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Biomedical subjects

A M Chang

Publications and source records attributed to A M Chang.

At least 91 records · Page 5Linked to original sources
PubMed1996

The effects of parity on birthweight using successive pregnancies.

OBJECTIVE: Accurate assessment of the difference in birthweight between first and second live-births to the same woman having excluded the effects of physiological factors known to affect birthweight. DESIGN: Retrospective longitudinal observational study. SETTING: Three large obstetric units in the East Midlands of the United Kingdom. SUBJECTS AND METHODS: Women in whom data were recorded for their first two pregnancies on the UK East Midlands Obstetric database which resulted in the delivery of a liveborn, singleton and congenitally normal baby. Six thousand five hundred and thirty such cases were identified, of which 3457 had complete datasets and delivered both babies at term (259 to 300 days). An analysis was performed of changes between the paired pregnancies of physiological factors known to affect birthweight. Regression analyses were used to enable prediction of the second birthweight with the knowledge of the first birthweight. RESULTS: The mean crude birthweight difference between first and second pregnancies was an increase of 138 g. Significant differences between the paired pregnancies were found in maternal booking visit weight, blood pressure, maternal age and gestation at delivery. Independent factors affecting difference in birthweight were gestation at delivery, maternal booking weight and baby's sex. Regression towards the mean was demonstrated which meant that a woman delivering a first baby weighing more than 3720 g could expect a lighter baby for her second delivery provided that all other factors remained constant. CONCLUSIONS: In general terms a woman is more likely to deliver a heavier baby in her second pregnancy than in her first pregnancy. However, maternal physiological factors differ in the two pregnancies and these differences have additional effects on birthweight. The effects of both these observations are tempered by regression towards the mean which has a profound influence in predicting the likely change in birthweight between first and second pregnancies. Clinical decisions should not be based on the assumption that a second baby will inevitably be heavier than the first baby.

Birth Order↗
PubMed1995

Frequent ras gene mutations in squamous cell cervical cancer.

Eighty samples of cervical invasive squamous cell carcinoma were examined for ras gene mutations using polymerase chain reaction (PCR) followed by restriction enzyme digestion. We found 28 (35%) cervical cancers contained ras mutations at H-ras codon 12, 49 (61%) at K-ras codon 12, and 5 (6%) at K-ras codon 13. There were no significant differences in incidence of the ras gene mutations among different histologic grades or clinical stages of the cancer (P > 0.05). This result suggests that ras mutation may be an important step involved in a substantial number of cervical carcinoma. The interaction of ras with other genes and/or events may also be involved in pathogenesis of this malignancy.

Alleles↗
PubMed1995

Postnatal development of cytochrome P4501A1 and 2B1 in rat lung and liver: effect of aged and diluted sidestream cigarette smoke.

Earlier studies have shown that both mainstream and sidestream cigarette smoke increase the activities of cytochrome P4501A1 and 2E1 in the lungs of adult animals; however, little information is available on the influence of ambient levels of sidestream cigarette smoke on cytochrome P450 monooxygenase activity in the developing lung. The present studies were conducted to define the developmental profiles of cytochrome P450 monooxygenases 1A1 and 2B1 in rat lung and liver and to assess the effects of aged and diluted sidestream cigarette smoke (ADSS) on the developmental profile of these two enzymes. Accordingly, pulmonary and hepatic microsomal P4501A1 and 2B1 activities were determined by measuring ethoxy- and pentoxyresorufin-O-delakylase (EROD and PROD, respectively) activity in animals exposed to filtered air or ADSS from birth to 7, 14, 21, 50, and 100 days of age. Pulmonary P4501A1 activity in control rats was not detected until 14 days of age. Activities increased threefold between 14 and 21 days of age and remained unchanged to 100 days of age. In animals exposed to ADSS from birth, pulmonary EROD activities were detected as early as 7 days postnatal and were elevated three- to fourfold above control at all other ages examined. Hepatic EROD activities were unaltered by ADSS exposure. Short-term (4-day) ADSS exposure was as effective in upregulating pulmonary microsomal EROD activities as 100-day exposures. Induction of pulmonary EROD activities and the associated increases in mRNA levels were dependent upon the particulate fraction. Stimulation of EROD activities in major and minor daughter subcompartments was three- to fourfold higher in ADSS-exposed animals compared to controls, while there was no induction in the trachea and less than a twofold increase in the parenchyma. Pulmonary PROD activities developed more slowly than EROD and did not reach adult levels until Day 50. ADSS did not alter pulmonary or hepatic PROD activities. These studies show that P4501A1 and 2B1 develop at different rates in rat lung and liver and that exposure to ADSS markedly increases P4501A1 activities in the lung at all ages examined.

