scholarly journals Progesterone and the metabolic control of the lactose biosynthetic pathway during lactogenesis in the rat

1973 ◽  
Vol 136 (4) ◽  
pp. 1105-1116 ◽  
Author(s):  
Gillian Murphy ◽  
Ari D. Ariyanayagam ◽  
N. J. Kuhn
Keyword(s):  
Adenine Nucleotide ◽  
Equilibrium Constants ◽  
Energy Charge ◽  
Mass Action ◽  
Mammary Tissue ◽  
Protein Activity ◽  
Pregnant Rats ◽  
Metabolic Intermediates ◽  
Lactose Synthesis ◽  
Glucose 6 Phosphate Dehydrogenase

1. Lactogenesis was initiated in pregnant rats by ovariectomy, thereby causing progesterone withdrawal, after which the mammary tissue was analysed for contents of enzymes and metabolites concerned with the biosynthesis of lactose. 2. Lactose synthesis increased about 126-fold with little or no accompanying change in the contents of most metabolic intermediates or in the adenine nucleotide energy charge. 3. Comparison of mass-action ratios with equilibrium constants showed that phosphoglucomutase (EC 2.7.5.1), UDP-glucose pyrophosphorylase (EC 2.7.7.9) and UDP-glucose epimerase (EC 5.1.3.2.) catalysed reactions close to equilibrium. Nucleoside diphosphokinase (EC 2.7.4.6.) activity was very high and probably equilibrates the UTP–UDP and ATP–ADP couples. Lactose synthetase and hexokinase (EC 2.7.1.1) appeared to catalyse rate-limiting reactions. 4. Large increases were seen of UDP-glucose pyrophosphorylase (5-fold), lactose synthetase A protein (3.8-fold) and α-lactalbumin (28-fold), but not of hexokinase, phosphoglucomutase, UDP-glucose epimerase, nucleoside diphosphokinase or glucose 6-phosphate dehydrogenase (EC 1.1.1.49) activities. 5. It appeared that the increased lactose synthesis was largely accounted for by the increased lactose synthetase A protein activity and α-lactalbumin.

scholarly journals Calmodulin content of rat mammary tissue and isolated cells during pregnancy and lactation

1984 ◽  
Vol 219 (3) ◽  
pp. 927-934 ◽  
Author(s):  
T L Riss ◽  
P J Bechtel ◽  
C R Baumrucker
Keyword(s):  
Marked Change ◽  
Myoepithelial Cells ◽  
Mammary Tissue ◽  
Secretory Cells ◽  
Isolated Cells ◽  
Pregnant Rats ◽  
Heat Treated ◽  
Pregnancy And Lactation ◽  
Cell Fractions ◽  
Glucose 6 Phosphate Dehydrogenase

The calmodulin content of heat-treated extracts of rat mammary tissue and isolated cells was measured by using stimulation of cyclic nucleotide phosphodiesterase (PDE) activity and radioimmunoassay (r.i.a.) procedures. The calmodulin content of mammary tissue increased 2.5-fold near the time of parturition, remained at the elevated level during lactation, then, after the onset of involution, decreased to values similar to those measured from mammary tissue of pregnant rats. When tissue from 15 animals in different stages of pregnancy, lactation and involution were compared, the r.i.a. gave 2.6-fold higher results than the PDE assay. To investigate further the increase in calmodulin content of mammary tissue, secretory and myoepithelial cells were enzymically dissociated from rat mammary tissue during different stages of pregnancy, lactation and involution. Protein, DNA, lactose, glucose-6-phosphate dehydrogenase and alkaline phosphatase were assayed to characterize the cell fractions. By using r.i.a., the calmodulin content per mg of protein in isolated secretory-cell fractions was high near parturition, then decreased and remained relatively constant during lactation. The amount of calmodulin expressed per mg of DNA in secretory cells did not show a marked change near parturition, suggesting a constant amount of calmodulin per cell. The calmodulin content of myoepithelial cells dissociated from mammary tissue and measured by using r.i.a. was 6-fold lower than in secretory cells and remained relatively constant during the course of lactation. The changing levels of calmodulin in rat mammary tissue during development are suggested to be related to proliferation and destruction of secretory epithelial cells, events that occur near parturition and involution respectively.

