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Biomedical subjects

M Yamada

Publications and source records attributed to M Yamada.

At least 181 records · Page 10Linked to original sources
PubMed2001

Extra-anatomical bypass grafting for coarctation of the aorta associated with annuloaortic ectasia. Long-term outcome.

Two patients each with a rare combination of aortic coarctation and annuloaortic ectasia underwent successful single-stage repair in which the aortic root was reconstructed with a valved conduit, and an extra-anatomical bypass was made by grafting from the ascending to the abdominal aorta. Although the long-term outcome of such a long extra-anatomical bypass graft has not yet been established, the use of the graft for reducing the risk to coarctation-related complications during the early and late postoperative periods appears promising.

Adult↗
PubMed2001

Antitumor immunity induced by irradiated tumor cells producing macrophage colony-stimulating factor.

We previously reported that administration into mice of mouse lymphoid leukemia L1210 cells engineered to secrete macrophage colony-stimulating factor (M-CSF) could lead to tumor rejection. Here, we demonstrate that inoculation with irradiated M-CSF-producing cells protects mice against a subsequent challenge with unmodified parental tumor cells. We used 2 experimental protocols: the inoculation with irradiated M-CSF-producing L1210 cells (EM5) before the challenge with parental cells and after the challenge with parental cells. Both protocols effectively improved the survival rate of mice compared with protocols in which irradiated non-M-CSF-producing L1210 cells (EM-mock) were inoculated. Inoculation with 1 x 10(2) irradiated EM5 cells was sufficient to prolong the survival time of mice subsequently challenged with 1 x 10(4) parental cells. In vivo depletion experiments with administration of antibodies suggested the involvement of CD4+ T cells, CD8+ T cells, and natural killer (NK) cells in the antitumor effect. Consistent with these findings, the cytotoxic T lymphocyte activity of splenocytes from EM5-inoculated mice was higher than that from EM-mock-inoculated mice, and L1210 tumors were heavily infiltrated by CD4+ T cells and NK cells as well as macrophages in EM5-inoculated mice.

Animals↗
PubMed2001

Involvement of the cerebral cortex and autonomic ganglia in Machado-Joseph disease.

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder caused by expansion of a polyglutamine tract in the disease protein. In this study of brains from four autopsied MJD patients, we have demonstrated immunohistochemically that expanded polyglutamine stretches largely accumulate as inclusions in neuronal nuclei, and less frequently are distributed in the nucleoplasm in a diffuse pattern. These nuclear abnormalities involved many neurons covering a wide range of central and peripheral nervous system regions, including the cerebral cortex, thalamus and autonomic ganglia that have been categorized previously as spared regions by conventional pathological studies. These lesions, newly recognized by polyglutamine immunohistochemistry, may be responsible for the cerebral cortical dysfunctions or autonomic abnormalities pointed out in MJD patients by the recent clinical and neuroradiological studies.

Adult↗
PubMed2001

Co-localization of alpha-synuclein and phosphorylated tau in neuronal and glial cytoplasmic inclusions in a patient with multiple system atrophy of long duration.

Neuronal and glial cytoplasmic inclusions (NCIs and GCIs), which contain alpha-synuclein as a major component, are characteristic cytopathological features of multiple system atrophy (MSA). We report MSA of 19 years' duration in a 73-year-old woman. Her initial symptom was parkinsonism, with dementia appearing about 8 years later. Postmortem examination showed marked atrophy of the frontal and temporal white matter and limbic system, in addition to the pathology typical of MSA. In the limbic system, severe neuronal loss and astrocytosis were observed, and the remaining neurons often had lightly eosinophilic, spherical cytoplasmic inclusions. Interestingly, a double-labeling immunofluorescence study revealed that the NCIs in the dentate gyrus and amygdaloid nucleus, and the GCIs in the frontal and temporal white matter often expressed both alpha-synuclein NACP-5 and phosphorylated tau AT8 epitopes. Double-immunolabeling electron microscopy of the NCIs in the dentate gyrus and the GCIs in the temporal white matter clearly revealed labeling of their constituent granule-associated filaments with NACP-5, and some of them were also labeled with AT8. These findings strongly suggested that some alpha-synuclein filaments were decorated with phosphorylated tau without formation of fibrils such as paired helical filaments. Immunoblotting of sarkosyl-insoluble tau indicated that the accumulated tau consisted mainly of four-repeat tau isoforms of 383 amino acids and 412 amino acids. We consider that the limbic system can be a major site of neurodegeneration in MSA of long duration. The mechanisms of such abnormal tau accumulation in the NCIs and GCIs are unknown.

