Biomedical subjects

J M Yang

Publications and source records attributed to J M Yang.

At least 109 records · Page 6Linked to original sources

PubMed1997

Regulation of the function of P-glycoprotein by epidermal growth factor through phospholipase C.

Many multidrug-resistant (MDR) cell lines overexpress the epidermal growth factor receptor (EGFR) as well as P-glycoprotein (P-gp). However, the role of the increased EGFR in P-gp-mediated drug resistance remains unclear. Since recent studies suggest that activation of phospholipase C (PLC) could increase the phosphorylation of P-gp, and activation of the EGFR would also activate PLC, we investigated whether the effect of epidermal growth factor (EGF) on the phosphorylation of P-gp was mediated through PLC. Treatment of the human MDR breast cancer cell line, MCF-7/AdrR, with EGF increased the phosphorylation of P-gp by 20-50%. The increased phosphorylation of P-gp was accompanied by stimulation of PLC activity, as measured by the production of inositol, 1,4,5-trisphosphate and diacylglycerol, products of phosphatidylinositol-4,5-bisphosphate hydrolysis. Treatment of MDR cells with EGF also had detectable effects on P-gp function. For example, following incubation of MCF-7/AdrR cells with ECF, we observed a consistent decrease in total vinblastine (VBL) accumulation. Kinetic analysis revealed this change to be due to an increase in membrane efflux. The latter was measured by the initial uptake velocity, which was inhibited by EGF. VBL uptake measured at 0-320 sec was inhibited by 20-40%, which was associated with a similar increase in VBL efflux. EGF had no effect on drug accumulation, uptake, or efflux in sensitive MCF-7 cells. These data indicate that EGF can modulate the phosphorylation and function of P-gp, and suggest that this effect may be initiated by the activation of PLC.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Activity of UDP-GlcNAc:GlcNAc beta 1-->6(GlcNAc beta 1-->2) Man alpha 1-->R[GlcNAc to Man] beta 1-->4N-acetylglucosaminyltransferase VI (GnT VI) from the ovaries of Oryzias latipes (Medaka fish).

UDP-GlcNAc:GlcNAc beta 1-->(GlcNAc beta 1-->2)Man alpha 1-R[GlcNAc to Man] beta 1-->4N-acetylglucosaminyltransferase VI (GnT VI) activity was shown to be present in crude homogenates of Medaka fish (Oryzias latipes) ovaries using UDP-[14C]GlcNAc and synthetic GlcNAc beta 1-->6 (GlcNAc beta 1-->2)Man alpha 1-->6Glc beta 1-->octyl as substrates. Characterization of this activity showed a pH optimum at about pH 7.0 and an absolute requirement for divalent cations. The optimum concentration of Mn2+ was at about 25 mM. This finding is the first report on GnT VI activity in fish; the enzyme has previously been described only in avian tissues.

Animals↗

PubMed1997

Preparation and properties of SBS-g-DMAEMA copolymer membrane by ultraviolet radiation.

A styrene-butadiene-styrene triblock copolymer (SBS) membrane was prepared by solvent casting. Grafting of dimethyl amino ethyl methacrylate (DMAEMA) to this SBS membrane was subsequently conducted by ultraviolet radiation-induced graft copolymerization without degassing to obtain a SBS-g-DMAEMA copolymer membrane. The graft copolymer was characterized by infrared spectroscopy and scanning electron microscopy. The degree of grafting and the mechanical properties of SBS and SBS-g-DMAEMA were measured. Contact angle, water content, and protein absorption of fibrinogen and albumin experiments were also performed to evaluate the biocompatibility of SBS-g-DMAEMA graft copolymer membranes. It was found that the degree of grafting was related to the irradiation time, DMAEMA concentration, and temperature. The tensile strength of the SBS-g-DMAEMA membrane increased with an increase in the degree of grafting. By using Kaelble's equation and the contact angle data, the surface tension of SBS-g-DMAEMA was determined. It was found that with an increase in the degree of grafting, the surface tension and water content of SBS-g-DMAEMA membrane increased, whereas the contact angle decreased. The amount of absorption of albumin and fibrinogen decreased with an increase in amount of grafting. However, there was a minimum for the adsorption of proteins in the SBS-g-DMAEMA membrane.

Absorption↗

PubMed1997

Mechanical properties of acrylic bone cement containing PMMA-SiO2 hybrid sol-gel material.

