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Biomedical subjects

T Chiba

Publications and source records attributed to T Chiba.

At least 199 records · Page 11Linked to original sources
PubMed1999

Effects of phosphatidylcholine/phosphatidylethanolamine composition in cholesteryl ester-micellar substrates on neutral cholesterol esterase activity.

The effect of phospholipid composition in cholesteryl ester (CE)-micellar substrates on neutral cholesterol esterase (N-CEase) activity was examined. N-CEase preparation was incubated with micelles composed of cholesteryl-[1-14C]-oleate, sodium taurocholate, and phosphatidylcholine (PC)/phosphatidylethanolamine (PE) at varying ratios (%PE:0 = PC only, 17, 33, 50, 66, 83). The activity increased dependently with the increase in PE content; the activity with the micelles containing the highest ratio of PE was 2.5-fold compared with the micelles consisting of PC only. Vmax with the micelles of 83, 66, and 50% PE was 3.1-, 2.7-, and 1.9-fold, respectively, compared with the micelles of PC only. Each micellar preparation was chromatographed through a Superose 6 column by the FPLC system. In 66 and 83% PE-containing micelles, PC, PE, CE, and part of sodium taurocholate eluted completely together in a single peak, whereas in micelles with 33 and 50% PE they eluted loosely together. The micelles with PC only or 17% PE formed PC-micelles without including CE and PE. It is concluded that PE plays a critical role in the formation of CE micelles with PC, and in the interaction with N-CEase. The CE-micelles with 66-83% PE serve as substrates for sensitive and reproducible N-CEase assay.

Adipose Tissue↗
PubMed1999

IkappaBalpha ubiquitination is catalyzed by an SCF-like complex containing Skp1, cullin-1, and two F-box/WD40-repeat proteins, betaTrCP1 and betaTrCP2.

Destruction of the transcriptional inhibitor IkappaB by the ubiquitin (Ub) system is required for signal-dependent activation of the multifunctional transcriptional factor NF-kappaB, but details of this ubiquitination are largely unknown. We report here that the IkappaBalpha-ubiquitin ligase (IkappaBalpha-E3) is an SCF-like complex containing Skp1, cullin-1, and two homologous F-box/WD40-repeat proteins, betaTrCP1 and betaTrCP2. Intriguingly, all these components are cooperatively recruited to bind to a phosphorylated IkappaBalpha (pIkappaBalpha) produced by tumor necrosis factor-alpha (TNF-alpha) stimulation. IkappaBalpha-E3 bound to pIkappaBalpha catalyzed in vitro ubiquitination of pIkappaBalpha in the presence of ATP, Ub, and E1-activating and E2-conjugating enzymes. Forced expression of betaTrCP1 and betaTrCP2 resulted in dramatic augmentation of the in vitro polyubiquitination activity of IkappaBalpha-E3. These results indicate that the long-sought IkappaBalpha-E3 is an SCF-like complex consisting of multiple proteins which are coordinately assembled during phosphorylation of IkappaBalpha in response to external signals.

Amino Acid Sequence↗
PubMed1999

In vivo and in vitro recruitment of an IkappaBalpha-ubiquitin ligase to IkappaBalpha phosphorylated by IKK, leading to ubiquitination.

Activation of the transcriptional factor NF-kappaB is triggered by signal-dependent degradation of its inhibitor protein IkappaB through the ubiquitin (Ub)-proteasome pathway. We found here that a phosphorylated IkappaBalpha immunoprecipitated (IP-pIkappaBalpha) from the crude extract of HeLa cells which had been treated with tumor necrosis factor-alpha (TNFalpha) caused a dramatic ubiquitination of itself, termed autoubiquitination, when incubated with ATP, Ub, and E1-activating and E2-conjugating enzymes. IP-pIkappaBalpha also catalyzed ubiquitination of an in vitro synthesized 35S-IkappaBalpha previously phosphorylated by IkappaB-kinase (IKK) which is referred to as transubiquitination. No appreciable activity of auto- and transubiquitination was observed in an unphosphorylated IP-IkappaBalpha. Moreover, the putative IkappaBalpha-Ub ligase (IkappaBalpha-E3) present in HeLa cell cytosol associated in vitro with an IKK-phosphorylated recombinant IkappaBalpha, a process independent of NF-kappaB binding to IkappaBalpha or TNFalpha stimulation. Replacement of the two Ser residues at positions 32 and 36 corresponding to IKK phosphorylation sites by Ala resulted in almost complete prevention of binding of an IkappaBalpha-E3 to IkappaBalpha. These results indicate that phosphorylation of IkappaBalpha is necessary and sufficient for recruitment of this IkappaBalpha-E3 to associate with IkappaBalpha.

