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Biomedical subjects

Yang Zhao

Publications and source records attributed to Yang Zhao.

At least 55 records · Page 3Linked to original sources
PubMed2005

Effects of x-ray and CT image enhancements on the robustness and accuracy of a rigid 3D/2D image registration.

A rigid body three-dimensional/two-dimensional (3D/2D) registration method has been implemented using mutual information, gradient ascent, and 3D texturemap-based digitally reconstructed radiographs. Nine combinations of commonly used x-ray and computed tomography (CT) image enhancement methods, including window leveling, histogram equalization, and adaptive histogram equalization, were examined to assess their effects on accuracy and robustness of the registration method. From a set of experiments using an anthropomorphic chest phantom, we were able to draw several conclusions. First, the CT and x-ray preprocessing combination with the widest attraction range was the one that linearly stretched the histograms onto the entire display range on both CT and x-ray images. The average attraction ranges of this combination were 71.3 mm and 61.3 deg in the translation and rotation dimensions, respectively, and the average errors were 0.12 deg and 0.47 mm. Second, the combination of the CT image with tissue and bone information and the x-ray images with adaptive histogram equalization also showed subvoxel accuracy, especially the best in the translation dimensions. However, its attraction ranges were the smallest among the examined combinations (on average 36 mm and 19 deg). Last the bone-only information on the CT image did not show convergency property to the correct registration.

Algorithms↗
PubMed2005

Predicting pharmacy costs and other medical costs using diagnoses and drug claims.

BACKGROUND: Predicting health care costs for individuals and populations is essential for managing care. However, the comparative power of diagnostic and drug data for predicting future costs has not been closely examined. OBJECTIVE: We sought to compare the predictive performance of claims-based models using diagnoses, drugs claims, and combined data to predict health care costs. SUBJECTS: More than 1 million commercially insured, nonelderly individuals in a national (MEDSTAT MarketScan) research database comprised our sample. MEASURES: We used 1997 and 1998 drug and diagnostic profiles to predict costs in 1998 and 1999, respectively. To assess model performance, we compared R2 values and predictive ratios (predicted costs/actual costs) for important subgroups. RESULTS: Models using both drug and diagnostic data best predicted subsequent-year total health care costs (highest R2 = 0.168 versus 0.116 and 0.146 for models based on drug or diagnostic data alone, respectively), with highly accurate predictive ratios (0.95-1.05) for subgroups of patients with major medical conditions. Models predicting pharmacy costs had substantially higher R2 values than models predicting other medical costs (highest R2 0.493 versus 0.124). Drug-based models predicted future pharmacy costs better than diagnosis-based models (highest R2 = 0.482 versus 0.243), whereas diagnosis-based models predicted total costs (highest R2 = 0.146 versus 0.116) and nonpharmacy costs (highest R2 = 0.116 versus 0.071) more effectively than drug-based models. Newer models had markedly higher R values than older ones, largely because of richer data rather than model refinements. CONCLUSIONS: Combined drug and diagnostic data predicts total health care costs better than either type of data alone. Pharmacy spending is particularly predictable from drug data, whereas diagnoses are more useful than drugs for predicting other medical costs and total costs. Using even slightly more recent data can substantially boost model performance measures; thus, model comparisons should be conducted on the same dataset.

Actuarial Analysis↗
PubMed2005

Worms in space? A model biological dosimeter.

Although it is well known that radiation causes mutational damage, little is known about the biological effects of long-term exposure to radiation in space. Exposure to radiation can result in serious heritable defects in experimental animals, and in humans, susceptibility to cancer, radiation-sickness, and death at high dosages. It is possible to do ground controlled studies of different types of radiation on experimental animals and to physically measure radiation on the space station or on space probes. However, the actual biological affects of long-term exposure to the full range of space radiation have not been studied, and little information is available about the biological consequences of solar flares. Biological systems are not simply passive recording instruments. They respond differently under different conditions, and thus it is important to be able to collect data from a living animal. There are technical difficulties that restrict the placement of an experimental organism in a space environment for long periods of time, in a manner that allows for the recovery of genetic data. Use of the self-fertilizing hermaphroditic nematode, Caenorhabditis elegans offers potential for the design of a biological dosimeter. In this paper, we describe the advantages of this model system and review the literature of C. elegans in space.

