Biomedical subjects

Yoshimune Shiratori

Publications and source records attributed to Yoshimune Shiratori.

8 recordsLinked to original sources

PubMed2006

Pancreas: optimal scan delay for contrast-enhanced multi-detector row CT.

PURPOSE: To prospectively determine optimal scan delays for multiphasic contrast medium-enhanced imaging of the pancreas with multi-detector row computed tomography (CT). MATERIALS AND METHODS: This study was approved by an institutional review committee, and patients gave written informed consent. One hundred ninety-one patients underwent three-phase CT of the pancreas after receiving intravenous contrast medium with a fixed duration injection of 30 seconds. Patients were prospectively assigned among four groups with scan delays of 25, 45, and 65 seconds (group 1); 30, 50, and 70 seconds (group 2); 35, 55, and 75 seconds (group 3); and 40, 60, and 80 seconds (group 4). Mean CT numbers of abdominal aorta, spleen, pancreatic parenchyma, superior mesenteric artery and vein, splenic vein, and hepatic parenchyma were measured, and increases in contrast enhancement on enhanced images were assessed. Qualitative analysis was performed with a four-point scale. RESULTS: Abdominal aorta and superior mesenteric artery enhanced at a mean of 35 seconds from the start of injection (both P < .001). Pancreatic parenchyma enhanced most intensely at 35-45 seconds (P < .001) with a peak enhancement at the mean of 40 seconds. Liver parenchyma enhanced most intensely at 55-65 seconds with a peak at 60 seconds (P < .001). The mean time to peak enhancement was 45 seconds for the splenic vein and 55 seconds for the superior mesenteric vein. Qualitative results were in good agreement with quantitative results (both P < .001). CONCLUSION: With the injection protocol used in this study, optimal scan delays for imaging the pancreas were 30-35 seconds for the abdominal aorta and the superior mesenteric artery, 35-45 seconds for the pancreas, 45 seconds for the splenic vein, and 55 seconds or later for the liver.

Adult↗

PubMed2006

Double hepatic arterial phase MRI of the liver with switching of reversed centric and centric K-space reordering.

OBJECTIVE: The purpose of our study was to evaluate the clinical feasibility and usefulness of a 2D spoiled gradient-recalled echo MR sequence with serial switching of reversed centric and centric k-space reordering for high-spatial-resolution gadolinium-enhanced double hepatic arterial phase (HAP) MRI of the liver. SUBJECTS AND METHODS: MR images (frequency, 512; phase encoding without interpolation, 224; 6-mm thickness with 1-mm gap; 30 slices per 18 seconds) were obtained with multiphase imaging in which central k-space line data were filled 10, 21, 49, and 181 seconds after arrival of contrast medium in the abdominal aorta for the early HAP (reversed centric reordering, center of k-space lines acquired at end of acquisition), late HAP (centric reordering, center of k-space lines at beginning of acquisition), portal venous phase (centric reordering), and equilibrium phase (centric reordering), respectively, in 102 consecutive patients with suspected liver disease, including 48 untreated hepatocellular carcinomas (HCCs) in 35 patients. Images were quantitatively assessed for degree of contrast enhancement in the abdominal aorta, spleen, portal trunk, liver parenchyma, hepatic veins, and HCCs. Images were qualitatively assessed for the effectiveness of contrast enhancement in each phase and for degree of image degradation due to artifacts. RESULTS: Enhancement of the abdominal aorta peaked in the early HAP, of the portal trunk in the late HAP, and of the hepatic parenchyma and veins in the portal venous phase. Mean HCC-to-liver contrast peaked in the early HAP and turned to a negative value in the portal venous and equilibrium phases. Sufficient image quality was achieved in 99 (97%) of the patients. One of the other three patients had motion artifacts due to body motion, and the other two had unsatisfactory respiratory suspension. Scan timing for early and late HAP was optimal in 74 (73%) of the patients, for late HAP lagged in 20 (20%), for early HAP was premature in six (6%), and for early HAP lagged in five (5%) of the patients. CONCLUSION: We confirmed the feasibility and usefulness of a 2D gadolinium-enhanced double HAP spoiled gradient-recalled echo sequence incorporating serial switching of reversed centric and centric k-space reordering. This method has the potential for use in high-spatial-resolution double HAP MRI for the diagnosis of hypervascular HCC.

