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Biomedical subjects

Ying Xiao

Publications and source records attributed to Ying Xiao.

At least 37 records · Page 2Linked to original sources
PubMed2004

The effect of sterol regulatory element-binding protein 2 polymorphism on the serum lipid in northern Chinese subjects.

Sterol regulatory element-binding protein 2 (SREBP-2) is an important nuclear transcription factor in the regulation of cellular cholesterol metabolism. To determine allele frequency of the 1784G>C polymorphism at the SREBP-2 locus and investigate the relationship between this polymorphism and serum lipid levels in Chinese people, we selected 486 individuals (118 men and 368 women) from the Xicheng District of Beijing. The subjects were divided into four groups: hypercholesterolemic subjects, hypertriglyceridemic subjects, combined hyperlipidemic subjects, and normal subjects. Serum lipid profiles were measured in all subjects, and 1784G>C was analyzed using polymerase chain reaction-restriction fragment length polymorphism analysis. There was no significant difference in genotype frequencies or allele frequencies of this polymorphism between the hyperlipidemic and control groups. The serum total cholesterol (TC) and LDL cholesterol (LDL-C) levels of the individuals carrying the C allele were higher than the noncarriers in both males and females in the hypercholesterolemic group, but statistical significance was only observed in females. The results of this study indicate that the SREBP-2 polymorphism is related to elevated concentrations of serum TC and LDL-C in hypercholesterolemic subjects. Further work is necessary to confirm the role of 1784G>C in the development of hyperlipidemia.

Adult↗
PubMed2004

Induction of cell-cycle arrest by all-trans retinoic acid in mouse embryonic palatal mesenchymal (MEPM) cells.

all-trans retinoic acid (atRA), the oxidative metabolite of vitamin A, is essential for normal embryonic development. Also, high levels of atRA are teratogenic in many species and can effectively induce cleft palate in the mouse. Most cleft palate resulted from the failed fusion of secondary palate shelves, and maintenance of the normal cell proliferation is important in this process of shelf growth. To clarify the mechanism by which atRA causes cleft palate, we investigated the effect of atRA on proliferation activity and cell cycle distribution in mouse embryonic palatal mesenchymal (MEPM) cells. atRA inhibited the growth of MEPM cells by inducing apoptosis in a dose-dependent manner. atRA also caused a G1 block in the cell cycle with an increase in the proportion of cells in G0/G1 and a decrease in the proportion of cells in S phase, as determined by flow cytometry. We next investigated the effects of atRA on molecules that regulate the G1 to S phase transition. These studies demonstrated that atRA inhibited expression of cyclins D and E at the protein level. Furthermore, atRA treatment reduced phosphorylated Rb and decreased cdk2 and cdk4 kinase activity. These data suggest that atRA had antiproliferative activity by modulating G1/S cell cycle regulators and by inhibition of Rb phosphorylation in MEPM cells, which might account for the pathogenesis of cleft palate induced by retinoic acid.

Animals↗
PubMed2004

Inherent smoothness of intensity patterns for intensity modulated radiation therapy generated by simultaneous projection algorithms.

The efficient delivery of intensity modulated radiation therapy (IMRT) depends on finding optimized beam intensity patterns that produce dose distributions, which meet given constraints for the tumour as well as any critical organs to be spared. Many optimization algorithms that are used for beamlet-based inverse planning are susceptible to large variations of neighbouring intensities. Accurately delivering an intensity pattern with a large number of extrema can prove impossible given the mechanical limitations of standard multileaf collimator (MLC) delivery systems. In this study, we apply Cimmino's simultaneous projection algorithm to the beamlet-based inverse planning problem, modelled mathematically as a system of linear inequalities. We show that using this method allows us to arrive at a smoother intensity pattern. Including nonlinear terms in the simultaneous projection algorithm to deal with dose-volume histogram (DVH) constraints does not compromise this property from our experimental observation. The smoothness properties are compared with those from other optimization algorithms which include simulated annealing and the gradient descent method. The simultaneous property of these algorithms is ideally suited to parallel computing technologies.

Algorithms↗
PubMed2004

Identification of a new chloroplast carbonic anhydrase in Chlamydomonas reinhardtii.

