Biomedical subjects

Z Q Chen

Publications and source records attributed to Z Q Chen.

At least 19 recordsLinked to original sources

PubMed2001

Ion-beam-sputtering/mixing deposition of calcium phosphate coatings. I. Effects of ion-mixing beams.

Ion-beam-sputtering/mixing deposition was used to produce thin calcium phosphate coatings on titanium substrate from the hydroxyapatite target. The mixing beam could be either Ar(+) or N(+) ions. It was found that as-deposited coatings were amorphous. No distinct peak of the hydroxyl group was observed in FTIR spectra of the coatings, but new spectral peaks, brought about during the deposition process, were present for CO(3)(2-). Scanning electron microscopy revealed that the deposited coatings had a uniform and dense structure. The calcium-to-phosphorous ratio of these coatings varied between 2.0 and 3.0. Compared with the calcium phosphate coatings produced by Ar(+) beam-mixing deposition, the calcium phosphate coatings produced by N(+) beam-mixing deposition exhibited a higher dissolution rate in the physiologic saline solution and showed a lower proliferation rate of osteoblast cells.

Bone Remodeling↗

PubMed2001

Surface modification of titanium through amino group implantation.

We modified Ti surfaces by implantation of amino (NH(2+)) groups at 10(16) and 10(17) cm(-2). The implanted surfaces were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning Auger electron spectroscopy (AES), and second ion mass spectroscopy (SIMS). The experimental results showed that the implanted Ti specimens were covered by a dominant hydrocarbon overlayer due to contamination and the surface oxide layer of implanted specimens became thicker. XPS, AES, and SIMS depth profiles showed that implanted elements had a typical ion implantation distribution and that titanium nitride (TiN) was formed.

Amines↗

PubMed2001

Local gene transfer of tissue factor pathway inhibitor regulates intimal hyperplasia in atherosclerotic arteries.

Tissue factor (TF), the initiator of blood coagulation and thrombosis, is up-regulated after vascular injury and in atherosclerotic states. Systemic administration of recombinant TF pathway inhibitor (TFPI) has been reported to decrease intimal hyperplasia after vascular injury and also to suppress systemic mechanisms of blood coagulation and thrombosis. Here we report that, in heritable hyperlipidemic Watanabe rabbits, adenoviral gene transfer of TFPI to balloon-injured atherosclerotic arteries reduced the extent of intimal hyperplasia by 43% (P < 0.05) compared with a control vector used at identical titer (1 x 10(10) plaque-forming units/ml). Platelet aggregation and coagulation studies performed 7 days after local gene transfer of TFPI failed to show any impairment in systemic hemostasis. At time of sacrifice, 4 weeks after vascular injury, the 10 Ad-TFPI treated carotid arteries were free of thrombi, whereas two control-treated arteries were occluded (P, not significant). These findings suggest that TFPI overexpressed in atherosclerotic arteries can regulate hyperplastic response to injury in the absence of changes in the hemostatic system, establishing a role for local TF regulation as target for gene transfer-based antirestenosis therapies.

Adenoviridae↗

PubMed2001

The effect of flow-through leaching on the diffusivity of heavy metals in stabilized/solidified wastes.

The flow-through leaching test is a test method employed to study the leaching behavior of monolithic stabilized/solidified (S/S) hazardous wastes under the condition that the leachate flows through the sample. This method simulates the leaching process of the S/S hazardous waste disposed under a particular landfill condition when the S/S waste is more permeable than its surrounding materials or when the deterioration of the solidified waste form has reached a state that ground water can flow-through the waste via the porosity system of the S/S waste matrix. This paper describes a study on the long-term performance of the cement-based S/S heavy metal wastes using a flow-through leaching test method. Two series of leaching tests with different synthetic heavy metal waste samples were carried out. The S/S samples were made from five types of heavy metals with two kinds of binders. The metals were Pb(2+), Zn(2+), Cu(2+), Ni(2+) (positive ions as nitrates), and Cr(6+) (a negative ion as potassium dichromate), and the binders were type I ordinary portland cement (OPC) and pulverised fuel ash (PFA). The model developed by Godbee and Joy for simulating the leaching behavior was modified to estimate the diffusivity parameter in this study. The results obtained indicate that since the matrix of the solidified waste in a flow-through leaching tests is always being degraded, the values of diffusivities increase continuously during the leaching period. The diffusivity variation range was from 10(-13) to 10(-3)cm(2)/s, and were normally higher than those obtained from other test methods such as ANS 16.1 test and other dynamic leaching tests.

