Biomedical subjects

Biao Zhang

Publications and source records attributed to Biao Zhang.

10 recordsLinked to original sources

PubMed2007

Smooth semiparametric receiver operating characteristic curves for continuous diagnostic tests.

We propose a semiparametric kernel distribution function estimator, based on which a new smooth semiparametric estimator of the receiver operating characteristic (ROC) curve is constructed. We derive the asymptotic bias and variance of the newly proposed distribution function estimator and show that it is more efficient than the traditional non-parametric kernel distribution estimator. We also derive the asymptotic bias and variance of our new ROC curve estimator and show that it is more efficient than the smooth non-parametric ROC curve estimator proposed by Zou et al. (Stat. Med. 1997; 16:2143-2156) and Lloyd (J. Am. Stat. Assoc. 1998; 93:1356-1364). For our proposed estimators, we derive data-based methods for bandwidth selection. In addition, we present some results on the analysis of two real data sets. Finally, a simulation study is presented to show that our estimators are better than the non-parametric counterparts in terms of bias, standard error, and mean-square error.

Area Under Curve↗

PubMed2006

F344 rat liver nonparenchymal cell transplantation can increase the number of albumin-positive hepatocytes in the liver following hematopoietic reconstitution in irradiated analbuminemic rats.

The adult liver contains hematopoietic stem cells that can reconstitute the bone marrow. We tested whether bone marrow cells (BMCs) derived from liver nonparenchymal cells (LNPCs) can increase the number of hepatocytes within livers. LNPCs from Fischer 344 rats (F344) were infused into the penile veins of F344 congenic Nagase's analbuminenic rats (F344alb) immediately after whole-body irradiation, and the recipients were sacrificed 8 weeks later. Eleven of 15 (73.3%) F344alb that received the LNPC transplantation after irradiation survived, while only 1 of 8 (12.5%) F344alb that received irradiation alone was alive after 8 weeks. Normal albumin gene sequences were detected by PCR in BMCs of the recipient F344alb that received LNPC transplantation after irradiation, indicating that F344alb bone marrow was reconstituted by F344 LNPCs. Although single or pairs of albumin-positive (Alb+) hepatocytes were seen in the liver of untreated F344alb and those with irradiation or LNPC transplantation alone, clusters consisting of >3 Alb+ hepatocytes were detected in the livers of F344alb with the LNPC or BMC transplantation after irradiation together with single or double Alb+ cells. Normal albumin gene sequences were detected by PCR in the DNA isolated from such Alb+ hepatocyte clusters microdissected from the immunostained sections. The data indicate that BMCs derived from F344 LNPCs could increase the number Alb+ hepatocytes within the F344alb liver.

Albumins↗

PubMed2006

A multi-needle-assisted transformation of soybean cotyledonary node cells.

A new and simple method for wounding cotyledonary node cells of soybean [Glycine max (L) Merrill] was developed for obtaining a high frequency of transformants. Soybean seeds were germinated for 1 day, and the cotyledonary node cells of half-seeds were wounded mechanically by using a multi-needle consisting of thin 30 fibers. The wounded half-seeds were inoculated with Agrobacterium tumefaciens cells harboring a recombinant DNA that contained the bar and sgfp genes conferring phosphinothricin (PPT)-resistance and green fluorescent protein (GFP) activity, respectively. The inoculated explants were selected on medium containing 5 or 3 mg PPT/l. The transformation efficiency of soybean was up to 12%. Polymerase chain reaction and genomic Southern blot analysis confirmed stable integration of the transgenes in the genome of the PPT-resistant plants. GFP analysis revealed that the transgenes were highly expressed in the plantlets. Adult plants were resistant to 100 mg PPT/l applied on the leaves, demonstrating their herbicide-resistance.

Cotyledon↗

PubMed2006

[Human inward rectifying potassium current and Kir2.1 mRNA expression in myocytes isolated from patients with chronic atrial fibrillation].

