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Biomedical subjects

M Sekiguchi

Publications and source records attributed to M Sekiguchi.

At least 109 records · Page 6Linked to original sources
PubMed1998

Cerebellar microfolia and other abnormalities of neuronal growth, migration, and lamination in the Pit1dw-J homozygote mutant mouse.

The Snell dwarf mouse (Pit1dw-J homozygote) has a mutation in the Pit1 gene that prevents the normal formation of the anterior pituitary. In neonates and adults there is almost complete absence of growth hormone (GH), prolactin (PRL), thyroxin (T4), and thyroid-stimulating hormone (TSH). Since these hormones have been suggested to play a role in normal development of the central nervous system (CNS), we have investigated the effects of the Pit1dw-J mutation on the cerebellum and hippocampal formation. In the cerebellum, there were abnormalities of both foliation and lamination. The major foliation anomalies were 1) changes in the relative size of specific folia and also the proportional sizes of the anterior vs posterior cerebellum; and 2) the presence of between one and three microfolia per half cerebellum. The microfolia were all in the medial portion of the hemisphere in the caudal part of the cerebellum. Each microfolium was just rostral to a normal fissure and interposed between the fissure and a normal gyrus. Lamination abnormalities included an increase in the number of single ectopic granule cells in the molecular layer in both cerebellar vermis (86%) and hemisphere (40%) in comparison with the wild-type mouse. In the hippocampus of the Pit1dw-J homozygote mouse, the number of pyramidal cells was decreased, although the width of the pyramidal cell layer throughout areas CA1-CA3 appeared to be normal, but less densely populated than in the wild-type mouse. Moreover, the number of granule cells that form the granule cell layer was decreased from the wild-type mouse and some ectopic granule cells (occurring both as single cells and as small clusters) were observed in the innermost portion of the molecular layer. The abnormalities observed in the Pit1dw-J homozygote mouse seem to be caused by both direct and indirect effects of the deficiency of TSH (or T4), PRL, or GH rather than by a direct effect of the deletion of Pit1.

Animals↗
PubMed1998

Potential of Escherichia coli GTP cyclohydrolase II for hydrolyzing 8-oxo-dGTP, a mutagenic substrate for DNA synthesis.

MutT protein of Escherichia coli prevents the occurrence of A:T --> C:G transversion by hydrolyzing an oxidized form of dGTP, 8-oxo-7, 8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP), which is produced by active oxygen species. In a search for mutT-related genes, we found that the ribA gene, encoding GTP cyclohydrolase II, is able to reduce the increased level of mutation frequency of the mutT strain to almost the normal level, provided that the gene product is overproduced. Purified preparations of Escherichia coli GTP cyclohydrolase II protein as well as the histidine hexamer-tagged recombinant GTP cyclohydrolase II protein efficiently hydrolyze 8-oxo-dGTP and 8-oxo-GTP, producing 8-oxo-dGMP and 8-oxo-GMP, respectively. dGTP was not hydrolyzed by these preparations. GTP cyclohydrolase II catalyzes conversion of GTP to 2, 5-diamino-6-hydroxy-4-(5-phosphoribosylamino)-pyrimidine, which constitutes the first step for riboflavin synthesis. The Km values for the three types of guanine nucleotides, GTP, 8-oxo-GTP, and 8-oxo-dGTP, were almost the same. In the mutT- background, ribA- cells showed higher spontaneous mutation frequencies as compared with that of ribA+ cells. Thus, GTP cyclohydrolase II, the ribA gene product, has a potential to protect genetic material from the untoward effects of endogenous oxygen radicals.

Base Sequence↗
PubMed1998

Comparison of clinical features and prognosis of cardiac sarcoidosis and idiopathic dilated cardiomyopathy.

In the present study, clinical findings of 15 patients with cardiac sarcoidosis presenting as dilated cardiomyopathy were compared with those of 30 consecutive patients with idiopathic dilated cardiomyopathy. The sarcoidosis patients had different clinical features, including female predominance, a high incidence of grave conduction disturbance and abnormal wall thickness, uneven wall motion abnormalities, and perfusion defects preferentially affecting the anteroseptal and apical regions, and poor prognosis compared with those with idiopathic dilated cardiomyopathy.

