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Biomedical subjects

J Ye

Publications and source records attributed to J Ye.

At least 19 recordsLinked to original sources
PubMed2006

The development of a real-time biosensor for the detection of trace levels of trinitrotoluene (TNT) in aquatic environments.

This paper describes the development of a highly sensitive TNT immunosensor consisting of a highly specific monoclonal antibody coupled with a prototype fluorescence-based detector system (KinExA Inline Biosensor, Sapidyne Instrument Inc). The antibody developed possesses a high affinity for TNT (association constant, aK 8.2) with minimal cross reactivity with other compounds such as tetryl, 2,4-dinitrotoluene and 2-amino-4,6-dinitrotoluene. This system provides sample assessment within 160 s from source acquisition and possesses sensitivity for TNT of 0.05 microg/L in ground water. The sensor can be regenerated in 8 min, allows a minimum of 40 repeated readings, and has a standard error of 0.1-0.4% between repeat readings. The fluidics and software allow samples to be obtained from up to eight different sources allowing the user to examine the stratification of the pollutant in the water column. We believe that this immunosensor can be used to rapidly assess trace levels of TNT in environmental water samples.

Biosensing Techniques↗
PubMed2006

AAV serotype-1 mediates early onset of gene expression in mouse hearts and results in better therapeutic effect.

Adeno-associated viral vectors (AAV) are attractive tool for gene therapy for coronary artery disease. However, gene expression in myocardium mediated by AAV serotype 2 (AAV2) does not peak until 4-6 weeks after gene transfer. This delayed gene expression may reduce its therapeutic potential for acute cardiac infarction. To determine whether earlier gene expression and better therapeutic effect could be achieved using a different serotype, CMV promoter driving the EPO gene (AAV-EPO) was packaged into AAV serotypes 1-5 capsids and injected into mouse myocardium. EPO expression was studied by measuring the hematocrits and EPO mRNA. After we found that AAV1 mediates the highest gene expression after 4 days of gene transduction, AAV-LacZ (CMV promoter driving LacZ gene expression) and MLCVEGF (hypoxia-inducible and cardiac-specific VEGF expression) were packaged into AAV1 and 2 capsids. LacZ expression was detected in AAV1-LacZ but not in AAV2-LacZ-injected hearts 1 day after vector injection. Compared to AAV2-MLCVEGF that mediated no significant VEGF expression, AAV1-MLCVEGF mediated 13.7-fold induction of VEGF expression in ischemic hearts 4 days after gene transduction and resulted in more neovasculatures, better cardiac function and less myocardial fibrosis. Thus, AAV1 mediates earlier and higher transgene expression in myocardium and better therapeutic effects.

Animals↗
PubMed2006

Narrow line photoassociation in an optical lattice.

With ultracold 88Sr in a 1D magic wavelength optical lattice, we performed narrow-line photoassociation spectroscopy near the 1S0 - 3P1 intercombination transition. Nine least-bound vibrational molecular levels associated with the long-range 0u and 1u potential energy surfaces were measured and identified. A simple theoretical model accurately describes the level positions and treats the effects of the lattice confinement on the line shapes. The measured resonance strengths show that optical tuning of the ground state scattering length should be possible without significant atom loss.

Journal Article↗
PubMed2006

Mesenchymal stem cell transplantation in a rabbit corneal alkali burn model: engraftment and involvement in wound healing.

