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Littlejohns LR, Bader MK, March K. Brain tissue oxygen monitoring in severe brain injury, I. Research and usefulness in critical care. Crit Care Nurse 2003; 23:17-25; quiz 26-7. [PMID: 12961780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
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Sharma HA, Balcavage WX, Waite LR, Johnson MT, Nindl G. Characterization of a real time H2O2 monitor for use in studies on H2O2 production by antibodies and cells. BIOMEDICAL SCIENCES INSTRUMENTATION 2003; 39:554-60. [PMID: 12724951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
It was recently shown that antibodies catalyze a reaction between water and ultraviolet light (UV) creating singlet oxygen and ultimately H2O2. Although the in vivo relevance of these antibody reactions is unclear, it is interesting that among a wide variety of non-antibody proteins tested, the T cell receptor is the only protein with similar capabilities. In clinical settings UV is believed to exert therapeutic effects by eliminating inflammatory epidermal T cells and we hypothesized that UV-triggered H2O2 production is involved in this process. To test the hypothesis we developed tools to study production of H2O2 by T cell receptors with the long-term goal of understanding, and improving, UV phototherapy. Here, we report the development of an inexpensive, real time H2O2 monitoring system having broad applicability. The detector is a Clark oxygen electrode (Pt, Ag/AgCl) modified to detect UV-driven H2O2 production. Modifications include painting the electrode black to minimize UV effects on the Ag/AgCl electrode and the use of hydrophilic, large pore Gelnots electrode membranes. Electrode current was converted to voltage and then amplified and recorded using a digital multimeter coupled to a PC. A reaction vessel with a quartz window was developed to maintain constant temperature while permitting UV irradiation of the samples. The sensitivity and specificity of the system and its use in cell-free and cell-based assays will be presented. In a cellfree system, production of H2O2 by CD3 antibodies was confirmed using our real time H2O2 monitoring method. Additionally we report the finding that splenocytes and Jurkat T cells also produce H2O2 when exposed to UV light.
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MESH Headings
- Animals
- Antibodies/analysis
- Antibodies/metabolism
- Antibodies, Catalytic/chemistry
- Antibodies, Catalytic/metabolism
- Antibodies, Catalytic/radiation effects
- CD3 Complex/metabolism
- CD3 Complex/radiation effects
- Calibration
- Cell-Free System/metabolism
- Electrodes
- Equipment Design
- Humans
- Hydrogen Peroxide/analysis
- Hydrogen Peroxide/metabolism
- Jurkat Cells/metabolism
- Jurkat Cells/radiation effects
- Male
- Membranes, Artificial
- Oxidation-Reduction
- Polarography/instrumentation
- Rats
- Rats, Sprague-Dawley
- Receptors, Antigen, T-Cell/chemistry
- Receptors, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/radiation effects
- Sensitivity and Specificity
- Spleen/chemistry
- Spleen/metabolism
- Spleen/radiation effects
- Temperature
- Ultraviolet Rays
- Water/chemistry
- Water/metabolism
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Ibrahim F, el-Enany N. Anodic polarographic determination of ciclopirox olamine in pure and certain pharmaceutical preparations. J Pharm Biomed Anal 2003; 32:353-9. [PMID: 12763546 DOI: 10.1016/s0731-7085(02)00709-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The anodic polarographic behavior of ciclopirox have been studied in Britton Robinson buffer (BRb) over the pH range 6-11. In BRb of pH 7 a well defined anodic wave was produced with diffusion current constant (Id) of 4.86+/-0.048 (n=6) using DC(t) mode. Adopting both of direct current (DC(t)) and differential pulse polarographic (DPP) modes, the current-concentration relationship was found to be rectilinear over the range 4 to 24 and 2 to 12 microg ml(-1) respectively, with minimum detectability (S/N=2) of 0.2 microg ml(-1) (1 x 10(-6) M) using the DPP mode. The average percent recovery was favourably compared to a reference method, with a satisfactory standard deviation, the proposed method was further applied to the determination of ciclopirox olamine in certain pharmaceutical preparations including lotion and cream. The average percentage recoveries for lotion were 100.06+/-0.94 and 100.06+/-1.08 using DC(t) and DPP modes respectively, and for cream were 100.17+/-0.64 and 100.34+/-1.28 using DC(t) and DPP modes, respectively. A pathway for the electrode reaction was postulated.
