Biomedical subjects

M Yamada

Publications and source records attributed to M Yamada.

At least 199 records · Page 11Linked to original sources

PubMed2001

Niflumic acid reduces the hyperpolarization-activated current (I(h)) in rod photoreceptor cells.

We examined the effects of niflumic acid (NFA), a chloride channel blocker, on the hyperpolarization-activated current (I(h)) in newt rod photoreceptors. At 100 microM, NFA delayed the activation of I(h) induced by hyperpolarizing voltage pulses to -83 mV from a holding potential of -43 mV, and reduced the steady-state current. However, reduction by NFA was weakened when I(h) was activated by hyperpolarizing steps to -123 mV, suggesting that these effects were voltage-dependent. The suppressive effects of NFA on I(h) were accompanied by a negative shift in activation voltage. NFA also delayed the relaxation of I(h) tail currents, showing that this drug also inhibited deactivation of the current. The reversal potential and the fully activated conductance were not affected. These observations suggest that NFA reduces I(h) by modifying the gating kinetics of the underlying channels. The suppressive actions of NFA remained when intracellular Ca2+ was strongly chelated, and the failure of suppression by NFA in inside-out patches suggests that the agent may act on the I(h) channel from the extracellular side. These results, obtained in rod photoreceptors, are consistent with similar effects of NFA on I(f) in cardiac myocytes, suggesting that both currents share similar pharmacological properties.

Animals↗

PubMed2001

Sedimentable amyloplasts in starch sheath cells of woody stems of Japanese cherry.

We examined whether sedimentable amyloplasts act as statolith in the perception of gravity in woody stems using the elongated internodes of Japanese cherry (Prunus jamasakura Sieb. ex Koidz.). In the internode of the seedlings grown on earth, amyloplasts were found sedimented at the distal end of each cell of the endodermal starch sheath tissue. In the internode grown on three-dimensional (3-D) clinostat, amyloplasts were dispersed throughout the cell matrix in the endodermal starch sheath tissue. After changing the positions of the internode from vertical to horizontal, re-sedimentation of amyloplasts toward the direction of gravity was completed in 1h, whereas the bending of the internode was observed after 12 days. We propose that sedimentable amyloplasts in the endodermal starch sheath cells may play a role in gravity perception leading to secondary xylem formation in the secondary thickening growth and eccentric growth in gravi-bending of tree stems.

Gravitation↗

PubMed2001

Expression of Jagged1 gene in macrophages and its regulation by hematopoietic growth factors.

OBJECTIVE: Serrate/Jagged and Delta are cell surface ligands for Notch receptors that may influence hematopoietic cell fate decisions and are known to be expressed in bone marrow stromal cells. In a series of screenings of cDNAs constructed by a cDNA library subtraction technique, we identified Jagged1, one of the Notch ligands, as a gene up-regulated by macrophage colony-stimulating factor (M-CSF) in bone marrow macrophages. Therefore, we compared stromal cells and macrophages for expression of Notch ligands including Jagged1 and analyzed the regulation of their expression by cytokines. MATERIALS AND METHODS: Murine bone marrow macrophages were prepared by culturing femoral bone marrow cells with M-CSF. Primary bone marrow fibroblastic stromal cells were prepared by a culture system that we recently developed. The expression of Notch ligands was analyzed by either Northern blot analysis or reverse transcriptase polymerase chain reaction. RESULTS: The bone marrow macrophages expressed Jagged1 but not Jagged2 and Delta1 at a level that was detectable by Northern blot analysis. Expression of the Jagged1 gene was markedly up-regulated by growth factors for the cells, i.e., M-CSF, granulocyte-macrophage colony-stimulating factor, and interleukin-3. Expression of Jagged2 and Delta1 seldom was affected by the stimuli. The primary bone marrow fibroblastic stromal cells, and murine stromal cell lines, such as PA6 and ST2, also expressed Jagged1 transcript, at levels comparable to the steady-state level in macrophages. However, expression of the Jagged1 gene was little affected when these cells were stimulated with fibroblastic growth factor and platelet-derived growth factor. CONCLUSIONS: We demonstrated that bone marrow macrophages as well as stromal cells constitutively produced Jagged1 and that the expression was markedly up-regulated by hematopoietic growth factors, M-CSF, granulocyte-macrophage colony-stimulating factor, and interleukin-3. The results highlight the involvement of macrophages and these growth factors in hematopoietic cell fate decisions via the production of Jagged1.

