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Biomedical subjects

M Ohsawa

Publications and source records attributed to M Ohsawa.

At least 37 records · Page 2Linked to original sources
PubMed2000

Decreased opioid-induced antinociception but unaltered G-protein activation in the genetic-diabetic NOD mouse.

Previous evaluation of antinociceptive action in experimental diabetes has been conducted almost exclusively in chemically induced diabetes mellitus. The purpose of the present study was to evaluate antinociceptive response and G-protein activation by mu-opioid receptor and delta-opioid receptor agonists in the genetic non-obese diabetic (NOD) mouse, a model of type I insulin-dependent diabetes mellitus (IDDM). Tail-flick latency before and after hyperglycemia was unaltered. Hyperglycemic NOD mice were hyporesponsive to intracerebroventricular (i.c.v.) injections of [D-Ala(2)]deltorphin II but not to [D-Ala(2), N-MePhe(4), Gly-ol(5)]enkephalin (DAMGO); however, G-protein activation in pons/medulla assessed by [35S]GTPgammaS binding was not diminished. This suggests that a G-protein defect in signaling cannot account for the hyporesponsiveness of antinociception in this genetic model of IDDM.

Analgesics, Opioid↗
PubMed2000

Effects of a mu-opioid receptor agonist on G-protein activation in streptozotocin-induced diabetic mice.

Many clinical and experimental studies have suggested that diabetes or hyperglycemia alter pain sensitivity, and sensitivity to several drugs. It has been reported that the antinociceptive potency of morphine is decreased in several rodent models of hyperglycemia, including streptozotocin-induced diabetes, an animal models of type I diabetes. The present study was designed to investigate in streptozotocin-induced diabetic mice the effect of the selective micro-opioid agonist [D-Ala(2), NMePhe(4), Gly-ol(5)]enkephalin (DAMGO) on G-protein activation by monitoring guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) binding to pons/medulla membranes, which contain the key areas for opioid antinociception. In the tail-flick test, DAMGO (1-10 ng, intracerebroventricularly) produced a marked dose-dependent antinociception in non-diabetic mice. In streptozotocin-induced diabetic mice, the effect of DAMGO was significantly attenuated as compared to that in non-diabetic mice. In the [35S]GTPgammaS binding assay, DAMGO (0.1-10 microM) increased the binding of [35S]GTPgammaS to pons/medulla membranes from non-diabetic mice in a concentration-dependent manner, affording approximately 100% maximal stimulation at 10 microM. The maximal stimulation of [35S]GTPgammaS binding by DAMGO (10 microM) in streptozotocin-induced diabetic mice (100.55+/-3.12%), was similar to non-diabetic mice. The present results indicated that the antinociceptive effect of DAMGO given supraspinally was less potent in streptozotocin-induced diabetic mice than that in non-diabetic mice, whereas the mu-opioid receptor-mediated G-protein activation in pons/medulla was unaltered in streptozotocin-induced diabetic mice. Thus, the attenuation of DAMGO-induced antinociception in streptozotocin-induced diabetic mice is probably caused by dysfunction in cellular pathways after the activation of G-proteins.

Analgesics, Opioid↗
PubMed2000

Novel responses of ZRF, a variant of human MTF-1, to in vivo treatment with heavy metals.

Heavy metal-dependent transcriptional activation of metallothionein (MT) genes is mediated by multiple enhancer sequences, metal responsive element (MRE), located in the upstream region of the genes. Previously, we have reported purification of a zinc-dependent MRE-binding protein, zinc regulatory factor (ZRF), from HeLa cells, and have pointed to the close relationship between ZRF and mouse MRE-binding transcription factor-1 (MTF-1) according to the analysis of partial amino acid sequences. By means of cDNA cloning and the product analyses, we show that ZRF is a variant of human MTF-1 (hMTF-1), which carries a single amino acid exchange in the zinc finger domain. Accordingly, ZRF is renamed hMTF-1b. Expression of hMTF-1b in HeLa cells is constitutive at both mRNA and protein levels, and is unaffected by treatment with cadmium (Cd). On the other hand, when cells were fractionated into nuclear extract and cytosol, a large part of the hMTF-1b was recovered in the cytosol fraction. A significant increase in the amount of nuclear hMTF-1b occurs when cells are treated with various heavy metals, including Cd, Zn, Cu and Ag, which is associated with concomitant decrease in the amount recovered in the cytosol fraction. Since immunocytochemical analysis revealed that intracellular distribution of hMTF-1b is restricted to the nucleus irrespective of the heavy metal treatment, such an increment in the nuclear extracts apparently results from promotion of nuclear retention of hMTF-1b by the heavy metal treatment. Analysis by native gel electrophoresis shows that the mobility of hMTF-1b significantly changes in association with Cd treatment, raising the possibility that a conformational change of hMTF-1b occurs in response to treatment with heavy metals in vivo.