Carbonic anhydrases (CA) are zinc-containing metalloenzymes that catalyze the reversible hydration of CO2. The three evolutionarily unrelated families of CAs are designated alpha-, beta-, and gamma-CA. Aquatic photosynthetic organisms have evolved different forms of CO2 concentrating mechanisms (CCMs) to aid Rubisco in capturing CO2 from the surrounding environment. One aspect of all CCMs is the critical roles played by various specially localized extracellular and intracellular CAs. Five CAs have previously been identified in Chlamydomonas reinhardtii, a green alga with a well-studied CCM. Here we identify a sixth gene encoding a beta-type CA. This new beta-CA, designated Cah6, is distinct from the two mitochondrial beta-CAs in C. reinhardtii. Nucleotide sequence data show that the Cah6 cDNA contains an open reading frame encoding a polypeptide of 264 amino acids with a leader sequence likely targeting the protein to the chloroplast stroma. We have fused the Cah6 open reading frame to the coding sequence of maltose-binding protein in a pMal expression vector. The purified recombinant fusion protein is active and was used to partially characterize the Cah6 protein. The purified recombinant fusion protein was cleaved with protease Factor Xa to separate Cah6 from the maltose-binding protein and the purified Cah6 protein was used to raise an antibody. Western blots, immunolocalization studies, and northern blots collectively indicated that Cah6 is constitutively expressed in the stroma of chloroplasts. A possible role for Cah6 in the CCM of C. reinhardtii is proposed.

Amino Acid Sequence↗
PubMed2004

The dose-volume constraint satisfaction problem for inverse treatment planning with field segments.

The prescribed goals of radiation treatment planning are often expressed in terms of dose-volume constraints. We present a novel formulation of a dose-volume constraint satisfaction search for the discretized radiation therapy model. This approach does not rely on any explicit cost function. Inverse treatment planning uses the aperture-based approach with predefined, according to geometric rules, segmental fields. The solver utilizes the simultaneous version of the cyclic subgradient projection algorithm. This is a deterministic iterative method designed for solving the convex feasibility problems. A prescription is expressed with the set of inequalities imposed on the dose at the voxel resolution. Additional constraint functions control the compliance with selected points of the expected cumulative dose-volume histograms. The performance of this method is tested on prostate and head-and-neck cases. The relationships with other models and algorithms of similar conceptual origin are discussed. The demonstrated advantages of the method are: the equivalence of the algorithmic and prescription parameters, the intuitive setup of free parameters, and the improved speed of the method as compared to similar iterative as well as other techniques. The technique reported here will deliver approximate solutions for inconsistent prescriptions.

Algorithms↗
PubMed2004

Comparison of three IMRT inverse planning techniques that allow for partial esophagus sparing in patients receiving thoracic radiation therapy for lung cancer.

The purpose of this study is to compare 3 intensity-modulated radiation therapy (IMRT) inverse treatment planning techniques as applied to locally-advanced lung cancer. This study evaluates whether sufficient radiotherapy (RT) dose is given for durable control of tumors while sparing a portion of the esophagus, and whether large number of segments and monitor units are required. We selected 5 cases of locally-advanced lung cancer with large central tumor, abutting the esophagus. To ensure that no more than half of the esophagus circumference at any level received the specified dose limit, it was divided into disk-like sections and dose limits were imposed on each. Two sets of dose objectives were specified for tumor and other critical structures for standard dose RT and for dose escalation RT. Plans were generated using an aperture-based inverse planning (ABIP) technique with the Cimmino algorithm for optimization. Beamlet-based inverse treatment planning was carried out with a commercial simulated annealing package (CORVUS) and with an in-house system that used the Cimmino projection algorithm (CIMM). For 3 of the 5 cases, results met all of the constraints from the 3 techniques for the 2 sets of dose objectives. The CORVUS system without delivery efficiency consideration required the most segments and monitor units. The CIMM system reduced the number while the ABIP techniques showed a further reduction, although for one of the cases, a solution was not readily obtained using the ABIP technique for dose escalation objectives.

Esophagus↗
PubMed2004

Output ratio in air for MLC shaped irregular fields.

