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Biomedical subjects

K Ishida

Publications and source records attributed to K Ishida.

At least 145 records · Page 8Linked to original sources
PubMed1999

Mutagenicity of 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) in the new gpt delta transgenic mouse.

Gender differences and organ specificity of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mutagenesis were examined with the new gptdelta transgenic mouse (T. Nohmi, M. Katoh, H. Suzuki, M. Matsui, M. Yamada, M. Watanabe, M. Suzuki, N. Horiya, O. Ueda, T. Shibuya, H. Ikeda, T. Sofuni, A new transgenic mouse mutagenesis test system using Spi-and 6-thioguanine selections (Environ. Mol. Mutagen. 28 (1996) 465-470). In this mouse model, two distinct selections are employed to efficiently detect different types of mutations, i.e 6-thioguanine (6-TG) selection for point mutations and Spi-selection for deletions, respectively. In both selections, the highest mutant frequencies were observed in colon, followed by in spleen and liver. No increases in mutations were observed in testis, brain and bone marrow in PhIP-treated male mice. No significant differences in 6-TG and Spi- mutant frequencies were observed in colon and liver between male and female treated mice. The correlation between PhIP-induced mutagenesis and carcinogenesis in colon is discussed.

Animals↗
PubMed1999

Occurrence and identification of UDP-N-acetylmuramyl-pentapeptide from the cyanobacterium Anabaena cylindrica.

UDP-N-acetylmuramyl-pentapeptide (UDP-MurNAc-pentapeptide) is well known to be a key intermediate of bacterial peptidoglycan biosynthesis. We first detected the occurrence of UDP-MurNAc-pentapeptide in the cyanobacterium Anabaena cylindrica (NIES-19), and identified the structure of this pentapeptide by two-dimensional 1H-1H and 1H-13C NMR correlation experiments and mass spectra.

Anabaena↗
PubMed1999

Anabaenopeptins G and H, potent carboxypeptidase A inhibitors from the cyanobacterium Oscillatoria agardhii (NIES-595).

Anahaenopeptins G (1) and H (2) were isolated from the cultured cyanobacterium Oscillatoria agardhii (NIES-595) as potent carboxypeptidase A (CPA) inhibitors. The gross structure of 1 and 2 were established by spectroscopic analysis including the 2D NMR technique and the absolute configurations of 1 and 2 were determined by the spectral and chemical methods. 1 and 2 inhibited CPA with IC50's of 0.0018 and 3.4 microg/mL, respectively.

Carboxypeptidases↗
PubMed1999

Thiopentone inhibits endothelium-dependent relaxations of rat aortas regulated by endothelial Ca2+-dependent K+ channels.

The present study was designed to examine the mechanisms of inhibitory effect of barbiturates on endothelial function by determining whether thiopentone and phenobarbitone reduce relaxations to acetylcholine mediated by endothelial Ca2+-dependent K+ channels in rat aortas. Cumulative applications (10(-9) to 10(-5) M) of acetylcholine induced endothelium-dependent relaxations, which are abolished by inhibitors of nitric oxide synthase (N(G)-nitro-L-arginine methyl ester, 10(-4) M) and of soluble guanylate cyclase (1H-[1,2,4]oxadiazolo [4,3,-a]quinoxaline-1-one; ODQ, 5 x 10(-6) M). Selective inhibitors of large-conductance Ca2+-dependent K+ channels (iberiotoxin, 5 x 10(-8) M), but not of those with small-conductance (apamin, 5 x 10(-8) M), significantly reduced the acetylcholine-induced vasorelaxation. ODQ, but neither iberiotoxin nor apamin, blocked the relaxations of arteries without endothelium induced by nitric oxide donors, sodium nitroprusside (10(-9) to 10(-5) M) and 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC-7; 10(-10) to 10(-5) M). Thiopentone (10(-4) and 3 x 10(-4) M) but not phenobarbitone (3 x 10(-4) M) significantly impaired relaxations to acetylcholine, whereas thiopentone did not alter relaxations to sodium nitroprusside. Thiopentone (3 x 10(-4) M) did not affect relaxations to acetylcholine in arteries treated with iberiotoxin (5 x 10(-8) M), whereas it reduced these relaxations in arteries treated with apamin (5 x 10(-8) M). These results suggest that in rat aortas, large-conductance, but not small-conductance, Ca2+-dependent K+ channels in endothelial cells, play a role in endothelium-dependent relaxations to acetylcholine, and that thiopentone, but not phenobarbitone, impairs relaxations to acetylcholine mediated by these channels.

Acetylcholine↗
PubMed1999

Microsphere embolism-induced elevation of nerve growth factor level and appearance of nerve growth factor immunoreactivity in activated T-lymphocytes in the rat brain.

