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Dive into the research topics where Ryuhei Sasaki is active.

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Featured researches published by Ryuhei Sasaki.


Leukemia Research | 1996

B cell malignancy and hepatitis C virus infection

Tohru Izumi; Ryuhei Sasaki; Yasusada Miura; Hiroaki Okamoto

Italian authors report that hepatitis C virus (HCV) infection may be one of the causes of lymphoid malignancy such as non-Hodgkins lymphoma (NHL) and Waldenstroms macroglobulinemia (WM). To assess the relationship between HCV infection and B cell malignancy (BCM) in Japan, we analyzed HCV-RNA in 50 patients with BCM [25 cases of NHL, 4 of WM and 21 of multiple myeloma (MM)] and determined genotype of infected HCV(Okamotos classification) using reverse transcription-polymerase chain reaction assay .Eight (16.0 %) of 50 patients with BCM were HCV-RNA positive [HCV(+)], while no patients were HCV(+) in control group (18 patients of non-B cell NHL). Numbers of HCV(+) cases in each group examined were as follows; four (16.0%) in B cell NHL (genotype II/III/IV were 3/1/0, respectively), one (25.0%) in WM (genotype III) and three (14.3%) in MM (genotype II/III/IV were 1/1/1, respectively). All patients examined had no symptoms and signs suggesting vasculitis. The incidence of HCV infection in the patients with BCM was markedly higher than that (approximately 1%) of healthy blood donors in Japan. We also experienced four B cell NHL cases with splenic or hepatic origin in the course of chronic hepatitis C. These results implicate the association between persistent HCV infection and the occurrence of BCM.


Biochimica et Biophysica Acta | 1976

Premature induction of amylase in pancreas and parotid gland of growing rats by dexamethasone.

Ryuhei Sasaki; Michiko Mura; Toshiyuki Takeuchi; Chie Furihata; Taijiro Matsushima; Takashi Sugimura

Studies were made on changes in the contents of alpha-amylase (EC 3.2.1.1) in the pancreas and parotid gland of rats during postnatal development, on the premature induction of this enzyme by hormones and on the existence of specific glucocorticoid receptors in these tissues. The amylase content in the pancreas increased from the 9th day after birth and reached the adult level on the 28th day, its content in the parotid gland increased rapidly from the 16th to the 28th day after birth and then rose more gradually to the adult level. Injection of dexamethasone into rats 6--8 days after birth induced increase in the amylase of the pancreas but not the parotid gland. However, injection of dexamethasone into weanling rats 21--23 days after birth resulted in precocious induction of amylase in both tissues. Specific glucocorticoid receptors were detectable in the parotid gland of rats from 6 days after birth but were almost undetectable in the pancreas until adolescence.


Biochimica et Biophysica Acta | 1975

Comparative studies on electrophoretic mobility and immunogenicity of pancreatic and parotid amylases of rat

Toshiyuki Takeuchi; Michiko Mura; Ryuhei Sasaki; Taijiro Matsushima; Takashi Sugimura

1. The alpha-amylases (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) of rat serum, urine, pancreas, parotid gland and liver were separated by electrophoresis on a cellulose acetate membrane. They were found to be of three different types: a parotid gland type, a pancreatic type and a liver type. Rat serum and urine contained parotid type amylase only. 2. Antisera were prepared in rabbits against purified rat pancreatic amylase and parotid amylase. In addition to strong reactions between pancreatic amylase and its antiserum and between parotid amylase and its antiserum, a weak cross-reaction was observed between parotid amylase and anti-pancreatic amylaseserum. Anti-parotid-amylase serum gave an immunoprecipitation line with rat serum and urine, but anti-pancreatic-amylase serum did not, indicating that the amylases in serum and urine originate from parotid amylase.


Leukemia Research | 1990

Polyadenylic acid polymerase activity in chronic myelogenous leukemia

Ryuhei Sasaki; Jun Minowada; Frederick J. Bollum; Yasusada Miura

Poly(A) polymerase activity was markedly elevated in CML in the blastic phase, moderately high in the accelerated phase and low in the chronic phase. The activity was significantly higher in the myeloid crisis than in the lymphoid crisis and elevated with increasing ratio of blasts in leukemia cases. In TPA or retinoic acid-treated leukemia cells poly(A) polymerase activity was decreased. These results suggest that poly(A) polymerase activity changes, depending on the maturation of leukemic cells and the assay of this enzyme activity may be useful for the early detection of the exacerbation of CML cases.


Cancer Genetics and Cytogenetics | 1985

Characterization of extramedullary tumors in a case of Ph-positive chronic myelogenous leukemia: Possible involvement of immature T lymphocytes

Kazuma Ohyashiki; Mitsuo Oshimura; Hiroyuki Uchida; Tsunemichi Shirota; Nobuhiko Sakai; Noburo Hiramine; Hiroji Okawa; Ryuhei Sasaki; Akira Tonomura; Hisao Ito

A 42-year-old male with chronic myelogenous leukemia (CML) developed acute transformation associated with subcutaneous tumors. Histopathologic examinations of the tumors were done on two occasions; the first study revealed reticulum cell sarcoma-like features, and the second suggested a blastoma. Chromosomal analysis showed that the cells of the tumors originated from the CML clone. The cells had a negative reaction for myeloperoxidase by electron microscopy. Furthermore, biochemical and surface marker studies revealed that the tumor cells contained a significant terminal transferase activity. However, they did not express E- or EAC-rosette receptors, Ia-like antigens, or common ALL antigens.


