Biomedical subjects

Y Ge

Publications and source records attributed to Y Ge.

At least 55 records · Page 3Linked to original sources

PubMed2001

[A two-years clinical observation of all-ceramic restorations using Vita In-Ceram glass-infiltrated ceramic].

OBJECTIVE: This paper observed the clinical effect of Vita In-Ceram glass-infiltrated ceramic restorations. METHOD: A total of 194 restorations (124 maxillary and 70 mandibular prostheses) made with Vita In-Ceram glass-infiltrated ceramic were examined in 45 patients. There were 165 anterior tooth crowns, 21 posterior tooth crowns, and 8 FPDs. Surface, color, anatomic form, and marginal integrity of restorations were assessed at 3 months, 6 months, 1 year and 2 years after cementation with the California Dental Association (CDA) quality assessment evaluation system. RESULTS: It showed that the marginal fitness, color stability and strength of crowns were considered to be satisfactory. Only 0.01% (two crowns) were not acceptable. Two FPDs were not acceptable at 6-month visit, however, the anterior FPDs were considered to be satisfactory. CONCLUSION: It is possible to constructexcellent all-ceramic prostheses with the Vita In-Ceram glass-infiltrated ceramic system.

Ceramics↗

PubMed2001

[Basic assessment of trust level in medical apparatus and instruments sales systems by medical organization].

Purchase of medical apparatus and instruments is a strict work of taking the patient as a consuming objection. To analyze the trust level in medical apparatus and instruments sales systems and to set up the method of trust level assessment before the purchase, is an important link of ensuring the reality of medical products and consumerism. According to the principle mentioned about, the present article analyses the basic content of assessing factors and their inter-relationship, summarizes their expressions, studies and sets up the mathematical modal and it method. All these are of some value to medical organization in choosing factory owners and their products while the purchasing.

Commerce↗

PubMed2001

[The structures and characteristic infrared spectra of beta-DDB and its derivatives].

The characteristic infrared bands of the 3, 4-methylenedioxy-5-methoxybenzoate, 6-Br-3, 4-methylenedioxy-5-methoxybenzoate, beta-DDB (6, 6'-dimethoxy-4, 5, 4', 5'-dimethylenedioxy-2, 2'-dimethoxycarbonylbiphenyl) and its five derivatives were assigned. The effects of the substituents of these compounds on their IR data were discussed. The results indicated the varying of ester alkyl mainly influences the C=O double band stretching mode, but has little effects on the C=C double band stretching mode of the phenyl. When the H atom was substituted by other substituents, the absorptions of the C=O and C=C both changed.

Biphenyl Compounds↗

PubMed2000

Electrochemically controlled hydrogen bonding. o-Quinones as simple redox-dependent receptors for arylureas.

9,10-Phenanthrenequinone and acenaphthenequinone are shown to act as simple redox-dependent receptors toward aromatic ureas in CH(2)Cl(2) and DMF. Reduction of the o-quinones to their radical anions greatly increases the strength of hydrogen bonding between the quinone carbonyl oxygens and the urea N-hydrogens. This is detected by large positive shifts in the redox potential of the quinones with no change in electrochemical reversibility upon addition of urea guests. Cyclic voltammetric studies with a variety of possible guests show that the effect is quite selective. Only guests with two strong hydrogen donors, such as O-H bonds or amide N-H bonds, that are capable of simultaneously interacting with both carbonyl oxygens give large shifts in the redox potential of the quinones. The electronic character and conformational preference of the guest are also shown to significantly affect the magnitude of the observed potential shift. In the presence of strong proton donors the electrochemistry of the quinone becomes irreversible indicating that proton transfer has taken place. Experiments with compounds of different acidity show that the pK(a) of the protonated quinone radical is about 15 on the DMSO scale, >4 pK(a) units smaller than that of 1,3-diphenylurea. This is further proof that hydrogen bonding and not proton transfer is responsible for the large potential shifts observed with this and similar guests.

Electrochemistry↗

PubMed2000

Cystathionine-beta-synthase cDNA transfection alters the sensitivity and metabolism of 1-beta-D-arabinofuranosylcytosine in CCRF-CEM leukemia cells in vitro and in vivo: a model of leukemia in Down syndrome.

