scholarly journals A method for determination in situ of variations within the hepatic lobule of hepatocyte function and metabolite concentrations

1997 ◽  
Vol 322 (3) ◽  
pp. 951-951
Author(s):  
S. P. BURNS ◽  
R. D. COHEN ◽  
R. A. ILES ◽  
J. P. GERMAIN ◽  
T. C. H. GOING ◽  
...  
Keyword(s):  
Hepatic Lobule ◽  
Metabolite Concentrations

scholarly journals A method for determination in situ of variations within the hepatic lobule of hepatocyte function and metabolite concentrations

1996 ◽  
Vol 319 (2) ◽  
pp. 377-383 ◽  
Author(s):  
Shamus P BURNS ◽  
Robert D. COHEN ◽  
Richard A ILES ◽  
Jocelyn P. GERMAIN ◽  
Thomas C. H. GOING ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
31P Nmr ◽  
Single Cells ◽  
Isolated Hepatocytes ◽  
Metabolite Concentration ◽  
Nmr Studies ◽  
Hepatic Lobule ◽  
Wide Range ◽  
Metabolite Concentrations

A method is described for the production of detailed maps of intralobular variations of hepatocyte function and metabolite concentrations, based on variable destruction by digitonin of the lobule from the centrilobular direction. Instead of the conventional approach, in which isolated hepatocytes are then prepared and studied in suspension, perfusion is continued after digitonin treatment and the function of the unaffected lobular remnants is determined, or mean metabolite concentrations are measured by 31P-NMR. These measurements are plotted against the degree of destruction, determined precisely after each study by automated quantitative histomorphometry. These plots are transformed into curves of the function or metabolite concentration of nominal single cells at any point along the radius of the lobule. Gluconeogenesis from lactate remained stable, although reduced, even after 85–90% lobular destruction, predominated periportally and disappeared by 50% along the radius of the lobule. In 31P-NMR studies, employing 1.5 mM lactate as substrate, narrowing of the intracellular Pi resonance was observed as digitonin destruction increased; this was attributed to a decrease in the intralobular heterogeneity of the intracellular pH, which fell from approx. 7.9 to < 7.4 along the first 16% of the lobular radius (from the periportal end) and to < 7.3 in the remainder of the lobule. The ATP concentration rose, and then fell, along the radius of the lobule in a centripetal direction. The method is potentially generally applicable to a wide range of hepatocellular functions and to the measurement of metabolite concentrations, most conveniently those susceptible to estimation by NMR.

Intracellular diffusion gradients of O2 and ATP

1986 ◽  
Vol 250 (5) ◽  
pp. C663-C675 ◽  
Author(s):  
D. P. Jones
Keyword(s):  
Mathematical Modeling ◽  
High Flux ◽  
Concentration Gradients ◽  
Electron Microscopic ◽  
Intracellular Diffusion ◽  
Metabolite Concentrations ◽  
Major Factors ◽  
Atp Supply ◽  
Endogenous Enzymes

Endogenous enzymes with different subcellular localizations provide in situ probes to study O2 and ATP concentration at various sites within cells. Results from this approach indicate that substantial intracellular concentration gradients occur under some O2- and ATP-limited conditions. These studies, along with electron microscopic analyses and mathematical modeling, indicate that clustering and distribution of mitochondria are major factors in determining the magnitude and location of the concentration gradients. The mitochondria appear to be clustered in sites of high ATP demand to maximize ATP supply under conditions of limited production. The size of such clusters is limited by the magnitude of the O2 gradient needed to provide adequate O2 concentrations for mitochondrial function within the clusters. Thus microheterogeneity of metabolite concentrations can occur in cells without membranal compartmentation and may be important in determining the rates of various high-flux processes.

Hepatic intralobular mapping of fructose metabolism in the rat liver

2000 ◽  
Vol 349 (2) ◽  
pp. 539-545 ◽  
Author(s):  
Shamus P. BURNS ◽  
Helena C. MURPHY ◽  
Richard A. ILES ◽  
Rosemary A. BAILEY ◽  
Robert D. COHEN
Keyword(s):  
31P Nmr ◽  
Direct Conversion ◽  
31P Nmr Spectroscopy ◽  
Lactate Metabolism ◽  
Hepatic Lobule ◽  
Lactate Output ◽  
Lactate Uptake ◽  
Rat Livers ◽  
Substantial Extent

Detailed mapping of glucose and lactate metabolism along the radius of the hepatic lobule was performed in situ in rat livers perfused with 1.5 mM lactate before and during the addition of 5 mM fructose. The majority of fructose uptake occurred in the periportal region; 45% of fructose taken up in the periportal half of the lobular volume being converted into glucose. Periportal lactate uptake was markedly decreased by addition of fructose. Basal perivenous lactate output, which was derived from glucose synthesized periportally, was increased in the presence of fructose. During fructose infusion there was a small decrease in cell pH periportally, but acidification of up to 0.5 pH units perivenously. The evidence suggests that in situ the apparent direct conversion of fructose into lactate represents, to a substantial extent, the result of periportal conversion of fructose into glucose and the subsequent uptake and glycolysis to lactate in the perivenous zone of some of that glucose. 31P NMR spectroscopy showed that the cellular concentration of phosphomonoesters changes very little periportally during fructose infusion, but there was an approximate twofold increase perivenously, presumably due to the accumulation of fructose 1-phosphate. It may be inferred that fructokinase activity is expressed throughout the hepatic lobule.

