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BMC Cancer Jun 2007The present study was conducted to analyze the value of ([18F] fluoromisonidazole (FMISO) and [18F]-2-fluoro-2'-deoxyglucose (FDG) PET as well as color pixel density... (Comparative Study)
Comparative Study
pO polarography, contrast enhanced color duplex sonography (CDS), [18F] fluoromisonidazole and [18F] fluorodeoxyglucose positron emission tomography: validated methods for the evaluation of therapy-relevant tumor oxygenation or only bricks in the puzzle of tumor hypoxia?
BACKGROUND
The present study was conducted to analyze the value of ([18F] fluoromisonidazole (FMISO) and [18F]-2-fluoro-2'-deoxyglucose (FDG) PET as well as color pixel density (CPD) and tumor perfusion (TP) assessed by color duplex sonography (CDS) for determination of therapeutic relevant hypoxia. As a standard for measuring tissue oxygenation in human tumors, the invasive, computerized polarographic needle electrode system (pO2 histography) was used for comparing the different non invasive measurements.
METHODS
Until now a total of 38 Patients with malignancies of the head and neck were examined. Tumor tissue pO2 was measured using a pO2-histograph. The needle electrode was placed CT-controlled in the tumor without general or local anesthesia. To assess the biological and clinical relevance of oxygenation measurement, the relative frequency of pO2 readings, with values < or = 2.5, < or = 5.0 and < or = 10.0 mmHg, as well as mean and median pO2 were stated. FMISO PET consisted of one static scan of the relevant region, performed 120 min after intravenous administration. FMISO tumor to muscle ratios (FMISOT/M) and tumor to blood ratios (FMISOT/B) were calculated. FDG PET of the lymph node metastases was performed 71 +/- 17 min after intravenous administration. To visualize as many vessels as possible by CDS, a contrast enhancer (Levovist, Schering Corp., Germany) was administered. Color pixel density (CPD) was defined as the ratio of colored to grey pixels in a region of interest. From CDS signals two parameters were extracted: color hue--defining velocity (v) and color area--defining perfused area (A). Signal intensity as a measure of tissue perfusion (TP) was quantified as follows: TP = vmean x Amean.
RESULTS
In order to investigate the degree of linear association, we calculated the Pearson correlation coefficient. Slight (|r| > 0.4) to moderate (|r| > 0.6) correlation was found between the parameters of pO2 polarography (pO2 readings with values < or = 2.5, < or = 5.0 and < or = 10.0 mmHg, as well as median pO2), CPD and FMISOT/M. Only a slight correlation between TP and the fraction of pO2 values < or = 10.0 mmHg, median and mean pO2 could be detected. After exclusion of four outliers the absolute values of the Pearson correlation coefficients increased clearly. There was no relevant association between mean or maximum FDG uptake and the different polarographic- as well as the CDS parameters.
CONCLUSION
CDS and FMISO PET represent different approaches for estimation of therapy relevant tumor hypoxia. Each of these approaches is methodologically limited, making evaluation of clinical potential in prospective studies necessary.
Topics: Carcinoma, Squamous Cell; Cell Hypoxia; Fluorodeoxyglucose F18; Head and Neck Neoplasms; Humans; Lymphatic Metastasis; Misonidazole; Oxygen Consumption; Polarography; Positron-Emission Tomography; Prognosis; Ultrasonography, Doppler, Color
PubMed: 17598907
DOI: 10.1186/1471-2407-7-113 -
Journal of Applied Physiology... Sep 2010Breathing hyperbaric oxygen (HBO) is common practice in hyperbaric and diving medicine. The benefits of breathing HBO, however, are limited by the risk of central...