For accurate monitor unit calculation, it is important to calculate the output ratio in air, Sc, for an irregular field shaped by MLC. We have developed an algorithm to calculate Sc based on an empirical model [Med. Phys. 28, 925-937 (2001)] by projecting each leaf position to the isocenter plane. Thus it does not require the exact knowledge of the head geometry. Comparisons were made for three different types of MLC: those with MLC replacing the inner collimator jaws; those with MLC replacing the outer collimator jaws; and those with MLC as a tertiary attachment. When the MLC leaf positions are substantially different from the secondary collimators (or the rectangular field encompassing the irregular field), one observes an up to 5% difference in the value of head-scatter correction factor, HCF, defined as the ratio of output ratio in air between the MLC shaped irregular field and that of the rectangular field encompassing the irregular field. No collimator exchange effect was observed for rectangular fields shaped by MLC (e.g., 5x30 and 30x5 cm2 diagonal) when the secondary collimators are fixed, unlike that for the rectangular fields shaped by the inner and outer collimator jaws, where it can be 1-2%. For the same MLC shaped irregular field, the value of Sc increases from the Elekta, to the Siemens, to the Varian accelerators, with an up to 4% difference. The calculation agrees with measurement to within 1.2% for points both on and off the central-axis. The fitting parameters used in the algorithm are derived from measurements for square field sizes on the central-axis.

Algorithms↗
PubMed2004

Two novel dicoumaro-p-menthanes from Gerbera piloselloides (L.) CASS.

Two new type dicoumarins (dicoumaro-p-menthanes), named dibothrioclinins I (1) and II (2) were isolated from the roots and rhizomes of Gerbera piloselloides (L.) CASS., collected in Yunnan Province, China. Their structures were elucidated on the basis of MS, 1D ((1)H-NMR, (13)C-NMR, DEPT and NOE) and 2D ((1)H-(1)H COSY, HMQC, HMBC) NMR spectral analyses. The relative structures of the two compounds were established by NOE difference spectroscopy and further confirmed by single-crystal X-ray diffraction studies.

Asteraceae↗
PubMed2004

[Identification of differentially expressed genes involved in multidrug resistance in K562/A02 by cDNA microarray].

OBJECTIVE: To study the molecular mechanism underlying multidrug resistance (MDR) and identify unknown genes that might be involved in drug resistance development in K562/A02 cells. METHODS: K562/A02 was induced by gradually increasing the ADM concentration in culture medium of K562 cells, the differential expression of associated genes between K562 and K562/A02 was determined with cDNA microarray. Overexpression of neurofilament protein NF-H gene in K562/A02 cells was confirmed with RT-PCR and immunocytochemistry. Anti-sense oligodeoxynucleotides were transfected into K562/A02 cells by lipofectamine in order to further analyze the role of NF-H in drug resistance. RESULTS: Comparing with the expression profiles, we found upregulation of 5 transcripts and downregulation of 7 transcripts in response to MDR of K562/A02 cells. The overexpression of NF-H, one of the 5 upregulated genes, was confirmed. After being treated with antisense oligodeoxynucleotides of NF-H and mdr1, the cellular adriamycin concentration increased significantly, but antisense NF-H alone did not have significant effect on drug resistance phenotype. CONCLUSION: The development of MDR in K562/A02 cells is multifactorial. NF-H may be involved in the drug resistance of K562/A02, which may provide a new marker of diagnosis and a new target of therapy.

Doxorubicin↗
PubMed2003

Dibothrioclinin I and II, epimers from Gerbera piloselloides (L.) Cass.

Dibothrioclinin I and II, namely (+)-(11R,12S,25R,27S)- and (+/-)-(11RS,12RS,25RS,27SR)-3,3,7,17,21-pentamethyl-4,12,18,26-tetraoxaheptacyclo[15.11.1.0(2,15).0(5,14).0(6,11).0(19,28).0(20,25)]nonacosa-5(14),6,8,10,19(28),20,22,24-octaene-13,27-dione, respectively, are C(30)H(28)O(6) epimers which are derived from two bothrioclinin moieties joined so as to create an additional six-membered ring. Structurally, the epimers differ only by inversion at one C atom of a central ring junction and the corresponding six-membered rings have similar conformations in each molecule, except for one ring adjacent to this inversion site.

