Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LACTIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed2003

Acylation of peptides by lactic acid solutions.

To simplify the search for effective mechanisms to suppress peptide acylation inside drug delivery devices made of poly(D,L-lactic acid) (PLA) and poly(lactic-co-glycolic acid), we were looking for a suitable model system that would allow screening of strategies for peptide stabilization. With their low pH and the presence of lactic acid oligomers, diluted lactic acid solutions promised to be a suitable test system that mimics the microclimate in degrading PLA devices. We created solutions of 1-50% (w/w) lactic acid by dilution of concentrated lactic acid. Using high performance liquid chromatography (HPLC) and high performance liquid chromatography coupled with mass spectrometry (HPLC-MS) analysis, oligomer hydrolysis was monitored during the equilibration process of the diluted solutions. Their final oligomer content was determined by titration and by calculations based on HPLC data. HPLC-MS analysis of human atrial natriuretic peptide (ANP) stability in different lactic acid solutions at 37 degrees C for 4 weeks demonstrated that ANP underwent acylation even in diluted solutions containing only 0.05% (w/w) lactic acid oligomers. Purity analysis of lactic acid solutions allowed us to compare the conditions in the solution test-system to the microclimate that prevails inside degrading PLA microspheres.

Acylation↗
PubMed1995

The VCO2/VO2 relationship during heavy, constant work rate exercise reflects the rate of lactic acid accumulation.

Oxygen uptake (VO2) kinetics have been reported to be modified when lactic acid accumulates; however little attention has been given to the simultaneous carbon dioxide production (VCO2) kinetics. To demonstrate how VCO2 changes as a function of VO2 when lactic acid is buffered by bicarbonate, eight healthy subjects performed 6-min constant work rate cycle ergometer exercise tests at moderate, heavy and very heavy exercise intensities. VCO2 and VO2 were measured breath-by-breath, and arterial blood samples were obtained every 7.5 s during the first 3 min of exercise, and were analyzed for pH, partial pressure of carbon dioxide, standard bicarbonate, and lactate. VCO2 abruptly increased relative to VO2 between 40 and 50 s after the start of exercise for the high exercise intensities. These gas exchange events were observed to correlate well with the time and VO2 at which lactic acid increased and plasma bicarbonate decreased (r = 0.90, r = 0.95, respectively). We conclude that bicarbonate buffering of lactic acid can be determined from the acceleration of VCO2 relative to VO2 kinetics in response to constant work rate exercise and the increase is quantitatively related to the magnitude of the lactic acid increase. This is easily visualized from a plot of VCO2 as a function of VO2.

Adult↗
PubMed1996

The Lactic Acid Stress Response of Lactococcus lactis subsp. lactis

The lactic acid tolerance response (LATR) of the lactic acid bacterium Lactococcus lactis subsp. lactis has been studied. A dramatic increase in survival to a severe acid stress (pH 3.9) was obtained by preexposing the cells for 30 min to a mildly acid shock at pH 5.5. Whole-cell protein extract analysis revealed that during the acid tolerance response 33 polypeptides are induced over the level of naive cells. Among these are the major heat shock proteins DnaK and GroEL. In conjunction with a previous report (Hartke et al. 1994), the results establish that L. lactis can adapt to lactic acid exposure in two different ways: a logarithmic phase LATR, which may be activated by protons, and a stationary-phase LATR, which needs no activation by protons. Both systems are independent of de novo protein synthesis.

Journal Article↗
PubMedDate not supplied

[Formation of pyruvic and lactic acids in muscles diluted homogenate differing from the generally accepted glycolysis scheme].

When studying formation of pyruvic and lactic acids from fructose diphosphate the effect of dilution is found in the process of muscles homogenate incubation. Pyruvic acid accumulates only in samples with magnesium chloride added. The increase of lactic acid remains constant irrespectively of availability of conditions for pyruvate formation. Phosphoglycerate and phosphoenolpyruvate form pyruvic acid only in samples with magnesium chloride added without forming lactic acid. It is shown that in the muscles diluted homogenate (25 mg per 6 ml of mixture) lactic acid is formed under conditions unsuitable for pyruvic acid formation. Lactic acid is formed omitting the stages of 2-phosphoglycerate, phosphoenolpyruvate and pyruvate i.e. in the pathway different from a classical scheme of glycolysis.