Animals↗
PubMed2004

Low-lying excited states of light-harvesting system II in purple bacteria.

The low-lying excited states of a B850 ring of Rhodospirillum (Rs.) molischianum are determined accurately by a semiempirical INDO/S method. Results obtained are found to fit extremely well with a Frenkel exciton model with long-range dipolar interactions, and the spatial size of the electron-hole pair is confirmed to fall predominantly within one bacteriochlorophyll with a small leakage to its nearest neighbors. More importantly, the nearest neighbor exciton coupling constants are found to be close to those evaluated directly from dimers, and thus, an existing discrepancy between calculated results of dimers and B850 rings has been resolved.

Computer Simulation↗
PubMed2004

Evidence that IGF binding protein-5 functions as a ligand-independent transcriptional regulator in vascular smooth muscle cells.

Insulin-like growth factor binding protein (IGFBP)-5 is a conserved protein synthesized and secreted by vascular smooth muscle cells (VSMCs). IGFBP-5 binds to extracellular IGFs and modulates IGF actions in regulating VSMC proliferation, migration, and survival. IGFBP-5 also stimulates VSMC migration through an IGF-independent mechanism, but the molecular basis underlying this ligand-independent action is unknown. In this study, we show that endogenous IGFBP-5 or transiently expressed IGFBP-5-EGFP, but not IGFBP-4-EGFP, is localized in the nuclei of VSMCs. Using a series of IGFBP-4/5 chimeras and IGFBP-5 points mutants, we demonstrated that the IGFBP-5 C-domain is necessary and sufficient for its nuclear localization, and residues K206, K208, K217, and K218 are particularly critical. Intriguingly, inhibition of protein secretion abolishes IGFBP-5 nuclear localization, suggesting the nuclear IGFBP-5 is derived from the secreted protein. When added exogenously, (125)I- or Cy3-labeled IGFBP-5 is capable of cellular entry and nuclear translocation. To identify potential transcriptional factor(s) that interact with IGFBP-5, a human aorta cDNA library was screened by a yeast two-hybrid screening strategy. Although this screen identified many extracellular and cytosolic proteins that are known to interact with IGFBP-5, no known transcription factors were found. Further motif analysis revealed that the IGFBP-5 N-domain contains a putative transactivation domain. When fused to GAL-4 DNA dinging domain and tested, the IGFBP-5 N-domain has strong transactivation activity. Mutation of the IGF binding domain or treatment of cells with IGF-I has little effect on transactivation activity. These results suggest that IGFBP-5 is localized in VSMC nucleus and possesses transcription-regulatory activity that is IGF independent.

Amino Acid Motifs↗
PubMed2004

Dual domain watermarking for authentication and compression of cultural heritage images.

This paper proposes an approach for the combined image authentication and compression of color images by making use of a digital watermarking and data hiding framework. The digital watermark is comprised of two components: a soft-authenticator watermark for authentication and tamper assessment of the given image, and a chrominance watermark employed to improve the efficiency of compression. The multipurpose watermark is designed by exploiting the orthogonality of various domains used for authentication, color decomposition and watermark insertion. The approach is implemented as a DCT-DWT dual domain algorithm and is applied for the protection and compression of cultural heritage imagery. Analysis is provided to characterize the behavior of the scheme under ideal conditions. Simulations and comparisons of the proposed approach with state-of-the-art existing work demonstrate the potential of the overall scheme.

Algorithms↗
PubMed2004

Identification of an antigenic determinant on the S2 domain of the severe acute respiratory syndrome coronavirus spike glycoprotein capable of inducing neutralizing antibodies.

Severe acute respiratory syndrome (SARS) is a life-threatening disease caused by a newly identified coronavirus (CoV), SARS-CoV. The spike (S) glycoprotein of CoV is the major structural protein responsible for induction of host immune response and virus neutralization by antibodies. Hence, knowledge of neutralization determinants on the S protein is helpful for designing protective vaccines. To analyze the antigenic structure of the SARS-CoV S2 domain, the carboxyl-terminal half of the S protein, we first used sera from convalescent SARS patients to test the antigenicity of 12 overlapping fragments spanning the entire S2 and identified two antigenic determinants (Leu 803 to Ala 828 and Pro 1061 to Ser 1093). To determine whether neutralizing antibodies can be elicited by these two determinants, we immunized animals and found that both of them could induce the S2-specific antisera. In some animals, however, only one determinant (Leu 803 to Ala 828) was able to induce the antisera with the binding ability to the native S protein and the neutralizing activity to the SARS-CoV pseudovirus. This determinant is highly conserved across different SARS-CoV isolates. Identification of a conserved antigenic determinant on the S2 domain of the SARS-CoV S protein, which has the potential for inducing neutralizing antibodies, has implications in the development of effective vaccines against SARS-CoV.

