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Biomedical subjects

Y Xu

Publications and source records attributed to Y Xu.

At least 1,333 records · Page 74Linked to original sources
PubMedDate not supplied

Accumulation and partition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in the muscle and liver of fish.

The present study monitored fish from sites contaminated for many years, and the data reflected the results of actual, long-term environmental exposure. The sum concentrations and TEQs of PCDD/F in the muscle of common carp (Cyprinus carpio (linnaeus)) and big head (Aristichthys nobilis) from the different site of a heavily polluted lake in China are decreased with decrease of PCDD/F concentration in sediment and water. Concentration in fish can be highly variable, but the concentration is comparable in muscle between different species of fish if the concentrations are normalized by lipid content. PCDD/F accumulate in certain tissues with the highest proportions found in the liver of fish. The concentrations and TEQs in livers were also decreased with concentrations of sediments and water. The concentrations of PCDD/F in muscle are significantly correlated with those in liver. BCFs of 2,3,7,8-substituted PCDD/F calculated directly from water were consistent with that calculated indirectly from sediment. PCDD/F concentrations in sediment are much higher than that in water, therefore the measurement is much easier and the results are more accurate. Estimated BCFs for superhydrophobic chemicals derived from sediment may also serve as acceptable surrogates for "true" bioaccumulation potential.

Animals↗
PubMedDate not supplied

Raman spectroscopic study of microcosmic photodamage of the space structure of DNA sensitized by Yangzhou haematoporphyrin derivative and Photofrin II.

After calf thymus DNA has been photodamaged by Yangzhou haematoporphyrin derivative (YHPD) or Photofrin II, the Raman characteristic frequencies and the intensities of the bands assigned to various groups of the components of DNA change considerably. As a result of damage, homogeneous B-form calf thymus DNA becomes a mixture containing: (1) modified B-form DNA, which is shorter than the original because of double-helical DNA scission; (2) single-stranded DNA due to the breakage of some H-bonds and the lack of some bases, etc.

Animals↗
PubMedDate not supplied

Algorithm for naming molecular equivalence classes represented by labeled pseudographs.

The emergence of large chemical databases imposes a need for organizing the compounds in these databases. Mapping the chemical graph in particular, and a molecular equivalence class represented by a labeled pseudograph in general, to a unique number or string facilitates high-throughput browsing, grouping, and searching of the chemical database. Computing this number using a naming adaptation of the Morgan algorithm, we observed a large classification noise in which nonisomorphic graphs were mapped to the same number. Our extensions to that algorithm greatly reduced the classification noise.

Journal Article↗
PubMedDate not supplied

Comparing SSRI treatment costs for depression using retrospective claims data: the role of nonrandom selection and skewed data.

BACKGROUND AND OBJECTIVES: Since conventional randomized clinical trials often do not reflect the real world circumstances of prescribing behavior and patient outcomes, the use of retrospective administrative claims databases (RACD) has become more common in treatment cost comparisons among alternative pharmaceutical compounds. Several recent RACD studies have compared treatment costs for depressed patients prescribed SSRIs such as fluoxetine, sertraline and paroxetine. These cost comparisons have reached mixed conclusions. To begin to explain and reconcile the mixed SSRI cost comparison evidence, we undertake a variety of alternative multivariate analyses using a publicly available RACD. METHODS AND DATA: The 1995 to 1996 data encompasses a time period when all three SSRIs had become well-established agents. We report and compare results from multivariate linear regressions, logistic regressions, ordered probits and sample selectivity models, and examine robustness when adjustments are made for outlier observations and skewed distributions. RESULTS AND CONCLUSIONS: While choice of initial SSRI is nonrandom, the effect of sample selectivity on total depression-related and total health care expenditure is neutral across SSRIs. Although most cost measures are numerically greatest for fluoxetine, depression-related outpatient and hospitalization costs do not significantly differ by choice of initial SSRI. These findings are robust to alternative assumptions, specifications, and procedures. Antidepressant medication costs, however, are significantly higher when fluoxetine is the initial SSRI rather than sertraline or paroxetine, reflecting the larger proportion of fluoxetine patients prescribed a daily dosage of two or more capsules. Both total depression-related and total health care log-transformed costs are significantly lower for sertraline than fluoxetine.

