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At least 1,279 records · Page 71Linked to original sources
PubMed1992

Lactic Acid efflux as a mechanism of hypoxic acclimation of maize root tips to anoxia.

Hypoxic pretreatment (3 kPa oxygen) of maize (Zea mays L.) root tips improved their survival time in a subsequent anoxic incubation from 10 h to more than 3 d, provided that glucose was added to the medium to sustain metabolism. The glycolytic flux (lactate + ethanol) was the same in both pretreated and untreated root tips during the 1st h after transfer to anoxia. It was only after 2 h that it declined sharply in untreated tips, but was sustained in pretreated ones. Right after the transition from normoxia to anoxia of untreated root tips, the only fermentative product detected was lactic acid, which accumulated in a 7:1 proportion after 30 min in tissue and medium, respectively. It took 10 min before ethanol could be detected and 20 min for it to be produced at its maximum rate at the expense of lactate production, which slowed down. In contrast, in hypoxically pretreated root tips, ethanol was produced at a maximum rate right after the transfer to anoxia. Concurrently, low amounts of lactic acid were produced that accumulated in a 1:1 proportion after 30 min in tissue and medium, respectively. This large efflux of lactic acid could account for the higher cytoplasmic pH values always found in pretreated tissues. The presence of cycloheximide during pretreatment abolished this difference, suggesting that the greater efficiency of lactate efflux was linked to protein synthesis. The role of lactate in cytosolic pH regulation and in sensitivity to anoxia is discussed.

Journal Article↗
PubMed2001

In situ forming lactic acid based orthopaedic biomaterials: influence of oligomer chemistry on osteoblast attachment and function.

The ability of osteoblasts to attach and function normally on scaffolds fabricated from synthetic materials is essential for musculoskeletal tissue engineering applications. In this study, the osteoconductivity of polymer networks formed from multifunctional lactic acid oligomers was assessed. These oligomers form highly crosslinked networks via a photoinitiated polymerization, which provides potential advantages for many orthopaedic applications. Depending on the initial oligomer chemistry and the resultant polymer hydrophobicity, protein adsorption and osteoblast function varied significantly between the various lactic acid based polymer chemistries. Results were compared to control polymers of tissue culture polystyrene (TCPS) and 50:50 poly(lactic-co-glycolic acid) (PLGA). The viability of osteoblasts attached to poly(2EG10LA) and poly(2EG6LA) was close to the TCPS and PLGA after 7 and 14 days of culture, whereas cell viability was approximately 50% lower on poly(8EG6LA). Additionally, the alkaline phosphatase activity and mineralization of attached osteoblasts were similar on poly(2EG10LA) and PLGA, whereas these markers of bone formation were significantly lower for poly(2EG6LA) and poly(8EG6LA). For example, the alkaline phosphatase activity of rat calvarial osteoblasts attached to poly(2EG10LA) was 0.048 +/- 0.006 micromol mg(-1) protein-min, but only 0.030 +/- 0.003 micromol mg(-1) protein-min for osteoblasts attached to poly(8EG6LA) after 14 days of culture. Finally, osteoblasts were seeded onto three-dimensional scaffolds to demonstrate the applicability of the scaffolds for bone tissue engineering.

Adsorption↗
PubMed2006

Copolymers of pharmaceutical grade lactic acid and sebacic acid: drug release behavior and biocompatibility.

Pharmaceutical grade D,L-lactic acid, which is rather an economic source in comparison to lactide monomer, was utilized for synthesis of a series of copolymers with sebacic acid. Polymers were characterized by GPC, FTIR, NMR and DSC techniques, and formulated into blank and methotrexate (MTX) loaded microspheres by emulsion-solvent evaporation method. In vitro degradation of blank microspheres was studied by FTIR, GPC and SEM analysis. MTX loaded microspheres showed the encapsulation efficiency of 44-64% and were in the size range of 40-60 microm. These were used to study the release profile of the encapsulated drug. The release was found to be affected by the pH and buffer concentration of the release medium which was in turn revealed by solubility studies of MTX. The overall study demonstrates significance of drug as well as polymer properties on release. Biocompatibility of polymer was evaluated by injecting microspheres subcutaneously into Sprague-Dawley (SD) rat and no local histopathological abnormalities were found.

