Biomedical subjects

N Saitoh

Publications and source records attributed to N Saitoh.

At least 55 records · Page 3Linked to original sources

PubMed1997

Expanded CTG repeats in myotonin protein kinase suppresses myogenic differentiation.

A full-length mutant human myotonin protein kinase (MtPK) cDNA having a 46 expanded CTG-repeat size or a wild type containing 5 CTG repeats was stably transfected into mouse C2C12 cell line in order to explore the effects of the expansion mutation of trinucleotide repeats in the 3' untranslated region on developing myogenic cells. Each established clone expressed a human 70 kDa MtPK protein without proteolytic processing. Differentiation experiments indicated that stable mutant MtPK cDNA-transformants suppressed myogenic differentiation, whereas wild-type transformants exhibited almost normal myogenesis. The disturbance of the expression of neuronal nitric oxide synthase, a mediator of myoblast fusion, suggests that signal transduction system might be involved in the muscle manifestations of mutant MtPK.

Animals↗

PubMed1997

Anti-endothelial cell antibodies to the endothelial hybridoma cell line (EAhy926) in systemic lupus erythematosus patients with antiphospholipid antibodies.

The endothelial hybridoma (EAhy926) cell line was employed to clarify whether antiphospholipid antibodies (aPA) [lupus anticoagulant (LA), antiprothrombin antibody (aPT) and/or anticardiolipin antibody (aCL)] and anti-endothelial cell antibodies (AECA) are identical, and establish whether beta2-glycoprotein I (beta2-GPI) is needed for reactivity of aPA to endothelial cells. Ig-G AECA was positive in 9/30 SLE patients with aPA (30.0%) and 10/22 SLE patients negative for aPA (45.5%). Ig-M AECA was positive in one SLE patient with aPA and one SLE patient without aPA. AECA-positivity was not significantly different among unfixed, TNF-stimulated and fixed EAhy926. The influence of beta2-GPI on the reactivity of serum to EAhy926 was minimal, and absorption experiments of serum with cardiolipin-liposome/beta2-GPI or phosphatidylserine-liposome/prothrombin gave little evidence of cross-reactivity of aPA and AECA. The results of our study suggest that aPA and AECA may have partially cross-reacted, but were different antibodies. However, further study is needed to clarify the clinico-pathological significance of AECA.

Antibodies↗

PubMed1997

Muscarinic autoinhibition and modulatory role of protein kinase C in acetylcholine release from the myenteric plexus of guinea pig ileum.

The modulatory role of protein kinase C on phospholipase A2, activation of which had been suggested to result in acetylcholine release from cholinergic neurons, was studied in longitudinal muscle preparations with the myenteric plexus of guinea pig ileum. The relationship of muscarinic autoinhibition to the modulation was also examined. Phorbol-12,13-dibutyrate (PDBu), an activator of protein kinase C, dose-dependently increased spontaneous and electrical field stimulation-induced acetylcholine releases from the preparation. The inhibitors of protein kinase C, staurosporine and calphostin C, inhibited the stimulatory effects of PDBu, but neither inhibitor affected spontaneous or electrical field stimulation-induced acetylcholine release in the absence of PDBu. On the other hand, atropine significantly increased electrical field stimulation-induced release by blocking a muscarinic autoinhibitory mechanism. Under the auto-inhibition blocked condition, U73122, an inhibitor of phospholipase C, and staurosporine significantly inhibited the effect of atropine on electrical field stimulation-induced release. An inhibitor of phospholipase A2, mepacrine, inhibited PDBu-induced acetylcholine release and also inhibited the effect of atropine on electrical field stimulation-induced release. An activator of phospholipase A2, melittin, and a product of the phospholipase, arachidonic acid, increased the spontaneous and electrical field stimulation-induced releases. These results suggest that the phospholipase C-protein kinase C system modulates acetylcholine release from cholinergic neurons by activating phospholipase A2 in the myenteric plexus of guinea pig ileum, and the activation of muscarinic autoreceptor may negatively modulate acetylcholine release at a point upstream of the system.

Acetylcholine↗

PubMed1997

Characterization of antimuscarinic effect of cimetropium bromide in guinea pig ileum.

Pharmacological characteristics of cimetropium bromide (cimetropium), a muscarinic receptor antagonist, were studied in longitudinal muscle preparations with myenteric plexus of guinea-pig ileum. Cimetropium was shown to have more potent antimuscarinic effect than butylscopolamine in inhibition of contraction of the preparations. Interestingly, when the inhibitory effects of cimetropium were compared in respect of relative potency to atropine between its effects on electrical field stimulation or nicotine-, and exogenous ACh-induced contraction, it has a more potent effect on the former contraction than that on the latter one. In the superfusion experiments of the preparation which had been preloaded with labelled choline, cimetropium decreased the labelled ACh release induced by electrical field stimulation under the muscarinic autoinhibition blocked-condition. From these findings, two pharmacologically characteristic effects of cimetropium in addition to post-synaptic muscarinic receptor antagonism were suggested: one is a weak effect on muscarinic autoreceptors in comparison to atropine and the other is an inhibitory effect on the ACh release.

