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Biomedical subjects

X E Zhang

Publications and source records attributed to X E Zhang.

15 recordsLinked to original sources
PubMed2006

Morphologies of fibroblast cells cultured on surfaces of PHB films implanted by hydroxyl ions.

Polyhydroxybutyrate (PHB) films were implanted with 40 keV hydroxyl ions with fluences ranging from 1 x 10(12) to 1 x 10(15) ions/cm2, respectively. The as-implanted PHB films were characterized by scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA) and water contact angle measurements. The surface structures and properties of the as-implanted PHB films were closely related with hydroxyl ion fluence. They were further investigated by inoculating 3T6 fibroblasts cells on their surfaces. Morphologies of the 3T6 fibroblast cells cultured on surfaces of the as-implanted PHB films were observed by SEM. Characterization of the cultural 3T6 cells was analyzed qualitatively. The preliminary experimental results reveal that the bioactivity of the PHB films modified by hydroxyl ion implantation was improved at different levels, and the fluence of 1 x 10(13) ions/cm2 is optimal for PHB film.

Animals↗
PubMed2001

Role integration and perceived health in Asian American women caregivers.

In this study, role involvement, role integration (including role stress and role satisfaction), and perceived health were examined in 50 Asian American women who were caregivers of aging parents in addition to being wives, mothers, and employees. Their mean age was 47.8 years. Twenty-nine of the participants were Chinese and 21 Filipino, with an average length of caregiving for each group of 11 years. All participants were born outside the United States. Instruments used in the study were translated and back-translated into Chinese and Tagalog and tested for validity and reliability. The association of role involvement, role integration, role stress, and role satisfaction with perceived physical and psychological health in the combined and separate groups was examined. Role involvement was not associated with health in the combined group of caregivers but was associated with overall health in the sample of Chinese women. Role integration was positively associated with all three perceived health measures in the Filipino group but not in the Chinese group. Role satisfaction was consistently high in both groups. Role satisfaction and psychological well-being were significantly correlated for the combined group and for the Filipino caregivers. Total role stress was significantly correlated with overall health and current health only in the combined group. Thus, support that helps to decrease role stress and to increase role satisfaction may be more effective than efforts to decrease the extent of role involvement.

Acculturation↗
PubMed2001

[Cloning and expression of Aspergillus niger glucose oxidase gene in methylotrophic yeast].

The DNA fragment encoding A. niger glucose oxidase was amplified by PCR using A. niger genomic DNA as template, and was cloned into vector of pPIC9 for expression in Pichia pastoris. When transformed into methylotrophic yeast Pichia pastoris GS115, The constructed plasmid pPICGOD1 directed the synthesis and secretion of functionally active GOD. After induction in MM medium for 4 days, the GOD activity in the medium reached 30-40 u/mL. SDS-PAGE revealed that recombinant yeast GOD was expressed up to 60%-70% of the total soluble protein, and the secreted GOD could be purified to electrophoretic homogeneity with one purification step using Q Sepharose Fast Flow ion exchange chromatography. The recombinant yeast GOD had very high catalytic activity, showed about 1.6-fold increase of specific activity over the commercial A. niger GOD. Kinetic analysis clearly demonstrated that recombinant yeast GOD showed similar substrate affinity for glucose to A. niger GOD, but the turnover number of the GOD from yeast was determined to be much higher than that of A. niger GOD. In addition, the linear range of glucose electrode made with recombinant yeast GOD was efficiently widened due to the high catalytic activity of yeast GOD.

Aspergillus niger↗
PubMed1999

Orthognathic surgery correction of mandibular hypoplasia accompanying obstructive sleep apnea syndrome.

OBJECTIVE: To examine the surgical correction methods for treating cases of severe mandibular hypoplasia accompanying obstructive sleep apnea syndrome (OSAS). METHODS: Sixteen cases of severe mandibular hypoplasia were studied in which OSAS was documented by polysomnography (PSG) and cephalometric study. The obstructive site was at the base of the tongue. Surgical procedures such as temporomandibular joint (TMJ) reconstruction and bimaxillary, chin, and hyoid bone advancement were performed to improve each patient's profile, function, and occlusion, and to treat the OSAS. RESULTS: There were great improvements in patient's sleep and daytime quality of life. The pre- and postoperative changes of most PSG values and some cephalometric values (SNB, PAS) were statistically significant. CONCLUSIONS: Severe mandibular hypoplasia can cause not only abnormalities in profile and occlusion but also OSAS. The evaluation of OSAS and its treatment effects depend on PSG. It is also very important to confirm the obstructive site in the upper airway by cephalometric study and fiberoptic endoscopy. Orthognathic surgery procedures can advance the maxillary, chin, and hyoid bone, and expand the upper airway simultaneously. These procedures can treat OSAS. Cases of TMJ ankylosis with OSAS should be treated step by step.

