Improved methods for ATP analysis

Adaptive mechanism of the marine bacterium Pseudomonas sihuiensis-BFB-6S towards pCO2 variation: Insights into synthesis of extracellular polymeric substances and physiochemical modulation

Marine bacteria can adapt to various extreme environments by the production of extracellular polymeric substances (EPS). Throughout this investigation, impact of variable pCO2 levels on the metabolic activity and physiochemical modulation in EPS matrix of marine bacterium Pseudomonas sihuiensis - BFB-6S was evaluated using a fluorescence microscope, excitation-emission matrix (EEM), 2D-Fourier transform infrared correlation spectroscopy (2D-ATR-FTIR-COS), FT-NMR and TGA-DSC. From the results at higher pCO2 levels, there was a substantial reduction in EPS production by 58-62.8 % (DW). In addition to the biochemical composition of EPS, reduction in carbohydrates (8.7-47.6 %), protein (7.1-91.5 %), and lipids (16.9-68.6 %) content were observed at higher pCO2 levels. Functional discrepancies of fluorophores (tyrosine and tryptophan-like) in EPS, speckled differently in response to variable pCO2. The 2D-ATR-FTIR-COS analysis revealed functional amides (CN, CC, CO bending, -NH bending in amines) of EPS were preferentially altered, which led to the domination of polysaccharides relevant functional groups at higher pCO2. 1H NMR analysis of EPS confirmed the absence of chemical signals from H-C-COOH of proteins, α, β anomeric protons, and acetyl group relevant region at higher pCO2 levels. These findings can contribute new insights into the influence of pCO2 on the adaptation of marine microbes in future ocean acidification scenarios.

Responses of intracellular cofactors to single and dual substrate limitations

The highly systematic responses of cellular cofactors to controlled substrate limitations of electron donor, electron acceptor, and both (dual limitation) were quantified using continuous-flow cultures of Pseudomonas putida. The results showed that the NADH concentration in the cells decreased gradually as the specific rate of electron-donor utilization (-q(d)) fell or increased systematically as oxygen limitation became more severe for fixed -q(d), while the NAD concentration was invariant. The NAD(H) responses demonstrated a common strategy; compensation for a low concentration of an externally supplied substrate by increasing (or decreasing) the concentration of its internal cosubstrate (or coproduct). The compensation was dramatic, as the NAD/NADH ratio showed a 24-fold modulation in response to depletion of dissolved oxygen (DO) or acetate. In the dual-limitation region, the compensating effects toward depletion of one substrate were damped, because the other substrate was simultaneously at low concentration. However, the NAD(H) responses minimized the adverse impact from substrate depletion on overall cell metabolism. Cellular contents of ATP, ADP, and P(i) were mostly affected by -q(d), such that the phosphorylation potential, ATP/ADP . P(i), increased as -q(d) fell due to depletion of acetate, DO, or both. Since the respiration rate should be slowed by high ATP/ADP . P(i), the cellular response seems to amplify an unfavorable environmental condition when oxygen is depleted. The likely reason for this apparent disadvantageous response is that the response of phosphorylation potential is more keenly associated with other aspects of metabolic control, such as for synthesis, which requires P(i) for production of phospholipids and nucleotides. (c) 1996 John Wiley & Sons, Inc.

Characterization of Saccharomyces cerevisiae strains expressing ira1 mutant alleles modeled after disease-causing mutations in NF1

The 2818 amino acids of neurofibromin, the product of the human NF1 gene, include a 230 amino acid Ras-GAP related domain (GRD). Functions which may be associated with the rest of the protein remain unknown. However, many NF1 mutations in neurofibromatosis 1 patients are found downstream of the GRD, suggesting that the C-terminal region of the protein is also functionally important. Since the C-terminal region of neurofibromin encompassing these mutations is homologous with the corresponding regions in the two Saccharomyces cerevisiae Ras-GAPs, Ira1p and Ira2p, we chose yeast as a model system for functional exploration of this region (Ira-C region). Three missense mutations that affect the Ira-C region of NF1 were used as a model for the mutagenesis of IRA1. The yeast phenotypes of heat shock sensitivity, iodine staining, sporulation efficiency, pseudohyphae formation, and GAP activity were scored. Even though none of the mutations directly affected the Ira1p-GRD, mutations at two of the three sites resulted in a decrease in the GAP activity present in ira1 cells. The third mutation appeared to disassociate the phenotypes of sporulation ability and GAP activity. This and other evidence suggest an effector function for Ira1p.

