Concentrations Of MB Research Articles

Myocardial Injury in Remifentanil-Based Anaesthesia for off-Pump Coronary Artery Bypass Surgery: An Equipotent Dose of Sevoflurane versus Propofol

This randomised controlled trial compared the effect of equipotent anaesthetic doses of sevoflurane (S group) versus propofol (P group), during remifentanil-based anaesthesia for off-pump coronary artery bypass surgery, on myocardial injury. Either sevoflurane or propofol was titrated to maintain bispectral index values between 40 and 50. In both groups, a targeted concentration of remifentanil 20 ng x ml(-1) was maintained during anaesthesia. The concentrations of creatine kinase MB and troponin I were measured before the start of surgery, on admission to the intensive care unit, and at 12 and 24 hours after intensive care unit admission. The postoperative values of creatine kinase MB (S group: 15.08 +/- 18.97, 20.78 +/- 20.92, 12.76 +/- 12.82 vs 2.09 +/- 1.54 ng x ml(-1); P group: 10.99 +/- 13.15 27.16 +/- 56.55 11.88 +/- 18.80 vs 1.84 +/- 1.67 ng x ml(-1)) and troponin I (S group: 3.56 +/- 5.19, 566 +/- 7.89, 3.35 +/- 4.55 vs 0.52 +/- 1.90 ng x ml(-1); P group: 2.42 +/- 3.33, 4.11 +/- 6.01, 3.04 +/- 5.31 vs 0.43 +/- 1.28 ng x ml(-1)) were significantly higher than preoperative values in both groups but there were no significant differences between the two groups. There were no significant differences in time to extubation (S group, 476 +/- 284 minutes; P group, 450 +/- 268 minutes) and intensive care unit length of stay (S group, 2775 +/- 1449 minutes; P group, 2797 +/- 1534 minutes) between the two groups. In conclusion, sevoflurane and propofol at equipotent doses guided by bispectral index with remifentanil 20 ng x ml(-1) had similar creatine kinase MB and troponin I values.

Adsorptive removal of Megenta MB cold brand reactive dye by modified activated carbons derived from agricultural waste

The activated carbon produced from agricultural waste, Tapioca Peel, was used for the adsorption of reactive dye Megenta MB from its aqueous solutions. The preparation of activated carbon from agricultural waste could increase economic return and reduce pollution. In our project, adsorption studies were performed by varying parameters such as dye concentration, pH of the dye solution and contact time. The study investigates the removal of Megenta MB dye from its aqueous solution. The equilibrium adsorption data obtained were used to calculate the Freundlich and Langmuir isotherm parameters. Higher adsorption percentages were observed at lower concentrations of Megenta MB. Optimum pH value for dye adsorption was determined as 7. Maximum dye was removed within 120 min after the beginning for every experiment. Keywords: Tapioca peel; Megenta MB; effluent treatment, textile dye, water pollution, environment, industry, India

Adsorptive Removal of Megenta MB Cold Brand Reactive Dye by Modified Activated Carbons Derived from Agricultural Waste

The activated carbon produced from agricultural waste, Tapioca Peel, was used for the adsorption of reactive dye Megenta MB from its aqueous solutions. The preparation of activated carbon from agricultural waste could increase economic return and reduce pollution. In our project, adsorption studies were performed by varying parameters such as dye concentration, pH of the dye solution and contact time. The study investigates the removal of Megenta MB dye from its aqueous solution. The equilibrium adsorption data obtained were used to calculate the Freundlich and Langmuir isotherm parameters. Higher adsorption percentages were observed at lower concentrations of Megenta MB. Optimum pH value for dye adsorption was determined as 7. Maximum dye was removed within 120 min after the beginning for every experiment.

