Search PubMed⌕ Search

Biomedical subjects

V Chan

Publications and source records attributed to V Chan.

At least 145 records · Page 8Linked to original sources
PubMed1988

Restriction fragment length polymorphisms associated with factor VIII:C gene in Chinese.

Twenty-six unrelated hemophilia A and 70 unrelated normal chromosomes in 184 subjects were studied to determine the frequencies of intragenic and intergenic restriction fragment length polymorphisms associated with the factor VIII:C gene. The incidences for positive BclI and BglI polymorphic sites in the Chinese were 82% and 100%, respectively. Both were higher than in other ethnic groups, while the incidence for XbaI polymorphism was 57%, which is similar to that reported in Caucasians. Using the St14.1 probe, two polymorphic TaqI allelic systems in the DXS52 region were detectable, with heterozygous rates of 0.712 (for system I, alleles 1 to 8) and 0.495 (for system II, alpha and beta alleles), respectively. Thus, using a combination of four polymorphisms, it would be possible to offer carrier detection or prenatal diagnosis in 96% of Chinese females at risk.

China↗
PubMed1988

Prognostic factors in diffuse proliferative lupus glomerulonephritis.

A number of clinical laboratory and biopsy-derived parameters were assessed for their prognostic significance in the short (24 months), intermediate (60 months) and long terms in 45 patients (43 female, 2 male) with diffuse proliferative lupus glomerulonephritis (DPGN). The factors evaluated were serum creatinine (SCr) and urinary protein at time of biopsy, initial dose of prednisone and immunosuppressive after biopsy, activity index (AI), chronicity index (CI), their individual components, extent of extraglomerular (tubulo-interstitial) immune deposits (EGD) and mean number of intraglomerular monocytes per glomerulus (NSE index). Using proportional hazards analysis to evaluate the parameters, SCr (P = 0.003), AI (P = 0.005) and NSE index (P = 0.038) were shown to be significant predictors of outcome when all variables except the components of AI and CI were considered. When AI and CI were omitted but their components included, SCr (P = 0.0005), NSE index (P = 0.024), extent of karyorrhexis (P = 0.035) and glomerulosclerosis (P = 0.033) were then demonstrated to be significant prognostic factors of DPGN. The results suggest that intraglomerular monocyte infiltration has a protective effect and confirm that AI index is a relatively powerful predictor of outcome. Histologic and nonhistologic biopsy factors contribute significant additional prognostic information to that provided by SCr.

Adult↗
PubMed1988

Beta-thromboglobulin in cerebral infarction.

Plasma beta-thromboglobulin (BTG) was significantly elevated in the acute phase of 116 atherosclerotic thrombotic (p less than 0.0001) and 36 cardioembolic (p less than 0.005) infarcts but normal for 96 lacunes compared with controls. This elevation persisted into the 6th week after the acute event. Among atherosclerotic thrombotic infarcts, the acute beta-thromboglobulin level showed a tendency to correlate with infarct size on CT and predicted mortality at 6 weeks. These results suggest that platelet aggregation plays a primary role in the pathogenesis of atherothrombosis.

Aged↗
PubMed1988

Prenatal diagnosis of alpha- and beta-thalassemias: experience in Hong Kong.

