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Biomedical subjects

B Chance

Publications and source records attributed to B Chance.

At least 451 records · Page 25Linked to original sources
PubMed1978

Two and three dimensional display of myocardial ischemic "border zone" in dogs.

It is intuitively apparent that the ultimate fate of reversibly damaged, peri-ischemic "border zone" tissue should relate to individual patient survival. The purpose of this study was: (1) to describe a technique of assessing the adequacy of epicardial and myocardial oxygenation, and (2) to examine the extent and character of the peri-ischemic "border zone" in the dog after coronary arterial ligation. A diagonal branch of the left anterior descending coronary artery was ligated in four anesthetized open chest, neurohormonally intact dogs. The same diagonal coronary artery was ligated in six isolated perfused canine heart preparations in which coronary partial pressures of oxygen and carbon dioxide, pH, blood flow and temperature were fixed. The ischemic zones were rapidly frozen and reduced nicotinamide adenine dinucleotide (NADH) fluorescence photographs were taken of the epicardium and at 0.5 mm depths into the myocardium. The distinction between perfused and ischemic myocardium is not apparent with the naked eye or natural light photography. Epicardial and myocardial oxidation-reduction status is well seen with NADH fluorophotography. In both the intact and perfused heart preparations the NADH-fluorescent (ischemic) border is jagged along all edges. Islands of perfused nonfluorescent tissue appear within the ischemic border. The transition between NADH-fluorescent ischemic cells and adjacent non-fluorescent tissue is less than 0.1 mm. The ischemic border is narrow. The distance between homogeneously NADH-fluorescent tissue and homogeneously nonfluorescent tissue (across the zone of island normoxia or microheterogeneity) may be as wide as 6 to 8 mm.

Animals↗
PubMed1978

Detection of 31P nuclear magnetic resonance signals in brain by in vivo and freeze-trapped assays.

The (31)P NMR spectrum of energy-related metabolites under strictly aerobic conditions in rapidly respiring tissues under physiological conditions has been approached by the study of the (31)P NMR signals in vivo and in freeze-trapped organs. Freezing the head of the anesthetized animal by liquid N(2), excision of the brain tissue (white and gray matter) at -196 degrees , and transfer to the NMR tube occurs without alteration of the metabolite concentrations. The sample is warmed to the region -15 degrees to -10 degrees , at which temperatures there is sufficient mobility for recording (31)P NMR at concentrations characteristic of brain tissues ( approximately 5 mM) with an adequate signal to noise ratio in 10 min but insufficient mobility for significant enzymatic activity. A approximately 0.4-sec acquisition time is adequate for nuclear relaxation and a 10-min scan gives an adequate signal to noise ratio. Metabolism of creatine phosphate, P(i), and sugar phosphates occurs by 1 hr at -10 degrees and 2 hr at -12 degrees . Extrapolation of the approximately zero order kinetics of disappearance of creatine phosphate and appearance of P(i) suggests that <10% of these two metabolites has been altered in the time of the first measurement.A comparison of the freeze-trapped state and the in vivo metabolite pattern is afforded in preliminary experiments on the head of the living mouse (brain and skeletal tissue) in aerobic and anaerobic states. Longer relaxation times and mild hypoxia due to the restricted diameter of the NMR tube gives significantly lower creatine phosphate/ATP values for this condition. Both direct in vivo and freeze-trapped assays of energy-related metabolites afford excellent approaches to the detection of anoxia and to the evaluation of metabolic control in hypoxic conditions.

Adenosine Triphosphate↗
PubMed1978

Heterogeneity of oxygen delivery in normoxic and hypoxic states: a fluorometer study.

An on-line, real-time histogram display of heterogeneity of oxygen delivery to perfused and in situ organs is afforded by a flying-spot fluorometer that provides excitation for either oxidized flavoprotein of the mitochondrial space or reduced pyridine nucleotide of mitochondrial and cytosolic spaces. Emission from the two fluorochromes is acquired at 10(4) to 10(5) data points/s and histograms of the fluorescence intensity versus the number of occurrences of that intensity are displayed at 1--10 times per second. The histograms show alterations of the intensity and of the degree of heterogeneity of the redox states of perfused heart with model coronary occlusion, of perfused and in situ rat liver, and of rat and gerbil models of stroke. The percentage change of oxygen delivery to the intracellular space can be calculated from the areas under the histogram.

Brain↗
PubMed1977

Properties of glutathione release observed during reduction of organic hydroperoxide, demethylation of aminopyrine and oxidation of some substances in perfused rat liver, and their implications for the physiological function of catalase.

