Cytotoxicity of sodium fluoride on human oral mucosal fibroblasts and its mechanisms

Because sodium fluoride (NaF) is widely used for prevention of dental caries, pathobiological effects of NaF were investigated on human oral mucosal fibroblasts. The results showed that NaF was cytotoxic to oral mucosal fibroblasts at concentrations of 4 mmol/L or higher. Exposure of cells to NaF for 2 h also inhibited protein synthesis, cellular ATP level and functional mitochondrial activities in a dose-dependent manner. However, incubation of cells with NaF up to 12 mmol/L for 2 h depleted only 13% of cellular glutathione level. The IC50 of NaF on cellular ATP level was about 5.75 mmol/L. Preincubation of the cells with pyruvate and succinate did not protect cells from NaF-induced ATP depletion. At concentrations of 4 mmol/L, 8 mmol/L and 12 mmol/L, NaF inhibited 31%, 56% and 57% of mitochondrial functions, respectively, after 2 h incubation. No significant inhibition for NaF was found at concentrations lower than 2 mmol/L (40 ppm). These results indicate that NaF can be toxic to oral mucosal fibroblasts in vitro by its inhibition of protein synthesis, mitochondrial function and depletion of cellular ATP. Because of repeated and long-term usage of NaF, more detailed studies should be undertaken to understand its toxic effects in vitro and in vivo.     

酚酸类物质的抑草效应分析

运用正交旋转回归试验设计分析5种常见的化感物质替代物水饧酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸对田间伴生杂草稗草的抑制效应．结果表明,肉桂酸对稗草根长抑制率的影响最显著。其关系函数的二次项系数为-6．18,达极显著水平,水杨酸、对羟基苯甲酸和阿魏酸对稗草根长的抑制效应趋势与肉桂酸相同,效应曲线均为“n”形抛物线;而香草酸的效应曲线则为“U”形抛物线．当水饧酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸浓度水平分别为0．06、0．60、0．24、0．02和0．02mmol·L^-1时,混合物对稗草根长的抑制率最大,达到78．65％。     

The minimum inhibitory concentration of oral antibacterial agents against cariogenic organisms

The minimum inhibitory concentrations (MIC) of eight common dental antibacterial agents against three genera of bacteria which have been implicated in dentine caries, namely streptococci, lactobacilli and actinomycetes were investigated. The ultimate aim was to determine the most appropriate antibacterial agent which could be added to dental restorative materials for filling cavities where there was residual dentine caries. The antibacterial agents tested were chlorhexidine diacetate, chlorhexidine dihydrochloride, chlorhexidine gluconate, benzalkonium chloride, cetrimide, cetylpyridinium chloride, thymol and sodium hypochlorite. Thymol and sodium hypochlorite did not inhibit microbial growth at any of the concentrations tested. For the active antibacterial agents tested the MIC values against lactobacilli and streptococci were 0.25 microg/ml to 8.0 microg/ml and for actinomycetes 0.125 to 8.0 microg/ml. These results illustrate the wide spectrum of sensitivity of caries associated bacteria against dental antibacterial agents. From the MIC values alone, it is difficult to recommend which of the active antibacterial agents would be most effective in eliminating cariogenic organisms.     

乳杆菌代谢产物对化脓性链球菌的抑制作用

【目的】分析乳杆菌代谢产物对化脓性链球菌的抑制作用。【方法】基于双层平板打孔法,通过测量抑菌圈大小来检测乳杆菌代谢产物对化脓性链球菌的抑菌作用;然后分别采用高效液相色谱法和4-氨酰安替比林法检测乳杆菌代谢产物中的有机酸和H2O2含量;最后,检测乳酸、乙酸和H2O2对化脓性链球菌的最小抑菌浓度(MIC)、最小杀菌浓度(MBC)。【结果】对化脓性链球菌的抑菌效果以植物乳杆菌KLDS1.0667最好,副干酪乳杆菌KLDS1.0342-1次之,瑞士乳杆菌KLDS1.0203抑菌效果最差;乳酸和乙酸产量KLDS1.0667>KLDS1.0342-1>KLDS1.0203;H2O2产量KLDS1.0203>KLDS1.0667>KLDS1.0342-1。在抑菌试验中,乳杆菌的发酵上清液经去除H2O2处理后抑菌圈直径都减小;将发酵上清液的p H调至7.0后均检测不到抑菌圈。结果表明,乳杆菌代谢产物中对化脓性链球菌起抑制作用的主要物质为有机酸和H2O2,其中乳酸是产生抑菌作用的最主要物质。乳酸、乙酸和H2O2对化脓性链球菌的最小抑菌浓度(MIC)分别为1.28、0.64和0.008 g/L,对化脓性链球菌的最小杀菌浓度(MBC)分别为5.12、2.56和0.032 g/L。【结论】乳杆菌可利用其代谢产物对化脓性链球菌产生抑制作用,主要抑菌物质为有机酸和H2O2。     

