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Biomedical subjects

Y H Lam

Publications and source records attributed to Y H Lam.

At least 55 records · Page 3Linked to original sources
PubMed1999

Nuchal translucency in fetuses affected by homozygous alpha-thalassemia-1 at 12-13 weeks of gestation.

OBJECTIVE: Fetuses affected by homozygous alpha-thalassemia-1 are anemic in the first trimester. We studied their nuchal translucency (NT) measurements at 12-13 weeks of gestation. METHODS: Nuchal translucency was measured prospectively in fetuses at risk of homozygous alpha-thalassemia-1. Measurements of those fetuses subsequently confirmed to be affected by homozygous alpha-thalassemia-1 but with a normal karyotype were compared to those of 440 controls. The controls were from the general obstetric population who had NT measurements at 12 or 13 weeks with known normal outcome. All the NT measurements were expressed as multiples of the median (MoM) for the gestational day. RESULTS: Between 1996 and 1998, 94 at-risk pregnancies were studied. Of these, 32 were subsequently confirmed to be affected by homozygous alpha-thalassemia-1. Chromosome study was not carried out in three cases and these were excluded from the analysis. Nuchal translucency MoMs for cases and controls were found to fit a log Gaussian distribution. The log means (standard deviation) for case and control NT MoM were 0.075 (0.156) and -0.0019 (0.091), respectively. The median NT MoM (95% CI) for cases was 1.19 (1.08-1.62) and was significantly higher than that of the controls (p < 0.001). However, there was extensive overlap of NT between cases and controls. CONCLUSION: Overall, there was a 19% increase in NT MoM in fetuses affected by homozygous alpha-thalassemia-1. This represents a difference of only 0.3-0.4 mm, which is clinically insignificant. This finding indirectly suggests that the increased NT in trisomic fetuses cannot be explained by fetal anemia. Conversely, the presence of increased NT in a fetus at risk of homozygous alpha-thalassemia-1 should alert one to the possibility of chromosomal abnormality rather than being attributed to fetal anemia.

Adolescent↗
PubMed1999

First-trimester ultrasound diagnosis of holoprosencephaly: three case reports.

We present three cases of fetal holoprosencephaly diagnosed by transabdominal and transvaginal ultrasound examinations at 10 and 13 weeks' gestation. The diagnosis was based on two sonographic criteria: first, the intracranial finding of a single ventricle with a cerebral mantle and no visible midline structures but fusion of the thalami and corpus striatum; and, second, facial abnormalities, including hypotelorism. The ultrasound findings were confirmed by embryoscopy before abortion in one case and by pathological examination after abortion in two cases. Chromosome study of the three fetuses showed trisomy 18, triploidy and mosaic 18p deletion and duplication.

Abortion, Therapeutic↗
PubMed1999

Sonographic features of fetal trisomy 18 at 13 and 14 weeks: four case reports.

Fetal trisomy 18 is the second most common multiple malformation syndrome. We present four cases of trisomy 18 with multiple sonographic abnormalities at 13 and 14 weeks of gestation. These cases demonstrated that fetal hand deformities can be a tell-tale sign of trisomy 18 with or without increased nuchal translucency at this gestation.

Abnormalities, Multiple↗
PubMed1999

Echogenic bowel in fetuses with homozygous alpha-thalassemia-1 in the first and second trimesters.

OBJECTIVE: Fetal echogenic bowel has been observed in fetuses with meconium peritonitis, cystic fibrosis, aneuploidy, congenital viral infection and intrauterine growth restriction. The pathogenesis of echogenic bowel is unknown, but it may be attributed to bowel ischemia. Fetuses affected by homozygous alpha-thalassemia-1 are severely anemic and hypoxic. We investigated the incidence of echogenic bowel in these hypoxic fetuses in the first and second trimesters. DESIGN: Prospective observational study. SUBJECTS: Women referred for the prenatal diagnosis of homozygous alpha-thalassemia-1 before 24 weeks' gestation. METHODS: All subjects had one or more abdominal and/or vaginal ultrasound examination between 12 and 24 weeks' gestation. Echogenic bowel was diagnosed if the bowel appeared either isoechogenic or more echogenic than the bone. RESULTS: Between March 1997 and July 1998, 126 pregnancies were studied. Thirty-six fetuses were confirmed to be affected by homozygous alpha-thalassemia-1, and 11 of them (31%, 95% CI 16-48%) had echogenic bowel. These observations were made before the invasive test results were available. None of the fetuses unaffected by homozygous alpha-thalassemia-1 had echogenic bowel. CONCLUSION: There is a strong association between homozygous alpha-thalassemia-1 and echogenic bowel. The pathogenesis is unknown. Speculations include bowel hypoperistalsis or bowel wall edema due to severe anemia and hypoxia.

