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J B Hanson

Publications and source records attributed to J B Hanson.

At least 55 records · Page 3Linked to original sources
PubMed1973

The Stoichiometry of Respiration-driven Potassium Transport in Corn Mitochondria.

Determinations were made for corn (Zea mays L., WF9-Tms x M14) mitochondria of the stoichiometric relationship between K(+) transport and bond energy produced in respiration (K(+)/ approximately ratio). With inward pumping of potassium acetate activated by NADH oxidation, the initial rate of K(+) transported into the sucrose inaccessible space varied between 0.58 and 0.97 K(+)/ approximately , assuming 2 high energy bond equivalents per NADH oxidized. Only small amounts of H(+) were ejected. Valinomycin did not alter the ratio.Efflux pumping of K(+) in KCl media gave a K(+)/ approximately of 0.92. Substituting sucrose for KCl caused a drop in respiration and H(+) ejection, indicating a requirement for cation efflux pumping in acceptorless respiration. Valinomycin added to the KCl medium accelerated passive swelling but did not impair subsequent efflux pumping, although respiration was partially uncoupled.

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PubMed1973

Increased Activity of Chromatin-bound Ribonucleic Acid Polymerase from Soybean Hypocotyl with Spermidine and High Ionic Strength.

Optimal activity of chromatin-bound RNA polymerase from soybeans is obtained with 1 mm Mn(2-), but only when high ionic strength or polyamines are included in the medium. Such inclusion does not increase the Mg(2+) activation of the polymerase, but it does lower the concentration needed for optimum activity from 10 mm to 1 mm. Mg(2-) activation is inhibited by added Mn(2+), and the inhibition is relieved by high ionic strength or spermidine. The RNA polymerase with either cation is almost entirely polymerase I at low and high ionic strength as evidenced by insensitivity to alpha-amanitin. Treatment of soybean seedlings with 2,4-dichlorophenoxyacetic acid does not change these characteristics; although the activity rises 3- to 4-fold.It is suggested that chromatin as prepared here may be a selected fraction enriched in polymerase I, which is activated by either Mg(2+) or Mn(2+), and that the Mn(2-) inhibition of activity is due to a known reaction of Mn(2-) with DNA which can be relieved by high ionic strength.

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PubMed1973

Inhibition of postoxidative calcium release in corn mitochondria by inorganic phosphate.

Respiration drives the accumulation of a small amount of calcium in corn (Zea mays L.) mitochondria, and this calcium is released when respiration ceases. A postenergized addition of phosphate leads to phosphate uptake and enhaced calcium retention. Oligomycin, KCN, 2,4-dinitrophenol, or mersalyl are without effect on the phosphate-induced calcium retention. Addition of phosphate also inhibits the release of endogenous phosphate which normally accompanies the calcium. It is suggested that passive phosphate uptake retards the release of endogenous phosphate which is complexed with the calcium.

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PubMed1973

Functioning of the adenine nucleotide transporter in the arsenate uncoupling of corn mitochondria.

Arsenate uncouples mitochondrial respiration in a process stimulated by ADP, inhibited by oligomycin, and competitively inhibited by inorganic phosphate. If mersalyl is added to corn mitochondria to block further transport of accumulated arsenate, the uncoupled respiration continues unabated due to recycling of matrix arsenate. Addition of ADP now inhibits rather than promotes respiration and the mitochondria shrink. It is established by arsenate analyses that arsenate is removed from the matrix. Oligomycin or atractyloside block the removal by inhibiting ADP-arsenate formation or transport, respectively. It is deduced that ADP-arsenate is stable in the membrane and is transported outward for hydrolysis in the external aqueous phase. Hence, ADP-arsenate formed in oxidative phosphorylation is not directly released to the matrix, and a mechanism must exist for its direct transfer to the transporter.

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PubMed1972

Induction and development of increased ion absorption in corn root tissue.