Animals↗

PubMed2001

Mutational analysis of MECP2 in Japanese patients with atypical Rett syndrome.

Rett syndrome (RTT) is one of the most common neurodevelopmental disorders in females. Recently, this disease was found to be linked with mutations in the methyl-CpG-binding protein 2 gene (MECP2) and various mutations have been reported. To explore the spectrum of phenotypes resulting from MECP2 mutations, we searched for mutations in the MECP2 of 20 Japanese patients who had more than five of the criteria necessary for RTT diagnosis proposed in 1988 (The Rett Syndrome Diagnostic Criteria Work Group, Ann Neurol 23 (1988) 425) and compared the phenotype between patients with and without mutation by giving a score to each diagnostic criterion. We found four missense mutations (T158M, R133C, Y120D, and R306C), two nonsense mutations (R168X and R270X), one frameshift (726delAAAG) mutation, and one polymorphism (A201V) in ten patients (50%). This included two novel mutations (726delAAAG and Y120D). All mutations were found in the highly conserved methyl-binding and transcription repression domains. Comparison of the mean total diagnostic criterion score of the groups with and without mutation did not reveal any statistically significantly difference (P=0.28). The only difference between the groups, which was of borderline significance (P=0.051), was the sum of the scores for diagnostic criteria 2 (apparently normal psychomotor development through the first 6 months) and 5 (loss of acquired purposeful hand skills between the ages of 6 and 30 months). From these results, it is suggested that the clinical phenotype of RTT is variable and it is important to investigate the MECP2 genotype for patients having more than five criteria and not only in those who exhibit all RTT diagnostic criteria. The diagnosis of RTT is clinically difficult before 3 years of age, especially in atypical cases, but molecular analysis of the MECP2 will assist diagnosis in some patients.

Adolescent↗

PubMed2001

Formation of 2-chloroinosine from guanosine by treatment of HNO(2) in the presence of NaCl.

We investigated the reaction of Guo with nitrous acid in the presence of NaCl. When 1 mM Guo was incubated with 100 mM NaNO(2) and 2M NaCl in sodium acetate buffer at pH 3.2 and 37 degrees C, 2-chloroinosine (2-Cl-Ino) was produced in addition to oxanosine (Oxo) and xanthosine (Xao). The yield of 2-Cl-Ino was 0.033 mM at an incubation time of 2 h. Under the same reaction conditions, GMP and dGuo gave rise to the corresponding 2-chloro derivatives with comparable yields. All the 2-chloro derivatives were fairly stable (t(12)>360 h) at physiological pH and temperature. To elucidate the reaction mechanism of the chlorination, the diazoate derivative of Guo, a reaction intermediate of the Guo-HNO(2) system, was employed as a starting compound. When the diazoate was incubated with 2M NaCl in a neutral solution, 2-Cl-Ino was produced in addition to Oxo and Xao. These results suggest that the 2-chloro derivatives can be produced from foodstuffs in the human stomach and may have potential importance as a carcinogen causing gastric cancer.

Digestion↗

PubMed2001

Mutant Plp/DM20 cannot be processed to secrete PLP-related oligodendrocyte differentiation/survival factor.

Most of the mutations within the PLP gene result in degeneration of oligodendrocytes and this is believed to be caused by intracellular trafficking defects. Previous studies have demonstrated that cells expressing the wild type PLP gene release a factor promoting differentiation/survival of oligodendrocyte and that this factor is the C-terminal portion of the protein itself. In this study we asked how the naturally occurring mutations of the PLP gene (jimpy, jimpy msd, and rumpshaker) affect this activity. We developed a transient expression system for retroviral production and transduction that enabled the expression of mutant PLP/DM20 cDNAs in NIH3T3 cells. None of the NIH3T3 cells producing mutant PLP/DM20s secreted the PLP-related factor that increases the number of oligodendrocytes. Since it has been shown that rumpshaker DM20 can be transported to the cell surface, but its folding is incorrect, absence of secretion of this factor is more heavily attributable to incorrect protein folding than to the defect in the PLP/DM20 trafficking.

