STIMULATORY EFFECT OF DL-3-HYDROXYBUTYRATE ON OXYGEN UPTAKE OF PERFUSED OMASAL LEAF

1984 ◽  
Vol 64 (5) ◽  
pp. 273-275 ◽  
Author(s):  
B. EMMANUEL ◽  
F. J. LOZEMAN ◽  
L. P. MILLIGAN
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake ◽  
Key Words ◽  
Rumen Microorganisms ◽  
Rumen Epithelium ◽  
Perfusion Chamber ◽  
Microbial Suspension

Oxygen uptake by the perfused omasal leaf was measured in the presence of mixed rumen microbial suspension which was kept anaerobically in the lumen side of a perfusion chamber. The addition of DL-3-hydroxybutyrate at 2, 4 and 8 mM concentrations to the microbial suspension increased oxygen withdrawal by 4.4, 11.1 and 15.5%, respectively. It is proposed that electron transfer through the coupled D(−)-3-hydroxybutyrate-acetoacetate reaction from rumen microorganisms to rumen epithelium yield energy for the latter tissue. Key words: Omasal leaf, oxygen uptake, microbes, DL-3-hydroxybutyrate

scholarly journals Cultivation at high osmotic pressure confers ubiquinone 8–independent protection of respiration on Escherichia coli

2019 ◽  
Vol 295 (4) ◽  
pp. 981-993 ◽  
Author(s):  
Laura Tempelhagen ◽  
Anita Ayer ◽  
Doreen E. Culham ◽  
Roland Stocker ◽  
Janet M. Wood
Keyword(s):  
Oxidative Stress ◽  
Gene Expression ◽  
Escherichia Coli ◽  
Electron Transfer ◽  
Oxygen Uptake ◽  
Osmotic Pressure ◽  
Respiratory Chain ◽  
Membrane Lipid ◽  
E Coli ◽  
Uptake Rates

Ubiquinone 8 (coenzyme Q8 or Q8) mediates electron transfer within the aerobic respiratory chain, mitigates oxidative stress, and contributes to gene expression in Escherichia coli. In addition, Q8 was proposed to confer bacterial osmotolerance by accumulating during growth at high osmotic pressure and altering membrane stability. The osmolyte trehalose and membrane lipid cardiolipin accumulate in E. coli cells cultivated at high osmotic pressure. Here, Q8 deficiency impaired E. coli growth at low osmotic pressure and rendered growth osmotically sensitive. The Q8 deficiency impeded cellular O2 uptake and also inhibited the activities of two proton symporters, the osmosensing transporter ProP and the lactose transporter LacY. Q8 supplementation decreased membrane fluidity in liposomes, but did not affect ProP activity in proteoliposomes, which is respiration-independent. Liposomes and proteoliposomes prepared with E. coli lipids were used for these experiments. Similar oxygen uptake rates were observed for bacteria cultivated at low and high osmotic pressures. In contrast, respiration was dramatically inhibited when bacteria grown at the same low osmotic pressure were shifted to high osmotic pressure. Thus, respiration was restored during prolonged growth of E. coli at high osmotic pressure. Of note, bacteria cultivated at low and high osmotic pressures had similar Q8 concentrations. The protection of respiration was neither diminished by cardiolipin deficiency nor conferred by trehalose overproduction during growth at low osmotic pressure, but rather might be achieved by Q8-independent respiratory chain remodeling. We conclude that osmotolerance is conferred through Q8-independent protection of respiration, not by altering physical properties of the membrane.

Validity and Reliability of the Cosmed K2 to Measure Oxygen Uptake

1993 ◽  
Vol 18 (2) ◽  
pp. 197-206 ◽  
Author(s):  
F. Lothian ◽  
M. R. Farrally ◽  
C. Mahoney
Keyword(s):  
Oxygen Uptake ◽  
Key Words ◽  
Female Subject ◽  
Peak Oxygen Uptake ◽  
Variation Coefficient ◽  
Validity And Reliability ◽  
System A ◽  
On Line ◽  
The Difference ◽  
Line Oxygen

The validity and reliability of the Cosmed K2 was tested in comparison with a Quinton on-line oxygen analysing system. A female subject was monitored on a treadmill using a progressive protocol and was measured on three occasions with each system. It was found at low workloads that the Cosmed K2 and the Quinton gave the same measure of oxygen uptake; at higher workloads the Cosmed K2 gave lower values, and at peak oxygen uptake the Cosmed K2 measured 22.2% less than the Quinton. The difference in the measurement of [Formula: see text] at peak oxygen uptake was 13%. The Cosmed K2's measurement of [Formula: see text] showed a greater variability between trials (variation coefficient 3.0-11.4%) than the Quinton (variation coefficient 1.1-3.9%). Key words: Cosmed K2, validity, telemetry

