(R/S)-lactate/2-hydroxybutyrate dehydrogenases in and biosynthesis of block copolyesters by Ralstonia eutropha.

Bacterial polyhydroxyalkanoates (PHAs) are promising bio-based biodegradable polyesters. It was recently reported that novel PHA block copolymers composed of (R)-3-hydroxybutyrate (3HB) and (R)-2-hydroxybutyrate (2HB) were synthesized by Escherichia coli expressing PhaCAR, a chimeric enzyme of PHA synthases derived from Aeromonas caviae and Ralstonia eutropha. In this study, the sequence-regulating PhaCAR was applied in the natural PHA-producing bacterium, R. eutropha. During the investigation, (R/S)-2HB was found to exhibit strong growth inhibitory effects on the cells of R. eutropha. This was probably due to formation of excess 2-ketobutyrate (2KB) from (R/S)-2HB and the consequent L-valine depletion caused by dominant L-isoleucine synthesis attributed to the excess 2KB. Deletion analyses for genes of lactate dehydrogenase homologs identified cytochrome-dependent D-lactate dehydrogenase (Dld) and [Fe-S] protein-dependent L-lactate dehydrogenase as the enzymes responsible for sensitivity to (R)-2HB and (S)-2HB, respectively. The engineered R. eutropha strain (phaCAR+, ldhACd-hadACd+ encoding clostridial (R)-2-hydroxyisocaproate dehydrogenase and (R)-2-hydoroxyisocaproate CoA transferase, ∆dld) synthesized PHA containing 10 mol% of 2HB when cultivated on glucose with addition of sodium (RS)-2HB, and the 2HB composition in PHA increased up to 35 mol% by overexpression phaCAR. The solvent fractionation and NMR analyses showed that the resulting PHAs were most likely to be block polymers consisting of P(3HB-co-3HV) and P(2HB) segments, suggesting that PhaCAR functions as the sequence-regulating PHA synthase independently from genetic and metabolic backgrounds of the host cell. KEY POINTS: (R/S)-2-hydroxubutyrates (2HB) caused l-valine deletion in Ralstonia eutropha (R)- and (S)-lactate/2HB dehydrogenases functional in R. eutropha were identified The engineered R. eutropha synthesized block copolymers of 2HB-containing polyhydroxyalkanoates on glucose and 2HB.

Response of aerobic granular sludge under polyethylene microplastics stress: Physicochemical properties, decontamination performance, and microbial community.

Microplastics are widely detected in sewage and sludge in wastewater treatment plants and can thereby influence biological processes. In this study, the overall impacts of polyethylene microplastics (PE MPs) and their toxicity mechanisms on aerobic granular sludge (AGS) were investigated. Particle structure, settling properties, particle size distribution, and extracellular polymeric substance characteristics of AGS were significantly affected by PE MPs with concentrations of 20 and 200 n/L. Increased relative contents of reactive oxygen species (ROS) (146.34% and 191.43%) and lactate dehydrogenase (LDH) (185.71% and 316.67%) under PE MPs (20 and 200 n/L) exposure resulted in disruption of cellular structure. The activities of enzymes related to denitrification and phosphorus removal were greatly decreased, while ammonia monooxygenase (AMO) was stable, supporting the high efficiency removal of ammonia nitrogen. High-throughput sequencing demonstrated that the relative abundance of nitrifying and denitrifying bacteria (Nitrospira, Thermomonas, Flavobacterium), and PAOs (Comamonas and Rhodocyclus) were significantly reduced from 4.47%, 3.57%, 2.02%, 9.38%, and 5.45%-2.95%, 2.88%, 1.77%, 8.01%, and 4.86% as the concentration of PE MPs increased from 0 to 200 n/L, respectively. Those findings were consistent with the deterioration in decontamination capability.

Biological Effects of Shikonin in Human Gingival Fibroblasts via ERK 1/2 Signaling Pathway.

