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Biomedical subjects

T Chiba

Publications and source records attributed to T Chiba.

At least 289 records · Page 16Linked to original sources
PubMed1997

An Nrf2/small Maf heterodimer mediates the induction of phase II detoxifying enzyme genes through antioxidant response elements.

The induction of phase II detoxifying enzymes is an important defense mechanism against intake of xenobiotics. While this group of enzymes is believed to be under the transcriptional control of antioxidant response elements (AREs), this contention is experimentally unconfirmed. Since the ARE resembles the binding sequence of erythroid transcription factor NF-E2, we investigated the possibility that the phase II enzyme genes might be regulated by transcription factors that also bind to the NF-E2 sequence. The expression profiles of a number of transcription factors suggest that an Nrf2/small Maf heterodimer is the most likely candidate to fulfill this role in vivo. To directly test these questions, we disrupted the murine nrf2 gene in vivo. While the expression of phase II enzymes (e.g., glutathione S-transferase and NAD(P)H: quinone oxidoreductase) was markedly induced by a phenolic antioxidant in vivo in both wild type and heterozygous mutant mice, the induction was largely eliminated in the liver and intestine of homozygous nrf2-mutant mice. Nrf2 was found to bind to the ARE with high affinity only as a heterodimer with a small Maf protein, suggesting that Nrf2/small Maf activates gene expression directly through the ARE. These results demonstrate that Nrf2 is essential for the transcriptional induction of phase II enzymes and the presence of a coordinate transcriptional regulatory mechanism for phase II enzyme genes. The nrf2-deficient mice may prove to be a very useful model for the in vivo analysis of chemical carcinogenesis and resistance to anti-cancer drugs.

Animals↗
PubMed1997

Developmental gene expression of gastrin receptor in rat stomach.

Gastrin, which is present in fetal plasma, may have important roles in the development of gastric mucosa, since it is not only a potent stimulator of gastric acid secretion but also a growth promoting factor. Gastrin regulates various cellular functions via its receptors on cell membrane. Therefore, in order to elucidate a role for gastrin in the development of gastrointestinal system during gestation, Northern blot analysis was performed. The results of the study suggested that gastrin receptor is mainly present on parietal cells. Furthermore, proton pump and gastrin receptor gene expressions in parietal cells were strongly stimulated by the administration of exogenous gastrin. In conclusion, gastrin may be involved in the developmental change of parietal cells through its receptors.

Animals↗
PubMed1997

Radiation tolerance of cirrhotic livers in relation to the preserved functional capacity: analysis of patients with hepatocellular carcinoma treated by focused proton beam radiotherapy.

PURPOSE: To determine the preserved functional capacity of the liver as a probable determinant of radiation tolerance in patients with cirrhosis and hepatocellular carcinoma, who underwent proton beam radiotherapy. MATERIALS AND METHODS: We reviewed computed tomographic (CT) scans of 26 patients with cirrhosis and hepatocellular carcinoma during a period of 12-27 months after proton beam radiotherapy. Tumors were treated with focused proton beams with target doses of 140-186 TDF (time, dose, and fractionation). We measured the degree of hypertrophy of the untreated liver volume by measuring the total liver volume and the treated liver volume which was radiologically identified on contrast-enhanced CT scans. The risk of radiation-induced liver failure was estimated using the prediction score (PS) originally used for estimating posthepatectomy liver failure, substituting the planned treated liver volume for the resection liver volume. RESULTS: The degree of hypertrophy ranged from -19% to 51%, and was significantly positively correlated with the ratio of the planned treated liver volume to the functional liver volume. The PS agreed well with observed radiation tolerance in 21 patients, but underestimated the tolerance in 5. This underestimation was diminished when the PS was recalculated using the identified untreated liver volume in lieu of the planned untreated liver volume. CONCLUSION: As in surgical treatment, radiation tolerance of the cirrhotic liver after focused treatment is closely related to the preserved functional capacity of the identified untreated liver volume, which shows compensatory hypertrophy following radiotherapy.

Aged↗
PubMed1997

Innervation of the lumbar facet joints. Origins and functions.