Adult↗
PubMed1998

Development of obstructive hypertrophic cardiomyopathy from nonobstructive hypertrophic cardiomyopathy.

A rare case of obstructive hypertrophic cardiomyopathy (HC) with mitral regurgitation (MR) is reported, which developed over 7 years from nonobstructive HC in an elderly woman. Systolic anterior motion of the anterior mitral leaflet was the most likely cause of the outflow obstruction and mitral valve replacement combined with septal myectomy resulted in complete abolition of the outflow tract gradient and MR.

Aged↗
PubMed1998

A prolactin-releasing peptide in the brain.

Hypothalamic peptide hormones regulate the secretion of most of the anterior pituitary hormones, that is, growth hormone, follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone and adrenocorticotropin. These peptides do not regulate the secretion of prolactin, at least in a specific manner, however. The peptides act through specific receptors, which are referred to as seven-transmembrane-domain receptors or G-protein-coupled receptors. Although prolactin is important in pregnancy and lactation in mammals, and is involved in the development of the mammary glands and the promotion of milk synthesis, a specific prolactin-releasing hormone has remained unknown. Here we identify a potent candidate for such a hormone. We first proposed that there may still be unknown peptide hormone factors that control pituitary function through seven-transmembrane-domain receptors. We isolated the complementary DNA encoding an 'orphan' receptor (that is, one for which the ligand is unknown). This receptor, hGR3, is specifically expressed in the human pituitary. We then searched for the hGR3 ligand in the hypothalamus and identified a new peptide, which shares no sequence similarity with known peptides and proteins, as an endogenous ligand. We show that this ligand is a potent prolactin-releasing factor for rat anterior pituitary cells; we have therefore named this peptide prolactin-releasing peptide.

Amino Acid Sequence↗
PubMed1998

Light-induced retinal degeneration suppresses developmental progression of flip-to-flop alternative splicing in GluR1.

AMPA receptors are hetero-oligomers composed of subsets of four distinct subunits, termed GluR1, GluR2, GluR3, and GluR4. Using quantitative reverse transcription-PCR analysis, we have found that light-induced degeneration of rat retina dramatically suppresses developmental progression of the flip-to-flop alternative splicing switch of retinal GluR1 mRNA. When animals were raised under standard conditions of a 12 hr light/dark cycle (LD 12:12), the flop-to-flip ratio in GluR1 and GluR2 dramatically increased between postnatal day 10 (P10) and P28, and the ratios continued to increase gradually up to P84. When animals were raised in complete darkness, this increase was delayed in GluR1 between P21 and P42. In addition, the increase of the flop-to-flip ratio in GluR1 was strongly suppressed after P21 under conditions of continuous illumination from P2. This is significant because P21 is just after the eye opening and is the timing of the onset of light-induced retinal degeneration. This suppression of the increase of the flop-to-flip ratio was specific to GluR1 and was not observed in GluR2-4. Immunocytochemistry and immunoblot analysis suggested no changes in either the distribution or expression of GluR1 protein in the light-damaged retina measured at P84. When rats were raised under continuous illumination from P2 to P21 followed by LD 12:12 from P22 to P84, retinal degeneration did not progress after P22. In such animals the flop-to-flip ratio, once decreased to approximately 50% of the control (LD 12:12) at P21, was restored to the control level at P84. These findings demonstrate that developmental progression of the flip-to-flop exon switch in retinal GluR1 is affected by lighting conditions, and that light-induced retinal degeneration contributes to the mechanism of suppression of this splicing switch.

Alternative Splicing↗
PubMed1998

Separation of killing and tumorigenic effects of an alkylating agent in mice defective in two of the DNA repair genes.

