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Biomedical subjects

J M Pearce

Publications and source records attributed to J M Pearce.

At least 19 recordsLinked to original sources
PubMed1992

Effects of discrimination training on responding during a compound conditioned stimulus.

Four experiments examined responding in the presence of a triple-element compound ABC after discrimination training in which 2 compounds, AB and BC, signaled the delivery of food and 1 element alone, B, signaled the absence of food. In Experiments 1 and 2, using rats, responding during ABC was more vigorous than in a control group for which A and C but not B had been individually paired with food. This finding was replicated in Experiment 3, which used pigeons, and in Experiment 4, where all 3 stimuli of the control condition were individually paired with food. The results are more consistent with a configural than with an elemental theory of learning.

Animals↗
PubMed1992

Perineal video-ultrasonography in the assessment of vaginal prolapse: early observations.

OBJECTIVE: To investigate the efficacy of perineal ultrasonography in the assessment of vaginal prolapse. DESIGN: A prospective descriptive study. SETTING: Urodynamic Unit, St. George's Hospital, London. SUBJECTS: Six women, three of them were awaiting colposuspension and three had had a colposuspension. INTERVENTIONS: Perineal ultrasound scans were performed on women with and without incontinence and prolapse, both before and after continence surgery. Movement of the bladder, urethra, uterus, vaginal vault and enterocele were observed during coughing and the valsalva manoeuvre. MAIN OUTCOME MEASURES: To assess reproducibility, six patients had six different measurements taken of bladder neck and prolapse position and movement relative to the symphysis. The measurements were plotted upon an X-Y co-ordinate axis. Each measurement was repeated three times and one way analysis of variance performed upon the readings. RESULTS: Perineal ultrasonography clearly demonstrated movement of the whole pelvic floor. Minor degrees of both anterior and posterior vaginal wall prolapse could be seen and quantified. An increase in posterior vaginal wall mobility was noted in women after colposuspension. All measurements taken were found to be reproducible. CONCLUSIONS: Perineal ultrasonography is easy to perform and is reproducible. It may improve understanding of why some women develop posterior vaginal wall prolapse after colposuspension and, conversely, why some women develop incontinence following anterior repair for prolapse.

Cough↗
PubMed1992

Determinants of pregnancy heartburn.

OBJECTIVE: To study the prevalence and severity of reflux symptoms in pregnancy. DESIGN: Self-administered questionnaire detailing age, race, gestational age, parity, weight, height, symptoms and severity of gastro-oesophageal reflux. SETTING: An antenatal clinic in a teaching hospital. SUBJECTS: 607 consecutive women at various stages of pregnancy were recruited during attendance at antenatal clinic. RESULTS: The prevalence of heartburn increased with gestational age (22% in the first, 39% in the second, and 72% in the third trimester; P < 0.0001), as did severity of heartburn (P < 0.0001). Pharyngeal regurgitation as a symptom showed little increase during advancing pregnancy. Symptoms of heartburn rapidly increased towards the end of the second trimester. The decrease in heartburn traditionally expected during the last three weeks of pregnancy (fetal head descent) was not observed. Logistic regression analysis showed increased risk of suffering heartburn with increasing gestational age (P < 0.0001), pre-pregnancy heartburn (P < 0.0001), parity (P < 0.0001) and inversely with maternal age (P < 0.05) but not with body mass index before pregnancy, race, or weight gain in pregnancy. CONCLUSION: Heartburn, but less so pharyngeal regurgitation, increases in prevalence and severity with gestational age and parity. We speculate that hormone-related impairment of distal oesophageal clearance mechanisms may have a crucial bearing on whether heartburn develops in those individuals at greatest risk.

Adult↗
PubMed1992

A configural analysis for feature-negative discrimination learning.

In 4 experiments, rats were initially trained with an A+ AXo discrimination in which Stimulus A by itself signaled the delivery of food, A+, whereas the simultaneous presentation of A and X was followed by nothing, AXo. In each experiment X was then paired with food prior to a test phase in which A and X were again presented for a discrimination. The discrimination was of the form A+ AXo in Experiments 1 and 2, whereas it was of the form X+ AXo for Experiments 3 and 4. In all 4 experiments the test discrimination was acquired more rapidly than a control discrimination. The results are interpreted in terms of the original A+ AXo discrimination resulting in the growth of an association between a representation of the entire AX compound and the effects of nonreinforcement.

