Implementation of high sensitivity troponin into routine clinical practice - results of the extended CARdiac MArkers guideline uptake in Europe group (CARMAGUE) survey

BACKGROUND

Measurement of cardiac troponin (cTn) by a high sensitivity method is now the recommended strategy for the detection of myocardial injury. An international survey was undertaken to assess how this has been implemented.

METHODS

A questionnaire based around 14 domains on cardiac biomarkers was distributed electronically with the aid of professional societies accessed by a web link within the invitation. Results were returned electronically then extracted into a relational database for analysis.

RESULTS

Responses were obtained from 663 laboratories across 76 countries ranging from 1 to 69 largest country. The majority of responses (79.6%) came from the European area. Responses were grouped into broad geographic areas for analysis. Most responses came from hospitals providing a local and regional service of which the majority provided angioplasty. cTn measurement was the dominant biomarker. The majority of laboratories include creatine kinase (CK) in their cardiac profile and approximately 50% also offer the MB isoenzyme of CK. The majority of laboratories (91.9%) measure cTn by a high sensitivity method. Sex specific reference ranges were typically implemented for cardiac troponin I but not for cardiac troponin T. The preferred unit of measurement was nanograms/L. A structured decision-making pathway utilising high sensitivity cTn measurement was used by 83.3% of laboratories who responded. Single sample rule out is common but the majority used serial sampling strategy based on measurement on admission and three hours.

CONCLUSIONS

Measurement of cTn by a high sensitivity method is now well established internationally, the use of rapid diagnostic protocols lags behind.

Extensive homology between the major immunodominant mitochondrial antigen in primary biliary cirrhosis and Helicobacter pylori does not lead to immunological cross-reactivity

BACKGROUND

Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic disease characterized by the presence of antibodies directed predominantly against the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2). What provokes tolerance breakdown in PBC remains to be established, though there is evidence to indicate that microbes may induce anti-mitochondrial antibodies (AMA) through a mechanism of molecular mimicry.

METHODS

Having found that urease beta (UREB)(22-36) antigen of Helicobacter pylori (HELPY) shares extensive (87%) similarity with PDC-E2(212-226), the major mitochondrial autoepitope, it was hypothesized that this would also lead to cross-reactivity. The UREB/PDC-E2 mimics were thus constructed and tested by ELISA in 112 PBC patients and 114 controls.

RESULTS

Reactivity to PDC-E2(212-226) was found in 104 patients but to UREB(22-36) in only 2. In these two patients, the double reactivity was not cross-reactive. The lack of surface antibody accessibility to UREB(22-36), as demonstrated through three-dimensional model prediction analysis, may explain this unexpected finding. There was some speculation on whether HELPY UREB(22-36) might act as a cross-reactive CD4 T-cell epitope. All seven PBC patients, tested in a standard proliferation assay against PDC-E2(212-226), gave a positive response. All seven were unresponsive to HELPY UREB(22-36). The pattern of reactivity to HELPY antigens by immunoblot was similar between anti-PDC-E2-positive and negative PBC cases, as well as between PBC patients and controls.

CONCLUSION

Contrary to common belief, extensive sequence homology (molecular mimicry) between self and microbe does not necessarily result in cross-reactivity. It is therefore likely that, when present, cross-reactivity between self and microbes is of biological importance.

Association between the primary biliary cirrhosis specific anti-sp100 antibodies and recurrent urinary tract infection

BACKGROUND AND AIMS

Recurrent urinary tract infections (rUTI) have been suggested to be involved in the induction of anti-mitochondrial antibodies (AMA), the serological hallmark of primary biliary cirrhosis (PBC), in view of the presence of AMA in rUTI women without liver disease and conversely of a high prevalence of rUTI in women with PBC. This prompted us to investigate whether PBC-specific anti-nuclear antibodies (ANA) to sp100, gp210 and lamin B receptor (LBR) antigens may also be related to rUTI.

METHODS AND SUBJECTS

PBC-specific ANA reactivities were investigated in 20 women with rUTI but without liver disease, some of whom were AMA-seropositive; 40 women with PBC, with or without rUTI; and 104 pathological and 23 healthy controls.

RESULTS

Among the women with rUTI but without liver disease, 8 (80%) of 10 AMA-positive women reacted with sp100 compared with none of the 10 AMA-negative women. Among the PBC patients, 14 (74%) of 19 with rUTI and 1 (4.8%) of the 21 without rUTI reacted with sp100. None of the rUTI women without liver disease reacted with gp210 or LBR. None of 127 pathological and healthy controls had PBC-specific ANA reactivity.

CONCLUSIONS

Anti-sp100 reactivity strongly correlates with AMA seropositivity in rUTI women, with or without evidence of primary biliary cirrhosis. These findings provide additional support to the notion that E. coli infection is involved in the induction of PBC-specific autoimmunity. Additional factors must be involved in the progression to overt autoimmune disease.

