Prevalence of hepatitis G virus infection in patients with liver diseases in Singapore.

The prevalence of hepatitis G virus (HGV) infection in patients with liver diseases in Singapore and its pathogenic role in these patients was studied. One hundred and forty-eight patients who had chronic hepatitis or acute non A-E hepatitis were studied. Presence of HGV RNA was determined by nested polymerase chain reaction of the 5'non-coding region of the virus in all the patients. Hepatitis G IgG antibody to the envelope (E2) antigen was tested with an enzyme immunoassay (Boehringer Mannheim, Singapore) in 76 of them. Most patients (93%) were ethnically Chinese, predominantly males (74%) and chronic hepatitis B (72%) patients. Others had chronic hepatitis C (19%) or cryptogenic cirrhosis (6%). Four patients had acute non A-E hepatitis. HGV RNA and anti-HGenv were present in 3.5% and 8.3% of those with chronic liver disease. HGV infection did not account for any of the acute non A-E hepatitis and most of the cryptogenic cirrhosis.

The development of PM emission factor for small incinerators and boilers.

This study is intended to develop the emission factors of particulate matter such as TPM (total particulate matter), PM-10 (particulate matter less than 10 micrometers in aerodynamic diameter), PM-2.5 (particulate matter less than 2.5 micrometers in aerodynamic diameters) and several types of inorganic matter from small-size incinerators (less than 250 kg hr(-1) capacity) and boilers (less than 5 ton hr(-1) capacity a s steam generation) for various compositions of wastes and fuels, respectively.The emission factors for particulate matter from boilers were similar to the US EPA data. However, the emission factors from small incinerators were higher than the emission factors developed in other countries because the emission characteristics were different, especially with respect to the combustor's capacity. Emission factors for heavy metals such as cadmium, manganese, chromium, magnesium, lead, zinc, and copper were also investigated. The emission factors in this study were higher than those in other studies. Particle size distribution of PM-10 and the ratio of submicron PM to TPM were observed and a mode (peak) of submicron size particles together with a higher concentration of them was found, which could be explained by the formation of fines from vaporized metals wastes.

Leaching behavior and characteristics of glass components and surrogate nuclides in radioactive vitrified waste forms.

Several vitrified waste forms were fabricated and characterized, which contain simulated radioactive waste incineration ash, and a long-term leaching test was conducted by an ISO method for 820 days to assess the chemical durability of vitrified waste forms. Two semi-empirical mechanism models were applied to find out the dominant leaching mechanism of glass elements. For glass elements, dissolution associated with diffusion was the dominant leaching mechanism and leaching characteristics also depend upon solubilities of components. A type of prediction model was applied to observe the long-term leaching behavior of major glass elements and surrogates. Diffusion coefficients and dissolution rate constants, the main parameters in the long-term prediction model, were obtained for glass elements and surrogate nuclides using experimental data for short and long-term periods. The model could be used to predict long-term behavior of such elements to observe and assess the stability of vitrified waste forms.

Detailed deletion mapping at chromosome 11q23 in colorectal carcinoma.

Loss of heterozygosity (LOH) is frequent at the chromosomal region 11q22-q23 in several types of tumours of diverse cell origin. Previous investigations of LOH at this chromosomal region in colorectal carcinoma have been contradictory in their findings, and have only included between 1-4 loci. In order to define any regions of LOH on 11q23, we investigated 16 loci between D11S940 and D11S934 on the long arm of chromosome 11 using microsatellite analysis. Of 57 colorectal carcinomas specimens, 36 (63.2%) demonstrated LOH at one or more marker, with the highest frequencies of LOH at D11S1340 (41.0%), located between 105.13-111.97 Mb from the centromere, and D11S924 (37.1%) and D11S4107 (40.5%), both located approximately 113 Mb from the centromere. No statistically significant associations between LOH and age-of-presentation or Dukes' stage were found. LOH was observed in colorectal tumours of all Dukes' stages, including Dukes' stages A and B, suggesting that the inactivation of a tumour suppressor gene(s) on 11q23 occurs in the early stages of colorectal carcinoma. These results confirm the presence of putative tumour suppressor gene(s) at chromosome 11q23, involved in the carcinogenesis of colorectal carcinoma, and will facilitate future identification of candidate genes.

Quantitation of hepatitis C viraemia by a competitive reverse transcription-polymerase chain reaction system.

Chronic hepatitis C infection is associated with the rapid development of cirrhosis and hepatocellular carcinoma. A quantitative assay to determine the level of hepatitis C (HCV) viraemia during treatment would be useful in determining the effect of antiviral agents. Such an assay has been developed with the principle of the method being the co-amplification of the viral genome isolated from the patient with an RNA competitor molecule (CM) using the competitive reverse transcription-polymerase chain reaction (RT-PCR). Known amounts of the CM compete for amplification with HCV RNA from the patient. To quantify each sample, 5 amplification reactions with titrated amounts of CM were performed. The CM can be distinguished from the normal HCV PCR product since it has been genetically altered to be a smaller molecule by the process of restriction digestion, ligation and reamplification. This quantitative method was used to monitor the viral load in 10 patients undergoing antiviral therapy with lymphoblastoid interferon. The level of HCV viraemia in these patients ranged from 10(9) to 10(12) genomes/ml serum. Declines in the level of viraemia were seen in 8 of the 10 patients after therapy. Since patients with low HCV viraemia levels are more likely to respond to interferon therapy in a sustained fashion, this method may also be employed to quantitate the level of viraemia in patients prior to interferon treatment, and may be an indicator of the dose and schedule of treatment. These results show that this quantitative method is useful in the monitoring of HCV viral load in patients.