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Biomedical subjects

A M Chang

Publications and source records attributed to A M Chang.

At least 37 records · Page 2Linked to original sources
PubMed2001

Computerised analysis of the fetal heart rate and relation to acidaemia at delivery.

OBJECTIVE: To identify the individual features of the computerised analysis of the cardiotocograph that relate to arterial pH and base deficit at delivery. DESIGN: Retrospective observational study. SETTING: Teaching hospital labour wards. PARTICIPANTS: 679 women requiring continuous intrapartum fetal monitoring. METHODS: Fetal heart and uterine contraction data were obtained using the Nottingham Fetal ECG monitor. Fetal heart rate patterns for the last half-hour preceding delivery were analysed using a computer algorithm developed for intrapartum application. The significance of the areas under receiver operator characteristic curves were calculated. MAIN OUTCOME MEASURES: Umbilical arterial pH and base deficit at delivery. RESULTS: Three parameters, fetal bradycardia, total deceleration area and the deceleration area after a contraction had receiver operator characteristic curves that significantly predict a low umbilical arterial pH and base deficit at delivery (areas under receiver-operator characteristic curves = 0.53, SD 0.01 P = 0.03; 0.60, SD 0.03 P = 0.002; 0.62 SD 0.04 P < 0.001, respectively). Tachycardia, accelerations and variability did not. CONCLUSIONS: The individual components of the computerised analysis of the fetal heart rate that predict acidaemia at delivery are identified.

Acidosis↗
PubMed2001

Oxidative stress in the fetal lamb brain following intermittent umbilical cord occlusion: a path analysis.

OBJECTIVE: To evaluate the relative contribution of cord occlusion length intervals between occlusions and experimental duration on oxidative stress in the fetal lamb brain. DESIGN: Acute, partially exteriorised fetal lambs with intermittent total cord occlusion. SETTING: The Vivarium of Westmead Hospital, University of Sydney, Australia and The Chinese University of Hong Kong. MAIN OUTCOME MEASURES: Arterio-venous differences in the concentration of organic hydroperoxides, measured in paired samples of carotid arterial and jugular venous blood, as an index of oxidative stress in the brain. METHODS: Thirty-two fetal lambs were exposed to graded hypoxia, induced by intermittent total umbilical cord compression of 30 seconds, 60 seconds and 90 seconds duration, occurring every minute for a total of 27 occlusions over 81 minutes. Three sham experiments were also performed. In addition to organic hydroperoxides, carotid arterial blood samples were also assayed in 15 animals (two sham) for oxygen saturation, pH, hypoxanthine, xanthine and urate concentrations. A causal model for oxidative stress was defined: occlusions leading to hypoxia with a rise in hypoxanthine; reperfusion during intervals between occlusions leading to the accelerated production of xanthine and uric acid and the generation of oxygen free radicals, which in turn, are responsible for the rise in lipid peroxidation. Path analysis was performed to assess the strength of the relationships between these variables and the cord occlusion length, the interval between occlusions and the duration of the experiment. RESULTS: Sham experiments showed no change in organic hydroperoxide production. Following 30-second umbilical cord occlusions a sixfold drop in mean organic hydroperoxides was observed between carotid arterial and jugular venous levels. In contrast, following occlusions of 60 seconds duration (or longer) a median 20-fold increase in organic hydroperoxide production was observed. Path analysis revealed a strong indirect pathway from occlusion length --> hypoxanthine --> urate and weak positive pathways from oxygen saturation --> urate and from interval between occlusions --> urate. After accounting for these pathways reflecting oxidative stress, a strong direct path remained from time from first occlusion --> organic hydroperoxide production. CONCLUSIONS: Peroxidation of lipids in the brain occurs under conditions of severe hypoxia and reperfusion associated with intermittent umbilical cord occlusions of 60 seconds or longer. The path analysis supported the causal model as originally defined, with the exception that the indirect pathway via pH was found to be trivial.

Animals↗
PubMed2001

Knowledge of and attitudes toward sex among Chinese adolescents.

This study was conducted to examine the knowledge of and attitudes toward sex of 178 Chinese secondary school students in Hong Kong. The data were collected using a questionnaire that comprised three parts: the Chinese version of the Mathtech Knowledge Test, the Chinese version of the Mathtech Attitude and Value Scale, and a demographic sheet seeking sociodemographic information. In general, students demonstrated a low level of sexual knowledge, especially in relation to adolescent marriage, the probability of pregnancy, and adolescent sexual activity. With regard to attitudes, students indicated positive attitudes toward importance of family and importance of birth control. Male students in comparison with their female counterparts had a higher level of agreement with premarital intercourse and the use of pressure and force in sexual activity.

