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Biomedical subjects

T Iwaki

Publications and source records attributed to T Iwaki.

At least 127 records · Page 7Linked to original sources
PubMed1996

Preferential replication-dependent mutagenesis in the lagging DNA strand in Escherichia coli.

The mutation frequencies attributable to -1 frameshift or one-base substitution in the structural genes coding for resistance to chloramphenicol (Cm) and tetracycline (Tc) were followed over several cycles of DNA replication, and found to differ several-fold, depending on the orientation of the gene on the plasmid with respect to the direction of (unidirectional ColE1-type) replication. The mutation frequency was higher when the reporter gene was present in the plasmid in the same orientation as the direction of the origin, i.e., when the transcription template is the lagging daughter strand, than when the gene was inserted in the opposite orientation. This significant difference in reversion frequencies of genes with different polarities was demonstrated only for a brief period of cell growth (several cycles of replication) after induction of the dnaQ49 mutator, but was not observed when an increased number of replication cycles, was permitted, most probably due to fixation of the mutation into both strands. The mutated intermediate DNA which possesses a misaligned basepair in the Cm gene was demonstrated to be replicated into two progeny DNA molecules; one is the chloramphenicol-resistant (CmR) DNA synthesized from the template strand having the mutation and the other is the CmS DNA from the template strand without mutation. Our results suggest that replication-dependent mutagenesis may occur preferentially in the lagging strand.

Bacteriocin Plasmids↗
PubMed1996

Distinctive immunohistochemical profiles of small heat shock proteins (heat shock protein 27 and alpha B-crystallin) in human brain tumors.

BACKGROUND: Recent studies have described alpha B-crystallin as a member of the small heat shock protein (HSP) family, and the expressions of alpha-crystallin-related small heat shock proteins, namely HSP27 and alpha B-crystallin, in the brain appear to be regulated in a similar way by various stress conditions. METHODS: A comparative immunohistochemical analysis was performed on 198 human brain tumors to examine the expressions of HSP27 and alpha B-crystallin. RESULTS: Positive staining with HSP27 was frequently observed in schwannomas, craniopharyngiomas, epidermoid cysts, and metastatic tumors to the brain. The immunopositivity of HSP27 was relatively low in tumors originating from neuroepithelium as well as in meningiomas; however, a statistically significantly higher percentage of HSP27-positive cells was noted in their anaplastic counterparts, such as glioblastomas, anaplastic oligodendrogliomas, anaplastic ependymomas, and anaplastic meningiomas (P < 0.005). Conversely, a positive immunoexpression of alpha B-crystallin was frequently observed among astrocytic tumors, schwannomas, hemangioblastomas, and chordomas. CONCLUSIONS: The immunohistochemical expression of HSP27 and alpha B-crystallin differed among histologic types of tumors. Furthermore, the immunopositivity of HSP27, which was considered to play a role not only in drug resistance but also in the regulation of cell proliferation, increased in proportion to the anaplasia of the tumors.

Astrocytoma↗
PubMed1996

Chronic active Epstein-Barr virus infection with giant coronary aneurysms.

Chronic active Epstein-Barr virus infection (CAEBV) is a nonfamilial syndrome that shows a specific immunodeficiency for the Epstein-Barr virus (EBV). Prolonged fever, hepatosplenomegaly, lymphadenopathy, and liver dysfunction were seen in CAEBV, but cardiac complications are rare. An autopsy case of CAEBV with giant coronary aneurysms and aortic aneurysms is reported. The patient was a 5-year-old Japanese girl. At autopsy, the heart weighed 110 g, and bilateral coronary aneurysms were found. Microscopic studies revealed lymphoid vasculitis of coronary arteries, coronary venules, and aortic arteries. Immunohistochemically, infiltrating small lymphocytes were positive for CD3, CD45RO(UCHL-1), CD43(DF-T1). The presence of EBV in most of these T lymphocytes was proven by in situ hybridization using an EBV-encoded RNA-1 (EBER1) probe. To the best of the author's knowledge, pathology of aneurysms caused by lymphoid vasculitis in CAEBV has not been reported until now.

Child, Preschool↗
PubMed1996

Establishment and characterization of choroid plexus carcinoma cell lines: connection between choroid plexus and immune systems.

