Biomedical subjects

D F Bowen-Pope

Publications and source records attributed to D F Bowen-Pope.

97 records · Page 6Linked to original sources

PubMed1982

Similar effects of platelet-derived growth factor and epidermal growth factor on the phosphorylation of tyrosine in cellular proteins.

Platelet-derived growth factor (PDGF) stimulates the phosphorylation of proteins at tyrosine when added to quiescent 3T3 cells, as evidenced by the increase in the amount of phosphotyrosine, relative to phosphoserine and phosphothreonine, in cellular proteins. The increase was detected within 1 min of adding PDGF and was maximal by 5 min. This effect showed the same dependence on PDGF concentration as did association of 125I-PDGF with the cells. In different 3T3 cell lines the magnitude of the increase was approximately proportional to the number of PDGF receptors per cell. A number of proteins phosphorylated at tyrosine in response to PDGF have been detected by two-dimensional gel electrophoresis. They include a pair of related 45 kilodalton phosphoproteins, a pair of related 43 kilodalton phosphoproteins and a 42 kilodalton phosphoprotein. Similar changes were noted when quiescent 3T3 cells were incubated with epidermal growth factor. Possibly, these phosphoproteins are primary substrates of the tyrosine protein kinases activated by the receptors for PDGF and epidermal growth factor, and are involved in physiological effects common to the two growth factors.

Amino Acids↗

PubMed1979

Coordinate control of Balb/c3T3 cell survival and multiplication by serum or calcium pyrophosphate complexes.

Balb/c3T3 cells in crowded cultures detach from the dish when deprived of serum, and the survivors incorporate 3H-thymidine at a reduced rate. The detachment becomes pronounced two hours after removal of serum, and reaches its maximum rate between two and four hours. Cells in sparse culture are not detached by serum removal, and their rate of 3H-thymidine incorporation is only slightly reduced. As the sparse cultures grow into more crowded cultures, and the serum is depleted, increasing numbers detach. The detached cells are incapable of reattaching when placed in a new dish with ample fresh serum. The cells are leaky to cellular constituents and appear to be dead. Detachment is a consequence rather than the cause of cell death, and can be produced by agents which inhibit cellular energy metabolism. The cells on the dish which survive serum deprivation are fully viable and grow rapidly when serum is added. When they become crowded they are as sensitive to serum deprivation as was the original population. They are therefore not selected for a low serum requirement but apparently survive because they spread into the space vacated by the detaching cells and then behave as sparse cultures in response to serum variations. Insoluble complexes of Ca2+ and pyrophosphate (Ca2+-PPi) show the same concentration dependence in promoting cell survival as in stimulating 3H-thymidine incorporation, showing that a single substance can be responsible for both activities. It is concluded that survival and growth are part of the coordinate response of 3T3 cells to single external effectors. The results are discussed in terms of a simple model in which the coordinate response is regulated by the availability of Mg2+ for transphosphorylation reactions within the cell, and the availability depends on the binding affinity of cellular membranes for Mg2+. The difference between survival and multiplication is postulated to be in the intensity and duration rather than the kind of stimulus.

Calcium Pyrophosphate↗

PubMed1979

Separate roles for calcium and magnesium in their synergistic effect on uridine uptake by cultured cells: significance for growth control.

The uptake of uridine by BALB/c3T3 cells is markedly inhibited by reducing the concentration of Mg(2+) in medium containing only traces of Ca(2+). When physiological [Ca(2+)] is present in the medium, omission of Mg(2+) has no effect on uridine uptake, and when Mg(2+) is present, omission of Ca(2+) has only a slight inhibitory effect. When both Ca(2+) and Mg(2+) are omitted, the concentration of Ca(2+) in the cells is not reduced, but that of Mg(2+) is reduced to about one-half in 3 hr. The concentration of K(+) is also reduced, and that of Na(+) is increased, suggesting increased membrane permeability to cations. The rate of diffusion of the nontransported hexose, L-glucose, into the cells is greatly increased. Changes in intracellular Na(+) and K(+) concentrations do not in themselves affect uridine uptake. When Ca(2+) alone is restored to the medium of cells that had been deprived of both Ca(2+) and Mg(2+), there is no increase in the greatly depressed rate of uridine uptake, but when Mg(2+) alone is restored, the rate of uridine uptake returns to control values. We conclude that the omission of Ca(2+) from the medium has no direct effect on uridine uptake, but acts by increasing the exchange of Mg(2+) between cells and medium and by otherwise altering the availability of Mg(2+) for this reaction. A similar conclusion is reached in considering the role of these ions in the regulation of other reactions of the coordinate response, including the initiation of DNA synthesis and the control growth.