Adolescent↗
PubMed2001

Metabolic capabilities of CYP2F2 with various pulmonary toxicants and its relative abundance in mouse lung subcompartments.

The tissue- and species-selective toxicity of a number of pulmonary toxicants has been attributed to the presence and distribution of activating enzymes with high k(cat) in target airways of susceptible species. The mouse is especially sensitive to a variety of metabolically activated lung toxicants. Recombinant CYP2F2 (mouse) was recently shown to effectively metabolize the species-selective pulmonary toxicant naphthalene. Here we show that the pulmonary toxicants 1-nitronaphthalene and 2-methylnaphthalene are metabolized readily with high k(cat) values (17.1 and 67.6 min(-1), respectively) to potentially cytotoxic intermediates at biologically relevant K(m) values (21.5 and 3.7 microM, respectively). Additionally, anthracene and benzo[a]pyrene are both metabolized by CYP2F2 (0.14 +/- 0.04 and 0.04 +/- 0.00 nmol/nmol/min, respectively), albeit at much lower rates. The levels of total CYP in mouse airways are considerably higher than those in parenchyma and trachea, and this is consistent with much higher rates of naphthalene metabolism in microsomal preparations from airways compared with the other subcompartments. The data suggest that CYP2F2 is a prominent cytochrome P450 in mouse lung that metabolizes a number of pulmonary toxicants. The presence of CYP2F2 may be important in the susceptibility of the mouse to metabolically activated pulmonary toxicants.

Animals↗
PubMed2000

Locomotor response to an open field during C57BL/6J active and inactive phases: differences dependent on conditions of illumination.

Time of day has proven to be a source of variability in diverse behavioral measures. Knowledge of the pattern of this temporal effect as well as its origin (exogenous or endogenous) is essential for a precise description of any behavior. This study analyzed the effect of the external light-dark cycle and the internal rest-activity rhythm on the response of C57BL/6J mice to a novel environment. In a first experiment, animals maintained in a 12:12-h light-dark cycle were tested in an open field at six different times of day. A diurnal rhythm of ambulation in the open field was observed with greater levels of activity exhibited by those groups tested at night. Long-term and short-term behavioral habituation to spatial novelty were also affected by phase of the light-dark cycle. A second experiment was designed to control for any direct effect of the light-dark cycle by keeping the animals in dim green light where entrainment was maintained by a skeleton photoperiod (two 15-min bright-light pulses separated by 12 hours of green, dim light). This second group of animals was tested at two different circadian phases under the same conditions of illumination. One group was tested during the subjective night and another group during the subjective day, i.e., 2 or 14 h after the onset of the active phase, as assessed by wheel-running behavior. No effect of circadian phase on ambulation or habituation of this response to the open field was observed in these animals. Taken together, these results suggest that spatial novelty is equally arousing regardless of circadian phase and that the conditions of illumination can dramatically alter the response to a novel environment.

Animals↗
PubMed2000

Disposition towards critical thinking: a study of Chinese undergraduate nursing students.

The purpose of this study was to explore empirically whether undergraduate nursing students at a selected university in Hong Kong display a disposition towards critical thinking. The California Critical Thinking Dispositions Inventory (CCTDI) was used to measure the key theoretical aspects of the overall dispositional dimension of critical thinking. A cross-sectional descriptive design was used to examine 122 Chinese students who were completing their 1st, 2nd and 3rd year of a university baccalaureate nursing programme. In the majority of sub-scales of CCTDI, students showed a negative disposition towards critical thinking. A one-way ANOVA indicated that year 3 students scored significantly lower than their junior counterparts (P < 0. 001). Pearson product moment correlation coefficient yielded a significant positive relationship between critical thinking dispositions and term grade point average (P < 0.05). Consistent with the findings of western studies, the students scored lowest on the truth-seeking sub-scale and highest on the inquisitiveness. Discussion of the findings with regard to nursing education, curriculum and research is delineated.

Adult↗
PubMed2000

Development of a customised birthweight standard for ethnic Chinese subjects.

