Respiratory Carbon Dioxide Research Articles

The synthesis of neomycin-C 14 by Streptomyces fradiae

When glucose uniformly labeled with carbon-14 was added to a growing culture of Streptomyces fradiae, 68.4 % of the total radioactivity was recovered in the respiratory carbon dioxide, 19.5 % was incorporated into neomycin, and the rest was distributed in the culture fluid and in the mycelium. Since the addition to the media of several compounds other than glucose resulted in an increased amount of this antibiotic, their labeled forms might possibly be considered as potential precursors of radioactive neomycin.

METABOLISM OF RADIOACTIVE β-(3,4-DIHYDROXYPHENYL)-ALANINE-α-C14IN THE ALBINO RAT

When DL-3,4-dihydroxyphenylalanine-α-C14(DL-dopa-α-C14) was injected into rats, 80% of the radioactivity was recovered from urine and 2% from respiratory carbon dioxide. The urine was examined by descending paper chromatography and the following radioactive substances have been identified: dopa, hydroxytyramine, 3,4-dihydroxyphenylpyruvic acid, and 3,4-dihydroxyphenylacetic acid. The urinary hydroxytyramine is partially conjugated, presumably as a glucuronide or as a sulphate. Evidence is also presented which indicates that 5,6-dihydroxyindole is one of the metabolites present in urine. Radioactive epinephrine or norepinephrine could not be detected in either urine or suprarenal gland.

STUDIES ON THE DORMANCY AND SPROUTING OF POTATOES

Although the concentration of carbon dioxide or of oxygen in the storage atmosphere have a considerable effect upon the sprouting of potatoes, it has been shown that changes in the carbon dioxide and oxygen tension in the internal atmosphere of the tuber, prior to the natural break of dormancy, are negligible (Burton, I950, I95i). Further, where sprout inhibition has resulted from storage in high concentrations of carbon dioxide these high concentrations have usually been achieved by means which allowed also the accumulation in the storage atmosphere of volatile respiratory products other than carbon dioxide. Thus Kidd (I9I9) inhibited the sprouting of non-dormant potatoes by storing them in three artificial gas mixtures containing zo % of carbon dioxide, and 5, io and 20 % of oxygen respectively. He did not pass these mixtures continuously through the desiccators in which the tubers were contained, but adjusted their composition every two days (see Kidd, I914). The accumulation, to some extent, of volatiles other than carbon dioxide was thus possible. In experiments in which a concentration of io% carbon dioxide was used, the reduction of sprouting which normally resulted was due more to a reduction in the number than in the size of sprouts, and there were instances in which the sprouting in I0 % carbon dioxide and in the absence of carbon dioxide did not markedly differ. Braun (I93I) used three methods of adjusting the composition of the atmospheres in which he stored potato tubers. The first, which he dismissed as unsatisfactory, was to allow the respiratory carbon dioxide to accumulate for from i to 3 days, the highest concentration reached being zo2z 0. The atmosphere was then replaced by air-it is in this complete replacement that the method differs from that of Kidd-and the process repeated. In the second method, which was that adopted by Braun for most of his work, carbon dioxide was allowed to accumulate as above, and it was then attempted to keep it at the desired level by continuous ventilation. The technique was not altogether satisfactory. Thus a concentration of carbon dioxide described as 9g I3 % was in reality the mean, weighted for time, of concentrations ranging from 3.5 to I2z6 %. The third, and most satisfactory, method was continuously to ventilate, with artificial gas mixtures, the desiccators in which the tubers were contained. It will be seen that, in the first of the methods described above, volatiles other than carbon dioxide would accumulate for a few days and would then be removed; in the

Distribution of label from metabolism of radioactive leucine, norleucine and norvaline in tissues, excreta and respiratory carbon dioxide

