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Biomedical subjects

U Kim

Publications and source records attributed to U Kim.

At least 109 records · Page 6Linked to original sources
PubMed1977

Concomitant elevations in serum sialytransferase activity and sialic acid content in rats with metastasizing mammary tumors.

Rats with transplantable spontaneously metastasizing mammary tumors have elevated levels of both serum sialoglycoconjugate and serum sialytransferase activity compared with normal female rats or rats with various nonmetastasizing mammary tumors. A direct relationship was observed between the amount of serum protein-bound sialic acid and serum sialyltransferase activity in all rats studied. Serum sialyltransferase activity in rats with a representative metastasizing mammary tumor, SMT-2A, was also correlated with tumor age. Microsomes prepared from the SMT-2A tumor have a sixfold higher sialyltransferase activity than do microsomes prepared from the nonmetastasizing mammary tumor MT-W9B. Normal rat liver microsomes have the same level of activity as microsomes prepared from livers of animals with either SMT-2A or MT-W9B tumors. The data indicate that spontaneously metastasizing mammary tumor cells have an increased production and release, perhaps through cell surface shedding, of a sialyltransferase. It is suggested that this sialyltransferase may increase the serum half-life of certain tumor-specific circulating glycoconjugates by increasing the content of protein-bound sialic acid and may thereby play a role in the immune escape mechanism of metastasizing tumor cells.

Animals↗
PubMed1977

Nephrotic syndrome associated with gastric cancer.

A patient whose nephrotic syndrome was controlled by steroids and cyclophosphamide was found to have gastric cancer. After removal of the tumor and discontinuing the steroid therapy, no recurrence of the clinical signs of nephrotic syndrome appeared, but moderate proteinuria persisted. The literature regarding the association of nephrotic syndrome with malignancies is reviewed.

Adenocarcinoma↗
PubMed1977

Estrogen receptor levels in hormonally progressive mammary tumors.

Tumor samples from 4 different stages of hormonal progression in the MT-W9 series of rat mammary tumors were analyzed for estrogen receptors by the dextran-coated charcoal method in order to further explore the clinical implications of the estrogen receptor assay. The findings indicate that although the presence of estrogen receptors is not an exclusive characteristic of hormonal dependency, their absence is indicative of a later stage of hormonal progression which might be of more immediate clinical consequence because hormonally autonomous tumors have faster growth rates than hormonally dependent tumors. It is also suggested that it may be necessary to initiate chemotherapy as an adjuvant to endocrine therapy for metastatic breast cancer patients with hormonally dependent tumors in order to avoid the eventual proliferation of hormonally autonomous tumor cells which are present in hormonally dependent tumors.

Animals↗
PubMed1977

Galactosyltransferase activity in metastasizing and nonmetastasizing rat mammary carcinomas and its possible relationship with tumor cell surface antigen shedding.

In order to study the mechanism of tumor cell surface antigen shedding, galactosyltransferase levels were compared in 5 spontaneously metastasizing and 3 nonmetastasizing rat mammary tumors. The enzyme activity both with or without exogenous acceptors was higher in the metastasizing group. This difference did not seem to be due to the variation in levels of degrading enzymes such as pyrophosphatase or beta-galactosidase found in these tumors. Little difference in the biochemical properties of the enzyme was found between the two groups. Most of the enzyme activity (60-70%) was recivered in the microsomal frctosyltransferase was assayed in "purified" plasma membrane fractions, 70% of the activity was associated with the plasma membrane vesicles, in which the enzyme was enriched by factors of 10-40. The number of galactose acceptor sites on the plasma membranes increased in parallel to the metastasizing capacity, indicating the presence of larger numbers of incomplete glycopeptides on their cell surfaces. These findings seemed to indicate that the greater turnover of glycoprotein in the spontaneously metastasizing tumor cell surface was caused by the shedding of surface antigens into the systemic circulation of the host.

Animals↗
PubMed1976

Plasma membrane associated enzymes of mammary tumours as the biochemical indicators of metastasizing capacity. Analyses of enriched plasma membrane preparations.

