Net Oxygen Uptake Research Articles

Glucose and lactate oxidation rates in the fetal lamb.

Both glucose and lactate are nutrients of the ovine fetus. Each may be used by the fetus as a fuel for oxidation or as a source of carbon for energy storage and net tissue accretion. The present report describes the oxidation rates of glucose and lactate in vivo for the fetal lamb over a relatively short time period. The fraction of fetal glucose or lactate oxidized was defined as the ratio of 14CO2 excretion across the umbilical circulation to the net entry of [14C]glucose or [14C]lactate into fetal tissues. The fraction of glucose oxidized over a 3-hr study averaged 61.2%, accounting for 2.55 mg X min-1 X kg-1 of glucose oxidized and for 28% of the simultaneous net oxygen uptake. The fraction of lactate oxidized averaged 71.5%, accounting for 4.12 mg X min-1 X kg-1 of lactate oxidized. Oxidation fractions and rates for both glucose and lactate increased with their concentrations in fetal blood suggesting sparing of other fuels for oxidation at higher glucose and lactate concentrations.

Salt relations of Dunaliella. Transitional changes in glycerol content and oxygen exchange reactions on water stress

Changes in glycerol content are reported for Dunaliella tertiolecta over an 8 h period after a salt stress or dilution stress. Under the experimental conditions, the new glycerol level was reached in about 30 min in light or dark but there was evidence of oscillations after that, particularly on dilution stress. Glycerol disappearance on dilution stress is caused predominantly by dissimilation. A salt stress immediately inhibited photosynthetic oxygen evolution and caused net oxygen uptake for a period of about 36 h after the stress. Oxygen evolution was reestablished after that and the process of recovery to the point of resumption of net evolution was not affected by conditions designed to inhibit protein synthesis. Dilution stress of comparable magnitude diminished but did not eliminate photosynthetic oxygen evolution and recovery to a pre-stress level took about 18 h. Effects of HCO3-concentration suggested that photorespiration was not the sole determinant of oxygen uptake induced by salt stress but it was not possible to apportion with confidence the contribution of mitochondrial and other types of respiration. There was no evidence that modification by stress of energy-induced proton fluxes across the plasma membrane constituted an osmoregulatory signal in either species.

Mechanism of the hypolipemic effect of clofibrate in glucose-fed men

Studies were undertaken in man to ascertain the mechanism of the triglyceride-lowering effect of clofibrate in the glucose-fed state. Test subjects received 0.5 g clofibrate four times daily for 3 wk prior to the study of splanchnic metabolism. Splanchnic metabolism of triglycerides and other substrates was studied during prolonged intravenous administration of labeled palmitic acid and glucose (30 g/hr) to hypertriglyceridemic men maintained on a high carbohydrate diet for 2 wk. The secretion of plasma triglycerides from the splanchnic region was quantified from splanchnic flow and radiochemical measurements of the transsplanchnic gradients of labeled free fatty acids and triglycerides. Total transport of plasma triglycerides was also estimated in the test subjects from teh turnover of plasma very low density lipoproteins (VLDL)- 3H-triglycerides following pulse labeling with 2- 3H-glycerol. Clofibrate prevented the rise in fasting plasma triglyceride concentration which was expected to occur during the administration of the hypercaloric high carbohydrate diet. Mean plasma triglyceride fatty acids were 35% lower than control values (6.5 ± 1.3 vs. 10.0 ± 2.2 m M) and splanchnic secretion of triglycerides 68% lower in clofibrate-treated subjects than controls (32 ± 6 vs. 100 ± 40 μmol/min.m 2, p<0.05). Although systemic transport and splanchnic uptake and conversion of free fatty acids to plasma triglycerides were unaltered by clofibrate, the mean fraction of triglyceride fatty acids of plasma VLDL derived from precursors other than free fatty acids was significantly lower in subjects receiving clofibrate than controls (73 ± 6 vs. 91 ± 1%). Net splanchnic uptake of oxygen and glycerol and the release of lactate were lower in test subjects than controls, whereas splanchnic uptake of serine, histidine, and aspartate was increased. The triglyceride-lowering effect of clofibrate in the glucose-fed state was attributable to inhibition of hepatic secretion of triglycerides.