Acetylcholine↗

PubMed1997

Novel isoform of myotonin protein kinase: gene product of myotonic dystrophy is localized in the sarcoplasmic reticulum of skeletal muscle.

It is quite important to know the exact localization and function of myotonin protein kinase (MtPK), identified as the gene product of myotonic dystrophy, the most prevalent disease with multisystem disorders among muscular dystrophies. To investigate the localization of MtPK, we raised a polyclonal antibody against a synthetic peptide chosen within the deduced sequence of MtPK. This antibody detected both a membrane-bound 70-kd protein and a soluble 55-kd protein on Western blots of human muscles. By using this antibody for immunohistochemical studies of both biopsied human skeletal muscle fibers and mature innervated cultured muscle fibers, we can now demonstrate by confocal laser scanning microscopy that MtPK is localized mainly in the I-band. By immunoelectron microscopy, it was determined that MtPK is a membrane-bound protein localized mainly in the terminal cisternae of the sarcoplasmic reticulum. To our knowledge, this is the first documentation of the ultrastructural localization of MtPK. This finding is quite important for clarifying the pathophysiological basis of myotonic dystrophy, which might be due to a dysregulation of calcium metabolism.

Actins↗

PubMed1996

Immunocytochemical localization of a full-length myotonin protein kinase in rat L6 myoblasts.

Expansion mutation of CTG-repeat motifs within myotonin protein kinase (MtPK) gene is responsible for pathological changes in myotonic dystrophy (DM). To explore its pathological role in skeletal muscle, a full-length human MtPK cDNA was transfected into rat L6 myogenic cell line. Recombinantly expressed human MtPK protein in L6 cell line has a predicted molecular mass of 70 kDa. We have raised a polyclonal antibody against a synthetic peptide in the deduced sequence of the C-terminal portion of MtPK. MtPK in L6 cell is localized to perinuclear region, that resembles with sarcoplasmic reticulum. The MtPK-transfected myoblast cells established in this study will allow us to elucidate the molecular pathomechanism of muscle manifestations in DM.

Animals↗

PubMed1996

Effect of artificial (CTG) repeat expansion on the expression of myotonin protein kinase (MtPK) in COS-1 cells.

A major challenge in the study of a new genetic entity called triplet-repeat disease is to identify the role of triplet repeats in the pathogenesis of the disease. We have developed a strategy to demonstrate the effect in the 3'-untranslated end of the (CTG) repeats in myotonic dystrophy gene (MtPK) and found that repeat expansion (CTG46) causes a slight decrease in the translation rate of MtPK cDNA which correlates with the finding in patients with myotonic dystrophy of a low amount of MtPK protein in muscle. These results provide an important clue for characterizing the genetic abnormality in other triplet-repeat diseases.

Animals↗

PubMed1996

Negligible synergistic effect of beta2-glycoprotein I on the reactivity of antioxidized low-density lipoprotein antibody to oxidized low-density lipoprotein.

We conducted this study to investigate whether antioxidized low-density lipoprotein (a-oxLDL) is an antibody to cryptic and/or neo-antigen on beta2-glycoprotein I (GPI), which is introduced by binding to anionic phospholipid, similar to that of GPI-dependent anticardiolipin antibody (aCL) employing a-oxLDL ELISA. We found that no significant optical density differences existed among systemic lupus erythematosus patients, including cases with aCL and/or lupus anticoagulant positivity, before and after the addition of GPI. Our results suggest that a-oxLDL is not an antibody to denatured GPI, but rather to oxLDL.

Autoantibodies↗

PubMed1996

Buffer may be the critical factor in measurement of anti-prothrombin antibody on a gamma-ray-irradiated plate by enzyme-linked immunosorbent assay.

We investigated the influence of different buffers (Tris-buffer and phosphate buffered saline (PBS)/Tween-20 buffer) on anti-prothrombin antibody (aPT) measurement by enzyme-linked immunosorbent assay (ELISA), employing a gamma-ray-irradiated plate. We found considerable discrepancies in aPT positivity between each buffer, and we suggest that the use of Tris-buffer is not suitable for aPT measurement with a gamma-ray-irradiated plate to measure aPT.