PURPOSE: To investigate whether systemically transplanted mesenchymal stem cells (MSCs) can home and engraft in tissue to promote cornea wound healing after alkali burn, as a new source for treatment. METHODS: Corneal alkali burn was created in four group rabbits: Group I, normal bone marrow function, without MSCs transplantation; Group II, normal bone marrow function, with MSCs transplantation; Group III, bone marrow suppressed by cyclophosphamide, without MSCs; Group IV, bone marrow suppressed by cyclophosphamide, with MSCs. Clinical outcome was evaluated by cornea re-epithelization, cornea opacity, and neovascularization. Cell engraftment into bone marrow, circulation, and cornea was monitored. Immunohistochemistry, using proliferating cell nuclear antigen (PCNA), P63, vimentin, and alpha-smooth muscle actin (alpha-SMA) was carried out to assess the cell proliferative and differentiative ability. RESULTS: At the time of 1-month follow-up, Group II rabbits showed the best clinical results with a clearer healed cornea compared with other groups. Well-formed neovascularization appeared on day 14 after alkali burn in Group II, that coincided with the maximum engraftment of MSCs. PCNA, P63, vimentin were more strongly expressed in Group II at multiple time points. DiI-labelled MSCs were differentiated into myofibroblast by the expression of alpha-SMA. Delayed and insufficient cell engraftment, with malformed neovascularization and retarded corneal wound healing was found in Groups III and IV. CONCLUSIONS: Systemically transplanted MSCs can engraft to injured cornea to promote wound healing, by differentiation, proliferation, and synergizing with haemotopoietic stem cells.

Alkalies↗
PubMed2006

Characterization of depolarization-evoked ERG K currents in interstitial cells of Cajal.

Interstitial cells of Cajal (ICC) harbour the ether-a-go-go related gene (ERG) channel as shown by its characteristic rapidly deactivating current upon hyperpolarization. This property, however, does not explain the marked increase in cell excitability by ERG channel blockers, namely an increase in slow wave plateau duration and action potential generation. The objective of the present study was to characterize the depolarization-activated, E4031-sensitive ERG currents in murine ICC within a range of physiologically relevant membrane potentials. Whole cell currents were recorded from ICC isolated from murine neonatal jejunum, superfused with a physiological salt solution and with high intracellular Cs(+) to block most other K(+) currents. Upon depolarizing the cell from the resting membrane potential (approximately -60 mV) towards the region of the slow wave plateau (approximately -30 mV), significant sustained (window) current was generated between the potentials of -40 to 0 mV (maximal at -30 mV) and inhibited by the ERG specific blocker E4031. Channel activation followed by rapid inactivation produced a steady state conductance at -30 mV which was 51.6 +/- 11% of the hyperpolarization-evoked peak conductance value at -100 mV. When the cell repolarized from -30 mV, again, significant currents were generated, indicating recovery from inactivation, a typical characteristic of ERG channels. These data provide evidence that the ERG channel is of significance in the regulation of ICC excitability and provide the mechanism by which ERG channel blockade increases the slow wave duration.

Animals↗
PubMed2006

Interspecies variation in Candida biofilm formation studied using the Calgary biofilm device.

An in vitro assay to study multiple Candida biofilms, in parallel, has been carried out using the Calgary biofilm device (CBD). We here report: i) standardization of the CBD for Candida albicans biofilm formation, ii) kinetics of C. albicans biofilm formation, iii) biofilm formation by five Candida species, and iv) effect of dietary carbohydrates on biofilm formation. The biofilm metabolic activity on all CBD pegs was similar (p=0.6693) and C. albicans biofilm formation revealed slow growth up to 36 h and significantly higher growth up to 48 h (p<0.001). Significant differences in total biofilm metabolic activity were seen for glucose, fructose and lactose grown C. albicans compared with sucrose and maltose grown yeasts. Candida krusei developed the largest biofilm mass (p<0.05) relative to C. albicans, C. glabrata, C. dubliniensis and C. tropicalis. Scanning electron microscopy revealed that C. krusei produced a thick multilayered biofilm of pseudohyphal forms embedded within the polymer matrix, whereas C. albicans, C. dubliniensis and C. tropicalis biofilms consisted of clusters or chains of cells with sparse extracellular matrix material. We conclude that CBD is a useful, simple, low cost miniature device for parallel study of Candida biofilms and factors modulating this phenomenon.

Biofilms↗
PubMed2005

In vitro method to study antifungal perfusion in Candida biofilms.

