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J M Pearce

Publications and source records attributed to J M Pearce.

At least 127 records · Page 7Linked to original sources
PubMed1994

Problems in the clinical use of intrapartum fetal ECG monitoring.

Commercial machines are now available to monitor the fetal electrocardiograph in labour (Cinventa, Sweden). We report our experience of the first one hundred women we monitored by this method. They were divided into five groups dictated by the change in the fetal scalp electrode used for monitoring and the changes made in the computer software used for signal processing. There were progressive significant improvements in the ability of the system to produce a continuous heart rate trace such that it became acceptable for routine fetal monitoring. The quality of the electrocardiogram improved to 50% of the 'check ECG complexes' being printed accurately. Electrical signal distortion causing baseline wander is however the significant remaining problem. On-line analysis of the T/QRS ratio improved very significantly from 36% to 84% of the monitoring time. There were no significant improvements in the recordings made in the second stage, which remained poorer in quality and reliability in all groups. As well as changes in the computer software, the use of a single helix electrode and practical experience contributed to the improvements.

Cardiotocography↗
PubMed1993

Lymphocyte responses and virus excretion as risk factors for intrauterine infection with cytomegalovirus.

Serological screening of pregnant women in this and a previous study identified 28 cases of primary infection with cytomegalovirus, 7 (25%) of whom transmitted the infection to their fetuses. Risk factors for intrauterine infection were: 1) age less than 20 years, 2) Caucasian rather than non-Caucasian race, 3) a weak response to cytomegalovirus antigen in the lymphocyte transformation test, and 4) the excretion of cytomegalovirus in the urine. The greatest risk was when a weak lymphoproliferative response was detected in combination with a positive result for virus isolation, in which case the chance of fetal infection was 83%. Despite these associations, there was one important anomalous result of a woman who demonstrated a strong lymphocyte response during pregnancy and a negative result for virus isolation, but who gave birth to an infected baby who developed unilateral hearing loss.

Adult↗
PubMed1993

Resolution of phospholipid molecular species by 31P NMR.

Phosphorus-31 NMR chemical shifts of phospholipids (PLs) solubilized in bile salts were studied with respect to variations in the structure of the acyl substituents. The presence of double bonds in the acyl chains of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidic acid (PA) induced small but consistent upfield shifts relative to the corresponding disaturated acyl PL signals. The magnitudes of the unsaturation-related upfield shifts were approximately twice as large in sodium cholate as in sodium deoxycholate. Chemical shift separations of PC, PE, and PG dipalmitoyl-dioleoyl species pairs increased slightly at lower temperatures. Resolution of the PC species pair was maximized and nearly independent of cholate-to-PL ratio at values greater than about 100 in 2% cholate. Only the PA species resolution varied significantly over the pH range 6.5 to 9.5, in the vicinity of its pK2. Shift differences for a homologous series of disaturated acyl PCs showed a logarithmic dependence on chain length. Spectra for a variety of PC standards were used to interpret the composite PC signals from egg yolk extract, soybean extract and whole human amniotic fluid. The 31P NMR analyses were consistent with published chromatographic studies. Interpretation of composite PL signals in the cholate system is simplified for mixtures having restricted acyl chain length and degree of unsaturation.

Amniotic Fluid↗
PubMed1993

Analysis of saturated phosphatidylcholine in amniotic fluid by 31P NMR.

A technique using solubilization with sodium cholate to resolve 31P NMR resonances of phospholipid molecular species was applied to amniotic fluid samples from 16 subjects. Gestational ages from 25 to 40 weeks were represented, and two subjects were sampled sequentially. Fitting of the partially resolved 31P NMR signal of phosphatidylcholine (PC) generated an estimate of percent disaturated acyl PC (%dsPC) which correlated more highly with gestational age than did several other potential indices of fetal lung maturation, such as the ratio of PC to inorganic phosphate from the solubilized spectra, or PC to sphingomyelin from extract spectra. In a few cases, enzyme-catalyzed PC hydrolysis limited the precision, but did not appear to affect the accuracy, of the %dsPC estimates. Resolution of palmitoyl and oleoyl lyso-PC species was observed for both the 1- and 2-acyl isomers. Upfield shifts due to the presence of cis double bonds in the lone acyl chain of the lyso-PCs were analogous to those observed for the diacyl PCs.

Amniocentesis↗
PubMed1993

Estimation of in situ ultrasound exposure during obstetric examinations.

Layered tissue models are developed to estimate in situ ultrasound intensity during common obstetric examinations by incorporation of measured overlying tissue thicknesses with data on the attenuation properties of tissues. Results are compared with attenuation models recommended by the United States Food and Drug Administration (FDA) and National Council on Radiation Protection and Measurements (NCRP). For abdominal and transvaginal scanning in the first trimester, fixed attenuation models based on attenuation values of 1.2 dB/MHz and 0.6 dB/MHz, respectively, are representative of worst-case exposure conditions. For second and third trimesters, a fixed attenuation value of 0.8 dB/MHz is representative of worst-case exposure conditions. A fixed attenuation value of 1.0 dB/MHz is suggested for common Doppler examinations. The study suggests that the FDA-derating factor of 0.3 dB/cm.MHz may not give a conservative estimate of in situ intensity for certain obstetric examinations.

Embryonic and Fetal Development↗
PubMed1993

Limiting dilution analysis of the allo-MHC anti-paternal cytotoxic T cell response. I: Normal primigravid and multiparous pregnancies.