Shikonin, an active ingredient of Lithospermum erythrorhizon, exerts anti-inflammatory and antibacterial effects, and promotes wound healing. We investigated whether shikonin stimulated gingival tissue wound healing in human gingival fibroblasts (hGF). In addition, we evaluated the effects of shikonin on the mitogen-activated protein kinase (MAPK) signaling pathway, which has an important role in wound healing. hGF were subjected to primary culture using gingiva collected from patients. The cells were exposed to/treated with Shikonin at concentrations ranging from 0.01 to 100 µM. The optimal concentration was determined by cell proliferation and migration assays. Type I collagen and fibronectin synthesis, the gene expression of vascular endothelial growth factor (VEGF) and FN, and the phosphorylation of Extracellular signal-regulated kinase (ERK) 1/2 were investigated. Identical experiments were performed in the presence of PD98059 our data suggest, a specific ERK 1/2 inhibitor. Shikonin significantly promoted hGF proliferation and migration. Shikonin (1 µM) was chosen as the optimal concentration. Shikonin promoted type I collagen and FN synthesis, increased VEGF and FN expression, and induced ERK 1/2 phosphorylation. These changes were partially suppressed by PD98059. In conclusion, Shikonin promoted the proliferation, migration, type I collagen and FN synthesis, and expression of VEGF and FN via ERK 1/2 signaling pathway in hGFs. Therefore, shikonin may promote periodontal tissue wound healing.

Nanocomposite particles with improved microstructure for 3D culture systems and bone regeneration.

Nano-apatite and gelatin-alginate hydrogel microparticles have been prepared by a one-step synthesis combined with electrostatic bead generation, for the reconstruction of bone defects. Based on the analysis of bone composition, architecture and embryonic intramembranous ossification, a bio-inspired fabrication has been developed. Accordingly, the mineral phase has been in situ synthesized, calcifying the hydrogel matrix while the latter was crosslinked, finally generating microparticles that can assemble into a bone defect to ensure interconnected pores. Although nano-apatite-biopolymer composites have been widely investigated, microstructural optimization to provide improved distribution and stability of the mineral is rarely achieved. The optimization of the developed method progressively resulted in two types of formulations (15P and 7.5P), with 15 and 7.5 (wt%) phosphate content in the initial precursor. The osteolytic potential was investigated using differentiated macrophages. A commercially available calcium phosphate bone graft substitute (Eurocer 400) was incorporated into the hydrogel, and the obtained composites were in vitro tested for comparison. The cytocompatibility of the microparticles was studied with mouse osteoblast-like cell line MC3T3-E1. Results indicated the best in vitro performance have been obtained for the sample loaded with 7.5P. Preliminary evaluation of biocompatibility into a critical size (3 mm) defect in rabbits showed that 7.5P nanocomposite is associated with newly formed bone in the proximity of the microparticles, after 28 days.

Carbon Flux Trapping: Highly Efficient Production of Polymer-Grade d-Lactic Acid with a Thermophilic d-Lactate Dehydrogenase.

High production of polymer-grade d-lactic acid is urgently required, particularly for the synthesis of polylactic acid. High-temperature fermentation has multiple advantages, such as lower equipment requirement and energy consumption, which are essential for lowering operating costs. We identified and introduced a unique d-lactate dehydrogenase into a thermotolerant butane-2,3-diol-producing strain. Carbon flux "trapping" was achieved by a "trapping point" created by combination of the introduced enzyme and the host efflux pump, which afforded irreversible transport of d-lactic acid. The overall carbon flux of the engineered strain was significantly enhanced and was redistributed predominantly to d-lactic acid. Under optimized conditions at 50 °C, d-lactic acid reached the highest titer (226.6 g L(-1) ) reported to date. This discovery allows us to extend the carbon flux trapping strategy to engineering complex metabolic networks.

Evaluation of lactate dehydrogenase enzyme activity in saliva and serum of oral submucous fibrosis patients.