3T3 Cells↗

PubMed2001

Soluble products from Eikenella corrodens stimulate oral epithelial cells to induce inflammatory mediators.

In the inflammatory response elicited by bacterial colonization in periodontal pockets, pocket epithelial cells not only serve as a barrier to isolate the pocket microenvironment from external stimuli but also regulate the functions of neighboring cells including fibroblasts and inflammatory cells. To elucidate this mechanism, we characterized the effects of periodontopathic bacterium Eikenella corrodens 1073 components on the production of some inflammatory mediators in a human oral epithelial cell line (KB). In enzyme-linked immunosorbent assay (ELISA), the E. corrodens supernatant induced interleukin-6 (IL-6), IL-8 and prostaglandin E2 but not interferon-gamma (IFN-gamma) production by KB cells. After incubation with E. corrodens supernatant, KB cells showed a marked increase in the levels of IL-6, IL-8 and PG G/H synthase (cyclooxygenase)-2, but not IFN-gamma, gene expression by reverse-transcriptase polymerase chain reaction. All these E. corrodens products responsible for production of these inflammatory mediators resisted freezing and boiling and were present in a 10-kDa filtrate. These results imply that these soluble small-molecular-mass products from E. corrodens stimulate various inflammatory mediator productions by human oral epithelial cells and may play a role in the initiation of periodontal inflammation and subsequently perpetuate the inflammatory response during chronic infection.

Bacterial Adhesion↗

PubMed2001

Analysis of immunoglobulin secretion by lymph organs with myasthenia gravis.

OBJECTIVES: To investigate in vitro anti-acetylcholine receptor (AChR) antibody secretion by lymph organs with myasthenia gravis (MG) with special attention to clinical status and stages. MATERIALS AND METHODS: Twenty MG patients before therapy were included in this study. Four patients were negative for serum anti-AChR antibodies (AChRAb). All patients received extended thymectomy. Thymic cells, bone marrow (BM) cells and peripheral blood mononuclear cells (PBMC) were cultured for 1 week. AChRAb secretion and IgG secretion in the culture medium were determined by immunoprecipitation assays and ELISA respectively. RESULTS: PBMC secreted AChRAb and IgG most efficiently, followed by BM cells, and then thymic cells. Even in patients whose diseases were of short duration (less than 2 months), the tendency was not changed. AChRAb secretion by BM cells and PBMC significantly correlated with serum AChRAb levels. Thymectomy did not change AChRAb or IgG secretion by PBMC within 3 months. AChRAb secretion by PBMC paralleled the clinical status. Some seronegative patients turned positive by culturing PBMC. CONCLUSION: PBMC is the most efficient site at producing AChRAb, even in patients of short duration (equal to, or less than, 2 months). Monitoring AChRAb secretion by PBMC is useful to estimate the autoimmune activity of MG.

Adolescent↗

PubMed2001

Extended polyglutamine selectively interacts with caspase-8 and -10 in nuclear aggregates.

A growing number of inherited neurodegenerative disorders, including Huntington's disease, have been shown to be caused by the expansion of CAG/polyglutamine repeats. The molecular mechanism underlying these disorders, however, has yet to be clarified. We and others previously demonstrated that caspase-8 was activated by proteolysis in association with the expression of extended polyglutamine. Here, we further analyzed the selectivity of caspases in the process mediated by extended polyglutamine. Among upstream caspases, caspase-10, a close homolog of caspase-8, was also proteolytically activated, but caspase-9 was not. Caspase-8 and -10 were recruited into nuclear aggregates of extended polyglutamine, where at least a fraction of these caspases was converted to the activated forms. Caspase-8 and -10 were co-immunoprecipitated with polyglutamine only when the polyglutamine was pathologically extended, whereas caspase-2, -3, -6, -7 and -9 were not co-immunoprecipitated with polyglutamine regardless of its size. A dominant-negative form of caspase-8 with a mutation at the catalytic cysteine residue inhibited polyglutamine-mediated nuclear apoptotic phenotype. These results suggest that caspase-8 and -10 are autoactivated as a result of close proximity of the proforms of these molecules that occurs due to aggregate formation, which reveals a novel toxic gain-of-function mechanism for the pathogenesis of CAG-repeat disorders.

