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Biomedical subjects

B Chance

Publications and source records attributed to B Chance.

At least 469 records · Page 26Linked to original sources
PubMed1976

Synthesis, structure determination, spectral properties, and energy-linked spectral responses of the extrinsic probe oxonol V in membranes.

The direct synthesis of bis]3-phenyl-5-oxoisoxazol-4-yl]pentamethineoxonol, which is shown to be the fluorescent probe OX-V (formerly MC-V), is described. The emission lifetime (0.9 +/- 0.1 ns) and the spectral properties of this dye in a number of systems are presented as well as the relative polarizations associated with the transition moments of the observable electronic transitions. The structure of OX-V was determined using elemental analysis and infrared and 1H nuclear magnetic resonance (NMR) spectroscopy. The use of the contact shift reagent, Eu(fod)3-d27, greatly facilitated the interpretation of the NMR results. In aqueous media, the anionic form of OX-V is present virtually exclusively due to the low solubility of the neutral species; formation of the latter species occurs when ethanol or methanol solutions of OX-V are acidiied. Both neutral and anionic dye forms can be detected in chloroform-ethanol solvents. The fluorescence intensity from excitation of the neutral species is an order of magnitude weaker than that from excitation of the anionic form and may result from the formation of excited anions due to the loss of a proton by the neutral species in the excited state. Polarization results indicate that the visible absorption of the dye is due to a single electronic transition. OX-V has been employed as a probe primarily in beef heart submitochondrial particles, reconstituted ATPase vesicles,a nd pigeon heart mitochondria. The energy-linked spectral changes of the probe in these preparations are described and mechanisms proposed for the spectral effects.

Animals↗
PubMed1976

Oxygen toxicity in the perfused rat liver and lung under hyperbaric conditions.

1. In the lung and liver of tocopherol-deficient rats, the activities of glutathione peroxidase and glucose 6-phosphate dehydrogenase were increased substantially, suggesting an important role for both enzymes in protecting the organ against the deleterious effects of lipid peroxides. 2. Facilitation of the glutathione peroxidase reaction by infusing t-butyl hydroperoxide caused the oxidation of nicotinamide nucleotides and glutathione, resulting in a concomitant increase in the rate of release of oxidized glutathione into the perfusate. Thus the rate of production of lipid peroxide and H2O2 in the perfused organ could be compared by simultaneous measurement of the rate of glutathione release and the turnover number of the catalase reaction. 3. On hyperbaric oxygenation at 4 X 10(5)Pa, H2O2 production, estimated from the turnover of the catalase reaction, was increased slightly in the liver, and glutathione release was increased slightly, in both lung and liver. 4. Tocopherol deficiency caused a marked increase in lipid-peroxide formation as indicated by a corresponding increase in glutathione release under hyperbaric oxygenation, with a further enhancement when the tocopherol-deficient rats were also starved. 5. The study demonstrates that the primary response to hyperbaric oxygenation is an elevation of the rate of lipid peroxidation rather than of the rate of formation of H2O2 or superoxide.

Animals↗
PubMed1976

Ischemic areas in perfused rat hearts: measurement by NADH fluorescence photography.

Fluorescence emission of reduced nicotinamide adenine dinucleotide (NADH) from the surface of perfused rat hearts was photographed to provide a two-dimensional recording of NADH levels. Sodium Amytal inhibition of NADH oxidation resulted in a homogeneous increase in NADH fluorescence, while lowering perfusion pressure from 55 to 10 torr caused a heterogeneous increase in NADH fluorescence, reflecting the heterogeneous oxygen delivery at this low pressure. Local ischemia resulted in a well-defined region of high NADH fluorescence that corresponded to the region of ischemic inslut. The sharp transition between the ischemic and normoxic areas demonstrated that the hypoxic interface separating the two areas must be quite small.

Animals↗
PubMed1976

Intermediates in the interconversion of acid and alkaline ferrihemoglobin. Structural and kinetic aspects.