Amino Acid Sequence↗
PubMed2000

Low frequency of HLA-A*0201 allele in patients with Epstein-Barr virus-positive nasal lymphomas with polymorphic reticulosis morphology.

Lymphoproliferative diseases of the nasal cavity and paranasal sinuses occur frequently in Asian countries and are histologically categorized as monomorphic ordinary lymphoma and polymorphic reticulosis (PR) with apparent inflammatory cell infiltration. The large atypical cells in PR show natural-killer cell nature and frequently contain Epstein-Barr virus (EBV) DNA. Among the EBV genes involved in latent infection, those encoding EBV latent membrane proteins are frequently expressed in PR. Several cytotoxic T-lymphocyte (CTL) defined epitopes have been mapped to latent membrane proteins restricted with HLA-A2, -A11 or -A24 antigens. Thus, the HLA-A allele may affect the development of PR. To examine this possibility, HLA-A alleles of 25 patients with EBV(+) PR were determined with low-resolution polymerase chain reaction-based typing using HLA-A locus sequence-specific primer combinations. The frequency of HLA-A alleles including HLA-A2 and -A24 antigens in PR patients was lower than that in the normal Japanese population, but the difference was not significant. Since HLA-A2-restricted CTL responses are well delineated at the A2-subtype level, the A2-subtype of PR cases with HLA-A2 antigen was further determined by high-resolution genetic typing. The frequency of HLA-A*0201 in PR was significantly lower than in the normal population (p=0.0314). The HLA-A*0201-restricted CTL responses may thus function in vivo to suppress the development of overt lymphoma.

Adult↗
PubMed2000

Decrease of hindpaw withdrawal latency by cocaine- and amphetamine-regulated transcript peptide to the mouse spinal cord.

Immunohistochemical studies with the use of an antiserum against the cocaine- and amphetamine-regulated transcript (CART) peptide-(55-102) showed an abundance of CART-immunoreactive fibers in the mouse dorsal horn laminae I and II. A few CART-positive somata were scattered in the dorsal horn and around the central canal. Intrathecal injection of the CART peptide-(55-102) at doses 3, 10 and 100 ng caused a dose-dependent and significant decrease of paw withdrawal latency; whereas, saline injection was without significant effect. Our results provide the first evidence that CART-immunoreactive fibers are present in the dorsal horn and that the peptide administered intrathecally produces hyperalgesia, as assessed by paw withdrawal latency in mice.

Animals↗
PubMed2000

Modulation of the formalin-induced nociceptive response by diabetes: possible involvement of intracellular calcium.

We examined the involvement of cytosolic calcium in the modulation of the formalin-induced nociceptive response by diabetes. Injection of formalin into the hindpaw of mice produced a biphasic nociceptive response consisting of immediate (first phase) and tonic (second phase) components. Although the duration of the first-phase response was significantly longer in diabetic mice than in non-diabetic mice, the second phase was significantly shorter in diabetic mice. The first-phase response was dose-dependently and significantly reduced by pretreatment with ryanodine, which blocks Ca(2+) release from Ca(2+)/caffeine-sensitive microsomal pools. The second-phase response was also significantly increased when diabetic mice were pretreated with ryanodine. However, ryanodine had no significant effect on either the first-phase or second-phase response in non-diabetic mice. On the other hand, pretreatment with thapsigargin, which inhibits Ca(2+) uptake into the inositol-1,4, 5-trisphosphate-sensitive microsomal Ca(2+) pool, significantly enhanced the first-phase response in non-diabetic mice. Furthermore, thapsigargin significantly and dose-dependently reduced the second phase of the formalin-induced nociceptive response in non-diabetic mice. Thapsigargin administered i.t. did not significantly affect either the first- or the second-phase response in diabetic mice. These results suggest that the change in the formalin-induced nociceptive response in diabetic mice may be due, at least in part, to the modification of nociceptive transmission in the spinal cord by intracellular calcium.