Antimycotic perfusion through Candida biofilms was demonstrated by a modification of a simple in vitro diffusion cell bioassay system. Using this model, the perfusion of three commonly used antifungal agents, amphotericin B, fluconazole, and flucytosine, was investigated in biofilms of three different Candida species (i.e., Candida albicans, Candida parapsilosis, and Candida krusei) that were developed on microporous filters. Scanning electron microscopy revealed that C. albicans formed a contiguous biofilm with tightly packed blastospores and occasional hyphae compared with C. parapsilosis and C. krusei, which developed confluent biofilms displaying structural heterogeneity and a lesser cell density, after 48 h of incubation on nutrient agar. Minor structural changes were also perceptible on the superficial layers of the biofilm after antifungal perfusion. The transport of antifungals to the distal biofilm-substratum interface was most impeded by C. albicans biofilms in comparison to C. parapsilosis and C. krusei. Fluconazole and flucytosine demonstrated similar levels of perfusion, while amphotericin B was the least penetrant through all three biofilms, although the latter appeared to cause the most structural damage to the superficial cells of the biofilm compared with the other antifungals. These results suggest that the antifungal perfusion through biofilm mode of growth in Candida is dependent both on the antimycotic and the Candida species in question, and in clinical terms, these phenomena could contribute to the failure of Candida biofilm-associated infections. Finally, the in vitro model we have described should serve as a useful system to investigate the complex interactions that appear to operate in vivo within the biofilm-antifungal interphase.

Amphotericin B↗
PubMed2005

Competition between R1 and R2 transposable elements in the 28S rRNA genes of insects.

R1 and R2 are non-LTR retrotransposons that insert in the 28S rRNA genes of arthropods. R1 elements insert into a site that is 74 bp downstream of the R2 insertion site, thus the presence of an R2 in the same 28S gene may inhibit the expression of R1. Consistent with such a suggestion, the R1 elements of Drosophila melanogaster have a strong bias against inserting into 28S genes already containing an R2 element. R2 elements, on the other hand, are only 2-3 fold inhibited from inserting into a 28S gene already containing an R1. D. melanogaster R1 elements are unusual in that they generate a 23-bp deletion of the target site upstream of the insertion. Using in vitro assays developed to study R2 integration, we show that the presence of R1 sequences 51 bp downstream of the R2 insertion site changes the nucleosomal structure that can be formed by the R2 target site. The R2 endonuclease is inhibited from cleaving these altered nucleosomes. We suggest that R1 elements have been selected to make this large deletion of the 28S gene to block the insertion of an upstream R2 element. These findings are consistent with the model that R1 and R2 are in competition for the limited number of insertion sites available within their host's genome.

Animals↗
PubMed2004

Experimental implementation of optical clockwork without carrier-envelope phase control.

We demonstrate optical clockwork without the need for carrier-envelope phase control by use of sum-frequency generation between a continuous-wave optical parametric oscillator at 3.39 microm and a femtosecond mode-locked Ti:sapphire laser with two strong spectral peaks at 834 and 670 nm, a spectral difference matched by the 3.39-microm radiation.

Journal Article↗
PubMed2004

Dynamic changes in meiotic progression and improvement of developmental competence of pig oocytes in vitro by follicle-stimulating hormone and cycloheximide.