Alkylation of DNA at the O6-position of guanine is one of the most critical events leading to mutation, cancer, and cell death. The enzyme O6-methylguanine-DNA methyltransferase repairs O6-methylguanine as well as a minor methylated base, O4-methylthymine, in DNA. Mouse lines deficient in the methyltransferase (MGMT) gene are hypersensitive to both the killing and to the tumorigenic effects of alkylating agents. We now show that these dual effects of an alkylating agent can be dissociated by introduction of an additional defect in mismatch repair. Mice with mutations in both alleles of the MGMT gene and one of the mismatch repair genes, MLH1, are as resistant to methylnitrosourea (MNU) as are wild-type mice, in terms of survival, but do have numerous tumors after receiving MNU. In contrast to MGMT-/- MLH1(+/+) mice with decrease in size of the thymus and hypocellular bone marrow after MNU administration, no conspicuous change was found in MGMT-/- MLH1(-/-) mice treated in the same manner. Thus, killing and tumorigenic effects of an alkylating agent can be dissociated by preventing mismatch repair pathways.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Association of high-altitude pulmonary edema with the major histocompatibility complex.

BACKGROUND: A constitutional susceptibility has been suggested in the development of high-altitude pulmonary edema (HAPE) because HAPE generally affects healthy young people, some of whom suffer recurrent episodes. We examined whether immunogenetic susceptibility is present in HAPE-susceptible subjects. METHODS AND RESULTS: The frequencies of human leukocyte antigen (HLA) alleles in 28 male and 2 female subjects with a history of HAPE were compared with those in 100 healthy volunteers. We assayed the HLA-A, -B, -C, -DR, and -DQ antigens serologically. The pulmonary hemodynamics on admission to the hospital and the ventilatory response to hypoxia and hypercapnia were retrospectively examined in 10 of the HAPE-susceptible subjects. HLA-DR6 was positive in 14 (46.7%) of the subjects with HAPE but only 16.0% of the control subjects (P=.0005), and HLA-DQ4 was positive in 12 (40.0%) of the subjects with HAPE but only 10.0% of the control subjects (P=.0001). HLA-DR6 or HLA-DQ4 was positive in 8 (100%) of the subjects with recurrent HAPE. The pulmonary arterial pressure on admission of the HLA-DR6-positive subjects with HAPE was significantly higher than that of the HLA-DR6-negative subjects with HAPE. CONCLUSIONS: There were significant associations of HAPE with HLA-DR6 and HLA-DQ4 and of pulmonary hypertension with HLA-DR6. An immunogenetic susceptibility, which is associated with HLA class II alleles located within the major histocompatibility complex, may underlie the development of HAPE, at least in some of its forms.

Adolescent↗
PubMed1998

Lecithinized superoxide dismutase attenuates phorbol myristate acetate-induced injury in isolated dog lung.

Lecithinized superoxide dismutase, a lecithin derivative bound to recombinant human CuZn superoxide dismutase, has a higher affinity for cells such as polymorphonuclear leukocytes and endothelial cells than recombinant human CuZn superoxide dismutase has. We determined the protective effects of lecithinized superoxide dismutase on the increased microvascular permeability induced by phorbol myristate acetate (PMA) in isolated dog lungs. Microvascular permeability was assessed by the capillary filtration coefficient (Kf,c) and solvent drag reflection coefficient (sigma(f)). PMA (13.3 microg) increased microvascular permeability, as evidenced by an increase in Kf,c and the small sigma(f) value. Lecithinized superoxide dismutase at both low (4800 U) and high doses (48,000 U) inhibited the PMA-induced increase in Kf,c, but only the high dose of lecithinized superoxide dismutase attenuated the decrease in sigma(f). Recombinant human CuZn superoxide dismutase did not affect the PMA-induced increase in vascular permeability at either a low (4800 U) or a high dose (48,000 U). These findings suggest that lecithinized superoxide dismutase has a protective effect against oxygen radical-induced lung injury in isolated dog lungs.

Animals↗
PubMed1998

Ultrastructural and immunohistochemical analysis of biopsy-proven chronic active mycocarditis with numerous clusters of lymphocytes.

