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Biomedical subjects

T Kokubo

Publications and source records attributed to T Kokubo.

At least 343 records · Page 19Linked to original sources
PubMed1980

An ultrastructural study of precancerous and cancerous lesions of the pancreas in Syrian golden hamsters induced by N-nitrosobis(2-oxopropyl)amine.

Transmission electron microscopic studies of precancerous and cancerous lesions in the pancreas of hamsters induced by N-nitrosobis(2-oxopropyl)amine (BOP) are presented. BOP was injected subcutaneously once weekly for 10 weeks and hamsters were sacrificed every 5 weeks after initiation of the experiment. The ultrastructural findings indicated that serial changes occurred in the epithelium of the pancreatic duct. The epithelial cells became cuboidal and showed increased secretions at 5 weeks. Probably precancerous cells with prominent nucleoli and irregular rough endoplasmic reticulum were found in the main duct at 10 weeks. At 15 weeks, pancreatic tumors forming a duct arrangement were seen, in good accord with the histological appearance. Well differentiated adenocarcinoma cells showing a tubular pattern had oval nuclei with granular chromatin. Poorly developed rough endoplasmic reticulum was irregularly distributed throughout the cytoplasm and the cell surface was covered with microvilli. Poorly differentiated adenocarcinoma showed poor gland formation and had distorted nuclei with prominent nucleoli. These cells were loosely joined. Mitochondria and rough endoplasmic reticulum were poorly developed, and the tumor cells were devoid of secretory granules. The most characteristic and common change of the precancerous and cancerous lesions in this experiment was the appearance of numerous microvilli on the luminal surface and loss of cytodifferentiation. These findings were obviously different from those of normal epithelial cells or those seen in inflammation. The findings in this study confirm that the pancreatic carcinoma induced by N-nitrosobis(2-oxopropyl)amine in Syrian hamsters is of duct cell origin. No evidence of acinar cells was obtained.

Adenocarcinoma↗
PubMed1979

Toxicological evaluation of arsenic in edible seaweed, Hizikia species.

Young male Wistar rats were fed with chows containing marketed Hizikia preparation. Hizikia-arsenic could be absorbed at the rate comparable to arsenic trioxide, and accumulated primarily in blood. Intake and excretion of arsenic from Hizikia-diet reached a steady state within 4 days of administration as was the case of arsenic trioxide. Biological half-life in blood and urine was also essentially the same in the 2 groups. Rats kept for 3 weeks on the chows containing up to 20% Hizikia did not show significant growth retardation as compared with the controls, while those on 50% Hizikia-diet were markedly emaciated. In a 38-week feeding experiment, 4 groups of rats were given 20% Hizikia-diets made from various Hizikia preparations (final arsenic concentrations; 9, 16, 21 and 21 ppm, respectively). For positive controls, 2 groups were given arsenic trioxide diets (24 and 50 ppm as arsenic). Growth retardation was minimum both in Hizikia and arsenic groups with no relation to the arsenic dose. Changes in hematology, blood biochemistry and pathology of major organs and skin were also essentially negative in all groups. The maximum no-effect level observed in the present study was compared with the possible amount of arsenic taken via seaweed in mankind.

Animal Feed↗
PubMed1979

Bronchogenic carcinoma producing ectopic steroid hormones.

A patient with steroid hormones or androgen producing bronchogenic adenocarcinoma was presented. Clinically he had a mediastinal mass and bilateral multiple pulmonary nodules which showed a rapid growth despite cancer chemotherapy. At postmortem examination, radioimmunoassay of the tumor tissue revealed androgen and their precursors. The mitochondria of the tumor cells resembled those of cells in the zona reticularis of the adrenal cortex.

Adult↗
PubMedDate not supplied

A new glass-ceramic for bone replacement: evaluation of its bonding to bone tissue.

Glass powders (350 mesh) of the composition MgO, 4.6; CaO, 44.9; SiO, 34.2; PO, 16.3; CaF, 0.5 in weight ratio were compacted, heated to 1050 degrees C at a rate of 5 degrees C/min and kept at 1050 degrees C for 2 h. The resultant glass-ceramic having oxyapatite, fluoroapatite, and wollastonite crystals showed high bending and compressive strengths of 157 and 1060 MPa, respectively. The biocompatibility and bonding ability of this new glass-ceramic to the bone tissue was evaluated using rabbit tibial bones, and the failure load to break the bonding of several ceramics (the new glass-ceramic, dense hydroxyapatite, 45S5 Bioglass, alumina-ceramic) to bone tissues was measured. The new glass-ceramic showed tight bonding to bone comparable with dense hydroxyapatite, and in 25 weeks its load was 70% of that of bone tissue.

Animals↗
PubMedDate not supplied

Bone bonding behavior of three kinds of apatite containing glass ceramics.

