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

The purpose of this study was to investigate whether barrier membranes that were earlier shown to promote bone healing in the craniofacial skeleton are capable of producing bone healing in long bone. defects by themselves or in combination with recombinant human bone morphogenetic protein 2 (rhBMP-2). Segmental defects (10 mm long) in the rabbit radius, known to heal as pseudoarthrosis-like defects, were used as the experimental model. Treatment with expanded polytetrafluoroethylene membranes (GORE-TEX Membrane) (n = 10) resulted in only minor amounts of bone formation within the defect and collapse of the membranes was common. When placement of membranes was combined with implantation of rhBMP-2 in a beaded biodegradable copolymeric PLA/PGA carrier, total bony bridging of the defects was accomplished within 10 weeks (n = 5). Osteopromotive membranes combined with mBMP-2 can therefore bring about complete healing of long bones. The membranes exclude soft tissue from the defect and at the same time keep the growth-stimulatory implant in place and maintain the anatomical contour of the bone. The combination of osteopromotive membranes and rhBMP-2 may be of. value in reconstructive bone surgery.
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PMID:Treatment of segmental defects in long bones using osteopromotive membranes and recombinant human bone morphogenetic protein-2. An experimental study in rabbits. 923 93

Since the early 1970s, bioabsorbable polymers have been used increasingly as suture and device materials. Bioabsorbable materials are high-molecular-weight polymers of polylactide (PLA; poly[lactic acid]) or polyglycolide (PGA; poly[glycolic acid]). The mechanical properties of self-reinforced (SR) devices (SR-PGA, SR-PLLA, and SR-PLA96 spiral stents) are acquired by special processing methods from polymer materials. As a result, the spiral stent has an expansion property of up to 70% of its original outer diameter, 50% of which may occur in 30 minutes. The stent may also have variable degradation properties in different parts of the device. The use of bioabsorbable devices in urology is novel. Today, SR-PGA spirals (Biofix) to be used for the prostatic urethra are commercially available but with restrictions. Their indications are the prevention of urinary retention after thermal therapy of prostatic hyperplasia, temporary treatment of urinary retention in patients waiting for surgery, and the early-phase resolution of bladder outlet obstruction in patients waiting for the effect of medical therapy. Stents can be also used to observe the effects of prostatic surgery on bladder function. The SR-PLLA and SR-PLA96 spiral stents are still under development for use in the anterior urethra, prostatic urethra, and ureters. Further experimental and controlled clinical studies are needed to find out the suitability of bioabsorbable devices in urology. Many efforts have been made to discover the best possible materials, models, coating materials, and additives of bioabsorbable stents in urology.
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PMID:Bioabsorbable and biodegradable stents in urology. 944 Aug 46

In adult rabbits, mid-diaphyseal segments of the radius or ulna were excised to produce defects greater than the critical size for spontaneous bone repair. The defects were enveloped in sleeves composed of nonbiodegradable expanded polyfluoroethylene (ePTFE), pore size 30, 60, 90 microns, and compared with sleeves of three biodegradable materials. Bone morphogenetic protein and associated noncollagenous bone matrix protein (BMP/NCP) or recombinant human morphogenetic protein (rhBMP-2) were implanted inside the sleeves. Albumin was implanted for a control system. Without intracompartmental BMP, only about 10%-15% of the defect was repaired by bone growth extending from the bone ends into the sleeves composed of ePTFE, pore size 30 microns. With sleeves with pore size 60 or 90 microns and intracompartmental BMP/NCP, 54%-96% regeneration occurred within 8 weeks after the operation. Sleeves of biodegradable nonimmunogenic materials such as polyorthoester (POE) and polylactic-polyglycollic acids (PLA/PGA) permitted 86%-98% restoration of bone continuity, but only when BMP was present in the lumen. With puncture holes (0.5 mm in diameter), implants of BMP/NCP in the 30-micron PTFE sleeve produced transmembrane external callus formation and bone regeneration to 147%. Sleeves composed of aorta first calcified, then induced complete intracompartmental bone regeneration. Atelocollagen sleeves incited a low-grade inflammatory cell reaction and did not promote complete regeneration. Under conditions presently undisclosed segments of the ulna bridged with ePTFE, were incompletely paired, even with intracompartmental BMP/NCP. Puncture holes of 0.5 mm admitted ingrowth of capillaries and introduced local conditions favorable for the response to BMP/NCP. BMP/NCP may promote proliferation of nutrient vessels and differentiation of bone marrow stroma cells between the open bone ends. For further investigation, the hypothesis to be examined is that the optimum response to BMP/NCP and rhBMP-2 would emerge in compartments containing first a high concentration gradient and second proliferating perivascular cells.
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PMID:Bone morphogenetic protein induced repair of compartmentalized segmental diaphyseal defects. 945 32

