Biomedical subjects

O C Ma

Publications and source records attributed to O C Ma.

10 recordsLinked to original sources

PubMed1999

Beta-fibrinogen gene G/A-455 polymorphism in relation to fibrinogen concentrations and ischaemic heart disease in Chinese patients with type II diabetes.

AIMS/HYPOTHESIS: We investigated the relation between the G/A-455 (Hae III) beta-fibrinogen gene polymorphism and plasma fibrinogen concentration and its role in ischaemic heart disease in 264 Chinese patients with Type II (non-insulin-dependent) diabetes mellitus and 182 non-diabetic control subjects. METHODS: The G/A-455 polymorphism was determined in genomic DNA using polymerase chain reaction and Hae III restriction enzyme digestion. Fibrinogen was measured with the Claus method. RESULTS: Fibrinogen concentrations were higher in diabetic patients (3.3 +/- 0.5 vs 2.5 +/- 0.9 g/l in controls, p < 0. 0001) and in women (p < 0.03 vs men). Allele frequency of the variant A allele was 27 % in both diabetic patients and control subjects' similar to findings in Caucasians. In control subjects, the AA genotype was associated with higher fibrinogen concentrations (2.8 +/- 0.38 g/l vs 2.5 +/- 0.5 in GG or GA, p < 0.03), contributing to 4 % of the variance in plasma fibrinogen. The genotype effect was smaller and not significant among non-smokers, women and diabetic patients. Higher fibrinogen concentrations and AA genotype frequency were found in diabetic patients with ischaemic heart disease (p < 0.05 and p < 0.005, respectively vs unaffected patients). In a multiple logistic regression model, AA genotype, age and mean arterial pressure were associated with ischaemic heart disease, with odds ratios of 4.19 (p < 0.01), 1.05 (p < 0.0001) and 1.03 (p < 0.03), respectively. CONCLUSION/INTERPRETATION: The G/A-455 polymorphism is a genetic determinant of fibrinogen concentrations and ischaemic heart disease in this Chinese cohort. It also interacts with environmental influences associated with smoking, the female sex and Type II diabetes in determining plasma fibrinogen concentrations. [Diabetologia (1999) 42: 1250-1253]

Age Factors↗

PubMed1998

Genetic influence of the R/Q353 genotype on factor VII activity is overwhelmed by environmental factors in Chinese patients with Type II (non-insulin-dependent) diabetes mellitus.

We studied the effects of genetic and environmental influences on factor VII coagulant activity (VIIc) in Chinese diabetic patients (263 with Type II [non-insulin-dependent] diabetes mellitus, 78 with Type I [insulin-dependent] diabetes mellitus) and 143 normal control subjects. VIIc was measured by a one-stage biological assay. The R/Q353 or Msp1 polymorphism at codon 353 of the factor VII gene was detected after Msp1 digestion of polymerase chain reaction-amplified genomic DNA. In both diabetic and control subjects the allele frequencies of the R (M1) and Q (M2) alleles were 0.96 and 0.04; the corresponding reported frequencies in Caucasians being 0.90 and 0.10: VIIc were 21% lower in Chinese control subjects and Type I diabetic patients with R/Q, compared with R/R subjects (p < 0.001 and p < 0.05). The corresponding difference was 4% for Type II diabetc patients (p = NS). Type II diabetic patients had higher mean VIIc levels than control subjects and Type I diabetic patients (p < 0.01); they were also older, and had higher serum creatinine and triglyceride (all p < 0.01). They also had higher VIIc levels than an age-matched older control group (p < 0.01; n = 182) in whom the genotype effect was clearly seen. On stepwise linear regression analysis, the significant independent determinants of VIIc were serum triglyceride (contributing 20% and 25% to variance in control subjects and diabetic patients), the R/Q353 genotype (contributing to 12% of the variance in control subjects but only 1% in diabetic patients), age and total cholesterol in all subjects, and in the diabetic patients female sex, urinary albumin excretion rate and serum creatinine. VIIc was higher in diabetic patients with macroangiopathy and retinopathy (both p < 0.0001). We conclude that compared with Caucasians, the Q allele frequency is significantly lower in these Chinese subjects. Plasma VIIc is determined by both genetic and environmental influences such that in Chinese Type II diabetic patients, the effect of environmental factors predominates, almost negating the influence of the R/Q353 genotype. High VIIc may contribute to the increased cardiovascular risk in Type II diabetic patients.

Adult↗

PubMed1997

G/A1947 polymorphism in catechol-O-methyltransferase (COMT) gene in Parkinson's disease.

