scholarly journals Alterations induced by glucose deprivation and tunicamycin in the kinetic parameters of hexose transport in hybrid cells

1984 ◽  
Vol 68 (1) ◽  
pp. 257-270
Author(s):  
M.K. White ◽  
M.E. Bramwell ◽  
H. Harris
Keyword(s):  
Maximum Velocity ◽  
Glucose Deprivation ◽  
Malignant Cell ◽  
Matched Pairs ◽  
Hexose Transport ◽  
Malignant Cells ◽  
Hybrid Cells ◽  
Membrane Glycoproteins ◽  
Michaelis Constant ◽  
Hexose Uptake

Matched pairs of malignant and non-malignant hybrid cells were compared in their response to glucose deprivation and to tunicamycin. Glucose deprivation induced an increase in the maximum velocity in the malignant cells, but not in the non-malignant cells. The Michaelis constant of hexose uptake was largely unchanged by glucose deprivation except in the case of one melanoma derivative, PG19 G-, which showed a large increase in Michaelis constant when deprived of glucose. Tunicamycin increased the Michaelis constant of hexose uptake in both malignant and non-malignant cell lines. It is therefore possible that the Michaelis constant of hexose uptake is affected by the extent of glycosylation of one or more of the cell membrane glycoproteins.

Kinetic parameters of hexose transport in hybrids between malignant and nonmalignant cells

1983 ◽  
Vol 62 (1) ◽  
pp. 49-80
Author(s):  
M.K. White ◽  
M.E. Bramwell ◽  
H. Harris
Keyword(s):  
Kinetic Parameters ◽  
Malignant Cell ◽  
Hexose Transport ◽  
Hybrid Cells ◽  
Michaelis Constant ◽  
Independent Measurement ◽  
The Difference ◽  
Hexose Uptake ◽  
Derivatives Of

Matched pairs of isogeneic hybrid cells, in which one member of the pair was malignant and the other not, were used to examine the linkage between malignancy and functional alterations in hexose transport. The kinetic parameters of uptake of 2-deoxy-D-glucose were measured in a range of such hybrids, both human and murine. Some other malignant cell lines were also examined and were compared with non-tumorigenic derivatives of tumour cells selected by exposure to the lectin, wheat-germ agglutinin. In every case, malignancy, as defined by the ability of cells to grow progressively in vivo, was found to be linked to a decrease in the Michaelis constant of hexose uptake. Independent measurement of the transport and phosphorylation reactions involved in hexose uptake revealed that this decrease was determined by the membrane transport system. The difference in Michaelis constant between malignant and non-malignant cells was observed with 3-O-methylglucose, a hexose that is transported into the cell but not further metabolized. The activity of hexokinase in cell homogenates was higher than the level that would be required to cope with transport and showed no correlation with tumorigenicity. Measurement of the uptake of D-glucose itself, by a rapid filtration centrifugation method, gave results similar to those obtained with 2-deoxy-D-glucose.

Studies on the surface properties of hybrid cells. II. Sialyl-transferase activity on the surface of malignant and non-malignant cells

1980 ◽  
Vol 46 (1) ◽  
pp. 203-220
Author(s):  
M.A. Atkinson ◽  
M.E. Bramwell
Keyword(s):  
Surface Properties ◽  
Surface Activity ◽  
Cell Lines ◽  
Plasma Membranes ◽  
Malignant Cell ◽  
Transferase Activity ◽  
Malignant Cells ◽  
Hybrid Cells ◽  
Wide Range ◽  
The Difference

A measurable surface activity of sialyl-transferase is demonstrated by a number of different methods to exist on the plasma membranes of both malignant and non-malignant cells. The amount of enzyme present on the surface of malignant cells is found to be higher than that on the non-malignant ones in a wide range of malignant and non-malignant cell lines. It is proposed that the difference in apparent activity results in part from the presence of incomplete glycoproteins in the surface membranes of the malignant cells and in part from an increased rate of membrane synthesis in these cells.

Studies on the surface properties of hybrid cells. I. Sialyl-transferase activity in homogenates of malignant and non-malignant cells

1980 ◽  
Vol 46 (1) ◽  
pp. 187-201
Author(s):  
M.A. Atkinson ◽  
M.E. Bramwell
Keyword(s):  
Tissue Culture ◽  
Sialic Acid ◽  
Elevated Level ◽  
Malignant Cell ◽  
Cell Populations ◽  
Transferase Activity ◽  
Malignant Cells ◽  
Hybrid Cells ◽  
Cell Homogenate ◽  
Wide Range

We report here a method for the assay of the sialyl-transferase activity in crude homogenates of a wide range of cell lines growing in tissue culture. Our results indicate that particulate preparations from both malignant and non-malignant cells show a Km of 0.25 mM towards CMP-sialic acid in the presence of an excess of glycoprotein acceptor. There appear to be increased amounts of the enzyme associated with the preparations from malignant sources which are reflected in an increase in the apparent Vmax of these. The elevated level of sialyl-transferase activity seen in the malignant cell populations is, paradoxically, associated with a decrease in the amount of bound sialic acid associated with both the whole cell homogenate preparations and the surface of these cells.