Adenosine Triphosphate↗
PubMed1999

Internal processing of hepatitis C virus NS3 protein.

Hepatitis C virus (HCV) NS3 protein contains at least three enzymatic activities: NS2-3 protease, NS3 serine protease, and NTPase/RNA helicase. It has been shown that NS2/3 cleavage is mediated by NS2-3 protease, whereas NS3 serine protease is responsible for the other four cleavage sites of the nonstructural (NS) region. In this study, we showed that the internal cleavage of NS3 protein produced two products of 49 kDa (NS3a) and 23 kDa (NS3b) when the entire NS3 region (aa 1027-1657) or the whole open reading frame (aa 1-3010) was expressed in mammalian and insect cells. By means of site-directed mutagenesis, we demonstrated that NS3a/NS3b cleavage occurs within the RNA helicase sequence motif that is highly conserved in the Flaviviridae family and that neither NS2-3 protease nor NS3 serine protease was responsible for this cleavage. The NS3 protease of flaviviruses, dengue virus type 2, for example, has been shown to mediate the internal cleavage of NS3. The NS3 proteins of HCV and dengue virus may thus be cleaved internally at the same sequence by different mechanisms of proteolysis. Also discussed is a possible role for the internal processing of HCV NS3 in the viral life cycle and its pathogenesis.

Adenosine Triphosphatases↗
PubMed1999

Acute pancreatitis secondary to 5-aminosalicylic acid therapy in a patient with ulcerative colitis.

Therapy with oral 5-aminosalicylic acid (5-ASA) for ulcerative colitis has been reported to be effective and safe. We describe a case of biochemically proven mild acute pancreatitis occurring after 9 d of oral 5-ASA therapy for ulcerative colitis. A hypersensitivity mechanism seemed to be involved in the development of pancreatitis probably owing to erratic systemic absorption of the drug. We suggest clinical and biochemical monitoring for early diagnosis of pancreatitis in patients with ulcerative colitis receiving 5-ASA administration. This is the first report of acute pancreatitis developed by oral 5-ASA therapy for the treatment of ulcerative colitis in the literature of Japan.

Acute Disease↗
PubMed1999

Identification of peak bone mass QTL in a spontaneously osteoporotic mouse strain.

The whole genome scan for quantitative trait loci (QTLs) specifying peak bone mass was performed with the F2 intercrosses of SAMP6, an established murine model of senile osteoporosis, exhibiting a significantly lower peak bone mass, and SAMP2, exhibiting a higher peak bone mass. Cortical thickness index (CTI), a parameter of bone mass of femurs, was measured in 488 F2 progeny at 4 months of age, when the animals attained peak bone mass by microphotodensitometry. Genetic markers were typed at 90 loci spanning all chromosomes except the Y. By interval mapping of 246 male F2 mice, two loci were identified with significant linkage to peak bone mass, one on Chromosome (Chr) 11 and another on Chr 13, with a maximum lod score of 10.8 (22.2% of the total variance) and 5.8 (10.0%), respectively. Another locus on the X Chr was suggestive of a QTL associated oppositely with a low peak bone mass to the SAMP2 allele. This association was consistent with the distribution of peak bone mass in the F1 and F2. These findings should be useful to elucidate the genetics of osteoporosis.

Animals↗
PubMed1999

Genetic typing of the senescence-accelerated mouse (SAM) strains with microsatellite markers.

