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Biomedical subjects

M H Tang

Publications and source records attributed to M H Tang.

At least 19 recordsLinked to original sources
PubMed2001

The effect of fetal gender on nuchal translucency at 10-14 weeks of gestation.

Recent data have suggested that fetal nuchal translucency (NT) is affected by fetal gender. We investigated the size of this effect in 12 189 unselected pregnancies with known normal outcomes that had undergone NT measurements between 10 and 14 weeks of gestation. NT increased with gestation and was converted to multiples of the median (MoM) for the gestational day. The median NT MoM (95% CI) for female fetuses was 0.98 (0.97-0.99). This was significantly lower than that of the male fetuses (1.03; range 1.02-1.04) (p<0.0005; Wilcoxon rank-sum test). The gender difference was not observed at 10 weeks but was observed from 11 weeks onwards. There is no obvious explanation for the above findings.

Adult↗
PubMed2001

Embryonic and fetal globins are expressed in adult erythroid progenitor cells and in erythroid cell cultures.

The understanding of human hemoglobin ontogeny during development is of biological and clinical importance. Molecular and immunocytological techniques were used to study the expression of embryonic zeta (zeta), epsilon (epsilon), and fetal gamma (gamma) globin genes in newborn cord blood, peripheral blood from men, pregnant and non-pregnant women, and in vitro mononuclear cell cultures. We have shown that embryonic and fetal globin mRNA and peptides are expressed in cultured erythroid cells and in circulating blood cells from newborns, adult non-pregnant women and from men. The findings suggest that during erythroid cell differentiation in newborns and adults, there is a transient recapitulation of sequential globin chain expression as found during embryonic and fetal development. Furthermore, these findings underscore the need for caution in using embryonic and fetal globin chains as markers to identify erythroid cells of fetal origin in maternal circulation for prenatal diagnosis.

Adult↗
PubMed2001

Ductus venosus Doppler study in fetuses with homozygous alpha-thalassemia-1 at 12 to 13 weeks of gestation.

OBJECTIVE: Fetuses affected by homozygous alpha-thalassemia-1 are anemic from the first trimester of pregnancy. We investigated ductus venosus Doppler velocimetry in these affected fetuses at 12-13 weeks of gestation. DESIGN: Prospective observational study. SUBJECTS: Women referred for the prenatal diagnosis of homozygous alpha-thalassemia-1 before 14 weeks of gestation. METHODS: All fetuses underwent pulsed Doppler investigations following color flow mapping at 12 or 13 weeks of gestation. Homozygous alpha-thalassemia-1 was diagnosed by DNA or hemoglobin study. The ductus venosus Doppler indices--Vmax (peak velocity during ventricular systole), Vmin (minimum forward velocity during atrial systole), TAMX (time-averaged maximum velocity), PIV (pulsatility index for veins, Vmax-Vmin/TAMX), PLI (preload index, Vmax-Vmin/Vmax) and Vmax/Vmin ratio--were compared between the affected fetuses and fetuses unaffected by homozygous alpha-thalassemia-1. RESULTS: Between June 1998 and October 1999, 102 eligible women were recruited. Fetal ductus venosus Doppler study was successful in 96 pregnancies (94%). Of these, 20 fetuses were affected by homozygous alpha-thalassemia-1. None of them showed hydropic changes at the time of Doppler study. The affected fetuses had significantly higher ducts venosus Vmax (30% increase), Vmin (50% increase) and TAMX (20% increase) and significantly lower Vmax/Vmin ratio, PIV and PLI values. CONCLUSION: Fetuses affected by homozygous alpha-thalassemia-1 at 12-13 weeks had increased forward flow velocities in the ductus venosus throughout the cardiac cycle. The increase of venous return is consistent with our previous report of cardiac dilatation and an increase of cardiac output in the affected fetuses at this stage as a compensatory mechanism for anemia and hypoxia. However, extensive overlap of the ductus venosus Doppler indices between affected and unaffected fetuses precludes its use in predicting anemia at 12-13 weeks.

Blood Flow Velocity↗
PubMed2001

The effect of fetal gender on second-trimester maternal serum inhibin-A concentration.

