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PubMed1979

Synthesis of 5-selenium-substituted uracil derivatives. Inhibition of thymidylate synthetase by 5-hydroseleno-2'-deoxyuridylate.

5-Selenium-substituted derivatives (diselenides) or uracil, 2'-deoxyuridine, and 2'-deoxyuridylic acid were synthesized via the addition of methyl hypobromite to the 5,6 double bond, followed by reaction of the adducts with sodium diselenide. The physical and chemical properties of these compounds (including their facile reduction by dithiothreitol and rapid reoxidation) were similar to those of the corresponding 5-sulfur analogues. 5-Hydroseleno-2'-deoxyuridylic acid was as potent as 5-mercapto-2'-deoxyuridylate in inhibiting thymidylate synthetase from L. casei (ki approximately 6 X 10(-8) M) but the nucleoside III was considerably less active than 5-mercapto-2'-deoxyuridine in the inhibition of growth of the leukemia L1210 cell in culture.

Animals↗
PubMed2002

Lactobacillus casei is able to survive and initiate protein synthesis during its transit in the digestive tract of human flora-associated mice.

Live Lactobacillus casei is present in fermented dairy products and has beneficial properties for human health. In the human digestive tract, the resident flora generally prevents the establishment of ingested lactic acid bacteria, the presence of which is therefore transient. The aim of this work was to determine if L. casei DN-114 001 survives during transit and how this bacterium behaves in the digestive environment. We used the human flora-associated (HFA) mouse model. L. casei DN-114 001 was genetically modified by the introduction of erm and lux genes, encoding erythromycin resistance and luciferase, respectively. For this modified strain (DN-240 041), light emission related to luciferase expression could easily be detected in the contents of the digestive tract. When inoculated into the digestive tract of HFA mice, L. casei (DN-240 041) survives but is eliminated with the same kinetics as an inert transit marker, indicating that it does not establish itself. In pure culture of L. casei, luciferase activities were high in the exponential and early stationary growth phases but decreased to become undetectable 1 day after inoculation. Viability was only slightly reduced even after more than 5 days. After transit in HFA mice, luciferase activity was detected even when 5-day-old L. casei cultures were given to the mice. In culture, the luciferase activity could be restored after 0.5 to 7 h of incubation in fresh medium or milk containing glucose, unless protein synthesis was inhibited by the addition of chloramphenicol or rifampin. These results suggest that in HFA mice L. casei DN-240 041, and thus probably L. casei DN-114 001, is able to initiate new protein synthesis during its transit with the diet. The beneficial properties of L. casei-fermented milk for human health might be related to this protein synthesis in the digestive tract.

Animals↗
PubMed1995

Viable versus inactivated lactobacillus strain GG in acute rotavirus diarrhoea.

The effect of viable or heat inactivated human Lactobacillus casei strain GG on rotavirus immune responses in patients with rotavirus diarrhoea was assessed. Rotavirus serum IgA enzyme immunoassay antibody responses were higher in infants treated with viable L casei strain GG than in those treated with inactivated L casei strain GG. There was a significant difference at convalescence with rotavirus specific IgA secreting cells found in 10/12 infants receiving viable but only 2/13 infants receiving inactivated L casei strain GG. The results indicate that viable L casei strain GG stimulate rotavirus specific IgA antibody responses, theoretically significant in the prevention of reinfections.

Acute Disease↗
PubMed1988

Detection of a Lactobacillus substance that inhibits Escherichia coli.

Recent studies have shown that certain lactobacilli strains have the ability to interfere with the adherence and growth of uropathogenic bacteria. This interaction is believed to be important in the maintenance of a normal urogenital flora and in the prevention of infection in females. In the present study, Lactobacillus casei ssp. rhamnosus GR-1 and Lactobacillus acidophilus 76 were found to exert an inhibitory effect on pyelonephritogenic mutant Escherichia coli Hu 734 and E. coli ATCC 25922. The bioactivity of the inhibitor produced by strain GR-1 was retained under pH buffered conditions and was bactericidal. The bioactive substance was heat labile, not precipitated by up to 80% ammonium sulphate, and extractable in chloroform. The data indicated that the inhibitor is not lactic acid or hydrogen peroxide and has a molecular weight greater than 12,000-14,000. Human urine supported production of the inhibitor and reduced and delayed outgrowth of the E. coli. The ability of L. casei GR-1 and possibly other lactobacilli strains to produce inhibitors of uropathogenic bacteria may have clinical importance and significance in the microbial ecology of the urogenital tract.