Breathing hyperbaric oxygen (HBO) is common practice in hyperbaric and diving medicine. The benefits of breathing HBO, however, are limited by the risk of central nervous system O2 toxicity, which presents as seizures. We tested the hypothesis that excitability increases in CA1 neurons of the rat hippocampal slice (400 microm) over a continuum of hyperoxia that spans normobaric and hyperbaric pressures. Amplitude changes of the orthodromic population spike were used to assess neuronal O2 sensitivity before, during, and following exposure to 0, 0.6, 0.95 (control), 2.84, and 4.54 atmospheres absolute (ATA) O2. Polarographic O2 electrodes were used to measure tissue slice PO2 (PtO2). In 0.95 ATA O2, core PtO2 at 200 microm deep was 115±16 Torr (mean±SE). Increasing O2 to 2.84 and 4.54 ATA increased core PtO2 to 1,222±77 and 2,037±157 Torr, respectively. HBO increased the orthodromic population spike amplitude and usually induced hyperexcitability (i.e., secondary population spikes) and, in addition, a long-lasting potentiation of the orthodromic population spike that we have termed "oxygen-induced potentiation" (OxIP). Exposure to 0.60 ATA O2 and hypoxia (0.00 ATA) decreased core PtO2 to 84±6 and 20±4 Torr, respectively, and abolished the orthodromic response. Reoxygenation from 0.0 or 0.6 ATA O2, however, usually produced a response similar to that of HBO: hyperexcitability and activation of OxIP. We conclude that CA1 neurons exhibit increased excitability and neural plasticity over a broad range of PtO2, which can be activated by a single, hyperoxic stimulus. We postulate that transient acute hyperoxia stimulus, whether caused by breathing HBO or reoxygenation following hypoxia (e.g., disordered breathing), is a powerful stimulant for orthodromic activity and neural plasticity in the CA1 hippocampus.
Topics: Action Potentials; Animals; CA1 Region, Hippocampal; Hyperbaric Oxygenation; Hyperoxia; In Vitro Techniques; Ion-Selective Electrodes; Male; Neuronal Plasticity; Neurons; Oxygen; Polarography; Pressure; Rats; Rats, Sprague-Dawley; Time Factors
PubMed: 20558753
DOI: 10.1152/japplphysiol.91429.2008 -
Analytical and Bioanalytical Chemistry May 2019The origin of the method of standard additions (SAM) and of the use of internal standard (IS) in instrumental chemical analysis and their spread into other areas has...
The origin of the method of standard additions (SAM) and of the use of internal standard (IS) in instrumental chemical analysis and their spread into other areas has been reviewed. Recorded applications of IS range from flame spectroscopy in 1877 through multiple techniques to current use in NMR and standard additions with isotopically labelled internal standards in hyphenated techniques. For SAM, applications stemmed from polarography in 1937 and spread to most instrumental methods. Some misconceptions on priorities are corrected.
PubMed: 30941480
DOI: 10.1007/s00216-019-01754-w -
British Journal of Industrial Medicine Oct 1967The absorption of ethylbenzene through the skin of the hand and the forearm in men was investigated experimentally. Both the absorption of liquid ethylbenzene and the...
The absorption of ethylbenzene through the skin of the hand and the forearm in men was investigated experimentally. Both the absorption of liquid ethylbenzene and the absorption from aqueous solutions were studied. The rate of absorption of liquid ethylbenzene was 22 to 33 mg./cm./hr, and the rates from aqueous solutions were 118 and 215 μg./cm./hr from mean concentrations of 112 and 156 mg./litre. The mandelic acid excreted in urine was equivalent to about 4·6% of the absorbed dose—much less than after lung absorption. Urinary mandelic acid does not provide a reliable index of absorption when there is simultaneous skin and lung exposure.
Topics: Benzene Derivatives; Humans; Male; Mandelic Acids; Occupational Diseases; Polarography; Skin Absorption; Spectrophotometry
PubMed: 6073092
DOI: 10.1136/oem.24.4.330 -
European Journal of Biochemistry Jan 2001An enzyme degrading cytokinins with isoprenoid side chain, previously named cytokinin oxidase, was purified to near homogeneity from wheat and barley grains. New... (Comparative Study)
Comparative Study
An enzyme degrading cytokinins with isoprenoid side chain, previously named cytokinin oxidase, was purified to near homogeneity from wheat and barley grains. New techniques were developed for the enzyme activity assay and staining on native electrophoretic gels to identify the protein. The purified wheat enzyme is a monomer 60 kDa, its N-terminal amino-acid sequence shows similarity to hypothetical cytokinin oxidase genes from Arabidopsis thaliana, but not to the enzyme from maize. N6-isopentenyl-2-(2-hydroxyethylamino)-9-methyladenine is the best substrate from all the cytokinins tested. Interestingly, oxygen was not required and hydrogen peroxide not produced during the catalytic reaction, so the enzyme behaves as a dehydrogenase rather than an oxidase. This was confirmed by the ability of the enzyme to transfer electrons to artificial electron acceptors, such as phenazine methosulfate and 2,6-dichlorophenol-indophenol. 2,3-Dimethoxy-5-methyl-1,4-benzoquinone, a precursor of the naturally occurring electron acceptor ubiquinone, readily interacts with the enzyme in micromolar concentrations. Typical flavoenzyme inhibitors such as acriflavine and diphenyleneiodonium inhibited this enzyme activity. Presence of the flavin cofactor in the enzyme was confirmed by differential pulse polarography and by measuring the fluorescence emission spectrum. Possible existence of a second redox centre is discussed.