Detection limit, cut-off and specificity of an improved rapid assay for cardiac troponin T

The performance of an improved version of the troponin T rapid test TROPT Sensitive was investigated in a multicentre evaluation at twelve centres. The detection limit and the cut-off were determined in a method comparison with Elecsys Troponin T using a total of 365 samples from patients with suspected acute coronary syndromes and 91 samples from healthy blood donors or non-cardiological patients. The analytical specificity was determined by measuring 1271 blood samples from blood donors without any myocardial injury. The test cut-off (90% of results positive) is 0.08 microg/L, and the detection limit is about 0.05 microg/L. The analytical specificity of the test is between 99.7 and 99.9%. With its small area of undefined significance between positive and negative results and its high sensitivity and specificity, TROPT Sensitive is very well suited to the reliable detection of troponin T positive patients with acute coronary syndromes.

Decreased Pasteur effect in platelets of aged individuals

We have investigated the mitochondrial energy state in human platelets of young (19-30 years old) and aged individuals (65-87 years old) exploiting the Pasteur effect, i.e. stimulation of lactate production by incubation of the purified platelets with the mitochondrial respiratory chain inhibitor, antimycin A. This assay allows the determination of mitochondrial function with respect to glycolysis, and the ratio of mitochondrial adenosine triphosphate (ATP) to glycolytic ATP. A significant increase of basal, non-stimulated lactate production and decrease of the stimulation by antimycin A were observed in the older individuals, suggesting that the impairment of oxidative phosphorylation detectable in post-mitotic tissues of aged individuals can be observed also in easily collectable blood cells.

Effects of implantable cardioverter defibrillator implantation and shock application on biochemical markers of myocardial damage

BACKGROUND

Implantable cardioverter defibrillator (ICD) implantation is a common approach in patients at high risk of sudden cardiac death. To check for normal function, it is necessary to test the ICD. For this purpose, repetitive induction and termination of ventricular fibrillation by direct current shocks is required. This may lead to minor myocardial damage. Cardiac troponin T (cTnT) and I (cTnI) are specific markers for the detection of myocardial injury. Because these proteins usually are undetectable in healthy individuals, they are excellent markers for detecting minimal myocardial damage. The objective of this study was to evaluate the effect of defibrillation of induced ventricular fibrillation on markers of myocardial damage.

METHODS

This study included 14 patients who underwent ICD implantation and intraoperative testing. We measured cTnT, cTnI, creatine kinase MB (CK-MB) mass, CK activity, and myoglobin before and at definite times after intraoperative shock application.

RESULTS

Depending on the effectiveness of shocks and the energy applied, the cardiac-specific markers cTnT and cTnI, as well as CK-MB mass, showed a significant increase compared with the baseline value before testing and peaked for the most part 4 h after shock application. In contrast, the increases in CK activity and myoglobin were predominantly detectable in patients who received additional external shocks.

CONCLUSIONS

ICD implantation and testing leads to a short release of cardiac markers into the circulation. This release seems to be of cytoplasmic origin and depends on the number and effectiveness of the shocks applied.

Expression of messenger RNA of the cardiac isoforms of troponin T and I in myopathic skeletal muscle

In the absence of clinical signs, elevated values of the cardiac isoforms of troponin T (cTnT) and I (cTnI) can be found in the serum samples of some patients with skeletal muscle myopathies; the cause is unclear. We studied the messenger RNA (mRNA) expression of cTnT and cTnI in the skeletal muscles of 24 patients with histologically proven myopathies and in 18 patients in whom a myopathy could be excluded. For cTnT- and cTnI-mRNA determination, we designed specific primer pairs for nested polymerase chain reaction. After amplification, the products were digested with 2 restriction enzymes and visualized. We found cTnT mRNA in 7 skeletal muscle biopsy specimens (6 patients with Duchenne muscular dystrophy, 1 patient with a primary sarcoglycanopathy) and cTnI mRNA in 6 (5 with Duchenne muscular dystrophy, 1 patient with a histologically negative biopsy). The mRNA of the cardiac isoforms, cTnT and cTnI, is expressed in the skeletal muscles of patients with Duchenne muscular dystrophy, but also in some other myopathies. Further studies are needed to show whether the mRNA is translated into the protein, but serum levels of cTnT and cTnI in patients with Duchenne muscular dystrophy would seem to indicate this.

Cardiac troponin T and I in end-stage renal failure

BACKGROUND

In patients suffering from end-stage renal failure, cardiac troponin T (cTnT) and I (cTnI) may be increased in serum without other signs of acute myocardial damage. Whether these increases are specific to myocardial injury or nonspecific is not completely clear.