A 60-year-old women was admitted to our hospital with deteriorating congestive heart failure. Although the diagnosis of active myocarditis was confirmed by right ventricular endomyocardial biopsy, this patient died of refractory heart failure during corticosteroid treatment. Numerous lymphocytic clusters were observed microscopically in the heart at autopsy. Most of the infiltrating cells in the clusters were positive for CD 8, HAM 56 or MHC class 2 antigen; few cells were positive for CD 56. Expression of perforin was found in some of the infiltrating cells. Electron microscopic examination revealed small lymphocytes adhering to the surface of injured cardiac myocytes. Close contact of these lymphocytes to macrophages was shown in the clusters. ICAM-1 and MHC class 1 antigens were strongly expressed in the cardiac tissue. These results indicate that cytotoxic T lymphocyte-mediated cytotoxicity had continued to operate during immunosuppressive therapy. Corticosteroids may not be suitable for the treatment of chronic active myocarditis when persistent expression of ICAM-1 is observed.

Antibodies↗
PubMed1998

Molecular cloning of AtMMH, an Arabidopsis thaliana ortholog of the Escherichia coli mutM gene, and analysis of functional domains of its product.

We isolated and characterized cDNAs and a genomic clone encoding an Arabidopsis thaliana MutM homolog (AtMMH). AtMMH is a single-copy gene spanning about 3 kb in the nuclear genome, and comprises ten exons. The AtMMH gene encodes two types of mRNA (AtMMH-1 and AtMMH-2) formed by alternative splicing of exon 8. Western analysis of a crude extract from leaves of A. thaliana, using polyclonal antibodies against the recombinant proteins, demonstrated the presence in vivo of a single 44-kDa polypeptide that comigrates with the product of in vitro translation of the AtMMH-1 mRNA. AtMMH-1 protein prepared in vitro is able to nick double-stranded oligonucleotides containing 8-oxo-7,8-dihydroguanine (8-oxoG) and to bind such oligonucleotides, as does the Escherichia coli MutM protein, which possesses 8-oxoG DNA glycosylase and apurinic/apyrimidinic (AP) lyase activities. Deletion of six amino acids (PELPEV), which are conserved among all known MutM homologs, from the N-terminal end of the AtMMH-1 protein abolishes its nicking but not its DNA-binding activity, indicating that these residues are essential for catalytic activity. Although the AtMMH-1 protein has a unique structure at its C-terminal end, which consists of alternating repeats of basic and acidic amino acids, this structure is dispensable for activity. However, the adjacent amino acid sequence (residues 268 to 281) is essential for repair activity.

Amino Acid Sequence↗
PubMed1998

Churg-Strauss syndrome (allergic granulomatous angitis) presenting with ileus caused by ischemic ileal ulcer.

We report a rare case of Churg-Strauss syndrome (CSS) in a 41-year-old Japanese man with a history of middle-age onset of bronchial asthma who had severe abdominal pain. He presented with ileus caused by an annular ulcer of the ileum, attributable to mucosal ischemia resulting from necrotizing vasculitis of the mesenteric artery. He also had marked hypereosinophilia (51.5%), elevated serum IgE levels (34040 IU/ml), and generalized enlargement of the superficial cervical lymph nodes, containing eosinophilic granulomas. A stenotic lesion caused by an annular ulcer in the ileum was found and resected by laparotomy. Microscopic examination of the resected specimen revealed luminal narrowing or occlusion of small arteries in the ulcer base, subserosa, and mesenterium resulting from marked fibrotic intimal thickening with fragmentation or lack of the internal elastic lamina. These findings were diagnosed as vasculitis, scar stage. The postoperative course was uneventful, with the patient receiving a maintenance dose of prednisolone (10-15 mg/day) for 7 years subsequently. We must carefully diagnose and treat patients with middle-age onset asthma, because the symptom may be a lung manifestation of CSS, in which various organs including gastrointestinal tract are involved as a result of systemic necrotizing vasculitis.

Adult↗
PubMed1998

Smoke extract stimulates lung epithelial cells to release neutrophil and monocyte chemotactic activity.

