Biomedical subjects

Y M Li

Publications and source records attributed to Y M Li.

At least 55 records · Page 3Linked to original sources

PubMed1999

Arsenic targets tubulins to induce apoptosis in myeloid leukemia cells.

Arsenic exhibits a differential toxicity to cancer cells. At a high concentration (>5 microM), As2O3 causes acute necrosis in various cell lines. At a lower concentration (0.5-5 microm), it induces myeloid cell maturation and an arrest in metaphase, leading to apoptosis. As2O3-treated cells have features found with both tubulin-assembling enhancers (Taxol) and inhibitors (colchicine). Prior treatment of monomeric tubulin with As2O3 markedly inhibits GTP-induced polymerization and microtubule formation in vitro but does not destabilize GTP-induced tubulin polymers. Cross-inhibition experiments indicate that As2O3 is a noncompetitive inhibitor of GTP binding to tubulin. These observations correlate with the three-dimensional structure of beta-tubulin and suggest that the cross-linking of two vicinal cysteine residues (Cys-12 and Cys-213) by trivalent arsenic inactivates the GTP binding site. Furthermore, exogenous GTP can prevent As2O3-induced mitotic arrest.

Apoptosis↗

PubMed1999

Continuous beds for microchromatography: chromatofocusing and anion exchange chromatography.

A method was developed for the preparation of continuous beds derivatized with polyethyleneimine (PEI) for chromatofocusing and anion exchange chromatography in the capillary mode. First, a continuous bed activated by epoxy groups was synthesized inside a fused silica capillary and became at the same time covalently attached to the inner wall of the capillary. A PEI solution was then pumped through the continuous bed to allow the imine groups in PEI to react with the epoxy groups in the bed. Efficient immobilization of PEI was indicated by the high-resolution separation of standard proteins (hemoglobins C, S, F, and A) in both chromatofocusing and anion exchange chromatography on a capillary column prepared by this method.

Buffers↗

PubMed1999

Micellar electrokinetic capillary chromatography for the separation of cefalexin and its related substances.

Micellar electrokinetic capillary chromatography (MEKC) was examined for analysis of cefalexin and its related substances. Good selectivity was obtained with two different buffer solutions: a sodium acetate buffer (50 mM, pH 5.25) containing sodium dodecyl sulfate (50 mM SDS) or sodium phosphate buffer (40 mM, pH 7.0) containing 100 mM SDS. Both methods permit cefalexin to be completely separated from its ten related substances within 20 min. The robustness of the method, using pH 5.25 acetate buffer, was examined by means of a full-fraction factorial design to test the influence of buffer pH, concentration of SDS and buffer concentration. The parameters for validation such as linearity, precision, limit of detection and limit of quantitation are also reported. The results show that method 1 is suitable for the analysis of cefalexin.

Cephalexin↗

PubMed1999

Analysis of spiramycin by capillary electrophoresis.

The development and validation of an analytical method for the determination of spiramycin I in the presence of its related substances by capillary electrophoresis is shown. The separation, performed in a phosphate buffer (80 mM, pH 7.5) containing 12 mM cetyltrimethylammonium bromide (CTAB) and 20 mM sodium cholate, with a 50 microm ID and 44 cm long fused-silica capillary (36 cm effective length), applying a voltage of 12 kV (l approximately 80 microA), at 25 degrees C, is achieved in 15 min. Good selectivity among spiramycin I and its related substances was obtained. The influence of the buffer pH, and of the CTAB and sodium cholate concentrations was investigated. The method robustness, examined by means of a full-fraction factorial design, shows that it can be used within the limits set for the three parameters that were investigated. The method is linear (r = 0.9992) and precise (day-to-day corrected peak area repeatability, n = 18, relative standard deviation = 1.3%). The limits of detection and quantitation are 7 pg (0.025%) and 22 pg (0.08%), respectively, relative to a 2 mg/mL solution.

Aminoglycosides↗

PubMed1999

The genotype and epigenotype synergize to diversify the spatial pattern of expression of the imprinted H19 gene.