BACKGROUND: Of all oral precancerous conditions, Oral Submucous Fibrosis is of greater concern because of its disabling nature and relative greater chances of malignant transformation. This malignant transformation involves glycolytic pathways that can alter lactate dehydrogenase levels. Therefore the aim of this study was to estimate the LDH levels in saliva and serum of subjects with OSMF and to compare them with healthy controls and to correlate the relationship between pathogenesis of OSMF and the LDH enzyme. METHODS: Sixty Subjects were recruited for this study and divided into two groups, 30 subjects with OSMF (Group A) and 30 healthy controls (Group B). Venous blood and unstimulated whole saliva measuring 1 ml was collected from each of these evaluated for LDH levels using the standard kit method. The data obtained were subjected to statistical analysis using the SPSS software version 17. RESULTS: The average salivary LDH value for Group A was 606.83 ± 60.09 U/l and for Group B was 80.73 ± 20.06 U/l. salivary LDH was greater in group A than Group B and this was statistically significant. On comparing the serum and salivary LDH in Group A with the clinical staging of OSMF, the results were not statistically significant. Similarly no statistically significant relationship was found on comparing the serum and salivary LDH in Group A (OSMF subjects) with duration of habit. CONCLUSION: This study provides additional rationale for the role of salivary LDH in the early diagnosis and prognosis of oral submucous fibrosis.

Evolution of D-lactate dehydrogenase activity from glycerol dehydrogenase and its utility for D-lactate production from lignocellulose.

Lactic acid, an attractive, renewable chemical for production of biobased plastics (polylactic acid, PLA), is currently commercially produced from food-based sources of sugar. Pure optical isomers of lactate needed for PLA are typically produced by microbial fermentation of sugars at temperatures below 40 °C. Bacillus coagulans produces L(+)-lactate as a primary fermentation product and grows optimally at 50 °C and pH 5, conditions that are optimal for activity of commercial fungal cellulases. This strain was engineered to produce D(-)-lactate by deleting the native ldh (L-lactate dehydrogenase) and alsS (acetolactate synthase) genes to impede anaerobic growth, followed by growth-based selection to isolate suppressor mutants that restored growth. One of these, strain QZ19, produced about 90 g L(-1) of optically pure D(-)-lactic acid from glucose in < 48 h. The new source of D-lactate dehydrogenase (D-LDH) activity was identified as a mutated form of glycerol dehydrogenase (GlyDH; D121N and F245S) that was produced at high levels as a result of a third mutation (insertion sequence). Although the native GlyDH had no detectable activity with pyruvate, the mutated GlyDH had a D-LDH specific activity of 0.8 µmoles min(-1) (mg protein)(-1). By using QZ19 for simultaneous saccharification and fermentation of cellulose to D-lactate (50 °C and pH 5.0), the cellulase usage could be reduced to 1/3 that required for equivalent fermentations by mesophilic lactic acid bacteria. Together, the native B. coagulans and the QZ19 derivative can be used to produce either L(+) or D(-) optical isomers of lactic acid (respectively) at high titers and yields from nonfood carbohydrates.

Mitigative effect of erythromycin on PMMA challenged preosteoblastic MC3T3-E1 cells.

BACKGROUND: Aseptic loosening (AL) is a major complication of total joint replacement. Recent approaches to limiting AL have focused on inhibiting periprosthetic inflammation and osteoclastogenesis. QUESTIONS/PURPOSES: The purpose of this study was to determine the effects of erythromycin (EM) on polymethylmethacrylate (PMMA) particle-challenged MC3T3 osteoblast precursor cells. MetHODS: MC3T3 cells were pretreated with EM (0-10 µg/mL) and then stimulated with PMMA (1 mg/mL). Cell viability was evaluated by both a lactate dehydrogenase (LDH) release assay and cell counts. Cell differentiation was determined by activity of alkaline phosphatase (ALP). Gene expression was measured via real-time quantitative RT-PCR. RESULTS: We found that exposure to PMMA particles reduced cellular viability and osteogenetic potential in MC3T3 cell line. EM treatment mitigated the effects of PMMA particles on the proliferation, viability and differentiation of MC3T3 cells. PMMA decreased the gene expression of Runx2, osterix and osteocalcin, which can be partially restored by EM treatment. Furthermore, EM suppressed PMMA- induced increase of NF-κB gene expression. CONCLUSIONS: These data demonstrate that EM mitigates the effects of PMMA on MC3T3 cell viability and differentiation, in part through downregulation of NF-κB pathway. EM appeared to represent an anabolic agent on MC3T3 cells challenged with PMMA particles.

