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Biomedical subjects

B Chance

Publications and source records attributed to B Chance.

At least 19 recordsLinked to original sources
PubMed1992

Linear correlation between acetoacetate/beta-hydroxybutyrate in arterial blood and oxidized flavoprotein/reduced pyridine nucleotide in freeze-trapped human liver tissue.

A comparison of two methods of measuring liver mitochondrial redox state demonstrated that a linear correlation exists between acetoacetate/beta-hydroxybutyrate ratio in arterial blood (arterial ketone body ratio; AKBR) and oxidized flavoprotein/reduced pyridine nucleotide in human liver tissue (FP/PN) as measured by tissue fluorescence spectroscopy, such that [FP/PN] = 0.64 + 0.49 x [AKBR] (r = 0.84, P less than 0.001). This result supports the validity of AKBR as a method of measuring the hepatic mitochondrial redox state of pyridine nucleotide using arterial blood.

3-Hydroxybutyric Acid↗
PubMed1992

X-ray absorption fine structure study of the active site of zinc and cobalt carboxypeptidase A in their solution and crystalline forms.

A comparative study on the metal environment of Zn(II)-carboxypeptidase A (ZnCPD) and Co(II)-carboxypeptidase A (CoCPD) in their solution and crystalline forms using the X-ray absorption fine structure (XAFS) technique has been conducted. The first coordination sphere of Zn for ZnCPD in its solution state is found to consist of two distributions of atoms, with four atoms (N or O) located at an average distance of 2.03 +/- 0.01 A and one atom (N or O) located at 2.57 +/- 0.04 A. The four-atom distribution remains the same for ZnCPD in its crystalline state, but the fifth atom is found at 2.36 +/- 0.04 A. Examination of the higher coordination shell, between 2.7 and 4.2 A, reveals the presence of two imidazoles. Combined with X-ray crystallographic results, a structural model is proposed. The four atoms at an average distance of 2.03 A are assigned to the two delta 1 nitrogens of His-69 and His-196, one epsilon 1 oxygen of Glu-72, and the oxygen of a coordinated water molecule. The atom at 2.57 A for ZnCPD in solution is assigned to the epsilon 2 oxygen of Glu-72. The results for CoCPD in solution are similar with the four atoms at an average distance of 2.08 +/- 0.01 A and one atom at 2.50 +/- 0.04 A, which moves to 2.34 +/- 0.04 A in the crystalline enzyme. The intensity of the 3d "pip" peak for CoCPD is consistent with a distorted tetragonal metal geometry for the solution form of the enzyme which is converted to a more pentacoordinated metal site for the crystalline enzyme. The first shell distribution of crystalline CoCPD is quite disordered, which may be largely due to the disorder of His-69 and His-196 as indicated by higher shell analysis. Thus, the XAFS studies show that the metal coordination spheres in the zinc and cobalt enzymes are quite similar in the solution state but differ from their crystalline counterparts. The XAFS studies provide the necessary background for measurement of substrate- and inhibitor-promoted structural changes in the metal coordination sphere of the zinc and other metal-substituted carboxypeptidases in the solution state.

Animals↗
PubMed1992

Quantitation of tissue optical characteristics and hemoglobin desaturation by time- and frequency-resolved multi-wavelength spectrophotometry.

Photon migration in highly scattering tissues such as muscle and brain gives optical pathlengths that are dependent upon absorption and scattering parameters, mu a, mu s'. Determination of these parameters gives the correct concentration of principal absorber such as hemoglobin in the red region of the spectrum. Determinations of scatter factor in functioning and pathological tissues are made.

Alzheimer Disease↗
PubMed1992

Monitoring of redox-state of respiratory enzymes and myoglobin oxygenation in the working rat heart in normoxia and oxygen deficiency.

The cellular oxygen supply in the isolated, hemoglobin-free perfused, working rat heart can be determined by measurements of myoglobin oxygenation. However, for a precise analysis of mitochondrial hypoxia and anoxia (pO2 < 0.01 Torr) redox-state of respiratory enzymes must be known. By use of the EMPHO (Frank et al. 1989) it is possible to perform a high speed spectrometry within very small tissue volumes. Because of the characteristic absorption spectra of oxygenated and deoxygenated myoglobin and of the oxidized and reduced cytochrome aa3 within the wavelength interval from 500 to 630 nm it is possible to isolate these two pigments from the remission spectra and to determine the oxygenation state of myoglobin and the redox-state of cytochrom aa3.

