Biomedical subjects

Madoka Yoshida

Publications and source records attributed to Madoka Yoshida.

9 recordsLinked to original sources

PubMed2006

Polymorphisms in Complement Factor H and Hemicentin-1 genes in a Japanese population with dry-type age-related macular degeneration.

PURPOSE: To determine whether polymorphisms in the Complement Factor H (CFH) gene and the Hemicentin-1 gene at the ARMD1 locus are associated with dry age-related macular degeneration (AMD) in Japanese patients. DESIGN: Clinically relevant laboratory investigation. METHODS: Eighty unrelated Japanese patients with dry AMD and 196 Japanese control patients were studied. Two exons of the CFH gene and four exons of the Hemicentin-1 gene were amplified by polymerase chain reaction and sequenced directly. RESULTS: For the CFH gene, the frequency of the previously reported Tyr402His variant was not significantly higher in the AMD group than in the control group (P = .31). In the Hemicentin-1 gene, three sequence alterations (Asp5088Val, IVS99-13C/T, and His5245Gln) were detected, and the originally reported Gln5346Arg was not detected. CONCLUSION: The CFH gene and Hemicentin-1 genes do not appear to be involved in a statistically significant fraction of dry AMD cases in the Japanese population.

Aged↗

PubMed2006

Poly(A) binding protein (PABP) homeostasis is mediated by the stability of its inhibitor, Paip2.

The poly(A)-binding protein (PABP) is a unique translation initiation factor in that it binds to the mRNA 3' poly(A) tail and stimulates recruitment of the ribosome to the mRNA at the 5' end. PABP activity is tightly controlled by the PABP-interacting protein 2 (Paip2), which inhibits translation by displacing PABP from the mRNA. Here, we describe a close interplay between PABP and Paip2 protein levels in the cell. We demonstrate a mechanism for this co-regulation that involves an E3 ubiquitin ligase, EDD, which targets Paip2 for degradation. PABP depletion by RNA interference (RNAi) causes co-depletion of Paip2 protein without affecting Paip2 mRNA levels. Upon PABP knockdown, Paip2 interacts with EDD, which leads to Paip2 ubiquitination. Supporting a critical role for EDD in Paip2 degradation, knockdown of EDD expression by siRNA leads to an increase in Paip2 protein stability. Thus, we demonstrate that the turnover of Paip2 in the cell is mediated by EDD and is regulated by PABP. This mechanism serves as a homeostatic feedback to control the activity of PABP in cells.

Feedback, Physiological↗

PubMed2006

Hypothermia of 8 degrees C protects cultured retinal pigment epithelial cells and retinal ganglion cells against trypan blue toxicity.

PURPOSE: To determine whether hypothermia of 8 degrees C can protect cultured human retinal pigment epithelial (ARPE-19) cells and rat retinal ganglion cells (RGC-5) against trypan blue (TB) toxicity. DESIGN: Laboratory investigation. METHODS: ARPE-19 cells and RGC-5 were exposed to balanced salt solution as controls, and 0.05% and 0.5% TB at 37 degrees C, and at 8 degrees C for one minute. The percentage of surviving cells was determined by the resazurin test. RESULTS: TB induced a statistically significant decrease in the percentage of ARPE-19 cells surviving at 0.5% TB at 37 degrees C (P < .01). Conversely, TB induced a statistically significant decrease in the percentage of RGC-5 surviving at all conditions except for 0.05% TB at 8 degrees C (0.05% 37 degrees C; P < .05, 0.5% 37 degrees C and 8 degrees C; P < .01). CONCLUSIONS: These results indicate that reducing the temperature to 8 degrees C has a protective effect against the TB toxicity for ARPE-19 cells and RGC-5 in culture.

Animals↗

PubMed2006

Evaluation of indocyanine green toxicity to rat retinas.

PURPOSE: To investigate the toxicity of indocyanine green (ICG) on retinal cells using cultured retinal pigment epithelium (RPE) cells and the effects of intravitreous injection of ICG into rat eyes. METHODS: Cultured RPE cells were exposed to various concentrations of ICG for 2 min, a viability assay was performed 1 day after exposure. For an in vivo study, 5 microl of ICG (5 or 25 mg/ml) were injected into the vitreous cavity of rat eyes, which were examined 1, 3 and 7 days after the injection by histological and glutamine synthetase (GS) immunohistological evaluation. RESULTS: Viabilities of RPE cells were decreased dependent on the ICG dose. In the histological evaluation, we observed differences of effects of ICG between the central retinal area and the peripheral area. ICG injection caused degeneration of all retinal layers in the central retinal area. GS immunoreactivities decreased by ICG injection, which corresponded to an area of severe destruction. CONCLUSION: A high concentration of ICG may cause toxic effects on retinal cells. Mueller cell dysfunction may play some role in the retinal toxicity caused by ICG.

Animals↗

PubMed2005

Translational control of hippocampal synaptic plasticity and memory by the eIF2alpha kinase GCN2.

Studies on various forms of synaptic plasticity have shown a link between messenger RNA translation, learning and memory. Like memory, synaptic plasticity includes an early phase that depends on modification of pre-existing proteins, and a late phase that requires transcription and synthesis of new proteins. Activation of postsynaptic targets seems to trigger the transcription of plasticity-related genes. The new mRNAs are either translated in the soma or transported to synapses before translation. GCN2, a key protein kinase, regulates the initiation of translation. Here we report a unique feature of hippocampal slices from GCN2(-/-) mice: in CA1, a single 100-Hz train induces a strong and sustained long-term potentiation (late LTP or L-LTP), which is dependent on transcription and translation. In contrast, stimulation that elicits L-LTP in wild-type slices, such as four 100-Hz trains or forskolin, fails to evoke L-LTP in GCN2(-/-) slices. This aberrant synaptic plasticity is mirrored in the behaviour of GCN2(-/-) mice in the Morris water maze: after weak training, their spatial memory is enhanced, but it is impaired after more intense training. Activated GCN2 stimulates mRNA translation of ATF4, an antagonist of cyclic-AMP-response-element-binding protein (CREB). Thus, in the hippocampus of GCN2(-/-) mice, the expression of ATF4 is reduced and CREB activity is increased. Our study provides genetic, physiological, behavioural and molecular evidence that GCN2 regulates synaptic plasticity, as well as learning and memory, through modulation of the ATF4/CREB pathway.