Aged↗
PubMed2001

Expression of calbindin D-28k and parvalbumin in cerebral cortical dysgenesis induced by administration of ethylnitrosourea to rats at the stage of neurogenesis.

It has been reported that transplacental administration of ethylnitrosourea (ENU), which is cytotoxic immediately after administration, to rat fetuses at the neurogenesis stage induces dysgenesis of the cerebral cortex, characterized by neuronal sparseness and architectural irregularity. In the present study, we examined the topographic distribution of neurons containing 5-bromo-2-deoxyuridine (BrdU), and those containing calbindin D-28k (CaBP) and parvalbumin (PV), most of latter two are considered to be interneurons located in particular layers of the normal cerebral cortex in rats with experimentally induced cerebral cortical dysgenesis. Pregnant Wistar albino rats were given a single transplacental administration of ENU on embryonic day 16, followed 4, 8, 16, 24, 36, or 48 h later by a single intraperitoneal injection of BrdU. The pups were killed 10 weeks after birth. In the normal cerebral cortex, BrdU-immunopositive neurons showed an inside-out pattern according to the time of BrdU injection, whereas in ENU-treated rats the topographic localization of the BrdU-immunopositive neurons was irregular and the inside-out pattern was disrupted. Although the number of CaBP- and PV-immunopositive neurons was lower in ENU-treated animals, no topographic difference was evident between the normal and the dysgenetic cerebral cortices. These findings indicate that the expression of CaBP and PV in the neurons of the rat cerebral cortex is extrinsic, and depends on the position of the neurons rather than on the time of their formation or on genetic control. This suggests the existence of re-regulation of the expression of CaBP and PV in the developing brain, which may be one of the effective mechanisms by which the cerebral cortex can maintain its normal function in spite of cytoarchitectural abnormality.

Abnormalities, Drug-Induced↗
PubMed2001

Roles of chromosomal and episomal dinB genes encoding DNA pol IV in targeted and untargeted mutagenesis in Escherichia coli.

DNA polymerase IV (pol IV) in Escherichia coli is a member of a novel family of DNA polymerases (the DinB/UmuC/Rad30/Rev1 super-family or the DNA polymerase Y family). Although expression of the dinB gene encoding DNA pol IV is known to result in an enhancement of untargeted mutagenesis, it remains uncertain whether DNA pol IV is involved in a variety of lesion-induced mutagenesis (targeted mutagenesis), and the relationship between expression levels of dinB and the mutagenesis that DNA pol IV promotes has not been investigated thoroughly. Here, we report that DNA pol IV is involved in -1 frameshift mutagenesis induced by 4-nitroquinoline N-oxide (4-NQO) and that the expression level of the chromosomal pol IV gene is 6-12 times higher than those for other SOS-inducible DNA polymerases in E. coli, i.e., DNA pol II (PolB) or DNA pol V (UmuDC), respectively. Interestingly, the dinB gene is present not only on the chromosome but also on the F' plasmid in the E. coli CC108 strain. In this strain, 750 molecules of DNA pol IV are expressed from the F' dinB gene in the uninduced state and 250 molecules are expressed from the chromosomal gene. These cellular expression levels strongly affect -1 frameshifts induced by 4-NQO in runs of six guanine bases: mutagenicity was highest in the strain CC108, followed by strains YG2242 (chromosome deltadinB/F' dinB+), YG2247 (chromosome dinB+/F' deltadinB) and FC1243 (chromosome deltadinB/F' deltadinB). The incidence of untargeted -1 frameshifts was reduced by two-thirds on deletion of dinB from the F' episome. The chromosomal dinB gene appeared to have little or no effect on the untargeted mutagenesis. These results suggest that DNA pol IV efficiently mediates targeted mutagenesis by 4-NQO, and that the cellular levels of expression substantially affect targeted and untargeted mutagenesis.

4-Nitroquinoline-1-oxide↗
PubMed2001

Extended surgery with en bloc resection of the right common iliac vessels for lymph node metastasis of mucinous colon carcinoma: report of a case.

