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PubMed1980

Inhibition of the Anaerobic Growth of Brochothrix thermosphacta by Lactic Acid.

Brochothrix thermosphacta can grow aerobically in the presence of 210 mM l-lactate and anaerobically in its absence at pH values down to at least 5.5. Anaerobic growth is, however, inhibited by l-lactate, the concentration of undissociated lactic acid being the governing factor. Postrigor meat usually contains sufficient lactic acid to select against the anaerobic growth of B. thermosphacta. At least some Lactobacillaceae strains are more resistant to lactic acid and so their growth is favored on vacuum-packaged meat.

Journal Article↗
PubMedDate not supplied

Poly-L-lactic acid tack synovitis after arthroscopic stabilization of the shoulder.

BACKGROUND: Progress has been made in the design of bioabsorbable implants, with reduced complication rates and slower degradation times. PURPOSE: To report on complications related to use of poly-L-lactic acid implants after arthroscopic shoulder stabilization procedures. STUDY DESIGN: Retrospective cohort study. METHODS: Between 1997 and 1999, 52 patients underwent arthroscopic stabilization at one institution with an average of 2.2 poly-L-lactic acid tacks. Ten patients (19%), with an average age of 30 years, developed delayed onset of symptoms at an average of 8 months after surgery, including pain in all 10 and progressive stiffness in 6. The patients underwent magnetic resonance imaging and arthroscopic evaluation and debridement. RESULTS: Nine patients had gross implant debris. Evidence of glenohumeral synovitis was seen arthroscopically in all 10 patients. Three patients had significant full-thickness chondral damage on the humeral head. All preexisting labral lesions were healed. One year after arthroscopic debridement, loose body removal, and synovectomy, seven patients reported no or minimal pain and full return of motion. Two patients continued to have persistent pain and stiffness, and one patient reported discomfort with overhand throwing; all three had chondral lesions. CONCLUSIONS: Patients with symptoms of delayed pain and progressive stiffness after arthroscopic stabilization with poly-L-lactic acid implants should be evaluated for synovitis and chondral injury. Arthroscopic treatment provides a significant decrease in symptoms and increased range of motion.

Adolescent↗
PubMedDate not supplied

The effects of lactic acid production on contraction and intracellular pH during hypoxia in cardiac muscle.

During hypoxia cardiac contraction declines and there is an intracellular acidosis. We find that, if this acidosis is abolished by decreasing pCO2 there is little restoration of force. Therefore the acidosis is not the major cause of the decline of force. The acidosis may partly result from the generation of lactic acid. No acidosis, is however, seen in isolated cardiac cells. Furthermore a theoretical model shows that lactic acid production would be expected to produce a transient acidosis. We suggest that the observed maintained acidosis may be a consequence of extracellular lactic acid accumulation affecting intracellular pH.

Animals↗
PubMed1991

Neutron-activated holmium-166-poly (L-lactic acid) microspheres: a potential agent for the internal radiation therapy of hepatic tumors.

Biodegradable Poly(L-lactic acid) microspheres containing neutron-activable 165Ho were designed for internal radiation therapy of hepatic tumors. Spheres composed of Poly(L-lactic acid) (PLA) were prepared with excellent reproducibility containing up to 36% of a holmium complex. The prepared spheres were irradiated in a high neutron flux converting 165Ho to 166Ho (Emax = 1.84 MeV, half-life = 26.9 hr). Thus, these microspheres can be prepared under conditions that do not require the handling of a hazardous radionuclide, and then irradiated just prior to administration. In vitro studies in plasma (n = 6) revealed 97.3% (+/- 1.9) retention of 166Ho in the microspheres after 240 hr. PLA spheres administered via the portal vein in rabbits (n = 6) show 94.5% (+/- 3.4) retention of the original 166Ho activity in the liver after 6 days.

Animals↗
PubMed2001

Biogenic amines in wines: role of lactic acid bacteria.

Biogenic amines have undesirable physiological effects when absorbed at too high a concentration. Several kinds of food and beverages contain biogenic amines. Lactic acid bacteria can decarboxylate amino acids. Since winemaking involves the growth of lactic acid bacteria for malolactic fermentation, biogenic amines may occur. However, not all bacterial strains carry these activities. In the same wine-producing area, some wines may contain very low amounts of biogenic amines while others may have relatively large quantities. It is now possible to detect the presence of undesirable histamine-producing strains by PCR test or DNA probe based on the presence of the gene encoding histidine decarboxylase. Other strains have the ornithine and/or tyrosine decarboxylase. When biogenic amine-producing strains are present, the winemaker is encouraged to inoculate selected malolactic starters to replace the indigenous microflora.

