronic situations.

Aorta↗

PubMed1995

The inflammatory reaction in mucosa during healing of gastric ulcers in humans.

To evaluate the inflammatory changes during ulcer healing, we measured myeloperoxidase (MPO) activity and the inflammatory cytokine interleukin-8 (IL-8) in the gastric mucosa of 51 patients with gastric ulcers and 5 normal controls. MPO activity was measured by enzyme assay and IL-8 by ELISA, using biopsy samples taken from the ulcer margin and at 3 and 6 cm from the ulcer. Levels of MPO activity were significantly higher than in normal controls and peaked at the A2 (active) stage, and then gradually decreased and returned to basal levels at the S2 (scarring) stage. The area of increased MPO activity around the gastric ulcer was approximately 6 cm in diameter at the A2 stage, and this area decreased as the ulcer healed. IL-8 levels in gastric mucosa also increased significantly at the A2 stage, and the changes paralleled those of MPO activity during ulcer healing. MPO activity correlated well with the IL-8 level.

Biopsy↗

PubMed1995

In vivo transfection of rat liver with hepatitis C virus cDNA using cationic liposome-mediated gene delivery.

The lack of a small animal model for hepatitis C virus (HCV) infection has impeded elucidation of the pathogenesis of this virus. The aim of this study was to develop an HCV-expressing animal model using cationic liposome-mediated in vivo gene transfer. To examine the feasibility of this strategy, an expression vector composed of the LacZ gene driven by the beta-actin promoter, pActLacZ, was injected retrogradely into the common bile ducts of adult rats. X-Gal histochemical staining clearly showed that the LacZ gene was expressed in hepatocytes. Maximal expression was observed at a DNA:lipofectin ratio of 1:4. Based on this observation, an expression vector containing the full-length of HCV cDNA, pAGS3M091, was evaluated in adult rats. Two days after intrabiliary administration of pAGS3M091, PCR amplification of reverse-transcribed liver RNA demonstrated the 5' and 3' portions of HCV transcripts derived from pAGS3M091. Immunohistochemical analysis revealed the HCV core protein in a small number of hepatocytes scattered in the lobules. Thus, the full-length of the HCV genome was successfully expressed in adult rat liver using liposome-mediated in vivo gene transfer.

Animals↗

PubMed1994

Hypoxia/reoxygenation-mediated induction of astrocyte interleukin 6: a paracrine mechanism potentially enhancing neuron survival.

To elucidate mechanisms underlying neuroprotective properties of astrocytes in brain ischemia, production of neurotrophic mediators was studied in astrocytes exposed to hypoxia/reoxygenation (H/R). Rat astrocytes subjected to H/R released increased amounts of interleukin (IL) 6 in a time-dependent manner, whereas levels of tumor necrosis factor and IL-1 remained undetectable. IL-6 transcripts were induced in hypoxia and the early phase of reoxygenation, whereas synthesis and release of IL-6 antigen/activity occurred during reoxygenation. Elevated levels of IL-6 mRNA were due, at least in part, to increased transcription, as shown by nuclear runoff analysis. The mechanism stimulating synthesis and release of IL-6 antigen by astrocytes was probably production of reactive oxygen intermediates (ROIs), which occurred within 15-20 minutes after placing hypoxia cultures back into normoxia, as the inhibitor diphenyl iodonium inhibited the burst of ROIs and subsequent IL-6 generation (blockade of nitric oxide formation had no effect on ROI generation or IL-6 production). Enhanced IL-6 generation was also observed in human astrocytoma cultures exposed to H/R. Survival of differentiated PC12 cells exposed to H/R was potentiated by conditioned medium from H/R astrocytes, an effect blocked by neutralizing anti-IL-6 antibody. In a gerbil model of brain ischemia, IL-6 activity was lower in the hippocampus, an area sensitive to ischemia, compared with IL-6 activity in the cortex, an area more resistant to ischemia. IL-6 antigen, demonstrated immunohistochemically, was increased in astrocytes from ischemic regions of gerbil brain. These data suggest that H/R enhances transcription of IL-6, resulting in increased translation and release of IL-6 antigen after the burst of ROI generated early during reoxygenation. Release of IL-6 from astrocytes could exert a paracrine neurotrophic effect in brain ischemia.

Animals↗

PubMed1994

Vagally mediated heart rate recovery after exercise is accelerated in athletes but blunted in patients with chronic heart failure.

OBJECTIVES: Vagally mediated heart rate recovery after exercise was assessed in patients with chronic heart failure and in well trained athletes by analyzing the postexercise heart rate decay. BACKGROUND: Vagal reactivation is an important cardiac deceleration mechanism after exercise. However, alterations of this mechanism under pathologic conditions have not been characterized because of the lack of a specific index. METHODS: To find a vagally mediated component of heart rate recovery, the time constants of the beat-by-beat heart rate decay for the first 30 s (T30) and the first 120 s (T120) after exercise were obtained at six levels of exercise in eight normal volunteers: 1) at maximal exercise, 2) at anaerobic threshold, 3) at anaerobic threshold with propranolol administration, 4) at anaerobic threshold with atropine administration, 5) at anaerobic threshold with concomitant administration of both drugs, and 6) at 50% of anaerobic threshold. To investigate the effects of heart failure and endurance training on vagally mediated heart rate recovery, T30 and T120 at anaerobic threshold were obtained in 20 patients with chronic heart failure and in 9 cross-country skiers. RESULTS: In normal volunteers, T30 and T120 were markedly prolonged by atropine administration, indicating that both time constants are mediated by vagal reactivation. Moreover, T30 was almost independent of the exercise intensity and sympathetic blockade, whereas T120 was affected by sympathetic nerve activity and exercise work load. These results indicate that T30 is mediated primarily by vagal reactivation, independent of sympathetic withdrawal, and is significantly smaller in athletes (p < 0.01) and significantly larger in patients with chronic heart failure (p < 0.01) than that in respective age-matched normal control subjects. CONCLUSIONS: The T30 value could be a specific index for vagally mediated heart rate recovery. Vagally mediated heart rate recovery after exercise is accelerated in well trained athletes but blunted in patients with chronic heart failure.