Target integration of an exogenous ß-glucosidase enhances cellulose degradation and ethanol production in Clostridium cellulolyticum.

The bacteria Clostridium cellulolyticum is a promising candidate for consolidated bioprocessing (CBP). However, genetic engineering is necessary to improve this organism's cellulose degradation and bioconversion efficiencies to meet standard industrial requirements. In this study, CRISPR-Cas9n was used to integrate an efficient ß-glucosidase into the genome of C. cellulolyticum, disrupting lactate dehydrogenase (ldh) expression and reducing lactate production. The engineered strain showed a 7.4-fold increase in ß-glucosidase activity, a 70% decrease in ldh expression, a 12% increase in cellulose degradation, and a 32% increase in ethanol production compared to wild type. Additionally, ldh was identified as a potential site for heterologous expression. These results demonstrate that simultaneous ß-glucosidase integration and lactate dehydrogenase disruption is an effective strategy for increasing cellulose to ethanol bioconversion rates in C. cellulolyticum.

Near-ultraviolet irradiation to stimulate unmodified polyether ether ketone to achieve stable and sustainable antibacterial activity.

OBJECTIVES: This study aims to investigate the cytotoxicity and sustainable antibacterial activity of unmodified PEEK under specific wavelength light treatment (365 nm), and its antibacterial mechanism was also preliminarily discussed. METHODS: A near-ultraviolet source with a wavelength of 365 nm and a power of 5 W were selected. The irradiation time was 30 min, and the distance was 100 mm. A water contact angle tester was used to characterize the surface of the PEEK after 1-15 light treatments. MC3TC-E1 cells were used to evaluate the cytotoxicity of the materials under light treatment. Five kinds of common oral bacteria were detected in vitro, and antibacterial efficiency was determined by colony-forming unit (CFU) and scanning electron microscope (SEM). The antibacterial mechanism of PEEK under light was preliminarily discussed by spectrophotometry. The membrane rupture of Staphylococcus aureus and Escherichia coli was detected by lactate dehydrogenase. Staphylococcus aureus and Staphylococcus mutans were selected for the cyclic antibacterial test. Statistical analysis was performed by one-way analysis of variance and Tukey multiple range test. A significance level of 0.05 was considered (α = 0.05). RESULTS: The results of the cell experiment showed that PEEK had no cytotoxicity (P > 0.05). CFU results showed that PEEK had an obvious antibacterial effect on Staphylococcus aureus, Staphylococcus mutans, Staphylococcus gordonii and Staphylococcus sanguis, but had no antibacterial effect on Escherichia coli (P < 0.05). The SEM results also verified the above antibacterial effect. The existence of singlet oxygen was confirmed by spectrophotometry. Meanwhile, the rupture of Staphylococcus aureus membrane was verified by lactate dehydrogenase assay. The water contact angle of the PEEK surface did not change significantly after 15 cycles of light treatment. Cyclic antibacterial experiments showed that the antibacterial effect was sustainable. CONCLUSIONS: This study showed that PEEK has good cytocompatibility with stable and sustainable antibacterial properties under near-ultraviolet. It provides a new idea to solve the non-antibacterial property of PEEK, and also provides a theoretical basis for its further application in dentistry.

Biological characterization of D-lactate dehydrogenase responsible for high-yield production of D-phenyllactic acid in Sporolactobacillus inulinus.

