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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have shown that the capacity for local release of tissue-type plasminogen activator (tPA) from the vascular endothelium is impaired in patients with primary hypertension. Because this response is an important protective mechanism against intravascular clotting, we investigated whether this system is also defective in patients with advanced chronic kidney disease and hypertension. Nine nondiabetic nonsmoking men with chronic kidney disease (glomerular filtration rate 11 to 28 mL/min x 1.73 m2; aged 33 to 75 years) were compared with age-matched healthy controls. Intraarterial infusions of desmopressin, methacholine, and sodium nitroprusside were given locally in the brachial artery. Forearm blood flow was measured by venous occlusion plethysmography and blood collected repeatedly during the desmopressin infusion for determination of stimulated net and total cumulated release of tPA. The maximal release rate of active tPA (P<0.05) and the capacity for acute tPA release were markedly impaired in the renal patients as compared with healthy subjects (ANOVA, P=0.013). Accordingly, the accumulated release of tPA was 1905 (SEM 366) and 3387 (718) ng/L tissue, respectively (P<0.05). However, there were no significant differences in vasodilator responses between the groups. Thus, patients with advanced chronic kidney disease and hypertension have a markedly impaired capacity for acute release of tissue plasminogen activator, despite preserved endothelium-dependent vasodilation. This defect may contribute to a defective local defense against arterial thrombosis.
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PMID:Impaired endothelial release of tissue-type plasminogen activator in patients with chronic kidney disease and hypertension. 1524 48

The aim of this study was to develop a bioactive membrane for inducing bone regeneration. The membrane was composed of polylactic acid, collagen, recombinant human bone morphogenetic protein-2 (rhBMP-2). The PLA + collagen + rhBMP-2 membrane was fabricated by solvent-casting and cool-drying. The mechanic properties of this compound membrane were tested. The two surfaces of membrane were observed by SEM. Degradability of PLA was evaluated by SEM observation and molecular weight measure in vitro and in vivo. The compound membranes were implanted in rabbit muscles. The samples were obtained when animals were sacrificed at different periods: 2 weeks, 1, 2, 3, 6 months after surgery. The biodegradability and biocompatibility of the membrane were evaluated. The heterotopic bone inducing activity of BMP was identified. The results indicated that the strength at extension to failure of the compound membrane was 36.4MPa at 2.3% strain. The compound membrane was found bearing active factor on its coarse side, which can induce bone regeneration. After implantation in vivo, the membrane maintained the structure for three months and degraded in 6 months. Based on histological analysis, there was no obvious inflammation. Heterotopic bone was induced. We could conclude that the PLA + collagen + rhBMP-2 membrane is an absorbable compound membrane that possesses good biocompatibility, adequate mechanic properties and excellent property of bone induction. It could be applied as an ideal membrane for inducing bone regeneration.
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PMID:[Experimental study on the fabrication of bioactive membrane for inducing bone regeneration]. 1555 72

Poly(lactic acid) microspheres with different surface charges have been prepared by using cationic, anionic or nonionic surfactants as the microspheres' surface stabilizers. Embedded with these microspheres, the modified PLA membranes with different surface charges have been obtained. The test of stability by CLSM and the morphological test by SEM confirmed that we obtained the microspheres modified PLA membranes with different surface charges successfully. The chondrocyte compatibility test of these modified PLA membranes showed that the attachment, proliferation and activity of chondrocytes on the positive surface of the modified PLA were better than those of other modified PLA membranes. The positive charge on the surface of PLA membrane could improve the cell-compatibility of PLA well.
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PMID:[A study on cytocompatibility of poly (lactic acid) membrane modified by polymer microspheres with different surface charges]. 1629 32

Uniform stereo-complex microparticles ranging from nanometer to micrometer size are prepared by using stereo multiblock co-poly(rac-lactide)s (smb-PLAs) with different stereo-regularity. At comparable molecular weights, as the smb-PLA stereo-regularity decreases from 88% to 76%, the crystallinity of the microparticles decreases noticeably, as proved by DSC and WAXD. At the same time, the shape of the microparticles varies from the flower shape to the sphere shape and the particle size increases markedly from 700-2700 nm as shown by SEM. However, all insulin-loaded microparticles are of cake-shape and their sizes depend on the stereo-regularity. The crystallization of smb-PLAs facilitated by insulin is evidenced by the increase of T(m) and DeltaH(f) in DSC. The highest insulin-loading content of 14.2% and -entrapment efficiency of 82.8% are obtained from the smb-PLA with the highest stereo-regularity of 88%. Release studies in vitro show the least first-day release at about 25% followed by continuous release of another 70% of insulin over one month. Stereo-complex microparticles of smb-PLAs with lower stereo-regularity resulted in a relatively lower insulin-entrapment efficiency and -loading content, a larger first-day release, and also complete release of 90% of the total amount within one month. The release system follows a diffusion mechanism. By contrast, atactic PLA shows a very low entrapment efficiency of 16.7%. Structure of a stereo multiblock co-poly(rac-lactide).
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PMID:Effects of stereo-regularity of multiblock co-poly(rac-lactide)s on stereo-complex microparticles and their insulin delivery. 1630 90