Anti-paternal cytotoxic T lymphocyte precursor frequencies (CTLpF) were determined by limiting dilution analysis (LDA) in the peripheral blood of eight primigravid and seven multiparous women during the three trimesters of pregnancy. In five of these women the responses to cord blood lymphocytes (CBL) and paternal lymphocytes were also determined at the time of delivery and at 6 weeks post delivery. As controls, CTLpF against unrelated third party donors were determined. A wide range of CTLpF against all three groups of targets was found in both the primigravid and multiparous women, reflecting the wide range of frequencies found in random populations. These frequencies remained fairly constant during and 6 weeks after the pregnancy. Splitwell analysis demonstrated that the responses generated in our culture system were specific to the stimulator. The LDA data conform to single-hit kinetics, indicating that only cytotoxic T cells were limiting in the assay. Proliferative responses of maternal lymphocytes to paternal, cord blood and third party MHC antigens also remained unchanged as determined by time-course mixed lymphocyte reactions (MLR). Our data suggest that there is no significant allo-stimulation or suppression of the maternal immune system during normal pregnancy. The mother remains immunocompetent and is capable of both cytotoxic and proliferative responses to paternally-derived fetal MHC antigens. Our findings confirm that in normal pregnancy the trophoblast, which is devoid of classical MHC antigens, forms an effective immune barrier which prevents interaction of the maternal and fetal immune systems.

Cells, Cultured↗
PubMed1993

Limiting dilution analysis of the allo-MHC anti-paternal cytotoxic T cell response. II: Recurrent spontaneous abortion and the effect of immunotherapy.

Using limiting dilution analysis (LDA) we determined anti-paternal cytotoxic T lymphocyte precursor (CTLp) frequencies in the peripheral blood of 10 women with unexplained recurrent spontaneous abortion (RSA) before and after immunization with paternal lymphocytes. The women and their partners were HLA tissue-typed and none of the women had anti-paternal cytotoxic antibodies (APCA) before immunization. All other known causes of RSA were excluded. All 10 women were found to have high frequencies of specific anti-paternal cytotoxic T cells before immunization (range 1/1030 to 1/9574). Splitwell analysis showed that these cytotoxic cells were specific to paternal MHC antigens. These frequencies rose significantly following immunization (range 1/683 to 1/4652). The cytotoxic T lymphocyte frequencies against an HLA-mismatched third party varied from woman to woman, but were not affected by the immunization. The LDA data conformed to single-hit kinetics, indicating that only cytotoxic T cells were limiting in the assay. Our data are in sharp contrast to the previously held view that women with RSA may be hyporesponsive to paternal MHC antigens. Immunizing such women with paternal leucocytes further sensitizes them. These findings cannot be reconciled with a favourable outcome in the treatment of RSA with immunotherapy. We would argue that this treatment is at best of unproven value, and may even be harmful. That these women may sometimes have successful pregnancies following immunotherapy testifies to the effectiveness of the classical MHC antigen-deficient trophoblast as an immunological barrier between mother and fetus.

Abortion, Habitual↗
PubMed1993

The design, effectiveness and acceptability of the arm sleeve for the prevention of body fluid contamination during obstetric procedures.

OBJECTIVES: 1. To design a device that would reduce contamination of staff during obstetric procedures. 2. To undertake clinical trials to assess the effectiveness and acceptability of such a device. DESIGN: A prospective study. The arm sleeve is made of a nonwoven material laminated on polyethylene film making it waterproof. It has an elastomeric cuff with adhesive that ensures a watertight seal between it and the glove. SETTING: Delivery suite in a teaching hospital. METHODS: Doctors and midwives were requested to wear the sleeve on top of the standard gown and gloves. Each user was assessed for blood contamination at the end of the procedure and a questionnaire detailing the extent of contamination and the views of the user was completed. RESULTS: Eighty questionnaires were completed. The contamination of arms and hands was 3.8% and 5%, respectively. Eighty-nine percent thought the sleeve had served its purpose and 76% said they would use it regularly. CONCLUSIONS: The sleeve is an effective protective device which complements the glove and gown. We recommend that it should be used during all obstetric procedures.

Blood↗
PubMed1993

An audit of general practitioner requests for pelvic ultrasound: analysis of referral patterns and outcome.

OBJECTIVES: 1. To assess the information supplied by general practitioners on the gynaecological ultrasound request form and to determine how this information influences the interpretation of scans; and 2. To examine the influence of scans on the subsequent management of patients both by general practitioners and, where relevant, by hospital gynaecologists. DESIGN: Retrospective analysis of gynaecological ultrasound requests made by general practitioners. Postal questionnaire and assessment of outcome according to general practitioners' records and, where appropriate, the hospital notes. SETTING: A London teaching hospital gynaecological ultrasound department and associated general practices. SUBJECTS: Four hundred ninety-eight women referred by general practitioners for a gynaecological ultrasound scan over a one year period (1990). RESULTS: The 498 requests for gynaecological ultrasound scans included 472 primary diagnostic referrals. Seventy-one percent of general practitioners replied to the questionnaires. Overall, 46% of the scans were normal, but the proportion of normal scans fell to 21% if the date of the last menstrual period and a pregnancy test result were included on the form. Forty per cent of women scanned subsequently were referred for hospital care. CONCLUSIONS: General practitioners would appear to use the ultrasound service in a rational way and therefore there can be no justification for not allowing them open access. The positive diagnostic yield can be further improved if time is taken to supply simple relevant information which may be facilitated by a specific request form.

Abortion, Threatened↗
PubMed1993

Natural history of cluster headache.

A follow-up study of 123 patients with episodic cluster headaches and of 9 patients with chronic cluster headaches was undertaken after 10-25 years, (mean 14.7 and 13.9 years respectively). This shows a significant but low remission rate for both episodic and chronic cluster headache. It confirms the observation that some patients change from episodic to chronic pattern, and that occasionally chronic clusters may become episodic.

Adult↗