PLA (3-D-phenyllactic acid) is an ideal antimicrobial and immune regulatory compound present in honey and fermented foods. Sporolactobacillus inulinus is regarded as a potent D-PLA producer that reduces phenylpyruvate (PPA) with D-lactate dehydrogenases. In this study, PLA was produced by whole-cell bioconversion of S. inulinus ATCC 15538. Three genes encoding D-lactate dehydrogenase (d-ldh1, d-ldh2, and d-ldh3) were cloned and expressed in Escherichia coli BL21 (DE3), and their biochemical and structural properties were characterized. Consequently, a high concentration of pure D-PLA (47 mM) was produced with a high conversion yield of 88%. Among the three enzymes, D-LDH1 was responsible for the efficient conversion of PPA to PLA with kinetic parameters of Km (0.36 mM), kcat (481.10 s-1 ), and kcat /Km (1336.39 mM-1  s-1 ). In silico structural analysis and site-directed mutagenesis revealed that the Ile307 in D-LDH1 is a key residue for excellent PPA reduction with low steric hindrance at the substrate entrance. This study highlights that S. inulinus ATCC 15538 is an excellent PLA producer, equipped with a highly specific and efficient D-LDH1 enzyme.

Cannabis smoke condensate induces human gingival epithelial cell damage through apoptosis, autophagy, and oxidative stress.

OBJECTIVES: This study aims to investigate the effects of cannabis smoke condensate (CSC) on the adhesion, growth, and signaling pathways of human gingival epithelial cells. DESIGN: The effects of CSC on cell shape and adhesion, and viability were evaluated after 30 min, 60 min, 2 h, and 24 h of exposure using microscopic observation, cell metabolic activity, and lactate dehydrogenase activity assays. The effects of CSC on cell apoptosis, necrosis, autophagy, and oxidative stress were determined through flow cytometry, while apoptotic and autophagic gene expression were identified via an RT2-PCR array. Phosphorylated signaling pathway proteins were measured using flow cytometry. RESULTS: CSC deregulated gingival epithelial cell shape and adhesion, decreased cell viability, and increased lactate dehydrogenase release. Its toxic effects included apoptosis, autophagy, and oxidative stress. Moreover, it modulated seven specific apoptotic and six autophagic genes. Furthermore, it decreased phosphorylation in signaling proteins, such as STAT5, ERK12, P38, and nuclear factor κB. CONCLUSIONS: CSC has notable adverse effects on gingival epithelial cells. This finding indicates that cannabis smoke could impair gingival epithelial cell innate immune function, leading to gingivitis and periodontitis. Oral health professionals may need to document observed modifications in the oral cavity of patients who smoke cannabis and consider these potential changes during clinical care.

Impact of pegfilgrastim approval on relative dose intensity and outcomes of R-CHOP for diffuse large B-cell lymphoma.

ABSTRACT: Maintaining relative dose intensity (RDI) of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) improves the prognosis of patients with diffuse large B-cell lymphoma (DLBCL). Pegfilgrastim was approved in Japan in November 2014 to prevent febrile neutropenia (FN) and maintain RDI.In this retrospective study, we reviewed 334 patients with DLBCL who received 6 or more courses of R-CHOP and analyzed the differences in the RDI, overall survival (OS), and progression-free survival between patients whose treatment started after November 2014 (postapproval group) and those whose treatment started before October 2014 (pre-approval group).The incidence of FN was lower (20% vs 38.3%, P < .001) and the RDI of R-CHOP was higher (86.8% vs 67.8%, P < .001) in the postapproval group. Pegfilgrastim was administered to many of these patients (76.8%) and was thought to have contributed to the high RDI maintenance in the postapproval group. Interrupted time-series analysis showed a significant rise of the RDI at the timing of pegfilgrastim approval in patients aged <70 years (estimated change: 18.1%, P < .001). The 5-year OS (85.7% vs 69.9%, P = .009) and progression-free survival (81.4% vs 64.4%, P = .011) were superior in the postapproval group. However, the differences were not significant in matched-pair analysis matching National Comprehensive Cancer Network-International Prognostic Index scores. Improved survival outcomes in this group were observed only among patients with Ann Arbor stage 3/4 (5-year OS: 83.7% vs 61.3%, P = .019) and high-risk on the National Comprehensive Cancer Network-International Prognostic Index (5-year OS: 80.7% vs 32.4%, P = .014). Multivariate analysis showed that a high RDI and low lactate dehydrogenase were associated with superior OS (RDI ≥ 85%, hazard ratio: 0.48, P = .016; lactate dehydrogenase > institutional upper limit of normal, hazard ratio: 2.38, P = .005).The RDI of R-CHOP was able to be maintained at higher levels, the incidence of FN was lower, and significantly better clinical outcomes were achieved in clinically high-risk groups after pegfilgrastim approval. Maintaining a high RDI in R-CHOP by administering pegfilgrastim to those who are likely to have low RDI without it is important for achieving favorable outcomes in patients with DLBCL.

