scholarly journals The Effects of the Dipyridyl Diquat on the Metabolism of Chlorella Vulgaris III. Dark Metabolism: Effects on Respiration Rate and the Path of Carbon

1971 ◽  
Vol 24 (3) ◽  
pp. 433 ◽  
Author(s):  
DM Stokes ◽  
JS Turner
Keyword(s):  
Citric Acid ◽  
Oxygen Uptake ◽  
Carbohydrate Metabolism ◽  
Chlorella Vulgaris ◽  
Dark Respiration ◽  
Complete Darkness ◽  
Tracer Studies ◽  
Rapid Accumulation ◽  
Dark Metabolism ◽  
Stimulation Of

When O. vulgaris is treated in complete darkness with diquat at concentrations which are toxic in the light, there is a rapid and large stimulation of oxygen uptake with no significant alteration in the R,Q. If the O. vulgaris has been darkened for some hours before the addition of diquat there is a two- to threefold stimulation of the rate of respiration, which subsequently remains constant or falls only slowly for up to 500 min. With pre-illuminated or glucose-treated O. vulgaris, diquat causes a much greater stimulation of dark respiration, rapidly declining to near the control rate. Tracer studies with 14C02 and [14C]glucose show that diquat when added in darkness to O. vulgaris accelerates the breakdown of starch and the loss of 14C from most intermediate substances of carbohydrate metabolism. The exception to this is the rapid accumulation of 14C counts in citric acid. These results are discussed and a mechanism for the action of diquat in darkness is proposed.

scholarly journals STUDIES ON PHOTOSYNTHESIS

1940 ◽  
Vol 24 (1) ◽  
pp. 45-67 ◽  
Author(s):  
Jack Myers ◽  
G. O. Burr
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Evolution ◽  
Chlorella Vulgaris ◽  
Dark Respiration ◽  
Previous History ◽  
A Value ◽  
Light Intensities ◽  
Constant Rate ◽  
Alternative Hypotheses ◽  
History Of

1. The effect on oxygen evolution of Chlorella vulgaris produced by light intensities up to about 40,000 f.-c. has been studied by the use of the Warburg technique. 2. Above a certain critical intensity, which is determined by the previous history of the cells, the rate of oxygen evolution decreases from the maximum to another constant rate. This depression is at first a completely reversible effect. 3. With a sufficiently high intensity this constant rate represents an oxygen uptake greater than the rate of dark respiration. During such a constant rate of oxygen uptake a progressive injury to the photosynthetic mechanism takes place. After a given oxygen consumption the rate falls off, approaching zero, and the cells are irreversibly injured. 4. The constant rate of oxygen evolution (2 and 3) decreases in a continuous manner with increasing light intensities, approaching a value which is approximately constant for all lots of cells regardless of previous history. 5. Two alternative hypotheses have been presented to explain the observed phenomena. The more acceptable of these proposes quick inactivation of the photosynthetic mechanism, the extent of inhibition depending on the light intensity. 6. In Chlorella vulgaris solarization is influenced by the previous history of the cells.

PATHWAYS OF CARBOHYDRATE METABOLISM IN LOBSTER HEPATOPANCREAS

1962 ◽  
Vol 40 (8) ◽  
pp. 1043-1050 ◽  
Author(s):  
P. W. Hochachka ◽  
J. M. Teal ◽  
M. Telford
Keyword(s):  
Citric Acid ◽  
Oxygen Uptake ◽  
Carbohydrate Metabolism ◽  
Citric Acid Cycle ◽  
The Other ◽  
Short Term ◽  
Acid Cycle

Oxygen uptake by homogenates of lobster hepatopancreas was stimulated by the addition of Embden–Meyerhof, pentose cycle, and citric acid cycle intermediates as well as xylose. Acetate-1-C14oxidation was blocked by fluoracetate and glucose-1-C14oxidation fell by 80% with iodoacetate treatment. TPN and DPN increased glucose-1-C14oxidation by 140% and 20% and acetate-1-C14oxidation by 50% and 100% respectively. Large amounts of C14enter polysaccharide following treatment with glucose-1-C14or acetate-1-C14but very little enters after treatment with the same amount of gluconate-1-C14. Gluconate and xylose oxidation occurs in mitochondria-free preparations. In short-term tests with acetate-1-C14as substrate, most of the label in glycogen is on carbons 3 and 4 and the amount in the other positions can be explained on the basis of a 5–10% participation of the pentose cycle.

scholarly journals The Effeots of the Dipyridyl Diquat on the Metabolism of Chlorella Vulgaris I. Gas Exchange in the Light

1970 ◽  
Vol 23 (1) ◽  
pp. 43 ◽  
Author(s):  
JS Turner ◽  
DM Stokes ◽  
Lynnor B Gilmore
Keyword(s):  
Gas Exchange ◽  
Oxygen Uptake ◽  
Chlorella Vulgaris ◽  
Maximum Rate ◽  
Toxic Substance ◽  
Irreversible Inhibition ◽  
Green Tissue ◽  
Rapid Fall ◽  
Dark Metabolism ◽  
Respiratory Apparatus