Nutritional studies with Pseudomonas aeruginosa grown on inorganic sulfur sources

Pseudomonas aeruginosa was grown on a succinate-basal salts medium supplemented with various inorganic sulfur compounds as its sole source of sulfur. The organism was able to grow on the sodium salts of sulfide, thiosulfate, tetrathionate, dithionite, metabisulfite, sulfite, or sulfate, but not on those of dithionate. Analyses of the culture media after 24 h of growth indicated accumulation of sulfate from each inorganic sulfur source except sulfate. Manometric studies with resting cells obtained by growth on each of these sulfur sources yielded net oxygen uptake for all substrates except sulfite and dithionate. Similar results were obtained with extracts from these cells by spectrophotometric techniques. Thiosulfate oxidase activity appeared to be induced by growth on sulfide, thiosulfate, or tetrathionate, with little or no activity observed when cells were grown on inorganic sulfur sources of higher oxidative states. Metabisulfite oxidase appeared to be associated with growth on all inorganic sulfur compounds. Rhodanese activity appeared to be constitutively present, and its activity, observed only in soluble fraction, seemed independent of the growth medium employed. Thiosulfate and tetrathionate oxidase activities were studied in greater detail than some of the other sulfur oxidases, and both were found to be distributed between particulate and soluble fractions.

Functional and structural changes after disuse of human muscle.

1. Seven patients who had suffered unilateral leg fracture were studied after removal of immobilizing plaster casts. 2. Leg volume measured anthropometrically was reduced by 12% in the injured leg (5-68 +/- 1-05 litres) compared with the uninjured (6-43 +/- 0-87 litres). Associated with this loss was a similar reduction in the net maximum oxygen uptake achieved in one-leg cycling, from 1-89 +/- 0-21 1/min in the uninjured leg to 1-57 +/- 0-18 1/min in the injured. 3. Measured by a percutaneous needle biopsy technique, a reduction of 42% was found in the cross-sectional area of the muscle fibres sampled from the vastus lateralis of the injured compared with the uninjured leg. 4. Staining for myosin adenosine triphosphatase activity showed that both type I and II fibres were affected, being reduced respectively from 3410 to 1840 micronm2 and from 3810 to 2390 micronm2 cross-sectional area. 5. Possible reasons and implications are discussed for the discrepancy between the magnitude of the difference observed in the gross measurement of leg function (maximum oxygen uptake) and structure (leg volume) as compared with the cellular level (cross-sectional fibre area).

Some Physiological Responses ofChlorella pyrenoidosato 2,4-Dichlorophenoxyacetic Acid

An 18-h treatment of synchronously-grown Chlorella pyrenoidosa with 2,4-D did not signi ficantly alter the size, dry weight, degree of synchrony, or pigment content of the cells, nor were detectable quantities of ethylene produced. When Chlorella pyrenoidosa was treated with 5x 10 4 M 2,4-D, there was a statistically significant stimulation of both net oxygen uptake and production while 5 x 10~3 M 2,4-D inhibited both processes. When Chlorella pyrenoidosa was treated with 5 x 10~4 M and 5 X 10~3 M 2,4-D, significantly greater amounts of glycollate were present in the culture medium, even though an assay for glycollate dehydrogenase showed that the activity of this enzyme from 2,4-D-treated Chlorella pyrenoidosa was three times greater than in control cells. Loosely bound 2,4-D was partitioned from a nonaqueously isolated chloroplast fraction, while other cell fractions failed to show detectable quantities of 2,4-D. It is postulated that in Chlorella pyrenoidosa the chloroplast is a target for 2,4-D action and that interference in photorespiratory processes may underlie the observed responses.

The sulfur cycle of a marine sediment model system

In a laboratory sediment model consisting of sand and chopped Zostera marina leaves, the sulfur cycle and the succession and zonation patterns of sulfur bacteria were studied for a period of 7 months. The pool size of different forms of sulfur was quantified, and the rate of sulfate reduction was measured with an in situ radio-tracer technique at regular intervals. From these data, transfer rates of the sulfur cycle in the system could be calculated for different periods. The rate of sulfate reduction was initially 80 nMS·cm3·day-1; this decreased to 25 nMS·cm3·day-1 towards the end of the experiment as the system started to become oxidized. There was a transient accumulation of elemental sulfur in the bacterial plate at the sediment surface. More than 50% of the total mineralization of the organic material was due to sulfate reduction. Comparison with the net oxygen uptake showed that, during the first 2 to 3 months (when the sediment closely resembled a natural, reduced shallow water sediment), SO4- was equally as important as O2 for transporting oxidacion equivalents from the water to the sediment.

The effect of oxygen on fermentation of sucrose by rumen micro-organisms in vitro.