A comparative study has been made of the pathways for the metabolism of the carbon chain of d-, l-, and dl-leucine-2-C 14 by enzymatically resolving the dl-isomer. dl-Norleucine-3-C 14 and dl-norvaline 3-C 14 were also studied for comparative purposes. l-Leucine was oxidized most rapidly and the d-leucine the least rapidly. The initial rate of oxidation of dl-leucine was greater than that of norleucine and norvaline, but the total amount of radioactivity in the expired air after 8 hr. was greater in the case of the last two amino acids. The partition of the radioactive carbon of each of the amino acids was determined in the expired CO 2, proteins of the body, and in the urine. The metabolically active proteins were isolated, hydrolyzed, and the amino acids separated chromatographically on an ion-exchange resin column. The highest specific activity with leucine was found in this amino acid. No norvaline was found to be incorporated in body protein, and both norvaline and norleucine can continue to be regarded as unnatural amino acids. Of the derived amino acids, the ones of highest specific activity were glutamic acid, aspartic acid, and alanine. Some activity was also found in glycine, serine, and arginine.

Metabolism of C13-carboxyl-labeled malonate by the intact mouse.

SummaryWhen C13 - carboxyl - labeled malonate was injected subcutaneously into mice, 20-32% of the labeled carbon was recovered in the respiratory carbon dioxide in 6 hours.At body temperature, dog plasma showed little or no ability to decarboxylate malonate.These results are interpreted to indicate the probable occurrence in mammalian cells of enzymatic mechanisms for conversion of malonate to carbon dioxide.

Respiration of barley plants; protein catabolism and the formation of amides in starving leaves.

In a continuation of earlier studies the nitrogenous constituents of barley leaves have been investigated with the object of gaining more direct evidence on the nature of protein catabolism in starving leaves. Particular attention was given to the origin and identification of the amides. Tissue proteins were separated and partially analyzed by direct and indirect methods. The amino-acids of the barley-leaf protein were very similar to those of the proteins prepared from grasses. From these and other data estimates of the amide-N, glutamic acid and aspartic acid were obtained. The amide-N content of the whole protein of the leaves agreed closely with that of the separated protein. There was evidence that the release of amide-N proceeded uniformly as the proteins were broken down during starvation. Asparagine was identified as a product of catabolism by direct isolation from starved leaves; recovery of the crystalline product amounted to 60% of the total stable amide-N of the crude extract. Glutamine was not isolated, but additional evidence of its presence in the leaves was obtained. An analysis of the relation between proteolysis and formation of amides confirmed several of the suggestions made in a previous discussion. Most of the amide-N of the starved leaves was of secondary origin, and there were clear indications of a secondary synthesis of the aspartic acid combined in asparagine. Glutamine amide-N was formed secondarily during the early stages of starvation, but evidence of the origin of glutamic acid was inconclusive. The data of different experiments indicated that the breakdown of tissue proteins contributed between 20 and 40% of the total carbon lost from the leaves as respiratory carbon dioxide.

Bemerkungen zur Mitteilung von E. H. Reinau: Zur CO2-Resttheorie im Pflanzenbau

In a brief communication to “Nature”1 I have introduced the term “Threshold Value” to design the lowest carbon dioxide concentration in the atmosphere at which photosynthesis of green leaves can take place. The final proof for the existence of this threshold is found in my experiments with leaves exposed to high light intensities in air poor in carbon dioxide1,2. These experiments show that respiratory carbon dioxide is expired until the threshold value for photosynthesis is reached at 0.0090 vol. %. To avoid confusion it is considered best to use the term “Threshold Value” only in the sense stated above.Reinau's use of the term to designate equilibria between consumption and production of carbon dioxide, found in the open air, seems to be without any adequate basis.

AN IMPROVED ARRANGEMENT FOR THE MEASUREMENT OF CARBON DIOXIDE OUTPUT OF RESPIRING PLANT MATERIAL BY THE ELECTRICAL CONDUCTIVITY METHOD

A brief review of the application of the electrical conductivity method of estimating carbon dioxide in respiration measurements is given and an apparatus which employs this method is described. The apparatus was designed and constructed by the authors for the purpose of recording respiratory carbon dioxide output of plant material; it comprises an oscillator, amplifier, and vacuum tube voltmeter that work in conjunction with a special type of absorption tube. Sodium hydroxide solution is used as the absorbing reagent. A simple set-up for automatic recording is described.