Myoglobin Induces Oxidative Stress and Decreases Endocytosis and Monolayer Permissiveness in Cultured Kidney Epithelial Cells without Affecting Viability

Background: Muscle degradation caused by severe burn releases myoglobin (Mb), which accumulates in the kidney (termed myoglobinuria). Mb is a pro-oxidant. Aim: To demonstrate that Mb promotes oxidative stress and dysfunction in cultured Madin-Darby canine kidney type II (MDCK II) cells. Methods: The glutathione redox ratio was used to monitor oxidative stress. Regulation of antioxidant response genes was determined with RT-PCR. Propidium iodide and annexin V staining were markers of necrosis and apoptosis, respectively. Mitochondrial function was assessed by monitoring mitochondrial depolarisation. Endocytosis was determined with immune fluorescence microscopy, and monolayer permeability was monitored with labelled inulin. Results: Kidney epithelial cells exposed to (0–100 µM) Mb showed a dose-dependent decrease in the glutathione redox ratio indicative of enhanced oxidative stress. In parallel, the expression of antioxidant genes for superoxide dismutase (SOD)-1/2, inducible haemoxygenase (HO-1) and catalase (CAT) increased in MDCK II cells, coupled with increases in corresponding activity. Notably, apoptosis and necrosis remained unaffected. However, transferrin endocytosis and monolayer permeability decreased significantly, while clathrin distribution and mitochondrial function were unaffected. Conclusion: Low concentrations of Mb promote oxidative stress in kidney epithelial cells that manifest as subtle changes to function without decreasing viability. Whether this impairs kidney function in burns patients is not clear.

The disk of bileaflet mechanical mitral valve prosthesis jammed by ruptured papillary muscle

The disk of bileaflet mechanical mitral valve prosthesis jammed by ruptured papillary muscle

Effects of total iron, myoglobin, hemoglobin, and lipid oxidation of uncooked muscles on livery flavor development and volatiles of cooked beef steaks

Infraspinatus (IN), gluteus medius (GM), and psoas major (PM) steaks were obtained from A- and B-maturity carcasses with either high (⩾6.0) or normal (⩽5.7) pH, and either Slight or Small marbling. Steaks were vacuum aged either 7, 14, 21, or 35 d postmortem, and were broiled and served to a highly trained, flavor-profile sensory panel. Steaks with livery flavor were analyzed by gas chromatography/mass spectrometry for flavor compounds. Steaks aged 7 or 35 d postmortem were analyzed for myoglobin (Mb) and hemoglobin (Hb) concentrations and for total iron (Fe) (35 d steaks only). The IN had greater Fe ( P < 0.05) than did the GM or PM. Livery flavor increased ( P < 0.05) and beef flavor identification decreased ( P < 0.05) in the GM as Fe increased. The PM had the lowest ( P < 0.05) Mb/Fe ratios and highest ( P < 0.05) Hb/Fe ratios. Several statistically significant, but relatively low correlations between 16-, 17-, and 18-carbon chain fatty acids and livery flavor resulted. Thirteen volatile compounds had higher concentrations in steaks with livery flavor than in those without livery flavor. Livery flavor development is a complex trait that can be affected by concentrations of total Fe, Mb, and fatty acids, but the relationships are relatively low.

Antioxidants increase tissue plasminogen activator (tPA) levels in human mesothelial cells

Abdominal operations are thought to impair local fibrinolytic activity, thereby allowing adhesions to form. Postoperative oxidative stress may contribute to adhesion formation by inhibiting peritoneal fibrinolysis. Peritoneal fibrinolytic activity is primarily regulated by tPA, the major source of which is mesothelial cells. The aim of this study was to determine the effect of antioxidant administration on tPA synthesis in LP-9 cells, a non-transformed human mesothelial cell line. Methods LP-9 cells at 80% confluence were administered substances with known antioxidant capacity: trolox (.05, .5, 5 mM); methylene blue (MB; .025, .25, 2.5, 25 μM); and neurokinin-1 receptor antagonist (NK-1RA [CJ-12,255, Pfizer] .1, 1, 10, 100 μM). MB and NK-1RA were determined to have antioxidant capacity by the Total Antioxidant Status kit (Randox). Cells underwent oxidative stress by the administration of H2O2 (50, 100, 250, 500 μM). The media was collected after 48hrs for tPA analysis (TintElize kit; DiaPharma). NFκB and MAPK activation were determined in cells administered MB (25 μM) or NK-1RA (1000 nM). Results The highest concentrations of trolox, MB and NK-1RA increased (p≤0.05) tPA synthesis by 278%, 337% and 147%, respectively. H2O2 had no effect. MB increased (p≤0.05) nuclear levels of NFκB by 145% at 60 min and increased (p≤0.05) MAPK phosphorylation by 541% after 5 min of exposure. NK-1RA had no effect on NFκB or MAPK activation. Conclusion These data suggest that mesothelial cell synthesis of tPA may be regulated by the oxidant status of the peritoneum, and further suggest a prophylactic role for antioxidants in adhesion prevention.