Second-trimester serum inhibin-A is increasingly used as a fourth marker in addition to the triple test to screen for Down syndrome. We investigated whether fetal gender had an effect on serum inhibin-A concentration. A retrospective analysis was done on 316 normal pregnancies and 48 Down syndrome pregnancies in which maternal serum inhibin-A assays were performed between 15 and 20 weeks of gestation and in which the fetal sex was known. The median inhibin-A MoM (95% CI) for normal pregnancies in the presence of a male fetus was 0.93 (range 0.88-1.03). This was significantly lower than that in the presence of a female fetus (median MoM=1.04). The gender difference was not observed in the Down syndrome pregnancies. The increased inhibin-A concentration would lead to a 2.3-fold higher false-positive rate in the presence of a female fetus (10.6% vs. 4.6%; p<0.05, Chi-square test). Because of the small number of cases studied, the results need to be substantiated by a larger series. If the gender effect is confirmed, adjustment for fetal sex may be necessary when inhibin-A is used as a screening marker.

Adult↗
PubMed2001

Isolated foetal ascites.

The prenatal diagnosis and perinatal outcome of two patients with isolated foetal ascites compatible with chyloperitoneum is described. The foetal ascites resolved spontaneously after delivery with good perinatal outcome in both cases. A good prognosis can be anticipated in such cases. Antepartum and intrapartum interventions are seldom necessary.

Adult↗
PubMed2000

Base-catalyzed epimerization of the butenolide in annonaceous acetogenins.

The elusive epimerization process in the chiral butenolide moiety of Annonaceous acetogenins was examined under several sets of conditions commonly used for elimination leading to the alpha, beta-unsaturated lactone and the results provide practical guidance in choosing elimination conditions.

4-Butyrolactone↗
PubMed2000

Acceptability of serum screening as an alternative to cytogenetic diagnosis of down syndrome among women 35 years or older in Hong Kong.

The addition of second trimester serum markers to maternal age increases the efficacy of screening for Down syndrome by maternal age alone. Among women aged 35 years or older, serum screening makes a large proportion of amniocentesis unnecessary. However, there are ethical and medicolegal concerns about serum screening in 'old' women, largely because some of the pregnancies affected by Down syndrome and other chromosomal abnormalities may not be detected. We investigated the acceptability of serum screening in women aged 35 years or older when it was offered as an alternative to prenatal cytogenetic diagnosis after detailed counselling. Women referred for prenatal diagnosis of Down syndrome because of advanced maternal age were given the options of cytogenetic diagnosis by chorionic villus sampling (CVS) or amniocentesis. As an alternative, they could choose to undergo second trimester serum human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP) screening first before deciding on whether to undergo amniocentesis. Between January 1997 and October 1999, 3419 subjects were recruited. 1807 women (52. 9%) chose to undergo serum screening, 1516 women (44.3%) chose to have amniocentesis and 96 women chose to have CVS (2.8%). The proportion of women who chose serum screening rose steadily from 38. 8% in the year of 1997 to 63.4% in 1999. Significantly fewer Chinese women chose serum screening than non-Chinese. The decision as to whether to undergo an invasive diagnostic procedure or to be content with the relatively safer but less accurate screening test varies, being affected by the women's background and culture.

Adult↗
PubMed2000

Prenatal diagnosis of haemoglobin Bart's disease by cordocentesis at 12-14 weeks--experience with the first 59 cases.

We have shown that fetuses affected by haemoglobin (Hb) Bart's disease can be reliably identified by their sonographic manifestation of cardiac enlargement at 12-14 weeks. Between 1995 and 1999, 282 couples were seen before 15 weeks. They were offered the options of chorionic villus sampling, or amniocentesis and DNA study, or ultrasound examination at 12-14 weeks, followed by cordocentesis and Hb study only when the ultrasound findings were abnormal. Two hundred and thirty-four at-risk pregnancies had ultrasound assessment at 12-14 weeks, 62 fetuses showed enlarged cardiothoracic ratio [mean (SD) 0.54 (0.02)] and four of them also had hydropic changes. Fifty-nine women agreed to undergo cordocentesis at 12-14 weeks and the procedure was successful in 57 cases (97%). Cordocentesis were performed by a freehand technique using a 26- or 24-gauge spinal needle with a 20-gauge introducer. Fifteen fetuses (25%) had bleeding from the cord and 12 fetuses (20%) had bradycardia following cordocentesis. The fetal loss rate was 8% (5/59). Hb Bart's disease was confirmed in all the 62 fetuses with cardiac enlargement. Their Hb concentration ranged between 3.1 to 8.4 g/dl. One hundred and seventy-two fetuses had normal ultrasound assessment and 148 of them were confirmed to be unaffected by Hb Bart's disease. Twenty-three pregnancies were ongoing and one miscarried at 15 weeks. We believe that sonographic assessment followed by selective cordocentesis at 12-14 weeks is a feasible prenatal diagnostic option for Hb Bart's disease.

