Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 127 records · Page 7Linked to original sources

PubMed2001

Telomere shortening and decline in replicative potential as a function of donor age in human adrenocortical cells.

Telomere shortening is the cause of replicative senescence of mammalian cells in culture and may be a cause of cellular aging in vivo. Some tissues clearly show telomere shortening during aging in humans, but the relationship between replication history and telomere length is obscured by complex relationships between stem cells and more differentiated cell types. Previous experiments on the adrenal cortex and human adrenocortical cells in culture indicate that the proliferative biology of this tissue is relatively simple; cell division occurs continuously throughout life, without evidence for a distinct stem cell compartment. In this tissue we investigated the relationship between telomere biology and replicative senescence by measuring replicative capacity and telomere length as a function of donor age. Cells cultured from adrenal tissue from donors of different ages showed a strong age-related decline in total replicative capacity, falling from about 50 population doublings for fetal cells to an almost total lack of division in culture for cells from older donors. Telomere restriction fragment (TRF) length was analyzed in the same sets of cells and decreased from a value of about 12 kb in fetal cells to approximately 7 kb in cells from older donors. The latter value is consistent with that in fibroblasts which have reached replicative senescence. Furthermore, there was a good correlation in individual donor samples between TRF length and replicative capacity in culture. To confirm the relationship between telomere length, telomerase, and replicative capacity, we measured telomere length in cells before and after infection with a retrovirus encoding hTERT, the catalytic component of human telomerase. The adult adrenal cortex does not have telomerase activity; cells after transduction with the hTERT retrovirus had high telomerase activity. Whereas control cells underwent a replication-dependent shortening in telomeres during long-term growth in culture, hTERT-modified cells maintained telomere length and are probably immortalized. Symmetric cell division in human adrenocortical cells, occurring slowly over the life span, is associated with progressive telomere shortening and may result in proliferative defects in vivo in old age, which could partly account for the age-related changes in the structure and function of the human adrenal cortex.

Adolescent↗

PubMed2001

Neurotransmitter dopamine applied in electrochemical determination of aluminum in drinking waters and biological samples.

It was demonstrated that the decrease of the differential pulse voltammetric (DPV) anodic peak current of dopamine (3,4-dihydroxyphenylethylamine, DA) was linear with the increase of aluminum (Al) concentration. Under optimum experimental conditions (pH 4.6, 1.2 x 10(-3) M DA, and 0.04 M NaAc-HAc buffer solution), the linear range is 4.0 x 10(-7)-8.0 x 10(-5) M, the detection limit is 1.4 x 10(-7) M, and the relative standard deviation for 4 x 10(-5) M Al(III) is 3.5% (n=8). Many foreign species, especially some low-molecule-weight biological molecules, were chosen for interference testing. The proposed method was applied to the determination of Al in biological samples such as synthetic renal dialysate, Ringer's solution, human blood, cerebrospinal fluid of a patient, and urine of a diabetic patient. The corresponding recoveries were generally between 95 and 105%. The basic principle of the method was determined by examining Al complexed with DA. This results in the blockage of the electroactive sites on DA, followed eventually by the reduction of the electrochemical response of DA. This result was verified by examining the behavior of DA, both in the presence and absence of Al, using electrochemical, UV-Vis, Raman, and (13)C NMR spectroscopic methods.

Aluminum↗

PubMed2001

Farnesyl diphosphate synthase is abundantly expressed and regulated by androgen in rat prostatic epithelial cells.

Farnesyl diphosphate synthase (FPPS) has been identified as an androgen-response gene in the rat ventral prostate using a highly sensitive PCR-based cDNA subtraction technique. FPPS is an essential enzyme that catalyzes the synthesis of farnesyl diphosphate (FPP), which is required for cholesterol biosynthesis as well as protein prenylation. We have characterized the expression of FPPS in the rat prostate in response to androgen manipulation. Northern blot analysis showed that castration induced a 10-fold down-regulation of FPPS mRNA within 24 h in the ventral prostate and androgen replacement up-regulated FPPS mRNA rapidly in the regressed ventral prostate of a castrated rat. The expression of FPPS was also regulated by androgen in the lateral and dorsal prostate, indicating that FPPS is important to androgen action in all three lobes of the prostate. Western blot analysis showed that FPPS protein level was also regulated by androgen in the prostate. Northern blot analysis of tissue specificity indicated that FPPS was most abundantly expressed in the ventral prostate of a mature rat and was responsive to androgen manipulation in the prostate and seminal vesicles, but not in other tissues. In situ hybridization study showed that FPPS mRNA was localized to the prostatic epithelium. Interestingly, the expression of FPPS was elevated in Dunning rat prostate tumor cell lines. The above findings suggest that FPPS has the potential to play an important role in androgen action and prostate cancer progression.