Asteraceae↗
PubMed2003

Guidance document on delivery, treatment planning, and clinical implementation of IMRT: report of the IMRT Subcommittee of the AAPM Radiation Therapy Committee.

Intensity-modulated radiation therapy (IMRT) represents one of the most significant technical advances in radiation therapy since the advent of the medical linear accelerator. It allows the clinical implementation of highly conformal nonconvex dose distributions. This complex but promising treatment modality is rapidly proliferating in both academic and community practice settings. However, these advances do not come without a risk. IMRT is not just an add-on to the current radiation therapy process; it represents a new paradigm that requires the knowledge of multimodality imaging, setup uncertainties and internal organ motion, tumor control probabilities, normal tissue complication probabilities, three-dimensional (3-D) dose calculation and optimization, and dynamic beam delivery of nonuniform beam intensities. Therefore, the purpose of this report is to guide and assist the clinical medical physicist in developing and implementing a viable and safe IMRT program. The scope of the IMRT program is quite broad, encompassing multileaf-collimator-based IMRT delivery systems, goal-based inverse treatment planning, and clinical implementation of IMRT with patient-specific quality assurance. This report, while not prescribing specific procedures, provides the framework and guidance to allow clinical radiation oncology physicists to make judicious decisions in implementing a safe and efficient IMRT program in their clinics.

Algorithms↗
PubMed2003

[Prevalence of hypertension and the relationship between dietary pattern and hypertension in rural middle-aged and elderly in HeNan Province].

6186 subjects (age > or = 40) from a cross sectional study named Dietary, Life Style and Chronic Diseases cooperated by Chinese Academy of Preventive Medicine and BioSignia Inc. in 1997 were included in this analysis. The prevalence rate of hypertension and the dietary intakes were analyzed. The results showed that the prevalence rate was 44.8% in the corresponding, which were obviously increased compared with the results in 1991, and were higher than other areas in this same period in China. The dietary pattern was obviously unreasonable in this population. The prevalence rate of hypertension was higher in the population who eat less vegetable, fruit, fishes or eat more salted vegetable. And the results indicated that improving dietary pattern may be an inexpensive and effective way to prevent hypertension and to promote people's health in rural area.

Aged↗
PubMed2003

[Effect of nuts enrich in monounsaturated acid on serum lipid of hyperlipidemia rats].

In order to observe the regulatory effect of monounsaturated acid-enriched almond and macadamia nuts on blood lipid-level (TC, TG, HDL-C), the hyperlipidemia Wistar rats were used as the model and a diet containing almond and macadamia at the doses of between 12.5% and 25.0% was given for six weeks. The results showed that the level of the serum TC and TG in each study group was significantly lower than that of high fat chow control group (P < 0.05). There was a significant increase (P < 0.05) in the serum HDL-C level in the high fat chow group with high-dose macadamias compared with that in the high fat chow control group. The findings suggested that nuts enrich in monounsaturated acid could decrease the level of serum TC and TG and macadamias could increased the level of serum HDL-C in the hyperlipidemia rats.

Animals↗
PubMed2003

Effects of dietary intervention on hyperlipidemia in eight communities of Beijing, China.

OBJECTIVE: To examine the effect of community-based dietary intervention on hyperlipidemia. METHODS: A total of 180 hyperlipidemia individuals with TG>2.26 mmol x L(-1) (200 mg x dL(-1)) and/or TC>5.72 mmol x L(-1) (220 mg x dL(-1)) were selected from 428 eligible subjects in eight communities of Beijing. They were randomly divided into intervention group (n=108) and control group (n=72). Dietary intervention was provided for the intervention group for 6 months. Information on dietary intakes, physical examinations and blood samples was collected. Serum lipids were assayed at baseline and endpoint of the study period. RESULTS: Respective decrease in dietary intake of total calories, fat, cholesterol and cooking oil by 13.62%, 24.75%, 24.40%, and 22.43%, in the intervention group was observed. The percentages of total calories from fat, carbohydrate and protein appeared to be desirable after study. Reduced body weight and BMI were also observed. There was a respective 5.61% and 7.06% decrease in total serum cholesterol and low-density lipoprotein cholesterol in the intervention group, while no significant changes were found in the control group. CONCLUSIONS: Community-based dietary intervention can effectively improve dietary patterns, control body weight, and decrease the levels of total serum cholesterol and low-density lipoprotein cholesterol.