Decontamination↗

PubMed2001

Functionally graded calcium phosphate coatings produced by ion beam sputtering/mixing deposition.

Ar+ ion beam sputtering/mixing deposition was used to produce thin calcium phosphate coatings on titanium substrate from hydroxyl-poly-calcium sodium phosphate (HPPA) and HPPA + Ti targets. Three types of coatings (one type of monolayer coating and two types of functionally graded coating) were manufactured. It was found that as-sputtered coatings were amorphous. No distinct hydroxyl band was observed in the FTIR spectra, but new absorption bands were determined for CO3(2-), which resulted during the deposition process. Compositional gradients from the surface to the interior (i.e. adjacent to the substrate) were achieved for the functionally graded coatings. Post-deposition heat treatment indicated that the bonding strength between the coating and the substrate was improved by the use of functionally graded structures.

Argon↗

PubMed2001

Geometrical rectification for images from a mobile large container inspection system.

The mobile large container inspection system (MLCIS) is a more flexible X-ray radiographic system than conventional fixed systems. Ideally, the X-ray detectors should be arranged along an arc with the source at the center. However, detectors of the MLCIS are arranged in an L-shaped frame and result in a factual image which is distorted compared with the ideal image. We propose a geometrical rectification algorithm to convert the factual image to the ideal image. We choose the dimension ratios of identical objects shown on the factual and processed images with our algorithm as a measure, and the results is desirable.

Journal Article↗

PubMed2000

Thromboresistance of balloon-injured porcine carotid arteries after local gene transfer of human tissue factor pathway inhibitor.

BACKGROUND: Tissue factor pathway inhibitor (TFPI) is an endogenous inhibitor of factor Xa and the coagulant initiator complex tissue factor/factor VIIa. METHODS AND RESULTS: To study the effects of TFPI gene transfer on thrombus formation, balloon-injured porcine carotid arteries were treated locally with an adenovirus encoding human TFPI (Ad-TFPI) or control virus. Gene transfer of TFPI was confirmed by detection of human TFPI in the conditioned medium of porcine carotid arteries kept in culture after in vivo transduction. When carotid flow was measured with Doppler probe 5 days after surgery, cyclic flow variations (CFVs) developed in 7 of 8 control pigs after constriction of the injured carotid artery by 40%, and all control-treated arteries occluded after 70% constriction. In contrast, CFVs were observed in only 1 of 8 Ad-TFPI-treated pigs after 40% constriction, and only 3 of 8 occluded after constriction by 70% (P=0.0027 and P=0.007, respectively). None of the 5 TFPI-transduced arteries open after 70% constriction developed CFVs during an incremental epinephrine infusion. CONCLUSIONS: Compared with baseline, systemic hemostatic variables and platelet aggregation were unimpaired, suggesting that TFPI gene transfer can prevent arterial thrombosis in the presence of severe shear stress and without detectable hemostatic impairment.

Adenoviridae↗

PubMed2000

Preparation of graded porous titanium coatings on titanium implant materials by plasma spraying.

Graded porous titanium coatings have been deposited on titanium substrates for dental implants by plasma spraying in an argon atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness measurement, and tensile strength tests were performed on graded porous coatings. The results showed that Ti(3)O(5) was formed in the outermost surface of the porous coatings due to oxidation. The graded porous coatings consisted of three layers. The outer layer was full of macropores with a surface roughness of approximately 100 microm. The diameter of many macropores reached and even surpassed 150 microm, which could be beneficial for tissue to grow into the coating. The middle layer consisted of a mixture of micropores and macropores. The inner layer was a very dense and tight interface layer that included mechanical, physical, and metallurgical bonding. In tensile strength tests, testing bars peeled off the coatings, because the adhesive agent fractured, but the coatings remained intact.

