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C S Chan

Publications and source records attributed to C S Chan.

100 records · Page 6Linked to original sources

Unusual DNA sequences associated with the ends of yeast chromosomes.

The genome of the yeast Saccharomyces cerevisiae, like those of other eukaryotes, contains multiple sequences that hybridize with a poly(GT) probe. We have shown previously that some of the sequences that hybridize with the poly(GT) probe are located near the tips of the yeast chromosomes. We report here that many of the remaining poly(GT)-hybridizing sequences are associated with a family of putative replication origins localized near the chromosome ends. These sequences have the general form poly(C1-3A), similar to sequences reported to occur at the tips of chromosomes in the accompanying paper. In addition to poly(C1-3A) tracts, yeast cells contain tracts of alternating C and A bases, similar to those seen in mammalian genomes. These results are used as the basis for a new model of telomere replication.

Base Sequence↗

Evaluation of the number of laser-Doppler measurements in assessing regional diaphragmatic microcirculation.

As regional diaphragmatic microvascular blood flow varies widely, the aim in this study was to estimate the number of repeated measurements, obtained by Laser-Doppler flowmetry (LDF), required to achieve a standard level of precision. In 40 urethane-anesthetized Sprague-Dawley rats, computer-aided LDF scanning coupled with a microscope generated diaphragmatic blood flow (Qdi) ranging between 94 and 944 mV with the frequency histogram displaying non-Gaussian distributions. A sampling technique was used to assess the number of measuring sites required for valid estimates of the regional diaphragmatic microvascular flow. From a total of 1,000 Qdi values, random samples of sizes between 5 and 100 were repeatedly drawn to estimate the variability of median flow. Our data shows that the 95th percentile decreased gradually, from a +30% error at n = 5 down to +20% at n = 15-20, remained between +20 and +15% up to n = 35, and reached +10% at n = 50. Moreover, by expressing the precision level of measurements as the length of a 95% confidence interval (beta), a linear relationship between beta values obtained either by the sampling method or repeated measures analysis of variance can be shown (r = 0.902, p < 0.001); beta values by either method were within +/-20% error of the mean values at sample sizes above n = 15. It is therefore recommended that for microscope-guided LDF scanning in the assessment of the distribution of diaphragmatic microvascular blood flow, at least 15 repeated measurements should be done to reach an acceptable standard level of precision. However, facing with clinical situations where 'blind' LDF scanning inevitably includes measurements over large vessels, the minimal sample sizes required to represent tissue perfusion demand further exploration.

Analysis of Variance↗

The effectiveness of serum alpha-fetoprotein level in anti-HCV positive patients for screening hepatocellular carcinoma.

BACKGROUND/AIMS: In Taiwan, most cases of hepatocellular carcinoma (HCC) are hepatitis B virus (HBV) or hepatitis C virus (HCV) related. The serum alpha-fetoprotein (AFP) level is an important factor in the diagnosis of HCC. There have been many studies discussing the role of AFP in diagnosing HBV-related HCC, but only few concerning HCV-related HCC. In this study, we aimed at analyzing the distribution of AFP levels in anti-HCV positive patients with and without HCC and evaluating the effectiveness of serum AFP levels in screening HCV-related HCC. METHODOLOGY: From 1993-1996, we collected the AFP data of 205 HCC patients retrospectively, who were anti-HCV positive. For comparison, 131 randomized anti-HCV positive patients without evidence of HCC served as the control group. We analyzed the AFP distribution in both groups over the following ranges: < or = 5 ng/ml, > 5-20 ng/ml, > 20-50 ng/ml, > 50-100 ng/ml, > 100-200 ng/ml and > 200-400 ng/ml, and > 400 ng/ml. RESULTS: The distributions of AFP levels in anti-HCV positive patients with HCC were 13.2%, 21.5%, 11.2%, 4.9%, 4.4%, 7.3%, and 37.6%. The distributions in anti-HCV positive patients without evidence of HCC were 34.3%, 55.0%, 8.4%, 1.5%, 0.8%, 0%, 0%. CONCLUSIONS: We found the differences in AFP to be statistically significant between anti-HCV positive patients with and without HCC. A serum AFP level of more than 200 ng/ml highly indicates HCC. However, there is a large overlap between these 2 groups. Thus, in anti-HCV positive patients, AFP level is not a good single reference for diagnosis of HCC. Anti-HCV positive patients should be routinely screened for HCC by image studies along with serum AFP level.

Adult↗

Comparison in leprosy patients of Fernandex and Mitsuda reactions using human and armadillo antigens. A double-blind study.

The Mitsuda and Fernandez reactions to bacilli prepared from lesions of human patients and bacilli from infected armadillos were studied in 112 leprosy patients. It was observed that there is no substantial difference when armadillo lepromin is used instead of human lepromin except that a larger induration occurs with the use of the armadillo lepromin in a majority of cases. The number of those reporting a burning sensation at the armadillo lepromin injection site was slightly higher in lepromatous patients; whereas the burning sensation was observed at the human lepromin injection site by the tuberculoid cases. With the significant information compiled in this study, it is concluded that lepromin prepared from bacilli obtained from infected armadillos is as effective as that prepared from bacilli obtained from the lesions of leprosy patients.

Adult↗

Intrathoracic migration of Kirschner wires.

Two cases of intrathoracic migration of Kirschner wires are reported. Two wires were used to fix a left clavicle fracture in case 1. Two months later, a chest film showed a broken wire migrating into the mediastinum. A chest computed tomogram revealed the Kirschner wire penetrating into the main pulmonary artery. The broken wire was removed through sternothoracotomy after a pericardiotomy. In case 2, repeated blood-tinged sputum was experienced 5 years and 6 months after Kirschner wire fixation of 2 left clavicle fractures. Chest film showed the migrated wire located in the right thorax. The wire was removed through right thoracotomy. In both cases, the foreign bodies were successfully removed and vascular and pulmonary repair were performed without morbidity.

Adult↗