Search PubMed⌕ Search

Biomedical subjects

Y Sakamoto

Publications and source records attributed to Y Sakamoto.

At least 109 records · Page 6Linked to original sources
PubMed2000

Morphological and immunocytochemical analyses on the effects of diet-induced hypocalcemia on enamel maturation in the rat incisor.

During the maturation stage of amelogenesis, the loss of matrix proteins combined with an accentuated but regulated influx of calcium and phosphate ions into the enamel layer results in the "hardest" tissue of the body. The aim of the present investigation was to examine the effects of chronic hypocalcemia on the maturation of enamel. Twenty-one-day old male Wistar rats were given a calcium-free diet and deionized water for 28 days, while control animals received a normal chow. The rats were perfused with aldehyde and the mandibular incisors were processed for histochemical and ultrastructural analyses and for postembedding colloidal gold immunolabeling with antibodies to amelogenin, ameloblastin, and albumin. The maturation stage enamel organ in hypocalcemic rats exhibited areas with an apparent increase in cell number and the presence of cyst-like structures. In both cases the cells expressed signals for ameloblastin and amelogenin. The content of the cysts was periodic acid-Schiff- and periodic acid-silver nitrate-methanamine-positive and immunolabeled for amelogenin, ameloblastin, and albumin. Masses of a similar material were also found at the enamel surface in depressions of the ameloblast layer. In addition, there were accumulations of glycoproteinaceous matrix at the interface between ameloblasts and enamel. In decalcified specimens, the superficial portion of the enamel matrix sometimes exhibited the presence of tubular crystal "ghosts." The basal lamina, normally separating ameloblasts and enamel during the maturation stage, was missing in some areas. Enamel crystals extended within membrane invaginations at the apical surface of ameloblasts in these areas. Immunolabeling for amelogenin, ameloblastin, and albumin over enamel was variable and showed a heterogeneous distribution. In contrast, enamel in control rats exhibited a homogeneous labeling for amelogenin, a concentration of ameloblastin at the surface, and weak reactivity for albumin. These results suggest that diet-induced chronic hypocalcemia interferes with both cellular and extracellular events during enamel maturation.

Albumins↗
PubMed2000

Release of endothelins and platelet-activating factor by a rat pleural mesothelial cell line.

Thrombin is a multifunctional serine protease. It is generated in inflammatory processes and induces the proliferation and chemotaxis of a variety of cells including mesothelial cells (MTCs). MTCs are epithelial cells derived from the mesoderm, as are the vascular endothelial cells. Since thrombin acts on endothelial cells to produce platelet-activating factor (PAF) and endothelin (ET)-1, it was hypothesized that MTCs also produce PAF and ET via the action of thrombin. Rat pleural MTC (RMTC, 4/4 R.M.-4) monolayers were cultural in tissue culture dishes for various periods. The supernatants were fractionated by means of high-performance liquid chromatography to determine the ET isoforms and PAF species present. Immunoreactive ET was measured using an enzyme-linked immunosorbent assay, and PAF was measured by means of a bioassay using a platelet aggregometer. ET-1, ET-2 and ET-3 were detected in RMTC-conditioned medium, and the predominant isoforms were ET-1 and ET-2. RMTCs mainly released C16:0 PAF into the supernatant. Immunoreactive ET and PAF were released via the action of thrombin. Synthetic PAF significantly induced secretion of ET, but the PAF receptor antagonists, WEB2086 and E6123, failed to modulate thrombin-induced ET release. These results indicate that thrombin acts on pleural rat mesothelial cells to release ET and PAF, which may play a role in the development of pleurisy.

Animals↗
PubMed2000

Correlation between neurotoxic events and intracerebral concentration of tacrolimus in rats.

