scholarly journals SILICON METABOLISM IN DIATOMS

1955 ◽  
Vol 39 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Joyce C. Lewin
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Respiratory Quotient ◽  
Aerobic Respiration ◽  
Carbon Dioxide Evolution ◽  
Exogenous Glucose ◽  
Silicon Uptake ◽  
Silicon Metabolism ◽  
Respiratory Stimulation ◽  
Stimulation Of

1. Evidence is presented that silicon uptake in the diatom Navicula pelliculosa is linked with aerobic respiration. 2. Cyanide, fluoride, iodoacetate, arsenite, azide, and fluoroacetate, at concentrations inhibitory to respiration, were also inhibitory to silicon uptake. 3. 2,4-Dinitrophenol (1 to 2 x 10–5 M) stimulated respiration by 100 per cent, but almost completely inhibited silicon uptake. 4. The respiratory quotient of non-Si-deficient cells decreased from 0.93 to 0.75 after 4 days of starvation in darkness. Glucose (1 per cent) raised the respiratory quotient of such starved cells to 1.05. 5. Silicate (20 mg. Si/liter) stimulated respiration of unstarved Si-deficient cells by about 40 per cent. The effect of silicate on the respiration of Si-deficient cells which had been starved in darkness for 4 days was less marked. 6. The respiratory quotient of Si-deficient cells decreased from 0.8–0.9 to 0.3 after 4 days of starvation in darkness. The addition of silicate to starved cells raised the quotient to 0.5. This represented a 25 per cent stimulation of oxygen uptake concomitant with a 90 per cent stimulation of carbon dioxide evolution. 7. Glucose (1 per cent) caused an increase of respiratory quotient in starved cells from 0.3 to 0.7–0.8. The addition of silicate had no effect on the R.Q. during the oxidation of exogenous glucose. 8. Substrates (glucose, fructose, galactose, lactate, succinate, citrate, glycerol), which caused a stimulation of respiration in starved cells, also stimulated silicon uptake by those cells. However, the stimulation of silicon uptake (50 to 100 per cent) was not proportional to the respiratory stimulation by these substrates (30 to 300 per cent).

RESPIRATION OF INTACT CELLS OF A LOW-TEMPERATURE BASIDIOMYCETE

1966 ◽  
Vol 44 (8) ◽  
pp. 1077-1086 ◽  
Author(s):  
E. W. B. Ward
Keyword(s):  
Carbon Dioxide ◽  
Low Temperature ◽  
Oxygen Uptake ◽  
Respiratory Quotient ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Sources ◽  
Endogenous Respiration ◽  
Starvation Period ◽  
Intact Cells ◽  
Exogenous Glucose

Conventional manometric procedures were used to measure oxygen uptake and carbon dioxide evolution by cells of a low-temperature basidiomycete. Total respiration was lowest and, relatively, endogenous respiration was highest in old cells. During starvation, endogenous respiration decreased but did so most rapidly in young cells. Maximum response to exogenous glucose was obtained from young cells after starvation. The respiratory quotient of endogenous respiration fell from 1.0 to approximately 0.7 during starvation, indicating a change in endogenous substrate. Conversely the respiratory quotient for exogenous respiration of added glucose increased with the starvation period. The level of oxidative assimilation of glucose was shown to be high (80-90%) and evidence was obtained that exogenous glucose did not suppress endogenous respiration.The optimum temperature for oxygen uptake was 25 °C, below which the Q10 was approximately 2. At 30 °C the rate, while initially highest, decreased during the 6-hour incubation period.The fungus utilized various compounds as carbon sources, but not sucrose in short-term experiments. Glucose, but not xylose was fermented, although the ratio of carbon dioxide to ethanol was not 1:1. Inhibition by fluoride, arsenite, iodoacetate, fluoroacetate, and malonate suggested that both glucose and xylose are respired at least in part by the Embden-Meyerof pathway and the tricarboxylic acid cycle. Endogenous respiration was only slightly affected by these inhibitors.