Animals↗
PubMed1992

Instabilities of metabolic regulations in aging.

1) That non-invasive NMR and optical methods can a) quantify the work stress on mitochondria for ATP production, and b) indicate the tissue O2 tension in the capillary bed that is responsible for the rate of radical generation. 2) That free radical damage to mitochondrial function can be quantified by reciprocal plots of inverse slope giving the extrapolated Vm of mitochondria. 3) That a particular genetically deficient individual requiring high dosages of menadione has survived over 9 years. 4) That mitochondrial deficiency leads to an exercise hyperoxia.

Adenosine Diphosphate↗
PubMed1992

Dual wavelength spectrophotometry as a diagnostic test of the pulp chamber contents.

The purpose of this in vitro study was to determine the feasibility of using dual wavelength spectrophotometry to identify teeth with pulp chambers that are either empty, filled with fixed pulp tissue, or filled with oxygenated blood. In phase I of the experiment, a human third molar was prepared so that its pulp space could be filled with oxygenated blood and later emptied. In phase II, the lower jaw of a beagle dog was removed and placed in formalin, thereby fixing the pulps of the teeth. The pulp of the right canine was removed via an apical approach, and attachments were placed in a similar position to those on the human tooth, to allow filling and emptying of the pulp space. Cavit was placed over the exposed fixed pulp in the left canine. Ten readings, which were separated by light source and detector removal and replacement, were taken of the right canine pulp space when it was empty or filled with oxygenated blood, or the left canine pulp space when it was filled with fixed tissue. Distinct and reproducible changes were measured for pulp spaces filled with air, tissue, or oxygenated blood. In phase III, simulated pulp testing on a dog tooth model was performed. Blood was introduced into the root canal space, the chamber was rinsed with water and replaced with air, according to a predetermined code. Spectrophotometer readings were recorded. The identification of pulpal contents was correctly determined in all 20 of the predetermined conditions. The findings indicate that continuous wave spectrophotometry may become a useful pulp testing method.

Animals↗
PubMed1992

Glutathione and ischemia-reperfusion injury in the perfused rat liver.

Using the isolated perfused rat liver, we investigated the relationship of glutathione (GSH) with reactive oxygen species (ROS) generation and liver cell damage during ischemia/reperfusion in normal and GSH-depleted conditions. Lucigenin-enhanced chemiluminescence was used as a sensitive index of tissue ROS generation. After 30 minutes of equilibration, livers were subjected to global ischemia for various times (60 or 90 minutes) and then reperfused for another 120 minutes. Intracellular ROS levels increased sharply at the onset of reperfusion and then declined slowly. After 30 to 60 minutes of reperfusion, ROS levels started to increase progressively in a linear fashion. However, sinusoidal glutathione disulfide release did not increase during reperfusion in the same livers, suggesting that intracellular ROS generation is too low to cause a significant increase in GSH oxidation. Pretreatment with phorone (300 mg/kg intrapentoneally [ip]), which reduced hepatic GSH by 90%, did not cause any difference in intracellular ROS generation compared with the control livers. There were also no significant differences in lactate dehydrogenase and thiobarbituric acid reactive substances (TBARS) release between the control and phorone-treated livers during reperfusion after various times of ischemia. These data indicate that ROS generation in the normal isolated perfused liver during ischemia/reperfusion is extremely low and intracellular GSH does not serve as a major intracellular defense system against such a low oxidative stress.

Acridines↗
PubMed1992

Changes in the redox distribution of rat liver by ischemia.

The changes in the redox distribution of the ischemic rat liver were studied using the redox scanner, which is a time-sharing, tissue fluorescence and reflectance spectroscopy with fine spatial resolution, with the results presented as a histogram and a gray-scaled picture. Hepatic inflow was clamped for 10 min (group 1), 20 min (group 2), and 30 min (group 3). The ratio of oxidized flavoprotein to reduced pyridine nucleotide fluorescence (FP/PN), representing the intracellular redox state, and hemoglobin reflectance were measured prior to clamping and at subsequent times following declamping in each group. The mean and the range width of FP/PN histogram decreased with the prolongation of ischemic time. In group 1, FP/PN histogram showed a remarkably wide range at 2 min after declamping but was almost completely recovered to preischemic levels at 10 min after declamping. In contrast, in groups 2 and 3, the mean of FP/PN histogram was only partially recovered at 10 min after declamping and the range width continued to increase. The correlation between FP/PN fluorescence and hemoglobin reflectance pictures suggested that the local stagnation of blood flow caused tissue hypoxia, preventing the recovery of the redox state probably in the centrilobular area.