OBJECTIVE: To compare the changes of both inward rectifying K(+) (Kir) current(I(k1)) density and mRNA expression level of Kir2.1, a major subfamily of Kir in chronic human atrial fibrillation (CAF) with those in normal sinus rhythm (NSR). METHODS: I(k1) density was measured with whole-cell patch clamp technique in single myocyte isolated by an enzymatic dissociation method from right atrial appendages in patients with CAF (n = 8) and those with NSR (n = 12). The mRNA expression levels of Kir2.1 was determined in right atrial appendages from CAF (n = 19) and NSR (n = 18) by semiquantitative reverse-transcription polymerase chain reaction (RT-PCR). RESULT: The average resting membrane potentials were similar between CAF and NSR (-78.95 mV +/- 4.67 mV and -70.22 mV +/- 11.08 mV, P>0.05). I(k1) density in single myocyte significantly increased at hyperpolarized potential level (-100 mV) in CAF compared to that in NSR (-9.59 pA/pF +/- 2.47 pA/pF vs. -5.58 pA/pF +/- 2.52 pA/pF, P<0.01). The mRNA level of Kir2.1 was also significantly higher in CAF than that of NSR (0.50+/-0.16 vs. 0.34+/-0.09, P<0.05). CONCLUSION: The data suggest that Kir2.1 up-regulation and I(k1) current increase might contribute to the electrical remodeling in CAF patients.

Atrial Fibrillation↗

PubMed2006

[Human inward rectifying potassium current in myocytes isolated from patients with rheumatic atrial fibrillation].

OBJECTIVE: To compare the changes of inward rectifying K(+) (Kir) current (I(K1)) density in atrial myocytes of patients with rheumatic atrial fibrillation (RAF) less or longer than 6 months. METHOD: I(K1) density was measured with whole-cell patch clamp technique in single myocyte isolated by an enzymatic dissociation method from right atrial appendages in patients with RAF less than 6 months (n = 18) and longer than 6 months (n = 18), RAF patients with normal sinus rhythm (NSR, n = 18) served as control. RESULTS: The average resting membrane potentials were similar between various groups. I(K1) density in single myocyte at -50 to -100 mV of patients with RAF longer than 6 months was significantly increased compared to that in patients with RAF less than 6 months and NSR patients. I(K1) density in single myocyte at hyperpolarized potential level (-100 mV) was also significantly increased in patients with RAF longer than 6 months (8.94 +/- 0.15) than that in patients with RAF less than 6 months (4.35 +/- 0.49) and NSR patients compared to that in NSR (4.05 +/- 0.96, P < 0.05 vs RAF longer than 6 months). CONCLUSION: The data suggest I(K1) current increase might contribute to the electrical remodeling in RAF patients.

Adult↗

PubMed2005

[Heteroexpression of Rhizopus arrhizus delta6-fatty acid desaturase gene in Pichia pastoris].

Delta6-fatty acid desaturase is a membrane-bound enzyme, which is rate-limiting for the biosynthesis of polyunsaturated fatty acids. A cDNA sequence putatively encoding a delta6-fatty acid desaturase was isolated from Rhizopus arrhizus NK300037 using RT-PCR and RACE methods in our previous work. Sequence and function analysis indicated that this sequence was a novel delta6-fatty acid desaturase gene which had an open reading frame of 1377bp coding 458 amino acids of 52kD. The methylotrophic yeast Pichia pastoris, has been developed into a highly successful system for the production of a variety of heterologous proteins during the past 20 years. In this work, the Rhizopus arrhizus delta6-fatty acid desaturase gene (RAD6) was subcloned into expression vector pPIC3.5K to generate a recombinant plasmid pPICRAD6, which was subsequently transformed into Pichia pastoris strain GS115 for heterologous expression by electroporation method. Total fatty acids were extracted from the induced cells and methylated. The resultant fatty acid methyl esters (FAME) were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Fatty acids analysis showed that the coding product introduced a new double bond at delta6 position of appropriate fatty acid substrates including C16:1, C17:1, C18:1, linoleic acid and alpha-linolenic acid without chain length specificity of fatty acids. Furthermore, modification of sequence flanking AUG codon of this delta6-fatty acid desaturase gene increased the expression of target gene in P. pastoris. All of these results suggest that P. pastoris is an optimal expression system of delta6-fatty acid desaturase gene.

Cloning, Molecular↗

PubMed2004

Hydrothermal synthesis, crystal structure, conductivity, and thermal decomposition of [Cu(4,4'-bipy)(H2O)(Mo3O10)].H2O.