Animals↗
PubMed2000

The antinociceptive effects of endomorphin-1 and endomorphin-2 in diabetic mice.

The antinociceptive effects of endomorphin-1 and endomorphin-2, endogenous mu-opioid receptor agonists, were examined using the tail-flick test in non-diabetic and diabetic mice. Endomorphin-1, at doses of 1 to 10 microg, i.c.v., and endomorphin-2, at doses of 3 to 30 microg, i.c.v., each dose dependently inhibited the tail-flick response in both non-diabetic and diabetic mice. There was no significant difference between the antinociceptive effects of endomorphin-1 in non-diabetic mice and diabetic mice. The antinociceptive effect of endomorphin-2 was greater in non-diabetic mice than in diabetic mice. In non-diabetic mice, the antinociceptive effects of endomorphin-1 and endomorphin-2 were significantly reduced by beta-funaltrexamine, a mu-opioid receptor antagonist, and naloxonazine, a selective mu(1)-opioid receptor antagonist, but not by naltrindole, a delta-opioid receptor antagonist, or nor-binaltorphimine, a kappa-opioid receptor antagonist. In diabetic mice, the antinociceptive effect of endomorphin-2 was significantly reduced by beta-funaltrexamine and naloxonazine. However, these micro-opioid receptor antagonists had no significant effect on the antinociceptive effect of endomorphin-1 in diabetic mice. The antinociception induced by endomorphin-1 in diabetic mice was significantly reduced by naltrindole and 7-benzylidenenaltrexon, a selective delta(1)-opioid receptor antagonist, administered i.c.v. However, nor-binaltorphimine had no significant effect on the antinociceptive effects of endomorphin-1 and endomorphin-2 in diabetic mice. These results indicate that the antinociceptive effects of endomorphin-1 and endomorphin-2 in non-diabetic mice are mediated through the activation of mu(1)-opioid receptors, whereas in diabetic mice, endomorphin-1 and endomorphin-2 may produce antinociception through different actions at delta(1)- and mu(1)-opioid receptors, respectively.

Analgesics, Opioid↗
PubMed2000

Effect of diabetes on bradykinin-induced thermal hyperalgesia in mice.

To investigate the role of protein kinase C in the attenuation of bradykinin-induced thermal hyperalgesia in diabetic mice, we examined the effects of a protein kinase C activator or inhibitor on the i.t. bradykinin-induced hyperalgesia in diabetic and non-diabetic mice. Intrathecal injection of bradykinin caused a transient antinociceptive effect, which diminished within 30 min, and then produced a thermal hyperalgesia, which lasted about 120 min, in non-diabetic mice. Although the duration of the antinociceptive phase was longer in diabetic mice than in non-diabetic mice, the hyperalgesic response was not observed in diabetic mice. The bradykinin-induced hyperalgesia was dose-dependently and significantly enhanced by pretreatment with calphostin C (0.3 to 3 pmol, i.t.), a specific protein kinase C inhibitor, in diabetic mice. However, calphostin C (3 pmol, i.t.) had no significant effect on bradykinin-induced hyperalgesia in non-diabetic mice. On the other hand, pretreatment with phorbol-12, 13-dibutyrate (12.5 to 50 pmol, i.t.), a protein kinase C activator, significantly and dose-dependently reduced bradykinin-induced hyperalgesia in non-diabetic mice. However, phorbol-12, 13-dibutyrate (50 pmol, i.t. ) had no significant effect on bradykinin-induced hyperalgesia in diabetic mice. These results suggest that the change in bradykinin-induced thermal hyperalgesia in diabetic mice may be due, at least in part, to the modification of nociceptive transmission in the spinal cord by the activation of protein kinase C.

