scholarly journals Uptake and metabolism of myo-inositol by L1210 leukaemia cells

1988 ◽  
Vol 254 (1) ◽  
pp. 95-100 ◽  
Author(s):  
J D Moyer ◽  
N Malinowski ◽  
E A Napier ◽  
J Strong
Keyword(s):  
Steady State ◽  
De Novo ◽  
Initial Rate ◽  
Geometric Isomer ◽  
Passive Diffusion ◽  
Concentration Addition ◽  
Free Medium ◽  
Extracellular Concentration ◽  
L1210 Cells ◽  
Uptake And Metabolism

The initial rate of uptake of [3H]myo-inositol by L1210 murine leukaemia cells is directly proportional to the extracellular concentration and unaffected by several analogues of myo-inositol even at millimolar concentrations. Scyllitol, a geometric isomer of myo-inositol, partially inhibited the uptake of myo-inositol (40% at 0.1 mM). A portion of the uptake of myo-inositol was not inhibited even at 5 mM-scyllitol. At steady-state the intracellular concentration of [3H]myo-inositol is directly proportional to the extracellular concentration. Addition of myo-inositol to medium does not enhance the growth of L1210 cells; these cells can maintain an extracellular concentration of 20 microM-myo-inositol even when grown in myo-inositol-free medium. Synthesis of myo-inositol from glucose by L1210 cells was demonstrated by use of [13C]glucose and m.s. L1210 cells maintain myo-inositol pools by a combination of synthesis de novo and uptake of exogenous myo-inositol by either passive diffusion or a low affinity carrier.

scholarly journals A steady-state mechanism can account for the properties of inositol 2,4,5-trisphosphate-stimulated Ca2+ release from permeabilized L1210 cells

1993 ◽  
Vol 289 (3) ◽  
pp. 861-866 ◽  
Author(s):  
J W Loomis-Husselbee ◽  
A P Dawson
Keyword(s):  
Steady State ◽  
Small Proportion ◽  
Time Course ◽  
Initial Rate ◽  
Atpase Inhibitor ◽  
Efflux Rate ◽  
Rapid Phase ◽  
L1210 Cells ◽  
Low Concentrations ◽  
Stimulation Of

We have investigated the effects of sub-maximal Ins(2,4,5)P3 concentrations on the Ca2+ permeability of the residual undischarged Ca2+ stores in electroporated or digitonin-permeabilized L1210 cells by measuring Ca(2+)-efflux rate after addition of the ATPase inhibitor thapsigargin. Low concentrations of Ins(2,4,5)P3, causing rapid discharge of a small proportion of the releasable Ca2+, result in a substantial stimulation of Ca2+ efflux after thapsigargin addition. This indicates firstly that in the absence of thapsigargin there must have been a substantial, counterbalancing, increase in rate of Ca2+ pumping, and secondly that the increased Ca2+ permeability is more consistent with a steady state than with a quantal model of Ca2+ release. Similar increases in passive Ca2+ permeability are produced by addition of concentrations of ionomycin which produce equivalent changes in Ca2+ loading to those produced by Ins(2,4,5)P3, although the time course and initial rate of Ca2+ release are very much slower. In the presence of a Ca(2+)-buffering system, the time course of Ca2+ release by Ins(2,4,5)P3 becomes superimposable on that of ionomycin, indicating that the initial rapid phase of Ins(2,4,5)P3-stimulated Ca2+ is at least partially due to positive feedback from extravesicular Ca2+.

Evidence for active H+ secretion by rat alveolar epithelial cells

1989 ◽  
Vol 257 (6) ◽  
pp. L438-L445 ◽  
Author(s):  
R. L. Lubman ◽  
S. I. Danto ◽  
E. D. Crandall
Keyword(s):  
Plasma Membrane ◽  
Steady State ◽  
Epithelial Cells ◽  
Initial Rate ◽  
Alveolar Epithelial Cells ◽  
Metabolic Inhibitor ◽  
Free Medium ◽  
Atpase Inhibitor ◽  
Alveolar Epithelial ◽  
Ethanesulfonic Acid

