Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pseudolatexes of the biodegradable polyesters poly(D,L-lactide) (PLA) and poly(epsilon-caprolactone) (PCL) have been developed as potential aqueous coatings for sustained release. Since PLA and PCL are known to hydrolyze, the influence of the surfactant system, temperature, pH, and particle size on the chemical stability of the polymers as aqueous colloidal dispersions was investigated. Pseudolatexes of PLA and PCL formulated with a nonionic surfactant system were the most stable. When these dispersions were stored in unbuffered media for 350 days at 5 degrees C, only small changes in the weight-average molecular weights (Mw) of the polymers were observed. At 37 degrees C there was rapid degradation of both polymers in the dispersions. Arrhenius plots for the degradation of PLA and PCL resulted in a linear relationship for PCL. The nonlinear relationship for PLA was attributed to the polymer being in two different physical states within the 5 to 37 degrees C range which was used for the Arrhenius plots. PCL was in the rubbery state at all temperatures studied. Storage of the pseudolatexes in pH 1.65 buffer at 37 degrees C catalyzed the rates of degradation of both PLA and PCL. However, refrigeration of the pseudolatexes stabilized the polymers even at pH 1.65 for up to 4 months. Particle size had an insignificant effect on PLA and PCL stability in pseudolatexes prepared with either a nonionic or an anionic surfactant system.
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PMID:Biodegradable pseudolatexes: the chemical stability of poly(D,L-lactide) and poly(epsilon-caprolactone) nanoparticles in aqueous media. 155 42

Poly(DL-lactic acid) (PLA), poly(epsilon-caprolactone) (PCL), and their copolymers (PLA-CL) with various monomer compositions were synthesized, and their properties as matrix for the sustained release of drugs were evaluated. The copolymerization technique produced very soft films which incorporated the drugs without deterioration of the elastic properties. Cisplatin and MD-805 were loaded in the films by casting the polymer solution containing the drugs. Fractions of the drugs released from the PLA-CL films were governed by the initial loading, the film thickness, and the polymer molecular weight. The drug release profiles obeyed the classical Fickian diffusion equation at least in the early stage, but significant hydrolytic degradation of the matrix polymers occurred in the later stage, influencing the kinetics of drug release. The monomer composition of copolymer affected the release profile more strongly than the initial molecular weight of the copolymer.
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PMID:In vitro evaluation of sustained drug release from biodegradable elastomer. 179 48

In this article we report on the development, introduction, and maintenance of a policy to promote rational use of thrombolytic drugs by hospital doctors. The work was undertaken within the framework of the voluntarily operated Riverside East drugs guide (formulary) management system (FMS). The policy was introduced in October 1988 and revised in November 1989 to coincide with the launch of the new, expensive thrombolytic drugs, alteplase (rt-PA, Actilyse) in 1988 and antistreplase (APSAC, Eminase) in 1989. Streptokinase was recommended as the first-line drug for patients who had not received it within the last 6 months. The policy was communicated to all staff in meetings and a drugs guide bulletin and reinforced by ward pharmacists. Results over a 15 month period show voluntary compliance by prescribers with the recommended policy. One hundred and seventy-four patients (22% cardiac admissions) presented with acute myocardial infarction. Of these 43 (25%) received streptokinase, the first-line recommended drug, 7 received alteplase and none received anistreplase. The savings in drug expenditure from using streptokinase rather than alteplase or anistreplase for the 15-month period of investigation were over pounds 27,000. This work represents an example of the effectiveness of the Riverside East FMS model in influencing prescribing behaviour.
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PMID:Medical audit and formulary management: a policy for rational use of thrombolytic drugs. 190 56

Several angiogenic preparations that have been shown to stimulate plasminogen activator (PA) and collagenase production by cultured bovine capillary endothelial (BCE) cells were tested for their ability to stimulate BCE cell motility in the phagokinetic track assay. Bovine retinal extract, medium conditioned by 3T3-F442A differentiated mouse adipocytes, SK HEP-1 human hepatoma cell lysate, mouse sarcoma 180 cell lysate, and medium conditioned by mouse sarcoma 180 cells stimulated motility 68.7%, 48.5%, 140.9%, 56.5%, and 102.1%, respectively, relative to untreated cells. The motility-stimulating activity of these preparations was dose dependent and linear over the 16-h assay period. Several hormones and growth factors were tested for BCE cell motility-stimulating activity, including insulin, vasopressin, fibroblast growth factor, and a partially purified preparation of sarcoma growth factor, and were found to be ineffective. 12-0-tetradecanoyl-phorbol-acetate (TPA), a potent stimulator of both PA and collagenase activities in BCE cells, also did not stimulate motility, indicating that protease production is not sufficient to stimulate BCE cell motility in this assay. Neither SK HEP-1 hepatoma cell lysate nor TPA was effective in stimulating motility in bovine aortic endothelial (BAE) cells. The inability of SK HEP-1 hepatoma cell lysate to stimulate movement in BAE cells is consistent with the observation that angiogenesis occurs by sprouting of capillaries, not large vessels.
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PMID:Stimulation of motility in cultured bovine capillary endothelial cells by angiogenic preparations. 632 76

