Biomedical subjects

S Mao

Publications and source records attributed to S Mao.

At least 19 recordsLinked to original sources

PubMed2002

Constraints on cosmological parameters from the analysis of the cosmic lens all sky survey radio-selected gravitational lens statistics.

We derive constraints on cosmological parameters and the properties of the lensing galaxies from gravitational lens statistics based on the final Cosmic Lens All Sky Survey data. For a flat universe with a classical cosmological constant, we find that the present matter fraction of the critical density is Omega(m)=0.31(+0.27)(-0.14) (68%)+0.12-0.10 (syst). For a flat universe with a constant equation of state for dark energy w=p(x)(pressure)/rho(x)(energy density), we find w<-0.55(+0.18)(-0.11) (68%).

Journal Article↗

PubMed2002

A heat-stable component of Bartonella henselae upregulates intercellular adhesion molecule-1 expression on vascular endothelial cells.

Bartonella henselae upregulated the expression of intercellular adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells (HUVECs). The induction level of ICAM-1 depended on the inoculation bacterial dose. ICAM-1 expression began increasing 4 h after infection and reached a sustained peak beginning at 12 h after B. henselae infection; this time course was similar to that of lipopolysaccharide (LPS) of Escherichia coli. The stimulatory effect was abolished when live B. henselae were separated from HUVECs by a filter membrane. The nonpiliated strain, which is unable to invade endothelial cells, induced ICAM-1 expression to the same extent as the piliated strain. Inactivation of B. henselae by ultraviolet (UV) irradiation, heat (56 degrees C, 30 min), or sonication did not alter its stimulatory activity. Polymyxin B, which strongly inhibited the effect of LPS, did not exert any influence on the stimulatory activity of B. henselae. Furthermore, the effect of sonicated B. henselae was not inhibited even by boiling, which was also the case with LPS. Our data suggest that some heat-stable component of B. henselae binds to the endothelial cell surface, inducing ICAM-1 expression. Though the participation of LPS could not be completely ruled out, we suppose that some unidentified heat-stable proteins, lipids, or polysaccharides may be the stimulatory factor(s). The ability of B. henselae to enhance the expression of adhesion molecules on endothelial cells may be an important mechanism in the pathogenesis of B. henselae infection.

Animals↗

PubMed2002

CD14-mediated induction of interleukin-8 and monocyte chemoattractant protein-1 by a heat-resistant constituent of Porphyromonas gingivalis in endothelial cells.

Viable and inactivated Porphyromonas gingivalis dose-dependently induced interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) secretion in human umbilical vein endothelial cells (HUVECs). The inactivated P. gingivalis, in comparison with viable bacteria, tended to enhance the production of both chemokines more strongly. The production of MCP-1 protein began increasing immediately after stimulation by P. gingivalis, and there was a nearly linear increase from 0 to 8 h of incubation, whereas IL-8 production showed a linear increase between 4 and 12 h of incubation. The IL-8 and MCP-1 mRNA expressions in HUVECs as determined by reverse transcriptase-polymerase chain reaction (RT-PCR) or Quantikine mRNA colorimetric quantification kits were found to be enhanced by P. gingivalis. Furthermore, the time courses of IL-8 and MCP-1 mRNA expressions were in accordance with those of protein production. Addition of polymyxin B or boiling did not weaken the stimulatory effect of P. gingivalis, which inhibited the effect of Escherichia coli lipopolysaccharide (E. coli LPS) and tumour necrosis factor-alpha (TNF-alpha), respectively. In contrast, the induction of IL-8 and MCP-1 by P. gingivalis was significantly reduced by anti-CD14 antibody. Our results suggest that some heat-stable component of P. gingivalis, including LPS, may be responsible for the induction of IL-8 and MCP-1 in HUVECs by a CD14-dependent mechanism. These effects might be involved in the accumulation and activation of neutrophils and monocytes at an early stage of the periodontal pathogenesis.

