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Biomedical subjects

K Toyoda

Publications and source records attributed to K Toyoda.

At least 127 records · Page 7Linked to original sources
PubMed1993

The rat urinary bladder as a new target of heterocyclic amine carcinogenicity: tumor induction by 3-amino-1-methyl-5H-pyrido[4,3-b]indole acetate.

In order to examine the carcinogenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole acetate (Trp-P-2), 30 male and 30 female F344 rats were maintained on diet containing 0, 30, or 100 ppm Trp-P-2 for 112 weeks. The overall mean chemical intakes in the 100 ppm and 30 ppm groups were 3.84 and 1.14 mg/kg/day in males, and 4.57 and 1.34 mg/kg/day in females, respectively. Females of the 100 ppm group showed increased mortality in the late period of the study. In the 100 ppm group, significant increases in the incidences of neoplastic lesions were found in the liver, urinary bladder and mammary gland in males, and in the mammary gland, hematopoietic system and clitoral gland in females. Histologically, tumors induced by Trp-P-2 were hepatocellular adenomas, transitional cell tumors (papillomas and carcinomas) of the urinary bladder, fibroadenomas/fibromas of the mammary gland, malignant lymphomas and clitoral gland tumors (adenomas and adenocarcinomas). These results indicate multi-target carcinogenicity of Trp-P-2 in F344 rats and provide evidence that the urinary bladder is also a target for heterocyclic amine action.

Animals↗
PubMed1993

Transesophageal echocardiography for detecting intracardiac thrombi in embolic stroke.

The authors studied 56 patients with cardioembolic stroke to search for intracardiac thrombi by use of transesophageal and transthoracic echocardiography. Forty consecutive patients were examined within four weeks of stroke onset and the remaining 16 in the chronic stage. They also performed ultrafast computed tomography in 9 of them. Underlying heart disease was present in all subjects. Anticoagulant therapy had already been started in 29 at the time of examinations. Using their own criteria for echocardiography, they diagnosed intracardiac thrombus in 7 cases and valvular vegetation in 1. Six thrombi were located in the left atrial appendage, 4 of which were smaller than 10 mm in diameter. These small thrombi were not found by either transthoracic echocardiography or computed tomography. Transesophageal echocardiography appears to be superior to the other two methods, especially for detecting small intracardiac thrombi in the left atrial appendage.

Adult↗
PubMed1993

Mechanisms of the hypolipidemic effect of NIP-200 in rats.

We studied the mechanisms of hypolipidemic effects of NIP-200 (3,5-dimethyl-4,6-diphenyltetrahydro-2H-1,3,5-thiadiazine- 2-thione), a potent hypolipidemic compound, in cholesterol biosynthesis in the liver, cholesterol absorption in small intestine, and cholesterol catabolism and excretion in rats. NIP-200 did not reduce cholesterol biosynthesis and had no effects on cholesterol absorption in the small intestine. In the cholesterol catabolism and excretion, NIP-200 induced increases in cholesterol and bile acids levels in the bile and acidic steroids in the feces, and it enhanced cholesterol 7 alpha-hydroxylase activity in the liver. These results suggest that NIP-200 increases the synthesis of bile acids as a result of the activation of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in the conversion of cholesterol to bile acids. Therefore, it is considered that one of the probable mechanisms of the serum total cholesterol lowering action of NIP-200 involves the enhancement of catabolism and excretion of cholesterol in the liver.

Animals↗
PubMed1993

[Quantitative histopathological study on the adriamycin testicular toxicity in rats].

Testicular toxicity induced by adriamycin (ADR) was studied using quantitative histopathological methods. Nine-week old male rats were received a single dose of 8 mg/kg ADR. At 3, 7, 14 and 21 days after the treatment, animals were sacrificed for histopathological evaluation. Numbers of seminiferous epithelia were counted in seminiferous tubule of spermatogenic stages I, II, V, VII and XII. A decrease in spermatogonia was observed in seminiferous tubules of stages I, II and V at 3 days after the treatment. Thereafter, numbers of other types of seminiferous epithelia decreased following progress of spermatogenic cycle. Analysis of spermatogenic cycle movement and germ cell differentiation suggested that ADR was highly effective in killing spermatogonia type A, and the severity of ADR damage would be different depending on subtypes of spermatogonia type A and spermatogenic stages.

