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Biomedical subjects

Y C Chow

Publications and source records attributed to Y C Chow.

13 recordsLinked to original sources
PubMed2003

Genetic authentication of ginseng and other traditional Chinese medicine.

The main objective of this paper is to review the chemical and genetic methods used in authentication of ginseng, especially the recent advances in microsatellite genotyping and its application to the authentication of other traditional Chinese medicines (TCM). The standardization and modernization of TCM hinge on the authentication of their botanical identities. Analysis of well-characterized marker compounds is now the most popular method for identifying the herbal materials and quality control of TCM, eg, ginsenoside profiling for authentication of Panax species. However, in many herbal species the chemical composition of the plant changes with the external environment and processing conditions, which lowers the reliability of these authentication methods. In the light of the advances in molecular biotechnology in the past few decades, genetic tools are now considered to provide more standardized and reliable methods for authentication of herbal materials at the DNA level. These genetic tools include random amplified polymorphic DNA (RAPD), DNA fingerprinting using multi-loci probes, restriction fragment length polymorphism (RFLP), amplified fragment length polymorphism (AFLP), and microsatellite marker technology. The practicality of these methods varies in terms of their sensitivity, reliability, reproducibility, and running cost. Using ginseng as an example, we reviewed the advantages and limitations of these molecular techniques in TCM authentication. We have developed a set of microsatellite markers from American ginseng that are able to differentiate Panax ginseng and Panax quinquetolius with the resolution down to farm level, ie, confirmation of its botanical identity and origin. Compared with other molecular techniques, microsatellite marker technology is more robust, accurate, reproducible, reliable, and sensitive. This is essential for large-scale TCM authentication centers.

DNA Fingerprinting↗
PubMed1998

Correlation of chi orientation with transcription indicates a fundamental relationship between recombination and transcription.

Cross-over hot-spot instigator (Chi) sequences (5'-GCTGGTGG-3') are abundant, strand-specific, sequences, which locally increase recombination in Escherichia coli. Located within G-rich 'recombination islands', Chi orientations correlate with the orientations both of DNA replication and of transcription. Consistent with evidence from eukaryotic systems for a fundamental relationship between recombination and transcription, we find for E. coli Chi sequences, and for Haemophilus influenzae Chi-like sequences, that orientations correlate better with transcription than with replication. Complying with Szybalski's transcription direction rule, open reading frames in these prokaryotes have purine-rich mRNA-synonymous DNA strands. Hence, the G-richness of 'recombination islands' may reflect their correspondence with 'transcriptional islands' (genes). Comparison of a natural with the corresponding shuffled sequence, indicates a base order-dependent island unit of approx. 1kb. 1998 Elsevier Science B.V.

Base Composition↗
PubMed1992

Cloning and differential expression during the sexual cycle of a meiotic endonuclease-encoding gene from the basidiomycete Coprinus cinereus.

The naturally synchronous meiosis of the fungus, Coprinus cinereus, provides an ideal system for the investigation of differential gene expression in relation to meiosis and fruiting body development. We have cloned a cDNA from the fruiting body of C. cinereus encoding the 12-kDa subunit of a meiotic endonuclease (mENase). The identification of the 12-kDa subunit cDNA clone was achieved by the mENase antiserum against a lambda gt11 cDNA expression library. It was confirmed by a direct match of the amino acid (aa) sequence obtained from purified 12-kDa polypeptide with the nucleotide sequence. Northern blot analysis using the cDNA clone as a probe showed that the mENase-encoding gene (MenA) for the 12-kDa subunit was expressed mainly in fruiting bodies and at a very low level in the asexual vegetative mycelium. In addition, it was differentially expressed in the early meiotic stages. The MenA transcript was most abundant in fruiting body primordia prior to the premeiotic S-phase; it remained high from karyogamy to early pachytene, declined drastically by late pachytene and diplotene, and was undetectable by sterigma stage. Western blot analysis showed that the mENase protein was produced at a very low level in mycelium; it was produced in great quantity during the early meiotic stages and decreased to a low level at the end of meiosis.

Amino Acid Sequence↗
PubMed1990

Preventing alcohol problems: survey of Canadian medical schools.

In preparation for a national conference on medical education in the prevention of alcohol problems, a survey of conference participants was conducted. Participants were undergraduate and postgraduate representatives from each Canadian medical school and representatives from 11 provincial and territorial alcohol and other drug agencies. There was agreement that physicians and medical schools have important roles in prevention and treatment of alcohol problems, with "traditional" medical roles seen as the most important. Current training is variable and was seen as inadequate, with more time devoted to treatment than prevention. To correct this situation, renewed priorities and faculty leadership are needed. Respondents felt that there should be uniform standards for assessing undergraduate students' skills in dealing with alcohol problems. Provincial alcohol and other drug agencies are underused in medical education in the prevention and treatment of alcohol problems.