Changes in nerve growth factor (NGF) level and type of cells producing NGF were investigated in the rat brain after sustained cerebral embolism. The NGF level was determined by a two-site enzyme immunoassay specific for NGF. The cerebral cortex, striatum, and hippocampus of the embolized hemisphere maximally contained 2.4-, 2.4-, and 1.7-times higher NGF levels than the corresponding regions of the nonembolized hemisphere. A significant increase was transiently observed for 1 week in the cerebral cortex and striatum, whereas the increase was longer lasting, at least of 4 weeks' duration, in the hippocampus. To examine the localization of NGF-like immunoreactivity (NGF-LI), we used a newly developed anti-NGF peptide antiserum that specifically recognized a 30-kDa molecule(s) in the hippocampal extracts or in NGF cDNA-transfected cells, suggesting that the antibody predominantly reacted with the putative NGF precursor protein(s). NGF-LI, which was localized in neurons of the normal or non-embolized hemisphere, was reduced, and on the embolized side new signals emerged in small non-neuronal cells having a round shape. These included cells with common leukocyte antigen CD45 and T-lymphocyte antigen CD3, which did not appear in the normal or non-embolized hemisphere. NGF-LI and CD3 were colocalized in a substantial number of the cells, suggesting that some activated T-lymphocytes produce NGF for neuronal regeneration after sustained cerebral embolism.

Animals↗
PubMed1999

The alkaline single cell gel electrophoresis assay with mouse multiple organs: results with 30 aromatic amines evaluated by the IARC and U.S. NTP.

The genotoxicity of 30 aromatic amines selected from IARC (International Agency for Research on Cancer) groups 1, 2A, 2B and 3 and from the U.S. NTP (National Toxicology Program) carcinogenicity database were evaluated using the alkaline single cell gel electrophoresis (SCG) (Comet) assay in mouse organs. We treated groups of four mice once orally at the maximum tolerated dose (MTD) and sampled stomach, colon, liver, kidney, bladder, lung, brain, and bone marrow 3, 8 and 24 h after treatment. For the 20 aromatic amines that are rodent carcinogens, the assay was positive in at least one organ, suggesting a high predictive ability for the assay. For most of the SCG-positive aromatic amines, the organs exhibiting increased levels of DNA damage were not necessarily the target organs for carcinogenicity. It was rare, in contrast, for the target organs not to show DNA damage. Organ-specific genotoxicity, therefore, is necessary but not sufficient for the prediction of organ-specific carcinogenicity. For the 10 non-carcinogenic aromatic amines (eight were Ames test-positive and two were Ames test-negative), the assay was negative in all organs studied. In the safety evaluation of chemicals, it is important to demonstrate that Ames test-positive agents are not genotoxic in vivo. Chemical carcinogens can be classified as genotoxic (Ames test-positive) and putative non-genotoxic (Ames test-negative) carcinogens. The alkaline SCG assay, which detects DNA lesions, is not suitable for identifying non-genotoxic carcinogens. The present SCG study revealed a high positive response ratio for rodent genotoxic carcinogens and a high negative response ratio for rodent genotoxic non-carcinogens. These results suggest that the alkaline SCG assay can be usefully used to evaluate the in vivo genotoxicity of chemicals in multiple organs, providing for a good assessment of potential carcinogenicity.

Amines↗
PubMed1999

Serial passage of MC3T3-E1 cells alters osteoblastic function and responsiveness to transforming growth factor-beta1 and bone morphogenetic protein-2.

The murine-derived clonal MC3T3-E1 cell is a well-studied osteoblast-like cell line. To understand the effects of serial passages on its cellular function, we examined changes in cell morphology, gap junctional intercellular communication (GJIC), proliferation, and osteoblastic function between early passage (<20) and late passage (>65) cells. MC3T3-E1 cells developed an elongated, spindle shape after multiple passages. Intercellular communication decreased significantly (33%) in late vs. early passage cells. Transforming growth factor-beta1 (TGF-beta1) stimulated cell proliferation in early passage cells and induced c-fos expression, while it inhibited proliferation in late passage cells. Using alkaline phosphatase (ALP) activity and osteocalcin (OC) secretion as markers for osteoblastic function and differentiation, we demonstrated that both markers were significantly reduced after multiple cell passages. Bone morphogenetic protein-2 (BMP-2) significantly enhanced ALP activity and OC secretion in early passage cells while TGF-beta1 exerted an opposite effect. Both BMP-2 and TGF-beta1 had minimal effects on late passage cells. We conclude that serial passage alters MC3T3-E1 cell morphology, and significantly diminishes GJIC, osteoblastic function, TGF-beta1-mediated cell proliferation, and responsiveness to TGF-beta1 and BMP-2. Cell passage numbers should be clearly defined in functional studies involving MC3T3-E1 cells.