Apoptosis↗

PubMed2001

Chemiluminescent flow-through sensor for 1,10-phenanthroline based on the combination of molecular imprinting and chemiluminescence.

A functional polymer for the catalysis of the chemiluminescent reaction and molecular recognition ability of 1,10-phenanthroline was prepared based on the molecular imprinting method. The structural and catalytic roles of transition metal ion interactions were applied in the material design. A ternary complex, 4-vinylpyridine-Cu(II)-1,10-phenanthroline (2:1:1), was synthesized and used as a functional monomer. The ligand 1,10-phenanthroline in the ternary complex was the template used to form the molecularly imprinted polymer. Another monomer, styrene, and the cross-linking reagent divinylbenzene were copolymerized with the ternary complex. The polymer containing the ternary complex is an efficient catalyst for the decomposition of hydrogen peroxide. During the hydrogen peroxide decomposition, superoxide radical ion is formed, which reacts with 1,10-phenanthroline and gives a chemiluminescent emission. The 1,10-phenanthroline was destroyed during the chemiluminescent reaction, leaving a cavity and copper binding sites for another 1,10-phenanthroline molecule. The prepared polymer particles were packed into a glass tube and developed as a molecular recognition chemiluminescent flow-through sensor for 1,10-phenanthroline. The sensitivity and selectivity of the sensor were tested.

Journal Article↗

PubMed2001

No evidence of deregulated patched-hedgehog signaling pathway in trichoblastomas and other tumors arising within nevus sebaceous.

Nevus sebaceous is a congenital malformation of the skin within which a number of neoplasms showing adnexal differentiation may arise. Recently, deletions in the patched gene region were reported in nevus sebaceous and constitutive activation of the patched-hedgehog signaling pathway was implicated in the development of tumors arising within nevus sebaceous. To substantiate further a role of the patched-hedgehog signaling pathway in secondary tumors arising within nevus sebaceous, we examined 11 nevus sebaceous associated with secondary tumors for loss of heterozygosity of the patched gene region by microsatellite polymerase chain reaction and patched mRNA expression by in situ hybridization. Unexpectedly, however, none of the tumors (including eight trichoblastomas) and nevus sebaceous lesions showed loss of heterozygosity at any polymorphic loci close to the patched gene. Further more, none of the nevus sebaceous lesions and secondary tumors gave detectable signals for patched mRNA. In contrast, four of 11 sporadic basal cell carcinomas, that were examined for comparison, showed loss of heterozygosity at the patched gene locus (p <0.05), and moderate to strong signals for patched mRNA was observed in all seven basal cell carcinoma tumors examined (p <0.0001). Additional investigation by reverse transcription-polymerase chain reaction in four basal cell carcinomas and two nevus sebaceous tumors also showed the expression of Gli-1, another target gene in the patched-hedgehog signaling pathway, in all the basal cell carcinomas samples but not in any of the nevus sebaceous tumors examined. The findings in this study do not support the view that the deregulation of the patched-hedgehog signaling pathway is involved in the pathogenesis of nevus sebaceous and associated tumors, and show that, although morphologically similar, trichoblastomas and basal cell carcinomas have a different molecular pathogenesis.

Adult↗

PubMed2001

Erythropoietin synthesis by tumour tissues in a patient with uterine myoma and erythrocytosis.