Female↗
PubMed1999

ERCP and pyogenic liver abscess.

BACKGROUND: Liver abscess is commonly biliary in origin. We assessed the role of endoscopic retrograde cholangiopancreatography (ERCP) in patients with pyogenic liver abscesses. METHODS: Between January 1986 and December 1997, 63 patients with pyogenic liver abscesses were referred for ERCP. Twenty-one patients had a history of previous biliary procedures including cholecystectomy (21), biliary-enteric bypass (9), surgical sphincteroplasty (5), and endoscopic sphincterotomy (2). Demographic data, clinical features, biochemical parameters, treatment, clinical progress, and follow-up were recorded and analyzed. RESULTS: Two patients required laparotomy and 61 patients underwent guided aspiration and/or drainage at a median interval of 3 days after presentation. ERCP was performed at a median of 8 days (range 1 to 69 days) after initial treatment and succeeded in 90% of cases with no associated complication or death. Abnormalities were shown in 29 (46%) patients: biliary obstruction due to stones or strictures (15), ductal dilatation alone (7), spontaneous choledochoduodenal fistula (3), communication between abscesses and biliary tree (3), and splaying of biliary ducts by space-occupying effect (2). No abnormality was found in 34 patients. Eight patients underwent endoscopic therapy including sphincterotomy (5), stone extraction (6), and nasobiliary drainage (2). Overall mortality rate from liver abscesses was 6%. CONCLUSIONS: ERCP is useful in the treatment of patients with pyogenic liver abscesses.

Adolescent↗
PubMed1999

Maternal serum alpha-fetoprotein and human chorionic gonadotrophin in pregnancies conceived after intracytoplasmic sperm injection and conventional in-vitro fertilization.

Data in the Caucasian population suggest that maternal serum alpha-fetoprotein (AFP) and unconjugated oestriol concentrations are reduced and human chorionic gonadotrophin (HCG) concentrations are elevated in pregnancies conceived after in-vitro fertilization (IVF), leading to a higher than expected Down's syndrome screen-positive rate. There are no previous reports on the serum marker values in pregnancies conceived after intracytoplasmic injection (ICSI). Between 1996 and 1998, we measured maternal serum total HCG and AFP concentrations between 15 and 20 weeks gestation in 42 in-vitro fertilization (IVF) pregnancies and 23 ICSI pregnancies with known normal outcome. The results were compared with that of 2799 naturally occurring singleton pregnancies who were known to have a normal outcome. Median AFP multiple of the median (MOM) in ICSI pregnancies was significantly reduced to 0.76 compared with both that of the controls and that of the IVF pregnancies. For the IVF pregnancies, median HCG MOM was elevated to 1.15, and median AFP MOM was reduced to 0.88 compared with the controls, but these differences were not statistically significant. In both the IVF and ICSI pregnancies the changes might result in a falsely high Down's syndrome risk. In particular, the reduced AFP concentration in ICSI pregnancies was substantial. If this preliminary finding is substantiated by other series, the appropriate adjustment needs to be made to allow for valid interpretation of the screen result and to avoid an unnecessarily high false positive rate.

Adult↗
PubMed1999

Assessing chemotherapy response of squamous cell oesophageal carcinoma with spiral CT.

45 patients with squamous cell carcinoma of the oesophagus were examined prior to, and following, pre-operative chemotherapy by spiral CT. Oesophageal CT was performed following gaseous distention of the oesophagus. TNM stage and perceived resectability on CT before and after chemotherapy were compared and related to surgical resectability and pathological staging. T-stage changed in 26% and N-stage changed in 9% of tumours after chemotherapy. Post-chemotherapy CT predicted pathological T-stage with an accuracy of 88% and N-stage with an accuracy of 84%. Six of 14 tumours considered irresectable on CT pre-chemotherapy were considered resectable on post-chemotherapy CT. Five of these six tumours were resectable at surgery. Post-chemotherapy CT predicted surgical resectability with an accuracy of 88%, the main pitfall being underestimation and overestimation of tracheobronchial invasion. CT prediction of chemotherapy response as judged by change in tumour volume was compared with a quantitative pathological assessment of chemotherapy response. 93% of oesophageal tumours changed volume after chemotherapy with 51% having a volume reduction of > or = 50%. However, no correlation was found between tumour volume reduction on serial CT examinations and either a quantitative pathological assessment of tumour response or patient survival.