Reduction of Nitrite to Nitric Oxide by Myoglobin Modulates Mitochondrial Respiration during Ischemia and Limits Reperfusion Injury.

We recently described a role for the circulating anion nitrite as a hypoxic vasodilator, mediated by reduction of nitrite to nitric oxide (NO) by a reaction with deoxyhemoglobin (deoxyHb) (Cosby et al, Nat Med, 2003). The rate of deoxyHb dependent reduction of nitrite is regulated by the structural transition of deoxyHb from T (deoxy) to R (oxy) state, with maximal NO production (and vasodilatory activity) occurring at the P50 of Hb (Huang et al, J Clin Invest, 2005). New studies from our laboratory suggest that this paradigm may extend beyond Hb to other heme proteins, and that hypoxia dependent production of NO from nitrite mediates hypoxic responses beyond vasodilation. Particularly, in a murine model of ischemia/reperfusion (I/R), low doses of nitrite (48nmol) have been shown to protect cardiac and hepatic tissue against reperfusion injury (Duranski et al, J Clin Invest, 2005). One major characteristic of I/R injury is mitochondrial damage, resulting in decreased respiratory rate, decreased ATP production and increased reactive oxygen species production. Since NO is a known reversible inhibitor of mitochondrial respiration and the rate of deoxymyoglobin (deoxyMb) dependent reduction of nitrite to NO is approximately 50-fold higher than the deoxyHb-nitrite reaction, we sought to determine whether the reaction between deoxyMb and nitrite in tissues, where concentrations of Mb and nitrite can reach micromolar levels, could produce bioavailable NO to regulate mitochondrial respiration, and whether this could protect mitochondria against I/R injury. Here we show evidence that nitrite has both acute and chronic effects on mitochondrial respiration. In experiments using respiring isolated rat liver mitochondria, the addition of Mb (25μM) and nitrite (100μM) results in the inhibition of respiratory rate only at oxygen tensions below 2.7mmHg (the P50of Mb), while nitrite or Mb alone have no significant effect on respiration. This acute effect is consistent with spectrophotometric data showing that the rate of reduction of nitrite (100μM) by deoxyMb (25μM) to NO is 9 nM/sec, suggesting that within 20 seconds enough NO would be produced to inhibit respiration (IC50=100nM). In an in vitro model of anoxia-induced mitochondrial injury, respiration rates of isolated rat liver mitochondria were measured before and after the organelles were subjected to anoxia for 30 minutes. In untreated control mitochondria, respiration rate decreased by 50% after the anoxia, consistent with ischemic injury, while mitochondria treated with nitrite (10μM) during anoxia had only a 25% decrease in respiratory rate. Preservation of post-anoxic respiratory rate was dependent on nitrite concentration (5–50μM,) with the maximal effect occurring at 10μM, a concentration coinciding with the tissue levels of nitrite at the nitrite dose which conferred maximal protection in previous animal models of I/R. Remarkably, administration of nitrite (480nmol) to rats 24 hours before the isolation of mitochondria was also shown to prevent the anoxia-induced decrease in respiration rate. In summary, these data suggest that nitrite bioactivation in tissue, both by Mb-dependent and independent mechanisms, modulates mitochondrial respiration and stress response. These data support a more global role for nitrite as a biochemical HIF-1 alpha with pleiotropic effects on both vascular and tissue response to hypoxia.