Aging↗
PubMed1995

Perceived functions and usefulness of health service support workers.

Support workers have been advocated as a means of overcoming a shortage of professional nursing practice, whether this shortage is derived from a decrease in budgeted positions or from a lack of persons to fill positions. The demand for nursing practice has increased because of a rise in the intensity and complexity of patient care. The purpose of this study was to examine professional nurses' views on the non-nursing duties they were currently performing and the possible use of support personnel to assist them in their role of providing patient care. Group interviews of qualified nurses were used to develop a questionnaire comprising 40 items concerning support worker duties, 26 non-nursing duties and one item requesting respondents to indicate if a support worker would be useful: 408 (60%) nurses completed the questionnaire and 71% agreed that a support worker would be useful. Twenty-three support worker activities were statistically significant (P < 0.01) in the level of agreement and variation from the undecided position. The significant groups of support worker activities determined by principal component analysis using a single factor were clerical, cleaning and stocking and direct patient care, while the indirect patient care group of activities was not significant. Forty-six per cent of the non-nursing duties were agreed to, while 50% were seen to be the role of the nurse. There were areas of support worker activity which were related to agreed non-nursing duties and other areas where there was an overlap, with the duties being seen as both nursing and suitable for the support worker.

Adult↗
PubMed1995

Role determination in nursing--implications for service provision.

The current changes in nursing practice which have placed a greater need than ever before for nurses to have clearly defined roles, has resulted from the demand for cost-effective care and for nurses to justify their contribution to that care. This two stage, descriptive study was undertaken as part of a larger study to determine the implications of definition of the role of nursing for service provision in Hong Kong. The initial data collected using group interviews to generate ideas about the activities of the registered nurse (RN) and enrolled nurse (EN), was followed by a questionnaire to a sample of 410 RNs, representing three different grades of nursing staff. The 5-point Likert type questionnaire asked respondents to indicate levels of agreement with 67 activities. Sixty-five of the 67 activities of the RN were agreed to and were statistically significant (P < 0.001) in the difference from the undecided position. The findings also demonstrated a lack of agreement amongst grades of staff in their perception of nursing role. Fifty-six of the same 67 activities were agreed to for the EN and were statistically significant (P < 0.001) in the difference from the undecided position. This similarity between perceptions of EN and RN activities highlights the need to reconsider the contribution of ENs to patient care within the nursing structure in Hong Kong. These findings have implications not only for the management of nursing but also for further research in determining the interpretation of role in nursing to high quality patient care.

Adult↗
PubMed1995

Second and early third trimester atrial natriuretic peptide (ANP) levels in pregnancies subsequently complicated by hypertension.

OBJECTIVE: To explore the clinical utility of measuring atrial natriuretic peptide (ANP) in the second and early third trimesters of pregnancy in order to predict pregnancy induced hypertension (PIH). METHODS AND MATERIALS: The study was done in a University Teaching Hospital. A prospective study of 200 women in their first pregnancy was conducted. ANP was measured at 2 gestational windows, 20-26 weeks and 30-34 weeks. This was correlated with pregnancy outcomes, in particular PIH. Student's t-test was used to compare ANP levels between women who developed PIH and those who did not. The receiver operator curve (ROC) was used to determine its clinical utility. RESULTS: ANP levels were lower at 20-26 weeks in women who subsequently developed PIH but there was no significant difference at 30-34 weeks between women who had normotensive pregnancies and those who later developed PIH. The character of the ROC would indicate that it is not useful for prediction. CONCLUSION: ANP levels in the second and early third trimesters has limited clinical utility for the prediction of PIH.

Adult↗
PubMed1995

A randomised double blind comparison of Syntometrine and Syntocinon in the management of the third stage of labour.