Animals↗

PubMed2004

A unifying model for the role of polyamines in bacterial cell growth, the polyamine modulon.

We reported previously that the synthesis of specific proteins such as OppA, Cya, and RpoS (sigma(38)), which are important for cell growth and viability, is stimulated by polyamines at the level of translation. In this study we found that the synthesis of FecI and Fis was also stimulated by polyamines at the level of translation. The FecI and Fis proteins enhance the expression of mRNAs that are involved in iron uptake and energy metabolism and the expression of rRNA and some tRNAs. The Shine-Dalgarno (SD) sequence of their mRNAs was not obvious or was not located at the usual position. When the SD sequences were created at the normal position on these mRNAs, protein synthesis was no longer influenced by polyamines. Thus, the common characteristic of these mRNAs was to have a weak or ineffective SD sequence. We propose that a group of genes whose expression is enhanced by polyamines at the level of translation be referred to as a "polyamine modulon." By DNA microarray, we found that 309 of 2,742 mRNA species were upregulated by polyamines. Among the 309 up-regulated genes, transcriptional enhancement of at least 58 genes might be attributable to increased levels of the transcription factors Cya, RpoS, FecI, and Fis, which are all organized in the polyamine modulon. This unifying molecular mechanism is proposed to underlie the physiological role of polyamines in controlling the growth of Escherichia coli.

Biogenic Polyamines↗

PubMed2002

Decrease in cell viability in an RMF, sigma(38), and OmpC triple mutant of Escherichia coli.

In a speG-disrupted Escherichia coli mutant, which cannot metabolize spermidine to acetylspermidine, addition of spermidine to the medium caused a decrease in cell viability at the late stationary phase of growth. There were parallel decreases in the levels of ribosome modulation factor (RMF), the sigma(38) subunit of RNA polymerase, and the outer membrane protein C (OmpC). To clarify that these three proteins are strongly involved in cell viability, the rmf, rpoS (encoding sigma(38)), and ompC genes were disrupted. Viability of the triple mutant decreased to less than 1% of normal cells. The triple mutant had a reduced cell viability compared to any combination of double mutants, which also had a reduced cell viability. The single rmf and rpoS, but not ompC, mutant only slightly reduced cell viability. The results indicate that cooperative functions of these three proteins are necessary for cell viability at the late stationary phase. The triple mutant had a reduced level of ribosomes and of intracellular cations.

Bacterial Proteins↗

PubMed2002

Polyamines enhance synthesis of the RNA polymerase sigma 38 subunit by suppression of an amber termination codon in the open reading frame.

The mechanisms by which polyamines stimulate synthesis of the RNA polymerase sigma(38) subunit in Escherichia coli were studied. Polyamine stimulation was observed only in strains in which the 33rd codon of RpoS mRNA is a UAG termination codon instead of a CAG codon for glutamine in wild-type E. coli. Readthrough of the termination codon by Gln-tRNA(supE) was stimulated by polyamines. This stimulation was found to be caused by an increase in both the level of suppressor tRNA(supE) and the binding affinity of Gln-tRNA(supE) for ribosomes. The stimulatory effect was observed with a UAG termination codon but not with UGA and UAA codons. Readthrough of the UAG termination codon at the 270th amino acid position of RpoS mRNA was also stimulated by polyamines, indicating that polyamines stimulate readthrough of a UAG codon regardless of its location within the RpoS mRNA. When cell viability of an E. coli strain having a termination codon in the 33rd position of RpoS mRNA was compared using cells cultured with or without putrescine, it was higher in cells cultured with putrescine than in cells cultured without putrescine. The level of sigma(38) subunit in the cells cultured with putrescine was higher than that in cells cultured without putrescine on days 2, 4, and 8, but the level of sigma(70) subunit was almost the same in cells cultured with or without putrescine. These results confirm that elevated expression of the rpoS gene is important for cell viability at late stationary phase.

Base Sequence↗

PubMedDate not supplied

Clinical features of bilateral acute idiopathic maculopathy.

PURPOSE: To describe the clinical course of bilateral acute idiopathic maculopathy (BAIM), and to analyze its pathophysiology. CASE: A 33-year-old Japanese woman presented with a sudden, severe, bilateral visual disturbance following a flu-like illness. She was examined by fluorescein angiography (FA), indocyanine green angiography (IA), scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), and multifocal electroretinography (mfERG). OBSERVATIONS: A diagnosis of BAIM was made in this patient based on typical ophthalmoscopic features, which included a pathognomonic yellowish-white foveal lesion. FA demonstrated a breakdown of the outer blood-retinal barrier, with the size and location corresponding to the white lesion, and IA disclosed a choroidal circulatory disturbance. SLO demonstrated that the deep retinal and choroidal layers were disorganized, and OCT showed retinal edema. Electrophysiological dysfunction was detected by mfERGs. After steroid therapy, the patient's visual acuity recovered to normal. The pooling of fluorescein dye and the OCT-determined retinal edema were resolved. However, the physiological dysfunction detected by mfERGs remained. CONCLUSIONS: We conclude that the major abnormality in BAIM is an alteration of the retinal pigment epithelium causing severe edema.

Acute Disease↗