Search PubMed⌕ Search

Biomedical subjects

J M Pearce

Publications and source records attributed to J M Pearce.

At least 37 records · Page 2Linked to original sources
PubMed1995

Supernormal conditioning.

In Experiment 1, rats received an A+AX degrees discrimination in which food was presented after Stimulus A by itself but not after a simultaneous compound of A with Stimulus X. AX was then paired with food in a 2nd stage, followed by test trials with A alone. Responding on the test trials with A was more vigorous than during a control stimulus that had been consistently paired with food. The remaining experiments were of similar design to Experiment 1, except that the 2nd stage also contained conditioning trials with X. The results from the test trials were essentially the same as for Experiment 1. The high level of responding during the test trials with Stimulus A is regarded as evidence of supernormal conditioning. Overall, the results are more consistent with a configural than an elemental theory of conditioning.

Animals↗
PubMed1995

Stimulus salience and negative patterning.

Rats in Experiment 1 received a negative patterning discrimination in which food was delivered after either of two auditory stimuli when they were presented individually, but not when they were presented in compound. The stimuli were of different intensity. The discrimination between the compound and the stimulus of lower intensity was acquired more readily than was the discrimination between the compound and the more intense stimulus. A similar pattern of results was found in the remaining two experiments, which also employed a negative patterning discrimination, but either with stimuli from different modalities (Experiment 2) or with pigeons rather than rats (Experiment 3). The results were predicted more readily by a configural than by an elemental theory of conditioning.

Animals↗
PubMed1995

The placebo enigma.

Explore the source record for details and available documents.

Anti-Anxiety Agents↗
PubMed1994

Transmission of varicella-zoster virus from a vaccinee with leukemia, demonstrated by polymerase chain reaction.

A 5-year-old white boy in remission from acute lymphoblastic leukemia who was receiving maintenance anticancer chemotherapy had approximately 200 vesicular skin lesions 1 month after receiving live attenuated varicella vaccine. About 2 to 3 weeks later, a mild illness resembling varicella occurred in his susceptible siblings and in three of his classmates. Vaccine-type varicella-zoster virus was demonstrated by polymerase chain reaction in swab specimens from vesicular lesions in his two siblings, in whom antibody to varicella-zoster virus also developed.

Chickenpox↗
PubMed1994

Similarity and discrimination: a selective review and a connectionist model.

The 1st part of this article evaluates the extent to which 2 elemental theories of conditioning, stimulus sampling theory and the Rescorla-Wagner (1972) theory, are able to account for the influence of similarity on discrimination learning. A number of findings are reviewed that are inconsistent with predictions derived from these theories, either in their present form or in various modified forms. The 2nd part of the article is concerned with developing an alternative, configural account for discrimination learning. In contrast to previous configural theories, the present version is set within the framework of a connectionist network.

Animals↗
PubMed1994

Doppler ultrasound of the uteroplacental circulation in the prediction of pregnancy outcome in women with raised maternal serum alpha-fetoprotein.

OBJECTIVE: To determine whether Doppler waveforms from the uteroplacental circulation could improve the prediction of pregnancy outcome in women with raised maternal serum alpha-fetoprotein and a structurally normal fetus. The study further attempts to determine whether the presence of an early diastolic notch would constitute a better screening test than waveform patterns. DESIGN: An observational study. SETTING: A tertiary referral obstetric service. SUBJECTS: All women referred to St George's Hospital with a raised maternal serum alpha-fetoprotein had waveform measurements from the uteroplacental circulation after exclusion of fetal abnormalities. Pregnancy outcome was determined by questionnaire sent to the referring clinicians. MAIN OUTCOME MEASURES: Adverse perinatal outcome in the form of preterm labour, low birthweight and perinatal mortality. RESULTS: Data from 332 cases were available for analysis. Women with a normal pattern of uteroplacental waveforms had a perinatal mortality of 9.6/1000. Women with a uniform high resistance pattern had a perinatal mortality of 846/1000, and those with a mixed resistance pattern had a perinatal mortality of 268/1000. Overall there were 27 cases of placental abruption which accounted for eight of the 50 perinatal deaths. The remainder were due to prematurity or low birthweight or both. The presence of the early diastolic notch did not improve on the waveform patterns in the prediction of perinatal death. CONCLUSION: Women with raised maternal serum alpha-fetoprotein and normal Doppler waveform patterns from the uteroplacental circulation can be reassured, but mixed or uniform high resistance patterns should encourage increased surveillance and a search for intervention therapies.

Blood Flow Velocity↗
PubMed1994

Low dose aspirin in women with raised maternal serum alpha-fetoprotein and abnormal Doppler waveform patterns from the uteroplacental circulation.

