16 results on '"V, Beckers"'
Search Results
2. RESPONSE TEMPERATURE MODELING AND ITS POTENTIAL ROLE IN TMDL DEVELOPMENT
- Author
-
Scott Brown, Charles V. Beckers, and Timothy J. Groninger
- Subjects
General Engineering ,Environmental science ,Environmental planning - Published
- 2003
3. Adenine Nucleotides and Inhibition of Protein Synthesis in Isolated Hepatocytes Incubated under Different pO2 Levels
- Author
-
Pedro Buc-Calderon, M. Vansteenbrugge, Marcel Roberfroid, V. Beckers, and Véronique Lefebvre
- Subjects
Male ,Transcription, Genetic ,Cell Survival ,Partial Pressure ,Biophysics ,Cell Separation ,Fructose ,Protein degradation ,Biology ,Biochemistry ,chemistry.chemical_compound ,Adenosine Triphosphate ,Adenine nucleotide ,medicine ,Protein biosynthesis ,Animals ,Amino Acids ,Rats, Wistar ,Hypoxia ,Molecular Biology ,Incubation ,chemistry.chemical_classification ,Adenine Nucleotides ,Biological Transport ,Adenosine Monophosphate ,Rats ,Amino acid ,medicine.anatomical_structure ,Liver ,chemistry ,Protein Biosynthesis ,Hepatocyte ,Leucine - Abstract
Hepatocytes incubated at a pO2 of 0 mm Hg (N2/CO2, 95%/5%) loose their intracellular ATP content and their ability to synthesize RNA and proteins. Protein synthesis is virtually inhibited from the beginning of the incubation, while ATP content is gradually lost, thus suggesting a primary response of the cell to the absence of O2 rather than to ATP depletion. Such an early decrease of protein synthesis (as estimated as the incorporation of [14C]Leu into cell proteins) is unlikely the result of inhibition of amino acids uptake, enhanced protein degradation, or decreased RNA synthesis. Reoxygenation of such previously hypoxic cells with O2/CO2 at 95%/5% (pO2 of 700 mm Hg), leads to the recovery of both ATP and protein synthesis, even better the hypoxic period is not longer than 30 min. In hepatocytes incubated for 30 min under a pO2 of 700, 80, or 50 mm Hg, cell survival and ADP content are almost identical. Incorporation of radiolabelled leucine is linear in cells incubated under 700 mm Hg O2, but it rather stops at a pO2 of 80 or 50 mm Hg. The time course of both ATP and GTP content behaves in a similar way: it is fairly constant at a pO2 of 700 mm Hg, but a depletion is initiated after 20 min of incubation at a pO2 of 50 or 80 mm Hg. Finally, incubation of hepatocytes either at 700 or 0 mm Hg O2, in the presence of fructose (10 mM), shows that ATP content is maintained at the same level whatever the pO2 level. AMP content is increased only in cells incubated at 0 mm Hg O2 in the absence of fructose. Incorporation of radiolabelled leucine is stopped in such hypoxic cells incubated or not in the presence of fructose. From these results it appears that the presence or the absence of O2 might represent a turn on/off signal to which hepatocytes respond immediately by important metabolic changes like the inhibition of protein synthesis.
