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Biomedical subjects

T H Bui

Publications and source records attributed to T H Bui.

At least 19 recordsLinked to original sources
PubMed2001

[Twin-twin transfusion syndrome--front line in fetal medicine].

Twin-twin transfusion develops in 10-20% of monochorionic twin pregnancies. As far as we know the underlying disturbance is an unbalanced anastomosis between the two fetuses on the placental surface. Without treatment mortality is as high as 80% if diagnosed before viability. One of this article's authors spent two months in Hamburg at the "Allgemeine Krankenhaus", Barmbeck in Germany and describes the technique used there to coagulate these anastomoses via fetoscope. The outcome seems very promising with overall survival of 80% using this method. In the article pathogenesis and alternative treatments are also discussed.

Female↗
PubMed2001

[Twin-twin transfusion syndrome--front line in fetal medicine].

Twin-twin transfusion develops in 10-20% of monochorionic twin pregnancies. As far as we know the underlying disturbance is an unbalanced anastomosis between the two fetuses on the placental surface. Without treatment mortality is as high as 80% if diagnosed before viability. One of this article's authors spent two months in Hamburg at the 'Allgemeine Krankenhaus', Barmbeck in Germany and describes the technique used there to coagulate these anastomoses via fetoscope. The outcome seems very promising with overall survival of 80% using this method. In the article pathogenesis and alternative treatments are also discussed.

Female↗
PubMed2001

Second-trimester biochemical screening.

The past years have seen considerable progress in the area of biochemical screening. Increasing data have now clearly shown the advantages of multiple markers, particularly beta-hCG over AFP alone. There continues to be considerable controversy over the best mathematic algorithm and which markers are best (e.g., beta-HCG, uE3, and so forth). There seems to be a plateau of detection frequencies at about 65% to 70% with current methodologies. Further work needs to be done, however, including some new approaches, if there is to be substantial improvement of screening sensitivity. The combination of biochemical with biophysical parameters as discussed elsewhere in this issue represents the next level of sophistication in the attempt to identify the highest proportion of abnormalities with the fewest false-positives.

Algorithms↗
PubMed2000

Early prenatal diagnosis of the ICF syndrome.

The ICF syndrome (immunodeficiency, (para)centromeric instability and facial abnormalities) is a rare autosomal recessive disorder with characteristic cytogenetic aberrations of chromosomes 1, 9 and 16 in lymphocytes. Previously, only one case has been diagnosed prenatally in the second trimester of pregnancy by fetal blood sampling. We report the first early prenatal exclusion of the ICF syndrome by chorionic villous sampling (CVS) and linkage analysis in a family with a previous affected child. The fetus was heterozygous for marker D20S850 closely linked to the ICF locus. The family was counselled of a probability of over 90% that the fetus would be unaffected. Postnatal chromosome analysis on peripheral blood was normal and thus confirmed the prenatal diagnosis.

Adult↗
PubMed2000

Stereospecific versus nonstereospecific assessments for the bioequivalence of two formulations of racemic chlorpheniramine.

Chlorpheniramine (chlorphenamine, CPAM) is a racemic antihistaminic H1 drug containing two enantiomers. The aim of this study was to assess the bioequivalence of two formulations (reference and Vietnamese-tested formulation) of racemic chlorpheniramine combined with phenylpropanolamine in an open-labeled, randomized, crossover two-period study, after administration of 8 mg of racemic chlorpheniramine in 12 healthy Vietnamese subjects. First, dissolution of both formulations was tested in vitro according to USP requirements. Then the 12 subjects received both formulations after an overnight fast and a 7-day wash-out period. Plasma samples were collected up to 168 h. Plasma concentrations of total chlorpheniramine and its individual enantiomers were determined with a validated chiral HPLC method and pharmacokinetic parameters were estimated using model-independent analysis. For the reference formulation, Cmax and AUC values were higher for (+)S-chlorpheniramine ((+)S-CPAM) compared to (-)R-chlorpheniramine ((-)R-CPAM) (13.3 vs. 6.8 ng/ml and 409 vs. 222 ng/ml/h, respectively) while Clt/F and Vd/F were lower (9.8 vs. 17.6 l/h and 321 vs. 627 l, respectively). No difference was observed for Tmax, t(1/2), and MRT. Pharmacokinetic parameters were similar for the reference and the Vietnamese-tested formulation. Bioequivalence was assessed by Schuirmann test, as recommended by the current FDA and European Community criteria. Dissolution tests showed that both formulations were equivalent. A nonstereospecific, but not a stereospecific, approach indicated bioequivalence between the formulations.

Adult↗
PubMed2000

Successful EXIT (ex utero intrapartum treatment) procedure in a fetus diagnosed prenatally with congenital high-airway obstruction syndrome due to laryngeal atresia.