Autoantibodies↗

PubMed1996

Ileocolic intussusception in adult due to malignant lymphoma in the cecum with intramural metastasis.

A rare adult case of intussusception caused by malignant lymphoma of the cecum with intramural metastasis is reported. The patient was a 24-year-old man. Ileocolic intussusception was diagnosed by characteristic findings on abdominal computed tomography. Endoscopic examination revealed a massive protuberant tumor, 3 cm in diameter, and a semipedunculated polyp, 1 cm in diameter, in the cecum, which had caused the ileocolic intussusception. Endoscopic biopsy specimens failed to yield a definitive diagnosis histologically, but right hemicolectomy with lymph node dissection was performed. On histologic examination of the surgical specimens, both the tumor and the polyp were diagnosed as diffuse lymphoma of medium-sized cell type, and no lymph node involvement was found. The patient responded well to surgical and chemotherapeutic treatment, and has had no recurrence of malignant lymphoma in the 2 years since the surgical treatment. This was a very rare case of an intussusception in an adult patient due to malignant lymphoma in the cecum with intramural metastasis and without lymph node involvement.

Adult↗

PubMed1996

Phosphatidyl serine-dependent antiprothrombin antibody is exclusive to patients with lupus anticoagulant.

We conducted this study to determine whether antiprothrombin antibody (aPT) [to prothrombin (PT) alone or PT/phosphatidyl serine (PS) complex] actually existed in patients with lupus anticoagulant (LA) and/or anticardiolipin antibody (aCL). aPT to PT alone was positive in 2/7 LA-positive (29%) and 3/7 LA/aCL-positive (43%) patients. aPT to PT/PS complex was positive in 4/7 LA-positive (57%) and 4/7 LA/aCL-positive (57%) patients in the presence of Ca2+. However, none of the aCL-positive patients without LA or the LA/aCL-negative patients were positive for aPT and aPT/PS. Thus, we confirmed the existence of aPT and aPT/PS specifically among LA-positive patients. However, the clinicopathological significance of aPT and aPT/PS in this clinical setting is yet to be clarified.

Antibodies, Anticardiolipin↗

PubMed1995

Inhibitory activity of anti-beta 2-glycoprotein I antibody on factor Va degradation by activated-protein C and its cofactor protein S.

We investigated the influence of anti-beta 2-glycoprotein I (aGPI), which recently has come to be regarded as anti-cardiolipin antibody (aCL) itself, on factor Va (FVa) degradation by activated protein C/protein S system. We found that aGPI had an inhibitory effect on FVa degradation with beta 2-glycoprotein I-dependency, thus suggesting aGPI/aCL is a highly possible factor as the pathogenesis of thrombosis observed in aGPI/aCL-positive patients.

Animals↗

PubMed1995

The SMC proteins and the coming of age of the chromosome scaffold hypothesis.

The mechanism of chromosome condensation is one of the classic mysteries of mitosis. A number of years ago, it was suggested that nonhistone proteins of the chromosome scaffold fraction might help chromosomes to condense, possibly by constructing a framework for the condensed structure. Recent results have shown that topoisomerase II and the SMC proteins, two abundant members of the scaffold fraction, are required for chromosome condensation and segregation during mitosis. Topoisomerase II is a well-characterized enzyme. In contrast, nothing is yet known about the function of the SMC proteins. We summarize evidence suggesting that these proteins may be enzymes whose activity is somehow involved in the establishment and maintenance of mitotic chromosome morphology.

Animals↗

PubMed1995

Resistance to activated protein C activity of an anti-beta 2-glycoprotein I antibody in the presence of beta 2-glycoprotein I.

Some researchers claim that lupus anticoagulant-positive plasma may cause a false-positive reaction in the test for activated protein C (APC) resistance, a hereditary thrombophilic state characterized by abnormal factor V, which frequently causes venous thrombosis. We investigated whether anti-beta 2-glycoprotein I antibody (aGPI), which has recently come to be regarded as an anti-cardiolipin antibody (aCL) itself, might have an effect on the APC resistance test.

Antibodies, Anticardiolipin↗

PubMed1995

Prevalence of beta 2-glycoprotein I antibody in systemic lupus erythematosus patients with beta 2-glycoprotein I dependent antiphospholipid antibodies.