The neurotoxicity associated with tacrolimus is one of the major limitations for its administration after organ transplantation. This study investigated the correlation between neurotoxicity and the intracerebral concentration of tacrolimus. Rats were given one of three doses of tacrolimus (5, 10, and 20 mg/kg/d) orally twice a day for 2 weeks and neurotoxic events were observed. The rats were sacrificed on either day 7 or 14. The trough values of the whole blood and the corresponding intracerebral concentrations were then measured. None of the rats receiving dosage of 5 mg/kg/d showed any neurotoxic symptoms throughout the two-week test period. In rats receiving a dosage of 10 mg/kg/d, however, all seven surviving rats presented tremors or seizures during the second week. In rats receiving a dosage of 20 mg/kg/d, 40% of the rats presented tremors or seizures during the first week. The threshold concentration of tacrolimus in the brain resulting in neurotoxic events was therefore estimated as approximately 700 ng/g. At concentrations over this threshold value, the intensity of the neurological event increases with the concentrations of tacrolimus in the brain. Using a linear correlation between the whole blood and intracerebral concentrations (r=0.967) of tacrolimus, the pharmacological threshold for the whole blood trough level was estimated as approximately 20 ng/ml, which falls into the same value reported for the incidental threshold of neurotoxicity in renal transplant recipients [Böttiger et al., Br. J. Clin. Pharmacol., 48, 445--448 (1999)]. Therefore, it is suggested that the rat is a good animal model to quantitatively evaluate the risk of neurotoxicity associated with tacrolimus in human, and that frequent measurement of whole blood tacrolimus concentrations is important for predicting and preventing neurotoxic events.

Animals↗
PubMed2000

Anterior tributaries of the portal vein at the superior margin of the pancreas: is "tunneling" procedure safe during pancreatic surgery?

BACKGROUND: It is widely believed that using the "tunneling" procedure during pancreatoduodenectomy is a safe maneuver because the anterior tributaries of the portal vein (PV) are absent or very rare. METHODS: The head of the pancreas with the duodenum and the common bile duct (CBD) was obtained from 22 autopsy cases. Three colors of silicon-polymerase dyes were injected into the pancreatic artery, PV, and bile duct. The tributaries of the PV at the superior margin of the pancreas were studied. RESULTS: There was no anterior branch of the intrapancreatic PV. The anterior superior pancreaticoduodenal vein (ASPDV) gave a definite branch to the anterior aspect of the PV at the superior margin of the pancreas in 4 of 22 cases. When the posterior superior pancreaticoduodenal vein (PSPDV) was located in front of the CBD (5 of 22 cases), the ASPDV and PSPDV had a thick common trunk at the right side of the PV. In these 5 cases, no individual branch from the ASPDV was found at the anterior aspect of the PV. CONCLUSION: PV sometimes has a definite anterior tributary at the superior margin of the pancreas; this must be kept in mind to perform the tunneling procedure during pancreatic surgery.

Adult↗
PubMed2000

Overexpression of MMP-9 correlates with growth of small hepatocellular carcinoma.

Matrix metalloproteinases (MMP) play an important role in tumor cell invasion and metastasis. We examined the expression of MMPs in hepatocellular carcinoma (HCC) to determine whether they may help indicate the progression of HCC and patient outcome. The expression of MMP-1, -2, -7, -9, and MT1-MMP were determined in 37 pairs of HCC and adjacent non-tumor tissue specimens by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). The tumor to non-tumor (T/N) ratios for mRNA expression of each MMP were compared with the clinicopathological findings and two-year disease-free survival rates. Immunohistochemical analysis for MMP-1 and -9 was performed in 30 specimens. MMP-1 and -9 expression was significantly higher in tumor tissue than in non-tumor tissue (p=0.001 and 0.0078, respectively). By contrast, the expression of MMP-2 and -7 was significantly lower in tumor tissue than in non-tumor tissue (p=0. 003 and 0.03, respectively). A higher MMP-9 T/N ratio was significantly associated with small HCCs (</=2 cm) and higher serum AFP values (>/=20 ng/ml) (p=0.013 and 0.028, respectively). Immunohistochemical analysis suggested that well differentiated HCC showed stronger immunoreactivity for MMP-9 than moderately differentiated HCC. MMP T/N ratio was not significantly associated with the disease-free survival rates. Overexpression of MMP-9 mRNA (T/N ratio >/=2) may be associated with the progression of small HCC (</=2 cm).