Adult↗
PubMed2003

[Study on the absorption, distribution and excretion of 3-chloro-1,2-propandiol in rats].

OBJECTIVE: To explore the absorption, distribution and excretion of 3-Chloro-1,2-propandiol (3-MCPD) in healthy male SD rats after oral administration. METHODS: 3-MCPD was administrated with a single oral dosage of 75 mg/kg BW to each rat. Samples of blood, tissues (including liver, kidney, brain and testicle) and excreta were then collected, and analyzed by the GC-MS method to determine 3-MCPD concentrations. The reported value is the mean value of three rats. RESULTS: At 2 h after the administration, 3-MCPD concentrations in blood, testicle and kidney were (67.46 +/- 7.72), (78.37 +/- 5.15) and (56.21 +/- 3.64) microg/g, respectively. At 24 h, however, the corresponding values changed to (1.07 +/- 0.97) microg/g, (49.43 +/- 28.18) microg/g and (11.41 +/- 2.55) microg/g. During the 24-hour period, 9.74 +/- 3.05% of the given parent compound was excreted in urine, whereas 0.56 +/- 0.22% and 0.28 +/- 0.03% were excreted in feces and bile, respectively, which implies that kidney is a major organ for excretion 3-MCPD. CONCLUSIONS: 3-MCPD was quickly absorbed through the alimentary tract and quickly distributed into a number of tissues, and then accumulated in the target organs, especially in the testicle. The excretion of the parent compound was largely through the kidney. It was inferred that 3-MCPD was mainly metabolized in the liver.

Absorption↗
PubMed2002

The use of mixed-integer programming for inverse treatment planning with pre-defined field segments.

Complex intensity patterns generated by traditional beamlet-based inverse treatment plans are often very difficult to deliver. In the approach presented in this work the intensity maps are controlled by pre-defining field segments to be used for dose optimization. A set of simple rules was used to define a pool of allowable delivery segments and the mixed-integer programming (MIP) method was used to optimize segment weights. The optimization problem was formulated by combining real variables describing segment, weights with a set of binary variables, used to enumerate voxels in targets and critical structures. The MIP method was compared to the previously used Cimmino projection algorithm. The field segmentation approach was compared to an inverse planning system with a traditional beamlet-based beam intensity optimization. In four complex cases of oropharyngeal cancer the segmental inverse planning produced treatment plans, which competed with traditional beamlet-based IMRT plans. The mixed-integer programming provided mechanism for imposition of dose-volume constraints and allowed for identification of the optimal solution for feasible problems. Additional advantages of the segmental technique presented here are: simplified dosimetry, quality assurance and treatment delivery.

Algorithms↗
PubMed2002

Comparison of characteristics of photon and electron beams generated by Philips/Elekta and Varian linear accelerators.

Commissioning data of the common energy of 6 MV photon beams are analyzed for seven Philips/ Elekta linacs of five different models: SL 75/5, SL 15, SL 25, SLi Precise, and SLi. The observed beam quality %dd(10)x of 67.7% +/- 0.3 agrees with the manufacturer's specification of 67.5% +/- 2% but with a much smaller variation, suggesting the possibility of a more accurate beam quality guideline for acceptance commissioning of these linac models. Field size factors are less uniform, especially for the biggest field size of 40 x 40 cm2, but all agree within 1.1% between the five models. These 6 MV photon beams are also shown to be 0.4 MV harder than the Varian 2100C model. For commissioning electron beams generated by the Philips/Elekta models SL 15, SLi Precise and SLi, guidelines can be found from this work for the following parameters: actual field size at 100 SSD (up to +/- 0.6%) (different from manufacturer specified values at 95 SSD), and virtual source distance (up to +/- 0.7%). Significant differences are seen for R50 (up to 3.7 mm), sigma-theta-x, effective source distance, and cone size factor. However, except for R50 where Varian 2100C datasets are not available for comparison, the differences between the different Philips/Elekta models are comparable to those between the same Varian 2100C model linacs measured by us and Watts.

Electrons↗