The incidence of alpha-thalassemia trait (alpha-thal-1 and alpha-thal-2) among Southern Chinese in Hong Kong is about 3%. From June 1983 to September 1987, prenatal diagnosis for homozygous alpha-thal-1 was performed in 88 pregnancies at risk, using direct DNA analysis of amniotic fluid cells or chorionic villi. Twenty-one homozygous alpha-thal-1 fetuses were aborted and confirmed as Hb Bart's hydrops fetalis, and two were "Hb H" hydrops fetalis. Of 47 pregnancies delivered, 26 were alpha-thal-1 heterozygotes, 10 normal, eight alpha-thal-1/normal. Twenty-one pregnancies, diagnosed as alpha-thal-1/normal, await delivery. Based on a 6% incidence of beta-thalassemia minor among pregnant women in Hong Kong, the number of pregnancies at risk for beta-thalassemia major should be 288 per annum. However, since February 1984, only 25 diagnoses were performed. Comprehensive screening and education programs need to be implemented. The majority of beta-thalassemia defects in Southern Chinese are point mutations, single nucleotide insertions or minor deletions, not detectable by standard gene mapping techniques. With linkage analysis of the defective gene to polymorphic restriction sites, a definitive diagnosis can be obtained in 50% of the families, while in the remaining there is a 50% exclusion rate. We routinely use the Hind III-3' beta, Bam HI-3' beta, Ava II-beta, and Hinc II-psi beta sites for linkage analysis. For first pregnancies, the marked linkage disequilibrium of the Bam HI polymorphism can be applied in 29% of the cases. In nonconclusive cases, fetal blood beta/gamma globin chain synthetic ratio was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1988

A novel beta-thalassemia frameshift mutation (codon 14/15), detectable by direct visualization of abnormal restriction fragment in amplified genomic DNA.

A new frameshift mutation due to an insertion of G between codon 14/15 of the beta-globin gene was found in two unrelated Chinese patients with Cooley's anemia. The first patient (W.S.) was homozygous for haplotype 5 (Chinese) and carried a codon 41/42 (four base pair deletion) mutant, while the second patient (C.K.) was homozygous for haplotype 2 (Chinese), and also had a codon 17 (A----T) nonsense mutation. Molecular cloning and M13 sequencing of the beta gene in patient W.S. revealed that the new mutant was found in a beta-globin gene framework type 3 (Asian). Direct sequencing was performed on polymerase chain reaction-amplified genomic DNA from patient C.K. With the new mutation, an additional BstNI or EcoRII recognition site is generated and the abnormal restriction fragment (134 basepair) can be directly visualized on polyacrylamide gel electrophoresis of the amplified genomic DNA.

Base Sequence↗
PubMed1987

Liver microsomal membrane fluidity and lipid characteristics in vitamin A-deficient rats.

Rat liver microsomes (microsomal fraction) were isolated from vitamin A-deficient and -sufficient rats and analysed for membrane lipid characteristics. Membrane fluidity was found to be significantly decreased in microsomes from the vitamin A-deficient rats, but not in liposomes prepared from lipid extracts. Microsomes from vitamin A-deficient animals showed a significant decrease in C18:2, omega 6 and an increase in C22:5, omega 6 fatty acids.

Animals↗
PubMed1987

Application of DNA polymorphisms for prenatal diagnosis of beta thalassemia in Chinese.

Forty-seven Chinese suffering from beta thalassemia major and their parents were studied to establish linkage of the beta thal and beta A genes with 11 restriction site polymorphisms. There is marked linkage disequilibrium at the BamH I site 3' to the beta globin gene, such that, in 31% of pregnancies, absence of the site in the fetus can exclude beta thalassemia major. Using four restriction sites (Hinc II psi beta, Ava II beta, Hind III beta, and BamH I beta), prenatal diagnosis is feasible in all families. In 46% of all cases, a definitive diagnosis can be made, and in the remaining cases, a 50% chance of exclusion is possible. Fetal blood globin chain analysis would be required for the failures. Our experience in nine successive beta thalassemia prenatal diagnosis is also reported.

China↗
PubMed1987

Ultrasound evaluation of pregnancies at risk for homozygous alpha-thalassaemia-1.