The significantly higher event-free survival rates of Down syndrome (DS) children with acute myeloid leukemia compared with non-DS children is linked to increased sensitivity of DS myeloblasts to 1-beta-D-arabinofuranosylcytosine (ara-C) and the enhanced metabolism of ara-C to ara-C triphosphate (J. W. Taub et al., Blood, 87: 3395-3403, 1996). The cystathionine-beta-synthase (CBS) gene (localized to chromosome 21q22.3) may have downstream effects on reduced folate and S-adenosylmethionine pathways; ara-C metabolism and folate pools are linked by the known synergistic effect of sequential methotrexate and ara-C therapy. We have shown that relative CBS transcripts were significantly higher in DS compared with non-DS myeloblasts, and CBS transcript levels correlated with in vitro ara-C sensitivity (J. W. Taub et al., Blood, 94: 1393-1400, 1999). A leukemia cell line model to study the relationship of the CBS gene and ara-C metabolism/sensitivity was developed by transfecting CBS-null CCRF-CEM cells with the CBS cDNA. CBS-transfected cells were a median 15-fold more sensitive in vitro to ara-C compared with wild-type cells and generated 8.5-fold higher [3H]ara-C triphosphate levels after in vitro incubation with [3H]ara-C. Severe combined immunodeficient mice implanted with CBS-transfected CEM cells demonstrated greater responsiveness to therapy, reflected in significantly prolonged survivals after ara-C administration compared with mice implanted with wild-type cells and treated with the same dosage schedule. The transfected cells also demonstrated increased in vitro and in vivo sensitivity to gemcitabine. Deoxycytidine kinase (dCK) activity was approximately 22-fold higher in transfected CEM cells compared with wild-type cells. However, levels of dCK transcripts on Northern blots and protein levels on Western blots were nearly identical between CBS-transfected and wild-type cells. Collectively, these results suggest a posttranscriptional regulation of dCK in CBS-overexpressing cells that contributes to increased ara-C phosphorylation and drug activity. Further elucidating the mechanisms of increased sensitivity of DS cells to ara-C related to the CBS gene may lead to the application of these novel approaches to acute myeloid leukemia therapy for non-DS patients.

Animals↗

PubMed2000

Activated ion electron capture dissociation for mass spectral sequencing of larger (42 kDa) proteins.

In previous studies, electron capture dissociation (ECD) has been successful only with ionized smaller proteins, cleaving between 33 of the 153 amino acid pairs of a 17 kDa protein. This has been increased to 99 cleavages by colliding the ions with a background gas while subjecting them to electron capture. Presumably this ion activation breaks intramolecular noncovalent bonds of the ion's secondary and tertiary structure that otherwise prevent separation of the products from the nonergodic ECD cleavage of a backbone covalent bond. In comparison to collisionally activated dissociation, this "activated ion" (AI) ECD provides more extensive, and complementary, sequence information. AI ECD effected cleavage of 116, 60, and 47, respectively, backbone bonds in 29, 30, and 42 kDa proteins to provide extensive contiguous sequence information on both termini; AI conditions are being sought to denature the center portion of these large ions. This accurate "sequence tag" information could potentially identify individual proteins in mixtures at far lower sample levels than methods requiring prior proteolysis.

Amino Acid Sequence↗

PubMed2000

Long-term differential modulation of genes encoding orexigenic and anorexigenic peptides by leptin delivered by rAAV vector in ob/ob mice. Relationship with body weight change.

We investigated the long-term effects of physiological levels of leptin produced by gene therapy on body weight (BW) and expression of genes that encode orexigenic and anorexigenic peptides in the hypothalamus. Recombinant adeno-associated viral vector (rAAV), a non-pathogenic and non-immunogenic vector, encoding leptin (betaOb) was generated and administered iv to ob/ob mice lacking endogenous leptin. Whereas the lowest dose of rAAV-betaOb (6x10(9) particles) was ineffective, the middle dose (6x10(10) particles) curbed BW gain without affecting food consumption for 75 days of observation. A ten-fold higher dose (6x10(11) particles) resulted in increased blood leptin levels and suppressed both BW gain and food consumption throughout the duration of the experiment. rAAV-betaOb doses that either curbed BW without affecting food consumption or evoked BW loss and reduced food intake, decreased the expression of genes encoding the orexigenic peptides, neuropeptide Y and agouti-related peptide in the ARC, and the two doses were equally effective. Concomitantly, the expression of genes encoding the anorexigenic peptide, alpha-melanocyte stimulating hormone and cocaine-and-amphetamine regulatory transcript, was augmented with the latter gene displaying a dose-dependant response. These results document the efficacy of delivering biologically active leptin for extended periods by an iv injection of rAAV-betaOb and show that physiological leptin concentrations simultaneously exert a tonic inhibitory effect on orexigenic and a stimulatory effect on anorexigenic signaling in the hypothalamus. This intricate dynamic interplay induced by leptin regulates BW with or without an effect on food intake in leptin-deficient ob/ob mice. Further, these results suggest that gene therapy is an effective mode of delivery to the hypothalamus of those therapeutic proteins that cross the blood-brain barrier to ameliorate neuroendocrine disorders.

