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1.
Kirsten murine sarcoma virus (Ki-MSV) transformed Balb/eT3 mouse cells (K-Balb) were found to have altered membrane glycoconjugates compared to normal Balb/3T3 cells. There were reduced amounts of mono- and disialogangliosides, GM1 and GD1a, and activity of the specific galactosyltransferase required for synthesis of these gangliosides was reduced to between 0 and 18.5% of normal in the several K-Balb clones examined. When fucose-labeled glycopeptides derived from the surfaces of Balb/3T3 and K-Balb cells were compared by gel filtration chromatography, the glycopeptides from the transformed cells were enriched in earlier eluting components. These differences were also observed when the glycopeptides were derived from the entire cell and were diminished when the surface or cellular glycopeptides from Balb/3T3 and K-Balb were digested with neuraminidase prior to chromatographic analysis. Changes in these membrane sialoglycolipids and sialoglycopeptides were not influenced by Rauscher leukemia virus infection. In marked contrast, these changes in membrane glycoconjugates were not observed in Wooley monkey sarcoma virus (WSV) transformed Balb/3T3 cells (W-Balb). Although W-Balb cells like K-Balb were transformed by tissue culture criteria, their ganglioside composition, galactosyltransferase activity, and glycopeptide patterns were similar to normal Balb/3T3. These findings have potential implications concerning the role of these complex carbohydrates in the phenotypic alterations of transformed cells. 相似文献
2.
Presence of retrovirus in the B95-8 Epstein-Barr virus-producing cell line from different sources 总被引:1,自引:0,他引:1
Joseph J. Tumilowicz Gary E. Gallick James L. East Sen Pathak John J. Trentin Ralph B. Arlinghaus 《In vitro cellular & developmental biology. Plant》1984,20(6):486-492
Summary The B95-8 cell line, a widely used source of highly transforming Epstein-Barr virus (EBV), obtained from the laboratory of
origin, harbored an infectious retrovirus. This retrovirus generally resembled the Type D retroviruses structurally and developmentally
and like the Type D retroviruses preferred Mg2+ to Mn2+ in its RNA-directed DNA polymerase reaction. Evidence for the presence of retrovirus was found in B95-8 cultures from two
other sources within the United States, either by assay for polymerase or by electron microscopy. Comparison of two B95-8
cell lines showed cytogenetic differences as well as differences in retroviral activities. The results suggest that any B95-8
culture should be tested for the presence of retrovirus before its use as a source of EBV.
This research was supported through the National Research and Demonstration Center (HL-17269-07) awarded to Baylor College
of Medicine by the National Heart, Lung, and Blood Institute, Bethesda, MD, by RD-125 from the American Cancer Society, by
K06 CA14219, CA16781, CA25465, and CA16672 from the National Cancer Institute, Bethesda, MD, and by G-429 from the Robert
A. Welch Foundation. G. E. G. was supported by Public Health Service training Grant CA-09299. 相似文献
3.
4.
Activation of MAP kinase and enhanced phosphorylation of the 350-kDa protein by mitogenic stimuli in quiescent Balb/c 3T3 cells. 总被引:2,自引:0,他引:2
M Kawakami E Nishida K Tobe M Hoshi T Kadowaki M Kasuga H Sakai 《Experimental cell research》1991,193(1):120-126
In quiescent Balb/c 3T3 cells, competence factors such as platelet-derived growth factor and 12-O-tetradecanoylphorbol-13-acetate (TPA) activated MAP kinase, whereas progression factors such as insulin did not. Insulin was, however, capable of activating MAP kinase in cells pretreated with TPA. Moreover, TPA plus insulin activated MAP kinase more strongly and for a longer time period than did TPA alone. Treatment of Balb/c 3T3 cells with competence factors stimulated phosphorylation of the 350-kDa protein which was immunoprecipitated with antibodies against brain high-molecular-weight microtubule-associated protein MAP1, whereas insulin treatment did not stimulate the phosphorylation. Insulin could induce, however, further increase in the phosphorylation of the 350-kDa protein, when added simultaneously with TPA or added to the TPA-treated cells. The enhanced phosphorylation of the 350-kDa protein thus correlated with the MAP kinase activation. As insulin acts synergistically with TPA to induce initiation of DNA synthesis in the quiescent Balb/c 3T3 cells, it seems that activation of MAP kinase and enhanced phosphorylation of the 350-kDa protein are accompanied by the initiation of DNA synthesis. 相似文献
5.
The phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) exerts a dose-dependent effect on Daudi cell proliferation. A low concentration has a slight mitogenic effect but higher concentrations inhibit proliferation. The inhibitory effect is associated with increases in cell size, macromolecular content, and incorporation of precursors into RNA and protein. Cell cycle analysis indicates that TPA at 1–10 nM leads to an apparent accumulation of cells in G2/M phase. However, within this population a significant proportion of cells undergo nuclear division but fail to carry out cytokinesis, giving rise to cells with two or more nuclei. Consistent with this, DNA synthesis continues in cells which cease to divide in the presence of TPA. The ability of the phorbol ester to inhibit proliferation can thus be attributed mainly to an inhibition of cytokinesis rather than DNA replication 相似文献
6.
William A. Suk Lisa M. Ceccorulli Cedric W. Long 《In vitro cellular & developmental biology. Plant》1981,17(5):412-420
Summary Juvenile hormones (JH), congeners of retinoic acid, were examined for their capacity to inhibit cell cycle progression and
chemically induced expression of endogenous xenotropic retrovirus in Kirsten sarcoma virus-transformed BALB (K-BALB) mouse
cells. JHI, II, and III were found to inhibit induction of virus by 5-iododeoxyuridine (IUdR) and histidinol (Hdl) in a concentration-dependent
fashion. Some inhibition of macromolecular synthesis was observed upon culture of the cells with JH; the most affected was
RNA synthesis, which was reduced 27 to 40% within 4 h by the juvenoids. Epoxide hydrase (EH) activity, as determined by high-pressure
liquid chromatography (HPLC), was present in amounts sufficient for the cells to convert the hormones metabolically to an
ultimate form. A contact-inhibited K-BALB variant was synchronized by mitotic arrest and the cell cyclespecific effect of
JHIII on virus induction during S phase was studied. JHIII added during G1 phase, and followed by induction, inhibited virus expression 95 and 76% by IUdR and Hdl, respectively. Induction was inhibited
only 35% when JHIII was added during S phase concomitantly with the inducers and no inhibition was observed when JHIII was
added during G2 phase followed by the inducers. JHIII added to synchronous cells in G1 phase inhibited progression of cells into S phase and the onset of DNa synthesis. The results indicate that mouse fibroblasts
have a juvenile hormone-sensitive restriction point in G1 phase that might relate to the effects these hormones have on cell replication and differentiation.
This work was supported under Contract NO-1-CO-75380 with the National Cancer Institute, National Institutes of Health, Bethesda,
Maryland 20205. 相似文献
7.
Altered growth kinetics precede calcium-induced differentiation in mouse epidermal cells 总被引:1,自引:0,他引:1
K. Elgjo H. Hennings O. P. F. Clausen 《In vitro cellular & developmental biology. Plant》1986,22(6):332-336
Summary Primary cultures of newborn mouse epidermal cells proliferate rapidly and with a high growth fraction for several months when
grown in medium with low calcium (0.02 to 0.1 mM). Addition of calcium to levels generally used in culture medium (1.2 mM) was followed by rapid changes in the pattern of proliferation. By using a combination of technics (a stathmokinetic method,
autoradiography, [3H]thymidine incorporation into DNA, DNA flow cytometry) it was found that cell flux was blocked for 5 to 6 h, followed by
a short rise in the mitotic rate at 10 h, and a gradual fall in all growth parameters until about 32 h after the calcium switch.
There was no accumulation of cells in any particular cell cycle phase. The results indicate that the calcium switch is followed
by a strong reduction in cell flux from G1 whereas the majority of the cells that had left G1 at the time of the switch completed one cell division before cessation of all proliferative activity. Both before and after
the switch the primary epidermal cultures consisted of one diploid and one tetraploid G1 DNA stemline that seemed to react in the same way to calcium.