A plasma membrane proton-translocating adenosinetriphosphatase (ATPase) has been identified in rat alveolar pneumocytes in primary culture using the pH-sensitive fluorescent probe 2',7'-biscarboxyethyl-5,6-carboxyfluorescein. Intracellular pH (pHi) was acutely lowered by NH3 prepulse in HCO3(-)-free medium buffered with 6 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, and its recovery was measured thereafter under control conditions, in the presence of amiloride to inhibit Na(+)-H+ antiport, and in the presence of N-ethylmaleimide (NEM), a plasma membrane H(+)-ATPase inhibitor. Initial rate of pHi recovery was reduced by 67% in the presence of amiloride, 52% in the presence of NEM, and 96% in the presence of both. Recovery was decreased but not abolished in Na(+)-free buffer, was essentially abolished when NEM was present in the absence of Na+, and was also abolished by addition of the metabolic inhibitor KCN in glucose- and Na(+)-free medium. These data suggest that alveolar epithelial cells possess a plasma membrane H(+)-ATPase. In Na(+)-containing buffer at pH 7.4, steady-state pHi was 7.50. This value was unaffected by amiloride but decreased to 7.01 in the presence of NEM, suggesting active H(+)-ATPase and inactive Na(+)-H+ antiport at steady-state pHi. We conclude that this plasma membrane proton-translocating ATPase in alveolar pneumocytes may be an important mechanism contributing to regulation of steady-state pHi, recovery from acute intracellular acidification, and modulation of extracellular alveolar fluid pH.

Divergent effects of intravenous GSH and cysteine on renal and hepatic GSH

1992 ◽  
Vol 263 (2) ◽  
pp. R348-R352 ◽  
Author(s):  
S. Aebi ◽  
B. H. Lauterburg
Keyword(s):  
Steady State ◽  
De Novo ◽  
Feedback Inhibition ◽  
Therapeutic Use ◽  
Steady State Concentration ◽  
De Novo Synthesis ◽  
State Concentration ◽  
Cellular Thiol

There is a growing interest in the therapeutic use of sulfhydryls. To assess the effect of glutathione (GSH) and cysteine on the cellular thiol status, thiols were administered intravenously to rats in doses ranging from 1.67 to 8.35 mmol/kg with and without pretreatment with 4 mmol/kg buthionine-[S,R]-sulfoximine (BSO), an inhibitor of GSH synthesis. One hour after administration of 1.67 mmol/kg GSH, the concentration of GSH rose from 5.2 +/- 1.0 to 8.4 +/- 0.9 mumol/g and from 2.5 +/- 0.5 to 3.7 +/- 0.7 mumol/g in liver and kidneys, respectively. After 8.35 mmol/kg, hepatic GSH did not increase further, but renal GSH rose to 6.7 +/- 1.8 mumol/g. Infusion of cysteine increased hepatic GSH to the same extent as intravenous GSH, but renal GSH did not increase after 1.67 mmol/kg and even significantly decreased to 0.6 +/- 0.2 mumol/g after 8.35 mmol/kg. In the presence of BSO, GSH resulted in a significant increase in renal but not hepatic GSH, suggesting that the kidneys take up intact GSH and indicating that the increment in hepatic GSH was due to de novo synthesis. The present data show that hepatic GSH can be markedly increased in vivo by increasing the supply of cysteine. Measurements of hepatic cysteine indicate that up to a concentration of approximately 0.5 mumol/g cysteine is a key determinant of hepatic GSH, such that the physiological steady-state concentration of GSH in the liver appears to be mainly determined by the availability of cysteine. At higher concentrations GSH does not increase further, possibly due to feedback inhibition of GSH synthesis or increased efflux.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals IL-6: A Potential Role in Cardiac Metabolic Homeostasis

2018 ◽  
Vol 19 (9) ◽  
pp. 2474 ◽  
Author(s):  
Yitao Xu ◽  
Yubin Zhang ◽  
Junmei Ye
Keyword(s):  
Lipid Metabolism ◽  
Neural Development ◽  
Potential Role ◽  
De Novo ◽  
Myocardial Dysfunction ◽  
Current Evidence ◽  
Metabolic Homeostasis ◽  
Cardiac Lipotoxicity ◽  
Working Heart ◽  
Uptake And Metabolism

Interleukin-6 (IL-6) is implicated in multiple biological functions including immunity, neural development, and haematopoiesis. Recently, mounting evidence indicates that IL-6 plays a key role in metabolism, especially lipid metabolic homeostasis. A working heart requires a high and constant energy input which is largely generated by fatty acid (FA) β-oxidation. Under pathological conditions, the precise balance between cardiac FA uptake and metabolism is perturbed so that excessive FA is accumulated, thereby predisposing to myocardial dysfunction (cardiac lipotoxicity). In this review, we summarize the current evidence that suggests the involvement of IL-6 in lipid metabolism. Cardiac metabolic features and consequences of myocardial lipotoxicity are also briefly analyzed. Finally, the roles of IL-6 in cardiac FA uptake (i.e., serum lipid profile and myocardial FA transporters) and FA metabolism (namely, β-oxidation, mitochondrial function, biogenesis, and FA de novo synthesis) are discussed. Overall, understanding how IL-6 transmits signals to affect lipid metabolism in the heart might allow for development of better clinical therapies for obesity-associated cardiac lipotoxicity.

