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Biomedical subjects

R Yamada

Publications and source records attributed to R Yamada.

At least 127 records · Page 7Linked to original sources
PubMed1997

Magnetic resonance cholangiography in hepatolithiasis.

OBJECTIVES: Our objective was to examine the usefulness of magnetic resonance cholangiography in hepatolithiasis. METHODS: Ten patients with hepatolithiasis were studied by ultrasonography, computed tomography, direct cholangiography, and magnetic resonance cholangiography to detect stones and to determine the morphological features of the bile ducts. In nine patients who underwent surgery, dilation and stenosis of the bile ducts were confirmed by intraoperative cholangioscopy, pathology, or both. RESULTS: Stones were demonstrated in seven patients by ultrasonography, in eight by computed tomography, in seven by direct cholangiography, and in all by magnetic resonance cholangiography. The locations of stones were identified in four patients by ultrasonography, in seven by computed tomography, in six by direct cholangiography, and in nine by magnetic resonance cholangiography. Among nine patients with dilation of the bile ducts, the dilation was shown by ultrasonography in seven, by computed tomography in eight, by direct cholangiography in six, and by magnetic resonance cholangiography in eight. Among seven patients with stenosis of the bile ducts, this stenosis was shown by direct cholangiography in four and by magnetic resonance cholangiography in six. Ultrasonography and computed tomography did not show the stenosis. Sensitivity for detection of biliary stenosis was significantly higher in magnetic resonance cholangiography. CONCLUSIONS: This study shows that magnetic resonance cholangiography not only detects stones, but can also delineate detailed information on the bile ducts, which is useful in the planning of treatment for hepatolithiasis.

Adult↗
PubMed1997

[Evaluation of hepatic encephalopathy and portal hemodynamics by Doppler ultrasonography after a transjugular intrahepatic portosystemic shunt].

TIPS (transjugular intrahepatic portosystemic shunt) is an efficacious treatment for esophagogastric varices, ascites and hypertensive gastrointestinal vasculopathy associated with portal hypertension. The main complication after the procedure is hepatic encephalopathy. We tried to elucidate the correlation between hepatic encephalopathy and changes in portal hemodynamics after TIPS, based on observation by Doppler ultrasonography. We carried out Doppler ultrasonography in 28 cases of TIPS to assess hepatopetal and hepatofugal blood flow in the right and left portal branches. Hepatic encephalopathy occurred after TIPS in 9 cases out of 28 (32%), and new onset of disease was observed in 6 of 9. Doppler ultrasonography revealed hepatofugal blood flow in both right and left portal branches in 6 cases, 5 of which showed encephalopathy. Hepatopetal blood flow of the right and left portal branches was observed in 17 of 28 cases after TIPS. Hepatic encephalopathy occurred in only 2 of 17 cases. The changes in portal vein hemodynamics after TIPS were investigated by color Doppler ultrasonography, which were considered to be very useful for prediction of hepatic encephalopathy and indication of medical treatment to prevent the occurrence of this disease.

Adult↗
PubMed1997

[A case of an adult neuroblastoma with bone-marrow metastases: 131I-MIBG scintigraphy in comparison with MRI].

To detect a primary neuroblastoma lesion and its metastases, 131I-MIBG scintigraphy was performed for a 24-year-old woman who had a high level of serum catecholamine. 131I-MIBG scintigrams showed high radioactivity in the left upper quadrant, pelvic bone, and vertebral bodies. A biopsy of the pelvic bone revealed metastasis from the neuroblastoma. After four chemotherapy courses, the accumulation of 131I-MIBG decreased after each course; however, scintigraphy performed after the last chemotherapy course showed focal mild uptake in the right sacroiliac. The presence of residual tumor in the sacroiliac was confirmed histologically. On the other hand, T1-weighted and T2-weighted MR images performed before the treatment showed low signal intensity and high signal intensity in the pelvic bone, respectively. After the fourth chemotherapy course, T2-weighted MR images showed low signal intensity in the pelvic bone; however, it was difficult to determinate whether it should improve. To assess the effect of treatment of neuroblastoma, 131I-MIBG scintigraphy was considered more useful than MRI.