Adult↗

PubMed2005

Prevention of second primary tumors by an acyclic retinoid in patients with hepatocellular carcinoma. Updated analysis of the long-term follow-up data.

Oral administration with acyclic retinoid, a synthetic vitamin A analog, for a limited period of 12 months (48 weeks) prevented the development of second primary hepatocellular carcinoma (HCC) and also improved the survival of patients who underwent curative treatments of the initial tumor. Following that randomized controlled study reported in 1996 and 1999, we have continued to follow up the patients by medical imaging and blood chemical analyses, and found that the preventive effect of acyclic retinoid lasted up to 199 weeks after randomization (or 151 weeks after completion of retinoid administration). The retinoid's effect was not mediated by reduction in hepatic necro-inflammation since no significant decrease in serum aminotransferase activity was seen in the retinoid group. Such observation seems quite distinct from the cancer-preventive mechanism of interferon, a potent immunopreventive agent for HCC. We have also shown here the reduction by the retinoid in serum levels of lectin-reactive alpha-fetoprotein (AFP-L3) and protein induced by vitamin K absence or antagonist-II (PIVKA-II), both of which indicate the presence of latent HCC cells. These results suggest that acyclic retinoid may delete such malignant clones before they expand to clinically detectable tumors and thereby inhibited second primary HCC. Once such latent clones are eradicated, it may well take at least several years for the next cancer clone to arise clinically. This may possibly explain a reason for the long-term effect of the retinoid even after the limited period of administration.

Antineoplastic Agents↗

PubMed2002

Retinoids in liver fibrosis and cancer.

Pathobiological functions and metabolism of retinoids (vitamin A and its derivatives) in liver fibrosis and hepatocellular carcinoma (HCC) are discussed in the present review. Retinoic acid (RA, active metabolite) exacerbates liver fibrosis that is not accompanied by hepatic necroinflammation, in which RA acts directly on hepatic stellate cells (HSCs); RA enhances plasminogen activator/plasmin levels and thereby induces proteolytic activation of latent transforming growth factor-beta (TGF-beta), a strong fibrogenic cytokine, resulting in enhanced collagen production. We have developed a protease inhibitor, camostat mesilate, that suppresses TGF-beta activation and thereby inhibits the transformation of HSCs, leading to reduced matrix production by the cells. The compound is effective not only in preventing but also in reducing hepatic fibrosis in rats when administered orally. HCC is refractory to RA due to its local depletion in the tumors and also due to malfunction of its nuclear receptor, retinoid X receptor-alpha (RXRalpha) Oral supplementation of a synthetic retinoid named acyclic retinoid led to the disappearance of serum lectin-reactive alpha-fetoprotein (AFP-L3) and subsequently suppressed posttherapeutic recurrence of HCC in cirrhotic patients. These results suggest eradication of AFP-L3-producing latent malignant clones from the liver by the retinoid. We propose the concept of "clonal deletion" therapy for cancer chemoprevention, a new category of cancer chemotherapy.

Animals↗

PubMed2002

Therapeutic effect of intraarterial prednisolone injection in severe intestinal Behçet's disease.

A 64-year-old woman with severe intestinal Behçet's disease who was unresponsive to conventional therapies, including intensive intravenous steroid injections, underwent intraarterial steroid injection therapy. After the infusion of prednisolone into the mesenteric arteries, her colon ulcers improved markedly, and the frequency of bloody stools decreased immediately. The present case suggests that intraarterial steroid injection therapy may be potentially useful in severe intestinal Behçet's disease.

Anti-Inflammatory Agents↗

PubMed2002

Acyclic retinoid induces partial differentiation, down-regulates telomerase reverse transcriptase mRNA expression and telomerase activity, and induces apoptosis in human hepatoma-derived cell lines.