Several chromosomal regions are found to be consistently amplified in human breast cancers. For two of these regions, 8p12 and 10q26, we previously reported the amplification of genes encoding FGF receptors, FGFRI/FLG and FGFR2/BEK, in about 12% of breast tumors. The PLAT gene, encoding the tissue-type plasminogen activator, is also located close to or within the 8p12 region. In the present study, we show that both FGFRI and PLAT can be amplified in breast as well as ovarian carcinomas. FGFRI amplification was detected in 14.5% of breast and 7.8% of ovarian tumors, whereas PLAT was found to be amplified in 15.6% and 19.4% of the tumors, respectively. Each gene could be amplified independently of the other. These data raised the question of which gene is selected for amplification at 8p12. In most cases, the levels of expression of FGFRI and PLAT in breast tumors were comparable to their level of expression in normal mammary tissue. However, FGFRI was expressed above the normal level in a certain number of cases. This gene could be a good candidate as "driver" of the 8p12 amplification, but it cannot account for all complex molecular events taking place in this region.
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PMID:FGFRI and PLAT genes and DNA amplification at 8p12 in breast and ovarian cancers. 769 48

EGF receptors are expressed on most fetal and adult cells but their precise roles are not well known. We previously reported that, in P19 embryonal carcinoma cells, the expression of kinase-negative EGFR inhibits retinoic acid (RA)-induced differentiation to nervous tissue, suggesting that EGFR plays a role in differentiation (J.-X. Wu and E. D. Adamson (1993) Dev. Biol. 159, 208-222). Embryo stem (ES) cells differentiate into a wide range of tissue types after the removal of the cytokine LIF from the culture medium. We demonstrate here that the induction of some early markers of differentiation, tissue-type plasminogen activator (tPA), AFP and keratins 8 and 19 is inhibited, whilst brachyury and myosin are increased, in clones containing kinase-negative mutant EGFR. After an extended period of differentiation, the cell types present in mutant and control cultures differed. Mutant clones produced frequent cardiac and skeletal muscle as the predominant differentiated cell types in vitro; other cells types were sparse or absent. Teratocarcinomas formed by EGFR-deltakinase-expressing ES cells contained frequent skeletal and cardiac muscle as well as apoptotic nuclei, while normal ES cells produced no detectable muscle and less apoptoses. Since mutant differentiated cultures had slower growth rates and increased levels of cell death, we concluded that: (1) inactive EGFR does not allow some cell types to survive and/or proliferate; (2) tissues that do not require EGFR for their survival, development or function predominate in long-term mutant cultures; (3) EGFR activity is not necessary for cardiac and skeletal muscle or endoderm formation and (4) Impaired survival of EGF-dependent lineages leads to preferential selection of muscle in differentiating ES cells.
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PMID:Kinase-negative mutant epidermal growth factor receptor (EGFR) expression during embryonal stem cell differentiation favours EGFR-independent lineages. 889 44

A bioresorbable aliphatic polyester was synthesized by bulk copolymerization of a 1/1 M/M L,L-lactide/epsilon-caprolactone mixture using zinc metal as initiator. The actual composition of the copolymer was found to be 1.5/1 as deduced from 1H NMR spectra obtained in DMSO-d6 solutions where higher resolution was obtained as compared with chlorinated solvents. Resonances due to L-lactyl units (L) exhibited triads stereosensitivity, epsilon-oxycaproyl units (C) being sensitive to dyads. Average lengths of both poly(lactic acid) and polycaprolactone sequences were evaluated and showed the presence of rather long PLA blocks. Furthermore, no CLC triad signal was found, suggesting the absence of transesterification rearrangements. 10 x 10 x 2 mm specimens made of the copolymer were allowed to age in isoosmolar pH = 7.4 phosphate buffer at 37 degrees C. Degradation was monitored by various analytical techniques such as SEC, X-ray diffractometry, DSC, and 1H NMR. Data were compared with the behaviour of PCL and PLA homopolymers allowed to age under similar conditions. Crystallinity and composition changes are discussed in terms of preferential degradation in L- and C-containing amorphous domains, crystallized long PLA blocks being much more resistant.
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PMID:Structural characterization and hydrolytic degradation of a Zn metal initiated copolymer of L-lactide and epsilon-caprolactone. 899 92