Twenty-six pregnant Chinese women who were at risk of giving birth to a fetus affected with homozygous alpha-thalassaemia-1 were examined serially by ultrasound. Six of these 26 pregnancies were affected. In one third of the affected pregnancies progressive fetal ascites appeared before 24 weeks gestation and these pregnancies were terminated. In the remaining two thirds abnormal estimated fetal weight-placental volume (EFW-PV) ratio and fetal growth retardation as evidenced by a falling biparietal diameter (BPD), femur length (FL) but a normal abdominal circumference (AC) was apparent by 28 weeks gestation. Increased transverse cardiac (TC) diameter was another consistent finding but appeared late. All these features appeared before the onset of fetal ascites. A normal EFW-PV ratio and fetal growth until 28 weeks gestation was a reassuring sign of normality. Abnormal EFW-PV ratio was the earliest sign to appear in affected pregnancies and a normal ratio until 28 weeks gestation had a 100 per cent predictive value.

Female↗
PubMed1987

Distribution of beta-thalassemia mutations in south China and their association with haplotypes.

DNA from 93 Chinese beta-thalassemia chromosomes were hybridized to eight different mutant oligomers to determine their specific mutation. Four mutations accounted for 87% of the chromosomes; in descending frequencies, these mutations were codon 41/42, IVS-2 nt654, codon 17, and -28. Since codon 41/42 mutation can be associated with multiple beta-thalassemia haplotypes, codon 41/42 is probably a hot spot for the 4-bp deletion. The distributions of these mutations were mapped to various regions in south China. These data are useful for the planning of prenatal diagnosis programs in other Chinese communities worldwide.

China↗
PubMed1986

Characteristics and distribution of beta thalassemia haplotypes in South China.

Eleven restriction site polymorphisms in the beta-globin gene cluster were determined in 48 Chinese with homozygous beta-thalassemia and their parents. Seven haplotypes were identified as associated with the beta thal chromosome and 25 with the beta A chromosome. The distribution of the various beta thal haplotypes in different regions of South China was mapped and discussed in relation to prenatal diagnosis and migration of the Chinese people.

China↗
PubMed1986

[Clinical amyotrophic lateral sclerosis syndromes in gammapathies: clinical, electrophysiologic and histoimmunologic aspects].

Eleven patients with motor neuron disease associated with a monoclonal gammopathy were studied. One patient had a previously known multiple myeloma. In the other patients neurological symptoms preceded diagnosis of the gammopathy by one month to 8 years. They were 5 multiple myeloma, 1 macroglobulinemia, 1 chronic lymphatic leukemia, 1 lymphoma and 3 benign monoclonal gammopathies. EMG and motor conduction velocities results were consistent with anterior horn cell disease but sensory conduction studies were abnormal in seven cases out of eight. Superficial peroneal nerve biopsy performed in all patients confirmed peripheral nerve involvement. The relations between gammopathy, clinical symptoms and electrophysiological data are discussed. The interest of sensory conduction studies in every patient with motor neuron disease is emphasized.

Aged↗
PubMed1986

Organization of the zeta-alpha genes in Chinese.

Analysis of alpha and zeta genes in 101 healthy normals and hospitalized patients with non-haematological diseases revealed a 3% incidence of alpha thalassaemia in the local Chinese population of Hong Kong. Triple alpha genes were found in only one person while triple zeta genes were more prevalent, occurring in 13 subjects. Studies of 28 unselected patients with Hb H disease indicated a predominance of the rightward alpha gene deletion. The extent of alpha gene deletion in homozygous alpha thalassaemia 1 was at least 18.1 kb, beginning from the BamH I site 3' to the zeta 1 gene and includes the psi alpha, alpha 2 and alpha 1 genes. Nineteen of the 20 chromosomes bearing the alpha thalassaemia 1 deletion had identical zeta-intergenic hypervariable region suggesting a common origin of this mutation. The co-inheritance of alpha thalassaemia in beta thalassaemia subjects was 8%, but did not ameliorate the clinical features of those with homozygous beta thalassaemia.

China↗
PubMed1986

Glomerulonephritis associated with hepatitis B surface antigenemia. Report of a case with features of both membranous and IgA nephropathy.

