Biomedical subjects
J M Pearce
Publications and source records attributed to J M Pearce.
Adrenal and nigral transplants for Parkinson's disease.
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Variability in biothesiometry: an error of technique?
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Doppler ultrasound of the uteroplacental circulation as a screening test for severe pre-eclampsia with intra-uterine growth retardation.
Two hundred primiparae underwent continuous-wave Doppler investigation of the uteroplacental circulation at 18-20 weeks gestation as a possible screening test for hypertension in pregnancy. Seventy-five women with abnormal waveforms suggestive of high uteroplacental resistance were tested again at 24 weeks when 21 demonstrated a persistent abnormality. Only nine (43%) of these went on to have an uncomplicated pregnancy, as compared with 150 (84%) of the remainder. Seventeen (8.5%) of the women in the study developed a hypertensive disorder of pregnancy, five of whom had abnormal waveforms at 18-20 weeks and at 24 weeks. These five women had a more severe degree of hypertension with proteinuria or intra-uterine growth retardation, and two required clinical intervention before term. The remaining 12 women were delivered at term of average, or heavier than average babies. Doppler investigation of the uteroplacental circulation at 24 weeks may prove to be a sensitive screening test for later severe pre-eclampsia with intra-uterine growth retardation.
Maternal blood viscosity and uteroplacental blood flow velocity waveforms in normal and complicated pregnancies.
According to the Poiseuille-Hagen law, viscosity influences flow resistance. A possible effect of blood viscosity upon the resistance index of the uteroplacental circulation as measured by continuous wave Doppler ultrasound was investigated in 50 pregnant women. It was found that blood viscosity variables explained only about 10% of the variation in the resistance index in all patients, which was not statistically significant. It is suggested, therefore, that the vascular contribution to flow resistance may be more important.
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.
Brown-Séquard's description of spontaneous cerebellar haemorrhage.
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The thalamic syndrome of Dejerine and Roussy.
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Specific therapy in severe fetal intrauterine growth retardation: failure of prostacyclin.
Two case histories of severe, early onset intrauterine growth retardation are presented. Intravenous prostacyclin was administered in an attempt to promote fetal growth and thus prolong the pregnancy, but was unsuccessful and resulted in intrauterine death in each case. The possible reasons for the failure of this treatment and alternative therapeutic options are discussed.
Interactions between conditioned stimuli for food and water in the rat.
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Optic neuropathy and multiple myeloma.
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Effect of changing the unconditioned stimulus on appetitive blocking.
In four experiments we examined the effects of changing the unconditioned stimulus (US) on appetitive blocking. In Experiments 1A, 1B, and 2 we established that substituting food for water, or water for food, in the compound stage did not attenuate blocking relative to groups that received the same US throughout conditioning. Experiment 3 showed that satiation with the US used prior to compound conditioning with a different US does not affect blocking. Experiment 4 revealed that changing the location of US delivery, as well as the quality of the US, also leaves blocking unaffected. It is suggested that these results demonstrate that blocking occurs, provided that there is no change in the affective properties of the US.
The orienting response as an index of stimulus associability in rats.
The strength of the orienting response (OR) to a light and its associability was studied in three experiments. In Experiment 1, three groups of rats received serial conditioning in which the light served as the first element of a serial compound. For Group Diff the light was followed by a conditioned stimulus (CS) of 10-s duration on some trials and by a different CS of 30-s duration on others. For the other groups, the light was also followed by different stimuli, but these had equivalent durations. This procedure resulted in a stronger OR toward the light in Group Diff than in either of the other groups. In Experiments 2 and 3 the OR was stronger to a light that was followed by a 10-s CS on some trials and by a 30-s CS on others than to one that was followed by different CSs that were both randomly either 10 s or 30 s. Following this training, both excitatory and inhibitory conditioning with the light was faster in those groups for which the light elicited a strong rather than a weak OR. These results are most readily explained by the proposal that the strength of the OR toward a CS is determined by the accuracy with which the value of its immediate consequences can be predicted and that this OR can be used as an index of the associability of the CS.
The locked in syndrome.
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Doppler studies in the growth retarded fetus and prediction of neonatal necrotising enterocolitis, haemorrhage, and neonatal morbidity.
In 82 consecutive cases of intrauterine growth retardation managed by established criteria fetal Doppler studies identified 29 fetuses with absence of end diastolic frequencies in the fetal aorta. These same fetuses were significantly more growth retarded (p less than 0.001) and had an earlier gestational age at delivery (p less than 0.001) than those with end diastolic frequencies present. A subgroup of these cases was analysed in more detail to examine the prognostic value of this phenomenon for the neonate. Two groups of neonates of equivalent gestational age and with a birth weight below 2000 g were compared. There were 26 neonates with absent end diastolic frequencies (group 1) and 20 with end diastolic frequencies (group 2) in the fetal aorta. Those in group 1 were more likely to suffer perinatal death (p less than 0.05), necrotising enterocolitis (p less than 0.01), and haemorrhage (p less than 0.05). Only 4 (15%) of the babies in group 1 had an uncomplicated neonatal period compared with 15 (75%) in group 2 (p less than 0.001). The circulatory changes identified in these cases may provide a more sensitive measure of critical fetal compromise than current techniques and thus allow the clinician to deliver the fetus before irreversible tissue damage has occurred.
Changes in the VEP in preterm neonates with arousal states, as assessed by EEG monitoring.
The effect of sleep state on the visual evoked potentials (VEPs) in neonates was investigated in 7 preterm infants. Polygraphic monitoring including EEG, EOG, ECG, respirogram and submental EMG for the purpose of sleep staging was carried out on all infants simultaneously with VEP testing. Awake-sleep stages were classified into 4 states: awake, transitional or atypical, quiet sleep and active sleep. VEPs were recorded from Oz, referenced to Fz, in response to binocular stimulation with light-emitting diode goggles. Polygraphic and EEG data were analyzed separately. Reproducible VEPs that were appropriate for their ages were seen in all infants in the awake state. The N300 was the most reliable component across sleep states but there was a significant decrease in amplitude with quiet sleep. There were no significant differences among awake, atypical or active sleep states. The other two VEP components followed the same trends as the N300. The P200, present in the older infants, disappeared in both active and quiet sleep states; the P400 was typically variable but reliably present in the awake or atypical states. When a distinction is made between quiet sleep and other arousal states, consistent and significant differences emerge. Our results emphasize the need to test infants in the same arousal states in studies of VEPs in order to make valid comparisons of latency or amplitude changes, particularly with longitudinal or follow-up studies.
Acute atherosis in preeclampsia: maternal determinants and fetal outcome in the presence of the lesion.
In 39 patients with preeclampsia a detailed analysis of some maternal factors, fetal outcome, and a histologic assessment of the presence or absence of acute atherosis in maternal intrauterine vessels has been done. There was no statistically significant relation between acute atherosis and parity, degree of proteinuria, severity and duration of hypertension, or antihypertensive therapy. These findings do not support a purely hemodynamic pathogenesis for the vasculopathy. Fetal outcome was only marginally worse in the preeclamptic patients who developed acute atherosis.
Making waves: current controversies in obstetric ultrasound.
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