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Articles by Y Kobayashi
Total Records ( 6 ) for Y Kobayashi
  G Xu , T Watanabe , Y Iso , S Koba , T Sakai , M Nagashima , S Arita , S Hongo , H Ota , Y Kobayashi , A Miyazaki and T. Hirano
 

Rationale: Human heregulins, neuregulin-1 type I polypeptides that activate proliferation, differentiation, and survival of glial cells, neurons, and myocytes, are expressed in macrophage foam cells within human coronary atherosclerotic lesions. Macrophage foam cell formation, characterized by cholesterol ester accumulation, is modulated by scavenger receptor class A (SR-A), acyl-coenzyme A:cholesterol acyltransferase (ACAT)1, and ATP-binding cassette transporter (ABC)A1.

Objective: The present study clarified the roles of heregulins in macrophage foam cell formation and atherosclerosis.

Methods and Results: Plasma heregulin-β1 levels were significantly decreased in 31 patients with acute coronary syndrome and 33 patients with effort angina pectoris compared with 34 patients with mild hypertension and 40 healthy volunteers (1.3±0.3, 2.0±0.4 versus 7.6±1.4, 8.2±1.2 ng/mL; P<0.01). Among all patients with acute coronary syndrome and effort angina pectoris, plasma heregulin-β1 levels were further decreased in accordance with the severity of coronary artery lesions. Expression of heregulin-β1 was observed at trace levels in intracoronary atherothrombosis obtained by aspiration thrombectomy from acute coronary syndrome patients. Heregulin-β1, but not heregulin-, significantly reduced acetylated low-density lipoprotein–induced cholesterol ester accumulation in primary cultured human monocyte-derived macrophages by reducing SR-A and ACAT1 expression and by increasing ABCA1 expression at both mRNA and protein levels. Heregulin-β1 significantly decreased endocytic uptake of [125I]acetylated low-density lipoprotein and ACAT activity, and increased cholesterol efflux to apolipoprotein (Apo)A-I from human macrophages. Chronic infusion of heregulin-β1 into ApoE–/– mice significantly suppressed the development of atherosclerotic lesions.

Conclusions: This study provided the first evidence that heregulin-β1 inhibits atherogenesis and suppresses macrophage foam cell formation via SR-A and ACAT1 downregulation and ABCA1 upregulation.

  H Nozaki , M Yanagida , K. i Koide , K Shiotani , M Kinoshita , Y Kobayashi , S Watarai , K Nakamura , A Suzuki , T Ariga and Y. Kushi
 

We have established hybridoma cell lines producing monoclonal antibodies (mAbs) directed to N-acetylglucosaminylβ1-3galactose (GlcNAcβ1-3Gal) residue by immunizing BALB/c mice with lactotriaosylceramide (Lc3Cer). These obtained hybridoma cells, specific to Lc3Cer, were dual immunoglobulin (Ig)-producing cells which secreted both IgM and IgG molecules as antibodies. The established mAbs are able to react with not only Lc3Cer but also GlcNAcβ1-3-terminal glycosphingolipids (GSLs) despite branching or lactosamine chain lengths and human transferrin with terminal GlcNAc residues. Comparison of the variable regions of the cloned IgM and IgG by reversed transcription-polymerase chain reaction analysis confirmed that the variable regions determine the specificity, the other amino acids are conserved, and these mAbs are encoded by J558 and V-21family genes. Furthermore, we have analyzed the expression of GSLs with GlcNAcβ1-3 epitope in acute leukemia cell lines and mouse fetal tissues using these mAbs, in which antigens were distributed comparatively. These mAbs are useful for studying the precise distribution of GlcNAcβ1-3Gal-terminating GSL expression in tissues as well as for detecting GSLs carrying terminal GlcNAcβ1-3Gal carbohydrate structure.

  M Yonemura , N Katsumata , H Hashimoto , S Satake , M Kaneko , Y Kobayashi , A Takashima , Y Kato , M Takeuchi , Y Fujiwara , H Yamamoto and T. Hojo
  Objective

The aim of this study was to assess the non-inferiority of 1 mg to 3 mg granisetron (GRN) injection for the treatment of acute chemotherapy-induced nausea and vomiting (CINV) and to evaluate the tolerability of GRN given at 1 mg in Japanese cancer patients.

Methods

Patients with cancer receiving highly emetogenic chemotherapy were enrolled in this single-blind randomized controlled study. Patients were randomly assigned to receive GRN at a single dose of 1 or 3 mg. The primary endpoint was the rate of complete protection from emetic events (no vomiting, no retching and no need for rescue medication) during the first 24 h following the initiation of chemotherapy.

Results

There were 89 patients in the 1 mg group and 90 patients in the 3 mg group. Complete protection was achieved in 70 patients (78.7%) in the 1 mg group and 73 (81.1%) patients in the 3 mg group. The one-sided test did not reveal non-inferiority of either dose of GRN to the other at a 5% significance level.