This work reported in this paper was undertaken during the tenure of an American Cancer Society-Eleanor Roosevelt-International
Cancer Fellowship awarded by the International Union Against Cancer (K. E.). The project was supported by funds partly provided
by the International Cancer Research Data Bank Program of the National Cancer Institute, National Institutes of Health, Bethesda,
MD, under contract N01-C0-65341 (International Cancer Research Technology Transfer) and partly by the International Union
Against Cancer (O.P.F.C.). 相似文献
8.
Summary Cloned mouse keratinocytes (MK-1 cells) display density-dependent growth arrest when reaching confluency in a serum-free medium
with a calcium concentration <0.1 mM, supplemented only with insulin and transferrin. In this quiescent state, greater than 95% of the cell population is in the
G0/1 phase of the cell cycle. Treatment of quiescent MK-1 cells with 1 to 10 ng/ml epidermal growth factor (EGF) resulted in a
sharp burst of DNA synthetic activity. Both insulin and cholera toxin potentiated the mitogenic effect of EGF, but neither
agent was necessary or sufficient to induce thymidine incorporation into DNA. Dexamethasone abolished the effect of insulin,
but not the mitogenic effect of EGF alone. In contrast, retinoic acid (RA) did not possess any mitogenic effect for quiescent
MK-1 cells, nor did it modulate the actions of EGF or dexamethasone. A number of commercially available crude extracts of
bovine brain and pituitary were also capable of initiating DNA synthesis in resting MK-1 cells. Finally, transforming growth
factor type beta (TGFβ) proved to be a potent inhibitor of the mitogen-induced DNA synthesis in MK-1 cells (IC50∶10pM). This defined culture system is eminently suited to study the regulation of DNA synthesis of epidermal cells. In addition,
it can be used as a sensitive bioassay for the detection of epidermal mitogens, as well as inhibitors of DNA synthesis such
as TGFβ.
Supported by PHS Award CA-41556 from the National Cancer Institute, Bethesda, MD. 相似文献
9.
Akio Nishikawa Keiko Shimizu-Nishikawa Leo Miller 《In vitro cellular & developmental biology. Plant》1990,26(12):1128-1134
Summary Methods for the isolation and in vitro culture of larval and adultXenopus laevis epidermal cells have been developed. Epidermal cells of stage 52–54 tadpoles and adult epidermal cells were enzymatically
dissociated and purified (98%) by Percoll-density centrifugation and unit-gravity sedimentation. Both cell types attached
on fibronectin-coated dishes and proliferated for 1 wk when the proper medium was used. There were four significant differences
between larval and adult cells: a) Adult cells had a greater buoyant density than larval cells. b) Keratin synthesis patterns
were markedly different. c) A combination of medium F12 and Eagle's minimum essential medium was optimal for growth of larval
cells whereas MCDB151 medium was optimal for adult cells. d) Adult cells needed fetal bovine serum (>5%) whereas larval cells
grew without fetal bovine serum. In contrast to these differences, larval and adult cells had two similar properties: a) Insulin
had a potent effect on the growth of both cells, and b) The optimal Ca++ concentration for cell growth was quite low for both cell types; 0,1 mM for larval cells and below 0.05 mM for adult cells. These results suggest that low Ca++ levels are essential for both cornifying (adult) and uncornifying (larval) amphibian keratinocytes. The culture techniques
described herein for larval and adult epidermal cells provide a new in vitro model for analyzing development of the epidermis
during amphibian metamorphosis.
This study was supported by grant (HD 24438) from the National Institutes of Health, Bethesda, MD. 相似文献
10.
We have constructed a regulated plasmid vector for Streptococcus pneumoniae, based on the streptococcal broad-host-range replicon pLS1. As a reporter gene, we subcloned the gfp gene from Aequorea victoria, encoding the green fluorescent protein. This gene was placed under the control of the inducible PM promoter of the S. pneumoniae malMP operon which, in turn, is regulated by the product of the pneumococcal malR gene. Binding of MalR protein to the PM promoter is inactivated by growing the cells in maltose-containing media. Highly regulated gene expression was achieved by cloning in the same plasmid the PM-gfp cassette and the malR gene, thus providing the MalR regulator in cis. Pneumococcal cells harboring this vector gave a linear response of GFP synthesis in a maltose-dependent mode without detectable background levels in the absence of the inducer. 相似文献
11.