Simultaneous Determination of Mebeverine Hydrochloride and Sulpiride Using the First Derivatives of Ratio Spectra and Chemometric Methods

Two methods are described for the simultaneous determination of mebeverine hydrochloride (MB) and sulpiride (SU) in their combinations. The first method depends on the first derivative of the ratio spectra by measurement of the amplitudes at 263.7 and 234.9 nm for MB and SU, respectively. The linear ranges and detection limits are 4.0-40.0 and 0.72 microg/ml for MB and 1.0-10.0 and 0.34 microg/ml for SU. In the second case, a chemometric (classical least squares) method was developed. The concentration data matrices were obtained by using different concentrations of pure drugs in 0.1 M HCl. The absorbance data matrix corresponding to each concentration data matrix was obtained by the measurements of absorbances in the range 200-300 nm in their zero order spectra; then calibration was obtained by using the absorbance data matrix and the concentration data matrix for the prediction of the unknown concentrations of MB and SU in their mixture. The numerical values were calculated by using Matlab R12 version 6.0 and Origin 5.0 software. The procedures do not require any separation steps. These two methods were successfully applied for assaying the pharmaceutical formulation, of Colona tablets.

Electrochemical behavior of electrodeposited film derived from rhein and its activity towards myoglobin reduction

The stable electroactive thin film of rhein has been investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy of the electrodeposited film derived from rhein indicated the electrode reaction was kinetically controlled in the region of higher frequency, the charge transfer resistance was 2.6×103 Ω cm2 and capacitance value was 13.2 μF cm2 . The electrodeposited film derived from rhein exhibited a good electrocatalytic activity for myoglobin (Mb) reduction. In 0.30 mol dm−3 H2SO4solution, the catalysis currents were proportional to the concentrations of Mb over the range of 1.5×10−7–1.3×10−5 mol dm−3. The detection limit is 1.0×10−7 mol dm−3 (S/N=3). The relative standard deviation is 4.8% for eight successive determinations of 5.0×10−7 mol dm−3 Mb.

Nicorandil reduces the incidence of minor cardiac marker elevation after coronary stenting

Background Minor cardiac marker elevation after percutaneous coronary intervention has long-term prognostic significance. We examined whether nicorandil, a nicotinamide-nitrate ester, reduces the incidence of minor cardiac marker elevation after coronary stenting. Methods Patients ( n = 192) undergoing coronary stenting were randomly assigned to receive nicorandil (nicorandil group, n = 91) or vehicle (control group, n = 101). Nicorandil (2 μg/kg/min, intravenously) was administered immediately after the patients were transferred into the catheterization laboratory and continued for 6 h. We measured the serum concentrations of creatine kinase isoenzyme MB (CK-MB) before, immediately after, and 6, 12, and 24 h after the procedure, and those of cardiac troponin T (cTnT) 24 h after the procedure. Results There was no significant difference in clinical background between the 2 groups. The nicorandil group showed a significantly lower incidence of CK-MB elevation (> 1 × upper limit of control range, 20 IU/l) than the control group (8.8% vs 21.8%, p < 0.05). The levels of serum CK-MB in the nicorandil group were significantly lower than those in the control group (13.4 ± 5.7 vs 16.5 ± 9.7 IU/l, p < 0.01). Similarly, the nicorandil group showed a significantly lower incidence of cTnT elevation [> 1 × (0.1 ng/ml) or > 2 × (0.2 ng/ml)] upper limit of control range than the control group (14.3% vs 26.7%, p < 0.05, or 7.7% vs 17.8%, p < 0.05). Serum cTnT levels were also significantly lower in the nicorandil group than in the control group (0.05 ± 0.10 vs 0.15 ± 0.36 ng/ml, p < 0.05). Conclusions The results demonstrated that nicorandil reduces minor cardiac marker elevation after coronary stenting.