We report herein the case of a 63-year-old woman who underwent surgery for recurrent mucinous carcinoma of the cecum. Recurrent metastatic lymph nodes had invaded the right common iliac vessels and right ureter, but she had no distant metastases and no peritoneal dissemination. Extended surgery with en bloc resection of the right iliac vessels and right ureter, and femorofemoral bypass were performed. Postoperatively, several complications developed which were successfully treated by further operations. By 1 year after surgery, she had no recurrent tumors on radiological examination, suggesting that our aggressive surgery with resection of the invaded regional vessels had effectively removed the recurrent tumors. This procedure may therefore significantly prolong the survival time and improve the quality of life of such patients.

Adenocarcinoma, Mucinous↗
PubMed2001

Immunoblot detection and expression of enamel proteins at the apical portion of the forming root in porcine permanent incisor tooth germs.

There have been many immunohistochemical studies of enamel proteins during root formation. In the present article, the detection and expression of enamel proteins in tissue samples prepared from the apical portion of the forming root (APFR) in porcine permanent incisor tooth germs were studied. Amelogenin, enamelin, and sheathlin were detected by immunoblot analysis, but only in small amounts. The detection of their derivatives indicated their degradation. It is, at present, unclear as to which proteinases are involved in these degradations, because activity of enamel matrix serine proteinase 1 and enamelysin was not detected on gelatin and casein zymograms. The expression of enamel proteins was also proved in the APFR sample by the detection of polymerase chain reaction products of their cDNAs, and this may be related to cells of fragmentized Hertwig's epithelial root sheath. Amelogenin expression was not greater than that of enamelin and sheathlin. It was different from the expression pattern of secretory ameloblasts involved in enamel matrix formation. These results suggest that the amelogenins found in the APFR do not form a three-dimensional structure of amelogenin micelles, which has been proposed for the secretory enamel matrix structure. In this case, the enamel proteins could spread out easily following degradation into the matrix of future cementum. Some of their derivatives may play a role in the formation of the cementum.

Amelogenin↗
PubMed2001

Fat adherence syndrome after retinal surgery treated with amniotic membrane transplantation.

PURPOSE: We present favorable results with amniotic membrane transplantation in a patient who developed fat adherence syndrome after retinal surgery. DESIGN: Interventional case report. METHODS: A 37-year-old man had diplopia resulting from hypotropia of the left eye after retinal detachment surgery. Removal of a previously implanted silicon sponge had little effect because of fibrous adhesion between the inferior rectus muscle and adjacent periorbital fat. We performed amniotic membrane transplantation combined with conventional extraocular muscle surgery. RESULTS: Postoperatively, supraduction of the left eye became almost full. The field of binocular vision was extended markedly by treatment, both in the primary position and with downward gaze. These improvements remained stable over 1 year of follow-up. CONCLUSION: Amniotic membrane transplantation appears to be effective for preventing regrowth of restrictive scar tissue in the fat adherence syndrome.

Adipose Tissue↗
PubMed2001

Interaction between neuronal intranuclear inclusions and promyelocytic leukemia protein nuclear and coiled bodies in CAG repeat diseases.

Neuronal intranuclear inclusions (NIIs) are a pathological hallmark of CAG repeat diseases. To elucidate the influence of NII formation on intranuclear substructures, we investigated the relationship of NIIs with nuclear bodies in brains of dentatorubral-pallidoluysian atrophy and Machado-Joseph disease. In both diseases, promyelocytic leukemia protein, a major component of the promyelocytic leukemia protein nuclear bodies, altered the normal distribution and was rearranged around NII, forming a single capsular structure. We further demonstrated that NIIs were present in close contact with coiled bodies, a highly dynamic domain that may be involved in the biogenesis of small nuclear ribonucleoproteins. The preferential association of intranuclear polyglutamine aggregates with coiled bodies was also confirmed in the dentatorubral-pallidoluysian atrophy transgenic mouse brain and culture cells expressing mutant atrophin-1. The results suggest that the interaction between NIIs and nuclear bodies may play a role in the pathogenesis of CAG repeat diseases.

Adult↗
PubMed2001

Structural and functional disruption of vascular smooth muscle cells in a transgenic mouse model of amyloid angiopathy.