Adult↗
PubMed2000

[Antitumor effects of TZT-1027, a novel dolastatin 10 derivative, on human tumor xenografts in nude mice].

TZT-1027 was evaluated for its antitumor effects in sixteen human tumors xenografted in nude mice from gastric (H-81, H-106, H-30, H-154), breast (H-31, H-62), colon (H-110, H-143), lung (LC-376, H-74, Mqnu-1, LC-351), liver (H-181), renal cell (H-12) and ovarian (H-OC-3, SOC-4) cancer lines. In the latter three and lung (Mqnu-1, LC-351) cancers the results were compared with those obtained with CPT-11, VCR, CDDP, ADM. TZT-1027 showed effective antitumor activity (IR > or = 58%) against fifteen of the tumor lines, all but LC-351, and showed markedly effective activity (IR > or = 80%) against twelve tumor lines, including drug-resistant colon (H-110), lung (H-74) and ovarian (SOC-4) cancer lines. The complete regression was shown in five H-OC-3 tumor-bearing mice out of seven. Moreover, TZT-1027 was shown to be more potent in three cancer models (Mqnu-1, H-81, SOC-4) than CPT-11, and to have markedly effective antitumor activity in two cancers (H-12, H-OC-3) in which VCR was ineffective and in ovarian cancer (SOC-4) in which CPT-11, CDDP and ADM were ineffective. The administration of TZT-1027 induced fewer side effects; transient reduction of body weight was observed in four lines out of sixteen tested. These results suggest that TZT-1027 is an excellent candidate for clinical trials for the treatment of cancer.

Animals↗
PubMed2000

[Midterm results of total aortic root replacement with pulmonary autograft (Ross operation)].

Between February 1995 and December 1999, 18 patients underwent Ross operation. Age at the operation ranged from 2 to 31 years. Diagnosis includes congenital aortic stenosis and/or regurgitation in 15, and adult aortic regurgitation in 3. In all cases autograft was implanted by the method of total aortic root replacement, associated with annuloplasty for the dilated aortic annulus in 2 and aortoventriculotomy by the Konno procedure in 3 (Ross-Konno). Right ventricular outflow tract was reconstructed by a pulmonary homograft in 12, a xenopericardial conduit in 3, or the other reconstructive procedures with autologous tissue and outflow patch in 3. There was no operative and late death. Reoperation was needed in 1 patient due to stenosis of pericardial conduit 4 years after the initial operation. Pressure gradient across implanted autograft valve was negligible (4.8 +/- 0.5 mmHg), and echocardiography revealed no aortic regurgitation in 12 cases and trivial to mild in 6, over a mean follow-up period of 23 +/- 18 months (range 2 to 60 months), signifying excellent durability of implanted autograft. Right ventricular outflow tract reconstruction with the homograft resulted in excellent mid-term performance as showing pressure gradient of 9.0 +/- 4.6 mmHg and no regurgitation in 11 of 12 cases, whereas pressure gradient was 17.9 +/- 13.1 mmHg in the patients underwent the other reconstructive procedures. We conclude that Ross procedure associated with the concomitant procedures to adjust the size discrepancy between the native aortic annulus and autograft has provided good midterm results with excellent autograft durability. And this procedure was thought to be a preferable method for children as well as young adults with congenital aortic stenosis.

Adolescent↗
PubMed2000

Streptozotocin-induced diabetic hyperglycaemia produces more EEG activity than normoglycaemia and hypoglycaemia during and after anoxia loading in rats.

