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Biomedical subjects

F Y Chan

Publications and source records attributed to F Y Chan.

At least 55 records · Page 3Linked to original sources
PubMed1995

Nucleophosmin/B23 (NPM) oligomer is a major and stable entity in HeLa cells.

HeLa cell extract was separated by 7% polyacrylamide gel electrophoresis without SDS and subsequently stained with anti-nucleophosmin/B23 (NPM) antibody in a Western blot analysis. Two immunobands were obtained. The major band with a slower electromobility (RF = 0.23) is the NPM oligomer, while the fast-moving minor band is the monomer (RF = 0.56). The oligomer constitutes about 95% of total NPM. The oligomer sedimented faster (10 s) than the monomer in sucrose density gradient centrifugation. Three oligomer bands were identified. NPM oligomer is not affected by treatments with DNase. RNase, 10 mM EDTA, 1 M NaCl, and lyophilization. However, 3 M urea causes reversible dissociation of NPM oligomer into monomer. The level of NPM oligomer remains unchanged in HeLa cells after treatment with the cytotoxic agents, actinomycin D, toyocamycin and camptothecin. These results indicate that NPM oligomer is the major and stable NPM entity in HeLa cells.

Biological Transport↗
PubMed1995

Pregnancy screening by uterine artery Doppler velocimetry--which criterion performs best?

OBJECTIVE: To test whether repeating Doppler studies of the uteroplacental circulation late in gestation will improve the test's power for predicting pregnancy-induced hypertension and fetal growth restriction (FGR), and whether analysis based on a combination of quantitative and qualitative assessments of the uterine arterial waveforms will yield better results than analysis based on either alone. METHODS: A total of 358 patients considered to be at medium risk for the development of pregnancy-induced hypertension and FGR were recruited. Continuous-wave Doppler studies of the uterine arteries were performed serially at 20, 28, and 36 weeks' gestation. The values of various Doppler indices in the prediction of subsequent pregnancy complications were tested at different gestations and different cutoff levels. The overall significance of performance of the Doppler indices was assessed by the Cohen kappa index, which tests the extent of agreement between the test and the "truth" over that by random chance agreement. RESULTS: A total of 974 examination results on 334 patients were available for analysis. We found that Doppler studies of the uterine arteries at 28 and 36 weeks were less useful than studies performed at 20 weeks. Serial studies at 20 and 28 weeks showed only marginal improvement when compared with a single study at 20 weeks. The best criteria were a mean resistance index (RI) of uterine arteries above the 90th percentile and the presence of diastolic notches in both uterine arteries at 20 weeks. Although the overall kappa index only suggested fair to good agreement beyond chance, the positive predictive value for subsequent complications was good: 57% for severe complications and 93% for any complications. CONCLUSION: Doppler studies of the uterine artery as a test for the subsequent development of pregnancy complications are best performed at 20 weeks with a combination of RI measurements and the assessment of the presence of diastolic notches.

Adult↗
PubMed1995

A comparison of colour Doppler sonography and the pelvic arteriogram in assessment of patients with gestational trophoblastic disease.

OBJECTIVE: To assess whether colour Doppler sonography can replace pelvic arteriography in the assessment of patients with gestational trophoblastic disease. DESIGN: An observational study in which patients with gestational trophoblastic disease were assessed with both pelvic arteriography and colour Doppler sonography. SETTING: The oncology unit of the Department of Obstetrics and Gynaecology, University of Hong Kong. The unit is the main tertiary referral centre for treatment of trophoblastic diseases in Hong Kong. SUBJECTS: Thirty-two consecutive women referred over an 18 month period. MAIN OUTCOME MEASURES: The site of localisation of the tumour and the size of the tumour as assessed by both methods. RESULTS: Eleven patients had a spontaneous fall of beta-hCG titres and did not have pelvic arteriograms performed. The remaining 21 patients had both investigations performed. Four patients had no evidence of abnormal pelvic vessels either on colour Doppler sonography or on pelvic arteriography. Their raised beta hCG titres were due to metastatic disease elsewhere. In the remaining patients the location of the tumour vessels was found to be concordant between the two methods of imaging. Measurements of the mean diameter of tumour bulk by the two methods also agreed well (r = 0.93, P < 0.0001). Pelvic arteriogram over-estimated the size of the tumour in two patients by 2 and 3 cm, respectively, but this did not alter the risk categories of the patients. CONCLUSION: Colour Doppler sonography is a noninvasive technique that can replace pelvic arteriography in the assessment of patients with trophoblastic diseases.