Amino Acid Sequence↗
PubMed2004

The three-dimensional structure and the relationship between external and internal vascularizations in the brain of rat embryos.

BACKGROUND: There have been no detailed reports of the three-dimensional structure and the relationship between the external and internal vascularizations observed successively for a long duration in the rat fetus, although many authors have studied the vascular morphology of the developing brain. This study examined the three-dimensional structure of both the external and internal vascularizations of the prenatal rat telencephalon from embryonic days 12 (E12) to 20 (E20). METHOD: A microvascular casting method for scanning electron microscopy (SEM) was used in this study, along with vascular staining using gold-gelatin solution-autometallography (GGS-AMG) after intravascular injection of colloidal gold, as well as hematoxylin-eosin (HE) staining for paraffin embedded specimens. RESULTS: In GGS-AMG stains, E16 fetuses had a few short perforating cortical blood vessels (SPCVs); E17 fetuses had long perforating cortico-medullary vessels (LPCVs). Older fetuses had specific patterns of vascular networks in the cortex and the deeper subcortical part of the telencephalon. In the cortex, fine longitudinal blood vessels were connected by transverse channels. The deep telencephalon had fine blood vessels running in all directions. Using SEM, the external vascularization was already visible in E12 fetuses as arborizations of arterial branches, forming a mesh of fine vascular networks covering the telencephalon. A coralliform fine venous plexus was observed in the external vascularization of E16 fetuses. There were ring-like anastomoses and bud-like protrusions in the network of small blood vessels, most likely the angiogenesis of fetal vessels. From E12 to E16, an immature and incomplete internal vascularization began to appear. There were short blood vessels with ballooned terminals branching from the external vascularization. They penetrated the brain tissue to form networks in the superficial layer, comparable to SPCVs. In E17 to E20 fetuses, tortuous venous branches, straight arterial blood vessels, and a fine network of small blood vessels formed the external vascularization. There were fewer arterial than venous branches connecting to the fine networks of small blood vessels. LPCVs were noted at E17, at the time the white matter emerged. They branched from the external vascularization, and perpendicularly penetrated the brain surface, traversing the cortical plate, and entering into the deep brain. At E17, arterial and venous blood vessels could be clearly distinguished in the external vascularization. At E20, the cortex and white matter contained specific arrangements of networks of fine blood vessels, as seen by GGS-AMG staining. CONCLUSION: These findings show that the development of both the external and internal vascularization follows the development of the telencephalon. In particular, the emergence of the cortical plate and white matter on E16 and E17 influence the development of both the internal and the external vascularization. The laminal arrangement of blood vessels was not observed corresponding to the respective laminal neuronal layers.

Animals↗
PubMed2004

Prokaryotic expression of Chinese bovine enterokinase catalytic subunit.

BACKGROUND: To express in vitro the bovine enterokinase catalytic subunit (EKL) protein, which could be used in the future for the cleavage and purification of fusion proteins. METHODS: Bovine enterokinase catalytic subunit cDNA was obtained by RT-PCR from duodenal mucosa of a bovine obtained at wholesale market, and then cloned into a pUCmT cloning vector and sequenced. The desired gene fragment was inserted into a pET39b expression plasmid and the recombinant vector pET39b-EKL was transformed into E. coli BL21 (DE3). Protein expression was induced using IPTG. The recombinant DsbA-EKL was purified with His.Tag affinity chromatography, and it bioactivity was analyzed. RESULTS: Compared with the sequence deposited in GenBank, the sequence of the EKL gene cloned in the present study is correct. It was also confirmed that the nucleotide sequence of expression plasmid pET39b-EKL was correct at the conjunction site between the recombinant DNA 5' terminal multi-cloning site and the recombinant fragment. SDS-PAGE analysis indicated that the target product was about 65 kDa and represented 28% of total cell protein. Purified recombinant protein was obtained by metal chelating chromatography using Ni-IDA resin. After desalting and changing the buffer, the crude kinase was incubated at 21 degrees C overnight and shown to have a high autocatalytic cleavage activity. CONCLUSIONS: The EKL gene from Chinese bovine has been cloned successfully and expressed. This investigation has layed the foundation for future enterokinase activity research and for further large-scale application of expression products.