Differential lobular induction in rat liver of glutathioneS-transferase A1/A2 by phenobarbital

2000 ◽  
Vol 278 (4) ◽  
pp. G542-G550 ◽  
Author(s):  
Niazy Selim ◽  
Gene D. Branum ◽  
Xia Liu ◽  
Richard Whalen ◽  
Thomas D. Boyer
Keyword(s):  
Transcriptional Activity ◽  
Drug Metabolizing Enzymes ◽  
Glutathione S Transferase ◽  
Hepatic Lobule ◽  
Metabolizing Enzymes ◽  
Transcript Levels ◽  
Mrna Transcripts ◽  
Phenobarbital Administration ◽  
Rat Livers

Phenobarbital and other xenobiotics induce drug-metabolizing enzymes, including glutathione S-transferase A1/A2 (rGSTA1/A2). We examined the mechanism of induction of rGSTA1/A2 in rat livers after phenobarbital treatment. The induction of rGSTA1/A2 was not uniform across the hepatic lobule; steady-state transcript levels were threefold higher in perivenous hepatocytes relative to periportal hepatocytes when examined by in situ hybridization 12 h after a single dose of phenobarbital. Administration of a second dose of phenobarbital 12 or 24 h after the first dose did not equalize the induction of rGSTA1/A2 across the lobule. The transcriptional activity of the rGSTA1/A2 gene was increased 3.5- to 5.5-fold in whole liver by phenobarbital, but activities were the same in enriched periportal and perivenous subpopulations of hepatocytes from phenobarbital-treated animals. The half-life of rGSTA1/A2 mRNA in control animals was 3.6 h, whereas it was 10.2 h in phenobarbital-treated animals. We conclude that phenobarbital induces rGSTA1/A2 expression by increasing transcriptional activity across the lobule but induction of rGSTA1/A2 is greater in perivenous hepatocytes due to localized stabilization of mRNA transcripts.

scholarly journals Ischaemia and reperfusion injury of rat liver increases expression of glutathione S-transferase A1/A2 in zone 3 of the hepatic lobule

1998 ◽  
Vol 330 (1) ◽  
pp. 73-79 ◽  
Author(s):  
D. Gene BRANUM ◽  
Niazy SELIM ◽  
Xia LIU ◽  
Richard WHALEN ◽  
D. Thomas BOYER
Keyword(s):  
Reperfusion Injury ◽  
Fold Increase ◽  
Glutathione S Transferase ◽  
Hepatic Lobule ◽  
Ischaemia Reperfusion Injury ◽  
Transcript Levels ◽  
Protein Levels ◽  
Run Off ◽  
Liver Ischaemia

Effects of ischaemia-reperfusion injury (I/R) of liver on expression of rat glutathione S-transferase (rGST) isoenzymes that metabolize products of oxidative stress were examined. Rats underwent lobar liver ischaemia for 30 min followed by reperfusion. In ischaemic lobes, rGSTA1/A2 transcript levels increased significantly 12 h after I/R (2.94-fold) and protein levels increased significantly at 24 h (1.45-fold); increased transcript levels were also observed in nonischaemic lobes (1.78-fold). Superoxide dismutase prevented I/R and the increases in transcript and protein levels in ischaemic and non-ischaemic lobes. By in-situ hybridization, increases in transcript levels at 6 h were present in zones 2 and 3 of the ischaemic lobes and peaked at 12 h (2.5-fold zone 2, 4.5-fold zone 3). Significant increases in transcript levels also were observed at 24 h in zones 2 (2.0-fold) and 3 (2.9-fold) of non-ischaemic lobes. Nuclear run-off assays showed a 1.8-fold increase in rGSTA1/A2 transcription rates in ischaemic lobes at 3 h. We conclude that I/R causes increased rGSTA1/A2 expression in the zone of the hepatic lobule most susceptible to oxidative injury and that this expression may be an important defence against injury.

scholarly journals Generalization of the double-modulation method for in situ determination of elasticities

1997 ◽  
Vol 327 (1) ◽  
pp. 217-223 ◽  
Author(s):  
Luis ACERENZA ◽  
Athel CORNISH-BOWDEN
Keyword(s):  
Steady State ◽  
Modulation Method ◽  
Practical Implementation ◽  
Matrix Formulation ◽  
Metabolic Systems ◽  
Metabolite Concentrations ◽  
Double Modulation

The double-modulation method [Kacser and Burns (1979) Biochem. Soc. Trans. 7, 1149–1160] was the first method proposed for determining elasticities in situ. It is based on measuring changes in steady-state metabolite concentrations and fluxes induced by parameter modulations. It has the important advantage that it is not necessary to know the values of the changes in the parameters. Here we develop a matrix formulation of the double-modulation method that allows it to be applied to metabolic systems of any structure and size. It also shows which parameters need to be modulated and which variables need to be measured in order to calculate the elasticities that correspond to particular rates. Some suggestions for the practical implementation of the method are given, including various ways of testing the reliability of the results.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

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