An organic-inorganic hybrid material, poly(methyl methacrylate) (PMMA)-SiO2 (SiO2 content of 72 wt%), was prepared by incorporating PMMA structure units covalently into an SiO2 glass network via the sol-gel approach. The hybrid sol-gel material PMMA-SiO2 was subsequently used as the solid powder component of bone cement and its mechanical properties were evaluated. The effects of the addition of tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA) on the properties of the sol-gel hybrid bone cement were also investigated. The influence of these components on the temperature rise during polymerization was discussed. It was found that the new bone cement containing PMMA-SiO2 hybrid sol-gel material had higher modulus than that of Simplex-P bone cement. The addition of TCP in the new bone cement increased the Young's modulus and the polymerization time; the inverse was observed for the tensile, bending, and compressive strengths, and the polymerization temperature. The addition of HEMA and EGDMA in the new bone cement had the opposite effect of TCP. The comparison between the new sol-gel bone cement and the commercial Simplex P bone cement was discussed.

Biocompatible Materials↗

PubMed1997

Effect of MMA-g-UHMWPE grafted fiber on mechanical properties of acrylic bone cement.

Ultrahigh molecular weight polyethylene (UHMWPE) fibers were treated with argon plasma for 5 min, followed by uv irradiation in methyl methacrylate (MMA)-chloroform solution for 5 h to obtain MMA-g-UHMWPE grafted fiber. The grafting content was estimated by the titration of esterification method. The grafting amount of 5280 nmol/g was the largest for the MMA concentration at 18.75 vol%. To improve the mechanical properties of acrylic bone cement, pure UHMWPE fiber and MMA-g-UHMWPE fiber were added to the surgical Simplex. P radiopaque bone cement. The mechanical properties including tensile strength, tensile modulus, compressive strength, bending strength, and bending stiffness were measured. Dynamic mechanical analysis was also performed. By comparing the effect of the pure UHMWPE fiber and MMA-g-UHMWPE grafted fiber on the mechanical properties of acrylic bone cement, it was found that the acrylic bone cement with MMA-g-UHMWPE grafted fiber had a more significant reinforcing effect than that with untreated UHMWPE fiber. This might be due to the improvement of the interfacial bonding between the grafted fibers and the acrylic bone cement matrix.

Acrylates↗

PubMed1997

Polymerization of acrylic bone cement using differential scanning calorimetry.

The polymerization of acrylic bone cement using differential scanning calorimetry (DSC) was investigated. The polymerization reaction of the acrylic bone cement was found to be an approximately first order reaction. Two kinds of reaction rate constants for the polymerization reaction were observed. Both rate constants were calculated before and after the peak time. The effects of the addition of tricalcium phosphate (TCP) on the polymerization reaction of standard Surgical Simplex-P Radiopaque Bone Cement have been investigated by DSC. The TCP content had a strong retardation effect on the rate constants. The thermal stability of the acrylic bone cement was also studied by thermogravimetric analysis.

Acrylates↗

PubMed1997

Electrical and mechanical effects of a novel antihypertensive quinazoline derivative, 3-[[4-(2-methoxyphenyl) piperazin-1-ly]methyl]-5-(methylthio)-2,3-dihydroimidazo [1,2-c]quinazoline, on guinea pig ventricular muscles.

Electrical and mechanical effects of 3-[[4-(2-methoxyphenyl)piperazin-1-ly]methyl]-5-(methylthio)-2,3-+ ++dihydroimidazo[1,2-c]quinazoline (DL-017), a new synthesized antihypertensive agent, were studied in guinea-pig ventricular papillary muscles. In muscle fibers driven at 1 Hz, DL-017 decreased the twitch force in a concentration-dependent manner and significantly increased the action-potential duration and decreased intracellular Na+ activity (ai(Na)) and maximal rate of upstroke of action-potential (Vmax) when concentrations were greater than 1 microM. Phenylephrine in the presence of 1 microM propranolol produced a concentration-dependent positive inotropy. DL-017 (0.01 microM) antagonized the positive inotropic effect of phenylephrine and shifted the concentration-response curve to the right. In K+-depolarized muscle fibers, 0.1 microM DL-017 significantly decreased the contractile force without changing the slow action potential. In low-[K+]o and high-[Ca2+]o solutions, a train of stimuli triggered a spontaneous rhythm that could be abolished by 3 microM DL-017. Our results suggest that DL-017 not only exhibits an alpha1-antagonistic effect but also induces negative inotropy by a decrease in myofibrillar calcium sensitivity and inhibits Na+ channels at higher concentrations, contributing to the drug's negative inotropic and type-I antiarrhythmic effects.