- Published
- 1993
4. [Prolonged treatment with recombined growth hormone improves bone measures: study of body composition in 21 deficient adults on treatment]
- Author
-
V, Beckers, J, Milet, and J J, Legros
- Subjects
Adult ,Male ,Time Factors ,Adolescent ,Bone and Bones ,Hypopituitarism ,Absorptiometry, Photon ,Bone Density ,Humans ,Insulin-Like Growth Factor I ,Child ,Muscle, Skeletal ,Aged ,Hypophysectomy ,Minerals ,Human Growth Hormone ,Infant, Newborn ,Middle Aged ,Water-Electrolyte Balance ,Hormones ,Recombinant Proteins ,Adipose Tissue ,Body Composition ,Drug Evaluation ,Female ,Follow-Up Studies - Abstract
Adult growth hormone deficiency is characterized by changes in body composition: increase in total fat, decrease in lean mass and osteopenia, with a fall in Bone Mineral Content (BMC) and in Bone Mineral density (BMD) leading to a rise in risk of fracture. We have analyzed the changes in body composition in 21 adults treated from 9 to 78 months, by dual X-RAY absorptiometry (DEXA). We've demonstrated a gain in bone mass and density, particularly of axial skeleton; a latence of minimum 12 months has been necessary to objective these changes. The balance of fat and lean mass has been poorly modified by treatment except for the lean mass of the trunk, which is significantly increased. We think that the usual doses of rGH, based on IGF-1 level, are perhaps underestimated.
- Published
- 2002
5. [Clinical case of the month. Value of a pentagastrin test in the early detection of thyroid medullary cancer]
- Author
-
J J, Legros, V, Beckers, J, Milet, D, Denis, and C, Innocenti
- Subjects
Calcitonin ,Carcinoma, Medullary ,Humans ,Female ,Pentagastrin ,Thyroid Neoplasms ,Aged ,Carcinoembryonic Antigen - Published
- 1995
6. QUANTITATIVE METHODS FOR PRELIMINARY DESIGN OF WATER QUALITY SURVEILLANCE SYSTEMS
- Author
-
G. Paul Grimsrud, Stanley G. Chamberlain, Charles V. Beckers, and Roger Don Shull
- Subjects
Hydrology ,Measure (data warehouse) ,Systems analysis ,Ecology ,Cost effectiveness ,Environmental science ,Systems design ,Sampling (statistics) ,Water quality ,Earth-Surface Processes ,Water Science and Technology ,Reliability engineering - Abstract
To assure attainment and maintenance of desired water quality levels in our rivers and streams, systematic monitoring must be performed. A preliminary phase of the design of water quality surveillance systems is the specification of sampling frequencies and station locations throughout the basin; that is, the development of an adequate space/time sampling plan. The purpose of this paper is to present some quantitative methods which have been developed to identify candidate sets of sampling frequencies and station locations, and to establish priorities for implementing the different frequencies and locations. These methods are useful in the cost/effectiveness trade-off analyses in surveillance system design, and are based on the surveillance system objective of pollution abatement in which it is desired to detect violations in state-federal water quality standards. A spatial priority measure is developed which is dependent both on the water quality profile in the stream and on the information obtained from monitoring stations located in other reaches. Also, a temporal sampling priority rating is presented which is a measure of the effectiveness of the surveillance system with respect to its ability to detect the violations in the standards. To illustrate the quantitative methods, the procedures are applied to the Wabash River Basin.
- Published
- 1974
7. Location of medial collateral ligament tears: introduction to a magnetic resonance imaging-based classification.
- Author
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von Rehlingen-Prinz F, Krishnan KR, Rilk S, Tomanek F, Goodhart GC, Beckers V, O'Brien R, DiFelice GS, and Mintz DN
- Abstract
Purpose: Despite established tear grade classifications, there is currently no radiological classification for sMCL tear locations. This study aims to establish a magnetic resonance imaging (MRI) tear location classification system for sMCL tears, to enhance understanding and guide treatment decisions by categorizing tear types., Methods: A retrospective search in a single institution's MRI database identified patients with acute, Grade III sMCL tears (< 30 days between injury and MRI) from January to December 2022. Non-acute and partial tears were excluded, and three observers assessed tear types based on the proposed sMCL MRI tear location system: type I (proximal 25%), Ib (proximal femoral bony avulsion), II (midsubstance, 25-75%), III (distal 25%), IIIb (distal tibial bony avulsion), IIIs (Stener-like lesion). The interclass correlation coefficient (ICC) was used to assess interrater and intrarater reliability for continuous data; Fleiss and Cohen's kappa assessed interrater and intrarater reliability for categorical data., Results: MRI scans of thirty patients with diagnosed sMCL injuries (53% female, mean age 37 ± 13 years, range 16-68 years) were included based on inclusion/exclusion criteria. Interrater reliability was excellent (ICC: 0.968, 95% CI, 0.933-0.985), and intrarater reliability was excellent (ICC: 0.938, 95% CI: 0.874-0.970 & 0.900, 95% CI, 0.789-0.952). Type I injuries were most common (60%), followed by type III (33.3%), type II (3.3%), type Ib (3.3%), type IIIb (0.0%), and type IIIs (0.0%)., Conclusion: The presented MRI-based sMCL tear location classification provides a reproducible system for grading high-grade sMCL injuries. We propose that this framework will significantly unify tear location understanding and support more informed treatment decisions., (© 2024. The Author(s), under exclusive licence to International Skeletal Society (ISS).)