Conclusions

Our data failed to show the non-inferiority of 1 mg of GRN to 3 mg of GRN administered as a single dose. However, the rate of complete protection from nausea and vomiting was similar in the two groups. Given the recommended dosage in the guidelines and the economic need for reduction of medical care expenses in Japan, prophylactic administration of GRN at 1 mg may be an appropriate, alternative treatment for acute CINV in cancer patients.

  M Hino , N Hamada , Y Tajika , T Funayama , Y Morimura , T Sakashita , Y Yokota , K Fukamoto , Y Mutou , Y Kobayashi and H. Yorifuji
 

Autophagy is one of the major processes involved in the degradation of intracellular materials. Here, we examined the potential impact of heavy ion irradiation on the induction of autophagy in irradiated C2C12 mouse myoblasts and their non-targeted bystander cells. In irradiated cells, ultrastructural analysis revealed the accumulation of autophagic structures at various stages of autophagy (i.e. phagophores, autophagosomes and autolysosomes) within 20 min after irradiation. Multivesicular bodies (MVBs) and autolysosomes containing MVBs (amphisomes) were also observed. Heavy ion irradiation increased the staining of microtubule-associated protein 1 light chain 3 and LysoTracker Red (LTR). Such enhanced staining was suppressed by an autophagy inhibitor 3-methyladenine. In addition to irradiated cells, bystander cells were also positive with LTR staining. Altogether, these results suggest that heavy ion irradiation induces autophagy not only in irradiated myoblasts but also in their bystander cells.

  Y Kobayashi , K Yasuda , E Kondo , T Katsura , Y Tanabe , M Kimura and H. Tohyama
  Background

Concerning meniscal tissue regeneration, many investigators have studied the development of a tissue-engineered meniscus. However, the utility still remains unknown.

Hypothesis

Implantation of autogenous meniscal fragments wrapped with a fascia sheath into the donor site meniscal defect may significantly enhance fibrocartilage regeneration in vivo in the defect.

Study Design

Controlled laboratory study.

Methods

Seventy-five mature rabbits were used in this study. In each animal, an anterior one-third of the right medial meniscus was resected. Then, the animals were divided into the following 3 groups of 25 rabbits each: In group 1, no treatment was applied to the meniscal defect. In group 2, the defect was covered with a fascia sheath. In group 3, after the resected meniscus was fragmented into small pieces, the fragments were grafted into the defect. Then, the defect with the meniscal fragments was covered with a fascia sheath. In each group, 5 rabbits were used for histological evaluation at 3, 6, and 12 weeks after surgery, and 5 rabbits were used for biomechanical evaluation at 6 and 12 weeks after surgery.

Results

Histologically, large round cells in group 3 were scattered in the core portion of the meniscus-shaped tissue, and the matrix around these cells was positively stained by safranin O and toluisin blue at 12 weeks. The histological score of group 3 was significantly higher than that of group 1 and group 2. Biomechanically, the maximal load and stiffness of group 3 were significantly greater than those of groups 1 and 2.

Conclusion

This study clearly demonstrated that implantation of autogenous meniscal fragments wrapped with a fascia sheath into the donor site meniscal defect significantly enhanced fibrocartilage regeneration in vivo in the defect at 12 weeks after implantation in the rabbit.

Clinical relevance

This study proposed a novel strategy to treat a large defect after a meniscectomy.

  R Takahashi , S Nakamura , T Nakazawa , K Minoura , T Yoshida , Y Nishi , Y Kobayashi and T. Ohkubo
 

Nicotinamide (NM) phosphoribosyltransferase (NMPRTase) catalyzes the reaction of NM and 5'-phosphoribosyl-1'-pyrophosphate (PRPP) to form NM mononucleotide (NMN) and pyrophosphate (PPi) in the pathway of NAD-biosynthesis. Monitoring the 1H and 31P NMR spectra of the reaction mixture, we found that this reaction is reversible as dictated by the equilibrium constant K = [NMN][PPi]/([NM][PRPP]) = 0.14, which agreed well with the ratio of second-order rate constants for forward and backward reactions, K = 0.16. The crystal structures of this enzyme in the free form and bound to NM and PRPP at the resolution of 2.0–2.2 Å were essentially identical to that of the complex with NMN, except for some variations that could facilitate the substitution reaction by fixing the nucleophile and the leaving group for the requisite inversion of configuration at the C1’ carbon of the ribose ring. In the active site near the C1’ atom of the bound PRPP or NMN, there was neither negatively charged group nor waterproof environment necessary to support the feasibility of a ribo-oxocarbocation intermediate inherent in the SN1 mechanism. The structures and catalytic mechanism thus revealed are also discussed in connection with the multiple biological functions of NMPRTase.

 
 
 
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