Agouti-Related Protein↗

PubMed2000

Localization of endotoxin in the rat intestinal epithelium.

High levels of circulating lipopolysaccharide (LPS) cause intestinal inflammation and increased permeability to bacteria and toxins. To better understand the effects of LPS on the gut, confocal microscopy and immunofluorescence staining were used to examine the distribution of LPS in the rat intestine after intravenous or enteral administration. LPS was localized in macrophages in the lamina propria from 1 h to >28 days after intravenous injection. LPS was also detected in the epithelial cells from 8 h to 7 days after injection. In contrast, LPS administered enterally was found in the gut lumen in close proximity to the mucosa but was not detected in enterocytes at any time. The concentration of LPS in enterocytes near the villus tip provides a mechanism for the clearance of endotoxin, by the turnover and shedding of LPS-containing enterocytes into the gut lumen, that has not been previously described.

Animals↗

PubMed2000

The effect of gadolinium-enhancing lesions on whole brain atrophy in relapsing-remitting MS.

OBJECTIVE: To determine the relationship between gadolinium-enhancing lesions and changes in whole brain parenchymal volume in patients with relapsing-remitting MS, and to test the hypothesis that gadolinium enhancement is a predictor of whole brain atrophy. METHODS: Twenty-four patients with clinically definite MS were imaged over 2 years. A computer-assisted segmentation technique based on high-resolution MRI was used to quantify gadolinium-enhancing T1 lesion volume and brain parenchyma and CSF volumes. Percent brain parenchymal volume (PBV) relative to the total intracranial volume was calculated, and changes in PBV were used to represent the degree of whole brain atrophy over 2 years. RESULTS: PBV at baseline was dependent on duration of MS, and a significant decrease in PBV was observed over the course of the study. Changes in enhanced T1 lesion load failed to correlate with changes in PBV, and multiple regression analyses determined that enhanced T1 lesion load at baseline was not a significant predictor of subsequent change in PBV. CONCLUSIONS: MR visible inflammation as demonstrated by enhanced T1 lesions is not a significant factor in the pathogenesis of whole brain atrophy in relapsing-remitting MS, suggesting that a more global pathologic process is responsible for the loss of brain parenchymal volume.

Adult↗

PubMed2000

Identification of mammalian-like purple acid phosphatases in a wide range of plants.

Purple acid phosphatases (PAPs) comprise a family of binuclear metal-containing hydrolases, members of which have been isolated from plants, mammals and fungi. Polypeptide chains differ in size (animal approximately 35kDa, plant approximately 55kDa) and exhibit low sequence homology between kingdoms but all residues involved in co-ordination of the metal ions are invariant. A search of genomic databases was undertaken using a sequence pattern which includes the conserved residues. Several novel potential PAP sequences were detected, including the first known examples from bacterial sources. Ten plant ESTs were also identified which, although possessing the conserved sequence pattern, were not homologous throughout their sequences to previously known plant PAPs. Based on these EST sequences, novel cDNAs from sweet potato, soybean, red kidney bean and Arabidopsis thaliana were cloned and sequenced. These sequences are more closely related to mammalian PAP than to previously characterized plant enzymes. Their predicted secondary structure is similar to that of the mammalian enzyme. A model of the sweet potato enzyme was generated based on the coordinates of pig PAP. These observations strongly suggest that the cloned cDNA sequences represent a second group of plant PAPs with properties more similar to the mammalian enzymes than to the high molecular weight plant enzymes.

Acid Phosphatase↗

PubMed2000

Development of chemical sensors based on redox-dependent receptors. Preparation and characterization of phenanthrenequinone-modified electrodes

The study of phenanthrenequinone(PQ)-modified electrodes, prepared by electropolymerization of a phenanthrenequinone-pyrrole derivative, is described. The surface-confined PQ is shown to behave similarly to PQ in solution, acting as a redox-dependent receptor toward aromatic ureas in aprotic solvents. Large, positive shifts in the E1/2 of the PQ0/- redox couple are observed in the presence of these ureas, due to a strong hydrogen bonding interaction between the PQ radical anion and urea. The effect is fully reversible. Of the substrates examined, only aromatic ureas produce a significant shift. Nonaromatic ureas or other HN and HO containing compounds have little effect on the E1/2. The magnitude of the shift is also independent of electrode coverage, allowing reproducible measurements to be made despite significant loss in material from the surface.