- Published
- 2024
- Full Text
- View/download PDF
8. In silico metabolic network analysis of Arabidopsis leaves.
- Author
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Beckers V, Dersch LM, Lotz K, Melzer G, Bläsing OE, Fuchs R, Ehrhardt T, and Wittmann C
- Subjects
- Arabidopsis radiation effects, Darkness, Energy Metabolism radiation effects, Oxidation-Reduction, Photosynthesis radiation effects, Plant Leaves radiation effects, Systems Biology, Arabidopsis metabolism, Computer Simulation, Metabolic Networks and Pathways radiation effects, Plant Leaves metabolism
- Abstract
Background: During the last decades, we face an increasing interest in superior plants to supply growing demands for human and animal nutrition and for the developing bio-based economy. Presently, our limited understanding of their metabolism and its regulation hampers the targeted development of desired plant phenotypes. In this regard, systems biology, in particular the integration of metabolic and regulatory networks, is promising to broaden our knowledge and to further explore the biotechnological potential of plants., Results: The thale cress Arabidopsis thaliana provides an ideal model to understand plant primary metabolism. To obtain insight into its functional properties, we constructed a large-scale metabolic network of the leaf of A. thaliana. It represented 511 reactions with spatial separation into compartments. Systematic analysis of this network, utilizing elementary flux modes, investigates metabolic capabilities of the plant and predicts relevant properties on the systems level: optimum pathway use for maximum growth and flux re-arrangement in response to environmental perturbation. Our computational model indicates that the A. thaliana leaf operates near its theoretical optimum flux state in the light, however, only in a narrow range of photon usage. The simulations further demonstrate that the natural day-night shift requires substantial re-arrangement of pathway flux between compartments: 89 reactions, involving redox and energy metabolism, substantially change the extent of flux, whereas 19 reactions even invert flux direction. The optimum set of anabolic pathways differs between day and night and is partly shifted between compartments. The integration with experimental transcriptome data pinpoints selected transcriptional changes that mediate the diurnal adaptation of the plant and superimpose the flux response., Conclusions: The successful application of predictive modelling in Arabidopsis thaliana can bring systems-biological interpretation of plant systems forward. Using the gained knowledge, metabolic engineering strategies to engage plants as biotechnological factories can be developed.