Little is known of how the genetic background effects the phenomenon of genomic imprinting. The H19 gene belongs to a cluster of imprinted genes on human chromosome 11. Here we show that the alternative splicing of a human H19 transcript is genotype-specific. Moreover, this variant transcript, which lacks exon 4, is either not found at all, is widely expressed or is confined to extra-villous cytotrophoblasts in first trimester placenta, depending on a combination of the genotype and the sex of the transmitting parent.

Alleles↗

PubMed1999

The effect of wheat bran particle size on laxation and colonic fermentation.

OBJECTIVE: Due to perceived inferior fecal bulking ability, finely ground wheat bran is not recommended for treatment of colonic disorders, despite possible short chain fatty acid generation with potential benefits for colonic mucosal health. We therefore tested the effects of very fine particle size wheat bran on colonic function. METHODS: Two studies, each with three phases, were undertaken in healthy subjects in a randomized crossover design. In one study (metabolic, n=23) subjects took three diets containing either an additional 19 g/d dietary fiber with mean particle size (MPS) 50 microm or 758 microm in bread or a control low fiber bread. In the other study where the supplement was provided as a breakfast cereal (ad libitum, n=24) the respective wheat bran MPS were 692 microm and 1158 microm and the control was low fiber. Fecal collections were obtained during the last week of each diet. In the metabolic study, fecal short chain fatty acids were measured and 12-hour breath gas collections obtained. RESULTS: In both studies, wheat bran supplements significantly increased fecal bulk compared to the control (p<0.004), with no significant differences between brans of different particle size and no differences in fecal water content. However, higher fecal butyrate concentrations (p<0.007), butyrate output and breath CH4 levels (p=0.025) were seen on the low MPS wheat bran compared to the other two treatments, suggesting increased bacterial fermentation. CONCLUSIONS: Fine MPS wheat bran is an effective fecal bulking agent and may have added advantages if increased butyrate concentrations promote colonic mucosal integrity.

Adult↗

PubMed1999

Blood alcohol concentration among injured drivers in Hualien County.

Vehicle-related injuries are the major cause of death and injuries in Hualien County. Driving under the influence of alcohol plays a major role in such crashes. From December 1997 to May 1998, we determined the blood alcohol concentrations of 750 injured drivers from vehicle crashes, visiting the two emergency rooms of teaching hospitals in Hualien. The objectives of this study were to investigate the incidence of alcohol used in vehicle crashes, to identify the prevalence groups for prevention and to discuss alcohol testing at emergency services. Sixty-four percent were male; 27.5% were aborigines. The mean age was 36.5 +/- 16.5 years. About 54.1% tested positive for blood alcohol concentration (BAC), which ranged from 13 to 611 mg/dL; 38.6% had BAC levels exceeding 50 mg/dL and 21.1% exceeding 200 mg/dL. The mean BAC was 85.9 mg/dL (+/- 118.5). Middle-aged males and aborigines were more likely to drive under the influence of alcohol. We recommend blood alcohol testing to be mandatory at the emergency service and to be used as evidence for prosecution in a court of law. Preventing drunk driving through community programs is imperative, especially in the aboriginal communities.

Adolescent↗

PubMed1998

The H19 transcript is associated with polysomes and may regulate IGF2 expression in trans.

The imprinted H19 gene produces a fully processed transcript that does not exhibit any conserved open reading frame between mouse and man. Although transcriptional control elements associated with the mouse H19 locus have been shown to control the neighboring Igf2 gene in cis, the prevailing view is that the cytoplasmic H19 transcript does not display any function. In contrast to earlier reports, we show here that the H19 transcript is associated with polysomes in a variety of cell types, in both mouse and man. A possible trans-function of the H19 gene is suggested by a reciprocal correlation in trans between cytoplasmic H19 and IGF2 mRNA levels, as well as IGF2 mRNA translatability. We discuss these results in terms of their challenge to the prevailing dogma on the function of the enigmatic H19 gene, as well as with respect to the ontogeny of the Beckwith-Wiedemann syndrome, and propose that the human H19 gene is an antagonist of IGF2 expressivity in trans.

Animals↗

PubMed1998

Analysis of cefadroxil by micellar electrokinetic capillary chromatography: development and validation.