Poly(epsilon-caprolactone) (PCL) microspheres containing c. 3% bovine serum albumin (BSA) were prepared by melt encapsulation and solvent evaporation techniques. PCL, because of its low Tm, enabled the melt encapsulation of BSA at 75 degrees C thereby avoiding potentially toxic organic solvents such as dichloromethane (DCM). Unlike the solvent evaporation method, melt encapsulation led to 100% incorporation efficiency which is a key factor in the microencapsulation of water-soluble drugs. Examination of the stability of the encapsulated protein by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that protein integrity was unaffected by both methods of encapsulation. In vitro release of the protein into phosphate buffer examined at 37 degrees C from microspheres prepared by both techniques showed that the release rate from melt-encapsulated microspheres was somewhat slower compared to the release from solvent-evaporated spheres. Both released around 20% of the incorporated protein in 2 weeks amounting to approximately 6.5 micrograms mg-1 of microspheres. Although the diffusivity of macromolecules in PCL is rather low, it is shown that PCL microspheres are capable of delivering sufficient quantity of proteins by diffusion for prolonged periods to function as a carrier for many vaccines. Unlike poly(lactic acid) (PLA) and poly(glycolic acid) (PGA) polymers which generate extreme acid environments during their degradation, the delayed degradation characteristics of PCL do not generate an acid environment during protein release and, therefore, may be advantageous for sustained delivery of proteins and polypeptides.
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PMID:Protein release from poly(epsilon-caprolactone) microspheres prepared by melt encapsulation and solvent evaporation techniques: a comparative study. 915 Nov 93

Hepatocyte transplantation may provide an alternative to orthotopic liver transplantation to treat liver failure. However, suitable systems to transplant hepatocytes and promote long-term engraftment must be developed. In this study, highly porous, biodegradable sponges were fabricated from poly (L-lactic acid) (PLA), and poly (DL-lacticco-glycolic acid) (PLGA), and utilized to transplant hepatocytes into the mesentery of three groups of Lewis rats. The portal vein was shunted to the inferior vena cava in one group of rats (PCS). The second group of animals received a PCS and a 70% hepatectomy on the day of sponge-hepatocyte implantation (PCS + HEP), and the control group (CON) received no surgical stimulation. The sponges were vascularized by ingrowth of fibrovascular tissue over the first 7 days in vivo. Approximately 95-99% of the implanted hepatocytes (determined utilizing computer-assisted image analysis) died in all three experimental groups during this time. The number of engrafted hepatocytes in the CON group further decreased over the next 7 days to 1.3 +/- 1.1% of the original cell number. However, the number of engrafted hepatocytes in the PCS and PCS + HEP increased over this time to 6 +/- 1% and 5 +/- 2%, respectively. The number of engrafted hepatocytes in the PCS group continued to increase over the next 2.5 months to a value of 26 +/- 12% of the initial cell number, and a large number of engrafted hepatocytes was still present at 6 months. These results indicate that stable new tissues can be engineered by transplanting hepatocytes on biodegradable sponges into heterotopic locations if appropriate stimulation is provided.
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PMID:Long-term engraftment of hepatocytes transplanted on biodegradable polymer sponges. 936 46

Vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) are structurally related growth factors for endothelial cells. VEGF binds to the related receptor tyrosine kinases Flt 1 and KDR/Flk 1 with high affinity, whereas PlGF binds only to Flt 1. Ligand-stimulated KDR is known to transduce signals for cellular activity such as proliferation and migration, whereas weak or no responses have been recorded for Flt 1. We examined VEGF and PlGF for their capacity to stimulate signal transduction in porcine aortic endothelial cells expressing Flt 1 or KDR. VEGF had essentially no effect on Flt 1 expressing cells, but induced DNA synthesis and migration of KDR expressing cells. PIGF on the other hand induced DNA synthesis but not migration of the Flt 1 cells. In agreement, MAP kinase, examined as a marker for DNA synthesis, was activated both by VEGF-stimulation of the KDR cells and by PlGF-stimulation of the Flt 1 cells. In contrast, phospholipase C-gamma (PLC-gamma), was tyrosine phosphorylated only in VEGF stimulated KDR cells, and not in the PlGF-stimulated Flt 1 cells, which is in agreement with a role for PLC-gamma in cellular migration. We furthermore examined induction of protein levels of plasminogen activator (PA), which was evident in the PlGF-stimulated Flt 1 cells, but not in the VEGF-stimulated KDR cells. These data show that Flt 1 is able to mediate an array of biological signals when appropriately stimulated and that the pattern of responses of PlGF-stimulation of Flt 1 is distinct from the pattern of responses to VEGF-stimulation of KDR.
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PMID:Placenta growth factor stimulates MAP kinase and mitogenicity but not phospholipase C-gamma and migration of endothelial cells expressing Flt 1. 946 61


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