Congenital high-airway obstruction syndrome (CHAOS) is due to rare malformations and has been reported previously in only few cases. If the diagnosis can be made prenatally, the ex utero intrapartum treatment (EXIT) procedure may be life-saving. A healthy 28-year old nulli-para was referred because of isolated ascites found at gestational week 16 during routine ultrasound scan. Repeated scans showed overdistended hyperechogenic lungs with inverted diaphragm and a dilated trachea, which was interpreted as a CHAOS resulting from laryngeal atresia. The ascites eventually disappeared. An EXIT procedure was performed at 35 weeks of gestation. Anesthesia of the mother was induced with thiopental, succinylcholine and fentanyl followed by intubation, and maintained with isoflurane and nitrous oxide. A low abdominal midline incision was performed followed by a low transverse incision of the uterus. The fetal head, right arm and shoulder were delivered and intramuscular anesthesia was administered to the fetus. Immediate laryngoscopy confirmed the diagnosis and a tracheostomy was therefore performed. Surfactant was given after a few minutes of ventilation. Compliance improved and when the fetus was easy to ventilate, it was delivered. The baby is developing normally at 18 months of age. Surgical correction of the malformation will be performed after two years of age. It is concluded that some fetuses with a prenatal diagnosis of CHAOS can benefit from the EXIT procedure at delivery. This necessitates a multidisciplinary management team.

Adult↗
PubMed2000

Complex genetic counselling and prenatal analysis in a woman with external ophthalmoplegia and deleted mtDNA.

Single large mitochondrial DNA deletions (DeltamtDNA) are usually spontaneously occurring and cause a wide variety of symptoms, ranging from severe infantile multisystem disorders to adult onset progressive external ophthalmoplegia (PEO). There is always heteroplasmy with a mixture of normal and mutant mtDNA and the levels usually vary widely between tissues. There is at present insufficient scientific basis for accurate genetic counselling of women with DeltamtDNA, but it is reasonable to assume that DeltamtDNA can be transmitted if it is present in the female germ cells. Here, we present the results of prenatal analysis in a woman with DeltamtDNA and PEO. No DeltamtDNA was detected by Southern blot and PCR analyses of chorionic villi from the first trimester of pregnancy, in cord blood obtained at birth or in peripheral blood from the child at six months of age. This makes it unlikely that the child will develop a severe infantile mitochondrial disorder due to transmission of high levels of DeltamtDNA. However, the complex mitochondrial genetics and the limited access to human tissues makes it impossible to exclude transmission of low levels of DeltamtDNA that possibly could cause disease later in life.

Adult↗
PubMed1999

[Folic acid protects against neural tube defects. But how many women of reproductive age have been informed about this fact?].

The involvement of folic acid in the aetiology of neural tube defects (NTDs) has been discussed for decades. Both observational and controlled intervention trials have shown periconceptional folic acid supplementation (PFAS) to significantly reduce the incidence both of first-time and recurrent NTDs. PFAS may also be associated with reduction in the incidence of certain other congenital malformations, preterm delivery, and intra-uterine growth retardation. However, the mechanism whereby folic acid exerts its protective effect remains unclear. Thermolabile 5,10-methyl-enetetrahydrofolate reductase was the first folate-related enzyme to be associated with an increased risk of NTDs. This genetic variant may result in increased plasma homocysteine levels, which have been linked to an increased risk of NTDs. The folate-dependent genetic variants known today can explain no more than 30-50 per cent of the observed protective effect of folate. However, available evidence suggests low maternal folate status itself to be the major determinant of NTD risk. Since the vast majority of NTDs are first occurrences, and in Sweden a large proportion of fetuses with spina bifida remain undetected at routine ultrasonography during pregnancy, primary prevention by means of PFAS represents a major potential public health asset, capable of reducing both mortality and morbidity due to NTDs. Accordingly, implementation of a national strategy to reduce the incidence of NTDs, and promote awareness among health care providers and women of reproductive age of the benefits of PFAS is strongly to be recommended. Although supplemental folic acid tablets are the best proven means of improving folate status, compliance may be a problem, which emphasises the importance of considering a nutrient fortification programme as a complementary strategy for reducing the incidence of NTDs.

Female↗
PubMed1999

International, collaborative assessment of 146,000 prenatal karyotypes: expected limitations if only chromosome-specific probes and fluorescent in-situ hybridization are used.