In vitro studies on the growth of Shigella sonnei by Lactobacillus casei and Lact. acidophilus.

The inhibitory effect of lactobacilli on growth of Shigella sonnei was studied. The effect was not due to pH alone, as addition of hydrochloric, lactic or acetic acids to culture media did not inhibit the normal growth of the shigellas. The degree of inhibition was measured by disc assay and showed that the inhibitory substance(s) can be extracellular and diffusible, varying the degrees of inhibition depending on the media tested. When broth was inoculated with mixed cultures of Lactobacillus and Shigella strains, the inhibition began at 6 h and the death phase at 9 h. The higher inhibition was produced by the mixture of lactobacilli (35.5 +/- 2.5% at 6 h culture, 57.4 +/- 1.9% at 9 h and 91.2 +/- 1.2% at 14 h). The degree of inhibition was higher when the relationship pathogen : lactobacilli was 1:10(3). The specific growth rate of lactobacilli and shigella was different in pure or mixed cultures. When the lactobacillus alone was grown for 12 h and the shigellas then added, the numbers of shigellas began to decrease immediately at 37 degrees C. This work shows that the Lactobacillus strains employed in fermented milk can be used to inhibit the growth of Sh. sonnei.     

Lactobacilli and enterococci — Potential probiotics for dogs

Forty strains of enterococci and forty strains of lactobacilli isolated from feces of 10 healthy dogs were tested for the antimicrobial activity, tolerance to bile and adhesion activity. The total count of fecal enterococci reached 5.5 log CFU/g and of lactobacilli 7.6 log CFU/g. Screening for production of bacteriocin-like substances showed an to partly inhibit the growth of Enterobacter sp. (hazy zones of inhibition). Ten strains of Enterococcus sp. and nine strains of Lactobacillus sp. were found without any inhibitory activity against all indicators used. Seven enterococcal strains and six lactobacilli with the broadest antimicrobial spectrum were selected for further probiotic assays. In the presence of 1% bile, the survival rate of selected enterococci (71.7-97.5%) was higher than that of lactobacilli (66.7-75.4%). The adhesion of strains to human intestinal mucus (5.1-8.2% by enterococci, 2.7-8.3% by lactobacilli) was found to be similar as adhesion to canine intestinal mucus (3.7-10.6% by enterococci, 2.1-6.0% by lactobacilli). Strain AD1, one lactobacillus isolate, reduced the higher level of serum cholesterol and alanine aminotransferase after oral administration to dogs suffering from diseases of the gastrointestinal tract.     

Lactobacilli in human dental caries and saliva

Samples (98 plaque and 72 saliva) from 93 patients with dental caries were investigated for Lactobacillus species which comprised 65 (62.5%) of 104 isolates. Yeasts (20.1%), Streptococcus spp. (8.7%), Staphylococcus spp. (2.9%) and a few unidentified species (5.8%), were also found. The Lactobacillus isolates were L. brevis (24.6%) L. fermentum (18.5%) L. casei (16.9%), L. delbrueckii (15.4%), L. plantarum (9.23%), L. acidophilus (7.69%), L. jensenii (4.62%), L. salivarius (1.54%) and L. gasseri (1.54%). The most common species was L. brevis (24.6%). The strains tested for beta-lactamase production showed 75.4% positive. All the Lactobacillus strains were tested for bacteriocin production against Escherichia coli, Salmonella spp., Shigella dysenteriae, S. sonnei, Klebsiella spp. and Campylobacter sp. All the lactobacilli except L. jensenii produced bacteriocin against at least one of the indicator organisms. The involvement of Lactobacillus in dental caries was established, although its role and mechanism is not well understood. The ability of Lactobacillus spp. to protect their host against certain diseases by inhibiting the growth of potential pathogens was evident.     

