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Biomedical subjects

B Chance

Publications and source records attributed to B Chance.

At least 397 records · Page 22Linked to original sources
PubMed1980

Low-level chemiluminescence of hydroperoxide-supplemented cytochrome c.

Ferricytochrome c showed low-level chemiluminescence, with a light-emission measured of about 1x10(3)-3x10(3) counts/s, when supplemented with organic hydroperoxides. Tertiary hydroperoxides (cumene hydroperoxide and t-butyl hydroperoxide) showed a saturation behaviour at about 5mm-hydroperoxide, whereas primary hydroperoxides showed a quadratic dependence on the hydroperoxide concentration. Chemiluminescence depended linearly on cytochrome c concentration, and optimal light-emission was observed at [t-butyl hydroperoxide]/[ferricytochrome c] ratios of 160-500. Hydroperoxide-supplemented ferricytochrome c consumed O(2) at a rate of 1.0mumol/min per mumol of cytochrome c; the rate of O(2) uptake was linearly related to the concentration of cytochrome c. The Soret absorption band of ferricytochrome c decreased about 64% after incubation with t-butyl hydroperoxide, whereas the 530nm band was almost totally abolished. Light-emission was (a) inhibited competitively by cyanide. (b) inhibited by singlet-oxygen quenchers (e.g. beta-carotene), scavengers (e.g. dimethylfuran) and traps (e.g. histidine and tryptophan) and (c) increased by singlet-oxygen-chemiluminescence enhancer 1,4-diazabicyclo[2.2.2]-octane. Superoxide dismutase had no effect on the present system. The participation of free radicals is suggested by the effect of the radical trap 2,5-di-t-butylquinol. Singlet-oxygen dimol emission seems to be mainly responsible for the observed light-emission; a mechanism that can account for the major part of the present experimental observations is proposed.

Benzene Derivatives↗
PubMed1980

Low-level chemiluminescence of bovine heart submitochondrial particles.

Submitochondrial particles from bovine heart mitochondria showed low-level chemiluminescence when supplemented with organic hydroperoxides. Chemiluminescence seems to measure integratively radical reactions involved in lipid peroxidation and related processes. Maximal light-emission was about 1500 counts/s and was reached 2-10min after addition of hydroperoxides. Ethyl hydroperoxide, cumene hydroperoxide and t-butyl hydroperoxide were effective in that order. Antimycin and rotenone increased chemiluminescence by 50-60%; addition of substrates, NADH and succinate did not produce marked changes in the observed chemiluminescence. Cyanide inhibited chemiluminescence; half-maximal inhibitory effect was obtained with 0.03mm-cyanide and the inhibition was competitive with respect to t-butyl hydroperoxide. Externally added cytochrome c (10-20mum) had a marked stimulatory effect on chemiluminescence, namely a 12-fold increase in light-emission of antimycin-inhibited submitochondrial particles. Stimulation of hydroperoxide-induced chemiluminescence of submitochondrial particles by cytochrome c was matched by a burst of O(2) consumption. O(2) is believed to participate in the chain radical reactions that lead to lipid peroxidation. Superoxide anion seems to be involved in the chemiluminescence reactions as long as light-emission was 50-60% inhibitible by superoxide dismutase. Singlet-oxygen quenchers, e.g. beta-carotene and 1,4-diazabicyclo[2,2,2]-octane, affected light-emission. beta-Carotene was effective either when incorporated into the membranes or added to the cuvette. The present paper suggests that singlet molecular oxygen is mainly responsible for the light-emission in the hydroperoxide-supplemented submitochondrial particles.

Animals↗
PubMed1980

The interrelation between brain PO2 and NADH oxidation-reduction state in the gerbil.

The present investigation was aimed at studying the interrelation between hemodynamic, metabolic and oxygen tension in the brain of the gerbil exposed to various physiological and pathological conditions in the awake and anesthetized states. The hemodynamic and metabolic activities were evaluated by the DC fluorometer/reflectometer and were correlated to the pO2 values obtained by a surface electrode. When the awake brain was exposed to spreading depression (SD), a typical oxidation cycle of the NADH was recorded concomitant with a decrease cycle of the pO2. Under anesthetic effect the same dip in pO2 response was found but the NADH showed a "reduction cycle." The pO2 values were in a very good correlation with the changes in the reflectance trace, namely, the pO2 was a good indicator of the vasoconstriction-vasodilatation responses under various conditions. The same model was used under hypoxic and ischemic conditions, as well as under the effects of anesthetics.

Anesthesia, General↗
PubMed1980

Oscillations of redox states in synchronously dividing cultures of Acanthamoeba castellanii and Schizosaccharomyces pombe.