Adult↗

PubMed1994

DNA cleavage induced by glycation of Cu,Zn-superoxide dismutase.

Human Cu,Zn-superoxide dismutase (Cu,Zn-SOD) undergoes site-specific and random fragmentation by non-enzymic glycosylation (glycation). Released Cu2+ from the glycated Cu,Zn-SOD probably facilitates a Fenton reaction to convert H2O2 into hydroxy radical, which then participates in the non-specific fragmentation [Ookawara et al. (1992) J. Biol. Chem. 267, 18505-18510]. In the present study, we investigated the effects of glycated Cu,Zn-SOD on cloned DNA fragments and nuclear DNA and analysed the formation of 8-hydroxydeoxyguanosine (8-OH-dG). Incubation of cloned DNA fragments with Cu,Zn-SOD and reducing sugars resulted in cleavage of the DNA. The extent of the cleavage corresponded to the reducing capacity of the sugar. Metal-chelating reagents, EDTA and bathocuproine, and an H2O2 scavenger, catalase, inhibited the DNA cleavage. Hydroxy radical scavengers and aminoguanidine, an inhibitor of glycation, also inhibited the reaction. Moreover, the glycation of Cu,Zn-SOD caused the substantial formation of 8-OH-dG in DNA. When isolated nuclei were incubated with CuCl2 plus H2O2, nuclear DNA cleavage was observed. Incubation of isolated nuclei with Cu,Zn-SOD that had been pre-incubated with glucose also resulted in nuclear DNA cleavage. These results suggest that hydroxy radical is produced through a Fenton reaction by Cu2+ and H2O2 released from the glycated Cu,Zn-SOD, and participates in nuclear DNA cleavage. This mechanism may partly explain the deterioration of organs under diabetic conditions.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1994

gamma-Glutamylcysteine ethyl ester for myocardial protection in dogs during ischemia and reperfusion.

OBJECTIVES: The aim of this study was to examine the infarct-limiting effects of gamma-glutamylcysteine ethyl ester, a newly discovered synthetic precursor of glutathione biosynthesis, in a canine model of myocardial infarction. BACKGROUND: Reduced glutathione plays an important role in protecting cells against damage induced by reactive oxygen species during myocardial ischemia and reperfusion. Gamma-glutamylcysteine ethyl ester is capable of penetrating into cells in its intact form and increasing intracellular glutathione levels. METHODS: Dogs were subjected to a 90-min coronary occlusion followed by 5 h of reperfusion. An intravenous bolus injection of gamma-glutamylcysteine ethyl ester (3 or 10 mg/kg body weight) was administered immediately before reperfusion. Regional myocardial blood flow was measured with the use of colored microspheres. RESULTS: Gamma-glutamylcysteine ethyl ester effectively reduced infarct size in a dose-dependent manner (mean +/- SEM 26.4 +/- 3.5% in the low dose group [3 mg/kg, n = 10] and 19.0 +/- 3.4% in the high dose group [10 mg/kg, n = 10]; each p < 0.05 vs. the value in the control group [40.6 +/- 4.8%, n = 10]). There were no differences between the control and treated groups in hemodynamic variables or regional myocardial blood flow either during the ischemic period or after reperfusion. The reduced glutathione content of ischemic myocardium in the control group (0.62 +/- 0.11 mumol/g, p < 0.01) was significantly lower than that in nonischemic myocardium (1.46 +/- 0.07 mumol/g), and it was preserved by treatment in a dose-dependent manner (3 mg/kg, 0.83 +/- 0.06 mumol/g; 10 mg/kg, 0.92 +/- 0.14 mumol/g; each p < 0.05 vs. control level). There were no differences in oxidized glutathione content between nonischemic and ischemic myocardium or among the three groups. CONCLUSIONS: Gamma-glutamylcysteine ethyl ester, a precursor of glutathione, significantly attenuates myocardial ischemia and reperfusion injury when administered immediately before reperfusion.

Animals↗

PubMed1994

Role of Fas ligand in apoptosis induced by hepatitis C virus infection.

To investigate the role that Fas ligand plays in the apoptosis of hepatocytes induced by hepatitis C virus infection, we isolated a cDNA clone for human Fas ligand and examined the expression of Fas ligand in liver-infiltrating mononuclear cells obtained from patients with chronic hepatitis C. The amino acid sequence of human Fas ligand showed 76% and 77% identity with those of rat and mouse Fas ligand, respectively. When the expression of Fas ligand transcripts was tested by reverse transcription-polymerase chain reaction, the amplified signal was detected in liver-infiltrating mononuclear cells and peripheral blood mononuclear cells, whereas only a weak signal or none at all was detected in liver tissues. These findings suggest that the Fas ligand-Fas antigen system may play an important role in liver cell injury by hepatitis C virus infection.

Amino Acid Sequence↗