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Biomedical subjects

J Yao

Publications and source records attributed to J Yao.

At least 163 records · Page 9Linked to original sources
PubMed1998

Three-dimensional echocardiographic assessment of the extension of dysfunctional mass in patients with coronary artery disease.

Two-dimensional (2D) echocardiographic estimation of infarcted mass is limited by having only a few selected nonparallel views for data analysis. Volume-rendered three-dimensional (3D) echocardiography may be able to overcome the above limitations, because it uses multiple, parallel 2D images to derive quantitative data. Previous experimental studies demonstrated that 3D echocardiography is an accurate and reproducible method to assess dysfunctional mass. To estimate the accuracy of 3D echocardiography in humans, we evaluated 10 patients who had a single myocardial infarction. All patients underwent 2D and 3D echocardiography using the transesophageal approach, and contrast (gadolinium) magnetic resonance imaging (MRI), considered a reference standard for infarcted tissue detection. The mean extent of dysfunctional mass by MRI was 28 +/- 13 g and by 3D echocardiography was 30 +/- 12 g; the mean difference was 1.9 +/- 2.3 g (p = not significant). Linear regression analysis between the 2 measurements was y = 0.97x - 1.12, r = 0.98. Dysfunctional mass derived from 3D echocardiography reflects the real site and extension of damaged myocardium.

Coronary Disease↗
PubMed1998

Hyperresponsiveness of vitamin D receptor gene expression to 1,25-dihydroxyvitamin D3. A new characteristic of genetic hypercalciuric stone-forming rats.

Hypercalciuria in genetic hypercalciuric stone-forming (GHS) rats is accompanied by intestinal Ca hyperabsorption with normal serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] levels, elevation of intestinal, kidney, and bone vitamin D receptor (VDR) content, and greater 1,25(OH)2D3-induced bone resorption in vitro. To test the hypothesis that hyperresponsiveness of VDR gene expression to 1,25(OH)2D3 may mediate these observations, male GHS and wild-type Sprague- Dawley normocalciuric control rats were fed a normal Ca diet (0.6% Ca) and received a single intraperitoneal injection of either 1,25(OH)2D3 (10-200 ng/100 g body wt) or vehicle. Total RNAs were isolated from both duodenum and kidney cortex, and the VDR and calbindin mRNA levels were determined by Northern blot hybridization using specific cDNA probes. Under basal conditions, VDR mRNA levels in GHS rats were lower in duodenum and higher in kidney compared with wild-type controls. Administration of 1,25(OH)2D3 increased VDR gene expression significantly in GHS but not normocalciuric animals, in a time- and dose-dependent manner. In vivo half-life of VDR mRNA was similar in GHS and control rats in both duodenum and kidney, and was prolonged significantly (from 4-5 to > 8 h) by 1,25(OH)2D3 administration. Neither inhibition of gene transcription by actinomycin D nor inhibition of de novo protein synthesis with cycloheximide blocked the upregulation of VDR gene expression stimulated by 1,25(OH)2D3 administration. No alteration or mutation was detected in the sequence of duodenal VDR mRNA from GHS rats compared with wild-type animals. Furthermore, 1,25(OH)2D3 administration also led to an increase in duodenal and renal calbindin mRNA levels in GHS rats, whereas they were either suppressed or unchanged in wild-type animals. The results suggest that GHS rats hyperrespond to minimal doses of 1,25(OH)2D3 by an upregulation of VDR gene expression. This hyperresponsiveness of GHS rats to 1,25(OH)2D3 (a) occurs through an increase in VDR mRNA stability without involving alteration in gene transcription, de novo protein synthesis, or mRNA sequence; and (b) is likely of functional significance, and affects VDR-responsive genes in 1, 25(OH)2D3 target tissues. This unique characteristic suggests that GHS rats may be susceptible to minimal fluctuations in serum 1, 25(OH)2D3, resulting in increased VDR and VDR-responsive events, which in turn may pathologically amplify the actions of 1,25(OH)2D3 on Ca metabolism that thus contribute to the hypercalciuria and stone formation.

Animals↗
PubMed1998

Retinoic acid selectively inhibits lipopolysaccharide induction of tissue factor gene expression in human monocytes.

