Search PubMed⌕ Search

Biomedical subjects

B Chance

Publications and source records attributed to B Chance.

At least 325 records · Page 18Linked to original sources
PubMed1985

Oxygen dependence of energy metabolism in contracting and recovering rat skeletal muscle.

The relationship between the oxygen supply and the energy metabolism in perfused rat hindlimb muscles was evaluated both during contractions and during recovery from contractions. The 31P-nuclear magnetic resonance (NMR) technique and conventional biochemical methods were used. Significant correlations were found between the oxygen delivery and the oxygen consumption, lactate release and glucose uptake, respectively. An increased degree of fatigue was observed at the lower oxygen deliveries. In both the soleus and gastrocnemius muscles the oxygen delivery correlated with the intramuscular concentrations of phosphocreatine, lactate, and glycogen. The 31P-NMR experiments showed a correlation between the oxygen delivery and the steady-state level of the phosphocreatine-to-inorganic phosphate (PCr+Pi) ratio during the contraction period. The rate of recovery in PCr/Pi after the contractions was also dependent on the oxygen delivery. The results demonstrate a causal relationship between the oxygen supply and the energy state in contracting as well as recovering skeletal muscles.

Animals↗
PubMed1985

Evaluation of energy metabolism in skeletal muscle of patients with heart failure with gated phosphorus-31 nuclear magnetic resonance.

Exertional fatigue is a major limiting symptom in patients with heart failure. To investigate the metabolic basis of this fatigue, we used gated nuclear magnetic resonance spectroscopy to compare inorganic phosphate (Pi), phosphocreatine (PCr) and pH levels, and fatigue (1 to 4+) during mild forearm exercise in eight normal men and nine men with heart failure. Wrist flexion every 5 sec for 7 min was performed at 1, 2, and 3 J (average power output = 0.2, 0.4, and 0.6 W). In both groups linear relationships were noted between power output and Pi/PCr; the slope of this relationship was used to compare PCr depletion patterns. At rest both groups had similar Pi/PCr ratios (normal subjects 0.12 +/- 0.06, those with heart failure 0.15 +/- 0.03) and pH (normal subjects 7.04 +/- 0.13, those with heart failure 7.10 +/- 0.11). In normal subjects exercise resulted in a progressive increase in Pi/PCr (slope = 1.17 +/- 0.20 Pi/PCr units/W), a reduction in pH only at 0.6 W (0.2 W: 7.03 +/- 0.10, 0.4 W: 7.01 +/- 0.10, 0.6 W: 6.88 +/- 16) and moderate fatigue (0.2 W: 0 +/- 0, 0.4 W: 1.3 +/- 0.5, 0.6 W: 1.9 +/- 0.6). In patients with heart failure exercise resulted in significantly greater fatigue at all workloads (0.2 W: 1.0 +/- 0.5, 0.4 W: 1.9 +/- 0.6, 0.6 W: 2.9 +/- 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1985

Optimizing tourniquet application and release times in extremity surgery. A biochemical and ultrastructural study.

Despite numerous studies investigating the pathophysiology of tourniquet ischemia, definitive data at the cellular level have been lacking and no consensus regarding safe tourniquet-application times in extremity surgery has emerged. In light of the particular vulnerability of skeletal muscle to ischemic injury, we determined the degree of muscular metabolic derangement and cell damage produced by seven different protocols of tourniquet application and release, each providing three hours of total tourniquet time. We performed thirty-six experiments on canine hind limbs, comparing the following time-patterns of tourniquet application: I--three sequential one-hour periods, II--two sequential one and one-half-hour periods, III--two hours followed by one hour, and IV--a single continuous three-hour application. Five and fifteen-minute reperfusion intervals between ischemic periods were compared for the first three time-patterns, creating a total of seven different tourniquet protocols. Muscular metabolic derangement and cell injury were evaluated by monitoring changes in the cellular bioenergetic state (high-energy phosphate profile), cell pH, post-ischemic leakage of creatine phosphokinase, and ultrastructural cell degeneration. At the intracellular level, the metabolic recovery of muscle during reperfusion was much faster than previous studies focusing on extracellular parameters have indicated. In all instances complete intracellular bioenergetic recovery occurred within five minutes after tourniquet release. The use of one or more five-minute reperfusion intervals significantly reduced the degree of ischemic cell injury, as indicated by a decrease in creatine phosphokinase leakage and myofibrillar destruction. No additional benefit was derived by extending the reperfusion periods to fifteen minutes. The longest period of continuous ischemia in each tourniquet-application protocol bore the closest relationship with the amount of cell damage produced. Within the spectrum of observed pathological changes, time-patterns I and II produced comparatively little muscle damage.

