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PubMed1992

Determination on the microscale of plasmatic lactic acid as its t-butyldimethylsilyl derivative by stable-isotope dilution using capillary gas chromatography/mass spectrometry.

A new sensitive and precise method for the determination of lactic acid in plasmatic microsamples (50 microL) has been developed. Lactic acid was directly extracted from plasma by ethyl acetate in acidic conditions, and analysed as its di-t-butyldimethylsilyl derivative by capillary gas chromatography/electron-impact mass spectrometry (GC/MS). The internal standard was a previously synthesized deuterated compound, 3-[2H]-(2R)-lactic acid. The method gives good reproductibility and precision, the overall standard deviation being better than 3%. The GC/MS assay was in good agreement with the enzymatic determination.

Gas Chromatography-Mass Spectrometry↗
PubMed2000

Oxygen consumption, carbon dioxide production and lactic acid during normothermic cardiopulmonary bypass.

The objective of this study was to measure oxygen consumption, carbon dioxide production and lactic acid levels during normothermic cardiopulmonary bypass. A prospective study was undertaken in a tertiary care community hospital, involving 20 adults undergoing cardiopulmonary bypass with prolonged (>65 min) crossclamping of the aorta. O2 consumption, CO2 production, hemoglobin and lactic acid levels were measured 5, 35 and 65 min after crossclamping of the aorta. O2 consumption was 79.7 +/- 14.5, 78.8 +/- 15.4 and 81.5 +/- 14.1 ml/min/m2 at 5, 35 and 65 min after crossclamping the aorta. CO2 production was 61.8 +/- 42.9, 60.6 +/- 26.3 and 62.2 +/- 35.9 ml/min/m2 at the same times. Lactic acid levels were 1.6 +/- 0.5 mM/dl at all three times and did not correlate with O2 consumption or CO2 production. In conclusion, although oxygen consumption was low, there was no evidence of abnormal lactate or anaerobic metabolism to suggest tissue ischemia.

Acidosis, Lactic↗
PubMed1996

Sustained release of fleroxacin in vitro from lactic acid polymer.

The time-delayed release of fleroxacin, a newer fluoroquinolone, from a mixture of racemic D-L-Lactic acid is reviewed. Ten in vitro experiments for each fleroxacin concentration of 1% and 10%, were performed. Pre-formed D-L-Lactic acid, plus fleroxacin clots were preserved in sterile 1 cm diameter tubes with one ml of nutrient broth at 37 degrees C until they were fully disintegrated. Every 24 hours the tubes were sampled and replaced by standard broth volumes. Fleroxacin levels were measured by a microbiological method. The release of fleroxacin impregnated in D-L-Lactic acid clots in these two concentrations (1% and 10%) is very promising; the levels obtained over a two month period were much higher than the minimum bacterial concentration of the expected pathogens implicated in bone infections.

Delayed-Action Preparations↗
PubMed2005

Analysis of nonlinear coupled diffusion of oxygen and lactic acid in intervertebral discs.

The transport of oxygen and lactate (i.e., lactic acid) in the human intervertebral disc was investigated accounting for the measured coupling between species via the pH level in the tissue. Uncoupled cases were also analyzed to identify the extent of the effect of such coupling on the solute gradients across the disc. Moreover, nonlinear lactic production rate versus lactic concentration and oxygen consumption rate versus oxygen concentration were considered. The nonlinear coupled diffusion equations were solved using an in-house finite element program and an axisymmetric model of the disc with distinct nucleus and anulus regions. A pseudotransient approach with a backward integration scheme was employed to improve convergence. Coupled simulations influenced the oxygen concentration and lactic acid concentration throughout the disc, in particular the gradient of concentrations along the disc mid-height to the nucleus-anulus boundary where the solutes reached their most critical values; minimum for the oxygen tension and maximum for the lactate. Results suggest that for realistic estimates of nutrient and metabolite gradients across the disc, it could be important to take into account the coupling between the rates of synthesis and overall local metabolite/nutrient concentration.

Computer Simulation↗
PubMed1995

Contribution of oligosaccharide and polysaccharide digestion, and excreta losses of lactic acid and short chain fatty acids, to dietary metabolisable energy values in broiler chickens and adult cockerels.