Biocompatible Materials↗

PubMed2000

Expression and regulation of the messenger ribonucleic acid encoding the prostaglandin F(2alpha) receptor in the rat myometrium during pregnancy and labor.

OBJECTIVE: We examined expression of messenger ribonucleic acid encoding the prostaglandin F(2alpha) receptor in the rat myometrium throughout late gestation and its regulation by progesterone and mechanical stretch. STUDY DESIGN: Normal pregnant rats were killed on gestational day 15, 22, or 23 (during labor) or 1 day post partum. The effects of progesterone on prostaglandin F(2alpha) receptor messenger ribonucleic acid levels were investigated by daily injections of progesterone (4 mg) from day 20 of normal gestation or from day 17 in rats bilaterally ovariectomized on day 17. To investigate the effects of myometrial stretch, unilaterally pregnant rats underwent either sham surgery or placement of a polyvinyl tube 3 mm in diameter in the nongravid uterine horn on day 15 or 18 and were killed 5 days later. Prostaglandin F(2alpha) receptor messenger ribonucleic acid levels in the myometrium were determined by a semiquantitative reverse transcription-polymerase chain reaction method. RESULTS: Myometrial prostaglandin F(2alpha) receptor messenger ribonucleic acid levels significantly increased during both term and ovariectomy-induced preterm labor. This increase was blocked by progesterone. In rats with unilateral pregnancies prostaglandin F(2alpha) receptor messenger ribonucleic acid levels in the nongravid horns were similar to those in the contralateral gravid horns on day 20 and during labor regardless of whether they were stretched by a 3-mm tube. CONCLUSION: Increased myometrial expression of prostaglandin F(2alpha) receptor messenger ribonucleic acid during term and preterm labor is temporally associated with progesterone withdrawal but is not dependent on mechanical stretch of the myometrium.

Animals↗

PubMed2000

Investigation of defects in high-energy heavy ion implanted GaAs.

Undoped semi-insulating GaAs were implanted with 500 MeV Ne ions. Monte Carlo simulation revealed that the largest concentration of vacancies induced was around the end of the Ne ion range. Positron Annihilation measurement showed that after lower dose implantation, divacancies were formed, which coexisted with monovacancies. On increasing the dose, all the monovacancies changed to divacancies. The temperature dependence of positron lifetime suggested the existence of negatively charged antisites GaAs. Near infra-red spectra were also measured to study the implantation induced amorphous layers.

Journal Article↗

PubMed2000

Inhibition of coronary thrombosis and local inflammation by a noncarbohydrate selectin inhibitor.

We tested the hypothesis that selectin inhibition with blocking antibodies or a small-molecular-weight inhibitor of L-, P-, and E-selectin, methoxybenzoylpropionic acid (MBPA), prevents thrombus formation in a canine coronary Folts' model. Cyclic flow variations (CFVs) were induced by crush injury and constriction of the left anterior descending coronary artery in dogs. Systemic infusion of antibodies to P- and L-selectin abolished CFVs, respectively, in 50% and 17% of treated dogs [P = not significant (NS)]. The combination of P- and L-selectin antibodies suppressed CFVs in 60% of treated dogs (P = NS). In contrast, systemic selectin blockade by intravenous infusion or local adventitial application of MBPA markedly reduced CFVs and, in addition, reduced myocardial myeloperoxidase (MPO) activity. We conclude that inhibition of L-, P-, and E-selectin binding by a small-molecular-weight, noncarbohydrate compound markedly reduces arterial thrombosis, whereas systemic administration of antibodies to L- and P-selectin fail to reproduce this antithrombotic effect. These results underscore the role of selectins in the pathogenesis of arterial thrombosis under high shear stress and suggest that inhibition of P- and L- selectin may not suffice to prevent thrombus formation in this model. The role of E-selectin in thrombus formation in this model awaits further testing.