H. Rex Gaskins Jong-Won Kim Gary J. Hausman 《In vitro cellular & developmental biology. Plant》1990,26(11):1049-1056
Summary To better understand possible autocrine or paracrine mechanisms involved in adipose tissue development, we have studied the
biosynthesis of insulinlike growth factor I (IGF-I) and prostaglandin E2 (PGE2) by cultured porcine preadipocytes in response to factors known to modulate cell growth and differentiation. The expression
of c-fos was also monitored because of the potential role of that proto-oncogene in coordination of growth and differentiation. Preadipocytes
were grown to confluence and then maintained in one of three media treatments: a) standard medium supplemented with 10% fetal
bovine serum (FBS), b) FBS supplemented with dexamethasone (Dex), c) FBS supplemented with dibutryladenosine 3′–5′-cyclic
monophosphate. Indirect measurements of growth indicated that cell proliferation did not differ due to media type. Histochemical
and enzymatic measurements of adipocyte development revealed that differentiation occurred only in those cultures exposed
to Dex. The increase in adipocyte differentiation in response to Dex was associated with a decrease in c-fos and actin RNA expression whereas the decrease in c-fos RNA expression in response to Dex was small (approximately 40%); immunocytochemical analysis indicated that induction of
Fos protein occurred only in undifferentiated cells. Thus, the cells responsible for the decrease in c-fos RNA expression are possibly those signaled to differentiate into adipocytes. Expression of IGF-I RNA and secretion of IGF-I
and PGE2 were also decreased in response to Dex treatment. These data provide the first demonstration that biosynthesis of IGF-I by
preadipocytes can be modulated by a potent inducer of adipocyte differentiation. The combined results indicate that glucocorticoids
may stimulate adipocyte differentiation by suppressing intracellular and putative intercellular mitogenic signals.
This work was supported in part by grant HD 18447 from the National Institutes of Health, Bethesda, MD (G. J. H.).
Mention of a trade mark, proprietary product, or specific equipment does not constitute a guarantee or warranty by the U.
S. Department of Agriculture or University of Georgia and does not imply its approval to the exclusion of other products that
may be suitable. 相似文献
12.
Transcriptional induction of urokinase in cultured human kidney carcinoma cells by tetradecanoyl-phorbol-acetate 总被引:6,自引:0,他引:6
R Ferraiuolo M P Stoppelli P Verde S Bullock P Lazzaro F Blasi T C Pietropaolo 《Journal of cellular physiology》1984,121(2):368-374
A cell line derived from a human kidney carcinoma produces in vitro the urinary type of plasminogen activator (urokinase). The synthesis of plasminogen activator is enhanced by 12-O-tetradecanoyl-phorbol-13-acetate(TPA); the increase can be followed both in the cell lysate and in the culture medium. The effect requires RNA and protein synthesis as well as the continuous presence of the inducer. Immunofluorescence and immunoprecipitation experiments with monospecific antiurokinase IgG show that kidney carcinoma cells synthesize a 50,000-dalton urokinase and TPA enhances the synthesis of the same molecular species. Hybridization of the total cellular RNA to a human urokinase cDNA probe shows that TPA increases the urokinase mRNA level. 相似文献
13.
Toshihiro Mitaka Gerald L. Sattler Henry C. Pitot 《In vitro cellular & developmental biology. Animal》1991,27(7):549-556
Summary Bicarbonate in the culture medium is essential for DNA synthesis of primary cultured rat hepatocytes stimulated by epidermal
growth factor (EGF). When primary cultured hepatocytes in supplemented Leibovitz L15 medium were placed in a 100% air incubator,
no increase in DNA synthesis was observed even after stimulation by EGF. However, when these cells were cultured with NaHCO3 and EGF and placed in a 5% CO2:95% air incubator, a stimulus of DNA synthesis more than 10-fold greater than in cultures in air only was seen, and many
mitotic figures could be identified. Furthermore, NaHCO3 added to supplemented DMEM/F12 medium enhanced the DNA synthesis of primary cultured rat hepatocytes in this medium. The
ideal pH of the medium for DNA synthesis of cultured hepatocytes was in the range of 7.6 to 8.0. A dose response of NaHCO3 in several media showed that DNA synthesis of the cells increased as the concentration of NaHCO3 increased and that 25 to 30 mM NaHCO3 in the medium was optimal for the replication of DNA by primary cultured rat hepatocytes.