The aim of this study was to evaluate the characteristics of resorption and the pattern of bacterial collonisation of polyglycolic and polylactic resorbable membranes under controlled experimental conditions. A removable cobalt-chromium device was applied to the lower jaw of 5 students for a period of 4 weeks. 8 composite resin chambers were glued to the device, 4 on each side of the mouth. A small piece of PLA/PGA membrane separated the composite chambers into 2 parts. The subjects wore the devices 24 h a day, except for the time necessary for oral hygiene procedures, during which time, the structure was submerged in a 0.2% chlorexidine solution. Every week, 2 of the chambers were removed; one was processed for scanning electron microscopy, to be observed both on the external and internal surface, and the other one for light microscopy examination. Both the electron microscopic and histologic observations showed a progressive increase in the plaque layer on the external surface of the membrane during the period of observation. The light microscopy showed an early invasion of the membrane, starting about 1 week after the exposure. On all the 3- and 4-week specimens, a complete bacterial invasion over the whole thickness of the membrane was visible. After 3 weeks of plaque accumulation, bacterial colonisation of the inner portion of the membrane was detectable in all the specimens. At 3-weeks, we observed in the light microscopy group in 4 out of 5 specimens, a large reduction of the thickness of the material and small voids in the membrane structure. In 1 specimen, the membrane was no more detectable. Only in 5 specimens of the 4-week group was the membrane still recognizable, though reduced to fragments. In conclusion, once exposed to the oral cavity, the PLA/PGA membranes start to resorb in the early stages: this process concludes itself between the 3rd and 4th weeks of exposure. However, the particular conditions of the experimental design nevertheless classify this study as an in vitro, more than as an in vivo experimentation.
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PMID:Bacterial penetration through Resolut resorbable membrane in vitro. An histological and scanning electron microscopic study. 958 53

A bioabsorbable, injectable microsphere formulation containing ivermectin in poly-(lactide-co-glycolide) copolymer (PLA/PGA) was developed to provide long-lasting delivery of the drug for control of livestock pests. A solvent-evaporation technique was used to produce the spherical beads containing approximately 30% ivermectin and ranging in size from 25-250 microns. The pattern of delivery of the drug into the blood stream of Spanish goats was characterized for a 50:50 PLA/PGA, a 90:10 PLA/PGA copolymer formulation, and a PLA monomer formulation. When the 50:50 PLA/PGA formulation was used in cattle at the rate of 2 mg (AI)/kg body weight, 2 peaks of 45-50 ppb of ivermectin in serum were observed. The 1st peak was at approximately 1 wk after injection and the 2nd peak, which was broader than the 1st, occurred at approximately 6-7 wk after injection. Percentage of inhibition of estimated larvae for the lone star tick, Amblyomma americanum (L.), placed on treated cattle was 100% for the first 8 wk after injection and was 75, 57, 46 and 44% for wk 9, 10, 11, and 12, respectively. The treatment provided 98-100% control of larval horn flies, Haematobia irritans (L.), in the manure of treated cattle for 10 wk. The bioassay results against lone star ticks and larval horn flies were in agreement with the serum concentration data. The injectable microsphere formulation of ivermectin should be useful in a variety of other applications ranging from the control of Boophilus spp. ticks in south Texas to heartworms in pets.
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PMID:Delivery of ivermectin by injectable microspheres. 965 May 14