Animals↗
PubMed1984

Structure and reactivity of multiple forms of cytochrome oxidase as evaluated by X-ray absorption spectroscopy and kinetics of cyanide binding.

The extended X-ray absorption fine structure (EXAFS) data show differences between the active site structures of different cytochrome oxidase preparations. In the resting (as isolated) state of the Yonetani preparation, the bridging atom between Fe3+a3 and Cu2+a3 is present [Powers, L., Chance, B., Ching, Y., & Angiolillo, P. (1981) Biophys. J. 34, 465], whereas in another preparation (e.g., Hartzell-Beinert), this atom seems to be bound only to Fe3+a3 in a significant fraction of the molecules. Both preparations bind cyanide in a multiphasic fashion, suggesting that the resting cytochrome oxidase is not homogeneous but rather is a mixture of several forms. The proportion of these forms as detected by cyanide binding kinetics differs for different preparations. However, upon reduction and reoxidation (conversion to the "oxygenated" form) the cyanide binding kinetics become monophasic and all preparations of the oxygenated form bind cyanide at the same rate. Thus, a combination of structural and kinetic approaches seems necessary for evaluation of the nature of the active site of cytochrome oxidase in its various forms.

Animals↗
PubMed1984

Phosphorylethanolamine--the major constituent of the phosphomonoester peak observed by 31P-NMR on developing dog brain.

31P-NMR spectra of newborn dog brains exhibit a prominent phosphomonoester (PME) peak (6.78 +/- SD 0.05 ppm from phosphocreatine peak), similar to those of human neonates. Studies were undertaken to identify the chemical constituents of this peak. Brains of puppies were funnel frozen for methanol-HCl-perchloric acid extraction after in vivo 31P-NMR spectra were taken. The pK of the major component of the PME region in the NMR spectrum of extract was 5.4, corresponding to that of phosphorylethanolamine (PEt). Addition of PEt increased the major peak on the PME region over a wide range of pH, while addition of phosphorylcholine or ribose 5-phosphate yielded distinct peaks. We suggest that the major constituent of phosphomonoester peak of 31P-NMR spectra of newborn dog brain is phosphorylethanolamine. Biochemical mechanisms relevant to changes of phosphorylethanolamine during brain development are discussed.

Animals↗
PubMed1984

CO bond angle changes in photolysis of carboxymyoglobin.

Previous studies [Chance, B., Fischetti, B., & Powers, L. (1983) Biochemistry 22, 3820-3829] of the local structure changes around the iron in carboxymyoglobin on photolysis at 4 K revealed that the iron-carbon distance increased approximately 0.05 A but was accompanied by a lengthening of the iron-pyrrole nitrogen bonds of the heme (approximately 0.03 A) that was not as large as that found in the deoxy form. Further analysis of these data together with comparison to model compounds indicates that the Fe-C-O bond angle in carboxymyoglobin is bent (127 +/- 4 degrees), having a structure identical, within the error, with the "pocket" porphyrin model compound FePocPiv(1-MeIm)(CO) [Collman, J. P., Brauman, J. I., Collins, T. J., Iverson, B. L., Lang, G., Pettman, R., Sessler, J. L., & Walters, M. A. (1983) J. Am. Chem Soc. 105, 3038-3052]. On photolysis, this angle decreases by 5-10 degrees. In addition, correlation is observed between the increase in the length of the Fe-C bond and the decrease of the Fe-C-O angle. These results suggest that the rate-limiting step in recombination is the thermal motion of CO in the pocket to achieve an appropriate bonding angle with respect to the iron. These changes constitute the first molecular picture of the photolysis process, as well as the structure of the geminate state, and are important in clarifying nuclear tunneling parameters.

Carbon↗
PubMed1984

Pulsed cytochrome c oxidase from the thermophilic bacterium PS3.