Animals↗
PubMed2002

L-lactic acid: a human-signifying host cue for the anthropophilic mosquito Anopheles gambiae.

Using a dual-choice olfactometer, the role of L-lactic acid was investigated in relation to host-seeking and selection by female Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) mosquitoes in a Y-tube bioassay. L-lactic acid alone was not attractive, but it significantly augmented the attractiveness of CO2, skin odour and skin-rubbing extracts from humans and other vertebrates. Comparing the left and right index fingers of the same person, one could be made more attractive than the other by adding L-lactic acid to the air stream over that finger. The difference in L-lactic acid concentration between the two air streams offered to the mosquitoes fell within the natural range of variation emanating from a human hand, suggesting that L-lactic acid modulates intraspecific host selection by An. gambiae. Analysis of skin rubbings from various vertebrates (carnivores, chickens, primates, rodents, ungulates) indicated that humans have uniquely high levels of L-lactic acid on their skin. Tests with extracts of skin rubbings from cows and humans, with and without added L-lactic acid, suggest that naturally lower levels of L-lactic acid contribute to the lesser attractiveness of non-humans to An. gambiae s.s.

Animals↗
PubMed1993

Effects of contraction and lactic acid on the discharge of group III muscle afferents in cats.

1. In barbiturate-anesthetized cats we examined the interaction of lactic acid and static contraction on the discharge of group III muscle afferents. Only afferents whose receptive fields were located in the triceps surae muscles were studied. 2. Twelve of 20 afferents were stimulated by a 60-s static contraction. The majority of firing occurred within the first few seconds of contraction. Thirteen of 20 afferents were stimulated by femoral arterial injections of 24 mM lactic acid (1-4 ml) with the muscle at rest. Repeated injections of lactic acid with the muscle at rest led to tachyphylaxis. Lactic acid was then injected (24 mM; 4 ml) during the last 15 s of static contraction. In eight of nine afferents that were tachyphylactic to lactic acid with the muscle at rest, we noted a restored sensitivity to lactic acid during contraction. 3. In separate experiments we examined the effects of dichloroacetate (DCA) on the responses of group III muscle afferents to static contraction. DCA reduces the production of lactic acid by increasing levels of the active form of the enzyme pyruvate dehydrogenase. 4. DCA lowered arterial and venous lactate concentrations at rest and during contraction. DCA significantly decreased (31%; P < 0.05) the responses of the afferents to contraction. This effect was most prominent within the first 10 s of contraction and was not due to a reduced level of mechanical stimulation after DCA, because peak tension levels were the same during the two bouts of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of short-term carbon tetrachloride administration on blood lactic acid levels.

1. A short-term CCl4 administration was used in vivo as a model to produce a rise in lactic acid levels and to explain the probable interaction of CCl4 and lactic acid elevation with hepatic fibrogenesis. 2. A single dose of CCl4 produced an increase in lactic acid levels from 16.6 +/- 3.57 to 24.2 +/- 4.2 mg/dl. Three consecutive doses produced an elevation to 33.28 +/- 10.07 mg/dl, thus describing a direct relationship between lactic acid levels and CCl4 administration in a short-term fashion. 3. A morphological evaluation was performed to show hepatic changes caused by CCl4 administration. No clue of fibrogenesis was found. However, we conclude that an elevation in lactic acid exists, prior to cirrhosis. Therefore, chronic presence of lactic acid may lead to cirrhosis.

Alanine Transaminase↗
PubMed2005

Isolation and identification of lactic acid bacteria from soil using an enrichment procedure.

AIMS: To survey, and identify and classify the ecological distribution of lactic acid bacteria from soil in Japan and Taiwan. METHODS AND RESULTS: Acid-producing bacteria were isolated from 68 soil samples, collected from Japan and Taiwan, in the rhizospheres of fruit trees, from the floor of a henhouse and around a horse farm. All isolates were identified by physiological and genetic tests. Thirty-two of the 54 isolates were identified as lactic acid bacteria (LAB), 16 as spore-forming lactic acid bacteria, five as Clostridium and one as Bacillus. These lactic acid bacteria represent five genera: Lactobacillus, Lactococcus, Enterococcus, Leuconostoc and Weissella. CONCLUSIONS: A high rate of isolating lactic acid bacteria was obtained from soil. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that soil may be a common source for the isolation of lactic acid bacteria.

