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Excerpt To the Editors: Serial creatine kinase and creatine kinase-MB measurements with clinical history findings, physical examination findings, and electrocardiographic (ECG) changes are the stan...

Serum samples from 14 men and 8 women were obtained pre-marathon (48 h) and at 24, 48, 72, and 96 h post-race to quantitate total serum creatine kinase activity (TCK), percentage of creatine kinase MB (CK-MB), and clearance rates (half-lives) of TCK and CK-MB. TCK was measured enzymatically, and the CK-MB isoenzyme was separated by agarose electrophoresis and quantitated by densitometry. The men's and women's post-race mean TCK levels were significantly elevated (P less than 0.05) above pre-race values at 24 h (3322 U . l-1, 946 U . l-1 and 48 h (1787 U . l-1, 508 U . l-1). In addition, CK-MB was significantly elevated both 24 h (5.1%, 3.3%) and 48 h (2.5%, 1.8%) post-race (P less than 0.05). The men's 24-h TCK was 22.3 times the pre-race value, while the women had an 8.6-fold increase in TCK. The mean 24-h post-race CK-MB activities were 166 U . l-1 for the men and 31 U . l-1 for the women. The mean increase in CK-MB activity was 41.5-fold for the men and 7.8-fold for the women. Furthermore, the men had a mean half-life (t1/2) of 30.4 h for TCK and 12.0 h for CK-MB; the women's t1/2's were 29.4 and 16.8 h, respectively. At all time points, the men evidenced significantly (P less than 0.05) higher TCK and CK-MB enzyme activities than did the women.(ABSTRACT TRUNCATED AT 250 WORDS)

Following acute myocardial infarction, total CK and CK-MB levels begin to rise 5 to 6 hours after the onset of chest pain. The serial profile of the rise and fall of both activities is nearly always indicative of AMI. The recent increase in the use of thrombolytic agents in an attempt to attain reperfusion of occluded coronary arteries alters the enzyme profiles observed in blood after AMI. After successful reperfusion a washout phenomenon occurs in which early restoration of blood flow to damaged myocardium causes an early rise in total CK and MB levels above the normal range 2 to 4 hours after AMI, with earlier and higher peak enzyme values. Recently reports have appeared describing numerous serum and plasma CK-MM and CK-MB isoform patterns after AMI. Following release from injured myocardium CK-MM3 and CK-MB2 (designated the tissue isoforms) are converted in the circulation to post-translation products (MM2, MM1, MB1, respectively). Studies have now shown that CK-MM isoform patterns provide a unique means of assessing the time of onset of necrosis and a monitor of the duration of enzyme release from the site of injury. Following AMI, MM3, the MM3/MM1 ratio, or both rises and peaks earlier than either total CK or CK-MB levels. During successful reperfusion, the rate of rise of CK-MM3 is more rapid and the MM3/MM1 ratio peaks earlier than without reperfusion. However, any concomitant release of CK-MM3 from skeletal muscle would decrease the clinical utility of MM isoforms in detecting myocardial damage. Recent advances in technology have shown that CK-MB2 rise parallels the CK-MM increase and also rises earlier than total CK and total MB levels and provides increased specificity for the myocardium. The full potential of the diagnostic utility of MM and MB isoforms will not be realized until a reliable, sensitive, simple, and rapid quantitative assay becomes available.

The iron status of nine female marathon runners was evaluated during 11 weeks of training for a marathon race and following a marathon race. Venous blood samples were obtained at the start of the training period, weekly during training, and 1, 2, 3, and 4 days post-race. The subjects completed menstrual and dietary histories, and the diet content of energy, protein, iron, and ascorbic acid was calculated. Serum iron, total iron binding capacity, and transferrin saturation showed no significant change at weeks 1, 7, and 11 during training. The mean values of serum iron and transferrin saturation were low. During training, eight of the nine women averaged serum ferritin levels below 50 ng/ml, one of the eight having values consistently less than 10 ng/ml. Ferritin values were significantly elevated for 3 days after the marathon. No subject reported abnormally heavy menstrual bleeding, and nutrient intakes were near recommended levels, except for iron. Thus, the iron status of these women marathon runners was poor, suggesting that women runners may have higher dietary needs for iron than sedentary women. Serum ferritin levels were also elevated after a marathon run and may not adequately reflect iron stores.