STUDY DESIGN: The levels of dorsal root ganglia and paravertebral sympathetic ganglia innervating the lumbar facet joint were investigated in rats using the retrograde transport method. The pathways and functions of the nerve fibers supplying the lumbar facet joint were determined immunohistochemically. OBJECTIVES: To study lumbar facet pain in relation to its innervation. SUMMARY OF BACKGROUND DATA: The lumbar facet joints have been reported to be innervated segmentally. Little is known, however, about the origins and functions of the nerve fibers. METHODS: Cholera toxin B subunit, a neural tracer, was placed in the L5-L6 facet joint, and the bilateral dorsal root ganglia and paravertebral sympathetic ganglia were examined immunohistochemically. The serial sections of lumbar vertebrae of newborn rats and the sections of the facet joint capsules, dorsal root ganglia, and paravertebral sympathetic ganglia of adult rats were investigated immunohistochemically. The pathways of the nerve fibers supplying the facet joint were reconstituted. RESULTS: Labeled neurons existed in ipsilateral dorsal root ganglia from L1 to L5 and in paravertebral sympathetic ganglia from T12 to L6. The dorsal ramus of the spinal nerve and rami communicantes were connected to each other by calcitonin gene-related peptide immunoreactive fibers and dopamine beta-hydroxylase immunoreactive fibers. CONCLUSIONS: The L5-L6 facet joint was innervated by ipsilateral dorsal root ganglia and paravertebral sympathetic ganglia, segmentally and nonsegmentally. Some of the sensory fibers from the facet joint may pass through the paravertebral sympathetic trunk, reaching L1 and/or L2 dorsal root ganglia. Inguinal and/or anterior thigh pain with lower lumbar facet joint lesions may be explained as referred pain.

Animals↗
PubMed1997

Regenerating gene expression in normal gastric mucosa and indomethacin-induced mucosal lesions of the rat.

Regenerating (reg) gene expression was tested in rat gastrointestinal mucosa to investigate the role played by this gene in the healing of mucosal lesions. Expression of reg mRNA was higher in the stomach than in any other region of the gastrointestinal tract. The gastric cells that expressed reg mRNA were located in the deepest mucosal layer and were small in diameter. In an injured state following indomethacin treatment, reg gene expression was markedly augmented, accompanied by an increase of c-fos expression and healing of the mucosal lesions. These results suggest a role of the reg gene in the healing of gastrointestinal mucosal lesions.

Animals↗
PubMed1997

Helicobacter pylori induces proinflammatory cytokines and major histocompatibility complex class II antigen in mouse gastric epithelial cells.

Although Helicobacter pylori has been reported to stimulate the release of various cytokines from gastric tissue, it remains unknown whether normal and nontumorous gastric epithelial cells produce these cytokines. Therefore, in this study, we used a normal mouse gastric surface mucous cell line (GSM06) to determine whether gastric epithelial cells produce proinflammatory cytokines in response to H. pylori. The expression of MHC class II antigen was also examined, to investigate whether gastric epithelial cells participate in the immune response to H. pylori. In the study, GSM06 cells were incubated with H. pylori or its lipopolysaccharide (LPS). Proinflammatory cytokines were detected by Northern and Western blot analysis. The expression of MHC class II antigen was examined by fluorescence activated cell sorter (FACS) analysis. Genetic expression of proinflammatory cytokines such as interleukin-1alpha, tumor necrosis factor-alpha, and cytokine-induced neutrophil chemoattractant-2beta was enhanced by both intact and sonicated H. pylori, but not by H. pylori LPS. The expression of MHC class II antigen was induced by H. pylori more strongly than by interferon-gamma. We conclude that H. pylori induces the expression of proinflammatory cytokines and MHC class II antigen in gastric epithelial cells. Gastric epithelial cells may act as antigen-presenting cells and participate in the immune response to H. pylori infection.

Animals↗
PubMed1997

Distribution of prostaglandin E receptors in the rat gastrointestinal tract.

