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Biomedical subjects

G Hackett

Publications and source records attributed to G Hackett.

9 recordsLinked to original sources
PubMed1991

Extraction of DNA from amniotic fluid cells for the early prenatal diagnosis of genetic disease.

Ten-ml samples of amniotic fluid were taken from pregnancies being terminated at 8-14 weeks' gestation. DNA was extracted from the amniotic cells by sequential centrifugation and analysed using the polymerase chain reaction (PCR). Fifteen samples were analysed for evidence of maternal contamination using Mfd5 oligonucleotide primers for repeat polymorphisms. Ten amniotic fluid samples were tested for the Delta-F508 deletion characteristic of cystic fibrosis to demonstrate a diagnostic application for the technique. In each case, DNA extracted from fetal tissue from the same pregnancy was included in the controls. In 14 of the 15 cases tested with the Mfd5 primers, both the amniotic fluid DNA and the fetal DNA showed no evidence of contaminating DNA. In one case, neither the amniotic fluid cells nor the fetal cells yielded results. In nine of the ten cases tested with the Delta-F508 primers, the amniotic fluid cell DNA provided accurate information about the genetic status of the fetus; in the tenth, the fetal DNA failed to amplify. The results indicate that adequate DNA can be extracted from amniotic fluid from 8 weeks' gestation onward and these samples are suitable for prenatal diagnosis using PCR.

Adult↗
PubMed1988

References ranges and sources of variation for indices of pulsed Doppler flow velocity waveforms from the uteroplacental and fetal circulation.

Variation in indices used to characterize the maximum frequency outline of waveforms obtained from the uteroplacental and fetal circulations by duplex Doppler ultrasound was studied between observers, over a 24-h period and before and after a meal. No significant differences were found. Reference ranges were derived for three indices, the A/B ratio, the resistance index and the pulsatility index, for waveforms from the fetal descending aorta, umbilical artery, and the placental and maternal sides of the uteroplacental circulation. Indices from waveforms from the uteroplacental circulation demonstrated a fall from 16 to 24 weeks gestation with no change thereafter. The umbilical artery indices demonstrated a continuing fall with increasing gestation but the A/B ratio and resistance index from the fetal descending aorta did not change with gestation. The pulsatility index from the aorta demonstrated a gentle rise.

Adult↗
PubMed1986

Early diagnosis of intrauterine growth retardation by Doppler ultrasound.

The significance of intrauterine growth retardation (IUGR) and the methods currently available for assessment of fetal growth are briefly reviewed. The use of Doppler ultrasound assessment of the flow velocity waveform (FVW) of the uteroplacental waveform at 16-18 weeks of gestation is outlined. A pilot study of 127 pregnancies suggested that the sensitivity of the test was 67% and the specificity 65%. The prediction value of a negative test was 92%. Six of the 14 cases of IUGR had a normal FVW, but 3 of these had asymmetrical morphology. Four of the 8 IUGR cases with an abnormal FVW required delivery by cesarean section. The FVW also appears to be a valuable predictor of pregnancy-induced hypertension and fetal asphyxia.

Blood Flow Velocity↗
PubMed1986

Qualitative assessment of uteroplacental blood flow: early screening test for high-risk pregnancies.

A pulsed Doppler apparatus was used to assess the blood flow velocity profiles in uterine vessels (arcuate arteries) at 16 to 18 weeks' gestation to determine if complications associated with impaired trophoblastic invasion of the placental bed (ie, pregnancy-induced hypertension, intrauterine growth retardation, and fetal asphyxia) could be predicted by this measurement. Thirty-one of 126 consecutive pregnancies developed one or more of the above complications. The sensitivity was 68% and the specificity 69%; the predictive value of a positive test was 42% and that of a negative test 87%. These results seem to represent an improvement over existing predictive techniques. Early identification of such a high-risk group might allow more discerning use of antenatal resources and may lead to new therapeutic measures.

Blood Flow Velocity↗
PubMed1979

Improving exposure component and generalization potential of stress inoculation for pain.

Stress inoculation for pain involves education about the psychological dimensions of pain, training in a number of coping skills, and practice in applying these skills during exposure to the noxious stimulus. In a previous study the exposure component (which involved six practice sessions) proved ineffective; moreover the efficacy of the other components was not repeated on the generalization measures. The present study compared three variations in the exposure component and found that training with a single practice session on the cold pressor task proved more helpful than training with no practice at all, which in turn was no worse than training with six practice sessions. Moreover, therapeutic attention to generalization resulted in increased pain tolerance on the pressure algometer task.

Behavior Therapy↗