Sodium was determined by flame photometry and by direct potentiometry in 56 serum or plasma samples from 24 patients with multiple myeloma or macroglobulinemia. We observed differences between the two techniques as large as 17 mmol/L (12%). The flame-photometric values decreased relative to the direct-potentiometric values as protein increased or water content decreased. Moreover, the two sodium measurements could not be interconverted simply on the basis of correcting for protein or water content. There was significantly lower residual variance (p less than 0.005) when the direct-potentiometric sodium values were compared with the osmolality (corrected for the influence of glucose and urea nitrogen) than when the flame-photometric values for sodium were so compared. We conclude that direct potentiometric measurements of sodium in patients with multiple myeloma gives clinically relevant results but flame photometry does not. Clearly, the method by which sodium is measured in patients with multiple myeloma must be considered if results are to be interpreted correctly.

We investigated the patterns of variants of creatine kinase isoenzyme MM (CK-MM) in gastrocnemius muscle and plasma sampled from male and female long-distance runners before and after a marathon race. The proportions of CK-MM variants MM1 (pI 6.90) and MM2 (pI 6.62), identified in the skeletal muscle from both sexes, did not differ significantly from those in skeletal muscle from nonrunning controls or from heart muscle. CK-MM1 was the major (84-85% of total CK-MM) variant form. Patterns of CK-MM in plasma collected from male runners 24, 48, 72, and 96 h after the race were similar to those for female runners, but we detected two new additional variants, which we designate MM1B (pI 6.76) and MM2B (pI 6.49). For both sexes the total CK-MM activities in plasma were significantly (p less than 0.05) greater after the race, but the women's total CK-MM activities were significantly (p less than 0.05) less than the men's. The rates of disappearance of MM1, MM2, and MM3 from plasma after the race differed significantly (p less than 0.05) between men and women, MM1 clearing the fastest. Determination of the CK-MM variants in plasma after strenuous exercise may be of help in assessing CK release from injured skeletal muscle.

The creatine kinase (CK) isoenzyme composition was determined in serial gastrocnemius muscle biopsies obtained from 12 male marathon runners. The mean muscle CK-MB composition significantly increased after chronic exercise (training) from 5.3% (pretraining) to 7.7% (premarathon) as well as after acute exercise (postmarathon) to 10.5% of the total CK activity (P less than 0.05). However, no significant differences in total CK activities were detected. Additionally, mitochondrial CK and CK-BB isoenzymes were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (3,322 U/l) and CK-MB (174 U/l) activities 24 h after the race (r = 0.98, P less than 0.05). These results show that gastrocnemius muscle adapts to long-distance training and racing with increased CK-MB activities and imply that skeletal muscle is the major source of elevated serum CK-MB activities in marathon runners.

The proportion of creatine kinase (CK; EC 2.7.3.2) isoenzyme MB activity was increased in skeletal muscle biopsies obtained from five long-distance runners, both 2 h before (mean 7.7%, SD 2.4%) and 30 min after (mean 7.2%, SD 1.2%) a marathon race, as compared with that in biopsies from five nonrunners (controls less than or equal to 1.0%). Further, mitochondrial CK and CK-BB isoenzymes were present in homogenates of the runners' skeletal muscle samples but not in those of the nonrunners. However, there were no substantial differences in the mean total CK activities per gram (wet wt.) of muscle tissue among premarathon samples, postmarathon samples, and nonrunners' samples (3148, 3365, and 3049 U/g, respectively). We conclude that the metabolically active gastrocnemius muscle of long-distance runners is qualitatively similar to the heart muscle in its CK isoenzyme composition.