Washing excised or intact primary roots of corn (Zea mays L., WF9 x M14) in aerated distilled water or dilute salt solutions for 2 hours induced doubling of the rate of accumulation of various nutrient ions and solutes. This response to washing depended upon aerobic metabolism, but involved no increase in aerobic respiration. Excision of root tissue was not required as the effect could be obtained with intact root systems. Increased phosphate absorption followed after a lag period of 30 to 40 minutes and continued for 6 hours before leveling off at about 3.5 times the initial rate. Chloramphenicol was not inhibitory to the development of increased absorption, while inhibitors of RNA and protein synthesis were. Auxins and kinetin were also inhibitory, but so was the antiauxin, 2,4,6-trichlorophenoxyacetic acid.Kinetic analyses of phosphate and potassium ((86)Rb) absorption showed no change in apparent Michaelis constant. Electron microscopic examination and analysis for membrane protein and lipid-phosphate content after washing showed no proliferation of membrane or other changes in cell structure and composition. It appears that washing augments or activates existing membrane transport mechanisms by processes involving protein synthesis.

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PubMed1972

Increased Membrane-bound Adenosine Triphosphatase Activity Accompanying Development of Enhanced Solute Uptake in Washed Corn Root Tissue.

Washing of excised corn (Zea mays L., variety WF9xM14) root tissue is accompanied by an increase in (Mg(2+) + K(+))-stimulated adenosine triphosphatase. This is the adenosine triphosphatase described by Fisher, Hansen, and Hodges as positively correlated with ion accumulation rates. The increase in activity is confined to the microsomal fraction. A close parallel exists between increases in adenosine triphosphatase and phosphate absorption, and they respond similarly to inhibitors of RNA and protein synthesis. However, the amplitude of change is much smaller in adenosine triphosphatase. Possible reasons for this discrepancy are discussed.

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PubMed1972

Ion transport induced by polycations and its relationship to loose coupling of corn mitochondria.

Treatment of corn mitochondria (Zea mays L., WF9 (Tms) x M14) with polycations (protamine, pancreatic ribonuclease, or polylysine) releases acceptorless respiration if phosphate is present. Concurrently, there is extensive active swelling which is reversed when respiration is uncoupled or stopped. Mersalyl, the phosphate transport inhibitor, blocks both the release of respiration and the active swelling. Diversion of energy into phosphate transport lowers respiratory control and ADP: O ratios. This response is termed "loose coupling" in distinction to "uncoupling" in which energy is made unavailable for either transport or ATP formation. Corn mitochondria as used here are endogenously loose coupled to some extent, and show state 4 respiration linked to active transport.The action of polycations can be partially mimicked by lowering pH of the suspending medium; both give swelling in sucrose medium and increased light absorbancy. Triton X-100, a nonionic detergent, will uncouple and accentuate active swelling, but unlike polycations it will not release state 4 respiration. Calcium ion acts something like polycation in activating phosphate transport and releasing respiration, and polycation appears to block entry of Ca(2+).It is speculated that neutralization of certain negatively charged acid groups on the membranes by polycations increases permeability to solutes and decreases coulombic repulsion of phosphate in approaching transport sites. In consequence, respiration rates and active transport rates increase.

Journal Article↗
PubMed1972

Phosphate-induced Stimulation of Acceptorless Respiration in Corn Mitochondria.

By use of the organic mercurial mersalyl to block phosphate transport, it has been shown that only a small fraction of the respiratory increase of corn mitochondria in response to additions of inorganic phosphate is due to energy expended in phosphate accumulation. Most of the respiratory release occurs from accelerated turnover of the coupling mechanism with internal phosphate in an oligomycin-sensitive reaction. Addition of ADP to mersalyl-blocked mitochondria depletes internal phosphate in ATP formation and respiration declines. Arsenate produces the same responses as phosphate but is more effective in respiratory release.Inhibition of the ADP-ATP antiporter with atractyloside shows that the increased respiration with internal phosphate is not due to turnover of ADP acceptor through exogenous ATPase.Use of valinomycin to facilitate movement of K(+) greatly accelerates the rate of phosphate swelling, but there is no consistent correlation between respiration and swelling. In the absence of phosphate, valinomycin dramatically releases respiration with only trivial swelling.The data indicate that loose coupling in due only fractionally to energy expenditure in ion transport. An explanation consistent with the observations can be derived by assuming that both a high energy intermediate (I approximately X) and a proton motive force-or its electrochemical equivalent-arise at coupling sites.