- Published
- 2016
- Full Text
- View/download PDF
9. Integrated analysis of gene expression and metabolic fluxes in PHA-producing Pseudomonas putida grown on glycerol.
- Author
-
Beckers V, Poblete-Castro I, Tomasch J, and Wittmann C
- Subjects
- Biomass, Carbon metabolism, Isocitrate Dehydrogenase metabolism, Metabolic Flux Analysis, Metabolic Networks and Pathways, Nitrogen metabolism, Pseudomonas putida growth & development, Gene Expression Regulation, Bacterial, Glycerol metabolism, Polyhydroxyalkanoates metabolism, Pseudomonas putida genetics, Pseudomonas putida metabolism, Transcriptome
- Abstract
Background: Given its high surplus and low cost, glycerol has emerged as interesting carbon substrate for the synthesis of value-added chemicals. The soil bacterium Pseudomonas putida KT2440 can use glycerol to synthesize medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHA), a class of biopolymers of industrial interest. Here, glycerol metabolism in P. putida KT2440 was studied on the level of gene expression (transcriptome) and metabolic fluxes (fluxome), using precisely adjusted chemostat cultures, growth kinetics and stoichiometry, to gain a systematic understanding of the underlying metabolic and regulatory network., Results: Glycerol-grown P. putida KT2440 has a maintenance energy requirement [0.039 (mmolglycerol (gCDW h)(-1))] that is about sixteen times lower than that of other bacteria, such as Escherichia coli, which provides a great advantage to use this substrate commercially. The shift from carbon (glycerol) to nitrogen (ammonium) limitation drives the modulation of specific genes involved in glycerol metabolism, transport electron chain, sensors to assess the energy level of the cell, and PHA synthesis, as well as changes in flux distribution to increase the precursor availability for PHA synthesis (Entner-Doudoroff pathway and pyruvate metabolism) and to reduce respiration (glyoxylate shunt). Under PHA-producing conditions (N-limitation), a higher PHA yield was achieved at low dilution rate (29.7 wt% of CDW) as compared to a high rate (12.8 wt% of CDW). By-product formation (succinate, malate) was specifically modulated under these regimes. On top of experimental data, elementary flux mode analysis revealed the metabolic potential of P. putida KT2440 to synthesize PHA and identified metabolic engineering targets towards improved production performance on glycerol., Conclusion: This study revealed the complex interplay of gene expression levels and metabolic fluxes under PHA- and non-PHA producing conditions using the attractive raw material glycerol as carbon substrate. This knowledge will form the basis for the development of future metabolically engineered hyper-PHA-producing strains derived from the versatile bacterium P. putida KT2440.
- Published
- 2016
- Full Text
- View/download PDF
10. Novel Approach for High-Throughput Metabolic Screening of Whole Plants by Stable Isotopes.
- Author
-
Dersch LM, Beckers V, Rasch D, Melzer G, Bolten C, Kiep K, Becker H, Bläsing OE, Fuchs R, Ehrhardt T, and Wittmann C
- Subjects
- Amino Acids metabolism, Amino Acids, Branched-Chain drug effects, Amino Acids, Branched-Chain metabolism, Carbon chemistry, Carbon metabolism, Carbon Dioxide chemistry, Carbon Isotopes chemistry, Carbon Isotopes metabolism, Cell Respiration, Chromatography, Gas, Glycolysis, Herbicides pharmacology, Hydroponics methods, Imidazoles pharmacology, Mass Spectrometry, Metabolic Networks and Pathways drug effects, Metabolic Networks and Pathways physiology, Metabolomics, Niacin analogs & derivatives, Niacin pharmacology, Nitrates chemistry, Nitrogen chemistry, Nitrogen metabolism, Nitrogen Isotopes chemistry, Nitrogen Isotopes metabolism, Oryza drug effects, Oryza growth & development, Pentose Phosphate Pathway, Plant Leaves metabolism, Plant Proteins analysis, Plant Proteins metabolism, Plant Roots metabolism, Plant Shoots metabolism, Salts metabolism, Seedlings drug effects, Seedlings metabolism, High-Throughput Screening Assays methods, Isotope Labeling methods, Metabolome, Oryza metabolism, Oryza physiology
- Abstract
Here, we demonstrate whole-plant metabolic profiling by stable isotope labeling and combustion isotope-ratio mass spectrometry for precise quantification of assimilation, translocation, and molecular reallocation of (13)CO2 and (15)NH4NO3 The technology was applied to rice (Oryza sativa) plants at different growth stages. For adult plants, (13)CO2 labeling revealed enhanced carbon assimilation of the flag leaf from flowering to late grain-filling stage, linked to efficient translocation into the panicle. Simultaneous (13)CO2 and (15)NH4NO3 labeling with hydroponically grown seedlings was used to quantify the relative distribution of carbon and nitrogen. Two hours after labeling, assimilated carbon was mainly retained in the shoot (69%), whereas 7% entered the root and 24% was respired. Nitrogen, taken up via the root, was largely translocated into