This review of the current periodontal literature evaluates clinical regeneration with guided tissue barriers in infrabony defects and furcations. A meta-analysis was conducted by calculating weighted means with confidence intervals for each treatment group. Clinical improvement in infrabony defects was best for polylactic acid/polyglactin (PLA/PGA) barriers, with a mean pocket reduction of 5.3 mm and a mean gain in clinical probing attachment level of 4.7 mm. For furcations, special attention was given to the frequency of either complete or partial (> or = 50%) furcation closure. Complete furcation closure was an infrequent result of guided tissue regeneration, occurring in only 7% to 19% of furcations treated with barriers. For the time period reported, the best clinical results in furcations and infrabony defects occurred with PLA/PGA-type barriers. However, there were no statistically significant differences among the various barriers in infrabony defects or furcations.
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PMID:Clinical regeneration with guided tissue barriers. 965 25

The aim of this study was to evaluate the bacterial adherence to biodegradable self-reinforced polyglycolic acid (SR-PGA) and self-reinforced poly-DL-lactic acid (SR-PLA 96) spiral stents in vitro. They are used as temporary urethral stents in urology. Gold-plated metal wire, polyurethane and latex were used as controls. Materials were incubated up to 28 days in artificial urine, after which a bacterial suspension was added. After detaching by sonication the adhesive bacteria were analysed as colony forming units (CFUs) and by scanning electron microscopy (SEM) analysis. Adhesion was more significantly correlated to stent bacterial type than to the tested material in both assays. No encrustation was seen on SR-PGA or SR-PLA 96. SR-PGA and SR-PLA 96 had no effect on the bacterial growth. In conclusion, the bacterial properties are equally or more important than the material properties in the adhesion process.
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PMID:Bacterial adherence to self-reinforced polyglycolic acid and self-reinforced polylactic acid 96 urological spiral stents in vitro. 966 40

There has been extensive research on drug delivery by biodegradable polymeric devices since bioresorbable surgical sutures entered the market two decades ago. Among the different classes of biodegradable polymers, the thermoplastic aliphatic poly(esters) such as poly(lactide) (PLA), poly(glycolide) (PGA), and especially the copolymer of lactide and glycolide referred to as poly(lactide-co-glycolide) (PLGA) have generated tremendous interest because of their excellent biocompatibility, biodegradability, and mechanical strength. They are easy to formulate into various devices for carrying a variety of drug classes such as vaccines, peptides, proteins, and micromolecules. Most importantly, they have been approved by the United States Food and Drug Administration (FDA) for drug delivery. This review presents different preparation techniques of various drug-loaded PLGA devices, with special emphasis on preparing microparticles. Certain issues about other related biodegradable polyesters are discussed.
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PMID:Controlled drug delivery by biodegradable poly(ester) devices: different preparative approaches. 987 19

Since the degradability of the synthetic polymers used for fracture fixation is still unclear, a research project with biodegradable interlocking nails with a longterm implantation period has been started. In 21 female sheep a complete mid-shaft osteotomy of the left femur was performed to mimic a fracture of the femoral shaft. For the fixation, an intramedullary stainless-steel interlocking nail, a PLA rod or a PLA/PGA rod was used. After 30 months of implantation the histological results of these three materials were examined. In contrast to most reports the degradation rate of both polymers was much lower than the suggested ultimate period of two years. Even the tissue response was more pronounced than expected and this reaction can imply certain risks for repulsion. One can conclude that the volume quantity of polymeric implant in the bony tissue must be reduced if possible to avoid severe foreign body responses. The immunologic responses and the clinical consequences need more studies. The degradation behavior of the polymer is still not under control.
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PMID:Bone tissue response to biodegradable polymers used for intra medullary fracture fixation: a long-term in vivo study in sheep femora. 1002 81

The aim of this in-vitro study was to compare the physical properties of three suture materials used in periodontal surgery: silk, expanded polytetrafluoroethylene (e-PTFE), and polylactic acid/polyglycolic and (PLA/PGA). Five physical tests were carried out on each of the three suture materials: strain to failure, tensile strength, knot tensile strength, knot slippage, and capillarity. For each test, 30 samples of each suture material were used. In all cases, the statistical results showed that the e-PTFE and the PLA/PGA threads were superior.
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PMID:Comparative study of physical properties of three suture materials: silk, e-PTFE (Gore-Tex), and PLA/PGA (Vicryl). 1006 82


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