3-Iodobenzylguanidine↗
PubMed1996

Phosphorothiolate ribozyme against the conserved sequence in V3 loop of HIV-1.

Fluorescent-labeled phosphorothiolate DNA-RNA chimeric hammerhead ribozyme (thio-Rz) was synthesized. The ribozyme recognizes relatively conserved sequences in the functionally important region (V3 loop) of envelope protein of HIV-1. The thio-Rz as well as wild-type ribozyme cleaved RNA transcripts (414 base) of V3 region in a dose-dependent manner. After delivery into the cells, both wild-type and thio-Rz were able to be readily detected. The positive signals faded within 12 h in the former case, while they lasted 24 h in the latter case. The inhibitory effect by thio-Rz on cell fusion between envelope-expressing CHO cells and CD4+ cells appeared to be time-dependent, and about 70% of inhibition was seen at 72 h. Possible applications of the ribozyme against HIV-1 infection were discussed.

Base Sequence↗
PubMed1996

Purification and properties of D-aspartate oxidase from Cryptococcus humicolus UJ1.

D-Aspartate oxidase (EC 1.4.3.1), which is highly specific to D-aspartate, was inducibly produced by a yeast strain which was isolated from soil and identified as Cryptococcus humicolus UJ1. The enzyme was purified to homogeneity as indicated on SDS-polyacrylamide gel electrophoresis. The molecular mass of the monomer subunit was determined to be 40 kDa. The native enzyme was suggested to be a homotetramer by its behavior on gel filtration. The enzyme was shown to be a flavoprotein by its absorption spectral properties, and the flavin was found to be tightly, but not covalently, bound FAD. The purified preparation had a specific activity of 76.1 mumol/min per mg protein with D-aspartate as substrate. Optimum pH was 7.5 and optimum temperature was around 35 degrees C. D-Glutamate was a very poor substrate for the enzyme. N-Methyl-D-aspartate was better than D-glutamate as substrate but markedly poorer than D-aspartate. Malonate was the most effective competitive inhibitor of the compounds tested. The N-terminal amino-acid sequence of the enzyme showed a significant homology with those of D-aspartate oxidases from beef kidney and Octopus vulgaris and those of D-amino-acid oxidases from various sources.

Amino Acid Oxidoreductases↗
PubMed1996

Activation of glutathione transferase P gene by lead requires glutathione transferase P enhancer I.

Glutathione transferase P (GST-P) is specifically induced in rat liver and kidney by lead cation. The increase of GST-P mRNA after lead administration is blocked by actinomycin D, suggesting that GST-P production by lead is regulated at the transcriptional level. To further determine which part of the flanking region of the GST-P gene has the lead-responsive cis-element in vivo, we utilized transgenic rats with five different constructs having GST-P and/or chloramphenicol acetyl-transferase coding sequence. We studied the effect of lead on these transgenic rats and on transfected NRK (normal rat kidney) cells and found that GST-P induction by lead is indeed regulated at the transcriptional level and that the GST-P enhancer I (GPEI) enhancer is an essential cis-element required for the activation of the GST-P gene by lead. GPEI consists of two AP-1 (c-Jun/c-Fos heterodimer) site-like sequences that are palindromically arranged and can bind AP-1, c-jun mRNA in the liver increased after lead administration and GST-P, and c-Jun had patchy expression in the same hepatocytes 24 h after lead exposure. These results suggest that activation of the GST-P gene by lead is mediated in major part by enhancer GPEI and that AP-1 may be involved at least partially. GPEI has been shown to have essential sequence information for the trans-activation of the GST-P gene during chemical hepatocarcinogenesis of the rat (Morimura, S., Suzuki, T., Hochi, S., Yuki, A., Nomura, K., Kitagawa, T., Nagatsu, I., Imagawa, M., and Muramatsu, M. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 2065-2068; Suzuki, T., Imagawa, M., Hirabayashi, M., Yuki, A., Hisatake, K., Nomura, K., Kitagawa, T., and Muramatsu, M. (1995) Cancer Res. 55, 2651-2655). The present study establishes that the same enhancer element does operate in the activation of the GST-P gene by lead regardless of the trans-activators involved.