We examined the clinical and analytical performance of two immunoassays (Becton Dickinson CK-MB; Ciba-Corning Magic Lite CK-MB) in which monoclonal anti-CK-MB antibodies are used for directly measuring creatine kinase (EC 2.7.3.2) isoenzyme MB (CK-MB) in serum, and also one electrophoretic method (Ciba-Corning). Within- and between-assay precision for both immunoassays was good at the upper reference limits (less than 10% CV). Analytical recoveries ranged from 102 to 114%. Both immunoassays were free from interference by CK-BB, mitochondrial-CK, macro-CK, adenylate kinase, and CK-MM. Retrospectively, we evaluated four categories of patients, using both immunoassays and electrophoresis: normal controls, acute myocardial infarction (AMI) patients, severe skeletal muscle trauma patients, and acutely ill patients known not to have AMI. In general, there were excellent correlations among all three methods. CK-MB activity (U/L) measured by the Becton Dickinson immunoassay was approximately 50% of the mass concentration (microgram/L) of the Magic Lite immunoassay and 50% of the activity concentration (U/L) determined by electrophoresis. Both immunoassays were easy to perform and sensitive to the low CK-MB concentrations often found with low total-CK activities.

Isoenzymes and isoforms of creatine kinase (CK, EC 2.7.3.2) were measured to assess reperfusion after acute myocardial infarction (AMI). In streptokinase-treated and in spontaneously reperfused AMI patients, total CK, CK-2 activity and concentration, and CK-3(3) isoform activity peaked significantly (p less than 0.05) earlier than conventionally treated, non-reperfused patients. The ratio for CK-3(3) to CK-3(1) activities peaked significantly (p less than 0.05) earlier in both the streptokinase-treated and spontaneously reperfused groups, and indicated a greater release of enzyme (higher ratio) than in the conventionally treated patients. The ratio of CK-3(3)/3(1) also peaked significantly (p less than 0.05) earlier in all three groups than did total CK, CK-2, and CK-3(3) activities or concentrations. The clearance rates of total CK, CK-2, and CK-3(3) were not significantly different in all three groups. Thus, the ratio CK-3(3)/3(1) was the earliest indicator of infarction in both reperfused and non-reperfused patients.

The response of the myocardial creatine kinase system to acute coronary artery occlusion is not well defined. In the present study, we measured serial changes in myocardial creatine kinase and creatine kinase-MB activities after acute occlusion of the left anterior descending (LAD) coronary artery in 20 open-chest pentobarbital-anesthetized dogs. Tissue samples were obtained from both ischemic and nonischemic left ventricular myocardium at base line and 1-, 3-, and 5-h intervals after LAD occlusion and assayed for total creatine kinase and the isoenzymes creatine kinase-MM, and creatine kinase-MB. Total creatine kinase activity declined significantly in both the ischemic and the nonischemic tissue because of a decline in creatine kinase-MM activity. Concomitantly, creatine kinase-MB activity increased significantly in both the ischemic and the nonischemic tissue. These changes were observed when the duration of the LAD occlusion was 3 h or longer, but not when the duration of the occlusion was 1 h. Thus acute myocardial ischemia causes pronounced changes in the canine myocardial creatine kinase system. These rapid biochemical alterations occur both locally in ischemic tissue and remotely in nonischemic tissue.

Total creatine kinase (CK) and CK MB activities were determined in gastrocnemius muscle and serum obtained from 14 female marathon runners. The level of CK MB in muscle increased significantly (p less than 0.05) after chronic exercise training from 5.3% to 10.5% of the total CK activity, but not after acute exercise (post-marathon 8.9%). No significant differences in total CK activities were detected. However, the total CK activity in the muscles were significantly (p less than 0.05) less than those previously reported from the muscle of men runners (1800 U/g, 3000 U/g respectively). No significant correlation existed between fiber type and muscle CK MB activity. Additionally, trace amounts of mitochondrial CK and CK BB were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (597 UL-1) and CK MB (23 UL-1) activities 24 h after the race (r = 0.97, p less than 0.05). These results suggest that gastrocnemius muscle in women adapts to training with increased CK MB activities and imply that skeletal muscle is the major source of elevated serum CK MB activities in women marathon runners.