A method is developed and validated for analysis of the antibiotic cefadroxil using micellar electrokinetic capillary chromatography. It permits cefadroxil to be completely separated from ten of its known related substances within 15 min (including the washing procedure). The separation is performed in an acetate buffer (50 mM, pH 5.25) containing sodium dodecyl sulfate (SDS; 110 mM). The fused-silica capillary was 44 cm long (36 cm effective length), 50 microm ID; the voltage, 18 kV; temperature, 15 degrees C; and the detection wavelength; 254 nm. The influence of the type of buffer, buffer pH and concentration, and of the SDS concentration was investigated. The robustness of the method was examined by means of a full-fraction factorial design. The parameters for validation such as linearity, precision, limit of detection and limit of quantitation are also reported.

Cefadroxil↗

PubMed1998

Glycation ligand binding motif in lactoferrin. Implications in diabetic infection.

Lactoferrin and lysozyme are two important, naturally occurring antibacterial proteins found in saliva, nasal secretions, milk, mucus, serum and in the lysosomes of neutrophils and macrophages. Both proteins bind specifically to glucose-modified proteins bearing advanced glycation endproducts (AGEs). Exposure to AGE-modified proteins blocks the bacterial agglutination and bacterial killing activities of lactoferrin and also inhibits the bactericidal and enzymatic activity of lysozyme. Peptide mapping by AGE ligand blot revealed two AGE-binding domains in lactoferrin, and a single AGE-binding domain in lysozyme. None of these AGE-binding domains displayed any significant homology in their primary sequences; however, a common 17-18 amino acid cysteine loop motif (CX15-16C) was identified among them, which we named an ABCD motif (AGE-Binding Cysteine-bounded Domain). Similar domains are also present in other antimicrobial proteins such as defesins. Hydrophilicity analysis indicated that each of these ABCD loops is markedly hydrophilic. Synthetic peptides, corresponding to these motifs in lactoferrin and lysozyme, exhibited AGE-binding activity. Since diabetes is associated with abnormally high levels of tissue and serum AGEs, the elevated AGEs may inhibit endogenous antibacterial proteins by binding to the conserved ABCD motif, thereby increasing susceptibility to bacterial infections in diabetic individuals. These results may provide a basis for the development of new approaches to prevent diabetic infections.

Amino Acid Sequence↗

PubMed1998

Characterization of immunoreactive dynorphin B and beta-endorphin in human plasma.

Dynorphins and beta-endorphin in human plasma were characterized and studied quantitatively using radioimmunoassay, high-performance liquid chromatography (HPLC), and mass spectrometry. Most immunoreactive (ir) dynorphin B and beta-endorphin in human plasma coeluted with authentic peptides in analysis. Dynorphin A was not detected. Added to human plasma it was rapidly converted into Leu-enkephalin-Arg6 followed by elimination of the C-terminal arginine after prolonged incubation. The rate of dynorphin A conversion was estimated at 40 pmol/min/microl plasma. This process was inhibited by the thiol protease inhibitor, PHMB and by EDTA. Dynorphin B, alpha-neoendorphin and big dynorphin were virtually not metabolized by plasma proteases under the same conditions. beta-endorphin was processed into beta-endorphin(1-19) and the corresponding C-terminal counterpart beta-endorphin(20-31) at a rate of about 25 pmol/min/microl of plasma. Based on the above data, a reliable strategy was established to measure dynorphin B- and beta-endorphin-ir in human plasma samples. The basal levels in a male control group were 0.99 +/- 0.11 (n = 11) and 16.3 +/- 1.5 (n = 11) fmol/ml plasma, respectively.

Adult↗

PubMed1998

Daily life stress and its correlates among high school students in Hualien city.

Adolescence is a period of physical, cognitive, social and psychosexual changes. These developmental tasks make adolescents particularly vulnerable to life stress. The purpose of this study was to assess high school students' perception of stress from daily events and to identify its associated factors. A total of 1,195 high school students were selected via stratified cluster sampling method from nine high schools. Data from 1,141 valid answers were analyzed. A self-administrated questionnaire was used to assess students' demographic characteristics, personal traits (self-acceptance, neurotic trait), social support and perceived daily life stress. From principal component analysis, school work, concern with prospects, parent-teen relationship and peer relationship were found to be the main sources of daily life stress perceived. Personalities with high neurotic trait or low self-acceptance, perceived low social support, Chinese Hans and study at regular high school were important related factors. Screening by personality trait and social support questionnaire is suggested to be a routine at school to find out the high risk individuals and give them assistance in coping with stress.