Adolescent↗
PubMed1998

DNA optical sensor: a rapid method for the detection of DNA hybridization.

A DNA optical sensor system is proposed based on the combination of sandwich solution hybridization, magnetic bead capture, flow injection and chemiluminescence for rapid detection of DNA hybridization. Bacterial alkaline phosphatase (phoA) gene and Hepatitis B virus (HBV) DNA were used as target DNA. A biotinylated DNA probe was used to capture the target gene onto the streptavidin-coated magnetic beads and a calf intestine alkaline phosphatase (CAP)-labelled DNA probe was used for subsequent enzymatic chemiluminescence detection. The detection cycle was less than 30 min, excluding the DNA hybridization time, which was about 100 min. Both the phoA gene and HBV DNA could be detected at picogramme or femtomole level. No response signal was obtained when target DNA did not exist in the sample. Successive sample detection could be made by removing the magnetic field and a washing step.

Biosensing Techniques↗
PubMed1998

Simultaneous determination of maltose and glucose using a screen-printed electrode system.

A screen-printed sensor system consisting of a glucose oxidase (GOD) electrode and an amyloglucosidase/glucose oxidase (A/G) electrode was constructed to determine maltose and glucose simultaneously in a mixture. Sensor construction was optimised so that it contained 20 units of GOD/40 units of amyloglucosidase and 0.2 mM 1,1'-ferrocenedimethanol. These components were deposited onto a screen-printed carbon electrode and an outer membrane was printed from 3.5% hydroxyethyl cellulose (HEC) solution. The optimum pH was 4.8. The linear range of the system was up to 40 mM glucose or 20 mmol/L maltose with coefficients of variation (CVs) ranging from 3.5% to 5.29%. The results obtained by using the enzyme electrode system agreed well with those obtained by the Fehling titration method. When stored dry, especially at 4 degrees C, the enzyme electrodes showed good stability over four months.

Biosensing Techniques↗
PubMed1992

[Acute and chronic hypotensive effect of m-nifedipine].

Three groups of adult stroke--prone spontaneously hypertensive rats (SHRsp) were treated with m-nifedipine (m-Nif) 2.5, 5 and 10 mg.kg-1 by intraperitoneal injection. The systolic blood pressure (SBp) decreased significantly. The hypotensive effect persisted for 2-4, 6-8, and 12 h respectively and the peak effect appeared in 1 h. The range of hypotension was markedly greater than that of nifedipine (Nif). In SHPsp, treatment with m-Nif 10 or 30 mg.kg-1.d-1 for 4 weeks reduced significantly the SBp, but the hypotensive action is about the same as Nif.

Animals↗
PubMed1989

Calcium antagonists in prevention of hypertension and stroke in stroke-prone spontaneously hypertensive rats.

To investigate the effect of Calcium antagonists (Ca-An) with different tissue specificity in the development of hypertension and stroke in salt-loading SHRSP, three experiments were conducted. In experiment I (1), 50 8-week-old male SHRSP were divided into three groups and given nifedipine (NF, 32 mg/kg/day), menidipine (MN 32 mg/kg/day) and placebo (control group) respectively. In the control group 83.3% (15/18) died of stroke and 17 showed renal vascular sclerosis. Their average lifespan was 84 days. NF and MN significantly reduced systolic blood pressure (SBP), and no stroke of renal vascular sclerosis developed. In experiment I (2), 54 7-week-old male SHRSP were divided into three groups (18 in each group). They were treated with nimodipine (NM) 20 mg/kg/day, 2 mg/kg/day and placebo respectively. NM (20 mg/kg/day) markedly lowered SBP and postponed the onset of stroke. Only 11% died in 17 weeks. NM (2 mg/kg/day did not lower SBP but postpond the onset of stroke. In experiment II (1), 29 10-week-old female SHRSP were divided into three groups: Group A was given NF 32 mg/kg/day, group B was parathyroidectomized (PTX) and group C served as control. PTX group did not lower SBP but could postpone the onset of stroke. In experiment II (2), 33 male SHRSP were divided into three groups and ticated as described above in experiment II (1) (11 in each group). Seven weeks after the experiment, the brain blood flow of NF group was significantly greater (67.5%) than that of the control and PTX groups. In experiment III, 27 7-week-old male SHRSP were divided into three groups as described above in experiment I (2).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Anchor-chain molecular system for orientation control in enzyme immobilization.