In vitro studies on the inhibition of the growth of Shigella sonnei by Lactobacillus casei and Lact. acidophilus

The inhibitory effect of lactobacilli on growth of Shigella sonnei was studied. The effect was not due to pH alone, as addition of hydrochloric, lactic or acetic acids to culture media did not inhibit the normal growth of the shigellas. The degree of inhibition was measured by disc assay and showed that the inhibitory substance(s) can be extracellular and diffusible, varying the degrees of inhibition depending on the media tested.
When broth was inoculated with mixed cultures of Lactobacillus and Shigella strains, the inhibition began at 6 h and the death phase at 9 h. The higher inhibition was produced by the mixture of lactobacilli (35.5 ± 2.5% at 6 h culture, 57.4 ± 1.9% at 9 h and 91.2 ± 1.2% at 14 h). The degree of inhibition was higher when the relationship pathogen: lactobacilli was 1: 10³. The specific growth rate of lactobacilli and shigella was different in pure or mixed cultures. When the lactobacillus alone was grown for 12 h and the shigellas then added, the numbers of shigellas began to decrease immediately at 37°C. This work shows that the Lactobacillus strains employed in fermented milk can be used to inhibit the growth of Sh. sonnei.     

不同氮素水平下二氧化碳加富对草莓叶片光抑制的影响

用便携式调制叶绿素荧光仪和光合仪研究了强光下不同供氮水平（12、4和0.4 mmol·L^-1）和不同CO₂浓度下（700和390 μl·L^-1）丰香草莓叶片的荧光参数及净光合速率的变化.结果表明,CO₂和氮素对草莓叶片光抑制有明显的互作效应.在富CO₂下,12 mmol·L^-1供氮水平的草莓叶片净光合速率升高了62.7%,4和0.4 mmol·L^-1供氮水平则分别降低了7.4%和21.3%;12 mmol·L^-1供氮水平的F_m和F_v/F_m在强光胁迫时降辐减小,暗恢复时F_m和F_v/F_m恢复程度提高,而4和0.4 mmol·L^-1供氮水平却相反.表明氮素供应不足时草莓叶片在富CO₂环境下光合作用出现适应性下调,光抑制增强.     

Detection of Caries-Inducing Microorganisms in Hyposalivated Rats without Infection of Mutans Streptococci

Rampant dental caries was induced in hyposalivated rats fed a high sucrose diet without infection of mutans streptococci, in which increased numbers of lactobacilli and S. aureus were demonstrated in the oral flora. Administration of either penicillin or piperacillin, effective against all isolates of lactobacilli, markedly inhibited the caries induction in these rats, while severe dental caries was induced in hyposalivated rats given vancomycin that is inhibitory against S. aureus. These results suggested that certain lactobacilli might induce dental caries in hyposalivated rats fed a sucrose diet. Three strains of Lactobacillus species isolated from the hyposalivated rats were made resistant to erythromycin. The caries-inducing activity of these erythromycin-resistant lactobacilli was studied in hyposalivated rats giving erythromycin in the drinking water at a concentration of 500 μg/ml. After a 61-day experimental period, severe dental caries was induced in hyposalivated rats infected with L. fermentum TY1R. On the other hand, low caries incidence was found in hyposalivated rats infected with either L. acidophilus TY7R or L. plantarum TY3R. These results indicate that L. fermentum may be one of causative agents of dental caries in hyposalivated rats fed a sucrose diet.     