Alkyl and Aryl Transferases↗

PubMed2001

Is deep hypothermia necessary for unilateral antegrade cerebral perfusion during circulatory arrest? A magnetic resonance study in a pig model.

OBJECTIVE: Localized (31)P magnetic resonance spectroscopy (MRS) was used to investigate whether unilateral antegrade cerebral perfusion (U-ACP) could maintain normal energy metabolism and intracellular pH (pHi) in both hemispheres of the brain during deep (15 degrees C) and moderate (28 degrees C) hypothermic circulatory arrest (HCA). METHODS: Eleven pigs were exposed to 120 min of U-ACP during HCA at 15 degrees C (group I, n=6) or 28 degrees C (group II, n=5), followed by 60 min of cardiopulmonary bypass (CPB) at 37 degrees C. Localized (31)P MR spectra were acquired every 30 min. Histopathology was performed at the completion of each experiment. RESULTS: MR recorded no changes in energy metabolites (phosphocreatine and ATP), or pHi during U-ACP in either group, and no significant differences were found in any of the energy metabolites or pHi between the left and right hemispheres. Histopathology showed no significant morphological changes in the neurons. CONCLUSIONS: During either deep or moderate HCA, unilateral ACP through the right axillary artery prevents ischemic events in both hemispheres of normal pig brains. Deep hypothermia may not be necessary when using U-ACP.

Animals↗

PubMed2001

Fatigue testing median sternotomy closures.

OBJECTIVE: Sternal dehiscence is commonly due to wire cutting through bone. With a biological model, we measured the rate of cutting through bone, of standard steel wire closure, peristernal steel wire, figure-of-eight closure, polyester and sternal bands sternotomy closure techniques. METHODS: Polyester, figure-of-eight, peristernal and sternal band closures were tested against standard closure eight times using adjacent paired samples, to eliminate biological variables. Fatigue testing was performed by a computerized materials-testing machine, cycling between loads of 1 and 10 kg. The displacements at maximum and minimum loads were measured during each cycle. Cutting through, manifested by the displacement at the maximum load between the 1st and 150th cycles was measured. The percentage cut-through of each closure method versus standard closure was calculated. RESULTS: The differences in the displacement between each of the polyester (1.01 mm), figure-of-eight (0.52 mm), peristernal (0.72 mm) and sternal band (0.66 mm) groups versus standard closure (0.22, 0.22, 2.1, 3.2 mm) in the paired samples were statistically significant (Student's paired t-test; P<0.01). There were statistically significant differences in the percentage cut-through of polyester, figure-of-eight, peristernal and sternal bands (ANOVA, P<0.001), versus standard closure. CONCLUSIONS: In our sheep sternum model, we have quantified the differing rate of cutting through bone of five types of median sternotomy closure techniques. We have controlled for bone variables by testing each closure versus standard closure using paired adjacent bone samples. Peristernal and sternal band closure techniques are significantly superior to standard closure. The use of polyester and figure-of-eight closures requires caution.

Analysis of Variance↗

PubMed2001

Genetic diversity among different clones of the gynogenetic silver crucian carp, Carassius auratus gibelio, revealed by transferrin and isozyme markers.

Genetic diversity among four clones (A, D, E, F) of gynogenetic silver crucian carp was studied using transferrin and isozymes in the blood as markers. Of the five proteins investigated, three (transferrin, esterase and superoxide dismutase) indicated polymorphism and eight polymorphic loci were detected. These loci were probably encoded by codominant alleles and their inheritance patterns were analyzed. Intraclonal homogeneity and interclonal heterogeneity were observed in these clones, which allowed us to infer the clonal nature and evolutionary relationship between them. Clonal diversity in this population of silver crucian carp in China was also compared with data reported from gynogenetic crucian carp in Germany.

