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Dive into the research topics where Yoshiaki Hamamoto is active.

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Featured researches published by Yoshiaki Hamamoto.


Vox Sanguinis | 1989

A novel method for removal of human immunodeficiency virus: Filtration with porous polymeric membranes

Yoshiaki Hamamoto; Shinji Harada; Susumu Kobayashi; Kazuhito Yamaguchi; Hideki Iijima; Sei-ichi Manabe; Takashi Tsurumi; Hiizu Aizawa; Naoki Yamamoto

Abstract. We propose a new method to rid solutions of a virus by using a novel regenerated multilayered structured cellulose membrane (BMM). When the filtrate of human immunodeficiency virus (HIV) preparation was obtained through BMM it showed no infectivity. Electron microscopic observation revealed that HIV was completely caught by the multilayers of the BMM. Conveniently, BMM was seldomly found to adsorb protein molecules and also to have a high filtration rate. These characteristics may have a use in the removal of other variously sized pathogenic agents from plasma.


Virology | 1990

The phorbol ester TPA strongly inhibits HIV-1- induced syncytia formation but enhances virus production : possible involvement of protein kinase C pathway

Md.Iqbal Hossain Chowdhury; Yoshio Koyanagi; Susumu Kobayashi; Yoshiaki Hamamoto; Hironori Yoshiyama; Tsutomu Yoshida; Naoki Yamamoto

Cocultivation of MOLT-4 and MOLT-4/HIVHTLV-IIIB cells with more than 0.01 ng/ml of 12-O-tetradecanoylphorbol-13-acetate (TPA) for 20 hr strikingly inhibited HIV-induced syncytia formation resulting from cell to cell infection. Interestingly, the production of HIV-specific p24 antigen in the culture fluid was significantly enhanced by TPA. TPA down-modulated the expression of CD4. CD4 is essential for syncytia formation through interaction with viral envelope protein gp120 on the surface of MOLT-4 cells. The effects of TPA on syncytia formation and on CD4 expression were specifically interfered with by nontoxic doses of blockers of protein kinase C (PKC) such as staurosporine and H7. These data suggest that (1) TPA inhibits HIV-induced syncytia formation through down-modulation of CD4 molecules on the surface of MOLT-4 cells and (2) PKC may play an important role in cell to cell as well as in cell-free infection of HIV.


Vox Sanguinis | 1989

INACTIVATION AND ELIMINATION OF VIRUSES DURING THE FRACTIONATION OF AN INTRAVENOUS IMMUNOGLOBULIN PREPARATION: LIQUID HEAT TREATMENT AND POLYETHYLENE GLYCOL FRACTIONATION

Yahiro Uemura; Katsuhiro Uriyu; Yutaka Hirao; Kazuo Takechi; Hideyuki Ishikawa; Tsunetaka Nakajima; Yoshio Kagitani; Kazumasa Yokoyama; Satoshi Funakoshi; Masayuki Nishida; Sadao Yabushita; Koichi Furuta; Yoshiaki Hamamoto; Tadafumi S. Tochikura; Naoki Yamamoto

Abstract. A method for the heat treatment of human IgG solution at 60 °C for 10 h was established. Human immunodeficiency, mumps, vaccinia and 4 other viruses were added to the IgG solution in 33% sorbitol and heated at 60 °C. Those viruses were inactivated within 1 h. Heat‐treated intravenous IgG (IVIG‐H) was prepared by heat treatment and polyethylene glycol (PEG) fractionation. Conventional nonheated intravenous IgG (IVIG‐C) was prepared from the same source paste by the fractionation method. No physicochemical or biological difference was observed between the heated and control IVIG preparations.


Journal of Dermatology | 2004

Successful Treatment of Pyogenic Granuloma with Injection of Absolute Ethanol

Makoto Ichimiya; Yoshiaki Yoshikawa; Yoshiaki Hamamoto; Masahiko Muto

Pyogenic granuloma (PG) is a small, almost always solitary, sessile or pedunculated, raspberry‐like vegetation of exuberant granulation tissue. Conservative treatment by techniques such as cryosurgery, laser surgery, and electrodesiccation are usually adequate, whereas excisional treatment can often result in noticeable scars. We attempted a different approach using an injection of absolute ethanol in five patients with recurrence due to inadequate cryosurgery. This therapy is less invasive than surgical excision and appears to be an alternative therapy for PG.


Vox Sanguinis | 1987

Elimination of Viruses (Human Immunodeficiency, Hepatitis B, Vesicular Stomatitis and Sindbis Viruses) from an Intravenous Immunoglobulin Preparation

Yoshiaki Hamamoto; Shinji Harada; Naoki Yamamoto; Yahiro Uemura; Takashi Goto; Tadakazu Suyama

Abstract. More than 104 plaque‐forming units (pfu)/ml of HIV are inactivated during the alcohol fractionation step from plasma to fraction (Fr)‐II+III, >104 pfu/ml is inactivated from Fr‐II+III to Fr‐II and >104 pfu/ml is inactivated during the polyethylene glycol (PEG) fractionation process from Fr‐II+III to intravenous IgG (IVIG). The total inactivation rate from plasma to IVIG via Fr‐II+III or Fr‐II was calculated to be greater than 108 or 1012, respectively. The PEG fractionation method produces an intact and unmodified IVIG. In addition, the PEG fractionation method at a low ionic strength was found to be effective for the elimination of greater than 105 units of other viruses, including hepatitis B, vesicular stomatitis and Sindbis viruses.