A model to establish customised birthweight standards for the Chinese population was developed, using data from a cohort of 1564 Chinese women with normal singleton pregnancies. Multiple regression analysis was performed using maternal height, weight, parity, gestation at delivery and fetal sex as independent (predictor) variables. From this, a customised ideal birthweight for each baby can be estimated, and the normality of the actual birthweight can be evaluated according to this, rather than from population standards. The results of this study show that birthweights are strongly influenced by maternal characteristics, confirming conclusions from similar studies in other ethnic populations. The overall mean birthweight at 280 days of gestation was 3252 g, which was smaller than that of the Caucasian population. Birthweight increased with maternal height (5.1 g/cm), maternal booking weight (10.2 g/kg) and gestation at delivery (18.3 g/day from 280 days). Babies from women who had two previous deliveries weighed 145.2 g more than the nulliparous. Male babies were 84.8 g heavier than females. Adjustment using these results produces a customised ideal birthweight for each baby. When compared with population based standards, customised birthweight standards identified significantly fewer small for gestational age (SGA - birthweight below 10th centile, McNemar Chi square = 19.1, p < 0.01) and fewer large for gestational age (LGA - birthweight above 90th centile, McNemar Chi square = 23.7, p < 0.01) cases.

Asian People↗
PubMed2000

p53 polymorphism and human papillomavirus infection in Hong Kong women with cervical cancer.

In this study we investigated the involvement of p53 polymorphism at codon 72, the infection and typing of human papillomavirus (HPV) and the correlation of p53 polymorphism with HPV type and other clinicopathologic characteristics in 72 Hong Kong women with cervical cancer. We developed a simple and nonradioactive method for determining polymorphism at codon 72 of the p53 gene. The homozygous p53 arginine allele (Arg/Arg) was detected in 22 (31%), the homozygous p53 proline allele (Pro/Pro) in 14 (19%) and the heterozygous allele (Arg/Pro) in 36 (50%) cases, respectively. Using the consensus primers MY11 and MY09, HPV infection was detected in 55 of 72 (76%) cases. The prevalent types were HPV-16 (55%), HPV-18 (16%) and HPV-58 (9%). The number of HPV-positive cases with Arg/Arg, Pro/Pro and Arg/Pro were 17 (31%), 12 (22%) and 26 (47%), respectively. The p53 polymorphism at codon 72 was not significantly correlated with any of the HPV types (p > 0.05). No striking overrepresentation of homozygous arginine-72 p53 was observed in HPV-associated cervical cancer. The results in this study did not show that any p53 polymorphic form has a prognostic significance for cervical cancer.

Codon↗
PubMed2000

Quantitative analysis of the bidirectional fetomaternal transfer of nucleated cells and plasma DNA.

BACKGROUND: Recently, much interest has been generated on the fetomaternal transfer of nucleated cells and plasma DNA. However, there has been no systematic quantitative comparison of these two directions and two modalities of trafficking within the same study population. METHODS: The fetus-to-mother transfer of nucleated cells and plasma DNA in pregnant women carrying male babies was studied using a real-time quantitative PCR assay for the S:RY gene. For mother-to-fetus transfer, real-time quantitative PCR assays for the insertion/deletion polymorphisms involving the glutathione S:-transferase M1 and angiotensin-converting enzyme genes were used. RESULTS: Of the 50 informative mother-baby pairs, maternal DNA was detected in the cellular fraction of umbilical cord blood in 24% of cases (12 of 50), at a median fractional concentration of 2.6 x 10(-4) (interquartile range, 1.7 x 10(-4) to 3.6 x 10(-4)). In the plasma fraction of cord blood, maternal DNA was detected in 30% (15 of 50) of cases at a median fractional concentration of 3 x 10(-3) (interquartile range, 1 x 10(-3) to 1.6 x 10(-2)). For the other direction of trafficking, fetus-to-mother transfer of nucleated cells was detected in 26% of cases (13 of 50) at a median fractional concentration of 3.2 x 10(-4) (interquartile range, 0.6 x 10(-4) to 7.6 x 10(-4)). In the plasma fraction, fetal DNA was detected in 100% of maternal plasma (50 of 50) at a median fractional concentration of 3 x 10(-2) (interquartile range, 1.4 x 10(-2) to 5. 3 x 10(-2)). CONCLUSIONS: This study indicated that significantly more fetal DNA is present in the plasma of pregnant women compared with DNA from the cellular fraction of maternal blood. In addition, maternal DNA was demonstrated in both the cellular and plasma fractions of cord blood after delivery. This study has therefore determined the fundamental quantitative values for the bidirectional fetomaternal cellular and plasma DNA traffic.