Effects of oxygen and nitrate on ammonium uptake kinetics and adenylate pools in Phalaris arundinacea L. and Glyceria maxima (Hartm.) Holmb

1994 ◽  
Vol 102 ◽  
pp. 333-342 ◽  
Author(s):  
H. Brix ◽  
B. Lorenzen ◽  
J. T. Morris ◽  
H.-H. Schierup ◽  
B. K. Sorrell
Keyword(s):  
Adenine Nucleotide ◽  
Block Design ◽  
Energy Charge ◽  
Estimation Procedure ◽  
Dry Weight ◽  
Phalaris Arundinacea ◽  
Uptake Kinetics ◽  
Charge Ratio ◽  
Ammonium Uptake ◽  
Root Dry Weight

SynopsisWe studied the effects of oxygen (aerated versus O2 depleted ∼0.5 mg 1−1 O2) and nitrate (none versus 10 μmol 1−1) on the ammonium uptake kinetics and adenylate pools in two wetland plants differing in their degree of flood tolerance (Phalaris arundinacea L. and Glyceria maxima (Hartm.) Holmb.). The study was performed as a random block design in a growth chamber. The -uptake kinetics were estimated by using a computerised nonlinear parameter estimation procedure to fit the differential form of a modified Michaelis–Menten model to solution depletion curves. The uptake kinetics for differed between the two species: Vmax was significantly higher for P. arundinacea (24.7 to 29.6 μmol h−1 g−1 root dry weight) than for G. maxima (4.6–10.3 μmol h−1 g−1 root dry weight). The concentration at which uptake ceases (Cmin) was 0.2 to 0.5 μmol 1−1 for P. arundinacea and significant higher (1.1–2.7 μmol 1−1) for G. maxima.Km varied between 3.1 and 6.2 μmol 1−1 for P. arundinacea, and 1.6 and 3.0 μmol 1−1 for G. maxima. The different uptake kinetics of the two species reflect the different structure of their root systems: P. arundinacea has an extensive root system consisting of many thin roots whereas G. maxima has fewer but thicker roots. The uptake kinetics also suggest that P. arundinacea is adapted to growing at lower ambient concentrations than G. maxima. Oxygen had no consistent effect on uptake kinetics. However, the plants that had in the nutrient solution as well as had slightly higher Vmax values and lower Cmin and Km values than those without . Thus, both species were able to sustain their uptake characteristics at low external O2 concentrations, probably because of internal aeration through the air-space tissue of the plants. Nitrate deprivation also lowered the energy charge ratio and adenine nucleotide content in roots. The roots recovered quickly from deprivation once was resupplied. The stresses imposed by partially O2-depleted conditions and lack of nitrate were therefore relatively mild and reversible. It seems that the inherent aerenchyma development under aerated conditions in these species is sufficient to maintain adequate root oxygenation under partially O2-depleted conditions.

scholarly journals Labeling of the releasable adenine nucleotides of washed human platelets

Blood ◽  
1977 ◽  
Vol 49 (1) ◽  
pp. 89-99 ◽  
Author(s):  
HJ Reimers ◽  
MA Packham ◽  
JF Mustard
Keyword(s):  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Human Platelets ◽  
Transport Processes ◽  
Adenylate Energy Charge ◽  
Prolonged Incubation ◽  
Atp Pool ◽  
Adenine Nucleotide Pool