The investigations described in this study were supported in part by grants CA-07175, CA-22484, and CA-45700 from the National
Cancer Institute, Bethesda, MD. 相似文献
14.
Ching Chow Chen Chin San Cheng Jacque Chang Huei Chen Huang 《Journal of neurochemistry》1995,64(2):818-824
Abstract: Correlation between translocation and down-regulation of conventional protein kinase Cα (cPKCα) and new PKCδ (nPKCδ) induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) at different time courses (5 min, 30 min, 1 h, 3 h, 6 h, 10 h, 17 h, and 24 h) was studied in C6 glioma cells. From the dose-dependent translocations of these two isoforms by 10-min treatment with TPA (1, 3, 10, 30, 100, 300, and 1,000 nM), we found that cPKCα was translocated by 3–1,000 nM and nPKCδ was translocated by 10–1,000 nM TPA. Both isoforms were maximally translocated by 100–1,000 nM TPA, whereas 1 nM did not translocate these two isoforms. When the cells were treated with 1,000 nM TPA for 5 min to 17 h, the translocation of these two isoforms occurred rapidly after 5-min treatment and could be sustained for 1 h, whereas down-regulation occurred after 3-h treatment and almost complete down-regulation was observed after 17-h treatment. However, the extent of down-regulation of nPKCδ was greater than that of cPKCα at 3-, 6-, and 10-h treatment. Further studies by using different doses of TPA (100, 10, 3, and 1 nM) and extending the time to 24 h showed that cPKCα was more resistant to down-regulation. This conventional isoform was maintained at a translocation state even after long-term treatment with 3–100 nM TPA, and complete down-regulation was only shown after 1,000 nM treatment. On the other hand, nPKCδ was almost completely down-regulated by long-term treatment with a translocation dose of 10–1,000 nM TPA despite higher membrane content of this new isoform. Therefore, the differential translocation and down-regulation of cPKCα and nPKCδ was demonstrated in C6 glioma cells and this will be useful for exploring cPKCα- or nPKCδ-specific functional roles in cellular functions and different signal transduction pathways in these cells. 相似文献
15.
Alterations of protein synthesis in arbovirus-infected L cells 总被引:3,自引:0,他引:3
G Lust 《Journal of bacteriology》1966,91(4):1612-1617
Lust, George (Fort Detrick, Frederick, Md.). Alterations of protein synthesis in arbovirus-infected L cells. J. Bacteriol. 91:1612-1617. 1966.-Cellular protein synthesis and ribonucleic acid (RNA) synthesis in mouse L cells were markedly depressed 1 hr after infection with Venezuelan equine encephalomyelitis virus. Host RNA and protein synthesis were inhibited more rapidly by the virus infection than by actinomycin D. In cells infected 4 hr, a cytoplasmic RNA polymerase was demonstrated which was absent in uninfected cells. At this time, deoxyribonucleic acid-directed RNA synthesis catalyzed by the nuclear RNA polymerase was inhibited in vitro in enzyme preparations from nuclei of virus-infected cells. For optimal activity, the cytoplasmic RNA polymerase required the four nucleoside triphosphates, Mg(++), and RNA. The enzyme was insensitive to actinomycin D and deoxyribonuclease, indicating that it catalyzed RNA-directed RNA synthesis. Attempts to purify the induced polymerase further were unsuccessful. Fresh preparations had to be used because the enzymatic activity was unstable. 相似文献
16.
Heather W. Weber Shawn Vallett Lorna Neilson Mark Grotke Yesu Chao Mark Brudnak Alan San Juan Maria Pellegrini 《Molecular and cellular biochemistry》1991,104(1-2):201-207
The expression of genes that code for the large ribosomal RNAs (rRNAs) and tRNAs can be regulated by calcium, serum, insulin and a tumor-promoting phorbol ester, TPA. These effectors can rapidly alter rRNA and tRNA synthesis in dividing and nondividing Drosophila cells. In an in vitro assay system of the nondividing cells of the male accessory glands, calcium, insulin and TPA were shown to increase both rRNA and tRNA synthesis. Exposure of actively dividing Drosophila culture cells to differing serum concentrations or TPA also altered rRNA and tRNA synthesis. Nuclear run-on assays demonstrate that the exposure of these cells to increased serum concentrations coordinately alters RNA polymerase I loading on both 18S and 28S rDNA. These data indicate that calcium, growth factors and a tumor-promoter each can signal changes in ribosomal and tRNA gene expression. 相似文献
17.