Topics: Amino Acid Sequence; Cytokinins; Edible Grain; Electron Transport; Flavoproteins; Genes, Plant; Hordeum; Hydrogen Peroxide; Isopentenyladenosine; Molecular Sequence Data; Oxidoreductases; Seeds; Sequence Analysis, Protein; Sequence Homology, Amino Acid; Substrate Specificity; Triticum
PubMed: 11168382
DOI: 10.1046/j.1432-1033.2001.01910.x -
Acta Ophthalmologica Scandinavica Aug 2006Earlier studies have demonstrated that carbonic anhydrase inhibitors (CAIs) increase optic nerve oxygen tension (ONPO(2)) in pigs. We hypothesized that the mechanism of...
PURPOSE
Earlier studies have demonstrated that carbonic anhydrase inhibitors (CAIs) increase optic nerve oxygen tension (ONPO(2)) in pigs. We hypothesized that the mechanism of this effect was either a CO(2) increase or a pH decrease in tissue and blood. To test this hypothesis we investigated and compared how optic nerve pH (ONpH) and ONPO(2) are affected by: (1) carbonic anhydrase inhibition; (2) respiratory acidosis, and (3) metabolic acidosis. We measured ONpH with a glass pH electrode and ONPO(2) with a polarographic oxygen electrode. One of the electrodes was placed in the vitreous cavity 0.5 mm over the optic nerve in the eyes of domestic pigs.
METHODS
We measured ONpH during carbonic anhydrase inhibition and ONpH or ONPO(2) during NH(4)Cl-induced metabolic acidosis and during CO(2) breathing (respiratory acidosis).
RESULTS
Baseline ONpH was 0.12 +/- 0.06 lower than arterial pH (mean +/- SD, n = 10, p < 0.001). Optic nerve pH decreased with arterial pH during carbonic anhydrase inhibition, metabolic and respiratory acidosis. Optic nerve oxygen tension was not affected by metabolic acidosis but increased during CO(2) breathing, as it has been shown to do during carbonic anhydrase inhibition.
CONCLUSIONS
There is a close correlation between arterial blood pH and intraocular pH. Isolated ONpH changes do not affect ONPO(2), thus the ONPO(2) increase seen with carbonic anhydrase inhibition is probably not only due to pH changes in the blood and optic nerve. Accumulation of CO(2), either alone or in combination with a pH change, is likely to cause the ONPO(2) increase, but a direct vascular effect should also be considered.
Topics: Acidosis, Respiratory; Ammonium Chloride; Animals; Carbonic Anhydrase Inhibitors; Carbonic Anhydrases; Hydrogen-Ion Concentration; Ion-Selective Electrodes; Optic Disk; Optic Nerve; Oxygen; Oxygen Consumption; Partial Pressure; Polarography; Sulfonamides; Swine; Thiophenes
PubMed: 16879567
DOI: 10.1111/j.1600-0420.2006.00709.x -
Colloids and Surfaces. B, Biointerfaces May 2016Copper nanoparticles (Cu NPs) are increasingly used in various biologically relevant applications and products, e.g., due to their antimicrobial and catalytic...