the shoot (85%). Salt-stressed seedlings showed decreased uptake and translocation of nitrogen (69%), whereas carbon metabolism was unaffected. Coupled to a gas chromatograph, labeling analysis provided enrichment of proteinogenic amino acids. This revealed significant protein synthesis in the panicle of adult plants, whereas protein biosynthesis in adult leaves was 8-fold lower than that in seedling shoots. Generally, amino acid enrichment was similar among biosynthetic families and allowed us to infer labeling dynamics of their precursors. On this basis, early and strong (13)C enrichment of Embden-Meyerhof-Parnas pathway and pentose phosphate pathway intermediates indicated high activity of these routes. Applied to mode-of-action analysis of herbicides, the approach showed severe disturbance in the synthesis of branched-chain amino acids upon treatment with imazapyr. The established technology displays a breakthrough for quantitative high-throughput plant metabolic phenotyping., (© 2016 American Society of Plant Biologists. All Rights Reserved.)
- Published
- 2016
- Full Text
- View/download PDF
11. Green pathways: Metabolic network analysis of plant systems.
- Author
-
Dersch LM, Beckers V, and Wittmann C
- Subjects
- Computer Simulation, Gene Expression Profiling methods, Green Chemistry Technology methods, Models, Biological, Metabolic Flux Analysis methods, Metabolic Networks and Pathways physiology, Metabolome physiology, Plant Proteins metabolism, Plants metabolism, Signal Transduction physiology
- Abstract
Metabolic engineering of plants with enhanced crop yield and value-added compositional traits is particularly challenging as they probably exhibit the highest metabolic network complexity of all living organisms. Therefore, approaches of plant metabolic network analysis, which can provide systems-level understanding of plant physiology, appear valuable as guidance for plant metabolic engineers. Strongly supported by the sequencing of plant genomes, a number of different experimental and computational methods have emerged in recent years to study plant systems at various levels: from heterotrophic cell cultures to autotrophic entire plants. The present review presents a state-of-the-art toolbox for plant metabolic network analysis. Among the described approaches are different in silico modeling techniques, including flux balance analysis, elementary flux mode analysis and kinetic flux profiling, as well as different variants of experiments with plant systems which use radioactive and stable isotopes to determine in vivo plant metabolic fluxes. The fundamental principles of these techniques, the required data input and the obtained flux information are enriched by technical advices, specific to plants. In addition, pioneering and high-impacting findings of plant metabolic network analysis highlight the potential of the field., (Copyright © 2015 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
12. Prediction of hospitalization duration for acute stroke in Belgium.
- Author
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Beckers V, De Smedt A, Van Hooff RJ, De Raedt S, Van Dyck R, Putman K, De Keyser J, and Brouns R
- Subjects
- Age Factors, Aged, Aged, 80 and over, Belgium epidemiology, Female, Humans, Male, Middle Aged, Odds Ratio, Predictive Value of Tests, Reproducibility of Results, Retrospective Studies, Sensitivity and Specificity, Time Factors, Hospitalization statistics & numerical data, Length of Stay statistics & numerical data, Stroke epidemiology, Stroke therapy
- Abstract
We aim to predict the duration of hospitalization for acute stroke in Belgium by evaluating the external validity of the prolonged length of stay (PLOS) score and by formulating a new prediction score that may be better suited for the Belgian healthcare system. This single-center retrospective study is based on data collected prospectively from the departmental stroke registry. To validate the PLOS score, receiver operating characteristic curves were constructed and Hosmer-Lemeshow tests were implemented. Odds ratios were calculated by models of logistic regression, based on predictors of length of stay (LOS) with significance in univariate analyses, and were translated into a new risk score. C-statistics for prediction of LOS ≥7 days, LOS ≥14 days, and LOS ≥30 days using the PLOS score were in the range of 0.6-0.7. Thrombolytic therapy, mortality, and need for institutionalization had a notable negative influence on the discrimination of the PLOS score. Overall, the PLOS score performed better for prediction of LOS ≥14 days than for LOS ≥7 days and ≥30 days. The Belgian length of stay for stroke (BLOSS) score is proposed as a simplified prediction model based only on the NIHSS score and age. The PLOS score showed moderate value for prediction of hospitalization duration for acute stroke in this Belgian cohort. A prediction model based only on age and stroke severity may be a worthy alternative.