METHODS

We investigated time courses of cTnT and cTnI over 1 year and the clinical outcome over 2 years in 59 patients with end-stage renal failure undergoing chronic hemodialysis. At the start of the study, we divided the patients into two groups, group 1, without history of cardiac failure, and group 2, with history of cardiac failure, and looked for differences between the groups in later adverse outcome. cTnT was measured using the Enzymun((R)) troponin T assay on an ES 700 analyzer (Roche). cTnI was measured on a Stratus((R)) II analyzer (Dade Behring). Creatinine and blood urea nitrogen were measured on a Vitros((R)) 950 IRC (Ortho).

RESULTS

Dialysis acutely increased cTnT (P: <0.01) and decreased cTnI (P: <0.001) regardless of the dialysis membrane used. Although statistically not significant, cTnT but not cTnI was increased more frequently in group 2 than in group 1, in some cases over the whole study period. Five patients (8.5%) died of cardiac complications within 2 years; all of them had mostly increased cTnT and, in one or more samples, increased cTnI.

CONCLUSIONS

Dialysis alters measured cTnT and cTnI concentrations in serum. In patients suffering from end-stage renal failure, sporadic or persistently increased cTnT and cTnI appear to predict cardiac complications. Because of the effects of the dialysis procedure on troponin values, we recommend that blood be collected before dialysis.

Two cases of fulminant Mycoplasma pneumoniae pneumonia within 4 months

We report the clinical course and diagnostic findings in two patients with life-threatening Mycoplasma pneumoniae (MP) pneumonia who were treated in the same hospital in the course of only 4 months. The patients were previously healthy adults, aged 31 and 37 years, respectively. In both of them severe complications occurred which coincided with the acute MP respiratory infection.

Spontaneous T-cell proliferation in the non-obese diabetic mouse to a peptide from the unique class II MHC molecule, I-Ag7, which is also protective against the development of autoimmune diabetes

AIMS/HYPOTHESIS

Major histocompatibility complex class II molecules present antigenic peptides to T-cells and have an important role in T-cell thymic education. The mechanism by which major histocompatibility complex alleles confer a high genetic risk for autoimmune diabetes is not known. One hypothesis is that during positive thymic selection, the peripheral T-cell repertoire is modelled by major histocompatibility complex-restricted presentation of self major histocompatibility complex molecule-derived peptides, some of which mimic tissue autoantigens. The sequence similarity between a known T-cell epitope of glutamic acid decarboxylase-65, 509:VPPSLRTLED and the non-obese diabetic mouse class II major histocompatibility complex molecule I-Ag7 86:VPTSLRRLEQ is consistent with this.

METHODS

We measured spontaneous proliferation of peripheral T-cells from non-obese diabetic mice and other, non-diabetes-prone strains, to the I-Ag7 86-101 and glutamic acid decarboxylase-65(509-524) peptides, binding of these peptides to intact I-Ag7 and assessed the effect of tolerance induction on diabetes development, by injecting young non-obese diabetic mice with high doses of peptide.

RESULTS

T-cells from non-obese diabetic, but not other mice strains, spontaneously proliferate to the I-Ag7 86-101 and glutamic acid decarboxylase-65(509-524) peptides, but not control peptides. Both test peptides bind I-Ag7. Tolerance induction prolongs diabetes-free survival in non-obese diabetic mice when either the I-Ag7 86-101 or glutamic acid decarboxylase-65(509-524) peptide, but not control peptide, is used.

CONCLUSION/INTERPRETATION

A peptide from the unique class II major histocompatibility complex, diabetes-susceptibility molecule, I-Ag7, presented by I-Ag7 is a target of T-cell responses in diabetes-prone nonobese diabetic mice and tolerance induction against the peptide offers appreciable protection against the development of diabetes.

Lipoprotein(a) and coronary thrombosis and restenosis after stent placement

OBJECTIVES

The objective of this prospective study was to evaluate the relation between high lipoprotein(a) levels and thrombotic and restenotic events after coronary stent implantation.

BACKGROUND

Lipoprotein(a) may promote atherogenesis, coronary thrombosis and restenosis after balloon angioplasty, but the clinical significance remains unclear.

METHODS

The study included 2,223 consecutive patients with successful coronary stent placement. According to the serum level of lipoprotein(a), patients were divided in two groups: 457 patients of the highest quintile formed the high lipoprotein(a) group, and 1,766 patients of the lower four quintiles formed the low lipoprotein(a) group. Primary end points were the incidence of angiographic restenosis at six months and the event-free survival at one year. Secondary end point was the incidence of angiographic stent occlusion.