Animals↗
PubMed1996

A prospective randomized trial of the preventive effect of pre-operative transcatheter arterial embolization against recurrence of hepatocellular carcinoma.

To clarify whether pre-operative transcatheter arterial embolization (TAE) improves survival after hepatectomy, a prospective randomized comparative study was done. Of a total of 115 registered patients having solitary hepatocellular carcinoma (HCC) 2 to 5 cm in diameter, 18 (15.7%) were excluded after randomization. As a result, 97 patients were chosen as subjects and divided into two groups: hepatectomy with (group A: n=50) and without (group B: n=47) pre-operative TAE. The period of observation of the patients who survived the surgery was between 4.0 and 6.6 years. The randomization appeared to have provided well-balanced groups of patients and the clinico-pathological characteristics of the two groups were quite similar. The necrotic part of the cancerous lesions, as confirmed by operative specimens, amounted to 74.8+/-33.4% (mean +/-SD) in group A and 6.8+/-7.2% in group B (P<0.01). However, the cancer-free survival rates after hepatectomy in both groups showed little difference (39.1+/-7.0 (%+/-SE) and 31.1+/-0.1, respectively). We speculate that TAE is not effective against such HCC accessory lesions as minute intrahepatic metastasis and tumor thrombus and that pre-operative TAE does not improve post-operative survival.

Adult↗
PubMed1996

MR imaging of liver cirrhosis.

PURPOSE: The objective of this study was to identify the factors affecting the visualization of regenerating nodules in cirrhotic liver by MR imaging. MATERIAL AND METHODS: MR images from patients with liver cirrhosis and normal subjects were studied, and signal intensity within the liver was measured and correlated with histologic findings. A reference phantom was also used as a standard. RESULTS: The signal intensity of the liver on T2-weighted (T2WI) spin-echo (SE) images was significantly increased in patients with liver cirrhosis. Multiple ring-like or reticular high-intensity areas (RHAs) were demonstrated on T2WI SE images in 44 of 125 cirrhotic livers. Histologic examination in 44 cases revealed various degrees of inflammatory changes in fibrous septa surrounding regenerative nodules in all specimens, vascular dilation in fibrous septa in 4 specimens, and no hemosiderin deposition in some specimens. The results of linear discriminant analysis showed that inflammatory changes in fibrous septa were significantly more pronounced in cases with RHAs on MR. CONCLUSION: RHAs seen on T2WI SE images may correspond to fibrous septa with inflammation. The signal intensity of fibrous septa surrounding regenerative nodules on T2WI SE images may be increased in liver cirrhosis due to inflammation or vascular dilation, contributing to the visualization of regenerating nodules as relatively low-intensity regions on MR.

Adult↗
PubMed1996

Novel approach for determination of correlation between in vivo and in vitro dissolution using the optimization technique.

A new approach to determination of good correlations between in vivo and in vitro dissolution was studied using the optimization technique. Ibuprofen, which exhibits dissolution rate-limiting absorption, was used as a model drug. Ibuprofen capsules of two different release types were prepared, and their in vivo dissolution profiles were obtained from measurements of plasma concentration following oral administration of the capsules to beagle dogs by the mathematical deconvolution method using solution data of oral administration as a weight function. For the dissolution test to correspond to the in vivo dissolution profiles, the test was carried out at 12 levels (9 different sets of conditions) and results were analyzed with the optimization technique to deal with two factors. The first-order rate constant (kappa d) and the dissolution time at 50% (t50%) of the in vivo dissolution were selected for use as the response variables. Regression analysis was performed to describe the in vitro dissolution characteristics as functions of the pH of dissolution medium and paddle rotation speed in the paddle method. The in vivo/in vitro correlation obtained from the kappa d was better than that obtained from the t50%. The optimum conditions for dissolution testing corresponding to the in vivo kappa d were determined to be a pH 6.6 for the dissolution medium and a 56 rpm paddle rotation rate. The experimental data obtained by dissolution testing was well fit by the predicted curve derived from in vivo and in vitro dissolution profiles. This dissolution test is applicable to the formulations containing ibuprofen of particle size within the experimental range.

Animals↗
PubMed1996

Technical note: use of a PCR-single strand conformation polymorphism (PCR-SSCP) for detection of a point mutation in the swine ryanodine receptor (RYR1) gene.

