Search PubMed⌕ Search

Biomedical subjects

B Chance

Publications and source records attributed to B Chance.

At least 343 records · Page 19Linked to original sources
PubMed1984

31P NMR study of improvement in oxidative phosphorylation by vitamins K3 and C in a patient with a defect in electron transport at complex III in skeletal muscle.

The bioenergetic capacity of skeletal muscle in a 17-year-old patient with a severe defect in complex III of the electron transport chain has been examined by 31P NMR measurements of the molar ratio of phosphocreatine to inorganic phosphate (PCr/Pi). Resting ratios were 1.3-2.5, which can be compared with roughly 8.6 for a young, normal female control at rest. Quantitative evaluation of the activity of oxidative metabolism was afforded by the rate of recovery of PCr/Pi from exercise and was found to be 2.5% of normal. After administration of menadione and ascorbate, we found a 21-fold increase of the recovery rate relative to the pretherapy value, to within 56% of the recovery rate of the young female control. Thus, NMR examinations of skeletal muscle at rest and in recovery from activity document marked improvement to specific drug therapy in the electron transport capabilities and the ATP synthesis rate of a patient with a deficiency in a cytochrome b-containing complex III. Improvements in functional ability, although not as dramatic as biochemical changes, are also apparent.

Adenosine Triphosphate↗
PubMed1984

Applications of 31P NMR to clinical biochemistry.

In summary, phosphorus NMR presents a well documented, continuous, and noninvasive assay of cell energy metabolism in a variety of body organs. In the form used here, it is appropriate to the study of vascular and genetic diseases of the skeletal tissues of adults and energy-related diseases of the body organs in neonates. Under these conditions, 31P NMR is not an expensive installation, has a small up-keep cost, and one which in our experience can be operated by a college graduate technician with ease. We foresee a significant and generalized application to tissue biochemistry in humans.

Adult↗
PubMed1984

Cytochrome o as a terminal oxidase and receptor for aerotaxis in Salmonella typhimurium.

Cytochrome o was the only oxidase of the electron transport system that was present in exponentially growing Salmonella typhimurium ST1. Identification of cytochrome o was made by the (CO-reduced)-minus-(reduced) difference spectra and by the photochemical action spectrum of the relief, by light, of CO-inhibited respiration. Cytochrome o also functioned as the receptor for chemotaxis to oxygen (aerotaxis). The concentration of oxygen that elicits the maximum response for aerotaxis (0.7 microM) was similar to the Km for respiration (0.74 microM), and both aerotaxis and respiration were blocked 5 mM KCN.

Cell Movement↗
PubMed1984

Muscle ischemia and hypothermia: a bioenergetic study using 31phosphorus nuclear magnetic resonance spectroscopy.

UNLABELLED: Following traumatic limb amputation it is common clinical practice to maintain the ischemic tissues in a hypothermic state until surgical reimplantation. Of all extremity tissues, muscle is the most sensitive to ischemia; it is therefore imperative that reperfusion be established before diffuse muscle necrosis. Although it has been shown both clinically and experimentally that hypothermia prolongs the viability of ischemic skeletal muscle, the presumed mechanism by which this occurs has not been confirmed at the cellular level. This study was undertaken to quantify the effect of conventional iced-saline hypothermia on anaerobic cell metabolism and high-energy phosphate depletion in traumatically devascularized muscle. METHODS: Phosphorus nuclear magnetic resonance spectroscopy (31P NMR) was employed to noninvasively monitor cellular phosphocreatine (PCr), ATP, and intracellular pH over time in ischemic cat hindlimb muscle under room temperature (22 degrees C) and 1 degree C hypothermic conditions. RESULTS: Muscular PCr depletion was significantly retarded by tissue hypothermia but the rate of ATP depletion was not. A progressive, severe cellular acidosis was observed in the room-temperature muscle. Iced tissue cooling produced a dramatic initial rise in cell pH which significantly reduced the absolute degree of subsequent acidotic changes. SIGNIFICANCE: These findings question our understanding of hypothermic tissue preservation, which has generally been assumed to work on the basis of decreased tissue metabolism, thus conserving critical cellular ATP levels. The empirical benefit derived by cooling muscle in an iced medium may actually be related to the cellular alkalinization produced by tissue cooling, as this significantly mitigates the profound acidosis that would otherwise occur.

Adenosine Triphosphate↗
PubMed1983

Spectral evidence for the existence of a second cytochrome o in whole cells of Vitreoscilla.