Alleles↗

PubMed2001

A critical role for NF-kappa B in GATA3 expression and TH2 differentiation in allergic airway inflammation.

The transcription factor GATA-3 is expressed in T helper 2 (TH2) but not TH1 cells and plays a critical role in TH2 differentiation and allergic airway inflammation in vivo. Mice that lack the p50 subunit of nuclear factor kappa B (NF-kappa B) are unable to mount airway eosinophilic inflammation. We show here that this is not due to defects in TH2 cell recruitment but due to the inability of the p50-/- mice to produce interleukin 4 (IL-4), IL-5 and IL-13: cytokines that play distinct roles in asthma pathogenesis. CD4+ T cells from p50-/- mice failed to induce Gata3 expression under TH2-differentiating conditions but showed unimpaired T-bet expression and interferon gamma (IFN-gamma) production under TH1-differentiating conditions. Inhibition of NF-kappa B activity prevented GATA-3 expression and TH2 cytokine production in developing, but not committed, TH2 cells. Our studies provide a molecular basis for the need for both T cell receptor and cytokine signaling for GATA-3 expression and, in turn, TH2 differentiation.

Animals↗

PubMed2001

Enantioselective separation of epoxides by capillary electrophoresis employing sulfated beta-cyclodextrin as chiral selector.

A capillary electrophoresis method was developed for the enantioseparation of epoxide compounds. Sulfated beta-cyclodextrin was employed as a chiral selector. Phosphate-triethanolamine buffer showed a chiral separation effect when employing charged sulfated beta-cyclodextrin. The effect of pH, triethanolamine concentration and sulfated beta-cyclodextrin concentration on the resolution was studied. Methanol was tested as an organic modifier. Several other epoxides were successfully separated by the proposed method.

Journal Article↗

PubMed2001

Expression of proteins that inhibit calcium oxalate crystallization in vitro in the urine of normal and stone-forming individuals.

The factors precipitating clinically active calcium oxalate (CaOx) urolithiasis are not known. This study examined the relationships between urinary proteins that inhibit CaOx crystallization in vitro and the incidence of CaOx urolithiasis. The first hypothesis is that levels of urinary CaOx crystallization inhibitors differ between clinically active stone formers (SFs) and normal individuals. The second hypothesis is that lower levels of urinary CaOx crystallization inhibitors contribute to the two- to threefold greater incidence of CaOx urolithiasis in males compared with females. These hypotheses were derived from previous observations on the expression of urinary inter-alpha-trypsin inhibitor trimer (IalphaTI-trimer) in normal and stone-forming individuals. The proteins of void urine samples from normal volunteers (24 males, 19 females) and CaOx-SFs (26 males, 16 females) were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoreactive IalphaTI-trimer, osteopontin, and prothrombin were detected by immunoblot plus enhanced chemiluminescence; the relative densities of the bands were then determined. With the exception of IalphaTI-trimer (P: </= 0.026, approximately twofold), there was no difference in the relative densities of CaOx crystallization inhibitors in the urine of normal and CaOx stone-forming individuals. Thus, there does not appear to be a generalized increase or decrease in levels of CaOx crystallization inhibitory proteins between normal and CaOx stone-forming individuals. The relative density of IalphaTI-trimer was approximately threefold greater in females than in males (P: </= 0.001). Differences in the relative densities of the other CaOx crystallization inhibitors were small and of questionable physiological importance. These data do not support the hypothesis that males have a greater incidence of CaOx urolithiasis because of a generalized decrease in urinary CaOx crystallization inhibitory protein levels.

Adult↗

PubMed2001

Nitrogen removal from sewage by continuous flow SBR system with intermittent aeration.