Animals↗
PubMed1980

Influence of EDTA and its metal complexes on lactic acid fermentation.

A comparative study of the influence of EDTA and its metal complexes with Fe, Co, and Ce on lactic acid fermentation by Lactobacillus delbrueckii was done. It was observed that EDTA alone and its complex with Ce could increase the yield of lactic acid up to 1--2%, while complexes of EDTA with Fe and Co enhanced the yield up to 4--5%.

Cesium↗
PubMed2000

Purification and characterization of an extracellular alpha-amylase produced by Lactobacillus manihotivorans LMG 18010(T), an amylolytic lactic acid bacterium.

This work presents the purification and characterization of an extracellular alpha-amylase (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) produced by a new lactic acid bacterium: Lactobacillus manihotivorans able to produce L(+) lactic acid from starch. The molecular weight was found to be 135 kDa. The temperature and pH optimum were 55 degrees C and 5.5, respectively, and pI was 3.8. The alpha-amylase had good stability at pH range from 5 to 6 and the enzyme was sensitive to temperature, losing activity within 1 h of incubation at 55 degrees C. Higher thermal stability was observed when the enzyme was incubated in presence of soluble starch. K(m) value and activation energy were 3.44 mg/ml and 32.55 kJ/mol, respectively. Amylose was found to be a better substrate than soluble starch and amylopectin. Al(3+), Fe(3+), and Hg(2+) (10 mM) almost completely inhibited the alpha-amylase.

Journal Article↗
PubMed2001

[Surface characteristic of domestic poly-DL-lactic acid membrane for periodontal guided tissue regeneration].

OBJECTIVE: To evaluate the surface characteristic of domestic poly-DL-lactic acid membrane for periodontal guided tissue regeneration. METHODS: Three guided tissue regeneration membranes (PDLLA, ePTFE, COL)were implanted in rats subcutaneously, then they were removed 2,4,8 weeks after surgery for examination under scanning electron microscope. The membranes in vitro served as control. RESULTS: The surface of PDLLA membrane was characterized by unorganized smooth film structure. After 2 weeks implanted subcutaneously, its surface became rough with numerous oval micropores in it. These oval micropores were 5 microm in size.The micropores increased gradually in size and number 4, 8 weeks after implantation,there were many shindle shaped cells inlayed. CONCLUSION: Domestic Poly-DL-lactic acid membrane exhibits excellent biocompatibility,which meets the criterion for GTR.

English Abstract↗
PubMed2006

Preparation and characterization of novel hybrid of chitosan-g-lactic acid and montmorillonite.

The utilization of biopolymers and the development of organic-inorganic hybrids are ever increasing interest of material science researchers around the globe for various applications. The present attempt is intended to prepare nanocomposites of lactic acid grafted chitosan and layered silicates. Nanocomposites were prepared by dissolving chitosan and dispersing sodium montmorillonite in aqueous solution of L-lactic acid with subsequent heating and film casting. They were characterized by conventional techniques such as Fourier transform infrared spectroscopy, X-ray diffractometry, thermogravimetric analysis, energy dispersive X-ray spectroscopy, and elemental analysis. The results from polar optical and transmission electron microscopic measurements are also discussed. Sorption behavior of samples has been followed by measuring swelling degree and contact angle. The films have shown enhanced hydrophilicity when compared with polylactic acid (PLA). Issues on the interactions of polycationic chitosan with clay are also discussed. It is observed that nanocomposites are exhibiting better thermal and physical properties than neat chitosan-g-LA and PLA.

Bentonite↗
PubMed1997

Rapid detection method for bacteriocin and distribution of bacteriocin-producing strains in Lactobacillus acidophilus group lactic acid bacteria isolated from human feces.