Adolescent↗

PubMed1998

Self-rated psychiatric symptoms and their correlates among senior high school students in Hualien City.

The association between mental health disorders beginning in adolescence and disorders in early adulthood is increasingly acknowledged. The mental health of adolescents has not been studied in the eastern area of Taiwan, where the mortality of teenagers is highest in Taiwan. The purpose of this study was to assess psychiatric symptoms among senior high school students in Hualien City, and to identify their associated factors. A total of 1,195 students were selected, via a stratified cluster sampling method, from nine high schools in Hualien City. A self-administered questionnaire was used to assess students' demographic characteristics, neurotic traits, perceived daily-life stress, social support, and psychiatric symptoms. There were 1,141 valid responses. From principal components analysis, depression-anxiety, impulsivity-paranoia, and psychoticism-obsession were found to be the most common self-rated psychiatric symptoms. About 70% of the students felt blue, 48.2% reported urges to injure someone, and 25% felt tense. Overall, about 5% to 10% of high school students had severe psychiatric symptoms. Stress from schoolwork, peer relationships, and neurotic traits were important predictors of psychiatric symptoms. The findings of this study imply that screening for psychiatric symptoms at senior high schools is essential for improving the mental health of students. The mental health care of adolescents should be school-based and in collaboration with medical professionals. Life skills must be taught at school.

Adolescent↗

PubMed1997

Standardizing the immunological measurement of advanced glycation endproducts using normal human serum.

Advanced glycation endproducts (AGEs) have been linked to many sequelae of diabetes, renal disease and aging. To detect AGE levels in human tissues and blood samples, a competitive enzyme-linked immunosorbent assay (ELISA) has been widely used. As no consensus or standard research method for the quantitation of AGEs currently exists, nor a universally defined AGE unit available, the comparative quantitation of AGEs between research laboratories is problematic and restricts the usefulness of interlaboratory clinical data. By comparing the cross-reactivities of five different anti-AGE antisera with five different in vitro AGE-modified proteins, we found that the immunological recognition of AGEs by competitive ELISA is both AGE-carrier protein- and anti-AGE antibody-dependent. This suggests that in vitro AGE-modified proteins might not be appropriate standards for AGEs that occur naturally in vivo. Based on our observation that serum AGE levels in the normal human population are consistently within a narrow range and several folds lower than in diabetics, we propose a method to standardize AGE units against normal human serum (NHS). In this new method, one AGE unit is defined as the inhibition that results from 1:5 diluted NHS in the competitive AGE-ELISA; thus the AGE value in NHS is 5 units/ml. This NHS method requires a competitive AGE-ELISA with reasonable sensitivity such that 1:5 NHS produces a 25 to 40% inhibition of anti-AGE antibody binding to immobilized AGE-proteins. By using this standardized method we found that the AGE levels in normal human serum (5.0 +/- 2.2 units/ml; mean +/- SD, n = 34) fit a normal distribution (chi 2-test, p < 0.01), and the serum AGE levels in diabetic patients (20.3 +/- 3.8 units/ml, n = 7) are significantly higher than that of the normal population (p < 0.0001). Since AGE units can now be defined against a universally available standard, NHS, the results of quantitative AGE measurements using this method should be comparable between assays and between different laboratories. Taken together, standardizing the AGE-ELISA protocol as described here provides a simple and quantitative method that should facilitate the expanded application of clinical AGE data.

Adult↗

PubMed1997

Depletion of reactive advanced glycation endproducts from diabetic uremic sera using a lysozyme-linked matrix.