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Doll CM, Milosevic M, Pintilie M, Hill RP, Fyles AW. Estimating hypoxic status in human tumors: a simulation using Eppendorf oxygen probe data in cervical cancer patients. Int J Radiat Oncol Biol Phys 2003; 55:1239-46. [PMID: 12654433 DOI: 10.1016/s0360-3016(02)04474-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE To define the minimal number of pO(2) measurements, with 90% sensitivity and 90% specificity, needed to categorize cervical tumors as either hypoxic or oxic. METHODS AND MATERIALS Using Eppendorf oxygen probe data from our ongoing prospective trial, we simulated the measurement of tumor oxygenation with a smaller number of data points in 135 patients with cervical cancer. The hypoxic proportion, defined as the percentage of pO(2) values <5 mm Hg (HP5), was calculated for each tumor. Hypoxic tumors were defined as those with a median HP5 >50%, and tumors with normal oxygen levels as those with a median HP5 < or =50%. A small number of pO(2) measurements were randomly selected from the Eppendorf measurements in each tumor, or per Eppendorf track, and used to define the tumor as hypoxic or oxic. The sensitivity and specificity were calculated, considering the classification as given by the complete set of Eppendorf measurements as the reference standard. RESULTS The probability of falsely classifying the tumor decreased as the selected number of pO(2) measurements per tumor increased, and at 16 measurements was approximately 10%. Adding additional measurements per tumor beyond 24 improved the ability to classify the tumor accurately only slightly. The probability of falsely classifying the tumor decreased as the pO(2) measurements per track increased. At five measurements per track, the probability of falsely classifying the tumor was approximately 9%. CONCLUSION Approximately 20 measurements per tumor, or five measurements per track, using the Eppendorf pO(2) histograph, are sufficient to categorize cervical tumors as hypoxic or oxic. The results of this study will serve as a guide for research clinicians in the use of this and other systems in the assessment of tumor oxygenation in humans.
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Misfeld M, Heinze H, Sievers HH, Kraatz EG. Intramyocardial Oxygen Monitoring in Coronary Artery Bypass Surgery. J Clin Monit Comput 2003; 18:93-101. [PMID: 15362271 DOI: 10.1023/b:jocm.0000032697.95793.44] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE In coronary artery bypass surgery various parameters have been used to monitor patients clinical status. Direct monitoring of myocardial oxygenation can be performed by measuring intramyocardial partial oxygen tension pressure (p ti O2). This study was performed to determine the perioperative time course of this parameter in correlation to standard monitoring parameters. METHODS Twenty-three patients underwent standard coronary artery bypass grafting (CABG). A special polarographic microprobes was inserted into the myocardium in the distribution zone of the left anterior descending artery which was one of the target vessels of myocardial revascularization. Intramyocardial p ti O2 was monitored intra- and up to 12 hours postoperatively. Values were correlated to hemodynamic, oxygenation and procedure associated parameters. RESULTS Myocardial oxygenation during CABG is characterized by a significant decrease of p ti O2 during cross-clamping and a significant increase after removal of the cross-clamp. The postoperative time course of p ti O2 shows a steady increase of p ti O2 in the first 12 postoperative hours investigated. Preoperative ejection fraction as well as cardio-pulmonary bypass time does not seem to have an influence on the postoperative p ti O2 in these patients. Various standard monitoring parameters show complex influence on intramyocardial p ti O2- CONCLUSIONS Determination of intramyocardial partial oxygen pressure in patients undergoing bypass surgery shows characteristic changes. Changes in p ti O2 as a direct online parameter of myocardial oxygenation occur immediately after procedures that influence myocardial perfusion and therefore, may help to detect potential complications earlier than standard monitoring parameters in cardiac surgery.