The redox state of the mitochondria of Acanthamoeba castellanii and Schizosaccharomyces pombe was assessed with a flying-spot fluorometer (Chance et al. 1978. Am. J. Physiol. 235:H 809) that provides excitation appropriate for oxidized flavoprotein or reduced pyridine nucleotide. Fluorescence signals could be resolved from the thin films of cultures that were only one cell deep. In both organisms anoxia was associated with an increased pyridine nucleotide and decreased flavoprotein fluorescence. The addition of mitochondrial uncoupling agents increased the flavoprotein fluorescence and the fluorometer was able to resolve uncoupler-sensitive and uncoupler-insensitive fractions of S. pombe cultures. In both synchronous and asynchronous cultures of A. castellanii and S. pombe the mitochondrial redox state oscillates with a period of 4.5 +/- 1.0 min. Oscillations with much longer period, of the order of an hour, are observed in synchronous cultures and these oscillations correlate with similar oscillations in respiratory rate, uncoupler sensitivity, and adenine nucleotide pool sizes. The results are consistent with the hypothesis that synchronous cultures of A. castellanii and S. pombe oscillate between the ADP-limited (state 4) and ADP-sufficient (state 3) respiratory states, i.e., exhibit in vivo respiratory control.

Amoeba↗
PubMed1980

Organ chemiluminescence: noninvasive assay for oxidative radical reactions.

In situ and perfused rat livers showed a spontaneous chemiluminescence of 7-12 counts/sec . cm2 (corresponding to 7-12 x 10(3) photons/sec . cm2); chemiluminescence was increased up to 30 times by infusion of exogenous hydroperoxides. The chemiluminescence of the perfused liver was oxygen dependent. Ethyl, t-butyl, and cumene hydroperoxides were almost equally effective in inducing light emission in the perfused liver. Glutathione release and chemiluminescence showed a parallel increase upon hydroperoxide supply to the perfused liver. A partial spectral analysis of the chemiluminescence of the perfused liver showed a predominance of red-light-emitting species, presumably arising from the singlet oxygen dimol-emission peaks. Many side reactions derived from the complex free radical sequence of lipid peroxidation could afford the chemistry leading to light emission, which represents only about 10(-14) of the utilization of peroxide.

Animals↗
PubMed1980

Noninvasive, nondestructive approaches to cell bioenergetics.

To demonstrate the feasibility of using NMR spectra of human limbs and larger animals for continuous, noninvasive, nondestructive evaluation of cell bioenergetics, we have constructed a relatively simple and inexpensive 31P NMR apparatus. This apparatus consists of an 18-cm (7-in.) bore superconducting magnet and appropriate transmit-receive components for Fourier transform NMR. The principal signals observed by this instrument in the tissues are due to phosphocreatine and inorganic phosphate. The apparatus can be used to detect tissue normoxia and hypoxia. The large phosphocreatine/phosphate ratio (greater than 10:1), and the low phosphate signal from normoxic tissue (approximately 10% of the phosphocreatine signal from brain and human skeletal tissue) make an increased phosphate peak a very sensitive indicator of tissue hypoxia. Direct experiments on the human forearm and leg and the brains of dog and rabbit suggest the applicability of 31P NMR to humans and animals. This method and optical methods can both be used for quantitative determination of oxygen delivery to tissue, function of mitochondria, and the coupling of bioenergetic processes to functional activity in skeletal tissue and brain.

Animals↗
PubMed1980

Flying spot studies of brain flavoproteins in the gerbil.

The flying spot fluorometer/reflectometer for flavoprotein (Fp) was used in the present study in order to evaluate energy metabolism in the anesthetized gerbil brain. This model was exposed to various conditions, such as anoxia, spreading depression, and ischemia. The fluorescence and reflected light were analyzed in terms of intensities of histograms, and the fractional changes were calculated and compared between the metabolic states. The results show that under various conditions, the fluorescence of Fp changed together with the reflectance change, and the net mitochondrial change was not always clear. The results presented in the study are in good agreement with the previously-published results.

Animals↗
PubMed1980

Surface fluorescence of reduced pyridine nucleotide of the perfused rat kidney: interrelation between metabolic and functional states.

Surface fluorescence of reduced pyridine nucleotide (PN) was recorded continously with a DC fluorormeter and correlated with changes in experimental conditions. As a light source for fluorescence excitation, an Hg arc lamp with a 340-375 nm filter in front was used; the fluorescence response of reduced PN was measured at 450-510 nm. The DC fluormeter and the Hg arc lamp were connected to the kidney by a trifurcated fiber optics light guide. Reduced PN fluorescence emission was corrected for changes in tissue opacity by a 1:1 subtraction of reflectance changes at 340-375 nm from the fluorescence (PN-deltaR). To obtain further information about the PN redox state of the total surface area of kidney cortex and to evaluate whether certain areas were insufficiently perfused, fluorescence photographs of the total surface area were taken. The results demonstrate that the described method is simple and provides specific information about the mitochondrial oxidation reduction state.

Animals↗