3T3 Cells↗
PubMed1999

Use of the Harmonic Scalpel in open abdominoperineal surgery for rectal carcinoma.

We describe a technique of open abdominoperineal resection with the use of the Harmonic Scalpel in seven patients. Using this instrument we dissected all pelvic vessels, including the middle hemorrhoidal artery, with no subsequent bleeding. In addition, we divided the levator ani muscles completely in the abdominal procedure alone.

Abdomen↗
PubMed1999

Problems in neoadjuvant chemoradiotherapy preceding surgery for advanced squamous cell carcinoma of the thoracic esophagus.

The adverse effect of neoadjuvant chemoradiotherapy on the postoperative course in esophageal cancer was studied in 9 patients undergoing neoadjuvant chemoradiotherapy preceding surgery for thoracic esophageal carcinoma possibly involving adjacent organs (neoadjuvant group), and 13 patients undergoing surgery without neoadjuvant therapy for same disease (control group). The two groups were compared for volume of intraoperative hemorrhage, surgical duration, frequency of postoperative morbidity, and for postoperative changes in blood platelet counts, and serum thrombopoietin and interleukin-6 levels. Mean intraoperative blood loss was 1121 g (580-1,662 g) in the neoadjuvant group and 546.5 g (274.7-778.3 g) in controls group (Student's T test: p < 0.01). No significant difference was seen found between the two groups in the degree of postoperative deterioration in cardiopulmonary function or in interleukin-6 levels. Blood platelet counts decreased in both groups until postoperative day 7, but recovery on postoperative day 14 was significantly depressed in the neoadjuvant group compared to controls. Serum thrombopoietin levels were higher in the neoadjuvant group than in controls (Mann-Whitney U-test: p < 0.05). We found that neoadjuvant chemoradiotherapy induces latent postoperative myelosuppression and may lead to intractable infection.

Aged↗
PubMed1999

Optic disc changes in normotensive persons with unilateral exfoliation syndrome: a 3-year follow-up study.

BACKGROUND: If, at the time of glaucoma diagnosis, the intraocular pressure (IOP) is higher and the initial field loss more advanced in glaucomatous eyes with than without exfoliation, the cause of the optic disc damage has been suggested to be the high IOP associated with the exfoliation syndrome (EXS). We decided to investigate whether EXS alone, without the contributory effect of measured raised IOP, is a risk factor for optic nerve damage. METHODS: Twenty-two non-glaucomatous, normotensive persons with clinically unilateral EXS were examined for IOP, visual fields (Octopus G1) and disc topography (Imagenet, Topcon) and followed up for 3 years. RESULTS: At the start, the paired exfoliative (E) and non-exfoliative (NE) eyes did not differ in IOP, disc, rim, or cup areas, or cup volumes. They differed in R/D (rim/disc) radius ratio in the inferior section of the optic disc. During the follow-up period, the IOP increased in the E and the NE eyes, and changes indicative of nerve fiber loss were measured in both eyes. In those (n=14) in whom the IOP in the two eyes was equal throughout the follow-up period, disc changes took place only in the E eye. CONCLUSION: The exfoliative process in itself may be a risk factor for optic disc changes.

Aged↗
PubMed1999

Helicobacter pylori-induced chronic active gastritis, intestinal metaplasia, and gastric ulcer in Mongolian gerbils.

The establishment of persisting Helicobacter pylori infection in laboratory animals has been difficult, but in 1996 Hirayama reported the development of a successful Mongolian gerbil model. The present study was undertaken with two aims: to better characterize the normal histological structure and histochemical properties of the gastric mucosa of the Mongolian gerbil; and to evaluate the progression of the histopathological features of H. pylori-induced gastritis in this animal model for one year after the experimental infection. Seventy-five Mongolian gerbils were used. Mongolian gerbils were sacrificed at 2, 4, 8, 12, 26, 38, and 52 weeks after H. pylori inoculation. Sections prepared from stomachs immediately fixed in Carnoy's solution were stained with hematoxylin and eosin and Alcian blue at pH 2.5/periodic acid-Schiff, a dual staining consisting of the galactose oxidase-cold thionin Schiff reaction and paradoxical Concanavalin A staining, and with immunostaining for H. pylori and BrdU. H. pylori infection induced in the Mongolian gerbil a chronic active gastritis, in which a marked mucosal infiltration of neutrophils on a background of chronic inflammation became detectable 4 weeks after inoculation and continued up to 52 weeks. Intestinal metaplasia and gastric ulcers appeared after 26 weeks in some of the animals, whereas others developed multiple hyperplastic polyps. The Mongolian gerbil represents a novel and useful model for the study of H. pylori-induced chronic active gastritis and may lend itself to the investigation of the epithelial alterations that lead to intestinal metaplasia and gastric neoplasia.