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Matloob MH. Determination of cadmium, lead, copper and zinc in Yemeni khat by anodic stripping voltammetry. EASTERN MEDITERRANEAN HEALTH JOURNAL = LA REVUE DE SANTE DE LA MEDITERRANEE ORIENTALE = AL-MAJALLAH AL-SIHHIYAH LI-SHARQ AL-MUTAWASSIT 2003; 9:28-36. [PMID: 15562730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
Trace element concentrations in khat were investigated as they can disturb trace element levels in the body. Cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) levels in khat and 6 leafy vegetables commonly consumed in the Republic of Yemen were determined by differential pulse anodic stripping voltammetry after wet digestion of the organic matter. Khat had significantly higher concentrations of Cu and Zn than did the leafy vegetables, but similar amounts of Cd and Pb. The average daily intake of khat consumers of Cd, Pb, Cu and Zn from khat only was estimated to be 2.0-10.2 microg/day, 23.6-118.0 microg/day, 530-2654 microg/day and 662-3311 microg/day respectively. Although high, these values were within Food and Agriculture Organization/World Health Organization tolerance limits.
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Braun RD, Lanzen JL, Snyder SA, Dewhirst MW. Comparison of tumor and normal tissue oxygen tension measurements using OxyLite or microelectrodes in rodents. Am J Physiol Heart Circ Physiol 2001; 280:H2533-44. [PMID: 11356608 DOI: 10.1152/ajpheart.2001.280.6.h2533] [Citation(s) in RCA: 194] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study we compare oxygen tension (Po 2) histograms measured with O2 microelectrodes and a new optical Po 2 measurement device, the OxyLite, in normal tissues (mouse spleen and thymus) and in tumors (R3230Ac in rats) ( n = 5–6). The transient response to glucose infusion or 100% O2 breathing (hyperoxia) was also measured in tumors. Po 2 histograms of spleen and thymus with the two devices were not different. The OxyLite tumor Po 2 histogram, however, was left-shifted compared with the microelectrode (median Po 21.0 vs. 4.0 mmHg, P = 0.016). Both probes responded to acute hyperglycemia with a mean increase of 3–6 mmHg, but the microelectrode change was not significant. The OxyLite consistently recorded large Po 2 increases (∼28 mmHg) with hyperoxia, whereas the microelectrode response was variable. The OxyLite averages Po 2 over an area that contains interstitial and vascular components, whereas the microelectrode measures a more local Po 2. This study demonstrates the importance of considering the features of the measurement device when studying tissues with heterogeneous Po 2 distributions (e.g., tumors).
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Abstract
A micro-polarimeter with a 40 nL probe volume was configured so that it is compatible with capillary-scale flowing stream analysis. The optical configuration consists of two polarizing optics, a capillary, a laser source and a photodetector which is very simple to configure with low cost components. This unique polarimeter is based upon the interaction of a linearly polarized laser beam and a capillary tube, in this case one with an inner diameter of 250 microns. Side illumination of the tube results in a 360 degrees fan of scattered light, which contains a set of interference fringes that change in response to optically active solutes. Solutes that exhibit optical activity are quantifiable and are detected by analyzing the polarization state of the backscattered light. The ability of the instrument to make extremely sensitive optical activity measurements in flowing streams is shown by the determination of (R)-mandelic acid, with a detection limit of 66 x 10(-6) M (507 x 10(-12) g), and the non-optically active control, glycerol. Additionally, the detector was configured to minimize refractive index perturbations.
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Kumar SM, Porterfield DM, Muller KJ, Smith PJ, Sahley CL. Nerve injury induces a rapid efflux of nitric oxide (NO) detected with a novel NO microsensor. J Neurosci 2001; 21:215-20. [PMID: 11150338 PMCID: PMC6762443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023] Open
Abstract
An early step in repair of the leech CNS is the appearance of endothelial nitric oxide synthase (eNOS) immunoreactivity and NOS activity, but coincident generation of NO at the lesion after injury has not been shown. This is important because NO can regulate microglial cell motility and axon growth. Indirect measurement of NO with the standard citrulline assay demonstrated that NO was generated within 30 min after nerve cord injury. A polarographic NO-selective self-referencing microelectrode that measures NO flux noninvasively was developed to obtain higher spatial and temporal resolution. With this probe, it was possible to demonstrate that immediately after the leech CNS was injured, NO left the lesion with a mean peak efflux of 803 +/- 99 fmol NO cm(-2) sec(-1). NO efflux exponentially declined to a constant value, as described through the equation f(t) = y(o) + ae(-t/tau), with tau = 117 +/- 30 sec. The constant y(o) = 15.8 +/- 4.5 fmol cm(-2) represents a sustained efflux of NO. Approximately 200 pmol NO cm(-2) is produced at the lesion (n = 8). Thus, injury activates eNOS already present in the CNS and precedes the accumulation of microglia at the lesion, consistent with the hypothesis that NO acts to stop the migrating microglia at the lesion site.