In cultured chick embryo fibroblasts the hexose transport components are not the 75 000 and 95 000 dalton polypeptides synthesized following glucose deprivation

1980 ◽  
Vol 58 (10) ◽  
pp. 1179-1188 ◽  
Author(s):  
Cedric A. Zala ◽  
Milagros Salas-Prato ◽  
Wing-Tat Yan ◽  
Batya Banjo ◽  
James F. Perdue
Keyword(s):  
Chick Embryo ◽  
Glucose Uptake ◽  
Glucose Deprivation ◽  
Protein Glycosylation ◽  
Hexose Transport ◽  
Molecular Weights ◽  
Uptake Activity ◽  
Embryo Fibroblasts ◽  
Hexose Uptake ◽  
Stimulation Of

Glucose deprivation of chick embryo fibroblasts results in a cycloheximide-sensitive stimulation of hexose transport and an increase in the levels of glucose-regulated polypeptides of molecular weights 75 000 and 95 000. The relationship between these two phenomena is evaluated in this study. The glucose deprivation-induced stimulation of hexose transport was observed to occur in two phases: a rapid (complete by 15 min) cycloheximide-insensitive increase of 50–100% and a slower (observable by 6 h) cycloheximide-sensitive increase in transport to about five times the basal level. The time course of the latter increase preceded that of the appearance of the 75 000 and 95 000 dalton polypeptides; by the time that increases in the levels of these polypeptides were observed, the hexose uptake rates had almost reached their maximum value. Upon cellular fractionation, the greatest enrichment of the 75 000 and 95 000 dalton polypeptides was observed in the endoplasmic reticulum fraction, which was devoid of vesicular stereo specific D-glucose uptake activity. The plasma membrane fraction was enriched in stereospecific D-glucose uptake activity but not in the 75 000 and 95 000 dalton polypeptides. The glucose deprivation-induced increase in hexose uptake was not prevented by tunicamycin, although this inhibitor of protein glycosylation decreased the hexose uptake of glucose-fed cells by 80% after 24 h. However, under these latter conditions an increase in the levels of the 75 000 and 95 000 dalton polypeptides was observed. On the basis of this data, we conclude that the polypeptides of molecular weights 75 000 and 95 000 are not involved in glucose transport.

Amino acid and hexose transport by cultured crypt cells from rat small intestine

1980 ◽  
Vol 239 (5) ◽  
pp. C190-C196 ◽  
Author(s):  
K. Inui ◽  
A. Quaroni ◽  
L. G. Tillotson ◽  
K. J. Isselbacher
Keyword(s):  
Amino Acid ◽  
Sugar Transport ◽  
Epithelial Cell Line ◽  
Acid Uptake ◽  
Substrate Uptake ◽  
Hexose Transport ◽  
Intestinal Crypt ◽  
Morphological Criteria ◽  
Hexose Uptake ◽  
Crypt Cells

The characteristics of amino acid and sugar transport in intestinal crypt epithelial cells have been examined by measuring substrate uptake in an established epithelial cell line. These cells (IEC-6 cells) have been characterized as derived from rat small intestinal crypt cells on the basis of morphological criteria (J. Cell. Biol. 80: 248-265, 1979). Amino acid transport appeared to be mediated by both Na+-dependent and Na+-independent systems. Hexose uptake was stereospecific and Na+ independent, and was markedly inhibited by phloretin and cytochalasin B. Since glucocorticoids are known to have profound effects on maturation of the intestinal epithelium in vivo, their effects on transport properties of the cultured crypt cells were studied. Hydrocortisone, while completely inhibiting cell growth, increased the initial uptake rates of various hexoses, while having little or nor effect on the initial rate of amino acid uptake. The increased hexose uptake appeared to be due to a change in Vmax rather than Km. Appearance of the Na+-dependent hexose transport system, which is present in differentiated enterocytes, was not elicited by in vitro treatment with glucocortcoids.