The Senescence-Accelerated Mouse (SAM) strains constitute a murine model of accelerated senescence originating from the ancestral AKR/J strains and consist of nine senescence-prone (SAMP) strains and four senescence-resistant (SAMR) strains. The chromosomes (Chrs) of the SAM strains were typed with 581 microsatellite markers amplified by PCR, and the fundamental genetic information of the SAM strains was obtained. One-third of the examined markers displayed polymorphism among the strains, and only two alleles were detected in almost all loci among the SAM and AKR/J strains. However, in 12 loci (5.6% of total 215 polymorphic markers), the third allele was detected among the SAM strains. The genetic typing and developmental history suggested that the SAM strains were related inbred strains developed by the accidental crossing between the AKR/J strain and other unknown strain(s). Comparison of the distribution of the loci in the SAMP and the SAMR series revealed notable differences in the four regions on Chrs 4, 14, 16, and 17. This indicated that some of these chromosomal sites might contain the genes responsible for accelerated senescence in the SAMP series.

Aging↗
PubMed1999

Massive rectal bleeding due to ileal tuberculosis.

A patient with massive rectal bleeding due to ileal tuberculosis is reported. Technetium-99m labelled red blood cell scintigraphy indicated hemorrhage from the ileum, and laparotomy was then carried out. A 70-cm segment of ileum containing ulcers and erosions was resected, and epitheloid granuloma with Langhans-type giant cell was found in the resected specimen. Massive rectal bleeding is considered a rare presenting symptom of intestinal tuberculosis. Intestinal tuberculosis, including small intestinal tuberculosis, although uncommon, should be taken into consideration as a cause of rectal bleeding.

Feces↗
PubMed1999

The vast majority of gastric T cells are polarized to produce T helper 1 type cytokines upon antigenic stimulation despite the absence of Helicobacter pylori infection.

Helicobacter pylori infection is associated with chronic infiltration by various cell types, including T cells, whose cytokine production may regulate the inflammatory reaction as well as local immune response to the bacterium. We prospectively analyzed the constituents of the cellular infiltrates and the cytokines produced by T cells in antral biopsies obtained from 73 subjects with and without H. pylori infection, before and after eradication therapy, and compared them with a histological grade of gastritis. We found that T cells predominated in cell number, followed by granulocytes/monocytes and plasma cells in both H. pylori-infected and H. pylori-uninfected subjects. Despite the absence of H. pylori infection, more than 70% of gastric CD4-positive T cells obtained from uninfected tissue produced interferon-gamma (IFN-gamma) in the cytosol. Upon receptor cross-linking of a CD3 and a CD28 molecule, T cells in both infected and uninfected tissue continuously secreted a far greater amount of IFN-gamma than those in peripheral blood mononuclear cell controls for a period of cell culture, whereas the increase in interleukin-4 (IL-4) was very small, and no increase in IL-2 secretion was seen. In H. pylori-infected patients, IFN-gamma secretion was correlated with the grade of mononuclear cell infiltration and decreased to an uninfected control level after eradication therapy. We did not see the effect of eradication on IL-4 secretion. Anti-H. pylori antibody of the IgG2 subclass was remarkably increased in H. pylori-infected subjects. These results together suggest that gastric T cells are already differentiated to produce a large amount of IFN-gamma by a mechanism unrelated to H. pylori infection. H. pylori infection appeared to activate T cells to secrete even more IFN-gamma, which may contribute to maintaining a perpetual inflammation in H. pylori-infected stomach.

Adult↗
PubMed1999

Mouse senile amyloid deposition is suppressed by adenovirus-mediated overexpression of amyloid-resistant apolipoprotein A-II.