The deposition of amyloid Abeta peptide in the wall of cerebral vessels (cerebral amyloid angiopathy), can lead to weakness and rupture of the vessel wall, resulting in hemorrhagic stroke. The Tg2576 transgenic mouse line, overexpressing mutant amyloid precursor protein in an age-dependent manner, forms amyloid angiopathy morphologically similar to that seen in the human. We report here the structural and functional disruption of smooth muscle cells (SMCs) in the walls of pial vessels affected by amyloid deposition in the Tg2576 mouse. We demonstrate, using multiphoton imaging, that the arrangement of SMCs becomes disorganized before the onset of cell death, and that these disorganized SMCs are unable to respond appropriately to application of endothelial-dependent and endothelial-independent vasodilators in a closed-cranial window preparation.

Acetylcholine↗
PubMed2001

Different angiotensin II-forming pathways in human and rat vascular tissues.

We studied the angiotensin II-forming pathways in extracts from human and rat vascular tissues. In the extract from human artery, angiotensin I mainly converted to two products, angiotensin-(1-9) and angiotensin II, while in the extract from rat artery, the major angiotensin I products were angiotensin II and angiotensin-(5-10). The concentrations of angiotensin II and angiotensin-(1-9) generated in the human extract (1 mg protein/ml) after incubation for 30 min were 3.2 and 2.5 nmol, respectively, and that of angiotensin II and angiotensin-(5-10) generated in the rat extract (1 mg protein/ml) were 0.28 and 2.3 nmol, respectively. In the extract from human vascular tissues, the angiotensin II formation was inhibited by 8% with lisinopril and by 95% with chymostatin. The other product, angiotensin-(1-9) was inhibited completely by carboxypeptidase inhibitor. In the extract from rat vascular tissues, the angiotensin II formation was suppressed to 4% by lisinopril, but not by chymostatin. The angiotensin-(5-10) formation was completely inhibited by chymostatin. These findings suggest clearly that human vascular tissues contain two angiotensin II-forming enzymes, angiotensin-converting enzyme and chymase, but rat vascular tissues have no chymase-dependent angiotensin II-forming pathway.

Adult↗
PubMed2001

Standing stock and production rate of phytoplankton and a red tide outbreak in a heavily eutrophic embayment, Dokai Bay, Japan.

The seasonal variation of phytoplankton biomass and primary productivity in a heavily eutrophic embayment, Dokai Bay, Japan, was determined. Dokai Bay was characterized by high phytoplankton biomass and productivity during summer and low phytoplankton biomass and productivity during other seasons. The results suggested that phytoplankton growth was limited by only irradiance and water temperature under the high nutrient concentrations available for phytoplankton growth in the entire year. Moreover, in spite of sufficient nutrient for phytoplankton growth in the entire year, a red tide occurred only in the summer period in this bay. Our results suggested that a red tide occurred by the high phytoplankton growth rate in the summer season, but in other periods surface phytoplankton was flushed out of the bay before forming the red tide, because phytoplankton growth rate was low and could not form the red tide due to low irradiance and low water temperature.

Animals↗
PubMed2001

UV-irradiation-induced DNA immobilization and functional utilization of DNA on nonwoven cellulose fabric.

Immobilization of double-stranded DNA onto nonwoven cellulose fabric by UV irradiation and utilization of DNA-immobilized cloth were examined. The immobilized DNA was found to be stable in water, with the maximum amount of fabric-immobilized DNA being approximately 20 mg/g of nonwoven fabric. The DNA-immobilized cloth could effectively accumulate endocrine disruptors and harmful DNA intercalating pollutants, such as dibenzo-p-dioxin, dibenzofuran, biphenyl, benzo[a]pyrene and ethidium bromide. Additionally, DNA-immobilized cloth was found to bind metal ions, such as Ag+, Cu2+, and Zn2+. The maximum amounts of bound Ag+, Cu2+, and Zn2+ onto DNA-immobilized cloth (1 g) were approximately 5, 2, and 1 mg, respectively. DNA-immobilized cloth containing Ag+ showed antibacterial activity against Escherichia coli and Staphylococcus aureus. DNA-immobilized cloth without metal ion and with Cu2+ or Zn2+ did not show antibacterial activity. These results suggest that immobilized DNA imparts useful functionality to cloth. DNA-immobilized cloth prepared by UV irradiation has potential to serve as a useful biomaterial for medical, engineering, and environmental application.