High and low catechol-O-methyltransferase (COMT) activity is significantly determined by thermostability, which is caused by a valine/methionine108 polymorphism associated with polymorphic G/A1947 bases, in exon 4 of the COMT gene. Our allelic association study on this polymorphism did not find any statistically significant difference between our Chinese Parkinson's disease and that of control subjects. These results show that this polymorphism and hence the thermostability of COMT enzyme are not related to a risk of developing Parkinson's disease.

Aged↗

PubMed1997

High resolution single strand conformation polymorphism analysis using formamide and ethidium bromide staining.

Single strand conformation polymorphism (SSCP) analysis using ethidium bromide can be improved by adding formamide as the denaturant. This gives higher resolution than previous SSCP methods; it had 100% sensitivity in the discrimination of 14 PCR samples from two different genes, even for a long fragment close to the upper limit of 250 base pairs. This modified procedure is a rapid, simple, safe, and yet highly sensitive method for detecting structural differences in DNA fragments.

Catechol O-Methyltransferase↗

PubMed1993

Long-term follow-up of chronic hepatitis B patients treated with interferon alfa.

BACKGROUND: There is very little data on the long-term outcome of patients with chronic hepatitis B after interferon therapy. A 6-year follow-up of two interferon trials in chronic hepatitis B patients is reported. METHODS: One hundred twenty-eight Chinese adults with chronic hepatitis B who received interferon therapy were followed for 19-79 months (median 41 months). Twenty-nine patients lost hepatitis B e antigen and two also lost hepatitis B surface antigen within 1 year of treatment. RESULTS: Seven (24%) responders reactivated. Twenty-eight (28%) nonresponders had sustained clearance of hepatitis B e antigen during follow-up. Delayed clearance of hepatitis B e antigen occurred more frequently in nonresponders who had elevated pretreatment serum transaminase levels. (P = 0.002). Serum hepatitis B virus DNA became undetectable by polymerase chain reaction assay in both responders who lost hepatitis B surface antigen but in only 8 (17%) patients who lost hepatitis B e antigen only. Delayed clearance of hepatitis B surface antigen was not seen in any of the 48 patients who had sustained clearance of hepatitis B e antigen. CONCLUSIONS: Contrary to reports from Western countries, complete elimination of markers of hepatitis B virus infection was uncommon in Chinese patients with chronic hepatitis B who underwent interferon therapy despite similar duration of follow-up.

Adult↗

PubMed1992

A controlled trial of interferon with or without prednisone priming for chronic hepatitis B.

In a randomized, controlled trial of recombinant interferon alfa-2b with or without prednisone priming in Chinese adults with chronic hepatitis B virus infection, stratified randomization for pretreatment serum alanine aminotransferase levels was done. Partial or complete antiviral responses were achieved in 17 (21.5%) of 79 treated patients and 3 (8.3%) of 36 controls (P = 0.14). The response to interferon treatment was significantly better in those who had elevated pretreatment transaminase levels and comparable to that reported in white patients [15 (38.5%) of 39 patients compared with 2 (5%) of 40 who had normal pretreatment transaminase levels (P = 0.0005)]. The spontaneous seroconversion rate was also higher among the controls with elevated transaminase levels [3 (18.8%) of 16 compared with 0 of 20 with normal transaminase levels], but this difference was not statistically significant (P = 0.16). Among the interferon-treated patients, prednisone priming appeared to have a marginal benefit over treatment with interferon alone in patients with elevated transaminase levels (43% vs. 33%), but not in those with normal transaminase levels (0% vs. 9.5%). It was confirmed that Chinese patients with normal transaminase levels respond very poorly to interferon alfa therapy. However, the response was significantly better in patients with elevated transaminase levels.

Adult↗

PubMed1992

Precore sequence variation in Chinese isolates of hepatitis B virus.

Direct sequencing of polymerase chain reaction-amplified serum hepatitis B virus (HBV) DNA was used to characterize the precore region of HBV from Chinese patients with chronic hepatitis. Two types of mutually exclusive variants were found in hepatitis B e antigen (HBeAg)-negative patients. The first (M1) contains a substitution from proline to serine at codon 15. A second group were infected with a previously described mutant (M2) containing a translational stop codon. HBeAg-positive patients were infected with the wild-type virus or the M1-containing strain. M2 emerged in patients with wild-type infection after seroconversion to anti-HBe, whereas M1 was present during the HBeAg-positive phase. In those with fluctuating HBe status, there was no correlation between prevailing HBe serology and sequence. There was an association between infection with variants and severe chronic hepatitis. Patients infected with strains containing M1 while HBeAg positive had a worse prognosis after seroconversion to anti-HBe.