Steven C. Miller George Melnykovych 《In vitro cellular & developmental biology. Plant》1983,19(11):853-862
Summary In a previous study glucocorticoids have been shown to depress the rate of fluid-phase endocytosis in a macrophage cell line,
P388D1. This effect was observed when either fluorescein-labeled dextran or horseradish peroxidase (HRP) was used to measure endocytosis.
In this report the relationship between cholesterol synthesis and endocytosis was examined in light of the ability of glucocorticoids
to inhibit cholesterol biosynthesis. Two known inhibitors of cholesterol biosynthesis, ML-236B and 25-hydroxycholesterol (25-OH),
were compared with dexamethasone (dex) for the ability to suppress endocytosis in cells grown in media supplemented with either
10% whole or delipidized neonatal bovine serum (NBS). In 10% whole serum all inhibitors reduced the uptake of HRP after 12
h incubation. Dexamethasone (1 μM) suppressed endocytosis by 30% whereas 25-OH (2.5 μM) and ML-236B (11.6 μM) inhibited by 38 and 52%, respectively. Supplementation of the growth medium with mevalonolactone (3.4 mM) prevented the inhibition of endocytosis by ML-236B. In contrast, mevalonolactone supplementation did not prevent either
dex or 25-OH from suppressing endocytosis. The same pattern of results was obtained when cultures were grown in delipidized
NBS.
After 4 h all inhibitors caused a decrease in amount of [14C]acetate incorporated into both nonsaponifiable lipids and digitonin precipitable sterols. Although dex inhibited cholesterol
biosynthesis, total cellular cholesterol was unaffected by dex treatment after 24 h incubation. It is suggested that in addition
to suppressing mevalonate synthesis, 25-OH, and by analogy dex, may act at some metabolic site(s) distal to the formation
of mevalonate.
This investigation was supported, in part, by a Public Health Service Research grant (CA-08315) from the National Cancer Institute,
Bethesda, MD. 相似文献
18.
William J. DeVito Crystal Avakian Scott Stone William C. Okulicz 《Journal of neurochemistry》1993,60(3):835-842
Abstract: Prolactin (PRL) has been reported to activate cellular proliferation in nonreproductive tissue, such as liver, spleen, and thymus. Recently, we have extended the possible role of PRL as a mammalian mitogen by demonstrating a mitogenic effect of PRL in cultured astrocytes. Although the cellular mechanisms by which PRL regulates cell growth are not fully understood, protein kinase C (PKC) has been implicated as one of the transmembrane signaling systems involved in the regulation of PRL-induced cell proliferation in Nb2 lymphoma cells and liver. In the present studies, we examined the possible role of PKC in PRL-induced proliferation of cultured astrocytes. Incubation of cultured astrocytes with 1 nM PRL resulted in a rapid translocation of PKC from the cytosol to the membrane, with maximal PKC activity in the membrane occurring 30 min after exposure to PRL. Translocation of PKC activity occurred over a physiological range of PRL, with maximal PKC activation occurring at 1 nM. At concentrations greater than 10 nM PRL, there was a decrease in the amount of PKC activity associated with the membrane fraction compared with that of cells stimulated with 1 nM PRL. Incubation of astrocytes with PRL in the presence of the PKC inhibitors staurosporine, 1-(-5-isoquinolinesulfonyl)-2-methylpiperazine, or polymyxin B blocked the PRL-induced increase in cell number with IC50 values of approximately 2 nM, 10 μM, and 6 μM, respectively. PKC is the only known cellular receptor for 12-O-tetradecanoylphorbol 13-acetate (TPA), which stimulates the translocation of PKC from the cytosol to the membrane. Incubation of astrocytes with 20 nM TPA resulted in an increase in the expression of proliferating cell nuclear antigen and cell number, whereas 4α-phorbol 12,13-didecanoate, an inactive phorbol ester, was ineffective. To examine further the effect of TPA and PRL on cellular proliferation, cultured astrocytes were incubated with increasing concentrations of TPA in the presence or absence of a minimal effective dose of PRL (100 pM). In the absence of PRL, incubation with TPA resulted in an inverted U-shaped dose-response curve, with 100 nM TPA resulting in a maximal increase in cell number. In the presence of 100 pM PRL, the TPA dose-response curve was shifted to the left, with maximal activity occurring with 10 nM TPA. Chronic stimulation of astrocytes with 500 nM TPA depleted the cells of PKC and blocked the PRL-induced increase in cell number. Finally, TPA treatment decreased cell-surface binding of 125I-PRL. These data indicate that the PKC is involved in the mitogenic effect of PRL in cultured astrocytes. 相似文献
19.