Murine choroid plexus cell lines were produced from choroid plexus carcinoma generated in transgenic mice harboring the viral oncogene simian virus 40 large tumor antigen under transcriptional control of an intronic enhancer region from the human immunoglobulin heavy chain (IgH) gene. Two morphologically distinct cell lines have been cloned. These established cell lines retained the characteristics of choroid plexus cells in that they expressed such choroid plexus cell marker or related proteins as transthyretin and alpha2-macroglobulin. They were tumorigenic in nude mice. In the cell lines, the muA and muB (HE2) motifs within the IgH intronic enhancer were active and we also demonstrated the existence of the proteins binding to these motifs, suggesting a potential link between the choroid plexus and immune systems. It is considered that these binding proteins act as trans-activators for the enhancer and may belong to the class of ETS-related proteins. These cell lines and xenografts should be useful materials for analyses of choroid plexus functions.

Animals↗
PubMed1996

Hyperbaric oxygenation prevents delayed neuronal death following transient ischaemia in the gerbil hippocampus.

The mechanism of the neuroprotective effect of hyperbaric oxygenation remains unclear although its clinical benefits have been well recognized for human ischaemic neuronal disease. The preventive effect of hyperbaric oxygenation against delayed neuronal death was investigated in the gerbil following transient forebrain ischaemia. Delayed neuronal death in the gerbil was produced by clips on both the common carotid arteries (10 min). Morphological examination was carried out after several protocols of hyperbaric oxygenation, modified from the protocols for human ischaemic neuronal disease. Neurons in the hippocampal CA1 were well preserved in the gerbils treated with hyperbaric oxygenation, more so than in the gerbils with no hyperbaric oxygenation. Moreover, more neurons were preserved in the CA1 treated with hyperbaric oxygenation within 6 h of the ischaemia, than when the hyperbaric oxygenation was started 24 h after the ischaemia. The induction of heat shock proteins (HSP72 and HSP27) became weaker in the gerbils with hyperbaric oxygenation than in those without hyperbaric oxygenation, as seen immunohistochemically. We also observed an increase in dense bodies, that were shown to be lysosomes and myelinoid structures in the cytoplasm of the neurons ultrastructurally, in the hippocampus with hyperbaric oxygenation. However, no oxygen toxicity to the neurons was detected, up to at least two atmospheres absolute. This experimental system was useful to investigate the preventive mechanism of hyperbaric oxygenation against delayed neuronal death in the gerbil, and to determine the clinical indications and the most effective protocol for hyperbaric oxygenation for ischaemic neuronal damage in the human brain.

Animals↗
PubMed1996

Advanced glycosylation end-products and heat shock proteins accumulate in the basophilic degeneration of the myocardium and the corpora amylacea of the glia.

Using monospecific antibody for the advanced glycosylation end-products (AGEP), it was revealed that the AGEP localized in the basophilic degeneration of the myocardium and the corpora amylacea of the glia. The stability of the proteins that constitute those degenerative deposits suggests that they would be ideal substrates for non-enzymatic glycation, a process that occurs over a long time under a high glucose content, and ultimately results in the formation of the AGEP. Such deposits also exhibited evidence of stress reactions: the accumulation of HSP72, heme oxygenase-1 and ubiquitin. As recent studies have shown that AGEP-modified proteins aggregate and that they generate reactive oxygen intermediates, the accumulation of such heat shock proteins may reflect the oxidative stress concomitant with AGEP accumulation, and thereby promote their cellular dysfunction. Hereby, it is proposed that the age-related increase in the AGEP, that is, a fundamental aging process, is involved in the formation of the basophilic degeneration in the myocardium and the corpora amylacea of the glia.

Aged↗
PubMed1996

Differential expression of CD44 variants among meningioma subtypes.

Aims/background-CD44 is a widely distributed cell surface molecule which has numerous isoforms generated by alternative splicing. The diverse functions related to the CD44 variants (CD44v) have been reported in various physiological and pathological conditions. The pattern of expression of CD44v among meningioma subtypes was investigated to ascertain whether CD44 variants play a role in a variety of biological processes, such as epithelial differentiation and extracranial metastasis.Methods-Twenty three meningiomas were studied immunohistochemically using novel antibodies directed against CD44 isoforms. Six of the 23 samples were analysed by reverse transcription polymerase chain reaction (RT-PCR), followed by Southern blotting with CD44v specific probes.Results-In meningothelial, fibrous and anaplastic meningiomas, a standard form of CD44 was detected by RT-PCR and was homogeneously expressed in tumour cells when studied immunohistochemically. CD44v was not detected in these subtypes. In secretory meningiomas, however, CD44v isoforms were strongly expressed in the cell clusters that produce secretory granules and also accumulated in the granules. The population of tumour cells immunopositive for CD44v was similar to that which stained with antibodies directed against carcinoembryonic antigen, epithelial membrane antigen and ezrin. On RT-PCR with Southern blotting, only the secretory type showed high level expression of CD44v.Conclusions-CD44v in meningiomas is expressed in relation to tumour cell differentiation towards the epithelial type.