Angiography↗
PubMed1994

Umbilical artery Doppler velocimetry compared with fetal heart rate monitoring as a labor admission test.

A total of 155 patients admitted in early labor to the delivery unit of the University of Hong Kong were recruited into a study comparing the value of umbilical artery Doppler velocimetry and fetal heart rate (FHR) monitoring in early labor as an admission test. FHR monitoring for 30 min was recorded on admission, and umbilical A/B ratio was simultaneously performed. The FHR tracing was scored according to the Lyons score by a third independent observer after delivery. Outcome variables studied included small for gestational age (SGA), intrapartum FHR abnormalities, operative deliveries for fetal distress, umbilical cord pH, Apgar scores, admission into the special care baby unit, and a combination of the variables. It was found that at cut-off values of Lyons score < 7 and umbilical A/B ratio > 2.6 at term, about 19% of cases were abnormal for either tests, with only a few cases of overlap. Umbilical A/B ratio was found to be significantly correlated with SGA. The sensitivity and positive predictive values were, however, low. Both tests were relatively poor predictors for most of the outcome variables studied. Interestingly, FHR monitoring did not seem to have any advantage over Doppler velocimetry as a labor admission test. Further larger scale studies to evaluate their usefulness in medium and low risk populations are indicated.

Apgar Score↗
PubMed1994

The safety of vaginal prostaglandin F2 alpha for the stimulation of labour.

In an audit of 15,102 consecutive deliveries between 1986 and 1991, 3,168 labours were induced with intravenous oxytocin and 824 with 40 mg prostaglandin F2 alpha (PGF2 alpha) vaginal gel. Four hundred and twenty women received PGF2 alpha alone and 404 received PGF2 alpha followed by oxytocin. The main aim of the study was to audit the safety of PGF2 alpha gel to stimulate labour. There were no maternal or neonatal complications attributable to this therapy. In particular, there were no cases of uterine rupture or hyperstimulation requiring surgical or pharmacological intervention. There was little difference in the evidence for fetal distress between induction methods. Although the prostaglandin and oxytocin groups were not comparable in all respects, the results of this large retrospective study confirmed the results of smaller prospective randomized trials showing a significantly shorter labour and reduced analgesia, surgical delivery and postpartum haemorrhage rates in women treated with PGF2 alpha alone. This is the largest reported series of PGF2 alpha induced labours and provides evidence of its safety and is in keeping with physiological data suggesting that PGF2 alpha is the main prostaglandin and oxytocic associated with normal progressive labour. Its apparent safety and potential to reduce both intervention in labour and postpartum complications merits greater attention.

Adult↗
PubMed1994

Limitations of transvaginal sonography and color Doppler imaging in the differentiation of endometrial carcinoma from benign lesions.

We conducted this study to test the hypothesis that transvaginal ultrasonography and color Doppler imaging of the uterine arteries are complementary methods in the assessment of patients with postmenopausal bleeding. Sixty-seven patients were studied. Seventeen suffered from endometrial carcinoma, 12 from benign endometrial lesions (six polyp, six hyperplasia) and 38 had no organic pathology. Transvaginal ultrasonography was found to be superior to CDI in the detection of pathologic conditions of the endometrium, but neither method can distinguish benign lesions from their malignant counterparts. CDI does not give additional information over that obtained by transvaginal ultrasonography in the assessment of patients with postmenopausal bleeding, and the limitations of both methods in the differentiation of endometrial carcinoma from benign lesions need to be recognized.