Determination of myoglobin based on its enzymatic activity by stopped-flow spectrophotometry

A new method has been developed for the determination of myoglobin (Mb) based on its enzymatic activity for the oxidation of o-phenylenediamine (OPDA) with hydrogen peroxide. Stopped-flow spectrophotometry was used to study the kinetic behavior of the oxidation reaction. The catalytic activity of Mb was compared to other three kinds of catalyst. The time dependent absorbance of the reaction product, 2,3-diamimophenazine (DAPN), at a wavelength of 426 nm was recorded. The initial reaction rate obtained at 40 °C was found to be proportional to the concentration of Mb in the range of 1.0 × 10 −6 to 4.0 × 10 −9 mol L −1. The detection limit of Mb was found to be 9.93 × 10 −10 mol L −1. The relative standard deviations were within 5% for the determination of different concentrations of Mb. Excess of bovine serum albumin (BSA), Ca(II), Mg(II), Cu(II), glucose, caffeine, lactose and uric acid did not interfere.

Binding, aggregation and photochemical properties of methylene blue in mitochondrial suspensions

AbstractMethylene Blue (MB) has well‐established photochemical properties and has been used in a variety of photochemical applications including photodynamic therapy. Despite the fact that most of MB's cytotoxic effects in cells are attributed to mitochondrial damage, the interactions of this dye with mitochondria and the consequent effects on photochemical properties have not yet been fully determined. We monitored MB binding, aggregation and its ability to release singlet oxygen (1O2) on irradiation when interacting with mitochondrial suspensions. MB actively binds to mitochondria and enters the matrix in a manner stimulated by the mitochondrial proton potential and by the increase in mitochondrial concentrations. The greater accumulation of MB in mitochondria with elevated proton potentials or those treated with high concentrations of MB results in the formation of MB dimers, previously shown to be less effective generators of 1O2. Accumulation of MB within mitochondria with high membrane potentials also results in the reduction of MB to the photochemically inactive leuco‐MB. Indeed, irradiation of mitochondria with high proton potentials in the presence of MB results in the generation of approximately half the quantity of 1O2 compared with 1O2 generated in mitochondria with low proton potentials. These differences in photochemical properties should influence the cytotoxic effects of photodynamic treatment in the presence of MB.

Modulation of methylene blue photochemical properties based on adsorption at aqueous micelle interfaces

Methylene Blue (MB+) is a sensitizer that has been used for a variety of applications including energy conversion and photodynamic therapy (PDT). Although its photochemical properties in isotropic solution are well established, its effect in vivo and in restricted reaction environments is somewhat erratic. In order to understand its photochemical behavior when it interacts with biomolecules, in particular with membranes, MB+ properties were studied in sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB) solutions. Because of an electrostatic attraction, SDS and MB+ form complexes, changing the properties of both the micelles and the MB+ solutions. Surface tension measurements show that the c.m.c. of SDS decreases from ∼7 mM to ∼70 μM when the MB+ concentration increases from 0 to 45 μM. Above the c.m.c., binding of MB+ in the micelle pseudo-phase causes the formation of aggregates (mostly dimers) as attested by the increase in the absorption at 580 nm and the decrease in fluorescence emission. The extent of dimer formation is dependent on the relative concentrations of MB+ and SDS. In the presence of excess of SDS, MB+ is mainly in the monomer form and at low SDS concentration dimers are favored. Such effect, which was not observed in CTAB micelles, was modeled qualitatively by considering that MB+ molecules partition to the micelle pseudo-phase which favors or disfavors dimers as a function of its volume. MB+ transient species were characterized by laser flash photolysis and NIR emission showing the presence of triplets and subsequently singlet oxygen at high SDS concentration and semi-reduced and semi-oxidized MB+ radicals at low SDS concentration. Therefore it was shown that, depending on the ground state MB+ monomer/dimer equilibrium, induced by the micelles, the photochemical properties of MB+ can be shifted from a Type II (energy transfer to oxygen forming singlet oxygen) to a Type I mechanism (electron transfer forming the semi-reduced and the semi-oxidized radicals of MB+).