AIMS: In order to study the role of prostaglandin in the regulation of the gastrointestinal functions, gene expression of prostaglandin receptors along the rat gastrointestinal tracts were investigated. METHODS: Rats were used for the study. The combination of counterflow elutriation separation of mucosal cells and Northern blot analysis was used to detect the gene expression of prostaglandin receptors in gastrointestinal tracts. RESULTS: In small intestine and colon, prostaglandin E2 EP1 and EP3 receptor mRNAs were mainly localized in the deeper intestinal wall containing muscle layers. EP4 receptor gene expression, on the other hand, was detected in the intestinal mucosal layer. In the stomach, EP1 mRNA was detected in gastric muscle layers, whereas EP3 and EP4 receptor gene expression was mainly present in the gastric mucosal layer containing epithelial cells. In gastric epithelial cells, parietal cells were found to have both EP3 and EP4 receptors. At lower concentrations, prostaglandin E2 inhibited gastric acid secretion by parietal cells probably through EP4 receptors. At higher concentrations, however, it stimulated it. On the other hand, mucous cells possessed only EP4 receptor mRNA. CONCLUSIONS: Thus, it is suggested that prostaglandin E2 modulates gastrointestinal functions through at least three different prostaglandin receptors (EP1, EP3, and EP4), each of which has a distinct contribution in the gastrointestinal tract.

Aminopyrine↗
PubMed1997

Gray scale second harmonic imaging of the liver: a preliminary animal study.

Gray scale second harmonic imaging (2.5 MHz/5.0 MHz) was evaluated in preliminary animal studies with a new ultrasound contrast agent (FS069). FS069 was administered intravenously in 10 rabbits (6 with normal liver, and 4 with implanted VX-2 tumors) and two woodchucks with hepatocellular carcinomas. The vasculature (including tumor vessels) and liver parenchyma were clearly enhanced at a low dosage (optimal dose was from 0.1 to 0.2 mL/kg) in all cases. Enhancement was reproducible and generally dose-dependent. Tumors were enhanced well during the early phase and tumor enhancement disappeared earlier than that of surrounding normal liver. Arterial phase and portal phase were easily distinguished and patterns of enhancement were diagnostic of the tumors. Gray scale second harmonic imaging is useful in the detection of hepatic tumors and in diagnosis of their hemodynamics.

Albumins↗
PubMed1997

Clinical application of hepatic venous hemodynamics by Doppler ultrasonography in chronic liver disease.

The phase differences of the hepatic vein (HV) Doppler waveform might be influenced by fibrosis and steatosis of the liver when using HV Doppler and pressure curve analysis. Because HV catheterization is invasive, we have advocated the noninvasive comparative index (QXs ratio) of the HV Doppler waveform phases recorded simultaneously with electrocardiography and phgonocardiography. Forty-three controls and 169 patients with a variety of liver diseases were enrolled in this study. The mean QXs ratio was 0.75 in the controls, 0.6 in the chronic hepatitis patients, 0.45 in the cirrhosis patients, and 0.90 in the fatty liver patients. There were significant differences between all pairs of these groups (p < 0.001). The QXs ratio may be used to assess the degree of hepatic fibrosis or steatosis.

Adult↗
PubMed1997

Phase shift of the hepatic vein flow velocity waveform in chronic liver disease: experimental and clinical studies.

We examined animal models and studied patients with chronic liver disease to evaluate phase shift of the flow-velocity waveform of the hepatic vein (HV). We decided the Doppler-Pressure (DP) ratio using electrocardiography, the HV Doppler waveform and HV pressure curves, and we calculated the DP ratios. In animal models, the mean DP ratio was 1.04 in controls, 0.68 in cirrhosis, and 1.22 in fatty liver. There were significant differences among these groups (p < 0.005). In the clinical study, the mean DP ratio was 1.03 in controls, 0.95 in chronic hepatitis and 0.79 in cirrhosis. The DP ratio in the Cirrhosis Group was significantly different from that in the Control Group (p < 0.001) and that in the Chronic Hepatitis Group (p < 0.05). We conclude that the DP ratio is decreased in certain hepatic disease states.

Adult↗
PubMed1997

Flow injection analysis for measurement of activity of matrix metalloproteinase-7 (MMP-7).