We report a patient with uterine myoma (leiomyoma) and erythrocytosis in whom erythropoietin (Epo) production in the leiomyoma tissue was identified by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). A 48-year-old Japanese woman with uterine myoma showed marked erythrocytosis (haemoglobin: 20.2 g/dl, haematocrit: 61.1%, red blood cells: 6.51 x 10(12)/1). After hysterectomy, erythrocytosis rapidly disappeared. In the leiomyoma tissue collected from the patient, Epo mRNA expression was confirmed using RT-PCR. Furthermore, ELISA showed that the Epo protein level was significantly increased compared with those in control tissues. It is suggested that the pathogenesis of erythrocytosis in patients with uterine myoma involves ectopic Epo production by leiomyoma tissues.

Enzyme-Linked Immunosorbent Assay↗

PubMed2001

Autoimmune neutropenia in pregnant women causing neonatal neutropenia.

Autoimmune neutropenia (AIN) can occur during pregnancy. However, neonatal neutropenia occurring in an infant born to a mother with AIN has only rarely been documented. Recently, we have experienced two cases of AIN during pregnancy, both of which caused severe yet transient neonatal neutropenia (< 0.3 x 10(9)/l), probably as a result of transplacental maternal anti-neutrophil autoantibodies. The anti-neutrophil antibodies seemed to be against antigens other than NA1/NA2 because the autoantibodies did not bind to neutrophils of specific NA types selectively in the granulocyte indirect immunofluorescence test. Although AIN is a relatively uncommon disease, neonatal neutropenia caused by maternal AIN may not be quite as rare.

Adult↗

PubMed2001

Type 2-biased expression of cytokine genes in lung granulomatous lesions induced by Nippostrongylus brasiliensis infection.

Infections with helminthic parasites occasionally induce pulmonary diseases with possible involvement of immunological mechanisms. In rats infected with the nematode Nippostrongylus brasiliensis, pulmonary granulomatous lesions develop and persist after the larvae have migrated through the lungs. To determine the pathogenesis of this lesion, we examined cytokine gene expression in the lungs using RT-PCR and in situ hybridization. Two weeks after infection, when fully developed lesions appeared, levels of IL-3 and of type2 cytokines IL-4, IL-5, IL-6 and IL-13 gene expression were markedly enhanced in whole lung homogenates. Those of IL-2 and IFN-gamma were also slightly increased 2 weeks postinfection. IL-12 mRNA level did not change after 2 weeks but was slightly increased after 4 weeks. Levels of IL-10 and proinflammatory cytokine TNF gene expression did not show significant changes, although a slight increase was observed in IL-1beta message after 2 weeks. In situ hybridization studies showed that lung granulomatous lesions were composed mainly of lymphoid cells expressing IL-3, IL-4 and IL-13 mRNA, but not IFN-gamma mRNA. IL-5 mRNA-expressing cells were fewer in number than these cells. RMCP II immunohistochemistry revealed that mast cells increased in number in the lung granulomas. From these results, it was concluded that the nematode infection-associated lung granuloma was a type 2 lesion.

Animals↗

PubMed2001

A new portable measuring cup for voided volume.

When recording daily urine volumes for the frequency-volume chart, a patient must measure voided urine volume throughout the whole day. Unless the patient stays at home, the conventional 500-mL paper or plastic cup must be carried with at all times, which can be very embarrassing and troublesome for the patient, so a collapsible, portable measuring cup has been developed. To determine the measuring accuracy of the new cup, the visual estimate was compared with the actual volume. The cup was found to be a highly accurate and useful container for measuring voided urine volume.

Drinking↗

PubMed2001

Differences in survival-promoting effects and intracellular signaling properties of BDNF and IGF-1 in cultured cerebral cortical neurons.

Brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1) act on various neurons of the CNS as neurotrophic factors promoting neuronal differentiation and survival. We examined the survival-promoting effects of BDNF and IGF-1 on serum deprivation-induced death in cultured cerebral cortical neurons, and compared the intracellular signaling pathways stimulated by BDNF and IGF-1 in the neurons. We found that the survival-promoting effect of BDNF was much weaker than that of IGF-1 in serum deprivation-induced death of cultured cortical neurons. We found no differences in the levels of phosphatidylinositol 3-kinase (PtdIns3-K) activity or Akt (also called PKB) phosphorylation induced by BDNF and IGF-1 in the cultured cortical neurons, although many reports suggest that PtdIns3-K and Akt are involved in survival promotion. In addition, phosphorylation signals of mitogen-activated protein kinase (MAPK) and cAMP responsive element-binding protein (CREB), which have also been reported to be involved in survival promotion, were stimulated by BDNF much more potently than by IGF-1. These results show that there may be, as yet unidentified, intracellular signaling pathways other than the PtdIns3-K-Akt, MAPK and CREB signaling, to regulate survival promotion. These unidentified signaling pathways may be responsible for the distinct strengths of the survival-promoting effects of BDNF and IGF-1.

Animals↗

PubMed2001

Mast cell chymase expression and mast cell phenotypes in human rejected kidneys.

BACKGROUND: Mast cells (MCs) are known to participate in various types of chronic disease, but their role in chronic renal rejection is poorly understood. Recently, distinct phenotypes of MCs have been described in humans by the demonstration of one protease, chymase. Hence, we questioned whether chymase in MCs could play a role in the pathogenesis of renal rejection in humans. METHODS: We investigated MC chymase expression and MC phenotypes, using immunohistochemical single- and double-staining techniques, in nephrectomy (N = 13) and biopsy (N = 8) specimens of human rejected kidneys. Tissue chymase levels were determined by enzymatic assay for chymase activity. We also examined the association between MC chymase expression and the degree of interstitial fibrosis in these renal allografts. RESULTS: Based on chymase positivity, rejected kidneys were divided into two groups, a chymase-negative [Chy(-)] group and a chymase-positive [Chy(+)] group. Quantitative analysis showed that the number of chymase-positive MCs and tissue chymase levels were significantly higher in the Chy(+) group than in the Chy(-) group. Furthermore, the interstitial fibrotic area in the Chy(+) group was significantly larger than that in the Chy(-) group. Immunodouble staining analysis also demonstrated that a new MC phenotype, positive for chymase but negative for tryptase, was present in the human rejected kidney. CONCLUSIONS: These results show that increased expression of chymase in MCs is related to the severity of interstitial fibrosis in human rejected kidneys.

Adolescent↗

PubMed2001

Chymase-dependent angiotensin II formation in the saphenous vein versus the internal thoracic artery.

OBJECTIVES: The great saphenous vein graft is known to be less patent than the internal thoracic artery graft. Recently, we reported that chymase-dependent angiotensin II formation plays an important role in the development of intimal hyperplasia in dog grafted veins. In this study we investigated the levels of angiotensin II-forming enzymes, angiotensin-converting enzyme, and chymase in human saphenous veins and internal thoracic arteries. METHODS: The saphenous vein and internal thoracic artery specimens were obtained from coronary artery bypass grafts of patients during surgical procedures (saphenous vein, n = 16; internal thoracic artery, n = 16). Activities of angiotensin-converting enzyme and chymase were determined by using the extract from the saphenous vein or internal thoracic artery. Sections of the saphenous vein or internal thoracic artery were stained with van Gieson's elastin stain and were immunostained with anti-human chymase antibody. RESULTS: The activities of angiotensin-converting enzyme in the saphenous vein and internal thoracic artery were 0.34 +/- 0.12 and 0.32 +/- 0.17 mU/mg protein, respectively, and the difference was not significant. The chymase activity in the saphenous vein was significantly higher than that in the internal thoracic artery (saphenous vein, 10.1 +/- 0.81 mU/mg protein; internal thoracic artery, 6.21 +/- 1.86 mU/mg protein). Chymase-positive cells in the saphenous vein were located in both the media and adventitia, and those in the internal thoracic artery were located only in the adventitia. The number of chymase-positive cells in the saphenous vein was about 2.6 times that in the internal thoracic artery. CONCLUSION: The chymase activity, but not the angiotensin-converting enzyme activity, was significantly higher in the saphenous vein, suggesting that the high levels of chymase activity may be related to the poorer performance of the saphenous vein for use as a bypass conduit.

Aged↗