We measured creatinine in plasma and urine samples from 17 normal subjects and 10 renally impaired subjects by four different methods: two enzymatic--Ektachem iminohydrolase and Boehringer Mannheim amidohydrolase--and two Jaffé reaction based--Beckman Astra 8 and Technicon AutoAnalyzer I. Creatinine clearances, standardized for body surface area, were also calculated. In both groups of subjects plasma creatinine values were significantly (p less than 0.05) lower, by 3 to 4 mg/L, when measured enzymatically than when measured by the Jaffé reaction. Additionally, creatinine clearances were significantly (p less than 0.05) greater by at least 30 mL/min when calculated from enzymatically measured creatinine values vs Jaffé method values for creatinine. The benefits of lack of interference with enzymatically measured creatinine concentrations and clearances should be assessed in relation to the lack of agreement with long-established (Jaffé) methods for determining creatinine (and inulin) clearances.

We compared creatinine clearances determined by enzymatic (Kodak Ektachem 700 single-slide, Boehringer Mannheim creatinine PAP) and nonenzymatic (Jaffé, HPLC) methods with glomerular filtration rate measured by inulin clearance in patients with varying degrees of renal function. The Kodak enzymatic assay gave values for creatinine 2 to 3 mg/L higher than the other methods. This resulted in significantly lower creatinine clearances than inulin clearances and creatinine clearances determined by the other methods. However, correlations between all methods for serum and urinary creatinine values and clearances were good. To avoid between assay (enzymatic vs nonenzymatic) discrepancies, manufacturers should agree to an acceptable standard of calibration under the usual conditions used with patients.

Individual human muscle fibers from the vastus lateralis were isolated from age-matched endurance-trained and strength-trained athletes and untrained controls. Slow- (ST) and fast-twitch (FT) fibers were assayed for total creatine kinase (CK), CK-MB, total lactate dehydrogenase (LD), the LD isozyme that predominates in the heart muscle of most vertebrates (LD1), and citrate synthase (CS). Regardless of training of the athletes, both CK-MB and CS were higher in ST than in FT fibers. Also, irrespective of fiber type, CK-MB and CS were greatest in the endurance-trained group. A positive correlation existed between CK-MB and CS, relating oxidative capacity of individual fibers with CK-MB. Total CK varied little among the fiber types, trained groups, or controls. Total LD in FT fibers was greater than in ST fibers in all groups, with only ST fibers from the endurance-trained group containing substantial amounts of LD1. These findings suggest that specific training, endurance exercise, causes a favorable metabolic adaptation of CK and LD isozymes at the individual fiber level, allowing for the muscle to cope with increased energy demands during prolonged exercise.

In human gastrocnemius muscle obtained from long-distance runners, mitochondrial creatine kinase (CK) activities were significantly greater than nonrunning control skeletal muscle and significantly increased during training for and after a marathon race. Thus skeletal muscle tended to become similar to heart muscle in its mitochondrial CK composition. Total muscle CK activity was significantly different in males and females, was unaffected by marathon training and racing, and was similar to gastrocnemius muscle obtained from nonrunning controls. There was an inverse correlation between the maximum O2 uptake and the percentage increase in mitochondrial CK activity after training. These studies suggest that mitochondrial CK may play a key role in the intracellular transport of energy from mitochondrial to myofibrils in skeletal muscle during endurance exercise such as long-distance running.

The present study assessed creatine kinase (CK) activity, CK MM isoforms, and muscle soreness following an exercise regimen designed to induce skeletal muscle damage. Eight college-age subjects performed 40 maximal isometric contractions of the knee extensor muscles (10-second contraction/20-second rest). Serum samples and soreness ratings were taken prior to and 2, 6, 18, and 24 hours after the exercise. The CK MM1 and CK MM3 isoforms were determined by flatbed isoelectric focusing (IEF). In serum, the MM1 isoform (the pure gene product) is considered to be evidence of newly released CK from muscle, as upon entering the plasma, the CK MM1 is converted to MM2 and then MM3. A significant increase in serum CK activity was found at 6 hours and remained elevated at 24 hours. CK MM1 increased significantly at 2 hours, peaked at 6 hours, then approached baseline. Soreness did not increase significantly until 18 hours. Analysis of CK isoforms in serum can provide an earlier indicator of skeletal muscle damage than total CK or perception of soreness and may be useful in tracking the time course of skeletal muscle damage and repair.