Lactobacillus-mediated inhibition of clinical toxic shock syndrome Staphylococcus aureus strains and its relation to acid and peroxide production

The inhibitory activities of 39 strains representing 20 different species of Lactobacillus toward a menstrual toxic shock syndrome (TSS) Staphylococcus aureus archetype strain MN8 were investigated. Nearly every strain (38 of 39) produced an inhibitory effect under both aerobic and anaerobic conditions when assayed on agar medium. In addition, the MN8 inhibition was conserved against at least 10 other clinical TSS S. aureus isolates and, interestingly, required actively growing cultures of Lactobacillus (verified with a two-well co-culture system in broth medium). This general uniform inhibition could be ameliorated by organic buffer (PIPES) supplied in the growth medium and, with only one exception, MRS medium adjusted with non-organic acid (HCl) failed to support growth of TSS strains at or below pH 5.5. By comparison, the vast majority of lactobacilli in this study decreased culture pH to a range of 4-5. Hydrogen peroxide production by the lactobacilli was also assessed and verified by two different methodologies revealing a broad spectrum of phenotypes that, contrary to reports touting its effectiveness, did not seem to correspond with our inhibition studies. Furthermore, resistances to peroxide by MN8, other TSS strains, and a subset of lactobacilli used in this study were nearly identical whereas the S. aureus collection was slightly more sensitive to racemic lactic acid than the lactobacilli. Collectively, these data suggest that the underlying inhibition toward Staphylococcus is generally conserved in Lactobacillus sp. and is related to a common factor in this genus involving promotion of acidic conditions.     

Evidence for in vitro anti-genotoxicity of cheese non-starter lactobacilli

The inhibition of direct acting DNA reactive agents by 63 non-starter lactobacilli isolated from raw ewes milk cheeses was examined by short-term assay (SOS-Chromotest) and compared with already characterized starter lactobacilli. The screening revealed strains active against the nitroarene 4-nitroquinoline-1-oxide (NQO) and the alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) in different species of the genus Lactobacillus (L. rhamnosus, L. casei, L. plantarum, L. brevis, Lactobacillus spp.). It was proved that the anti-genotoxicity was strain-dependent, and always associated with spectroscopic modification of genotoxins. The frequency of strains inhibiting nitroarene genotoxicity was comparable for non-starter and starter lactobacilli, whereas inhibition of the alkylating agent was largely predominant in non-starter isolates. Seventeen strains presented inhibitory activity against both genotoxins. DNA RAPD-PCR performed with M13, Pro-Up and RPO2 primers on the lactobacilli under examination showed genetic diversity in these strains. The non-starter isolates clustered in seven groups and the strains presenting a high degree of activity against 4-nitroquinoline-1-oxide clustered in a single group with a similarity around 75%. Interestingly, the strains with anti-genotoxic properties also showed acid-bile tolerance, indicating that the autochthonous lactobacilli which survive cheese ripening may also reach the gut as viable cells and could prevent genotoxin DNA damage to enterocytes, as is desirable for probiotic bacteria.     

Growth inhibition of Staphylococcus aureus by H2O2-producing Lactobacillus paracasei subsp. paracasei isolated from the human vagina

H2O2 production by certain Lactobacillus strains is one of the mechanisms that helps to regulate the vaginal ecosystem. This paper describes the kinetics of H2O2 production by two different strains of Lactobacillus paracasei subsp. paracasei under different culture conditions and the effect of this metabolite on the growth of Staphylococcus aureus. L. paracasei F2 produced 2.72 mmol 1-1 H2O2 while L. paracasei F28 produced 1.84 mmol l(-1), both in agitated cultures. Although L. paracasei F2 produced a higher H2O2 concentration than L. paracasei F28, H2O2 production per number of live bacterial cells was 10-fold higher for F28. The latter also showed a faster decrease in viability during the stationary phase. There were no detectable levels of H2O2 in cultures without agitation. H2O2-producing lactobacilli inhibited growth of S. aureus in a plaque assay and in mixed cultures, depending on the initial inoculum of the pathogen.     