Journal Article↗
PubMed1996

AlphaB-crystallin protects glial cells from hypertonic stress.

AlphaB-crystallin and the small stress protein, heat shock protein of 27 kDa (HSP27), share structural similarities and are coordinately induced by classical stress stimuli. We have recently observed that hypertonic stress produced by high NaCl concentrations selectively induces alphaB-crystallin in glial cells. To examine divergence of the functional properties of these two related proteins, we have constructed stable alphaB-crystallin-expressing glial cell lines from the U-251 MG glioma cells, which are normally deficient in alphaB-crystallin expression but constitutively express HSP27. These transfected cells lines are more resistant to acute hypertonic stress than the parental line from which they were derived. Moreover, the parental line acclimates to stepwise increases in hypertonicity and upregulates endogenous alphaB-crystallin in the process but not HSP27. The overexpression of HSP27 and alphaB-crystallin in NIH/3T3 fibroblasts, a cell line that normally expresses little alphaB-crystallin and no HSP27, does not result in increased survival. This suggests that alphaB-crystallin interacts with cell-type specific mechanisms to aid in protection from hypertonic stress.

3T3 Cells↗
PubMed1996

Effects of smoking on EEG alpha asymmetry during production of random sequences of numbers.

This study was conducted to evaluate the effects of smoking on EEG alpha asymmetry which occurs during the production of random sequences of numbers. The subjects were 10 students. The randomness of orally generated sequences was measured by the randomization index based on the Polya-Eggenberger distribution RIPE. The randomness decreased in the postsmoking sessions. Smoking increased EEG alpha asymmetry by reducing alpha activities in the left hemisphere (left-hemisphere activation) but not by increasing alpha activities (deactivation) of the right hemisphere. The self-reported stress related to task was lower in the postsmoking sessions. The cognitive facilitation model of smoking is discussed from a psychophysiological point of view.

Adult↗
PubMed1996

Auditory plasticity in cochlear implant patients.

Dynamic range (DR) of cochlear implant electrodes and speech recognition scores (SRS) were chronologically studied in 23 post-lingually deaf subjects over a period of one year. DR significantly increased over one year (ANOVA, p = 0.03). When DR was compared among three groups of electrodes which were located in the inferior, ascending and superior segments of the cochlear basal turn, that in the superior segment showed the largest increase (p = 0.001), followed by those in the ascending and inferior segments. Vowel and consonant recognition scores with auditory cue were best 6 months after operation and were maintained at the level for one year. Although the time course of improvement differed between DR and SRS, a significant positive correlation was observed at 12 months after operation. Improvement of SRS could be a result of a DR increase in the superior segment of the cochlea, which should convey pitch information over the mid-frequency region.

Adolescent↗
PubMed1996

Developmental study of Taenia mustelae in the intermediate and definitive hosts, with a note on the life cycle of T. mustelae in Hokkaido, Japan.

The gray red-backed vole Clethrionomys rufocanus bedfordiae and laboratory mice were fed eggs of Taenia mustelae via a stomach tube. Fully developed metacestodes were recovered from the voles fed the eggs at 25 days postinfection; voles were considered to be more suitable intermediate hosts for T. mustelae than laboratory mice. The prepatent period for the metacestodes from voles was shorter (16 days) in the mink than previously reported. A field survey was performed on hepatic cestodes of small mammals in Hokkaido, Japan in August 1993. We found T. mustelae metacestodes from C. rufocanus bedfordiae, representing a new host record.

Animals↗
PubMed1996

[A case of progressive multifocal leukoencephalopathy with methionine uptake demonstrated by PET].

We report here a 55-year-old man with progressive multifocal leukoencephalopathy (PML) associated with chronic adult T cell leukemia (ATL). Neurological examination revealed mild dementia, right homonymous hemianopsia and visual agnosia. Serologically anti-HTLV-I antibody was positive. Peripheral blood analysis showed ATL cells up to 23% in white blood cells. Because he did not have symptoms or signs directly related to ATL, it was considered that he had chronic ATL. T2-weighted cranial MRI demonstrated multiple hyperintensity lesions confined to the white matter from the bilateral occipital to parietal lobes, without enhancement after gadolinium administration or mass effect. We performed stereotactic biopsy of the left occipitoparietal white matter. Histological examination of the biopsied specimens showed demyelinated lesions, containing foamy macrophages and bizarre astrocytes. Oligodendrocytes contained nuclear inclusions which reacted with an antibody against the JC virus (JCV) antigen. These findings were consistent with those of PML. The genomic analysis of JCV from the biopsied brain revealed deletions in the regulatory region. We investigated cerebral blood flow, glucose and amino acid metabolism in this patient using positron emission tomography, and obtained the following three characteristic findings in the lesions: 1) luxury perfusion state, 2) decreased fluorodeoxyglucose (FDG) uptake, and 3) increased methionine (Met) uptake. These findings resembled those of low grade tumors.