RESULTS

Early stent occlusion occurred in four of the 457 patients (0.9%) with high and 37 of the 1,766 patients (2.1%) with low lipoprotein(a) levels, odds ratio of 0.41 (95% confidence interval, 0.15 to 1.16). Angiographic restenosis occurred in 173 of the 523 lesions (33.2%) in the high lipoprotein(a) group and 636 of the 1,943 lesions (32.7%) in the low lipoprotein(a) group, odds ratio of 1.02 (0.83 to 1.25). The probability of event-free survival was 73.0% in the high lipoprotein(a) group and 74.8% in the low lipoprotein(a) group (p = 0.45). On the basis of the findings in the low lipoprotein(a) group, the power of this study to detect a 25% increase in the incidence of restenosis and adverse events in the group with elevated lipoprotein(a) was 90% and 75%, respectively.

CONCLUSIONS

Elevated lipoprotein(a) levels did not influence the one-year clinical and angiographic outcome after stent placement. Thrombotic events and measures of restenosis were not adversely affected by the presence of high lipoprotein(a) levels.

Clinical performance of the new cardiac markers troponin T and CK-MB on the Elecsys 2010. A multicentre evaluation

Elecsys assays for the cardiac markers Troponin T (cTnT) and CK-MB have been evaluated in an international multicenter study on the random access analyzer Elecsys 2010 to characterize their clinical performance and their comparability with respective established routine methods. In method comparison studies of Elecsys Troponin T (TnT) with Enzymun-Test TnT, good correlations (r > or = 0.95) and a high degree of correspondence (slopes in 4 laboratories between 0.95 and 1.05) were found. The method comparison studies of Elecsys CK-MB with various CK-MB routine methods lead to good correlations but some systematic deviation in the slopes due to varying standardization. In a reference population of 350 persons upper reference limits (97.5th percentile) of 0.03 milligrams/l for Elecsys TnT and 3.1 milligrams/l for Elecsys CK-MB were found. In cardiosensitivity studies the equivalent diagnostic information of the new Elecsys assays to routine methods was confirmed in the early diagnosis of acute myocardial infarction (AMI), the detection of minor myocardial damages in patients with unstable angina pectoris (UAP) and in time course data monitoring of AMI and bypass surgery patients. The superior sensitivity of cTnT versus CK-MB has been established in a screening situation where in 29 patients with cardiac diseases only cTnT, but not CK-MB, was found pathologically increased; this was due either to the larger diagnostic window of cTnT in AMI or to the more sensitive recognition of minor myocardial damage. In the same study, the cardiospecificity of Elecsys TnT was found to be at least 99.5%. This has also been demonstrated in an earlier study for Enzymun-Test TnT. Further cardiospecificity testing, e.g. in renal failure patients, showed results equivalent to those of Enzymun-Test TnT. An extended clinical study involving 294 patients with chest pain, of whom 58 had a final diagnosis of AMI, revealed highly comparable sensitivity and specificity for the Elecsys assays and routine methods. Thus, the already recommended clinical cut-off values of 0.1 milligrams/l for cTnT and 5 milligrams/l for CK-MB are also valid for the Elecsys assays. The slightly improved sensitivity of Elecsys TnT in the lower range even allows the recognition of pathological increase at cTnT concentrations below 0.1 milligrams/l in special situations with sufficient additional clinical information. Summarizing, provide the two cardiac markers on the Elecsys 2010 at least equivalent or even superior diagnostic information in various clinical situations of cardiac disease compared with routine methods. The short turn-around time and reliable performance qualify the Elecsys assays as new methods of choice for routine and emergency use.

A physical method for separating spermatozoa from epithelial cells in sexual assault evidence

The analysis of genetic markers for the purpose of individualization of semen specimens is extremely important in cases of sexual abuse and assault. The serological analysis of sexual assault evidence can sometimes be complicated because stains are often composed of a mixture of spermatozoa, vaginal epithelial cells and white and red blood cells. A filtration method has been developed to cleanly separate spermatozoa from epithelial cells based upon differences in size and shape. Nylon mesh filters of the appropriate pore size can be used to separate the smaller oval shaped spermatozoal cells from the larger and flatter epithelial cells. The former pass freely through the membrane while the latter are retained on the filter. In this study, cell separation was demonstrated by (a) microscopic observation of stained cells, (b) amplified fragment length polymorphism analysis of DNA obtained from separated cells. The results of these analyses indicate that: (1) Approximately 70% of spermatozoa in the mixed cell sample will penetrate the 10 microns pore size filter, (2) Only about 1-2% of intact epithelial cells will do so, and (3) A small number of nuclei from spontaneously lysed epithelial cells will cross the filter. Experimental results using mixtures of spermatozoa and vaginal epithelial cells prepared in different ratios support the conclusion that the filtration process is an efficient and reliable method to separate spermatozoa from epithelial cells in casework specimens for subsequent DNA analysis.