Copper nanoparticles (Cu NPs) are increasingly used in various biologically relevant applications and products, e.g., due to their antimicrobial and catalytic properties. This inevitably demands for an improved understanding on their interactions and potential toxic effects on humans. The aim of this study was to investigate the corrosion of copper nanoparticles in various biological media and to elucidate the speciation of released copper in solution. Furthermore, reactive oxygen species (ROS) generation and lung cell (A549 type II) membrane damage induced by Cu NPs in the various media were studied. The used biological media of different complexity are of relevance for nanotoxicological studies: Dulbecco's modified eagle medium (DMEM), DMEM(+) (includes fetal bovine serum), phosphate buffered saline (PBS), and PBS+histidine. The results show that both copper release and corrosion are enhanced in DMEM(+), DMEM, and PBS+histidine compared with PBS alone. Speciation results show that essentially no free copper ions are present in the released fraction of Cu NPs in neither DMEM(+), DMEM nor histidine, while labile Cu complexes form in PBS. The Cu NPs were substantially more membrane reactive in PBS compared to the other media and the NPs caused larger effects compared to the same mass of Cu ions. Similarly, the Cu NPs caused much more ROS generation compared to the released fraction only. Taken together, the results suggest that membrane damage and ROS formation are stronger induced by Cu NPs and by free or labile Cu ions/complexes compared with Cu bound to biomolecules.
Topics: A549 Cells; Cell Membrane; Copper; Culture Media; Extracellular Space; Humans; Lung Neoplasms; Metal Nanoparticles; Models, Biological; Particle Size; Reactive Oxygen Species
PubMed: 26859121
DOI: 10.1016/j.colsurfb.2016.01.052 -
British Journal of Anaesthesia Apr 2004
Topics: Anesthesia; Anesthesia, Conduction; Blood Gas Monitoring, Transcutaneous; Humans; Hypercapnia; Oxygen; Polarography; Postoperative Complications; Surgical Wound Infection; Wound Healing
PubMed: 15013958
DOI: 10.1093/bja/aeh090 -
Nanomaterials (Basel, Switzerland) Nov 2017This study presents the impact of carbon nanotubes (CNTs) on mitochondrial oxygen mass flux () under three experimental conditions. New experimental results and a new...
Carbon Nanotubes' Effect on Mitochondrial Oxygen Flux Dynamics: Polarography Experimental Study and Machine Learning Models using Star Graph Trace Invariants of Raman Spectra.
This study presents the impact of carbon nanotubes (CNTs) on mitochondrial oxygen mass flux () under three experimental conditions. New experimental results and a new methodology are reported for the first time and they are based on CNT Raman spectra star graph transform (spectral moments) and perturbation theory. The experimental measures of showed that no tested CNT family can inhibit the oxygen consumption profiles of mitochondria. The best model for the prediction of for other CNTs was provided by random forest using eight features, obtaining test R-squared (²) of 0.863 and test root-mean-square error (RMSE) of 0.0461. The results demonstrate the capability of encoding CNT information into spectral moments of the Raman star graphs (SG) transform with a potential applicability as predictive tools in nanotechnology and material risk assessments.
PubMed: 29137126
DOI: 10.3390/nano7110386 -
Proceedings of the National Academy of... Jan 1976The association constant for myosin subfragment-1 (S-1) and actin was measured, using a new application of fluorescence depolarization which capitalizes on the fact that...
The association constant for myosin subfragment-1 (S-1) and actin was measured, using a new application of fluorescence depolarization which capitalizes on the fact that S-1 has high rotational mobility while F-actin does not. Uncoupling of the time dependences of the anisotropy decay and the association/dissociation phenomena allowed the experimentally determined anisotropy decay curve to be fitted by a sum of two terms weighted by the mole fractions of the free and bound S-1. At 4 degrees C, ionic strength 0.16 M, and pH 7.0, the association constant Ka is (1.73 +/- 0.35) X 10(6) M-1 at infinite dilution. This makes the -deltaG degrees of binding of F-actin to S-1 similar to the -deltaG degrees of binding of ATP to S-1, and the possible physiological relevance of the similarity to muscle contraction is discussed.
Topics: Actins; Fluorometry; Muscle Contraction; Myosins; Polarography; Thermodynamics
PubMed: 1061107
DOI: 10.1073/pnas.73.1.133