Animals↗
PubMed1995

Alpha B-crystallin in C6 glioma cells supports their survival in elevated extracellular K+: the implication of a protective role of alpha B-crystallin accumulation in reactive glia.

It has been shown by immunohistochemical studies that alpha B-crystallin accumulates in the reactive and neoplastic glial cells in a variety of pathologic situations. However, the molecular mechanism for the induction of alpha B-crystallin in diseased brains is still unknown. Since any destructive brain lesions cause an abnormal elevation in the potassium (K+) concentration of the extracellular space, which disturbs the regulatory mechanism of glial cell volume, we investigated the influence of elevated extracellular K+ on the expression of alpha B-crystallin in glial cells. The treatment of rat C6 glioma cells with augmented K+ in the culture media induced an accumulation of alpha B-crystallin mRNA in a dose-dependent manner and an accumulation of the alpha B-crystallin as well. Furthermore, an overexpression of alpha B-crystallin in the C6 transformant transfected with a rat alpha B-crystallin cDNA conferred a resistant phenotype against the insult of elevated extracellular K+ on the glioma cells. Thus, alpha B-crystallin may contribute to the survival of reactive glia in the presence of a high extracellular K+ concentration.

Animals↗
PubMed1995

Solution structure of the DNA binding domain of a nucleoid-associated protein, H-NS, from Escherichia coli.

The three-dimensional structure of the C-terminal domain (47 residues) obtained from the hydrolysis of H-NS protein with bovine trypsin was determined by NMR measurements and distance geometry calculations. It is composed of an antiparallel beta-sheet, an alpha-helix and a 3(10)-helix which form a hydrophobic core, stabilizing the whole structure. This domain has been found to bind to DNA. Possible DNA binding sites are discussed on the basis of the solution structure of the C-terminal domain of H-NS.

Amino Acid Sequence↗
PubMed1995

Anti-dorsal root ganglion neuron antibody in a case of dorsal root ganglionitis associated with Sjögren's syndrome.

We report the case of a 59-year-old woman with primary Sjögren's syndrome who developed hypesthesia, hypalgesia, and neurogenic arthropathy in her lower limbs. Neurological examination and electrophysiological studies indicated involvement of the dorsal root ganglia. The immunohistochemistry of sections of rat dorsal root ganglion (DRG) showed that the IgG in the serum and cerebrospinal fluid (CSF) from the patient bound to the neuronal perikarya of small DRG neurons but not to the cerebellum or peripheral nerves. These results, consistent with particular impairment of pain and touch senses, suggest that dorsal root ganglionitis in primary Sjögren's syndrome is mediated by humoral autoimmunity.

Blotting, Western↗
PubMed1995

IgH intronic enhancer element HE2 (mu B) functions as a cis-activator in choroid plexus cells at the cellular level as well as in transgenic mice.

Immunoglobulin heavy-chain (IgH) gene expression is regulated largely by the IgH gene intronic enhancer (ENHiH), which is composed of multiple protein-binding motifs. These motifs are DNA elements that are important for the regulation of IgH gene transcription. It has been reported that the HE2 (mu B) and mu A motifs within the ENHiH affect B cell-specific gene expression. To examine the function of the HE2 and mu A elements in vivo, we established transgenic mouse lines. A deletion mutant of the human ENHiH that contains the HE2 and mu A motifs, but lacks the motifs corresponding to murine E5, E3, and octamer, functioned not only in B lymphocytes but also in choroid plexus cells, which secrete CSF. As a result, we obtained choroid plexus tumor-bearing transgenic mice and could establish choroid plexus carcinoma cell lines. In addition, using the luciferase assay, we confirmed at the cellular level that the HE2 motif shows a fair degree of enhancer activity in cultured choroid plexus carcinoma cells. These results suggest the existence of a trans-acting factor for the HE2 motif in choroid plexus cells. Actually, in this cultured cell line, the existence of a protein binding to the HE2 motif was demonstrated by a gel retardation assay. Due to the sequence homology between the HE2 motif and the Ets-binding sites, an Ets-related protein is a highly probable candidate for being the binding factor.

Animals↗