Potential Mechanisms of Photodynamic Inactivation of Virus by Methylene Blue I. RNA–Protein Crosslinks and Other Oxidative Lesions in Qβ Bacteriophage

A spectrum of oxidative lesions was observed in a bacteriophage-based model system that is very sensitive to the photodynamic activity of selected dyes. When suspensions of the intact bacteriophage Q beta were exposed to methylene blue plus light (MB + L), inactivating events, or "hits" occurred that were oxygen-dependent and that were associated with the formation of several specific lesions: (1) carbonyl moieties on proteins, (2) 8-oxo-7,8-dihydroguanine (8-oxoGua), and (3) single-strand breaks (ssb) in the RNA genome and (4) RNA-protein crosslinks. Formation of carbonyl groups associated with protein in the Q beta phage preparation correlated positively with photoinactivation of the phage with increasing doses of either of the sensitizers MB or rose bengal. Strand breaks in the Q beta genomic RNA were observable at high MB concentrations but appeared not to be significant at the lower concentrations of MB, as full-length Q beta RNA was observable well beyond the 99% inactivation point in MB dosage. It was shown that the number of 8-oxoGua lesions were unlikely to be sufficient to account for the number of lethal events. Following exposure to MB + L, crosslink formation between Q beta RNA and protein was observed by virtue of the location of RNA at the interface of phenol-aqueous extractions of phage suspensions. A significant increase over background of RNA-protein complexes (including full-length Q beta RNA) was observed at the lowest concentration of MB tested (0.5 microM), which corresponded roughly to an average of 2 lethal hits per phage or approximately 13% survival compared to the zero MB control (100% survival). Due to its close correlation with Q beta inactivation and its expected lethality, RNA-protein crosslink formation may be important as an inactivating lesion in bacteriophage Q beta following MB + L exposure.

Proton-Coupled Electron Transfer from Electrodes to Myoglobin in Ordered Biomembrane-like Films

Voltammetry and visible and infrared spectroscopy were used to explore protonation equilibria coupled to electron transfer between electrodes and the heme protein myoglobin (Mb) in thin liquid crystal films of didodecyldimethylammonium bromide (DDAB) and phosphatidylcholines (PC). Mb conformation and heme iron ligation in the films were controlled by the pH of the external solution. Acid−base equilibrium models successfully explained pH dependencies of Soret band absorbances, formal potentials, electron transfer rate constants, and electroactive surface concentrations of Mb in the films. A pKa1 of 4.6 in the Mb−lipid films is associated with protonation of histidine residues in hydrophobic regions of the Mb structure, possibly involving the proximal histidine bound to iron and/or the distal histidine in the heme pocket. At pH < 4.6, a partly unfolded molten globule form of Mb predominates in the films and is reduced directly. Native metmyoglobin [MbFe(III)−H2O] appears to be the major species in films between pH 5.5 and 8. In this pH range, protonation of MbFe(III)−H2O occurs prior to electron transfer, and a protonated form which may be a kinetic conformer accepts the electron. MbFe(III)−OH is formed in the films at pH > 9, and its one-electron reduction is also coupled to protonation.

A novel method for detection of nitric oxide binding sites by using a chemiluminescence-headspace gas technique

Nitric oxide (NO) is important in many physiological, pharmacological, and pathological processes. According to current concepts, guanylyl cyclase is considered to be a receptor for NO in vascular and nonvascular smooth muscle and other tissues. Since there are no suitable radioisotopes of oxygen and nitrogen available for conventional radioligand-receptor binding studies for NO, a novel method was developed to identify NO binding site(s). A chemiluminescence-headspace gas assay was utilized to measure the sequestration of NO in biological systems, and this was used as an index of NO binding. In the present report, myoglobin (a hemoprotein, Mb) was used as a prototype macromolecule to develop the binding assay for subsequent application to studies of putative NO receptors. Solutions containing various concentrations of Mb were incubated with NO in sealed micro-Fernbach flasks at 37°C in an argon atmosphere for 30 min; NO remaining in the headspace gas was analyzed by means of the chemiluminescence assay. The magnitude of NO sequestration was dependent on Mb concentration, and 5 nM Mb was the lowest Mb concentration for which NO sequestration was measurable. Application of the method to the measurement of NO sequestration by bovine serum albumin (BSA) and pulmonary artery medial layer homogenate (BPA-M) revealed that the lowest BSA concentration at which NO sequestration was measurable was 1.6 μM, which was 320 times greater than that for Mb. Applicability of the method to address the question of putative NO receptors was indicated by significant NO sequestration after incubation with 20% (w/v) homogenate of BPA-M, which is responsive to NO and putative NO prodrugs.

