Biomedical subjects

Y H Cheng

Publications and source records attributed to Y H Cheng.

At least 19 recordsLinked to original sources

PubMed2006

Characterization and adsorption properties of eggshells and eggshell membrane.

The objective of this work was to study the chemical and physical characterization of eggshell and eggshell membrane particles prepared from the hen eggshell waste. Under the characterization measurements investigated, it was found that the pore structures of the two biomaterials belong to a typical Type II, indicating that they should be basically characteristic of nonporous materials or materials with macropores or open voids. Further, the chemical composition of the resulting eggshell particle was strongly associated with the presence of carbonate minerals from the Fourier transform infrared (FTIR) spectra. In contrast to the resulting eggshell membrane particle, the presence of functional groups of amines and amides was observable because of its chemical composition of fibrous proteins. From the isotherm data of methylene blue at 25 degrees C, the Freundlich model yielded a somewhat better fit than the Langmuir model. The adsorption isotherms revealed the eggshell biosorbents could only uptake the basic dye of less than 1.0mg/g in aqueous medium, which was attributed to their poor pore properties.

Adsorption↗

PubMed2004

Low literacy Chinese patients: how are they affected and how do they cope with health matters? A qualitative study.

BACKGROUND: Low literacy is common in Hong Kong and China, especially among the females and the elderly. These are often the patients with the greatest health care needs. However little is known about how low literacy affects the ability of patients to obtain adequate medical care and comply with the recommendations of health professionals. METHODS: Qualitative study of subjects' opinions using semi-structured group and individual interviews. Thirty-six participants took part in 6 group and 9 individual interviews. RESULTS: Participants' opinions towards low literacy were explored in the interviews. They expressed diverse views on how they perceived low literacy. Some thought they were handicapped by it but others felt it was not a problem. Age, gender, chronic illnesses and their attitudes towards self were found to be major factors affecting their perception. Despite their low literacy, some had their specific ways to overcome the difficulties, for example, drawing symbols to help with the timing of taking the medications. Most of them felt better explanation by the health care workers was most important. CONCLUSIONS: It is highly relevant for health care workers to be aware of the low literacy status of their patients and to explain information so that patients understand it.

Adaptation, Psychological↗

PubMed2004

Utilizing Solanum glaucophyllum alone or with phytase to improve phosphorus utilization in broilers.

Experiments were conducted to determine if Solanum glaucophyllum (SG), a plant containing a glycoside of 1,25-dihydroxyvitamin D, could be used as a feed additive to improve P utilization of broilers. SG leaves (1, 2.5, or 5 g/kg), 1,25-dihydroxyvitamin D (15 microg/kg), or Ca and P (to achieve a 0.92% Ca:0.65% P:0.41% nonphytate P control diet) were added to a 0.56% Ca/0.45% P/0.28% nonphytate P basal diet and fed to broilers from 7 to 28 d of age. Birds fed basal ration alone exhibited reduced weight gain, bone density, and bone mineral content when compared with birds fed the 0.92% Ca:0.65% P diet. Adding 5 g SG leaves or 15 microg of 1,25-dihydroxyvitamin D/kg to the basal diet increased body weight gain, plasma Ca and P, bone ash, and bone density above basal diet levels. Plasma P and weight gain of birds fed 5 g SG or 15 microg of 1,25-dihydroxyvitamin D/kg basal diet were equivalent to those observed in birds fed the 0.92% Ca:0.65% P diet. In experiment 2, the effect of higher doses of SG, as well as the additive effect of SG with 1,200 phytase units/kg diet, were examined in chicks fed a 0.59% Ca and 0.42% P basal diet. Two levels of SG leaves (7.5 g and 10 g), phytase, or both SG (7.5 g) and phytase were added per kilogram of basal diet. Adding SG or phytase to the basal diet increased weight gain, plasma Ca, plasma P, and bone mineral content over that observed in birds fed basal diet alone. Combining SG with phytase provided no significant gains in growth or bone parameters over treatment with phytase alone.

6-Phytase↗

PubMed2004

The first batch of graduates of a new medical curriculum in Asia: how their teachers see them.

OBJECTIVE: To examine teachers' views of the first batch of graduates of a revised medical curriculum in Asia. METHODS: A cross-sectional study using a structured questionnaire was carried out to obtain the views of all the clinical teachers involved in teaching final year students of the old curriculum in 2000-01 and the new curriculum in 2001-02 at the University of Hong Kong, which commenced curricular reform in 1997. RESULTS: Nearly 62% of respondents felt that better graduates were being produced with the new curriculum. The majority of them rated the new curriculum students better in nearly all the major goals of the new curriculum, such as self-directed learning initiative, problem solving skills, interpersonal skills and clinical performance in patient care. However, the core knowledge of the new curriculum students was of concern to some teachers. CONCLUSION: This study focused on the first complete cycle of a revised medical curriculum in Asia. Teachers' views of the new curriculum students were highly positive and they felt that better graduates were being produced.