The acid-alkaline pH-jump in suspension of crystalline sheep hemoglobin has been studied in the range of 5.95 to 8.94. Crystals suspended in 3.8 M Cs2SO4 show a rapid optical transition of half-time equal to or less than 2 ms. As the ammonia concentration is increased in the Cs2SO4-suspended crystals, a second optical transition is observed as a pseudo-first-order reaction, with a rate constant of between 10 and 15 s-1. The alkaline-acid pH-jump proceeds through a very rapid shift of the alkaline-acid equilibrium and is followed by a first-order dissociation constant between 9 and 12 s-1. The dissociation of the ammonia is biphasic, and the ratio between the fast and slow phases is 9.

Animals↗
PubMed1976

The reaction kinetics of fluoride and ammonia with acid and alkaline ferrimyoglobin in a crystalline state.

Differences between the reactivity of amorphous and crystalline myoglobin have been studied by the rapid-flow method combined with dual-wavelength spectrophotometry. The binding of ammonia to the hydroxide compound has a half-time of 55 ms. The reverse reaction has a half-time of 70 ms. At pH 7.0 the relative half-times of combination and dissociation with fluoride are 10 min for crystalline and 1.8 min for amorphous materials. Reactivity of the crystals to fluoride at pH 6.0 greatly increased as compared with pH 8.7. Half-time at pH 8.7 is 10 min, while at pH 6.0 the half-time is 2.5 s for the crystalline material and 1.4 s for the amorphous material. The exchange of fluoride by azide at pH 6.0 is 3.1-fold faster in amorphous material than in crystalline material.

Ammonia↗
PubMed1976

Luft's disease. Further biochemical and ultrastructural studies of skeletal muscle in the second case.

In the second known case of non-thyroidal hypermetabolism (Luft's disease), there were large areas of mitochondrial aggregates in all fibers. Many mitochondria were abnormally large and contained packed cristae. In isolated mitochondrial fractions, studies of oxidative phosphorylation showed defective respiratory control and normal phosphorylation capacity ("loose coupling"). Spectra and content of cytochromes were normal. Basal ATPase activity was seven times greater than normal and poorly stimulated by 2,4-dinitrophenol. The rate of energy-dependent calcium uptake by isolated mitochondria was normal, but the amount of calcium accumulated was much decreased. Calcium could not be retained and was spontaneously released into the medium within 30 seconds. "Recycling" of calcium between mitochondria and cytosol may take place in vivo and result in sustained stimulation of respiration and loose coupling.

Adult↗
PubMed1976

Phosphorus nuclear magnetic resonance studies on normoxic and ischemic cardiac tissue.

The intact heart of a young rat was excised rapidly and cooled to 0 degree C; its energy-rich compounds were examined by 31P Fourier Transform nuclear magnetic resonance. The heart showed the characteristic spectrum of sugar phosphates, inorganic phosphate, phosphocreatine, and magniesium phates, inorganic phosphate, phosphocreatine, and magnesium ATP, characteristics of the energizing state of the nonbeating tissue. Warming to 30 degrees C imposes an energy load upon the heart consistent with short-term resumption of beating, concomitant intracellular acidosis, and decomposition of all detectable energy-rich compounds. The intracellular acidity causes a shift from pH 7.0 to 6.0. The effects of possible interferences with this pH measurement are considered. The method appears to have wide usefulness in cardiac infarct models for detecting the fraction of the total volume occupied by the infarct and for studying the effect of various proposed therapies upon this infarcted volume.

Adenosine Triphosphate↗
PubMed1976

Evaluation of redox state of isolated perfused rat lung.