OBJECTIVE: To compare the effect of intramuscular Syntometrine and Syntocinon in the management of the third stage of labour. DESIGN: A randomised double blind prospective study. SETTING: Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Hong Kong. SUBJECTS: One thousand consecutive patients with singleton pregnancy and vaginal delivery in February and March 1993. RESULTS: The use of Syntometrine in the management of the third stage not only reduced the blood loss after delivery but was associated with a 40% reduction in the risk of postpartum haemorrhage (odds ratio 0.60; 95% CI 0.21-0.88), and the need for repeat oxytocic injections (odds ratio of 0.63; 95% CI 0.44-0.89). The two drugs did not differ in their effect on the duration of the third stage. However, the incidence of manual removal of the placenta was higher when Syntometrine was used (odds ratio 3.7; 95% CI 1.03-12.5), although the overall incidence remained low. Side effects from both drugs, such as nausea, vomiting, headache and hypertension, were uncommon. CONCLUSION: Intramuscular Syntometrine is a better choice than Syntocinon in the management of the third stage of labour.

Adult↗
PubMed1995

The prediction of fetal acidosis at birth by computerised analysis of intrapartum cardiotocography.

OBJECTIVE: To assess the capability of a computer software interpretation program, using intrapartum fetal heart rate and intrauterine pressure as recorded in a cardiotocogram to predict fetal acidosis at birth. DESIGN AND SUBJECTS: A retrospective analysis of digitised fetal heart rate and uterine activity values obtained from 73 high risk women in labour. SETTING: Two university teaching hospitals. METHODS: A computer software program was constructed to analyse the digitised data and predict acidosis. The results of the analysis were compared with actual umbilical arterial blood pH and base excess at delivery. RESULTS: The software cardiotocogram interpreter was able to predict a pH of less than 7.15 with an accuracy of 77%, a sensitivity of 88% and specificity of 75% in this set of data. It was able to predict a base excess of less than -8 mmol/l with an accuracy of 81%, a sensitivity of 76% and specificity of 82%. CONCLUSIONS: A computerised method of analysing fetal heart rate and uterine activity using a simple algorithm has demonstrated a capability to predict fetal acidosis at the time of delivery. Further research in this area is warranted.

Acidosis↗
PubMed1995

Relationship of cytochrome P450 activity to Clara cell cytotoxicity. IV. Metabolism of naphthalene and naphthalene oxide in microdissected airways from mice, rats, and hamsters.

Parenteral administration of naphthalene produces a dose-dependent and tissue-, species-, and cell-selective lesion of murine Clara cells. The rate and stereoselectivity of naphthalene metabolism by microsomal preparations correlate with tissue and species differences in cytotoxicity. Because earlier studies used microsomes obtained from whole tissue, differences in susceptibility of proximal and distal airways could not be related to differences in the metabolic activation or detoxication of naphthalene. Specific subcompartments of the respiratory system, obtained by microdissection, have been used to study the cytochrome P450-dependent metabolism of naphthalene and the epoxide hydrolase/glutathione transferase-dependent metabolism of naphthalene oxide. The rates of naphthalene metabolism were substantially higher in mouse airways than in comparable airways of hamsters or rats. Rates of metabolism were higher in distal airways than in the trachea of all species studied. Metabolism in mouse airways was highly stereoselective, whereas that in hamster and rat tissues was not. Nonciliated cells at all airway levels in mice were heavily labeled with an antibody to cytochrome P450 2F2; little labeling was observed in any portion of rat and hamster lungs. Postmitochondrial supernatants prepared from mouse and hamster airways metabolized racemic naphthalene oxide to diol and glutathione adducts at substantially higher rates than did comparable preparations from rats. Although glutathione levels varied 2-4-fold at different airway levels in the three species studied, levels at the most susceptible site (mouse distal bronchioles) were as high as or higher than those at other, less susceptible, sites. These studies support the view that the rate and stereoselectivity of naphthalene metabolism to naphthalene 1R,2S-oxide catalyzed by cytochrome P450 2F2 are critical determinants in the species-specific and region-selective cytotoxicity of naphthalene in mice. The lack of major differences in the catalytic activity or enantioselectivity of putative detoxication enzymes (epoxide hydrolase or glutathione transferases) between mouse and hamster tissue, combined with data showing that the differences in the metabolic fate of naphthalene oxide in proximal versus distal airways are not dramatic, suggests that the initial epoxidation of naphthalene is an important factor in site-selective toxicity. These studies support the need to use tissue from defined airway levels for studies on the relationship of biochemical and metabolic factors important in cellular injury by lung toxicants, such as naphthalene, where there are dramatic regional differences in susceptibility to injury within the respiratory system.

Animals↗
PubMed1994

Mutagenesis and mapping of a mouse gene, Clock, essential for circadian behavior.