Cytochrome o, a protoheme IX pigment, has been proposed as the terminal oxidase of the filamentous bacterium, Vitreoscilla. Aerobic and anaerobic photolysis of CO-liganded whole cells demonstrated the presence of a second CO-reactive pigment, cytochrome o'. At temperatures lower than -100 degrees C, anaerobic photolysis dissociated only about 25% of the total CO-liganded components to reveal the unliganded cytochrome o'. At these temperatures, the photolysis of cytochrome o could not be demonstrated. At warmer temperatures, recombination of CO with the reduced cytochrome o' occurred with an apparent energy of activation of 5.8 kcal/mol. Aerobic photolysis of whole cells demonstrated two oxygen-bound intermediates. At temperatures lower than -95 degrees C, a spectrally distinct compound with absorption maxima at 428, 534, and 564 nm appeared (form I'); the apparent second order rate constant (k+1) for the formation of this intermediate was found to be 9.1 M-1 s-1, the reverse rate (k-1) was 9.9 X 10(-5) s-1, and the equilibrium constant (Kd) was 1.1 X 10(-5) M. This oxygen intermediate of cytochrome o' is spectrally and kinetically similar to the oxygen intermediate of cytochrome o seen in Escherichia coli. At temperatures warmer than -90 degrees C, photolysis of aerobic samples resulted in the immediate formation of a second oxygen-bound intermediate (form I) with absorption maxima at 422, 534, and 564 nm. This second intermediate results from the binding of oxygen to the cytochrome o (oxygenated cytochrome o). These data support the proposal that whole cells of Vitreoscilla contain two alternative pathways of electron transport, one terminating with cytochrome o and the other with cytochrome o'.

Anaerobiosis↗
PubMed1983

Brain metabolic responses to ischemia in the mongolian gerbil: in vivo and freeze trapped redox scanning.

The interrelation between the metabolic responses to ischemia and seizure propensity was studied in two groups of seizure prone (SP) and non-seizure prone (NSP) gerbils. The metabolic state was evaluated in vivo using the light guide surface fluorometry as well as in the frozen brain scanned at liquid N2 temperature for Fp/PN ratio after monitoring the brain in vivo. The results could be summarized as follows. (1) Unilateral carotid artery occlusion led to partial ischemia in the ipsilateral hemisphere while the contralateral hemisphere remained normoxic. (2) Animal variability in the degree of the ischemia insult due to unilateral occlusion was not side dependent or in correlation with seizure propensity. (3) Significant correlation was found between the NADH increase during ischemia and the redox state measurements done in the same brain after funnel freezing with liquid nitrogen. (4) In a large number of the gerbils (not depending on the origin or strain) a peculiar inter-hemispheric blood supply connection was found. A narrow band (1 mm in width) of tissue near the midline obtained its blood via the same vessels supplying the contralateral hemisphere. (5) We did not find any correlation between blood vessel anatomy to the brain and seizure propensity.

Animals↗
PubMed1983

Effects of glucose, anoxia, and adriamycin on the chemiluminescence of Ehrlich Ascites cells.

Glucose and anoxia accelerate the photocount due to luminescence of Ehrlich Ascites cells. Adriamycin also has this effect if glucose is present. Comparison with a chemical standard combined with estimates of cellular and population transmittance yield a photon generation rate of at least 10 . s-1 . cell-1 in the presence of 10(-2) M glucose, and twice this with anoxic conditions or 10(-5) M adriamycin. Effects of adriamycin on Ehrlich Ascites cell respiration may depend on the presence of glucose.

Animals↗
PubMed1983

Structure and kinetics of the photoproduct of carboxymyoglobin at low temperatures: an X-ray absorption study.

Photolysis and recombination of carboxymyoglobin at low temperatures have been studied by a variety of methods. This paper combines optical and structural studies of carboxymyoglobin photolysis and recombination in the temperature range 4-120 K. The absorbance changes indicate ablation of the characteristic optical transitions of carboxymyoglobin and formation of a photoproduct (Mb*CO) differing from deoxymyoglobin. When the X-ray absorption changes in the 7150-7200-eV region of the X-ray absorption spectrum are used as an indicator of structural change, the photoproduct at 4 K as measured with respect to the unphotolyzed sample is 60% of that observed for the chemically produced deoxy form. Saturation of the change is obtained with repetitive flashes totaling several thousand joules of energy from a xenon flash lamp by using a thin sample (1 mm) at 4 mM concentration as measured by both optical transmission and X-ray absorption criteria. The kinetics of the reaction show the change to occur at 10 K within the resolving time currently available (2 s) in the X-ray absorption measurements. The amplitude of the light-induced change decreases to half its maximal value at 40 K and to zero at 90 K. Steady illumination suggests at least two recombination processes. Analysis of the extended X-ray absorption fine structure (EXAFS) data on Mb*CO indicates small distance changes in the first shell of Fe-N and Fe-C that can be attributed to lengthening of the pyrrole nitrogen bonds and proximal histidine motion, together with a small displacement of the CO molecule on photolysis--a form here designated Mb*CO. This structure of the germinate state, Mb*CO, may elucidate the nature of elementary steps in chemical reactions and in tunneling processes.