黄瓜砧用白籽南瓜对不同盐胁迫的耐性评价

采用营养液栽培,研究Ca(NO3)2和NaCl胁迫对黄瓜嫁接用砧木南瓜幼苗生长和抗氧化酶活性的影响,并用隶属函数法综合评价其耐盐性.结果表明:低浓度盐30 mmol·L-1Ca(NO3)2和等渗的45 mmol·L-1 NaCl处理促进砧木幼苗生长;高浓度盐60、120 mmol·L-1Ca(NO3)2和等渗的90、180 mmol·L-1NaCl胁迫下,各砧木幼苗的生长和抗氧化酶系统均受到不同程度的抑制,其中,‘青砧1号’的盐害指数最小,生物量及超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性的下降幅度以及相对电导率的上升幅度均小于其他砧木.高盐Ca(NO3)2胁迫下,各砧木SOD、POD和CAT酶活性均高于等渗的NaCl,而盐害指数和相对电导率低于NaCl,表明Ca(NO3)2对砧木南瓜幼苗生长的危害小于NaCl.4个砧木品种的耐盐性顺序为‘青砧1号’＞‘佐木南瓜’＞‘丰源铁甲’＞‘超霸南瓜’.     

Factors affecting growth and lipase production by meat lactobacilli strains and Brochothrix thermosphacta

Lipolytic activity of lactobacilli strains and Brochothrix thermosphacta was cellrelated; no significant activity was found in the supernatant fluids. Most lipase was produced during the logarithmic phase of growth and was greatly affected by growth conditions. The optimal temperatures for growth and lipase production were respectively 24°C for B. thermosphacta and 30°C for lactobacilli. For all strains, an initial pH of around 7-0 for the medium and low glucose concentration stimulated lipase production. Tributyrin inhibited both growth and lipase production at a concentration of 0-1% for B. thermosphacta or 1% for lactobacilli. Butyric acid (0-1%) and anaerobic culture inhibited lipase production by B. thermosphacta while these two factors had no effect on enzyme production by lactobacilli.     

落叶松幼苗光合特性对氮和磷缺乏的响应

为探讨落叶松幼苗光合特性对氮、磷营养缺乏的响应规律,在温室内用砂培方法培养和处理落叶树幼苗,测定了净光合速率和叶绿素荧光等反映其光合能力的参数,分析了落叶松幼苗的光合特性对氮、磷营养缺乏的响应规律.结果表明,氮素供应不足(1mmol·L^-1)时,落叶松幼苗针叶的全氮含量、叶绿素含量和净光合速率与对照相比都显著降低,分别下降了37%、31%和59%,同时,F_v/F_m(反映光系统II最大光能转换效率)和F_v/F_o(反映光系统II潜在活性)也分别下降了22%和57%,而叶片可溶性蛋白含量只有微弱下降.磷素供应不足(1/8mmol·L^-1)时,叶片全氮和全磷含量、叶绿素含量、叶片可溶性蛋白含量和F_v/F_m与对照相比差异均不显著,净光合速率和F_v/F_o下降13%.氮、磷同时缺乏时,上述各项指标的变化与单独缺氮处理的相似,这意味着本实验中缺磷处理(1/8mmol·L^-1)对落叶松幼苗光合特性影响相对较小.     

不同磷水平下外生菌根真菌对铅的耐性反应

采用液体离体培养的方法,研究了不同磷和铅水平对3个外生菌根真菌生物量、ZC₁菌丝含磷量和含铅量的影响.结果表明,不同水平的磷和铅胁迫下,菌种ZC₁和ZC₂的生物量显著高于菌种GV(Gomphidius viscidus);低磷时（0.16 mmol·L^-1）,3个菌种的生物量随着铅浓度的增加都受到了抑制,在较高的磷水平下(0.81和2.42 mmol·L^-1),铅浓度的增加显著的抑制了菌种GV的生物量,但对菌种ZC₁和ZC₂的生物量没有显著抑制.GV的菌丝含铅量在各处理水平下都显著高于ZC₁和ZC₂.同一铅水平下,GV的菌丝含磷量在低磷时高于ZC₁和ZC₂,在较高磷浓度时却低于ZC₁和ZC₂;铅浓度的增加降低了菌种ZC₂和GV的菌丝含磷量,但菌种ZC₁的菌丝含磷量没有受到显著的抑制.与无污染地采集的菌种GV相比,污染地采集的菌种ZC₁和ZC₂表现出快速生长、低铅积累以及高磷吸收的特点,显示出较高的抗环境胁迫能力.     

Identification of tyrosylprotein sulfotransferase in rat gastric mucosa.

