Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0038187 (starvation)
24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the effect of glucose starvation on glucose uptake and thymidine uptake and incorporation in cultures of normal chicken embryo cells and those transformed by Rous sarcoma virus. Resting normal fibroblasts increased the rate of glucose transport up to tenfold when they were starved for glucose, whereas fast-growing normal cells doubled the rate of uptake after starvation. Transformed cells did not show any change in the rate of glucose uptake during starvation. Thymidine uptake and incorporation by normal and transformed cells were not affected by glucose starvation. These results showed that a decrease in the glucose concentration of the medium induced a specific increase in the rate of glucose transport by normal chick fibroblasts, but did not change the transport of glucose by transformed cells. Therefore, it is suggested that glucose or one of its metabolic products regulated the hexose uptake of normal chick fibroblasts. Virus-transformed cells were insensitive to this regulation.
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PMID:Effects of glucose starvation on normal and rous sarcoma virus-transformed chick cells. 16 6

The mode of induction of sugar transport by serum-stimulation of growth and hexose-starvation in chick embryo fibroblasts (CEF) has been studied using metabolic inhibitors. We have concluded from these studies that the sugar transport increases induced by serum-stimulation are regulated by post-transcriptional mechanisms while sugar transport increases induced by hexose-starvation are regulated by a transcriptional mechanism. CEF infected with a temperature-sensitive mutant of the Rous sarcoma virus. Ts68 and incubated at the nonpermissive temperature for transformation, 41 degrees, retain the capacity to regulate sugar transport in a manner similar to uninfected CEF. However, Ts68-infected CEF maintained at the permissive temperature for transformation, 37 degrees, have lost the ability to regulate sugar transport at the post-transcriptional and post-translational levels.
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PMID:Regulation of sugar transport in chick embryo fibroblasts and in fibroblasts transformed by a temperature-sensitive mutant of the Rous sarcoma virus. 18 41

A study was made of the transport of a variety of amino acids by uninfected and Rous sarcoma virus-infected chicken embryo fibroblasts. Following a period of amino acid starvation, transformed, but not normal cells, showed increased levels of transport for alpha-aminoisobutyric acid, proline and alanine, three amino acids which are transported primarily by the A transport system. There was no starvation-induced increase in the transport of leucine, phenylalanine, lysine, or cycloleucine. In the absence of starvation, normal and transformed cells exhibited comparable rates of amino acid transport. Cycloheximide was able to block the increase in uptake. The enhanced uptake was characterized by an increase in Vmax for transport and little change in Km. The data demonstrate that an alteration in the regulation of the A amino acid transport system is an early event in malignant transformation by Rous sarcoma virus. However, since this alteration in made manifest only following a period of starvation, our findings suggest that increased amino acid uptake does not play a role in generating the other manifestations of the transformed state seen in cell culture.
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PMID:Amino acid transport in normal and Rous sarcoma virus-transformed chicken embryo fibroblasts. 22 76

A temperature sensitive mutant of Rous sarcoma virus (tsNY68) was used to obtain cultures of quiescent virus-infected chicken embryo fibroblasts arrested by serum starvation at the non-permissive temperature. Upon shift to the permissive temperature, these cells enter the replicative cell cycle as evidenced by increases in 2-deoxyglucose uptake, 3H-thymidine incorporation and percent labeled nuclei. These changes occur in the absence of serum and the cells become morphologically transformed within eight to ten hours after the temperature shift. Entry into the S phase temporally resembles that of normal quiescent fibroblasts stimulated with serum. This experimental system was used to examine the proliferative response of transformed cells to serum and purified multiplication-stimulating activity (MSA) during the transition from the resting to the growing state. Data are presented which show that the presence of serum in the medium enhances the proliferative response of quiescent infected cells shifted to the permissive temperature over those shifted in the absence of serum. In contrast, the presence of MSA has no additional effect on the response exhibited by infected cells shifted to the permissive temperature in serum-free medium. Labeled MSA binding experiments show that this lack of response is not due to a loss of MSA receptors on the cell surface since transformed cells are still capable of binding MSA at the same level as normal cells. The results are consistent with the hypothesis that the set of biochemical events initiated by MSA in normal cells are turned on in infected cells shifted to the permissive temperature by the activation of the src gene product.
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PMID:Regulation of the proliferative response in Rous sarcoma virus transformed chicken embryo fibroblasts by serum and multiplication-stimulating activity (MSA). 22 14

