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PubMed1988

Conformational free energies of myoglobins of small mammals.

Myoglobins from three small placental mammals and one small marsupial were isolated from cardiac or skeletal muscle. The conformational free energies of these four myoglobins were estimated from guanidinium chloride unfolding data at pH 8 and 25 degrees. The myoglobins from rat and rabbit are more stable than that of the most stable myoglobin previously studied, that of the sperm whale. In addition, these two myoglobins unfold with greater cooperativity than previously characterized myoglobins. The data obtained herein demonstrate unequivocally for the first time that the stability of homeotherm myoglobins correlates with neither the size of the organism nor its metabolic rate.

Amino Acids↗
PubMed1996

Linear epitopes of sperm whale myoglobin identified by polyclonal antibody screening of random peptide library.

Distinct enhancement of antibody-specific clones was apparent during the screening against random peptide libraries with antigen-specific polyclonal antibodies. Several sequence motifs obtained from these screenings were homologous with the primary sequence of myoglobin. Two of these motifs have been confirmed as antigenic determinants by competitive inhibition tests using eight-branched synthetic peptides. One of the peptides has a sequence that corresponds to amino acid residues 42-50, KFDRFKHLK, of the myoglobin sequence. This is a new epitope of myoglobin that is reported for the first time. The epitope is located precisely in the "turn' or "loop' region between helices C and D of the crystal structure of myoglobin. The second antibody binding site has a sequence of DIAAKYKELGYQG, and this is located between residues 141-153, which is the C-terminus of myoglobin. This epitope encompassed two linear epitopes of myoglobin, amino acid residues 145-151 and 147-153, that have been reported earlier based on immunochemical characterisation of cleavage fragments of the protein. These results clearly indicate that epitope mapping using polyclonal antibodies against random peptide libraries can identify new epitopes precisely, as well as confirm epitopes of myoglobin obtained earlier using established methodologies.

Animals↗
PubMed1995

Peroxidative interaction of myoglobin and myosin.

Met-myoglobin [Fe(III)] was found to induce myosin cross-linking in the presence of H2O2 [Bhoite-Solomon, V. & Shaklai, N. (1992) Biochem. Int. 26, 181-189]. To assess the relevance of these findings to cellular pathology, peroxidation of myosin was performed with physiological divalent iron [Fe(II)] myoglobins in the oxy and deoxy forms. Both myoglobin forms were capable of mediating cross-linking of myosin. Deoxymyoglobin reactivity was similar to that of met-myoglobin, but the reactivity of oxymyoglobin was retarded compared to deoxymyoglobin. Cross-linking of myosin occurred under a low flow rate of H2O2 (3 microM/min) and in the presence of excess oxymyoglobin over H2O2, known to diminish the steady state of the myoglobin active heme [ferryl, Fe(IV)]state. The adenosinetriphosphatase activity of myosin was reduced to about half due to cross-linking. Addition of myoglobin/H2O2 to high myosin concentrations (> = 20 microM) turned the solutions into gels, a phenomenon explained by the further formation of intermolecular super cross-links of soluble myosin. Thus, at cellular ionic strength in which myosin is insoluble, cross-linking of myosin could still be triggered by myoglobin and H2O2. Based on these data, it is suggested that myoglobin-induced cross-linking of myosin and the consequent loss of adenosinetriphosphatase activity may be involved in muscle malfunction under hypoxia when cellular peroxidants increase and the deoxymyoglobin form prevails.

Adenosine Triphosphatases↗
PubMed1983

Immunohistochemistry of myoglobin in rhabdomyosarcomas.

Immunoperoxidase staining for myoglobin was performed on formalin-fixed, paraffin-embedded tissues of normal human skeletal muscle and rhabdomyosarcomas in order to assess its potential diagnostic value. Myoglobin-positive cells were observed in normal adult and fetal muscles, and in 13 of 26 rhabdomyosarcomas. In normal skeletal muscle, the intensity of staining for myoglobin varied in individual cells. Of the 13 myoglobin-positive rhabdomyosarcomas tested, 6 showed cross striations in tumor cells, whereas the others did not. Myoglobin-positive tumor cells were not demonstrated in two rhabdomyosarcomas in which cross striations were observed. In other types of tumors examined that sometimes resembled rhabdomyosarcomas, no myoglobin was detected. Thus tests for myoglobin by the immunoperoxidase method seem helpful in identifying rhabdomyosarcomas and confirming their histological diagnosis.