Animals↗
PubMed1991

Changes in platelet function in pregnancies complicated by fetal growth retardation.

Platelet function was investigated in three patients with severely decreased fetal growth rates detected by ultrasound scanning. Only one patient had hypertension, which was mild and developed after decreased fetal growth and altered platelet responses had been detected. Much higher concentrations of platelet-activating factor (PAF) (20-500 nM) were required to stimulate maximal platelet aggregation in all three patients compared with the concentrations of PAF (5-10 nM) required in control pregnancies of similar gestational age. In a fourth patient, platelet desensitisation was observed 5 weeks before the detection of decreased fetal growth. These results are similar to those observed in women with hypertensive disorders of pregnancy, and indicate that there may be a similar change in platelet function in gestational hypertension and in fetal growth retardation, although the clinical manifestations are different.

Blood Platelets↗
PubMed1991

[Correlation between the results of Doppler velocimetry with spectral analysis and the viscosity of cord blood].

The contribution of rheological factors to be impedance of blood flow in the umbilical artery as determined by continuous wave Doppler ultrasound was investigated. Of the 51 pregnancies recruited, six were complicated by pre-eclampsia, 10 by intrauterine growth retardation, 15 by both pre-eclampsia and fetal growth retardation, and there were 20 controls. A significant correlation was demonstrated between both plasma viscosity and gestational age and the resistance index used to characterize the Doppler waveform. Multiple regression analysis demonstrated that changes in plasma viscosity explained 55 p. cent of the variance seen in the resistance index and that this was statistically significant. This finding is, however, unlikely to be of clinical significance as whole blood viscosity had an insignificant effect on the impedance in the umbilical artery. We postulate that vascular factors such as the number and calibre of the placenta arterioles are a more important determinant of umbilical artery impedance.

Blood Flow Velocity↗
PubMed1991

Analysis of phospholipids in human amniotic fluid by 31P NMR.

A recently described solvent-reagent system for obtaining narrow linewidths in 31P NMR spectra of phospholipid extracts was applied to human amniotic fluid. Resolution of the major components was achieved by manipulating the solvent composition, and assignments were made by spiking samples with standard compounds. Spin-lattice relaxation times were determined and used to optimize data acquisition. NMR estimates of the phosphatidylcholine to sphingomyelin ratio for 33 patients were compared to those obtained by TLC densitometry, a common clinical assay for fetal pulmonary maturity. Estimates of the levels of phosphatidylglycerol and phosphatidylinositol could also be obtained from 31P NMR. High-resolution 31P NMR in this solvent-reagent system provides a relatively straightforward and reliable alternative method for assessing fetal pulmonary status by phospholipid quantitation in human amniotic fluid. The 31P NMR method has the advantage that it is sensitive to total, and not just unsaturated, phosphatidylcholine.

Amniotic Fluid↗
PubMed1991

A comparison of Doppler flow velocity waveforms, amniotic fluid columns, and the nonstress test as a means of monitoring post-dates pregnancies.

Five hundred thirty-four pregnancies exceeding 294 days were monitored by weekly sonographic estimations of amniotic fluid columns, daily maternal recordings of fetal movements, and thrice-weekly nonstress tests. In addition, each woman received twice-weekly studies of the uteroplacental and umbilical circulations by means of Doppler ultrasound. There were no fetal deaths in the study. Of the individual methods of fetal surveillance, absence of end-diastolic frequencies in the umbilical artery was the most sensitive, predicting 91% of fetuses who developed fetal distress in the first stage. Combining the test with sonographic estimation of amniotic fluid columns improved the prediction to 100%, with only a minimal fall in the specificity. These results strongly suggest that a combination of umbilical artery Doppler waveforms and amniotic fluid determinations is an adequate method of monitoring the post-dates pregnancy.

Adult↗