scholarly journals Identification of AtENT3 as the main transporter for uridine uptake in Arabidopsis roots

Cell Research ◽  
2006 ◽  
Vol 16 (4) ◽  
pp. 377-388 ◽  
Author(s):  
Kun Ling Chen ◽  
Min Xin Xu ◽  
Guang Yong Li ◽  
Hui Liang ◽  
Zong Liang Xia ◽  
...  
Keyword(s):  
Uridine Uptake

Stimulierung von Kulturen embryonaler Rattenzellen durch Kälberserum, III / Stimulation of Embryonic Rat Cells in Culture by Calf Serum, III

1972 ◽  
Vol 27 (11) ◽  
pp. 1399-1404 ◽  
Author(s):  
Michael Humpel ◽  
Werner Frank
Keyword(s):  
Rna Synthesis ◽  
De Novo ◽  
Calf Serum ◽  
Serum Free Medium ◽  
Free Medium ◽  
Serum Free ◽  
Uridine Uptake ◽  
Insoluble Material ◽  
Turn Over ◽  
Precursor Molecules

Embryonic rat cells which have been stopped in G1-phase of their cell cycle by incubation in serum-free medium can be triggered by the addition of calf serum.Expamination of uridine uptake and RNA synthesis after stimulation gave the following results:1) Uridine uptake into the acid soluble pool is increased within a few minutes.2) 2 hours after the addition of serum cells incorporate twice as much 3H-uridine into the acid insoluble material as do cells in serum-free medium; this is not the result of a higher rate of RNA synthesis but is due to an increased uridine uptake.As demonstrated by isolation of RNA and electrophoresis in polyacrylamide gels a significant de novo synthesis can be detected 4 hours after stimulation. Sedimentation coefficients of these RNA species are between 28S and 18S, and 18S and 4/5S, resp.; they turn over quite rapidly as was demonstrated by chase experiments.3) When cells are grown for 2 hours in medium containing 3H-uridine, little label can be detected in the ribosomal 18S- and 28S-RNA. Radioaktivity in these species is, however, strongly increased after another incubation period of 2 hours in culture medium without 3H-uridine. This indicates that precursor molecules ars synthetized and subsequently degrated into 28S- and 18S-rRNA.

Transport characteristics of renal brush border Na(+)- and K(+)-dependent uridine carriers

1990 ◽  
Vol 258 (5) ◽  
pp. F1203-F1210 ◽  
Author(s):  
C. W. Lee ◽  
C. I. Cheeseman ◽  
S. M. Jarvis
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Positive Charge ◽  
Membrane Vesicles ◽  
Transport Processes ◽  
Transport Systems ◽  
Uridine Uptake ◽  
Renal Brush Border Membrane ◽  
Coupling Stoichiometry ◽  
Renal Brush Border

The uptake of uridine into rat renal brush-border membrane vesicles is mediated by Na(+)- and K(+)-dependent concentrative transport processes. At a 100 mM extravesicular cation concentration the apparent Km values were 9.7 +/- 4.2 and 28 +/- 5 microM, and Vmax values were 28 +/- 4 and 7 +/- 1 pmol.mg protein-1.s-1 for the Na(+)- and K(+)-dependent systems, respectively. Uracil, D-ribose, and D-glucose failed to inhibit the uptake processes, indicating that these carriers are specific for nucleosides. Other purines and pyrimidines inhibited uridine uptake competitively, although these two transport systems seem to favor adenosine and pyrimidines as permeants. Evidence is also given that transport is rheogenic, involving a net transfer of positive charge. The Na+:uridine and K+:uridine coupling stoichiometry was found to be 1:1 and 3:2, respectively. Both systems can also be driven by an anion gradient with apparent NO3- affinity (KNO3-) values of 42 +/- 13 and 163 +/- 54 mM for Na(+)- and K(+)-dependent systems, respectively.

scholarly journals Nucleoside uptake in rat liver parenchymal cells

1996 ◽  
Vol 317 (3) ◽  
pp. 835-842 ◽  
Author(s):  
Joan MERCADER ◽  
Mireia GOMEZ-ANGELATS ◽  
Belén del SANTO ◽  
Javier CASADO ◽  
Antonio F. FELIPE ◽  
...  
Keyword(s):  
Rat Liver ◽  
Nucleoside Transport ◽  
Transport Systems ◽  
Dependent Manner ◽  
Transport Activity ◽  
Liver Parenchymal ◽  
Uridine Uptake ◽  
High Concentrations ◽  
Parenchymal Cells ◽  
Dose Dependent