Diabetic uremic sera contain excessive amounts of reactive advanced glycation endproducts (AGEs), which accelerate the vasculopathy of diabetes and end-stage renal disease. To capture in vivo-derived toxic AGEs, high affinity AGE-binding protein lysozyme (LZ) was linked to a Sepharose 4B matrix. Initial studies showed that > 80% of 125I-AGE-BSA was retained by the LZ matrix, compared with < 10% retained by a control matrix. More than 60% of AGE-lysine was captured by the LZ matrix, and the LZ-bound fraction retained immunoreactivity and cross-linking activity, but had little intrinsic fluorescence (370/440 nm). After passage through the LZ matrix, AGE levels in diabetic sera (0.37+/-0.04 U/mg) were significantly reduced to a level (0.09+/-0.01 U/mg; n = 10; P < 0. 0001) comparable with the level of normal human serum, whereas total protein absorption was < 3%. The AGE-enriched serum fraction exhibited cross-linking activity, which was completely prevented by aminoguanidine. Among numerous LZ-bound proteins in diabetic uremic sera, three major proteins "susceptible" to AGE modification were identified: the immunoglobulin G light chain, apolipoprotein J (clusterin/SP-40,40), and the complement 3b beta chain. These findings indicate that the LZ-linked AGE affinity column may serve as an efficient method for the depletion of toxic AGEs from sera, including specific AGE-modified proteins that may be linked to altered immunity, lipoprotein metabolism, and accelerated vasculopathy in renal failure patients with or without diabetes.

Adult↗

PubMed1997

Enhanced binding of advanced glycation endproducts (AGE) by the ApoE4 isoform links the mechanism of plaque deposition in Alzheimer's disease.

Alzheimer's disease (AD) brains contain high levels of advanced glycation endproducts (AGEs). Double immunostaining using anti-AGE and anti-apolipoprotein E (apoE) antibodies demonstrated that AGEs co-localized to a very high degree with apoE. We examined the binding of apoE to in vitro-prepared AGE-bovine serum albumin (AGE-BSA), using Western ligand blot analysis. ApoE exhibited AGE-specific binding activity in the presence of excess native BSA, with the dimeric form of apoE binding better than the monomeric form. Other apolipoproteins including apo A1, B, CI and CII, and serum beta2-microglobulin, did not bind AGE-BSA. ApoE4 exhibited a 3-fold greater AGE-binding activity than the apoE3 isoform. These results suggest that apoE may participate in aggregate formation in the AD brain by binding to AGE-modified plaque components. It is possible that enhanced binding of apoE4 might have pathogenic consequences in vivo.

Alleles↗

PubMed1997

Glycation products in aged thioglycollate medium enhance the elicitation of peritoneal macrophages.

Thioglycollate medium (TGM) is widely used as a stimulatory agent to induce non-infectious peritoneal inflammation for elicitation of macrophages from mice and rats. It has been known for a long time that aged, autoclaved TGM is more efficient than freshly prepared TGM, however, the mechanism responsible for this enhanced activity of aged TGM remains obscure. The aging of TGM apparently favors the non-enzymatic reactions between proteins and reducing sugars in TGM that may lead to the generation of advanced glycation endproducts (AGEs). We have found that aged TGM contains 40-fold more AGEs than fresh TGM. The formation of AGEs in TGM was completely blocked by co-incubation with an AGE inhibitor, aminoguanidine. Intraperitoneal injection of aged TGM into rats elicited approximately 2-fold more macrophages than fresh TGM. However, the addition of AGE-modified proteins to fresh TGM increased the yield of peritoneal cells to a level which was significantly higher than both fresh and aged TGM. The injection of AGE-modified proteins alone did not elicit significantly more macrophages than the level of resident peritoneal cells. These results suggest that the formation of AGEs during aging of TGM is responsible for the enhanced macrophage-eliciting activity in aged TGM. AGEs may act as an enhancing agent to augment the existing inflammatory responses. AGE-supplemented TGM may provide an efficient method for eliciting peritoneal macrophages or establishing an inflammatory animal model.

Animals↗

PubMed1997

Optimized methods for capillary electrophoresis of tetracyclines.

Optimized methods for the analysis of some tetracyclines by capillary electrophoresis are described. Different buffer systems were employed for the separation of tetracycline, oxytetracycline and demeclocycline from their respective major impurities, including the 2-acetyl-2-decarboxamido derivatives. The influence of buffer pH and buffer concentration was systematically investigated. Non-ionic surfactant Triton X-100 and methyl-beta-cyclodextrin were used to obtain improved selectivity in the case of oxytetracycline and demeclocycline. The results are compared with those of previously established liquid chromatography methods. Good correlations were obtained.

Buffers↗