Attitude↗

PubMed2004

Fermentation acids, aerobic fungal growth, and intake of napiergrass ensiled with nonfiber carbohydrates.

This study evaluated fermentation characteristics and fungal numbers of napiergrass silages prepared with and without added raw or heated corn meal (10%, fresh-weight basis) at ensiling. Corn was added to napiergrass so that the silage would contain concentrate similar to that of corn silage with minimum grain content. The silages treated with raw or heated corn were fed to dairy does to compare voluntary silage consumption. After 8 wk of fermentation, pH for silage treated with heated corn was lowest, and that for napiergrass ensiled alone was highest among the treatments. The addition of corn increased lactic acid, but propionic and butyric acids were also elevated. Acetic acid decreased in response to the supplementation of corn but remained the dominant acid for all silages. Numbers of fungi (yeasts plus molds) in silages did not differ significantly at silo opening or after 24 h of exposure to air. However, the numbers of fungi at 48 h in aerated silages containing corn were lower than were the fungi counts in the control silage. When the silages were offered free choice along with concentrate at a fixed rate, dairy does tended to consume more silage treated with heated corn than raw corn. Whole-tract nutrient digestibility and serum glucose and urea N were not altered. These results indicate that the addition of either raw or heated corn meal to napiergrass at ensiling was beneficial to silage fermentation quality because it decreased pH, increased lactic acid, and apparently suppressed fungal populations via elevated antifungal acids. A further advantage of heated corn vs. raw corn was increased silage intake.

Acetic Acid↗

PubMed2003

A transitional course from high school to medical school in a new medical curriculum in Asia: how do the students see it?

The objective of this study was to examine the students' views on a transitional course for Asian freshers in a revised medical curriculum. Data were collected through the year-end questionnaire distributed to all first-year students over three academic years from 1997 to 2000. The students considered the transitional course had encouraged them to become more active and self-directed although there were different views about its overall effectiveness. Students appeared uncertain as to the depth in which they were expected to master the subjects, thus leading them to call for more clearly stated learning objectives to help relieve the anxiety they had towards the examinations. Lectures and self-assessment exercises were seen to be providing the general guides for that.

Asia↗

PubMed2002

Self-rated economic condition and the health of elderly persons in Hong Kong.

Studies have documented that health and income are important variables affecting the quality of life in old age. However, there is little knowledge about whether perceived financial sufficiency affects the health of elderly persons. Recent research has documented that in addition to material and behavioural determinants, psychosocial pathways also have an influence on health inequalities. This is the first paper to examine the relation between self-rated economic condition (measured with a single item question) and reported health conditions (i.e., somatic complaints, diagnosed physical diseases, functional health (Activities of Daily Living), self-rated health, and mental health status (General Health Questionnaire-30 [GHQ-30]) among elderly persons in Hong Kong. The respondents of the study were persons aged 65 and over residing in public housing estates in the Southern District of Hong Kong Island. Four hundred and fifty respondents were interviewed in 1995 by means of a structured questionnaire. The study found that although it did not record the actual income levels of the respondents, the subjective measure vividly demonstrated the health differentials among the elderly respondents. Multiple regression analyses suggested that self-rated economic condition was a significant predictor of the number of somatic complaints and physical illnesses reported, as well as of functional health, self-rated health, and mental health status (controlling for socio-demographic variables). However, the measure explained a higher proportion of variance in models related to psychological health than those related to physical health. The findings substantiated the role of psychosocial processes in understanding perceived health and illness and health inequalities in particular.

Activities of Daily Living↗

PubMed2001

Differential expression of AP-2gamma and AP-2alpha during human trophoblast differentiation.

Previous studies from our laboratory demonstrated that AP-2alpha induces the expression of the hPL and hCG genes in cultured trophoblast cells. In the current study, we have shown by transient transfection studies that AP-2gamma, which is the product of a separate gene from AP-2alpha, also stimulates hPL and hCGbeta promoter activities. However, AP-2gamma mRNA levels during in vitro differentiation of human cytotrophoblast cells were strikingly different than those of AP-2alpha mRNA levels, with AP-2alpha increasing and AP-2gamma markedly decreasing during the differentiation process. The amount of AP-2gamma protein binding to AP-2 elements on the hPL promoter, as determined by supershift assays, also markedly decreased during the differentiation process. These findings strongly suggest that AP-2gamma action in cytotrophoblast cells is repressed by a co-factor(s) that inhibits AP-2gamma action or is prevented by the absence of a co-factor(s) that is essential for AP-2gamma action.