Journal Article↗

PubMed2000

Glatiramer acetate (Copaxone) treatment in relapsing-remitting MS: quantitative MR assessment.

OBJECTIVE: To evaluate the efficacy of glatiramer acetate (GA, Copaxone; Teva Pharmaceutical Industries, Ltd., Petah Tiqva, Israel) by MRI-based measures in patients with relapsing-remitting (RR) MS. METHODS: Twenty-seven patients with clinically definite RR-MS were treated with either 20 mg of GA by daily subcutaneous self-injection (n = 14) or placebo (n = 13) for approximately 24 months. Axial dual-echo fast-spin-echo T2-weighted images and T1-weighted images before and after gadolinium (Gd) were acquired at 1.5 tesla and transferred into an image processing computer system. The main outcome measures were the number of Gd-enhanced T1 and T2 lesions and their volume as well as brain parenchyma volume. RESULTS: The values of age, disease duration, Expanded Disability Status Scale (EDSS) score, the number of T1- and T2-weighted lesions, and their volume were similar between GA- and placebo-receiving groups at the entry of this study. There was a decrease in the number of T1-enhanced lesions (p = 0.03) and a significant percent annual decrease of their volume in GA recipients compared with those of placebo recipients. There were no significant differences between changes in the two groups in the number of T2 lesions and their volume. The loss of brain tissue was significantly smaller in the GA group compared with that of the placebo group. CONCLUSIONS: These results show that GA treatment may decrease both lesion inflammation and the rate of brain atrophy in RR-MS.

Adult↗

PubMed2000

Total brain N-acetylaspartate: a new measure of disease load in MS.

OBJECTIVE: To quantitate the extent of neuronal cell loss in MS via the whole brain's N-acetylaspartate (NAA) concentration (WBNAA). METHODS: Because NAA is assumed to be present only in neuronal cell bodies and their axons, we measured WBNAA as a marker for viable neurons in 12 patients (9 women and 3 men, 26 to 53 years of age) suffering from relapsing-remitting (RR) MS for at least 5 years and compared them with 13 age- and sex-matched normal controls. Total brain NAA was determined with proton MR spectroscopy, and WBNAA was obtained by dividing it by the total brain volume, calculated from high resolution MRI. RESULTS: The WBNAA of the RR MS patients was lower than their matched controls (p<0.005). This difference was greater among older than younger subjects. The linear prediction equations of WBNAA with age indicate a faster, x10, decline in the patients, approximately 0.8% per year of age (p = 0.022). CONCLUSION: The age-dependent decrease of whole brain N-acetylaspartate (WBNAA) in the patients suggests that progressive neuronal cell loss is a cardinal feature of this disease. WBNAA offers a quick, highly reproducible measure of disease progression and may be an important marker of treatment efficacy in MS as well as other neurodegenerative diseases.

Adolescent↗

PubMed2000

Numerical tissue characterization in MS via standardization of the MR image intensity scale.

Image intensity standardization is a recently developed postprocessing method that is capable of correcting the signal intensity variations in MR images. We evaluated signal intensity of healthy and diseased tissues in 10 multiple sclerosis (MS) patients based on standardized dual fast spin-echo MR images using a numerical postprocessing technique. The main idea of this technique is to deform the volume image histogram of each study to match a standard histogram and to utilize the resulting transformation to map the image intensities into standard scale. Upon standardization, the coefficients of variation of signal intensities for each segmented tissue (gray matter, white matter, lesion plaques, and diffuse abnormal white matter) in all patients were significantly smaller (2.3-9.2 times) than in the original images, and the same tissues from different patients looked alike, with similar intensity characteristics. Numerical tissue characterizability of different tissues in MS achieved by standardization offers a fixed tissue-specific meaning for the numerical values and can significantly facilitate image segmentation and analysis.

Adult↗

PubMed2000

The p53-independent tumoricidal activity of an adenoviral vector encoding a p27-p16 fusion tumor suppressor gene.