Alanine Transaminase↗
PubMed1992

Fluctuations in cerebral oxygenation and blood volume during endotracheal suctioning in premature infants.

To investigate the effect that suctioning of the endotracheal tube has on the cerebral circulation, we monitored brain intravascular hemoglobin saturation (tHbo2%), cerebral blood volume (CBV), and arterial hemoglobin saturation (Spo2) during suctioning in 12 infants (24 to 33 weeks of gestational age) with respiratory distress syndrome treated with mechanical ventilation. The tHbo2% and CBV values were monitored over the forebrain by dual-wavelength near-infrared spectroscopy, and Spo2 was monitored by pulse oximetry of a finger. The monitored variables were stable during the baseline period. With suctioning, Spo2 decreased from 94% +/- 1% to 84% +/- 1%, tHbo2% decreased, and CBV increased (p less than 0.05). Desaturation in the arterial and cerebral circulations began within 5 seconds of the onset of suctioning. Arterial reoxygenation began with the onset of reventilation, whereas reoxygenation in the brain was delayed by 15 seconds. The Spo2, tHbo2%, and CBV values returned to baseline within 1 minute of reventilation. Studies were repeated in six of the infants after the fraction of inspired oxygen was increased to attain a baseline Spo2 of 100%. In the preoxygenated infants, tHbo2%, CBV, and Spo2 remained constant during suctioning. These studies confirm that endotracheal suctioning results in transient hypoxemia, and demonstrate that this is reflected in the brain by vasodilation and deoxygenation. These effects are preventable by preoxygenation before suctioning.

Brain↗
PubMed1992

Kinetics of cerebral deoxygenation during deep hypothermic circulatory arrest in neonates.

Brain injury associated with neonatal congenital heart operations performed during deep hypothermia and/or total circulatory arrest is often attributed to cerebral hypoxia. We studied the kinetic changes in cerebrovascular hemoglobin O2 saturation (HbO2%) and total hemoglobin concentration (Hbtotal) in 17 neonates undergoing cardiac surgery as they were cooled to 15 degrees C, underwent total circulatory arrest, and were rewarmed. HbO2% and Hbtotal in brain vasculature were monitored noninvasively by near-infrared spectroscopy. Neonates were cooled over 12 min and rewarmed over 15 min while being perfused using cardiopulmonary bypass (CPB). Total circulatory arrest lasted from 20 to 70 min. We found that HbO2% in brain vasculature increased during the initial 8 min of CPB as nasopharyngeal temperature decreased, and then remained constant until circulatory arrest. After the onset of circulatory arrest, cerebrovascular HbO2% decreased curvilinearly for 40 min; no further hemoglobin desaturation was observed from 40 to 70 min of arrest. The changes in cerebrovascular Hbtotal were quite different from those in HbO2%, as Hbtotal decreased during the initial minute of CPB and circulatory arrest and then remained constant until recirculation. Brain intravascular HbO2% and Hbtotal increased within 3 min after the onset of recirculation to prearrest levels, and during rewarming, HbO2% decreased to normothermic baseline values. The results demonstrate that cerebral oxygenation increased during CPB cooling; O2 was consumed by the neonatal brain during the initial 40 min of deep hypothermic circulatory arrest; and cerebral oxygenation was restored on recirculation. These observations may be important in identifying the etiologies of brain injury during neonatal congenital heart surgery.

Brain↗
PubMed1992

Comparison of the effect of a mitochondrial uncoupler, 2,4-dinitrophenol and adrenaline on oxygen radical production in the isolated perfused rat liver.