Bacteroidaceae Infections↗

PubMed2001

Inducible activation of c-Myc in adult myocardium in vivo provokes cardiac myocyte hypertrophy and reactivation of DNA synthesis.

c-Myc, a protooncogene, mediates both proliferative and cellular growth in many cell types. Although not expressed in the adult heart under normal physiological conditions, Myc expression is rapidly upregulated in response to hypertrophic stimuli. Although Myc is capable of sustaining hyperplastic growth in fetal myocytes, the effects of its re-expression in adult postmitotic myocardium and its role in mediating cardiac hypertrophy are unknown. To determine the effects of de novo Myc activity in adult postmitotic myocardium in vivo, we created a novel transgenic model in which Myc is expressed and inducibly activated specifically in cardiac myocytes. Activation of Myc in adult myocardium was sufficient to reproduce the characteristic changes in myocyte size, protein synthesis, and cardiac-specific gene expression seen in cardiac hypertrophy. Despite the increased cardiac mass, left ventricular function remained normal. Activation of Myc also provoked cell cycle reentry in postmitotic myocytes, which led to increased nuclei per myocyte and DNA content per nuclei.

Animals↗

PubMed2001

Synthesis of solid-supported mirror-image sugars: a novel method for selecting receptors for cellular-surface carbohydrates.

We introduced a novel method, through mirror-image phage display, for the identification of high-affinity D-peptides to target specific cell-surface carbohydrates. Both 3-deoxy-alpha-L-manno-2-octulosonic acid (L-KDO) and L-sialic acid and an L-sialo-disaccharide have been synthesized and attached to a solid support for selection of high-affinity peptide binders displayed on phages. Our initial studies in this effort produce single-chain Fab sequences and dodecapeptides that bind to sialic acid and KDO with nanomolar and high micromolar affinity.

Amino Acid Sequence↗

PubMed2001

Cyclin A-dependent phosphorylation of the ETS-related protein, MEF, restricts its activity to the G1 phase of the cell cycle.

MEF, a recently identified member of the E74 family of ETS-related transcription factors, is a strong transcriptional activator of cytokine gene expression. Using a green fluorescent protein gene reporter plasmid regulated by an MEF-responsive promoter, we determined that the transcriptional activity of MEF is largely restricted to the G1 phase of the cell cycle. MEF-dependent transcription was suppressed by the expression of cyclin A but not by cyclin D or cyclin E. This effect was due to the kinase activity generated by cyclin A expression, as co-expression of the cyclin-dependent kinase inhibitors p21 or p27, or a dominant negative form of CDK2 (DNK2), abrogated the reduction of MEF transcriptional activity by cyclin A. Cyclin A-CDK2 phosphorylated MEF protein in vitro more efficiently than cyclin D-CDK4 or cyclin E-CDK2, and phosphorylation of MEF by cyclin A-CDK2 reduced its ability to bind DNA. We determined one site of phosphorylation by cyclin A-CDK2 at the C terminus of MEF, using mass-spectrometry; mutation of three serine or threonine residues in this region significantly reduced phosphorylation of MEF by cyclin A and reduced cyclin A-mediated suppression of its transactivating activity. These amino acid substitutions also reduced the restriction of MEF activity to G1. Phosphorylation of MEF by the cyclin A-CDK2 complex controls its transcriptional activity during the cell cycle, establishing a novel link between the ETS family of proteins and the cell cycle machinery.

Amino Acid Sequence↗

PubMed2001

Room-temperature ultraviolet nanowire nanolasers.

Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated. The self-organized, <0001> oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process. These wide band-gap semiconductor nanowires form natural laser cavities with diameters varying from 20 to 150 nanometers and lengths up to 10 micrometers. Under optical excitation, surface-emitting lasing action was observed at 385 nanometers, with an emission linewidth less than 0.3 nanometer. The chemical flexibility and the one-dimensionality of the nanowires make them ideal miniaturized laser light sources. These short-wavelength nanolasers could have myriad applications, including optical computing, information storage, and microanalysis.