Adolescent↗
PubMed2000

Binding and utilization of myoglobin by Porphyromonas gingivalis.

Myoglobin was found to bind reversibly to the envelope of Porphyromonas gingivalis in a pH-dependent manner; the binding took place below neutral pHs of the incubation mixtures and myoglobin bound released from the envelope at high pHs. The amounts of myoglobin bound to 1 mg of the envelope at pH 5.0 per min under the presence of sufficient myoglobin were 1.4 microg. K(d) for the reaction at pH 5.0 was 2.2 x 10(-10) M. From the dot blot assay, myoglobin obviously bound to hemoglobin-binding protein (HbBP) of P. gingivalis, however, the amounts of myoglobin that bound to HbBP were half those of hemoglobin. One of the fractions, separated by gel filtration, of the digested materials of myoglobin by the detergent-solubilized envelope containing proteinases was found to support the growth of P. gingivalis in the iron source-depleted medium.

Bacterial Proteins↗
PubMed1987

Effect of albumin on the osmotic pressure exerted by myoglobin across capillary walls in frog mesentery.

1. Individual capillaries in mesenteries of pithed frogs were perfused sequentially with two frog Ringer solutions containing myoglobin at a concentration of 70 mg/ml. The first perfusate solution contained bovine serum albumin at a concentration of 10 mg/ml. The second perfusate contained no albumin. The modified Landis micro-occlusion technique (Michel, Mason, Curry & Tooke, 1974) was used to measure the capillary hydraulic conductivity and the effective osmotic pressure of the myoglobin solution across the capillary wall under conditions where the transcapillary concentration difference was established by steady-state ultrafiltration. 2. In six capillaries the effective osmotic pressure of the myoglobin solution at 20-22 degrees C was 15.9 +/- 2.2 (S.E. of mean) cmH2O when albumin was in the perfusate and 10.1 +/- 1.1 cmH2O after albumin was removed from the perfusate. 3. The hydraulic conductivity of the capillary wall increased from a mean value of 6.5 +/- 1.4 X 10(-7) cm/(s cmH2O) when albumin was in the perfusate to 15.6 +/- 3.8 X 10(-7) cm/(s cmH2O) during perfusion with Ringer solution containing myoglobin alone. 4. Control experiments to measure steady-state filtration rates at pressures 10-30 cmH2O were carried out to check the assumption in the method that the reduction in the measured osmotic pressure of myoglobin was the result of changes in the properties of the molecular sieve within the capillary wall and was not simply the result of solute accumulation on the tissue side of the capillary wall. 5. The measured reduction in the effective osmotic pressure of myoglobin when albumin was removed from the perfusate does not conform to the hypothesis (Crone, 1984) that the tight segment of the intercellular junction is the principal molecular filter for myoglobin in the wall of frog mesenteric capillaries. 6. Our results do conform to the hypothesis that a network of fibrous molecules, reinforced by adsorbed albumin, forms the principal molecular filter at the capillary wall in frog mesenteric capillaries.

Albumins↗
PubMed1977

Serum myoglobin level as diagnostic test in patients with acute myocardial infarction.

Serum myoglobin levels were measured in normal subjects and patients by means of a newly developed radioimmunoassay. Myoglobin was identified in all of 135 sera from normal adults and ranged between 6 and 85 ng/ml (mean +/- SE 31 +/- 1.3). Raised myoglobin levels were present in 62 of 64 patients with documented acute myocardial infarction, the mean serum concentration being 528 +/- 76 ng/ml. Serial determinations in 46 patients with acute infarct showed that maximum values usually occurred within 4 hours after admission. In 19 of 42 cases, raised myoglobin levels preceded the rise in creatine kinase (CK) values; in the remaining patients, both serum myoglobin and creatine kinase were increased on admission. Only 2 of an additional 44 patients admitted with chest pain but without subsequent electrocardiographic, enzyme, or technetium-99m stannous pyrophosphate myocardial scintigraphic evidence of acute myocardial infarction had raised myoglobin levels; the mean value for this group was within the normal range (44 +/- 6 ng/ml). Serum myoglobin values also were normal in patients with congestive heart failure without acute myocardial infarction, and in patients after moderate exercise and cardiac catheterisation. Trasient myoglobinaemia appears to be one of the earliest laboratory abnormalities occurring in acute myocardial infarction and, therefore, should prove useful as a diagnostic aid in patients.

