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Biomedical subjects

Y Miyata

Publications and source records attributed to Y Miyata.

At least 361 records · Page 20Linked to original sources
PubMed1978

Effect of vitamin A acetate on urinary bladder carcinogenesis induced by N-butyl-N-(4-hydroxybutyl)nitrosamine in rats.

The effect of vitamin A acetate on the urinary bladder carcinogenicity of N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) was determined in male Wistar rats. Vitamin A acetate at the dose administered induced no changes in the urinary bladder or other organs when administered without the carcinogen. However, hypervitaminosis A inhibited keratinization and squamous metaplasia in bladder lesions induced by BBN, and the incidence of transitional cell carcinoma and papilloma of the urinary bladder was significantly reduced at a dose greater than 100 IU/g diet (P less than 0.02). The present experiment suggests that for the urinary bladder epithelium of rats hypervitaminosis A reduced susceptibility to the tumorigenicity of BBN.

Animals↗
PubMed1977

Reaction of intact spinal motoneurones to partial denervation of the muscle.

1. The properties of soleus motoneurones of the cat were examined with intracellular electrodes about 3 weeks after partial denervation of the soleus muscle. Soleus motoneurones whose axons had been left intact were distinguished from those whose axons had been sectioned by the presence or absence of muscle contraction in response to intracellular stimulation of each motoneurone. 2. The average twitch tension of motor units evoked by intracellular stimulation of intact soleus motoneurones after partial denervation of the muscle was not significantly different from that observed in control, unoperated cats. Therefore, it was assumed that the majority of intact motoneurones had not been subject to injuries in their axons upon partial denervation. 3. Soleus motoneurones whose axons had been sectioned showed a significant increase in overshoot of action potentials and a significant decrease in resting membrane potential, in axonal conduction velocity and in the duration of after-hyperpolarization. 4. Soleus motoneurones whose axons had been left intact also showed a significantly shorter after-hyperpolarization than that seen in control, unoperated cats. Other electrophysiological properties of the intact soleus motoneurones were indistinguishable from those observed in unoperated animals. 5. The decrease of the duration of after-hyperpolarization in intact soleus motoneurones was greater in highly denervated preparations than in moderately denervated preparations. 6. The decrease of the duration of after-hyperpolarization in intact soleus motoneurones was associated with a decrease in contraction times of the innervated muscle fibres, the former preceding the latter by one to two weeks. 7. It is concluded that motoneurone properties can be modified without injury to their axons and that alterations in the properties of intact motoneurones depend upon the degree of partial denervation of the muscle. The possible signal for alterations of motoneurone properties is discussed. 8. It is also concluded that the contractile properties of muscle fibres can be modified without cross-union of the nerves. It is suggested that the contractile properties of muscle fibres may be linked to the duration of after-hyperpolarization or to some mechanism related to this factor in the innervating motoneurones.

Action Potentials↗
PubMed1977

Effect of N-(3,5-dichlorophenyl)succinimide on the histological pattern and incidence of kidney tumors induced by streptozotocin rats.

The effect of the nephrotoxic substance, N-(3,5-dichlorophenyl)succinimide, on the histological pattern and incidence of kidney tumors induced by streptozotocin in rats was studied. In groups administered streptozotocin alone or in combination with nicotinamide, the histological pattern and the incidence of kidney tumors in rats were similar; renal cell tumors developed in 1 of 9 rats (11.1%) and in 2 of 17 rats (11.8%), respectively. However, post-treatment with N-(3,5-dichlorophenyl)succinimide increased the induction of epithelial tumors by streptozotocin, and embryonal cell tumors were also induced nearly as frequently. Administration of nicotinamide alone did not result in the development of kidney tumors.

Adenoma, Islet Cell↗
PubMed1977

Damage and repair of DNA in urinary bladder epithelium of rats treated with N-butyl-N-(4-hydroxybutyl) nitrosamine.

N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN), which selectively induced urinary bladder tumors in several experimental animal species, was found to cause damage of DNA in the bladder epithelium. Wistar strain rats were given 100 mg/kg of BBN intravesically and killed after 2, 6, 12, 24, or 48 hr. DNA damage was examined by measuring the change in sedimentation pattern in an alkaline sucrose gradient. Amount of DNA in each fraction was determined by fluorescence spectrophotometry. At 2 hr, the sedimentation profile shifted from heavier (No 15, control peak) to lighter (Nos. 2 approximately 4) fractions, and the maximum effect appeared at 6 hr as a single peak in the lighter fractions. At 12 hr, damaged DNA was in the process of repair as two peaks were present, one light and one heavy. At 48 hr, the sedimentation profile showed a single peak identical with that of controls indicating complete repair of DNA.

Animals↗