Adult↗
PubMed2000

Serial sonographic features of a fetus with hydranencephaly from 11 weeks to term.

Fetal hydranencephaly is a rare congenital cerebral abnormality characterized by complete or near complete absence of the cerebral cortex. We present the sonographic evolution of a case of fetal hydranencephaly from 11 weeks of gestation to term. At 11 weeks, the fetal head appeared small and the forehead was sloping. The normal cerebral hemispheres could not be identified. Follow-up sonography showed that the cerebral hemispheres were almost entirely replaced by fluid, except in the occipital region. The baby died 2 weeks after birth. Post-mortem examination confirmed the diagnosis of hydranencephaly.

Adult↗
PubMed2000

Sonographic diagnosis of congenital megalourethra at 13 weeks of gestation.

Congenital megalourethra is a rare disorder characterized by the congenital absence of the corpus spongiosum and/or corpus cavernosum, leading to dilatation of the urethra. We present a case of congenital megalourethra diagnosed by ultrasound examination at 13 weeks of gestation. Transabdominal and transvaginal sonography showed gross megacystis, bilateral hydronephrosis and a cystic dilatation of the penis. Transabdominal needle embryoscopy confirmed a balloon dilatation of the fetal penis. The pregnancy was terminated by suction curettage.

Adult↗
PubMed2000

Thermocoagulation for selective reduction of conjoined twins at 12 weeks of gestation.

Conjoined twins occur rarely. Most of the prenatally diagnosed cases are terminated either because of extensive organ sharing or because of the presence of major structural abnormalities. We present a case of omphalopagus conjoined twins diagnosed at 10 weeks of gestation with selective reduction performed at 12 weeks. The twins were conjoined at the umbilicus with vascular communication demonstrated at the conjunction. Twin A was normal but twin B was growth restricted and hydropic. Thermocoagulation of twin B was performed at 12 weeks by passing an insulated electric wire through a 18-gauge needle placed close to the fetal heart. Reassessment at 15 weeks showed that twin A was growing normally with a small dead twin B attached at its umbilicus. Twin B was subsequently sloughed off from this attachment and could be seen lying free in the amniotic cavity at 17 weeks. Twin A was delivered at term and was healthy. A small scar could be seen just above the umbilical cord insertion. This case represents the first antenatal example of selective reduction of conjoined twins by thermocoagulation.

Adult↗
PubMed2000

Limb reduction defects as the sonographic manifestation of hemoglobin Bart's disease at 10 weeks of gestation.

Fetuses affected by hemoglobin Bart's disease are anemic and hypoxic from the first trimester. They develop cardiac and placental enlargement and have a high incidence of limb reduction defects and hypospadias. We present a fetus at risk for hemoglobin Bart's disease with multiple limb reduction defects detected at 10 weeks of gestation, which allowed a strong presumptive diagnosis of hemoglobin Bart's disease to be made at the time of ultrasound examination. The limb defects were verified by direct visualization via needle embryoscopy. The present case suggests that sonographic identification of limb reduction defects may be a specific marker of hemoglobin Bart's disease at 10 weeks.

Adult↗
PubMed2000

[Expression and roles of hemoglobin gene in Bacillus subtilis].