Expression of tissue factor (TF) by activated monocytes in several diseases leads to disseminated intravascular coagulation. Lipopolysaccharide (LPS)-induced monocyte TF expression is downregulated by the nuclear hormone all-trans retinoic acid (ATRA). In this study, we examined the mechanism by which ATRA inhibits monocyte TF expression. We show that ATRA selectively inhibited LPS induction of TF expression in human monocytes and monocytic THP-1 cells without affecting LPS induction of tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8). Inhibition of TF expression occurred at the level of transcription as determined by nuclear run-on. ATRA did not significantly alter the binding or functional activity of the transcription factors c-Fos/c-Jun and c-Rel/p65, which are required for LPS induction of the TF promoter in monocytic cells. In contrast to the ATRA inhibition of the endogenous TF gene, LPS induction of the cloned TF promoter was not inhibited by ATRA in transiently transfected THP-1 cells. Our results demonstrate that ATRA selectively inhibited LPS-induced TF gene transcription in human monocytic cells by a mechanism that does not involve repression of AP-1- or NF-kappaB-mediated transcription.

Cells, Cultured↗
PubMed1998

Reversed-phase ion-pair chromatographic analysis of tetracycline antibiotics. Application to discolored teeth.

A high-performance liquid chromatographic method with diode array detection was developed to simultaneously separate tetracycline antibiotics and applied to the analysis of discolored teeth. By a reversed-phase ion-pair chromatographic system using pentanesulfonate as a counter ion, minocycline, oxytetracycline, tetracycline and demeclocycline were eluted in this order, and they showed base-line separation within 9 min. When using oxytetracycline as an internal standard, the quantitative ranges were between 2.5 ng/ml and 7.5 microg/ml. Powdered dentine (10 mg) and enamel (40 mg) prepared from discolored primary teeth were sonicated in 0.25 ml of 10 mM HCl containing oxytetracycline (0.75 microg/ml) and 50 mM EDTA-2Na, thereafter the supernatants were chromatographed. Eluates from both discolored tooth samples were identified as minocycline based on diode array spectra of their peaks, while minocycline was not detected in any samples from nondiscolored normal teeth, indicating that discoloration of the tested teeth was due to minocycline incorporated into dentine and enamel. Replicate quantitative analyses of the identical tooth substances showed that intra- and inter-assay C.V.s were 2.63 and 4.95% for dentine, and 5.42 and 10.88% for enamel. Application of the developed method to nine discolored teeth revealed that the incorporated minocycline ranged from 20.13 to 84.62 ng/mg of dentine and 0.89 to 7.87 ng/mg of enamel.

Anti-Bacterial Agents↗
PubMed1998

Morphological and molecular changes of maize plants after seeds been flown on recoverable satellite.

Dry seeds of Zea mays, heterozygous for Lw1/lw1 alleles, sandwiched between nuclear track detectors aboard Chinese satellite for 15 days, were recovered and mutations in morphological characters on plants developed from these seeds, as well as their selected progenies, were investigated. The dosimetric results indicated that 85% of the seeds received at least 1 hit with Z > or = 20. About 10% of plants developed from flown seeds and 40% of observed selfed lines from the first generation plants showed some morphological changes, such as yellow stripes displayed on leaves, dwarf, anomogensis of floral organs and yellow-green seedlings, when compared with those from ground control. Using yellow stripes on leaves as the main endpoint for evaluating mutation induced in space environment, the frequency of stripe occurrence was 4.6% in the first generation plants, comparable with the results obtained from Long Duration Exposure Facility (LDEF) mission (Mei et al., 1994), but much lower than those from ground based 60 Co-gamma treatment at a dose of 100 Gy, which reached 35.5% in the selfed lines of the second generation. One hundred and ten random primers were screened in RAPD analysis to detect the variation on genomic DNA of plants with stripes on leaves. Of these primers, 10.9% were able to generate polymorphic bands between mutated plants and control, also, common band patterns in several progenies with the same mutation phenotype were observed. These results demonstrated that space radiation environment could induce inheritable mutagenic effects on plant seeds, and verified the change in genetic material in the mutants. Further study will be needed for a better understand of the nature and mechanism of this induction of mutation.

Cobalt Radioisotopes↗
PubMed1998

Variation of anatomic valve area during ejection in patients with valvular aortic stenosis evaluated by two-dimensional echocardiographic planimetry: comparison with traditional Doppler data.

