PubMed Health⌕ Search

Biomedical subjects

Masafumi Kobayashi

Publications and source records attributed to Masafumi Kobayashi.

8 recordsLinked to original sources
PubMed2004

Perfluoropentacene: high-performance p-n junctions and complementary circuits with pentacene.

We report the synthesis and characterization of perfluoropentacene as an n-type semiconductor for organic field-effect transistors (OFETs). Perfluoropentacene is a planar and crystalline material that adopts a herringbone structure as observed for pentacene. OFETs with perfluoropentacene were constructed using top-contact geometry, and an electron mobility of 0.11 cm2 V-1 s-1 was observed. Bipolar OFETs with perfluoropentacene and pentacene function at both negative and positive gate voltages. The improved p-n junctions are probably due to the similar d-spacings of both acenes. Complementary inverter circuits were fabricated, and the transfer characteristics exhibit a sharp inversion of the output signal with a high-voltage gain.

Journal Article↗
PubMed2002

Irritant-induced cyclooxygenase-2 is involved in the defense mechanism of the gastric mucosa in mice.

BACKGROUND: Endogenous and exogenous prostaglandins (PGs) have been shown to contribute to reducing the gastric injury caused by irritants given subsequently. The aim of this study was to clarify whether cyclooxygenase-2 (COX-2) protein induced by pretreatment was involved in the prevention of subsequent ethanol-caused gastric injury in mice. METHODS: Mice were pretreated with acidified ethanol or saline and then COX-2 protein expression in the stomach was immunohistochemically determined every 8h. Mice were administered 95% ethanol 24h after the acidified ethanol pretreatment, and gastric mucosal damage was evaluated macroscopically and histologically. The effects of NS-398 or indomethacin on the 95% ethanol-caused damage were also examined. RESULTS: Acidified ethanol pretreatment induced COX-2 protein expression in lamina propria macrophages of the gastric mucosa, with a peak level 24h after the pretreatment. The 95% ethanol treatment caused gastric mucosal damage. The degree of the damage was not different between mice pretreated with acidified ethanol and those pretreated with saline. However, NS-398 aggravated the ethanol-caused damage only in mice pretreated with acidified ethanol, while indomethacin aggravated the damage, evaluated histologically, irrespective of the pretreatment. CONCLUSIONS: Pretreatment-induced COX-2, in addition to COX-1, seemed to be involved in the defense mechanism through minimizing the damage caused by a subsequent irritant.

Animals↗
PubMed2002

Chylomicronemia caused by lipoprotein lipase gene mutation related to a hyper-response of insulin secretion to glucose.

A 39-year-old man with lipoprotein lipase (LPL) deficiency (height 177.7 cm, body weight 67 kg, and body mass index 21.2 kg/m2) showed severe hypertriglyceridemia (2,032 mg/dl). LPL activity and concentration were markedly low in postheparin plasma. LPL gene analysis revealed a homozygous mutation, Asp204 --> Glu in exon 5. Fasting plasma glucose (81 mg/dl) and insulin (2.7 microU/ml) levels were normal. Plasma glucose pattern during oral glucose (75 g) tolerance test was normal, however 30 minutes after glucose-loading the insulin secretion unexpectedly increased to 89.4 microU/ml. These data suggested that chylomicronemia might be related to a hyper-response of insulin secretion to glucose without obesity.

Adult↗
PubMed2002

[Long-term efficacy of transjugular intrahepatic portosystemic shunt for the treatment of refractory ascites].

Eighteen patients with refractory ascites (Child-Pugh score 9.9) defined by our criteria were treated with transjugular intrahepatic portosystemic shunt (TIPS). The long-term efficacy of the treatment was studied in these patients. The complete and partial response rate of refractory ascites was 73% at 6 months, 90% at 1 year and 100% at 2 years. The cumulative survival rate was 89% at 6 months, 78% at 1 year and 48% at 2 years. A statistically significant(p < 0.05) increase was observed in performance status score following TIPS: Mean performance status score prior to TIPS was 43%, as opposed to 62% at 3 months after TIPS and 85% at 2 years. Child-Pugh score and liver function tests showed no significant change. During follow-up, shunt stenosis was noted in 14 patients, requiring shunt revision. Ascites recurrence was observed in 70% of patients with shunt stenosis and shunt revision resulted in good control of ascites. Post-TIPS encephalopathy was seen in 15 patients during follow-up. In conclusion, TIPS is effective on the treatment of refractory ascites and results in an improvement in quality of life. TIPS also may improve survival of the patients with refractory ascites. However, shunt stenosis and encephalopathy are common and require careful follow-up and adequate treatment.

Adult↗
PubMed2001

A randomized clinical trial comparing transjugular intrahepatic portosystemic shunt with endoscopic sclerotherapy in the long-term management of patients with cirrhosis after recent variceal hemorrhage.

The aim of this study was to compare the efficacy of transjugular intrahepatic portosystemic shunt (TIPS) with that of endoscopic sclerotherapy (ES) in the long-term management of patients with cirrhosis after variceal bleeding. Seventy-eight consecutive cirrhotic patients with recent variceal bleeding were randomly allocated to either TIPS (n=38) or ES (n=40). All patients were in good condition at randomization. The mean follow-up was 1116+/-92 days in the TIPS group and 1047+/-102 days in the ES group. Differences in rebleeding from any source (18.4% vs. 32.5%) and esophageal variceal rebleeding (15.7% vs. 27.5%) were not significantly different between the two groups (P>0.05). The mortality rates were similar in both treatment groups. Shunt dysfunction was noted in 27 patients (71%) in the TIPS group. There were more numbers of rehospitalization during follow-up in the TIPS group than in the ES group (2.6+/-0.4 vs. 1.1+/-0.2) (P<0.01). TIPS and ES are equally effective in the prevention of variceal rebleeding. However, TIPS is associated with high incidence of shunt dysfunction, which lead to more rehospitalization. Therefore, TIPS may not be a first-line treatment for the prevention of variceal rebleeding in cirrhotic patients who are in stable condition.

Journal Article↗
PubMedDate not supplied

Mean corpuscular volume (MCV) and the risk of colorectal adenoma in menopausal women.

BACKGROUND/AIMS: It has been reported that alcohol intake and folate deficiency are associated with an increased risk of colorectal adenomas and carcinomas. Mean corpuscular volume is increased under these conditions. We have reported that the mean corpuscular volume was higher in patients with adenoma than without adenoma in middle-aged men. The aim of this study was to assess the association between mean corpuscular volume and risk of colorectal adenoma in menopausal women. METHODOLOGY: The subjects were 415 menopausal women who underwent both barium enema examination and total colonoscopy, and their blood samples were analyzed. The subjects were divided into two groups with or without adenoma, and were divided into four groups according to the mean corpuscular volume value. Various variables were compared among the groups, and the odds ratios of adenoma were calculated. RESULTS: The mean corpuscular volume was higher in patients with adenoma than without adenoma (P = 0.002). As for the mean corpuscular volume value, the odds ratio (95% CI) of patients with adenoma was 1.00 (referent); (mean corpuscular volume (fl) < 90), 1.50 (0.93-2.07); (> or = 90 but < 92.5), 1.52 (0.97-2.07); (> or = 92.5 but < 95) and 2.87 (2.25-3.45); (> or = 95). CONCLUSIONS: Mean corpuscular volume > or = 95 may be used as an index of the risk for colorectal adenomas in menopausal women.

Adenoma↗