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PubMed1970

Divalent cation stimulation of substrate oxidation by corn mitochondria.

The oxidation of reduced nicotinamide adenine dinucleotide, malate-pyruvate, and succinate by corn mitochondria in buffered 0.2 m KCl was determined as a function of divalent cations. Ni(2+), Mg(2+), Co(2+), Ca(2+), Mn(2+), Sr(2+), and Ba(2+) stimulated reduced nicotinamide adenine dinucleotide oxidation in the absence of inorganic phosphate, with Ca(2+) and Sr(2+) having the greatest effect. Malate-pyruvate and succinate oxidation was stimulated by Ca(2+), Ba(2+), and Sr(2+), but only in the presence of inorganic phosphate. Ca(2+), Sr(2+), and Ba(2+) produced a simulated state 4 to state 3 transition with all three substrates, but only with malate-pyruvate and succinate was there a return to state 4. The order of divalent cation effectiveness suggests that the rate of water substitution from the cation inner coordination hydration sphere may be a rate-limiting step in certain mitochondrial reactions involving electron transport and phosphorylation.

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PubMed1969

The effect of reduced water potential on soybean mitochondria.

The respiration of excised hypocotyls and of isolated hypocotyl mitochondria from soybean [Glycine max (L.) Merr., var. Wayne] was determined in various concentrations of sucrose and potassium chloride. Hypocotyl oxygen uptake declined with increasing solute concentration; no specific effects of either solute were apparent. Mitochondrial state III respiration was strongly inhibited as the solute concentrations were raised and there was in addition a specific inhibitory effect of the salt. State IV respiration, however, was unaffected by the presence of osmoticum. ADP/O ratios were also unaffected, except at high potassium chloride concentrations (470 mm). The primary effect of solutes was thus to limit the rate of substrate oxidation.Hydrostatic pressure did not reverse the decline in net phosphorylation accompanying reduced oxidation. It was inferred therefore that the inhibition was not due to lower water potential per se, but rather to some other effect of water or solute concentration.The effect of solutes on a mitochondrial enzyme, malate dehydrogenase, was also examined. Sucrose inhibited malate oxidation by both the mitochondria and the isolated enzyme in parallel, while potassium chloride was more inhibitory on the isolated enzyme. It was concluded that although the addition of solute lowers the water potential, the primary effects are exerted through specific effects of the solute on enzyme activity.

Journal Article↗
PubMed1969

The effect of respiratory inhibitors on NADH, succinate and malate oxidation in corn mitochondria.

The effect of a series of respiratory inhibitors on the oxidation of NADH in state 4 and state 3 conditions was studied with corn shoot mitochondria. Comparisons were made using malate and succinate as substrates. The inhibitors, rotenone, amytal, antimycin A and cyanide, inhibited oxidation of NADH in state 3 but rotenone and amytal did not inhibit oxidation in state 4. The inhibition by antimycin A was partially overcome by the presence of cytochrome c. The results indicate the presence of alternative pathways available for NADH oxidation depending on the metabolic condition of the mitochondria. Under state 4 conditions, NADH oxidation bypasses the amytal and rotenone sensitive sites but under state 3 conditions a component of the NADH respiration appears to be oxidized by an internal pathway which is sensitive to these inhibitors. Still a third pathway for NADH oxidation is dependent on the addition of cytochrome c and is insensitive to antimycin A. Succinate oxidation was sensitive to cyanide and antimycin A under both state 4 and state 3 conditions as well as amytal and rotenone under state 3 conditions but was not inhibited by amytal and rotenone under state 4 conditions. Malate oxidation was inhibited by cyanide, rotenone and amytal under both state 4 and state 3 conditions. Antimycin A inhibited state 3 but did not appreciably alter state 4 rates of malate oxidation. With all substrates tested inhibition by antimycin A was greatly facilitated by preswelling the mitochondria for 10 min. This was interpreted to indicate that swelling increases the accessibility of antimycin A to the site of inhibition.

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