Acute Disease↗
PubMed1995

Value of myoglobin, troponin T, and CK-MBmass in ruling out an acute myocardial infarction in the emergency room.

BACKGROUND: Ruling out acute myocardial infarction (AMI) on the basis of rapid assays for cardiac markers will allow early triage of patients and cost-effective use of available coronary care facilities. METHODS AND RESULTS: We studied the value of myoglobin, creatine kinase (CK)-MBmass, and troponin T in ruling out an AMI in the emergency room in 309 consecutive patients presenting with chest pain. The gold standard for AMI was the combination of history, ECG, and a typical curve of the CK-MB activity (CK-MBact). Myoglobin was the earliest marker, and its negative predictive value (NPV) was significantly higher than for CK-MBmass and troponin T from 3 to 6 hours after the onset of symptoms (myoglobin versus CK-MBmass, P < .03; myoglobin versus troponin T, P < .01). The NPV of myoglobin reached 89% 4 hours after the onset of symptoms. The NPV of CK-MBmass reached 95% 7 hours after the onset of symptoms. Troponin T was not an early marker for ruling out AMI, and NPV changed over time, together with CK-MBact. The early NPV was higher in a subgroup of patients with a low probability of the presence of AMI for the three markers. Cardiac markers rise earlier in patients with large infarcts than in patients with small infarcts as indicated by the cumulative proportion of the marker above the upper reference limit at each time point (myoglobin, P = .04; CK-MBmass, P = .013; troponin T, P = .016). CONCLUSIONS: For ruling out AMI in the emergency room, myoglobin is a better marker than CK-MBmass or troponin T from 3 until 6 hours after the onset of symptoms, but the maximal NPV reaches only 89%. At 7 hours, the NPV of CK-MBmass is 95%. The test characteristics are influenced by the probability of the presence of AMI in the patients studied and by the size of their AMI. Infarct size of AMI patients should be reported in studies evaluating cardiac markers.

Aged↗
PubMed1997

Assessment of coronary reperfusion after thrombolysis with a model combining myoglobin, creatine kinase-MB, and clinical variables. TAMI-7 Study Group. Thrombolysis and Angioplasty in Myocardial Infarction-7.

BACKGROUND: Several biochemical markers have been investigated for the noninvasive assessment of reperfusion after myocardial infarction. Because myoglobin is released very soon after myocardial injury and clears rapidly after reperfusion, it may prove to be an excellent marker of occlusion and reperfusion. METHODS AND RESULTS: We examined the relation between various myoglobin measures and Thrombolysis In Myocardial Infarction (TIMI) flow grade in 96 patients enrolled in a study of front-loaded thrombolysis who underwent 90-minute angiography. We also combined myoglobin measures with models that include clinical and creatine kinase-MB variables. The myoglobin level measured within 10 minutes of acute angiography showed the best overall performance and was used for later analyses. Of the clinical variables examined, only time from symptom onset to thrombolysis and chest pain grade at angiography discriminated among TIMI flow grades. Combining the 90-minute myoglobin level and these clinical variables showed a significant difference (P<.0001) between both TIMI 3 versus TIMI 0 through 2 and TIMI 2 or 3 versus TIMI 0 or 1 flow. When the 90-minute myoglobin level was added to an established predictive model containing clinical variables and creatine kinase-MB measures, its contribution remained significant (P=.044). The area under the receiver operator characteristic curve for this combined model was .88. CONCLUSIONS: A single myoglobin measurement obtained 90 minutes after the start of thrombolysis, combined with select clinical variables and creatine kinase-MB levels, enhances the noninvasive prediction of reperfusion after myocardial infarction.

Adult↗
PubMed2005

Lack of myoglobin causes a switch in cardiac substrate selection.