Action Potentials↗

PubMed1997

A novel threonine --> proline mutation at the end of 2B rod domain in the keratin 2e chain in ichthyosis bullosa of Siemens.

We report a novel mutation in a case of ichthyosis bullosa of Siemens that results in a threonine --> proline substitution in a novel location, codon 485 in a highly conserved residue position of the IATYRKLLEGE consensus motif at the end of the 2B rod domain segment of the keratin 2e chain. The disease phenotype is consistent with the inappropriate substitution of a proline near the end of the rod domain, because it lies near the predicted molecular overlap region of coiled-coil molecules, which is critical for the maintenance of the structural integrity of keratin intermediate filaments.

Biopsy↗

PubMed1997

An alanine to proline mutation in the 1A rod domain of the keratin 10 chain in epidermolytic hyperkeratosis.

We report a mutation in a case of epidermolytic hyperkeratosis that results in a proline for alanine substitution in the residue position 12 of the 1A subdomain of the keratin 10 chain (codon 158). The disease phenotype is consistent with the inappropriate substitution of a proline near the beginning of the rod domain, because it is likely to seriously disrupt the structural organization of coiled-coil molecules within keratin intermediate filaments. Mutations/substitutions in this position have not been reported in any keratin disease. Position 12 is an alanine in all intermediate filament chains, and lies in the outer b heptad position of the coiled-coil. In vitro peptide interference assembly assays revealed that substitutions that alter residue size or charge at this position primarily interfere with keratin filament elongation.

Adolescent↗

PubMed1997

[A preliminary observation on effects of xiaochaihu decoction on uropathogenic E. coli].

OBJECTIVE: To study the effects of Xiaochaihu Decoction (XCHD) on uropathogenic E. coli (UEC). METHODS: In vitro bacterial inhibition test and in vitro adhesion of UEC to human uro-epithelial cell assay were used to investigate the anti-infectionary effects of XCHD. RESULTS: Proliferation inhibitory effect of E. Coli treated with XCHD, and a significant reduction in number of UEC to human uro-epithelial cells was observed in the XCHD treated group at a non-inhibitory concentration of the medication in comparison with the control groups. CONCLUSION: It is possible that XCHD could act against urinary infection.

Anti-Bacterial Agents↗

PubMed1997

The Pax-6 homeobox gene is expressed throughout the corneal and conjunctival epithelia.

PURPOSE: Heterozygous defects in the highly conserved PAX6 homeobox gene are associated with aniridia, an inherited human disorder affecting several ocular structures, including the adult cornea. This work establishes the pattern of Pax-6 gene expression in the surface epithelia of the late embryonic and adult eye. METHODS: Chick embryo sections and wholemounts, as well as adult mouse and monkey tissues, were analyzed by in situ hybridization and immunohistochemistry with probes specific to Pax-6. Western immunoblots were used to detect Pax-6 protein, and mRNA expression was analyzed by quantitative reverse transcription-polymerase chain reaction. RESULTS: In days 5 and 6 chick embryos, Pax-6 protein is found in the nuclei of all cells within the corneal epithelium and in the future conjunctiva. Although not detected in the cornea by in situ hybridization, Pax-6 mRNA is, in fact, present at levels comparable to those observed in the retina. In the mature mouse, Pax-6 protein was expressed in all cells of the corneal epithelium, the limbus, and the entire conjunctiva. Similar results were obtained for the monkey cornea. CONCLUSIONS: These data indicate that in addition to its role in the embryo, Pax-6 is expressed strongly in surface epithelia of the adult cornea and conjunctiva. In cells of these tissues, the gene may function by regulating structural or secretory specializations. Pax-6 might play a direct role in the maintenance and proliferation of corneal stem cells, a vital process that appears to be defective in aniridia.

Animals↗

PubMed1997

Increased chromosome 20 copy number detected by fluorescence in situ hybridization (FISH) in malignant melanoma.

DNA amplification is an important mechanism of tumor progression that allows cancer cells to up-regulate the expression of critical genes such as oncogenes and genes conferring drug resistance. Recent studies using comparative genomic hybridization (CGH) revealed increased DNA copies of 20q sequences in 7 melanoma cell lines and B archival metastatic melanoma lesions. To evaluate chromosome 20 abnormalities in more detail and to resolve discrepancies between karyotype and CGH findings, we performed FISH analysis of metaphase cells in 13 melanoma cell lines (including the 7 lines used for CGH) and 9 primary melanoma specimens by using a whole chromosome paint specific for chromosome 20. All 13 cell lines (100%) and 8/9 primary tumors (89%) showed extra copies of chromosome 20 relative to tumor ploidy. Additionally, 6/14 cell lines (43%) and 2/8 primary tumors (25%) showed translocated chromosome 20 material previously undetected by standard cytogenetics. Cytologic evidence for gene amplification was also found in one cell line, which contained an add(20)(p13), with additional DNA being derived from 20q sequences. These data suggest that overrepresentation of a gene or genes important for melanoma pathogenesis resides on the long arm of chromosome 20.

