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Biomedical subjects

F Cheung

Publications and source records attributed to F Cheung.

At least 19 recordsLinked to original sources
PubMed2006

Combining functional and linkage disequilibrium information in the selection of tag SNPs.

UNLABELLED: We have developed an online program, WCLUSTAG, for tag SNP selection that allows the user to specify variable tagging thresholds for different SNPs. Tag SNPs are selected such that a SNP with user-specified tagging threshold C will have a minimum R2 of C with at least one tag SNP. This flexible feature is useful for researchers who wish to prioritize genomic regions or SNPs in an association study. AVAILABILITY: The online WCLUSTAG program is available at http://bioinfo.hku.hk/wclustag/

Algorithms↗
PubMed2005

The TIGR Gene Indices: clustering and assembling EST and known genes and integration with eukaryotic genomes.

Although the list of completed genome sequencing projects has expanded rapidly, sequencing and analysis of expressed sequence tags (ESTs) remain a primary tool for discovery of novel genes in many eukaryotes and a key element in genome annotation. The TIGR Gene Indices (http://www.tigr.org/tdb/tgi) are a collection of 77 species-specific databases that use a highly refined protocol to analyze gene and EST sequences in an attempt to identify and characterize expressed transcripts and to present them on the Web in a user-friendly, consistent fashion. A Gene Index database is constructed for each selected organism by first clustering, then assembling EST and annotated cDNA and gene sequences from GenBank. This process produces a set of unique, high-fidelity virtual transcripts, or tentative consensus (TC) sequences. The TC sequences can be used to provide putative genes with functional annotation, to link the transcripts to genetic and physical maps, to provide links to orthologous and paralogous genes, and as a resource for comparative and functional genomic analysis.

Animals↗
PubMed2003

Enrichment of gene-coding sequences in maize by genome filtration.

Approximately 80% of the maize genome comprises highly repetitive sequences interspersed with single-copy, gene-rich sequences, and standard genome sequencing strategies are not readily adaptable to this type of genome. Methodologies that enrich for genic sequences might more rapidly generate useful results from complex genomes. Equivalent numbers of clones from maize selected by techniques called methylation filtering and High C0t selection were sequenced to generate approximately 200,000 reads (approximately 132 megabases), which were assembled into contigs. Combination of the two techniques resulted in a sixfold reduction in the effective genome size and a fourfold increase in the gene identification rate in comparison to a nonenriched library.

Chromosomes, Plant↗
PubMed2001

Inhibition by ginkgolides and bilobalide of the production of nitric oxide in macrophages (THP-1) but not in endothelial cells (HUVEC).

Nitric oxide (NO) is a principal mediator in many physiological and pathological processes. NO produced by constitutive nitric oxide synthase in endothelial cells (eNOS) acts as a vasodilator, whereas excess NO production due to elevated expression of inducible nitric oxide synthase (iNOS) may produce cytotoxic effects to cells in the vascular wall. We demonstrated in our previous work that the extract of Ginkgo biloba leaves (EGb) inhibits iNOS-mediated NO production. The objective of the present study was to investigate the effects of several active EGb components on iNOS-mediated NO production in macrophages derived from a human monocytic cell line (THP-1), as well as on eNOS-mediated NO production in human umbilical vein endothelial cells (HUVEC). Ginkgolide A, ginkgolide B, or bilobalide (0.25 to 1.0 microg/mL) caused a 30-65% reduction in the levels of NO metabolites released by THP-1 macrophages after 4 hr of incubation, with a corresponding decrease in iNOS activity. Western immunoblotting analysis coupled with a nuclease protection assay and reverse transcription-polymerase chain reaction revealed a concomitant reduction in the levels of iNOS protein mass and mRNA in ginkgolide A-, ginkgolide B-, or bilobalide-treated macrophages. On the other hand, these compounds did not affect eNOS-mediated NO production or the expression of eNOS protein and mRNA in HUVEC. Taken together, these results suggest that ginkgolide A, ginkgolide B, and bilobalide may contribute to the selective inhibitory effect of EGb on iNOS expression without affecting eNOS-mediated NO production.