A continuous-flow sequential batch reactor system with intermittent aeration known as the intermittent cycle extended aeration system was used to investigate the efficiencies of nitrogen removal for sewage. In the conventional intermittent cycle extend aeration system with continuous aeration process to treat the synthetic sewage wastewater under 3 cycles per day (cycle time = 8 hours), high COD removal efficiencies were achieved, but high levels of nitrate (22.3-23.6 mg l-1) and decreased pH values were also found in the effluent. In the intermittent aeration, the dissolved oxygen in the reactor was reduced from the range of 3.5-5.0 mg l-1 to 0.5-1.2 mg l-1, the nitrogen in the influent was partially oxidized to nitrite-nitrogen, although nitrate-nitrogen was also present in the effluent. In detailed cyclic study of the reactor with relatively low D.O. (0.3-1.0 mg l-1) and high MLSS (3200 mg l-1 at half full water level), the experimental results of intermittent aeration processes showed higher oxidation rates of ammonia to nitrite (1.44-3.55 mg N g-1 MLSS hr-1) than the conversion rates of nitrite to nitrate (0.00-1.22 mg N g-1 MLSS hr-1). It was thus, concluded that denitrification rates were not affected by the limited supplement of soluble organic carbon in the system. In addition, NOx(-)-N could be removed with a total nitrogen removal rate up to 94.9% when the MLSS was controlled in concentrations of 3200 mg l-1 at half full water level with low D.O. The process of intermittent aeration of ICEAS could provide an economic and effective means for nitrogen removal in treating sewage.

Bioreactors↗

PubMed2001

Epidemiologic and clinical characteristics of Kawasaki disease in Shaanxi Province, China, 1993-1997.

The objective of this paper is to describe the epidemiological and clinical characteristics of Kawasaki disease (KD) in Shaanxi Province, China during the 5-year period from January 1993 to December 1997. A province-wide epidemiological survey on KD was made by the China-Japan Kawasaki Disease Study Group. The questionnaire form and the diagnostic criteria of KD, which were prepared by the Japan Kawasaki Disease Research Committee and translated into Chinese, were sent to the departments of pediatrics of all the hospitals with 100 beds or more in Shaanxi province. All the KD patients who were diagnosed during the observation period from 1993 to 1997 were asked to take part in this survey. The databases of reported KD in this survey were analysed at the Department of Pediatrics of the Shaanxi Provincial People's Hospital, Xi'an, China. All the patients that satisfied the diagnostic criteria were included in the report. A total of 105 (70 per cent) hospitals responded and 376 cases of KD were confirmed. More cases were reported in 1993 and 1994. Of the total patients reported, 69 per cent were children under 3 years old with a male to female ratio of 1.6:1. The proportion of patients with cardiac sequelae was 19 per cent with a male to female ratio of 3:1. There were four fatal cases with a fatality rate of 1 per cent. It is concluded that KD is common in China. Continuous surveillance is necessary to maintain high awareness of KD so as to find possible risk factors and their association with the disease.

Adolescent↗

PubMed2001

BADGE, Beads Array for the Detection of Gene Expression, a high-throughput diagnostic bioassay.

Several methods are presently available for gene expression analysis. However, few of them are suitable for detection of moderate numbers of genes in thousands of samples with high speed and low cost. There is great demand for such a method for use in diagnostics and screening. To address this need, we have developed an assay for gene expression analysis using microspheres and a fluidic instrument made by Luminex. The assay is named Beads Array for the Detection of Gene Expression (BADGE). BADGE can monitor up to 100 genes in a single reaction, and it takes only 1 h to hybridize and <20 sec to read the results of all 100 genes in a sample for the detection process. For the genes detected in five independent replicate experiments, the standard deviation was <35% of the mean. We have monitored multiple pathogenesis-related genes simultaneously in chemical-treated and control Arabidopsis samples employing the BADGE assay. The data were compared with those obtained from an established technology, Affymetrix GeneChip. The changes in expression profiles were very similar. Our study showed that the BADGE assay was capable of profiling expression of multiple genes at affordable cost and rapid speed.

Arabidopsis↗

PubMed2001

The prediction of speech intelligibility in underground stations of rectangular cross section.

