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Biomedical subjects

Y Miyata

Publications and source records attributed to Y Miyata.

At least 379 records · Page 21Linked to original sources
PubMed1977

Summation effect of N-butyl-n-(4-hydroxybutyl)nitrosamine, N-(4-(5-nitro-2-furyl)-2-thiazoly)formamide, N-2-fluoroenylacetamide, and 3,3'-dichlorobenzidine on urinary bladder carcinogenesis in rats.

The effects of the sequential administration of 0.01% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), 0.15% N-(4-(5-nitro-2-furyl)-2-thiazoly)formamide (FANFT), 0.025% N-2-fluorenylacetamide (2-FAA), and 0.3% 3.3'-dichlorobenzidine (3,3'-DCB) on urinary bladder carcinogenesis were examined in male Wistar rats. Each chemical was administered for 4 weeks in various combinations. BBN for 4 weeks resulted in no histopathological changes, mild diffuse cell growth, and/or focal hyperplasia after 4, 8, 12, or 16 weeks of observation. No bladder carcinomas were present in rats given only BBN or any one of the other 3 chemicals. Statistically significant incidences of bladder carcinomas occurred with the sequential administration of all 4 chemicals or the first 3 chemicals without 3,3'-DCB. Bladder cancer was also present in rats administered the sequence of FANFT, 2-FAA, and 3,3'-DCB. No antagonistic effects between chemicals were observed.

2-Acetylaminofluorene↗
PubMed1976

Enhancement of pancreatic tumorigenesis of 4-hydroxyaminoquinoline 1-oxide by ethionine in rats.

The effect of ethionine on pancreatic tumorigenesis of 4-hydroxyaminoquinoline 1-oxide (4-HAQO) in rats was studied. The high incidence of hyperplastic nodules developed in the exocrine pancreas of animals receiving a single injection of 4-HAQO only or protein-deficient diet containing 0.5% ethionine for 4 days followed by 4-HAQO. The incidence of adenoma was higher than that of hyperplastic nodules and well-differentiated adenocarcinoma developed in 1 out of 12 animals receiving protein-deficient diet containing ethionine for 18 days followed by 4-HAQO. No tumor was found in the pancreas of animals that received 0.005N HCl without 4-HAQO. These results suggest that the pancreatic tumorigenesis of 4-HAQO is enhanced by ethionine.

4-Hydroxyaminoquinoline-1-oxide↗
PubMed1975

Electrophysiological properties of spinal motoneurones of normal and dystrophic mice.

1. The properties of spinal motoneurones of normal and dystrophic mice (129/ReJ) were examined with intracellular electrodes. 2. The following parameters of spinal motoneurones showed no significant differences between normal and dystrophic mice: resting and action potentials, the amplitude and duration of after-hyperpolarization, rheobasic current for excitation, threshold for excitation of the somadendritic membrane (IS-SD inflexion) and input resistance. 3. The changes in motoneurone properties observed 13-16 days after section of the sciatic nerve (axotomy) were similar in both normal and dystrophic mice. 4. The axonal conduction velocity of motoneurones in dystrophic mice was about ten times slower than that in normal mice. The conduction velocity of the sciatic nerve was only about 25% slower in dystrophic mice than in the normal animal. The estimated ventral root conduction velocity as well as the observed dorsal root conduction velocity in dystrophic mice was at least twenty times slower than that in normal mice. 5. In dystrophic mice, spinal motoneurones often showed multiple discharges in response to single, antidromic stimuli. The site of initiation of multiple discharge was located in the motor axon rather than in the motoneurone cell body. 6. In dystrophic mice, nerve impulses were transmitted from fibre to fibre ('cross-talk'). The site of impulse transmission among nerve fibres was near the distal portion of the spinal roots. 7. Synaptic potentials and peripheral reflex discharges evoked by stimulation of the dorsal roots showed a longer latency and were more prolonged in dystrophic mice than in the control mice. 8. The motoneurone properties of dystrophic mice showed no tendency of progressive changes with age ranging from 63 to 148 days. 9. It is concluded that the properties of motoneurone cell bodies examined in dystrophic mice are indistinguishable from those in normal mice and that the only abnormality in motoneurones of the former residues in the motor axon. 10. It is suggested that integrity of the discharge pattern of spinal motoneurones in dystrophic mice is interfered by anomalous impluse transmission in the motor axons and that the motoneurones in dystrophic mice are a homogeneous group rather than a mixture of "normal" and "abnormal" neurones.

Action Potentials↗
PubMed1975

Differentiation of motoneurones and skeletal muscles in kittens.