Cell Differentiation↗

PubMed2001

Effects of aflatoxin and carotenoids on growth performance and immune response in mule ducklings.

The purpose of this study was to investigate if carotenoids could alleviate the adverse effects caused by aflatoxin with respect to growth performance and immune response. In two experiments, a total of 320 mule ducklings were assigned to 5 treatments, i.e. control, aflatoxin B(1) (AFB(1)) 200 ppb, AFB(1) +beta-carotene (BC) 200 ppm, AFB(1)+BC 400 ppm, and AFB(1)+astaxanthin (AS) 200 ppm. In experiment 1, the addition of beta-carotene or astaxanthin in the diet containing AFB(1) 200 ppb resulted in a significant decrease in average daily gain as compared with the control. AFB(1) 200 ppb alone and the addition of BC or AS on top of AFB(1) resulted in a significantly lower daily feed intake than for the control group. There were no significant differences in relative organ weights among treatment groups. Both treatments of BC 400 ppm and AS 200 ppm had significantly more macrophages harvested per duck than the control and AFB(1) 200 ppb treatments. However, there were no significant differences among treatments in percentages of phagocytotic macrophages and number of Candida albican phagocytized by phagocytotic macrophages. In experiment 2, blood biochemical parameters and antibody titers were evaluated. There were no significant differences among treatments in total bilirubin content and alkaline phosphatase activity in the serum or in antibody titers against fowl cholera. However, AFB(1) treatment had the highest activities of AST and ALT in the serum. The addition of BC 400 ppm on top of AFB(1) significantly reduced ALT activity as compared with the AFB(1) 200 ppb treatment. These results suggest that carotenoids could provide a slightly toxic alleviating effect on growth performance, enhance the chemotaxis ability of macrophages, and reduce ALT activity elevated by AFB(1).

Aflatoxin B1↗

PubMed2000

Activator protein-2 regulates human placental lactogen gene expression.

DNase I footprint analysis of the human placental lactogen-A (hPL-A) promoter using nuclear extracts from purified human trophoblast cells and BeWo choriocarcinoma cells revealed five protected regions within the proximal 325 bp. Two of the protected regions, FP4 (-289--267) and FP5 (-167--154), are homologous to regions on the human growth hormone (hGH) promoter that bind transcription factors AP-2 and/or NFI. Competitive gel shift assays and supershift assays indicated that FP4 forms complexes with activator protein-2 (AP-2) and nuclear factor I (NFI), while FP5 forms a complex with AP-2 alone. In transient transfection studies in human trophoblast cells, hPL promoter constructs containing point mutations in the AP-2 binding sites of FP4 and/or FP5 were 60-80% less active than plasmids containing the wild-type promoter. A mutation in the NFI binding site of FP4, however, had little effect on promoter activity in these cells. Overexpression of AP-2 in HepG2 cells co-transfected with the wild-type hPL promoter resulted in a significant increase in promoter activity. Taken together, these findings suggest a critical role for AP-2 in the regulation of hPL gene expression.

Base Sequence↗

PubMed2000

Changed cellular membrane lipid composition and lipid peroxidation of kidney in rats with chronic fluorosis.

An animal model of chronic fluorosis was produced by subjecting Wistar rats to high doses of fluoride in drinking water for a prolonged period. Phospholipid and neutral lipid contents in rat kidney were then analyzed by high-performance liquid chromatography (HPLC), and fatty acid compositions from individual phospholipids were measured by gas chromatography. Lipid peroxidation was detected by the thiobarbituric-acid-reactive substance assay. Results showed that the total phospholipid content significantly decreased in the kidney of the rats treated with high doses of fluoride and the main species influenced were phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Decreased proportions of polyunsaturated fatty acids were observed in PE and PC in kidney of fluoride-treated animals compared to controls. No changes could be detected in the amounts of cholesterol and dolichol in kidneys between the rats treated with fluoride and controls. A significant decrease of ubiquinone in rat kidney was observed in the groups treated with excessive fluoride. High levels of lipid peroxidation were detected in kidney of the rats with fluorosis. It is plausible that the specific modification of lipid composition results from lipid peroxidation. The oxidative stress and modification of cellular membrane lipids may be involved in the pathogenesis of chronic fluorosis and provide a possible explanation for the gross system damage observed in the body, especially in soft tissues and organs.

Animals↗

PubMed2000

Corticotropin-releasing hormone gene expression in primary placental cells is modulated by cyclic adenosine 3',5'-monophosphate.