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Abstract
OBJECTIVES To use recently introduced polarographic technology to characterize the distribution of oxygenation in solid tumors, explore the differences between severe hypoxia and true necrosis, and evaluate the ability to predict treatment outcomes based on tumor oxygenation. STUDY DESIGN Prospective, nonrandomized trial of patients with advanced head and neck cancer, conducted at an academic institution. METHODS A total of 63 patients underwent polarographic oxygen measurements of their tumors. Experiment 1 was designed to determine whether a gradient of oxygenation exists within tumors by examining several series of measurements in each tumor. Experiment 2 was an analysis of the difference in data variance incurred when comparing oxygen measurements using oxygen electrodes of two different sizes. Experiment 3 compared the proportion of tumor necrosis to the proportion of very low (< or =2.5 mm Hg) polarographic oxygen measurements. Experiment 4 was designed to explore the correlation between oxygenation and treatment outcomes after nonsurgical management. RESULTS No gradient of oxygenation was found within cervical lymph node metastases from head and neck squamous cell carcinomas (P > .9). Tumor measurements achieved with larger (17 microm) electrodes displayed smaller variances than those obtained with smaller (12 microm) electrodes, although this difference failed to reach statistical significance (P = .60). There was no correlation between tumor necrosis and the proportion of very low (< or =2.5 mm Hg) oxygen measurements. There was a nonsignificant trend toward poorer locoregional control and overall survival in hypoxic tumors. CONCLUSIONS Hypoxia exists within cervical lymph node metastases from head and neck squamous carcinomas, but the hypoxic regions are distributed essentially randomly. As expected, measurements of oxygen achieved with larger electrodes results in lowered variance, but with no change in overall tumor mean oxygen levels. Polarographic oxygen measurements are independent of tumor necrosis. Finally, oxygenation as an independent variable is incapable of predicting prognosis, probably reflecting the multifactorial nature of the biological behavior of head and neck cancers.
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Baumgärtl H, Zimelka W, Lübbers DW. Simultaneous measurements of mechanical pressure and oxygen pressure during puncturing of semisolid polymeric networks by polarographic needle electrodes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 471:613-22. [PMID: 10659195 DOI: 10.1007/978-1-4615-4717-4_71] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
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Uslu B, Biryol I. Voltammetric determination of amoxicillin using a poly (N-vinyl imidazole) modified carbon paste electrode. J Pharm Biomed Anal 1999; 20:591-8. [PMID: 10701977 DOI: 10.1016/s0731-7085(99)00059-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Swinney K, Hankins J, Bornhop DJ. Laser-based capillary polarimeter. JOURNAL OF CAPILLARY ELECTROPHORESIS AND MICROCHIP TECHNOLOGY 1999; 6:93-6. [PMID: 11315158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
A laser-based capillary polarimeter has been configured to allow for the detection of optically active molecules in capillary tubes with a characteristic inner diameter of 250 microm and a 39-nL (10(-9)) sample volume. The simple optical configuration consists of a HeNe laser, polarizing optic, fused-silica capillary, and charge-coupled device (CCD) camera in communication with a laser beam analyzer. The capillary scale polarimeter is based on the interaction between a polarized laser beam and a capillary tube, which results in a 360 degree fan of scattered light. This array of scattered light contains a set of interference fringe, which respond in a reproducible manner to changes in solute optical activity. The polarimetric utility of the instrument will be demonstrated by the analysis of two optically active solutes, R-mandelic acid and D-glucose, in addition to the nonoptically active control, glycerol. The polarimetric response of the system is quantifiable with detection limits facilitating 1.7 x 10(-3) M or 68 x 10(-12) nmol (7 psi 10(-9) g) sensitivity.