Purine metabolism in Neisseria gonorrhoeae: the requirement for hypoxanthine

1980 ◽  
Vol 26 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Stephen A. Morse ◽  
Lynne Bartenstein
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Growth Medium ◽  
De Novo ◽  
Defined Medium ◽  
Purine Metabolism ◽  
Purine Biosynthesis ◽  
Free Medium ◽  
De Novo Purine Biosynthesis ◽  
Reduced Rate

Strains isolated from disseminated gonococcal infections often require hypoxanthine for growth. The biochemical bases for the requirement for hypoxanthine in strains isolated from both disseminated (Ile−Val−Arg−Hyx−Ura−phenotype) and non-disseminated (Hyx−phenotype) infections were compared. The requirement for hypoxanthine was dependent upon the composition of the growth medium. In a complete defined medium, hypoxanthine was replaced by a mixture of adenine and guanine but not by either purine alone. The addition of adenine alone inhibited gonococcal growth. This inhibition was reversed by the addition of guanine and most likely resulted from an inhibition of de novo purine biosynthesis. In a histidine-free medium, adenine replaced the hypoxanthine requirement in Ile−Val−Arg−Hyx−Ura− strains. Adenine did not replace the hypoxanthine requirement in Hyx− strains. The Ile−Val−Arg−Hyx−Ura− strains exhibited a markedly reduced rate of de novo purine biosynthesis while Hyx− strains were blocked in this pathway. In vivo concentrations of purines are important factors which may limit the intracellular or extracellular growth of these strains.

Uptake and metabolism of circulating fatty acids by rat intestine

1992 ◽  
Vol 263 (6) ◽  
pp. G927-G933 ◽  
Author(s):  
C. M. Mansbach ◽  
R. F. Dowell
Keyword(s):  
Fatty Acids ◽  
Steady State ◽  
Specific Activity ◽  
Femoral Vein ◽  
Tracer Injection ◽  
Previous Hypothesis ◽  
Injection Techniques ◽  
Lymph Duct ◽  
Glyceryl Trioleate ◽  
Uptake And Metabolism

The present study was designed to investigate the uptake and metabolism of circulating fatty acids by the intestinal mucosa in rats actively absorbing glyceryl trioleate given intraduodenally to determine the plasma fatty acid contribution to mucosal triacylglycerol. Rats with duodenal, femoral vein, carotid artery, and mesenteric lymph duct cannulas were used. [3H]oleate was constantly infused into the femoral vein while glyceryl trioleate was infused into the duodenum (135 mumol/h). After 5 h of infusion, a mass and radioactive steady state existed in the plasma and mucosa. At 6 h of infusion, the plasma oleate specific activity was sixfold greater than mucosal oleate and 50 times greater than mucosal triacylglycerol oleate; 86% of the mucosal oleate disintegrations/minute were in triacylglycerol. Chylomicron triacylglycerol oleate specific activity was less than that of the mucosa. Furthermore, the percentage of mucosal triacylglycerol acyl groups composed of oleate was greater than the percentage of oleate in mucosal free fatty acids. The data indicate that fatty acids are taken up by the mucosa during active fat absorption and metabolized primarily to triacylglycerols by the mucosa. The triacylglycerols in the mucosa synthesized from circulating fatty acids are selected against as a precursor of chylomicron triacylglycerol. The results support our previous hypothesis suggesting that the mucosa has at least two pools of neutral lipid (J. Lipid Res. 23: 1009-1019, 1982) and that steady-state conditions as performed here yield different results from previous work using bolus tracer injection techniques.

Kinetics of NO2 air space absorption in isolated rat lungs

1992 ◽  
Vol 73 (5) ◽  
pp. 1939-1945 ◽  
Author(s):  
E. M. Postlethwait ◽  
S. D. Langford ◽  
A. Bidani
Keyword(s):  
Steady State ◽  
Tidal Volume ◽  
Gas Phase ◽  
Initial Rate ◽  
Quasi Steady State ◽  
Closed Chamber ◽  
First Order ◽  
First Order Kinetics ◽  
Rat Lungs ◽  
Kinetics Of