Using the isolated perfused rat liver, we examined the effect of stimulation of mitochondrial respiration by 2,4-dinitrophenol (2,4-DNP) and adrenaline on reactive oxygen species (ROS) production, liver damage and lipid peroxidation. ROS production was monitored by luminol- and lucigenin-enhanced chemiluminescence and oxygen uptake was measured simultaneously. Liver damage and lipid peroxidation were evaluated by measuring hepatic lactate dehydrogenase (LDH) and thiobarbituric acid reacting substances (TBARS) release. Tissue ROS level decreased and oxygen uptake increased soon after 2,4-DNP infusion. On termination of 2,4-DNP infusion, there was a sharp increase in lucigenin-enhanced chemiluminescence, which declined slowly, but luminol-enhanced chemiluminescence did not change prominently. Hepatic LDH and TBARS release increased gradually during 2,4-DNP infusion and were manifested by termination of the infusion. Allopurinol did not affect ROS production and TBARS release, but delayed increases in LDH release after termination of 2,4-DNP infusion. Adrenaline, which stimulates mitochondrial respiration without uncoupling caused similar but smaller ROS changes observed in 2,4-DNP. LDH and TBARS release were not affected significantly by adrenaline infusion. These results indicate that uncoupling of oxidative phosphorylation decreases ROS production and restoration of oxidative phosphorylation enhances ROS production and liver damage. Xanthine oxidase is unlikely to contribute to enhanced ROS production after termination of 2,4-DNP but has some protective effect during uncoupling.

2,4-Dinitrophenol↗
PubMed1992

Recovery from exercise-induced desaturation in the quadriceps muscles of elite competitive rowers.

A simple muscle tissue spectrophotometer is adapted to measure the recovery time (TR) for hemoglobin/myoglobin (Hb/Mb) desaturation in the capillary bed of exercising muscle, termed a deoxygenation meter. The use of the instrument for measuring the extent of deoxygenation is presented, but the use of TR avoids difficulties of quantifying Hb/Mb saturation changes. The TR reflects the balance of oxygen delivery and oxygen demand in the localized muscles of the quadriceps following work near maximum voluntary contraction (MVC) in elite male and female rowers (a total of 22) on two occasions, 1 yr apart. TR ranged from 10 to 80 s and was interpreted as a measure of the time for repayment of oxygen and energy deficits accumulated during intense exercise by tissue respiration under ADP control. The Hb/Mb resaturation times provide a noninvasive localized indication of the degree of O2 delivery stress as evoked by rowing ergometry and may provide directions for localized muscle power output improvement for particular individuals in rowing competitions.

Capillaries↗
PubMed1992

Substrate regulation of mitochondrial oxidative phosphorylation in hypercapnic rabbit muscle.

Endurance muscle performance is highly dependent on ATP production from mitochondrial oxidative phosphorylation. To study the role of the mitochondrial oxidative enzymes in muscle fatigue, we analyzed the relationship between the concentrations of substrates associated with ATP synthesis and the muscle performance of electrically stimulated rabbit muscle under CO2-induced acidosis. Two different conditions of pacing-induced muscle performance were produced in the gastrocnemius and soleus muscle groups in anesthetized rabbits by stimulating the sciatic nerve submaximally at two frequencies. Phosphorus nuclear magnetic resonance was used to measure ATP, phosphocreatine, and Pi and to provide data for a calculation of intracellular pH and free ADP. To induce acidosis, the animal was ventilated with 20% CO2. The administration of CO2 effectively reduced the intracellular pH from 6.9 to 6.7 and reduced the isometric tension-time integral (TTI) to below half the value measured in normocapnia at the low pacing frequency. A twofold increase in the pacing frequency resulted in a doubling of the TTI in normocapnia and a tripling of TTI in hypercapnia. The increases in TTI corresponded with increases in free ADP and Pi concentrations. Under the various conditions, all free ADP values were near the in vitro Michaelis-Menten constant (Km) of ADP. The Michaelis-Menten relationship of the oxidative phosphorylative enzymes was applied to the change in substrate concentrations with respect to TTI. From this relationship we observed that the in vivo Km of free ADP was 26 microM, which is close to the in nitro Km, and that Km and maximal reaction velocity did not change under hypercapnia and increased pacing frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1992

A 31P-NMR study of tissue respiration in working dog muscle during reduced O2 delivery conditions.