A quantitative study of the Ca2+/calmodulin sensitivity of adenylyl cyclase in Aplysia, Drosophila, and rat

Studies in Aplysia and Drosophila have suggested that Ca2+/calmodulin-sensitive adenylyl cyclase may act as a site of convergence for the cellular representations of the conditioned stimulus (Ca2+ influx) and unconditioned stimulus (facilitatory transmitter) during elementary associative learning. This hypothesis predicts that the rise in intracellular free Ca2+ concentration produced by spike activity during the conditioned stimulus will cause an increase in the activity of adenylyl cyclase. However, published values for the Ca2+ sensitivity of Ca2+/calmodulin-sensitive adenylyl cyclase in mammals and in Drosophila vary widely. The difficulty in evaluating whether adenylyl cyclase would be activated by physiological elevations in intracellular Ca2+ levels is in part a consequence of the use of Ca2+/EGTA buffers, which are prone to several types of errors. Using a procedure that minimizes these errors, we have quantified the Ca2+ sensitivity of adenylyl cyclase in membranes from Aplysia, Drosophila, and rat brain with purified species-specific calmodulins. In all three species, adenylyl cyclase was activated by an increase in free Ca2+ concentration in the range caused by spike activity. Ca2+ sensitivity was dependent on both calmodulin concentration and Mg2+ concentration. Mg2+ raised the threshold for adenylyl cyclase activation by Ca2+ but also acted synergistically with Ca2+ to activate maximally adenylyl cyclase.

Separation and inhibitor specificity of a second unidirectional efflux route for methotrexate in L1210 cells

L1210 cells mediate the unidirectional and energy-dependent efflux of methotrexate. Efflux occurs primarily via a system which has a high sensitivity to prostaglandin A1, vincristine, reserpine, verapamil, and bromosulfophthalein, but evidence has also been obtained for a second efflux component with a lower response to these inhibitors. Pretreatment of L1210 cells with low concentrations of vincristine reduces methotrexate efflux by three fold and uncovers a second efflux component with an inhibitor specificity which is distinctly different from the primary efflux route. Vincristine treatment increased by 8-20-fold the concentration required for half-maximal efflux inhibition by prostaglandin A1, reserpine, bromosulfophthalein, and verapamil but had no effect on inhibition by probenecid, quinidine, or carbonylcyanide m-chlorophenylhydrazone. A selective block in the primary efflux system and retention of the second component was also achieved in cells exposed to low concentrations of prostaglandin A1 or bromosulfophthalein. These results support prior conclusions that L1210 cells contain both a primary and secondary unidirectional efflux route for methotrexate. The second system has been difficult to detect and quantitate since it comprises only 25% of total unidirectional efflux and shows a relatively low response to various efflux inhibitors.

Phosphoadenylate concentrations and adenylate energy charge of largemouth bass (Micropterus salmoides): relationship with condition factor and blood cortisol

1. Concentrations of phosphoadenylate nucleotides and adenylate energy charge in the dorsal muscle and blood of largemouth bass from a reservoir receiving heated effluent were investigated. These values were compared with the length, weight, body condition and blood cortisol concentrations. 2. Body condition of the largemouth bass ranged from 1043 to 2544, reflecting the range of condition due to starvation of some fish in the population. 3. Blood cortisol concentrations ranged from 4.0 to 23.1 micrograms/100 ml with a mean of 6.3 micrograms/100 ml. 4. The adenylate energy charge of muscle (MATP) and blood ranged from 0.37 to 0.98 and 0.74 to 0.99, respectively. 5. Blood cortisol concentration was positively correlated with body condition but not correlated with the adenylate energy charge of either blood or muscle. 6. Blood cortisol concentration was negatively correlated with concentration of adenylates in both muscle and blood.