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Manley GT, Pitts LH, Morabito D, Doyle CA, Gibson J, Gimbel M, Hopf HW, Knudson MM. Brain tissue oxygenation during hemorrhagic shock, resuscitation, and alterations in ventilation. THE JOURNAL OF TRAUMA 1999; 46:261-7. [PMID: 10029031 DOI: 10.1097/00005373-199902000-00011] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Recently developed polarographic microelectrodes permit continuous, reliable monitoring of oxygen tension in brain tissue (PbrO2). The aim of this study was to investigate the feasibility and utility of directly monitoring PbrO2 in cerebral tissue during changes in oxygenation or ventilation and during hemorrhagic shock and resuscitation. We also sought to develop a model in which treatment protocols could be evaluated using PbrO2 as an end point. METHODS Licox Clark-type polarographic probes were inserted in the brain tissue of 16 swine to monitor PbrO2. In eight swine, changes in PbrO2 were observed over a range of fractional concentrations of inspired O2 (FiO2) as well as during periods of hyperventilation and hypoventilation. In eight other swine, PbrO2 was monitored during a graded hemorrhage of up to 70% estimated blood volume and during the resuscitation period. RESULTS When FiO2 was elevated to 100%, PbrO2 increased from a baseline of 15+/-2 mm Hg to 36+/-11 mm Hg. Hyperventilation while breathing 100% oxygen resulted in a 40% decrease in PbrO2 (p < 0.05), whereas hypoventilation increased PbrO2 to 88 mm Hg (p < 0.01). A graded hemorrhage to 50% estimated blood volume significantly reduced PbrO2, mean arterial pressure, and intracranial pressure (p < 0.01). Continued hemorrhage to 70% estimated blood volume resulted in a PbrO2 of 2.9+/-1.5 mm Hg. After resuscitation, PbrO2 was significantly elevated, reaching 65+/-13 mm Hg (p < 0.01), whereas mean arterial pressure and cerebral perfusion pressure simply returned to baseline. CONCLUSION Directly measured PbrO2 was highly responsive to changes in FiO2, ventilatory rate, and blood volume in this experimental model. In particular, hypoventilation significantly increased PbrO2, whereas hyperventilation had the opposite effect. The postresuscitation increase in PbrO2 may reflect changes in both O2 delivery and O2 metabolism. These experiments set the stage for future investigations of a variety of resuscitation protocols in both normal and injured brain.
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Sherman RT. Necessity is the mother of invention. ARCHIVES OF SURGERY (CHICAGO, ILL. : 1960) 1999; 134:104. [PMID: 9927142 DOI: 10.1001/archsurg.134.1.104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Dings J, Meixensberger J, Jäger A, Roosen K. Clinical experience with 118 brain tissue oxygen partial pressure catheter probes. Neurosurgery 1998; 43:1082-95. [PMID: 9802852 DOI: 10.1097/00006123-199811000-00045] [Citation(s) in RCA: 255] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVE We assessed the technical and diagnostic reliability of partial pressure of oxygen (PO2) of brain tissue (P(ti)O2) monitoring. The monitoring system and the catheter probes were tested in vitro, and clinical experiences obtained with 118 brain P(ti)O2 catheter probes, used in 101 patients, are reported. METHODS The polarographic (LICOX; Medical Systems Corp., Greenvale, NY) P(ti)O2 catheter probe lies 22 to 27 mm below the dura level; its PO2-sensitive surface is 7.1 mm2. For 10 patients, the adaptation time (with initially unreliable signals after insertion) was determined. For 27 patients, the probe was removed in a stepwise fashion (three increments of 5 mm) and the heterogeneity of brain P(ti)O2 levels was investigated. After removal of the catheter probes, their PO2 and zero display error values were determined and compared with probe performance data obtained in vitro with unused PO2 catheter probes. RESULTS Small