The effects of diquat on gas exchange in illuminated C. vUlgaris have been studied by manometric procedures. Estimates of dark oxygen uptake were made by transfer of treated cells to darkness. Analysis of the results indicates that on adding diquat to C. vUlgariB there is a rapid fall in the rate of apparent photosynthesis. This is due to an immediate and large increase in dark metabolism (C02 and O2 exchange) accompanied by irreversible inhibition of real photosynthesis firstly, then of respiration. At some unspecified stage a light-dependent oxygen uptake begins, rises to a maximum rate, and declines to a low value, continuing after the inhibition of respiration. These results are discussed in relation to the known effects of diquat on plastid reactions and to the hypothesis that in illuminated green tissue diquat produces a toxic substance which damages both the photosynthetic and respiratory apparatus.

PATHWAYS OF CARBOHYDRATE METABOLISM IN LOBSTER HEPATOPANCREAS

1962 ◽  
Vol 40 (1) ◽  
pp. 1043-1050 ◽  
Author(s):  
P. W. Hochachka ◽  
J. M. Teal ◽  
M. Telford
Keyword(s):  
Citric Acid ◽  
Oxygen Uptake ◽  
Carbohydrate Metabolism ◽  
Citric Acid Cycle ◽  
The Other ◽  
Short Term ◽  
Acid Cycle

Oxygen uptake by homogenates of lobster hepatopancreas was stimulated by the addition of Embden–Meyerhof, pentose cycle, and citric acid cycle intermediates as well as xylose. Acetate-1-C14oxidation was blocked by fluoracetate and glucose-1-C14oxidation fell by 80% with iodoacetate treatment. TPN and DPN increased glucose-1-C14oxidation by 140% and 20% and acetate-1-C14oxidation by 50% and 100% respectively. Large amounts of C14enter polysaccharide following treatment with glucose-1-C14or acetate-1-C14but very little enters after treatment with the same amount of gluconate-1-C14. Gluconate and xylose oxidation occurs in mitochondria-free preparations. In short-term tests with acetate-1-C14as substrate, most of the label in glycogen is on carbons 3 and 4 and the amount in the other positions can be explained on the basis of a 5–10% participation of the pentose cycle.

The change from symmetry to asymmetry of a sodium transport system in red cell membranes

1985 ◽  
Vol 223 (1233) ◽  
pp. 449-457 ◽  
Keyword(s):  
Sodium Concentration ◽  
Tracer Studies ◽  
Chloride Medium ◽  
Sodium Influx ◽  
Nitrate Medium ◽  
Sodium Efflux ◽  
External Potassium ◽  
Red Cell Membranes ◽  
Stimulation Of ◽  
Human Red Cells

A study has been made with human red cells of sodium movements that are sensitive to the drug furosemide. The aim was to see if furosemide-sensitive movements that are symmetrical (exchange) became asymmetrical (net transport) on replacement of chloride with nitrate as the major external anion. Cells were incubated for 4 h at 37 °C with 140 mm sodium, and chloride or nitrate as the principal anion. Under a variety of conditions (presence and absence of ouabain or furosemide, or both) the cell sodium concentration was always higher when chloride was replaced with nitrate. The cells became leakier to sodium. Tracer studies indicated that, in contrast to the results in chloride medium, the decrease in sodium influx was greater than the fall in efflux when furosemide was added to cells in nitrate medium. The results confirm that the sensitivity of sodium efflux to furosemide depended on chloride. However, influx showed a different sensitivity in that furosemide still inhibited in cells incubated in nitrate medium. The stimulation of sodium influx with nitrate medium was independent of external potassium (10–50 mm) and the furosemide-sensitive influx was also constant. It is concluded that symmetrical transmembrane sodium movements with cells in chloride medium became downhill asymmetrical in nitrate medium, giving a net gain of cell sodium that was insensitive to ouabain and sensitive to furosemide. The drug thus partly retarded the gain of cell sodium that otherwise occurred in the somewhat leaky cells.