The development of chromosome-specific probes (CSP) and fluorescent in-situ hybridization (FISH) has allowed for very rapid identification of selected numerical abnormalities. We attempt here to determine, in principle, what percentage of abnormalities would be detectable if only CSP-FISH were performed without karyotype for prenatal diagnosis. A total of 146 128 consecutive karyotypes for prenatal diagnosis from eight centres in four countries for 5 years were compared with predicted detection if probes for chromosomes 13, 18, 21, X and Y were used, and assuming 100% detection efficiency. A total of 4163 abnormalities (2.85%) were found including 2889 (69. 4%) (trisomy 21, trisomy 18, trisomy 13, numerical sex chromosome abnormalities, and triploidies) which were considered detectable by FISH. Of these, 1274 were mosaics, translocations, deletions, inversions, rings, and markers which would not be considered detectable. CSP-FISH is a useful adjunct to karyotype for high risk situations, and may be appropriate in low risk screening, but should not be seen as a replacement for karyotype as too many structural chromosome abnormalities will be missed.

Chromosome Aberrations↗
PubMed1998

[Minimally invasive techniques make fetal surgery possible. Disabling abnormalities can be corrected].

Increases in our knowledge of the fetus and improved skill in early prenatal diagnosis inevitably result in attempts to treat some of the abnormalities detected. Although most fetal malformations diagnosed prenatally in continuing pregnancies are best managed by medical and surgical intervention after planned delivery, some structural defects may require in utero-treatment to forestall subsequent sequelae. The article consists in a review of the current status of ultrasound-guided invasive fetal therapy, including multifetal pregnancy reduction, manipulation of amniotic fluid, drainage and shunting procedures, fetal transfusion therapy, operative fetoscopy, and in utero stem cell transplantation. Future prospects and developments in this rapidly expanding field are also outlined.

Amniocentesis↗
PubMed1998

[Successively improved prognosis in erythrocyte immunization].

Prognosis in cases of erythrocyte immunisation has improved continuously over the past decades. Morbidity and mortality have been reduced by improvements in management, including screening programmes, non-invasive ultrasound evaluation and invasive procedures. The article provides an outline of the latest developments in the management of erythrocyte immunisation, and several controversial issues are discussed, such as antibody screening, strategies for the reduction of antibody titres, and the organisation of care.

Anemia, Neonatal↗
PubMed1998

Fetal therapy: prospects for transplantation early in pregnancy. In utero stem cell transplantation and gene therapy: second international meeting, Nottingham, UK, 1-2 September 1997.

The meeting was punctuated by discussion sessions enabling delegates and speakers to debate issues raised. A number of questions were aired and areas that need to be addressed with some urgency were highlighted. Tolerance induction in utero is now considered feasible and can be added to the potential outcomes of IUT. Agreement must be reached on the source of stem cells for IUT, and stem cell banking will need to meet internationally accepted standards. Finally, the transplantation protocol itself must be agreed, a challenge that must be met if IUT is to join the mainstream of therapeutic protocols.

Animals↗
PubMed1998

Stem cell transplantation into the fetal recipient: challenges and prospects.

The interest in therapeutic intervention for those inherited disorders that can be diagnosed early in pregnancy has recently intensified. In-utero transplantation of haematopoietic stem cells (IUT-HSC), a therapy which could be proffered before pathological manifestations of a disorder become apparent, offers considerable potential benefit. However, as reports of IUT-HSC procedures become more prolific, it is necessary to consider the optimum modus operandi for each group of disorders targeted for therapy in order to develop effective procedures that make a real difference to the outcome. This review outlines the current status and prospects of IUT-HSC. It also offers a view of some of the challenges for IUT-HSC to overcome to find wider clinical applications.

Female↗
PubMed1998

Long-term somatic follow-up of prenatally treated children with congenital adrenal hyperplasia.

Prenatal virilization of female fetuses is a serious symptom associated with severe congenital adrenal hyperplasia. In attempt to avoid sexual ambiguity, prenatal treatment of 21-hydroxylase deficiency was initiated in 1984, with the first Scandinavian case treated in 1985. Here we have studied the outcome of prenatal diagnosis and therapy of 44 at-risk pregnancies monitored during the years 1985-1995 in Scandinavia. Treated mothers and children were compared with matched controls. Compared to their elder affected sisters, all 5 girls with severe congenital adrenal hyperplasia who were treated until term showed little virilization. Only 1 required surgery for labial fusion. The majority of the 44 dexamethasone-treated fetuses demonstrated normal pre- and postnatal growth compared to matched controls. However, several adverse events such as failure to thrive and delayed psychomotor development, were reported among the treated infants. In addition, treated mothers reported more side-effects during pregnancy than did controls. A significant increase in weight gain was observed during early pregnancy when treatment was initiated, but this initial rapid weight gain declined during late pregnancy or when treatment was terminated. Thus, experience to date suggests that prenatal treatment of affected female fetuses is generally efficient in minimizing virilization of external genitalia. However, there is still a need to collect more data concerning possible rare unfavorable effects of this therapy on mother and child.

Adrenal Hyperplasia, Congenital↗