Serial total creatine kinase (CK) and CK MB activities were determined in the serum of seven runners following a marathon race and compared to enzyme activities in the sera from five patients following acute myocardial infarction (AMI). In the runner's sera, total CK and CK MB activities were significantly elevated at 1, 24, 48 and 72 hours post marathon race when compared to the 1 hour pre-marathon samples (p less than 0.01). Serum CK MB activities peaked at 24 hours in both groups of subjects. The MB activities 24 hours following the marathon were substantially higher (91 +/- 30 U/l; mean +/- SD) than the MB activities 24 hours following AMI (46 +/- 38 U/l). However, the percentages of CK MB 24 hours following the marathon and AMI were almost identical (7.0 +/- 2.4% and 7.2 +/- 2.3%, respectively). Furthermore, CK and CK MB clearances were significantly prolonged (p less than 0.02 and p less than 0.001, respectively) following the marathon race (T 1/2 CK, 49 hours; T 1/2 CK MB, 29 hours) as compared to following AMI (T 1/2 CK, 27 hours; T 1/2 CK MB, 12 hours). These results suggest release of CK MB from the skeletal muscle of marathon runners. Therefore, we recommend that elevation of CK MB in the range indicative of myocardial damage be interpreted with caution in long-distance runners.

Tricyclic antidepressants (TCAs) are one of the major causes of death from drug ingestions. Because TCAs are highly tissue bound, it has been postulated that postmortem tissue release would give rise to elevated blood levels. This study examines the authors' experience with TCAs as a cause of death and the reliability of postmortem liver and blood levels. Postmortem liver and blood TCA levels (parent drug and active metabolite) were quantitated by high-pressure liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC-MS). From 1977 through 1985 the number and percentage of deaths caused by TCA overdoses have remained constant in regard to the total number of deaths caused by poisonings and overdoses: range: 4-17; 5.6-20.2%, respectively. During a six-month period in 1986-1987, nine deaths were caused by six different TCAs. Substantial increases in blood TCA levels were observed as the postmortem interval increased. The mean liver and blood levels were as follows: 232 micrograms/g of tissue (SD, 168) and 6.2 mg/L (SD, 2.4). The liver to blood ratio for the nine cases was 37 (SD, 22):1. In comparison, in cases (n = 4) in which the causes of death were not TCA related but the patients were taking therapeutic doses of TCA, the mean liver and blood levels were 10.8 micrograms/g (SD, 6.0) and 0.26 mg/L (SD, 0.06), respectively. The liver to blood ratio of 39.2 (SD, 17.9): 1 was not different than in the overdose cases. This large tissue to blood gradient in both TCA overdose and therapeutic ingestion cases indicates that postmortem release of tissue-bound TCAs into the blood might falsely show elevated postmortem blood levels that could be indicative of a manner of death even in the nonoverdose, therapeutic ingestion. Thus, only liver TCA levels should be quantitated to specify the manner of death.

Skeletal muscle damage size (SMDS) was assessed in 35 women and 34 men runners after a 42.2-km race using a method developed for estimation of myocardial infarct size. SMDS was computed according to the following equation: SMDS = (BW) (K) (CKr), where BW is body weight, K is a constant, and CKr is the cumulative amount of creatine kinase (CK) released over time. The method takes into account CK distribution space, fractional disappearance rate of CK, proportion of CK degraded in skeletal muscle, and proportion of CK released into the circulation. Assumptions are made regarding the relative amount of CK lost from skeletal muscle into the circulation. The SMDS in men, 808 +/- 1,229 (SD) CK g-eq was significantly (P less than 0.05) greater than in women, 160 +/- 147 (SD) CK g-eq. The ranges of SMDS (CK g-eq) were 23-5,397 in men and 7-624 in women. A significant difference (P less than 0.05) also remained after correction for body surface area; men 432 +/- 583 (SD), women 100 +/- 63 (SD) CK g-eq/m2. In men and women, no significant correlation existed between SMDS and age or marathon finish time. Although relatively theoretical, results indicate that greater skeletal muscle damage occurred in men vs. women runners after a marathon. Whether the release of CK from skeletal muscle is the result of irreversible and/or reversible injury has not yet been determined.