OBJECTIVE: To investigate the use of low dose aspirin in the reduction of perinatal morbidity and mortality in women with unexplained raised maternal serum alpha-fetoprotein and abnormal uteroplacental Doppler waveform patterns. DESIGN: Prospective randomised controlled trial. SETTING: A tertiary referral obstetric service. SUBJECTS: One hundred and sixty-four women referred to our unit with raised maternal serum alpha-fetoprotein and a structurally normal fetus had abnormal uteroplacental Doppler waveform patterns at 24 weeks of gestation. INTERVENTION: Women were randomly allocated to two groups, receiving either low dose aspirin 75 mg (n = 76) or placebo (n = 88) daily until delivery. MAIN OUTCOME MEASURES: Preterm labour, low birthweight, the occurrence of placental abruptions and perinatal mortality. RESULTS: The frequency of severely small for gestational age infants (birthweight < 5th centile) was reduced in the aspirin treated group to 16% compared with 25% in the placebo group (95% CI-21% to 13%). The frequency of delivery before 34 weeks of gestation was 26% in the aspirin group and 42% in the placebo group (95% CI--30% to 1%). The perinatal mortality was 240/1000 in the aspirin group and 320/1000 in the placebo group (95% CI--22% to 6%). None of these reductions was statistically significant. Although the frequency of placental abruptions was similar in the two groups, significantly more babies died from abruption in the aspirin treated group (91% versus 30%, 95% CI 28% to 94%). Low dose aspirin did cause a significant reduction (P = 0.008) in deaths from causes other than placental abruption. CONCLUSION: This trial revealed a benefit of low dose aspirin therapy in women with raised maternal serum alpha-fetoprotein and abnormal uteroplacental Doppler waveform patterns, but the effect was smaller than expected. Although a reduction in deaths from small preterm babies was observed, there was an increase in the number of deaths following placental abruption without a significant increase in the number of abruptions. We recommend that this should be considered before giving aspirin to these high risk women and that other investigators should specifically look for this effect.

Adult↗
PubMed1994

Randomised controlled trial of the use of human chorionic gonadotrophin in recurrent miscarriage associated with polycystic ovaries.

OBJECTIVE: To determine whether the use of human chorionic gonadotrophin (hCG) would reduce the recurrent miscarriage rate in women with polycystic ovarian disease. DESIGN: Double-blind, prospective, randomised controlled trial. SETTING: A pregnancy loss clinic in a London teaching hospital. SUBJECTS: One hundred and ninety-one women with a history of three consecutive spontaneous first trimester miscarriages and polycystic ovary syndrome. INTERVENTION: 10,000 i.u. of hCG or a placebo were given when the leading follicle was > or = 21 mm, then 5000 i.u. of hCG or a placebo were given twice weekly until miscarriage or the tenth week of pregnancy. MAIN OUTCOME MEASURE: Miscarriage rate. RESULTS: Women with polycystic ovaries who received hCG treatment had a lower miscarriage rate (14%) compared with women who received placebo (43%). In women with follicular phase luteinising hormone > 10 iu/l, those who received hCG therapy had a miscarriage rate of 10% compared with a rate of 44% in women who received the placebo. When clomiphene was used for ovulation induction, women treated with hCG had a miscarriage rate of 14% compared with a rate 47% in women who received the placebo. There was no significant benefit from hCG therapy in natural cycles. CONCLUSION: The use of hCG in women with recurrent miscarriage and polycystic ovary syndrome improves the pregnancy outcome.

Abortion, Habitual↗
PubMed1994

A comparative study of the fetal electrocardiogram recorded by the STAN an Nottingham systems.

OBJECTIVE: To compare the T:QRS ratio recorded by the STAN and Nottingham fetal electrocardiogram (FECG) monitors. DESIGN: Prospective observational study. SETTING: London teaching hospital delivery suite and research unit. METHODS AND SUBJECTS: The T:QRS ratios generated by the STAN and Nottingham FECG monitors were simultaneously recorded and compared using signals generated from a computer-produced ECG signal and signals from 11 term fetuses recorded during labour. RESULTS: There was an acceptable level of agreement between the two systems with the computer-generated signals, but it was not clinically acceptable with the signals from the fetuses recorded during labour. Disagreements in the T:QRS values were probably due to differences in the reference points for the measurement of the S-T segment and T-wave height. CONCLUSION: The different points of reference for measurement of S-T segment and T-wave height can explain poor agreement between the two methods of FECG waveform analysis. The suggested adopted points of reference are those corresponding to adult electrocardiographic methodology.

Delivery, Obstetric↗
PubMed1994

Headache.

Explore the source record for details and available documents.

Headache↗