Animals↗
PubMed2004

[Killer immunoglobulin-like receptor gene distribution in Guangdong Han population].

OBJECTIVE: To investigate the distribution of killer immunoglobulin-like receptor (KIR) gene in Guangdong Han population. METHODS: KIR phenotype was examined by PCR with sequence-specific primers in 96 subjects of Han nationality in Guangdong Province of China, and KIR frequency was calculated and compared with those in Caucasian, north Indian and Japanese populations. RESULT: The gene expression frequency of KIR in Guangdong Han people was 2DL1(0.85), 2DL2(0.12), 2DL3(0.58), 2DL4(1), 2DL5(0.24), 3DL1(0.96), 3DL2(1), 3DL3(1), 2DP1(0.97), 2DP2(0.98), 2DS1(0.10), 2DS2(0.30), 2DS3(0.02), 2DS4(0.28), 1D(0.65), 2DS5(0.19), and 3DS1(0.23) respectively. Comparison of the KIR recognizing the same HLA ligand suggested significantly higher expression frequency of inhibitory KIR than that of activating KIR. Compared with Caucasian and north Indian populations, Guangdong Han population had significantly lower expression frequency of activating KIR gene with the exception of KIR2DS4. CONCLUSION: Different KIR genes have different expression frequencies in Guangdong Han population, and KIR gene distribution varies between populations of different races.

Adult↗
PubMed2003

Energy dissipation mechanisms in carbon nanotube oscillators.

Energy transfer from the translational degrees of freedom to phonon modes is studied for isolated systems of two coaxial carbon nanotubes, which may serve as a nearly frictionless nano-oscillator. It is found that for oscillators with short nanotubes (less than 30 A) a rocking motion, occurring when the inner tube is pulled about 1/3 out of the outer tube, is responsible for significant phonon energy acquisitions. For oscillators with long nanotubes translational energies are mainly dissipated via a wavy deformation in the outer tube undergoing radial vibrations. Frictional forces between 10(-17) and 10(-14) N per atom are found for various dissipative mechanisms.

Journal Article↗
PubMed2003

Spatial resolution enhancement of fiber-optic scanning white-light interferometer by use of a Vernier principle.

A Vernier principle is employed to improve the spatial resolution of a fiber-optic white-light interferometer to the accuracy of 0.2 microm. The Vernier principle is implemented by combination of interference fringes itself and a virtual fringe that is generated by means of software tracing the scanning mirror. Two rulers are read with respect to each other. This design is insensitive to intensity fluctuation of the interference fringe. The applications, submicrometer estimation for the quadrature-locking selection and the tolerance of the relative measurement, demonstrate its effectiveness.

Journal Article↗
PubMed2003

Metabolism and metabolic inhibition of cilnidipine in human liver microsomes.

AIM: To study the metabolism of cilnidipine and the effects of selective cytochrome P-450 (CYP450) inhibitors on the metabolism of cilnidipine in human liver microsomes in vitro. METHODS: Human liver microsomes were used to perform metabolism studies. Various selective CYP450 inhibitors were used to investigate their effects on the metabolism of cilnidipine and the principal CYP450 isoform involved in dehydrogenation of dihydropyridine ring of cilnidipine in human liver microsomes. RESULTS: Cilnidipine was rapidly metabolized to three metabolites. They are dehydrogenated metabolite of dihydropyridine ring of cilnidipine (M1), demethylation metabolite of lateral chain of dihydropyridine ring of cilnidipine (M2), and the dehydrogenation and demethylation metabolite of cilnidipine (M3). Ketoconazole (Ket) competitively inhibited the dehydrogenation of dihydropyridine ring of cilnidipine and lowered the metabolic rate of cilnidipine while alpha-naphthoflavone (alpha-Naph), sulfaphenazole (Sul), quinidine (Qui), diethyldithiocarbamate (DDC), and tranylcypromine (Tra) had a little or no inhibitory effects on the dehydrogenation of cilnidipine. CONCLUSION: Cilnidipine was rapidly metabolized in human liver microsomes and dehydrogenation of dihydropyridine ring of cilnidipine is crucial for the elimination of cilnidipine. Cytochrome P-4503A(CYP3A) is the major human CYP involved in the dehydrogenation of dihydropyridine ring of cilnidipine.