- Published
- 2012
- Full Text
- View/download PDF
13. [Prolonged treatment with recombined growth hormone improves bone measures: study of body composition in 21 deficient adults on treatment].
- Author
-
Beckers V, Milet J, and Legros JJ
- Subjects
- Absorptiometry, Photon, Adipose Tissue drug effects, Adipose Tissue pathology, Adolescent, Adult, Aged, Body Composition drug effects, Bone and Bones chemistry, Bone and Bones pathology, Child, Drug Evaluation, Female, Follow-Up Studies, Hormones blood, Human Growth Hormone administration & dosage, Human Growth Hormone deficiency, Humans, Hypophysectomy adverse effects, Hypopituitarism etiology, Hypopituitarism metabolism, Hypopituitarism pathology, Infant, Newborn, Insulin-Like Growth Factor I analysis, Male, Middle Aged, Minerals analysis, Muscle, Skeletal pathology, Recombinant Proteins administration & dosage, Recombinant Proteins therapeutic use, Time Factors, Water-Electrolyte Balance, Bone Density drug effects, Human Growth Hormone therapeutic use, Hypopituitarism drug therapy
- Abstract
Adult growth hormone deficiency is characterized by changes in body composition: increase in total fat, decrease in lean mass and osteopenia, with a fall in Bone Mineral Content (BMC) and in Bone Mineral density (BMD) leading to a rise in risk of fracture. We have analyzed the changes in body composition in 21 adults treated from 9 to 78 months, by dual X-RAY absorptiometry (DEXA). We've demonstrated a gain in bone mass and density, particularly of axial skeleton; a latence of minimum 12 months has been necessary to objective these changes. The balance of fat and lean mass has been poorly modified by treatment except for the lean mass of the trunk, which is significantly increased. We think that the usual doses of rGH, based on IGF-1 level, are perhaps underestimated.
- Published
- 2001
14. Daytime 50 Hz magnetic field exposure and plasma melatonin and urinary 6-sulfatoxymelatonin concentration profiles in humans.
- Author
-
Crasson M, Beckers V, Pequeux C, Claustrat B, and Legros JJ
- Subjects
- Adult, Circadian Rhythm, Double-Blind Method, Humans, Male, Pineal Gland physiology, Electromagnetic Fields, Melatonin analogs & derivatives, Melatonin blood, Melatonin urine, Pineal Gland radiation effects
- Abstract
Concern about the health effects of extremely low frequency (ELF) magnetic fields (MF) has been raised by epidemiological studies indicating an association between certain cancers and living near power lines or working in high electric field environments. Alterations in pineal function have been proposed as a mechanism through which power-frequency MFs may interact with living organisms. A double blind laboratory study was performed to evaluate daytime exposure effects of 100 microT root mean square (rms) 50 Hz MF. Three head exposure sessions of 30 min each were performed: sham, continuous, and intermittent (15 s on/off cycles) MFs were presented to each subject in early or late afternoon (13:30 or 16:30 hr). Twenty-one healthy male volunteers (20-27 yr old) participated in these 3-weekly experimental conditions. Blood samples were drawn for serum melatonin measurement, hourly at night (from 20:00 to 07:00 hr) under controlled environmental conditions. Urinary excretion of 6-sulfatoxymelatonin (aMT6s), the main melatonin metabolite, was measured for a 17 hr period, by means of urine samples taken at 19:00 hr (14:00-19:00 hr "afternoon period"), 23:00 hr (19:00-23:00 hr "evening period"), and 07:00 hr, day 2 (23:00-07:00 hr day 2 "night-time period"). There were no significant differences in either plasma melatonin or in aMT6s excretion profiles in the three experimental conditions. However, a tendency for a smaller increase of night-time urinary aMT6s after continuous MF exposure was found (P=0.08) particularly in men with the lower excretion rate of aMT6s ("Low Group") (P=0.07). We conclude that this study does not indicate that daytime acute MF exposure influences either melatonin secretion or aMT6s excretion. Inter-individual differences in pineal production of melatonin, however, have to be taken into account in further studies.