Behaviour of the fungus Rhizoctonia solani Kiihn in the soil

Rhizoctonia solani was found able to grow as a saprophyte through natural unsterilized soil. Its rate of growth under different soil conditions in glass tumblers was studied by the Rossi‐Cholodny soil‐plate method. Growth was most rapid at the lowest soil‐moisture content tested, viz. 30 % saturation, and was accelerated by forced aeration of the soil. The maximum distance to which mycelial growth could be supported on the food reserves of the agar inoculum alone was some 5 cm., as shown by extent of growth through tubes of moist sand, but in 23 days the fungus grew 21–24 cm through tubes of soil. Removal of the agar disk 2 days after inoculation of the tubes reduced growth through sand by more than half, but through soil by only a small proportion. In soil, Rhizoctonia was able to cause 100% damping‐off of radish seedlings planted at a radial distance of 4 cm. from the agar inoculum, and some 40 % damping‐off at a distance of 9 cm. The depressing effect of additions of 1 % ground‐wheat straw or dried grass to the soil upon growth of the fungus was attributed to (1) the negligible cellulose‐decomposing ability of Rhizoctonia, (2) nitrogen starvation of the mycelium, through rapid utilization of the available soil nitrogen by the cellulose‐decomposing micro‐organisms multiplying upon the fresh organic material, (3) fungistatic action on Rhizoctonia of the respiratory carbon dioxide produced by the cellulose‐decomposers.

Respiration of Leguminous Root Nodules

A PREVIOUS communication from one of us (G. B.1) referred to observations on the rate of evolution of respiratory carbon dioxide from leguminous root nodules still attached to the plant. Those observations have been extended and are being published elsewhere. A brief report is presented here of other observations (which will not be continued at present) on detached nodules, made by means of a respirometer designed by one of us (G. F. A.). This apparatus provides concurrent records of oxygen intake and carbon dioxide evolution and is being described in another publication. It is our belief that the only complete figures for the respiratory gaseous exchange of nodules so far published are those of Allison and his collaborators2,3, though recently Wilson4 has recorded observations on oxygen intake. Information concerning respiratory events within the nodule will contribute to an increased understanding of the general metabolism of the nodule, including the process of nitrogen fixation.

Utilization of Carbohydrates in Leguminous Symbiosis

EXPERIMENTS carried out in this department during the past summer may be of interest in connexion with a recent letter from Allison and his collaborators1 in which they conclude for field-grown leguminous plants that the associated nodule bacteria consume only a relatively small proportion of plant carbohydrates in their respiration. In these experiments, determinations have been made of the rate of evolution of respiratory carbon dioxide from the root systems of two series of soya bean plants growing in water culture (Crone's solution), one series (of fifteen plants) being nodulated, the other (of ten plants) being kept free of infection by the nodule organism and supplied with sodium nitrate. During the determinations, which were made at the flowering stage and at a temperature of 20°–21° C., air initially free of carbon dioxide was bubbled through the culture solution in which the root systems were growing and then passed into absorption towers containing standard baryta. For the nitrate plants the evolution of carbon dioxide was of the order of 0·8 c.c. (at N.T.P.) per hour per gm. dry weight of root tissues. Allison et al. report an average Qo2of 2·2 for detached root fragments, equivalent to an absorption of 2·2 c.c. of oxygen per hour per gm. dry weight. They used young roots only, whereas the figure of 0·8 c.c. is an average for the whole root system: again, it is probable that the Washington experiments were conducted at a higher temperature.

STABLE ISOTOPES AS INDICATORS IN BIOLOGY

STABLE ISOTOPES AS INDICATORS IN BIOLOGY

SOIL CONDITIONS AND THE TAKE‐ALL DISEASE OF WHEAT: THE RELATION BETWEEN SOIL REACTION AND SOIL AERATION

SUMMARYBy forced aeration, acid soils can be rendered quite as favourable for the growth, of Ophiobolus graminis along the roots of wheat seedlings as alkaline soils. This finding is in agreement with the hypothesis that growth of the fungus along the wheat roots in acid soils is retarded by the accumulation of respiratory carbon dioxide.