Carcinoma, Squamous Cell↗
PubMed1999

Variable levels of mosaicism for trisomy 21 in a non-immune hydropic infant with chylothorax.

We report the first case of mosaic trisomy 21 with non-immune hydrops fetalis and bilateral chylothoraces. Prenatal fetal blood karyotype analysis of 15 fetal cells revealed a 46,XX karyotype. Aggressive prenatal management, including fetal thoracocentesis and pleuro-amniotic shunt, was performed. A clinical phenotype of Down syndrome was apparent after the gross oedema had subsided. Subsequent chromosome study of neonatal blood lymphocytes showed mosaic trisomy 21 with 23 per cent trisomic cells. Review of the initial fetal blood sample identified trisomy in 5 per cent of 134 cells. Follow-up study at five months showed no trisomy 21 in 100 cells. This case illustrates the variable levels of mosaicism manifest in the peripheral blood of an infant with obvious Down syndrome phenotype, and the limitation of cytogenetic analysis of peripheral lymphocytes alone in prenatal and postnatal detection of low levels of mosaicism.

Adult↗
PubMed1999

Sonographic diagnosis of limb reduction defects in a fetus with haemoglobin Bart's disease at 12 weeks of gestation.

Limb reduction defect is a rare event but is found in eight per cent of fetuses affected by haemoglobin Bart's disease. We present a case of haemoglobin Bart's disease with terminal transverse limb reduction defects of all four limbs diagnosed by abdominal ultrasound examination at 12 weeks of gestation. The pregnancy was terminated by suction curettage. Just prior to the procedure, transabdominal needle embryoscopy was performed and this confirmed the sonographic diagnosis. The present case demonstrates the need and feasibility of a detailed anatomic survey of a fetus affected by haemoglobin Bart's disease at 12 weeks. This is particularly relevant if the patient is considering the option of intra-uterine therapy.

Adult↗
PubMed1999

Risk of neural tube defects in the offspring of thalassaemia carriers in Hong Kong Chinese.

The risk of having an offspring with neural tube defect is negatively correlated with early pregnancy maternal folate levels. Thalassaemia carriers often have subnormal folate levels. We postulate that their offspring may be at increased risk of having neural tube defect. We retrospectively reviewed the records of 1961 Chinese women referred to a tertiary centre for prenatal diagnosis between January 1997 and August 1998. Women with a mean corpuscular volume greater than 80 fl were assumed not to be alpha-thalassaemia-1 or beta-thalassaemia heterozygotes. alpha- and beta-thalassaemia heterozygotes were diagnosed by haemoglobin studies. Of the 1961 women studied, pregnancy outcome was not available in 20 and thalassaemia screening was not available in 109 and these were excluded from the final analysis. Two-hundred-and-six women were alpha-thalassaemia-1 heterozygotes, 102 women were beta-thalassaemia heterozygotes and one woman had HbE disease. Three alpha-thalassaemia carriers and one beta-thalassaemia carrier had a pregnancy affected by anencephaly (odds=1:76). In the 1523 non-carriers, five pregnancies were affected by spina bifida (odds=1:304). The odds ratio (95 per cent confidence interval) for neural tube defects in the alpha- and beta-thalassaemia carriers was 3.99 (1.07 to 14.94; p<0.05, Chi-square test). Because of the small number of affected pregnancies studied, the finding needs to be substantiated by a larger series. If the increased risk is genuine, women need to be screened for thalassaemia before conception and the thalassaemia carriers should be given periconceptional folate supplement to reduce the occurrence of neural tube defects.

Asian People↗
PubMed1998

Ultrasound diagnosis of fetal diaphragmatic hernia and complex congenital heart disease at 12 weeks' gestation--a case report.

Congenital diaphragmatic hernia is commonly associated with congenital heart disease. Their coexistence indicates a poor prognosis. Prenatal diagnosis of these conditions in early pregnancy allows the option of pregnancy termination. We present a case of left-sided fetal diaphragmatic hernia and complex congenital heart disease diagnosed by ultrasound examination at 12 weeks' gestation.

Abortion, Induced↗
PubMed1998

A randomized comparison of acute phase response and endotoxemia in patients with perforated peptic ulcers receiving laparoscopic or open patch repair.