Sulfonyl esters 7. The second and third sequences in the Trithioorthoformate Reaction

1996 ◽  
Vol 74 (9) ◽  
pp. 1638-1648 ◽  
Author(s):  
Kashyapa Ananda Ginige ◽  
John Edward Goehl ◽  
Richard Francis Langler
Keyword(s):  
Electron Transfer ◽  
Key Words ◽  
Single Electron ◽  
Single Electron Transfer ◽  
One Pot ◽  
The One ◽  
Sulfonate Ester

A previous report has established the intermediacy of a sulfide-sulfonate ester in the one-pot conversion of an aryl mercaptan and a sulfonate ester into the corresponding trithioorthoformate. This report describes evidence for the sequential intermediacy of a bissulfide-sulfonate ester and a dithiosulfène in the conversion of the sulfide-sulfonate ester into the trithioorthoformate. A new sulfonate ester is shown to give the highest yield of trithioorthoformate. Key words: single electron transfer, sulfonate esters, sulfenes.

scholarly journals Aspartate 205 in the Catalytic Domain of Naphthalene Dioxygenase Is Essential for Activity

1999 ◽  
Vol 181 (6) ◽  
pp. 1831-1837 ◽  
Author(s):  
Rebecca E. Parales ◽  
Juanito V. Parales ◽  
David T. Gibson
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake ◽  
Catalytic Domain ◽  
Mutant Protein ◽  
Wild Type ◽  
Naphthalene Dioxygenase ◽  
Major Pathway ◽  
Α Subunit ◽  
Mutant Proteins ◽  
Mononuclear Iron

ABSTRACT The naphthalene dioxygenase enzyme system carries out the first step in the aerobic degradation of naphthalene byPseudomonas sp. strain NCIB 9816-4. The crystal structure of naphthalene dioxygenase (B. Kauppi, K. Lee, E. Carredano, R. E. Parales, D. T. Gibson, H. Eklund, and S. Ramaswamy, Structure 6:571–586, 1998) indicates that aspartate 205 may provide the most direct route of electron transfer between the Rieske [2Fe-2S] center of one α subunit and mononuclear iron in the adjacent α subunit. In this study, we constructed four site-directed mutations that changed aspartate 205 to alanine, glutamate, asparagine, or glutamine to test whether this residue is essential for naphthalene dioxygenase activity. The mutant proteins were very inefficient in oxidizing naphthalene tocis-naphthalene dihydrodiol, and oxygen uptake in the presence of naphthalene was below detectable levels. The purified mutant protein with glutamine in place of aspartate 205 had identical spectral properties to wild-type naphthalene dioxygenase and was reduced by NADH in the presence of catalytic amounts of ferredoxinNAP and reductaseNAP. Benzene, an effective uncoupler of oxygen consumption in purified naphthalene dioxygenase, did not elicit oxygen uptake by the mutant protein. These results indicate that electron transfer from NADH to the Rieske center in the mutant oxygenase is intact, a finding consistent with the proposal that aspartate 205 is a necessary residue in the major pathway of electron transfer to mononuclear iron at the active site.

Hydrogen vs. electron transfer mechanisms in the chain decomposition of phenacyl bromides. Use of isotopic labeling as a mechanistic probe

1996 ◽  
Vol 74 (9) ◽  
pp. 1724-1730 ◽  
Author(s):  
Jocelyn Renaud ◽  
J. C. Scaiano
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Key Words ◽  
Hydrogen Transfer ◽  
Isotopic Labeling ◽  
Chain Reaction ◽  
Phenacyl Bromides ◽  
Mechanistic Probe ◽  
A Chain ◽  
Transfer Mechanisms

Ring-substituted α-bromoacetophenones react with alcohols in a chain reaction leading to the corresponding acetophenone, HBr, and the carbonyl compound from oxidation of the alcohol. Two different mechanisms, involving hydrogen or electron transfer by ketyl radicals, have been proposed in order to accommodate the unusual selectivities of these reactions. By studying the efficiency of isotope incorporation from deuterated alcohols, it has been possible to determine the relative contributions from both mechanisms. For example, electron transfer dominates in the case of 2-propanol, while hydrogen transfer is more important for methanol. The results demonstrate that ring substitution in the starting ketone is not a main contributing factor in the discrimination between the two mechanisms. The only parameter that seems to be playing a major role is the nature (reducing strength) of the ketyl radicals. Key words: dehydrobromination, charge transfer, isotope effect, ketyl radicals.

scholarly journals Stimulations of Oxygen Uptake by Electron Transfer Inhibitors

1966 ◽  
Vol 41 (5) ◽  
pp. 797-802 ◽  
Author(s):  
S. Herman Lips ◽  
Jacob B. Biale
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake

EFFECTS OF DIETARY UREA LEVEL ON AMINO ACID CONCENTRATIONS IN RUMINANT TISSUES

1973 ◽  
Vol 53 (4) ◽  
pp. 717-724 ◽  
Author(s):  
H. A. SALEM ◽  
T. J. DEVLIN ◽  
J. R. INGALLS ◽  
G. D. PHILLIPS
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Glutamic Acid ◽  
Latin Square ◽  
Essential Amino Acids ◽  
Plasma Amino Acid ◽  
Isoleucine Leucine ◽  
Rumen Microorganisms ◽  
Rumen Epithelium ◽  
Amino Acid Concentrations

The effects of a semipurified diet containing 0 (0% urea-N diet), 50 (39% urea-N diet), or 100% (76% urea-N diet) of added dietary nitrogen (N) as urea on the amino acid concentrations in ruminant tissues was investigated. Three rumen-fistulated bull calves averaging 240 kg were used in a latin square design. The calves were fed using a continuous feeder to provide 7 kg of feed daily. Each experimental period of the latin square was 40 days divided into four 10-day intervals. Liver samples were obtained on the 9th day of each 10-day interval and rumen epithelium and rumen microorganisms were obtained on the 10th day of each 10-day interval. Blood samples were collected on the 6th, 8th, and 10th day of each 10-day interval for the determination of plasma amino acid patterns as well as the amino acid concentrations in the tissues. Plasma amino acid patterns indicated that when the 76% urea-N diet was fed the levels of aspartic acid, citrulline, glutamic acid, glycine, and proline were increased. Most of the essential amino acids were decreased on the 76% urea-N diet as compared with the 0% urea-N diet. All amino acids of rumen microorganisms were increased on the 39% urea-N diet with the exception of arginine, lysine, and threonine, which decreased slightly or did not show any change. Most amino acids were lower on the 76% urea-N diet as compared with the 39% or 0% urea-N diets. All essential amino acids measured in the liver were reduced on the 76% urea-N diet. Cystine, glutamic acid, glycine, isoleucine, leucine, lysine, tryptophan, and valine were also reduced on the 39% urea-N diet. In rumen epithelium, there was a reduction of the essential amino acids and an increase of the nonessential amino acids on the 76% urea-N diet.

scholarly journals Solvent Surface Tension Effect on Passive Liquid Q – switch Pulse Duration

2008 ◽  
pp. 73-76
Keyword(s):  
Surface Tension ◽  
Electron Transfer ◽  
Carbon Tetrachloride ◽  
Key Words ◽  
Pulse Duration ◽  
Molar Concentration ◽  
Dye Molecules ◽  
Surface Tension Effect ◽  
Yag Laser ◽  
Q Switching

Nickel dye, Bis-(4-Dimethylaminodithobenzil)-Nickel (BDN-I) was used as liquid Q-switch for Nd: YAG laser. Solvent surface tension effect on the Q-switched pulse duration was investigated. Carbon tetrachloride (CCl4), Chloroform (CHCl3), and dioxin (C4H8O) were used as solvents to BDN-I at molar concentration of 59.52 M/l. The measured Qswitched pulse duration was 60± 2.33, 71± 1.95, and 84± 1.32 nsec respectively. The greatest pulse duration reduction was achieved by using CCl42which is of the lowest surface tension with respect to other olvents. The study related that to the low ability of electron transfer from this solvent to the dye molecules. Key words: Physics, Laser, Passive Q-switching, liquid dyes

Redox reactions with ferrocene/ferricenium species of radicals derived by H atom abstraction from alcohols and diols

1991 ◽  
Vol 69 (3) ◽  
pp. 540-544 ◽  
Author(s):  
S. R. Logan
Keyword(s):  
Electron Transfer ◽  
Hydroxyl Radical ◽  
Key Words ◽  
Rate Constants ◽  
Redox Reactions ◽  
Radical Reactions ◽  
Dehydration Process ◽  
Photo Oxidation ◽  
Redox Behaviour ◽  
Vicinal Diols

The effect of various alcohols and diols in diminishing the extent of the photo-oxidation of 4-ferrocenylbutanoate ion in the presence of N2O has been investigated. Where the hydroxyl radical generated in the photo-initiated electron transfer reacts with an alcohol by H atom abstraction at the α-position, the resulting radical is capable of reducing the ferricenium zwitterion to the ferrocenyl anion. Abstraction at other positions produces radicals that are essentially inert in this system and rate constants are derived for the reaction of OH with some such compounds. Non-vicinal diols behave similarly to the corresponding alcohols. With vicinal diols, a dehydration process, which occurs the more slowly the more highly substituted the diol, converts the radical -CR(OH)Ċ(OH)- into -ĊRCO-, which is an oxidizing species. The behaviour of pinacol was found to be anomalous. Key words: radical reactions, redox behaviour, alcohols.

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