Adult↗
PubMedDate not supplied

A rapid simplified purification of bovine thrombin.

A rapid simplified method was developed to obtain highly pure bovine thrombin. Prothrombin was directly activated when it was enriched from bovine plasma without prior purification. The activated thrombin was isolated by a single Heparin-Sepharose affinity chromatography step. About 87% of activated thrombin was recovered and the yield was 25.1 mg of thrombin per liter of starting plasma. Specific activity of the final preparation was 4018 NIH units/mg, representing a 402 fold purification over the starting material. Comparative experiments showed that the simplified method was about six times as effective as previous two-step methods.

Animals↗
PubMedDate not supplied

Synthesis and testing of new modified nucleosides.

New efficient routes for the high-yielding synthesis of several classes of modified nucleosides have been developed. We have prepared both the D- and L-enantiomers of the methylene-expanded oxetanocin isonucleosides 1a-c and the L-2',3'-dideoxy isonucleosides 2abc (both the oxa and thia analogues) as well as new routes for the preparation of L-ribose and 2-deoxy L-ribose 3ab and their modified nucleosides 4.

HIV↗
PubMedDate not supplied

Phosphorylation of anti-HIV nucleoside analogs by nucleoside diphosphate kinase.

The reaction of NDP kinase with antiviral nucleoside triphosphates used in antiviral therapies was studied at the presteady state by fluorescence stopped-flow and compared with the steady-state parameters. The affinity of the analogs was determined by fluorescence titration of a mutated enzyme with an inserted Trp in the binding site. The lack of the 3' hydroxyl in analogs is shown to decrease the kcat more than the KD.

Anti-HIV Agents↗
PubMedDate not supplied

The use and evaluation of 2 + 2 photoaddition in immobilization of oligonucleotides on a three dimensional hydrogel matrix.

Photochemical attachment of synthetic oligonucleotides on the three dimensional surface of a polyacrylamide based hydrogel was used in the specific detection of target oligonucleotides. Covalent attachment of the oligonucleotide to the hydrogel was mediated by the incorporation of a 2 + 2 photo-attachable functional group in both the hydrogel and the oligonucleotide probe. Expression and SNP assays were used to evaluate this platform.

Acrylic Resins↗
PubMedDate not supplied

Inheritance of resistance to zucchini yellow mosaic virus and watermelon mosaic virus in watermelon.

High resistance to zucchini yellow mosaic virus-China strain (ZYMV-CH) and moderate resistance to watermelon mosaic virus (WMV) were found in a selection of PI 595203 (Citrullus lanatus var. lanatus), an Egusi type originally collected in Nigeria. Mixed inoculations showed primarily that these two viruses have no cross-protection. This fact may explain the high frequency of mixed infection often observed in commercial fields. When plants were inoculated with a mixture of the two viruses, the frequency of plants resistant to ZYMV was lower than expected, indicating that WMV infection may reduce the ability of a plant to resist ZYMV. We studied inheritance of resistance to ZYMV-CH and WMV, using crosses between a single-plant selection of PI 595203 and the ZYMV-susceptible watermelon inbreds 9811 and 98R. According to virus ratings of the susceptible parents, the resistant parent, and the F1, F2, and BC1 generations, resistance to ZYMV-CH was conferred by a single recessive gene, for which the symbol zym-CH is suggested. The high tolerance to WMV was controlled by at least two recessive genes.

Citrullus↗
PubMedDate not supplied

Effective communication and supervision in the biomedical engineering department.

It is important for biomedical engineering supervisors to master the art of effective communication. Supervisors who have effective communication skills can successfully initiate creative programs and generate a harmonious working atmosphere. Using effective communication, they can promote good working conditions, such as high morale, worker initiative and loyalty to the department, which are almost impossible to measure but imperative for a successful department. However, effective communication tends to be neglected by supervisors who are either functional specialists or managerial generalists. This paper presents several cases of what effective communication truly is and discusses some potential factors that may lead to ineffective communication.