OBJECTIVES: Flow variations can affect valve-area calculation in aortic stenosis and lead to inaccuracies in the evaluation of the stenosis. Knowing that transvalvular flow varies normally within one beat, we designed this study to assess the response of the valve to intrabeat variation of flow during systole. Results were compared with flow-derived measurements. BACKGROUND: Technological improvements now allow us to evaluate aortic valve area directly by short axis planimetry. This offers the possibility to perform serial planimetries during one ejection phase and analyze the intrabeat dynamic behavior of the stenotic-aortic valve and compare these measurements with flow-derived measurements. METHODS: Forty echocardiograms displaying different degrees of aortic stenosis were analyzed by frame-by-frame planimetry of the valve area from onset of opening to complete closure. Maximal-mean area, opening and closing rates and ejection times were obtained and compared with Doppler-derived data. RESULTS: Valve area varied during ejection. Stenotic valves opened and closed more slowly than normals and remained maximally open for a shorter period. Mean area by Doppler data corresponded more closely to maximal than to mean-planimetered area. Duration of flow was shorter than valve opening in severely stenotic valves. Discrepancies between Doppler-derived and two-dimensional (2D) measurements decreased in less stenotic valves. CONCLUSIONS: Our observations reveal striking differences between the dynamics of normal and stenotic valves. Surprisingly, Doppler-derived mean-valve area correlated better with maximal-anatomic area than with mean-anatomic area in patients with aortic stenosis. Discrepancies between duration of flow and valve opening could explain this phenomenon.

Aged↗
PubMed1998

Importance of matrix:analyte ratio for buffer tolerance using 2,5-dihydroxybenzoic acid as a matrix in matrix-assisted laser desorption/ionization-Fourier transform mass spectrometry and matrix-assisted laser desorption/ionization-time of flight.

Many biological samples destined for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) contain buffers. The presence of these buffers often inhibits the ability to obtain spectra. Here, the results of a study of the effects of six different buffers on spectra of three representative small proteins are reported utilizing 2,5-dihydroxybenzoic acid as matrix. These proteins, bovine insulin, cytochrome c, and bovine albumin have masses from approximately 5000 to 66,000 Da. Three different sample preparation techniques were investigated: aerospray, dried-drop, and acetone redeposition. Both MALDI Fourier transform and time-of-flight mass spectrometry results show that buffer tolerance of MALDI-MS samples depends upon several factors, including the relative amount of the buffer in the MALDI matrix, as well as the identity of the specific buffer. Furthermore, the rate at which buffer tolerance decreases as buffer concentration is increased varies from buffer to buffer. The current results reveal that, at very high matrix:analyte ratios, buffer tolerance of MALDI is dramatically greater than concluded in previous literature reports.

Animals↗
PubMed1998

Investigation of low-voltage on-resonance ion selection for Fourier transform mass spectrometry.

Low-voltage on-resonance ion selection (LOIS) was recently introduced as an alternative technique for ion selection and storage. Under high pressure conditions and similar to the technique of quadrupolar axialization, unwanted (unselected) trapped ions are eliminated from the analysis cell through collisions with cell plates following orbital expansion. The ions remaining after tens of seconds of mass selection can be detected with better coherence, leading to improvements in ion detection and sensitivity. Here, experiments designed to test ion remeasurement and ion transfer capabilities are presented. Simulations of ion motion give insight into the possible mechanism of ion cooling, which does appear to be the same as that of the axialization process. Because of its ease of use, lack of need for additional hardware devices, and comparable ion selection results, LOIS is an attractive alternative for trapped ion experiments.

Computer Simulation↗
PubMed1998

Overexpression of ErbB2 blocks Taxol-induced apoptosis by upregulation of p21Cip1, which inhibits p34Cdc2 kinase.