Biogenic Amines↗
PubMed1985

[Effect of short-term hypoxia on body temperature and lactic acid in the blood of the mouse].

In mice, changes of body temperature and concentration of lactic acid in the blood were studied after three modes of barochamber hypoxia (altitude 8000 m) at the temperatures +10, +20 and +36 degrees C. The greatest drop of body temperature occurred at +10 degrees C, the least one at +36 degrees C. The lactic acid concentration was the greatest (up to 3.6 mM/l) at 2-min ascend and 2-min descend as well as at 2-min ascend, 15-min "altitude", 2-min descend, the temperatures being +20 and +36 degrees C. At 15-time 2-min ascend-descend, the concentration was the least (no more than 2 mM/l). Mechanisms of accelerated adaptation to hypoxia are considered from the standpoint of occurrence of repeated hyperventilation as the result of conditioning to repeated effects of hypoxia.

Adaptation, Physiological↗
PubMed2003

Exopolysaccharides from lactic acid bacteria: perspectives and challenges.

Some lactic acid bacteria (LAB) secrete a polysaccharide polymer. This extracellular polysaccharide, or "exopolysaccharide" (EPS), is economically important because it can impart functional effects to foods and confer beneficial health effects. LAB have a "Generally Recognized As Safe" (GRAS) classification and are likely candidates for the production of functional EPSs. Current challenges are to improve the productivity of EPSs from LAB and to produce EPSs of a structure and size that impart the desired functionality. The engineering of improvements in these properties will depend on a deep understanding of the EPS biosynthetic metabolism and of how the structure of EPSs relates to a functional effect when incorporated into a food matrix.

Gene Expression Regulation, Bacterial↗
PubMed1979

The influence of mutagenic chemicals on lactic acid fermentation by Lactobacillus bulgaricus AU.

Lactic acid fermentation from molasses by L. bulgaricus AU in the presence of caffeine and ammonium fluoride was studied. It was found that caffeine had a stimulating effect only at lower concentration (0.001%-0.002%), while at high concentration the acid-producing activity of the bacteria was considerably depressed. Ammonium fluoride, at a concentration of 0.001%-0.005%, had a stimulating effect on the activity of the bacteria, maximum activity was observed at a concentration of 0.003%.

Ammonium Compounds↗
PubMed2007

Vanillin production from simple phenols by wine-associated lactic acid bacteria.

AIMS: The ability of lactic acid bacteria (LAB) to metabolize certain phenolic precursors to vanillin was investigated. METHODS AND RESULTS: Gas chromatography-mass spectrometry (GC-MS) or HPLC was used to evaluate the biosynthesis of vanillin from simple phenolic precursors. LAB were not able to form vanillin from eugenol, isoeugenol or vanillic acid. However Oenococcus oeni or Lactobacillus sp. could convert ferulic acid to vanillin, but in low yield. Only Lactobacillus sp. or Pediococcus sp. strains were able to produce significant quantities of 4-vinylguaiacol from ferulic acid. Moreover, LAB reduced vanillin to the corresponding vanillyl alcohol. CONCLUSIONS: The transformation of phenolic compounds tested by LAB could not explain the concentrations of vanillin observed during LAB growth in contact with wood. SIGNIFICANCE AND IMPACT OF THE STUDY: Important details of the role of LAB in the conversion of phenolic compounds to vanillin have been elucidated. These findings contribute to the understanding of malolactic fermentation in the production of aroma compounds.

Benzaldehydes↗
PubMed1990

Uncommon pathways of metabolism among lactic acid bacteria.

A small number of lactic acid bacteria possess the ability to derive energy from organic molecules not utilized by the vast majority of representatives of this large group of microorganisms. Thus, strains of Lactobacillus casei and enterococci readily grow at the expense of substrates such as gluconate, malate and pentitols. Transport of gluconate and pentitols is catalysed by phosphotransferase systems unique to these bacteria. Similarly, the initial steps in pentitol dissimilation are mediated by enzymes found only in Lb. casei and Streptococcus avium.

Amino Acids↗
PubMed2004

Enhanced mucosal delivery of antigen with cell wall mutants of lactic acid bacteria.