Antibiosis↗
PubMed2003

Impact of nisin producing culture and liposome-encapsulated nisin on ripening of Lactobacillus added-Cheddar cheese.

This study aimed to evaluate the effects of incorporating liposome-encapsulated nisin Z, nisin Z producing Lactococcus lactis ssp. lactis biovar. diacetylactis UL719, or Lactobacillus casei-casei L2A adjunct culture into cheese milk on textural, physicochemical and sensory attributes during ripening of Cheddar cheese. For this purpose, cheeses were made using a selected nisin tolerant cheese starter culture. Proteolysis, free fatty acid production, rheological parameters and hydrophilic/hydrophobic peptides evolution were monitored over 6 mo ripening. Sensory quality of cheeses was evaluated after 6 mo. Incorporating the nisin-producing strain into cheese starter culture increased proteolysis and lipolysis but did not significantly affect cheese rheology. Liposome-encapsulated nisin did not appear to affect cheese proteolysis, rheology and sensory characteristics. The nisinogenic strain increased the formation of both hydrophilic and hydrophobic peptides present in the cheese water extract. Sensory assessment indicated that acidic and bitter tastes were enhanced in the nisinogenic strain-containing cheese compared to control cheese. Incorporating Lb. casei and the nisinogenic culture into cheese produced a debittering effect and improved cheese flavor quality. Cheeses with added Lb. casei and liposome-encapsulated nisin Z exhibited the highest flavor intensity and were ranked first for sensory characteristics.

Cheese↗
PubMed2004

Lactobacillus casei reduces CD8+ T cell-mediated skin inflammation.

Probiotics, including Lactobacilli, have been postulated to alleviate allergic and inflammatory diseases, but evidence that they exert an anti-inflammatory effect by immune modulation of pathogenic T cell effectors is still lacking. The aim of this study was to examine whether L. casei could affect antigen-specific T cell-mediated skin inflammation. To this end, we used contact hypersensitivity to the hapten 2,4-dinitrofluorobenzene, a model of allergic contact dermatitis mediated by CD8+ CTL and controlled by CD4+ regulatory T cells. Daily oral administration of fermented milk containing L. casei or L. casei alone decreased skin inflammation by inhibiting the priming/expansion of hapten-specific IFN-gamma-producing CD8+ effector T cells. The down-regulatory effect of the probiotics required the presence of CD4+ T cells, which control the size of the hapten-specific CD8+ T cell pool primed by skin sensitization. L. casei cell wall was as efficient as live L. casei to regulate both the CHS response and the hapten-specific CD8+ T cell response, suggesting that cell wall components contribute to the immunomodulatory effect of L. casei. This study provides the first evidence that oral administration of L. casei can reduce antigen-specific skin inflammation by controlling the size of the CD8+ effector pool.

Animals↗
PubMed1999

Enhancement of resistance in mice treated with Lactobacillus casei: effect on Trichinella spiralis infection.

The ability of viable Lactobacillus casei, administered by an intraperitoneal route, to induce resistance in mice against Trichinella spiralis infection was tested. The percent reduction of adult worms in the intestine 5 days after T. spiralis infection observed in L. casei-treated animals, compared with those of the control group, fluctuated between 70.9 and 88.5%; reductions of larvae per gram of muscle tissue, evaluated at 30 days after infection, varied from 46.6 to 84.4% in L. casei-treated mice compared with controls. At 5 days after infection, intestinal villus height was shorter in T. spiralis-infected animals than in L. casei-treated or uninfected mice. There were fewer mast cells/crypt unit in L. casei-treated and uninfected mice than in T. spiralis-infected animals. Lactobacilli-treated mice showed twice as many mononuclear cells/crypt unit as T. spiralis-infected animals. The IFN-gamma serum level was higher in L. casei-treated animals at the time of worm challenge as compared with T. spiralis-infected or uninfected mice. The results indicate that: (1) L. casei increased resistance that acted against T. spiralis infection in mice, (2) this resistance apparently was directed against adult worms in the intestine.