Animals↗
PubMed1999

Additional microvascular anastomosis in reconstruction after total esophagectomy for cervical esophageal carcinoma.

BACKGROUND: Maintaining sufficient blood flow to the substitute organ after total esophagectomy is essential for decreasing the risk of anastomotic leakage. Additional venous, or arterial and venous, anastomoses between the vessels of the gastric tube and the vessels in the neck after total esophagectomy are described for 11 patients with cervical esophageal carcinoma. METHODS: The tissue blood flow was measured by laser Doppler flowmetry before and after anastomosis. Venous anastomosis was performed for all 11 patients, and arterial anastomosis was added for 7 patients. RESULTS: A significant increase in tissue blood flow was observed after venous anastomosis alone (mean, 19%; P < 0.05) and after arterial and venous anastomoses (mean 43%; P < 0.01). There was no anastomotic leakage or hospital death. CONCLUSIONS: This procedure may reduce the risk of anastomotic leakage especially in the case of pharyngogastrostomy following total esophagectomy.

Anastomosis, Surgical↗
PubMed1999

Evaluation of the accuracy of preoperative staging in thoracic esophageal cancer.

BACKGROUND: Exact clinical staging before treatment of esophageal cancer has become increasingly important in the evaluation and comparison of the results of different treatment modalities, including surgery, chemotherapy, and radiotherapy. METHODS: The accuracy of preoperative tumor staging by using an esophagography, esophagoscopy, percutaneous and endoscopic ultrasonography, and computed tomography was assessed in 224 patients with resectable esophageal cancer. The results of tumor staging by these tests were compared prospectively with the pathologic stage of the esophagectomy specimens with respect to the T and N categories defined by the International Union Against Cancer TNM classification. RESULTS: For the T category, the overall accuracy was 80%. For the N category, overall accuracy was 72%, with a sensitivity of 78%, a specificity of 60%, and a positive predictive value of 78%. Overall, the accuracy of stage grouping was 56%. CONCLUSIONS: Either the T or N categories can be predicted reliably by clinical staging techniques. However, the preoperative stage grouping might not be valid in resectable, localized esophageal cancer.

Adult↗
PubMed1999

A micromechanical model of the cochlea with radial movement of the tectorial membrane.

The function of the tectorial membrane in the cochlear micromechanics is uncertain. In modeling approaches some models have assumed it to be a resonator that participates in the sharp tuning mechanisms of the cochlea with its mass coupled to the ciliary stiffness of outer hair cells, being driven by the shear force between the reticular lamina and itself. This paper presents a different type of micromechanical model which assumes that the tectorial membrane is driven by a lymphatic fluid flow that can be shown to have a substantial radial component. It also assumes that the reticular lamina is relatively stiff and thereby restrains the top end of outer hair cells that exert a force to the basilar membrane via Deiters cells. When combined with a three-dimensional block model, it can simulate the sharp tuning mechanisms of the cochlea well.

Acoustic Stimulation↗
PubMed1999

Pulmonary embolism: a case of sudden unexpected death in a psychiatric hospital.

We report a case of suspected fatal physical abuse in which the cause of death was proved to be pulmonary embolism. A patient with mental retardation presenting aggressive behavior was admitted to a psychiatric hospital and was treated with major tranquilizers. She suddenly died subsequent to an angina-like attack. For several days before her death, she had been confined to her bed because of very low physical and mental activity. Bruises and abrasions were observed on the extremities, suggesting the recent restraints. There was no positive evidence of physical abuse. At autopsy, the cause of death was elucidated to be pulmonary embolism originating from thrombi in the left popliteal vein. This case indicates the risk of pulmonary embolism in immobilized patients in psychiatric hospitals.

Journal Article↗
PubMed1999

A sudden death due to cardiac conduction system injury from a blunt chest impact.

We report a case of sudden death due to cardiac conduction system injury from a blunt chest impact. A 20 year old male, kicked in the precordial region, lost consciousness, and was confirmed dead on arrival at a hospital emergency care unit. According to his friends, they played a golf competition accompanied with a physical punishment. The victim, losing the game, allowed the winner to give him several kicks in the chest. Although well prepared against each kick, he fell down instantaneously after the final impact, and death was confirmed at a hospital. There was no apparent sign of injury on the body surface. At autopsy, there was no evident subcutaneous or intramuscular hemorrhages, rib or sternum fracture. Subendocardial hemorrhage in the region of the atrioventricular node and a contusion extending from the posterior wall of the left ventricle to the upper ventricular septum were observed. Histological examination revealed injury of atrioventricular node and His' bundle. Although the cardiac injury including contusion of the myocardium itself was not so extensive, it was considered that arrhythmia was induced by the cardiac conduction system failure, which was considered to be the cause of death.

Journal Article↗