Biomedical Engineering↗
PubMedDate not supplied

BrainImageJ: a Java-based framework for interoperability in neuroscience, with specific application to neuroimaging.

The Human Brain Project consortium continues to struggle with effective sharing of tools. To facilitate reuse of its tools, the Stanford Psychiatry Neuroimaging Laboratory (SPNL) has developed BrainImageJ, a new software framework in Java. The framework consists of two components-a set of four programming interfaces and an application front end. The four interfaces define extension pathways for new data models, file loaders and savers, algorithms, and visualization tools. Any Java class that implements one of these interfaces qualifies as a BrainImageJ plug-in-a self-contained tool. After automatically detecting and incorporating new plug-ins, the application front end transparently generates graphical user interfaces that provide access to plug-in functionality. New plug-ins interoperate with existing ones immediately through the front end. BrainImageJ is used at the Stanford Psychiatry Neuroimaging Laboratory to develop image-analysis algorithms and three-dimensional visualization tools. It is the goal of our development group that, once the framework is placed in the public domain, it will serve as an interlaboratory platform for designing, distributing, and using interoperable tools.

Algorithms↗
PubMedDate not supplied

Consistency of tone-syllable alignment across different syllable structures and speaking rates.

Previous studies have reported that F0 contours of lexical tones in Mandarin are closely aligned with the syllables that carry them and that this alignment is late-adjusted so that the most appropriate F0 contour of a tone occurs mainly in the later portion of the host syllable. These studies, however, examined tone alignment only in syllables with a simple CV structure. The present study compared tone-syllable alignment patterns in syllables with a final nasal (the only final consonant allowed in Mandarin) to those without a final nasal at three speaking rates - normal, fast and slow. Experiment 1 found that regardless of internal syllable structure, the F0 contours for all of the four Mandarin tones maintain a consistent alignment to the syllables that carry them. Experiment 2 found that whether or not the syllable has a final nasal and regardless of speaking rate, the F0 peak associated with the R (rising) tone always occurs near the offset of the R-tone-carrying syllable, the onset of the F0 rise always occurs near the center of the syllable and the slope of the rise does not vary systematically with either syllable structure or speaking rate. These findings are interpreted as indicating that the syllable is the proper domain for tone implementation and that tone contours such as rising and falling are probably implemented as integral dynamic targets rather than as sequences of static targets.

Humans↗
PubMedDate not supplied

Fundamental frequency peak delay in Mandarin.

Fundamental frequency (F0) peak delay (henceforth peak delay) refers to the phenomenon that an F0 peak sometimes occurs after the syllable it is associated with either lexically or prosodically. Although peak delay has been reported for various languages, the mechanism of its occurrence has so far remained unclear. In Mandarin, peak delay has been found to occur regularly in the rising (R) tone but not in the high (H) tone. The present study investigates the underlying mechanisms of peak delay by examining its relationship with tone, tonal context, and speech rate. An experiment was conducted to test the possibility that peak delay may occur also in the H tone in Mandarin if the H-carrying syllable is sufficiently shortened. Native speakers of Mandarin Chinese recorded three types of sentences each containing a H, a R, or a weakened H tone. The sentences were produced at three speech rates: normal, fast and slow. Analysis of F0 contours and peak alignment revealed that at normal speech rate, peak delay occurred regularly in both the R and weakened H tones but only occasionally in the H tone; at slow speech rate, peak delay continued to occur regularly in the R tone but only occasionally in weakened H and rarely in the H tone; at fast speech rate, peak delay occurred not only regularly in the R and weakened H tones, but also frequently in the H tone. Results of F0 contour alignment analysis indicate that peak delay occurs when there is a sharp F0 rise near the end of a syllable, regardless of the cause of the rise. The finding of this study provides support for the view that, rather than due to actual misalignment between underlying pitch units and segmental units, much of the variability in the shape and alignment of F0 contours in Mandarin is attributable to the interaction of underlying pitch targets with tonal contexts and articulatory constraints.