The potential of recombinant lactic acid bacteria (LAB) to deliver heterologous antigens to the immune system and to induce protective immunity has been best demonstrated by using the C subunit of tetanus toxin (TTFC) as a model antigen. Two types of LAB carriers have mainly been used, Lactobacillus plantarum and Lactococcus lactis, which differ substantially in their abilities to resist passage through the stomach and to persist in the mouse gastrointestinal tract. Here we analyzed the effect of a deficiency in alanine racemase, an enzyme that participates in cell wall synthesis, in each of these bacterial carriers. Recombinant wild-type and mutant strains of L. plantarum NCIMB8826 and L. lactis MG1363 producing TTFC intracellularly were constructed and used in mouse immunization experiments. Remarkably, we observed that the two cell wall mutant strains were far more immunogenic than their wild-type counterparts when the intragastric route was used. However, intestinal TTFC-specific immunoglobulin A was induced only after immunization with the recombinant L. plantarum mutant strain. Moreover, the alanine racemase mutant of either LAB strain allowed induction of a much stronger serum TTFC-specific immune response after immunization via the vagina, which is a quite different ecosystem than the gastrointestinal tract. The design and use of these mutants thus resulted in a major improvement in the mucosal delivery of antigens exhibiting vaccine properties.

Administration, Intravaginal↗
PubMed2005

CitI, a transcription factor involved in regulation of citrate metabolism in lactic acid bacteria.

A large variety of lactic acid bacteria (LAB) can utilize citrate under fermentative conditions. Although much information concerning the metabolic pathways leading to citrate utilization by LAB has been gathered, the mechanisms regulating these pathways are obscure. In Weissella paramesenteroides (formerly called Leuconostoc paramesenteroides), transcription of the citMDEFCGRP citrate operon and the upstream divergent gene citI is induced by the presence of citrate in the medium. Although genetic experiments have suggested that CitI is a transcriptional activator whose activity can be modulated in response to citrate availability, specific details of the interaction between CitI and DNA remained unknown. In this study, we show that CitI recognizes two A+T-rich operator sites located between citI and citM and that the DNA-binding affinity of CitI is increased by citrate. Subsequently, this citrate signal propagation leads to the activation of the cit operon through an enhanced recruitment of RNA polymerase to its promoters. Our results indicate that the control of CitI by the cellular pools of citrate provides a mechanism for sensing the availability of citrate and adjusting the expression of the cit operon accordingly. In addition, this is the first reported example of a transcription factor directly functioning as a citrate-activated switch allowing the cell to optimize the generation of metabolic energy.

Bacterial Proteins↗
PubMed2000

Gut mucosal immunostimulation by lactic acid bacteria.

The beneficial properties of lactic acid bacteria (LAB) on human health have been frequently demonstrated. The interaction of LAB with the lymphoid cells associated to the gut to activate the mucosal immune system and the mechanisms by which they can exert an adjuvant effect is still unclear, as well as if this property is common for all the LAB. We studied the influence of the oral administration of different geneous of LAB such as Lactobacillus casei, L. acidophilus, L. rhamnosus, L. delbrueckii subsp. bulgaricus, L. plantarum, Lactococcus lactis and Streptococcus thermophilus. We determined if the LAB assayed were able to stimulate the specific, the non-specific immune response (inflammatory response), or both. We demonstrated that all the bacteria assayed were able to increase the number of IgA producing cells associated to the lamina propria of small intestine. This effect was dose dependent. The increase in IgA+ producing cells was not always correlated with an increase in the CD4+ T cell number, indicating that some LAB assayed only induced clonal expansion of B cells triggered to produce IgA. Most of them, induced an increase in the number of cells involved in the inflammatory immune response. CD8+ T cell were diminished or not affected, with exception of L. plantarum that induced an increase at low dose. This fact would mean that LAB are unable to induce cytotoxicity mechanisms. We demonstrated the importance in the selection of LAB to be used as gut mucosal adjuvant. The different behaviours observed among them on the gut mucosal immune response, specially those that induce inflammatory immune response, show that not all the LAB can be used as oral adjuvant and that the beneficial effect of them can not generalized to genous or specie. The immunoadjuvant capacity would be a property of the strain assayed.

Adjuvants, Immunologic↗
PubMed2001

Physically crosslinked dextran hydrogels by stereocomplex formation of lactic acid oligomers: degradation and protein release behavior.

Hydrogels, physically crosslinked through stereocomplex formation, were obtained by mixing aqueous solutions of dextran with L-lactic acid grafts and dextran with D-lactic acid grafts. Protein-loaded hydrogels were simply prepared by dissolving the protein in these dextran solutions prior to mixing. It was shown that under physiological conditions the gels are fully degradable. When the gels were exposed to an aqueous buffer solution, they first showed a swelling phase in which their weight increased 2-3 times due to absorption of water, followed by a dissolution phase. The degradation time depended on the composition of the hydrogel, i.e., the number of lactate grafts, the length and polydispersity of the grafts and the initial water content, and varied from 1 to 7 days. Most likely, the degradation of the stereocomplex hydrogel started with hydrolysis of the carbonate ester, which links the lactate graft to dextran. The gels showed a release of the entrapped model proteins (IgG and lysozyme) over 6 days and the kinetics depended on the gel characteristics, such as the polydispersity of the lactate grafts and the initial water content. Lysozyme was mainly released by Fickian diffusion, indicating that its hydrodynamic diameter is smaller than the hydrogel mesh size. On the other hand the release of IgG was governed by diffusion as well as swelling/degradation of the hydrogel. Importantly, the proteins were quantitatively released from the gels and with full preservation of the enzymatic activity of lysozyme, emphasizing the protein-friendly preparation method of the protein-loaded stereocomplex hydrogel.