A new screening method, using micro plate wells, was developed for detecting the bacteriocin producer in lactic acid bacteria. The method was applied for screening the bacteriocin producer in L. acidophilus group lactic acid bacteria isolated from human feces with 19 bacteria used as indicator strains. Of the 98 strains, 62 were finally selected as the bacteriocin producers, including 39 strains positive against at least one of food-borne pathogenic bacteria.

Bacteriocins↗
PubMed2005

Inactivation kinetics of Yersinia enterocolitica by citric and lactic acid at different temperatures.

Inactivation of Yersinia enterocolitica by citric (1--20% w/v) and lactic (0.3--4.0% v/v) acids at different temperatures (4, 20, 40 degrees C) has been investigated. Inactivation effect of citric and lactic acids was dependent on time and temperature of exposure and acid concentration. Survival curves of Y. enterocolitica suspended in citric acid solutions at 4 and 20 degrees C displayed a shoulder followed by an exponential inactivation, but at 40 degrees C a shoulder was not observed. At all temperatures investigated, survival curves of Y. enterocolitica suspended in lactic acid solutions were linear or slightly concave upwards. A mathematical model based on the Weibull distribution accurately described the kinetics of inactivation of Y. enterocolitica by both acids. The influence of the citric acid concentration on Y. enterocolitica resistance was independent of the treatment temperature. However for lactic acid, the influence of the acid concentration on microbial inactivation depended on the temperature. At any temperature investigated, lactic acid was significantly more effective than citric acid.

Citric Acid↗
PubMed1998

A bioabsorbable self-expandable, self-reinforced poly-l-lactic acid urethral stent for recurrent urethral strictures: a preliminary report.

PURPOSE: We studied whether a new bioabsorbable self-expandable, self-retaining and self-reinforced poly-l-lactic acid double spiral stent is able to prevent the edges of a cut recurrent urethral stricture from adhering together and the scar from shrinking, thus obviating stricture recurrence. MATERIALS AND METHODS: A bioabsorbable spiral stent was inserted into the stricture site in the urethra immediately after optical urethrotomy in 22 patients with recurrent urethral stricture. Uroflowmetry, measurement of residual urine volume, urine culture and urethroscopy were performed before and 1, 3, 6 and 12 months after optical urethrotomy. RESULTS: All 22 patients voided freely on day 1 or 2 after urethrotomy. The stent slipped partially proximal to the stricture and had to be changed in only 1 patient. The stent was totally epithelialized in all but 1 patient at 6 months and had degraded in all at 12 months. The improvement in flow rate was maintained during followup except in 10 patients with stricture recurrence, which was outside the stent area usually close to the external sphincter in 7 and in the stent area in 3. All recurrences were treated with repeat optical urethrotomy and a new stent was inserted. Urinary infections developed in 2 patients and were successfully treated with oral antibiotics. CONCLUSIONS: The self-expandable self-reinforced poly-l-lactic acid double spiral stent is a promising new method in the treatment of recurrent urethral strictures. There is no need to remove the device and no foreign material remains in the urethra. However, longer followup and controlled studies are needed to evaluate all benefits and side effects of this new treatment modality.

Absorbable Implants↗
PubMed1988

Lactic acid bacteria: model systems for in vivo studies of sugar transport and metabolism in gram-positive organisms.

Lactic acid bacteria provide a model system for the in vivo study of mechanisms pertaining to the regulation of sugar transport and metabolism by microorganisms. Recent studies with resting and growing cells of the homofermentative Streptococci and Lactobacilli have yielded evidence for hitherto unsuspected regulatory mechanisms in this group of industrial and medically important bacteria. These regulatory mechanisms mediate the exclusion and expulsion of sugars, the preferential transport of sugar from sugar mixtures, resistance to non-metabolizable sugar analogs and participate in the establishment of energy-dissipating futile cycles. Transport experiments conducted with novel sugar analogs, data from enzymatic analyses and 31P-NMR spectroscopy studies with wild type and mutant strains of Streptococci, have provided new insight into the fine- and coarse-controls responsible for the modulation of activity of the sugar transport: glycolysis cycle. The purpose of this review is to summarize our current knowledge of these regulatory mechanisms and to suggest avenues for future investigation. Although specifically addressed to the lactic acid bacteria, it seems likely that some of the mechanisms described will be found in other Gram-positive species.