A caa3-type terminal cytochrome c oxidase (EC 1.9.3.1) from the thermophilic bacterium PS3 containing three subunits showed conversion from resting into pulsed form. Upon pulsing (reduction and re-oxidation), the cytochrome c oxidase activity increased over 10-fold. This enhanced activity of the pulsed enzyme gradually decayed. Addition of phospholipids, necessary for the enzyme activity, did not affect this decay process. Small changes in the absorption spectrum were observed for the resting-into-pulsed transition and for H2O2 ligation to the pulsed enzyme. The e.p.r. spectrum of the resting enzyme was very similar to that of mitochondrial enzyme, but the transient g = 5, 1.78 and 1.69 set of e.p.r. signals, associated with the pulsed bovine heart oxidase, were not observed in the case of pulsed bacterium-PS3 enzyme.

Bacteria↗
PubMed1984

Peroxide interaction with pulsed cytochrome oxidase. Optical and EPR studies.

EPR and optical analysis of the 420 nm form of cytochrome oxidase (Kumar, C., Naqui, A., and Chance, B. (1984) J. Biol. Chem. 259, 2073-2076) shows that 1) the 420 nm form possesses a 605 nm band, g = 5 EPR signals, and a slightly blue shifted 655 nm band; 2) the reaction of H2O2 with the 420 nm form generates the peroxide complex (Soret band at 427 nm) with the formation of a 580 nm band and abolition of both the 655 nm band and the g = 5 EPR signal. Comparison of our results with past data shows that various forms of oxidase formed from the resting oxidase through different protocols may be identified to be either the 420 nm or the 427 nm form and leads to identification of a peroxy intermediate during oxidase turnover.

Electron Spin Resonance Spectroscopy↗
PubMed1984

A semi-integrated method for the determination of enzyme kinetic parameters and graphical representation of the Michaelis-Menten equation.

A semi-integrated method for the determination of the enzyme kinetics parameters (Km and V) and graphical representation of the Michaelis-Menten equation is proposed as a variation of determination of initial reaction rate (v) as a function of initial substrate concentration ([S]0). The method is based on the determination of the time required to exhaust half of the initial substrate concentration as a function of the initial substrate concentration. The advantages and limitations of this method are discussed.

Enzyme Inhibitors↗
PubMed1984

Reaction of caa3-type terminal cytochrome oxidase from the thermophilic bacterium PS3 with oxygen and carbon monoxide at low temperatures.

Reaction of O2 and CO with a caa3-type terminal cytochrome oxidase (EC 1.9.3.1) from the thermophilic bacterium PS3 grown with high aeration was studied at low temperatures. The CO recombination at the temperature range studied (-50 degrees C to -80 degrees C) followed first-order kinetics with an activation energy of 29.3 kJ/mol (7.0 kcal/mol). In the presence of O2 at -113 degrees C the photolysed reduced form binds O2 to form an 'oxy' intermediate similar to Compound A. At a higher temperature (-97 degrees C) another intermediate, similar to Compound B, is formed as a result of electron transfer from the enzyme to the liganded O2.

Carbon Monoxide↗
PubMed1984

The identity of pulsed cytochrome oxidase.

Reduction and reoxidation of beef heart cytochrome oxidase, under conditions that ensure the strict absence of hydrogen peroxide, produce a fully oxidized form of the enzyme that has the Soret band at 420 nm, as opposed to the 428 nm band normally associated with the pulsed or oxygenated enzyme. The 420 nm form shows the enhancement of catalytic activity associated with the pulsed enzyme. Addition of hydrogen peroxide to the 420 nm form gives rise to the 428 nm band of the oxygenated enzyme, thereby clearly establishing that the 428 nm form is a peroxide derivative of the fully oxidized enzyme. Previous data from other groups are re-evaluated in the light of our experiments.

Animals↗
PubMed1984

X-ray absorption studies of the Zn2+ site of glyoxalase I.

X-ray edge and extended absorption fine structure spectra of Zn2+ at the active site of glyoxalase I have been measured. The edge spectrum reveals a simple set of transitions consistent with a 7-coordinate or distorted octahedral Zn2+ model complex. Analysis of the fine structure rules out sulfur ligands to Zn2+ and yields a best fit complex with Zn2+-N (or Zn2+-O) distances of 2.04 and 2.10 A, which are too great for tetrahedral Zn2+ coordination but are appropriate for an octahedral or more highly coordinated complex. Peaks of electron density in the Fourier-transformed region of the higher order shells at distances of 3-4 A from the Zn2+-imidazole model similar to those found with known Zn2+-imidazole model complexes, including carbonic anhydrase [Yachandra, V., Powers, L., & Spiro, T.G. (1983) J. Am. Chem. Soc. 105, 6596-6604], indicating at least two imidazole ligands to Zn2+ on glyoxalase I. Binding of the heavy atom substrate analogue S-(p-bromobenzyl)glutathione did not significantly alter the number of atoms directly bonded to Zn2+ or their distances. No evidence for coordination of the cysteine sulfur of glutathione by the Zn2+ was obtained, and no heavy atom signal from bromine was detected, indicating this atom to be greater than or equal to 4 A from the Zn2+. However, conformational changes of the imidazole ligands of Zn2+ upon binding of the substrate analogue were suggested by changes in the relative intensity of the doublet peaks at 3-4 A from the Zn2+ and assignable to imidazole.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1984

