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Serial electrocardiograms and creatine kinase (CK) isoenzyme activities were studied prospectively in 20 asphyxiated term newborn infants and 43 normal neonates. By adapting a previously described grading system for ischaemic changes, a degree of electrocardiographic ischaemia was defined which occurred almost solely in asphyxiated infants. Infants with this degree of abnormality had significantly higher mean CK-MB and MM activities than other asphyxiated infants at 0, 8 and 28 hours. Histological changes of peripartum myocardial necrosis were seen in 4 of the 5 infants on whom an autopsy was performed, and either electrocardiogram or CK-MB was abnormal in all four. It is concluded that myocardial injury in the newborn period is often associated with CK-MB release, but in view of the lack of cardiac-specificity of CK-MB in newborn infants, caution is urged in the interpretation of elevated isoenzyme activity in the neonate.

We analyzed 240 samples for 17 alpha-hydroxyprogesterone (17-OHP) with the direct-assay kit ("Coat-A-Count" method for serum samples) from Diagnostic Products Corp. (DPC). The specimens were from 50 patients with known or suspected congenital adrenal hyperplasia (CAH); 74 mostly hospitalized neonates and infants, ages three days to three months; and 116 other patients, ages six months to 23 years. Samples from the CAH group were also analyzed with our in-house assay. For 39 of the neonatal samples, the analysis with the DPC assay was repeated with re-solubilized material that had been extracted from the serum with organic solvents. Values for "17-OHP" measured with the DPC direct assay were high, not only in CAH patients, but also in many of the unaffected neonates and infants. The extraction properties of the cross-reacting immunoreactive material into various organic solvent systems were different from those of 17-OHP, and were more like those of steroid sulfates. Because of this significant cross-reactivity, we recommend that the DPC kit not be used for sera from children younger than six months of age, unless the method is modified to include an extraction step.

Isoenzymes of creatine kinase (ATP:creatine phosphotransferase; EC 2.7.3.2; CK) were measured by electrophoresis in serum from cord blood and skin-puncture blood taken from 45 healthy full-term infants during the first three postnatal days. Mean total CK activities (in U/L at 30 degrees C) were 185 in cord samples, 536 in samples taken between 5--8 h postnatally, 494 between 24--33 h, and 288 in the 72-100 h samples. Values for all three isoenzymes increased to a peak over this period, with the highest values generally being found in the samples taken 5--33 h after birth; the subsequent decline was most rapid for CK-BB. Serum CK isoenzymes in cord samples and those taken at 72--100 h in the 11 babies delivered by cesarian section did not differ significantly from those of babies delivered vaginally. However the postnatal increases in total CK, CK-MM, and CK-MB (but not in CK-BB) were significantly greater in those patients born by vaginal delivery. The reasons for the increases in CK isoenzymes after birth are not clear, but our results and reported studies on the ontogeny of CK suggest that CK-MB cannot be regarded as a "cardiac-specific" isoenzyme in the neonatal period.