Plasma membranes from 6 spontaneously metastasizing and 4 non-metastasizing rat mammary carcinomata were isolated by discontinuous sucrose density gradient centrifugation of microsomal pellets. The starting microsomal fraction contained 40-50% plasma membranes as determined by the levels of 5'-nucleotidase activity, with a negligible amount of nuclear (1%), mitochondrial (5%) and lysomal (7%) contamination. Five distinct fractions (F1-F5) were banded at densities 1 X 09, 1 X 13, 1 X 15, 1 X 17 and 1 X 21 at 25 degrees C, in addition to a pellet (F6) obtained by centrifuging at 76,000 g for 17 h. The fractions F1 through F5, all contained various concentrations of membranous structures, while the pellet (F6) contained only amorphous materials as evidenced by electron microscopy. The F3 fraction at the gradient 1 X 15 had the highest specific as well as total activity of the plasma membrane marker enzyme, with aggregates of the least contaminated plasma membranes in vesicular forms. This fraction also had the lowest specific activity for glucose-6-phosphatase (smooth ER marker) and for beta-D-glucuronidase (lysomal marker), and therefore was considered to be the "cleanest" plasma membrane fraction. When the activity of 4 additional plasma membrane marker enzymes, i.e., alkaline phosphatase, phosphodiesterase I, nucleotide pyrophosphatase and alkaline ribonuclease was determined in the same F3 fraction, their levels were significantly lower in every metastasizing tumour than in the non-metastasizing ones, with the enzyme activity decreasing in direct proportion to the metastasizing capacity. On the other hand, the marker enzymes were high in all non-metastasizing tumours, with the activity seemingly increasing with the immunogenicity of tumour cells. There was no significant difference between the 2 groups of mammary tumours in the levels of sialic acid, hexosamine, phospholipid or cholesterol in the plasma membranes. Thus, the level of plasma membrane marker enzymes is considered an accurate indicator for metastasizing capacity in the rat mammary tumour system.

Alkaline Phosphatase↗
PubMed1976

Biochemical properties of cyclic nucleotide phosphodiesterase in metastasizing and nonmetastasizing rat mammary carcinomas.

The biochemical properties of cyclic nucleotide phosphodiesterases in a nonmetastasizing and a spontaneously metastasizing rat mammary carcinoma were compared. The phosphooiesterases in both tumors had a pH optimum of around 8.0 and preferentially hydrolysed cyclic purine nucleotides. The rate of hydrolysis of purine nucleotides in the nonmetastasizing tumor was two times higher than in the metastasizing tumor, but the rate of pyrimidine nucleotide hydrolysis was equal in both tumors. Theophylline, caffeine, and D,L-4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro20-1724) inhibited the enzyme activity in both tumors; the percent inhibition was the same by each inhibitor. The cyclic nucleotie phosphodiesterase activity in either tumor was stimulated by Mg++, Mn++, and Co++ and suppressed by Ca++, Zn,++, and Ni++. EDTA inhibited the activity below the basal level (activity in the absence of added cation), an this inhibition could be recovered up to the basal level by an equimolar quantity of either Mn++ or Mg++. Further stimulation of the enzyme activity with increasing concentrations of divalent cations was observed only with Mn++. Similar effects were observe with ethylene glycol bis(beta-aminoethyl ether)-tn,n-tetraacetic acid. The stimulatory cations affected both the low and high Michaelis constant (tkm) enzymes in these tumors by increasing the maximum velocity. In the low Km enzyme, the Km was also slightly increased. Neither guanosine 3',5'-cyclic monophosphate nor adenosine 3',5'-cyclic monophosphate had any effect on the hydrolysis of the other at physiologic levels.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1975

Immunological escape mechanism in spontaneously metastasizing mammary tumors.

Immunological and biochemical studies of spontaneously metastasizing and nonmetastasizing rat mammary carcinomas and their plasma membranes indicated that: (i) all spontaneously metastasizing tumors have little or no demonstrable glycocalyx, while all nonmetastasizing tumors have a thick glycocalyx; (ii) there is a direct relationship between the glycocalyx and immunogenicity, and an inverse relationship with the metastasizing capacity of tumor cells, properties which can be quantitated by levels of the plasma membrane marker enzyme 5'-nucleotidase (EC3.1.3.5;5'-ribonucleotide phosphohydrolase) activity; (iii) the absence of glycocalyx from the metastasizing tumor cell surface seems to result from its dissociation from plasma membranes, for solubilized cell surface antigen is readily found in the blood of metastasizing tumor bearing rats, while there was no detectable tumor cell surface antigen in the blood of the nonmetastasizing tumor hosts tested; (iv) both metastasizing and nonmetastasizing mammary tumors appear to have a common soluble cell surface antigen; (v) in addition to this common antigen, there is another membrane-bound antigen in the nonmetastasizing, immunogenic tumor cell surface which presumably is the tumor specific transplantation antigen; and (vi) this antigen is immunobiologically unique, but seems to be immunochemically related to the common soluble antigen. It is postulated that the lack of an immunogenic coat and/or the presence of solubilized tumor cell surface antigen in the blood may provide an immune escape mechanism for tumor cells by interfering with cell-mediated immune response of tumor hosts, leading to their dissemination.