1. Isometric contractions of the medial gastrocnemius (fast switch) and soleus (slow twitch) muscles were recorded in kittens ranging in age from 3 to 112 days, as well as in adult cats. 2. It was confirmed that the speed of contraction of the gastrocnemius muscle becomes progressively faster during the first few weeks after birth, whereas contraction times of the soleus muscle show little changes or a slight prolongation during the period of post-natal development. 3. The properties of gastrocnemius (fast alpha) and soleus (slow alpha) motoneurons were examined with intracellular electrodes in kittens at three different stages; 16-20, 61-71 and 100-112 days in age. 4. The axonal conduction velocities of both gastrocnemius and soleus motoneurones increased monotonically throughout the period of development and showed no correlation with post-natal changes in contraction times of the innervated muscles. 5. The duration of after-hyperpolarization in soleus motoneurones became progressively longer with age, while that in gastrocnemius motoneurones remained virtually unchanged during development. 6. The relation between the duration of after-hyperpolarization and the axonal conduction velocity in kitten motoneurones was similar to that observed in axotomized motoneurones of adult cats. 7. It is suggested that fast and slow alpha motoneurones show postnatal differentiation in terms of the duration of after-hyperpolarization and that axotomy leads to 'dedifferentiation' of the motoneurone properties. 8. Post-natal changes in the contractile properties of skeletal muscles were independent of the changes in the duration of after-hyperpolarization of the innervating motoneurones. However, it remains uncertain whether muscle differentiation is independent of the discharge pattern of the innervating motoneurones.

Age Factors↗
PubMed1975

Pathologic analysis of chemical nephritis in rats induced by N-(3,5-dichlorophenyl)succinimide.

The effects of N-(3,5-dichlorophenyl)succinimide (NDPS) administration to rats were studied by blood chemical, histopathologic, histochemical, and ultrastructural examinations. Administration of 5000 p.p.m. of NDPS induced severe damage of the kidneys, but did not affect other organs. Administration of 2500 p.p.m. of NDPS had little effect, even on the kidneys. Chemical analysis of the blood showed that the urea nitrogen level increased with the increase in the period of NDPS administration. Histopathologic examination showed intensive cell infiltration, mainly of lymphocytes, into the renal interstitium after NDPS administration for only 4 weeks. After NDPS administration for 12 weeks or more, typical interstitial nephritis was observed. Histochemical analysis showed that after only 1 week various enzymatic activities in the proximal convoluted tubules were markedly decreased whereas their activities in the distal convoluted tubules were relatively well preserved for at least 4 weeks. These results indicate that NDPS predominantly attacked the proximal convoluted tubules. After 4 weeks, the most prominent ultrastructural changes were seen in the proximal convoluted tubules where the epithelial cells lost their polarity and had a very abnormal arrangement. These cells showed well developed, edematous microvilli, poorly developed basal infoldings, swollen mitochondria of various sizes, aggregated beta-type glycogen granules, and debris of erythrocytes. Development of the endoplasmic reticulum, Golgi complex, ribosomes, and lysosomes was poor in the cytoplasm. These investigations indicate that NDPS affects the function of the proximal convoluted tubules. NDPS is a selective nephrotoxic substance. That is, it initially damages the proximal convoluted tubules, and subsequently causes interstitial nephritis. It is suggested that nephritis induced by NDPS is useful as a model of interstitial nephritis in man.

Animals↗
PubMed1975

Development of hepatocellular carcinomas in rats treated with benzene hexachloride.

The effects of prolonged oral administration of the alpha-, beta-, and gamma-isomers of benzene hexachloride (BHC) on rat liver were examined histologically. Well-differentiated hepatocellular carcinomas were observed in the liver of rats fed a basal diet containing 1,500 or 1,000 parts per million (ppm) of alpha-BHC for 72 weeks. Many typical nodular hyperplasias developed in all groups given 1,500 or 1,000 ppm alpha-BHC. In non-neoplastic areas, slight oval cell infiltration and bile duct proliferation were seen. No neoplastic changes or other abnormal findings, such as oval cell infiltration, fatty changes, fibrosis, or bile duct proliferation of the liver, were observed in groups receiving 500 ppm alpha-, beta-, gamma-, or gamma-BHC.

Administration, Oral↗
PubMed1975

Effect of various factors on induction of liver tumors in animals by the alpha-isomer of benzene hexachloride.

The tumorigenic effect of a diet containing the alpha-isomer of benzene hexachloride (alpha-BHC) on the liver of various animals was examined. It was found that alpha-BHC induced liver tumors in male and female mice but not in rats or hamsters in the present observations. Histological changes in the liver of mice induced by alpha-BHC were also much greater than those induced in rats or hamsters. Male animals were more susceptible to the tumorigenic action of alpha-BHC than females. Among different strains of mice, the DDY showed greatest susceptibility and the C57BL/6 showed the least. Induction oflpha-BHC was not inhibited by concomitant feeding of 1-naphthyl isothiocyanate or p- hydroxypropiophenone. However, 3-methylcholanthrene slightly inhibited their induction by alpha-BHC.

Animals↗