Animals↗

PubMed1977

Magnesium and calcium effects on uptake of hexoses and uridine by chick embryo fibroblasts.

Cultures of chick embryo fibroblasts were incubated for varying periods in media containing different concentrations of Ca2+ and Mg2+-Mg2+ deprivation produced a gradual decrease in the Vmax of the glucose transport system for the D-glucose analogues 3-O-[3H]methyl-D-glucose and 2-deoxy-D-[3H]glucose and a parallel decrease in the rate of production of lactate from glucose in the medium. It greatly reduced the rates of [3H]uridine uptake and incorporation by decreasing the Vmax of the uridine transport system. Addition of Mg2+ to Mg2+-deprived cultures rapidly increased the rate of [3H]uridine uptake without requiring protein synthesis and increased the rate of 2-deoxy-D-[3H]glucose uptake without requiring RNA synthesis. These effects of changes in Mg2+ concentration qualitatively reproduce the effects of such variables as cell density and serum and insulin concentrations. Ca2+ deprivation resulted in similar, though much smaller, changes in the activities of the two transport systems, but also greatly increased the "leakiness" of the cells to the nontransported hexose L-[3H]glucose.

Animals↗

PubMedDate not supplied

Developmentally regulated production of platelet-derived growth factor-like molecules.

Platelet-derived growth factor (PDGF) is thought to mediate the proliferation of smooth muscle cells in injured arteries, and may be involved in the pathogenesis of atherosclerosis. PDGF-like molecules from non-platelet sources may also play a role in the regulation of cell activity in other circumstances. Transformation of cells by a wide range of oncongenic agents appears to activate a cellular gene encoding a PDGF-like molecule, possibly accounting for the ability of transformed cells to grow without addition of exogenous mitogens. We show here that a molecule (PDGF-c) which can compete with 125I-PDGF for binding to PDGF receptors is secreted by cultured rat aortic smooth muscle cells (rASMC) isolated from 13 to 18-day-old rats (pups) but not from three-month-old animals (adults). Thus, production of PDGF-c appears to be developmentally regulated and may be a factor in the more rapid proliferation of rASMC and synthesis of connective tissue components which occurs during growth of the aorta in vivo.

Aging↗

PubMedDate not supplied

Matrix metalloproteinase-9 overexpression enhances vascular smooth muscle cell migration and alters remodeling in the injured rat carotid artery.

Matrix metalloproteinase-9 (MMP-9) has been implicated in the pathogenesis of atherosclerosis as well as intimal hyperplasia after vascular injury. We used Fischer rat smooth muscle cells (SMCs) overexpressing MMP-9 to determine the role of MMP-9 in migration and proliferation as well as in vessel remodeling after balloon denudation. Fischer rat SMCs were stably transfected with a cDNA for rat MMP-9 under the control of a tetracycline-regulatable promoter. In this system, MMP-9 was overexpressed in the absence, but not in the presence, of tetracycline. In vitro SMC migration was determined using a collagen invasion assay as well as a Boyden chamber assay. In vivo migration was determined by measuring the invasion into the medial and intimal layers of transduced SMCs seeded on the outside of the artery. Transduced SMCs were also seeded on the luminal surface, and the effect of local MMP-9 overexpression on vascular structure was measured morphometrically at intervals up to 28 days. MMP-9 overexpression enhanced SMC migration in both the collagen invasion assay and Boyden chamber in vitro, increased SMC migration into an arterial matrix in vivo, and altered vessel remodeling by increasing the vessel circumference, thinning the vessel wall and decreasing intimal matrix content. These results demonstrate that MMP-9 enhances vascular SMC migration in vitro and in vivo and alters postinjury vascular remodeling.

Animals↗

PubMedDate not supplied

Is PDGF really important? Testing the hypotheses.

Platelet-derived growth factor (PDGF) has been proposed to be one of the growth factors that drive proliferation during normal development and in various pathological conditions. Support for these hypotheses has been largely circumstantial. We discuss the pros and cons of the different experimental approaches that have been taken to test these hypotheses, and evaluate the information to be gained by characterizing the consequences of deletion of one of the PDGF receptor genes in the Patch mutant mouse.

Animals↗