Correct integration of retroviral DNA in vitro

We have developed a cell-free system for studying the integration of retroviral DNA. In our assay, amber mutations in a bacteriophage lambda genome that serves as the target for integration are suppressed by integration of an MLV derivative that carries the E. coli supF gene. The structure of the reaction products is that expected from an authentic MLV integration reaction. Linear viral DNA from the cytoplasm of infected cells serves as a precursor, though not necessarily the immediate precursor, to the provirus integrated in vitro. The viral DNA in the infected cell appears to be tightly associated with the enzymatic machinery required for its integration. Supercoiling, chromatin structure, transcription, and replication are not required of the target DNA. Since no high-energy cofactor is necessary, the DNA breakage and joining steps in the integration reaction are probably coupled.

Inhibitory effects of probenecid on the individual transport routes which mediate the influx and efflux of methotrexate in L1210 cells

L1210 cells contain a single transport system which mediates the influx of methotrexate and at least three routes for drug efflux [G. B. Henderson and E. M. Zevely, J. biol. Chem. 259, 1526 (1984)]; each of these processes is sensitive to probenecid. The influx carrier was inhibited reversibly and completely by probenecid with a Ki of 0.25 mM, while efflux via the same system was relatively unaffected by this compound (50% inhibition above 2.0 mM). The two remaining efflux routes (which do not contribute to methotrexate influx) showed a much higher sensitivity to probenecid. Efflux via these components was reduced half-maximally at probenecid concentrations of 0.08 and 0.22 mM, respectively, and a complete block was achieved with excess amounts (2.0 mM) of the inhibitor. Intracellular levels of ATP, glucose metabolism, and the membrane potential were also reduced by probenecid, indicating that the mechanism for inhibiting methotrexate efflux may involve the ability of probenecid to act as a metabolic inhibitor. Probenecid may have a broad capacity for inhibiting anion transport processes since it also reduced sulfate influx and efflux via the general anion carrier system.

Biocompatibility test procedures for materials evaluation in vitro. II. Objective methods of toxicity assessment

Methods of assessing the biocompatibility of materials for use in medical devices were evaluated. Ten materials were tested using quantitative, objectively graded in vitro biochemical and functional assays employing four cell lines (CCL 1, 74, 76, and 131) used in previous work and five primary cell types (human lymphocytes, polymorphonuclear leukocytes, and mixed leukocytes, mouse macrophages, and mouse embryo). The biochemical methods (DNA synthesis, protein synthesis, and ATP activity) demonstrated good agreement in toxicity ranking of the materials, regardless of which cell culture was used and, also, the cell cultures responded similarly for each method. Methods that measured functional characteristics of cells (adhesion and phagocytosis) were highly sensitive but had low toxicity ranking agreement and reproducibility. Assays (defined as method and cell culture combinations) using cell lines were more reproducible than assays using primary cell types. Significant differences in sensitivity were noted among the assay systems for particular material types. The in vitro assays were more sensitive to differences in material composition than was a 90-day assay by subcutaneous implantation in rats.

Two endogenous neuropeptides modulate the gill and siphon withdrawal reflex in Aplysia by presynaptic facilitation involving cAMP-dependent closure of a serotonin-sensitive potassium channel

We have found that two endogenous neuropeptides in Aplysia, the small cardioactive peptides SCPA and SCPB, facilitate synaptic transmission from siphon mechano-sensory neurons and enhance the defensive withdrawal reflex that these sensory neurons mediate. Single-channel recording revealed that these peptides close a specific K+ channel, the S channel, which is sensitive to cAMP. Moreover, the peptides increase cAMP levels in these sensory neurons. This reduction in K+ current slows the repolarization of the action potential in these cells, which increases transmitter release. In these actions, the SCPs resemble both noxious sensitizing stimuli, which enhance the reflex, and serotonin. Bioassay of HPLC fractions of abdominal ganglion extracts and immunocytochemistry indicate that both the SCPs and serotonin are present in the ganglion and are found in processes close to the siphon sensory neurons, suggesting that these transmitters may be involved in behavioral sensitization. Recent evidence suggests that one group of identified facilitatory interneurons, the L29 cells, does not appear to contain either the SCPs or serotonin but may use yet another facilitatory transmitter. Thus, it appears that several transmitters can converge to produce presynaptic facilitation in the sensory neurons of the defensive withdrawal reflex. All of the transmitters studied here, the SCPs and serotonin, act via an identical molecular cascade: cAMP-dependent closure of the S-K+ channel, broadening of the presynaptic action potential, and facilitation of transmitter release.