Inflammatory cells accumulate within the lungs of cigarette smokers. Current concepts suggest that these cells can induce protease-antiprotease and/or oxidant-antioxidant imbalance(s), which may damage the normal lung alveolar and interstitial structures. Because type II pneumocytes line the alveolar space, and because the inflammatory cells migrate and reside at the alveolus, we postulated that the type II pneumocytes might release chemotactic activity for neutrophils and monocytes in response to smoke extract. To test this hypothesis, A549 cells were cultured and the supernatant fluids were evaluated for the neutrophil and monocyte chemotactic activity (NCA and MCA) by a blind-well chamber technique. A549 cells released NCA and MCA in response to smoke extract in a dose- and time-dependent manner (P < 0.05). Checkerboard analysis showed that the activity was chemotactic. Partial characterization of NCA and MCA revealed that the activity was partly heat labile, trypsin sensitive, and ethyl acetate extractable. Lipoxygenase inhibitors and cycloheximide inhibited the release of NCA and MCA. Molecular sieve column chromatography showed multiple peaks for both NCA and MCA. NCA was inhibited by anti-human-interleukin (IL)-8 antibody, granulocyte colony-stimulating factor (G-CSF) antibody, or leukotriene (LT)B4 receptor antagonist. Monocyte chemoattractant protein (MCP)-1 antibody or LTB4 receptor antagonist inhibited MCA. Immunoreactive IL-8, G-CSF, MCP-1, and LTB4 significantly increased in the supernatant fluids in response to smoke extract. These data suggest that the type II pneumocytes may release NCA and MCA and modulate the inflammatory cell recruitment into the lung.

Antibodies↗
PubMed1998

Sensitive diagnosis of cardiac allograft rejection by detection of cytokine transcription in situ.

OBJECTIVE: In situ transcription of cytokines which are important in the development of cardiac rejection has not been evaluated for diagnosing rejection. The objective was to evaluate the usefulness of in situ reverse transcriptase polymerase chain reaction (RT-PCR) for sensitive detection of acute cardiac rejection. METHODS: We studied interferon (IFN)-gamma and interleukin (IL)-2 expression using immunohistochemistry and in situ RT-PCR in murine cardiac transplant models. Hearts were heterotopically transplanted (BALB/c to C3H/He) and some mice were not treated (n = 23); others were treated with anti-intercellular adhesion molecule (ICAM)-1 and anti-lymphocyte function associated antigen (LFA)-1 monoclonal antibodies (mAbs) (n = 23). Allografts were removed at days 1 to 7. For control, isografts were harvested at day 7 (n = 2). RESULTS: Mice without treatment rejected allografts within 7 days, while all mAb-treated recipients accepted allografts for the same period. At day 1, allografts of both groups showed scattered myocardial cell infiltration which increased in non-treated allografts, but remained stable in mAb-treated grafts thereafter. In situ RT-PCR showed that IL-2 and IFN-gamma mRNA positive cells were present in non-treated allografts, while few mRNA positive cells were expressed in infiltrating cells in the mAb-treated allografts (IL-2, day 3: 88.8 +/- 28.3 vs. 7.2 +/- 6.4, p < 0.05, positive cells within 10 fields per section). However, immunohistochemistry could not reveal the difference at day 3. CONCLUSION: In situ RT-PCR is a sensitive method for diagnosing acute rejection, and it reveals the characteristics of myocardial infiltrate cells to determine their role in the process of rejection.

Animals↗
PubMed1998

A case of pathophysiologic study in Kimura's disease: measurement of cytokines and surface analysis of eosinophils.

BACKGROUND: Kimura's disease is a rare but distinctive eosinophilic inflammatory disorder of unknown etiology; few reported case studies have focused on the immunopathologic background of this unique disease. OBJECTIVE: To define better the immunopathogenetic features of Kimura's disease, we attempted to quantitatively analyze values of cytokines and soluble interleukin-2 receptor (sIL-2R) in peripheral blood (PB), as well as perform surface immunophenotypic analysis of eosinophils from a Japanese patient with chronic relapsing Kimura's disease. RESULTS: Granulocyte macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor-alpha (TNF-alpha) and sIL-2R were elevated, and newly expressed antigens on eosinophils CD4, CD25, and HLA-DR were found to be involved in the pathophysiology of this disorder. CONCLUSIONS: Kimura's disease may be a disease in which activated lymphocytes release cytokines, and these released cytokines, such as GM-CSF and TNF-alpha cause eosinophil activation. These processes may be related to the pathogenesis of this disorder.