Biological Transport↗
PubMed2002

Effects of lactic acid bacteria on the uptake and distribution of the food mutagen Trp-P-2 in mice.

BACKGROUND: Lactic acid bacteria have been reported to have antimutagenic and anticarcinogenic properties in vivo and in vitro. Lactobacillus acidophilus and Bifidobacterium longum have earlier been shown to bind the food mutagen Trp-P-2 in vitro. METHODS: The influence of oral supplementation with L. acidophilus NCFB 1748 and B. longum BB 536 on the uptake and distribution of 14C-labelled Trp-P-2 in several mouse tissues was quantified by liquid scintillation measurements and examined by tape section autoradiography (gives an unbiased qualitative registration of differences in overall tissue distribution) in the present investigation. Furthermore, the effect of 13-naphthoflavone (BNF), a cytochrome P4501A (CYP1A)-inducing agent, on the distribution of 14C-labelled Trp-P-2 was examined. RESULTS: After oral (6 mg/kg; 5 microCi) or iv (1.2 mg/kg; 1 microCi) administration of 14C-labelled Trp-P-2, high levels of radioactivity were observed in the bile, urine and contents of the gastrointestinal tract. Lower levels were present in the liver, lung, kidney, intestines, brown fat, submaxillary salivary gland and thymus. In mice supplemented with lactic acid bacteria there was a significantly decreased level (29%-73%) of radioactivity in the lung, thymus, liver, kidney, submaxillary salivary gland and small intestine as compared with controls. In mice pretreated with BNF, a low but distinct localization of radioactivity in the lung was observed, whereas no similar localization occurred in controls. CONCLUSIONS: The results suggest that (i) there is a decreased bioavailability of the Trp-P-2 in the majority of the tissues examined in bacteria supplemented mice and (ii) there is a low but distinct CYP1A-dependent activation of Trp-P-2 in the lung of BNF-treated mice.

Animals↗
PubMed1991

The lactic acid and citric acid content in the gingival fluid of orthodontic patients.

Alveolar bone turnover has two phases: bone resorption and formation. Bone resorption entails both mineral removal and collagenolysis. A pH decrease over the local bone surface is required for mineral removal. Both lactic acid and citric acid has been suggested as the acids which remove crystals. During the orthodontic movement of teeth, a process of overall bone resorption occurs during displacement, whereas at the retention stage this process needs to be stopped in order to stabilize the alveolar bone. Thus, lactic acid and citric acid may be valid parameters of bone resorption intensity. The purpose of this investigation is firstly to test if these acids can be detected in gingival fluid around the moving teeth, and secondly to find if any changes occur before, during and after orthodontic tooth movement. The results indicate that these acids can be good parameters which show how favorably tooth movement is proceeding. They also show how stable the teeth are when orthodontic force is stopped to apply.

Adolescent↗
PubMed1995

Effect of lactic acid and proteolytic enzymes on the release of organic matrix components from human root dentin.

The mechanisms of organic matrix breakdown in the root caries process are not well understood. Therefore, the combined and separate effects of lactic acid and proteolytic enzymes on the degradation of human dentin collagen, glycoproteins, proteoglycans and phosphoproteins were investigated in the present study. Dentin powder was pretreated with lactic acid (pH 4.0), distilled and deionized (dd) water (pH 7.0) and EDTA/guanidine HCl (pH 7.4) for 24 h. Pellets of acid- or dd water-pretreated dentin powder were washed, dried, and then treated with trypsin, bacterial or mammalian tissue collagenase, or control buffer for 3 h. The released dentin proteins were analyzed by reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting to identify degraded type I collagen, proteoglycans, glycoproteins and phosphoproteins. All water and acid pretreatment and enzyme treatment groups demonstrated two collagen fragment bands with molecular weights at approximately 79 kD. Further studies showed that the 79 kD proteins from acid-pretreated dentin collagen were degraded by tissue collagenase, suggesting that endogenous collagenase may be involved in the degradation of root dentin collagen. Dentin proteoglycans were detectable in all the treatment groups by protein slot blotting. Relatively few distinct glycoproteins and proteoglycans, and no phosphoproteins were detected by immunoblotting. Results from this study suggest that both acids and proteolytic enzymes from either host or microbial origin are important in the degradation of human dentin matrix and the mechanisms involved in the release of various noncollagenous proteins may be different.

