We describe a pilot study to determine the effect of delays in blood sample processing under simulated field conditions on measurement of corticotropin-releasing hormone (CRH) levels in pregnant women. CRH, a peptide secreted by the placenta into the maternal blood, is of interest in epidemiological studies of gestational duration. Many investigators suspected that CRH might break down quickly after collection, and believed the optimal treatment of blood samples for CRH must include immediate processing under chilled conditions and quick freezing of plasma. Epidemiological studies often have logistical constraints that make such rapid processing unfeasible. To examine how delays in the processing of blood samples might affect the level of measured CRH, we collected whole blood samples from 33 pregnant women attending a prenatal clinic in Boston. We compared CRH levels measured following three different processing delays with the levels of samples that were processed immediately after blood collection, the 'gold standard'. The delayed strategies involved placing the freshly collected whole blood in a cooler or refrigerator for up to 22 h prior to processing. Correlation coefficients comparing delayed with gold standard processing exceeded 0.96. These results suggest that CRH may be measured in blood samples that were spun and frozen up to 22 h after blood collection.
The supernatant and pellet retentate fractions obtained from sera from pregnant mice by ammonium sulfate fractionation and extensive dialysis cannot alone induce increased rosette inhibition titres in the rosette inhibition assay. In combination, however, the mixtures can induce increased rosette inhibition titres mimicking the activity of pregnancy sera previously ascribed to the early pregnancy factor. The studies described herein demonstrated that the supernatant retentate fractions derived from sera of pregnant mice were functionally equivalent to a platelet-activating factor (PAF) or a serum stimulus because they stimulated the spleen cells used in the assay to produce active moieties and cooperated with pure thioredoxin in allowing for expression of activity. Conversely, the pellet retentate fractions obtained from sera of pregnant mice were shown to be functionally equivalent to thioredoxin in that they cooperated with a PAF stimulus to allow for the expression of increased rosette inhibition titres. The supernatant retentate fractions obtained from sera from male mice were found to be functionally equivalent to the corresponding supernatant retentate fractions obtained from sera from pregnant mice in stimulating the production of active moieties and in cooperating with thioredoxin or the pellet fractions derived from sera from pregnant mice in allowing for increased rosette inhibition titres. The pellet retentate fractions obtained from male mouse sera, however, were not functionally equivalent to either thioredoxin or the corresponding pellet retentate fractions obtained from pregnancy sera. Consideration of these data led to a basic description of the system of components in pregnancy sera which is responsible for the expression of early pregnancy factor activity.
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