The brain requires oxygen and glucose for energy metabolism. Electroencephalogram (EEG) was recorded to determine the effect of glucose concentration on the cerebral function in hypoxic episode. Rats were divided into 3 groups: a streptozotocin-induced diabetic hyperglycaemic group, a normoglycaemic group, and an insulin-induced hypoglycaemic group. Hypoxia was induced by ventilating with 100% N2 for 3 min. EEG amplitude both 5 and 10 min after anoxia loading was higher in the diabetic hyperglycaemic than in the normoglycaemic group, though not significantly. Time for decreasing the EEG amplitude during anoxia loading was significantly longer in the hyperglycaemic than in the normoglycaemic group. Time for recovering the EEG amplitude after anoxia loading was significantly shorter in the hyperglycaemic group and was longer, though not significantly, in the hypoglycaemic group than in the normoglycaemic one. These results suggest the brain is more tolerant to hypoxia during diabetic hyperglycaemia than during normoglycaemia.

Animals↗
PubMed2000

[Benefits of 0.5T MR diffusion-weighted images for super-acute-phase cerebral infarction].

Though diffusion-weighted images (DWI) have been increasingly used to detect super-acute-phase cerebral infarction in recent years, they have primarily been obtained through the use of high magnetic machines of more than 1.5T. In this study, we discussed the usefulness of DWI obtained using 0.5T MRI in comparison with CT, MRI (FLAIR and T2 weighted image) and SPECT (99mTc-HMPAO). DWI were able to detect ischemic lesions earlier than FLAIR or T2-weighted images. Scanning time was short at four seconds for eight slices, and the quality of image was sufficient for clinical usage. The most available b-value seems to be 800. There were less susceptibility artifacts in the 0.5T DWI than in the 1.5T DWI. From these data, we presume that it is possible to detect super-acute-phase cerebral ischemia on the 0.5T DWI, proving the clinical usefulness of DWI. Furthermore, DWI is considered useful in observing chronological changes in cerebral infarction, differentiation of abscess or brain tumor, diagnosis of moyamoya disease, degenerative disease and so on.

Acute-Phase Reaction↗
PubMed2000

[Inhibitory effect of suplatast tosilate on eosinophil migration].

Suplatast tosilate has been shown to inhibit generation of Th2-type cytokines in vitro and used in the treatment of allergic diseases. Although the exact mechanism remains unknown, this compound attenuates the eosinophil infiltration in the asthmatic airway. In the present study, we examined whether suplatast tosilate directly modulates eosinophil migration in response to inflammatory mediators in vitro. Suplatast did not modify the spontaneous migration of eosinophils. On the other hand, eosinophil migration in response to PAF (1 microM) was significantly inhibited by 1 microM suplatast. Similarly, IL-5 (100 pM)-induced eosinophil migration was inhibited by 1 microM suplatast. These results suggest that suplatast tosilate inhibits eosinophil locomotion in response to PAF or IL-5 and thereby attenuates infiltration of the cells in allergic inflammation.

Anti-Allergic Agents↗
PubMed2000

[Acute eosinophilic pneumonia induced by cigarette smoking--a challenge test utilizing another brand of cigarette].

A 15-year-old boy was hospitalized with complaints of fever, dry cough, and dyspnea. Chest X-ray films demonstrated diffuse infiltrates with peripheral dominance and blood gas analysis disclosed hypoxemia. Examination of bronchoalveolar lavage fluid revealed an increased eosinophil count. Transbronchial lung-biopsy specimens revealed the infiltration of eosinophils into alveolar walls. A conclusive diagnosis of acute eosinophilic pneumonia (AEP) was made on these grounds. We suspected the disease was associated with smoking because the patient had begun smoking cigarettes two weeks before admission. A challenge test was performed using a cigarette brand different from the one the patient had smoked, and was positive. Our findings supported the view that cigarette smoking in general can be a cause of AEP.

Acute Disease↗
PubMed2000

[A case of Terson's syndrome with an interesting MRI finding].