In a search for genes that regulate circadian rhythms in mammals, the progeny of mice treated with N-ethyl-N-nitrosourea (ENU) were screened for circadian clock mutations. A semidominant mutation, Clock, that lengthens circadian period and abolishes persistence of rhythmicity was identified. Clock segregated as a single gene that mapped to the midportion of mouse chromosome 5, a region syntenic to human chromosome 4. The power of ENU mutagenesis combined with the ability to clone murine genes by map position provides a generally applicable approach to study complex behavior in mammals.

Animals↗
PubMed1994

Laparoscopic removal of retained surgical gauze after vaginal hysterectomy.

Surgical gauze was retained intraabdominally in a woman who had undergone a vaginal hysterectomy with anterior colporrhaphy. Laparoscopic removal was successfully performed with minimal risk or trauma to the patient. The integrity of the vaginal vault support was maintained and the need for a laparotomy avoided. The use of laparoscopy in vaginal hysterectomy should be considered as this offers the chance to assess the pelvis pre- and post-operatively and to remove the ovaries, where indicated.

Female↗
PubMed1994

The influence of obstetric workload on cesarean section rate.

The cesarean section rate in a busy obstetric unit was studied in relation to the monthly confinement rate. A total of 30,825 births over a period of 5 years were analyzed. There was a negative correlation between the emergency cesarean section rate and the unit workload (correlation = -.498, 2 tailed p = 0.0001) whilst there was no relationship between workload and the elective cesarean section rate. This suggested that the unit may reach a certain saturation level as far as the emergency cases were concerned during the busy periods. However, there was no evidence that the perinatal outcome was affected by this variation in emergency cesarean section rate.

Cesarean Section↗
PubMed1994

Prediction of caesarean section from ultrasound and clinical assessment of fetal size.

One hundred and five women with singleton pregnancies and cephalic presentation were assessed. Fundal height and a clinical estimate of fetal weight were recorded. The fetal biparietal diameter, abdominal circumference and femur length were measured with ultrasound. Ultrasound estimated fetal weight was calculated using 3 different formulas (Shepard, Campbell and CUHK). The liquor volume was assessed using the amniotic fluid index. Ultrasound was able to predict Caesarean section with more reliability than clinical assessment of fetal size or weight. The biparietal diameter, fundal height and amniotic fluid index were poor predictors of mode of delivery. The measurements which best predicted the mode of delivery were the fetal femur length and abdominal circumference. Femur length, but not abdominal circumference, was a statistically better predictor of Caesarean section than clinical estimation of fetal weight. There was no improvement in prediction using ultrasound estimated fetal weight.

Anthropometry↗
PubMed1994

Spontaneous abortion: a medical approach to management.

The conventional management of spontaneous abortion is surgical evacuation of the uterus to prevent complications which may arise from retained products of conception (POC). This procedure is not without complications and also demands operating theatre resources. The purpose of this study was to determine the efficacy of a medical approach to the management of spontaneous abortion using the prostaglandin analogue, gemeprost. From an initial 212 women presenting with spontaneous abortion, 4 groups were defined according to what they required in the way of initial management. A group of 20 women were excluded from conservative medical management at presentation because they were bleeding heavily and judged to be unsuitable. Sixty women initially required no further management other than determining that they had a complete abortion using transvaginal sonography (TVS). The 132 women were treated with the prostaglandin analogue, gemeprost. Sixty were judged to need no further management afterwards and were initially discharged. The remaining 72 women underwent evacuation of retained products of conception (ERPC) after the gemeprost treatment as medical evacuation of the uterus appeared to had been incomplete. In each of these 4 groups so defined, there was 1 case where an ERPC was required after the patients have been discharged because of complications attributable to retained POC. We therefore found that no ERPC was necessary in the management of 118 out of 212 (55.6%) women who presented with spontaneous abortion. This has important implications in patient management and economical use of hospital resources.

Abortifacient Agents, Nonsteroidal↗
PubMed1993

Ultrasound fetal weight estimation: precision or guess work?

We compared the prediction of birth-weight based on factors shown by epidemiological studies to influence it with the performance of 2 clinical examples of ultrasonic fetal weight estimation reported in the literature. The standardized absolute error of the 2 examples of ultrasonic fetal weight estimation was similar to estimation by multiple regression of birth-weight on maternal age, parity, height and weight in 11,516 Chinese mothers. This severely limits the clinical utility of the estimation derived from these ultrasonic measurements.

Birth Weight↗