We used the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis for screening the point mutation (C1843 to T) in the porcine ryanodine receptor (RYR1) gene. The PCR products (659 bp) were heat-denatured and separated by polyacrylamide gel electrophoresis. On silver-stained gels, the point mutation within the RYR1 gene could be detected clearly by mobility shifts. The best conditions for detecting the point mutation were by using a 5% polyacrylamide gel without glycerol and loading at 3 degrees C. The RYR1 genotypes diagnosed by PCR-SSCP were identical to the genotypes diagnosed by restriction enzyme fragment length polymorphism in all cases examined (n = 606).

Animals↗
PubMed1996

Evaluation of tissue plasminogen activator and plasminogen activator inhibitor-I levels in acute myocardial infarction.

Fluctuations in tissue plasminogen activator (t-PA) activity, t-PA antigen, and plasminogen activator inhibitor-I (PAI-1) antigen levels were evaluated in blood samples obtained from 84 patients with initial uneventful acute myocardial infarction (AMI) and 35 patients with reinfarction and fatal infarction (patients with bad prognoses). Patients with initial AMI had significantly higher levels of t-PA activity than those of 14 patients with angina pectoris. Tissue plasminogen activator activity peaked between day 7 and 19 after the initial attack of AMI. Plasminogen activator inhibitor-I antigen level decreased significantly between day 2 and 19, then returned to the baseline levels of patients with angina pectoris nearly 4 weeks later. The t-PA activity levels of patients with reinfarction were significantly lower than those in patients without events between day 0 and 3 and between day 7 and 19. The percentage stenosis in the coronary arteries measured by coronary angiography was negatively correlated with t-PA activity. This information may help in selecting aggressive treatments such as thrombolysis by recombinant t-PA and predicting the prognosis for patients with AMI.

Aged↗
PubMed1996

[Color Doppler sonographic assessment of intrahepatic hemodynamics and shunt patency after transjugular intrahepatic portosystemic shunt (TIPS)].

The usefulness of color Doppler sonography for the assessment of intrahepatic hemodynamics and shunt patency was evaluated in a total of eight patients in whom the intrahepatic hemodynamics before and after transjugular intrahepatic portosystemic shunt (TIPS) could be serially examined by color Doppler sonography. In six of these patients the serial sonographic examinations could be followed for more than one year after TIPS creation. Within one month after TIPS creation, Vmax in the shunt was ranged from 87 cm/sec to 242 cm/sec (mean: 142.5 cm/ sec), and the flow direction in the right anterior portal vein was reversed in all patients. More than 70% stenosis of the shunt could be diagnosed by color Doppler sonography. When the shunt was confirmed by angiography to be more than 70% stenotic or occluded, Vmax in the shunt was decreased to less than 50 cm/sec and the blood flow in the right anterior portal vein become hepatopetal. From three months before stenosis or occlusion of the shunt, it was confirmed that Vmax in the shunt was less than 70 cm/sec or the blood flow of right anterior portal vein was hepatopetal. Color Doppler sonography was useful for the assessment of intrahepatic hemodynamics, and shunt patency and prediction of shunt stenosis or occlusion following TIPS creation.

Adult↗
PubMed1996

[Shunt patency after creation of a transjugular intrahepatic portosystemic shunt: evaluation with Doppler ultrasound].

TIPS (transjugular intrahepatic portosystemic shunt) is a new interventional radiologic procedure that is useful in the treatment of variceal bleeding and ascites due to portal hypertension. It is most important that the shunt remains patent for a long time after placement. The potential role of ultrasound in evaluating the patency of the shunt after TIPS has been studied. Duplex and color doppler sonography were performed in 20 patients with portal hypertension after TIPS. Imaging was done in 38 case. The findings were compared with those of follow-up angiography. Shunt patency was evaluated with Doppler US in 28 case. In 27 of them, the equivalent patent shunt was confirmed by angiography; the exception was one case of occlusion in follow-up angiography. Doppler signals in the shunt could not be detected in 10 cases. Follow-up angiography showed occlusion in 7 cases and patency in the other 3. Doppler US sensitivity was 90%, and its specificity was 88%. These results indicate that Doppler US is one of the most useful methods for evaluating shunt patency after TIPS.