We report a case of a 62-year-old woman admitted to our hospital in a semicomatose state. CT scan and MRI on admission revealed a dense subarachnoid hemorrhage and intracerebral hematoma in the right frontal lobe. Digital subtraction angiography showed a saccular aneurysm located in the anterior communicating artery, so radical neck clipping of the aneurysm was performed via the right pterional approach. The operation was unevential. The patient complained of bilateral visual disturbance on the next day and FLAIR image of MRI demonstrated clearly crescent shaped and mobile high intense lesions corresponding to subhyaloid vitreous hemorrhage in both eye balls. The fundoscopic examination revealed an intravitreous hemorrhage which gradually disappeared over the next 12 days. Terson's syndrome after subarachnoid hemorrhage has been linked to an entity of poor prognosis, so it is beneficial that characteristic findings in FLAIR image of MRI can lead to correct diagnosis of Terson's syndrome earlier.

Female↗
PubMed1999

Ursodeoxycholic acid protects hepatocytes against oxidative injury via induction of antioxidants.

The therapeutic efficacy of ursodeoxycholic acid (UDCA) has been widely demonstrated in various liver diseases, suggesting that UDCA might protect hepatocytes against common mechanisms of liver damage. A candidate for such protection is oxidative injury induced by reactive oxygen species. This study was designed to assess the effects of UDCA on oxidative injury and antioxidative systems in cultured rat hepatocytes. The viability of the hepatocytes dose-dependently decreased after hydrogen peroxide or cadmium administration. Pretreatment with UDCA significantly prevented this decrease in viability. The amounts of glutathione (GSH) and protein thiol increased significantly, but the activities of antioxidative enzymes such as superoxide dismutase, glutathione peroxidase and catalase were unchanged in UDCA-treated hepatocytes. The mRNA levels of gamma-glutamylcysteine synthetase and metallothionein (MT) were significantly higher in UDCA-treated hepatocytes than in controls. In conclusion, UDCA increased hepatocyte levels of GSH and thiol-containing proteins such as MT, thereby protecting hepatocytes against oxidative injury. Our results provide a new perspective on the hepatoprotective effect of UDCA.

Animals↗
PubMed1999

Improved human islet isolation by a tube method for collagenase infusion.

BACKGROUND: Collagenase infusion into the pancreatic duct is an essential step in human islet isolation. We developed a new method for ductal canulation and collagenese infusion. METHODS: A total of 53 pancreata were divided into two groups: group 1 (n=23), the new tube method, and group 2 (n=30), the standard angiocatheter method. In group 1, a polyethylene tube was inserted into the duct and pushed to the tail. The tail was first expanded, followed by expansion of the body and then the head, by pulling out the tube. RESULTS: Total islet number and number/g pancreas (mean+/-SE) were significantly higher in group 1 (481,123+/-43,218 and 8,010+/-722) (mean+/-SE) than in group 2 (300,974+/-35,122 and 5,090+/-515, P<0.01). Total islet equivalent number and islet equivalent number per gram pancreas were also significantly higher in group 1 (319,176+/-39,354 and 5,455+/-652) than in group 2 (202,022+/-23,331 and 3,722+/-468, P<0.04). Islet purity and fragmentation showed no differences between the groups. CONCLUSIONS: The tube method improved islet yields. We recommended this method for human islet isolation.

Catheterization↗
PubMed1999

Expression of the MAGE gene family in human hepatocellular carcinoma.