Algorithms↗
PubMed1999

Lactic acid does not directly activate hypothalamic-pituitary corticotroph function.

The role that metabolic products play in regulating the hypothalamic-pituitary-adrenal (HPA) axis during strenuous exercise is speculative. This investigation examined the extent to which lactic acid, a major metabolite of anaerobic exercise, directly affects hypothalamic-pituitary function. Specifically, beta-endorphin secretion was measured from AtT-20 (D-16) mouse corticotroph tumor cells treated either acutely (15 min - 180 min) or chronically (1 day - 3 day) with physiologic levels of lactate (0. 5 x 10-3 M to 5 x 10-2 M) or lactate in combination with the corticotroph releasing factors: corticotroph releasing hormone (CRH), arginine vasopressin (AVP), norepinephrine and/or epinephrine. Findings with AtT-20 cell cultures were shown to be representative of responses in primary cultures of rat anterior pituitary. Lactic acid did not alter the spontaneous release of beta-endorphin by AtT-20 cells under either acute or chronic conditions. While CRH, norepinephrine, and epinephrine evoked significant increases in beta-endorphin release, lactate, in combination with these secretagogues did not alter their effects. Similarly, lactic acid failed to alter basal or stimulated release of beta-endorphin by primary cultures of rat anterior pituitary. The addition of lactate (3 x 103 M) to rat hypothalamic explants did, however, produce a modest but significant reduction in spontaneous CRH release, suggesting that lactate may facilitate the return to basal secretion following exercise. The present findings show that physiologic concentrations of lactate have no effect, either alone or in combination with other pituitary secretagogues, on corticotroph secretion. Whereas a physiologic action for lactate within the hypothalamus is possible, the present findings indicate that lactate is an inhibitor of CRH release. Thus, lactate does not appear to play a direct role in the profound activation of the HPA axis that occurs in response to strenuous exercise.

Animals↗
PubMed2004

Purification of bacteriocins produced by lactic acid bacteria.

Bacteriocins are antibacterial substances of a proteinaceous nature that are produced by different bacterial species. Lactic acid bacteria (LAB) produce biologically active peptides or protein complexes that display a bactericidal mode of action almost exclusively toward Gram-positive bacteria and particularly toward closely related species. Generally they are active against food spoilage and foodborne pathogenic microorganisms including Bacillus cereus, Clostridium perfringens, Staphylococcus aureus, and Listeria monocytogenes. There is an increased tendency to use natural occurring metabolites to prevent the growth of undesirable flora in foodstuffs. These metabolites could replace the use of chemical additives such as sorbic acid, sulfur dioxide, nitrite, nitrate, and others. For instance, bacteriocins produced by LAB may be promising for use as bio-preservaties. Bacteriocins of lactic acid bacteria are typically cationic, hydrophobic peptides and differ widely in many characteristics including molecular weight, presence of particular groups of amino acids, pI, net positive charge, and post-translational modifications of certain amino acids. This heterogeneity within the LAB bacteriocins may explain the different procedures for isolation and purification developed so far. The methods most frequently used for isolation, concentration, and purification involve salt precipitation of bacteriocins from culture supernatants, followed by various combinations of gel filtration, ion-exchange chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). In this chapter, a protocol is described that combines several methods used in our laboratory for the purification of two cationic bacteriocins, Lactocin 705AL and Enterocin CRL10, produced by Lactobacillus casei CRL705 and Enterococcus mundtii CRL10, respectively.

Bacteriocins↗
PubMed1994

Reverse dot blot hybridization: a useful method for the direct identification of lactic acid bacteria in fermented food.

A rapid method for a reliable and simultaneous identification of different lactic acid bacteria in fermented food has been developed. Various 16S and 23S rRNA-targeted, species-specific oligonucleotides were applied as capture probes in a non-radioactive reverse dot blot hybridization. A simple and fast DNA extraction method in combination with in vitro amplification of rRNA gene fragments enables the direct detection of typical starter organisms without any preceding enrichment or cultivation steps. Various lactic acid bacteria occurring in cheese, yogurt, sausages, sauerkraut and sourdough could be identified at the species level within 1 day.

Base Sequence↗