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Hiroshi Tamada

Publications and source records attributed to Hiroshi Tamada.

8 recordsLinked to original sources
PubMed2006

Requirement of the protein B23 for nucleolar disassembly induced by the FRGY2a family proteins.

In Xenopus somatic cell nuclear cloning, the nucleoli of donor nuclei rapidly and almost completely disappear in egg cytoplasm. We previously showed that the germ cell-specific proteins FRGY2a and FRGY2b were responsible for this unusually drastic nucleolar disassembly. The nucleolar disassembly occurs without inhibition of pre-rRNA transcription, a well known trigger for nucleolar segregation, and the mechanism for the nucleolar disassembly by FRGY2a and FRGY2b remains largely unknown. In this study, we searched for FRGY2a-interacting proteins and investigated the functional consequences of their interactions through a series of experiments. We showed that during the nucleolar disassembly, FRGY2a localized to the nucleoli of isolated nuclei and was capable of disassembling purified nucleoli, suggesting a direct interaction between FRGY2a and nucleolar components. Using a His tag pulldown approach, we identified the abundant and multifunctional nucleolar protein B23 as a potential target of FRGY2a and its related human protein YB1. A specific interaction between FRGY2a/YB1 and B23 was confirmed by co-immunoprecipitation. Finally, B23 knockdown using short interfering RNA and a subsequent add-back experiment confirmed that B23 was necessary for nucleolar disassembly by YB1. We propose that FRGY2a and YB1 disassemble nucleoli by sequestering B23, which is associated with pre-ribosomes and other structurally important nucleolar components.

Animals↗
PubMed2006

Chromatin decondensation and nuclear reprogramming by nucleoplasmin.

Somatic cell nuclear cloning has repeatedly demonstrated striking reversibility of epigenetic regulation of cell differentiation. Upon injection into eggs, the donor nuclei exhibit global chromatin decondensation, which might contribute to reprogramming the nuclei by derepressing dormant genes. Decondensation of sperm chromatin in eggs is explained by the replacement of sperm-specific histone variants with egg-type histones by the egg protein nucleoplasmin (Npm). However, little is known about the mechanisms of chromatin decondensation in somatic nuclei that do not contain condensation-specific histone variants. Here we found that Npm could widely decondense chromatin in undifferentiated mouse cells without overt histone exchanges but with specific epigenetic modifications that are relevant to open chromatin structure. These modifications included nucleus-wide multiple histone H3 phosphorylation, acetylation of Lys 14 in histone H3, and release of heterochromatin proteins HP1beta and TIF1beta from the nuclei. The protein kinase inhibitor staurosporine inhibited chromatin decondensation and these epigenetic modifications with the exception of H3 acetylation, potentially linking these chromatin events. At the functional level, Npm pretreatment of mouse nuclei facilitated activation of four oocyte-specific genes from the nuclei injected into Xenopus laevis oocytes. Future molecular elucidation of chromatin decondensation by Npm will significantly contribute to our understanding of the plasticity of cell differentiation.

Animals↗
PubMed2004

Inflammatory pseudotumor of the kidney.

A 38-year-old man without prior contributory history presented complaining of a tumor in the left upper abdomen without tenderness. Suspecting renal cell carcinoma of the dark cell type, a nephrectomy was performed. Microscopic examination showed a proliferation of spindle cells containing numerous blood vessels. A diffuse infiltrate of lymphocytes and plasma cells was scattered throughout the lesion.

Adult↗
PubMed2003

Fracture of the penis: nine cases with evaluation of reported cases in Japan.

BACKGROUND: Fracture of the penis is a relatively rare condition that is defined as a rupture of the tumescent corpora cavernosa as a result of blunt trauma, most commonly during sexual intercourse or masturbation. The fracture is easy to recognize but treatment remains controversial. We, therefore, examined the treatment methods for penile fracture. METHODS: Between December 1990 and March 2001, eight patients underwent immediate surgical repair on the first or second day after fracture of the penis, and one patient underwent surgery on the 30th day after fracture, at Kansai Rosai Hospital. Patient age at presentation ranged from 15 to 55 years. Eight patients came to the hospital 2-23 h after the fracture occurred. All patients complained of penile swelling and ecchymosis. Three patients reported hearing a snapping sound. None of the patients demonstrated macroscopic hematuria. RESULTS: We treated all of the patients surgically. All patients showed a unilateral injured corporeal rupture. We took a circumferential coronal incision under the glans and repaired with absorbable stitch. At follow-up, eight of the nine patients who were available reported the achievement of an adequate erection for intercourse without erectile or voiding dysfunction. CONCLUSION: All patients were treated surgically and recovered successfully. Therefore, immediate repair is recommended for the treatment of penile fracture.

Adolescent↗
PubMed2003

[Diagnostic availability of magnetic resonance angiography (MRA) in a case of cirsoid-type renal arteriovenous fistula].

We report a case of cirsoid-type renal arteriovenous fistula (RAVF), which was difficult to differentiate from renal pelvic tumor by intravenous pyelography and computed tomographic (CT) scan. A 76-year-old woman visited our department complaining of sudden asymptomatic macroscopic hematuria. A CT scan showed an irregular mass (3 x 2 x 2 cm) in the right kidney. MRA revealed a cirsoid-type renal arteriovenous fistula. The patient was treated with TAE using ethanol, geratin sponge, and a coil. It is suggested that MRA is useful for the diagnosis of renal arteriovenous fistula.

Aged↗
PubMed2002

cDNA cloning and characterization of Drb1, a new member of RRM-type neural RNA-binding protein.

Neural RNA recognition motif (RRM)-type RNA-binding proteins play essential roles in neural development. To search for a new member of neural RRM-type RNA-binding protein, we screened rat cerebral expression library with polyclonal antibody against consensus RRM sequences. We have cloned and characterized a rat cDNA that belongs to RRM-type RNA-binding protein family, which we designate as drb1. Orthologs of drb1 exist in human and mouse. The predicted amino acid sequence reveals an open reading frame of 476 residues with a corresponding molecular mass of 53kDa and consists of four RNA-binding domains. drb1 gene is specifically expressed in fetal (E12, E16) rat brain and gradually reduced during development. In situ hybridization demonstrated neuron-specific signals in fetal rat brain. RNA-binding assay indicated that human Drb1 protein possesses binding preference on poly(C)RNA. These results indicate that Drb1 is a new member of neural RNA-binding proteins, which expresses under spatiotemporal control.

Amino Acid Sequence↗