The enhanced reduction of t-butyl hydroperoxide by glutathione peroxidase is accompanied by a decrease in the cellular concentration of both glutathione and NADPH in isolated liver cells, resulting in the release of GSSG (oxidized glutathione) from the perfused rat liver. This phenomenon, first reported by H. Sies, C. Gerstenecker, H. Menzel & L. Flohé (1972) (FEBS Lett. 27, 171-175), can be observed under a variety of conditions, not only with the acceleration of the glutathione peroxidase reaction by organic peroxides, but also during the oxidation of glycollate and benzylamine, during demethylation of aminopyrine in the liver of the phenobarbital-pretreated rat and during oxidation of uric acid in the liver of the starved rat pretreated with 3-amino-1,2,4-triazole. The rate of release of GSSG is altered markedly by changes in the metabolic conditions which affect the rate of hepatic NADPH generation. Thus, regardless of whether achieved by enhanced oxidation of glutathione by glutathione peroxidase or by oxidation of NADPH through other metabolic pathways, an increase in the cellular concentration of GSSG appears to facilitate its release. It has been found that, in addition to the hexose monophosphate shunt, the mitochondrial NADH-NADP+ transhydrogenase reaction plays an important role in supplying reducing equivalents to the glutathione peroxidase reaction and in maintaining the cellular oxidation-reduction state of the nicotinamide nucleotides. Spectrophotometric analysis of the steady-state concentration of the catalase-H2O2 intermediate with simultaneous measurement of the rate of release of GSSG leads to the conclusion that intracellular compartmentation of catalase in the peroxisomes and glutathione peroxidase in the cytosol and mitochondria distinguishes the reactivities of these enzymes one from the other, and facilitates their effective cooperation in hydroperoxide metabolism in the liver.

Aminopyrine↗
PubMed1977

Spectrophotometric studies on NAD(P)H oxidase of leukocytes. 1. The relationship between granule-NAD(P)H oxidase and myeloperoxidase.

The NAD(P)H oxidase located in granules from resting leukocytes seems to be identical with myeloperoxidase on the basis of the following results. Spectral changes representing the difference between granules with and without NAD(P)H under various conditions represented the formation of compound III of myeloperoxidase, corresponding to the oxidation of NAD(P)H. The KCN difference spectrum of granules from both resting and phagocytizing leukocytes was in agreement with the KCN difference spectrum of myeloperoxidase. The affinity of KCN for myeloperoxidase was the same in both resting and phagocytizing leukocytes. The KCN-sensitive portion of NAD(P)H oxidase of granules from phagocytizing leukocytes seems to be identical with isolated myeloperoxidase and the myeloperoxidase of resting leukocytes. The KCN-insensitive oxidation of NAD(P)H by granules from phagocytizing leukocytes has not been found to be identical with myeloperoxidase.

Animals↗
PubMed1977

Two-dimensional analysis of the redox state of the rat cerebral cortex in vivo by NADH fluorescence photography.

A photographic method for measuring two-dimensional changes in NADH fluorescence and hemoglobin distributions in the rat cerebral cortex in vivo has been developed. Intracellular NADH was excited by UV light peaking at 360 nm and the emission was observed through a window with the maximum transmission at 450 nm. The fluorescence photographs (360 leads to 450 nm) required 20-25 sec exposures at the aperture opening of f/5.6 and the reflectance photographs (360 leads to 360 nm) 10 sec exposures at f/32. The digitization of photographic images was achieved either by a PDP-8-controlled microdensitometer coupled to an A/D converter or by a combination of a manually operated microdensitometer and a computer-controlled digitizer. In the latter case, a photographic negative was scanned with a Joyce-Loebl microdensitometer in parallel lines 170 mum apart, and the densitometric tracings were digitized with a PDP-8-controlled TV digitizer. The digital data were processed by DEC PDP-10 computer and the results were displayed in 3-dimensional surfaces. Nitrogen anoxia caused increases in fluorescence at 450 nm ranging from 10 to 75% fo the normoxic fluorescence intensities (after correcting for the logarithmic characteristics of the photographic films) and decreases in reflectance intensities in the range of 10-30%. The spatial resolution of the present technique is limited to approximately 30 mum X 30 mum on the cortical surface and the time resolution to 10-25 sec. The optical properties of the cerebral cortex in vivo appear to be controlled primarily by blood vessel patterns and hemodynamic factors and secondarily by the redox state of the tissue. Evidence for a heterogeneous redox response of the cerebral cortex toward N2 anoxia was obtained.

Animals↗
PubMed1977

Regulatory factors of acetaldehyde metabolism in isolated rat liver mitochondria.