Cells, Cultured↗
PubMed2001

RESOURCERER: a database for annotating and linking microarray resources within and across species.

Microarray expression analysis is providing unprecedented data on gene expression in humans and mammalian model systems. Although such studies provide a tremendous resource for understanding human disease states, one of the significant challenges is cross-referencing the data derived from different species, across diverse expression analysis platforms, in order to properly derive inferences regarding gene expression and disease state. To address this problem, we have developed RESOURCERER, a microarray-resource annotation and cross-reference database built using the analysis of expressed sequence tags (ESTs) and gene sequences provided by the TIGR Gene Index (TGI) and TIGR Orthologous Gene Alignment (TOGA) databases [now called Eukaryotic Gene Orthologs (EGO)].

Animals↗
PubMed2000

Effect of magnesium tanshinoate B on the production of nitric oxide in endothelial cells.

Nitric oxide (NO) is a potent vasodilator which plays an important role in regulating vascular tones. Danshen, a Chinese herbal medicine has been widely used for the treatment of cardiovascular diseases. The objective of this study was to investigate the effect of magnesium tanshinoate B (MTB), a compound purified from Danshen, on the production of NO in human endothelial cell line (ECV304). After cells were incubated with MTB (1-10 microM) for 1 or 4 h, amounts of NO metabolites released by cells were quantified and cellular NOS activities were determined following the conversion of [3H]arginine to [3H]citrulline. The NOS protein expression was determined by Western immunoblotting analysis. MTB (1-10 microM) stimulated the release of NO and its metabolites from endothelial cells. Following MTB treatment, the cellular NOS activities were significantly enhanced with a concomitant increase in the levels of constitutive NOS (cNOS) protein mass (110-178%). Selective activation of cNOS by MTB may be employed therapeutically in modulating NO production in endothelial cells.

Blotting, Western↗
PubMed1999

Inhibitory effect of Ginkgo biloba extract on the expression of inducible nitric oxide synthase in endothelial cells.

Excessive production of nitric oxide (NO) may have cytotoxic effects through the formation of peroxynitrite with superoxide. The extract of Ginkgo biloba leaves (EGb) has been demonstrated to be a potent scavenger of free radicals. Although EGb has been shown recently to inhibit NO production in macrophages, its effect on NO production in endothelial cells is largely unknown. The objective of this study was to elucidate the mechanism by which EGb affects NO production in a human endothelial cell line (ECV304). After cells were incubated with EGb (10-100 microg/mL) for 2 or 4 hr, the amounts of NO metabolites released by the cells were quantitated, and cellular NOS activities were determined following the conversion of [3H]arginine to [3H]citrulline. NOS protein expression was determined by western immunoblotting analysis. mRNA levels were examined by reverse transcription-polymerase chain reaction (RT-PCR) analysis. EGb (50 microg/mL) caused a 30% reduction of NO metabolites released by endothelial cells. Following EGb treatment, cellular inducible NO synthase (iNOS) activity was reduced by 28% with a concomitant reduction in the levels of iNOS protein mass and mRNA. There was no change in the activity or protein mass of constitutive NO synthase in these cells. EGb inhibited NO production by attenuating the level of iNOS mRNA in ECV304 cells. Selective inhibition of iNOS by EGb may be therapeutically relevant in modulating NO production in endothelial cells.

Cell Line↗
PubMed1999

Cognitive behavioral therapy of minor depressive symptoms in elderly Chinese Americans: a pilot study.