iatrogenic hematomas were observed for two patients (1.7%). No infection occurred after 6.7 +/- 3.9 days (mean +/- standard deviation) of monitoring. The technical complication (dislocation or defect) rate was 13.6%. The mean adaptation time was 79.0 +/- 51.7 min. A flow chart is presented, which helps to rule out artifacts. The mean P(ti)O2 measured at 22 to 27 mm below the dura was 23.8 +/- 8.1 mm Hg, at 17 to 22 mm was 25.7 +/- 8.3 mm Hg, at 12 to 17 mm was 33.0 +/- 13.3 mm Hg (P < 0.01, compared with the initial value), and at 7 to 12 mm was 33.3 +/- 13.3 mm Hg (P < 0.01). Recent catheter probe versions exhibited a PO2 display error of -1.2 +/- 5.1% (mean +/- standard deviation, n = 38) and a mean zero display error of 1.1 +/- 0.9 mm Hg (n = 34). The greatest PO2 display errors were measured during the first 4 days of continuous monitoring. In the in vitro test (of 12 unused catheter probes), the maximal probe display error was 1.07 +/- 2.14%, tested at temperatures between 22 degrees C and 37 degrees C and tested at oxygen pressures of 0, 44, and 150 mm Hg. In vitro, the zero display error was -0.21 +/- 0.25 mm Hg. CONCLUSION Brain P(ti)O2 monitoring, reflecting an area 17 to 27 mm below the dura, is a safe and reliable technique for monitoring cerebral oxygenation. Excluding the first 1 hour after insertion, data are reliable, with almost 100% good data quality.
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Ichijima H, Hayashi T, Mitsunaga S, Hamano H. Determination of oxygen tension on rabbit corneas under contact lenses. THE CLAO JOURNAL : OFFICIAL PUBLICATION OF THE CONTACT LENS ASSOCIATION OF OPHTHALMOLOGISTS, INC 1998; 24:220-6. [PMID: 9800061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
PURPOSE To determine oxygen tension (PO2) on rabbit corneas beneath rigid gas permeable (RGP), hydrogel, and silicone elastomer lenses under open- and closed-eye conditions and to demonstrate the relationship between PO2 and overnight corneal swelling response in the rabbit model. METHODS An improved PO2 monitoring system (PO-2080) with a platinum-micro-wire-electrode was used to measure PO2. An ultrasonic pachymeter (DGH-2000) was used to measure corneal thickness after overnight wear. RESULTS The relationship between PO2 and oxygen transmissibility (Dk/ L) of the contact lens was linear for Dk/L between 0 and 70 x 10(-9) (cm/ sec)(mLO2/mL x mmHg). For Dk/L greater than 70 x 10(-9), PO2 gradually reached a plateau at 120 mmHg for open-eye conditions and 20 mmHg for closed-eye conditions. PO2 was inversely related to the overnight corneal swelling, ranging from 5.1% swelling at PO2 113.5/17.5 mmHg (open/closed-eye) for a hyper Dk/L lens (125 x 10(-9)) to 15.1% swelling at PO2 10.4/5.1 mmHg for a low Dk/L lens (11.5 x 10(-9)). CONCLUSIONS Polarographic determination of PO2 provides reliable information about the amount of oxygen available to the cornea under a lens for both open-eye and closed-eye conditions. The data demonstrate that it is not possible to achieve normal oxygen levels with contact lens wear, even when hyper Dk/L lenses are worn.
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Saam BT, Conradi MS. Low frequency NMR polarimeter for hyperpolarized gases. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1998; 134:67-71. [PMID: 9740732 DOI: 10.1006/jmre.1998.1515] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
An inexpensive and self-contained apparatus for pulsed NMR at 30-250 kHz is described. The intended application is monitoring of the spin polarization of rare gas nuclei in a laser-polarizing apparatus in fields of order 30 G. In addition, the device provides a convenient method for following the polarization decay during storage and transport. Some of the features are a flexible pulse generator, splitting of transmitter RF cycles by the RF gate, a Q switch, and a wide range of receiver gains.
