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Biomedical subjects

T C Cheng

Publications and source records attributed to T C Cheng.

At least 55 records · Page 3Linked to original sources
PubMed1989

Dosimetry of high dose rate intracavitary radiation therapy using Co-60 and Ir-192 sources.

For decades, the high dose rate sources of Co-60 and Ir-192 have been used in remote controlled afterloading brachytherapy. A small volume ion chamber was used to measure the dose rate in varying distances from the sources. The entire dose distribution around the source was tabulated and the data were used to calculate the treatment time for individualized patient setting. A solid diode detector was used to plot the relative distance dose and the symmetrical dose distribution of the sources. Thermoluminescence dosimetry (TLD) was used for spot-checking of the dose. The dose distribution in the clinically useful range of 2-5 cm was carefully estimated. When normalized at 2.0 cm from the source, the dose rate at 5.0 cm was 17.1% for the Co-60 source and 18.4% for the Ir-192 source. It is clearly demonstrated that Ir-192 offers no dosimetric advantages, which is contrary to what used to be believed by some clinicians. The parameters of the computer treatment planning system have to be corrected and then adopted into clinical application.

Brachytherapy↗
PubMed1988

Human stomach alcohol and aldehyde dehydrogenases (ALDH): a genetic model proposed for ALDH III isozymes.

Isozyme phenotypes of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) from human gastroendoscopic as well as surgical gastric biopsies were determined by starch gel electrophoresis and agarose isoelectric focusing. gamma gamma ADH isozymes were expressed predominantly in the mucosal layer of the stomach, whereas beta beta isozymes were in the muscular layer. In the 56 gastroendoscopic mucosal biopsies examined, the homozygous ADH3 1-1 phenotype was found in 75% of the samples, and the heterozygous ADH3 2-1 phenotype in 25%. Accordingly, the gene frequencies of the alleles ADH1/3 and ADH2/3 were calculated to be 0.88 and 0.12, respectively. Using a modified agarose isoelectric focusing procedure, gastric ALDH I, ALDH II, and up to five ALDH III forms could be clearly resolved. The ALDH III isozymes accounted for more than 80% of the total ALDH activities in gastric mucosa and exhibited Km values in the millimolar range for propionaldehyde at pH 9.0. Forty-five percent of the 55 gastroendoscopic biopsies studied lacked ALDH I isozyme. The complex gastric ALDH III isozyme phenotypes seen in these biopsies fall into three patterns. They can be interpreted by a genetic hypothesis, based on a dimeric molecule, in which there are two separate genes, ALDH3a and ALDH3b, with the ALDH3b locus exhibiting polymorphism. The homozygous phenotypes ALDH3b 1-1 and ALDH3b 2-2 were found to be 4 and 76%, respectively, and the heterozygous ALDH3b 2-1 phenotype 20%, of the total. Therefore, the allele frequencies for ALDH1/3b and ALDH2/3b were calculated to be 0.14 and 0.86, respectively. Several lines of biochemical evidence consistent with this genetic model are discussed.

Alcohol Dehydrogenase↗
PubMed1988

Diaphragmatic defect as a cause of massive hydrothorax in cirrhosis of liver.

A 56-year-old woman with a 2-year history of cirrhosis of the liver and frequent right pleural effusion was admitted with intractable shortness of breath. Chest x-ray examination showed marked pleural effusion of the right lung field with a shift of the mediastinum to the left. Ascites was not conspicuous. Except for the liver cirrhosis, there was no clinical evidence of other underlying diseases. The patient died with a relatively short course after hospitalization. At autopsy, an apparent bleb with 1-mm hole in the tendinous portion of the right diaphragm was noted. We suggest that the ascitic fluid directly crossed the diaphragmatic defect to the pleural cavity, which contributed to the hydrothorax. In this article we review the pertinent literature.

Diaphragm↗
PubMed1988

Hepatitis B virus-associated membranous glomerulonephropathy.

A variety of extrahepatic abnormalities have been described in patients with hepatitis B viral infection, including the prodromal arthritis (serum sickness-like) syndrome, polyarteritis nodosa, and glomerulonephropathy. Five patients with hepatitis B virus (HBV)-associated membranous glomerulonephropathy (MGN) were persistent carriers of HBsAg. The deposition of HBsAg in the renal lesions of these patients was proved by using monospecific antibody and immunofluorescence technique. These findings support the hypothesis of an etiological correlation of hepatitis B viral infection with some cases of MGN. HBV-associated MGN may be much more frequent in the world than previously reported, and more cases must be collected for the understanding of this unique entity.

Adult↗
PubMed1987

A case study of hospital operations management.

This paper discusses a study to investigate various operations management problems in a newly opened, modern regional hospital in Hong Kong. The findings of the study reveal that there exist in the hospital a number of current and potential problem areas. Recommendations for solving these problems are suggested with a view to improving the overall operational efficiency and effectiveness of the hospital.

Appointments and Schedules↗
PubMed1986

Specificity and the role of lysosomal hydrolases in molluscan inflammation.

Evidence supporting the occurrence of the following phases of cellular inflammatory response in molluscs are reviewed: chemotactic attraction, surface recognition, endocytosis and/or encapsulation, and intracellular degradation. In each of these phases of cellular reaction to foreign substances, molecular specificity is involved or its occurrence is suggested. Therefore, the concept is advanced that inflammatory responses which have been referred to as "nonspecific" do not exist. In addition, the evidence indicating the hypersynthesis and release of lysosomal hydrolases from molluscan phagocytes into serum subsequent to challenge are reviewed. The evidence indicates that this phenomenon is also specific at the molecular level. The elevated levels of lysosomal enzymes in serum also contribute to the inflammatory response.

Animals↗
PubMed1985

Thalassemia due to a mutation in the cleavage-polyadenylation signal of the human beta-globin gene.

A beta-globin gene cloned from a person with beta-thalassemia contained a T----C substitution within the conserved sequence AATAAA that forms a portion of the recognition signal for endonucleolytic cleavage and polyadenylation of primary mRNA transcripts. By Northern blot analysis a novel beta-globin RNA species, 1500 nucleotides in length, was detected in erythroid RNA. Nuclease protection studies of erythroid RNA, as well as RNA generated upon transient expression of the cloned mutant gene in HeLa cells, located the 3' terminus of this novel, polyadenylated RNA 900 nucleotides downstream of the normal poly(A) addition site, within 15 nucleotides of the first AATAAA in the 3'-flanking region of the beta-globin gene. These findings define the in vivo terminus of an elongated RNA and establish that human beta-globin transcription may extend at least 900 nucleotides 3' of the normal polyadenylation site.

Base Sequence↗