We investigated the Chromatographie behavior of CK isoenzymes and immunoglobulin-bound macro-CK by discontinuous gradient elution from DEAE-Sephadex A-50 at pH 7 and 8. In four of five patients with macro-CK, the macro-CK was eluted with the MB buffer at pH 8, but a significant portion of the complex was eluted with the MM buffer at pH 7, in a region between CK-MM and CK-MB. In the fifth patient, the macro-CK was eluted with the MB buffer at both pH values. The immunoglobulin patterns of all five patients and of normal serum showed that IgG and IgM are eluted mainly with the MM and MB buffers, respectively, at both pH values, whereas IgA is eluted mainly with the MB buffer at pH 8, but at pH 7, shows a significant shift similar to that of macro-CK. These characteristic patterns allowed the identification of the immunoglobulin in macro-CK as IgA in the first four patients, and as IgM in the fifth patient.

We could detect skeletal muscle injury early after an acute exercise bout by measuring creatine kinase (CK, EC 2.7.3.2) MM isoforms in serum. Eleven men performed 120 alternating-arm, eccentric (muscle lengthening) biceps contractions with the intensity of each contraction being 110% of maximal concentric strength--a form of exercise previously shown to cause significant increases of CK in serum at 24 h and muscle soreness 48 h after exercise. Total CK and CK-MM isoform activities in serum were determined before and at 0.5, 0.75, 1, 1.5, 2, and 6 h after exercise. Using thin-film agarose gels and a rapid isoelectric focusing technique, we separated the MM isoforms into MM3 (skeletal muscle form), MM2, and MM1 (in vivo conversion forms). The isoforms reflected the MM form released into the serum from tissue as well as the conversion of one form to another. There were no significant increases in total CK from before to 6 h after exercise: 75 (SD 36) vs 91 (SD 33) U/L. However, CK MM3 in serum increased significantly (P less than 0.01) within 2 h after exercise from 22 (SD 6)% to 28 (SD 6)%. The MM3 to MM1 ratio also increased significantly (P less than 0.05) during this time, from 0.6 (SD 0.3) to 0.9 (SD 0.4). Thus, quantification of CK MM isoforms permitted very early detection of skeletal muscle enzyme release.

Background Circulating B-type natriuretic peptide (BNP) is widely accepted as a diagnostic and risk assessment biomarker of cardiac function. Studies suggest that there are significant differences in measured concentrations among different commercial BNP immunoassays. The purpose of our study was to compare BNP-related proteins to determine a form that could be used as a common calibrator to improve the comparability of commercial BNP immunoassay results. Methods BNP was measured in 40 EDTA-plasma samples from acute and chronic heart failure patients using five commercial BNP assays: Alere Triage, Siemens Centaur XP, Abbott I-STAT, Beckman Access2 and ET Healthcare Pylon. In parallel with internal calibrators from each manufacturer, six preparations containing BNP 1–32 motif a) synthetic BNP, b) recombinant BNP (E. coli), c) recombinant nonglycosylated proBNP (E. coli), d) recombinant His-tagged (N-terminal) nonglycosylated proBNP (E. coli), e) recombinant glycosylated proBNP (HEK cells), and f) recombinant glycosylated proBNP (CHO cells) were also used as external calibrators for each assay. Results Using the internal standards provided by manufacturers and for five of six external calibrators, up to 3.6-fold differences (mean 1.9-fold) were observed between BNP immunoassays (mean between-assay CV 24.5–47.2%). A marked reduction of the between-assay variability was achieved, when glycosylated proBNP expressed in HEK cells was used as the common calibrator for all assays (mean between-assay CV 14.8%). Conclusions Our data suggest that recombinant glycosylated proBNP could serve as a common calibrator for BNP immunoassays to reduce between-assay variability and achieve better comparability of BNP concentrations of commercial BNP immunoassays.