CRH, the principal neuropeptide regulator of pituitary ACTH secretion, is also expressed in placenta. Placental CRH has been linked to the process of human parturition. However, the mechanisms regulating transcription of the CRH gene in placenta remain unclear. cAMP signaling pathways play important roles in regulating the expression of a diverse range of endocrine genes in the placenta. Therefore, we have explored the effect of cAMP on CRH promoter activity in primary cultures of human placental cells. Both forskolin and 8-bromo-cAMP, activators of protein kinase A, can increase CRH promoter activity 5-fold in transiently transfected human primary placental cells, in a manner that parallels the increase in endogenous CRH peptide. Maximal stimulation of CRH promoter activity occurs at 500 micromol/L 8-bromo-cAMP and 10 micromol/L forskolin. Electrophoretic mobility shift assay and mutation analysis combined with transient transfection demonstrate that in placental cells cAMP stimulates CRH gene expression through a cAMP regulatory element in the proximal CRH promoter region and involves a placental nuclear protein interacting specifically with the cAMP regulatory element.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2000

Glucocorticoid stimulation of corticotropin-releasing hormone gene expression requires a cyclic adenosine 3',5'-monophosphate regulatory element in human primary placental cytotrophoblast cells.

Production of placental CRH, which is identical to the peptide synthesized and secreted in the hypothalamus, has been linked to human parturition. Glucocorticoids stimulate placental CRH secretion and messenger ribonucleic acid expression, in contrast to their inhibition of CRH synthesis in the hypothalamus. A positive feedforward loop involving glucocorticoid-CRH-ACTH-glucocorticoid is thought to drive the exponential increase in placental CRH leading to delivery. Tissue-specific effects of glucocorticoids on CRH expression are therefore of interest. Using human primary placental cells, we investigated the mechanism by which glucocorticoids stimulate placental CRH gene expression. Nuclear run-on transcription shows that in human placental cells glucocorticoids up-regulate transcription of human CRH (hCRH). Using transient transfection assays we demonstrate that dexamethasone up-regulates both basal and cAMP-stimulated hCRH promoter activity, correlating well with the increase in endogenous CRH peptide levels. Through mutagenesis and deletion analyses we show that dexamethasone stimulation of hCRH gene transcription requires a functional cAMP regulatory element (CRE); this CRE is adequate to confer dexamethasone stimulation upon a heterologous promoter, and electrophoretic mobility shift assay studies show that a placental nuclear protein specifically binds to the hCRH CRE.

Cell Nucleus↗

PubMed2000

Mitogen-activated protein kinase activates human placental lactogen-B enhancer by an NF-IL6-dependent pathway.

Computer analysis of the human placental lactogen-B (hPL-B) enhancer reveals two putative binding sites for the transcription factor NF-IL6, but the role of NF-IL6 in the regulation of the enhancer is unknown. Using gel mobility shift and supershift assays, we demonstrated that NF-IL6 binds to both enhancer sites. Transient transfection studies indicated that the transcription factor NF-IL6 stimulates hPL-B enhancer activity by 4.4-fold in primary cultures of human trophoblast cells and by 32.0- and 8.4-fold in JAR and BeWo choriocarcinoma cells, respectively. Overexpression of MEK (mitogen-activated protein [MAP] kinase kinase), which is known to stimulate phosphorylation of NF-IL6, induced a 3.6-fold increase in hPL-B enhancer activity. The induction by MEK was completely inhibited by an expression plasmid for a dominant/negative mutant of NF-IL6 or by mutation of the NF-IL6 binding sites on the enhancer. PD98059, an inhibitor of MEK, inhibited hPL release from cultured trophoblast cells by about 50%. Taken together, these results indicate that MAP kinase stimulates the hPL-B enhancer by an NF-IL-6-dependent pathway.

CCAAT-Enhancer-Binding Proteins↗

PubMed2000

Schizophrenia and drug delivery systems.

Schizophrenia is a severe non-curable illness of the brain with serious consequences if not properly treated and kept under control. Antipsychotic drugs have revolutionised the therapy and management of schizophrenia. However, patient compliance rates are notoriously poor due to the nature of the disease and troublesome side-effects, and are major causes of symptom recurrence. Although some new antipsychotic agents have been marketed to offer broader efficacy with much reduced side-effect profiles, the drug delivery systems for antipsychotics are still in the stage of conventional dosage forms, such as tablets, capsules and solutions, and need to be dosed at the frequency of 2-4 times daily. Doubtless. novel drug delivery systems, such as sustained and controlled release systems, will be useful for antipsychotics. They should reduce the frequency of dosing. enhance drug bioavailability and improve patient compliance. In this article, the specificity and characterisation of schizophrenia and pathophysiology. drug therapy. and the development and future prospects of neuroleptic drug delivery systems are reviewed.