1. Two experiments were conducted, using both adult cockerels from a layer strain and 3-week-old broiler chickens. In the first experiment, one of the 2 diets investigated was composed mainly of maize and soyabean meals, the other one containing the latter ingredients diluted with 475 g/kg mature pea seeds. For these 2 diets, the apparent metabolisable energy values corrected to 0 nitrogen retention (AMEn) were derived, together with the apparent digestibilities of nitrogen, amino acids, total lipids, starch, individual oligosaccharides, and non-starch polysaccharides (NSP). Excretions of lactic acid and short chain fatty acids (SCFA) were also determined. 2. In the first experiment, the mean apparent digestibilities of starch, lipids, total amino acids, NSP, sucrose and alpha-galacto-oligosaccharides in adult cockerels were 0.946, 0.785, 0.835, 0.045, 0.99 and 0.99, respectively. In broiler chickens, they were 0.938, 0.675, 0.830, -0.016, 0.988 and 0.867, respectively. The bird type effects were significant (P < 0.05) for the digestibilities of starch, lipids, NSP (for the maize-soyabean meal diet, only) and alpha-galacto-oligosaccharides. Broiler chickens excreted a mean of 11.032 g organic acids/kg diet against 4.190 in adult cockerels (P < 0.001). These digestibility measurements enabled the contribution made by each dietary component to the AMEn value of the diets to be calculated. AMEn values were lower in broiler chickens than in adult cockerels, with on average 0.8 MJ/kg dry matter difference resulting from bird type. This difference was accounted for by differences between bird types in energy supplied by lipids (34.0%), starch (7.5%), alpha-galacto-oligosaccharides (8.7%), NSP (14.2%), and in energy losses from lactic acid excretion (16.4% of the difference in AMEn between bird types). 3. In the second experiment 2 diets were studied, consisting of a basal and the basal diluted with 30 g/kg lactose (a fermentable sugar in chickens) and 12 g/kg of a water-soluble gel-forming component containing 50% polygalacturonic acids. Lactose digestibilities reached 0.928 and 0.712 in adult cockerels and chickens, respectively. The digestibilities of the water-soluble polygalacturonic acids were similar in cockerels and broiler chickens, with a mean value of 0.672. Figures similar to those of the first experiment were found in the comparison between cockerels and broiler chickens, for the AMEn values of diets, the digestibilities of starch and lipids and the excretion of lactic acid. Broiler chickens excreted 4.580 g lactic acid/kg dry food intake, compared with 0.740 g in the adult.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1978

Pancreatic response to intestinal perfusion with lactic acid or acidified albumin.

To test the hypothesis that the permeability of weak acids across the intestinal mucosa affects their ability to stimulate pancreatic bicarbonate output, we compared pancreatic bicarbonate secretion in response to intestinal perfusion with an acid presumed to be permeable to cell membranes, lactic acid (90 daltons), and an acid presumed to be impermeable, acidified bovine serum albumin (about 70,000 daltons). These two substances have similar titration curves from pH 2.00 to pH 4.50. In four conscious dogs with pancreatic fistulas, solutions of these weak acids were perfused at 50 ml/15 min into the intestine at concentrations adjusted to deliver 1, 2, or 4 mmol/15 min of acid titratable to pH 4.50 (threshold pH for bicarbonate stimulation) from an initial pH of 2.00 or 3.50. At both pH 2.00 and 3.50 and at all titratable acid loads, bicarbonate secretory responses to lactic acid and acidified albumin were not significantly different. Equal titratable acid loads of HCl produced much larger secretory responses. The data do not support the hypothesis that permeability of weak acids is a factor, but confirm the observation that weak acids are less potent than strong acids in stimulating pancreatic bicarbonate secretion.

Acids↗
PubMed2004

In vitro microleakage of adhesive-sealed dentin with lactic acid and saliva exposure: a radio-isotope analysis.

OBJECTIVES: The aim of this study was to evaluate the dentin-protective potential of two dentin-bonding systems (Syntac and Clearfil SE Bond) on artificial saliva and lactic acid exposure. METHODS: Radiochemical analysis in combination with polarization-microscopy was used in the current study. Different applications in MOD preparations in irradiated human molars were compared. Untreated cavities and cavities covered with flowable resin served as controls. Forty-eight specimens were immersed in artificial saliva (pH 7.5), 48 in lactic acid (pH 4). Activity of (32)P was measured between days 1 and 21 and loss of mineralized tissue was estimated. RESULTS: In lactic acid, cavities sealed with single bond, double bond or bond plus cavity sealer application resulted in significantly lower mineralized tissue loss compared to negative controls (p < 0.05). Upon both saliva and lactic acid exposure, bonding plus sealer application proved to be the most protective treatment (p < 0.05). CONCLUSIONS: Based on these in vitro findings it may be advisable to use a filled cavity sealer or a flowable resin to protect dentin from demineralization. The radiochemical analysis appeared to be valuable in evaluating the protective potential of bonding agents against dentin demineralization.

Acid Etching, Dental↗
PubMed2003

Lactic acid production by Saccharomyces cerevisiae expressing a Rhizopus oryzae lactate dehydrogenase gene.