Animals↗
PubMed2000

Socio-psychological stress-induced antinociception in diabetic mice.

RATIONALE: Although it is well established that different forms of stress produce a pronounced antinociception, the effect of diabetes on psychological stress-induced antinociception is not yet clear. OBJECTIVES: The effect of diabetes on psychological stress-induced antinociceptive effect was assessed in mice. METHODS: Animals were rendered diabetic by an injection of streptozotocin (200 mg/kg, i.v.). Mice were exposed to psychological stress in the compartment of a communication box. The antinociceptive response was evaluated by the tail-flick test, using radiant heat as a stimulus, which was performed before stress (pre-stress latency) and 0, 30 and 60 min after stress. RESULTS: Exposure to socio-psychological stress for 5, 10 and 15 min produced duration-dependent antinociception in diabetic mice. However, in non-diabetic mice, no appreciable antinociception was found even in the case of socio-psychological stress for 15 min. Pretreatment with diazepam (0.3 mg/kg, i.p.) significantly attenuated socio-psychological stress-induced antinociception in diabetic mice (vehicle: 62.9 +/- 5.5%, n = 10; diazepam: 22 +/- 1%, n = 10). Furthermore, pretreatment with flumazenil (1 mg/kg, i.v.), a benzodiazepine receptor antagonist, also significantly reduced socio-psychological stress-induced antinociception in diabetic mice (vehicle: 77.9 +/- 5.0%, n = 10; flumazenil: 5.8 +/- 1.2%, n = 10). In contrast, pretreatment with methyl beta-carboline-3-carboxylate (beta-CCM, 2 mg/kg, i.v.), a benzodiazepine receptor inverse agonist, significantly enhanced socio-psychological stress-induced antinociception in non-diabetic mice (vehicle: 4.9 +/- 0.6%, n = 10; beta-CCM: 61.5 +/- 5.9%, n = 10), but not in diabetic mice (vehicle: 50.7 +/- 4.5%, n = 10; beta-CCM: 64.4 +/- 7.2%, n = 10). CONCLUSIONS: These results indicate that emotional stress can readily induce antinociception in diabetic mice. Furthermore, this enhanced emotional stress-induced antinociception might be attributable to an increase in the production and/or release of endogenous ligands for benzodiazepine receptors, such as diazepam binding inhibitor, which act as inverse benzodiazepine receptor agonists.

Animals↗
PubMed2000

Effect of 1,25(OH)2D3 on expression of estrogen receptor-alpha mRNA on rat osteosarcoma cell line (ROS 17/2.8).

In order to investigate the regulatory mechanisms of estrogen receptors (ER) in bone cells, changes in ER-alpha mRNA levels of rat osteosarcoma cell line (ROS 17/2.8) before and after exposure to 1,25(OH)2D3 and 17-beta estradiol respectively were measured by quantitative polymerase chain reaction using an internal standard. ER mRNA levels in the ROS 17/2.8 cultured with the medium alone had 5.029 +/- 1.623 mol/g total RNA x 10(-13) and were not statistically different from those cultured in the presence of 1,25(OH)2D3 at concentrations of 10(-12) M and less. ER mRNA levels in the ROS 17/2.8 cell line showed a small but a significant increase as a result of stimulation by 1,25(OH)2D3 at concentrations of 10(-10) and 10(-11) M. However, ER mRNA levels in ROS 17/2.8 cultured in the presence of 1,25(OH)2D3 at concentrations of 10(-9) M were not statistically different from those of the control. On the other hand, the expression of ER in ROS 17/2.8 cells cultured for 3 hours with various doses of 1,25(OH)2D3 showed, by immunoblotting methods, a significant increase at the dose of 10(-10) M in the expression of ER. Although a physiological significance is obscure, these observations suggest that 1,25(OH)2D3 plays a part in the expression of ER in ROS 17/2.8. No significant changes were seen in the expression of ER mRNA and the synthesis of ER as a result of stimulation by the estradiol.