Animals↗
PubMed1993

Inhibition of ATPase activity in pea plasma membranes by fungal suppressors from Mycosphaerella pinodes and their peptide moieties.

The effects of two suppressors of the defense reactions of host plants, which had been purified from the pea pathogen Mycosphaerella pinodes, as well as the effects of peptide moieties, on the ATPase activity in pea plasma membranes were examined in vitro. One of the suppressors, Supprescin B, inhibited the ATPase activity in a non-competitive manner, but the other suppressor, Supprescin A, did not. Supprescin A was observed to reduce the inhibitory effect of Supprescin B. A tripeptide, Ser-Ser-Gly, and a hexapeptide, Ser-Ser-Gly-Asp-Glu-Thr, which were the respective peptide moieties of Supprescin A and B, inhibited the ATPase activity in a competitive manner. Supprescin B and fragments of the hexapeptide, such as Asp-Glu-Thr and Gly-Asp-Glu, inhibited not only the ATPase activity but also the acid phosphatase activity of plasma membranes in vitro. These results indicate that the acidic amino-acid residues of the "Asp-Glu" moiety seem to act as inhibitors of the phosphatase activity. Thus, the peptide moiety of Supprescin B consists of at least two functional elements.

Acid Phosphatase↗
PubMed1992

[MR imaging of degenerative lumbar disc disease emphasizing on signal intensity changes in vertebral body].

Magnetic resonance imaging was performed in 400 patients with degenerative disc disease. Signal changes and their sites in the vertebral body were classified and referred to narrowing of the intervertebral disc space. MR findings were compared with those of plain roentgenograms of the lumbar spine. Signal changes in the vertebral body were noted in 83 cases (102 vertebral bodies). Low-intensity abnormality on both T1- and T2-weighted images (WI) was the most common finding, and was most frequently seen at the end plate and/or the angle. These changes were correlated with narrowing of the disc space and osteosclerosis on the plain roentgenogram of the lumbar spine. Signal changes occasionally occurred in the inner region of the vertebral body, and these lesions tended to show a high-intensity abnormality on T1-WI. We conclude that signal changes in degenerative disc disease are not specific, but are sometimes difficult to distinguish from the signal changes in other conditions such as spinal tumor or bone marrow disorder.

Humans↗
PubMed1992

Comparative studies by cell culture and in vivo implantation test on the toxicity of natural rubber latex materials.

Colony assay using V79 cells, the agar diffusion assay with L929 cells, and the 7-day rabbit muscle implantation test were employed to evaluate the cytotoxicity and tissue toxicity of natural rubber latex (NRL) materials. The in vivo implantation test showed that, among 13 histological parameters, thickness of inflammatory layer was the most useful index to evaluate tissue responses quantitatively. A comparison of the in vivo and in vitro parameters revealed the following correlations between the thickness of the inflammatory layer and cytotoxicity indices: Colony assay of the extracts, IC50: r = 0.80; Agar diffusion assay, Zone index: r = 0.73; Lysis index: r = 0.61. From these results, it appears that the colony assay provides a more reliable prediction of the tissue response than the agar diffusion assay.

Animals↗
PubMed1992

Lack of carcinogenicity of ferric chloride in F344 rats.

The carcinogenicity of ferric chloride, a compound that is used as a food additive, a haemostatic or treatment for hypochromic anaemia, was examined in F344 rats of both sexes. It was dissolved in distilled water at levels of 0, 0.25 or 0.5%, and groups of 50 male and 50 female rats were given one of these solutions ad lib. as their drinking water for up to 2 yr. The mean body weights of the treated rats were lower than control group values for both males and females. A variety of tumours developed in all groups, including the control group, but all these neoplasms were histologically similar to those known to occur spontaneously in this strain of rats, and no statistically significant increase in the incidence of any tumour was found in the treated groups of either sex. Thus it is concluded that under the conditions of this experiment, ferric chloride exerts no carcinogenic potential in F344 rats.

Animals↗
PubMed1992

Correlation between cataract and retinopathy due to lighting in F344 rats used in a long-term carcinogenicity study.