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Furlanetto S, Pinzauti S, La Porta E, Chiarugi A, Mura P, Orlandini S. Development and validation of a differential pulse polarographic method for quinolinic acid determination in human plasma and urine after solid-phase extraction: a chemometric approach. J Pharm Biomed Anal 1998; 17:1015-28. [PMID: 9884191 DOI: 10.1016/s0731-7085(98)00067-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A chemometric approach was applied for determining quinolinic acid in human plasma by differential pulse polarography after solid phase extraction. A fractional factorial design was used to examine the significant experimental variables for the peak height maximization. A Doehlert design, which allowed a sequential response surface methodology to be performed, was applied to the variables scan rate and drop size. The results indicated that the scan rate had the greatest effect on the response peak height. The linear range was extended from 8.52 x 10(-8) to 1.34 x 10(-5) M and the limit of detection was 2.9 x 10(-8) M. The validation process consisted of a pre-validation study followed by the main validation in the plasma matrix. The robustness and the intermediate precision were evaluated by means of experimental design. A 3(4)//9 screening symmetric matrix and a central composite design were used to optimize the solid phase extraction procedure of the analyte from human plasma using anion exchange cartridges. The goal was to select the best retention, wash and elution solvents and their volumes in order to maximize the extraction efficiency using as the response the polarographic peak height. An extraction efficiency of 90% was found. The method was also applied to the determination of quinolinic acid in urine and the mean concentration in human plasma and urine, was found to be 3.7 x 10(-7) and 4.9 x 10(-5) M respectively.
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Ovchinnikov AV, Gabdullin MG. [Time-base sweep unit for polarograph PA-2]. MEDITSINSKAIA TEKHNIKA 1998:46. [PMID: 9791856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
A time-base sweep unit is proposed for a PA-2 polarograph (Czechia). The apparatus as a further development of a series of voltamperometric analyzers of the known mark "LP" has a number of additional modes of polarographic analysis expanding the possibilities of recording the volt-ampere characteristics of the analyzed objects. However, the apparatus cannot solve the problems pertaining to a temporal evaluation of biochemical processes, for estimation of oxygen consumption in particular as it has no a time-base sweep function (I/t), which records only volt-ampere characteristics. In this connection, a time-base sweep unit was elaborated and included into the apparatus complex that provides time-base sweep along the coordinate. The modularity of the proposed elaboration permits its use in other types of polarographs that have no time-base sweep function.
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Maisch C, Hofmann V, Benda N, Luft D. Evaluation of polarographic measurements of basal muscle oxygen tension in type I diabetic patients. Angiology 1998; 49:203-10. [PMID: 9523543 DOI: 10.1177/000331979804900306] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Microcirculatory changes occur early in insulin-dependent diabetes mellitus (IDDM) and are believed to be an early feature of late diabetic complications, leading to reduced oxygen pressure and hypoxia in the skin and other tissues. Whether muscle oxygen supply is also altered is unknown. Therefore, the authors analyzed polarographic measurements of muscle oxygen tension in 44 healthy type I diabetic patients (mean age 28 years; mean diabetes duration 7 years) and in 57 healthy controls, matched for age, sex, and body mass index, and the corresponding influencing factors. Two measurements were taken at rest 60 minutes apart in the anterior tibial muscle. Muscle oxygen tensions did not differ between IDDM patients and controls (23.0 +/- 8.6 vs 25.3 +/- 9.0 mmHg) and were reproducible on repeated measurements (25.3 +/- 9.7 vs 25.5 +/- 7.4 mmHg). Coefficients of variation were 13.5 +/- 10.8% in IDDM patients and 13.1 +/- 9.3% in controls. Compared with controls, in IDDM patients hemoglobin A1c (HbA1c) and blood glucose concentrations were elevated, and arterial oxygen pressure was significantly lower. Muscle oxygen tensions were positively correlated with blood glucose concentrations in IDDM patients (Rho=0.48, P=0.002) but not with HbA1c or with insulin concentrations. The authors conclude that the polarographic measurement of muscle oxygen tension is a reliable method with good reproducibility. Hypoxia in the anterior tibial muscle of type I diabetic patients can be excluded. In IDDM patients the level of muscle oxygen tension is correlated with the level of blood glucose concentration.