Female↗
PubMedDate not supplied

Particulate matter, sulfur dioxide, and pulmonary function in never-smoking adults in Chongqing, China.

Chongquing is one of the most polluted cities in China. To study the respiratory health effects of air pollution for this city, the authors monitored the ambient levels of particulate matter (PM2.5) and sulfur dioxide (SO2) in urban and suburban areas and performed pulmonary function testing on 1,075 adults 35 to 60 years of age who had never smoked and did not use coal stoves for cooking or heating. The mean concentration of SO2 in the urban areas (213 micrograms/m3) was twice as high as that in suburban areas (103 micrograms/m3). Mean PM2.5 levels were high in both urban (143 micrograms/m3) and suburban (139 micrograms/m3) areas. A generalized additive model was used to estimate the differences between the two areas in FEV1, FVC, and FEV1/FVC%, with adjustment for potential confounding factors, including sex, age, height, education, passive smoking, and occupational exposures to dust, gas, or fumes. Estimated differences in FEV1 between the urban and suburban areas were 199 mL (SE = 50 mL) for men and 87 mL (SE = 30 mL) for women, both statistically significant. When the men and women were pooled, the estimated difference in FEV1 was 126 mL (SE = 27 mL). Similar trends were observed for FVC and FEV1/FVC%. After exclusion of 104 subjects with histories of occupational exposures to dust, gas, or fumes, the estimated difference was some-what smaller than that of the total samples. However, the effects on FEV1 and FEV1/FVC% remained significant for both men and women.

Adult↗
PubMedDate not supplied

Immunohistochemical study of Muc1, Muc2 and human gastric mucin in breast carcinoma: relationship with prognostic factors.

We investigated the expression of mucin core proteins, Muc1, Muc2, and human gastric mucin (HGM) immunohistochemically in 5 non-invasive, 62 invasive ductal carcinomas and 3 mucinous carcinomas of the breast and statistically examined the relationship with prognostic factors. Muc1 was expressed in almost all breast carcinomas and there was a reverse correlation with tumor size (r = -0.25). However, Muc1 was not significantly correlated with the other tumor characteristics such as lymphocytic infiltration, axillary lymph node metastasis, TNM and plasma levels of CA153. Muc2 and HGM were expressed in 5 cases each in invasive ductal carcinomas, 0 and 3 in non-invasive ductal carcinomas, and 2 and 1 in mucinous carcinomas, respectively. Muc 2 expression correlated with lymph node metastasis. HGM was found in the tumors without lymph node metastasis and lower levels of serum CA153.

Adenocarcinoma, Mucinous↗
PubMedDate not supplied

The role and clinical applications of bioactive lysolipids in ovarian cancer.

OBJECTIVE: To review the current understanding of the role of bioactive lysolipids in ovarian cancer and their potential clinical applications. METHODS: A MEDLINE search and our own work, including some unpublished work, are the major sources of the review. The MEDLINE search terms used included lysophosphatidic acid, lysophophatidylcholine (LPC), lysophosphatidylinositol (LPI), sphingosine-1-phosphate, and sphingosylphosphorylcholine (SPC). RESULTS: Elevated lysolipid levels were detected in plasma and ascites samples from patients with ovarian cancer compared with samples from healthy controls or patients with nonmalignant diseases. These lysolipids regulate growth adhesion, production of angiogenic factors, and chemotherapeutic drug resistance in ovarian cancer cells. Ovarian cancer cells were likely to be at least one of the sources for elevated lysolipid levels in the blood and ascites of patients with ovarian cancer. CONCLUSIONS: Bioactive lysolipid levels might be sensitive markers for detecting gynecologic cancers, particularly ovarian cancer. The prognostic value of lysolipids in ascites is worth further investigation. Bioactive lysolipid molecules can affect both the proliferative and metastatic potentials of ovarian cancer cells; therefore, regulation of the production or degradation of these lipids and interception of the interaction between these lipids and their receptors could provide novel and useful preventative or therapeutic measures.

Cell Adhesion↗