Cardiac troponin T (cTnT) and troponin I (cTnI) have been suggested as new, more specific markers of myocardial cellular damage. The objective of this study was to examine how the distributions of cTnI and cTnT were affected in postinfarction left ventricular remodeled (LVR) myocardium. At 2 months postinfarct in a porcine heart failure model, both Western blot and biochemical assay analyses were performed on left ventricular myocardium remote from the infarct zone in ligation animals (n = 8). Results were compared with data from the left ventricular myocardium from similar sized healthy (control) pigs (n = 7). Autoradiograms from Western blot analysis showed that the protein mass for cTnI and cTnT in LVR hearts decreased 80% (P

Sera from patients with above-normal gamma-globulin concentrations give sodium values as much as 10% higher when measured in the Kodak Ektachem 400 analyzer than results obtained with the Beckman Astra-8 analyzer. Results obtained with the Astra were in agreement with flame photometry. A similar relative bias was observed for potassium measurement in the Ektachem. This discrepancy was corrected when we used a new generation of reference fluid provided by Kodak, which is currently available for general use.

In 9 of 13 medical examiner cases in which death was caused by tricyclic antidepressant (TCA) overdose, the mean postmortem liver and blood concentrations were 200 micrograms/g and 4.0 micrograms/mL, respectively. In comparison, in 4 of 13 cases in which the causes of death were not TCA related but involved therapeutic doses of TCA, the mean liver and blood levels were 29.0 micrograms/g and 1.3 micrograms/mL, respectively. The parent drug to major metabolite ratio in liver was 6.3:1 in overdose cases and 0.5:1 in therapeutic cases. The ratio in blood was greater than 1.0 in both overdose and therapeutic ingestions. We concluded that liver TCA concentrations should be quantitated to specify manner of death. For cases in which the manner of death was ambiguous, the liver parent drug to major metabolite ratio aided in the decision process.

To the Editor.— Marathon running has been shown to induce a variety of chemical changes in runners' serum. 1 In the clinical laboratory, increases in serum alanine aminotransferase (ALT) activity have been shown to be very hepatospecific. 2 Also, it has been suggested that ALT testing is potentially useful for screening blood donors to reduce incidence of non-A, non-B viral hepatitis. 3,4 This report describes the changes in skeletal muscle and serum ALT activities in runners before and after a marathon race and discusses the potential for false biochemical indices for liver damage. Serum was obtained from 22 male (aged 21 to 36 years) and eight female (aged 24 to 35 years) runners two days before and 24, 48, 72, and 96 hours after a marathon race (26.2 miles). Gastrocnemius muscle biopsy specimens were obtained nine weeks before, two days before, and one day after the race from 14 male

Urea nitrogen, glucose, sodium, potassium, and chloride were measured in common vitreous humor samples using a variety of instruments. There was found to be variation in values obtained by the different procedures for each of these constituents. The variation in electrolyte values between the different procedures can pose real problems in attempting to determine the presence of an antemortem dehydration or low salt condition. Possible reasons for these variations are discussed, and the normal range of values of both sodium and chloride for the different instrumentalities is provided. However, variations in values for both urea nitrogen and glucose would not pose any problems of interpretation for forensic science evaluations.

Excerpt Serum from patients with hyperlipemia has been clearly shown to have low sodium values when analyzed by flame photometry (1-10). This artifactually low sodium value is due to a decrease in ...

Chronic kidney disease (CKD) is an independent risk factor for coronary disease. However, the relationship between impaired renal function and myocardial necrosis determined by a contemporary cardiac troponin I (cTnI) assay in patients presenting to the emergency department (ED) with symptoms

Numerous pathologies aside from ACS are associated with an increased cardiac troponin (cTn). We hypothesized that delta cTn would be useful for improving diagnostic accuracy and distinguishing outcomes of spontaneous MI (type 1) versus MI secondary to supply/demand imbalance (type 2). We