STUDIES IN THE MODE OF ACTION OF ROYAL JELLY IN HONEYBEE DEVELOPMENT: II. RESPIRATION OF NEWLY EMERGED LARVAE ON VARIOUS SUBSTRATES

1959 ◽  
Vol 37 (5) ◽  
pp. 803-813 ◽  
Author(s):  
R. W. Shuel ◽  
S. E. Dixon
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Mode Of Action ◽  
Royal Jelly ◽  
Water Soluble ◽  
Older Worker ◽  
Carbon Dioxide Evolution ◽  
Carbon Dioxide Output ◽  
Nutritional Balance

Measurements were made of oxygen uptake and carbon dioxide evolution, during the first 24 hours of life, by larvae on substrates of different age and type. These substrates included royal jelly, the pharyngeal secretion fed to larvae destined to become queens, which varied in age from 0 to 96 hours; the pharyngeal secretion fed to young larvae destined to be workers, which varied in age from 0 to 60 hours and which was termed "worker jelly"; and the food supplied to older worker larvae, composed of a pharyngeal secretion modified by an admixture of honey and pollen, and termed "modified jelly". The pattern and magnitude of oxygen uptake was similar on all substrates. Net carbon dioxide evolution by larvae on royal jelly or modified jelly was highly positive; net carbon dioxide evolution by larvae on worker jelly was slightly negative. Microchemical analyses showed that royal jelly differed in composition from worker jelly and modified jelly. The composition of royal jelly remained relatively constant with age. The addition of sugars to worker jelly produced an increase in carbon dioxide output which was nullified by the further addition of an extract of the water-soluble acids of royal jelly. The differences observed in carbon dioxide evolution by young larvae on worker jelly and royal jelly are considered to be an expression of the initiation of female dimorphism. An hypothesis of nutritional balance is advanced to account for this dimorphism.

ON THE MECHANISM OF INDOLEACETIC ACID OXIDATION BY WHEAT LEAF ENZYMES

1956 ◽  
Vol 34 (1) ◽  
pp. 54-59 ◽  
Author(s):  
E. R. Waygood ◽  
Ann Oaks ◽  
G. A. Maclachlan
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Induction Period ◽  
Indoleacetic Acid ◽  
Acid Oxidation ◽  
Not Given ◽  
Carbon Dioxide Evolution ◽  
Enzyme Preparations ◽  
Wheat Leaf ◽  
Wheat Leaves

Partially purified enzyme preparations of wheat leaves oxidize indoleacetic acid completely in the presence of manganese and a monohydroxyphenol or resorcinol. A characteristic feature of the oxygen uptake is an induction period followed by a rapid oxygen uptake which ceases when 1 mole of oxygen is consumed per mole indoleacetic acid added. One mole of carbon dioxide is evolved per mole indoleacetic acid. There is no lag in carbon dioxide evolution, but it is not given off anaerobically. Oxygen, blue light, and acetaldehyde overcome the induction period. Hydrogen peroxide formed in a final aerobic dehydrogenase step is utilized to provide a source of manganic ions which act as an electron acceptor in an initial oxidative step.

THE METABOLISM OF YEAST SPORULATION: III. RESPIRATION OF SPORULATING AND GROWING CELLS

1959 ◽  
Vol 5 (2) ◽  
pp. 153-159 ◽  
Author(s):  
J. J. Miller ◽  
O. Hoffmann-Ostenhof ◽  
Eszter Scheiber ◽  
O. Gabriel
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Growth Medium ◽  
Respiratory Quotient ◽  
The Other ◽  
Clear Correlation ◽  
Endogenous Respiration ◽  
Anaerobic Conditions ◽  
Sodium Pyruvate ◽  
Carbon Dioxide Output

Cells from growth medium had a strong endogenous respiration under aerobic conditions with a respiratory quotient of approximately unity. In M/300 glucose, their oxygen uptake was somewhat greater than the endogenous, but the aerobic carbon dioxide output was approximately twice the oxygen uptake. When such cells were incubated in buffer no change in their respiration in glucose was noted in 2 days, but when incubated in 0.3% acetate the respiratory quotient declined to 1.3–1.5. This decline was evident within six hours of the time the cells were placed in acetate. Glucose (0.1%) also depressed the respiratory quotient. With two other sporulation substrates, sodium pyruvate (0.13%) and lactic acid (0.1%), the effect was not so pronounced, and a fifth, dihydroxyacetone (0.1%), seemed to have little or no effect. Spores developed more rapidly and became more abundant in the acetate than in any of the other compounds. The changes in the respiratory quotient did not show a clear correlation with either the amount or the rapidity of sporulation in the five sporulation substrates. When cells were incubated in acetate or in glucose for a day under anaerobic conditions their respiratory quotient did not decline. Some success was obtained in separating sporulated from non-sporulated cells by centrifuging. No difference was noted in the respiration of sporulated and non-sporulated cells. The respiratory quotient of cells from sporulated cultures returned to values characteristic of growing cells after 2 to 4 hours in growth medium.

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