1. The effect of oxygen on the fermentation of sucrose by mixed rumen micro-organisms in vitro was studied by adding oxygen to the gas phase in three ways: at the beginning of incubation, at two hourly intervals during incubation and continuously.2. The additions of oxygen had no measurable effect on the utilization of sucrose or on the production of carbon dioxide, steam-volatile acids and particulate organic matter by the micro-organisms. The addition of oxygen at the beginning of incubation inhibited methane production and increased the accumulation of hydrogen. Similar but much less pronounced changes occurred when the oxygen was infused continuously.3. In all the experiments there was a net uptake of oxygen by micro-organisms. When large amounts of oxygen were present in the gas phase the rates of uptake were proportional to these amounts. When small amounts of oxygen were added, the rates of uptake were independent of the amount added and had a value of approximately 5 ml/h when 100 ml of strained rumen contents were incubated.

Reversal of copper inhibition in chloroplast reactions by manganese.

In the Mehler reaction, a Hill reaction utilizing molecular oxygen as the electron acceptor, rates of net oxygen uptake are stimulated by added manganous ions. Both whole cell photosynthesis and the Mehler reaction are inhibited by copper. Copper inhibition of the Mehler reaction can be reversed by manganese salts. Glutathione. which alone has no effect on Mehler reaction rates, enhances the effect of manganese in reversing copper inhibition. The effects of added Cu(2+), Cu(2+) and Mn(2+), or Cu(2+), Mn(2+), and glutathione exhibit no induction phenomena when measured manometrically. Furthermore, the order of addition of these factors is unimportant: final rates are dependent only on the composition of reaction mixtures. Compared to the Mehler reaction, conventional Hill reactions are less sensitive to copper poisoning, while certain chloroplast mediated photoxidations (e.g. the photoxidation of diketogulonic acid) are far more sensitive. In all of the chloroplast mediated photoreactions tested, manganese is effective in reducing the sensitivity to copper poisoning.

Uptake of lactate and pyruvate by intact kidney of the dog.

In dogs anesthetized with pentobarbital, mean renal blood flow was 312 ml/min/100 g kidney wt., and mean renal O2 consumption was 6.46 ml/min/100 g. Under control conditions mean net uptake of lactate was 20.7 µM/min/100 g. The precise metabolic fate of lactate could not be ascertained from these studies. If it were completely oxidized, it would account for 21.6% of the total O2 consumption. When blood lactate levels were raised by infusion of L(+)lactate, there was a progressive increase in rate of uptake. Under control conditions, the net handling of pyruvate delivered to the kidney was negligible. When blood levels were elevated by pyruvate infusions, there was significant net uptake; when pyruvate levels increased as the result of lactate infusions, there was no augmentation of net uptake. Similarly, elevated levels of lactate occurring during pyruvate infusions did not elicit significant acceleration of lactate uptake. When renal blood flow was acutely reduced, renal extraction of oxygen, lactate, and pyruvate remained remarkably constant. Thus, a decrease in net uptake of oxygen and lactate was proportional to the rate of blood flow, and pyruvate uptake was negligible over the entire range of blood flows.

Light dependent oxygen metabolism of chloroplast preparations. III. Photooxidation of ascorbic acid