Animals↗
PubMed2000

Role of the phosphatidylinositol-specific phospholipase C pathway in delta-opioid receptor-mediated antinociception in the mouse spinal cord.

Stimulation of delta-opioid receptors has been shown to activate phospholipase C via the activation of G-proteins in vitro. The present study was designed to determine, with the tail-flick method, whether the stimulatory effect of delta-opioid receptor agonists on phospholipase C and inositol lipid turnover participates in the mechanisms of the delta-opioid receptor-mediated antinociception in the mouse spinal cord. Intrathecal pretreatment with the phospholipase C inhibitors neomycin and U73122, which produced no changes in the basal tail-flick latencies when they were injected alone, significantly attenuated the antinociception induced by intrathecal administration of the selective delta-opioid receptor agonist [D-Ala(2)]deltorphin II in mice. The selective phosphatidylinositol-specific phospholipase C inhibitor ET-18-OCH(3) inhibited the antinociception induced by intrathecal administration of [D-Ala(2)]deltorphin II in a dose-dependent manner. In mice undergoing treatment with LiCl, which impairs phosphatidylinositol synthesis, the antinociception induced by intrathecal administration of [D-Ala(2)]deltorphin II was significantly reduced. Co-administration of D-myo-inositol-1,4,5-trisphosphate restored the [D-Ala(2)]deltorphin II-induced antinociception in LiCl-pretreated mice. On the other hand, intrathecal pretreatment with the selective protein kinase C inhibitor calphostin C, but not the protein kinase A inhibitor KT5720, resulted in a dose-dependent enhancement of the [D-Ala(2)]deltorphin II-induced antinociception. These results indicate a potential role for the phospholipase C-inositol-1,4, 5-trisphosphate pathway in the expression of delta-opioid receptor-mediated antinociception in the mouse spinal cord. Furthermore, activation of protein kinase C by the stimulation of delta-opioid receptors may constitute a significant pathway involved in negative modulation of spinal delta-opioid receptor-mediated antinociception.

Analgesics↗
PubMed2000

The role of lipopolysaccharide injected systemically in the reactivation of collagen-induced arthritis in mice.

1. We investigated the role of bacterial lipopolysaccharide (LPS) in the reactivation of autoimmune disease by using collagen-induced arthritis (CIA) in mice in which autoimmunity to the joint cartilage component type II collagen (CII) was involved. 2. CIA was induced by immunization with CII emulsified with complete Freund's adjuvant at the base of the tail (day 0) followed by a booster injection on day 21. Varying doses of LPS from E. coli were i.p. injected on day 50. 3. Arthritis began to develop on day 25 after immunization with CII and reached a peak on day 35. Thereafter, arthritis subsided gradually but moderate joint inflammation was still observed on day 50. An i.p. injection of LPS on day 50 markedly reactivated arthritis on a dose-related fashion. Histologically, on day 55, there were marked oedema of synovium which had proliferated by the day of LPS injection, new formation of fibrin, and intense infiltration of neutrophils accompanied with a large number of mononuclear cells. The reactivation of CIA by LPS was associated with increases in anti-CII IgG and IgG2a antibodies as well as various cytokines including IL-12, IFN-gamma, IL-1beta, and TNF-alpha. LPS from S. enteritidis, S. typhimurium, and K. neumoniae and its component, lipid A from E. coli also reactivated the disease. Polymyxin B sulphate suppressed LPS- or lipid A-induced reactivation of CIA. 4. These results suggest that LPS may play an important role in the reactivation of autoimmune joint inflammatory diseases such as rheumatoid arthritis in humans.

Animals↗
PubMed2000

Bacterial lipopolysaccharide acts as an adjuvant to induce autoimmune arthritis in mice.