Alcoholism↗
PubMed1990

Refractive errors in Singapore medical students.

The refraction of 128 third-year medical students aged 20-22 was studied using a Topcon autorefractometer. The population was predominantly Chinese and comprised 44% females and 56% males. The mean refractive error was -3.75 D for males and -4.76D for females. In all, 82% of the students were myopic, 72% were found to have astigmatism. This study confirms clinical impressions that Singapore students have one of the highest prevalence rates of myopia and astigmatism in the world.

Adult↗
PubMed1986

Effect of incomplete obstruction on feline esophageal function with a clinical correlation.

This study was performed because of the observation of unexplained esophageal dysfunction in patients with incomplete esophageal obstruction. A Gore-Tex band, measuring 110% of resting esophageal circumference, was placed about the esophagus at the gastroesophageal junction of 17 cats to produce incomplete obstruction by limiting the normal distention that occurs with swallowing. Esophageal manometry was performed before surgery and at 1 and 4 weeks after surgery. Lower esophageal high-pressure zone pressure was not influenced, but sphincter relaxation was impaired. Evaluation of esophageal body contractions showed that simultaneous contractions increased from 0% before surgery to 68% at 1 week and 85% at 4 weeks after surgery (p less than 0.001 versus preoperative for both comparisons). The incidence of repetitive contractions increased from 3.1% before surgery to 10.5% at 1 week and 10.9% at 4 weeks after surgery (p = NS). The average contraction pressure decreased from 22.5 mm Hg before surgery to 13.9 mm Hg at 4 weeks after surgery (p less than 0.05). Barium swallows showed esophageal dilatation, that was confirmed on gross examination. Histologic examination was remarkable only for retention esophagitis. Sham surgery in three cats with identical mobilization of the gastroesophageal junction did not affect motility. Motility returned to normal after the band was removed in three cats. Manometric evaluation of 15 patients with distal esophageal peptic strictures and 17 patients with excessively tight antireflux repairs showed a significantly increased (p less than 0.001) frequency of simultaneous contractions, 35% and 34%, compared with the 2.1% of 25 normal subjects. The following conclusions can be drawn: Partial obstruction alters feline esophageal body function and these achalasia-like changes are reversible on relief of the obstruction and similar motility aberrations occur in patients because of mechanical or functional distal obstruction; this suggests that dysmotility can synergistically contribute to dysphagia.

Animals↗
PubMed1985

Critical evaluation of results of extension of indication for surgery for primary bronchogenic carcinoma.

Among 3,120 surgically resected cases (1957-1983) in Shanghai Chest Hospital, 1,476 resections (47.3%) were performed under extended indication. Six categories--(1) aged 70-87 years (102), (2) associated with severe impairment of pulmonary function (25), (3) small-cell anaplastic type (143), (4) stage III lesion (1,145), (5) invading carina (29), (6) with disseminated pleural metastasis and effusion (32)--were critically evaluated. For the first four categories, long-term survival rates were very encouraging, whereas only technical advancement and short-term results were discussed for the last two. The authors present strategic points significant in availing higher overall operability and hence the overall survival rate, shedding light on the increase of curative potential for lung cancer.

Adult↗
PubMed1984

Electrophysiological properties of osteoblastlike cells from the cortical endosteal surface of rabbit long bones.

The mean transmembrane potential of cultured osteoblastlike cells isolated from the cortical endosteal surface of rabbit long bones was -16.9 +/- 0.64 mV (n = 335). Elevation of potassium concentration in medium caused a decrease in potential. As the external concentration of potassium reached 15 mmol/liter and above, there was a linear relationship between the potassium concentration in log scale and the membrane potential with a slope of -13 mV per 10-fold change in external potassium concentration. Dibutyryladenosine 3',5'-cyclic monophosphate, parathyroid extract, hydrocortisone, and sodium fluoride all depolarized the membrane of osteoblast-like cells after both short (1-2 h) and long (24 h) exposures at suitable doses, whereas calcitonin and prostaglandin E2 hyperpolarized the membrane after long exposures. The Na+, K+ and Cl- concentrations of cultured osteoblastlike cells were 0.538, 0.984, and 0.358 mmol/g protein or 52.6, 96.3, and 35.0 mmol/liter cell water, respectively. The protein content of these cells was 8.18 +/- 0.6 g/100 g cells and the water content was 83.7 g/100 g cells. The above-mentioned chemical and hormonal preparations in doses that produced significant changes in the membrane potential of these cultured cells did not alter their electrolyte or protein contents 24 h after exposure. Intracellular pH of cultured osteoblastlike cells as determined by [14C]-dimethyloxazolidine-2,4-dione and 3H2O averaged 7.03 +/- 0.11 when the pH of culture medium was maintained at 7.4. Calculations based on the values for the membrane potential and the electrolyte concentrations observed in this study indicate that Na+, and H+, and Cl- are actively transported out of the cells and K+ into the cells.

Animals↗