Aged↗
PubMed1998

Pharmacological detection of AMPA receptor heterogeneity by use of two allosteric potentiators in rat hippocampal cultures.

1. In order to examine whether a recently developed allosteric potentiator for AMPA receptors, 4-[2-(phenylsulphonylamino)ethylthio]-2,6-difluoro-phenoxyaceta mide (PEPA), can be utilized as an indicator of AMPA receptor heterogeneity, the action of PEPA upon the increase of intracellular free calcium ion concentration ([Ca2+]i) elicited by AMPA was investigated in rat hippocampal cultures, and the action was compared with that of cyclothiazide, a well characterized allosteric modulator of AMPA receptors. 2. PEPA dose-dependently potentiated AMPA-induced increase of [Ca2+]i. In 90% (72 out of 80) of the cells in which cyclothiazide acts, PEPA potentiated the increased [Ca2+]i induced by AMPA with pronounced cell-to-cell variation in rat hippocampal cultures. 3. The ratio of the potentiation by PEPA to the potentiation by cyclothiazide (P/C ratio) also varied with cells between 0 and 2.15. It was found that the cultured hippocampal cells consisted of multiple populations with different P/C ratios. Among them two populations exhibited characteristic P/C ratios; low (0 to 0.15; 27 out of 80 cells, 34%) and high (> or = 2.00; 1 out of 80 cells, 1%) P/C ratios. The P/C ratios of the other populations were between 0.25 and 1.20, and these cells constituted 65% (52 out of 80 cells) of the cells tested. 4. Reverse transcriptase-polymerase chain reaction analysis suggested that GluR2-flip, GluR1-flip, GluR2-flop, and GluR1-flop were abundantly expressed (in this rank order) in the cultures used. 5. In Xenopus oocytes expressing GluR1, GluR3, or these subunits plus GluR2, the potentiation of AMPA response by PEPA and by cyclothiazide varied with subunit and splice-variant combinations, and the P/C ratio was between 0.19 and 2.20. Oocytes with low P/C ratios (0.19 to 0.50) and low sensitivity to PEPA potentiation (1.9 fold to 6.41 fold) were those expressing flip variants predominantly, and oocytes with high P/C ratios (1.8 to 2.2) were those expressing flop variants predominantly. Oocytes with intermediate P/C ratios (0.51 to 1.20) were those expressing various combinations of flip and flop variants, and it was impossible to specify the relative abundance of flip and flop variants in these cells. Therefore, the P/C ratio can be used to infer subunit/splice variant expression only when the ratio is low or high. 6. These results suggest that the potentiation by PEPA alone reveals cell-to-cell heterogeneity of AMPA receptors, but a comparison of the actions of PEPA and cyclothiazide further facilitates the detection of the heterogeneity.

Allosteric Regulation↗
PubMed1998

Pharmacokinetic disposition and arthropathic potential of oral ofloxacin in dogs.

We examined the relation between the pharmacokinetic disposition and arthropathic potential of ofloxacin, a new quinolone antibacterial agent, using both male immature (3-month-old) and mature (18-month-old) beagles. Ofloxacin was orally administered to these dogs at 20 mg/kg once daily for 8 consecutive days, and the animals were killed 2 h after the last treatment. Serum ofloxacin concentrations were repeatedly measured on days 1 and 7 by use of high-performance liquid chromatography (HPLC), and pharmacokinetic parameters were calculated. In addition, on day 8, the drug concentrations in the joint synovial fluid and humeral and femoral condyles were measured. Clinico-pathological tests of blood and serum or histopathological examination of bone specimens were also performed. Arthropathy was macroscopically observed in the cartilage surface of all immature dogs, but not in mature dogs. There were, however, no noticeable differences in pharmacokinetic parameters between the two age groups of dogs or between single and 7-day treatments. In contrast to the occurrence of arthropathic lesions, the synovial fluid and condylar drug concentrations in immature dogs was equal to or lower than those in mature dogs, suggesting that the pharmacokinetic disposition of ofloxacin may not be essential for cartilage lesions.

Administration, Oral↗