This work demonstrates the first example of a fungal lactate dehydrogenase (LDH) expressed in yeast. A L(+)-LDH gene, ldhA, from the filamentous fungus Rhizopus oryzae was modified to be expressed under control of the Saccharomyces cerevisiae adh1 promoter and terminator and then placed in a 2 micro -containing yeast-replicating plasmid. The resulting construct, pLdhA68X, was transformed and tested by fermentation analyses in haploid and diploid yeast containing similar genetic backgrounds. Both recombinant strains utilized 92 g glucose/l in approximately 30 h. The diploid isolate accumulated approximately 40% more lactic acid with a final concentration of 38 g lactic acid/l and a yield of 0.44 g lactic acid/g glucose. The optimal pH for lactic acid production by the diploid strain was pH 5. LDH activity in this strain remained relatively constant at 1.5 units/mg protein throughout the fermentation. The majority of carbon was still diverted to the ethanol fermentation pathway, as indicated by ethanol yields between 0.25-0.33 g/g glucose. S. cerevisiae mutants impaired in ethanol production were transformed with pLdhA68X in an attempt to increase the lactic acid yield by minimizing the conversion of pyruvate to ethanol. Mutants with diminished pyruvate decarboxylase activity and mutants with disrupted alcohol dehydrogenase activity did result in transformants with diminished ethanol production. However, the efficiency of lactic acid production also decreased.

Culture Media↗
PubMed1999

Porous poly(L-lactic acid)/apatite composites created by biomimetic process.

Highly porous poly(L-lactic acid)/apatite composites were prepared through in situ formation of carbonated apatite onto poly(L-lactic acid) foams in a simulated body fluid. The highly porous polymer foams (up to 95% porosity) were prepared from polymer solution by solid-liquid phase separation and subsequent sublimation of the solvent. The foams were then immersed in the simulated body fluid at 37 degrees C to allow the in situ apatite formation. After incubation in the simulated body fluid for a certain period of time, a large number of characteristic microparticles formed on the surfaces of pore walls throughout the polymer foams. The microparticles were characterized with scanning electron microscopy, energy dispersive spectroscopy, Fourier transform IR spectroscopy, and X-ray diffractometry. These porous spherical microparticles were assemblies of microflakes. They were found to be carbonated bonelike apatite. A series of composite foams with varying sizes and concentrations of the apatite particles was obtained by varying incubation time and conditions. These porous composites may be promising scaffolding materials for bone tissue engineering and regeneration because the excellent bone-bonding properties of the apatite may provide a good environment for osteoblast and osteoprogenitor cells' attachment and growth.

Apatites↗
PubMed2002

[Treatment of bacterial vaginosis with high dosage metronidazole and lactic acid].

INTRODUCTION: Bacterial vaginosis (BV) is one of the most frequent vaginal infections in women of reproductive age. This condition is a disbalance of vaginal flora that is expressed in a considerable displacement of normal lactobacilli flora by opportunistic and facultative microorganisms. Despite the moderate or missing clinical manifestation this dysbacteriosis is linked with many complications in obstetrics and gynecology. AIM: To evaluate the effect of treatment of bacterial vaginosis with the product Arilin rapid containing vaginal Metronidazole in high doses and a following vaginal application of lactic acid in a part of the patients. MATERIALS AND METHODS: For the period May 2001-August 2001, bacterial vaginosis was established in 45 patients of the Specialized hospital for active treatment in obstetrics and gynecology "Maichin Dom", Sofia and the Military medical academy-Sofia, gynecology ward. The diagnosis of bacterial vaginosis was established in accordance to Amsel's criteria and the results that were obtained from samples colored by Gram. For the treatment of BV were used local Metronidazole (Arilin rapid) and vaginal tablets containing lactic acid. The patients were divided into 3 groups. In the first group (18 women) vaginal suppositoria of 100 mg Metronidazole (Arilin rapid) were used for 2 days, in the second (20 women)--Arilin rapid x 1 glob./2 days and a following therapy with vaginal tablets containing lactic acid x 1 glob. for 7 days. The third group (7 women) was the control receiving placebo therapy--shampoo Dercome Femme containing lactic acid for external application. RESULTS: In the group receiving Arilin rapid we observed a normalization of vaginal flora in 71.43% (5/7), intermediate vaginal flora in 14.3% (1/7) and no change caused by therapy in 14.3% (1/7). In the second group, where lactic acid was included, cure was established in 94.1% (16/17) and in only one (5.9%) case was established intermediate vaginal flora. In the control group in 85.7% (6/7) of the cases was registered a lack of effect. CONCLUSION: Treatment with Arilin rapid showed good results in 71% of cases. Adding lactate to therapy improved the therapeutic effect and achieved cure in over 94%. The following application of vaginal lactate is an additional step helping the recolonisation of the vagina with lactobacilli and is a contribution to the struggle with recurrent forms.

Administration, Intravaginal↗
PubMed1968

Lactic acid bacterial fermentation of burong dalag.