BACKGROUND: In patients with peritonitis from perforated peptic ulcers, we compared acute stress responses, endotoxemia, and bacteremia following laparoscopic or open surgery. PATIENTS AND METHODS: Consecutive patients with peritonitis from perforated peptic ulcers were randomized to receive laparoscopic sutured or open omental repair. Undiluted peritoneal fluid was obtained at surgery for quantitative bacterial and endotoxin (Limulus Amoebocyte Lysate) assay. Serial blood samples were taken at 0, 30, 60, 90, 120, and 180 minutes, and at 12, 24, 48, 72, and 120 hours for determinations of quantitative bacterial and endotoxin assays, interleukin-6 (IL-6), C-reactive protein (CRP), and cortisol. RESULTS: Twenty-two patients were randomized: laparoscopy group (n = 12), open repair group (n = 10). Conversions were required in 3 patients assigned to laparoscopy, leaving 9 patients for analysis. The two groups were comparable in their demographic data, median duration of perforation (13.5 hours versus 10 hours), severity of peritoneal contamination as indicated by viable bacterial count (5.9 x 102 versus 1.5 x 10(2) colony forming unit/mL) and endotoxin concentration in peritoneal fluid (27.2 versus 24.6 EU/mL). No significant endotoxemia or bacteremia was detected in these patients. Median interleukin-6 was highest at 0 hour (1520 versus 962 pg/mL) and fell rapidly following surgery. C-reactive protein peaked at 24 hours and plateaued thereafter. Cortisol was highest intraoperatively and fell thereafter. No difference was noted between the two treatment groups with respect to these inflammatory markers (IL-6 P = 0.19, CRP P = 0.14, cortisol P = 0.56, multivariate analysis of variance). CONCLUSION: Endotoxemia and bacteremia are insignificant in most patients with perforated peptic ulcers. In patients with perforated peptic ulcers, laparoscopic patch repair does not reduce acute stress responses when compared with open surgery.

Acute-Phase Proteins↗
PubMed1998

A solid-state NMR study of protein hydration and stability.

PURPOSE: The mobility of protein in powders at different hydration levels was studied in relation to aggregation and activity. METHODS: Magic angle spinning 13C, 15N, 1H, 2H, and 17O NMR techniques were used to determine changes in the mobility of surface residues in proteins as a function of hydration and related to changes in activity. NMR relaxation measurements of high frequency (omega0, T1) and low frequency (omega1,T1p) motions have been carried out on lyophilized DNase, insulin and lysozyme stored at different relative humidities. Moisture-induced aggregation and enzymatic activity of the lyophilized proteins was determined by high performance size exclusion chromatography and bioassays. RESULTS: There was little change in T1p observed with increasing humidity. The results show, however, that there is a decrease in T1 for DNase, insulin and lysozyme at relative humidities ranging from 0-98%, and we propose that the reduction in T1 is related to the aggregation susceptibility of proteins during storage at different humidities. The water mobility was determined directly using 17O NMR experiments. We found that as the amount of weakly-bound water increases, the protein surface mobility decreases and is coupled with increased aggregation. Aggregation measurements at different humidities were correlated with bioassays for lysozyme and found to be consistent with the hydration data. CONCLUSIONS: Mobility of protein molecules was determined by solid-state NMR over a wide range of % RH and it was found that water content leads to a change in mobility of protein molecules. The aggregation and activity of proteins were strongly correlated to change in molecular mobility.

Carbon Isotopes↗
PubMed1998

Clinical significance of amniotic-fluid-cell culture failure.

Recent reports suggest an increased incidence of chromosomal abnormalities in pregnancies with amniotic fluid-cell culture failure. We retrospectively reviewed the cytogenetic results of 14,165 amniotic fluid samples processed in our laboratory from 1987 to 1996. Ninety-eight per cent of the samples were obtained before 24 weeks' gestation, mainly because of advanced maternal age; 2 per cent were obtained after or at 24 weeks because of the ultrasonographic finding of fetal structural defects. Amniotic-fluid-cell culture failure occurred in 62 cases (0.44 per cent). Culture failure was more common in samples obtained after or at 24 weeks' gestation (10 per cent) than in those obtained before 24 weeks (0.27 per cent) (P < 0.001, chi-square test). This difference was also observed when the results were analysed according to the cases with known normal or abnormal karyotypes. The frequency of culture failure did not differ significantly between the groups with normal and abnormal karyotypes. We conclude that amniotic-fluid-cell culture failure is more common in advanced pregnancy with an ultrasonographic finding of fetal structural defects and is not associated with a higher incidence of chromosomal abnormalities.

Amniotic Fluid↗