There is a high prevalence of suicide among elderly Chinese, and particularly among elderly Chinese women in Mainland China with a prevalence of 19.6 per hundred thousand. Since Chinese individuals may much more highly value education, a cognitive-behavioral package originated by Ricardo Munoz, Ph.D. was adapted for Chinese American subjects. The material was videotaped in eight sessions, approximately 25 minutes in length, to be shown to community subjects who were at least 40 years and over. In addition, a videotape of muscular relaxation techniques was made. A manual written in Chinese about the content of each class, was given to each subject when he/she attended. The experimental group showed significant improvement in the scores in the Hamilton Depression Scale, including the Somatic Subscale in the Hamilton Anxiety Scale. There was no significant improvement in the control group on any of the measures. Thus the study suggests the efficacy of psychoeducational classes in reducing symptoms of depression in non-patient community elderly. Other studies are being conducted among Korean Americans and Japanese Americans in the United States, and also in the Orient among Japanese elderly.

Aged↗
PubMed1999

Mental health issues for Asian Americans.

One of fastest-growing population groups in recent decades, Asian Americans represent a vastly diversified and rich mixture of cultures, languages, beliefs, and practices, many of which differ widely from those of European Americans. As immigrants, Asian Americans have experienced and continue to experience various emotional and behavioral problems. However, they tend to underuse existing services except those that are culturally appropriate and linguistically compatible. Misdiagnosis frequently occurs, and the existence of culture-bound syndromes points to a lack of precise correspondence between indigenous labels and established diagnostic categories. Due to Asian traditions of viewing the body and mind as unitary rather than dualistic, patients tend to focus more on physical discomforts than emotional symptoms, leading to an overrepresentation of somatic complaints. Traditional practices and healing methods are frequently used to alleviate distress both before and after patients and their family members approach the conventional mental health care system. Help seeking typically is a family venture. Asian patients respond well to highly structured therapeutic interventions such as those used in behavioral, cognitive, and interpersonal models. When applying pharmacotherapy, clinicians should pay attention to Asians' unique responses to psychotropics, especially in regard to dosage requirements and side effects. Research in this area as well as on other important issues is in the early stage of development.

Asian↗
PubMed1998

Nasopharyngeal carcinoma in situ: two cases of an emerging diagnostic entity.

BACKGROUND: The association of Epstein-Barr virus (EBV) with the oncogenesis of nasopharyngeal carcinoma (NPC) is well established. Latent infection by EBV with clonal proliferation has also been demonstrated in preinvasive lesions of NPC. In situ hybridization for EBV-encoded RNA (ISH EBER) now serves as an ancillary test in the definitive diagnosis of these lesions. METHODS: Two cases of nasopharyngeal carcinoma in situ (NPCIS) are presented in this study. Their biopsies were studied by ordinary light microscopy, the ISH EBER technique, and immunostaining for bcl-2. Tissue samples from 100 high risk subjects negative for NPC and NPCIS, who served as controls, were also studied using the ISH EBER technique. RESULTS: NPCIS was characterized by abnormal light microscopic appearance as well as positive staining by the ISH EBER technique; these features were not observed in samples from the 100 high risk subjects. Immunostaining for bcl-2 protein was positive but less specific. Postradiotherapy biopsies of the two patients were negative for NPCIS. CONCLUSIONS: With the help of the ISH EBER technique, the diagnosis of NPCIS is now possible in routine surgical pathology. As this entity is rare, it is necessary to have a high degree of suspicion when evaluating biopsies from high risk individuals. Radiotherapy for patients with NPCIS is justified in view of the risk of cancer progression and the possibility of a coexisting invasive carcinoma.

Carcinoma in Situ↗
PubMed1997

Variability in anticancer lignan levels in flaxseed.