Characterization of a Streptococcus pneumoniae mutant with altered electric transmembrane potential

It is possible to select transmembrane potential (delta psi)-altered mutants in Streptococcus pneumoniae on the basis of their resistance to the antifolate methotrexate. Comparison of such a mutant strain ( amiA9 ) with its parent was used to evaluate the role of delta psi in the uptake of certain amino acids. The delta psi-dependent uptake of isoleucine, leucine, valine, and asparagine showed a reduced maximum velocity of uptake, and decrease in the transport constant of the energy-dependent, delta psi-independent uptake of lysine, methionine, and glutamine was observed. No reduction of the intracellular pool of ATP or of lactate excretion could be detected in the mutant strain. Moreover, studies on membrane preparations suggest that the phenotype expressed by the amiA mutation is not a consequence of alteration of its ATPase activity or susceptibility to N,N'-dicyclohexylcarbodiimide. Therefore, it is unlikely that the amiA mutation affects the H+ F1F0 ATPase which is involved in the establishment of the proton motive force in anaerobic bacteria. We propose that another function contributes to delta psi in S. pneumoniae. The amiA gene may be the structural gene of that function.

Effect of warfarin on ATP content, viability, glycosylation and protein synthesis in isolated rat hepatocytes

The effect of warfarin on ATP content, viability and incorporation of labelled glucosamine and leucine into protein was studied in suspensions of rat hepatocytes. When incubated with warfarin the synthesis of total protein and glycoprotein was equally inhibited, and the viability and ATP content of the cells were also lowered. These observations suggest that warfarin is not an inhibitor of glycosylation of proteins in isolated hepatocytes, however, the presence of warfarin leads to reduced ATP content of the cells which causes a decrease in protein synthesis and viability.

Radioisotopic assay of femtomole quantities of total adenine nucleotides, ATP plus ADP, and AMP

AMP is converted to ATP by incubating overnight with pyruvate kinase, phosphoenolpyruvate and adenylate kinase in the presence of endogenous ATP (ADP) as primer. In a subsequent incubation in the presence of pyruvate kinase, phosphoenolpyruvate, radioactive glucose and hexokinase, ATP and ADP are estimated together by coupling their recycling to the formation of glucose 6-phosphate. The latter is separated by precipitation using 76% (v/v) acetone for radioactivity measurement in the same Eppendorf tube. The sensitivity of these simple procedures matches or exceeds those of luciferase methods of nucleotide determination.

Changes in hormone responsiveness and cyclic AMP metabolism in rat hepatocytes during primary culture and effects of supplementing the medium with insulin and dexamethasone

Primary monolayer cultures of rat hepatocytes were used for studies of long-term and acute effects of hormones on the cyclic AMP system. When hepatocyte lysates were assayed at various times after plating of the cells three major changes in the metabolism of cyclic AMP and its regulation were observed: Glucagon-sensitive adenylate cyclase activity gradually declined in culture. In contrast, catecholamine-sensitive activity, being very low in normal adult male rat liver and freshly isolated hepatocytes, showed a strong and rapid increase after seeding of the cells. Concomitantly, there was an early elevation (peak approximately equal to 6 h) and a subsequent decrease in activity of both high-Km and low-Km cyclic AMP phosphodiesterase. These enzymic changes probably explained the finding that in intact cultured cells the cyclic AMP response to glucagon was diminished for 2-24 h after seeding, followed by an increase in the responsiveness to glucagon as well as to adrenergic agents up to 48 h of culture. Supplementation of the culture media with dexamethasone and/or insulin influenced the formation and breakdown of cyclic AMP in the hepatocytes. Insulin added at the time of plating moderately increased the adenylate cyclase activity assayed at 48 h, while dexamethasone had no significant effect. In the presence of dexamethasone, insulin exerted a stronger, and dose-dependent (1 pM - 1 microM), elevation of the adenylate cyclase activity in the lysates, particularly of the glucagon responsiveness. Thus, insulin plus dexamethasone counteracted the loss of glucagon-sensitive adenylate cyclase activity occurring in vitro. Kinetic plots of the cyclic AMP phosphodiesterase activity showed three affinity regions for the substrate. Of these, the two with high and intermediate substrate affinity (Km approximately equal to 1 and approximately equal to 10 microM) were decreased in the dexamethasone-treated cells. Insulin partly prevented this effect of dexamethasone. Accumulation of cyclic AMP in intact cells in response to glucagon or beta-adrenergic agents was strongly increased in cultures pretreated with dexamethasone. The results suggest that insulin and glucocorticoids modulate the effects of glucagon and epinephrine on hepatocytes by exerting long-term influences on the cyclic AMP system.