Apolipoprotein A-II (apoA-II), the second most abundant apolipoprotein of serum high density lipoprotein, deposits as an amyloid fibril (AApoAII) in old mice. Mouse strains with a high incidence of senile amyloidosis have the type C apoA-II gene (Apoa2(c)), whereas the strains with a low incidence of amyloidosis have the type B apoA-II gene (Apoa2(b)). In this study, to investigate whether the type B apoA-II protein inhibits the extension of amyloid fibrils, we constructed an adenovirus vector bearing the Apoa2(b) cDNA (Adex1CATApoa2(b)), which is expressed under the control of a hepatocyte-specific promoter. The mice were infected with Adex1CATApoa2(b) before induction of amyloidosis by the injection of AApoAII amyloid fibril seeds. Compared with the mice infected with the control virus, amyloid deposition was suppressed significantly in the mice infected with Adex1CATApoa2(b). Fluorometry using thioflavine T also revealed that AApoAII fibril extension was inhibited by the addition of type B apoA-II in vitro. Thus, we propose that Apoa2(b) contributes as an active inhibitor of amyloid fibril extension and overexpression of amyloid-resistant gene variant may be an attractive therapeutic target in amyloidosis.

Adenoviridae↗
PubMed1999

Midkine gene expression in the healing process of gastric ulcer.

Midkine is a newly cloned growth-promoting factor for fibroblastic cells. This study was performed to investigate the possible role of midkine in the stomach. Rats with acute or chronic gastric mucosal lesions were used. Histologically, acute mucosal lesions are not accompanied by the formation of granulation tissue; conversely, chronic mucosal lesions are accompanied by the formation of granulation tissue. The expression of the midkine gene was found in the normal intact gastrointestinal tract, especially the submucosal and muscle layers. Midkine mRNA increased during the healing stage of chronic gastric ulcer accompanied by a fibroblastic reaction. Furthermore, the fibroblast cell line MRC-5 expressed midkine mRNA strongly. Therefore, midkine may have some role in the healing of gastric deep ulcers that is accompanied by fibroblast proliferation.

Acetic Acid↗
PubMed1999

Transabdominal oxygenation using perfluorocarbons.

PURPOSE: Evaluation of the intraabdominal (intraperitoneal and intraluminal) administration of oxygen-saturated perfluorocarbon on both portal and arterial blood oxygenation. METHODS: Eight male rabbits were divided into the test (n = 5) and control (n = 3) groups. Each underwent intrajejunal, intraperitoneal, and intravascular (artery, portal vein) catheter placements along with ligation of the duodenum and the terminal ileum under general anesthesia. The test group received oxygen-saturated perfluorotripropylamine (FTPA), and the control group received oxygen desaturated FTPA. The oxygen delivery was assessed by serial blood gas measurements before and after the administration of FTPA. RESULTS: The administration of oxygen-saturated FTPA significantly increased the partial pressure of oxygen within both the arterial and the portal venous blood (PaO2, PpVO2) without significant changes in PCO2 values. Oxygen desaturated FTPA failed to show any effects on blood gas values. Compared with oxygen desaturated FTPA, oxygen-saturated FTPA increased PaO2, PpVO2, and oxygen saturation (artery, portal vein) significantly at some, but not all of the time-points measured. CONCLUSIONS: The intraabdominal administration of saturated FTPA improved both the portal venous and the arterial oxygenation. This new mode of oxygenation may be helpful as an adjunct to conventional oxygen delivery systems.

Animals↗
PubMed1999

Growth inhibitory effects of somatostatin on human leukemia cell lines mediated by somatostatin receptor subtype 1.

Reverse transcription polymerase chain reaction analysis revealed that only somatostatin receptor (SSTR) 1 mRNA was expressed in Ball-1 B-, Jurkat T-, and HL60 leukemia cell lines. In contrast, human normal mononuclear cells expressed the mRNA of all five subtypes of SSTR, although the expression level of SSTR1 was the highest. A binding study, revealed that [125I]-somatostatin bound specifically to HL60 cells and this binding was inhibited concentration-dependently by unlabeled somatostatin (SS). A [3H]thymidine incorporation study showed that SS significantly and concentration-dependently inhibited HL60 and BALL-1 leukemia cell growth. Furthermore, this inhibition of leukemia cell growth was associated with reduces c-fos gene expression. These data indicate that leukemia cells express SSTR1 and SS reduce c-fos gene expression with resultant suppression of leukemia cell growth, possibly mediated by the SSTRI.

Cell Division↗