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F S Apple

Publications and source records attributed to F S Apple.

117 records · Page 7Linked to original sources
PubMed1982

Relationship between direct-potentiometric and flame-photometric measurement of sodium in blood.

The relationship between direct-potentiometric and flame-photometric measurements of sodium has been studied in human sera and other, simpler systems. When water content was varied by using an inert substance (silica), de-ionized sera, or de-ionized individual proteins, the percentage that the flame photometric values were of the direct potentiometric Na+ values was identical to the measured water content. However, in 35 patients the percentage of Na+ values was 99.1% and the water content was 92.0%, a discrepancy of 7.1%. De-ionization of sera removed this discrepancy, apparently because of the lower pH of the de-ionized sera. The percentage of flame-photometric to direct-potentiometric Na+ values varied as a function of pH in pooled sera; in lyophilized and reconstituted sera; and in de-ionized, lyophilized, and reconstituted sera. Four explanations for the discrepancy between the percentage of Na+ values and the water content are discussed: a calibration problem, a measurement artifact, Na+ binding, and water binding. At this time there are no definitive data concerning which explanation is correct. We expect that our finding of a pH dependency for the percentage of measured Na+ values can be used to develop model systems to elucidate the mechanism producing the discrepancy between the percentage of Na+ values and the water content.

Bicarbonates↗
PubMedDate not supplied

Cardiac biomarkers in the new millennium.

Cardiac disease is the major cause of death in patients with end-stage renal disease (ESRD), accounting for about 45% of all deaths. In dialysis patients about 20% of cardiac deaths are attributed to acute myocardial infarction (AMI). The survival of dialysis patients after AMI is poor, with nearly three-quarters of patients dead at 2 years after AMI. The definition of AMI is based on symptoms, electrocardiography, and cardiac biomarkers. In the non-ESRD population, it has been recognized that sensitive markers of myocardial injury (cardiac troponin I and troponin T) define a group of patients who are increased risk for adverse cardiac outcomes and who are more likely to benefit from treatment. Elevated cardiac troponin levels in nonhospitalized ESRD patients without other evidence of ongoing myocardial ischemia may also prospectively identify a subgroup of ESRD patients at increased risk for death. This editorial is an overview of cardiac biomarkers (specifically troponin I and troponin T) in the management of acute coronary syndromes in ESRD patients. A potential role of cardiac troponin testing for risk stratification in the outpatient dialysis unit is also presented.

Biomarkers↗
PubMedDate not supplied

Postmortem tricyclic antidepressant concentrations: assessing cause of death using parent drug to metabolite ratio.

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.

Antidepressive Agents, Tricyclic↗
PubMedDate not supplied

Cocaine-associated fetal death in utero.

Cocaine and its principle metabolite benzoylecgonine were quantitated in blood and liver in six cocaine-related deaths within the Hennepin County Medical Examiner's jurisdiction. Postmortem blood cocaine and benzoylecgonine concentrations ranged from 0 to 5.6 mg/L and 0.6 to 18.7 mg/L respectively. Postmortem liver concentrations ranged from 0 to 5.0 mg/kg and 0.4 to 24.1 mg/kg, respectively. All cases had benzoylecgonine concentrations greater than cocaine concentrations. Most alarming were the findings regarding the cocaine and benzoylecgonine concentrations in the case of a dead pregnant woman. The amniotic fluid cocaine and benzoylecgonine concentrations of 3.3 mg/L and 1.6 mg/L displayed at parent drug to metabolite ratio greater than 1.0 compared to the blood (0.30) and liver (0.21) ratios. This was likely indicative of very recent exposure.

Adolescent↗
PubMedDate not supplied

The specificity of biochemical markers of cardiac damage: a problem solved.

This paper reviews the tissue specificity of cardiac troponin I (cTnl), cardiac troponin T (cTnT) and creatine kinase (CK) MB in human and animal heart and skeletal muscles. Studies reveal that CK-MB can be expressed up to 20% of total CK activity in human skeletal muscle; and therefore is not 100% specific for the heart. One cTnl isoform has been described and shown to be 100% specific for the heart. While one to four cTnT isoforms are expressed in diseased and regenerating human skeletal muscle, these isoforms are not the same as the cTnT isoforms expressed in the human heart and are not detected by the cTnT diagnostic assays used in clinical practice. Representative cases are described demonstrating the role of monitoring cardiac troponins in blood for differentiating false positive CK-MB increases due to skeletal muscle injury. Further, sufficient reactivity and tissue specificity of cTnl and cTnT assays are demonstrated for use as markers of myocardial injury in laboratory animals. Monitoring cTnl and cTnT concentrations in the circulation appears poised as the new standards for detection of myocardial injury.

Animals↗
PubMedDate not supplied

Serum creatinine concentration and the discrepancy between enzyme multiplied immunoassay technique and gas-liquid chromatographic phenytoin levels.

In patients on phenytoin therapy and with renal failure, the enzyme multiplied immunoassay technique (EMIT), unlike gas-liquid chromatographic techniques (GLC), can give falsely elevated serum phenytoin concentrations. In 25 patients (creatinine less than or equal to 1.5 mg per dl), discrepancies between the serum EMIT and GLC phenytoin concentrations were accounted for by the inherent imprecision of the methods. However, in 16 of 18 uremic patients (creatinine greater than or equal to 1.7 mg per dl), the discrepancies were greater than could be accounted for by imprecision. For these 18 patients the correlation (r = 0.49) between the discrepancies and the creatinine concentrations appeared to be statistically significant (P less than 0.05). The linear regression relationship was inadequate for accurate correction of the EMIT values using the creatinine concentrations. Another original observation was that in most cases renal dialysis decreases the EMIT to GLC discrepancy. However, post-dialysis serum samples with a creatinine concentration greater than 1.7 mg per dl usually still showed a falsely elevated EMIT phenytoin concentration.

Chromatography, Gas↗
PubMedDate not supplied

Elevation of creatine kinase BB CK in hospitalized patients. Importance of distinguishing BB CK from MB CK.

Nine hundred and forty patients (1023 samples) were analyzed by cellulose acetate electrophoresis for creating kinase MB (MB CK) in the routine clinical chemistry laboratory during screening for acute myocardial infarction. Thirty patients showed the presence of BB CK and the associated disease states were identified. Rigid criteria were applied to demonstrate the activity observed was genuinely BB CK. It is noted and demonstrated that careful attention must be paid to the methodology used to distinguish CK isoenzymes, because some assays do not differentiate between BB CK and MB CK. It was shown by us that the false positive rate for MB CK could be as great as 19 percent in laboratories using non-discriminant assays for MB CK. Thus, the laboratory must know the limitations of the assays employed to avoid potential errors in MB CK results that could be misused as biochemical evidence of a myocardial infarction.

Chromatography, Ion Exchange↗