The effects of FSH, LH, and epidermal growth factor (EGF) on the dynamics of nuclear maturation and subsequent embryo development were examined in pig oocytes cultured either conventionally or after preincubation with cycloheximide (CHX). In conventional culture, FSH or EGF significantly increased the rate of attainment of metaphase II (MII) for both gilt (50.0%+/-4.2% and 54.8%+/-4.3%, respectively; control, 5.8%+/-1.8%; P<0.001) and sow (87.6%+/-3.4% and 78.8%+/-3.9%, respectively; control, 7.8%+/-2.5%; P<0.001) oocytes. Gilt oocytes treated with both FSH and EGF showed an additive response (93.7%+/-2.1%). Treatment with LH had no effect. Preincubation with CHX caused the majority (84-100%) of both gilt and sow oocytes to undergo germinal vesicle breakdown. Compared to those treated with LH and/or EGF (both>80%), fewer FSH-treated oocytes reached metaphase I (43.8%+/-5.3%, P<0.001) by 14 h and MII (48.4%+/-5.9%, P<0.001) by 24 h, although the majority (71%) did mature to MII by 36 h after removal of CHX. After in vitro fertilization, higher proportions of both CHX-pretreated and untreated, FSH-exposed oocytes cleaved (71.3%+/-2.9% and 75.3%+/-3.1%, respectively) compared with those not treated with FSH (37.7%+/-3.0% and 43.0%+/-2.9%, respectively; P<0.001). Pretreatment with CHX significantly increased blastocyst yield for both FSH-treated (32.8%+/-2.0% and 10.3%+/-1.5%, respectively; P<0.001) and untreated (16.7%+/-1.5% and 9.4%+/-1.2%, respectively; P<0.001) oocytes. Polyspermy rates were unaffected. In conclusion, pig oocytes meiotically arrested by CHX before maturation retain and improve their developmental competence. FSH stimulates nuclear maturation but slows meiotic progression.

Animals↗
PubMed2004

Involvement of bone marrow-derived stem and progenitor cells in the pathogenesis of pterygium.

AIMS: To evaluate the involvement of multipotential stem and progenitor cells in the pathogenesis of pterygium. METHODS: Paraffin-embedded and snap-frozen primary pterygium (n = 10) were serially sectioned and analysed immunohistochemically to determine the expression level of AC133 (marker for the primitive haematopoietic progenitors), CD34 (marker for the haematopoietic progenitor cells and endothelium), c-Kit (marker for haematopoietic and stromal progenitor cells), and STRO-1 (a differentiation antigen present on bone marrow fibroblast cells and on various nonhaematopoietic progenitor cells). RESULTS: In all the primary pterygium, immunoreactivity of AC133 and STRO-1 was found in some of the epithelial and stromal cells, CD34 was observed in the vascular endothelium, and some scattered ovoidal cells were found in the subepithelial connective tissue. C-Kit was expressed mainly in the basal epithelium of the head portions, and some spindle-shaped stromal cells. There is no immunoreactivity of AC133, c-Kit, and STRO-1 in normal conjunctiva, whereas CD34 was mildly stained with vessel wall. CONCLUSION: Multipotential stem and progenitor cells may be involved in the pathogenesis of pterygium through its differentiation into fibroblasts and vascular endothelial cells.

AC133 Antigen↗
PubMed2004

Ultraviolet light selection assay to optimize oligonucleotide correction of mutations in endogenous xeroderma pigmentosum genes.

Various oligonucleotide (ODN)-based approaches have been proposed for their ability to correct mutated genes at the normal chromosomal locations. However, the reported gene correction frequencies of these approaches have varied markedly in different experimental settings, including when different tissues or cell types are targeted. In order to find the optimal ODN-based approach for a specific target tissue, an assay system that allows direct comparison of the different methods on that tissue is necessary. Herein, we describe an XP-UVC selection assay that can be used to evaluate and compare gene correction frequencies in different cell types obtained from a xeroderma pigmentosum (XP) patient, following treatment by different ODN-based approaches. As an experimental example, the XP-UVC selection assay was used to assess the ability of chimeric RNA/DNA ODN to correct point mutations in the XPA gene. This assay can be used to assess and evaluate other types of ODN-based approaches, and to further optimize them.

Base Sequence↗
PubMed2003

Relation of risk of systemic lupus erythematosus to west African admixture in a Caribbean population.