Effects of histamine and various histamine receptor antagonists on gene expression profiles of macrophages during compressive strain.

PURPOSE: Tissue hormone histamine can accumulate locally within the periodontal ligament via nutrition or may be released during allergic reactions by mast cells, which may have an impact on orthodontic tooth movement. In addition to periodontal ligament fibroblasts, cells of the immune system such as macrophages are exposed to compressive strain. The aim of this study was thus to investigate the impact of histamine on the gene expression profile of macrophages in the context of simulated orthodontic compressive strain. METHODS: Macrophages were incubated with different histamine concentrations (50, 100, 200 µM) for 24 h and then either left untreated or compressed for another 4 h. To assess the role of different histamine receptors, we performed experiments with antagonists for histamine 1 receptor (cetirizine), histamine 2 receptor (ranitidine) and histamine 4 receptor (JNJ7777120) under control and pressure conditions. We tested for lactate dehydrogenase release and analyzed the expression of genes involved in inflammation and bone remodeling by reverse transcription quantitative polymerase chain reaction (RT-qPCR). RESULTS: Histamine elevated gene expression of tumor necrosis factor under control conditions and in combination with pressure application. Increased prostaglandin-endoperoxide synthase­2 mRNA was observed when histamine was combined with compressive force. Interleukin­6 gene expression was not affected by histamine treatment. In macrophages, compressive strain increased osteoprotegerin gene expression. Histamine further elevated this effect. Most of the observed histamine effects were blocked by the histamine 1 receptor antagonist cetirizine. CONCLUSIONS: Histamine has an impact on the gene expression profile of macrophages during compressive strain in vitro, most likely having an impairing effect on orthodontic tooth movement by upregulation of osteoprotegerin expression.

A pH-Responsive Cluster Metal-Organic Framework Nanoparticle for Enhanced Tumor Accumulation and Antitumor Effect.

As a result of the deficient tumor-specific antigens, potential off-target effect, and influence of protein corona, metal-organic framework nanoparticles have inadequate accumulation in tumor tissues, limiting their therapeutic effects. In this work, a pH-responsive linker (L) is prepared by covalently modifying oleylamine (OA) with 3-(bromomethyl)-4-methyl-2,5-furandione (MMfu) and poly(ethylene glycol) (PEG). Then, the L is embedded into a solid lipid nanoshell to coat apilimod (Ap)-loaded zeolitic imidazolate framework (Ap-ZIF) to form Ap-ZIF@SLN#L. Under the tumor microenvironment, the hydrophilic PEG and MMfu are removed, exposing the hydrophobic OA on Ap-ZIF@SLN#L, increasing their uptake in cancer cells and accumulation in the tumor. The ZIF@SLN#L nanoparticle induces reactive oxygen species (ROS). Ap released from Ap-ZIF@SLN#L significantly promotes intracellular ROS and lactate dehydrogenase generation. Ap-ZIF@SLN#L inhibits tumor growth, increases the survival rate in mice, activates the tumor microenvironment, and improves the infiltration of macrophages and T cells in the tumor, as demonstrated in two different tumor-bearing mice after injections with Ap-ZIF@SLN#TL. Furthermore, mice show normal tissue structure of the main organs and the normal serum level in alanine aminotransferase and aspartate aminotransferase after treatment with the nanoparticles. Overall, this pH-responsive targeting strategy improves nanoparticle accumulation in tumors with enhanced therapeutic effects.