Biochemical and Biophysical Research Communications | 1989

Effect of interleukin-1 on the augmentation of human immunodeficiency virus gene expression

Nobuyuki Kobayashi; Yoshiaki Hamamoto; Yoshio Koyanagi; Irvin S. Y. Chen; Naoki Yamamoto

Among the cytokines tested here (IL-2, IL-3, IL-4, IL-5, IL-6, granulocyte colony stimulating factor (G-CSF), granulocyte/macrophage colony stimulating factor (GM-CSF), interferon-alpha (IFN-alpha), interferon-beta (IFN-beta) and interferon-gamma (IFN-gamma] only interleukin 1(IL-1) augmented HIV-long terminal repeat(LTR) directed chloramphenicol acetyl transferase(CAT) activity in protein kinase C(PKC)-independent manner. However, a stimulation by IL-1 was not as efficient as that due to tumor necrosis factor and the HIV production was not significant. IL-1 was not cytotoxic to MOLT-4/HIV cells.


Medical Microbiology and Immunology | 1988

Enhancement of human immunodeficiency virus production by natural lymphotoxin.

Toshifumi Matsuyama; Yoshiaki Hamamoto; Susumu Kobayashi; Masashi Kurimoto; Jun Minowada; Nobuyuki Kobayashi; Naoki Yamamoto

The effect of natural lymphotoxin (n-LT) on CD4+ MOLT-4 cells and those cells producing human immunodeficiency virus (HIV), MOLT-4/ HIVHTLV-IIIB cells, was studied. Four days after treatment with n-LT, a significant cytotoxic/cytostatic effect was observed predominantly on MOLT-4/HIVHTLV-IIIB cells. Furthermore, with regard to the production of HIV, an almost 3- to 5-fold increase of viral particles was observed in MOLT-4/HIVHTLV-IIIB cells 6 h after treatment with n-LT. These data indicate the possibility that this cytotoxic factor is one of the responsible molecules in the pathogenesis of the acquired immunodeficiency syndrom (AIDS).


Experimental Dermatology | 1993

Inhibitory effect of azelastine, a potent antiallergic agent, on release of tumor necrosis factor-alpha from activated human peripheral blood mononuclear cells and U937 cells.

Yoshiaki Hamamoto; Kou Nagai; Masahiko Muto; Chidori Asagami

Abstract It is generally accepted that tumor necrosis factor‐α (TNF‐α) is a multifunctional cytokine which is involved in the regulation of inflammation as well as immunity. In the present study, we investigated whether azelastine, a potent antiallergic agent, affects release of TNF‐α from peripheral blood mononuclear cells (PBMC) and U937 cell line in vitro. When human PBMC and U937 cells were stimulated by phytohemagglulinin (PHA) and 12‐0‐letradecanoyl‐phorbol‐13‐acetate (TPA). respectively, the cells released significant amounts of TNF‐α as determined by TNF‐α‐specific enzyme immunoassay. TNF‐α levels in the culture supernatant of PHA‐stimulated human PBMC and TPA‐activated U937 cells decreased in a dose‐dependent manner when these cells were cultured in the presence of azelastine. This inhibitory effect of azelastine was obtained at concentrations where the drug produced no toxicity. Moreover, azelastine also inhibited release of TNF‐α from U937 cells which were already activated by TPA. These results suggest that the inhibitory effect of azelastine on TNF‐α release plays an important role in its antiallergic action in addition to inhibition and/or antagonism of histamine and leukolriens, which has been previously reported.


Journal of Dermatology | 2006

A case of carotenemia associated with ingestion of nutrient supplements

Yuko Takita; Makoto Ichimiya; Yoshiaki Hamamoto; Masahiko Muto

Carotenemia is characterized by an abnormal yellowish orange pigmentation of the skin, most prominently seen on the palms and soles. Although it is associated with several disease such as diabetes, hypothyroidism and anorexia nervosa, it is caused by excessive intake of carotene‐rich food such as oranges and carrots in most cases. Herein, we describe an interesting case of carotenemia in a 66‐year‐old female secondary to increased ingestion of oral supplements of carotene in order to improve hemorrhage in the eyeground. There could be an increasing trend of intake of commercial nutrient supplements in which case it is necessary to remind ourselves that commercial nutrient supplements could cause various skin disorders as side‐effects.


Biochemical and Biophysical Research Communications | 1989

Comparison of effects of protein kinase C inhibitors on phorbol ester-induced CD4 down-regulation and augmentation of human immunodeficiency virus replication in human T cell lines

Yoshiaki Hamamoto; Yasuhiro Hayashida; Susumu Kobayashi; Tatsuya Tamaoki; Naoki Yamamoto; Nobuyuki Kobayashi

The potent protein kinase C inhibitors staurosporine, H-7, and UCN-01 were investigated for their effects on 12-0-tetradecanoylphorbol-13-acetate (TPA)--mediated CD4 down-regulation and on the augmentation of human immunodeficiency virus (HIV) expression. Staurosporine was the most effective TPA inhibitor for both of these actions. Because of its high cytotoxicity, the effect of H-7 on augmentation of HIV expression could not be determined. UCN-01 had no cytotoxic effect, but caused only little inhibition of the augmentation of HIV expression.

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