Ascorbic acid is a normal constituent not only of the chloroplasts but also of the other protoplasmic components of the cells of green leaves. In spite of its known widespread occurrence in plants, few functions of ascorbic acid in plant metabolism have been established (see review by Mapson, 15). The participation of ascorbic acid as an intermediate hydrogen carrier in photosynthesis has been suggested (16, 17) and certainly the experiments of Krasnovsky on the photochemical reduction of chlorophyll in vitro by ascorbic acid (13, 14) have added new interest to these suggestions.. Ascorbic acid was at one time considered to be ,a necessary component of the photosyntheticf phosphorylation system but more recently it has been regarded as having a protective role in preventing inactivation of essential components of the chloroplasts (Arnon, 1). Soon after he discovered that chloroplasts could use oxygen as a Hill reagent, Mehler (18, 19) reported that rates of net oxygen uptake in the light by reaction mixtures containing chloroplasts, ethanol, and catalase were stimulated several fold if the chloroplasts had first reduced quinone. To determine if it was necessary for chloroplasts to reduce quinone in the light, Mehler added ascorbic acid to the reaction mixture to reduce quinone in the dark. When an excess of ascorbic acid was addeJ, an extremely rapid oxygen consumption occurred on illumnination. The nature of this rapid uptake in the presence of ascorbic acid was of particular interest because of the apparent increase in the efficiency of utilization of light energy. Later, Vernon and Kamen compared the photooxidations of various redox couples by spinach leaf homogenates and sonic extracts of Rhodospirillum rubrum (21). The most active couple which they found was the combination of 2,6-dichlorophenolindophenol (DPIP, acting as an electron carrier) and ascorbic acid (acting as the ultimate electron donor). In both plant and bacterial extracts, oxygen uptake in the light continued until oxygen equivalent to the excess ascorbic acid in the system had been consumed. The nature of this rapid DPIP-mediated photooxidation of ascorbic acid has since been investigated using tracer oxygen techniques (Habermann & Vernon, 10). The results of these studies support the hypothesis that ascorbic acid can be oxidized by the oxidized product of photolysis. This paper describes investigations of the mechanism of the photooxidation of ascorbic acid mediated by chloroplast reaction systems.4 Addition of ascorbic acid during either a Mehler or exchange reaction results in an immediate acceleration of the rate of net oxygen uptake. Just as the rates of the Mehler and exchange reactions are accelerated after a chloroplast preparation has reduced quinone (19, 8), previous reduction of quinone has a stimulating effect on rates Hill reaction (production only):

Effect of diet on rate of alcohol oxidation by the liver.

Summary1. Weanling rat liver homogenate had about one-half the level of alcohol oxidation activity eventually achieved by adult rats on a chow diet (net oxygen uptake of 24 cmm per 10 minutes per 200 mg fresh liver for the adult normal rat). 85% or 75% respectively of this normal level of activity was reached by feeding chow or a purified 24% casein diet for 2 weeks. A protein-free diet removed about 85% of this enzymatic activity from the liver. 2. Adult rats responded similarly to these diets. Complete starvation for 7 days reduced this activity about 50%, while a 50% food restriction for 2 weeks gave less than a 20% decrease in the rate of alcohol oxidation.

紅色細菌による脂肪酸の酸化について

(1) A non-sulfur purple bacterium, Rhodobacillus palustris, can utilize various fatty acids as substrates of respiration. The initial rate of respiration can be “saturated” by a very low concentrations of fatty acids, such as one several thousandsth of a mole/lit. The minimum “saturating” concentration of substrate becomes smaller as the length of carbon chain of fatty acids increases.(2) The initial rate of oxygen uptake, measured at the saturating concentration of substrate, increases with the increase of the carbon atom up to C7-C9 (Heptoic and pelargonic acids); with further increase of C, however, it decreases gradually until at C17-C18 (margalic and stearic acids) no positive O2-uptake occurs.(3) The rate of oxygen uptake caused by the addition of oxidizable fatty acids falls off abruptly to the value corresponding to endogeneous respiration when the fatty acids are used up. The amount of net oxygen uptake corresponding to the oxidation of fatty acid is directly proportional to the concentration of the acid initially added. The net oxygen uptake (in mole) per mole of fatty acid used, which is denoted by q, is the function of the number (n) of carbon atom in the acid molecule. In the case of normal fatty acids, except for acetic and propionic acid, the following linear relationship was found to hold approximately between q and n, q=0.5(n-2)This relation implies that for normal fatty acids longer than propionic acid, increase of one atom in the molecule entails increase of the net oxygen consumption by 1/2 O2. Propionic and isovaleric acids consumed 2-2.5 times as much oxygen as was predicted by this relation. On the other hand crotonic acid took up only half as much oxygen as did butyric acid.(4) The oxidation of fatty acids (tested with propionic, acetic, valeric, octanoic and isobutyric acids) seems to take place without liberation of carbon dioxide.(5) By the inhibition technique using cyanide and carbon monoxide, as well as by measuring the velocity of oxidation of para-phenylendiamine with and without butyric acid, it was shown that the oxidation of fatty acids by the organismis catalyzed by the function of cytochrome system.(6) Malonic acid, eyen in a concentration of M/100, does not exert any inhibitory action upon the oxidation of fatty acids, while monoiodoacetic acid causes about 50% inhibition in a concentration of M/10000.(7) Using Thunberg's technique it was shown that the dehydrogenase system of fatty acid oxidation cannot utilize redox-dyes such as Janus green, Nile blue, methylene blue, thionine, toluilene blue and 2, 6-dichlorophenol-indophenol, as hydrogen acceptor.