The fermented food, burong dalag, prepared in many Filipino homes, was studied to determine the nature of the microbiological and chemical changes that occur during fermentation. This is a lactic acid bacterial fermentation in which the species Leuconostoc mesenteroides, Pediococcus cerevisiae, and Lactobacillus plantarum played the major acid-producing role. The pH was lowered to below 4.0, and about 0.9% acid as lactic acid was attained in 1 week. It was essential to keep the product covered well to exclude air and subsequent growth of yeasts and mold.

Acids↗
PubMed2006

[Composition diversity of lactic acid bacteria (LAB) community Al2 used for alfalfa silage].

Alfalfa is the most important forage grass that is difficult to ensile for good quality. Using silage inoculants are the important way for preservation of alfalfa silage. Through continuous restricted subcultivation, a lactic acid bacteria (LAB) community Al2 was selected from well-fermented alfalfa silage. Plate isolation and Denaturing Gradient Gel Electrophoresis (DGGE), construction of 16S rDNA clone library were used to identify the composition diversity of Al2 community, with 7 strains detected, and they were all belonged to Lactobacillus. The composition ratios of the 7 strains were 55.21%, 19.79%, 14.58%, 3.13%, 3.13%, 3.13%, 1.03% according to 16S rDNA clone library. Al2-1i, Al2-2i, Al2-3i, corresponding to L. plantarum (99.9%), L. kimchii (99.4%), L. farciminis (100%) were detected by plate isolation. Among 3 isolates, Al2-1i had the highest ability of dropping pH and producing lactic acid, and the amount of lactic acid was reach to 18g/L at 24h cultivated in MRS media. The ability of dropping pH and producing lactic acid of Al2-3i was the lowest. From DGGE profiles, the dominant strains in Al2 community were L. plantarum and L. kimchii. L. plantarum was detected during the whole process, and L. kimchii was detected in the later phase.

Electrophoresis, Polyacrylamide Gel↗
PubMed2000

Stimulatory effect of honey on multiplication of lactic acid bacteria under in vitro and in vivo conditions.

The effect of honey and sucrose on lactic acid bacteria in vitro and in rat gut was studied to determine whether these organisms were affected differently by honey compared with sucrose. Under in vitro conditions, the number of Lactobacillus acidophilus and Lactobacillus plantarum counts increased 10-100 fold in the presence of honey compared with sucrose. Feeding of honey to rats also resulted in significant increase in counts of lactic acid bacteria. Although there was no significant difference in the counts of lactic acid bacteria in the small and large intestines of different groups, the honey-fed group showed a significant increase (P<0.05) in counts over the control and sucrose-fed animals. The results support the fact that consumption of honey has a beneficial effect on the physiological constitution of animals fed with it.

Animals↗
PubMed1976

Lactic acid in human aqueous humour.

We wished to assess the contribution of the lens to the maintenance of the high level of lactic acid found in human aqueous humour. The lactic acid in aqueous humour was estimated by Pryce's modification of the Barker-Summerson method in 41 subjects who were divided into four groups: those with early cataract, those with advanced nuclear cataract, those with mature cataract and those with hypermature (morgagnian type) cataract. Statistical evaluation of the results showed that there was no significant difference in the lactic acid level between the four groups. We assume that the lens does not contribute significantly to the high concentration of lactate found in human aqueous humour.

Aqueous Humor↗
PubMed2006

Formation of lactic acid from glycolaldehyde by alkaline hydrothermal reaction.

Alkali hydrothermal experiments with glycolaldehyde were carried out at 300 degrees C. Glycolaldehyde was converted into lactic acid in a yield of 28% based on the starting carbon mass of glycolaldehyde. A conversion pathway for glycolaldehyde into lactic acid is proposed and our results suggest that the pathway via glycolaldehyde is also important in the conversion of glucose into lactic acid.

Acetaldehyde↗
PubMed1990

D-lactic acid metabolism after an oral load of DL-lactate.

We have investigated in normal human volunteers the short-term and long-term metabolic consequences of the oral intake of d-lactic acid. After the consumption of 6.4 or 12.8 mmol/kg(0.75) body weight of racemic dl-lactic acid, d-lactate was eliminated from plasma with half-lives of 28.6 +/- 4.3 and 40.4 +/- 5.4 min; its maximum plasma concentrations were 0.34 +/- 0.05 and 0.45 +/- 0.06 mmol/l, respectively. Less than 2% of the administered dose of d-lactic acid was excreted in urine during the 24 hours following intake. There was only a slight, non-significant decrease in blood pH by 0.02 units, accompanied by signs of a mild, compensated metabolic acidosis. A 5 weeks chronic experiment with daily consumption of 6.4 mmol/kg(0.75) body weight dl-lactic acid in 5 volunteers did not result in the accumulation of plasma d-lactate.

Journal Article↗