Arteries↗
PubMed1993

Prenatal quantitation of number of X-chromosomes by slot blot hybridization and autoradiography.

OBJECTIVE: To study the use of slot blot hybridization as a method of prenatal quantification of the number of X-chromosomes in chorionic villi samples. METHOD: DNA of chorionic villi from fetuses with karyotypes of 46,XY; 45,XO; 47,XXX; 69,XXX and 48,XXXX were extracted, slot blotted and hybridized to the following radioactive probes: beta 0.9, FVIII, pY3.4 and pBLUR. DNA of chorionic villi from five other fetuses with unknown karyotypes were similarly blotted and hybridized. Autoradiography with pre-exposed films was carried out and the density of each of the hybridized bands was scanned by a laser densitometer. RESULTS: It was found that with increasing amounts of DNA in the samples, the intensity of the bands hybridized with FVIII and beta 0.9 probes increased proportionately. However, the intensity of the bands obtained with the probes pY3.4 and pBLUR (probes containing multiple repeat sequences) varied little with increasing DNA concentrations. The ratios of radioactivity obtained for the two probes FVIII/beta 0.9, were well correlated with the number of X-chromosomes in the samples. Calculations of the FVIII/beta 0.9 ratio for the five samples with the unknown karyotypes gave a correct prediction of the number of X-chromosomes in each case. CONCLUSION: Slot blot hybridization can be used as a method of prenatal quantitation of the number of X-chromosomes in chorionic villi samples. The method could be useful for rapid prenatal diagnosis of other numerical chromosomal abnormalities.

Adult↗
PubMed1993

Shared antenatal care between family health services and hospital (consultant) services for low risk women.

Four thousand four hundred and seventy-two patients were recruited into a project to test the efficacy of a Shared Care System in the management of low risk antenatal patients. The patients were scored according to a simple point scoring system. Three thousand three hundred and fourty-seven (74.8%) were scored as low risk. Fifty point two percent (1,682) of these low risk patients received the conventional system of care and acted as controls; while 49.8% (1,665) received shared care, where they were seen jointly by midwives, general doctors and hospital specialists. It was found that with the use of shared care, there was a significant decrease in workload to the hospital specialty clinics. Not only was the antenatal diagnostic rate of intrauterine growth retardation (IUGR) significantly improved, but the mean gestations at which IUGR, malpresentations, and pregnancy induced hypertension were diagnosed were also significantly earlier. The number of antenatal cardiotocographs performed, as well as the number of hospital admissions and mean duration of stay were decreased in the study group. The overall cost savings to the hospital was calculated if the shared care system was generally adopted.

Adolescent↗
PubMed1991

A comparative study of continuous- and pulsed-wave Doppler velocimetry in fetal and uteroplacental circulation.

Continuous-wave and pulsed-wave Doppler ultrasonography are the two common methods used to study the fetal and uteroplacental circulation. We used both methods in the same patient population in three different gestations and in various fetal and uteroplacental vessels to compare the results from both machines. Thirty-one normal patients were studied at 20, 28, and 36 weeks gestation. The results showed significant correlation with no statistically significant differences between the two types of machines for the peak systolic/end-diastolic ratios and resistance index for the umbilical artery and uterine arteries. Significant differences, however, were demonstrated when the arcuate artery was studied, or when the pulsatility index was used for comparison. We therefore conclude that when different machines are used for study, comparison of the results is only valid for selected vessels and indices. Results for arcuate arteries and pulsatility index should be compared with caution.

Blood Flow Velocity↗
PubMed1991

Outcome of pregnancy in patients with systemic lupus erythematosus. A prospective study.