Biological Transport↗
PubMed1999

Dichotomization of continuous measurements using generalized additive modelling--application in predicting intrapartum caesarean delivery.

In prediction model development, continuous variables are often dichotomized at empirically chosen thresholds to simplify calculations and facilitate decision making. However, these choices are often made in the absence of estimated covariate effects and may be inaccurate, thus weakening the models. To improve this approach, generalized additive modelling that allows non-parametric estimation of the true covariate effects is used for threshold selection. In this study, this approach is illustrated by development of prediction models for intrapartum Caesarean deliveries. The prediction performance of the models thus developed is significantly better than that developed using empirically chosen thresholds for dichotomization.

Adolescent↗
PubMed1999

Methylation of p16INK4A in primary gynecologic malignancy.

The p16INK4A gene mapped on band p21 of chromosome 9 can be inactivated via multiple mechanisms including homozygous deletion, point mutation and promoter hypermethylation in various human tumors. A polymerase chain reaction (PCR) based analysis was performed to examine methylation of the p16INK4A gene promoter in 196 primary gynecologic malignancies including 98 cervical, 49 endometrial and 49 ovarian carcinomas. Methylation of p16INK4A was detected in 31% of cervical, 20% of endometrial, and 4% of ovarian carcinomas, respectively. The incidence of p16INK4A methylation in patients with cervical and endometrial carcinomas at advanced stages (stages III-IV) was statistically higher than those at early stages (stages I-II). There were also significant differences in the incidence of p16INK4A methylation in both cancers between the patients who had died of their disease or were alive with evidence of disease, and those without evidence of disease. The results indicate that methylation of the p16INK4A gene is present in a proportion of primary gynecologic malignancies and this alteration may be associated with poor outcome in cervical and endometrial carcinomas.

Adult↗
PubMed1999

Spontaneous abortion: a randomized, controlled trial comparing surgical evacuation with conservative management using misoprostol.

OBJECTIVE: To compare the efficacy of surgical evacuation of the uterus with medical evacuation using misoprostol in cases of spontaneous abortion. DESIGN: A prospective, randomized, controlled trial. SETTING: A university teaching hospital. PATIENT(S): Six hundred thirty-five women who aborted spontaneously and who consented to pretreatment randomization. INTERVENTION(S): Routine surgical evacuation or medical evacuation of the uterus using misoprostol. MAIN OUTCOME MEASURE(S): Immediate, short-term (2-3 weeks), and medium-term (6 months) medical complications. RESULT(S): There was a significantly lower incidence of immediate and short-term complications in the group treated with misoprostol compared with the surgically treated group. There were also fewer major complications in the 6 months after treatment in the medically treated group. Approximately 50% of the medically treated group subsequently required surgical evacuation, and these subjects required significantly more analgesia. CONCLUSION(S): Treatment with misoprostol can reduce the demand for surgical evacuation in cases of spontaneous abortion, and its use is associated with fewer medical complications.

Abortifacient Agents, Nonsteroidal↗
PubMed1999

The effect of percutaneous oestradiol on atheroma formation in ovariectomized cholesterol-fed rabbits.

OBJECTIVE: The aim of this study was to examine the effect of percutaneous oestradiol on the lipid profile and on atheroma formation using an animal model. METHODS: The study was of 12 weeks duration. Fifty sexually mature female New Zealand White rabbits were divided into five groups of equal size. Two groups acted as controls and received normal rabbit chow. Rabbits in one of these groups were ovariectomized. The remaining three groups were ovariectomized but received 1% cholesterol enriched rabbit chow. One of these cholesterol-fed groups received 0.3 mg/kg percutaneous oestradiol daily whilst another received 0.1 mg/kg oral oestradiol daily. Measurements of concentrations of total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and triglycerides (TG) were made at the beginning and end of the study. Aortic atheroma formation was measured using computerized image analysis of uptake of Sudan III staining. RESULTS: After 12 weeks there were significant increases in the mean concentrations of TC in the three cholesterol-fed groups compared with controls (P < 0.001). Changes in HDL-C and TG concentrations were less consistent. The mean area of aortic atheroma formation was significantly less in both the percutaneous oestradiol group (4.9%) and the oral oestradiol group (8.6%) compared with the non-oestrogen-treated cholesterol-fed group (19.5%) (P < 0.001, < 0.01 respectively). CONCLUSION: These results suggest that percutaneous oestradiol has a direct protective effect on atheroma formation independent of serum concentrations of total cholesterol.