A Drug-Free, Hair Follicle Cycling Regulatable, Separable, Antibacterial Microneedle Patch for Hair Regeneration Therapy.

The development of painless hair loss therapy without side-effect is challenging. The dermal papilla is the signal center of hair follicles and plays a key role in the regulation of their cycling. Activation of dermal papilla cells (DPCs) would promote hair regeneration. In this study, a separable microneedle patch comprised of chitosan lactate (CL) and exosomes (EXO) from adipose-derived stem cells is fabricated. After insertion of the microneedle into the skin, the hyaluronic acid substrate dissolves fast and the swellable polyvinyl alcohol needles are retained. The EXO sustainedly released from needles can be endocytosed by DPCs and promote cell proliferation via the activation of the Wnt signaling pathway, while the L-lactate released by CL can promote cell growth by activating lactate dehydrogenase. CL and EXO synergetically facilitate hair regeneration through regulating hair follicle cycling. In animal tests, compared with topical administration of minoxidil, the drug-free microneedle patches can more significantly promote hair regeneration within 7 days with lower dosing frequency. Furthermore, the inherent antibacterial properties of CL make it possible to avoid potential infection. Such transdermally administrated drug-free microneedle patches provide a simple, safe, and efficient strategy for hair loss treatment and exhibit great potential in clinical application.

Effect of Lemon Essential Oil Microemulsion on the Cariogenic Virulence Factor of Streptococcus mutans via the Glycolytic Pathway.

PURPOSE: To investigate the effects and mechanisms of lemon essential oil products on dental caries prevention. MATERIALS AND METHODS: Lemon essential oil microemulsions (LEOM) with concentrations of 1/8 minimum inhibitory concentration (MIC), 1/4 MIC, and 1/2 MIC were applied to S. mutans at concentrations of 0.2%, 1%, and 5% glucose, respectively. Changes in acid production capacity of S. mutans were measured based on changes in pH. The effect of the reductive coenzyme I oxidation method on LDH activity was examined. The effect of lemon essential oil microemulsion on the expression of the lactate dehydrogenase gene (ldh) was detected by a quantitative real-time polymerase chain reaction. RESULTS: Lemon essential oil microemulsion at 1/2 MIC concentration reduced the environmental pH value at different glucose concentrations, compared to those observed in the control group (p < 0.05). LDH activity of S. mutans was decreased at three subinhibitory concentrations of lemon essential oil microemulsions (p < 0.05). The effect of lemon essential oil microemulsions on S. mutans LDH activity and bacterial acid production were positively correlated (r = 0.825, p < 0.05). Lemon essential oil microemulsion at 1/2 MIC concentration downregulated the expression of the ldh gene of S. mutans at different glucose concentrations (p < 0.05). In different glucose environments, lemon essential oil microemulsions at subminimum inhibitory concentrations can inhibit the acid production of S. mutans by reducing ldh expression and LDH activity in the glycolytic pathway, proving its anti-caries potential. CONCLUSIONS: LEOM can effectively prevent dental caries and maintain the microecological balance of the oral environment.

Elimination of D-lactate synthesis increases poly(3-hydroxybutyrate) and ethanol synthesis from glycerol and affects cofactor distribution in recombinant Escherichia coli.