Alanine Transaminase↗

PubMed1991

Overestimation of the prevalence of antibody to hepatitis C virus in retrospective studies on stored sera.

Serum samples (1,428) from 1,149 patients with chronic liver diseases and polytransfused subjects were tested for antibody to hepatitis C virus by first-generation enzyme immunoassays. Antibody to hepatitis C virus was detected in 87% of patients with transfusion-related chronic non-A, non-B hepatitis; 17.6% of patients with nonmalignant, chronic hepatitis B virus infection; 37.3% of patients with hepatocellular carcinoma; 14.3% of patients with alcoholic liver diseases; 22.2% of patients with cryptogenic cirrhosis; 76% of intravenous drug abusers; 16.4% of patients on hemodialysis; 1.8% of patients on peritoneal dialysis; 6.2% of kidney transplant recipients; and 3.1% of normal subjects. A high frequency of weakly positive results was found in "aged" samples: 61.9% of antibody to hepatitis C virus-positive patients whose sera had been stored for more than 2 yr had optical densities less than two times the cut-off values in contrast to 7.9% of those whose sera had been stored for less than 2 yr (p less than 0.0001). A significantly lower proportion of patients who had optical densities less than two times the cut-off values were reactive in subsequent samples, 27.5% vs. 87.5% (p less than 0.0001). On retests, only 70% and 56% of sera that were initially positive for antibody to hepatitis C virus remained antibody to hepatitis C virus positive using second-generation enzyme immunoassays and neutralization enzyme immunoassays, respectively. Our results suggest that retrospective studies on stored sera may have overestimated the prevalence of antibody to hepatitis C virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Viral↗

PubMed1991

Interferon alfa therapy in patients with chronic hepatitis B virus infection. Effects on hepatitis B virus DNA in the liver.

Pretrial and posttrial liver biopsy samples from 124 adult patients who participated in two randomized, controlled trials of interferon alfa therapy for chronic hepatitis B virus (HBV) infection were analyzed to determine the effects of interferon on the replication of HBV in the liver. Replicative forms of HBV DNA were detected in the pretrial biopsy samples from all and posttrial biopsy samples from 74% treated patients and 86% controls. Replicative forms of HBV DNA were detected in the posttrial biopsy samples from all patients who remained positive for hepatitis B e antigen and HBV DNA in the serum, in 77% treated patients and 80% controls who cleared HBV DNA in the serum but who remained positive for hepatitis B e antigen, but in only 19% treated patients and 40% controls who cleared HBV DNA as well as hepatitis B e antigen in the serum. Serum alanine aminotransferase levels were significantly lower in patients whose posttrial biopsies did not contain replicative forms of HBV DNA. In summary, we demonstrated that in most patients with chronic HBV infection treated with interferon alfa, serological response was associated with the disappearance of replicative forms of HBV DNA in the liver.

Adolescent↗

PubMed1990

Hepatitis B virus replication in Chinese patients with hepatocellular carcinoma.

We studied the frequency of hepatitis B virus replication in Chinese patients with hepatocellular carcinoma. Hepatitis B e antigen and hepatitis B virus DNA could be detected in the sera of 28% and 47% of 116 HBsAg-positive patients, but not in the sera of 15 HBsAg-negative patients. Replicative forms of hepatitis B virus DNA were detected in the neoplastic and nonneoplastic liver tissues from 34% and 62% of 29 HBsAg-positive patients and 0% and 20% of five HBsAg-negative patients by Southern blot hybridization analysis. Of the 10 patients with chronic hepatitis B virus infection in whom hepatocellular carcinoma developed during follow-up, hepatitis B e antigen and hepatitis B virus DNA were detected in the sera of seven and eight patients, respectively, at presentation, 13 to 43 mo before the diagnosis of hepatocellular carcinoma. In nine patients, hepatitis B virus DNA was persistently or intermittently detected in the serum during follow-up. Five patients remained hepatitis B e antigen-positive and seven were detectable for hepatitis B virus DNA in serum when hepatocellular carcinoma was diagnosed. Four patients had one or more episodes of exacerbations before the diagnosis of hepatocellular carcinoma; in three, the exacerbations were associated with changes in level of hepatitis B virus replication. Our study demonstrated that despite the long interval between the onset of hepatitis B virus infection and the development of hepatocellular carcinoma, hepatitis B virus replication persisted in most patients with hepatocellular carcinoma, albeit at a low level.

Adolescent↗