BACKGROUND: The 12 members of the MAGE gene family encode tumor specific antigens that are recognized by autologous cytotoxic T lymphocytes (CTL). The MAGE genes are expressed not only in melanoma but in the other malignant tumors as well. There is, however, little information on their expression in hepatocellular carcinoma (HCC). The authors thus studied the expression of the MAGE gene family in human HCC and discuss the possibility of specific immunotherapy using MAGE peptides. METHODS: Tumor tissue samples of HCC and paired nontumor tissues of the liver were obtained from 22 HCC patients. Total RNA was extracted and cDNA was synthesized. Polymerase chain reaction amplification using each MAGE gene specific primer was then performed to detect the expression of each MAGE gene. Immunoblotting and immunohistochemical analysis were performed to confirm the expression of MAGE-3 gene product in HCC. RESULTS: The expression rate of each MAGE gene was as follows: MAGE-1 and -3 were expressed in approximately 68% of the tumors; MAGE-8 was expressed in 46%; and MAGE-2, -6, -10, -11, and -12 were expressed in approximately 30%. Nineteen (86%) of 22 tumors expressed at least 1 MAGE gene. On the other hand, no expression was detected in the noncarcinomatous liver tissue specimens. Actual expression of the gene product of MAGE-3 was detected in 50% of tumors. Clinicopathologic data on the MAGE positive and negative cases were compared. Significant differences were observed between MAGE expression status and a few clinicopathologic factors; however, further investigation is required to elucidate these correlations completely. CONCLUSIONS: These findings demonstrated that MAGE gene expression is frequent in HCC, thus suggesting that HCC patients may be good candidates for specific immunotherapy using MAGE peptides.

Aged↗
PubMed1999

Inhibition of focus formation of transformed cloned cells by contact with non-transformed BALB/c 3T3 A31-1-1 cells.

When transformed cells were co-cultured with various densities of non-transformed BALB/c 3T3 A31-1-1 cells, the number of transformed cell foci decreased as the density of the A31-1-1 cells was increased. Under the condition of separate co-cultivation in which transformed cloned cells could not make contact with A31-1-1 cells, no inhibitory effect was induced. We examined with a dye-transfer assay the formation of heterologous gap-junctional intercellular communication (GJIC), links between the transformed cells and A31-1-1 cells before and after focus formation. Heterologous GJIC was observed almost always before, but almost never after, focus formation. Using time-lapse photography to record the fate of transformed cloned cells that did not form foci in the co-cultivation, it was noted that most of them were living, but did not proliferate. These results suggested that focus formation of transformed cloned cells was inhibited by contact with non-transformed A31-1-1 cells.

3T3 Cells↗
PubMed1999

No-mortality liver resection for hepatocellular carcinoma in cirrhotic and noncirrhotic patients: is there a way? A prospective analysis of our approach.

BACKGROUND: Low resectability rates and significant morbidity and mortality rates often make surgery for hepatocellular carcinomas (HCCs) unfeasible. HYPOTHESIS: Our policy for surgical treatment of cirrhotic and noncirrhotic patients with HCC is adequate and safe. DESIGN: Prospective validation cohort study. SETTING: University hospital. PATIENTS: One hundred seven consecutive patients with HCCs. Associated cirrhosis was present in 64 (59.8%), and only 7 (6.5%) had normal livers. INTERVENTIONS: The presence of ascites, serum bilirubin level, and indocyanine green retention rate at 15 minutes were considered when selecting patients for surgery. Preoperative recovery of liver function was achieved with portal venous branch embolization, liver volumetry, bed rest, and control of serum aminotransferase levels. The surgical techniques mainly involved bloodless dissection using intraoperative ultrasonography and intermittent warm ischemia. The main perioperative care regimen was fresh frozen plasma infusion and strict limitation of blood transfusion. MAIN OUTCOME MEASURES: The 30-day postoperative mortality and morbidity rates. RESULTS: All the patients underwent surgery (37 major resections, 45 segmentectomies, and 25 limited resections), with no 30-day postoperative mortality, overall morbidity of 26.2%, and no major complications. Multiple logistic regression analysis revealed that only the type of operation was associated with a significantly higher morbidity risk (P = .05). CONCLUSION: With high resectability, low morbidity, and no mortality, our policy represents a solution to the drawbacks of surgical resection for treatment of HCCs, especially in patients with associated liver cirrhosis.

Adolescent↗