The metabolic responsiveness of lung tissue to inhibition of oxidative metabolism was determined by measurement of the redox state of the isolated perfused and ventilated rat lung. Changes in redox state were evaluated by fluorescence from the lung surface at wavelengths suitable for reduced pyridine nucleotides and by measurement of the ratios of redox couples in rapidly frozen lung tissue. Maximal change of redox state was observed during ventilation with carbon monoxide; surface fluorescence increased 6.6%, lactate/pyruvate increased 5.8 times, glycerol 3-P/dihydroxyacetone-P increased fourfold and glutamate/alpha-ketoglutarate doubled. KCN infusion resulted in similar changes. Hypoxia produced with N2 ventilation resulted in less than maximal changes in redox couple ratios until alveolar PO2 was reduced below 0.1 mmHg. Redox changes observed during infusion of 0.5 mM aminoxyacetic acid suggested that maintenance of cytoplasmic redox state depended on functioning of a malate-aspartate "shuttle." The isolated perfused lung appears suitable to study factors controlling pulmonary parenchymal oxidative metabolism. The results emphasize the need for ventilation with CO to establish intracellular anoxia.

Amobarbital↗
PubMed1976

Oxygen delivery in perfused rat kidney: NADH fluorescence and renal functional state.

Changes in steady-state levels of reduced pyridine nucleotide (PN) recorded by continuous monitoring of surface fluorescence were correlated with changes in physiological function of perfused rat kidneys when subjected to anoxia, ischemia, hypothermia, variations in perfusion pressure, inhibition of Na-K ATPase, and uncoupling of oxidative phosphorylation. Biphasic responses of PN reduction and oxidation during ischemic cycles at varying temperatures and anoxic cycles at different perfusion pressures demonstrated the presence of two different cell populations in the kidney cortex, those with sufficient oxygen and those without. The magnitude of PN fluorescence change during ischemia increased with decreasing temperature demonstrating better tissue oxygenation during hypothermia. The measurement of mitochondrial NADH oxidation in the perfused kidney during transitions from CO anoxia to normoxia was made possible by flash photolytic activation of mitochondrial electron transport. The half time for NADH oxidation (125 ms) was independent of the rate of oxygen delivery while the initial rate and extent of reaction was faster and steeper, respectively, at higher perfusion pressure, due to a better tissue oxygenation and faster CO washout.

Adenosine Triphosphatases↗
PubMed1976

In vivo measurement of pyridine nucleotide fluorescence from cat brain cortex.

A modification of the methods is described which makes it possible to measure pyridine nucleotide fluorescence from the brain cortex in vivo without interference from movement and hemodynamic artifacts. Movement artifacts were eliminated by the use of a window technique. Fluorescence changes due to changes in hemoglobin oxygenation have been eliminated by measuring fluorescence at an isobestic wavelength of the hemoglobin-oxyhemoglobin reaction. The interference due to changes in red blood cell concentration has been studied by simultaneous measurements of fluorescence and ultraviolet reflection. Hemodilution revealed a linear relationship between the fluorescence from the pyridine nucleotide and reflected ultraviolet light. The ratio between the light absorption changes was approximately unity under the particular optical geometry employed in this study. This method has been used to measure fluorescence changes produced by nitrogen anoxia. The technique is discussed in relation to previous methods and the effects of anoxia are compared to previous findings.

Animals↗
PubMed1976

Pyridine nucleotide as an indicator of the oxygen requirements for energy-linked functions of mitochondria.

The responses of cardiac mitochondria to anoxia may be evaluated in terms of the oxidation-reduction state of the electron carriers and the ability of the mitochondria to function in energy-linked reactions. The previous detailed evaluation of the oxygen requirements for electron transfer in mitochondria is here extended to the oxygen requirements for energy-linked functions. Four functions are evaluated: the energy-dependent reduction of pyridine nucleotide, the phosphorylation of ADP, the retention of Ca2+, and the establishment of a membrane potential. All of these functions are half-maximally activated with 10-20% oxidation of cytochromes c and a + a3. Fifty percent oxidation of pyridine nucleotide is required for these functions. In a normoxic-anoxic titration, an increment of 50% in the reduction of pyridine nucleotide in intact tissue corresponds to the point at which the mitochondria are half-maximally active in energy coupling. Thus, the use of pyridine nucleotide fluorescence as an optimal indicator of tissue oxidation-reduction states has now been extended to the assay of energy-linked functions of mitochondria in situ in cardiac tissue.

Adenosine Triphosphate↗