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Abstract
Ellipsometry is an optical surface-sensitive method for the investigation of various aspects of protein adsorption mainly at reflecting metal surfaces and ceramic surfaces. One interesting feature of the method is the possibility of detailed and accurate determination of real-time adsorption kinetics of proteins without labelling of the protein. It is also possible to detect protein adsorption with the use of antibodies that adsorb onto the antigen-coated surfaces and to detect antibodies by their adsorption behaviour with regard to antigen-coated surfaces. Compared to other solid phase methods such as enzyme linked immunosorbent assay (ELISA), immunofluorescence and radioimmunoassay, ellipsometry has the advantage of not involving any labelling of the reactant and it is a relatively inexpensive method to maintain. This review is a current report of 15 years of contributions in biomaterials and biochemical research. Special consideration has been given to biologically related surface phenomena such as protein conformation changes, protein displacement effects, early events in blood clotting and complement activation. Among the technical achievements given prominence are the wettability gradient method and the rational use of silicon as an experimental surface. It is clear that ellipsometry and related methods such as reflectometry and surface plasmon resonance (Biacore) are now being increasingly used in biomaterial research as well as in other areas of research.
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Tengvall P, Lundström I, Liedberg B. Protein adsorption studies on model organic surfaces: an ellipsometric and infrared spectroscopic approach. Biomaterials 1998; 19:407-22. [PMID: 9677154 DOI: 10.1016/s0142-9612(97)00110-5] [Citation(s) in RCA: 146] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The development of accurate analytical tools to control the interfacial properties of solid substrates is of importance for the design of new biomaterials, as well as for the understanding of biomolecular interactions on surfaces. Considerable research efforts are presently devoted to this area on different levels of molecular complexity, i.e. both in the presence and in the absence of the biomolecules. In this contribution we review briefly applications of infrared reflection-absorption spectroscopy (IRAS) and ellipsometry as tools for analysis of the chemical properties of model surfaces, and their biological response in vitro when in contact with blood plasma or serum, respectively. The strength of the combination of the techniques is demonstrated by determination of protein adsorption patterns on a series of chemically well-defined so-called self-assembled alkanethiolate monolayers (SAMs) of 16-thiohexadecanol (HS-(CH2)16-OH) and n-hexadecanethiol (HS-(CH2)15-CH3) on gold. The protein adsorption patterns after incubations in plasma were determined by the specific binding of antibodies to the surfaces.
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Van de Merwe WP, Li ZZ, Bronk BV, Czégé J. Polarized light scattering for rapid observation of bacterial size changes. Biophys J 1997; 73:500-6. [PMID: 9199812 PMCID: PMC1180949 DOI: 10.1016/s0006-3495(97)78088-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The effect of changing growth conditions on the diameter of rod-shaped bacteria was studied in vivo with the use of polarized light scattering. The value of a ratio of scattering matrix elements was measured as a function of scattering angle at various times after nutritional "upshift" for two strains of Escherichia coli cells. The peak locations of the scattering function were calibrated against the diameter for rod-shaped bacteria. The peaks moved toward smaller angles as a function of time after upshift, indicating that the diameter was increasing. Under special conditions, substantial peak shifts occurred within a few minutes of growth condition change, indicating a rapid onset of growth in diameter. The rate of increase of the diameters after upshift was obtained from the angular shift of peak location. This rate was approximately 14 nm/min for E. coli K12 and approximately 9 nm/min for E. coli B/r at 37 degrees C. The rate of diameter increase is smaller at lower temperatures. Experiments with Bacillus megaterium showed that any diameter change after nutritional upshift at 37 degrees C is limited to at most a very small increase, at least for the strain and medium tested.
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Lübbers DW, Baumgärtl H. Heterogeneities and profiles of oxygen pressure in brain and kidney as examples of the pO2 distribution in the living tissue. Kidney Int 1997; 51:372-80. [PMID: 9027709 DOI: 10.1038/ki.1997.49] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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