The effect of eliminating D-lactate synthesis in poly(3-hydroxybutyrate) (PHB)-accumulating recombinant Escherichia coli (K24K) was analyzed using glycerol as a substrate. K24KL, an ldhA derivative, produced more biomass and had altered carbon partitioning among the metabolic products, probably due to the increased availability of carbon precursors and reducing power. This resulted in a significant increase of PHB and ethanol synthesis and a decrease in acetate production. Cofactor measurements revealed that cultures of K24K and K24KL had a high intracellular NADPH content and that the NADPH/NADP(+) ratio was higher than the NADH/NAD(+) ratio. The ldhA mutation affected cofactor distribution, resulting in a more reduced intracellular state, mainly due to a further increase in NADPH/NADP(+). In 60-h fed-batch cultures, K24KL reached 41.9 g·liter⁻¹ biomass and accumulated PHB up to 63% ± 1% (wt/wt), with a PHB yield on glycerol of 0.41 ± 0.03 g·g⁻¹, the highest reported using this substrate.

Salivary monitoring related to major surgery.

BACKGROUND: Prolonged surgical procedures involving stress, extended general anaesthesia and a long pre-surgical fasting period may have systemic effects such as alterations in saliva flow rate and composition. These may compromise the patient's electrolytes and fluid balance and cause dehydration, systemic stress and oxidative changes. PATIENTS AND METHODS: Saliva was collected prior and following surgery from 20 patients and 20 control subjects. The saliva samples were analysed for flow rates and levels of the following: calcium (Ca), magnesium (Mg), total protein, albumin and lactate dehydrogenase (LDH), total antioxidant status (TAS), uric acid (UA), superoxide dismutase (SOD), carbonyls, matrix metalloproteinases (MMPs) -2, -3 and -9 and heat shock proteins (HSPs) 70 and 90. RESULTS: Salivary levels of Ca, Mg, protein, albumin and LDH were higher in post-surgical patients by 70% (P = 0·002), 88% (P = 0·0001), 120% (P = 0·13), 111% (P = 0·039) and 492% (P = 0·006) respectively than that in healthy controls. Salivary antioxidants in the surgical patients were higher while salivary carbonyls remained unchanged. Salivary TAS levels in pre- and post-surgical patients were higher by 63% (P = 0·001) and 85% (P = 0·0001) respectively, UA concentrations by 92% (P = 0·014) and 81% (P = 0·036) respectively and SOD values by 47% (P = 0·61) and 112% (P = 0·049) respectively. Salivary concentrations of MMP3 were higher in pre- and post-surgical patients by 23% (P = 0·067) and 30% (P = 0·044) respectively. CONCLUSIONS: Local salivary, oral and systemic-induced alterations should be prevented. Moreover, salivary collection and analysis may be a new, efficient tool in the monitoring of patients undergoing major surgery. Further related research is necessary.

Short-term inhalation exposure to mild steel welding fume had no effect on lung inflammation and injury but did alter defense responses to bacteria in rats.

Many workers worldwide are continually exposed to complex aerosols generated from welding processes. The objective was to assess the effect of inhalation exposure to mild steel (MS) welding fume on lung injury, inflammation, and defense responses. Male Sprague-Dawley rats were exposed to MS fume at a concentration of 40 mg/m(3) x 3 h/day x 3 or 10 days using a robotic welding fume generator. Controls were exposed to filtered air. To assess lung defense responses, a group of animals were intratracheally inoculated with 5 x 10(4) Listeria monocytogenes 1 day after the last daily exposure. Welding particles were collected during exposure, and chemical composition and particle size were determined. After exposure, lung injury, inflammation, and host defense (bacterial clearance) were measured. The particles were composed of iron (80.6 %) and manganese (14.7 %) with a mass median aerodynamic diameter of 0.31 microm. No significant difference was observed in lung injury or inflammation after MS fume inhalation at 1, 4, and 11 days after the last exposure. However, there were significantly more bacteria at 3 days after infection in the lungs of the animals exposed to MS fume compared to air controls. Acute exposure of rats to MS fume had no effect on injury and inflammation, but suppressed lung defense responses after infection. More chronic inhalation studies are needed to further examine the immune effects and to elucidate the possible mechanisms of the suppressed lung defense response to infection associated with the inhalation of MS welding fume.