Administration, Oral↗
PubMed1999

Translation of questionnaires and issues of equivalence.

The validity of studies using translated instruments may be questioned when there is a lack of attention to and/or minimal explanation of the procedures used for determining the equivalence between the primary and secondary language tool. Ensuring equivalence of a translated Chinese version of the Menstrual Distress Questionnaire is an important prerequisite for identifying culturally specific expressions of concepts under investigation and for cross-cultural comparisons. This paper examines the principles and procedures for determining equivalence of translated tools and their application to the development of an equivalent Chinese version of the Menstrual Distress Questionnaire. Translation and back-translation were used to develop a Chinese version of the Menstrual Distress Questionnaire. Bilingual university students completed both versions of the Menstrual Distress Questionnaire. Most of the Menstrual Distress Questionnaire items had an acceptable Kappa of >0.4. Intraclass correlation coefficients indicated moderate to high levels of equivalence for total scores and all scales. Improvement in the translation of some items is needed to further enhance the equivalence of the Chinese version of the Menstrual Distress Questionnaire.

Adult↗
PubMed1999

Managing caregiver tasks among family caregivers of cancer patients in Hong Kong.

Twenty-nine family caregivers of terminally ill cancer patients in Hong Kong were asked about their perceived difficulty in managing caregiver tasks. Results showed that the level of difficulty in handling the three main aspects of tasks, that is the direct care, intrapersonal tasks, and interpersonal ties, were similar (chi2 = 0.71, P > 0.05). The individual tasks identified as extremely difficult included compensation for personal time (31%), updating knowledge of reimbursement mechanism (20.7%), and emotionally accepting the likelihood of a progressive downward course of illness (17.2%). Mann-Whitney tests indicated that caregivers who had a shorter duration of caregiving experience perceived significantly greater difficulty in direct care (P < 0.05), intrapersonal tasks (P < 0.05), and overall tasks (P < 0.05). These findings indicate the need for the provision of counselling and educational support for these caregivers.

Adaptation, Psychological↗
PubMed1999

Rapid clearance of fetal DNA from maternal plasma.

Fetal DNA has been detected in maternal plasma during pregnancy. We investigated the clearance of circulating fetal DNA after delivery, using quantitative PCR analysis of the sex-determining region Y gene as a marker for male fetuses. We analyzed plasma samples from 12 women 1-42 d after delivery of male babies and found that circulating fetal DNA was undetectable by day 1 after delivery. To obtain a higher time-resolution picture of fetal DNA clearance, we performed serial sampling of eight women, which indicated that most women (seven) had undetectable levels of circulating fetal DNA by 2 h postpartum. The mean half-life for circulating fetal DNA was 16.3 min (range 4-30 min). Plasma nucleases were found to account for only part of the clearance of plasma fetal DNA. The rapid turnover of circulating DNA suggests that plasma DNA analysis may be less susceptible to false-positive results, which result from carryover from previous pregnancies, than is the detection of fetal cells in maternal blood; also, rapid turnover may be useful for the monitoring of feto-maternal events with rapid dynamics. These results also may have implications for the study of other types of nonhost DNA in plasma, such as circulating tumor-derived and graft-derived DNA in oncology and transplant patients, respectively.

DNA↗
PubMed1999

Effects of an educational programme on adolescents with premenstrual syndrome.

An education program was developed and evaluated to determine its efficacy in increasing knowledge and decreasing the severity of symptoms of premenstrual syndrome (PMS). Participants from a sample of 94 schoolgirls aged between 14 and 18 years from four secondary schools in Hong Kong were assigned to either the experimental or control group. Immediately following the education program, the schoolgirls in the experimental group had significantly increased knowledge scores as measured by the Premenstrual Syndrome Knowledge Questionnaire. Three months following the education program, schoolgirls in the experimental group reported having a significant reduction in total PMS scores and three of the subscale scores as measured by a translated version of Abraham's Menstrual Symptom Questionnaire. In addition, no significant differences were found for the control group on pre-test and post-test PMS scores suggesting that the education program could have been the source of the reduction in PMS symptoms of the experimental group of young adolescents girls.

Adolescent↗