A simple and convenient method for measuring the activity of a recombinant human matrix metalloproteinase 7 (MMP-7, matrilysin) was developed by flow injection analysis (FIA). For this method, purified recombinant MMP-7 zymogen expressed in E. coli and the substrate peptide (MOCAc-Pro-Leu-Gly-Leu-A2pr(DNP)-Ala-Arg-NH2) were used. Following the incubation of substrate peptide with activated r-proMMP-7, the resulting fluorescent product peptide (MOCAc-Pro-Leu-GLY) was monitored with a fluorescence detector (lambda ex 328 mm, lambda em 393 mm) without chromatographic separation. In this FIA system, the analysis time is 2 min and the standard curve is linear from 5 to 100 pmol of the product peptide injected. In order to use this FIA system as a method for screening inhibitors against MMP-7, the effects of CaCl2, EDTA and of the tissue inhibitor of metalloproteinase-1, and -2, were tested. A synthetic PRCGXPD-containing peptide (BS-10) was also observed to inhibit MMP-7 activity, with an IC50 value of 104 microM. Thus, it was concluded that the activity of r-MMP-7 can be reliably measured by the proposed system. Furthermore, to confirm the utility of this FIA system as a screening method, the inhibitory activity of the MMP-related substance in Joro spider (Nephilia clavata) venom was measured by this method. This inhibitory activity was observed in an extract of a venom diluted 1000-fold. Thus, the FIA method is not only simple and quick, but also sensitive enough to screen and analyze the inhibitory properties of a large number of test compounds.

Enzyme Inhibitors↗
PubMed1997

Biphasic effects of carbamazepine on the dopaminergic system in rat striatum and hippocampus.

To clarify the effects of carbamazepine (CBZ) on dopamine (DA) release and their metabolism, the extracellular and total levels of DA, its metabolites (DOPAC and HVA) and precursor, 3,4-dihydroxyphenylalanine (DOPA) in the striatum and hippocampus were studied. DA re-uptake and DOPA accumulation in the striatum and hippocampus, and monoamine oxidase (MAO) activities were also determined. After acute and chronic administrations of CBZ, the plasma concentration of CBZ associated with therapeutic activity increased the extracellular and total levels of all substances determined, whereas supratherapeutic concentration of CBZ decreased extracellular and total levels of all substances. Neither therapeutic nor supratherapeutic concentrations of CBZ affected MAO-A nor -B activities, nor DA re-uptake. DOPA accumulation caused by NSD1015 was inhibited by therapeutic and supratherapeutic concentrations of CBZ. These results suggest that a therapeutic concentration of CBZ enhances DA turnover, whereas a supratherapeutic concentration of CBZ inhibits DA turnover. These effects of CBZ on dopaminergic systems may be, at least partially, involved in the mechanisms of action of CBZ.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1997

Characteristics of the myelin sheath membrane of the spiral ganglion cell and the cochlear nerve of guinea pig.

The membrane structures of the myelin sheath of guinea pig spiral ganglion cell and cochlear nerve were examined using freeze-fracturing, rapid freezing and freeze substitution, and deep-etching techniques. The intermediate dense lines of the myelin sheath were observed only in the outermost several layers using thin and thick (1 micron) section techniques. The spaces between the two adjacent major dense lines at any layer of myelin sheath were occupied by flocculent materials in the freeze-substituted specimen. Periods between the two adjacent major dense lines were 13.3 nm in conventional fixation and 11.7 nm in rapid freezing followed by freeze substitution, respectively. A freeze-fracturing study showed no differences in membrane structures at any layer of myelin sheath. Developed tight-junction strands were observed parallel to the long axis of the myelin sheath in the deep-etched specimen. These findings may show the characteristics of myelin sheath membrane in the spiral ganglion cell and cochlear nerve of the guinea pig.

Animals↗
PubMed1997

Gray-scale second harmonic imaging of the liver with galactose-based microbubbles.

