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Results for “MAMMARY NEOPLASMS, EXPERIMENTAL”

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PubMed1987

Ornithine aminotransferase turnover in host tissues of tumor-bearing rats.

The activity of ornithine-oxo-acid aminotransferase (OAT) in the liver and kidneys of rats was notably decreased as a consequence of tumor bearing. The decrease in the activity of OAT was closely related to a concomitant decrease in the rate of synthesis of the enzyme in both host tissues, while the rate of enzyme degradation remained unchanged. These results are concluded to be consistent with the proposal that host tissues of tumor-bearing animals may become "dedifferentiated," and in this example the mechanism of the expression of the dedifferentiation involved the significant decrease in specific enzyme production.

Animals↗
PubMed1979

Radioiodinated DNA as potential tumor-imaging agent.

Radiolabeled heat-denatured DNA and some related nucleic acids localize in tumor tissue following i.v. administration. Retention of radioactivity by tumors is longer than for other organs and localization of tumor tissues is possible by scintigraphic techniques 8-24 hr after injection.

Adenocarcinoma↗
PubMed1984

Syntheses of 18F-labeled pyrimidines and their usefulness for tumor imaging.

18F-Labeled 5-fluorouracil(FUra), 5-fluoro-2'-deoxyuridine(FdUrd) and 5-fluorouridine(FUrd) were synthesized with high radiochemical purities. Biodistribution of the 18F-pyrimidines in tumor-bearing rats, mice or a rabbit was examined. Blood clearance of the 18F-pyrimidines was very rapid. The kidney and liver showed the high uptake and rapid clearance which was due to the metabolism and excretion. The 18F-concentration in the tumor was due to the metabolism and excretion. The 18F-concentration in the tumor was also high and clearance was very slow compared with those in other organs. Tumor uptakes of 18F-FdUrd were also shown by positron emission tomography and autoradiography. Biodistributions of the 18F-FdUrd and radio-deoxythymidine(dThd) were different between several organs, but similar distribution patterns in the tumor were observed by autoradiography.

Animals↗
PubMedDate not supplied

[Regulatory enzymopathies].

Hereditary regulatory enzymopathies are considered, molecular-genetic mechanism of which involved a mutation of a structural gene in the locus, coding the much less than regular much greater than amino acid sequence in the allosteric site of regulatory enzyme or the site of the enzyme polypeptide chain, which is responsible for allosteric conformational transition. Dissimilar manifestations of regulatory and classical enzymopathies are discussed. Estimation of kinetic patterns might be very useful in diagnosis of regulatory enzymopathies as shown during study of some molecular pathologies, which occurred, for example, due to molecular pathology of phosphofructokinase and phosphoribosyl pyrophosphate synthetase. Impairment of allosteric regulation of L-threonine-L-serine dehydratase is considered as a model of regulatory enzymopathy, found in spontaneous hepatomas of highly carcinogenous CBA mice strain. Treatment of regulatory enzymopathies is considered depending on the effect of well known chemotherapeutic drugs (mainly, acetyl salicylic acid) on allosteric functions of regulatory enzymes acetyl-CoA-carboxylase and fructose-1,6-bisphosphatase from animal liver tissue.

Allosteric Regulation↗
PubMedDate not supplied

[Epiphysis and cancer].

Explore the source record for details and available documents.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Methionine uptake by tumor tissue: a microautoradiographic comparison with FDG.

UNLABELLED: L-methyl-11C-methionine (11C-Met) and 2-deoxy-2-18F-fluoro-D-glucose (18F-FDG) are used for tumor diagnosis and treatment evaluation by PET. In order to examine the role of these tracers in cancer imaging, intratumoral properties of 14C-Met were studied and compared to those of 18F-FDG. METHODS: The distribution of 14C-Met in various cellular elements of two different mouse malignant tumor tissues, MH134 and FM3A, was analyzed serially using microautoradiography within a period of 120 min after injection of the tracer. RESULTS: Carbon-14-Met and 18F-FDG showed different distributions in tumor tissue. Carbon-14-Met uptake by the tumor was mostly by viable cancer cells. The uptake by macrophages and other cellular components was low. The uptake was higher in the highly proliferative tumor but did not reflect protein synthesis. The rapid and slow growing tumors demonstrated that 14C-Met uptake ratio was lower than that of 18F-FDG, reflecting de novo DNA synthesis ratio. CONCLUSION: Carbon-14-Met uptake represents the presence of viable cancer cells. Carbon-11-Met may be suitable for treatment evaluation of individual tumors but not growth rates of different tumors. Fluorine-18-FDG reflects tumor-host immune system reaction and is an excellent tool for pretreatment evaluation of tumors and determination of tumor proliferative activity.

Animals↗
PubMed1994

Active and passive mechanisms of [fluorine-18] fluorodeoxyglucose uptake by proliferating and prenecrotic cancer cells in vivo: a microautoradiographic study.

UNLABELLED: In this study, [18F]FDG uptake mechanisms were investigated in neoplastic cells during cell proliferation and cell death. METHODS: Detailed analysis was performed on mouse tumor models of different growth rates using [18F]FDG, [6-13H]thymidine [3H]Thd (a precursor of DNA synthesis) and [125I]bovine serum albumin ([125I]BSA) (a marker of diffusion) with autoradiographic and histopathologic techniques and electron microscopy. RESULTS: The three compounds, [18F]FDG, [3H]Thd and [125I]BSA, showed different heterogeneous patterns of distribution within tumor tissue sections in neoplastic and non-neoplastic cellular elements. The uptake of [18F]FDG by prenecrotic (or necrobiotic) tumor cells surrounding focal necrotic cell debris was 1.5 to 2.3 times higher than that of viable tumor cells. Prenecrotic cells did not retain trapped [18F]FDG; therefore, the uptake was considered to be nonmetabolic. Inconspicuous cell membrane, vesicular cytoplasmic organelles and condensed nuclear chromatin were remarkable findings in the prenecrotic cells. A comparison of viable tumor cells in tumors undergoing different growth rates showed that the ratio of [18F]FDG uptake was similar to that of [3H]Thd uptake in each S-phase cell. Fluorine-18-FDG showed a cell cycle dependency, with a higher uptake observed in cells in G0/G1 and G2 phases of the cell cycle compared with the S and M phases. CONCLUSION: A passive mechanism of [18F]FDG uptake may exist in the necrobiotic/prenecrotic or hypoxic/anoxic cells in tumors. However, the discordance of [18F]FDG and [3H]Thd uptake may be the result of the different cell cycle dependency of tracer uptake in the same tumor.

Animals↗
PubMed1964

VIRUS PARTICLES IN THE THYMUS OF CONVENTIONAL AND GERM-FREE MICE.

Electron microscope study of thymuses of both conventional and germ-free mice has revealed the presence of typical virus particles associated with the thymic lymphocytes or with the thymic epithelial cells. The particles resemble those associated with several murine leukemias and their viral nature seems convincingly substantiated by morphological observation. Germ-free mice are therefore not virus-free. The biological significance of these particles is still unknown and we can only speculate as to the possible relationship of these particles to the incidence of "spontaneous" leukemia, to the lymphocytosis stimulating factor of Metcalf, and to the numerous latent viral infections of laboratory mice.

Animals↗