OBJECTIVE: To investigate whether beta 2-glycoprotein I antibody (aGPI) exists in sera that are positive for antiphospholipid antibodies (aPL). METHODS: Thirty six patients with systemic lupus erythematosus (SLE) and 20 healthy volunteers were recruited. GPI independent and dependent aPL (anticardiolipin (aCL), antiphosphatidylserine, antiphosphatidylinositol, antiphosphatidic acid) were measured using a conventional enzyme linked immunosorbent assay (ELISA). aGPI was measured by an ELISA using a gamma irradiated plate coated with purified GPI. RESULTS: Twenty of 36 SLE patients were positive for at least one of the GPI-dependent aPL. Five of these 20 were also positive for aGPI. Another five of the 20 showed low GPI dependency aCL antibodies; however, three of these patients required GPI for binding to phosphatidylserine, phosphatidylinositol, or both. CONCLUSION: We confirmed the existence of aGPI in patients with true GPI dependent aPL. From these results, we recommend the use of a gamma irradiated plate with GPI as antigen for the detection of true GPI dependent aPL or aGPI.

Antibodies, Anticardiolipin↗

PubMed1995

Endotoxemia and intestinal mucosal dysfunction after the relief of obstructive jaundice by internal and external drainage in rats.

We studied the effects of external and internal biliary drainage on the development of endotoxemia in a rat model of obstructive jaundice. Male Donryu rats were allocated to four groups: sham operation, common hepatic bile duct ligation (BDL), internal or external biliary drainage after BDL, and biliary drainage after BDL with oral endotoxin administration. Portal and systemic blood endotoxin concentrations were measured and the histomorphology of the intestinal mucosa was examined. Portal endotoxemia was observed 7 days after BDL and both portal and systemic endotoxemia were observed after 14 days. Portal endotoxemia was reversed by both internal and external biliary drainage and systemic endotoxemia was prevented. The ratio of villous height to crypt depth in the mucosa of the terminal ileum was decreased in rats with external drainage. Oral administration of endotoxin induced marked disruption of the mucosal epithelium in rats with external biliary drainage, but not in rats with internal biliary drainage. Significant increases in portal and systemic blood endotoxin concentrations were observed only in the external drainage group after oral endotoxin administration. The relief of biliary obstruction effectively relieved portal endotoxemia. External biliary drainage, however, has the potentially deleterious effect of disrupting the intestinal mucosa, which may promote the development of endotoxemia. These findings have implications for the use of biliary drainage procedures to reduce postoperative complications in jaundiced patients.

Animals↗

PubMed1995

High prevalence of anti-phospholipid antibodies and anti-thyroglobulin antibody in patients with hepatitis C virus infection treated with interferon-alpha.

OBJECTIVES AND METHODS: We investigated the prevalence rate of beta 2-glycoprotein I (beta 2-GPI)-dependent antiphospholipid antibodies (aPL)[anti-cardiolipin antibody (aCL), anti-phosphadidylserine antibody (aPS), and anti-phosphatidic acid antibody (aPA)], antinuclear antibody (ANA), anti-deoxyribonucleic acid antibody (aDNA), anti-thyroglobulin antibody (aTG), and anti-thyroid peroxidase antibody (aTPO) in 56 patients with hepatitis C virus (HCV) infection and correlated the results with inteferon-alpha (IFN) treatment. RESULTS: aCL, aPS, and aPA were positive in, respectively, 7/56 (13%), 12/56 (21%), and 13/56 (23%) patients before treatment. aPS and aPA appeared in 6/44 and 9/43 and disappeared in 6/12 and 2/13 patients, respectively, after IFN treatment; the differences were statistically significant. The changes in OD readings were higher in the group of patients who became positive for aPS and aPA than in those who became negative after treatment. The positive rates of aTG and aTPO in the patient group were statistically higher than in the healthy controls, and aTG developed in four patients and disappeared in two. No obvious changes in aTPO were observed; however, the aTPO titer was increased in four previously positive patients. None of the patients positive for any antibodies developed an abnormality associated with these antibodies during an observation period of up to 1 yr. CONCLUSIONS: The pathogenesis of production and clinical significance of aPL, ATG/aTPO in this clinical setting are unclear, but immunological disturbances, such as the effects of HCV infection and/or IFN treatment, were considered to be a possibility. Further investigation is needed to clarify whether HCV/aPL- and/or aTG/aTPO-positive patients treated with IFN might develop aPL-associated complications and/or autoimmune disease(es), in the future and to confirm whether IFN treatment justifies the outcome in this clinical setting.

Adult↗

PubMed1995

[Myotonin protein kinase].

The mutation underlying myotonic dystrophy is the expansion of polymorphic CTG repeat in the 3'-noncoding region of the myotonin protein kinase (MtPK) gene mapping to chromosome 19q13.3. A full-length cDNA of human MtPK was cloned and expressed in COS-1 cells. MtPK is recovered from the COS cell extract as a 70 kDa protein, which coincides with the size deduced from the predicted amino acid sequence. Biochemical characteristics of MtPK expressed in COS cells and its expression are investigated.

Chromosomes, Human, Pair 19↗