A 40-year-old man with hepatitis B surface (HBs) antigenemia developed the nephrotic syndrome. Renal biopsy revealed a glomerulonephritis with features of both membranous glomerulonephropathy and IgA nephropathy. Histologically some glomeruli showed mesangial expansion and hypercellularity only, while others contained sclerotic segments. Direct immunofluorescence demonstrated granular IgG-bearing deposits along the peripheral glomerular capillaries and IgA-containing ones in the mesangium. HBs antigen was detected by indirect immunofluorescence both along the glomerular capillary walls and within the mesangium. Granular epimembranous and mesangial deposits were observed by electron microscopy. A few mesangial deposits consisted of spherical particles, 35-100 nm in diameter. Although 3 cases of mixed membranous and IgA nephropathy have been previously reported, this appears to be the first one to be associated with HBs antigenemia.

Adult↗
PubMed1985

[Electro-clinical data in medullary forms of the Chiari malformation without syringomyelia].

The electrophysiological findings in 18 patients with Arnold-Chiari malformation (ACM) revealed by spinal symptoms excluding syringomyelic syndrome (Brown-Sequard syndrome, paraparesis with or without posterior column involvement, motor neuron syndrome or more complex myelopathies) are reported. In 16 cases, EMG disclosed abnormalities consistent with lesion of anterior horn cells restricted to upper limb in 7 cases, and generalized in 9 cases. In 2 cases, motor and sensory conductions were abnormal. The occurrence of such abnormalities in patients with ACM is emphasized as they could lead to confusion with amyotrophic lateral sclerosis or spinal muscular atrophy. Neuroradiological studies are therefore necessary owing to possible surgical treatment. The hypothesis relating lower motor involvement and ACM are reviewed.

Adult↗
PubMed1985

Homozygous alpha-thalassaemia: clinical presentation, diagnosis and management. A review of 46 cases.

Forty-six hydropic infants with homozygous alpha-thalassaemia born during a period of 10 years have been reviewed. The incidence was 1:1550 total births, and accounted for 81% of all non-immune hydrops. The male to female ratio was 1:1.4. There was increased incidence of anaemia, pregnancy induced hypertension, antepartum haemorrhage, malpresentation, prematurity, fetal distress, difficult vaginal delivery, caesarean section, retained placenta, postpartum haemorrhage and congenital abnormalities. Antenatal diagnosis by DNA hybridization with subsequent abortion of the affected fetuses is the best method to decrease maternal morbidity and to reduce the incidence of hydrops fetalis in couples at risk. For those with no previous history, but with early onset hypertension and/or polyhydramnios, sonography is useful in making an earlier diagnosis, and in reducing avoidable morbidity, because DNA analysis can be done before caesarean section and aggressive neonatal management is instituted.

Adolescent↗
PubMed1985

Hydrops fetalis due to an unusual form of Hb H disease.

The occurrence of Hb H hydrops fetalis is reported for the first time. The mother has zeta-alpha thalassemia 1 (zeta zeta alpha alpha/----) and the father has non-deletion alpha thalassemia [zeta zeta alpha alpha/zeta zeta (alpha alpha)T]. The complete deletion of the zeta alpha cluster on one chromosome was confirmed by quantitation of alpha and zeta gene numbers, the normal alpha and zeta gene patterns arising from the remaining normal chromosome, and the decreased alpha/beta globin chain ratio of 0.57. The non-deletion alpha thalassemia defect could only be identified by the imbalanced alpha/beta globin chain ratio of 0.65 in the presence of normal gene numbers and patterns. The newborn was markedly anemic, unlike those with classical Hb H disease, because the non-deletion alpha thalassemia defect is more severe than alpha thalassemia 2. The decreased zeta genes during fetal life might have additional deleterious effects. In this family, the distinct BamHI restriction fragment length polymorphism in the hypervariable region of the zeta genes may be used for future prenatal diagnosis.

DNA Restriction Enzymes↗