Journal Article↗

PubMed2001

Comparison of spiral and electron beam tomography in the evaluation of coronary calcification in asymptomatic persons.

Recently, investigators have begun evaluating the ability of spiral computed tomography (sequence scan mode-SEQ) to measure coronary calcium. Electron Beam Tomography (EBT) and SEQ studies were performed in 10 women and 23 men, with a mean age of 54+/-9 years. The EBT study was performed within 4 weeks (mean 11+/-4 days) of the SEQ with no clinical interval event (MI, revascularization). The mean EBT calcium score (Agatston method) was 52.1+/-58.6, with a range of 0 to 175. The SEQ mean score was 60.1+/-71.1 (range 0 to 253). There were 7 persons with scores of 0 on both scans, and 9 persons with scores of zero on either EBT or spiral CT, but not both. Three persons had negative EBT studies where SEQ detected calcium, and 6 persons had EBT detected calcium and negative SEQ studies. The six patients with negative SEQ and positive EBT studies had a mean score of 47+/-25.7 (range 9 to 99). The remaining sixteen persons had coronary calcium detected on both studies. As compared to EBT, spiral CT had a sensitivity of 74% and a specificity of 70%, for an overall diagnostic accuracy of 73%. The positive and negative predictive values were 85 and 54%, respectively for SEQ in this study. The absolute difference in scores between the two tests was 29.1+/-28.5 (mean+/-S.D.). The inter-test variability, defined as the mean values of the differences between the calcium scores in the two scans on the same subjects divided by the mean of the two scores (Absolute Difference between tests/mean), was 84.5% in this study. In asymptomatic persons, spiral CT (using SEQ) provides a limited sensitivity (74%) and specificity (70%) for coronary calcium when compared to EBT. Caution should be used when evaluating the results of spiral CT coronary calcium especially in patients with relatively low calcium scores (<200).

Calcinosis↗

PubMed2001

Optimal ECG trigger point in electron-beam CT studies: three methods for minimizing motion artifacts.

RATIONALE AND OBJECTIVES: The authors hypothesized that electrocardiographic triggering near end systole could minimize motion artifacts in electron-beam computed tomography (CT) of the coronary artery. MATERIALS AND METHODS: The study included 2,660 patients who underwent coronary artery calcium scanning with electron-beam CT. Trigger times were as follows: end of T wave, 120 to 25 msec before end of T wave, 25-50 msec after end of T wave, 40%, 45%, 50%, 55%, 60%, 70%, 75%, 80%, 90%, and 100% of R-R interval. The authors divided each group into seven subgroups according to heart rate. The percentages of cases with motion artifact in the right coronary artery were computed. Optimal trigger times were defined for each group, as well as for scan acquisitions of 250 and 200 msec. RESULTS: The optimal trigger times were as follows for heart rates of less than 50, 51-60, 61-70, 71-80, 81-90, 91-100, and more than 100 beats per minute, respectively: for 100-msec scans, 359 (27% of the R-R interval), 228 (31%), 314 (34%), 304 (38%), 289 (41%), 283 (45%), and 274 msec (48%) after the R wave; for 250-msec scans, 840 (63%), 654 (60%), 240 (26%), 224 (28%), 219 (31%), 208 (33%), and 200 msec (35%) after the R wave; and for 200-msec scans, 722 (65%), 687 (63%), 249 (27%), 248 (31%), 244 (35%), 233 (37%), and 223 msec (39%) after the R wave. CONCLUSION: The use of these new electrocardiographic triggers before end systole yielded the lowest percentage of motion artifacts (<3% across all heart rates), much lower than for conventional triggers (51% of cases with motion artifact for 80% trigger, P < .001).

Artifacts↗

PubMed2001

Four new steroidal saponins from the seeds of Allium tuberosum.