Animals↗
PubMed1979

Transfer of plasmid-mediated antibiotic resistance from streptococci to lactobacilli.

The transmissible plasmid pAMbeta1, which codes for erythromycin and lincomycin resistance, was conjugally transferred from a Lancefield group F Streptococcus to a strain of Streptococcus avium. Both organisms served as pAMbeta1 donors for three strains of Lactobacillus casei. Introduction of pAMbeta1 into one of the L. casei strains caused the organism to lose its native 6.7 X 10(6)-dalton plasmid. Loss of the native plasmid produced no alterations in the organism's growth characteristics or fermentation pattern.

Conjugation, Genetic↗
PubMed1997

The lac operon of Lactobacillus casei contains lacT, a gene coding for a protein of the Bg1G family of transcriptional antiterminators.

The 5' region of the lac operon of Lactobacillus casei has been investigated. An open reading frame of 293 codons, designated lacT, was identified upstream of lacE. The gene product encoded by lacT is related to the family of transcriptional antiterminator proteins, which includes BglG from Escherichia coli, ArbG from Erwinia chrysanthemi, SacT, SacY, and LicT from Bacillus subtilis, and BglR from Lactococcus lactis. Amino acid sequence identities range from 35 to 24%, while similarities range from 56 to 47%. The transcriptional start site of the lac operon was identified upstream of lacT. The corresponding mRNA would contain in the 5' region a sequence with high similarity to the consensus RNA binding site of transcriptional antiterminators overlapping a sequence capable of folding into a structure that resembles a rho-independent terminator. LacT was shown to be active as an antiterminator in a B. subtilis test system using the sacB target sequence. lacT directly precedes lacEGF, the genes coding for enzyme IICB, phospho-beta-galactosidase, and enzyme IIA, and these genes are followed by a sequence that appears to encode a second rho-independent transcription terminator-like structure. Northern hybridizations with probes against lacT, lacE, and lacF revealed transcripts of similar sizes for the lac mRNAs of several L. casei strains. Since the length of the lac mRNA is just sufficient to contain lacTEGF, we conclude that the lac operon of L. casei does not contain the genes of the accessory tagatose-6-phosphate pathway as occurs in the lac operons of Lactococcus lactis, Streptococcus mutans, or Staphylococcus aureus.

Amino Acid Sequence↗
PubMed1976

[Elimination from the digestive tract of a "gnotoxenic" child of a "Lactobacillus casei" strain, isolated from a commercial preparation: antagonistic effect of an "Escherichia coli" strain of human origin, demonstrated in "gnotoxenic" mice (author's transl)].

A strain of Lactobacillus casei from a pharmaceutical preparation became established in the digestive tract of an axenic child. It was eliminated by the first bacteria occurring after inoculation of the child's digestive tract with a human flora, before the child was taken out of the isolator. Using "gnotoxenic" mice, we found that the elimination of L. casei was due to a bactericidal effect of the Escherichia coli of human origin, within the digestive tract.

Actinomycetaceae↗
PubMed2005

Oral probiotic bacterial administration suppressed allergic responses in an ovalbumin-induced allergy mouse model.