Correlations between light intensity of animal room lighting and both cataract and retinopathy of rats were examined, and relationships between the cataract and the retinopathy were further investigated. Seventy-nine male rats and 106 female rats surviving to the end of a 2-yr carcinogenicity study of monosodium succinate were used in this investigation. Animals were housed in polycarbonate cages, each containing 4 rats, with wire lids and hardwood chips for bedding and with a 12-h light/dark cycle. Individual groups comprising 13 cages were inserted into 3 by 5 cage hanging type racks. Light intensity was measured at the bottom (on the bedding) of individual cages. Statistically, both the incidence of cataracts and the severity of retinopathy were closely related to light intensity. The incidence of cataracts in males was significantly higher than that in females, while no sex difference was observed for the severity of retinopathy. Meanwhile, no differences in either the incidence of cataracts or the severity of retinopathy were observed between the monosodium succinate-treated and control groups and between the right and left eyes. While the occurrences of retinopathy and cataract were strongly associated, our results indicated that retinopathy occurs more frequently than cataracts, and thus the retina appeared to be more sensitive to the effects of lighting.

Animals↗
PubMed1992

Induction of pancreatic tumors in male Syrian golden hamsters by intraperitoneal N-methyl-N-nitrosourea injection.

The carcinogenic effects of N-methyl-N-nitrosourea (MNU) in male Syrian golden hamsters were investigated. After single i.p. administration of MNU at doses of 50 mg/kg or 10 mg/kg, or after five fractionated i.p. injections to make a total dose of 50 mg/kg body weight (10 mg x 5), histopathological examinations were performed at the end of 40th week of the experiment. Neoplastic changes were observed in various organs, and lesions in the pancreas, forestomach, and adrenal gland were predominant. In the pancreas, three tumor types were observed: ductal adenocarcinomas, acinar cell carcinomas, and islet cell carcinomas. The incidences of pancreatic ductal carcinomas were 56, 27, and 0% in the single 50-mg, fractionated 50-mg, and single 10-mg groups, respectively. Two islet carcinomas were observed in the single 50-mg group, and an islet carcinoma and an acinar cell carcinoma were also observed in the fractionated 50-mg group. Several miscellaneous neoplastic lesions, including squamous cell papillomas/carcinomas in the forestomach, cortical adenomas in the adrenal glands, and a seminoma in the testis were also observed. These results indicate MNU to be a multipotent carcinogen with the pancreas as a target organ in the Syrian golden hamster under this experimental condition. The observed high induction rate for pancreatic ductal carcinoma suggests that this MNU protocol is a useful candidate model for experimental pancreatic ductal carcinogenesis.

Animals↗
PubMed1992

Bilateral medial medullary infarction with oculomotor disorders.

BACKGROUND AND PURPOSE: We describe the first case of bilateral medial medullary infarction demonstrated by magnetic resonance imaging. We discuss the relation between this lesion and the oculomotor signs that were observed clinically. CASE DESCRIPTION: A 71-year-old man initially presented with pure motor hemiparesis, which progressed to complete quadriplegia. He also developed nearly complete vertical and horizontal ophthalmoplegia. Magnetic resonance imaging revealed upper medial medullary infarctions bilaterally that extended to the pontomedullary junction. CONCLUSIONS: We propose that the vertical oculomotor disorders resulted from involvement of the oculomotor system in the caudal brain stem, especially the caudal paramedian pontine reticular formations on both sides.

Aged↗
PubMed1992

Aortogenic embolic stroke: a transesophageal echocardiographic approach.

BACKGROUND AND PURPOSE: We studied the frequency and grade of atherosclerotic changes in the thoracic aorta and their significance as embologenic lesions in patients with stroke. METHODS: Using transesophageal echocardiography, we evaluated complicated lesions in the thoracic aortas of 62 patients who met our clinical criteria for embolic stroke. A complicated lesion was defined as a raised lesion with an irregular surface or acoustic shadow based on a comparative study of echocardiographic and histopathologic findings. The results were compared with plain radiographic findings and in some cases with computed tomographic or aortographic findings. RESULTS: Twenty-six patients (42%) showed complicated aortic arch lesions on echocardiogram. Transesophageal echocardiography brought us more abundant information than other techniques. Aortic knob calcification by plain radiography correlated well with the presence of echocardiographically complicated lesions, suggesting its utility for rough screening of atherosclerotic changes. Fifty-two patients had other potential embolic sources in the heart or cervical arteries. Among the remaining 10 patients without extra-aortic embolic sources, three showed complicated lesions and were diagnosed as having aortogenic embolic stroke. CONCLUSIONS: Aortic atherosclerosis should be recognized as an embolic source of stroke and the advantage of transesophageal echocardiography recognized in its evaluation.

Adult↗