Chromosome Aberrations↗

PubMed1997

Inhibitory effect of alkylating modulators on the function of P-glycoprotein.

Modulators of P-glycoprotein (P-gp) are often themselves transported out of cells, thereby limiting their effectiveness. It may be possible to develop more effective modulators of multidrug resistance by designing drugs that irreversibly block the function of P-gp. Therefore, we studied the effect of the mustard derivatives of fluphenazine (FPN) and trans-flupenthixol (FPT) on P-gp function. Both fluphenazine-mustard (FPN-M) and trans-flupenthixol-mustard (FPT-M) possessed alkylating activity, as assayed using 4-(p-nitrobenzyl) pyridine. Multidrug-resistant MCF-7/AdrR cells were incubated with FPN or FPN-M, or FPT or FPT-M for 1 h, washed for varying number of times in phosphate-buffered saline (PBS), then resuspended in medium containing [3H]vinblastine (VBL), and assayed for steady-state accumulation of the drug. Washing had far less of an effect on the ability of FPN-M and FPT-M to increase VBL accumulation compared to their parent compounds. After eight washes in excess PBS, the cells initially exposed to FPN or FPT accumulated only 30% and 50% of the initially accumulated drug, whereas the FPN-M- or FPT-M-treated cells accumulated approximately 75% and 90% of the control, respectively. FPN-M and FPT-M also increased the uptake and decreased the efflux of VBL from MDR cells despite repeated washing. We also examined the effects of these modulators on sensitivity of MDR cells to cytotoxic agents. FPN-M and FPT-M sensitized MCF-7/AdrR cells to VBL and doxorubicin to a greater extent than their parent compounds. These studies point out the potential of "irreversible" P-gp modulators to produce prolonged chemosensitization.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

Interaction of P-glycoprotein with protein kinase C in human multidrug resistant carcinoma cells.

Indirect evidence has suggested that P-glycoprotein (P-gp), the multidrug transporter, is phosphorylated by protein kinase C (PKC) and that phosphorylation modulates its transport function. To address the first premise more directly, ie., that P-gp is phosphorylated by PKC, we investigated the interaction between P-gp and PKC in sensitive and multidrug resistant MCF-7 and KB human carcinoma cell lines. We found that P-gp and PKC were coimmunoprecipitated from the multidrug-resistant cell lines MCF-7/AdrR and KB-V-1, using antibodies to either protein. The association between the two proteins was enhanced by phorbol 12-myristate 13-acetate, an analogue of diacylglycerol that induces translocation of PKC to the plasma membrane. The anti-P-gp immunoprecipitates contained PKC activity as measured by direct phosphorylation reactions. The interaction of PKC with P-gp displayed isozyme specificity: PKC-alpha, -beta, gamma, -epsilon, and -phi, but not -delta, -mu, -zeta, -lambda, were found to coimmunoprecipitate with P-gp. These studies indicate that P-gp closely interacts with PKC and serves as a substrate, and that specific isozymes of this kinase may be involved in the phosphorylation of the multidrug transporter.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

The proximal promoter of the human transglutaminase 3 gene. Stratified squamous epithelial-specific expression in cultured cells is mediated by binding of Sp1 and ets transcription factors to a proximal promoter element.

The transglutaminase 3 enzyme is expressed during the late stages of the terminal differentiation of the epidermis and in certain cell types of the hair follicle. The enzyme is thought to be critically involved in the cross-linking of structural proteins and in the formation of the cornified cell envelope, thereby contributing to rigid structures that play vital roles in shape determination and/or barrier functions. To explore the mechanisms regulating the expression of the transglutaminase 3 gene (TGM3), 3.0 kilobase pairs of sequences upstream from the transcription start site were assessed for their ability to control the expression of a chloramphenicol acetyltransferase reporter gene. Deletion analyses in transiently transfected epidermal keratinocytes defined sequences between -126 and -91 as the proximal promoter region of the gene, and which can confer epithelial-specific expression to the TGM3 gene in vitro. Mutation and DNA-protein binding analyses indicated that a complex interaction between adjacent Sp1- and ets-like recognition motifs with their cognate binding factors is required for the function of the TGM3 promoter. As these TGM3 sequences can confer promoter/enhancer activity to reporter genes at a level comparable to the powerful SV40 promoter, they may be useful for gene therapy in keratinocytes.