We investigated the ability of lipopolysaccharide (LPS) as an adjuvant to induce autoimmune arthritis. LPS from Escherichia coli was intraperitoneally injected into DBA/1J mice together with the joint cartilage component type II collagen (CII) on day 0. Thereafter, the injection of CII and LPS was continued every 2 weeks up to day 56. The results showed that mice injected with CII plus LPS had signs of arthritis on day 55 and the joint inflammation reached a peak on day 75. Injection of CII or LPS alone induced no arthritis. Histologically, marked oedema of synovium and intense infiltration of inflammatory cells, including neutrophils, were observed 3 days after the onset of joint inflammation. Twenty-one days later, there were marked proliferation of synovial tissues with many mononuclear cells and destruction of cartilage. Anti-CII immunoglobulin G (IgG) and IgG2a antibodies were markedly produced in mice injected with CII plus LPS. Pronounced secretion of cytokines, including interleukins-12 and -1beta, interferon-gamma and tumour necrosis factor-alpha, was also observed in these animals. Arthritis was passively transferred into naive syngeneic mice with sera but not with lymphoid cells from mice given CII with LPS. Other types of LPS from Salmonella enteritidis, Salmonella typhimurium and Klebsiella pneumoniae as well as lipid A from E. coli, induced inflammation in joints when administered with CII. Polymixin B sulphate mixed with LPS or lipid A blocked the induction of joint inflammation. These results indicate that LPS appears to play an important role as an adjuvant in the induction of arthritis in which autoimmunity to CII is involved.

Adjuvants, Immunologic↗
PubMed2000

Superparamagnetic iron oxide-enhanced magnetic resonance images of hepatocellular carcinoma: correlation with histological grading.

Superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging has been used for the detection of hepatic tumors. However, little is known about this technique in relation to hepatocellular carcinoma (HCC). The aim of this study was to investigate whether SPIO-enhanced MR imaging can be useful in assessing histological grades of HCC. The authors studied histologically proven tumors including 31 HCCs and 6 dysplastic nodules. The ratio of the Kupffer-cell count in the tumorous tissue relative to that in the nontumorous tissue (Kupffer-cell-count ratio) decreased as HCCs became less well differentiated. The ratio of the intensity of the tumorous lesion to that of the nontumorous area on SPIO-enhanced MR images (SPIO intensity ratio) correlated inversely with Kupffer-cell-count ratio in HCCs and dysplastic nodules (r = -.826, P <.001) and increased as the degree of differentiation of HCCs decreased, indicating that the uptake of SPIO in HCCs decreased as the degree of differentiation of HCCs declined. All of the dysplastic nodules and some well-differentiated HCCs showed hypointense or isointense enhancement, relative to the surrounding liver parenchyma, indicating greater or similar uptake of SPIO in the tumor when compared with nontumorous areas. These results suggest that SPIO-enhanced MR imaging reflects Kupffer-cell numbers in HCCs and dysplastic nodules, and is useful for estimation of histological grading in HCCs, although uncertainties persist in differentiating dysplastic nodules from well-differentiated HCCs.

Aged↗
PubMed2000

Genetic polymorphism of 5,10-methylenetetrahydrofolate increases risk of myocardial infarction and is correlated to elevated levels of homocysteine in the Japanese general population.

BACKGROUND: Hyperhomocysteinemia, an independent and graded risk factor for coronary artery disease, can result from both environmental and hereditary factors. C677T mutation of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene [alanine/valine (A/V) polymorphism], one of the key enzymes involved in catalyzing the remethylation of homocysteine, has recently been reported. OBJECTIVE: To evaluate the incidence of the MTHFR genotypes and their significance in determining the risk for myocardial infarction of Japanese men. METHOD: The subjects consisted of 199 healthy men (mean age, 60 years) and 230 male patients with myocardial infarction (mean age, 59 years). The coronary-artery lesions were evaluated by coronary angiography. The MTHFR genotype was analyzed by polymerase chain reaction and then by digestion with Hinfl. Total plasma levels of homocysteine for each MTHFR genotype were compared with those in healthy controls. RESULTS: The prevalences of the A and V alleles among the healthy male subjects were 0.652 and 0.348 in the Hardy-Weinberg equilibrium. The total levels of homocysteine in the plasma of the healthy male subjects were 8.6 +/- 3.3, 8.9 +/- 4.1, and 11.6 +/- 5.6 mumol/l, for AA, AV, and VV genotypes, respectively. Individuals with the VV homozygous mutant genotype thus had the highest plasma levels of homocysteine. Logistic analysis revealed that the levels of high-density lipoprotein cholesterol, hypertension, diabetes mellitus, MTHFR VV genotype, and triglycerides were all independent risk factors for myocardial infarction. The VV genotype was more prevalent among patients with myocardial infarction (mean age, 59 years) than it was among the control subjects (17.0 versus 10.6%, P < 0.05). However, there were no differences in the numbers of stenotic coronary arteries among the MTHFR genotypes. CONCLUSION: The VV genotype of MTHFR increases plasma levels of homocysteine in healthy controls, and this mutation indicates a genetic predisposition toward a greater than normal risk of myocardial infarction for Japanese men.