Myoglobin is an important intracellular O2 binding hemoprotein in heart and skeletal muscle. Surprisingly, disruption of myoglobin in mice (myo-/-) resulted in no obvious phenotype and normal cardiac function was suggested to be mediated by structural alterations that tend to steepen the oxygen pressure gradient from capillary to mitochondria. Here we report that lack of myoglobin causes a biochemical shift in cardiac substrate utilization from fatty acid to glucose oxidation. Proteome and gene expression analysis uncovered key enzymes of mitochondrial beta-oxidation as well as the nuclear receptor PPAR to be downregulated in myoglobin-deficient hearts. Using FDG-PET we showed a substantially increased in vivo cardiac uptake of glucose in myo-/- mice (6.7+/-2.3 versus 0.8+/-0.5% of injected dose in wild-type, n=5, P<0.001), which was associated with an upregulation of the glucose transporter GLUT4. The metabolic switch was confirmed by 13C NMR spetroscopic isotopomer studies of isolated hearts which revealed that [1,6-13C2]glucose utilization was increased in myo-/- hearts (38+/-8% versus 22+/-5% in wild-type, n=6, P<0.05), and concomitantly, [U-13C16]palmitate utilization was decreased in the myoglobin-deficient group (42+/-6% versus 63+/-11% in wild-type, n=6, P<0.05). Because of the O2-sparing effect of glucose utilization, the observed shift in substrate metabolism benefits energy homoeostasis and therefore represents a molecular adaptation process allowing to compensate for lack of the cytosolic oxygen carrier myoglobin. Furthermore, our data suggest that an altered myoglobin level itself may be a critical determinant for substrate selection in the heart. The full text of this article is available online at http://circres.ahajournals.org.

Animals↗
PubMed1975

Radioimmunoassay of myoglobin in human serum. Results in patients with acute myocardial infarction.

A radioimmunoassay has been developed for the measurement of serum myoglobin in order to evaluate the time-course and frequency of myoglobinemia in patients with acute myocardial infarction. The method can detect as little as 0.5 ng of myoglobin and is not affected by hemolysis or storage of serum at -- 20 degrees C. Myoglobin was detected in all of 92 sera from normal adults and ranged between 6 and 85 ng/ml. Levels were markedly elevated in sera from 18 of 20 patients with acute myocardial infarction when samples were obtained within 12 h after hospital admission, the mean concentration being 380+/-53 ng/ml. Wehn the initial sample was drawn between 12 and 24 h after admission in another group of 20 patients with acute myocardial infarcts, the mean serum myoglobin concentration was 195+/-47 ng/ml, and 11 of these individuals had normal levels. Serial determinations performed on nine patients with acute infarction demonstrated that maximum myoglobin levels occurred within the first 8-12 h after admission and fell rapidly toward normal thereafter. The serum concentration of myoglobin in 21 additional patients admitted with chest pain but without acute myocardial infarction was 41+/-6 ng/ml. Radioimmunoassay of serum myoglobin appears to be useful and sensitive test for the early detection of myocardial infarction.

Acute Disease↗
PubMed2004

Diagnostic value of heart fatty acid binding protein and myoglobin in patients admitted with chest pain.

INTRODUCTION: Patients presenting with chest pain do so at varying times following its onset. In addition, their histories can be unreliable, making the interpretation of time-dependent biochemical markers difficult. Patients are therefore subsequently managed according to measurements of specific markers, such as troponin, taken many hours following their admission. Earlier markers such as myoglobin and heart fatty acid binding protein (hFABP) may provide information earlier; however, the true role of such markers remains unclear when applied to real life patient cohorts. We aimed to evaluate and compare the diagnostic accuracy of the early markers hFABP and myoglobin (in terms of area under ROC curves, sensitivity and specificity) to troponin I (cTnI) in a pragmatic group of patients presenting with chest pain. METHODS: 302 patients presenting with chest pain had blood samples withdrawn both on admission and 12 h later. These were analysed for cTnI, myoglobin and hFABP. Standard clinical and electrocardiographic data were also obtained. Only the cTnI results were reported back to the clinicians and hence only they would have affected clinical care. Patients were grouped clinically according to both the American College of Cardiology/European Society of Cardiology new definition of myocardial infarction (MI) and by clinicians' diagnosis of MI. RESULTS: Median time from onset of symptoms to admission was 5.0 h (IQR 3.0-12 h). Greater ROC curve areas for the diagnosis of MI by both sets of criteria were obtained for cTnI over both myoglobin and hFABP. ROC curve areas for myoglobin and hFABP were also no better than that for cTnI in those patients presenting less than 4 h after the onset of chest pain. Both myoglobin and hFABP also performed poorly in those patients who were cTnI negative on admission. CONCLUSION: Myoglobin and hFABP provide little clinical value when measured on admission in patients presenting with chest pain.