Four new steroidal saponins, 26-O-beta-D-glucopyranosyl-(25S,20R)-20-O-methyl-5alpha-furost-22(23)-en-2alpha,3beta,20,26-tetraol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (1); 26-O-beta-D-glucopyranosyl-(25S,20R)-5alpha-furost-22(23)-en-2alpha,3beta,20,26-tetraol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L- rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (2); 26-O-beta-D-glucopyranosyl-(25S,20S)-5alpha-furost-22(23)-en-2alpha,3beta,20,26-tetraol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L- rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (3); and 26-O-beta-D-glucopyranosyl-(25S,20S)-5alpha-furost-22(23)-en-3beta,20,26-triol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (4), have been isolated from the seeds of Allium tuberosum. Their structures were established by spectroscopic studies such as MS, IR, NMR, and 2D-NMR and the results of acid hydrolysis and named tuberosides F, G, H, and I, respectively.

Allium↗

PubMed2001

Improved reproducibility of coronary artery calcium scoring by electron beam tomography with a new electrocardiographic trigger method.

RATIONALE AND OBJECTIVES: To improve the interscan reproducibility with electron beam tomography (EBT) by choosing an optimal electrocardiographic (ECG) trigger time. METHODS: Two hundred fourteen asymptomatic subjects found to have coronary artery calcium (CAC) on EBT were rescanned immediately to measure the interscan variability. Subjects were randomized to one of two different ECG trigger interval groups: the new trigger method (group 1) and the 80% R-R interval trigger method (group 2). The new trigger method was derived from a previous study of motion in the coronary arteries. In group 1 (new trigger method), the ECG trigger was programmed for a certain time (in ms) after the R wave, based on the resting heart rate. The triggers for group 1 were 360 (heart rate <50 beats per minute [bpm]), 340 (51--60 bpm), 314 (61--70 bpm), 300 (71--80 bpm), 290 (81--90 bpm), 280 (91--100 bpm), and 270 ms (>100 bpm). The interscan variation (CAC area and Agatston score) was compared between the two groups. RESULTS: The interscan variability was significantly reduced using the new trigger method for both CAC area and score compared with the 80% trigger method. The individual lesion variation was also significantly reduced by the new trigger method compared with the 80% trigger method. Area measure had a significantly lower variability compared with the Agatston score. CONCLUSIONS: These results strongly support the use of this new ECG trigger that relies on a rate-adjusted millisecond delay after the R wave instead of the more commonly used 80% R-R interval in EBT calcium studies.

Artifacts↗

PubMed2001

Effect of electrocardiogram triggering on reproducibility of coronary artery calcium scoring.

PURPOSE: To test the hypothesis that computed tomographic (CT) scanning during early rather than middle diastole can significantly reduce the interscan variability of coronary artery calcium (CAC) scores. MATERIALS AND METHODS: Five hundred thirty-eight patients were initially enrolled; 282 of them were found to have CAC at electron-beam CT and underwent repeat scanning to measure interscan variability with different electrocardiogram (ECG) triggers. Eight patients were excluded owing to respiratory motion; thus, 274 asymptomatic patients were examined. Patients were randomly assigned to different ECG trigger interval groups: 40% (group 1), 50% (group 2), 60% (group 3), and 80% (group 4). Patients in whom more than one-third of sections had greater than 10% ECG trigger variability were classified in the untriggered group (group 5). Interscan variation was compared among all five groups. RESULTS: Interscan variabilities in CAC groups 1-5 were 11.5%, 15.3%, 20.3%, 17.4%, and 33.1%, respectively, for total calcium area, and 15.0%, 23.3%, 25.6%, 24.0%, and 42.4%, respectively, for total calcium score. CAC score variability was reduced by 34%; and calcium area variability, by 38% in group 1, as compared with the reduced variabilities in group 4 (P <.01 for both measures). Breath holding was adequate in 812 cases, and ECG triggering was correct in 790 of cases. CONCLUSION: Study results strongly support the use of an ECG trigger of 40% rather than 80% of the R-R interval in electron-beam CT calcium studies.