Cellulose↗
PubMed2001

Effect of microsome-liposome fusion on the rotational mobility of cytochrome P450IIB4 in rabbit liver microsomes.

Membrane fusion of microsomes with soybean phospholipid vesicles was performed at pH 6.5 to investigate the effect of lipid-enrichment in the membrane on the rotational mobility of cytochrome P450. Rotational diffusion of cytochrome P450 in the microsomal membrane of phenobarbital-induced rabbit liver was measured by detecting the decay of absorption anisotropy after photolysis of the heme CO complex by a vertically polarized laser flash. The fusion procedures yielded three separate fractions upon sucrose density gradient centrifugation with lipid-to-protein ratio in weight (L/P) as follows: 1.5 in the bottom fraction, 2.2 in the middle fraction, and 3.9 in the top fraction. In each fraction, co-existence of mobile and immobile cytochrome P450 was observed. The percentage of rotationally mobile P450 (with the mean rotational relaxation time of phi=505-828 micros) in each of the different bands was found to be 59% in the bottom fraction, 61% in the middle fraction, and 68% in the top fraction. This increase in mobile population of P450 due to lipid-enrichment indicates that aggregated proteins in microsomal membranes dissociate with increasing L/P which is inversely proportional to the protein concentration in the membrane. With freeze-fracture electron microscopy, it was shown that the average distance increased between intramembrane particles by lipid-enrichment. Thus, the significant immobile population (32%) of P450 in microsomal membranes can be explained by nonspecific protein aggregation which is a consequence of the low L/P of 0.8. The decrease in the mobile population in the bottom fraction compared with intact microsomes was shown to be due to the pH 6.5 incubation used for fusion.

Animals↗
PubMed2001

Analysis of spontaneous EPSCs in retinal horizontal cells of the carp.

Spontaneous excitatory postsynaptic currents (sEPSCs) were recorded under Whole-cell voltage clamp from carp type 1 horizontal cells (H1 cells) uncoupled by dopamine in retinal slices. Red light steps, which hyperpolarise cones and reduce glutamate release, induced outward current responses accompanied by a suppression of sEPSCs. sEPSCs decayed exponentially with a mean time constant of 0.71+/-0.07 ms and had a reversal potential near 0 mV. Power spectral analysis of sEPSCs revealed a similar decay time constant. They were suppressed by a non-NMDA receptor antagonist, CNQX at 10 microM, and a relatively specific AMPA receptor antagonist, GYKI52466 at 20 microM. The presence of sEPSCs suggests that the release of glutamate from cone synaptic terminals is vesicular. The reduction in mean sEPSC frequency with red light was not accompanied by a significant change in the mean sEPSC conductance increase (482+/-59 pS), suggesting that a decrease in the vesicular release rate from cones does not alter the vesicular glutamate concentration (quantal contents). The results suggest that the spontaneous events in H1 cells were contributed by non-NMDA (possibly AMPA) type glutamate receptors modulated by the red cone input.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2001

Blocking AMPA receptor desensitization prolongs spontaneous EPSC decay times and depolarizes H1 horizontal cells in carp retinal slices.

Desensitization of H1 horizontal cell (H1 HC) glutamate receptors was investigated in carp retinal slices using cyclothiazide (CTZ), an inhibitor of AMPA receptor desensitization. 100 microM CTZ depolarized H1 HCs and increased the amplitude of light responses, without any prominent changes in their kinetics. Spontaneous EPSCs (sEPSCs) in H1 HCs were observed in the presence of 2.5 mM heptanol, an uncoupling agent of gap junctions. 20 microM GYKI52466 (an AMPA receptor antagonist) blocked the sEPSCs, consistent with the sEPSCs being mediated by AMPA receptors. 100 microM cobalt suppressed the frequency of sEPSCs without changing their mean peak amplitude, suggesting that calcium-dependent transmitter release from cones was not affected by heptanol. CTZ increased the total inward charge transferred per sEPSC by increasing the sEPSC decay time constant twofold, without any significant change in their frequency and mean peak amplitude. This suggests that the depolarizing effect of CTZ on H1 HCs was due to blocking desensitization of AMPA receptors, increasing the inward current induced by glutamate released from cone synaptic terminals. The desensitization of glutamate receptors may function to extend the dynamic range of H1 HC light responses.

Animals↗