A prospective study was performed to investigate the outcome and complications of pregnancy in patients with systemic lupus erythematosus. Twenty-nine pregnancies occurred in 22 patients. There were 12 abortions, two spontaneous and 10 induced. Fifteen women had 17 live-born neonates. Neonatal complications included nine premature deliveries, two cases of intrauterine growth retardation, and one of Treacher Collins syndrome. Obstetric complications included threatened abortion (two), placenta previa (two), and preeclampsia (three). Cesarean sections were necessary in five patients. There was no maternal or neonatal mortality. Thirteen episodes of systemic lupus erythematosus relapses were detected by incidents of increasing proteinuria (six), arthritis (four), and vasculitic rash (two). There were no statistical differences in changes in hemoglobin level, erythrocyte sedimentation rate, albumin level, antinuclear antibody titer, or C3 or C4 level between the patients who relapsed and those who did not. Pregnancy could induce a flare of systemic lupus erythematosus in previously normal patients or patients with previously inactive disease. The overall neonatal and maternal survival was good, even in patients who presented during pregnancy. Spontaneous fetal loss was low (2/29 [6.9%]); both cases occurred in mothers with inactive lupus.

Abortion, Induced↗
PubMed1990

Simultaneous pulsed Doppler velocimetry of fetal aorta and inferior vena cava. Diagnosis of fetal congenital heart block; two case reports.

A simple technique for the diagnosis of fetal congenital heart block by simultaneous Doppler blood-flow velocimetry of the fetal abdominal aorta and inferior vena cava is described. Furthermore, a simple method of monitoring the fetal atrial reactivity during the antenatal period; and simultaneous recording of atrial and ventricular rates during labour are also described. These simple techniques can be applied for the diagnosis and monitoring of the fetus in other types of cardiac arrhythmias.

Adult↗
PubMed1990

Prenatal diagnosis of congenital fetal arrhythmias by simultaneous pulsed Doppler velocimetry of the fetal abdominal aorta and inferior vena cava.

Various methods have been used for the diagnosis of congenital fetal arrhythmias. Currently, M-mode echocardiography is the most widely used method. However, good tracings are often difficult to obtain because of unfavorable fetal positions, resulting in long durations of examination. In early gestation, the fetal heart is often too small for clear M-mode echocardiography. Doppler velocity waveforms of the fetal inferior vena cava represent the right atrial activity, whereas those of the aorta reflect ventricular contraction. Because of the proximity of the vessels, it is easy to obtain simultaneous recording in opposite channels of Doppler waveforms from both vessels. A visual relationship between the atrial and ventricular contractions may be clearly established and a diagnosis may be made. The findings of simultaneous pulsed Doppler velocimetry of the fetal aorta and inferior vena cava were assessed in different types of congenital fetal arrhythmia: congenital heart block, premature atrial ectopic contractions, premature ventricular ectopic contractions, and supraventricular tachycardia. The correct diagnosis was made as early as 13 weeks' gestation, showing the application of this method in early pregnancy.

Aorta, Abdominal↗
PubMed1989

In situ prosthetic graft replacement for mycotic aneurysm of the aorta.

Mycotic aneurysms as defined in this study include only those naturally occurring aortic aneurysms that result from or are secondarily infected by bacteria arising in a distant site of infection. Of the 2,585 patients treated for aortic aneurysm during the past 8 1/2 years, 22 patients had disease conforming to this definition. The aneurysms were located in the ascending aorta in 2 patients, ascending aorta and arch in 5, arch and descending aorta in 1, descending thoracic aorta in 1, separate descending and abdominal aorta in 1, thoracoabdominal aorta in 5, upper abdominal aorta in 6, and infrarenal abdominal aorta in 1. The primary source of infection was the urinary tract in 2 patients, salmonellosis in 4, pneumonia in 3, sub-acute bacterial endocarditis in 2, ear, nose, and throat in 2, cellulitis of the hand in 1, chronic wounds in 2, dental extraction in 1, lumbar disc space infection in 1, septic thrombophlebitis in 1, and generalized febrile illness in 3. The duration of febrile illness ranged from 2 weeks to 1 year. All patients were treated with antibiotics and operation was performed within 24 hours after admission in 11 patients and within one to eight days after admission in 11. Treatment consisted of in situ graft replacement. Appropriate antibiotics were given intravenously for 4 to 6 weeks in patients with positive cultures and continued orally for the rest of the patients' lives. Of the 22 patients, 19 (86%) were early survivors, and all are still alive 3 months to 8 years postoperatively. Only 1 had a recurrent infection, which involved the intervertebral disc space.