Development and application of monoclonal antibodies to human cardiac myoglobin in a rapid fluorescence immunoassay

Myoglobin (Mb) is considered a useful marker for early detection of myocardial infarction and for monitoring cardiac reperfusion after thrombolytic therapy. We developed eight monoclonal antibodies to human cardiac Mb, characterized their epitopic reactivity, and determined which combinations of the antibodies are useful in two-site immunoassays. We configured two of the monoclonal antibodies in a one-step, two-site particle concentration fluorescence immunoassay (PCFIA) for measurement of Mb. The PCFIA has rapid kinetics of reaction, being complete in 15 min, and has a linear analytical range of 20-675 micrograms/L for human Mb. Although the PCFIA has a high-dose "hook" effect, this is of no analytical importance at concentrations of Mb less than or equal to 148,000 micrograms/L. The assay is not subject to interference from icterus (bilirubin less than or equal to 360 mg/L), has no cross-reaction with hemoglobin (less than or equal to 42 g/L), and may be performed with either plasma or serum in approximately 1 h. The intra- and interassay imprecisions (CV) of the method are less than 10% for concentrations of Mb within the normal range and less than 4% at higher concentrations. A comparison of the PCFIA with a commercial radioimmunoassay showed that results of the two assays correlate well (PCFIA = 0.88 x RIA + 18, r = 0.990, n = 171).

S-troponin T in suspected ischemic myocardial injury compared with mass and catalytic concentrations of S-creatine kinase isoenzyme MB

In a multicenter study we compared three tests for ischemic myocardial injury (IMI): a new, automated enzyme immunoassay for S-troponin T (S-TNT; Boehringer Mannheim) and two S-creatine kinase (CK) isoenzyme MB assays (mass and catalytic concentrations). For critical evaluation of clinical sensitivity, we studied 243 cases with an IMI prevalence of 43% and an 18% prevalence of cases with unstable angina. Relative peak values of S-TNT and S-CK-MB (mass) after onset of pain were four- to fivefold higher than S-CK-MB (catalytic) results. Increases of S-TNT and S-CK-MB (mass), even though still within their reference ranges, indicated minor myocardial damage in about one-third of the cases primarily classified as unstable angina. The diagnostic window for S-TNT ranged from hours to weeks after the acute episode. The time courses were frequently biphasic, with the initial S-TNT peak closely paralleling that of the mass concentrations of S-CK-MB. With a biological half-life for S-TNT of 2 h, the prolonged increases in S-TNT indicate a continuous release of S-TNT from necrotizing cells. Clinical specificities of S-TNT and S-CK-MB (mass) were greater than that of S-CK-MB (catalytic), even in the presence of 30% to 40% severe skeletal muscle injuries. The combination of S-TNT and S-CK-MB (mass) is excellent for detection of acute IMI, including minor myocardial damage.

Fast time-resolved i.r. spectroscopy of biological molecules in aqueous solution: The reaction kinetics of myoglobin with carbon monoxide

The recombination of myoglobin (Mb) and CO, generated by the u.v. flash photolysis of carboxymyoglobin (MbCO) is monitored by time-resolved i.r. spectroscopy (TRIR) on a microsecond timescale. The TRIR measurements are made on the ν(CO) i.r. band of MbCO centered at 1945 cm −1. Experiments have been performed over a wide range of concentrations of both Mb and CO and the rate constants derived are in excellent agreement with those obtained by conventional flash photolysis. The results represent a significant improvement in sensitivity over previous i.r. experiments of this type.