Overexpression of the receptor tyrosine kinase p185ErbB2 confers Taxol resistance in breast cancers. Here, we investigated the underlying mechanisms and found that overexpression of p185ErbB2 inhibits Taxol-induced apoptosis. Taxol activates p34Cdc2 kinase in MDA-MB-435 breast cancer cells, leading to cell cycle arrest at the G2/M phase and, subsequently, apoptosis. A chemical inhibitor of p34Cdc2 and a dominant-negative mutant of p34Cdc2 blocked Taxol-induced apoptosis in these cells. Overexpression of p185ErbB2 in MDA-MB-435 cells by transfection transcriptionally upregulates p21Cip1, which associates with p34Cdc2, inhibits Taxol-mediated p34Cdc2 activation, delays cell entrance to G2/M phase, and thereby inhibits Taxol-induced apoptosis. In p21Cip1 antisense-transfected MDA-MB-435 cells or in p21-/- MEF cells, p185ErbB2 was unable to inhibit Taxol-induced apoptosis. Therefore, p21Cip1 participates in the regulation of a G2/M checkpoint that contributes to resistance to Taxol-induced apoptosis in p185ErbB2-overexpressing breast cancer cells.

Animals↗
PubMed1998

SURF1, encoding a factor involved in the biogenesis of cytochrome c oxidase, is mutated in Leigh syndrome.

Leigh Syndrome (LS) is a severe neurological disorder characterized by bilaterally symmetrical necrotic lesions in subcortical brain regions that is commonly associated with systemic cytochrome c oxidase (COX) deficiency. COX deficiency is an autosomal recessive trait and most patients belong to a single genetic complementation group. DNA sequence analysis of the genes encoding the structural subunits of the COX complex has failed to identify a pathogenic mutation. Using microcell-mediated chromosome transfer, we mapped the gene defect in this disorder to chromosome 9q34 by complementation of the respiratory chain deficiency in patient fibroblasts. Analysis of a candidate gene (SURF1) of unknown function revealed several mutations, all of which predict a truncated protein. These data suggest a role for SURF1 in the biogenesis of the COX complex and define a new class of gene defects causing human neurodegenerative disease.

Amino Acid Sequence↗
PubMed1998

Structural and dynamic characterization of partially folded states of apomyoglobin and implications for protein folding.

The structure and dynamics of two partially folded states of apomyoglobin have been characterized at equilibrium using multi-dimensional NMR spectroscopy. Residue-specific measurements of chemical shift and internal dynamics in these states and in the native apoprotein and holoprotein indicate progressive accumulation of secondary structure and increasing restriction of backbone dynamics as the chain collapses to form increasingly compact states. Under weakly folding conditions, the polypeptide fluctuates between unfolded states and local elements of structure that become extended and stabilized as the chain becomes more compact. These results provide a detailed model for molecular events that are likely to occur during folding of myoglobin.

Animals↗
PubMed1998

Combinatorial expression patterns of individual TLE proteins during cell determination and differentiation suggest non-redundant functions for mammalian homologs of Drosophila Groucho.

The Drosophila protein Groucho is involved in the regulation of cell-determination events during insect neurogenesis and segmentation. A group of mammalian proteins, referred to as transducin-like Enhancer of split (TLE) 1 through 4, share with Groucho identical structures and molecular properties. The aim was to determine whether individual TLE proteins participate in the regulation of cell determination in mammals like their Drosophila counterpart. It is here reported that TLE family members are expressed in combinatorial ways during the in vitro differentiation of mouse P19 embryonic carcinoma cells (a model for neural determination) and rat CFK2 cells (a model for chondrocytic determination). TLE1 is up-regulated and TLE2 and TLE4 are down-regulated to different extents during early stages of differentiation. In contrast, later stages correlate with up-regulation of TLE2 and TLE4, and decreased expression of TLE1. Individual TLE proteins are also expressed in combinatorial as well as complementary patterns during the development of the cerebral cortex and spinal cord of mouse embryos. In particular, TLE1 is robustly expressed in both neural progenitor cells and postmitotic neurons of the outer layers of the cortical plate, whereas TLE4 expression marks preferentially postmitotic neurons of the inner layers. Taken together, these results strongly suggest non-redundant roles for individual TLE proteins during both cell-determination and cell-differentiation events.

Animals↗
PubMed1998

Exogenous nitric oxide inhibits mesangial cell adhesion to extracellular matrix components.