We have produced three kinds of apatite-containing glass ceramics of the same chemical composition: MgO (4.6), CaO (44.9), SiO2 (34.2), P2O5 (16.3), CaF2 (0.5) (in weight ratio). They contain different crystal combinations and have different mechanical properties. The first glass ceramic (A-GC) was prepared by heating a glass plate to 870 degrees C. It contains only oxy- and fluoroapatite (35 wt%). The second glass ceramic (A-W-GC), and the third (A-W-CP-GC), were prepared by heating glass powder compacts to 1050 degrees C and 1200 degrees C, respectively. A-W-GC contains oxyapatite and fluoroapatite (Ca10(PO4)6(O,F2] (35 wt%) and beta-wollastonite (40 wt%). A-W-CP-GC contains oxyapatite and fluoroapatite (20 wt%), beta-wollastonite (CaO X SiO2) (55 wt%), and beta-whitlockite (3CaO X P2O5) (15 wt%). The bending strengths of A-GC, A-W-GC, and A-W-CP-GC were 88MPa, 178MPa, and 213MPa, respectively, in air. Rectangular ceramic plates (15mm X 10mm X 2mm) were implanted into a rabbit tibia. Ten and 25 weeks after implantation, the segment of tibia with implant was excised for examination. The segment was held by a special jig and the traction breaking load (failure load) was measured by an autograph. A-GC showed a lower load than A-W-GC and A-W-CP-GC. The loads for A-W-GC and A-W-CP-GC were almost equal. The failure loads did not change significantly between 10 and 25 weeks for any of the materials. The interface was examined by Giemsa surface staining, contact micro-radiography, and SEM-EPMA. Giemsa surface staining and CMR revealed direct bonding between the materials and the bone for all the three materials. SEM-EPMA showed that Si and Mg content decreased, Ca content did not change, and P content increased at the reaction zone between all three glass ceramics and bone. This was observed at 10 weeks, as well as at 25 weeks, after implantation. The reaction zone was narrowest with A-GC, wider with A-W-GC, and widest with A-W-CP-GC.

Animals↗
PubMedDate not supplied

Retroperitoneal malignant mesenchymoma: imaging findings in five cases.

BACKGROUND: To describe computed tomographic (CT), magnetic resonance (MR), ultrasonographic (US), and angiographic findings of retroperitoneal malignant mesenchymoma with emphasis on CT findings. METHODS: Five CT, four US, four angiography, and two MR studies were obtained in five patients with pathologically proven retroperitoneal malignant mesenchymoma. RESULTS: Tumors were larger than 10 cm (n = 4), well-circumscribed and heterogeneous (n = 4), and with massive intratumorous calcifications (n = 3) on plain CT or US. Tumors showed heterogeneous enhancement on contrast-enhanced CT scans (n = 4) and moderate hypervascularity with heterogeneous staining on angiography (n = 3). Tumors were essentially hypointense on T1-weighted MR images (n = 2) and heterogeneous hyperintense on T2-weighted MR images (n = 2). Plain CT showed a fat-dense structure in a tumor in one patient. CONCLUSIONS: The radiologic findings of large expansile heterogeneous masses in the retroperitoneum, especially with massive calcifications, were considered to be typical of malignant mesenchymomas.

Aged↗
PubMedDate not supplied

Six-month toxicity study of butylated hydroxyanisole in beagle dogs.

Groups of three or four male and female beagle dogs were maintained for 6 months on diets containing BHA at concentrations of 0 (control group), 0.25, 0.5 and 1.0% (w/w). The average daily intake of BHA was about 60 mg/kg body weight in the 0.25% group, 110 mg/kg in the 0.5% group and 220 mg/kg in the 1.0% group. All animals survived the entire experimental period without showing signs of toxicity other than a dose-related retardation of growth. Serum biochemical examinations conducted at 1, 3 and 6 months revealed a slight decrease in albumin concentration and an elevation of alkaline phosphatase and leucine aminopeptidase activity in the higher dose groups. Histopathological and histometrical examination showed no evidence of mucosal alteration in the stomach, oesophagus or duodenum attributable to the administration of BHA. The mitotic index in the squamous epithelium of the distal oesophagus was comparable in the control and BHA-treated groups. Liver weights were increased in BHA-treated groups, but there were no related histopathological changes. From these data it is concluded that feeding of BHA-supplemented diets at palatable concentrations for 6 months has no pathological effects on the stomach, oesophagus, duodenum or liver of beagle dogs.

Administration, Oral↗
PubMedDate not supplied

Portosystemic collaterals on MR imaging.

Fourteen patients with various portosystemic collaterals (seven esophageal varices, three paraumbilical veins, two splenorenal shunts, and two mesenteric varices) were imaged with magnetic resonance (MR) imaging using a superconducting imager. Collateral pathways were demonstrated as tortuous structures of no or low signal intensity on spin-echo image, and flow related enhancement did not cause any difficulty in evaluation. Direct sagittal images are especially useful for paraumbilical vein and coronal images for esophageal and mesenteric varix. The clinical role of MR in the assessment of portosystemic collaterals is discussed also in comparison with CT and ultrasound.

Adult↗
PubMedDate not supplied

MR imaging of hepatoma treated by embolization.

The magnetic resonance findings of two hepatomas treated by embolization are presented. The T2-weighted spin echo images showed an increase in signal intensity in the tumor after embolization. This phenomenon corresponded to a decrease in tumor density on CT and to necrosis observed histologically. Magnetic resonance also demonstrated gas bubbles as low signal foci within the embolized tumor.

Carcinoma, Hepatocellular↗