A DISCRETE SIMULATION OF TUMOR GROWTH CONCERNING NUTRIENT INFLUENCE

2004 ◽  
Vol 18 (17n19) ◽  
pp. 2651-2657 ◽  
Author(s):  
L. SUN ◽  
Y. F. CHANG ◽  
X. CAI
Keyword(s):  
Cell Growth ◽  
Tumor Growth ◽  
Potts Model ◽  
Discrete Model ◽  
Malignant Cell ◽  
Healthy Tissue ◽  
Thermodynamic Method ◽  
Malignant Cells ◽  
Discrete Simulation ◽  
Adjustment Factors

We develop a 2-D discrete model to simulate malignant cells growing in healthy tissues using a thermodynamic method on the basis of Potts model. After introducing a malignant seed in a healthy tissue, we use a set of adjustment factors, including the interaction between cells and nutrient, to simulate the growth of malignant cells under different environments. This allows us to investigate the effects of environment on malignant cell growth and the formation of cancer.

Mechanisms of potassium transfer across the dually perfused rat placenta

1993 ◽  
Vol 265 (2) ◽  
pp. R341-R347 ◽  
Author(s):  
T. Mohammed ◽  
J. Stulc ◽  
J. D. Glazier ◽  
R. D. Boyd ◽  
C. P. Sibley
Keyword(s):  
Diffusion Coefficient ◽  
Maximum Velocity ◽  
T Test ◽  
Michaelis Constant ◽  
Diffusion Limited ◽  
51Cr Edta ◽  
The Asymmetry ◽  
Paired T Test

The purpose of this study was to directly investigate the mechanisms of K+ transfer across the rat placenta, which was isolated and perfused through both its maternal and fetal circulations. Unidirectional maternofetal (Kmf) and fetomaternal (Kfm) clearances for 42K, 51Cr-labeled EDTA (used as a diffusion-limited paracellular marker), and 3H2O (used as a flow-limited marker) were respectively 232 +/- 36, 12 +/- 4, and 1,020 +/- 260 (mf) and 96 +/- 26, 18 +/- 6, and 737 +/- 176 (fm) microliters.min-1 x g placenta-1. Calculated K+ fluxes were asymmetric, being 0.75 +/- 0.12 and 0.41 +/- 0.12 mumol.min-1 x g placenta-1 for maternofetal and fetomaternal, respectively (mean +/- SE, n = 6; P < 0.01, paired t test). Although Kmf for 3H2O was 28% higher than Kfm, this could not completely account for the asymmetry in K+ fluxes. Kmf for 42K was 12-70 times higher than that for 51Cr-EDTA (presumed to be a paracellular marker), although its diffusion coefficient is only 2.5 times higher. An apparent Michaelis constant (Km) of 11.0 +/- 2.4 mM and maximum velocity (Vmax) of 3.8 +/- 0.33 mumol.min-1 x g placenta-1 was calculated by Michaelis-Menten analysis of the transcellular component of maternofetal flux (Jmf) for K+. Ouabain or barium (1 mM in maternal and fetal perfusate) reduced Kmf for 42K from 250 +/- 38 to 76 +/- 13 microliters.min-1 x g placenta-1 (n = 4; P < 0.01) and from 358 +/- 31 to 106 +/- 18 microliters.min-1 x g placenta-1 (n = 5; P < 0.001). Neither drug had any effect on Kmf for 51Cr-EDTA or 3H2O.(ABSTRACT TRUNCATED AT 250 WORDS)

Copper transport and kinetics in cultured C6 rat glioma cells

1995 ◽  
Vol 269 (4) ◽  
pp. C892-C898 ◽  
Author(s):  
Y. Qian ◽  
E. Tiffany-Castiglioni ◽  
E. D. Harris
Keyword(s):  
Membrane Fraction ◽  
Glioma Cells ◽  
Maximum Velocity ◽  
C6 Cells ◽  
Michaelis Constant ◽  
Rat Glioma ◽  
Saturation Kinetics ◽  
Efflux Mechanism ◽  
Import And Export ◽  
P Type

C6 rat glioma cells accumulate and efflux 67Cu. Both processes showed saturation kinetics with increasing 67Cu concentration. The Michaelis constant (Km) for uptake was 0.63 +/- 0.14 microM; maximum velocity (Vmax) was 3.29 +/- 0.57 pmol Cu.mg protein-1.min-1. The Km for efflux was 0.15 +/- 0.06 microM; Vmax was 1.08 +/- 0.71 pmol Cu.mg protein-1.min-1. p-Chloromercuribenzoate (p-CMB) totally blocked 67Cu efflux but had no effect on Km or Vmax of uptake. Total 67Cu in the cell after 50 min was partitioned equally between particulate and soluble fractions. p-CMB-treated cells accumulated more 67Cu, but < 10% was bound to the particulate (membrane) fraction. Pb also increased 67Cu accumulation without affecting Km and Vmax of 67Cu uptake. These data suggest that carriers for import and export of Cu in C6 cells are distinct or operate in two different cellular environments. Efflux is a sulfhydryl-dependent process subject to inhibition by Pb. The data are consistent with a P-type ATPase in the efflux of Cu from cells and the potential for Pb to inhibit the efflux mechanism.

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