Abstract In rabbit platelets, the metabolically active ATP pool equilibrates with the releasable ATP pool within 1 day. The studies showing this have now been extended to human platelets. Human platelets labeled with 14C-adenosine or 14C-adenine were incubated for up to 10 hr in vitro at 37 degrees C. After 10 hr, about 12% of the total platelet 14C-ATP and 14C-ADP had become releasable with thrombin (4.2 units/ml). Lysis of platelets did not occur, since less than 1% of the platelet-bound 51Cr from platelets labeled with this radioisotope appeared in the ambient fluid upon thrombin treatment. The 14C-ATP/14C-ADP ratio of the released adenine nucleotides (7.6) was similar to the 14C-ATP/14C-ADP ratio of the nonreleasable adenine nucleotides (7.1) 2 hr after the labeling with 14C-adenosine. However, upon prolonged incubation (10 hr) in vitro, the 14C-ATP/14C-ADP ratio of the releasable adenine nucleotides decreased to 2.7. The adenylate energy charge and the 14C- ATP/14C-ADP ratio of the metabolic adenine nucleotide pool did not change significantly during the time of observation. The 14C-ATP content of the platelets decreased by less than 1% hr of incubation at 37 degrees C. These observations are interpreted to mean that the 14C is transferred from the metabolically active, nonreleasable adenine nucleotide pool of human platelets into the releasable adenine nucleotide pool as ATP and is partially hydrolyzed there to yield ADP. The transfer of ATP across the storage organelle membrane of platelets may be similar to transport processes in the chromaffin cells of the adrenal medulla and may represent a general phenomenon in cells that possess storage organelles containing adenine nucleotides.

Glucose-6-phosphate dehydrogenase from Neisseria gonorrhoeae: partial characterization of the enzyme and inhibition by long-chain fatty acid acyl-coenzyme A derivatives

1980 ◽  
Vol 26 (8) ◽  
pp. 863-873 ◽  
Author(s):  
Anthony F. Cacciapuoti ◽  
Stephen A. Morse
Keyword(s):  
Fatty Acid ◽  
Neisseria Gonorrhoeae ◽  
Coenzyme A ◽  
Energy Charge ◽  
Chain Fatty Acid ◽  
Adenylate Energy Charge ◽  
Long Chain Fatty Acid ◽  
Acyl Coenzyme A ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Long Chain

The glucose-6-phosphate dehydrogenase from Neisseria gonorrhoeae was inhibited by long-chain fatty acid acyl-coenzyme A derivatives. The inhibition was increased at low concentrations of glucose 6-phosphate and was greater with the NAD-linked activity (ca. 0.05 mM inhibitor required for 50% inhibition) than with the NADP-linked activity (ca. 0.2 mM required for 50% inhibition). Bovine serum albumin and spermine could prevent the inhibition by the acyl-coenzyme A derivatives, but neither of these compounds nor high concentrations of cofactors or substrate could reverse the effect. Dilution of enzyme–inhibitor preincubation mixtures appeared to reverse the inhibition. The inhibition by stearoyl-coenzyme A was of the mixed type, and the inhibitor appeared to have a greater affinity for the free enzyme (Ki = 0.016–0.05 mM) than for enzyme bound to cofactor or substrate (Kis = 0.07–0.08 mM). Glucose-6-phosphate dehydrogenase activity was also inhibited competitively by adenosine 5′-triphosphate and was strongly regulated by adenylate energy charge values between 0.9 and 1.0. Kinetic and other characteristics of the enzyme are presented, and the possible role of glucose-6-phosphate dehydrogenase as a target for fatty acid toxicity in gonococci, mediated in the form of the acyl-coenzyme A derivatives, is discussed.

Energy status of the rat lung after exposure to elevated PO2

1978 ◽  
Vol 45 (1) ◽  
pp. 56-59 ◽  
Author(s):  
A. B. Fisher
Keyword(s):  
Bovine Serum Albumin ◽  
Bovine Serum ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Rat Lung ◽  
Energy Status ◽  
Hyperoxic Exposure ◽  
Isolated Lung ◽  
Lactate And Pyruvate

To study hyperoxic effects on adenine nucleotide content and lactate and pyruvate production by lungs, rats were exposed to oxygen at 1 ATA for 18, 24, or 48 h or to 4 ATA for 1 h. Subsequently, lungs were removed from rats, placed in an isolated-lung apparatus, ventilated with 5% CO2 in O2, and perfused with Krebs-Ringer bicarbonate medium containing 5.5 mM glucose and 4% bovine serum albumin. Uptake of serotonin from the perfusate was depressed 28% in rats exposed to hyperbaric oxygen compared with unexposed controls. Concentrations of adenine nucleotides, the ATP/ADP ratio, and the “energy charge” were similar in control and oxygen-exposed rats. The production of lactate and the ratio of lactate to pyruvate production were significantly higher in rats exposed to oxygen for 48 h compared with other exposure regimens. Comparison of these results with those previously reported for serotonin uptake in lungs after hyperoxic exposure indicates that serotonin clearance is depressed prior to alteration of the energy status of the rat lung.

