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Biomedical subjects

K Toyoda

Publications and source records attributed to K Toyoda.

At least 19 recordsLinked to original sources
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↗
PubMed1992

A case of panic disorder induced by oral contraceptive.

A 27-year-old woman experienced feelings of unreality and fear after taking an oral contraceptive in the form of birth control pills. She subsequently experienced a panic attack just after she had stopped taking the pills. This was characterized by palpitation, general fatigue, trembling of the whole body, and dyspnea. The panic disorder experienced by the patient could have been due to the drug's potentiating of the sympathoadrenal response to simple physiological stimuli, or possibly to a disorder in psychological functioning caused by an anxiotropic effect of rapid endocrinological change.

Adult↗
PubMed1992

[Twenty-eight-day repeated dose toxicity test of pentaerythritol in F344 rats].

A twenty-eight-day repeated dose toxicity test of pentaerythritol at dose levels of 1000 or 0 mg/kg/day was carried out in male and female F344 rats. Thirteen animals of each sex were divided into 2 groups with 7 rats receiving pentaerythritol treatment and 6 rats served saline as control. All groups received an i.g. administration daily for 28 days. As to serum biochemical and hematological examinations, there were no serious differences between the pentaerythritol-treated rats and the control rats. On histopathological examination, no specific changes were observed in the pentaerythritol-treated rats. Based on these results, the no-observed-effect level of pentaerythritol can be concluded to be more than 1000 mg/kg/day.

Administration, Oral↗
PubMed1991

Evaluation of biocompatibility, based on quantitative determination of the vascular response induced by material implantation.

The biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using V79 chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using Laser Doppler Flowmetry (LDF) over 14 days following implantation. In addition, for some materials, different modes of sterilization were compared. Although the three methods explore different reactive systems, the material ranking obtained was highly similar for the three methods, suggesting a relative accuracy between them. For one latex however, an absence of cytotoxic effect in culture and a highly intense response by LDF investigation of the same order of magnitude as for the positive reference implant suggest that bioincompatibility may result from the material itself and cannot be exclusively investigated by the leaching of toxic components.

Anesthesia↗
PubMed1991

Localization of the sensory neurons in the canine nodose ganglion sending fibers into the internal branch of the superior laryngeal nerve.

The distinct localization of the sensory neurons in the canine nodose ganglion that send fibers into the internal branch of the superior laryngeal nerve (the main sensory pathway from the larynx) was studied using horseradish peroxidase technique. The labeled cells were located mainly in the rostral one-third of the lateral side of the nodose ganglion. We conclude that the localization of these labeled cells does not reflect a difference in cellular role or function but is due to the course of the nerve's fibers.

Animals↗
PubMed1991

Enhanced lipid peroxidation in rat gastric mucosa caused by NaCl.

The effects of NaCl on lipid peroxidation levels in gastric mucosa and urine were investigated in male Wistar rats. The animals were fed NaCl-supplemented diet at concentrations of 4.0, 2.0, 1.0, 0.5, 0.25 and 0% (control) for 5 weeks. Further groups were maintained on the 4.0 or 0% NaCl diets and simultaneously administered 20 p.p.m. indomethacin dissolved in the drinking water. When the rats were killed, a dose-related increase of malondialdehyde (MDA) was found in both gastric mucosa and urine, the urinary MDA levels clearly correlating with those for stomach tissue. Cell proliferation of fundic mucosa was also significantly increased in rats fed 4.0 or 2.0% NaCl-supplemented diet. Indomethacin suppressed the 4% NaCl-associated MDA increase in both gastric mucosa and urine as well as the elevation in cell proliferation. The results clearly show that administration of NaCl, a gastric tumor promoter, is associated with enhanced lipid peroxidation in the gastric mucosa.

Animals↗
PubMed1991

[Localization of sensory neurons in the canine nodose ganglion sending fibers to the laryngeal nerves].

Afferent fibers from the larynx traverse through the superior laryngeal nerve (SLN) and the inferior laryngeal nerve (ILN), and the parent cell bodies of these fibers are located in the nodose ganglion (NG). However, the exact location and form of these neurons in the NG have not been clarified. The aim of this study is to determine the exact location and form of the sensory neurons in the canine NG which send fibers to the laryngeal nerves, using the retrograde tracer technique with wheat germ agglutinin-horseradish peroxidase (WGA-HRP). The cell bodies sending sensory fibers to the internal and external branches of the SLN (SLNI & SLNE) were localized on the rostro-lateral side of the NG, but the cell bodies sending fibers to the ILN were widely distributed. These findings suggest that the location of cells does not reflect differences in the roles of the cells, but is due to the courses of nerve fibers. The cell bodies sending sensory fibers to the SLNI accounted for about 11% of all cells in the NG; about 0.1% of cells sending fibers to the SLNE; and about 0.2% in the ILN. The cell bodies sending sensory fibers to each laryngeal nerve varied in size, from 15 to 60 microns, suggesting differences in the roles of these cells.

Animals↗
PubMed1991

[Twenty-eight-day repeated dose toxicity test of p-phenetidine in F344 rats].

A twenty-eight-day repeated dose toxicity test of p-phenetidine was carried out in male and female F344 rats at dose levels of 160, 40, 10 or 0 mg/kg/day. Thirty animals of both sexes were divided into 6 groups of equal number. All groups were treated daily by i.g. administration for 28 days, two extra groups of animals at dose levels of 160 and 0 mg/kg being used for investigation of recovery over 14 days. Hematological and urinary examinations revealed decrease in erythrocytes and increased serum reticulocytes and urinary urobilinogen in the 160 and 40 mg/kg groups of both sexes, and methemoglobinemia occurred in the 160 mg/kg group. Increase in spleen weight was noted in the 160 and 40 mg/kg groups. On histopathological examination, hemosiderosis, increased extramedullary hemopoiesis, congestion of the spleen and myeloid hyperplasia of the bone marrow were observed in the 160 and 40 mg/kg groups of both sexes. Repair of these lesions occurred within 14 days after the cessation of administration. Based on these findings, a no-observed-effect level for p-phenetidine would be concluded 10 mg/kg/day.

Animals↗