Bacteriological Techniques↗
PubMed2001

Resin selection and single-step production and recovery of lactic acid from pretreated wood.

Four ion-exchange resins (Amberlite IRA 900, IRA 400, IRA 96, and IRA 67) were employed for lactic acid recovery from simultaneous saccharification and fermentation (SSF) media. The best resins (Amberlite IRA 900 and IRA 400) were assayed for capacity, regenerant consumption, percentage of lactic acid recovery, and product concentration. Almost quantitative lactic acid recoveries at constant capacities were achieved in four sequential loading/regeneration cycles. A strong-base resin (Amberlite IRA 400) was selected for intermittent lactic acid separation in a typical SSF process, in which pretreated wood was saccharified by cellulases in the presence of Lactobacillus delbrueckii. The dynamics of lactic acid generation and lactic acid recovery were established.

Biotechnology↗
PubMed1988

Effects of Lactic Acid Bacteria and Organic Acids on Growth and Germination of Bacillus cereus.

Growth and germination of vegetative cells and endospores of Bacillus cereus were affected by Streptococcus lactis, Streptococcus thermophilus, Lactobacillus acidophilus, and Lactobacillus bulgaricus in nonfat milk medium and by salts of organic acids in broth medium. Growth of the lactic acid bacteria was not affected by B. cereus. B. cereus increased rapidly to about 10 CFU/ml when cells were added at the beginning of growth of lactic acid bacteria; it was inactivated slowly when added after 24 h and rapidly when added after 72 h of lactic acid bacterial growth. Streptococci were more inhibitory to the growth of B. cereus than lactobacilli were at 24 h. Spore germination was not affected after 24 h, but it was inhibited after 48 and 72 h of lactic acid bacterial growth. Acetate was more inhibitory to the growth of vegetative cells, while formate was more inhibitory to spore germination. Acetate, formate, and lactate (all at 0.1 M) completely inactivated multiplication of B. cereus at pH 6.1, 6.0, and 5.6, respectively. Spores of B. cereus were more resistant to these organic acids compared with the resistance of vegetative cells. Formate, lactate, and acetate (all at 0.1 M) caused 50% inhibition of spore germination at pH 4.4, 4.3, and 4.2, respectively.

Journal Article↗
PubMed2003

Recovery of lactic acid from simultaneous saccharification and fermentation media using anion exchange resins.

The physicochemical properties (capacity, kinetics and selectivity) of the ion exchange resins Amberlite IRA900, IRA400, IRA96 and IRA67 were determined to evaluate their comparative suitability for lactic acid recovery. Both the kinetics of lactic acid sorption from aqueous solutions and the equilibrium were assessed using mathematical models, which provided a close interpretation of the experimental results. The best resins (Amberlite IRA96 and IRA67) were employed in further fixed-bed operation using aqueous lactic acid solutions as feed. In this set of experiments, parameters such as capacity, regenerant consumption, percentage of lactic acid recovery and product concentration were measured. Amberlite IRA67, a weak base resin, was selected for lactic acid recovery from SSF (simultaneous saccharification and fermentation) broths. Owing to the presence of nutrients and ions other than lactate, a slightly decreased capacity was determined when using SSF media instead aqueous lactic acid solutions, but quantitative lactic acid recoveries at constant capacities were obtained in four sequential load/regeneration cycles.

Journal Article↗
PubMed2003

Comparison of isotopic fractionation in lactic acid and ethanol fermentations.

Pure D(-) and L(+) enantiomers of lactic acid were prepared by fermentation reactions with specific bacteria. In addition, naturally deuterated ethanol was prepared and converted into diastereoisomers using mandelic acid. Various sugars and nutrients were fermented into lactic acid in water having different deuterium contents and ethanol samples were obtained from yeast fermentation of sugars from different botanical origins. The methine and methylene groups in lactic acid and ethanol respectively show similar deuterium contents which are related to that found in the fermentation water. However, the methyl groups of both molecules are significantly different whatever the botanical origin of the carbon source in the fermentation medium.

Biotransformation↗