Animals↗

PubMed1999

Surface modification of A12O3 bioceramic by NH2+ ion implantation.

Ion implantation technique was applied to graft the -NH2 amidogen radicals onto the surface of Al2O3 bioceramic. Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of the implanted radicals on the Al2O3 ceramic surface. It was found that the amount of grafted amidogen radicals was proportional to the dosage of NH2+ ions used during the ion implantation. Furthermore, when implantation energy of 100 keV was used, maximum amount of -NH2 radicals would be grafted on the Al2O3 ceramic surface. The biocompatibility of the implanted Al2O3 ceramic was also investigated, and the results indicate that the implanted surface has better biocompatibility with animal bone tissue than the plain ceramic surface.

Aluminum Oxide↗

PubMed1999

The emerging clinical potential of cardiovascular gene therapy.

Despite considerable progress, pharmacological therapies have not provided a complete solution for common cardiovascular problems, including recurrent thrombosis, restenosis, and vein graft deterioration. Optimal drug dosage, reproducing plasma concentrations achieved in animal studies establishing proof-of-principle, would often be too toxic to administer, especially when given over prolonged periods of time. Local gene therapy aims at overexpressing proteins that: (1) regulate the cell cycle of VSMC; (2) inhibit VSMC migration; (3) endow the endothelium with its vasoprotective properties; and (4) stimulate growth of endothelium and angiogenesis. Alternatively, some approaches tend to suppress gene expression of proteins believed to promote VSMC proliferation and migration. In sharp contrast to drug treatments, local gene therapy limits expression of the beneficial agent to the injured vascular site, and there, it can extend the presence of this agent to weeks and, with some gene vectors, to many months. The clinical potential of this approach has led to the initiation of trials that currently evaluate gene therapy approaches to the attenuation of peripheral and myocardial ischaemia and the prevention of vein graft disease.

Animals↗

PubMed1999

Extensive conservation of sex chromosome organization between cat and human revealed by parallel radiation hybrid mapping.

A radiation hybrid (RH)-derived physical map of 25 markers on the feline X chromosome (including 19 Type I coding loci and 6 Type II microsatellite markers) was compared to homologous marker order on the human and mouse X chromosome maps. Complete conservation of synteny and marker order was observed between feline and human X chromosomes, whereas the same markers identified a minimum of seven rearranged syntenic segments between mouse and cat/human X chromosome marker order. Within the blocks, the feline, human, and mouse marker order was strongly conserved. Similarly, Y chromosome locus order was remarkably conserved between cat and human Y chromosomes, with only one marker (SMCY) position rearranged between the species. Tight linkage and a conserved gene order for a segment encoding three genes, DFFRY-DBY-UTY in human, mouse, and cat Y chromosomes, coupled with demonstrated deletion effects of these genes on reproductive impairment in both human and mouse, implicates the region as critical for Y-mediated sperm production.

Animals↗

PubMed1999

Xylene-induced effects on brain neurotransmitters, behavior and fos protein in rats.

Male Sprague-Dawley rats administered xylene intraperitoneally on alternate days at a dose of 125 or 250 mg/kg for 30 days exhibited no marked changes in locomotor activity, learning and memory capacity. However in rats given xylene on alternate day at a dose of 500 mg/kg for 30 days, a significant decrease in locomotor activity, deficits in learning ability and memory loss were detected. These xylene-induced behavioral changes were associated with a decrease in beta-endorphin and leuenkaphlin concentrations in the pons-medulla. On the contrary, xylene at a dose of 500 mg/kg increased the beta-endorphin level in caudate and c-fos expression in hippocampus. These data suggest that the xylene-induced behavioral alterations might be associated with the expression of Fos protein in the hippocampus.