- Published
- 2001
- Full Text
- View/download PDF
15. [Clinical case of the month. Value of a pentagastrin test in the early detection of thyroid medullary cancer].
- Author
-
Legros JJ, Beckers V, Milet J, Denis D, and Innocenti C
- Subjects
- Aged, Calcitonin blood, Carcinoembryonic Antigen analysis, Carcinoma, Medullary surgery, Female, Humans, Thyroid Neoplasms surgery, Carcinoma, Medullary diagnosis, Pentagastrin, Thyroid Neoplasms diagnosis
- Published
- 1995
16. Adenine nucleotides and inhibition of protein synthesis in isolated hepatocytes incubated under different pO2 levels.
- Author
-
Lefebvre VH, Van Steenbrugge M, Beckers V, Roberfroid M, and Buc-Calderon P
- Subjects
- Adenosine Monophosphate analysis, Adenosine Triphosphate analysis, Amino Acids metabolism, Animals, Biological Transport, Cell Separation, Cell Survival, Fructose pharmacology, Liver cytology, Male, Partial Pressure, Rats, Rats, Wistar, Transcription, Genetic, Adenine Nucleotides metabolism, Hypoxia metabolism, Liver metabolism, Protein Biosynthesis
- Abstract
Hepatocytes incubated at a pO2 of 0 mm Hg (N2/CO2, 95%/5%) loose their intracellular ATP content and their ability to synthesize RNA and proteins. Protein synthesis is virtually inhibited from the beginning of the incubation, while ATP content is gradually lost, thus suggesting a primary response of the cell to the absence of O2 rather than to ATP depletion. Such an early decrease of protein synthesis (as estimated as the incorporation of [14C]Leu into cell proteins) is unlikely the result of inhibition of amino acids uptake, enhanced protein degradation, or decreased RNA synthesis. Reoxygenation of such previously hypoxic cells with O2/CO2 at 95%/5% (pO2 of 700 mm Hg), leads to the recovery of both ATP and protein synthesis, even better the hypoxic period is not longer than 30 min. In hepatocytes incubated for 30 min under a pO2 of 700, 80, or 50 mm Hg, cell survival and ADP content are almost identical. Incorporation of radiolabelled leucine is linear in cells incubated under 700 mm Hg O2, but it rather stops at a pO2 of 80 or 50 mm Hg. The time course of both ATP and GTP content behaves in a similar way: it is fairly constant at a pO2 of 700 mm Hg, but a depletion is initiated after 20 min of incubation at a pO2 of 50 or 80 mm Hg. Finally, incubation of hepatocytes either at 700 or 0 mm Hg O2, in the presence of fructose (10 mM), shows that ATP content is maintained at the same level whatever the pO2 level. AMP content is increased only in cells incubated at 0 mm Hg O2 in the absence of fructose. Incorporation of radiolabelled leucine is stopped in such hypoxic cells incubated or not in the presence of fructose. From these results it appears that the presence or the absence of O2 might represent a turn on/off signal to which hepatocytes respond immediately by important metabolic changes like the inhibition of protein synthesis.
- Published
- 1993
- Full Text
- View/download PDF
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