scholarly journals Theoretische Behandlung flüssiger Mischungen mit Hilfe von Gleichgewichtsmodellen. Teil I: Binäre symmetrische Mischungen / Theoretical Treatment of Liquid Mixtures by Means of Equilibrium Models

1972 ◽  
Vol 27 (11) ◽  
pp. 1611-1624
Author(s):  
F. Becker ◽  
M. Kiefer ◽  
P. Rhensius
Keyword(s):  
Molecular Model ◽  
Equilibrium Constants ◽  
Energy Parameter ◽  
Liquid Mixtures ◽  
Mass Action ◽  
Theoretical Treatment ◽  
Excess Functions ◽  
Solution Point ◽  
Self Association ◽  
Point G

Abstract A thermodynamic theory of liquid mixtures based on a simple molecular model is developed which describes the equilibrium state as the result of a coupling between a "chemical" and a "statistical" equilibrium. The intermolecular interactions are taken into account by considering "complexes" formed between a given molecule and its z nearest neighbours. The equilibrium mole fractions of these complexes are calculated by application of the ideal law of mass action to an appropriate set of "exchange equilibria". Formulae for the excess functions GE and HE and for the activities of the components are derived for the cases z=1 and z=4. GE depends on an equilibrium constant K describing the deviation from random distribution of the equilibrium mole fractions of the complexes. HE depends on K and on an energy parameter w which is related to differences of pair interactions. K and w are independent parameters, and there is no limitation in respect to amount and sign of the excess functions. The conditions for the existence of a critical solution point are formulated; at this point GE has a value of about 0.56 R T. If a model with two equilibrium constants is used allowing for instance competition between "self-association" and "complex-formation", the existence of closed miscibility gaps becomes possible. Closed miscibility curves are calculated and the conditions for their appearance are discussed. The relations between this theory and Guggenheim's statistical lattice theory of symmetrical mixtures are pointed out.

Metabolism of adenine nucleotides in the cultured fetal mouse heart

1977 ◽  
Vol 233 (2) ◽  
pp. H282-H288
Author(s):  
I. A. Kaufman ◽  
N. F. Hall ◽  
M. A. DeLuca ◽  
J. S. Ingwall ◽  
S. E. Mayer
Keyword(s):  
Organ Culture ◽  
Adenosine Deaminase ◽  
De Novo ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Mouse Heart ◽  
Nucleotide Synthesis ◽  
Fetal Mouse ◽  
Deprivation Period

Intact beating fetal mouse hearts in organ culture were deprived of oxygen and glucose for up to 4 h, resulting in loss of beating, an 80% fall in ATP, reduction of energy charge from 0.85 to 0.48, and doubling of total nucleoside concentration. Radiolabeled adenine nucleotides were degraded to hypoxanthine and inosine, which were lost from the hearts into the medium during the deprivation period. Adenosine and adenine also appeared in the medium when adenosine deaminase was inhibited. After 24 h of O2 and glucose resupply, ATP returned to 60% of control, and energy charge rose to 0.76. Labeled nucleosides and bases remaining in the heart or exogenous labeled adenine were utilized to resynthesize ATP. [14C]glycine was rapidly taken up by recovering hearts but was not used for de novo adenine nucleotide synthesis. Ability to recover ATP and spontaneous contraction appear related to residual nucleotide and nucleoside content rather than to energy charge.

Adenine nucleotide contents and energy charge of Azotobacter vinelandii grown at low phosphate concentration

1987 ◽  
Vol 147 (4) ◽  
pp. 354-357 ◽  
Author(s):  
T. de la Rubia ◽  
J. Gonzalez-Lopez ◽  
J. Moreno ◽  
M. V. Martinez-Toledo ◽  
A. Ramos-Cormenzana
Keyword(s):  
Azotobacter Vinelandii ◽  
Adenine Nucleotide ◽  
Energy Charge ◽  
Phosphate Concentration
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