《Genesis (New York, N.Y. : 2000)》2000,27(3):136-136
"Mesenchymal-Epithelial Transition in the Developing Metanephric Kidney: Gene Expression Study by Differential Display," by Sergei Y. Plisov, Sergey V. Ivanov, Kiyoshi Yoshino, Lee F. Dove, Tatiana M. Plisova, Kathleen G. Higinbotham, Irina Karavanova, Michael Lerman, and Alan O. Perantoni The above article originally appeared in Volume 27, Number 1, the May 2000 issue, of genesis on pp. 22-31. The wrong affiliations were listed for two of the co-authors: Sergey V. Ivanov is affiliated with Intramural Research Support Program, SAIC-Frederick, Laboratory of Immunobiology, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland. Michael Lerman is affiliated with Laboratory of Immunobiology, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland. On page 24, left column, under "In situ mRNA Hybridization" in the "Results" section, the sentence, "To verify the results of DD and to determine in which cells of the developing kidney the differentially displayed genes were expressed we applied mRNA hybridization (ISH)," should read: "To verify the results of DD and to determine in which cells of the developing kidney the differentially displayed genes were expressed we applied in situ mRNA hybridization (ISH)." On page 27, the legend for Figure 2, should read: "In situ RNA hybridization with thin sections of 19 dpc fetal kidney. Labeled antisense RNA was in vitro transcribed from cloned cDNA fragments obtained after differential display." On page 30, right column, under "In situ Hybridization" in the "Methods" section, the sentence, "To generate sense or antisense probes, 5 &mgr;g of plasmids with cloned cDNA fragments were linearized either with NcoI or SpeI (Promega) restriction enzymes and transcribed with T7 or SP6 RNA polymerase in the presence of alpha-35S-dCTP," should read: "To generate sense or antisense probes, 5 &mgr;g of plasmids with cloned cDNA fragments were linearized either with NcoI or SpeI (Promega) restriction enzymes and transcribed with T7 or SP6 RNA polymerase in the presence of alpha-35S-CTP." The authors regret these errors. 相似文献
20.
Activation of latent Epstein-Barr virus genomes: selective stimulation of synthesis of chromosomal proteins by a tumor promoter. 总被引:6,自引:5,他引:1
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The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) is a potent inducer of Epstein-Barr virus (EBV) gene expression. The optimal conditions for maximum activation of latent EBV genomes by TPA were determined. Although TPA is able to induce replication of EBV genomes in P3HR-1 cells in all phases of growth, the greatest increase in viral genome copies per cell (15-fold above the control level) occurred in nonproliferating cells as opposed to cells growing exponentially (6-fold above the control level). The synthesis of chromosomal proteins in nonproliferating cells under the conditions that induce maximum activation of latent virus genomes by TPA was studied. Selective stimulation in chromosomal protein synthesis accompanied the increase in EBV genomes in P3HR-1 cells despite an overall reduction in total cellular protein synthesis. Comparison of the chromosomal proteins from TPA-induced P3HR-1 cells and from superinfected Raji cells revealed comigrating chromosomal polypeptides of 145K, 140K, 135K, 110K, 85K, and 55K that are presumably EBV associated. The selective stimulation of synthesis of these chromosomal proteins in TPA-treated P3HR-1 cells was closely associated with the activation of latent EBV genomes. 相似文献