To investigate the role of tissue oxygenation as one of the control factors regulating tissue respiration, 31P-nuclear magnetic resonance spectroscopy (31P-NMR) was used to estimate muscle metabolites in isolated working muscle during varied tissue oxygenation conditions. O2 delivery (muscle blood flow x arterial O2 content) was varied to isolated in situ working dog gastrocnemius (n = 6) by decreases in arterial PO2 (hypoxemia; H) and by decreases in muscle blood flow (ischemia; I). O2 uptake (VO2) was measured at rest and during work at two or three stimulation intensities (isometric twitch contractions at 3, 5, and occasionally 7 Hz) during three separate conditions: normal O2 delivery (C) and reduced O2 delivery during H and I, with blood flow controlled by pump perfusion. Biochemical metabolites were measured during the last 2 min of each 3-min work period by use of 31P-NMR, and arterial and venous blood samples were drawn and muscle blood flow measured during the last 30 s of each work period. Muscle [ATP] did not fall below resting values at any work intensity, even during O2-limited highly fatiguing work, and was never different among the three conditions. Muscle O2 delivery and VO2 were significantly less (P < 0.05) at the highest work intensities for both I and H than for C but were not different between H and I. As VO2 increased with stimulation intensity, a larger change in any of the proposed regulators of tissue respiration (ADP, P(i), ATP/ADP.P(i), and phosphocreatine) was required during H and I than during C to elicit a given VO2, but requirements were similar for H and I.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobiosis↗
PubMed1992

Phorbol myristate acetate-induced lung injury: involvement of reactive oxygen species.

Using lucigenin-enhanced chemiluminescence, isolated rat lungs perfused with physiological salt-Ficoll solution were studied to test whether phorbol myristate acetate (PMA)-induced lung injury was mediated by reactive oxygen species (ROS). PMA (0.03 micrograms ml-1) caused small but significant increases in lung ROS levels and pulmonary arterial perfusion pressure (Ppa) but did not induce lung oedema. PMA (0.15 micrograms ml-1) induced lung oedema with large increases in ROS production and Ppa. Superoxide dismutase (SOD) inhibited the increases in ROS, Ppa, and lung oedema. Catalase and dimethylthiourea inhibited lung oedema but did not attenuate the increases in ROS and Ppa entirely. Indomethacin attenuated lung oedema partially but did not inhibit the increases in ROS and Ppa. These data indicate that PMA-induced lung injury is dependent on PMA concentration and ROS are responsible for such lung injury. Thromboxane plays a minor role for PMA-induced lung injury. The different effects of oxygen radical scavengers suggest that different radical species contribute to the increased pulmonary vascular response and lung injury.

Acridines↗
PubMed1992

The effect of ruthenium red during Ca2+ depletion and repletion in the isolated perfused rat liver.

Perfusion of rat liver with Ca(2+)-depleted buffer induces oxidative stress and liver damage, which can be prevented by Ca2+ repletion (Okuda et al. J Lab Clin Med). In the present study, we investigated the action of ruthenium red on acute Ca2+ loading after Ca2+ depletion in the isolated perfused rat liver. The major findings of this study are that 1) Ca2+ depletion-induced liver damage was related to mitochondrial disfunction; 2) ruthenium red inhibited the oxidative stress and liver damage normally seen during Ca2+ depletion; 3) ruthenium red inhibited the Ca2+ depletion-induced mitochondrial disfunction. These observations suggest that mitochondrial Ca2+ cycling is responsible for Ca2+ depletion-induced oxidative stress and liver damage.

Animals↗
PubMed1992

Oxygen radical generation during ischemia-reperfusion in the isolated perfused rat liver monitored by enhanced chemiluminescence.

Using luminol- and lucigenin-enhanced chemiluminescence (Lm-CL and Lg-CL), we monitored oxygen radical generation during ischemia-reperfusion in the isolated perfused rat liver. Both enhanced chemiluminescence levels decreased during 30 min of ischemia and increased markedly at the onset of reperfusion. When the liver was subjected to another 30 min of ischemia, reperfusion caused a progressive increase in both types of enhanced chemiluminescence. Administration of superoxide dismutase (SOD) into the perfusate strongly attenuated Lm-CL, but had a limited effect on Lg-CL. Catalase (CAT) and allupurionol (ALP) failed to attenuate both types of enhanced chemiluminescence. Thus the predominant oxygen radicals in the liver during reperfusion is superoxide and the lack of effect of ALP on oxygen radical generation indicates that hypoxanthine-xanthine oxidase reaction is unlikely to be a primary source of oxygen radicals. The different response to SOD in Lm-CL and Lg-CL is considered to be based on the diffusion space of luminol and lucigenin in the tissue. The relationship between oxygen radical levels and tissue damage, and the site of oxygen radical detection are discussed.

Acridines↗