Area Under Curve↗
PubMed1996

The role of fetal myoglobin in the initiation of human parturition.

The aim of the present investigation is to study the effect of amniotic fluid myoglobin on prostaglandin synthesis by the fetal membranes. The paper presents results of radioimmunologic studies of myoglobin levels in various biological fluids during pregnancy: amniotic fluid, maternal serum samples obtained from an antecubital vein and the cervix, and neonatal urine. Amniotic fluid myoglobin levels were found to be significantly higher at term. Our results suggest that amniotic fluid myoglobin is likely to be derived from the fetus and excreted into amniotic fluid through fetal urine. Incubation of the fetal membrane with amniotic fluid, neonatal urine, and commercially available myoglobin enhanced phospholipase A2 activity, as well as arachidonic acid and prostaglandin F2 alpha production was compared to incubation with normal saline. The addition of anti-myoglobin antibodies to incubation media was found to block these effects. The results of our study show that myoglobin activates prostaglandin synthesis by the fetal membranes and stimulates the onset of labor.

Amniotic Fluid↗
PubMed2005

Molecular dynamics simulation of sperm whale myoglobin: effects of mutations and trapped CO on the structure and dynamics of cavities.

The results of extended (80-ns) molecular dynamics simulations of wild-type and YQR triple mutant of sperm whale deoxy myoglobin in water are reported and compared with the results of the simulation of the intermediate(s) obtained by photodissociation of CO in the wild-type protein. The opening/closure of pathways between preexistent cavities is different in the three systems. For the photodissociated state, we previously reported a clear-cut correlation between the opening probability and the presence of the photolyzed CO in the proximity of the passage; here we show that in wild-type deoxy myoglobin, opening is almost random. In wild-type deoxy myoglobin, the passage between the distal pocket and the solvent is strictly correlated to the presence/absence of a water molecule that simultaneously interacts with the distal histidine side chain and the heme iron; conversely, in the photodissociated myoglobin, the connection with the bulk solvent is always open when CO is in the vicinity of the A pyrrole ring. In YQR deoxy myoglobin, the mutated Gln(E7)64 is stably H-bonded with the mutated Tyr(B10)29. The essential dynamics analysis unveils a different behavior for the three systems. The motion amplitude is progressively restricted in going from wild-type to YQR deoxy myoglobin and to wild-type myoglobin photoproduct. In all cases, the principal motions involve mainly the same regions, but their directions are different. Analysis of the dynamics of the preexisting cavities indicates large fluctuations and frequent connections with the solvent, in agreement with the earlier hypothesis that some of the ligand may escape from the protein through these pathways.

Animals↗
PubMed1988

Early diagnosis of acute myocardial infarction by myoglobin latex agglutination test.

Early elevation of the serum myoglobin level in acute myocardial infarction (AMI) has been noted for years. In this study, 39 patients admitted to the Coronary Care Unit with acute chest pain within 72 hours (mean 12 +/- 15 hours) or electrocardiographic changes suspected of acute myocardial infarction had a serum myoglobin latex agglutination test to evaluate its diagnostic accuracy in acute myocardial infarction. Of these 39 patients, 24 had documented acute myocardial infarction as their final diagnosis. By the time of admission, 18 of the 24 cases with infarction had positive myoglobin tests (sensitivity 75%). Of those 15 cases without myocardial infarction, 13 had negative myoglobin tests (specificity 87%). If only those 17 cases admitted within 5 hours of the onset of chest pain were analyzed, the serum myoglobin test became positive in 8 of 10 cases with documented AMI but the 2 cases with negative results turned positive 2 hours later (sensitivity 80% to 100%). Due to the fact that myoglobin tests were negative in all other 7 cases without infarction, the specificity was 7/7 (100%). In contrast, the creatine phosphokinase isoenzyme study was positive only in 3 of these 10 patients with documented AMI in the first blood sample taken during admission. In conclusion, the serum myoglobin latex agglutination test is a quick and reliable method that helps in the early diagnosis of acute myocardial infarction.