Flaxseed and its major mammalian lignan precursor secoisolariciresinol diglycoside have been shown to be protective against chemically induced carcinogenesis in animal models. Although flaxseed is the richest source of mammalian lignan precursors, it is not known whether these levels vary with source. Thus the objective of this study was to determine how lignan levels in flaxseed are affected by variety, growing location, harvest year, and seeding time. Ten varieties of flaxseed (AC Linora, Andro, Flanders, Linott, McGregor, Noralta, NorLin, NorMan, Somme, and Vimy) were subjected to 1) in vitro fermentation with human fecal inoculum for 24 hours under anaerobic conditions to assess mammalian lignan production and 2) high-performance liquid chromatography (HPLC) analysis for secoisolariciresinol levels. Three of these varieties (Linott, McGregor, and NorLin) were grown in four locations, seeded early (May) for three different years, and, in one year, seeded early (May) or late (June). Significant differences in lignan production were observed among the different varieties, ranging from 0.96 mumol/g for Linott to 3.15 mumol/g for Somme flaxseed (p < 0.05). Growing location had significant effects on lignan production from all three varieties. Harvest year significantly affected only the Linott variety (p < 0.05), whereas seeding time had no effect. A significant correlation (r = 0.572, p < 0.003) was observed between lignan values obtained from HPLC and in vitro fermentation methods, indicating that HPLC analysis of flaxseed may be used as a predictor of its lignan production levels. Differences due to variety, harvest location, and harvest year of flaxseed should be taken into consideration when tumorigenesis studies are designed.

Antineoplastic Agents↗
PubMed1997

Atypical manifestations in a patient with systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a chronic systemic inflammatory disease associated with the production of various autoantibodies and involvement of multiple organs. Necropsy findings in a 65 year old woman with SLE who had multiple aortic aneurysms and dissections, as well as other unusual manifestations, are described. The case illustrates the occurrence of and the difficulties encountered in the diagnosis of several diseases, namely aortic aneurysm, aortic dissection, acute pancreatitis, and Penicillium marneffei infection.

Aged↗
PubMed1997

Mammary hamartoma: is clinical diagnosis possible?

Mammary hamartoma is a rare benign lesion of the female breast. Diagnosis is usually made by either radiological and or histological means. Clinical diagnosis has been reported to be difficult. Between December 1994 and June 1995, three patients were found to have mammary hamartomas. All of them presented with breast lump greater than 6 cm in size. All hamartomas were well-delineated, soft and lobulated. Mammogram in these patients showed typical radiological 'breast in the breast' appearance of mammary hamartoma. A correct clinical diagnosis of mammary hamartoma was made in the third patient after the experience of management gained through the first two patients with mammary hamartoma. We believe that clinical diagnosis of mammary hamartoma is possible with both awareness of and experience of examining patients with this rare disease.

Adult↗
PubMed1991

Mammalian lignan production from various foods.

Mammalian lignans such as enterolactone and enterodiol, which are produced in the colon from precursors in foods, have been suggested as playing a role in the cancer-protective effect of vegetarian diets. Despite this, very little is known regarding the amount that is produced from different food products. Therefore, the objective of this study was to determine the production of mammalian lignans from 68 common plant foods by using the technique of in vitro fermentation with human fecal microbiota, which simulates colonic fermentation. Results showed a wide range (21-67,541 microgram(s)/100 g sample) in the amount of lignans produced. On the average as a group, the oilseeds produced the highest amounts (20,461 +/- 12,685), followed by the dried seaweeds (900 +/- 247), whole legumes (562 +/- 211), cereal brans (486 +/- 90), legume hulls (371 +/- 52), whole grain cereals (359 +/- 81), vegetables (144 +/- 23), and fruits (84 +/- 22). The vegetables produced the second highest concentration of lignans (1,546 +/- 280) when the data were expressed on a moisture-free basis. Flaxseed flour and its defatted meal were the highest producers of lignans (mean 60,110 +/- 7,431). Lignan production with the in vitro method related well to the urinary lignan excretion observed in rats and humans. The data should be useful in the estimation of lignan production from a given diet and in the formulation of high-lignan-producing diet for the purpose of reducing the cancer risk.

4-Butyrolactone↗