Multicenter evaluation of a second-generation assay for cardiac troponin T

We report on the evaluation of the second-generation assay for cardiac troponin T (cTnT) on the Enzymun system. This new assay is completely specific for the cardiac isoform of TnT, utilizing two cardiospecific monoclonal antibodies. The assay time is reduced to 45 min. The interassay precision shows a median CV of 5.5%; 20% interassay CV was found between 0.05 and 0.1 microg/L. The cardiosensitivity of the second-generation cTnT assay in patients with ischemic myocardial injury appears equivalent when compared with the first-generation assay. We found no falsely positive results in patients with skeletal muscle damage including multitraumas, surgery patients, and marathon runners who showed highly increased values with the unspecific first-generation assay. In Duchenne disease cTnT was still increased, but to a much lower extent. cTnT remains increased in renal failure, but to a lesser degree than with the first-generation assay. The cause of this increase remains unclear. Although a cross-reactivity of skeletal muscle TnT in the second-generation assay could be excluded by our findings, minor myocardial damage or expression of the cardiac isoform of TnT in regenerating muscles cannot be ruled out in those cases with apparently falsely increased cTnT values. The second-generation cTnT assay is a step forward in the combination of cardiosensitivity and cardiospecificity in biochemical markers for diagnosis of heart disease.

An assessment of DNA contamination risks in New York City Medical Examiner facilities

DNA evidence holds an important position in criminal investigations and proceedings. The polymerase chain reaction (PCR) is often utilized to amplify polymorphic regions of DNA which are subsequently typed to produce distinct genotypes. The sensitivity of PCR-based techniques provides a major advantage over other DNA or conventional serological typing systems. Samples containing quantities of DNA in the picogram range are often typed. However, the unprecedented sensitivity of PCR is often cited as a criticism. One concern is that the interpretation of PCR typing can be affected by DNA contaminants from foreign sources. In this report, the level of DNA contamination in New York City Medical Examiner facilities and its potential affects on HLA-DQA1 typing were assessed. Two related studies conducted over a five week period measured and typed HLA-DQA1 from accumulated DNA on autopsy room and Forensic DNA Laboratory structures. The potential for DNA contamination from airborne sources was also evaluated in the autopsy suites. This study demonstrated the presence of small amounts of DNA on structural surfaces, but little evidence of airborne DNA contamination.

MHC-derived peptides and the CD4+ T-cell repertoire: implications for autoimmune disease

The receptor repertoire of peripheral CD4+ cells is primarily determined by selection processes in the thymus. These result in the positive selection of T cells whose receptors weakly recognize self-peptides restricted by class II self-MHC heterodimers. A majority of such self-peptide partial agonists are likely to be derived from self-MHC molecules. It is suggested that these thymically selected, weakly autoreactive T cells may subsequently be stimulated by peripheral exposure to microbially derived agonists that 'mimic' corresponding self-MHC peptides. In turn, 'molecular mimicry' between microbial agonists and tissue-specific self-peptides may lead to T-cell-mediated autoimmune disease. Hence such disease may reflect 'three-way mimicry' between peptides of respectively target tissue, pathogen and self-MHC (or other self-peptide dominantly presented in the thymus). This hypothesis accounts for the role of MHC haplotype in determining susceptibility to (or protection from) autoimmune disease. Direct evidence is presented in favour of the model as applied to diseases such as rheumatoid arthritis, autoimmune uveitus and autoimmune diabetes. Strong circumstantial evidence, based primarily on sequence similarities, is also presented for other autoimmune diseases. However, it is noted that the statistics of database searches, and the lack of predictable correlation between sequence similarity and T-cell cross-reactivity, require that such evidence be substantiated by further direct experiment.

Evaluation of a rapid, quantitative cardiac troponin I immunoassay

We evaluated a rapid, quantitative immunoassay for the detection of cardiac troponin I. Coefficient of variation is between 1.29 and 13.63% for intra-assay and between 3.88 and 10.15% for inter-assay imprecision. Linearity is given up to 35 micrograms/l. Possible interfering substances (haemoglobin, bilirubin, triacylglycerol and rheuma factors) do not disturb the assay. The analyte is stable under normal storage conditions (+20 degrees C/48 h and +4 degrees C/l week) with decrease up to 30% after 3 months at -20 degrees C. Reference value for apparently healthy individuals is < 0.1 microgram/l. In plasma cardiac troponin I is measured up to 30% depressed compared to serum. Comparison with another cardiac troponin I assay (y = 0.92x + 2.42, r = 0.940) and cardiac troponin T is good with y = 6.61x - 1.94, r = 0.91 for the first generation cardiac troponin T assay and y = 5.59x - 0.68, r = 0.87 for the second generation cardiac troponin T assay. In summary, the evaluated assay is fast, easy to perform, and can be used not only in a specialized laboratory, but is also suitable for emergency laboratory or smaller laboratory units.