Electron Probe Microanalysis↗
PubMed1983

In vivo one-dimensional imaging of phosphorus metabolites by phosphorus-31 nuclear magnetic resonance.

A phosphorus-31 nuclear magnetic resonance imaging technique has been used to obtain information on phosphorus metabolites from different spatial regions of tissues in vivo. The technique for selection of planes through the tissue is based on phase-encoding of spin echoes and was used to obtain one-dimensional discrimination of phosphorus-31 spectra from different parts of the tissue simultaneously. Specimens were resolved into 16 distinct slices and a signal-to-noise ratio of about 20 to 1 was obtained in 1/2 hour. Results are presented for phantoms, rat legs, and gerbil heads.

Adenosine Triphosphate↗
PubMed1983

Spontaneous chemiluminescence of human breath. Spectrum, lifetime, temporal distribution, and correlation with peroxide.

Human breath spontaneously emits photons at a rate of approximately 7,000/liter-s. The emission has a peak in the red part of the spectrum and an ultraviolet contribution. The emission count rate correlates with peroxide concentration in a saturating manner under normal breathing conditions. When trapped in a balloon, the breath luminescence count rate has a half-decay time of approximately 20 min and exhibits more than one mode of decay. The photomultiplier pulses generated by breath luminescence arrive in bursts. The chemiluminescence process appears by these criteria to include chain reactions, long-lived emitters, or both.

Breath Tests↗
PubMed1983

31P NMR spectroscopy of brain and heart.

31P NMR technique was applied to monitor changes in the energy metabolism of the brain and heart of unanesthetized cats during shock, stroke, hypoxia and increased functional activity. The results show that in these tissues content of inorganic phosphate, sugar phosphates, phosphocreatine and of ATP can be measured decently in awake animals. At the same time this technique has the great advantage over the disruptive biochemical methods that it gives a semi-continuous reading and it is non-invasive. Our findings are summarized as follows: Hemorrhagic shock resulted in an irreversible deterioration of the energy state of the brain. Our stroke model led to a very marked increase in Pi and a decrease CP in the brain but these changes were reversible. The ATP levels of the brain as it was indicated by 31p NMR spectra were not affected by hemorrhagic shock and stroke which can be attributed probably by the reduced rate of ATP consumption. The verification of this hypothesis needs further work. During increased mechanical performance the levels of SP, and Pi increased, ATP decreased, while CP was not influenced in the heart.

Animals↗
PubMed1983

Pyridine nucleotides of rabbit cornea with histotoxic anoxia: chemical analysis, non-invasive fluorometry and physiological correlates.

The pyridine nucleotides from both the epithelium and the endothelium of rabbit cornea were measured by the cycling assay. Sodium azide (10 mM) applied for 1 hr to induce histotoxic anoxia decreased the endothelial NAD+/NADH ratio from 4.62 to 1.49 and decreased the epithelial NAD+/NADH ratio from 2.56 to 1.08. The larger NAD+/NADH ratio for the endothelium as compared to the epithelium corresponds to a more oxidized state. The corresponding ratios for NADP+/NADPH were 1.2 for the endothelium and 0.70 for the epithelium. Sodium azide had no effect on the NADP+/NADPH ratio for the endothelium, but decreased the epithelial ratio to 0.62. Pyridine nucleotide fluorescence was measured with a difference corneal fluorometer on the perfused whole cornea preparation and the perfused everted corneal preparation. Sodium azide (10 mM) for 30 min resulted in a 19.4 +/- 0.7% increase in the pyridine nucleotide fluorescence from the whole corneal preparation and a 4.5 +/- 0.6% increase from the everted endothelial preparation. Corneal anoxia induced by stopping the perfusion on the endothelial side resulted in a 18.7 +/- 0.6% increase in pyridine nucleotide fluorescence for the whole corneal preparation. Sodium azide (10 mM) resulted in a 35% decrease in the transendothelial potential difference and a 76% decrease in the rate of transendothelial fluid transport. A comparison is made between invasive chemical analysis and real time, non-invasive fluorometry to measure histotoxic corneal anoxia.