Adolescent↗
PubMed2004

Evaluation of a poly-l-lactic acid membrane and membrane fixing pin for guided tissue regeneration on bone defects in dogs.

OBJECTIVES: The purpose of the study was to clarify the usefulness of a poly-l-lactic acid and membrane fixing pin, used in combination with guided bone regeneration, on bone defects in dogs. STUDY DESIGN: Osteotomies bone defects were created in 8 beagle dogs. Group I: one defect was covered with test membrane and held by fixing pins. Group II: the other defect was covered test membrane and not held by fixing pins. The control group received no membrane. The dogs were killed after 24 or 36 weeks of healing. Sections were stained and evaluated microscopically. Data were analyzed statistically. RESULTS: The degradation and resorption of test membrane was not observed at 24 weeks but was noted at 36 weeks. After 24 and 36 weeks, most of Group I defects were completely closed with new bone, while in the control defects, only a small amount of new bone was observed at the bottom of the bone defects. After 36 weeks, the percentage of new bone volume (62.2%) in the space beneath the test membrane and membrane fixing pin (Group I) was greater than that without a membrane fixing pin-53.2% (Group II), whereas only 43.9% of the defect area in the control group was filled with new bone. CONCLUSION: The results of this study show that a poly-l-lactic acid membrane and membrane fixing pin permit bone regeneration that can be ensured by excluding surrounding soft tissues from the wound area.

Absorbable Implants↗
PubMed2006

Synthesis and characterization of cholesterol-poly(ethylene glycol)-poly(D,L-lactic acid) copolymers for promoting osteoblast attachment and proliferation.

A novel cholesterol-poly(ethylene glycol)-poly(D,L-lactic acid) copolymer (CPEG-PLA) has been synthesized as a potential surface additive for promoting osteoblast attachment and proliferation. The gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR) results indicated the product had expected structure with low polydispersities in the range of 1.1-1.5. By blending the poly(D,L-lactic acid) (PLA) with CPEG-PLA, the surface of modified PLA membrane was investigated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle. The results revealed the enrichment of PEG chain on the surface. Osteoblast cell line (MC3T3) was chosen to test the cell behavior on modified PLA membranes. The osteoblast test about cell attachment, proliferation, cell viability and cell morphology investigation on CPEG-PLA modified PLA substrates showed the CPEG-PLA with 15 and 5 ethylene glycol units promoted osteoblast attachment and growth, while the CPEG-PLA with 30 ethylene glycol units prevent osteoblast adhesion and proliferation. This simple surface treatment method may have potentials for tissue engineering and other biomedical applications.

3T3 Cells↗
PubMed1994

The effects of lactic acid on PGE2 production by macrophages and human synovial fibroblasts: a possible explanation for problems associated with the degradation of poly(lactide) implants?

The aim of this study was to investigate the effects of lactic acid on cells found at the bone-implant interface in order to try to discover more about the effects of degradation of implants manufactured from poly(lactide). This study shows that human synovial fibroblasts and murine macrophages release prostaglandin E2 (PGE2) a bone resorbing and inflammatory mediator, into the surrounding medium when exposed to lactic acid. The production of PGE2 in response to lactate may help to explain isolated cases of inflammation and discomfort seen some time after fracture fixation with poly(lactide) implants.

Animals↗