Calcium↗

PubMed2001

Tissue-specific alterations in lipoprotein lipase activity in copper-deficient rats.

Copper deficiency results in alterations in lipid metabolism that include elevations in serum cholesterol and triglycerides and a decrease in whole-body respiratory quotient. Copper-deficient animals are also leaner even though electron micrographs of the myocardium present increased lipid droplet accumulation. To address whether a compromised copper status impacts triglyceride deposition in a tissue-specific manner, the activity of lipoprotein lipase was measured in adipose tissue and cardiac and skeletal muscle. Weanling rats fed a copper-restricted diet (<1 ppm) for 6 wk demonstrated a greater than twofold increase in cardiac lipoprotein lipase activity concomitant with a significant reduction in adipose tissue lipoprotein lipase activity. Skeletal muscle lipoprotein lipase activity was not altered by the copper-deficient state. The results of this study suggest that copper deficiency may induce a tissue-specific alteration in lipoprotein lipase activity in rats, which may contribute to the notable deposition of lipid substance in myocardium and the concomitant general body leanness.

Adipose Tissue↗

PubMed2001

Nuclear respiratory factors 1 and 2 are upregulated in hearts from copper-deficient rats.

It is known that mitochondrial transcription factor A (mtTFA) plays a pivotal role in coordinating the expression of proteins in the nuclear and mitochondrial genomes as it pertains to mitochondrial biogenesis. Hearts from copper-deficient rats have elevated mtTFA levels compared to copper-adequate rats. This study evaluated whether two proteins that control activation of mtTFA by binding to its promotor, nuclear respiratory factors 1 (NRF-1) and 2 (NRF-2), are also upregulated prior to any upregulation of mtTFA. Long-Evans male rats were fed either copper-adequate or copper-deficient diets from weanling for periods of time up to 26 d. At d 26, mtTFA levels were elevated in the hearts from the copper-deficient rats, but not at earlier time points of 14, 18, and 22 d. However, NRF-1 and NRF-2 levels were increased at d 14 and 18, but not at the other two later time-points. These results revealed that the upregulation of mtTFA and mitochondrial biogenesis is preceded by upregulation of NRF-1 and NRF-2, which is consistent with the known molecular events controlling mitochondrial biogenesis in other systems.

Animals↗

PubMed2001

[Use of microsatellites in zygosity diagnosis of twins].

OBJECTIVE: To diagnose zygosity of twins by microsatellite polymorphism. METHODS: One hundred and eighty-four samples, including 69 pairs of twins with the same gender and 6 pairs of twins with different gender were recruited. Seventeen sib pairs were also collected for controls. Nine highly polymorphic microsatellite loci were amplified by polymerase chain reaction (PCR) using fluorescence-labeled primers and the products were sized by automated fragment analysis after electrophoresis and laser detection. Zygosity was diagnosed by comparing the concordance of the genotype of the 9 markers. RESULTS: Sixty-three pairs of monozygotic (MZ) and 12 pairs of dizygotic (DZ) twins were assigned their zygosity by comparison of polymorphism of 9 microsatellite loci. Within each of the 63 monozygotic (MZ) pairs there was complete concordance. However, within each of the 12 dizygotic pairs and other 17 sib pairs, discordant loci were found. With five or six markers, the probability that any twin pair was MZ if all markers were concordant was 99% or 99.6%, respectively. With all the nine markers, the probability that any twin pair was MZ if all markers were concordant was 99.95%. CONCLUSION: The technology of gene scan and genotyping provides a rapid and reliable approach to zygosity detection.

DNA↗

PubMed2000

Inhibition of the transforming growth factor beta 1 signaling pathway by the AML1/ETO leukemia-associated fusion protein.