Interactions of mesangial cells (MCs) with components of the extracellular matrix (ECM) profoundly influence the MC phenotype, such as attachment, contraction, migration, survival and proliferation. Here, we investigated the effects of exogenous nitric oxide (NO) on the process of MC adhesion to ECM molecules. Incubation of rat MCs with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) dose- and time-dependently inhibited MC adhesion and spreading on various ECM substrata, being more pronounced on collagen type I than on collagen type IV, laminin or fibronectin. In contrast, SNAP did not inhibit MC adhesion to L-polylysine-coated plates. The inhibitory effects of SNAP were reduced by hemoglobin and enhanced by superoxide dismutase. The anti-adhesive action of SNAP was mimicked not only by other NO donors but also by 8-bromo-cGMP, and significantly reversed by the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-alpha]quinoxalin-1-one (ODQ). Moreover, SNAP and 8-bromo-cGMP decreased the adhesion-induced phosphorylation of focal adhesion kinase (pp125FAK). In the presence of SNAP or 8-bromo-cGMP, adherent MCs exhibited disturbed organization of alpha-actin filaments and reduced numbers of focal adhesions, as shown by immunocytochemistry. In additional experiments with adherent MCs, it was found that exposure to SNAP or 8-bromo-cGMP for 12 and 24 hours induced detachment of MCs. The results indicate that exogenous NO interferes with the establishment and maintenance of MC adhesion to ECM components. This inhibitory NO effect is mediated predominantly by cGMP-signaling. Disturbance of MC attachment to ECM molecules could represent an important mechanism by which NO affects MC behavior in vitro and in vivo.

Animals↗
PubMed1998

Fusion expression of human pro-urokinase with E. coli thioredoxin.

Human pro-urokinase (pro-UK) was cloned into plasmid pET32b and fused to the E. coli thioredoxin (trxA). When expressed in E. coli AD494(DE3), the fusion protein Trx-pro-UK accumulated as insoluble inclusion bodies and amounted to 35% of total cellular proteins. When co-expressed with molecular chaperones human protein disulfide isomerase (PDI) and E. coli GroESL, all the expressed products still existed in the form of insoluble inclusion bodies.

Bacterial Proteins↗
PubMed1998

Escherichia coli prlC gene encodes a trypsin-like proteinase regulating the cell cycle.

Proteinase In has previously been described as displaying a trypsin-like proteinase activity that momentarily appears immediately before DNA synthesis in the cell cycle of Escherichia coli synchronized by phosphate starvation and which is closely related to the initiation of DNA replication [Kato, M., Irisawa, T., Ohtani, M., and Muramatu, M. (1992) Eur. J. Biochem. 210, 1007-1014]. We purified the proteinase In from E. coli C600 and found that the 15 amino acid residues of its amino-terminal were identical with those of oligopeptidase A (OpdA), the product of the E. coli prlC gene. The purified proteinase had a molecular mass of approximately 67 kDa, which was also the same as that of oligopeptidase A. To further elucidate the relationship between proteinase In and oligopeptidase A, we assembled an expression vector to direct the synthesis of E. coli oligopeptidase A. The protein was expressed at a high level in E. coli BL21(DE3) and was produced mostly in the soluble, active form. Both the recombinant enzyme (rPrlC) and the purified proteinase In could hydrolyze trypsin substrates for proteinase In as well as benzyloxycarbonyl Ala- Ala-Leu p-nitroanilide (Z-AALpNA), described as a synthetic substrate for oligopeptidase A. The effects of various protease inhibitors on rPrlC were also very similar to those on proteinase In. The trypsin inhibitors 4-guanidino benzoic acid 4-tert-butylphenyl ester and antipain strongly inhibited the trypsin-like proteinase activity of the recombinant enzyme, but had no effect on its Z-AALpNA hydrolyzing activity. Cobalt ion, which greatly enhanced the OpdA activity, slightly inhibited the trypsin-like activity of the recombinant enzyme. These results strongly suggest that proteinase In is encoded by the E. coli prlC gene and is a multi-functional proteinase with two separate active sites.

Base Sequence↗
PubMed1998

Three-dimensional echocardiography.

Three-dimensional echocardiography depicts the heart and its structures in their realistic forms. This capability decreases variability both in the quality and the interpretation of complex pathology, among investigators. Therefore, it is likely that the method will become the standard echocardiography examination in the future. The availability and versatility in use of the volumetric data set allow us to retrieve an infinite number of cardiac cross-sections, and thus, more accurate and reproducible measurements of valve areas, masses, and cavity volumes by obviating geometric assumptions. In the future, new physiologic parameters will provide additional information and address new clinical questions.

Echocardiography, Three-Dimensional↗