RATIONALE AND OBJECTIVES: The authors evaluate the efficacy of SHU 508A, a galactose-based contrast agent used in gray-scale second harmonic imaging in vitro and in vivo experiments. METHODS: A Toshiba prototype harmonic imaging system (2.5/5.0 MHz) was used with SHU 508A in a phantom experiment and to image the liver in five healthy rabbits and one rabbit that had VX-2 tumors in the liver. RESULTS: In the second harmonic imaging, most of the fundamental components of the backscattered echo were eliminated, and good images with high contrast were obtained in the phantom experiment. Liver parenchyma was enhanced clearly in all rabbits at 0.3 mL/kg, an effect that lasted for 90 seconds. The tumor, which was mostly necrotic, was depicted clearly as a negative enhanced area surrounded by enhanced healthy liver. CONCLUSIONS: Gray-scale second harmonic imaging is a promising new method for visualization of perfusion of organs.

Animals↗
PubMed1997

Intragastric distribution of nonsteroidal anti-inflammatory drug-related ulcers in patients without collagen diseases.

During the long-term administration of nonsteroidal anti-inflammatory drugs (NSAIDs), approximately 3% of patients have gastric ulcers develop in each year. Although much is known about the endoscopic characteristics of NSAID-induced gastric ulcers in patients with rheumatoid arthritis (RA), it is not clear where in the stomach NSAIDs induce ulcers in patients without RA. We looked at that question. During the 1-year study period, 29 patients with gastric ulcer, who had been taking NSAIDs regularly for more than 4 weeks mainly for osteoarthritis, were identified. Seventy-five patients with gastric ulcers who had not taken NSAID also were found. The sites of gastric ulcers of these two groups were quite different. The NSAID-induced ulcers mainly were found in the gastric antrum, whereas the majority of NSAID-unrelated ulcers were in the gastric corpus. We conclude that NSAID-induced ulcers in non-RA patients mainly are formed in the gastric antrum.

Adult↗
PubMed1997

Efficient gene transfer into various mammalian cells, including non-hepatic cells, by baculovirus vectors.

A baculovirus (Autographa californica nucleopolyhedrovirus) vector containing a strong promoter, the CAG promoter, was developed to introduce foreign genes into mammalian cells. Recombinant baculoviruses carrying a reporter gene under the control of the CAG promoter were inoculated into various mammalian cell lines. High-level expression was observed not only in hepatocytes but also in other non-hepatic cell lines tested. Expression of the reporter gene was detected even 14 days after infection. The infectious titre of the recovered baculoviruses decreased significantly after infection, indicating that the baculoviruses did not replicate in mammalian cells. We then compared the efficiencies of gene expression by the baculovirus vector with that of a replication-defective adenovirus vector by using the same expression unit. The same level of expression was observed in HepG2, HeLa and COS7 cells by both vectors. Efficient expression and proper processing were observed in mammalian cells infected with baculoviruses carrying genes coding for structural regions of hepatitis C virus. These results suggest that the baculovirus vector is a good tool for gene delivery into various mammalian cells in order to study the function of foreign genes.

Adenoviridae↗
PubMed1997

Membrane interaction of synthetic peptides related to the putative fusogenic region of PH-30 alpha, a protein in sperm-egg fusion.

In order to investigate the relationship between structure and function of a putative fusogenic region of PH-30a, a protein active in sperm-egg fusion, two peptides, SFP22 and SFP23, whose sequences correspond to the residues 90-111 and 89-111 of PH-30 alpha, respectively, were chemically synthesized. An analog of SFP23, SFP23AA, which has an Ala-Ala sequence instead of the Pro-Pro sequence in SFP23, was also prepared. The CD study indicated that SFP22 and SFP23 mainly took a beta-structure in the presence of DPPC and DPPC/DPPG (3/1) vesicles, while SFP23AA showed an alpha-helical pattern though the alpha-helical content calculated was low (25-30%). alpha-Helical CD curve was observed for these peptides in trifluoroethanol. The membrane-perturbing activity of SFP22 and SFP23 was weaker than that of SFP23AA. On the other hand, the membrane-fusogenic activity of SFP22 and SFP23 to acidic phospholipid bilayers was much stronger than that of SFP23AA. All the peptides caused very weak cell lysis. These results are consistent with the reported speculation [Blobel, C. P. et al. (1992), Nature (London) 356, 248-252] that residues 90-111 of PH-30 alpha may be the fusogenic region and suggest that the Pro-Pro sequence is one of the important factors for holding the active secondary structure of the fusogenic region of PH-30 alpha in membranes.

ADAM Proteins↗