This study investigated whether orally administered probiotic bacteria (Bifidobacterium bifidum and Lactobacillus casei) and a gram-negative bacterium (Escherichia coli) function as allergic immune modulators to prevent food allergy, according to the hygiene hypothesis. C3H/HeJ mice were sensitized with ovalbumin (OVA) and cholera toxin for 5 weeks. After sensitization, the OVA-induced mice that were not treated with bacteria had significantly increased levels of OVA-specific IgE, total IgE, and IgG1 in sera, as well as scab-covered tails. In comparison, groups treated with B. bifidum BGN4 (BGN4), L. casei 911 (L. casei), or Escherichia coli MC4100 (E. coli) had decreased levels of OVA-specific IgE, total IgE, and IgG1, and decreased levels of mast cell degranulation and tail scabs. OVA-specific IgA levels were decreased in BGN4- and L. casei-treated groups. In conclusion, administration of E. coli, BGN4, or L. casei decreased the OVA-induced allergy response. However, a normal increase in body weight was inhibited in the E. coli-treated mice and in the montreated mice groups during allergy sensitization. Thus, BGN4 and L. casei appear to be useful probiotic bacteria for the prevention of allergy.

Administration, Oral↗
PubMed2001

Acoustic field assisted enhanced demixing of aqueous two-phase systems.

Aqueous two-phase extraction has been recognized as a versatile downstream processing technique for the recovery of biomolecules. A major deterrent to its industrial exploitation is the slow demixing of the two aqueous phases after extraction, due to their similar physical properties. A method to decrease the demixing times of these systems, employing a travelling acoustic wave field, is reported. The effects of phase composition and microbial cells on demixing in a polyethylene glycol/potassium phosphate two-phase system are studied in detail. As phase composition increased, demixing time decreased gradually. Phase volume ratio was found to have a significant effect on demixing time at low phase compositions. However, at intermediate and high phase compositions, only a small effect on demixing time was observed. The effect of phase composition and volume ratio on demixing behavior was explained based on the droplet size of the dispersed phase, which is the resultant effect of the physical properties of the phases. At all the phase compositions studied, the acoustically assisted process decreased the demixing time by 17-60% when compared to demixing under gravity alone. Increasing the cell concentration increased the demixing time markedly in case of yeast cells. However, it remained practically constant in the case of Lactobacillus casei cells. Application of an acoustic field reduced the demixing times up to 60% and 40% in the case of yeast and L. casei cells, respectively. Visual observations indicated that ultrasonication caused mild circulation currents in the phase dispersion enhancing droplet-droplet interaction, which in turn enhanced the rate of coalescence, eventually resulting in an enhanced demixing rate.

Countercurrent Distribution↗
PubMed1980

Primary structure of chicken liver dihydrofolate reductase.

The complete covalent structure of dihydrofolate reductase from chicken liver is described. The S-carboxymethylated protein was subjected to cleavage by cyanogen bromide which produced five fragments. Fragment CB2 contained an internal homoserine residue which was not cleaved by cyanogen bromide. Sequences and ordering of the cyanogen bromide fragments were established by means of automated sequencer analyses of the fragments and from smaller peptides generated by proteolysis with trypsin and staphylococcal protease. The covalent structure of the single polypeptide chain comprises 189 residues of molecular weight 21,651. The chicken liver enzyme is homologous to that from L1210 cells and shows regions of homology to dihydrofolate reductases from Streptococcus faecium, Escherichia coli, and Lactobacillus casei. These homologous regions in the chicken liver enzyme are primarily related to conserved amino acid residues implicated in the binding of NADPH and methotrexate by bacterial dihydrofolate reductases.

Amino Acid Sequence↗
PubMed1985

Quantitative structure-activity relationship of antifolate inhibition of bacteria cell cultures resistant and sensitive to methotrexate.

Sets of 5-(substituted benzyl)-2,4-diaminopyrimidines and 4,6-diamino-1,2-dihydro-2,2-dimethyl-1-(3-substituted phenyl)-s-triazines as well as several other antifolates were tested as inhibitors of Escherichia coli dihydrofolate reductase and E. coli cell cultures both sensitive and resistant to methotrexate. From the results quantitative structure-activity relationships (QSAR) were formulated. The triazines were found to inhibit sensitive and resistant cell cultures to the same degree, but the benzylpyrimidines showed marked differences against the two types of cells. Increased hydrophobicity produced benzylpyrimidines more active against the resistant E. coli cell. Metroprine did not discriminate between the two types of cells cultures, but pyrimethamine and 2,4-diamino-6-(2,5-dimethoxybenzyl)-5-methylpyrido[2,3-d]pyrimidin e (BW 301U) did. The results are compared with triazines and benzylpyrimidines acting on Lactobacillus casei and murine tumor cells sensitive and resistant to methotrexate. QSAR is shown to be an effective means for detecting receptor differences.