Risk of systemic lupus erythematosus (SLE) is higher in people of west African descent than in Europeans. The objective of this study was to distinguish between genetic and environmental explanations for this ethnic difference by examining the relationship of disease risk to individual admixture (defined as the proportion of the genome that is of west African ancestry); 124 cases of SLE and 219 matched controls resident in Trinidad were studied. Analysis of admixture was restricted to 52 cases and 107 controls who reported no Indian or Chinese ancestry. These individuals were typed with a panel of 26 single-nucleotide polymorphisms and five insertion/deletion polymorphisms chosen to have large allele frequency differentials between west African, European and Native American populations. A Bayesian model for population admixture, individual admixture and locus ancestry was fitted by Markov chain simulation. Mean west African admixture (M) was 0.81 in cases and 0.74 in controls (P=0.01). The risk ratio for SLE associated with unit change in M was estimated as 32.5 with a 95% confidence interval (CI) of 2.0-518. Adjustment for measures of socioeconomic status (household amenities in childhood and years of education) altered this risk ratio only slightly (adjusted risk ratio: 28.4, 95% CI 1.7-485). These results support an additive genetic model for the ethnic difference in risk of SLE between west Africans and Europeans, rather than an environmental explanation or an "overdominant" model in which risk is higher in heterozygous than in homozygous individuals. This conclusion lays a basis for localizing the genes underlying this ethnic difference in risk of SLE by admixture mapping.

Adult↗
PubMed2003

Image registration via level-set motion: applications to atlas-based segmentation.

Image registration is an often encountered problem in various fields including medical imaging, computer vision and image processing. Numerous algorithms for registering image data have been reported in these areas. In this paper, we present a novel curve evolution approach expressed in a level-set framework to achieve image intensity morphing and a simple non-linear PDE for the corresponding coordinate registration. The key features of the intensity morphing model are that (a) it is very fast and (b) existence and uniqueness of the solution for the evolution model are established in a Sobolev space as opposed to using viscosity methods. The salient features of the coordinate registration model are its simplicity and computational efficiency. The intensity morph is easily achieved via evolving level-sets of one image into the level-sets of the other. To explicitly estimate the coordinate transformation between the images, we derive a non-linear PDE-based motion model which can be solved very efficiently. We demonstrate the performance of our algorithm on a variety of images including synthetic and real data. As an application of the PDE-based motion model, atlas based segmentation of hippocampal shape from several MR brain scans is depicted. In each of these experiments, automated hippocampal shape recovery results are validated via manual "expert" segmentations.

Adult↗
PubMed2003

Molecular genetic analysis of glycogen storage disease type Ia in 26 Chinese patients.

Sequence analysis of 26 patients from Mainland China with glycogen storage disease type Ia revealed a high frequency of two mutations in the glucose-6-phosphatase gene. These mutations, 727G>T and R83H, were also found to be in linkage disequilibrium with a polymorphism at position 1176. These findings have implications for carrier detection and prenatal diagnosis of this disease in the Chinese population.

Asian People↗
PubMed2003

Analysis of marker or complex chromosomal rearrangements present in pre- and post-natal karyotypes utilizing a combination of G-banding, spectral karyotyping and fluorescence in situ hybridization.

The significance of complex chromosomal rearrangements presents a diagnostic dilemma. In the past, the use of G-banding coupled with fluorescence in situ hybridization (FISH) has been the standard approach. The recent development of spectral karyotyping (SKY) and multicolor FISH (M-FISH) has resulted in an increased accuracy of identification of marker or other complex chromosomal rearrangements. However, owing to the additional cost and time associated with SKY or M-FISH, and the restricted availability of such imaging facilities in many centers, it is not feasible to perform these procedures routinely on every sample. In addition, the identification of an aberration by SKY or M-FISH will often require confirmation by FISH. A practical approach is needed to take advantage of the complementary strengths of each method. In our center we utilize an algorithm that dictates the use of routine G-banding for the initial preliminary evaluation of a patient, followed by SKY characterization if marker chromosomes or complex translocations are detected by the G-banding analysis. According to this algorithm, FISH is used to verify the results once the origin of the abnormal chromosome has been determined by SKY. To demonstrate the effectiveness of this algorithm, we have analyzed both amniocyte and lymphocyte slides, using a combination of G-banding, SKY, and FISH. Our results confirm that an algorithm which selectively uses SKY or M-FISH will provide an efficient and improved method for pre- and post-natal chromosomal analysis.

Algorithms↗