Cohort Studies↗
PubMed2000

Molecular and biological analysis of carcinoma of the small intestine: beta-catenin gene mutation by interstitial deletion involving exon 3 and replication error phenotype.

The genetic mechanisms of carcinomas of the small intestine are not well understood. We report the results of analysis of genetic alterations in a case of small intestinal carcinoma. A tumor in the terminal ileum was resected in a 59-yr-old woman. Histologically, the tumor was classified as well-differentiated adenocarcinoma. We screened for genetic alterations in adenomatous polyposis coli (APC), beta-catenin, K-ras, and p53 genes, as well as microsatellite instability, which are known to be involved in colorectal tumorigenesis. The tumor exhibited somatic interstitial deletion of 425-bp, which included the entire exon 3 in beta-catenin gene. Immunohistochemical staining confirmed accumulation of aberrant beta-catenin protein in the cytoplasm and nuclei of the malignant tissue. Furthermore, a frameshift mutation in the transforming growth factor beta receptor type II gene with replication error phenotype was detected in the tumor DNA. In contrast, no genetic alterations were found in the APC, K-ras, and p53 genes. Our results suggested that both beta-catenin gene mutation and replication error phenotype might contribute to carcinogenesis of the small intestinal tumor in our case. This is the first report that activation of beta-catenin gene by somatic gene mutation is involved in the development of carcinoma of the small intestine.

Amino Acid Sequence↗
PubMed2000

Mechanism of superoxide dismutase-like activity of Fe(II) and Fe(III) complexes of tetrakis-N,N,N',N'(2-pyridylmethyl)ethylenediamine.

The superoxide dismutase (SOD) activity of iron(II) tetrakis-N,N,N',N'(2-pyridylmethyl)ethylenediamine complex (Fe-TPEN) was reexamined using a pulse radiolysis method. In our previous study (J. Biol. Chem., 264, 9243-9249 (1989)), we reported that this complex has a potent SOD activity in a cyt. c (cytochrome c)-based system (IC50 = 0.8 microM) and protects E. coli cells against paraquat toxicity. The present pulse radiolysis experiment revealed that Fe(II)TPEN reacts stoichiometrically with superoxide to form Fe(III)TPEN with a second-order rate constant of 3.9 x 10(6) M-1 S-1 at pH 7.1, but superoxide did not reduce Fe(III)TPEN to Fe(II)TPEN. The reaction of Fe(III)TPEN and superoxide was biphasic. In the fast reaction, an adduct (Fe(III)TPEN-superoxide complex) was formed at the second-order rate constant of 8.5 x 10(5) M-1 S-1 at pH 7.4. In the slow one, the adduct reacted with another molecule of the adduct, regenerating Fe(III)TPEN. In the cyt. c method with catalase, this Fe(III)TPEN-superoxide complex showed cyt. c oxidation activity, which had led to overestimation of its SOD activity. Based on the titration data, the main species of complex in aqueous media at neutral pH was indicated to be Fe(III)TPEN(OH-). A spectral change after the reduction with hydrated electron indicates that the OH- ion coordinates directly to Fe(III) by displacing one of the pyridine rings. The X-ray analysis of [Fe(II)TPEN]SO4 supported this structure. From the above results we propose a novel reaction mechanism of FeTPEN and superoxide which resembles a proton catalyzed dismuting process, involving Fe(III)TPEN-superoxide complex.

Antioxidants↗