Multiplexing of Y chromosome specific STRs and performance for mixed samples

A combination of four Y-specific polymorphic STR loci was amplified simultaneously using fluorescently labeled primers. Multiplex conditions required optimization to eliminate constant bands and amplification products for female DNA. A series of experiments was carried out for mixtures of DNA from two males, and from male and female individuals for the Y-specific STRs and an autosomal locus. For the male/male mixtures amplified with the Y specific system, and amplified for an autosomal locus, the minor component in the mixture could only be identified up to a ratio of 1:10, 1:50 respectively. In male/female DNA mixtures the Y STR alleles could be identified for the highest ratio tested, 400 pg male in DNA in 800 ng female DNA which amounts to a ratio of 1:2000.

Effects of short-term recombinant human insulin-like growth factor I administration on bone turnover in osteopenic women with anorexia nervosa

Significant osteoporosis affects over half of all women with anorexia nervosa (AN). The mechanisms of bone loss in this condition are not known, and estrogen administration alone has not been shown to prevent bone loss. Insulin-like growth factor I (IGF-I), a nutritionally dependent bone trophic hormone, is know to stimulate osteoblast function and collagen synthesis in vivo and in vitro. We hypothesized that short term administration of recombinant human IGF-I (rhIGF-I) would increase bone turnover in young women with AN. We studied 23 women, aged 18-29 yr (mean +/- SD, 23 +/- 4 yr) with AN. Spinal bone density was significantly reduced compared to that in age-matched controls (0.85 +/- 0.11 vs. 1.19 +/- 0.12 g/cm2 by dual energy x-ray absorptiometry; P < 0.001) and was below the normal mean in 54% of the women. Patients were randomized to receive rhIGF-I (100 or 30 micrograms/kg) or placebo sc twice a day for 6 days. Bone turnover was assessed at baseline and after 3 and 6 days of treatment using two markers of bone formation [osteocalcin (OC) and type I procollagen carboxyl-terminal propeptide (PICP)] and three specific markers of bone resorption [pyridinoline (PYRX), deoxypyridinoline (DPYRX), and N-telopeptide (NTX)]. Serum OC was reduced significantly (P < 0.001) in women with AN compared to normal premenopausal women (5.4 +/- 3.8 vs. 8.6 +/- 4.5 ng/mL) and correlated with percent fat mass (r = 0.60;P < 0.01) and body mass index (r = 0.50;P < 0.05). Markers of bone resorption were elevated significantly compared to normal levels [DPYRX, 18.2 +/- 7.0 vs. 11.4 +/- 5.2 nmol/mmol creatinine, (P < 0.001); NTX, 53.5 +/- 22.5 vs. 36.5 +/- 14.6 nmol BCE/mmol creatinine (P < 0.01)]. IGF-I levels were relatively low at baseline compared to those in age-matched controls (203 +/- 93 vs. 262 +/- 84 ng/mL;P < 0.01) and increased to 673 +/- 268 ng/mL [P < 0.05; 100 micrograms/kg twice daily (BID)] and 545 +/- 255 ng/mL (P < 0.05; 30 micrograms/kg BID). During short term administration of rhIGF-I at a dose of 100 micrograms/kg BID, there was a significant (P < 0.05) increase in markers of bone formation, as assessed by both PICP (147 +/- 33 to 303 +/- 187 ng/mL) and OC (5.3 +/- 3.8 to 10.9 +/- 7.4 ng/mL). There was also a significant (P < 0.05) increase in markers of bone resorption as assessed by PYRX (51.0 +/- 16.6 to 87.1 +/- 8.2 nmol/mmol creatinine) and DPYRX (17.3 +/- 4.5 to 26.3 +/- 3.7 nmol/mmol creatinine). The group randomized to receive short term administration of rhIGF-I at a dose of 30 micrograms/kg BID demonstrated a significant (P < 0.05) increase in PICP (110.9 +/- 47.0 to 134.8 +/- 43.2 ng/mL) and an insignificant increase in OC levels (4.5 +/- 3.2 to 6.8 +/- 5.9 ng/mL). However, markers of bone resorption were unchanged during rhIGF-I administration at this dose. Serum PTH and serum and urinary calcium were unchanged in both treatment groups compared to placebo levels. These data demonstrate that young women with anorexia nervosa have decreased markers of bone formation and increased bone resorption. This is the first demonstration that short term rhIGF-I administration increases markers of bone turnover in severely osteopenic women with AN. The effects of short term rhIGF-I on bone turnover are dose dependent. At a dose of 100 micrograms BID, rhIGF-I administration significantly stimulated both markers of bone formation and bone resorption. At a dose of rhIGF-I of 30 micrograms BID, there was an increase in one marker of bone formation, PICP, without a change in markers of bone resorption. Further studies are required to determine whether chronic administration of rhIGF-I can affect bone mass in young women with profound osteopenia due to anorexia nervosa.