To investigate the effect of three kinds of polymeric scaffolds on attachment, proliferation and differentiation of bone marrow mesenchymal stem cells, the cells were different polymeric scaffolds of PLA-PEG, PLA, PLGA, respectively. The proliferation of cell was evaluated by cell count; the attachment and morphology of BMSCs were observed by SEM; and differentiation was detected by alkaline phosphatase activity, fluorescence, and RT-PCR methods. Results showed that the cells in PLGA group spread better among BMSCs adhered to the three polymeric scaffolds. The activity of ALP was detected after 3 days culture in these three groups. There were no significant differences between PLA-PEG and PLGA groups, but the activity of ALP was higher than PLA group. The gene expressions of osteocalicin and collagen I were also observed in the early culture time. Calcium nodes formation in these polymeric scaffolds were detected. BMSC spreading first, then overlapping growth and secretion of matrix around the bottom and surface of scaffolds were observed through SEM. In summary, PLA-PEG and PLGA are better polymeric scaffolds for the bone tissue engineering, compared with PLA.
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PMID:[Effect of polymeric scaffolds on attachment and growth of bone marrow mesenchymal stem cells]. 1642 95

Nanofibers have recently gained substantial interest for potential applications in tissue engineering. The objective of this study was to determine whether electrospun nanofibers accommodate the viability, growth, and differentiation of human mesenchymal stem cells (hMSCs) as well as their osteogenic (hMSC-Ob) and chondrogenic (hMSC-Ch) derivatives. Poly(d,l-lactide-co-glycolide) (PLGA) beads with a PLA:PGA ratio of 85:15 were electrospun into non-woven fibers with an average diameter of 760+/-210 nm. The average Young's modulus of electrospun PLGA nanofibers was 42+/-26 kPa, per nanoindentation with atomic force microscopy (AFM). Human MSCs were seeded 1-4 weeks at a density of 2 x 10(6)cells/mL in PLGA nanofiber sheets. After 2 week culture on PLGA nanofiber scaffold, hMSCs remained as precursors upon immunoblotting with hKL12 antibody. SEM taken up to 7 days after cell seeding revealed that hMSCs, hMSC-Ob and hMSC-Ch apparently attached to PLGA nanofibers. The overwhelming majority of hMSCs was viable and proliferating in PLGA nanofiber scaffolds up to the tested 14 days, as assayed live/dead tests, DNA assay and BrdU. In a separate experiment, hMSCs seeded in PLGA nanofiber scaffolds were differentiated into chodrogenic and osteogenic cells. Histological assays revealed that hMSCs continuously differentiated into chondrogenic cells and osteogenic cells after 2 week incubation in PLGA nanofibers. Taken together, these data represent an original investigation of continuous differentiation of hMSCs into chondrogenic and osteogenic cells in PLGA nanofiber scaffold. Consistent with previous work, these findings also suggest that nanofibers may serve as accommodative milieu for not only hMSCs, but also as a 3D carrier vehicle for lineage specific cells.
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PMID:Continuing differentiation of human mesenchymal stem cells and induced chondrogenic and osteogenic lineages in electrospun PLGA nanofiber scaffold. 1701 Apr 25