Animals↗
PubMed1983

31-P NMR in the study of liver metabolism in vivo.

Continuous noninvasive readout of biochemical events in body tissues is the goal of many techniques and optical and nuclear magnetic resonance (NMR) approaches seem to be at the forefront of these. Here we present a review of NMR methods for studying liver metabolism in vivo with special emphasis on methods of localizing the response appropriate to the liver itself and to the exclusion of surrounding tissues. The simplest and most direct method appears with the use of an implanted coil which enables a variety of NMR magnets to be used in this study.

Adenosine Monophosphate↗
PubMed1983

"Peroxidatic" form of cytochrome oxidase as studied by X-ray absorption spectroscopy.

X-ray absorption spectroscopy shows pulsed oxidase to be similar to resting oxidase but to lack the sulfur bridge between iron and copper of active sites (Powers, L., Y. Ching, B. Chance, and B. Muhoberac, 1982, Biophys. J., 37[2, Pt. 2]: 403a. [Abstr.] ) The first shell ligands and bond lengths of the pulsed oxidase active site heme most clearly fit the ferric peroxidases from horseradish and yeast, and the pulsed oxidase cyanide compound resembles the low spin hemoprotein cyanide compounds. The structural results are consistent with an aquo or a peroxo form for pulsed oxidase as is also observed by optical studies. These structural and chemical data are consistent with a role for the pulsed forms in a cyclic peroxidatic side reaction in which the pulsed and pulsed peroxide compounds act as peroxide scavengers. The peroxidatic role of cytochrome oxidase in the nonsulfur bridged form suggests the renaming of the "oxygenated" or "pulsed" forms on a functional basis as "peroxidatic" forms of cytochrome oxidase.

Chemical Phenomena↗
PubMed1983

The 650 and chromophore in Escherichia coli is an 'oxy-' or oxygenated compound, not the oxidized form of cytochrome oxidase d: an hypothesis.

The form of cytochrome d in Escherichia coli and Azotobacter vinelandii that shows an absorption maximum at 648 to 652 nm ('cytochrome d650') is generally regarded as the oxidized form of this terminal oxidase. Membranes from E. coli grown under oxygen-limited conditions, when treated with ferricyanide, do not reveal cytochrome d650, whereas a sharp symmetrical band at 652 nm results from the reaction of the reduced enzyme with O2 at either room temperature or after flash photolysis of the CO-liganded form at -130 degrees C. Electron paramagnetic resonance spectroscopy of cytochrome d650 trapped at -130 degrees C shows that its spectrum is indistinguishable from the CO-liganded form and does not reveal resonances of high spin ferric haem previously attributed to cytochrome d. An hypothesis is proposed in which cytochrome d650 is an early intermediate in the reaction of reduced cytochrome d650 and oxyhaemoglobin is presented and the hypothesis discussed in relation to earlier work, in which the indirect interconversions of reduced cytochrome d and d650 have been explained by proposing the existence of an 'invisible' form. It is suggested that this form could be the oxidized enzyme.

Cytochrome d Group↗
PubMed1983

The reaction with oxygen of cytochrome oxidase (cytochrome d) in Escherichia coli K12: optical studies of intermediate species and cytochrome b oxidation at sub-zero temperatures.

Optical changes in d- and b-type cytochromes, following initiation of the reaction of cytochrome oxidase d with O2, have been studied in cells and derived membrane particles from oxygen-limited cultures of Escherichia coli K12. At successively higher temperatures between -132 and -88 degrees C, the first scan after photolysis of the Co-liganded, reduced oxidase in the presence of O2 and a slow increase in absorbance at 675 to 680 nm due to an unidentified chromophore. A similar sequence occurs when a single sample is scanned repetitively at -91 degrees C. At higher temperatures, oxidation of at least two spectrally distinct cytochromes b occurs. Selective photolysis of the cytochrome d-CO complex with a He-Ne laser shows that neither of these cytochromes is the CO-binding cytochrome o436. In all oxidation states examined, no absorbance in the 720 to 860 nm region was observed; it is concluded that both cytochromes d and o436 lack redox-active copper that has an environment similar to the copper(s) in mitochondrial cytochrome c oxidase. The amount of cytochrome d650 (but not the amount of reduced cytochrome o436) formed after photolysis is directly proportional to the oxygen concentration in the sample at the time of freeze trapping. The results are discussed in relation to the composition and mechanism of action of cytochrome d.

Carbon Monoxide↗