Mouse 3T3 cells transformed by a conditional mutant of Rous sarcoma virus (LA90) can assume either a normal or a transformed phenotype, depending on the temperature of cultivation. These cells (LA90) were arrested at the G0/G1 phase of the cell cycle by starvation for serum growth factors at the nonpermissive temperature (39 degrees C). Release from the G0/G1 phase by serum growth factors resulted in a rapid stimulation of Rb+ influx. To investigate whether the stimulation of Rb+ influx is obligatory for cell proliferation, the cultures were released from the G0/G1 phase by a temperature decrease in the absence of serum. A temperature decrease from 39 to 32 degrees C activated the viral pp60src gene mitogenic activity. Under these conditions, no rapid stimulation of Rb+ influx was observed. These results suggest that the rapid stimulation of Rb+ influx induced by serum growth factors is not an essential signal for cell release from the G0/G1 phase. However, a delayed increase in Rb+ influx concomitant with an increase in the cell content of K+ was observed in the cultures released from the G0/G1 phase by temperature decrease in the absence of serum growth factors. We found that the LA90 cells incubated at the permissive temperature (32 degrees C) secreted a mitogenic activity into the medium. Moreover, the conditioned medium from cultures incubated at 32 degrees C, but not at 39 degrees C, stimulate Rb+ influx in G0/G1 cells. These results indicate that Rous sarcoma virus pp60src induces a slow autocrine secretion of a mitogenic activity. This mitogenic activity slowly modulates the K+ content. Therefore, the slow elevation in cellular content of K+ is proposed to be an obligatory event for proliferation in normal and transformed cells.
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PMID:Control of K+ influx in 3T3 cells transformed by a conditional mutant of Rous sarcoma virus. 299 33

Photoaffinity labeling with [3H]cytochalasin B detects two D-glucose-sensitive proteins in the chicken embryo fibroblast (CEF) plasma membrane, which accumulate under conditions of glucose starvation and are probably involved in the glucose transport system (Pessin, J.E., et al. (1982) Proc. Natl. Acad. Sci. U.S. 79, 2286-2290). The two labeled components, designated as peak I (Mr 45,000) and II (Mr 52,000) components, were separated by preparative gel electrophoresis in the presence of sodium dodecyl sulfate. The fractions were digested with S. aureus V8 or papain, and the radioactive products were analyzed by one-dimensional gel electrophoresis. The peptide maps showed that they have different peptide structures. Peptide maps of authentic actin, a possible contaminant of the peak I fractions, were quite different from those of the peak I component. Rous sarcoma virus-transformed CEF have two components similar as to apparent molecular size and peptide maps to those present in glucose-starved cells. The peak I and II components show minimal affinity to agarose-bound Ricinus communis agglutinin which binds the human erythrocyte glucose transporter quite well. The peak II component was more susceptible to proteolysis than the peak I one or the human erythrocyte glucose transporter. However, the peptide maps of the peak II component were similar to those of the human erythrocyte glucose transporter.
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PMID:Separation and proteolytic mapping of the two [3H]cytochalasin B photoaffinity labeled D-glucose-sensitive proteins in the chicken embryo fibroblast plasma membrane. 351 90

Normal as well as Rous sarcoma virus-infected chicken pectoral and chicken embryo fibroblasts proliferate actively in a plasma containing medium of physiological ion concentrations (Ca2+, 1.2 mM; Mg2+, 0.7 mM). Reduction of medium calcium and magnesium concentrations is necessary to achieve selective quiescence of normal fibroblasts in these cell systems. By contrast, normal chicken heart mesenchymal cells proliferate only sluggishly (one doubling or less during a 6-day period) in a plasma containing medium of physiologic ion concentrations, whereas Rous sarcoma virus-infected heart mesenchymal cells proliferate actively (more than four doublings during an initial 2-day phase of exponential growth). The chicken heart mesenchymal cell system therefore has great potential for studies of the mechanism that initiates cell replication and of the failure in cellular regulatory processes that is responsible for the autonomous initiation of replication of neoplastic cells. From comparison of the chicken heart mesenchymal cell system to dialyzed plasma-based systems in which 3T3 cells tend to proliferative quiescence, it is argued that this proliferative quiescence of 3T3 cells is a result of cell starvation and is not physiologically meaningful.
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PMID:Active proliferation of Rous sarcoma virus-infected, but not normal, chicken heart mesenchymal cells in culture medium of physiological composition. 625 50