BACKGROUND/AIMS: Acyclic retinoid (AR; all trans-3,7,11,15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid) prevented hepatocarcinogenesis in animal models and in a randomized clinical trial by eradicating premalignant and latent malignant clones of transformed cells from the liver. We investigated the possible mechanism of this clonal deletion at the cellular level. METHODS: Human hepatoma-derived cell lines, PLC/PRF/5, HuH-7, and JHH-7, were treated in vitro with AR. Secretion of albumin and that of lectin-reactive isoform of alpha-fetoprotein (AFP-L3) were measured as markers of differentiation and dedifferentiation of the cells, respectively. Telomerase reverse transcriptase (TERT) mRNA expression and telomerase activity were measured by reverse transcriptase polymerase chain reaction (RT-PCR) and stretch PCR assay, respectively. Caspase activities were measured by colorimetric protease assay. Mitochondrial membrane permeability transition was examined by Rhodamine staining. RESULTS: Production of albumin was recovered while that of AFP-L3 was reduced after exposure of the cells to 10 microM AR for 2 days. This differentiation was maintained for another 2 days without retinoid. In parallel, both TERT mRNA expression and telomerase activity were down-regulated. The cells subsequently died due to apoptosis after 4-6 experimental days. Serial increases in mitochondrial membrane permeability and caspase-9 and -3 activities induced apoptosis. CONCLUSIONS: AR first induces differentiation and reduces telomerase activity. Subsequent apoptosis may contribute to the eradication of the clone.

Alitretinoin↗

PubMed2002

Synergistic induction of apoptosis by acyclic retinoid and interferon-beta in human hepatocellular carcinoma cells.

Acyclic retinoid, a synthetic retinoid analog, as well as interferon alfa (IFN-alpha) and IFN-beta induce apoptosis in hepatocellular carcinoma (HCC) cells and are used clinically in the prevention of HCC. Here, we show that acyclic retinoid acts synergistically with IFNs in suppressing the growth and inducing apoptosis (as characterized by DNA fragmentation and chromatin condensation) in 5 human HCC cell lines (JHH7, HuH7, PLC/PRF/5, HLE, and HLF). This synergism was only observed when cells were pretreated with the acyclic retinoid, whereas natural retinoic acids (all-trans and 9-cis retinoic acid) were ineffective. This promotion may be due to up-regulation of type 1 IFN receptor (IFNR) expression by the retinoid. Accordingly, incubation with antitype 1 IFNR antibody abolished the synergy. Enhanced IFNR expression was accompanied by increased expression and DNA-binding activity of STAT1, an intracellular signal transducing molecule of IFNR, and increased induction of 2', 5'-oligoadenyl-5'-triphosphate synthetase, which is a target gene of STAT1. Acyclic retinoid did not have any effects on the growth of normal human hepatocytes (Hc) probably because of a lack of IFNR and STAT1 up-regulation. In conclusion, these results provide a rationale for combined biochemoprevention of HCC using acyclic retinoid and IFN-beta.

Antineoplastic Agents↗

PubMed2002

Thick-section half-Fourier rapid acquisition with relaxation enhancement MR cholangiopancreatography: effects of i.v. administration of gadolinium chelate.

OBJECTIVE: Our purpose was to investigate the effects of i.v. administration of gadolinium chelate on thick-section MR cholangiopancreatography performed with half-Fourier rapid acquisition with relaxation enhancement sequence. SUBJECTS AND METHODS: Unenhanced and enhanced MR cholangiopancreatograms obtained in 50 consecutive patients were quantitatively analyzed with region-of-interest measurements and were qualitatively evaluated by three independent radiologists unaware the patient information. A phantom study was performed to verify the effects. RESULTS: The mean contrast-to-noise ratios of the gallbladder, common bile duct, and main pancreatic duct significantly increased after gadolinium chelate administration (p < 0.005). The mean depiction score of the main pancreatic duct increased significantly with one radiologist (p < 0.05) and marginally with another (p < 0.06), and the mean depiction scores of the background structures and renal pelvis significantly decreased with all three radiologists (p < 0.001). The phantom study showed the results, indicating that T2- and T2(*)-shortening effects of gadolinium chelate caused the effects in vivo. CONCLUSION: i.v. administration of gadolinium chelate improves the depiction of pancreaticobiliary ducts in some selected patients, while decreasing the depiction in others with less frequency. There may be a value of enhanced MR cholangiopancreatography when unenhanced MR cholangiopancreatography is not sufficient.

Adult↗