Long enclosures are spaces with nondiffuse sound fields, for which the classical theory of acoustics is not appropriate. Thus, the modeling of the sound field in a long enclosure is very different from the prediction of the behavior of sound in a diffuse space. Ray-tracing computer models have been developed for the prediction of the sound field in long enclosures, with particular reference to spaces such as underground stations which are generally long spaces of rectangular or curved cross section. This paper describes the development of a model for use in underground stations of rectangular cross section. The model predicts the sound-pressure level, early decay time, clarity index, and definition at receiver points along the enclosure. The model also calculates the value of the speech transmission index at individual points. Measurements of all parameters have been made in a station of rectangular cross section, and compared with the predicted values. The predictions of all parameters show good agreement with measurements at all frequencies, particularly in the far field of the sound source, and the trends in the behavior of the parameters along the enclosure have been correctly predicted.

Confined Spaces↗

PubMed2001

Antigenic importance of the carboxy-terminal beta-strand of the porcine reproductive and respiratory syndrome virus nucleocapsid protein.

Five domains of antigenic importance were previously mapped on the nucleocapsid protein (N) of the porcine reproductive and respiratory syndrome virus (PRRSV), and a domain comprised of the 11 C-terminal-most amino acids (residues 112 to 123) was shown to be essential for binding of N-specific conformation-dependent monoclonal antibodies (MAbs). In the present study, the importance of individual residues within this C-terminal domain for antigenicity was investigated using eight different mutant constructs of N expressed in HeLa cells. Single amino acid substitutions were introduced into the C-terminal domain of the N protein, and the significance of individual amino acids for MAb reactivity was determined by immunoprecipitation. None of the MAbs tested recognized the mutant with a leucine-to-proline substitution at residue 114 (L114P), while V112P, R113P, R113D, I115P, and R116P reduced MAb binding significantly. Conversely, substitution of amino acids at positions 118 (T118S) and 121 (P121A) had little effect on MAb binding. Secondary-structure predictions indicate that amino acids 111 to 117 form a beta-strand. In view of the fact that replacement of beta-strand-forming amino acids with proline elicited the greatest effect on MAb binding, it appears that secondary structure in the C terminus of the N protein is an important determinant of conformational epitope formation. While the crystal structure of the PRRSV N protein remains to be determined, results from these studies broaden our understanding of the secondary structures that make up the PRRSV N protein and shed some light on how they may relate to function.

Amino Acid Sequence↗

PubMed2001

c-Jun N-terminal kinase is required for metalloproteinase expression and joint destruction in inflammatory arthritis.

Mitogen-activated protein kinase (MAPK) cascades are involved in inflammation and tissue destruction in rheumatoid arthritis (RA). In particular, c-Jun N-terminal kinase (JNK) is highly activated in RA fibroblast-like synoviocytes and synovium. However, defining the precise function of this kinase has been difficult because a selective JNK inhibitor has not been available. We now report the use of a novel selective JNK inhibitor and JNK knockout mice to determine the function of JNK in synoviocyte biology and inflammatory arthritis. The novel JNK inhibitor SP600125 (anthra[1,9-cd]pyrazol-6(2H)-one) completely blocked IL-1--induced accumulation of phospho-Jun and induction of c-Jun transcription in synoviocytes. Furthermore, AP-1 binding and collagenase mRNA accumulation were completely suppressed by SP600125. In contrast, complete inhibition of p38 had no effect, and ERK inhibition had only a modest effect. The essential role of JNK was confirmed in cultured synoviocytes from JNK1 knockout mice and JNK2 knockout mice, each of which had a partial defect in IL-1--induced AP-1 activation and collagenase-3 expression. Administration of SP600125 modestly decreased the rat paw swelling in rat adjuvant-induced arthritis. More striking was the near-complete inhibition of radiographic damage that was associated with decreased AP-1 activity and collagenase-3 gene expression. Therefore, JNK is a critical MAPK pathway for IL-1--induced collagenase gene expression in synoviocytes and in joint arthritis, indicating that JNK is an important therapeutic target for RA.

Activating Transcription Factor 2↗

PubMed2001

Central infusions of the recombinant human prolactin receptor antagonist, S179D-PRL, delay the onset of maternal behavior in steroid-primed, nulliparous female rats.