Animals↗
PubMed1975

Adenosine-3',5'-cyclic monophosphate levels and adenosine-3',5'-cyclic monophosphate phosphodiesterase activity in metastasizing and nonmetastasizing rat mammary carcinomas.

The adenosine-3, 5-cyclic monophosphate phosphodiesterase (cPDE) activity in the homogenates of 6 spontaneously metastasizing, nonimmunogenic, glycocalyx-shedding rat mammary carcinomas (MT) was assayed and compared with four histologically and growth rate-matched nonmetastasizing, immunogenic MT. The levels of this enzyme were 2.5 times higher in the nonmetastasizing tumors. To rule out the possibility of the presence of inhibitor(s) or stimulator(s) of cPDE, homogenates from a nonmetastasizing and from a widely metastasizing tumor were mixed. cPDE from both nonmetastasizing and metastasizing MT showed two apparent Km and two corresponding Vmax. The activity of the enzyme at concentrations of 1 muM (low Km) and 100 muM (high Km) adenosine-3, 5-cyclic monophosphate (cAMP) decreased in parallel with increasing metastasizing capacity. About 50% of the low and the high Km cPDE was in the cytosol in both groups, whereas the rest was particulate. The proportion of low and high Km activity was similar in all the fractions except in the plasma membrane of the metastasizing tumors where the percent of low Km enzyme was three times higher than that of the high Km. The steady-state levels of cAMP were 1.3-2.0 times higher in the metastasizing tumors, inversely proportional to their cPDE activities.

Animals↗
PubMed1975

The association of carcinoembryonic antigen and peripheral lymphocytes.

A significant association between carcinoembryonic antigen (CEA) assay titers and peripheral lymphocyte counts was observed in 148 simultaneous determinations. The association was present in a high cancer risk study group of patients with myasthenia gravis and in a control group of patients with granulomatous disease of the bowel, ulcerative colitis, and colonic neoplasms. A highly significant difference in the percentage of positive CEA assays in relation to lymphocyte counts was noted both in the study and control groups. In the study group CEA was positive in seven of 41 patients (17 percent) with counts above 2,000 per cubic millimeter, and in 26 of 56 (43 percent) of those with lower counts (X2 = 9.06, p smaller than 0.005). The corresponding percentages in the control group were 20 and 61 percent (X2 = 5.60, p smaller than 0.025). A significant difference between the means of lymphocytes in groups with different CEA titers also was found (F = 6.77, p smaller than 0.05). The finding of lower peripheral lymphocytes and/or higher titers of CEA in groups with increased risk of cancer, i.e., severe myasthenia gravis, patients with thymomas and patients with long history of granulomatous disease of the bowel, suggests on association between the results of the two tests and cancer risk. The observations indicate that the yield of CEA assay in cancer detection may be higher in patients with lwo lymphocytes, and that these determinations used in conjunction may serve better as diagnostic and prognostic aids in patients with known neoplasms or in high cancer risk groups.

Adolescent↗
PubMed1975

Progression from hormone dependence to autonomy in mammary tumors as an in vivo manifestation of sequential clonal selection.

The natural history of breast cancer with respect to its progression from hormone dependence to autonomy was studied by successively transplanting the earliest possible form of a rat mammary adenocarcinoma in syngeneic rats and isolating sublines of this tumor manifesting new endocrinological and other biological characteristics over a period of 15 years. The original, fully mannotropin-dependent tumor MT-W9, whose growth is dependent entirely on pharmacological levels of mannotropin supplied by an extraneous source, gave rise to an estrogen-dependent variant, MT-W9A. This MT-W9A growns only in normal adult female hosts and regresses promptly upon oophorectomy. Subsequently, this tumor produced a subline, the fully autonomous MT-W9B, which grows well in any syngeneic rats regardless of their hormonal status. The third subline derived from the autonomous tumor was designated MT-W9C, the androgen-responsive line, because it growns better in male than in female rats. Having reversed its original female preference, it might also be characterized as reversely responsive. Chromosomal analysis of these 4 tumors disclosed 4 distinct stem cell lines, but each tumor also contained small numbers of cells from other stem lines. The progression from mammotropin dependence to androgen responsiveness in this mammary tumor system seems to have been accomplished by merely shifting from 1 stem line to another in an orderly sequence, and it appears to be an irreversible process. In addition to the hormone dependency, the progression of the tumor is accompanied by a gradual increase of cachexia-producing effects on the host that may be related to the immunogenicity of tumor cells. These 4 distinct hormonal characteristics encompass the entire known spectrum of breast cancer in man and animals with the exception of the metastasizing property. These tumors are being studied by many investigators and are maintained vertically and horizontally in syngeneic rats by us. The hormonal and cytogenetic characteristics of each stem cell line have been stable for over a decade.

Adenocarcinoma↗