Unique aspects of human newborn cerebral metabolism evaluated with phosphorus nuclear magnetic resonance spectroscopy.

In vivo phosphorus nuclear magnetic resonance spectroscopy (31P NMR) was used to evaluate the pattern of phosphate compounds in seven newborn babies (mean gestational age, 32 weeks; birth weight, 1,430 gm; age, 37 days) with a history of perinatal asphyxia. Spectra were collected in a 1.9 Tesla superconductive magnet with surface coil techniques. The spectra had characteristic peaks for phosphorylated monoesters (PME), inorganic phosphate (Pi), phosphodiesters (PD), phosphocreatine (PCr), and ATP. In contrast to cortical spectra from mature animals, these newborn infant 31P NMR spectra were dominated by a large PME peak and had small PCr, Pi, and PD peaks. Intracellular pH, as measured from the chemical shift of the Pi peak relative to the PCr peak, was 7.1 +/- 0.1 (SD). We studied one infant postmortem, and a large PME peak was present in his spectrum. The presence of PME 3 hours after death strongly suggests that it is not a sugar phosphate. In NMR spectroscopy, compounds are identified by their chemical shift relative to a known standard (PCr); the chemical shift of the PME peak was 6.5 ppm, suggesting that it is a mixture of phosphoryl ethanolamine and phosphoryl choline. The PCr/Pi ratio (1.3 +/- 0.7) and the PCr/ATP ratio (0.7 +/- 0.4) were lower in these babies than in mature animals (greater than 2 and greater than 1.4, respectively); the PME/PD ratio (1.2 +/- 0.6), however, was much greater in the infants (mature animals, less than 0.2). These findings suggest that there are unique aspects of human newborn cerebral metabolites and bioenergetic reserve.

Adenosine Diphosphate↗
PubMed1984

X-ray absorption studies of intermediates in peroxidase activity.

The structures of the enzyme-substrate compounds of peroxidases and catalase determined by X-ray absorption spectroscopy are presented. The valence state of the iron in Compounds I and II is determined from the edge to be higher than Fe+3. A short Fe-Ne (proximal histidine) distance is observed in all forms except Compound II, forcing the Fe-Np average distance to be long, a result which differentiates the peroxidases from the oxygen transport hemoproteins and plays a pivotal role in the mechanism. A correlation is shown between the ratio of peaks in the low k (ligand field indicator ratio) region, the Fe-Np (heme pyrrole nitrogen) average distance, and the magnetic susceptibility, which provides a sensitive indicator of spin state. The mechanism of H2O2 reduction is shown by analysis of the structural changes observed in the intermediates. Possible relationship of these compounds to that of the peroxidatic form of cytochrome oxidase is suggested by these results.

Catalase↗
PubMed1984

In vivo time-resolved brain phosphorus nuclear magnetic resonance.

Methods used to obtain and quantify high-quality time-resolved dog brain phosphorus nuclear magnetic resonance (31P NMR) spectra are described. In eight animals the normoxic dog brain spectra showed 10% of total phosphorus in ATP, 14% in phosphocreatine (PCr), and 38% in brain phospholipids containing phosphodiesters. The chemical shift between PCr and inorganic phosphate, 5.09, corresponded to an intracellular brain pH of 7.2. During hypoxia, PCr declined to 0.5 +/- 0.3 (n = 8) of starting levels, prior to any changes in brain ATP. Simultaneous recording of the EEG was obtained in two animals. During hypoxia, progressive PCr depletion was associated with progressive slowing of the EEG, which was essentially silent before significant changes occurred in brain ATP. Finally, the brain 31P NMR spectrum and pH were measured at 90-s intervals, and the sequential changes that followed respiratory arrest were monitored in one dog until high-energy phosphate depletion was complete.

Adenosine Triphosphate↗