We previously showed, during quasi-steady-state exposures, that the rate of inhaled NO2 uptake displays reaction-mediated characteristics (J. Appl. Physiol. 68: 594–603, 1990). In vitro kinetic studies of pulmonary epithelial lining fluid (ELF) demonstrated that NO2 interfacial transfer into ELF exhibits first-order kinetics with respect to NO2, attains [NO2]-dependent rate saturation, and is aqueous substrate dependent (J. Appl. Physiol. 71: 1502–1510, 1991). We have extended these observations by evaluating the kinetics of NO2 gas phase disappearance in isolated ventilating rat lungs. Transient exposures (2–3/lung at 25 degrees C) employed rebreathing (NO2-air) from a non-compliant continuously stirred closed chamber. We observed that 1) NO2 uptake rate is independent of exposure period, 2) NO2 gas phase disappearance exhibited first-order kinetics [initial rate (r*) saturation occurred when [NO2] > 11 ppm], 3) the mean effective rate constant (k*) for NO2 gas phase disappearance ([NO2] < or = 11 ppm, tidal volume = 2.3 ml, functional residual capacity = 4 ml, ventilation frequency = 50/min) was 83 +/- 5 ml/min, 4) with [NO2] < or = 11 ppm, k* and r* were proportional to tidal volume, and 5) NO2 fractional uptakes were constant across [NO2] (< or = 11 ppm) and tidal volumes but exceeded quasi-steady-state observations. Preliminary data indicate that this divergence may be related to the inspired PCO2. These results suggest that NO2 reactive uptake within rebreathing isolated lungs follows first-order kinetics and displays initial rate saturation, similar to isolated ELF.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

scholarly journals Exploiting the Diversity of Saccharomycotina Yeasts To Engineer Biotin-Independent Growth of Saccharomyces cerevisiae

2020 ◽  
Vol 86 (12) ◽  
Author(s):  
Anna K. Wronska ◽  
Meinske P. Haak ◽  
Ellen Geraats ◽  
Eva Bruins Slot ◽  
Marcel van den Broek ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Large Scale ◽  
De Novo ◽  
Laboratory Strain ◽  
Optimal Growth ◽  
Industrial Applications ◽  
Fast Growth ◽  
Growth Media ◽  
Free Medium ◽  
Content Type

ABSTRACT Biotin, an important cofactor for carboxylases, is essential for all kingdoms of life. Since native biotin synthesis does not always suffice for fast growth and product formation, microbial cultivation in research and industry often requires supplementation of biotin. De novo biotin biosynthesis in yeasts is not fully understood, which hinders attempts to optimize the pathway in these industrially relevant microorganisms. Previous work based on laboratory evolution of Saccharomyces cerevisiae for biotin prototrophy identified Bio1, whose catalytic function remains unresolved, as a bottleneck in biotin synthesis. This study aimed at eliminating this bottleneck in the S. cerevisiae laboratory strain CEN.PK113-7D. A screening of 35 Saccharomycotina yeasts identified six species that grew fast without biotin supplementation. Overexpression of the S. cerevisiae BIO1 (ScBIO1) ortholog isolated from one of these biotin prototrophs, Cyberlindnera fabianii, enabled fast growth of strain CEN.PK113-7D in biotin-free medium. Similar results were obtained by single overexpression of C. fabianii BIO1 (CfBIO1) in other laboratory and industrial S. cerevisiae strains. However, biotin prototrophy was restricted to aerobic conditions, probably reflecting the involvement of oxygen in the reaction catalyzed by the putative oxidoreductase CfBio1. In aerobic cultures on biotin-free medium, S. cerevisiae strains expressing CfBio1 showed a decreased susceptibility to contamination by biotin-auxotrophic S. cerevisiae. This study illustrates how the vast Saccharomycotina genomic resources may be used to improve physiological characteristics of industrially relevant S. cerevisiae. IMPORTANCE The reported metabolic engineering strategy to enable optimal growth in the absence of biotin is of direct relevance for large-scale industrial applications of S. cerevisiae. Important benefits of biotin prototrophy include cost reduction during the preparation of chemically defined industrial growth media as well as a lower susceptibility of biotin-prototrophic strains to contamination by auxotrophic microorganisms. The observed oxygen dependency of biotin synthesis by the engineered strains is relevant for further studies on the elucidation of fungal biotin biosynthesis pathways.

scholarly journals Altered steady state and activity-dependent de novo protein expression in fragile X syndrome

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Heather Bowling ◽  
Aditi Bhattacharya ◽  
Guoan Zhang ◽  
Danyal Alam ◽  
Joseph Z. Lebowitz ◽  
...  
Keyword(s):  
Steady State ◽  
Protein Expression ◽  
Fragile X Syndrome ◽  
De Novo ◽  
Fragile X ◽  
Activity Dependent
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