Adult↗
PubMed1979

An enzyme-immunoassay for myoglobin in human serum and urine. Method development, normal values and application to acute myocardial infarction.

An enzyme-immunoassay has been developed for the detection of myoglobin in human serum and urine which is specific, accurate, precise, and has a sensitivity of 3 ng/ml. When compared with radioimmunoassay, the enzyme-immunoassay gives markedly similar results. Sera from normal adults had a myoglobin concentration in the range 3-65 ng/ml, and 64% of the same group had detectable myoglobinuria (range 3-11.5 ng/ml). All of 8 patients with definite acute myocardial infarction had raised serum myoglobin levels (range 200-1125 ng/ml) either at admission or 4 h later. Myoglobin concentration returned to normal in 6 patients, and in the remaining 2 patients there was evidence of infarct extension. Urinary myoglobin excretion was variable. One patient with possible acute myocardial infarction had elevated serum myoglobin (413 ng/ml 4 h post admission) and 5 patients with no evidence of infarction had normal levels (15-53 ng/ml). The results suggest that detection of serum myoglobin by enzyme-immunoassay may be a valuable test in the early diagnosis of acute myocardial infarction.

Acute Disease↗
PubMed1986

Myofascial pain and the role of myoglobin.

The plasma myoglobin concentration was measured before and after massage of 26 patients with myofascial pain. Twenty-one patients had a successful treatment and a significant increase was observed in the plasma myoglobin concentration (median 125 micrograms/l, range 35-439) within a maximum of 2 hours after the first massage treatment (p less than 0.0001). A positive correlation was found between the degree of muscle tension and pain, and the increase in plasma myoglobin concentration. After repeated massage treatment a gradual decline in the increase in plasma myoglobin concentration could be demonstrated parallel to a reduction in the muscle tension and pain. Five patients did not benefit from massage treatment and no significant increase in the myoglobin in plasma was measured. These patients were in pain and had a high degree of muscle tension. The observed increase in myoglobin in plasma after massage indicates a leak of myoglobin from the muscle fibres in 21 patients, whose myofascial pain seem to be linked with a muscle fibre disease. It is suggested that 5 patients with the same muscle symptoms have another, still unknown muscle disease.

Adult↗
PubMed1996

Effect of oral L-carnitine on serum myoglobin in hemodialysis patients.

Oral L-carnitine has been reported to lower the elevated serum myoglobin of renal failure in chronic peritoneal dialysis patients, and intravenous L-carnitine can improve muscle fatigue and cramps in chronic hemodialysis patients. In this study oral L-carnitine, 1.98 g/day, was administered to 6 chronic hemodialysis patients for 8 weeks. Serum levels of myoglobin, creatine kinase, and aldolase, as well as skeletal muscle symptoms (cramps during dialysis, fatigue, and weakness) were monitored biweekly for 12 weeks. Mean baseline serum myoglobin level was 337 +/- 34 ng/mL. By 6 and 8 weeks mean serum myoglobin was 234 +/- 39 and 233 +/- 40 ng/mL, significantly lower by the Friedman test (p < 0.05). Four weeks after carnitine was discontinued, mean serum myoglobin had risen to 320 +/- 118 ng/mL. Serum creatine kinase and aldolase levels were normal throughout the study. All 6 patients noted improvement in muscular symptoms, with maximal effect at 8 weeks, although 2 patients did not improve until 2 to 4 weeks after carnitine was stopped. We conclude that oral L-carnitine may lower serum myoglobin and improve muscle cramps and weakness in hemodialysis patients. The maximal effect of carnitine on myoglobin occurs 2 weeks before the maximal improvement in muscular symptoms.

Administration, Oral↗