Biomedical subjects

R Totsuka

Publications and source records attributed to R Totsuka.

6 recordsLinked to original sources

PubMed1998

Dexamethasone prevents the decrease of bone mineral density in type II collagen-induced rat arthritis model.

This study demonstrated the decrease of bone mineral density (BMD) in the type II collagen (CII)-induced arthritis (CIA) model in rats and the relationship between BMD and paw edema and the effect of dexamethasone-21-phosphate (DEX). The paw swelling occurred on Day 10 and reached its peak on Day 18 after CII injection. BMD in the CII-injected group is lower than that in the control group. BMD in the proximal and distal regions of the femur largely decreased in comparison with that of the middle region. The oral administration of DEX (0.1 mg/kg) inhibited the swelling and decrease of BMD in all three regions of the femur.

Animals↗

PubMed1997

The effect of dexamethasone on the expression of activated NF-kappa B in adjuvant arthritis.

The transcription factor NF-kappa B plays a significant role in inflammatory diseases. In this study we have investigated the expression of activated NF-kappa B p65 subunit in the rat adjuvant arthritis model in a 28-day time-course experiment using immunohistochemistry. The expression of p65 was detected in the synovial lining layer and around the blood vessels in the inflamed synovium as early as Day 3 post-adjuvant injection. The cells that expressed p65 in the synovial lining were thought to be macrophage-like synoviocytes. The expression was stronger in the injected hindpaw than that in the noninjected hindpaw. Dexamethasone treatment at 1 mg/kg p.o. (Days 0-20) suppressed both the hindpaw edema and increase in p65 expression. Withdrawal of the treatment caused increases in both p65 expression and paw volume. Together these suggest that activated NF-kappa B was specifically expressed in the arthritic synovium and may play a significant role in the development of arthritis.

Animals↗

PubMed1997

Changes in bone mineral density in rat adjuvant arthritis.

This study demonstrates that systemic and local decreases in bone mineral density (BMD) occurred with Freund's complete adjuvant injection in the rat right footpad using dual energy X-ray absorptiometry. The rats were assigned to either adjuvant-treated or non-treated control groups composed of eight animals each. There was significant decrease in BMD in the adjuvant group compared to the control group at the distal region of femur or proximal region of tibia on Day 7 post-adjuvant injection (P < 0.05). On the other hand, the femur or tibia of the noninjected side showed a smaller and delayed decrease in BMD than did the injected side. These decreases in BMD were seen in not only the trabecular but also the cortical bone. In addition, the vertebrae also showed delayed but significant decrease (P < 0.05) in BMD on Day 21.

Animals↗

PubMed1997

Selective cleavages of tRNAPhe with secondary and tertiary structures by enediyne antitumor antibiotics.

Some enediyne antitumor antibiotics induce site-selective cleavages for yeast tRNA(Phe) with three-dimensional structure. Of special interest is the fact that tRNA(Phe) is specifically cleaved at the anticodon arm regions by C-1027 and esperamicin A1 in the presence of Mg2+ ions. Although neocarzinostatin strongly breaks tRNA(Phe) at 5'-GPu steps in the absence of magnesium ions, its cleavage ability is completely lost in the presence of 100 microM Mg2+ ions. Dynemicin A, which favors an intercalative binding, causes no strand scissions for the RNA with secondary and tertiary structures. This cutting of tRNA(Phe) may reveal that RNA as well as DNA constitutes a therapeutically relevant target for certain enediyne antitumor antibiotics.

Antibiotics, Antineoplastic↗

PubMed1995

RNA cleavage by C-1027 chromophore, an enediyne antitumor antibiotic: high selectivity to an anticodon arm.

This study demonstrates unique reactivity of the C-1027 chromophore toward a tRNA(phe). In the presence of Mg2+ ions where the tRNA(phe) attains a stable three-dimensional structure, the enediyne chromophore exhibits high cleavage selectivity to the anticodon arm. The present reactivity of the C-1027 chromophore is useful in development of new chemical probes for mapping of tertiary RNA structure. Considering the paucity of RNA repair mechanisms, RNA may be also an important biological target for certain enediyne antibiotics.

Aminoglycosides↗

PubMed1993

Cleavage of yeast tRNA(phe) with Ni(III) and Co(III) complexes of bleomycin.

The BLM-Ni(III) complex preferentially cleaves guanine residues at D loop and anticodon loop of yeast tRNA(phe) by aniline treatment, whereas the BLM-Co(III) complex degrades certain 5'-AN sites of the minor groove region after irradiation of UV light. These cleavage features are clearly different from that of the BLM-Fe(II) complex.

Base Sequence↗