3T3 Cells↗

PubMed1996

Factors affecting urethrocystographic parameters in urinary continent women.

To evaluate the urethrocystographic changes in different conditions, 154 women were evaluated by using introital sonography. Patients were divided into three groups: group 1 (n = 103) normal, including 10 postmenopausal women; group 2 (n = 46) pregnant, including 16 women in the first trimester, 15 in the second trimester, and 15 in the third trimester; group 3 (n = 15) severe genitourinary prolapse. None of the 154 women had a history of urinary incontinence. The following parameters were measured at rest: urethral thickness, uretheral length, urethral inclination, and posterior urethrovesical angle. On maximum straining, urethral inclination, posterior urethrovesical angle, and rotational angle were measured. In general, age, parity, and menopause did not affect the urethrocystographic parameters in Group 1 patients. Postmenopausal women had a significant decrease in the urethral thickness compared with the premenopausal women (p = 0.026). Patients in Groups 2 and 3 had a significantly lower urethral position than those in group 1. However, hypermobility of the urethra was found only in Group 3. Different menstrual ages did not affect the urethral position but could affect the posterior urethrovesical angle at rest in the first trimester. Introital sonography, without the risk of radiation exposure, enables the observation of static and dynamic changes in the lower urinary tract, both repeatedly and reproducibly.

Adult↗

PubMed1996

Chicken homeobox gene Prox 1 related to Drosophila prospero is expressed in the developing lens and retina.

Prox 1 is the vertebrate homolog of Drosophila prospero, a gene known to be expressed in the lens-secreting cone cells of fly ommatidia. Chicken Prox 1 cDNAs were isolated from 14 day embryonic chicken lenses, and a complete open reading frame encoding an 83 kDa protein was elucidated. The homeodomains of chicken and mouse Prox 1 are identical at the amino acid level and are 65-67% similar to the homeodomains of Drosophila and C. elegans prospero. The homology between these proteins extends beyond the homeodomain. There is 56% identity between chicken Prox 1 and Drosophila prospero in the C-terminal region downstream of the homeodomain, whereas there is little similarity upstream of the homeodomain. Prox 1 is expressed most actively in the developing lens and midgut and at lower levels in the developing brain, heart, muscle, and retina. cDNA sequencing has established that there are alternatively spliced forms of the single Prox 1 gene, which probably account for the two abundant RNAs of about 2 and 8 kb and two less abundant RNAs close to 3.5 kb in length in the lens. In the lens fibers, only the shortest mRNA was present, whereas, in the epithelial cells, both short and long mRNAs were detected. By using in situ hybridization, expression of the Prox 1 gene was first detected at stage 14 in the early lens placode and slightly preceded the expression of delta 1-crystallin, the first crystallin gene expressed in the developing chicken lens. At later stages of development, Prox 1 mRNA was observed throughout the lens, but it appeared more abundant around the bow region of the equator than in the anterior epithelium or the fibers. In the retina, expression of the Prox 1 gene was detected mainly in the inner nuclear layer during later stages of histogenesis. The conserved pattern of Prox 1/prospero gene expression in vertebrates and Drosophila suggests that Prox 1, like Pax-6, may be essential for eye development in different systematic groups.

Amino Acid Sequence↗

PubMed1996

Radiation-induced graft copolymer SBS-g-VP for biomaterial usage.

The grafting of 4-vinyl pyridine (VP) to styrene-butadienestyrene triblock copolymer (SBS) by radiation-induced graft copolymerization was studied. The cohesive properties such as cohesive energy (Ecoh), molar volume (V), solubility parameter (delta), molar molecular weight (WM), specific volume (Vg), and density (1/Vg) of SBS-g-VP graft copolymer were calculated according to the group contribution of Fedors. The morphology of SBS-g-VP was studied by optical polarizing microscopy. We also measured the glass transition temperature and the mechanical properties of SBS-g-VP graft copolymer. Contact angle and blood-clotting time experiments were also performed to evaluate the biocompatibility of SBS-g-VP. A second domain was found in the SBS-g-VP graft copolymer, which resulted in different properties between SBS-g-VP and SBS. The blood compatibility of SBS-g-VP as measured by the Lee-White clotting test was better than that of SBS and polystyrene.

Biocompatible Materials↗