Rat liver parenchymal cells express Na+-dependent and Na+-independent nucleoside transport activity. The Na+-dependent component shows kinetic properties and substrate specificity similar to those reported for plasma membrane vesicles [Ruiz-Montasell, Casado, Felipe and Pastor-Anglada (1992) J. Membr. Biol. 128, 227–233]. This transport activity shows apparent Km values for uridine in the range 8–13 μM and a Vmax of 246 pmol of uridine per 3 min per 106 cells. Most nucleosides, including the analogue formycin B, cis-inhibit Na+-dependent uridine transport, although thymidine and cytidine are poor inhibitors. Inosine and adenosine inhibit Na+-dependent uridine uptake in a dose-dependent manner, reaching total inhibition. Guanosine also inhibits Na+-dependent uridine uptake, although there is some residual transport activity (35% of the control values) that is resistant to high concentrations of guanosine but may be inhibited by low concentrations of adenosine. The transport activity that is inhibited by high concentrations of thymidine is similar to the guanosine-resistant fraction. These observations are consistent with the presence of at least two Na+-dependent transport systems. Na+-dependent uridine uptake is sensitive to N-ethylmaleimide treatment, but Na+-independent transport is not. Nitrobenzylthioinosine (NBTI) stimulates Na+-dependent uridine uptake. The NBTI effect involves a change in Vmax, it is rapid, dose-dependent, does not need preincubation and can be abolished by depleting the Na+ transmembrane electrochemical gradient. Na+-independent uridine transport seems to be insensitive to NBTI. Under the same experimental conditions, NBTI effectively blocks most of the Na+-independent uridine uptake in hepatoma cells. Thus the stimulatory effect of NBTI on the concentrative nucleoside transporter of liver parenchymal cells cannot be explained by inhibition of nucleoside efflux.

THE INCORPORATION OF TRITIATED URIDINE IN THE UTERUS AND VAGINA OF THE MOUSE DURING EARLY PREGNANCY

1968 ◽  
Vol 41 (2) ◽  
pp. 189-195 ◽  
Author(s):  
B. G. MILLER ◽  
W. H. OWEN ◽  
C. W. EMMENS
Keyword(s):  
Early Pregnancy ◽  
Ovarian Stimulation ◽  
Pregnant Mouse ◽  
Uridine Uptake ◽  
Pregnant Mice ◽  
Stimulation Of

SUMMARY In the uterus of pregnant mice an increase in uptake of tritiated uridine occurs between days 2 and 3 of pregnancy, followed by a further increase from day 4 onwards. Uridine uptake changes in the same manner in pseudopregnant mice up to day 4, but thereafter declines to a minimum at day 6. The non-pregnant horn of the unilaterally pregnant mouse shows the same changes as the uterus of the pseudopregnant mouse. The results suggest that implantation occurs during a period of declining ovarian stimulation of the uterus and that the increased uptake of uridine in pregnant mice is stimulated locally by implantation.

Effects of ACTH on RNA synthesis and migration in the adrenal cortex cells of the young rat, as shown by radioautography

1986 ◽  
Vol 112 (1) ◽  
pp. 114-121 ◽  
Author(s):  
Maria C. Magalhães ◽  
A. Bonito Vitor ◽  
M. M. Magalhães
Keyword(s):  
Rna Synthesis ◽  
Zona Fasciculata ◽  
Short Term ◽  
Time Intervals ◽  
Uridine Uptake ◽  
Young Rat ◽  
And Migration ◽  
And Control ◽  
Adrenal Zona Fasciculata ◽  
Rna Formation

Abstract. The effect of ACTH on the RNA synthesis in adrenal zona fasciculata cells of the young rat were studied by light and electron microscope radioautography. Two units of ACTH were administered sc to animals and immediately followed by an iv injection of [3H]uridine. ACTH-injected and control rats, which received the isotope alone, were sacrificed at various time intervals. Labelling over extranucleolar areas was higher in the ACTH-treated animals at 20 min, then becoming lower than in the controls at 60 min and 24 h. Nucleolar radioactivity, however, was consistently decreased by ACTH at all experimental times. Apart from these changes in the rate of synthesis, the over-all curves of labelling were similar to those in the control animals with a striking peak at 1 h. The short-term increase in extranucleolar RNA synthesis observed after ACTH injection was considered to be consistent with the hypothesis that an enhanced extranucleolar synthesis of mRNA takes place early in stimulated animals and is associated with the synthesis of steroidogenic proteins. On the other hand, the relatively decreased uridine uptake of the label by the nucleolus in ACTH-treated animals, suggests an inhibition of nucleolar transcription with diminished pre-rRNA formation in treated animals.

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