Hemoglobin of the Gram-negative bacterium Vitreoscilla can bind oxygen strongly and reduce the oxygen requirement of the bacterium. A recombinant plasmid pAV was constructed by inserting the hemoglobin gene (Vgb) to the downstream of the promoter of beta-lactase gene of the B. subtilis plasmid pAK4. The plasmid pAV was transferred into strain DB104, G331 (a subtilisin-producing B. subtilis) and B53 (a xylanase-producing B. subtilis). The subclones and transfer of the Vgb gene into pAK4 were detected and confirmed by Dot blotting and electrophoresis analysis. The expression of homoglobin was measured by recording CO-difference spectra after bubbling CO into the sample cuvette. The production of subtilisin and xylanase was increased in the fermentation of the Vgb-expressing strains. These results provided a new way to reduce the oxygen requirement and to increase the biomass production in the fermentation industry.

Bacillus subtilis↗
PubMed2000

Schistosomiasis of the ovary with endometriosis and corpus hemorrhagicum: a case report.

We present a case of Schistosomiasis of the ovary associated with endometriosis and corpus hemorrhagicum. This association has not been reported previously. A 31-year-old Filipino woman visited Li Shin Hospital because of several weeks' history of lower abdominal pain. An ultrasound study revealed a right ovarian mass, and a right oophorectomy was performed. The gross findings included a corpus hemorrhagicum and endometriosis. The histopathologic findings revealed Schistosoma japonicum eggs in the fibrous wall of the ovary with evidence of a chronic inflammatory response containing eosinophils. After a second surgery and medical treatment with antiparasitic drugs, her symptoms were relieved. Adhesions resulting from the oophorectomy and endometriosis of the ovary had resulted in alteration of the blood channels and contributed to the aberrant spread of the Schistosoma eggs. The migration of overseas workers from endemic countries and the growing popularity of worldwide tourism may increase the incidence of parasitic infections.

Adult↗
PubMed1999

Second-trimester maternal serum inhibin-A screening for fetal Down syndrome in Asian women.

Case control studies in the Caucasian population showed that maternal serum inhibin-A is elevated in Down syndrome pregnancies and may be a useful second-trimester marker in addition to human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP). Data in the Asian population are lacking. We measured inhibin-A levels in the stored maternal sera of 49 Down syndrome pregnancies and 341 controls with a commercially available assay and expressed them as the multiples of the median of the gestational week. The log means and standard deviations for case and control inhibin-A MOMs were 0.209, 0.226, and 0.002 and 0.177, respectively. Median inhibin-A MOM in Down syndrome cases was elevated to 1.62 (95 per cent confidence interval, 1.29-1.82). 36 per cent of Down syndrome cases were expected to be detected at a 5 per cent false-positive rate. However, inhibin-A MOMs were strongly correlated with hCG MOMs in the cases (r=0.73, p<0.001) and the controls (r=0.56, p<0.001). This will diminish the value of adding inhibin-A to the existing hCG and AFP screening protocol.

Adult↗
PubMed1999

Histological findings in a case of alobar holoprosencephaly diagnosed at 10 weeks of pregnancy.

A case of alobar holoprosencephaly diagnosed at 10 + 3 weeks' gestation by transabdominal and transvaginal ultrasound examination followed by histological confirmation is presented. The diagnosis was based on two sonographic criteria: intracranial finding of a single ventricle with a mantle and no visible midline structures but fusion of the thalami and corpus striatum, and facial abnormalities, including hypotelorism and proboscis. The fetal karyotype was triploidy. The ultrasound findings were confirmed by pathological examination. The histological findings of proboscis, single lens and single ventricle with neural tissue remnants are presented.

Adult↗
PubMed1999

Prenatal ultrasonographic prediction of homozygous type 1 alpha-thalassemia at 12 to 13 weeks of gestation.

We determined the feasibility of prenatal prediction of type 1 homozygous alpha-thalassemia at 12 to 13 weeks of gestation by either abdominal or vaginal (or both) ultrasonographic examination to measure the fetal cardiothoracic ratio in 135 at-risk pregnancies. Forty-three fetuses were affected by homozygous type 1 alpha-thalassemia. The mean cardiothoracic ratio was significantly larger than that of the unaffected fetuses (0.54 vs 0.45, P <.0005), with no overlap between the 2 groups. A cardiothoracic ratio cutoff point of >/=0.5 was 100% sensitive and specific for disease.

Feasibility Studies↗