Adult↗
PubMed1996

[Clinical evaluation of power Doppler sonography for the diagnosis of hepatocellular carcinoma].

We compared power Doppler sonography (PDS) with conventional color Doppler sonography (CDS) in the visualization of intratumoral blood flow of hepatocellular carcinoma (HCC) and evaluated the usefulness of PDS for assessing of the effects of TAE with Lipiodol and anticancer agents (Lp-TAE) and for the diagnosis of recurrence of HCC after Lp-TAE. The ability of PDS and CDS to visualize intratumoral blood flow was compared in 36 patients with HCC, and the usefulness of PDS for the diagnosis of HCC was evaluated. Also, in 17 patients with HCC who underwent Lp-TAE, the usefulness of PDS for evaluating the therapeutic effects of Lp-TAE and the diagnosis of recurrence after Lp-TAE was examined. The ability of PDS to visualize intratumoral blood flow and delineate tortuous and meandering intratumoral vasculature was superior to that of CDS. The effects of Lp-TAE could be evaluated and recurrence detected accurately and easily by PDS on the basis of residual intratumoral blood flow and the appearance of new blood flow. PDS is expected to achieve widespread acceptance as a useful imaging modality for the diagnosis of HCC, assessment of therapeutic effects of TAE, and detection of recurrence of HCC after TAE.

Carcinoma, Hepatocellular↗
PubMed1996

[Atherosclerosis obliterance; thrombolytic therapy].

Thrombolytic therapy used to be considered ineffective for chronic arteriosclerotic obiterance. However, direct infusion of a thrombotic agent into the thrombus through a vascular catheter was shown to be more effective than expected. We have performed high-dose intra-thrombotic urokinase injection for arteriosclerotic obiterance of iliac and femoropopliteal arterial region since 1985. In this procedure, urokinase is infused at 10,000 unit/ minute through a catheter inserted into the thrombus. In the 65 lesions treated by this method, the initial success rate was 85%, and the cumulative 1-year patency rate was 72%. The mean total dose of urokinase was 620,000 units. Here we discussed thrombolytic therapy for chronic arteriosclerosis obliterance based on our experience.

Arteriosclerosis Obliterans↗
PubMed1996

[Transjugular intrahepatic portosystemic shunt: a new therapy for portal hypertension].

Thirty-five patients with portal hypertension due to liver cirrhosis secondary to chronic viral hepatitis underwent transjuglar intrahepatic portosystemic shunt for the last 3-year period. Shunts were successfully completed in 31 of 35 patients at 89%. Portal vein pressure was markedly reduced on average in the all cases until 6 months after TIPS. The endoscopic findings of varices much improved in 90% of the patients. Long-term patency rates of TIPS were 97% after 4 weeks, 79% after 6 months, 76% after a year and 55% after 2 years, respectively. The authors concluded that TIPS was an effective and reliable means of lowering portal pressure, improving endoscopic findings of varices and controlling of refractory ascites.

Esophageal and Gastric Varices↗
PubMed1996

[A comparative study of caregivers of the elderly with dementia between 1982 and 1991].

The purpose of this study is to clarify the changes of the caregivers'status with comparison of two cross-sectional studies. The subjects were 658 (primary, in 1982) and 705 (secondary, in 1991) group members of "The Association of Families Caring for Elderly Persons with Dementia". The summary of results are as follows: 1) The mean life span of a person suffering dementia was found to be longer in 1991 than 1992. 2) In 1991, about 30 percent of the patients in all age groups were hospitalized and about 70 percent of the patients were treated at home. These facts indicated that the medical facilities had expanded their capacities during the 9 year period for receiving the elderly with dementia. 3) Family members who wished to live independently supported the idea that care should be given by a decreased number of individuals within the family. In that sense, the family's power of caregiving was decreased. 4) The range of main caregivers' informal social-support-network was remarkably expanded. 5) The more the service were expanded, the more the service were utilized by the caregivers. However, the quality and the quantity of the services provided are still not sufficient to meet the caregivers' need. 6) In balance, the difficulties caregivers used to face, seemed to be decreased in 1991.

Aged↗