Biological Transport, Active↗
PubMed2005

Improving specificity vs bacterial thymidylate synthases through N-dansyl modulation of didansyltyrosine.

N,O-Didansyl-L-tyrosine (DDT) represented the starting lead for further development of novel non-substrate-like inhibitors of bacterial thymidylate synthase. The N-dansyl structure modulation led to a submicromolar inhibitor of Lactobacillus casei TS (LcTS), which is highly specific with respect to human TS (hTS). Using molecular dynamics simulation, a binding mode for DDT vs LcTS was predicted, explaining activity and species-specificity along the series.

Bacteria↗
PubMed2005

Mucosal colonisation with Lactobacillus casei mitigates barrier injury induced by exposure to trinitronbenzene sulphonic acid.

BACKGROUND: Trinitrobenzene sulphonic acid (TNBS) induces chronic transmural inflammatory lesions in the rat colon. Injury is facilitated by barrier disruption and invasion of commensal bacteria. However, certain bacteria have shown anti-inflammatory properties in in vitro models. AIM: To investigate in vivo the anti-inflammatory effect of Lactobacillus casei DN-114 001. METHODS: Rats with a colonic segment excluded from faecal transit were surgically prepared. After washing the lumen with antibiotics, the excluded segment was recolonized (control group: standard flora of rat origin; test group: standard flora and L casei). Microbial colonisation was confirmed by culture of segment washing, and colitis was then induced by instillation of TNBS. One day after, intestinal lesions were blindly graded by macro- and microscopic scores, and myeloperoxidase activity measured in tissue homogenates. Translocation of bacteria to mesenteric lymph nodes, spleen and liver was investigated. RESULTS: Test rats showed a smaller area of mucosal injury than control rats (p<0.05). Maximum depth lesion scores were similar in both groups but myeloperoxidase activity was lower in test than in control rats (p<0.05). Remarkably, bacterial translocation was quantitatively lower (p<0.01) and less frequent (p<0.05) in test than in control rats. CONCLUSION: In rats colonised with L casei, mucosal injury, inflammatory response, and barrier disruption after TNBS challenge were attenuated. Bacterial communities colonising the mucosa can modify inflammatory responses to luminal challenges.

Animals↗
PubMed2006

[Intake of fermented milk containing Lactobacillus casei DN-114 001 and its effect on gut flora].

OBJECTIVE: To study the gut flora in infants who received fermented milk containing Lactobacillus casei and Streptococcus termophilus and its effect on secretory immunoglobulin levels. MATERIAL AND METHODS: An experimental, randomized, prospective, parallel group study was carried out. Thirty-five infants were included (18 in the treatment group and 17 in the control group) with a mean age of 2 years (SD: 0.6 years; range: 1-3 years). The experimental group received both fermented milk (0.5 l/day) containing L. casei and S. termophilus for 6 weeks and standard cow's milk for the following 6 weeks. The control group received standard cow's milk (0.5 l/day) for 12 weeks. Secretory IgA levels in saliva were evaluated in the experimental group at the start of the study (baseline levels) and 6 weeks later. In both groups, stools were collected to study gut flora at 0, 6 and 12 week. RESULTS: Secretory IgA levels significantly increased (p =0.0063) from a mean baseline value of 2.5 mg/dl to a mean of 3.4 mg/dl at 6 weeks. Gram-negative aerobic flora were decreased in the experimental group after 6 weeks compared with the control group (p =0.0203). The number of infants with Lactobacillus spp in their gut flora was greater in the experimental group than in the control group at week 6 and this difference was statistically significant (p =0.028) at week 12. Conclusion The present study provides evidence of L. casei survival in the gastrointestinal tract and of its effect of increasing secretory IgA.

Animals↗