The factors affecting acetaldehyde oxidation were studied by direct measurement of redox changes of NADH and cytochrome c in isolated rat liver mitochondria which contain the natural complement of mitochondrial substrates and co-factors, etc. Thus, this system affords a quantitative model for mitochondrial acetaldehyde metabolism simulating in vivo conditions. The activity of acetaldehyde dehydrogenase, as measured by the turnover number of cytochrome c, k3, depends upon the substrate concentration in a complex way. It reaches a maximum below 0.033 mM acetaldehyde and decreases abruptly at higher acetaldehyde concentration, interpreted here to be due to substrate inhibition. When mitochondria undergo hypotonic swelling, the maximal value of k3 is lowered by a factor of 15 and the substrate inhibition largely disappears. When mitochondria are stripped of the outer membrane and are suspended in pyrophosphate buffer, similar effects are obtained. It is concluded that acetaldehyde oxidation in mitochondria is dependent upon the state of mitochondria and the substrate concentration, and that the mitochondrial metabolism of acetaldehyde cannot be accurately predicted from in vitro data of solubilized enzyme.

Acetaldehyde↗
PubMed1977

Oxygen intermediates and mixed valence states of cytochrome oxidase: infrared absorption difference spectra of compounds A, B, and C of cytochrome oxidase and oxygen.

A study of the near-infrared absorption spectra of three oxygen compounds of membrane-bound cytochrome oxidase (ferrocytochrome c:oxygen oxidoreductase; EC 1.9.3.1) shows that the formation of compound A (oxycytochrome oxidase) causes no significant infrared absorbance changes at -103 degrees. At -64 degrees, the formation of compound C from the mixed-valence state of the oxidase leads to increased absorption at 740-750 nm. The formation of compound B at -84 degrees from the fully reduced state of the oxidase causes increased absorption at 790-800 nm. Further oxidation of cytochrome oxidase results in increased infrared absorption at 820-830 nm at -60 degrees. The position of the infrared absorption band in compound C thus depends at least upon the oxidation-reduction state of heme a and its associated copper atom. Compound C contains two types of oxidized (cupric) copper; that associated with heme a is initially oxidized, and that associated with heme a3 is oxidized as a second step in the reaction with oxygen. Compound C exhibits a unique intense absorption band at 606-609 nm that is tentatively assigned to a charge transfer interaction between heme a3 in the reduced state and its associated copper in the oxidized state, with heme a and its associated copper in the oxidized state.

Chemical Phenomena↗
PubMed1977

Evaluation of cardiac ischemia by NADH fluroescence photography.

A direct, noninvasive method of assessing the oxidation-reduction potential of an intramyocardial respiratory chain component is described. The technique is based on the differences in spectral properties between the oxidized and reduced forms of nicotinamide adenine dinucleotide (NADH). The tissue surface fluorescence from intracellular NADH may be measured and documented photographically. Noose occlusion of a coronary artery produced detectable NADH fluorescence in 15 seconds in the subtended ischemic epicardium. This fluorescence of reduced pyridine nucleotide resolved following 60 seconds of reperfusion of the ischemic myocardium. The reduction of epicardial NADH with ischemia is a rapid and reversible process. A subsequent noose reocclusion resulted in a reproducible pattern of fluorescence. The technique of NADH fluorescence photography appears superior to current methods of assessing tissue oxygen supply:demand.

Animals↗
PubMed1977

Heterogeneity of the hypoxic state in perfused rat heart.

Tissue oxygen gradients were examined in the saline-perfused rat heart by NADH fluorescence photography. In high flow hypoxia, where the coronary flow was maintained and the arterial oxygen tension was gradually reduced, oxygen extraction was virtually complete before oxygen consumption was significantly diminished. Inadequate oxygen delivery resulted in a well defined pattern of anoxic zones. The anoxic zones were several hundred microns in width, an order of magnitude greater than intercapillary distances. In low flow hypoxia (ischemia), where the arterial oxygen tension remained at its control value and the coronary flow was diminished, anoxic zones also developed, following the same pattern as in high flow hypoxia. However, in ischemia, the anoxic areas developed while the effluent oxygen tesion was significantly greater than zero. Whereas respiratory acidosis between pH 7.3 and 6.9 resulted in vasodilation, below PH 6.8 there was a marked increase in vascular resistance. Anoxic zones appeared despite only a slight change in effluent oxygen tension from the control. In high flow hypoxia, ischemia, and acidosis-induced ischemia, the anoxic zones disappeared when control perfusion conditions were restored. The data demonstrate that tissue oxygen gradients are very steep in the hypoxic state, so that ischemia and hypoxia result in discrete heterogeneous areas of anoxic tissue bounded by sharp areas where the oxygen supply is sufficient to maintain normal mitochondrial oxidative function. In these states in which oxygen delivery is less than oxygen demand, coronary perfusion appears to be regulated at the level of the arterioles rather than the capillaries.

Animals↗