Effect of sodium selenite on the ciliary activity, adenosine triphosphate, and protein synthesis in mouse trachea organ cultures

Trachea from albino mice were cut transversely into nearly identical rings and incubated in medium 199 with Hanks salts and HEPES buffer at 37 degrees C. Sodium selenite at 0.5-5 mM depressed the ciliary activity. With 1 and 5 mM sodium selenite, a 50% reduction in the activity index was observed after approximately 5 and 1.5 h, respectively. The ATP content in trachea rings was reduced with 0.05-5 mM sodium selenite, and increasing concentrations gave decreasing amount of ATP after incubation for 4 and 21 h. The rate of protein synthesis as determined by incorporation of radioactive leucine was reduced with 0.5 and 2 mM sodium selenite. The synthesis was reduced quickly by 2 mM sodium selenite, which gave a 30% reduction after incubation for 1 h. It seems that the ATP levels may be used as the most sensitive indication of sodium selenite toxicity in mouse trachea.

Relation of rumen ATP concentration to bacterial and protozoal numbers

Cultures of Streptococcus bovis and mixed populations of rumen bacteria were used to investigate the concentration of ATP and rumen bacterial numbers at various stages of growth. ATP, extracted with Tris buffer, was analyzed using the firefly luciferin-luciferase bioluminescent reaction. ATP concentrations of S. bovis and mixed cultures of rumen bacteria significantly correlated with live cell counts during the log phase of growth but not during the stationary phase. The average cellular ATP concentration of rumen bacteria was calculated to be 0.3 fg of ATP per cell. Studies done with in vivo artificial rumen apparatus revealed that the protozoal contribution to rumen fluid ATP pool size was much more substantial than was the bacterial contribution. The rumen fluid ATP concentration was greater in cattle with protozoa than in those that were defaunated. Differences in ATP concentration due to size differences of ciliate protozoa were observed. Due to the unbalanced distribution of ATP in rumen microbes, ATP appears to be an unsuitable indicator of rumen microbial biomass.

Bioluminescence assay of calcium with a liquid scintillation counter

The luminescence produced by Ca aequorin reaction in dilute solutions decays exponentially over a relatively prolonged period of time. The concentration of total Ca and of free Ca in Ca-EGTA buffers could be determined by measuring the decay of luminescence in a liquid scintillation counter. The method is also suitable for determining total Ca concentration in small tissue samples.

Coupling of energy to folate transport in Lactobacillus casei

Lactobacillus casei cells can accumulate folate to an intracellular concentration in excess of 500 muM and to concentration gradients (relative to the extracellular compartment) of several thousand-fold. Maximum rates of folate transport are achieved rapidly (t(1/2) < 1 min) after the addition of glucose to energy-depleted cells and occur at intracellular adenosine 5'-triphosphate concentrations above 625 muM. The rate of folate transport and the adenosine 5'-triphosphate content of cells are both extremely sensitive to arsenate and decrease in parallel with increasing concentrations of the inhibitor, indicating a requirement for phosphate-bond energy in the transport process. The energy source is not a membrane potential or a pH gradient generated via the membrane-bound adenosine triphosphatase, since dicyclohexylcarbodiimide (an adenosine triphosphatase inhibitor) and carbonyl cyanide m-chlorophenylhydrazone (a proton conductor) have little effect on the uptake process. The K(+)-ionophore, valinomycin, is an inhibitor of folate transport, but does not act via a mechanism involving dissipation of the membrane potential. This can be deduced from the facts that the inhibition by valinomycin is relatively insensitive to pH, is considerably greater in Na(+)- than in K(+)-containing buffers, and is not enhanced by the addition of proton conductors. Folate efflux is not affected by valinomycin, glucose, or various metabolic inhibitors, although a rapid release of the accumulated vitamin can be achieved by the addition of unlabeled folate together with an energy source (glucose). These results suggest that the active transport of folate into L. casei is energized by adenosine 5'-triphosphate or an equivalent energy-rich compound, and that coupling occurs not via the membrane-bound adenosine triphosphatase but by direct interaction of the energy source with a component of the transport system.