The purpose of this work was to study the effect of organic solvent and surfactant type on the in vitro release behavior in general and on the burst release in particular of beta-estradiol from PLA/PLGA microspheres. Also the effect of these variables on the encapsulation efficiency was investigated. The microspheres were prepared by solvent evaporation technique using dichloromethane (DCM), ethyl acetate (EtAc), tetrahydrofuran (THF), chloroform (CHCl3) or acetone (AC) as organic solvent and polyvinyl alcohol (PVA), Tween 80, sodium lauryl sulfate (SLS) or benzalkonium chloride (BKCI) as surfactant. The obtained microspheres were tested for encapsulation efficiency and in vitro drug release using 50% methanol/buffer pH 7.4 as dissolution medium. EtAC and PVA formulations showed the highest encapsulation efficiency and the lowest burst release. These microspheres were further characterized for particle size distribution, SEM and zeta potential. The results suggested that these materials could be starting materials to prepare a beta-estradiol biodegradable controlled delivery system.
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PMID:beta-Estradiol biodegradable microspheres: effect of formulation parameters on encapsulation efficiency and in vitro release. 1702 Jan 54

We have investigated the degradation of pure Polycaprolactone (PurePCL) and chitin short fiber reinforced Polycaprolactone composite (SFRP) in vitro in order to provide useful scientific basis for clinical application. PurePCL, SFRP and DL-PLA were immersed in 0.9% NaCL solution for periods of 2, 4, 8, 12, 16 and 24 weeks. Then pH values in immersing solution, weight loss and mechanical properties of tested materials were measured and SEM was used to study the change of the materials in the process of degradation. It was shown that the initial strength of SFRP was much higher than that of PurePCL. In the process of degradation of SFRP, the pH values maintained weak acid or remianed neutral. The rate of weight loss of SFRP was faster than that of PurePCL, but slower than that of DL-PLA. The strength and modulus of SFRP did not change much in 24 weeks, compared with the initial ones. In conclusion, the composites have excellent properties and may be optimal for clinical use in reconstruction of chest wall defects as well as in internal fixation of bone fracture.
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PMID:[The degradation performance of chitin short fiber reinforced polycaprolactone composite in vitro]. 1771 66

Poly(lactic acid) (PLA) was modified by maleic anhydride (MAH), then the resultant MAH modified PLA (MPLA) was acylated with ethylenediamine (EDA), so EDA-MAH modified PLA (EMPLA) was prepared. The results of DSC, FT-IR and NMR testified that MAH and EAD were successfully introduced into the original polymer. The hydrophilicity of EMPLA was considerably increased compared with that of PLA. The degradation experiment showed that the introduction of EDA into the original polymer could neutralize the carboxyl end groups of the degradation products. The results of SEM and MTT of rat osteoblasts cultured in vitro showed that the cytocompatibility and cell adhesion of the modified materials were significantly increased compared with the original polymer, especially EMPLA; the number of cells were obviously increased and cells attached firmly to the material; these were ascribed to the EDA neutralizing the carboxyl end groups of the degradation products.
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PMID:Two-step modification of poly(D, L-lactic acid) by ethylenediamine-maleic anhydride. 1845 89

We investigated the effect of atorvastatin monotherapy and combined treatment with atorvastatin and pioglitazone on intima-media thickness, vascular function and the cardiovascular risk profile. In all, 148 patients (76 male, 72 female; aged 61.4+/-6.5 years; body mass index [BMI] 29.2+/-4.1 kg/m2; mean +/- SD) with increased cardiovascular (CV) risk factors were randomised. Intima-media thickness (IMT), the augmentation index (Aix@75), the microvascular response to acetylcholine (LDF), lipid status, and plasma levels of intact proinsulin, adiponectin, interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9), sCD40L, P-selectin, tissue plasminogen activator (t-PA) and blood lipids were monitored over six months. Atorvastatin treatment, alone and in combination with pioglitazone, revealed a significant regression in IMT (0.923+/-0.013 to 0.874+/-0.012 mm and 0.921+/-0.015 to 0.882+/-0.015 mm; mean +/- SEM; p<0.05 respectively) and Aix@75 (27.3+/-1.2 to 25.9+/-1.4; and 25.6+/-1.4 to 24.8+/-1.7%; p<0.05). The endothelial response to acetylcholine as measured by laser Doppler fluximetry (LDF) improved during combined treatment (373+/-57 to 576+/-153 AU; p<0.05). Addition of pioglitazone to atorva-statin resulted in significant further effects on high-sensitivity C-reactive protein (hsCRP), t-PA, P-selectin, adiponectin, triglycerides and high-density lipoprotein (HDL) cholesterol (p<0.05 respectively). Atorvastatin significantly improved IMT and vascular elasticity. Co-administration of pioglitazone provided additional effects on endothelial function, lipid profile and laboratory markers of inflammation.
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PMID:Investigation of the vascular and pleiotropic effects of atorvastatin and pioglitazone in a population at high cardiovascular risk. 1895 40


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