The expression of maternal behavior in the newly parturient rat is under endocrine regulation. Blocking endogenous PRL secretion with bromocriptine delays the normal rapid expression of maternal care shown toward foster young in steroid-primed virgin female rats. The recent development of the PRL receptor antagonist S179D-PRL, a mutant of human PRL in which the serine residue at the 179 position is replaced with aspartate, provides a potentially useful tool to examine the role of PRL in neural processing. In the present report, three experiments were conducted that examined the effects of this PRL antagonist on the induction of maternal behavior. In each experiment, ovariectomized, nulliparous rats were treated sequentially with SILASTIC capsules implanted sc with progesterone (days 1-11) and estradiol (days 11-17), a treatment that stimulates a rapid onset of maternal behavior in virgin rats. On day 11, females were implanted with Alzet miniosmotic pumps connected to cannulae directed unilaterally at the lateral ventricle (Exp 1) or bilaterally at the medial preoptic area (MPOA; Exp 2 and 3). Pumps contained either doses of S179D-PRL (0.115 or 1.15 mg/ml; Exp 1 and 2), wild-type human PRL (1.15 mg/ml; Exp 3), or the saline vehicle (Exp 1-3). Testing for maternal behavior began on day 12, a day after pump insertion, and animals were tested daily for 6 days. Latencies to contact, retrieve, and group foster test young were recorded. Administration of both the high and low doses of S179D-PRL infused into the lateral ventricle (Exp 1) or MPOA (Exp 2) significantly delayed the onset of maternal behavior. In contrast, MPOA infusions of the control hormone, wild-type human PRL, in Exp 3 did not delay the onset of maternal behavior. These findings support the concept that the effects of S179D-PRL are caused by its actions as a PRL receptor antagonist rather than by a nonspecific effect of the protein. Overall, these results demonstrate the effectiveness of S179D-PRL acting at the level of the central nervous system (and, more specifically, within the MPOA) to regulate maternal behavior, a PRL-mediated response.

Animals↗

PubMed2001

Role of the EGFR/Ras/Raf pathway in specification of photoreceptor cells in the Drosophila retina.

The Drosophila EGF receptor is required for differentiation of many cell types during eye development. We have used mosaic analysis with definitive null mutations to analyze the effects of complete absence of EGFR, Ras or Raf proteins during eye development. The Egfr, ras and raf genes are each found to be essential for recruitment of R1-R7 cells. In addition Egfr is autonomously required for MAP kinase activation. EGFR is not essential for R8 cell specification, either alone or redundantly with any other receptor that acts through Ras or Raf, or by activating MAP kinase. As with Egfr, loss of ras or raf perturbs the spacing and arrangement of R8 precursor cells. R8 cell spacing is not affected by loss of argos in posteriorly juxtaposed cells, which rules out a model in which EGFR acts through argos expression to position R8 specification in register between adjacent columns of ommatidia. The R8 spacing role of the EGFR was partially affected by simultaneous deletion of spitz and vein, two ligand genes, but the data suggest that EGFR activation independent of spitz and vein is also involved. The results prove that R8 photoreceptors are specified and positioned by distinct mechanisms from photoreceptors R1-R7.

Animals↗

PubMed2001

Isolation and characterization of the Enterobacter cloacae cheR mutant defective in phosphate taxis.

A chemotaxis-defective mutant of Enterobacter cloacae IFO3320, designated EC1, was isolated after N-methyl-N'-nitro-N-nitrosoguanidine (NTG) mutagenesis. Computer-assisted capillary assays showed that EC1 failed to show chemotactic responses to peptone and inorganic phosphate (Pi). Cloning and sequence analysis showed that EC1 is a cheR mutant, suggesting that Pi taxis by E. cloacae is dependent on a methyl-accepting chemotaxis protein(s) (MCP). EC1 was further mutagenized with NTG to construct cheR pstS and cheR pstA double mutants. A recombinant plasmid pECT01.2, which contained the E. cloacae cheR gene, restored the ability of these double mutants to show chemotaxis toward peptone but not Pi. These results suggest that the phosphate-specific transport (Pst) system, together with a MCP(s), is required for detecting Pi in E. cloacae.

Chemotaxis↗