Aryl Hydrocarbon Hydroxylases↗
PubMed2003

[Clinical application and animal experiment of thoracic tracheal reconstruction by using pulmonary tissue flap].

OBJECTIVE: To study the usability of pulmonary tissue flap in the reconstruction of the thoracic trachea. METHODS: Over half perimeter anterior and posterior wall and 6 to 8 tracheal cartilagious rings of dog trachea were resected. The nickel-titanium alloy mesh stent was placed inside the lumen for repair of the defect of the tracheal wall by nearby pulmonary tissue flap with the vascularized segment. The dogs were killed from 2 months to 12 months after operation. Specimens were taken and observed under light and electron microscope. Clinically, 4 patients were treated by this way operation [right common tracheal scarred stenosis and atresia (1), mixed cancerization in the lower part of the common trachea (1) and left common tracheal carcinoid (2)]. RESULTS: No stenosis and granulation tissue were observed in the prosthetic lumen, in which there was comparative continuous stratified ciliated columnar epithelium. All patients recovered respiratory function. CONCLUSION: Pulmonary tissue flap is a promising prosthesis of thoracic tracheal reconstruction.

Animals↗
PubMed2002

Plasma homocysteine is regulated by phospholipid methylation.

Mild hyperhomocysteinemia is an independent risk factor for cardiovascular disease. Homocysteine, a non-protein amino acid, is formed from S-adenosylhomocysteine and partially secreted into plasma. A potential source for homocysteine is methylation of the lipid phosphatidylethanolamine to phosphatidylcholine by phosphatidylethanolamine N-methyltransferase in the liver. We show that mice that lack phosphatidylethanolamine N-methyltransferase have plasma levels of homocysteine that are approximately 50% of those in wild-type mice. Hepatocytes isolated from methyltransferase-deficient mice secrete approximately 50% less homocysteine. Rat hepatoma cells transfected with phosphatidylethanolamine N-methyltransferase secrete more homocysteine than wild-type cells. Thus, phosphatidylethanolamine N-methyltransferase is an important source of plasma homocysteine and a potential therapeutic target for hyperhomocysteinemia.

Animals↗
PubMed2002

An unexpected requirement for phosphatidylethanolamine N-methyltransferase in the secretion of very low density lipoproteins.

Phosphatidylethanolamine N-methyltransferase (PEMT) catalyzes the conversion of phosphatidylethanolamine to phosphatidylcholine (PC). We investigated whether there was diminished secretion of lipoproteins from hepatocytes derived from mice that lacked PEMT (Pemt(-/-)) compared with Pemt(+/+) mice. Hepatocytes were incubated with 0.75 mm oleate, the media were harvested, and triacylglycerol (TG), PC, apolipoprotein (apo) B100, and apoB48 were isolated and quantified. Compared with hepatocytes from Pemt(+/+) mice, hepatocytes from Pemt(-/-) mice secreted 50% less TG, whereas secretion of PC was unaffected. Fractionation of the secreted lipoproteins on density gradients demonstrated that the decrease in TG was in the very low density lipoprotein (VLDL)/low density lipoprotein fractions. The secretion of apoB100 was decreased by approximately 70% in VLDLs/low density lipoproteins, whereas there was no significant decrease in apoB48 secretion in any fraction. Transfection of McArdle hepatoma cells (that lack PEMT) with PEMT cDNA enhanced secretion of TG in the VLDLs. Because the levels of PC in the hepatocytes and hepatoma cells were unaffected by the lack of PEMT expression, there appears to be an unexpected requirement for PEMT in the secretion of apoB100-containing VLDLs.

Animals↗
PubMed2002

Disease burden profiles: an emerging tool for managing managed care.

As health plans assume financial risk for providing health care services, effectively managing the health of a population remains one of the toughest challenges. This article shows how risk assessment methods can be used to measure disease burden in the full population and to discriminate levels of future health care needs within specific disease cohorts. We also examine and compare the predictive power of claims-based models within a diabetic cohort.

Chronic Disease↗