Resolution of apolipoprotein B repeat unit position variants on agarose, denaturing, and native polyacrylamide gels

Utilizing three different electrophoresis systems for the separation of variable number of tandem repeats (VNTR) alleles of the high variable region 3' from the apolipoprotein B (Apo B) locus, it could be shown that apparent allele subtypes on native polyacrylamide gels comigrated with the regular ladder alleles on agarose and denaturing polyacrylamide gels. Two subtypes, one with a shift towards the cathode and one shifted towards the anode, and the corresponding ladder alleles were sequenced in order to determine the molecular basis for this aberrant electrophoretical mobility. Subtype and ladder alleles displayed the same number of repeat units but differed in the number and order of different types of repeats. Depending on the variation in the region of pure AT repeat units, the potential secondary structures of hairpin loop formation differed for subtypes and ladder alleles, which is thought to explain the shift in electrophoretic mobility on native polyacrylamide gel electrophoresis.

Molecular mimicry in the MHC: hidden clues to autoimmunity?

The term 'molecular mimicry' has been used to describe a spectrum of antigenic crossreactivities thought to underlie autoimmune disease. For T-cell crossreactivities to occur, appropriate T-cell clones must be available. Here, Harold Baum, Huw Davies and Mark Peakman speculate that an important source of self-peptides that govern thymic selection of such clones are MHC molecules themselves.

Mitochondrial antigens, molecular mimicry and autoimmune disease

The immune system is normally tolerant to mitochondrial self-antigens, but responsive against bacteria. Low-titre anti-mitochondrial antibodies (AMA) might be involved in this discrimination. Tolerance is broken in diseases characterised by high titre AMA. Some of these AMA, against cardiolipin, cross-react with DNA. The best studied AMA are those characterising primary biliary cirrhosis (PBC). These are directed against E2 subunits of the oxo-acid dehydrogenase complexes, and also against subunits E1 alpha, E1 beta and X of the pyruvate dehydrogenase complex. AMA of PBC patients also react with bacterial E2s. Reactivities are primarily peptide-specific but with cross-reactivity between mitochondrial and microbial antigens and between E2s of respective complexes. Immunodominant epitopes, for anti E2 AMA, include the conserved sequence flanking the site of lipoyl attachment. It is proposed that the initial stimulus for antibody production is chronic urinary tract infection. AMA themselves are not pathogenic, but CD4+ T-cells would be primed, recognising the lipoyl domain epitope in association with class II HLA. Inappropriate expression of class II antigens on bile duct epithelia, (as found in PBC), might lead to presentation of a particular fragment of HLA-DR alpha, known to be a major MHC presented self-peptide in the mouse. That sequence strongly mimics the lipoyl domain and might be recognised by primed T-cells, initiating the autoimmune cascade. In the mouse, a peptide of ND1 of Complex I is presented in association with class I MHC. Cells exhibiting somatic mutation of such a peptide might thus be subject to attack by CD8+ T-cells. If such peptides were presented by class II HLA, autoimmune diseases might arise, related to mimicry between such peptides and microbial sequences and/or self-antigens. These considerations might apply in Leber's disease and in age-related pathology.

Detection of M2 antibodies in patients with recurrent urinary tract infection using an ELISA and purified PBC specific antigens. Evidence for a molecular mimicry mechanism in the pathogenesis of primary biliary cirrhosis?

Primary Biliary Cirrhosis (PBC) is a chronic liver disease of unknown aetiology. The main characteristic feature of the disease is the presence of circulating antimitochondrial antibodies (AMA) to components (collectively named M2) of the mitochondrial 2-oxo-acid multienzyme complexes; pyruvate, oxoglutarate and branched chain oxo-acid dehydrogenase complexes. As these enzymes are phylogenetically conserved, AMA also exhibit reactivity against a range of microorganisms. PBC patients have an increased incidence of recurrent urinary tract infection (UTI) compared to other chronic liver disease controls. Interestingly, we have recently detected low titre AMA in patients with a history of recurrent UTI but normal liver function using crude bovine heart mitochondrial preparations and immunoblotting techniques. Here we confirm these findings using purified M2 antigens and ELISA. We found that 52% of "normal" subjects with a history of recurrent UTI had AMA specifically to M2 antigens. The percentage was significantly higher than that found for chronic liver disease (19%, p < 0.01) and normal controls (4%, p < 0.001). These results support our hypothesis for molecular mimicry in PBC. We propose that a bacterial trigger, possibly resulting from recurrent UTIs, is responsible for initiating an autoimmune response in a predisposed host because of a cross-reactivity between mitochondrial and bacterial antigens.