The increased rate of glucose uptake found in cells transformed by Rous sarcoma virus was shown to be enhanced relative to the changes in uptake induced in nontransformed cells by deprivation of glucose (deprivation derepression). Glucose-specific uptake sites were distinguished from glucose-galactose sites in nontransformed cells, and the capacities for glucose uptake and for galactose uptake were increased to about the same extent by the exclusion of glucose from the cell culture medium. Deprivation derepression occurred without a requirement for new RNA or protein synthesis, suggesting that preexisting inactivate uptake sites were activated. Deprivation derepression could be mimicked by the treatment of cells with adenosine triphosphatase activators, and adenosine triphosphate levels were reduced in glucose-deprived cells and in cells treated with adenosine triphosphatase activators. Cells transformed by the Bryan strain of Rous sarcoma virus were unresponsive to addition of high concentrations of glucose, to glucose starvation, or to treatment with adenosine triphosphatase activators, and the relative capacity for glucose uptake in these transformed cells was enhanced much more than the capacity of galactose uptake. It was concluded that cells infected by the Bryan strain of rous sarcoma virus in the process of transformation selectively synthesize more sites specific for glucose uptake. Lower levels of adenosine triphosphate found in transformed cells possibly contribute to a chronic derepression of uptake sites.
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PMID:Increased glucose uptake capacity of Rous-transformed cells and the relevance of deprivation derepression. 626 Mar 48

The avian neural retina (NR) is derived from proliferating neuroectodermal precursors which differentiate after terminal mitosis and become organized in cell strata. Proliferation of postmitotic NR cells can be induced by infection with Rous sarcoma virus (RSV) and requires the expression of a functional v-Src protein. QR1 is a retina-specific gene expressed exclusively at the stage of growth arrest and differentiation during retinal development. In NR cells infected with tsPA101, an RSV mutant conditionally defective in pp60v-src mitogenic capacity, QR1 expression is downregulated in proliferating cells at 37 degrees C and is fully restored when the cells become quiescent as a result of pp60v-src inactivation at 41 degrees C. We were able to arrest proliferation of tsPA101-infected quail NR cells expressing an active v-Src protein by serum starvation at 37 degrees C. This allowed us to investigate the role of cell growth in regulating QR1 transcription. We report that QR1 transcription is stimulated in growth-arrested cells at 37 degrees C compared with that in proliferating cells maintained at the same temperature. Growth arrest-dependent stimulation of QR1 transcription requires the integrity of the A box, a previously characterized cis-acting element responsible for QR1 transcriptional stimulation upon v-Src inactivation and during retinal differentiation. We also show that formation of the C1 complex on the A box is increased upon growth arrest by serum starvation in the presence of an active v-Src oncoprotein. Thus, the C1 complex represents an important link between cell cycle and developmental control of QR1 gene transcription during NR differentiation and RSV infection. By using antibodies directed against different Maf proteins of the leucine zipper family and competition with Maf consensus site-containing oligonucleotides in a gel shift assay, we show that the C1 complex is likely to contain a Maf-related protein. We also show that a purified bacterially expressed v-Maf protein is able to bind the A box and that the level of a 43-kDa Maf-related protein is increased upon growth arrest in infected retinal cells. Moreover, ectopic expression of c-mafI, c-mafII, and mafB cDNAs in quiescent tsPA101-infected quail NR cells is able to stimulate transcription of a QR1 reporter gene through the A box. Therefore, QR1 appears to be the first target gene for a Maf-related protein(s) in the NR.
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PMID:Transcriptional stimulation of the retina-specific QR1 gene upon growth arrest involves a Maf-related protein. 756 8

Gene transfer vectors based on adeno-associated virus (AAV) are emerging as highly promising for use in human gene therapy by virtue of their characteristics of wide host range, high transduction efficiencies, and lack of cytopathogenicity. To better define the biology of AAV-mediated gene transfer, we tested the ability of an AAV vector to efficiently introduce transgenes into nonproliferating cell populations. Cells were induced into a nonproliferative state by treatment with the DNA synthesis inhibitors fluorodeoxyuridine and aphidicolin or by contact inhibition induced by confluence and serum starvation. Cells in logarithmic growth or DNA synthesis arrest were transduced with vCWR:beta gal, an AAV-based vector encoding beta-galactosidase under Rous sarcoma virus long terminal repeat promoter control. Under each condition tested, vCWR:beta Gal expression in nondividing cells was at least equivalent to that in actively proliferating cells, suggesting that mechanisms for virus attachment, nuclear transport, virion uncoating, and perhaps some limited second-strand synthesis of AAV vectors were present in nondividing cells. Southern hybridization analysis of vector sequences from cells transduced while in DNA synthetic arrest and expanded after release of the block confirmed ultimate integration of the vector genome into cellular chromosomal DNA. These findings may provide the basis for the use of AAV-based vectors for gene transfer into quiescent cell populations such as totipotent hematopoietic stem cells.
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PMID:Efficient gene transfer into nondividing cells by adeno-associated virus-based vectors. 805 46


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