An enzyme activity which catalyzes the transfer of the sulfate group from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to poly-Glu6,Ala3,Tyr1 (EAY; M(r) 47,000) has been demonstrated in the antral and body mucosa of the rat stomach. The distribution of this tyrosylprotein sulfotransferase was similar to that of the Golgi marker enzyme, glycoprotein sulfotransferase, and its activity from body mucosa was 23% higher than that from the antrum. The optimum for tyrosylprotein sulfotransferase activity was obtained at pH 6.8, in the presence of 0.5% Triton X-100, 20 mmol/l MnCl2, 50 mmol/l NaF, 2 mmol/l 5'-AMP, and 1 mmol/l DTT, whereas Ca2+, Mg2+, Cu2+, Zn2+, EDTA, NEM, NaCl and Na2SO4 were inhibitory. The apparent Km of the sulfotransferase for EAY was 1.5 x 10(-6) mol/l and for PAPS 0.75 x 10(-6) mol/l. The enzyme was 28 times less susceptible to 2,6-dichloro-4-nitrophenol inhibition as compared to that required for phenol sulfotransferase inhibition. The tyrosine sulfation by the tyrosylprotein sulfotransferase was independent of the sulfation of carbohydrate residues in mucous glycoproteins and glycolipids, thus indicating that the identified sulfotransferase is specific for sulfation of the tyrosyl residues in the peptide core.     

Inhibition of enterobacteria and Listeria growth by lactic, acetic and formic acids

Minimum inhibitory concentrations (MIC) of undissociated lactic, acetic and formic acids were evaluated for 23 strains of enterobacteria and two of Listeria monocytogenes. The evaluation was performed aerobically and anaerobically in a liquid test system at pH intervals of between 4.2 and 5.4. Growth of the enterobacteria was inhibited at 2–11 mmol 1⁻¹, 0.5–14 mmol 1⁻¹ and 0.1–1.5 mmol 1⁻¹ of undissociated lactic, acetic and formic acids, respectively. The MIC value was slightly lower with anaerobic conditions compared with aerobic conditions. The influence of protons on the inhibition was observed for acetic acid at the low pH values. Undissociated lactic acid was 2 to 5 times more efficient in inhibiting L. monocytogenes than enterobacteria. Acetic acid had a similar inhibitory action on L. monocytogenes compared with enterobacteria. Inorganic acid (HCl) inhibited most enterobacteria at pH 4.0; some strains, however, were able to initiate growth to pH 3.8. The results indicate that the values of undissociated acid which occur in a silage of pH 4.1–4.5 are about 10–100 times higher than required in order to protect the forage from the growth of enterobacteria and L. monocytogenes.     

白桦、落叶松不同器官水浸液对种子萌发和播种苗生长的种间化感作用

研究了白桦的根、枝、叶,落叶松的根、枝、叶和皮不同浓度水浸液(5.0、12.5、25.0、50.0和100.0 mg·mL-1)对另一树种种子萌发和当年生播种苗生长的化感作用.结果表明:落叶松不同器官水浸液(根5.0 mg·mL-1除外)处理均抑制白桦种子的萌发,其平均发芽率为:对照(75％)＞根(66％)＞皮(59％)＞枝(58％)＞叶(54％),随浓度增加,根、枝水浸液的抑制作用增强,而叶、皮水浸液的抑制作用减弱.落叶松各器官水浸液对白桦胚根和胚轴生长具有较强的抑制作用,且以100.0 mg·mL-1浓度的叶水浸液抑制作用最强,胚根和胚轴长分别降低38％和55％(P＜0.05).落叶松枝、叶水浸液处理对白桦播种苗的苗高、地径及生物量有一定的促进作用,根、皮水浸液则具有抑制作用.白桦各器官水浸液能促进落叶松种子的萌发,根和枝的水浸液促进胚轴生长,叶的水浸液抑制胚轴生长,50.0和100.0 mg·mL-1浓度的叶水浸液处理的种子胚轴分别较对照降低27％和28％(P＜0.05).其对落叶松播种苗生长的影响以促进作用为主,5.0 mg·mL-1浓度的白桦叶水浸液处理的落叶松苗高、地径、生物量分别较对照高54％、60％和100％ (P＜0.05).白桦与落叶松之间存在明显的化感作用,混交可能对林木生长产生一定的促进作用.