The hydrothermal reaction of (NH(4))(6)Mo(7)O(24).4H(2)O, CuCl(2).2H(2)O, and 4,4'-bipyridine yields bipyridine-ligated copper-trimolybdate monohydrate [Cu(4,4'-bipy)(H(2)O)(Mo(3)O(10))].H(2)O in the monoclinic system with space group of C(2/c) and cell parameters of a = 15.335(2) A, b = 15.535(2) A, c = 15.106(2) A, beta = 101.162(2) degrees, V = 3530.7(9) A(3), and Z = 8. Its structure consists of one-dimensional infinite ([Mo3O10]2-)( infinity ) chains linked through [Cu2(H2O)2(4,4'-bipy)] units. The Mo-O chain contains distorted [MoO(6)] octahedra connected through corner-sharing oxygen atoms into infinite chains along the c direction and each chain is located in the channel formed by four adjacent crossing chains of [Cu(4,4'-bipy)(H2O)](n)(2n+). The crystal shows weak conductivity through Mo-O chain along the c direction and insulating property along either a or b direction. Furthermore, a crystalline bimetallic oxide, CuMo3O10, forms when the title compound undergoes thermal treatment in N(2) atmosphere after the complete removal of the ligands.

Copper↗

PubMed2003

[Study on thermal treatment schedule of leucite microcrystallization to reinforce dental glass ceramics].

OBJECTIVE: To explore the thermal treatment schedule of leucite microcrystallization to reinforce dental glass ceramics. METHODS: After component analysis and selection, the raw material were treated by different temperature schedules. The products were analyzed by polaring microscope and X-ray diffractometer to determine the appropriate thermal treatment schedule. RESULTS: The temperature of melting, nuclearing and crystalizing was 1,600 degrees C, 1,200 degrees C and 1,500 degrees C. Leucite microcrystals dispersed in the glass matrix evenly and the size of leucite particle was about 0.8 micro m. CONCLUSION: Leucite can be microcrystalized according to an appropriate thermal treatment schedule.

Aluminum Silicates↗

PubMed2002

Study on some mechanism of leucite microcrystallization to reinforce dental glass ceramics.

OBJECTIVE: To research the influence of K(2)O composition in the raw material on leucite microcrystallization and to study the effect of leucite content on compressive strength of the dental glass ceramics reinforced by leucite microcrystallization. METHODS: The raw materials with different K(2)O content were treated by a decided thermal treatment system. The products were analyzed by polaring microscope and X-ray diffractometer, and their compressive strength was also tested. RESULTS: The microstructure of products from high K(2)O component was remarkably good, at microcrystal size of 0.8 micro m and the compressive strength was 206.6 MPa. A positive correlation was found between leucite volume and the compressive strength when leucite volume was less than 50% (Vol%). CONCLUSIONS: The component of K(2)O has a great effect on the microstructure and the properties of the leucite-microcrystal-reinforced dental glass ceramics and the content of leucite microcrystals has a notable influence on the compressive strength of the dental glass ceramics.

Compressive Strength↗

PubMed2002

[Study on influencing factors of the by-product CHCl3 produced in the electrochemical sterilization process].

OBJECTIVE: To gain an understanding of the progressive course and influencing factors of the by-product CHCl3 produced in the electrochemical sterilization process. METHODS: Taking filtering water, using graphite and Ti(matrix)-Ti as electrodes, adding different concentrations of SO4(2-) and Cl- in the filtering water, adjusting the electric current for analyzing sample in different times, and reviewing the production of CHCl3 under different conditions. RESULTS: The quantity of CHCl3 produced in the electrolysis using Ti (matrix)-Ti was greater than that using graphite. Besides, it was found that the more the current density increased, the more would be the production of CHCl3. No significant difference in the quantity of CHCl3 was seen after the addition of trace electrolyte Na2SO4; however, after the addition of trace electrolyte NaCl, (CHCl3) increased with the increase of (Cl-). CONCLUSION: The graphite electrode should be the best and choicest electrode for use in the electrochemical sterilization of drinking water; the time of electrolysis should not be more than 10 minutes; the appropriate current density current is 1 mA/cm2. These suggestions may conduce to minimizing the production of CHCl3.

Chloroform↗