Laryngeal and tracheobronchial cough in anesthetized dogs

1994 ◽  
Vol 76 (6) ◽  
pp. 2672-2679 ◽  
Author(s):  
M. Tatar ◽  
G. Sant′Ambrogio ◽  
F. B. Sant′Ambrogio
Keyword(s):  
Citric Acid ◽  
Mechanical Stimulation ◽  
Esophageal Pressure ◽  
Afferent Fibers ◽  
Anesthetized Dogs ◽  
Conduction Cooling ◽  
Chemical Stimuli ◽  
Alpha Chloralose ◽  
Tracheal Bifurcation ◽  
Stimulation Of

Tussigenic sensitivity of laryngeal and tracheobronchial regions to mechanical and chemical stimuli was compared in 22 urethan-alpha-chloralose-anesthetized dogs. In addition, the contribution of myelinated and unmyelinated vagal fibers in mediating laryngeal and tracheobronchial cough was investigated. The intensity of cough was evaluated from changes in esophageal pressure. Whereas all mechanical stimulations and citric acid inhalations into tracheobronchial region elicited cough, only 56.7% of mechanical stimulation and 33.3% of citric acid challenges to larynx were effective. The intensity of tracheobronchial cough was significantly higher than that of laryngeal cough. When mechanical stimulation was conducted under visual control (bronchofiberscope), cough elicitability was found to be higher from tracheal bifurcation and main stem bronchi (62.5–87.5%) than from any laryngeal structure (0–42.9%). During partial block of vagal conduction (cooling to 6 degrees C), mechanical and citric acid tracheobronchial stimulations failed to elicit cough and mechanical laryngeal stimulation was effective only in 1 of 10 dogs. Intensity of cough was strongly decreased when mechanical stimulation followed capsaicin administration into trachea (0.3 ml; 100 micrograms/ml) or intravenously (10 micrograms/kg). We conclude that, in anesthetized dogs, stimulation of tracheobronchial region is more effective and prompt in eliciting cough than stimulation of larynx, myelinated vagal afferent fibers play an important role in mediating mechanically and citric acid-induced tracheobronchial cough and mechanically induced laryngeal cough, and stimulation of tracheobronchial and pulmonary capsaicin-sensitive receptors strongly inhibits mechanically induced cough.

scholarly journals PHYSIOLOGICAL AND BIOCHEMICAL CHANGES IN ALGAL CULTURES OF CHLORELLA VULGARIS AND SYNECHOCYSTIS SALINA (MESOPHILIC AND ANTARCTIC ISOLATES) OCCURING AFTER TREATMENT WITH UV-B RADIATION

2017 ◽  
pp. 73-82
Author(s):  
Dilyana Doneva ◽  
Juliana Ivanova ◽  
Lyudmila Kabaivanova
Keyword(s):  
Oxidative Stress ◽  
Chlorophyll A ◽  
Chlorella Vulgaris ◽  
Markers Of Oxidative Stress ◽  
Protective Strategies ◽  
The Antarctic ◽  
Antarctic Algae ◽  
Β Carotene ◽  
Stimulation Of

Determination of biomass production and viability of algal cells of Chlorella vulgaris and Synechocystis salina exposed to UV-B radiation were carried out in this study together with comparison of the mesophilic and antarctic isolates of both investigated strains. Estimation of the content of the pigments: chlorophyll a, chlorophyll b, β-carotene, C-phycocyanin and allo-phycocyanin in algal cells exposed to UV-B radiation was also accomplished. The obtained results showed that the antarctic algae are more resistant to oxidative stress than their mesophilic counterparts. The antarctic isolates of Ch. vulgaris and S. salina compared with the mesophilic ones - up to 72 h showed tolerance to low exposures of radiation, expressed in a slight stimulation of growth and viability of the cells. Antarctic isolates also showed greater resistance to low doses of UV-B radiation manifested by stimulation of the synthesis of chlorophyll a and β-carotene. The registered increase in the amount of C- and allo-phycocyanin in antarctic isolates of S. salina showed that they had developed protective strategies against UV-B radiation by increasing the concentration of the phycobiliproteins. As a result of increased UV-B background, in antarctic isolates, stronger antioxidant defence mechanisms are triggered, which proved the possibility of using them as markers of oxidative stress.

Effect of stimulation of hepatic nerves on hepatic O2 uptake and blood flow

1977 ◽  
Vol 232 (6) ◽  
pp. H652-H656
Author(s):  
W. W. Lautt
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Oxygen Uptake ◽  
Portal Vein ◽  
Hepatic Artery ◽  
Venous Blood ◽  
Neurogenic Vasoconstriction ◽  
Pressure Changes ◽  
Hepatic Nerves ◽  
Stimulation Of

Acute denervation of the liver did not result in changes of oxygen uptake or hemodynamics in the intact liver of the cat. Stimulation of the hepatic nerves resulted in a marked reduction of vascular conductance of the hepatic artery and portal vein (intrahepatic) resulting in almost complete cessation of arterial flow and increased portal blood pressure. The hepatic artery showed a more complete escape from the neurogenic vasoconstriction than did the portal vein. During the stable "escape phase" oxygen delivery was 86% of control, but hepatic extraction of oxygen increased so that oxygen uptake was not altered from control values. The return of oxygen consumption to normal during nerve stimulation suggests that redistribution of hepatic blood flow did not occur. In spite of arterial and portal venous blood pressure changes and changes in gut conductance, oxygen extraction of the gut did not change.

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