European Journal of Haematology | 2009

Behenoyl cytosine arabinoside, aclacinomycin A, 6-mercaptopurine, and prednisolone combination therapy for acute non-lymphocytic leukaemia in adults

Minoru Yoshida; Keiichi Suda; Akihiro Tsuboyama; Ryuhei Sasaki; Seiichi Kitagawa; Yasuhiko Kano; Yoshitomo Muto; Fumimaro Takaku; Shinobu Sakamoto; Yasusada Miura

38 consecutive, previously untreated adult patients with acute non‐lymphocytic leukaemia (ANLL) were treated with BHAC‐AMP (N4‐behenoyl‐1‐β‐D‐arabinofuranosyl‐cytosine, aclacinomycin A, 6‐mercaptopurine, and prednisolone) therapy between March 1980 and February 1985. 25 patients (65.8%) achieved complete remission (CR). Median CR duration and median survival of patients who achieved CR were 14, and 24 months, respectively. The Kaplan‐Meier analysis revealed a probability for remaining in CR of 18.0% at 5 years. Analysis of failure cases revealed that most of them were due to resistant disease. Major toxicities were infection, diarrhoea, liver dysfunction, nausea and vomiting but these were acceptable. The results indicate that BHAC‐AMP therapy is comparable to the regimen with daunorubicin and cytosine arabinoside and a further clinical trial is necessary for previously untreated adult patients with ANNL.


Leukemia Research | 1982

Sialyltransferase activity in leukemia.

Ryuhei Sasaki; Fumimaro Takaku; Ying-Lung Lin; Frederick J. Bollum

Sialyltransferase activity in blasts from acute lymphoblastic leukemia (ALL) was markedly lower (1.68 +/- 1.23 pmol/mg protein) than those (6.18 +/- 2.22 pmol/mg protein) of lymphocytes from normal volunteers (t less than 0.001). On the contrary, enzyme activity was significantly increased in blasts (1.21 +/- 0.38 pmol/mg protein) from acute non-lymphoblastic leukemia, compared to the level (0.53 +/- 0.32 pmol/mg protein) of mature granulocytes (t less than 0.001). In TdT-negative CML in blast crisis, sialytransferase activity (2.11 +/- 0.88 pmol/mg protein) was significantly higher than those of mature granulocytes (t less than 0.001), whereas no significant difference in the enzyme activity was noted between the blasts from TdT-positive CML in blast crisis and from ALL. In TdT-positive ALL cases, there was an inverse relationship (r = -0.85, t less than 0.01) between sialytransferase activity and terminal deoxynucleotidyl transferase (TdT) activity of the blasts. Therefore, sialytransferase in leukocytes may be a unique enzyme in which changes in activity relate to the differentiation or malignant transformation of leukocytes.


Leukemia Research | 1989

Medium pH determines the differentiation of human promyelocytic leukemia cells to basophils or eosinophils by culturing in a protein- and serum-free medium

Kazuo Muroi; Ryuhei Sasaki; Yasusada Miura; Kazuma Ohyashiki

Cells containing large basophilic granules in the cytoplasm appeared after culturing human promyelocytic leukemia cells (HL-60) in a protein- and serum-free alkaline medium. These granules were stained with toluidine blue and alcian blue. Cells were morphologically and cytochemically similar to basophils. The existence of histamine in the cell lysates was detected in both uninduced and alkaline medium-induced HL-60 cells. After culturing HL-60 cells in a protein- and serum-free acidic medium, cells containing eosin-stained small granules (eosinophils) appeared. The differentiation of HL-60 cells to basophils or eosinophils may therefore depend on medium pH by culturing in a protein- and serum-free medium.


Leukemia Research | 1991

Erythroid differentiation of K-562 cells induced by ethidium bromide

Ryuhei Sasaki; Haruhiro Yoshida; Yasusada Miura; Fumimaro Takaku

The exposure of K-562 cells to ethidium bromide or acridine orange as DNA-intercalating agents induced their differentiation to hemoglobin-producing cells. The addition of L-ethionine or dimethylsulfoxide induced neither such differentiation nor changes in poly(A) polymerase activity of K-562 cells, though the addition of ethidium bromide, acridine orange, hydroxyurea, or 1-beta-arabinofuranosylcytosine induced erythroid differentiation and decreases in poly(A) polymerase activity. These results suggest that DNA-intercalation is one of the pathways triggering differentiation of K-562 cells and the decrease in poly(A) polymerase activity may be an important change associated with differentiation of K-562 cells.


Leukemia Research | 1995

The extracts from rat submandibular glands induce the erythroid differentiation of K-562 cells

Ryuhei Sasaki; Akihiro Masuyama; Yuzuru Etoh; Haruhiro Yoshida; Yasusada Miura; Hiroshi Sasaki

The extracts from rat submandibular glands (SMGs) induced erythroid differentiation of K-562. The activity was non-dialysable and abolished by heat, trypsin or 2-mercaptoethanol. Follistatin, which neutralizes the erythroid differentiation factor (EDF), had no effects on this activity. Analysis by gel chromatography and polyacrylamide gel electrophoresis-isoelectric focussing showed that the characteristics of this substance were different from those of erythropoietin, TGF-beta 1, EDF, stem cell factor and insulin-like growth factor-1. These results suggest the presence of a novel substance in rat SMGs which induces erythroid differentiation of K-562.

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Yasusada Miura

Jichi Medical University

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Kazuo Muroi

Jichi Medical University

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Haruhiro Yoshida

Tokyo University of Agriculture

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Sakamoto S

Jichi Medical University

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Frederick J. Bollum

Uniformed Services University of the Health Sciences

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