Adult↗
PubMed1989

Multiple XbaI polymorphisms for carrier detection and prenatal diagnosis of haemophilia A.

Three XbaI restriction fragment length polymorphisms (RFLPs) can be detected using the factor VIII-intron 22 probe (p482.6) in a XbaI-KpnI double digest of genomic DNA. The XbaI (A) site had been reported by Wion et al (1986) to be in intron 22, while the two additional sites. XbaI (B) and XbaI (C), are shown here to be X-linked and close to the XbaI (A) site. The frequencies of heterozygosity for these three sites are 0.49, 0.18 and 0.30 respectively. In 75 females the observed heterozygosity rate for the XbaI (A) site is 0.41 and this increased to 0.57 with the two additional sites. Care should be exercised when interpreting the XbaI RFLPs, since the 1.4 kb XbaI/KpnI fragment and the 4.8 kb XbaI fragment are associated with both positive XbaI (A) and XbaI (B) sites. By the combined use of the multiple XbaI polymorphisms with the BclI site in intron 18, the carrier detection rate would increase to 67%. Four prenatal diagnoses had been performed using the multiple XbaI polymorphisms.

Factor VIII↗
PubMed1987

Doppler blood flow velocity waveforms in alpha-thalassemia hydrops fetalis.

Doppler shift blood flow velocity-time waveforms in the umbilical arteries (UA), aorta (A), and inferior vena cava (IVC) in eight fetuses with alpha-thalassemia (alpha-thal) hydrops fetalis were described. The UA waveforms in these fetuses with anemia in utero depicted a hyperdynamic circulatory state with a relative increase in acceleration slope, more linear decline from maximum systole to end diastole, and reduced spectral broadening. The aortic waveforms similarly displayed distorted systolic peaks, flow turbulence, and greatly elevated diastolic frequencies. Reversal of end diastolic flow in the IVC also indicated cardiac decompensation in these fetuses. Progressive changes in these waveforms were apparent in two fetuses that had serial evaluation. In another four fetuses in which alpha-thal major was diagnosed in the second trimester by DNA analysis and had Doppler evaluation before termination of pregnancy, consistent changes in the UA, A, and IVC waveforms were not observed. This study confirms the potential usefulness of Doppler spectral waveforms in depicting altered hemodynamic changes in the fetus and in the evaluation of hydrops fetalis. Doppler ultrasound examination can be included as part of the routine workup of hydrops fetalis.

Aorta, Thoracic↗
PubMed1987

Middle cerebral artery Doppler flow velocity waveforms.

Doppler flow velocity-time waveforms of the middle cerebral arteries at their origin from the internal carotid arteries were obtained serially on 14 patients to determine the alterations of these waveforms with gestational age. Satisfactory recordings were obtained from all patients. The middle cerebral artery waveforms demonstrated a typically biphasic pattern with continuing forward flow in diastole. The peak systolic to end-diastolic ratio (A/B ratio) showed a progressive and significant decline from 6.89 +/- 1.48 at around 25 weeks to 4.23 +/- 0.67 at term. Elevation of diastolic velocities and diminished A/B ratio in the middle cerebral arteries were noted in four fetuses, in whom severe antepartum compromise was diagnosed. The ratio also appeared to decrease with worsening of fetal condition. Because the fetus compensates for hypoxia by increasing blood flow to the brain, Doppler middle cerebral artery waveforms may permit evaluation of fetal compromise and hypoxia.

Blood Flow Velocity↗