Animals↗

PubMed1998

Localization of the human CXC chemokine subfamily on the long arm of chromosome 4 using radiation hybrids.

All 12 of the human CXC chemokine genes were physically mapped using gene-specific PCR primers and the GenBridge 4 radiation hybrid panel. Nine genes, PF4, PF4V1, GRO1, GCP2, PPBP, IL8, GRO2, GRO3, and SCYB5, were assigned within a 1.8-cR interval of one another on 4q. Two additional genes, MIG and INP10, map within 0.5 cR of each another and 6 cR distal to the above-mentioned group. The final gene, SDF1, is localized on 10q. Phylogenetic analyses of amino acid sequences revealed that SDF1 is the most divergent member and that the physically separated MIG-INP10 pair constitutes a distinct evolutionary lineage.

Chemokines, CXC↗

PubMed1998

A human vascular endothelial cell model to study angiogenesis and tumorigenesis.

Endothelial cell biology has recently been the subject of considerable interest in thrombosis and cancer research. However, the successful establishment of immortalized human endothelial cells which retain differentiated cell characteristics has been rare. We have successfully established immortalized human umbilical vein endothelial cells (HUVECs) by human papilloma virus (HPV)-16 E6-E7. HPV-16 E6, E7 and E6-E7 were successfully introduced into HUVEC cells. Both E6 and E7 cultures had an extended lifespan but eventually underwent senescence. E6-E7 cultures 4-5-2G, however, acquired an indefinite lifespan in culture but did not undergo malignant conversion. Telomerase activity was not detected in either E6 or E7 cultures; however, telomerase was detected in E6-E7 4-5-2G cells. The cells exhibited a 'cobblestone' morphology and developed a capillary-like tube structure upon reaching confluence. The 4-5-2G line expressed Factor VIII related antigen and took up DiI-Ac-LDL as markers of endothelial origin. The line expressed integrin subunits (alpha(v)beta3, alph(v)beta5, beta1, alpha2, alpha3, beta4 and alpha6) consistent with an endothelial origin. The higher passage of 4-5-2G line showed a similar intensity of integrin immunostaining to that of primary HUVECS. Subsequent infection of these immortal cells with the Kirsten murine sarcoma virus which contains an activated K-ras oncogene induced morphological transformation that led to the acquisition of invasion capability and neoplastic properties. Telomerase was also detected in the tumorigenic v-Ki-ras transformed cell line. These cell lines should be useful for studies of the molecular mechanisms underlying normal and neoplastic endothelial cell proliferation and migration, and might also provide an in vitro model for development of pharmacologic and gene therapy for cardiovascular thrombosis and cancer.

Cell Line, Transformed↗

PubMed1998

Increased expression of the rat myometrial oxytocin receptor messenger ribonucleic acid during labor requires both mechanical and hormonal signals.

We investigated the expression of the mRNA encoding the oxytocin receptor (OTR) in rat myometrium throughout gestation and its regulation by progesterone and mechanical stretch. Using a semiquantitative reverse transcription-polymerase chain reaction approach, OTR mRNA was found to increase abruptly at the onset of spontaneous labor at term. Progesterone (4 mg/day) starting on Day 20 of gestation blocked this increase. Ovariectomy on Day 17 induced preterm labor 96 h after surgery and a significant increase in myometrial OTR mRNA levels 48 and 96 h after surgery. Both preterm labor and the rise in myometrial OTR expression were blocked by progesterone. To investigate the effects of stretch on myometrial OTR mRNA expression, unilaterally pregnant rats underwent either sham operation or placement of a tube in the nongravid uterine horn to distend the myometrium. On Day 20, stretch had no effect on OTR expression in the nongravid horns. During labor, OTR mRNA was highly expressed in the gravid horns as well as the nongravid stretched horns. In contrast, the level remained low in the nongravid unstretched horns. These results indicate that expression of rat myometrial OTR mRNA during pregnancy and labor is regulated by coordinated interactions between mechanical and endocrine signals.

Animals↗