False negative results from using common PCR reagents

Background\ud The sensitivity of the PCR reaction makes it ideal for use when identifying potentially novel viral infections in human disease. Unfortunately, this same sensitivity also leaves this popular technique open to potential contamination with previously amplified PCR products, or "carry-over" contamination. PCR product carry-over contamination can be prevented with uracil-DNA-glycosylase (UNG), and it is for this reason that it is commonly included in many commercial PCR master-mixes. While testing the sensitivity of PCR assays to detect murine DNA contamination in human tissue samples, we inadvertently discovered that the use of this common PCR reagent may lead to the production of false-negative PCR results.\ud \ud Findings\ud We show here that contamination with minute quantities of UNG-digested PCR product or any negative control PCR reactions containing primer-dimers regardless of UNG presence can completely block amplification from as much as 60 ng of legitimate target DNA.\ud \ud Conclusions\ud These findings could potentially explain discrepant results from laboratories attempting to amplify MLV-related viruses including XMRV from human samples, as none of the published reports used internal-tube controls for amplification. The potential for false negative results needs to be considered and carefully controlled in PCR experiments, especially when the target copy number may be low - just as the potential for false positive results already is

Identification, characterisation, and molecular analysis of the alternatively spliced forms of the Luteinizing hormone receptor on the ovine ovary / Dean J. Bacich.

Errata posted onto front end paper.Bibliography: leaves 264-330.xxiii, 330 leaves : ill. (some col.) ; 30 cm.Provides evidence that the alternatively spliced LHR transcripts are translated in vivo and consequently suggests the alternatively spliced products may play an important role in ovarian function.Thesis (Ph.D.)--University of Adelaide, Dept. of Obstetrics and Gynaecology, 199

False negative results from using common PCR reagents

Abstract Background The sensitivity of the PCR reaction makes it ideal for use when identifying potentially novel viral infections in human disease. Unfortunately, this same sensitivity also leaves this popular technique open to potential contamination with previously amplified PCR products, or "carry-over" contamination. PCR product carry-over contamination can be prevented with uracil-DNA-glycosylase (UNG), and it is for this reason that it is commonly included in many commercial PCR master-mixes. While testing the sensitivity of PCR assays to detect murine DNA contamination in human tissue samples, we inadvertently discovered that the use of this common PCR reagent may lead to the production of false-negative PCR results. Findings We show here that contamination with minute quantities of UNG-digested PCR product or any negative control PCR reactions containing primer-dimers regardless of UNG presence can completely block amplification from as much as 60 ng of legitimate target DNA. Conclusions These findings could potentially explain discrepant results from laboratories attempting to amplify MLV-related viruses including XMRV from human samples, as none of the published reports used internal-tube controls for amplification. The potential for false negative results needs to be considered and carefully controlled in PCR experiments, especially when the target copy number may be low - just as the potential for false positive results already is.</p

From Initial Deterrence to Longterm Escalation: Short-Custody Arrest for Poverty Ghetto Domestic Violence

Persons arrested for misdemeanor domestic violence are held in custody for widely varying lengths of time. To test the effects of this variance, we randomly assigned short (X̄= 2.8 hours), full (X̄= 11.1 hours), and no arrests (warning only) to a sample of 1,200 cases with predominantly unemployed suspects concentrated in black ghetto poverty neighborhoods in Milwaukee. Victim interviews and one official measure showed that short arrest had a substantial initial deterrent effect relative to the warning group. Longer term follow‐up and before‐after analysis, however, found neither arrest group reflected any deterrence. On the most comprehensive official measure, short arrest consistently showed significantly higher long‐term recidivism than no arrest. Its deterrent effect ended at 30 days, but its criminogenic effect was significant after one year. We conclude that short‐custody arrests for domestic violence in poverty ghetto areas may pose a dilemma between short‐ and long‐term crime control, but longer custody arrests have no clear long‐term effect in either direction