A rapid assay for the quantification of myoglobin: evaluation and diagnostic relevance in the diagnosis of acute myocardial infarction

We evaluated a new, fast, quantitative, turbidimetric assay (TurbiTimeSystem, Behringwerke AG, Marburg, Germany) for the determination of myoglobin concentration in serum. Within-run imprecision (n = 10) was < 3.7% in controls ranging from 81.1 to 621.4 micrograms/l and between-day imprecision (n = 50) was < 6% in controls ranging from 69.5 to 623.4 micrograms/l. The assay is linear over the measuring range and interfering substances such as bilirubin, haemoglobin or haptoglobin do not interfere but triacylglycerol-rich samples are only measurable after brief ultracentrifugation. EDTA- or citrate-treated samples display depressed myoglobin concentration when compared with serum samples. The upper reference limit for apparently healthy individuals (n = 100, 50 female and 50 male) is 61.5 micrograms/l. Comparison with nephelometry revealed a good correlation (r = 0.982) between the two methods with the regression equation: turbidimetric assay = 5.53 + 1.02x nephelometric assay. Serial determination of myoglobin concentration and creatine kinase in 18 patients with proven acute myocardial infarction showed in general an equal diagnostic significance for both analytes. In the first 4 hours after onset of chest pain, the determination of myoglobin can have an advantage, since it is released into the blood stream at an earlier stage, but thereafter myoglobin can lead to false negative diagnosis. Therefore, determination of creatine kinase and its isoenzyme MB is still the diagnostic strategy of choice in the diagnosis of acute myocardial infarction.

Plasma coenzyme Q (ubiquinone) concentrations in patients treated with simvastatin

Plasma coenzyme Q (CoQ) was measured in 20 hyperlipidaemic patients treated with diet and simvastatin (an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase); 22 hyperlipidaemic patients treated with diet with alone; and 20 normal controls. Patients treated with simvastatin had a significantly lower plasma CoQ and CoQ: cholesterol ratio than either patients receiving diet alone or normal controls. Use of simvastatin was inversely and independently correlated with both CoQ (p < 0.0001) and CoQ: cholesterol ratio (p < 0.01). There was a significant inverse association between CoQ and dose of simvastatin (p < 0.001). It is concluded that simvastatin may lower the plasma CoQ concentration and this may be greater than the reduction in cholesterol. The possible adverse effect of simvastatin on the metabolism of CoQ may be clinically important and requires further study.

Autoimmune disease and molecular mimicry: an hypothesis

Helper T lymphocytes are normally only stimulated to initiate an immune reaction through the recognition of peptides bound to class II major histocompatibility complex (MHC) molecules. Class II MHC molecules are constitutively expressed on antigen-presenting cells which play a critical role in the initiation of immune responses. In disease states, however, other cells often express class II MHC molecules inappropriately. This article suggests an hypothesis for the pathogenesis of autoimmune diseases based on molecular mimicry. The mimicry described is between microbial or viral peptides presented by antigen-presenting cells and self peptides presented inappropriately on a target tissue. This leads to helper T cells, stimulated by peptides derived from infectious organisms, initiating an autoimmune attack on the target tissue.

M2 mitochondrial antibodies and urinary rough mutant bacteria in patients with primary biliary cirrhosis and in patients with recurrent bacteriuria

Primary biliary cirrhosis (PBC) patients have a higher incidence of recurrent urinary tract infection and an increased prevalence of rough forms (mutants) of E. coli in their stool samples than other chronic liver disease patients. PBC patients exhibit autoantibody reactivity against mitochondria, the most common antigen (M2) being a family of antigens with the major components having approximate molecular weights of 74, 56, 52 and 48 kD. Cross-reactivity between M2 antigen components and corresponding antigenic bands of bacteria has been demonstrated with PBC sera. Patients with recurrent urinary tract infections, all of whom had normal liver function and were taking prophylactic antibiotic treatment, had weak anti-mitochondrial antibody (AMA) reactivity (69%), with reactivity against the 74-kD antigen alone being the most common. When antibody to the 74-kD band was eluted, it was found to cross-react with bacterial membrane fractions. In the controls, 12/77 chronic liver disease patients and 2/24 normals possessed AMA. Rough forms of bacteria were found in the urine of patients with significant bacteriuria: 39% PBC, 5.3% chronic liver disease and 41% of the recurrent urinary tract infection group. M2 antibodies may be induced by urinary organisms in 'normal' women with recurrent bacteriuria and in females with PBC.

Serum catalase as the protective agent against inactivation of alpha 1-proteinase inhibitor by hydrogen peroxide; comparison between normal and rheumatoid sera

Human serum contains catalase activity, which can protect alpha 1-proteinase inhibitor from inactivation by H2O2. The primary source of serum catalase is probably erythrocytic. The enzyme activity correlates with haemoglobin concentration in sera from control subjects but not in sera from patients with rheumatoid arthritis. Catalase is inactivated by oxidants, such as H2O2 and hypochlorous acid and it is suggested that the decrease in catalase/haemoglobin ratio observed in rheumatoid serum is due to oxidant stress associated with inflammation.