The t(8;21) translocation, found in adult acute myelogenous leukemia, results in the formation of an AML1/ETO chimeric transcription factor. AML1/ETO expression leads to alterations in hematopoietic progenitor cell differentiation, although its role in leukemic transformation is not clear. The N-terminal portion of AML1, which is retained in AML1/ETO, contains a region of homology to the FAST proteins, which cooperate with Smads to regulate transforming growth factor beta1 (TGF-beta1) target genes. We have demonstrated the physical association of Smad proteins with AML1 and AML1/ETO by immunoprecipitation and have mapped the region of interaction to the runt homology domain in these AML1 proteins. Using confocal microscopy, we demonstrated that AML1, and ETO and/or AML1/ETO, colocalize with Smads in the nucleus of t(8;21)-positive Kasumi-1 cells, in the presence but not the absence of TGF-beta1. Using transient transfection assays and a reporter gene construct that contains both Smad and AML1 consensus binding sequences, we demonstrated that overexpression of AML1B cooperates with TGF-beta1 in stimulating reporter gene activity, whereas AML1/ETO represses basal promoter activity and blocks the response to TGF-beta1. Considering the critical role of TGF-beta1 in the growth and differentiation of hematopoietic cells, interference with TGF-beta1 signaling by AML1/ETO may contribute to leukemogenesis.

3T3 Cells↗

PubMed2000

Rates of progression of coronary calcium by electron beam tomography.

In this study, we sought to determine the rate of progression of atherosclerosis using coronary calcium scores derived from electron beam tomography (EBT). We studied a variety of disease states (hypertension, high cholesterol, tobacco use, diabetes mellitus) followed for 1 to 6.5 years. We evaluated 299 asymptomatic persons (227 men and 72 women) who underwent 2 consecutive EBT scans at least 12 months apart. The average change in the calcium score (Agatston method) for the entire group was 33.2 +/- 9.2%/year. The treated group (receiving statins) demonstrated an average increase in calcium scores of 15 +/- 8%/year compared with 39 +/- 12%/year for untreated patients (p <0.001). Among the 60 patients on statin monotherapy, 37% had a decrease in the calcium score from baseline to follow-up scan. The relative increase in calcium scores did not vary significantly by gender or risk factors, with the exception of statin-treated hypercholesterolemic subjects. Scores of zero on the initial scan portend a low likelihood of significant calcific deposits on repeat scanning. Only 2 of 81 participants (2%) with scores of zero at baseline had scores >10 on repeat study. In this study, statin therapy induced a 61% reduction in the rate of coronary calcium progression. This study demonstrates that EBT may be a useful tool in assessing efficacy of different interventions to retard progression of atherosclerosis, noninvasively, over relatively short time periods.

Adult↗

PubMed2000

Preview method for electron-beam CT scanning of the coronary arteries.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate a method that uses electron-beam computed tomography to obtain the most appropriate starting level for complete imaging of the coronary tree and to compare it with the existing method. A second aim was to evaluate the spatial location of the coronary arteries relative to different anatomic cardiac and chest landmarks. MATERIALS AND METHODS: Two hundred forty consecutive patients were randomly assigned to imaging with either a six-level preview (new) method or the traditional preview method. The accuracy of each preview method to encompass the coronary anatomy was compared. RESULTS: All coronary arteries were included in 3-mm scans obtained starting three levels above the origin of the left main coronary artery. The left anterior descending coronary artery extended 3-9 mm above the left main artery in 33 patients (14%). The coronary arteries were encompassed by scans depicting 72-105 mm; thus, with 3-mm sections, up to 35 scans are necessary to cover the entire coronary tree. No stable relationship between the coronary arteries and the pulmonary artery or carina could be found. CONCLUSION: The six-level preview method that identifies the left main coronary artery and begins 9 mm above this level is the most accurate method for depicting the coronary anatomy. No anatomic landmarks in the heart or chest can be used reliably to identify the position of the coronary arteries in individual patients.

Coronary Angiography↗