An anchor-chain molecular system was constructed for controlled orientation and high activity in enzyme immobilization. A streptavidin recognition peptide (streptag) coding sequence was fused to the 3' end of the phoA gene, which codes for E. coli alkaline phosphatase (EAP). Both the wild-type (WT) and the Asp-101 --> Ser (D1O1S) mutant were modified with the streptag sequence with or without the insertion of a flexible linker peptide [-(Gly-Ser)(5)-] coding sequence. The fused genes were cloned into the vector pASK75 and expressed in the periplasm of the host cell Escherichia coli SM547. The proteins were released by osmotic shock and purified by ion-exchange chromatography. Enzyme activities of all proteins were measured spectrophotometrically with rho-nitrophenyl phosphate as the substrate. Specific activities of D101S-streptag and D101S-linker-streptag enzymes were increased 25- or 34-fold over the WT, respectively. These fusion proteins were then immobilized on microtiter plates through streptag-streptavidin binding reaction. After immobilization, the D101S-linker-streptag enzyme displayed the highest residual activity and the ratio of enzyme activities of the linker to nonlinker enzymes was 8.4. These results show that the addition of a linker peptide provides a spacer so as to minimize steric hindrance between the enzyme and streptavidin. The method provides a solution for controlled enzyme immobilization with high recover activity, which is especially important in construction of biosensors, biochips, or other biodevices.

Amino Acid Sequence↗
PubMedDate not supplied

Construction of a fusion enzyme system by gene splicing as a new molecular recognition element for a sequence biosensor.

A bifunctional fusion enzyme system constructed by gene splicing is proposed as a new model to develop sequence biosensors, taking maltose biosensor as an example. The cDNA fragment of Aspergillus niger glucoamylase (E.C 3.2.1.3, GA) was fused to the 3' end of Aspergillus niger glucose oxidase (E.C 1.1.3.4, GOD) gene with the insertion of a flexible linker peptide [-(Ser-Gly)5-] coding sequence. The fusion gene was cloned into the vector pPIC9 and expressed in Pichia pastoris GS115 under the control of the AOX1 promoter. It was found that a bifunctional hybrid protein with a molecular weight of 430 kDa was secreted after induction with methanol. The fusion enzyme GOD-(Ser-Gly)5-GA (GLG) was purified using Q Sepharose Fast Flow ion-exchange chromatography. Kinetic analysis demonstrated that GLG retained the typical kinetic properties of both GA and GOD. After being immobilized on an aminosilanized glass slide through covalent bonding by glutaraldehyde, GLG showed much higher sequential catalytic efficiency than the mixture of separately expressed GA and GOD (GA/GOD). Maltose biosensors were fabricated with GLG and GA/GOD, respectively. The performance characteristics of the maltose biosensor with respect to reproducibility, signal level, and linearity were effectively improved by using the fusion enzyme. Our findings offer a basis for the development of other sequence biosensors.

Artificial Gene Fusion↗
PubMedDate not supplied

An adaptation of Brislin's translation model for cross-cultural research.

BACKGROUND: The number of nurse scientists pursuing cross-cultural research using quantitative designs is increasing. Preparation of instruments that are conceptually and functionally appropriate in the language of the participants is a complex process that needs examination. OBJECTIVES: Brislin's classic model for translation and validation of instruments for cross-cultural research is critiqued. Adaptations and extensions of that model are recommended. METHODS: Brislin's model guided tool preparation in a cross-cultural investigation. The process is described and lessons learned are outlined and discussed. CONCLUSIONS: Steps toward a more efficient and valid approach to the preparation of instruments are suggested.

Asian↗