We describe here that DE1-adenovirus vectors (AV) expressing a p27-p16 fusion molecule, termed W9, induce tumor cell apoptosis when overexpressed in a wide range of tumor cell types. However, in primary human cells derived from a variety of normal tissues, AV-W9 induced minimal apoptosis. In tumor cells AV-W9 demonstrated 5- to 50-fold greater tumoricidal activity than either of the parental molecules p16 and p27. In these studies, AV-W9 elicited apoptosis independent of the p53 and Rb status of the tumor cells. In several murine tumor models AV-W9 demonstrated p53-independent antitumor activity. It completely prevented tumor formation in two ex vivo models, whereas the parental molecules resulted in partial protection. Furthermore, AV-W9 induced tumor regression or suppressed tumor growth when introduced intratumorally into preestablished tumors in mice. This effect may be mediated through tumor cell apoptosis or antiangiogenic activity of AV-W9. Thus, this novel chimeric molecule is more potent and capable of killing a broader spectrum of tumors than the parental p16 and p27 molecules independent of the tumor cell p53 and phenotype and represents a powerful new therapeutic agent for cancer gene therapy.

Adenoviridae↗

PubMed2000

In vivo detection of human vascular endothelial growth factor promoter activity in transgenic mouse skin.

We have generated transgenic mice expressing green fluorescent protein (GFP) driven by 2.453-kb (-2,362 to +91) of the 5'-upstream region of the human vascular endothelial growth factor (VEGF) promoter to monitor changes of VEGF gene transcription in situ. Neonatal transgenic mice exhibited GFP-derived fluorescence in tissues that have been previously reported to express VEGF mRNA expression, including lung, cartilage, and brain. In normal skin during postnatal development, moderate fluorescence was observed in the upper epidermis and, more prominently, in the outer root sheath keratinocytes of hair follicles. Strong up-regulation of GFP fluorescence was observed in the hyperplastic epidermis of the wound edge at 48 hours after wounding, whereas little GFP fluorescence was detected in the dermis. In situ hybridization confirmed an identical expression pattern of VEGF mRNA in these wounds. Topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) induced strong VEGF-GFP expression in suprabasal epidermis. Little or no fibroblast-derived fluorescence was seen both in the wound model and after TPA application. By confocal laser microscopy, increased GFP fluorescence was detectable in the epidermis of intact mouse ear skin as early as 6 hours after topical TPA treatment. Importantly, GFP fluorescence was also measurable in the skin of living transgenic mice. These results resolve the present controversy regarding the ability of VEGF-GFP transgenic mouse models to correctly reflect established patterns of VEGF expression, and show the model to be a powerful tool for the in vivo monitoring of VEGF gene expression.

Animals↗

PubMed2000

Trace metal speciation and bioavailability in urban soils.

Urban soils often contain concentrations of trace metals that exceed regulatory levels. However, the threat posed by trace metals to human health and the environment is thought to be dependent on their speciation in the soil solution rather than the total concentration. Three inactive railway yards in Montréal, Québec, were sampled to investigate the speciation and bioavailability of Cd, Cu, Ni, Pb and Zn. Soil solutions were obtained by centrifuging saturated soil pastes. In the soil solutions, up to 59% of the dissolved Cd was in its free ionic form. For Cu, Pb and Zn, organic complexes were the predominant species. Over 40% of Ni was present as inorganic complexes if the solution pH exceeded 8.1. Multiple regression analyses showed that pH and total metals in soil were significantly correlated with the activities of free metal ions, except for Cd(2+), which only had a weak correlation with soil pH. Free, dissolved and total soil metals were tested for their ability to predict metal uptake by plants in the field. However, none of these metal pools were satisfactory predictors. The results indicated that in these urban soils, trace metals were mainly in stable forms and bioavailability was extremely low.

Journal Article↗

PubMed2000

Evaluating three trace metal contaminated sites: a field and laboratory investigation.

Selecting guidelines to evaluate elevated metals in urban brownfields is hindered by the lack of information for these sites on ecosystem structure and function. A study was performed to compare three trace metal-contaminated sites in the metropolitan Montreal area. The goal was to obtain an idea of the organisms that may be present on urban brownfields and to measure if elevated metals alter the presence and activity of the indigenous biota. Field and laboratory studies were conducted using simple methodologies to determine the extent to which microbial activity affected by trace metal content, to assess diversity of plant and soil invertebrate communities and to measure phytoaccumulation of trace metals. It was found that microbial activity, as measured by substrate-induced respiration (SIR) and nitrification, was not affected by the levels of soil Cd, Cu, Ni, Pb and Zn recorded on the sites. Seven of the 12 invertebrate groups collected were sampled on soils with similar Cd, Cu, Ni, Pb and Zn concentrations. Diversity of plant species increased as a function of the length of time the sites had been inactive. Levels of metals in plant tissue were influenced by soil characteristics and not by total soil Cd, Cu, Ni, Pb and Zn.

Journal Article↗