Antipsychotic Agents↗

PubMed2000

[Bone dynamics of repair of mandibular defect with collagen/hydroxyapatite].

OBJECTIVE: To study the effect of collagen/hydroxyapatite(CHA) instead of autogenous bone transplantation on repairing the mandibular defects. METHODS: Ten Chinese experimental minipigs were made 2 cm bone defects in diameter in the mandible. The experimental group was implanted CHA, while the control group was implanted autogenous bone. The basic parameters of bone dynamics were determined by bone metrology. RESULTS: There was remarkable difference between the two groups in the mean distance and mineralization apposition rate of double label bands marked by tetracycline(P < 0.05), while the mean osteoid seam width and mineralization lag time had no remarkable difference(P > 0.05). It suggested that CHA had good osteogenesis. The collagen in CHA offered the condition of bone mineralization, and the mineralization peak of experimental group was present at 4 weeks earlier than that of control group (8 weeks). CONCLUSION: CHA may be a substitute of autogenous bone transplantation in repairing the mandibular defects, and the second operation for offering the implanting bone is avoidable, therefore, CHA may be an ideal material to repair bone defects.

Animals↗

PubMed1998

A poly(D,L-lactide-co-glycolide) microsphere depot system for delivery of haloperidol.

Haloperidol-loaded biodegradable poly(d,l-lactide-co-glycolide) (PLG) microspheres, with theoretical mean particle sizes of about 0. 8, 2 and 8 micrometer, have been successfully prepared by using an emulsification-solvent evaporation method. The effect of various processing parameters such as the content of polymer in dichloromethane, the content of polyvinyl alcohol in the aqueous phase, and the stirring speed of emulsification on the particle size and size distribution of microspheres has been investigated and three optimal procedures suggested. The influence of particle size on drug content and incorporation efficiency of haloperidol-loaded PLG microspheres also has been evaluated. In vitro a linear release of haloperidol from PLG microspheres over an extended period of time without a significant burst effect has been achieved; the time of 50% drug release (T50%) being around 55 days. The effect of drug content and particle size on the cumulative release of haloperidol from PLG microspheres was also studied together with the reproducibility of drug content and release profile from batch-to-batch with different particle sizes.

Antipsychotic Agents↗

PubMed1998

Rat testicular extracellular superoxide dismutase: its purification, cellular distribution, and regulation.

Using multiple HPLC steps, we have identified and purified a 68-kDa polypeptide (as estimated by gel permeation HPLC) to apparent homogeneity, from primary Sertoli cell-enriched culture medium, that consisted of two monomers of 35 (alpha chain) and 33 kDa (ss chain) on SDS-polyacrylamide gel running under reducing conditions. Partial N-terminal amino acid sequence analysis of these two monomers revealed sequences of NH2-DXGESGVDLADRL (SODEX-alpha) and NH2-XXDTGESGVDLADXL (SODEX-ss), which are identical to rat extracellular superoxide dismutase (SODEX) with the exceptions that SODEX-alpha and SODEX-ss are missing, respectively, four (Trp-Thr-Met-Ser) and two (Trp-Thr) amino acids from their N-termini, compared to rat SODEX, suggesting that the cleavage sites of the SODEX gene in the testis are different from that of other organs. Studies by sequential use of reverse transcription and polymerase chain reaction (PCR) using two SODEX primers have demonstrated the expression of SODEX in the heart, brain, lung, kidney, epididymis, testis, Sertoli, and germ cells, with low expression in the liver and ovary and no expression in the uterus, spleen, or thymus. Nucleotide sequence analysis of this 447-base pair PCR product from Sertoli cells revealed that its sequence is equivalent to the sequence of previously published rat SODEX. During testicular maturation, the SODEX steady-state mRNA level increased significantly from 20 to 60 days of age and then declined at 90 days of age. Such an increase in the testicular SODEX expression during maturation is not likely a result of an up-regulation by germ cells, since germ cells isolated from either 20- or 60-day-old rats when cocultured with Sertoli cells failed to elicit an increase in SODEX expression in the cocultures. Using primary Sertoli cell cultures in vitro, it was found that Sertoli cell SODEX expression was stimulated by interleukin-1alpha but not by either interferon-gamma or basic fibroblast growth factor. These results illustrate that Sertoli cells as well as germ cells synthesize and/or secrete a testicular variant of SODEX that may provide essential clues to understanding superoxide radical-mediated damage in the gonad.

Animals↗