Relationship of endogenous ATP to flagellar beat frequency in ejaculated bull spermatozoa

The relationship between endogenous ATP and flagellar beat frequency of bull spermatozoa was investigated using cinematographic and biochemical criteria. ATP content was measured by the luciferin-luciferase method. Potassium, sodium, chloride, and viscosity were used to alter motility to establish the concomitant effects on ATP content. Beat frequency was correlated to endogenous ATP in potassium-supplemented media. Increased sodium concentration was related to ATP content, but not to beat frequency. With increasing viscosity of the medium, the frequency of flagellary beat decreased dramatically, while ATP content of the cells remained unchanged.

Mechanism of folate transport in Lactobacillus casei: evidence for a component shared with the thiamine and biotin transport systems

Lactobacillus casei cells have been shown previously to utilize two separate binding proteins for the transport of folate and thiamine. Folate transport, however, was found to be strongly inhibited by thiamine in spite of the fact that the folate-binding protein has no measurable affinity for thiamine. This inhibition, which did not fluctuate with intracellular adenosine triphosphate levels, occurred only in cells containing functional transport systems for both vitamins and was noncompetitive with folate but competitive with respect to the level of folate-binding protein. Folate uptake in cells containing optimally induced transport systems for both vitamins was inhibited by thiamine (1 to 10 muM) to a maximum of 45%; the latter value increased to 77% in cells that contained a progressively diminished folate transport system and a normal thiamine system. Cells preloaded with thiamine could transport folate at a normal rate, indicating that the inhibition resulted from the entry of thiamine rather than from its presence in the cell. In a similar fashion, folate (1 to 10 muM) did not interfere with the binding of thiamine to its transport protein, but inhibited thiamine transport (to a maximum of 25%). Competition also extended to biotin, whose transport was strongly inhibited (58% and 73%, respectively) by the simultaneous uptake of either folate or thiamine; biotin, however, had only a minimal effect on either folate or thiamine transport. The nicotinate transport system was unaffected by co-transport with folate, thiamine, or biotin. These results are consistent with the hypothesis that the folate, thiamine, and biotin transport systems of L. casei each function via a specific binding protein, and that they require, in addition, a common component present in limiting amounts per cell. The latter may be a protein required for the coupling of energy to these transport processes.

The effect of non-steroidal anti-inflammatory drugs on adenosine triphosphate content and histamine release from rat peritoneal cell suspensions rich in mast cells

1 Non-steroidal anti-inflammatory drugs (NSAID) suppressed compound 48/80-induced histamine release from rat peritoneal cells in vitro in a dose-dependent manner. 2 NSAID suppressed the adenosine triphosphate (ATP) content of rat peritoneal cells in vitro and this correlated strongly with the suppression of compound 48/80-induced histamine release. 3 The correlation demonstrated suggests that the mechanism of action of NSAID in the rat peritoneal cells is via depletion of cellular ATP.

Computer-assisted analysis of adenosine triphosphate data

A computer program has been written to assist in the analysis of adenosine 5'-triphosphate data. The program is designed to calculate a dilution curve and to correct sample and adenosine 5'-triphosphate standard data for background and dilution effects. In addition, basic statistical parameters and estimates of biomass carbon are also calculated for each group of samples and printed in a convenient format. The versatility of the program to analyze data from both qauatic and terrestrial samples is noted as well as its potential use with various types of instrumentation and extraction techniques.